Hypoxia-induced autophagy in endothelial cells: a double-edged sword in the progression of infantile haemangioma?

The aim of this study was to investigate the precise role of hypoxia-induced autophagy in endothelial cells, and whether it contributes to the distinctive progression of infantile haemangioma (IH). The endothelial cells (EOMA and HUVECs) were cultured under hypoxic conditions for indicated times (072 h). The results showed that short exposure of the endothelial cells to hypoxia resulted in increased cell survival and proliferation, accompanied by occurrence of autophagy. Prolonged hypoxia-induced autophagy, correlating with increased cell death, was also detected afterwards. Correspondingly, autophagy inhibition prevented the enhanced cell survival and proliferation capacity, advanced the occurrence of cell-death in early hypoxic stage, and meanwhile attenuated the ability of prolonged hypoxia in cell-death induction. Moreover, our data demonstrated that the functional transformation of hypoxia-induced autophagy, pro-survival to pro-death, was rigorously regulated by the switch between hypoxia-inducible factor-1 (HIF-1) and mammalian target of rapamycin (mTOR) pathways. Importantly, we also revealed the activation levels of HIF-1 and mTOR, as well as the autophagy status during the progression of IH. This study unmasks the functional switch between HIF-1 and mTOR in regulating hypoxia-induced autophagy in endothelial cells and, more importantly, indicates its potential role in the progression of IH.