Interactions of nitroaromatic compounds with the mammalian selenoprotein thioredoxin reductase and the relation to induction of apoptosis in human cancer cells
Interactions of nitroaromatic compounds with the mammalian selenoprotein thioredoxin reductase and the relation to induction of apoptosis in human cancer cells
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DOI：
10.1074/jbc.m511972200
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发表时间：
2006-03-03
影响因子：
4.8
通讯作者：
Arnér, ESJ
中科院分区：
文献类型：
--
作者：
Cenas, N;Prast, S;Arnér, ESJ
在这里，我们描述了哺乳动物硒蛋白硫氧还蛋白还原酶（TrxR）与硝基芳香族环境污染物和药物的新的相互作用。我们发现，TrxR可以催化硝基还原酶反应，无论是一个或两个电子还原，使用其硒代半胱氨酸的活性位点和另一个氧化还原活性中心，推测FAD。在pH7.0和25 ℃下，使用50 μ M NADPH，四苯基和对二硝基苯是最有效的硝基芳香底物，k（cat）分别为1.8和2.8 s（-1）。作为一种硝基还原酶，TrxR在四电子还原态和两电子还原态之间循环。单电子反应导致超氧化物的形成，如通过细胞色素c还原所检测到的，有趣的是，四苯基或2，4-二硝基苯-N-甲基亚硝胺的还原性N-取代，导致亚硝酸盐的释放。大多数硝基芳烃对NADPH和二硫化物底物5，5 '-二硫代双（2-硝基苯甲酸）分别是非竞争性和非竞争性抑制剂。然而，Tetryl和4，6-二硝基苯并氧化呋咱是相对于5，5 '-二硫代双（2-硝基苯甲酸）的竞争性抑制剂，并且显然是酶的硒醇硫醇基序的底物。此外，四甲苯和4，6-二硝基苯并氧化呋咱有效地灭活了TrxR，这可能是通过硒醇硫醇基序的烷基化来实现的，就像1-氯-2，4-二硝基苯/二硝基氯苯（DNCB）或胡桃醌对TrxR的抑制一样。后一种化合物是细胞环境中TrxR活性的最有效抑制剂。DNCB，胡桃醌，和tetryl是高度细胞毒性和诱导caspase-3/7激活HeLa细胞。此外，DNCB和胡桃醌也是Bcl 2过表达的HeLa细胞或A549细胞中的细胞凋亡的有效诱导剂。基于这些发现，我们认为，通过烷基化硝基芳香族或醌化合物靶向细胞内TrxR可能有助于诱导暴露的人癌细胞的凋亡。
Here we described novel interactions of the mammalian selenoprotein thioredoxin reductase (TrxR) with nitroaromatic environmental pollutants and drugs. We found that TrxR could catalyze nitroreductase reactions with either one- or two-electron reduction, using its selenocysteine-containing active site and another redox active center, presumably the FAD. Tetryl and p-dinitrobenzene were the most efficient nitroaromatic substrates with a k(cat) of 1.8 and 2.8 s(-1), respectively, at pH 7.0 and 25 degrees C using 50 mu M NADPH. As a nitroreductase, TrxR cycled between four- and two-electron-reduced states. The one- electron reactions led to superoxide formation as detected by cytochrome c reduction and, interestingly, reductive N-denitration of tetryl or 2,4-dinitrophenyl-N-methylnitramine, resulting in the release of nitrite. Most nitroaromatics were uncompetitive and noncompetitive inhibitors with regard to NADPH and the disulfide substrate 5,5'-dithiobis(2-nitrobenzoic acid), respectively. Tetryl and 4,6-dinitrobenzofuroxan were, however, competitive inhibitors with respect to 5,5'-dithiobis( 2-nitrobenzoic acid) and were clearly substrates for the selenolthiol motif of the enzyme. Furthermore, tetryl and 4,6-dinitrobenzofuroxan efficiently inactivated TrxR, likely by alkylation of the selenolthiol motif as in the inhibition of TrxR by 1-chloro-2,4-dinitrobenzene/ dinitrochlorobenzene ( DNCB) or juglone. The latter compounds were the most efficient inhibitors of TrxR activity in a cellular context. DNCB, juglone, and tetryl were highly cytotoxic and induced caspase-3/7 activation in HeLa cells. Furthermore, DNCB and juglone were potent inducers of apoptosis also in Bcl2 overexpressing HeLa cells or in A549 cells. Based on these findings, we suggested that targeting of intracellular TrxR by alkylating nitroaromatic or quinone compounds may contribute to the induction of apoptosis in exposed human cancer cells.