As a nutritionally important amino acid, cysteine (Cys) could attenuate oxidative damage on growth performance and intestinal barrier function in piglets. However, the mechanism of Cys in attenuating intestinal injury remains unclear. The aim of this study was to investigate the mechanism of Cys in defending against intestinal inflammation in piglets. A total of twenty-four piglets were divided into four groups and fed a diet with or without 0.1% BPA or Cys for a 28 d feeding trial. The results showed that Cys supplementation reinstated the jejunal barrier by increasing cell proliferation and the goblet cell number, and decreased cell apoptosis upon BPA exposure. Cys supplementation also decreased serum and jejunal pro-inflammatory cytokine and immunoglobulin levels in BPA-challenged piglets. Furthermore, Cys mitigated inflammation by normalizing the activation of the toll-like receptor 4 (TLR4)-JNK/MAPK-nuclear factor-kappa B (NF-κB) pathway caused by BPA. Additionally, dietary Cys supplementation restored the levels of butyrate, valerate and isovalerate in cecum contents that were decreased by BPA exposure. Meanwhile, Cys supplementation normalized the abundances of Prevotellaceae and Romboutsia upon BPA exposure. In conclusion, Cys is critical to nutrition through attenuating intestinal inflammation by regulating gut microbial balance and suppressing the TLR4-JNK/MAPK-NF-κB pathway.

Zearalenone (ZEN) and its masked form, zearalenone-14-glucoside (Z14G), are common mycotoxins found in feed that can threaten the intestinal health of piglets. To date, there has been a lack of systematic research on the toxic effects and molecular mechanisms of Z14G alone and in combination with ZEN on intestinal porcine epithelial cell-jejunal 2 (IPEC-J2) cells. This study found 80 µmol/L ZEN and 100 µmol/L Z14G were the selected experimental concentrations based on cell viability assays. Both ZEN and Z14G significantly inhibited cell viability and proliferation, induced apoptosis, and disrupted the expression of associated genes. They altered the expression of barrier-associated genes, evidenced by increase in lactate dehydrogenase release and downregulation of tight junction gene mRNA. ZEN and Z14G exposure increased oxidative stress, altered antioxidant defense, and modulated inflammatory responses, accompanied by changes in the expression of genes related to the TLR4/MyD88 and NLRP3 signaling pathways. Notably, Z14G alone exhibited a distinct transcriptional response of inflammatory-related genes, failing to upregulate IL-1β, TNF-α and STING. In conclusion, ZEN and Z14G disrupt intestinal epithelium homeostasis via interlinked oxidative, inflammatory and barrier-damaging pathways. The findings reveal the direct toxicity and unique properties of ZEN and Z14G, underscoring the need to consider masked mycotoxins in combined risk assessment.