Effects of dietary supplementation with eicosapentaenoic acid or gamma-linolenic acid on neutrophil phospholipid fatty acid composition and activation responses

Previous data that alimentation with fish oil rich in eicosapentaenoic acid (EPA; 20: 5n-3) or vegetable oil rich in gamma-linolenic acid (GLA; 18: 3n-6) can reduce symptoms of inflammatory skin disorders lead us to determine the effects of dietary supplements of oils rich in EPA or GLA on guinea pig (GP) neutrophil (PMN) membrane potential (), secretion, and Superoxide (O₂^–) responses. Weanling GPs were initially fed diets supplemented with olive oil (<0.1% EPA; <0.1% GLA) for 2 weeks, followed by a crossover by two sets of animals to diets supplemented with fish oil (19% EPA) or borage oil (25% GLA). At 4-week intervals, 12% sterile casein-elicited peritoneal neutrophils (PMN) were assessed for membrane polyunsaturated fatty acid (PUFA) profiles and FMLP-, LTB₄^s-, and PMA-stimulated changes, changes in flow cytometrically measured forward scatter (FWD-SC) (shape change), 90 scatter (90-SC) in cytochalasin B-pretreated-PMN (secretion response), and Superoxide responses. GP incorporated EPA and GLA (as the elongation product, dihomo-GLA or DGLA) into their PMN phospholipids by 4 weeks. The peritoneal PMN of all groups demonstrated broad resting FWD-SC and poor activation-related FWD-SC increases, suggesting in vivo activation. While secretion was comparable in the three groups in response to FMLP, there was a trend toward inhibition of LTB₄-stimulated 90-SC loss in both fish and borage oil groups. This was significant only with borage oil (21.7±2.1 vs 15.3±1.2% loss of baseline 90-SC, olive vs borage;P=0.03). PMN from borage- and fish oil-fed GPs showed a progressively lower O₂^– response to FMLP than the olive oil group (73.9±3.9 and 42.9±6.8% of olive oil response for borage and fish oils, respectively;P< 0.005 andP<0.01, respectively, at 12 weeks), while PMA-stimulated O₂^– was inhibited only in the fish oil-fed group and only at 12 weeks (62.0±2.7% of control;P<0.025). We conclude that dietary supplementation with oils rich in PUFAs can modify PMN activation responses.This work was supported in part by Research Grants AM-30679, AR 39040, and P30-AM 35747-02 from the U.S. Public Health Service.