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Reduction of sulfamethoxazole hydroxylamine (SMX-HA) by the mitochondrial amidoxime reducing component (mARC)

Gudrun Ott1, Birte Plitzko, Carmen Krischkowski

  • 1Department of Pharmaceutical and Medicinal Chemistry, Pharmaceutical Institute, Christian-Albrechts-University of Kiel , Gutenbergstrasse 76, D-24118 Kiel, Germany.

Chemical Research in Toxicology
|August 30, 2014
PubMed

Insights

The mARC enzyme system may reduce sulfamethoxazole hydroxylamine (SMX-HA), a step in sulfamethoxazole (SMX) drug toxicity. While mARC-1 and mARC-2 reduce SMX-HA, human variants did not show significant differences in activity.

Area of Science:

  • Biochemistry
  • Pharmacology
  • Toxicology

Background:

  • High-dose sulfamethoxazole (SMX)/trimethoprim (TMP) treatment is linked to frequent hypersensitivity reactions.
  • The precise mechanism underlying these adverse drug reactions remains incompletely understood.
  • Investigating the toxification pathway of SMX is crucial for understanding its adverse effects.

Purpose of the Study:

  • To investigate the potential role of the mARC-containing N-reductive enzyme system in the reduction of sulfamethoxazole hydroxylamine (SMX-HA).
  • To explore the involvement of mARC-1 and mARC-2 in the SMX toxification pathway.
  • To analyze the kinetic parameters of human mARC-1 and mARC-2 variants in relation to SMX-HA reduction.

Main Methods:

  • Western blot analyses of porcine tissue subcellular fractions using antibodies against mARC-1, mARC-2, cytochrome b5 type B, and NADH cytochrome b5 reductase.
  • Incubation studies with SMX-HA using porcine and human subcellular tissue fractions and heterologously expressed human N-reductive enzyme system components.
  • mARC-1 and mARC-2 knockdown in HEK-293 cells and kinetic analysis of expressed human protein variants.

Main Results:

  • Western blot results supported the hypothesis that the mARC-containing N-reductive enzyme system is involved in SMX-HA reduction.
  • Highest reduction rates of SMX-HA were observed in mitochondrial fractions of porcine tissue and outer membrane vesicles of human liver tissue.
  • Knockdown studies confirmed that mARC-1 and mARC-2 can reduce SMX-HA in cellular metabolism, with mARC-2 exhibiting higher catalytic efficiency than mARC-1.

Conclusions:

  • The mARC-containing N-reductive enzyme system plays a role in the reduction of SMX-HA.
  • While mARC-1 and mARC-2 are capable of reducing SMX-HA, investigated human variants did not show significant differences in N-reductive activity.
  • Further research is needed to fully elucidate the role of these enzymes and their variants in SMX-induced hypersensitivity reactions.

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