Pasteurella multocida causes liver pyroptosis in broilers through the MAPK-NLRP3-GSDMD signaling pathway

Avian cholera is a bacterial disease caused by infection with Pasteurella multocida (P. multocida), which seriously threatens the poultry industry. Liver injury is a key factor in the acute death of infected chickens. This study sought to clarify how P. multocida causes liver injury in broilers, specifically examining liver pyroptosis and the involvement of oxidative stress and inflammation. Experiments with 28-day-old broilers infected with P. multocida showed that post-infection serum indicators were significantly higher for ALT, AST, and T-Bil, but lower for ALB. Histopathological evaluation revealed localized areas of necrosis and structural disruption within liver tissue. Oxidative stress analysis showed that P. multocida infection decreased activities of SOD, GSH-PX, CAT, and T-AOC, while raising MDA and H₂O₂ levels. Liver ELISA results showed notably higher levels of TNF-α, IL-1β, IL-6, IL-18, and IFN-γ in infected liver tissue. Immunofluorescence showed higher levels of 8-OHdG, NLRP3, Caspase-1, and GSDMD in infected tissues versus controls. Transcriptome analysis identified 3392 differentially expressed genes after infection, notably enriched in MAPK signaling pathways. Further analysis at the gene and protein levels confirmed that P. multocida infection activated pathways related to oxidative stress (Keap1, Nrf2, HO-1), inflammation (NF-κB, JNK, p38), and pyroptosis (NLRP3, ASC, Caspase-1, GSDMD, GSDME, IL-1β, IL-18), causing severe liver damage and death in broilers. This study revealed the key role of the MAPK-NLRP3-GSDMD pathway in P. multocida infection, offering new targets and a basis for strategies to prevent and control avian cholera.