Stimulation of adenosine A(2B) receptors induces interleukin-6 secretion in cardiac fibroblasts via the PKC-delta-P38 signalling pathway.
OBJECTIVE
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).


METHODS
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-delta (PKC-delta) were determined by Western blot analysis.


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-delta 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-delta functioned as an upstream regulator of p38 MAPK in this process.


CONCLUSIONS
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 PKCdelta-P38 pathway.
Feng
Wei
W
Institute of Vascular Medicine, Peking University Third Hospital, Ministry of Education, Beijing, China.
Song
Yao
Y
Chen
Chao
C
Lu
Zhi Zhen
ZZ
Zhang
Youyi
Y
D058908:Adenosine A2 Receptor Agonists; D019830:Adenosine-5'-(N-ethylcarboxamide) / Q000494:pharmacology*; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D017931:DNA Primers; D004797:Enzyme-Linked Immunosorbent Assay; D005347:Fibroblasts / Q000201:enzymology / Q000378:metabolism; D007093:Imidazoles / Q000494:pharmacology; D015850:Interleukin-6 / Q000378:metabolism*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008856:Microscopy, Fluorescence; D009206:Myocardium / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D041681:NIH 3T3 Cells; D010766:Phosphorylation; D051745:Protein Kinase C-delta / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D058908:Adenosine A2 Receptor Agonists; D017931:DNA Primers; D007093:Imidazoles; D015850:Interleukin-6; D011725:Pyridines; D019830:Adenosine-5'-(N-ethylcarboxamide); D051745:Protein Kinase C-delta; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580