Possible involvement of aiPLA2 in the phosphatidylserine-containing liposomes induced production of PGE2 and PGD2 in microglia

Liposomes containing phosphatidylserine (PSL) produce PGE(2) after being phagocytosed by microglia, but the precise underlying mechanism behind it still remains unclear. Here, we showed that liposomes consisting of phosphatidylserine and lysophosphatidylcholine, a lipolysis product of phosphatidylcholine by PLA(2), were phagocytosed by microglia, but failed to induce secretion of PGE(2). Furthermore, PSL-induced PGE(2) secretion was significantly inhibited by MJ33, an aiPLA(2) inhibitor, but not by AACOCF(3), a cPLA(2) inhibitor. PSL also produced PGD(2) and 15d-PGJ(2) in microglia. We thus hypothesize that free arachidonic acid is supplied through aiPLA(2)-mediated lipolysis of phagocytosed phosphatidylcholine, leading to the production of PGH(2) and its downstream metabolites. (C) 2013 Elsevier B.V. All rights reserved.