Modulation of Pulmonary Vascular Smooth Muscle Cell Phenotype in Hypoxia: Role of cGMP‐Dependent Protein Kinase

Abstract

Chronic hypoxia triggers pulmonary vascular remodeling, which is associated with a modulation of the vascular smooth muscle cell (SMC) phenotype from a contractile, differentiated to a synthetic, de-differentiated state. We tested if altered expression of PKG could explain SMC phenotype modulation after exposure to hypoxia. Hypoxia-induced reduction in PKG expression correlated strongly with the repressed expression of SMC phenotypic markers myosin heavy chain, calponin, vimentin, α-smooth muscle actin and thrombospondin, indicating that exposure to hypoxia resulted in phenotype modulation to de-differentiated state and PKG may be involved in SMC phenotype modulation. The results from PKG-specific small interfering RNA (siRNA) transfection and treatment with DT-3 (a peptide inhibitor of PKG, 30μM) in FPVSMC indicate that the expression of SMC phenotype protein expression decreased by hypoxia was also similarly impacted by PKG inhibition. Over-expression of PKG in FPVSMC by transfection of FPVSMC with a full length PKG construct tagged with GFP (PKG-GFP) reversed the effect of hypoxia on the expression of SMC phenotype marker proteins. These results suggest that PKG could be one of the determinants for the expression of SMC phenotype maker proteins and may be involved in the maintenance of the differentiated phenotype in pulmonary vascular SMCs in hypoxia.