Rapid changes in microRNA-146a expression negatively regulate the IL-1beta-induced inflammatory response in human lung alveolar epithelial cells

Epigenetic Regulation of Innate Immunity by microRNAs

The innate immune response, which is usually referred to as the first line of defense, protects the hosts against pathogenic micro-organisms. Some of the biomolecules released from the pathogens, such as proteins, lipoproteins and nucleic acids, which are collectively termed as pathogen-associated molecular patterns (PAMPs), elicit signaling mechanisms that trigger immune responses in the hosts. Pathogen recognition receptors (PRRs) on the host cells recognize these PAMPs and initiate intracellular signaling through toll-like receptors (TLRs), RIG-I-like receptors (RLRs), and other pathways which induce production of pro-inflammatory cytokines and type I interferons. Recently, different members of tripartite motif containing proteins (TRIM) family of proteins were identified to intercept and regulate these cellular pathways. Specific targets of TRIM proteins have been identified and their molecular mechanisms were unraveled and identified unique domains involved in protein-protein interactions. Though innate immunity represents a tight and well conserved immune system in the host, gene expression in innate immunity was identified to be influenced by several epigenetic mechanisms including regulation by microRNAs (miRNAs). In this review, we present critical analysis of the findings on the identification of specific miRNAs that modulate expression of target genes involved in the regulation of innate immunity.

Changes in microRNAs expression profile of olive flounder (Paralichthys olivaceus) in response to viral hemorrhagic septicemia virus (VHSV) infection

To know the effect of viral hemorrhagic septicemia virus (VHSV) infection on the cellular microRNA expression profile in olive flounder (Paralichthys olivaceus), fish were infected with VHSV, and cellular microRNAs expression was analyzed at 0 (control), 6, 12, 24, 48 and 72 h post-infection (h.p.i.) by the high-throughput sequencing. A total of 372 mature miRNAs were identified, and, among them, 63 miRNAs were differentially expressed during VHSV infection. The differentially expressed microRNAs number was greatly increased from 24 h.p.i. compared to the number at 6 and 12 h.p.i., suggesting that the alteration of microRNAs expression by VHSV infection may be related to the progression of VHSV disease. The target prediction analysis, the GO enrichment analysis, and the KEGG pathway analysis of the predicted target genes showed that various biological pathways could be affected by VHSV infection through the down-regulation or up-regulation of host miRNAs. The present results provide a basic information on the microRNAs related to VHSV infection in olive flounder. Considering broad effects of microRNAs on various biological pathways, data in this study can be used to interpret the mechanism of VHSV pathogenesis, which, vice versa, can be used to develop control measures against VHSV.

Resolution of inflammation: a new therapeutic frontier

Dysregulated inflammation is a central pathological process in diverse disease states. Traditionally, therapeutic approaches have sought to modulate the pro- or anti-inflammatory limbs of inflammation, with mixed success. However, insight into the pathways by which inflammation is resolved has highlighted novel opportunities to pharmacologically manipulate these processes - a strategy that might represent a complementary (and perhaps even superior) therapeutic approach. This Review discusses the state of the art in the biology of resolution of inflammation, highlighting the opportunities and challenges for translational research in this field.

Type I Interferon Inhibition of MicroRNA-146a Maturation Through Up-Regulation of Monocyte Chemotactic Protein-Induced Protein 1 in Systemic Lupus Erythematosus

OBJECTIVE

Systemic lupus erythematosus (SLE) is characterized by the uncontrolled production of inflammatory cytokines, among which type I interferon (IFN) is recognized as a crucial pathogenic factor. The expression of microRNA-146a (miR-146a) is reduced in the white blood cells of SLE patients and accounts for their overactivated inflammatory responses. However, the mechanism of the reduction of miR-146a is still not fully understood. This study was undertaken to test whether the key pathogenic cytokine, type I IFN, is responsible for the dysregulation of miR-146a in SLE.

METHODS

Gene and protein expression was measured in all cells by reverse transcription-quantitative polymerase chain reaction, Northern blotting, or Western blotting. In THP-1 cells, expression of monocyte chemotactic protein-induced protein 1 (MCPIP-1) was knocked down with a lentivirus encoding a short hairpin RNA targeting MCPIP1. The cells were pretreated with type I IFN and assessed for gene expression levels of miR-146a. White blood cells from patients with SLE were analyzed for the expression of the IFN-inducible genes MCPIP1 and miR-146a, and the gene expression data were compared for correlation.

RESULTS

Pretreatment of THP-1 cells with type I IFN attenuated the induction of miR-146a posttranscriptionally, by down-regulating the expression of pre-miR-146a but not pri-miR-146a or its original unspliced transcript. Expression of MCPIP-1, which was enhanced by type I IFN, was found to be responsible for the inhibition of miR-146a. In white blood cells from patients with SLE, MCPIP1 expression was elevated, and its expression correlated positively with the IFN score and negatively with the miR-146a transcript level.

CONCLUSION

Type I IFN inhibits the maturation of miR-146a through the up-regulation of MCPIP-1, and thus contributes to the uncontrolled inflammation and excessive inflammatory gene expression in SLE.

miRNA Profiling Reveals Dysregulation of RET and RET-Regulating Pathways in Hirschsprung's Disease

Hirschsprung's disease (HSCR), the most common congenital malformation of the gut, is regulated by multiple signal transduction pathways. Several components of these pathways are important targets for microRNAs (miRNAs). Multiple miRNAs have been associated with the pathophysiology of HSCR, and serum miRNAs profiles of HSCR patients have been reported, but miRNA expression in HSCR colon tissue is almost completely unexplored. Using microarray technology, we screened colon tissue to detect miRNAs whose expression profiles were altered in HSCR and identify targets of differentially expressed miRNAs. Following filtering of low-intensity signals, data normalization, and volcano plot filtering, we identified 168 differentially expressed miRNAs (104 up-regulated and 64 down-regulated). Fifty of these mRNAs represent major targets of dysegulated miRNAs and may thus important roles in the pathophysiology of HSCR. Pathway analysis revealed that 7 of the miRNA targets encode proteins involved in regulation of cell proliferation and migration via RET and related signaling pathways (MAPK and PI3K/AKT). Our results identify miRNAs that play key roles in the pathophysiology of the complex multi-factorial disease HSCR.

Self-assembled biosensor with universal reporter and dual-quenchers for detection of unlabelled nucleic acids

A novel biosensor with universal reporter and dual quenchers was developed for rapid, sensitive, selective, and inexpensive detection of unlabelled nucleic acids. The biosensor is based on a single-strand DNA stem-loop motif with an extended universal reporter-binding region, a G-base rich stem region, and a universal address-binding region. The self-assembly of these stem-loop probes with fluorescence labeled universal reporter and a universal address region conjugated to gold nanoparticles forms the basis of a biosensor for DNA or microRNA targets in solution. The introduction of dual quenchers (G-base quenching and gold surface plasmon resonance-induced quenching) significantly reduces the fluorescence background to as low as 12% of its original fluorescence intensity and hence enhances the detection limit to 0.01 picomoles without signal ampilication.

Inflammatory gene networks in term human decidual cells define a potential signature for cytokine-mediated parturition

BACKGROUND

Inflammation is a proximate mediator of preterm birth and fetal injury. During inflammation several microRNAs (22 nucleotide noncoding ribonucleic acid (RNA) molecules) are up-regulated in response to cytokines such as interleukin-1β. MicroRNAs, in most cases, fine-tune gene expression, including both up-regulation and down-regulation of their target genes. However, the role of pro- and antiinflammatory microRNAs in this process is poorly understood.

OBJECTIVE

The principal goal of the work was to examine the inflammatory genomic profile of human decidual cells challenged with a proinflammatory cytokine known to be present in the setting of preterm parturition. We determined the coding (messenger RNA) and noncoding (microRNA) sequences to construct a network of interacting genes during inflammation using an in vitro model of decidual stromal cells.

STUDY DESIGN

The effects of interleukin-1β exposure on mature microRNA expression were tested in human decidual cell cultures using the multiplexed NanoString platform, whereas the global inflammatory transcriptional response was measured using oligonucleotide microarrays. Differential expression of select transcripts was confirmed by quantitative real time-polymerase chain reaction. Bioinformatics tools were used to infer transcription factor activation and regulatory interactions.

RESULTS

Interleukin-1β elicited up- and down-regulation of 350 and 78 nonredundant transcripts (false discovery rate < 0.1), respectively, including induction of numerous cytokines, chemokines, and other inflammatory mediators. Whereas this transcriptional response included marked changes in several microRNA gene loci, the pool of fully processed, mature microRNA was comparatively stable following a cytokine challenge. Of a total of 6 mature microRNAs identified as being differentially expressed by NanoString profiling, 2 (miR-146a and miR-155) were validated by quantitative real time-polymerase chain reaction. Using complementary bioinformatics approaches, activation of several inflammatory transcription factors could be inferred downstream of interleukin-1β based on the overall transcriptional response. Further analysis revealed that miR-146a and miR-155 both target genes involved in inflammatory signaling, including Toll-like receptor and mitogen-activated protein kinase pathways.

CONCLUSION

Stimulation of decidual cells with interleukin-1β alters the expression of microRNAs that function to temper proinflammatory signaling. In this setting, some microRNAs may be involved in tissue-level inflammation during the bulk of gestation and assist in pregnancy maintenance.

Altered miRNA expression in pulmonary sarcoidosis

Background

miRNAs control important cellular functions including angiogenesis/angiostasis or fibrosis and reveal altered expression during pathological processes in the lung.

Methods

The aim of the study was to investigate the expression of selected miRNAs (miR-let7f, miR-15b, miR-16, miR-20a, miR-27b, miR-128a, miR-130a, miR-192 miR-221, miR-222) in patients with pulmonary sarcoidosis (n = 94) and controls (n = 50). The expression was assessed by q-PCR in BALF cells and peripheral blood lymphocytes (PB lymphocytes). For statistical analysis, the Kruskal–Wallis test, Mann–Whitney U- test, Neuman–Keuls’ multiple comparison test, and Spearman’s rank correlation were used.

Results

In BALF cells, significantly higher expression of miR-192 and miR-221 and lower expression of miR-15b were found in patients than controls. MiR-27b, miR-192 and miR-221 expression was significantly higher in patients without parenchymal involvement (stages I) than those at stages II-IV. Patients with acute disease demonstrated significantly higher miR-27b, miR-192 and miR-221 expression than those with insidious onset. For PB lymphocytes, patients demonstrated significantly greater miR-15b, miR-27b, miR-192, miR-221 and miR-222 expression, but lower miR-let7f and miR-130a expression, than controls. Stage I patients demonstrated significantly higher miR-16 and miR-15b expression than those in stages II-IV, and patients with the acute form demonstrated higher miR-130a and miR-15b expression. In BALF cells, miR-16 and miR-20a expression was significantly higher in patients with lung volume restriction, and miR-let7f was higher in the PB lymphocytes in patients with obturation. Several correlations were observed between the pattern of miRNA expression, lung function parameters and selected laboratory markers.

Conclusion

The obtained results suggest that the studied miRNAs play a role in the pathogenesis of sarcoidosis, and that some of them might have negative prognostic value.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-016-0266-6) contains supplementary material, which is available to authorized users.

MicroRNAs: The Role in Autoimmune Inflammation

MicroRNAs (miRNAs) are small non-coding RNA molecules that regulate gene expression at the post-transcriptional level through base-pairing predominantly with a 3'-untranslated region of target mRNA, followed by mRNA degradation or translational repression. Totally, miRNAs change, through a complex regulatory network, the expression of more than 60% of human genes. MiRNAs are key regulators of the immune response that affect maturation, proliferation, differentiation, and activation of immune cells, as well as antibody secretion and release of inflammatory mediators. Disruption of this regulation may lead to the development of various pathological conditions, including autoimmune inflammation. This review summarizes the data on biogenesis and the mechanisms of miRNA action. We discuss the role of miRNAs in the development and the action of the immune system, as well as in the development of an autoimmune inflammatory response. Special attention is given to the role of miRNAs in the autoimmune inflammation in multiple sclerosis, which is a serious socially significant disease of the central nervous system. Currently, a lot of research is focused on this problem.

Functions of miR-146a and miR-222 in Tumor-associated Macrophages in Breast Cancer

Tumor-associated macrophages (TAMs) play critical roles in promoting tumor progression and invasion. However, the molecular mechanisms underlying TAM regulation remain to be further investigated and may make significant contributions to cancer treatment. Mammalian microRNAs (miRNAs) have recently been identified as important regulators of gene expression that function by repressing specific target genes mainly at the post-transcriptional level. However, systematic studies of the functions and mechanisms of miRNAs in TAMs in tumor tissues are rare. In this study, miR-146a and miR-222 were shown to be significantly decreased in TAMs associated with the up-regulated NF-κB p50 subunit. miR-146a promoted the expression of some M2 macrophage phenotype molecules, and miR-146a antagomir transfected RAW264.7 monocyte-macrophage cells inhibited 4T1 tumor growth in vivo. Meanwhile, overexpression of miR-222 inhibited TAM chemotaxis, and miR-222 in TAMs inhibited 4T1 tumor growth by targeting CXCL12 and inhibiting CXCR4. These data revealed that miRNAs influence breast tumor growth by promoting the M2 type polarization or regulating the recruitment of TAMs. These observations suggest that endogenous miRNAs may exert an important role in controlling the polarization and function of TAMs in breast cancer.

Circulating Microvesicles Regulate Treg and Th17 Differentiation in Human Autoimmune Thyroid Disorders

BACKGROUND

Microvesicles (MVs) are emerging as important contributors to the development of inflammatory and autoimmune diseases. MVs can mediate immune modulation carrying genetic information, including microRNAs that can be transferred between cells.

DESIGN

We determined the plasma levels of annexin-V+ MVs derived from different immune cells and platelets in patients with autoimmune thyroid diseases (AITDs) and in healthy controls. T lymphocyte polarization assays were performed in the presence of MVs to evaluate their effect in T regulatory and T helper 17 cells differentiation. microRNA content into plasma MVs and their corresponding mRNA targets were evaluated by RT-PCR.

RESULTS

The percentage of platelet-derived MVs (CD41a+) was significantly increased in plasma samples from AITD patients compared with healthy controls. In contrast, patients with AITD showed a lower percentage of leukocyte and endothelial cell-derived MVs compared with controls. In addition, functional assays showed that MVs from AITD patients inhibited the in vitro differentiation of Foxp3+ T regulatory cells (11.35% vs 4.40%, P = .01) and induced the expression of interferon-γ by CD4+ lymphocytes (10.91% vs 13.99%, P = .01) as well as the differentiation of T helper 17 pathogenic (IL-17+interferon-γ+) cells (1.98% vs 5.13%, P = .03). Furthermore, in AITD patients, whereas miR-146a and miR-155 were increased in circulating MVs, their targets IL-8 and SMAD4 were decreased in peripheral blood mononuclear cells.

CONCLUSIONS

Our data indicate that circulating MVs seem to have a relevant role in the modulation of the inflammatory response observed in AITD.

MicroRNAs in Breastmilk and the Lactating Breast: Potential Immunoprotectors and Developmental Regulators for the Infant and the Mother

Human milk (HM) is the optimal source of nutrition, protection and developmental programming for infants. It is species-specific and consists of various bioactive components, including microRNAs, small non-coding RNAs regulating gene expression at the post-transcriptional level. microRNAs are both intra- and extra-cellular and are present in body fluids of humans and animals. Of these body fluids, HM appears to be one of the richest sources of microRNA, which are highly conserved in its different fractions, with milk cells containing more microRNAs than milk lipids, followed by skim milk. Potential effects of exogenous food-derived microRNAs on gene expression have been demonstrated, together with the stability of milk-derived microRNAs in the gastrointestinal tract. Taken together, these strongly support the notion that milk microRNAs enter the systemic circulation of the HM fed infant and exert tissue-specific immunoprotective and developmental functions. This has initiated intensive research on the origin, fate and functional significance of milk microRNAs. Importantly, recent studies have provided evidence of endogenous synthesis of HM microRNA within the human lactating mammary epithelium. These findings will now form the basis for investigations of the role of microRNA in the epigenetic control of normal and aberrant mammary development, and particularly lactation performance.

MicroRNA-146a-5p attenuates neuropathic pain via suppressing TRAF6 signaling in the spinal cord

Glia-mediated neuroinflammation plays an important role in the pathogenesis of neuropathic pain. Our recent study demonstrated that TNF receptor associated factor-6 (TRAF6) is expressed in spinal astrocytes and contributes to the maintenance of spinal nerve ligation (SNL)-induced neuropathic pain. MicroRNA (miR)-146a is a key regulator of the innate immune response and was shown to target TRAF6 and reduce inflammation. In this study, we found that in cultured astrocytes, TNF-α, IL-1β, or lipopolysaccharide (LPS) induced rapid TRAF6 upregulation and delayed miR-146a-5p upregulation. In addition, miR-146a-5p mimic blocked LPS-induced TRAF6 upregulation, as well as LPS-induced c-Jun N-terminal kinase (JNK) activation and chemokine CCL2 expression in astrocytes. Notably, LPS incubation with astrocytes enhanced the DNA binding activity of AP-1 to the promoters of mir-146a and ccl2. TRAF6 siRNA or JNK inhibitor SP600125 significantly reduced LPS-induced miR-146a-5p increase in astrocytes. In vivo, intrathecal injection of TNF-α or LPS increased spinal TRAF6 expression. Pretreatment with miR-146a-5p mimic alleviated TNF-α- or LPS-induced mechanical allodynia and reduced TRAF6 expression. Finally, SNL induced miR-146a-5p upregulation in the spinal cord at 10 and 21days. Intrathecal injection of miR-146a-5p mimic attenuated SNL-induced mechanical allodynia and decreased spinal TRAF6 expression. Taken together, the results suggest that (1) miR-146a-5p attenuates neuropathic pain partly through inhibition of TRAF6 and its downstream JNK/CCL2 signaling, (2) miR-146a-5p is increased by the activation of TRAF6/JNK pathway. Hence, miR-146a-5p may be a novel treatment for chronic neuropathic pain.

MicroRNAs in lung diseases: Recent findings and their pathophysiological implications

Lung diseases are one of the leading causes of mortality and morbidity worldwide and effective therapies are imperfect. Nonetheless, recently some novel strategies have been developed to treat and curtail their debilitating impact. Some of the treatments include the role of MicroRNAs (miRNAs) in stemming the spread of lung morbidities. Micro RNAs are small non-coding RNAs which are known as important players in the posttranscriptional regulation of gene expression in mammalian cells by regulating translation. MiRNAs are involved in basic regulatory mechanisms of cells including influencing inflammation. MiRNA dysregulation, resulting in aberrant expression of a gene, is suggested to play a key role in susceptibility of diseases. MiRNAs are involved in the pathogenesis of lung diseases such as cystic fibrosis, lung cancer, asthma, chronic obstructive pulmonary disease, and Idiopathic pulmonary fibrosis. A better understanding of the involvement of miRNAs in pathogenesis of these diseases could result in the development of new therapeutic and diagnostic tools. In this review, we provide an overview of the current understanding of miRNA biogenesis and role as well as recent insights into role of some miRNAs in different pulmonary diseases.

Unravelling the complexity of COPD by microRNAs: it's a small world after all

Chronic obstructive pulmonary disease (COPD) is a progressive lung disease and is currently the fourth leading cause of death worldwide. Chronic inflammation and repair processes in the small airways are characteristic of COPD. Despite extensive efforts from researchers and industry, there is still no cure for COPD, hence an urgent need for new therapeutic alternatives. MicroRNAs are such an option; they are small noncoding RNAs involved in gene regulation. Their importance has been shown with respect to maintaining the balance between health and disease. Although previous reviews have discussed the expression of microRNAs related to lung disease, a detailed discussion regarding the function of differential miRNA expression in the pathogenesis of COPD is lacking.In this review we link the expression of microRNAs to different features of COPD and explain their importance in the pathogenesis of this disease. We further discuss their potential to contribute to the development of future therapeutic strategies.

Unlocking the door to new therapies in cardiovascular disease: microRNAs hold the key

MicroRNAs are the most abundant class of regulatory noncoding RNA and are estimated to regulate over half of all human protein-coding genes. The heart is comprised of some of the most complex and highly conserved genetic networks and is thus under tight regulation by post-transcriptional mechanisms. MicroRNAs (miRNAs) have been found to regulate virtually all aspects of cardiac physiology and pathophysiology, from the development of inflammatory atherosclerosis to hypertrophic remodeling in heart failure. Owing to the wide-spread involvement of miRNAs in the development of and protection from many diseases, there has been increasing excitement surrounding their potential as novel therapeutic targets to treat and prevent the worldwide epidemic of cardiovascular disease.

miR-146a targets Fos expression in human cardiac cells

miR-146a is a microRNA whose transcript levels are induced in the heart upon activation of NF-κB, a transcription factor induced by pro-inflammatory molecules (such as TNF-α) that is strongly related to the pathogenesis of cardiac disorders. The main goal of this study consisted of studying new roles of miR-146a in cardiac pathological processes caused by the pro-inflammatory cytokine TNF-α. Our results demonstrate that miR-146a transcript levels were sharply increased in cardiac ventricular tissue of transgenic mice with specific overexpression of TNF-α in the heart, and also in a cardiomyocyte cell line of human origin (AC16) exposed to TNF-α. Among all the in silico predicted miR-146a target genes, Fos mRNA and protein levels notably decreased after TNF-α treatment or miR-146a overexpression. These changes correlated with a diminution in the DNA-binding activity of AP-1, the Fos-containing transcription factor complex. Interestingly, AP-1 inhibition was accompanied by a reduction in matrix metalloproteinase (MMP)-9 mRNA levels in human cardiac cells. The specific regulation of this MMP by miR-146a was further confirmed at the secretion and enzymatic activity levels, as well as after anti-miR-mediated miR-146a inhibition. The results reported here demonstrate that Fos is a direct target of miR-146a activity and that downregulation of the Fos–AP-1 pathway by miR-146a has the capacity to inhibit MMP-9 activity. Given that MMP-9 is an AP-1 target gene involved in cardiac remodeling, myocardial dysfunction and progression of heart failure, these findings suggest that miR-146a might be a new and promising therapeutic tool for treating cardiac disorders associated with enhanced inflammation in the heart.

Summary: These findings demonstrate that Fos is a direct target of miR-146a activity and that downregulation of the Fos–AP-1 pathway by miR-146a can inhibit MMP-9 activity.

Type 2 Diabetes Monocyte MicroRNA and mRNA Expression: Dyslipidemia Associates with Increased Differentiation-Related Genes but Not Inflammatory Activation

OBJECTIVE

To study the expression pattern of microRNAs and mRNAs related to inflammation in T2D monocytes.

DESIGN

A microRNA finding study on monocytes of T2D patients and controls using array profiling was followed by a quantitative Real Time PCR (qPCR) study on monocytes of an Ecuadorian validation cohort testing the top over/under-expressed microRNAs. In addition, monocytes of the validation cohort were tested for 24 inflammation-related mRNAs and 2 microRNAs previously found deregulated in (auto)-inflammatory monocytes.

RESULTS

In the finding study, 142 significantly differentially expressed microRNAs were identified, 15 having the strongest power to discriminate T2D patients from controls (sensitivity 66%, specificity 90%). However, differences in expression of these microRNAs between patients and controls were small. On the basis of >1.4 or <0.6-fold change expression 5 microRNAs were selected for further validation. One microRNA (miR-34c-5p) was validated as significantly over-expressed in T2D monocytes. In addition, we found over expression of 3 mRNAs (CD9, DHRS3 and PTPN7) in the validation cohort. These mRNAs are important for cell morphology, adhesion, shape change, and cell differentiation. Classical inflammatory genes (e.g. TNFAIP3) were only over-expressed in monocytes of patients with normal serum lipids. Remarkably, in dyslipidemia, there was a reduction in the expression of inflammatory genes (e.g. ATF3, DUSP2 and PTGS2).

CONCLUSIONS

The expression profile of microRNAs/mRNAs in monocytes of T2D patients indicates an altered adhesion, differentiation, and shape change potential. Monocyte inflammatory activation was only found in patients with normal serum lipids. Abnormal lipid values coincided with a reduced monocyte inflammatory state.

Interleukin 1β-Responsive MicroRNA-146a Is Critical for the Cytokine-Induced Tolerance and Cross-Tolerance to Toll-Like Receptor Ligands

Unwarranted overproduction of cytokines, such as interleukin (IL)-1β, can cause moderate to severe pathological complications, and thus elaborate mechanisms are needed to regulate its onset and termination. One such, well-known, mechanism is endotoxin tolerance, generally described as controlling lipopolysaccharide Toll-like receptor 4 (LPS-TLR4) signaling. Similarly, cytokine-induced tolerance plays an important role in regulating an overactive cytokine response. In this report, the capability of IL-1β to induce tolerance and cross-tolerance to various inflammatory ligands was investigated. IL-1β-stimulated THP-1 monocytes showed a gradual increase of microRNA (miR)-146a, reaching 15-fold expression by 24 h. miR-146a upregulation induced tolerance toward subsequent challenges of IL-1β, LPS, peptidoglycan, Pam and flagellin in THP-1 cells. The induction of tolerance was dependent on the IL-1β priming dose and associated increase of miR-146a expression. Moreover, IL-1β-treated THP-1 cells showed sustained miR-146a upregulation that repressed IRAK1 and TRAF6 adaptor molecules. Transfection of miR-146a alone mimicked IL-1β-induced tolerance in monocytes, while cells transfected with miR-146a inhibitor increased chemokine production. A comparable cytokine response regulated by miR-146a was also detected in lung epithelial A549 cells, purified human monocytes and mouse peritoneal macrophages. Thus, our studies showed that miR-146a was crucial for monocytic cell-based IL-1β tolerance and cross-tolerance, and thus opens the way for future research in the development of therapeutics for inflammatory diseases.

Using a novel microRNA delivery system to inhibit osteoclastogenesis

Previously, we developed a novel microRNA (miRNA) delivery system based on bacteriophage MS2 virus-like particles (MS2 VLPs). In this current study, we used this system to transport miR-146a into human peripheral blood mononuclear cells (PBMCs), and demonstrated the inhibition of osteoclastogenesis in precursors. Two cytokines, receptor activator of NF-κB ligand (RANKL), and macrophage-colony stimulating factor (M-CSF) were used to induce osteoclastogenesis. MS2 VLPs were transfected into PBMCs. qRT-PCR was applied to measure expression levels of miR-146a and osteoclast (OC)-specific genes. Western blot (WB) was conducted to evaluate miR-146a downstream target proteins: epidermal growth factor receptor (EGFR) and tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6). The formation and activity of OCs were assessed by cytochemical staining and bone resorption assay, respectively. In PBMCs treated with MS2-miR146a VLPs, qRT-PCR assays showed increased expression of miR-146a (p < 0.01) and decreased expression of all four OC-specific genes (p < 0.05). WB results indicated decreased expression of EGFR (p < 0.01) and TRAF6 (p < 0.05). The number of OCs decreased markedly and bone resorption assay demonstrated inhibited activity. This miR-146a delivery system could be applied to induce overexpression of miR-146a and to inhibit the differentiation and function of OCs.

Upregulation of microRNA-146a by hepatitis B virus X protein contributes to hepatitis development by downregulating complement factor H

Hepatic injuries in hepatitis B virus (HBV) patients are caused by immune responses of the host. In our previous study, microRNA-146a (miR-146a), an innate immunity-related miRNA, and complement factor H (CFH), an important negative regulator of the alternative pathway of complement activation, were differentially expressed in HBV-expressing and HBV-free hepatocytes. Here, the roles of these factors in HBV-related liver inflammation were analyzed in detail. The expression levels of miR-146a and CFH in HBV-expressing hepatocytes were assessed via analyses of hepatocyte cell lines, transgenic mice, adenovirus-infected mice, and HBV-positive human liver samples. The expression level of miR-146a was upregulated in HBV-expressing Huh-7 hepatocytes, HBV-expressing mice, and patients with HBV infection. Further results demonstrated that the HBV X protein (HBx) was responsible for its effects on miR-146a expression through NF-κB-mediated enhancement of miR-146a promoter activity. HBV/HBx also downregulated the expression of CFH mRNA in hepatocyte cell lines and the livers of humans and transgenic mice. Furthermore, overexpression and inhibition of miR-146a in Huh-7 cells downregulated and upregulated CFH mRNA levels, respectively. Luciferase reporter assays demonstrated that miR-146a downregulated CFH mRNA expression in hepatocytes via 3′-untranslated-region (UTR) pairing. The overall effect of this process in vivo is to promote liver inflammation. These results demonstrate that the HBx–miR-146a–CFH–complement activation regulation pathway might play an important role in the immunopathogenesis of chronic HBV infection. These findings have important implications for understanding the immunopathogenesis of chronic hepatitis B and developing effective therapeutic interventions.

Hepatitis B virus (HBV) remains an important pathogen and can cause severe liver diseases, including hepatitis, liver cirrhosis, and hepatocellular carcinoma. Although HBV was found in 1966, the molecular mechanisms of pathogenesis are still poorly understood. In the present study, we found that the HBV X protein (HBx) promoted the expression of miR-146a, an innate immunity-related miRNA, through the NF-κB signal pathway and that increasingly expressed miR-146a downregulated its target complement factor H (CFH), an important negative regulator of the complement alternative pathway, leading to the promotion of liver inflammation. We demonstrated that the HBx–miR-146a–CFH–complement activation regulation pathway is potentially an important mechanism of immunopathogenesis caused by chronic HBV infection. Our data provide a novel molecular mechanism of HBV pathogenesis and thus help to understand the correlations between the complement system, an important part of innate immunity, and HBV-associated disease. These findings will also be important to identify potential therapeutic targets for HBV infection.

Decreased miR-146 expression in peripheral blood mononuclear cells is correlated with ongoing islet autoimmunity in type 1 diabetes patients 1miR-146

BACKGROUND

Type 1 diabetes mellitus (T1D) is a common autoimmune disease mediated by autoimmune attack against pancreatic β-cells. It has been reported that dysregulation of microRNAs (miRNAs) may contribute to the pathogenesis of autoimmune diseases, including T1D. The aim of the present study was to identify pathogenic miRNAs in peripheral blood mononuclear cells (PBMC) of T1D patients.

METHODS

Global miRNA and mRNA expression was profiled in PBMC from 12 patients with newly diagnosed T1D and 10 normal controls. Differently expressed miRNAs were validated in an independent set of patients and controls. The dynamic changes in miRNA and target gene expression were analyzed in T1D patients treated with either a short (6 months) or long (12-24 months) course of insulin. The association between miRNA expression and serum glutamic acid decarboxylase antibody (GADA) titers was also investigated.

RESULTS

Compared with normal controls, there were 26 miRNAs and 1218 genes differently expressed in PBMC of patients with newly diagnosed T1D. The greatest downregulation was for miR-146a (48% decrease; P < 0.05). Expression of its target genes, predicted to be tumor necrosis factor receptor-associated factor 6 (TRAF6), B cell CLL/lymphoma 11A (BCL11A), syntaxin 3 (STX3) and numb homolog (NUMB), was upregulated. Moreover, T1D patients on long-course insulin and optimized glucose control had sustained low expression of miR-146. Interestingly, decreased miR-146a expression was significantly associated with high serum GADA titers (P < 0.05).

CONCLUSIONS

The results suggest that dysregulation of miR-146 expression in PBMC may be associated with the ongoing autoimmune imbalance in T1D patients.

BET bromodomains regulate transforming growth factor-β-induced proliferation and cytokine release in asthmatic airway smooth muscle

Airway smooth muscle (ASM) mass is increased in asthma, and ASM cells from patients with asthma are hyperproliferative and release more IL-6 and CXCL8. The BET (bromo- and extra-terminal) family of proteins (Brd2, Brd3, and Brd4) govern the assembly of histone acetylation-dependent chromatin complexes. We have examined whether they modulate proliferation and cytokine expression in asthmatic ASM cells by studying the effect of BET bromodomain mimics JQ1/SGCBD01 and I-BET762. ASM cells from healthy individuals and nonsevere and severe asthmatics were pretreated with JQ1/SGCBD01 and I-BET762 prior to stimulation with FCS and TGF-β. Proliferation was measured by BrdU incorporation. IL-6 and CXCL8 release was measured by ELISA, and mRNA expression was measured by quantitative RT-PCR. ChIP using a specific anti-Brd4 antibody and PCR primers directed against the transcriptional start site of IL-6 and CXCL8 gene promoters was performed. Neither JQ1/SGCBD01 nor I-BET762 had any effect on ASM cell viability. JQ1/SGCBD01 and I-BET762 inhibited FCS+TGF-β-induced ASM cell proliferation and IL-6 and CXCL8 release in healthy individuals (≥ 30 nm) and in nonsevere and severe asthma patients (≥100 nm), with the latter requiring higher concentrations of these mimics. JQ1/SGCBD01 reduced Brd4 binding to IL8 and IL6 promoters induced by FCS+TGF-β. Mimics of BET bromodomains inhibit aberrant ASM cell proliferation and inflammation with lesser efficiency in those from asthmatic patients. They may be effective in reducing airway remodeling in asthma.

MicroRNAs and dendritic cell-based vaccination in melanoma patients

MicroRNAs are increasingly being recognized to play an important role in finely tuning gene expression; therefore, their dysregulation in cancer has been investigated extensively. In terms of melanoma, they are involved in the regulation of many genes and pathways impacting invasiveness, dissemination, and disease progression. Many microRNAs also target genes regulating ontogenesis and functions of the immune system. Indeed, fine-tuning of gene expression by microRNAs is necessary for normal differentiation of the various components of the immune system and for mounting an effective innate and cell-mediated response, which has been shown to be able to control tumor growth. Dendritic cells, by presenting antigens to and activating naive T cells, constitute a critical aspect and have been therefore been used in many studies of cancer vaccination with promising results. Many genes regulating functions and plasticity of dendritic cells are indeed targeted by microRNAs, whose expression is also dependent on maturation status. Therefore, microRNAs could provide new potential therapeutic targets both on the tumor and on the immune system, and could also be used to characterize dendritic cells utilized in immunotherapy trials.

Decreased serum level of miR-146a as sign of chronic inflammation in type 2 diabetic patients

BACKGROUND

There is increasing evidence that chronic inflammation is an important determinant in insulin resistance and in the pathogenesis of type 2 diabetes (T2D). MicroRNAs constitute a newly discovered system of cell regulation and in particular two microRNAs (miR-146a and miR-155) have been described as regulators and biomarkers of inflammation.

AIM

To determine a putative association between the levels of miR-146a and miR-155 in serum of T2D patients, clinical parameters and serological indicators of inflammation.

METHODS

We performed quantitative Real Time PCR (qPCR) of microRNAs from serum (56 Ecuadorian T2D ambulatory patients and 40 non-diabetic controls). In addition, we evaluated T2D-related serum cytokines.chemokines and growth factors using a commercially available multi-analyte cytometric bead array system. We correlated outcomes to clinical parameters, including BMI, HbA1c and lipid state.

RESULTS

The Ecuadorian non-diabetic controls appeared as overweight (BMI>25: patients 85%, controls 82.5%) and as dyslipidemic (hypercholesterolemia: patients 60.7%, controls 67.5%) as the patients. The serum levels of miR-146a were significantly reduced in T2D patients as compared to these non-diabetic, but obese/dyslipidemic control group (mean patients 0.61, mean controls set at 1; p = 0.042), those of miR-155 were normal.The serum levels of both microRNAs correlated to each other (r = 0.478; p<0.001) and to leptin levels. The microRNAs did not correlate to BMI, glycemia and dyslipidemia.From the tested cytokines, chemokines and growth factors, we found IL-8 and HGF significantly raised in T2D patients versus non-diabetic controls (p = 0.011 and 0.023 respectively).

CONCLUSIONS

This study shows decreased serum anti-inflammatory miR-146a, increased pro-inflammatory IL-8 and increased HGF (a vascular/insular repair factor) as discriminating markers of failure of glucose control occurring on the background of obesity and dyslipidemia.

miR-146a functions as a tumor suppressor in prostate cancer by targeting Rac1

BACKGROUND

miR-146a (miR-146a-5p) has been reported to be aberrantly expressed in different types of cancers, the current knowledge about the role of miR-146a in prostate cancer is still limited.

METHODS

The expression levels of miR-146a in cell lines and tissues were measured by qRT-PCR and in situ hybridization. Effects of miR-146a on cell growth and migration were evaluated by colony formation assay and RTCA assay, respectively. The dual luciferase assay was used to examine the binding between miR-146a and the 3'UTR of potential targets.

RESULTS

We found that enforced over-expression of miR-146a in prostate cancer cells suppressed whereas knockdown of miR-146a increased anchorage-independent growth, migration, and invasion. Mechanistic studies revealed that miR-146a repressed the expression of Rac1 through binding to its 3'UTR. Consistently, knockdown of Rac1 phenocopied the anti-migration effect of overexpressing miR-146a, and knockdown of Rac1 in miR-146a-silencing cells antagonized the increase in cell motility induced by silencing miR-146a. Furthermore, miR-146a was found to be inversely correlated with Rac1 in human prostate cancer tissues.

CONCLUSIONS

Our data suggest that miR-146a plays a suppressive role in prostate cancer through down-regulation of Rac1. The miR-146a/Rac1 signaling axis may be a potential therapeutic target to prevent prostate cancer progression.

MicroRNA-146a: A Dominant, Negative Regulator of the Innate Immune Response

MicroRNAs (miRNAs) are a class of small non-coding RNA molecules that can play critical roles as regulators of numerous pathways and biological processes including the immune response. Emerging as one of the most important miRNAs to orchestrate immune and inflammatory signaling, often through its recognized target genes, IRAK1 and TRAF6, is microRNA-146a (miR-146a). MiR-146a is one, of a small number of miRNAs, whose expression is strongly induced following challenge of cells with bacterial endotoxin, and prolonged expression has been linked to immune tolerance, implying that it acts as a fine-tuning mechanism to prevent an overstimulation of the inflammatory response. In other cells, miR-146a has been shown to play a role in the control of the differentiation of megakaryocytic and monocytic lineages, adaptive immunity, and cancer. In this review, we discuss the central role prescribed to miR-146a in innate immunity. We particularly focus on the role played by miR-146a in the regulation and signaling mediated by one of the main pattern recognition receptors, toll/IL-1 receptors (TLRs). Additionally, we also discuss the role of miR-146a in several classes of autoimmune pathologies where this miRNA has been shown to be dysregulated, as well as its potential role in the pathobiology of neurodegenerative diseases.

Model systems to analyze the role of miRNAs and commensal microflora in bovine mucosal immune system development

Information is rapidly accumulating regarding the role of miRNAs as key regulators of immune system development and function. It is also increasingly evident that miRNAs play an important role in host-pathogen interactions through regulation of both innate and acquired immune responses. Little is known, however, about the specific role of miRNAs in regulating normal development of the mucosal immune system, especially during the neonatal period. Furthermore, there is limited knowledge regarding the possible role the commensal microbiome may play in regulating mucosal miRNAs expression, although evidence is emerging that a variety of enteric pathogens influence miRNA expression. The current review focuses on recent information that miRNAs play an important role in regulating early development of the bovine mucosal immune system. A possible role for the commensal microbiome in regulating mucosal development by altering miRNA expression is also discussed. Finally, we explore the potential advantages of using the newborn calf as a model to determine how interactions between developmental programming, maternal factors in colostrum, and colonization of the gastrointestinal tract by commensal bacteria may alter mucosal miRNA expression and immune development. Identifying the key factors that regulate mucosal miRNA expression is critical for understanding how the balance between protective immunity and inflammation is maintained to ensure optimal gastrointestinal tract function and health of the whole organism.

New insights into lung development and diseases: the role of microRNAs

MicroRNAs (miRNAs) are short endogenous noncoding RNA molecules (∼ 22 nucleotides) that can regulate gene expression at the post-transcription level. Research interest in the role of miRNAs in lung biology is emerging. MiRNAs have been implicated in a range of processes such as development, homeostasis, and inflammatory diseases in lung tissues and are capable of inducing differentiation, morphogenesis, and apoptosis. In recent years, several studies have reported that miRNAs are differentially regulated in lung development and lung diseases in response to epigenetic changes, providing new insights for their versatile role in various physiological and pathological processes in the lung. In this review, we discuss the contribution of miRNAs to lung development and diseases and possible future implications in the field of lung biology.

Immunosuppressive/anti-inflammatory cytokines directly and indirectly inhibit endothelial dysfunction--a novel mechanism for maintaining vascular function

Endothelial dysfunction is a pathological status of the vascular system, which can be broadly defined as an imbalance between endothelium-dependent vasoconstriction and vasodilation. Endothelial dysfunction is a key event in the progression of many pathological processes including atherosclerosis, type II diabetes and hypertension. Previous reports have demonstrated that pro-inflammatory/immunoeffector cytokines significantly promote endothelial dysfunction while numerous novel anti-inflammatory/immunosuppressive cytokines have recently been identified such as interleukin (IL)-35. However, the effects of anti-inflammatory cytokines on endothelial dysfunction have received much less attention. In this analytical review, we focus on the recent progress attained in characterizing the direct and indirect effects of anti-inflammatory/immunosuppressive cytokines in the inhibition of endothelial dysfunction. Our analyses are not only limited to the importance of endothelial dysfunction in cardiovascular disease progression, but also expand into the molecular mechanisms and pathways underlying the inhibition of endothelial dysfunction by anti-inflammatory/immunosuppressive cytokines. Our review suggests that anti-inflammatory/immunosuppressive cytokines serve as novel therapeutic targets for inhibiting endothelial dysfunction, vascular inflammation and cardio- and cerebro-vascular diseases.

Different signal pathways regulate IL-1β-induced mature and primary miRNA-146a expression in human alveolar epithelial cells

It was known that IL-1β-induced rapid expression of miR-146a, which regulated the secretion of inflammatory chemokines in human A549 alveolar epithelial cells. However, little is known about the level of primary miR-146a and the downstream biogenesis of miR-146a in A549 cells. We examined the levels of primary miR-146a and mature miR-146a in A549 cells following treatment with pharmacological inhibitors of IKK-2 (TPCA-1), MEK-1/2 (PD098059), JNK-1/2 (SP600125), p38 MAPK (SB 203580) and PI-3k (LY294002). Our studies showed that exposure to PD98059, TPCA-1 and LY294002 resulted in a dose-dependent reduction in the expression of mature miR-146a while the primary miR-146a expression was not changed by any inhibitor. Western blot showed that IL-1β induced an increase of TRBP at 30 min, following by an extended expression at 24 h compared to the non-IL-1β controls in A549 cells. In conclusion, our studies indicated that miR-146a expression in alveolar epithelial cells was regulated at the post-transcriptional level via a MEK-1/2 and IKK2 pathway, and also for the first time via PI-3k pathway. The longer expression of TRBP following stimulation with IL-1β suggests that TRBP might play a role in the process of regulating the processing of primary miR-146a to mature miR-146a in human alveolar epithelial cells.

MicroRNA regulation in human CD8+ T cell subsets--cytokine exposure alone drives miR-146a expression

Background

microRNAs (miRNAs) are emerging as key regulators of the immune system, but their role in CD8+ T cell differentiation is not well explored. Some evidence suggests that signals from cell surface receptors influence the expression of miRNAs in CD8+ T cells, and may have consequent effects on cell phenotype and function. We set out to investigate whether common gamma chain cytokines modulated human CD8+ T cell expression of miR-146a, which previous studies have associated with different stages of CD8+ differentiation. We also investigated how changes in miR-146a related to other miRNAs that alter with CD8+ differentiation status.

Methods

We treated human CD8+ T cells with the cytokines IL-2, IL-7 or IL-15 either at rest or after stimulation with anti-CD3 and anti-CD28. For some experiments we also purified human CD8+ T cell subsets ex vivo. Flow cytometry was used in parallel to assess cell surface memory marker expression. Total RNA from these cells was subjected to microarray analysis and real-time PCR for miRNA expression. Nucleofection studies were performed to assess potential mRNA targets of miR-146a.

Results

We find that miR-146a is up-regulated in naïve CD8+ T cells exposed to IL-2 or IL-15, even in the absence of an activating T cell receptor stimulus, but not when IL-7 is also present. miR-146a expression correlates with a memory phenotype in both ex vivo and in vitro cultured cells although in our hands overexpression of miR-146a was not sufficient alone to drive a full memory phenotype. In ex vivo analysis, miR-146a was one of a small number of miRNAs that was differentially expressed between naïve and memory CD8+ T cells.

Conclusions

miR-146a is emerging as a critical regulator of immune system. Our data shows that miR-146a expression is strongly influenced by the cytokine milieu even in the absence of a T cell receptor stimulus. Our results have implications for studies designed to assess the function of miR-146a, help to define a fingerprint of miRNA expression in CD8+ T cell subsets and may be useful when designing optimal protocols for T cell expansion as efficacy of T cell immunotherapy is correlated with an ‘early’ memory phenotype.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-014-0292-0) contains supplementary material, which is available to authorized users.

Expression of micro-RNAs in peripheral blood mononuclear cells from primary biliary cirrhosis patients

AIM

The aim of this study was to clarify the relationship between the expression of micro-RNAs (miRNAs) in peripheral blood mononuclear cells (PBMCs) and clinical presentation in patients with primary biliary cirrhosis (PBC).

METHODS

This study involved 58 patients with PBC, patients with control diseases including 25 patients with autoimmune hepatitis (AIH), six patients with PBC-AIH overlap syndrome, 23 patients with systemic lupus erythematosus (SLE), and 30 healthy controls. After miRNA was extracted from PBMCs, the expressions of miR-26a, miR-328, miR-299-5p, miR-146a, miR-155, miR-16, miR-132 and let7a were quantified by real-time PCR. The relationships between all miRNA expressions and clinical test parameters were also examined.

RESULTS

In PBC, the expressions of miR-155 and miR-146a were significantly increased compared to those in healthy controls. For miR-26a, miR-299-5p, miR-328 and let-7a, although no significant difference was observed in expression between patients and healthy controls, expressions were significantly increased in PBC compared to those in AIH. Expressions of miR-299-5p were significantly increased in PBC patients resistant to treatment with ursodeoxycholic acid (n = 18) compared to those in healthy controls. In the evaluation of the relationship between miRNA expression and clinical test parameters, significant and positive correlations were found for miR-299-5p with alkaline phosphatase, gamma-glutamyl transpeptidase, total bilirubin and immunoglobulin M levels.

CONCLUSION

The preset results suggest the existence of miRNAs that exhibit disease-specific increases in expression and miRNAs closely correlated with clinical test values in PBC. Further analyses of these miRNAs may contribute to the elucidation of the pathology of PBC.

Differential expression of dicer, miRNAs, and inflammatory markers in diabetic Ins2+/- Akita hearts

Diabetic cardiomyopathy is a leading cause of morbidity and mortality, and Insulin2 mutant (Ins2+/-) Akita is a genetic mice model of diabetes relevant to humans. Dicer, miRNAs, and inflammatory cytokines are associated with heart failure. However, the differential expression of miRNAs, dicer, and inflammatory molecules are not clear in diabetic cardiomyopathy of Akita. We measured the levels of miRNAs, dicer, pro-inflammatory tumor necrosis factor alpha (TNFα), and anti-inflammatory interleukin 10 (IL-10) in C57BL/6J (WT) and Akita hearts. The results revealed increased heart to body weight ratio and robust expression of brain natriuretic peptide (BNP: a hypertrophy marker) suggesting cardiac hypertrophy in Akita. The multiplex RT-PCR, qPCR, and immunoblotting showed up regulation of dicer, whereas miRNA array elicited spread down regulation of miRNAs in Akita including dramatic down regulation of let-7a, miR-130, miR-142-3p, miR-148, miR-338, miR-345-3p, miR-384-3p, miR-433, miR-450, miR-451, miR-455, miR-494, miR-499, miR-500, miR-542-3p, miR-744, and miR-872. Conversely, miR-295 is induced in Akita. Cardiac TNFα is upregulated at mRNA (RT-PCR and qPCR), protein (immunoblotting), and cellular (immunohistochemistry and confocal microscopy) levels, and is robust in hypertrophic cardiomyocytes suggesting direct association of TNFα with hypertrophy. Contrary to TNFα, cardiac IL-10 is downregulated in Akita. In conclusion, induction of dicer and TNFα, and attenuation of IL-10 and majority of miRNA are associated with cardiomyopathy in Akita and could be used for putative therapeutic target for heart failure in diabetics.

MicroRNA-146a and microRNA-146b expression and anti-inflammatory function in human airway smooth muscle

MicroRNA (miR)-146a and miR-146b are negative regulators of inflammatory gene expression in lung fibroblasts, epithelial cells, monocytes, and endothelial cells. The abundance of cyclooxygenase-2 (COX-2) and IL-1β is negatively regulated by the miR-146 family, suggesting miR-146a and/or miR-146b might modulate inflammatory mediator expression in airway smooth muscle thereby contributing to pathogenesis of asthma. To test this idea we compared miR-146a and miR-146b expression in human airway smooth muscle cells (hASMCs) from nonasthmatic and asthmatic subjects treated with cytomix (IL-1β, TNF-α, and IFNγ) and examined the miRNAs' effects on COX-2 and IL-1β expression. We found that cytomix treatment elevated miR-146a and miR-146b abundance. Induction with cytomix was greater than induction with individual cytokines, and asthmatic cells exhibited higher levels of miR-146a expression following cytomix treatment than nonasthmatic cells. Transfection of miR-146a or miR-146b mimics reduced COX-2 and IL-1β expression. A miR-146a inhibitor increased COX-2 and IL-1β expression, but a miR-146b inhibitor was ineffective. Repression of COX-2 and IL-1β expression by miR-146a correlated with reduced abundance of the RNA-binding protein human antigen R. These results demonstrate that miR-146a and miR-146b expression is inducible in hASMCs by proinflammatory cytokines and that miR-146a expression is greater in asthmatic cells. Both miR-146a and miR-146b can negatively regulate COX-2 and IL-1β expression at pharmacological levels, but loss-of-function studies showed that only miR-146a is an endogenous negative regulator in hASMCs. The results suggest miR-146 mimics may be an attractive candidate for further preclinical studies as an anti-inflammatory treatment of asthma.

Pre-miR-146a (rs2910164 G>C) single nucleotide polymorphism is genetically and functionally associated with leprosy

Mycobacterium leprae infects macrophages and Schwann cells inducing a gene expression program to facilitate its replication and progression to disease. MicroRNAs (miRNAs) are key regulators of gene expression and could be involved during the infection. To address the genetic influence of miRNAs in leprosy, we enrolled 1,098 individuals and conducted a case-control analysis in order to study four miRNAs genes containing single nucleotide polymorphism (miRSNP). We tested miRSNP-125a (rs12975333 G>T), miRSNP-223 (rs34952329 *>T), miRSNP-196a-2 (rs11614913 C>T) and miRSNP-146a (rs2910164 G>C). Amongst them, miRSNP-146a was the unique gene associated with risk to leprosy per se (GC OR = 1.44, p = 0.04; CC OR = 2.18, p = 0.0091). We replicated this finding showing that the C-allele was over-transmitted (p = 0.003) using a transmission-disequilibrium test. A functional analysis revealed that live M. leprae (MOI 100∶1) was able to induce miR-146a expression in THP-1 (p<0.05). Furthermore, pure neural leprosy biopsies expressed augmented levels of that miRNA as compared to biopsy samples from neuropathies not related with leprosy (p = 0.001). Interestingly, carriers of the risk variant (C-allele) produce higher levels of mature miR-146a in nerves (p = 0.04). From skin biopsies, although we observed augmented levels of miR-146a, we were not able to correlate it with a particular clinical form or neither host genotype. MiR-146a is known to modulate TNF levels, thus we assessed TNF expression (nerve biopsies) and released by peripheral blood mononuclear cells infected with BCG Moreau. In both cases lower TNF levels correlates with subjects carrying the risk C-allele, (p = 0.0453 and p = 0.0352; respectively), which is consistent with an immunomodulatory role of this miRNA in leprosy.

In spite of the successful drug therapy, leprosy is still affecting people worldwide. It is well known that host genetic background influences leprosy development and that genetic variants have been associated with the disease. Therefore we conducted a study to evaluate the role of microRNAs (miRNAs) polymorphisms in leprosy. We observed that a polymorphism in miR-146a is associated with the risk to develop leprosy in Brazilians. Based on the analysis of clinical specimens, we found that the genetic variant was correlated with elevated levels of miR-146a and it is also a negative regulator of tumor necrosis factor (TNF), an important inflammatory mediator in the leprosy context. These findings provide tenable evidences that miR-146a is important in the control of gene expression during M. leprae infection and also may contribute with leprosy development by controlling TNF levels.

Regulation of COX-2 expression by miR-146a in lung cancer cells

Prostaglandins are a class of molecules that mediate cellular inflammatory responses and control cell growth. The oxidative conversion of arachidonic acid to prostaglandin H2 is carried out by two isozymes of cyclooxygenase, COX-1 and COX-2. COX-1 is constitutively expressed, while COX-2 can be transiently induced by external stimuli, such as pro-inflammatory cytokines. Interestingly, COX-2 is overexpressed in numerous cancers, including lung cancer. MicroRNAs (miRNAs) are small RNA molecules that function to regulate gene expression. Previous studies have implicated an important role for miRNAs in human cancer. We demonstrate here that miR-146a expression levels are significantly lower in lung cancer cells as compared with normal lung cells. Conversely, lung cancer cells have higher levels of COX-2 protein and mRNA expression. Introduction of miR-146a can specifically ablate COX-2 protein and the biological activity of COX-2 as measured by prostaglandin production. The regulation of COX-2 by miR-146a is mediated through a single miRNA-binding site present in the 3' UTR. Therefore, we propose that decreased miR-146a expression contributes to the up-regulation and overexpression of COX-2 in lung cancer cells. Since potential miRNA-mediated regulation is a functional consequence of alternative polyadenylation site choice, understanding the molecular mechanisms that regulate COX-2 mRNA alternative polyadenylation and miRNA targeting will give us key insights into how COX-2 expression is involved in the development of a metastatic condition.

Tristetraprolin is involved in the glucocorticoid-mediated interleukin 8 repression

Glucocorticoids have been widely used in various inflammatory disorders, and the transcriptional repression of inflammatory mediators has been considered to be the main mechanism of action. However, a previous study showed that dexamethasone inhibited interleukin 8 (IL-8) expression by promoting IL-8 mRNA decay, which implies a posttranscriptional regulation. Nevertheless, by which mechanism dexamethasone destabilized IL-8 mRNA was unclear. Another study indicated that an RNA-binding protein, tristetraprolin (TTP), could be induced by dexamethasone. TTP can bind to AU-rich elements (ARE) in the 3'-untranslated region of target mRNAs and promotes mRNA degradation. So, we speculated that dexamethasone destabilized IL-8 mRNA by upregulating TTP expression. Here, we report that dexamethasone reduced IL-8 expression through destabilizing IL-8 mRNA in human pulmonary microvascular endothelial cells (HPMECs). Dexamethasone stimulation increased TTP mRNA and protein levels. TTP silencing led to mRNA stabilization and protein upregulation of IL-8. These results provide the evidence that the glucocorticoid, in HPMECs, inhibits IL-8 expression through TTP at the posttranscriptional level.

Chikungunya virus exploits miR-146a to regulate NF-κB pathway in human synovial fibroblasts

OBJECTIVES

Chikungunya virus causes chronic infection with manifestations of joint pain. Human synovial fibroblasts get infected with CHIKV and could lead to pro-inflammatory responses. MicroRNAs have potentials to regulate the gene expression of various anti-viral and pro-inflammatory genes. The study aims to investigate the role of miR-146a in modulation of inflammatory responses of human synovial fibroblasts by Chikungunya virus.

METHODS

To study the role of miR-146a in CHIKV pathogenesis in human synovial cells and underlying inflammatory manifestations, we performed CHIKV infection in primary human synovial fibroblasts. Western blotting, real-time PCR, luciferase reporter assay, overexpression and knockdown of cellular miR-146a strategies have been employed to validate the role of miR-146a in regulation of pro-inflammatory NF-κB pathway.

RESULTS

CHIKV infection induced the expression of cellular miR-146a, which resulted into down-regulation of TRAF6, IRAK1, IRAK2 and increased replication of CHIKV in human synovial fibroblasts. Exogenous expression of miR-146a in human synovial fibroblasts led to decreased expression of TRAF6, IRAK1, IRAK2 and decreased replication of CHIKV. Inhibition of cellular miR-146a by anti-miR-146a restored the expression levels of TRAF6, IRAK1 and IRAK2. Downregulation of TRAF6, IRAK1 and IRAK2 led to downstream decreased NF-κB activation through negative feedback loop.

CONCLUSION

This study demonstrated the mechanism of exploitation of cellular miR-146a by CHIKV in modulating the host antiviral immune response in primary human synovial fibroblasts.

Role of microRNA-146a in normal and malignant hematopoietic stem cell function

Regulation of hematopoiesis is controlled by microRNAs (miRNAs). In this review, we focus on miR-146a, and its role in regulating normal and malignant hematopoiesis. miR-146a is a negative regulator of immune cell activation by repressing two targets, TRAF6 and IRAK1. Genetic deletion of miR-146a confirmed a role of miR-146a during innate immune signaling as well as for hematopoietic stem cell function. miR-146a is also implicated in the pathogenesis of human myelodysplastic syndromes (MDSs) as it is located within a commonly deleted region on chromosome 5, and miR-146a-deficient mice exhibit features of an MDS-like disease. With new insight into miR-146a through genetic and expression analyses, we highlight and discuss the recent advances in the understanding of miR-146a in physiological hematopoiesis during steady-state and inflammation, as well as in MDS.

MicroRNA-146a alleviates chronic skin inflammation in atopic dermatitis through suppression of innate immune responses in keratinocytes

BACKGROUND

Chronic skin inflammation in atopic dermatitis (AD) is associated with elevated expression of proinflammatory genes and activation of innate immune responses in keratinocytes. microRNAs (miRNAs) are short, single-stranded RNA molecules that silence genes via the degradation of target mRNAs or inhibition of translation.

OBJECTIVE

The aim of this study was to investigate the role of miR-146a in skin inflammation in AD.

METHODS

RNA and protein expression was analyzed using miRNA and mRNA arrays, RT-quantitative PCR, Western blotting, and immunonohistochemistry. Transfection of miR-146a precursors and inhibitors into human primary keratinocytes, luciferase assays, and MC903-dependent mouse model of AD were used to study miR-146a function.

RESULTS

We show that miR-146a expression is increased in keratinocytes and chronic lesional skin of patients with AD. miR-146a inhibited the expression of numerous proinflammatory factors, including IFN-γ-inducible and AD-associated genes CCL5, CCL8, and ubiquitin D (UBD) in human primary keratinocytes stimulated with IFN-γ, TNF-α, or IL-1β. In a mouse model of AD, miR-146a-deficient mice developed stronger inflammation characterized by increased accumulation of infiltrating cells in the dermis, elevated expression of IFN-γ, CCL5, CCL8, and UBD in the skin, and IFN-γ, IL-1β, and UBD in draining lymph nodes. Both tissue culture and in vivo experiments in mice demonstrated that miR-146a-mediated suppression in allergic skin inflammation partially occurs through direct targeting of upstream nuclear factor kappa B signal transducers caspase recruitment domain-containing protein 10 and IL-1 receptor-associated kinase 1. In addition, human CCL5 was determined as a novel, direct target of miR-146a.

CONCLUSION

Our data demonstrate that miR-146a controls nuclear factor kappa B-dependent inflammatory responses in keratinocytes and chronic skin inflammation in AD.

The regulatory roles of microRNA-146b-5p and its target platelet-derived growth factor receptor α (PDGFRA) in erythropoiesis and megakaryocytopoiesis

Emerging evidence has shown that microRNAs have key roles in regulating various normal physiological processes, whereas their deregulated expression is correlated with various diseases. The miR-146 family includes miR-146a and miR-146b, with a distinct expression spectrum in different hematopoietic cells. Recent work indicated that miR-146a has a close relationship with inflammation and autoimmune diseases. miR-146-deficient mice have developed some abnormal hematopoietic phenotypes, suggesting the potential functions of miR-146 in hematopoietic development. In this study, we found that miR-146b was consistently up-regulated in both K562 and CD34(+) hematopoietic stem/progenitor cells (HSPCs) undergoing either erythroid or megakaryocytic differentiation. Remarkably, erythroid and megakaryocytic maturation of K562 cells was induced by excess miR-146b but inhibited by decreased miR-146b levels. More importantly, an mRNA encoding receptor tyrosine kinase, namely platelet-derived growth factor receptor α (PDGFRA), was identified and validated as a direct target of miR-146b in hematopoietic cells. Gain-of-function and loss-of-function assays showed that PDGFRA functioned as a negative regulator in erythroid and megakaryocytic differentiation. miR-146b could ultimately affect the expression of the GATA-1 gene, which is regulated by HEY1 (Hairy/enhancer-of-split related with YRPW motif protein 1), a transcriptional repressor, via inhibition of the PDGFRA/JNK/JUN/HEY1 pathway. Lentivirus-mediated gene transfer also demonstrated that the overexpression of miR-146b promoted erythropoiesis and megakaryocytopoiesis of HSPCs via its regulation on the PDGFRA gene and effects on GATA-1 expression. Moreover, we confirmed that the binding of GATA-1 to the miR-146b promoter and induction of miR-146b during hematopoietic maturation were dependent on GATA-1. Therefore, miR-146b, PDGFRA, and GATA-1 formed a regulatory circuit to promote erythroid and megakaryocytic differentiation.

Role of microRNAs in lung development and pulmonary diseases

MicroRNAs (miRNAs) are a class of small noncoding RNA which exert post-transcriptional gene regulation activity by targeting messenger RNAs. miRNAs have been found to be involved in various fundamental biological processes and deregulation of miRNAs is known to result in pathological conditions. In this review, we provide an overview of recent discoveries on the role played by this class of molecules in lung development and in pulmonary diseases, such as asthma, cystic fibrosis, chronic obstructive pulmonary disease, and pulmonary artery hypertension. Considering the relevant role of these miRNAs under physiological and pathological conditions, they represent new clinical targets as well as diagnostic and prognostic tools. Therefore, this review pays special attention to recent advances and possible future directions for the use of miRNAs for clinical applications.

Induction of the cellular miR-29c by influenza virus inhibits the innate immune response through protection of A20 mRNA

Influenza A viruses (IAVs) are negative-sense, single-stranded, segmented RNA viruses, which primarily targets respiratory epithelial cells and produces clinical outcomes ranging from mild upper respiratory infection to severe pneumonia. MicroRNAs (miRNAs) represent a family of small noncoding RNAs controlling translation and transcription of many genes. The human miR-29 family of miRNAs has three mature members, miR-29a, miR-29b, and miR-29c. Recent studies have revealed that miR-29 is involved in regulation of the innate and adaptive immune responses. However, the function of miR-29 in the immune response to IAV infection remains to be further explored. Our previous study has shown that miR-29 family members are up-regulated during IAV infection, especially miR-29c. Here we report that miR-29c is involved in inhibition of IAV-induced innate immune responses. We found that posttranscriptional regulation was involved in IAV-induced A20 expression in A549 cells. Consistent with a previous report, miR-29c functionally protected A20 transcripts in A549 cells. Overexpression of miR-29c with miR-29c mimic enhanced IAV-induced A20 protein expression and conversely that miR-29c inhibitor significantly blocked IAV-induced A20 protein expression in A549 cells. Furthermore, functional results showed that IAV-induced miR-29c expression correlated with decreased NF-κB activity and expression of several antiviral and proinflammatory cytokines via up-regulation of A20. Together, the findings indicate a new role of miR-29c in IAV infection and suggest its induction may contribute to counteract the innate immune response.

Angiotensin-converting enzyme 2 is subject to post-transcriptional regulation by miR-421

ACE2 (angiotensin converting enzyme 2) plays a critical role in the local tissue RAS (renin-angiotensin system) by hydrolysing the potent hypertensive and mitogenic peptide AngII (angiotensin II). Changes in the levels of ACE2 have been observed in a number of pathologies, including cardiovascular disease, but little is known of the mechanisms regulating its expression. In the present study, therefore, the potential role of miRNAs in the regulation of ACE2 expression in primary human cardiac myofibroblasts was examined. Putative miRNA-binding sites were identified in the 3'-UTR of the ACE2 transcript using online prediction algorithms. Two of these, miR-200b and miR-421, were selected for further analysis. A reporter system using the 3'-UTR of ACE2 fused to the coding region of firefly luciferase was used to determine the functionality of the identified binding sites in vitro. This identified miR-421, but not miR-200b, as a potential regulator of ACE2. The ability of miR-421, an miRNA implicated in the development of thrombosis, to down-regulate ACE2 expression was subsequently confirmed by Western blot analysis of both primary cardiac myofibroblasts and transformed cells transfected with a synthetic miR-421 precursor. Real-time PCR analysis of miR-421 revealed widespread expression in human tissues. miR-421 levels in cardiac myofibroblasts showed significant inter-patient variability, in keeping with the variability of ACE2 expression we have observed previously. In conclusion, the present study is the first to demonstrate that ACE2 may be subject to post-transcriptional regulation and reveals a novel potential therapeutic target, miR-421, which could be exploited to modulate ACE2 expression in disease.