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Inhibition of glutathione reductase by isoproterenol oxidation products

F Remião1, H Carmo, F D Carvalho

  • 1ICETA/CEQUP, Toxicology Department, Faculty of Pharmacy, Porto, Portugal. remiao@mail.ff.up.pt

Journal of Enzyme Inhibition
|June 13, 2000
PubMed

Insights

Oxidative stress from catecholamines can harm the heart. Isoproterenol oxidation products (IOP) were found to competitively inhibit glutathione reductase (GR) activity in vitro.

Area of Science:

  • Biochemistry
  • Cardiovascular Toxicology

Background:

  • Catecholamines induce oxidative stress, leading to cellular damage, particularly in the heart.
  • This oxidative stress involves the formation of reactive intermediates like o-quinones and aminochromes.
  • Aminochromes can cause significant cellular damage through protein modification and enzyme inhibition.

Purpose of the Study:

  • To investigate the in vitro effects of isoproterenol oxidation products (IOP) on glutathione reductase (GR) activity.
  • To determine the mechanism and kinetics of IOP-induced GR inhibition.

Main Methods:

  • Isoproterenol (ISO) was autoxidized at 37°C, pH 7.0 for 4 hours.
  • UV spectrophotometry was used to monitor the autoxidation process.
  • The inhibitory effect of IOP on GR activity was assessed in the presence of GSSG and NADPH, with varying concentrations of protective agents.

Main Results:

  • Isoproterenol oxidation products (IOP) were found to inhibit glutathione reductase (GR) activity in a competitive manner.
  • The inhibitory effect of IOP on GR increased with the duration of isoproterenol autoxidation.
  • Reduced glutathione (GSH), L-cysteine, and ascorbic acid partially protected GR from IOP-induced inhibition.

Conclusions:

  • Oxidative stress from catecholamines, exemplified by isoproterenol, can significantly impair crucial enzyme function like glutathione reductase.
  • The findings highlight a potential mechanism for catecholamine-induced cellular dysfunction and provide insights into protective strategies.

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