HDAC inhibitors are under clinical development for the treatment of hypertrophic cardiomyopathy and heart failure although the mechanisms of protection are incompletely understood. Micro-RNA 126, an endothelium-specific miR has been assigned essential developmental roles in the heart by activating survival kinases ERK1/2 and Akt and increasing pro-angiogenic signaling. Here we provide the first evidence that hypoxia and HDAC inhibitors selectively and synergistically stimulate expression of miR-126 in cardiac myocytes. MiR-126 expression was increased 1.7-fold (p < 0.05) after 1 h of hypoxic exposure and this was further enhanced to 3.0-fold (p < 0.01) by simultaneously blocking HDAC with the pan-HDAC inhibitor Tricostatin A (TSA). TSA alone did not increase miR-126. In parallel, hypoxia and TSA synergistically increased p-ERK and p-Akt without effecting VEGF-A level. Knockdown of miR-126 with si-RNA eliminated inductions of p-ERK and p-Akt by hypoxia, whereas miR-126 overexpression mimicked hypoxia and amplified p-ERK and p-Akt in parallel with miR-126. The results suggest that miR-126 is a hypoxia-inducible target of HAT/HDAC and its activation in cardiac myocytes may contribute to cardioprotection by activating cell survival and pro-angiogenic pathways selectively during ischemia. (C) 2012 Elsevier Inc. All rights reserved.