SUPEROXIDE GENERATION FROM ENOS DEPENDENT REDOX CYCLING OF ADRIAMYCIN

含醌类化疗药物的临床应用 阿霉素受到严重的剂量依赖性心脏毒性的限制。 细胞毒性的机制已经被认为与增加 产生超氧化物。依赖NAD(P)H的酶 阿霉素的单电子还原生成阿霉素 在存在的情况下进行氧化还原循环的半醌基团 产生超氧化物和阿霉素的氧气。从而阿霉素 为氧的单电子还原提供了一个动力学机制 NAD(P)H.我们在这里展示了内皮型一氧化氮合酶(ENOS) 刺激阿霉素产生超氧化物。阿霉素 与eNOS捆绑在一起，长度约为1公里。5.0微摩尔，由 超氧化物的NADPH消耗和ESR自旋俘获。超氧化物 ENOS/阿霉素的生成不依赖于 Ca(2)/CaM，并被黄素蛋白抑制剂取消 去苯碘。这有力地表明阿霉素经历了 ENOS还原酶域的还原。其中一个后果就是 ENOS介导的阿霉素还原活性降低 一氧化氮的产生和超氧化物的形成增加。这 可能导致eNOS产生过氧亚硝酸盐，这是一种牵涉到的强有力的氧化剂 在几种血管病变中。

The clinical use of the quinone-containing chemotherapeutic agent adriamycin is restricted by a severe dose-dependent cardiotoxicity. The mechanism underlying cytotoxicity has been linked to an increased generation of superoxide. The NAD(P)H-dependent enzymatic one-electron reduction of adriamycin generates the adriamycin semiquinone radical which undergoes redox-cycling in the presence of oxygen to generate superoxide and adriamycin. Thereby adriamycin provides a kinetic mechanism for one-electron reduction of oxygen by NAD(P)H. Here we show that endothelial nitric oxide synthase (eNOS) stimulates the generation of superoxide from adriamycin. Adriamycin binds to eNOS with a Km of approx. 5.0 micromole as determined from NADPH consumption and ESR spin-trapping of superoxide. Superoxide generation from eNOS/adriamycin is not dependent on the presence of CA(2+)/CaM and is abolished by the flavoprotein inhibitor dephenyleneiodonium. This strongly suggests that adriamycin undergoes reduction at the reductase domain of eNOS. One of the consequences of eNOS-mediated reductive activation of adriamycin is decreased production of nitric oxide and increased superoxide formation. This may lead eNOS to generate peroxynitrite, a potent oxidant implicated in several vascular pathologies.