Cinnamaldehyde improved intestine immune function and alleviated inflammation associated with NF-κB pathways in grass carp (Ctenopharyngodon idella) after infection with Aeromonas hydrophila

Abstract In this study, we investigated the effect of dietary cinnamaldehyde (CIN) on the intestinal immune function of the foregut, midgut, and hindgut in grass carp (Ctenopharyngodon idella). Fish were fed five diets containing different levels of CIN (0–144 mg/kg of CIN) for 60 days and then challenged with Aeromonas hydrophila for 14 days. Compared with the control group, CIN enhanced the intestinal activities of lysozyme and acid phosphatase, and also increased the intestinal levels of complement 3, complement 4, and immunoglobulin M. CIN supplementation also up-regulated the intestinal mRNA levels of interleukin-10 (IL-10), IL-4/13B (but not IL-4/13A), transforming growth factor-β2 (TGF-β2) (not in the hindgut), and down-regulated the mRNA levels of tumor necrosis factor α (TNF-α), interferon γ2 (IFN-γ2), IL-1β (not in the hindgut), IL-15 (not in the foregut), IL-17D (not in the foregut), and triggered the NF-κBp65 signaling pathway Collectively, these observations indicated that CIN improved the intestinal immune function of C. idella. Finally, based on morbidity associated with enteritis, lysozyme activity in the hindgut, and complement 4 content in the midgut, the optimal CIN supplementations for C. idella were estimated to be 75.06, 79.79, and 81.49 mg/kg of diet, respectively.