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Alarcón-Vila C, Insausti-Urkia N, Torres S, Segalés-Rovira P, Conde de la Rosa L, Nuñez S, Fucho R, Fernández-Checa JC, García-Ruiz C. Dietary and genetic disruption of hepatic methionine metabolism induce acid sphingomyelinase to promote steatohepatitis. Redox Biol 2023; 59:102596. [PMID: 36610223 PMCID: PMC9827379 DOI: 10.1016/j.redox.2022.102596] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Accepted: 12/28/2022] [Indexed: 01/03/2023] Open
Abstract
Alcoholic (ASH) and nonalcoholic. (NASH).steatohepatitis are advanced.stages.of.fatty.liver.disease.Methionine adenosyltransferase 1A (MAT1A) plays a key role in hepatic methionine metabolism and germline Mat1a deletion in mice promotes NASH. Acid sphingomyelinase (ASMase) triggers hepatocellular apoptosis and liver fibrosis and has been shown to downregulate MAT1A expression in the context of fulminant liver failure. Given the role of ASMase in steatohepatitis development, we investigated the status of ASMase in Mat1a-/- mice and the regulation of ASMase by SAM/SAH. Consistent with its role in NASH, Mat1a-/- mice fed a choline-deficient (CD) diet exhibited macrosteatosis, inflammation, fibrosis and liver injury as well as reduced total and mitochondrial GSH levels. Our data uncovered an increased basal expression and activity of ASMase but not neutral SMase in Mat1a-/- mice, which further increased upon CD feeding. Interestingly, adenovirus-mediated shRNA expression targeting ASMase reduced ASMase activity and protected Mat1a-/- mice against CD diet-induced NASH. Similar results were observed in CD fed Mat1a-/- mice by pharmacological inhibition of ASMase with amitriptyline. Moreover, Mat1a/ASMase double knockout mice were resistant to CD-induced NASH. ASMase knockdown protected wild type mice against NASH induced by feeding a diet deficient in methionine and choline. Furthermore, Mat1a-/- mice developed acute-on-chronic ASH and this outcome was ameliorated by amitriptyline treatment. In vitro data in primary mouse hepatocytes revealed that decreased SAM/SAH ratio increased ASMase mRNA level and activity. MAT1A and ASMase mRNA levels exhibited an inverse correlation in liver samples from patients with ASH and NASH. Thus, disruption of methionine metabolism sensitizes to steatohepatitis by ASMase activation via decreased SAM/SAH. These findings imply that MAT1A deletion and ASMase activation engage in a self-sustained loop of relevance for steatohepatitis.
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Affiliation(s)
- Cristina Alarcón-Vila
- Cell Death and Proliferation, Instituto de Investigaciones Biomédicas de Barcelona, CSIC, Barcelona, Spain; Liver Unit, Hospital Clínic I Provincial, IDIBAPS, Barcelona, Spain; CIBERehd, University of Barcelona, Spain
| | - Naroa Insausti-Urkia
- Cell Death and Proliferation, Instituto de Investigaciones Biomédicas de Barcelona, CSIC, Barcelona, Spain; Liver Unit, Hospital Clínic I Provincial, IDIBAPS, Barcelona, Spain; CIBERehd, University of Barcelona, Spain
| | - Sandra Torres
- Cell Death and Proliferation, Instituto de Investigaciones Biomédicas de Barcelona, CSIC, Barcelona, Spain; Liver Unit, Hospital Clínic I Provincial, IDIBAPS, Barcelona, Spain; CIBERehd, University of Barcelona, Spain
| | - Paula Segalés-Rovira
- Cell Death and Proliferation, Instituto de Investigaciones Biomédicas de Barcelona, CSIC, Barcelona, Spain; Liver Unit, Hospital Clínic I Provincial, IDIBAPS, Barcelona, Spain; CIBERehd, University of Barcelona, Spain
| | - Laura Conde de la Rosa
- Cell Death and Proliferation, Instituto de Investigaciones Biomédicas de Barcelona, CSIC, Barcelona, Spain; Liver Unit, Hospital Clínic I Provincial, IDIBAPS, Barcelona, Spain; CIBERehd, University of Barcelona, Spain
| | - Susana Nuñez
- Cell Death and Proliferation, Instituto de Investigaciones Biomédicas de Barcelona, CSIC, Barcelona, Spain; Liver Unit, Hospital Clínic I Provincial, IDIBAPS, Barcelona, Spain; CIBERehd, University of Barcelona, Spain
| | - Raquel Fucho
- Cell Death and Proliferation, Instituto de Investigaciones Biomédicas de Barcelona, CSIC, Barcelona, Spain; Liver Unit, Hospital Clínic I Provincial, IDIBAPS, Barcelona, Spain; CIBERehd, University of Barcelona, Spain
| | - Jose C Fernández-Checa
- Cell Death and Proliferation, Instituto de Investigaciones Biomédicas de Barcelona, CSIC, Barcelona, Spain; Liver Unit, Hospital Clínic I Provincial, IDIBAPS, Barcelona, Spain; CIBERehd, University of Barcelona, Spain; University of Southern California Research Center for Liver Diseases, Keck School of Medicine, USC, Los Angeles, CA, USA.
| | - Carmen García-Ruiz
- Cell Death and Proliferation, Instituto de Investigaciones Biomédicas de Barcelona, CSIC, Barcelona, Spain; Liver Unit, Hospital Clínic I Provincial, IDIBAPS, Barcelona, Spain; CIBERehd, University of Barcelona, Spain; University of Southern California Research Center for Liver Diseases, Keck School of Medicine, USC, Los Angeles, CA, USA.
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de Wit NM, Mol K, Rodríguez-Lorenzo S, de Vries HE, Kooij G. The Role of Sphingolipids and Specialized Pro-Resolving Mediators in Alzheimer's Disease. Front Immunol 2021; 11:620348. [PMID: 33633739 PMCID: PMC7902029 DOI: 10.3389/fimmu.2020.620348] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Accepted: 12/14/2020] [Indexed: 12/14/2022] Open
Abstract
Alzheimer’s disease (AD) is the leading cause of dementia worldwide giving rise to devastating forms of cognitive decline, which impacts patients’ lives and that of their proxies. Pathologically, AD is characterized by extracellular amyloid deposition, neurofibrillary tangles and chronic neuroinflammation. To date, there is no cure that prevents progression of AD. In this review, we elaborate on how bioactive lipids, including sphingolipids (SL) and specialized pro-resolving lipid mediators (SPM), affect ongoing neuroinflammatory processes during AD and how we may exploit them for the development of new biomarker panels and/or therapies. In particular, we here describe how SPM and SL metabolism, ranging from ω-3/6 polyunsaturated fatty acids and their metabolites to ceramides and sphingosine-1-phosphate, initiates pro- and anti-inflammatory signaling cascades in the central nervous system (CNS) and what changes occur therein during AD pathology. Finally, we discuss novel therapeutic approaches to resolve chronic neuroinflammation in AD by modulating the SPM and SL pathways.
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Affiliation(s)
- Nienke M de Wit
- Department of Molecular Cell Biology and Immunology, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Kevin Mol
- Department of Molecular Cell Biology and Immunology, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Sabela Rodríguez-Lorenzo
- Department of Molecular Cell Biology and Immunology, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Helga E de Vries
- Department of Molecular Cell Biology and Immunology, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Gijs Kooij
- Department of Molecular Cell Biology and Immunology, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
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Aberrant activation of super enhancer and choline metabolism drive antiandrogen therapy resistance in prostate cancer. Oncogene 2020; 39:6556-6571. [PMID: 32917955 DOI: 10.1038/s41388-020-01456-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Revised: 08/20/2020] [Accepted: 09/02/2020] [Indexed: 12/28/2022]
Abstract
Next generation antiandrogens such as enzalutamide (Enz) are effective initially for the treatment of castration-resistant prostate cancer (CRPC). However, the disease often relapses and the underlying mechanisms remain elusive. By performing H3-lysine-27 acetylation (H3K27ac) ChIP-seq in Enz-resistant CRPC cells, we identified a group of super enhancers (SEs) that are abnormally activated in Enz-resistant CRPC cells and associated with enhanced transcription of a subset of tumor promoting genes such as CHPT1, which catalyzes phosphatidylcholine (PtdCho) synthesis and regulates choline metabolism. Increased CHPT1 conferred CRPC resistance to Enz in vitro and in mice. While androgen receptor (AR) primarily binds to a putative CHPT1 enhancer and mediates androgen-dependent expression of CHPT1 gene in Enz-sensitive prostate cancer cells, AR binds to a different enhancer within the CHPT1 SE locus and facilities androgen-independent expression of CHPT1 in Enz-resistant cells. We further identified a long-non coding RNA transcribed at CHPT1 enhancer (also known as enhancer RNA) that binds to the H3K27ac reader BRD4 and participates in regulating CHPT1 SE activity and CHPT1 gene expression. Our findings demonstrate that aberrantly activated SE upregulates CHPT1 expression and confers Enz resistance in CRPC, suggesting that SE-mediated expression of downstream effectors such as CHPT1 can be viable targets to overcome Enz resistance in PCa.
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Molecular Docking Reveals the Binding Modes of Anticancer Alkylphospholipids and Lysophosphatidylcholine within the Catalytic Domain of Cytidine Triphosphate: Phosphocholine Cytidyltransferase. EUR J LIPID SCI TECH 2020. [DOI: 10.1002/ejlt.201900422] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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5
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Uzunova V, Tzoneva R, Stoyanova T, Pankov R, Skrobanska R, Georgiev G, Maslenkova L, Tsonchev Z, Momchilova A. Dimethylsphingosine and miltefosine induce apoptosis in lung adenocarcinoma A549 cells in a synergistic manner. Chem Biol Interact 2019; 310:108731. [PMID: 31265827 DOI: 10.1016/j.cbi.2019.108731] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Revised: 06/11/2019] [Accepted: 06/27/2019] [Indexed: 10/26/2022]
Abstract
Lung cancer is one of the most common and lethal types of oncological diseases. Despite the advanced therapeutic approaches, the prognosis for lung cancer still remains poor. Apparently, there is an imperative need for more efficient therapeutic strategies. In this work we report that concurrent treatment of human adenocarcinoma A549 cells with specific concentrations of two antitumor agents, the sphingosine kinase 1 inhibitor N, N dimethylsphingosine (DMS) and the alkylphosphocholine miltefosine, induced synergistic cytotoxic effect, which was confirmed by calculation of the combination index. The simultaneous action of these agents, induced significant decrease of A549 cell number, as well as pronounced morphological alterations. Combined drugs caused substantial apoptotic events, and significant reduction of the pro-survival marker sphingosine- 1-phosphate (S1P), when compared to the individual treatments with each of the anticancer drugs alone. Miltefosine is known to affect the synthesis of choline-containing phospholipids, including sphingomyelin, but we report for the first time that it also reduces S1P. Here we suggest a putative mechanism underlying the effect of miltefosine on sphingosine kinase 1, involving miltefosine-induced inhibition of protein kinase C. In conclusion, our findings provide a possibility for treatment of lung cancer cells with lower concentrations of the two antitumor drugs, DMS and miltefosine, which is favorable, regarding their potential cytotoxicity to normal cells.
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Affiliation(s)
- Veselina Uzunova
- Department of Lipid-Protein Interactions, Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev str. bl 21, 1113, Sofia, Bulgaria
| | - Rumiana Tzoneva
- Department of Lipid-Protein Interactions, Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev str. bl 21, 1113, Sofia, Bulgaria
| | - Tihomira Stoyanova
- Department of Lipid-Protein Interactions, Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev str. bl 21, 1113, Sofia, Bulgaria
| | - Roumen Pankov
- Department of Cytology, Histology and Embryology, Biological Faculty, Sofia University, 8, Dragan Tzankov str, 1164, Sofia, Bulgaria
| | - Ralica Skrobanska
- Department of Cytology, Histology and Embryology, Biological Faculty, Sofia University, 8, Dragan Tzankov str, 1164, Sofia, Bulgaria
| | - Georgi Georgiev
- Department of Cytology, Histology and Embryology, Biological Faculty, Sofia University, 8, Dragan Tzankov str, 1164, Sofia, Bulgaria
| | - Liliana Maslenkova
- Department of Lipid-Protein Interactions, Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev str. bl 21, 1113, Sofia, Bulgaria
| | - Zlatan Tsonchev
- Department of Neurology, ISUL Hospital Tsaritsa Yoanna, 8 Bialo more str, 1527, Sofia, Bulgaria
| | - Albena Momchilova
- Department of Lipid-Protein Interactions, Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev str. bl 21, 1113, Sofia, Bulgaria.
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Myers WA, Rico JE, Davis AN, Fontoura ABP, Dineen MJ, Tate BN, McFadden JW. Effects of abomasal infusions of fatty acids and one-carbon donors on hepatic ceramide and phosphatidylcholine in lactating Holstein dairy cows. J Dairy Sci 2019; 102:7087-7101. [PMID: 31178188 DOI: 10.3168/jds.2018-16200] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 04/04/2019] [Indexed: 12/18/2022]
Abstract
Our objectives were to (1) determine whether the abomasal infusion of behenic acid (C22:0) elevated hepatic ceramide relative to palmitic acid (C16:0) or docosahexaenoic acid (C22:6n-3) infusion; (2) assess whether the abomasal infusion of choline chloride or l-serine elevated hepatic phosphatidylcholine (PC) in cows abomasally infused with C16:0; and (3) characterize the PC lipidome in cows abomasally infused with C22:6n-3, relative to C16:0 or C22:0 infusion. In a 5 × 5 Latin square design, 5 rumen-cannulated Holstein cows (214 ± 4.9 DIM; 3.2 ± 1.1 parity) were enrolled in a study with 6-d periods. Abomasal infusates consisted of (1) palmitic acid (PA; 98% C16:0); (2) PA + choline chloride (PA+C; 50 g/d choline chloride); (3) PA + l-serine (PA+S; 170 g/d l-serine); (4) behenic acid (BA; 92% C22:0); and (5) an algal oil rich in docosahexaenoic acid (DHA; 44% C22:6n-3). Emulsion infusates provided 301 g/d of total fatty acids containing a minimum of 40 g/d of C16:0. Cows were fed a corn silage-based diet. Milk was collected on d -2, -1, 5, and 6. Blood was collected and liver biopsied on d 6 of each period. Although we did not detect differences in milk yield, milk fat yield and content were lower in cows infused with DHA relative to PA. Plasma triacylglycerol concentrations were lower with DHA treatment relative to PA or BA. Cows infused with DHA had lower plasma insulin concentrations relative to cows infused with PA only. For objective 1, hepatic ceramide-d18:2/22:0 was highest in cows infused with BA relative to other treatments. For objective 2, plasma free choline concentrations were greater in PA+C cows relative to PA; however, we did not observe this effect with PA+S. Plasma total PC concentrations were similar for all treatments. Regarding the hepatic lipidome, a total of 18 hepatic PC were higher (e.g., PC-16:1/18:2) and 25 PC were lower (e.g., PC-16:0/22:6) with PA+C infusion relative to PA. In addition, 17 PC were higher (e.g., PC-20:3/22:5) and 21 PC were lower (e.g., PC-18:0/22:6) with PA+S infusion relative to PA. For objective 3, hepatic concentrations of many individual saturated PC (e.g., PC-18:0/15:0) were lower with DHA relative to other treatments. Hepatic concentrations of highly unsaturated PC with very-long-chain fatty acids (e.g., PC-14:0/22:6) were higher in DHA-infused cows relative to PA, PA+C, PA+S, or BA. The abomasal infusion of emulsions containing palmitic acid, palmitic acid with choline chloride or serine, behenic acid, or docosahexaenoic acid influence the hepatic ceramide and PC profiles of lactating cows.
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Affiliation(s)
- W A Myers
- Department of Animal Science, Cornell University, Ithaca, NY 14853
| | - J E Rico
- Department of Animal Science, Cornell University, Ithaca, NY 14853
| | - A N Davis
- Department of Animal Science, Cornell University, Ithaca, NY 14853
| | - A B P Fontoura
- Department of Animal Science, Cornell University, Ithaca, NY 14853
| | - M J Dineen
- Department of Animal Science, Cornell University, Ithaca, NY 14853
| | - B N Tate
- Department of Animal Science, Cornell University, Ithaca, NY 14853
| | - J W McFadden
- Department of Animal Science, Cornell University, Ithaca, NY 14853.
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Rodriguez-Cuenca S, Pellegrinelli V, Campbell M, Oresic M, Vidal-Puig A. Sphingolipids and glycerophospholipids - The "ying and yang" of lipotoxicity in metabolic diseases. Prog Lipid Res 2017; 66:14-29. [PMID: 28104532 DOI: 10.1016/j.plipres.2017.01.002] [Citation(s) in RCA: 92] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Revised: 11/30/2016] [Accepted: 01/05/2017] [Indexed: 12/14/2022]
Abstract
Sphingolipids in general and ceramides in particular, contribute to pathophysiological mechanisms by modifying signalling and metabolic pathways. Here, we present the available evidence for a bidirectional homeostatic crosstalk between sphingolipids and glycerophospholipids, whose dysregulation contributes to lipotoxicity induced metabolic stress. The initial evidence for this crosstalk originates from simulated models designed to investigate the biophysical properties of sphingolipids in plasma membrane representations. In this review, we reinterpret some of the original findings and conceptualise them as a sort of "ying/yang" interaction model of opposed/complementary forces, which is consistent with the current knowledge of lipid homeostasis and pathophysiology. We also propose that the dysregulation of the balance between sphingolipids and glycerophospholipids results in a lipotoxic insult relevant in the pathophysiology of common metabolic diseases, typically characterised by their increased ceramide/sphingosine pools.
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Affiliation(s)
- S Rodriguez-Cuenca
- Metabolic Research Laboratories, Wellcome Trust MRC Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge. Cambridge, UK.
| | - V Pellegrinelli
- Metabolic Research Laboratories, Wellcome Trust MRC Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge. Cambridge, UK
| | - M Campbell
- Metabolic Research Laboratories, Wellcome Trust MRC Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge. Cambridge, UK
| | - M Oresic
- Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, FI -20520 Turku, Finland
| | - A Vidal-Puig
- Metabolic Research Laboratories, Wellcome Trust MRC Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge. Cambridge, UK; Wellcome Trust Sanger Institute, Hinxton, UK.
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Alkyl ether lipids, ion channels and lipid raft reorganization in cancer therapy. Pharmacol Ther 2016; 165:114-31. [DOI: 10.1016/j.pharmthera.2016.06.003] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 05/26/2016] [Indexed: 12/21/2022]
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Lovastatin reversed the enhanced sphingomyelin caused by 27-hydroxycholesterol in cultured vascular endothelial cells. Biochem Biophys Rep 2015; 5:127-133. [PMID: 28955814 PMCID: PMC5600430 DOI: 10.1016/j.bbrep.2015.11.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Revised: 11/03/2015] [Accepted: 11/30/2015] [Indexed: 11/20/2022] Open
Abstract
Statins have pleiotropic properties which are involved in inhibiting the thrombogenic response. In this study, the effects of lovastatin on two phospholipids, phosphatidylcholine and sphingomyelin, were studied in cultured endothelial cells in the presence of an oxysterol, 27-hydroxycholesterol. After the cells were cultured with 50 nM of lovastatin for 60 h, lovastatin was found to decrease the incorporation of [3H]choline into phosphatidylcholine and sphingomyelin, inhibited CTP: phosphocholine cytidylyltransferase (CT) activity without altering the activity of sphingomyelin synthase and neutral sphingomyelinase. And lovastatin was not found to have a direct inhibitive effect on activity of CT. Exogenous mevalonic acid or cholesterol reversed the reduction of cholesterol concentration that was caused by lovastatin, but had no significant effect on the diminished [3H]sphingomyelin by lovastatin. The increase of [3H]sphingomyelin by 27-hydroxycholesterol was not detected in the presence of lovastatin. These findings suggest that (1) lovastatin can reduce sphingomyelin content by means of inhibiting phosphatidylcholine synthesis; and (2) The decrease in sphingomyelin is not related to the diminished cholesterol concentration or mevalonate-derived intermediates. This inhibitive effect of lovastatin on sphingomyelin may benefit cellular calcification caused by sphingomyelin.
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Acid sphingomyelinase-ceramide system in steatohepatitis: a novel target regulating multiple pathways. J Hepatol 2015; 62:219-33. [PMID: 25281863 DOI: 10.1016/j.jhep.2014.09.023] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Revised: 09/13/2014] [Accepted: 09/24/2014] [Indexed: 02/07/2023]
Abstract
Steatohepatitis (SH) is an intermediate stage of fatty liver disease and is one of the most common causes of chronic liver disease worldwide that may progress to cirrhosis and liver cancer. SH encompasses alcoholic and non-alcoholic steatohepatitis, the latter being of particular concern as it is associated with obesity and insulin resistance and has become a major cause of liver transplantation. The molecular mechanisms governing the transition from steatosis to SH are not fully understood. Here we discuss emerging data indicating that the acid sphingomyelinase (ASMase), a specific mechanism of ceramide generation, is required for the activation of key pathways that regulate steatosis, fibrosis and lipotoxicity, including endoplasmic reticulum stress, autophagy and lysosomal membrane permeabilization. Moreover, ASMase modulates alterations of the methionine cycle and phosphatidylcholine homeostasis, two crucial events involved in SH that regulate methylation reactions, antioxidant defence and membrane integrity. These new findings suggest that targeting ASMase in combination with restoring methionine metabolism and phosphatidylcholine levels may be of utility in the treatment of SH.
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Lagace TA, Ridgway ND. The role of phospholipids in the biological activity and structure of the endoplasmic reticulum. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:2499-510. [PMID: 23711956 DOI: 10.1016/j.bbamcr.2013.05.018] [Citation(s) in RCA: 153] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Revised: 05/09/2013] [Accepted: 05/15/2013] [Indexed: 01/22/2023]
Abstract
The endoplasmic reticulum (ER) is an interconnected network of tubular and planar membranes that supports the synthesis and export of proteins, carbohydrates and lipids. Phospholipids, in particular phosphatidylcholine (PC), are synthesized in the ER where they have essential functions including provision of membranes required for protein synthesis and export, cholesterol homeostasis, and triacylglycerol storage and secretion. Coordination of these biological processes is essential, as highlighted by findings that link phospholipid metabolism in the ER with perturbations in lipid storage/secretion and stress responses, ultimately contributing to obesity/diabetes, atherosclerosis and neurological disorders. Phospholipid synthesis is not uniformly distributed in the ER but is localized at membrane interfaces or contact zones with other organelles, and in dynamic, proliferating ER membranes. The topology of phospholipid synthesis is an important consideration when establishing the etiology of diseases that arise from ER dysfunction. This review will highlight our current understanding of the contribution of phospholipid synthesis to proper ER function, and how alterations contribute to aberrant stress responses and disease. This article is part of a Special Issue entitled: Functional and structural diversity of endoplasmic reticulum.
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Affiliation(s)
- Thomas A Lagace
- University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
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Anticancer mechanisms and clinical application of alkylphospholipids. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1831:663-74. [PMID: 23137567 DOI: 10.1016/j.bbalip.2012.10.008] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Revised: 10/28/2012] [Accepted: 10/29/2012] [Indexed: 11/20/2022]
Abstract
Synthetic alkylphospholipids (ALPs), such as edelfosine, miltefosine, perifosine, erucylphosphocholine and erufosine, represent a relatively new class of structurally related antitumor agents that act on cell membranes rather than on DNA. They selectively target proliferating (tumor) cells, inducing growth arrest and apoptosis, and are potent sensitizers of conventional chemo- and radiotherapy. ALPs easily insert in the outer leaflet of the plasma membrane and cross the membrane via an ATP-dependent CDC50a-containing 'flippase' complex (in carcinoma cells), or are internalized by lipid raft-dependent endocytosis (in lymphoma/leukemic cells). ALPs resist catabolic degradation, therefore accumulate in the cell and interfere with lipid-dependent survival signaling pathways, notably PI3K-Akt and Raf-Erk1/2, and de novo phospholipid biosynthesis. At the same time, stress pathways (e.g. stress-activated protein kinase/JNK) are activated to promote apoptosis. In many preclinical and clinical studies, perifosine was the most effective ALP, mainly because it inhibits Akt activity potently and consistently, also in vivo. This property is successfully exploited clinically in highly malignant tumors, such as multiple myeloma and neuroblastoma, in which a tyrosine kinase receptor/Akt pathway is amplified. In such cases, perifosine therapy is most effective in combination with conventional anticancer regimens or with rapamycin-type mTOR inhibitors, and may overcome resistance to these agents. This article is part of a Special Issue entitled Phospholipids and Phospholipid Metabolism.
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Castorena KM, Stapleford KA, Miller DJ. Complementary transcriptomic, lipidomic, and targeted functional genetic analyses in cultured Drosophila cells highlight the role of glycerophospholipid metabolism in Flock House virus RNA replication. BMC Genomics 2010; 11:183. [PMID: 20236518 PMCID: PMC2847973 DOI: 10.1186/1471-2164-11-183] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Accepted: 03/17/2010] [Indexed: 12/11/2022] Open
Abstract
Background Cellular membranes are crucial host components utilized by positive-strand RNA viruses for replication of their genomes. Published studies have suggested that the synthesis and distribution of membrane lipids are particularly important for the assembly and function of positive-strand RNA virus replication complexes. However, the impact of specific lipid metabolism pathways in this process have not been well defined, nor have potential changes in lipid expression associated with positive-strand RNA virus replication been examined in detail. Results In this study we used parallel and complementary global and targeted approaches to examine the impact of lipid metabolism on the replication of the well-studied model alphanodavirus Flock House virus (FHV). We found that FHV RNA replication in cultured Drosophila S2 cells stimulated the transcriptional upregulation of several lipid metabolism genes, and was also associated with increased phosphatidylcholine accumulation with preferential increases in lipid molecules with longer and unsaturated acyl chains. Furthermore, targeted RNA interference-mediated downregulation of candidate glycerophospholipid metabolism genes revealed a functional role of several genes in virus replication. In particular, we found that downregulation of Cct1 or Cct2, which encode essential enzymes for phosphatidylcholine biosynthesis, suppressed FHV RNA replication. Conclusion These results indicate that glycerophospholipid metabolism, and in particular phosphatidylcholine biosynthesis, plays an important role in FHV RNA replication. Furthermore, they provide a framework in which to further explore the impact of specific steps in lipid metabolism on FHV replication, and potentially identify novel cellular targets for the development of drugs to inhibit positive-strand RNA viruses.
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Affiliation(s)
- Kathryn M Castorena
- Departments of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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Long-chain ceramide produced in response to N-hexanoylsphingosine does not induce apoptosis in CHP-100 cells. Lipids 2009; 44:1039-46. [PMID: 19784683 DOI: 10.1007/s11745-009-3350-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2009] [Accepted: 09/15/2009] [Indexed: 12/11/2022]
Abstract
It has been previously reported that treatment of CHP-100 human neuroepithelioma cells with N-hexanoylsphingosine (C6-Cer) induces intracellular accumulation of long-chain ceramide (LC-Cer) and apoptosis. Herein, we investigated the existence of any causal relationship between the two phenomena. We report that C6-Cer-evoked LC-Cer accumulation is potently attenuated by the ceramide synthase inhibitor fumonisin B1; however, fumonisin B1 neither affects the apoptotic response evoked by C6-Cer administration, nor is toxic by itself to CHP-100 cells. Different to fumonisin B1, the serine-palmitoyltransferase inhibitor L: -cycloserine does not attenuate C6-Cer-evoked LC-Cer accumulation, thus suggesting that LC-Cer is produced via the sphingosine salvage pathway. Consistently, CHP-100 cells accumulate LC-Cer in response to sphingosine administration; however, their viability is not affected. The above-reported results indicate that, in the cell system investigated, C6-Cer, but not LC-Cer, is involved in apoptosis induction. As this finding is discussed in the light of the evidence that C6-Cer-induced apoptosis associates with cytochrome c release into the cytosol and caspase-9 activation, thus calling for an involvement of the mitochondrial pathway, it also lends support to the notion that caution must be exercised when investigating the biological effects of endogenous ceramide by use of exogenously administered short-chain analogues.
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Gubern A, Barceló-Torns M, Casas J, Barneda D, Masgrau R, Picatoste F, Balsinde J, Balboa MA, Claro E. Lipid droplet biogenesis induced by stress involves triacylglycerol synthesis that depends on group VIA phospholipase A2. J Biol Chem 2008; 284:5697-708. [PMID: 19117952 DOI: 10.1074/jbc.m806173200] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
This work investigates the metabolic origin of triacylglycerol (TAG) formed during lipid droplet (LD) biogenesis induced by stress. Cytotoxic inhibitors of fatty acid synthase induced TAG synthesis and LD biogenesis in CHO-K1 cells, in the absence of external sources of fatty acids. TAG synthesis was required for LD biogenesis and was sensitive to inhibition and down-regulation of the expression of group VIA phospholipase A(2) (iPLA(2)-VIA). Induction of stress with acidic pH, C(2)-ceramide, tunicamycin, or deprivation of glucose also stimulated TAG synthesis and LD formation in a manner dependent on iPLA(2)-VIA. Overexpression of the enzyme enhanced TAG synthesis from endogenous fatty acids and LD occurrence. During stress, LD biogenesis but not TAG synthesis required phosphorylation and activation of group IVA PLA(2) (cPLA(2)alpha). The results demonstrate that iPLA(2)-VIA provides fatty acids for TAG synthesis while cPLA(2)alpha allows LD biogenesis. LD biogenesis during stress may be a survival strategy, recycling structural phospholipids into energy-generating substrates.
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Affiliation(s)
- Albert Gubern
- Institut de Neurociències and Departament de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona (UAB), Edifici M2, Campus de la UAB, Barcelona E-08193, Spain
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16
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Tian Y, Zhou R, Rehg JE, Jackowski S. Role of phosphocholine cytidylyltransferase alpha in lung development. Mol Cell Biol 2006; 27:975-82. [PMID: 17130238 PMCID: PMC1800673 DOI: 10.1128/mcb.01512-06] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lung development depends upon the differentiation and expansion of a variety of specialized epithelial cell types, including distal type I and type II pneumocytes in the late term. Previous studies have shown a strict dependence on the choline cytidylyltransferase alpha isoform (CCTalpha) to mediate membrane phospholipid formation in cultured cells and during preimplantation embryogenesis. CCTalpha expression is highest in lung, and there has long been speculation about its precise role, due to the dual requirement for phospholipid in proliferating cell membranes and for lung surfactant production from alveolar type II cells. We investigated the function of CCTalpha in lung development, using an inducible, epithelial cell-specific CCTalpha knockout mouse line. Deletion of CCTalpha beginning at embryonic day 7.5 did not restrict lung development but resulted in severe respiratory failure at birth. Alveolar lavage and lung lipid analyses showed significant decreases in the major surfactant phospholipid, dipalmitoyl-phosphatidylcholine. The fatty acids destined for the surfactant phospholipid were redirected to an expanded triglyceride pool. Transcripts encoding type II cell-specific markers were expressed in the knockout mice, indicating the expected progression of differentiation in lung epithelia. However, surfactant protein levels were reduced, with the exception of that for surfactant protein B, which was elevated. Ultrastructural analysis of the type II cells showed Golgi complex abnormalities and aberrant lamellar bodies, which deliver surfactant lipid and protein to the alveolar lumen. Thus, CCTalpha was not required for the proliferation or differentiation of lung epithelia but was essential for the secretory component of phospholipid synthesis and critical for the proper formation of lamellar bodies and surfactant protein homeostasis.
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Affiliation(s)
- Yong Tian
- Department of Infectious Diseases, St. Jude Children's Research Hospital, 332 N. Lauderdale, Memphis, TN 38105-2794, USA
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17
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Sinha Roy S, Mukherjee S, Kabir S, Rajaratnam V, Smith M, Das SK. Inhibition of cholinephosphotransferase activity in lung injury induced by 2-chloroethyl ethyl sulfide, a mustard analog. J Biochem Mol Toxicol 2006; 19:289-97. [PMID: 16292752 DOI: 10.1002/jbt.20092] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Exposure to mustard gas causes inflammatory lung diseases including acute respiratory distress syndrome (ARDS). A defect in the lung surfactant system has been implicated as a cause of ARDS. A major component of lung surfactant is dipalmitoyl phosphatidylcholine (DPPC) and the major pathway for its synthesis is the cytidine diphosphocholine (CDP-choline) pathway. It is not known whether the ARDS induced by mustard gas is mediated by its direct effects on some of the enzymes in the CDP-choline pathway. In the present study we investigated whether mustard gas exposure modulates the activity of cholinephosphotransferase (CPT) the terminal enzyme by CDP-choline pathway. Adult guinea pigs were intratracheally infused with single doses of 2-chloroethyl ethyl sulfide (CEES) (0.5 mg/kg b.wt. in ethanol). Control animals were injected with vehicles only. The animals were sacrificed at different time and the lungs were removed after perfusion with physiological saline. CPT activity increased steadily up to 4 h and then decreased at 6 h and stabilized at 7 days in both mitochondria and microsomes. To determine the dose-dependent effect of CEES on CPT activity we varied the doses of CEES (0.5-6.0 mg/kg b.wt.) and sacrificed the animals at 1 h and 4 h. CPT activity showed a dose-dependent increase of up to 2.0 mg/kg b.wt. of CEES in both mitochondria and microsomes then decreased at 4.0 mg/kg b.wt. For further studies we used a fixed single dose of CEES (2.0 mg/kg b.wt.) and fixed exposure time (7 days). Lung injury was determined by measuring the leakage of iodinated-bovine serum albumin into lung tissue and expressed as the permeability index. CEES exposure (2.0 mg/kg b.wt. for 7 days) caused a significant decrease of both CPT gene expression (approximately 1.7-fold) and activity (approximately 1.5-fold) in the lung. This decrease in CPT activity was not associated with any mutation of the CPT gene. Previously we reported that CEES infusion increased the production of ceramides which are known to modulate PC synthesis. To determine whether ceramides affect microsomal CPT activity the lung microsomal fraction was incubated with different concentrations of C(2)-ceramide prior to CPT assay. CPT activity decreased significantly with increasing dose and time. The present study indicates that CEES causes lung injury and significantly decreases CPT gene expression and activity. This decrease in CPT activity was not associated with any mutation of the CPT gene is probably mediated by accumulation of ceramides. CEES induced ceramide accumulation may thus play an important role in the development of ARDS by modulating CPT enzyme.
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Affiliation(s)
- Somdutta Sinha Roy
- Department of Biochemistry, Meharry Medical College, 1005 David Todd Blvd, Nashville, TN 37208, USA
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18
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Sarri E, Garcia-Dorado D, Abellan A, Soler-Soler J. Effects of hypoxia, glucose deprivation and acidosis on phosphatidylcholine synthesis in HL-1 cardiomyocytes. CTP:phosphocholine cytidylyltransferase activity correlates with sarcolemmal disruption. Biochem J 2006; 394:325-34. [PMID: 16236026 PMCID: PMC1386031 DOI: 10.1042/bj20050834] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A decrease in [3H]Cho (choline) incorporation in to PtdCho (phos-phatidylcholine) preceded the onset of LDH (lactate dehydrogenase) release in HL-1 cardiomyocytes submitted to simulated ischaemia. This observation led us to examine the role of PtdCho synthesis in sarcolemmal disruption in HL-1 cardiomyocytes. To address this objective we analysed the individual effects of hypoxia, glucose deprivation and acidosis, three prominent components of ischaemia, on the different steps of the Kennedy pathway for the synthesis of PtdCho. Pulse and pulse-chase experiments with [3H]Cho, performed in whole HL-1 cells submitted to hypoxia or normoxia, in the presence or absence of glucose at different pHs indicated first, that CK (choline kinase) was inhibited by hypoxia and acidosis, whereas glucose deprivation exacerbated the inhibition caused by hypoxia. Second, the rate-limiting reaction in PtdCho synthesis, catalysed by CCT (CTP:phosphocholine cytidylyltransferase), was inhibited by hypoxia and glucose deprivation, but unexpectedly activated by acidosis. In cellfree system assays, acidosis inhibited both CK and CCT. In experiments performed in whole cells, the effect of acidosis was likely to be direct on CK, but indirect or intact-cell-dependent on CCT. Since hypoxia and glucose deprivation favoured membrane disruption, but acidosis prevented it, we hypothesized that the modulation of CCT could be an important determinant of cell survival. Supporting this hypothesis, we show that CCT activity in whole-cell experiments clearly correlated with LDH release, but not with ATP concentration. Altogether our results suggest a significant role for CCT activity in sarcolemmal disruption during ischaemia.
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Affiliation(s)
- Elisabet Sarri
- Cardiology Service, Institut de Recerca Hospital Universitari Vall d'Hebron, Pg. Vall d'Hebron 119-129, 08035 Barcelona, Spain
| | - David Garcia-Dorado
- Cardiology Service, Institut de Recerca Hospital Universitari Vall d'Hebron, Pg. Vall d'Hebron 119-129, 08035 Barcelona, Spain
- To whom correspondence should be addressed (email )
| | - Arancha Abellan
- Cardiology Service, Institut de Recerca Hospital Universitari Vall d'Hebron, Pg. Vall d'Hebron 119-129, 08035 Barcelona, Spain
| | - Jordi Soler-Soler
- Cardiology Service, Institut de Recerca Hospital Universitari Vall d'Hebron, Pg. Vall d'Hebron 119-129, 08035 Barcelona, Spain
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19
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Kodvawala A, Ghering AB, Davidson WS, Hui DY. Carboxyl Ester Lipase Expression in Macrophages Increases Cholesteryl Ester Accumulation and Promotes Atherosclerosis. J Biol Chem 2005; 280:38592-8. [PMID: 16166077 DOI: 10.1074/jbc.m502266200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Carboxyl ester lipase (CEL, also called cholesterol esterase or bile salt-dependent lipase) is a lipolytic enzyme capable of hydrolyzing cholesteryl esters, triacylglycerols, and phospholipids in a trihydroxy bile salt-dependent manner but hydrolyzes ceramides and lysophospholipids via bile salt-independent mechanisms. Although CEL is synthesized predominantly in the pancreas, a low level of CEL expression was reported in human macrophages. This study used transgenic mice with macrophage CEL expression at levels comparable with that observed in human macrophages to explore the functional role and physiological significance of macrophage CEL expression. Peritoneal macrophages from CEL transgenic mice displayed a 4-fold increase in [(3)H]oleate incorporation into cholesteryl [(3)H]oleate compared with CEL-negative macrophages when the cells were incubated under basal conditions in vitro. When challenged with acetylated low density lipoprotein, cholesteryl ester accumulation was 2.5-fold higher in macrophages expressing the CEL transgene. The differences in cholesteryl ester accumulation were attributed to the lower levels of ceramide and lysophosphatidylcholine in CEL-expressing cells than in CEL-negative cells. CEL transgenic mice bred to an atherosclerosis susceptible apoE(-/-) background displayed an approximate 4-fold higher atherosclerotic lesion area than apoE(-/-) mice without the CEL transgene when both were fed a high fat/cholesterol diet. Plasma level of the atherogenic lysophosphatidylcholine was lower in the CEL transgenic mice, but plasma cholesterol level and lipoprotein profile were similar between the two groups. These studies documented that CEL expression in macrophages is pro-atherogenic and that the mechanism is because of its hydrolysis of ceramide and lysophosphatidylcholine in promoting cholesterol esterification and decreasing cholesterol efflux.
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Affiliation(s)
- Ahmer Kodvawala
- Department of Pathology and Laboratory Medicine, Genome Research Institute, University of Cincinnati College of Medicine, Cincinnati, Ohio 45237, USA
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20
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Mravljak J, Zeisig R, Pecar S. Synthesis and Biological Evaluation of Spin-Labeled Alkylphospholipid Analogs. J Med Chem 2005; 48:6393-9. [PMID: 16190765 DOI: 10.1021/jm050189v] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Alkylphospholipid analogues of perifosine and miltefosine bearing a nitroxide moiety at different positions on an alkyl chain were synthesized as electron paramagnetic resonance (EPR) probes. Their amphiphilic properties were characterized by determining their critical micelle concentration (cmc) and hemolytic activity on erythrocytes both in free and liposomal form. Spin-labeled analogues as membrane components of large unilamellar liposomes containing cholesterol and dicetyl phosphate or in free solution were evaluated using the MTT assay to determine growth inhibition on MT1, MT3, and MCF7 breast cancer cell lines. 4a (IC50 = 56.4 microM) was found to be significantly more active than the perifosine against the MCF-7 cell line. Its high cmc (194.03 microM) and low hemolytic activity shows that its cytotoxic activity might be more specific; therefore, 4a can be an important molecular tool for further EPR investigations.
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Affiliation(s)
- Janez Mravljak
- Faculty of Pharmacy, University of Ljubljana, Askerceva 7, SI-1000 Ljubljana, Slovenia.
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21
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Wang L, Magdaleno S, Tabas I, Jackowski S. Early embryonic lethality in mice with targeted deletion of the CTP:phosphocholine cytidylyltransferase alpha gene (Pcyt1a). Mol Cell Biol 2005; 25:3357-63. [PMID: 15798219 PMCID: PMC1069620 DOI: 10.1128/mcb.25.8.3357-3363.2005] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
CTP:phosphocholine cytidylyltransferase (CCT) catalyzes a rate-controlling step in the biosynthesis of phosphatidylcholine (PtdCho). Multiple CCT isoforms, CCTalpha, CCTbeta2, and CCTbeta3, are encoded by two genes, Pcyt1a and Pcyt1b. The importance of CCTalpha in mice was investigated by deleting exons 5 and 6 in the Pcyt1a gene using the Cre-lox system. Pcyt1a-/- zygotes failed to form blastocysts, did not develop past embryonic day 3.5 (E3.5), and failed to implant. In situ hybridization in E11.5 embryos showed that Pcyt1a is expressed ubiquitously, with the highest level in fetal liver, and CCTalpha transcripts are significantly more abundant than transcripts encoding CCTbeta or phosphatidylethanolamine (PtdEtn) N-methyl transferase, two other enzymes capable of producing PtdCho. Reduction of the CCTalpha transcripts in heterozygous E11.5 embryos was accompanied by upregulation of CCTbeta and PtdEtn N-methyltransferase transcripts. In contrast, enzymatic and real-time PCR data revealed that CCTbeta (Pcyt1b) expression is not upregulated to compensate for the reduction in CCTalpha expression in adult liver and other tissues from Pcyt1a+/- heterozygous mice. PtdCho biosynthesis measured by choline incorporation into isolated hepatocytes was not compromised in the Pcyt1a+/- mice. Liver PtdCho mass was the same in Pcyt1a+/+ and Pcyt1a+/- adult animals, but lung PtdCho mass decreased in the heterozygous mice. These data show that CCTalpha expression is required for early embryonic development, but that a 50% reduction in enzyme activity has little detectable impact on the operation of the CDP-choline metabolic pathway in adult tissues.
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Affiliation(s)
- Limin Wang
- Department of Infectious Diseases, St. Jude Children's Research Hospital, 332 N. Lauderdale, Memphis, TN 38105-2794, USA
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22
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Xu Z, Zhou J, McCoy DM, Mallampalli RK. LASS5 is the predominant ceramide synthase isoform involved in de novo sphingolipid synthesis in lung epithelia. J Lipid Res 2005; 46:1229-38. [PMID: 15772421 DOI: 10.1194/jlr.m500001-jlr200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Ceramide is a key bioactive mediator that inhibits surfactant phosphatidylcholine (PtdCho) synthesis in lung epithelia. Ceramide availability is governed by sphingomyelin (SM) hydrolysis, but less is known regarding its de novo synthesis. In this study, we observed that ceramide synthesis within murine lung epithelia was associated with high-level ceramide synthase (dihydroceramide synthase) activity. Longevity assurance homolog 5 (LASS5) was the predominant ceramide synthase isoform detected in lung epithelia, whereas relatively lower level expression was detected for the other five mammalian homologs. Pulmonary LASS5 was developmentally regulated, but its expression was spatially and gender nonspecific. Exogenously expressed LASS5 in lung epithelia was membrane-associated, triggering increased ceramide synthesis, whereas knockdown studies using fumonisin B1 or LASS5 small, interfering RNA reduced ceramide synthase activity by 78% or 45%, respectively. Overexpression of LASS5 also reduced PtdCho synthesis, but maximal inhibition was achieved when LASS5 was coexpressed with a plasmid encoding a neutral sphingomyelinase involved in SM hydrolysis. These results demonstrate that LASS5 is the major ceramide synthase gene product involved in sphingolipid production that may also regulate PtdCho metabolism in pulmonary epithelia.
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Affiliation(s)
- Zhiwei Xu
- Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
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23
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Ryan A, Fisher K, Thomas C, Mallampalli R. Transcriptional repression of the CTP:phosphocholine cytidylyltransferase gene by sphingosine. Biochem J 2005; 382:741-50. [PMID: 15139854 PMCID: PMC1133833 DOI: 10.1042/bj20040105] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2004] [Revised: 04/19/2004] [Accepted: 05/13/2004] [Indexed: 11/17/2022]
Abstract
We examined the effects of the bioactive lipid, sphingosine, on the expression of the rate-limiting enzyme involved in surfactant phosphatidylcholine synthesis, CCTalpha (CTP:phosphocholine cytidylyltransferase alpha). Sphingosine decreased phosphatidylcholine synthesis by inhibiting CCT activity in primary alveolar type II epithelia. Sphingosine decreased CCTalpha protein and mRNA levels by approx. 50% compared with control. The bioactive lipid did not alter CCTalpha mRNA stability, but significantly inhibited its transcriptional rate. In murine lung epithelia, sphingosine selectively reduced CCTalpha promoter-reporter activity when transfected with a 2 kb CCTalpha promoter/luciferase gene construct. Sphingosine also decreased transgene expression in murine type II epithelia isolated from CCTalpha promoter-reporter transgenic mice harbouring this 2 kb proximal 5'-flanking sequence. Deletional analysis revealed that sphingosine responsiveness was mapped to a negative regulatory element contained within 814 bp upstream of the coding region. The results indicate that bioactive sphingolipid metabolites suppress surfactant lipid synthesis by inhibiting gene transcription of a key surfactant biosynthetic enzyme.
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Affiliation(s)
- Alan J. Ryan
- *Department of Veterans Affairs Medical Center, University of Iowa College of Medicine, Iowa City, IA 52242, U.S.A
| | - Kurt Fisher
- †Departments of Internal Medicine and Biochemistry, University of Iowa College of Medicine, Iowa City, IA 52242, U.S.A
| | - Christie P. Thomas
- †Departments of Internal Medicine and Biochemistry, University of Iowa College of Medicine, Iowa City, IA 52242, U.S.A
| | - Rama K. Mallampalli
- *Department of Veterans Affairs Medical Center, University of Iowa College of Medicine, Iowa City, IA 52242, U.S.A
- †Departments of Internal Medicine and Biochemistry, University of Iowa College of Medicine, Iowa City, IA 52242, U.S.A
- To whom correspondence should be addressed, at Pulmonary and Critical Care Division, C-33K, GH, Departments of Internal Medicine and Biochemistry (email )
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24
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Jackowski S, Fagone P. CTP: Phosphocholine cytidylyltransferase: paving the way from gene to membrane. J Biol Chem 2004; 280:853-6. [PMID: 15536089 DOI: 10.1074/jbc.r400031200] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- Suzanne Jackowski
- Protein Science Division, Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
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25
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Zweigner J, Jackowski S, Smith SH, Van Der Merwe M, Weber JR, Tuomanen EI. Bacterial inhibition of phosphatidylcholine synthesis triggers apoptosis in the brain. ACTA ACUST UNITED AC 2004; 200:99-106. [PMID: 15238609 PMCID: PMC2213312 DOI: 10.1084/jem.20032100] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Streptococcus pneumoniae is the most common cause of bacterial meningitis of high mortality and morbidity. Neurological sequelae include paralysis, mental retardation, and learning disorders. In humans, neurons of the hippocampus undergo apoptosis as a result of meningitis. Phosphatidylcholine (PtdCho) is an essential component of mammalian cell membranes and PtdCho deficiency, either due to chemicals or altered nutrition, leads to apoptosis, especially in hippocampal neurons. We show that apoptosis of a variety of brain cells after pneumococcal infection arises from inhibition of PtdCho biosynthesis, the first such activity described for a bacterium. Apoptosis inhibitors did not prevent the bacterial-dependent inhibition of PtdCho biosynthesis. Supplementation with exogenous lyso-phosphatidylcholine prevents cell death and treatment of mice with cytidine diphosphocholine attenuates hippocampal damage during meningitis, even after the onset of infection. We conclude that bacterial inhibition of PtdCho biosynthesis activates an apoptotic cascade that is a causative event in pathogenesis and amenable to therapeutic intervention.
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Affiliation(s)
- Janine Zweigner
- Department of Infectious Diseases, St. Jude Children's Research Hospital, 332 North Lauderdale Street, Memphis, TN 38105, USA
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26
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Delon C, Manifava M, Wood E, Thompson D, Krugmann S, Pyne S, Ktistakis NT. Sphingosine kinase 1 is an intracellular effector of phosphatidic acid. J Biol Chem 2004; 279:44763-74. [PMID: 15310762 DOI: 10.1074/jbc.m405771200] [Citation(s) in RCA: 154] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sphingosine kinase 1 (SK1) phosphorylates sphingosine to generate sphingosine 1-phosphate (S1P). Because both substrate and product of the enzyme are potentially important signaling molecules, the regulation of SK1 is of considerable interest. We report that SK1, which is ordinarily a cytosolic enzyme, translocates in vivo and in vitro to membrane compartments enriched in phosphatidic acid (PA), the lipid product of phospholipase D. This translocation depends on direct interaction of SK1 with PA, because recombinant purified enzyme shows strong affinity for pure PA coupled to Affi-Gel. The SK1-PA interaction maps to the C terminus of SK1 and is independent of catalytic activity or of the diacylglycerol kinase-like domain of the enzyme. Thus SK1 constitutes a novel, physiologically relevant PA effector.
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Affiliation(s)
- Christine Delon
- Department of Signalling, Babraham Institute, Cambridge CB2 4AT, United Kingdom
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27
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Larvor MP, Cerdan R, Gumila C, Maurin L, Seta P, Roustan C, Vial H. Characterization of the lipid-binding domain of the Plasmodium falciparum CTP:phosphocholine cytidylyltransferase through synthetic-peptide studies. Biochem J 2003; 375:653-61. [PMID: 12901716 PMCID: PMC1223718 DOI: 10.1042/bj20031011] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2003] [Accepted: 08/05/2003] [Indexed: 11/17/2022]
Abstract
Phospholipid biosynthesis plays a key role in malarial infection and is regulated by CCT (CTP:phosphocholine cytidylyltransferase). This enzyme belongs to the group of amphitropic proteins which are regulated by reversible membrane interaction. To assess the role of the putative membrane-binding domain of Plasmodium falciparum CCT (PfCCT), we synthesized three peptides, K21, V20 and K54 corresponding to residues 274-294, 308-327 and 274-327 of PfCCT respectively. Conformational behaviour of the peptides, their ability to bind to liposomes and to destabilize lipid bilayers, and their insertion properties were investigated by different biophysical techniques. The intercalation mechanisms of the peptides were refined further by using surface-pressure measurements on various monolayers at the air/water interface. In the present study, we show that the three studied peptides are able to bind to anionic and neutral phospholipids, and that they present an alpha-helical conformation upon lipid binding. Peptides V20 and the full-length K54 intercalate their hydrophobic parts into an anionic bilayer and, to a lesser extent, a neutral one for V20. Peptide K21 interacts only superficially with both types of phospholipid vesicles. Adsorption experiments performed at the air/water interface revealed that peptide K54 is strongly surface-active in the absence of lipid. Peptide V20 presents an atypical behaviour in the presence of phosphatidylserine. Whatever the initial surface pressure of a phosphatidylserine film, peptide V20 and phosphatidylserine entities seem linked together in a special organization involving electrostatic and hydrophobic interactions. We showed that PfCCT presents different lipid-dependence properties from other studied CCTs. Although the lipid-binding domain seems to be located in the C-terminal region of the enzyme, as with the mammalian counterpart, the membrane anchorage, which plays a key role in the enzyme regulation, is driven by two alpha-helices, which behave differently from one another.
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Affiliation(s)
- Marie-Pierre Larvor
- CNRS (UMR 5539) Laboratoire de Dynamique Moléculaire des Interactions Membranaires, Université Montpellier II, cc 107, Place Eugène Bataillon, 34095 Montpellier, cedex 5, France
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28
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Ramos B, Lahti JM, Claro E, Jackowski S. Prevalence of necrosis in C2-ceramide-induced cytotoxicity in NB16 neuroblastoma cells. Mol Pharmacol 2003; 64:502-11. [PMID: 12869656 DOI: 10.1124/mol.64.2.502] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The mechanism of cell death triggered by C2-ceramide was investigated using the NB16 neuroblastoma cell line. Treatment of NB16 cells with 20 microM C2-ceramide for 20 h resulted in approximately 75% loss of cell viability, but only 25% of cells were scored as apoptotic based on terminal deoxynucleotidyl transferase nick-end labeling. Ultrastructural analysis revealed early development of necrotic cytoplasmic vacuolization. After 20 h of treatment with C2-ceramide, the majority of cells possessed necrotic morphology with pronounced cytoplasmic vacuolization and without any nuclear changes, although a quarter of the cell population also exhibited clear perinuclear chromatin condensation characteristic of apoptosis. Flow cytometric analysis of cells labeled with both annexin V and propidium iodide showed the rapid accumulation of C2-ceramide-treated cells in the necrotic/late apoptotic fraction. In contrast, cells treated with tumor necrosis factor alpha plus cycloheximide (TNFalpha + CHX) first appeared in the early apoptotic fraction and then accumulated in the necrotic/late apoptotic fraction. Both C2-ceramide and TNFalpha + CHX increased caspase 8- and 3-like activities in cytosolic extracts; however, treatment of cells with the broad-spectrum caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone protected NB16 cells from TNFalpha + CHX-induced cell death but did not prevent C2-ceramide cytotoxicity. Although C2-ceramide triggered apoptosis in a fraction of the cells, cell death in the population was primarily caused by necrosis. Thus, C2-ceramide does not faithfully mimic the effects of apoptotic ligands such as TNFalpha, which are thought to be mediated by an accumulation of endogenous ceramide. The inhibition of phosphatidylcholine synthesis is a target for C2-ceramide-mediated cytotoxicity, and this work suggests that other agents that kill cells by inhibiting this pathway may also use a mixture of mechanisms, including necrosis as well as apoptosis.
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Affiliation(s)
- Belen Ramos
- Departamento de Fisiología, Universidad de Extremadura, Cáceres, Spain
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van Blitterswijk WJ, van der Luit AH, Veldman RJ, Verheij M, Borst J. Ceramide: second messenger or modulator of membrane structure and dynamics? Biochem J 2003; 369:199-211. [PMID: 12408751 PMCID: PMC1223095 DOI: 10.1042/bj20021528] [Citation(s) in RCA: 335] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2002] [Revised: 10/30/2002] [Accepted: 10/31/2002] [Indexed: 12/18/2022]
Abstract
The physiological role of ceramide formation in response to cell stimulation remains controversial. Here, we emphasize that ceramide is not a priori an apoptotic signalling molecule. Recent work points out that the conversion of sphingomyelin into ceramide can play a membrane structural (physical) role, with consequences for membrane microdomain function, membrane vesiculation, fusion/fission and vesicular trafficking. These processes contribute to cellular signalling. At the Golgi, ceramide takes part in a metabolic flux towards sphingomyelin, diacylglycerol and glycosphingolipids, which drives lipid raft formation and vesicular transport towards the plasma membrane. At the cell surface, receptor clustering in lipid rafts and the formation of endosomes can be facilitated by transient ceramide formation. Also, signalling towards mitochondria may involve glycosphingolipid-containing vesicles. Ceramide may affect the permeability of the mitochondrial outer membrane and the release of cytochrome c. In the effector phase of apoptosis, the breakdown of plasma membrane sphingomyelin to ceramide is a consequence of lipid scrambling, and may regulate apoptotic body formation. Thus ceramide formation serves many different functions at distinct locations in the cell. Given the limited capacity for spontaneous intracellular diffusion or membrane flip-flop of natural ceramide species, the topology and membrane sidedness of ceramide generation are crucial determinants of its impact on cell biology.
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Affiliation(s)
- Wim J van Blitterswijk
- Division of Cellular Biochemistry, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands.
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