Protein Kinase G-I Deficiency Induces Pulmonary Hypertension through Rho A/Rho Kinase Activation

Protein kinase G (PKG) plays an important role in the regulation of vascular smooth cell contractility and is a critical mediator of nitric oxide signaling, which regulates cardiovascular homeostasis. PKG-I-knockout (Prkg1−/−) mice exhibit impaired nitric oxide/cGMP-dependent vasorelaxation and systemic hypertension. However, it remains unknown whether PKG-I deficiency induces pulmonary hypertension. In this study, we characterized the hypertensive pulmonary phenotypes in Prkg1−/− mice and delineated the underlying molecular basis. We observed a significant increase in right ventricular systolic pressure in Prkg1−/− mice in the absence of systemic hypertension and left-sided heart dysfunction. In addition, we observed marked muscularization of distal pulmonary vessels in Prkg1−/− mice. Microangiography revealed impaired integrity of the pulmonary vasculature in Prkg1−/− mice. Mechanistically, PKG-I-mediated phosphorylation of Rho A Ser188 was markedly decreased, and the resultant Rho A activation was significantly increased in Prkg1−/− lung tissues, which resulted in Rho kinase activation. The i.t. administration of fasudil, a Rho kinase inhibitor, reversed the hypertensive pulmonary phenotype in Prkg1−/− mice. Taken together, these data show that PKG-I deficiency induces pulmonary hypertension through Rho A/Rho kinase activation-mediated vasoconstriction and pulmonary vascular remodeling.