Background: Cardiac reperfusion injury can have devastating consequences.
Histone deacetylase (HDAC) inhibitors are potent cytoprotective agents, but their role in
the prevention of cardiac injury remains ill-defined.
Objective: We sought to determine the therapeutic potential of HDAC inhibitors in an in
vitro model of cardiomyocyte hypoxia-reoxygenation (H/R).
Method: H9c2 cardiomyocytes were subjected to H/R and treated with various classspecific
and pan-HDAC inhibitors in equal concentrations (5µM). Biological activity of
inhibitors was determined, as a proxy for concentration adequacy, by Western blot for
acetylated histone H3 and α-tubulin. Cell viability and cytotoxicity were measured by
methyl thiazolyl tetrazolium and lactate dehydrogenase assays, respectively.
Mechanistic studies were performed to better define the effects of the most effective
agent, Tubastatin-A (Tub-A), on the phosphoinositide 3-kinase (PI3K)/mammalian target
of rapamycin (mTOR) pathway effectors, and on the degree of autophagy.
Results: All inhibitors acetylated well-known target proteins (histone H3 and α-tubulin),
suggesting that concentrations were adequate to induce a biological effect. Improved
cell viability and decreased cell cytotoxicity were noted in cardiomyocytes exposed to
Tub-A, whereas the cytoprotective effects of other HDAC inhibitors were inconsistent.
Pro-survival mediators in the PI3K/mTOR pathway were up-regulated and the degree of
autophagy was significantly attenuated in cells that were treated with Tub-A.
Conclusion: HDAC inhibitors improve cell viability in a model of cardiomyocyte H/R,
with Class IIb inhibition (Tub-A) demonstrating superior cellular-level potency and
effectiveness. This effect is, at least in part, related to an increased expression of prosurvival
mediators and a decreased degree of autophagy.