| Myocardial infarction(MI)is caused by the formation of plaque on the inner wall of the artery,which reduces blood flow to the heart and do damage to the myocardium due to ischemia and hypoxia.MI is the main cause of death of cardiovascular disease patients worldwide,and it brings a huge burden to human health and economy.For patients with acute MI,timely and effective myocardial reperfusion therapy including thrombolytic therapy and percutaneous coronary intervention is the main treatment option at present.However,MI often causes decreased heart function and arrhythmia,which seriously affect the prognosis of patients.In recent years,studies have shown that inflammation is one of the important reasons leading to the abnormal structure and function of the cardiovascular system,and a variety of inflammatory factors are closely related to the occurrence and development of cardiovascular diseases.Decreased heart function and arrhythmia after MI is a process of multiple mechanisms working together.Inflammatory factors such as TNF-α,IL-lb and IL-6 can aggravate the sympathetic nerve remodeling and myocardial remodeling after MI,so the inflammatory response plays an important role in heart failure and arrhythmia after MI.In addition,JAK2/STAT3 and Smad2/3signaling pathway were significantly activated in infarcted cardiomyocytes and cardiac interstitial cells,thus stimulating the synthesis of matrix proteins.Therefore,it is of great significance to explore the application of anti-inflammatory and antifibrotic drugs to improve the heart function of patients and reduce the susceptibility to arrhythmia.Urolithin B(UB)is the most biologically active intestinal metabolite of ellagitannin,which has powerful anti-inflammatory and antioxidant effects.Therefore,we tend to study the specific mechanism of UB to improve cardiac function and arrhythmia after MI and hope to provide a new theoretical basis for the treatment of clinical MI by using UB to in the rat model of MI and observing the occurrence of cardiac function and arrhythmia in each group of rats.Part Ⅰ The effect and mechanism of urolithin B in improving cardiac function after myocardial infarction Objective:To investigate the cardiac function after myocardial infarction(MI)in rats,and to detect the improvement of cardiac function in rats with myocardial infarction before and after the effect of urolithin B(UB).Method:1.Experimental grouping: 40 SD rats were randomly selected and divided into four groups,10 in each group,namely the(1)sham group(only thoracotomy without causing MI),(2)MI group,(3)MI + UB group(2.5 mg/kg/day),(4)MI + UB group(5.0mg/kg/day).2.Construction of rat MI model: After the rat was anesthetized,a ventilator was given to assist breathing.The anterior descending coronary artery was ligated between the left atrial appendage and the pulmonary artery cone at a distance of 3mm from the aortic root.Penicillin was injected intramuscularly every day after surgery to prevent infection.3.Using echocardiography to detect the level of cardiac function of each group after MI.4.Using HE staining,WGA staining,Masson trichrome staining and collagen I staining to detect the heart structure of rats in each group.5.qPCR and Elisa were used to detect the effects of intraperitoneal injection of UB(5.0 mg/kg/day)on the levels of inflammatory factors TNF-α,IL-6 and IL-10 in rats with myocardial infarction.6.Western blot(WB)analysis was used to detect the effect of intraperitoneal injection of UB(5.0 mg/kg/day)on JAK/STAT3 and Smad2/3 signaling pathways in rats with myocardial infarction.Results:1.The level of cardiac function in the MI group was significantly lower than that in the sham operation group(P<0.05).2.The levels of cardiac fibrosis and inflammation factors in the MI group were higher than those in the sham operation group.3.Compared with rats in the MI group,2.5 mg/kg/day U B treatment has no significant effect on the LVEDD,EF%,FS% or d P/dt min of myocardial infarction rats,but it can increase d P/dt max and inhibit the secretion of BNP.However,5.0mg/kg/day UB can fully inhibit the changes in the above-mentioned cardiac function indicators.4.Compared with rats in the MI group,the level of cardiac tissue fibrosis in the5.0 mg/kg/day UB treatment group was significantly lower.5.Compared with the rats in MI group,the rats in the MI + UB(5.0 mg/kg/day)group showed decreased TNF-α and IL-6,and increased IL-10 levels(P<0.05).6.Compared with rats in MI group,treatment with 5.0 mg/kg/day UB can significantly inhibit the phosphorylation levels of JAK/STAT3 and Smad2/3 pathways in rats.Conclusion:MI can significantly reduce the cardiac function of rats,and lead to increased fibrosis and inflammation in cardiomyocytes.After treatment with 5.0 mg/kg/day UB,the cardiac function of rats with MI were significantly improved.Moreover,compared with the control group,UB can reduce the degree of fibrosis and proinflammatory factors in the ventricular ischemic area and increase of antiinflammatory factors.Besides,UB partly played a role through the JAK/STAT3 and Smad2/3 pathways.Part Ⅱ The effect and mechanism of urolithin B in reducing the susceptibility of arrhythmia after myocardial infarctionObjective:To investigate the occurrence of arrhythmia in animal model of MI,and to detect the change of arrhythmia susceptibility in MI rats model after the treatment of UB.In addition,we studied the effects and specific mechanisms of UB on cardiomyocyte apoptosis,gap junction and sympathetic nerve remodeling by hypoxia stimulation in vitro.Method:1.Experimental grouping in vivo: 30 SD rats were randomly selected and divided into three groups,10 in each group,namely sham operation group(only thoracotomy without causing MI),MI group,MI + UB group(5.0 mg/kg/day).In vitro experimental grouping: Cardiomyocytes from neonatal mice were cultured in conventional incubator,hypoxia incubator or hypoxia + UB.2.Construction of rat MI model: After the rat was anesthetized,a ventilator was given to assist breathing.The anterior descending coronary artery was ligated between the left atrial appendage and the pulmonary artery cone at a distance of 3mm from the aortic root.Penicillin was injected intramuscularly every day after surgery to prevent infection.3.Connecting rats to the electrocardiograph and recording the electrocardiogram waveform of each group,and comparing the changes of P wave and QJ interval of each group of rats.4.Using Langendorff perfusion heart system to detect the susceptibility to ventricular arrhythmia after MI in rats,and recording the number of ventricular tachycardia and ventricular fibrillation in rats within 3 minutes.5.The levels of cardiomyocyte apoptosis,gap junction and sympathetic nerve remodeling of rats model were detected by WB.6.The levels of cardiomyocyte apoptosis,gap junction and sympathetic nerve remodeling of control and hypoxia stimulation groups were evaluated by q PCR and WB.7.The levels of cardiomyocyte apoptosis,gap junction and sympathetic nerve remodeling in hypoxia stimulation groups and hypoxia + UB treatment group were evaluated by q PCR and WB.8.The effects of UB treatment on Akt/m TOR pathway and NF-κB nuclear translocation in cardiomyocytes from neonatal mice were analyzed by q PCR and WB.Results:1.Compared with the sham operation group,the electrocardiogram of the rats in the MI group showed that significantly prolonged P wave and QJ interval,and UB treatment could reverse this change.2.The frequency of ventricular arrhythmia in rats after MI was significantly increased,and UB treatment can reduce the frequency of arrhythmia after MI.3.Compared with the sham operation group,the protein levels of bcl2 and CX43 decreased,while the protein levels of Bax,caspase3,TH and GAP43 increased in the MI group.4.Compared with the conventional oxygen culture group,hypoxia culture can increase the apoptosis rate,IL-6,TH and GAP43 levels of cardiomyocytes and inhibite the expression of CX43.However,UB treatment can inhibit the changes of these indexes.5.Compared with cardiomyocytes cultured in hypoxia group,the addition of UB significantly activated Akt/m TOR pathway and effectively inhibited NF-κB nuclear translocation.Conclusion:MI can significantly promote the occurrence of ventricular arrhythmia in rats model,and lead to the increase of proinflammatory factors,cell apoptosis,sympathetic nerve remodeling and gap junction changes.After treatment with UB,the frequency of ventricular arrhythmia in MI rats was reduced.Besides,UB can significantly inhibite the the apoptosis level caused by MI or hypoxia and inhibit sympathetic nerve remodeling and promote gap junction remodeling partly through the Akt/m TOR and NF-κB signal pathway. |
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