GC-C信号通路在溃疡性结肠炎肠粘膜屏障维护中的作用机制研究

The incidence of ulcerative colitis (UC) is increasing in recent years, but the etiology of UC is not clear. Our preliminary studies have shown that the expressions of guanylate cyclase-C (GC-C), guanylin (Gn) and uroguanylin (Ugn) in colonic mucosa of UC patients were significantly decreased, GC-C signaling pathway played a protective role in the function of intestinal mucosal barrier. According to the report, normal flora is an important part of the intestinal mucosal barrier. The intestinal mucosal immune barrier maintains the normal immune response of the intestinal tract, and the damage of biological and immune barrier is closely related to the occurrence of UC. Therefore, we speculated that the GC-C signaling pathway mediates the occurrence of UC by regulating intestinal mucosa biology and immune barrier. In this study, we aim to further characterize the roles of GC-C in UC pathogenesis. So, various research will be carry out in this project: (1) in the clinical level, define the relationship between GC-C signaling pathway and the changes of intestine microbiome in UC patients; (2) in cellular level, define the roles of GC-C signaling pathway in the function of intestine immune cell; (3) in animal level, knock out and overexpression of GC-C in the DSS-induced UC mice, define the effect of GC-C signaling pathway on the intestine microbiome, cellular and humoral immune in mice. Our results will uncover the mechanism of GC-C during the progression of UC, and will help with the therapeutic interventions of UC.

溃疡性结肠炎（UC）发病率逐年升高，但发病机制不清。我们前期研究发现：UC患者肠粘膜组织鸟苷酸环化酶C（GC-C）及其配体Gn、Ugn的表达降低；GC-C信号通路在肠粘膜屏障功能中发挥保护作用。正常菌群是肠粘膜屏障的重要组成部分，肠粘膜免疫屏障维持肠道正常的免疫反应，生物、免疫屏障损伤与UC的发生密切相关。因此，我们推测GC-C信号通路通过调控肠粘膜生物及免疫屏障介导UC的发生。本项目拟通过：①临床水平，研究UC患者GC-C信号通路和肠道微生态变化的关系；②细胞水平，研究GC-C信号通路对免疫细胞功能的影响；③动物水平，研究GC-C基因敲除或过表达对UC小鼠肠道微生态、细胞和体液免疫的影响。旨在探索GC-C信号通路在UC中的作用机制，为研发UC新的治疗靶点提供理论依据。

溃疡性结肠炎（UC）发病率逐年增高，造成重大的社会负担。其发病与遗传易感、免疫失调、肠上皮机械屏障破损、肠道微生态失调和环境因素刺激五大因素相关，目前发病机理尚未完全阐明。课题组前期工作发现UC患者肠粘膜组织GC-C信号通路关键因子GC-C、Gn和Ugn表达降低，GC-C信号通路可能在肠粘膜屏障功能中发挥保护作用。本部分研究是在前期工作的基础上，通过宏基因组学测序分析及临床样本、细胞实验、动物实验研究，结果发现：（1）UC患者活动期和缓解期粪便样本中13个物种的丰度存在明显差异，PCA分析表明这13个物种可有效地鉴别UC患者活动期和缓解期；（2）功能注释分析显示在UC缓解期，孢子形成和生物合成下调，过氧化氢分解代谢过程上调；（3）受体GC-C及其配体Gn的表达相互调节，Gn可激活处于静止状态的GC-C信号通路；（4）活化的GC-C信号通路可保护肠上皮细胞与上皮内淋巴细胞(IELs)的肠粘膜免疫屏障；（5）GC-C基因敲除（GC-C-/-）小鼠在化学物质右旋糖酐硫酸酯钠（DSS）诱导下肠道炎症损伤加重；（6）Gn过表达载体可改善结肠炎小鼠肠道炎症损伤，修复肠黏膜屏障功能。通过以上研究，进一步明确了同一UC患者活动期与缓解期的肠道微生物特征，为UC患者的粪菌移植治疗提供有价值的参考依据；Gn可通过激活GC-C信号通路而发挥肠粘膜免疫屏障保护作用，GC-C受体激动剂可能是UC潜在的干预靶点，为探寻UC新的治疗靶点提供有效的实验依据。