Tabatabaie T, Potts J D, Floyd R A
Free Radical Biology and Aging Research Program, Oklahoma Medical Research Foundation, 825 N.E. 13th Street, Oklahoma City, Oklahoma, 73104, USA.
Arch Biochem Biophys. 1996 Dec 15;336(2):290-6. doi: 10.1006/abbi.1996.0560.
Brain ischemia reperfusion causes increased formation of reactive oxygen species (ROS). Activity of the mitochondrial enzyme pyruvate dehydrogenase (PDH) has been shown to undergo a significant decrease following reperfusion of the ischemic tissue. We have examined the effect of a superoxide radical-generating system (xanthine oxidase/hypoxanthine, XO/HX) on the activity of this enzyme. Incubation of PDH in the presence of XO/HX resulted in its inactivation. The degree of the inactivation was dependent on the amount of XO present, which correlated linearly with the concentration of superoxide radical generated by this system. The activity of lactate dehydrogenase, an enzyme resistant to inactivation by ischemia reperfusion, was not affected by this system. Superoxide dismutase partially prevented and catalase exerted a nearly complete protective effect against the inactivation of PDH. Deferoxamine was partially protective. The sulfhydryl protective reagents, dithiothreitol and glutathione, prevented the inactivation of PDH, even though to varying degrees, which implicates sulfhydryl oxidation. A hydroxyl radical-generating system (hydrogen peroxide irradiated with ultraviolet radiation) effectively inactivated PDH. These results demonstrate that PDH is susceptible to damage and inactivation by ROS and point to the involvement of Fenton chemistry and hydroxyl radicals formed through it in PDH inactivation by XO/HX. A similar mechanism may be responsible for the PDH inactivation during ischemia/reperfusion.
脑缺血再灌注会导致活性氧（ROS）生成增加。线粒体酶丙酮酸脱氢酶（PDH）的活性在缺血组织再灌注后已显示出显著下降。我们研究了超氧自由基生成系统（黄嘌呤氧化酶/次黄嘌呤，XO/HX）对该酶活性的影响。在XO/HX存在的情况下孵育PDH会导致其失活。失活程度取决于XO的量，这与该系统产生的超氧自由基浓度呈线性相关。乳酸脱氢酶是一种对缺血再灌注失活有抗性的酶，其活性不受该系统影响。超氧化物歧化酶部分预防了这种失活，而过氧化氢酶对PDH失活发挥了几乎完全的保护作用。去铁胺有部分保护作用。巯基保护试剂二硫苏糖醇和谷胱甘肽，尽管程度不同，但都能防止PDH失活，这表明涉及巯基氧化。羟基自由基生成系统（用紫外线照射过氧化氢）能有效使PDH失活。这些结果表明，PDH易受ROS的损伤和失活影响，并指出通过Fenton化学反应形成的羟基自由基参与了XO/HX导致的PDH失活。类似的机制可能是缺血/再灌注期间PDH失活的原因。
