title: Interleukin-1beta induces chronic activation and de novo synthesis of neutral ceramidase in renal mesangial cells.
abstract: The lipid signaling molecule ceramide is formed by the action of acid and neutral sphingomyelinases and degraded by acid and neutral ceramidases. Short-term stimulation of mesangial cells with the pro-inflammatory cytokine interleukin-1beta (IL-1beta) leads to a rapid and transient increase in neutral sphingomyelinase activity (Kaszkin, M., Huwiler, A., Scholz, K., van den Bosch, H., and Pfeilschifter, J. (1998) FEBS Lett. 440, 163-166). In this study, we report on a second delayed peak of activation occurring after hours of IL-1beta treatment. This second phase of activation was first detectable after 2 h of treatment and steadily increased over the next 2 h, reaching maximal values after 4 h. In parallel, a pronounced increase in neutral ceramidase activity was observed, accounting for a constant or even decreased level of ceramide after long-term IL-1beta treatment, despite continuous sphingomyelinase activation. The increase in neutral ceramidase activity was due to expressional up-regulation, as detected by an increase in mRNA levels and enhanced de novo protein synthesis. The increase in neutral ceramidase protein levels and activity could be blocked dose- dependently by the p38 MAPK inhibitor SB 202190, whereas the classical MAPK pathway inhibitor U0126 and the protein kinase C inhibitor Ro 318220 were ineffective. Moreover, cotreatment of cells for 24 h with IL-1beta and SB 202190 led to an increase in ceramide formation. Interestingly, IL-1beta-stimulated neutral ceramidase activation was not reduced in mesangial cells isolated from mice deficient in MAPK-activated protein kinase-2, which is a downstream substrate of p38 MAPK, thus suggesting that the p38 MAPK-mediated induction of neutral ceramidase occurs independently of the MAPK-activated protein kinase-2 pathway. In summary, our results suggest a biphasic regulation of sphingomyelin hydrolysis in cytokine-treated mesangial cells with delayed de novo synthesis of neutral ceramidase counteracting sphingomyelinase activity and apoptosis. Neutral ceramidase may thus represent a novel cytoprotective enzyme for mesangial cells exposed to inflammatory stress conditions.
authors.affiliation: Pharmazentrum Frankfurt, Klinikum der J. W. Goethe-Universität, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Franzen
authors.forename: A
authors.initials: A
authors.lastname: Pautz
authors.forename: L
authors.initials: L
authors.lastname: Bräutigam
authors.forename: G
authors.initials: G
authors.lastname: Geisslinger
authors.forename: J
authors.initials: J
authors.lastname: Pfeilschifter
authors.forename: A
authors.initials: A
authors.lastname: Huwiler
mesh_terms: D000581:Amidohydrolases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D055572:Ceramidases; D017931:DNA Primers; D004789:Enzyme Activation; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D007375:Interleukin-1 / Q000494:pharmacology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D055576:Neutral Ceramidase; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D013108:Sphingomyelin Phosphodiesterase / Q000235:genetics; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D017931:DNA Primers; D007375:Interleukin-1; D012333:RNA, Messenger; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D013108:Sphingomyelin Phosphodiesterase; D000581:Amidohydrolases; C526747:Asah2 protein, mouse; C526748:Asah2 protein, rat; D055572:Ceramidases; D055576:Neutral Ceramidase