Yamaguchi Taro, Yoneyama Masanori, Hinoi Eiichi, Ogita Kiyokazu
Laboratory of Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, Hirakata, Osaka 573-0101, Japan; Laboratory of Molecular Pharmacology, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Ishikawa 920-0934, Japan.
Laboratory of Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, Hirakata, Osaka 573-0101, Japan.
J Pharmacol Sci. 2015 Oct;129(2):127-34. doi: 10.1016/j.jphs.2015.09.005. Epub 2015 Oct 8.
The endocochlear potential in the inner ear is essential for hearing ability, and maintained by various K(+) transport apparatuses including Na(+), K(+)-ATPase and gap junction-mediated intercellular communication (GJ-IC) in the lateral wall structures of the cochlea. Noise-induced hearing loss is known at least in part due to disruption of GJ-IC resulting from an oxidative stress-induced decrease in connexins (Cxs) level in the lateral wall structures. The purpose of this study was to investigate, using primary cultures of fibrocytes from the cochlear spiral ligament of mice, the mechanism underlying GJ-IC disruption induced by 4-hydroxynonenal (4-HNE), which is formed as a mediator of oxidative stress. An exposure to 4-HNE produced the following events: i.e., an increase in 4-HNE-adducted proteins; a decrease in the protein levels of Cx43, β-catenin, and Cx43/β-catenin complex along with intracellular translocation of this complex from the cell membrane to the cytoplasm; enhanced calpain-dependent degradation of endogenous α-fodrin; and disruption of GJ-IC. The 4-HNE-induced decrease in these protein levels and disruption of GJ-IC were most completely abolished by the calpain inhibitor PD150606. Taken together, our data suggest that 4-HNE disrupted GJ-IC through calpain-mediated degradation of Cx43 and β-catenin in primary cultures of fibrocytes derived from the cochlear spiral ligament.
内耳中的内淋巴电位对于听力至关重要，它由包括钠钾ATP酶以及耳蜗侧壁结构中缝隙连接介导的细胞间通讯（GJ-IC）在内的多种钾离子转运装置维持。已知噪声性听力损失至少部分是由于耳蜗侧壁结构中氧化应激诱导的连接蛋白（Cxs）水平降低导致GJ-IC破坏所致。本研究的目的是利用从小鼠耳蜗螺旋韧带分离的成纤维细胞原代培养物，研究由作为氧化应激介质而形成的4-羟基壬烯醛（4-HNE）诱导GJ-IC破坏的机制。暴露于4-HNE会产生以下事件：即4-HNE加合物蛋白增加；Cx43、β-连环蛋白以及Cx43/β-连环蛋白复合物的蛋白水平降低，同时该复合物从细胞膜向细胞质发生细胞内转运；钙蛋白酶依赖性内源性α-辅肌动蛋白降解增强；以及GJ-IC破坏。钙蛋白酶抑制剂PD150606最完全地消除了4-HNE诱导的这些蛋白水平降低以及GJ-IC破坏。综上所述，我们的数据表明，4-HNE通过钙蛋白酶介导的耳蜗螺旋韧带来源的成纤维细胞原代培养物中Cx43和β-连环蛋白的降解破坏了GJ-IC。
