PAD4-generated citrullinated histones are triggers for autoinflammation in cryopyrin-associated periodic syndrome

Cryopyrin-associated periodic syndromes (CAPS) are autoinflammatory disorders caused by gain-of-function NLRP3 variants. Although NLRP3 inflammasomes mediate IL-1β secretion through Gasdermin D (GSDMD), we show that GSDMD deletion did not prevent autoinflammation in mice ubiquitously expressing the Nlrp3 ^A350V variant. Inflamed skin of Nlrp3 ^A350V -expressing GSDMD-deficient mice displayed citrullinated histone 3-containing neutrophil extracellular traps (CitH3-NETs). CitH3-NETs induced IL-1β secretion from murine Nlrp3 ^A350V -expressing GSDMD-deficient macrophages as well as from human CAPS patient monocytes and macrophages. Blocking protein arginine deiminase-4 (PAD4) prevented CitH3 release and disabled the IL-1β-inducing NET effects, identifying CitH3 as crucial trigger. Mechanistically, CitH3-NETs activated GSDME in GSDMD-deficient Nlrp3 ^A350V macrophages, and GSDME deletion prevented pathology in Nlrp3 ^A350V -expressing GSDMD-deficient mice. In addition to this GSDME-dependent autoinflammation axis, PAD4 deletion also prevented autoinflammation in mice with neutrophil-specific Nlrp3 ^A350V expression that develop CAPS in a GSDMD-dependent manner. These observations support a CAPS model in which PAD4-mediated CitH3-NET release can trigger both GSDMD-dependent and GSDME-dependent autoinflammation.