Micro-ribonucleic Acid 494 regulation of protein S expression

The Role of TAM Receptors in Bone

The TAM (TYRO3, MERTK, and AXL) family of receptor tyrosine kinases are pleiotropic regulators of adult tissue homeostasis maintaining organ integrity and self-renewal. Disruption of their homeostatic balance fosters pathological conditions like autoinflammatory or degenerative diseases including rheumatoid arthritis, lupus erythematodes, or liver fibrosis. Moreover, TAM receptors exhibit prominent cell-transforming properties, promoting tumor progression, metastasis, and therapy resistance in various cancer entities. Emerging evidence shows that TAM receptors are involved in bone homeostasis by regulating osteoblastic bone formation and osteoclastic bone resorption. Therefore, TAM receptors emerge as new key players of the regulatory cytokine network of osteoblasts and osteoclasts and represent accessible targets for pharmacologic therapy for a broad set of different bone diseases, including primary and metastatic bone tumors, rheumatoid arthritis, or osteoporosis.

Post-transcriptional control of haemostatic genes: mechanisms and emerging therapeutic concepts in thrombo-inflammatory disorders

The haemostatic system is pivotal to maintaining vascular integrity. Multiple components involved in blood coagulation have central functions in inflammation and immunity. A derailed haemostasis is common in prevalent pathologies such as sepsis, cardiovascular disorders, and lately, COVID-19. Physiological mechanisms limit the deleterious consequences of a hyperactivated haemostatic system through adaptive changes in gene expression. While this is mainly regulated at the level of transcription, co- and posttranscriptional mechanisms are increasingly perceived as central hubs governing multiple facets of the haemostatic system. This layer of regulation modulates the biogenesis of haemostatic components, for example in situations of increased turnover and demand. However, they can also be 'hijacked' in disease processes, thereby perpetuating and even causally entertaining associated pathologies. This review summarizes examples and emerging concepts that illustrate the importance of posttranscriptional mechanisms in haemostatic control and crosstalk with the immune system. It also discusses how such regulatory principles can be used to usher in new therapeutic concepts to combat global medical threats such as sepsis or cardiovascular disorders.

MicroRNAs as prognostic biomarkers for (cancer-associated) venous thromboembolism

MicroRNAs (miRNAs) are small noncoding RNAs with gene regulatory functions and are commonly dysregulated in disease states. As miRNAs are relatively stable, easily measured, and accessible from plasma or other body fluids, they are promising biomarkers for the diagnosis and prediction of cancer and cardiovascular diseases. Venous thromboembolism (VTE) is the third most common cardiovascular disease worldwide with high morbidity and mortality. The suggested roles of miRNAs in regulating the pathophysiology of VTE and as VTE biomarkers are nowadays more evidenced. Patients with cancer are at increased risk of developing VTE compared to the general population. However, current risk prediction models for cancer-associated thrombosis (CAT) perform suboptimally, and novel biomarkers are therefore urgently needed to identify which patients may benefit the most from thromboprophylaxis. This review will first discuss how miRNAs mechanistically contribute to the pathophysiology of VTE. Next, the potential use of miRNAs as predictive biomarkers for VTE in subjects without cancer is reviewed, followed by an in-depth focus on CAT. Several of the identified miRNAs in CAT were found to be differentially regulated in VTE as well, giving clues on the pathophysiology of CAT. We propose that subsequent studies should be adequately sized to determine which panel of miRNAs best predicts VTE and CAT. Thereafter, validation studies using comparable patient populations are required to ultimately unveil whether miRNAs-as standalone or incorporated into existing risk models-are promising valuable VTE and CAT biomarkers.

Albumin, Oral Contraceptives, and Venous Thromboembolism Risk in Astronauts

BACKGROUND

A venous thromboembolism (VTE) event occurred in a female astronaut during long-duration spaceflight. Multiple factors may have contributed to this risk, including the use of combined (progestin + estrogen) oral contraceptives (cOC).

METHODS

Biochemistry data from 65 astronauts were evaluated for associations with cOC use and with sex.

RESULTS

The female astronauts who used cOCs had lower concentrations of serum albumin and higher concentrations of transferrin, a protein involved in the clotting cascade, than the male astronauts and the female astronauts who were not taking cOCs (P<0.001). The women who used cOCs had higher serum concentrations of the acute phase reactant ceruloplasmin during flight and cortisol (P<0.001) than the men and the women who were not taking cOCs; they also had higher calculated whole blood viscosity than women not taking cOCs (P<0.001).

CONCLUSIONS

Lower circulating concentrations of albumin, higher concentrations of transferrin, and elevated markers of inflammation all could contribute to an increased risk of VTE during spaceflight. These changes, in association with a higher blood viscosity can directly affect endothelial glycocalyx integrity and hypercoagulability status, both of which contribute to VTE risk in terrestrial populations.

MicroRNAs and their delivery in diabetic fibrosis

The global prevalence of diabetes mellitus was estimated to be 463 million people in 2019 and is predicted to rise to 700 million by 2045. The associated financial and societal costs of this burgeoning epidemic demand an understanding of the pathology of this disease, and its complications, that will inform treatment to enable improved patient outcomes. Nearly two decades after the sequencing of the human genome, the significance of noncoding RNA expression is still being assessed. The family of functional noncoding RNAs known as microRNAs regulates the expression of most genes encoded by the human genome. Altered microRNA expression profiles have been observed both in diabetes and in diabetic complications. These transcripts therefore have significant potential and novelty as targets for therapy, therapeutic agents and biomarkers.

The Function of microRNAs in Pulmonary Embolism: Review and Research Outlook

Pulmonary embolism (PE) is a common pathologic condition that frequently occurs in patients with deep venous thrombosis. Severe PE may critically suppress cardiopulmonary function, thereby threatening the life of patients. Chronic pulmonary hypertension caused by PE may lead to deterioration of respiratory dysfunction, resulting in complete disability. MicroRNAs (miRNAs) are a group of abundantly expressed non-coding RNAs that exert multiple functions in regulating the transcriptome via post-transcriptional targeting of mRNAs. Specifically, miRNAs bind to target mRNAs in a matching mechanism between the miRNA seed sequence and mRNA 3ʹ UTR, thus modulating the transcript stability or subsequent translation activity by RNA-induced silencing complex. Current studies have reported the function of miRNAs as biomarkers of PE, revealing their mechanism, function, and targetome in venous thrombophilia. This review summarizes the literature on miRNA functions and downstream mechanisms in PE. We conclude that various related miRNAs play important roles in PE and have great potential as treatment targets. For clinical application, we propose that miRNA biomarkers combined with traditional biomarkers or miRNA signatures generated from microchips may serve as a great predictive tool for PE occurrence and prognosis. Further, therapies targeting miRNAs or their upstream/downstream molecules need to be developed more quickly to keep up with the progress of routine treatments, such as anticoagulation, thrombolysis, or surgery.

Estradiol-Responsive miR-365a-3p Interacts with Tissue Factor 3'UTR to Modulate Tissue Factor-Initiated Thrombin Generation

BACKGROUND

 High estradiol (E₂) levels are linked to an increased risk of venous thromboembolism; however, the underlying molecular mechanism(s) remain poorly understood. We previously identified an E₂-responsive microRNA (miR), miR-494-3p, that downregulates protein S expression, and posited additional coagulation factors, such as tissue factor, may be regulated in a similar manner via miRs.

OBJECTIVES

 To evaluate the coagulation capacity of cohorts with high physiological E₂, and to further characterize novel E₂-responsive miR and miR regulation on tissue factor in E₂-related hypercoagulability.

METHODS

 Ceveron Alpha thrombin generation assay (TGA) was used to assess plasma coagulation profile of three cohorts. The effect of physiological levels of E₂, 10 nM, on miR expression in HuH-7 cells was compared using NanoString nCounter and validated with independent assays. The effect of tissue factor-interacting miR was confirmed by dual-luciferase reporter assays, immunoblotting, flow cytometry, biochemistry assays, and TGA.

RESULTS

 Plasma samples from pregnant women and women on the contraceptive pill were confirmed to be hypercoagulable (compared with sex-matched controls). At equivalent and high physiological levels of E₂, miR-365a-3p displayed concordant E₂ downregulation in two independent miR quantification platforms, and tissue factor protein was upregulated by E₂ treatment. Direct interaction between miR-365a-3p and F3-3'UTR was confirmed and overexpression of miR-365a-3p led to a decrease of (1) tissue factor mRNA transcripts, (2) protein levels, (3) activity, and (4) tissue factor-initiated thrombin generation.

CONCLUSION

 miR-365a-3p is a novel tissue factor regulator. High E₂ concentrations induce a hypercoagulable state via a miR network specific for coagulation factors.

The Role of Epigenetics in the Regulation of Hemostatic Balance

Epigenetics, a term conventionally used to explain the intricate interplay between genes and the environment, is now regarded as the fundament of developmental biology. Several lines of evidence garnered over the past decades suggest that epigenetic alterations, mostly encompassing DNA methylation, histone tail modifications, and generation of microRNAs, play an important, though still incompletely explored, role in both primary and secondary hemostasis. Epigenetic variations may interplay with platelet functions and their responsiveness to antiplatelet drugs, and they may also exert a substantial contribution in modulating the production and release into the bloodstream of proteins involved in blood coagulation and fibrinolysis. This emerging evidence may have substantial biological and clinical implications. An enhanced understanding of posttranscriptional mechanisms would help to clarify some remaining enigmatic issues in primary and secondary hemostasis, which cannot be thoughtfully explained by genetics or biochemistry alone. Increased understanding would also pave the way to developing innovative tests for better assessment of individual risk of bleeding or thrombosis. The accurate recognition of key epigenetic mechanisms in hemostasis would then contribute to identify new putative therapeutic targets, and develop innovative agents that could be helpful for preventing or managing a vast array of hemostasis disturbances.

Role of microRNAs in Hemophilia and Thrombosis in Humans

MicroRNAs (miRNA) play an important role in gene expression at the posttranscriptional level by targeting the untranslated regions of messenger RNA (mRNAs). These small RNAs have been shown to control cellular physiological processes including cell differentiation and proliferation. Dysregulation of miRNAs have been associated with numerous diseases. In the past few years miRNAs have emerged as potential biopharmaceuticals and the first miRNA-based therapies have entered clinical trials. Our recent studies suggest that miRNAs may also play an important role in the pathology of genetic diseases that are currently considered to be solely due to mutations in the coding sequence. For instance, among hemophilia A patients there exist a small subset, with normal wildtype genes; i.e., lacking in mutations in the coding and non-coding regions of the F8 gene. Similarly, in many patients with missense mutations in the F8 gene, the genetic defect does not fully explain the severity of the disease. Dysregulation of miRNAs that target mRNAs encoding coagulation factors have been shown to disturb gene expression. Alterations in protein levels involved in the coagulation cascade mediated by miRNAs could lead to bleeding disorders or thrombosis. This review summarizes current knowledge on the role of miRNAs in hemophilia and thrombosis. Recognizing and understanding the functions of miRNAs by identifying their targets is important in identifying their roles in health and diseases. Successful basic research may result in the development and improvement of tools for diagnosis, risk evaluation or even new treatment strategies.

Role of microRNAs in Venous Thromboembolism

MicroRNAs (miRNAs) are non-coding RNAs that execute their function by targeted downregulation of gene expressions. There is growing evidence from epidemiological studies and animal models suggesting that the expression level of miRNAs is dysregulated in venous thromboembolism (VTE). In this review, we summarize the current knowledge on the role of miRNAs as biomarkers for VTE and provide general insight into research exploring the modulation of miRNA activity in animal models of venous thrombosis. Up to now, published studies have yielded inconsistent results on the role of miRNAs as biomarkers for VTE with most of the reports focused on diagnostic research. The limited statistical power of the individual studies, due to the small sample sizes, may substantially contribute to the poor reproducibility among studies. In animal models, over-expression or inhibition of some miRNAs appear to influence venous thrombus formation and resolution. However, there is an important gap in knowledge on the potential role of miRNAs as therapeutic targets in VTE. Future research involving large cohorts should be designed to clarify the clinical usefulness of miRNAs as biomarkers for VTE, and animal model studies should be pursued to unravel the role of miRNAs in the pathogenesis of VTE and their potential as therapeutic targets.

Pulmonary deregulation of expression of miR-155 and two of its putative target genes; PROS1 and TP53INP1 associated with gold nanoparticles (AuNPs) administration in rat

Background: Gold nanoparticles (AuNPs) have been considered as an ideal candidate in various biomedical applications due to their ease of tailoring into different size, shape, and decorations with different functionalities. The current study was conducted to investigate the epigenetic alteration in the lung in response to AuNPs administration regarding microRNA-155 (miR-155) gene which can be involved in AuNP-induced lung pathogenesis. Methods: Thirty-two Wister rats were divided into two equal groups, control group and AuNPs treated group which received a single intravenous (IV) injection of plain spherical AuNPs (0.015 mg/kg body wt) with an average diameter size of 25±3 nm. Lung samples were collected from both the control and injected groups at one day, one week, one month and two months post-injection. The alteration of relative expression of miR-155 gene and two of its putative target genes; tumor protein 53 inducible nuclear protein 1 (TP53INP1) and protein S (PROS1) was investigated by real time PCR and protein S (PS) expression was analyzed by Western blotting technique. Results: The obtained results revealed that AuNPs administration significantly increases the expression level of miR-155 and reduce relative mRNA expression of TP53INP1 and PROS1 genes at one day post-injection. In contrast, a significant down-regulation of miR-155 level of expression concurrent with up-regulation of expression level of TP53INP1 and PROS1 genes were shown at one week, one month and two months post-injection. PS levels were mirrored to their PROS1 mRNA levels except for two month post-injection time point. Conclusions: These findings indicate epigenetic modulation in the lung in response to AuNPs administration regarding the miR-155 gene which can be involved in AuNP-induced lung pathogenesis.

Effects of low-dose combined oral contraceptives and protein S K196E mutation on anticoagulation factors: a prospective observational study

The association between low-dose combined oral contraceptives (COCs) and anticoagulation factors in Japanese women has been rarely studied. A total of 394 Japanese women with a new beginning cycle of COC use were enrolled, of whom 335 women visited the clinic within 4 weeks after starting the first cycle of COC. Visits occurred in the active phase (272 women) and the placebo phase (63 women). Free protein S (PS) antigen and activity levels and antithrombin activity levels decreased significantly in both the active and placebo phase groups. Protein C (PC) activity levels increased significantly in both groups. Larger reductions in free PS antigen and activity levels occurred with COC comprising either 30 µg ethinylestradiol/desogestrel or 20 µg ethinylestradiol/drospirenone than that comprising 35 µg ethinylestradiol/norethisterone. In four women with the Japanese-specific PS K196E mutation, mean PS activity was 65% before COC use and 57% during COC use, indicating further decrease with COC use. In conclusion, decreased antigen and activity levels of PS and antithrombin and increased activity levels of PC were observed even during the first cycle of low-dose COC use. The effects on PS and PC activities were also observed in the hormone-free interval.

microRNAs in the haemostatic system: More than witnesses of thromboembolic diseases?

MicroRNAs (miRNAs) are small endogenous RNAs that post-transcriptionally regulate gene expression. In the last few years, these molecules have been implicated in the regulation of haemostasis, and an increasing number of studies have investigated their relationship with the development of thrombosis. In this review, we discuss the latest developments regarding the role of miRNAs in the regulation of platelet function and secondary haemostasis. We also discuss the genetic and environmental factors that regulate miRNAs. Finally, we address the potential use of miRNAs as prognostic and diagnostic tools in thrombosis.

Protein S Protects against Podocyte Injury in Diabetic Nephropathy

Background Diabetic nephropathy (DN) is a leading cause of ESRD in the United States, but the molecular mechanisms mediating the early stages of DN are unclear.Methods To assess global changes that occur in early diabetic kidneys and to identify proteins potentially involved in pathogenic pathways in DN progression, we performed proteomic analysis of diabetic and nondiabetic rat glomeruli. Protein S (PS) among the highly upregulated proteins in the diabetic glomeruli. PS exerts multiple biologic effects through the Tyro3, Axl, and Mer (TAM) receptors. Because increased activation of Axl by the PS homolog Gas6 has been implicated in DN progression, we further examined the role of PS in DN.Results In human kidneys, glomerular PS expression was elevated in early DN but suppressed in advanced DN. However, plasma PS concentrations did not differ between patients with DN and healthy controls. A prominent increase of PS expression also colocalized with the expression of podocyte markers in early diabetic kidneys. In cultured podocytes, high-glucose treatment elevated PS expression, and PS knockdown further enhanced the high-glucose-induced apoptosis. Conversely, PS overexpression in cultured podocytes dampened the high-glucose- and TNF-α-induced expression of proinflammatory mediators. Tyro3 receptor was upregulated in response to high glucose and mediated the anti-inflammatory response of PS. Podocyte-specific PS loss resulted in accelerated DN in streptozotocin-induced diabetic mice, whereas the transient induction of PS expression in glomerular cells in vivo attenuated albuminuria and podocyte loss in diabetic OVE26 mice.Conclusions Our results support a protective role of PS against glomerular injury in DN progression.

miR-494 Contributes to Estrogen Protection of Cardiomyocytes Against Oxidative Stress via Targeting (NF-κB) Repressing Factor

Oxidative stress plays a pivotal role in the initiation and progression of cardiac diseases. Estrogens have been demonstrated to exert pleiotropic cardioprotective effects, among which antioxidative stress is one of the key effects linking estrogens to cardioprotection. By using a microRNAs (miRs) microarray screening approach, we discovered an increase in miR-494, which is known to exert cardioprotective effects, in estrogen-treated cardiomyocytes. We hypothesized that the upregulation of miR-494 might contribute to estrogen-mediated cardioprotection against oxidative stress. We found that E₂ stimulates miR-494 expression via ERα in both cardiomyocytes and the myocardium of female mice. The miR-494 inhibitor attenuated the protective effect of 17β-estradiol (E₂) against oxidative stress-induced injury in cardiomyocytes. By contrast, the miR-494 mimic protected cardiomyocytes against oxidative stress-induced cardiomyocyte injury. Using real-time PCR, western blot and dual-luciferase reporter gene analyses, we identified nuclear factor kappa B (NF-κB) repressing factor (NKRF) as the miR-494 target in cardiomyocytes. E₂ was found to inhibit NKRF, thus activating NF-κB through a miR-494-dependent mechanism. In addition, the protective effects of E₂ and miR-494 against oxidative stress in cardiomyocytes were eliminated by the NF-κB inhibitor. In summary, this study demonstrates for the first time that estrogen inhibits NKRF expression through ERα-mediated upregulation of miR-494 in cardiomyocytes, leading to the activation of NF-κB, which in turn results in an increase in antioxidative defense. ERα-mediated upregulation of miR-494 may contribute to estrogen protection of cardiomyocytes against oxidative stress.

Identification of reference miRNAs in plasma useful for the study of oestrogen-responsive miRNAs associated with acquired Protein S deficiency in pregnancy

Background

Accumulating evidence indicate that circulating microRNAs (miRNAs) are useful independent non-invasive biomarkers, with unique miRNA signatures defined for various pathophysiological conditions. However, there are no established universal housekeeping miRNAs for the normalisation of miRNAs in body fluids. We have previously identified an oestrogen-responsive miRNA, miR-494, in regulating the anticoagulant, Protein S, in HuH-7 liver cells. Moreover, increased thrombotic risk associated with elevated circulating oestrogen levels is frequently observed in pregnant women and oral contraceptive users. In order to identify other oestrogen-responsive miRNAs, including miR-494, that may be indicative of increased thrombotic risk in plasma, we used nanoString analysis to identify robust and stable endogenous reference miRNAs for the study of oestrogen-responsive miRNAs in plasma.

Results

We compared the plasma miRNA expression profile of individuals with: (1) Low circulating oestrogens (healthy men and non-pregnant women not taking oral contraceptives), (2) High circulating synthetic oestrogens, (women taking oral contraceptives) and (3) High circulating natural oestrogens (pregnant females >14 weeks gestation). From the nanoString analyses, 11 candidate reference miRNAs which exhibited high counts and not significantly differentially expressed between groups were selected for validation using realtime quantitative polymerase chain reaction (RT-qPCR) and digital droplet PCR (DDPCR) in pooled plasma samples, and the stability of their expression evaluated using NormFinder and BestKeeper algorithms. Four miRNAs (miR-25-5p, miR-188-5p, miR-222-3p and miR-520f) demonstrated detectable stable expression between groups and were further analysed by RT-qPCR in individual plasma samples, where miR-188-5p and miR-222-3p expression were identified as a stable pair of reference genes. The miRNA reference panel consisting of synthetic spike-ins cel-miR-39 and ath-miR159a, and reference miRNAs, miR-188-5p and miR-222-3p was useful in evaluating fold-change of the pregnancy-associated miRNA, miR-141-3p, between groups.

Conclusion

The miRNA reference panel will be useful for normalising qPCR data comparing miRNA expression between men and women, non-pregnant and pregnant females, and the potential effects of endogenous and synthetic oestrogens on plasma miRNA expression.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-017-2636-3) contains supplementary material, which is available to authorized users.

Regulation of TFPIα expression by miR-27a/b-3p in human endothelial cells under normal conditions and in response to androgens

The increased risk of cardiovascular events in older men is multifactorial, but the significant reduction of testosterone levels has been involved. As this hormone regulates the expression of TFPI by unknown mechanisms, we aimed to evaluate the role of miRNAs in the regulation of TFPIα expression under normal conditions and in response to androgens. In silico studies allowed the selection of 4 miRNAs as potential TFPIα regulators. Only miR-27a/b-3p significantly reduced TFPIα expression in two endothelial cell lines. Luciferase assays demonstrated a direct interaction between miR-27a/b-3p and TFPI 3′UTR. Ex vivo analysis of TFPI and miRNA levels in 74 HUVEC samples from healthy subjects, showed a significant and inverse correlation between TFPI and miR-27a-3p. Moreover, anticoagulant activity of TFPIα from cells supernatants decreased ~30% with miR-27a/b-3p and increased ~50% with anti-miR-27a/b-3p. Interestingly, treatment of EA.hy926 with a physiological dose of dihydrotestosterone (30 nM) significantly increased (~40%) TFPIα expression with a parallel decreased (~50%) of miR-27a/b-3p expression. In concordance, increased levels of miR-27a/b-3p normalized the up-regulation induced by testosterone. Our results suggest that testosterone is a hinge in miR-27/TFPIα regulation axis. Future studies are needed to investigate whether testosterone variations are involved in a miR-27/TFPIα dysregulation that could increase the cardiovascular risk.

Progestin isoforms provide different levels of protein S expression in HepG2 cells

INTRODUCTION

Use of combined oral contraceptives (COCs) results in acquired protein S (PS) deficiency, a well-established risk factor for venous thromboembolism (VTE). The risk of VTE due to COCs containing newer-generation progestins is double compared with COCs containing older-generation progestins, although there is little difference in estrogen contents between the generations. In contrast, progestin-only contraceptives do not confer an increased risk of VTE. In this study, we aimed to investigate how different isoforms of progestin in COCs affect the risk of VTE by measuring PS expression.

MATERIALS AND METHODS

The effect of progestin, levonorgestrel (LNG) or drospirenone (DRSP), on PS mRNA expression in HepG2 cells was measured using reverse transcription-quantitative PCR; PS level was determined using Western blot analysis. PROS1 promoter activity, PS mRNA stability, and de novo synthesis of PS mRNA were examined in HepG2 cells after treatment with progestin.

RESULTS AND CONCLUSIONS

In the presence of progestins, PS mRNA and protein expressions were significantly upregulated in HepG2 cells due to the augmentation of de novo PS mRNA expression modulated by RNA polymerase II (Pol II), thereby facilitating PS transcription elongation. Moreover, the transcription elongation inhibitor blocked progestin-mediated de novo PS mRNA expression. Conversely, progestin did not affect PROS1 promoter activity and PS mRNA stability. Pol II elongation efficiency in the newer-generation progestin (DRSP) treatment was not as strong compared with older-generation progestin (LNG), suggesting the difference in VTE risk between COC generations.

The role of microRNA-27a/b and microRNA-494 in estrogen-mediated downregulation of tissue factor pathway inhibitor α

Essentials Estrogens are known to influence the expression of microRNAs in breast cancer cells. We looked at microRNAs in estrogenic regulation of tissue factor pathway inhibitor α (TFPIα). Estrogen upregulated microRNA-27a/b and microRNA-494 through the estrogen receptor α. MicroRNA-27a/b and microRNA-494 are partly involved in estrogenic downregulation of TFPIα.

SUMMARY

Background Tissue factor pathway inhibitor (TFPI) has been linked to breast cancer pathogenesis. We have recently reported TFPI mRNA levels to be downregulated by estrogens in a breast cancer cell line (MCF7) through the estrogen receptor α (ERα). Accumulating evidence also indicates that activation of ERα signaling by estrogens may modulate the expression of target genes indirectly through microRNAs (miRNAs). Objectives To examine if miRNAs are involved in the estrogenic downregulation of TFPIα. Methods Computational analysis of the TFPI 3'-untranslated region (UTR) identified potential binding sites for miR-19a/b, miR-27a/b, miR-494, and miR-24. Transient overexpression or inhibition of the respective miRNAs was achieved by transfection of miRNA mimics or inhibitors. Direct targeting of TFPI 3'-UTR by miR-27a/b and miR-494 was determined by luciferase reporter assay in HEK293T cells. Effects of 17α-ethinylestradiol (EE2) and fulvestrant on relative miR-27a/b, miR-494, and TFPI mRNA levels in MCF7 cells were determined by qRT-PCR and secreted TFPIα protein by ELISA. Transient knockdown of ERα was achieved by siRNA transfection. Results EE2 treatment lead to a significant increase in miR-19a, miR-27a/b, miR-494, and miR-24 mRNA levels in MCF7 cells through ERα. miR-27a/b and miR-494 mimics lead to reduced TFPI mRNA and protein levels. Luciferase assay showed direct targeting of miR-27a/b and miR-494 on TFPI mRNA. Impaired estrogen-mediated downregulation of TFPI mRNA was detected in anti-miR-27a/b and anti-miR-494 transfected cells. Conclusions Our results provide evidence that miR-27a/b and miR-494 regulate TFPIα expression and suggest a possible role of these miRNAs in the estrogen-mediated downregulation of TFPIα.

Therapeutic Potential of miR-494 in Thrombosis and Other Diseases: A Review

Functional nucleic acids, such as microRNAs (miRNAs), have been implicated in the pathophysiology of many diseases. The miRNA expression profiles of various cancers including haematological malignancies are well defined, but the role of miRNAs in haemostasis and the regulation of coagulation is poorly understood. We identified that miR-494 is oestrogen responsive and directly targets the anticoagulant protein, Protein S, as a mechanism for acquiring Protein S deficiency under high oestrogenic conditions such as during pregnancy and oral contraceptive use. Furthermore, previous studies have also characterised miR-494 to be involved in many biological processes. This paper reviews the current knowledge in the role of miRNAs in regulating haemostatic proteins and the known biological functions of miR-494, highlighting miR-494 as an emerging therapeutic target, with an overview of the strategy we have employed in identifying functional nucleic acids such as miRNAs that target haemostatic factors and the therapeutic potential of miR-494-directed therapy for the treatment of thrombotic disorders.

MicroRNAs in hemostasis

Epidemiologic studies have revealed that modification of the levels of individual components of the hemostatic system may have effects on the development of thrombosis or hemorrhage. To maintain the necessary equilibrium, the hemostatic system is finely regulated. It is known that acquired factors and/or alterations in genes (single-nucleotide polymorphisms or mutations) may be the cause of interindividual differences or exacerbated levels of hemostatic proteins in plasma, but there are still many non-characterized factors that provoke such variations. The search for new elements, such as microRNAs (miRNAs), a family of small non-coding RNAs that are novel regulators of protein expression, may reveal an additional layer at which to investigate the causes of hemostatic diseases. In this review, we discuss the latest developments in research into the role of miRNAs in the regulation of several hemostatic factors, and the potential use of miRNAs as prognostic or diagnostic tools in hemostasis and thrombosis.

Regulation of coagulation factor XI expression by microRNAs in the human liver

High levels of factor XI (FXI) increase the risk of thromboembolic disease. However, the genetic and environmental factors regulating FXI expression are still largely unknown. The aim of our study was to evaluate the regulation of FXI by microRNAs (miRNAs) in the human liver. In silico prediction yielded four miRNA candidates that might regulate FXI expression. HepG2 cells were transfected with miR-181a-5p, miR-23a-3p, miR-16-5p and miR-195-5p. We used mir-494, which was not predicted to bind to F11, as a negative control. Only miR-181a-5p caused a significant decrease both in FXI protein and F11 mRNA levels. In addition, transfection with a miR-181a-5p inhibitor in PLC/PRF/5 hepatic cells increased both the levels of F11 mRNA and extracellular FXI. Luciferase assays in human colon cancer cells deficient for Dicer (HCT-DK) demonstrated a direct interaction between miR-181a-5p and 3′untranslated region of F11. Additionally, F11 mRNA levels were inversely and significantly correlated with miR-181a-5p levels in 114 healthy livers, but not with miR-494. This study demonstrates that FXI expression is directly regulated by a specific miRNA, miR-181a-5p, in the human liver. Future studies are necessary to further investigate the potential consequences of miRNA dysregulation in pathologies involving FXI.