Table3_Electroacupuncture Reduces Visceral Pain Via Cannabinoid CB2 Receptors in a Mouse Model of Inflammatory Bowel Disease.XLSX

Inflammatory bowel disease (IBD) results in chronic abdominal pain in patients due to the presence of inflammatory responses in the colon. Electroacupuncture (EA) is effective in alleviating visceral pain and colonic inflammation associated with IBD. Cannabinoid CB2 receptor agonists also reduce colonic inflammation in a mouse model of IBD. However, whether EA reduces visceral pain and colonic inflammation via the CB2 receptor remains unknown. Here, we determined the mechanism of the antinociceptive effect of EA in a mouse model of IBD induced by rectal perfusion of 2,4,6-trinitrobenzenesulfonic acid solution (TNBS). EA or sham EA was performed at the bilateral Dachangshu (BL25) point for seven consecutive days. The von Frey and colorectal distension tests were performed to measure mechanical referred pain and visceral pain. Western blotting and immunohistochemistry assays were carried out to determine the expression of IL-1β and iNOS and activation of macrophages in the colon tissues. We found that EA, but not sham EA, attenuated visceral hypersensitivity and promoted activation of CB2 receptors, which in turn inhibited macrophage activation and the expression of IL-1β and iNOS. The effects of EA were blocked by AM630, a specific CB2 receptor antagonist, and by CB2 receptor knockout. Our findings suggest that EA attenuates mechanical allodynia and visceral hypersensitivity associated with IBD by activating CB2 receptors and subsequent inhibition of macrophage activation and expression of IL-1β and iNOS.

炎症性肠病（Inflammatory Bowel Disease, IBD）是一类因结肠存在炎症反应，导致患者出现慢性腹痛的疾病。电针（Electroacupuncture, EA）可有效缓解炎症性肠病相关的内脏痛与结肠炎症。大麻素CB2受体（Cannabinoid CB2 Receptor）激动剂同样可在炎症性肠病小鼠模型中减轻结肠炎症。然而，电针是否通过CB2受体发挥内脏痛缓解与结肠炎症改善的作用，目前仍不明确。本研究旨在阐明电针在2,4,6-三硝基苯磺酸（2,4,6-Trinitrobenzenesulfonic Acid, TNBS）直肠灌注诱导的炎症性肠病小鼠模型中的镇痛作用机制。我们对双侧大肠俞（BL25）穴实施连续7天的电针或假电针干预。采用冯·弗雷（von Frey）试验与结直肠扩张试验，分别检测机械性牵涉痛与内脏痛水平。通过蛋白质印迹法（Western Blotting）与免疫组织化学（Immunohistochemistry）实验，测定结肠组织中白细胞介素1β（IL-1β）、诱导型一氧化氮合酶（Inducible Nitric Oxide Synthase, iNOS）的表达情况，以及巨噬细胞的活化状态。结果显示，相较于假电针，电针可缓解内脏痛觉过敏，并促进CB2受体活化，进而抑制巨噬细胞活化以及IL-1β与iNOS的表达。特异性CB2受体拮抗剂AM630与CB2受体基因敲除均可阻断电针的上述效应。本研究结果表明，电针可通过激活CB2受体，后续抑制巨噬细胞活化以及IL-1β与iNOS的表达，从而改善炎症性肠病相关的机械性痛觉异常与内脏痛觉过敏。