Superoxide dismutase reduces injury in many disease processes, implicating superoxide anion radical (O2-.) as a toxic species in vivo. A critical target of superoxide may be nitric oxide (NO.) produced by endothelium, macrophages, neutrophils, and brain synaptosomes. Superoxide and NO. are known to rapidly react to form the stable peroxynitrite anion (ONOO-). We have shown that peroxynitrite has a pKa of 7.49 +/- 0.06 at 37 degrees C and rapidly decomposes once protonated with a half-life of 1.9 sec at pH 7.4. Peroxynitrite decomposition generates a strong oxidant with reactivity similar to hydroxyl radical, as assessed by the oxidation of deoxyribose or dimethyl sulfoxide. Product yields indicative of hydroxyl radical were 5.1 +/- 0.1% and 24.3 +/- 1.0%, respectively, of added peroxynitrite. Product formation was not affected by the metal chelator diethyltriaminepentaacetic acid, suggesting that iron was not required to catalyze oxidation. In contrast, desferrioxamine was a potent, competitive inhibitor of peroxynitrite-initiated oxidation because of a direct reaction between desferrioxamine and peroxynitrite rather than by iron chelation. We propose that superoxide dismutase may protect vascular tissue stimulated to produce superoxide and NO. under pathological conditions by preventing the formation of peroxynitrite.

https://www.pnas.org/content/pnas/87/4/1620.full.pdf

Apparent hydroxyl radical production by peroxynitrite: implications for endothelial injury from nitric oxide and superoxide.

For a long time, superoxide generation by an NADPH oxidase was considered as an oddity only found in professional phagocytes. Over the last years, six homologs of the cytochrome subunit of the phag...

/pdf/the-nox-family-of-ros-generating-nadph-oxidases-physiology-zjc88zvh59.pdf

The NOX Family of ROS-Generating NADPH Oxidases: Physiology and Pathophysiology

The discovery that mammalian cells have the ability to synthesize the free radical nitric oxide (NO) has stimulated an extraordinary impetus for scientific research in all the fields of biology and medicine. Since its early description as an endothelial-derived relaxing factor, NO has emerged as a fundamental signaling device regulating virtually every critical cellular function, as well as a potent mediator of cellular damage in a wide range of conditions. Recent evidence indicates that most of the cytotoxicity attributed to NO is rather due to peroxynitrite, produced from the diffusion-controlled reaction between NO and another free radical, the superoxide anion. Peroxynitrite interacts with lipids, DNA, and proteins via direct oxidative reactions or via indirect, radical-mediated mechanisms. These reactions trigger cellular responses ranging from subtle modulations of cell signaling to overwhelming oxidative injury, committing cells to necrosis or apoptosis. In vivo, peroxynitrite generation represents a crucial pathogenic mechanism in conditions such as stroke, myocardial infarction, chronic heart failure, diabetes, circulatory shock, chronic inflammatory diseases, cancer, and neurodegenerative disorders. Hence, novel pharmacological strategies aimed at removing peroxynitrite might represent powerful therapeutic tools in the future. Evidence supporting these novel roles of NO and peroxynitrite is presented in detail in this review.

/pdf/nitric-oxide-and-peroxynitrite-in-health-and-disease-3uuuqgfdcz.pdf

Nitric Oxide and Peroxynitrite in Health and Disease

Assay for lipid peroxides in animal tissues by thiobarbituric acid reaction

Publisher Summary This chapter discusses the role of free radicals and catalytic metal ions in human disease. The importance of transition metal ions in mediating oxidant damage naturally leads to the question as to what forms of such ions might be available to catalyze radical reactions in vivo . The chapter discusses the metabolism of transition metals, such as iron and copper. It also discusses the chelation therapy that is an approach to site-specific antioxidant protection. The detection and measurement of lipid peroxidation is the evidence most frequently cited to support the involvement of free radical reactions in toxicology and in human disease. A wide range of techniques is available to measure the rate of this process, but none is applicable to all circumstances. The two most popular are the measurement of diene conjugation and the thiobarbituric acid (TBA) test, but they are both subject to pitfalls, especially when applied to human samples. The chapter also discusses the essential principles of the peroxidation process. When discussing lipid peroxidation, it is essential to use clear terminology for the sequence of events involved; an imprecise use of terms such as initiation has caused considerable confusion in the literature. In a completely peroxide-free lipid system, first chain initiation of a peroxidation sequence in a membrane or polyunsaturated fatty acid refers to the attack of any species that has sufficient reactivity to abstract a hydrogen atom from a methylene group.

Role of free radicals and catalytic metal ions in human disease: an overview.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/0014-5793%2886%2981035-3

Effect of chronic ethanol consumption on microsomal lipid peroxidation. Role of iron and comparison between controls.

NADH-dependent microsomal interaction with ferric complexes and production of reactive oxygen intermediates.

Ethanol inhibits the JAK-STAT signaling pathway in freshly isolated rat hepatocytes but not in cultured hepatocytes or HepG2 cells: evidence for a lack of involvement of ethanol metabolism.

Acetonitrile is a common industrial solvent and laboratory agent, which can be toxic if ingested. The toxicity of nitriles appears to be due to the production of cyanide, and detailed studies by Freeman and Hayes [(1988) Biochem. Pharmacol. 37, 1153-1159; (1987) Fundam. Appl. Toxicol. 8, 263-271] have shown that microsomes oxidize acetonitrile to cyanide. Treatment of rats with inducers of cytochrome P-450 IIE1 such as pyrazole, 4-methylpyrazole, and ethanol resulted in a 4- to 5-fold increase in cyanide production from acetonitrile by isolated microsomes. Phenobarbital treatment had a small stimulatory effect, whereas 3-methylcholanthrene treatment decreased microsomal oxidation of acetonitrile. Pyrazole treatment increased Vmax per milligram of microsomal protein and per nanomole of P-450 but did not affect the apparent km for acetonitrile, whereas the 4-methylpyrazole treatment increased Vmax and the apparent affinity for acetonitrile. Cyanide production was inhibited by carbon monoxide as well as by substrates and compounds that interact with the P-450 IIE1 isozyme such as ethanol, 2-butanol, DMSO, and 4-methylpyrazole. Oxidation of acetonitrile to cyanide by microsomes from rats treated with pyrazole or 4-methylpyrazole was nearly completely inhibited by anti-P-450 3a IgG. These results implicate a role for P-450 in the oxidation of acetonitrile to cyanide and suggest that P-450 IIE1 may be an especially effective catalyst for this oxidation. Acetonitrile oxidation was not affected by hydroxyl radical scavengers or by desferrioxamine, indicating no role for hydroxyl radicals in the overall mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

Arthur I. Cederbaum

Papers

Effect of chronic ethanol consumption on microsomal lipid peroxidation. Role of iron and comparison between controls.

NADH-dependent microsomal interaction with ferric complexes and production of reactive oxygen intermediates.

Ethanol inhibits the JAK-STAT signaling pathway in freshly isolated rat hepatocytes but not in cultured hepatocytes or HepG2 cells: evidence for a lack of involvement of ethanol metabolism.

Role of cytochrome P-450 IIE1 and catalase in the oxidation of acetonitrile to cyanide.

Effect of chronic clofibrate administration on mitochondrial fatty acid oxidation.