Enhanced autophagy by everolimus contributes to the antirestenotic mechanisms in vascular smooth muscle cells.

OBJECTIVE: The present study aims to investigate the underlying mechanisms accounting for the activities of everolimus to inhibit the growth of vascular smooth muscle cells (VSMCs), which contributes to restenosis.

METHODS: Primary VSMCs were cultured in media containing smooth muscle growth supplements and incubated with testing agents. Cell proliferation, cell cycle distribution, apoptosis and autophagy, and the key molecules involved, were examined.

RESULTS: Everolimus inhibited the proliferation of VSMCs by inhibiting the activation of ribosomal protein S6 kinase and phosphorylation of eukaryotic translation initiation factor 4E-binding protein 1, and downregulating proliferating cellular nuclear antigen. Everolimus induced cell cycle arrest at the G1 phase by downregulating cyclin D1 and upregulating p27, and increased apoptosis by downregulating Bcl-2, upregulating Bad and activating capsase-3 and poly ADP ribose polymerase. Everolimus enhanced autophagy by increasing the conversion of microtubule-associated protein 1 light chain 3 (LC3)-I to LC3-II, and upregulating Beclin 1. Specific autophagy inhibitors, 3-methyladenine and bafilomycin A1, significantly attenuated the inhibition of cell proliferation, the increased apoptosis and the altered expression of the above key proteins induced by everolimus.

CONCLUSIONS: Enhanced autophagy by everolimus contributes to its antirestenotic activity and its abilities to inhibit cell proliferation and to induce apoptosis of VSMCs.