Dietary resveratrol alleviated lipopolysaccharide-induced ileitis through Nrf2 and NF-κB signalling pathways in ducks (Anas platyrhynchos)

Gram-negative bacteria contamination of feed can occur at all the stage of feed production, storage, transportation and utilization. Lipopolysaccharide (LPS) is a major toxic metabolite of Gram-negative bacteria. The aim of this study was to explore the effect of dietary resveratrol on the duck ileitis caused by LPS and its optimum addition level in diet. The results showed that LPS-induced duck ileitis with the destruction of intestinal structure, oxidative stress, mitochondrial dysfunction, inflammatory response and permeability alteration. Dietary resveratrol alleviated LPS-induced intestinal dysfunction and the increase of intestinal permeability by linearly increasing mRNA levels of tight junction protein genes (Claudin-1, Occludin-1, ZO-1) (p < 0.05) and protein expression of Claudin-1 (p < 0.01). In addition, dietary resveratrol improved the antioxidant capacity of duck ileum by reducing the production of MDA and increasing the activity of T-SOD (p < 0.01) and CAT. Lipopolysaccharide increased Keap1 at mRNA and protein level (p < 0.01) and decreased the protein level of Nrf2 (p < 0.05). Dietary resveratrol significantly downregulated expression of Keap1 and upregulated expression of Nrf2 in duck (p < 0.05). Dietary resveratrol suppressed the TLR4/NF-κB signalling pathway and the expression of its downstream genes including IKK, TXNIP, NLRP3, Caspase-1, IL-6 and IL-18. Meanwhile, the levels of inflammatory cytokines (IL-6, IL-18 and TNF-α) showed a linearly decrease (p < 0.01) with increasing dietary resveratrol level. These results demonstrated that resveratrol alleviated the LPS-induced acute ileitis of duck through Nrf2 and NF-κB signalling pathways, and the dietary resveratrol of 500 mg/kg is more efficiently.