Naturally Evolved Cellular Adaptations to Anoxia

自然进化的细胞对缺氧的适应

• 批准号: RGPIN-2015-06588
• 负责人: Buck, Leslie
• 金额: $ 5.17万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=591156
• 关键词: Naturally; Evolved; Cellular; Adaptations; Anoxia

The Buck lab is investigating the cellular mechanisms that permit some vertebrate species, such as freshwater turtles and goldfish to survive without oxygen (anoxia) for days to months. We are interested in the fundamental mechanisms underlying this ability but our results will have clear clinical significance and application in the treatment of stroke, heart attack and organ storage for transplant. Both brain and liver cell models are used to study the cellular mechanisms of anoxia tolerance in tissue that is electrically excitable and one that is not. Key to surviving anoxia is the shutting off of energy utilizing cellular activities, such as the synthesis of new proteins and maintaining ion gradients across cell membranes. We have previously shown that protein synthesis decreases by about 90%, the pump that maintains ion gradients across cell membranes decreases by 75%, and ion channel activity (pathways for ions to cross membranes) decreases and in one special case increases. The ability to reduce the rate of these energy consuming reactions is something that mammals (humans) lack. However, basic biochemical pathways are common to most species, certainly amongst reptiles (turtles), fish, birds and mammals. Our goal is to determine the natural cellular pathways responsible for shutting off energy consuming processes in anoxia-tolerant species. We have already identified several possible pathways and discovered that brain excitatory signaling by pyramidal neurons involving glutamate is decreased, while inhibitory activity involving GABA (gamma-aminobutyric acid) and stellate neurons is increased during anoxic periods. In fact, GABA currents double in magnitude during anoxia and are larger than any GABA current observed in mammal brain. A major focus of this grant is to measure the electrical activity of GABA releasing stellate neurons during anoxia to understand what triggers this large release of neurotransmitter. Furthermore, using high-powered microscopy we will visualize the position of the stellate neurons in relation to the pyramidal neurons to determine if the stellate neurons are specialized for a recently discovered form of neurotransmission – volume transmission. Brain is an electrically excitable tissue and we are also investigating anoxic regulation of ion channels in non-excitable tissue - liver. In this grant cycle we will continue to explore the electrophysiological properties and second messenger pathways of brain and liver tissue to better understand which ion channels are regulated in a way that reduces energetic demands and permits anoxic survival.  Importantly, our work will demonstrate that different cell types, even within a single tissue, respond differently to an anoxic challenge; therefore, multiple different strategies are needed to protect tissues from anoxic injury.

Buck Lab正在研究允许某些脊椎动物物种的细胞机制，例如淡水海龟和金鱼在没有氧气（缺氧）的情况下存活几天到几个月。我们对这种能力的基本机制感兴趣，但是我们的结果将在中风，心脏病发作和器官存储移植时具有明显的临床意义和应用。大脑和肝细胞模型均用于研究组织中缺氧耐受性的细胞机制，而这是电上令人兴奋的，而不是。生存缺氧的关键是利用细胞活性（例如合成新蛋白质和跨细胞膜维持离子梯度）关闭能量。我们先前已经表明，蛋白质合成下降了约90％，维持整个细胞膜离子梯度的泵下降了75％，离子通道活性（离子跨膜的途径）降低，并且在一种特殊情况下增加。降低这些能量消耗反应速率的能力是哺乳动物（人类）所缺乏的。但是，基本的生化途径对于大多数物种来说都是常见的，当然是重复（海龟），鱼类，鸟类和哺乳动物。我们的目标是确定负责关闭耐缺氧物种中消耗能量过程的自然细胞途径。我们已经确定了几种可能的途径，并发现涉及谷氨酸的锥体神经元的大脑兴奋信号得到改善，而在缺氧期间，涉及GABA（γ-氨基丁酸）和星状神经元的抑制活性增加了。实际上，在缺氧期间，GABA电流的幅度高两倍，并且比在哺乳动物大脑中观察到的任何GABA电流大。该赠款的主要重点是测量GABA在缺氧过程中释放星状神经元的电活动，以了解是什么触发了这种大量神经递质的释放。此外，使用高功率显微镜，我们将可视化星状神经元相对于金字塔神经元的位置，以确定星状神经元是否专门用于最近发现的神经传递形式 - 体积传播。大脑是一种具有电子激动人心的组织，我们还正在研究非驱动组织 - 肝脏中离子通道的缺氧调节。在这个赠款周期中，我们将继续探索大脑和肝组织的电生理特性和第二信使途径，以更好地了解哪些离子通道的调节方式可以减少能量需求并允许缺氧生存。重要的是，我们的工作将证明，即使在单个组织中，不同的细胞类型也对缺氧挑战的反应不同。因此，需要多种不同的策略来保护时间免受缺氧伤害。