Acute exercise stress promotes Ref1/Nrf2 signalling and increases mitochondrial antioxidant activity in skeletal muscle.

Abstract

What is the central question of this study? How does acute exercise affect the redox effector factor-1 (Ref1) and nuclear factor erythroid 2-related factor 2 (Nrf2) signalling and its association with mitochondrial H(2)O(2) production and antioxidant capacity? What is the main finding and its importance? Ref1/Nrf2 signalling in skeletal muscles was activated by acute exercise, and this activation was correlated with increased mitochondrial H(2)O(2) content and antioxidant capacity (reduced glutathione and manganese superoxide dismutase). The finding indicates that the oxidative stress induced by acute exercise in skeletal muscle mitochondria is associated with the upregulation of Ref1/Nrf2 signalling and enhancement of antioxidant defense pathways. This mechanism may play a role in preventing cellular oxidative stress resistance during acute exercise. The molecular mechanism of exercise-induced oxidative stress and adaptive activation of antioxidant responses in skeletal muscle has not been fully elucidated. This study aimed to investigate the effect of acute exercise on redox effector factor-1 (Ref1) and nuclear factor erythroid 2-related factor 2 (Nrf2) signalling and associations with mitochondrial H(2)O(2) production and antioxidant mechanisms in skeletal muscles. Groups of male ICR/CD-1 mice were subjected to an acute exercise bout of different durations (45, 90, 120 or 150 min). Muscle tissues (gastrocnemius and quadriceps femoris) were harvested after exercise to measure mitochondrial manganese superoxide dismutase (MnSOD) and copper-zinc superoxide dismutase (CuZnSOD) activities, reduced glutathione (GSH) content and expression of Ref1/Nrf2 genes and Ref1/Nrf2 proteins. The acute exercise increased oxidative stress and activated Ref1/Nrf2 signalling in a time-dependent manner, with a linear correlation between the mitochondrial H(2)O(2) content and Ref1/Nrf2 expressions. The GSH content and MnSOD activity were also significantly increased, but CuZnSOD activity was not significantly affected. The findings indicate that the H(2)O(2) production induced by acute exercise in skeletal muscle mitochondria in the mouse is closely associated with upregulation of the Ref1/Nrf2 signalling pathway and enhancement of antioxidant defense components, including GSH and MnSOD. Activation of Ref1/Nrf2/antioxidant defense pathways may play a role in preventing cellular oxidative stress resistance during acute exercise.