Chen F, Ye J, Zhang X, Rojanasakul Y, Shi X
Milton S. Hershey Medical Center, Pennsylvania State University, Hershey, Pennsylvania, 17033, USA.
Arch Biochem Biophys. 1997 Feb 15;338(2):165-72. doi: 10.1006/abbi.1996.9849.
Reaction of chromium(VI) with alpha-lipoic acid (reduced form, also called 1,2-dithiolane-3-pentanoic acid) generated Cr(V) and hydroxyl radical (*OH) as measured by electron spin resonance and ESR spin trapping. 5,5-Dimethyl-1-pyrroline was used as a spin trapping agent. Catalase inhibited the *OH generation and enhanced the Cr(V) formation. Superoxide dismutase had an opposite effect. H2O2 enhanced the *OH generation and decreased the Cr(V) formation in a dose-dependent manner. Metal chelators, EDTA, diethylenetriaminepentaacetic acid, deferoxamine, and 1, 10-phenanthroline inhibited *OH radical generation in the order of EDTA > 1,10-phenanthroline > DTPA > deferoxamine. Oxygen consumption measurements indicated that molecular oxygen was used to generate *OH radical in the mixture of Cr(VI) and alpha-lipoic acid. H2O2 and superoxide radical (O2-) were involved as reactive intermediates. The *OH radical was generated via Cr(V)-mediated Fenton-like reaction (Cr(V) + H2O2 --> Cr(VI) + OH- + *OH). HPLC measurements show that the *OH radical generated by this reaction is capable of generating 8-hydroxyl-2'-deoxyguanosine from 2-deoxyguanosine. Incubation of Cr(VI) with cultured Jurkat cells resulted in an activation of DNA binding activity of the nuclear factor (NF)-kappaB. Addition of alpha-lipoic acid enhanced the NF-kappaB activation, while the *OH radical scavenger, sodium formate, inhibited it, showing that alpha-lipoic acid enhanced Cr(VI)-induced NF-kappaB activation via free radical reactions. The results indicate that while alpha-lipoic acid is considered to be an antioxidant, it may be a cellular one-electron Cr(VI) reductant and could be involved in the mechanism of Cr(VI)-induced carcinogenesis.
通过电子自旋共振和电子顺磁共振自旋捕获法测量发现，铬（VI）与α-硫辛酸（还原形式，也称为1,2 - 二硫戊环-3 - 戊酸）反应生成了Cr（V）和羟基自由基（OH）。5,5 - 二甲基-1 - 吡咯啉被用作自旋捕获剂。过氧化氢酶抑制OH的生成并增强Cr（V）的形成。超氧化物歧化酶则有相反的作用。过氧化氢以剂量依赖的方式增强OH的生成并降低Cr（V）的形成。金属螯合剂乙二胺四乙酸（EDTA）、二乙烯三胺五乙酸（DTPA）、去铁胺和1,10 - 菲咯啉抑制OH自由基生成的顺序为EDTA > 1,10 - 菲咯啉 > DTPA > 去铁胺。耗氧量测量表明，在铬（VI）和α-硫辛酸的混合物中，分子氧被用于生成*OH自由基。过氧化氢（H2O2）和超氧自由基（O2-）作为反应中间体参与其中。OH自由基是通过Cr（V）介导的类芬顿反应（Cr（V）+ H2O2 --> Cr（VI）+ OH- + OH）生成的。高效液相色谱测量表明，该反应生成的OH自由基能够从2 - 脱氧鸟苷生成8 - 羟基-2'-脱氧鸟苷。铬（VI）与培养的Jurkat细胞孵育导致核因子（NF）-κB的DNA结合活性激活。添加α-硫辛酸增强了NF-κB的激活，而OH自由基清除剂甲酸钠则抑制了它，这表明α-硫辛酸通过自由基反应增强了铬（VI）诱导的NF-κB激活。结果表明，虽然α-硫辛酸被认为是一种抗氧化剂，但它可能是细胞内的单电子铬（VI）还原剂，并且可能参与铬（VI）诱导致癌的机制。
