In this study, we explore the roles of the delta isoform of PKC (PKCd) in the regulation of endothelial nitric oxide synthase (eNOS) activity in pulmonary arterial endothelial cells isolated from fetal lambs (FPAECs). Pharmacological inhibition of PKCd with either rottlerin or with the peptide, dV1-1, acutely attenuated NO production, and this was associated with a decrease in phosphorylation of eNOS at Ser1177 (S1177). The chronic effects of PKCd inhibition using either rottlerin or the overexpression of a dominant negative PKCd 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 PKCd inhibition blunted Akt activation as observed by a reduction in phosphorylated Akt at position Ser473. Thus, we conclude that PKCd 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 PKCd-mediated Akt activation and NO generation in maintaining eNOS expression.

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