SIGNAL-TRANSDUCTION PATHWAY(S) INVOLVED IN PHORBOL ESTER AND AUTOCRINE INDUCTION OF INTERLEUKIN-1-ALPHA MESSENGER-RNA IN MURINE KERATINOCYTES

We investigated the signal transduction pathways leading to the 12-O-t etradecanoylphorbol-13-acetate (TPA) and interleukin-1 alpha (IL-1)-in duced IL-1 alpha mRNA in mouse keratinocytes. Induction of IL-1 alpha mRNA by TPA or IL-1 alpha was followed by increases in cell-associated IL-1 alpha protein measured by enzyme linked immunosorbent assay. Alt hough protein kinase C (PKC) was involved in TPA-induced IL-1 alpha mR NA, down-regulation of PKC did not block the induction of this gene by TPA. The autocrine induction of IL-1 alpha was not mediated through P KC or cAMP. IL-1 alpha did activate mitogen activated protein kinase. Genistein, a tyrosine kinase inhibitor, blocked both IL-1 alpha induce d mitogen-activated protein kinase activation as well as IL-1 alpha mR NA expression. Genistein, at an unsaturating dose, plus a serine/threo nine kinase inhibitor, H7, completely blocked the autocrine induction of IL-1 alpha suggesting that expression of this gene is regulated by tyrosine kinase(s) in combination or independently with serine/threoni ne kinase(s). In addition, both TPA and IL-1 alpha caused increases no t only in the phosphorylation of c-Jun and c-Fos protein but also in t he transactivating activity of AP-1 nuclear transcription factor. Neit her TPA nor IL-1 alpha induced NF-kappa B binding activity, as assesse d by electrophoretic mobility shift analysis. This study suggests that the activation of AP-1 may be a common event through which TPA and IL -1 alpha induce IL-1 alpha mRNA.