The circadian clock component BMAL1 enhances macrophage inflammation by nuclear translocation of peroxisomal β-oxidation enzyme MFP2.

The circadian clock regulates diverse immune functions, yet the role of clock components in macrophage inflammation remains controversial, with both pro- and anti-inflammatory effects reported. Here, we identify a previously unrecognized mechanism by which the core circadian clock component BMAL1 enhances the inflammatory response of macrophages through the nuclear translocation of the peroxisomal β-oxidation enzyme multi-functional protein 2 (MFP2). BMAL1 drives MFP2 accumulation in the nucleus, where MFP2 contributes to acetyl-CoA production and acetylation of the NF-κB subunit p65, thereby facilitating M1 polarization and inflammatory chemokine expression. Nuclear MFP2 levels oscillate in a diurnal manner in the liver, but this rhythmicity is abolished in Bmal1-deficient mice. Macrophage-specific deletion of BMAL1 alleviates diethylnitrosamine-induced hepatic inflammation and tumorigenesis, concomitant with reduced inflammatory gene expression. These findings uncover a BMAL1-dependent nuclear metabolic pathway that links circadian regulation of macrophage inflammation and suggest that targeting nuclear MFP2 may offer a therapeutic approach for inflammatory diseases and tumorigenesis.