Abstract
Prostaglandin E2 (PGE2) suppresses macrophage effector mechanisms; however, little is known about the function of PGD2 in infected alveolar macrophages (AMs). Using serum-opsonized Histoplasma capsulatum (Ops-H. capsulatum) in vitro, we demonstrated that AMs produced PGE2 and PGD2 in a time-dependent manner, with PGE2 levels exceeding those of PGD2 by 48 h postinfection. Comparison of the effects of both exogenous PGs on AMs revealed that PGD2 increased phagocytosis and killing through the chemoattractant receptor-homologous molecule expressed on Th2 lymphocytes receptor, whereas PGE2 had opposite effects, through E prostanoid (EP) receptor 2 (EP2)/EP4-dependent mechanisms. Moreover, PGD2 inhibited phospholipase C-γ (PLC-γ) phosphorylation, reduced IL-10 production, and increased leukotriene B4 receptor expression. In contrast, exogenous PGE2 treatment reduced PLC-γ phosphorylation, p38 and nuclear factor κB activation, TNF-α, H2O2, and leukotriene B4, but increased IL-1β production. Using specific compounds to inhibit the synthesis of each PG in vitro and in vivo, we found that endogenous PGD2 contributed to fungicidal mechanisms and controlled inflammation, whereas endogenous PGE2 decreased phagocytosis and killing of the fungus and induced inflammation. These findings demonstrate that, although PGD2 acts as an immunostimulatory mediator to control H. capsulatum infection, PGE2 has immunosuppressive effects, and the balance between these two PGs may limit collateral immune damage at the expense of microbial containment.