MicroRNA-152 mediates DNMT1-regulated DNA methylation in the estrogen receptor α gene

Exploring regulatory mechanisms on miRNAs and their implications in inflammation-related diseases

This comprehensive exploration delves into the pivotal role of microRNAs (miRNAs) within the intricate tapestry of cellular regulation. As potent orchestrators of gene expression, miRNAs exhibit diverse functions in cellular processes, extending their influence from the nucleus to the cytoplasm. The complex journey of miRNA biogenesis, involving transcription, processing, and integration into the RNA-induced silencing complex, showcases their versatility. In the cytoplasm, mature miRNAs finely tune cellular functions by modulating target mRNA expression, while their reach extends into the nucleus, influencing transcriptional regulation and epigenetic modifications. Dysregulation of miRNAs becomes apparent in various pathologies, such as cancer, autoimmune diseases, and inflammatory conditions. The adaptability of miRNAs to environmental signals, interactions with transcription factors, and involvement in intricate regulatory networks underscore their significance. DNA methylation and histone modifications adds depth to understanding the dynamic regulation of miRNAs. Mechanisms like competition with RNA-binding proteins, sponging, and the control of miRNA levels through degradation and editing contribute to this complex regulation process. In this review, we mainly focus on how dysregulation of miRNA expression can be related with skin-related autoimmune and autoinflammatory diseases, arthritis, cardiovascular diseases, inflammatory bowel disease, autoimmune and autoinflammatory diseases, and neurodegenerative disorders. We also emphasize the multifaceted roles of miRNAs, urging continued research to unravel their complexities. The mechanisms governing miRNA functions promise advancements in therapeutic interventions and enhanced insights into cellular dynamics in health and disease.

Insight into vitamin D3 action within the ovary-Basic and clinical aspects

Vitamin D3 is a fat-soluble secosteroid predominantly synthesized in the skin or delivered with a diet. Nevertheless, recently it is considered more as a hormone than a vitamin due to its pleiotropic function within the organism ensured by widely distributed vitamin D receptors and metabolic enzymes. Besides the main role in calcium and phosphorus homeostasis, vitamin D3 was shown to regulate many cellular and metabolic processes in normal and cancerous tissues within the immune system, the cardiovascular system, the respiratory system and the endocrine system. The ovary is an important extraskeletal tissue of vitamin D3 action and local metabolism, indicating its role in the regulation of ovarian functions upon physiological and pathological conditions. This chapter reviews firstly the updated information about vitamin D3 metabolism and triggered intracellular pathways. Furthermore, the basic information about ovarian physiology and several aspects of vitamin D3 effects within the ovary are presented. Finally, the special attention is paid into possible mechanism of vitamin D3 action within ovarian pathologies such as premature ovarian failure, polycystic ovary syndrome, and ovarian cancer, considering its clinical application as alternative therapy.

Progress in the Understanding of Estrogen Receptor Alpha Signaling in Triple-Negative Breast Cancer: Reactivation of Silenced ER-α and Signaling through ER-α36

Triple-negative breast cancer (TNBC) is an aggressive tumor that accounts for approximately 15% of total breast cancer cases. It is characterized by poor prognosis and high rate of recurrence compared to other types of breast cancer. TNBC has a limited range of treatment options that include chemotherapy, surgery, and radiation due to the absence of estrogen receptor alpha (ER-α) rendering hormonal therapy ineffective. However, possible targets for improving the clinical outcomes in TNBC exist, such as targeting estrogen signaling through membranous ER-α36 and reactivating silenced ER-α. It has been shown that epigenetic drugs such as DNA methyltransferase and histone deacetylase inhibitors can restore the expression of ER-α. This reactivation of ER-α, presents a potential strategy to re-sensitize TNBC to hormonal therapy. Also, this review provides up-to-date information related to the direct involvement of miRNA in regulating the translation of ER-α mRNA. Specific epi-miRNAs can regulate ER-α expression indirectly by post-transcriptional targeting of mRNAs of enzymes that are involved in DNA methylation and histone deacetylation. Furthermore, ER-α36, an alternative splice variant of ER-α66, is highly expressed in ER-negative breast tumors and activates MAPK/ERK pathway, promoting cell proliferation, escaping apoptosis, and enhancing metastasis. In the future, these recent advances may be helpful for researchers working in the field to obtain novel treatment options for TNBC, utilizing epigenetic drugs and epi-miRNAs that regulate ER-α expression. Also, there is some evidence to suggest that drugs that decrease the expression of ER-α36 may be effective in treating TNBC.

Crosstalk between miRNAs and DNA Methylation in Cancer

miRNAs are some of the most well-characterized regulators of gene expression. Integral to several physiological processes, their aberrant expression often drives the pathogenesis of both benign and malignant diseases. Similarly, DNA methylation represents an epigenetic modification influencing transcription and playing a critical role in silencing numerous genes. The silencing of tumor suppressor genes through DNA methylation has been reported in many types of cancer and is associated with tumor development and progression. A growing body of literature has described the crosstalk between DNA methylation and miRNAs as an additional layer in the regulation of gene expression. Methylation in miRNA promoter regions inhibits its transcription, while miRNAs can target transcripts and subsequently regulate the proteins responsible for DNA methylation. Such relationships between miRNA and DNA methylation serve an important regulatory role in several tumor types and highlight a novel avenue for potential therapeutic targets. In this review, we discuss the crosstalk between DNA methylation and miRNA expression in the pathogenesis of cancer and describe how miRNAs influence DNA methylation and, conversely, how methylation impacts the expression of miRNAs. Finally, we address how these epigenetic modifications may be leveraged as biomarkers in cancer.

Identification of the Mechanism of Matrine Combined with Glycyrrhizin for Hepatocellular Carcinoma Treatment through Network Pharmacology and Bioinformatics Analysis

Matrine and glycyrrhizin are representative active ingredients of traditional Chinese medicine (TCM) used in clinical practice. Studies have demonstrated that matrine has antitumor pharmacological effects and that glycyrrhizin protects liver function. However, the potential bioactive compounds and mechanisms remain unknown, as well as whether they have synergistic effects in killing cancer cells and protecting liver cells. To investigate the synergistic effects and mechanism of matrine combined with glycyrrhizin in hepatocellular carcinoma (HCC) treatment, we used both network pharmacology and bioinformatics analyses. First, the chemical gene interaction information of matrine and glycyrrhizin was obtained from the PubChem database. The pathogenic genes of HCC were accessed from five public databases. The RNA sequencing data and clinical information of HCC patients were downloaded from The Cancer Genome Atlas (TCGA). Next, the overlapping genes among the potential targets of matrine and glycyrrhizin and HCC-related targets were determined using bioinformatics analysis. We constructed the drug-target interaction network. Prognosis-associated genes were acquired through the univariate Cox regression model and Lasso-Cox regression model. The results were verified by the International Cancer Genome Consortium (ICGC) database. Finally, we predicted the immune function of the samples. The drug-target interaction network consisted of 10 matrine and glycyrrhizin targets. We selected a Lasso-Cox regression model consisting of 3 differentially expressed genes (DEGs) to predict the efficacy of the combination in HCC. Subsequently, we successfully predicted the overall survival of HCC patients using the constructed prognostic model and investigated the correlation of the immune response. Matrine and glycyrrhizin have synergistic effects on HCC. The model we obtained consisted of three drug-target genes by Lasso-Cox regression analysis. The model independently predicted the combined effect of matrine and glycyrrhizin in HCC treatment and OS, which will be helpful for guiding clinical treatment. The prognostic model was correlated with the immune cells and immune checkpoints of patients, which had an adjuvant effect on HCC immunotherapy. Matrine and glycyrrhizin can have therapeutic effects on HCC by promoting the production or enhancing the core gene activity in the drug network and improving the immune system function of patients.

The Regulation of Adipose Tissue Health by Estrogens

Obesity and its' associated metabolic diseases such as type 2 diabetes and cardiometabolic disorders are significant health problems confronting many countries. A major driver for developing obesity and metabolic dysfunction is the uncontrolled expansion of white adipose tissue (WAT). Specifically, the pathophysiological expansion of visceral WAT is often associated with metabolic dysfunction due to changes in adipokine secretion profiles, reduced vascularization, increased fibrosis, and enrichment of pro-inflammatory immune cells. A critical determinate of body fat distribution and WAT health is the sex steroid estrogen. The bioavailability of estrogen appears to favor metabolically healthy subcutaneous fat over visceral fat growth while protecting against changes in metabolic dysfunction. Our review will focus on the role of estrogen on body fat partitioning, WAT homeostasis, adipogenesis, adipocyte progenitor cell (APC) function, and thermogenesis to control WAT health and systemic metabolism.

Epigenetic Studies of Chinese Herbal Medicine: Pleiotropic Role of DNA Methylation

Accumulating knowledge has been achieved on DNA methylation participating in numerous cellular processes and multiple human diseases; however, few studies have addressed the pleiotropic role of DNA methylation in Chinese herbal medicine (CHM). CHM has been used worldwide for the prevention and treatment of multiple diseases. Newly developed epigenetic techniques have brought great opportunities for the development of CHM. In this review, we summarize the DNA methylation studies and portray the pleiotropic role of DNA methylation in CHM. DNA methylation serves as a mediator participating in plant responses to environmental factors, and thus affecting CHM medicinal plants growth and bioactive compound biosynthesis which are vital for therapeutic effects. Furthermore, DNA methylation helps to uncover the pharmaceutical mechanisms of CHM formulae, herbs, and herbal-derived compounds. It also provides scientific validation for constitution theory and other essential issues of CHM. This newly developed field of DNA methylation is up-and-coming to address many complicated scientific questions of CHM; it thus not only promotes disease treatment but also facilitates health maintenance.

An update on the phenotypic switching of vascular smooth muscle cells in the pathogenesis of atherosclerosis

Vascular smooth muscle cells (VSMCs) are involved in phenotypic switching in atherosclerosis. This switching is characterized by VSMC dedifferentiation, migration, and transdifferentiation into other cell types. VSMC phenotypic transitions have historically been considered bidirectional processes. Cells can adopt a physiological contraction phenotype or an alternative "synthetic" phenotype in response to injury. However, recent studies, including lineage tracing and single-cell sequencing studies, have shown that VSMCs downregulate contraction markers during atherosclerosis while adopting other phenotypes, including macrophage-like, foam cell, mesenchymal stem-like, myofibroblast-like, and osteochondral-like phenotypes. However, the molecular mechanism and processes regulating the switching of VSMCs at the onset of atherosclerosis are still unclear. This systematic review aims to review the critical outstanding challenges and issues that need further investigation and summarize the current knowledge in this field.

Dysregulated epigenetic modifications in psoriasis

The observed incidence of psoriasis has been gradually increasing over time (J Am Acad Dermatol, 03, 2009, 394), but the underlying pathogenic factors have remained unclear. Recent studies suggest the importance of epigenetic modification in the pathogenesis of psoriasis. Aberrant epigenetic patterns including changes in DNA methylation, histone modifications and non-coding RNA expression are observed in psoriatic skin. Reversing these epigenetic mechanisms has showed improvement in psoriatic phenotypes, making epigenetic therapy a potential avenue for psoriasis treatment. Here, we summarize relevant evidence for epigenetic dysregulation contributing to psoriasis susceptibility and pathogenesis, and the factors responsible for epigenetic modifications, providing directions for potential future clinical avenues.

DNA Methylation in Atherosclerosis: A New Perspective

Atherosclerotic cardiovascular diseases, in which atherosclerosis (AS) is the main pathologic basis, are currently the primary diseases leading to human deaths. Emerging evidence showed that DNA methylation, which could affect the transcription and expression of critical regulatory genes, has key roles in AS. Aberrant DNA methylation including aberrant hypomethylation and hypermethylation plays key roles in endothelial-cell dysfunction, macrophage inflammation, abnormal proliferation of vascular smooth muscle cells, plaque rupture, and thrombosis in AS. Chinese herbal medicines, including single compounds and formulations, showed light on the treatment of AS through regulating the aberrant DNA methylation in AS. Targeting the aberrant DNA methylation may be one of the most important treatment strategies in the cure and prevention of AS. In this review, we focus on the relationship between DNA methylation and AS, as well as the beneficial effects of Chinese herbal medicines on DNA methylation in AS.

Adenosine kinase is critical for neointima formation after vascular injury by inducing aberrant DNA hypermethylation

AIMS

Adenosine receptors and extracellular adenosine have been demonstrated to modulate vascular smooth muscle cell (VSMC) proliferation and neointima formation. Adenosine kinase (ADK) is a major enzyme regulating intracellular adenosine levels but is function in VSMC remains unclear. Here, we investigated the role of ADK in vascular injury-induced smooth muscle proliferation and delineated the mechanisms underlying its action.

METHODS AND RESULTS

We found that ADK expression was higher in the neointima of injured vessels and in platelet-derived growth factor-treated VSMCs. Genetic and pharmacological inhibition of ADK was enough to attenuate arterial injury-induced neointima formation due to inhibition of VSMC proliferation. Mechanistically, using infinium methylation assays and bisulfite sequencing, we showed that ADK metabolized the intracellular adenosine and potentiated the transmethylation pathway, then induced the aberrant DNA hypermethylation. Pharmacological inhibition of aberrant DNA hypermethylation increased KLF4 expression and suppressed VSMC proliferation as well as the neointima formation. Importantly, in human femoral arteries, we observed increased ADK expression and DNA hypermethylation as well as decreased KLF4 expression in neointimal VSMCs of stenotic vessels suggesting that our findings in mice are relevant for human disease and may hold translational significance.

CONCLUSION

Our study unravels a novel mechanism by which ADK promotes VSMC proliferation via inducing aberrant DNA hypermethylation, thereby down-regulating KLF4 expression and promoting neointima formation. These findings advance the possibility of targeting ADK as an epigenetic modulator to combat vascular injury.

Interaction Between microRNA and DNA Methylation in Atherosclerosis

Atherosclerosis (AS) is a chronic inflammatory disease accompanied by complex pathological changes, such as endothelial dysfunction, foam cell formation, and vascular smooth muscle cell proliferation. Many approaches, including regulating AS-related gene expression in the transcriptional or post-transcriptional level, contribute to alleviating AS development. The DNA methylation is a crucial epigenetic modification in regulating cell function by silencing the relative gene expression. The microRNA (miRNA) is a type of noncoding RNA that plays an important role in gene post-transcriptional regulation and disease development. The DNA methylation and the miRNA are important epigenetic factors in AS. However, recent studies have found a mutual regulation between these two factors in AS development. In this study, recent insights into the roles of miRNA and DNA methylation and their interaction in the AS progression are reviewed.

Statins: Epidrugs with effects on endothelial health?

BACKGROUND

Epigenetic events involving the methylation of CpG cites in DNA, histone modifications and noncoding RNAs correlated with many essential processes in human cells and diseases, such as cancer and cardiovascular diseases. HMG-CoA reductase inhibitors (statins)-the LDL cholesterol-lowering drugs-are broadly used in cardio- and cerebro-vascular diseases. It is well established that statins exert pleiotropic functions, but how they exert effects on epigenetic modifications independently of HMG-CoA reductase inhibition is not yet clear. Thereby, understanding these mechanisms may pave the way for further clinical application of statin therapy.

DESIGN

Following and electronic database search, studies reporting substantial effects of statins on epigenetic reprogramming in both cultured cells and in vivo models were retrieved and reviewed.

RESULTS

Epigenetic mechanisms play an essential role in cellular development and function, and data collected in the past few years have revealed that many of the pleiotropic properties of statins are mediated by epigenetic mechanisms. Furthermore, those 'nonclassical' effects are not limited to CV field but they would extend to other conditions such as malignancies.

CONCLUSION

This review suggests that the epigenetic effects of statins mediate, at least in part, the pleiotropic actions of these drugs but further validation of such effects in clinical studies is yet to be provided.

Aging mechanisms-A perspective mostly from Drosophila

A mechanistic understanding of the natural aging process, which is distinct from aging-related disease mechanisms, is essential for developing interventions to extend lifespan or healthspan. Here, we discuss current trends in aging research and address conceptual and experimental challenges in the field. We examine various molecular markers implicated in aging with an emphasis on the role of heterochromatin and epigenetic changes. Studies in model organisms have been advantageous in elucidating conserved genetic and epigenetic mechanisms and assessing interventions that affect aging. We highlight the use of Drosophila, which allows controlled studies for evaluating genetic and environmental contributors to aging conveniently. Finally, we propose the use of novel methodologies and future strategies using Drosophila in aging research.

Exosomal MicroRNA-126 from RIPC Serum Is Involved in Hypoxia Tolerance in SH-SY5Y Cells by Downregulating DNMT3B

Ischemic tolerance in the brain can be induced by transient limb ischemia, and this phenomenon is termed remote ischemic preconditioning (RIPC). It still remains elusive how this transfer of tolerance occurs. Exosomes can cross the blood-brain barrier, and some molecules may transfer neuroprotective signals from the periphery to the brain. Serum miRNA-126 is associated with ischemic stroke, and exosomal miRNA-126 has shown protective effects against acute myocardial infarction. Therefore, this study aims to explore whether exosomal miRNA-126 from RIPC serum can play a similar neuroprotective role. Exosomes were isolated from the venous serum of four healthy young male subjects, both before and after RIPC. Exosomal miRNA-126 was measured by real-time PCR. The miRNA-126 target sequence was predicted by bioinformatics software. SH-SY5Y neuronal cells were incubated with exosomes, and the cell cycle was analyzed by flow cytometry. The expression and activity of DNA methyltransferase (DNMT) 3B, a potential target gene of miRNA-126, were examined in SH-SY5Y cells. The cell viability of SH-SY5Y cells exposed to oxygen-glucose deprivation (OGD) was also investigated. To confirm the association between miRNA-126 and DNMT3B, we overexpressed miRNA-126 in SH-SY5Y cells using lentiviral transfection. miRNA-126 expression was upregulated in RIPC exosomes, and bioinformatics prediction showed that miRNA-126 could bind with DNMT3B. DNMT levels and DNMT3B activity were downregulated in SH-SY5Y cells incubated with RIPC exosomes. After overexpression of miRNA-126 in SH-SY5Y cells, global methylation levels and DNMT3B gene expression were downregulated in these cells, consistent with the bioinformatics predictions. RIPC exosomes can affect the cell cycle and increase OGD tolerance in SH-SY5Y cells. RIPC seems to have neuroprotective effects by downregulating the expression of DNMTs in neural cells through the upregulation of serum exosomal miRNA-126.

Roles and Functions of Exosomal Non-coding RNAs in Vascular Aging

Aging is a progressive loss of physiological integrity and functionality process which increases susceptibility and mortality to diseases. Vascular aging is a specific type of organic aging. The structure and function changes of endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) are the main cause of vascular aging, which could influence the threshold, process, and severity of vascular related diseases. Accumulating evidences demonstrate that exosomes serve as novel intercellular information communicator between cell to cell by delivering variety biologically active cargos, especially exosomal non-coding RNAs (ncRNAs), which are associated with most of aging-related biological and functional disorders. In this review, we will summerize the emerging roles and mechanisms of exosomal ncRNAs in vascular aging and vascular aging related diseases, focusing on the role of exosomal miRNAs and lncRNAs in regulating the functions of ECs and VSMCs. Moreover, the relationship between the ECs and VSMCs linked by exosomes, the potential diagnostic and therapeutic application of exosomes in vascular aging and the clinical evaluation and treatment of vascular aging and vascular aging related diseases will also be discussed.

Diagnostic and theranostic microRNAs in the pathogenesis of atherosclerosis

MicroRNAs (miRNAs) are a group of small single strand and noncoding RNAs that regulate several physiological and molecular signalling pathways. Alterations of miRNA expression profiles may be involved with pathophysiological processes underlying the development of atherosclerosis and cardiovascular diseases, including changes in the functions of the endothelial cells and vascular smooth muscle cells, such as cell proliferation, migration and inflammation, which are involved in angiogenesis, macrophage function and foam cell formation. Thus, miRNAs can be considered to have a crucial role in the progression, modulation and regulation of every stage of atherosclerosis. Such potential biomarkers will enable us to predict therapeutic response and prognosis of cardiovascular diseases and adopt effective preclinical and clinical treatment strategies. In the present review article, the current data regarding the role of miRNAs in atherosclerosis were summarized and the potential miRNAs as prognostic, diagnostic and theranostic biomarkers in preclinical and clinical studies were further discussed. The highlights of this review are expected to present opportunities for future research of clinical therapeutic approaches in vascular diseases resulting from atherosclerosis with an emphasis on miRNAs.

miR-221 Alleviates the Ox-LDL-Induced Macrophage Inflammatory Response via the Inhibition of DNMT3b-Mediated NCoR Promoter Methylation

Atherosclerosis (AS) is a chronic inflammatory disease, and macrophages play a key role in all phases of AS. Recent studies have shown that miR-221 is a biomarker for AS and stroke; however, the role and mechanism of miR-221 in AS are unclear. Herein, we found that miR-221 and NCoR levels were decreased in ox-LDL-treated THP-1-derived macrophages. In contrast, DNMT3b, IL-6, and TNF-α expression levels were increased under these conditions. Upregulation of miR-221 or NCoR could partially inhibit ox-LDL-induced IL-6 and TNF-α expression. Further studies showed that DNMT3b was a target of miR-221. DNMT3b inhibition also suppressed IL-6 and TNF-α expression and increased NCoR expression in the presence of ox-LDL. Moreover, DNMT3b was involved in ox-LDL-induced DNA methylation in the promoter region of NCoR. These findings suggest that miR-221 suppresses ox-LDL-induced inflammatory responses via suppressing DNMT3b-mediated DNA methylation in the promoter region of NCoR. These results provide a rationale for using intracellular miR-211 as a possible antiatherosclerotic target.

The impact of epigenetics on cardiovascular disease

Mortality and morbidity from cardiovascular diseases (CVDs) represents a huge burden to society. It is recognized that environmental factors and individual lifestyles play important roles in disease susceptibility, but the link between these external risk factors and our genetics has been unclear. However, the discovery of sequence-independent heritable DNA changes (epigenetics) have helped us to explain the link between genes and the environment. Multiple diverse epigenetic processes, including DNA methylation, histone modification, and the expression of non-coding RNA molecules affect the expression of genes that produce important changes in cellular differentiation and function, influencing the health and adaptability of the organism. CVDs such as congenital heart disease, cardiomyopathy, heart failure, cardiac fibrosis, hypertension, and atherosclerosis are now being viewed as much more complex and dynamic disorders. The role of epigenetics in these and other CVDs is currently under intense scrutiny, and we can expect important insights to emerge, including novel biomarkers and new approaches to enable precision medicine. This review summarizes the recent advances in our understanding of the role of epigenetics in CVD.

micro-RNAs dependent regulation of DNMT and HIF1α gene expression in thrombotic disorders

MicroRNAs (miRNAs) are involved in a wide variety of cellular processes and post-transcriptionally regulate several mechanism and diseases. However, contribution of miRNAs functioning during hypoxia and DNA methylation together is less understood. The current study was aimed to find a shared miRNAs signature upstream to hypoxia (via HIF gene family members) and methylation (via DNMT gene family members). This was followed by the global validation of the hypoxia related miRNA signature using miRNA microarray meta-analysis of the hypoxia induced human samples. We further concluded the study by looking into thrombosis related terms and pathways enriched during protein-protein interaction (PPI) network analysis of these two sets of gene family. Network prioritization of these shared miRNAs reveals miR-129, miR-19band miR-23b as top regulatory miRNAs. A comprehensive meta-analysis of microarray datasets of hypoxia samples revealed 29 differentially expressed miRNAs. GSEA of the interacting genes in the DNMT-HIF PPI network indicated thrombosis associated pathways including “Hemostasis”, “TPO signaling pathway” and “angiogenesis”. Interestingly, the study has generated a novel database of candidate miRNA signatures shared between hypoxia and methylation, and their relation to thrombotic pathways, which might aid in the development of potential therapeutic biomarkers.

Network Pharmacology-Based Study on the Mechanism of Bushen-Jianpi Decoction in Liver Cancer Treatment

To investigate the mechanism of a Bushen-Jianpi decoction (BSJPD) in liver cancer (LC) treatment, we analyzed clinical therapy data, conducted network pharmacology analysis, and performed pharmacological experimental verification in vitro and in vivo. The univariate analysis of clinical therapy showed that the BSJPD was protective factor (p < 0.05). The network pharmacology analysis showed that 9 compounds were important nodes of BSJPD-LC therapy network. In experimental verification, the rate of apoptosis increased in the liver tumors of mice treated with the BSJPD (p < 0.05); drug serum with 20 % BSJPD inhibited cell viability (p < 0.05) and reduced the expression of PI3K, the Bcl-xL/BAD ratio, and the levels of p53 and p-Akt in HepG2 cells. Moreover, licochalcone A, alisol B, and hederagenin inhibited cell viability (p < 0.05), induced cell apoptosis (p < 0.01), reduced p-Akt levels, and increased cleaved-CASP3 (p < 0.05) and p53 expression levels in HepG2 cells. These data suggest that the BSJPD prolongs the survival of LC patients and induces apoptosis and that it may be associated with the regulation of PI3K, Akt, p53, CASP3, and Bcl-xL/BAD expression.

The microRNAs Regulating Vascular Smooth Muscle Cell Proliferation: A Minireview

Vascular smooth muscle cell (VSMC) proliferation plays a critical role in atherosclerosis. At the beginning of the pathologic process of atherosclerosis, irregular VSMC proliferation promotes plaque formation, but in advanced plaques VSMCs are beneficial, promoting the stability and preventing rupture of the fibrous cap. Recent studies have demonstrated that microRNAs (miRNAs) expressed in the vascular system are involved in the control of VSMC proliferation. This review summarizes recent findings on the miRNAs in the regulation of VSMC proliferation, including miRNAs that exhibit the inhibition or promotion of VSMC proliferation, and their targets mediating the regulation of VSMC proliferation. Up to now, most of the studies were performed only in cultured VSMC. While the modulation of miRNAs is emerging as a promising strategy for the regulation of VSMC proliferation, most of the effects of miRNAs and their targets in vivo require further investigation.

Downregulation of miR-152 contributes to DNMT1-mediated silencing of SOCS3/SHP-1 in non-Hodgkin lymphoma

Understanding the molecular mechanisms for the development of non-Hodgkin lymphoma (NHL) will improve our ability to cure the patients. qRT-PCR was applied for the examination of the efficiency of shRNA for DNMT1, the expression of suppressor genes, miRNA-152. The MTT analysis, cell cycle analysis, clonal formation, and apoptotic analysis were used to examine the functions of DNMT1 and miR-152 in lymphoma cells. Methylation-specific polymerase chain reaction (MSP) was used to examine the methylation of tumor suppressor genes. The dual luciferase assay and western blot were used to validate if DNMT1 is the target of miR-152. For the in vivo experiments, the lymphoma cells were injected into the nude mice for quantification of the tumor growth after transfection of miR-152 mimics. Knockdown of DNMT1 by shRNA (sh-DNMT1) in OCI-Ly10 and Granta-159 cells significantly upregulated the expression of tumor suppressor genes (SOCS3, BCL2L10, p16, p14, and SHP-1) via decreasing their methylation level. At the cellular level, we found sh-DNMT1 inhibited the proliferation, clonal formation and cell cycle progression and induced the cell apoptosis of lymphoma cells. Furthermore, we found miR-152 can downregulates the expression of DNMT1 via directly targeting the gene. Overexpression of miR-152 also increased the expression of tumor suppressor genes SOCS3 and SHP-1. And miR-152 also can inhibit the cell proliferation and induce the cell apoptosis. Moreover, we found overexpression of miR-152 significantly repressed the tumor growth with decreased DNMT1 expression and increased expression of tumor suppressor genes in vivo. Our study demonstrates that miR-152 can inhibit lymphoma growth via suppressing DNMT1-mediated silencing of SOCS3 and SHP-1. These data demonstrate a new mechanism for the development of NHL and this may provide a new therapeutic target for NHL.

TLR3 Mediates Repair and Regeneration of Damaged Neonatal Heart through Glycolysis Dependent YAP1 Regulated miR-152 Expression

The present study investigated whether TLR3 is required for neonatal heart repair and regeneration following myocardial infarction (MI). TLR3 deficient neonatal mice exhibited impaired cardiac functional recovery and a larger infarct size, while wild type neonatal mice showed cardiac functional recovery and small infarct size after MI. The data suggest that TLR3 is essential for the regeneration and repair of damaged neonatal myocardium. In vitro treatment of neonatal cardiomyocytes with a TLR3 ligand, Poly (I:C), significantly enhances glycolytic metabolism, YAP1 activation and proliferation of cardiomyocytes which were prevented by a glycolysis inhibitor, 2-deoxyglucose (2-DG). Administration of 2-DG to neonatal mice abolished cardiac functional recovery and YAP activation after MI, suggesting that TLR3-mediated regeneration and repair of the damaged neonatal myocardium is through glycolytic-dependent YAP1 activation. Inhibition of YAP1 activation abolished Poly (I:C) induced proliferation of neonatal cardiomyocytes. Interestingly, activation of YAP1 increases the expression of miR-152 which represses the expression of cell cycle inhibitory proteins, P27kip1 and DNMT1, leading to cardiomyocyte proliferation. We conclude that TLR3 is required for neonatal heart regeneration and repair after MI. The mechanisms involve glycolytic-dependent YAP1 activation, resulting in miR-152 expression which targets DNMT1/p27kip1.

Silencing DNA methyltransferase 1 (DNMT1) inhibits proliferation, metastasis and invasion in ESCC by suppressing methylation of RASSF1A and DAPK

Our previous study showed DNMT1 is up-regulated in esophageal squamous cell carcinoma (ESCC), which is associated with methylation of tumor suppressors. In the current study, we investigate the role of DNMT1 in ESCC. We found silencing DNMT1 inhibited proliferation, metastasis and invasion of three different ESCC cells, K150, K410 and K450. We also found silencing DNMT1 induced G1 arrest and cell apoptosis in K150, K410 and K450 cells. In vivo study showed silencing DNMT1 suppressed tumor growth in nude mice. In addition, silencing DNMT1 increased expression of tumor suppressor genes, RASSF1A and DAPK, in ESCC cells and ESCC xenograft in nude mice. Moreover, silencing DNMT1 decreased methylation in promoter of RASSF1A and DAPK. In conclusion, our data demonstrated that silencing DNMT1 inhibits proliferation, metastasis and invasion in ESCC by suppressing methylation of RASSF1A and DAPK.

Neuronal Dnmt1 Deficiency Attenuates Diet-Induced Obesity in Mice

Aberrant neuronal DNA methylation patterns have been implicated in the promotion of obesity development; however, the role of neuronal DNA methyltransferases (Dnmts), enzymes that catalyze DNA methylation, in energy balance remains poorly understood. We investigated whether neuronal Dnmt1 regulates normal energy homeostasis and obesity development using a neuronal Dnmt1 knockout (ND1KO) mouse model, Dnmt1fl/fl Synapsin1Cre, which specifically deletes Dnmt1 in neurons. Neuronal Dnmt1 deficiency reduced adiposity in chow-fed mice and attenuated obesity in high-fat diet (HFD)-fed male mice. ND1KO male mice had reduced food intake and increased energy expenditure with the HFD. Furthermore, these mice had improved insulin sensitivity, as measured using an insulin tolerance test. The HFD-fed ND1KO mice had smaller fat pads and upregulation of thermogenic genes in brown adipose tissue. These data suggest that neuronal Dnmt1 plays an important role in regulating energy homeostasis. Notably, ND1KO male mice had elevated estrogen receptor-α (ERα) gene expression in the medial hypothalamus, which previously has been shown to control body weight. Immunohistochemistry experiments revealed that ERα protein expression was upregulated specifically in the dorsomedial region of the ventromedial hypothalamus, a region that might mediate the central effect of leptin. We conclude that neuronal Dnmt1 regulates energy homeostasis through pathways controlling food intake and energy expenditure. In addition, ERα expression in the dorsomedial region of the ventromedial hypothalamus might mediate these effects.

miRNA-148a regulates the expression of the estrogen receptor through DNMT1-mediated DNA methylation in breast cancer cells

Breast cancer remains the most prevalent cancer among women worldwide. The expression of estrogen receptor-α (ER-α) is an important marker for prognosis. ER-α status may be positive or negative in breast cancer cells, although the cause of negative or positive status is not yet fully characterized. In the present study, the expression of ER-α and miRNA-148a was assessed in two breast cancer cell lines, HCC1937 and MCF7. An association between ER-α and miRNA-148a expression was identified. It was then demonstrated that DNA methyltransferase 1 (DNMT1) is a target of miRNA-148a, which may suppress the expression of ER-α via DNA methylation. Finally, an miRNA-148a mimic or inhibitor was transfected into MCF7 cells; the miRNA-148a mimic increased ER-α expression whereas the miRNA-148a inhibitor decreased ER-α expression. In conclusion, it was identified that miRNA-148a regulates ER-α expression through DNMT1-mediated DNA methylation in breast cancer cells. This may represent a potential miRNA-based strategy to modulate the expression of ER-α and provide a novel perspective for investigating the role of miRNAs in treating breast cancer.

Lipopolysaccharide induced vascular smooth muscle cells proliferation: A new potential therapeutic target for proliferative vascular diseases

Vascular smooth muscle cells (VSMCs) proliferation is involved in vascular atherosclerosis and restenosis. Recent studies have demonstrated that lipopolysaccharide (LPS) promotes VSMCs proliferation, but the signalling pathways which are involved are not completely understood. The purpose of this review was to summarize the existing knowledge of the role and molecular mechanisms involved in controlling VSMCs proliferation stimulated by LPS and mediated by toll-like receptor 4 (TLR4) signalling pathways. Moreover, the potential inhibitors of TLR4 signalling for VSMCs proliferation in proliferative vascular diseases are discussed.

The Yin–Yang Dynamics of DNA Methylation Is the Key Regulator for Smooth Muscle Cell Phenotype Switch and Vascular Remodeling

Objective—

DNA methylation plays an important role in chronic diseases such as atherosclerosis, yet the mechanisms are poorly understood. The objective of our study is to indicate the regulatory mechanisms of DNA methylation in vascular smooth muscle cells (VSMCs) and its roles in atherosclerosis.

Approach and Results—

In ApoE −/− mice fed a Western diet, DNA methyltransferase inhibitor, 5-aza-2′-deoxycytidine, significantly attenuated atherosclerotic lesions (20.1±2.2% versus 30.8±7.5%; P =0.016) and suppressed DNA methyltransferase activity and concomitantly decreased global 5-methylcytosine content in atherosclerotic lesions of ApoE −/− mice. Using a carotid ligation model, we found that 5-aza-2′-deoxycytidine also dramatically inhibited neointimal formation (intimal area: 2.25±0.14×10 4 versus 4.07±0.22×10 4 μm 2 ; P <0.01). Abnormal methylation status at the promoter of ten–eleven translocation 2, one of the key demethylation enzymes in mammals, was ameliorated after 5-aza-2′-deoxycytidine treatment, which in turn caused an increase in global DNA hydroxymethylation and 5-hydroxymethylcytosine enrichment at the promoter of Myocardin. In vitro, 5-aza-2′-deoxycytidine treatment or DNA methyltransferase 1 knockdown decreased global 5-methylcytosine content and restored Myocardin expression in VSMCs induced by platelet-derived growth factor, thus preventing excessive VSMCs dedifferentiation, proliferation, and migration. Furthermore, DNA methyltransferase 1 binds to ten–eleven translocation 2 promoter and is required for ten–eleven translocation 2 methylation in VSMCs.

Conclusions—

The inhibitory effects of DNA demethylation on global 5-methylcytosine content and ten–eleven translocation 2 hypermethylation in atherosclerotic aorta can recover 5-hydroxymethylcytosine enrichment at the Myocardin promoter and prevent VSMC dedifferentiation and vascular remodeling.

Epigenetic regulation of estrogen receptor α contributes to age-related differences in transcription across the hippocampal regions CA1 and CA3

The expression of estrogen receptor alpha (ERα) varies across brain regions and changes with age and according to the previous history of estradiol exposure. ERα is regulated by a number of mechanisms including the level of mRNA (Esr1) expression. For this study, we took advantage of regional differences in hippocampal ERα expression to investigate DNA ERα promoter methylation at CpG dinucleotide sites as a potential epigenetic mechanism for regulating gene expression. Young and aged female Fischer 344 rats were ovariectomized, and Esr1 expression and ERα promoter methylation were examined in hippocampal regions CA1 and CA3, either 3 or 14 weeks following surgery. The results indicate that reduced Esr1 expression in region CA1 relative to CA3 was associated with an increase in DNA methylation in region CA1, particularly for the first CpG site. Additionally, differential methylation of distal CpG sites, 11-17, was associated with altered Esr1 expression during aging or following long-term hormone deprivation. The results support the idea that methylation of site 1 may be the primary regulatory region for cross-regional patterns in ERα expression, while distal sites are modifiable across the life span and may act as a feedback mechanism for ERα activity.

DNA methylation and not H3K4 trimethylation dictates the expression status of miR-152 gene which inhibits migration of breast cancer cells via DNMT1/CDH1 loop

MicroRNAs (miRNA) are small non-coding RNAs which targets most protein-coding transcripts (mRNA) and destroy them. Thus miRNA controls the abundance of those specific proteins and impact on developmental, physiological and pathological processes. Dysregulation of miRNA function thus may lead to various clinicopathological complications, including breast cancer. Silencing of miR-152 gene due to promoter DNA methylation alter the expression pattern of several other genes. E-cadherin (CDH1) forms the core of adherent junctions between surrounding epithelial cells, link with actin cytoskeleton and affects cell signaling. CDH1 gene is down regulated by promoter DNA methylation during cancer progression. In this investigation, we attempt to elucidate the correlation of miR-152 and CDH1 function, as it is well known that the loss of CDH1 function is one of the major reasons for cancer metastasis and aggressiveness of spreading. For the first time we have shown that loss of CDH1 expression is directly proportional to the loss of miR-152 function in breast cancer cells. mRNA and protein expression profile of DNMT1 implicate that miR-152 targets DNMT1 mRNA and inhibits its protein expression. Tracing the molecular marks on DNA and histone 3 for understanding the mechanism of gene regulation by ChIP analyses leads to a paradoxical result that shows DNA methylation adjacent to active histone marking (enrichment of H3K4me3) silence miR-152 gene. Further experiments revealed that DNMT1 plays crucial role for regulation of miR-152 gene. When DNMT1 protein function is blocked miR-152 expression prevails and destroys the mRNA of DNMT1; this molecular regulatory mechanism is creating a cyclic feedback loop, which is now focused as DNMT1/miR-152 switch for on/off of DNMT1 target genes. We discovered modulation of CDH1 gene expression by DNMT1/miR-152 switches. We have demonstrated further that DNMT1 down regulation mediated upregulation of CDH1 (hereafter, DNMT1/CDH1 loop) in presence of ectopic-excess of miR-152 prevents migration of cancer cells. Our data provides novel insights into the regulation mechanism of miRNA and mRNA/protein coding genes and enhances the amplitude of cancer epigenome.

Down-regulation of hsa-miR-1264 contributes to DNMT1-mediated silencing of SOCS3

Previously we found decreased expression of SOCS3 in neointimal hyperplastic region following balloon angioplasty in atherosclerotic micro swine. In our recent in vitro studies using human coronary artery smooth muscle cells (HCASMC), we observed the inhibition of SOCS3 expression in the presence of both TNF-α and IGF-1, correlating with the in vivo findings in microswine. We also reported that two independent mechanisms, JAK/STAT3/NFκB and promoter methylation of SOCS3 were responsible for TNF-α and IGF-1 induced SOCS3 inhibition. In this study, using miRNA array and gene expression approaches, we explored the molecular mechanisms involved in the above SOCS3 repression and identified several miRNAs that are associated with the regulation of SOCS3 expression. Our miRNA expression profiling revealed profound down-regulation of two specific miRNAs, hsa-miR-758 and hsa-miR-1264, whose expression levels were decreased by 8-10 folds in HCASMCs that were treated with both TNF-α and IGF-1. This was accompanied with a significant up-regulation of three specific miRNAs, hsa-miR-155, hsa-miR-146b-5p and hsa-miR-146a, which showed about 3-7 fold increases in their expression levels. Importantly, we also found that the miRNA hsa-miR-1264 targets DNA methyltransferase-1 (DNMT1) transcripts by binding to its 3'UTR region to affect its expression. Expression of hsa-miR-1264 in HCASMCs not only resulted in decreased DNMT1 mRNA transcripts but it also increased SOCS3 expression. The treatment with TNF-α and IGF-1 resulted in drastic decrease in hsa-miR-1264 levels with no change in the expression of DNMT1. Consequently, the DNMT1 activity caused hypermethylation in the CpG island of the SOCS3 promoter region and inhibited its expression. This could be a causative epigenetic mechanism associated with TNF-α and IGF-1 induced smooth muscle cell proliferation involved in the pathogenesis of coronary artery hyperplasia and restenosis.

Methylation and microRNA-mediated epigenetic regulation of SOCS3

Epigenetic gene silencing of several genes causes different pathological conditions in humans, and DNA methylation has been identified as one of the key mechanisms that underlie this evolutionarily conserved phenomenon associated with developmental and pathological gene regulation. Recent advances in the miRNA technology with high throughput analysis of gene regulation further increased our understanding on the role of miRNAs regulating multiple gene expression. There is increasing evidence supporting that the miRNAs not only regulate gene expression but they also are involved in the hypermethylation of promoter sequences, which cumulatively contributes to the epigenetic gene silencing. Here, we critically evaluated the recent progress on the transcriptional regulation of an important suppressor protein that inhibits cytokine-mediated signaling, SOCS3, whose expression is directly regulated both by promoter methylation and also by microRNAs, affecting its vital cell regulating functions. SOCS3 was identified as a potent inhibitor of Jak/Stat signaling pathway which is frequently upregulated in several pathologies, including cardiovascular disease, cancer, diabetes, viral infections, and the expression of SOCS3 was inhibited or greatly reduced due to hypermethylation of the CpG islands in its promoter region or suppression of its expression by different microRNAs. Additionally, we discuss key intracellular signaling pathways regulated by SOCS3 involving cellular events, including cell proliferation, cell growth, cell migration and apoptosis. Identification of the pathway intermediates as specific targets would not only aid in the development of novel therapeutic drugs, but, would also assist in developing new treatment strategies that could successfully be employed in combination therapy to target multiple signaling pathways.

Demethylation of Circulating Estrogen Receptor Alpha Gene in Cerebral Ischemic Stroke

Background

Estrogen is involved in neuron plasticity and can promote neuronal survival in stroke. Its actions are mostly exerted via estrogen receptor alpha (ERα). Previous animal studies have shown that ERα is upregulated by DNA demethylation following ischemic injury. This study investigated the methylation levels in the ERα promoter in the peripheral blood of ischemic stroke patients.

Methods

The study included 201 ischemic stroke patients, and 217 age- and sex-comparable healthy controls. The quantitative methylation level in the 14 CpG sites of the ERα promoter was measured by pyrosequencing in each participant. Multivariate regression model was used to adjust for stroke traditional risk factors. Stroke subtypes and sex-specific analysis were also conducted.

Results

The results demonstrated that the stroke cases had a lower ERα methylation level than controls in all 14 CpG sites, and site13 and site14 had significant adjusted p-values of 0.035 and 0.026, respectively. Stroke subtypes analysis showed that large-artery atherosclerosis and cardio-embolic subtypes had significantly lower methylation levels than the healthy controls at CpG site5, site9, site12, site13 and site14 with adjusted p = 0.039, 0.009, 0.025, 0.046 and 0.027 respectively. However, the methylation level for the patients with small vessel subtype was not significant. We combined the methylation data from the above five sites for further sex-specific analysis. The results showed that the significant association only existed in women (adjusted p = 0.011), but not in men (adjusted p = 0.300).

Conclusions

Female stroke cases have lower ERα methylation levels than those in the controls, especially in large-artery and cardio-embolic stroke subtypes. The study implies that women suffering from ischemic stroke of specific subtype may undergo different protective mechanisms to reduce the brain injury.

DNMT1 activates the canonical Wnt signaling in rheumatoid arthritis model rats via a crucial functional crosstalk between miR-152 and the DNMT1, MeCP2

In previous study, we identified that microRNA (miR)-152 expression was down-regulated in RA model rats, and overexpression of miR-152 inhibited the canonical Wnt signaling through the DNA methyltransferase (DNMT1) inhibition. However, the exact molecular mechanisms of DNMT1 were unclear. In this work, we investigate whether DNMT1 affects the pathogenesis of RA model rats and targets the miR-152 promoter. The effects of DNMT1 on the canonical Wnt signaling, the pathogenesis of RA model rats and the SFRP1 expression were detected by the real time qPCR, Western blotting, ELISA, MTT and viable cell number assay. The interaction between miR-152 and DNMT1, methyl CpG binding protein 2 (MeCP2) was investigated by real time qPCR and chromatin immunoprecipitation (ChIP). Our results revealed that increased DNMT1 activated the canonical Wnt signaling could not only by targeting SFRP4 may also by SFRP1 in RA model rats. Furthermore, treatment of DNMT1 inhibitor, 5-aza-2'-deoxycytidine (5-azadC), or knockdown of DNMT1, or knockdown of MeCP2 led to increased miR-152 expression by reversion of its promoter hypermethylation, DNMT1 and MeCP2 binding to the CpG islands of miR-152 promoter. Interestingly, it is proved a synergistic inhibition effect of DNMT1 and MeCP2 in this process. Moreover, overexpression of miR-152 could inhibit DNMT1 expression and result in a decrease of DNMT1 and MeCP2 binding to miR-152 promoter, and inhibition of miR-152 expression would reverse it. These observations demonstrate a crucial functional crosstalk between miR-152 and the DNMT1, MeCP2 by a double-negative circuit involved in the pathogenesis of RA model rats.

DNA Methylation Changes Induced by a High-Fat Diet and Fish Oil Supplementation in the Skeletal Muscle of Mice

BACKGROUND/AIMS

To investigate the global changes in DNA methylation and methylation of the promoter region of the peroxisome proliferator-activated receptor gamma transcript variant 2 (Pparg2) gene resulting from a high-fat diet (HFD) and/or fish oil supplementation.

METHODS

Fish oil, rich in omega-3 polyunsaturated fatty acids, or water was orally administered to male mice for 12 weeks. After the first 4 weeks, the animals were fed a control diet or an HFD until the end of the experimental protocol, when the epididymal fat, gastrocnemius muscle and liver were excised.

RESULTS

Pparg2 mRNA expression was upregulated by obesity and downregulated by fish oil supplementation in the liver. In the gastrocnemius muscle, diet-induced obesity increased global DNA methylation. Fish oil prevented the decrease in Pparg2 promoter methylation induced by obesity in the gastrocnemius muscle. Regardless of the diet given, fish oil supplementation increased Pparg2 promoter methylation at CpG-263 in muscle and adipose tissue.

CONCLUSION

HFD and fish oil modified global and Pparg2 promoter DNA methylation in a tissue-specific manner. Fish oil supplementation attenuated body weight gain, abolished the increase in Pparg2 expression in the liver and prevented the decrease in Pparg2 promoter methylation in the muscle induced by the HFD.

Hypoxia Represses ER-α Expression and Inhibits Estrogen-Induced Regulation of Ca2+-Activated K+ Channel Activity and Myogenic Tone in Ovine Uterine Arteries: Causal Role of DNA Methylation

Previous in vivo study demonstrated that chronic hypoxia during gestation was associated with estrogen receptor-α (ER-α) gene repression in ovine uterine arteries. Yet, it remains undetermined whether hypoxia had a direct effect and if DNA methylation played a causal role in hypoxia-mediated ER-α gene repression. Thus, this study tested the hypothesis that prolonged hypoxia has a direct effect and increases promoter methylation resulting in ER-α gene repression and inhibition of estrogen-mediated adaptation of uterine vascular tone. Uterine arteries isolated from nonpregnant and pregnant sheep were treated ex vivo with 21.0% O2 and 10.5% O2 for 48 hours. Hypoxia significantly increased ER-α promoter methylation at both specificity protein-1 and upstream stimulatory factor binding sites, decreased specificity protein-1 and upstream stimulatory factor binding to the promoter, and suppressed ER-α expression in uterine arteries of pregnant animals. Of importance, the effects of hypoxia were blocked by a methylation inhibitor 5-aza-2'-deoxycytidine. In addition, hypoxia abrogated steroid hormone-mediated increase in ER-α expression and inhibited the hormone-induced increase in large-conductance Ca(2+)-activated K(+) channel activity and decrease in myogenic tone in uterine arteries of nonpregnant animals, which were reversed by 5-aza-2'-deoxycytidine. The results provide novel evidence of a direct effect of hypoxia on heightened promoter methylation that plays a causal role in ER-α gene repression and ablation of steroid hormone-mediated adaptation of uterine arterial large conductance Ca(2+)-activated K(+) channel activity and myogenic tone in pregnancy.

Small RNA-mediated DNA (cytosine-5) methyltransferase 1 inhibition leads to aberrant DNA methylation

Mammalian cells contain copious amounts of RNA including both coding and noncoding RNA (ncRNA). Generally the ncRNAs function to regulate gene expression at the transcriptional and post-transcriptional level. Among ncRNA, the long ncRNA and small ncRNA can affect histone modification, DNA methylation targeting and gene silencing. Here we show that endogenous DNA methyltransferase 1 (DNMT1) co-purifies with inhibitory ncRNAs. MicroRNAs (miRNAs) bind directly to DNMT1 with high affinity. The binding of miRNAs, such as miR-155-5p, leads to inhibition of DNMT1 enzyme activity. Exogenous miR-155-5p in cells induces aberrant DNA methylation of the genome, resulting in hypomethylation of low to moderately methylated regions. And small shift of hypermethylation of previously hypomethylated region was also observed. Furthermore, hypomethylation led to activation of genes. Based on these observations, overexpression of miR-155-5p resulted in aberrant DNA methylation by inhibiting DNMT1 activity, resulting in altered gene expression.

Mir-152 inhibits cell proliferation and colony formation of CD133(+) liver cancer stem cells by targeting KIT

miR152 is involved in diverse biological functions and development of disease. This study investigates the role of mir-152 in cell proliferation and colony formation of liver cancer stem cells. We show that exogenous overexpression of mir-152 suppresses cell proliferation and colony formation in CD133(+) hep3B cells. We also show that KIT is a direct target of miR-152 and miR-152 downregulates protein expression of KIT by directly binding to 3' untranslated region of KIT. Downregulation of KIT by specific siRNAs inhibits proliferation and colony formation of CD133(+) hep3B cells, which is similar to inhibitory effects of miR-152. Moreover, exogenous expression of KIT compromises inhibitory effects of miR-152 on cell proliferation and colony formation. Our findings suggest that mir-152 inhibits cell proliferation and colony formation of CD133(+) hep3B cells by targeting KIT.

miRNA and methylation: a multifaceted liaison

miRNAs and DNA methylation are both critical regulators of gene expression. Aberration in miRNA expression or DNA methylation is a causal factor for numerous pathological conditions. DNA methylation can inhibit the transcription of miRNAs, just like coding genes, by methylating the CpG islands in the promoter regions of miRNAs. Conversely, certain miRNAs can directly target DNA methyltransferases and bring about their inhibition, thereby affecting the whole genome methylation pattern. Recently, methylation patterns have also been revealed in mRNA. Surprisingly, the two most commonly studied methylation states in mRNA (m6A and m5C) are found to be enriched in 3'-UTRs (untranslated regions), the target site for the majority of miRNAs. Whereas m5C is reported to stabilise mRNA, m6A has a destabilising effect on mRNA. However, the effect of mRNA methylation on its interaction with miRNAs is largely unexplored. The review highlights the complex interplay between microRNA and methylation at DNA and mRNA level.

MicroRNA-152 modulates the canonical Wnt pathway activation by targeting DNA methyltransferase 1 in arthritic rat model

Rheumatoid arthritis (RA) is an autoimmune and progressive systemic disease of unknown etiology. Research shows that fibroblast-like synoviocytes (FLS) participate in the cartilage erosion, synovial hyperplasia, inflammatory cytokine secretion and suggests that fibroblast-like synoviocytes (FLS) display a crucial role in RA pathogenesis. Recent studies have suggested the role of the Wnt signaling pathway in the pathogenesis of RA. In previous study, we identified that increased methyl-CpG-binding protein 2 (MeCP2) reduced the secreted frizzled-related protein 4 (SFRP4) expression in FLS in Arthritic rat model and the DNA methyltransferase (DNMT) inhibitor 5-Aza-2'-deoxycytidine (5-azadC) could induce the SFRP4 expression, indicating that DNMT has a key role in the differential expression of SFRP4. MicroRNAs (MiRNAs), which are small non-coding RNAs, are involved in diverse biological functions, regulation of gene expression, pathogenesis of autoimmune disease and carcinogenesis. In light of the directly down-regulation of miR-152 on DNMT1 expression by targeting the 3' untranslated regions of its transcript in nickel sulfide (NiS)-transformed human bronchial epithelial cells, we investigated whether miR-152 is aberrantly expressed and targets DNMT1 in FLS in Arthritic rat model. Our results demonstrated that the expression of miR-152 was specifically down-regulated in Arthritic rat model, whereas up-regulation of miR-152 in FLS resulted in a marked reduction of DNMT1 expression. Further experiments revealed that increased miR-152 indirectly up-regulated the SFRP4 expression, a negative regulator of WNT signaling pathway, by targeting the DNMT1. Moreover, activation of miR-152 expression in FLS could inhibit the canonical Wnt pathway activation and result in a significant decrease of FLS proliferation. MiR-152 and DNA methylation may provide molecular mechanisms for the activation of canonical Wnt pathway in RA. Combination of miR-152 and DNMT1 may be a promising treatment strategy for RA patients in which SFRP4 is inactivated.

Epigenetic regulation of smooth muscle cell plasticity

Smooth muscle cells (SMC) are the major cell type in blood vessels. Their principal function in the body is to regulate blood flow and pressure through vessel wall contraction and relaxation. Unlike many other mature cell types in the adult body, SMC do not terminally differentiate but retain a remarkable plasticity. They have the unique ability to toggle between a differentiated and quiescent "contractile" state and a highly proliferative and migratory "synthetic" phenotype in response to environmental stresses. While there have been major advances in our understanding of SMC plasticity through the identification of growth factors and signals that can influence the SMC phenotype, how these regulate SMC plasticity remains unknown. To date, several key transcription factors and regulatory cis elements have been identified that play a role in modulating SMC state. The frontier in understanding the molecular mechanisms underlying SMC plasticity has now advanced to the level of epigenetics. This review will summarize the epigenetic regulation of SMC, highlighting the role of histone modification, DNA methylation, and our most recent identification of a DNA demethylation pathway in SMC that is pivotal in the regulation of the SMC phenotypic state. Many disorders are associated with smooth muscle dysfunction, including atherosclerosis, the major underlying cause of stroke and coronary heart disease, as well as transplant vasculopathy, aneurysm, asthma, hypertension, and cancer. An increased understanding of the major regulators of SMC plasticity will lead to the identification of novel target molecules that may, in turn, lead to novel drug discoveries for the treatment of these diseases. This article is part of a Special Issue entitled: Stress as a fundamental theme in cell plasticity.