Menuet Arnaud, Anglade Isabelle, Le Guevel Remy, Pellegrini Elisabeth, Pakdel Farzad, Kah Olivier
Endocrinologie Moléculaire de la Reproduction, UMR CNRS 6026, Campus de Beaulieu, 35042 Rennes cedex, France.
J Comp Neurol. 2003 Jul 21;462(2):180-93. doi: 10.1002/cne.10726.
Recent data indicate that estrogens locally produced in the brain by aromatization of androgens could be important for neurogenesis and brain repair. In this respect, fish are interesting because of the extremely high aromatase activity of their brain. In this study, the rainbow trout brain aromatase was cloned and riboprobes were used to map the distribution of cells expressing the corresponding mRNAs. A very strong hybridization signal was detected in the pituitary and in cells bordering the ventricles in the telencephalon and ventral diencephalon, with the highest expression in the preoptic area and hypothalamus. A weaker signal was detected in the ependymal layer bordering the torus semicircularis and optic tectum. This localization was fully confirmed by immunohistochemistry using antibodies against a teleost aromatase. In addition, this antibody showed that aromatase expression in fact corresponds to radial glial cells because immunoreactive cells had long cytoplasmic processes extending toward the pial surface. Because brain aromatase was shown to be upregulated by estradiol in fish, the distribution of aromatase mRNAs was compared with that of rainbow trout estrogen receptor alpha (rtERalpha) on adjacent sections. Although the highest aromatase expression was found in regions expressing rtERalpha, no obvious coexpression was found, as rtERalpha was never observed in radial cells. However, reverse transcriptase-polymerase chain reaction experiments performed on brain cell cultures enriched in glial cells suggest that a weak expression of rtERalpha in glial cells cannot be excluded. The possible role of the high brain aromatase content in fish could be related to the continuous growth of their central nervous system during adulthood.
近期数据表明,雄激素经芳香化作用在大脑中局部产生的雌激素可能对神经发生和脑修复具有重要意义。在这方面,鱼类因其大脑具有极高的芳香化酶活性而备受关注。在本研究中,克隆了虹鳟鱼脑芳香化酶,并使用核糖探针来绘制表达相应mRNA的细胞分布图谱。在垂体以及端脑和腹侧间脑与脑室相邻的细胞中检测到非常强的杂交信号,在视前区和下丘脑表达最高。在与半规管隆起和视顶盖相邻的室管膜层检测到较弱的信号。使用针对硬骨鱼芳香化酶的抗体进行免疫组织化学充分证实了这种定位。此外,该抗体表明芳香化酶的表达实际上对应于放射状胶质细胞,因为免疫反应性细胞具有伸向软脑膜表面的长细胞质突起。由于已证明鱼类脑芳香化酶受雌二醇上调,因此在相邻切片上比较了芳香化酶mRNA与虹鳟鱼雌激素受体α(rtERα)的分布。尽管在表达rtERα的区域发现了最高的芳香化酶表达,但未发现明显的共表达,因为在放射状细胞中从未观察到rtERα。然而,对富含胶质细胞的脑细胞培养物进行的逆转录聚合酶链反应实验表明,不能排除胶质细胞中rtERα的弱表达。鱼类脑中高含量芳香化酶的可能作用可能与其成年期中枢神经系统的持续生长有关。