Abstract

Enterotoxigenic Escherichia coli (ETEC) is a major cause of diarrhea in humans and animals worldwide. Porcine β-defensin 2 (pBD2) is an antimicrobial peptide secreted by pigs that exhibits broad antimicrobial and immunomodulatory activities, playing an important role in host defense and intestinal homeostasis. However, its effects and mechanisms against ETEC remain poorly understood. In this study, mice were orally administered different concentrations of pBD2 before ETEC K88 challenge. pBD2 treatment restored body weight loss, alleviated intestinal epithelial damage, and strengthened the intestinal barrier by upregulating intestinal barrier proteins, including ZO-1, occludin, claudin-1, and MUC-1, as well as immunoglobulins (IgG, IgM, and IgA). Moreover, pBD2 reduced the expression of pro-inflammatory cytokines (TNF-α, IL-6) while enhancing anti-inflammatory cytokines (IL-2, IL-10), increased SOD and T-AOC activities, and decreased MDA levels, thereby suppressing ETEC-induced inflammation and oxidative stress. Mechanistically, pBD2 inhibited NF-κB and MAPK signaling while activating Nrf2 signaling. In addition, pBD2 elevated short-chain fatty acid (SCFA) levels and modulated the cecal microbiota by enriching beneficial bacteria and suppressing potential pathogens. In summary, pBD2 protects against ETEC-induced intestinal injury by regulating NF-κB, MAPK and Nrf2 pathways and modulating gut microbiota and SCFAs, highlighting its potential role in improving animal intestinal health.