Mechanism of GSDMD in the Pathogenesis of Pasteurella multocida PmCQ2

Pasteurella multocida serotype A (PmCQ2), a Gram-negative zoonotic pathogen, causes severe respiratory disease in a variety of domestic and wild animals, leading to high morbidity and mortality and substantial agricultural economic losses. Pyroptosis, a gasdermin-mediated programmed cell death mechanism, facilitates pathogen clearance but exacerbates tissue damage through inflammatory cytokine release. While our prior work established PmCQ2-driven NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome activation, the role of pyroptosis in pulmonary pathology during infection remains unresolved. Here, we demonstrate that PmCQ2 induces macrophage pyroptosis via gasdermin D (GSDMD) cleavage, evidenced by lactate dehydrogenase (LDH) release, membrane pore formation under transmission electron microscopy (TEM), and proteolytic generation of GSDMD-N termini. Pharmacological inhibition of NLRP3 (MCC950) and genetic ablation of caspase-11 significantly attenuated GSDMD activation, IL-1β secretion, and pyroptotic cell death, implicating both canonical (NLRP3/caspase-1) and noncanonical (caspase-11) pathways. Crucially, GSDMD knockout mice exhibited markedly reduced lung injury, evidenced by diminished inflammatory infiltration and preserved alveolar architecture, compared to wild-type (WT) counterparts following PmCQ2 challenge. This study provides the first evidence that PmCQ2 triggers GSDMD-dependent pyroptosis through dual signaling axes, directly linking this inflammatory cell death pathway to pathogen-induced pulmonary damage. Our findings position GSDMD as a central therapeutic target to mitigate tissue injury during P. multocida infection, offering a framework for novel interventions that balance antimicrobial defense and inflammation control in zoonotic pathogens.