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Kawashima T, Yamazaki R, Matsuzawa Y, Yamaura E, Takabatake M, Otake S, Ikawa Y, Nakamura H, Fujino H, Murayama T. Contrary effects of sphingosine-1-phosphate on expression of α-smooth muscle actin in transforming growth factor β1-stimulated lung fibroblasts. Eur J Pharmacol 2012; 696:120-9. [PMID: 23041148 DOI: 10.1016/j.ejphar.2012.09.038] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Revised: 09/13/2012] [Accepted: 09/22/2012] [Indexed: 12/20/2022]
Abstract
Transforming growth factor-β1 (TGFβ1) plays a pivotal role in fibrosis in various organs including the lung. Following pulmonary injury, TGFβ1 stimulates conversion of fibroblasts to myofibroblasts that are mainly characterized by up-regulation of α-smooth muscle actin (αSMA) expression, and the resulting excess production of extracellular matrix proteins causes fibrosis with loss of alveolar function. The present study was undertaken to define the role of the sphingosine-1-phosphate (S1P) pathway in TGFβ1-induced expression of αSMA in human fetal lung fibroblasts, HFL1 cells. Analysis of mRNA revealed the existence of S1P(1), S1P(2), and S1P(3) receptor mRNAs. Treatment with TGFβ1 increased sphingosine kinase (SphK) activity and S1P(3) receptor mRNA at 24h after stimulation, and pharmacological data showed the involvement of sphingomyelinase, SphK, and S1P(3) receptor in the TGFβ1-induced up-regulation of αSMA with and without serum. Treatment with pertussis toxin and S1P(1) receptor antagonist W146 enhanced αSMA expression by TGFβ1/serum, and S1P decreased and increased αSMA levels with and without serum, respectively. TGFβ1 increased cyclooxygenase-2 expression in a manner dependent on serum and the sphingomyelinase/SphK pathway, and the response was decreased by pertussis toxin. Prostaglandin E(2), formed by TGFβ1/serum stimulation, decreased the TGFβ1-induced expression of αSMA via EP prostanoid receptor. These data suggest that S1P formed by TGFβ1 stimulation has diverse effects on the expression of αSMA, inhibition via the S1P(1) receptor-mediated and serum-dependent expression of cyclooxygenase-2 and the resulting formation of prostaglandin E(2), and stimulation via the S1P(3) receptor in a serum-independent manner.
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Affiliation(s)
- Tatsuo Kawashima
- Department of Internal Medicine, Toho University School of Medicine, Sakura Hospital, Sakura City, Chiba 285-8741, Japan
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102
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Filippov V, Song MA, Zhang K, Vinters HV, Tung S, Kirsch WM, Yang J, Duerksen-Hughes PJ. Increased ceramide in brains with Alzheimer's and other neurodegenerative diseases. J Alzheimers Dis 2012; 29:537-47. [PMID: 22258513 DOI: 10.3233/jad-2011-111202] [Citation(s) in RCA: 177] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Ceramide has been suggested to participate in the neuronal cell death that leads to Alzheimer's disease (AD), but its role is not yet well-understood. We compared the levels of six ceramide subspecies, which differ in the length of their fatty acid moieties, in brains from patients who suffered from AD, other neuropathological disorders, or both. We found elevated levels of Cer16, Cer18, Cer20, and Cer24 in brains from patients with any of the tested neural defects. Moreover, ceramide levels were highest in patients with more than one neuropathologic abnormality. Interestingly, the range of values was higher among brains with neural defects than in controls, suggesting that the regulation of ceramide synthesis is normally under tight control, and that this tight control may be lost during neurodegeneration. These changes, however, did not alter the ratio between the tested ceramide species. To explore the mechanisms underlying this dysregulation, we evaluated the expression of four genes connected to ceramide metabolism: ASMase, NSMase 2, GALC, and UGCG. The patterns of gene expression were complex, but overall, ASMase, NSMase 2, and GALC were upregulated in specimens from patients with neuropathologic abnormalities in comparison with age-matched controls. Such findings suggest these genes as attractive candidates both for diagnostic purposes and for intervening in neurodegenerative processes.
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Affiliation(s)
- Valery Filippov
- Loma Linda University, Department of Basic Science, Loma Linda University School of Medicine, Loma Linda, CA 92354, USA
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103
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Chen SD, Yin JH, Hwang CS, Tang CM, Yang DI. Anti-apoptotic and anti-oxidative mechanisms of minocycline against sphingomyelinase/ceramide neurotoxicity: implication in Alzheimer's disease and cerebral ischemia. Free Radic Res 2012; 46:940-50. [PMID: 22583533 DOI: 10.3109/10715762.2012.674640] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Sphingolipids represent a major class of lipids in which selected family members act as bioactive molecules that control diverse cellular processes, such as proliferation, differentiation, growth, senescence, migration and apoptosis. Emerging evidence reveals that sphingomyelinase/ceramide pathway plays a pivotal role in neurodegenerative diseases that involve mitochondrial dysfunction, oxidative stress and apoptosis. Minocycline, a semi-synthetic second-generation tetracycline derivative in clinical use for infection control, is also considered an effective protective agent in various neurodegenerative diseases in pre-clinical studies. Acting via multiple mechanisms, including anti-inflammatory, anti-oxidative and anti-apoptotic effects, minocycline is a desirable candidate for clinical trials in both acute brain injury as well as chronic neurodegenerative disorders. This review is focused on the anti-apoptotic and anti-oxidative mechanisms of minocycline against neurotoxicity induced by sphingomyelinase/ceramide in relation to neurodegeneration, particularly Alzheimer's disease and cerebral ischemia.
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Affiliation(s)
- Shang-Der Chen
- Department of Neurology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan
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104
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Abstract
PURPOSE OF REVIEW Extracellular microRNAs (miRNAs) are uniquely stable in plasma, and the levels of specific circulating miRNAs can differ with disease. Extracellular miRNAs are associated with lipid-based carriers and lipid-free proteins. miRNAs can be transferred from cell-to-cell by lipid-based carriers and affect gene expression. This review summarizes recent studies that demonstrate the transfer of miRNA between cells and their potential role in intercellular communication. RECENT FINDINGS Microvesicles, exosomes, apoptotic bodies, lipoproteins, and large microparticles contain miRNAs. Recent studies have demonstrated that miRNAs are transferred between dendritic cells, hepatocellular carcinoma cells, and adipocytes in lipid-based carriers. miRNAs are also transferred from T cells to antigen-presenting cells, from stem cells to endothelial cells and fibroblasts, from macrophages to breast cancer cells, and from epithelial cells to hepatocytes in lipid-based carriers. The cellular export of miRNAs in lipid-based carriers is regulated by the ceramide pathway, and the delivery of lipid-associated miRNAs to recipient cells is achieved by various routes, including endocytotic uptake, membrane-fusion, and scavenger receptors. SUMMARY Cellular miRNAs are exported in and to lipid-based carriers (vesicles and lipoprotein particles) and transferred to recipient cells with gene expression changes as intercellular communication.
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Affiliation(s)
- Kasey C Vickers
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
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105
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Meyers-Needham M, Lewis JA, Gencer S, Sentelle RD, Saddoughi SA, Clarke CJ, Hannun YA, Norell H, da Palma TM, Nishimura M, Kraveka JM, Khavandgar Z, Murshed M, Cevik MO, Ogretmen B. Off-target function of the Sonic hedgehog inhibitor cyclopamine in mediating apoptosis via nitric oxide-dependent neutral sphingomyelinase 2/ceramide induction. Mol Cancer Ther 2012; 11:1092-102. [PMID: 22452947 DOI: 10.1158/1535-7163.mct-11-0705] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Sonic hedgehog (SHh) signaling is important in the pathogenesis of various human cancers, such as medulloblastomas, and it has been identified as a valid target for anticancer therapeutics. The SHh inhibitor cyclopamine induces apoptosis. The bioactive sphingolipid ceramide mediates cell death in response to various chemotherapeutic agents; however, ceramide's roles/mechanisms in cyclopamine-induced apoptosis are unknown. Here, we report that cyclopamine mediates ceramide generation selectively via induction of neutral sphingomyelin phosphodiesterase 3, SMPD3 (nSMase2) in Daoy human medulloblastoma cells. Importantly, short interfering RNA-mediated knockdown of nSMase2 prevented cyclopamine-induced ceramide generation and protected Daoy cells from drug-induced apoptosis. Accordingly, ectopic wild-type N-SMase2 caused cell death, compared with controls, which express the catalytically inactive N-SMase2 mutant. Interestingly, knockdown of smoothened (Smo), a target protein for cyclopamine, or Gli1, a downstream signaling transcription factor of Smo, did not affect nSMase2. Mechanistically, our data showed that cyclopamine induced nSMase2 and cell death selectively via increased nitric oxide (NO) generation by neuronal-nitric oxide synthase (n-NOS) induction, in Daoy medulloblastoma, and multiple other human cancer cell lines. Knockdown of n-NOS prevented nSMase2 induction and cell death in response to cyclopamine. Accordingly, N-SMase2 activity-deficient skin fibroblasts isolated from homozygous fro/fro (fragilitas ossium) mice exhibited resistance to NO-induced cell death. Thus, our data suggest a novel off-target function of cyclopamine in inducing apoptosis, at least in part, by n-NOS/NO-dependent induction of N-SMase2/ceramide axis, independent of Smo/Gli inhibition.
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Affiliation(s)
- Marisa Meyers-Needham
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA
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106
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Tanaka K, Tamiya-Koizumi K, Hagiwara K, Ito H, Takagi A, Kojima T, Suzuki M, Iwaki S, Fujii S, Nakamura M, Banno Y, Kannagi R, Tsurumi T, Kyogashima M, Murate T. Role of down-regulated neutral ceramidase during all-trans retinoic acid-induced neuronal differentiation in SH-SY5Y neuroblastoma cells. ACTA ACUST UNITED AC 2012; 151:611-20. [DOI: 10.1093/jb/mvs033] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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107
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The Roles of Neutral Sphingomyelinases in Neurological Pathologies. Neurochem Res 2012; 37:1137-49. [DOI: 10.1007/s11064-011-0692-y] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2011] [Revised: 11/25/2011] [Accepted: 12/29/2011] [Indexed: 12/14/2022]
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108
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Thomas P, Pang Y. Membrane progesterone receptors: evidence for neuroprotective, neurosteroid signaling and neuroendocrine functions in neuronal cells. Neuroendocrinology 2012; 96:162-71. [PMID: 22687885 PMCID: PMC3489003 DOI: 10.1159/000339822] [Citation(s) in RCA: 127] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Accepted: 05/27/2012] [Indexed: 12/15/2022]
Abstract
Membrane progesterone receptors (mPRs) are novel G protein-coupled receptors belonging to the progestin and adipoQ receptor family (PAQR) that mediate a variety of rapid cell surface-initiated progesterone actions in the reproductive system involving activation of intracellular signaling pathways (i.e. nonclassical actions). The mPRs are highly expressed in the brain, but research on their neural functions has only been conducted in a single neuronal cell line, GT1-7 cells, which have negligible nuclear progesterone receptor (PR) expression. GT1-7 cells express mPRα and mPRβ on their plasma membranes which is associated with the presence of high-affinity, specific [(3)H]-progesterone receptor binding. The neurosteroid, allopregnanolone, is an effective ligand for recombinant mPRα with a relative binding affinity of 7.6% that of progesterone. Allopregnanolone acts as a potent mPR agonist on GT1-7 cells, mimicking the progesterone-induced decrease in cAMP accumulation and its antiapoptotic actions at low nanomolar concentrations. The decrease in cAMP levels is associated with rapid progesterone-induced downregulation of GnRH pulsatile secretion from perifused GT1-7 cells. The recent suggestion that mPRs are alkaline ceramidases and mediate sphingolipid signaling is not supported by empirical evidence that TNFα does not bind to mPRs overexpressed in human cells and that exogenous sphingomyelinase is ineffective in mimicking progestin actions through mPRs to induce meiotic maturation of fish oocytes. Taken together, these recent studies indicate that mPRs mediate neuroprotective effects of progesterone and allopregnanolone and are also the likely intermediaries in progesterone-induced inhibition of pulsatile GnRH secretion in GT1-7 cells.
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Affiliation(s)
- Peter Thomas
- The University of Texas at Austin Marine Science Institute, Port Aransas, TX 78373, USA.
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109
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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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110
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Abstract
Abnormal choline metabolism is emerging as a metabolic hallmark that is associated with oncogenesis and tumour progression. Following transformation, the modulation of enzymes that control anabolic and catabolic pathways causes increased levels of choline-containing precursors and breakdown products of membrane phospholipids. These increased levels are associated with proliferation, and recent studies emphasize the complex reciprocal interactions between oncogenic signalling and choline metabolism. Because choline-containing compounds are detected by non-invasive magnetic resonance spectroscopy (MRS), increased levels of these compounds provide a non-invasive biomarker of transformation, staging and response to therapy. Furthermore, enzymes of choline metabolism, such as choline kinase, present novel targets for image-guided cancer therapy.
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Affiliation(s)
- Kristine Glunde
- The Johns Hopkins University In Vivo Cellular and Molecular Imaging Center, The Russell H. Morgan Department of Radiology and Radiological Science, 720 Rutland Avenue, 212 Traylor Building, Baltimore, Maryland 21205, USA
- Sidney Kimmel Comprehensive Cancer Center, Baltimore, Maryland 21231, USA
| | - Zaver M. Bhujwalla
- The Johns Hopkins University In Vivo Cellular and Molecular Imaging Center, The Russell H. Morgan Department of Radiology and Radiological Science, 720 Rutland Avenue, 212 Traylor Building, Baltimore, Maryland 21205, USA
- Sidney Kimmel Comprehensive Cancer Center, Baltimore, Maryland 21231, USA
| | - Sabrina M. Ronen
- Department of Radiology, University of California San Francisco School of Medicine, UCSF Mission Bay Campus, Byers Hall, San Francisco, California CA94158-2330, USA
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111
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Filosto S, Ashfaq M, Chung S, Fry W, Goldkorn T. Neutral sphingomyelinase 2 activity and protein stability are modulated by phosphorylation of five conserved serines. J Biol Chem 2011; 287:514-522. [PMID: 22074919 DOI: 10.1074/jbc.m111.315481] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
We previously presented that the neutral sphingomyelinase 2 (nSMase2) is the only SMase activated in human airway epithelial (HAE) cells following exposure to oxidative stress (ox-stress), yielding ceramide accumulation and thereby inducing apoptosis. Furthermore, we reported that nSMase2 is a phospho-protein in which the level of phosphorylation controls nSMase2 activation induced by ox-stress. Here we identify five specific serines that are phosphorylated in nSMase2 and demonstrate that their phosphorylation controls the nSMase2 activity upon ox-stress exposure in an interdependent manner. Furthermore, we show that the nSMase2 protein stability and thus its level of expression is also post-translationally regulated by these five serine phosphorylation sites. This study provides initial structure/function insights regarding nSMase2 phosphorylation sites and offers some new links for future studies aiming to fully elucidate nSMase2 regulatory machinery.
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Affiliation(s)
- Simone Filosto
- Department of Internal Medicine, Genome and Biomedical Sciences Facility, University of California School of Medicine, Davis, California 95616
| | - Majid Ashfaq
- Department of Internal Medicine, Genome and Biomedical Sciences Facility, University of California School of Medicine, Davis, California 95616
| | - Samuel Chung
- Department of Internal Medicine, Genome and Biomedical Sciences Facility, University of California School of Medicine, Davis, California 95616
| | - William Fry
- Department of Internal Medicine, Genome and Biomedical Sciences Facility, University of California School of Medicine, Davis, California 95616
| | - Tzipora Goldkorn
- Department of Internal Medicine, Genome and Biomedical Sciences Facility, University of California School of Medicine, Davis, California 95616.
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112
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Merrill AH. Sphingolipid and glycosphingolipid metabolic pathways in the era of sphingolipidomics. Chem Rev 2011; 111:6387-422. [PMID: 21942574 PMCID: PMC3191729 DOI: 10.1021/cr2002917] [Citation(s) in RCA: 527] [Impact Index Per Article: 40.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Indexed: 12/15/2022]
Affiliation(s)
- Alfred H Merrill
- School of Biology, and the Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, Georgia 30332-0230, USA.
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113
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Canals D, Perry DM, Jenkins RW, Hannun YA. Drug targeting of sphingolipid metabolism: sphingomyelinases and ceramidases. Br J Pharmacol 2011; 163:694-712. [PMID: 21615386 DOI: 10.1111/j.1476-5381.2011.01279.x] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Sphingolipids represent a class of diverse bioactive lipid molecules that are increasingly appreciated as key modulators of diverse physiologic and pathophysiologic processes that include cell growth, cell death, autophagy, angiogenesis, and stress and inflammatory responses. Sphingomyelinases and ceramidases are key enzymes of sphingolipid metabolism that regulate the formation and degradation of ceramide, one of the most intensely studied classes of sphingolipids. Improved understanding of these enzymes that control not only the levels of ceramide but also the complex interconversion of sphingolipid metabolites has provided the foundation for the functional analysis of the roles of sphingolipids. Our current understanding of the roles of various sphingolipids in the regulation of different cellular processes has come from loss-of-function/gain-of-function studies utilizing genetic deletion/downregulation/overexpression of enzymes of sphingolipid metabolism (e.g. knockout animals, RNA interference) and from the use of pharmacologic inhibitors of these same enzymes. While genetic approaches to evaluate the functional roles of sphingolipid enzymes have been instrumental in advancing the field, the use of pharmacologic inhibitors has been equally important in identifying new roles for sphingolipids in important cellular processes.The latter also promises the development of novel therapeutic targets with implications for cancer therapy, inflammation, diabetes, and neurodegeneration. In this review, we focus on the status and use of pharmacologic compounds that inhibit sphingomyelinases and ceramidases, and we will review the history, current uses and future directions for various small molecule inhibitors, and will highlight studies in which inhibitors of sphingolipid metabolizing enzymes have been used to effectively treat models of human disease.
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Affiliation(s)
- Daniel Canals
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, USA
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114
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Khavandgar Z, Poirier C, Clarke CJ, Li J, Wang N, McKee MD, Hannun YA, Murshed M. A cell-autonomous requirement for neutral sphingomyelinase 2 in bone mineralization. ACTA ACUST UNITED AC 2011; 194:277-89. [PMID: 21788370 PMCID: PMC3144407 DOI: 10.1083/jcb.201102051] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
nSMase2, which cleaves sphingomyelin to generate bioactive lipids, is required for chondrocyte apoptosis and, cell autonomously, for bone mineralization. A deletion mutation called fro (fragilitas ossium) in the murine Smpd3 (sphingomyelin phosphodiesterase 3) gene leads to a severe skeletal dysplasia. Smpd3 encodes a neutral sphingomyelinase (nSMase2), which cleaves sphingomyelin to generate bioactive lipid metabolites. We examined endochondral ossification in embryonic day 15.5 fro/fro mouse embryos and observed impaired apoptosis of hypertrophic chondrocytes and severely undermineralized cortical bones in the developing skeleton. In a recent study, it was suggested that nSMase2 activity in the brain regulates skeletal development through endocrine factors. However, we detected Smpd3 expression in both embryonic and postnatal skeletal tissues in wild-type mice. To investigate whether nSMase2 plays a cell-autonomous role in these tissues, we examined the in vitro mineralization properties of fro/fro osteoblast cultures. fro/fro cultures mineralized less than the control osteoblast cultures. We next generated fro/fro;Col1a1-Smpd3 mice, in which osteoblast-specific expression of Smpd3 corrected the bone abnormalities observed in fro/fro embryos without affecting the cartilage phenotype. Our data suggest tissue-specific roles for nSMase2 in skeletal tissues.
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Affiliation(s)
- Zohreh Khavandgar
- Faculty of Dentistry, McGill University, Montreal, Quebec QC H3A 1A4, Canada
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115
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Neutral sphingomyelinase 2 (nSMase2) is the primary neutral sphingomyelinase isoform activated by tumour necrosis factor-α in MCF-7 cells. Biochem J 2011; 435:381-90. [PMID: 21303347 DOI: 10.1042/bj20101752] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Activation of N-SMase (neutral sphingomyelinase) is an established part of the response of cytokines such as TNF (tumour necrosis factor)-α. However, it remains unclear which of the currently cloned N-SMase isoforms (nSMase1, nSMase2 and nSMase3) are responsible for this activity. In MCF-7 cells, we found that TNF-α induces late, but not early, increases in N-SMase activity, and that nSMase2 is the primary isoform activated, most likely through post-transcriptional mechanisms. Surprisingly, overexpression of tagged or untagged nSMase3 in multiple cell lines had no significant effect on in vitro N-SMase activity. Moreover, only overexpression of nSMase2, but not nSMase1 or nSMase3, had significant effects on cellular sphingolipid levels, increasing ceramide and decreasing sphingomyelin. Additionally, only siRNA (small interfering RNA) knockdown of nSMase1 significantly decreased basal in vitro N-SMase activity of MCF-7 cells, whereas nSMase2 but not nSMase3 siRNA inhibited TNF-α-induced activity. Taken together, these results identify nSMase2 as the major TNF-α-responsive N-SMase in MCF-7 cells. Moreover, the results suggest that nSMase3 may not possess in vitro N-SMase activity and does not affect cellular sphingolipid levels in the cell lines evaluated. On the other hand, nSMase1 contributes to in vitro N-SMase activity, but does not affect cellular sphingolipids much.
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116
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Clarke CJ, Mediwala K, Jenkins RW, Sutton CA, Tholanikunnel BG, Hannun YA. Neutral sphingomyelinase-2 mediates growth arrest by retinoic acid through modulation of ribosomal S6 kinase. J Biol Chem 2011; 286:21565-76. [PMID: 21536668 DOI: 10.1074/jbc.m110.193375] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
All-trans-retinoic acid (ATRA) induces growth arrest of many cell types. Previous studies have reported that ATRA can modulate cellular sphingolipids, but the role of sphingolipids in the ATRA response is not clear. Using MCF-7 cells as a model system, we show that ATRA stimulates an increase in ceramide levels followed by G(0)/G(1) growth arrest. Notably, induction of nSMase2 was the primary effect of ATRA on the sphingolipid network and was both time- and dose-dependent. Importantly, pretreatment with nSMase2 siRNA significantly inhibited ATRA effects on ceramide levels and growth arrest. In contrast, nSMase2 overexpression was sufficient to increase ceramide levels and induce G(0)/G(1) growth arrest of asynchronous MCF-7 cells. Surprisingly, neither ATRA stimulation nor nSMase2 overexpression had significant effects on classical cell cycle regulators such as p21/WAF1 or retinoblastoma. In contrast, ATRA suppressed phosphorylation of ribosomal S6 kinase (S6K) and its downstream targets S6 and eIF4B. Importantly, these effects were significantly inhibited by nSMase2 siRNA. Reciprocally, nSMase2 overexpression was sufficient to suppress S6K phosphorylation and signaling. Notably, neither ATRA effects nor nSMase2 effects on S6K phosphorylation required the ceramide-activated protein phosphatase PP2A, previously identified as important for S6K regulation. Finally, nSMase2 overexpression was sufficient to decrease translation as measured by methionine incorporation and analysis of polyribosome profiles. Taken together, these results implicate nSMase2 as a major component of ATRA-induced growth arrest of MCF-7 cells and identify S6K as a novel downstream target of nSMase2.
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Affiliation(s)
- Christopher J Clarke
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29425, USA
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117
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Expression profiles of podocytes exposed to high glucose reveal new insights into early diabetic glomerulopathy. J Transl Med 2011; 91:488-98. [PMID: 21102505 PMCID: PMC3068212 DOI: 10.1038/labinvest.2010.188] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Podocyte injury has been suggested to have a pivotal role in the pathogenesis of diabetic glomerulopathy. To glean insights into molecular mechanisms underlying diabetic podocyte injury, we generated temporal global gene transcript profiles of podocytes exposed to high glucose for a time interval of 1 or 2 weeks using microarrays. A number of genes were altered at both 1 and 2 weeks of glucose exposure compared with controls grown under normal glucose. These included extracellular matrix modulators, cell cycle regulators, extracellular transduction signals and membrane transport proteins. Novel genes that were altered at both 1 and 2 weeks of high-glucose exposure included neutrophil gelatinase-associated lipocalin (LCN2 or NGAL, decreased by 3.2-fold at 1 week and by 7.2-fold at 2 weeks), endothelial lipase (EL, increased by 3.6-fold at 1 week and 3.9-fold at 2 week) and UDP-glucuronosyltransferase 8 (UGT8, increased by 3.9-fold at 1 week and 5.0-fold at 2 weeks). To further validate these results, we used real-time PCR from independent podocyte cultures, immunohistochemistry in renal biopsies and immunoblotting on urine specimens from diabetic patients. A more detailed time course revealed changes in LCN2 and EL mRNA levels as early as 6 hours and in UGT8 mRNA level at 12 hours post high-glucose exposure. EL immunohistochemistry on human tissues showed markedly increased expression in glomeruli, and immunoblotting readily detected EL in a subset of urine samples from diabetic nephropathy patients. In addition to previously implicated roles of these genes in ischemic or oxidative stress, our results further support their importance in hyperglycemic podocyte stress and possibly diabetic glomerulopathy pathogenesis and diagnosis in humans.
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118
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Matsubara T, Tanaka N, Patterson AD, Cho JY, Krausz KW, Gonzalez FJ. Lithocholic acid disrupts phospholipid and sphingolipid homeostasis leading to cholestasis in mice. Hepatology 2011; 53:1282-93. [PMID: 21480330 PMCID: PMC3077083 DOI: 10.1002/hep.24193] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
UNLABELLED Lithocholic acid (LCA) is an endogenous compound associated with hepatic toxicity during cholestasis. LCA exposure in mice resulted in decreased serum lysophosphatidylcholine (LPC) and sphingomyelin levels due to elevated lysophosphatidylcholine acyltransferase (LPCAT) and sphingomyelin phosphodiesterase (SMPD) expression. Global metabolome analysis indicated significant decreases in serum palmitoyl-, stearoyl-, oleoyl-, and linoleoyl-LPC levels after LCA exposure. LCA treatment also resulted in decreased serum sphingomyelin levels and increased hepatic ceramide levels, and induction of LPCAT and SMPD messenger RNAs (mRNAs). Transforming growth factor-β (TGF-β) induced Lpcat2/4 and Smpd3 gene expression in primary hepatocytes and the induction was diminished by pretreatment with the SMAD3 inhibitor SIS3. Furthermore, alteration of the LPCs and Lpcat1/2/4 and Smpd3 expression was attenuated in LCA-treated farnesoid X receptor-null mice that are resistant to LCA-induced intrahepatic cholestasis. CONCLUSION This study revealed that LCA induced disruption of phospholipid/sphingolipid homeostasis through TGF-β signaling and that serum LPC is a biomarker for biliary injury.
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Affiliation(s)
- Tsutomu Matsubara
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Naoki Tanaka
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Andrew D. Patterson
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Joo-Youn Cho
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Kristopher W. Krausz
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Frank J. Gonzalez
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892,Correspondence: Frank J. Gonzalez, Laboratory of Metabolism, National Cancer Institute, Building 37, Room 3106, Bethesda, MD 20892, Tel: 301–496–9067, Fax: 301–496–8419,
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Nagai KI, Takahashi N, Moue T, Niimura Y. Alteration of fatty acid molecular species in ceramide and glucosylceramide under heat stress and expression of sphingolipid-related genes. ACTA ACUST UNITED AC 2011. [DOI: 10.4236/abc.2011.13006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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120
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Clarke CJ, Wu BX, Hannun YA. The neutral sphingomyelinase family: identifying biochemical connections. ACTA ACUST UNITED AC 2010; 51:51-8. [PMID: 21035485 DOI: 10.1016/j.advenzreg.2010.09.016] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Accepted: 09/30/2010] [Indexed: 01/31/2023]
Abstract
Neutral sphingomyelinases (N-SMases) are considered to be key mediators of stress-induced ceramide production. The extended family of N-SMases is a subset of the DNaseI superfamily and comprises members from bacteria, yeast and mammals. In recent years, the identification and cloning of mammalian N-SMase family members has led to significant advances in understanding their physiological roles and regulation. However, there is still limited information on their regulation at the biochemical and molecular level. In this review, we summarize current knowledge about the biochemical regulation of the eukaryotic N-SMases and identify the major areas where knowledge is lacking. In recent years, research into the roles and regulation of N-SMases has moved in great strides with the cloning and characterization of multiple N-SMase isoforms and the development of knockout mice. However, as researchers continue to move forward in understanding the physiological functions of these various N-SMase isoforms, it has become exceedingly important to define howthese isoforms are regulated at the biochemical and molecular level. This is crucial for the development of future tools to study N-SMase signaling such as, for example, phospho-specific antibodies designating activation states. This is also an important part of identifying novel roles of N-SMases in physiological and pathological states. Finally, only by obtaining a more complete understanding of the workings of these enzymes at the molecular level, will investigators be able to design appropriate compounds that can target and inhibit their activity both efficiently and specifically. Certainly, the last of these is crucial when considering the potential of N-SMases as therapeutic targets. With this in mind, we sincerely hope that the next decade of research will even surpass the last ten years in advancing our understanding of the eukaryotic N-SMase family.
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Affiliation(s)
- Christopher J Clarke
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA
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Portt L, Norman G, Clapp C, Greenwood M, Greenwood MT. Anti-apoptosis and cell survival: a review. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1813:238-59. [PMID: 20969895 DOI: 10.1016/j.bbamcr.2010.10.010] [Citation(s) in RCA: 430] [Impact Index Per Article: 30.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2010] [Revised: 10/04/2010] [Accepted: 10/11/2010] [Indexed: 02/08/2023]
Abstract
Type I programmed cell death (PCD) or apoptosis is critical for cellular self-destruction for a variety of processes such as development or the prevention of oncogenic transformation. Alternative forms, including type II (autophagy) and type III (necrotic) represent the other major types of PCD that also serve to trigger cell death. PCD must be tightly controlled since disregulated cell death is involved in the development of a large number of different pathologies. To counter the multitude of processes that are capable of triggering death, cells have devised a large number of cellular processes that serve to prevent inappropriate or premature PCD. These cell survival strategies involve a myriad of coordinated and systematic physiological and genetic changes that serve to ward off death. Here we will discuss the different strategies that are used to prevent cell death and focus on illustrating that although anti-apoptosis and cellular survival serve to counteract PCD, they are nevertheless mechanistically distinct from the processes that regulate cell death.
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Affiliation(s)
- Liam Portt
- Department of Chemistry and Chemical Engineering, Royal Military College, Ontario, Canada
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