Mitochondrial metabolic reprogramming, quality control, and intercellular transfer in regulating macrophage plasticity.

Macrophage functional plasticity is intrinsically linked to metabolic reprogramming, including mitochondrial function, substrate utilization, and redox signaling. In response to hypoxia, infection, or tissue injury, macrophages rely on mitochondria not only for energy provision but, critically, for metabolic intermediates and reactive oxygen species (ROS) that serve as signaling molecules to guide gene expression reprogramming. While macrophage activation exists along a continuous spectrum, this review summarizes the distinct metabolic paradigms characterizing the classical M1-like (glycolysis-dominant) and M2-like (oxidative phosphorylation, OXPHOS-dominant) extremes, highlighting the molecular mechanisms where metabolic events-specifically tricarboxylic acid (TCA) cycle truncation and succinate accumulation-drive inflammatory polarization. Furthermore, we discuss the role of mitochondrial quality control, particularly dynamics and mitophagy, in maintaining macrophage homeostasis. Notably, recent evidence identifies "intercellular mitochondrial transfer" as a novel mode of immune microenvironment regulation, enabling damaged macrophages to restore function by acquiring exogenous mitochondria. A deeper understanding of these mechanisms offers new intervention targets for metabolic immunotherapy in sepsis, cancer, and chronic inflammatory diseases. Importantly, we emphasize that many of these metabolic and mitochondrial regulatory mechanisms are highly context-dependent, varying significantly across different tissues and disease microenvironments.