Role of autophagy in myocardial injury induced by Akt/HIF-1α signaling pathway in I/R rats

Objective: To investigate the role of autophagy in myocardial injury induced by protein kinase B(Akt)/ hypoxia inducible factor 1-α(HIF-1α) signaling pathway in rats with ischemia/reperfusion(I/R). Methods: The H9c2 cells were divided into the control(Con) group,hypoxia/reoxygenation(H/R) group and H/R+human insulin-like growth factor 1(IGF-1) group.The autophagy flux of cells in each group was evaluated by using mCherry-GFP-LC3 adenovirus.The nuclear translocation of HIF-1α was analyzed by immunofluorescence and Western blotting.Rats were randomly divided into the sham operation group,I/R group and I/R+IGF-1 group.I/R models were established in other groups except sham operation group.Five minutes before modeling,the IGF-1(Akt agonist,dosage 20 mg/kg) were intraperitoneally injected into rats in the I/R+IGF-1 group.Cardiac function was evaluated by echocardiography.Evans blue (EB)/2,3,5-triphenyltetrazole staining(TTC) was used to estimate the infarct area.Quantitative Western blotting was used to analyze the autophagy-related proteins. Results: The increasing of LC3Ⅱ and p62 protein levels were induced by H/R,and the increasing of LC3Ⅱ and p62 spots was partially eliminated by IGF-1 pretreatment(P<0.05).Compared with the control group,the fluorescence intensity ratio and protein expression of HIF-1α nucleus/cytoplasm in H9c2 cells of H/R group increased significantly(P<0.05),and the fluorescence intensity ratio and protein expression of HIF-1α nucleus/cytoplasm in H9c2 cells of H/R+IGF-1 group were further increased(P<0.05).Compared with the control group,the apoptosis rate of H9c2 cells in H/R group increased significantly(P<0.05),while the pretreatment of IGF-1 reversed the apoptosis of H9c2 cells induced by H/R (P<0.05).After 24 hours of reperfusion,compared with I/R group,the area of myocardial infarction in I/R+IGF-1 group decreased significantly (P<0.05).In addition,after 7 days of reperfusion,the left ventricular ejection fraction and shortening rate in the I/R group were significantly lower than those in sham operation group(P<0.05),which could be partially reversed by IGF-1 treatment (P<0.05).Compared with I/R group,the protein expressions of LC3-Ⅱ/LC3-Ⅰ and P62 were significantly down-regulated(P<0.05),and the expressions of Akt and HIF-1α were significantly up-regulated in I/R+IGF-1 group(P<0.05). Conclusions: Activation of Akt/HIF-1α pathway can alleviate the myocardial I/R injury by improving the impaired autophagy flux,which provides a new insight into the cardioprotective effect of autophagy.