Autophagy activation and the mechanism of retinal microvascular endothelial cells in hypoxia

To explore the state of autophagy and related mechanisms in the murine retinal microvascular endothelial cells (RMECs) under hypoxia stimulation.

The murine RMECs were primarily cultured and randomly divided into three groups: hypoxia group (cultured in 1% O₂ environment), hypoxia+autophagy inhibition group [pretreated with 5 mmol/L 3-methyladenine (3-MA) for 4h followed by incubation in 1% O₂] and control group (cultured under normoxic condition). The state of autophagy in RMECs was examined by assaying the turnover of light chain 3B (LC3BB) and expression of Beclin-1, Atg3 and Atg5 proteins with Western blotting, by detecting formation of autophagosomes with transmission electron microscopy (TEM) and by counting the number of GFP+ puncta in RMECs. The protein levels of AMPK, P-AMPK, Akt, P-Akt, m-TOR and P-mTOR were also assayed by Western blotting.

Primary murine RMECs were successfully cultured. Under hypoxic conditions, the ratio of LC3BB-II/I and the expression of Beclin-1, Atg3 and Atg5 proteins were increased when compared with the control group. In addition, the numbers of autophagosome and the GFP+ puncta were also increased under hypoxia. However, pre-treatment with 3-MA obviously attenuated these changes in autophagy in RMECs under hypoxia. Protein expression of P-Akt and P-AMPK was increased but P-mTOR level was decreased in cells exposed to hypoxia.

In murine RMECs autophagy is activated under hypoxia possibly through activation of the AMPK/mTOR signaling pathway.