Apoptotic and Necrotic Death of OHCs in NIHL

NIHL 中 OHC 的凋亡和坏死

• 批准号: 6743419
• 负责人: BO HUA HU
• 金额: $ 7.85万
• 依托单位: STATE UNIVERSITY OF NEW YORK AT BUFFALO
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-12-08 至 2006-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6743419
• 关键词: adenosine triphosphate; antioxidants; apoptosis; auditory stimulus; buthionine sulfoximine; cellular pathology; chinchilla; cysteine endopeptidases; densitometry; ear hair cell; enzyme activity; evoked potentials; glutathione; glutathione analog; necrosis; noise biological effect; noise induced deafness; oxidative phosphorylation; propionates; succinate dehydrogenase; terminal nick end labeling

DESCRIPTION (provided by applicant): Our previous studies have found that following a high level of noise exposure, outer hair cells (OHCs) die by both apoptosis and necrosis. The prevalence of apoptosis or necrosis is associated with the noise level and post-exposure progression of the cochlear lesion; however, the cellular mechanisms responsible for determining the pathways of OHC death following noise exposure are still not known. This application focuses on the general hypothesis that the propensity of OHCs to die by apoptosis or necrosis is regulated by the energy level and/or oxidative status of dying OHCs. To test this hypothesis, chinchillas will be exposed to an octave band noise centered at 4 kHz at 110 dB SPL for 1 hour. In the first part of the experiment, the activity of succinate dehydrogenase (SDH), an important mitochondrial enzyme that participates in ATP synthesis in the electron transport chain, will be examined in apoptotic and necrotic OHCs after the noise exposure. In the second part of the study, the synthesis of ATP by OHCs will be blocked by intracochlear application of 3-nitropropionic acid (3-NP), an irreversible inhibitor of SDH. The effect of intracellular ATP depletion on generation of apoptosis and necrosis following the noise exposure will be examined. In the last part of the study, the effect of the alteration of the cochlear antioxidant capacity on the death pathways will be examined. The cochlear antioxidant capacity will be manipulated by changing the level of cochlear glutathione (GSH) either with L-buthionine-[S, R]-sulfoximine, a GSH synthesis inhibitor, or with glutathione monoethyl ester, an analog of GSH. These data will help to elucidate the role of the cochlear energy level and the antioxidant level in determining the prevalence of either apoptosis or necrosis after noise exposure. Our long-term goal is to explore effective therapeutic strategies to reduce noise-induced hearing loss. Since necrotic OHCs potentially create a significantly greater level of toxic stress on surviving OHCs through release of intracellular contents, preventing the conversion of apoptosis to necrosis may ameliorate the overall cochlear damage. The knowledge of the biological mechanisms responsible for modulation of the cell death pathways will provide the basis for eventually developing a rational protective strategy.

描述(申请人提供)：我们先前的研究发现，在高水平的噪音暴露后，外毛细胞(OHC)会因细胞凋亡和坏死而死亡。细胞凋亡或坏死的流行与噪声水平和暴露后耳蜗病的进展有关；然而，负责确定噪声暴露后OHC死亡途径的细胞机制仍不清楚。这一应用侧重于一般假设，即死于细胞凋亡或坏死的倾向受死亡细胞的能量水平和/或氧化状态的调节。为了验证这一假设，龙猫将暴露在以4 kHz为中心、110分贝SPL为中心的倍频程频带噪声中1小时。在实验的第一部分，琥珀酸脱氢酶(SDH)是参与电子传递链中ATP合成的一种重要的线粒体酶，将在噪声暴露后检测凋亡和坏死的内皮层细胞的琥珀酸脱氢酶(SDH)活性。在研究的第二部分，毛细胞合成三磷酸腺苷的过程将被SDH的不可逆抑制剂3-硝基丙酸(3-NP)阻断。细胞内ATP耗竭对噪声暴露后的细胞凋亡和坏死的产生的影响将被检测。在这项研究的最后部分，我们将考察耳蜗抗氧化能力的改变对死亡途径的影响。通过使用谷胱甘肽合成抑制剂L-丁硫氨酸-[S，R]-亚磺胺或谷胱甘肽类似物谷胱甘肽单乙酯，通过改变耳蜗还原型谷胱甘肽(GSH)的水平来调节耳蜗组织的抗氧化能力。这些数据将有助于阐明耳蜗能量水平和抗氧化剂水平在确定噪声暴露后细胞凋亡或坏死发生率方面的作用。我们的长期目标是探索有效的治疗策略，以减少噪音导致的听力损失。由于坏死性内耳毛囊可能通过释放细胞内内容物而对存活的内耳毛囊细胞产生显著更大的毒性应激，因此阻止细胞凋亡向坏死的转化可能会改善整体耳蜗损伤。对调控细胞死亡途径的生物学机制的了解将为最终制定合理的保护策略提供基础。