Effect of oxidative stress on AIF-mediated apoptosis and bovine muscle tenderness during postmortem aging

This study aimed to explore the effect exerted by oxidative stress on apoptosis-inducing factors (AIF)-mediated apoptosis and bovine muscle tenderness during postmortem aging. We investigated the reactive oxygen species (ROS) content, mitochondrial membrane permeability, AIF expression level, nucleus apoptosis, shear force, myofibril fragmentation index, pH, and energy level. According to the results, a rise in ROS content was accompanied by the rise in mitochondrial membrane permeability from 6 to 72 hr. In the meantime, the AIF expression in mitochondria was downregulated significantly within 72 hr. However, samples treated with N-acetylcysteine had significantly lower ROS content (6 to 72 hr) and mitochondrial membrane permeability (12 to 72 hr) than the control group. Moreover, during postmortem aging, the variations in AIF levels in mitochondria were closely associated with meat tenderization and nucleus apoptosis. These findings demonstrated that oxidative stress induced by ROS significantly promoted AIF release from mitochondria by enhancing the mitochondrial membrane permeability, and the released AIF mediated nucleus apoptosis that further enhanced bovine muscle tenderness. Besides, results suggest that in the early stage, the environmental factors (ATP content and pH) significantly decreased (0 to 72 hr), whereas ROS-induced oxidative stress had no significant effect on environmental factors. These observations further suggested that during postmortem aging, the decrease of pH and ATP consumption are required by AIF release. We conclude that ROS-induced oxidative stress and internal environment are vital for meat tenderization through the regulation of AIF-mediated apoptosis pathway. PRACTICAL APPLICATION: ROS-induced oxidative stress contributes to bovine muscle tenderization by promoting cell apoptosis. It is likely to lay a theoretical foundation for developing innovative tenderization techniques by altering the internal oxidation environment of postmortem muscles.