Abstract 21116: Adenosine Kinase Regulation of Cardiomyocyte Hypertrophy
A deficiency in adenosine production(CD73 KO mice) exacerabates cardiac hypertrophy and heart failure in response to systolic overload(transverse aortic constriction; TAC), but genetic disruption of A1 or A3 receptors does not, suggesting additional non-receptor dependent mechanisms by which adenosine attenuates hypertrophy. Here we investigated the role of adenosine receptors and adenosine metabolism in attenuation of cardiomyocyte hypertrophy at the cellular level. In neonatal cardiomyocytes, 5 μM 2-chloroadenosine(CADO; adenosine deaminase resistant adenosine analogue) or 10 μM Adenosine attenuated phenylephrine induced increases in cell surface area, protein synthesis, and ANF expression. Antagonism of adenosine receptors partially blocked the reduction of ANF expression by CADO, but did not restore cell size or protein synthesis. We hypothesized that adenosine uptake/metabolism may contribute to attenuation of hypertrophy. In support of a role for intracellular adenosine metabolism in regulating hypertrophy, Adenosine Kinase(AK) inhibitors Iodotubercidin(ITU) and ABT-702 completely reversed attenuation of cell size, protein synthesis and expression of ANF by CADO or ADO. RNAi depletion of AK in cardiomyocytes also promoted hypertrophy, ANF expression, and insensitivity to CADO. Examination of phenylephrine induced phospho-signaling pathways revealed that CADO had little effect on AKTSer473 phosphorylation, but did reduce sustained phosphorylation of RafSer338, mTORSer2448, and p70S6kThr389 (sites associated with activation). Inhibition of AK completely reversed inhibition of these pathways by CADO. Using dominant negative Raf adenovirus, we found that Raf is necessary for phenylephrine to activate mTOR/p70S6k and hypertrophy. In the presence of constitutively active Raf however, CADO still inhibited mTOR/p70S6k and hypertrophy without reducing phosphorylation of ERKThr204/Tyr202 or AKTSer473. Again, reduction of mTOR/p70S6k signaling by CADO was dependent upon adenosine kinase. Together, these results identify adenosine kinase as an important mediator of adenosine attenuation of cardiomyocyte hypertrophy which acts, in part, through inhibition of RAF signaling to mTOR/p70S6k(mTORC1).
- © 2010 by American Heart Association, Inc.