Binding of NF-kappaB p65 subunit to the promoter elements is involved in LPS-induced transactivation of miRNA genes in human biliary epithelial cells

Oxidative stress activates endothelial innate immunity via sterol regulatory element binding protein 2 (SREBP2) transactivation of microRNA-92a

BACKGROUND

Oxidative stress activates endothelial innate immunity and disrupts endothelial functions, including endothelial nitric oxide synthase-derived nitric oxide bioavailability. Here, we postulated that oxidative stress induces sterol regulatory element-binding protein 2 (SREBP2) and microRNA-92a (miR-92a), which in turn activate endothelial innate immune response, leading to dysfunctional endothelium.

METHODS AND RESULTS

Using cultured endothelial cells challenged by diverse oxidative stresses, hypercholesterolemic zebrafish, and angiotensin II-infused or aged mice, we demonstrated that SREBP2 transactivation of microRNA-92a (miR-92a) is oxidative stress inducible. The SREBP2-induced miR-92a targets key molecules in endothelial homeostasis, including sirtuin 1, Krüppel-like factor 2, and Krüppel-like factor 4, leading to NOD-like receptor family pyrin domain-containing 3 inflammasome activation and endothelial nitric oxide synthase inhibition. In endothelial cell-specific SREBP2 transgenic mice, locked nucleic acid-modified antisense miR-92a attenuates inflammasome, improves vasodilation, and ameliorates angiotensin II-induced and aging-related atherogenesis. In patients with coronary artery disease, the level of circulating miR-92a is inversely correlated with endothelial cell-dependent, flow-mediated vasodilation and is positively correlated with serum level of interleukin-1β.

CONCLUSIONS

Our findings suggest that SREBP2-miR-92a-inflammasome exacerbates endothelial dysfunction during oxidative stress. Identification of this mechanism may help in the diagnosis or treatment of disorders associated with oxidative stress, innate immune activation, and endothelial dysfunction.

The miRNA23b-regulated signaling network as a key to cancer development--implications for translational research and therapeutics

A growing body of evidence indicates that microRNA23b (miR23b) is pleiotropic-it plays important roles in regulating physiological functions of cells, in regulating differentiation of cells and in regulating cellular immune responses. Our review of the literature showed that dysregulation of miR23b expression is implicated in the disruption of these cellular mechanisms and development of diseases such as cancer. MiR23b dysregulation appears to do this by modulating the expression level of candidate gene products involved in a network of signaling pathways including TGF-beta and Notch pathways that govern malignant properties of cancer cells such as motility and invasiveness. More recently, miR23b regulation of gene expression has also been associated with cancer stem cells and chemoresistance. Our review covers miR23b's role in immunity, endothelial function, differentiation, and cancer as well as its potential for translation into future cancer diagnostics and therapeutics.

NFkappaB activation is essential for miR-21 induction by TGFβ1 in high glucose conditions

Transforming growth factor beta1 (TGFβ1) is a pleiotropic growth factor with a very broad spectrum of effects on wound healing. Chronic non-healing wounds such as diabetic foot ulcers express reduced levels of TGFβ1. On the other hand, our previous studies have shown that the microRNA miR-21 is differentially regulated in diabetic wounds and that it promotes migration of fibroblast cells. Although interplay between TGFβ1 and miR-21 are studied in relation to cancer, their interaction in the context of chronic wounds has not yet been investigated. In this study, we examined if TGFβ1 could stimulate miR-21 in fibroblasts that are subjected to high glucose environment. MiR-21 was, in fact, induced by TGFβ1 in high glucose conditions. The induction by TGFβ1 was dependent on NFκB activation and subsequent ROS generation. TGFβ1 was instrumental in degrading the NFκB inhibitor IκBα and facilitating the nuclear translocation of NFκB p65 subunit. EMSA studies showed enhanced DNA binding activity of NFκB in the presence of TGFβ1. ChIP assay revealed binding of p65 to miR-21 promoter. NFκB activation was also required for the nuclear translocation of Smad 4 protein and subsequent direct interaction of Smad proteins with primary miR-21 as revealed by RNA-IP studies. Our results show that manipulation of TGFβ1-NFκB-miR-21 pathway could serve as an innovative approach towards therapeutics to heal diabetic ulcers.

Methylation by NSun2 represses the levels and function of microRNA 125b

Methylation is a prevalent posttranscriptional modification of RNAs. However, whether mammalian microRNAs are methylated is unknown. Here, we show that the tRNA methyltransferase NSun2 methylates primary (pri-miR-125b), precursor (pre-miR-125b), and mature microRNA 125b (miR-125b) in vitro and in vivo. Methylation by NSun2 inhibits the processing of pri-miR-125b2 into pre-miR-125b2, decreases the cleavage of pre-miR-125b2 into miR-125, and attenuates the recruitment of RISC by miR-125, thereby repressing the function of miR-125b in silencing gene expression. Our results highlight the impact of miR-125b function via methylation by NSun2.

Ischemic brain extract increases SDF-1 expression in astrocytes through the CXCR2/miR-223/miR-27b pathway

Ischemic cerebral stroke is one of the leading global causes of mortality and morbidity. Ischemic preconditioning (IPC) refers to a sublethal ischemia and resulting in tolerance to subsequent severe ischemic injury. Although several pathways are reportedly involved in IPC-mediated neuroprotection, the functional role of astrocytes is not fully understood. Stromal cell-derived factor-1 (SDF-1), a CXC chemokine produced mainly in astrocytes, is a ligand for chemokine receptor CXCR4. SDF-1 is reported to play a critical role in neuroprotection after stroke by mediating the migration of neuronal progenitor cells. We hypothesized that stimuli derived from ischemic brain were involved in the protective effects of IPC. To investigate this hypothesis, the mechanism in which ischemic brain extract (IBE) induced SDF-1 expression was investigated in C6 astrocytoma cells. IBE treatment of C6 cells increased SDF-1 expression compared to that in untreated or normal brain extract (NBE)-treated cells by downregulating SDF-1 targeting miRNA, miR-27b. MiR-223 was inversely upregulated in IBE-treated cells; overexpression of miR-223 decreased the expression of miR-27b by suppressing IKKα expression. Analysis of cytokine array data revealed an IBE associated enhanced expression of CINC-1 (CXCL1) and LIX1 (CXCL5). Knockdown or inhibition of their receptor, CXCR2, abolished IBE-mediated increased expression of SDF-1. These results were confirmed in primary cultured astrocytes. Taken together, the data demonstrate that IBE-elicited signals increase SDF-1 expression through the CXCR2/miR-223/miR-27b pathway in C6 astrocytoma cells and primary astrocytes, supporting the view that increased expression of SDF-1 by ischemic insults is a possible mechanism underlying therapeutic application of IPC.

NF-κB-modulated miR-130a targets TNF-α in cervical cancer cells

Background

Nuclear factor-κB (NF-κB) induces a variety of biological processes through transcriptional gene control whose products are components in various signaling pathways. MicroRNAs are a small endogenous non-coding RNAs that regulate gene expression and are involved in tumorigenesis. Using human cervical cancer cell lines, this study aimed to investigate whether NF-κB could regulate miR-130a expression and the functions and targets of miR-130a.

Methods

We used the HeLa and C₃₃A cervical cancer cell lines that were transfected with NF-κB or miR-130a overexpression plasmids to evaluate their effects on cell growth. We utilized bioinformatics, a fluorescent reporter assay, qRT-PCR and Western blotting to identify downstream target genes.

Results

In HeLa and C₃₃A cells, NF-κB and miR-130a overexpression promoted cell growth, but genetic knockdowns suppressed growth. TNF-α was identified as a target of miR-130a by binding in a 3’-untranslated region (3’UTR) EGFP reporter assay and by Western blot analysis. Furthermore, low TNF-α concentrations stimulated NF-κB activity and then induced miR-130a expression, and TNF-α overexpression rescued the effects of miR-130a on cervical cancer cells.

Conclusions

Our findings indicate that TNF-α can activate NF-κB activity, which can reduce miR-130a expression, and that miR-130a targets and downregulates TNF-α expression. Hence, we shed light on the negative feedback regulation of NF-κB/miR-130a/TNF-α/NF-κB in cervical cancer and may provide insight into the carcinogenesis of cervical cancer.

MicroRNAs: New therapeutic targets for intestinal barrier dysfunction

Defects in intestinal barrier function characterized by an increase in intestinal permeability contribute to intestinal inflammation. Growing evidence has shown that an increase in intestinal permeability has a pathogenic role in diseases such as inflammatory bowel disease (IBD) and celiac disease, and functional bowel disorders such as irritable bowel syndrome. Therefore, clarification of the inflammatory responses, the defense pathway and the corresponding regulatory system is essential and may lead to the development of new therapies. MicroRNAs (miRNAs) are small (19-22 nt) noncoding RNA molecules that regulate genes at the post-transcriptional level by base-pairing to specific messenger RNAs for degradation to repress translation. Recent studies suggested that miRNAs are important in the immune response and mediate a critical role in multiple immune response-related disorders. Based on these discoveries, attention has been focused on understanding the role of miRNAs in regulating intestinal barrier dysfunction, especially in IBD. Here, we provide a review of the most recent state-of-the-art research on miRNAs in intestinal barrier dysfunction.

Expression differences of miRNAs and genes on NF-κB pathway between the healthy and the mastitis Chinese Holstein cows

In order to discover the variation of microRNAs and genes associated with NF-κB signaling pathway between the healthy and the mastitis Chinese Holstein cows, Illumina Deep Sequencing and qRT-PCR are applied to detect 25 kinds of miRNAs (miR-16, miR-125b, miR-15, miR-29a, miR-23b, miR-146, miR-301a, miR-181b, let-7, miR-30b, miR-21, miR-223, miR-27b, miR-10a, miR-143, etc.) expression levels in blood samples and 14 genes (RelA, RelB, Rel, p105, p100, IκBα, IκBβ, IκBδ, IκBε, IκBζ, Bcl-3, IKKα, IKKβ, IKKγ/NEMO) relative expression levels in nine tissues. The total number of miRNAs is declining, and RelA, Rel, p105, p100, IκBα, IκBβ, IκBδ, IκBζ, Bcl-3, and IKKα expressions are rising in mastitis individuals. So, we suppose that NF-κB pathway is active in mastitis individuals as a result of the decrease inhibition of miRNAs. While in healthy ones, the NF-κB pathway is inactive, because of the miRNAs enhanced inhibition action. However, the specific regulatory mechanism of miRNAs on NF-κB pathway in mastitis Holstein cows needs further investigation. Moreover, due to obvious expression differences, some miRNAs, especially miR-16 and miR-223, may be used as new markers for the dairy mastitis prognosing.

MicroRNAs: new regulators of Toll-like receptor signalling pathways

Toll-like receptors (TLRs), a critical family of pattern recognition receptors (PRRs), are responsible for the innate immune responses via signalling pathways to provide effective host defence against pathogen infections. However, TLR-signalling pathways are also likely to stringently regulate tissue maintenance and homeostasis by elaborate modulatory mechanisms. MicroRNAs (miRNAs) have emerged as key regulators and as an essential part of the networks involved in regulating TLR-signalling pathways. In this review, we highlight our understanding of the regulation of miRNA expression profiles by TLR-signalling pathways and the regulation of TLR-signalling pathways by miRNAs. We focus on the roles of miRNAs in regulating TLR-signalling pathways by targeting multiple molecules, including TLRs themselves, their associated signalling proteins and regulatory molecules, and transcription factors and functional cytokines induced by them, at multiple levels.

NF-κB target microRNAs and their target genes in TNFα-stimulated HeLa cells

As a transcription factor, NF-κB was demonstrated to regulate the expressions of miRNAs. However, only a few miRNAs have been identified as its targets so far. In this study, by using ChIP-Seq, Genechip and miRNA-Seq techniques, we identified 14 NF-κB target miRNAs in TNFα-stimulated HeLa Cells, including miR-1276, miR-1286, miR-125b-1-3p, miR-219-1-3p, miR-2467-5p, miR-3200-3p, miR-449c-5p, miR-502-5p, miR-548d-5p, miR-30b-3p, miR-3620-5p, miR-340-3p, miR-4454 and miR-4485. Of these miRNAs, 8 detected miRNAs were also NF-κB target misRNAs in TNFα-stimulated HepG2 cells. We also identified 16 target genes of 6 miRNAs including miR-125b-1-3p, miR-1286, miR-502-5p, miR-1276, miR-219-1-3p and miR-30b-3p, in TNFα-stimulated HeLa cells. Target genes of miR-125b-1-3p and miR-1276 were validated in HeLa and HepG2 cells by transfecting their expression plasmids and mimics. Bioinformatic analysis revealed that two potential target genes of miR-1276, BMP2 and CASP9, were enriched in disease phenotypes. The former is enriched in osteoarthritis, and the latter is enriched in Type 2 diabetes and lung cancer, respectively. These findings suggested that this little known miRNA might play roles in these diseases via its two target genes of BMP2 and CASP9. The expression of miR-125b-1 regulated by NF-κB has been reported in diverse cell types under various stimuli, this study found that its expression was also significantly regulated by NF-κB in TNFα-stimulated HeLa and HepG2 cells. Therefore, this miRNA was proposed as a central mediator of NF-κB pathway. These findings provide new insights into the functions of NF-κB in its target miRNA-related biological processes and the mechanisms underlying the regulation of these miRNAs.

Apoptosis induction by 13-acetoxyrolandrolide through the mitochondrial intrinsic pathway

The aim of this study was to evaluate the mechanisms of cytotoxicity of the sesquiterpene lactone 13-acetoxyrolandrolide, a nuclear factor kappa B (NF-κB) inhibitor that was previously isolated from Rolandra fruticosa. The effects associated with the inhibition of the NF-κB pathway included dose-dependent inhibition of the NF-κB subunit p65 (RelA) and inhibition of upstream mediators IKKβ and oncogenic Kirsten rat sarcoma (K-Ras). The inhibitory concentration of 13-acetoxyrolandrolide on K-Ras was 7.7 µM. The downstream effects of the inhibition of NF-κB activation were also investigated in vitro. After 24 h of treatment with 13-acetoxyrolandrolide, the mitochondrial transmembrane potential was depolarized in human colon cancer (HT-29) cells. The mitochondrial oxidative phosphorylation was also negatively affected, and reduced levels of nicotinamine adenine dinucleotide phosphate (NAD(P)H) were detected after 2 h of 13-acetoxyrolandrolide exposure. Furthermore, the expression of the pro-apoptotic protein caspase-3 increased in a concentration-dependent manner. Cell flow cytometry showed that 13-acetoxyrolandrolide induced cell cycle arrest at G1 , indicating that the treated cells had undergone caspase-3-mediated apoptosis, indicating negative effects on cancer cell proliferation. These results suggest that 13-acetoxyrolandrolide inhibits NF-κB and K-Ras and promotes cell death mediated through the mitochondrial apoptotic pathway.

NF-κB mediated miR-21 regulation in cardiomyocytes apoptosis under oxidative stress

Oxidative stress, defined as an excess production of reactive oxygen species (ROS), is shown to play an important role in the pathophysiology of cardiac remodeling including cell death and contractile dysfunction. Therefore, the balance between ROS production and removal of excess ROS is essential in maintaining the redox state and homeostasis balance in the cell. The increased ROS further activates nuclear factor-κB (NF-κB), a redox-sensitive transcription factor and promotes cell death. Recently, microRNAs (miRNAs) have been identified as critical regulators of various pathophysiological processes of cardiac remodeling; however, NF-κB-mediated miRNA's role in cardiomyocytes under oxidative stress remains undetermined. The miR-21 has been implicated in diverse cardiac remodeling; but, NF-κB-mediated miR-21 modulation in oxidative stress is currently unknown. Neonatal cardiomyocytes were transfected with IκBα mutant, miR-21 mimetic, and inhibitors separately, and were challenged with H2O2. The target gene, programmed cell death 4 (PDCD4), ROS activity, and NF-κB translocation were analyzed. Our results indicated that NF-κB positively regulated miR-21 expression under oxidative stress, and PDCD4 was a direct target for miR-21. NF-κB further regulated the expression of PDCD4 in H2O2-induced oxidative stress. Moreover, H2O2-induced ROS activity and cardiomyocytes apoptosis were partly protected by overexpression of miR-21 and displayed an important role in ROS-mediated cardiomyocytes injury. We evaluated a critical role of NF-κB-mediated miR-21 modulation in H2O2-induced oxidative stress in cardiomyocytes by targeting PDCD4. Our data may provide a new insight of miR-21's role in cardiac diseases primarily mediated by ROS.

Essential role of NADPH oxidase-dependent reactive oxygen species generation in regulating microRNA-21 expression and function in prostate cancer

AIMS

Oncogenic microRNAs (miRs) promote tumor growth and invasiveness. One of these, miR-21, contributes to carcinogenesis in prostate and other cancers. In the present study, we tested the hypothesis that NADPH oxidase-dependent reactive oxygen species (ROS) regulate the expression and function of miR-21 and its target proteins, maspin and programmed cell death 4 (PDCD4), in prostate cancer cells.

RESULTS

The highly aggressive androgen receptor negative PC-3M-MM2 prostate cancer cells demonstrated high expression of miR-21 and p47(phox) (an essential subunit of NADPH oxidase). Using loss-of-function strategy, we showed that transfection of PC-3M-MM2 cells with anti-miR-21- and p47(phox) siRNA (si-p47(phox)) led to reduced expression of miR-21 with concurrent increase in maspin and PDCD4, and decreased the invasiveness of the cells. Tail-vein injections of anti-miR-21- and si-p47(phox)-transfected PC-3M-MM2 cells in severe combined immunodeficient mice reduced lung metastases. Clinical samples from patients with advanced prostate cancer expressed high levels of miR-21 and p47(phox), and low expression of maspin and PDCD4. Finally, ROS activated Akt in these cells, the inhibition of which reduced miR-21 expression.

INNOVATION

The levels of NADPH oxidase-derived ROS are high in prostate cancer cells, which have been shown to be involved in their growth and migration. This study demonstrates that ROS produced by this pathway is essential for the expression and function of an onco-miR, miR-21, in androgen receptor-negative prostate cancer cells.

CONCLUSION

These data demonstrate that miR-21 is an important target of ROS, which contributes to the highly invasive and metastatic phenotype of prostate cancer cells.

NF-κB-mediated miR-30b regulation in cardiomyocytes cell death by targeting Bcl-2

Angiotensin II(Ang II)-stimulated cardiomyocytes hypertrophy and apoptosis are associated with nuclear factor-κB (NF-κB) activation. NF-κB, a redox-sensitive transcription factor, contributes a critical role in cell death, but, Ang II-stimulated NF-κB-mediated cardiomyocytes apoptosis remains less understood. Recently, microRNAs (miRNAs) have been shown to be critical regulators in various cardiac remodeling processes; however, NF-κB-mediated miRNA's role in cardiomyocytes apoptosis remains undetermined. The miR-30b has been implicated in diverse cardiac remodeling; but, NF-κB-mediated miR-30b modulation in Ang II-induced cardiomyocytes death is currently unknown. In the present study, neonatal cardiomyocytes were pretreated with SN50, a selective cell permeable peptide inhibitor of NF-κB, or transfected with miR-30b mimetic and inhibitors separately, and then challenged with Ang II. The target gene, Bcl-2, and NF-κB transcriptional activity were analyzed. Our results demonstrated that NF-κB positively regulated miR-30b expression in Ang II-induced cardiomyocytes apoptosis, and Bcl-2 was a direct target for miR-30b. NF-κB further regulated the expression of Bcl-2 in the above setting. Furthermore, Ang II-induced cardiomyocytes apoptosis rescued by inhibiting either NF-κB or miR-30b provided an important role in cardiomyocytes cell death. We evaluated a critical role of NF-κB-mediated miR-30b modulation in Ang II-stimulated cardiomyocytes targeting Bcl-2. Our data may provide a new insight of miR-30b's role in myocardial infarction or ischemia.

Integrative genomics identifies candidate microRNAs for pathogenesis of experimental biliary atresia

Background

Biliary atresia is a fibroinflammatory obstruction of extrahepatic bile duct that leads to end-stage liver disease in children. Despite advances in understanding the pathogenesis of biliary atresia, very little is known about the role of microRNAs (miRNAs) in onset and progression of the disease. In this study, we aimed to investigate the entire biliary transcriptome to identify miRNAs with potential role in the pathogenesis of bile duct obstruction.

Results

By profiling the expression levels of miRNA in extrahepatic bile ducts and gallbladder (EHBDs) from a murine model of biliary atresia, we identified 14 miRNAs whose expression was suppressed at the times of duct obstruction and atresia (≥2 fold suppression, P < 0.05, FDR 5%). Next, we obtained 2,216 putative target genes of the 14 miRNAs using in silico target prediction algorithms. By integrating this result with a genome-wide gene expression analysis of the same tissue (≥2 fold increase, P < 0.05, FDR 5%), we identified 26 potential target genes with coordinate expression by the 14 miRNAs. Functional analysis of these target genes revealed a significant relevance of miR-30b/c, -133a/b, -195, -200a, -320 and −365 based on increases in expression of at least 3 target genes in the same tissue and 1^st-to-3^rd tier links with genes and gene-groups regulating organogenesis and immune response. These miRNAs showed higher expression in EHBDs above livers, a unique expression in cholangiocytes and the subepithelial compartment, and were downregulated in a cholangiocyte cell line after RRV infection.

Conclusions

Integrative genomics reveals functional relevance of miR-30b/c, -133a/b, -195, -200a, -320 and −365. The coordinate expression of miRNAs and target genes in a temporal-spatial fashion suggests a regulatory role of these miRNAs in pathogenesis of experimental biliary atresia.

Inhibition of protein kinase C signaling maintains rat embryonic stem cell pluripotency

Embryonic stem cell (ESC) pluripotency is orchestrated by distinct signaling pathways that are often targeted to maintain ESC self-renewal or their differentiation to other lineages. We showed earlier that inhibition of PKC signaling maintains pluripotency in mouse ESCs. Therefore, in this study, we investigated the importance of protein kinase C signaling in the context of rat ESC (rESC) pluripotency. Here we show that inhibition of PKC signaling is an efficient strategy to establish and maintain pluripotent rESCs and to facilitate reprogramming of rat embryonic fibroblasts to rat induced pluripotent stem cells. The complete developmental potential of rESCs was confirmed with viable chimeras and germ line transmission. Our molecular analyses indicated that inhibition of a PKCζ-NF-κB-microRNA-21/microRNA-29 regulatory axis contributes to the maintenance of rESC self-renewal. In addition, PKC inhibition maintains ESC-specific epigenetic modifications at the chromatin domains of pluripotency genes and, thereby, maintains their expression. Our results indicate a conserved function of PKC signaling in balancing self-renewal versus differentiation of both mouse and rat ESCs and indicate that targeting PKC signaling might be an efficient strategy to establish ESCs from other mammalian species.

MicroRNAs as pharmacological targets in diabetes

Diabetes is characterized by high levels of blood glucose due to either the loss of insulin-producing beta-cells in the pancreas, leading to a deficiency of insulin in type 1 diabetes, or due to increased insulin resistance, leading to reduced insulin sensitivity and productivity in type 2 diabetes. There is an increasing need for new options to treat diabetes, especially type 2 diabetes at its early stages due to an ineffective control of its development in patients. Recently, a novel class of small noncoding RNAs, termed microRNAs (miRNAs), is found to play a key role as important transcriptional and posttranscriptional inhibitors of gene expression in fine-tuning the target messenger RNAs (mRNAs). miRNAs are implicated in the pathogenesis of diabetes and have become an intriguing target for therapeutic intervention. This review focuses on the dysregulated miRNAs discovered in various diabetic models and addresses the potential for miRNAs to be therapeutic targets in the treatment of diabetes.

Histone deacetylases and NF-kB signaling coordinate expression of CX3CL1 in epithelial cells in response to microbial challenge by suppressing miR-424 and miR-503

The NF-kB pathway is key to epithelial immune defense and has been implicated in secretion of antimicrobial peptides, release of cytokines/chemokines to mobilize immune effector cells, and activation of adaptive immunity. The expression of many inflammatory genes following infection involves the remodeling of the chromatin structure. We reported here that histone deacetylases (HDACs) and NF-kB signaling coordinate expression of CX3CL1 in epithelial cells following Cryptosporidium parvum infection. Upregulation of CX3CL1 was detected in cultured human biliary epithelial cells following infection. Expression of miR-424 and miR-503 was downregulated, and was involved in the induction of CX3CL1 in infected cells. C. parvum infection suppressed transcription of the mir-424-503 gene in a NF-kB- and HDAC-dependent manner. Increased promoter recruitment of NF-kB p50 and HDACs, and decreased promoter H3 acetylation associated with the mir-424-503 gene were observed in infected cells. Upregulation of CX3CL1 in biliary epithelial cells and increased infiltration of CX3CR1⁺ cells were detected during C. parvum infection in vivo. Induction of CX3CL1 and downregulation of miR-424 and miR-503 were also detected in epithelial cells in response to LPS stimulation. The above results indicate that HDACs and NF-kB signaling coordinate epithelial expression of CX3CL1 to promote mucosal antimicrobial defense through suppression of the mir-424-503 gene.

Tumor necrosis factor α-induced microRNA-18a activates rheumatoid arthritis synovial fibroblasts through a feedback loop in NF-κB signaling

OBJECTIVE

To elucidate whether the microRNA (miRNA) cluster miR-17-92 contributes to the activated phenotype of rheumatoid arthritis synovial fibroblasts (RASFs).

METHODS

RASFs were stimulated with tumor necrosis factor α (TNFα), and the expression and regulation of the miR-17-92 cluster were studied using real-time quantitative PCR (PCR) and promoter activity assays. RASFs were transfected with single precursor molecules of miRNAs from miR-17-92 and the expression of matrix-degrading enzymes and cytokines was measured by quantitative PCR and enzyme-linked immunosorbent assay. Potential miRNA targets were identified by computational prediction and were validated using reporter gene assays and Western blotting. The activity of NF-κB signaling was determined by reporter gene assays.

RESULTS

We found that TNFα induces the expression of miR-17-92 in RASFs in an NF-κB-dependent manner. Transfection of RASFs with precursor molecules of single members of miR-17-92 revealed significantly increased expression levels of matrix-degrading enzymes, proinflammatory cytokines, and chemokines in precursor miR-18a (pre-miR-18a)-transfected RASFs. Using reporter gene assays, we identified the NF-κB pathway inhibitor TNFα-induced protein 3 as a new target of miR-18a. In addition, pre-miR-18a-transfected RASFs showed stronger activation of NF-κB signaling, both constitutively and in response to TNFα stimulation.

CONCLUSION

Our data suggest that the miR-17-92-derived miR-18a contributes to cartilage destruction and chronic inflammation in the joint through a positive feedback loop in NF-κB signaling, with concomitant up-regulation of matrix-degrading enzymes and mediators of inflammation in RASFs.

Identification of direct targets of FUSCA3, a key regulator of Arabidopsis seed development

FUSCA3 (FUS3) is a B3 domain transcription factor that is a member of the LEAFY COTYLEDON (LEC) group of genes. The LEC genes encode proteins that also include LEC2, a B3 domain factor related to FUS3, and LEC1, a CCAAT box-binding factor. LEC1, LEC2, and FUS3 are essential for plant embryo development. All three loss-of-function mutants in Arabidopsis (Arabidopsis thaliana) prematurely exit embryogenesis and enter seedling developmental programs. When ectopically expressed, these genes promote embryo programs in seedlings. We report on chromatin immunoprecipitation-tiling array experiments to globally map binding sites for FUS3 that, along with other published work to assess transcriptomes in response to FUS3, allow us to determine direct from indirect targets. Many transcription factors associated with embryogenesis are direct targets of FUS3, as are genes involved in the seed maturation program. FUS3 regulates genes encoding microRNAs that, in turn, control transcripts encoding transcription factors involved in developmental phase changes. Examination of direct targets of FUS3 reveals that FUS3 acts primarily or exclusively as a transcriptional activator. Regulation of microRNA-encoding genes is one mechanism by which FUS3 may repress indirect target genes. FUS3 also directly up-regulates VP1/ABI3-LIKE1 (VAL1), encoding a B3 domain protein that functions as a repressor of transcription. VAL1, along with VAL2 and VAL3, is involved in the transition from embryo to seedling development. Many genes are responsive to FUS3 and to VAL1/VAL2 but with opposite regulatory consequences. The emerging picture is one of complex cross talk and interactions among embryo transcription factors and their target genes.

A functional genomics screen for microRNA regulators of NF-kappaB signaling

BACKGROUND

The nuclear factor-KappaB (NF-κB) pathway is conserved from fruit flies to humans and is a key mediator of inflammatory signaling. Aberrant regulation of NF-κB is associated with several disorders including autoimmune disease, chronic inflammation, and cancer, making the NF-κB pathway an attractive therapeutic target. Many regulatory components of the NF-κB pathway have been identified, including microRNAs (miRNAs). miRNAs are small non-coding RNAs and are common components of signal transduction pathways. Here we present a cell-based functional genomics screen to systematically identify miRNAs that regulate NF-κB signaling.

RESULTS

We screened a library of miRNA mimics using a NF-κB reporter cell line in the presence and absence of tumor necrosis factor (+/- TNF). There were 9 and 15 hits in the -TNF and +TNF screens, respectively. We identified putative functional targets of these hits by integrating computational predictions with NF-κB modulators identified in a previous genome-wide cDNA screen. miR-517a and miR-517c were the top hits, activating the reporter 86- and 126-fold, respectively. Consistent with these results, miR-517a/c induced the expression of endogenous NF-κB targets and promoted the nuclear localization of p65 and the degradation of IκB. We identified TNFAIP3 interacting protein1 (TNIP1) as a target and characterized a functional SNP in the miR-517a/c binding site. Lastly, miR-517a/c induced apoptosis in vitro, which was phenocopied by knockdown of TNIP1.

CONCLUSIONS

Our study suggests that miRNAs are common components of NF-κB signaling and miR-517a/c may play an important role in linking NF-κB signaling with cell survival through TNIP1.

Human bronchial epithelial cells exposed in vitro to cigarette smoke at the air-liquid interface resemble bronchial epithelium from human smokers

Organotypic culture of human primary bronchial epithelial cells is a useful in vitro system to study normal biological processes and lung disease mechanisms, to develop new therapies, and to assess the biological perturbations induced by environmental pollutants. Herein, we investigate whether the perturbations induced by cigarette smoke (CS) and observed in the epithelium of smokers' airways are reproducible in this in vitro system (AIR-100 tissue), which has been shown to recapitulate most of the characteristics of the human bronchial epithelium. Human AIR-100 tissues were exposed to mainstream CS for 7, 14, 21, or 28 min at the air-liquid interface, and we investigated various biological endpoints [e.g., gene expression and microRNA profiles, matrix metalloproteinase 1 (MMP-1) release] at multiple postexposure time points (0.5, 2, 4, 24, 48 h). By performing a Gene Set Enrichment Analysis, we observed a significant enrichment of human smokers' bronchial epithelium gene signatures derived from different public transcriptomics datasets in CS-exposed AIR-100 tissue. Comparison of in vitro microRNA profiles with microRNA data from healthy smokers highlighted various highly translatable microRNAs associated with inflammation or with cell cycle processes that are known to be perturbed by CS in lung tissue. We also found a dose-dependent increase of MMP-1 release by AIR-100 tissue 48 h after CS exposure in agreement with the known effect of CS on this collagenase expression in smokers' tissues. In conclusion, a similar biological perturbation than the one observed in vivo in smokers' airway epithelium could be induced after a single CS exposure of a human organotypic bronchial epithelium-like tissue culture.

MicroRNA-92a negatively regulates Toll-like receptor (TLR)-triggered inflammatory response in macrophages by targeting MKK4 kinase

Toll-like receptors (TLRs) play a critical role in the initiation of immune responses against invading pathogens. MicroRNAs have been shown to be important regulators of TLR signaling. In this study, we have found that the stimulation of multiple TLRs rapidly reduced the levels of microRNA-92a (miRNA-92a) and some other members of the miRNA-92a family in macrophages. miR-92a mimics significantly decreased, whereas miR-92a knockdown increased, the activation of the JNK/c-Jun pathway and the production of inflammatory cytokines in macrophages when stimulated with ligands for TLR4. Furthermore, mitogen-activated protein kinase kinase 4 (MKK4), a kinase that activates JNK/stress-activated protein kinase, was found to be directly targeted by miR-92a. Similar to the effects of the miR-92a mimics, knockdown of MKK4 inhibited the activation of JNK/c-Jun signaling and the production of TNF-α and IL-6. In conclusion, we have demonstrated that TLR-mediated miR-92a reduction feedback enhances TLR-triggered production of inflammatory cytokines in macrophages, thus outlining new mechanisms for fine-tuning the TLR-triggered inflammatory response.

Prooncogenic factors miR-23b and miR-27b are regulated by Her2/Neu, EGF, and TNF-α in breast cancer

miRNAs (miR) are a critical class of small (21-25 nucleotides) noncoding endogenous RNAs implicated in gene expression regulation. We identified miR-23b and miR-27b as miRNAs that are highly upregulated in human breast cancer. We found that engineered knockdown of miR-23b and miR-27b substantially repressed breast cancer growth. Nischarin (NISCH) expression was augmented by knockdown of miR-23b as well as miR-27b. Notably, these miRNAs and Nischarin were inversely expressed in human breast cancers, underscoring their biologic relevance. We showed the clinical relevance of the expression of these miRNAs and showed that high expression of miR-23b and miR-27b correlates with poor outcome in breast cancer. Moreover, intraperitoneally delivered anti-miR-27b restored Nischarin expression and decreased tumor burden in a mouse xenograft model of human mammary tumor. Also, we report for the first time that HER2/neu (ERBB2), EGF, and TNF-α promote miR-23b/27b expression through the AKT/NF-κB signaling cascade. Nischarin was found to regulate miR-27b/23b expression through a feedback loop mechanism by suppressing NF-κB phosphorylation. Because anti-miR-27b compounds that suppress miR-27b inhibit tumor growth, the anti-miR-27b seems to be a good candidate for the development of new antitumor therapies.

MicroRNAs in the regulation of TLR and RIG-I pathways

The innate immune system recognizes invading pathogens through germline-encoded pattern recognition receptors (PRRs), which elicit innate antimicrobial and inflammatory responses and initiate adaptive immunity to control or eliminate infection. Toll-like receptors (TLRs) and retinoic acid-inducible gene I (RIG-I) are the key innate immune PRRs and are tightly regulated by elaborate mechanisms to ensure a beneficial outcome in response to foreign invaders. Although much of the focus in the literature has been on the study of protein regulators of inflammation, microRNAs (miRNAs) have emerged as important controllers of certain features of the inflammatory process. Several miRNAs are induced by TLR and RIG-I activation in myeloid cells and act as feedback regulators of TLR and RIG-I signaling. In this review, we comprehensively discuss the recent understanding of how miRNA networks respond to TLR and RIG-I signaling and their role in the initiation and termination of inflammatory responses. Increasing evidence also indicates that both virus-encoded miRNAs and cellular miRNAs have important functions in viral replication and host anti-viral immunity.

Set9, NF-κB, and microRNA-21 mediate berberine-induced apoptosis of human multiple myeloma cells

AIM

To investigate the mechanisms by which berberine suppressed the proliferation of human multiple myeloma cells.

METHODS

Human U266 multiple myeloma cell line was tested. Cell proliferation, apoptosis, ultramicrostructure and secretion function were examined using Cell Counting Kit-8 (CCK8), flow cytometry (FCM), electron and fluorescence microscopy, as well as ELISA assay. The microRNAs (miRs) and transcription factors in U266 cells were detected using arrays and verified by qRT-PCR. EMSA and luciferase assays were used to verify the p65-dependent transactivation of miR-21 gene.

RESULTS

Treatment of U266 cells with berberine (40-160 μmol/L) suppressed cell proliferation and IL-6 secretion in dose- and time-dependent manners. Meanwhile, berberine dose-dependently induced ROS generation, G(2)/M phase arrest and apoptosis in U266 cells, and decreased the levels of miR-21 and Bcl-2. Overexpression of miR-21 counteracted berberine-induced suppression of cell proliferation and IL-6 secretion. In U266 cells treated with berberine (80 μmol/L), the activity of NF-κB was decreased by approximately 50%, followed by significant reduction of miR-21 level. berberine (80-160 μmol/L) increased the level of Set9 (lysine methyltransferase) by more than 2-fold, caused methylation of the RelA subunit, which inhibited NF-κB nuclear translocation and miR-21 transcription. In U266 cells treated with berberine (80 μmol/L), knockdown of Set9 with siRNAs significantly increased NF-κB protein level accompanying with a partial recovery of proliferation.

CONCLUSION

In U266 cells, berberine suppresses NF-κB nuclear translocation via Set9-mediated lysine methylation, leads to decrease in the levels miR21 and Bcl-2, which induces ROS generation and apoptosis.

Induction of differentiation-specific miRNAs in TPA-induced myeloid leukemia cells through MEK/ERK activation

Cellular microRNAs (miRNAs) are pivotal regulators involved in various biological processes through the post-transcriptional regulation of gene expression. Signaling pathways are extensively activated during 12-O-Tetradecanoylphorbol-13-acetate (TPA)-induced differentiation of human leukemia cells, but the modulation of miRNA expression and processing in this context has yet to be fully explored. In this study, we comprehensively analyzed 10 miRNAs that are consistently upregulated during TPA-induced differentiation of various leukemia cell lines by employing microarray technology. The upregulation of these miRNAs was further verified by quantitative RT-PCR, and, markedly, a subset of the miRNAs was found to be induced via the MEK/ERK signaling pathway using TPA and specific pharmacological inhibitors. Moreover, immunoblotting and quantitative RT-PCR analysis demonstrated that the expression levels of key miRNA processing machineries (i.e., Drosha, Dicer, Ago1 and Ago2) were not induced in this context, but the transcription of the miRNA products was triggered by MEK/ERK activation. Therefore, we identified the unique miRNAs that respond to TPA treatment in leukemia cells and demonstrated the essential role of the MEK/ERK signaling pathway in the induction of these miRNA transcripts.

MicroRNAs in cancer diagnosis and therapy: from bench to bedside

Epigenetic changes, such as DNA methylation and histone modifications, regulate gene expression. It is speculated that investigating the fundamental epigenetic mechanisms and their gene regulation will promote a better understanding of cancer development. The idea of epigenetic modification has been extended to microRNAs (miRs). MiRs are single-stranded RNA molecules, about 19-25 ribonucleotides in length, which regulate gene expression post-transcriptionally and can act as tumor suppressors or oncogenes. We review the most recent findings related to their mechanisms of action, the modification of miR expression, and their relationship to cancer. We also discuss the potential application of miRs in the clinical setting, such as for biomarkers and therapy.

Mechanical stretch modulates microRNA 21 expression, participating in proliferation and apoptosis in cultured human aortic smooth muscle cells

Objectives

Stretch affects vascular smooth muscle cell proliferation and apoptosis, and several responsible genes have been proposed. We tested whether the expression of microRNA 21 (miR-21) is modulated by stretch and is involved in stretch-induced proliferation and apoptosis of human aortic smooth muscle cells (HASMCs).

Methods and Results

RT-PCR revealed that elevated stretch (16% elongation, 1 Hz) increased miR-21 expression in cultured HASMCs, and moderate stretch (10% elongation, 1 Hz) decreased the expression. BrdU incorporation assay and cell counting showed miR-21 involved in the proliferation of HASMCs mediated by stretch, likely by regulating the expression of p27 and phosphorylated retinoblastoma protein (p-Rb). FACS analysis revealed that the complex of miR-21 and programmed cell death protein 4 (PDCD4) participated in regulating apoptosis with stretch. Stretch increased the expression of primary miR-21 and pre-miR-21 in HASMCs. Electrophoretic mobility shift assay (EMSA) demonstrated that stretch increased NF-κB and AP-1 activities in HASMCs, and blockade of AP-1 activity by c-jun siRNA significantly suppressed stretch-induced miR-21 expression.

Conclusions

Cyclic stretch modulates miR-21 expression in cultured HASMCs, and miR-21 plays important roles in regulating proliferation and apoptosis mediated by stretch. Stretch upregulates miR-21 expression at least in part at the transcription level and AP-1 is essential for stretch-induced miR-21 expression.

Transcriptional and translational regulation of cytokine signaling in inflammatory β-cell dysfunction and apoptosis

Disease is conventionally viewed as the chaotic inappropriate outcome of deranged tissue function resulting from aberrancies in cellular processes. Yet the patho-biology of cellular dysfunction and death encompasses a coordinated network no less sophisticated and regulated than maintenance of homeostatic balance. Cellular demise is far from passive subordination to stress but requires controlled coordination of energy-requiring activities including gene transcription and protein translation that determine the graded transition between defensive mechanisms, cell cycle regulation, dedifferentiation and ultimately to the activation of death programmes. In fact, most stressors stimulate both homeostasis and regeneration on one hand and impairment and destruction on the other, depending on the ambient circumstances. Here we illustrate this bimodal ambiguity in cell response by reviewing recent progress in our understanding of how the pancreatic β cell copes with inflammatory stress by changing gene transcription and protein translation by the differential and interconnected action of reactive oxygen and nitric oxide species, microRNAs and posttranslational protein modifications.

MicroRNA-21 blocks abdominal aortic aneurysm development and nicotine-augmented expansion

Identification and treatment of abdominal aortic aneurysm (AAA) remains among the most prominent challenges in vascular medicine. MicroRNAs are crucial regulators of cardiovascular pathology and represent possible targets for the inhibition of AAA expansion. We identified microRNA-21 (miR-21) as a key modulator of proliferation and apoptosis of vascular wall smooth muscle cells during development of AAA in two established murine models. In both models (AAA induced by porcine pancreatic elastase or infusion of angiotensin II), miR-21 expression increased as AAA developed. Lentiviral overexpression of miR-21 induced cell proliferation and decreased apoptosis in the aortic wall, with protective effects on aneurysm expansion. miR-21 overexpression substantially decreased expression of the phosphatase and tensin homolog (PTEN) protein, leading to increased phosphorylation and activation of AKT, a component of a pro-proliferative and antiapoptotic pathway. Systemic injection of a locked nucleic acid-modified antagomir targeting miR-21 diminished the pro-proliferative impact of down-regulated PTEN, leading to a marked increase in the size of AAA. Similar results were seen in mice with AAA augmented by nicotine and in human aortic tissue samples from patients undergoing surgical repair of AAA (with more pronounced effects observed in smokers). Modulation of miR-21 expression shows potential as a new therapeutic option to limit AAA expansion and vascular disease progression.

MicroRNAs in inflammatory bowel disease - pathogenesis, diagnostics and therapeutics

The pathogenesis of inflammatory bowel disease (IBD) is complex and largely unknown. Until recently, research has focused on the study of protein regulators in inflammation to reveal the cellular and molecular networks in the pathogenesis of IBD. However, in the last few years, new and promising insights have been generated from studies describing an association between an altered expression of a specific class of non-coding RNAs, called microRNAs (miRs or miRNAs) and IBD. The short (approximately 22 nucleotides), endogenous, single-stranded RNAs are evolutionary conserved in animals and plants, and regulate specific target mRNAs at the post-transcriptional level. MiRNAs are involved in several biological processes, including development, cell differentiation, proliferation and apoptosis. Furthermore, it is estimated that miRNAs may be responsible for regulating the expression of nearly one-third of the genes in the human genome. Thus, miRNA deregulation often results in an impaired cellular function, and a disturbance of downstream gene regulation and signaling cascades, suggesting their implication in disease etiology. Despite the identification of more than 1900 mature human miRNAs, very little is known about their biological functions and functional targets. Recent studies have identified dysregulated miRNAs in tissue samples of IBD patients and have demonstrated similar differences in circulating miRNAs in the serum of IBD patients. Thus, there is great promise that miRNAs will aid in the early diagnosis of IBD, and in the development of personalized therapies. Here, we provide a short review of the current state-of-the-art of miRNAs in IBD pathogenesis, diagnostics and therapeutics.

miR-125b Is an adhesion-regulated microRNA that protects mesenchymal stem cells from anoikis

Mesenchymal stem cells (MSCs) have the capacity for multilineage differentiation and are being explored as a source for stem cell-based therapies. Previous studies have shown that adhesion to extracellular matrix plays a critical role in guiding MSC differentiation to distinct lineages. Here, we conducted a focused screen of microRNAs to reveal one microRNA, miR-125b, whose expression changes as a function of cell adhesion. miR-125b expression was upregulated by limiting cell-matrix adhesion using micropatterned substrates, knocking down beta5 integrin or placing cells in suspension culture. Interestingly, we noted that suspending human MSCs (hMSCs) did not induce substantial apoptosis (anoikis) as is typically observed in adherent cells. Although miR-125b appeared to have some effects on hMSC differentiation, we demonstrated a striking role for miR-125b in protecting hMSCs from anoikis. Knockdown of miR-125b increased anoikis while expressing a mimic protected cells. Mechanistic studies demonstrated that miR-125b protected against anoikis by increasing ERK phosphorylation and by suppressing p53. Lastly, we found that miR-125b expression is quite limited in endothelial cells and mouse embryonic fibroblasts (MEFs). The rapid anoikis normally observed in endothelial cells was antagonized by transfection of a miR-125b mimic, suggesting that miR-125b can confer resistance to anoikis in multiple cell types. We also found that endogenous miR-125b was significantly upregulated during reprogramming of MEFs to induced pluripotent cells, suggesting that miR-125b expression may be associated with stem cell populations. Collectively, these observations demonstrate a novel link between cell-matrix adhesion, miR-125b expression, and a stem cell-specific survival program triggered in adhesion-limited contexts such as might occur in early development and wound healing.

MicroRNAs, new effectors and regulators of NF-κB

Since its discovery 25 years ago, nuclear factor-κB (NF-κB) has emerged as a transcription factor that controls diverse biological functions, ranging from inflammation to learning and memory. Activation of NF-κB initiates an elaborate genetic program. Some of the NF-κB-driven genes do not encode proteins but rather are precursors to microRNAs. These microRNAs play important roles in the regulation of the inflammatory process, some being inhibitory and others activating. Here, we discuss both the regulation of their expression and the function of some of these non-coding RNA genes. We also include a personal discussion of how NF-κB was first discovered.

Inhibitory effects of microRNA 19b in hepatic stellate cell-mediated fibrogenesis

Hepatic stellate cell (HSC) activation is a pivotal event in initiation and progression of hepatic fibrosis and a major contributor to collagen deposition driven by transforming growth factor beta (TGF-β). MicroRNAs (miRs), small noncoding RNAs modulating messenger RNA (mRNA) and protein expression, have emerged as key regulatory molecules in chronic liver disease. We investigated differentially expressed miRs in quiescent and activated HSCs to identify novel regulators of profibrotic TGF-β signaling. miR microarray analysis was performed on quiescent and activated rat HSCs. Members of the miR-17-92 cluster (19a, 19b, 92a) were significantly down-regulated in activated HSCs. Because miR 19b showed the highest fold-change of the cluster members, activated HSCs were transfected with miR 19b mimic or negative control and TGF-β signaling and HSC activation assessed. miR 19b expression was determined in fibrotic rat and human liver specimens. miR 19b mimic negatively regulated TGF-β signaling components demonstrated by decreased TGF-β receptor II (TGF-βRII) and SMAD3 expression. Computational prediction of miR 19b binding to the 3' untranslated region of TGF-βRII was validated by luciferase reporter assay. Inhibition of TGF-β signaling by miR 19b was confirmed by decreased expression of type I collagen and by blocking TGF-β-induced expression of α1(I) and α2(I) procollagen mRNAs. miR 19b blunted the activated HSC phenotype by morphological assessment and decreased smooth muscle α-actin expression. Additionally, miR 19b expression was markedly diminished in fibrotic rat liver compared with normal liver; similarly, miR 19b expression was markedly down-regulated in fibrotic compared with normal human livers.

CONCLUSION

miR 19b is a novel regulator of TGF-β signaling in HSCs, suggesting a potential therapeutic approach for hepatic fibrosis.

Changes in microRNA expression contribute to pancreatic β-cell dysfunction in prediabetic NOD mice

During the initial phases of type 1 diabetes, pancreatic islets are invaded by immune cells, exposing β-cells to proinflammatory cytokines. This unfavorable environment results in gene expression modifications leading to loss of β-cell functions. To study the contribution of microRNAs (miRNAs) in this process, we used microarray analysis to search for changes in miRNA expression in prediabetic NOD mice islets. We found that the levels of miR-29a/b/c increased in islets of NOD mice during the phases preceding diabetes manifestation and in isolated mouse and human islets exposed to proinflammatory cytokines. Overexpression of miR-29a/b/c in MIN6 and dissociated islet cells led to impairment in glucose-induced insulin secretion. Defective insulin release was associated with diminished expression of the transcription factor Onecut2, and a consequent rise of granuphilin, an inhibitor of β-cell exocytosis. Overexpression of miR-29a/b/c also promoted apoptosis by decreasing the level of the antiapoptotic protein Mcl1. Indeed, a decoy molecule selectively masking the miR-29 binding site on Mcl1 mRNA protected insulin-secreting cells from apoptosis triggered by miR-29 or cytokines. Taken together, our findings suggest that changes in the level of miR-29 family members contribute to cytokine-mediated β-cell dysfunction occurring during the initial phases of type 1 diabetes.

miR-21 is targeted by omega-3 polyunsaturated fatty acid to regulate breast tumor CSF-1 expression

Increasing evidence shows the beneficial effects of fish oil on breast cancer growth and invasion in vitro and in animal models. Expression of CSF-1 (colony stimulating factor-1) by breast cancer cells acts as potent activator of malignancy and metastasis. In this report, we used two human breast cancer cell lines, MDA-MB-231 and MCF-7, to show that the bioactive fish oil component DHA (docosahexaenoic acid) inhibits expression of CSF-1 and its secretion from these cancer cells. We found that the tumor suppressor protein PTEN regulates CSF-1 expression through PI 3 kinase/Akt signaling via a transcriptional mechanism. The enhanced abundance of microRNA-21 (miR-21) in breast cancer cells contributes to the growth and metastasis. Interestingly, DHA significantly inhibited expression of miR-21. miR-21 Sponge, which derepresses the miR-21 targets, markedly decreased expression of CSF-1 and its secretion. Furthermore, miR-21-induced upregulation of CSF-1 mRNA and its transcription were prevented by expression of PTEN mRNA lacking 3'-untranslated region (UTR) and miR-21 recognition sequence. Strikingly, miR-21 reversed DHA-forced reduction of CSF-1 expression and secretion. Finally, we found that expression of miR-21 as well as CSF-1 was significantly attenuated in breast tumors of mice receiving a diet supplemented with fish oil. Our results reveal a novel mechanism for the therapeutic function of fish oil diet that blocks miR-21, thereby increasing PTEN levels to prevent expression of CSF-1 in breast cancer.

A miR-19 regulon that controls NF-κB signaling

Fine-tuning of inflammatory responses by microRNAs (miRNAs) is complex, as they can both enhance and repress expression of pro-inflammatory mediators. In this study, we investigate inflammatory responses following global miRNA depletion, to better define the overall contribution of miRNAs to inflammation. We demonstrate that miRNAs positively regulate Toll-like receptor signaling using inducible Dicer1 deletion and global miRNA depletion. We establish an important contribution of miR-19b in this effect, which potentiates nuclear factor-κB (NF-κB) activity in human and mouse cells. Positive regulation of NF-κB signaling by miR-19b involves the coordinated suppression of a regulon of negative regulators of NF-κB signaling (including A20/Tnfaip3, Rnf11, Fbxl11/Kdm2a and Zbtb16). Transfection of miR-19b mimics exacerbated the inflammatory activation of rheumatoid arthritis primary fibroblast-like synoviocytes, demonstrating its physiological importance in the pathology of this disease. This study constitutes, to our knowledge, the first description of a miR-19 regulon that controls NF-κB signaling, and suggests that targeting this miRNA and linked family members could regulate the activity of NF-κB signaling in inflammation.

microRNA-21 governs TORC1 activation in renal cancer cell proliferation and invasion

Metastatic renal cancer manifests multiple signatures of gene expression. Deviation in expression of mature miRNAs has been linked to human cancers. Importance of miR-21 in renal cell carcinomas is proposed from profiling studies using tumor tissue samples. However, the role of miR-21 function in causing renal cancer cell proliferation and invasion has not yet been shown. Using cultured renal carcinoma cells, we demonstrate enhanced expression of mature miR-21 along with pre-and pri-miR-21 by increased transcription compared to normal proximal tubular epithelial cells. Overexpression of miR-21 Sponge to quench endogenous miR-21 levels inhibited proliferation, migration and invasion of renal cancer cells. In the absence of mutation in the PTEN tumor suppressor gene, PTEN protein levels are frequently downregulated in renal cancer. We show that miR-21 targets PTEN mRNA 3'untranslated region to decrease PTEN protein expression and augments Akt phosphorylation in renal cancer cells. Downregulation of PTEN as well as overexpression of constitutively active Akt kinase prevented miR-21 Sponge-induced inhibition of renal cancer cell proliferation and migration. Moreover, we show that miR-21 Sponge inhibited the inactivating phosphorylation of the tumor suppressor protein tuberin and attenuated TORC1 activation. Finally, we demonstrate that expression of constitutively active TORC1 attenuated miR-21 Sponge-mediated suppression of proliferation and migration of renal cancer cells. Our results uncover a layer of post-transcriptional regulation of PTEN by transcriptional activation of miR-21 to force the canonical oncogenic Akt/TORC1 signaling conduit to drive renal cancer cell proliferation and invasion.

Temporal expression of microRNA cluster miR-17-92 regulates effector and memory CD8+ T-cell differentiation

MicroRNAs are important regulators of various developmental and physiological processes. However, their roles in the CD8(+) T-cell response are not well understood. Using an acute viral infection model, we show that microRNAs of the miR-17-92 cluster are strongly induced after T-cell activation, down-regulated after clonal expansion, and further silenced during memory development. miR-17-92 promotes cell-cycle progression of effector CD8(+) T cells, and its expression is critical to the rapid expansion of these cells. However, excessive miR-17-92 expression enhances mammalian target of rapamycin (mTOR) signaling and strongly skews the differentiation toward short-lived terminal effector cells. Failure to down-regulate miR-17-92 leads to a gradual loss of memory cells and defective central memory cell development. Therefore, our results reveal a temporal expression pattern of miR-17-92 by antigen-specific CD8(+) T cells during viral infection, the precise control of which is critical to the effector expansion and memory differentiation of CD8(+) T cells.

miR-27b targets KSRP to coordinate TLR4-mediated epithelial defense against Cryptosporidium parvum infection

Cryptosporidium is a protozoan parasite that infects the gastrointestinal epithelium and causes a diarrheal disease. Toll-like receptor (TLR)- and NF-κB-mediated immune responses from epithelial cells, such as production of antimicrobial peptides and generation of reactive nitrogen species, are important components of the host's defense against cryptosporidial infection. Here we report data demonstrating a role for miR-27b in the regulation of TLR4/NF-κB-mediated epithelial anti-Cryptosporidium parvum responses. We found that C. parvum infection induced nitric oxide (NO) production in host epithelial cells in a TLR4/NF-κB-dependent manner, with the involvement of the stabilization of inducible NO synthase (iNOS) mRNA. C. parvum infection of epithelial cells activated NF-κB signaling to increase transcription of the miR-27b gene. Meanwhile, downregulation of KH-type splicing regulatory protein (KSRP) was detected in epithelial cells following C. parvum infection. Importantly, miR-27b targeted the 3′-untranslated region of KSRP, resulting in translational suppression. C. parvum infection decreased KSRP expression through upregulating miR-27b. Functional manipulation of KSRP or miR-27b caused reciprocal alterations in iNOS mRNA stability in infected cells. Forced expression of KSRP and inhibition of miR-27b resulted in an increased burden of C. parvum infection. Downregulation of KSRP through upregulating miR-27b was also detected in epithelial cells following LPS stimulation. These data suggest that miR-27b targets KSRP and modulates iNOS mRNA stability following C. parvum infection, a process that may be relevant to the regulation of epithelial anti-microbial defense in general.

MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression at the posttranscriptional level. Accumulating data indicate that miRNAs are an essential part of the complex regulatory networks that control various cellular processes, including host antimicrobial immune responses. Toll-like receptors (TLRs) play an essential role in the activation of innate immunity by recognizing specific patterns of microbial components and activating downstream intracellular signaling pathways, including NF-κB. However, the role of miRNAs in the regulation of TLR/NF-κB-mediated epithelial antimicrobial defense is still unclear. Cryptosporidium is a protozoan parasite that infects the gastrointestinal epithelium in humans. Here, we show that KSRP, an RNA-binding protein and a key mediator of mRNA decay, is a target for miR-27b. Infection by Cryptosporidium parvum activates TLR4/NF-κB signaling and increases miR-27b expression, causing a suppression of KSRP in infected host epithelial cells. Functionally, downregulation of KSRP stabilizes iNOS mRNA and promotes epithelial production of nitric oxide, a molecule with antimicrobial activity. Therefore, miR-27b confers TLR4/NF-κB-mediated epithelial cell anti-Cryptosporidium parvum defense though regulating KSRP. Our study provides a new area of exploration for fine-tuning TLR/NF-κB-mediated host reactions in response to microbial challenge.

miRNA-125b regulates TNF-α production in CD14+ neonatal monocytes via post-transcriptional regulation

Neonates, although deficient in cell immunity, frequently reveal sepsis with augmented proinflammatory reactions. Here, we found that neonatal monocytes produced significantly higher TNF-α mRNA and protein than adult monocytes. Assessment of the transcriptional factor found no significant difference of NF-κB p65 level between neonatal and adult monocytes. Addition of Act D to access the half-life of TNF-α mRNA revealed no significant difference of the LPS-induced TNF-α mRNA half-life between them, whereas CHX increased neonatal TNF-α mRNA significantly. This suggests that a post-transcriptional mechanism involves the augmentation of TNF-α production by neonatal monocytes. To examine whether miRNA was involved in the post-transcriptional regulation, differential displays of miRNA array between neonatal and adult MNCs were performed, along with the discovery of hsa-miR-103, hsa-miR-125b, hsa-miR-130a, hsa-miR-454-3p, and hsa-miR-542-3p, which were greater than a twofold decrease or increase after LPS treatment for 4 h. The functional validation identified that miR-125b decreased significantly in association with higher TNF-α expression by neonatal monocytes after LPS stimulation. Transfection of the miR-125b precursor into neonatal monocytes significantly repressed the TNF-α mRNA and protein expression, suggesting that miR-125b negatively regulates TNF-α expression in neonatal monocytes. Modulation of miRNA expression may be used to regulate TNF-α production in newborns with altered proinflammatory reactions.

MiR-125 in normal and malignant hematopoiesis

MiR-125 is a highly conserved microRNA throughout many different species from nematode to humans. In humans, there are three homologs (hsa-miR-125b-1, hsa-miR-125b-2 and hsa-miR-125a). Here we review a recent research on the role of miR-125 in normal and malignant hematopoietic cells. Its high expression in hematopoietic stem cells (HSCs) enhances self-renewal and survival. Its expression in specific subtypes of myeloid and lymphoid leukemias provides resistance to apoptosis and blocks further differentiation. A direct oncogenic role in the hematopoietic system has recently been demonstrated by several mouse models. Targets of miR-125b include key proteins regulating apoptosis, innate immunity, inflammation and hematopoietic differentiation.

MicroRNA-130a represses transcriptional activity of aquaporin 4 M1 promoter

Aquaporins (AQPs) are transmembrane water channels ubiquitously expressed in mammalian tissues. They play prominent roles in maintaining cellular fluid balance. Although expression of AQP1, -3, -4, -5, -8, -9, and -11 has been reported in the central nervous system, it is AQP4 that is predominately expressed. Its importance in fluid regulation in cerebral edema conditions has been highlighted in several studies, and we have also shown that translational regulation of AQP4 by miR-320a could prove to be useful in infarct volume reduction in middle cerebral artery occluded rat brain. There is evidence for the existence of two AQP4 transcripts (M1 and M23) in the brain arising from two alternative promoters. Because the AQP4 M1 isoform exhibits greater water permeability, in this study, we explored the possibility of microRNA-based transcriptional regulation of the AQP4 M1 promoter. Using RegRNA software, we identified 34 microRNAs predicted to target the AQP4 M1 promoter region. MicroRNA profiling, quantitative stem-loop PCR, and luciferase reporter assays revealed that miR-130a, -152, -668, -939, and -1280, which were highly expressed in astrocytes, could regulate the promoter activity. Of these, miR-130a was identified as a strong transcriptional repressor of the AQP4 M1 isoform. In vivo studies revealed that LNA(TM) anti-miR-130a could up-regulate the AQP4 M1 transcript and its protein to bring about a reduction in cerebral infarct and promote recovery.

Sulindac inhibits tumor cell invasion by suppressing NF-κB-mediated transcription of microRNAs

Non-steroidal anti-inflammatory drugs (NSAIDs) have been widely reported to display strong efficacy for cancer chemoprevention, although their mechanism of action is poorly understood. The most well-documented effects of NSAIDs include inhibition of tumor cell proliferation and induction of apoptosis, but their effect on tumor cell invasion has not been well studied. Here, we show that the NSAID, sulindac sulfide (SS) can potently inhibit the invasion of human MDA-MB-231 breast and HCT116 colon tumor cells in vitro at concentrations less than those required to inhibit tumor cell growth. To study the molecular basis for this activity, we investigated the involvement of microRNA (miRNA). A total of 132 miRNAs were found to be altered in response to SS treatment, including miR-10b, miR-17, miR-21 and miR-9, which have been previously implicated in tumor invasion and metastasis. We confirmed that these miRNA can stimulate tumor cell invasion and show that SS can attenuate their invasive effects by downregulating their expression. Employing luciferase and chromatin immunoprecipitation assays, NF-κB was found to bind the promoters of all four miRNAs to suppress their expression at the transcriptional level. We show that SS can inhibit the translocation of NF-κB to the nucleus by decreasing the phosphorylation of IKKβ and IκB. Analysis of the promoter sequences of the miRNAs suppressed by SS revealed that 81 of 115 sequences contained NF-κB-binding sites. These results show that SS can inhibit tumor cell invasion by suppressing NF-κB-mediated transcription of miRNAs.