Bactericidal activity of peroxynitrite.
Peroxynitrite is a strong oxidant formed by macrophages and potentially by other cells that produce nitric oxide and superoxide. Peroxynitrite was highly bactericidal, killing Escherichia coli in direct proportion to its concentration with an LD50 of 250 microM at 37 degrees C in potassium phosphate, pH 7.4. The apparent bactericidal activity of a given concentration peroxynitrite at acidic pH was less than that at neutral and alkaline pH. However, after taking the rapid pH-dependent decomposition of peroxynitrite into account, the rate of the killing was not significantly different at pH 5 compared to pH 7.4. Metal chelators did not decrease peroxynitrite-mediated killing, indicating that exogenous transition metals were not required for toxicity. The hydroxyl radical scavengers mannitol, ethanol, and benzoate did not significantly affect toxicity while dimethyl sulfoxide enhanced peroxynitrite-mediated killing. Dimethyl sulfoxide is a more efficient hydroxyl radical scavenger than the other three scavengers and increased the formation of nitrogen dioxide from peroxynitrite. In the presence of 100 mM dimethyl sulfoxide, 60.0 +/- 0.3 microM nitrogen dioxide was formed from 250 microM peroxynitrite as compared to 2.0 +/- 0.1 microM in buffer alone. Thus, formation of nitrogen dioxide may have enhanced the toxicity of peroxynitrite decomposing in the presence of dimethyl sulfoxide.
Zhu
L
L
Department of Anesthesiology, University of Alabama, Birmingham 35233.
Gunn
C
C
Beckman
J S
JS
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001565:Benzoates / Q000494:pharmacology; D019817:Benzoic Acid; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development; D000431:Ethanol / Q000494:pharmacology; D016166:Free Radical Scavengers; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008163:Luminescent Measurements; D008353:Mannitol / Q000494:pharmacology; D009566:Nitrates / Q000494:pharmacology*; D009585:Nitrogen Dioxide / Q000032:analysis
D000900:Anti-Bacterial Agents; D001565:Benzoates; D016166:Free Radical Scavengers; D009566:Nitrates; C039642:peroxynitric acid; D000431:Ethanol; D008353:Mannitol; D019817:Benzoic Acid; D009585:Nitrogen Dioxide; D004121:Dimethyl Sulfoxide