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Objective: To investigate the effect and mechanism of atorvastatin on myocardial fibrosis in rats after acute myocardial infarction.Methods: Healthy male Sprague Dawley rats were used and anesthesiaed by intraperitoneal injection of chloral hydrate(10%). After endotracheal intubation, thoracotomy was performed, MI group was produced by ligation of anterior descending coronary artery, the sham group underwent the same procedure without coronary artery ligation. They were assigned randomly to intragastrically receive atorvastatin (10 mg/ kg/d), named MI intervention group, or saline, named MI group, 24 hours after surgery for 5 weeks. A total of 20 rats survived after 5 weeks, 6 rats were in sham group, 6 rats were in MI intervention group and 8 rats were in MI group. The rats were killed and left ventricle weight weighed. Non-infarcted left ventricular myocardium was taken and frozed in liquid nitrogen. The concentration of O2- and the activity of NADPH oxidase were measured by WST-1, the expression level of gp91phox mRNA, p22phox mRNA, MMP-2 mRNA and MMP-9 mRNA were detected with RT-qPCR, and the content of myocardial collagen was measured with Coomassie brilliant blue.Results: 1. Left ventricular mass index (LVMI)was (3.18±0.33) mg/g in MI group, sham group was (2.69±0.21) mg/g, there was significant difference between the two groups(P<0.01). MI intervention group was (2.94±0.17) mg/g, reduced significantly than MI group(P<0.01), but without significance compared with sham group (P>0.05). Left ventricular weight and body weight were not statistically significant among MI group, sham group and MI intervention group (P>0.05).2. (1)The concentration of superoxide anion(O2-) and the activity of NADPH oxidase were (12550.47±7726.33)RLU/mg and (4.98±0.65)RLU/mg respectively in MI group, significantly increased compared to sham group [ ( 2181.01±236.8 ) RLU/mg and (2.62±0.29)RLU/mg respectively] (P<0. 01). The concentration of superoxide anion and the activity of NADPH oxidase in MI intervention group were (4145.96±1229.83)RLU/mg and (3.33±0.44)RLU/mg respectively, significantly decreased than MI group(P<0.01), increased than sham group,but there was no significant difference in the concentration of superoxide anion between the MI intervention group and sham group. (2) The expression level of gp91phox mRNA in MI group was [2.73±0.78] times than sham group, significantly different between the two groups (P<0.01), the expression level of gp91phox mRNA in MI group was [1.37±0.39] times than MI intervention group, significantly decreased(P < 0.05). The expression level of gp91phox mRNA in MI intervention group was [2.13±0.90] times than sham group, there was statistical difference also(P<0.01). The expression level of p22phox mRNA in MI group was [23.42±7.06] times than sham group, significantly different between the two groups(P<0.01), the expression level of p22phox mRNA in MI group was [4.16±2.10] times than MI intervention group, the latter group decreased significantly(P<0.01). The expression level of p22phox mRNA in MI intervention group was [6.68±3.49] times than sham group, there was statistical difference also(P<0.01). (3)The concentration of O2- positively correlated to the activity of NADPH oxidase(R=0. 865,P<0.01), the expression level of gp91phox mRNA(R=0.656,P<0.01) and p22phox mRNA (R=0.449,P<0.05).3. The expression level of MMP-2 mRNA in MI group was [29.14±9.33] times than sham group, significantly different between the two groups(P<0. 01), the expression level of MMP-2 mRNA in MI group was [3.78±1.24] times than MI intervention group, the latter group decreased significantly(P<0.01). The expression level of MMP-2 mRNA in MI intervention group was [8.37±3.18] times than sham group, there was statistical difference also(P<0.01). The expression level of MMP-9 mRNA in MI group was [4.94±0.66] times than sham group, significantly different between the two groups(P<0. 01). The expression level of MMP-9 mRNA in MI group was [2.52±0.50] times than MI intervention group, the latter group decreased significantly(P<0.01). The expression level of MMP-9 mRNA in MI intervention group was [1.99±0.28] times than sham group, there was statistical difference also(P<0.01). (2) The expression level of MMP-2 mRNA and MMP-9 mRNA positively correlated to the concentration of O2- (R=0.676,P<0.01;R=0.700,P<0.01).4. The content of hydroxyproline and collagen content were (1.97±1.03)μg/mg and (14.72±7.67)μg/mg respectively in non-infarcted myocardium in sham group, and (9.82±1.52)μg/mg and (73.26±11.37)μg/mg respectively in MI group, there was significant difference between the two groups(P < 0.01), while the content of hydroxyproline and collagen content were (6.23±1.38)μg/mg and(46.46±10.3)μg/mg respectively in MI intervention group, significantly increased than sham group(P<0.01) and significantly decreased than MI group(P<0.01). The concentration of O2- positively correlated to the content of collagen content(R=0.648,P<0.01).Conclusion: 1. The concentration of superoxide anion, the activity of the NADPH oxidase, the expression level of gp91phox and p22phox mRNA in MI group increased significantly compared to sham group, and the concentration of O2- positively correlated to the activity of NADPH oxidase, the expression level of gp91phox and p22phox mRNA. The concentration of the superoxide anion, the activity of NADPH oxidase, the expression level of gp91phox and p22phox mRNA in non-infarcted left ventricular myocardium in MI intervention group decreased significantly than MI group. This illustrates that atorvastatin reduces the production of O2- by inhibiting NADPH oxidase activity and its expression.2. The expression level of MMP-2 and MMP-9 mRNA in MI group were significantly higher than sham group, while the expression level of MMP-2 and MMP-9 mRNA in MI intervention group significantly decreased than MI group. Besides they positively correlated to the concentration of O2-. This indicates that atorvastatin decreases the expression of MMP-2 and MMP-9 mRNA by inhibiting O2-.3. The content of hydroxyproline, collagen content and LVMI in MI group were significantly higher than sham group, while MI intervention group was significantly decreased than MI group, which demonstrates that atorvastatin decreases the concentration of O2- ,and thereby relieves myocardial fibrosis and left ventricular remodeling after MI.
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