Abstract 106: A Novel Small Molecule Protects Against Myocardial Ischemia and Doxorubicin-Induced Cardiomyopathy Through Heat Shock Response and Proteostasis Regulation In Vivo
Background: A potentially new non-cell-based therapy is the systemic delivery of small molecules to revive or protect injured myocardium. By screening a drug library, we identified a novel small molecule, sk421, and tested its effectiveness in two myocardial injury models in vivo: a myocardial infarction model and doxorubicin (DOX)-induced cardiomyopathy model.
Results: Sk421 significantly increased cellular viability of DOX-injured cardiomyocytes by preventing apoptosis in vitro, demonstrated by assays for MTT (p=0.042), annexin-V, and active caspase-3 (p=0.004). Sk421 increased the concentrations of the GATA4 and the heat shock proteins (HSPs) in cardiomyocytes (by 1.5-fold), and fibroblasts (by 1.2-fold), but was unable to rescue DOX-injured fibroblast cells depleted of HSPs. Sk421 maintained the total proteosome by a 3.5-fold inhibition of ubiquitinized GATA4 degradation, as shown by immunoprecipitation assays. Oral administration of sk421(4mg/kg) rescued DOX-injured mice by significantly preserving cardiac function, weight gain, cardiomyocyte lesion size and abundance, and by reducing overall mortality (20% in treated groups) compared to control DOX-injured mice (80% in untreated groups, p<0.03). The levels of GATA4 and HSPs were increased in the sk421-rescued mice. In the MI model, (n=5/group), sk421 reduced myocardial infarct size, and protected heart function evaluated by ejection fraction 45.8 ± 2.4 vs. 34.8 ± 3.3, p=0.005 (day7), and 44.3 ± 2.8 vs. 34.4 ± 4.1, p=0.011 (day28). Sk421 treatment of MI rats resulted in a higher fraction of viable tissue (within the LV (70.20 ± 0.5024, n=3) as compared to only MI group (56.38 ± 3.879%, n=3) and the infiltration of CD68+ cells was found to be more in the infarct region of LV of MI group rats as compared to MI+CEL. Quantitative analysis showed a significantly higher proportion of TUNEL positive cells and mRNA levels of IL-1β, IL-6, TNF-α and MMP2 in the myocardium of MI rats compared to MI+SK421 rats.
Conclusion: This study demonstrates the broad therapeutic benefit of sk421 in animal model of myocardial injury by mechanism of inducing the heat shock response and preserving GATA levels. The ease of oral delivery makes sk421 a potentially clinically useful adjunct for myocardial preservation.
- © 2012 by American Heart Association, Inc.