Mechanism of arachidonic acid liberation in ethanol-treated mouse peritoneal macrophages

Ethanol has previously been found to induce the release of unmetabolized free arachidonic acid from resident peritoneal macrophages (Diez, E., Balsinde, J., Aracil, M. and Schüller, A. (1987) Biochim. Biophys. Acta 921, 82-89). The molecular mechanism by which ethanol promoted this effect has been investigated in this report. The results reported herein suggest that ethanol stimulated [3H]arachidonate liberation from prelabeled macrophages by inhibiting AA reesterification into phospholipids rather than by enhancing phospholipase A2 activity. Evidence supporting this view was 3-fold. First, ethanol-induced [3H]arachidonic acid release was neither affected by depletion of extracellular Ca2+ nor by cell treatment with the protein kinase C inhibitor staurosporine, two conditions which are known to prevent agonist-induced phospholipase A2 activation in macrophages. Second, ethanol appreciably inhibited the uptake and esterification of [3H]arachidonate into phospholipids of unlabeled cells. Third, combined treatment with ethanol and albumin resulted in an additive release of radiolabel. Altogether, the results of this study underscore the importance of the reacylation pathway in controlling free arachidonic acid levels in macrophages.