Pharmacological priming of adipose-derived stem cells promotes myocardial repair.

Adipose-derived stem cells (ADSCs) have myocardial regeneration potential, and transplantation of these cells following myocardial infarction (MI) in animal models leads to modest improvements in cardiac function. We hypothesized that pharmacological priming of pre-transplanted ADSCs would further improve left ventricular functional recovery after MI. We previously identified a compound from a family of 3,5-disubstituted isoxazoles, ISX1, capable of activating an Nkx2-5-driven promoter construct. Here, using ADSCs, we found that ISX1 (20 mM, 4 days) triggered a robust, dose-dependent, fourfold increase in Nkx2-5 expression, an early marker of cardiac myocyte differentiation and increased ADSC viability in vitro. Co-culturing neonatal cardiomyocytes with ISX1-treated ADSCs increased early and late cardiac gene expression. Whereas ISX1 promoted ADSC differentiation toward a cardiogenic lineage, it did not elicit their complete differentiation or their differentiation into mature adipocytes, osteoblasts, or chondrocytes, suggesting that re-programming is cardiomyocyte specific. Cardiac transplantation of ADSCs improved left ventricular functional recovery following MI, a response which was significantly augmented by transplantation of ISX1- pretreated cells. Moreover, ISX1-treated and transplanted ADSCs engrafted and were detectable in the myocardium 3 weeks following MI, albeit at relatively small numbers. ISX1 treatment increased histone acetyltransferase (HAT) activity in ADSCs, which was associated with histone 3 and histone 4 acetylation. Finally, hearts transplanted with ISX1-treated ADSCs manifested significant increases in neovascularization, which may account for the improved cardiac function. These findings suggest that a strategy of drug-facilitated initiation of myocyte differentiation enhances exogenously transplanted ADSC persistence in vivo, and consequent tissue neovascularization, to improve cardiac function.

Regulation of autophagy by cytosolic acetyl-coenzyme A.

Acetyl-coenzyme A (AcCoA) is a major integrator of the nutritional status at the crossroads of fat, sugar, and protein catabolism. Here we show that nutrient starvation causes rapid depletion of AcCoA. AcCoA depletion entailed the commensurate reduction in the overall acetylation of cytoplasmic proteins, as well as the induction of autophagy, a homeostatic process of self-digestion. Multiple distinct manipulations designed to increase or reduce cytosolic AcCoA led to the suppression or induction of autophagy, respectively, both in cultured human cells and in mice. Moreover, maintenance of high AcCoA levels inhibited maladaptive autophagy in a model of cardiac pressure overload. Depletion of AcCoA reduced the activity of the acetyltransferase EP300, and EP300 was required for the suppression of autophagy by high AcCoA levels. Altogether, our results indicate that cytosolic AcCoA functions as a central metabolic regulator of autophagy, thus delineating AcCoA-centered pharmacological strategies that allow for the therapeutic manipulation of autophagy.

Histone deacetylase inhibition blunts ischemia/reperfusion injury by inducing cardiomyocyte autophagy.

BACKGROUND: Reperfusion accounts for a substantial fraction of the myocardial injury occurring with ischemic heart disease. Yet, no standard therapies are available targeting reperfusion injury. Here, we tested the hypothesis that suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor approved for cancer treatment by the US Food and Drug Administration, will blunt reperfusion injury. METHODS AND RESULTS: Twenty-one rabbits were randomly assigned to 3 groups: (1) vehicle control, (2) SAHA pretreatment (1 day before and at surgery), and (3) SAHA treatment at the time of reperfusion only. Each arm was subjected to ischemia/reperfusion surgery (30 minutes coronary ligation, 24 hours reperfusion). In addition, cultured neonatal and adult rat ventricular cardiomyocytes were subjected to simulated ischemia/reperfusion to probe mechanism. SAHA reduced infarct size and partially rescued systolic function when administered either before surgery (pretreatment) or solely at the time of reperfusion. SAHA plasma concentrations were similar to those achieved in patients with cancer. In the infarct border zone, SAHA increased autophagic flux, assayed in both rabbit myocardium and in mice harboring an RFP-GFP-LC3 transgene. In cultured myocytes subjected to simulated ischemia/reperfusion, SAHA pretreatment reduced cell death by 40%. This reduction in cell death correlated with increased autophagic activity in SAHA-treated cells. RNAi-mediated knockdown of ATG7 and ATG5, essential autophagy proteins, abolished SAHA's cardioprotective effects. CONCLUSIONS: The US Food and Drug Administration-approved anticancer histone deacetylase inhibitor, SAHA, reduces myocardial infarct size in a large animal model, even when delivered in the clinically relevant context of reperfusion. The cardioprotective effects of SAHA during ischemia/reperfusion occur, at least in part, through the induction of autophagic flux.