Effect of Staurosporine on Transcription Factor NF-κB in Human Keratinocytes

Activation of the transcription factor NF-kappa B is known to be important in the regulated expression of a large number of pro-inflammatory genes including interleukin-8 (IL-8). Previously, we showed that the protein kinase inhibitor staurosporine potentiates IL-1-stimulated IL-8 production in human keratinocytes. Moreover, recent studies by other investigators demonstrated that staurosporine treatment alone results in a concentration dependent increase in IL-8 mRNA and protein production. Therefore, in order to understand the mechanism underlying this observation, the effect of staurosporine on the activation of NF-kappa B was investigated. Electrophoretic mobility shift assays using an oligonucleotide containing the: NF-kappa B consensus motif demonstrated that staurosporine treatment resulted in the activation of NF-kappa B by 15 min post-treatment. The ability of staurosporine to activate NF-kappa B was investigated further, using luciferase reporters under the control of the HIV-LTR or IL-8 core promoter transfected into human U937 cells. Stimulation with staurosporine resulted in a concentration-dependent induction of luciferase activity. In contrast, the very selective protein kinase C inhibitor 3 [8-[(dimethylamino)methyl]-6,7,8,9-tetrahydropyrido-[1,2-a]indol-10-yl]-4-(1-methyl-3-indolyl)-1H-pyrrole-2,5-dione hydrochloride (Ro32-0432) did not stimulate the activation of NF-kappa B, as measured in the luciferase reporter assay. The mechanism underlying NF-kappa B activation does not appear to involve the classical activation pathways in that staurosporine does not induce the disappearance of -kappa B family members. In conclusion, staurosporine appears to stimulate the activation of NF-kappa B in at least two cell types, and this effect appears to be independent of protein kinase C. BIOCHEM PHARMACOL 56;1:71-78, 1998. (C) 1998 Elsevier Science Inc.