Microtubule dysfunction by posttranslational nitrotyrosination of alpha-tubulin: a nitric oxide-dependent mechanism of cellular injury

Morphologic assessment of oxidative damage: A review

Biochemical studies have indicated changes in anti-oxidant enzyme activities and increased oxidative damage products in many disease states, particularly aging and diseases associated with aging, such as neurodegenerative diseases and cancer. To try to determine cellular and subcellular localization of oxidative damage, our laboratory has developed quantitative light and electron microscopy immunogold techniques using specific antibodies to oxidative damage products. Results from studies of different pathologic processes are presented, illustrating that both localization and quantitation of oxidative damage products is possible. These analyses give important insights into the nature of various pathologic processes.

Requirements for heme and thiols for the nonenzymatic modification of nitrotyrosine

Peroxynitrite-dependent formation of nitrotyrosine has been associated with inactivation of various enzymes and proteins possessing functionally important tyrosines. We have previously reported an enzymatic activity modifying the nitrotyrosine residues in nitrated proteins. Here we are describing a nonenzymatic reduction of nitrotyrosine to aminotyrosine, which depends on heme and thiols. Various heme-containing proteins can mediate the reaction, although the reaction also is catalyzed by heme. The reaction is most effective when vicinal thiols are used as reducing agents, although ascorbic acid also can replace thiols with lesser efficiency. The reaction could be inhibited by (z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1- ium-1, but not other tested NO donors. HPLC with electrochemical detection analysis of the reaction identified aminotyrosine as the only reaction product. The reduction of nitrotyrosine was most effective at a pH close to physiological and was markedly decreased in acidic conditions. Various nitrophenol compounds also were modified in this reaction. Understanding the mechanism of this reaction could help define the enzymatic modification of nitrotyrosine-containing proteins. Furthermore, this also could assist in understanding the role of nitrotyrosine formation and reversal in the regulation of various proteins containing nitrotyrosine. It also could help define the role of nitric oxide and other reactive species in various disease states.