IL-23受体基因多态性与炎症性肠病发病的关系及机理研究

Inflammatory bowel diseases (IBDs) are complex, multifactorial intestinal disorders. Genome-wide association studies(GWAS) have found significant association between IBD and one single nucleotide polymorphism (SNP) rs11209026 of IL-23 receptor (IL-23R) gene which results in one amino acid change Arg381Gln in the IL-23 receptor. However, the underlying mechanism has not been defined. Our preliminary study indicated that IL-23 could inhibit the differentiation of Foxp3+ regulatory T cells. We hypothesize that one amino acid change Arg381Gln in the IL-23 receptor might change the IL-23 signaling pathway and the inhibitory affect on the differentiation of Foxp3+ regulatory T cells therefore affect the susceptibility to inflammatory bowel diseases. In order to address this possibility, we will over express IL23R with SNP on Na?ve T cells from PBMC using retrovirus system. Differentiation of Foxp3+ regulatory T cells and phenotype of in vitro differentiated T cells will be assessed through flow cytometry after both intracellular and cell surface staining. Functionality analysis will be performed on these in vitro differentiated regulatory T cells after stimulation with IL-23 through suppression assay. Further more, IL-23/IL-23R signaling pathway and the association with Foxp3+ regulatory T cell induction will be identified through Westernblot and gene knock down technology. More importantly, we will directly evaluate the cell number, phenotype and function of Foxp3+ regulatory T cells derived from colon biopsies from individuals carrying IL-23R SNP. Our study will address the question how IL-23R single nucleotide polymorphism rs11209026 affects the IL-23/IL-23R signaling pathway and the differentiation as well as the function of Foxp3+ regulatory T cells. Therefore, the results will provide the critical evidence on the mechanism underlying the association of IL-23R single nucleotide polymorphism rs11209026 and the development of inflammatory bowel diseases. Thus, our study will imply a new therapeutic target through IL-23/IL23R pathway for the treatment of inflammatory bowel diseases and the prevention of severe complications such as colon cancer.

全基因组关联研究GWAS发现IL-23受体(IL-23R)基因多态性与炎症性肠病的发病有很高的相关性，然而，迄今IL-23及其受体在炎症性肠病中的作用机理尚未被阐明。我们的前期研究提示IL-23对人调节性T细胞的诱导分化有直接抑制作用，但其作用机制有待探讨。为此，我们提出假说：IL-23R基因多态性可能直接影响了IL-23信号通路对调节性T细胞的诱导分化的抑制作用，从而改变机体对炎症性肠病的易感性。为了验证这一假说，我们拟以人初始T细胞以及不同IL-23R基因型个体为研究对象，通过采用逆转录病毒表达载体、调节性T细胞的诱导分化、功能试验及细胞内信号传导通路的研究，从分子、细胞和人体整体水平等多方面探讨IL-23R基因多态性影响调节性T细胞的诱导分化及其功能的作用机理，为揭示IL-23R基因多态性影响机体对炎症性肠病易感性的分子机理奠定基础，进而为炎症性肠病及其并发症如结肠癌的防治提供新思路

炎症性肠病是指反复发作的肠道黏膜炎症性疾病，临床分为两大类：Crohn氏病和溃疡性结肠炎,前者可累及消化道的任何部位而后者仅局限于结肠黏膜，严重威胁人类健康，降低患者生活质量。炎症性肠病的发病率在我国的发病率直线上升，达到万分之三，而且发病人群集中于青壮年，对患者及其家庭造成巨大影响， 然而，由于发病机理未明该病至今尚无根治方法，因此，可以预见炎症性肠病将成为威胁我国人民健康的重要病种之一。炎症性肠病的病因和发病机理尚未完全明确，目前认为该病是由机体对肠道内的抗原物质产生的以T细胞介导为主的过度免疫反应所致，病因包括三大类：遗传因素，个体的免疫系统和环境因素。针对遗传因素与炎症性肠病发病之间的关系及其机理的研究是当前该领域的热点和难点，人群全基因组关联研究证实IL-23R蛋白第381位氨基酸为谷氨酰胺的个体患炎症性肠病的可能性仅为第381位氨基酸为精氨酸的个体的0.26 倍。然而，IL-23R基因多态性在炎症性肠病中的作用机理及临床意义目前还未被阐明。通过建立急、慢性ＤＳＳ结肠炎小鼠模型，我们发现在小鼠结肠粘膜发生炎症时粘膜内的ＩＬ－２３、ＴＮＦ－ａ、ＩＦＮ－ｇ等促炎症性细胞因子的表达明显增高，同时我们也检测到了结肠粘膜内的ＩＬ－２３Ｒ的表达也相应增高，这些异常与结肠粘膜的炎症程度一致；我们进一步检测结肠炎症时粘膜内Foxp3 + Rorgt +细胞的数量，发现在结肠炎症时粘膜内Foxp3 + Rorgt +细胞增加，提示在结肠粘膜炎症时肠黏膜内调节性Ｔ细胞的诱导分化出现了异常，我们的研究证实了ＩＬ－２３／ＩＬ－２３Ｒ在结肠粘膜炎症时通过影响调节性Ｔ细胞的稳定性激活Ｔｈ１介导的炎症反应，提示ＩＬ－２３／ＩＬ－２３Ｒ在炎症性肠病发病中的重要作用，为揭示IL-23R基因多态性影响机体对炎症性肠病易感性的分子免疫学机理奠定基础，进而为炎症性肠病及其并发症如结肠癌的防治提供新的思路。