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

- Microglia produced PGE2 after phagocytosis of PS liposomes.
- PGE2 was not produced after phagocytosis of liposomes containing lipolysis products.
- PS liposome-induced PGE2 production by microglia was inhibited by MJ33.
- Microglia produced PGD2 and 15d-PGJ2 after phagocytosis of PS liposomes.
- Lipolysis of PS liposomes by aiPLA2 supplies arachidonic acid to the COX-1 pathway.

Liposomes containing phosphatidylserine (PSL) produce PGE2 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 PLA2, were phagocytosed by microglia, but failed to induce secretion of PGE2. Furthermore, PSL-induced PGE2 secretion was significantly inhibited by MJ33, an aiPLA2 inhibitor, but not by AACOCF3, a cPLA2 inhibitor. PSL also produced PGD2 and 15d-PGJ2 in microglia. We thus hypothesize that free arachidonic acid is supplied through aiPLA2-mediated lipolysis of phagocytosed phosphatidylcholine, leading to the production of PGH2 and its downstream metabolites.