Glutamate uptake is inhibited by arachidonic acid and oxygen radicals via two distinct and additive mechanisms.
Glutamate uptake is inhibited by arachidonic acid and oxygen radicals via two distinct and additive mechanisms.
复制标题
花生四烯酸和氧自由基通过两种不同的附加机制抑制谷氨酸的吸收。
作者：
A. Volterra;D. Trotti;G. Racagni
星形胶质细胞中谷氨酸的再摄取是维持生理兴奋性氨基酸神经传递的关键机制，通过不完全定义的分子机制被花生四烯酸（AA）和活性氧（ROS）抑制。由于ROS在AA代谢过程中产生，并且AA可以作为ROS介导的磷脂酶A2活化的结果而释放，因此它们对摄取的影响似乎可能是由共同的机制介导的。然而，在这里，我们表明，快速（10分钟）的吸收抑制AA或由黄嘌呤加黄嘌呤氧化酶（XO）反应产生的活性氧被选择性地取消由不同的代理商;牛血清白蛋白（BSA）只作用于AA，而清除酶超氧化物歧化酶（SOD）和过氧化氢酶（CAT）和二硫还原剂二硫苏糖醇（DTT）只作用于活性氧。此外，当加在一起时，黄嘌呤/XO和AA以完全相加的方式降低摄取。特别地，在存在最大AA抑制的情况下也观察到黄嘌呤/XO的作用。AA和自由基之间没有细胞损伤或化学反应的主要迹象，伴随着它们对摄取的累积效应。最后，由AA和黄嘌呤/XO一起引起的摄取抑制被减弱，但不被BSA、DTT或SOD/CAT单独阻断，而被SOD/CAT和BSA或SOD/CAT、DTT和BSA的组合完全阻断并基本上逆转。总之，这些数据表明，AA和ROS作用于神经胶质细胞谷氨酸转运通过不同的非相互作用机制。因此，它们可以独立地和相加地导致再摄取功能的损害，这是在病理条件如缺血/再灌注损伤中观察到的现象。
Reuptake of glutamate in astrocytes, a critical mechanism involved in the maintenance of physiological excitatory amino acid neurotransmission, is inhibited by both arachidonic acid (AA) and reactive oxygen species (ROS), via incompletely defined molecular mechanisms. Because ROS are generated during AA metabolism and AA can be released as a result of ROS-mediated phospholipase A2 activation, it seems likely that their effects on uptake are mediated by a common mechanism. However, here we show that rapid (10-min) uptake inhibitions by AA or by ROS generated by the xanthine plus xanthine oxidase (XO) reaction are selectively abolished by distinct agents; bovine serum albumin (BSA) acts only on AA, whereas the scavenger enzymes superoxide dismutase (SOD) and catalase (CAT) and the disulfide-reducing agent dithiothreitol (DTT) act only on ROS. Moreover, when added together, xanthine/XO and AA decrease uptake in a fully additive manner. In particular, the effect of xanthine/XO is seen also in the presence of maximal AA inhibition. No major signs of cell damage or chemical reaction between AA and radicals accompany their cumulative effects on uptake. Finally, uptake inhibition elicited by AA and xanthine/XO together is attenuated but not blocked by either BSA, DTT, or SOD/CAT individually, whereas it is fully blocked and substantially reversed by a combination of SOD/CAT and BSA or SOD/CAT, DTT, and BSA. Together, these data indicate that AA and ROS act on glial glutamate transport via distinct noninteracting mechanisms. Therefore, they could independently and additively contribute to the impairment of reuptake function, a phenomenon observed in pathological conditions such as ischemia/reperfusion injury.