POLYUNSATURATED FATTY-ACID ENRICHMENT INCREASES ULTRAVIOLET-A-INDUCEDLIPID-PEROXIDATION IN NCTC-2544 HUMAN KERATINOCYTES

The influence of cell enrichment with fatty acids with increasing degr ee of unsaturation on the ultraviolet A-induced formation of lipid-per oxidation products (thiobarbituric acid reactive substances [TEARS]) h as been investigated in NCTC 2544 human keratinocytes. A 48-h precultu re of cells in controlled medium supplemented with unsaturated fatty a cids resulted in a marked increase in TEARS appearance under ultraviol et A exposure. This effect was dependent upon the degree of unsaturati on of the fatty acids, with the following order of efficiency: arachid onic > linolenic > linoleic > oleic acid. For arachidonic acid (AA), t he potentiating effect on ultraviolet A-induced lipid peroxidation was dependent upon the fatty acid concentration, with about a 2.5-fold in crease 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 format ion by AA was almost totally prevented by supplementation of cells wit h 5 x 10(-5) M vitamin E, whereas buthionine sulfoximine, a chemical w hich 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 es pecially the ultraviolet A-induced lipid peroxidation.