Baicalein Attenuates Monocrotaline-induced Pulmonary Artery Hypertension Via Inhibiting Vascular Remodeling In Rats

Background and Objective:Pulmonary arterial hypertension(PAH)is a devastating cardiopulmonary disorder characterized by vascular remodeling leading to elevated pulmonary arterial pressure(PAP)and right ventricular hypertrophy(RVH).Reversing vascular remodeling is an important concept in PAH disease therapy.Proliferation and apoptosis imbalance in different cells of lung tissue and inflammation have been implicated in remodeling processes.Baicalein is a natural flavonoid that has been shown to possess anti-proliferative,anti-inflammatory,and cardioprotective properties.The effect of Baicalein Associated with the MAPK and NF-κB pathways.This study was designed to investigate the effects of Baicalein on the vascular remodeling of monocrotaline-induced pulmonary artery hypertension and its mechanisms.Methods:1.Male Sprague-Dawley rats were distributed randomly into 4 groups,10 rats in each group: control,MCT-exposed,MCT-exposed plus Baicalein treated rats(50 and 100 mg/kg)from days 14-28.Given daily by intragastric administration,2 weeks after the MCT injection and were maintained daily for 2 weeks.Hemodynamic changes,RVH,and lung morphological features were examined on day 28.2.H&E and Masson trichrome staining were performed to detect the medial wall thickness in small pulmonary arteries,and H&E staining were performed to measure the right ventricular free wall thickness and the size of myocardial cells to observe the remodeling of pulmonary artery and right ventricle.3.H&E staining was used to observe the inflammation reaction in lung tissue.The mRNA levels of tumor necrosis factor alpha(TNF-α),interleukin-1β(IL-1β),and IL-6 were detected using qRT-PCR analysis.4.Apoptosis was determined by TUNEL staining.The expression levels of Bax,Bcl-2,cleaved caspase-3 were assessed by Western blot.5.The activation of mitogen-activated protein kinase(MAPK)and NF-κB were assessed by Western blot.Results:1.MCT induced an increase in hemodynamic parameters and RVH,which were attenuated by Baicalein treatment.The right ventricular systolic pressure(RVSP)date showed that the MCT-treated rats developed severe PAH as reflected by a significant elevation of RVSP in comparison to that in the control group.Oral treatment with Baicalein effectively inhibited the MCT-induced increase in RVSP.The data of RVH index(RV/(LV + S)),RV / BW,RV free wall thickness and cardiomyocyte size showed that right ventricular free wall thickness was increased significantly in untreated MCT-exposed rats compared with the control group,meanwhile,hypertrophied and disordered cardiomyocytes in the RV of the MCT-exposed rats compared with control group,and this maladaptive change was restored in the 50 and 100 mg/kg/day Baicalein-treated rats.2.Baicalein also blocked MCT-induced pulmonary arterial remodeling.The results of H&E and Masson trichrome staining showed that injection of MCT led to pulmonary artery remodeling and a significant increase in fibrosis in comparison to the control group,and the lumen appeared stenosed or occluded,and these vascular pathological changes appeared to be attenuated in lung tissue from the MCT + Baicalein group.Indexes of wall thickness of pulmonary arterioles(WT % and WA %)showed that WT % and WA% were significantly increased in rats treated with MCT compared with the control group.In contrast,in the MCT + Baicalein(50 and 100 mg/kg/day)group,WT % and WA% was significantly reduced compared with the MCT group.3.Baicalein also blocked MCT-induced pulmonary arterial inflammatory responses.HE analysis showed that marked perivascular and peribronchiolar inflammatory cell infiltration of lung tissues was found in the MCT group,and the overall inflammatory response induced by MCT was significantly reduced by both doses of Baicalein.qRT-PCR analysis showed that Baicalein inhibited MCT-induced elevation of mRNA levels of IL-6,TNF-α,and IL-1β in lung tissue of rats.4.Baicalein also blocked MCT-induced pulmonary arterial apoptosis.TUNEL staining analysis showed MCT injection resulted in increased percentage of the median percentage of TUNEL-positive cells compared with the control group.However,the 50 and 100 mg/kg/day Baicalein-treated group showed a significant reduction of TUNEL-positive cells compared with the MCT-treated rats.Western Blot analysis showed that Baicalein blocked MCT-induced up-regulation of Bax / Bcl-2 ratio and cleaved caspase-3 in lung tissue of rats.5.Baicalein inhibited MCT-induced activation of MAPK and NF-κB pathways.Western Blot analysis showed that activation of p38,ERK,and JNK was notably greater in the lung tissue of MCT-treated rats in comparison to the control group.However,the increased phosphorylation of p38,ERK,and JNK was attenuated by Baicalein(50 and 100 mg/kg/day)treatment.The level of NF-κB p65 was significantly increased in the lung tissue of MCT-treated vehicle group,whereas treatment with Baicalein(50 and 100 mg/kg/day)significantly inhibited MCT-induced NF-κB up-regulation.Conclusion:1.Baicalein has a positive effect on MCT-induced PAH in rats.The mechanism of baicalein in the treatment of MCT-induced PAH may be related to its inhibition of vascular remodeling in rats.2.The molecular mechanism of baicalein in the treatment of MCT-induced PAH may be partially related to the MAPK and NF-κB signaling pathways in rats.