PILOT STUDY--ASTROCYTE GENE EXPRESSION AND METHYL MERCURY NEUROTOXICITY

甲基汞（MeHg）中毒是有据可查的化学品 人类历史上的灾难。 大量甲基汞的情况 强烈支持对中枢神经系统（CNS）的毒性 通过体内和体外研究。 直到最近 发现星形胶质细胞优先积累甲基汞， 在甲基汞诱导的神经元反应的病因学考虑的反应 毒性 甲基汞暴露导致星形胶质细胞肿胀， 伴随的谷氨酸摄取抑制，调节性 体积减少，兴奋性氨基酸释放增加 （EAA），例如谷氨酸。 这一研究的主要假设是 合作提案假定， 甲基汞与细胞外 谷氨酸，反过来，导致神经元N-甲基-D- 天冬氨酸受体 所援引的机制 细胞外谷氨酸浓度的改变包括酶促 谷氨酰胺合成酶和转氨酶的活性，以及 这些酶和谷氨酸转运蛋白的水平。 我们最初 方法将应用最先进的分子生物学 分离谷氨酰胺合成酶和谷氨酰胺酶的方法，以及 研究它们在急性、慢性和原位甲基汞中的活动 暴露的星形胶质细胞 谷氨酰胺合成酶、谷氨酰胺酶 谷氨酸转运蛋白将由Western blot 印迹技术 这些基因在对照中的表达 而甲基汞处理过的细胞将与 通过RNA过量定量的相应信使RNA 溶液杂交法 我们还将研究 编码谷氨酰胺合成酶的基因突变， 用PCR-SSCP技术研究谷氨酸转运蛋白与转氨酶的关系 （PCR指导的单链构象多态性）和 对照组和甲基汞暴露星形胶质细胞的双脱氧DNA测序。 这项合作研究的总体长期目标是 继续阐明甲基汞神经毒性的机制， 星形胶质细胞无法控制 谷氨酸体内平衡在其病因学。

Methylmercury (MeHg) poisonings are well documented chemical disasters in human history. The case for significant MeHg toxicity to the central nervous system (CNS) is strongly supported by both in vivo and in vitro studies. Only recently have astrocytes been found to preferentially accumulate MeHg and their responses considered in the etiology of MeHg-induced neuronal toxicity. Exposure to MeHg results in astrocytic swelling with concomitant inhibition of glutamate uptake, changes in regulatory volume decrease, and increased release of excitatory amino acids (EAAs), such as glutamate. The primary working hypothesis of this collaborative proposal postulates that the neurotoxic effect of MeHg is associated with elevated concentrations of extracellular glutamate, in turn, leading to activation of neuronal N-methyl-D- aspartate receptors. Mechanisms invoked for the increased concentration of extracellular glutamate include altered enzymatic activities of glutamine synthetase and glutaminase, as well as the levels of these enzymes and glutamate transporters. Our initial approach will e apply state-of-the-art molecular biology approaches to isolate glutamine synthetase and glutaminase, and study their activities in acutely-, chronically-, and in situ-MeHg exposed astrocytes. Levels of glutamine synthetase, glutaminase and the glutamate transporters will be determined by Western blotting technique. Expression of these genes both in controls and MeHg-treated cells will be correlated to the availability of the respective messenger RNA, quantified by means of RNA-excess solution hybridization method. We will also study possible mutations of the genes coding for glutamine synthetase, glutaminase and the glutamate transporters by means of PCR-SSCP (PCR-directed single strand conformational polymorphism) and dideoxy DNA sequencing in controls and MeHg exposed astrocytes. The overall long term objective of this collaborative research is to continue to elucidate the mechanisms of MeHg neurotoxicity and the potential deleterious effects of astrocytic failure to control glutamate homeostasis in its etiology.