EP2 receptor activation by prostaglandin E2 leads to induction of HO-1 via PKA and PI3K pathways in C6 cells

Recently we proposed that COX-2 induction precedes expression of HO-1 in ischemic preconditioned rat brain. In the current study, we investigated the molecular mechanism by which prostaglandin E2, one of COX-2 metabolites, induces HO-1 in rat C6 brain cells. We demonstrated that concentration of PGE2 increased HO-1 expression in C6 cells in vitro. The effects of PGE2 were mimicked by PGE2 receptor EP2 agonists, 11-deoxy PGE2, and cAMP analog, dibutyl-cAMP. HO-1 expression by PGE2 was inhibited by LY294002, PI3K inhibitor and H89, PKA inhibitor. The EP2-specific antagonist, AH8006 also inhibited PGE2-mediated HO-1 expression in a concentration-dependent manner. Finally, PGE2 inhibited GOX-induced apoptosis as assayed by FACS analysis or DNA strand breaks assay, and this cell death was reversed by ZnPPIX, HO-1 inhibitor. In addition to HO-1 induction, PGE2 also increased phosphorylation of Bad by PKA- and PI3K-depednent manner. Taken together, we conclude that PGE2 induces HO-1 protein expression through PKA and PI3K signaling pathways via EP2 receptor in C6 cells. The induction of HO-1 along with increase of p-Bad by PGE2 is responsible for anti-apoptosis against oxidant stress.