Palmitic Acid Amplifies Microglial Inflammatory Activation Involving C5aR1-Sensitive Inflammatory Signaling and JMJD3/H3K27me3-Related Epigenetic Changes

Microglial pro-inflammatory activation contributes to neuroinflammatory processes in many neurological disorders. Saturated fatty acids such as palmitic acid (PA) are increasingly recognized as inflammatory cues, yet the molecular mechanisms linking PA to microglial inflammatory responses remain incompletely defined. In this study, using BV-2 microglia as an exploratory in vitro model, we investigated whether C5aR1-sensitive signaling and JMJD3/H3K27me3-related epigenetic changes are involved in PA-associated inflammatory responses. PA exposure increased Iba1 expression, altered CD86/CD206 expression, and enhanced the secretion of IL-1β, IL-6 and TNF-α. Exogenous C5a produced broadly similar inflammatory changes. Under heat-inactivated serum conditions, PA increased cell-associated C5a immunoreactivity and extracellular C5a levels, and these C5a-related readouts were reduced by PMX53. PMX53 also attenuated PA-associated increases in inflammatory markers and in the expression of TLR4, total NF-κB p65, c-Fos, and c-Jun. In parallel, PA and C5a increased JMJD3 expression and JMJD3 enrichment at selected IL-1β and IL-6 promoter regions, accompanied by reduced H3K27me3 enrichment at these loci. Pharmacological KDM6 inhibition with GSK-J4 attenuated PA-associated increases in IL-1β and IL-6 expression. Together, these findings support the involvement of C5aR1-sensitive inflammatory signaling and JMJD3/H3K27me3-related epigenetic regulation in PA-associated microglial inflammatory responses.