Modulation of GABAA receptor subtypes by neurosteroids and anesthetics: Identification of molecular targets for neuroprotection

神经类固醇和麻醉剂对 GABAA 受体亚型的调节：神经保护分子靶标的鉴定

• 批准号: 396715552
• 负责人: Professor Dr. Bernd Antkowiak
• 金额: --
• 依托单位: Klinik für Anästhesiologie und Intensivmedizin
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/396715552?language=en
• 关键词: Modulation; GABAA; receptor; subtypes; neurosteroids

Several naturally occurring neurosteroids possess neuroprotective, sedative, anxiolytic and anaesthetic properties. It is a fascinating concept that these compounds, synthetized in and released by neurons and astrocytes, act as powerful allosteric modulators of GABAA receptors. Similar to neurosteroids, benzodiazepines (BZDs) and general anaesthetics enhance GABAA receptor function, thereby causing sedation, anxiolysis, amnesia, muscle relaxation and unconsciousness. GABAA receptors are pentameric ion channels that can assemble from nineteen protein subunits, giving rise to a large number of receptor subtypes with different physiological functions. Receptors containing alpha1-subunits contribute to the sedative, alpha2-receptors to the anxiolytic and alpha5-receptors to the amnestic effects of BZDs. Endogenous neurosteroid synthesis in the brain is regulated by ligands of the mitochondrial translocator protein (TSPO). We recently showed that the TSPO agonist XBD173 enhances neurosteroidogenesis, increases GABAA receptor-mediated inhibition and causes anxiolysis in rats and humans in the absence of sedation and tolerance development. In another study we identified synergistic interactions between the neurosteroid allopregnanolone and propofol on GABAA receptor-mediated synaptic transmission. There is evidence in the literature that dissimilar GABAA receptor subtypes are not equally sensitive to neurosteroids, with delta-subunit containing receptors being among the very responsive ones. In addition, our observation that XBD173 produces anxiolysis in the absence of sedation prompts the hypothesis that alpha1-GABAA receptors are not a major target for endogenously synthesized neurosteroids. The primary goal of this application is to investigate how enhanced neurosteroidogenesis modulates the function of the most important GABAA receptor subtypes on the synaptic, cellular and network level. Specifically, XBD173 will be tested for its potential to alter inhibitory synaptic transmission and signal processing in the hippocampus. Furthermore, we aim to identify GABAA receptor subtypes contributing to potentially synergistic interactions between neurosteroids and anaesthetic drugs. By investigating the molecular and cellular mechanisms how neurosteroids reverse detrimental hypoxic effects on long-term potentiation, a cellular correlate for learning and memory, and apoptosis we intend to identify synaptic and extrasynaptic GABAA receptors involved in mediating neurosteroid-induced neuroprotection. To address these issues, we will employ optogenetics, optical and electrophysiological monitoring of neuronal in wild type and delta-subunit knockout mice and point-mutated mice expressing only one BZD-sensitive GABAA receptor subtype. Altogether, the present proposal intends to elaborate the molecular actions of neurosteroids and their interactions with anaesthetic agents in order to evaluate future applications in clinical anaesthesia.

几种天然存在的神经类固醇具有神经保护、镇静、抗焦虑和麻醉特性。这是一个迷人的概念，这些化合物，合成和释放的神经元和星形胶质细胞，作为强大的变构调节剂的GABAA受体。与神经类固醇类似，苯二氮卓类（BZD）和全身麻醉剂可增强GABAA受体功能，从而引起镇静、抗焦虑、健忘、肌肉松弛和无意识。GABAA受体是五聚体离子通道，其可以由十九个蛋白质亚基组装，产生大量具有不同生理功能的受体亚型。含有α 1-亚基的受体有助于镇静，α 2-受体有助于抗焦虑，α 5-受体有助于BZD的遗忘作用。脑中内源性神经类固醇的合成受线粒体转运蛋白（TSPO）的配体调节。我们最近表明，TSPO激动剂XBD 173增强神经甾体生成，增加GABAA受体介导的抑制，并在没有镇静和耐受性发展的情况下引起大鼠和人类的抗焦虑作用。在另一项研究中，我们确定了神经甾体别孕烯醇酮和丙泊酚对GABAA受体介导的突触传递的协同作用。文献中有证据表明，不同的GABAA受体亚型对神经类固醇的敏感性不同，其中含有δ亚基的受体是非常敏感的受体。此外，我们观察到XBD 173在没有镇静作用的情况下产生抗焦虑作用，这提示了α 1-GABAA受体不是内源性合成神经类固醇的主要靶点的假设。本申请的主要目的是研究增强的神经类固醇生成如何在突触、细胞和网络水平上调节最重要的GABAA受体亚型的功能。具体而言，将测试XBD 173改变海马体中抑制性突触传递和信号处理的潜力。此外，我们的目标是确定GABAA受体亚型有助于神经类固醇和麻醉药物之间的潜在协同作用。通过研究神经甾体如何逆转有害的缺氧对长时程增强的影响的分子和细胞机制，我们打算鉴定参与介导神经甾体诱导的神经保护的突触和突触外GABAA受体。为了解决这些问题，我们将采用光遗传学，光学和电生理监测的神经元在野生型和δ-亚基敲除小鼠和点突变的小鼠只表达一个BZD敏感的GABAA受体亚型。总之，本建议旨在阐述神经甾体的分子作用及其与麻醉剂的相互作用，以评估未来在临床麻醉中的应用。