5-Aminosalicylic Acid Attenuates Monocrotaline-Induced Pulmonary Arterial Hypertension in Rats by Increasing the Expression of Nur77

The aim of this study is to investigate the effect of 5-aminosalicylic acid (5-ASA) on monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH) in rats and its molecular mechanism. Sixty male Sprague–Dawley rats (250–300 g) were evenly randomized into six groups: control group; PAH group induced by MCT intraperitoneal injection (50 mg/kg) on day 1; and four PAH groups treated for 30 days from day 2 with 5-ASA at 50 (5-ASA-50 group), 100 (5-ASA-100 group), 150 (5-ASA-150 group), and 200 mg/kg/day (5-ASA-200 group), respectively. Body mass, weight increment, survival rates, pulmonary artery pressure (PAP), right ventricular hypertrophy index (RVHI), and the signal pathway regulated by 5-ASA were assessed. (1) Compared with the control group, the PAH group had lower body mass and weight increment, and relative to the latter, 5-ASA-treated groups had larger body mass and weight increment except for groups 5-ASA-150 and 5-ASA-200 and greater overall survival rates; (2) SPAP, DPAP, MPAP, and RVHI in 5-ASA-treated groups, except for MPAP and RVHI in 5-ASA-200 group, were lower than those in the PAH group; (3) compared with the PAH group, Nur77 expression in the pulmonary arteries of 5-ASA-treated groups was increased; and (4) expression of inflammatory mediators (NF-κB p65) was lower, while that of IκBα was higher in the pulmonary arteries of 5-ASA-treated groups and control group than that in the PAH group (all P < 0.05). 5-ASA attenuates PAH in MCT-injected rats, reducing pulmonary arterial pressures and right ventricular hypertrophy and improving survival rates, via the Nur77-NF-κB/IκBα pathway involved in modulating the pulmonary vascular remodeling.