Abstract P348: High Glucose Induces Smad Activation via the Transcriptional Coregulator P300 and Contributes to Cardiac Fibrosis and Hypertrophy
Background: Despite advances in the treatment of heart failure (HF), the mortality remains high, particularly in those individuals with diabetes mellitus. Activated transforming growth factor beta (TGF-ß) contributes to the pathogenesis of diabetic cardiomyopathy. We hypothesized that the transcriptional co-activator p300 regulates glucose induced activation of TGF-ß via acetylation of a specific Lysine residue (Lys19) in the Mad homology 1 domain of Smad 2, and that by inhibiting p300, TGF-ß activity will be reduced and heart failure ameliorated/prevented.
Methods: p300 activity and Smad acetylation in normal glucose (5.6 mmol/L - NG) and high glucose (25 mmol/L - HG) media were assessed in H9c2 rat cardiomyoblasts. [H]3 proline incorporation was assessed in cardiac fibroblasts as a marker of collagen synthesis. The role of increased p300 activity was assessed in vitro by using a known p300 inhibitor, curcumin or siRNA directed at p300 and in vivo in a hemodynamically validated model of diabetic cardiomyopathy, the (mRen)2-27 transgenic rat.
Results: H9c2 cells exposed to HG demonstrated increased p300 activity c/w NG media, that was reduced by p300 inhibition using curcumin or p300 siRNA (all p<0.01). Increased p300 activity in HG media increased [H]3 proline incorporation (p<0.05). This effect was attenuated by treatment with curcumin/p300 siRNA (p<0.01). Finally, H9c2 cells were stimulated, extracted protein was immunoprecipitated with Smad2, and lys19 acetylation assessed. Acetylation of the Lys19 was reduced in cells pre-incubated with the p300 inhibitor (p<0.05). To determine the functional significance of p300 inhibition, diabetic Ren-2 rats were randomised to receive either curcumin/vehicle for 6 weeks. Curcumin treated diabetic rats had reduced cardiac hypertrophy and improved chamber compliance when c/w untreated diabetic counterparts (all p<0.01).
Conclusions: These findings demonstrate that high glucose increases activity of the transcriptional coregulator p300, acetylating Smad2 and promoting cardiac fibrosis and hypertrophy. Inhibition of p300 reduces cardiac hypertrophy and results in improved diastolic function. Modulation of the p300 may be a novel strategy to treat diabetes induced heart failure.
- © 2011 by American Heart Association, Inc.