Rapid uptake and esterification of arachidonic acid and other fatty acids by microfilariae of Brugia malayi

We have examined the differential incorporation and esterification of exogenous fatty acids by microfilariae of the human filarial parasite Brugia malayi. Microfilariae incubated with 2 nM [3H]arachidonic acid over 1 h rapidly took up this fatty acid. Palmitic, oleic and linoleic acids were also incorporated by parasites. In contrast to these other fatty acids, little incorporated arachidonic acid remained as free fatty acid within microfilariae. Arachidonate was rapidly esterified into phospholipids, with 66% of incorporated arachidonate esterified into phospholipids at 1 min. Esterification of other fatty acids into phospholipids was quantitatively lesser and occurred into phosphatidylcholine and phosphatidylethanolamine. Arachidonate was preferentially esterified into phosphatidylinositol, which constituted only 10% of the total parasite phospholipid pool, and into phosphatidylcholine. By 1 min these two phospholipid classes, respectively, comprised 53% and 43% of [3H]arachidonyl-phospholipids. Neither the microfilarial incorporation of arachidonate nor its esterification into parasite phospholipids could be saturated by noncytotoxic concentrations of up to 600 microM. Microfilariae, which in vivo are exposed to arachidonate in blood, can rapidly, avidly and with high capacity incorporate exogenous arachidonate and esterify it preferentially into specific classes of phospholipids, including phosphatidylinositol. Like many mammalian cells, these phylogenetically distinct metazoan parasites possess efficient means for utilizing host-derived arachidonic acid.