糖酵解关键酶HK2在缺血性脑卒中的神经元损伤新角色

The cerebral stroke is harming the health of the people seriously, and its not fully illustrated pathological mechanism is one of reasons for the failure in the drug research and development. In our previous study, we found that the inhibition of hexokinase 2 (HK2), a glycolytic key enzyme whose upregulation dependently was required by activation of microglia, efficiently attenuated the brain injury caused by acute ischemic stroke in rat model via an epigenetic regulation for IL-1β, indicating the vital role of specific microglial HK2 in neuroinflammatory damage of brain. Currently it’s not fully demonstrated that if HK2 cause the injury to neurons directly, which is required to answer the question of that if the activated glycolytic key enzymes during the stroke is involved in cerebral damage via a pathway other than their metabolic functions. Basing on our previous study of selective the nuclear redistribution of HK2 in neuron induced by hypoxia, we aim to illustrated the direct damage effects of HK2 in neurons by a specific neuronal HK2 knockout using in vitro and in vivo model of ischemic stroke, and explore the possible mechanism of activating the pro-apoptosis transcript factor of Egr-1 by the nuclear redistribution of HK2 and its interaction with hnRNP K induced by pathological factors including hypoxia. Our study hope to uncover the novel role of HK2 in neuronal injury via a pathway characterized by transcriptional regulation, which providing the experimental data for the research and development of drug targeting HK2 for cerebral stroke.

脑卒中严重危害人民身体健康，药物研发失败的重要原因之一是病理机制未被充分阐明。课题组前期研究显示，抑制糖酵解关键酶己糖激酶2（hexokinase 2, HK2）可有效减轻急性缺血性脑卒中模型的脑损伤，小胶质细胞激活依赖于HK2上调表达，HK2介导了IL-1β表观调节，证明小胶质细胞HK2导致了炎性脑损伤。并不清楚HK2是否对神经元也产生直接损伤作用，这对于回答“被激动的糖酵解关键酶是否通过代谢以外的功能，参与了缺血性脑卒中脑损伤过程”这一问题非常重要。预实验发现缺氧引起HK2选择性神经元核分布，本项目拟选择性在神经元敲除HK2，并应用体内外脑卒中模型，确证HK2对神经元的直接损伤作用，并探讨缺氧等病理因素诱导HK2核分布、和hnRNP K相互作用，激活促神经元凋亡转录因子EGR-1的分子机制。项目有望阐明HK2以转录调节为特征的神经元损伤新效应，为研发靶向HK2的脑卒中治疗药物提供依据。

急性缺血性脑卒中(Acute Ischemic Stroke，AIS)是世界范围致死、致残和致痴呆的重大疾病，具有高发病率、高死亡率、高致残率、高复发率以及高医疗负担的特点，严重危害身体健康。卒中脑损伤由一系列复杂的病理生理事件引起，包括兴奋性毒性、氧化应激和硝化应激、炎症等。但是目前靶向这些损伤事件的脑卒中药物在临床试验未显示出益处，重要原因之一是脑损伤的病理机制未被充分阐明，迫切需要进一步探索卒中损伤中新机制和脑保护药物新的靶点。.脑卒中病理情况下，糖酵解被增强，一些代谢产物如乳酸、NADPH通过酸中毒、氧化应激等机制产生了脑损伤效应。课题组前期发现，糖酵解关键酶己糖激酶2（Hexokinase 2, HK2）是缺血性脑卒中炎症损伤的关键分子，是候选脑卒中药物靶点。我们发现，HK2介导了缺氧缺血刺激下小胶质细胞的激活，通过上调白介素1β（Interleukin-1β, IL-1β）启动子组蛋白乙酰化水平促进IL-1β的表达造成脑损伤。但是缺血脑卒中损伤下HK2对神经元的效应及分子机制有待进一步阐明。.项目首先考察了不同脑卒中病理因素对神经元HK2的影响，发现OGD是引起HK2的神经元核聚集的主要原因，而兴奋性谷氨酸引起HK2表达增加但没有显著核聚集。在这两种不同的卒中病理因素下，项目进一步考察了神经元HK2两种异常对神经元损伤的效应与分子机制。我们发现抑制HK2抑制剂、可抑制HK2表达的神经元保护剂TRIOL以及选择性干扰HK2或敲除HK2可减轻神经元损伤或MCAO急性缺血性脑损伤。机制研究表明胞浆HK2通过与PARKIN相互作用启动神经元线粒体自噬损伤，而核聚集HK2与CDK5相互作用，引起CDK5入核并转录激活其下游凋亡调节蛋白Bim，直接参与神经元损伤。.本项目确证HK2存在糖代谢以外的新功能新效应，揭示了HK2在神经元中的损伤效应与机制。项目为进一步确证HK2是缺血性脑损伤关键损伤因子提供新的证据，并为靶向HK2的神经保护药物研发提供实验依据。由于HK2仅仅在胚胎发育期表达水平较高，而HK2在成年组织在胰岛素敏感组织中少量表达，因此未来靶向HK2的选择性抑制剂至少在脑卒中药物的安全性方面提供了先天性的优势。