Stimulation of adenosine A_2B receptors induces interleukin‐6 secretion in cardiac fibroblasts via the PKC‐δ–P38 signalling pathway

Abstract

Background and purpose: Inflammatory response and cytokine activation are markedly stimulated after myocardial infarction, and contribute to cardiac remodelling. Interleukin-6 (IL-6), a pro-inflammatory cytokine, has pleiotropic effects on cardiac remodelling. Adenosine, released by all cell types, binds to a class of G protein-coupled receptors to induce various cardiovascular effects. The aim of this work was to investigate whether activation of adenosine receptors, particularly A2B adenosine receptors, could stimulate IL-6 secretion in cardiac fibroblasts (CFs). Experimental approach: ELISA was used to assess IL-6 concentration in supernatant, and immunostaining was used to analyse IL-6 protein level in CFs. The levels of phosphorylated and total p38, extracellular signal-regulated kinase, c-Jun N-terminal kinase and protein kinase C-d (PKC-d) were determined by Western blot analysis. Key results: Adenosine-5′-N-ethyluronamide (NECA), a stable adenosine analogue, dose-and time-dependently stimulated IL-6 secretion in CFs. The effect of NECA was dose-dependently inhibited by an A2B antagonist, and silencing of the A2B receptor also inhibited IL-6 secretion. By using PKC isoform-selective inhibitors and translocation peptide inhibitors, the PKC-d isoform was found to be involved in the up-regulation of IL-6 production. Inhibition of p38 by SB203580, and adenoviral transfer of dominant-negative p38 inhibited NECA-induced IL-6 production. Furthermore, PKC-d functioned as an upstream regulator of p38 MAPK in this process. Conclusions and implications:We demonstrated a novel relationship between adenosine and IL-6 secretion, in that IL-6 secretion induced by NECA was mediated by adenosine A2B receptor activation in CFs and was dependent on a PKCd-P38 pathway.

Impaired Inhibitory Function of Presynaptic A1-Adenosine Receptors in SHR Mesenteric Arteries

“…In the literature there are reports indicating the presence of different adenosine receptor subtypes on immune cells (38) and cultured cardiac fibroblasts (39). We can speculate that adenosine might play an additional role in systemic hypertension mediating inflammatory cell recruitment and/or vascular remodeling.…”

GPR84 and TREM-1 Signaling Contribute to the Pathogenesis of Reflux Esophagitis

“…In our model, TNF-α or NF-κB (tissue mRNA, proteome profiler/ELISA and WB) were not clearly involved. However, the release of IL-6 and IL-8 is known to be linked to p38 signaling (19,20) and has so far not been reported for reflux esophagitis.…”

A2b adenosine receptors can change their spots

“…This receptor fickleness was confirmed by Feng et al (2009) in the current edition of the British Journal of Pharmacology. They examined production of the proinflammatory cytokine interleukin-6 (IL-6) by mouse cardiac fibroblasts following exposure to 5′-(N-ethylcarboxamido) adenosine (NECA), a potent, albeit not selective, A2b receptor agonist.…”

“…Clearly IL-6 production by cardiac fibroblasts was greatly influenced by stimulation of A2b receptors. When Feng et al (2009) studied the downstream signalling they found involvement of Gq and not Gs. Pretreatment with either the cAMP-competitive analog Rp-cAMPS or 1 of two protein kinase A (PKA) inhibitors, H-89 or KT 5720, before exposure to NECA failed to block NECAinduced IL-6 production.…”