Protein kinase C-mediated phospholipase D activity is increased by linolenic acid supplementation in NG 108-15 cells

Phospholipase D activation was studied in NG 108-15 cells after manipulation of the phospholipid fatty acid composition. Cultivation of cells in media containing different polyunsaturated fatty acids induced extensive and specific changes in the phospholipid fatty acid composition. General for all phospholipids was an increase in polyunsaturated fatty acids at the expense of monounsaturated fatty acids. To examine phospholipase D activation, cells were stimulated with phorbol esters in the presence of ethanol and the formation of phosphatidylethanol was analyzed. In cells cultured with linolenic acid, a significantly higher amount of phosphatidylethanol was formed compared to control cells. On the other hand, supplementation with linoleic, arachidonic or docosahexaenoic acids did not induce any changes in phospholipase D activity. The effect was not due to free fatty acids in the cell culture medium and thus probably induced by fatty acids incorporated into membrane phospholipids or fatty acid metabolites. The results indicate a specific effect of linolenic acid and/or its metabolites on protein kinase C-mediated phospholipase D activity.