Genome-Wide Mapping Defines a Role for C/EBPβ and c-Jun in Non-Canonical Cyclic AMP Signalling

Protein interaction, cytotoxic, transcriptomic and proteomic responses to structurally distinct EPAC1 activators in HUVECs

The N-acylsulfonamide derivative, I942, represents the first non-cyclic nucleotide partial agonist of EPAC1. This was soon followed by the identification of the I942 analogues, PW0381, PW0521 and PWO577 and a series of benzofuran oxoacetic acid EPAC1 activators, SY006, SY007 and SY009. Protein interaction, cytotoxicity and EPAC1 activation assays applied here identify PWO577 and SY007 as being effective EPAC1 binders that are well tolerated in HUVECs at concentrations greater than 100 μM and up to 48 h incubation and are effective activators of transfected EPAC1 in U2OS cells. Using RNAseq in HUVECs we show that PWO577 and SY007 regulate approximately 11,000 shared genes, with only few differential gene changes being “off-target”. The genes significantly regulated by both PWO577 and SY007 included a subset of genes normally associated with endothelial activation, including ICAM1, MMP1 and CCL2. Of these, only the expression of MMP1 was markedly increased at the protein level, as determined by LC–MS-based proteomics. Both PWO577 and SY007 suppressed IL-6-induced STAT3 activation and associated downstream gene expression, including inhibition of SOCS3, STAT3, IL6ST and JAK3 genes. Together these results demonstrate the utility of structurally distinct, specific and non-toxic EPAC1 activators. Future modifications will be aimed at eliminating the few noted off-target effects.

The P2Y11 receptor of human M2 macrophages activates canonical and IL-1 receptor signaling to translate the extracellular danger signal ATP into anti-inflammatory and pro-angiogenic responses

The cytoprotective ATP receptor P2Y₁₁ is upregulated during M2 macrophage differentiation and contributes to the anti-inflammatory properties of this macrophage subset. Here, we studied P2Y₁₁-induced reprogramming of human M2 macrophages at the level of mRNA and protein expression. Upregulation of IL-1 receptor (IL-1R) and its known downstream effectors VEGF, CCL20 and SOCS3 as well as downregulation of the ATP-degrading ecto-ATPase CD39 emerged as hallmarks of P2Y₁₁ activation. The anti-inflammatory signature of the P2Y₁₁ transcriptome was further characterized by the downregulation of P2RX7, toll-like receptors and inflammasome components. P2Y₁₁-induced IL-1R upregulation formed the basis for reinforced IL-1 responsiveness of activated M2 macrophages, as IL-1α and IL-1ß each enhanced P2Y₁₁-induced secretion of VEGF and CCL20 as well as the previously reported shedding of soluble tumor necrosis factor receptor 2 (sTNFR2). Raising intracellular cyclic AMP (cAMP) in M2 macrophages through phosphodiesterase 4 inhibition enhanced P2Y₁₁-driven responses. The cAMP-binding effector, exchange protein activated by cAMP 1 (Epac1), which is known to induce SOCS3, differentially regulated the P2Y₁₁/IL-1R response because pharmacological Epac1 inhibition enhanced sTNFR2 and CCL20 release, but had no effect on VEGF secretion. In addition to cAMP, calcium and protein kinase C participated in P2Y₁₁ signaling. Our study reveals how P2Y₁₁ harnesses canonical and IL-1R signaling to promote an anti-inflammatory and pro-angiogenic switch of human M2 macrophages, which may be controlled in part by an Epac1-SOCS3 axis.

Unraveling the role of Epac1-SOCS3 signaling in the development of neonatal-CRD-induced visceral hypersensitivity in rats

Aims

Visceral hypersensitivity in irritable bowel syndrome (IBS) is widespread, but effective therapies for it remain elusive. As a canonical anti‐inflammatory protein, suppressor of cytokine signaling 3 (SOCS3) reportedly relays exchange protein 1 directly activated by cAMP (Epac1) signaling and inhibits the intracellular response to inflammatory cytokines. Despite the inhibitory effect of SOCS3 on the pro‐inflammatory response and neuroinflammation in PVN, the systematic investigation of Epac1‐SOCS3 signaling involved in visceral hypersensitivity remains unknown. This study aimed to explore Epac1‐SOCS3 signaling in the activity of hypothalamic paraventricular nucleus (PVN) corticotropin‐releasing factor (CRF) neurons and visceral hypersensitivity in adult rats experiencing neonatal colorectal distension (CRD).

Methods

Rats were subjected to neonatal CRD to simulate visceral hypersensitivity to investigate the effect of Epac1‐SOCS3 signaling on PVN CRF neurons. The expression and activity of Epac1 and SOCS3 in nociceptive hypersensitivity were determined by western blot, RT‐PCR, immunofluorescence, radioimmunoassay, electrophysiology, and pharmacology.

Results

In neonatal‐CRD‐induced visceral hypersensitivity model, Epac1 and SOCS3 expressions were downregulated and IL‐6 levels elevated in PVN. However, infusion of Epac agonist 8‐pCPT in PVN reduced CRF neuronal firing rates, and overexpression of SOCS3 in PVN by AAV‐SOCS3 inhibited the activation of PVN neurons, reduced visceral hypersensitivity, and precluded pain precipitation. Intervention with IL‐6 neutralizing antibody also alleviated the visceral hypersensitivity. In naïve rats, Epac antagonist ESI‐09 in PVN increased CRF neuronal firing. Consistently, genetic knockdown of Epac1 or SOCS3 in PVN potentiated the firing rate of CRF neurons, functionality of HPA axis, and sensitivity of visceral nociception. Moreover, pharmacological intervention with exogenous IL‐6 into PVN simulated the visceral hypersensitivity.

Conclusions

Inactivation of Epac1‐SOCS3 pathway contributed to the neuroinflammation accompanied by the sensitization of CRF neurons in PVN, precipitating visceral hypersensitivity and pain in rats experiencing neonatal CRD.

Meta-analysis of transcriptome datasets: An alternative method to study IL-6 regulation in coronavirus disease 2019

In coronavirus disease 2019 (COVID-19) patients, interleukin (IL)-6 is one of the leading factors causing death through cytokine release syndrome. Hence, identification of IL-6 downstream from clinical patients’ transcriptome is very valid for analyses of its mechanism. However, clinical study is conditional and time consuming to collect optional size of samples, as patients have the clinical heterogeneity. A possible solution is to deeply mine the relative existing data. Several transcriptome-based studies on other diseases or treatments have revealed different genes to be regulated by IL-6. Through our meta-analysis of these transcriptome datasets, 352 genes were suggested to be regulated by IL-6 in different biological conditions, some of which were related to virus infection and cardiovascular disease. Among them, 232 genes were not identified by current transcriptome studies from clinical research. ICAM1 and PFKFB3 were the most significantly upregulated genes in our meta-analysis and could be employed as biomarkers in patients with severe COVID-19. In general, a meta-analysis of transcriptome datasets could be an alternative way to analyze the immune response and complications of patients suffering from severe COVID-19 and other emergency diseases.

Special Issue on "New Advances in Cyclic AMP Signalling"-An Editorial Overview

The cyclic nucleotides 3′,5′-adenosine monophosphate (cyclic AMP) signalling system underlies the control of many biological events and disease processes in man. Cyclic AMP is synthesised by adenylate cyclase (AC) enzymes in order to activate effector proteins and it is then degraded by phosphodiesterase (PDE) enzymes. Research in recent years has identified a range of cell-type-specific cyclic AMP effector proteins, including protein kinase A (PKA), exchange factor directly activated by cyclic AMP (EPAC), cyclic AMP responsive ion channels (CICs), and the Popeye domain containing (POPDC) proteins, which participate in different signalling mechanisms. In addition, recent advances have revealed new mechanisms of action for cyclic AMP signalling, including new effectors and new levels of compartmentalization into nanodomains, involving AKAP proteins and targeted adenylate cyclase and phosphodiesterase enzymes. This Special Issue contains 21 papers that highlight advances in our current understanding of the biology of compartmentlised cyclic AMP signalling. This ranges from issues of pathogenesis and associated molecular pathways, functional assessment of novel nanodomains, to the development of novel tool molecules and new techniques for imaging cyclic AMP compartmentilisation. This editorial aims to summarise these papers within the wider context of cyclic AMP signalling.