title: Cytotoxicity of sulfonamide reactive metabolites: apoptosis and selective toxicity of CD8(+) cells by the hydroxylamine of sulfamethoxazole.
abstract: Treatment with sulfonamide antibiotics in HIV-infected patients is associated with a high incidence (> 40%) of adverse drug events, including severe hypersensitivity reactions. Sulfonamide reactive metabolites have been implicated in the pathogenesis of these adverse reactions. Sulfamethoxazole hydroxylamine (SMX-HA) induces lymphocyte toxicity and suppression of proliferation in vitro; the mechanism(s) of these immunomodulatory effects remain unknown. We investigated the cytotoxicity of SMX-HA via apoptosis on human peripheral blood mononuclear cells and purified cell subpopulations in vitro. CD19(+), CD4(+), and CD8(+) cells were isolated from human peripheral blood by positive selection of cell surface molecules by magnetic bead separation. SMX-HA induced significant CD8(+) cell death (67 +/- 7%) at 100 microM SMX-HA, with only minimal CD4(+) cell death (8 +/- 4%). No significant subpopulation toxicity was shown when incubated with parent drug (SMX). Flow cytometry measuring phosphatidylserine externalization 24 h after treatment with 100 microM and 400 microM SMX-HA revealed 14.1 +/- 0.7% and 25. 6 +/- 4.2% annexin-positive cells, respectively, compared to 3.7 +/- 1.2% in control PBMCs treated with 400 microM SMX. Internucleosomal DNA fragmentation was observed in quiescent and stimulated PBMCs 48 h after incubation with SMX-HA. Our data show that CD8(+) cells are highly susceptible to the toxic effects of SMX-HA through enhanced cell death by apoptosis.
authors.affiliation: Department of Pharmacology and Toxicology, University of Western Ontario, London, Ontario, Canada.
authors.forename: D A
authors.initials: DA
authors.lastname: Hess
authors.forename: M E
authors.initials: ME
authors.lastname: Sisson
authors.forename: H
authors.initials: H
authors.lastname: Suria
authors.forename: J
authors.initials: J
authors.lastname: Wijsman
authors.forename: R
authors.initials: R
authors.lastname: Puvanesasingham
authors.forename: J
authors.initials: J
authors.lastname: Madrenas
authors.forename: M J
authors.initials: MJ
authors.lastname: Rieder
mesh_terms: D017209:Apoptosis; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000187:drug effects*; D053938:DNA Fragmentation; D004305:Dose-Response Relationship, Drug; D006801:Humans; D018189:Immunomagnetic Separation; D010718:Phosphatidylserines / Q000378:metabolism; D013420:Sulfamethoxazole / Q000031:analogs & derivatives* / Q000633:toxicity; D013449:Sulfonamides / Q000009:adverse effects*; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000187:drug effects*
chemical_list: D010718:Phosphatidylserines; D013449:Sulfonamides; C059873:sulfamethoxazole hydroxylamine; D013420:Sulfamethoxazole