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Kiser PD, Kolesnikov AV, Kiser JZ, Dong Z, Chaurasia B, Wang L, Summers SA, Hoang T, Blackshaw S, Peachey NS, Kefalov VJ, Palczewski K. Conditional deletion of Des1 in the mouse retina does not impair the visual cycle in cones. FASEB J 2019; 33:5782-5792. [PMID: 30645148 PMCID: PMC6436658 DOI: 10.1096/fj.201802493r] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cone photoreceptors are essential for vision under moderate to high illuminance and allow color discrimination. Their fast dark adaptation rate and resistance to saturation are believed to depend in part on an intraretinal visual cycle that supplies 11-cis-retinaldehyde to cone opsins. Candidate enzymes of this pathway have been reported, but their physiologic contribution to cone photoresponses remains unknown. Here, we evaluate the role of a candidate retinol isomerase of this pathway, sphingolipid δ4 desaturase 1 (Des1). Single-cell RNA sequencing analysis revealed Des1 expression not only in Müller glia but also throughout the retina and in the retinal pigment epithelium. We assessed cone functional dependence on Müller cell–expressed Des1 through a conditional knockout approach. Floxed Des1 mice, on a guanine nucleotide-binding protein subunit α transducin 1 knockout (Gnat1−/−) background to allow isolated recording of cone-driven photoresponses, were bred with platelet-derived growth factor receptor α (Pdgfrα)-Cre mice to delete Des1 in Müller cells. Conditional knockout of Des1 expression, as shown by tissue-selective Des1 gene recombination and reduced Des1 catalytic activity, caused no gross changes in the retinal structure and had no effect on cone sensitivity or dark adaptation but did slightly accelerate the rate of cone phototransduction termination. These results indicate that Des1 expression in Müller cells is not required for cone visual pigment regeneration in the mouse.—Kiser, P. D., Kolesnikov, A.V., Kiser, J. Z., Dong, Z., Chaurasia, B., Wang, L., Summers, S. A., Hoang, T., Blackshaw, S., Peachey, N. S., Kefalov, V. J., Palczewski, K. Conditional deletion of Des1 in the mouse retina does not impair the visual cycle in cones.
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Affiliation(s)
- Philip D Kiser
- Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio, USA.,Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Alexander V Kolesnikov
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Jianying Z Kiser
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | | | - Bhagirath Chaurasia
- Department of Nutrition and Integrative Physiology (NUIP), University of Utah, Salt Lake City, Utah, USA.,Diabetes and Metabolism Research Center, University of Utah, Salt Lake City, Utah, USA
| | - Liping Wang
- Department of Nutrition and Integrative Physiology (NUIP), University of Utah, Salt Lake City, Utah, USA.,Diabetes and Metabolism Research Center, University of Utah, Salt Lake City, Utah, USA
| | - Scott A Summers
- Department of Nutrition and Integrative Physiology (NUIP), University of Utah, Salt Lake City, Utah, USA.,Diabetes and Metabolism Research Center, University of Utah, Salt Lake City, Utah, USA
| | - Thanh Hoang
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Seth Blackshaw
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Neal S Peachey
- Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio, USA.,Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | - Vladimir J Kefalov
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Krzysztof Palczewski
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.,Department of Ophthalmology, Gavin Herbert Eye Institute, University of California-Irvine, School of Medicine, Irvine, California, USA
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Kiser PD, Zhang J, Sharma A, Angueyra JM, Kolesnikov AV, Badiee M, Tochtrop GP, Kinoshita J, Peachey NS, Li W, Kefalov VJ, Palczewski K. Retinoid isomerase inhibitors impair but do not block mammalian cone photoreceptor function. J Gen Physiol 2018; 150:571-590. [PMID: 29500274 PMCID: PMC5881442 DOI: 10.1085/jgp.201711815] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Revised: 12/18/2017] [Accepted: 01/22/2018] [Indexed: 12/11/2022] Open
Abstract
RPE65 is a retinoid isomerase essential for rod function, but its contribution to cone vision is enigmatic. Using selective RPE65 inhibitors, Kiser et al. demonstrate that cone function depends only partially on continuous RPE65 activity, providing support for cone-specific regeneration mechanisms. Visual function in vertebrates critically depends on the continuous regeneration of visual pigments in rod and cone photoreceptors. RPE65 is a well-established retinoid isomerase in the pigment epithelium that regenerates rhodopsin during the rod visual cycle; however, its contribution to the regeneration of cone pigments remains obscure. In this study, we use potent and selective RPE65 inhibitors in rod- and cone-dominant animal models to discern the role of this enzyme in cone-mediated vision. We confirm that retinylamine and emixustat-family compounds selectively inhibit RPE65 over DES1, the putative retinoid isomerase of the intraretinal visual cycle. In vivo and ex vivo electroretinography experiments in Gnat1−/− mice demonstrate that acute administration of RPE65 inhibitors after a bleach suppresses the late, slow phase of cone dark adaptation without affecting the initial rapid portion, which reflects intraretinal visual cycle function. Acute administration of these compounds does not affect the light sensitivity of cone photoreceptors in mice during extended exposure to background light, but does slow all phases of subsequent dark recovery. We also show that cone function is only partially suppressed in cone-dominant ground squirrels and wild-type mice by multiday administration of an RPE65 inhibitor despite profound blockade of RPE65 activity. Complementary experiments in these animal models using the DES1 inhibitor fenretinide show more modest effects on cone recovery. Collectively, these studies demonstrate a role for continuous RPE65 activity in mammalian cone pigment regeneration and provide further evidence for RPE65-independent regeneration mechanisms.
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Affiliation(s)
- Philip D Kiser
- Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, OH .,Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH
| | - Jianye Zhang
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH
| | - Aditya Sharma
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, Saint Louis, MO
| | - Juan M Angueyra
- Retinal Neurophysiology Section, National Eye Institute, Bethesda, MD
| | - Alexander V Kolesnikov
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, Saint Louis, MO
| | - Mohsen Badiee
- Department of Chemistry, College of Arts and Sciences, Case Western Reserve University, Cleveland, OH
| | - Gregory P Tochtrop
- Department of Chemistry, College of Arts and Sciences, Case Western Reserve University, Cleveland, OH
| | | | - Neal S Peachey
- Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, OH.,Cole Eye Institute, Cleveland Clinic, Cleveland, OH.,Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH
| | - Wei Li
- Retinal Neurophysiology Section, National Eye Institute, Bethesda, MD
| | - Vladimir J Kefalov
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, Saint Louis, MO
| | - Krzysztof Palczewski
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH
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Bellini L, Campana M, Mahfouz R, Carlier A, Véret J, Magnan C, Hajduch E, Le Stunff H. Targeting sphingolipid metabolism in the treatment of obesity/type 2 diabetes. Expert Opin Ther Targets 2015; 19:1037-50. [PMID: 25814122 DOI: 10.1517/14728222.2015.1028359] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
INTRODUCTION Obesity is a major factor that is linked to the development of type 2 diabetes (T2D). Excess circulating fatty acids (FAs), which characterize obesity, induce insulin resistance, steatosis, β cells dysfunction and apoptosis. These deleterious effects have been defined as lipotoxicity. AREAS COVERED FAs are metabolized to different lipid species, including ceramides which play a crucial role in lipotoxicity. The action of ceramides on tissues, such as muscle, liver, adipose tissue and pancreatic β cells, during the development of T2D will also be reviewed. In addition, the potential antagonist action of other sphingolipids, namely sphingoid base phosphates, on lipotoxicity in skeletal muscle and β cells will be addressed. EXPERT OPINION Ceramide is a critical mediator to the development of T2D linked to obesity. Targeting proteins involved in ceramide's deleterious action has not been possible due to their involvement in many other intracellular signaling pathways. A possible means of counteracting ceramide action would be to prevent the accumulation of the specific ceramide species involved in both insulin resistance and β-cell apoptosis/dysfunction. Another possibility would be to adjust the dynamic balance between ceramide and sphingoid base phosphate, both known to display opposing properties on the development of T2D-linked obesity.
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Affiliation(s)
- Lara Bellini
- Université PARIS-DIDEROT (7), Unité Biologie Fonctionnelle et Adaptative - UMR CNRS 8251, Équipe Régulation de la glycémie par le système nerveux central (REGLYS) , 4, rue Marie-Andrée Lagroua Weill-Halle, 75205 PARIS Cedex 13 , France +01 57 27 77 97 ; +01 57 27 77 96 ;
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Skolová B, Jandovská K, Pullmannová P, Tesař O, Roh J, Hrabálek A, Vávrová K. The role of the trans double bond in skin barrier sphingolipids: permeability and infrared spectroscopic study of model ceramide and dihydroceramide membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:5527-5535. [PMID: 24779554 DOI: 10.1021/la500622f] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Dihydroceramides (dCer) are members of the sphingolipid family that lack the C4 trans double bond in their sphingoid backbone. In addition to being precursors of ceramides (Cer) and phytoceramides, dCer have also been found in the extracellular lipid membranes of the epidermal barrier, the stratum corneum. However, their role in barrier homeostasis is not known. We studied how the lack of the trans double bond in dCer compared to Cer influences the permeability, lipid chain order, and packing of multilamellar membranes composed of the major skin barrier lipids: (d)Cer, fatty acids, cholesterol, and cholesteryl sulfate. The permeability of the membranes with long-chain dCer was measured using various markers and was either comparable to or only slightly greater than (by up to 35%, not significant) that of the Cer membranes. The dCer were less sensitive to acyl chain shortening than Cer (the short dCer membranes were up to 6-fold less permeable that the corresponding short Cer membranes). Infrared spectroscopy showed that long dCer mixed less with fatty acids but formed more thermally stable ordered domains than Cer. The key parameter explaining the differences in permeability in the short dCer and Cer was the proportion of the orthorhombic phase. Our results suggest that the presence of the trans double bond in Cer is not crucial for the permeability of skin lipid membranes and that dCer may be underappreciated members of the stratum corneum lipid barrier that increase its heterogeneity.
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Affiliation(s)
- Barbora Skolová
- Skin Barrier Research Group, Faculty of Pharmacy in Hradec Králové, Charles University in Prague , Heyrovského 1203, 50005 Hradec Králové, Czech Republic
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Shin KO, Park NY, Seo CH, Hong SP, Oh KW, Hong JT, Han SK, Lee YM. Inhibition of sphingolipid metabolism enhances resveratrol chemotherapy in human gastric cancer cells. Biomol Ther (Seoul) 2013; 20:470-6. [PMID: 24009836 PMCID: PMC3762276 DOI: 10.4062/biomolther.2012.20.5.470] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Revised: 09/03/2012] [Accepted: 09/03/2012] [Indexed: 12/22/2022] Open
Abstract
Resveratrol, a chemopreventive agent, is rapidly metabolized in the intestine and liver via glucuronidation. Thus, the pharmacokinetics of resveratrol limits its efficacy. To improve efficacy, the activity of resveratrol was investigated in the context of sphingolipid metabolism in human gastric cancer cells. Diverse sphingolipid metabolites, including dihydroceramides (DHCer), were tested for their ability to induce resveratrol cytotoxicity. Exposure to resveratrol (100 μM) for 24 hr induced cell death and cell cycle arrest in gastric cancer cells. Exposure to the combination of resveratrol and dimethylsphingosine (DMS) increased cytotoxicity, demonstrating that sphingolipid metabolites intensify resveratrol activity. Specifically, DHCer accumulated in a resveratrol concentration-dependent manner in SNU-1 and HT-29 cells, but not in SNU-668 cells. LC-MS/MS analysis showed that specific DHCer species containing C24:0, C16:0, C24:1, and C22:0 fatty acids chain were increased by up to 30-fold by resveratrol, indicating that resveratrol may partially inhibit DHCer desaturase. Indeed, resveratrol mildly inhibited DHCer desaturase activity compared to the specific inhibitor GT-11 or to retinamide (4-HPR); however, in SNU-1 cells resveratrol alone exhibited a typical cell cycle arrest pattern, which GT-11 did not alter, indicating that inhibition of DHCer desaturase is not essential to the cytotoxicity induced by the combination of resveratrol and sphingolipid metabolites. Resveratrol-induced p53 expression strongly correlated with the enhancement of cytotoxicity observed upon combination of resveratrol with DMS or 4-HPR. Taken together, these results show that DHCer accumulation is a novel lipid biomarker of resveratrol-induced cytotoxicity in human gastric cancer cells.
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Affiliation(s)
- Kyong-Oh Shin
- College of Pharmacy and MRC, Chungbuk National University, Chongju 361-763, Republic of Korea
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6
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Azzam R, Hariri F, El-Hachem N, Kamar A, Dbaibo G, Nemer G, Bitar F. Regulation of de novo ceramide synthesis: the role of dihydroceramide desaturase and transcriptional factors NFATC and Hand2 in the hypoxic mouse heart. DNA Cell Biol 2013; 32:310-9. [PMID: 23672204 DOI: 10.1089/dna.2013.1993] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We have previously shown that ceramide, a proapoptotic molecule decreases in the mouse heart as it adapts to hypoxia. We have also shown that its precursor, dihydroceramide, accumulates with hypoxia. This implicates the enzyme dihydroceramide desaturase (DHC-DS), which converts dihydroceramide to ceramide, in a potential regulatory checkpoint in cardiomyocytes. We hypothesised that the regulation of de novo ceramide synthesis plays an important role in the cardiomyocyte adaptation to hypoxia. We used an established mouse model to induce acute and chronic hypoxia. Cardiac tissues were extracted and quantitative real-time polymerase chain reaction (qRT-PCR) was used to evaluate the expression levels of DHC-DS. Electrophoretic Mobility Shift Assays (EMSAs) and qRT-PCR were used to evaluate the activity and expression levels of an array of transcription factors that might regulate DEGS1 gene expression. We demonstrated that DEGS1 mRNA levels decrease with time in hypoxic mice concurrent with the decrease in HAND2 transcripts. Interestingly, the DEGS1 promoter harbors overlapping sites for Hand2 and Nuclear Factor of Activated T-cells (NFATC) transcription factors. We have demonstrated a physical interaction between NFATC1 and the E-Box proteins with EMSA and coimmunoprecipitation assays. The regulation of de novo ceramide synthesis in response to hypoxia and this newly described interaction between E-box and NFATC transcription factors will pave the way to identify new pathways in the adaptation of the cardiomyocyte to stress. The elucidation of these pathways will in the long-term provide insights into potential targets for novel therapeutic regimens.
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Affiliation(s)
- Raed Azzam
- Department of Pediatrics, American University of Beirut-Medical Center, Beirut, Lebanon
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7
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van Echten-Deckert G, Walter J. Sphingolipids: Critical players in Alzheimer’s disease. Prog Lipid Res 2012; 51:378-93. [DOI: 10.1016/j.plipres.2012.07.001] [Citation(s) in RCA: 121] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Accepted: 07/06/2012] [Indexed: 12/20/2022]
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Spassieva SD, Rahmaniyan M, Bielawski J, Clarke CJ, Kraveka JM, Obeid LM. Cell density-dependent reduction of dihydroceramide desaturase activity in neuroblastoma cells. J Lipid Res 2012; 53:918-928. [PMID: 22377532 DOI: 10.1194/jlr.m019075] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
We applied a metabolic approach to investigate the role of sphingolipids in cell density-induced growth arrest in neuroblastoma cells. Our data revealed that sphingolipid metabolism in neuroblastoma cells significantly differs depending on the cells' population context. At high cell density, cells exhibited G0/G1 cell-cycle arrest and reduced ceramide, monohexosylceramide, and sphingomyelin, whereas dihydroceramide was significantly increased. In addition, our metabolic-labeling experiments showed that neuroblastoma cells at high cell density preferentially synthesized very long chain (VLC) sphingolipids and dramatically decreased synthesis of sphingosine-1-phosphate (S1P). Moreover, densely populated neuroblastoma cells showed increased message levels of both anabolic and catabolic enzymes of the sphingolipid pathway. Notably, our metabolic-labeling experiments indicated reduced dihydroceramide desaturase activity at confluence, which was confirmed by direct measurement of dihydroceramide desaturase activity in situ and in vitro. Importantly, we could reduce dihydroceramide desaturase activity in low-density cells by applying conditional media from high-density cells, as well as by adding reducing agents, such as DTT and L-cysteine to the media. In conclusion, our data suggest a role of the sphingolipid pathway, dihydroceramides desaturase in particular, in confluence-induced growth arrest in neuroblastoma cells.
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Affiliation(s)
- Stefka D Spassieva
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425
| | - Mehrdad Rahmaniyan
- Department of Pediatrics Division of Hematology/Oncology, Medical University of South Carolina, Charleston, SC 29425; and
| | - Jacek Bielawski
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425; and
| | - Christopher J Clarke
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425; and
| | - Jacqueline M Kraveka
- Department of Pediatrics Division of Hematology/Oncology, Medical University of South Carolina, Charleston, SC 29425; and
| | - Lina M Obeid
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425; Division of General Internal Medicine, Ralph H. Johnson Veterans Affairs Hospital, Charleston, SC 29401.
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Dihydroceramide desaturase and dihydrosphingolipids: debutant players in the sphingolipid arena. Prog Lipid Res 2011; 51:82-94. [PMID: 22200621 DOI: 10.1016/j.plipres.2011.12.002] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Abstract
Sphingolipids are a wide family of lipids that share common sphingoid backbones, including (2S,3R)-2-amino-4-octadecane-1,3-diol (dihydrosphingosine) and (2S,3R,4E)-2-amino-4-octadecene-1,3-diol (sphingosine). The metabolism and biological functions of sphingolipids derived from sphingosine have been the subject of many reviews. In contrast, dihydrosphingolipids have received poor attention, mainly due to their supposed lack of biological activity. However, the reported biological effects of active site directed dihydroceramide desaturase inhibitors and the involvement of dihydrosphingolipids in the response of cells to known therapeutic agents support that dihydrosphingolipids are not inert but are in fact biologically active and underscore the importance of elucidating further the metabolic pathways and cell signaling networks involved in the biological activities of dihydrosphingolipids. Dihydroceramide desaturase is the enzyme involved in the conversion of dihydroceramide into ceramide and it is crucial in the regulation of the balance between sphingolipids and dihydrosphingolipids. Furthermore, given the enzyme requirement for O₂ and the NAD(P)H cofactor, the cellular redox balance and dihydroceramide desaturase activity may reciprocally influence each other. In this review both dihydroceramide desaturase and the biological functions of dihydrosphingolipids are addressed and perspectives on this field are discussed.
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Novgorodov SA, Wu BX, Gudz TI, Bielawski J, Ovchinnikova TV, Hannun YA, Obeid LM. Novel pathway of ceramide production in mitochondria: thioesterase and neutral ceramidase produce ceramide from sphingosine and acyl-CoA. J Biol Chem 2011; 286:25352-62. [PMID: 21613224 DOI: 10.1074/jbc.m110.214866] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Reports suggest that excessive ceramide accumulation in mitochondria is required to initiate the intrinsic apoptotic pathway and subsequent cell death, but how ceramide accumulates is unclear. Here we report that liver mitochondria exhibit ceramide formation from sphingosine and palmitoyl-CoA and from sphingosine and palmitate. Importantly, this activity was markedly decreased in liver from neutral ceramidase (NCDase)-deficient mice. Moreover, the levels of ceramide were dissimilar in liver mitochondria of WT and NCDase KO mice. These results suggest that NCDase is a key participant of ceramide formation in liver mitochondria. We also report that highly purified liver mitochondria have ceramidase, reverse ceramidase, and thioesterase activities. Increased accessibility of palmitoyl-CoA to the mitochondrial matrix with the pore-forming peptide zervamicin IIB resulted in 2-fold increases in palmitoyl-CoA hydrolysis by thioesterase. This increased hydrolysis was accompanied by an increase in ceramide formation, demonstrating that both outer membrane and matrix localized thioesterases can regulate ceramide formation. Also, ceramide formation might occur both in the outer mitochondrial membrane and in the mitochondrial matrix, suggesting the existence of distinct ceramide pools. Taken together, these results suggest that the reverse activity of NCDase contributes to sphingolipid homeostasis in this organelle in vivo.
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Affiliation(s)
- Sergei A Novgorodov
- Ralph H. Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29401, USA
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11
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Hu W, Ross J, Geng T, Brice SE, Cowart LA. Differential regulation of dihydroceramide desaturase by palmitate versus monounsaturated fatty acids: implications for insulin resistance. J Biol Chem 2011; 286:16596-605. [PMID: 21454530 PMCID: PMC3089502 DOI: 10.1074/jbc.m110.186916] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Revised: 02/18/2011] [Indexed: 11/06/2022] Open
Abstract
Much data implicate saturated fatty acids in deleterious processes associated with obesity, diabetes, and the metabolic syndrome. Many of these changes may be due to aberrant generation of bioactive lipids when saturated fatty acid availability to tissues is increased. On the other hand, studies are emerging that implicate the monounsaturated fatty acid oleate in protection from saturated fat mediated toxicity; however, the mechanisms are not well understood. Our data demonstrate a novel role for palmitate in increasing mRNA encoding DES1, which is the enzyme responsible for generating ceramide from its precursor dihydroceramide and thus controls synthesis of the bioactive lipid ceramide. Moreover, co-treatment with oleate prevented the increase in ceramide, and this occurred through attenuation of the increase in message and activity of DES1. Knockdown of DES1 also protected from palmitate-induced insulin resistance, and overexpression of this enzyme ameliorated the protective effect of oleate. Together, these findings provide insight into the mechanisms of oleate-mediated protection against metabolic disease and provide novel evidence for fatty acid-mediated regulation of a key enzyme of ceramide biosynthesis.
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Affiliation(s)
- Wei Hu
- From the Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29403 and
| | - Jessica Ross
- From the Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29403 and
| | - Tuoyu Geng
- From the Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29403 and
| | - Sarah E. Brice
- From the Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29403 and
| | - L. Ashley Cowart
- From the Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29403 and
- the Ralph H. Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29403
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12
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Rahmaniyan M, Curley RW, Obeid LM, Hannun YA, Kraveka JM. Identification of dihydroceramide desaturase as a direct in vitro target for fenretinide. J Biol Chem 2011; 286:24754-64. [PMID: 21543327 DOI: 10.1074/jbc.m111.250779] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The dihydroceramide desaturase (DES) enzyme is responsible for inserting the 4,5-trans-double bond to the sphingolipid backbone of dihydroceramide. We previously demonstrated that fenretinide (4-HPR) inhibited DES activity in SMS-KCNR neuroblastoma cells. In this study, we investigated whether 4-HPR acted directly on the enzyme in vitro. N-C8:0-d-erythro-dihydroceramide (C(8)-dhCer) was used as a substrate to study the conversion of dihydroceramide into ceramide in vitro using rat liver microsomes, and the formation of tritiated water after the addition of the tritiated substrate was detected and used to measure DES activity. NADH served as a cofactor. The apparent K(m) for C(8)-dhCer and NADH were 1.92 ± 0.36 μm and 43.4 ± 6.47 μm, respectively; and the V(max) was 3.16 ± 0.24 and 4.11 ± 0.18 nmol/min/g protein. Next, the effects of 4-HPR and its metabolites on DES activity were investigated. 4-HPR was found to inhibit DES in a dose-dependent manner. At 20 min, the inhibition was competitive; however, longer incubation times demonstrated the inhibition to be irreversible. Among the major metabolites of 4-HPR, 4-oxo-N-(4-hydroxyphenyl)retinamide (4-oxo-4-HPR) showed the highest inhibitory effect with substrate concentration of 0.5 μm, with an IC(50) of 1.68 μm as compared with an IC(50) of 2.32 μm for 4-HPR. N-(4-Methoxyphenyl)retinamide (4-MPR) and 4-Oxo-N-(4-methoxyphenyl)retinamide (4-oxo-4-MPR) had minimal effects on DES activity. A known competitive inhibitor of DES, C(8)-cyclopropenylceramide was used as a positive control. These studies define for the first time a direct in vitro target for 4-HPR and suggest that inhibitors of DES may be used as therapeutic interventions to regulate ceramide desaturation and consequent function.
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Affiliation(s)
- Mehrdad Rahmaniyan
- Division of Hematology/Oncology, Department of Pediatrics, Medical University of South Carolina, Charleston, South Carolina 29425, USA
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Abstract
Oxidative stress has been implicated previously in the regulation of ceramide metabolism. In the present study, its effects on dihydroceramide desaturase were investigated. To stimulate oxidative stress, HEK (human embyronic kidney)-293, MCF7, A549 and SMS-KCNR cells were treated with H2O2, menadione or tert-butylhydroperoxide. In all cell lines, an increase in dihydroceramide was observed upon oxidative stress as measured by LC (liquid chromatography)/MS. In contrast, total ceramide levels were relatively unchanged. Mechanistically, dihydroceramide desaturase activity was measured by an in situ assay and decreased in a time- and dose-dependent fashion. Interestingly, no detectable changes in the protein levels were observed, suggesting that oxidative stress does not induce degradation of dihydroceramide desaturase. In summary, oxidative stress leads to potent inhibition of dihydroceramide desaturase resulting in significant elevation in dihydroceramide levels in vivo.
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Błachnio-Zabielska A, Baranowski M, Zabielski P, Górski J. Effect of exercise duration on the key pathways of ceramide metabolism in rat skeletal muscles. J Cell Biochem 2008; 105:776-84. [PMID: 18680146 DOI: 10.1002/jcb.21877] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Ceramide is the key compound on crossroads of sphingolipid metabolism. The content and composition of ceramides in skeletal muscles have been shown to be affected by prolonged exercise. The aim of this study was to examine the effect of exercise on the activity of key enzymes of ceramide metabolism in skeletal muscles. The experiments were carried out on male Wistar rats (200-250 g) divided into four groups: sedentary, exercised for 30 min, 90 min, and until exhaustion. The activity of serine palmitoyltransferase (SPT), neutral and acid sphingomyelinase (nSMase and aSMase), neutral and alkaline ceramidases (nCDase and alCDase) and the content of ceramide, sphingosine, sphinganine and sphingosine-1-phosphate were determined in three types of muscle. We have found that the activity and expression of SPT increase gradually in each muscle with duration of exercise. These changes were followed by elevation in the content of sphinganine. These data indicate that exercise increases de novo synthesis of ceramide. The aSMase activity gradually decreased with duration of exercise in each type of muscle. After exhaustive exercise the activity of both isoforms of ceramidase were reduced in each muscle. The ceramide level depends both on duration of exercise and muscle type. The ceramide level in the soleus and white gastrocnemius decreased after 30 min of running. After exhaustive exercise it was elevated in the soleus and red gastrocnemius. It is concluded that exercise strongly affects the activity of key enzymes involved in ceramide metabolism and in consequence the level of sphingolipid intermediates in skeletal muscles.
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Baranowski M, Zabielski P, Blachnio A, Gorski J. Effect of exercise duration on ceramide metabolism in the rat heart. Acta Physiol (Oxf) 2008; 192:519-29. [PMID: 17970831 DOI: 10.1111/j.1748-1716.2007.01755.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
AIM We aimed at gaining more insight into the mechanisms underlying exercise-induced alterations in myocardial ceramide (CER) content by employing physical activity of various durations and examining all key pathways of CER metabolism. METHODS The experiments were carried out on male Wistar rats divided into four groups (n = 6 in each case): control, exercised for 30 and 90 min and until exhaustion on the electrically driven treadmill moving with a speed of 1200 m h(-1) and set at +10 degrees incline. The animals were anaesthetized and samples of the heart's left ventricle were excised. RESULTS Thirty-minute exercise decreased the level of CER in the heart by 15%. However, after 90 min of running it returned to the baseline and at the point of exhaustion it exceeded that of the control animals by 26%. The initial reduction in the content of CER was probably a result of its augmented degradation, as a concomitant elevation in the activity of acid ceramidase and the level of sphingosine was observed. The transition from reduction in CER content after 30 min of exercise to its accumulation at the point of exhaustion was a consequence of gradual reduction in the activity of acid ceramidase and simultaneous increase in the rate of de novo CER synthesis, as evidenced by progressive activation of serine palmitoyltransferase and accumulation of sphinganine. CONCLUSION We conclude that the effect of physical effort on myocardial CER content and metabolism depends to a large extent on exercise duration.
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Affiliation(s)
- M Baranowski
- Department of Physiology, Medical University of Bialystok, Bialystok, Poland.
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Stiban J, Caputo L, Colombini M. Ceramide synthesis in the endoplasmic reticulum can permeabilize mitochondria to proapoptotic proteins. J Lipid Res 2007; 49:625-34. [PMID: 18073406 DOI: 10.1194/jlr.m700480-jlr200] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Increased mitochondrial ceramide levels are associated with the initiation of apoptosis. There is evidence that ceramide is causal. Thus, the conversion of the precursor, dihydroceramide, to ceramide by the enzyme dihydroceramide desaturase may be important in preparing the cell for apoptosis. Ceramide can initiate apoptosis by permeabilizing the mitochondrial outer membrane to apoptosis-inducing proteins. However, the mitochondrion's ability to produce ceramide may be limited by its proteome. Here, we show that ceramide synthesized in isolated mammalian endoplasmic reticulum (ER) vesicles from either C8-dihydroceramide or sphingosine to produce long-chain ceramide can transfer to isolated mitochondria. The rate of transfer is consistent with a simple collision model. The transfer of the long-chain ceramide is faster than expected for an uncatalyzed process. Sufficient ceramide is transferred to permeabilize the outer membrane to cytochrome c and adenylate kinase. The mitochondria-associated membranes, ER-like membranes that are tightly associated with isolated mitochondria, can produce enough ceramide to permeabilize the outer membrane transiently. Thus, this ceramide exchange obviates the need for a complete ceramide de novo pathway in mitochondria to increase ceramide levels to the critical value required for functional changes, such as ceramide channel self-assembly followed by protein release.
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Affiliation(s)
- Johnny Stiban
- Department of Biology, University of Maryland, College Park, MD 20742, USA
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Kraveka JM, Li L, Szulc ZM, Bielawski J, Ogretmen B, Hannun YA, Obeid LM, Bielawska A. Involvement of dihydroceramide desaturase in cell cycle progression in human neuroblastoma cells. J Biol Chem 2007; 282:16718-28. [PMID: 17283068 PMCID: PMC2084375 DOI: 10.1074/jbc.m700647200] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The role of dihydroceramide desaturase as a key enzyme in the de novo pathway of ceramide generation was investigated in human neuroblastoma cells (SMS-KCNR). A novel assay using water-soluble analogs of dihydroceramide, dihydroceramidoids (D-erythro-dhCCPS analogs), was used to measure desaturase activity in situ. Conversion of D-erythro-2-N-[12'-(1''-pyridinium)-dodecanoyl]-4,5-dihydrosphingosine bromide (C(12)-dhCCPS) to its 4,5-desaturated counterpart, D-erythro-2-N-[12'-(1''-pyridinium)dodecanoyl]sphingosine bromide (C(12)-CCPS), was determined by liquid chromatography/mass spectrometry analysis. The validity of the assay was confirmed using C(8)-cyclopropenylceramide, a competitive inhibitor of dihydroceramide desaturase. A human homolog (DEGS-1) of the Drosophila melanogaster des-1 gene was recently identified and reported to have desaturase activity. Transfection of SMS-KCNR cells with small interfering RNA to DEGS-1 significantly blocked the conversion of C(12)-dhCCPS to C(12)-CCPS. The associated accumulation of endogenous dihydroceramides confirmed DEGS-1 as the main active dihydroceramide desaturase in these cells. The partial loss of DEGS-1 inhibited cell growth, with cell cycle arrest at G(0)/G(1). This was accompanied by a significant decrease in the amount of phosphorylated retinoblastoma protein. This hypophosphorylation was inhibited by tautomycin and not by okadaic acid, suggesting the involvement of protein phosphatase 1. Additionally, we found that treatment of SMS-KCNR cells with fenretinide inhibited desaturase activity in a dose-dependent manner. An increase in dihydroceramides (but not ceramides) paralleled this process as measured by liquid chromatography/mass spectrometry. There were no effects on the mRNA or protein levels of DEGS-1, suggesting that fenretinide acts at the post-translational level as an inhibitor of this enzyme. Tautomycin was also able to block the hypophosphorylation of the retinoblastoma protein observed upon fenretinide treatment. These findings suggest a novel biological function for dihydroceramides.
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Affiliation(s)
- Jacqueline M Kraveka
- Division of Hematology/Oncology, Department of Pediatrics, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
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Triola G, Fabrias G, Dragusin M, Niederhausen L, Broere R, Llebaria A, van Echten-Deckert G. Specificity of the dihydroceramide desaturase inhibitor N-[(1R,2S)-2-hydroxy-1-hydroxymethyl-2-(2-tridecyl-1-cyclopropenyl)ethyl]octanamide (GT11) in primary cultured cerebellar neurons. Mol Pharmacol 2004; 66:1671-8. [PMID: 15371559 DOI: 10.1124/mol.104.003681] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Dihydroceramide desaturase catalyzes the conversion of the innocuous precursor dihydroceramide into a highly bioactive product ceramide. We studied the effect of N-[(1R,2S)-2-hydroxy-1-hydroxymethyl-2-(2-tridecyl-1-cyclopropenyl)ethyl]octanamide (GT11), the first inhibitor of this enzyme, in primary cultured cerebellar neurons. Although desaturase was efficiently inhibited (IC50 of 23 nM), the compound lost its specificity at higher concentrations. From 5 microM upward, GT11 also decreased de novo sphingolipid biosynthesis. Studies with two differentially labeled radioactive analogs of GT11 support that the inhibitor itself and not a downstream metabolic product, interferes with sphingolipid biosynthesis. It is interesting that serine palmitoyltransferase activity decreased in the presence of high concentrations of GT11 in intact cells, but not when added directly into cell homogenates. However, suppression of enzyme transcription could not be detected. But at high concentrations GT11 provoked an accumulation of sphingosine-1-phosphate and especially of dihydrosphingosine-1-phosphate, suggesting a decreased activity of sphingosine-1-phosphate lyase. Enzyme activity measurements indeed supported this assumption. Thus, at higher concentrations, GT11 interferes with lyase activity, inducing an accumulation of sphingoid base phosphates that, in turn, down-regulate serine palmitoyltransferase activity. At low concentrations, however, GT11 is the first specific inhibitor of dihydroceramide desaturase described so far. Considering the proapoptotic and proinflammatory effect of ceramide, GT11 could also turn out to be a novel cell-protective agent.
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Affiliation(s)
- Gemma Triola
- Research Unit on Bioactive Molecules, Department of Biological Organic Chemistry, Institut d'Investigacions Químiques i Ambientals de Barcelona, Consejo Superior de Investigaciones, Cientificas, Barcelona, Spain
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Omae F, Miyazaki M, Enomoto A, Suzuki M, Suzuki Y, Suzuki A. DES2 protein is responsible for phytoceramide biosynthesis in the mouse small intestine. Biochem J 2004; 379:687-95. [PMID: 14731113 PMCID: PMC1224108 DOI: 10.1042/bj20031425] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2003] [Revised: 12/16/2003] [Accepted: 01/19/2004] [Indexed: 11/17/2022]
Abstract
The C-4 hydroxylation of sphinganine and dihydroceramide is a rate-limiting reaction in the biosynthesis of phytosphingolipids. Mouse DES1 (MDES1) cDNA homologous to the Drosophila melanogaster degenerative spermatocyte gene-1 (des-1) cDNA leads to sphingosine Delta4-desaturase activity, and another mouse homologue, MDES2, has bifunctional activity, producing C-4 hydroxysphinganine and Delta4-sphingenine in yeast [Ternes, Franke, Zahringer, Sperling and Heinz (2002) J. Biol. Chem. 277, 25512-25518]. Here, we report the characterization of mouse DES2 (MDES2) using an in vitro assay with a homogenate of COS-7 cells transfected with MDES2 cDNA and N -octanoyl-sphinganine and sphinganine as substrates. MDES2 protein prefers dihydroceramide as a substrate to sphinganine, and exhibits dihydroceramide Delta4-desaturase and C-4 hydroxylase activities. MDES2 mRNA content was high in the small intestine and abundant in the kidney. In situ hybridization detected signals of MDES2 mRNA in the crypt cells. Immunohistochemistry using an anti-MDES2 peptide antibody stained the crypt cells and the adjacent epithelial cells. These results suggest that MDES2 is the dihydroceramide C-4 hydroxylase responsible for the biosynthesis of enriched phytosphingoglycolipids in the microvillous membranes of intestinal epithelial cells.
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Affiliation(s)
- Fumio Omae
- Sphingolipid Expression Laboratory, Frontier Research System, RIKEN, 2-1, Hirosawa, Wako, Saitama 351-0198, Japan
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Affiliation(s)
- A H Merrill
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322-3050, USA
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Smith ER, Merrill AH, Obeid LM, Hannun YA. Effects of sphingosine and other sphingolipids on protein kinase C. Methods Enzymol 2001; 312:361-73. [PMID: 11070884 DOI: 10.1016/s0076-6879(00)12921-0] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- E R Smith
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322-3050, USA
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