ERβ、SRC-1介导STAT3信号通路调节Th17/Treg细胞分化在CD发病中的作用

The pathogenesis of Crohn's disease (CD) is not very clearly, and the imbalance of Th17/Treg cells was thought to have significant relationship with the pathogenesis. STAT3 signal pathway may act the key role of the differentiation and activation of Th17/Treg cells. It has reported that estrogen receptor beta (ERβ) and steroid receptor coactivator-1(SRC-1) are abundantly expressed in colonic tissue. Furthermore, there was reported that ERβ expression was decreased in TNBS induced mice colitis, which is an animal model of CD. Besides, ERβ agonist application plays a markedly therapeutic role in this animal model, suggesting that ERβ has an anti-inflammatory effect. However, the mechanism is not clear yet. We already demonstrated that ERβ，SRC-1 were expressed in CD4+ T cells in colon tissue, and ERβ was involved in the Th17/Treg cell differentiation from CD4+ naïve T cell, also ERβ-p-STAT3 or SRC-1-p-STAT3 compound were existed in colon tissue. Therefore, we suggest the hypothesis that ERβ and SRC-1 maybe involved in STAT3 signal pathway to regulate the balance of Th17/Treg cell differentiation. We try to use contiditional gene knockout mice technique and other methods to testify the hypothesis which ERβ and SRC-1 are mediated in STAT3 pathway to regulate Th17/Treg cell differentiation from Naïve T cell. This study will help us to further clarify the pathogenesis of CD and to find new breaking point on intervention of Crohn’s disease.

克罗恩病(CD)发病机制尚未完全阐明，Th17/Treg细胞失衡认为与CD发病密切相关，STAT3通路在调节其分化中起关键作用。已发现雌激素受体β（ERβ）和类固醇辅激活因子-1（SRC-1）在肠道表达丰富，ERβ在CD模型小鼠肠道表达下调，ERβ激动剂可减轻肠道炎症，提示ERβ具有抗炎效应，但具体机制不详。本课题组前期研究证实ERβ、SRC-1存在于肠道CD4+T细胞，ERβ参与CD4+T细胞向Th17/Treg细胞分化，且肠道存在ERβ-p-STAT3、SRC-1-p-STAT3复合物。据此提出ERβ、SRC-1可能通过STAT3信号通路参与CD4+T细胞生物学行为调节。本项目拟采用条件基因敲除等方法从在体和体外分别研究ERβ、SRC-1是否参与STAT3调节CD4+T细胞向Th17/Treg细胞分化并阐明机制，为进一步明确CD发病机制并寻找新的CD干预突破点奠定基础。

溃疡性结肠炎(UC)和克罗恩病(CD)是炎症性肠病(IBD)的两种主要形式，其特征是由环境或遗传易感引起的肠道微生物群的异常粘膜免疫反应。CD4+FoxP3+调节性T细胞(Tregs)和效应T细胞(Teff) 之间的不平衡对IBD的发生和进展至关重要。雌激素受体(ER) β是核受体家族的一员，是炎症、免疫反应、癌症、神经退行性变和代谢的关键调节因子。先前的研究表明，ERβ具有强大的抗炎活性，然而，ERβ是否在结肠炎发展过程中调节肠道免疫反应的作用尚未被彻底研究。类固醇受体辅激活剂(SRC-1)属于介导核受体依赖或转录因子依赖转录的辅激活剂(SRC-1/2/3）家族，研究认为SRC参与诸多生命过程的调控。在本研究中的SRC-1相关的部分，我们证实在下丘脑中，SRC-1通过与磷酸化STAT3直接相互作用，调节POMC神经元的表达；此外，Src-1L1376P变异导致小鼠肥胖，突变基因通过瘦素依赖以及非依赖途径降低和POMC神经元的兴奋性。在ERβ研究的相关部分，我们首先证实了ERβ在人体肠道内大量表达，并且我们发现：炎症性肠病的患者其肠道内ERβ的表达量相对于正常人降低，这就突显出了研究ERβ的突出意义。实验数据表明ERβ和FOXP3具有共同定位的基础;进一步的实验证明了ERβ在DSS诱导的慢性结肠炎的进展过程中可以调节Treg的功能；发现ERβ特异性激动剂ERB041激活ERβ可明显减轻小鼠结肠炎相关的病理改变，抑制炎症反应，抑制促炎T细胞浸润以及炎症因子的产生；有意思的是，ERB041可显著提高小鼠结肠抗炎细胞因子（如IL-10和TGFβ1）基因的相对表达水平；ERB041还能恢复结肠炎小鼠ERβ+CD4+T细胞、Treg和FOXP3的表达，体外的研究中我们发现也发现ERB041可以促进Treg的分化，并增强生长因子介导的幼稚T细胞向Tregs的分化，而ERβ特异性拮抗剂PHTPP则消除并显著减轻了这种分化，这些数据提示ERB041治疗可以调节结肠炎小鼠结肠中致病性和调节性T细胞反应之间的失衡；我们发现ERβ激活增强了Tregs对CD4+、CD8+T细胞增殖的抑制活性，因此，ERβ的激活可能与TGF-β1相关的SMAD信号通路产生下游信号串扰，促进FOXP3的表达和功能性Treg的发育，从而抑制自身免疫性炎症。该项目为ERβ活化可以改善结肠炎提供了新的免疫学解释。