Different metabolic behavior of long-chain n-3 polyunsaturated fatty acids in human platelets.
Whereas numerous studies deal with the effects and metabolism of eicosapentaenoic acid (20:5(n - 3)) in platelets, very few concern docosahexaenoic acid (22:6(n - 3)), although both acids are consumed in equal amounts from most fish fat. The present paper reports the modulation of 22:6(n - 3) oxygenation as well as that of endogenous arachidonic acid (20:4(n - 6)) in 22:6(n - 3)-rich platelets. Like the oxygenation of 20:5(n - 3), the lipoxygenation of 22:6(n - 3) occurred at a low level when incubated alone, but was markedly increased in the presence of 20:4(n - 6), suggesting a similar peroxide tone dependency. 20:5(n - 3) could not replace 20:4(n - 6) in the increasing 22:6(n - 3) lipoxygenation, whereas 22:6(n - 3) shared the potentiating effect of 20:4(n - 6) on both the cyclooxygenation and the lipoxygenation of 20:5(n - 3). On the other hand, 20:5(n - 3), 22:6(n - 3) or 20:5(n - 3) + 22:6(n - 3) enrichment of platelet phospholipids inhibited the formation of cyclooxygenase but not lipoxygenase products from endogenous 20:4(n - 6) in thrombin-stimulated platelets. In doing so, 22:6(n - 3) appeared even more potent than 20:5(n - 3), although it was not liberated after acylation in phospholipids, the opposite of what was observed with 20:5(n - 3). Therefore, it seems that, in contrast to 20:5(n - 3), which may compete with endogenous 20:4(n - 6) at the cyclooxygenase level, 22:6(n - 3) would affect the latter enzyme activity in a different way. We conclude that 20:5(n - 3) and 22:6(n - 3) behave differently and might act synergistically on the inhibition of platelet functions after fish fat intake.
Croset
M
M
INSERM U63, Institut Pasteur, Laboratoire d'Hémobiologie, Faculté Alexis Carrel, Lyon, France.
Guichardant
M
M
Lagarde
M
M
D001095:Arachidonic Acids / Q000378:metabolism; D001792:Blood Platelets / Q000378:metabolism*; D004281:Docosahexaenoic Acids / Q000378:metabolism*; D015118:Eicosapentaenoic Acid / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D008084:Lipoxygenase / Q000502:physiology; D013931:Thromboxanes / Q000378:metabolism
D001095:Arachidonic Acids; D013931:Thromboxanes; D004281:Docosahexaenoic Acids; D015118:Eicosapentaenoic Acid; D008084:Lipoxygenase