Previously published work has indicated that polyunsaturated fatty acids (PUFA) may enhance neutrophil-mediated damage to host tissues. We have found that endothelial detachment was significantly increased by neutrophils pretreated with docosahexaenoic (22:6, n-3) and arachidonic (20:4, n-6) acids at 10-40 microM but not by eicosapentaenoic acid (20:5, n-3). Endothelial cell lysis as measured by 51Cr release was unaffected. The extent of detachment was dependent on both fatty acid and neutrophil pretreatment concentrations. A specific leukocyte elastase inhibitor abrogated the increased detachment but catalase had no effect. Measurement of prostaglandin I2 synthesis as an alternative nonlytic assay of endothelial function indicated that 20:4 but not 20:5 was able to stimulate neutrophil-induced endothelial PGI2 synthesis. Although all three PUFA (3-33 microM) were found to stimulate release from neutrophil-specific granules, only 22:6 and 20:4 could stimulate release of the azurophilic granules containing elastase to any significant extent. Saturated fatty acids (20:0 and 22:0) and the methyl ester of 22:6 did not cause either neutrophil-mediated endothelial detachment or degranulation. We conclude that neutrophils pretreated with 22:6 or 20:4 but not 20:5 can decrease endothelial integrity through detachment involving neutrophil elastase. These findings may have important implications for the dietary use of fish oils rich in n-3 fatty acids.

Fish oils are abundant in polyunsaturated fatty acids of the n-3 series (in particular eicosapentaenoic, 20:5 and docosahexaenoic acid, 22:6). Such fatty acids are generally considered to be beneficial in the prevention of cardiac disease and to have anti-inflammatory properties. Neutrophil adherence is an essential early event in an acute inflammatory response, and we have demonstrated that both 20:5 and 22:6 stimulate adherence in vitro. Arachidonic acid (20:4, n-6) was also stimulatory. Significant simulation of adherence was seen from 5 to 80 microM (nontoxic concentrations) 22:6, 20:5, or 20:4. At the lower fatty acid concentrations tested (< or = 40 microM) 20:5 was less active than 22:6 or 20:4 at stimulating adherence. Above 40 microM there was no difference in the ability of the three fatty acids to stimulate adherence. At the lower fatty acid concentrations tested (< or = 10 microM) 22:6 was less active than 20:4, whereas above 10 microM they were equally active. Immunofluorescent flow cytometric analysis of neutrophil integrin (adherence) receptors showed that the complement C3bi receptor (CD11b) was up-regulated by these fatty acids. There was no change in CD11a or CD11c. Saturated fatty acids of the same chain length were without effect on adherence or receptor expression. The findings suggest that these polyunsaturated fatty acids may, under certain conditions, be proinflammatory with respect to their acute effects on the interaction of neutrophils with microbes, endothelium, and other tissues.