Comparative effects of retinoic acid, vitamin D and resveratrol alone and in combination with adenosine analogues on methylation and expression of phosphatase and tensin homologue tumour suppressor gene in breast cancer cells. Br J Nutr. 2012;107:781-790. [PMID: 21801466 DOI: 10.1017/s0007114511003631]

A lifelong exposure to a Western-style diet, but not aging, alters global DNA methylation in mouse colon

BACKGROUND/OBJECTIVES

Previous studies have indicated that when compared to young mice, old mice have lower global DNA methylation and higher p16 promoter methylation in colonic mucosa, which is a common finding in colon cancer. It is also known that a Western-style diet (WSD) high in fat and calories, and low in calcium, vitamin D, fiber, methionine and choline (based on the AIN 76A diet) is tumorigenic in colons of mice. Because DNA methylation is modifiable by diet, we investigate whether a WSD disrupts DNA methylation patterns, creating a tumorigenic environment.

SUBJECTVIES/METHODS

We investigated the effects of a WSD and aging on global and p16 promoter DNA methylation in the colon. Two month old male C57BL/6 mice were fed either a WSD or a control diet (AIN76A) for 6, 12 or 17 months. Global DNA methylation, p16 promoter methylation and p16 expression were determined by LC/MS, methyl-specific PCR and real time RT-PCR, respectively.

RESULTS

The WSD group demonstrated significantly decreased global DNA methylation compared with the control at 17 months (4.05 vs 4.31%, P = 0.019). While both diets did not change global DNA methylation over time, mice fed the WSD had lower global methylation relative to controls when comparing all animals (4.13 vs 4.30%, P = 0.0005). There was an increase in p16 promoter methylation from 6 to 17 months in both diet groups (P < 0.05) but no differences were observed between diet groups. Expression of p16 increased with age in both control and WSD groups.

CONCLUSIONS

In this model a WSD reduces global DNA methylation, whereas aging itself has no affect. Although the epigenetic effect of aging was not strong enough to alter global DNA methylation, changes in promoter-specific methylation and gene expression occurred with aging regardless of diet, demonstrating the complexity of epigenetic patterns.

Antiasthmatic effects of resveratrol in ovalbumin-induced asthma model mice involved in the upregulation of PTEN

Resveratrol, a natural polyphenolic compound known for its antioxidative and antiinflammatory effects, exerts antiasthmatic effects, although the mechanism underlying these effects remains elusive. The phosphatase and tensin homology deleted on chromosome ten gene (PTEN) is involved in the pathogenesis of asthma, and PTEN overexpression in asthmatic mice improved asthma symptoms. To investigate whether the antiasthmatic mechanisms of resveratrol correlated with the upregulation of PTEN expression, an ovalbumin (OVA)-induced murine asthma model was used to determine the effectiveness of resveratrol treatment. PTEN mRNA and protein expression was assessed with real-time polymerase chain reaction (PCR) and immunochemistry. To determine whether airway remodeling occurred, the inner airway wall, mucous layer, and smooth muscle areas were each determined using an image analysis system. The lung epithelial cell line 16HBE was used to study the regulation of PTEN expression levels by resveratrol in vitro. Our data demonstrated that resveratrol inhibited OVA-induced airway inflammation and airway remodeling in asthmatic mice. PTEN expression was decreased in the murine asthma model, although the expression of PTEN was restored following treatment with resveratrol. Correlation efficiency analysis showed that PTEN expression was associated with the degree of airway remodeling. Further in vitro studies demonstrated that the inhibition of Sirtuin 1 (SIRT1) activity by a SIRT1 inhibitor and RNA interference decreased PTEN protein expression, while resveratrol attenuated the decreases in PTEN expression induced by the SIRT1 inhibitor. These data suggest the mechanism of the antiasthmatic effects of resveratrol in an OVA-induced murine asthma model, which resulted in the upregulation of PTEN via SIRT1 activation.

Enhanced antioxidant capacity and anti-ageing biomarkers after diet micronutrient supplementation

A growing number of studies confirm an important effect of diet, lifestyle and physical activity on health status, the ageing process and many metabolic disorders. This study focuses on the influence of a diet supplement, NucleVital^®Q10 Complex, on parameters related to redox homeostasis and ageing. An experimental group of 66 healthy volunteer women aged 35–55 supplemented their diet for 12 weeks with the complex, which contained omega-3 acids (1350 mg/day), ubiquinone (300 mg/day), astaxanthin (15 mg/day), lycopene (45 mg/day), lutein palmitate (30 mg/day), zeaxanthine palmitate (6 mg/day), L-selenomethionine (330 mg/day), cholecalciferol (30 µg/day) and α-tocopherol (45 mg/day). We found that NucleVital^®Q10 Complex supplementation significantly increased total antioxidant capacity of plasma and activity of erythrocyte superoxide dismutase, with slight effects on oxidative stress biomarkers in erythrocytes; MDA and 4-hydroxyalkene levels. Apart from the observed antioxidative effects, the tested supplement also showed anti-ageing activity. Analysis of expression of SIRT1 and 2 in PBMCs showed significant changes for both genes on a mRNA level. The level of telomerase was also increased by more than 25%, although the length of lymphocyte telomeres, determined by RT-PCR, remained unchanged. Our results demonstrate beneficial effects concerning the antioxidant potential of plasma as well as biomarkers related to ageing even after short term supplementation of diet with NucleVital^®Q10 Complex.

Nuclear receptors and epigenetic regulation: opportunities for nutritional targeting and disease prevention

Posttranslational modifications of histones, alterations in the recruitment and functions of non-histone proteins, DNA methylation, and changes in expression of noncoding RNAs contribute to current models of epigenetic regulation. Nuclear receptors (NRs) are a group of transcription factors that, through ligand-binding, act as sensors to changes in nutritional, environmental, developmental, pathophysiologic, and endocrine conditions and drive adaptive responses via gene regulation. One mechanism through which NRs direct gene expression is the assembly of transcription complexes with cofactors and coregulators that possess chromatin-modifying properties. Chromatin modifications can be transient or become part of the cellular "memory" and contribute to genomic imprinting. Because many food components bind to NRs, they can ultimately influence transcription of genes associated with biologic processes, such as inflammation, proliferation, apoptosis, and hormonal response, and alter the susceptibility to chronic diseases (e.g., cancer, diabetes, obesity). The objective of this review is to highlight how NRs influence epigenetic regulation and the relevance of dietary compound-NR interactions in human nutrition and for disease prevention and treatment. Identifying gene targets of unliganded and bound NRs may assist in the development of epigenetic maps for food components and dietary patterns. Progress in these areas may lead to the formulation of disease-prevention models based on epigenetic control by individual or associations of food ligands of NRs.

In vitro exposure of human blood mononuclear cells to active vitamin D does not induce substantial change to DNA methylation on a genome-scale

It is well-established that vitamin D impacts gene regulation via vitamin D response elements (VDREs) across the genome. Recent evidence, primarily at a locus-specific level, suggests that alterations to DNA methylation may also be a relevant mechanism through which vitamin D regulates gene expression. Given the intense interest in vitamin D, particularly as an immune modifier, we sought to examine the impact of vitamin D exposure on the immune cell methylome in vitro. We exposed primary human blood mononuclear cells with up to 100nM calcitriol for up to 120h, and measured genome-scale DNA methylation response using the Illumina Infinium HumanMethylation450 beadchip array. We observed that, while the expression of known vitamin D responsive genes was clearly altered by calcitriol exposure, substantial genome-scale changes to DNA methylation were not induced. Our data suggests that, over the exposure period measured, changes to DNA methylation may not be a predominant mechanism through which vitamin D impacts gene expression in human immune cells.

Influence of bacteria on epigenetic gene control

Cellular information is inherited by daughter cells through epigenetic routes in addition to genetic routes. Epigenetics, which is primarily mediated by inheritable DNA methylation and histone post-translational modifications, involves changes in the chromatin structure important for regulating gene expression. It is widely known that epigenetic control of gene expression plays an essential role in cell differentiation processes in vertebrates. Furthermore, because epigenetic changes can occur reversibly depending on environmental factors in differentiated cells, they have recently attracted considerable attention as targets for disease prevention and treatment. These environmental factors include diet, exposure to bacteria or viruses, and air pollution, of which this review focuses on the influence of bacteria on epigenetic gene control in a host. Host-bacterial interactions not only occur upon pathogenic bacterial infection but also continuously exist between commensal bacteria and the host. These bacterial stimuli play an essential role in various biological responses involving external stimuli and in maintaining physiological homeostasis by altering epigenetic markers and machinery.

Retinoids and breast cancer: from basic studies to the clinic and back again

All-trans retinoic acid (ATRA) is the most important active metabolite of vitamin A controlling segmentation in the developing organism and the homeostasis of various tissues in the adult. ATRA as well as natural and synthetic derivatives, collectively known as retinoids, are also promising agents in the treatment and chemoprevention of different types of neoplasia including breast cancer. The major aim of the present article is to review the basic knowledge acquired on the anti-tumor activity of classic retinoids, like ATRA, in mammary tumors, focusing on the underlying cellular and molecular mechanisms and the determinants of retinoid sensitivity/resistance. In the first part, an analysis of the large number of pre-clinical studies available is provided, stressing the point that this has resulted in a limited number of clinical trials. This is followed by an overview of the knowledge acquired on the role played by the retinoid nuclear receptors in the anti-tumor responses triggered by retinoids. The body of the article emphasizes the potential of ATRA and derivatives in modulating and in being influenced by some of the most relevant cellular pathways involved in the growth and progression of breast cancer. We review the studies centering on the cross-talk between retinoids and some of the growth-factor pathways which control the homeostasis of the mammary tumor cell. In addition, we consider the cross-talk with relevant intra-cellular second messenger pathways. The information provided lays the foundation for the development of rational and retinoid-based therapeutic strategies to be used for the management of breast cancer.

Clofarabine, a novel adenosine analogue, reactivates DNA methylation-silenced tumour suppressor genes and inhibits cell growth in breast cancer cells

Clofarabine (2-chloro-2'-fluoro-2'-deoxyarabinosyladenine, ClF) is a second-generation 2'-deoxyadenosine analogue that is structurally related to cladribine (2-chloro-2'-deoxyadenosine, 2CdA) and fludarabine (9-beta-d-arabinosyl-2-fluoroadenine, F-ara-A). It demonstrates potent antitumour activity at much lower doses than parent compounds with high therapeutic efficacy in paediatric blood cancers. Our previous studies in breast cancer cells indicate that 2CdA and F-ara-A are involved in epigenetic regulation of gene transcription. We therefore investigated whether ClF influences methylation and expression of selected tumour suppressor genes, such as adenomatous polyposis coli (APC), phosphatase and tensin homologue (PTEN), and retinoic acid receptor beta 2 (RARbeta2), as well as expression of p53, p21 and DNA methyltransferase 1 (DNMT1) in MCF-7 and MDA-MB-231 breast cancer cell lines with different invasive potential. Promoter methylation and gene expression were estimated using methylation-sensitive restriction analysis (MSRA) and real-time PCR, respectively. ClF demonstrated potent growth inhibitory activity in MCF-7 and MDA-MB-231 cells after 96h treatment with IC50 determined as equal to 640nM and 50nM, respectively. In both breast cancer cell lines, ClF led to hypomethylation and up-regulation of APC, PTEN and RARbeta2 as well as increase in p21 expression. Only in non-invasive MCF-7 cells, these changes were associated with down-regulation of DNMT1. Our results provide first evidence of ClF implications in epigenetic regulation of transcriptional activity of selected tumour suppressor genes in breast cancer. It seems to be a new important element of ClF anticancer activity and may indicate its potential efficacy in epigenetic therapy of solid tumours, especially at early stages of carcinogenesis.

The epigenome as a potential mediator of cancer and disease prevention in prenatal development

Epigenetic events establish a particular gene expression signature for each cell type during differentiation and fertilization. Disruption of these epigenetic programs in response to environmental stimuli during prenatal exposure dysregulates the fetal epigenome, potentially impacting susceptibility to disease later in life (the fetal basis of adult disease). Maternal dietary modifications during gestation and lactation play a pivotal role in the period of fetal (re)programming. Recently, many studies have demonstrated the impact of maternal nutrition on the fetal epigenome. This review discusses the complex interplay among various environmental factors and epigenetic mechanisms that have been found to affect offspring in human and animal models. Further, it summarizes the impact of various dietary phytochemicals capable of modulating the epigenome with regard to diverse human cancers and childhood cancer, specifically those with potential environmental etiology through maternal consumption during pregnancy and lactation. Other dietary agents that are still untested as to their effectiveness in transplacental studies are also discussed. The recent developments discussed herein enhance current understanding of how chemopreventive agents act and their potential to impact the prenatal epigenome; they may also aid efforts to identify dietary interventions that can be beneficial in treating and preventing disease.

Seven sirtuins for seven deadly diseases of aging

Sirtuins are a class of NAD(+)-dependent deacetylases having beneficial health effects. This extensive review describes the numerous intracellular actions of the seven mammalian sirtuins, their protein targets, intracellular localization, the pathways they modulate, and their role in common diseases of aging. Selective pharmacological targeting of sirtuins is of current interest in helping to alleviate global disease burden. Since all sirtuins are activated by NAD(+), strategies that boost NAD(+) in cells are of interest. While most is known about SIRT1, the functions of the six other sirtuins are now emerging. Best known is the involvement of sirtuins in helping cells adapt energy output to match energy requirements. SIRT1 and some of the other sirtuins enhance fat metabolism and modulate mitochondrial respiration to optimize energy harvesting. The AMP kinase/SIRT1-PGC-1α-PPAR axis and mitochondrial sirtuins appear pivotal to maintaining mitochondrial function. Downregulation with aging explains much of the pathophysiology that accumulates with aging. Posttranslational modifications of sirtuins and their substrates affect specificity. Although SIRT1 activation seems not to affect life span, activation of some of the other sirtuins might. Since sirtuins are crucial to pathways that counter the decline in health that accompanies aging, pharmacological agents that boost sirtuin activity have clinical potential in treatment of diabetes, cardiovascular disease, dementia, osteoporosis, arthritis, and other conditions. In cancer, however, SIRT1 inhibitors could have therapeutic value. Nutraceuticals such as resveratrol have a multiplicity of actions besides sirtuin activation. Their net health benefit and relative safety may have originated from the ability of animals to survive environmental changes by utilizing these stress resistance chemicals in the diet during evolution. Each sirtuin forms a key hub to the intracellular pathways affected.

Xenohormetic and anti-aging activity of secoiridoid polyphenols present in extra virgin olive oil: a new family of gerosuppressant agents

Aging can be viewed as a quasi-programmed phenomenon driven by the overactivation of the nutrient-sensing mTOR gerogene. mTOR-driven aging can be triggered or accelerated by a decline or loss of responsiveness to activation of the energy-sensing protein AMPK, a critical gerosuppressor of mTOR. The occurrence of age-related diseases, therefore, reflects the synergistic interaction between our evolutionary path to sedentarism, which chronically increases a number of mTOR activating gero-promoters (e.g., food, growth factors, cytokines and insulin) and the "defective design" of central metabolic integrators such as mTOR and AMPK. Our laboratories at the Bioactive Food Component Platform in Spain have initiated a systematic approach to molecularly elucidate and clinically explore whether the "xenohormesis hypothesis," which states that stress-induced synthesis of plant polyphenols and many other phytochemicals provides an environmental chemical signature that upregulates stress-resistance pathways in plant consumers, can be explained in terms of the reactivity of the AMPK/mTOR-axis to so-called xenohormetins. Here, we explore the AMPK/mTOR-xenohormetic nature of complex polyphenols naturally present in extra virgin olive oil (EVOO), a pivotal component of the Mediterranean style diet that has been repeatedly associated with a reduction in age-related morbid conditions and longer life expectancy. Using crude EVOO phenolic extracts highly enriched in the secoiridoids oleuropein aglycon and decarboxymethyl oleuropein aglycon, we show for the first time that (1) the anticancer activity of EVOO secoiridoids is related to the activation of anti-aging/cellular stress-like gene signatures, including endoplasmic reticulum (ER) stress and the unfolded protein response, spermidine and polyamine metabolism, sirtuin-1 (SIRT1) and NRF2 signaling; (2) EVOO secoiridoids activate AMPK and suppress crucial genes involved in the Warburg effect and the self-renewal capacity of "immortal" cancer stem cells; (3) EVOO secoiridoids prevent age-related changes in the cell size, morphological heterogeneity, arrayed cell arrangement and senescence-associated β-galactosidase staining of normal diploid human fibroblasts at the end of their proliferative lifespans. EVOO secoiridoids, which provide an effective defense against plant attack by herbivores and pathogens, are bona fide xenohormetins that are able to activate the gerosuppressor AMPK and trigger numerous resveratrol-like anti-aging transcriptomic signatures. As such, EVOO secoiridoids constitute a new family of plant-produced gerosuppressant agents that molecularly "repair" the aimless (and harmful) AMPK/mTOR-driven quasi-program that leads to aging and aging-related diseases, including cancer.

Epigenetic mechanisms in anti-cancer actions of bioactive food components--the implications in cancer prevention

The hallmarks of carcinogenesis are aberrations in gene expression and protein function caused by both genetic and epigenetic modifications. Epigenetics refers to the changes in gene expression programming that alter the phenotype in the absence of a change in DNA sequence. Epigenetic modifications, which include amongst others DNA methylation, covalent modifications of histone tails and regulation by non-coding RNAs, play a significant role in normal development and genome stability. The changes are dynamic and serve as an adaptation mechanism to a wide variety of environmental and social factors including diet. A number of studies have provided evidence that some natural bioactive compounds found in food and herbs can modulate gene expression by targeting different elements of the epigenetic machinery. Nutrients that are components of one-carbon metabolism, such as folate, riboflavin, pyridoxine, cobalamin, choline, betaine and methionine, affect DNA methylation by regulating the levels of S-adenosyl-L-methionine, a methyl group donor, and S-adenosyl-L-homocysteine, which is an inhibitor of enzymes catalyzing the DNA methylation reaction. Other natural compounds target histone modifications and levels of non-coding RNAs such as vitamin D, which recruits histone acetylases, or resveratrol, which activates the deacetylase sirtuin and regulates oncogenic and tumour suppressor micro-RNAs. As epigenetic abnormalities have been shown to be both causative and contributing factors in different health conditions including cancer, natural compounds that are direct or indirect regulators of the epigenome constitute an excellent approach in cancer prevention and potentially in anti-cancer therapy.

Synergistic effect of retinoic acid and vitamin D analog EB1089-induced apoptosis of hepatocellular cancer cells

Previous report showed that leukemia cells' differentiation could be induced by retinoic acid (RA), and prostate cancer cells' proliferation could be inhibited by Vitamin D or its analog. This study aimed to examine whether RA and vitamin D analog EB1089 have synergistic effect on hepatocellular cancer cells' apoptosis. The hepatocellular cancer cell lines' viability was determined by MTT method after treating by RA and EB1089 alone or in combination, cell cycle of SSMC-7721 cell analyzed by FACS, mitochondrial membrane potential of SSMC-7721 under different treatments were detected using MitoTracker Red CMXRos. TUNEL analysis was also used for cell apoptosis detection. Real time-PCR and Western Blot assay were used to detect the expression of Bcl-2 and Bax. Moreover, hepatocellular cancer model was developed by subcutaneously (S.C.) challenging H22 cells to nude mice. In the combination group (10 μmol/L RA, 10 nmol/L EB1089), the viability of hepatocellular cancer cells decreased significantly compared with drugs used alone (P < 0.05). From the TUNEL analysis, SSMC-7721 cells have a higher apoptotic ratio in the combined drug group than in the groups for which the drugs were used separately. In a hepatocellular cancer model, the tumor weight of H22 tumor bearing mice was more reduced in the combined drug treated group when compared to the groups for which the drugs were used alone (P < 0.05), in addition, significantly prolonged survival was observed. Combination of RA and EB1089 exert synergistic growth inhibition and apoptosis induction on hepatocellular cancers cells.

Cancer chemoprevention and nutriepigenetics: state of the art and future challenges

The term "epigenetics" refers to modifications in gene expression caused by heritable, but potentially reversible, changes in DNA methylation and chromatin structure. Epigenetic alterations have been identified as promising new targets for cancer prevention strategies as they occur early during carcinogenesis and represent potentially initiating events for cancer development. Over the past few years, nutriepigenetics - the influence of dietary components on mechanisms influencing the epigenome - has emerged as an exciting new field in current epigenetic research. During carcinogenesis, major cellular functions and pathways, including drug metabolism, cell cycle regulation, potential to repair DNA damage or to induce apoptosis, response to inflammatory stimuli, cell signalling, and cell growth control and differentiation become deregulated. Recent evidence now indicates that epigenetic alterations contribute to these cellular defects, for example epigenetic silencing of detoxifying enzymes, tumor suppressor genes, cell cycle regulators, apoptosis-inducing and DNA repair genes, nuclear receptors, signal transducers and transcription factors by promoter methylation, and modifications of histones and non-histone proteins such as p53, NF-κB, and the chaperone HSP90 by acetylation or methylation.The present review will summarize the potential of natural chemopreventive agents to counteract these cancer-related epigenetic alterations by influencing the activity or expression of DNA methyltransferases and histone modifying enzymes. Chemopreventive agents that target the epigenome include micronutrients (folate, retinoic acid, and selenium compounds), butyrate, polyphenols from green tea, apples, coffee, black raspberries, and other dietary sources, genistein and soy isoflavones, curcumin, resveratrol, dihydrocoumarin, nordihydroguaiaretic acid (NDGA), lycopene, anacardic acid, garcinol, constituents of Allium species and cruciferous vegetables, including indol-3-carbinol (I3C), diindolylmethane (DIM), sulforaphane, phenylethyl isothiocyanate (PEITC), phenylhexyl isothiocyanate (PHI), diallyldisulfide (DADS) and its metabolite allyl mercaptan (AM), cambinol, and relatively unexplored modulators of histone lysine methylation (chaetocin, polyamine analogs). So far, data are still mainly derived from in vitro investigations, and results of animal models or human intervention studies are limited that demonstrate the functional relevance of epigenetic mechanisms for health promoting or cancer preventive efficacy of natural products. Also, most studies have focused on single candidate genes or mechanisms. With the emergence of novel technologies such as next-generation sequencing, future research has the potential to explore nutriepigenomics at a genome-wide level to understand better the importance of epigenetic mechanisms for gene regulation in cancer chemoprevention.

Environmental toxicants--induced epigenetic alterations and their reversers

Epigenetics has been emphasized in the postgenome era to clarify obscure health risks of environmental toxicants including endocrine disrupting chemicals (EDCs). In addition, mixed exposure in real life can modify health consequences of the toxicants. Particularly, some nutritional and dietary materials modify individual susceptibility through changes in the epigenome. Therefore, we focused on some environmental toxicants that induce epigenetic alterations, and introduced chemopreventive materials to reverse the toxicants-induced epigenetic alterations. Methodologically, we used global and specific DNA methylation as epigenetic end points and searched epigenetic modulators in food. We reviewed various epigenetic end points induced by environmental toxicants including alcohol, asbestos, nanomaterials, benzene, EDCs, metals, and ionizing radiation. The epigenetic end points can be summarized into global hypomethylation and specific hypermethylation at diverse tumor suppress genes. Exposure timing, dose, sex, or organ specificity should be considered to use the epigenetic end points as biomarkers for exposure to the epimutagenic toxicants. Particularly, neonatal exposure to the epimutagens can influence their future adult health because of characteristics of the epimutagens, which disrupt epigenetic regulation in imprinting, organogenesis, development, etc. Considering interaction between epimutagenic toxicants and their reversers in food, we suggest that multiple exposures to them can alleviate or mask epigenetic toxicity in real life. Our present review provides useful information to find new end points of environmental toxicants and to prevention from environment-related diseases.