Sprague-Dawley rats were continuously exposed to 10% O2 for 4 weeks to induce PH. The effect of
chrysin (50 or 100 mg/kg/d, subcutaneous) on
vascular remodeling was investigated in
hypoxia-induced PH model. At the end of the experiments, the indexes for pulmonary
vascular remodeling and right ventricle
hypertrophy were measured by vascular medial wall thickness and the ratio of right ventricle to (left ventricle plus septum). The expressions of NOX4,
collagen I, and
collagen III were analyzed by immunohistochemistry, real-time PCR, or western blotting. The proliferation of cultured pulmonary artery smooth muscle cells (PASMCs) was determined by
BrdU incorporation and flow cytometry. The levels of
malondialdehyde (MDA) and
reactive oxygen species (ROS) were also determined by
thiobarbituric acid reactive substances assay and 2'7'-dichlorofluorescein diacetate method.
RESULTS:
Chrysin treatment for 4 weeks significantly attenuated pulmonary
vascular remodeling and improved
collagen accumulation and down-regulated
collagen I and
collagen III expressions, accompanied by downregulation of NOX4 expression in the pulmonary artery (P = 0.012 for 50 mg/kg/d, P < 0.001 for 100 mg/kg/d) and lung tissue (P = 0.026, P < 0.001). In vitro,
chrysin (1, 10, and 100 μM) remarkably attenuated PASMC proliferation (P = 0.021 for 1 μM, P < 0.001 for 10 μM, and P < 0.001 for 100 μM),
collagen I expression (P = 0.035, P < 0.001, and P < 0.001), and
collagen III expression (P = 0.027, P < 0.001, and P < 0.001) induced by
hypoxia, and these inhibitory effects of
chrysin were accompanied by inhibition of NOX4 expression (P = 0.019, P < 0.001, and P < 0.001), ROS production (P = 0.038, P < 0.001, and P < 0.001), and MDA generation (P = 0.024, P < 0.001, and P < 0.001).
CONCLUSIONS: This study demonstrated that
chrysin treatment in
hypoxia-induced PH in rats reversed the
hypoxia-induced (1) elevations of NOX4 expression, (2) productions of ROS and MDA, (3) proliferation of PASMC, and (4) accumulation of
collagen.