Itaconate is an inhibitor of TET DNA dioxygenases

Immune-response gene 1 (IRG1) transcription is rapidly induced by pathogen infections and inflammatory conditions primarily in cells of myeloid lineage. Deletion of Irg1 in mice causes severe defects in response to bacterial and viral infection and rapid death. IRG1 encodes a mitochondrial metabolic enzyme, aconitate decarboxylase 1 (ACOD1), that catalyzes the decarboxylation of cis-aconitate, a tricarboxylic acid cycle intermediate, to produce the anti-inflammatory metabolite itaconic acid (ITA). ITA can inhibit SDH5, resulting in elevated levels of succinate and metabolic reprogramming, or alkylate protein cysteine residues to induce electrophilic stress response mediated by NRF2 and I?B?. Here we show that ITA is an antagonist of a-ketoglutarate (a-KG) and a potent inhibitor of a-KG/Fe2+-dependent TET family of DNA dioxygenases. In vitro, ITA binds to TET2 and inhibits the catalytic activity of TET2 and, reciprocally, a-KG blocks ITA binding to and inhibition of TET2. In vivo, lipopolysaccharides (LPS) treatment, which induces IRG1 expression and causes the intracellular accumulation of ITA, inhibits TET activity in Irg1-WT, but not Irg1-KO macrophages. Moreover, TET2 is a major target of ITA function in suppressing LPS-induced genes. LPS stimulates p65 NF-?B/RelA to bind with and recruit TET2 to hydroxymethylate and activate the Nfkbiz gene, which encodes I?B?. Our results thus identify a physiological metabolite inhibitor of TET enzymes and reveal a novel mechanism for the anti-inflammatory function of ITA through dampening TET2-mediated NF-?B signaling. Overall design: 5hmC profiling of mouse BMDMs treated with or without octyl-ITA or with octyl-ITA pre-treatment of wildtype or IRG1_KO BMDMs also treated with LPS for 0, 4 or 12 hours.