Ketogenic diet attenuates microglia-mediated neuroinflammation by inhibiting NLRP3 inflammasome activation via HDAC3 inhibition to activate mitophagy in experimental autoimmune encephalomyelitis

Abstract

The activation of microglia is an important cause of central nervous system (CNS) inflammatory cell infiltration and inflammatory demyelination in multiple sclerosis (MS). NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome-mediated signaling plays a decisive role in the microglia activation. Mitophagy is closely related to NLRP3-mediated neuroinflammation. Previous studies have shown that ketogenic diet (KD) suppresses microglial NLRP3 inflammasome activation and exerts mitophagy-stimulating effects, but the specific mechanism remains unclear. The current study examined the mechanism underlying the anti-inflammatory effect of KD on experimental autoimmune encephalomyelitis (EAE). Our data demonstrate that KD inhibited demyelination, increased co-staining of translocase of outer mitochondrial membrane (TOM20) and Microtubule-associated protein 1A/1B-light chain 3 (LC3II), decreased microglial NLRP3 inflammasome activation and histone deacetylase 3 (HDAC3) in the hippocampus of EAE mice. Further correlation analysis showed that the reduction of HDAC3 was negatively correlated with NLRP3 activation and positively correlated with the induction of mitophagy in KD-fed EAE mice. In BV2 microglia cells, we confirmed that inhibition of HDAC3 promoted 5' adenosine monophosphate -activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR)/unc-51 like autophagy activating kinase (ULK)1 and PTEN induced putative kinase 1 (PINK1)/Parkin meditated mitophagy, led to up-regulation of acetylated AMPK, acetylated ULK1 and acetylated Parkin, and subsequently reduced ROS accumulation and inhibited activation of the NLRP3 inflammasome. In addition, treatment with 3-methyladenine (3-MA), a specific autophagy inhibitor, abolished the anti-inflammatory effect of a selective inhibitor of HDAC3 (RGFP966) in BV2 cells. The study illustrates that KD ameliorates EAE by reducing NLRP3 mediated-inflammation in microglia cells via HDAC3 inhibition and enhancement of mitophagy-related protein acetylation.