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.