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: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=646471
• 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. **

巴克实验室正在研究允许一些脊椎动物物种（例如淡水龟和金鱼）在没有氧气（缺氧）的情况下生存数天到数月的细胞机制，我们对这种能力的基本机制感兴趣，但我们的结果将具有明确的临床意义。脑细胞和肝细胞模型均用于研究电兴奋组织和非电兴奋组织的缺氧耐受性的细胞机制，以及在治疗中风、心脏病和移植器官储存中的应用。关闭利用细胞活动消耗能量，例如新蛋白质的合成和维持细胞膜上的离子梯度，我们之前已经表明蛋白质合成减少了约 90%，维持细胞膜上离子梯度的泵减少了 75%，并且离子通道活性（离子跨膜的途径）降低，在一种特殊情况下降低这些能量消耗反应的速率的能力是哺乳动物（人类）所缺乏的。然而，基本的生化途径是常见的。对于大多数物种，尤其是爬行动物（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能量消耗过程的细胞自然途径。我们已经确定了几种可能的途径，并发现了大脑。在缺氧期间，锥体神经元谷氨酸的兴奋性信号传导减少，而涉及 GABA（γ-氨基丁酸）和星状神经元的抑制活性增加。事实上，GABA 电流在缺氧期间增加了一倍。缺氧状态下的 GABA 电流大于在哺乳动物大脑中观察到的任何 GABA 电流，这项资助的一个主要重点是测量缺氧期间 GABA 释放星状神经元的电活动，以了解是什么触发了神经递质的大量释放。将可视化星状神经元相对于锥体神经元的位置，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——容量传递。我们还在研究非兴奋组织（肝脏）中离子通道的缺氧调节。在本次资助周期中，我们将继续探索大脑和肝脏组织的电生理特性和第二信使通路，以更好地了解哪些离子通道的调节方式是：重要的是，我们的工作将证明不同的细胞类型，即使在单一组织内，对缺氧挑战的反应也不同；因此，需要多种不同的策略来保护组织免受缺氧的影响。受伤。 **