The huge world of small RNAs: regulating networks of microRNAs (review)

Elevation of Plasminogen Activator Inhibitor-1 promotes differentiation of Cancer Stem-like Cell state by Hepatitis C Virus infection

Plasminogen activator inhibitor-1 (PAI-1) is a critical factor that regulates protein synthesis and degradation. The increased PAI-1 levels are detectable in the serum of patients with chronic hepatitis C virus (HCV) liver disease. The differentiation state and motility of HCV-induced cancer stem-like cells (CSC) play a major role in severe liver disease progression. However, the role of PAI-1 in the pathological process of chronic liver diseases remains unknown. In this study, we determined how PAI-1 affects the differentiation of CSC state in hepatocytes upon HCV infection. We found that HCV infection induced the expression of PAI-1 while decreasing miR-30c expression in Huh7.5.1 cells. Similar results were obtained from isolated hepatocytes from humanized liver mice after HCV infection. Moreover, decreased miR-30c expression in HCV-infected hepatocytes was associated with the increased levels of PAI-1 mRNA and protein. Notably, the increased PAI-1 levels resulted in the activation of Protein Kinase B/AKT, a major mediator of cell proliferation, in HCV-infected hepatocytes along with the increased expression of CSC markers such as Human Differentiated Protein (CD) 133, Epithelial cell adhesion molecule (EpCAM), Octamer 4 (Oct4), Nanog, Cyclin D1, and MYC. Moreover, blockade of PAI-1 activity by miR-30c mimic and anti-PAI-1 mAb abrogated the AKT activation with decreased expression of CSC markers. Our findings suggest that HCV infection induces the CSC state via PAI-1-mediated AKT activation in hepatocytes. It implicates that the manipulation of PAI-1 activity could provide potential therapeutics to prevent the development of HCV-associated chronic liver diseases.IMPORTANCEThe progression of chronic liver disease by HCV infection is considered a major risk factor for hepatocellular carcinoma (HCC), one of the major causes of death from cancer. Recent studies have demonstrated that increased CSC properties in HCV-infected hepatocytes are associated with the progression of HCC. Since proteins and miRNAs production by HCV-infected hepatocytes can play various roles in physiological processes, investigating these factors can potentially lead to new therapeutic targets. However, the mechanism of HCV associated progression of hepatocytes to CSC remains unclear. Here we identify the roles of PAI-1 and miR-30c in the progression of CSC during HCV infection in hepatocytes. Our data shows that increased secretion of PAI-1 following HCV infection promotes this CSC state and activation of AKT. We report that the inhibition of PAI-1 by miR-30c mimic reduces HCV associated CSC properties in hepatocytes. Taken together, targeting this interaction of secreted PAI-1 and miR-30c in HCV-infected hepatocytes may provide a potential therapeutic intervention against the progression to chronic liver diseases and HCC.

miR-30c may serve a role in endometriosis by targeting plasminogen activator inhibitor-1

The present study aimed to investigate the role of miR-30c in endometriosis (EMs) and the underlying mechanism. The expression of miR-30c and plasminogen activator inhibitor type 1 (PAI-1) mRNA in EMs tissues was detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and the expression of PAI-1 protein was detected by western blot analysis. The proliferation, migration, invasion and adhesion of endometrial stromal cells (ESCs) in different groups transfected with miR-30c mimic or inhibitor were compared. It was demonstrated that miR-30c expression in ectopic and eutopic endometriosis tissues were significantly lower than in normal endometrial tissue. However, PAI-1 mRNA expression in ectopic and eutopic endometrial tissues was higher than in normal endometrial tissues. Furthermore, the expression of PAI-1 protein was higher in ectopic and eutopic endometrosis tissues than in normal tissues. RT-qPCR results indicated that miR-30c expression was significantly increased or decreased in ESCs following transfection of mimic or inhibitor of miR-30c, respectively. Overexpression of miR-30c repressed the expression of PAI-1 mRNA and protein, while inhibition of miR-30c upregulated the expression of PAI-1 in ESCs. In addition, the invasion, migration, proliferation and adhesion of ESCs was repressed following the overexpression of miR-30c, whereas they were promoted when miR-30c expression was downregulated. The results of the present study indicated that miR-30c serves an important role in the development and progression of EMs by regulating the expression of PAI-1.

Expression and role of microRNA 18b and hypoxia inducible factor-1α in placental tissues of preeclampsia patients

Abnormal expression of hypoxia inducible factor-1α (HIF-1α) is closely associated with various diseases. By detecting the mRNA and protein expression levels of microRNA 18b (miR-18b) and HIF-1α in placental tissues of preeclampsia (PE) patients and studying the effects of miR-18b on total cellular metabolic activity, migration and invasion in normal human trophoblast cell lines (HTR-8/SVneo), the present study aimed to investigate the effect of miR-18b on targeted regulation of HIF-1α and its clinical significance in the development of PE. Expression levels of miR-18b and HIF-1α mRNA in PE placental tissues were detected by reverse transcription-quantitative polymerase chain reaction and corresponding expression levels of HIF-1α protein were analyzed by western blotting. miR-18b overexpression and inhibited miR-18b expression in HTR-8/SVneo cells, which were constructed by transfecting miR-18b mimic and inhibitor, respectively, were investigated and the total cellular metabolic activity, migration and invasion abilities in different groups of cells were compared. Expression levels of miR-18b were significantly reduced in PE placental tissues and miR-18b inhibitor-transfected HTR-8/SVneo cells, whereas the expression levels of HIF-1α were significantly increased in PE placental tissues and significantly decreased in miR-18b mimic-transfected HTR-8/SVneo cells. Overexpression of miR-18b inhibited the expression of HIF-1α and reduced the cell invasion, migration and viability of HTR-8/SVneo cells. However, inhibition of miR-18b expression promoted the expression of HIF-1α and increased the cell invasion, migration and total cellular metabolic activity of HTR-8/SVneo cells. The present study indicated that abnormal expression of HIF-1α exhibited in PE placental tissues was regulated by miR-18b. Furthermore miR-18b expression was demonstrated to affect cell invasion, migration and viability through target regulation of HIF-1α. The results of the present study suggest that miR-18b and HIF-1α may have important roles in the development of PE.

Association of the miR-17-5p variants with susceptibility to cervical cancer in a Chinese population

MicroRNAs (miRNAs) are key regulators of gene expression; however, the extent to which single nucleotide polymorphisms (SNPs) interfere with miRNA gene regulation and affect cervical cancer (CC) susceptibility remains largely unknown. Here, we systematically analyzed miRNA-related SNPs and their association with CC risk, and performed a case-control study of miR-17-5p SNPs and CC risk in a Chinese population. Sixteen SNPs were genotyped in 247 CC cases and 285 controls. Three were associated with CC risk (p < 0.05): the minor allele (A) of rs217727 in H19 increased risk (OR = 1.53, p = 0.002), while the minor alleles (T) of rs9931702 and (T) of rs9302648 in AKTIP decreased CC risk (p = 0.018, p = 0.014). Analysis of the SNPs after stratification based on CC clinical stage and subtype revealed that rs1048512, rs6659346, rs217727, rs9931702, and rs9302648 were associated with CC risk in clinical stages I-II; rs2862833, rs2732044, rs1030389, and rs1045935 were associated with CC risk in clinical stages III-IV; and rs217727, rs9931702, and rs9302648 were associated with CC risk in squamous carcinomas. These data could serve as a useful resource for understanding the miR-17 function, identification of miRNAs associated with CC, and development of better CC screening strategies.

MicroRNAs and their relevance to ABC transporters

MicroRNAs (miRNAs) are small noncoding RNAs, which regulate the expression of their target genes post-transcriptionally by RNA interference. They are involved in almost all cellular processes, including proliferation, differentiation, apoptosis, cell survival and the maintenance of tissue specificity. Recent findings also suggest that efflux pumps of the ABC (ATP-binding cassette) transporter family are subject to miRNA-mediated gene regulation. Moreover, it seems that ABC transporters are embedded in a concerted and miRNA-guided network of concurrently regulated proteins that mediate altered drug transport and cell survival in changing environmental conditions. In this review, we summarize recent findings of miRNAs interacting with ABC transporters, which have been connected with drug distribution as well as with drug resistance. Additionally, we specify findings of complex miRNA-protein pathways conferring increased drug export and cell survival.

MicroRNAs regulate tight junction proteins and modulate epithelial/endothelial barrier functions

Tightly controlled epithelial and endothelial barriers are a prerequisite for life as these barriers separate multicellular organisms from their environment and serve as first lines of defense. Barriers between neighboring epithelial cells are formed by multiple intercellular junctions including the ‘apical junctional complex—AJC’ with tight junctions (TJ), adherens junctions (AJ), and desmosomes. TJ consist of tetraspan transmembrane proteins like occludin, various claudins that directly control paracellular permeability, and the ‘Junctional Adhesion Molecules’ (JAMs). For establishing tight barriers TJ are essential but at the same time have to allow also selective permeability. For this, TJ need to be tightly regulated and controlled. This is organized by a variety of adaptor molecules, i.e., protein kinases, phosphatases and GTPases, which in turn are regulated and fine-tuned involving microRNAs (miRNAs). In this review we summarize available data on the role and targeting of miRNAs in the maintenance of epithelial and/or endothelial barriers.

Exploring sRNA-mediated gene silencing mechanisms using artificial small RNAs derived from a natural RNA scaffold in Escherichia coli

An artificial small RNA (afsRNA) scaffold was designed from an Escherichia coli sRNA, SibC. Using the lacZ reporter system, the gene silencing effects of afsRNAs were examined to explore the sRNA-mediated gene-silencing mechanisms in E. coli. Substitution of the original target recognition sequence with a new sequence recognizing lacZ mRNA led to effective reduction of lacZ gene expression. Single-strandedness of the target recognition sequences in the scaffold was essential for effective gene silencing. The target recognition sequence was shortened to 10 nt without significant loss of gene silencing, although this minimal length was limited to a specific target mRNA sequence. In cases where afsRNAs had mismatched (forming internal loops) or unmatched (forming bulges) regions in the middle of the target recognition sequence, internal loop-forming afsRNAs were more effective in gene silencing than those that formed bulges. Unexpectedly, gene silencing by afsRNA was not decreased but increased on hfq disruption in E. coli, particularly when interactions between afsRNA and mRNA were weak, suggesting that Hfq is possibly involved in destabilization of the RNA–RNA duplex, rather than enhancement of base pairing.

MicroRNAs in kidney disease: an emerging understanding

MicroRNAs (miRNAs) are short noncoding RNA molecules that function by negatively regulating the expression of their target genes in a tightly controlled manner. Accumulating evidence, based in part on effects seen after miRNA overexpression and/or knockdown, points to the critical involvement of miRNAs in kidney function in health and disease. In this review, we provide a quick overview of the biogenesis of miRNAs and their potential involvement in kidney development and normal function. We also discuss the current literature that has begun to uncover the role of miRNAs in the pathogenesis of kidney diseases, including diabetic nephropathy, hypertension, glomerulonephritis, and cancer. As such, miRNAs have potential utility in the clinical realm as disease biomarkers. Moreover, miRNAs represent an attractive therapeutic target for a number of kidney diseases. We close by discussing a number of potential challenges that face the field of miRNA research and clinical use.

miRNAs as mediators of drug resistance

Chemoresistance of tumors is often reported to be due to overexpression of efflux transporters or genetic alterations of signaling pathways. More recently, there is increasing evidence that epigenetic modification contributes to the phenomenon of drug resistance. Despite alteration of DNA methylation or histone modifications, deregulated miRNA expression patterns of tumor cells have been identified as interfering with drug response. Attempts to modify the expression of selected miRNAs have partly led to intriguing improvements of chemotherapy response. This review focuses on the major epigenetic mechanisms, including the role of miRNA expression contributing to drug resistance and the role of epigenetic drugs to overcome nonresponse arising under conventional chemotherapy.

MiR-17-5p targets TP53INP1 and regulates cell proliferation and apoptosis of cervical cancer cells

MicroRNAs are a class of small endogenous noncoding RNAs that function as post-transcriptional regulators. Tumor protein p53-induced nuclear protein 1 (TP53INP1) is a p53 target gene and is a major player in the stress response. Here, we identified TP53INP1 as a target of miR-17-5p. miR-17-5p suppressed cell growth and promoted apoptosis of cervical cancer cells, whereas the effects of TP53INP1 were opposite, and ectopic expression of TP53INP1 counteracted the suppression of cell growth caused by miR-17-5p. The same correlations between miR-17-5p and TP53INP1 were observed in cervical cancer tissues. Together, these results indicated that miR-17-5p functions as a tumor suppressor in cervical cancer cells by targeting TP53INP1.