HDAC11 Deacetylates BRAF to Regulate Kinase Activity and Cell Proliferation.

Combination Of Selective HDAC Inhibitors That Target Specific HDAC Isoforms Synergistically Inhibits T Cell Lymphoma

Histone deacetylase 8 (HDAC8) and its inhibitors with selectivity to other isoforms: An overview

HDAC Inhibitors As Potential New Agents Improving the Efficacy of Monoclonal Antibodies

Lithium is an effective mood stabilizer that has been clinically used to treat bipolar disorder for several decades. Recent studies have suggested that lithium possesses robust neuroprotective and anti-tumor properties. Thus far, a large number of lithium targets have been discovered. Here, we report for the first time that HDAC1 is a target of lithium. Lithium significantly down-regulated HDAC1 at the translational level by targeting HDAC1 mRNA. We also showed that depletion of HDAC1 is essential for the neuroprotective effects of lithium and for the lithium-mediated degradation of mutant huntingtin through the autophagic pathway. Our studies explain the multiple functions of lithium and reveal a novel mechanism for the function of lithium in neurodegeneration.

Multiple myeloma (MM) is a neoplastic proliferation of plasma cells and remains an incurable disease because of the development of drug resistance. Histone deacytylase (HDAC) inhibitors are a new class of chemotherapeutic reagents that cause growth arrest and apoptosis of neoplastic cells. Depsipeptide, a new member of the HDAC inhibitors, was found to be safe in humans and has been shown to induce apoptosis in various cancers. In order to evaluate the effects of depsipeptide, a MM cell line, U266 [interleukin (IL)-6 dependent], was analysed for viability and apoptosis. The combined effect of depsipeptide with melphalan and changes in BCL-2 family proteins (BCL-2, BCL-XL, BAX and MCL-1) were also investigated. In addition, the RPMI 8226 cell line (IL-6 independent), and primary patient myeloma cells were also analysed for apoptosis after depsipeptide treatment. Depsipeptide induced apoptosis in both U266 and RPMI 8226 cell lines in a time- and dose-dependent fashion, and in primary patient myeloma cells. We also demonstrated that depsipeptide had an additive effect with melphalan (10 micromol/l). BCL-2, BCL-XL and MCL-1 showed decreased expression in depsipeptide-treated samples. Based on recent clinical trials demonstrating minimal clinical toxicity, our study supports the future clinical utilization of depsipeptide in the management of MM.

BackgroundHistone acetylation is an epigenetic modification involved in the regulation of gene expression, balanced by histone acetyl transferases and histone deacetylase (HDAC) enzymes. HDAC inhibitors (HDACi) induce growth arrest and cell death in transformed cells, and are currently in many clinical cancer trials. The transcriptional response to HDACi is complex, as is the response to HDAC isoform knockdown (KD). Here, we describe for the first time in a human cancer cell line, a transcriptional comparison of treatment by two structurally unrelated HDACi; belinostat and valproic acid with the KD of HDAC1, 2 and 3 isoforms.ResultsHDAC KD showed anti-proliferative effects, although to a lesser extent than HDACi treatment. Moreover, we found a 2-fold increased resistance of HDAC1 knockdown cells to belinostat, suggesting this isoenzyme as a selective target. While both HDACi treatment and individual class I HDAC KD produce significant transcriptional effects, three-times higher for HDACi, the gene-expression profiles of class I HDAC KD compared with that obtained by HDACi treatment exhibited less than 4% of altered genes in common between the two modes of inhibition. Further, cell-specific effects of HDAC KD are evident by comparison with a recent study in a different cell line.ConclusionThe increased resistance to belinostat in response to HDAC1 depletion indicates the possibility of using this isoform as a predictive biomarker of response to HDACi treatment. Further, the transcriptional response to chemical inhibition of HDACs is very different from that of KD of individual class I HDAC isoforms. These data suggest that the anti-tumor effect of HDACi is indeed linked to class I inhibition, but may be more complex than simply targeting individual HDAC enzymes.

Aberrant Histone Deacetylase2–Mediated Histone Modifications and Synaptic Plasticity in the Amygdala Predisposes to Anxiety and Alcoholism

Ischemia-induced retinopathy is a hallmark finding of common visual disorders including diabetic retinopathy (DR) and central retinal artery and vein occlusions. Treatments for ischemic retinopathies fail to improve clinical outcomes and the design of new therapies will depend on understanding the underlying disease mechanisms. Histone deacetylases (HDACs) are an enzyme class that removes acetyl groups from histone and non-histone proteins, thereby regulating gene expression and protein function. HDACs have been implicated in retinal neurovascular injury in preclinical studies in which nonspecific HDAC inhibitors mitigated retinal injury. Histone deacetylase 3 (HDAC3) is a class I histone deacetylase isoform that plays a central role in the macrophage inflammatory response. We recently reported that myeloid cells upregulate HDAC3 in a mouse model of retinal ischemia-reperfusion (IR) injury. However, whether this cellular event is an essential contributor to retinal IR injury is unknown. In this study, we explored the role of myeloid HDAC3 in ischemia-induced retinal neurovascular injury by subjecting myeloid-specific HDAC3 knockout (M-HDAC3 KO) and floxed control mice to retinal IR. The M-HDAC3 KO mice were protected from retinal IR injury as shown by the preservation of inner retinal neurons, vascular integrity, and retinal thickness. Electroretinography confirmed that this neurovascular protection translated to improved retinal function. The retinas of M-HDAC3 KO mice also showed less proliferation and infiltration of myeloid cells after injury. Interestingly, myeloid cells lacking HDAC3 more avidly engulfed apoptotic cells in vitro and after retinal IR injury in vivo compared to wild-type myeloid cells, suggesting that HDAC3 hinders the reparative phagocytosis of dead cells, a process known as efferocytosis. Further mechanistic studies indicated that although HDAC3 KO macrophages upregulate the reparative enzyme arginase 1 (A1) that enhances efferocytosis, the inhibitory effect of HDAC3 on efferocytosis is not solely dependent on A1. Finally, treatment of wild-type mice with the HDAC3 inhibitor RGFP966 ameliorated the retinal neurodegeneration and thinning caused by IR injury. Collectively, our data show that HDAC3 deletion enhances macrophage-mediated efferocytosis and protects against retinal IR injury, suggesting that inhibiting myeloid HDAC3 holds promise as a novel therapeutic strategy for preserving retinal integrity after ischemic insult.

ObjectiveTo investigate the relationship between cisplatin resistance and histone deacetylase (HDAC) isoform overexpression in ovarian cancer cell lines.MethodsExpression of four HDAC isoforms (HDAC 1, 2, 3, and 4) in two ovarian cancer cell lines, SKOV3 and OVCAR3, exposed to various concentrations of cisplatin was examined by western blot analyses. Cells were transfected with plasmid DNA of each HDAC. The overexpression of protein and mRNA of each HDAC was confirmed by western blot and reverse transcriptase-polymerase chain reaction analyses, respectively. The cell viability of the SKOV3 and OVCAR3 cells transfected with HDAC plasmid DNA was measured using the cell counting kit-8 assay after treatment with cisplatin.ResultsThe 50% inhibitory concentration of the SKOV3 and OVCAR3 cells can be determined 15-24 hours after treatment with 15 µg/mL cisplatin. The expression level of acetylated histone 3 protein in SKOV3 cells increased after exposure to cisplatin. Compared with control cells at 24 hours after cisplatin exposure, the viability of SKOV3 cells overexpressing HDAC 1 and 3 increased by 15% and 13% (p<0.05), respectively. On the other hand, OVCAR3 cells that overexpressed HDAC 2 and 4 exhibited increased cell viability by 23% and 20% (p<0.05), respectively, compared with control cells 24 hours after exposure to cisplatin.ConclusionIn SKOV3 and OVCAR3 epithelial ovarian cancer cell lines, the correlation between HDAC overexpression and cisplatin resistance was confirmed. However, the specific HDAC isoform associated with resistance to cisplatin varied depending on the ovarian cancer cell line. These results may suggest that each HDAC isoform conveys cisplatin resistance via different mechanisms.

It is well known that atherosclerosis and restenosis are common cardiovascular diseases and major health care problems. Vascular remodeling and migration and proliferation of vascular smooth muscle cells (VSMCs) are key features of these pathologies. There has been enormous progress in drug development and clinical management of these disorders, with angioplasty and drug eluting stents being standard procedures to treat vascular obstruction. However, despite their benefits, these current treatment modalities are not always efficacious. Furthermore, they can also be associated with postoperative complications and graft failures, some of which can be life threatening. Evaluation of newer mechanisms involved in VSMC proliferation aimed at uncovering additional therapeutic approaches to curb VSMC dysfunction in cardiovascular diseases is clearly warranted. See accompanying article on page 851 Accumulating evidence suggests that several common diseases, including cardiovascular disorders, diabetes, and the vascular complications of diabetes, are governed by a combination of genetic and environmental factors and that epigenetic mechanisms, such as DNA methylation and histone modifications in chromatin, form a key link between them.1–3 Epigenetics is the added layer of gene regulation that occurs in chromatin without changes in the actual underlying DNA sequence and plays a major role in dictating cell-specific gene expression patterns and transcriptional outcomes.4,5 Along with DNA methylation, key posttranslational modifications of histone N-terminal tails can alter chromatin structure to form an added layer of gene regulation and modulate gene transcription.5 Therefore, gene transcription depends on chromatin structure, which is very dynamic, depending on a multitude of histone posttranslational modifications that allow for the conversion of inaccessible, compact, or …

Short-term and longitudinal studies have shown that endurance exercise training extends life expectancy and reduces risk for many chronic disorders, including obesity, insulin resistance and type 2 diabetes (Hawley, 2004). Endurance exercise training orchestrates numerous morphological and metabolic adaptations in skeletal muscle, including mitochondrial biogenesis and an enhanced capacity to oxidize glucose and fats (Hawley, 2004). We have previously utilized global transcriptome expression technologies such as oligonucleotide arrays, targeted gene expression analysis, etc., to demonstrate that these changes are the culmination of transcriptional adaptations induced with individual acute bouts of endurance exercise (Mahoney et al. 2005). What has received less attention is how alterations in exercise-mediated DNA transcription are a function of post-translational modifications of histone proteins, which regulate transcriptional repression and/or initiation via chromatin remodelling. Acetylation of histone 3, one of the four types of histones important for genomic DNA packaging, at lysine residues 9, 14 and 36 (H3K9/14/36) is associated with transcription initiation and elongation. Histone acetylation is modulated by histone acetyltransferase (HAT) and histone deacetylase (HDAC) activity, which in turn can be regulated by post-translational modifications such as phosphorylation, ubiquitination-mediated proteosomal degradation, sumolation, etc. Potthoff and colleagues (2007) have illustrated that over-expression of HDAC5 is negatively correlated with endurance training-mediated adaptations in mouse skeletal muscle. It remains unknown how histone acetylation and HDAC activity are modulated in response to an acute bout of exercise in humans. McGee et al. (2009), in a recent article in The Journal of Physiology, sought to address this issue by examining the effects of an acute bout of exercise on histone 3 modification, in conjunction with analysing the regulation of class IIa HDAC enzymes (McGee et al. 2009). McGee and colleagues subjected young men to an acute bout of cycling exercise (60 min at ∼75%) (McGee et al. 2009). Muscle biopsies were obtained from the vastus lateralis muscle before and immediately after the exercise bout. Western blot analysis was carried out on nuclear and whole muscle extracts to access the global histone 3 acetylation and class IIa HDACs (isoforms 4, 5, 7 and 9) protein content in response to an acute bout of exercise. Real-time PCR was used to measure the mRNA content of the HDAC isoforms immediately post-exercise. The authors also measured global HDAC activity and immunoprecipitated ubiquitinated HDACs as a marker of HDAC targeted for proteasomal degradation. Lastly, phosphorylation-mediated activation of class IIa HDAC kinases, AMPK, PKD and CaMKII, were measured in whole muscle extracts.

BackgroundEnhanced activity of histone deacetylases (HDAC) is associated with more aggressive tumour behaviour and tumour progression in various solid tumours. The over-expression of these proteins and their known functions in malignant neoplasms has led to the development of HDAC inhibitors (HDI) as new anti-neoplastic drugs. However, little is known about HDAC expression in renal cell cancer.MethodsWe investigated the expression of HDAC 1, 2 and 3 in 106 renal cell carcinomas and corresponding normal renal tissue by immunohistochemistry on tissue micro arrays and correlated expression data with clinico-pathological parameters including patient survival.ResultsAlmost 60% of renal cell carcinomas expressed the HDAC isoforms 1 and 2. In contrast, HDAC 3 was only detected in 13% of all renal tumours, with particular low expression rates in the clear cell subtype. HDAC 3 was significantly higher expressed in pT1/2 tumours in comparison to pT3/4 tumours. Expression of class I HDAC isoforms correlated with each other and with the proliferative activity of the tumours. We found no prognostic value of the expression of any of the HDAC isoforms in this tumour entity.ConclusionClass I HDAC isoforms 1 and 2 are highly expressed in renal cell cancer, while HDAC 3 shows low, histology dependent expression rates. These unexpected differences in the expression patterns suggests alternative regulatory mechanisms of class I HDACs in renal cell cancer and should be taken into account when trials with isoform selective HDI are being planned. Whether HDAC expression in renal cancers is predictive of responsiveness for HDI will have to be tested in further studies.

Epigenetic regulation of gene expression is mediated by DNA methylation as well as by modification of nucleosome structure and cofactor recruitment through histone modifications. Specific methylation and acetylation of histone lysine residues, which comprise the so-called histone code, are marks of different chromatin states related to the expression of neighboring genes and the activity of promoters and enhancers. Histone acetylation and methylation, along with their role in regulating transcription has been known since the 1960s. The enzymes that make these modifications can be thought of as chromosome writers, whereas the enzymes that remove these marks can be referred to as chromosome erasers. Another set of proteins sense these marks and alter gene expression, which can be termed chromosome readers. Histone acetylation is performed by members of the histone acetyltransferase gene family, which use acetyl-CoA as a cofactor to modify specific e-amino group of lysine residues on different histone proteins. This modification eliminates lysine’s positive charge and reduces the affinity of the histone for DNA, which can result in a more relaxed chromatin conformation that can facilitate the recruitment of DNA binding effector proteins. Thus, histone acetylation is most often associated with increased transcriptional activity, and in the most extreme case, acetylation of lysine 16 on histone H4 (H4K16ac) is involved in the switch from inactive heterochromatin to euchromatin.1 Histone acetylation is reversible, allowing for environmental and developmental gene regulation, usually repression; and this process is performed by members of the …

In order to determine the contributions of histone deacetylase (HDAC) isoforms to the beneficial effects of dual phosphodiesterase 5 (PDE5) and pan-HDAC inhibitors on in vivo models of Alzheimer's disease (AD), we have designed, synthesized, and tested novel chemical probes with the desired target compound profile of PDE5 and class I HDAC selective inhibitors. Compared to previous hydroxamate-based series, these molecules exhibit longer residence times on HDACs. In this scenario, shorter or longer preincubation times may have a significant impact on the IC50 values of these compounds and therefore on their corresponding selectivity profiles on the different HDAC isoforms. On the other hand, different chemical series have been explored and, as expected, some pairwise comparisons show a clear impact of the scaffold on biological responses (e.g., 35a vs 40a). The lead identification process led to compound 29a, which shows an adequate ADME-Tox profile and in vivo target engagement (histone acetylation and cAMP/cGMP response element-binding (CREB) phosphorylation) in the central nervous system (CNS), suggesting that this compound represents an optimized chemical probe; thus, 29a has been assayed in a mouse model of AD (Tg2576).

HDAC1 Acetylation Is Linked to Progressive Modulation of Steroid Receptor-Induced Gene Transcription