Enterotoxigenic Escherichia coli (ETEC) Infection Triggers Pyroptosis Through ER Stress Response-Mediated Mitochondrial Impairment and STING Activation in Intestinal Epithelial Cells

Enterotoxigenic <i>Escherichia coli</i> (ETEC) is a major cause of diarrhea in pigs. Virulence factors, such as colonization factors and enterotoxins, bind to specific receptors on intestinal epithelial cells (IECs), impairing the integrity of the IEC barrier by inducing cell death. Pyroptosis is a newly discovered form of programmed cell death (PCD), which is widely involved in the pathogenesis of multiple infectious gastrointestinal diseases. However, it is still unclear whether pyroptosis contributes to the ETEC-mediated damage of IECs. This study demonstrated that ETEC infection activated NLRP3 inflammasome and triggered gasdermin D (GSDMD)-executed pyroptosis of mouse IECs in vitro and in vivo. Mechanistically, ETEC infection triggered endoplasmic reticulum (ER) stress response to increase the expression of thioredoxin-interacting protein (TXNIP) by upregulation of C/EBP homologous protein (CHOP), which subsequently activated NLRP3 inflammasome. Removal of ER stress by tauroursodeoxycholic acid (TUDCA) alleviated the pyroptosis of IECs that was caused by ETEC infection. In addition, the induced ER stress impaired mitochondria and led to mitochondrial reactive oxygen species (mtROS) overproduction and cytosolic release of mitochondrial DNA (mtDNA), which activated STING, another factor that contributed to ETEC-triggered pyroptosis. Chemical inhibition of STING attenuated ETEC-induced pyroptosis of IECs. Collectively, this study demonstrated that the activation of the STING/ER stress/mitochondrial impairment/NLRP3 inflammasome axis is a critical pathway in the ETEC infection-derived pyroptosis of IECs. Hence, targeting ER stress response may serve as a promising therapeutic strategy to prevent ETEC infection caused damage to IECs.