The Mechanism Of Apigenin Protects Isolated Rat Hearts Against Anoxia/reoxygenation Injury

Background and Objective:Apigenin is a type of flavonoids,which has been demonstrated to protect myocardium against ischemia/reperfusion（I/R）injury.However,the mechanism is still unclear.We hypothesized that the mechanism of cardioprotective action of apigenin on the I/R-induced injury might be caused via B cell lymphoma（Bcl）signaling pathway.Methods:30 of 250-300g healthy adult male SD rats were divided into five groups at random:Control group,Anoxia/reoxygenation（A/R）group,A/R+Api group,A/R+Api+ABT-737 group and A/R+ABT-737 group.The intraperitoneal injection of Api（2,4,8mg/kg）and/or ABT-737（20μmol/kg）were given to rats of the groups of A/R+Api,A/R+Api+ABT-737 and A/R+ABT-737 24h before the establishment of the isolated myocardial ischemia/reperfusion model.Control group was injected with the same amount of normal saline.Power Lab was used to collect the data of systolic blood pressure,heart rate and maximum rate of rise/fall of left ventricular pressure(dp/dt_max)isolated rat hearts.Triphenyltetrazolium chloride（TTC）was used to investigate infarct size of isolated rat hearts.Collection of perfusion fluid for detection of the concentration of lactate dehydrogenase（LDH）adn creatine kinase（CK）.Western blotting was used to investigate the expression level of Bcl-2,caspase-3 and cytochrome c.Terminal dexynucleotidyl transferase（TdT）-mediated dUTP nick end labeling（TUNEL）was used to observe the level of apoptosis of myocardium.Results:（1）Compared with the control group,the concentration of LDH and CK in A/R group was significantly increased in the isolated perfused rat hearts（p<0.01）.Compared with A/R,the concentration of LDH and CK in the isolated perfused rat hearts of apigenin was significantly lower than that in the isolated perfused rat hearts.And the effect was best when the dose was 4mg/kg.But in the intervention group,the effect of apigenin was diminished（p<0.05）.（2）Compared with the control group,the systolic blood pressure,heart rate and dp/dt_maxax was significantly decreased in the isolated perfused rat hearts（p<0.01）.Compared withthe A/R group,the indexes of the heart function in apigenin group could be improved significantly（p<0.05）.But in the intervention group,the effect of apigenin was diminished（p<0.05）.（3）Compared with the control group,the infarct size of the isolated rat heart increased significantly after A/R（p<0.01）.The apigenin intervention group could significantly reduce the infarct size induced by A/R（p<0.05）.Compared with the apigenin intervention group,the effect of the reduction of the infarct size was significantly decreased in the ABT-737 intervention group（p<0.05）.（4）Compared with the control group,the protein expression of Bcl-2 in isolated rat hearts was down regulated by A/R（p<0.01）.In the apigenin intervention group,the expression of Bcl-2 protein was significantly up regulated（p<0.05 VS A/R group）.But compared with the apigenin intervention group,the Bcl-2 protein expression was up-regulated in the ABT-737 ntervention group（p<0.05）.（5）Compared with the control group,the protein expression of full-length caspase-3 and the activity of caspase-3 in isolated rat hearts were down regulated and the expression of cleaved caspase-3 was up regulated by A/R（p<0.01）.In the apigenin intervention group,the expression of full-length caspase-3 protein was significantly up regulated and the cleaved was down regulated（p<0.05 VS A/R group）.But compared with the apigenin intervention group,the full-length caspase-3 protein expression was down regulated and the cleaved was up regulated in the ABT-737 ntervention group（p<0.05）.（6）Compared with the control group,the protein expression of cytochrome c in cytosol in isolated rat hearts was up regulated by A/R（p<0.01）.In the apigenin intervention group,the expression of cytochrome c in cytosol was significantly down regulated（p<0.05 VS A/R group）.But compared with the apigenin intervention group,the cytochrome c expression in cytosol was up regulated in the ABT-737 ntervention group（p<0.05）.（7）Compared with the control group,the number of apoptotic cells in A/R group was significantly increased（p<0.01）.The apoptosis of the isolated heart of the rats in the apigenin intervention group was significantly decreased（p<0.05 VS A/R group）.But ABT-737could significantly inhibit the effect of apigenin’s inhibition of the apoptosis of the cells（P<0.05）.Conclusion:1.Apigenin has a protective effect on A/R damage in isolated rat heart.2.The effect of apigenin against A/R injury in cardiomyocytes involves Bcl-2signal pathway,and at least partly depends on its effect of upregulating the expression of Bcl-2.