Blockage of citrate export prevents TCA cycle fragmentation via Irg1 inactivation

Summary 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-1 α (HIF-1 α ) 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- 13 C 6 ] glucose shows that CIC blockage prevents citrate accumulation and itaconate production by reducing glycolytic flux and facilitating metabolic flux in the TCA cycle. Isotopic tracing of [U- 13 C 5 ] glutamine reveals that CIC inhibition reduces succinate accumulation from glutaminolysis and the gamma-aminobutyric acid shunt by enhancing mitochondrial oxidation. By restraining glycolysis, CIC inhibition increases NAD + content to ensure mitochondrial biogenesis for oxidative phosphorylation. Furthermore, blockage of citrate export reduces cerebral thrombosis by inactivation of peripheral macrophages.