水通道蛋白4在小鼠嗅觉系统中的表达及功能

Expression and function of aquaporin-4 in olfactory system of mice

目的研究水通道蛋白4(aquaporin 4,AQP4)在小鼠嗅觉系统中的表达及功能。方法应用免疫荧光和免疫印迹技术研究野生型和AQP4基因敲除小鼠嗅觉系统中AQP4的表达差异;采用埋藏食物小球实验、嗅觉迷宫实验两种嗅觉行为学方法以及气体刺激性嗅觉电位记录(electroolfactogram,EOG)检测两组小鼠嗅觉功能的差异。结果免疫荧光和免疫印迹结果均证实了AQP4基因敲除小鼠嗅觉系统中没有AQP4的表达。免疫荧光结果表明AQP4主要分布于嗅黏膜上皮层中支持细胞膜、Bowmann’s腺管上皮细胞膜以及基底细胞膜上,还分布于嗅黏膜固有层中Bowman’s腺上皮细胞膜、嗅神经束周围的嗅鞘细胞膜,以及嗅球的嗅神经层和小球层。行为学检测结果显示,埋藏食物小球实验和嗅觉迷宫实验中除对照实验外,野生型和AQP4基因敲除小鼠在所有测试时间点的差异具有统计学意义(P<0.05)。气体刺激性诱发电位结果发现,两组小鼠嗅黏膜在不同气压强度饱和三甲胺(trimethylamine)作用下的嗅觉电位波形相似,波幅均随气压的逐渐增加而增大;而在相同气压作用下,AQP4基因敲除小鼠嗅觉电位的波幅低于野生型小鼠,差异具有统计学意义(P<0.05)。结论 AQP4广泛分布于嗅觉系统包括嗅黏膜、嗅神经和嗅球的多个部位,其可能具有保护嗅神经束和促进神经信号传递的作用。

Objective To investigate the expression and function of aquaporin-4（AQP4） in the olfactory system of mice.Methods The differences of AQP4 expression in olfaction system between wild-type and AQP4-null mice were studied by immunoblotting and immunofluorescence methods. The differences of mouse olfactory functions in the two groups were examined by two olfactory behavioral assays： the buried food pellet test and olfaction maze test,and the odorant-stimulated electroolfactogram（EOG） recording.Results The results of immunoblotting and immunofluorescence showed no AQP4 expression in the olfactory system in AQP4-null mice.Immunofluorescence result also indicated that AQP4 was mainly distributed in the membrane of support cells,duct cells of Bowmann＇s gland,basal cells of olfactory epithelium,membrane of Bowmann＇s gland epithelial cells,olfactory sheath cells surrounding the olfactory bundles,and the membrane of cells in the olfactory bundle layer and glomeruler layer.The results of olfactory behavioral assay were significantly different between the two groups at all time points tested in both the olfaction maze test and the buried food pellet test（P0.05）.It was showed that the EOGs under different pressures of saturated trimethylamine had a similar shape in both groups,and the amplitude of EOGs increased with the increase of pressure.While under the same pressure,the EOG amplitude of AQP4-null mice was significantly lower than that of wild-type mice（P0.05）.Conclusion AQP4 is widely distributed in the olfactory system of mice,including the olfactory mucosa,olfactory nerve,and olfactory bulb,which can protect the olfactory neural bundle and facilitate neural signal transfer.