Homocysitaconate controls inflammation through reshaping methionine metabolism and N-homocysteinylation.

Inflammation and its metabolic-network interactions generate novel regulatory molecules with translational implications. Here, we identify the immunometabolic crosstalk that generates homocysitaconate, a metabolite formed by homocysteine and itaconate adduction catalyzed by S-adenosyl-L-homocysteine hydrolase (AHCY). Homocysitaconate increases 152-fold during inflammation and exhibits anti-inflammatory effects. Mechanistically, homocysitaconate binds to the D312 residue of the pro-inflammatory protein methionyl-tRNA synthetase (MARS), inhibiting its function and reshaping methionine metabolism to feedback-brake the early activation of the N-homocysteinylation pathway. This metabolic switch facilitates NLR family pyrin domain-containing 3 (NLRP3) ubiquitination to control inflammation. Homocysitaconate demonstrates therapeutic effects in sepsis, high-fat-diet-induced inflammation, and colitis models. Boosting endogenous homocysitaconate synthesis through nicotinamide adenine dinucleotide (NAD)-dependent AHCY activation (using nicotinamide riboside and pyruvate) also inhibits inflammation by targeting the MARS/NLRP3-N-homocysteinylation cascade. This study establishes homocysitaconate as an anti-inflammatory metabolite that serves as a homeostatic governor by reprogramming protein modification switches, introducing both metabolic timing regulation and clinical strategies to manage inflammatory complications.