Abstract
Sunitinib (SUN) is a multi-targeted tyrosine kinase inhibitor used for the treatment of gastrointestinal stromal tumors and renal cell carcinoma. Cardiotoxicity has been reported as a significant side effect associated with the SUN treatment, yet the mechanism is poorly understood. The main purpose of this study was to investigate the potential effects of SUN on cardiac hypertrophic genes and the role of mitogen-activated protein kinases (MAPKs) signaling pathway in rat cardiomyocyte H9c2 cell line. In the present study, real-time quantitative polymerase chain reaction showed that the treatment of H9c2 cells with increasing concentrations of SUN (0, 1, 2.5, and 5 A mu M) significantly induced hypertrophic gene markers, such as brain natriuretic peptides (BNP) and myosin heavy chain (beta-MHC and alpha-MHC) in concentration- and time-dependent manners. The onset of mRNA induction was observed as early as 9 h and remained elevated for at least 18 h after treatment with SUN 5 A mu M. At the protein level, Western blot analysis showed that SUN increased BNP and beta-MHC, while it inhibited alpha-MHC protein levels in a concentration-dependent manner. These SUN-mediated effects were associated with increase in cell size and hypertrophy by approximately 70 % at the highest concentration, 5 A mu M. Importantly, inhibition of the MAPK signaling pathway using SB203580 (p38 MAPK inhibitor), U0126 (extracellular signal-regulated kinase inhibitor), and SP600125 (c-Jun NH2-terminal kinase inhibitor) significantly potentiated the SUN-induced BNP and beta-MHC mRNA levels, but did alter the alpha-MHC level. Whereas at the protein level, MAPK inhibitors generally decreased the SUN-induced BNP, whereas only SB and U0 increased beta-MHC protein levels with no effect on alpha-MHC, which were associated with a significant decrease in cell size. Together, these results indicate that SUN induced hypertrophic gene expression through MAPK-dependent mechanisms.