Dietary fish oil decreases superoxide generation by human neutrophils: Relation to cyclooxygenase pathway and lysosomal enzyme release

12 volunteers with slightly elevated serum triglyceride levels were given 30 ml fish oil (5.4 g eicosapentaenoic acid and 3.2 g docosahexaenoic acid) daily for 4 weeks. The percentage of eicosapentaenoic acid increased (P < 0.01) and the percentage of linoleic (P < 0.05) and arachidonic acid (P < 0.01) decreased in neutrophil phospholipids. Superoxide generation by neutrophils initiated by phorbol myristate acetate decreased significantly from 48.6 +/- 8.8 to 34.7 +/- 11.1 nmol/10 min/400 000 cells (means +/- SD, P < 0.01, n = 11). Treatment of the cells with the cyclooxygenase inhibitor indomethacin had no significant influence on the decrease in superoxide generation, indicating that cyclooxygenase products were not involved in this effect of fish oil. Neutrophil elastase release did not change significantly, suggesting that neutrophil lysosomal enzyme release and superoxide generation may be under separate control. In conclusion, dietary fish oil decreased superoxide generation by human neutrophils without involvement of the cyclooxygenase pathway and without altering neutrophil lysosomal enzyme release. Dietary fish oil could have beneficial effects in pathological conditions with activated neutrophils, such as ischaemic heart disease.