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

Bone marrow-derived progenitor cells prevent thrombin-induced increase in lung vascular permeability

Since thrombin activation of endothelial cells (ECs) is well-known to increase endothelial permeability by disassembly of adherens junctions (AJs) and actinomyosin contractility mechanism involving myosin light chain (MLC) phosphorylation, we investigated the effects of bone marrow-derived progenitor cells (BMPCs) on the thrombin-induced endothelial permeability response. We observed that addition of BMPCs to endothelial monolayers at a fixed ratio prevented the thrombin-induced decrease in transendothelial electrical resistance, a measure of AJ integrity, and increased mouse pulmonary microvessel filtration coefficient, a measure of transvascular liquid permeability. The barrier protection was coupled to increased vascular endothelial cadherin expression and increased Cdc42 activity in ECs. Using small interfering RNA (siRNA) to deplete Cdc42 in ECs, we demonstrated a key role of Cdc42 in signaling the BMPC-induced endothelial barrier protection. Endothelial integrity induced by BMPCs was also secondary to inhibition of MLC phosphorylation in ECs. Thus BMPCs interacting with ECs prevent thrombin-induced endothelial hyperpermeability by a mechanism involving AJ barrier annealing, inhibition of MLC phosphorylation, and activation of Cdc42

Inhibited lung inflammation in mice treated with fCB-CD34⁺ cells.

<p>Lung tissues at indicated times post-LPS challenge were collected for MPO activity determination. Data are expressed as mean ± SD (<i>n</i> = 4/group). *, <i>P</i><0.05 versus PBS or CD34⁻.</p