Effects of 3-indoleacrylic acid on alleviating lipopolysaccharide-induced liver inflammatory damage in laying hens

Abstract

This study investigates the effects of 3-indoleacrylic acid (IAA), a bacterial metabolite of tryptophan, on LPS-induced liver injury in laying hens. The aim is to explore the potential hepatoprotective mechanisms of IAA, particularly through the modulation of inflammatory and antioxidant pathways. A total of 48, 24-week-old No. 6 Jingfen laying hens were randomly divided into four groups of 12 hens each: the CON group (basal diet), IAA group (basal diet + 150 mg/kg IAA), LPS group (basal diet), and IAA+LPS group (basal diet + 150 mg/kg IAA). The feeding period lasted 8 weeks, and at the end of the 8th week, the laying hens in the LPS and IAA+LPS groups were intraperitoneally injected with 0.5 mg/kg LPS. The four groups were uniformly slaughtered and sampled 12 h after LPS injection. The expression of pro-inflammatory cytokines (IL-1β, TNF-α, IL-6) was significantly alleviated (P < 0.05), and antioxidant enzymes (T-SOD, CAT, GSH-PX) were significantly elevated (P < 0.05) in the serum and liver of the IAA+LPS group. Histological analysis revealed reduced hepatocyte necrosis and inflammation in the IAA-treated groups (P < 0.05). Additionally, the activation of MAPK and Toll-like receptor (TLR) signaling pathways was modulated through transcript analyses, thereby reducing inflammation and oxidative stress. In summary, IAA effectively mitigates liver inflammation and oxidative stress through the regulation of MAPK and TLR signaling pathways, providing a promising strategy for improving liver health in hens. This study represents the first report on the application of IAA in poultry, demonstrating its potential as a novel therapeutic agent for alleviating liver injury.

Keywords: 3-Indoleacrylic acid; Lay hens; Liver inflammatory damage; MAPK signaling pathway; Oxidative stress.

Fig. 1

Effects of 3-indoleacrylic acid on inflammatory cytokines and oxidative stress in a lipopolysaccharide-induced liver injury model in laying hens. Serum biochemical indices. (A) IL-1β (B) IL-6 (C) IL-8 (D) IL-10 (E) TNF-α (F) CAT (G) T-SOD (H) GSH-PX (I) T-AOC (J) MDA. All data are presented as mean ± standard deviation. *P < 0.05, **P < 0.01, *** P < 0.001.

Fig. 2

Effects of 3-indoleacrylic acid on liver morphology and inflammation and antioxidant indexes in a lipopolysaccharide-induced liver injury model in laying hens. (A) ALT in serum. (B) AST in serum (C) HDL-C in serum (D) LDL-C in serum (E) TG in serum (F) TC in serum (G) Pathological histological sections stained with Hematoxylin and Eosin (HE) of the liver. (H) IL-1β in liver (I) IL-6 in liver (J) IL-8 in liver (K) IL-10 in liver (L) TNF-α in liver (M) CAT in liver (N) T-SOD in liver (O) GSH-PX in liver (P) T-AOC in liver (Q) MDA in liver. All data are presented as mean ± standard deviation. *P < 0.05, **P < 0.01, *** P < 0.001.

Fig. 3

Transcriptomic analysis of differentially expressed genes and functional enrichment based on the comparison between the LPS and IAA+LPS groups (the IAA+LPS group as the test group and the LPS group as the control). (A) Number of differentially expressed genes (DEGs). (B) Volcano plot analysis of DEGs between LPS and IAA+LPS groups. (C) EggNOG classification of DEGs. (D) Heatmap of DEGs. (E) GO classification enrichment analysis of DEGs. (F) KEGG pathway enrichment analysis of DEGs.

Fig. 4

Transcriptomic analysis reveals the regulatory mechanisms based on the comparison between the LPS and IAA+LPS groups (the IAA+LPS group as the test group and the LPS group as the control). (A) GO enrichment analysis of genes downregulated by IAA. (B) GO enrichment analysis of genes upregulated by IAA. (C) KEGG pathway enrichment analysis of genes downregulated by IAA. (D) KEGG pathway enrichment analysis of genes upregulated by IAA. (E) Expression levels of DEGs between LPS and IAA groups. All data are presented as mean ± standard deviation. *P < 0.05, **P < 0.01, *** P < 0.001.

Fig. 5

TEM and TUNEL analysis of liver and Relative mRNA expression of genes in laying hens. (A) Transmission electron microscopy (Gultemirian et al.) analysis of liver tissue. (B) TUNEL staining analysis of liver tissue. Relative mRNA expression levels of (C) IL-1β, (D) TNF-α, (E) IL-6, (F) T-SOD, (G) CAT, (H) GSH-PX in liver. All data are presented as mean ± standard deviation. *P < 0.05, **P < 0.01, *** P < 0.001.

Fig. 6

Immunofluorescence analysis of TGR5 protein expression in liver tissue. All data are presented as mean ± standard deviation. *P < 0.05, **P < 0.01.