Prostaglandin E2-induced IL-23p19 is regulated by CREB and C/EBP beta in bone marrow derived dendritic cells

Abstract

We reported previously that prostaglandin E2 (PGE2) upregulates IL-23 in vitro in bone marrow-derived dendritic cells (DC), and in vivo in models of collagen-induced arthritis and inflammatory bowel disease, leading to preferential Th17 development and activity. There is very little information on the molecular mechanisms involved in the PGE2-induced upregulation of Il23a gene expression. In the present study we investigated the signaling pathways and transcription factors involved in the stimulatory effect of PGE2. Although PGE2 does not induce IL-23p19 expression by itself, it synergizes with both extra- and intracellular TLR ligands and with inflammatory cytokines such as TNFα. We established that the effect of PGE2 in conjunction with either LPS or TNFα is mediated through the EP4 receptor and the cAMP-dependent activation of both PKA and EPAC. Using the EP4 agonist PGE1OH in conjunction with TNFα, we found that PKA-induced PCREB and EPAC-induced PC/EBPβ mediate the stimulatory effect of PGE2 on IL-23p19 expression. This is the first report of CREB and C/EBPβ involvement in Il23a promoter activation. Mutation within the putative CREB and C/EBP sites combined with in vivo DNA binding (ChIP) assays identified the distal CREB site (-1125) and the two proximal C/EBP sites (-274 and -232) as essential for PKA-activated CREB and EPAC-activated C/EBPβ induced IL-23p19 expression.