The suppressive effect of triptolide on chronic colitis and TNF-α/TNFR2 signal pathway in interleukin-10 deficient mice
Introduction
Crohn's disease (CD) and ulcerative colitis (UC) are chronic, relapsing, immunologically mediated disorders that are collectively referred to as inflammatory bowel diseases (IBD). The precise pathogenesis of IBD is still unclear, but activated innate (macrophage, neutrophil) and acquired (particularly Th-1T cell) immune have been reported to play a pivotal role in the development of CD [1]. Recently, many animal models have been developed to elucidate the immunopathological causes of IBD. Among these unique models are interleukin-10 deficient (IL-10−/−) mice, which were reported to spontaneously develop a Th1-mediated chronic colitis under specific-pathogen-free (SPF) conditions with many similarities to CD [2].
Elevated levels of interferon γ (IFN-γ) and tumor necrosis factor α (TNF-α) characterize the Th1 reaction. TNF-α is a multifunctional cytokine known to play a key role in the pathogenesis of IBD [1], [3]. TNF-α responses are mediated through binding to either of its receptors, TNFR1 or TNFR2. TNFR1 possesses an intracellular death domain which is required for the signaling of apoptosis [4]. Signals from TNFR1 that initiate apoptosis in activated T lymphocytes have the activities of antivirus and stimulating growth. TNFR2 does not contain the death domain [5]. Signaling through TNFR2 promotes thymocyte differentiation and T-cell proliferation [5]. There are increasing clinical and experimental evidences suggesting a distinct role of TNFR2 versus TNFR1 signaling in a variety of inflammatory disease states, in particular CD [6]. Overexpression of TNFR2 could promote Th1 cytokines expression and inhibit T cell apoptosis through activating nuclear factor κB (NF-κB) [6], [7], [8], [9], [10]. NF-κB has also been found to be related to the activation and perpetuation of inflammation [11].
Available therapies for CD based on immunosuppressive agents are still not satisfactory or entirely effective [12]. This illustrates the need for novel therapeutic approaches that specifically modulate both components of the disease—that is, the inflammatory and Th1 driven responses.
Extracts of the Chinese herbal remedy Tripterygium wilfordii Hook. f. (TWHF) have been reported to be therapeutically efficacious in some autoimmune diseases such as rheumatoid arthritis [13]. Triptolide, an active component of extracts derived from TWHF, is proved to have anti-inflammatory and immunosuppressive activities. Recent studies have shown that triptolide can inhibit lymphocyte proliferation, synthesis and secretion of proinflammatory cytokines [14], [15]. In addition, triptolide can induce apoptosis in T cells and dendritic cells as a potent NF-κB inhibitor [16], [17]. Triptolide has displayed a myriad of therapeutic uses against cancer, inflammation, and autoimmune diseases. However, the therapeutic effect of triptolide on IBD is relatively unknown.
In this study, we used triptolide as a therapeutic agent in inflammatory bowel disease. We hypothesized that the administration of triptolide to IL-10−/− mice would decrease the Th1T cell-mediated inflammatory cytokine production in the colon mucosa, and eventually ameliorate chronic colitis. Especially, we examined the effect of triptolide on TNFR expression and NF-κB activation for further study.
Section snippets
Animals
Male C57BL/6 IL-10−/− and wild-type mice (5 weeks old at the beginning of the study) were obtained from the Jackson Laboratory (Bar Harbor, Maine). Previous experiment demonstrated that since 4–5 weeks old, IL-10−/− mice would develop progressive chronic colitis with retarded growth under SPF conditions [2]. The mice were bred and maintained in a SPF animal facility at the Model Animal Research Center in Nanjing University (Nanjing, China). All mice received humane care in accordance with the
Treatment with triptolide protects against chronic colitis development
The control IL-10−/− mice spontaneously developed chronic colitis with diarrhea and retarded growth, while the triptolide-treated mice grew more steadily (Fig. 1). None of the mice developed diarrhea after 4 weeks administration of triptolide. The colon of control IL-10−/− mice was edematous, thickened and shortened by inflammation. In contrast, the colon of triptolide-treated mice seemed to be normal macroscopically (Fig. 2). Histological examination revealed edema, severe hyperplasia,
Discussion
According to a previous study, the maximum tolerated dose of triptolide for mice was 0.07 mg/kg/24 h i.p with no discernable adverse effects [19]. We chose 0.07 mg/kg/48 h to avoid the subchronic intoxication of triptolide. In fact, no apparent toxicity was observed in wild-type mice when triptolide was given intraperitoneally for 8 weeks at this dosage (data not shown).
As a murine model of CD, IL-10−/− mice spontaneously develop enterocolitis under SPF conditions as a result of their extreme
Acknowledgments
This work was supported in part by the Model Animal Research Center, Nanjing University (Nanjing, China). The authors thank Genbao Feng (Jinling Hospital of Nanjing, China) for the excellent technical assistances.
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2013, Molecular ImmunologyCitation Excerpt :As an active component of TWHF, triptolide has been used in the treatment of several autoimmune diseases such as IBD. Numerous mechanisms of triptolide have been obtained in previous study such as TLRs/NF-κB signaling pathway (Yu et al., 2011), TNF-α/TNFR2 signal pathway (Wei et al., 2008), IL-6/STAT3 signaling pathway (Li et al., 2010) and other mechanisms (Tao et al., 2007) although the therapeutic effects of this agent still remain obscure. MiR-155/SHIP-1 pathway was investigated in rheumatoid arthritis (RA), but it has not been investigated in the IBD condition.
Triptolide induces suppressor of cytokine signaling-3 expression and promotes lamina propria mononuclear cells apoptosis in Crohn's colitis
2013, International ImmunopharmacologyCitation Excerpt :Under normal conditions, to limit a potentially harmful immune reaction, activated T lymphocytes are rapidly eliminated by apoptosis, while in patients with CD, a defect of T lymphocyte apoptosis was observed [24–26]. Previous studies demonstrated that treatment with triptolide significantly improved the colitis, together with lower production of TNF-α, IL-12, IL-23, IL-17and IFN-γ in the colon [16,17], TLR signaling pathway and NF-кB activation in the colon were also downregulated after therapeutics [18–27]. In the present study we showed that the triptolide treatment induced apoptosis of LPMCs in IL-10−/− mice colitis.
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