Modulation of rabbit neutrophil aggregation and degranulation by free fatty acids

We have examined the effects of free fatty acids on the unstimulated and N-formyl-methionyl-leucyl-phenylalanine (f-Met-Leu-Phe) stimulated rabbit neutrophil aggregation and degranulation. As previously reported, arachidonic acid was found to induce by itself an aggregatory response, and in the presence of cytochalasin B, a degranulation response from the neutrophils. The aggregatory property, but not the secretory activity of arachidonic acid, was shared by oleic acid, linoleic acid, linolenic acid, linoelaidic acid, and lauric acid but not by elaidic acid, caproic acid, stearic acid, and arachidic acid. In addition, several free fatty acids (oleic acid, linoleic acid, linolenic acid, arachidonic acid, and linoelaidic acid) were found to inhibit the aggregatory and secretory responses of the neutrophils to the addition of f-Met-Leu-Phe. Caproic acid and lauric acid were found to stimulate to a small extent the aggregatory response of the neutrophils to f-Met-Leu-Phe and to leave unaffected their secretory response. Elaidic acid, stearic acid, and arachidic acid, on the other hand, left both stimulated responses unaffected. These results demonstrate that at least two neutrophil functions can be modulated (both positively and negatively) by free fatty acids.