The therapeutic effect and mechanism of Rapamycin combined with HO-3867 on monocrotaline-induced pulmonary hypertension in rats

This study test was designed to investigate the possible modulatory effect of rapamycin combined with HO-3867 in monocrotaline(MCT)-induced pulmonary arterial hypertension in rats. We hypothesized that combined treatment with rapamycin and HO-3867 is superior to either alone in attenuating MCT-induced rat pulmonary arterial hypertension (PAH). Pulmonary arterial hypertension was induced by a single intraperitoneal injection of monocrotaline (60 mg/kg). 2 weeks later, rapamycin (2 mg/kg i.p.) and HO3867 (10 mg/kg i.h.) were administered daily, alone and in combination, for 2 weeks. Right ventricular systolic pressure, echocardiography were recorded and then rats were sacrificed. Histological analysis of pulmonary arteries medial wall thickness, right ventricular hypertrophy index (RVHI), the ratio of right ventricular to body weight, and collagen volume fraction (CVF) of right ventricular were performed. Moreover, the expression of t-STAT3, p-STAT3, t-Akt, p-Akt in lung and t-STAT3, p-STAT3, t-S6, p-S6 in right ventricular were examined. The result showed that combined treatment provided a considerable improvement toward maintaining hemodynamic changes, lung vascular remodeling as well as amending RV remodeling and function. Furthermore, Combined treatment can normalize the protein levels of two signal pathways in lung and heart tissue, where p-S6 or p-Akt significantly decreased compared to HO-3867 alone, or p-STAT3 significantly reduced compared to rapamycin alone. In conclusion, combined treatment with rapamycin and HO-3867 is superior to either alone in attenuating MCT-induced PAH in rats.