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Marchesini N, Hannun YA. Acid and neutral sphingomyelinases: roles and mechanisms of regulation. Biochem Cell Biol 2004; 82:27-44. [PMID: 15052326 DOI: 10.1139/o03-091] [Citation(s) in RCA: 259] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Ceramide, an emerging bioactive lipid and second messenger, is mainly generated by hydrolysis of sphingomyelin through the action of sphingomyelinases. At least two sphingomyelinases, neutral and acid sphingomyelinases, are activated in response to many extracellular stimuli. Despite extensive studies, the precise cellular function of each of these sphingomyelinases in sphingomyelin turnover and in the regulation of ceramide-mediated responses is not well understood. Therefore, it is essential to elucidate the factors and mechanisms that control the activation of acid and neutral sphingomyelinases to understand their the roles in cell regulation. This review will focus on the molecular mechanisms that regulate these enzymes in vivo and in vitro, especially the roles of oxidants (glutathione, peroxide, nitric oxide), proteins (saposin, caveolin 1, caspases), and lipids (diacylglycerol, arachidonic acid, and ceramide).
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Affiliation(s)
- Norma Marchesini
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, 29425, USA
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52
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Lee JT, Xu J, Lee JM, Ku G, Han X, Yang DI, Chen S, Hsu CY. Amyloid-beta peptide induces oligodendrocyte death by activating the neutral sphingomyelinase-ceramide pathway. ACTA ACUST UNITED AC 2004; 164:123-31. [PMID: 14709545 PMCID: PMC2171973 DOI: 10.1083/jcb.200307017] [Citation(s) in RCA: 210] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Amyloid-beta peptide (Abeta) accumulation in senile plaques, a pathological hallmark of Alzheimer's disease (AD), has been implicated in neuronal degeneration. We have recently demonstrated that Abeta induced oligodendrocyte (OLG) apoptosis, suggesting a role in white matter pathology in AD. Here, we explore the molecular mechanisms involved in Abeta-induced OLG death, examining the potential role of ceramide, a known apoptogenic mediator. Both Abeta and ceramide induced OLG death. In addition, Abeta activated neutral sphingomyelinase (nSMase), but not acidic sphingomyelinase, resulting in increased ceramide generation. Blocking ceramide degradation with N-oleoyl-ethanolamine exacerbated Abeta cytotoxicity; and addition of bacterial sphingomyelinase (mimicking cellular nSMase activity) induced OLG death. Furthermore, nSMase inhibition by 3-O-methyl-sphingomyelin or by gene knockdown using antisense oligonucleotides attenuated Abeta-induced OLG death. Glutathione (GSH) precursors inhibited Abeta activation of nSMase and prevented OLG death, whereas GSH depletors increased nSMase activity and Abeta-induced death. These results suggest that Abeta induces OLG death by activating the nSMase-ceramide cascade via an oxidative mechanism.
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Affiliation(s)
- Jiunn-Tay Lee
- Center for the Study of Nervous System Injury, Dept. of Neurology, Washington University School of Medicine, 660 S. Euclid Ave., Box 8111, St. Louis, MO 63110, USA
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53
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Gao L, Mejías R, Echevarría M, López-Barneo J. Induction of the glucose-6-phosphate dehydrogenase gene expression by chronic hypoxia in PC12 cells. FEBS Lett 2004; 569:256-60. [PMID: 15225644 DOI: 10.1016/j.febslet.2004.06.004] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2004] [Accepted: 06/03/2004] [Indexed: 12/01/2022]
Abstract
We studied the regulation of glucose-6-phosphate dehydrogenase (G6PD) gene expression by chronic hypoxia. G6PD mRNA level and activity were increased in PC12 cells by hypoxia in a dose- and time-dependent manner. Cobalt chloride and dimethyloxalylglycine, which can mimic hypoxia, also activated G6PD gene expression. Interestingly, hypoxia-induced G6PD expression followed a time course much slower than that of phosphoglycerate kinase 1 (PGK1), a hypoxia-inducible factor (HIF)-dependent glycolytic enzyme. Hypoxic-G6PD induction was almost negligible in non-excitable Buffalo rat liver cells, although in these cells PGK1 was strongly upregulated by low PO(2). Furthermore, G6PD but not PGK1 induction was blocked by the antioxidants glutathione and N-acetylcysteine. These results suggest the dependence of G6PD gene expression on HIF and intracellular redox status and the differential hypoxic regulation of glucose-metabolizing enzymes.
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Affiliation(s)
- Lin Gao
- Laboratorio de Investigaciones Biomédicas, Departamento de Fisiología and Hospital Universitario Virgen del Rocío, Universidad de Sevilla, E-41013 Seville, Spain
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54
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Ochiai T, Ohno S, Soeda S, Tanaka H, Shoyama Y, Shimeno H. Crocin prevents the death of rat pheochromyctoma (PC-12) cells by its antioxidant effects stronger than those of alpha-tocopherol. Neurosci Lett 2004; 362:61-4. [PMID: 15147781 DOI: 10.1016/j.neulet.2004.02.067] [Citation(s) in RCA: 145] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2004] [Revised: 02/17/2004] [Accepted: 02/20/2004] [Indexed: 10/26/2022]
Abstract
Crocin is a pharmacologically active component of Crocus sativus L. (saffron) used in traditional Chinese medicine. We report here the effects of crocin on neuronally differentiated pheochromocytoma (PC-12) cells deprived of serum/glucose. Depriving the PC-12 cells of serum/glucose caused peroxidation of their cell membrane lipids and decreased intercellular superoxide dismutase (SOD) activity. Treating the PC-12 cells with 10 microM crocin inhibited the formation of peroxidized lipids, partly restored the SOD activity, and maintained the neuron's morphology. These antioxidant effects of crocin were more effective than those of alpha-tocopherol at the same concentration. Crocin also suppressed the activation of caspase-8 caused by serum/glucose deprivation. These results together with our previous data suggest that crocin is a unique and potent antioxidant that combats oxidative stress in neurons.
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Affiliation(s)
- Takashi Ochiai
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 814-180, Japan
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55
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Sawada M, Kiyono T, Nakashima S, Shinoda J, Naganawa T, Hara S, Iwama T, Sakai N. Molecular mechanisms of TNF-α-induced ceramide formation in human glioma cells:P53-mediated oxidant stress-dependent and -independent pathways. Cell Death Differ 2004; 11:997-1008. [PMID: 15131591 DOI: 10.1038/sj.cdd.4401438] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The present study was designed to examine the roles of p53, reactive oxygen species (ROS), and ceramide, and to determine their mutual relationships during tumor necrosis factor (TNF)-alpha-induced apoptosis of human glioma cells. In cells possessing wild-type p53, TNF-alpha stimulated ceramide formation via the activation of both neutral and acid sphingomyelinases (SMases), accompanied by superoxide anion (O2-*) production, and induced mitochondrial depolarization and cytochrome c release, whereas p53-deficient cells were partially resistant to TNF-alpha and lacked O2-* generation and neutral SMase activation. Restoration of functional p53 sensitized glioma cells expressing mutant p53 to TNF-alpha by accumulation of O2-*. z-IETD-fmk (benzyloxycarbonyl-Ile-Glu-Thr-Asp fluoromethyl ketone), but not z-DEVD-fmk (benzyloxycarbonyl-Asp-Glu-Val-Asp fluoromethyl ketone), blocked TNF-alpha-induced ceramide formation through both SMases as well as O2-* generation. Caspase-8 was processed by TNF-alpha regardless of p53 status of cells or the presence of antioxidants. Two separate signaling cascades, p53-mediated ROS-dependent and -independent pathways, both of which are initiated by caspase-8 activation, thus contribute to ceramide formation in TNF-alpha-induced apoptosis of human glioma cells.
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Affiliation(s)
- M Sawada
- Department of Neurosurgery, Gifu University School of Medicine, Tsukasamachi-40, Gifu 500-8705, Japan.
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56
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Ochiai T, Soeda S, Ohno S, Tanaka H, Shoyama Y, Shimeno H. Crocin prevents the death of PC-12 cells through sphingomyelinase-ceramide signaling by increasing glutathione synthesis. Neurochem Int 2004; 44:321-30. [PMID: 14643749 DOI: 10.1016/s0197-0186(03)00174-8] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Crocin is a pharmacologically active component of Crocus sativus L. (saffron) that has been used in traditional Chinese medicine. In a previous study, we demonstrated that crocin inhibits apoptosis in PC-12 cells by affecting the function of tumor necrosis factor-alpha. In this study, we found that depriving cultured PC-12 cells of serum/glucose causes a rapid increase in cellular ceramide levels, followed by an increase in the phosphorylation of c-jun kinase (JNK). The accumulation of ceramide was found to depend on the activation of magnesium-dependent neutral sphingomyelinase (N-SMase), but not on de novo synthesis. The serum/glucose-deprived PC-12 cells also decreased the cellular levels of glutathione (GSH), which is the potent inhibitor of N-SMase. Treating the PC-12 cells with crocin prevented N-SMase activation, ceramide production, and JNK phosphorylation. We also found that the chemical can enhance the activities of GSH reductase and gamma-glutamylcysteinyl synthase (gamma-GCS), contributing to a stable GSH supply that blocks the activation of N-SMase. Thus our data suggest that crocin combats the serum/glucose deprivation-induced ceramide formation in PC-12 cells by increasing GSH levels and prevents the activation of JNK pathway, which is reported to have a role of the signaling cascade downstream ceramide for neuronal cell death.
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Affiliation(s)
- Takashi Ochiai
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan
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57
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Haughey NJ, Cutler RG, Tamara A, McArthur JC, Vargas DL, Pardo CA, Turchan J, Nath A, Mattson MP. Perturbation of sphingolipid metabolism and ceramide production in HIV-dementia. Ann Neurol 2004; 55:257-67. [PMID: 14755730 DOI: 10.1002/ana.10828] [Citation(s) in RCA: 199] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Infection by the human immunodeficiency virus type 1 (HIV-1) often results in neurological dysfunction including HIV dementia (HIVD). Alterations in cytokine and redox balance are thought to play important roles in the pathogenesis of HIVD, but the specific mechanisms underlying neuronal dysfunction and death are unknown. Activation of cytokine receptors and oxidative stress can induce the production of ceramide from membrane sphingomyelin, and recent findings suggest that ceramide is an important mediator of a form of programmed cell death called apoptosis. We now report that levels of ceramide, sphingomyelin, and hydroxynonenal (HNE) are significantly increased in brain tissues and cerebrospinal fluid of HIVD patients. Exposure of cultured neurons to the neurotoxic HIV proteins gp120 and Tat resulted in increased cellular levels of sphingomyelin, ceramide, and HNE. The ceramide precursor palmitoyl-CoA sensitized neurons to Tat and gp120 toxicity, whereas an inhibitor of ceramide production reduced Tat and gp120-induced increases of ceramide and HNE and protected the neurons from Tat and gp120-induced death. These results suggest that HIV-1 infection may promote a lipid imbalance in neural cells, resulting in an overproduction of ceramide and consequent cellular dysfunction and death.
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Affiliation(s)
- Norman J Haughey
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
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58
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Cutler RG, Kelly J, Storie K, Pedersen WA, Tammara A, Hatanpaa K, Troncoso JC, Mattson MP. Involvement of oxidative stress-induced abnormalities in ceramide and cholesterol metabolism in brain aging and Alzheimer's disease. Proc Natl Acad Sci U S A 2004; 101:2070-5. [PMID: 14970312 PMCID: PMC357053 DOI: 10.1073/pnas.0305799101] [Citation(s) in RCA: 813] [Impact Index Per Article: 40.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Alzheimer's disease (AD) is an age-related disorder characterized by deposition of amyloid beta-peptide (Abeta) and degeneration of neurons in brain regions such as the hippocampus, resulting in progressive cognitive dysfunction. The pathogenesis of AD is tightly linked to Abeta deposition and oxidative stress, but it remains unclear as to how these factors result in neuronal dysfunction and death. We report alterations in sphingolipid and cholesterol metabolism during normal brain aging and in the brains of AD patients that result in accumulation of long-chain ceramides and cholesterol. Membrane-associated oxidative stress occurs in association with the lipid alterations, and exposure of hippocampal neurons to Abeta induces membrane oxidative stress and the accumulation of ceramide species and cholesterol. Treatment of neurons with alpha-tocopherol or an inhibitor of sphingomyelin synthesis prevents accumulation of ceramides and cholesterol and protects them against death induced by Abeta. Our findings suggest a sequence of events in the pathogenesis of AD in which Abeta induces membrane-associated oxidative stress, resulting in perturbed ceramide and cholesterol metabolism which, in turn, triggers a neurodegenerative cascade that leads to clinical disease.
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Affiliation(s)
- Roy G Cutler
- Laboratory of Neurosciences, National Institute on Aging Gerontology Research Center, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA
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59
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Taguchi M, Goda KI, Sugimoto K, Akama T, Yamamoto K, Suzuki T, Tomishima Y, Nishiguchi M, Arai K, Takahashi K, Kobori T. Biological evaluation of sphingomyelin analogues as inhibitors of sphingomyelinase. Bioorg Med Chem Lett 2003; 13:3681-4. [PMID: 14552757 DOI: 10.1016/j.bmcl.2003.08.020] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Seeking neutral sphingomyelinase inhibitors, we designed and synthesized hydrolytically stable analogues of sphingomyelin. These novel analogues replace the phosphodiester moiety of sphingomyelin with carbamate and urea moiety, resulting in inhibition of neutral sphingomyelinase. Compound 1 prevented ceramide generation and apoptotic neuronal cell death in a model of ischemia based on organotypic hippocampal slice cultures.
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Affiliation(s)
- Minoru Taguchi
- Medicinal Research Laboratories, Taisho Pharmaceutical Co., Ltd., 1-403 Yoshino-cho, Kita-ku, Saitama-shi, Saitama 331-9530, Japan.
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60
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Iwai K, Kondo T, Watanabe M, Yabu T, Kitano T, Taguchi Y, Umehara H, Takahashi A, Uchiyama T, Okazaki T. Ceramide increases oxidative damage due to inhibition of catalase by caspase-3-dependent proteolysis in HL-60 cell apoptosis. J Biol Chem 2003; 278:9813-22. [PMID: 12511568 DOI: 10.1074/jbc.m201867200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
We investigated through which mechanisms ceramide increased oxidative damage to induce leukemia HL-60 cell apoptosis. When 5 microm N-acetylsphingosine (C(2)-ceramide) or 20 microm H(2)O(2) alone induced little increase of reactive oxygen species (ROS) generation as judged by the 2'-7'-dichlorofluorescin diacetate method, 20 microm H(2)O(2) enhanced oxidative damage as judged by ROS accumulation, and thiobarbituric acid-reactive substance production after pretreatment with 5 microm C(2)-ceramide at least for 12 h. The treatment with a catalase inhibitor, 3-amino-1h-1,2,4-triazole, increased oxidative damage and apoptosis induced by H(2)O(2), and in contrast, purified catalase inhibited the enhancement of oxidative damage by H(2)O(2) in ceramide-pretreated cells, suggesting that the oxidative effect of ceramide is involved in catalase regulation. Indeed, C(2)-ceramide inhibited the activity of immunoprecipitated catalase and decreased the levels of catalase protein in a time-dependent manner. Moreover, acetyl-Asp-Met-Gln-Asp-aldehyde, which dominantly inhibited caspase-3 and blocked the increase of oxidative damage and apoptosis due to C(2)-ceramide-induced catalase depletion at protein and activity levels. In vitro, active and purified caspase-3, but not caspase-6, -8, and -9, inhibited catalase activity and induced the proteolysis of catalase protein whereas these in vitro effects of caspase-3 were blocked by acetyl-Asp-Met-Gln-Asp-aldehyde. Taken together, it is suggested that H(2)O(2) enhances apoptosis in ceramide-pretreated cells, because ceramide increases oxidative damage by inhibition of ROS scavenging ability through caspase-3-dependent proteolysis of catalase.
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Affiliation(s)
- Kazuya Iwai
- Department of Hematology, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan
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61
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Yamada J, Yoshimura S, Yamakawa H, Sawada M, Nakagawa M, Hara S, Kaku Y, Iwama T, Naganawa T, Banno Y, Nakashima S, Sakai N. Cell permeable ROS scavengers, Tiron and Tempol, rescue PC12 cell death caused by pyrogallol or hypoxia/reoxygenation. Neurosci Res 2003; 45:1-8. [PMID: 12507718 DOI: 10.1016/s0168-0102(02)00196-7] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The role of superoxide anion (O(2)*-) in neuronal cell injury induced by reactive oxygen species (ROS) was examined in PC12 cells using pyrogallol (1,2,3-benzenetrior), a donor to release O(2)*-. Pyrogallol induced PC12 cell death at concentrations, which evidently increased intracellular O(2)*-, as assessed by O(2)(*-)-sensitive fluorescent precursor hydroethidine (HEt). Caspase inhibitors, Z-VAD-FMK and Z-Asp-CH(2)-DCB, failed to protect cells from injury caused by elevation of intracellular O(2)*-, although these inhibitors had effects on hypoxia- or hydrogen peroxide (H(2)O(2))-induced PC12 cell death. Two known O(2)*- scavengers, Tiron (4,5-dihydroxy-1,3-benzenedisulfonic acid) and Tempol (4-hydroxy-2,2,6,6-tetramethylpiperydine-1-oxyl) rescued PC12 cells from pyrogallol-induced cell death. Hypoxia/reoxygenation injury of PC12 cells was also blocked by Tiron and Tempol. Further understanding of the underlying mechanism of the protective effects of these radical scavengers reducing intracellular O(2)*- on neuronal cell death may lead to development of new therapeutic treatments for hypoxic/ischemic brain injury.
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Affiliation(s)
- Jun Yamada
- Department of Neurosurgery, Gifu University School of Medicine, Tsukasamachi 40, Gifu 500-8705, Japan
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62
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Sphingomyelin and ceramide in brain aging, neuronal plasticity and neurodegenerative disorders. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s1566-3124(03)12006-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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63
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Promising Pharmacological Actions of Crocin in Crocus Sativus on the Central Nervous System. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s1572-5995(03)80144-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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64
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Andrieu-Abadie N, Levade T. Sphingomyelin hydrolysis during apoptosis. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1585:126-34. [PMID: 12531545 DOI: 10.1016/s1388-1981(02)00332-3] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Sphingolipid breakdown products are now being recognized as important players in apoptosis. Ceramide, which is considered to serve as second messenger, is mainly generated by hydrolysis of the membrane sphingophospholipid sphingomyelin (SM) through the action of a sphingomyelinase (SMase). However, little is known about the localization and regulation of this phenomenon. Here, we summarize the current knowledge on the function of SM hydrolysis in apoptosis signaling. In particular, the present review focuses on the role of neutral sphingomyelinase (N-SMase) in the generation of the proapoptotic ceramide. This enzyme is regulated by several mechanisms, including the tumor necrosis factor (TNF) receptor-associated protein FAN (for factor associated with N-SMase activation) and oxidative stress. These observations place SMase activation and SM hydrolysis as early events in the apoptosis signaling cascade.
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Affiliation(s)
- Nathalie Andrieu-Abadie
- INSERM Unit 466, Laboratoire de Biochimie Médicale, Institut Louis Bugnard, Centre Hospitalier Universitaire de Rangueil, TSA 50032 31059 Toulouse Cedex 9, France.
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65
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Martin D, Salinas M, Fujita N, Tsuruo T, Cuadrado A. Ceramide and reactive oxygen species generated by H2O2 induce caspase-3-independent degradation of Akt/protein kinase B. J Biol Chem 2002; 277:42943-52. [PMID: 12213802 DOI: 10.1074/jbc.m201070200] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
This study was designed to elucidate the mechanisms leading to down-regulation of the Akt/protein kinase B (PKB) survival pathway during H2O2-induced cell death. H2O2 produced early activation of Akt/PKB and also DNA damage that was followed by stabilization of p53 levels, formation of reactive oxygen species (ROS), and generation of ceramide through activation of a glutathione-sensitive neutral sphingomyelinase. These events correlated with long term dephosphorylation and subsequent degradation of Akt. A membrane-targeted active Akt version attenuated apoptosis but not necrosis induced by H2O2 and was more resistant to dephosphorylation and proteolysis induced by apoptotic concentrations of H2O2. Proteolysis of Akt was prevented by exogenous addition of glutathione, indicating a role of ROS and ceramide in Akt degradation. However, Akt was degraded similarly in cells transfected with wild type and dominant negative p53 mutant, indicating that degradation of Akt under oxidative injury may be p53-independent. Specific inhibitors of caspase groups I and III prevented proteolysis of Akt/PKB and poly(ADP-ribose) polymerase in cells submitted to apoptotic but not necrotic H2O2 concentrations. Surprisingly, in caspase-3-deficient MCF-7 cells Akt was more sensitive to H2O2-induced degradation than the caspase-3 substrate poly(ADP-ribose) polymerase. Moreover, the Akt/PKB double mutant Akt(D108A,D119A), which is not cleaved by caspase-3, and a triple mutant (D453A,D455A,D456A), which lacks the consensus sequence for caspase-3 cleavage, were also degraded in H2O2-treated cells. Our results suggest that strong oxidants generate intracellular ROS and ceramide which in term lead to down-regulation of Akt by dephosphorylation and caspase-3-independent proteolysis.
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Affiliation(s)
- Daniel Martin
- Departamento de Bioquimica and Instituto de Investigaciones Biomédicas Alberto Sols, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid 28029, Spain
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66
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Pollet S, Bottex-Gauthier C, Li M, Potier P, Favier A, Vidal D. Insight into some of the signaling pathways triggered by a lipid immunomodulator. Immunopharmacol Immunotoxicol 2002; 24:527-46. [PMID: 12510789 DOI: 10.1081/iph-120016034] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The use of non specific immunomodulatory agents takes an important place in the aspecific host response to invading microorganisms. In this context, antimicrobial properties of royal jelly have been ascribed to organic acids (mainly 10 hydroxy-2-decenoic acid or 10-HDA) and proteins. We synthesized a derivative of 10-HDA, the 1-(2-methoxyethoxymethyl)2,3-(10-hydroxy2-decenoyl)(E) glycerol referred as diHDA-glycerol which was previously found to protect mice against virulent Salmonella typhimurium challenge through more adequate immune regulations. This study was conducted to further investigate some of the signaling pathways followed by diHDA-glycerol in cell transduction. Members of NF-kappaB transcription factors are key regulators of many cytokines acting on immunity and they control genes involved in responses to numerous signals such as bacterial products. Therefore, we investigated some parameters acting on NF-kappaB translocation in U937 cells after diHDA-glycerol treatment. Due to the chemical structure of the molecule we also investigated the sphingomyelinase pathway. Our results showed that diHDA-glycerol induced a rapid NF-kappaB translocation as a consequence of IkappaB-alpha proteolysis. An intracellular production of reactive oxygen species (ROS) may also account for NF-kappaB activation, without de novo protein synthesis. DiHDA-glycerol induced a strong activation of neutral sphingomyelinase, suggesting an important role of sphingolipids in the regulatory responses induced by diHDA-glycerol.
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Affiliation(s)
- S Pollet
- Centre de Recherches du Service de Santé des Armées Emile Pardé, 24 avenue des Maquis du Grésivaudan, 38702 La Tronche cedex, France
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67
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Luberto C, Hassler DF, Signorelli P, Okamoto Y, Sawai H, Boros E, Hazen-Martin DJ, Obeid LM, Hannun YA, Smith GK. Inhibition of tumor necrosis factor-induced cell death in MCF7 by a novel inhibitor of neutral sphingomyelinase. J Biol Chem 2002; 277:41128-39. [PMID: 12154098 DOI: 10.1074/jbc.m206747200] [Citation(s) in RCA: 252] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
A high throughput screen for neutral, magnesium-dependent sphingomyelinase (SMase) was performed. One inhibitor discovered in the screen, GW4869, functioned as a noncompetitive inhibitor of the enzyme in vitro with an IC(50) of 1 microm. It did not inhibit acid SMase at up to at least 150 microm. The compound was then evaluated for its ability to inhibit tumor necrosis factor (TNF)-induced activation of neutral SMase (N-SMase) in MCF7 cells. GW4869 (10 microm) partially inhibited TNF-induced sphingomyelin (SM) hydrolysis, and 20 microm of the compound was protected completely from the loss of SM. The addition of 10-20 microm GW4869 completely inhibited the initial accumulation of ceramide, whereas this effect was partially lost at later time points (24 h). These data therefore support the inhibitory action of GW4869 on N-SMase not only in vitro but also in a cellular model. The addition of GW4869 at both 10 and 20 microm did not modify cellular glutathione levels in response to TNF, suggesting that the action of GW4869 occurred downstream of the drop in glutathione, which was shown previously to occur upstream of the activation of N-SMase. Further, whereas TNF treatment also caused a 75% increase of de novo synthesized ceramide after 20 h of incubation, GW4869, at either 10 or 20 microm, had no effect on this pathway of ceramide generation. In addition, GW4869 did not significantly impair TNF-induced NF-kappaB translocation to nuclei. Therefore, GW4869 does not interfere with other key TNF-mediated signaling effects. GW4869 was able, in a dose-dependent manner, to significantly protect from cell death as measured by nuclear condensation, caspase activation, PARP degradation, and trypan blue uptake. These protective effects were accompanied by significant inhibition of cytochrome c release from mitochondria and caspase 9 activation, therefore localizing N-SMase activation upstream of mitochondrial dysfunction. In conclusion, our results indicate that N-SMase activation is a necessary step for the full development of the cytotoxic program induced by TNF.
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Affiliation(s)
- Chiara Luberto
- Department of Biochemistry, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA
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68
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Abstract
Recent studies demonstrate a role for intracellular oxidation in the regulation of neutral sphingomyelinase (N-SMase). Glutathione (GSH) has been shown to regulate N-SMase in vitro and in cells. However, it has not been established whether the effects of GSH in cells are due to direct action on N-SMase. In this study, treatment of human mammary carcinoma MCF-7 cells with diamide, a thiol-depleting agent, caused a decrease in intracellular GSH and degradation of sphingomyelin (SM) to ceramide. The SM pool hydrolyzed in response to diamide belonged to the bacterial SMase-resistant pool of SM. Importantly, pretreatment of MCF-7 cells with GSH, N-acetylcysteine, an antioxidant, or GW69A, a specific N-SMase inhibitor, prevented diamide-induced degradation of SM to ceramide, suggesting that intracellular levels of GSH regulate the extent to which SM is degraded to ceramide and that this probably involves a GW69A-sensitive N-SMase. Unexpectedly, expression of Bcl-xL prevented tumor necrosis factor-alpha-induced SM hydrolysis and ceramide accumulation but not the decrease in intracellular GSH. Furthermore, Bcl-xL inhibited diamide-induced SM hydrolysis and ceramide accumulation but not the decrease in intracellular GSH. These results suggest that the site of action of Bcl-xL is downstream of GSH depletion and upstream of ceramide accumulation, and that GSH probably does not exert direct physiologic effects on N-SMase.
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Affiliation(s)
- Yasuo Okamoto
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, 173 Ashley Ave., 29425, USA
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69
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Cutler RG, Pedersen WA, Camandola S, Rothstein JD, Mattson MP. Evidence that accumulation of ceramides and cholesterol esters mediates oxidative stress-induced death of motor neurons in amyotrophic lateral sclerosis. Ann Neurol 2002; 52:448-57. [PMID: 12325074 DOI: 10.1002/ana.10312] [Citation(s) in RCA: 219] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) is characterized by degeneration of motor neurons in the spinal cord resulting in progressive paralysis and death. The pathogenic mechanism of ALS is unknown but may involve increased oxidative stress, overactivation of glutamate receptors, and apoptosis. We report abnormalities in sphingolipid and cholesterol metabolism in the spinal cords of ALS patients and in a transgenic mouse model (Cu/ZnSOD mutant mice), which manifest increased levels of sphingomyelin, ceramides, and cholesterol esters; in the Cu/ZnSOD mutant mice, these abnormalities precede the clinical phenotype. In ALS patients and Cu/Zn-SOD mutant mice, increased oxidative stress occurs in association with the lipid alterations, and exposure of cultured motor neurons to oxidative stress increases the accumulation of sphingomyelin, ceramides, and cholesterol esters. Pharmacological inhibition of sphingolipid synthesis prevents accumulation of ceramides, sphingomyelin, and cholesterol esters and protects motor neurons against death induced by oxidative and excitotoxic insults. These findings suggest a pivotal role for altered sphingolipid metabolism in the pathogenesis of ALS.
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Affiliation(s)
- Roy G Cutler
- Laboratory of Neurosciences, National Institute on Aging Gerontology Research Center, Baltimore, MD, USA
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70
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Borg J, London J. Copper/zinc superoxide dismutase overexpression promotes survival of cortical neurons exposed to neurotoxins in vitro. J Neurosci Res 2002; 70:180-9. [PMID: 12271467 DOI: 10.1002/jnr.10404] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Oxidative stress and excitotoxicity have been implicated as triggering factors in various neurodegenerative diseases or acute neurological insults. Cu/Zn superoxide dismutase (SOD1), a potent free radical scavenging factor, may prevent the progression of such diseases. In the present study, we show that SOD1 overexpression promoted the survival of cortical neuronal cultures originating from mice carrying the human SOD1 transgene. SOD1 overexpression significantly protected against the deleterious effect of reactive oxygen species, ceramide, or N-methyl-D-aspartate (NMDA). It also preserved cortical neurons against apoptosis induced by NMDA or ceramide, as revealed by a smaller increase in caspase 3 activity. SOD1 overexpression was correlated with higher SOD1 activity, and neurotoxins induced an increase in SOD1 activity in cultures from both mice. Moreover, the ratio of increase of SOD1 in cultures from nontransgenic vs. transgenic mice was similar in control cultures or following neurotoxins administration. The highest amount of neurotoxin-induced SOD1 activity was generated by NMDA. Moreover, following exposure to hydrogen peroxide, the cytoskeletal organization was altered, as evidenced by modifications of beta-tubulin or MAP2 labelling. The fact that increased superoxide dismutase activity protected neurons suggests that appropriate control of SOD1 activity is required for neuronal survival under stressful conditions.
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Affiliation(s)
- Jacques Borg
- Faculté de Médecine, Laboratoire de Survie Cellulaire et Handicaps Neurologiques, Strasbourg, France.
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71
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Claycombe KJ, Wu D, Nikolova-Karakashian M, Palmer H, Beharka A, Paulson KE, Meydani SN. Ceramide mediates age-associated increase in macrophage cyclooxygenase-2 expression. J Biol Chem 2002; 277:30784-91. [PMID: 12072440 DOI: 10.1074/jbc.m204463200] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Previously, we showed that macrophages (MØ) from old mice have significantly higher levels of lipopolysaccharide (LPS)-induced prostaglandin E(2) (PGE(2)) production than young mice, due to increased cyclooxygenase-2 (COX-2) mRNA levels. The aim of the current study was to determine the underlying mechanisms of age-associated increase in COX-2 gene expression. The results demonstrate that increased COX-2 mRNA expression in the old mice is due to a higher rate of transcription rather than increased stability of COX-2 mRNA. Furthermore, the results show that LPS-induced ceramide levels from the old mice are significantly higher than those of young mice, whereas there is no age-related difference in concentration of its down stream metabolite, sphingosine. The addition of ceramide in the presence or absence of LPS resulted in a significant increase in PGE(2) production in a dose- and time-dependent manner. Inhibition of ceramide conversion to sphingosine had no effect on this ceramide-induced effect. The ceramide-induced up-regulation in PGE(2) production was mediated through increase in COX activity and transcriptional up-regulation of COX-2 mRNA. Collectively, these data suggest that the age-associated increase in MØ COX-2 mRNA is due to transcriptional up-regulation. Furthermore, this increase in transcription is mediated by higher cellular ceramide concentration in old MØ compared with that of young MØ.
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Affiliation(s)
- Kate J Claycombe
- Nutritional Immunology Laboratory, Jean Mayer United States Department of Agriculture/Human Nutrition Research Center at Tufts University, 711 Washington Street, Boston, MA 02111
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72
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Luberto C, Kraveka JM, Hannun YA. Ceramide regulation of apoptosis versus differentiation: a walk on a fine line. Lessons from neurobiology. Neurochem Res 2002; 27:609-17. [PMID: 12374196 DOI: 10.1023/a:1020267831851] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
One of the characteristics of ceramide-mediated biology is the variety of biological outcomes observed in response to its intracellular accumulation. The molecular mechanisms that govern the cell "decision-making" in response to ceramide remain largely unclear. In this perspective, the study of neural models has begun to provide important insight into the understanding of these mechanisms that regulate differentiation and cell death. Indeed, differentiation and cell death are among the most common effects elicited by ceramide in most cell types and in neural cells, too. Therefore, the lessons we may learn from the study of ceramide regulation of neurobiology would also shed light on the regulation of ceramide-mediated biology in other cellular models. Since increasing evidence links aberrant metabolism of ceramide to different pathologies, the understanding of the mechanisms underlying these events may represent the key to the design of novel therapeutic approaches.
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Affiliation(s)
- Chiara Luberto
- Department of Biochemistry, Medical University of South Carolina, Charleston 29425, USA
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73
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Toman RE, Movsesyan V, Murthy SK, Milstien S, Spiegel S, Faden AI. Ceramide-induced cell death in primary neuronal cultures: upregulation of ceramide levels during neuronal apoptosis. J Neurosci Res 2002; 68:323-30. [PMID: 12111862 DOI: 10.1002/jnr.10190] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Ceramide is a sphingolipid that has been implicated both in apoptosis and protection from cell death. We show that in both rat cerebellar granule cells and cortical neuronal cultures application of C(2)-ceramide causes cell death in a dose- and time-dependent manner. Similar effects were observed with the exogenous application of bacterial sphingomyelinase, which hydrolyzes sphingomyelin located on the outer leaflet of the plasma membrane and leads to endogenous ceramide accumulation. Furthermore, endogenous ceramide levels were increased during apoptosis induced by nutrient deprivation or etoposide treatment. These findings suggest that upregulation of ceramide levels, which may be generated through activation of sphingomyelinase, contributes to neuronal apoptosis.
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Affiliation(s)
- Rachelle E Toman
- Interdisciplinary Program in Neuroscience, Georgetown University Medical Center, Washington, DC, USA
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74
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Armstrong JS, Steinauer KK, Hornung B, Irish JM, Lecane P, Birrell GW, Peehl DM, Knox SJ. Role of glutathione depletion and reactive oxygen species generation in apoptotic signaling in a human B lymphoma cell line. Cell Death Differ 2002; 9:252-63. [PMID: 11859408 DOI: 10.1038/sj.cdd.4400959] [Citation(s) in RCA: 343] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2001] [Revised: 08/24/2001] [Accepted: 09/09/2001] [Indexed: 12/13/2022] Open
Abstract
The primary objective of this study was to determine the sequence of biochemical signaling events that occur after modulation of the cellular redox state in the B cell lymphoma line, PW, with emphasis on the role of mitochondrial signaling. L-Buthionine sulphoximine (BSO), which inhibits gamma glutamyl cysteine synthetase (gammaGCS), was used to modulate the cellular redox status. The sequence and role of mitochondrial events and downstream apoptotic signals and mediators was studied. After BSO treatment, there was an early decline in cellular glutathione (GSH), followed by an increase in reactive oxygen species (ROS) production, which induced a variety of apoptotic signals (detectable at different time points) in the absence of any external apoptotic stimuli. The sequence of biochemical events accompanying apoptosis included a 95% decrease in total GSH and a partial (25%) preservation of mitochondrial GSH, without a significant increase in ROS production at 24h. Early activation and nuclear translocation of the nuclear factor kappa B subunit Rel A was observed at approximately 3h after BSO treatment. Cytochrome c release into the cytosol was also seen after 24h of BSO treatment. p53 protein expression was unchanged after redox modulation for up to 72 h, and p21waf1 independent loss of cellular proliferation was observed. Surprisingly, a truncated form of p53 was expressed in a time-dependent manner, beginning at 24h after BSO incubation. Irreversible commitment to apoptosis occurred between 48 and 72 h after BSO treatment when mitochondrial GSH was depleted, and there was an increase in ROS production. Procaspase 3 protein levels showed a time-dependent reduction following incubation with BSO, notably after 48 h, that corresponded with increasing ROS levels. At 96 h, caspase 3 cleavage products were detectable. The pan-caspase inhibitor zVADfmk, partially blocked the induction of apoptosis at 48 h, and was ineffective after 72 h. PW cells could be rescued from apoptosis by removing them from BSO after up to 48, but not 72 h incubation with BSO. Mitochondrial transmembrane potential (DeltaPsi(m)) remained intact in most of the cells during the 72 h observation period, indicating that DeltaPsi(m) dissipation is not an early signal for the induction of redox dependent apoptosis in PW cells. These data suggest that a decrease in GSH alone can act as a potent early activator of apoptotic signaling. Increased ROS production following mitochondrial GSH depletion, represents a crucial event, which irreversibly commits PW cells to apoptosis.
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Affiliation(s)
- J S Armstrong
- Department of Radiation Oncology, Stanford University, Stanford, California, CA 94305-5105, USA
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75
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Sawada M, Nakashima S, Kiyono T, Yamada J, Hara S, Nakagawa M, Shinoda J, Sakai N. Acid sphingomyelinase activation requires caspase-8 but not p53 nor reactive oxygen species during Fas-induced apoptosis in human glioma cells. Exp Cell Res 2002; 273:157-68. [PMID: 11822871 DOI: 10.1006/excr.2001.5437] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
During apoptosis of human glioma cells induced by anti-Fas antibody, ceramide formation with activation of acid, but not neutral sphingomyelinase (SMase), was observed. A potent inhibitor of acid SMase, SR33557, effectively inhibited ceramide formation and apoptosis. Fas-induced apoptosis and ceramide formation proceeded regardless of p53 status. The agents, which modify intracellular levels of reactive oxygen species (ROS) and reduced glutathione (GSH), failed to modulate Fas-induced acid SMase activation and apoptosis. Moreover, expression of functional p53 protein using a temperature-sensitive human p53val(138) induced ceramide generation by activation of neutral SMase but not acid SMase through ROS formation. Peptide inhibitors for caspases-8 (z-IETD-fmk) and -3 (z-DEVD-fmk) suppressed Fas-induced apoptosis. However, activation of acid SMase was inhibited only by z-IETD-fmk. Thus, ceramide generated by acid SMase may take a part in Fas-induced apoptosis of human glioma cells and acid SMase activation may be dependent on caspase-8 activation, but not on p53 nor ROS.
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Affiliation(s)
- Motoshi Sawada
- Department of Neurosurgery, Gifu University School of Medicine, Tsukasamachi-40, Gifu 500-8705, Japan.
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76
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Bielak-Zmijewska A, Koronkiewicz M, Skierski J, Piwocka K, Radziszewska E, Sikora E. Effect of curcumin on the apoptosis of rodent and human nonproliferating and proliferating lymphoid cells. Nutr Cancer 2002; 38:131-8. [PMID: 11341039 DOI: 10.1207/s15327914nc381_18] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Curcumin, a major active component of turmeric, has been recognized as an anticarcinogenic agent because of its propensity to induce apoptosis in vivo and in vitro. Previously, we showed that curcumin protects cells against oligonucleosomal DNA fragmentation and induces a novel apoptosis-like pathway in Jurkat cells (Piwocka et al. Exp Cell Res 249, 299-307, 1999). Here, we have studied the ability of curcumin to induce cell death in other human and rodent transformed as well as normal cells. Normal cells were quiescent or stimulated to proliferate. We showed that 50 microM pigment is able to induce cell death in all studied cells, but cell death symptoms varied for different cells. All the cells died as assessed by the TdT-mediated UTP nick end labeling method or trypan blue exclusion test. No one type of cells showed oligonucleosomal DNA fragmentation (DNA "ladder") due to curcumin action, although in HL-60 cells, we were able to observe sub-G1 formation and caspase-3 activation. Together, these data showed that curcumin induces cell death in all tested cells that can be classified as apoptosis-like, and only in HL-60 cells can it be recognized as classical apoptosis.
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Affiliation(s)
- A Bielak-Zmijewska
- Molecular Bases of Aging Laboratory, Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland
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77
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Lavrentiadou SN, Chan C, Kawcak T, Ravid T, Tsaba A, van der Vliet A, Rasooly R, Goldkorn T. Ceramide-mediated apoptosis in lung epithelial cells is regulated by glutathione. Am J Respir Cell Mol Biol 2001; 25:676-84. [PMID: 11726392 PMCID: PMC4370277 DOI: 10.1165/ajrcmb.25.6.4321] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Reactive oxygen species (ROS) are mediators of lung injury, and glutathione (GSH) is the major nonprotein antioxidant that protects the cell from oxidative stress. We have recently shown that H(2)O(2) induces ceramide-mediated apoptosis in human lung epithelial cells. We hypothesized that ROS-mediated depletion of GSH plays a regulatory role in ceramide generation, and thus in the induction of apoptosis. Our present studies demonstrate that GSH at physiologic concentrations (1 to 10 mM) inhibits ceramide production in a time- and dose-dependent manner in A549 human alveolar epithelial cells. On the other hand, buthionine-sulfoximine-mediated depletion of intracellular GSH induces elevation of ceramide levels and apoptosis. In addition, GSH blocks H(2)O(2)-mediated induction of intracellular ceramide generation and apoptosis. These effects were not mimicked by oxidized GSH (GSSG) or other thiol antioxidants, such as dithiothreitol and 2-mercaptoethanol. Moreover, increase of intracellular H(2)O(2), mediated by inhibition of catalase by aminotriazole, also induces ceramide generation and apoptosis. These effects were blocked by N-acetylcysteine. Our results suggest that GSH depletion may be the link between oxidative stress and ceramide-mediated apoptosis in the lung.
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Affiliation(s)
- S N Lavrentiadou
- Center for Comparative Respiratory Biology and Medicine, Department of Internal Medicine, University of California, Davis, California 95616, USA
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78
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Hayter HL, Pettus BJ, Ito F, Obeid LM, Hannun YA. TNFalpha-induced glutathione depletion lies downstream of cPLA(2) in L929 cells. FEBS Lett 2001; 507:151-6. [PMID: 11684089 DOI: 10.1016/s0014-5793(01)02967-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Both glutathione (GSH) depletion and arachidonic acid (AA) generation have been shown to regulate sphingomyelin (SM) hydrolysis and are known components in tumor necrosis factor alpha (TNFalpha)-induced cell death. In addition, both have hypothesized direct roles in activation of N-sphingomyelinase (SMase); however, it is not known whether these are independent pathways of N-SMase regulation or linked components of a single ordered pathway. This study was aimed at differentiating these possibilities using L929 cells. Depletion of GSH with L-buthionin-(S,R)-sulfoximine (BSO) induced 50% hydrolysis of SM at 12 h. In addition, TNF induced a depletion of GSH, and exogenous addition of GSH blocked TNF-induced SM hydrolysis as well as TNF-induced cell death. Together, these results establish GSH upstream of SM hydrolysis and ceramide generation in L929 cells. We next analyzed the L929 variant, C12, which lacks both cytosolic phospholipase A(2) (cPLA(2)) mRNA and protein, in order to determine the relationship of cPLA(2) and GSH. TNF did not induce a significant drop in GSH levels in the C12 line. On the other hand, AA alone was capable of inducing a 60% depletion of GSH in C12 cells, suggesting that these cells remain responsive to AA distal to the site of cPLA(2). Furthermore, depleting GSH with BSO failed to effect AA release, but caused a drop in SM levels, showing that the defect in these cells was upstream of the GSH drop and SMase activation. When cPLA(2) was restored to the C12 line by expression of the cDNA, the resulting CPL4 cells regained sensitivity to TNF. Treatment of the CPL4 cells with TNF resulted in GSH levels dropping to levels near those of the wild-type L929 cells. These results demonstrate that GSH depletion following TNF treatment in L929 cells is dependent on intact cPLA(2) activity, and suggest a pathway in which activation of cPLA(2) is required for the oxidation and reduction of GSH levels followed by activation of SMases.
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Affiliation(s)
- H L Hayter
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA
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79
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Osawa Y, Banno Y, Nagaki M, Nozawa Y, Moriwaki H, Nakashima S. Caspase activation during hepatocyte apoptosis induced by tumor necrosis factor-alpha in galactosamine-sensitized mice. LIVER 2001; 21:309-19. [PMID: 11589767 DOI: 10.1034/j.1600-0676.2001.210503.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
BACKGROUND/AIMS To clarify the mechanism of hepatocyte apoptosis induced by tumor necrosis factor-alpha (TNF-alpha), caspase cascade and ceramide formation were investigated in the liver of D-galactosamine (GalN)-sensitized mice treated with TNF-alpha. METHODS Seven-week-old male BALB/c mice were intraperitoneally injected with 20 mg GalN 30 min prior to the intravenous injection of recombinant mouse TNF-alpha (0.5 microg/mouse). Cytochrome c release and processing of procaspases in the liver were analyzed by Western blotting. Activities of caspases were measured using chromogenic peptides as substrates. Ceramide content was determined using Escherichia coli diacylglycerol kinase. RESULTS Apoptosis of hepatocytes was observed in mice treated with both GalN and TNF-alpha (GalN/TNF-alpha), but not GalN or TNF-alpha alone. Activation of caspases-9 and -3, and cytochrome c release were observed only in liver from mice treated with GalN/TNF-alpha. In a cell-free system, processing of procaspases-9 and -3, and cytochrome c release were observed in the postnuclear fraction of liver obtained from GalN/TNF-alpha-treated mice, but not in that from control mice. Processing of procaspase-3 was inhibited by a caspase-9 inhibitor, but not by inhibitor for caspase-8 or -2. In a reconstitution assay system, procaspase-9 processing occurred, when both cytosol and membrane fractions were obtained from the liver of mice treated with GalN/TNF-alpha. Ceramide accumulation was observed only in apoptotic liver and preceded cytochrome c release and caspase activation. CONCLUSION Cytochrome c release and caspase-9 activation are required for the activation of executor caspase-3 in TNF-alpha-induced hepatocyte apoptosis, but caspases-8 and -2 play, if any, a minimal role. Ceramide may be implicated in this apoptotic process.
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Affiliation(s)
- Y Osawa
- First Department of Internal Medicine, Gifu University School of Medicine, Gifu, Japan
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80
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Andrieu-Abadie N, Gouazé V, Salvayre R, Levade T. Ceramide in apoptosis signaling: relationship with oxidative stress. Free Radic Biol Med 2001; 31:717-28. [PMID: 11557309 DOI: 10.1016/s0891-5849(01)00655-4] [Citation(s) in RCA: 206] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Ceramide is one of the major sphingosine-based lipid second messengers that is generated in response to various extracellular agents. However, while widespread attention has focused on ceramide as a second messenger involved in the induction of apoptosis, important issues with regard to the mechanisms of ceramide formation and mode of action remain to be addressed. Several lines of evidence suggest that ceramide and oxidative stress are intimately related in cell death induction. This review focuses on the putative relationships between oxidative stress and sphingolipid metabolism in the apoptotic process and discusses the potential mechanisms that connect and regulate the two phenomena.
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Affiliation(s)
- N Andrieu-Abadie
- INSERM Unit 466, Laboratoire de Biochimie Médicale, Centre Hospitalier Universitaire de Rangueil, Toulouse, France.
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81
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Piwocka K, Jaruga E, Skierski J, Gradzka I, Sikora E. Effect of glutathione depletion on caspase-3 independent apoptosis pathway induced by curcumin in Jurkat cells. Free Radic Biol Med 2001; 31:670-8. [PMID: 11522452 DOI: 10.1016/s0891-5849(01)00629-3] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Curcumin, a yellow pigment from Curcuma longa, exhibits anti-inflammatory, antitumor, and antioxidative properties. Although its precise mode of action has not been elucidated so far, numerous studies have shown that curcumin may induce apoptosis in normal and cancer cells. Previously, we showed that in Jurkat cells curcumin induced nontypical apoptosis-like pathway, which was independent of mitochondria and caspase-3. Now we show that the inhibition of caspase-3 by curcumin, which is accompanied by attenuation of internucleosomal DNA fragmentation, may be due to elevation of glutathione, which increased in curcumin-treated cells to 130% of control. We have demonstrated that glutathione depletion does not itself induce apoptosis in Jurkat cells; though, it can release cytochrome c from mitochondria and caspase-3 from inhibition by curcumin, as shown by Western blot. The level of Bcl-2 protein was not affected by glutathione depletion even upon curcumin treatment. Altogether, our results show that in Jurkat cells curcumin prevents glutathione decrease, thus protecting cells against caspase-3 activation and oligonucleosomal DNA fragmentation. On the other hand, it induces nonclassical apoptosis via a still-unrecognized mechanism, which leads to chromatin degradation and high-molecular-weight DNA fragmentation.
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Affiliation(s)
- K Piwocka
- Laboratory of Molecular Bases of Aging, Nencki Institute of Experimental Biology, Warsaw, Poland
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82
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Abstract
The sphingolipid ceramide is an important second signal molecule that regulates diverse signaling pathways involving apoptosis, cell senescence, the cell cycle, and differentiation. For the most part, ceramide's effects are antagonistic to growth and survival. Interestingly, ceramide and the pro-growth agonist, diacylglycerol (DAG) appear to be regulated simultaneously but in opposite directions in the sphingomyelin cycle. While ceramide stimulates signal transduction pathways that are associated with cell death or at least are inhibitory to cell growth (eg stress-activated protein kinase, SAPK, pathways), DAG activates the classical and novel isoforms of the protein kinase C (PKC) family. These PKC isoforms are associated with cell growth and cell survival. Furthermore, DAG activation of PKC stimulates other signal transduction pathways that support cell proliferation (eg mitogen-activated protein kinase, MAPK, pathways). Thus, ceramide and DAG generation may serve to monitor cellular homeostasis by inducing pro-death or pro-growth pathways, respectively. The production of ceramide is emerging as a fixture of programmed cell death. Ceramide levels are elevated in response to diverse stress challenges including chemotherapeutic drug treatment, irradiation, or treatment with pro-death ligands such as tumor necrosis factor alpha, TNF alpha. Consistent with this notion, ceramide itself is a potent apoptogenic agent. Ceramide activates stress-activated protein kinases like c-jun N-terminal kinase (JNK) and thus affects transcription pathways involving c-jun. Ceramide activates protein phosphatases such as protein phosphatase 1 (PP1) and protein phosphatase 2 (PP2A). Ceramide activation of protein phosphatases has been shown to promote inactivation of a number of pro-growth cellular regulators including the kinases PKC alpha and Akt, Bcl2 and the retinoblastoma protein. A new role has recently emerged for ceramide in the regulation of protein synthesis. Ceramide-induced activation of double-stranded RNA-dependent protein kinase (PKR), a protein kinase important in anti-viral host defense mechanisms and recently implicated in cellular stress pathways, results in the inhibition of protein synthesis as a prelude to cell death. Taken together, these properties of ceramide suggest that this important second-signal molecule may have useful properties as an anti-neoplastic agent. Thus, strategies to promote ceramide metabolism or use of ceramide analogs directly may one day become useful in the treatment of diseases like leukemia.
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Affiliation(s)
- P P Ruvolo
- University of Florida Shands Cancer Center and The Department of Medicine, Gainesville 32610-0232, USA
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83
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Yamakawa H, Banno Y, Nakashima S, Yoshimura S, Sawada M, Nishimura Y, Nozawa Y, Sakai N. Crucial role of calpain in hypoxic PC12 cell death: calpain, but not caspases, mediates degradation of cytoskeletal proteins and protein kinase C-alpha and -delta. Neurol Res 2001; 23:522-30. [PMID: 11474809 DOI: 10.1179/016164101101198776] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Ca2+ influx is one of the main causative events in hypoxic PC12 cell death, because an extracellular Ca2+ chelator, ethylene glycol bis (2-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) inhibited and Ca2+ ionophore A23187 mimicked the hypoxic cell death. The hypoxic cell death was markedly prevented by a broad spectrum caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (z-VAD-FMK) as well as a calpain inhibitor, calpeptin, as assessed by nuclear staining with Hoechst 33258 and lactate dehydrogenase release. The processing of procaspase-3 was inhibited by z-VAD-FMK, but not by calpeptin. In contrast, z-VAD-FMK failed to block the proteolytic cleavage of fodrin-alpha, a preferential substrate for calpain. On the other hand, degradation of actin and fodrin-alpha was prevented by calpeptin but not by z-VAD-FMK. In addition, not only protein kinase C (PKC)-alpha but also PKC-delta were cleaved to generate approximately 46 kDa fragments. The PKC fragmentation was inhibited by calpeptin but not by z-VAD-FMK. These findings suggest that the extracellular Ca2+ influx induced by hypoxic stress activates calpain, resulting in the degradation of cytoskeletal proteins and generation of PKC fragments almost independently of caspase activation. Therefore, calpain may play an important role in hypoxic PC12 cell death.
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Affiliation(s)
- H Yamakawa
- Department of Neurosurgery, Gifu University School of Medicine, Tsukasamachi-40, Gifu 500-8705, Japan.
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84
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Sawada M, Nakashima S, Kiyono T, Nakagawa M, Yamada J, Yamakawa H, Banno Y, Shinoda J, Nishimura Y, Nozawa Y, Sakai N. p53 regulates ceramide formation by neutral sphingomyelinase through reactive oxygen species in human glioma cells. Oncogene 2001; 20:1368-78. [PMID: 11313880 DOI: 10.1038/sj.onc.1204207] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2000] [Revised: 12/28/2000] [Accepted: 01/03/2001] [Indexed: 11/09/2022]
Abstract
The present study was designed to elucidate the relationship between p53 and ceramide, both of which are involved in apoptotic signaling. Treatment of human glioma cells with etoposide caused apoptosis only in cells expressing functional p53. p53 activation was followed by the formation of reactive oxygen species (ROS), superoxide anion (O2-*) measured by hydroethidium oxidation into ethidium and hydrogen peroxide (H2O2) measured by oxidation of 2',7'-dichlorofluorescin (DCFH) into 2',7'-dichlorofluorescein (DCF), which was accompanied with ceramide generation through the activation of neutral, but not acid, sphingomyelinase. Superoxide dismutase (SOD), a selective antioxidant for O2-*, had no effects on p53 expression but inhibited ceramide generation and apoptotic cell death caused by etoposide. However, catalase, a specific antioxidant for H2O2, only weakly inhibited and sodium formate, a hydroxyl radical (* OH) scavenger, unaffected etoposide-induced apoptosis. Like etoposide-induced cell death, treatment of glioma cells with the O2-*-releasing agent, pyrogallol, induced typical apoptosis and ceramide generation even in the presence of catalase. In contrast, human glioma cells lacking functional p53, either due to mutation or the expression of E6 protein of human papillomavirus, were highly resistant to etoposide and exhibited no significant change in the ceramide level. Moreover, expression of functional p53 protein in glioma cells expressing mutant p53 using a temperature-sensitive human p53(Val138) induced ceramide accumulation by the activation of neutral sphingomyelinase which was dependent on the generation of O2-*. Taken together, these results suggest that p53 may modulate ceramide generation by activation of neutral sphingomyelinase through the formation of O2-*, but not its downstream compounds H2O2 or * OH.
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Affiliation(s)
- M Sawada
- Department of Neurosurgery, Gifu University School of Medicine, Tsukasamachi-40, Gifu 500-8705, Japan
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85
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Denisova NA, Cantuti-Castelvetri I, Hassan WN, Paulson KE, Joseph JA. Role of membrane lipids in regulation of vulnerability to oxidative stress in PC12 cells: implication for aging. Free Radic Biol Med 2001; 30:671-8. [PMID: 11295365 DOI: 10.1016/s0891-5849(00)00513-x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Previously, we reported that PC12 cells showed increased vulnerability to oxidative stress (OS) induced by H2O2 (as assessed by decrements in calcium recovery, i.e., the ability of cells to buffer Ca(2+) after a depolarization event) when the membrane levels of cholesterol (CHL) and sphingomyelin (SPH) were modified to approximate those seen in the neuronal membranes of old animals. The present study was designed to examine whether the enrichment of the membranes with SPH-CHL and increased cellular vulnerability to OS are mediated by neutral SPH-specific phospholipase C (N-Sase) and the intracellular antioxidant GSH. The results showed a significant up-regulation of N-Sase activity by both low (5 microM) and high (300 microM) doses of H2O2. However, under high doses of H2O2 the up-regulation of N-Sase is accompanied by a significant increase in reactive oxygen species and by a decrease in intracellular GSH. The enrichment of membranes with SPH-CHL significantly potentiated the effects of high doses of H2O2, by further reducing the intracellular GSH and further up-regulating the N-Sase activity. Furthermore, repleting intracellular GSH with 20 mM N-acetylcysteine treatment was sufficient to attenuate the effect of a low dose of H2O2 on Ca(2+) recovery in SPH-CHL-treated cells. Thus, these results suggested that age-related alterations in the membrane SPH-CHL levels could be important determinants of the susceptibility of neuronal cells to OS.
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Affiliation(s)
- N A Denisova
- United States Department of Agriculture, Jean Mayer Human Nutrition Research Center on Aging at Tufts University, Boston, MA 02111, USA.
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86
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Noda S, Yoshimura S, Sawada M, Naganawa T, Iwama T, Nakashima S, Sakai N. Role of ceramide during cisplatin-induced apoptosis in C6 glioma cells. J Neurooncol 2001; 52:11-21. [PMID: 11451199 DOI: 10.1023/a:1010624823158] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cisplatin is commonly used for the treatment of malignant brain tumors. However, the mechanisms of cell death by cisplatin are not fully understood. Therefore, the present study was designed to elucidate the apoptotic signaling pathway(s) activated by cisplatin in a C6 rat glioma cell line. C6 cells were treated with various concentrations of cisplatin (0.2-10 microg/ml) for 24-72 h. At 10 microg/ml cisplatin, over 90% of the cells became dead at 72 h. Apoptotic death was confirmed by condensation and fragmentation of nuclei, and DNA laddering. Even in cells treated with 1.5 microg/ml cisplatin, typical apoptotic cells were observed at 72 h. The intracellular level of ceramide, measured Escherichia coli diacylglycerol kinase markedly increased during 24-72 h after the addition of 10 microg/ml cisplatin. The activity of caspase-3(-like) proteases increased and reached a peak at 48 h. Inhibitors of caspases reduced the number of apoptotic cells. Pretreatment of C6 cells with glutathione or N-acetyl-cysteine, which are known to block the activation of neutral magnesium-dependent sphingomyelinase, inhibited ceramide formation, leading to suppression of both activation of caspase-3(-like) proteases and apoptosis by cisplatin. In contrast, pretreatment of the cells with N-oleoylethanolamine (OE), a ceramidase inhibitor, potentiated apoptosis induced by cisplatin. Furthermore, OE enhanced sensitivity of the cisplatin-resistant cells to cisplatin. These results suggest that ceramide is closely implicated in apoptosis of glioma cells by cisplatin through activation of caspase-3(-like) proteases.
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Affiliation(s)
- S Noda
- Department of Neurosurgery, Gifu University School of Medicine, Japan.
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87
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Yu ZF, Nikolova-Karakashian M, Zhou D, Cheng G, Schuchman EH, Mattson MP. Pivotal role for acidic sphingomyelinase in cerebral ischemia-induced ceramide and cytokine production, and neuronal apoptosis. J Mol Neurosci 2000; 15:85-97. [PMID: 11220788 DOI: 10.1385/jmn:15:2:85] [Citation(s) in RCA: 147] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2000] [Accepted: 06/21/2000] [Indexed: 11/11/2022]
Abstract
Stroke is a major cause of long-term disability, the severity of which is directly related to the numbers of neurons that succumb to the ischemic insult. The signaling cascades activated by cerebral ischemia that may either promote or protect against neuronal death are not well understood. One injury-responsive signaling pathway that has recently been characterized in studies of non-neural cells involves cleavage of membrane sphingomyelin by acidic and/or neutral sphingomyelinase (ASMase) resulting in generation of the second messenger ceramide. We now report that transient focal cerebral ischemia induces large increases in ASMase activity, ceramide levels, and production of inflammatory cytokines in wild-type mice, but not in mice lacking ASMase. The extent of brain tissue damage is decreased and behavioral outcome improved in mice lacking ASMase. Neurons lacking ASMase exhibit decreased vulnerability to excitotoxicity and hypoxia, which is associated with decreased levels of intracellular calcium and oxyradicals. Treatment of mice with a drug that inhibits ASMase activity and ceramide production reduces ischemic neuronal injury and improves behavioral outcome, suggesting that drugs that inhibit this signaling pathway may prove beneficial in stroke patients.
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Affiliation(s)
- Z F Yu
- Sanders-Brown Research Center on Aging, University of Kentucky, Lexington 40536, USA
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88
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Carratù MR, Cagiano R, Tattoli M, Trabace L, Borracci P, Cuomo V. Prenatal exposure model simulating CO inhalation in human cigarette smokers: sphingomyelin alterations in the rat sciatic nerve. Toxicol Lett 2000; 117:101-6. [PMID: 11033239 DOI: 10.1016/s0378-4274(00)00248-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Prenatal exposure to low concentrations of carbon monoxide (CO, 150 ppm) causes long-term alterations in sphingomyelin (SM) homeostasis in peripheral nervous system, but not brain of male rat offspring. In particular, unlike sphinganine (intermediate of complex sphingolipid biosynthesis de novo), the concentrations of sphingosine (intermediate of complex sphingolipid turnover) were increased by 2.35-fold in the sciatic nerve of CO-exposed offspring with respect to controls (P<0.05, overall one-way ANOVA). These subtle alterations were not accompanied by changes in motor activity (F=0.25, df=1/10, n.s., overall one-way-ANOVA). The results suggest that the SM homeostasis in the sciatic nerve is particularly susceptible to prenatal CO exposure resulting in maternal carboxyhaemoglobin (HbCO) levels equivalent to those found in human cigarette smokers.
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Affiliation(s)
- M R Carratù
- Department of Pharmacology and Human Physiology, School of Medicine, University of Bari, Policinico-Piazza Giulio Cesare 11, 70124, Bari, Italy
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89
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Sawada M, Nakashima S, Banno Y, Yamakawa H, Hayashi K, Takenaka K, Nishimura Y, Sakai N, Nozawa Y. Ordering of ceramide formation, caspase activation, and Bax/Bcl-2 expression during etoposide-induced apoptosis in C6 glioma cells. Cell Death Differ 2000; 7:761-72. [PMID: 11042671 DOI: 10.1038/sj.cdd.4400711] [Citation(s) in RCA: 136] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Etoposide (VP-16) a topoisomerase II inhibitor induces apoptosis of tumor cells. The present study was designed to elucidate the mechanisms of etoposide-induced apoptosis in C6 glioma cells. Etoposide induced increased formation of ceramide from sphingomyelin and release of mitochondrial cytochrome c followed by activation of caspase-9 and caspase-3, but not caspase-1. In addition, exposure of cells to etoposide resulted in decreased expression of Bcl-2 with reciprocal increase in Bax protein. z-VAD.FMK, a broad spectrum caspase inhibitor, failed to suppress the etoposide-induced ceramide formation and change of the Bax/Bcl-2 ratio, although it did inhibit etoposide-induced death of C6 cells. Reduced glutathione or N-acetylcysteine, which could reduce ceramide formation by inhibiting sphingomyelinase activity, prevented C6 cells from etoposide-induced apoptosis through blockage of caspase-3 activation and change of the Bax/Bcl-2 ratio. In contrast, the increase in ceramide level by an inhibitor of ceramide glucosyltransferase-1, D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol caused elevation of the Bax/Bcl-2 ratio and potentiation of caspase-3 activation, thereby resulting in enhancement of etoposide-induced apoptosis. Furthermore, cell-permeable exogenous ceramides (C2- and C6-ceramide) induced downregulation of Bcl-2, leading to an increase in the Bax/Bcl-2 ratio and subsequent activation of caspases-9 and -3. Taken together, these results suggest that ceramide may function as a mediator of etoposide-induced apoptosis of C6 glioma cells, which induces increase in the Bax/Bcl-2 ratio followed by release of cytochrome c leading to caspases-9 and -3 activation.
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Affiliation(s)
- M Sawada
- Department of Neurosurgery, Gifu University School of Medicine, Tsukasamachi-40, Gifu 500-8705, Japan.
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90
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Abstract
A significant corpus of work over the last decade has firmly established an important role for sphingolipids in a variety of important biological processes. Such processes include signaling events related to cell growth, differentiation, programmed cell death, and stress responses. These processes not only involve those sphingolipids that accumulate as a result of a variety of inherited lysosomal storage disorders, but, in addition, sphingolipids associated with long-chain base metabolism. This article reviews the chemical properties, pathways, regulated metabolism, and signaling function of sphingolipids. In addition, the potential roles of sphingolipids in renal-specific processes are considered. While a variety of cellular functions have been ascribed to sphingolipids, in many cases proof of the concept has yet to be well established. Thus, a number of critical questions can be posed in interpreting these studies. Several of these questions are considered.
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Affiliation(s)
- J A Shayman
- Nephrology Division, Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor 48109-0676, USA.
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91
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Abstract
Ceramide is a lipid second messenger, that is generated in response to stimulation of the cell death pathways by a number of ligands binding to surface receptors, growth factor withdrawal, treatment with chemotherapeutic agents, or high doses of ionizing radiation or oxidizing agents. Depending on the target cell, ceramide induces diverse biological responses including apoptosis, cell-cycle arrest, differentiation, and also proliferation. In this review we consider the evidence for its role in apoptosis in cells of the nervous system.
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Affiliation(s)
- R Goswami
- Departments of Pediatrics, University of Chicago, Chicago, Illinois, USA
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