脂氧合酶介导酚噻嗪类对联苯胺等氧化的增强作用

Stimulatory response to the oxidation of benzidine and other xenobiotics mediated by lipoxygenase in the presence of phenothiazines

目的 探讨脂氧合酶催化酚噻嗪类增强联苯胺氧化反应的可能性。方法 在过氧化氢参与下 ,大豆脂氧合酶 (SLO)或提取纯化的人足月胎盘脂氧合酶 (HTPLO)介导氯丙嗪 (CPZ)或其他酚噻嗪类与联苯胺 (BZ)等相互作用 ,用光谱学方法检测反应产物生成速率。结果 SLO介导产生的氯丙嗪阳离子自由基 (CPZ· + )能激发BZ快速氧化为二亚胺联苯胺阳离子。在实验条件下 ,代谢相互作用导致BZ氧化速率增至BZ单独氧化的 4 2倍。CPZ对BZ氧化增强作用的大小与反应介质的pH、酶量以及CPZ、BZ和过氧化氢的浓度相关。同时发现许多其他酚噻嗪类化合物也能增强BZ的氧化 ,只是作用稍弱。CPZ也能增强其他 6种受试外源化学物的氧化。增强倍数最高的 (94倍 )是四甲基对苯二胺氧化为武斯特兰自由基 ,最低 (2倍 )是二甲氧联苯胺 ;四甲基联苯胺、愈创木酚、邻苯三酚和对苯二胺的氧化增强分别为 8、4、2 4和 2 5倍。初步的资料提示 ,纯化的HTPLO也表现出在CPZ参与时对BZ氧化的增强作用。结论 SLO和HTPLO均能介导酚噻嗪类化合物对联苯胺等外源化合物氧化的增强作用。

Objective To test the possibility that certain efficient substrates for lipoxygenase(LOX) produce shuttle oxidants that stimulate the generation of reactive oxygen species from other chemicals. Methods Metabolic interactions were conducted in vitro between chlorpromazine(BZ) or other phenothiazines and benzidine or other xenobiotics mediated by soybean lipoxygenase(SLO) or purified human term placental lipoxygenase(HTPLO) in the presence of hydrogen peroxide,and the rates of xenobiotics oxidation were measured by spectroscopic analysis. ResultsChlorpromazine cation radical(CPZ ·+ ) generated by lipoxygenase triggered a rapid oxidation of benzidine to benzidine diimine cation.Under the experimental conditions used,the metabolic interaction resulted in a 42-fold greater stimulation than BZ alone in the rate of BZ oxidation.The magnitude of stimulation of benzidine oxidation exhibited a dependence on the pH of the reaction medium,amount of the enzyme,and concentration of chlorpromazine,BZ,and hydrogen peroxide.A number of other phenothiazines were also found to stimulate BZ oxidation,albeit to a lesser degree.Chlorpromazine cation radical stimulated the oxidation of all six other xenobiotics tested.The highest stimulation (94-fold) was noted in the oxidation of tetramethyl phenylenediamine to Wursters blue radical,while the lowest stimulatory response (2-fold) was observed in guaiacol.Preliminary data showed that purified HTPLO also displayed a similar stimulatory response to benzidine oxidation in the presence of chlorpromazine. Conclusion Both soybean lipoxygenase and purified human term placental lipoxygenase can mediate stimulatory response to the oxidation of benzidine and other xenobiotics in the presence of phenothiazines.