PGE2 Induces Macrophage IL-10 Production and a Regulatory-like Phenotype via a Protein Kinase A–SIK–CRTC3 Pathway

Abstract

The polarization of macrophages into a regulatory-like phenotype and the production of IL-10 plays an important role in the resolution of inflammation. We show in this study that PGE2, in combination with LPS, is able to promote an anti-inflammatory phenotype in macrophages characterized by high expression of IL-10 and the regulatory markers SPHK1 and LIGHT via a protein kinase A–dependent pathway. Both TLR agonists and PGE2 promote the phosphorylation of the transcription factor CREB on Ser133. However, although CREB regulates IL-10 transcription, the mutation of Ser133 to Ala in the endogenous CREB gene did not prevent the ability of PGE2 to promote IL-10 transcription. Instead, we demonstrate that protein kinase A regulates the phosphorylation of salt-inducible kinase 2 on Ser343, inhibiting its ability to phosphorylate CREB-regulated transcription coactivator 3 in cells. This in turn allows CREB-regulated transcription coactivator 3 to translocate to the nucleus where it serves as a coactivator with the transcription factor CREB to induce IL-10 transcription. In line with this, we find that either genetic or pharmacological inhibition of salt-inducible kinases mimics the effect of PGE2 on IL-10 production.

Small-molecule screening identifies inhibition of salt-inducible kinases as a therapeutic strategy to enhance immunoregulatory functions of dendritic cells

“…1C), which is consistent with the IL-10-potentiating effects of SIK inhibition in activated MΦs (20,21). In agreement with these reports, pretreating BMDCs with HG-9-91-01, a recently described inhibitor of SIK1-3, along with several other kinases (21), results in concentration-dependent potentiation of zymosaninduced IL-10 production with an EC 50 ∼ 200 nM and a maximum effect similar to that observed with PGE 2 (Fig.…”

“…Conversely, CREB activation by EP2/EP4 prostanoid receptor agonists like prostaglandin E 2 (PGE 2 ) promotes IL-10 production by myeloid cells (19). Recently, salt-inducible kinases (SIKs), which are members of the AMP-activated protein kinase family, have been identified as a key component of the CREB activation cascade (20,21). In quiescent myeloid cells, SIKs phosphorylate CREBregulated transcriptional coactivator-3 (CRTC3), which results in its sequestration by cytoplasmic 14-3-3 proteins.…”

14‐3‐3 proteins mediate inhibitory effects of cAMP on salt‐inducible kinases (SIKs)

“…4A) [7,28,29,37]. Similar to studies with SIK1, Ser/Ala mutants at each PKA phospho-acceptor site blocked Fsk-induced CRE reporter activation in comparison to SIK2 WT (SIK2 WT =~80% and PKA site mutants =~6-35% CRE reporter activity upon Fsk treatment; Fig.…”

Activation of prostaglandin E2-EP4 signaling reduces chemokine production in adipose tissue

“…This conclusion emerged Adipose tissue consists of adipocytes and SVCs, and both cell fractions can release chemokines. Earlier studies described PGE 2 -EP4 anti-infl ammatory signaling in macrophages, but not in vascular endothelial or smooth muscle cells ( 5,25 ). These observations led to the expectation that PGE 2 's anti-infl ammatory effects in adipose tissue may predominate in SVCs, the cell fraction containing macrophages.…”