ROLE OF HYDROXYLAMINE REDUCTION IN DRUG HYPERSENSITIVITY

磺胺甲恶唑（SMX）、磺胺嘧啶、氨苯砜、喷他脒、普鲁卡因胺是临床上重要的药物，但部分患者发生超敏反应，限制了其使用。这些反应被认为与有毒羟胺代谢物及其自发副产物亚硝基代谢物的存在有关。与母体化合物不同，这些代谢物具有细胞毒性和免疫原性。对SMX和相关药物的超敏反应发生在很高比例（25- 60%）的艾滋病患者中。这种高发病率的原因尚不清楚，但体外细胞毒性测定外周血单核细胞（PBMC）的数据表明，hiv阳性和hiv阴性患者都有这种超敏反应的羟胺或亚硝基解毒缺陷。我们假设羟胺和亚硝基代谢物通过还原解毒是对磺胺和相关药物过敏的重要决定因素。我们进一步假设NADH细胞色素b5还原酶在某些物种中参与羟胺还原，对人类羟胺解毒很重要。此外，我们有新的数据表明黄素（FAD和FMN）；在谷胱甘肽存在的情况下，它们能够非酶还原羟胺。因此，我们提出NADH或黄素依赖性羟胺和亚硝基代谢物的还原缺陷与磺胺过敏的结果有关。为了解决这些假设，我们将使用表达的人重组b5R和人b5R抗体来研究NADH细胞色素b5还原酶（b5R）在肝脏和PBMC中羟胺和亚硝基还原中的作用。我们将在无细胞系统中使用体外化学计量法评估黄素在羟胺和亚硝基还原中的作用，以及黄素和谷胱甘肽含量与肝微粒体和PBMC活性的相关性。最后，我们将把羟胺和亚硝基还原、b5R表达和黄素含量与HIV感染患者SMX超敏反应的结果联系起来。这些研究的最终目的是更好地了解磺胺类药物和相关临床重要药物产生羟胺和亚硝基代谢物的毒性发病机制。这些实验的结果将确定参与这些代谢物解毒的途径，将为预防过敏和其他羟胺相关毒性提供更好的策略。

Sulfamethoxazole (SMX), sulfadiazine, dapsone, pentamidine, and procainamide are clinically important drugs, the use of which is limited by the occurrence of hypersensitivity reactions in some patients. These reactions are thought to be related to the presence of a toxic hydroxylamine metabolite and its spontaneous byproduct, the nitroso metabolite. Unlike the parent compounds, these metabolites are both cytotoxic and immunogenic. Hypersensitivity reactions to SMX and related drugs occur in a high percentage (25-60 percent) of patients with AIDS. The reason for this high incidence is unclear, but data from in vitro cytotoxicity assays in peripheral blood mononuclear cells (PBMC's) suggest that both HIV-positive and HIV-negative patients with such hypersensitivity have a defect in hydroxylamine or nitroso detoxification. We hypothesize that detoxification of hydroxylamine and nitroso metabolites by reduction is an important determinant of hypersensitivity to sulfonamide and related drugs. We further hypothesize that NADH cytochrome b5 reductase, which is involved in hydroxylamine reduction in some species, is important for hydroxylamine detoxification in humans. In addition, we have novel data to suggest that flavins (FAD and FMN); in the presence of glutathione, are capable of non- enzymatic reduction of hydroxylamines. We therefore propose that defects in either NADH- or flavin-dependent reduction of hydroxylamines and nitroso metabolites are associated with the outcome of sulfonamide hypersensitivity. To address these hypotheses, we will examine the role of NADH cytochrome b5 reductase (b5R) in hydroxylamine and nitroso reduction in both liver and PBMC's, using expressed human recombinant b5R and antibodies to human b5R. We will evaluate the role of flavins in hydroxylamine and nitroso reduction using in vitro stoichiometric assays in a cell-free system, and correlation of flavin and glutathione content with activity in hepatic microsomes and PBMC's. Finally, we will correlate hydroxylamine and nitroso reduction, b5R expression, and flavin content with the outcome of SMX hypersensitivity in patients with HIV infection. The ultimate goal of these studies is to better understand the pathogenesis of toxicity to sulfonamides and a related group of clinically important drugs which generate hydroxylamine and nitroso metabolites. The results of these experiments, which will identify the pathways involved in the detoxification of these metabolites, will suggest better strategies for the prevention of hypersensitivity and other hydroxylamine-related toxicity.