| Acute myocardial infarction(AMI)is a major cause of morbidity and mortality worldwide.With the development and application of PCI,the mortality rate of AMI was decreased significantly.However,due to acute myocardial infarction caused by myocardial necrosis and cardiomyocytes were unable to regenerate,cardiac ventricular remodeling was then occurred,leading to myocardial fibrosis,left ventricular expansion and decreased cardiac output,ultimately,it progressed to heart failure.Therefore,how to maintain the survival of ischemic cardiomyocyte has become the key to improve the prognosis of AMI.Apoptosis is an important form of cell death,which is intrinsically programmed by genes regulation.Apoptosis is one of the important factors that induces cardiomyocyte loss after AMI.A large number of studies has confirmed that inhibition of myocardial apoptosis can reduce the loss of cardiomyocyte caused by MI and also improve cardiac function after MI.It is well known that the renal sympathetic denervation(RSD)is a new method for the treatment of resistant hypertension.Previous studies have shown that RSD can inhibit the excessive activation of the renin-angiotensin-aldosterone system(RAAS),reduce sodium retention and improve cardiac function.It has also been reported that RSD can improve the myocardial remodeling after MI and the prognosis of patients.However,whether RSD has the ability to improve cardiac function by reducing myocardial apoptosis after MI,and the related mechanisms have not been studied clearly.Part I Effect of renal sympathetic denervation on RAAS and cardiac function after myocardial infarctionObjective:To investigate the impact of renal sympathetic denervation on RAAS,myocardial remodeling and cardiac function post myocardial infarction.Methods:64 male Sprague-Dawley rats were anesthetized with pentobarbital.RSD was performed through stripping and cutting all the renal arteriovenous adventitial sympathetic nerve,then moistening the local tissues with 10%phenol/ethanol solution.3 days later,MI was induced by ligating the left anterior descending branch.Afterwards,they were randomly assigned to Sham group(Sham,n =16),RSD group(RSD,n=16),Sham+MI group(MI occurred three days after sham denervation,n=16),RSD+MI(M1 occurred three days after RSD,n=16).4 weeks after MI induction,left ventricular end diastolic diameter(LVEDD),left ventricular end systolic diameter(LVESD),LV ejection fraction(LVEF)and left ventricular fractional shortening(LVFS)were measured by transthoracic echocardiography.The left ventricular systolic pressure(LVSP),left ventricular end-diastolic pressure(LVEDP),maximal rate of left ventricular pressure(dP/dtmax)and minimal rate of left ventricular pressure(dP/dtmin)were measured with a Millar Microtip catheter inserted into the right carotid artery and advanced into the LV.ELISA kits were used to measure levels of plasma aldosterone(ALD),angiotensin II(Ang II)and noradrenaline(NE).The size of infarction and collagen volume fraction(CVF)of non-infarction myocardium were assessed or calculated with compute-assisted image analysis system(Image-Pro Plus)after immunohistochemistry staining.Results:Four weeks after MI,rats LVEDD in RSD+MI group was significantly decreased compared with that of the Sham+MI group(P<0.01),whilst LVEF and LVFS were significantly improved(P<0.01).The decrease of LVSP,dP/dtmax and dP/dtmin in RSD+MI group was significantly attenuated compared with those of the Sham+MI group,and a significant increase was shown in LVSP(P<0.05).Compared with the values in the sham group or the RSD group,the plasma levels of NE,Ang II and ALD significantly increased in the sham+MI group(P<0.01).NE,Ang II and ALD in the RSD+MI group were significantly decreased compared with those of the sham+MI group(674.33±38.01 VS 1421.62±301.11,211.94±21.0 VS 1032.79±251.86,311.8139.1 VS 1103.69±326.28,respectively,all P<0.01).The area of MI in the RSD + MI group was smaller than that in the sham + MI group,but there was no significant difference(36.9 + 1.8%VS 38.3 + 2.1,P>0.05).The collagen volume fraction(CVF)of non-infarction myocardium was substantially higher in the sham+MI group than that of the RSD+MI group(7.83%± 0.85%VS 6.35%±1.24%;P<0.01).Conclusions:RSD can substantially reduce the myocardial remodeling and improve cardiac function in rats after AMI.Partn ? Experimental study of RSD on myocardial apoptosis after myocardial infarctionObjective:To explore the effects of RSD on myocardial apoptosis after myocardial infarction.Methods:64 male Sprague-Dawley rats were anesthetized with pentobarbital.Surgical and chemical RDNs were approached,then MI was induced by surgical ligation of proximal left anterior descending coronary.Afterwards,they were randomly assigned to Sham group(Sham,n =17),RSD group(RSD,n=17),Sham+MI group(MI occurred three days after Sham denervation,n=17),RSD+MI(MI occurred three days after RSD,n=17).After 4 weeks,TUNEL assay was carried out to calculate the apoptotic cardiomyocytes as the percentage of apoptotic nuclei/total number of nuclei.The mRNA expression levels of bax,bcl-2 and caspase-3 in the LV non-infarct areas were evaluated using real-time PCR.Western blot analysis was used to evaluate the protein expression levels of bax,bcl-2 and caspase-3.Results:The level of apoptosis in the RSD+MI group was significantly lower compared with that in the sham+MI group(11.5±1.12%VS 18.511.33%,P<0.01).Both mRNA levels of bax and caspase-3 in the RSD+MI group were significantly lower than that in the sham+MI group(1.73±0.41 VS 2.49±0.39,1.78±0.14 VS 2.67±0.23,respectively,all P<0.01),while the mRNA level of bcl-2 was higher than that in the RSD+MI group(0.63±0.10 VS 0.33±0.09,P<0.01).Expression changes of three proteins were concordant with their mRNA levels.Both levels of bax and cleaved caspase-3 in the RSD+MI group were significantly lower than those in the sham+MI group(0.58±0.02 VS 0.79±0.10,0.45±0.05 VS 0.62±0.13,respectively,all P<0.01),while Bcl-2 level was significantly increased in the RSD+MI group compared with that in the sham+MI group(0.54±0.04 VS 0.36±0.02,P<0.01).Conclusions:Renal sympathetic denervation can obviously attenuate myocardial apoptosis after myocardial infarction in rats.Part ? Experimental Study of Molecular Mechanism of Renal Sympathetic Denervation on Attenuating Myocardial Apoptosis after Myocardial Infarction Objective:To investigate the relevant molecules mechanisms of RSD on myocardial apoptosis after myocardial infarction.Methods:64 male Sprague-Dawley rats were anesthetized with pentobarbital to establish the RSD model.After 3 days,acute myocardial infarction model was built.Afterwards,they were randomly assigned to Sham group(Sham,n =16),RSD group(RSD,n=16),Sham+MI group(MI occurred three days after Sham denervation,n=16),RSD+MI(MI occurred three days after RSD,n=16).After 4 weeks,the expression of miRNA-133 in rats' cardiomyocyte was detected by RT-PCR.The mRNA expression level of TGF-?1 in the non-infarct areas of LV were evaluated using real-time PCR.Western blot analysis was used to evaluate the protein expression level of TGF-?1.Results:The level of miRNA-133 in the Sham+MI and RSD+MI groups was significantly lower than that in the sham and RSD groups in the non-infarct areas of LV.Compared with that in the sham+MI group,the level of miRNA-133 in RSD+MI group was significantly increased(0.58±0.04 VS 0.28±0.03,P<0.01).Both mRNA and protein levels of TGF-?1 in Sham+MI and RSD+MI groups were higher than those in the sham and RSD groups in the non-infarct areas of LV.The mRNA and protein levels of TGF-?1 in the RSD+MI group were significantly lower than those in the sham+MI group(1.76±0.08 VS 2.99±0.30,0.73±0.03 VS 0.91 ±0.03,respectively,all P<0.01).Conclusions:Renal sympathetic denervation can obviously increase the expression of miRNA-133 whilst decrease the expression of TGF-?1.This may be one of the molecular mechanisms by which RSD can attenuate the myocardial apoptosis after myocardial infarction in rats. |
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