4-Terpineol attenuates pulmonary vascular remodeling via suppressing PI3K/Akt signaling pathway in hypoxia-induced pulmonary hypertension rats

The hyperproliferation of pulmonary arterial smooth muscle cells (PASMCs) plays a pivotal role in pulmonary arterial remodeling (PAR) of hypoxia-induced pulmonary hypertension (HPH). 4-Terpineol is a constituent of Myristic fragrant volatile oil in Santan Sumtang. Our previous study found that Myristic fragrant volatile oil alleviated PAR in HPH rats. However, the effect and pharmacological mechanism of 4-terpineol in HPH rats remain unexplored. Male Sprague-Dawley rats were exposed to hypobaric hypoxia chamber (simulated altitudes of 4500 m) for 4 weeks to establish an HPH model in this study. During this period, rats were intragastrically administrated with 4-terpineol or sildenafil. After that, hemodynamic indexes and histopathological changes were assessed. Moreover, a hypoxia-induced cellular proliferative model was established by exposing PASMCs to 3% O2. PASMCs were pretreated with 4-terpineol or LY294002 to explore whether 4-terpineol targeted PI3K/Akt signaling pathway. The PI3K/Akt-related proteins expression was also accessed in lung tissues of HPH rats. We found that 4-terpineol attenuated mPAP and PAR in HPH rats. Then, cellular experiments showed 4-terpineol inhibited hypoxia-induced PASMCs proliferation via down-regulating PI3K/Akt expression. Furthermore, 4-terpineol decreased the p-Akt, p-p38, and p-GSK-3 & beta; protein expression, as well as reduced the PCNA, CDK4, Bcl-2 and Cyclin D1 protein levels, while increasing levels of cleaved caspase 3, Bax, and p27kip1in lung tissues of HPH rats. Our results suggested that 4-terpineol mitigated PAR in HPH rats by inhibiting the proliferation and inducing apoptosis of PASMCs through suppression of the PI3K/Akt-related signaling pathway.