Cell fatty acid composition affects free radical formation during lipid peroxidation

Area of Science:

• Biochemistry
• Cell Biology
• Free Radical Chemistry

Background:

• Oxidative stress plays a role in various pathologies.
• Understanding lipid peroxidation mechanisms is crucial for disease intervention.
• Monocytes are key immune cells susceptible to oxidative damage.

Purpose of the Study:

• To detect and characterize lipid-derived free radicals in human monocytes under oxidative stress.
• To investigate the influence of polyunsaturated fatty acids (PUFAs) on radical formation.
• To explore the cellular location and potential interactions of these radicals.

Main Methods:

• Human U937 monocytes were exposed to iron-induced oxidative stress.
• Electron paramagnetic resonance (EPR) spectroscopy with alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN) spin trapping was employed.
• Gas chromatography was used to measure ethane generation.
• Computer simulations analyzed EPR spectral data.

Main Results:

• Lipid radical formation was detected and enhanced in cells enriched with n-3 or n-6 PUFAs.
• EPR analysis identified at least two carbon-centered POBN spin adducts, likely formed by beta-scission of alkoxyl radicals.
• Radical formation correlated with ethane generation and was cell-dependent.
• Ascorbate increased radical signal intensity; radicals were detected extracellularly in intact cells.

Conclusions:

• Cellular PUFA composition significantly influences lipid radical formation during oxidative stress.
• Carbon-centered lipid radicals are generated extracellularly by intact monocytes.
• These findings suggest potential extracellular interactions of lipid radicals with cellular structures.