Curcumin, a novel p300/CREB-binding protein-specific inhibitor of acetyltransferase, represses the acetylation of histone/nonhistone proteins and histone acetyltransferase-dependent chromatin transcription

Epigenetic treatment of pancreatic cancer: is there a therapeutic perspective on the horizon?

Pancreatic ductal adenocarcinoma (PDAC) constitutes one of the most aggressive malignancies with a 5-year survival rate of <7%. Due to growing incidence, late diagnosis and insufficient treatment options, PDAC is predicted to soon become one of the leading causes of cancer-related death. Although intensified cytostatic combinations, particularly gemcitabine plus nab-paclitaxel and the folinic acid, fluorouracil, irinotecan, oxaliplatin (FOLFIRINOX) protocol, provide some improvement in efficacy and survival compared with gemcitabine alone, a breakthrough in the treatment of metastatic pancreatic cancer remains out of sight. Nevertheless, recent translational research activities propose that either modulation of the immune response or pharmacological targeting of epigenetic modifications alone, or in combination with chemotherapy, might open highly powerful therapeutic avenues in GI cancer entities, including pancreatic cancer. Deregulation of key epigenetic factors and chromatin-modifying proteins, particularly those responsible for the addition, removal or recognition of post-translational histone modifications, are frequently found in human pancreatic cancer and hence constitute particularly exciting treatment opportunities. This review summarises both current clinical trial activities and discovery programmes initiated throughout the biopharma landscape, and critically discusses the chances, hurdles and limitations of epigenetic-based therapy in future PDAC treatment.

Histone deacetylase and acetyltransferase inhibitors modulate behavioral responses to social stress

Histone acetylation has emerged as a critical factor regulating learning and memory both during and after exposure to stressful stimuli. There are drugs that we now know affect histone acetylation that are already in use in clinical populations. The current study uses these drugs to examine the consequences of acutely increasing or decreasing histone acetylation during exposure to social stress. Using an acute model of social defeat in Syrian hamsters, we systemically and site-specifically administered drugs that alter histone acetylation and measured subsequent behavior and immediate-early gene activity. We found that systemic administration of a histone deacetylase inhibitor enhances social stress-induced behavioral responses in males and females. We also found that systemic administration completely blocks defeat-induced neuronal activation, as measured by Fos-immunoreactivity, in the infralimbic cortex, but not in the amygdala, after a mild social defeat stressor. Lastly, we demonstrated that site-specific administration of histone deacetylase inhibitors in the infralimbic region of the prefrontal cortex, but not in the basolateral amygdala, mimics the systemic effect. Conversely, decreasing acetylation by inhibiting histone acetyltransferases in the infralimbic cortex reduces behavioral responses to defeat. This is the first demonstration that acute pharmacological manipulation of histone acetylation during social defeat alters subsequent behavioral responses in both males and females. These results reveal that even systemic administration of drugs that alter histone acetylation can significantly alter behavioral responses to social stress and highlight the importance of the infralimbic cortex in mediating this effect.

DIFFERENTIAL SUSCEPTIBILITY OF HUMAN SP-B GENETIC VARIANTS ON LUNG INJURY CAUSED BY BACTERIAL PNEUMONIA AND THE EFFECT OF A CHEMICALLY MODIFIED CURCUMIN

Staphylococcus aureus is a common cause of nosocomial pneumonia frequently resulting in acute respiratory distress syndrome (ARDS). Surfactant protein B (SP-B) gene expresses two proteins involved in lowering surface tension and host defense. Genotyping studies demonstrate a significant association between human SP-B genetic variants and ARDS. Curcumins have been shown to attenuate host inflammation in many sepsis models. Our hypothesis is that functional differences of SP-B variants and treatment with curcumin (CMC2.24) modulate lung injury in bacterial pneumonia. Humanized transgenic mice, expressing either SP-B T or C allele without mouse SP-B gene, were used. Bioluminescent labeled S. aureus Xen 36 (50 μL) was injected intratracheally to cause pneumonia. Infected mice received daily CMC2.24 (40 mg/kg) or vehicle alone by oral gavage. Dynamic changes of bacteria were monitored using in vivo imaging system. Histological, cellular, and molecular indices of lung injury were studied in infected mice 48 h after infection. In vivo imaging analysis revealed total flux (bacterial number) was higher in the lung of infected SP-B-C mice compared with infected SP-B-T mice (P < 0.05). Infected SP-B-C mice demonstrated increased mortality, lung injury, apoptosis, and NF-κB expression compared with infected SP-B-T mice. Compared with controls, CMC2.24 treatment significantly reduced the following: mortality, total bacterial flux and lung tissue apoptosis, inflammatory cells, NF-κB expression (P < 0.05), and MMPs-2, -9, -12 activities (P < 0.05). We conclude that mice with SP-B-C allele are more susceptible to S. aureus pneumonia than mice with SP-B-T allele, and that CMC2.24 attenuates lung injury thus reducing mortality.

Treatment of cardiovascular pathology with epigenetically active agents: Focus on natural and synthetic inhibitors of DNA methylation and histone deacetylation

Cardiovascular disease (CVD) retains a leadership as a major cause of human death worldwide. Although a substantial progress was attained in the development of cardioprotective and vasculoprotective drugs, a search for new efficient therapeutic strategies and promising targets is under way. Modulation of epigenetic CVD mechanisms through administration epigenetically active agents is one of such new approaches. Epigenetic mechanisms involve heritable changes in gene expression that are not linked to the alteration of DNA sequence. Pathogenesis of CVDs is associated with global genome-wide changes in DNA methylation and histone modifications. Epigenetically active compounds that influence activity of epigenetic modulators such as DNA methyltransferases (DNMTs), histone acetyltransferases, histone deacetylases (HDACs), etc. may correct these pathogenic changes in the epigenome and therefore be used for CVD therapy. To date, many epigenetically active natural substances (such as polyphenols and flavonoids) and synthetic compounds such as DNMT inhibitors or HDAC inhibitors are known. Both native and chemical DNMT and HDAC inhibitors possess a wide range of cytoprotective activities such as anti-inflammatory, antioxidant, anti-apoptotic, anti-anfibrotic, and anti-hypertrophic properties, which are beneficial of treatment of a variety of CVDs. However, so far, only synthetic DNMT inhibitors enter clinical trials while synthetic HDAC inhibitors are still under evaluation in preclinical studies. In this review, we consider epigenetic mechanisms such as DNA methylation and histone modifications in cardiovascular pathology and the epigenetics-based therapeutic approaches focused on the implementation of DNMT and HDAC inhibitors.

Regulation of transcription by the Arabidopsis UVR8 photoreceptor involves a specific histone modification

The photoreceptor UV RESISTANCE LOCUS 8 (UVR8) specifically mediates photomorphogenic responses to UV-B wavelengths. UVR8 acts by regulating transcription of a set of genes, but the underlying mechanisms are unknown. Previous research indicated that UVR8 can associate with chromatin, but the specificity and functional significance of this interaction are not clear. Here we show, by chromatin immunoprecipitation, that UV-B exposure of Arabidopsis increases acetylation of lysines K9 and/or K14 of histone H3 at UVR8-regulated gene loci in a UVR8-dependent manner. The transcription factors HY5 and/or HYH, which mediate UVR8-regulated transcription, are also required for this chromatin modification, at least for the ELIP1 gene. Furthermore, sequencing of the immunoprecipitated DNA revealed that all UV-B-induced enrichments in H3K9,14diacetylation across the genome are UVR8-dependent, and approximately 40 % of the enriched loci contain known UVR8-regulated genes. In addition, inhibition of histone acetylation by anacardic acid reduces the UV-B induced, UVR8 mediated expression of ELIP1 and CHS. No evidence was obtained in yeast 2-hybrid assays for a direct interaction between either UVR8 or HY5 and several proteins involved in light-regulated histone modification, nor for the involvement of these proteins in UVR8-mediated responses in plants, although functional redundancy between proteins could influence the results. In summary, this study shows that UVR8 regulates a specific chromatin modification associated with transcriptional regulation of a set of UVR8-target genes.

The combination of dimethoxycurcumin with DNA methylation inhibitor enhances gene re-expression of promoter-methylated genes and antagonizes their cytotoxic effect

Curcumin and its analogs exhibited antileukemic activity either as single agent or in combination therapy. Dimethoxycurcumin (DMC) is a more metabolically stable curcumin analog that was shown to induce the expression of promoter-methylated genes without reversing DNA methylation. Accordingly, co-treatment with DMC and DNA methyltransferase (DNMT) inhibitors could hypothetically enhance the re-expression of promoter-methylated tumor suppressor genes. In this study, we investigated the cytotoxic effects and epigenetic changes associated with the combination of DMC and the DNMT inhibitor decitabine (DAC) in primary leukemia samples and cell lines. The combination demonstrated antagonistic cytotoxic effects and was minimally cytotoxic to primary leukemia cells. The combination did not affect the metabolic stability of DMC. Although the combination enhanced the downregulation of nuclear DNMT proteins, the hypomethylating activity of the combination was not increased significantly compared to DAC alone. On the other hand, the combination significantly increased H3K27 acetylation (H3K27Ac) compared to the single agents near the promoter region of promoter-methylated genes. Furthermore, sequential chromatin immunoprecipitation (ChIP) and DNA pyrosequencing of the chromatin-enriched H3K27Ac did not show any significant decrease in DNA methylation compared to other regions. Consequently, the enhanced induction of promoter-methylated genes by the combination compared to DAC alone is mediated by a mechanism that involves increased histone acetylation and not through potentiation of the DNA hypomethylating activity of DAC. Collectively, our results provide the mechanistic basis for further characterization of this combination in leukemia animal models and early phase clinical trials.

Interplay Between Inflammation and Epigenetic Changes in Cancer

Immune responses can suppress tumorigenesis, but also contribute to cancer initiation and progression suggesting a complex interaction between the immune system and cancer. Epigenetic alterations, which are heritable changes in gene expression without changes to the DNA sequence, also play a role in carcinogenesis through silencing expression of tumor suppressor genes and activating oncogenic signaling. Interestingly, epithelial cells at sites of chronic inflammation undergo DNA methylation alterations that are similar to those present in cancer cells, suggesting that inflammation may initiate cancer-specific epigenetic changes in epithelial cells. Furthermore, epigenetic changes occur during immune cell differentiation and participate in regulating the immune response, including the regulation of inflammatory cytokines. Cancer cells utilize epigenetic silencing of immune-related genes to evade the immune response. This chapter will detail the interactions between inflammation and epigenetics in tumor initiation, promotion, and immune evasion and how these connections are being leveraged in cancer prevention and treatment.

Epigenetic regulation of active Chinese herbal components for cancer prevention and treatment: A follow-up review

Epigenetic modifications include DNA methylation, histone modification, and other patterns. These processes are associated with carcinogenesis and cancer progression. Thus, epigenetic modification-related enzymes, such as DNA methyltransferases (DNMTs), histone methyltransferases (HMTs), histone demethylases (HDMTs), histone acetyltransferases (HATs), and histone deacetylases (HDACs), as well as some related proteins, including methyl-CpG binding proteins (MBPs) and DNMT1-associated protein (DMAP 1), are considered as potential targets for cancer prevention and therapy. Numerous natural compounds, mainly derived from Chinese herbs and chemically ranging from polyphenols and flavonoids to mineral salts, inhibit the growth and development of various cancers by targeting multiple genetic and epigenetic alterations. This review summarizes the epigenetic mechanisms by which active compounds from Chinese herbs exert their anti-cancer effect. A subset of these compounds, such as curcumin and resveratrol, affect multiple epigenetic processes, including DNMT inhibition, HDAC inactivation, MBP suppression, HAT activation, and microRNA modulation. Other compounds also regulate epigenetic modification processes, but the underlying mechanisms and clear targets remain unknown. Accordingly, further studies are required.

Epigenetic modulators as therapeutic targets in prostate cancer

Prostate cancer is one of the most common non-cutaneous malignancies among men worldwide. Epigenetic aberrations, including changes in DNA methylation patterns and/or histone modifications, are key drivers of prostate carcinogenesis. These epigenetic defects might be due to deregulated function and/or expression of the epigenetic machinery, affecting the expression of several important genes. Remarkably, epigenetic modifications are reversible and numerous compounds that target the epigenetic enzymes and regulatory proteins were reported to be effective in cancer growth control. In fact, some of these drugs are already being tested in clinical trials. This review discusses the most important epigenetic alterations in prostate cancer, highlighting the role of epigenetic modulating compounds in pre-clinical and clinical trials as potential therapeutic agents for prostate cancer management.

Selection of cell fate in the organ of Corti involves the integration of Hes/Hey signaling at the Atoh1 promoter

Determination of cell fate within the prosensory domain of the developing cochlear duct relies on the temporal and spatial regulation of the bHLH transcription factor Atoh1. Auditory hair cells and supporting cells arise in a wave of differentiation that patterns them into discrete rows mediated by Notch-dependent lateral inhibition. However, the mechanism responsible for selecting sensory cells from within the prosensory competence domain remains poorly understood. We show in mice that rather than being upregulated in rows of cells, Atoh1 is subject to transcriptional activation in groups of prosensory cells, and that highly conserved sites for Hes/Hey repressor binding in the Atoh1 promoter are needed to select the hair cell and supporting cell fate. During perinatal supporting cell transdifferentiation, which is a model of hair cell regeneration, we show that derepression is sufficient to induce Atoh1 expression, suggesting a mechanism for priming the 3' Atoh1 autoregulatory enhancer needed for hair cell expression.

Curcumin Inhibits 5-Fluorouracil-induced Up-regulation of CXCL1 and CXCL2 of the Colon Associated with Attenuation of Diarrhoea Development

The compound 5-fluorouracil (5-FU) is used in cancer chemotherapy and is known to cause diarrhoea. We recently reported that chemokine (C-X-C motif) ligand 1 (CXCL1) and neutrophils in the colonic mucosa were markedly increased by the administration of 5-FU in mice. Curcumin has anti-inflammatory, antitumour and antioxidant properties. Therefore, we examined the effect of curcumin on 5-FU-induced diarrhoea development and CXCL1 and CXCL2 up-regulation in the colon. Mice were given 5-FU (50 mg/kg, i.p.) daily for 4 days. Curcumin (100 or 300 mg/kg, p.o.) was administered on the day before the first administration of 5-FU and administered 30 min. before the administration of 5-FU. Gene expression levels of CXCL1 and CXCL2 in the colon were examined by real-time RT-PCR. Curcumin reduced the 5-FU-induced diarrhoea development. Under this condition, the CXCL1 and CXCL2 gene up-regulated by 5-FU administration was inhibited by curcumin. The gene expression of CXCL1 and CXCL2 was also enhanced by 5-FU application in vitro. The 5-FU-induced up-regulated CXCL1 and CXCL2 gene expressions were inhibited by curcumin, Bay-117082 and bortezomib, nuclear factor kappa B (NF-κB) inhibitors, C646, a p300/cyclic adenosine monophosphate response element-binding protein-histone acetyltransferase (HAT) inhibitor. In conclusion, these findings suggested that curcumin prevented the development of diarrhoea by inhibiting NF-κB and HAT activation.

Neuroprotective effects of Paeonia Lactiflora extract against cell death of dopaminergic SH-SY5Y cells is mediated by epigenetic modulation

Background

The Paeonia lactiflora extract (PLE) has been reported to have neuroprotective effect against neurodegeneration that are induced by cellular stress such as oxidative stress. Its underlying mechanisms, however, remain unclear. In latest decades, emerging evidence has suggested that epigenetic mechanisms play a key role in gene regulation in response to the cellular stress. We investigated whether epigenetic modulation was involved in neuronal cell death by the neurotoxicant, 1-Methyl-4-phenylpyridinium (MPP⁺), and the neuroprotective effect of PLE.

Methods

Differentiated SH-SY5Y, which is a well-established dopaminergic cell line model, was treated with 0 ~ 200 μg/ml PLE for 4 h prior to MPP⁺ treatment. The effect of PLE on cell viability was determined by MTT assays. Gene expression levels of oxidative stress responsive genes, such as Heme oxygenase 1 (HMOX1), and histone modifiers, such as histone acetyltransferases (HATs) and deacetylases (HDACs) were measured by quantitative RT PCR. In order to investigate the changes in epigenetic modifications, the acetylated lysine 9 (H3K9ac) and lysine 27 (H3K27ac) of Histone H3 were measured by western blot using histones extracted from the cells.

Results

MPP⁺-induced cell death in SH-SY5Y cells was significantly reduced by PLE pretreatment in a dose-dependent manner, indicating the potent neuroprotective effects of PLE. It was accompanied by induced expression of HMOX1. MPP⁺ treatment increased the expression of HATs and consistently increased H3K9ac and H3K27ac of Histone H3. PLE pretreatment impeded the changes in H3K9ac and H3K27ac, coincided with increased expression of HDAC5 without changes in HAT expression.

Conclusions

The results suggested that MPP⁺-induced cell death in the dopaminergic SH-SY5Y cells was related with transcriptional induction of HATs and increased histone H3 acetylation and that PLE might prevent the cells from MPP⁺-induced cell death via tempering histone H3 acetylation.

The model beetle Tribolium castaneum can be used as an early warning system for transgenerational epigenetic side effects caused by pharmaceuticals

Pharmaceuticals are not currently tested for transgenerational and epigenetic side effects. The use of vertebrates as preclinical research models is limited by their long generation times, low numbers of progeny and ethical concerns. In contrast, invertebrates such as insects breed rapidly, produce many offspring and are more ethically acceptable, allowing them to be used for high-throughput screening. Here, we established Tribolium castaneum as a model to screen for the effect of drugs on complex fitness parameters and the expression of epigenetic regulatory genes. We tested diets supplemented with the psychoactive drug valproic acid (VPA), which is a histone deacetylase inhibitor, or the antioxidant curcumin, which is a histone acetyltransferase inhibitor. We found that VPA delayed development, reduced longevity, and increased female body weight compared to a control diet. Fertility and fecundity declined and the expression of epigenetic regulatory genes was induced in the untreated F1 generation. In contrast, curcumin did not affect development or body weight, but it increased longevity, caused a significant reduction in fertility, and induced the expression of epigenetic regulatory genes mostly in the treated F0 generation. VPA and curcumin administered to vertebrate models have similar effects to those we observed in T. castaneum, confirming that this beetle is potentially useful as an alternative model to screen for the epigenetic effect of drugs. T. castaneum also provides a valuable early warning system for transgenerational epigenetic risk factors that are difficult to detect in mammals.

Effects of caffeine on cell viability and activity of histone deacetylase 1 and histone acetyltransferase in glioma cells

OBJECTIVE

The prognosis of patients with glioblastoma remains poor even after various treatments such as surgery, radiotherapy, and chemotherapy. Thus, development of new drugs is urgently needed. The mechanisms underlying the cytotoxicity of caffeine in glioma cells are not clearly understood. This study aimed to assess the activities of histone deacetylase 1 (HDAC1) and histone acetyltransferase (p300) in RT2 glioma cells treated with caffeine.

MATERIALS AND METHODS

Cell viability and activity of HDAC1 and p300 in RT2 glioma cells were assayed after treatment with caffeine for 48 hours.

RESULTS

Cell viability decreased significantly after treatment with 0.5mM, 1mM, and 2mM caffeine. HDAC1 protein activity decreased significantly with various concentrations of caffeine, whereas the activity of p300 increased significantly. In addition, the viability of RT2 cells remained high, but HDAC1 activity decreased, and p300 activity increased markedly with 0.5mM caffeine treatment. We used microRNA and small interfering RNA (siRNA) to regulate HDAC1 and p300 to further understand the impact on glioblastomas. siRNA downregulated p300 and thus increased the viability of RT2 cells, therefore, caffeine combined with siRNA abolished the efficacy of caffeine, which confirmed that caffeine upregulated p300 and reduced cell viability. We also found increased HDAC1 activity when RT2 cells were treated with a combination of caffeine and miR-449a and thus increased the viability of RT2 cells.

CONCLUSION

Our data suggest that a new strategy, caffeine, could increase glioma cell death by decreasing HDAC1 activity and/or by increasing p300 activity. The changes in HDAC1 and p300 activities appeared to occur earlier than loss of RT2 cells.

Clinacanthus nutans Extracts Modulate Epigenetic Link to Cytosolic Phospholipase A2 Expression in SH-SY5Y Cells and Primary Cortical Neurons

Clinacanthus nutans Lindau (C. nutans), commonly known as Sabah Snake Grass in southeast Asia, is widely used in folk medicine due to its analgesic, antiviral, and anti-inflammatory properties. Our recent study provided evidence for the regulation of cytosolic phospholipase A2 (cPLA2) mRNA expression by epigenetic factors (Tan et al. in Mol Neurobiol. doi: 10.1007/s12035-015-9314-z , 2015). This enzyme catalyzes the release of arachidonic acid from glycerophospholipids, and formation of pro-inflammatory eicosanoids or toxic lipid peroxidation products such as 4-hydroxynonenal. In this study, we examined the effects of C. nutans ethanol leaf extracts on epigenetic regulation of cPLA2 mRNA expression in SH-SY5Y human neuroblastoma cells and mouse primary cortical neurons. C. nutans modulated induction of cPLA2 expression in SH-SY5Y cells by histone deacetylase (HDAC) inhibitors, MS-275, MC-1568, and TSA. C. nutans extracts also inhibited histone acetylase (HAT) activity. Levels of cPLA2 mRNA expression were increased in primary cortical neurons subjected to 0.5-h oxygen-glucose deprivation injury (OGD). This increase was significantly inhibited by C. nutans treatment. Treatment of primary neurons with the HDAC inhibitor MS-275 augmented OGD-induced cPLA2 mRNA expression, and this increase was modulated by C. nutans extracts. OGD-stimulated increase in cPLA2 mRNA expression was also reduced by a Tip60 HAT inhibitor, NU9056. In view of a key role of cPLA2 in the production of pro-inflammatory eicosanoids and free radical damage, and the fact that epigenetic effects on genes are often long-lasting, results suggest a role for C. nutans and phytochemicals to inhibit the production of arachidonic acid-derived pro-inflammatory eicosanoids and chronic inflammation, through epigenetic regulation of cPLA2 expression.

Histone acetyltransferases: challenges in targeting bi-substrate enzymes

Histone acetyltransferases (HATs) are epigenetic enzymes that install acetyl groups onto lysine residues of cellular proteins such as histones, transcription factors, nuclear receptors, and enzymes. HATs have been shown to play a role in diseases ranging from cancer and inflammatory diseases to neurological disorders, both through acetylations of histone proteins and non-histone proteins. Several HAT inhibitors, like bi-substrate inhibitors, natural product derivatives, small molecules, and protein–protein interaction inhibitors, have been developed. Despite their potential, a large gap remains between the biological activity of inhibitors in in vitro studies and their potential use as therapeutic agents. To bridge this gap, new potent HAT inhibitors with improved properties need to be developed. However, several challenges have been encountered in the investigation of HATs and HAT inhibitors that hinder the development of new HAT inhibitors. HATs have been shown to function in complexes consisting of many proteins. These complexes play a role in the activity and target specificity of HATs, which limits the translation of in vitro to in vivo experiments. The current HAT inhibitors suffer from undesired properties like anti-oxidant activity, reactivity, instability, low potency, or lack of selectivity between HAT subtypes and other enzymes. A characteristic feature of HATs is that they are bi-substrate enzymes that catalyze reactions between two substrates: the cofactor acetyl coenzyme A (Ac-CoA) and a lysine-containing substrate. This has important—but frequently overlooked—consequences for the determination of the inhibitory potency of small molecule HAT inhibitors and the reproducibility of enzyme inhibition experiments. We envision that a careful characterization of molecular aspects of HATs and HAT inhibitors, such as the HAT catalytic mechanism and the enzyme kinetics of small molecule HAT inhibitors, will greatly improve the development of potent and selective HAT inhibitors and provide validated starting points for further development towards therapeutic agents.

Chemoprevention in gastrointestinal physiology and disease. Targeting the progression of cancer with natural products: a focus on gastrointestinal cancer

The last decade has witnessed remarkable progress in the utilization of natural products for the prevention and treatment of human cancer. Many agents now in the pipeline for clinical trial testing have evolved from our understanding of how human nutritional patterns account for widespread differences in cancer risk. In this review, we have focused on many of these promising agents arguing that they may provide a new strategy for cancer control: natural products once thought to be only preventive in their mode of action now are being explored for efficacy in tandem with cancer therapeutics. Natural products may reduce off-target toxicity of therapeutics while making cancers more amenable to therapy. On the horizon is the use of certain natural products, in their own right, as mitigants of late-stage cancer, a new frontier for small-molecule natural product drug discovery.

Dietary phytochemicals as epigenetic modifiers in cancer: Promise and challenges

The influence of diet and environment on human health has been known since ages. Plant-derived natural bioactive compounds (phytochemicals) have acquired an important role in human diet as potent antioxidants and cancer chemopreventive agents. In past few decades, the role of epigenetic alterations such as DNA methylation, histone modifications and non-coding RNAs in the regulation of mammalian genome have been comprehensively addressed. Although the effects of dietary phytochemicals on gene expression and signaling pathways have been widely studied in cancer, the impact of these dietary compounds on mammalian epigenome is rapidly emerging. The present review outlines the role of different epigenetic mechanisms in the regulation and maintenance of mammalian genome and focuses on the role of dietary phytochemicals as epigenetic modifiers in cancer. Above all, the review focuses on summarizing the progress made thus far in cancer chemoprevention with dietary phytochemicals, the heightened interest and challenges in the future.

Therapeutics Targeting Protein Acetylation Perturb Latency of Human Viruses

Persistent viral infections are widespread and represent significant public health burdens. Some viruses endure in a latent state by co-opting the host epigenetic machinery to manipulate viral gene expression. Small molecules targeting epigenetic pathways are now in the clinic for certain cancers and are considered as potential treatment strategies to reverse latency in HIV-infected individuals. In this review, we discuss how drugs interfering with one epigenetic pathway, protein acetylation, perturb latency of three families of pathogenic human viruses-retroviruses, herpesviruses, and papillomaviruses.

Histone acetyltransferases: Rising ancient counterparts to protein kinases

Protein kinases catalyze phosphorylation, a posttranslational modification widely utilized in cell signaling. Histone acetyltransferases (HATs) catalyze a counterpart posttranslational modification of acetylation which marks histones for epigenetic signaling but in some cases modifies non-histone proteins to mediate other cellular activities. In addition, recent proteomic studies have revealed that thousands of proteins are acetylated throughout the cell to regulate diverse biological processes, thus placing acetyltransferases on the same playing field as kinases. Emerging biochemical and structural data further supports mechanistic and biological links between the two enzyme families. In this article, we will review what is known to date about the structure, catalysis and mode of regulation of HAT enzymes and draw analogies, where relevant, to protein kinases. This comparison reveals that HATs may be rising ancient counterparts to protein kinases.

LncRNA Khps1 Regulates Expression of the Proto-oncogene SPHK1 via Triplex-Mediated Changes in Chromatin Structure

Although thousands of long noncoding RNAs (lncRNAs) have been discovered, very little is known about their mode of action. Here we functionally characterize an E2F1-regulated lncRNA named Khps1, which is transcribed in antisense orientation to the proto-oncogene SPHK1. Khps1 activates SPHK1 expression by recruiting the histone acetyltransferase p300/CBP to the SPHK1 promoter, which leads to local changes of the chromatin structure that ensures E2F1 binding and enhances transcription. Mechanistically, this is achieved by direct association of Khps1 with a homopurine stretch upstream of the transcription start site of SPHK1, which forms a DNA-RNA triplex that anchors the lncRNA and associated effector proteins to the gene promoter. The results reveal an lncRNA- and E2F1-driven regulatory loop in which E2F1-dependent induction of antisense RNA leads to changes in chromatin structure, facilitating E2F1-dependent expression of SPHK1 and restriction of E2F1-induced apoptosis.

Quantitative Measurement of Histone Tail Acetylation Reveals Stage-Specific Regulation and Response to Environmental Changes during Drosophila Development

Histone modification plays a major role in regulating gene transcription and ensuring the healthy development of an organism. Numerous studies have suggested that histones are dynamically modified during developmental events to control gene expression levels in a temporal and spatial manner. However, the study of histone acetylation dynamics using currently available techniques is hindered by the difficulty of simultaneously measuring acetylation of the numerous potential sites of modification present in histones. Here, we present a methodology that allows us to combine mass spectrometry-based histone analysis with Drosophila developmental genetics. Using this system, we characterized histone acetylation patterns during multiple developmental stages of the fly. Additionally, we utilized this analysis to characterize how treatments with pharmacological agents or environmental changes such as γ-irradiation altered histone acetylation patterns. Strikingly, γ-irradiation dramatically increased the level of acetylation at H3K18, a site linked to DNA repair via nonhomologous end joining. In mutant fly strains deficient in DNA repair proteins, however, this increase in the level of H3K18 acetylation was lost. These results demonstrate the efficacy of our combined mass spectrometry system with a Drosophila model system and provide interesting insight into the changes in histone acetylation during development, as well as the effects of both pharmacological and environmental agents on global histone acetylation.

Epigenetic regulation of Atoh1 guides hair cell development in the mammalian cochlea

In the developing cochlea, sensory hair cell differentiation depends on the regulated expression of the bHLH transcription factor Atoh1. In mammals, if hair cells die they do not regenerate, leading to permanent deafness. By contrast, in non-mammalian vertebrates robust regeneration occurs through upregulation of Atoh1 in the surviving supporting cells that surround hair cells, leading to functional recovery. Investigation of crucial transcriptional events in the developing organ of Corti, including those involving Atoh1, has been hampered by limited accessibility to purified populations of the small number of cells present in the inner ear. We used µChIP and qPCR assays of FACS-purified cells to track changes in the epigenetic status of the Atoh1 locus during sensory epithelia development in the mouse. Dynamic changes in the histone modifications H3K4me3/H3K27me3, H3K9ac and H3K9me3 reveal a progression from poised, to active, to repressive marks, correlating with the onset of Atoh1 expression and its subsequent silencing during the perinatal (P1 to P6) period. Inhibition of acetylation blocked the increase in Atoh1 mRNA in nascent hair cells, as well as ongoing hair cell differentiation during embryonic organ of Corti development ex vivo. These results reveal an epigenetic mechanism of Atoh1 regulation underlying hair cell differentiation and subsequent maturation. Interestingly, the H3K4me3/H3K27me3 bivalent chromatin structure observed in progenitors persists at the Atoh1 locus in perinatal supporting cells, suggesting an explanation for the latent capacity of these cells to transdifferentiate into hair cells, and highlighting their potential as therapeutic targets in hair cell regeneration.

Dietary components as epigenetic-regulating agents against cancer

Carcinogenesis is a complicated process that involves the deregulation of epigenetics resulting in cellular transformational events, such proliferation, differentiation, and metastasis. Epigenetic machinery changes the accessibility of chromatin to transcriptional regulation through DNA modification. The collaboration of epigenetics and gene transcriptional regulation creates a suitable microenvironment for cancer development, which is proved by the alternation in cell proliferation, differentiation, division, metabolism, DNA repair and movement. Therefore, the reverse of epigenetic dysfunction may provide a possible strategy and new therapeutic targets for cancer treatment. Many dietary components such as sulforaphane and epigallocatechin- 3-gallate have been demonstrated to exert chemopreventive influences, such as reducing tumor growth and enhancing cancer cell death. Anticancer mechanistic studies also indicated that dietary components could display the ability to reverse epigenetic deregulation in assorted tumors via reverting the adverse epigenetic regulation, including alternation of DNA methylation and histone modification, and modulation of microRNA expression. Therefore, dietary components as therapeutic agents on epigenetics becomes an attractive approach for cancer prevention and intervention at the moment. In this review, we summarize the recent discoveries and underlying mechanisms of the most common dietary components for cancer prevention via epigenetic regulation.

Aberrant lysine acetylation in tumorigenesis: Implications in the development of therapeutics

The 'language' of covalent histone modifications translates environmental and cellular cues into gene expression. This vast array of post-translational modifications on histones are more than just covalent moieties added onto a protein, as they also form a platform on which crucial cellular signals are relayed. The reversible lysine acetylation has emerged as an important post-translational modification of both histone and non-histone proteins, dictating numerous epigenetic programs within a cell. Thus, understanding the complex biology of lysine acetylation and its regulators is essential for the development of epigenetic therapeutics. In this review, we will attempt to address the complexities of lysine acetylation in the context of tumorigenesis, their role in cancer progression and emphasize on the modalities developed to target lysine acetyltransferases towards cancer treatment.

Epigenetic associations in relation to cardiovascular prevention and therapeutics

Cardiovascular diseases (CVD) increasingly burden societies with vast financial and health care problems. Therefore, the importance of improving preventive and therapeutic measures against cardiovascular diseases is continually growing. To accomplish such improvements, research must focus particularly on understanding the underlying mechanisms of such diseases, as in the field of epigenetics, and pay more attention to strengthening primary prevention. To date, preliminary research has found a connection between DNA methylation, histone modifications, RNA-based mechanisms and the development of CVD like atherosclerosis, cardiac hypertrophy, myocardial infarction, and heart failure. Several therapeutic agents based on the findings of such research projects are currently being tested for use in clinical practice. Although these tests have produced promising data so far, no epigenetically active agents or drugs targeting histone acetylation and/or methylation have actually entered clinical trials for CVDs, nor have they been approved by the FDA. To ensure the most effective prevention and treatment possible, further studies are required to understand the complex relationship between epigenetic regulation and the development of CVD. Similarly, several classes of RNA therapeutics are currently under development. The use of miRNAs and their targets as diagnostic or prognostic markers for CVDs is promising, but has not yet been realized. Further studies are necessary to improve our understanding of the involvement of lncRNA in regulating gene expression changes underlying heart failure. Through the data obtained from such studies, specific therapeutic strategies to avoid heart failure based on interference with incRNA pathways could be developed. Together, research and testing findings raise hope for enhancing the therapeutic armamentarium. This review presents the currently available data concerning epigenetic mechanisms and compounds involved in cardiovascular diseases, as well as preventive and therapeutic approaches against them.

KATching-Up on Small Molecule Modulators of Lysine Acetyltransferases

The reversible acetylation of lysines is one of the best characterized epigenetic modifications. Its involvement in many key physiological and pathological processes has been documented in numerous studies. Lysine deacetylases (KDACs) and acetyltransferases (KATs) maintain the acetylation equilibrium at histones but also many other proteins. Besides acetylation, also other acyl groups are reversibly installed at the side chain of lysines in proteins. Because of their involvement in disease, KDACs and KATs were proposed to be promising drug targets, and for KDACs, indeed, five inhibitors are now approved for human use. While there is a similar level of evidence for the potential of KATs as drug targets, no inhibitor is in clinical trials. Here, we review the evidence for the diverse roles of KATs in disease pathology, provide an overview of structural features and the available modulators, including those targeting the bromodomains of KATs, and present an outlook.

Natural compound-derived epigenetic regulators targeting epigenetic readers, writers and erasers

Post-translational modifications can affect gene expression in a long-term manner without changes in the primary nucleotide sequence of the DNA. These epigenetic alterations involve dynamic processes that occur in histones, chromatin-associated proteins and DNA. In response to environmental stimuli, abnormal epigenetic alterations cause disorders in the cell cycle, apoptosis and other cellular processes and thus contribute to the incidence of diverse diseases, including cancers. In this review, we will summarize recent studies focusing on certain epigenetic readers, writers, and erasers associated with cancer development and how newly discovered natural compounds and their derivatives could interact with these targets. These advances provide insights into epigenetic alterations in cancers and the potential utility of these alterations as therapeutic targets for the future development of chemopreventive and chemotherapeutic drugs.

Epigenetic Modifications in Neurological Diseases: Natural Products as Epigenetic Modulators a Treatment Strategy

Epigenetic modifications, including DNA methylation, covalent histone modifications, and small noncoding RNAs, play a key role in regulating the gene expression. This regulatory mechanism is important in cellular differentiation and development. Recent advances in the field of epigenetics extended the role of epigenetic mechanisms in controlling key biological processes such as genome imprinting and X-chromosome inactivation. Aberrant epigenetic modifications are associated with the development of many diseases. The role of epigenetic modifications in various neurodegenerative disorders including Alzheimer's disease, Parkinson's disease, Huntington disease, epilepsy, and multiple sclerosis is rapidly emerging. The use of epigenetic modifying drugs to treat these diseases has been the interest in recent years. A number of natural products having diverse mechanism of action are used for drug discovery. For many years, natural compounds have been used to treat various neurodegenerative diseases, but the use of such compounds as epigenetic modulators to reverse or treat neurological diseases are not well studied. In this chapter, we mainly focus on how various epigenetic modifications play a key role in neurodegenerative diseases, their mechanism of action, and how it acts as a potential therapeutic target for epigenetic drugs to treat these diseases will be discussed.

Histone Acetylation and Its Modifiers in the Pathogenesis of Diabetic Nephropathy

Diabetic nephropathy (DN) remains a leading cause of mortality worldwide despite advances in its prevention and management. A comprehensive understanding of factors contributing to DN is required to develop more effective therapeutic options. It is becoming more evident that histone acetylation (HAc), as one of the epigenetic mechanisms, is thought to be associated with the etiology of diabetic vascular complications such as diabetic retinopathy (DR), diabetic cardiomyopathy (DCM), and DN. Histone acetylases (HATs) and histone deacetylases (HDACs) are the well-known regulators of reversible acetylation in the amino-terminal domains of histone and nonhistone proteins. In DN, however, the roles of histone acetylation (HAc) and these enzymes are still controversial. Some new evidence has revealed that HATs and HDACs inhibitors are renoprotective in cellular and animal models of DN, while, on the other hand, upregulation of HAc has been implicated in the pathogenesis of DN. In this review, we focus on the recent advances on the roles of HAc and their covalent enzymes in the development and progression of DN in certain cellular processes including fibrosis, inflammation, hypertrophy, and oxidative stress and discuss how targeting these enzymes and their inhibitors can ultimately lead to the therapeutic approaches for treating DN.

C646, a Novel p300/CREB-Binding Protein-Specific Inhibitor of Histone Acetyltransferase, Attenuates Influenza A Virus Infection

New strategies to develop novel broad-spectrum antiviral drugs against influenza virus infections are needed due to the emergence of antigenic variants and drug-resistant viruses. Here, we evaluated C646, a novel p300/CREB-binding protein-specific inhibitor of histone acetyltransferase (HAT), as an anti-influenza virus agent in vitro and in vivo and explored how C646 affects the viral life cycle and host response. Our studies highlight the value of targeting HAT activity for anti-influenza drug development.

A bivalent role of TIP60 histone acetyl transferase in human cancer

Acetylation is a major modification that is required for gene regulation, genome maintenance and metabolism. A dysfunctional acetylation plays an important role in several diseases, including cancer. A group of enzymes-lysine acetyltransferases are responsible for this modification and act in regulation of transcription as cofactors and by acetylation of histones and other proteins. Tip60, a member of MYST family, is expressed ubiquitously and is the acetyltransferase catalytic subunit of human NuA4 complex. This HAT has a well-characterized involvement in many processes, such as cellular signaling, DNA damage repair, transcriptional and cellular cycle. Aberrant lysine acetyltransferase functions promote or suppress tumorigenesis in different cancers such as colon, breast and prostate tumors. Therefore, Tip60 might be a potential and important therapeutic target in the cancer treatment; new histone acetyl transferase inhibitors were identified and are more selective inhibitors of Tip60.

Evasion of anti-growth signaling: A key step in tumorigenesis and potential target for treatment and prophylaxis by natural compounds

The evasion of anti-growth signaling is an important characteristic of cancer cells. In order to continue to proliferate, cancer cells must somehow uncouple themselves from the many signals that exist to slow down cell growth. Here, we define the anti-growth signaling process, and review several important pathways involved in growth signaling: p53, phosphatase and tensin homolog (PTEN), retinoblastoma protein (Rb), Hippo, growth differentiation factor 15 (GDF15), AT-rich interactive domain 1A (ARID1A), Notch, insulin-like growth factor (IGF), and Krüppel-like factor 5 (KLF5) pathways. Aberrations in these processes in cancer cells involve mutations and thus the suppression of genes that prevent growth, as well as mutation and activation of genes involved in driving cell growth. Using these pathways as examples, we prioritize molecular targets that might be leveraged to promote anti-growth signaling in cancer cells. Interestingly, naturally occurring phytochemicals found in human diets (either singly or as mixtures) may promote anti-growth signaling, and do so without the potentially adverse effects associated with synthetic chemicals. We review examples of naturally occurring phytochemicals that may be applied to prevent cancer by antagonizing growth signaling, and propose one phytochemical for each pathway. These are: epigallocatechin-3-gallate (EGCG) for the Rb pathway, luteolin for p53, curcumin for PTEN, porphyrins for Hippo, genistein for GDF15, resveratrol for ARID1A, withaferin A for Notch and diguelin for the IGF1-receptor pathway. The coordination of anti-growth signaling and natural compound studies will provide insight into the future application of these compounds in the clinical setting.

Designing a broad-spectrum integrative approach for cancer prevention and treatment

Targeted therapies and the consequent adoption of "personalized" oncology have achieved notable successes in some cancers; however, significant problems remain with this approach. Many targeted therapies are highly toxic, costs are extremely high, and most patients experience relapse after a few disease-free months. Relapses arise from genetic heterogeneity in tumors, which harbor therapy-resistant immortalized cells that have adopted alternate and compensatory pathways (i.e., pathways that are not reliant upon the same mechanisms as those which have been targeted). To address these limitations, an international task force of 180 scientists was assembled to explore the concept of a low-toxicity "broad-spectrum" therapeutic approach that could simultaneously target many key pathways and mechanisms. Using cancer hallmark phenotypes and the tumor microenvironment to account for the various aspects of relevant cancer biology, interdisciplinary teams reviewed each hallmark area and nominated a wide range of high-priority targets (74 in total) that could be modified to improve patient outcomes. For these targets, corresponding low-toxicity therapeutic approaches were then suggested, many of which were phytochemicals. Proposed actions on each target and all of the approaches were further reviewed for known effects on other hallmark areas and the tumor microenvironment. Potential contrary or procarcinogenic effects were found for 3.9% of the relationships between targets and hallmarks, and mixed evidence of complementary and contrary relationships was found for 7.1%. Approximately 67% of the relationships revealed potentially complementary effects, and the remainder had no known relationship. Among the approaches, 1.1% had contrary, 2.8% had mixed and 62.1% had complementary relationships. These results suggest that a broad-spectrum approach should be feasible from a safety standpoint. This novel approach has potential to be relatively inexpensive, it should help us address stages and types of cancer that lack conventional treatment, and it may reduce relapse risks. A proposed agenda for future research is offered.

The role of natural polyphenols in cell signaling and cytoprotection against cancer development

The cytoprotective and anticancer action of dietary in-taken natural polyphenols has for long been attributed only to their direct radical scavenging activities. Currently it is well supported that those compounds display a broad spectrum of biological and pharmacological outcomes mediated by their complex metabolism, interaction with gut microbiota as well as direct interactions of their metabolites with key cellular signaling proteins. The beneficial effects of natural polyphenols and their synthetic derivatives are extensively studied in context of cancer prophylaxis and therapy. Herein we focus on cell signaling to explain the beneficial role of polyphenols at the three stages of cancer development: we review the recent proceedings about the impact of polyphenols on the cytoprotective antioxidant response and their proapoptotic action at the premalignant stage, and finally we present data showing how phenolic acids (e.g., caffeic, chlorogenic acids) and flavonols (e.g., quercetin) hamper the development of metastatic cancer.

Improved bioavailability of targeted Curcumin delivery efficiently regressed cardiac hypertrophy by modulating apoptotic load within cardiac microenvironment

Cardiomyocyte apoptosis acts as a prime modulator of cardiac hypertrophy leading to heart failure, a major cause of human mortality worldwide. Recent therapeutic interventions have focussed on translational applications of diverse pharmaceutical regimes among which, Curcumin (from Curcuma longa) is known to have an anti-hypertrophic potential but with limited pharmacological efficacies due to low aqueous solubility and poor bioavailability. In this study, Curcumin encapsulated by carboxymethyl chitosan (CMC) nanoparticle conjugated to a myocyte specific homing peptide was successfully delivered in bioactive form to pathological myocardium for effective regression of cardiac hypertrophy in a rat (Rattus norvegicus) model. Targeted nanotization showed higher cardiac bioavailability of Curcumin at a low dose of 5 mg/kg body weight compared to free Curcumin at 35 mg/kg body weight. Moreover, Curcumin/CMC-peptide treatment during hypertrophy significantly improved cardiac function by downregulating expression of hypertrophy marker genes (ANF, β-MHC), apoptotic mediators (Bax, Cytochrome-c) and activity of apoptotic markers (Caspase 3 and PARP); whereas free Curcumin in much higher dose showed minimal improvement during compromised cardiac function. Targeted Curcumin treatment significantly lowered p53 expression and activation in diseased myocardium via inhibited interaction of p53 with p300-HAT. Thus attenuated acetylation of p53 facilitated p53 ubiquitination and reduced the apoptotic load in hypertrophied cardiomyocytes; thereby limiting cardiomyocytes' need to enter the regeneration cycle during hypertrophy. This study elucidates for the first time an efficient targeted delivery regimen for Curcumin and also attributes towards probable mechanistic insight into its therapeutic potential as a cardio-protective agent for regression of cardiac hypertrophy.

Polyphenols as Modulator of Oxidative Stress in Cancer Disease: New Therapeutic Strategies

Cancer onset and progression have been linked to oxidative stress by increasing DNA mutations or inducing DNA damage, genome instability, and cell proliferation and therefore antioxidant agents could interfere with carcinogenesis. It is well known that conventional radio-/chemotherapies influence tumour outcome through ROS modulation. Since these antitumour treatments have important side effects, the challenge is to develop new anticancer therapeutic strategies more effective and less toxic for patients. To this purpose, many natural polyphenols have emerged as very promising anticancer bioactive compounds. Beside their well-known antioxidant activities, several polyphenols target epigenetic processes involved in cancer development through the modulation of oxidative stress. An alternative strategy to the cytotoxic treatment is an approach leading to cytostasis through the induction of therapy-induced senescence. Many anticancer polyphenols cause cellular growth arrest through the induction of a ROS-dependent premature senescence and are considered promising antitumour therapeutic tools. Furthermore, one of the most innovative and interesting topics is the evaluation of efficacy of prooxidant therapies on cancer stem cells (CSCs). Several ROS inducers-polyphenols can impact CSCs metabolisms and self-renewal related pathways. Natural polyphenol roles, mainly in chemoprevention and cancer therapies, are described and discussed in the light of the current literature data.