Gpr37 contributes to inflammation-induced GI dysmotility by regulating enteric reactive gliosis.

The enteric nervous system (ENS) is contained within two layers of the gut wall and is made up of neurons, immune cells, and enteric glia cells (EGCs) that regulate gastrointestinal (GI) function. EGCs in both inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) change in response to inflammation, referred to as reactive gliosis. Whether EGCs restricted to a specific layer or region within the GI tract alone can influence intestinal immune response is unknown. Using bulk RNA-sequencing and in situ hybridization, we identify G-protein coupled receptor, Gpr37, as a gene expressed only in EGCs of the myenteric plexus, one of the two layers of the ENS. We show that Gpr37 contributes to key components of LPS-induced reactive gliosis including activation of NF-kB and IFN-y signaling and response genes, lymphocyte recruitment, and inflammation-induced GI dysmotility. Targeting Gpr37 in EGCs presents a potential avenue for modifying inflammatory processes in the ENS. Transcriptional profiles of EGCs from: (1) all four regions and layers of the GI tract in adult Plp1eGFP mice, n= 5-6. (2) LPS- or PBS-treated Plp1eGFP mice in the SI MP and colon MP, n=4, 2-hour timepoint. (3) LPS- or PBS-treated Gpr37WT; Plp1eGFP and Gpr37-/-; Plp1eGFP mice in the SI MP and colon MP, n=4-6, 24-hour timepoint.

肠神经系统（enteric nervous system, ENS）包被于两层肠壁之中，由调控胃肠道（gastrointestinal, GI）功能的神经元、免疫细胞与肠胶质细胞（enteric glia cells, EGCs）组成。在炎症性肠病（inflammatory bowel disease, IBD）与肠易激综合征（irritable bowel syndrome, IBS）患者体内，肠胶质细胞会响应炎症刺激发生变化，该过程被称为反应性胶质增生（reactive gliosis）。目前尚不明确，仅局限于胃肠道特定层区或区域的肠胶质细胞是否能够独立影响肠道免疫应答。
本研究通过批量RNA测序（bulk RNA-sequencing）与原位杂交（in situ hybridization）技术，鉴定出G蛋白偶联受体（G-protein coupled receptor）Gpr37仅在肠神经系统两层结构之一的肌间神经丛（myenteric plexus）的肠胶质细胞中表达。研究证实，Gpr37参与脂多糖（lipopolysaccharide, LPS）诱导的反应性胶质增生的关键环节，包括核因子κB（NF-κB）与干扰素γ（IFN-γ）信号通路及应答基因的激活、淋巴细胞招募，以及炎症介导的胃肠道动力障碍。靶向肠胶质细胞中的Gpr37，为干预肠神经系统的炎症过程提供了潜在途径。
本研究的肠胶质细胞转录谱来自以下三组样本：(1) 成年Plp1eGFP小鼠胃肠道全部四个区域及四层组织的肠胶质细胞，样本量n=5-6；(2) 小肠肌间神经丛（SI MP）与结肠肌间神经丛（colon MP）中，经脂多糖或磷酸盐缓冲液（PBS）处理的Plp1eGFP小鼠肠胶质细胞，样本量n=4，采集时间为处理后2小时；(3) 小肠肌间神经丛（SI MP）与结肠肌间神经丛（colon MP）中，经脂多糖或磷酸盐缓冲液处理的Gpr37野生型（Gpr37WT）; Plp1eGFP小鼠与Gpr37基因敲除型（Gpr37-/-）; Plp1eGFP小鼠肠胶质细胞，样本量n=4-6，采集时间为处理后24小时。