MicroRNA miR-155 Affects Antiviral Effector and Effector Memory CD8 T Cell Differentiation

MicroRNAs are key regulators of the immune response, but their role in CD8 T cell differentiation in vivo is not known. We show that miR-155 is important in both effector and memory antiviral CD8 T cell responses. Without miR-155, there was a weaker effector response and a skewing toward memory precursor cells. At the memory stage, miR-155-deficient CD8 T cells preferentially differentiated into central memory cells and were capable of mounting a potent secondary response.     

A Novel Transgenic Mouse Line for Tracing MicroRNA-155-5p Activity In Vivo

MicroRNA-155 (miR-155) plays significant role in various physiological processes involving both innate and adaptive immunity. miR-155 expression level changes dynamically during various immune responses. However, current approaches for miR-155 detection at the RNA level do not precisely reflect the real-time activity. Herein, we generated a transgenic mouse line (R26-DTR-155T) for determination of miR-155-5p activity in vivo by inserting miR-155-5p target sequence downstream of a reporter transgene comprising Diphtheria Toxin Receptor and TagBlue fluorescence protein. Using this approach, R26-DTR-155T mice were able to measure variation in levels of miR-155-5p activity in specific cell types of interest. The DTR expression levels were inversely correlated with the endogenous miR-155 expression pattern as detected by quantitative RT-PCR. Our data demonstrate a novel transgenic mouse line which could be useful for tracing miR-155-5p activity in specific cell types through measurement of miR-155-5p activity at single cell level.     

A functional MicroRNA-155 ortholog encoded by the oncogenic Marek's disease virus

Kaposi's sarcoma-associated herpesvirus-encoded microRNA (miRNA) MiR-K12-11 was recently shown to be a functional ortholog of miR-155, a miRNA that plays a major role in lymphoid malignancies and the modulation of immune responses. Here we show that miR-M4, encoded by the highly oncogenic Marek's disease virus of chickens, shares common targets with miR-155 and thus is also a functional ortholog of miR-155, the first one identified in an alphaherpesvirus. The observation that two distinct oncogenic herpesviruses associated with distinct types of lymphomas in different species encode functional miR-155 orthologs suggested the importance of this miRNA in regulatory pathways and the biology of lymphomagenesis.     

miR-155 promotes cutaneous wound healing through enhanced keratinocytes migration by MMP-2

Inflammation, re-epithelization and tissue remodeling are three essential steps during wound healing. The re-epithelization process plays the most important role which mainly involves keratinocyte proliferation and migration. miR-155 has been reported to participate in cell migration and transformation, however, its function in skin wound healing is largely unknown. Here we hypothesize that overexpression of miR-155 at wound edges could accelerate wound healing mediated by enhanced keratinocyte migration. To test this hypothesis, direct local injection of miR-155 expression plasmid to wound edges was conducted to overexpress miR-155 in vivo. Results shown that miR-155 significantly promoted wound healing and re-epithelization compared to control, while did not affect wound contraction. Also, miR-155 overexpression accelerated primarily cultured keratinocyte migration in vitro, but had no effect on cell proliferation. Importantly, western blot analysis shown that MMP-2 was significantly upregulated whiles its inhibitor TIMP-1 downregulated after miR-155 treatment. Moreover, the use of ARP-101, an MMP-2 inhibitor, effectively attenuated the accelerative effects on cell migration induced by miR-155. Taken together, our results suggest that miR-155 has the promote effect on wound healing that is probably mediated by accelerating keratinocyte migration via upregulated MMP-2 level. This study provides a rationale for the therapeutic effect of miR-155 on wound healing.     

miR-155 gene: A typical multifunctional microRNA

In the last years small RNA molecules, i.e. microRNA (miRNA) encoded by miR genes, have been found to play a crucial role in regulating gene expression of a considerable part of plant's and animal's genome. Here, we report the essential information on biogenesis of miRNAs and recent evidence on their important role in human diseases. Emphasis has been given to miR-155, since this molecule represents a typical multifunctional miRNA. Recent data indicate that miR-155 has distinct expression profiles and plays a crucial role in various physiological and pathological processes such as haematopoietic lineage differentiation, immunity, inflammation, cancer, and cardiovascular diseases. Moreover, miR-155 has been found to be implicated in viral infections, particularly in those caused by DNA viruses. The available experimental evidence indicating that miR-155 is over expressed in a variety of malignant tumors allows us to include this miRNA in the list of genes of paramount importance in cancer diagnosis and prognosis. Exogenous molecular control in vivo of miR-155 expression could open up new ways to restrain malignant growth and viral infections, or to attenuate the progression of cardiovascular diseases.     

miR-155-5p regulates mesenchymal stem cell osteogenesis and proliferation by targeting GSK3B in steroid-associated osteonecrosis

microRNAs (miRNAs) have recently been recognized as playing an important role in bone-associated diseases. This study investigated whether the reduced miR-155-5p in steroid-associated osteonecrosis of the femoral head (ONFH) attenuated osteogenic differentiation and cell proliferation by targeting GSK3B. Bone marrow was collected from the proximal femurs of patients with steroid-associated ONFH (n = 10) and patients with new femoral neck fracture (n = 10) and mesenchymal stem cells (MSCs) were isolated. The expression profile, the biological function of miR-155-5p, and the interaction between miR-155-5p and GSK3B were investigated by cell viability measurement, western blot, real-time polymerase chain reaction, luciferase reporter assay, and Alizarin Red S (ARS) staining of MSCs. The MSCs that were obtained from the femoral neck fracture group and from the steroid-associated ONFH group were transfected with or without miR-155-5p. We found that, in ONFH samples, the level of mature miR-155-5p was significantly lower than that of control samples. By inhibiting GSK3B, miR-155-5p promoted the nuclear translocation of β-catenin, increased the expression of osteogenesis-related genes, and facilitated the proliferation and differentiation of MSCs. Restoring the expression of GSK3B in MSCs partially reversed the effect of miR-155-5p. These findings suggest that reduced miR-155-5p in steroid-associated ONFH attenuates osteogenic differentiation and cell proliferation by increased levels of GSK3B and inhibition of Wnt signaling.     

Autocrine and paracrine modulation of microRNA-155 expression by globular adiponectin in RAW 264.7 macrophages: Involvement of MAPK/NF-κB pathway

Adiponectin, a hormone produced from adipose tissue, regulates various biological responses, including inflammation and many metabolic processes. MicroRNAs control expression of diverse target genes and various physiological responses. Many of these responses are commonly regulated by adiponectin. However, effects of adiponectin on microRNAs regulation are largely unknown. Herein we demonstrated that globular adiponectin induces increase in miR-155 expression, which plays an important role in inflammatory response, in RAW 264.7 macrophages. We further showed that this effect was modulated by and MANK/NF-κB dependent mechanisms. These results suggest that miR-155 would be a novel promising target mediating adiponectin-induced various biological responses.     

Improved repair of dermal wounds in mice lacking microRNA‐155

Wound healing is a well-regulated but complex process that involves haemostasis, inflammation, proliferation and maturation. Recent reports suggest that microRNAs (miRs) play important roles in dermal wound healing. In fact, miR deregulation has been linked with impaired wound repair. miR-155 has been shown to be induced by inflammatory mediators and plays a central regulatory role in immune responses. We have investigated the potential role of miR-155 in wound healing. By creating punch wounds in the skin of mice, we found an increased expression of miR-155 in wound tissue when compared with healthy skin. Interestingly, analysis of wounds of mice lacking the expression of miR-155 (miR-155^−/−) revealed an increased wound closure when compared with wild-type animals. Also, the accelerated wound closing correlated with elevated numbers of macrophages in wounded tissue. Gene expression analysis of wounds tissue and macrophages isolated from miR-155^−/− mice that were treated with interleukin-4 demonstrated an increased expression of miR-155 targets (BCL6, RhoA and SHIP1) as well as, the finding in inflammatory zone-1 (FIZZ1) gene, when compared with WT mice. Moreover, the up-regulated levels of FIZZ1 in the wound tissue of miR-155^−/− mice correlated with an increased deposition of type-1 collagens, a phenomenon known to be beneficial in wound closure. Our data indicate that the absence of miR-155 has beneficial effects in the wound healing process.     

miR-155在常见病原微生物感染中的研究进展

microRNAs(miRNAs)是一类长度为17~25 nt,进化上保守的非编码单链小RNA,成熟的miRNAs通过碱基互补配对的方式识别靶mRNA,并根据互补程度介导沉默复合体降解靶mRNA或者阻遏靶mRNA的翻译。miR-155是miRNAs家族中的典型代表,其不仅参与调控肿瘤细胞的增殖、分化和凋亡,而且在微生物感染过程及免疫炎症反应中也发挥着重要作用。将对miR-155在常见的几种病原微生物感染过程中发挥的作用做系统综述。     

Argonaute 2 sustains the gene expression program driving human monocytic differentiation of acute myeloid leukemia cells

MicroRNAs are key regulators of many biological processes, including cell differentiation. These small RNAs exert their function assembled in the RNA-induced silencing complexes (RISCs), where members of Argonaute (Ago) family of proteins provide a unique platform for target recognition and gene silencing. Here, by using myeloid cell lines and primary blasts, we show that Ago2 has a key role in human monocytic cell fate determination and in LPS-induced inflammatory response of 1,25-dihydroxyvitamin D₃ (D3)-treated myeloid cells. The silencing of Ago2 impairs the D3-dependent miR-17-5p/20a/106a, miR-125b and miR-155 downregulation, the accumulation of their translational targets AML1, VDR and C/EBPβ and monocytic cell differentiation. Moreover, we show that Ago2 is recruited on miR-155 host gene promoter and on the upstream region of an overlapping antisense lncRNA, determining their epigenetic silencing, and miR-155 downregulation. These findings highlight Ago2 as a new factor in myeloid cell fate determination in acute myeloid leukemia cells.     

miR-155 regulates the proliferation and cell cycle of colorectal carcinoma cells by targeting E2F2

MicroRNAs play important roles in carcinogenesis by negatively regulating the expression of target genes. Here we explore the biological function of miR-155 and the underlying mechanism in colorectal carcinoma. We validate, for the first time, that E2F2 is a direct target of miR-155 using western blot and a luciferase reporter assay and that miR-155 regulates the proliferation and cell cycle of colorectal carcinoma cells by targeting E2F2 using siRNA technology. We also found, for the first, time that E2F2 acts as a tumor suppressor in colorectal carcinoma. Overall, miR-155 plays an important role in colorectal carcinoma tumorigenesis by negative regulation of its targets including E2F2 and may be a potential therapeutic target for colorectal carcinoma treatment.     

MicroRNA-155 targets SMAD2 and modulates the response of macrophages to transforming growth factor-{beta}

Transforming growth factor-beta (TGF-β) is a pleiotropic cytokine with important effects on processes such as fibrosis, angiogenesis, and immunosupression. Using bioinformatics, we identified SMAD2, one of the mediators of TGF-β signaling, as a predicted target for a microRNA, microRNA-155 (miR-155). MicroRNAs are a class of small non-coding RNAs that have emerged as an important class of gene expression regulators. miR-155 has been found to be involved in the regulation of the immune response in myeloid cells. Here, we provide direct evidence of binding of miR-155 to a predicted binding site and the ability of miR-155 to repress SMAD2 protein expression. We employed a lentivirally transduced monocyte cell line (THP1-155) containing an inducible miR-155 transgene to show that endogenous levels of SMAD2 protein were decreased after sustained overexpression of miR-155. This decrease in SMAD2 led to a reduction in both TGF-β-induced SMAD-2 phosphorylation and SMAD-2-dependent activation of the expression of the CAGA(12)LUC reporter plasmid. Overexpression of miR-155 altered the cellular responses to TGF-β by changing the expression of a set of genes that is involved in inflammation, fibrosis, and angiogenesis. Our study provides firm evidence of a role for miR-155 in directly repressing SMAD2 expression, and our results demonstrate the relevance of one of the two predicted target sites in SMAD2 3'-UTR. Altogether, our data uncover an important role for miR-155 in modulating the cellular response to TGF-β with possible implications in several human diseases where homeostasis of TGF-β might be altered.     

Acetylbritannilactone Modulates MicroRNA-155-Mediated Inflammatory Response in Ischemic Cerebral Tissues

Inflammatory responses play a critical role in ischemic brain injury. MicroRNA-155 (miR-155) induces the expression of inflammatory cytokines, and acetylbritannilactone (ABL) exerts potent antiinflammatory actions by inhibiting expression of inflammation-related genes. However, the functions of miR-155 and the actual relationship between ABL and miR-155 in ischemia-induced cerebral inflammation remain unclear. In this study, cerebral ischemia of wild-type (WT) and miR-155^−/− mice was induced by permanent middle cerebral artery occlusion (MCAO). pAd-miR-155 was injected into the lateral cerebral ventricle 24 h before MCAO to induce miR-155 overexpression. MCAO mice and oxygen-glucose deprivation (OGD)-treated BV2 cells were used to examine the effects of ABL and miR-155 overexpression or deletion on the expression of proinflammatory cytokines. We demonstrated that ABL treatment significantly reduced neurological deficits and cerebral infarct volume by inhibiting tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) expression in ischemic cerebral tissue and OGD-treated BV2 cells. Mechanistic studies suggested that the observed decrease in TNF-α and IL-1β expression was attributable to the ABL-induced suppression of the expression of nuclear factor-kappa B (NF-κB) and Toll-like receptor 4 (TLR4). We further found that miR-155 promoted TNF-α and IL-1β expression by upregulating TLR4 and downregulating the expression of suppressor of cytokine signaling 1 (SOCS1) and myeloid differentiation primary response gene 88 (MyD88), while ABL exerted an inhibitory effect on miR-155-mediated gene expression. In conclusion, miR-155 mediates inflammatory responses in ischemic cerebral tissue by modulating TLR4/MyD88 and SOCS1 expression, and ABL exerts its antiinflammatory action by suppressing miR-155 expression, suggesting a novel miR-155-based therapy for ischemic stroke.     

Up-regulation of microRNA-155 in macrophages contributes to increased tumor necrosis factor {alpha} (TNF{alpha}) production via increased mRNA half-life in alcoholic liver disease

Activation of Kupffer cells (KCs) by gut-derived lipopolysaccharide (LPS) and Toll-Like Receptors 4 (TLR4)-LPS-mediated increase in TNFα production has a central role in the pathogenesis of alcoholic liver disease. Micro-RNA (miR)-125b, miR-146a, and miR-155 can regulate inflammatory responses to LPS. Here we evaluated the involvement of miRs in alcohol-induced macrophage activation. Chronic alcohol treatment in vitro resulted in a time-dependent increase in miR-155 but not miR-125b or miR-146a levels in RAW 264.7 macrophages. Furthermore, alcohol pretreatment augmented LPS-induced miR-155 expression in macrophages. We found a linear correlation between alcohol-induced increase in miR-155 and TNFα induction. In a mouse model of alcoholic liver disease, we found a significant increase in both miR-155 levels and TNFα production in isolated KCs when compared with pair-fed controls. The mechanistic role of miR-155 in TNFα regulation was indicated by decreased TNFα levels in alcohol-treated macrophages after inhibition of miR-155 and by increased TNFα production after miR-155 overexpression, respectively. We found that miR-155 affected TNFα mRNA stability because miR-155 inhibition decreased whereas miR-155 overexpression increased TNFα mRNA half-life. Using the NF-κB inhibitors, MG-132 or Bay11-7082, we demonstrated that NF-κB activation mediated the up-regulation of miR-155 by alcohol in KCs. In conclusion, our novel data demonstrate that chronic alcohol consumption increases miR-155 in macrophages via NF-κB and the increased miR-155 contributes to alcohol-induced elevation in TNFα production via increased mRNA stability.