诱生型一氧化氮合酶对耳蜗发育的影响

Nitric oxide takes important part in the cochlear physiology. In the pathological condition, inducible nitric oxide is expressed and catalyzed to produce long last amount of NO which is damage to cochlea. Previous studies showed that the expression of iNOS damaged the cochlea. iNOS is always not good for cochlea. Recently, it was observed in our research that there were varying degrees of loss of hair cell cilia accompanied with hearing loss in iNOS(-/-) knock out mice. This indicates that iNOS takes part in the development of cochlea and is related to hereditary hearing loss. ABR hearing threshold, cochlear ultrastructural and cochlear functional proteins are examined in different stages of iNOS(-/-) knock out mice and wild type mice. The contribution of iNOS for cochlear development and its relation to hereditary hearing loss will be analyzed from the comparison of ABR hearing threshold, cochlear ultrastructural and cochlear functional proteins between iNOS(-/-) knock out mice and wild type mice. Expected results: cochlear ultrastructural and cochlear functional proteins will be abnormally changed in iNOS knock out mice with hearing loss. It will be confirmed that iNOS takes part in the regulation of cochlear development and relates to hereditary hearing loss.

一氧化氮（NO）在耳蜗生理中起重要作用。耳蜗在病理条件下，诱生型一氧化氮合酶（iNOS）表达，持续催化产生大量NO,对耳蜗起损伤作用。以往研究认为iNOS表达引起耳蜗损伤，iNOS总是"无益"于耳蜗。近来我们观察到iNOS(-/-)基因缺失小鼠耳蜗毛细胞纤毛有不同程度的缺失，且伴随听功能减退。这一现象提示iNOS参与耳蜗发育，与遗传性聋相关。本研究通过检测并比较不同时期iNOS（-/-）基因缺失小鼠和同种野生型小鼠耳蜗ABR听阈、耳蜗超微结构、耳蜗功能蛋白表达，探讨iNOS对耳蜗发育的贡献及iNOS是否与遗传性聋相关。 预期结果：iNOS(-/-)基因缺失小鼠耳蜗超微结构、耳蜗功能蛋白表达会出现异常改变，同时伴有听功能减退。证实iNOS参与耳蜗发育调控，与遗传性聋相关。

本研究通过对不同日龄iNOS（-/-）基因缺失小鼠和同种野生型C57小鼠ABR听阈测定、耳蜗扫描电镜、透射电镜观察以及耳蜗功能蛋白（kcnq1/kcne1钾离子通道、prestin蛋白、kcnq4钾离子通道、缝隙连接蛋白connexins 26和30、cldn14蛋白、F-肌动蛋白、肌球蛋白）的检测来探讨iNOS基因对耳蜗及听力发育的影响。结果表明：iNOS（-/-）基因缺失小鼠出现不同程度的听力损失，并且其听力老化较野生型小鼠快。iNOS（-/-）基因缺失小鼠耳蜗外毛细胞纤毛有不同程度的缺失，随小鼠日龄增加iNOS（-/-）基因缺失小鼠耳蜗外毛细胞纤毛的缺失程度比野生型小鼠更重。iNOS（-/-）基因缺失小鼠耳蜗内外毛细胞、血管纹基底细胞和螺旋神经节细胞有不同程度的超微结构损伤，如：线粒体轻度、重度肿胀、空泡化和嵴脱落等，随小鼠日龄增加iNOS（-/-）基因缺失小鼠耳蜗内外毛细胞、血管纹基底细胞和螺旋神经节细胞超微结构损伤比野生型小鼠更重。iNOS（-/-）基因缺失小鼠耳蜗功能蛋白：kcnq1/kcne1、prestin、kcnq4、connexins 26和30、cldn14、F-肌动蛋白、肌球蛋白含量比野生型小鼠明显低，随小鼠日龄增加这些耳蜗蛋白含量下降比野生型小鼠下降更快。结论：iNOS(-/-)基因缺失小鼠听功能减退伴随耳蜗超微结构损伤、耳蜗功能蛋白表达下降。证实iNOS基因参与耳蜗发育调控，与遗传性聋相关。