Epac is required for exogenous and endogenous stimulation of adenosine A2B receptor for inhibition of angiotensin II-induced collagen synthesis and myofibroblast differentiation
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Angiotensin II (Ang II) plays an important role on the pathogenesis of cardiac fibrosis. Prolong and overstimulation of angiotensin II type 1 receptor with Ang II-induced collagen synthesis and myofibroblast differentiation in cardiac fibroblasts, leading to cardiac fibrosis. Although adenosine and its analogues are known to have cardioprotective effects, the mechanistic by which adenosine A2 receptors (A2Rs) inhibit Ang II-induced cardiac fibrosis is not clearly understood. In the present study, we examined the effects of exogenous adenosine and endogenous adenosine on Ang II-induced collagen and myofibroblast differentiation determined by α-smooth muscle action (α-SMA) overexpression and their underlying signal transduction. Elevation of endogenous adenosine levels resulted in the inhibition of Ang II-induced collagen type I and III and α-SMA synthesis in cardiac fibroblasts. Moreover, treatment with exogenous adenosine which selectively stimulated A2Rs also suppressed Ang II-induced collagen synthesis and α-SMA production. These antifibrotic effects of both endogenous and exogenous adenosines are mediated through the A2B receptor (A2BR) subtype. Stimulation of A2BR exhibited antifibrotic effects via the cAMP-dependent and Epac-dependent pathways. Our results provide new mechanistic insights regarding the role for cAMP and Epac on A2BR-mediated antifibrotic effects. Thus, A2BR is one of the potential therapeutic targets against cardiac fibrosis.
KeywordsAdenosine A2B receptor Angiotensin II Cardiac fibrosis Epac cAMP Collagen α-SMA
α-Smooth muscle actin
Adenosine A2 receptor
- Ang II
Cyclic adenosine monophosphate
Exchange protein directly activated by cAMP
Fetal calf serum
Protein kinase A
Myristoylated protein kinase A inhibitor amide 14–22
Small interfering RNA
Transforming growth factor beta
This study is funded by the Thailand Research Fund (TRF) through the Royal Golden Jubilee Ph.D. Program, the Office of the Higher Education Commission, Ministry of Education [Grant PHD/0179/2558] (to S.P.) and TRF Grant [Grant RSA6080061] (to S.M.). This study is part of a Ph.D. thesis of Mahidol University.
Participated in the study planning: S.P. and S.M.
Performed experiments and data analysis: S.P., K.B., and S.M.
Contributed to the discussion and reviewed/edited the manuscript: W.P. and V.H.S.
Wrote the manuscript: S.P. and S.M.
Compliance with ethical standards
Conflicts of interest
Sarawuth Phosri declares that he has no conflict of interest.
Kwanchai Bunrukchai declares that he has no conflict of interest.
Warisara Parichatikanond declares that she has no conflict of interest.
Vilasinee H. Sato declares that she has no conflict of interest.
Supachoke Mangmool declares that he has no conflict of interest.
This study was approved by the Institutional Animal Care and Use Committee of the Faculty of Pharmacy, Mahidol University (Protocol Nos. PYR005/2557 and PYR002/2560).
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