肠罗斯氏菌在炎症性肠病中通过肠上皮细胞TLR5/2诱导Treg细胞分化的抑炎机制研究

Inflammatory bowel disease (IBD), a chronic recurrent autoimmune disease, is currently associated with poor prognosis. Our previous study provided the first evidence that Roseburia intestinalis (R.intestinalis) was significantly reduced in the intestinal tract of the patients with Crohn’s disease(CD) in China, which may play the anti-inflammatory role by up-regulating the levels of TSLP, TGF-β, TLR5 and TLR2, and increasing the proportion of Treg cells. Accordingly, we speculate that R.intestinalis promotes the secretion of TSLP and TGF-β from intestinal epithelial cells via TLR5 and/or TLR2, thus inducing the differentiation of the tolerogenic DCs (tolDCs) and Treg cells. In this present study, we propose to investigate the effects of R.intestinalis on Disease Activity Index (DAI) score, intestinal pathology, the expressions of TSLP, TGF-β, TLR5 and TLR2 , and the differentiation of tolDCs and Treg cells by using murine TNBS colitis models of WT BM→TLR5-/- bone marrow chimeric mice, WT BM→TLR2-/- bone marrow chimeric mice, TLR5f/f;Villin-Cre, TLR2f/f;Villin-Cre, TSLP/TGF-β silenced mice, elucidating the molecular mechanisms of R.intestinalis inducing the differentiation of Treg cells via TLR5 and/or TLR2 of the intestinal epithelial cells in IBD. We will further confirm the above study in cells and human tissues. The proposed study may present a new rationale for identifying novel therapeutical target for the treatment of IBD.

炎症性肠病（IBD）是一种慢性复发性自身免疫性疾病，目前疗效及预后差。我们前期结果首次揭示：肠罗斯氏菌（R.I）在我国CD患者肠道中丰度明显降低；该菌株上调小鼠肠上皮细胞胸腺基质淋巴细胞生成素（TSLP）、TGF-β、TLR5及TLR2的表达，增加Treg细胞比例，可能是其抑炎机制。据此，我们推测R.I在IBD中通过TLR5和/或TLR2促进肠上皮分泌TSLP、TGF-β诱导耐受性DCs及Treg分化。我们将采用肠固有层TLR5/2敲除骨髓嵌合鼠、肠上皮特异性TLR5/2敲除鼠以及TSLP、TGF-β沉默的野生型鼠的结肠炎模型，分别以R.I干预，研究R.I对小鼠疾病活动指数（DAI）评分、肠组织病理及TSLP、TGF-β的表达、耐受性DCs及Treg分化的影响，阐明R.I通过肠上皮细胞TLR5/2诱导Treg分化的机制；并在细胞及临床组织水平验证。研究将为发现IBD治疗新靶点提供理论基础。

炎症性肠病（Inflammatory bowel disease, IBD），包括溃疡性结肠炎和克罗恩病（Crohn’s disease, CD），是一种免疫相关的慢性复发性肠道炎症性疾病。IBD的发病与肠道菌群失调密切相关。然而，肠道菌群在IBD相关的炎症反应中的调控作用尚未完全明确。本课题中，我们发现肠罗斯氏菌（Roseburia. Intestinalis，R. intestinalis)通过促进抗炎的调节性T细胞（Treg）的分化来抑制CD的肠道炎症。R. intestinalis通过Toll样受体-5（TLR5）而不是TLR2和TLR4诱导Treg分化发挥抑炎作用，并采用TLR5敲除鼠的结肠炎模型予以证实。进一步采用TLR5敲除骨髓嵌合鼠发现表达TLR5的IEC在其中发挥重要作用。在细胞水平我们发现IEC产生的TSLP诱导树突状细胞分泌IL-10和TGFβ，这对于诱导Treg分化是必需的。同时，TSLP沉默（使用抗TSLP中和抗体）的野生鼠的结肠炎模型证实TSLP对于R. intestinalis缓解TNBS诱导的小鼠结肠炎是必须的。此外，临床水平发现CD患者中TSLP的表达与R. intestinalis水平呈正相关。这些发现阐明了先前未知的R. intestinalis介导的肠道免疫调节的机制，这可能为开发新的CD治疗策略提供基础。