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: 8489278
• 负责人: Heather Colleen Jensen Smith
• 金额: $ 13.73万
• 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 2015-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8489278
• 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）：本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。活性氧（ROS），正常的代谢副产物，可以上升到致命的水平时，线粒体代谢受到干扰。大量研究表明，ROS的产生和破坏作用是多种听力损失（HL）病理学的共同特征，包括氨基糖苷类（AG）诱导的耳毒性、噪声诱导的HL（NIHL）和年龄相关HL（ARHL）。虽然内耳ROS引起HL几乎是毫无疑问的，但负责ROS产生的确切机制是有争议的。内源性NADH（代谢中间体）的双光子共聚焦成像的最新进展允许在活耳蜗制剂中对线粒体代谢的实时变化进行首次成像。将使用庆大霉素（GM）作为代表性AG/耳毒性药物，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。这一提议指出了ROS的产生是如何由GM直接诱导的线粒体代谢抑制引起的。在一系列的实验中，具体地阻止线粒体ROS的生产过程中，GM曝光，这一建议提供了第一次评估先前提出的ROS生产生物活性铁-AG复合物介导的AG诱导的ROS生产耳蜗毛细胞的作用。本文提出的创新模型描述了差异IHC和OHC ROS产生如何作为快速GM诱导的NADH产生、琥珀酸脱氢酶活性和通过电子传递链的电子流的OHC特异性抑制的结果而发生，同时IHC代谢保持相对不受约束。每个特定目的将测试由于直接调节线粒体代谢而引起的GM诱导耳毒性的拟定模型的有效性。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）区分即时和长期效应，2）确定GM诱导的ROS产生是否由线粒体功能障碍而不是生物活性铁-AG复合物引起，3）确定IHC和OHC线粒体代谢的根本差异是否决定了对耳毒性药物的反应差异。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HL预防和治疗策略的产生。位点特异性降低代谢ROS产生和随后HC损失的药剂将被鉴定为准备降低临床GM治疗期间经历的耳毒性的关键药物中间体。