Neuroinflammation, driven primarily by activated microglia, is a key contributor to neurological disorders. A promising therapeutic approach involves reprogramming microglia from a pro-inflammatory (M1) to an anti-inflammatory (M2) phenotype. While vitamin D (VitD) has demonstrated immunomodulatory potential, its specific mechanisms in mitigating microglial inflammation are not fully understood. This study investigated the ability of VitD to reprogram lipopolysaccharide (LPS)-activated microglia toward an M2 phenotype and to elucidate the underlying molecular pathways. Our results demonstrated that VitD attenuated LPS-induced microglial activation and pro-inflammatory cytokine release in vivo, while simultaneously promoting M2 polarization in both in vitro and in vivo models. Mechanistically, VitD was found to transcriptionally activate the RNA demethylase FTO through specific vitamin D receptor (VDR) binding to the FTO promoter. Upregulated FTO then reduced the m⁶A methylation on Mxd1 mRNA in a YTHDF2-dependent manner, thereby enhancing Mxd1 mRNA stability and protein expression. The increased Mxd1 protein subsequently bound to and repressed the promoter of PTEN. This downregulation of PTEN activated the PI3K/AKT signaling pathway, which facilitated the nuclear translocation of PGC-1α, a master regulator of M2 polarization. Collectively, our findings reveal a novel FTO/Mxd1/PTEN/AKT/PGC-1α axis that mediates VitD-induced microglial reprogramming, presenting new potential therapeutic targets for the treatment of neuroinflammatory diseases.
Hu et al. (2026) studied this question.