胆碱能受体失衡：急性肺损伤关键启动因子HMGB1在体外循环术中异常分泌的新机制

Our previous study revealed that high mobility group box 1(HMGB1), the key initiate factor of acute lung injury(ALI), released after lung ischemia reperfusion injury(IRI) during cardiopulmonary bypass(CPB). Cholinergic anti-inflammatory pathway(CAP) was proved to inhibite the release of HMGB1 during IRI. Although vagus nerve was proved to be excited and acetylcholine(Ace) to be secreted during CPB, however, the activation of CAP was inhibited and the release of HMGB1 was increased during this process, the underlying mechanism remains unknown. Previous studies have demonatrated that α7 nicotinic acetylcholine receptor (α7nAChR) expreossion was inhibited during IRI. We infer that the expression (and/or) the function of α7nAChR is also inhibited in the process of lung IRI during CPB, which result in the imbalance of M and N cholinergic receptors and inhibition of CAP, promoting HMGB1 release and ALI initiation. In this study, the expression and activation of α7nAChR will be observed in the rat model of CPB-induced ALI and the pulmonary alveolar macrophage model of oxygen-glucose deprivation(OGD)-induced HMGB1 secretion. Selective agonist or antagonist will be used to evalutate the role α7nAChR play in regulating the balance of cholinergic receptors and HMGB1 secretion. Antiinflammatory cytokines interleukin-10(IL-10) will be used in combination with M-ACh-receptor (M-AChR) antagonist anisodamine to synergistically inhibite HMGB1 secretion and ALI initiation by means of α7nAChR activaction and M-AChR inhibition. Our study will lay the foundation for the exploration of the mechanism and control methods of CPB-induced ALI.

我们以往发现体外循环（CPB）因肺缺血再灌注损伤（IRI）致HMGB1异常分泌，是急性肺损伤（ALI）的关键启动因子。胆碱能抗炎通路（CAP）可抑制其分泌。CPB中虽然存在迷走神经兴奋和乙酰胆碱释放，却未能活化CAP而抑制HMGB1分泌，其机制不明。有研究表明IRI可抑制α7烟碱受体表达。我们推测肺IRI可能抑制该受体表达或功能，引起M和N胆碱能受体失衡而抑制CAP活化，致HMGB1分泌和ALI。本研究通过大鼠CPB致ALI模型和氧糖剥夺致肺巨噬细胞HMGB1分泌模型，观察肺IRI中α7烟碱受体表达和功能变化情况，通过选择性激动或抑制该受体，评价其调控HMGB1分泌的作用。随后应用抗炎因子IL-10上调α7烟碱受体，并联合应用M受体拮抗剂山莨菪碱，发挥两者协同作用，从M和N受体两方面纠正胆碱能受体失衡，抑制HMGB1异常分泌和ALI发生，为CPB后ALI发病机制研究和防治方法探讨奠定基础。

由体外循环引起肺缺血再灌注损伤所致的胆碱能受体失衡是导致急性肺损伤的重要因素。在本课题中，我们重点研究并证实了肺组织α7烟碱型乙酰胆碱受体表达抑制是体外循环诱导急性肺损伤的致病机制，并且证实使用α7烟碱型乙酰胆碱受体激动剂PNU-282987以及电针刺激通过提高肺组织α7nAChR表达改善体外循环导致的急性肺损伤。.在大鼠体外循环模型中，我们发现体外循环-肺缺血再灌注损伤可抑制α7烟碱型乙酰胆碱受体的表达，促进M1型乙酰胆碱受体表达，导致胆碱能受体失衡并抑制胆碱能抗炎通路。在体外细胞学研究过程中，我们通过巨噬细胞氧糖剥夺模型证实氧糖剥夺能引起巨噬细胞α7烟碱型乙酰胆碱受体表达下降，M1型乙酰胆碱受体表达增加。在动物实验中，我们证实使用α7烟碱型乙酰胆碱受体激动剂PNU-282987能改善由体外循环导致的急性肺损伤严重程度，并进一步证实PNU-282987通过抑制巨噬细胞炎性介质HMGB1释放以及细胞因子IL-1β、TNF-α释放而改善体外循环导致的急性肺损伤过程。在细胞研究中我们证实：IL-10以及山莨菪碱（654-2）通过调节N型乙酰胆碱受体以及M乙酰胆碱受体失衡，减轻巨噬细胞在氧糖剥夺再复糖复氧条件下HMGB1的释放。同时，在体外循环过程中使用电针刺激亦能显著增加肺组织α7烟碱型乙酰胆碱受体表达而减轻急性肺损伤程度，提示电针刺激能发挥抗炎效应，减轻体外循环诱导的急性肺损伤作用。.本课题从胆碱能受体表达失衡的角度揭示了体外循环诱导急性肺损伤的机制，提示通过电针刺激等手段对胆碱能受体表达进行合理调控有望成为体外循环诱导急性肺损伤新的治疗方向，从而为该病防治手段的探索奠定基础。