Endothelial cell oxidant generation during K(+)-induced membrane depolarization

Area of Science:

• Cellular Physiology
• Oxidative Stress Research
• Endothelial Cell Biology

Background:

• Endothelial cells play a crucial role in vascular health.
• Oxidative stress is implicated in various cardiovascular diseases.
• The link between membrane potential and oxidant production in endothelial cells requires further elucidation.

Purpose of the Study:

• To investigate the hypothesis that membrane depolarization initiates oxidant generation in endothelial cells.
• To explore the role of potassium (K+) channels in this depolarization-induced oxidant production.

Main Methods:

• Bovine pulmonary arterial endothelial cells (BPAEC) were cultured and subjected to membrane depolarization using varying external K+ concentrations, glyburide, tetraethylammonium (TEA), gramicidin, and nigericin.
• Membrane potential changes were measured using bisoxonol fluorescence.
• Oxidant generation was quantified by measuring o-phenylenediamine dihydrochloride (o-PD) oxidation in the presence of horseradish peroxidase (HRP).

Main Results:

• High K+ concentrations and glyburide induced significant membrane depolarization in BPAEC.
• Depolarization with high K+, nigericin, and gramicidin led to a time-dependent increase in oxidant generation (o-PD oxidation).
• Catalase and Cu/Zn-superoxide dismutase (SOD) partially or fully inhibited the oxidant production, indicating the involvement of H2O2 and superoxide.
• Blockade of K+ channels with glyburide and TEA significantly increased oxidant generation.

Conclusions:

• Membrane depolarization in endothelial cells directly initiates the formation of hydrogen peroxide (H2O2) and potentially other oxidants.
• Potassium (K+) channels are involved in regulating depolarization-induced oxidant generation in these cells.
• These findings suggest a novel mechanism linking membrane potential to oxidative stress in the endothelium.