Effect of total triterpenoids of Chaenomeles speciosa on PPARγ/SIRT1/NF-κBp65 signaling pathway and intestinal mucosal barrier of ulcerative colitis induced by DSS in mice

Abstract

To observe the effect of total triterpenoids of Chaenomeles speciosa on PPARγ/SIRT1/NF-κBp65 signaling pathway and intestinal mucosal barrier of ulcerative colitis induced by dextran sulfate sodium (DSS) in mice, C57BL/6 mice were randomly divided into normal group, model group, total triterpenoids of C. speciosa (50, 100 mg·kg⁻¹) groups and sulfasalazine (250 mg·kg⁻¹) group. The ulcerative colitis (UC) model was induced by orally administering 2.5% DSS to the experimental mice, and the corresponding drugs were given to each group 3 days before the administration with 2.5% DSS. The normal group and the model group were given the equal volume of 0.5% carboxymethyl cellulose sodium solution by gavage continuously for 10 days, q.d. The general conditions of the mice were observed on a daily basis, and the disease activity index (DAI) score was recorded. On the 10th day after the treatment, mice were put to death, the contents of TNF-α, IL-1β, IL-6, IFN-γ, IL-4 and IL-10 in the blood were detected, colon length was measured, colon mucosa damage index (CMDI) score was calculated, and MPO activity detection and histomorphology analysis were conducted. Real-time PCR was applied to detect the mRNA expressions of E-cadherin, occluding,MUC2 and TFF3; the protein expressions of SIRT1, IKKβ, p-IKKβ, IκBα, p-IκBα and cytosol and nucleus PPARγ, NF-κBp65 in intestinal tissue were detected by western blot. The results indicated that total triterpenoids of C. speciosa (50, 100 mg·kg⁻¹) could significantly improve the general conditions of UC mice, reduce the DAI, CMDI and histopathological scores, increase the colon length, reduce the colonic mucosa ulcers, erosion and inflammatory infiltration, restore the normal intestinal mucosal barrier function, reduce the contents of TNF-α, IL-1β, IL-6, IFN-γ, increase the contents of IL-4 and IL-10 in the blood, inhibit MPO activity in colon tissue, up-regulate the mRNA expressions of E-cadherin, occludin, MUC2 and TFF3 in colon tissue, down-regulate the protein expressions of cytosol PPARγ, tissue p-IKKβ, p-IκBα and nucleus NF-κBp65 in the colon tissue, decrease the p-IKKβ/IKKβ and p-IκBα/IκBα ratios, up-regulate the protein expressions of nucleus PPARγ, tissue SIRT1 and cytosol NF-κBp65 (P<0.05 or P<0.01, respectively), with a dose-effect relationship between the total triterpenoids of C. speciosa treated groups. These findings suggested that total triterpenoids of C. speciosa had a significantly therapeutic effect on UC mice induced by DSS, its mechanism might be related to the regulation of PPARγ/SIRT1/NF-κBp65 signaling pathway, the inhibition of pro-inflammatory factor formation and the up-regulation of protein expression of protective factors.