Regulation of the inducible nitric oxide synthase (iNOS) promoter by PMA and cytoskeleton depolymerizing agents in cultured rat aortic smooth muscle cells

Nitric oxide plays important roles in ihe regulation of vascular tone. The LPS- and cytokine induced high ouptut NO production by vascular smooth musde cells (VSMC) is believed to he mediated by iNOS and to be responsibly for the cardiovascular collapse in septic shock. Recently, we have cloned the rat iNOS promoter and, in the present study, we report its regulation by PMA and nocodazole, a cytoskelelon depolymerizing agent, in VSMC transfected with the promoter-luciferase construct. Luciferase activity was induced 27+/-4 fold and 31+/-6 fold in response to LPS and cytokine mix. respectively. PMA alone (100-500 ng/ml) slightly increased luciferase activity (1.3+/-0.2 fold). However, PMA synergistically increased promoter activity up to 78+/-23 fold and 67+/-13 fold in the presence of LPS and cytokine mix, respectively. Nocodazole significantly decreased the promoter activity in the presence ofi LPS (21 v. 9 fold) or LPS and PMA (28 v. 13 fold). These data demonstrate that the transcriptional regulation of rat iNOS is cytoskeleton dependent and that PMA, an activator of PKC, is involved in the transcriptional regulation of iNOS in the presence of LPS and cytokines.