REGULATION OF INTERLEUKIN-1-STIMULATED GMCSF MESSENGER-RNA LEVELS IN HUMAN ENDOTHELIUM

The regulation of interleukin-1 (IL-1)-mediated increases in GMCSF mRN A levels in human endothelium was examined and determined to occur in a time- and protein kinase C (PKC)-dependent manner. IL-1 beta induced the early activation and translocation of PKC isotypes alpha and beta (2) to the nucleus and PKC inhibition attenuated the IL-1-mediated inc rease in GMCSF mRNA levels. PKC activation by PMA alone, in the absenc e of IL-1 beta activation, however, was insufficient to allow GMCSF mR NA detection. Increasing cyclic adenosine nucleotide (cAMP) levels sup pressed IL-1 beta-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-1 beta-induced GMCSF mRNA expression. Inhibition of protein synthesis (with cycloheximide) raised basal GMC SF mRNA transcripts to detectable levels, augmented IL-1-induced incre ases in GMCSF mRNA levels, and exhibited negative regulation by cAMP. Finally, disruption of either microtubules (with colchicine) or microf ilaments (with cytochalasin B) resulted in reduced GMCSF mRNA expressi on in response to IL-1 beta. These results are compatible with a model wherein IL-l-mediated increases in human endothelial cell GMCSF mRNA may be linked to both nuclear protein kinase C activation and activati on of a low molecular weight G-protein, although neither activity alon e is sufficient to increase the levels of GMCSF mRNA.