[Regulatory effect of Tripterygium wilfordii polycoride (TWP) towards TLR4/MyD88 independent pathway in TNBS/ethanol ulcerative colitis (UC) rat model]

Abstract

In order to study the regulatory effect of Tripterygium wilfordii polycoride (TWP) towards TLR4/MyD88 independent pathway in TNBS/ethanol ulcerative colitis (UC) rat model, TNBS/ethanol enema was adopted to build TNBS/ethanol UC rat model. After the successful modeling procedure, 90 male Wistar rats are were divided into 6 groups, including namely normal group, model group, TWP low, middle, high dose groups (3, 6, 12 mg•kg⁻¹)and azathioprine (AZA) group (6 g•kg⁻¹), with 15 rats in each group. All rats in each group were administrated with corresponding medicines for 14 days. After 14 days of administration, corresponding colon tissues were taken for general and microscopic evaluation. Western blotting analysis and RT-PCR were adopted to test the mRNA and protein expressions of TLR4/MyD88 independent pathway-related molecules, namely TLR4, TRAM, TRIF, NF-κB and IFN-γ. The results showed that DAI, general and microscopic evaluations all indicated that TNBS/ethanol UC rat model was successful. TWP can improve UC-related clinical manifestation and heal colonic mucosa, which was equal to AZA. RT-PCR and WB results showed that the expression of TLR4/MyD88 independent pathway-related molecules in model group were significantly superior to that in normal group at either mRNA or protein level (P<0.01). Compared with model group, TWP can inhibit the expression of each node in TLR4/MyD88 independent pathway in a dose-dependent manner. The inhibitory effect of TWP with high dose towards the above molecules was inferior to that in model group at either mRNA or protein level (P<0.05). The inhibitory effect of TWP with high dose towards upstream molecules of TLR4/MyD88 independent pathway (TLR4, TRAM, TRIF, NF-κB) was slightly superior to AZA group at either mRNA or protein level. However, such inhibitory effect towards terminal inflammatory cytokines (IFN-γ) was inferior to AZA group at either mRNA or protein level. All the above differences had no statistical significance. Therefore, in TNBS/ethanol UC rat model, TLR4/MyD88 independent pathway took part in regulating inflammation. TWP exerted its anti-inflammation effect by inhibiting the expression of TLR4/MyD88 independent pathway in a dose-dependent manner.

Keywords: TLR4/MyD88 independent pathway; Tripterygium wilfordii polycoride (TWP); ulcerative colitis (UC).