title: Antioxidant activity of lazaroid (U-75412E) and its protective effects against crystalline silica-induced cytotoxicity.
abstract: Lazaroids (21-amino steroids) are believed to be powerful scavengers of reactive oxygen species (ROS) and inhibitors of lipid peroxidation. Crystalline silica, a potent cytotoxic agent, causes pulmonary fibrosis in experimental animals and humans. ROS have been previously shown to be involved in crystalline silica-induced pulmonary injury and inflammation. In the present study, the reaction rate of lazaroid (U-75412E) with hydroxyl radical (.OH) generated by Fenton reaction (Fe(II) + H2O2 --> Fe(III) + OH- + .OH) was investigated using ESR spin-trapping competition reactions. The reaction rate constant was found to be 1.0 x 10(10) M(-1)s(-1), which was comparable with those of other efficient .OH radical scavengers. As indicators of crystalline silica-induced cytotoxicity and its protection by this antioxidant lazaroid (U-75412E) we measured lactate dehydrogenase, N-acetyl-beta-glucosaminidase, superoxide dismutase, glutathione peroxidase, and hydrogen peroxide released from rat alveolar macrophages. Lipid peroxidation, a prominent manifestation of .OH radical-induced cell injury, was also measured to evaluate the protective value of lazaroid. Alveolar macrophages treated with lazaroid (U-75412E) before crystalline silica exposure were protected against cell injury and lipid peroxidation as demonstrated by those indicators. Lazaroid (U-75412E) scavenges .OH radicals generated by crystalline silica-mediated reaction from H2O2 and inhibits lipid peroxidation in macrophages induced by these particles.
authors.affiliation: Pathology and Physiology Research Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV, USA.
authors.forename: S H
authors.initials: SH
authors.lastname: Huang
authors.forename: S
authors.initials: S
authors.lastname: Leonard
authors.forename: X
authors.initials: X
authors.lastname: Shi
authors.forename: M R
authors.initials: MR
authors.lastname: Goins
authors.forename: V
authors.initials: V
authors.lastname: Vallyathan
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D003460:Crystallization; D003497:Cyclic N-Oxides / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D016166:Free Radical Scavengers / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000378:metabolism; D017665:Hydroxyl Radical / Q000378:metabolism; D007700:Kinetics; D015227:Lipid Peroxidation / Q000187:drug effects; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012822:Silicon Dioxide / Q000737:chemistry / Q000633:toxicity*; D013113:Spin Labels; D013256:Steroids / Q000494:pharmacology*; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism
chemical_list: D000975:Antioxidants; D003497:Cyclic N-Oxides; D016166:Free Radical Scavengers; D013113:Spin Labels; D013256:Steroids; D017392:Thiobarbituric Acid Reactive Substances; C069980:U 75412E; D017665:Hydroxyl Radical; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D012822:Silicon Dioxide; D006861:Hydrogen Peroxide