Eriodictyol attenuates TNBS-induced ulcerative colitis through repressing TLR4/NF-kB signaling pathway in rats

Abstract

Ulcerative colitis (UC) is a chronic disease characterized by mucosal and submucosal inflammation, which has a low cure rate and is prone to relapse, due to the immune imbalance of the body. Inhibition of inflammation-related pathways can delay the progression of UC. Toll-like receptor 4 (TLR4) pathway is considered to be one of the important signaling pathways involved in colon inflammation. Eriodictyol (EDT) is a natural flavonoid widely distributed in foodborne plants. EDT plays an important role in the regulation of inflammation and related signaling pathways. However, whether EDT plays a role in UC remains unknown. Herein, we established a TNBS induced animal model of enteritis in Wistar rats. Our data confirmed the establishment of TNBS induced animal model of enteritis and the administration Eriodictyol in Wistar rats. EDT treatment alleviated TNBS-induced intestinal tissue injury in rats. We further found that EDT reduced MPO expression and regulated the cytokine parameters in TNBS-induced intestinal tissues of rats. The levels of TNF-α, IL-1β, IL-6, IL-10, IL-2, and IL-12 were also affected by the treatment of EDT. EDT also affected SOD, CAT, GSH-Px, and MDA level in rats with colitis. Moreover, EDT regulated TNBS-induced TLR4/NF-κB pathway activation, therefore inhibiting the progression of UC. Our results suggest that EDT could be a potential therapeutic agent for UC.

Keywords: NF-κB; TNBS; eriodictyol; toll-like receptor 4; ulcerative colitis.

FIGURE 1

EDT adminstration alleviates TNBS‐induced colitis in rats. A, The chemical formula of EDT. B, Rat weight change in TNBS and TNBS with EDT assumption group. C, D, The histological changes and the scores of colons in control, TNBS, TNBS+EDT 5 mg/kg, TNBS+EDT 20 mg/kg, TNBS+EDT 50 mg/kg groups. Data were presented as means ± SD (n = 6 in each group). TNBS versus control group, *p < 0.05, **p < 0.01. TNBS+EDT (5, 20, and 50 mg/kg) versus TNBS group, ^## p < 0.01

FIGURE 2

EDT reduces MPO level induced by TNBS in colons. MPO expression level in control, TNBS, TNBS+EDT 5 mg/kg, TNBS+EDT 20 mg/kg, TNBS+EDT 50 mg/kg groups were assessed by IHC and MPO positive cell number was analyzed. Three independent experiments were performed. Data were presented as means ± SD TNBS versus control group, **p < 0.01. TNBS+EDT (5, 20, and 50 mg/kg) versus TNBS group, ^## p < 0.01

FIGURE 3

EDT regulates the cytokine parameters in rat's colons with TNBS‐induced colitis. IL‐6, IL‐1β, TNF‐α, IL‐2, IL‐10, and IL‐12 level in control, TNBS, TNBS+EDT 5 mg/kg, TNBS+EDT 20 mg/kg, and TNBS+EDT 50 mg/kg groups was detected by ELISA assay. Three independent experiments were performed. Data were presented as means ± SD TNBS versus control group, **p < 0.01. TNBS+EDT (5, 20, and 50 mg/kg) versus TNBS group, ^## p < 0.01

FIGURE 4

EDT affects SOD, CAT, GSH‐Px, and MDA level in rats with colitis. SOD, CAT, GSH‐Px, and MDA level in rats in control, TNBS, TNBS+EDT 5 mg/kg, TNBS+EDT 20 mg/kg, TNBS+EDT 50 mg/kg groups were detected with respective ELISA kit. Three independent experiments were performed. Data were presented as means ± SD TNBS versus control group, **p < 0.01. TNBS+EDT (5, 20, and 50 mg/kg) versus TNBS group, ^## p < 0.01

FIGURE 5

EDT regulates TNBS induced TLR4/NF‐κB siganaling pathway. Immunoblot assay was performed and the protein levels of TLR4, IκBa, p‐IκBa, p65, and p‐p65 in control, TNBS, TNBS+EDT 5 mg/kg, TNBS+EDT 20 mg/kg, and TNBS+EDT 50 mg/kg groups were detected. Three independent experiments were performed. Data were presented as means ± SD TNBS versus control group, **p < 0.01. TNBS+EDT (5, 20, and 50 mg/kg) versus TNBS group, ^## p < 0.01