Redox regulation of ERK1/2 activation induced by sphingosine 1-phosphate in fibroblasts: involvement of NADPH oxidase and platelet-derived growth factor receptor.

BACKGROUND: Sphingosine 1-phosphate (S1P) is a sphingolipid metabolite synthesized after stimulation with growth factors or cytokines. S1P extracellular effects are mediated through specific Gi-protein coupled receptors (GPCRs). Recently, we demonstrated in NIH3T3 fibroblasts stimulated by platelet-derived growth factor (PDGF) or S1P the NADPH oxidase activation and the H(2)O(2) intracellular level increase trough the Gi protein involvement. METHODS: NIH3T3 fibroblast cell cultures were used. Western blot and quantitative analyses by Chemidoc-Quantity-One software were performed. H2O2 level was assayed by fluorescence spectrophotometric analysis, and cell proliferation by counted manually or ELISA kit. RESULTS: This study demonstrates, in NIH 3T3 fibroblasts, a novel redox regulated mechanism of S1P-induced activation of ERK 1/2 related to NADPH oxidase activity and intracellular H2O2 level increase with PDGF receptor tyrosine kinase involvement through a transactivation mechanism. This event is mediated by S1P(1) and S1P(3) receptors by Gi proteins and can contribute to S1P mitogenic signaling. CONCLUSION: These results can be related to mechanisms of cross-talk previously identified between receptor tyrosine kinase, including PDGFreceptor, and several GPCR ligands. GENERAL SIGNIFICANCE: The redox-sensitive ERK1/2 and PDGFr tyrosine kinase activity could be targets for therapies in diseases in which deregulation of intracellular oxidative status and the consequent alteration of S1P and/or PDGF signaling pathway are involved.