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Gulette GA, Hass DT, Pandey K, Zhang Q, Han JYS, Engel A, Chao JR, Philp NJ, Hurley JB, Miller JML. Reassessing retinal pigment epithelial ketogenesis: Enzymatic assays for ketone body levels provide inaccurate results. Exp Eye Res 2024; 245:109966. [PMID: 38857822 DOI: 10.1016/j.exer.2024.109966] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2024] [Accepted: 06/06/2024] [Indexed: 06/12/2024]
Abstract
The retinal pigment epithelium (RPE) is omnivorous and can utilize a wide range of substrates for oxidative phosphorylation. Certain tissues with high mitochondrial metabolic load are capable of ketogenesis, a biochemical pathway that consolidates acetyl-CoA into ketone bodies. Earlier work demonstrated that the RPE expresses the rate-limiting enzyme for ketogenesis, 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2), and that the RPE indeed produces ketone bodies, including beta-hydroxybutyrate (β-HB). Prior work, based on detecting β-HB via enzymatic assays, suggested that differentiated cultures of primary RPE preferentially export β-HB across the apical membrane. Here, we compare the accuracy of measuring β-HB by enzymatic assay kits to mass spectrometry analysis. We found that commercial kits lack the sensitivity to accurately measure the levels of β-HB in RPE cultures and are prone to artifact. Using mass spectrometry, we found that while RPE cultures secrete β-HB, they do so equally to both apical and basal sides. We also find RPE is capable of consuming β-HB as levels rise. Using isotopically labeled glucose, amino acid, and fatty acid tracers, we found that carbons from both fatty acids and ketogenic amino acids, but not from glucose, produce β-HB. Altogether, we substantiate β-HB secretion in RPE but find that the secretion is equal apically and basally, RPE β-HB can derive from ketogenic amino acids or fatty acids, and accurate β-HB assessment requires mass spectrometric analysis.
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Affiliation(s)
| | - Daniel T Hass
- Department of Biochemistry, University of Washington, United States
| | - Kriti Pandey
- Department of Biochemistry, University of Washington, United States
| | - Qitao Zhang
- Kellogg Eye Center, University of Michigan, United States
| | - John Y S Han
- Kellogg Eye Center, University of Michigan, United States
| | - Abbi Engel
- Center of Developmental Biology and Regenerative Medicine, Seattle Children's Research Hospital, United States
| | - Jennifer R Chao
- Department of Ophthalmology, University of Washington, United States
| | - Nancy J Philp
- Department of Pathology, Anatomy & Cell Biology, Thomas Jefferson University, United States
| | - James B Hurley
- Department of Biochemistry, University of Washington, United States
| | - Jason M L Miller
- Kellogg Eye Center, University of Michigan, United States; Cellular and Molecular Biology Program, University of Michigan, United States.
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2
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Kaufmann M, Han Z. RPE melanin and its influence on the progression of AMD. Ageing Res Rev 2024; 99:102358. [PMID: 38830546 DOI: 10.1016/j.arr.2024.102358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Accepted: 05/27/2024] [Indexed: 06/05/2024]
Abstract
OBJECTIVE The aim of this review article is to summarize the latest findings and current understanding of the origin of melanin in the retinal pigment epithelium (RPE), its function within the RPE, its role in the pathogenesis of age-related macular degeneration (AMD), its effect on retinal development, and its potential therapeutic benefit in the treatment of AMD. METHODS A comprehensive search of peer-reviewed journals was conducted using various combinations of key terms such as "melanin," "retinal pigment epithelium" or "RPE," "age-related macular degeneration" or AMD," "lipofuscin," "oxidative stress," and "albinism." Databases searched include PubMed, Scopus, Science Direct, and Google Scholar. 147 papers published between the years of 1957 and 2023 were considered with an emphasis on recent findings. SUMMARY OF FINDINGS AMD is thought to result from chronic oxidative stress within the RPE that results in cellular dysfunction, metabolic dysregulation, inflammation, and lipofuscin accumulation. Melanin functions as a photoscreener, free radical scavenger, and metal cation binding reservoir within the RPE. RPE melanin does not regenerate, and it undergoes degradation over time in response to chronic light exposure and oxidative stress. RPE melanin is important for retinal development and RPE function, and in the aging eye, melanin loss is associated with increased lipid peroxidation, inflammation, and the accumulation of toxic oxidized cellular products. Therefore, melanin-based treatments may serve to preserve RPE and retinal function in AMD. CONCLUSIONS The pathogenesis of AMD is not fully understood, but RPE dysfunction and melanin loss in response to chronic oxidative stress and inflammation are thought to be primary drivers of the disease. Due to melanin's antioxidative effects, melanin-based nanotechnology represents a promising avenue for the treatment of AMD.
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Affiliation(s)
- Mary Kaufmann
- University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Zongchao Han
- Department of Ophthalmology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Division of Pharmacoengineering & Molecular Pharmaceutics, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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3
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Gillingham MB, Choi D, Gregor A, Wongchaisuwat N, Black D, Scanga HL, Nischal KK, Sahel JA, Arnold G, Vockley J, Harding CO, Pennesi ME. Early diagnosis and treatment by newborn screening (NBS) or family history is associated with improved visual outcomes for long-chain 3-hydroxyacylCoA dehydrogenase deficiency (LCHADD) chorioretinopathy. J Inherit Metab Dis 2024. [PMID: 38623632 DOI: 10.1002/jimd.12738] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 03/26/2024] [Accepted: 03/27/2024] [Indexed: 04/17/2024]
Abstract
Long chain 3-hydroxyacyl-CoA dehydrogenase (LCHADD) is the only fatty acid oxidation disorder to develop a progressive chorioretinopathy resulting in vision loss; newborn screening (NBS) for this disorder began in the United States around 2004. We compared visual outcomes among 40 participants with LCHADD or trifunctional protein deficiency diagnosed symptomatically to those who were diagnosed via NBS or a family history. Participants completed ophthalmologic testing including measures of visual acuity, electroretinograms (ERG), fundal imaging, contrast sensitivity, and visual fields. Records were reviewed to document medical and treatment history. Twelve participants presented symptomatically with hypoglycemia, failure to thrive, liver dysfunction, cardiac arrest, or rhabdomyolysis. Twenty eight were diagnosed by NBS or due to a family history of LCHADD. Participants diagnosed symptomatically were older but had similar percent males and genotypes as those diagnosed by NBS. Treatment consisted of fasting avoidance, dietary long-chain fat restriction, MCT, C7, and/or carnitine supplementation. Visual acuity, rod- and cone-driven amplitudes on ERG, contrast sensitivity scores, and visual fields were all significantly worse among participants diagnosed symptomatically compared to NBS. In mixed-effects models, both age and presentation (symptomatic vs. NBS) were significant independent factors associated with visual outcomes. This suggests that visual outcomes were improved by NBS, but there was still lower visual function with advancing age in both groups. Early diagnosis and treatment by NBS is associated with improved visual outcomes and retinal function compared to participants who presented symptomatically. Despite the impact of early intervention, chorioretinopathy was greater with advancing age, highlighting the need for novel treatments.
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Affiliation(s)
- Melanie B Gillingham
- Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, Oregon, USA
| | - Dongseok Choi
- OHSU-PSU School of Public Health, Biostatistics, Oregon Health & Science University, Portland, Oregon, USA
- Casey Eye Institute, Oregon Health & Science University, Portland, Oregon, USA
| | - Ashley Gregor
- Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, Oregon, USA
| | - Nida Wongchaisuwat
- Casey Eye Institute, Oregon Health & Science University, Portland, Oregon, USA
| | - Danielle Black
- Division of Genetic and Genomic Medicine, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Hannah L Scanga
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Ken K Nischal
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Jose-Alain Sahel
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Georgianne Arnold
- Division of Genetic and Genomic Medicine, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Jerry Vockley
- Division of Genetic and Genomic Medicine, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Cary O Harding
- Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, Oregon, USA
| | - Mark E Pennesi
- Casey Eye Institute, Oregon Health & Science University, Portland, Oregon, USA
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4
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Abcouwer SF, Miglioranza Scavuzzi B, Kish PE, Kong D, Shanmugam S, Le XA, Yao J, Hager H, Zacks DN. The mouse retinal pigment epithelium mounts an innate immune defense response following retinal detachment. J Neuroinflammation 2024; 21:74. [PMID: 38528525 PMCID: PMC10964713 DOI: 10.1186/s12974-024-03062-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Accepted: 03/11/2024] [Indexed: 03/27/2024] Open
Abstract
The retinal pigment epithelium (RPE) maintains photoreceptor viability and function, completes the visual cycle, and forms the outer blood-retinal barrier (oBRB). Loss of RPE function gives rise to several monogenic retinal dystrophies and contributes to age-related macular degeneration. Retinal detachment (RD) causes separation of the neurosensory retina from the underlying RPE, disrupting the functional and metabolic relationships between these layers. Although the retinal response to RD is highly studied, little is known about how the RPE responds to loss of this interaction. RNA sequencing (RNA-Seq) was used to compare normal and detached RPE in the C57BL6/J mouse. The naïve mouse RPE transcriptome was compared to previously published RPE signature gene lists and from the union of these 14 genes (Bmp4, Crim1, Degs1, Gja1, Itgav, Mfap3l, Pdpn, Ptgds, Rbp1, Rnf13, Rpe65, Slc4a2, Sulf1 and Ttr) representing a core signature gene set applicable across rodent and human RPE was derived. Gene ontology enrichment analysis (GOEA) of the mouse RPE transcriptome identified expected RPE features and functions, such as pigmentation, phagocytosis, lysosomal and proteasomal degradation of proteins, and barrier function. Differentially expressed genes (DEG) at 1 and 7 days post retinal detachment (dprd) were defined as mRNA with a significant (padj≤0.05) fold change (FC) of 0.67 ≥ FC ≥ 1.5 in detached versus naïve RPE. The RPE transcriptome exhibited dramatic changes at 1 dprd, with 2297 DEG identified. The KEGG pathways and biological process GO groups related to innate immune responses were significantly enriched. Lipocalin 2 (Lcn2) and several chemokines were upregulated, while numerous genes related to RPE functions, such as pigment synthesis, visual cycle, phagocytosis, and tight junctions were downregulated at 1 dprd. The response was largely transient, with only 18 significant DEG identified at 7 dprd, including upregulation of complement gene C4b. Validation studies confirmed RNA-Seq results. Thus, the RPE quickly downregulates cell-specific functions and mounts an innate immune defense response following RD. Our data demonstrate that the RPE contributes to the inflammatory response to RD and may play a role in attraction of immune cells to the subretinal space.
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Affiliation(s)
- Steven F Abcouwer
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan Medicine, 1000 Wall Street, Ann Arbor, MI, 48105, USA.
| | - Bruna Miglioranza Scavuzzi
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan Medicine, 1000 Wall Street, Ann Arbor, MI, 48105, USA
| | - Phillip E Kish
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan Medicine, 1000 Wall Street, Ann Arbor, MI, 48105, USA
| | - Dejuan Kong
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan Medicine, 1000 Wall Street, Ann Arbor, MI, 48105, USA
| | - Sumathi Shanmugam
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan Medicine, 1000 Wall Street, Ann Arbor, MI, 48105, USA
| | - Xuan An Le
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan Medicine, 1000 Wall Street, Ann Arbor, MI, 48105, USA
| | - Jingyu Yao
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan Medicine, 1000 Wall Street, Ann Arbor, MI, 48105, USA
| | - Heather Hager
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan Medicine, 1000 Wall Street, Ann Arbor, MI, 48105, USA
| | - David N Zacks
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan Medicine, 1000 Wall Street, Ann Arbor, MI, 48105, USA
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Grubaugh CR, Dhingra A, Prakash B, Montenegro D, Sparrow JR, Daniele LL, Curcio CA, Bell BA, Hussain MM, Boesze-Battaglia K. Microsomal triglyceride transfer protein is necessary to maintain lipid homeostasis and retinal function. FASEB J 2024; 38:e23522. [PMID: 38445789 PMCID: PMC10949407 DOI: 10.1096/fj.202302491r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2023] [Revised: 02/07/2024] [Accepted: 02/16/2024] [Indexed: 03/07/2024]
Abstract
Lipid processing by the retinal pigment epithelium (RPE) is necessary to maintain retinal health and function. Dysregulation of retinal lipid homeostasis due to normal aging or age-related disease triggers lipid accumulation within the RPE, on Bruch's membrane (BrM), and in the subretinal space. In its role as a hub for lipid trafficking into and out of the neural retina, the RPE packages a significant amount of lipid into lipid droplets for storage and into apolipoprotein B (APOB)-containing lipoproteins (Blps) for export. Microsomal triglyceride transfer protein (MTP), encoded by the MTTP gene, is essential for Blp assembly. Herein we test the hypothesis that MTP expression in the RPE is essential to maintain lipid balance and retinal function using the newly generated RPEΔMttp mouse model. Using non-invasive ocular imaging, electroretinography, and histochemical and biochemical analyses we show that genetic depletion of Mttp from the RPE results in intracellular lipid accumulation, increased photoreceptor-associated cholesterol deposits, and photoreceptor cell death, and loss of rod but not cone function. RPE-specific reduction in Mttp had no significant effect on plasma lipids and lipoproteins. While APOB was decreased in the RPE, most ocular retinoids remained unchanged, with the exception of the storage form of retinoid, retinyl ester. Thus suggesting that RPE MTP is critical for Blp synthesis and assembly but is not directly involved in plasma lipoprotein metabolism. These studies demonstrate that RPE-specific MTP expression is necessary to establish and maintain retinal lipid homeostasis and visual function.
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Affiliation(s)
- Catharina R. Grubaugh
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Anuradha Dhingra
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Binu Prakash
- Department of Foundations of Medicine, New York University Grossman Long Island School of Medicine, Mineola, NY, 11501 USA
| | - Diego Montenegro
- Department of Ophthalmology and Department of Pathology and Cell Biology, Columbia University, New York, NY, 10027 USA
| | - Janet R. Sparrow
- Department of Ophthalmology and Department of Pathology and Cell Biology, Columbia University, New York, NY, 10027 USA
| | - Lauren L. Daniele
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Christine A. Curcio
- Department of Ophthalmology and Visual Sciences, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Brent A. Bell
- Department of Ophthalmology, University of Pennsylvania, Philadelphia, PA, 19104 USA
| | - M. Mahmood Hussain
- Department of Foundations of Medicine, New York University Grossman Long Island School of Medicine, Mineola, NY, 11501 USA
| | - Kathleen Boesze-Battaglia
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
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6
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Rizwan S, Toothman B, Li B, Engel AJ, Lim RR, Lu J, Chao JR, Du J. Metabolic phenotyping of healthy and diseased human RPE cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.28.582405. [PMID: 38464098 PMCID: PMC10925320 DOI: 10.1101/2024.02.28.582405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
Purpose Metabolic defects in retinal pigment epithelium (RPE) are underlying many retinal degenerative diseases. This study aims to identify the nutrient requirements of healthy and diseased human RPE cells. Methods We profiled the utilization of 183 nutrients in human RPE cells: 1) differentiated and dedifferentiated fetal RPE (fRPE), 2) induced pluripotent stem cell derived-RPE (iPSC RPE), 3) Sorsby fundus dystrophy (SFD) patient-derived iPSC RPE and its CRISPR-corrected isogenic SFD (cSFD) iPSC RPE, and 5) ARPE-19 cell lines cultured under different conditions. Results Differentiated fRPE cells and healthy iPSC RPE cells can utilize 51 and 48 nutrients respectively, including sugars, intermediates from glycolysis and tricarboxylic acid (TCA) cycle, fatty acids, ketone bodies, amino acids, and dipeptides. However, when fRPE cells lose epithelial phenotype through dedifferentiated, they can only utilize 17 nutrients, primarily sugar and glutamine-related amino acids. SFD RPE cells can utilize 37 nutrients; however, Compared to cSFD RPE and healthy iPSC RPE, they are unable to utilize lactate, some TCA cycle intermediates, and short-chain fatty acids. Nonetheless, they show increased utilization of branch-chain amino acids (BCAAs) and BCAA-containing dipeptides. The dedifferentiated ARPE-19 cells in traditional culture media cannot utilize lactate and ketone bodies. In contrast, nicotinamide supplementation promotes differentiation into epithelial phenotype, restoring the ability to use these nutrients. Conclusions Epithelial phenotype confers metabolic flexibility to the RPE for utilizing various nutrients. SFD RPE cells have reduced metabolic flexibility, relying on the oxidation of BCAAs. Our findings highlight the importance of nutrient availability and utilization in RPE differentiation and diseases.
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Affiliation(s)
- Saira Rizwan
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506
| | - Beverly Toothman
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506
| | - Bo Li
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506
- Department of Ophthalmology, Affiliated Hospital of Yangzhou University, Yangzhou University, Yangzhou, Jiangsu Province 225100, China
| | - Abbi J. Engel
- Department of Ophthalmology, University of Washington, Seattle, WA 98109, United States
| | - Rayne R Lim
- Department of Ophthalmology, University of Washington, Seattle, WA 98109, United States
| | - Jinyu Lu
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506
| | - Jennifer R. Chao
- Department of Ophthalmology, University of Washington, Seattle, WA 98109, United States
| | - Jianhai Du
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506
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7
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Różanowska MB. Lipofuscin, Its Origin, Properties, and Contribution to Retinal Fluorescence as a Potential Biomarker of Oxidative Damage to the Retina. Antioxidants (Basel) 2023; 12:2111. [PMID: 38136230 PMCID: PMC10740933 DOI: 10.3390/antiox12122111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Revised: 12/05/2023] [Accepted: 12/09/2023] [Indexed: 12/24/2023] Open
Abstract
Lipofuscin accumulates with age as intracellular fluorescent granules originating from incomplete lysosomal digestion of phagocytosed and autophagocytosed material. The purpose of this review is to provide an update on the current understanding of the role of oxidative stress and/or lysosomal dysfunction in lipofuscin accumulation and its consequences, particularly for retinal pigment epithelium (RPE). Next, the fluorescence of lipofuscin, spectral changes induced by oxidation, and its contribution to retinal fluorescence are discussed. This is followed by reviewing recent developments in fluorescence imaging of the retina and the current evidence on the prognostic value of retinal fluorescence for the progression of age-related macular degeneration (AMD), the major blinding disease affecting elderly people in developed countries. The evidence of lipofuscin oxidation in vivo and the evidence of increased oxidative damage in AMD retina ex vivo lead to the conclusion that imaging of spectral characteristics of lipofuscin fluorescence may serve as a useful biomarker of oxidative damage, which can be helpful in assessing the efficacy of potential antioxidant therapies in retinal degenerations associated with accumulation of lipofuscin and increased oxidative stress. Finally, amendments to currently used fluorescence imaging instruments are suggested to be more sensitive and specific for imaging spectral characteristics of lipofuscin fluorescence.
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Affiliation(s)
- Małgorzata B. Różanowska
- School of Optometry and Vision Sciences, College of Biomedical and Life Sciences, Cardiff University, Maindy Road, Cardiff CF24 4HQ, Wales, UK;
- Cardiff Institute for Tissue Engineering and Repair (CITER), Redwood Building, King Edward VII Avenue, Cardiff CF10 3NB, Wales, UK
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8
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Grubaugh CR, Dhingra A, Prakash B, Montenegro D, Sparrow JR, Daniele LL, Curcio CA, Bell BA, Hussain MM, Boesze-Battaglia K. Microsomal triglyceride transfer protein is necessary to maintain lipid homeostasis and retinal function. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.06.570418. [PMID: 38105975 PMCID: PMC10723417 DOI: 10.1101/2023.12.06.570418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
Lipid processing by the retinal pigment epithelium (RPE) is necessary to maintain retinal health and function. Dysregulation of retinal lipid homeostasis due to normal aging or to age-related disease triggers lipid accumulation within the RPE, on Bruch's membrane (BrM), and in the subretinal space. In its role as a hub for lipid trafficking into and out of the neural retina, the RPE packages a significant amount of lipid into lipid droplets for storage and into apolipoprotein B (apoB)-containing lipoproteins (Blps) for export. Microsomal triglyceride transfer protein (MTP), encoded by the MTTP gene, is essential for Blp assembly. Herein we test the hypothesis that MTP expression in the RPE is essential to maintain lipid balance and retinal function using the newly generated RPEΔMttp mouse model. Using non-invasive ocular imaging, electroretinography, and histochemical and biochemical analyses we show that genetic deletion of Mttp from the RPE results in intracellular lipid accumulation, increased photoreceptor -associated cholesterol deposits and photoreceptor cell death, and loss of rod but not cone function. RPE-specific ablation of Mttp had no significant effect on plasma lipids and lipoproteins. While, apoB was decreased in the RPE, ocular retinoid concentrations remained unchanged. Thus suggesting that RPE MTP is critical for Blp synthesis and assembly but not directly involved in ocular retinoid and plasma lipoprotein metabolism. These studies demonstrate that RPE-specific MTP expression is necessary to establish and maintain retinal lipid homeostasis and visual function.
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Affiliation(s)
- Catharina R. Grubaugh
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Anuradha Dhingra
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Binu Prakash
- Department of Foundations of Medicine, New York University Grossman Long Island School of Medicine, Mineola, NY, 11501 USA
| | - Diego Montenegro
- Department of Ophthalmology and Department of Pathology and Cell Biology, Columbia University, New York, NY,10027 USA
| | - Janet R. Sparrow
- Department of Ophthalmology and Department of Pathology and Cell Biology, Columbia University, New York, NY,10027 USA
| | - Lauren L. Daniele
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Christine A. Curcio
- Department of Ophthalmology and Visual Sciences, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Brent A. Bell
- Department of Ophthalmology, University of Pennsylvania, Philadelphia, PA, 19104 USA
| | - M. Mahmood Hussain
- Department of Foundations of Medicine, New York University Grossman Long Island School of Medicine, Mineola, NY, 11501 USA
| | - Kathleen Boesze-Battaglia
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
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9
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Zhu S, Xu R, Engel AL, Wang Y, McNeel R, Hurley JB, Chao JR, Du J. Proline provides a nitrogen source in the retinal pigment epithelium to synthesize and export amino acids for the neural retina. J Biol Chem 2023; 299:105275. [PMID: 37741457 PMCID: PMC10616405 DOI: 10.1016/j.jbc.2023.105275] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 09/07/2023] [Accepted: 09/11/2023] [Indexed: 09/25/2023] Open
Abstract
It is known that metabolic defects in the retinal pigment epithelium (RPE) can cause degeneration of its neighboring photoreceptors in the retina, leading to retinal degenerative diseases such as age-related macular degeneration. However, how RPE metabolism supports the health of the neural retina remains unclear. The retina requires exogenous nitrogen sources for protein synthesis, neurotransmission, and energy metabolism. Using 15N tracing coupled with mass spectrometry, we found human RPE can utilize the nitrogen in proline to produce and export 13 amino acids, including glutamate, aspartate, glutamine, alanine, and serine. Similarly, we found this proline nitrogen utilization in the mouse RPE/choroid but not in the neural retina of explant cultures. Coculture of human RPE with the retina showed that the retina can take up the amino acids, especially glutamate, aspartate, and glutamine, generated from proline nitrogen in the RPE. Intravenous delivery of 15N proline in vivo demonstrated 15N-derived amino acids appear earlier in the RPE before the retina. We also found proline dehydrogenase, the key enzyme in proline catabolism is highly enriched in the RPE but not the retina. The deletion of proline dehydrogenase blocks proline nitrogen utilization in RPE and the import of proline nitrogen-derived amino acids in the retina. Our findings highlight the importance of RPE metabolism in supporting nitrogen sources for the retina, providing insight into understanding the mechanisms of the retinal metabolic ecosystem and RPE-initiated retinal degenerative diseases.
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Affiliation(s)
- Siyan Zhu
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, USA; Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, USA; Department of Pharmaceutical and Pharmacological Sciences, West Virginia University, Morgantown, West Virginia, USA
| | - Rong Xu
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, USA; Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, USA
| | - Abbi L Engel
- Department of Ophthalmology, University of Washington, Seattle, Washington, USA
| | - Yekai Wang
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, USA; Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, USA
| | - Rachel McNeel
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, USA; Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, USA
| | - James B Hurley
- Department of Ophthalmology, University of Washington, Seattle, Washington, USA; Department of Biochemistry, University of Washington, Seattle, Washington, USA
| | - Jennifer R Chao
- Department of Ophthalmology, University of Washington, Seattle, Washington, USA.
| | - Jianhai Du
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, USA; Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, USA.
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10
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Hass DT, Zhang Q, Autterson GA, Bryan RA, Hurley JB, Miller JML. Medium Depth Influences O2 Availability and Metabolism in Human RPE Cultures. Invest Ophthalmol Vis Sci 2023; 64:4. [PMID: 37922158 PMCID: PMC10629522 DOI: 10.1167/iovs.64.14.4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2023] [Accepted: 10/13/2023] [Indexed: 11/05/2023] Open
Abstract
Purpose Retinal pigment epithelium (RPE) oxidative metabolism is critical for normal retinal function and is often studied in cell culture systems. Here, we show that conventional culture media volumes dramatically impact O2 availability, limiting oxidative metabolism. We suggest optimal conditions to ensure cultured RPE is in a normoxic environment permissive to oxidative metabolism. Methods We altered the availability of O2 to human primary and induced pluripotent stem cell-derived RPE cultures directly via a hypoxia chamber or indirectly via the amount of medium over cells. We measured oxygen consumption rates (OCRs), glucose consumption, lactate production, 13C6-glucose and 13C5-glutamine flux, hypoxia inducible factor 1α (HIF-1α) stability, intracellular lipid droplets after a lipid challenge, transepithelial electrical resistance, cell morphology, and pigmentation. Results Medium volumes commonly employed during RPE culture limit diffusion of O2 to cells, triggering hypoxia, activating HIF-1α, limiting OCR, and dramatically altering cell metabolism, with only minor effects on typical markers of RPE health. Media volume effects on O2 availability decrease acetyl-CoA utilization, increase glycolysis and reductive carboxylation, and alter the size and number of intracellular lipid droplets under lipid-rich conditions. Conclusions Despite having little impact on visible and typical markers of RPE culture health, media volume dramatically affects RPE physiology "under the hood." As RPE-centric diseases like age-related macular degeneration involve oxidative metabolism, RPE cultures need to be optimized to study such diseases. We provide guidelines for optimal RPE culture volumes that balance ample nutrient availability from larger media volumes with adequate O2 availability seen with smaller media volumes.
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Affiliation(s)
- Daniel T. Hass
- Department of Biochemistry, The University of Washington, Seattle, Washington, United States
| | - Qitao Zhang
- Kellogg Eye Center, University of Michigan, Ann Arbor, Michigan, United States
| | | | | | - James B. Hurley
- Department of Biochemistry, The University of Washington, Seattle, Washington, United States
| | - Jason M. L. Miller
- Kellogg Eye Center, University of Michigan, Ann Arbor, Michigan, United States
- Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, Michigan, United States
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11
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Kocherlakota S, Das Y, Swinkels D, Vanmunster M, Callens M, Vinckier S, Vaz FM, Sinha D, Van Veldhoven PP, Fransen M, Baes M. The murine retinal pigment epithelium requires peroxisomal β-oxidation to maintain lysosomal function and prevent dedifferentiation. Proc Natl Acad Sci U S A 2023; 120:e2301733120. [PMID: 37862382 PMCID: PMC10614831 DOI: 10.1073/pnas.2301733120] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Accepted: 08/14/2023] [Indexed: 10/22/2023] Open
Abstract
Retinal pigment epithelium (RPE) cells have to phagocytose shed photoreceptor outer segments (POS) on a daily basis over the lifetime of an organism, but the mechanisms involved in the digestion and recycling of POS lipids are poorly understood. Although it was frequently assumed that peroxisomes may play an essential role, this was never investigated. Here, we show that global as well as RPE-selective loss of peroxisomal β-oxidation in multifunctional protein 2 (MFP2) knockout mice impairs the digestive function of lysosomes in the RPE at a very early age, followed by RPE degeneration. This was accompanied by prolonged mammalian target of rapamycin activation, lipid deregulation, and mitochondrial structural anomalies without, however, causing oxidative stress or energy shortage. The RPE degeneration caused secondary photoreceptor death. Notably, the deterioration of the RPE did not occur in an Mfp2/rd1 mutant mouse line, characterized by absent POS shedding. Our findings prove that peroxisomal β-oxidation in the RPE is essential for handling the polyunsaturated fatty acids present in ingested POS and shed light on retinopathy in patients with peroxisomal disorders. Our data also have implications for gene therapy development as they highlight the importance of targeting the RPE in addition to the photoreceptor cells.
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Affiliation(s)
- Sai Kocherlakota
- Laboratory of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, Katholieke Universiteit Leuven, Leuven3000, Belgium
| | - Yannick Das
- Laboratory of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, Katholieke Universiteit Leuven, Leuven3000, Belgium
| | - Daniëlle Swinkels
- Laboratory of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, Katholieke Universiteit Leuven, Leuven3000, Belgium
| | - Maarten Vanmunster
- Laboratory of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, Katholieke Universiteit Leuven, Leuven3000, Belgium
| | - Manon Callens
- Laboratory of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, Katholieke Universiteit Leuven, Leuven3000, Belgium
| | - Stefan Vinckier
- Laboratory of Angiogenesis and Vascular Metabolism, Center for Cancer Biology, Vlaams Insituut voor Biotechnologie, Leuven3000, Belgium
- Department of Oncology, Leuven Cancer Institute, Katholieke Universiteit Leuven, Leuven3000, Belgium
| | - Frédéric M. Vaz
- Laboratory Genetic Metabolic Diseases, Department of Clinical Chemistry, Amsterdam Gastroenterology and Metabolism, Amsterdam University Medical Center, University of Amsterdam, Amsterdam1105AZ, The Netherlands
- Core Facility Metabolomics, Amsterdam University Medical Center, Amsterdam1105AZ, The Netherlands
| | - Debasish Sinha
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA15213
- Wilmer Eye Institute, The Johns Hopkins University School of Medicine, Baltimore, MD21287
| | - Paul P. Van Veldhoven
- Laboratory of Peroxisome Biology and Intracellular Communication, Department of Cellular and Molecular Medicine, Katholieke Universiteit Leuven, Leuven3000, Belgium
| | - Marc Fransen
- Laboratory of Peroxisome Biology and Intracellular Communication, Department of Cellular and Molecular Medicine, Katholieke Universiteit Leuven, Leuven3000, Belgium
| | - Myriam Baes
- Laboratory of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, Katholieke Universiteit Leuven, Leuven3000, Belgium
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12
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Wu J, Duan C, Yang Y, Wang Z, Tan C, Han C, Hou X. Insights into the liver-eyes connections, from epidemiological, mechanical studies to clinical translation. J Transl Med 2023; 21:712. [PMID: 37817192 PMCID: PMC10566185 DOI: 10.1186/s12967-023-04543-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2023] [Accepted: 09/19/2023] [Indexed: 10/12/2023] Open
Abstract
Maintenance of internal homeostasis is a sophisticated process, during which almost all organs get involved. Liver plays a central role in metabolism and involves in endocrine, immunity, detoxification and storage, and therefore it communicates with distant organs through such mechanisms to regulate pathophysiological processes. Dysfunctional liver is often accompanied by pathological phenotypes of distant organs, including the eyes. Many reviews have focused on crosstalk between the liver and gut, the liver and brain, the liver and heart, the liver and kidney, but with no attention paid to the liver and eyes. In this review, we summarized intimate connections between the liver and the eyes from three aspects. Epidemiologically, we suggest liver-related, potential, protective and risk factors for typical eye disease as well as eye indicators connected with liver status. For molecular mechanism aspect, we elaborate their inter-organ crosstalk from metabolism (glucose, lipid, proteins, vitamin, and mineral), detoxification (ammonia and bilirubin), and immunity (complement and inflammation regulation) aspect. In clinical application part, we emphasize the latest advances in utilizing the liver-eye axis in disease diagnosis and therapy, involving artificial intelligence-deep learning-based novel diagnostic tools for detecting liver disease and adeno-associated viral vector-based gene therapy method for curing blinding eye disease. We aim to focus on and provide novel insights into liver and eyes communications and help resolve existed clinically significant issues.
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Affiliation(s)
- Junhao Wu
- Division of Gastroenterology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1277 Jiefang Avenue, Wuhan, 430022 Hubei China
| | - Caihan Duan
- Division of Gastroenterology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1277 Jiefang Avenue, Wuhan, 430022 Hubei China
| | - Yuanfan Yang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Centre, Sun Yat-Sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Zhe Wang
- Division of Gastroenterology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1277 Jiefang Avenue, Wuhan, 430022 Hubei China
| | - Chen Tan
- Division of Gastroenterology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1277 Jiefang Avenue, Wuhan, 430022 Hubei China
| | - Chaoqun Han
- Division of Gastroenterology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1277 Jiefang Avenue, Wuhan, 430022 Hubei China
| | - Xiaohua Hou
- Division of Gastroenterology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1277 Jiefang Avenue, Wuhan, 430022 Hubei China
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13
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Cooper ID, Kyriakidou Y, Petagine L, Edwards K, Elliott BT. Bio-Hacking Better Health-Leveraging Metabolic Biochemistry to Maximise Healthspan. Antioxidants (Basel) 2023; 12:1749. [PMID: 37760052 PMCID: PMC10525476 DOI: 10.3390/antiox12091749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 09/01/2023] [Accepted: 09/05/2023] [Indexed: 09/29/2023] Open
Abstract
In the pursuit of longevity and healthspan, we are challenged with first overcoming chronic diseases of ageing: cardiovascular disease, hypertension, cancer, dementias, type 2 diabetes mellitus. These are hyperinsulinaemia diseases presented in different tissue types. Hyperinsulinaemia reduces endogenous antioxidants, via increased consumption and reduced synthesis. Hyperinsulinaemia enforces glucose fuelling, consuming 4 NAD+ to produce 2 acetyl moieties; beta-oxidation, ketolysis and acetoacetate consume 2, 1 and 0, respectively. This decreases sirtuin, PARPs and oxidative management capacity, leaving reactive oxygen species to diffuse to the cytosol, upregulating aerobic glycolysis, NF-kB and cell division signalling. Also, oxidising cardiolipin, reducing oxidative phosphorylation (OXPHOS) and apoptosis ability; driving a tumourigenic phenotype. Over time, increasing senescent/pathological cell populations occurs, increasing morbidity and mortality. Beta-hydroxybutyrate, an antioxidant, metabolite and signalling molecule, increases synthesis of antioxidants via preserving NAD+ availability and enhancing OXPHOS capacity. Fasting and ketogenic diets increase ketogenesis concurrently decreasing insulin secretion and demand; hyperinsulinaemia inhibits ketogenesis. Lifestyles that maintain lower insulin levels decrease antioxidant catabolism, additionally increasing their synthesis, improving oxidative stress management and mitochondrial function and, subsequently, producing healthier cells. This supports tissue and organ health, leading to a better healthspan, the first challenge that must be overcome in the pursuit of youthful longevity.
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Affiliation(s)
- Isabella D. Cooper
- Ageing Biology and Age-Related Diseases, School of Life Sciences, University of Westminster, 115 New Cavendish Street, London W1W 6UW, UK; (Y.K.); (L.P.); (K.E.); (B.T.E.)
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14
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Kim TJ, Shenker BJ, MacElroy AS, Spradlin S, Walker LP, Boesze-Battaglia K. Aggregatibacter actinomycetemcomitans cytolethal distending toxin modulates host phagocytic function. Front Cell Infect Microbiol 2023; 13:1220089. [PMID: 37719670 PMCID: PMC10500838 DOI: 10.3389/fcimb.2023.1220089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Accepted: 08/10/2023] [Indexed: 09/19/2023] Open
Abstract
Cytolethal distending toxins (Cdt) are a family of toxins produced by several human pathogens which infect mucocutaneous tissue and induce inflammatory disease. Human macrophages exposed to Aggregatibacter actinomycetemcomitans (Aa) Cdt respond through canonical and non-canonical inflammasome activation to stimulate cytokine release. The inflammatory response is dependent on PI3K signaling blockade via the toxin's phosphatidylinositol-3,4,5-triphosphate (PIP3) phosphatase activity; converting PIP3 to phosphatidylinsoitol-3,4-diphosphate (PI3,4P2) thereby depleting PIP3 pools. Phosphoinositides, also play a critical role in phagosome trafficking, serving as binding domains for effector proteins during phagosome maturation and subsequent fusion with lysosomes. We now demonstrate that AaCdt manipulates the phosphoinositide (PI) pools of phagosome membranes and alters Rab5 association. Exposure of macrophages to AaCdt slowed phagosome maturation and decreased phago-lysosome formation, thereby compromising macrophage phagocytic function. Moreover, macrophages exposed to Cdt showed decreased bactericidal capacity leading to increase in Aggregatibacter actinomycetemcomitans survival. Thus, Cdt may contribute to increased susceptibility to bacterial infection. These studies uncover an underexplored aspect of Cdt function and provide new insight into the virulence potential of Cdt in mediating the pathogenesis of disease caused by Cdt-producing organisms such as Aa.
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Affiliation(s)
- Taewan J. Kim
- Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, United States
- Department of Periodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Bruce J. Shenker
- Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Andrew S. MacElroy
- Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Samuel Spradlin
- Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Lisa P. Walker
- Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Kathleen Boesze-Battaglia
- Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, United States
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15
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Zhang KR, Jankowski CSR, Marshall R, Nair R, Más Gómez N, Alnemri A, Liu Y, Erler E, Ferrante J, Song Y, Bell BA, Baumann BH, Sterling J, Anderson B, Foshe S, Roof J, Fazelinia H, Spruce LA, Chuang JZ, Sung CH, Dhingra A, Boesze-Battaglia K, Chavali VRM, Rabinowitz JD, Mitchell CH, Dunaief JL. Oxidative stress induces lysosomal membrane permeabilization and ceramide accumulation in retinal pigment epithelial cells. Dis Model Mech 2023; 16:dmm050066. [PMID: 37401371 PMCID: PMC10399446 DOI: 10.1242/dmm.050066] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Accepted: 06/23/2023] [Indexed: 07/05/2023] Open
Abstract
Oxidative stress has been implicated in the pathogenesis of age-related macular degeneration, the leading cause of blindness in older adults, with retinal pigment epithelium (RPE) cells playing a key role. To better understand the cytotoxic mechanisms underlying oxidative stress, we used cell culture and mouse models of iron overload, as iron can catalyze reactive oxygen species formation in the RPE. Iron-loading of cultured induced pluripotent stem cell-derived RPE cells increased lysosomal abundance, impaired proteolysis and reduced the activity of a subset of lysosomal enzymes, including lysosomal acid lipase (LIPA) and acid sphingomyelinase (SMPD1). In a liver-specific Hepc (Hamp) knockout murine model of systemic iron overload, RPE cells accumulated lipid peroxidation adducts and lysosomes, developed progressive hypertrophy and underwent cell death. Proteomic and lipidomic analyses revealed accumulation of lysosomal proteins, ceramide biosynthetic enzymes and ceramides. The proteolytic enzyme cathepsin D (CTSD) had impaired maturation. A large proportion of lysosomes were galectin-3 (Lgals3) positive, suggesting cytotoxic lysosomal membrane permeabilization. Collectively, these results demonstrate that iron overload induces lysosomal accumulation and impairs lysosomal function, likely due to iron-induced lipid peroxides that can inhibit lysosomal enzymes.
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Affiliation(s)
- Kevin R. Zhang
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Connor S. R. Jankowski
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Rayna Marshall
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Rohini Nair
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Néstor Más Gómez
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Ahab Alnemri
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Yingrui Liu
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Elizabeth Erler
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Julia Ferrante
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Ying Song
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Brent A. Bell
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Bailey H. Baumann
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Jacob Sterling
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Brandon Anderson
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Sierra Foshe
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Jennifer Roof
- CHOP-PENN Proteomics Core Facility, The Children's Hospital of Philadelphia Research Institute, Philadelphia, PA 19104, USA
| | - Hossein Fazelinia
- CHOP-PENN Proteomics Core Facility, The Children's Hospital of Philadelphia Research Institute, Philadelphia, PA 19104, USA
| | - Lynn A. Spruce
- CHOP-PENN Proteomics Core Facility, The Children's Hospital of Philadelphia Research Institute, Philadelphia, PA 19104, USA
| | - Jen-Zen Chuang
- Department of Ophthalmology, Weill Cornell Medicine, New York, NY 10065, USA
- Department of Cell and Developmental Biology, Weill Cornell Medicine, New York, NY 10065, USA
| | - Ching-Hwa Sung
- Department of Ophthalmology, Weill Cornell Medicine, New York, NY 10065, USA
- Department of Cell and Developmental Biology, Weill Cornell Medicine, New York, NY 10065, USA
| | - Anuradha Dhingra
- Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Kathleen Boesze-Battaglia
- Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Venkata R. M. Chavali
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Joshua D. Rabinowitz
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Claire H. Mitchell
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Joshua L. Dunaief
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
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16
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Thee EF, Acar İE, Colijn JM, Meester-Smoor MA, Verzijden T, Baart SJ, Jarboui MA, Fauser S, Hoyng CB, Ueffing M, den Hollander AI, Klaver CCW. Systemic Metabolomics in a Framework of Genetics and Lifestyle in Age-Related Macular Degeneration. Metabolites 2023; 13:701. [PMID: 37367859 DOI: 10.3390/metabo13060701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 05/20/2023] [Accepted: 05/25/2023] [Indexed: 06/28/2023] Open
Abstract
Insights into the pathogenesis of age-related macular degeneration (AMD), a leading cause of blindness, point towards a complex interplay of genetic and lifestyle factors triggering various systemic pathways. This study aimed to characterize metabolomic profiles for AMD and to evaluate their position in the trias with genetics and lifestyle. This study included 5923 individuals from five European studies. Blood metabolomics were assessed using a nuclear magnetic resonance platform of 146 metabolites. Associations were studied using regression analyses. A genetic risk score (GRS) was calculated using β-values of 49 AMD variants, a lifestyle risk score (LRS) using smoking and diet data, and a metabolite risk score (MRS) using metabolite values. We identified 61 metabolites associated with early-intermediate AMD, of which 94% were lipid-related, with higher levels of HDL-subparticles and apolipoprotein-A1, and lower levels of VLDL-subparticles, triglycerides, and fatty acids (false discovery rate (FDR) p-value < 1.4 × 10-2). Late AMD was associated with lower levels of the amino acids histidine, leucine, valine, tyrosine, and phenylalanine, and higher levels of the ketone bodies acetoacetate and 3-hydroxybutyrate (FDR p-value < 1.5 × 10-3). A favorable lifestyle characterized by a healthy diet was associated with higher levels of amino acids and lower levels of ketone bodies, while an unfavorable lifestyle, including smoking, showed opposite effects (FDR p-value < 2.7 × 10-2). The MRS mediated 5% of the effect of the GRS and 20% of that of the LRS on late AMD. Our findings show that metabolomic profiles differ between AMD stages and show that blood metabolites mostly reflect lifestyle. The severity-specific profiles spur further interest into the systemic effects related to disease conversion.
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Affiliation(s)
- Eric F Thee
- Department of Ophthalmology, Erasmus University Medical Center, 3015 GD Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus University Medical Center, 3015 GD Rotterdam, The Netherlands
| | - İlhan E Acar
- Department of Ophthalmology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Johanna M Colijn
- Department of Ophthalmology, Erasmus University Medical Center, 3015 GD Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus University Medical Center, 3015 GD Rotterdam, The Netherlands
| | - Magda A Meester-Smoor
- Department of Ophthalmology, Erasmus University Medical Center, 3015 GD Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus University Medical Center, 3015 GD Rotterdam, The Netherlands
| | - Timo Verzijden
- Department of Epidemiology, Erasmus University Medical Center, 3015 GD Rotterdam, The Netherlands
| | - Sara J Baart
- Department of Epidemiology, Erasmus University Medical Center, 3015 GD Rotterdam, The Netherlands
- Department of Biostatistics, Erasmus University Medical Center, 3015 GD Rotterdam, The Netherlands
| | - Mohamed A Jarboui
- Department of Ophthalmology, Institute for Ophthalmic Research, Eberhard Karls University of Tübingen, 72076 Tübingen, Germany
- Department of Ophthalmology, University Eye Clinic, Eberhard Karls University of Tübingen, 72076 Tübingen, Germany
| | - Sascha Fauser
- Department of Ophthalmology, University Hospital Cologne, 50937 Cologne, Germany
- Hoffman-La Roche AG, 4070 Basel, Switzerland
| | - Carel B Hoyng
- Department of Ophthalmology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Marius Ueffing
- Department of Ophthalmology, Institute for Ophthalmic Research, Eberhard Karls University of Tübingen, 72076 Tübingen, Germany
- Department of Ophthalmology, University Eye Clinic, Eberhard Karls University of Tübingen, 72076 Tübingen, Germany
| | | | - Caroline C W Klaver
- Department of Ophthalmology, Erasmus University Medical Center, 3015 GD Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus University Medical Center, 3015 GD Rotterdam, The Netherlands
- Department of Ophthalmology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
- Institute of Molecular and Clinical Ophthalmology, University of Basel, 4070 Basel, Switzerland
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17
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Swinkels D, Baes M. The essential role of docosahexaenoic acid and its derivatives for retinal integrity. Pharmacol Ther 2023; 247:108440. [PMID: 37201739 DOI: 10.1016/j.pharmthera.2023.108440] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 05/08/2023] [Accepted: 05/15/2023] [Indexed: 05/20/2023]
Abstract
The fatty acid composition of photoreceptor outer segment (POS) phospholipids diverges from other membranes, being highly enriched in polyunsaturated fatty acids (PUFAs). The most abundant PUFA is docosahexaenoic acid (DHA, C22:6n-3), an omega-3 PUFA that amounts to over 50% of the POS phospholipid fatty acid side chains. Interestingly, DHA is the precursor of other bioactive lipids such as elongated PUFAs and oxygenated derivatives. In this review, we present the current view on metabolism, trafficking and function of DHA and very long chain polyunsaturated fatty acids (VLC-PUFAs) in the retina. New insights on pathological features generated from PUFA deficient mouse models with enzyme or transporter defects and corresponding patients are discussed. Not only the neural retina, but also abnormalities in the retinal pigment epithelium are considered. Furthermore, the potential involvement of PUFAs in more common retinal degeneration diseases such as diabetic retinopathy, retinitis pigmentosa and age-related macular degeneration are evaluated. Supplementation treatment strategies and their outcome are summarized.
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Affiliation(s)
- Daniëlle Swinkels
- Laboratory of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, 3000 Leuven, Belgium
| | - Myriam Baes
- Laboratory of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, 3000 Leuven, Belgium.
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18
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Zhu S, Xu R, Engel AL, Wang Y, McNeel R, Hurley JB, Chao JR, Du J. Proline provides a nitrogen source in the retinal pigment epithelium to synthesize and export amino acids for the neural retina. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.18.537355. [PMID: 37131780 PMCID: PMC10153141 DOI: 10.1101/2023.04.18.537355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
It is known that metabolic defects in the retinal pigment epithelium (RPE) can cause degeneration of its neighboring photoreceptors in the retina, leading to retinal degenerative diseases such as age-related macular degeneration. However, how RPE metabolism supports the health of the neural retina remains unclear. The retina requires exogenous nitrogen sources for protein synthesis, neurotransmission, and energy metabolism. Using 15N tracing coupled with mass spectrometry, we found human RPE can utilize the nitrogen in proline to produce and export 13 amino acids, including glutamate, aspartate, glutamine, alanine and serine. Similarly, we found this proline nitrogen utilization in the mouse RPE/choroid but not in the neural retina of explant cultures. Co-culture of human RPE with the retina showed that the retina can take up the amino acids, especially glutamate, aspartate and glutamine, generated from proline nitrogen in the RPE. Intravenous delivery of 15N proline in vivo demonstrated 15N-derived amino acids appear earlier in the RPE before the retina. We also found proline dehydrogenase (PRODH), the key enzyme in proline catabolism is highly enriched in the RPE but not the retina. The deletion of PRODH blocks proline nitrogen utilization in RPE and the import of proline nitrogen-derived amino acids in the retina. Our findings highlight the importance of RPE metabolism in supporting nitrogen sources for the retina, providing insight into understanding the mechanisms of the retinal metabolic ecosystem and RPE-initiated retinal degenerative diseases.
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Affiliation(s)
- Siyan Zhu
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506
- Department of Pharmaceutical and Pharmacological Sciences, West Virginia University, Morgantown, WV 26506
| | - Rong Xu
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506
| | - Abbi L. Engel
- Department of Ophthalmology, University of Washington, Seattle, WA 98109
| | - Yekai Wang
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506
| | - Rachel McNeel
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506
| | - James B. Hurley
- Department of Ophthalmology, University of Washington, Seattle, WA 98109
- Department of Biochemistry, University of Washington, Seattle, WA 98109
| | - Jennifer R. Chao
- Department of Ophthalmology, University of Washington, Seattle, WA 98109
| | - Jianhai Du
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506
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19
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Dhingra A, Tobias JW, Philp NJ, Boesze-Battaglia K. Transcriptomic Changes Predict Metabolic Alterations in LC3 Associated Phagocytosis in Aged Mice. Int J Mol Sci 2023; 24:6716. [PMID: 37047689 PMCID: PMC10095460 DOI: 10.3390/ijms24076716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 03/28/2023] [Accepted: 03/28/2023] [Indexed: 04/14/2023] Open
Abstract
LC3b (Map1lc3b) plays an essential role in canonical autophagy and is one of several components of the autophagy machinery that mediates non-canonical autophagic functions. Phagosomes are often associated with lipidated LC3b to promote phagosome maturation in a process called LC3-associated phagocytosis (LAP). Specialized phagocytes, such as mammary epithelial cells, retinal pigment epithelial (RPE) cells, and sertoli cells, utilize LAP for optimal degradation of phagocytosed material, including debris. In the visual system, LAP is critical to maintain retinal function, lipid homeostasis, and neuroprotection. In a mouse model of retinal lipid steatosis-mice lacking LC3b (LC3b-/-), we observed increased lipid deposition, metabolic dysregulation, and enhanced inflammation. Herein, we present a non-biased approach to determine if loss of LAP mediated processes modulate the expression of various genes related to metabolic homeostasis, lipid handling, and inflammation. A comparison of the RPE transcriptome of WT and LC3b-/- mice revealed 1533 DEGs, with ~73% upregulated and 27% downregulated. Enriched gene ontology (GO) terms included inflammatory response (upregulated DEGs), fatty acid metabolism, and vascular transport (downregulated DEGs). Gene set enrichment analysis (GSEA) identified 34 pathways; 28 were upregulated (dominated by inflammation/related pathways) and 6 were downregulated (dominated by metabolic pathways). Analysis of additional gene families identified significant differences for genes in the solute carrier family, RPE signature genes, and genes with a potential role in age-related macular degeneration. These data indicate that loss of LC3b induces robust changes in the RPE transcriptome contributing to lipid dysregulation and metabolic imbalance, RPE atrophy, inflammation, and disease pathophysiology.
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Affiliation(s)
- Anuradha Dhingra
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - John W. Tobias
- Penn Genomics and Sequencing Core, Department of Genetics, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Nancy J. Philp
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Kathleen Boesze-Battaglia
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
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20
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Dhingra A, Tobias JW, Philp NJ, Boesze-Battaglia K. Transcriptomic changes predict metabolic alterations in LC3 associated phagocytosis in aged mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.14.532586. [PMID: 36993501 PMCID: PMC10054970 DOI: 10.1101/2023.03.14.532586] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/21/2023]
Abstract
LC3b ( Map1lc3b ) plays an essential role in canonical autophagy and is one of several components of the autophagy machinery that mediates non-canonical autophagic functions. Phagosomes are often associated with lipidated LC3b, to pro-mote phagosome maturation in a process called LC3-associated phagocytosis (LAP). Specialized phagocytes such as mammary epithelial cells, retinal pigment epithelial (RPE) cells, and sertoli cells utilize LAP for optimal degradation of phagocytosed material, including debris. In the visual system, LAP is critical to maintain retinal function, lipid homeostasis and neuroprotection. In a mouse model of retinal lipid steatosis - mice lacking LC3b ( LC3b -/- ), we observed increased lipid deposition, metabolic dysregulation and enhanced inflammation. Herein we present a non-biased approach to determine if loss of LAP mediated processes modulate the expression of various genes related to metabolic homeostasis, lipid handling, and inflammation. A comparison of the RPE transcriptome of WT and LC3b -/- mice revealed 1533 DEGs, with ~73% upregulated and 27% down-regulated. Enriched gene ontology (GO) terms included inflammatory response (upregulated DEGs), fatty acid metabolism and vascular transport (downregulated DEGs). Gene set enrichment analysis (GSEA) identified 34 pathways; 28 were upregulated (dominated by inflammation/related pathways) and 6 were downregulated (dominated by metabolic pathways). Analysis of additional gene families identified significant differences for genes in the solute carrier family, RPE signature genes, and genes with potential role in age-related macular degeneration. These data indicate that loss of LC3b induces robust changes in the RPE transcriptome contributing to lipid dysregulation and metabolic imbalance, RPE atrophy, inflammation, and disease pathophysiology.
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21
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Hass DT, Zhang Q, Autterson G, Bryan R, Hurley JB, Miller JM. Medium depth influences O 2 availability and metabolism in cultured RPE cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.01.530623. [PMID: 36909658 PMCID: PMC10002737 DOI: 10.1101/2023.03.01.530623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/07/2023]
Abstract
PURPOSE RPE oxidative metabolism is critical for normal retinal function and is often studied in cell culture systems. Here, we show that conventional culture media volumes dramatically impact O 2 availability, limiting oxidative metabolism. We suggest optimal conditions to ensure cultured RPE is in a normoxic environment permissive to oxidative metabolism. METHODS We altered the availability of O 2 to human primary RPE cultures directly via a hypoxia chamber or indirectly via the amount of medium over cells. We measured oxygen consumption rates (OCR), glucose consumption, lactate production, 13 C-glucose flux, hypoxia inducible factor (HIF-1α) stability, intracellular lipid droplets after a lipid challenge, trans-epithelial electrical resistance, cell morphology, and pigmentation. RESULTS Medium volumes commonly employed during RPE culture limit diffusion of O 2 to cells, triggering hypoxia, activating HIF-1α, limiting OCR, and dramatically altering cell metabolism, with only minor effects on typical markers of RPE health. Media volume effects on O 2 availability decrease acetyl-CoA utilization, increase glycolysis, and alter the size and number of intracellular lipid droplets under lipid-rich conditions. CONCLUSIONS Despite having little impact on visible and typical markers of RPE culture health, media volume dramatically affects RPE physiology ″under the hood″. As RPE-centric diseases like age-related macular degeneration (AMD) involve oxidative metabolism, RPE cultures need to be optimized to study such diseases. We provide guidelines for optimal RPE culture volumes that balance ample nutrient availability from larger media volumes with adequate O 2 availability seen with smaller media volumes.
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22
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Liton PB, Boesze-Battaglia K, Boulton ME, Boya P, Ferguson TA, Ganley IG, Kauppinnen A, Laurie GW, Mizushima N, Morishita H, Russo R, Sadda J, Shyam R, Sinha D, Thompson DA, Zacks DN. AUTOPHAGY IN THE EYE: FROM PHYSIOLOGY TO PATHOPHYSOLOGY. AUTOPHAGY REPORTS 2023; 2:2178996. [PMID: 37034386 PMCID: PMC10078619 DOI: 10.1080/27694127.2023.2178996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 01/26/2023] [Indexed: 03/05/2023]
Abstract
Autophagy is a catabolic self-degradative pathway that promotes the degradation and recycling of intracellular material through the lysosomal compartment. Although first believed to function in conditions of nutritional stress, autophagy is emerging as a critical cellular pathway, involved in a variety of physiological and pathophysiological processes. Autophagy dysregulation is associated with an increasing number of diseases, including ocular diseases. On one hand, mutations in autophagy-related genes have been linked to cataracts, glaucoma, and corneal dystrophy; on the other hand, alterations in autophagy and lysosomal pathways are a common finding in essentially all diseases of the eye. Moreover, LC3-associated phagocytosis, a form of non-canonical autophagy, is critical in promoting visual cycle function. This review collects the latest understanding of autophagy in the context of the eye. We will review and discuss the respective roles of autophagy in the physiology and/or pathophysiology of each of the ocular tissues, its diurnal/circadian variation, as well as its involvement in diseases of the eye.
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Affiliation(s)
- Paloma B. Liton
- Departments of Ophthalmology & Pathology, Duke School of Medicine, Duke University, Durham, NC 27705, USA
| | - Kathleen Boesze-Battaglia
- Department of Basic and Translational Sciences, University of Pennsylvania, School of Dental Medicine, Philadelphia, PA 19104, USA
| | - Michael E. Boulton
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham (UAB), Birmingham, AL, USA
| | - Patricia Boya
- Department of Neuroscience and Movement Science. Faculty of Science and Medicine, University of Fribourg, 1700 Fribourg, Switzerland
| | - Thomas A. Ferguson
- Department of Ophthalmology and Visual Sciences, Washington University in St. Louis, St. Louis, MO 63110, USA
| | - Ian G. Ganley
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
| | - Anu Kauppinnen
- Faculty of Health and Sciences, School of Pharmacy, University of Eastern Finland, 70210 Kuopio, Finland
| | - Gordon W. Laurie
- Departments of Cell Biology, Ophthalmology and Biomedical Engineering, University of Virginia, Charlottesville, VA 22908, USA
| | - Noboru Mizushima
- Department of Biochemistry and Molecular Biology, Graduate School of Medicine, The University of Tokyo, 113-0033, Japan
| | - Hideaki Morishita
- Department of Biochemistry and Molecular Biology, Graduate School of Medicine, The University of Tokyo, 113-0033, Japan
- Department of Physiology, Juntendo University Graduate School of Medicine, Bunkyo-ku, Tokyo, 113-8421, Japan
| | - Rossella Russo
- Preclinical and Translational Pharmacology, Glaucoma Unit, Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, 87036 Rende, Italy
| | - Jaya Sadda
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan Medical School, Ann Arbor, MI, USA
| | | | - Debasish Sinha
- Department of Ophthalmology, Cell Biology, and Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
- Wilmer Eye Institute, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Debra A. Thompson
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan Medical School, Ann Arbor, MI, USA
| | - David N. Zacks
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan Medical School, Ann Arbor, MI, USA
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23
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Ciliary neurotrophic factor-mediated neuroprotection involves enhanced glycolysis and anabolism in degenerating mouse retinas. Nat Commun 2022; 13:7037. [PMID: 36396639 PMCID: PMC9672129 DOI: 10.1038/s41467-022-34443-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2021] [Accepted: 10/25/2022] [Indexed: 11/18/2022] Open
Abstract
Ciliary neurotrophic factor (CNTF) acts as a potent neuroprotective cytokine in multiple models of retinal degeneration. To understand mechanisms underlying its broad neuroprotective effects, we have investigated the influence of CNTF on metabolism in a mouse model of photoreceptor degeneration. CNTF treatment improves the morphology of photoreceptor mitochondria, but also leads to reduced oxygen consumption and suppressed respiratory chain activities. Molecular analyses show elevated glycolytic pathway gene transcripts and active enzymes. Metabolomics analyses detect significantly higher levels of ATP and the energy currency phosphocreatine, elevated glycolytic pathway metabolites, increased TCA cycle metabolites, lipid biosynthetic pathway intermediates, nucleotides, and amino acids. Moreover, CNTF treatment restores the key antioxidant glutathione to the wild type level. Therefore, CNTF significantly impacts the metabolic status of degenerating retinas by promoting aerobic glycolysis and augmenting anabolic activities. These findings reveal cellular mechanisms underlying enhanced neuronal viability and suggest potential therapies for treating retinal degeneration.
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24
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Tan LX, Li J, Germer CJ, Lakkaraju A. Analysis of mitochondrial dynamics and function in the retinal pigment epithelium by high-speed high-resolution live imaging. Front Cell Dev Biol 2022; 10:1044672. [PMID: 36393836 PMCID: PMC9651161 DOI: 10.3389/fcell.2022.1044672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 10/19/2022] [Indexed: 11/13/2022] Open
Abstract
Mitochondrial dysfunction is strongly implicated in neurodegenerative diseases including age-related macular degeneration (AMD), which causes irreversible blindness in over 50 million older adults worldwide. A key site of insult in AMD is the retinal pigment epithelium (RPE), a monolayer of postmitotic polarized cells that performs essential functions for photoreceptor health and vision. Recent studies from our group and others have identified several features of mitochondrial dysfunction in AMD including mitochondrial fragmentation and bioenergetic defects. While these studies provide valuable insight at fixed points in time, high-resolution, high-speed live imaging is essential for following mitochondrial injury in real time and identifying disease mechanisms. Here, we demonstrate the advantages of live imaging to investigate RPE mitochondrial dynamics in cell-based and mouse models. We show that mitochondria in the RPE form extensive networks that are destroyed by fixation and discuss important live imaging considerations that can interfere with accurate evaluation of mitochondrial integrity such as RPE differentiation status and acquisition parameters. Our data demonstrate that RPE mitochondria show localized heterogeneities in membrane potential and ATP production that could reflect focal changes in metabolism and oxidative stress. Contacts between the mitochondria and organelles such as the ER and lysosomes mediate calcium flux and mitochondrial fission. Live imaging of mouse RPE flatmounts revealed a striking loss of mitochondrial integrity in albino mouse RPE compared to pigmented mice that could have significant functional consequences for cellular metabolism. Our studies lay a framework to guide experimental design and selection of model systems for evaluating mitochondrial health and function in the RPE.
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Affiliation(s)
- Li Xuan Tan
- Department of Ophthalmology, School of Medicine, University of California, San Francisco, CA, United States
| | - Jianlong Li
- Department of Cell and Tissue Biology, School of Dentistry, University of California, San Francisco, CA, United States
| | - Colin J. Germer
- Department of Ophthalmology, School of Medicine, University of California, San Francisco, CA, United States
- Pharmaceutical Sciences and Pharmacogenomics Graduate Program, University of California, San Francisco, CA, United States
| | - Aparna Lakkaraju
- Department of Ophthalmology, School of Medicine, University of California, San Francisco, CA, United States
- Pharmaceutical Sciences and Pharmacogenomics Graduate Program, University of California, San Francisco, CA, United States
- Department of Anatomy, School of Medicine, University of California, San Francisco, CA, United States
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25
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Chang X, Yin Z, Zhang W, Shi J, Pu C, Shi Q, Wang J, Zhang J, Yan L, Yang W, Guo J. Data-independent acquisition-based quantitative proteomic analysis of m.3243A>G MELAS reveals novel potential pathogenesis and therapeutic targets. Medicine (Baltimore) 2022; 101:e30938. [PMID: 36254078 PMCID: PMC9575705 DOI: 10.1097/md.0000000000030938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
The pathogenesis of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke like episodes (MELAS) syndrome has not been fully elucidated. The m.3243A > G mutation which is responsible for 80% MELAS patients affects proteins with undetermined functions. Therefore, we performed quantitative proteomic analysis on skeletal muscle specimens from MELAS patients. We recruited 10 patients with definitive MELAS and 10 age- and gender- matched controls. Proteomic analysis based on nanospray liquid chromatography-mass spectrometry (LC-MS) was performed using data-independent acquisition (DIA) method and differentially expressed proteins were revealed by bioinformatics analysis. We identified 128 differential proteins between MELAS and controls, including 68 down-regulated proteins and 60 up-regulated proteins. The differential proteins involved in oxidative stress were identified, including heat shock protein beta-1 (HSPB1), alpha-crystallin B chain (CRYAB), heme oxygenase 1 (HMOX1), glucose-6-phosphate dehydrogenase (G6PD) and selenoprotein P. Gene ontology and kyoto encyclopedia of genes and genomes pathway analysis showed significant enrichment in phagosome, ribosome and peroxisome proliferator-activated receptors (PPAR) signaling pathway. The imbalance between oxidative stress and antioxidant defense, the activation of autophagosomes, and the abnormal metabolism of mitochondrial ribosome proteins (MRPs) might play an important role in m.3243A > G MELAS. The combination of proteomic and bioinformatics analysis could contribute potential molecular networks to the pathogenesis of MELAS in a comprehensive manner.
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Affiliation(s)
- Xueli Chang
- Department of Neurology, First Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| | - Zhaoxu Yin
- Department of Neurology, First Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| | - Wei Zhang
- Department of Neurology, First Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| | - Jiaying Shi
- Department of Neurology, First Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| | - Chuanqiang Pu
- Department of Neurology, Chinese People’s Liberation Army General Hospital, Beijing, China
| | - Qiang Shi
- Department of Neurology, Chinese People’s Liberation Army General Hospital, Beijing, China
| | - Juan Wang
- Department of Neurology, First Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| | - Jing Zhang
- Department of Neurology, First Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| | - Li Yan
- Department of Neurology, First Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| | - Wenqu Yang
- Department of Anesthesiology, Shanxi Bethune Hospital, Shanxi Academy of Medical Science, Taiyuan, Shanxi, China
| | - Junhong Guo
- Department of Neurology, First Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
- *Correspondence: Junhong Guo, Department of Neurology, First Hospital, Shanxi Medical University, No. 85, Jiefang South Road, Taiyuan, 030001, Shanxi, China (e-mail: )
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26
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Moran AL, Fehilly JD, Floss Jones D, Collery R, Kennedy BN. Regulation of the rhythmic diversity of daily photoreceptor outer segment phagocytosis in vivo. FASEB J 2022; 36:e22556. [PMID: 36165194 PMCID: PMC9828801 DOI: 10.1096/fj.202200990rr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 08/30/2022] [Accepted: 09/06/2022] [Indexed: 01/12/2023]
Abstract
Outer segment phagocytosis (OSP) is a highly-regulated, biological process wherein photoreceptor outer segment (OS) tips are cyclically phagocytosed by the adjacent retinal pigment epithelium (RPE) cells. Often an overlooked retinal process, rhythmic OSP ensures the maintenance of healthy photoreceptors and vision. Daily, the photoreceptors renew OS at their base and the most distal, and likely oldest, OS tips, are phagocytosed by the RPE, preventing the accumulation of photo-oxidative compounds by breaking down phagocytosed OS tips and recycling useful components to the photoreceptors. Light changes often coincide with an escalation of OSP and within hours the phagosomes formed in each RPE cell are resolved. In the last two decades, individual molecular regulators were elucidated. Some of the molecular machinery used by RPE cells for OSP is highly similar to mechanisms used by other phagocytic cells for the clearance of apoptotic cells. Consequently, in the RPE, many molecular regulators of retinal phagocytosis have been elucidated. However, there is still a knowledge gap regarding the key regulators of physiological OSP in vivo between endogenous photoreceptors and the RPE. Understanding the regulation of OSP is of significant clinical interest as age-related macular degeneration (AMD) and inherited retinal diseases (IRD) are linked with altered OSP. Here, we review the in vivo timing of OSP peaks in selected species and focus on the reported in vivo environmental and molecular regulators of OSP.
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Affiliation(s)
- Ailis L. Moran
- UCD School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland,UCD Conway InstituteUniversity College DublinDublinIreland
| | - John D. Fehilly
- UCD School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland,UCD Conway InstituteUniversity College DublinDublinIreland
| | - Daniel Floss Jones
- UCD School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland,UCD Conway InstituteUniversity College DublinDublinIreland
| | - Ross Collery
- Department of Cell Biology, Neurobiology and AnatomyMedical College of WisconsinMilwaukeeWisconsinUSA,Department of Ophthalmology and Visual SciencesMedical College of Wisconsin Eye InstituteMilwaukeeWisconsinUSA
| | - Breandán N. Kennedy
- UCD School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland,UCD Conway InstituteUniversity College DublinDublinIreland
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27
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Hazim RA, Paniagua AE, Tang L, Yang K, Kim KKO, Stiles L, Divakaruni AS, Williams DS. Vitamin B3, nicotinamide, enhances mitochondrial metabolism to promote differentiation of the retinal pigment epithelium. J Biol Chem 2022; 298:102286. [PMID: 35868562 PMCID: PMC9396405 DOI: 10.1016/j.jbc.2022.102286] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 07/14/2022] [Accepted: 07/15/2022] [Indexed: 01/04/2023] Open
Abstract
In the mammalian retina, a metabolic ecosystem exists in which photoreceptors acquire glucose from the choriocapillaris with the help of the retinal pigment epithelium (RPE). While the photoreceptor cells are primarily glycolytic, exhibiting Warburg-like metabolism, the RPE is reliant on mitochondrial respiration. However, the ways in which mitochondrial metabolism affect RPE cellular functions are not clear. We first used the human RPE cell line, ARPE-19, to examine mitochondrial metabolism in the context of cellular differentiation. We show that nicotinamide induced rapid differentiation of ARPE-19 cells, which was reversed by removal of supplemental nicotinamide. During the nicotinamide-induced differentiation, we observed using quantitative PCR, Western blotting, electron microscopy, and metabolic respiration and tracing assays that (1) mitochondrial gene and protein expression increased, (2) mitochondria became larger with more tightly folded cristae, and (3) mitochondrial metabolism was enhanced. In addition, we show that primary cultures of human fetal RPE cells responded similarly in the presence of nicotinamide. Furthermore, disruption of mitochondrial oxidation of pyruvate attenuated the nicotinamide-induced differentiation of the RPE cells. Together, our results demonstrate a remarkable effect of nicotinamide on RPE metabolism. We also identify mitochondrial respiration as a key contributor to the differentiated state of the RPE and thus to many of the RPE functions that are essential for retinal health and photoreception.
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Affiliation(s)
- Roni A Hazim
- Department of Ophthalmology and Stein Eye Institute
| | | | - Lisa Tang
- Department of Ophthalmology and Stein Eye Institute
| | - Krista Yang
- Department of Molecular and Medical Pharmacology, UCLA David Geffen School of Medicine, Los Angeles, CA 90095
| | - Kristen K O Kim
- Department of Molecular and Medical Pharmacology, UCLA David Geffen School of Medicine, Los Angeles, CA 90095
| | - Linsey Stiles
- Department of Molecular and Medical Pharmacology, UCLA David Geffen School of Medicine, Los Angeles, CA 90095; Department of Medicine, Endocrinology. UCLA David Geffen School of Medicine. Los Angeles, CA, 90095, USA
| | - Ajit S Divakaruni
- Department of Molecular and Medical Pharmacology, UCLA David Geffen School of Medicine, Los Angeles, CA 90095
| | - David S Williams
- Department of Ophthalmology and Stein Eye Institute; Department of Neurobiology, David Geffen School of Medicine at UCLA; Molecular Biology Institute; Brain Research Institute, University of California, Los Angeles, CA.
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28
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Qi J, Gan L, Fang J, Zhang J, Yu X, Guo H, Cai D, Cui H, Gou L, Deng J, Wang Z, Zuo Z. Beta-Hydroxybutyrate: A Dual Function Molecular and Immunological Barrier Function Regulator. Front Immunol 2022; 13:805881. [PMID: 35784364 PMCID: PMC9243231 DOI: 10.3389/fimmu.2022.805881] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 05/09/2022] [Indexed: 12/27/2022] Open
Abstract
Ketone bodies are crucial intermediate metabolites widely associated with treating metabolic diseases. Accumulating evidence suggests that ketone bodies may act as immunoregulators in humans and animals to attenuate pathological inflammation through multiple strategies. Although the clues are scattered and untrimmed, the elevation of these ketone bodies in the circulation system and tissues induced by ketogenic diets was reported to affect the immunological barriers, an important part of innate immunity. Therefore, beta-hydroxybutyrate, a key ketone body, might also play a vital role in regulating the barrier immune systems. In this review, we retrospected the endogenous ketogenesis in animals and the dual roles of ketone bodies as energy carriers and signal molecules focusing on beta-hydroxybutyrate. In addition, the research regarding the effects of beta-hydroxybutyrate on the function of the immunological barrier, mainly on the microbiota, chemical, and physical barriers of the mucosa, were outlined and discussed. As an inducible endogenous metabolic small molecule, beta-hydroxybutyrate deserves delicate investigations focusing on its immunometabolic efficacy. Comprehending the connection between ketone bodies and the barrier immunological function and its underlining mechanisms may help exploit individualised approaches to treat various mucosa or skin-related diseases.
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Affiliation(s)
- Jiancheng Qi
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Linli Gan
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Jing Fang
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Jizong Zhang
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Xin Yu
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Hongrui Guo
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Dongjie Cai
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Hengmin Cui
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Liping Gou
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Junliang Deng
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Zhisheng Wang
- Institute of Animal Nutrition, Sichuan Agricultural University, Chengdu, China
| | - Zhicai Zuo
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
- *Correspondence: Zhicai Zuo,
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Abdelrahman AA, Powell FL, Jadeja RN, Jones MA, Thounaojam MC, Bartoli M, Al-Shabrawey M, Martin PM. Expression and activation of the ketone body receptor HCAR2/GPR109A promotes preservation of retinal endothelial cell barrier function. Exp Eye Res 2022; 221:109129. [DOI: 10.1016/j.exer.2022.109129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 05/02/2022] [Accepted: 05/23/2022] [Indexed: 11/30/2022]
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30
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Lewandowski D, Sander CL, Tworak A, Gao F, Xu Q, Skowronska-Krawczyk D. Dynamic lipid turnover in photoreceptors and retinal pigment epithelium throughout life. Prog Retin Eye Res 2021; 89:101037. [PMID: 34971765 PMCID: PMC10361839 DOI: 10.1016/j.preteyeres.2021.101037] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 12/13/2021] [Accepted: 12/15/2021] [Indexed: 12/13/2022]
Abstract
The retinal pigment epithelium-photoreceptor interphase is renewed each day in a stunning display of cellular interdependence. While photoreceptors use photosensitive pigments to convert light into electrical signals, the RPE supports photoreceptors in their function by phagocytizing shed photoreceptor tips, regulating the blood retina barrier, and modulating inflammatory responses, as well as regenerating the 11-cis-retinal chromophore via the classical visual cycle. These processes involve multiple protein complexes, tightly regulated ligand-receptors interactions, and a plethora of lipids and protein-lipids interactions. The role of lipids in maintaining a healthy interplay between the RPE and photoreceptors has not been fully delineated. In recent years, novel technologies have resulted in major advancements in understanding several facets of this interplay, including the involvement of lipids in phagocytosis and phagolysosome function, nutrient recycling, and the metabolic dependence between the two cell types. In this review, we aim to integrate the complex role of lipids in photoreceptor and RPE function, emphasizing the dynamic exchange between the cells as well as discuss how these processes are affected in aging and retinal diseases.
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Affiliation(s)
- Dominik Lewandowski
- Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA
| | - Christopher L Sander
- Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA; Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Aleksander Tworak
- Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA
| | - Fangyuan Gao
- Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA
| | - Qianlan Xu
- Department of Physiology and Biophysics, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA; Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA
| | - Dorota Skowronska-Krawczyk
- Department of Physiology and Biophysics, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA; Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA.
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31
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Miyagishima KJ, Sharma R, Nimmagadda M, Clore-Gronenborn K, Qureshy Z, Ortolan D, Bose D, Farnoodian M, Zhang C, Fausey A, Sergeev YV, Abu-Asab M, Jun B, Do KV, Kautzman Guerin MA, Calandria J, George A, Guan B, Wan Q, Sharp RC, Cukras C, Sieving PA, Hufnagel RB, Bazan NG, Boesze-Battaglia K, Miller S, Bharti K. AMPK modulation ameliorates dominant disease phenotypes of CTRP5 variant in retinal degeneration. Commun Biol 2021; 4:1360. [PMID: 34887495 PMCID: PMC8660775 DOI: 10.1038/s42003-021-02872-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 11/09/2021] [Indexed: 12/13/2022] Open
Abstract
Late-onset retinal degeneration (L-ORD) is an autosomal dominant disorder caused by a missense substitution in CTRP5. Distinctive clinical features include sub-retinal pigment epithelium (RPE) deposits, choroidal neovascularization, and RPE atrophy. In induced pluripotent stem cells-derived RPE from L-ORD patients (L-ORD-iRPE), we show that the dominant pathogenic CTRP5 variant leads to reduced CTRP5 secretion. In silico modeling suggests lower binding of mutant CTRP5 to adiponectin receptor 1 (ADIPOR1). Downstream of ADIPOR1 sustained activation of AMPK renders it insensitive to changes in AMP/ATP ratio resulting in defective lipid metabolism, reduced Neuroprotectin D1(NPD1) secretion, lower mitochondrial respiration, and reduced ATP production. These metabolic defects result in accumulation of sub-RPE deposits and leave L-ORD-iRPE susceptible to dedifferentiation. Gene augmentation of L-ORD-iRPE with WT CTRP5 or modulation of AMPK, by metformin, re-sensitize L-ORD-iRPE to changes in cellular energy status alleviating the disease cellular phenotypes. Our data suggests a mechanism for the dominant behavior of CTRP5 mutation and provides potential treatment strategies for L-ORD patients.
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Affiliation(s)
- Kiyoharu J. Miyagishima
- grid.280030.90000 0001 2150 6316Section on Epithelial and Retinal Physiology and Disease, NEI, NIH, Bethesda, MD 20892 USA
| | - Ruchi Sharma
- grid.280030.90000 0001 2150 6316Ocular and Stem Cell Translational Research Section, NEI, NIH, Bethesda, MD 20892 USA
| | - Malika Nimmagadda
- grid.280030.90000 0001 2150 6316Ocular and Stem Cell Translational Research Section, NEI, NIH, Bethesda, MD 20892 USA
| | - Katharina Clore-Gronenborn
- grid.280030.90000 0001 2150 6316Ocular and Stem Cell Translational Research Section, NEI, NIH, Bethesda, MD 20892 USA
| | - Zoya Qureshy
- grid.280030.90000 0001 2150 6316Ocular and Stem Cell Translational Research Section, NEI, NIH, Bethesda, MD 20892 USA
| | - Davide Ortolan
- grid.280030.90000 0001 2150 6316Ocular and Stem Cell Translational Research Section, NEI, NIH, Bethesda, MD 20892 USA
| | - Devika Bose
- grid.280030.90000 0001 2150 6316Ocular and Stem Cell Translational Research Section, NEI, NIH, Bethesda, MD 20892 USA
| | - Mitra Farnoodian
- grid.280030.90000 0001 2150 6316Ocular and Stem Cell Translational Research Section, NEI, NIH, Bethesda, MD 20892 USA
| | - Congxiao Zhang
- grid.280030.90000 0001 2150 6316Section on Epithelial and Retinal Physiology and Disease, NEI, NIH, Bethesda, MD 20892 USA
| | - Andrew Fausey
- grid.280030.90000 0001 2150 6316Ocular and Stem Cell Translational Research Section, NEI, NIH, Bethesda, MD 20892 USA
| | - Yuri V. Sergeev
- grid.280030.90000 0001 2150 6316Ophthalmic Genetics and Visual Function Branch, National Eye Institute, NIH, Bethesda, MD 20892 USA
| | - Mones Abu-Asab
- grid.280030.90000 0001 2150 6316Section of Histopathology, National Eye Institute, NIH, Bethesda, MD 20892 USA
| | - Bokkyoo Jun
- grid.279863.10000 0000 8954 1233Neuroscience Center of Excellence, Louisiana State University Health, New Orleans, LA 70112 USA
| | - Khanh V. Do
- grid.279863.10000 0000 8954 1233Neuroscience Center of Excellence, Louisiana State University Health, New Orleans, LA 70112 USA
| | - Marie-Audrey Kautzman Guerin
- grid.279863.10000 0000 8954 1233Neuroscience Center of Excellence, Louisiana State University Health, New Orleans, LA 70112 USA
| | - Jorgelina Calandria
- grid.279863.10000 0000 8954 1233Neuroscience Center of Excellence, Louisiana State University Health, New Orleans, LA 70112 USA
| | - Aman George
- grid.280030.90000 0001 2150 6316Ophthalmic Genetics and Visual Function Branch, National Eye Institute, NIH, Bethesda, MD 20892 USA
| | - Bin Guan
- grid.280030.90000 0001 2150 6316Medical Genetics and Ophthalmic Genomics Unit, NEI, NIH, Bethesda, MD 20892 USA
| | - Qin Wan
- grid.280030.90000 0001 2150 6316Section on Epithelial and Retinal Physiology and Disease, NEI, NIH, Bethesda, MD 20892 USA
| | - Rachel C. Sharp
- grid.25879.310000 0004 1936 8972Department of Biochemistry University of Pennsylvania, 240 South 40th Street, Levy Building, Room 515, Philadelphia, PA 19104 USA
| | - Catherine Cukras
- grid.280030.90000 0001 2150 6316Division of Epidemiology and Clinical Applications and Ophthalmic Genetics and Visual Function Branch, NEI, NIH, Bethesda, MD 20892 USA
| | - Paul A. Sieving
- grid.280030.90000 0001 2150 6316Section for Translation Research in Retinal and Macular Degeneration, NEI, NIH, Bethesda, MD 20892 USA
| | - Robert B. Hufnagel
- grid.280030.90000 0001 2150 6316Medical Genetics and Ophthalmic Genomics Unit, NEI, NIH, Bethesda, MD 20892 USA
| | - Nicolas G. Bazan
- grid.279863.10000 0000 8954 1233Neuroscience Center of Excellence, Louisiana State University Health, New Orleans, LA 70112 USA
| | - Kathleen Boesze-Battaglia
- grid.25879.310000 0004 1936 8972Department of Biochemistry University of Pennsylvania, 240 South 40th Street, Levy Building, Room 515, Philadelphia, PA 19104 USA
| | - Sheldon Miller
- grid.280030.90000 0001 2150 6316Section on Epithelial and Retinal Physiology and Disease, NEI, NIH, Bethesda, MD 20892 USA
| | - Kapil Bharti
- Ocular and Stem Cell Translational Research Section, NEI, NIH, Bethesda, MD, 20892, USA.
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32
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Flores‐Bellver M, Mighty J, Aparicio‐Domingo S, Li KV, Shi C, Zhou J, Cobb H, McGrath P, Michelis G, Lenhart P, Bilousova G, Heissel S, Rudy MJ, Coughlan C, Goodspeed AE, Becerra SP, Redenti S, Canto‐Soler MV. Extracellular vesicles released by human retinal pigment epithelium mediate increased polarised secretion of drusen proteins in response to AMD stressors. J Extracell Vesicles 2021; 10:e12165. [PMID: 34750957 PMCID: PMC8575963 DOI: 10.1002/jev2.12165] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 10/06/2021] [Accepted: 10/25/2021] [Indexed: 12/22/2022] Open
Abstract
Age-related macular degeneration (AMD) is a leading cause of blindness worldwide. Drusen are key contributors to the etiology of AMD and the ability to modulate drusen biogenesis could lead to therapeutic strategies to slow or halt AMD progression. The mechanisms underlying drusen biogenesis, however, remain mostly unknown. Here we demonstrate that under homeostatic conditions extracellular vesicles (EVs) secreted by retinal pigment epithelium (RPE) cells are enriched in proteins associated with mechanisms involved in AMD pathophysiology, including oxidative stress, immune response, inflammation, complement system and drusen composition. Furthermore, we provide first evidence that drusen-associated proteins are released as cargo of extracellular vesicles secreted by RPE cells in a polarised apical:basal mode. Notably, drusen-associated proteins exhibited distinctive directional secretion modes in homeostatic conditions and, differential modulation of this directional secretion in response to AMD stressors. These observations underpin the existence of a finely-tuned mechanism regulating directional apical:basal sorting and secretion of drusen-associated proteins via EVs, and its modulation in response to mechanisms involved in AMD pathophysiology. Collectively, our results strongly support an active role of RPE-derived EVs as a key source of drusen proteins and important contributors to drusen development and growth.
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Affiliation(s)
- Miguel Flores‐Bellver
- CellSight Ocular Stem Cell and Regeneration ProgramDepartment of OphthalmologySue Anschutz‐Rodgers Eye CenterUniversity of Colorado, School of MedicineAuroraColoradoUSA
| | - Jason Mighty
- Lehman CollegeBronxNew YorkUSA
- Biology Doctoral ProgramThe Graduate School and University CenterCity University of New YorkNew YorkNew YorkUSA
| | - Silvia Aparicio‐Domingo
- CellSight Ocular Stem Cell and Regeneration ProgramDepartment of OphthalmologySue Anschutz‐Rodgers Eye CenterUniversity of Colorado, School of MedicineAuroraColoradoUSA
| | - Kang V. Li
- CellSight Ocular Stem Cell and Regeneration ProgramDepartment of OphthalmologySue Anschutz‐Rodgers Eye CenterUniversity of Colorado, School of MedicineAuroraColoradoUSA
| | - Cui Shi
- Lehman CollegeBronxNew YorkUSA
- Biology Doctoral ProgramThe Graduate School and University CenterCity University of New YorkNew YorkNew YorkUSA
| | | | - Hannah Cobb
- CellSight Ocular Stem Cell and Regeneration ProgramDepartment of OphthalmologySue Anschutz‐Rodgers Eye CenterUniversity of Colorado, School of MedicineAuroraColoradoUSA
| | - Patrick McGrath
- Department of DermatologyUniversity of Colorado School of MedicineAuroraColoradoUSA
| | - German Michelis
- Section of Protein Structure and FunctionNEINIHBethesdaMarylandUSA
| | - Patricia Lenhart
- CellSight Ocular Stem Cell and Regeneration ProgramDepartment of OphthalmologySue Anschutz‐Rodgers Eye CenterUniversity of Colorado, School of MedicineAuroraColoradoUSA
| | - Ganna Bilousova
- Department of DermatologyUniversity of Colorado School of MedicineAuroraColoradoUSA
- Charles C. Gates Center for Regenerative MedicineUniversity of Colorado School of MedicineAuroraColoradoUSA
- Linda Crnic Institute for Down SyndromeUniversity of Colorado School of MedicineAuroraColoradoUSA
| | - Søren Heissel
- Proteomics Resource CenterThe Rockefeller UniversityNew YorkNew YorkUSA
| | - Michael J. Rudy
- Department of NeurologyUniversity of Colorado School of MedicineAuroraColoradoUSA
| | - Christina Coughlan
- University of Colorado Alzheimer's and Cognition CenterDepartment of NeurologyLinda Crnic Institute for Down SyndromeUniversity of Colorado Anschutz Medical CampusAuroraColoradoUSA
| | - Andrew E. Goodspeed
- Department of PharmacologyUniversity of Colorado Anschutz Medical CampusAuroraColoradoUSA
- University of Colorado Cancer CenterUniversity of Colorado Anschutz Medical CampusAuroraColoradoUSA
| | | | - Stephen Redenti
- Lehman CollegeBronxNew YorkUSA
- Biology Doctoral ProgramThe Graduate School and University CenterCity University of New YorkNew YorkNew YorkUSA
- Biochemistry Doctoral ProgramThe Graduate SchoolCity University of New YorkNew YorkNew YorkUSA
| | - M. Valeria Canto‐Soler
- CellSight Ocular Stem Cell and Regeneration ProgramDepartment of OphthalmologySue Anschutz‐Rodgers Eye CenterUniversity of Colorado, School of MedicineAuroraColoradoUSA
- Charles C. Gates Center for Regenerative MedicineUniversity of Colorado School of MedicineAuroraColoradoUSA
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33
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Tsantilas KA, Cleghorn WM, Bisbach CM, Whitson JA, Hass DT, Robbings BM, Sadilek M, Linton JD, Rountree AM, Valencia AP, Sweetwyne MT, Campbell MD, Zhang H, Jankowski CSR, Sweet IR, Marcinek DJ, Rabinovitch PS, Hurley JB. An Analysis of Metabolic Changes in the Retina and Retinal Pigment Epithelium of Aging Mice. Invest Ophthalmol Vis Sci 2021; 62:20. [PMID: 34797906 PMCID: PMC8606884 DOI: 10.1167/iovs.62.14.20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Purpose The purpose of this study was to present our hypothesis that aging alters metabolic function in ocular tissues. We tested the hypothesis by measuring metabolism in aged murine tissues alongside retinal responses to light. Methods Scotopic and photopic electroretinogram (ERG) responses in young (3–6 months) and aged (23–26 months) C57Bl/6J mice were recorded. Metabolic flux in retina and eyecup explants was quantified using U-13C-glucose or U-13C-glutamine with gas chromatography-mass spectrometry (GC-MS), O2 consumption rate (OCR) in a perifusion apparatus, and quantifying adenosine triphosphatase (ATP) with a bioluminescence assay. Results Scotopic and photopic ERG responses were reduced in aged mice. Glucose metabolism, glutamine metabolism, OCR, and ATP pools in retinal explants were mostly unaffected in aged mice. In eyecups, glutamine usage in the Krebs Cycle decreased while glucose metabolism, OCR, and ATP pools remained stable. Conclusions Our examination of metabolism showed negligible impact of age on retina and an impairment of glutamine anaplerosis in eyecups. The metabolic stability of these tissues ex vivo suggests age-related metabolic alterations may not be intrinsic. Future experiments should focus on determining whether external factors including nutrient supply, oxygen availability, or structural changes influence ocular metabolism in vivo.
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Affiliation(s)
- Kristine A Tsantilas
- Department of Biochemistry, University of Washington, Seattle, Washington, United States
| | - Whitney M Cleghorn
- Department of Biochemistry, University of Washington, Seattle, Washington, United States
| | - Celia M Bisbach
- Department of Biochemistry, University of Washington, Seattle, Washington, United States
| | - Jeremy A Whitson
- Department of Biology, Davidson College, Davidson, North Carolina, United States
| | - Daniel T Hass
- Department of Biochemistry, University of Washington, Seattle, Washington, United States
| | - Brian M Robbings
- Department of Biochemistry, University of Washington, Seattle, Washington, United States.,UW Diabetes Institute, University of Washington, Seattle, Washington, United States
| | - Martin Sadilek
- Department of Chemistry, University of Washington, Seattle, Washington, United States
| | - Jonathan D Linton
- Department of Biochemistry, University of Washington, Seattle, Washington, United States
| | - Austin M Rountree
- UW Diabetes Institute, University of Washington, Seattle, Washington, United States
| | - Ana P Valencia
- Department of Radiology, University of Washington, Seattle, Washington, United States
| | - Mariya T Sweetwyne
- Department of Laboratory Medicine & Pathology, University of Washington, Seattle, Washington, United States
| | - Matthew D Campbell
- Department of Radiology, University of Washington, Seattle, Washington, United States
| | - Huiliang Zhang
- Department of Pharmacology and Toxicology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States
| | - Connor S R Jankowski
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, United States.,Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States
| | - Ian R Sweet
- UW Diabetes Institute, University of Washington, Seattle, Washington, United States
| | - David J Marcinek
- Department of Radiology, University of Washington, Seattle, Washington, United States
| | - Peter S Rabinovitch
- Department of Laboratory Medicine & Pathology, University of Washington, Seattle, Washington, United States
| | - James B Hurley
- Department of Biochemistry, University of Washington, Seattle, Washington, United States.,Department of Ophthalmology, University of Washington, Seattle, Washington, United States
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He J, Yamamoto M, Sumiyama K, Konagaya Y, Terai K, Matsuda M, Sato S. Two-photon AMPK and ATP imaging reveals the bias between rods and cones in glycolysis utility. FASEB J 2021; 35:e21880. [PMID: 34449091 DOI: 10.1096/fj.202101121r] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 08/08/2021] [Accepted: 08/11/2021] [Indexed: 12/15/2022]
Abstract
In vertebrates, retinal rod and cone photoreceptor cells rely significantly on glycolysis. Lactate released from photoreceptor cells fuels neighboring retinal pigment epithelium cells and Müller glial cells through oxidative phosphorylation. To understand this highly heterogeneous metabolic environment around photoreceptor cells, single-cell analysis is needed. Here, we visualized cellular AMP-activated protein kinase (AMPK) activity and ATP levels in the retina by two-photon microscopy. Transgenic mice expressing a hyBRET-AMPK biosensor were used for measuring the AMPK activity. GO-ATeam2 transgenic mice were used for measuring the ATP level. Temporal metabolic responses were successfully detected in the live retinal explants upon drug perfusion. A glycolysis inhibitor, 2-deoxy-d-glucose (2-DG), activated AMPK and reduced ATP. These effects were clearly stronger in rods than in cones. Notably, rod AMPK and ATP started to recover at 30 min from the onset of 2-DG perfusion. Consistent with these findings, ex vivo electroretinogram recordings showed a transient slowdown in rod dim flash responses during a 60-min 2-DG perfusion, whereas cone responses were not affected. Based on these results, we propose that cones surrounded by highly glycolytic rods become less dependent on glycolysis, and rods also become less dependent on glycolysis within 60 min upon the glycolysis inhibition.
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Affiliation(s)
- Jiazhou He
- Laboratory of Bioimaging and Cell Signaling, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Masamichi Yamamoto
- Department of Research Promotion and Management, National Cerebral and Cardiovascular Center Research Institute, Osaka, Japan
| | - Kenta Sumiyama
- Laboratory for Mouse Genetic Engineering, RIKEN Center for Biosystems Dynamics Research, Osaka, Japan
| | - Yumi Konagaya
- Laboratory of Bioimaging and Cell Signaling, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Kenta Terai
- Laboratory of Bioimaging and Cell Signaling, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Michiyuki Matsuda
- Laboratory of Bioimaging and Cell Signaling, Graduate School of Biostudies, Kyoto University, Kyoto, Japan.,Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Kyoto, Japan.,Institute for Integrated Cell-Material Sciences, Kyoto University, Kyoto, Japan
| | - Shinya Sato
- Laboratory of Bioimaging and Cell Signaling, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
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Absence of retbindin blocks glycolytic flux, disrupts metabolic homeostasis, and leads to photoreceptor degeneration. Proc Natl Acad Sci U S A 2021; 118:2018956118. [PMID: 33526685 DOI: 10.1073/pnas.2018956118] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
We previously reported a model of progressive retinal degeneration resulting from the knockout of the retina-specific riboflavin binding protein, retbindin (Rtbdn -/- ). We also demonstrated a reduction in neural retinal flavins as a result of the elimination of RTBDN. Given the role of flavins in metabolism, herein we investigated the underlying mechanism of this retinal degeneration by performing metabolomic analyses on predegeneration at postnatal day (P) 45 and at the onset of functional degeneration in the P120 retinas. Metabolomics of hydrophilic metabolites revealed that individual glycolytic products accumulated in the P45 Rtbdn -/- neural retinas along with the elevation of pentose phosphate pathway, while TCA cycle intermediates remained unchanged. This was confirmed by using 13C-labeled flux measurements and immunoblotting, revealing that the key regulatory step of phosphoenolpyruvate to pyruvate was inhibited via down-regulation of the tetrameric pyruvate kinase M2 (PKM2). Separate metabolite assessments revealed that almost all intermediates of acylcarnitine fatty acid oxidation, ceramides, sphingomyelins, and multiple toxic metabolites were significantly elevated in the predegeneration Rtbdn -/- neural retina. Our data show that lack of RTBDN, and hence reduction in flavins, forced the neural retina into repurposing glucose for free-radical mitigation over ATP production. However, such sustained metabolic reprogramming resulted in an eventual metabolic collapse leading to neurodegeneration.
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36
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HK2 Mediated Glycolytic Metabolism in Mouse Photoreceptors Is Not Required to Cause Late Stage Age-Related Macular Degeneration-Like Pathologies. Biomolecules 2021; 11:biom11060871. [PMID: 34208233 PMCID: PMC8230848 DOI: 10.3390/biom11060871] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 06/01/2021] [Accepted: 06/09/2021] [Indexed: 12/12/2022] Open
Abstract
Age-related macular degeneration (AMD) is a multifactorial disease of unclear etiology. We previously proposed that metabolic adaptations in photoreceptors (PRs) play a role in disease progression. We mimicked these metabolic adaptations in mouse PRs through deletion of the tuberous sclerosis complex (TSC) protein TSC1. Here, we confirm our previous findings by deletion of the other complex protein, namely TSC2, in rod photoreceptors. Similar to deletion of Tsc1, mice with deletion of Tsc2 in rods develop AMD-like pathologies, including accumulation of apolipoproteins, migration of microglia, geographic atrophy, and neovascular pathologies. Subtle differences between the two mouse models, such as a significant increase in microglia activation with loss of Tsc2, were seen as well. To investigate the role of altered glucose metabolism in disease pathogenesis, we generated mice with simulation deletions of Tsc2 and hexokinase-2 (Hk2) in rods. Although retinal lactate levels returned to normal in mice with Tsc2-Hk2 deletion, AMD-like pathologies still developed. The data suggest that the metabolic adaptations in PRs that cause AMD-like pathologies are independent of HK2-mediated aerobic glycolysis.
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Abstract
The outer retina is nourished from the choroid, a capillary bed just inside the sclera. O2, glucose, and other nutrients diffuse out of the choroid and then filter through a monolayer of retinal pigment epithelium (RPE) cells to fuel the retina. Recent studies of energy metabolism have revealed striking differences between retinas and RPE cells in the ways that they extract energy from fuels. The purpose of this review is to suggest and evaluate the hypothesis that the retina and RPE have complementary metabolic roles that make them depend on each other for survival and for their abilities to perform essential and specialized functions. Expected final online publication date for the Annual Review of Vision Science, Volume 7 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- James B Hurley
- Departments of Biochemistry and Ophthalmology, University of Washington, Seattle, Washington 98115, USA;
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38
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Bisbach CM, Hass DT, Robbings BM, Rountree AM, Sadilek M, Sweet IR, Hurley JB. Succinate Can Shuttle Reducing Power from the Hypoxic Retina to the O 2-Rich Pigment Epithelium. Cell Rep 2021; 31:107606. [PMID: 32375026 DOI: 10.1016/j.celrep.2020.107606] [Citation(s) in RCA: 53] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 02/21/2020] [Accepted: 04/10/2020] [Indexed: 12/19/2022] Open
Abstract
When O2 is plentiful, the mitochondrial electron transport chain uses it as a terminal electron acceptor. However, the mammalian retina thrives in a hypoxic niche in the eye. We find that mitochondria in retinas adapt to their hypoxic environment by reversing the succinate dehydrogenase reaction to use fumarate to accept electrons instead of O2. Reverse succinate dehydrogenase activity produces succinate and is enhanced by hypoxia-induced downregulation of cytochrome oxidase. Retinas can export the succinate they produce to the neighboring O2-rich retinal pigment epithelium-choroid complex. There, succinate enhances O2 consumption by severalfold. Malate made from succinate in the pigment epithelium can then be imported into the retina, where it is converted to fumarate to again accept electrons in the reverse succinate dehydrogenase reaction. This malate-succinate shuttle can sustain these two tissues by transferring reducing power from an O2-poor tissue (retina) to an O2-rich one (retinal pigment epithelium-choroid).
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Affiliation(s)
- Celia M Bisbach
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA
| | - Daniel T Hass
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA
| | - Brian M Robbings
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA; UW Diabetes Institute, University of Washington, Seattle, WA 98195, USA
| | - Austin M Rountree
- UW Diabetes Institute, University of Washington, Seattle, WA 98195, USA
| | - Martin Sadilek
- Department of Chemistry, University of Washington, Seattle, WA 98195, USA
| | - Ian R Sweet
- UW Diabetes Institute, University of Washington, Seattle, WA 98195, USA
| | - James B Hurley
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA; Department of Ophthalmology, University of Washington, Seattle, WA 98195, USA.
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39
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Dhingra A, Sharp RC, Kim T, Popov AV, Ying GS, Pietrofesa RA, Park K, Christofidou-Solomidou M, Boesze-Battaglia K. Assessment of a Small Molecule Synthetic Lignan in Enhancing Oxidative Balance and Decreasing Lipid Accumulation in Human Retinal Pigment Epithelia. Int J Mol Sci 2021; 22:5764. [PMID: 34071220 PMCID: PMC8198017 DOI: 10.3390/ijms22115764] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 05/24/2021] [Accepted: 05/26/2021] [Indexed: 01/03/2023] Open
Abstract
Visual function depends on the intimate structural, functional and metabolic interactions between the retinal pigment epithelium (RPE) and the neural retina. The daily phagocytosis of the photoreceptor outer segment tips by the overlaying RPE provides essential nutrients for the RPE itself and photoreceptors through intricate metabolic synergy. Age-related retinal changes are often characterized by metabolic dysregulation contributing to increased lipid accumulation and peroxidation as well as the release of proinflammatory cytokines. LGM2605 is a synthetic lignan secoisolariciresinol diglucoside (SDG) with free radical scavenging, antioxidant and anti-inflammatory properties demonstrated in diverse in vitro and in vivo inflammatory disease models. In these studies, we tested the hypothesis that LGM2605 may be an attractive small-scale therapeutic that protects RPE against inflammation and restores its metabolic capacity under lipid overload. Using an in vitro model in which loss of the autophagy protein, LC3B, results in defective phagosome degradation and metabolic dysregulation, we show that lipid overload results in increased gasdermin cleavage, IL-1 β release, lipid accumulation and decreased oxidative capacity. The addition of LGM2605 resulted in enhanced mitochondrial capacity, decreased lipid accumulation and amelioration of IL-1 β release in a model of defective lipid homeostasis. Collectively, these studies suggest that lipid overload decreases mitochondrial function and increases the inflammatory response, with LGM2605 acting as a protective agent.
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Affiliation(s)
- Anuradha Dhingra
- Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; (A.D.); (R.C.S.)
| | - Rachel C. Sharp
- Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; (A.D.); (R.C.S.)
| | - Taewan Kim
- Department of Periodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA;
| | - Anatoliy V. Popov
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA;
| | - Gui-Shuang Ying
- Center for Preventive Ophthalmology and Biostatistics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; (G.-S.Y.); (K.P.)
| | - Ralph A. Pietrofesa
- Department of Medicine, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; (R.A.P.); (M.C.-S.)
| | - Kyewon Park
- Center for Preventive Ophthalmology and Biostatistics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; (G.-S.Y.); (K.P.)
| | - Melpo Christofidou-Solomidou
- Department of Medicine, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; (R.A.P.); (M.C.-S.)
| | - Kathleen Boesze-Battaglia
- Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; (A.D.); (R.C.S.)
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40
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Zhang Q, Presswalla F, Ali RR, Zacks DN, Thompson DA, Miller JML. Pharmacologic activation of autophagy without direct mTOR inhibition as a therapeutic strategy for treating dry macular degeneration. Aging (Albany NY) 2021; 13:10866-10890. [PMID: 33872219 PMCID: PMC8109132 DOI: 10.18632/aging.202974] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 03/13/2021] [Indexed: 12/15/2022]
Abstract
Dry age-related macular degeneration (AMD) is marked by the accumulation of extracellular and intracellular lipid-rich deposits within and around the retinal pigment epithelium (RPE). Inducing autophagy, a conserved, intracellular degradative pathway, is a potential treatment strategy to prevent disease by clearing these deposits. However, mTOR inhibition, the major mechanism for inducing autophagy, disrupts core RPE functions. Here, we screened autophagy inducers that do not directly inhibit mTOR for their potential as an AMD therapeutic in primary human RPE culture. Only two out of more than thirty autophagy inducers tested reliably increased autophagy flux in RPE, emphasizing that autophagy induction mechanistically differs across distinct tissues. In contrast to mTOR inhibitors, these compounds preserved RPE health, and one inducer, the FDA-approved compound flubendazole (FLBZ), reduced the secretion of apolipoprotein that contributes to extracellular deposits termed drusen. Simultaneously, FLBZ increased production of the lipid-degradation product β-hydroxybutyrate, which is used by photoreceptor cells as an energy source. FLBZ also reduced the accumulation of intracellular deposits, termed lipofuscin, and alleviated lipofuscin-induced cellular senescence and tight-junction disruption. FLBZ triggered compaction of lipofuscin-like granules into a potentially less toxic form. Thus, induction of RPE autophagy without direct mTOR inhibition is a promising therapeutic approach for dry AMD.
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Affiliation(s)
- Qitao Zhang
- Kellogg Eye Center, University of Michigan, Ann Arbor, MI 48105, USA
| | - Feriel Presswalla
- Kellogg Eye Center, University of Michigan, Ann Arbor, MI 48105, USA
| | - Robin R. Ali
- Kellogg Eye Center, University of Michigan, Ann Arbor, MI 48105, USA
- KCL Centre for Cell and Gene Therapy, London, England WC2R 2LS, United Kingdom
| | - David N. Zacks
- Kellogg Eye Center, University of Michigan, Ann Arbor, MI 48105, USA
| | - Debra A. Thompson
- Kellogg Eye Center, University of Michigan, Ann Arbor, MI 48105, USA
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48105, USA
| | - Jason ML. Miller
- Kellogg Eye Center, University of Michigan, Ann Arbor, MI 48105, USA
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41
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Du J, Zhu S, Lim RR, Chao JR. Proline metabolism and transport in retinal health and disease. Amino Acids 2021; 53:1789-1806. [PMID: 33871679 PMCID: PMC8054134 DOI: 10.1007/s00726-021-02981-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 04/10/2021] [Indexed: 12/11/2022]
Abstract
The retina is one of the most energy-demanding tissues in the human body. Photoreceptors in the outer retina rely on nutrient support from the neighboring retinal pigment epithelium (RPE), a monolayer of epithelial cells that separate the retina and choroidal blood supply. RPE dysfunction or cell death can result in photoreceptor degeneration, leading to blindness in retinal degenerative diseases including some inherited retinal degenerations and age-related macular degeneration (AMD). In addition to having ready access to rich nutrients from blood, the RPE is also supplied with lactate from adjacent photoreceptors. Moreover, RPE can phagocytose lipid-rich outer segments for degradation and recycling on a daily basis. Recent studies show RPE cells prefer proline as a major metabolic substrate, and they are highly enriched for the proline transporter, SLC6A20. In contrast, dysfunctional or poorly differentiated RPE fails to utilize proline. RPE uses proline to fuel mitochondrial metabolism, synthesize amino acids, build the extracellular matrix, fight against oxidative stress, and sustain differentiation. Remarkably, the neural retina rarely imports proline directly, but it uptakes and utilizes intermediates and amino acids derived from proline catabolism in the RPE. Mutations of genes in proline metabolism are associated with retinal degenerative diseases, and proline supplementation is reported to improve RPE-initiated vision loss. This review will cover proline metabolism in RPE and highlight the importance of proline transport and utilization in maintaining retinal metabolism and health.
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Affiliation(s)
- Jianhai Du
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV, 26506, USA. .,Department of Biochemistry, West Virginia University, Morgantown, WV, 26506, USA. .,One Medical Center Dr, WVU Eye Institute, PO Box 9193, Morgantown, WV, 26505, USA.
| | - Siyan Zhu
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV, 26506, USA.,Department of Biochemistry, West Virginia University, Morgantown, WV, 26506, USA
| | - Rayne R Lim
- Department of Ophthalmology, University of Washington, Seattle, WA, 98109, USA
| | - Jennifer R Chao
- Department of Ophthalmology, University of Washington, Seattle, WA, 98109, USA
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42
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Viegas FO, Neuhauss SCF. A Metabolic Landscape for Maintaining Retina Integrity and Function. Front Mol Neurosci 2021; 14:656000. [PMID: 33935647 PMCID: PMC8081888 DOI: 10.3389/fnmol.2021.656000] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 03/22/2021] [Indexed: 01/27/2023] Open
Abstract
Neurons have high metabolic demands that are almost exclusively met by glucose supplied from the bloodstream. Glucose is utilized in complex metabolic interactions between neurons and glia cells, described by the astrocyte-neuron lactate shuttle (ANLS) hypothesis. The neural retina faces similar energy demands to the rest of the brain, with additional high anabolic needs to support continuous renewal of photoreceptor outer segments. This demand is met by a fascinating variation of the ANLS in which photoreceptors are the central part of a metabolic landscape, using glucose and supplying surrounding cells with metabolic intermediates. In this review we summarize recent evidence on how neurons, in particular photoreceptors, meet their energy and biosynthetic requirements by comprising a metabolic landscape of interdependent cells.
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Affiliation(s)
- Filipe O Viegas
- Department of Molecular Life Sciences, University of Zurich, Zurich, Switzerland.,Life Science Zurich Graduate School, Ph.D. Program in Molecular Life Sciences, Zurich, Switzerland
| | - Stephan C F Neuhauss
- Department of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
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43
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Das Y, Swinkels D, Baes M. Peroxisomal Disorders and Their Mouse Models Point to Essential Roles of Peroxisomes for Retinal Integrity. Int J Mol Sci 2021; 22:ijms22084101. [PMID: 33921065 PMCID: PMC8071455 DOI: 10.3390/ijms22084101] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 04/12/2021] [Accepted: 04/13/2021] [Indexed: 12/31/2022] Open
Abstract
Peroxisomes are multifunctional organelles, well known for their role in cellular lipid homeostasis. Their importance is highlighted by the life-threatening diseases caused by peroxisomal dysfunction. Importantly, most patients suffering from peroxisomal biogenesis disorders, even those with a milder disease course, present with a number of ocular symptoms, including retinopathy. Patients with a selective defect in either peroxisomal α- or β-oxidation or ether lipid synthesis also suffer from vision problems. In this review, we thoroughly discuss the ophthalmological pathology in peroxisomal disorder patients and, where possible, the corresponding animal models, with a special emphasis on the retina. In addition, we attempt to link the observed retinal phenotype to the underlying biochemical alterations. It appears that the retinal pathology is highly variable and the lack of histopathological descriptions in patients hampers the translation of the findings in the mouse models. Furthermore, it becomes clear that there are still large gaps in the current knowledge on the contribution of the different metabolic disturbances to the retinopathy, but branched chain fatty acid accumulation and impaired retinal PUFA homeostasis are likely important factors.
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44
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Fu Z, Qiu C, Cagnone G, Tomita Y, Huang S, Cakir B, Kotoda Y, Allen W, Bull E, Akula JD, Joyal JS, Hellström A, Talukdar S, Smith LEH. Retinal glial remodeling by FGF21 preserves retinal function during photoreceptor degeneration. iScience 2021; 24:102376. [PMID: 33937726 PMCID: PMC8079476 DOI: 10.1016/j.isci.2021.102376] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 02/13/2021] [Accepted: 03/25/2021] [Indexed: 12/18/2022] Open
Abstract
The group of retinal degenerations, retinitis pigmentosa (RP), comprises more than 150 genetic abnormalities affecting photoreceptors. Finding degenerative pathways common to all genetic abnormalities may allow general treatment such as neuroprotection. Neuroprotection may include enhancing the function of cells that directly support photoreceptors, retinal pigment epithelial cells, and Müller glia. Treatment with fibroblast growth factor 21 (FGF21), a neuroprotectant, from postnatal week 4-10, during rod and cone loss in P23H mice (an RP model) with retinal degeneration, preserved photoreceptor function and normalized Müller glial cell morphology. Single-cell transcriptomics of retinal cells showed that FGF21 receptor Fgfr1 was specifically expressed in Müller glia/astrocytes. Of all retinal cells, FGF21 predominantly affected genes in Müller glia/astrocytes with increased expression of axon development and synapse formation pathway genes. Therefore, enhancing retinal glial axon and synapse formation with neurons may preserve retinal function in RP and may suggest a general therapeutic approach for retinal degenerative diseases.
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Affiliation(s)
- Zhongjie Fu
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.,The Manton Center for Orphan Disease, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Chenxi Qiu
- Department of Medicine, Division of Translational Therapeutics, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA
| | - Gael Cagnone
- Department of Pediatrics, Pharmacology and Ophthalmology, CHU Sainte-Justine Research Center, Université de Montréal, Montreal, Qc H3A 0C4, Canada.,Department of Pharmacology and Therapeutics, McGill University, Montreal, Qc H3A 0C4, Canada
| | - Yohei Tomita
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Shuo Huang
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Bertan Cakir
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Yumi Kotoda
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - William Allen
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Edward Bull
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - James D Akula
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Jean-Sébastien Joyal
- Department of Pediatrics, Pharmacology and Ophthalmology, CHU Sainte-Justine Research Center, Université de Montréal, Montreal, Qc H3A 0C4, Canada.,Department of Pharmacology and Therapeutics, McGill University, Montreal, Qc H3A 0C4, Canada
| | - Ann Hellström
- Section for Ophthalmology, Department of Clinical Neuroscience, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Göteborg 405 30, Sweden
| | - Saswata Talukdar
- Cardiometabolic Diseases, Merck Research Laboratories, 33 Avenue Louis Pasteur, Boston, MA 02115, USA
| | - Lois E H Smith
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
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45
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AlMuzaini AAAY, Boesze-Battaglia K, Alawi F, Akintoye SO. Hypoxia enhances basal autophagy of epithelial-derived ameloblastoma cells. Oral Dis 2021; 28:2175-2184. [PMID: 33721362 DOI: 10.1111/odi.13848] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 02/11/2021] [Accepted: 02/28/2021] [Indexed: 11/28/2022]
Abstract
Ameloblastoma is a locally aggressive odontogenic tumor. Etiopathogenesis and locally aggressive growth properties of ameloblastoma can be attributed to a hypoxic microenvironment conducive to tumor cell survival. Epithelial-derived follicular ameloblastoma cells (EP-AMCs) display enhanced basal autophagy, but the interplay of hypoxia and autophagy in EP-AMCs survival and ameloblastoma recurrence is unclear. We evaluated differential expression of autophagic markers in primary and recurrent ameloblastomas and hypothesized that hypoxia-induced autophagy supports EP-AMC survival. Primary and recurrent ameloblastomas were comparatively assessed for expression levels of pan-cytokeratin, Vimentin, and autophagic markers SQSTM1/p62, LC3, and pS6. EP-AMCs compared with human odontoma-derived cells (HODCs) were subjected to severe hypoxia to determine the interplay of hypoxia and autophagic process in posthypoxia survival. Pan-cytokeratin and SQSTM1/p62 were expressed by both primary and recurrent ameloblastoma epithelial cells while the ameloblastoma connective tissues displayed weak reactivity to vimentin. Under hypoxia, EP-AMC expression levels of hypoxia-inducible factor (HIF)-1α, p62, and LC3 were increased while pS6 was decreased posthypoxia. The combined decrease in pS6 and enhanced LC3 in EP-AMCs under hypoxia indicate that EP-AMCs re-establish basal autophagy under hypoxia. Taken together, these suggest a possible role of LC3-associated phagocytosis (LAP) in ameloblastoma cell survival.
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Affiliation(s)
- Anwar A A Y AlMuzaini
- Department of Oral Medicine, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Kathleen Boesze-Battaglia
- Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Faizan Alawi
- Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Sunday O Akintoye
- Department of Oral Medicine, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
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46
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Murenu E, Kostidis S, Lahiri S, Geserich AS, Imhof A, Giera M, Michalakis S. Metabolic Analysis of Vitreous/Lens and Retina in Wild Type and Retinal Degeneration Mice. Int J Mol Sci 2021; 22:ijms22052345. [PMID: 33652907 PMCID: PMC7956175 DOI: 10.3390/ijms22052345] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 02/19/2021] [Accepted: 02/23/2021] [Indexed: 02/06/2023] Open
Abstract
Photoreceptors are the light-sensing cells of the retina and the major cell type affected in most inherited retinal degenerations. Different metabolic pathways sustain their high energetic demand in physiological conditions, particularly aerobic glycolysis. The principal metabolome of the mature retina has been studied, but only limited information is available on metabolic adaptations in response to key developmental events, such as eye opening. Moreover, dynamic metabolic changes due to retinal degeneration are not well understood. Here, we aimed to explore and map the ocular metabolic dynamics induced by eye opening in healthy (wild type) or Pde6b-mutant (retinal degeneration 1, Rd1) mice, in which photoreceptors degenerate shortly after eye opening. To unravel metabolic differences emerging before and after eye opening under physiological and pathophysiological conditions, we performed nuclear magnetic resonance (NMR) spectroscopy-based metabolome analysis of wild type and Rd1 retina and vitreous/lens. We show that eye opening is accompanied by changes in the concentration of selected metabolites in the retina and by alterations in the vitreous/lens composition only in the retinal degeneration context. As such, we identify NAcetylaspartate as a potential novel vitreous/lens marker reflecting progressive retinal degeneration. Thus, our data can help elucidating mechanisms underlying key events in retinal physiology and reveal changes occurring in pathology, while highlighting the importance of the vitreous/lens in the characterization of retinal diseases.
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Affiliation(s)
- Elisa Murenu
- Department of Ophthalmology, Ludwig-Maximilians-Universität München, Mathildenstraße 8, 80336 Munich, Germany;
- Department of Pharmacy, Ludwig-Maximilians Universität München, Butenandtstr. 7, 81377 Munich, Germany;
| | - Sarantos Kostidis
- Leiden University Medical Center, Center for Proteomics & Metabolomics, P.O. Box 9600, 2300 RC Leiden, The Netherlands; (S.K.); (M.G.)
| | - Shibojyoti Lahiri
- Biomedical Center Munich-Molecular Biology, Ludwig-Maximilians-Universität München, Großhaderner Strasse 9, 82152 Planegg-Martinsried, Germany; (S.L.); (A.I.)
| | - Anna S. Geserich
- Department of Pharmacy, Ludwig-Maximilians Universität München, Butenandtstr. 7, 81377 Munich, Germany;
| | - Axel Imhof
- Biomedical Center Munich-Molecular Biology, Ludwig-Maximilians-Universität München, Großhaderner Strasse 9, 82152 Planegg-Martinsried, Germany; (S.L.); (A.I.)
| | - Martin Giera
- Leiden University Medical Center, Center for Proteomics & Metabolomics, P.O. Box 9600, 2300 RC Leiden, The Netherlands; (S.K.); (M.G.)
| | - Stylianos Michalakis
- Department of Ophthalmology, Ludwig-Maximilians-Universität München, Mathildenstraße 8, 80336 Munich, Germany;
- Department of Pharmacy, Ludwig-Maximilians Universität München, Butenandtstr. 7, 81377 Munich, Germany;
- Correspondence: ; Tel.: +49-89-2180-77325
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47
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Fu Z, Kern TS, Hellström A, Smith LEH. Fatty acid oxidation and photoreceptor metabolic needs. J Lipid Res 2021; 62:100035. [PMID: 32094231 PMCID: PMC7905050 DOI: 10.1194/jlr.tr120000618] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 02/14/2020] [Indexed: 01/31/2023] Open
Abstract
Photoreceptors have high energy demands and a high density of mitochondria that produce ATP through oxidative phosphorylation (OXPHOS) of fuel substrates. Although glucose is the major fuel for CNS brain neurons, in photoreceptors (also CNS), most glucose is not metabolized through OXPHOS but is instead metabolized into lactate by aerobic glycolysis. The major fuel sources for photoreceptor mitochondria remained unclear for almost six decades. Similar to other tissues (like heart and skeletal muscle) with high metabolic rates, photoreceptors were recently found to metabolize fatty acids (palmitate) through OXPHOS. Disruption of lipid entry into photoreceptors leads to extracellular lipid accumulation, suppressed glucose transporter expression, and a duel lipid/glucose fuel shortage. Modulation of lipid metabolism helps restore photoreceptor function. However, further elucidation of the types of lipids used as retinal energy sources, the metabolic interaction with other fuel pathways, as well as the cross-talk among retinal cells to provide energy to photoreceptors is not fully understood. In this review, we will focus on the current understanding of photoreceptor energy demand and sources, and potential future investigations of photoreceptor metabolism.
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Affiliation(s)
- Zhongjie Fu
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA; Manton Center for Orphan Disease, Boston Children's Hospital, Boston, MA, USA.
| | - Timothy S Kern
- Center for Translational Vision Research, Gavin Herbert Eye Institute, Irvine, CA, USA
| | - Ann Hellström
- Section for Ophthalmology, Department of Clinical Neuroscience, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden
| | - Lois E H Smith
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.
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48
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Das Y, Swinkels D, Kocherlakota S, Vinckier S, Vaz FM, Wever E, van Kampen AHC, Jun B, Do KV, Moons L, Bazan NG, Van Veldhoven PP, Baes M. Peroxisomal Multifunctional Protein 2 Deficiency Perturbs Lipid Homeostasis in the Retina and Causes Visual Dysfunction in Mice. Front Cell Dev Biol 2021; 9:632930. [PMID: 33604342 PMCID: PMC7884615 DOI: 10.3389/fcell.2021.632930] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 01/11/2021] [Indexed: 01/09/2023] Open
Abstract
Patients lacking multifunctional protein 2 (MFP2), the central enzyme of the peroxisomal β-oxidation pathway, develop retinopathy. This pathway is involved in the metabolism of very long chain (VLCFAs) and polyunsaturated (PUFAs) fatty acids, which are enriched in the photoreceptor outer segments (POS). The molecular mechanisms underlying the retinopathy remain, however, elusive. Here, we report that mice with MFP2 inactivation display decreased retinal function already at the age of 3 weeks, which is accompanied by a profound shortening of the photoreceptor outer and inner segments, but with preserved photoreceptor ultrastructure. Furthermore, MFP2 deficient retinas exhibit severe changes in gene expression with downregulation of genes involved in the phototransduction pathway and upregulation of inflammation related genes. Lipid profiling of the mutant retinas revealed a profound reduction of DHA-containing phospholipids. This was likely due to a hampered systemic supply and retinal traffic of this PUFA, although we cannot exclude that the local defect of peroxisomal β-oxidation contributes to this DHA decrease. Moreover, very long chain PUFAs were also reduced, with the exception of those containing ≥ 34 carbons that accumulated. The latter suggests that there is an uncontrollable elongation of retinal PUFAs. In conclusion, our data reveal that intact peroxisomal β-oxidation is indispensable for retinal integrity, most likely by maintaining PUFA homeostasis.
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Affiliation(s)
- Yannick Das
- Laboratory of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium
| | - Daniëlle Swinkels
- Laboratory of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium
| | - Sai Kocherlakota
- Laboratory of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium
| | - Stefan Vinckier
- Laboratory of Angiogenesis and Vascular Metabolism, Department of Oncology, KU Leuven-VIB, Leuven, Belgium
| | - Frédéric M Vaz
- Laboratory of Genetic Metabolic Diseases, Department of Clinical Chemistry and Pediatrics, Amsterdam University Medical Center (UMC), University of Amsterdam, Amsterdam, Netherlands.,Core Facility Metabolomics, Amsterdam University Medical Center (UMC), Amsterdam, Netherlands
| | - Eric Wever
- Laboratory of Genetic Metabolic Diseases, Department of Clinical Chemistry and Pediatrics, Amsterdam University Medical Center (UMC), University of Amsterdam, Amsterdam, Netherlands.,Core Facility Metabolomics, Amsterdam University Medical Center (UMC), Amsterdam, Netherlands.,Bioinformatics Laboratory, Department of Epidemiology and Data Science, Amsterdam Public Health Research Institute, Amsterdam University Medical Center (UMC), University of Amsterdam, Amsterdam, Netherlands
| | - Antoine H C van Kampen
- Bioinformatics Laboratory, Department of Epidemiology and Data Science, Amsterdam Public Health Research Institute, Amsterdam University Medical Center (UMC), University of Amsterdam, Amsterdam, Netherlands.,Biosystems Data Analysis, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, Netherlands
| | - Bokkyoo Jun
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, LA, United States
| | - Khanh V Do
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, LA, United States
| | - Lieve Moons
- Animal Physiology and Neurobiology, Department of Biology, KU Leuven, Leuven, Belgium
| | - Nicolas G Bazan
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, LA, United States
| | - Paul P Van Veldhoven
- Lipid Biochemistry and Protein Interactions (LIPIT), Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Myriam Baes
- Laboratory of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium
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49
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Bullock J, Polato F, Abu-Asab M, Bernardo-Colón A, Aflaki E, Agbaga MP, Becerra SP. Degradation of Photoreceptor Outer Segments by the Retinal Pigment Epithelium Requires Pigment Epithelium-Derived Factor Receptor (PEDF-R). Invest Ophthalmol Vis Sci 2021; 62:30. [PMID: 33605986 PMCID: PMC7900850 DOI: 10.1167/iovs.62.2.30] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Accepted: 01/19/2021] [Indexed: 12/28/2022] Open
Abstract
Purpose To examine the contribution of pigment epithelium-derived factor receptor (PEDF-R) to the phagocytosis process. Previously, we identified PEDF-R, the protein encoded by the PNPLA2 gene, as a phospholipase A2 in the retinal pigment epithelium (RPE). During phagocytosis, RPE cells ingest abundant phospholipids and protein in the form of photoreceptor outer segment (POS) tips, which are then hydrolyzed. The role of PEDF-R in RPE phagocytosis is not known. Methods Mice in which PNPLA2 was conditionally knocked out (cKO) in the RPE were generated. Mouse RPE/choroid explants were cultured. Human ARPE-19 cells were transfected with siPNPLA2 silencing duplexes. POSs were isolated from bovine retinas. The phospholipase A2 inhibitor bromoenol lactone was used. Transmission electron microscopy, immunofluorescence, lipid labeling, pulse-chase experiments, western blots, and free fatty acid and β-hydroxybutyrate assays were performed. Results The RPE of the cKO mice accumulated lipids, as well as more abundant and larger rhodopsin particles, compared to littermate controls. Upon POS exposure, RPE explants from cKO mice released less β-hydroxybutyrate compared to controls. After POS ingestion during phagocytosis, rhodopsin degradation was stalled both in cells treated with bromoenol lactone and in PNPLA2-knocked-down cells relative to their corresponding controls. Phospholipase A2 inhibition lowered β-hydroxybutyrate release from phagocytic RPE cells. PNPLA2 knockdown also resulted in a decline in fatty acids and β-hydroxybutyrate release from phagocytic RPE cells. Conclusions PEDF-R downregulation delayed POS digestion during phagocytosis. The findings imply that the efficiency of RPE phagocytosis depends on PEDF-R, thus identifying a novel contribution of this protein to POS degradation in the RPE.
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Affiliation(s)
- Jeanee Bullock
- Section of Protein Structure and Function, Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
- Department of Biochemistry and Molecular & Cellular Biology, Georgetown University Medical Center, Washington DC, United States
| | - Federica Polato
- Section of Protein Structure and Function, Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Mones Abu-Asab
- Section of Histopathology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Alexandra Bernardo-Colón
- Section of Protein Structure and Function, Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Elma Aflaki
- Section of Protein Structure and Function, Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Martin-Paul Agbaga
- Departments of Cell Biology and Ophthalmology, Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - S. Patricia Becerra
- Section of Protein Structure and Function, Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
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Mitochondria: The Retina's Achilles' Heel in AMD. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1256:237-264. [PMID: 33848005 DOI: 10.1007/978-3-030-66014-7_10] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Strong experimental evidence from studies in human donor retinas and animal models supports the idea that the retinal pathology associated with age-related macular degeneration (AMD) involves mitochondrial dysfunction and consequent altered retinal metabolism. This chapter provides a brief overview of mitochondrial structure and function, summarizes evidence for mitochondrial defects in AMD, and highlights the potential ramifications of these defects on retinal health and function. Discussion of mitochondrial haplogroups and their association with AMD brings to light how mitochondrial genetics can influence disease outcome. As one of the most metabolically active tissues in the human body, there is strong evidence that disruption in key metabolic pathways contributes to AMD pathology. The section on retinal metabolism reviews cell-specific metabolic differences and how the metabolic interdependence of each retinal cell type creates a unique ecosystem that is disrupted in the diseased retina. The final discussion includes strategies for therapeutic interventions that target key mitochondrial pathways as a treatment for AMD.
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