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Sphingomyelinase Activity (sphingomyelinase + activity)
Selected AbstractsIncreased Acid Sphingomyelinase Activity in Peripheral Blood Cells of Acutely Intoxicated Patients With Alcohol DependenceALCOHOLISM, Issue 1 2010Martin Reichel Background:, Acid sphingomyelinase (ASM; EC 3.1.4.12) hydrolyses membrane sphingomyelin into the bioactive lipid ceramide and is thus involved in different cellular processes such as differentiation, immunity, or cell death. Activation of ASM has been reported in particular in conjunction with the cellular stress response to several external stimuli, and increased ASM activity was observed in a variety of human diseases. Ethanol-induced activation of ASM has been observed in different cell culture systems, thus raising the question about the effect of alcohol intoxication in human subjects on ASM activity in vivo. Methods:, We determined ASM activity in peripheral blood mononucleated cells of 27 patients suffering from alcohol dependence. Patients were classified according to their blood alcohol concentration at admission, and ASM activity was determined repeatedly from all patients during alcohol withdrawal. Results:, Acutely intoxicated patients displayed significantly higher ASM activity than patients in early abstinence (Mann,Whitney U test: Z = , 2.6, p = 0.009). ASM activity declined in acutely intoxicated patients to normal values with the transition from the intoxicated state to early abstinence (Wilcoxon test: Z = ,2.7, p = 0.007). At the end of withdrawal, ASM activity was significantly increased again compared to the early phase of abstinence in both patient groups (Wilcoxon test: Z = ,2.691, p = 0.007 and Z = ,2.275, p = 0.023, respectively). Conclusions:, Alcohol-induced activation of ASM occurs in human subjects and might be responsible for deleterious effects of ethanol intoxication. Chronic alcohol abuse may induce deregulation of sphingomyelin metabolism in general, and this impairment may cause side effects during withdrawal from alcohol. [source] Identification of residues critical for toxicity in Clostridium perfringens phospholipase C, the key toxin in gas gangreneFEBS JOURNAL, Issue 16 2000Alberto Alape-Girón Clostridium perfringens phospholipase C (PLC), also called ,-toxin, is the major virulence factor in the pathogenesis of gas gangrene. The toxic activities of genetically engineered ,-toxin variants harboring single amino-acid substitutions in three loops of its C-terminal domain were studied. The substitutions were made in aspartic acid residues which bind calcium, and tyrosine residues of the putative membrane-interacting region. The variants D269N and D336N had less than 20% of the hemolytic activity and displayed a cytotoxic potency 103 -fold lower than that of the wild-type toxin. The variants in which Tyr275, Tyr307, and Tyr331 were substituted by Asn, Phe, or Leu had 11,73% of the hemolytic activity and exhibited a cytotoxic potency 102 - to 105 -fold lower than that of the wild-type toxin. The results demonstrated that the sphingomyelinase activity and the C-terminal domain are required for myotoxicity in vivo and that the variants D269N, D336N, Y275N, Y307F, and Y331L had less than 12% of the myotoxic activity displayed by the wild-type toxin. This work therefore identifies residues critical for the toxic activities of C. perfringens PLC and provides new insights toward understanding the mechanism of action of this toxin at a molecular level. [source] Different apoptosis ratios and gene expressions in two human cell lines after sevoflurane anaesthesiaACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 9 2009S. KVOLIK Background: The aim of this study was to determine the effect of a single exposure of carcinoma cells (Caco-2 and HEp-2) to an anaesthetic gas mixture containing sevoflurane 3%, applied for a period of either 1 or 2 h, on the induction of apoptosis, propapototic gene expression and sphingomyelinase activity. Methods: Apoptosis was determined by flow cytometry. p53, caspase 3 and CYP2E1 gene expression was determined using reverse transcriptase polymerase chain reaction. Activities of acid (aSMase) and neutral sphingomyelinases (nSMase) were measured using methyl- 14C sphingomyeline, and for de novo ceramide and lipid synthesis [3H] palmitic acid was used. All results were compared with controls and analysed by Mann,Whitney and Kruskal,Wallis tests. Results: In the treated Caco-2 cells, the apoptotic ratio increased 24 h after anaesthesia (16.9%; P=0.04). The expression of both p53 and caspase-3 genes increased in Caco-2 and decreased in HEp-2 cells. The CYP2E1 gene expression was observed only in the Caco-2 cells. In control cells, the catalytic activity of aSMase was 2.3 times higher than that of nSMase activity. Decreased aSMase and nSMase activities were observed in Caco-2 cells 24 h after exposition. aSMase activity was halved (54.2%; P=0.06) in HEp-2 cells 24 h after anaesthesia. De novo ceramide synthesis correlated with SMase activity in Caco-2 cells. Conclusion: Sevoflurane anaesthesia induces late apoptosis in the colonic and laryngeal cancer cells investigated. Although the results obtained may indicate that an anaesthetic gas mixture containing sevoflurane induces p53-dependent apoptosis in the Caco-2 cells, the mechanism of apoptosis induction is unclear and remains to be elucidated. [source] Apoptosis and Dysregulated Ceramide Metabolism in a Murine Model of Alcohol-Enhanced Lipopolysaccharide HepatotoxicityALCOHOLISM, Issue 10 2000Ion V. Deaciuc Background: The role of apoptosis in EtOH-induced liver injury has not been investigated much. Therefore, the question whether apoptosis is a contributory factor to alcoholic liver disease remains to be answered. The purpose of this study was to characterize the liver apoptotic response in a murine model of alcohol-enhanced lipopolysaccharide (LPS) hepatotoxicity. Methods: Mice were fed an alcohol-containing liquid diet for 49 days followed by an acute LPS challenge. The liver state was judged on the basis of histological appearance, plasma liver enzyme activity (alanine:2-oxoglutarate and aspartate:2-oxoglutarate aminotransferases, as markers of hepatocytolysis), and plasma hyaluronan levels (as a marker of the sinusoidal endothelial cell scavenging function). The liver apoptotic response was assessed by DNA fragmentation (TUNEL procedure), and caspases-3 and -8 activity. To determine if ceramide played a role in the liver apoptotic response, the activity of acidic sphingomyelinase and tissue content of ceramide were also quantified. Results: Alcohol exposure induced fat accumulation and sensitized the liver to LPS injurious effects. Plasma liver enzyme activity was elevated by alcohol and this effect was potentiated by LPS. Liver apoptosis was augmented by both alcohol and LPS treatment as reflected by high frequency of positive TUNEL staining nuclei and by an increased activity of caspase-3 and -8. Acidic sphingomyelinase activity was also increased and it was associated with an elevated tissue content of ceramide. In addition, LPS also increased plasma TNF- , levels. These changes were accompanied by elevated plasma hyaluronan, reflecting an impaired sinusoidal endothelial cell scavenging function. Conclusions: These results provide a more complete description of the liver apoptotic response to both alcohol and LPS and may constitute the basis for further mechanistic studies on a possible role apoptosis may play in alcoholic liver injury. [source] Aggregated low density lipoprotein induces tissue factor by inhibiting sphingomyelinase activity in human vascular smooth muscle cellsJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 12 2009S. CAMINO-LÓPEZ Summary.,Background: Our previous results demonstrated that aggregated low density lipoprotein (agLDL) induces tissue factor (TF) expression and activation through Rho A translocation in human vascular smooth muscle cells (VSMC). We also previously demonstrated that membrane sphingomyelin (SM) content is higher in agLDL-exposed VSMC than in control cells. The main enzymes regulating cellular SM content are the family of sphingomyelinases (Smases) that hydrolize SM to phosphorylcholine and ceramide (CER). Objectives: We wished to investigate whether agLDL has the ability to modulate acidic- (A-) and neutral (N-) Smase activity and whether or not this effect is related to the upregulatory effect of agLDL on Rho A translocation and TF activation in human VSMC. Methods and Results: By measuring generated [14C]-phosphorylcholine, we found that agLDL significantly decreased A-Smase and specially N-Smase activity. Pharmacological Smase inhibitors increased Rho A and TF. Specific loss-of-function of A-Smase or N-Smase 1 (N1-Smase) by siRNA treatment (500 nmol L,1, 12 hours) dramatically increased membrane Rho A protein levels (5- and 3-fold, respectively). Concomitantly, TF protein expression and TF procoagulant activity were also increased. Inhibition of A-Smase or N-Smase activity by agLDL, siRNA-anti A- or N1-Smase or pharmacological treatment significantly increased the SM content of vascular cells. The inhibition of SM synthesis by fumonisin B1 (FB1) prevented the upregulatory effect of agLDL on TF. Conclusions: These results demonstrate that inhibition of both A- and N1-Smase might explain the upregulatory effect of agLDL on TF activation, and suggest that this effect is related, at least in part, to membrane SM enrichment. [source] Ceramide inhibits development and cytokinesis and induces apoptosis in preimplantation bovine embryosMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 6 2008de Castro e Paula Luiz Augusto Abstract Ceramide is a second messenger induced by various cellular insults that plays a regulatory role in apoptosis. The objective of the present study was to determine whether ceramide signaling can occur in the preimplantation embryo by testing (1) effects of ceramide on development, cytokinesis, and apoptosis and (2) whether heat shock, which can induce apoptosis in embryos, causes activation of neutral or acidic sphingomyelinases responsible for generation of ceramide. Treatment of embryos ,16 cells collected at Day 5 after insemination with 50 µM C(2)-ceramide increased caspase-9 activity and the proportion of blastomeres undergoing apoptosis but did not increase caspase-8 activity. Induction of apoptosis was more extensive when culture with ceramide was for 24 hr than for 9 hr. Ceramide also reduced the proportion of embryos that developed to the blastocyst stage when exposure was for 24 hr. At the two-cell stage, a period in development when apoptosis responses are blocked, culture of embryos with ceramide did not increase caspase-9 activity or the proportion of blastomeres that were apoptotic. However, culture with ceramide for 24 hr reduced cell proliferation and caused an increase in multinucleated cells because of inhibition of cytokinesis. Exposure of Day 5 embryos to a heat shock of 41°C for 15 hr increased neutral sphingomyelinase activity but did not change acid sphingomyelinase activity. In conclusion, ceramide can regulate embryo development and apoptosis in a time and stage-of-development dependent manner and ceramide generation can be activated by cellular insult. Thus, the ceramide signaling pathway is present in the preimplantation embryo. Mol. Reprod. Dev. 75: 1063,1070, 2007. © 2007 Wiley-Liss, Inc. [source] | ||||||||||