多巴胺通过DRD5受体调控肠道巨噬细胞极化影响肠炎发生作用的研究

肠道多巴胺（DA）水平下降与炎症性肠病（IBD）发生密切相关，然而多巴胺信号在肠炎发生中的具体角色及作用机制尚不清楚。我们前期工作报道了DA-DRD5信号可抑制金葡菌感染引起的巨噬细胞炎症反应。本申请预实验研究中，我们进一步发现DRD5受体在结肠巨噬细胞高表达，并且DA-DRD5信号能抑制M1但促进M2巨噬细胞极化，还发现DA-DRD5信号在肠道免疫细胞中发挥结肠炎保护作用。据此我们推论：多巴胺可通过激活DRD5受体调控结肠巨噬细胞向M2型极化，来维持肠道黏膜免疫稳态和抑制结肠炎发生。在本项目中，我们将采用条敲小鼠、流式分析以及细胞分选组学分析等方法，1）进一步明确肠道巨噬细胞DA-DRD5信号在调节结肠炎发生中作用；2）阐明DA-DRD5信号调控结肠巨噬细胞极化的作用机制；3）探究靶向DA-DRD5信号在缓解IBD病程中的作用。本研究将加深我们对肠多巴胺神经调节IBD发生作用机理的理解。

The decrease of neurotransmitter dopamine (DA) level in intestine is closely related to the development of inflammatory bowel disease (IBD) including ulcerative colitis and Crohn disease. However, the specific functional relevance and mechanistic basis to the effects of DA signaling on IBD remains unclear. Our previous published work reported that DA-DRD5 signaling can inhibit inflammation in macrophages to protect against S. aureus-induced sepsis and meningitis. In the preliminary study of this application, we further observed that DRD5 receptor is highly expressed in colonic macrophages, and DA-DRD5 signaling can inhibit M1 but promote M2 macrophage polarization. Moreover, we found that the deficiency of DA-DRD5 signaling in immune cells exacerbated experimental colitis independent of changes in the microbiota. Thus, we suppose that DA can regulate the polarization of colonic macrophages to M2 type by activating DRD5 receptor, thereby maintaining the immune homeostasis of intestinal mucosa and controlling the development of colitis. In this project, we will use conditional knockout mice, flow cytometry, cell sorting and RNA-seq analysis to 1) further clarify the role of DA-DRD5 signaling of colonic macrophages in the regulation of colitis; 2) uncover the underlying mechanism of DA-DRD5 signaling in controlling the polarization of colonic macrophages; 3) explore the function of targeting DA-DRD5 signaling in the alleviation of IBD. Taken together, this study will deepen our understanding of the function and mechanism of dopaminergic neuromodulation of intestinal mucosal immune system and IBD.