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 A 2B 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-δ (PKC-δ) 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 A 2B antagonist, and silencing of the A 2B receptor also inhibited IL-6 secretion. By using PKC isoform-selective inhibitors and translocation peptide inhibitors, the PKC-δ 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-δ 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 A 2B receptor activation in CFs and was dependent on a PKCδ-P38 pathway. © 2009 The British Pharmacological Society.