Regulation of interleukin-1-stimulated GMCSF mRNA levels in human endothelium

The regulation of interleukin-1 (IL-1)-mediated increases in GMCSF mRNA levels in human endothelium was examined and determined to occur in a time- and protein kinase C (PKC)-dependent manner. IL-1β induced the early activation and translocation of PKC isotypes α and β₂ to the nucleus and PKC inhibition attenuated the IL-1-mediated increase in GMCSF mRNA levels. PKC activation by PMA alone, in the absence of IL-1β activation, however, was insufficient to allow GMCSF mRNA detection. Increasing cyclic adenosine nucleotide (cAMP) levels suppressed IL-1β-induced increases in GMCSF mRNA levels. In contrast, botulinum toxin C, which mediates the ADP ribosylation of a 21 kD ras-related G protein, augmented IL-1β-induced GMCSF mRNA expression. Inhibition of protein synthesis (with cycloheximide) raised basal GMCSF mRNA transcripts to detectable levels, augmented IL-1-induced increases in GMCSF mRNA levels, and exhibited negative regulation by cAMP. Finally, disruption of either microtubules (with colchicine) or microfilaments (with cytochalasin B) resulted in reduced GMCSF mRNA expression in response to IL-1β. These results are compatible with a model wherein IL-1-mediated increases in human endothelial cell GMCSF mRNA may be linked to both nuclear protein kinase C activation and activation of a low molecular weight G-protein, although neither activity alone is sufficient to increase the levels of GMCSF mRNA.