Polyunsaturated Fatty Acid Enrichment Increases Ultraviolet A-Induced Lipid Peroxidation in NCTC 2544 Human Keratinocytes

The influence of cell enrichment with fatty acids with increasing degree of unsaturation on the ultraviolet A-induced formation of lipid-peroxidation products (thiobarbituric acid reactive substances [TEARS]) has been investigated in NCTC 2544 human keratinocytes. A 48-h preculture of cells in controlled medium supplemented with unsaturated fatty acids resulted in a marked increase in TEARS appearance under ultraviolet A exposure. This effect was dependent upon the degree of unsaturation of the fatty acids, with the following order of efficiency: arachidonic > linolenic > linoleic > oleic acid. For arachidonic acid (AA), the potentiating effect on ultraviolet A-induced lipid peroxidation was dependent upon the fatty acid concentration, with about a 2.5-fold increase in TEARS formation in cells pre-cultured with 5 x 10(-5) M AA, then exposed to a UVA dose of 13 J/cm(2). The increase in TEARS formation by AA was almost totally prevented by supplementation of cells with 5 x 10(-5) M vitamin E, whereas buthionine sulfoximine, a chemical which depletes cell glutathione, potentiated lipid peroxidation. These results suggest that the nature of the fatty acids of cellular lipids could influence the response of keratinocytes to ultraviolet A, and especially the ultraviolet A-induced lipid peroxidation.