The NLRP3–CASP1 Axis Contributes to Pyroptosis in Bovine Mammary Epithelial Cells During Clinical Mastitis

Pyroptosis is a pro-inflammatory form of programmed cell death mediated by inflammasomes and caspases and has been implicated in various inflammatory diseases. However, its function and regulatory role in dairy cows with clinical mastitis (CM) remain poorly understood. This study was conducted to investigate the differentially expressed proteins (DEPs) involved in biological processes (BPs) and the Kyoto Encyclopedia of Genes and Genomes pathways related to inflammasome-mediated pyroptosis based on proteomic data and to further explore their potential involvement in mastitis using in vivo and in vitro models. Histopathological analysis revealed morphological features consistent with pyroptosis in the mammary glands of CM-affected cows, including mammary epithelial cell (MEC) membrane disruption, increased reactive oxygen species production, elevated TUNEL–gasdermin D (GSDMD)-positive staining, and inflammatory cell infiltration. Proteomic profiling identified 276 DEPs and 17 BPs, among which NOD-like receptor family pyrin domain-containing 3 (NLRP3) was identified as a key candidate associated with cytokine production, immune defense, and inflammatory responses. Pathway enrichment analysis indicated that NLRP3, caspase-1 (CASP1), and GSDMD were enriched in the NOD-like receptor signaling pathway and were closely associated with mastitis. Immunohistochemical and molecular analyses demonstrated cytoplasmic localization and significant upregulation of NLRP3, CASP1, and GSDMD at both the mRNA and protein levels in CM-affected tissues. In both in vitro and in vivo models, a dose-dependent increase in the expression of pyroptosis-related targets and pro-inflammatory cytokines was observed with the progression of inflammation. Moreover, the pharmacological inhibition of CASP1 attenuated pyroptosis-associated changes and inflammatory responses in BMECs. Collectively, these findings suggest that the NLRP3–CASP1 axis is associated with inflammation-related pyroptosis in bovine mastitis and may represent a potential therapeutic target for clinical mastitis.