Na+/H+ EXCHANGER AND CARDIAC HYPOTHERMIA: ROLE ROS

Na /H 交换剂和心脏低温：ROS 的作用

• 批准号: 6797273
• 负责人: AMADOU K. CAMARA
• 金额: $ 14.48万
• 依托单位: MEDICAL COLLEGE OF WISCONSIN
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-09-01 至 2008-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6797273
• 关键词: calcium; cardiovascular disorder; fluorimetry; free radical oxygen; guinea pigs; heart arrest; hypothermia; ischemia; mitochondria; potassium channel; sodium hydrogen exchanger

DESCRIPTION (provided by applicant): Hypothermia is a very powerful temperature-dependent method to protect against clinical cardiac ischemia and reperfusion (I/R) injury. Hypothermia decreases energy utilization and preserves mechanisms to rapidly generate ATP on reperfusion. But hypothermia does not provide complete protection and has deleterious effects; cold perfusion can result in elevated cytosolic (cyt) Ca2+ and cause hyper-contracture and reduced compliance. Formation of reactive oxygen species, (ROS) and, mitochondrial (m) Ca2+ loading are major factors that cause reperfusion stunning and permanent damage after normothermic ischemia. The roles of mROS formation, m Ca2+ loading, mNADH, and other indices of mitochondrial bioenergetics during hypothermic perfusion and I/R have not been studied. Increased cellular sodium-hydrogen exchange (NHE) activity observed during I/R is an attractive candidate to link increased ROS production and m Ca2+ overload. These studies will assess hypothermic ischemia -induced effects on cyt Na+ and m Ca2+ loading, formation of ROS, KAav channels, and mitochondrial bioenergetics (NADH, ATP synthesis, O2 consumption) to determine the mechanism of protection by hypothermia and inhibition of NHE. Major aims are: 1) To Assess the deleterious effects of hypothermia on mitochondrial function and to evaluate the cardio protective role of cardioplegia, NHE inhibition, ROS scavengers, and Kxav channel opening during and after hypothermic ischemia. 2) To determine the mechanisms of cold perfusion and I/R -induced Na+ and m Ca2+ loading on mitochondrial and myocardial dysfunction using alkalosis, ROS generators and mKAav blockers alone and together with NIIE inhibition. We will use unique on-line fluorescence techniques to assess ROS formation, redox balance, cyt [Na+], and m [Ca2+] at 37 and 27 degrees C in intact guinea pig hearts and ROS release in coronary effluent. Protection will be evidenced in intact hearts by reduced global infarct size, enzyme release, and better mechanical and metabolic function. The mechanism of hypothermic protection will be further investigated in isolated mitochondria measured for NADH, membrane potential, ATP synthesis, and 02 consumption. Emphasis will be placed on the effects of drug-induced blockade of mitochondrial ROS formation, NHE activity and KAav channel opening on cellular cation balance and mitochondrial bioenergetics.

描述（由申请人提供）：低温是一种非常强大的温度依赖性方法，可防止临床心脏缺血和再灌注（I/R）损伤。 体温过低会降低能量利用率并保留再灌注时快速生成 ATP 的机制。 但体温过低并不能提供完全的保护，而且会产生有害影响；冷灌注可导致胞质 (cyt) Ca2+ 升高，并导致过度挛缩和顺应性降低。 活性氧 (ROS) 的形成和线粒体 (m) Ca2+ 负荷是常温缺血后导致再灌注抑制和永久性损伤的主要因素。 mROS 形成、m Ca2+ 负载、mNADH 和其他线粒体生物能指标在低温灌注和 I/R 过程中的作用尚未研究。 I/R 期间观察到的细胞钠氢交换 (NHE) 活性增加是将 ROS 产生增加与 m Ca2+ 超载联系起来的一个有吸引力的候选者。 这些研究将评估低温缺血对细胞色素 Na+ 和 m Ca2+ 负荷、ROS 形成、KAav 通道和线粒体生物能学（NADH、ATP 合成、O2 消耗）的影响，以确定低温保护和 NHE 抑制的机制。主要目的是： 1) 评估低温对线粒体功能的有害影响，并评估低温缺血期间和之后心脏停跳液、NHE 抑制、ROS 清除剂和 Kxav 通道开放的心脏保护作用。 2) 单独使用碱中毒、ROS 发生器和 mKAav 阻滞剂以及与 NIIE 抑制一起确定冷灌注和 I/R 诱导的 Na+ 和 m Ca2+ 负荷对线粒体和心肌功能障碍的机制。 我们将使用独特的在线荧光技术来评估 37 和 27 摄氏度下完整豚鼠心脏中的 ROS 形成、氧化还原平衡、细胞色素 [Na+] 和 m [Ca2+] 以及冠状动脉流出物中的 ROS 释放。完整心脏的保护作用将通过减少整体梗塞面积、酶释放以及更好的机械和代谢功能来证明。 将在分离的线粒体中进一步研究低温保护机制，测量NADH、膜电位、ATP合成和O 2 消耗。 重点将放在药物诱导的线粒体 ROS 形成阻断、NHE 活性和 KAav 通道开放对细胞阳离子平衡和线粒体生物能学的影响上。