Resveratrol alleviates heat-stress-induced impairment of the jejunal mucosa through TLR4/MAPK signaling pathway in black-boned chicken

Heat stress in chickens caused by high temperatures in summer is a serious issue faced by the poultry industry globally, which reduces product quality. The aim of this study is to investigate the role of resveratrol in alleviating heat stress injury and inflam-matory response of jejunal mucosa in black-boned chickens through TLR4/MAPK signaling pathway. In total, 240 black-boned chickens (28-day old) were randomly divided into 4 treatment groups as follows. The normal temperature (NT) and normal temperature with resveratrol (NT+Res) groups received a basal diet without and with 400 mg/kg resveratrol, respectively, and treated at 24 degrees C +/- 2 degrees C, 24 h/d. The high temperature (HT) and high temperature with resveratrol (HT +Res) groups received basal diet without and with 400 mg/kg resveratrol, respectively, and treated at 37 degrees C +/- 2 degrees C for 8 h/d and 24 degrees C +/- 2 degrees C for the rest of the time for 12 d. The results revealed the heat-stress responses impaired the villous structure of the jejunum, causing a rough and uneven surface of the jejunal villus, and local intestinal villi were even more prone to rupture. However, resveratrol significantly improved the morphology and structure of jejunal mucosa under heat stress. Heat stress increased the mRNA levels of toll-like receptor 4 (TLR4), c-Jun, c-fos, caspase-3, and p38 (P < 0.05), reduced mRNA level of Bcl-2, and reduced the expression of tight junction proteins Occludin, ZO-1, and Claudin1 (P < 0.05) in the jejunal mucosa. However, resveratrol inhibited the TLR4/ mitogen-activated protein kinase (MAPK) signaling pathway via downregulating TLR4, c-Jun, p38 , and caspase-3 (P < 0.05); upregulating Bcl-2 (P < 0.05); decreasing the protein levels of MKK3, p53, and myeloid differentiation factor 88 (MYD88); and increasing the protein levels of Occludin, ZO-1, and Claudin1. In addition, it reduced the levels of JNK and p38 proteins (P < 0.05) and inflammatory factors like tumor necrosis factor -a (TNF-a) in the jejunal mucosa of black-boned chickens under heat stress. In conclusion, resveratrol may play a regulatory role in heat-stress-induced damage and inflammatory response in the intestinal mucosa of black boned chickens under heat stress.