Neuroprotective effect of G14-humanin on global cerebral ischemia/reperfusion by activation of SOCS3-STAT3-MCL-1 signal transduction pathway in rats

Objective: Humanin (HN) has been identified to suppress neuron death. Gly(14)-HN (HNG), as a variant of HN, can decrease infarct volume after ischemia/reperfusion (I/R) injury. This study aimed to investigate the neuroprotective mechanism of HNG on global cerebral I/R (GI) in rats. Methods: Rats were randomly divided into 13 groups: Sham group, GI groups and HNG groups. Both GI group and HNG groups included six time points (1, 3, 6, 12, 24, and 72 h). At 24 h after reperfusion, Nissl staining was used to observe positive neurons, and p-STAT3, MCL-1, SOCS3, Bax and Caspase-3 in different groups were detected by immunohistochemistry. qRT-PCR and western blot were used to evaluate the expression of STAT3, p-STAT3, MCL-1, and SOCS3. Results: The immunohistochemistry also showed a significant increase in Bax (0.29 +/- 0.007 vs. 0.22 +/- 0.007, P < 0.01) and Caspase-3 (0.24 +/- 0.02 vs. 0.18 +/- 0.006, P < 0.01) in GI group compared with Sham group, while Bax (0.26 +/- 0.01 vs. 0.29 +/- 0.008, P < 0.01) and Caspase-3 (0.20 +/- 0.008 vs. 0.24 +/- 0.02, P < 0.01) were significantly decreased by HNG-treatment compared with GI group. Along with immunohistochemistry, western blot and qRT-PCR indicated that the protein and mRNA levels of STAT3, MCL-1, and SOCS3 were up-regulated after administration of HNG at six time points after global cerebral I/R in rat. Conclusion: HNG might exert neuroprotective effects through alleviating apoptosis and activating of SOCS3 - STAT3 - MCL-1 signal transduction pathway.