Impact of endogenous metabolic biases on ototoxic oxidative damage

内源性代谢偏差对耳毒性氧化损伤的影响

• 批准号: 8680203
• 负责人: Heather Colleen Jensen Smith
• 金额: $ 14.45万
• 依托单位: CREIGHTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-01 至 2016-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8680203
• 关键词: ATP Synthesis Pathway; Agonist; Aminoglycoside Antibiotics; Aminoglycosides; Apical; Bacterial Infections; Biological Assay; Cell Survival; Citric Acid Cycle; Clinical; Complex; Data; Development; Electron Transport; Electrons; Exposure to; Figs - dietary; Fluorescence; Gentamicins; Hair Cells; Image; Individual; Iron; Knowledge; Labyrinth; Lead; Life; Literature; Long-Term Effects; Measurement; Measures; Mediating; Metabolic; Metabolism; Mitochondria; Modeling; Multienzyme Complexes; NADH; Noise; Noise-Induced Hearing Loss; Outer Hair Cells; Oxidation-Reduction; Pathology; Pharmacologic Substance; Pilot Projects; Preparation; Presbycusis; Prevention strategy; Process; Production; Publishing; Reactive Oxygen Species; Regulation; Relative (related person); Research; Role; Series; Site; Source; Succinate Dehydrogenase; Succinates; Testing; Time; Uncertainty; Work; age related; aminoglycoside-induced ototoxicity; cell injury; deafness; equilibration disorder; experience; hair cell regeneration; hearing impairment; inhibitor/antagonist; innovation; mitochondrial dysfunction; ototoxicity; oxidative damage; prevent; research study; response; treatment strategy; two-photon

DESCRIPTION (provided by applicant): This project aims to identify the fundamental metabolic differences between cochlear inner and outer hair cells (IHC, OHC) and to determine how these differences mediate cellular responses to ototoxic agents. Reactive oxygen species (ROS), normal byproducts of metabolism, can rise to lethal levels when mitochondrial metabolism is perturbed. Numerous studies have shown that the production and destructive actions of ROS are common features of multiple hearing loss (HL) pathologies, including aminoglycoside (AG)-induced ototoxicity, noise-induced HL (NIHL), and age-related HL (ARHL). Although there is little doubt that inner ear ROS cause HL, the exact mechanism(s) responsible for ROS production is/are controversial. Recent advances in two-photon confocal imaging of endogenous NADH (metabolic intermediate) allowed the first imaging of real-time changes in mitochondrial metabolism in live cochlear preparations. Using gentamicin (GM) as a representative AG/ototoxic agent, the immediate metabolic responses (NADH fluorescence change) and subsequent production of ROS in IHCs and OHCs will be examined. This proposal pinpoints how ROS production results from a direct GM-induced inhibition of mitochondrial metabolism. In a series of experiments that specifically block mitochondrial ROS production during GM exposure, this proposal provides the first assessment of the previously proposed role of ROS-producing bioactive iron-AG complexes in mediating AG-induced ROS production in cochlear HCs. The innovative model proposed herein describes how differential IHC and OHC ROS production can occur as a consequence of a rapid GM-induced OHC-specific inhibition of NADH production, succinate dehydrogenase activity, and electron flow through the electron transport chain while IHC metabolism remains relatively unfettered. Each Specific Aim will test the validity of the proposed model of GM-induced ototoxicity due to direct modulations of mitochondrial metabolism. Results from these studies will revolutionize our knowledge of AG ototoxicity by 1) differentiating between immediate and long-term effects, 2) determining whether GM-induced ROS production results from mitochondrial dysfunction rather than bioactive iron-AG complexes, and 3) determining whether fundamental differences in IHC and OHC mitochondrial metabolism dictate differential responses to a host of ototoxic agents. By determining the exact site(s) of ROS production, this project spurs the production of new, optimized HL prevention and treatment strategies that specifically target key ROS production site(s). Agents that site- specifically reduce metabolic ROS production and subsequent HC loss will be identified as key pharmaceutical intermediates poised to reduce the ototoxicity experienced during clinical GM treatment.

描述（由申请人提供）：该项目旨在确定耳蜗内毛细胞和外毛细胞（IHC、OHC）之间的基本代谢差异，并确定这些差异如何介导细胞对耳毒性药物的反应。当线粒体代谢受到干扰时，活性氧（ROS）是新陈代谢的正常副产物，可能会升至致命水平。大量研究表明，ROS 的产生和破坏作用是多种听力损失 (HL) 病理的共同特征，包括氨基糖苷 (AG) 诱导的耳毒性、噪音诱导的 HL (NIHL) 和年龄相关 HL (ARHL)。尽管毫无疑问内耳 ROS 会导致 HL，但负责 ROS 产生的确切机制仍存在争议。内源性 NADH（代谢中间体）双光子共聚焦成像的最新进展使得首次能够对活体耳蜗制剂中线粒体代谢的实时变化进行成像。使用庆大霉素 (GM) 作为代表性 AG/耳毒性剂，将检查 IHC 和 OHC 中的即时代谢反应（NADH 荧光变化）和随后的 ROS 产生。该提案指出了 ROS 的产生是如何通过转基因诱导的线粒体代谢直接抑制而产生的。在一系列专门阻断 GM 暴露期间线粒体 ROS 产生的实验中，该提案首次评估了先前提出的产生 ROS 的生物活性铁-AG 复合物在介导耳蜗 HC 中 AG 诱导的 ROS 产生中的作用。本文提出的创新模型描述了由于 GM 诱导的 OHC 快速特异性抑制 NADH 产生、琥珀酸脱氢酶活性和通过电子传递链的电子流，而 IHC 代谢保持相对不受限制，从而导致不同的 IHC 和 OHC ROS 产生如何发生。每个具体目标将测试所提出的由于直接调节线粒体代谢而引起的转基因诱导的耳毒性模型的有效性。这些研究的结果将通过以下方式彻底改变我们对 AG 耳毒性的认识：1) 区分即时效应和长期效应；2) 确定 GM 诱导的 ROS 产生是否是由线粒体功能障碍而不是生物活性铁-AG 复合物引起的；3) 确定是否是根本原因IHC 和 OHC 线粒体代谢的差异决定了对多种耳毒性药物的不同反应。通过确定 ROS 产生的确切位点，该项目促进了专门针对关键 ROS 产生位点的新的、优化的 HL 预防和治疗策略的制定。位点特异性减少代谢性 ROS 产生和随后的 HC 损失的药物将被确定为关键的药物中间体，有望减少临床 GM 治疗期间经历的耳毒性。