Ghrelin inhibits autophagy mediated by AKT/mTOR pathway to ameliorate retinal angiogenesis induced by high glucose stress

To observe the effect of ghrelin, a growth hormone-releasing peptide, on retinal angiogenesis in vitro under high glucose (HG) stress and to explore the possible mechanism of autophagy.

Human retinal microvascular endothelial cells (HRMECs) were treated with high concentration of glucose alone or in combination with ghrelin. The cell migration, tube formation and the expression of the autophagy-related proteins LC3-Ⅱ/Ⅰ, Beclin-1, p62, phosphorylated AKT (p-AKT)/AKT and phosphorylated mammalian target of rapamycin (p-mTOR)/mTOR were detected. Then, to clarify the correlation between ghrelin effect and autophagy, AKT inhibitor Ⅷ was adopted to treat HRMECs, and cell migration, tube formation as well as the protein expressions of LC3-Ⅱ/Ⅰ, Beclin-1 and p62 were observed.

Under HG stress, ghrelin inhibited migration and tube formation of HRMECs. Ghrelin inhibited the increases in the protein levels of LC3-Ⅱ/Ⅰ, Beclin-1 and the decreases in the protein levels of p62, p-AKT/AKT and p-mTOR/mTOR induced by HG stress. Moreover, under the action of AKT/mTOR pathway inhibitors, the effects of ghrelin on migration and tube formation were both reduced. In addition, the expression of LC3-Ⅱ/Ⅰ and Beclin-1 were significantly up-regulated and the expression of p62 was down-regulated.

Retinal angiogenesis under in vitro HG stress can be inhibited by ghrelin through activating AKT/mTOR pathway to inhibit autophagy.