Magnolol attenuates right ventricular hypertrophy and fibrosis in hypoxia-induced pulmonary arterial hypertensive rats through inhibition of the JAK2/STAT3 signaling pathway / 中国药理学与毒理学杂志

ABSTRACT

OBJECTIVE Right ventricular (RV) remodeling is one of the essential pathological features in pulmonary arterial hypertension (PAH). RV hypertrophy or fibrosis are the leading causes of RV remodeling. Magnolol is a com?pound isolated from Magnolia officinalis. It possesses multiple pharmacological activities, such as anti-oxidation and anti-inflammation. This study aims to evaluate the effects and underlying mechanisms of magnolol on RV remodeling in hypoxia-induced PAH. METHODS ① Male SD rats (220 g) were randomly divided into 5 groups (n=10) the normoxia group, the hypoxia group, the hypoxia plus Magnolol (10 and 20 mg·kg-1·d-1) group, and the vehicle group. Rats in the normoxia group were kept in a normoxia environment for 4 weeks, while rats in the hypoxia group were kept in a hypoxic chamber (10％ O2). The rats in the hypoxia plus magnolol groups were administered with magnolol at 10 or 20 mg·kg-1 (ip) once a day for 4 weeks. At the end of 4 weeks, the heart function was assessed by Doppler echocardiography, and then the rats were anesthetized with sodium pentobarbital (30 mg·kg-1, ip). The RVSP was measured by the right heart catheterization method. The heart tissues were collected and dissected to calculate the index of RV remodeling (RV/LV+IVS, RV/tibial length, or RV/body weight). Part of the RV samples was fixed with 4％paraformaldehyde for morphological analysis, while other samples were frozen at-80℃for molecular studies (measurements of ANP, BNP,α-SMA, and col?lagen Ⅰ/Ⅲ mRNA expression as well as p-JAK2/JAK2 and p-STAT3/STAT3 protein levels). ② To evaluate the effect of magnolol on hypoxia-induced myocardial hypertrophy and fibrosis, H9c2 or cardiac fibroblasts were divided into 7 groups the control group, cells were cultured under normal conditions; the hypoxia group, cells were cultured under hypoxic condition (3％ O2);the hypoxia plus magnolol 10 mg·kg-1 group, magnolol10μmol·L-1 was added to the culture medium before the hypoxia treatment;the hypoxia plus magnolol 30 mg·kg-1 group, magnolol 20μmol·L-1 was added to the culture medium before the hypoxia treatment;the hypoxia plus TG-101348 group, TG-101348 (a specific inhibitor of JAK2) 1μmol·L-1 was added to the culture medium before the hypoxia treatment;the hypoxia plus JSI-124 group, JSI-124 (a specific inhibitor of JAK2) 1μmol·L-1 was added to the culture medium before the hypoxia treatment;and the hypoxia plus vehicle group, an equal volume of vehicle (DMSO) was added to the culture medium before the hypoxia treatment. At the end of the experiments, the cells were collected for morphological and molecular analysis. RESULTS In vivo, male Sprang-Daley rats were exposed to 10％ O2 for 4 weeks to establish an RV remodeling model, which showed hypertrophic and fibrotic features (increases of RV remodeling index, cellular size, hypertrophic and fibrotic marker expression), accompanied by an elevation in phosphorylation levels of JAK2 and STAT3;these changes were attenuated by treating rats with magnolol. In vitro, the cultured H9c2 cells or cardiac fibroblasts were exposed to 3％ O2 for 48 h to induce hypertrophy or fibrosis, which showed hypertrophic (increases in cellular size as well as the expression of ANP and BNP) or fibrotic features (increases in the expression of collagenⅠ, collagenⅢandα-SMA). Administration of mag?nolol and TG-101348 or JSI-124 (JAK2 selective inhibitors) could prevent the process of myocardial hypertrophy and fibrosis, accompanied by the decrease in the phosphorylation level of JAK2 and STAT3. CONCLUSION Magnolol can attenuate RV hypertrophy and fibrosis in hypoxia-induced PAH rats through a mechanism involving inhibition of the JAK2/STAT3 signaling pathway.