Analysis of Neurosteroid Synthesis in Grial Cells with a combined Imaging System

为了阐明神经类固醇合成的机制，我们用共聚焦显微镜和实时视频增强显微镜相结合的方法显示了神经胶质细胞和肾上腺皮质细胞内信号的过程。由于肾上腺皮质是产生类固醇激素的主要器官，肾上腺皮质细胞是神经胶质细胞合成神经类固醇的模型系统。ACTH刺激肾上腺皮质细胞后，观察到细胞内出现一系列钙峰和类固醇生成。钙信号与类固醇激素的合成有关，因为钙信号的抑制阻止了类固醇的合成。观察到一种低密度脂蛋白(LDL)的摄取，该低密度脂蛋白含有许多胆固醇分子，这些分子是类固醇激素的前体。还观察到内化低密度脂蛋白的转运和游离胆固醇在核周的分布。据报道，三磷酸腺苷是一种神经递质。三磷酸腺苷刺激神经胶质细胞后，细胞内出现一过性钙峰。正如肾上腺皮质细胞所显示的那样，胶质细胞也显示出对低密度脂蛋白的强烈摄取和内小体的定向运输。另一方面，神经胶质细胞中的游离胆固醇分子主要位于质膜中。

To elucidate the mechanism of neurosteroid synthesis, we have visualized the process of intracellular signaling in glial cells and adrenocortical cells.Visualization was performed with he combination of confocal microscopy and real-time video enhanced microscopy. Since adrenal cortex is a major organ which produces steroid hormone, adrenocortical cells were examined as a model system of neurosteroid synthesis in glial cells.After stimulation of adrenocortical cells with ACTH,a series of calcium spikes and steroidogenesis were observed in the cells. There was a relationship between calcium signaling and steroid horm one synthesis, because inhibition of calcium signaling stopped steroidogenesis. The uptake of a low density lipoprotein (LDL) which contains a number of cholesterol molecules, precursors of steroid hormone, was observed. The trafficking of internalized LDL and perinuclear distribution of the free cholesterol were also observed.ATP is reported to be a neurotrasmitter. The stimulation of glial cells by ATP induced a transient calcium spikes in the cells. Glial cells also showed a intensive uptake of LDL and a directed trafficking of endosomes as adrenocortical cells showed. On the other hand, free cholesterol molecules in a glial cell were mainly located in a plasma membrance.