The anti-inflammatory effect of lutein in broilers is mediated by regulating Toll-like receptor 4/myeloid-differentiation-factor 88 signaling pathway

The anti-inflammatory role of lutein has been widely recognized, however, the underlying mecha-nism is still not fully elucidated. Hence, the effects of lutein on the intestinal health and growth performance of broilers and the action of mechanism were investi-gated. 288 male yellow-feathered broilers (1-day old) were randomly allocated to 3 treatment groups with 8 replicates of 12 birds each, and the control group was fed a broken rice-soybean basal diet, while the test groups were fed a basal diet added with 20 mg/kg and 40 mg/kg of lutein (LU20, LU40), respectively. The feeding trial lasted for 21 d. The results showed that 40 mg/kg lutein supplementation tended to increase ADFI (P = 0.10) and ADG (P = 0.08) of broilers. More-over, the addition of lutein caused a decreasing trend of gene expression and concentration of proinflammatory cytokines IL-1b (P = 0.08, P = 0.10, respectively) and IL-6 (P = 0.06, P = 0.06, respectively) and also tended to decrease the gene expression of TLR4 (P = 0.09) and MyD88 (P = 0.07) while increasing gene expression and concentration of anti-inflammatory cytokines IL-4 and IL-10 (P < 0.05) in the jejunum mucosa of broilers. Additionally, lutein supplementation increased the jeju-nal villi height of broilers (P < 0.05) and reduced villi damage. The experiment in vitro showed that lutein treatment reduced the gene expression of IL-1b, IL-6, and IFN-g in chicken intestinal epithelial cells (P < 0.05). However, this effect was diminished after knock-down of TLR4 or MyD88 genes using RNAi technology. In conclusion, lutein can inhibit the expression and secretion of proinflammatory cytokines in the jejunum mucosa and promote intestinal development of broilers, and the anti-inflammatory effect may be achieved by regulating TLR4/MyD88 signaling pathway.