title: Differential effect of IL-18 on endothelial cell apoptosis mediated by TNF-alpha and Fas (CD95).
abstract: Interleukin-18 (IL-18) is a newly identified cytokine with proinflammatory activity. Numerous studies have shown that proinflammatory cytokines may regulate endothelial cells (EC) apoptosis mediated by members of the tumor necrosis factor (TNF) family, such as TNF-alpha and Fas. In this study we hypothesized that IL-18 may regulate the susceptibility of liver endothelial cells (LEC) to apoptosis induced by TNF and Fas. IL-18 increased the susceptibility of LEC to undergo apoptosis mediated by TNF but not by Fas. Since TNF-induced apoptosis is mediated by the type I TNF receptor (TNFRI), we investigated up-regulation of this receptor in IL-18-treated LEC. IL-18 induced up-regulation of the TNFRI on the surface of LEC. Partial blocking of LEC apoptosis induced by IL-18 and TNF was observed when the cells were pretreated with the broad-spectrum inhibitor of caspases z-VAD-fmk, suggesting involvement of the caspase pathway in apoptosis induced by these cytokines in these cells. Our results show that IL-18 differentially regulates apoptosis mediated by the death-inducing factors, TNF and Fas. To our knowledge, this is the first report that IL-18 may regulate endothelial cell apoptosis mediated by TNF. These results may have clinical implications in those clinical hepatic conditions associated with high levels of IL-18 and TNF.
authors.affiliation: Laboratorio de Patología Celular y Molecular, Centro de Medicina Experimental, Instituto Venezolano de Investigaciones Científicas (IVIC), Apartado 21827, Caracas 1020-A, Venezuela.
authors.forename: Eliana
authors.initials: E
authors.lastname: Mariño
authors.forename: José E
authors.initials: JE
authors.lastname: Cardier
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects*; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D006224:Cricetinae; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects*; D005434:Flow Cytometry; D005453:Fluorescence; D015870:Gene Expression; D020382:Interleukin-18 / Q000494:pharmacology*; D051379:Mice; D018124:Receptors, Tumor Necrosis Factor / Q000235:genetics / Q000378:metabolism; D047888:Receptors, Tumor Necrosis Factor, Type I; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism*; D019014:fas Receptor / Q000235:genetics / Q000378:metabolism*
chemical_list: D015703:Antigens, CD; D061945:Caspase Inhibitors; D020382:Interleukin-18; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D019014:fas Receptor; D020169:Caspases