The protective effects of melatonin in high glucose environment by alleviating autophagy and apoptosis on primary cortical neurons

Abstract Cognitive dysfunction has been regarded as a complication of diabetes. Melatonin shows a neuroprotective effect on various neurological diseases. However, it’s protective effect on cortical neurons in high glucose environment has not been reported. Our present study aims to observe the protective effect of melatonin on rat cortical neurons and its relationship with autophagy in high glucose environment. The rat primary cortical neurons damaged model was induced by high glucose. The CCK-8, flow cytometry, Western Blot and immunofluorescence methods were used to examine the cell viability, apoptosis rate and proteins expression. Our results showed that there were no differences in cell viability, apoptosis rate, and protein expression among the control MLT and mannitol group. The cell viability of the glucose group was significantly lower than that of the control group, and the apoptosis rate of the glucose group was significantly higher than that of the control group. Compared with the glucose group, the glucose + melatonin group showed a significant increase in cell viability and a notable decrease in apoptosis rate. Melatonin concentration of 0.1-1 mmol/L can significantly reduce the injury of cortical neurons by high glucose. Compared with the control group, the glucose group showed a significant reduction of Bcl-2 protein expression, while remarkable elevations of Bax, caspase-3, Beclin-1 and LC3B levels. The neurons pre-administered with melatonin obtained significantly reversed these changes induced by high glucose. The phosphorylation levels of Akt and mTOR in the glucose group were significantly lower than those in the control group, were significantly increased in the glucose + MLT group compared with the glucose group. These data indicated that melatonin has a neuroprotective effect on cortical neurons under high glucose environment, which may work by activating Akt/mTOR pathway and following the down-regulation of autophagy.