miR-200c-SUMOylated KLF4 feedback loop acts as a switch in transcriptional programs that control VSMC proliferation

Unravelling the molecular interplay: SUMOylation, PML nuclear bodies and vascular cell activity in health and disease

In the seemingly well-researched field of vascular research, there are still many underestimated factors and molecular mechanisms. In recent years, SUMOylation has become increasingly important. SUMOylation is a post-translational modification in which small ubiquitin-related modifiers (SUMO) are covalently attached to target proteins. Sites where these SUMO modification processes take place in the cell nucleus are PML nuclear bodies (PML-NBs) - multiprotein complexes with their essential main component and organizer, the PML protein. PML and SUMO, either alone or as partners, influence a variety of cellular processes, including regulation of transcription, senescence, DNA damage response and defence against microorganisms, and are involved in innate immunity and inflammatory responses. They also play an important role in maintaining homeostasis in the vascular system and in pathological processes leading to the development and progression of cardiovascular diseases. This review summarizes information about the function of SUMO(ylation) and PML(-NBs) in the human vasculature from angiogenesis to disease and highlights their clinical potential as drug targets.

Unraveling the miRNA Puzzle in Atherosclerosis: Revolutionizing Diagnosis, Prognosis, and Therapeutic Approaches

PURPOSE OF REVIEW

To eradicate atherosclerotic diseases, novel biomarkers, and future therapy targets must reveal the burden of early atherosclerosis (AS), which occurs before life-threatening unstable plaques form. The chemical and biological features of microRNAs (miRNAs) make them interesting biomarkers for numerous diseases. We summarized the latest research on miRNA regulatory mechanisms in AS progression studies, which may help us use miRNAs as biomarkers and treatments for difficult-to-treat diseases.

RECENT FINDINGS

Recent research has demonstrated that miRNAs have a regulatory function in the observed changes in gene and protein expression during atherogenesis, the process that leads to atherosclerosis. Several miRNAs play a role in the development of atherosclerosis, and these miRNAs could potentially serve as non-invasive biomarkers for atherosclerosis in various regions of the body. These miRNAs have the potential to serve as biomarkers and targets for early treatment of atherosclerosis. The start and development of AS require different miRNAs. It reviews new research on miRNAs affecting endothelium, vascular smooth muscle, vascular inflammation, lipid retention, and cholesterol metabolism in AS. A miRNA gene expression profile circulates with AS everywhere. AS therapies include lipid metabolism, inflammation reduction, and oxidative stress inhibition. Clinical use of miRNAs requires tremendous progress. We think tiny miRNAs can enable personalized treatment.

Proteomics Studies Suggest That Nitric Oxide Donor Furoxans Inhibit In Vitro Vascular Smooth Muscle Cell Proliferation by Nitric Oxide-Independent Mechanisms

Physiologically, smooth muscle cells (SMC) and nitric oxide (NO) produced by endothelial cells strictly cooperate to maintain vasal homeostasis. In atherosclerosis, where this equilibrium is altered, molecules providing exogenous NO and able to inhibit SMC proliferation may represent valuable antiatherosclerotic agents. Searching for dual antiproliferative and NO-donor molecules, we found that furoxans significantly decreased SMC proliferation in vitro, albeit with different potencies. We therefore assessed whether this property is dependent on their thiol-induced ring opening. Indeed, while furazans (analogues unable to release NO) are not effective, furoxans' inhibitory potency parallels with the electron-attractor capacity of the group in 3 of the ring, making this effect tunable. To demonstrate whether their specific block on G1-S phase could be NO-dependent, we supplemented SMCs with furoxans and inhibitors of GMP- and/or of the polyamine pathway, which regulate NO-induced SMC proliferation, but they failed in preventing the antiproliferative effect. To find the real mechanism of this property, our proteomics studies revealed that eleven cellular proteins (with SUMO1 being central) and networks involved in cell homeostasis/proliferation are modulated by furoxans, probably by interaction with adducts generated after degradation. Altogether, thanks to their dual effect and pharmacological flexibility, furoxans may be evaluated in the future as antiatherosclerotic molecules.

MicroRNA regulation of phenotypic transformations in vascular smooth muscle: relevance to vascular remodeling

Alterations in the vascular smooth muscle cells (VSMC) phenotype play a critical role in the pathogenesis of several cardiovascular diseases, including hypertension, atherosclerosis, and restenosis after angioplasty. MicroRNAs (miRNAs) are a class of endogenous noncoding RNAs (approximately 19-25 nucleotides in length) that function as regulators in various physiological and pathophysiological events. Recent studies have suggested that aberrant miRNAs' expression might underlie VSMC phenotypic transformation, appearing to regulate the phenotypic transformations of VSMCs by targeting specific genes that either participate in the maintenance of the contractile phenotype or contribute to the transformation to alternate phenotypes, and affecting atherosclerosis, hypertension, and coronary artery disease by altering VSMC proliferation, migration, differentiation, inflammation, calcification, oxidative stress, and apoptosis, suggesting an important regulatory role in vascular remodeling for maintaining vascular homeostasis. This review outlines recent progress in the discovery of miRNAs and elucidation of their mechanisms of action and functions in VSMC phenotypic regulation. Importantly, as the literature supports roles for miRNAs in modulating vascular remodeling and for maintaining vascular homeostasis, this area of research will likely provide new insights into clinical diagnosis and prognosis and ultimately facilitate the identification of novel therapeutic targets.

Noncoding RNAs in Vascular Cell Biology and Restenosis

In-stent restenosis (ISR), characterised by ≥50% re-narrowing of the target vessel, is a common complication following stent implantation and remains a significant challenge to the long-term success of angioplasty procedures. Considering the global burden of cardiovascular diseases, improving angioplasty patient outcomes remains a key priority. Noncoding RNAs (ncRNAs) including microRNA (miRNA), long noncoding RNA (lncRNA) and circular RNA (circRNA) have been extensively implicated in vascular cell biology and ISR through multiple, both distinct and overlapping, mechanisms. Vascular smooth muscle cells, endothelial cells and macrophages constitute the main cell types involved in the multifactorial pathophysiology of ISR. The identification of critical regulators exemplified by ncRNAs in all these cell types and processes makes them an exciting therapeutic target in the field of restenosis. In this review, we will comprehensively explore the potential functions and underlying molecular mechanisms of ncRNAs in vascular cell biology in the context of restenosis, with an in-depth focus on vascular cell dysfunction during restenosis development and progression. We will also discuss the diagnostic biomarker and therapeutic target potential of ncRNAs in ISR. Finally, we will discuss the current shortcomings, challenges, and perspectives toward the clinical application of ncRNAs.

Histone Modifications and Non-Coding RNAs: Mutual Epigenetic Regulation and Role in Pathogenesis

In the last few years, more and more scientists have suggested and confirmed that epigenetic regulators are tightly connected and form a comprehensive network of regulatory pathways and feedback loops. This is particularly interesting for a better understanding of processes that occur in the development and progression of various diseases. Appearing on the preclinical stages of diseases, epigenetic aberrations may be prominent biomarkers. Being dynamic and reversible, epigenetic modifications could become targets for a novel option for therapy. Therefore, in this review, we are focusing on histone modifications and ncRNAs, their mutual regulation, role in cellular processes and potential clinical application.

Discoidin Domain-Containing Receptor 2 Is Present in Human Atherosclerotic Plaques and Involved in the Expression and Activity of MMP-2

Discoidin domain-containing receptor 2 (DDR2) has been suggested to be involved in atherosclerotic progression, but its pathological role remains unknown. Using immunochemical staining, we located and compared the expression of DDR2 in the atherosclerotic plaques of humans and various animal models. Then, siRNA was applied to knock down the expression of DDR2 in vascular smooth muscle cells (VSMCs), and the migration, proliferation, and collagen Ι-induced expression of matrix metalloproteinases (MMPs) were evaluated. We found that an abundance of DDR2 was present in the atherosclerotic plaques of humans and various animal models and was distributed around fatty and necrotic cores. After incubation of oxidized low-density lipoprotein (ox-LDL), DDR2 was upregulated in VSMCs in response to such a proatherosclerotic condition. Next, we found that decreased DDR2 expression in VSMCs inhibited the migration, proliferation, and collagen Ι-induced expression of matrix metalloproteinases (MMPs). Moreover, we found that DDR2 is strongly associated with the protein expression and activity of MMP-2, suggesting that DDR2 might play a role in the etiology of unstable plaques. Considering that DDR2 is present in the atherosclerotic plaques of humans and is associated with collagen Ι-induced secretion of MMP-2, the clinical role of DDR2 in cardiovascular disease should be elucidated in further experiments.

Expression and Functional Analysis of lncRNAs Involved in Platelet-Derived Growth Factor-BB-Induced Proliferation of Human Aortic Smooth Muscle Cells

Abnormal proliferation of vascular smooth muscle cells (VSMCs) is a common feature of many vascular remodeling diseases. Because long non-coding RNAs (lncRNAs) play a critical role in cardiovascular diseases, we analyzed the key lncRNAs that regulate VSMC proliferation. Microarray analysis identified 2,643 differentially expressed lncRNAs (DELs) and 3,720 differentially expressed coding genes (DEGs) between fetal bovine serum (FBS) starvation-induced quiescent human aortic smooth muscle cells (HASMCs) and platelet-derived growth factor-BB (PDGF-BB)-stimulated proliferative HASMCs. Gene Ontology and pathway analyses of the identified DEGs and DELs demonstrated that many lncRNAs were enriched in pathways related to cell proliferation. One of the upregulated lncRNAs in proliferative HASMC was HIF1A anti-sense RNA 2 (HIF1A-AS2). HIF1A-AS2 suppression decreased HASMC proliferation via the miR-30e-5p/CCND2 mRNA axis. We have thus identified key DELs and DEGs involved in the regulation of PDGF-BB induced HASMC proliferation. Moreover, HIF1A-AS2 promotes HASMC proliferation, suggesting its potential involvement in VSMC proliferative vascular diseases.

Smooth muscle cell-specific knockout of interferon gamma (IFN-γ) receptor attenuates intimal hyperplasia via STAT1-KLF4 activation

BACKGROUND

Intimal hyperplasia is a main contributor to in-stent restenosis. Previous researches have shown that interferon-gamma (IFN-γ), a pleiotropic pro-inflammatory factor, plays a pathological role in intimal hyperplasia. However, the specific role and molecular mechanism of vascular smooth muscle cells (VSMCs)-derived IFN-γ receptor in intimal hyperplasia remains unknown.

METHODS

We examined the distribution of IFN-γ receptor in human restenosis arteries. Then, the role of IFN-γ receptor in intimal hyperplasia was detected using VSMC-specific IFN-γ receptor-knock out carotid ligation injury models. We performed immunostaining, transwell assay and EdU staining to identify the role of IFN-γ in VSMCs proliferation and migration. The effect of IFN-γ on VSMCs phenotype switching was also investigated. Finally, we evaluated whether the mechanism of IFN-γ on intimal hyperplasia is STAT1-KLF4 dependent.

RESULTS

The distribution of IFN-γ receptor in human restenosis arteries with VSMC-rich neointima is eventually upregulated. Specific deletion of IFN-γ receptor exhibits thinner intima and lesser proliferating VSMCs. In vitro, treatment with IFN-γ promotes human aortic VSMC (HAVSMCs) proliferation and migration, whereas specifically knock out IFN-γ receptor results in the opposite effect. Deficiency of IFN-γ receptor regulates VSMCs phenotypic switching, such as upregulated contractile markers and downregulated proliferation markers. Mechanistic studies suggest that ablation of IFN-γ receptor prevents VSMCs proliferation, migration and dedifferentiation via STAT1-KLF4 activation.

CONCLUSION

These results reveal that knockout of VSMC-derived IFN-γ receptor potentiates neointimal hyperplasia by preventing VSMCs proliferation, migration and dedifferentiation. Our finding implies that targeting IFN-γ-STAT1-KLF4 signaling could provide a new therapeutic strategy to attenuate vessel restenosis.

Zinc finger E-box binding homeobox 1 and atherosclerosis: New insights and therapeutic potential

Zinc finger E-box binding homeobox 1 (ZEB1), an important transcription factor belonging to the ZEB family, plays a crucial role in regulating gene expression required for both normal physiological and pathological processes. Accumulating evidence has shown that ZEB1 participates in the initiation and progression of atherosclerotic cardiovascular disease. Recent studies suggest that ZEB1 protects against atherosclerosis by regulation of endothelial cell angiogenesis, endothelial dysfunction, monocyte-endothelial cell interaction, macrophage lipid accumulation, macrophage polarization, monocyte-vascular smooth muscle cell (VSMC) interaction, VSMC proliferation and migration, and T cell proliferation. In this review, we summarize the recent progress of ZEB1 in the pathogenesis of atherosclerosis and provide insights into the prevention and treatment of atherosclerotic cardiovascular disease.

Di-n-butyl phthalate promotes lipid accumulation via the miR200c-5p-ABCA1 pathway in THP-1 macrophages

Di-n-butyl phthalate (DBP) is ubiquitously in the environment and has been detected in almost all of human bodies. Few data could be found about the effects of DBP on cardiovascular system, though its reproductive toxicities have been studied extensively. This study aimed to explore the effects of DBP on lipid metabolism, a key step during the formation of atherosclerosis, since DBP was recently reported to be associated with atherosclerosis. THP-1 macrophages were employed and exposed to various levels of DBP (10^-8, 10^-7, 10^-6, 10^-5 and 10^-4 mol/L) or DMSO as control. Lipid accumulation was determined by detection of cellular total cholesterol, free cholesterol, cholesterol ester and content of lipid drops. Expressions of mRNA/miRNAs and proteins were measured by qRT-PCR and western blotting, respectively. Bioinformatic analysis and dual luciferase reporter assay were used to analyze the combination between miR200c-5p and ATP-binding cassette transporter A1 (ABCA1). Cholesterol efflux assay was executed to study the inhibitory effects of DBP on cholesterol efflux capability. Results revealed that DBP at 10^-7 mol/L prompted THP-1 macrophages lipid accumulation by inhibiting cholesterol efflux via suppressing ABCA1 expression. In addition, a non-linear inverted U-shaped relationship between DBP and lipid accumulation could be observed. Moreover, miR200c-5p could directly targets to ABCA1 3'UTR and modulate ABCA1 expression. Besides, downregulation of ABCA1 expression and reduction of lipid efflux induced by DBP were due to the miR200c-5p upregulation. Collectively, these data suggested that DBP at levels relative to human exposure could increase lipid accumulation in THP-1 macrophages by decreasing cholesterol efflux through miR200c-5p-ABCA1, then potentiate the formation of atherosclerosis.

Tanshinone ⅡA inhibits VSMC inflammation and proliferation in vivo and in vitro by downregulating miR-712-5p expression

The inflammation and proliferation of vascular smooth muscle cells (VSMCs) are the basic pathological feature of proliferative vascular diseases. Tanshinone ⅡA (Tan ⅡA), which is the most abundant fat-soluble element extracted from Salvia miltiorrhiza, has potent protective effects on the cardiovascular system. However, the underlying mechanism is still not fully understood. Here, we show that Tan ⅡA significantly inhibits neointimal formation and decreases VSMC inflammation by upregulating the expression of KLF4 and inhibiting the activation of NFκB signaling. Using a microRNA array analysis, we found that miR-712-5p expression is significantly upregulated in tumor necrosis factor alpha (TNF-α)-treated VSMCs. Loss- and gain-of-function experiments revealed that transfection of miR-712-5p mimic promotes, whereas depletion of miR-712-5p suppresses TNF-α-induced VSMC inflammation, leading to amelioration of intimal hyperplasia induced by carotid artery ligation. Moreover, depletion of miR-712-5p by its antagomir largely abrogates TNF-α-induced VSMC proliferation. Our findings suggest that miR-712-5p mediates the stimulatory effect of TNF-α on VSMC inflammation, and that Tan ⅡA inhibits VSMC inflammation and proliferation in vivo and in vitro by suppression of miR-712-5p expression. Targeting miR-712-5p may be a novel therapeutic strategy to prevent proliferative vascular diseases.

Screening and functional prediction of differentially expressed circRNAs in proliferative human aortic smooth muscle cells

Vascular smooth muscle cell (VSMC) proliferation is the pathological base of vascular remodelling diseases. Circular RNAs (circRNAs) are important regulators involved in various biological processes. However, the function of circRNAs in VSMC proliferation regulation remains largely unknown. This study was conducted to identify the key differentially expressed circRNAs (DEcircRNAs) and predict their functions in human aortic smooth muscle cell (HASMC) proliferation. To achieve this, DEcircRNAs between proliferative and quiescent HASMCs were detected using a microarray, followed by quantitative real-time RT-PCR validation. A DEcircRNA-miRNA-DEmRNA network was constructed, and functional annotation was performed using Gene Ontology (GO) and KEGG pathway analysis. The function of hsa_circ_0002579 in HASMC proliferation was analysed by Western blot. The functional annotation of the DEcircRNA-miRNA-DEmRNA network indicated that the four DEcircRNAs might play roles in the TGF-β receptor signalling pathway, Ras signalling pathway, AMPK signalling pathway and Wnt signalling pathway. Twenty-seven DEcircRNAs with coding potential were screened. Hsa_circ_0002579 might be a pro-proliferation factor of HASMC. Overall, our study identified the key DEcircRNAs between proliferative and quiescent HASMCs, which might provide new important clues for exploring the functions of circRNAs in vascular remodelling diseases.

Transcription Factors Targeted by miRNAs Regulating Smooth Muscle Cell Growth and Intimal Thickening after Vascular Injury

Neointima formation after percutaneous coronary intervention (PCI) is a manifestation of “phenotype switching” by vascular smooth muscle cells (SMC), a process that involves de-differentiation from a contractile quiescent phenotype to one that is richly synthetic. In response to injury, SMCs migrate, proliferate, down-regulate SMC-specific differentiation genes, and later, can revert to the contractile phenotype. The vascular response to injury is regulated by microRNAs (or miRNAs), small non-coding RNAs that control gene expression. Interactions between miRNAs and transcription factors impact gene regulatory networks. This article briefly reviews the roles of a range of miRNAs in molecular and cellular processes that control intimal thickening, focusing mainly on transcription factors, some of which are encoded by immediate-early genes. Examples include Egr-1, junB, KLF4, KLF5, Elk-1, Ets-1, HMGB1, Smad1, Smad3, FoxO4, SRF, Rb, Sp1 and c-Myb. Such mechanistic information could inform the development of strategies that block SMC growth, neointima formation, and potentially overcome limitations of lasting efficacy following PCI.

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.

Imbalance of a KLF4-miR-7 auto-regulatory feedback loop promotes prostate cancer cell growth by impairing microRNA processing

The microRNA-transcription factor auto-regulatory feedback loop is a pivotal mechanism for homeostatic regulation of gene expression, and dysregulation of the feedback loop is tightly associated with tumorigenesis and progression. However, the mechanism underlying such dysregulation is still not well-understood. Here we reported that Krüppel-like factor 4 (KLF4), a stemness-associated transcription factor, promotes the transcription of miR-7 to repress its own translation so that a KLF4-miR-7 auto-regulatory feedback loop is established for mutual regulation of their expression. Interestingly, this feedback loop is unbalanced in prostate cancer (PCa) cell lines and patient samples due to an impaired miR-7-processing, leading to decreased mature miR-7 production and attenuated inhibition of KLF4 translation. Mechanistically, enhanced oncogenic Yes associated protein (YAP) nuclear translocation mediates sequestration of p72, a co-factor of the Drosha/DGCR8 complex for pri-miR-7s processing, leading to attenuation of microprocessors' efficiency. Knockdown of YAP or transfection with a mature miR-7 mimic can significantly recover miR-7 expression to restore this feedback loop, and in turn to inhibit cancer cell growth by repressing KLF4 expression in vitro. Thus, our findings indicate that targeting the KLF4-miR-7 feedback loop might be a potential strategy for PCa therapy.

SUMOylation of KLF4 promotes IL-4 induced macrophage M2 polarization

Macrophages, in response to different environmental cues, undergo the classical polarization (M1 macrophages) as well as the alternative polarization (M2 macrophages) that involve the functions of stimulus-specific transcription factors. Kruppel-like factor 4 (KLF4), a member of a subfamily of the zinc-finger class of DNA-binding transcription factors, plays as a critical regulator of macrophage polarization. KLF4 has been reported as a SUMOylated protein. In this study, we showed that SUMOylation of KLF4, is induced by IL-4 treatment in macrophages. IL4-induced KLF4 SUMOylation promotes RAW264.7 cells and bone marrow derived macrophages (BMDMs) to polarize into M2 subset. Thus, we identified an important post-translational modification (PTM), SUMOylation, plays a crucial role in regulating KLF4 activity during IL-4 induced macrophage M2 polarization. SUMOylation of KLF4 can be a potential therapeutic target in the resolution of inflammation.

miR-29a regulates vascular neointimal hyperplasia by targeting YY1

OBJECTIVES

The formation of vascular neointima is mainly related to impairment of the vascular endothelial barrier and abnormal proliferation and migration of smooth muscle cells. The objective of this study was to investigate whether miR-29a exerts any promoting effect on the vascular neointimal hyperplasia and if so, its mechanism.

MATERIALS AND METHODS

RT-qPCR was performed to determine expression of miR-29a in vascular smooth muscle cells (VSMC) and vascular neointimal hyperplasia. To further understand its role, we restored its expression in VSMCs by transfection with miR-29a mimics or inhibitors. Effects of miR-29a on cell proliferation were also determined.

RESULTS

In this study, we used two kinds of model to observe the role of miR-29a in neointimal hyperplasia induced by carotid ligation or balloon injury. The major findings were that: (i) miR-29a overexpression promoted neointimal hyperplasia induced by carotid ligation; (ii) miR-29a increased proliferation of VSMCs, one aspect of which was by targeting expression of Ying and yang 1 protein (YY1), a negative regulator of Cyclin D1. A further aspect, was by increasing expression of Krüppel-like factor 5, a positive regulator of Cyclin D1, thereby allowing formation a synergistic effect. (iii) Tongxinluo (TXL), a traditional Chinese medicine reduced neointimal formation in ligated vessels by inhibiting VSMC proliferation and migration.

CONCLUSIONS

These findings provide a new molecular mechanism of TXL in decreasing neointima hyperplasia.

SUMOylation of KLF4 acts as a switch in transcriptional programs that control VSMC proliferation

The regulation of vascular smooth muscle cell (VSMC) proliferation is an important issue due to its major implications for the prevention of pathological vascular conditions. The objective of this work was to assess the function of small ubiquitin-like modifier (SUMO)ylated Krϋppel-like transcription factor 4 (KLF4) in the regulation of VSMC proliferation in cultured cells and in animal models with balloon injury. We found that under basal conditions, binding of non-SUMOylated KLF4 to p300 activated p21 (p21(WAF1/CIP1))transcription, leading to VSMC growth arrest. PDGF-BB promoted the interaction between Ubc9 and KLF4 and the SUMOylation of KLF4, which in turn recruited transcriptional corepressors to the p21 promoter. The reduction in p21 enhanced VSMC proliferation. Additionally, the SUMOylated KLF4 did not affect the expression of KLF4, thereby forming a positive feedback loop enhancing cell proliferation. These results demonstrated that SUMOylated KLF4 plays an important role in cell proliferation by reversing the transactivation action of KLF4 on p21 induced with PDGF-BB.

Mechanical Stretch Inhibits MicroRNA499 via p53 to Regulate Calcineurin-A Expression in Rat Cardiomyocytes

BACKGROUND

MicroRNAs play an important role in cardiac remodeling. MicroRNA 499 (miR499) is highly enriched in cardiomyocytes and targets the gene for Calcineurin A (CnA), which is associated with mitochondrial fission and apoptosis. The mechanism regulating miR499 in stretched cardiomyocytes and in volume overloaded heart is unclear. We sought to investigate the mechanism regulating miR499 and CnA in stretched cardiomyocytes and in volume overload-induced heart failure.

METHODS & RESULTS

Rat cardiomyocytes grown on a flexible membrane base were stretched via vacuum to 20% of maximum elongation at 60 cycles/min. An in vivo model of volume overload with aorta-caval shunt in adult rats was used to study miR499 expression. Mechanical stretch downregulated miR499 expression, and enhanced the expression of CnA protein and mRNA after 12 hours of stretch. Expression of CnA and calcineurin activity was suppressed with miR499 overexpression; whereas, expression of dephosphorylated dynamin-related protein 1 (Drp1) was suppressed with miR499 overexpression and CnA siRNA. Adding p53 siRNA reversed the downregulation of miR499 when stretched. A gel shift assay and promoter-activity assay demonstrated that stretch increased p53 DNA binding activity but decreased miR499 promoter activity. When the miR499 promoter p53-binding site was mutated, the inhibition of miR499 promoter activity with stretch was reversed. The in vivo aorta-caval shunt also showed downregulated myocardial miR499 and overexpression of miR499 suppressed CnA and cellular apoptosis.

CONCLUSION

The miR499-controlled apoptotic pathway involving CnA and Drp1 in stretched cardiomyocytes may be regulated by p53 through the transcriptional regulation of miR499.

Differentiation-Dependent KLF4 Expression Promotes Lytic Epstein-Barr Virus Infection in Epithelial Cells

Epstein-Barr virus (EBV) is a human herpesvirus associated with B-cell and epithelial cell malignancies. EBV lytically infects normal differentiated oral epithelial cells, where it causes a tongue lesion known as oral hairy leukoplakia (OHL) in immunosuppressed patients. However, the cellular mechanism(s) that enable EBV to establish exclusively lytic infection in normal differentiated oral epithelial cells are not currently understood. Here we show that a cellular transcription factor known to promote epithelial cell differentiation, KLF4, induces differentiation-dependent lytic EBV infection by binding to and activating the two EBV immediate-early gene (BZLF1 and BRLF1) promoters. We demonstrate that latently EBV-infected, telomerase-immortalized normal oral keratinocyte (NOKs) cells undergo lytic viral reactivation confined to the more differentiated cell layers in organotypic raft culture. Furthermore, we show that endogenous KLF4 expression is required for efficient lytic viral reactivation in response to phorbol ester and sodium butyrate treatment in several different EBV-infected epithelial cell lines, and that the combination of KLF4 and another differentiation-dependent cellular transcription factor, BLIMP1, is highly synergistic for inducing lytic EBV infection. We confirm that both KLF4 and BLIMP1 are expressed in differentiated, but not undifferentiated, epithelial cells in normal tongue tissue, and show that KLF4 and BLIMP1 are both expressed in a patient-derived OHL lesion. In contrast, KLF4 protein is not detectably expressed in B cells, where EBV normally enters latent infection, although KLF4 over-expression is sufficient to induce lytic EBV reactivation in Burkitt lymphoma cells. Thus, KLF4, together with BLIMP1, plays a critical role in mediating lytic EBV reactivation in epithelial cells.

Lytic EBV infection of differentiated oral epithelial cells results in the release of infectious viral particles and is required for efficient transmission of EBV from host to host. Lytic infection also causes a tongue lesion known as oral hairy leukoplakia (OHL). However, surprisingly little is known in regard to how EBV gene expression is regulated in epithelial cells. Using a stably EBV- infected, telomerase-immortalized normal oral keratinocyte cell line, we show here that undifferentiated basal epithelial cells support latent EBV infection, while differentiation of epithelial cells promotes lytic reactivation. Furthermore, we demonstrate that the KLF4 cellular transcription factor, which is required for normal epithelial cell differentiation and is expressed in differentiated, but not undifferentiated, normal epithelial cells, induces lytic EBV reactivation by activating transcription from the two EBV immediate-early gene promoters. We also show that the combination of KLF4 and another differentiation-dependent cellular transcription factor, BLIMP1, synergistically activates lytic gene expression in epithelial cells. We confirm that KLF4 and BLIMP1 expression in normal tongue epithelium is confined to differentiated cells, and that KLF4 and BLIMP1 are expressed in a patient-derived OHL tongue lesion. These results suggest that differentiation-dependent expression of KLF4 and BLIMP1 in epithelial cells promotes lytic EBV infection.

miR-146b-5p promotes VSMC proliferation and migration

Vascular smooth muscle cells (VSMCs) play pivotal roles in the development of vascular diseases. While microRNAs are important in vascular pathologies, a few is known about their functional roles in VSMC phenotypes. We profiled microRNA expression in PDGF-BB treated VSMCs and found microRNA-146b-5p (miR-146b-5p) was upregulated. Inhibition of miR-146b-5p blocked in response to PDGF while reducing VSMC proliferation and migration. These studies implicate miR-146b-5p as necessary for PDGF-induced VSMC phenotype transition. Downstream miR-146b-5p targets modulating VSMC phenotypes will be further identified. Our study will help to understand the role of VSMCs in the pathology of vascular diseases.