Reduction of sulfamethoxazole and dapsone hydroxylamines by a microsomal enzyme system purified from pig liver and pig and human liver microsomes

Clement, Bernd; Behrens, Detlef; Amschler, Juliane; Matschke, Katrin; Wolf, Stephanie; Havemeyer, Antje

doi:10.1016/j.lfs.2004.12.028

Cited by 13 publications

(16 citation statements)

References 40 publications

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“…Although the acetylated form is inactive, it can be transformed back to the parent form in WWTPs [55]. A previous study showed that the hydroxylamine sulfamethoxazole metabolite can be reduced back to the parent form, sulfamethoxazole, by human and pig liver microsomes using the enzyme system of cytochrome b 5 , nicotinamide adenine dinucleotide-cytochrome b 5 reductase, and CYP2D [56]. Because biological wastewater treatment systems consist of myriad microbial enzymes, it is not unlikely for inactive sulfonamide conjugates such as acetylsulfamethoxazole to be converted back to the bioactive parent drug.…”

Section: Indirect Contribution Of Conjugated Metabolites Needs To Be mentioning

confidence: 99%

Pharmaceutical metabolites in the environment: Analytical challenges and ecological risks

Celiz

Tso

Aga

2009

Enviro Toxic and Chemistry

291

149

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Abstract-The occurrence of human and veterinary pharmaceuticals in the environment has been a subject of concern for the past decade because many of these emerging contaminants have been shown to persist in soil and water. Although recent studies indicate that pharmaceutical contaminants can pose long-term ecological risks, many of the investigations regarding risk assessment have only considered the ecotoxicity of the parent drug, with very little attention given to the potential contributions that metabolites may have. The scarcity of available environmental data on the human metabolites excreted into the environment or the microbial metabolites formed during environmental biodegradation of pharmaceutical residues can be attributed to the difficulty in analyzing trace amounts of previously unknown compounds in complex sample matrices. However, with the advent of highly sensitive and powerful analytical instrumentations that have become available commercially, it is likely that an increased number of pharmaceutical metabolites will be identified and included in environmental risk assessment. The present study will present a critical review of available literature on pharmaceutical metabolites, primarily focusing on their analysis and toxicological significance. It is also intended to provide an overview on the recent advances in analytical tools and strategies to facilitate metabolite identification in environmental samples. This review aims to provide insight on what future directions might be taken to help scientists in this challenging task of enhancing the available data on the fate, behavior, and ecotoxicity of pharmaceutical metabolites in the environment.

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Section: Indirect Contribution Of Conjugated Metabolites Needs To Be mentioning

confidence: 99%

Pharmaceutical metabolites in the environment: Analytical challenges and ecological risks

Celiz

Tso

Aga

2009

Enviro Toxic and Chemistry

291

149

View full text Add to dashboard Cite

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“…19,32 Ten years ago, we already demonstrated that the reduction of SMX-HA is catalyzed by porcine and human subcellular liver fractions. 33 After discovering the mARC-containing enzyme system in our laboratory, which is responsible for the reduction of Nhydroxylated substrates, and based on the finding that it consists of the components mARC, cytochrome b 5 type B, and NADH cytochrome b 5 reductase, we aimed to add a more detailed investigation of the reduction of SMX-HA with particular focus on a possible contribution of the mARCcontaining enzyme system. 1,34,35 Moreover, the influence of protein variants encoded by nonsynonymous SNPs on this reduction was likewise investigated in constitutive studies.…”

Section: ■ Introductionmentioning

confidence: 99%

Reduction of Sulfamethoxazole Hydroxylamine (SMX-HA) by the Mitochondrial Amidoxime Reducing Component (mARC)

Ott

Plitzko

Krischkowski

et al. 2014

Chem. Res. Toxicol.

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Under high dose treatment with sulfamethoxazole (SMX)/trimethoprim (TMP), hypersensitivity reactions occur with a high incidence. The mechanism of this adverse drug reaction is not fully understood. Several steps in the toxification pathway of SMX were investigated. The aim of our study was to investigate the reduction of sulfamethoxazole hydroxylamine (SMX-HA) in this toxification pathway, which can possibly be catalyzed by the mARC-containing N-reductive enzyme system. Western blot analyses of subcellular fractions of porcine tissue were performed with antibodies against mARC-1, mARC-2, cytochrome b5 type B, and NADH cytochrome b5 reductase. Incubations of porcine and human subcellular tissue fractions and of the heterologously expressed human components of the N-reductive enzyme system were carried out with SMX-HA. mARC-1 and mARC-2 knockdown was performed in HEK-293 cells. Kinetic parameters of the heterologously expressed human protein variants V96L, A165T, M187 K, C246S, D247H, and M268I of mARC-1 and G244S and C245W of mARC-2 and N-reductive activity of 2SF, D14G, K16E, and T22A of cytochrome b5 type B were analyzed. Western blot analyses were consistent with the hypothesis that the mARC-containing N-reductive enzyme system might be involved in the reduction of SMX-HA. In agreement with these results, highest reduction rates were found in mitochondrial subcellular fractions of porcine tissue and in the outer membrane vesicle (OMV) of human liver tissue. Knockdown studies in HEK-293 cells demonstrated that mARC-1 and mARC-2 were capable of reducing SMX-HA in cell metabolism. Investigations with the heterologously expressed human mARC-2 protein showed a higher catalytic efficiency toward SMX-HA than mARC-1, but none of the investigated human protein variants showed statistically significant differences of its N-reductive activity and was therefore likely to participate in the pathogenesis of hypersensitivity reaction under treatment with SMX.

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“…(20,34,35) This third protein has been reported to share homology with P450 2D, (20) although the protein fractions used in reconstituted activity assays have not been purified to homogeneity. (34) In addition, specific activities with this reconstituted system were more than 400-fold lower than those observed by our group for the same arylhydroxylamines, using only b5R and cyt b5. 14Finally, a third group, investigating amidoxime reduction, has reported a role for stearoyl CoA desaturase in amidoxime and hydroxylamine reduction in rodent adipose.…”

Section: Discussionmentioning

confidence: 99%

Reductive Detoxification of Arylhydroxylamine Carcinogens by Human NADH Cytochrome b₅ Reductase and Cytochrome b₅

Kurian

Chin

Longlais

et al. 2006

Chem. Res. Toxicol.

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Heterocyclic and aromatic amine carcinogens are thought to lead to tumor initiation via the formation of DNA adducts, and bioactivation to arylhydroxylamine metabolites is necessary for reactivity with DNA. Carcinogenic arylhydroxylamine metabolites are cleared by a microsomal, NADH-dependent, oxygen-insensitive reduction pathway in humans, which may be a source of interindividual variability in response to aromatic amine carcinogens. The purpose of this study was to characterize the identity of this reduction pathway in human liver. On the basis of our findings with structurally similar arylhydroxylamine metabolites of therapeutic drugs, we hypothesized that the reductive detoxification of arylhydroxylamine carcinogens was catalyzed by NADH cytochrome b5 reductase (b5R) and cytochrome b5 (cyt b5). We found that reduction of the carcinogenic hydroxylamines of the aromatic amine 4-aminobiphenyl (4-ABP; found in cigarette smoke) and the heterocyclic amine 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP; found in grilled meats) was indeed catalyzed by a purified system containing only human b5R and cyt b5. Specific activities were 56-346-fold higher in the purified system as compared to human liver microsomes (HLM), with similar Michaelis-Menten constants (K(m) values) in both systems. The stoichiometry for b5R and cyt b5 that yielded the highest activity in the purified system was also similar to that found in native HLM ( approximately 1:8 to 1:10). Polyclonal antisera to either b5R or cyt b5 significantly inhibited N-hydroxy-4-aminobiphenyl (NHOH-4-ABP) reduction by 95 and 89%, respectively, and immunoreactive cyt b5 protein content in individual HLM was significantly correlated with individual reduction of both NHOH-4-ABP and N-hydroxy-PhIP (NHOH-PhIP). Finally, titration of HLM into the purified b5R/cyt b5 system did not enhance the efficiency of reduction activity. We conclude that b5R and cyt b5 are together solely capable of the reduction of arylhydroxylamine carcinogens, and we further hypothesize that this pathway may be a source of individual variability with respect to cancer susceptibility following 4-ABP or PhIP exposure.

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Reduction of sulfamethoxazole and dapsone hydroxylamines by a microsomal enzyme system purified from pig liver and pig and human liver microsomes

Cited by 13 publications

References 40 publications

Pharmaceutical metabolites in the environment: Analytical challenges and ecological risks

Pharmaceutical metabolites in the environment: Analytical challenges and ecological risks

Reduction of Sulfamethoxazole Hydroxylamine (SMX-HA) by the Mitochondrial Amidoxime Reducing Component (mARC)

Reductive Detoxification of Arylhydroxylamine Carcinogens by Human NADH Cytochrome b₅ Reductase and Cytochrome b₅

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Reduction of sulfamethoxazole and dapsone hydroxylamines by a microsomal enzyme system purified from pig liver and pig and human liver microsomes

Cited by 13 publications

References 40 publications

Pharmaceutical metabolites in the environment: Analytical challenges and ecological risks

Pharmaceutical metabolites in the environment: Analytical challenges and ecological risks

Reduction of Sulfamethoxazole Hydroxylamine (SMX-HA) by the Mitochondrial Amidoxime Reducing Component (mARC)

Reductive Detoxification of Arylhydroxylamine Carcinogens by Human NADH Cytochrome b5 Reductase and Cytochrome b5

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Product

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About

Reductive Detoxification of Arylhydroxylamine Carcinogens by Human NADH Cytochrome b₅ Reductase and Cytochrome b₅