去乙酰化酶Sirtuin 1对老年性聋的治疗作用及其机理的研究

Presbycusis is one of the most common diseases affecting the living quality of general people. At present, the pathogenesis of presbycusis is unclear, and there are no effective methods to prevent or treat it. Recent researches indicate that the increase of mitochondrial DNA common deletion (CD) in the auditory system is an important causal factor for presbycusis. In the preliminary studies, we found that the expression of Deacetylase Sirtuin 1 was significantly decreased with the accumulation of CD in the inner ear of D-galactose-induced aging rats, and the spiral ganglion cells of Deacetylase Sirtuin 1 over-expression could effectively prevent the accumulation of CD. These findings implicate that Deacetylase Sirtuin 1 may have the ability to prevent or treat presbycusis by reducing the accumulating of CD in the auditory system. In this study, we plan to further investigate the therapeutical effects of Deacetylase Sirtuin 1 on presbycusis and its underlying mechanism in the designed project. The study aims includes: ① CD cellular models and animal models of auditory system will be developed; the inhibition of CD and the protection of auditory capacity induced by Sirtuin 1 gene transfection will be evaluated. ② To investigate into the mechanism of Sirtuin 1 in reducing the accumulation of CD. ③ To investigate into the mechanism of Sirtuin 1 in treating presbycusis. This study provides new insights into the pathogenesis of presbycusis, and also provides new target of clinical treatment for presbycusis.

老年性聋是影响人类生活质量的主要疾病之一，其发病机制不明，尚无有效的防治措施。研究表明线粒体DNA常见缺失（CD）在听觉系统的累积是导致老年性聋的重要原因。我们最近的研究发现D-半乳糖诱导的老化大鼠内耳CD增加的同时，去乙酰化酶Sirtuin 1表达显著降低，而过表达Sirtuin 1的内耳螺旋神经节细胞则可有效对抗CD累积。这些研究结果提示Sirtuin 1具有通过减少CD在听觉系统累积进而达到防治老年性聋的作用。在本课题中，我们计划进一步探讨去乙酰化酶Sirtuin 1对老年性聋的治疗作用及其作用机理。主要内容包括：①建立听觉系统CD细胞系和动物模型，检测Sirtuin 1基因转染对CD累积的抑制作用和对听功能的保护作用；②探讨Sirtuin 1减少CD累积的机理；③探讨Sirtuin 1对老年性聋的治疗作用机理。本项目将为老年性聋发病机制的研究提供新的思路，为临床治疗提供新的靶点。

背景：老年性聋又称为年龄相关性听力损失，是听觉系统的退行性变。目前，老年性聋的发病机制不明，尚无有效的药物治疗。去乙酰化酶sirtuins（SIRTs）对哺乳动物延长寿命和维持健康起着必不可少的作用。主要研究内容：① 6周龄雄性C57BL/6J小鼠颈背部皮下注射D-半乳糖1000 mg/kg，每日一次，连续6周，构建快速衰老的小鼠模型；② D-半乳糖诱导的衰老小鼠内耳水平半规管手术导入腺相关病毒（adeno-associated virus, AAV）携带的SIRT1基因（AAV-SIRT1），观察SIRT1过表达对耳蜗内毛细胞带状突触年龄相关性损伤的作用；③ 新生3-5天C57BL/6J小鼠耳蜗血管纹边缘细胞（strial marginal cells, SMCs）原代培养，培养基中加入25 mg/ml D-半乳糖，构建SMCs体外衰老模型；腺病毒（adenovirus, Ad）携带SIRT1基因转染体外培养的SMCs，观察过表达SIRT1的SMCs是否可有效对抗D-半乳糖诱导的衰老。重要结果及关键数据：① D-半乳糖诱导的衰老小鼠耳蜗病理主要表现为IHCs带状突触数量减少；② SIRT1在D-半乳糖诱导的衰老小鼠IHCs的过表达可显著减少带状突触的丢失，减少内毛细胞线粒体DNA氧化损伤，减少耳蜗线粒体DNA常见缺失突变的累积，增加耳蜗三磷酸腺苷（adenosine triphosphate, ATP）水平，降低耳蜗超氧化物岐化酶2（superoxide dismutase 2, SOD2）蛋白乙酰化水平；③ SIRT1在体外培养的小鼠耳蜗SMCs中过表达可显著抑制D-半乳糖诱导的SOD2表达降低，减轻D-半乳糖诱导的氧化应激、线粒体DNA 氧化损伤和线粒体功能紊乱，减少D-半乳糖诱导的CD突变累积和SMCs细胞凋亡。科学意义：我们证实① 耳蜗IHCs带状突触是老年性聋早期容易损伤的部位；② 在老年性聋耳蜗IHCs带状突触损伤过程中，SIRT1过表达去乙酰化SOD2，减少线粒体氧化损伤，改善线粒体功能，保护带状突触，延缓老年性聋；③ 在SMCs老化过程中，SIRT1过表达增加SOD2，减少线粒体氧化损伤和凋亡，保护SMCs。