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Title: Aryl radical involvement in amiodarone-induced pulmonary toxicity: Investigation of protection by spin-trapping nitrones

Abstract

Amiodarone (AM), an antidysrrhythmic drug, can produce serious adverse effects, including potentially fatal AM-induced pulmonary toxicity (AIPT). AM-induced cytotoxicity and pulmonary fibrosis are well recognized, but poorly understood mechanistically. The hypothesis of aryl radical involvement in AM toxicity was tested in non-biological and biological systems. Photolysis of anaerobic aqueous solutions of AM, or N-desethylamiodarone (DEA) resulted in the formation of an aryl radical, as determined by spin-trapping and electron paramagnetic resonance (EPR) spectroscopy experiments. The non-iodinated AM analogue, didesiodoamiodarone (DDIA), did not form aryl radicals under identical conditions. The toxic susceptibility of human lung epithelioid HPL1A cells to AM, DEA, and DDIA showed time- and concentration-dependence. DEA had a more rapid and potent toxic effect (LC{sub 50} = 8 {mu}M) than AM (LC{sub 50} = 146 {mu}M), whereas DDIA cytotoxicity was intermediate (LC{sub 50} = 26 {mu}M) suggesting a minor contribution of the iodine atoms. Incubation of human lung epithelial cells with the spin-trapping nitrones {alpha}-phenyl-N-t-butylnitrone (PBN, 10 mM) or {alpha}-(4-pyridyl N-oxide)-N-t-butylnitrone (POBN, 5.0 mM) did not significantly protect against AM, DEA, or DDIA cytotoxicity. Intratracheal administration of AM to hamsters produced pulmonary fibrosis at day 21, which was not prevented by 4 days of treatment with 150 mg/kg/day PBNmore » or 164 mg/kg/day POBN. However, the body weight loss in AM-treated animals was counteracted by PBN. These results suggest that, although AM can generate an aryl radical photochemically, its in vivo formation may not be a major contributor to AM toxicity, and that spin-trapping reagents do not halt the onset of AM toxicity.« less

Authors:
 [1];  [1];  [2];  [1];  [3];  [1];  [1];  [4]
  1. Department of Pharmacology and Toxicology, Queen's University, Kingston, ON, K7L 3N6 (Canada)
  2. Department of Biochemistry, Queen's University, Kingston, ON, K7L 3N6 (Canada)
  3. Division of Molecular Carcinogenesis, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550 (Japan)
  4. Department of Pharmacology and Toxicology, Queen's University, Kingston, ON, K7L 3N6 (Canada). E-mail: masseyt@post.queensu.ca
Publication Date:
OSTI Identifier:
20976898
Resource Type:
Journal Article
Resource Relation:
Journal Name: Toxicology and Applied Pharmacology; Journal Volume: 220; Journal Issue: 1; Other Information: DOI: 10.1016/j.taap.2006.12.031; PII: S0041-008X(06)00497-2; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; AQUEOUS SOLUTIONS; ARYL RADICALS; BROMIDES; DRUGS; ELECTRON SPIN RESONANCE; FIBROSIS; HAMSTERS; IN VIVO; LUNGS; OXIDES; OXYGEN; PHOTOLYSIS; SAFETY; SPECTROSCOPY; SPIN; TETRAZOLIUM; THIAZOLES; TOXICITY; TRAPPING

Citation Formats

Nicolescu, Adrian C., Comeau, Jeannette L., Hill, Bruce C., Bedard, Leanne L., Takahashi, Takashi, Brien, James F., Racz, William J., and Massey, Thomas E. Aryl radical involvement in amiodarone-induced pulmonary toxicity: Investigation of protection by spin-trapping nitrones. United States: N. p., 2007. Web. doi:10.1016/j.taap.2006.12.031.
Nicolescu, Adrian C., Comeau, Jeannette L., Hill, Bruce C., Bedard, Leanne L., Takahashi, Takashi, Brien, James F., Racz, William J., & Massey, Thomas E. Aryl radical involvement in amiodarone-induced pulmonary toxicity: Investigation of protection by spin-trapping nitrones. United States. doi:10.1016/j.taap.2006.12.031.
Nicolescu, Adrian C., Comeau, Jeannette L., Hill, Bruce C., Bedard, Leanne L., Takahashi, Takashi, Brien, James F., Racz, William J., and Massey, Thomas E. Sun . "Aryl radical involvement in amiodarone-induced pulmonary toxicity: Investigation of protection by spin-trapping nitrones". United States. doi:10.1016/j.taap.2006.12.031.
@article{osti_20976898,
title = {Aryl radical involvement in amiodarone-induced pulmonary toxicity: Investigation of protection by spin-trapping nitrones},
author = {Nicolescu, Adrian C. and Comeau, Jeannette L. and Hill, Bruce C. and Bedard, Leanne L. and Takahashi, Takashi and Brien, James F. and Racz, William J. and Massey, Thomas E.},
abstractNote = {Amiodarone (AM), an antidysrrhythmic drug, can produce serious adverse effects, including potentially fatal AM-induced pulmonary toxicity (AIPT). AM-induced cytotoxicity and pulmonary fibrosis are well recognized, but poorly understood mechanistically. The hypothesis of aryl radical involvement in AM toxicity was tested in non-biological and biological systems. Photolysis of anaerobic aqueous solutions of AM, or N-desethylamiodarone (DEA) resulted in the formation of an aryl radical, as determined by spin-trapping and electron paramagnetic resonance (EPR) spectroscopy experiments. The non-iodinated AM analogue, didesiodoamiodarone (DDIA), did not form aryl radicals under identical conditions. The toxic susceptibility of human lung epithelioid HPL1A cells to AM, DEA, and DDIA showed time- and concentration-dependence. DEA had a more rapid and potent toxic effect (LC{sub 50} = 8 {mu}M) than AM (LC{sub 50} = 146 {mu}M), whereas DDIA cytotoxicity was intermediate (LC{sub 50} = 26 {mu}M) suggesting a minor contribution of the iodine atoms. Incubation of human lung epithelial cells with the spin-trapping nitrones {alpha}-phenyl-N-t-butylnitrone (PBN, 10 mM) or {alpha}-(4-pyridyl N-oxide)-N-t-butylnitrone (POBN, 5.0 mM) did not significantly protect against AM, DEA, or DDIA cytotoxicity. Intratracheal administration of AM to hamsters produced pulmonary fibrosis at day 21, which was not prevented by 4 days of treatment with 150 mg/kg/day PBN or 164 mg/kg/day POBN. However, the body weight loss in AM-treated animals was counteracted by PBN. These results suggest that, although AM can generate an aryl radical photochemically, its in vivo formation may not be a major contributor to AM toxicity, and that spin-trapping reagents do not halt the onset of AM toxicity.},
doi = {10.1016/j.taap.2006.12.031},
journal = {Toxicology and Applied Pharmacology},
number = 1,
volume = 220,
place = {United States},
year = {Sun Apr 01 00:00:00 EDT 2007},
month = {Sun Apr 01 00:00:00 EDT 2007}
}
  • We sought to assess the role of gallium-67 lung scintigrams in the evaluation of amiodarone pulmonary toxicity. Images and laboratory studies were evaluated in 54 patients who had chest radiographs and scintigraphic studies during amiodarone treatment of more than one month's duration among 561 patients receiving the medication for refractory arrhythmias. There were 22 patients with pulmonary symptoms and clinical evidence of amiodarone pulmonary toxicity (group 1); 19 patients had other causes for pulmonary symptoms (group 2); and 21 patients were without symptoms or other clinical evidence of pulmonary toxicity (group 3). There was no difference among groups in treatmentmore » duration or total amiodarone dose. Symptomatic presentation could not differentiate between group 1 and group 2 patients. However, radiographic findings of isolated pulmonary congestion or a normal radiograph in the presence of symptoms made amiodarone toxicity unlikely, while the appearance of new, dense radiographic infiltrates--often in a nodular distribution--were more frequent among group 1 patients (p less than 0.01). During symptomatic periods, 18 of 22 group 1 patients had abnormal gallium lung uptake, while four revealed more subtle serial changes but there was only one abnormal scintigram among symptomatic group 2 patients. Nonspecific radiographic abnormalities in patients with pulmonary symptoms on amiodarone therapy were rarely attributed to toxicity in the presence of a normal scintigram. One group 3 patient developed scintigraphic abnormalities early during amiodarone treatment, suggesting toxicity in the presence of a normal chest x-ray examination. Comparison of radiographic and scintigraphic studies performed during symptoms with those performed prior to symptom development best indicated the diagnosis, while comparison with later images assessed the efficacy of treatment.« less
  • Circulatory shock is accepted as a consequence of an acute oxygen radical overgeneration. Spin-trapping nitrones inactivate free radicals by forming relatively stable adducts. Three spin-trapping nitrones (N-tert-phenyl-butyl-nitrone; alpha-4-pyridyl-oxide-N-tert-butyl-nitrone; 5-5,dimethyl,1,pyrroline-N-oxide) were tested regarding their role in the pathophysiology and evolution of circulatory shock in rats. A prospective, randomized, controlled trial of spin-trapping nitrones in rats experiencing three different models of circulatory shock was designed. In the first group, endotoxic, traumatic, and mesenteric artery occlusion shock (all 100% lethal in control experiments) was prevented by the ip administration of N-tert-phenyl-butyl-nitrone (150 mg/kg); alpha-4-pyridyl-oxide-N-tert-butyl-nitrone (100 mg/kg); or 5-5,dimethyl,1,pyrroline-N-oxide (100 mg/kg). However, the evolutionmore » of shock was unaffected by the same compounds when all three nitrones had been previously inactivated by exposure to light and air. In the second group, microcirculatory derangements that were provoked by endotoxin and were observed in the mesocecum of rats were completely prevented by pretreatment with either peritoneal administration of each of the three nitrones or by their topical application to the microscopic field. While the rats survived after systemic treatment, those rats receiving topical nitrones died from endotoxic shock. In the third group, cell-membrane stiffness (a sign of peroxidative damage) was measured by spin-probes and electron-spin resonance in mitochondrial and microsomal membranes. Cell membranes obtained from shocked rats were more rigid than those membranes of controls. However, the membranes obtained from rats that were submitted to trauma or endotoxin after pretreatment with N-tert-phenyl-butyl-nitrone had normal stiffness.« less
  • Amiodarone (AM), a drug used in the treatment of cardiac dysrrhythmias, can produce severe pulmonary adverse effects, including fibrosis. Although the pathogenesis of AM-induced pulmonary toxicity (AIPT) is not clearly understood, several hypotheses have been advanced, including increased inflammatory mediator release, mitochondrial dysfunction, and free-radical formation. The hypothesis that AM induces formation of reactive oxygen species (ROS) was tested in an in vitro model relevant for AIPT. Human peripheral lung epithelial HPL1A cells, as surrogates for target cells in AIPT, were susceptible to the toxicity of AM and N-desethylamiodarone (DEA), a major AM metabolite. Longer incubations ({>=} 6 h) ofmore » HPL1A cells with 100 {mu}M AM significantly increased ROS formation. In contrast, shorter incubations (2 h) of HPL1A cells with AM resulted in mitochondrial dysfunction and cytoplasmic cytochrome c translocation. Preexposure of HPL1A cells to ubiquinone and {alpha}-tocopherol was more effective than that with Trolox C (registered) or 5,5-dimethylpyrolidine N-oxide (DMPO) at preventing AM cytotoxicity. These data suggest that mitochondrial dysfunction, rather than ROS overproduction, represents an early event in AM-induced toxicity in peripheral lung epithelial cells that may be relevant for triggering AIPT, and antioxidants that target mitochondria may potentially have beneficial effects in AIPT.« less
  • Brain is extremely susceptible to oxidative damage. Utilizing a series of novel approaches, the authors have demonstrated that oxidative damage occurs during an ischemia/reperfusion insult (IRI) to brain. Thus, they have demonstrated that an IRI to Mongolian gerbil brain results in: (1) an enhanced rate of salicylate hydroxylation, implicating an increased flux of hydroxyl free radicals; (2) an enhanced flux of free radicals as determined by spin-trapping; (3) an enhanced level of endogenous protein oxidation; (4) a decrease in glutamine synthetase (GS) activity, an enzyme very sensitive to oxidative damage; and (5) demonstration of protection from an IRI by administeringmore » the spin-trapping agent alpha-phenyl-tert-butyl nitrone (PBN). The novel observation that PBN offers protection from the lethality brought on by a brain IRI appears to be clearly linked to the ability of the administered spin-trap to inhibit oxidative damage as evidenced by the decreased amount of brain protein oxidation and the prevention of an IRI-mediated loss of GS activity in treated animals. Aged gerbils are more sensitive to the lethal action of a brain IRI than younger animals, but they are protected by PBN administration as are the younger animals. Older gerbils have a significantly higher level of oxidized protein in the brain. Older gerbils have decreased activities of GS and neutral protease, the enzyme that removes oxidized protein, than younger animals. Chronic twice daily administration of PBN (32 mg/kg) for 14 days to older animals significantly lowered brain oxidized protein levels and raised GS and neutral protease activity to those observed in younger animals. Cessation of PBN administration resulted in a time-dependent restoration of protein oxidation levels and enzyme activities back to those observed prior to spin-trap administration.« less
  • The formation of radicals in ..gamma..-irradiated C/sub 5/-C/sub 9/ alkanes, cyclohexane, and isooctane were studied by means of spin traps. The following spin traps were used: 2,4,6-tri-tert-butylnitrosobenzene (BNB), nitrosodurene (ND), C-phenyl-N-tert-butylnitrone (phi BN), and tert-nitrosobutane (TNB). The syntheses of the spin traps BNB, ND, phi BN, and TNB, were conducted by known methods. The solutions of the spin traps in the alkanes were kept under a vacuum of 5 x 10/sup -5/ torr and were irradiated at 5/sup 0/C or -40/sup 0/C. The radical adducts of these compounds were identified by EPR spectra. 3 figures.