MicroRNA Regulation of SIRT1

SIRT1 is an NAD-dependent deacetylase that regulates stress response pathways. By deacetylating transcription factors and co-factors, SIRT1 modulates metabolism, inflammation, hypoxic responses, circadian rhythms, cell survival, and longevity. Since SIRT1 plays a key role in regulating pathways involved in cardiovascular diseases and metabolic diseases cancer, the regulation of SIRT1 has received intense scrutiny. The post-transcriptional regulation of SIRT1 is mediated by two classes of molecules, RNA-binding proteins (RBPs) and non-coding small RNAs. MicroRNAs (miRNAs) are short non-coding RNAs that regulate target gene expression in a post-transcriptional manner. More than 16 miRNAs modulate SIRT1 expression, including miR-34a. miR-34a induces colon cancer apoptosis through SIRT1, and miR-34a also promotes senescence in endothelial cells via SIRT1. This review describes the impact of miRNAs on SIRT1. The background of SIRT1 and miRNAs will be summarized, followed by the mechanism by which several key miRNAs alter SIRT1 levels, and how the RBP HuR regulates SIRT1. MicroRNA regulation of SIRT1 might affect a wide variety of pathways in humans, from metabolic diseases such as diabetes to cardiovascular diseases and cancer

p53 and Vascular Dysfunction: MicroRNA in Endothelial Cells

In many cancer cells, p53 gene is mutated and accumulated, which is considered as a mechanistical target of tumorigenesis. The role of p53 in non-cancerous cells has been focused on, since p53 activation diversely affects as human diseases, including vascular dysfunctions. p53 regulates vascular events, including vascular inflammation and senescence as well as cardiac dysfunction. Many researchers also have paid attention to the role of noncoding RNAs (ncRNAs), especially small-sized microRNAs (miRNAs) for the last decade and their noble biological cellular functions have been discovered. miRNAs expressed in endothelial cells (endothelial miRNAs) have been shown to control vascular events. Firstly, the importance of p53 in a variety of vascular events, such as vascular inflammation and senescence, are summarized. Secondly, the way to regulate miRNAs by p53 and the involvement of miRNAs on p53 function are demonstrated. Finally, several endothelial miRNAs that have important roles are focused on. The aim of this chapter is to understand the role of p53 in vascular diseases in the view of endothelial cell biology and the contribution of miRNAs related to p53

The Role of miRNAs in Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a genetic heterogeneous disease with high mortality and poor prognosis. IPF is characterized by persistent fibroblasts and relentless accumulation of collagen matrix. Epithelial-mesenchymal transition (EMT) and endothelial-to-mesenchymal transition (EndoMT) contribute to the progression of the fibrotic process. There are some therapeutic drugs that delay this progress, but eradicative medicine does not exist yet. MicroRNAs (miRNAs) are short single-stranded RNAs that regulate posttranscriptional silencing. Recent reports have shown that miRNAs play important roles in the development of IPF, as different expression levels of miRNAs in blood and lung tissue from IPF patients were closely associated with the occurrence of IPF disease. In this chapter, we will discuss the role of miRNAs in the pathogenesis, diagnosis, and treatment of IPF. In particular, we will focus on the regulation of EMT/EndoMT by miRNAs

Platelet Factor 4 Regulation of Monocyte KLF4 in Experimental Cerebral Malaria

Cerebral malaria continues to be a difficult to treat complication of Plasmodium falciparum infection in children. We have shown that platelets can have major deleterious immune functions in experimental cerebral malaria (ECM). One of the platelet derived mediators we have identified as particularly important is platelet factor 4/CXCL4. Our prior work demonstrated that PF4−/− mice are protected from ECM, have reduced plasma cytokines, and have reduced T-cell trafficking to the brain. We now show that PF4 drives monocyte cytokine production in a Kruppel like factor 4 (KLF4) dependent manner. Monocyte depleted Plasmodium berghei infected mice have improved survival, and KLF4 is greatly increased in control, but not monocyte depleted mice. PF4−/− mice have less cerebral monocyte trafficking and no change in KLF4 expression. These data indicate that PF4 induction of monocyte KLF4 expression may be an important step in the pathogenesis of ECM

Hydrogen peroxide regulation of endothelial exocytosis by inhibition of N-ethylmaleimide sensitive factor

Although an excess of reactive oxygen species (ROS) can damage the vasculature, low concentrations of ROS mediate intracellular signal transduction pathways. We hypothesized that hydrogen peroxide plays a beneficial role in the vasculature by inhibiting endothelial exocytosis that would otherwise induce vascular inflammation and thrombosis. We now show that endogenous H2O2 inhibits thrombin-induced exocytosis of granules from endothelial cells. H2O2 regulates exocytosis by inhibiting N-ethylmaleimide sensitive factor (NSF), a protein that regulates membrane fusion events necessary for exocytosis. H2O2 decreases the ability of NSF to hydrolyze adenosine triphosphate and to disassemble the soluble NSF attachment protein receptor complex. Mutation of NSF cysteine residue C264T eliminates the sensitivity of NSF to H2O2, suggesting that this cysteine residue is a redox sensor for NSF. Increasing endogenous H2O2 levels in mice decreases exocytosis and platelet rolling on venules in vivo. By inhibiting endothelial cell exocytosis, endogenous H2O2 may protect the vasculature from inflammation and thrombosis

Upregulated sirtuin 1 by miRNA-34a is required for smooth muscle cell differentiation from pluripotent stem cells

© 2015 Macmillan Publishers Limited. All rights reserved. microRNA-34a (miR-34a) and sirtuin 1 (SirT1) have been extensively studied in tumour biology and longevityaging, but little is known about their functional roles in smooth muscle cell (SMC) differentiation from pluripotent stem cells. Using well-established SMC differentiation models, we have demonstrated that miR-34a has an important role in SMC differentiation from murine and human embryonic stem cells. Surprisingly, deacetylase sirtuin 1 (SirT1), one of the top predicted targets, was positively regulated by miR-34a during SMC differentiation. Mechanistically, we demonstrated that miR-34a promoted differentiating stem cells' arrest at G0G1 phase and observed a significantly decreased incorporation of miR-34a and SirT1 RNA into Ago2-RISC complex upon SMC differentiation. Importantly, we have identified SirT1 as a transcriptional activator in the regulation of SMC gene programme. Finally, our data showed that SirT1 modulated the enrichment of H3K9 tri-methylation around the SMC gene-promoter regions. Taken together, our data reveal a specific regulatory pathway that miR-34a positively regulates its target gene SirT1 in a cellular context-dependent and sequence-specific manner and suggest a functional role for this pathway in SMC differentiation from stem cells in vitro and in vivo

Estrogen-dependent dynamic profile of eNOS-DNA associations in prostate cancer

In previous work we have documented the nuclear translocation of endothelial NOS (eNOS) and its participation in combinatorial complexes with Estrogen Receptor Beta (ERβ) and Hypoxia Inducible Factors (HIFs) that determine localized chromatin remodeling in response to estrogen (E2) and hypoxia stimuli, resulting in transcriptional regulation of genes associated with adverse prognosis in prostate cancer (PCa). To explore the role of nuclear eNOS in the acquisition of aggressive phenotype in PCa, we performed ChIP-Sequencing on chromatin-associated eNOS from cells from a primary tumor with poor outcome and from metastatic LNCaP cells. We found that: 1. the eNOS-bound regions (peaks) are widely distributed across the genome encompassing multiple transcription factors binding sites, including Estrogen Response Elements. 2. E2 increased the number of peaks, indicating hormone-dependent eNOS re-localization. 3. Peak distribution was similar with/without E2 with ≈ 55% of them in extragenic DNA regions and an intriguing involvement of the 5′ domain of several miRs deregulated in PCa. Numerous potentially novel eNOS-targeted genes have been identified suggesting that eNOS participates in the regulation of large gene sets. The parallel finding of downregulation of a cluster of miRs, including miR-34a, in PCa cells associated with poor outcome led us to unveil a molecular link between eNOS and SIRT1, an epigenetic regulator of aging and tumorigenicity, negatively regulated by miR-34a and in turn activating eNOS. E2 potentiates miR-34a downregulation thus enhancing SIRT1 expression, depicting a novel eNOS/SIRT1 interplay fine-tuned by E2-activated ER signaling, and suggesting that eNOS may play an important role in aggressive PCa

TransmiR: a transcription factor–microRNA regulation database

MicroRNAs (miRNAs) regulate gene expression at the posttranscriptional level and are therefore important cellular components. As is true for protein-coding genes, the transcription of miRNAs is regulated by transcription factors (TFs), an important class of gene regulators that act at the transcriptional level. The correct regulation of miRNAs by TFs is critical, and increasing evidence indicates that aberrant regulation of miRNAs by TFs can cause phenotypic variations and diseases. Therefore, a TF–miRNA regulation database would be helpful for understanding the mechanisms by which TFs regulate miRNAs and understanding their contribution to diseases. In this study, we manually surveyed approximately 5000 reports in the literature and identified 243 TF–miRNA regulatory relationships, which were supported experimentally from 86 publications. We used these data to build a TF–miRNA regulatory database (TransmiR, http://cmbi.bjmu.edu.cn/transmir), which contains 82 TFs and 100 miRNAs with 243 regulatory pairs between TFs and miRNAs. In addition, we included references to the published literature (PubMed ID) information about the organism in which the relationship was found, whether the TFs and miRNAs are involved with tumors, miRNA function annotation and miRNA-associated disease annotation. TransmiR provides a user-friendly interface by which interested parties can easily retrieve TF–miRNA regulatory pairs by searching for either a miRNA or a TF

Expression of the RNA helicase DDX3 and the hypoxia response in breast cancer

<p>Aims: DDX3 is an RNA helicase that has antiapoptotic properties, and promotes proliferation and transformation. In addition, DDX3 was shown to be a direct downstream target of HIF-1α (the master regulatory of the hypoxia response) in breast cancer cell lines. However, the relation between DDX3 and hypoxia has not been addressed in human tumors. In this paper, we studied the relation between DDX3 and the hypoxic responsive proteins in human breast cancer.</p> <p>Methods and Results: DDX3 expression was investigated by immunohistochemistry in breast cancer in comparison with hypoxia related proteins HIF-1α, GLUT1, CAIX, EGFR, HER2, Akt1, FOXO4, p53, ERα, COMMD1, FER kinase, PIN1, E-cadherin, p21, p27, Transferrin receptor, FOXO3A, c-Met and Notch1. DDX3 was overexpressed in 127 of 366 breast cancer patients, and was correlated with overexpression of HIF-1α and its downstream genes CAIX and GLUT1. Moreover, DDX3 expression correlated with hypoxia-related proteins EGFR, HER2, FOXO4, ERα and c-Met in a HIF-1α dependent fashion, and with COMMD1, FER kinase, Akt1, E-cadherin, TfR and FOXO3A independent of HIF-1α.</p> <p>Conclusions: In invasive breast cancer, expression of DDX3 was correlated with overexpression of HIF-1α and many other hypoxia related proteins, pointing to a distinct role for DDX3 under hypoxic conditions and supporting the oncogenic role of DDX3 which could have clinical implication for current development of DDX3 inhibitors.</p&gt