Apple polyphenol relieves hypoxia-induced pulmonary arterial hypertension via pulmonary endothelium protection and smooth muscle relaxation: In vivo and in vitro studies.

OBJECTIVE

This study aims to test the effect of apple polyphenol (APP) on hypoxia-induced pulmonary arterial hypertension (PAH) and explore its possible underlying mechanisms.

RESULTS

Rats were treated with control, APP, hypoxia (8 h/d), hypoxia + APP. Mean pulmonary arterial pressure (mPAP) and pulmonary vessel resistance (PVR) were examined. Phenylephrine (PE)-pretreated pulmonary vessel rings were prepared for observation of APP administration. eNOS, sGC inhibitors (L-NAME, MB), Ca2+ channel blockers (NiCl2, Calhex231), K+ channel blockers (4-AP, 5-HD, TEA, BaCl2) were applied to pulmonary vessel rings and pulmonary arterial smooth muscle cell (PASMC). Flow cytometry analysis and CCK-8 assay were applied to detect apoptosis of pulmonary artery endothelium cell (PAEC). Caspase-3, NO, eNOS, iNOS were detected in PAEC. APP reversed mPAP and PVR elevation in vivo. Contraction of pulmonary vessel rings with/without endothelium induced by hypoxia were inhibited by APP. APP effect was hindered by L-NAME or MB, and could be reduced by K+channel blockers. Further, APP was found to decrease cytosolic Ca2+ in PASMC and protect PAEC from apoptosis. In PAEC, Caspase-3, iNOS were decreased and NO, eNOS were increased after APP administration.

CONCLUSIONS

APP reverses pulmonary vasoconstriction through enzyme expression and cation channel activities, thus has effects of PASMC relaxation and PAEC protection.