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Targeting Ceramides and Adiponectin Receptors in the Islet of Langerhans for Treating Diabetes. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27186117. [PMID: 36144859 PMCID: PMC9502927 DOI: 10.3390/molecules27186117] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 09/14/2022] [Accepted: 09/15/2022] [Indexed: 11/17/2022]
Abstract
Ceramides belong to the sphingolipid family and represent the central hub of the sphingolipid network. In obesity, oversupply of saturated fatty acids including palmitate raises ceramide levels which can be detrimental to cells. Elevated ceramides can cause insulin resistance, endoplasmic reticulum stress, and mitochondrial dysfunction. Studies over the last few decades have highlighted the role played by ceramides in pancreatic islet β-cell apoptosis, especially under glucolipotoxic and inflammatory conditions. This review focuses on ceramides and adiponectin receptor signaling, summarizing recent advancements in our understanding of their roles in islet β-cells and the discovery of zinc-dependent lipid hydrolase (ceramidase) activity of adiponectin receptors. The therapeutic potential of targeting these events to prevent islet β-cell loss for treating diabetes is discussed.
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Sphingolipids in Type 1 Diabetes: Focus on Beta-Cells. Cells 2020; 9:cells9081835. [PMID: 32759843 PMCID: PMC7465050 DOI: 10.3390/cells9081835] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 08/01/2020] [Accepted: 08/03/2020] [Indexed: 12/28/2022] Open
Abstract
Type 1 diabetes (T1DM) is a chronic autoimmune disease, with a strong genetic background, leading to a gradual loss of pancreatic beta-cells, which secrete insulin and control glucose homeostasis. Patients with T1DM require life-long substitution with insulin and are at high risk for development of severe secondary complications. The incidence of T1DM has been continuously growing in the last decades, indicating an important contribution of environmental factors. Accumulating data indicates that sphingolipids may be crucially involved in T1DM development. The serum lipidome of T1DM patients is characterized by significantly altered sphingolipid composition compared to nondiabetic, healthy probands. Recently, several polymorphisms in the genes encoding the enzymatic machinery for sphingolipid production have been identified in T1DM individuals. Evidence gained from studies in rodent islets and beta-cells exposed to cytokines indicates dysregulation of the sphingolipid biosynthetic pathway and impaired function of several sphingolipids. Moreover, a number of glycosphingolipids have been suggested to act as beta-cell autoantigens. Studies in animal models of autoimmune diabetes, such as the Non Obese Diabetic (NOD) mouse and the LEW.1AR1-iddm (IDDM) rat, indicate a crucial role of sphingolipids in immune cell trafficking, islet infiltration and diabetes development. In this review, the up-to-date status on the findings about sphingolipids in T1DM will be provided, the under-investigated research areas will be identified and perspectives for future studies will be given.
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Buschard K. Fenofibrate increases the amount of sulfatide which seems beneficial against Covid-19. Med Hypotheses 2020; 143:110127. [PMID: 32759008 PMCID: PMC7372998 DOI: 10.1016/j.mehy.2020.110127] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 07/19/2020] [Indexed: 12/13/2022]
Abstract
Fenofibrate, which is a PPAR-alfpha agonist, increases the level of sulfatide. In this letter we hypothesize on the background of various findings that this is beneficial against COVID-19. Fenofibrate has been used for decades against hypercholesterolemia and has no serious side effects. Therefore, a trial giving fenofibrate to patients with corona virus infection is recommended.
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Kim HS, Han M, Park IH, Park CH, Kwak MS, Shin JS. Sulfatide Inhibits HMGB1 Secretion by Hindering Toll-Like Receptor 4 Localization Within Lipid Rafts. Front Immunol 2020; 11:1305. [PMID: 32655573 PMCID: PMC7324676 DOI: 10.3389/fimmu.2020.01305] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Accepted: 05/22/2020] [Indexed: 12/11/2022] Open
Abstract
The high mobility group box 1 (HMGB1) is a well-known late mediator of sepsis, secreted by multiple stimuli, involving pathways, such as the mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB) pathways, and reactive oxygen species (ROS) under inflammation. Sulfatide, in contrast, is a sphingolipid commonly found in myelin sheets with a disputed immunological role. We sought to determine the immunological characteristics of sulfatide in the periphery by analyzing the secretion of HMGB1 triggered by lipopolysaccharide (LPS) stimulation in Raw 264.7 cells. Suppression of HMGB1 secretion by inhibiting its cytosolic translocation was observed after pre-treatment with sulfatide before LPS stimulation. Further analysis of the downstream molecules of toll-like receptor (TLR) signaling revealed suppression of c-Jun N-terminal kinase (JNK) phosphorylation and p65 translocation. LPS-mediated ROS production was also decreased when sulfatide pre-treatment was provided, caused by the down-regulation of the phosphorylation of activators, such as IRAK4 and TBK1. Investigation of the upstream mechanism that encompasses all the aforementioned inhibitory characteristics unveiled the involvement of lipid rafts. In addition to the co-localization of biotinylated sulfatide and monosialotetrahexosylganglioside, a decrease in LPS-induced co-localization of TLR4 and lipid raft markers was observed when sulfatide treatment was given before LPS stimulation. Overall, sulfatide was found to exert its anti-inflammatory properties by hindering the co-localization of TLR4 and lipid rafts, nullifying the effect of LPS on TLR4 signaling. Similar effects of sulfatide were also confirmed in the LPS-mediated murine experimental sepsis model, showing decreased levels of serum HMGB1, increased survivability, and reduced pathological severity.
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Affiliation(s)
- Hee Sue Kim
- Department of Microbiology, Yonsei University College of Medicine, Seoul, South Korea.,Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, South Korea
| | - Myeonggil Han
- Department of Microbiology, Yonsei University College of Medicine, Seoul, South Korea.,Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, South Korea
| | - In Ho Park
- Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, South Korea.,Institute for Immunology and Immunological Diseases, Yonsei University College of Medicine, Seoul, South Korea
| | - Cheol Ho Park
- Department of Microbiology, Yonsei University College of Medicine, Seoul, South Korea
| | - Man Sup Kwak
- Department of Microbiology, Yonsei University College of Medicine, Seoul, South Korea.,Institute for Immunology and Immunological Diseases, Yonsei University College of Medicine, Seoul, South Korea
| | - Jeon-Soo Shin
- Department of Microbiology, Yonsei University College of Medicine, Seoul, South Korea.,Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, South Korea.,Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, South Korea.,Institute for Immunology and Immunological Diseases, Yonsei University College of Medicine, Seoul, South Korea
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5
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Tanphaichitr N, Kongmanas K, Faull KF, Whitelegge J, Compostella F, Goto-Inoue N, Linton JJ, Doyle B, Oko R, Xu H, Panza L, Saewu A. Properties, metabolism and roles of sulfogalactosylglycerolipid in male reproduction. Prog Lipid Res 2018; 72:18-41. [PMID: 30149090 PMCID: PMC6239905 DOI: 10.1016/j.plipres.2018.08.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 08/20/2018] [Accepted: 08/21/2018] [Indexed: 12/16/2022]
Abstract
Sulfogalactosylglycerolipid (SGG, aka seminolipid) is selectively synthesized in high amounts in mammalian testicular germ cells (TGCs). SGG is an ordered lipid and directly involved in cell adhesion. SGG is indispensable for spermatogenesis, a process that greatly depends on interaction between Sertoli cells and TGCs. Spermatogenesis is disrupted in mice null for Cgt and Cst, encoding two enzymes essential for SGG biosynthesis. Sperm surface SGG also plays roles in fertilization. All of these results indicate the significance of SGG in male reproduction. SGG homeostasis is also important in male fertility. Approximately 50% of TGCs become apoptotic and phagocytosed by Sertoli cells. SGG in apoptotic remnants needs to be degraded by Sertoli lysosomal enzymes to the lipid backbone. Failure in this event leads to a lysosomal storage disorder and sub-functionality of Sertoli cells, including their support for TGC development, and consequently subfertility. Significantly, both biosynthesis and degradation pathways of the galactosylsulfate head group of SGG are the same as those of sulfogalactosylceramide (SGC), a structurally related sulfoglycolipid important for brain functions. If subfertility in males with gene mutations in SGG/SGC metabolism pathways manifests prior to neurological disorder, sperm SGG levels might be used as a reporting/predicting index of the neurological status.
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Affiliation(s)
- Nongnuj Tanphaichitr
- Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada; Department of Obstetrics/Gynecology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada; Department of Biochemistry, Microbiology, Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada.
| | - Kessiri Kongmanas
- Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada; Department of Biochemistry, Microbiology, Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada; Division of Dengue Hemorrhagic Fever Research, Department of Research and Development, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand
| | - Kym F Faull
- Pasarow Mass Spectrometry Laboratory, University of California, Los Angeles, California, USA
| | - Julian Whitelegge
- Pasarow Mass Spectrometry Laboratory, University of California, Los Angeles, California, USA
| | - Federica Compostella
- Dipartimento di Biotecnologie Mediche e Medicina Traslazionale, Università degli Studi di Milano, Via Saldini 50, 20133 Milano, Italy
| | - Naoko Goto-Inoue
- Department of Marine Science and Resources, College of Bioresource Sciences, Nihon University, Kanagawa 252-0880, Japan
| | - James-Jules Linton
- Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
| | - Brendon Doyle
- Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada; Department of Biochemistry, Microbiology, Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Richard Oko
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Hongbin Xu
- Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada; Department of Biochemistry, Microbiology, Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Luigi Panza
- Department of Pharmaceutical Sciences, Università del Piemonte Orientale, Largo Donegani 2, 28100 Novara, Italy
| | - Arpornrad Saewu
- Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
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6
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Pituch KC, Moyano AL, Lopez-Rosas A, Marottoli FM, Li G, Hu C, van Breemen R, Månsson JE, Givogri MI. Dysfunction of platelet-derived growth factor receptor α (PDGFRα) represses the production of oligodendrocytes from arylsulfatase A-deficient multipotential neural precursor cells. J Biol Chem 2015; 290:7040-53. [PMID: 25605750 DOI: 10.1074/jbc.m115.636498] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The membrane-bound receptor for platelet-derived growth factor A (PDGFRα) is crucial for controlling the production of oligodendrocytes (OLs) for myelination, but regulation of its activity during OL differentiation is largely unknown. We have examined the effect of increased sulfated content of galactosylceramides (sulfatides) on the regulation of PDGFRα in multipotential neural precursors (NPs) that are deficient in arylsulfatase A (ASA) activity. This enzyme is responsible for the lysosomal hydrolysis of sulfatides. We show that sulfatide accumulation significantly impacts the formation of OLs via deregulation of PDGFRα function. PDGFRα is less associated with detergent-resistant membranes in ASA-deficient cells and showed a significant decrease in AKT phosphorylation. Rescue experiments with ASA showed a normalization of the ratio of long versus short sulfatides, restored PDGFRα levels, corrected its localization to detergent-resistant membranes, increased AKT phosphorylation, and normalized the production of OLs in ASA-deficient NPs. Moreover, our studies identified a novel mechanism that regulates the secretion of PDGFRα in NPs, in glial cells, and in the brain cortex via exosomal shedding. Our study provides a first step in understanding the role of sulfatides in regulating PDGFRα levels in OLs and its impact in myelination.
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Affiliation(s)
- Katarzyna C Pituch
- From the Department of Anatomy and Cell Biology, College of Medicine, and
| | - Ana L Moyano
- From the Department of Anatomy and Cell Biology, College of Medicine, and
| | - Aurora Lopez-Rosas
- From the Department of Anatomy and Cell Biology, College of Medicine, and
| | | | - Guannan Li
- the Department of Medical Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois, Chicago, Illinois 60612 and
| | - Chenqi Hu
- the Department of Medical Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois, Chicago, Illinois 60612 and
| | - Richard van Breemen
- the Department of Medical Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois, Chicago, Illinois 60612 and
| | - Jan E Månsson
- the Department of Clinical Chemistry, Sahlgren Academy, University of Gothenburg, SE-413 45 Gothenburg, Sweden
| | - Maria I Givogri
- From the Department of Anatomy and Cell Biology, College of Medicine, and
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7
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Moyano AL, Li G, Lopez-Rosas A, Månsson JE, van Breemen RB, Givogri MI. Distribution of C16:0, C18:0, C24:1, and C24:0 sulfatides in central nervous system lipid rafts by quantitative ultra-high-pressure liquid chromatography tandem mass spectrometry. Anal Biochem 2014; 467:31-9. [PMID: 25205652 DOI: 10.1016/j.ab.2014.08.033] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Accepted: 08/26/2014] [Indexed: 01/18/2023]
Abstract
Sulfated galactosylceramides (sulfatides) are glycosphingolipids associated with cholesterol- and sphingolipid-enriched membrane microdomains (lipid rafts) and are highly expressed in brain tissue. Although it is known that sulfatide species show heterogeneity in their fatty acid acyl group composition throughout brain development, their lipid raft distribution and biological relevance is poorly understood. We validated a fast and sensitive ultra-high-pressure liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method to measure developmentally regulated sulfatide species (C16:0, C18:0, C24:1, and C24:0) in central nervous system (CNS) lipid rafts isolated without using detergent. Our UHPLC-MS/MS assay showed good accuracy and precision with a linear range of 5 to 1,000 nM for C18:0 and C24:1 sulfatides and 10 to 1,000 nM for C16:0 and C24:0 sulfatides. We applied this quantitative analysis to detergent-free lipid rafts isolated from wild-type mice and arylsulfatase A-deficient (ASA knockout) mice that accumulate sulfatides. All four sulfatide species were more abundant in raft membranes than in non-raft membranes, with a significant increase in lipid rafts isolated from ASA knockout mice. This is the first description of an analytical method to study these sulfatide species in raft and non-raft membranes and has the potential to be applied to preparations from other tissues.
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Affiliation(s)
- Ana Lis Moyano
- Department of Anatomy and Cell Biology, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Guannan Li
- Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Aurora Lopez-Rosas
- Department of Anatomy and Cell Biology, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Jan-Eric Månsson
- Department of Clinical Chemistry, The Sahlgrenska Academy, University of Gothenburg, SE-413 45 Gothenburg, Sweden
| | - Richard B van Breemen
- Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Maria Irene Givogri
- Department of Anatomy and Cell Biology, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA.
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8
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Di Gialleonardo V, de Vries EFJ, Di Girolamo M, Quintero AM, Dierckx RAJO, Signore A. Imaging of β-cell mass and insulitis in insulin-dependent (Type 1) diabetes mellitus. Endocr Rev 2012; 33:892-919. [PMID: 22889646 DOI: 10.1210/er.2011-1041] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Insulin-dependent (type 1) diabetes mellitus is a metabolic disease with a complex multifactorial etiology and a poorly understood pathogenesis. Genetic and environmental factors cause an autoimmune reaction against pancreatic β-cells, called insulitis, confirmed in pancreatic samples obtained at autopsy. The possibility to noninvasively quantify β-cell mass in vivo would provide important biological insights and facilitate aspects of diagnosis and therapy, including follow-up of islet cell transplantation. Moreover, the availability of a noninvasive tool to quantify the extent and severity of pancreatic insulitis could be useful for understanding the natural history of human insulin-dependent (type 1) diabetes mellitus, to early diagnose children at risk to develop overt diabetes, and to select patients to be treated with immunotherapies aimed at blocking the insulitis and monitoring the efficacy of these therapies. In this review, we outline the imaging techniques currently available for in vivo, noninvasive detection of β-cell mass and insulitis. These imaging techniques include magnetic resonance imaging, ultrasound, computed tomography, bioluminescence and fluorescence imaging, and the nuclear medicine techniques positron emission tomography and single-photon emission computed tomography. Several approaches and radiopharmaceuticals for imaging β-cells and lymphocytic insulitis are reviewed in detail.
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Affiliation(s)
- Valentina Di Gialleonardo
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, 9700 AB, Groningen, The Netherlands
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9
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Arigi E, Blixt O, Buschard K, Clausen H, Levery SB. Design of a covalently bonded glycosphingolipid microarray. Glycoconj J 2011; 29:1-12. [PMID: 22102144 DOI: 10.1007/s10719-011-9359-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2011] [Revised: 10/03/2011] [Accepted: 10/28/2011] [Indexed: 11/30/2022]
Abstract
Glycosphingolipids (GSLs) are well known ubiquitous constituents of all eukaryotic cell membranes, yet their normal biological functions are not fully understood. As with other glycoconjugates and saccharides, solid phase display on microarrays potentially provides an effective platform for in vitro study of their functional interactions. However, with few exceptions, the most widely used microarray platforms display only the glycan moiety of GSLs, which not only ignores potential modulating effects of the lipid aglycone, but inherently limits the scope of application, excluding, for example, the major classes of plant and fungal GSLs. In this work, a prototype "universal" GSL-based covalent microarray has been designed, and preliminary evaluation of its potential utility in assaying protein-GSL binding interactions investigated. An essential step in development involved the enzymatic release of the fatty acyl moiety of the ceramide aglycone of selected mammalian GSLs with sphingolipid N-deacylase (SCDase). Derivatization of the free amino group of a typical lyso-GSL, lyso-G(M1), with a prototype linker assembled from succinimidyl-[(N-maleimidopropionamido)-diethyleneglycol] ester and 2-mercaptoethylamine, was also tested. Underivatized or linker-derivatized lyso-GSL were then immobilized on N-hydroxysuccinimide- or epoxide-activated glass microarray slides and probed with carbohydrate binding proteins of known or partially known specificities (i.e., cholera toxin B-chain; peanut agglutinin, a monoclonal antibody to sulfatide, Sulph 1; and a polyclonal antiserum reactive to asialo-G(M2)). Preliminary evaluation of the method indicated successful immobilization of the GSLs, and selective binding of test probes. The potential utility of this methodology for designing covalent microarrays that incorporate GSLs for serodiagnosis is discussed.
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Affiliation(s)
- Emma Arigi
- Department of Cellular and Molecular Medicine, University of Copenhagen, Denmark
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10
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Endosomes and lysosomes play distinct roles in sulfatide-induced neuroblastoma apoptosis: potential mechanisms contributing to abnormal sulfatide metabolism in related neuronal diseases. Biochem J 2008; 410:81-92. [PMID: 17939778 DOI: 10.1042/bj20070976] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Alterations in sulfatide metabolism, trafficking and homoeostasis are present at the earliest clinically recognizable stages of Alzheimer's disease and are associated with metachromatic leukodystrophy. However, the role of sulfatide in these disease states remains unknown. In the present study, we investigated the sequelae of NB (neuroblastoma) cells upon sulfatide supplementation and the biochemical mechanisms contributing to the sulfatide-induced changes. By using shotgun lipidomics, we showed dramatic accumulations of sulfatide, ceramide and sphingosine in NB cells in a time- and dose-dependent manner. Further studies utilizing subcellular fractionation and shotgun lipidomics analyses demonstrated that most of the increased ceramide content was generated in the endosomal compartment, whereas sulfatides predominantly accumulated in lysosomes. In addition, we determined that the sulfatide-mediated increase in endosomal ceramide content mainly resulted from beta-galactosidase activity, which directly hydrolyses sulfatide to ceramide without a prior desulfation step. Substantial cell apoptosis occurred in parallel with the accumulation of sulfatides and ceramides, as revealed by mitochondrial membrane depolarization, by phosphatidylserine translocation and by the TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling) assay. These findings were also demonstrated with primary neuron cultures. Collectively, our results demonstrate that abnormal sulfatide metabolism can induce cell apoptosis due to endosome-mediated ceramide generation and the accumulation of cytotoxic levels of sulfatides in lysosomes.
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Abstract
BACKGROUND AND PURPOSE Sulphatides are sulphated glycosphingolipids expressed on the surface of many cell types, particularly neurones. Changes in sulphatide species or content have been associated with epilepsy and Alzheimer's disease. As the large conductance, calcium sensitive K(+) channel (BK(Ca)) are modulated by membrane lipids, the aim of the study was to explore possible effects of sulphatides on BK(Ca) channels. EXPERIMENTAL APPROACH Using patch-clamp techniques, we studied effects of exogenous sulphatides on BK(Ca) channels expressed in Chinese hamster ovary cells. KEY RESULTS Sulphatides reversibly increased the whole-cell current and the single channel open probability of BK(Ca) channels dose-dependently. The EC(50) value on the channel at +10 mV was 1.6 microM and the Hill coefficient was 2.5. In inside-out patches, sulphatides increased the single channel open probability from both intra- and extra-cellular faces of the membrane, but more effectively with external application. Furthermore, activation of the channels by sulphatides was independent of intracellular Ca(2+) concentration. Sulphatides also shifted the activation curve of the channels to less positive membrane potentials. Mutant BK(Ca) channels lacking a 59 aminoacid region important for amphipath activation (STREX) were less activated by the sulphatides. CONCLUSIONS AND IMPLICATIONS Sulphatides are novel activators of BK(Ca) channels, independent of intracellular Ca(2+) or other signalling molecules but partly dependent on the STREX sequence of the channel protein. As changes of sulphatide content are associated with neuronal dysfunction, as in epilepsy and Alzheimer's disease, our results imply that these effects of sulphatides may play important pathophysiological roles in regulation of BK(Ca) channels.
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Affiliation(s)
- S Chi
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics Beijing, PR China
| | - Z Qi
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics Beijing, PR China
- Author for correspondence:
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Isaac G, Pernber Z, Gieselmann V, Hansson E, Bergquist J, Månsson JE. Sulfatide with short fatty acid dominates in astrocytes and neurons. FEBS J 2006; 273:1782-90. [PMID: 16623713 DOI: 10.1111/j.1742-4658.2006.05195.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Glycosphingolipids are located in cell membranes and the brain is especially enriched. We speculated that the subcellular location of glycosphingolipids depends on their fatty acid chain length because their sugar residues are constant, whereas fatty acid chain length can vary within the same molecule. To test this hypothesis we analysed the glycosphingolipid sulfatide, which is highly abundant in myelin and has mostly long fatty acids. We used a negative ion electrospray tandem mass spectrometry precursor ion scan to analyse the molecular species of sulfatide in cultured astrocytes and a mouse model of the human disease metachromatic leukodystrophy. In these arylsulfatase A (ASA)-deficient mice sulfatide accumulates intracellularly in neurons and astrocytes. Immunocytochemistry was also performed on cultured astrocytes and analysed using confocal laser scanning microscopy. Analyses of the molecular species showed that cultured astrocytes contained sulfatide with a predominance of stearic acid (C18), which was located in large intracellular vesicles throughout the cell body and along the processes. The same was seen in ASA-deficient mice, which accumulated a higher proportion (15 mol% compared with 8 mol% in control mice) of sulfatide with stearic acid. We conclude that the major fatty acid composition of sulfatide differs between white and grey matter, with neurons and astrocytes containing mostly short-chain fatty acids with an emphasis on stearic acid. Based on our results, we speculate that the fatty acid chain length of sulfatide might determine its intracellular (short chain) or extracellular (long chain) location and thereby its functions.
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Affiliation(s)
- Giorgis Isaac
- Department of Analytical Chemistry, Uppsala University, Sweden
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13
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Guchhait P, López JA, Thiagarajan P. Characterization of autoantibodies against sulfatide from a V-gene phage-display library derived from patients with systemic lupus erythematosus. J Immunol Methods 2004; 295:129-37. [PMID: 15627618 DOI: 10.1016/j.jim.2004.10.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2004] [Revised: 09/30/2004] [Accepted: 10/06/2004] [Indexed: 11/17/2022]
Abstract
Sulfatide, ceramide galactosyl-3'-sulfate, is mainly present in nervous tissue, kidney, testis, red blood cells, platelets and granulocyte. Antibodies to sulfatide are present in many patients with demyelinating peripheral neuropathy, HIV infection and systemic lupus erythematosus and may account for some of the clinical manifestations. To evaluate the effect of such antibodies, we have constructed a phage-display antibody fragment library from the lymphocytes of patients with systemic lupus erythematosus. Sulfatide-reactive phage were selected by absorption and elution on sulfatide liposomes and soluble single chain variable fragment (ScFv) were isolated from individual colonies and tested in an ELISA assay for binding to bovine brain sulfatide. Five ScFv clones that bound sulfatide were isolated. Two of the clones, PH5 and PA38, bound sulfatide but not phosphatidylserine, phosphatidylcholine, phosphatidylethanolamine, sphingomyelin or ceramide. These two clones also bound sulfatide from human red blood cells. The DNA encoding the fragments was sequenced, revealing predicted polypeptides of 19 kDa for PH5 containing only variable heavy (VH) sequences, and 31 kDa for PA38, with both VH and variable light (VL) sequences. Although they had similar antigen specificities, the VH domains of the two clones were derived from different heavy-chain families. The clustered mutational patterns in the complementarity-determining region (CDR) of the heavy chains in both clones suggest that the V-domains are the products of antigen-driven B cell clonal maturation leading to the development of sulfatide-binding specificity. These results show the presence of sulfatide-specific antibodies in lupus patients, and allow us to test the possibility that the interaction of the antibodies with sulfatide may contribute to some of the symptoms. In addition, the antibodies provide useful reagents to test the role of sulfatide in pathophysiological processes.
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Affiliation(s)
- Prasenjit Guchhait
- Thrombosis Research Section, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA
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