THE MECHANISM OF INHIBITORY EFFECT OF EICOSAPENTAENOIC ACID ON PHAGOCYTIC-ACTIVITY AND CHEMOTAXIS OF HUMAN NEUTROPHIL GRANULOCYTES

Free eicosapentaenoic acid (EPA) was found to inhibit dose dependently the chemiluminescence of human neutrophil granulocytes phagocytosing zymosan and their chemotaxis induced by C5a-containing zymosan-activat ed serum (ZAS) and platelet-activating factor, Rigidification of plasm a membranes in the ZAS-treated cells could be observed by measuring th e fluorescence anisotropy, The cells were labeled by 3-[p-(6-phenyl-1, 3,5-hexatrienoil) phenyl] propionic acid, reporting plasma membrane fo r determination of membrane fluidity. In resting, nonstimulated neutro phils, EPA dose dependently increased the fluidity of plasma membrane. In zymosan-activated cells, however, after a short fluidization, the basic effect of EPA was a rigidification compared to very low fluoresc ence anisotropy values of activated control cells. This diminished flu idity, increased membrane stability of plasma membranes can be one of the reasons for the decreased functions (phagocytosis and chemotaxis) of human EPA-treated neutrophils. (C) 1996 Academic Press, Inc.