Sphingosine-1-phosphate Ameliorates Cardiac Hypertrophic Response Through Inhibiting The Activity Of Histone Deacetylase-2

Background and Objective: Cardiac hypertrophy is a compensatory change induced by chronic pressure overload, which is one of the common complications of a variety of cardiovascular diseases. Persistent hypertrophy will result in cardiac dysfunction and subsequently heart failure. Previous studies indicate that histone deacetylase 2(HDAC2) plays an important role in the progression of cardiac hypertrophy and inhibition of its activity can blunt the progression. Sphingosine-1-phosphate(S1P) is a small endogenous HDAC2 inhibitor discovered in recent years, which is able to inhibit HDAC2 activity further to regulate gene transcription and can activate S1 P receptors to function in biology extensively. Our study is aimed to investigate the effect and possible mechanisms of S1 P on cardiac hypertrophic response with mice treated with transverse aortic constriction(TAC) and H9c2 cells treated with phenylephrine(PE).Methods: Male C57BL/6 mice(8 weeks old) were randomly divided into three different groups(Sham, TAC and TAC+S1P). After respective treatment, we evaluated cardiac function and hypertrophy by echocardiography, hemodynamic measurements, HW/BW ratios and histological assays(HE and WGA staining) and examined the expression of hypertrophic markers(ANP, BNP and ?-MHC) with western blotting. In cultured H9c2 cells which were assigned into 4 groups(Con, S1 P, PE and PE+S1P), we measured cardiomyocyte size and hypertrophic markers by immunocytofluorescence and western blotting. Meanwhile, we tested the expression and activity of HDAC2 in vivo and in vitro. The expression of H3K9 ac and the downstream anti-hypertrophic factor of HDAC2, KLF4, were also examined by western blotting. In addition, we investigated the expression of S1 PRs in TAC mice and if there be one acting in anti-hypertrophic effect using siRNAs targeting S1 PRs, further to test HDAC2 activity and KLF4 expression under the siRNA targeting the anti-hypertrophic S1 PR.Results:Compared to Sham group, TAC induced cardiac dysfunction and significantly increased heart size, HW/BW ratios and expression of hypertrophic markers. However, treatment of S1 P inhibited these changes. In cultured H9c2 cells, PE increased the size of cardiomyocyte and up-regulated hypertrophic markers expression compared to control group. Corresponding to our mice assays, S1 P treatment suppressed these effects. Additionally, no matter in vivo or in vitro experiments, we found that S1 P had no effect on HDAC2 expression, but significantly inhibited its activity. Compared with hypertrophic group, S1 P treatment increased the expression of H3K9 ac and anti-hypertrophic factor, KLF4. We also found that S1PR1 and S1PR3 were up-regulated while S1PR2 was down-regulated in TAC mice compared to Sham group and S1 P might ameliorate cardiac hypertrophy through S1PR2, which was unrelated to HDAC2.Conclusion: S1 P ameliorates cardiac hypertrophic response through inhibiting HDAC2 activity further to up-regulate KLF4.