Bacterial infection reinforces host metabolic flux from arginine to spermine for NLRP3 inflammasome evasion.

Hosts recognize cytosolic microbial infection via the nucleotide-binding domain-like receptor (NLR) protein family, triggering inflammasome complex assembly to provoke pyroptosis or cytokine-related caspase-1-dependent antimicrobial responses. Pathogens have evolved diverse strategies to antagonize inflammasome activation. Here, Edwardsiella piscicida gene-defined transposon library screening for lactate dehydrogenase (LDH) release in nlrc4-/- bone marrow-derived macrophages (BMDMs) demonstrates that genes clustered in the bacterial arginine metabolism pathway participate in NLRP3 inflammasome inhibition. Blocking arginine uptake or putrescine export significantly relieves NLRP3 inflammasome inhibition, indicating that this bacterium rewires its arginine metabolism network during infection. Moreover, intracellular E. piscicida recruits the host arginine importer (mCAT-1) and putrescine exporter (Oct-2) to bacterium-containing vacuoles, accompanied by reduced arginine and accumulated cytosolic spermine. Neutralizing E. piscicida-induced cytosolic spermine enhancement by spermine synthetase or extracellular spermine significantly alters NLRP3 inflammasome activation. Importantly, accumulated cytosolic spermine inhibits K+ efflux-dependent NLRP3 inflammasome activation. These data highlight the mechanism of bacterial gene-mediated arginine metabolism control for NLRP3 inflammasome evasion.