The Mechanism Of ACEI And AT₁ Receptor Antagonist Intervention On Pulmonary Vascular Remodeling In Rats With Pulmonary Hypertension

Objective:Based on the observation on effect of ACEI and AT₁ receptor antagonist on pulmonary vascular remodeling in rats with pulmonary hypertension, the mechanism of Angâ…¡role in the development of pulmonary vascular remodeling were explored.Methods:1. Study on the effect of ACEI and AT₁ receptor antagonist on pulmonary vascular remodeling in rats with pulmonary hypertension.1.1 The rat model of severe pulmonary hypertension was established with pneumonectomy plus MCT injection, mPAP and the weight ratio of RV to LV+S were measured at day 35, Morphologic parameters were observed which included neointima formation and its proliferation index as wellas vascular occlusion score(VOS). percentage of small pulmonary arteries media thickness, muscularization% of non-muscular arteriole. The expressions of a-actin in PASMC,PCNA positive cell expression were also determined by immunochemistry stain.1.2 Captopril and Losartan were given to pulmonary hypertension rats to examine the effect of ACEI and AT₁ receptor antagonist on pulmonary vascular remodeling in rats with pulmonary hypertension. Expression of MMP-2,9,TIMP-1 by immunohistochemistry and MMP-2,9,TIMP-1,collagenâ… -al,collagenâ…£-al,EVE and TN-C mRNA were assayed in pulmonary tissue by FQ-PCR; Gelatin zymography were used to measure the enzymatic activity of MMP-2,9. The content and distribution of collagenâ… and collagenâ…£were observed with sirus staining.1.3 Effects of ACEI and AT₁ receptor antagonist on pulmonary vascular cell apoptosis were observed with TUNEL and apoptosis gene Bax and Bcl-2 detected by lmmunohistochemistry2. In vitro study on the effect of angiotensinâ…¡and losartan on cultured PASMC of rat2.1 Primary generation of PASMC of rat were cultured, and 4-6th generation cells were used for the experiment.2.2 The optimal concentration of Angâ…¡(1X10^-8M) was determined with MTT assay, which was given to stimulate cultured PASMC and losartan was given to intervene the process, PASMC were divided randomly to different time point groups (1h 3h 12h 24h) The expression of MMP-2,9,TIMP-1,Collagenâ… -a 1,Collagenâ…£-a 1 mRNA in PASMC were detected with FQ-PCR.2.3 PASMC groups were divided randomly by different Angâ…¡density gradient (1×10^-9M,1×10^-8M,1×10^-7M) and different time points (8h,12h,24h,48h) as well, proliferation and apoptosis of PASMC were detected with flow cytometry.Result1. Pneumonectomy plus MCT injection induced severely pulmonary hypertension which was characterized by neointimal formation. Compared with other groups, the model group's mPAP, right ventricle weight, muscularization of small pulmonary arteries, percentage of small pulmonary arteries media thickness, and VOS were increased significantly(P＜0.05)2. Exprcssion of MMP-2,9,TIMP-1,EVE,TN-C,Collagenâ… -a 1,Collagenâ…£-a 1 mRNA in the lung tissue of the group of pulmonary hypertension were increased significantly than other groups (P＜0.05). All indexes above in the groups of captopril and losartan intervention were decreased significantly(P＜0.005)3. Proliferation and apoptosis of cells in the model group increased remarkably than the normal group (P＜0.05), which were suppressed in groups intervened by both drugs. (P＜0.05)4. In vitro study showed that PASMC proliferation were induced by Angâ…¡which reached at the maximum at 12h time point, However, Angâ…¡induced PASMC apoptosis which summit at 24h; Both cells proliferation and apoptosis in losartan group were suppressed and so did the expression of PASMC MMP-2,9,TIMP-1,Collagenâ… -a 1,Collagenâ…£-a 1 mRNA.Conclusion1. Pneumonectomy plus MCT injection can induce severely pulmonary hypertension characterized by neoimtima formation.2. Mechanisms of AnglI induced pulmonary vascular remodeling were probalbly related to its action on the regulation of cell proliferation and apoptosis as well as ECM component changes. In addition to its effect as a mitogen, it induces MMPs expression and activity which is also mediated by AT1 receptor and may play an important role in the development of vascular remodeling,3. ACEI and AT₁ receptor antagonist can suppress vascular remodeling and therefore prevent the development of pulmonary hypertension. ACEI and AT₁ receptor antagonist are valuable pharmatheutics in the treatment and prevention of pulmonary artery pressure, but their combained use does not result in effect summation or synergistic effect..