谷氨酸—N-甲基-D-天冬氨酸—一氧化氮合酶—活性氧通路在声损伤中的作用研究

发布时间：2018-05-02 02:44

本文选题：噪声 + 噪声性听力损伤　；参考：《第二军医大学》2005年博士论文

【摘要】：噪声对听觉的损伤是一个尚未完全清楚的多因素复杂机制,其机理是当前研究热点。高强度的噪声主要引起机械性损伤,造成不同程度的盖膜—毛细胞的机械性破坏,甚至螺旋器从基底膜上剥离,可立即产生永久性听力损失。中低强度的噪声则以代谢性损伤为主,引起耳蜗毛细胞、支持细胞的酶系统严重紊乱,导致能量代谢障碍,影响听觉功能。谷氨酸(glutamate, Glu)是耳蜗内毛细胞/传入神经突触的神经递质,同时又是一种神经毒物质。根据Glu对中枢神经元损伤的理论和模式,我们提出了Glu-NMDA-NOS-ROS通路在声损伤中的作用机理假设。该假设认为,噪声可引起毛细胞过量释放Glu;Glu通过物理扩散作用突触后膜,引起后膜上N-甲基-D-天冬氨酸(N-methyl-D-asparate, NMDA)受体的过度激活;进而引起突触间隙液中的Ca~(2+)大量内流,胞内高Ca~(2+)使结构型一氧化氮合成酶(constitutive nitric oxide synthase, cNOS)的活性提高,同时噪声本身也引起NOS活性的增强;NOS催化形成的大量一氧化氮(nitric oxide, NO),导致耳蜗内活性氧(reactive oxygen species, ROS)堆积;该通路的终产物ROS是引起毛细胞和螺旋神经节细胞损伤,导致听力下降的重要原因。本研究运用听觉电生理、超微结构、免疫组化等方法,豚鼠为实验对象,验证Glu-NMDA-NOS-ROS通路在声损伤中的作用。首先研究声刺激后耳蜗组织NO代谢产物和血清总抗氧化能力(total antioxidant capacity, TAC)的变化,探讨外源性NO对耳蜗功能、形态的影响,研究噪声刺激后耳蜗组织NOS活性的表达;在此基础上,研究NMDA受体的非竞争性拮抗剂MK-801在声损伤中的作用,认识NOS的竞争性拮抗剂N-硝基左旋精氨酸甲酯(N~G-nitro-L-arginine methyl ester, L-NAME)对声损伤的影响,最后,探讨在声损伤中,自由基清除剂α-硫辛酸对耳蜗保护作用。主要实验结果和结论如下:
[Abstract]:Noise damage to hearing is a complicated mechanism of multiple factors which is not fully understood, and its mechanism is a hot research topic at present. High intensity noise mainly causes mechanical damage, which results in the mechanical damage of capillary-hair cells to varying degrees, even when the spiral organ is removed from the basement membrane, which can cause permanent hearing loss immediately. The moderate and low intensity noise mainly caused metabolic injury, which caused serious disturbance of the enzyme system of cochlear hair cells and Sertoli cells, resulting in energy metabolism disorders and affecting auditory function. Glutamate glutamateis a neurotransmitter of hair cell / afferent synapse in cochlea and is also a neurotoxic substance. According to the theory and model of Glu damage to CNS, we propose the hypothesis of the mechanism of Glu-NMDA-NOS-ROS pathway in acoustic injury. It is assumed that noise can cause excessive release of Gluton-Glu from hair cells through physical diffusion to postsynaptic membrane, which leads to excessive activation of N-methyl-D-asparate (NMDA-N) receptor on the posterior membrane, and then to a large influx of Ca~(2 in synaptic interstitial fluid. High intracellular Ca~(2) increased the activity of structural nitric oxide synthase (nitric oxide synthase, cNOS), and the noise itself also led to the enhancement of NOS activity and the formation of a large amount of nitric oxide (NON) catalyzed by NOS, which resulted in the accumulation of reactive oxygen species, ROS) in the cochlea. The end product of this pathway, ROS, is an important cause of hair cell and spiral ganglion cell damage and hearing loss. In this study, auditory electrophysiology, ultrastructure and immunohistochemistry were used to investigate the role of Glu-NMDA-NOS-ROS pathway in acoustic injury in guinea pigs. The changes of no metabolites in cochlea and total antioxidation capacity of serum total antioxidant capacity, TAC) were studied to investigate the effects of exogenous no on cochlear function and morphology, and the expression of NOS activity in cochlea after noise stimulation. To study the role of MK-801, a non-competitive antagonist of NMDA receptor, in sound damage, and to understand the effect of NG-nitro-L-arginine methyl ester( L-NAME-NG-nitro-L-arginine methyl), a competitive antagonist of NOS, on sound injury. Free radical scavenger 伪-lipoic acid protects cochlea. The main results and conclusions are as follows:
【学位授予单位】：第二军医大学
【学位级别】：博士
【学位授予年份】：2005
【分类号】：R363

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