Effects Of Rho Kinase On P-Smad1 Unclear Translocation In Rat Pulmonary Artery Smooth Muscle Cells

AimTo explore the mechanism of Bone Morphogenetic Protein (BMP) and Rho Kinase signal pathways exerting on the proliferation of pulmonary artery smooth muscle cells.Materials and MethodsPulmonary smooth muscle cells were isolated from the distal pulmonary artery and cultured. BMP and Rho kinase pathways were activated by BMP-2 and PDGF-BB respectively. Rho kinase inhibitor Y-27632 or MEK inhibitor U0126 were also used. Immunofluorescent staining was applied to observe p-Smadl distribution across the nucleus, and the cells with positive p-Smad1 nuclear accumulation were counted and the cell nuclear translocation rate was calculated. The total p-Smadl and its distribution across the nucleus were quantitatively determined by Western blotting. The cell proliferation was analyzed by Cell Counting Kit-WST-8 kit.ResultsExposure to BMP-2 significantly increased both the total amount of p-Smad1 and its nuclear accumulation in pulmonary artery smooth muscle cells; pretreatment with PDGF-BB significantly decreased the nuclear accumulation of p-Smad1 induced by BMP-2 without decrease of the total p-Smad1.however, pretreatment with Y-27632 or U0126 reversed the inhibitory effect of p-Smadl nuclear accumulation by PDGF-BB. BMP-2 significantly inhibited the cell proliferation; but PDGF-BB blocked the effect of BMP-2 and significantly increased the cell proliferation. After pretreatment with Y-27632 or U0126, the PDGF-BB activated cell proliferation was suppressed.ConclusionPDGF-BB-activated Rho kinase inhibits BMP-2-induced p-Smadl nuclear translocation via MEK/ERK1/2, thus increases pulmonary artery smooth muscle cell proliferation leading to pulmonary blood vessels reconstruction.