Atherosclerosis-associated differentially methylated regions can reflect the disease phenotype and are often at enhancers

BACKGROUND AND AIMS

Atherosclerosis is a widespread and complicated disease involving phenotypic modulation and transdifferentiation of vascular smooth muscle cells (SMCs), the predominant cells in aorta, as well as changes in endothelial cells and infiltrating monocytes. Alterations in DNA methylation are likely to play central roles in these phenotypic changes, just as they do in normal differentiation and cancer.

METHODS

We examined genome-wide DNA methylation changes in atherosclerotic aorta using more stringent criteria for differentially methylated regions (DMRs) than in previous studies and compared these DMRs to tissue-specific epigenetic features.

RESULTS

We found that disease-linked hypermethylated DMRs account for 85% of the total atherosclerosis-associated DMRs and often overlap aorta-associated enhancer chromatin. These hypermethylated DMRs were associated with functionally different sets of genes compared to atherosclerosis-linked hypomethylated DMRs. The extent and nature of the DMRs could not be explained as direct effects of monocyte/macrophage infiltration. Among the known atherosclerosis- and contractile SMC-related genes that exhibited hypermethylated DMRs at aorta enhancer chromatin were ACTA2 (aorta α2 smooth muscle actin), ELN (elastin), MYOCD (myocardin), C9orf3 (miR-23b and miR-27b host gene), and MYH11 (smooth muscle myosin). Our analyses also suggest a role in atherosclerosis for developmental transcription factor genes having little or no previous association with atherosclerosis, such as NR2F2 (COUP-TFII) and TBX18.

CONCLUSIONS

We provide evidence for atherosclerosis-linked DNA methylation changes in aorta SMCs that might help minimize or reverse the standard contractile character of many of these cells by down-modulating aorta SMC-related enhancers, thereby facilitating pro-atherosclerotic phenotypic changes in many SMCs.

Elucidating the contributory role of microRNA to cardiovascular diseases (a review)

Cardiovascular diseases encompassing atherosclerosis, aortic aneurysms, restenosis, and pulmonary arterial hypertension, remain the leading cause of morbidity and mortality worldwide. In response to a range of stimuli, the dynamic interplay between biochemical and biomechanical mechanisms affect the behaviour and function of multiple cell types, driving the development and progression of cardiovascular diseases. Accumulating evidence has highlighted microRNAs (miRs) as significant regulators and micro-managers of key cellular and molecular pathophysiological processes involved in predominant cardiovascular diseases, including cell mitosis, motility and viability, lipid metabolism, generation of inflammatory mediators, and dysregulated proteolysis. Human pathological and clinical studies have aimed to identify select microRNA which may serve as biomarkers of disease and their progression, which are discussed within this review. In addition, I provide comprehensive coverage of in vivo investigations elucidating the modulation of distinct microRNA on the pathophysiology of atherosclerosis, abdominal aortic aneurysms, restenosis, and pulmonary arterial hypertension. Collectively, clinical and animal studies have begun to unravel the complex and often diverse effects microRNAs and their targets impart during the development of cardiovascular diseases and revealed promising therapeutic strategies through which modulation of microRNA function may be applied clinically.

Non-coding RNAs in vascular remodeling and restenosis

Vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) are crucial in vascular remodeling. They exert pivotal roles in the development and progression of atherosclerosis, vascular response to injury, and restenosis after transcatheter angioplasty. As a witness of their importance in the cardiovascular system, a large body of evidence has accumulated about the role played by micro RNAs (miRNA) in modulating both VSMCs and ECs. More recently, a growing number of long noncoding RNA (lncRNAs) came beneath the spotlights in this research field. Several mechanisms have been revealed by which lncRNAs are able to exert a relevant biological impact on vascular remodeling. The aim of this review is to provide an integrated summary of ncRNAs that exert a relevant biological function in VSMCs and ECs of the vascular wall, with emphasis on the available clinical evidence of the potential usefulness of these molecules as circulating biomarkers of in-stent restenosis.

Phenotype of Vascular Smooth Muscle Cells (VSMCs) Is Regulated by miR-29b by Targeting Sirtuin 1

Background

Phenotypic switch of vascular smooth muscle cells (VSMCs) participates in the etiology of various vascular diseases. It has been proved that microRNAs (miRNAs) serve as crucial regulators of functions of VSMCs. This study aimed to discover how miR-29b regulates the transformation of VSMCs phenotypes in mice.

Material/Methods

Primary VSMCs of aorta in mice were cultured in DMEM medium. A series of experiments involving transfection of oligonucleotides in cultured VSMCs, quantitative reverse transcription PCR (qRT-PCR), luciferase reporter assay, and Western blotting analysis were performed in this study.

Results

We found that in VSMCs cultured in presence of stimulator, platelet-derived growth factor-BB (PDGF-BB), miR-29b was upregulated significantly and expressions of VSMC-phenotype-related genes (α-SMA, calponin, and SM-MHC) were regulated by miR-29b. Moreover, through downregulation of sirtuin 1 (SIRT1), miR-29b affects phenotypic transformation of VSMCs. Luciferase report assay identified a significant increase of SIRT1 3′-UTR activity in treatment with miR-29b inhibitor, which, however, was reversed in the presence of miR-29b mimic. Suppression of miR-29b reversed the activation of NF-κB induced by PDGF-BB in VSMCs.

Conclusions

We concluded that miR-29b is an important regulator in the PDGF-BB-mediated VSMC phenotypic transition by targeting SIRT1. Interventions aimed at miR-29b may be promising in treating numerous proliferative vascular disorders.

MicroRNA-124-3p inhibits collagen synthesis in atherosclerotic plaques by targeting prolyl 4-hydroxylase subunit alpha-1 (P4HA1) in vascular smooth muscle cells

BACKGROUND AND AIMS

Collagen synthesis in vascular smooth muscle cells (VSMCs) is very important in atherosclerosis, as it affects plaque stability. In this study, we aim to assess whether miR-124-3p is involved in the collagen synthesis process in VSMCs and the role it might play in atherosclerotic development.

METHODS

We modulated the miR-124-3p expression in the aortic root plaques of high-fat-diet fed ApoE^-/- mice by lentivirus injection. To determine plaque size and the content of plaque-stability-related cells or molecules, stainings, including hematoxylin and eosin, Oil red O, Sirius Red and immunohistochemical staining, were performed. Fluorescence in situ hybridization (FISH) was used to locate miR-124-3p in atherosclerotic plaques. Western blotting and RT-qPCR were carried out to determine the level of P4HA1 as well as type I and type III collagen protein and mRNA expression.

RESULTS

Results showed that collagen and VSMC content of plaques was inversely correlated with miR-124-3p levels. By FISH, we identified that miR-124-3p was primarily expressed by VSMCs. We also found that protein levels of type I and type III collagen in aortas and atherosclerotic plaques were decreased by miR-124-3p. We modulated miR-124-3p level in vitro and found it could inhibit collagen expression in HASMCs. This might be caused by the downregulation of P4HA1. P4HA1 was predicted as miR-124-3p's direct target, which was verified with a dual luciferase reporter assay and RIP test.

CONCLUSIONS

The results presented here provide evidence that miR-124-3p inhibits VSMC collagen synthesis by directly targeting P4HA1, which might decrease atherosclerotic plaque stability.

Long Noncoding RNA XR007793 Regulates Proliferation and Migration of Vascular Smooth Muscle Cell via Suppressing miR-23b

Background

Long noncoding RNAs (lncRNAs) were identified as potential regulatory factor in vascular disease. However, the role of XR007793 in the regulation of neointima formation after vascular injury remains largely unknown.

Material/Methods

LncRNA expression levels were detected using real-time polymerase chain reaction (RT-PCR). In vivo and in vitro assay were performed in Sprague-Dawley rats and VSMCs. Cell Counting Kit-8 (CCK-8) assay, Transwell assay, and scratch wound healing assay were performed to detect cell proliferation and migration. Western blotting was used to detect protein expression.

Results

The results of qRT-PCR indicated that XR007793 expression was significantly increased in the injured carotid artery of Sprague-Dawley rats and platelet-derived growth factor-BB induced rat aortic smooth muscle cells. Knockdown of XR007793 repressed the proliferation and migration of VSMC in vitro. The expression level of miR-23b was reduced in mouse carotid injured tissues and cell line. Bioinformatics analysis and luciferase reporter assay revealed that XR007793 directly bonds to miR-23b. Pearson correlation analysis showed that XR007793a and miR-23b were negatively correlated in carotid samples. Furthermore, bioinformatics analysis and luciferase assay indicated that miR-23b targeted the Forkhead box O 4 (FOXO4) 3′-UTR to inhibit FOXO4 expression. After transfecting miR-23b inhibitor, the expression both of XR007793 and FOXO4 was increased. The effects on expression were reversed after transfected with miR-23b mimics. Rescue experiments results indicated that miR-23b inhibitor reduced the expression of VSMC marker and promoted proliferation and migration of VSMC.

Conclusions

This study shows that XR007793 aggravates the loss of function of VSMCs by negatively regulating miR-23b. It does so by targeting FOXO4, which could serve as a novel therapeutic target in post-angioplasty restenosis.

Epigenetics and Immunometabolism in Diabetes and Aging

SIGNIFICANCE

A strong relationship between hyperglycemia, impaired insulin pathway, and cardiovascular disease in type 2 diabetes (T2D) is linked to oxidative stress and inflammation. Immunometabolic pathways link these pathogenic processes and pose important potential therapeutic targets. Recent Advances: The link between immunity and metabolism is bidirectional and includes the role of inflammation in the pathogenesis of metabolic disorders such as T2D, obesity, metabolic syndrome, and hypertension and the role of metabolic factors in regulation of immune cell functions. Low-grade inflammation, oxidative stress, balance between superoxide and nitric oxide, and the infiltration of macrophages, T cells, and B cells in insulin-sensitive tissues lead to metabolic impairment and accelerated aging.

CRITICAL ISSUES

Inflammatory infiltrate and altered immune cell phenotype precede development of metabolic disorders. Inflammatory changes are tightly linked to alterations in metabolic status and energy expenditure and are controlled by epigenetic mechanisms.

FUTURE DIRECTIONS

A better comprehension of these mechanistic insights is of utmost importance to identify novel molecular targets. In this study, we describe a complex scenario of epigenetic changes and immunometabolism linking to diabetes and aging-associated vascular disease. Antioxid. Redox Signal. 29, 257-274.

MicroRNA‑26a protects vascular smooth muscle cells against H2O2‑induced injury through activation of the PTEN/AKT/mTOR pathway

Abdominal aortic aneurysm (AAA) is a common disease, which is characterized by the apoptosis of vascular smooth muscle cells (VSMCs). In previous years, microRNAs (miRNAs) have been associated with AAA and functionally implicated in the pathogenesis of this disease. However, the role of miRNAs in the apoptosis of VSMCs remains to be fully elucidated. The present study aimed to elucidate the role and mechanism of miRNAs in protecting against hydrogen peroxide (H₂O₂)-induced apoptosis in VSMCs. The expression of miRNAs in peripheral blood from patients diagnosed with AAA was analyzed using a microarray and reverse transcription polymerase chain reaction. A VSMC injury model induced by H₂O₂ was used to determine the potential role of miR-26a against cell injury. Cell viability, cell apoptosis and reactive oxygen species (ROS) generation were determined by a CCK8 assay, flow cytometry and a 2′,7′-DCF diacetate assay, respectively. It was observed that miRNA (miR)-26a (miR-26a-1-5p) was significantly downregulated in peripheral blood samples from patients with AAA. It was revealed that H₂O₂ treatment dose-dependently inhibited cell viability, enhanced apoptosis and induced the production of ROS, which indicated the success of the model establishment. It was also observed that miR-26a was downregulated in the VSMCs following H₂O₂ stimulation. The upregulation of miR-26a attenuated H₂O₂-induced cell injury, as evidenced by the enhancement of cell viability, and inhibition of the activity of caspase-3, apoptosis and ROS production. In addition, phosphatase and tensin homolog (PTEN), a well-known regulator of the AKT/mammalian target of rapamycin (mTOR) pathway, was found to be a direct target of miR-26a in the VSMCs and this was validated using a luciferase reporter assay. Overexpression of PTEN by pcDNA-PTEN plasmids markedly eliminated the protective effects of the overexpression of miR-26a on H₂O₂-induced cell injury. Finally, it was found that miR-26a mediated its anti-apoptotic action by reactivation of the AKT/mTOR pathway, as demonstrated by the upregulation of phosphorylated (p-)AKT and p-mTOR, and the Akt inhibitor API-2 reversing the protective effects on VSMCs mediated by miR-26a. These results indicated that miR-26a protected VSMCs against H₂O₂-induced injury through activation of the PTEN/AKT/mTOR pathway, and miR-26a may be considered as a potential prognostic biomarker and therapeutic target in the treatment of AAA.

Role of endothelial microRNA-23 clusters in angiogenesis in vivo

The capillary network is distributed throughout the body, and its reconstruction is induced under various pathophysiological conditions. MicroRNAs are small noncoding RNAs that regulate gene expression via posttranscriptional mechanisms and are involved in many biological functions, including angiogenesis. Previous studies have shown that each microRNA of miR-23 clusters, composed of the miR-23a cluster (miR-23a~27a~24-2) and miR-23b cluster (miR-23b~27b~24-1), regulates angiogenesis in vitro. However, the role of miR-23 clusters, located within a single transcription unit, in angiogenesis in vivo has not been elucidated. In the present study, we generated vascular endothelial cell (EC)-specific miR-23 cluster double-knockout (DKO) mice and demonstrated sprouting angiogenesis under various conditions, including voluntary running exercise, hindlimb ischemia, skin wound healing, and EC sprouting from aorta explants. Here, we demonstrated that EC-specific miR-23 DKO mice are viable and fertile, with no gross abnormalities observed in pups or adults. The capillary number was normally increased in the muscles of these DKO mice in response to 2 wk of voluntary running and hindlimb ischemia. Furthermore, we did not observe any abnormalities in skin wound closure or EC sprouting from aortic ring explants in EC-specific miR-23 cluster DKO mice. Our results suggest that endothelial miR-23 clusters are dispensable for embryonic development and postnatal angiogenesis in vivo. NEW & NOTEWORTHY We generated vascular endothelial cell (EC)-specific miR-23a/b cluster double-knockout mice and determined sprouting angiogenesis under various conditions, including voluntary running exercise, hindlimb ischemia, skin wound healing, and EC sprouting from aorta explants. We demonstrated that the double-knockout mice were viable and fertile, with no gross abnormalities in exercise- and ischemia-induced angiogenesis and skin wound closure or EC sprouting from aortic ring explants.

The role of infiltrating immune cells in dysfunctional adipose tissue

Adipose tissue (AT) dysfunction, characterized by loss of its homeostatic functions, is a hallmark of non-communicable diseases. It is characterized by chronic low-grade inflammation and is observed in obesity, metabolic disorders such as insulin resistance and diabetes. While classically it has been identified by increased cytokine or chemokine expression, such as increased MCP-1, RANTES, IL-6, interferon (IFN) gamma or TNFα, mechanistically, immune cell infiltration is a prominent feature of the dysfunctional AT. These immune cells include M1 and M2 macrophages, effector and memory T cells, IL-10 producing FoxP3+ T regulatory cells, natural killer and NKT cells and granulocytes. Immune composition varies, depending on the stage and the type of pathology. Infiltrating immune cells not only produce cytokines but also metalloproteinases, reactive oxygen species, and chemokines that participate in tissue remodelling, cell signalling, and regulation of immunity. The presence of inflammatory cells in AT affects adjacent tissues and organs. In blood vessels, perivascular AT inflammation leads to vascular remodelling, superoxide production, endothelial dysfunction with loss of nitric oxide (NO) bioavailability, contributing to vascular disease, atherosclerosis, and plaque instability. Dysfunctional AT also releases adipokines such as leptin, resistin, and visfatin that promote metabolic dysfunction, alter systemic homeostasis, sympathetic outflow, glucose handling, and insulin sensitivity. Anti-inflammatory and protective adiponectin is reduced. AT may also serve as an important reservoir and possible site of activation in autoimmune-mediated and inflammatory diseases. Thus, reciprocal regulation between immune cell infiltration and AT dysfunction is a promising future therapeutic target.

Inhibition of microRNA-23b prevents polymicrobial sepsis-induced cardiac dysfunction by modulating TGIF1 and PTEN

Cardiovascular dysfunction is a major complication associated with sepsis induced mortality. Cardiac fibrosis plays a critical role in sepsis induced cardiac dysfunction. The mechanisms of the activation of cardiac fibrosis is unclarified. In this study, we found that microRNA-23b (miR-23b) was up-regulated in heart tissue during cecal ligation and puncture (CLP)-induced sepsis and transfection of miR-23b inhibitor improved survival in late sepsis. Inhibition of miR-23b in the myocardium protected against cardiac output and enhanced left ventricular systolic function. miR-23b inhibitor also alleviated cardiac fibrosis in late sepsis. MiR-23b mediates the activation of TGF-β1/Smad2/3 signaling to promote the differentiation of cardiac fibroblasts through suppression of 5'TG3'-interacting factor 1 (TGIF1). MiR-23b also induces AKT/N-Cadherin signaling to contribute to the deposition of extracellular matrix by inhibiting phosphatase and tensin homologue (PTEN). TGIF1 and PTEN were confirmed as the targets of miR-23b in vitro by Dual-Glo Luciferase assay. miR-23b inhibitor blocked the activation of adhesive molecules and restored the imbalance of pro-fibrotic and anti-fibrotic factors. These data provide direct evidence that miR-23b is a critical contributor to the activation of cardiac fibrosis to mediate the development of myocardial dysfunction in late sepsis. Blockade of miR-23b expression may be an effective approach for prevention sepsis-induced cardiac dysfunction.

Understanding the role of non-coding RNA (ncRNA) in stent restenosis

Coronary heart disease (CHD) is one of the leading disorders with the highest mortality rate. Percutaneous angioplasty and stent implantation are the currently available standard methods for the treatment of obstructive coronary artery disease. However, the stent being an exogenous substance causes several complications by promoting the proliferation of vascular smooth muscle cells, immune responses and neointima formation after implantation, leading to post-stent restenosis (ISR) and late thrombosis. The prevention of these adverse vascular events is important to achieve long-term proper functioning of the heart after stent implantation. Non-coding ribonucleic acids (ncRNAs) are RNA molecules not translated into proteins, theyhave a great potential in regulating endothelial cell and vascular smooth muscle function as well as inflammatory reactions. In this review, we outline the regulatory functions of different classes of ncRNA in cardiovascular disease and propose ncRNAs as new targets for stent restonosis treatment.

Hypoxia-inducible factor 1a induces phenotype switch of human aortic vascular smooth muscle cell through PI3K/AKT/AEG-1 signaling

To date, hypoxia-inducible factor 1a (HIF-1a) and astrocyte elevated gene-1 (AEG-1) have been involved in the proliferation, migration and morphological changes of vascular smooth muscle cells. However, the potential relationship of HIF-1a-AEG-1 pathway in human aortic smooth muscle cell (HASMC) has not been reported. In the present study, in-vitro assays were utilized to explore the potential impact of HIF-1a-AEG-1 signaling on HASMC phenotype. Here, we found that HIF-1a expression was up-regulated in the media of thoracic aortic dissection tissues as compared with normal aortic tissues, and was associated with increased apoptotic SMCs and decreased AEG-1 expression. Mechanically, hypoxia promoted the expression of HIF-1a by PI3K-AKT pathway in HASMCs; HIF-1a further suppressed the expressions of AEG-1, a-SMA and SM22a, and promoted osteopontin (OPN) expression. Functionally, HIF-1a inhibited the proliferation and migration of HASMCs. However, si-HIF-1a or Akt inhibitor abrogated HIF-1a-mediated related expressions and biological effects above. In conclusion, HIF-1a induces HASMC phenotype switch, and closely related to PI3K/AKT and AEG-1 signaling, which may provide new avenues for the prevention and treatment of aortic dissection diseases.

Identification of long noncoding RNAs involved in muscle differentiation

Long noncoding RNAs (lncRNAs) are a large class of regulatory RNAs with diverse roles in cellular processes. Thousands of lncRNAs have been discovered; however, their roles in the regulation of muscle differentiation are unclear because no comprehensive analysis of lncRNAs during this process has been performed. In the present study, by combining diverse RNA sequencing datasets obtained from public database, we discovered lncRNAs that could behave as regulators in the differentiation of smooth or skeletal muscle cells. These analyses confirmed the roles of previously reported lncRNAs in this process. Moreover, we discovered dozens of novel lncRNAs whose expression patterns suggested their possible involvement in the phenotypic switch of vascular smooth muscle cells. The comparison of lncRNA expression change suggested that many lncRNAs have common roles during the differentiation of smooth and skeletal muscles, while some lncRNAs may have opposite roles in this process. The expression change of lncRNAs was highly correlated with that of their neighboring genes, suggesting that they may function as cis-acting lncRNAs. Furthermore, within the lncRNA sequences, there were binding sites for miRNAs with expression levels inversely correlated with the expression of corresponding lncRNAs during differentiation, suggesting a possible role of these lncRNAs as competing endogenous RNAs. The lncRNAs identified in this study will be a useful resource for future studies of gene regulation during muscle differentiation.

The Role of MicroRNAs in Arterial Stiffness and Arterial Calcification. An Update and Review of the Literature

Arterial stiffness is an independent risk factor for fatal and non-fatal cardiovascular events, such as systolic hypertension, coronary artery disease, stroke, and heart failure. Moreover it reflects arterial aging which in many cases does not coincide with chronological aging, a fact that is in large attributed to genetic factors. In addition to genetic factors, microRNAs (miRNAs) seem to largely affect arterial aging either by advancing or by regressing arterial stiffness. MiRNAs are small RNA molecules, ~22 nucleotides long that can negatively control their target gene expression posttranscriptionally. Pathways that affect main components of stiffness such as fibrosis and calcification seem to be influenced by up or downregulation of specific miRNAs. Identification of this aberrant production of miRNAs can help identify epigenetic changes that can be therapeutic targets for prevention and treatment of vascular diseases. The present review summarizes the specific role of the so far discovered miRNAs that are involved in pathways of arterial stiffness.

Effects of miR-23b on hypoxia-induced cardiomyocytes apoptosis

OBJECTIVES

The aim of this study was to investigate the role of miR-23b in hypoxic cardiomyocytes and the potential mechanism.

METHODS

Myocardial samples of patients with cyanotic or acyanotic congenital heart disease (CHD) were collected to evaluate miR-23b expression. Agomir or antagomir of miR-23b was transfected into H9C2 cells. MTT, LDH assay and TUNEL staining were used to determine the cell proliferation and apoptosis under hypoxic conditions. Besides, the expression levels of cleaved-caspase-3, cleaved-PARP, Bad, Bcl-2 and Bax in hypoxic H9C2 cells were determined by western blot and qRT-PCR, respectively.

RESULTS

Higher miR-23b expression levels were found in the patients with cyanotic CHD compared with the patients with acyanotic CHD. In addition, the expression of miR-23b was gradually up-regulated with prolonged hypoxia time in the H9C2 cells. Using MTT and LDH assays, cell growth was significantly decreased in the agomir group than that in the agomir-negative control (NC) group, while antagomir increased the cell growth. Using TUNEL staining and flow cytometry analysis, miR-23b promoted hypoxia-induced apoptosis. The expression levels of pro-apoptotic proteins, such as cleaved-caspase-3, cleaved-PARP and Bad, were significantly increased in the agomir group, while the Bcl-2 levels and Bcl-2/Bax ratio were decreased. Opposite tendency was observed in the antagomir group. Dual luciferase reporter assay and western blot analysis confirmed that Smad3 was a direct target of miR-23b.

CONCLUSION

Over-expression of miR-23b may increase cardiomyocyte apoptosis and reduce cell growth under hypoxic conditions.

Regulation and biological roles of the multifaceted miRNA-23b (MIR23B)

MicroRNAs (miRNAs) are important short endogenous non-coding RNAs that have critical biological roles by acting as post-transcriptional regulators of gene expression. Chromosomal region 9q22.32 encodes the miR-23b/27b/24-1 cluster and produces miR-23b, which is a pleiotropic modulator in many developmental processes and pathological conditions. Expression of miR-23b is actively suppressed and induced in response to many different stimuli. We discuss the biological functions and transcriptional regulation of this multifaceted miRNA in different tumor types, during development, upon viral infection, as well as in various clinical disorders, immune responses, as well as cardiovascular and thyroid functions. The combined body of work suggests that miR-23b expression is modulated by a diverse array of stimuli in cells from different lineages and participates in multiple gene regulatory feedback loops. Elevation of miR-23b levels appears to instruct cells to limit their proliferative and migratory potential, while promoting the acquisition of specialized phenotypes or protection from invading viruses and parasites. In contrast, loss of miR-23b can deregulate normal tissue homeostasis by removing constraints on cell cycle progression and cell motility. Collectively, the findings on miR-23b indicate that it is a very potent post-transcriptional regulator of growth and differentiation during development, multiple cancers and other biological processes. Understanding the regulation and activity of miR-23b has significant diagnostic value in many biological disorders and may identify cellular pathways that are amenable to therapeutic intervention.

MicroRNA-206 regulates vascular smooth muscle cell phenotypic switch and vascular neointimal formation

MiR-206 has been found to play a critical role in skeletal muscle proliferation, differentiation, and regeneration. However, little is known about the function of miR-206 in vascular smooth muscle cells (VSMCs) biology. In this study, we will investigate its roles in phenotypic switching of VSMCs and neointimal lesion formation. First, we identified the expression of miR-206 in VSMCs treated with various concentrations of TGFβ1 and in rat carotid arteries after angioplasty by using qPCR. TGFβ1 inhibited the expression of miR-206 and TGFβ1 inhibitor induced miR-206 expression. In VSMCs of injured vascular walls, miR-206 expression was upregulated. Then, we overexpressed miR-206 using lentivirus Lv-rno-mir-206 and knocked down miR-206 using LV-rno-mir-206-inhibitor in rat carotid arteries after angioplasty. Overexpression of miR-206 resulted in decreasing SM22α expression in VSMCs in vitro and knockdown of miR-206 suppressed neointimal lesion formation in vivo. Finally, ZFP580 (zinc finger protein 580) was identified as the direct target of miR-206 in VSMCs by using luciferase report assay. The results indicate that miR-206 is involved in phenotypic switching of VSMCs and neointimal lesion formation after angioplasty through targeting ZFP580. These findings may provide a novel therapeutic target in post-angioplasty restenosis.

MicroRNAs as regulators and mediators of forkhead box transcription factors function in human cancers

Evidence has shown that microRNAs are widely implicated as indispensable components of tumor suppressive and oncogenic pathways in human cancers. Thus, identification of microRNA targets and their relevant pathways will contribute to the development of microRNA-based therapeutics. The forkhead box transcription factors regulate numerous processes including cell cycle progression, metabolism, metastasis and angiogenesis, thereby facilitating tumor initiation and progression. A complex network of protein and non-coding RNAs mediates the expression and activity of forkhead box transcription factors. In this review, we summarize the current knowledge and concepts concerning the involvement of microRNAs and forkhead box transcription factors and describe the roles of microRNAs-forkhead box axis in various disease states including tumor initiation and progression. Additionally, we describe some of the technical challenges in the use of the microRNA-forkhead box signaling pathway in cancer treatment.

Posttranscriptional regulation of FOXO expression: microRNAs and beyond

Forkhead box, class O (FOXO) transcription factors are major regulators of diverse cellular processes, including fuel metabolism, oxidative stress response and redox signalling, cell cycle progression and apoptosis. Their activities are controlled by multiple posttranslational modifications and nuclear-cytoplasmic shuttling. Recently, post-transcriptional regulation of FOXO synthesis has emerged as a new regulatory level of their functions. Accumulating evidence suggests that this post-transcriptional mode of regulation of FOXO activity operates in response to stressful stimuli, including oxidative stress. Here, we give a brief overview on post-transcriptional regulation of FOXO synthesis by microRNAs (miRNAs) and by RNA-binding regulatory proteins, human antigen R (HuR) and quaking (QKI). Aberrant post-transcriptional regulation of FOXOs is frequently connected with various disease states. We therefore discuss characteristic examples of FOXO regulation at the post-transcriptional level under various physiological and pathophysiological conditions, including oxidative stress and cancer. The picture emerging from this summary points to a diversity of interactions between miRNAs/miRNA-induced silencing complexes and RNA-binding regulatory proteins. Better insight into these complexities of post-transcriptional regulatory interactions will add to our understanding of the mechanisms of pathological processes and the role of FOXO proteins.

LINKED ARTICLES

This article is part of a themed section on Redox Biology and Oxidative Stress in Health and Disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.12/issuetoc.

miR-125a-5p Modulates Phenotypic Switch of Vascular Smooth Muscle Cells by Targeting ETS-1

MicroRNAs are key regulators of vascular smooth muscle cells (VSMCs) phenotypic switch, one of the main events responsible for bare metal in-stent restenosis after percutaneous coronary intervention. miR-125a-5p is an important modulator of differentiation, proliferation, and migration in different cell types; however, its role in VSMCs is still unknown. The aim of this study was to evaluate the role of miR-125a-5p in VSMCs phenotypic switch. Our results suggest that miR-125a-5p is highly expressed in VSMCs, but it is down-regulated after vascular injury in vivo. Its overexpression is sufficient to reduce VSMCs proliferation and migration, and it is able to promote the expression of selective VSMCs markers such as alpha smooth muscle actin, myosin heavy chain 11, and smooth muscle 22 alpha. Interestingly, miR-125a-5p directly targets ETS-1, a transcription factor implicated in cell proliferation and migration and is crucial in PDGF-BB pathway in VSMCs. Thus, miR-125a-5p in this context inhibits PDGF-BB pathway and is therefore a potential regulator of VSMCs phenotypic switch.

Epigenetics and cardiovascular risk in childhood

Cardiovascular disease (CVD) can arise at the early stages of development and growth. Genetic and environmental factors may interact resulting in epigenetic modifications with abnormal phenotypic expression of genetic information without any change in the nucleotide sequence of DNA. Maternal dietary imbalance, inadequate to meet the nutritional needs of the fetus can lead to intrauterine growth retardation, decreased gestational age, low birth weight, excessive post-natal growth and metabolic alterations, with subsequent appearance of CVD risk factors. Fetal exposure to high cholesterol, diabetes and maternal obesity is associated with increased risk and progression of atherosclerosis. Maternal smoking during pregnancy and exposure to various environmental pollutants induce epigenetic alterations of gene expression relevant to the onset or progression of CVD. In children with hypercholesterolemia and/or obesity, oxidative stress activates platelets and monocytes, which release proinflammatory and proatherogenic substances, inducing endothelial dysfunction, decreased Doppler flow-mediated dilation and increased carotid intima-media thickness. Primary prevention of atherosclerosis should be implemented early. It is necessary to identify, through screening, high-risk apparently healthy children and take care of them enforcing healthy lifestyle (mainly consisting of Mediterranean diet and physical activity), prescribing nutraceuticals and eventual medications, if required by a high-risk profile. The key issue is the restoration of endothelial function in the reversible stage of atherosclerosis. Epigenetics may provide new markers for an early identification of children at risk and thereby develop innovative therapies and specific nutritional interventions in critical times.

Exosomal miRNAs in Heart Disease

Micro-RNAs (miRNAs) are small noncoding RNAs involved in the posttranscriptional regulation of gene expression. Exosomes have recently emerged as novel elements of intercellular communication in the cardiovascular system. Exosomal miRNAs could be key players in intercellular cross-talk, particularly during different diseases such as myocardial infarction (MI) and heart failure (HF). This review addresses the functional role played by exosomal miRNAs in heart disease and their potential use as new biomarkers.

MiR-23b controls TGF-β1 induced airway smooth muscle cell proliferation via direct targeting of Smad3

BACKGROUND

MicroRNAs are small yet versatile gene tuners that regulate a variety of cellular processes, including cell growth and proliferation. Here we report that miR-23b inhibited airway smooth muscle cells (ASMCs) proliferation through directly targeting of Smad3.

METHODS

We obtained ASMCs by laser capture microdissection of normal and asthmatic mice lung tissues. Mice ASMCs were cultured and induced by TGF-β1. The implication between TGF-β1 and miR-23b in ASMCs were detected by RT-PCR. The effects of miR-23b on ASMCs proliferation and apoptosis were assessed by transient transfection of miR-23b mimics and inhibitor. The expression of Smad3 in ASMCs were detected by RT-PCR and Western blotting analysis. Dual-Luciferase Reporter Assay System will be applied to identify whether Smad3 is a target gene of miR-23b.

RESULTS

TGF-β1 and miR-23b mRNA expression of in-situ bronchial ASMCs collected by laser capture microdissection were increased in asthmatic mice compared to non-asthma controls. This is accompanied by an increase in miR-23b mRNA expression in TGF-β1 induced ASMCs. miR-23b up-regulation significantly inhibited TGF-β1-induced ASMCs proliferation and promoted apoptosis. MiR-23b negatively regulates the expression of Smad3 in ASMCs. Dual-Luciferase Reporter Assay System demonstrated that Smad3 was a direct target of miR-23b.

CONCLUSIONS

MiR-23b may function as an inhibitor of asthma airway remodeling by suppressing ASMCs proliferation via direct targeting of Smad3.

Inflammation and vascular smooth muscle cell dedifferentiation following carotid artery ligation

Following vascular injury medial smooth muscle cells dedifferentiate and migrate through the internal elastic lamina where they form a neointima. The goal of the current study was to identify changes in gene expression that occur before the development of neointima and are associated with the early response to injury. Vascular injury was induced in C57BL/6 mice and in Myh11-creER(T2) mTmG reporter mice by complete ligation of the left carotid artery. Reporter mice were used to visualize cellular changes in the injured vessels. Total RNA was isolated from control carotid arteries or from carotid arteries 3 days following ligation of C57BL/6 mice and analyzed by Affymetrix microarray and quantitative RT-PCR. This analysis revealed decreased expression of mRNAs encoding smooth muscle-specific contractile proteins that was accompanied by a marked increase in a host of mRNAs encoding inflammatory cytokines following injury. There was also marked decrease in molecules associated with BMP, Wnt, and Hedgehog signaling and an increase in those associated with B cell, T cell, and macrophage signaling. Expression of a number of noncoding RNAs were also altered following injury with microRNAs 143/145 being dramatically downregulated and microRNAs 1949 and 142 upregulated. Several long noncoding RNAs showed altered expression that mirrored the expression of their nearest coding genes. These data demonstrate that following carotid artery ligation an inflammatory cascade is initiated that is associated with the downregulation of coding and noncoding RNAs that are normally required to maintain smooth muscle cells in a differentiated state.

Function, Role, and Clinical Application of MicroRNAs in Vascular Aging

Vascular aging, a specific type of organic aging, is related to age-dependent changes in the vasculature, including atherosclerotic plaques, arterial stiffness, fibrosis, and increased intimal thickening. Vascular aging could influence the threshold, process, and severity of various cardiovascular diseases, thus making it one of the most important risk factors in the high mortality of cardiovascular diseases. As endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) are the main cell biological basis of these pathology changes of the vasculature, the structure and function of ECs and VSMCs play a key role in vascular aging. MicroRNAs (miRNAs), small noncoding RNAs, have been shown to regulate the expression of multiple messenger RNAs (mRNAs) posttranscriptionally, contributing to many crucial aspects of cell biology. Recently, miRNAs with functions associated with aging or aging-related diseases have been studied. In this review, we will summarize the reported role of miRNAs in the process of vascular aging with special emphasis on EC and VSMC functions. In addition, the potential application of miRNAs to clinical practice for the diagnosis and treatment of cardiovascular diseases will also be discussed.

miR-503 inhibits platelet-derived growth factor-induced human aortic vascular smooth muscle cell proliferation and migration through targeting the insulin receptor

Abnormal proliferation and migration of vascular smooth muscle cells (VSMC) is a common feature of disease progression in atherosclerosis. Here, we investigated the potential role of miR-503 in platelet-derived growth factor (PDGF)-induced proliferation and migration of human aortic smooth muscle cells and the underlying mechanisms of action. miR-503 expression was significantly downregulated in a dose- and time-dependent manner following PDGF treatment. Introduction of miR-503 mimics into cultured SMCs significantly attenuated cell proliferation and migration induced by PDGF. Bioinformatics analyses revealed that the insulin receptor (INSR) is a target candidate of miR-503. miR-503 suppressed luciferase activity driven by a vector containing the 3'-untranslated region of INSR in a sequence-specific manner. Downregulation of INSR appeared critical for miR-503-mediated inhibitory effects on PDGF-induced cell proliferation and migration in human aortic SMCs. Based on the collective data, we suggest a novel role of miR-503 as a regulator of VSMC proliferation and migration through modulating INSR.

MicroRNAs for Restenosis and Thrombosis After Vascular Injury

Percutaneous revascularization revolutionized the therapy of patients with coronary artery disease. Despite continuous technical advances that substantially improved patients' outcome after percutaneous revascularization, some issues are still open. In particular, restenosis still represents a challenge, even though it was dramatically reduced with the advent of drug-eluting stents. At the same time, drug-eluting stent thrombosis emerged as a major concern because of incomplete or delayed re-endothelialization after vascular injury. The discovery of microRNAs revealed a previously unknown layer of regulation for several biological processes, increasing our knowledge on the biological mechanisms underlying restenosis and stent thrombosis, revealing novel promising targets for more efficient and selective therapies. The present review summarizes recent experimental and clinical evidence on the role of microRNAs after arterial injury, focusing on practical aspects of their potential therapeutic application for selective inhibition of smooth muscle cell proliferation, enhancement of endothelial regeneration, and inhibition of platelet activation after coronary interventions. Application of circulating microRNAs as potential biomarkers is also discussed.

Noncoding RNAs in smooth muscle cell homeostasis: implications in phenotypic switch and vascular disorders

Vascular smooth muscle cells (SMC) are a highly specialized cell type that exhibit extraordinary plasticity in adult animals in response to a number of environmental cues. Upon vascular injury, SMC undergo phenotypic switch from a contractile-differentiated to a proliferative/migratory-dedifferentiated phenotype. This process plays a major role in vascular lesion formation and during the development of vascular remodeling. Vascular remodeling comprises the accumulation of dedifferentiated SMC in the intima of arteries and is central to a number of vascular diseases such as arteriosclerosis, chronic obstructive pulmonary disease or pulmonary hypertension. Therefore, it is critical to understand the molecular mechanisms that govern SMC phenotype. In the last decade, a number of new classes of noncoding RNAs have been described. These molecules have emerged as key factors controlling tissue homeostasis during physiological and pathological conditions. In this review, we will discuss the role of noncoding RNAs, including microRNAs and long noncoding RNAs, in the regulation of SMC plasticity.

MiR-23b controls TGF-β1 induced airway smooth muscle cell proliferation via TGFβR2/p-Smad3 signals

BACKGROUND

Abnormal proliferation of ASM (airway smooth muscle) directly contributes to the airway remodeling during development of lung diseases such as asthma. Here we report that a specific microRNA (miR-23b) controls ASMCs proliferation through directly inhibiting TGFβR2/p-Smad3 pathway.

METHODS

The expression of miR-23b in ASMCs was detected by quantitative real-time polymerase chain reaction (RT-PCR). The effects of miR-23b on cell proliferation and apoptosis of ASMCs were assessed by transient transfection of miR-23b mimics and inhibitor. The target gene of miR-23b and the downstream pathway were further investigated.

RESULTS

Overexpression of miR-23b significantly inhibited TGF-β1-induced ASMCs proliferation and promoted apoptosis. RT-PCR and Western blotting analysis showed miR-23b negatively regulates the expression of TGFβR2 and p-Smad3 in ASMCs. Subsequent analyses demonstrated that TGFβR2 was a direct and functional target of miR-23b, which was validated by the dual luciferase reporter assay.

CONCLUSIONS

MiR-23b may function as an inhibitor of airway smooth muscle cells proliferation through inactivation of TGFβR2/p-Smad3 pathway.

C2238/αANP modulates apolipoprotein E through Egr-1/miR199a in vascular smooth muscle cells in vitro

Subjects carrying the T2238C ANP gene variant have a higher risk to suffer a stroke or myocardial infarction. The mechanisms through which T2238C/αANP exerts detrimental vascular effects need to be fully clarified. In the present work we aimed at exploring the impact of C2238/αANP (mutant form) on atherosclerosis-related pathways. As a first step, an atherosclerosis gene expression macroarray analysis was performed in vascular smooth muscle cells (VSMCs) exposed to either T2238/αANP (wild type) or C2238/αANP. The major finding was that apolipoprotein E (ApoE) gene expression was significantly downregulated by C2238/αANP and it was upregulated by T2238/αANP. We subsequently found that C2238/αANP induces ApoE downregulation through type C natriuretic peptide receptor (NPR-C)-dependent mechanisms involving the upregulation of miR199a-3p and miR199a-5p and the downregulation of DNAJA4. In fact, NPR-C knockdown rescued ApoE level. Upregulation of miR199a by NPR-C was mediated by a reactive oxygen species-dependent increase of the early growth response protein-1 (Egr-1) transcription factor. In fact, Egr-1 knockdown abolished the impact of C2238/αANP on ApoE and miR199a. Of note, downregulation of ApoE by C2238/αANP was associated with a significant increase in inflammation, apoptosis and necrosis that was completely rescued by the exogenous administration of recombinant ApoE. In conclusion, our study dissected a novel mechanism of vascular damage exerted by C2238/αANP that is mediated by ApoE downregulation. We provide the first demonstration that C2238/αANP downregulates ApoE in VSMCs through NPR-C-dependent activation of Egr-1 and the consequent upregulation of miR199a. Restoring ApoE levels could represent a potential therapeutic strategy to counteract the harmful effects of C2238/αANP.

Circulating microRNAs as Biomarkers in Cardiovascular Diseases

MicroRNAs, key regulators of biological processes, are involved in the pathophysiological mechanisms underlying human diseases, including cardiovascular diseases. Their recent discovery revealed a previously unknown layer of pathophysiologic regulators, which also play a key role in the regulation of several aspects of cardiovascular diseases. More recently, it was demonstrated that circulating microRNAs can be measured in the blood. Hence, the potential use of microRNAs as disease biomarkers attracted many research groups. Indeed, their unusual stability in the bloodstream and during prolonged storage make circulating miRs very interesting as potential biomarkers. Circulating microRNAs are emerging as the next generation "smart" biomarkers and could be helpful in further improving the diagnostic and therapeutic processes of cardiovascular diseases. The present chapter summarizes the most relevant experimental evidence on circulating microRNAs in cardiovascular diseases, including arterial remodeling, restenosis, coronary artery disease, acute coronary syndromes, hypertension, heart failure, and ischemic stroke, highlighting potential pathophysiological correlations to the mechanisms underlying cardiovascular diseases.