Significance: Macrophages are immune sentinels located throughout the body that function in both amplification and resolution of the inflammatory response. The circadian clock has emerged as a central regulator of macrophage inflammation. Reduction-oxidation (redox) reactions are central to both the circadian clock and macrophage function. Recent Advances: Circadian regulation of metabolism controls the macrophage inflammatory response, whereby disruption of the clock causes dysfunctional inflammation. Altering metabolism and reactive oxygen/nitrogen species (RONS) production rescues the inflammatory phenotype of clock-disrupted macrophages. Critical Issues: The circadian clock possesses many layers of regulation. Understanding how redox reactions coordinate clock function is critical to uncover the full extent of circadian regulation of macrophage inflammation. We provide insights into how circadian regulation of redox affects macrophage pattern recognition receptor signaling, immunometabolism, phagocytosis, and inflammasome activation. Future Directions: Many diseases associated with aberrant macrophage-derived inflammation exhibit time-of-day rhythms in disease symptoms and severity and are sensitive to circadian disruption. Macrophage function is highly dependent on redox reactions that signal through RONS. Future studies are needed to evaluate the extent of circadian control of macrophage inflammation, specifically in the context of redox signaling. Antioxid. Redox Signal. 37, 664-678.
Keywords: circadian biology; immunometabolism; inflammation; macrophage; reduction-oxidation (redox) reactions.