title: Direct evidence for in vivo nitroxide free radical production from a new antiarrhythmic drug by EPR spectroscopy.
abstract: The new Class I anti-arrhythmic agent 2,2,5,5-tetramethyl-3-pyrroline-1-carboxamide derivative, is currently being evaluated in clinical trials in patients with a high risk for cardiac arrhythmias. In this study we show that this antiarrhythmic drug can be chemically converted to the nitroxide free radical analog. Further, using an in vivo Electron Paramagnetic Resonance (EPR) spectroscopy model by detecting free radicals in the distal portion of the tail of an anesthetized mouse, we demonstrate that the drug is oxidized to the corresponding nitroxide. In vitro studies using Chinese hamster V79 cells suggest that the oxidation products of the drug, namely, the hydroxylamine and the nitroxide protect against oxidative damage induced by hydrogen peroxide (H2O2). Taken together, our results suggest that, in addition to the antiarrhythmic effects of the parent drug, sufficient levels of nitroxides may accumulate from the parent drug in vivo to provide antioxidant defense to cardiac tissue that may be subject to ischemia and oxidation-driven injury.
authors.affiliation: Radiation Biology Branch, National Cancer Institute, NIH, Bethesda, MD 20892, USA.
authors.forename: P
authors.initials: P
authors.lastname: Twomey
authors.forename: J
authors.initials: J
authors.lastname: Taira
authors.forename: W
authors.initials: W
authors.lastname: DeGraff
authors.forename: J B
authors.initials: JB
authors.lastname: Mitchell
authors.forename: A
authors.initials: A
authors.lastname: Russo
authors.forename: M C
authors.initials: MC
authors.lastname: Krishna
authors.forename: O H
authors.initials: OH
authors.lastname: Hankovszky
authors.forename: L
authors.initials: L
authors.lastname: Frank
authors.forename: K
authors.initials: K
authors.lastname: Hideg
mesh_terms: D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D000975:Antioxidants / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D001145:Arrhythmias, Cardiac / Q000188:drug therapy / Q000378:metabolism; D002460:Cell Line; D006224:Cricetinae; D004578:Electron Spin Resonance Spectroscopy; D005260:Female; D005609:Free Radicals / Q000378:metabolism; D006420:Hemeproteins / Q000378:metabolism; D006801:Humans; D051379:Mice; D008809:Mice, Inbred C3H; D015428:Myocardial Reperfusion Injury / Q000188:drug therapy / Q000378:metabolism; D009589:Nitrogen Oxides / Q000378:metabolism*; D010084:Oxidation-Reduction
chemical_list: D000889:Anti-Arrhythmia Agents; D000975:Antioxidants; D005609:Free Radicals; D006420:Hemeproteins; D009589:Nitrogen Oxides; C039900:nitroxyl