Background-Recent work has demonstrated the importance of chromatin remodeling, especially histone acetylation, in the control of gene expression in the heart. In cell culture models of cardiac hypertrophy, pharmacological suppression of histone deacetylases (HDACs) can either blunt or amplify cell growth. Thus, HDAC inhibitors hold promise as potential therapeutic agents in hypertrophic heart disease. Methods and Results-In the present investigation, we studied 2 broad-spectrum HDAC inhibitors in a physiologically relevant banding model of hypertrophy, observing dose-responsive suppression of ventricular growth that was well tolerated in terms of both clinical outcome and cardiac performance measures. In both short-term (3-week) and long-term (9-week) trials, cardiomyocyte growth was blocked by HDAC inhibition, with no evidence of cell death or apoptosis. Fibrotic change was diminished in hearts treated with HDAC inhibitors, and collagen synthesis in isolated cardiac fibroblasts was blocked. Preservation of systolic function in the setting of blunted hypertrophic growth was documented by echocardiography and by invasive pressure measurements. The hypertrophy-associated switch of adult and fetal isoforms of myosin heavy chain expression was attenuated, which likely contributed to the observed preservation of systolic function in HDAC inhibitor-treated hearts. Conclusions-Together, these data suggest that HDAC inhibition is a viable therapeutic strategy that holds promise in the treatment of load-induced heart disease.

Background-Cellular hypertrophy requires coordinated regulation of progrowth and antigrowth mechanisms. In cultured neonatal cardiomyocytes, Foxo transcription factors trigger an atrophy-related gene program that counters hypertrophic growth. However, downstream molecular events are not yet well defined. Methods and Results-Here, we report that expression of either Foxo1 or Foxo3 in cardiomyocytes attenuates calcineurin phosphatase activity and inhibits agonist-induced hypertrophic growth. Consistent with these results, Foxo proteins decrease calcineurin phosphatase activity and repress both basal and hypertrophic agonist-induced expression of MCIP1.4, a direct downstream target of the calcineurin/NFAT pathway. Furthermore, hearts from Foxo3-null mice exhibit increased MCIP1.4 abundance and a hypertrophic phenotype with normal systolic function at baseline. Together, these results suggest that Foxo proteins repress cardiac growth at least in part through inhibition of the calcineurin/NFAT pathway. Given that hypertrophic growth of the heart occurs in multiple contexts, our findings also suggest that certain hypertrophic signals are capable of overriding the antigrowth program induced by Foxo. Consistent with this, multiple hypertrophic agonists triggered inactivation of Foxo proteins in cardiomyocytes through a mechanism requiring the PI3K/Akt pathway. In addition, both Foxo1 and Foxo3 are phosphorylated and consequently inactivated in hearts undergoing hypertrophic growth induced by hemodynamic stress. Key Words: angiotensin Ⅲ calcineurin Ⅲ hypertrophy I n response to stress from neurohumoral activation, hypertension, or other myocardial injury, the heart initially compensates with an adaptive hypertrophic increase in mass. The resulting growth and remodeling response alters the balance between protein synthesis and protein degradation. In skeletal muscle, activation of progrowth signaling pathways is accompanied by deactivation of pathways that promote proteolysis. Prominent among the atrophy-inducing pathways are those governed by Forkhead box transcription factors, O subfamily (Foxo). Conclusions-This Clinical Perspective p 1168Foxo transcription factors regulate key physiological functions, including responses to stress, cell-cycle progression, protein degradation, and apoptosis. 1,2 There are 4 mammalian Foxo genes: Foxo1 (FKHR), Foxo3 (FKHRL1), Foxo4 (AFX), and Foxo6. The transcriptional activities of Foxo proteins are governed by posttranslational modifications such as phosphorylation and acetylation. With respect to myocyte growth and remodeling, Foxo proteins induce ubiquitin ligases and promote proteolysis in skeletal muscle. 3,4 In heart, a number of signaling cascades involving transcription factors, kinases, and G-protein-coupled receptors are implicated in the regulation of muscle growth (see reviews 5-7 ). Among these, the calcineurin/nuclear factor of activated T cells (NFAT) pathway has been shown to be a key signaling cascade that promotes cardiac hypertrophy. 8 It has been reported recently...

Mitogen-activated protein (MAP) kinases have been implicated in hemodynamic load induced heart failure. Both angiotensin II (Ang II) and mechanical stretch activate MAP kinases in cardiac myocytes. In this study, we used a neonatal rat ventricular myocyte (NRVM) model to determine the role of focal-adhesion kinase (FAK) in β 1 integrin mediated MAP kinase activation in response to mechanical stretch in presence and absence of Ang II receptor blockade (ATB). NRVM plated on deformable membranes coated with collagen IV were exposed to 20% equiaxial static-stretch. β 1 integrin signaling was blocked by adenovirus-mediated expression of a dominant-negative form of β 1D integrin (tac-β 1D ). FAK signaling was disrupted by infecting NRVM with adenovirus expressing FAK-related non-kinase (FRNK). Western blot analysis was used to assess the phosphorylation of MAP kinases. In the presence and absence of ATB, mechanical stretch caused maximal phosphorylation of ERK, p38 and JNK at 5 min, which was significantly attenuated in NRVM expressing tac-β 1D . In the presence of ATB, FRNK overexpression significantly increased basal phosphorylation of ERK (40.2 ± 8.6% p<0.05), p38 (39.5 ± 11.7%, P<0.05), JNK (86 ± 29.4%, P<0.05) and stretch-induced p38 (48.1 ± 8.7%, P<0.05) and JNK (85.0 ± 19.4%, P<0.05) phosphorylation. However, in the absence of ATB, FRNK overexpression significantly reduced basal and stretch-induced phosphorylation of only ERK. Examination of FAK activation revealed that β 1 integrin was required for stretch-induced phosphorylation of FAK at Y 397 and Y 925 , but not Y 861 . In summary, mechanical stretch-activated ERK1/2, p38 and JNK through FAK independent and dependent mechanisms. β 1 integrin was required for FAK independent activation of all three MAP kinases, whereas cross-talk between β 1 integrin and Ang II receptors mediated FAK dependent regulation of ERK1/2.

Glioblastoma multiforme (GBM), an extremely invasive and high-grade (grade IV) glioma, is the most common and aggressive form of brain cancer. It has a poor prognosis, with a median overall survival of only 11 months in the general GBM population and 14.6 to 21 months in clinical trial participants with standard GBM therapies, including maximum safe craniotomy, adjuvant radiation, and chemotherapies. Therefore, new approaches for developing effective treatments, such as a tool for assessing tumor cell drug response before drug treatments are administered, are urgently needed to improve patient survival. To address this issue, we developed an improved brain cancer chip with a diffusion prevention mechanism that blocks drugs crossing from one channel to another. In the current study, we demonstrate that the chip has the ability to culture 3D spheroids from patient tumor specimen-derived GBM cells obtained from three GBM patients. Two clinical drugs used to treat GBM, temozolomide (TMZ) and bevacizumab (Avastin, BEV), were applied and a range of relative concentrations was generated by the microfluidic channels in the brain cancer chip. The results showed that TMZ works more effectively when used in combination with BEV compared to TMZ alone. We believe that this low-cost brain cancer chip could be further developed to generate optimal combination of chemotherapy drugs tailored to individual GBM patients.