Acid-sensing ion channels and ischemic brain injury

酸敏感离子通道与缺血性脑损伤

• 批准号: 7069542
• 负责人: ROGER Pancoast SIMON
• 金额: $ 34.32万
• 依托单位: LEGACY EMANUEL HOSPITAL AND HEALTH CENTER
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-05-24 至 2010-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7069542
• 关键词: acidosis; acids; brain injury; calcium ion; cerebral ischemia /hypoxia; complementary DNA; cytotoxicity; electrophysiology; gene targeting; genetically modified animals; laboratory mouse; laboratory rat; membrane channels; site directed mutagenesis; sodium channel; transfection; voltage /patch clamp; zinc

DESCRIPTION (provided by applicant): Brain ischemia is characterized by a marked, rapid fall in pH, which is assumed to be injurious although through multiple or uncertain mechanisms. The recent discovery in brain of Acid Sensing Ion Channels (ASICs), which are ubiquitous and function physiologically in synaptic neurotransmission, offers a diffuse, membrane based, receptor gated ion channel system, which will respond to the pathologic pH fall in brain ischemia. These H+ receptor gated channels are Na+ channels, a portion of which is also Ca2+ permeable. Acid sensitivity and Ca2+ permeability suggest a role in ischemic brain injury. Using patch clamp techniques and Ca2+ imaging of native neurons in cortical cultures we show the pH sensitivity of these channels and acid induced Ca2+ uptake. Both the acid induced channel currents and Ca2+ uptake are greatly potentiated in the setting of modeled ischemia (Oxygen Glucose Deprivation-OGD or NaCN). Thus these channels respond to both acidosis and "ischemia" in a mutually potentiating manner. The channel current and Ca2+ uptake are glutamate independent, are inhibited by ASIC pharmacologic blockade and by specific blockade of the ASIC 1a channel subunit. Thus, our preliminary studies support new cellular and molecular mechanisms mediating ischemic-acidosis induced brain injury, which we offer to dissect with the following Specific Aims: Single cell recording and transfection of individual ASIC subunit cDNAs will show that: 1) Ca2+ permeable ASICs produce cell injury in modeled ischemia via a subunit specific mechanism. Using rat and mouse global ischemia models and ASIC1a & ASIC2a knockout mice, we propose that: 2) Blockade of ASICs protects against ischemic brain injury in vivo. With molecular techniques including site directed mutagenesis we will describe endogenous Zn2+ modulation of Ca2+permeable ASICs: 3) Characterize high-affinity Zn2+ modulation of ASIC currents in acidosis and ischemia -induced cell injury. These experiments will describe new, glutamate independent, mechanisms of ischemic brain injury and the central role of ischemic-acidosis. ASIC blockade will offer new and potent potential therapy for stroke.

描述（由申请人提供）：脑缺血的特征是 pH 值显着快速下降，尽管通过多种或不确定的机制，这被认为是有害的。最近在大脑中发现的酸感应离子通道 (ASIC) 无处不在，在突触神经传递中发挥生理功能，提供了一种弥散的、基于膜的、受体门控离子通道系统，该系统将对脑缺血时的病理性 pH 值下降做出反应。这些 H+ 受体门控通道是 Na+ 通道，其中一部分也是 Ca2+ 可渗透的。酸敏感性和 Ca2+ 通透性表明在缺血性脑损伤中发挥作用。使用膜片钳技术和皮质培养物中天然神经元的 Ca2+ 成像，我们显示了这些通道的 pH 敏感性和酸诱导的 Ca2+ 吸收。在模拟缺血（氧糖剥夺-OGD 或 NaCN）的情况下，酸诱导的通道电流和 Ca2+ 摄取均大大增强。因此，这些通道以相互增强的方式对酸中毒和“缺血”做出反应。通道电流和 Ca2+ 摄取与谷氨酸无关，可通过 ASIC 药理学阻断和 ASIC 1a 通道亚基的特异性阻断来抑制。因此，我们的初步研究支持介导缺血性酸中毒引起的脑损伤的新细胞和分子机制，我们将通过以下具体目标对其进行剖析：单细胞记录和单个 ASIC 亚基 cDNA 的转染将表明：1) Ca2+ 可渗透的 ASIC 产生通过亚基特异性机制模拟缺血中的细胞损伤。使用大鼠和小鼠全局缺血模型以及 ASIC1a 和 ASIC2a 敲除小鼠，我们提出：2）封锁 ASIC 可防止体内缺血性脑损伤。通过包括定点诱变在内的分子技术，我们将描述 Ca2+ 可渗透 ASIC 的内源 Zn2+ 调节：3) 表征酸中毒和缺血诱导的细胞损伤中 ASIC 电流的高亲和力 Zn2+ 调节。这些实验将描述缺血性脑损伤的新的、不依赖于谷氨酸的机制以及缺血性酸中毒的核心作用。 ASIC 封锁将为中风提供新的、有效的潜在疗法。