Genetic depletion of the early autophagy protein ATG13 impairs mitochondrial energy metabolism, augments oxidative stress, induces the polarization of macrophages to the M1 inflammatory mode, and compromises myelin integrity in skeletal muscle.

OBJECTIVE: M1 macrophage activation is crucial in chronic inflammatory diseases, yet its molecular mechanism is unclear. RESULTS: Our study showed that hemizygous deletion of the early autophagy gene atg13 (Tg+/-ATG13) disrupts cellular autophagy, hinders mitochondrial oxidative metabolism, and increases reactive oxygen species (ROS) levels in splenic macrophages, leading to M1 polarization. After reducing the expression of the autophagy markers WDFY3 and LC3, flow cytometric analysis of M1/M2 markers (CD40, CD86, CD115, CD163, and CD206), decreasing oxygen metabolism, as evaluated by the ROS-sensor dye DCFDA, and Seahorse oxygen consumption studies revealed that ablation of the atg13 gene impairs mitochondrial function, triggering M1 polarization. Additionally, redox imbalance may impair Sirtuin-1 activity via nitrosylation, increasing the level of acetylated p65 in macrophages and contributing to the inflammatory response in M1Mφs. Additionally, ablation of the atg13 gene resulted in increased infiltration of M1Mφs into the muscle vasculature, deterioration of myelin integrity in nerve bundles, and a reduction in muscle strength following treadmill exercise. CONCLUSIONS: Our study shows that impaired ATG13-driven autophagy increases inflammation through sirtuin-1 inactivation and NF-κB activation, suggesting a role for ATG13 in post-exertional malaise (PEM).