mTOR inhibition modulates apoptosis and oxidative stress in hindlimb ischemia/reperfusion injury

Abstract

Purpose: Ischemia/reperfusion (I/R)-induced injuries represent serious clinical events regarding profound target organ destructions followed by remote organ complications due to the loss of oxidant/antioxidant balance and apoptosis. Recent studies examining the mammalian target of rapamycin (mTOR) during I/R injury in different organs have remained a matter of debate. The current study aimed to explore further the protective and underlying antiapoptotic and antioxidant mechanisms of mammalian target of rapamycin (mTOR) inhibition in hindlimb (HL) schemia/reperfusion (I/R)injury. Materials and Methods: Occlusion of bilateral hindlimbs for 4 h with tourniquets was carried out under anesthesia to induce I/R for 4 h in rats. Rapamycin (1 mg/kg) or saline (4 mL/kg) was injected intraperitoneally 1 h before reperfusion. Gastrocnemius muscle, kidney, and blood were collected at the end of the experiments for analysis. Muscle and kidney damages were evaluated by measuring protein expression and/or phosphorylation of eukaryotic initiation factor 4E-binding protein 1 (4EBP1), ribosomal protein S6 (rpS6), B-cell lymphoma 2 (Bcl-2), caspase-3, and Bcl-2-associated X protein (Bax) with NADPH oxidase level and total antioxidant capacity in tissues or sera. Results: I/R-induced organ damages were demonstrated by enhanced phosphorylation and/or expression of rpS6, 4EBP1, caspase-3, and Bax with a significant reduction in Bcl-2 accompanied by a decreased total antioxidant capacity and increased level of NADPH oxidase. Administration of rapamycin, an inhibitor mTOR, protected against I/R-mediated injuries. Conclusion: Our findings suggest that the activation of mTOR signaling plays a crucial role in HL I/R-triggered organ damages presumably through the activation of apoptosis as a result of oxidant/antioxidant imbalance.