The cAMP Pathway Amplifies Early MyD88-Dependent and Type I Interferon-Independent LPS-Induced Interleukin-10 Expression in Mouse Macrophages

Abstract

Interleukin-10 (IL-10) is a key anti-inflammatory cytokine, secreted by macrophages and other immune cells to attenuate inflammation. Autocrine type I interferons (IFNs) largely mediate the delayed expression of IL-10 by LPS-stimulated macrophages. We have previously shown that IL-10 is synergistically expressed in macrophages following a costimulus of a TLR agonist and cAMP. We now show that the cAMP pathway directly upregulates IL-10 transcription and plays an important permissive and synergistic role in early, but not late, LPS-stimulated IL-10 mRNA and protein expression in mouse macrophages and in a mouse septic shock model. Our results suggest that the loss of synergism is not due to desensitization of the cAMP inducing signal, and it is not mediated by a positive crosstalk between the cAMP and type I IFN pathways. First, cAMP elevation in LPS-treated cells decreased the secretion of type I IFN. Second, autocrine/paracrine type I IFNs induce IL-10 promoter reporter activity only additively, but not synergistically, with the cAMP pathway. IL-10 promoter reporter activity was synergistically induced by cAMP elevation in macrophages stimulated by an agonist of either TLR4, TLR2/6, or TLR7, receptors which signal via MyD88, but not by an agonist of TLR3 which signals independently of MyD88. Moreover, MyD88 knockout largely reduced the synergistic IL-10 expression, indicating that MyD88 is required for the synergism displayed by LPS with cAMP. This report delineates the temporal regulation of early cAMP-accelerated vs. late type I IFN-dependent IL-10 transcription in LPS-stimulated murine macrophages that can limit inflammation at its onset.

Large-Scale Production of Human iPSC-Derived Macrophages for Drug Screening

“…Having established the differentiation protocol and confirmed an overall macrophage expression profile by RNAseq and flow cytometry, we next assessed whether the iPSC-derived macrophages faithfully recapitulate macrophage function. For this, we chose 16 compounds reported to modulate targets that are either affected by changes in cyclic adenosine monophosphate (cAMP) [ 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ] or to have immune modulatory effects [ 41 , 42 , 43 , 44 , 45 , 46 ] ( Figure S6 ). These compounds were screened for modulatory effects on the phagocytosis of Zymosan particles ( Figure 5 ) and on cytokine release ( Figure 6 ) to demonstrate the applicability of iPSC-derived macrophages in small molecule screens with functional endpoints.…”

Exclusive Temporal Stimulation of IL-10 Expression in LPS-Stimulated Mouse Macrophages by cAMP Inducers and Type I Interferons

“…Synergistic IL-10 expression has also been demonstrated in macrophages stimulated by a cAMP inducer and agonists of other TLRs (9, 10). Recently, we further demonstrated that the enhancement of LPS-stimulated IL-10 expression by cAMP and by autocrine type I IFN is temporally distinct (11). Exogenous agents that elevate cAMP, such as the β-adrenergic receptor (β-AR) agonist isoproterenol or the phosphodiesterase (PDE)-4 inhibitor rolipram, synergize with early type I IFN-independent IL-10 expression by LPS, but in contrast, are unable to amplify the late type I IFN-dependent activity (11).…”

“…Recently, we further demonstrated that the enhancement of LPS-stimulated IL-10 expression by cAMP and by autocrine type I IFN is temporally distinct (11). Exogenous agents that elevate cAMP, such as the β-adrenergic receptor (β-AR) agonist isoproterenol or the phosphodiesterase (PDE)-4 inhibitor rolipram, synergize with early type I IFN-independent IL-10 expression by LPS, but in contrast, are unable to amplify the late type I IFN-dependent activity (11). In the current study we explored the mechanism of IL-10 expression temporal regulation at the promoter level.…”

“…As expected, IL-10 expression is elevated in DUSP1-deficient macrophages in a p38-dependent manner (21). As the cAMP-DUSP1 axis down-regulates p38 activity and IL-10 expression in LPS-stimulated macrophages (20), whereas overall cAMP strongly amplifies IL-10 expression (11), we hypothesized that cAMP magnifies LPS-induced IL-10 via a p38-independent mechanism.…”

Changes in the expression of interleukin-10 in myocardial infarction and its relationship with macrophage activation and cell apoptosis

“…Recently, it has been reported that the target cells in which IL-10 plays anti-inflammatory effects are mainly macrophages. Mononuclear macrophages secrete IL-10 after activation by various endogenous and exogenous mediators, causing IL-10 genetic transcription via lipopolysaccharide activation pathway, protein kinase A-dependent activation pathway, etc [12,13]. Additionally, mononuclear macrophages also secrete IL-10 during the process of clearing apoptotic cells, and this process depends on the activation of p38 mitogen-activated protein kinase (MAPK) [14].…”