Characterization of Peroxidases Expressed in Human AntigenPresenting Cells and Analysis of the Covalent Binding of NitrosoSulfamethoxazole to Myeloperoxidase

Ogese, Monday O ORCID: 0000-0002-1873-4032, Jenkins,, Rosalind E, Maggs, James L, Meng, Xiaoli ORCID: 0000-0002-7774-2075, Whitaker, Paul, Peckham, Daniel, Faulkner, Lee, Park, B Kevin ORCID: 0000-0001-8384-824X and Naisbitt, Dean J (2015) Characterization of Peroxidases Expressed in Human AntigenPresenting Cells and Analysis of the Covalent Binding of NitrosoSulfamethoxazole to Myeloperoxidase Chemical Research in Toxicology, 28 (1). pp. 144-154. ISSN 0893-228X, 1520-5010

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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.

Item Type:	Article
Uncontrolled Keywords:	B-Lymphocytes, Antigen-Presenting Cells, T-Lymphocytes, HL-60 Cells, Humans, Sulfamethoxazole, Oxygenases, Peroxidases, Protein Binding
Subjects:	?? QD ?? ?? QP ??
Depositing User:	Symplectic Admin
Date Deposited:	16 Dec 2015 11:57
Last Modified:	01 Mar 2026 00:40
DOI:	10.1021/tx500458k
Related Websites:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/2015581
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