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Oxidant-induced inhibition of myocardial calcium-independent phospholipase A2

J McHowat1, L M Swift, N Sarvazyan

  • 1Department of Pathology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA.

Cardiovascular Toxicology
|September 6, 2002
PubMed

Insights

Oxidative stress from tert-butyl hydroperoxide and hydrogen peroxide acutely inhibits myocardial phospholipase A2 activity. This impairs the heart muscle cell

Area of Science:

  • Biochemistry
  • Cardiology
  • Cell Biology

Background:

  • Oxidative stress is implicated in cardiovascular disease.
  • Phospholipase A2 (PLA2) enzymes play roles in cellular signaling and membrane remodeling.
  • Myocardial cells possess mechanisms to repair oxidative damage to lipids.

Purpose of the Study:

  • To investigate the effect of common oxidants on myocardial phospholipase A2 activity.
  • To determine if oxidant-induced PLA2 inhibition impacts cellular repair mechanisms.
  • To assess the role of PLA2 in oxidant-induced cardiotoxicity.

Main Methods:

  • Isolated adult rat cardiomyocytes were treated with tert-butyl hydroperoxide and hydrogen peroxide.
  • Phospholipase A2 activity was measured in cytosolic and membrane fractions using radiolabeled substrates.
  • Cell viability was assessed via lactate dehydrogenase release and morphology.
  • The effect of a PLA2 inhibitor (bromoenol lactone) on cardiotoxicity was evaluated.

Main Results:

  • Micromolar concentrations of tert-butyl hydroperoxide and hydrogen peroxide acutely inhibited calcium-independent myocardial phospholipase A2 activity by approximately 50%.
  • This inhibition occurred at concentrations that did not immediately affect cell viability.
  • Inhibition of PLA2 activity by oxidants compromised the myocyte's ability to manage lipid peroxidation.
  • Pretreatment with a PLA2 inhibitor exacerbated oxidant-induced cardiotoxicity.

Conclusions:

  • Oxidants acutely inhibit myocardial phospholipase A2 activity, a key enzyme in lipid repair.
  • Inhibition of PLA2 by oxidants may contribute to cardiotoxicity by impairing lipid peroxidation repair.
  • Targeting PLA2 activity could be a strategy in managing oxidative stress-related heart conditions.

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