Effect of exogenous fatty acids with greater than 22 carbon atoms (very long chain fatty acids) on superoxide production by human neutrophils.

The effects of exogenous long chain fatty acids (LCFA) and very long chain fatty acids (VLCFA) on superoxide production by human neutrophils were compared. Superoxide production was greater and more rapid in response to arachidonic (20:4 (n-6)), eicosapentanoic (20:5 (n-3)), and docosahexanoic (22:6 (n-3)) acids than for triacontatetranoic (30:4 (n-6)), dotriacontatetranoic (32:4 (n-6)), and tetratriacontahexanoic (34:6 (n-3)) acids, although all of these fatty acids gave responses larger than FMLP. A similar decline in activity with increasing carbon chain length was observed for the monoenoic VLCFA (22:1 (n-9) to 34:1 (n-9)). 32:4 (n-6) did not affect responses to a maximally stimulatory concentration of 20:4 (n-6). However, the simultaneous addition of 20:4 (n-6) and 30:4 (n-6) gave additive responses if suboptimal dosages of 20:4 (n-6) were used. This suggests that the LCFA and VLCFA may use the same signal transduction systems. In addition, 30:4 (n-6) was only 10% as effective as was 20:4 (n-6) at gaining access to the organic solvent extractable cellular fraction. This figure correlated with the relative biologic potency of 20:4 (n-6) and 30:4 (n-6), suggesting that the extent of association with the cell may regulate the biologic activity of the fatty acids. The saturates, arachidic (20:0) and cerotic (26:0) acids, were either inactive or poor activators in all assay systems examined. The failure of 20:0 to induce superoxide production and the lower responses to 30:4 (n-6) and 34:6 (n-3) were not because of extracellular Ca2+, because the biologic potency of these fatty acids was not greatly enhanced by removing Ca2+ from the extracellular medium. In contrast, 20:4 (n-6)- and 22:6 (n-3)-induced superoxide production was markedly increased under Ca(2+)-free conditions.