INTERLEUKIN-1-BETA INDUCTION OF TNF-ALPHA GENE-EXPRESSION - INVOLVEMENT OF PROTEIN-KINASE-C

In the human astroglioma cell line CH235-MG, interleukin-1-beta (IL-1-beta) induces transcriptional activation of the tumor necrosis factor-alpha (TNF-alpha) gene, resulting in expression of TNF-alpha mRNA and biologically active TNF-alpha protein. This study was undertaken to elucidate intracellular signaling pathways involved in IL-1-beta induction of the TNF-alpha gene. We demonstrated that the protein kinase C (PKC) activator 4-beta-phorbol 12-beta-myristate 13-alpha-acetate (PMA) in concert with Ca++ ionophore A23187 induced expression of TNF-alpha mRNA and protein, whereas an inactive PMA analogue (alpha-PMA) had no effect. Various cyclic nucleotide activators such as 8-Bromo cAMP, cholera toxin, and forskolin had no effect on TNF-alpha production. Two PKC inhibitors, H7 and staurosporine (SS), abrogated IL-1-beta induced TNF-alpha expression in a dose-dependent fashion. Treatment of CH235-MG cells with a high concentration of PMA (1-mu-M) for an extended period of time (48 h) caused a greater than 90% reduction in total PKC activity. Further strengthening a role for PKC in this cytokine response is the fact that IL-1-beta was no longer able to induce TNF-alpha expression in these PKC depleted cells. Last, IL-1-beta treatment produced an increase of total PKC activity in CH235-MG cells. Taken together, these data demonstrate that IL-1-beta induces TNF-alpha gene expression in CH235-MG cells in a PKC-dependent manner.