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Huang D, Kidd JM, Zou Y, Wu X, Li N, Gehr TWB, Li PL, Li G. Podocyte-specific silencing of acid sphingomyelinase gene to abrogate hyperhomocysteinemia-induced NLRP3 inflammasome activation and glomerular inflammation. Am J Physiol Renal Physiol 2024; 326:F988-F1003. [PMID: 38634138 DOI: 10.1152/ajprenal.00195.2023] [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: 07/13/2023] [Revised: 04/11/2024] [Accepted: 04/16/2024] [Indexed: 04/19/2024] Open
Abstract
Acid sphingomyelinase (ASM) has been reported to increase tissue ceramide and thereby mediate hyperhomocysteinemia (hHcy)-induced glomerular nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasome activation, inflammation, and sclerosis. In the present study, we tested whether somatic podocyte-specific silencing of Smpd1 gene (mouse ASM gene code) attenuates hHcy-induced NLRP3 inflammasome activation and associated extracellular vesicle (EV) release in podocytes and thereby suppresses glomerular inflammatory response and injury. In vivo, somatic podocyte-specific Smpd1 gene silencing almost blocked hHcy-induced glomerular NLRP3 inflammasome activation in Podocre (podocyte-specific expression of cre recombinase) mice compared with control littermates. By nanoparticle tracking analysis (NTA), floxed Smpd1 shRNA transfection was found to abrogate hHcy-induced elevation of urinary EV excretion in Podocre mice. In addition, Smpd1 gene silencing in podocytes prevented hHcy-induced immune cell infiltration into glomeruli, proteinuria, and glomerular sclerosis in Podocre mice. Such protective effects of podocyte-specific Smpd1 gene silencing were mimicked by global knockout of Smpd1 gene in Smpd1-/- mice. On the contrary, podocyte-specific Smpd1 gene overexpression exaggerated hHcy-induced glomerular pathological changes in Smpd1trg/Podocre (podocyte-specific Smpd1 gene overexpression) mice, which were significantly attenuated by transfection of floxed Smpd1 shRNA. In cell studies, we also confirmed that Smpd1 gene knockout or silencing prevented homocysteine (Hcy)-induced elevation of EV release in the primary cultures of podocyte isolated from Smpd1-/- mice or podocytes of Podocre mice transfected with floxed Smpd1 shRNA compared with WT/WT podocytes. Smpd1 gene overexpression amplified Hcy-induced EV secretion from podocytes of Smpd1trg/Podocre mice, which was remarkably attenuated by transfection of floxed Smpd1 shRNA. Mechanistically, Hcy-induced elevation of EV release from podocytes was blocked by ASM inhibitor (amitriptyline, AMI), but not by NLRP3 inflammasome inhibitors (MCC950 and glycyrrhizin, GLY). Super-resolution microscopy also showed that ASM inhibitor, but not NLRP3 inflammasome inhibitors, prevented the inhibition of lysosome-multivesicular body interaction by Hcy in podocytes. Moreover, we found that podocyte-derived inflammatory EVs (released from podocytes treated with Hcy) induced podocyte injury, which was exaggerated by T cell coculture. Interstitial infusion of inflammatory EVs into renal cortex induced glomerular injury and immune cell infiltration. In conclusion, our findings suggest that ASM in podocytes plays a crucial role in the control of NLRP3 inflammasome activation and inflammatory EV release during hHcy and that the development of podocyte-specific ASM inhibition or Smpd1 gene silencing may be a novel therapeutic strategy for treatment of hHcy-induced glomerular disease with minimized side effect.NEW & NOTEWORTHY In the present study, we tested whether podocyte-specific silencing of Smpd1 gene attenuates hyperhomocysteinemia (hHcy)-induced nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasome activation and associated inflammatory extracellular vesicle (EV) release in podocytes and thereby suppresses glomerular inflammatory response and injury. Our findings suggest that acid sphingomyelinase (ASM) in podocytes plays a crucial role in the control of NLRP3 inflammasome activation and inflammatory EV release during hHcy. Based on our findings, it is anticipated that the development of podocyte-specific ASM inhibition or Smpd1 gene silencing may be a novel therapeutic strategy for treatment of hHcy-induced glomerular disease with minimized side effects.
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Affiliation(s)
- Dandan Huang
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, Virginia, United States
| | - Jason M Kidd
- Division of Nephrology, School of Medicine, Virginia Commonwealth University, Richmond, Virginia, United States
| | - Yao Zou
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, Virginia, United States
| | - Xiaoyuan Wu
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, Virginia, United States
| | - Ningjun Li
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, Virginia, United States
| | - Todd W B Gehr
- Division of Nephrology, School of Medicine, Virginia Commonwealth University, Richmond, Virginia, United States
| | - Pin-Lan Li
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, Virginia, United States
| | - Guangbi Li
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, Virginia, United States
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Bal Topcu D, Er B, Ozcan F, Aslan M, Coplu L, Lay I, Oztas Y. Decreased plasma levels of sphingolipids and total cholesterol in adult cystic fibrosis patients. Prostaglandins Leukot Essent Fatty Acids 2023; 197:102590. [PMID: 37741047 DOI: 10.1016/j.plefa.2023.102590] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 09/01/2023] [Accepted: 09/15/2023] [Indexed: 09/25/2023]
Abstract
BACKGROUND Sphingolipid species in the lung epithelium have a critical role for continuity of membrane structure, vesicular transport, and cell survival. Sphingolipid species were reported to have a role in the inflammatory etiology of cystic fibrosis by previous work. The aim of the study was to investigate the levels of plasma sphingomyelin and ceramide in adult cystic fibrosis (CF) patients and compared with healthy controls. MATERIALS AND METHODS Blood samples were obtained from CF patients at exacerbation (n = 15), discharge (n = 13) and stable periods (n = 11). Healthy individuals (n = 15) of similar age served as control. Levels of C16-C24 sphingomyelin and C16-C24 ceramide were measured in the plasma by LC-MS/MS. Also, cholesterol and triglyceride levels were determined in plasma samples of the patients at stable period. RESULTS All measured sphingomyelin and ceramide levels in all periods of CF patients were significantly lower than healthy controls except C16 sphingomyelin level in the stable period. However, plasma Cer and SM levels among exacerbation, discharge, and stable periods of CF were not different. CF patients had significantly lower cholesterol levels compared to healthy individuals. We found significant correlation of cholesterol with C16 sphingomyelin. CONCLUSION We observed lower plasma Cer and SM levels in adult CF patients at exacerbation, discharge, and stable periods compared to healthy controls. We didn't find any significant difference between patient Cer and SM levels among these three periods. Our limited number of patients might have resulted with this statistical insignificance. However, percentage of SM16 levels were increased at discharge compared to exacerbation levels, while percentage of Cer16 and Cer 20 decreased at stable compared to exacerbation. Inclusion of a larger number of CF patients in such a follow up study may better demonstrate any possible difference between exacerbation, discharge, and stable periods.
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Affiliation(s)
- Dilara Bal Topcu
- Hacettepe University, Faculty of Medicine, Department of Medical Biochemistry, 06100, Ankara, Turkey
| | - Berrin Er
- Hacettepe University, Faculty of Medicine, Department of Chest Diseases, 06100, Ankara, Turkey
| | - Filiz Ozcan
- Antalya Bilim University, Vocational School of Health Services, Department of Dialysis, 07190, Antalya, Turkey
| | - Mutay Aslan
- Akdeniz University, Faculty of Medicine, Department of Medical Biochemistry, Konyaaltı, 07070, Antalya, Turkey
| | - Lutfi Coplu
- Hacettepe University, Faculty of Medicine, Department of Chest Diseases, 06100, Ankara, Turkey
| | - Incilay Lay
- Hacettepe University, Faculty of Medicine, Department of Medical Biochemistry, 06100, Ankara, Turkey
| | - Yesim Oztas
- Hacettepe University, Faculty of Medicine, Department of Medical Biochemistry, 06100, Ankara, Turkey.
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3
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Lee M, Lee SY, Bae YS. Functional roles of sphingolipids in immunity and their implication in disease. Exp Mol Med 2023; 55:1110-1130. [PMID: 37258585 PMCID: PMC10318102 DOI: 10.1038/s12276-023-01018-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 03/14/2023] [Accepted: 03/16/2023] [Indexed: 06/02/2023] Open
Abstract
Sphingolipids, which are components of cellular membranes and organ tissues, can be synthesized or degraded to modulate cellular responses according to environmental cues, and the balance among the different sphingolipids is important for directing immune responses, regardless of whether they originate, as intra- or extracellular immune events. Recent progress in multiomics-based analyses and methodological approaches has revealed that human health and diseases are closely related to the homeostasis of sphingolipid metabolism, and disease-specific alterations in sphingolipids and related enzymes can be prognostic markers of human disease progression. Accumulating human clinical data from genome-wide association studies and preclinical data from disease models provide support for the notion that sphingolipids are the missing pieces that supplement our understanding of immune responses and diseases in which the functions of the involved proteins and nucleotides have been established. In this review, we analyze sphingolipid-related enzymes and reported human diseases to understand the important roles of sphingolipid metabolism. We discuss the defects and alterations in sphingolipid metabolism in human disease, along with functional roles in immune cells. We also introduce several methodological approaches and provide summaries of research on sphingolipid modulators in this review that should be helpful in studying the roles of sphingolipids in preclinical studies for the investigation of experimental and molecular medicines.
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Affiliation(s)
- Mingyu Lee
- Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University, Seoul, 06355, Republic of Korea
| | - Suh Yeon Lee
- Department of Biological Sciences, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Yoe-Sik Bae
- Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University, Seoul, 06355, Republic of Korea.
- Department of Biological Sciences, Sungkyunkwan University, Suwon, 16419, Republic of Korea.
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Tse CM, Zhang Z, Lin R, Sarker R, Donowitz M, Singh V. The Air-Liquid Interface Reorganizes Membrane Lipids and Enhances the Recruitment of Slc26a3 to Lipid-Rich Domains in Human Colonoid Monolayers. Int J Mol Sci 2023; 24:8273. [PMID: 37175979 PMCID: PMC10179158 DOI: 10.3390/ijms24098273] [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: 04/11/2023] [Revised: 05/02/2023] [Accepted: 05/03/2023] [Indexed: 05/15/2023] Open
Abstract
Cholesterol-rich membrane domains, also called lipid rafts (LRs), are specialized membrane domains that provide a platform for intracellular signal transduction. Membrane proteins often cluster in LRs that further aggregate into larger platform-like structures that are enriched in ceramides and are called ceramide-rich platforms (CRPs). The role of CRPs in the regulation of intestinal epithelial functions remains unknown. Down-regulated in adenoma (DRA) is an intestinal Cl-/HCO3- antiporter that is enriched in LRs. However, little is known regarding the mechanisms involved in the regulation of DRA activity. The air-liquid interface (ALI) was created by removing apical media for a specified number of days; from 12-14 days post-confluency, Caco-2/BBe cells or a colonoid monolayer were grown as submerged cultures. Confocal imaging was used to examine the dimensions of membrane microdomains that contained DRA. DRA expression and activity were enhanced in Caco-2/BBe cells and human colonoids using an ALI culture method. ALI causes an increase in acid sphingomyelinase (ASMase) activity, an enzyme responsible for enhancing ceramide content in the plasma membrane. ALI cultures expressed a larger number of DRA-containing platforms with dimensions >2 µm compared to cells grown as submerged cultures. ASMase inhibitor, desipramine, disrupted CRPs and reduced the ALI-induced increase in DRA expression in the apical membrane. Exposing normal human colonoid monolayers to ALI increased the ASMase activity and enhanced the differentiation of colonoids along with basal and forskolin-stimulated DRA activities. ALI increases DRA activity and expression by increasing ASMase activity and platform formation in Caco-2/BBe cells and by enhancing the differentiation of colonoids.
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Affiliation(s)
- C. Ming Tse
- Division of Gastroenterology & Hepatology, Department of Medicine, School of Medicine, The Johns Hopkins University, 720 Rutland Avenue, 933 Ross Research Building, Baltimore, MD 21205, USA
| | - Zixin Zhang
- Division of Gastroenterology & Hepatology, Department of Medicine, School of Medicine, The Johns Hopkins University, 720 Rutland Avenue, 933 Ross Research Building, Baltimore, MD 21205, USA
| | - Ruxian Lin
- Division of Gastroenterology & Hepatology, Department of Medicine, School of Medicine, The Johns Hopkins University, 720 Rutland Avenue, 933 Ross Research Building, Baltimore, MD 21205, USA
| | - Rafiquel Sarker
- Division of Gastroenterology & Hepatology, Department of Medicine, School of Medicine, The Johns Hopkins University, 720 Rutland Avenue, 933 Ross Research Building, Baltimore, MD 21205, USA
| | - Mark Donowitz
- Division of Gastroenterology & Hepatology, Department of Medicine, School of Medicine, The Johns Hopkins University, 720 Rutland Avenue, 933 Ross Research Building, Baltimore, MD 21205, USA
- Department of Cellular and Molecular Physiology, School of Medicine, The Johns Hopkins University, Baltimore, MD 21205, USA
| | - Varsha Singh
- Division of Gastroenterology & Hepatology, Department of Medicine, School of Medicine, The Johns Hopkins University, 720 Rutland Avenue, 933 Ross Research Building, Baltimore, MD 21205, USA
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Wang J, Chen YL, Li YK, Chen DK, He JF, Yao N. Functions of Sphingolipids in Pathogenesis During Host-Pathogen Interactions. Front Microbiol 2021; 12:701041. [PMID: 34408731 PMCID: PMC8366399 DOI: 10.3389/fmicb.2021.701041] [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: 04/27/2021] [Accepted: 06/21/2021] [Indexed: 12/23/2022] Open
Abstract
Sphingolipids are a class of membrane lipids that serve as vital structural and signaling bioactive molecules in organisms ranging from yeast to animals. Recent studies have emphasized the importance of sphingolipids as signaling molecules in the development and pathogenicity of microbial pathogens including bacteria, fungi, and viruses. In particular, sphingolipids play key roles in regulating the delicate balance between microbes and hosts during microbial pathogenesis. Some pathogens, such as bacteria and viruses, harness host sphingolipids to promote development and infection, whereas sphingolipids from both the host and pathogen are involved in fungus-host interactions. Moreover, a regulatory role for sphingolipids has been described, but their effects on host physiology and metabolism remain to be elucidated. Here, we summarize the current state of knowledge about the roles of sphingolipids in pathogenesis and interactions with host factors, including how sphingolipids modify pathogen and host metabolism with a focus on pathogenesis regulators and relevant metabolic enzymes. In addition, we discuss emerging perspectives on targeting sphingolipids that function in host-microbe interactions as new therapeutic strategies for infectious diseases.
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Affiliation(s)
- Jian Wang
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resource, School of Agriculture, Sun Yat-sen University, Guangzhou, China
| | - Yi-Li Chen
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resource, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Yong-Kang Li
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resource, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Ding-Kang Chen
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resource, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Jia-Fan He
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resource, School of Agriculture, Sun Yat-sen University, Guangzhou, China
| | - Nan Yao
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resource, School of Agriculture, Sun Yat-sen University, Guangzhou, China
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resource, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
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Liu J, Guan L, Wang E, Schuchman EH, He X, Zeng M. SiO 2 stimulates macrophage stress to induce the transformation of lung fibroblasts into myofibroblasts and its relationship with the sphingomyelin metabolic pathway. J Appl Toxicol 2021; 41:1584-1597. [PMID: 33559204 DOI: 10.1002/jat.4148] [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: 12/28/2020] [Revised: 01/22/2021] [Accepted: 01/28/2021] [Indexed: 11/11/2022]
Abstract
Silicosis is a serious occupational disease with the highest incidence in China. However, its pathogenesis has not been fully elucidated. Studies have shown that the sphingomyelin signaling pathway may play an important role in different fibrotic diseases but its role in silicosis-mediated fibrosis is still unclear. In this study, the supernatant of human peripheral blood mononuclear cell line (THP-1)-derived macrophages exposed to silica (SiO2 ) was used to stimulate the transformation of human embryonic lung fibroblast cell line (HFL-1) into myofibroblasts, and the intervention effect of recombinant human acid ceramidase (rAC) was observed. The results showed that SiO2 stimulated the production of reactive oxygen species and malondialdehyde in the supernatant of THP-1-derived macrophages and increased the secretion of TGF-β1, TNF-α, and IL-8. In addition, we found that the expression levels of α-SMA, FN, Col I, and Col III in HFL-1 cells increased. Meanwhile, the activities of ASMase and ACase and the expression levels of Cer, Sph, and S1P were increased. Intervention by rAC can suppress these changes to different degrees. In conclusion, the present study shows that SiO2 dust poisoning may stimulate HFL-1 cell differentiation into myofibroblasts by inducing oxidative stress in THP-1-derived macrophages, thereby promoting the secretion of a variety of inflammatory factors and activating the sphingolipid signaling pathway in HFL-1 cells. Exogenous rAC can effectively interfere with the stimulation of HFL-1 cells by silica in vitro.
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Affiliation(s)
- Jing Liu
- Department of Health Toxicology, Xiangya School of Public Health, Central South University, Changsha, China
| | - Lan Guan
- Department of Health Toxicology, Xiangya School of Public Health, Central South University, Changsha, China
| | - Erjin Wang
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macao SAR, China
| | - Edward H Schuchman
- Department of Human Genetics and Genomic Sciences, Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Xingxuan He
- Department of Human Genetics and Genomic Sciences, Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Ming Zeng
- Department of Health Toxicology, Xiangya School of Public Health, Central South University, Changsha, China
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Vitner EB. The role of brain innate immune response in lysosomal storage disorders: fundamental process or evolutionary side effect? FEBS Lett 2020; 594:3619-3631. [PMID: 33131047 DOI: 10.1002/1873-3468.13980] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Revised: 10/25/2020] [Accepted: 10/27/2020] [Indexed: 01/14/2023]
Abstract
Sphingolipidoses are diseases caused by mutations in genes responsible for sphingolipid degradation and thereby lead to sphingolipid accumulation. Most sphingolipidoses have a neurodegenerative manifestation characterized by innate immune activation in the brain. However, the role of the immune response in disease progression is ill-understood. In contrast to infectious diseases, immune activation is unable to eliminate the offending agent in sphingolipidoses resulting in ineffective, chronic inflammation. This paradox begs two fundamental questions: Why has this immune response evolved in sphingolipidoses? What role does it play in disease progression? Here, starting from the observation that sphingolipids (SLs) are elevated also in infectious diseases, I discuss the possibility that the activation of the brain immune response by SLs has evolved as a part of the immune response against pathogens and plays no major role in sphingolipidoses.
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Affiliation(s)
- Einat B Vitner
- Department of Infectious Diseases, Israel institute for Biological Research, Ness-Ziona, Israel
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8
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Bal Topçu D, Tugcu G, Ozcan F, Aslan M, Yalcinkaya A, Polat SE, Hizal M, Yalcin EE, Ersoz DD, Ozcelik U, Kiper N, Lay I, Oztas Y. Plasma Ceramides and Sphingomyelins of Pediatric Patients Increase in Primary Ciliary Dyskinesia but Decrease in Cystic Fibrosis. Lipids 2020; 55:213-223. [PMID: 32120452 DOI: 10.1002/lipd.12230] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 02/09/2020] [Accepted: 02/18/2020] [Indexed: 11/06/2022]
Abstract
We investigated plasma sphingomyelin (CerPCho) and ceramide (Cer) levels in pediatric patients with cystic fibrosis (CF) and primary ciliary dyskinesia (PCD). Plasma samples were obtained from CF (n = 19) and PCD (n = 7) patients at exacerbation, discharge, and stable periods. Healthy children (n = 17) of similar age served as control. Levels of 16-24 CerPCho and 16-24 Cer were measured by LC-MS/MS. Concentrations of all CerPCho and Cer species measured at exacerbation were significantly lower in patients with CF than PCD. 16, 18, 24 CerPCho, and 22, 24 Cer in exacerbation; 18, 24 CerPCho, and 18, 20, 22, 24 Cer at discharge; 18, 24 CerPCho and 24 Cer at stable period were significantly lower in CF patients than healthy children (p < 0.001 and p < 0.05). All CerPCho and Cer levels of PCD patients were significantly higher except 24 CerPCho and 24 Cer during exacerbation, 24 CerPCho at discharge, and 18, 22 CerPCho levels at stable period (p < 0.001 and p < 0.05) compared with healthy children. There was no significant difference among exacerbation, discharge, and stable periods in each group for Cer and CerPCho levels. This is the first study measuring plasma Cer and CerPCho levels in PCD and third study in CF patients. The dramatic difference in plasma levels of most CerPCho and Cer species found between two diseases suggest that cilia pathology in PCD and CFTR mutation in CF seem to alter sphingolipid metabolism possibly in opposite directions.
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Affiliation(s)
- Dilara Bal Topçu
- Department of Medical Biochemistry, Faculty of Medicine, Hacettepe University, Ankara, Sıhhıye, 06100, Turkey
| | - Gokcen Tugcu
- Department of Pediatric Pulmonology, Faculty of Medicine, Hacettepe University, Ankara, Sıhhıye, 06100, Turkey
| | - Filiz Ozcan
- Department of Medical Biochemistry, Faculty of Medicine, Akdeniz University, Antalya, Konyaaltı, 07070, Turkey
| | - Mutay Aslan
- Department of Medical Biochemistry, Faculty of Medicine, Akdeniz University, Antalya, Konyaaltı, 07070, Turkey
| | - Ahmet Yalcinkaya
- Department of Medical Biochemistry, Faculty of Medicine, Hacettepe University, Ankara, Sıhhıye, 06100, Turkey
| | - Sanem Eryilmaz Polat
- Department of Pediatric Pulmonology, Faculty of Medicine, Hacettepe University, Ankara, Sıhhıye, 06100, Turkey
| | - Mina Hizal
- Department of Pediatric Pulmonology, Faculty of Medicine, Hacettepe University, Ankara, Sıhhıye, 06100, Turkey
| | - Ebru Elmas Yalcin
- Department of Pediatric Pulmonology, Faculty of Medicine, Hacettepe University, Ankara, Sıhhıye, 06100, Turkey
| | - Deniz Dogru Ersoz
- Department of Pediatric Pulmonology, Faculty of Medicine, Hacettepe University, Ankara, Sıhhıye, 06100, Turkey
| | - Ugur Ozcelik
- Department of Pediatric Pulmonology, Faculty of Medicine, Hacettepe University, Ankara, Sıhhıye, 06100, Turkey
| | - Nural Kiper
- Department of Pediatric Pulmonology, Faculty of Medicine, Hacettepe University, Ankara, Sıhhıye, 06100, Turkey
| | - Incilay Lay
- Department of Medical Biochemistry, Faculty of Medicine, Hacettepe University, Ankara, Sıhhıye, 06100, Turkey
| | - Yesim Oztas
- Department of Medical Biochemistry, Faculty of Medicine, Hacettepe University, Ankara, Sıhhıye, 06100, Turkey
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Abstract
Sphingosine, ceramide, sphingosine-1-phosphate, and other related sphingolipids have emerged as important bioactive molecules involved in a variety of key cellular processes such as cell growth, differentiation, apoptosis, exosome release, and inter- and intracellular cell communication, making the pathways of sphingolipid metabolism a key domain in maintaining cell homeostasis (Hannun and Obeid, Trends Biochem Sci 20:73-77, 1995; Hannun and Obeid, Nat Rev Mol Cell Biol 9:139-150, 2008; Kosaka et al., J Biol Chem 288:10849-10859, 2013). Various studies have determined that these pathways play a central role in regulating intracellular production of ceramide and the other bioactive sphingolipids and hence are an important component of signaling in various diseases such as cancer, diabetes, and neurodegenerative and cardiovascular diseases (Chaube et al., Biochim Biophys Acta 1821:313-323, 2012; Clarke et al., Adv Enzyme Regul 51:51-58, 2011b; Horres and Hannun, Neurochem Res 37:1137-1149, 2012). In this chapter, we discuss one of the major enzyme classes in producing ceramide, sphingomyelinases (SMases), from a biochemical and structural perspective with an emphasis on their applicability as therapeutic targets.
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Affiliation(s)
- Prajna Shanbhogue
- Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, USA
| | - Yusuf A Hannun
- Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, USA.
- Stony Brook University Cancer Center, Stony Brook, NY, USA.
- Department of Medicine, Stony Brook University, Stony Brook, NY, USA.
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Neisseria meningitidis Type IV Pili Trigger Ca 2+-Dependent Lysosomal Trafficking of the Acid Sphingomyelinase To Enhance Surface Ceramide Levels. Infect Immun 2019; 87:IAI.00410-19. [PMID: 31160362 DOI: 10.1128/iai.00410-19] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Accepted: 05/24/2019] [Indexed: 01/26/2023] Open
Abstract
Acid sphingomyelinase (ASM) is a lipid hydrolase that converts sphingomyelin to ceramide and that can be activated by various cellular stress mechanisms, including bacterial pathogens. Vesicle transportation or trafficking of ASM from the lysosomal compartment to the cell membrane is a prerequisite for its activation in response to bacterial infections; however, the effectors and mechanisms of ASM translocation and activation are poorly defined. Our recent work documented the key importance of ASM for Neisseria meningitidis uptake into human brain microvascular endothelial cells (HBMEC). We clearly identified OpcA to be one bacterial effector promoting ASM translocation and activity, though it became clear that additional bacterial components were involved, as up to 80% of ASM activity and ceramide generation was retained in cells infected with an opcA-deficient mutant. We hypothesized that N. meningitidis might use pilus components to promote the translocation of ASM into HBMEC. Indeed, we found that both live, piliated N. meningitidis and pilus-enriched fractions trigger transient ASM surface display, followed by the formation of ceramide-rich platforms (CRPs). By using indirect immunocytochemistry and direct stochastic optical reconstruction microscopy, we show that the overall number of CRPs with a size of ∼80 nm in the plasma membrane is significantly increased after exposure to pilus-enriched fractions. Infection with live bacteria as well as exposure to pilus-enriched fractions transiently increased cytosolic Ca2+ levels in HBMEC, and this was found to be important for ASM surface display mediated by lysosomal exocytosis, as depletion of cytosolic Ca2+ resulted in a significant decrease in ASM surface levels, ASM activity, and CRP formation.
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Simonis A, Schubert-Unkmeir A. The role of acid sphingomyelinase and modulation of sphingolipid metabolism in bacterial infection. Biol Chem 2019; 399:1135-1146. [PMID: 29924727 DOI: 10.1515/hsz-2018-0200] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Accepted: 06/14/2018] [Indexed: 01/01/2023]
Abstract
Acid sphingomyelinase (ASM) is a key enzyme in sphingolipid metabolism that converts sphingomyelin to ceramide, thereby modulating membrane structures and signal transduction. Bacterial pathogens can manipulate ASM activity and function, and use host sphingolipids during multiple steps of their infection process. An increase in ceramides upon infection results in the formation of ceramide-enriched membrane platforms that serve to cluster receptor molecules and organize intracellular signaling molecules, thus facilitating bacterial uptake. In this review, we focus on how extracellular bacterial pathogens target ASM and modulate membrane properties and signaling pathways to gain entry into eukaryotic cells or induce cell death. We describe how intracellular pathogens interfere with the intralysosomal functions of ASM to favor replication and survival. In addition, bacteria utilize their own sphingomyelinases as virulence factors to modulate sphingolipid metabolism. The potential of ASM as a target for treating bacterial infections is also discussed.
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Affiliation(s)
- Alexander Simonis
- Division of Hematology, University Hospital Zurich, Rämistrasse 100, 8091 Zürich, Switzerland
| | - Alexandra Schubert-Unkmeir
- Institute of Hygiene and Microbiology, University of Würzburg, Josef-Schneider-Straße 2, D-97080 Würzburg, Germany
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12
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Wu Y, Gulbins E, Grassmé H. The function of sphingomyelinases in mycobacterial infections. Biol Chem 2019; 399:1125-1133. [PMID: 29924725 DOI: 10.1515/hsz-2018-0179] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Accepted: 06/06/2018] [Indexed: 12/21/2022]
Abstract
Tuberculosis (TB), caused by Mycobacterium tuberculosis, is one of the deadliest and most important infectious diseases worldwide. The sphingomyelinase/ceramide system, which has been shown several times to be a crucial factor in the internalization, processing and killing of diverse pathogens, also modulates the pro-inflammatory response and the state of mycobacteria in macrophages. Both acid and neutral sphingomyelinases are important in this activity. However, studies of the role of sphingomyelinases in TB are still at an early stage.
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Affiliation(s)
- Yuqing Wu
- Department of Molecular Biology, University of Duisburg-Essen, Hufelandstrasse 55, D-45122 Essen, Germany
| | - Erich Gulbins
- Department of Molecular Biology, University of Duisburg-Essen, Hufelandstrasse 55, D-45122 Essen, Germany.,Department of Surgery, University of Cincinnati, 231 Albert Sabin Way, Cincinnati, OH 45267, USA
| | - Heike Grassmé
- Department of Molecular Biology, University of Duisburg-Essen, Hufelandstrasse 55, D-45122 Essen, Germany
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13
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Karandashova S, Kummarapurugu A, Zheng S, Kang L, Sun S, Rubin BK, Voynow JA. Neutrophil elastase correlates with increased sphingolipid content in cystic fibrosis sputum. Pediatr Pulmonol 2018; 53:872-880. [PMID: 29624923 PMCID: PMC6566867 DOI: 10.1002/ppul.24001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Accepted: 03/07/2018] [Indexed: 12/31/2022]
Abstract
INTRODUCTION Sphingolipids are associated with the regulation of pulmonary inflammation. Although sphingolipids have been investigated in the context of cystic fibrosis (CF), the focus has been on loss of CF transmembrane conductance regulator (CFTR) function in mice, and in CF human lung epithelial cell lines. The sphingolipid content of CF sputum and the potential link between ceramide and airway inflammation in CF remain relatively unexplored. METHODS Fifteen patients with CF provided two spontaneously expectorated sputum samples, one collected during a hospitalization for an acute pulmonary exacerbation and one from an outpatient visit at a time of clinical stability. Sputum was processed, and the supernatant assessed for active neutrophil elastase (NE) using a chromogenic microplate assay and sphingolipid content using reverse phase high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). Relevant demographic data including age, sex, CF genotype, FEV1 % predicted, and sputum bacteriology were assessed as possible modifying factors that could influence the correlation between NE and sputum sphingolipids. Data were analyzed for linear correlation, with statistical significance pre-defined as P < 0.05. RESULTS There was a significant association between the concentration of active NE and ceramide, sphingomyelin, and monohexosylceramide moieties as well as sphingosine-1-phosphate. The presence of Methicillin-resistant Staphylococcus aureus (MRSA), FEV1 % predicted, and female gender further strengthened the association of NE and sphingolipids, but Pseudomonas aeruginosa had no effect on the association between NE and sphingolipids. CONCLUSIONS These data suggest that NE may increase pro-inflammatory sphingolipid signaling, and the association is strengthened in female patients and patients with MRSA.
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Affiliation(s)
- Sophia Karandashova
- Center for Clinical and Translational Research at Virginia Commonwealth University (VCU), Richmond, Virginia
| | - Apparao Kummarapurugu
- Division of Pediatric Pulmonology, Children's Hospital of Richmond at VCU, Richmond, Virginia
| | - Shuo Zheng
- Division of Pediatric Pulmonology, Children's Hospital of Richmond at VCU, Richmond, Virginia
| | - Le Kang
- Department of Biostatistics, VCU, Richmond, Virginia
| | - Shumei Sun
- Department of Biostatistics, VCU, Richmond, Virginia
| | - Bruce K Rubin
- Division of Pediatric Pulmonology, Children's Hospital of Richmond at VCU, Richmond, Virginia
| | - Judith A Voynow
- Division of Pediatric Pulmonology, Children's Hospital of Richmond at VCU, Richmond, Virginia
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14
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Wu Y, Gulbins E, Grassmé H. Crosstalk Between Sphingomyelinases and Reactive Oxygen Species in Mycobacterial Infection. Antioxid Redox Signal 2018; 28:935-948. [PMID: 28276697 DOI: 10.1089/ars.2017.7050] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Significance: Tuberculosis (TB), which is caused by Mycobacterium tuberculosis, is one of the most important infections worldwide. The sphingomyelinase/ceramide system, which has been shown to be a crucial factor in internalizing and killing various pathogens, modulates both the proinflammatory response and the state of mycobacteria in macrophages. However, studies about the role of sphingomyelinases in TB are still at an early stage. Recent Advances: Recent studies elucidated several roles of sphingomyelinases in manipulating mycobacterial infections. On the one hand, acid sphingomyelinase (Asm) promotes the fusion of bacteria-containing phagosomes and lysosomes, whereas on the other hand, Asm-derived ceramide induces cell death. Neutral sphingomyelinase (Nsm) enhances the release of reactive oxygen species, which suppress autophagy in infected macrophages in vitro and in vivo, allowing the pathogen to survive within macrophages. These findings indicate that the sphingomyelinase/ceramide system plays an important role in the attack of mycobacteria against the host. Critical Issues: Autophagy is a main strategy of mycobacterial clearance in TB, but the relevant mechanisms are still unknown. Additionally, there are indications that both Asm and Nsm are crucially involved in the formation of granulomas, which are a hallmark and a special structure of TB. However, very few findings have yet been published. Future Directions: Additional studies of the Nsm/ceramide system, which contributes to the resistance or susceptibility, respectively, of the host to mycobacterial infections, will detect currently unknown molecular mechanisms. Because inhibitors of Nsm already exist, targeting Nsm may be a novel approach to developing treatment options for mycobacterial infections. Antioxid. Redox Signal. 28, 935-948.
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Affiliation(s)
- Yuqing Wu
- Department of Molecular Biology, University of Duisburg-Essen, Essen, Germany
| | - Erich Gulbins
- Department of Molecular Biology, University of Duisburg-Essen, Essen, Germany.,Department of Surgery, University of Cincinnati, Cincinnati, Ohio
| | - Heike Grassmé
- Department of Molecular Biology, University of Duisburg-Essen, Essen, Germany
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15
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Evidence for the Involvement of Lipid Rafts and Plasma Membrane Sphingolipid Hydrolases in Pseudomonas aeruginosa Infection of Cystic Fibrosis Bronchial Epithelial Cells. Mediators Inflamm 2017; 2017:1730245. [PMID: 29333001 PMCID: PMC5733190 DOI: 10.1155/2017/1730245] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Revised: 08/02/2017] [Accepted: 08/30/2017] [Indexed: 12/28/2022] Open
Abstract
Cystic fibrosis (CF) is the most common autosomal genetic recessive disease caused by mutations of gene encoding for the cystic fibrosis transmembrane conductance regulator. Patients with CF display a wide spectrum of symptoms, the most severe being chronic lung infection and inflammation, which lead to onset of cystic fibrosis lung disease. Several studies indicate that sphingolipids play a regulatory role in airway inflammation. The inhibition and downregulation of GBA2, the enzyme catabolizing glucosylceramide to ceramide, are associated with a significant reduction of IL-8 production in CF bronchial epithelial cells. Herein, we demonstrate that GBA2 plays a role in the proinflammatory state characterizing CF cells. We also report for the first time that Pseudomonas aeruginosa infection causes a recruitment of plasma membrane-associated glycosphingolipid hydrolases into lipid rafts of CuFi-1-infected cells. This reorganization of cell membrane may be responsible for activation of a signaling cascade, culminating in aberrant inflammatory response in CF bronchial epithelial cells upon bacterial infection. Taken together, the presented data further support the role of sphingolipids and their metabolic enzymes in controlling the inflammatory response in CF.
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16
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Huang FC. The Role of Sphingolipids on Innate Immunity to Intestinal Salmonella Infection. Int J Mol Sci 2017; 18:ijms18081720. [PMID: 28783107 PMCID: PMC5578110 DOI: 10.3390/ijms18081720] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 07/25/2017] [Accepted: 07/27/2017] [Indexed: 02/06/2023] Open
Abstract
Salmonella spp. remains a major public health problem for the whole world. To reduce the use of antimicrobial agents and drug-resistant Salmonella, a better strategy is to explore alternative therapy rather than to discover another antibiotic. Sphingolipid- and cholesterol-enriched lipid microdomains attract signaling proteins and orchestrate them toward cell signaling and membrane trafficking pathways. Recent studies have highlighted the crucial role of sphingolipids in the innate immunity against infecting pathogens. It is therefore mandatory to exploit the role of the membrane sphingolipids in the innate immunity of intestinal epithelia infected by this pathogen. In the present review, we focus on the role of sphingolipids in the innate immunity of intestinal epithelia against Salmonella infection, including adhesion, autophagy, bactericidal effect, barrier function, membrane trafficking, cytokine and antimicrobial peptide expression. The intervention of sphingolipid-enhanced foods to make our life healthy or pharmacological agents regulating sphingolipids is provided at the end.
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Affiliation(s)
- Fu-Chen Huang
- Department of Pediatrics, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung 833, Taiwan.
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17
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Acid sphingomyelinase mediates human CD4 + T-cell signaling: potential roles in T-cell responses and diseases. Cell Death Dis 2017; 8:e2963. [PMID: 28749465 PMCID: PMC5550889 DOI: 10.1038/cddis.2017.360] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Revised: 06/11/2017] [Accepted: 06/14/2017] [Indexed: 12/13/2022]
Abstract
Acid sphingomyelinase (ASM) is a lipid hydrolase. By generating ceramide, ASM had been reported to have an important role in regulating immune cell functions inclusive of macrophages, NK cells, and CD8+ T cells, whereas the role of ASM bioactivity in regulation of human CD4+ T-cell functions remained uncertain. Recent studies have provided novel findings in this field. Upon stimulation of CD3 and/or CD28, ASM-dependent ceramide signaling mediates intracellular downstream signal cascades of CD3 and CD28, and regulates CD4+ T-cell activation and proliferation. Meanwhile, CD39 and CD161 have direct interactions with ASM, which mediates downstream signals inclusive of STAT3 and mTOR and thus defines human Th17 cells. Intriguingly, ASM mediates Th1 responses, but negatively regulates Treg functions. In this review, we summarized the pivotal roles of ASM in regulation of human CD4+ T-cell activation and responses. ASM/sphingolipid signaling may be a novel target for the therapy of human autoimmune diseases.
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18
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Sharma L, Prakash H. Sphingolipids Are Dual Specific Drug Targets for the Management of Pulmonary Infections: Perspective. Front Immunol 2017; 8:378. [PMID: 28400772 PMCID: PMC5372786 DOI: 10.3389/fimmu.2017.00378] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 03/16/2017] [Indexed: 11/13/2022] Open
Abstract
Sphingolipids are the major constituent of the mucus secreted by the cells of epithelial linings of lungs where they maintain the barrier functions and prevent microbial invasion. Sphingolipids are interconvertible, and their primary and secondary metabolites have both structural and functional roles. Out of several sphingolipid metabolites, sphingosine-1 phosphate (S1P) and ceramide are central molecules and decisive for sphingolipid signaling. These are produced by enzymatic activity of sphingosine kinase-1 (SK-1) upon the challenge with either biological or physiological stresses. S1P and ceramide rheostat are important for the progression of various pathologies, which are manifested by inflammatory cascade. S1P is a well-established secondary messenger and associated with various neuronal, metabolic, and inflammatory diseases other than respiratory infections such as Chlamydia pneumoniae, Streptococcus pneumoniae, and Mycobacterium tuberculosis. These pathogens are known to exploit sphingolipid metabolism for their opportunistic survival. Decreased sphingosine kinase activity/S1P content in the lung and peripheral blood of tuberculosis patients clearly indicated a dysregulation of sphingolipid metabolism during infection and suggest that sphingolipid metabolism is important for management of infection by the host. Our previous study has demonstrated that gain of SK-1 activity is important for the maturation of phagolysosomal compartment, innate activation of macrophages, and subsequent control of mycobacterial replication/growth in macrophages. Furthermore, S1P-mediated amelioration of lung pathology and disease severity in TB patients is believed to be mediated by the selective activation or rearrangement of various S1P receptors (S1PR) particularly S1PR2, which has been effective in controlling respiratory fungal pathogens. Therefore, such specificity of S1P-S1PR would be paramount for triggering inflammatory events, subsequent activation, and fostering bactericidal potential in macrophages for the control of TB. In this review, we have discussed and emphasized that sphingolipids may represent effective novel, yet dual specific drug targets for controlling pulmonary infections.
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Affiliation(s)
- Lalita Sharma
- Laboratory of Translational Medicine, School of Life Sciences, University of Hyderabad , Hyderabad, Telengana , India
| | - Hridayesh Prakash
- Laboratory of Translational Medicine, School of Life Sciences, University of Hyderabad , Hyderabad, Telengana , India
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19
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The impact of impaired macrophage functions in cystic fibrosis disease progression. J Cyst Fibros 2016; 16:443-453. [PMID: 27856165 DOI: 10.1016/j.jcf.2016.10.011] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 10/21/2016] [Accepted: 10/23/2016] [Indexed: 01/29/2023]
Abstract
The underlying cause of morbidity in cystic fibrosis (CF) is the decline in lung function, which results in part from chronic inflammation. Inflammation and infection occur early in infancy in CF and the role of innate immune defense in CF has been highlighted in the last years. Once thought simply to be consumers of bacteria, macrophages have emerged as highly sensitive immune cells that are located at the balance point between inflammation and resolution of this inflammation in CF pathophysiology. In order to assess the potential role of macrophage in CF, we review the evidence that: (1) CF macrophage has a dysregulated inflammatory phenotype; (2) CF macrophage presents altered phagocytosis capacity and bacterial killing; and (3) lipid disorders in CF macrophage affect its function. These alterations of macrophage weaken innate defense of CF patients and may be involved in CF disease progression and lung damage.
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Aureli M, Schiumarini D, Loberto N, Bassi R, Tamanini A, Mancini G, Tironi M, Munari S, Cabrini G, Dechecchi MC, Sonnino S. Unravelling the role of sphingolipids in cystic fibrosis lung disease. Chem Phys Lipids 2016; 200:94-103. [DOI: 10.1016/j.chemphyslip.2016.08.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 08/22/2016] [Accepted: 08/25/2016] [Indexed: 12/13/2022]
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21
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Wanitchakool P, Ousingsawat J, Sirianant L, MacAulay N, Schreiber R, Kunzelmann K. Cl - channels in apoptosis. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2016; 45:599-610. [PMID: 27270446 DOI: 10.1007/s00249-016-1140-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Revised: 05/06/2016] [Accepted: 05/14/2016] [Indexed: 12/28/2022]
Abstract
A remarkable feature of apoptosis is the initial massive cell shrinkage, which requires opening of ion channels to allow release of K+, Cl-, and organic osmolytes to drive osmotic water movement and cell shrinkage. This article focuses on the role of the Cl- channels LRRC8, TMEM16/anoctamin, and cystic fibrosis transmembrane conductance regulator (CFTR) in cellular apoptosis. LRRC8A-E has been identified as a volume-regulated anion channel expressed in many cell types. It was shown to be required for regulatory and apoptotic volume decrease (RVD, AVD) in cultured cell lines. Its presence also determines sensitivity towards cytostatic drugs such as cisplatin. Recent data point to a molecular and functional relationship of LRRC8A and anoctamins (ANOs). ANO6, 9, and 10 (TMEM16F, J, and K) augment apoptotic Cl- currents and AVD, but it remains unclear whether these anoctamins operate as Cl- channels or as regulators of other apoptotic Cl- channels, such as LRRC8. CFTR has been known for its proapoptotic effects for some time, and this effect may be based on glutathione release from the cell and increase in cytosolic reactive oxygen species (ROS). Although we find that CFTR is activated by cell swelling, it is possible that CFTR serves RVD/AVD through accumulation of ROS and activation of independent membrane channels such as ANO6. Thus activation of ANO6 will support cell shrinkage and induce additional apoptotic events, such as membrane phospholipid scrambling.
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Affiliation(s)
- Podchanart Wanitchakool
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Jiraporn Ousingsawat
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Lalida Sirianant
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Nanna MacAulay
- Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Rainer Schreiber
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Karl Kunzelmann
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany.
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22
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Abstract
Activation of ion channels and pores are essential steps during regulated cell death. Channels and pores participate in execution of apoptosis, necroptosis and other forms of caspase-independent cell death. Within the program of regulated cell death, these channels are strategically located. Ion channels can shrink cells and drive them towards apoptosis, resulting in silent, i.e. immunologically unrecognized cell death. Alternatively, activation of channels can induce cell swelling, disintegration of the cell membrane, and highly immunogenic necrotic cell death. The underlying cell death pathways are not strictly separated as identical stimuli may induce cell shrinkage and apoptosis when applied at low strength, but may also cause cell swelling at pronounced stimulation, resulting in regulated necrosis. Nevertheless, the precise role of ion channels during regulated cell death is far from being understood, as identical channels may support regulated death in some cell types, but may cause cell proliferation, cancer development, and metastasis in others. Along this line, the phospholipid scramblase and Cl(-)/nonselective channel anoctamin 6 (ANO6) shows interesting features, as it participates in apoptotic cell death during lower levels of activation, thereby inducing cell shrinkage. At strong activation, e.g. by stimulation of purinergic P2Y7 receptors, it participates in pore formation, causes massive membrane blebbing, cell swelling, and membrane disintegration. The LRRC8 proteins deserve much attention as they were found to have a major role in volume regulation, apoptotic cell shrinkage and resistance towards anticancer drugs.
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Affiliation(s)
- Karl Kunzelmann
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany.
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23
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Loring HS, ElMallah MK, Flotte TR. Development of rAAV2-CFTR: History of the First rAAV Vector Product to be Used in Humans. Hum Gene Ther Methods 2016; 27:49-58. [PMID: 26895204 PMCID: PMC4834522 DOI: 10.1089/hgtb.2015.150] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Accepted: 01/26/2016] [Indexed: 12/31/2022] Open
Abstract
The first human gene therapy trials using recombinant adeno-associated virus (rAAV) vectors were performed in cystic fibrosis (CF) patients. Over 100 CF patients were enrolled in 5 separate trials of rAAV2-CFTR administration via nasal, endobronchial, maxillary sinus, and aerosol delivery. Recombinant AAV vectors were designed to deliver the CF transmembrane regulator (CFTR) gene and correct the basic CFTR defect by restoring chloride transport and reverting the upregulation of proinflammatory cytokines. However, vector DNA expression was limited in duration because of the low incidence of integration and natural airway epithelium turnover. In addition, repeated administration of AAV-CFTR vector resulted in a humoral immune response that prevented effective gene transfer from subsequent doses of vector. AAV serotype 2 was used in human trials before the comparison with other serotypes and determination that serotypes 1 and 5 not only possess higher tropism for the airway epithelium, but also are capable of bypassing the binding and trafficking processes-both were important hindrances to the effectiveness of rAAV2. Although rAAV-CFTR gene therapy does not appear likely to supplant newer small-molecule CFTR modulators in the near future, early work with rAAV-CFTR provided an important foundation for later use of rAAV in humans.
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Affiliation(s)
- Heather S. Loring
- Horae Gene Therapy Center, University of Massachusetts Medical School, Worcester, Massachusetts
| | - Mai K. ElMallah
- Horae Gene Therapy Center, University of Massachusetts Medical School, Worcester, Massachusetts
- Department of Pediatrics, University of Massachusetts Medical School, Worcester, Massachusetts
| | - Terence R. Flotte
- Horae Gene Therapy Center, University of Massachusetts Medical School, Worcester, Massachusetts
- Department of Pediatrics, University of Massachusetts Medical School, Worcester, Massachusetts
- Microbiology & Physiologic Systems, University of Massachusetts Medical School, Worcester, Massachusetts
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24
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Abstract
Acid sphingomyelinase (ASM), a lipid hydrolase enzyme, has the potential to modulate various cellular activation responses via the generation of ceramide and by interaction with cellular receptors. We have hypothesized that ASM modulates CD4+ T-cell receptor activation and impacts immune responses. We first observed interactions of ASM with the intracellular domains of both CD3 and CD28. ASM further mediates T-cell proliferation after anti-CD3/CD28 antibody stimulation and alters CD4+ T-cell activation signals by generating ceramide. We noted that various pharmacological inhibitors of ASM or knockdown of ASM using small hairpin RNA inhibit CD3/CD28-mediated CD4+ T-cell proliferation and activation. Furthermore, such blockade of ASM bioactivity by biochemical inhibitors and/or molecular-targeted knockdown of ASM broadly abrogate T-helper cell responses. In conclusion, we detail immune, pivotal roles of ASM in adaptive immune T-cell responses, and propose that these pathways might provide novel targets for the therapy of autoimmune and inflammatory diseases.
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25
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Managò A, Becker KA, Carpinteiro A, Wilker B, Soddemann M, Seitz AP, Edwards MJ, Grassmé H, Szabò I, Gulbins E. Pseudomonas aeruginosa pyocyanin induces neutrophil death via mitochondrial reactive oxygen species and mitochondrial acid sphingomyelinase. Antioxid Redox Signal 2015; 22:1097-110. [PMID: 25686490 PMCID: PMC4403017 DOI: 10.1089/ars.2014.5979] [Citation(s) in RCA: 95] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
AIMS Pulmonary infections with Pseudomonas aeruginosa are a serious clinical problem and are often lethal. Because many strains of P. aeruginosa are resistant to antibiotics, therapeutic options are limited. Neutrophils play an important role in the host's early acute defense against pulmonary P. aeruginosa. Therefore, it is important to define the mechanisms by which P. aeruginosa interacts with host cells, particularly neutrophils. RESULTS Here, we report that pyocyanin, a membrane-permeable pigment and toxin released by P. aeruginosa, induces the death of wild-type neutrophils; its interaction with the mitochondrial respiratory chain results in the release of reactive oxygen species (ROS), the activation of mitochondrial acid sphingomyelinase, the formation of mitochondrial ceramide, and the release of cytochrome c from mitochondria. A genetic deficiency in acid sphingomyelinase prevents both the activation of this pathway and pyocyanin-induced neutrophil death. This reduced death, on the other hand, is associated with an increase in the release of interleukin-8 from pyocyanin-activated acid sphingomyelinase-deficient neutrophils but not from wild-type cells. INNOVATION These studies identified the mechanisms by which pyocyanin induces the release of mitochondrial ROS and by which ROS induce neutrophil death via mitochondrial acid sphingomyelinase. CONCLUSION These findings demonstrate a novel mechanism of pyocyanin-induced death of neutrophils and show how this apoptosis balances innate immune reactions.
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26
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Airola MV, Tumolo JM, Snider J, Hannun YA. Identification and biochemical characterization of an acid sphingomyelinase-like protein from the bacterial plant pathogen Ralstonia solanacearum that hydrolyzes ATP to AMP but not sphingomyelin to ceramide. PLoS One 2014; 9:e105830. [PMID: 25144372 PMCID: PMC4140839 DOI: 10.1371/journal.pone.0105830] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Accepted: 07/25/2014] [Indexed: 11/18/2022] Open
Abstract
Acid sphingomyelinase (aSMase) is a human enzyme that catalyzes the hydrolysis of sphingomyelin to generate the bioactive lipid ceramide and phosphocholine. ASMase deficiency is the underlying cause of the genetic diseases Niemann-Pick Type A and B and has been implicated in the onset and progression of a number of other human diseases including cancer, depression, liver, and cardiovascular disease. ASMase is the founding member of the aSMase protein superfamily, which is a subset of the metallophosphatase (MPP) superfamily. To date, MPPs that share sequence homology with aSMase, termed aSMase-like proteins, have been annotated and presumed to function as aSMases. However, none of these aSMase-like proteins have been biochemically characterized to verify this. Here we identify RsASML, previously annotated as RSp1609: acid sphingomyelinase-like phosphodiesterase, as the first bacterial aSMase-like protein from the deadly plant pathogen Ralstonia solanacearum based on sequence homology with the catalytic and C-terminal domains of human aSMase. A biochemical characterization of RsASML does not support a role in sphingomyelin hydrolysis but rather finds RsASML capable of acting as an ATP diphosphohydrolase, catalyzing the hydrolysis of ATP and ADP to AMP. In addition, RsASML displays a neutral, not acidic, pH optimum and prefers Ni2+ or Mn2+, not Zn2+, for catalysis. This alters the expectation that all aSMase-like proteins function as acid SMases and expands the substrate possibilities of this protein superfamily to include nucleotides. Overall, we conclude that sequence homology with human aSMase is not sufficient to predict substrate specificity, pH optimum for catalysis, or metal dependence. This may have implications to the biochemically uncharacterized human aSMase paralogs, aSMase-like 3a (aSML3a) and aSML3b, which have been implicated in cancer and kidney disease, respectively, and assumed to function as aSMases.
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Affiliation(s)
- Michael V. Airola
- Department of Medicine and the Stony Brook University Cancer Center, Stony Brook University, Stony Brook, New York, United States of America
| | - Jessica M. Tumolo
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina, United States of America
| | - Justin Snider
- Department of Medicine and the Stony Brook University Cancer Center, Stony Brook University, Stony Brook, New York, United States of America
| | - Yusuf A. Hannun
- Department of Medicine and the Stony Brook University Cancer Center, Stony Brook University, Stony Brook, New York, United States of America
- * E-mail:
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Loberto N, Tebon M, Lampronti I, Marchetti N, Aureli M, Bassi R, Giri MG, Bezzerri V, Lovato V, Cantù C, Munari S, Cheng SH, Cavazzini A, Gambari R, Sonnino S, Cabrini G, Dechecchi MC. GBA2-encoded β-glucosidase activity is involved in the inflammatory response to Pseudomonas aeruginosa. PLoS One 2014; 9:e104763. [PMID: 25141135 PMCID: PMC4139313 DOI: 10.1371/journal.pone.0104763] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 07/16/2014] [Indexed: 11/19/2022] Open
Abstract
Current anti-inflammatory strategies for the treatment of pulmonary disease in cystic fibrosis (CF) are limited; thus, there is continued interest in identifying additional molecular targets for therapeutic intervention. Given the emerging role of sphingolipids (SLs) in various respiratory disorders, including CF, drugs that selectively target the enzymes associated with SL metabolism are under development. Miglustat, a well-characterized iminosugar-based inhibitor of β-glucosidase 2 (GBA2), has shown promise in CF treatment because it reduces the inflammatory response to infection by P. aeruginosa and restores F508del-CFTR chloride channel activity. This study aimed to probe the molecular basis for the anti-inflammatory activity of miglustat by examining specifically the role of GBA2 following the infection of CF bronchial epithelial cells by P. aeruginosa. We also report the anti-inflammatory activity of another potent inhibitor of GBA2 activity, namely N-(5-adamantane-1-yl-methoxy)pentyl)-deoxynojirimycin (Genz-529648). In CF bronchial cells, inhibition of GBA2 by miglustat or Genz-529648 significantly reduced the induction of IL-8 mRNA levels and protein release following infection by P. aeruginosa. Hence, the present data demonstrate that the anti-inflammatory effects of miglustat and Genz-529648 are likely exerted through inhibition of GBA2.
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Affiliation(s)
- Nicoletta Loberto
- Department of Medical Biotechnology and Translational Medicine, University of Milano, Milano, Italy
| | - Maela Tebon
- Laboratory of Molecular Pathology, Department of Pathology and Diagnostics, University Hospital of Verona, Verona, Italy
| | - Ilaria Lampronti
- Department of Life Sciences and Biotechnology, Section of Biochemistry and Molecular Biology, University of Ferrara, Ferrara, Italy
| | - Nicola Marchetti
- Department of Chemistry and Pharmaceutical Sciences, University of Ferrara, Ferrara, Italy
| | - Massimo Aureli
- Department of Medical Biotechnology and Translational Medicine, University of Milano, Milano, Italy
| | - Rosaria Bassi
- Department of Medical Biotechnology and Translational Medicine, University of Milano, Milano, Italy
| | - Maria Grazia Giri
- Medical Physics Unit, Department of Pathology and Diagnostics, University Hospital of Verona, Verona, Italy
| | - Valentino Bezzerri
- Laboratory of Molecular Pathology, Department of Pathology and Diagnostics, University Hospital of Verona, Verona, Italy
| | - Valentina Lovato
- Laboratory of Molecular Pathology, Department of Pathology and Diagnostics, University Hospital of Verona, Verona, Italy
| | - Cinzia Cantù
- Laboratory of Molecular Pathology, Department of Pathology and Diagnostics, University Hospital of Verona, Verona, Italy
| | - Silvia Munari
- Laboratory of Molecular Pathology, Department of Pathology and Diagnostics, University Hospital of Verona, Verona, Italy
| | - Seng H. Cheng
- Genzyme, a Sanofi Company, Framingham, Massachusetts, United States of America
| | - Alberto Cavazzini
- Department of Chemistry and Pharmaceutical Sciences, University of Ferrara, Ferrara, Italy
| | - Roberto Gambari
- Department of Life Sciences and Biotechnology, Section of Biochemistry and Molecular Biology, University of Ferrara, Ferrara, Italy
| | - Sandro Sonnino
- Department of Medical Biotechnology and Translational Medicine, University of Milano, Milano, Italy
| | - Giulio Cabrini
- Laboratory of Molecular Pathology, Department of Pathology and Diagnostics, University Hospital of Verona, Verona, Italy
| | - Maria Cristina Dechecchi
- Laboratory of Molecular Pathology, Department of Pathology and Diagnostics, University Hospital of Verona, Verona, Italy
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Administration of antenatal glucocorticoids and postnatal surfactant ameliorates respiratory distress syndrome-associated neonatal lethality in Erk3(-/-) mouse pups. Pediatr Res 2014; 76:24-32. [PMID: 24732107 PMCID: PMC4062596 DOI: 10.1038/pr.2014.54] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Accepted: 01/03/2014] [Indexed: 11/18/2022]
Abstract
BACKGROUND Respiratory distress syndrome (RDS) persists as a prevalent cause of infant morbidity and mortality. We have previously demonstrated that deletion of Erk3 results in pulmonary immaturity and neonatal lethality. Using RNA sequencing, we identified corticotrophin releasing hormone (CRH) and surfactant protein B (SFTPB) as potential molecular mediators of Erk3-dependent lung maturation. In this study, we characterized the impact of antenatal glucocorticoids and postnatal surfactant on neonatal survival of Erk3 null mice. METHODS In a double crossover design, we administered dexamethasone (dex) or saline to pregnant dams during the saccular stage of lung development, followed by postnatal surfactant or saline via inhalation intubation. Survival was recorded, and detailed lung histological analysis and staining for CRH and SFTPB protein expression were performed. RESULTS Without treatment, Erk3 null pups die within 6 h of birth with reduced aerated space, impaired thinning of the alveolar septa, and abundant glycogen stores, as described in human RDS. The administration of dex and surfactant improved RDS-associated lethality of Erk3(-/-) pups and partially restored functional fetal lung maturation by accelerating the downregulation of pulmonary CRH and partially rescuing the production of SFTPB. CONCLUSION These findings emphasize that Erk3 is integral to terminal differentiation of type II cells, SFTPB production, and fetal pulmonary maturity.
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Becker KA, Henry B, Ziobro R, Riethmüller J, Gulbins E. Lipids in cystic fibrosis. Expert Rev Respir Med 2014; 5:527-35. [DOI: 10.1586/ers.11.36] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Venkatakrishnan V, Packer NH, Thaysen-Andersen M. Host mucin glycosylation plays a role in bacterial adhesion in lungs of individuals with cystic fibrosis. Expert Rev Respir Med 2014; 7:553-76. [DOI: 10.1586/17476348.2013.837752] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Yu H, Valerio M, Bielawski J. Fenretinide inhibited de novo ceramide synthesis and proinflammatory cytokines induced by Aggregatibacter actinomycetemcomitans. J Lipid Res 2013; 54:189-201. [PMID: 23139430 PMCID: PMC3520524 DOI: 10.1194/jlr.m031427] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2012] [Revised: 11/08/2012] [Indexed: 01/02/2023] Open
Abstract
Ceramides play an essential role in modulating immune signaling pathways and proinflammatory cytokine production in response to infectious pathogens, stress stimuli, or chemotherapeutic drugs. In this study, we demonstrated that Aggregatibacter actinomycetemcomitans, the pathogen for aggressive periodontitis, induced de novo synthesis of ceramide in Raw 264.7 cells. In addition, we identified that fenretinide, a synthetic retinoid, suppressed the de novo synthesis of ceramide induced by A. actinomycetemcomitans. Moreover, fenretinide attenuated interleukin (IL)-1β, IL-6, and cyclooxygenase-2 mRNA expression induced by A. actinomycetemcomitans. Fenretinide also decreased IL-1β, IL-6, and prostaglandin E2 proinflammatory cytokine levels in Raw 264.7 cells induced by A. actinomycetemcomitans. However, fenretinide had no significant effects on tumor necrosis factor alpha mRNA or protein levels. Furthermore, we showed that fenretinide inhibited the janus kinase-signal transducer and activator of transcription, phosphatidylinositol 3-kinase-Akt, protein kinase C, and nuclear factor-kappaB signaling pathways, whereas fenretinide up-regulated the mitogen-activated protein kinase signaling pathways after bacterial stimulation. This study emphasizes the de novo ceramide synthesis pathway in response to bacterial stimulation and demonstrates the anti-inflammatory role of fenretinide in the bacteria-induced immune response.
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Affiliation(s)
- Hong Yu
- Department of Craniofacial Biology, Medical University of South Carolina, Charleston, SC, USA.
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Jbeily N, Suckert I, Gonnert FA, Acht B, Bockmeyer CL, Grossmann SD, Blaess MF, Lueth A, Deigner HP, Bauer M, Claus RA. Hyperresponsiveness of mice deficient in plasma-secreted sphingomyelinase reveals its pivotal role in early phase of host response. J Lipid Res 2012; 54:410-24. [PMID: 23230083 PMCID: PMC3541704 DOI: 10.1194/jlr.m031625] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Plasma secretion of acid sphingomyelinase is a hallmark of cellular stress
response resulting in the formation of membrane embedded ceramide-enriched lipid
rafts and the reorganization of receptor complexes. Consistently,
decompartmentalization of ceramide formation from inert sphingomyelin has been
associated with signaling events and regulation of the cellular phenotype.
Herein, we addressed the question of whether the secretion of acid
sphingomyelinase is involved in host response during sepsis. We found an
exaggerated clinical course in mice genetically deficient in acid
sphingomyelinase characterized by an increased bacterial burden, an increased
phagocytotic activity, and a more pronounced cytokine storm. Moreover, on a
functional level, leukocyte-endothelial interaction was found diminished in
sphingomyelinase-deficient animals corresponding to a distinct leukocytes’
phenotype with respect to rolling and sticking as well as expression of cellular
surface proteins. We conclude that hydrolysis of membrane-embedded
sphingomyelin, triggered by circulating sphingomyelinase, plays a pivotal role
in the first line of defense against invading microorganisms. This function
might be essential during the early phase of infection leading to an adaptive
response of remote cells and tissues.
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Affiliation(s)
- Nayla Jbeily
- Center of Sepsis Control and Care, Jena University Hospital, Jena, Germany
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Truman JP, Al Gadban MM, Smith KJ, Jenkins RW, Mayroo N, Virella G, Lopes-Virella MF, Bielawska A, Hannun YA, Hammad SM. Differential regulation of acid sphingomyelinase in macrophages stimulated with oxidized low-density lipoprotein (LDL) and oxidized LDL immune complexes: role in phagocytosis and cytokine release. Immunology 2012; 136:30-45. [PMID: 22236141 DOI: 10.1111/j.1365-2567.2012.03552.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Oxidized low-density lipoprotein (oxLDL) and oxLDL-containing immune complexes (oxLDL-IC) contribute to the formation of lipid-laden macrophages (foam cells). Fcγ receptors mediate uptake of oxLDL-IC, whereas scavenger receptors internalize oxLDL. We have previously reported that oxLDL-IC, but not free oxLDL, activate macrophages and prolong their survival. Sphingomyelin is a major constituent of cell membranes and lipoprotein particles and acid sphingomyelinase (ASMase) hydrolyses sphingomyelin to generate the bioactive lipid ceramide. ASMase exists in two forms: lysosomal (L-ASMase) and secretory (S-ASMase). In this study we examined whether oxLDL and oxLDL-IC regulate ASMase differently, and whether ASMase mediates monocyte/macrophage activation and cytokine release. The oxLDL-IC, but not oxLDL, induced early and consistent release of catalytically active S-ASMase. The oxLDL-IC also consistently stimulated L-ASMase activity, whereas oxLDL induced a rapid transient increase in L-ASMase activity before it steadily declined below baseline. Prolonged exposure to oxLDL increased L-ASMase activity; however, activity remained significantly lower than that induced by oxLDL-IC. Further studies were aimed at defining the function of the activated ASMase. In response to oxLDL-IC, heat-shock protein 70B' (HSP70B') was up-regulated and localized with redistributed ASMase in the endosomal compartment outside the lysosome. Treatment with oxLDL-IC induced the formation and release of HSP70-containing and IL-1β-containing exosomes via an ASMase-dependent mechanism. Taken together, the results suggest that oxLDL and oxLDL-IC differentially regulate ASMase activity, and the pro-inflammatory responses to oxLDL-IC are mediated by prolonged activation of ASMase. These findings may contribute to increased understanding of mechanisms mediating macrophage involvement in atherosclerosis.
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Affiliation(s)
- Jean-Philip Truman
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC 29425, USA
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Dechecchi MC, Nicolis E, Mazzi P, Cioffi F, Bezzerri V, Lampronti I, Huang S, Wiszniewski L, Gambari R, Scupoli MT, Berton G, Cabrini G. Modulators of Sphingolipid Metabolism Reduce Lung Inflammation. Am J Respir Cell Mol Biol 2011; 45:825-33. [DOI: 10.1165/rcmb.2010-0457oc] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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Wargo MJ, Gross MJ, Rajamani S, Allard JL, Lundblad LKA, Allen GB, Vasil ML, Leclair LW, Hogan DA. Hemolytic phospholipase C inhibition protects lung function during Pseudomonas aeruginosa infection. Am J Respir Crit Care Med 2011; 184:345-54. [PMID: 21562128 DOI: 10.1164/rccm.201103-0374oc] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
RATIONALE The opportunistic pathogen Pseudomonas aeruginosa causes both acute and chronic lung infections and is particularly problematic in patients with cystic fibrosis and those undergoing mechanical ventilation. Decreased lung function contributes significantly to morbidity and mortality during P. aeruginosa infection, and damage inflicted by P. aeruginosa virulence factors contributes to lung function decline. OBJECTIVES We sought to describe direct contribution of a bacterial phospholipase C/sphingomyelinase, PlcHR, to alteration of host lung physiology and characterize a potential therapeutic for protection of lung function. METHODS We infected C57Bl/6 mice with P. aeruginosa wild-type or isogenic plcHR deletion strains and measured lung function using computer-controlled ventilators. For in vivo testing, miltefosine was delivered intraperitoneally 1 hour after infection. Infection and respiratory endpoints were at 24 hours after infection. MEASUREMENTS AND MAIN RESULTS P. aeruginosa wild-type infection caused significant lung function impairment, whereas the effects of a ΔplcHR strain infection were much less severe. Surfactometry analysis of bronchoalveolar lavage fluid indicated that PlcHR decreased pulmonary surfactant function. Miltefosine has structural similarity to the PC and sphingomyelin substrates of PlcHR, and we found that it inhibits the cleavage of these choline-containing lipids in vitro. Miltefosine administration after P. aeruginosa infection limited the negative effects of PlcHR activity on lung function. CONCLUSIONS We have directly linked production of a single virulence factor in P. aeruginosa with effects on lung function, and demonstrated that the inhibitor miltefosine protects lung function from PlcHR-dependent surfactant dysfunction.
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Affiliation(s)
- Matthew J Wargo
- Department of Microbiology and Molecular Genetics, University of Vermont College of Medicine, Burlington, VT 05405, USA.
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Truman JP, Al Gadban MM, Smith KJ, Hammad SM. Acid sphingomyelinase in macrophage biology. Cell Mol Life Sci 2011; 68:3293-305. [PMID: 21533981 DOI: 10.1007/s00018-011-0686-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2011] [Revised: 03/28/2011] [Accepted: 04/05/2011] [Indexed: 12/21/2022]
Abstract
Macrophages play a central role in innate immune responses, in disposal of cholesterol, and in tissue homeostasis and remodeling. To perform these vital functions macrophages display high endosomal/lysosomal activities. Recent studies have highlighted that acid sphingomyelinase (ASMase), which generates ceramide from sphingomyelin, is involved in modulation of membrane structures and signal transduction in addition to its metabolic role in the lysosome. In this review, we bring together studies on ASMase, its different forms and locations that are necessary for the macrophage to accomplish its diverse functions. We also address the importance of ASMase to several disease processes that are mediated by activated macrophages.
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Affiliation(s)
- Jean-Philip Truman
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC 29425, USA
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Wojewodka G, De Sanctis JB, Radzioch D. Ceramide in cystic fibrosis: a potential new target for therapeutic intervention. J Lipids 2010; 2011:674968. [PMID: 21490807 PMCID: PMC3066841 DOI: 10.1155/2011/674968] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Revised: 10/04/2010] [Accepted: 11/11/2010] [Indexed: 12/21/2022] Open
Abstract
Patients with cystic fibrosis (CF) are afflicted with many symptoms but the greatest challenge is the fight against chronic bacterial infections, leading to decreased lung function and ultimately death. Our group has recently found reduced levels of ceramides in CF patients and mice. Ceramides are sphingolipids involved in the structure of cell membranes but also participate in the inflammatory response, in cell signalling through membrane microdomains (lipid rafts), and in apoptosis. These characteristics of ceramides make them strong candidates for therapeutic intervention in CF. As more studies have come to evaluate the role of ceramide in CF, conflicting results have been described. This paper discusses various views regarding the potential role of ceramide in CF, summarizes methods of ceramide detection and their role in the regulation of cellular and molecular processes.
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Affiliation(s)
- Gabriella Wojewodka
- Human Genetics, McGill University Health Center Research Institute, 1650 Cedar Avenue L11-218, Montreal, QC, Canada H3G 1A4
| | - Juan B. De Sanctis
- Institute of Immunology, Central University of Venezuela, Apartado Postale 50109, Caracas 1050A, Venezuela
| | - Danuta Radzioch
- Departments of Medicine and Human Genetics, McGill University Health Center Research Institute, 1650 Cedar Avenue L11-218, Montreal, QC, Canada H3G 1A4
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Martino AT, Mueller C, Braag S, Cruz PE, Campbell-Thompson M, Jin S, Flotte TR. N-glycosylation augmentation of the cystic fibrosis epithelium improves Pseudomonas aeruginosa clearance. Am J Respir Cell Mol Biol 2010; 44:824-30. [PMID: 20693405 DOI: 10.1165/rcmb.2009-0285oc] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Chronic lung colonization with Pseudomonas aeruginosa is anticipated in cystic fibrosis (CF). Abnormal terminal glycosylation has been implicated as a candidate for this condition. We previously reported a down-regulation of mannose-6-phosphate isomerase (MPI) for core N-glycan production in the CFTR-defective human cell line (IB3). We found a 40% decrease in N-glycosylation of IB3 cells compared with CFTR-corrected human cell line (S9), along with a threefold-lower surface attachment of P. aeruginosa strain, PAO1. There was a twofold increase in intracellular bacteria in S9 cells compared with IB3 cells. After a 4-hour clearance period, intracellular bacteria in IB3 cells increased twofold. Comparatively, a twofold decrease in intracellular bacteria occurred in S9 cells. Gene augmentation in IB3 cells with hMPI or hCFTR reversed these IB3 deficiencies. Mannose-6-phosphate can be produced from external mannose independent of MPI, and correction in the IB3 clearance deficiencies was observed when cultured in mannose-rich medium. An in vivo model for P. aeruginosa colonization in the upper airways revealed an increased bacterial burden in the trachea and oropharynx of nontherapeutic CF mice compared with mice treated either with an intratracheal delivery adeno-associated viral vector 5 expressing murine MPI, or a hypermannose water diet. Finally, a modest lung inflammatory response was observed in CF mice, and was partially corrected by both treatments. Augmenting N-glycosylation to attenuate colonization of P. aeruginosa in CF airways reveals a new therapeutic avenue for a hallmark disease condition in CF.
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Affiliation(s)
- Ashley T Martino
- Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, Florida, USA
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Brodlie M, McKean MC, Johnson GE, Gray J, Fisher AJ, Corris PA, Lordan JL, Ward C. Ceramide is increased in the lower airway epithelium of people with advanced cystic fibrosis lung disease. Am J Respir Crit Care Med 2010; 182:369-75. [PMID: 20395562 DOI: 10.1164/rccm.200905-0799oc] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
RATIONALE Ceramide accumulates in the airway epithelium of mice deficient in cystic fibrosis transmembrane conductance regulator, resulting in susceptibility to Pseudomonas aeruginosa infection and inflammation. OBJECTIVES To investigate quantitatively ceramide levels in the lower airway of people with cystic fibrosis compared with pulmonary hypertension, emphysema, and lung donors. METHODS Immunohistochemistry was performed on the lower airway epithelium of explanted lungs (eight cystic fibrosis, emphysema, and pulmonary hypertension, respectively) and eight donor lungs using ceramide, neutrophil elastase, and myeloperoxidase antibodies. High-performance liquid chromatography-mass spectrometry was performed on tissue from five lungs with cystic fibrosis and five with pulmonary hypertension. MEASUREMENTS AND MAIN RESULTS Staining for ceramide was significantly increased in the lower airway epithelium of people with cystic fibrosis (median, 14.11%) compared with pulmonary hypertension (3.03%; P = 0.0009); unused lung donors (3.44%; P = 0.0009); and emphysema (5.06%; P = 0.01). Ceramide staining was increased in emphysematous lungs compared with pulmonary hypertension (P = 0.0135) and unused donors (P = 0.0009). The number of neutrophil elastase- and myeloperoxidase-positive cells in the airway was positively correlated with the percentage of epithelium staining for ceramide (P = 0.001). Ceramide staining was significantly increased in lungs colonized with Pseudomonas aeruginosa (10.1%) compared with those not colonized (3.14%; P = 0.0106). Significantly raised levels of ceramides C16:0, C18:0, and C20:0 were detected by mass spectrometry in lungs with cystic fibrosis compared with pulmonary hypertension. Differences in C22:0 were not significant. CONCLUSIONS Immunoreactive ceramide is increased in the lower airway epithelium of people with advanced cystic fibrosis. Detected by mass-spectrometry ceramide species C16:0, C18:0, and C20:0 but not C22:0 are increased.
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Affiliation(s)
- Malcolm Brodlie
- Sir William Leech Centre For Lung Research, Freeman Hospital, Newcastle upon Tyne, UK.
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DiMagno MJ, Lee SH, Owyang C, Zhou SY. Inhibition of acinar apoptosis occurs during acute pancreatitis in the human homologue DeltaF508 cystic fibrosis mouse. Am J Physiol Gastrointest Liver Physiol 2010; 299:G400-12. [PMID: 20522641 PMCID: PMC2928535 DOI: 10.1152/ajpgi.00061.2010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Previously, we found that the University of North Carolina cystic fibrosis (UNC-CF) mouse had more severe experimental acute pancreatitis (AP) than wild-type (WT) mice characterized by exuberant pancreatic inflammation and impaired acinar apoptosis. Because exon 10 CFTR gene mutations exhibit different phenotypes in tissues such as the mouse lung, we tested the hypothesis that DeltaF508-CF mice also develop severe AP associated with an antiapoptotic acinar phenotype, which requires indirect effects of the extracellular milieu. We used cerulein hyperstimulation models of AP. More severe pancreatitis occurred in cerulein-injected DeltaF508-CF vs. WT mice based on histological severity (P < 0.01) and greater neutrophil sequestration [P < 0.0001; confirmed by myeloperoxidase activity (P < 0.005)]. In dispersed acini cerulein-evoked necrosis was greater in DeltaF508-CF acini compared with WT (P < 0.05) and in WT acini pretreated with CFTR(inh)-172 compared with vehicle (P < 0.05). Cerulein-injected DeltaF508-CF vs. WT mice had less apoptosis based on poly(ADP-ribose) polymerase (PARP) cleavage (P < 0.005), absent DNA laddering, and reduced terminal deoxynucleotidyltransferase biotin-dUTP nick end labeling (TUNEL) staining (P < 0.005). Unexpectedly, caspase-3 activation was greater in DeltaF508-CF vs. WT acini at baseline (P < 0.05) and during AP (P < 0.0001). Downstream, DeltaF508-CF pancreas overexpressed the X-linked inhibitor of apoptosis compared with WT (P < 0.005). In summary, the DeltaF508-CF mutation, similar to the UNC-CF "null" mutation, causes severe AP characterized by an exuberant inflammatory response and impaired acinar apoptosis. Enhanced acinar necrosis in DeltaF508-CF occurs independently of extracellular milieu and correlates with loss of CFTR-Cl conductance. Although both exon 10 models of CF inhibit acinar apoptosis execution, the DeltaF508-CF mouse differs by increasing apoptosis signaling. Impaired transduction of increased apoptosis signaling in DeltaF508-CF acini may be biologically relevant to the pathogenesis of AP associated with CFTR mutations.
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Affiliation(s)
- Matthew J. DiMagno
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, University of Michigan School of Medicine, Ann Arbor, Michigan
| | - Sae-Hong Lee
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, University of Michigan School of Medicine, Ann Arbor, Michigan
| | - Chung Owyang
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, University of Michigan School of Medicine, Ann Arbor, Michigan
| | - Shi-yi Zhou
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, University of Michigan School of Medicine, Ann Arbor, Michigan
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Becker KA, Riethmüller J, Zhang Y, Gulbins E. The role of sphingolipids and ceramide in pulmonary inflammation in cystic fibrosis. Open Respir Med J 2010; 4:39-47. [PMID: 20556203 DOI: 10.2174/1874306401004020039] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2009] [Revised: 10/20/2009] [Accepted: 10/21/2009] [Indexed: 01/01/2023] Open
Abstract
Sphingolipids and in particular ceramide have been shown to be critically involved in the response to many receptor-mediated, but also receptor-independent, mainly stress stimuli. Recent studies demonstrate that ceramide plays an important role in the pathogenesis of cystic fibrosis, a hereditary metabolic disorder caused by mutations of the Cystic Fibrosis Transmembrane Conductance Regulator. Patients with cystic fibrosis suffer from chronic pulmonary inflammation and microbial lung infections, in particular with Pseudomonas aeruginosa. Chronic pulmonary inflammation in these patients seems to be the initial pathophysiological event. Inflammation may finally result in the high infection susceptibility of these patients, fibrosis and loss of lung function. Recent studies demonstrated that ceramide accumulates in lungs of cystic fibrosis mice and causes age-dependent pulmonary inflammation as indicated by accumulation of neutrophils and macrophages in the lung and increased pulmonary concentrations of Interleukins 1 and 8, death of bronchial epithelial cells, deposition of DNA in bronchi and high susceptibility to Pseudomonas aeruginosa infections. Genetic or pharmacological inhibition of the acid sphingomyelinase blocks excessive ceramide production in lungs of cystic fibrosis mice and corrects pathological lung findings. First clinical studies confirm that inhibition of the acid sphingomyelinase with small molecules might be a novel strategy to treat patients with cystic fibrosis.
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Affiliation(s)
- Katrin Anne Becker
- Department of Molecular Biology, University of Duisburg-Essen, Hufelandstrasse 55, D-45122 Essen, Germany
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Zhang Y, Li X, Grassmé H, Döring G, Gulbins E. Alterations in ceramide concentration and pH determine the release of reactive oxygen species by Cftr-deficient macrophages on infection. THE JOURNAL OF IMMUNOLOGY 2010; 184:5104-11. [PMID: 20351190 DOI: 10.4049/jimmunol.0902851] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We recently demonstrated that the accumulation of ceramide in Cftr-deficient epithelial cells is important for the pathophysiology of CF. However, the role of ceramide in other lung cells, particularly lung macrophages, requires definition. In this study, we report that ceramide is accumulated in Cftr-deficient lung macrophages. Alveolar macrophages contain a vesicle population, which is stained with LysoSensor probes but not by tetramethylrhodamine dextran. These vesicles, presumably secretory lysosomes, exhibit a higher pH in Cftr-deficient macrophages than the corresponding vesicles in lung macrophages isolated from wild-type (WT) mice. Alkalinization of these vesicles in Cftr-deficient macrophages correlates with a failure of the macrophages to respond to infection with various Pseudomonas aeruginosa strains by acutely activating acid sphingomyelinase, releasing ceramide, forming ceramide-enriched membrane platforms that serve to cluster gp91(phox), and, most importantly, releasing reactive oxygen species (ROS). In contrast, these events occur rapidly in WT lung macrophages postinfection. Inhibiting ROS in WT macrophages prevents the killing of P. aeruginosa. These findings provide evidence for a novel pH-controlled pathway from acid sphingomyelinase activation via ceramide and clustering of gp91(phox) to the release of ROS in lung macrophages.
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Affiliation(s)
- Yang Zhang
- Department of Molecular Biology, University of Duisburg-Essen, Hufelandstrasse 55, 45122, Essen, Germany
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Hare NJ, Cordwell SJ. Proteomics of bacterial pathogens: Pseudomonas aeruginosa infections in cystic fibrosis - a case study. Proteomics Clin Appl 2010; 4:228-48. [PMID: 21137046 DOI: 10.1002/prca.200900144] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Revised: 09/09/2009] [Accepted: 09/30/2009] [Indexed: 12/20/2022]
Abstract
Technology development in the high throughput sciences of genomics, transcriptomics and proteomics, has been driven by bacteriological research. These organisms are excellent models for testing new methodology due to their comparatively small genome size, the relative ease of culturing large amounts of material, and the inherent biomedical, environmental and biotechnological interest in their underlying biology. Techniques developed in prokaryotes have since become applicable to higher organisms and human disease, opening vast research opportunities for understanding complex molecular processes. Pseudomonas aeruginosa is an excellent example of a microbe with fascinating properties suitable for stretching the boundaries of technology, and with underlying biology that remains poorly understood. P. aeruginosa is an opportunistic pathogen in humans and contains one of the largest genetic capabilities for a single-celled organism (approximately 5500 genes), which allows it to encode a wide variety of surface-associated and secreted virulence factors, as well as adapt to harsh environments, forming resistance to an array of antibacterial agents. While it is a major threat as a nosocomial pathogen, and particularly in the immunocompromised, it is also the most significant cause of mortality in patients suffering from the genetic disorder, cystic fibrosis. This review examines the role of proteomics in gaining a better understanding of the molecular basis of P. aeruginosa infection and persistence in the lungs of cystic fibrosis patients.
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Affiliation(s)
- Nathan J Hare
- School of Molecular and Microbial Biosciences, The University of Sydney, Sydney, Australia
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Schuchman EH. Acid sphingomyelinase, cell membranes and human disease: lessons from Niemann-Pick disease. FEBS Lett 2009; 584:1895-900. [PMID: 19944693 DOI: 10.1016/j.febslet.2009.11.083] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Accepted: 11/24/2009] [Indexed: 12/11/2022]
Abstract
Acid sphingomyelinase (ASM) plays an important role in normal membrane turnover through the hydrolysis of sphingomyelin, and is one of the key enzymes responsible for the production of ceramide. ASM activity is deficient in the genetic disorder Types A and B Niemann-Pick disease (NPD). ASM knockout (ASMKO) mice were originally constructed to study this disorder, and numerous defects in ceramide-related signaling have been shown. Studies in these mice have further suggested that ASM may be involved in the pathogenesis of several common diseases through the reorganization of membrane microdomains. This review will focus on the role of ASM in membrane biology, with a specific emphasis on what a rare genetic disorder (NPD) has taught us about more common events.
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Affiliation(s)
- Edward H Schuchman
- Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, Icahn Medical Institute, New York, NY 10029, USA.
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Vasil ML, Stonehouse MJ, Vasil AI, Wadsworth SJ, Goldfine H, Bolcome RE, Chan J. A complex extracellular sphingomyelinase of Pseudomonas aeruginosa inhibits angiogenesis by selective cytotoxicity to endothelial cells. PLoS Pathog 2009; 5:e1000420. [PMID: 19424430 PMCID: PMC2673038 DOI: 10.1371/journal.ppat.1000420] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2008] [Accepted: 04/08/2009] [Indexed: 11/19/2022] Open
Abstract
The hemolytic phospholipase C (PlcHR) expressed by Pseudomonas aeruginosa is the original member of a Phosphoesterase Superfamily, which includes phosphorylcholine-specific phospholipases C (PC-PLC) produced by frank and opportunistic pathogens. PlcHR, but not all its family members, is also a potent sphingomyelinase (SMase). Data presented herein indicate that picomolar (pM) concentrations of PlcHR are selectively lethal to endothelial cells (EC). An RGD motif of PlcHR contributes to this selectivity. Peptides containing an RGD motif (i.e., GRGDS), but not control peptides (i.e., GDGRS), block the effects of PlcHR on calcium signaling and cytotoxicity to EC. Moreover, RGD variants of PlcHR (e.g., RGE, KGD) are significantly reduced in their binding and toxicity, but retain the enzymatic activity of the wild type PlcHR. PlcHR also inhibits several EC-dependent in vitro assays (i.e., EC migration, EC invasion, and EC tubule formation), which represent key processes involved in angiogenesis (i.e., formation of new blood vessels from existing vasculature). Finally, the impact of PlcHR in an in vivo model of angiogenesis in transgenic zebrafish, and ones treated with an antisense morpholino to knock down a key blood cell regulator, were evaluated because in vitro assays cannot fully represent the complex processes of angiogenesis. As little as 2 ng/embryo of PlcHR was lethal to approximately 50% of EGFP-labeled EC at 6 h after injection of embryos at 48 hpf (hours post-fertilization). An active site mutant of PlcHR (Thr178Ala) exhibited 120-fold reduced inhibitory activity in the EC invasion assay, and 20 ng/embryo elicited no detectable inhibitory activity in the zebrafish model. Taken together, these observations are pertinent to the distinctive vasculitis and poor wound healing associated with P. aeruginosa sepsis and suggest that the potent antiangiogenic properties of PlcHR are worthy of further investigation for the treatment of diseases where angiogenesis contributes pathological conditions (e.g., vascularization of tumors, diabetic retinopathy).
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Affiliation(s)
- Michael L Vasil
- Department of Microbiology, University of Colorado Denver, Anschutz Medical Center, Aurora, Colorado, United States of America.
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