Cell fatty acid composition affects free radical formation during lipid peroxidation.
Lipid-derived free radicals generated from intact human U937 monocytes exposed to iron-induced oxidative stress were detected by electron paramagnetic resonance (EPR) with the spin trap alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN). Lipid radical formation was enhanced when the cells were enriched with n-3 or n-6 polyunsaturated fatty acids. Computer simulation indicated that at least two POBN spin adducts were formed, having spectral characteristics consistent with carbon-centered radicals (aN = 15.9 G and aH = 2.6 G; aN = 15.1 G and aH = 2.8 G). These alkyl radicals are probably formed by beta-scission of alkoxyl radicals. POBN spin adduct formation correlated with ethane generation. Addition of ascorbate to the assay medium greatly increased the radical signal intensity. Although radical generation was cell dependent and POBN spin adducts were observed in cell homogenates, the adducts formed by the intact cells were detected only in the extracellular medium. These findings indicate that the extent of lipid radical formation in response to oxidative stress can be influenced by changes in the polyunsaturated fatty acid composition of the cell lipids and suggest the possibility that carbon-centered lipi radicals may interact with extracellular structures.
North
J A
JA
Department of Biochemistry, College of Medicine, University of Iowa, Iowa City 52242.
Spector
A A
AA
Buettner
G R
GR
D001205:Ascorbic Acid / Q000494:pharmacology; D004281:Docosahexaenoic Acids / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D004980:Ethane / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism* / Q000494:pharmacology; D005609:Free Radicals / Q000378:metabolism; D006801:Humans; D050356:Lipid Metabolism; D008054:Lipid Peroxides / Q000378:metabolism*; D009000:Monocytes / Q000378:metabolism*; D014018:Tissue Distribution; D014407:Tumor Cells, Cultured
D005227:Fatty Acids; D005609:Free Radicals; D008054:Lipid Peroxides; D004281:Docosahexaenoic Acids; D004980:Ethane; D001205:Ascorbic Acid