Blockage of citrate export prevents TCA cycle fragmentation via Irg1 inactivation

The metabolism of activated macrophages relies on aerobic glycolysis, while mitochondrial oxidation is disrupted. In lipopolysaccharide-activated macrophages, the citrate carrier (CIC) exports citrate from mitochondria to enhance glycolytic genes through histone acetylation. CIC inhibition or Slc25a1 knockdown reduces the occupancy of H3K9ac to hypoxia-inducible factor-1α (HIF-1α) binding sites in promoters of glycolytic genes to restrain glycolysis. HIF-1α also transcriptionally upregulates immune-responsive gene 1 for itaconate production, which is inhibited by CIC blocking. Isotopic tracing of [U-