Survivin role in pulmonary arterial hypertension

Abstract

Purpose: Survivin is an inhibitor of apoptosis expressed in the vascular lesions of pulmonary arterial hypertension (PAH) and is also involved in myocardial remodeling during left heart failure. The current work aims at: investigating right ventricular (RV) expression of survivin and smac/DIABLO (an inhibitor of survivin) throughout the hemodynamic and morphometric progression of monocrotaline (MCT)-induced PAH; and characterizing the effects of the survivin antagonist terameprocol in pulmonary artery smooth muscle cells (PASMC). Methods: Animal experiments were performed according to the Portuguese law for animal welfare and to the Principles of laboratory animal care (NIH Publication no. 85-23 revised 1985). Adult male Wistar rats received a subcutaneous injection of MCT (60 mg/kg) or equal volume of vehicle. On days 1, 3, 7, 14 and 21 after injection (n=7-12 per group per time-point), RV pressures were measured, heart and lungs were weighted and RV and lung samples were collected for histological analysis. Survivin and smac/DIABLO expression in the RV was determined by immunohistochemistry and western blotting. In a different protocol, a primary culture of PASMC isolated from sham and MCT-treated rats (day 21) was established and the effects of terameprocol in cell proliferation and apoptosis were evaluated by BrdU and TUNEL assays, respectively. Results: RV survivin expression was significantly increased in the MCT groups since day 7, when compared with the SHAM groups. Smac/DIABLO followed an inverse expression pattern with a significant decrease in the MCT groups identified since day 7. This time-point corresponded to the first evidence of RV hypertrophy in MCT-treated rats. Survivin overexpression preceded hemodynamic manifestations of the disease, which started at day 14 with significant increases in RV peak systolic pressure and absolute values of dP/dtmax and dP/dtmin. Terameprocol significantly inhibited proliferation and induced apoptosis of PASMC from sham and pulmonary hypertensive rats in a dose-dependent manner. The pattern of proliferation and apoptosis did not differ significantly between SHAM and MCT groups. Conclusions: Our results demonstrate that survivin upregulation and smac/DIABLO downregulation in the RV precede hemodynamic manifestations of PAH and pair RV hypertrophy, strongly suggesting a role in cardiac remodeling. Pharmacological inhibition of survivin halted cell proliferation and induced apoptosis of PASMC. These findings suggest that targeting survivin in PAH could have dual beneficial effects by reversing pulmonary vascular remodeling and myocardial hypertrophy.