Epigallocatechin Gallate Alleviates Lipopolysaccharide-Induced Intestinal Inflammation in Wenchang Chicken by Inhibiting the TLR4/MyD88/NF-κB Signaling Pathway

Abstract

Intestinal inflammation significantly compromises broiler health and adversely affects growth performance. Epigallocatechin gallate (EGCG) was found to maintain the gut health of animals. However, the role and mechanism of EGCG in preventing lipopolysaccharide (LPS)-induced intestinal inflammation in chicks have not yet been fully elucidated. In the 35-day study, 140 one-day-old Wenchang chickens were randomly assigned to four treatments: CON (basal diet), LPS (basal diet + 1 mg/kg body weight (BW) LPS), L-EGCG (basal diet + 40 mg/kg BW EGCG + 1 mg/kg BW LPS), and H-EGCG (basal diet + 60 mg/kg BW EGCG + 1 mg/kg BW LPS). On days 31, 33, and 35 of age, broilers in the LPS, L-EGCG, and H-EGCG treatments received intraperitoneal injections of LPS. The LPS reduced jejunal villus height, villus height/crypt depth ratio, Claudin1 mRNA, catalase (CAT) activity, and interleukin-10 (IL-10) levels compared to CON while elevating diamine oxidase (DAO), interleukin-1β (IL-1β), and tumor necrosis factor α (TNF-α). EGCG improved growth performance in LPS-challenged broilers, elevating jejunal villus height and Claudin1/ZO-1 mRNA with reduced serum DAO. It enhanced antioxidant capacity via increased serum total antioxidant capacity (T-AOC), total superoxide dismutase (T-SOD), CAT, glutathione peroxidase (GSH-Px) activities, and a decreased malondialdehyde (MDA) concentration. Concurrently, EGCG lowered IL-1β/TNF-α and raised IL-10 in serum/jejunum. Crucially, EGCG suppressed jejunal TLR4/MyD88/NF-κB mRNA and protein expression under LPS. These findings demonstrate EGCG's protective role against LPS-induced intestinal inflammation in Wenchang chickens through TLR4/MyD88/NF-κB pathway inhibition.

Keywords: Lipopolysaccharide; TLR4/MyD88/NF-κB; Wenchang chicken; epigallocatechin gallate; intestinal inflammation.

Figure 1

Effects of epigallocatechin gallate (EGCG) on growth performance of Wenchang chicks challenged with lipopolysaccharide (LPS). (A) Body weight gain (BWG); (B) average daily feed intake (ADFI); (C) feed conversion ratio (FCR). The results are expressed as mean ± the standard error of the mean (** p < 0.01, not significant (ns) p > 0.05).

Figure 2

The effects of EGCG on the jejunum morphology of Wenchang chicks challenged with LPS. The morphological structure of the jejunum of Wenchang chicks after (A) CON treatment, (B) LPS treatment, (C) L-EGCG treatment, (D) H-EGCG treatment. (E) The jejunal villus height, (F) jejunal crypt depth, (G) jejunal villus height/crypt depth ratio of the jejunum. The results are expressed as mean ± the standard error of the mean (**** p < 0.0001, not significant (ns) p > 0.05).

Figure 3

The effects of EGCG on the jejunum permeability of LPS-challenged Wenchang chicks. The mRNA expression levels of (A) Claudin1, (B) ZO-1, and (C) Occludin in the jejunum; (D) the serum diamine oxidase (DAO) concentration. The results are expressed as mean ± the standard error of the mean (* p < 0.05, **** p < 0.0001, not significant (ns) p > 0.05.).

Figure 4

The effects of EGCG on the relative expression of TLR4/MyD88/NF-κB mRNA and protein levels in the jejunum of Wenchang chicks challenged with LPS. (A–C) The relative mRNA expression of NF-κB, TLR4, and MyD88. (D) Representative Western blot images. (E–G) The protein levels of MyD88, TLR4, and p-p65. The results are expressed as mean ± the standard error of the mean. (* p < 0.05, ** p < 0.01; *** p < 0.001, **** p < 0.0001, not significant (ns) p > 0.05). The original images of the Western blot are published as supplementary material.