Abstract
The higher norepinephrine (NE) concentration induced by sympathetic nerve hyperactivation participated in pulmonary artery smooth muscle cells (PASMCs) over-proliferation and led to pulmonary vascular remodeling (PVR), which played an important role in pulmonary artery hypertension (PAH). However, the underlying mechanism by which NE induced PASMCs proliferation had not been fully elucidated. In the present study, we found that prazosin, the inhibitor of α1-AR, reversed hypoxia-induced changes in pulmonary circulatory function which were analyzed by echocardiography to measure pulmonary artery acceleration time (PAT) and pulmonary arterial velocity time integral (PAVTI) and right heart catheterization to test right ventricular systolic pressure (RVSP), respectively. Western blotting analysis showed that the expression of alpha1B-adreneroceptor (α1B-AR) increased under hypoxic conditions both in vivo and in vitro. Antagonism of α1B-AR by chloroethylclonidine dihydrochloride (CEC) reversed the NE-induced proliferation in rat PASMCs, which was confirmed by applying Western blotting to test proliferating cell nuclear antigen (PCNA) expression, CCK8 assay to test cell viability, scratch-wounding cellular migration assay to show cell proliferative capacity and immunofluorescence to show Ki67 expression. Furthermore, we revealed that antagonism of α1B-AR alleviated NE-induced acceleration of cell-cycle progression by Western blotting to detect cell-cycle-related protein. In addition, Western blotting results showed that antagonism of α1B-AR reversed NE-promoted phosphorylation of p38 (p-p38) under hypoxia. SB202190, an inhibitor of p38, reversed NE-induced proliferation and acceleration of cell-cycle progression of PASMCs. These results suggested that α1B-AR was involved in NE-induced PASMCs proliferation via p38 signaling pathway, which might be downstream of α1B-AR.