Pathophysiological Role of Cholinergic Anti-inflammatory Pathway via Nicotinic Acetylcholine Receptors in Experimental Ulcerative Colitis

据报道，由迷走神经控制的胆碱能抗炎通路抑制局部细胞因子释放。流行病学报告表明，吸烟和尼古丁可以改善溃疡性结肠炎（UC）的症状。本研究旨在探讨迷走神经在恶唑酮（oxazolone，OXZ）诱导的Th 2型UC模型中的病理生理作用。方法：将OXZ注射于BALB/c小鼠（Th 2优势株）的结肠。采用疾病活动性评分（DAS）、病理性结肠损伤评分（CDS）和髓过氧化物酶（MPO）对OXZ结肠炎进行评分。结果：OXZ处理的小鼠发生结肠炎，以OXZ结肠炎结肠中DAS、CDS和MPO的增加为标志。2-脱氧-d-葡萄糖中枢刺激迷走神经可显著改善DAS、CDS和MPO，尼古丁以剂量依赖方式显著减轻OXZ结肠炎。值得注意的是，六甲双铵和α7-烟碱乙酰胆碱受体（nAChR）拮抗剂甲基乌头碱显著阻止了尼古丁在OXZ结肠炎中的治疗作用。Th 2细胞因子（IL-4、IL-5和IL-10）的转录水平在OXZ结肠炎小鼠的脾和结肠中显著增加。Th 1细胞因子IFN-γ mRNA在脾脏中表达显著降低，在中结肠中表达显著升高。值得注意的是，在尼古丁处理的小鼠的脾和结肠中，Thl和Th 2细胞因子mRNA均显著下调。此外，为了鉴定结肠中的α7-nAChR，用FITC标记的α-银环蛇毒素（α-BTx; α7-nAChR拮抗剂）对OXZ结肠炎小鼠结肠的未固定冷冻切片进行染色。在OXZ结肠炎结肠中，Α-BTx结合细胞上调，尼古丁预处理消除了α-BTx的荧光。结论：迷走神经抗炎免疫途径通过结肠黏膜α7-nAChR发挥作用，减轻结肠炎症反应。

It has been reported that the cholinergic anti-inflammatory pathway that is controlled by the vagus nerve inhibits local cytokine release. Epidemiologic reports suggest that smoking and nicotine may improve the symptoms of ulcerative colitis(UC. The purpose of the present study was to investigate the pathophysiological role of vagus nerve in oxazolone (OXZ)-induced Th2 type UC model. METHODS: OXZ was injected into the colon of BALB/c mice (Th2 dominant strain). OXZ colitis was assessed in the colon with the disease activity score(DAS), pathological colonic damage score(CDS) by macroscopic evaluation and MPO. RESULT: OXZ-treated mice developed colitis marked by increase of DAS, CDS and MPO in the colon of the OXZ colitis. The central stimulation of vagus nerves by 2-deoxy-d-glucose significantly improved DAS, CDS and MPO and nicotine significantly alleviated the OXZ colitis in a dose-dependent fashion. Notably, hexamethonium and α7-nicotinic acetylcholine receptor (nAChR) antagonist methyllycaconitine significantly prevented the therapeutic effects of nicotine in OXZ colitis. Transcript levels of Th2 cytokines (IL-4, IL-5, and IL-10) significantly increased in the spleen and the colon of OXZ colitis mice. On the other hand, Thl cytokine, IFN-γ mRNA significantly decreased in the spleen and significantly increased in the middle colon. Noteably, both Thl and Th2 cytokines mRNAs were significantly down-regulated in the spleen and colon of nicotine-treated mice. Moreover, to identify α7-nAChR in the colon, unfixed cryosections of colon from OXZ colitis mice were stained with FITC-labelled α-bungarotoxin (α-BTx; α7-nAChR antagonist). Α-BTx-binding cells were upregulated in the OXZ colitis colon, and nicotine pretreatment abolished the fluorescence of α-BTx. CONCLUSION: The vagal anti-inflammatory and immune pathway acts through α7-nAChR in the mucosa of the colon to alleviate inflammation in the colon.