R-4733

Pulmonary hypertension (PH) is a condition in which the smooth muscle cells (SMCs) in the pulmonary arteries multiply excessively, causing the arteries to narrow. This can ultimately result in right heart failure and premature death. Notch3 is an important factor involved in pulmonary vascular remodeling in PH. RO4929097, as a γ-secretase inhibitor that inhibits Notch3 signaling pathway, may be a potential drug for the treatment of PH, but its feasibility and related mechanism of action need to be further investigated. In vitro modeling by hypoxic incubation of human pulmonary artery SMCs (HPASMCs). RO4929097 and plasmids including overexpression-NICD3 (oe-NICD3) and NICD3 small interfering RNA (siRNA) were used to alter the expression of NICD3, and HIF-2α inhibitor PT-2385 was used to alter the expression of HIF-2α. Western blot, EdU incorporation assay was used to investigate the alteration of NICD3, HIF-2α, FoxM1 protein expression, and cell proliferation. The severity of PH in rats was assessed by measuring the weight ratio of right ventricle (RV) to left ventricle (LV) and septum (S) (RV/[LV + S]) and hematoxylin-eosin (H&E) staining of lung tissues in a hypoxia-induced PH rat model. We first determined that hypoxia induction for 48 h had the strongest induction of NICD3 and Notch3 in HPASMCs, and the strongest inhibition by 10 μM RO4929097. Treatment of HPASMCs under hypoxic conditions with RO4929097 inhibited hypoxia-induced expression of NICD3, HIF-2α, FoxM1, and proliferation of HPASMCs. The inhibitory effect of RO4929097 was reversed after overexpression of NICD3 in HPASMCs. Further, we found that PT-2385 reversed the promotional effect of overexpression of NICD3 on the proliferation of HPASMCs. In vivo experiments, hypoxia-induced PH rats treated with RO4929097 showed a reduction in right ventricular hypertrophy index (RVHI) and a return to normal pulmonary artery morphology, indicating a reduction in the severity of PH. Our data suggest that RO4929097 regulates the Notch3/HIF-2α/FoxM1 signaling pathway by inhibiting the expression of NICD3, thereby inhibiting hypoxia-induced proliferation of HPASMCs. In vivo experiments also confirmed that RO4929097 could alleviate PH as a potential therapeutic strategy.