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Protein kinase C regulates endothelial nitric oxide synthase expression via Akt activation and nitric oxide generation

¹Vascular Biology Center, Medical College of Georgia, Augusta, Georgia; and ²Department of Pediatrics, Northwestern University, Chicago, Illinois

Submitted 28 August 2007 ; accepted in final form 1 January 2008

In this study, we explore the roles of the delta isoform of PKC (PKC) in the regulation of endothelial nitric oxide synthase (eNOS) activity in pulmonary arterial endothelial cells isolated from fetal lambs (FPAECs). Pharmacological inhibition of PKC with either rottlerin or with the peptide, V1-1, acutely attenuated NO production, and this was associated with a decrease in phosphorylation of eNOS at Ser1177 (S1177). The chronic effects of PKC inhibition using either rottlerin or the overexpression of a dominant negative PKC mutant included the downregulation of eNOS gene expression that was manifested by a decrease in both eNOS promoter activity and protein expression after 24 h of treatment. We also found that PKC inhibition blunted Akt activation as observed by a reduction in phosphorylated Akt at position Ser473. Thus, we conclude that PKC is actively involved in the activation of Akt. To determine the effect of Akt on eNOS signaling, we overexpressed a dominant negative mutant of Akt and determined its effect of NO generation, eNOS expression, and phosphorylation of eNOS at S1177. Our results demonstrated that Akt inhibition was associated with decreased NO production that correlated with reduced phosphorylation of eNOS at S1177, and decreased eNOS promoter activity. We next evaluated the effect of endogenously produced NO on eNOS expression by incubating FPAECs with the eNOS inhibitor 2-ethyl-2-thiopseudourea (ETU). ETU significantly inhibited NO production, eNOS promoter activity, and eNOS protein levels. Together, our data indicate involvement of PKC-mediated Akt activation and NO generation in maintaining eNOS expression.

cell signaling; gene expression; endothelial