title: Characterization of Peroxidases Expressed in Human Antigen Presenting Cells and Analysis of the Covalent Binding of Nitroso Sulfamethoxazole to Myeloperoxidase.
abstract: Drug hypersensitivity remains a major concern, as it causes high morbidity and mortality. Understanding the mechanistic basis of drug hypersensitivity is complicated by the multiple risk factors implicated. This study utilized sulfamethoxazole (SMX) as a model drug to (1) relate SMX metabolism in antigen presenting cells (APCs) to the activation of T-cells and (2) characterize covalent adducts of SMX and myeloperoxidase, which might represent antigenic determinants for T-cells. The SMX metabolite nitroso-SMX (SMX-NO) was found to bind irreversibly to APCs. Time- and concentration-dependent drug-protein adducts were also detected when APCs were cultured with SMX. Metabolic activation of SMX was significantly reduced by the oxygenase/peroxidase inhibitor methimazole. Similarly, SMX-NO-specific T-cells were activated by APCs pulsed with SMX, and the response was inhibited by pretreatment with methimazole or glutaraldehyde, which blocks antigen processing. Western blotting, real-time polymerase chain reaction (RT-PCR), and mass spectrometry analyses suggested the presence of low concentrations of myeloperoxidase in APCs. RT-PCR revealed mRNA expression for flavin-containing monooxygenases (FMO1-5), thyroid peroxidase, and lactoperoxidase, but the corresponding proteins were not detected. Mass spectrometric characterization of SMX-NO-modified myeloperoxidase revealed the formation of N-hydroxysulfinamide adducts on Cys309 and Cys398. These data show that SMX's metabolism in APCs generates antigenic determinants for T-cells. Peptides derived from SMX-NO-modified myeloperoxidase may represent one form of functional antigen.
authors.affiliation: MRC Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, University of Liverpool , Ashton Street, Liverpool L69 3GE, United Kingdom.
authors.forename: Monday O
authors.initials: MO
authors.lastname: Ogese
authors.affiliation: MRC Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, University of Liverpool , Ashton Street, Liverpool L69 3GE, United Kingdom.
authors.forename: Rosalind E
authors.initials: RE
authors.lastname: Jenkins
authors.affiliation: MRC Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, University of Liverpool , Ashton Street, Liverpool L69 3GE, United Kingdom.
authors.forename: James L
authors.initials: JL
authors.lastname: Maggs
authors.affiliation: MRC Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, University of Liverpool , Ashton Street, Liverpool L69 3GE, United Kingdom.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Meng
authors.affiliation: Regional Adult Cystic Fibrosis Unit, St James's University Hospital , Leeds LS9 7TF, United Kingdom.
authors.forename: Paul
authors.initials: P
authors.lastname: Whitaker
authors.affiliation: Regional Adult Cystic Fibrosis Unit, St James's University Hospital , Leeds LS9 7TF, United Kingdom.
authors.forename: Daniel
authors.initials: D
authors.lastname: Peckham
authors.affiliation: MRC Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, University of Liverpool , Ashton Street, Liverpool L69 3GE, United Kingdom.
authors.forename: Lee
authors.initials: L
authors.lastname: Faulkner
authors.affiliation: MRC Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, University of Liverpool , Ashton Street, Liverpool L69 3GE, United Kingdom.
authors.forename: B Kevin
authors.initials: BK
authors.lastname: Park
authors.affiliation: MRC Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, University of Liverpool , Ashton Street, Liverpool L69 3GE, United Kingdom.
authors.forename: Dean J
authors.initials: DJ
authors.lastname: Naisbitt
mesh_terms: D000938:Antigen-Presenting Cells / Q000378:metabolism*; D001402:B-Lymphocytes / Q000378:metabolism; D018922:HL-60 Cells; D006801:Humans; D010105:Oxygenases / Q000378:metabolism; D010544:Peroxidases / Q000378:metabolism*; D011485:Protein Binding; D013420:Sulfamethoxazole / Q000378:metabolism*; D013601:T-Lymphocytes / Q000378:metabolism
chemical_list: D010544:Peroxidases; D010105:Oxygenases; D013420:Sulfamethoxazole