Sulfamethoxazole (SMX), sulfadiazine, dapsone, pentamidine, and procainamide are clinically important drugs, the use of which is limited by the occurrence of hypersensitivity reactions in some patients. These reactions are thought to be related to the presence of a toxic hydroxylamine metabolite and its spontaneous byproduct, the nitroso metabolite. Unlike the parent compounds, these metabolites are both cytotoxic and immunogenic. Hypersensitivity reactions to SMX and related drugs occur in a high percentage (25-60 percent) of patients with AIDS. The reason for this high incidence is unclear, but data from in vitro cytotoxicity assays in peripheral blood mononuclear cells (PBMC's) suggest that both HIV-positive and HIV-negative patients with such hypersensitivity have a defect in hydroxylamine or nitroso detoxification. We hypothesize that detoxification of hydroxylamine and nitroso metabolites by reduction is an important determinant of hypersensitivity to sulfonamide and related drugs. We further hypothesize that NADH cytochrome b5 reductase, which is involved in hydroxylamine reduction in some species, is important for hydroxylamine detoxification in humans. In addition, we have novel data to suggest that flavins (FAD and FMN); in the presence of glutathione, are capable of non- enzymatic reduction of hydroxylamines. We therefore propose that defects in either NADH- or flavin-dependent reduction of hydroxylamines and nitroso metabolites are associated with the outcome of sulfonamide hypersensitivity. To address these hypotheses, we will examine the role of NADH cytochrome b5 reductase (b5R) in hydroxylamine and nitroso reduction in both liver and PBMC's, using expressed human recombinant b5R and antibodies to human b5R. We will evaluate the role of flavins in hydroxylamine and nitroso reduction using in vitro stoichiometric assays in a cell-free system, and correlation of flavin and glutathione content with activity in hepatic microsomes and PBMC's. Finally, we will correlate hydroxylamine and nitroso reduction, b5R expression, and flavin content with the outcome of SMX hypersensitivity in patients with HIV infection. The ultimate goal of these studies is to better understand the pathogenesis of toxicity to sulfonamides and a related group of clinically important drugs which generate hydroxylamine and nitroso metabolites. The results of these experiments, which will identify the pathways involved in the detoxification of these metabolites, will suggest better strategies for the prevention of hypersensitivity and other hydroxylamine-related toxicity.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM061753-03
Application #
6520308
Study Section
Pharmacology A Study Section (PHRA)
Program Officer
Okita, Richard T
Project Start
2000-07-01
Project End
2005-06-30
Budget Start
2002-07-01
Budget End
2003-06-30
Support Year
3
Fiscal Year
2002
Total Cost
$216,000
Indirect Cost
Name
University of Wisconsin Madison
Department
Other Basic Sciences
Type
Schools of Veterinary Medicine
DUNS #
161202122
City
Madison
State
WI
Country
United States
Zip Code
53715
Blanke, Kristina L; Sacco, James C; Millikan, Robert C et al. (2014) Polymorphisms in the carcinogen detoxification genes CYB5A and CYB5R3 and breast cancer risk in African American women. Cancer Causes Control 25:1513-21
Sacco, James C; Abouraya, Mahmoud; Motsinger-Reif, Alison et al. (2012) Evaluation of polymorphisms in the sulfonamide detoxification genes NAT2, CYB5A, and CYB5R3 in patients with sulfonamide hypersensitivity. Pharmacogenet Genomics 22:733-40
Abouraya, Mahmoud; Sacco, James C; Hayes, Kristie et al. (2012) Dapsone-associated methemoglobinemia in a patient with slow NAT2*5B haplotype and impaired cytochrome b5 reductase activity. J Clin Pharmacol 52:272-8
Funk-Keenan, J; Sacco, J; Wong, Y Y Amos et al. (2012) Evaluation of polymorphisms in the sulfonamide detoxification genes CYB5A and CYB5R3 in dogs with sulfonamide hypersensitivity. J Vet Intern Med 26:1126-33
Rhoads, Keelia; Sacco, James C; Drescher, Nicholas et al. (2011) Individual variability in the detoxification of carcinogenic arylhydroxylamines in human breast. Toxicol Sci 121:245-56
Abouraya, Mahmoud; Sacco, James C; Kahl, Brad S et al. (2011) Evaluation of sulfonamide detoxification pathways in haematologic malignancy patients prior to intermittent trimethoprim-sulfamethoxazole prophylaxis. Br J Clin Pharmacol 71:566-74
Bhusari, Sachin; Abouraya, Mahmoud; Padilla, Marcia L et al. (2010) Combined ascorbate and glutathione deficiency leads to decreased cytochrome b5 expression and impaired reduction of sulfamethoxazole hydroxylamine. Arch Toxicol 84:597-607
Sacco, James C; Trepanier, Lauren A (2010) Cytochrome b5 and NADH cytochrome b5 reductase: genotype-phenotype correlations for hydroxylamine reduction. Pharmacogenet Genomics 20:26-37
Gan, Lu; von Moltke, Lisa L; Trepanier, Lauren A et al. (2009) Role of NADPH-cytochrome P450 reductase and cytochrome-b5/NADH-b5 reductase in variability of CYP3A activity in human liver microsomes. Drug Metab Dispos 37:90-6
Lavergne, S N; Drescher, N J; Trepanier, L A (2008) Anti-myeloperoxidase and anti-cathepsin G antibodies in sulphonamide hypersensitivity. Clin Exp Allergy 38:199-207

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