Acidic pH amplifies iron-mediated lipid peroxidation in cells

Area of Science:

• Biochemistry
• Cell Biology
• Oxidative Stress

Background:

• Extracellular pH influences cellular processes, including iron solubility and reactivity.
• Iron-mediated lipid peroxidation is a key mechanism in oxidative damage.
• Fenton-type reactions involving ferrous iron and hydroperoxides initiate free radical chain reactions.

Purpose of the Study:

• To investigate the mechanism by which extracellular pH affects lipid peroxidation.
• To determine the role of iron solubility and reactivity in pH-dependent lipid peroxidation.
• To assess the impact of acidic pH on iron-mediated free radical formation and cell membrane integrity.

Main Methods:

• Utilized Photofrin, a photosensitizer, to induce lipid hydroperoxides in leukemia cell lines (HL-60, K-562, L1210).
• Employed Electron Paramagnetic Resonance (EPR) spin trapping with POBN to detect free radical formation.
• Measured membrane permeability using trypan blue dye exclusion in K-562 cells.

Main Results:

• Free radical formation was detected only in the presence of Photofrin, light, and ferrous iron.
• Radical formation increased with iron concentration and was significantly higher at lower extracellular pH (7.5-5.5).
• Acidic pH (lower pH) correlated with increased membrane permeability in K-562 cells.

Conclusions:

• Decreasing extracellular pH enhances iron-mediated lipid peroxidation processes.
• Acidic conditions facilitate iron release from cellular stores and increase its damaging potential.
• The study demonstrates a direct link between acidic extracellular pH and increased oxidative stress via iron-mediated lipid peroxidation.