Roles of endogenous ascorbate and glutathione in the cellular reduction and cytotoxicity of sulfamethoxazole-nitroso.
Sulfamethoxazole (SMX) is an effective drug for the management of opportunistic infections, but its use is limited by hypersensitivity reactions, particularly in HIV-infected patients. The oxidative metabolite SMX-nitroso (SMX-NO), is thought to be a proximate mediator of SMX hypersensitivity, and can be reduced in vitro by ascorbate or glutathione. Leukocytes from patients with SMX hypersensitivity show enhanced cytotoxicity from SMX metabolites in vitro; this finding has been attributed to a possible "detoxification defect" in some individuals. The purpose of this study was to determine whether variability in endogenous ascorbate or glutathione could be associated with individual differences in SMX-NO cytotoxicity. Thirty HIV-positive patients and 23 healthy control subjects were studied. Both antioxidants were significantly correlated with the reduction of SMX-NO to its hydroxylamine, SMX-HA, by mononuclear leukocytes, and both were linearly depleted during reduction. Controlled ascorbate supplementation in three healthy subjects increased leukocyte ascorbate with no change in glutathione, and significantly enhanced SMX-NO reduction. Ascorbate supplementation also decreased SMX-NO cytotoxicity compared to pre-supplementation values. Rapid reduction of SMX-NO to SMX-HA was associated with enhanced direct cytotoxicity from SMX-NO. When forward oxidation of SMX-HA back to SMX-NO was driven by the superoxide dismutase mimetic, Tempol, SMX-NO cytotoxicity was increased, without enhancement of adduct formation. This suggests that SMX-NO cytotoxicity may be mediated, at least in part, by redox cycling between SMX-HA and SMX-NO. Overall, these data indicate that endogenous ascorbate and glutathione are important for the intracellular reduction of SMX-NO, a proposed mediator of SMX hypersensitivity, and that redox cycling of SMX-HA to SMX-NO may contribute to the cytotoxicity of these metabolites in vitro.
Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI 53706-1102, USA.
Sidonie N
SN
Lavergne
Joseph R
JR
Kurian
Sunil U
SU
Bajad
Jennifer E
JE
Maki
Andrea R
AR
Yoder
Margaret V
MV
Guzinski
Frank M
FM
Graziano
Lauren A
LA
Trepanier
D000328:Adult; D000368:Aged; D000975:Antioxidants / Q000494:pharmacology; D001205:Ascorbic Acid / Q000008:administration & dosage / Q000032:analysis / Q000378:metabolism*; D002469:Cell Separation; D003497:Cyclic N-Oxides / Q000494:pharmacology; D004342:Drug Hypersensitivity / Q000209:etiology; D005260:Female; D005978:Glutathione / Q000032:analysis / Q000378:metabolism*; D015658:HIV Infections / Q000097:blood / Q000378:metabolism*; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D010084:Oxidation-Reduction; D013113:Spin Labels; D013420:Sulfamethoxazole / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity
D000975:Antioxidants; D003497:Cyclic N-Oxides; D013113:Spin Labels; C059873:sulfamethoxazole hydroxylamine; C072956:4-nitrososulfamethoxazole; D005978:Glutathione; D013420:Sulfamethoxazole; D001205:Ascorbic Acid; C001803:tempol