Department of Environmental Biochemistry, Kyoto Pharmaceutical University, 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan.
Department of Environmental Biochemistry, Kyoto Pharmaceutical University, 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan.
Life Sci. 2016 Apr 15;151:305-312. doi: 10.1016/j.lfs.2016.03.025. Epub 2016 Mar 12.
Zinc released from glutamatergic boutons and astrocytes acts as neuro- and glio-transmitters, and thus its extracellular level has to be strictly regulated. We previously revealed that uptake of zinc by astrocytes plays a critical role in its clearance, and zinc transporter Zrt/Irt-like protein 1 (ZIP1) is the molecule responsible for the uptake. However, it is unknown whether or not the functionality of the zinc clearance system is altered under oxidative stress-loaded conditions. Here, we characterized zinc uptake by oxidative stress-loaded astrocytes.
Cultured mouse astrocytes were treated with hydrogen peroxide (H2O2) to load oxidative stress. Functional expression of ZIP1 in astrocytes was evaluated by means of (65)Zn uptake, Western blotting and immunocytochemical analysis.
Treatment of astrocytes with 0.4mM H2O2 for 24h increased the expression levels of glial fibrillary acidic protein and 4-hydroxynonenal without significant decreases in their viability, indicating that induction of oxidative stress in astrocytes. Under oxidative stress-loaded conditions, astrocytes exhibited increased (65)Zn uptake activity, and the maximum uptake velocity for the uptake was significantly increased compared to that in the control group, while there was no change in the Michaelis constants, which were almost identical to that of mouse ZIP1. In the H2O2-treated astrocytes, the expression levels of ZIP1 were significantly increased in the cellular and plasma membrane fractions.
It appears that under oxidative stress-loaded conditions, astrocytes exhibit increased zinc clearance activity and this is due, at least in part, to increased ZIP1 expression.
谷氨酸能末梢和星形胶质细胞释放的锌作为神经递质和神经胶质递质发挥作用，因此其细胞外水平必须严格调节。我们之前揭示了星形胶质细胞摄取锌在其清除中起关键作用，锌转运蛋白 Zrt/Irt 样蛋白 1（ZIP1）是负责摄取的分子。然而，在氧化应激负荷条件下，锌清除系统的功能是否改变尚不清楚。在这里，我们研究了氧化应激负荷星形胶质细胞对锌的摄取。
用过氧化氢（H2O2）处理培养的小鼠星形胶质细胞以加载氧化应激。通过（65）Zn 摄取、Western blot 和免疫细胞化学分析评估星形胶质细胞中 ZIP1 的功能表达。
用 0.4mM H2O2 处理星形胶质细胞 24 小时会增加胶质纤维酸性蛋白和 4-羟基壬烯醛的表达水平，而其活力没有明显下降，表明星形胶质细胞中诱导了氧化应激。在氧化应激负荷条件下，星形胶质细胞表现出增加的（65）Zn 摄取活性，最大摄取速率与对照组相比显著增加，而米氏常数没有变化，几乎与小鼠 ZIP1 相同。在 H2O2 处理的星形胶质细胞中，ZIP1 的表达水平在细胞和质膜部分显著增加。
在氧化应激负荷条件下，星形胶质细胞表现出增强的锌清除活性，这至少部分归因于 ZIP1 表达的增加。
