Ramakrishna Rao D N, Cederbaum A I
Department of Biochemistry, Mount Sinai School of Medicine, New York, 10029, USA.
Biochim Biophys Acta. 1996 Mar 15;1289(2):195-202. doi: 10.1016/0304-4165(95)00158-1.
The formation of oxygen species during the redox cycling of sodium nitroprusside by rat liver microsomes and by chemical reductants was evaluated. The reduction of sodium nitroprusside by ascorbate and glutathione results in formation of the nitroprusside nitroxide radical which, on freezing at 77 K, results exclusively in the tetracyano [Fe(CN4)NO]2- and pentacyano [Fe(CN5)NO]3- forms of nitroxide radicals, respectively. The role of reducing agents on the inter-conversion of these two forms of nitroxide radical is discussed. The NADH and NADPH dependent microsomal reduction of nitroprusside results in the production of nitroprusside nitroxide radical, which in the presence of oxygen undergoes redox cycling to generate superoxide radical, and eventually hydroxyl radical is formed by a Fenton-type of reaction. Studies on the effect of several biologically or toxicologically relevant iron chelators on NADPH-dependent microsomal reduction of nitroprusside and subsequent formation of hydroxyl radical indicate that certain iron chelators such as isocitrate act as hydroxyl radical scavengers (depending on its concentration), but other chelators such as EDTA and DPTA function as good catalysts for the generation of hydroxyl radicals. The NADH and nitroprusside dependent microsomal production of hydroxyl radical is better in the presence of ATP, or equal in the presence of acetate, or diminished in the presence of DTPA when compared to the NADPH- and nitroprusside-dependent microsomal production of hydroxyl radicals. The effect of these chelates on the redox cycling of iron and nitroprusside by microsomes is discussed. Rat liver sub-mitochondrial particles and human hepatoblastoma cells (HepG2 cell line) also generated superoxide and hydroxyl radicals during the redox cycling of nitroprusside. These results provide direct evidence for the production of reactive oxygen species during the redox cycling of nitroprusside, The use of nitroprusside as a nitric oxide donor in biological systems may be complicated by the necessity to consider the generation of reactive oxygen species due to redox cycling of this compound by cellular reductases and low-molecular weight reductants.
评估了大鼠肝微粒体和化学还原剂在硝普钠氧化还原循环过程中氧物种的形成。抗坏血酸和谷胱甘肽对硝普钠的还原导致硝普氮氧自由基的形成，该自由基在77K冷冻时分别仅产生四氰基[Fe(CN4)NO]2-和五氰基[Fe(CN5)NO]3-形式的氮氧自由基。讨论了还原剂对这两种形式氮氧自由基相互转化的作用。NADH和NADPH依赖的微粒体对硝普钠的还原导致硝普氮氧自由基的产生，该自由基在有氧存在的情况下进行氧化还原循环以产生超氧自由基，最终通过芬顿型反应形成羟基自由基。对几种具有生物学或毒理学相关性的铁螯合剂对NADPH依赖的微粒体对硝普钠的还原以及随后羟基自由基形成的影响的研究表明，某些铁螯合剂如异柠檬酸作为羟基自由基清除剂（取决于其浓度），但其他螯合剂如EDTA和DPTA作为羟基自由基生成的良好催化剂。与NADPH和硝普钠依赖的微粒体产生羟基自由基相比，在ATP存在下，NADH和硝普钠依赖的微粒体产生羟基自由基的情况更好，在乙酸盐存在下相当，而在DTPA存在下则减少。讨论了这些螯合物对微粒体中铁和硝普钠氧化还原循环的影响。大鼠肝亚线粒体颗粒和人肝癌细胞（HepG2细胞系）在硝普钠的氧化还原循环过程中也产生超氧和羟基自由基。这些结果为硝普钠氧化还原循环过程中活性氧物种的产生提供了直接证据。在生物系统中使用硝普钠作为一氧化氮供体可能会因需要考虑该化合物被细胞还原酶和低分子量还原剂氧化还原循环而产生活性氧物种而变得复杂。
