低氧对豚鼠耳蜗螺旋动脉和血管纹毛细血管细胞间缝隙连接的影响及机制研究

Disorder of the inner ear circulation caused by ischemia/hypoxia is closely related to hearing loss. Spiral modiolar artery (SMA) is the only artery providing blood to cochlea. The electric and mechanical synchronicity of SMA relies on gap junctions among vascular cells. Gap junction channel is an important structure to maintain normal function of blood vessels. Studies have demonstrated that hypoxia can cause alteration in gap junctions in cardiac and pulmonary arteries. Our previous study has also showed that hypoxic exposure inhibited inter-cellular gap junction communication of SMA. However, the exact mechanism(s) are still unclear. In this study, we tested the hypothesis that the disorder of inner ear circulation caused by hypoxia is mediated by the changes in protein expression of connexins that construct gap junction channels, which causes the abnormality of gap junction communication in SMA. The altered response of SMA to vasoactive substances further aggravates the effects of hypoxia on SMA, that eventually will cause sudden deafness or cochlea disfunction. Results from this study will provide better understanding of the mechanism(s) that inner ear circulation disorder causes hearing loss.

缺血/低氧造成的内耳循环紊乱与听力丧失有密切关联。耳蜗螺旋动脉（SMA）是供应耳蜗血液的唯一动脉，依靠相邻细胞间缝隙连接通道所介导的电、化学信息的传递，可保障其在纵向和横向上电、机械活动的同步性。缝隙连接是维持血管正常舒缩功能的重要结构, 有研究发现低氧可造成心肌和肺动脉中缝隙连接的异常，我们前期的工作也证实低氧能够抑制SMA细胞间的缝隙连接通讯，但确切的作用机制仍不明了。由此我们假设低氧造成的内耳循环紊乱可能由于缝隙连接通道蛋白表达的改变，引起SMA细胞间缝隙连接通讯异常，而造成SMA舒缩功能对血管活性物质的反应失常，又会更进一步加剧低氧引起的血管功能的异常，而引发突发性耳聋或耳蜗功能失调等疾病。本研究将为内耳循环系统紊乱而造成的听力丧失提供理论基础。

缺血/低氧造成的内耳循环紊乱与听力丧失有密切关联。耳蜗螺旋动脉（SMA）是供应耳蜗血液的唯一动脉，依靠相邻细胞间缝隙连接通道所介导的电、化学信息的传递，可保障其在纵向和横向上电、机械活动的同步性。本研究假设低氧造成的内耳循环紊乱可能由于缝隙连接通道蛋白表达的改变，引起SMA细胞间缝隙连接通讯异常，而造成SMA舒缩功能对血管活性物质的反应失常。本研究发现，通过联合应用胰酶消化法和组织块贴壁法，可以短期内得到大量高纯度高活性的豚鼠耳蜗螺旋动脉平滑肌细胞。CoCl2呈时间依赖性的降低细胞活性，增加细胞凋亡率，且CoCl2干预细胞24 h后，细胞内的SOD含量明显下降，MDA含量明显上升，同时，CoCl2能显著上调BAX及活化的caspase 3的蛋白的表达，下调Bcl2的表达，同时，CoCl2能显著上调cAMP及PKA的蛋白的表达，下调Cx43的表达。不同浓度的脂联素均能不同程度地逆转上述变化情况，即脂联素对豚鼠耳蜗螺旋动脉平滑肌细胞的保护作用是通过cAMP/PKA信号通路及调节Cx43的表达来实现的。此外，低氧可能通过抑制缝隙连接通讯功能影响血管的收缩。