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Puentes B, Hisey EA, Ferneding M, Ureno VN, Do MAH, Karpinen PM, Luo CC, Thomasy SM, Leonard BC. Development and validation of a method to generate phenol red thread tests. Ocul Surf 2024; 34:262-266. [PMID: 39127389 DOI: 10.1016/j.jtos.2024.08.007] [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: 07/02/2024] [Revised: 08/05/2024] [Accepted: 08/07/2024] [Indexed: 08/12/2024]
Abstract
PURPOSE The aim of this study was to develop and validate a method to generate phenol red thread tests (PRTT) due to the lack of availability of commercial PRTT. METHODS White cotton thread was dyed with phenol red (pH indicator) for 48 h, dried, cut, and sterilized. To validate its wicking ability, the thread was inserted into solutions of varying pH, flanking the pH of healthy tears, for different time intervals. To assess its diagnostic utility, PRTTs were performed in vivo on wildtype and a murine model of evaporative dry eye, acyl-coA: wax alcohol acyltransferase 2 knockout (Awat2 KO) mice. RESULTS Two batches of PRTT were produced that had a similar appearance and function to the commercial product. In vitro testing revealed no significant differences in the wicking kinetics at any time point across the pH solutions for batch 1 and only one difference for batch 2 (pH 7.4 vs 7.8 at 5 s, P = 0.029). When comparing both batches, similar wicking kinetics were found with only two significant differences identified (pH 7.6 at 40 s and pH 7.8 at 35 s, P < 0.01). In vivo, our PRTT yielded similar measurements to the commercial PRTT in wildtype and Awat2 KO mice and detected a significant increase in aqueous tear volume in the Awat2 KO mice (commercial: P = 0.015, our PRTT: P = 0.002). CONCLUSION Our method provides a reproducible diagnostic test that performs similarly to its commercial counterpart in a relevant dry eye model indicating that it can serve as a valid and reliable replacement.
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Affiliation(s)
- Bryan Puentes
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, CA, 95616, USA
| | - Erin A Hisey
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, CA, 95616, USA
| | - Michelle Ferneding
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, CA, 95616, USA
| | - Vanessa N Ureno
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, CA, 95616, USA
| | - Maria A H Do
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, CA, 95616, USA
| | - Paige M Karpinen
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, CA, 95616, USA
| | - Chung-Chih Luo
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, CA, 95616, USA
| | - Sara M Thomasy
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, CA, 95616, USA; Department of Ophthalmology & Vision Science, School of Medicine, University of California Davis, Davis, CA, 95616, USA
| | - Brian C Leonard
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, CA, 95616, USA; Department of Ophthalmology & Vision Science, School of Medicine, University of California Davis, Davis, CA, 95616, USA.
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Wiedemann J, Kashgari G, Lane S, Leonard BC, Knickelbein KE, Andersen B, Jester JV. The effects of age and dysfunction on meibomian gland population dynamics. Ocul Surf 2024; 34:194-209. [PMID: 39122180 DOI: 10.1016/j.jtos.2024.08.005] [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: 04/06/2024] [Revised: 07/11/2024] [Accepted: 08/06/2024] [Indexed: 08/12/2024]
Abstract
PURPOSE While meibomian gland dysfunction (MGD) is widely recognized as a major cause of evaporative dry eye disease, little is known about normal gland differentiation and lipid synthesis or the mechanism underlying gland atrophy and abnormal lipid secretion. The purpose of this study was to use single-cell and spatial transcriptomics to probe changes in cell composition, differentiation, and gene expression associated with two murine models of MGD: age-related gland atrophy in wild-type mice and altered meibum quality in acyl-CoA wax alcohol acyltransferase 2 (Awat2) knockout (KO) mice. METHODS Young (6 month) and old (22 month) wild type, C57Bl/6 mice and young (3 month) and old (13 month) Awat2 KO mice were used in these studies. For single-cell analysis, the tarsal plate was dissected from the upper and lower eyelids, and single cells isolated and submitted to the UCI Genomic Core, while for the spatial analysis frozen tissue sections were shipped to Resolve Biosciences on dry ice and sections probed in duplicate using a meibomian gland specific, 100 gene Molecular Chartography panel. RESULTS Analysis of gene expression patterns identified the stratified expression of lipogenic genes during meibocyte differentiation, which may control the progressive synthesis of meibum lipids; an age-related decrease in meibocytes; and increased immune cell infiltration. Additionally, we detected unique immune cell populations in the Awat2 KO mouse suggesting activation of psoriasis-like, inflammatory pathways perhaps caused by ductal dilation and hyperplasia. CONCLUSION Together these findings support novel mechanism controlling gland function and dysfunction.
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Affiliation(s)
- Julie Wiedemann
- Mathematical, Computational and Systems Biology (MCSB) Program, University of California, Irvine, Irvine, CA, USA
| | - Ghaidaa Kashgari
- Department of Biological Chemistry and Medicine, School of Medicine, University of California, Irvine, Irvine, CA, USA
| | - Shelley Lane
- Department of Ophthalmology and Biomedical Engineering, University of California, Irvine, Irvine, CA, USA
| | - Brian C Leonard
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, Davis, CA, USA; Department of Ophthalmology & Vision Science, School of Medicine, University of California, Davis, Davis, CA, USA
| | - Kelly E Knickelbein
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, Davis, CA, USA
| | - Bogi Andersen
- Mathematical, Computational and Systems Biology (MCSB) Program, University of California, Irvine, Irvine, CA, USA; Department of Biological Chemistry and Medicine, School of Medicine, University of California, Irvine, Irvine, CA, USA.
| | - James V Jester
- Department of Ophthalmology and Biomedical Engineering, University of California, Irvine, Irvine, CA, USA.
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3
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Isom M, Go EP, Desaire H. Enabling Lipidomic Biomarker Studies for Protected Populations by Combining Noninvasive Fingerprint Sampling with MS Analysis and Machine Learning. J Proteome Res 2024; 23:2805-2814. [PMID: 38171506 DOI: 10.1021/acs.jproteome.3c00368] [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] [Indexed: 01/05/2024]
Abstract
Triacylglycerols and wax esters are two lipid classes that have been linked to diseases, including autism, Alzheimer's disease, dementia, cardiovascular disease, dry eye disease, and diabetes, and thus are molecules worthy of biomarker exploration studies. Since triacylglycerols and wax esters make up the majority of skin-surface lipid secretions, a viable sampling method for these potential biomarkers would be that of groomed latent fingerprints. Currently, however, blood-based sampling protocols predominate in the field. The invasiveness of a blood draw limits its utility to protected populations, including children and the elderly. Herein we describe a noninvasive means for sample collection (from fingerprints) paired with fast MS data-acquisition (MassIVE data set MSV000092742) and efficient data analysis via machine learning. Using both supervised and unsupervised classification, we demonstrate the usefulness of this method in determining whether a variable of interest imparts measurable change within the lipidomic data set. As a proof-of-concept, we show that the method is capable of distinguishing between the fingerprints of different individuals as well as between anatomical sebum collection regions. This noninvasive, high-throughput approach enables future lipidomic biomarker researchers to more easily include underrepresented, protected populations, such as children and the elderly, thus moving the field closer to definitive disease diagnoses that apply to all.
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Affiliation(s)
- Madeline Isom
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - Eden P Go
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - Heather Desaire
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
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4
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Beatty CJ, Ruiz-Lozano RE, Quiroga-Garza ME, Perez VL, Jester JV, Saban DR. The Yin and Yang of non-immune and immune responses in meibomian gland dysfunction. Ocul Surf 2024; 32:81-90. [PMID: 38224775 DOI: 10.1016/j.jtos.2024.01.004] [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: 09/24/2023] [Revised: 01/04/2024] [Accepted: 01/12/2024] [Indexed: 01/17/2024]
Abstract
Meibomian gland dysfunction (MGD) is a leading cause of dry eye disease and one of the most common ophthalmic conditions encountered in eye clinics worldwide. These holocrine glands are situated in the eyelid, where they produce specialized lipids, or meibum, needed to lubricate the eye surface and slow tear film evaporation - functions which are critical to preserving high-resolution vision. MGD results in tear instability, rapid tear evaporation, changes in local microflora, and dry eye disease, amongst other pathological entities. While studies identifying the mechanisms of MGD have generally focused on gland obstruction, we now know that age is a major risk factor for MGD that is associated with abnormal cell differentiation and renewal. It is also now appreciated that immune-inflammatory disorders, such as certain autoimmune diseases and atopy, may trigger MGD, as demonstrated through a T cell-driven neutrophil response. Here, we independently discuss the underlying roles of gland and immune related factors in MGD, as well as the integration of these two distinct mechanisms into a unified perspective that may aid future studies. From this unique standpoint, we propose a revised model in which glandular dysfunction and immunopathogenic pathways are not primary versus secondary contributors in MGD, but are fluid, interactive, and dynamic, which we likened to the Yin and Yang of MGD.
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Affiliation(s)
- Cole J Beatty
- Department of Integrative Immunobiology, Duke University School of Medicine, Durham, NC, USA; Duke Eye Center, Duke University School of Medicine, Foster Center for Ocular Immunology at Duke Eye Center, Durham, NC, USA
| | - Raul E Ruiz-Lozano
- Duke Eye Center, Duke University School of Medicine, Foster Center for Ocular Immunology at Duke Eye Center, Durham, NC, USA
| | - Manuel E Quiroga-Garza
- Duke Eye Center, Duke University School of Medicine, Foster Center for Ocular Immunology at Duke Eye Center, Durham, NC, USA
| | - Victor L Perez
- Duke Eye Center, Duke University School of Medicine, Foster Center for Ocular Immunology at Duke Eye Center, Durham, NC, USA.
| | - James V Jester
- Department of Ophthalmology and Biomedical Engineering, Gavin Herbert Eye Institute, University of California Irvine, Irvine, CA, USA.
| | - Daniel R Saban
- Department of Integrative Immunobiology, Duke University School of Medicine, Durham, NC, USA; Duke Eye Center, Duke University School of Medicine, Foster Center for Ocular Immunology at Duke Eye Center, Durham, NC, USA.
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5
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Luo S, Djotyan GP, Joshi R, Juhasz T, Brown DJ, Jester JV. Modeling meibum secretion: Alternatives for obstructive Meibomian Gland Dysfunction (MGD). Ocul Surf 2024; 31:56-62. [PMID: 38042297 DOI: 10.1016/j.jtos.2023.11.005] [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: 08/22/2023] [Revised: 11/07/2023] [Accepted: 11/19/2023] [Indexed: 12/04/2023]
Abstract
PURPOSE While changes in meibum quality are correlated with severity of meibomian gland dysfunction (MGD) and dry eye disease, little is known regarding the mechanics of meibum secretion. The purpose of this study was to develop a finite element model of meibum secretion and evaluate the effect of various factors that might impact meibum delivery to the ocular surface. METHODS A finite element analysis in COMSOL 6.0 was used to simulate the flow of meibum within the gland's terminal excretory duct. Historical normal human meibum rheology data taken over the meibum melting range from fluid (35-40 °C) to solid (25-30 °C) were then used to calculate the minimum yield stress and plastic viscosity of meibum. The effects of meibum melting state, eyelid pressure and terminal duct diameter on meibum flow rates were then systematically investigated. RESULTS The melting state of meibum from liquid to solid was associated with an increase in the minimum yield stress and plastic viscosity that caused an exponential decrease in meibum flow. Modeling also established that there was a linear correlation between meibum flow rate and eyelid pressure needed to express meibum and the 4th power of the terminal duct radius. CONCLUSIONS Our results suggest that changes in the melting state of meibum from fluid to solid, as well as changes in the radius of the terminal excretory duct and the force exerted by the eyelid can lead to dramatic decreases in the flow of meibum. Together these findings suggest alternative mechanisms for meibomian gland obstruction.
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Affiliation(s)
- Shangbang Luo
- Department of Ophthalmology, University of California, Irvine, CA, USA; Department of Biomedical Engineering, University of California, Irvine, CA, USA
| | - Gagik P Djotyan
- Institute for Particle & Nuclear Physics, Wigner Research Center, Budapest, Hungary
| | - Rohan Joshi
- Department of Ophthalmology, University of California, Irvine, CA, USA; Department of Biomedical Engineering, University of California, Irvine, CA, USA
| | - Tibor Juhasz
- Department of Ophthalmology, University of California, Irvine, CA, USA; Department of Biomedical Engineering, University of California, Irvine, CA, USA
| | - Donald J Brown
- Department of Ophthalmology, University of California, Irvine, CA, USA
| | - James V Jester
- Department of Ophthalmology, University of California, Irvine, CA, USA; Department of Biomedical Engineering, University of California, Irvine, CA, USA.
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Yang Y, Zhong J, Cui D, Jensen LD. Up-to-date molecular medicine strategies for management of ocular surface neovascularization. Adv Drug Deliv Rev 2023; 201:115084. [PMID: 37689278 DOI: 10.1016/j.addr.2023.115084] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 08/30/2023] [Accepted: 09/04/2023] [Indexed: 09/11/2023]
Abstract
Ocular surface neovascularization and its resulting pathological changes significantly alter corneal refraction and obstruct the light path to the retina, and hence is a major cause of vision loss. Various factors such as infection, irritation, trauma, dry eye, and ocular surface surgery trigger neovascularization via angiogenesis and lymphangiogenesis dependent on VEGF-related and alternative mechanisms. Recent advances in antiangiogenic drugs, nanotechnology, gene therapy, surgical equipment and techniques, animal models, and drug delivery strategies have provided a range of novel therapeutic options for the treatment of ocular surface neovascularization. In this review article, we comprehensively discuss the etiology and mechanisms of corneal neovascularization and other types of ocular surface neovascularization, as well as emerging animal models and drug delivery strategies that facilitate its management.
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Affiliation(s)
- Yunlong Yang
- Department of Cellular and Genetic Medicine, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China.
| | - Junmu Zhong
- Department of Ophthalmology, Longyan First Hospital Affiliated to Fujian Medical University, Longyan 364000, Fujian Province, China
| | - Dongmei Cui
- Shenzhen Eye Hospital, Jinan University, Shenzhen Eye Institute, Shenzhen 518040, Guangdong Province, China
| | - Lasse D Jensen
- Department of Health, Medicine and Caring Sciences, Division of Diagnostics and Specialist Medicine, Unit of Cardiovascular Medicine, Linköping University, Linköping, Sweden.
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Butovich IA, Wilkerson A, Goggans KR, Belyaeva OV, Kedishvili NY, Yuksel S. Sdr16c5 and Sdr16c6 control a dormant pathway at a bifurcation point between meibogenesis and sebogenesis. J Biol Chem 2023; 299:104725. [PMID: 37075844 PMCID: PMC10206187 DOI: 10.1016/j.jbc.2023.104725] [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: 02/21/2023] [Revised: 03/23/2023] [Accepted: 04/13/2023] [Indexed: 04/21/2023] Open
Abstract
Genes Sdr16c5 and Sdr16c6 encode proteins that belong to a superfamily of short-chain dehydrogenases/reductases (SDR16C5 and SDR16C6). Simultaneous inactivation of these genes in double-KO (DKO) mice was previously shown to result in a marked enlargement of the mouse Meibomian glands (MGs) and sebaceous glands, respectively. However, the exact roles of SDRs in physiology and biochemistry of MGs and sebaceous glands have not been established yet. Therefore, we characterized, for the first time, meibum and sebum of Sdr16c5/Sdr16c6-null (DKO) mice using high-resolution MS and LC. In this study, we demonstrated that the mutation upregulated the overall production of MG secretions (also known as meibogenesis) and noticeably altered their lipidomic profile, but had a more subtle effect on sebogenesis. The major changes in meibum of DKO mice included abnormal accumulation of shorter chain, sebaceous-type cholesteryl esters and wax esters (WEs), and a marked increase in the biosynthesis of monounsaturated and diunsaturated Meibomian-type WEs. Importantly, the MGs of DKO mice maintained their ability to produce typical extremely long chain Meibomian-type lipids at seemingly normal levels. These observations indicated preferential activation of a previously dormant biosynthetic pathway that produce shorter chain, and more unsaturated, sebaceous-type WEs in the MGs of DKO mice, without altering the elongation patterns of their extremely long chain Meibomian-type counterparts. We conclude that the Sdr16c5/Sdr16c6 pair may control a point of bifurcation in one of the meibogenesis subpathways at which biosynthesis of lipids can be redirected toward either abnormal sebaceous-type lipidome or normal Meibomian-type lipidome in WT mice.
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Affiliation(s)
- Igor A Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA; Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
| | - Amber Wilkerson
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Kelli R Goggans
- Department of Biochemistry and Molecular Genetics, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Olga V Belyaeva
- Department of Biochemistry and Molecular Genetics, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Natalia Y Kedishvili
- Department of Biochemistry and Molecular Genetics, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Seher Yuksel
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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Nuwormegbe S, Park NY, Park HJ, Jin Y, Kim SW, Jester JV. Induction of meibocyte differentiation by three-dimensional, matrigel culture of immortalized human meibomian gland epithelial cells to form acinar organoids. Ocul Surf 2022; 26:271-282. [PMID: 36341959 PMCID: PMC10364613 DOI: 10.1016/j.jtos.2022.10.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 09/20/2022] [Accepted: 10/19/2022] [Indexed: 11/05/2022]
Abstract
PURPOSE Recent studies have shown that two-dimensional (2D) culture of primary rabbit and immortalized human meibomian gland epithelial cells (iHMGEC) do not recapitulate normal meibocyte differentiation and fail to express critical enzymes necessary for synthesis of meibum lipids. The purpose of this study was to test the hypothesis that 3D-spheroid culture of iHMGEC can facilitate meibocyte differentiation and induce the expression of acyl-CoA wax-alcohol acyltransferase 2 (AWAT2), shown to be required for synthesis of meibum wax esters. METHODS iHMGEC were suspended in matrigel/basement membrane matrix and grown in proliferation media to form distinct cell clusters or spheroids. Cells were then treated with serum-free, differentiation media (advanced DMEM/F12) with and without FGF10 and synthetic agonists for the nuclear lipid receptor, peroxisome proliferator activator receptor gamma (PPARγ). Cells were then evaluated for differentiation markers using western blotting, immunocytochemistry (ICC) and real-time PCR. Control cells were grown in standard 2D culture systems. RESULTS Under proliferative conditions, 3D culture induced the formation of KRT5+ spheroids that contained a Ki67+/P63+ undifferentiated, basal cell population. When spheroids were switched to differentiation media containing PPARγ agonists, two different organoid populations were detected, a KRT6low population that was AWAT2+/PPARγ+ and a KRT6high population that was AWAT2-/PPARγ-, suggesting that iHMGEC exhibit a dual differentiation potential toward either a ductal or meibocyte organoid phenotype. CONCLUSION The 3D culturing of iHMGEC can induce the formation of both meibocyte and ductal organoids and may thus serve as a better in vitro model system for studying the regulatory mechanisms controlling meibomian gland function.
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Affiliation(s)
- Selikem Nuwormegbe
- Research Institute of Metabolism and Inflammation, Yonsei University, Wonju College of Medicine, Wonju, Ilsan-ro, Gangwon-do, 26426, Republic of Korea
| | - Na-Young Park
- Research Institute of Metabolism and Inflammation, Yonsei University, Wonju College of Medicine, Wonju, Ilsan-ro, Gangwon-do, 26426, Republic of Korea
| | - Hee Joo Park
- Research Institute of Metabolism and Inflammation, Yonsei University, Wonju College of Medicine, Wonju, Ilsan-ro, Gangwon-do, 26426, Republic of Korea
| | - Yeonwoo Jin
- Department of Ophthalmology, Yonsei University, Wonju College of Medicine, Wonju, Ilsan-ro, Gangwon-do, 26426, Republic of Korea
| | - Sun Woong Kim
- Department of Ophthalmology, Yonsei University, Wonju College of Medicine, Wonju, Ilsan-ro, Gangwon-do, 26426, Republic of Korea; Research Institute of Metabolism and Inflammation, Yonsei University, Wonju College of Medicine, Wonju, Ilsan-ro, Gangwon-do, 26426, Republic of Korea.
| | - James V Jester
- Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA, USA.
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Butovich IA, Wilkerson A. Dynamic Changes in the Gene Expression Patterns and Lipid Profiles in the Developing and Maturing Meibomian Glands. Int J Mol Sci 2022; 23:7884. [PMID: 35887230 PMCID: PMC9321132 DOI: 10.3390/ijms23147884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Revised: 07/11/2022] [Accepted: 07/13/2022] [Indexed: 11/30/2022] Open
Abstract
Meibomian glands (MGs) and their holocrine secretion-meibum-play crucial roles in the physiology of the eye, providing protection from environmental factors and desiccation, among other functions. Importantly, aging was implicated in the deterioration of the morphology and functions of MGs, and the quantity and quality of meibum they produce, leading to a loss of its protective properties, while the meibum of young individuals and experimental animals provide ample protection to the eye. Currently, the molecular mechanisms of meibum biosynthesis (termed meibogenesis) are not fully understood. To characterize the physiological changes in developing and maturing MGs, we studied the lipidomes and transcriptomes of mouse MGs ranging from newborns to adults. The results revealed a gradual increase in the critical genes of meibogenesis (such as Elovl3, Elovl4, Awat2, and Soat1, among others) that positively correlated with the biosynthesis of their respective lipid products. The MG transcriptomes of young and adult mice were also analyzed using single-cell RNA sequencing. These experiments revealed the existence of multiple unique populations of MG cells (meibocytes, epithelial cells, and others) with specific combinations of genes that encode meibogenesis-related proteins, and identified clusters and subclusters of cells that were tentatively classified as meibocytes at different stages of differentiation/maturation, or their progenitor cells. A hypothesis was formulated that these cells may produce different types of lipids, and contribute differentially to the Meibomian lipidome.
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Affiliation(s)
- Igor A. Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA;
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10
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Association of Serum Lipid Level with Meibum Biosynthesis and Meibomian Gland Dysfunction: A Review. J Clin Med 2022; 11:jcm11144010. [PMID: 35887773 PMCID: PMC9323051 DOI: 10.3390/jcm11144010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 06/27/2022] [Accepted: 07/05/2022] [Indexed: 11/16/2022] Open
Abstract
The primary role of meibomian glands (MGs) is to actively synthesize and secret lipids and proteins spread onto the tear film, and the glandular lipids promote tear stability, prevent evaporation, and reduce friction. Meibomian gland dysfunction (MGD) is the leading cause of dry eye disease and one of the most common ophthalmic problems worldwide. MGs are densely innervated and regulated by hormones and growth factors. However, since the polar and nonpolar lipids are produced through processes in MGs that are not completely understood, a relevant question has been raised: Would the altered systemic lipids metabolism affect the physiology and structure of MGs? This review introduces the recent update regarding the relationships between serum lipid and MGD in clinical and basic research while providing answers to this question. A causal relationship remains to be established; however, serum lipid level or dyslipidemia may be related to MGD directly or indirectly, or both. Further studies are warranted to establish the role of serum lipid level and meibocyte differentiation/maturation and lipid synthesis.
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11
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Widjaja-Adhi MAK, Kolesnikov AV, Vasudevan S, Park PSH, Kefalov VJ, Golczak M. Acyl-CoA:wax alcohol acyltransferase 2 modulates the cone visual cycle in mouse retina. FASEB J 2022; 36:e22390. [PMID: 35665537 DOI: 10.1096/fj.202101855rrr] [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: 12/01/2021] [Revised: 05/12/2022] [Accepted: 05/23/2022] [Indexed: 11/11/2022]
Abstract
The daylight and color vision of diurnal vertebrates depends on cone photoreceptors. The capability of cones to operate and respond to changes in light brightness even under high illumination is attributed to their fast rate of recovery to the ground photosensitive state. This process requires the rapid replenishing of photoisomerized visual chromophore (11-cis-retinal) to regenerate cone visual pigments. Recently, several gene candidates have been proposed to contribute to the cone-specific retinoid metabolism, including acyl-CoA wax alcohol acyltransferase 2 (AWAT2, aka MFAT). Here, we evaluated the role of AWAT2 in the regeneration of visual chromophore by the phenotypic characterization of Awat2-/- mice. The global absence of AWAT2 enzymatic activity did not affect gross retinal morphology or the rate of visual chromophore regeneration by the canonical RPE65-dependent visual cycle. Analysis of Awat2 expression indicated the presence of the enzyme throughout the murine retina, including the retinal pigment epithelium (RPE) and Müller cells. Electrophysiological recordings revealed reduced maximal rod and cone dark-adapted responses in AWAT2-deficient mice compared to control mice. While rod dark adaptation was not affected by the lack of AWAT2, M-cone dark adaptation both in isolated retina and in vivo was significantly suppressed. Altogether, these results indicate that while AWAT2 is not required for the normal operation of the canonical visual cycle, it is a functional component of the cone-specific visual chromophore regenerative pathway.
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Affiliation(s)
| | - Alexander V Kolesnikov
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, California, USA
| | - Sreelakshmi Vasudevan
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio, USA
| | - Paul S-H Park
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio, USA
| | - Vladimir J Kefalov
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, California, USA.,Department of Physiology and Biophysics, University of California, Irvine, California, USA
| | - Marcin Golczak
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio, USA.,Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
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Asiedu K. Candidate Molecular Compounds as Potential Indicators for Meibomian Gland Dysfunction. Front Med (Lausanne) 2022; 9:873538. [PMID: 35685417 PMCID: PMC9170961 DOI: 10.3389/fmed.2022.873538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 04/08/2022] [Indexed: 11/16/2022] Open
Abstract
Meibomian gland dysfunction (MGD) is the leading cause of dry eye disease throughout the world. Studies have shown that several molecules in meibum, including but not limited to interleukins, amino acids, cadherins, eicosanoids, carbohydrates, and proteins, are altered in meibomian gland dysfunction compared with healthy normal controls. Some of these molecules such as antileukoproteinase, phospholipase A2, and lactoperoxidase also show differences in concentrations in tears between meibomian gland dysfunction and dry eye disease, further boosting hopes as candidate biomarkers. MGD is a complex condition, making it difficult to distinguish patients using single biomarkers. Therefore, multiple biomarkers forming a multiplex panel may be required. This review aims to describe molecules comprising lipids, proteins, and carbohydrates with the potential of serving various capacities as monitoring, predictive, diagnostic, and risk biomarkers for meibomian gland dysfunction.
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Domergue F, Miklaszewska M. The production of wax esters in transgenic plants:
towards a sustainable source of bio-lubricants. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:2817-2834. [PMID: 35560197 PMCID: PMC9113324 DOI: 10.1093/jxb/erac046] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2022] [Accepted: 02/03/2022] [Indexed: 05/08/2023]
Abstract
Wax esters are high-value compounds used as feedstocks for the production of lubricants, pharmaceuticals, and cosmetics. Currently, they are produced mostly from fossil reserves using chemical synthesis, but this cannot meet increasing demand and has a negative environmental impact. Natural wax esters are also obtained from Simmondsia chinensis (jojoba) but comparably in very low amounts and expensively. Therefore, metabolic engineering of plants, especially of the seed storage lipid metabolism of oil crops, represents an attractive strategy for renewable, sustainable, and environmentally friendly production of wax esters tailored to industrial applications. Utilization of wax ester-synthesizing enzymes with defined specificities and modulation of the acyl-CoA pools by various genetic engineering approaches can lead to obtaining wax esters with desired compositions and properties. However, obtaining high amounts of wax esters is still challenging due to their negative impact on seed germination and yield. In this review, we describe recent progress in establishing non-food-plant platforms for wax ester production and discuss their advantages and limitations as well as future prospects.
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Affiliation(s)
- Frédéric Domergue
- Univ. Bordeaux, CNRS, LBM, UMR 5200, F-33140 Villenave d’Ornon, France
| | - Magdalena Miklaszewska
- Department of Functional and Evolutionary Ecology, Division of Molecular Systems Biology (MOSYS), Faculty of Life Sciences, University of Vienna, Djerassiplatz 1, 1030, Vienna, Austria
- Department of Plant Physiology and Biotechnology, University of Gdańsk, Wita Stwosza 59, 80-308, Gdańsk, Poland
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Widjaja-Adhi MAK, Chao K, Golczak M. Mouse models in studies on the etiology of evaporative dry eye disease. Exp Eye Res 2022; 219:109072. [DOI: 10.1016/j.exer.2022.109072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Revised: 03/28/2022] [Accepted: 04/05/2022] [Indexed: 11/26/2022]
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Otsuka K, Sawai-Ogawa M, Kihara A. Formation of fatty alcohols-components of meibum lipids-by the fatty acyl-CoA reductase FAR2 is essential for dry eye prevention. FASEB J 2022; 36:e22216. [PMID: 35238077 DOI: 10.1096/fj.202101733r] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 02/07/2022] [Accepted: 02/08/2022] [Indexed: 12/15/2022]
Abstract
Various lipids (mainly meibum lipids secreted by the meibomian glands) are present in the tear film lipid layer and play important roles in tear stability and the health of the cornea and conjunctiva. Many meibum lipids contain fatty alcohols (FAls) with chain lengths ≥C24, but the fatty acyl-CoA reductases (FARs) that produce them remain unclear. Here, using cell-based assays, we found that the two FAR isozymes (FAR1 and FAR2) show different substrate specificities: FAR1 and FAR2 are involved in the production of C16-C18 and ≥C20 FAls, respectively. Next, we generated Far2 knockout (KO) mice and examined their dry eye phenotype and meibum lipid composition. These mice showed a severe dry eye phenotype, characterized by plugged meibomian gland orifices, corneal damage, and tear film instability. The plugging was attributed to an increase in the melting point of the meibum lipids. Liquid chromatography coupled with tandem mass spectrometry revealed that FAl-containing meibum lipids (wax monoesters and types 1ω, 2α, and 2ω wax diesters) with a hydroxyl group at position 1 were almost completely absent in Far2 KO mice. The levels of di-unsaturated (O-acyl)-ω-hydroxy fatty acids were higher in Far2 KO mice than in wild type mice, but those of tri-unsaturated ones were comparable, suggesting the presence of two synthesis pathways for type 1ω wax diesters. These results indicate the importance of FAl-containing meibum lipids in the formation of a functional tear film lipid layer. In addition, our study provides clues to the molecular mechanism of the biosynthesis of meibum lipids.
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Affiliation(s)
- Kento Otsuka
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Megumi Sawai-Ogawa
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Akio Kihara
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
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16
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Expression of Acyl-CoA wax-alcohol acyltransferase 2 (AWAT2) by human and rabbit meibomian glands and meibocytes. Ocul Surf 2021; 23:60-70. [PMID: 34838721 PMCID: PMC10393063 DOI: 10.1016/j.jtos.2021.11.010] [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: 07/26/2021] [Revised: 11/18/2021] [Accepted: 11/20/2021] [Indexed: 11/22/2022]
Abstract
PURPOSE Previously, we showed that Acyl-CoA wax-alcohol acyltransferase 2 (AWAT2), an essential enzyme required for meibum wax ester synthesis, was not expressed by immortalized human meibomian gland epithelial cells (hMGEC) in culture. To begin to understand the mechanisms controlling AWAT2 expression, we have analyzed its expression in human and rabbit meibomian glands and cultured meibocytes. METHODS Rabbit meibocyte progenitor cells (rMPC) were first grown in Cnt-BM.1 basal medium (Cellntec) supplemented with rhEGF, FGF10, and ROCK inhibitor (Y-27632 dihydrochloride), and then passed at 70-80% confluency with Accutase. Differentiation of rMPC to meibocytes (rMC) was induced by removal of Y-27632 and addition of 1 mM calcium with and without PPARγ agonists. RNA from the tissue, primary, passaged rMPC and differentiated rMC were obtained for AWAT2 qPCR analysis. Proteins and cells were evaluated for western blotting and neutral lipid synthesis, respectively. For comparison, human meibomian glands were separated for RNA and protein analysis. hMGEC was cultured to collect RNA and protein. RESULTS Rabbit rMPCs were successfully grown, passaged, and differentiated, showing a significant increase in lipid droplet accumulation. AWAT2 RNA was highly expressed in tissue but showed a -16.9 log2 fold decrease in primary and passaged rMPCs and was not induced by differentiation to rMC. By comparison, human meibomian glands showed high expression of AWAT2, and hMGEC expressed non-detectable levels of AWAT2 transcripts or protein. CONCLUSIONS AWAT2 expression is lost in cultured rMPC and rMC suggesting that cells in culture do not undergo complete meibocyte differentiation and require yet to be identified culture conditions.
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Butovich IA, Wilkerson A, Yuksel S. Differential effects of dietary cholesterol and triglycerides on the lipid homeostasis in Meibomian glands. J Steroid Biochem Mol Biol 2021; 211:105894. [PMID: 33819631 PMCID: PMC8217181 DOI: 10.1016/j.jsbmb.2021.105894] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Revised: 03/21/2021] [Accepted: 03/31/2021] [Indexed: 12/20/2022]
Abstract
Exocrine Meibomian glands (MG) play a central role in the ocular surface physiology by producing meibum - a lipid secretion composed of cholesteryl esters (CE), cholesterol (Chl), triacylgycerols (TAG), waxes and other types of lipids. MG were previously shown to synthesize Meibomian lipids (ML) in situ via a complex array of reactions termed meibogenesis. However, questions remain about the role of dietary lipids in meibogenesis. To establish if dietary Chl (DC) and TAG (DT) can participate in meibogenesis, we studied mice whose diet was supplemented with trace amounts of deuterated Chl (2H-Chl) and 13C-labeled triolein (13C-TO), and the products of their biosynthetic transformations were analyzed using LC/MS. We demonstrated that 2H-Chl, but not 13C-TO, could be directly incorporated into meibum. Furthermore, 2H-Chl was esterified into MG-specific ultra long 2H-CE, which were vastly different from plasma CE and 2H-CE. The measured 2H-Chl/Chl and 2H-CE/CE ratios in meibum increased in a time-dependent manner reaching ∼5% and ∼1.2 %, respectively. The 2H-Chl/2H-CE ratio was about 3.5x higher than that for endogenous unlabeled Chl and CE, indicating accumulation of 2H-Chl in meibum. The elongation pattern of Meibomian 2H-CE closely replicated that of unlabeled CE. On the other hand, 13C-TO was not detected in any of the ML samples as an intact lipid or its metabolized/hydrolyzed products. We conclude that DC can be directly esterified into MG-specific CE, while DT undergo extensive catabolic transformations before reaching MG. These findings demonstrate that DC can have a direct impact on MG and ocular surface lipid homeostasis and pathophysiology.
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Affiliation(s)
- Igor A Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX, 75390-9057, USA; The Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, TX, 75390-9057, USA.
| | - Amber Wilkerson
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX, 75390-9057, USA
| | - Seher Yuksel
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX, 75390-9057, USA
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Sawai M, Watanabe K, Tanaka K, Kinoshita W, Otsuka K, Miyamoto M, Sassa T, Kihara A. Diverse meibum lipids produced by Awat1 and Awat2 are important for stabilizing tear film and protecting the ocular surface. iScience 2021; 24:102478. [PMID: 34113821 PMCID: PMC8169949 DOI: 10.1016/j.isci.2021.102478] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 02/17/2021] [Accepted: 04/23/2021] [Indexed: 12/16/2022] Open
Abstract
A lipid layer consisting of meibum lipids exists in the tear film and functions in preventing dry eye disease. Although the meibum lipids include diverse lipid classes, the synthesis pathway and role of each class remain largely unknown. Here, we created single and double knockout (KO and DKO, respectively) mice for the two acyl-CoA wax alcohol acyltransferases (Awat1 and Awat2) and investigated their dry eye phenotypes and meibum lipid composition. Awat2 KO and DKO mice exhibited severe dry eye with meibomian gland dysfunction, whereas Awat1 KO mice had mild dry eye. In these mice, specific meibum lipid classes were reduced: (O-acyl)-ω-hydroxy fatty acids and type 1ω wax diesters in Awat1 KO mice, wax monoesters and types 1ω and 2ω wax diesters in Awat2 KO mice, and most of these in DKO mice. Our findings reveal that Awat1 and Awat2 show characteristic substrate specificity and together produce diverse meibum lipids.
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Affiliation(s)
- Megumi Sawai
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Kita 12-jo, Nishi 6-chome, Kita-ku 060-0812, Japan
| | - Keisuke Watanabe
- Pharmaceutical Research Laboratories, Research and Development Headquarters, Lion Corporation, Odawara 256-0811, Japan
| | - Kana Tanaka
- Pharmaceutical Research Laboratories, Research and Development Headquarters, Lion Corporation, Odawara 256-0811, Japan
| | - Wataru Kinoshita
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Kita 12-jo, Nishi 6-chome, Kita-ku 060-0812, Japan
| | - Kento Otsuka
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Kita 12-jo, Nishi 6-chome, Kita-ku 060-0812, Japan
| | - Masatoshi Miyamoto
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Kita 12-jo, Nishi 6-chome, Kita-ku 060-0812, Japan
| | - Takayuki Sassa
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Kita 12-jo, Nishi 6-chome, Kita-ku 060-0812, Japan
| | - Akio Kihara
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Kita 12-jo, Nishi 6-chome, Kita-ku 060-0812, Japan
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Silvaroli JA, Plau J, Adams CH, Banerjee S, Widjaja-Adhi MAK, Blaner WS, Golczak M. Molecular basis for the interaction of cellular retinol binding protein 2 (CRBP2) with nonretinoid ligands. J Lipid Res 2021; 62:100054. [PMID: 33631211 PMCID: PMC8010219 DOI: 10.1016/j.jlr.2021.100054] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 02/06/2021] [Accepted: 02/17/2021] [Indexed: 01/14/2023] Open
Abstract
Present in the small intestine, cellular retinol binding protein 2 (CRBP2) plays an important role in the uptake, transport, and metabolism of dietary retinoids. However, the recent discovery of the interactions of CRBP2 with 2-arachidonoylglycerol and other monoacylglycerols (MAGs) suggests the broader involvement of this protein in lipid metabolism and signaling. To better understand the physiological role of CRBP2, we determined its protein-lipid interactome using a fluorescence-based retinol replacement assay adapted for a high-throughput screening format. By examining chemical libraries of bioactive lipids, we provided evidence for the selective interaction of CRBP2 with a subset of nonretinoid ligands with the highest affinity for sn-1 and sn-2 MAGs that contain polyunsaturated C18-C20 acyl chains. We also elucidated the structure-affinity relationship for nonretinoid ligands of this protein. We further dissect the molecular basis for this ligand's specificity by analyzing high-resolution crystal structures of CRBP2 in complex with selected derivatives of MAGs. Finally, we identify T51 and V62 as key amino acids that enable the broadening of ligand selectivity to MAGs in CRBP2 as compared with retinoid-specific CRBP1. Thus, our study provides the molecular framework for understanding the lipid selectivity and diverse functions of CRBPs in controlling lipid homeostasis.
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Affiliation(s)
- Josie A Silvaroli
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Jacqueline Plau
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Charlie H Adams
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Surajit Banerjee
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, USA; Northeastern Collaborative Access Team, Argonne National Laboratory, Argonne, IL, USA
| | | | - William S Blaner
- Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Marcin Golczak
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA; Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA.
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Butovich IA, Wilkerson A, Yuksel S. Depletion of Cholesteryl Esters Causes Meibomian Gland Dysfunction-Like Symptoms in a Soat1-Null Mouse Model. Int J Mol Sci 2021; 22:1583. [PMID: 33557318 PMCID: PMC7915537 DOI: 10.3390/ijms22041583] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 02/01/2021] [Accepted: 02/01/2021] [Indexed: 02/08/2023] Open
Abstract
Previous studies on ablation of several key genes of meibogenesis related to fatty acid elongation, omega oxidation, and esterification into wax esters have demonstrated that inactivation of any of them led to predicted changes in the meibum lipid profiles and caused severe abnormalities in the ocular surface and Meibomian gland (MG) physiology and morphology. In this study, we evaluated the effects of Soat1 ablation that were expected to cause depletion of the second largest class of Meibomian lipids (ML)-cholesteryl esters (CE)-in a mouse model. ML of the Soat1-null mice were examined using liquid chromatography high-resolution mass spectrometry and compared with those of Soat1+/- and wild-type mice. Complete suppression of CE biosynthesis and simultaneous accumulation of free cholesterol (Chl) were observed in Soat1-null mice, while Soat1+/- mutants had normal Chl and CE profiles. The total arrest of the CE biosynthesis in response to Soat1 ablation transformed Chl into the dominant lipid in meibum accounting for at least 30% of all ML. The Soat1-null mice had clear manifestations of dry eye and MG dysfunction. Enrichment of meibum with Chl and depletion of CE caused plugging of MG orifices, increased meibum rigidity and melting temperature, and led to a massive accumulation of lipid deposits around the eyes of Soat1-null mice. These findings illustrate the role of Soat1/SOAT1 in the lipid homeostasis and pathophysiology of MG.
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Affiliation(s)
- Igor A. Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA; (A.W.); (S.Y.)
- The Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA
| | - Amber Wilkerson
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA; (A.W.); (S.Y.)
| | - Seher Yuksel
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA; (A.W.); (S.Y.)
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