Iron drives protease-independent cleavage of gasdermin D in allergic airway diseases.

Gasdermin D (GSDMD)-mediated interleukin (IL)-33 secretion by lung epithelial cells initiates airway inflammation upon allergen challenge. How environmental allergens activate GSDMD remains elusive. Here, we demonstrate that exposing epithelial cells to allergens triggers protease-activated receptor 1 (PAR1)-dependent ferritinophagy, elevating intracellular labile iron. This iron pool is essential for noncanonical, protease-independent GSDMD activation. The iron chaperone poly(rC)-binding protein 2 (PCBP2) delivers iron directly to GSDMD, initiating a highly localized Fenton reaction. This generates constrained hydroxyl radicals that cleave GSDMD, releasing the active N-terminal p40 fragment to form pores for IL-33 release. Blocking any step of this iron-GSDMD pathway, via iron chelation or genetic ablation, abolishes IL-33 secretion, prevents group 2 innate lymphoid cell (ILC2) activation, and mitigates allergic airway inflammation and tissue damage in mice. Our findings reveal an unconventional, iron-catalyzed, and protease-independent mechanism for GSDMD activation, offering potential new therapeutic targets for allergic inflammatory diseases.