Defective autophagy triggered by arterial cyclic stretch promotes neointimal hyperplasia in vein grafts via the p62/nrf2/slc7a11 signaling pathway

Autophagy is an adaptation mechanism to keep cellular homeostasis, and its deregulation is implicated in various cardiovascular diseases. After vein grafting, hemodynamic factors play crucial roles in neointimal hyperplasia, but the mechanisms are poorly understood. Here, we investigated the impacts of arterial cyclic stretch on autophagy of venous smooth muscle cells (SMCs) and its role in neointima formation after vein grafting. Rat jugular vein graft were generated via the ‘cuff’ technique. Autophagic flux in venous SMCs is impaired in 3-day, 1-week and 2-week grafted veins. 10%-1.25 Hz cyclic stretch (arterial stretch) loaded with FX5000 stretch system on venous SMCs blocks cellular autophagic flux in vitro and shows no significant impact on activity of mTORC1 and AMPK. Microtubule depolymerization but not lysosome dysfunction nor autophagosome/amphisome-lysosomal membrane fusion blockade is involved in the impairment of autophagic flux. Microtubule stabilization, induced by paclitaxel treatment and external stents intervention respectively, restores venous SMC autophagy and ameliorates neointimal hyperplasia in vivo. Moreover, autophagy impairment causes accumulation of the cargo receptor p62, which sequesters keap1 to p62 aggregates and results in the stabilization and nuclear translocation of nrf2 to modulate its target antioxidative gene SLC7A11. p62 silencing abrogates the increases of nrf2 and slc7a11 protein expression, glutathione level and venous SMC proliferation triggered by arterial cyclic stretch in vitro, and further hinders nrf2 nuclear translocation, reduces neointimal thickness after vein grafting in vivo. p62 (T349A) mutation also inhibited venous SMC proliferation and alleviated neointimal formation in vivo. These findings suggest that stabilization of microtubules to rescue autophagic flux or direct silencing of p62 are potential therapeutic strategies for neointimal hyperplasia.