ERK1/2通路在远端肢体缺血预处理对氯胺酮麻醉后脑发育期神经凋亡中的作用及机制

The nerve cell apoptosis in rodents and primates brain induced by ketamine, the general anesthetics in children commonly used clinically, has become a research hotspot in the area of postoperative cognitive dysfunction in developing brain in recent years, among which the ketamine-induced neurotoxicity has not been fully elucidated and effective preventive treatment measures yet. Neuroinflammation and MAPK-Erk1/2 signaling pathway was shown to be involved in ketamine-induced neuronal cell apoptosis, leading to developing brain cognitive impairment. Application of remote limb ischemia preconditioning (RIPC) was confirmed play a role in the protection of ischemic hypoxic brain damage, through mechanisms of adjusting the related signaling pathways and anti-inflammation and antiapoptotic ,et al. Thus, we speculated that the RIPC may be an effective measures to prevent ketamine-induced neurotoxicity. This study is thus designed to investigate the ultrastructural and functional alterations of nerve cell, the expression of inflammation factors, as well as neuronal apoposis in newborn rat brain after ketamine exposure with RIPC pre-treatment. Furthermore, the potential mechanism of RIPC, which might be a safer strategy for ketamine-induced neuronal apoposis in newborn rats, will be explored by gavage of MAPK-Erk1/2 inhibitor. The results of the study will may provide experimental evidence for reveal the role of RIPC to improve anesthetic neurotoxicity in newborn rats, and provide a new theoretical basis for protective measure.

儿童常用麻醉剂氯胺酮导致动物脑神经细胞凋亡是发育期大脑术后认知功能障碍研究的热点。已报道氯胺酮引起的脑内炎症反应与MAPK-Erk1/2信号通路参与并影响神经细胞的凋亡导致发育期大脑认知障碍。远端肢体缺血预处理(remote ischemic preconditioning，RIPC )被证实通过调节相关信号通路和抗炎、抗凋亡等机制对缺血缺氧性脑损伤发挥保护作用。因此推测RIPC可能是预防氯胺酮发育期神经毒性的有效措施。本研究拟采用新生大鼠模型，给予RIPC预处理，观察氯胺酮麻醉对神经细胞超微结构及功能、神经炎症和脑内神经细胞凋亡发生的影响；给予MAPK-Erk1/2的抑制剂干预信号代谢通路，探讨RIPC对氯胺酮麻醉后神经细胞结构及功能的改变、神经炎症与凋亡的影响机制。研究结果将揭示RIPC在新生大鼠氯胺酮麻醉所致神经毒性中的预防作用，为阐明寻找预防氯胺酮引起的发育期神经毒性提供实验依据。

婴幼儿常用麻醉药氯胺酮可导致脑细胞凋亡，引起发育期大脑认知功能障碍，其机制可能与干扰ERK1/2信号通路及引起神经炎症有关。远端肢体缺血预处理(remote ischemic preconditioning，RIPC )已被证实可通过调节相关信号通路及抗炎、抗凋亡等机制对缺血缺氧性脑损伤发挥保护作用，但对氯胺酮造成的神经毒性是否有影响尚不明确。因此课题组建立氯胺酮致新生大鼠神经毒性模型，给予RIPC预处理，观察氯胺酮麻醉对神经细胞结构及功能、神经炎症和凋亡发生的影响；给予ERK1/2通路抑制剂干扰信号通路相关蛋白，探讨RIPC对氯胺酮诱导神经毒性的影响及机制。研究结果表明，反复暴露氯胺酮后的早期，氯胺酮可导致大脑皮层和海马神经细胞凋亡，KTM组凋亡蛋白caspase-3、bax增加，抗凋亡蛋白bcl-2减少，炎性因子TNF-α、 IL-6、 IL-1β水平增加，p-ERK1/2蛋白水平下降，而RIPC预处理可以减轻氯胺酮的神经毒性，减少神经细胞凋亡，相比于KTM组，RIPC+KTM组caspase-3、bax减少，bcl-2增加，TNF-α、 IL-6、 IL-1β水平降低，p-ERK1/2蛋白水平增加；而反复暴露氯胺酮后的晚期，炎性因子TNF-α、 IL-6、 IL-1β水平恢复至正常水平，p-ERK1/2蛋白水平恢复正常。同时发育期暴露于氯胺酮可导致长期的认知功能障碍，水迷宫结果显示，KTM组大鼠学习记忆能力下降，而RIPC+KTM组学习记忆能力得到改善。研究结果揭示了氯胺酮诱导发育期神经毒性的机制，同时RIPC这一简单易行的措施可改善氯胺酮的神经毒性。