MicroRNA-mediated regulation of T helper cell differentiation and plasticity

MicroRNA regulation of type 2 innate lymphoid cell homeostasis and function in allergic inflammation

Singh et al. examined microRNA expression and physiological requirements in type 2 innate lymphoid cells (ILC2s). The miR-17∼92 cluster promotes ILC2 growth, cytokine expression, and function in allergic inflammation.

MicroRNAs (miRNAs) exert powerful effects on immunity through coordinate regulation of multiple target genes in a wide variety of cells. Type 2 innate lymphoid cells (ILC2s) are tissue sentinel mediators of allergic inflammation. We established the physiological requirements for miRNAs in ILC2 homeostasis and immune function and compared the global miRNA repertoire of resting and activated ILC2s and T helper type 2 (T_H2) cells. After exposure to the natural allergen papain, mice selectively lacking the miR-17∼92 cluster in ILC2s displayed reduced lung inflammation. Moreover, miR-17∼92–deficient ILC2s exhibited defective growth and cytokine expression in response to IL-33 and thymic stromal lymphopoietin in vitro. The miR-17∼92 cluster member miR-19a promoted IL-13 and IL-5 production and inhibited expression of several targets, including SOCS1 and A20, signaling inhibitors that limit IL-13 and IL-5 production. These findings establish miRNAs as important regulators of ILC2 biology, reveal overlapping but nonidentical miRNA-regulated gene expression networks in ILC2s and T_H2 cells, and reinforce the therapeutic potential of targeting miR-19 to alleviate pathogenic allergic responses.

Heterogeneity of Human CD4(+) T Cells Against Microbes

CD4(+) T helper (Th) cells play a central role in the adaptive immune response by providing help to B cells and cytotoxic T cells and by releasing different types of cytokines in tissues to mediate protection against a wide range of pathogenic microorganisms. These functions are performed by different types of Th cells endowed with distinct migratory capacities and effector functions. Here we discuss how studies of the human T cell response to microbes have advanced our understanding of Th cell functional heterogeneity, in particular with the discovery of a distinct Th1 subset involved in the response to Mycobacteria and the characterization of two types of Th17 cells specific for extracellular bacteria or fungi. We also review new approaches to dissect at the clonal level the human CD4(+) T cell response induced by pathogens or vaccines that have revealed an unexpected degree of intraclonal diversification and propose a progressive and selective model of CD4(+) T cell differentiation.

miR-21 silencing ameliorates experimental autoimmune encephalomyelitis by promoting the differentiation of IL-10-producing B cells

IL-10-producing regulatory B (IL-10⁺ Breg) cells promote tolerance in autoimmune diseases and transplantation. However, it remains unclear whether microRNAs are involved in the development of IL-10⁺ Breg cells. Here, we found that microRNA-21 (miR-21) acts as an upstream regulator of IL-10 by targeting the 3' untranslated region of IL-10 mRNA. We also demonstrated that IL-10⁺ Breg cells exhibit lower miR-21 expression than non-Breg cells and that miR-21 acts as a potent negative regulator of the differentiation of IL-10⁺ Breg cells. Accordingly, specific inhibition of miR-21 using antisense oligonucleotides markedly promoted B cell IL-10 expression. Thus, IL-10 is a direct target of miR-21. Moreover, silencing of miR-21 significantly alleviated the severity of experimental autoimmune encephalomyelitis (EAE), and this change was associated with an increase in the number of IL-10⁺ Breg cells. Finally, we demonstrated that miR-21-silenced B cells exert their suppressive activity through effector T cells in an IL-10-dependent manner.

Thus, we characterized a B cell-intrinsic microRNA pathway that inhibits the differentiation of IL-10⁺ Breg cells and promotes autoimmunity. miR-21 silencing therefore represents a new therapeutic strategy for the treatment of autoimmune diseases.

Separation of Circulating MicroRNAs Using Apheresis in Patients With Systemic Lupus Erythematosus

MicroRNAs (miRNAs), which are important inhibitors of mRNA translation, participate in differentiation, migration, cell proliferation, and cell death. The pathology of miRNAs results in alterations in protein expression. Recently, miRNAs circulating in peripheral blood have been shown to control the synthesis and translation of proteins at distal sites after intake into local cells. A number of studies are currently being conducted to investigate how to use miRNAs in disease treatment, but no studies have attempted to alleviate disease by directly eliminating miRNAs from blood. Therefore, we examined whether the removal or reduction of circulating miRNAs with apheresis improved pathologies caused by miRNAs. After approval of the study by our medical school's ethics committee, we collected blood and separated plasma samples from three patients with systemic lupus erythematosus who were undergoing plasmapheresis at our hospital. Peripheral blood was collected before and after it was passed through a primary membrane, centrifuged, and used to extract circulating miRNAs. A comprehensive expression analysis was then performed with a miRNA array chip. The levels of expression of a large number of circulating miRNAs were measured in the plasma samples separated by the primary membranes from all 3 patients with systemic lupus erythematosus. We present the first report that circulating miRNAs in peripheral blood can be separated and possibly directly removed using membrane separation apheresis.

The Clinical Application of MicroRNAs in Infectious Disease

MicroRNAs (miRNAs) are short single-stranded non-coding RNA sequences that posttranscriptionally regulate up to 60% of protein encoding genes. Evidence is emerging that miRNAs are key mediators of the host response to infection, predominantly by regulating proteins involved in innate and adaptive immune pathways. miRNAs can govern the cellular tropism of some viruses, are implicated in the resistance of some individuals to infections like HIV, and are associated with impaired vaccine response in older people. Not surprisingly, pathogens have evolved ways to undermine the effects of miRNAs on immunity. Recognition of this has led to new experimental treatments, RG-101 and Miravirsen—hepatitis C treatments which target host miRNA. miRNAs are being investigated as novel infection biomarkers, and they are being used to design attenuated vaccines, e.g., against Dengue virus. This comprehensive review synthesizes current knowledge of miRNA in host response to infection with emphasis on potential clinical applications, along with an evaluation of the challenges still to be overcome.

Immune Modulatory microRNAs Involved in Tumor Attack and Tumor Immune Escape

Current therapies against cancer utilize the patient's immune system for tumor eradication. However, tumor cells can evade immune surveillance of CD8+ T and/or natural killer (NK) cells by various strategies. These include the aberrant expression of human leukocyte antigen (HLA) class I antigens, co-inhibitory or costimulatory molecules, and components of the interferon (IFN) signal transduction pathway. In addition, alterations of the tumor microenvironment could interfere with efficient antitumor immune responses by downregulating or inhibiting the frequency and/or functional activity of immune effector cells and professional antigen-presenting cells. Recently, microRNAs (miRNAs) have been identified as major players in the post-transcriptional regulation of gene expression, thereby controlling many physiological and also pathophysiological processes including neoplastic transformation. Indeed, the cellular miRNA expression pattern is frequently altered in many tumors of distinct origin, demonstrating the tumor suppressive or oncogenic potential of miRNAs. Furthermore, there is increasing evidence that miRNAs could also influence antitumor immune responses by affecting the expression of immune modulatory molecules in tumor and immune cells. Apart from their important role in tumor immune escape and altered tumor-host interaction, immune modulatory miRNAs often exert neoplastic properties, thus representing promising targets for future combined immunotherapy approaches. This review focuses on the characterization of miRNAs involved in the regulation of immune surveillance or immune escape of tumors and their potential use as diagnostic and prognostic biomarkers or as therapeutic targets.

The MicroRNA-183-96-182 Cluster Promotes T Helper 17 Cell Pathogenicity by Negatively Regulating Transcription Factor Foxo1 Expression

T helper 17 (Th17) cells are key players in autoimmune diseases. However, the roles of non-coding RNAs in Th17 cell development and function are largely unknown. We found that deletion of the endoribonuclease-encoding Dicer1 specifically in Th17 cells protected mice from experimental autoimmune encephalomyelitis. We found that the Dicer1-regulated microRNA (miR)-183-96-182 cluster (miR-183C) was highly expressed in Th17 cells and was induced by cytokine IL-6-STAT3 signaling. miR-183C expression enhanced pathogenic cytokine production from Th17 cells during their development and promoted autoimmunity. Mechanistically, miR-183C in Th17 cells directly repressed expression of the transcription factor Foxo1. Foxo1 negatively regulated the pathogenicity of Th17 cells in part by inhibiting expression of cytokine receptor IL-1R1. These findings indicate that the miR-183C drives Th17 pathogenicity in autoimmune diseases via inhibition of Foxo1 and present promising therapeutic targets.

MicroRNA-mediated regulation of immune responses to intestinal helminth infections

Intestinal helminth infections are highly prevalent in the developing world, often resulting in chronic infection and inflicting high host morbidity. With the emergence of drug-resistant parasites, a limited number of chemotherapeutic drugs available and stalling vaccine efforts, an increased understanding of antihelminth immunity is essential to provide new avenues to therapeutic intervention. MicroRNAs are a class of small, nonprotein coding RNAs which negatively regulate mRNA translation, thus providing finite control over gene expression in a plethora of biological settings. The miRNA-mediated coordinated control of gene expression has been shown to be essential in infection and immunity, in promoting and fine-tuning the appropriate immune response. This review gathers together and discusses observations of miRNA-mediated effects on the immune system and the subsequent impact on our understanding of antihelminth immunity.

miR-146a modulates autoreactive Th17 cell differentiation and regulates organ-specific autoimmunity

Autoreactive CD4 T cells that differentiate into pathogenic Th17 cells can trigger autoimmune diseases. Therefore, investigating the regulatory network that modulates Th17 differentiation may yield important therapeutic insights. miR-146a has emerged as a critical modulator of immune reactions, but its role in regulating autoreactive Th17 cells and organ-specific autoimmunity remains largely unknown. Here, we have reported that miR-146a-deficient mice developed more severe experimental autoimmune encephalomyelitis (EAE), an animal model of human multiple sclerosis (MS). We bred miR-146a-deficient mice with 2D2 T cell receptor-Tg mice to generate 2D2 CD4 T cells that are deficient in miR-146a and specific for myelin oligodendrocyte glycoprotein (MOG), an autoantigen in the EAE model. miR-146a-deficient 2D2 T cells induced more severe EAE and were more prone to differentiate into Th17 cells. Microarray analysis revealed enhancements in IL-6- and IL-21-induced Th17 differentiation pathways in these T cells. Further study showed that miR-146a inhibited the production of autocrine IL-6 and IL-21 in 2D2 T cells, which in turn reduced their Th17 differentiation. Thus, our study identifies miR-146a as an important molecular brake that blocks the autocrine IL-6- and IL-21-induced Th17 differentiation pathways in autoreactive CD4 T cells, highlighting its potential as a therapeutic target for treating autoimmune diseases.

MicroRNA: Dynamic Regulators of Macrophage Polarization and Plasticity

The ability of a healthy immune system to clear the plethora of antigens it encounters incessantly relies on the enormous plasticity displayed by the comprising cell types. Macrophages (MΦs) are crucial member of the mononuclear phagocyte system (MPS) that constantly patrol the peripheral tissues and are actively recruited to the sites of injury and infection. In tissues, infiltrating monocytes replenish MΦ. Under the guidance of the local micro-milieu, MΦ can be activated to acquire specialized functional phenotypes. Similar to T cells, functional polarization of macrophage phenotype viz., inflammatory (M1) and reparative (M2) is proposed. Equipped with diverse toll-like receptors (TLRs), these cells of the innate arm of immunity recognize and phagocytize antigens and secrete cytokines that activate the adaptive arm of the immune system and perform key roles in wound repair. Dysregulation of MΦ plasticity has been associated with various diseases and infection. MicroRNAs (miRNAs) have emerged as critical regulators of transcriptome output. Their importance in maintaining health, and their contribution toward disease, encompasses virtually all aspects of human biology. Our understanding of miRNA-mediated regulation of MΦ plasticity and polarization can be utilized to modulate functional phenotypes to counter their role in the pathogenesis of numerous disease, including cancer, autoimmunity, periodontitis, etc. Here, we provide an overview of current knowledge regarding the role of miRNA in shaping MΦ polarization and plasticity through targeting of various pathways and genes. Identification of miRNA biomarkers of diagnostic/prognostic value and their therapeutic potential by delivery of miRNA mimics or inhibitors to dynamically alter gene expression profiles in vivo is highlighted.

MicroRNAs as Important Players in Host-Adenovirus Interactions

MicroRNAs (miRNAs) are powerful regulators of gene expression and fine-tuning genes in all tissues. Cellular miRNAs can control 100s of biologic processes (e.g., morphogenesis of embryonic structures, differentiation of tissue-specific cells, and metabolic control in specific cell types) and have been involved in the regulation of nearly all cellular pathways. Inherently to their involvement in different physiologic processes, miRNAs deregulation has been associated with several diseases. Moreover, several viruses have been described as either, avoid and block cellular miRNAs or synthesize their own miRNA to facilitate infection and pathogenesis. Adenoviruses genome encodes two non-coding RNAs, known as viral-associated (VA) RNA_I and VA RNA_II, which seem to play an important role either by blocking important proteins from miRNA pathway, such as Exportin-5 and Dicer, or by targeting relevant cellular factors. Drastic changes in cellular miRNA expression profile are also noticeable and several cellular functions are affected by these changes. This review focuses on the mechanisms underlying the biogenesis and molecular interactions of miRNAs providing basic concepts of their functions as well as in the interplay between miRNAs and human adenoviruses.

Heterogeneity and Stability in Foxp3+ Regulatory T Cells

Foxp3+ regulatory T cells (Tregs) play an indispensable role in controlling tolerance and immunity against self- and foreign antigens. The failure of Tregs to properly function is the direct cause of systemic and chronic inflammation as well as immune suppression. It is now evident that Tregs are highly heterogeneous populations depending on the surface phenotypes, cytokine profiles, and anatomical locations. Yet, our understanding of the cellular and molecular pathways underlying such heterogeneity is very limited. Furthermore, some Tregs lose the phenotype (and suppressive functions) and instead acquire pathogenicity. Since utilizing Tregs as a tool for immunotherapy is being implemented in many clinical settings, it is of utmost importance to understand the precise mechanisms by which the loss of Treg phenotype (and function) is prevented. In this review, both cellular and molecular factors involved in Treg heterogeneity and stability are discussed.

miR-551b regulates epithelial-mesenchymal transition and metastasis of gastric cancer by inhibiting ERBB4 expression

Epithelial-mesenchymal transition (EMT) is an important biological process that is characteristic of malignant tumor cells with metastatic potential. We investigated the role of miR-551b in EMT and metastasis in gastric cancer (GC). We found that low miR-551b levels were associated with EMT, metastasis and a poor prognosis in GC patients. Further, two GC cell lines, MNK45 and SGC7901, exhibited lower miR-551b levels than the GES normal stomach cell line. Exposing MNK45 and SGC7901 cells to TGF-β1 resulted in cell morphology changes characteristic of EMT, which was confirmed by Western blot analysis demonstrating low E-Cadherin and high N-Cadherin and Vimentin levels. Treatment with miR-551b mimics inhibited these EMT changes as well as Transwell migration and invasiveness. We identified ERBB4 as a potential target of miR-551b based on patient data from the TCGA. ERBB4 was upregulated in GC specimens, and its high expression correlated with a poor prognosis of GC patients. Dual luciferase assays revealed that miR-551b directly inhibited ERBB4 by binding to its 3'UTR. Moreover, treatment with miR-551b mimics or the ERBB4 inhibitor AST-1306 inhibited EMT in the GC cell lines. Finally, nude mice xenografted with GC cancer cell lines expressing miR-551b mimics exhibited smaller tumors and longer survival than mice engrafted with control GC cancer cells. These data indicate that miR-551b inhibits EMT and metastasis in GC by inhibiting ERBB4. miR-551b and ERBB4 are thus potential therapeutic targets for the treatment of GC.

Radiation-Induced Fibrosis: Mechanisms and Opportunities to Mitigate. Report of an NCI Workshop, September 19, 2016

A workshop entitled "Radiation-Induced Fibrosis: Mechanisms and Opportunities to Mitigate" (held in Rockville, MD, September 19, 2016) was organized by the Radiation Research Program and Radiation Oncology Branch of the Center for Cancer Research (CCR) of the National Cancer Institute (NCI), to identify critical research areas and directions that will advance the understanding of radiation-induced fibrosis (RIF) and accelerate the development of strategies to mitigate or treat it. Experts in radiation biology, radiation oncology and related fields met to identify and prioritize the key areas for future research and clinical translation. The consensus was that several known and newly identified targets can prevent or mitigate RIF in pre-clinical models. Further, basic and translational research and focused clinical trials are needed to identify optimal agents and strategies for therapeutic use. It was felt that optimally designed preclinical models are needed to better study biomarkers that predict for development of RIF, as well as to understand when effective therapies need to be initiated in relationship to manifestation of injury. Integrating appropriate endpoints and defining efficacy in clinical trials testing treatment of RIF were felt to be critical to demonstrating efficacy. The objective of this meeting report is to (a) highlight the significance of RIF in a global context, (b) summarize recent advances in our understanding of mechanisms of RIF,

MicroRNAs associated with inflammation in shoulder tendinopathy and glenohumeral arthritis

Inflammation is associated with glenohumeral arthritis and rotator cuff tendon tears. Epigenetically, miRNAs tightly regulate various genes involved in the inflammatory response. Alterations in the expression profile of miRNAs and the elucidation of their target genes with respect to the pathophysiology could improve the understanding of their regulatory role and therapeutic potential. Here, we screened key miRNAs that mediate inflammation and linked with JAK2/STAT3 pathway with respect to the coincidence of glenohumeral arthritis in patients suffering from rotator cuff injury (RCI). Human resected long head of the biceps tendons were examined for miRNA profile from two groups of patients: Group 1 included the patients with glenohumeral arthritis and massive rotator cuff tears and the Group 2 patients did not have arthritis or rotator cuff tears. The miRNA profiling revealed that 235 miRNAs were highly altered (fold change less than -3 and greater than +2 were considered). Data from the NetworkAnalyst program revealed the involvement and interaction between 3,430 different genes associated with inflammation out of which 284 genes were associated with JAK2/STAT3 pathway and interconnect 120 different pathways of inflammation. Around 1,500 miRNAs were found to play regulatory role associated with these genes of inflammatory responses and 77 miRNAs were found to regulate more than 10 genes. Among them, 25 genes with less than tenfold change were taken to consideration which altogether constitute for the regulation of 102 genes. Targeting these miRNAs and the underlying regulatory mechanisms may advance our knowledge to develop promising therapies in the management of shoulder tendon pathology.

MicroRNAs as regulatory elements in immune system logic

MicroRNAs (miRNAs) are crucial post-transcriptional regulators of haematopoietic cell fate decisions. They act by negatively regulating the expression of key immune development genes, thus contributing important logic elements to the regulatory circuitry. Deletion studies have made it increasingly apparent that they confer robustness to immune cell development, especially under conditions of environmental stress such as infectious challenge and ageing. Aberrant expression of certain miRNAs can lead to pathological consequences, such as autoimmunity and haematological cancers. In this Review, we discuss the mechanisms by which several miRNAs influence immune development and buffer normal haematopoietic output, first at the level of haematopoietic stem cells, then in innate and adaptive immune cells. We then discuss the pathological consequences of dysregulation of these miRNAs.

A Distinct Inhibitory Function for miR-18a in Th17 Cell Differentiation

Th17 cell responses orchestrate immunity against extracellular pathogens but also underlie autoimmune disease pathogenesis. In this study, we uncovered a distinct and critical role for miR-18a in limiting Th17 cell differentiation. miR-18a was the most dynamically upregulated microRNA of the miR-17-92 cluster in activated T cells. miR-18a deficiency enhanced CCR6⁺ RAR-related orphan receptor (ROR)γt⁺ Th17 cell differentiation in vitro and increased the number of tissue Th17 cells expressing CCR6, RORγt, and IL-17A in airway inflammation models in vivo. Sequence-specific miR-18 inhibitors increased CCR6 and RORγt expression in mouse and human CD4⁺ T cells, revealing functional conservation. miR-18a directly targeted Smad4, Hif1a, and Rora, all key transcription factors in the Th17 cell gene-expression program. These findings indicate that activating signals influence the outcome of Th cell differentiation via differential regulation of mature microRNAs within a common cluster.

3' Uridylation controls mature microRNA turnover during CD4 T-cell activation

Activation of T lymphocytes requires a tight regulation of microRNA (miRNA) expression. Terminal uridyltransferases (TUTases) catalyze 3' nontemplated nucleotide addition (3'NTA) to miRNAs, which may influence miRNA stability and function. Here, we investigated 3'NTA to mature miRNA in CD4 T lymphocytes by deep sequencing. Upon T-cell activation, miRNA sequences bearing terminal uridines are specifically decreased, concomitantly with down-regulation of TUT4 and TUT7 enzymes. Analyzing TUT4-deficient T lymphocytes, we proved that this terminal uridyltransferase is essential for the maintenance of miRNA uridylation in the steady state of T lymphocytes. Analysis of synthetic uridylated miRNAs shows that 3' addition of uridine promotes degradation of these uridylated miRNAs after T-cell activation. Our data underline post-transcriptional uridylation as a mechanism to fine-tune miRNA levels during T-cell activation.

MicroRNAs regulate T-cell production of interleukin-9 and identify hypoxia-inducible factor-2α as an important regulator of T helper 9 and regulatory T-cell differentiation

MicroRNAs (miRNAs) regulate many aspects of helper T cell (Th) development and function. Here we found that they are required for the suppression of interleukin-9 (IL-9) expression in Th9 cells and other Th subsets. Two highly related miRNAs (miR-15b and miR-16) that we previously found to play an important role in regulatory T (Treg) cell differentiation were capable of suppressing IL-9 expression when they were over-expressed in Th9 cells. We used these miRNAs as tools to identify novel regulators of IL-9 expression and found that they could regulate the expression of Epas1, which encodes hypoxia-inducible factor (HIF)-2α. HIF proteins regulate metabolic pathway usage that is important in determining appropriate Th differentiation. The related protein, HIF-1α enhances Th17 differentiation and inhibits Treg cell differentiation. Here we found that HIF-2α was required for IL-9 expression in Th9 cells, but its expression was not sufficient in other Th subsets. Furthermore, HIF-2α suppressed Treg cell differentiation like HIF-1α, demonstrating both similar and distinct roles of the HIF proteins in Th differentiation and adding a further dimension to their function. Ironically, even though miR-15b and miR-16 suppressed HIF-2α expression in Treg cells, inhibiting their function in Treg cells did not lead to an increase in IL-9 expression. Therefore, the physiologically relevant miRNAs that regulate IL-9 expression in Treg cells and other subsets remain unknown. Nevertheless, the analysis of miR-15b and miR-16 function led to the discovery of the importance of HIF-2α so this work demonstrated the utility of studying miRNA function to identify novel regulatory pathways in helper T-cell development.

MicroRNA-22-3p as a novel regulator and therapeutic target for autoimmune diseases

MicroRNAs (miRNAs) are a class of noncoding RNAs and have emerged as critical regulators of gene expression. Some miRNAs play important roles in regulating the function of the immune system and are involved in the pathogenesis of autoimmune diseases. Recent studies suggested that microRNA-22-3p (miR-22-3p) was able to regulate the function of several types of immune cells and may be involved in the development of autoimmune diseases. We systematically reviewed relevant literatures to provide a comprehensive review of the possible roles of miR-22-3p in autoimmune diseases. Published studies suggest that miR-22-3p can act as a novel regulator of autoimmune diseases via several pathways. More studies are needed to further elucidate the exact roles of miR-22-3p in autoimmune diseases. Treatment strategy targeting miR-22-3p is also a promising therapy for autoimmune diseases.

Promoting tissue regeneration by modulating the immune system

The immune system plays a central role in tissue repair and regeneration. Indeed, the immune response to tissue injury is crucial in determining the speed and the outcome of the healing process, including the extent of scarring and the restoration of organ function. Therefore, controlling immune components via biomaterials and drug delivery systems is becoming an attractive approach in regenerative medicine, since therapies based on stem cells and growth factors have not yet proven to be broadly effective in the clinic. To integrate the immune system into regenerative strategies, one of the first challenges is to understand the precise functions of the different immune components during the tissue healing process. While remarkable progress has been made, the immune mechanisms involved are still elusive, and there is indication for both negative and positive roles depending on the tissue type or organ and life stage. It is well recognized that the innate immune response comprising danger signals, neutrophils and macrophages modulates tissue healing. In addition, it is becoming evident that the adaptive immune response, in particular T cell subset activities, plays a critical role. In this review, we first present an overview of the basic immune mechanisms involved in tissue repair and regeneration. Then, we highlight various approaches based on biomaterials and drug delivery systems that aim at modulating these mechanisms to limit fibrosis and promote regeneration. We propose that the next generation of regenerative therapies may evolve from typical biomaterial-, stem cell-, or growth factor-centric approaches to an immune-centric approach.

STATEMENT OF SIGNIFICANCE

Most regenerative strategies have not yet proven to be safe or reasonably efficient in the clinic. In addition to stem cells and growth factors, the immune system plays a crucial role in the tissue healing process. Here, we propose that controlling the immune-mediated mechanisms of tissue repair and regeneration may support existing regenerative strategies or could be an alternative to using stem cells and growth factors. The first part of this review we highlight key immune mechanisms involved in the tissue healing process and marks them as potential target for designing regenerative strategies. In the second part, we discuss various approaches using biomaterials and drug delivery systems that aim at modulating the components of the immune system to promote tissue regeneration.

A Novel miR-24-TCF1 Axis in Modulating Effector T Cell Responses

miR-23∼27∼24 was recently implicated in restricting Th2 immunity, as well as the differentiation and function of other effector T cell lineages. Interestingly, miR-24, unlike other family members, actually promotes Th1 and Th17 responses. In this article, we show that miR-24 drives the production of IFN-γ and IL-17 in T cells at least in part through targeting TCF1, a transcription factor known for its role in limiting Th1 and Th17 immunity. Surprisingly, whereas TCF1 was previously shown to promote Th2 responses through inducing GATA3, enforced TCF1 expression in miR-24-overexpressing T cells led to further downregulation of IL-4 and GATA3 expression, suggesting miR-24-mediated inhibition of Th2 immunity cannot be attributed to TCF1 repression by miR-24. Together, our data demonstrate a novel miR-24-TCF1 pathway in controlling effector cytokine production by T cells and further suggest miR-24 could function as a key upstream molecule regulating TCF1-mediated immune responses.

The Microbiota and Epigenetic Regulation of T Helper 17/Regulatory T Cells: In Search of a Balanced Immune System

Immune cells not only affect tissue homeostasis at the site of inflammation but also exert systemic effects contributing to multiple chronic conditions. Recent evidence clearly supports an altered T helper 17/regulatory T cell (Th17/Treg) balance leading to the development and progression of inflammatory diseases that not only affect the gastrointestinal tract but also have whole-body manifestations, including insulin resistance. Epigenetic mechanisms are amenable to both environmental and circulating factors and contribute to determining the T cell landscape. The recently identified participation of the gut microbiota in the remodeling of the epigenome of immune cells has triggered a paradigm shift in our understanding of the etiology of various inflammatory diseases and opened new paths toward therapeutic strategies. In this review, we provide an overview of the contribution of the Th17/Treg balance in the development and progression of inflammatory bowel diseases and metabolic diseases. We discuss the involvement of epigenetic mechanisms in the regulation of T cell function in the particular context of dysbiosis. Finally, we examine the potential for nutritional interventions affecting the gut microbiota to reshape the T cell epigenome and address the inflammatory component of various diseases.

Inhibition of MicroRNA-21 by an antagomir ameliorates allergic inflammation in a mouse model of asthma

AIM OF THE STUDY

MicroRNA-21 (miR-21) is up-regulated during allergic airway inflammation, reflecting a Th2 immune response. We investigated the effects of an miR-21 antagomir and its mechanism of action in a mouse model of acute bronchial asthma.

MATERIALS AND METHODS

BALB/c mice were sensitized and challenged with ovalbumin (OVA). The anti-miR-21 antagomir was administered by intranasal inhalation from the day of sensitization. Changes in cell counts, Th2 cytokine levels in bronchoalveolar (BAL) fluid, and airway hyper-responsiveness (AHR) were examined. Histopathological changes and expression levels of miR-21 in lung tissues were analyzed. The mechanism of action of the antagomir was investigated by counting CD4⁺/CD8^- T cells in splenocytes and by measuring the expression levels of transcription factors associated with T cell polarization.

RESULTS

MiR-21 expression was selectively down-regulated in the lung tissues of mice treated with anti-miR-21. The antagomir suppressed AHR compared with that of the OVA-challenged and scrambled RNA-treated groups. It also reduced the total cell and eosinophil counts in BAL fluid and the levels of Th2 cytokines, including IL-4, IL-5, and IL-13. The direct target of miR-21, IL-12p35, was induced in the antagomir-treated group, decreasing the CD4⁺/CD8^- T cell proportions in splenocytes. The levels of transcription factors involved in the Th2-signaling pathway were reduced in lung tissues on treatment with the antagomir.

CONCLUSIONS

The miR-21 antagomir suppresses the development of allergic airway inflammation in a mouse model of acute bronchial asthma, inhibiting Th2 activation. These results suggest that this antagomir might be useful for treating bronchial asthma.

Genetic Association of Hematopoietic Stem Cell Transplantation Outcome beyond Histocompatibility Genes

The outcome of hematopoietic stem cell transplantation (HSCT) is controlled by genetic factors among which the leukocyte antigen human leukocyte antigen (HLA) matching is most important. In addition, minor histocompatibility antigens and non-HLA gene polymorphisms in genes controlling immune responses are known to contribute to the risks associated with HSCT. Besides single-nucleotide polymorphisms (SNPs) in protein coding genes, SNPs in regulatory elements such as microRNAs (miRNAs) contribute to these genetic risks. However, genetic risks require for their realization the expression of the respective gene or miRNA. Thus, gene and miRNA expression studies may help to identify genes and SNPs that indeed affect the outcome of HSCT. In this review, we summarize gene expression profiling studies that were performed in recent years in both patients and animal models to identify genes regulated during HSCT. We discuss SNP–mRNA–miRNA regulatory networks and their contribution to the risks associated with HSCT in specific examples, including forkheadbox protein 3 and regulatory T cells, the role of the miR-155 and miR-146a regulatory network for graft-versus-host disease, and the function of MICA and its receptor NKG2D for the outcome of HSCT. These examples demonstrate how SNPs affect expression or function of proteins that modulate the alloimmune response and influence the outcome of HSCT. Specific miRNAs targeting these genes and directly affecting expression of mRNAs are identified. It might be valuable in the future to determine SNPs and to analyze miRNA and mRNA expression in parallel in cohorts of HSCT patients to further elucidate genetic risks of HSCT.

Roles of microRNAs in psoriasis: Immunological functions and potential biomarkers

MicroRNAs (miRNAs) are small non-coding RNA molecules, which function in RNA silencing and post-transcriptional regulation of gene expression. Psoriasis is an inflammatory skin disease characterized by the dysfunction of keratinocytes, with the immune dysregulation. We reviewed the recent studies on the roles of miRNAs in psoriasis and showed that miRNAs play key roles in psoriasis, including the regulation of hyperproliferation, cytokine and chemokine production in keratinocyte, as well as mediating immune dysfunction in psoriasis. Furthermore, miRNAs, particularly, circulating miRNAs may serve as novel biomarkers for diagnosis, monitoring therapy response and reflecting the disease severity. Thus, targeting specific miRNAs may be used to develop new therapeutic methods for psoriasis.

Cancer-derived Circulating MicroRNAs Promote Tumor Angiogenesis by Entering Dendritic Cells to Degrade Highly Complementary MicroRNAs

Understanding the interaction between cancer cells and immunocytes will inspire new cancer therapy strategies. However, how cancer-derived circulating miRNAs modulate such interaction remains unclear. Here we discovered that circulating miR-410-5p, secreted by prostate cancer cells, entered dendritic cells (DCs), with the aid of argonaute-2 protein. The cancer cell antigens stimulated the DCs to produce miR-410-3p, a highly complementary counterpart of miR-410-5p derived from pre-miR-410. The DC-internalized miR-410-5p degraded the miR-410-3p by base pairing and thus inhibited its function in suppressing tumor angiogenesis, promoting tumor growth. Furthermore, blockade of the miR-410-5p upregulated the miR-410-3p to inhibit tumor growth. Our work suggests a new miRNA-mediated role of immunocytes in cancer progression and a new strategy of cancer therapy through suppressing circulating miRNAs.

MicroRNA expression profiles in human CD3+ T cells following stimulation with anti-human CD3 antibodies

Background

Anti-CD3 therapy can induce immunosuppression by several non mutually exclusive mechanisms that have been proposed to explain the therapeutic effect the administration anti-CD3 mAb, but its immunoregulatory mechanism is still not completely clear. In T cells, microRNAs (miRNAs) regulate several pathways, including those associated with immune tolerance. Here, we report changes in miRNA expression in T cells following treatment with anti-human CD3 antibodies. Peripheral blood mononuclear cells were cultured in the presence of the monoclonal antibody OKT3 or a recombinant fragment of humanized anti-CD3. Following these treatments, the expression profiles of 31 miRNA species were assessed in T cells using TaqMan arrays.

Results

Eight of the tested miRNAs (miR-155, miR-21, miR-146a, miR-210, miR-17, miR-590-5p, miR-106b and miR-301a) were statistically significantly up- or down-regulated relative to untreated cells.

Conclusions

Stimulation of T cells with anti-human CD3 antibodies alters miRNA expression patterns, including of miRNA species associated with immune regulatory pathways.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-017-2442-y) contains supplementary material, which is available to authorized users.

Negative Regulation of Type 2 Immunity

Type 2 immunity encompasses the mechanisms through which the immune system responds to helminths and an array of environmental substances such as allergens. In the developing world, billions of individuals are chronically infected with endemic parasitic helminths. In comparison, in the industrialized world, millions of individuals suffer from dysregulated type 2 immunity, referred to clinically as atopic diseases including asthma, allergic rhinitis, and atopic dermatitis. Thus, type 2 immunity must be carefully regulated to mount protective host responses yet avoid inappropriate activation and immunopathology. In this review, we describe the key players and connections at play in type 2 responses and focus on the emerging mechanisms involved in the negative regulation of type 2 immunity.

Fighting Viral Infections and Virus-Driven Tumors with Cytotoxic CD4+ T Cells

CD4+ T cells have been and are still largely regarded as the orchestrators of immune responses, being able to differentiate into distinct T helper cell populations based on differentiation signals, transcription factor expression, cytokine secretion, and specific functions. Nonetheless, a growing body of evidence indicates that CD4+ T cells can also exert a direct effector activity, which depends on intrinsic cytotoxic properties acquired and carried out along with the evolution of several pathogenic infections. The relevant role of CD4+ T cell lytic features in the control of such infectious conditions also leads to their exploitation as a new immunotherapeutic approach. This review aims at summarizing currently available data about functional and therapeutic relevance of cytotoxic CD4+ T cells in the context of viral infections and virus-driven tumors.

Increasing JAK/STAT Signaling Function of Infant CD4+ T Cells during the First Year of Life

Most infant deaths occur in the first year of life. Yet, our knowledge of immune development during this period is scarce and derived from cord blood (CB) only. To more effectively combat pediatric diseases, a deeper understanding of the kinetics and the factors that regulate the maturation of immune functions in early life is needed. Increased disease susceptibility of infants is generally attributed to T helper 2-biased immune responses. The differentiation of CD4+ T cells along a specific T helper cell lineage is dependent on the pathogen type, and on costimulatory and cytokine signals provided by antigen-presenting cells. Cytokines also regulate many other aspects of the host immune response. Therefore, toward the goal of increasing our knowledge of early immune development, we defined the temporal development of the Janus kinase (JAK)/signal transducers and activators of transcription (STAT) signaling function of CD4+ T cells using cross-sectional blood samples from healthy infants ages 0 (birth) to 14 months. We specifically focused on cytokines important in T cell differentiation (IFN-γ, IL-12, and IL-4) or in T cell survival and expansion (IL-2 and IL-7) in infant CD4+ T cells. Independent of the cytokine tested, JAK/STAT signaling in infant compared to adult CD4+ T cells was impaired at birth, but increased during the first year, with the most pronounced changes occurring in the first 6 months. The relative change in JAK/STAT signaling of infant CD4+ T cells with age was distinct for each cytokine tested. Thus, while about 60% of CB CD4+ T cells could efficiently activate STAT6 in response to IL-4, less than 5% of CB CD4+ T cells were able to activate the JAK/STAT pathway in response to IFN-γ, IL-12 or IL-2. By 4-6 months of age, the activation of the cytokine-specific STAT molecules was comparable to adults in response to IL-4 and IFN-γ, while IL-2- and IL-12-induced STAT activation remained below adult levels even at 1 year. These results suggest that common developmental and cytokine-specific factors regulate the maturation of the JAK/STAT signaling function in CD4+ T cells during the first year of life.

Fingolimod alters the transcriptome profile of circulating CD4+ cells in multiple sclerosis

Multiple sclerosis is a demyelinating disease affecting the central nervous system. T cells are known to contribute to this immune-mediated condition. Fingolimod modulates sphingosine-1-phosphate receptors, thereby preventing the egress of lymphocytes, especially CCR7-expressing CD8+ and CD4+ T cells, from lymphoid tissues. Using Affymetrix Human Transcriptome Arrays (HTA 2.0), we performed a transcriptome profiling analysis of CD4+ cells obtained from the peripheral blood of patients with highly active relapsing-remitting multiple sclerosis. The samples were drawn before the first administration of fingolimod as well as 24 hours and 3 months after the start of therapy. Three months after treatment initiation, 890 genes were found to be differentially expressed with fold-change >2.0 and t-test p-value < 0.001, among them several microRNA precursors. A subset of 272 genes were expressed at lower levels, including CCR7 as expected, while 618 genes showed an increase in expression, e.g., CCR2, CX3CR1, CD39, CD58 as well as LYN, PAK1 and TLR2. To conclude, we studied the gene expression of CD4+ cells to evaluate the effects of fingolimod treatment, and we identified 890 genes to be altered in expression after continuous drug administration. T helper cells circulating in the blood during fingolimod therapy present a distinct gene expression signature.

miR-155 Modifies Inflammation, Endothelial Activation and Blood-Brain Barrier Dysfunction in Cerebral Malaria

miR-155 has been shown to participate in host response to infection and neuro-inflammation via negative regulation of blood-brain-barrier (BBB) integrity and T cell function. We hypothesized that miR-155 may contribute to the pathogenesis of cerebral malaria (CM). To test this hypothesis, we used a genetic approach to modulate miR-155 expression in an experimental model of cerebral malaria (ECM). In addition, an engineered endothelialized microvessel system and serum samples from Ugandan children with CM were used to examine an anti-miR-155 as a potential adjunctive therapeutic for severe malaria. Despite higher parasitemia, survival was significantly improved in miR-155^-/- mice vs. wild-type littermate mice in ECM. Improved survival was associated with preservation of BBB integrity and reduced endothelial activation, despite increased levels of pro-inflammatory cytokines. Pre-treatment with antagomir-155 reduced vascular leak induced by human CM sera in an ex vivo endothelial microvessel model. These data provide evidence supporting a mechanistic role for miR-155 in host response to malaria via regulation of endothelial activation, microvascular leak and BBB dysfunction in CM.

Regulation of T Cell Activation and Differentiation by Extracellular Vesicles and Their Pathogenic Role in Systemic Lupus Erythematosus and Multiple Sclerosis

How autoreactive tissue-infiltrated effector T cells are induced and sustained in autoimmune disease, usually dominated by the Th1 and Th17 subsets, is still largely unknown. In organ-specific autoimmunity, self-reactive T cells initially activated by dendritic cells (DCs) in the lymph nodes migrate and infiltrate into the target tissues where their reactivation by peripheral tissue antigen is a prerequisite for effector cytokine production and tissue destruction. The target tissue microenvironment, as well as the local microenvironment at the immune synapse formed by T cells that encounter cognate antigen presenting cells (APCs) shave recently emerged as critical factors in shaping the differentiation and function of self-reactive effector T cells, providing the signals required for their activation in the form of the self-antigen and cytokine milieu. Moreover, depending on the specific microenvironment, self-reactive effector T cells have the ability to change their phenotype, especially Th17 and regulatory T (Treg) cells, which are characterized by the highest instability. In this context, cell-derived extracellular vesicles, i.e., vesicles carrying cytosolic proteins and nucleic acids protected by a phospholipid bilayer, as well as membrane-associated proteins, with the ability to spread throughout the body by means of biological fluids, are emerging as key mediators in intercellular communications and in the modulation of the microenvironment. In this review, we will discuss recent findings implicating extracellular vesicles (EVs) at different steps of CD4+ T cell differentiation to specific effectors, with a focus on the Th17/Treg balance and its alterations in systemic lupus erythematosus and multiple sclerosis.

miRNA profiling of human naive CD4 T cells links miR-34c-5p to cell activation and HIV replication

Cell activation is a vital step for T-cell memory/effector differentiation as well as for productive HIV infection. To identify novel regulators of this process, we used next-generation sequencing to profile changes in microRNA expression occurring in purified human naive CD4 T cells in response to TCR stimulation and/or HIV infection. Our results demonstrate, for the first time, the transcriptional up-regulation of miR-34c-5p in response to TCR stimulation in naive CD4 T cells. The induction of this miR was further consistently found to be reduced by both HIV-1 and HIV-2 infections. Overexpression of miR-34c-5p led to changes in the expression of several genes involved in TCR signaling and cell activation, confirming its role as a novel regulator of naive CD4 T-cell activation. We additionally show that miR-34c-5p promotes HIV-1 replication, suggesting that its down-regulation during HIV infection may be part of an anti-viral host response.

Micro RNA-550a interferes with vitamin D metabolism in peripheral B cells of patients with diabetes

The pathogenesis of diabetes is to be further investigated. Vitamin D3 (VitD3) can improve diabetes. Micro RNAs (miR) are involved in regulating cell activities. This study tests a hypothesis that miR-550a interferes with the metabolism of VitD3 in peripheral B cells. In this study, blood samples were collected from patients with diabetes and healthy persons. The B cells were isolated from the blood samples to be treated with tumor necrosis factor (TNF)-α. The B cells were then collected and analyzed for the expression of miR-550a and cyp27b1. The results showed that B cells from healthy subjects were capable of converting VitD metabolite calcidiol to calcitriol, which was impaired in B cells collected from diabetic patients. The diabetic patients showed lower bone mineral density than that in healthy subject. The miR-550a was negatively correlated with bone mineral density and the Levels of cyp27b1 in peripheral B cells of patients with diabetes. In vitro study showed that TNF-α increased miR-550a expression and inhibited the expression of cyp27b1 in B cells. miR-550a mediated the effects of TNF-α on inducing chromatin remodeling at the cyp27b1 gene locus. In conclusion, miR-550a mediates the TNF-α-induced suppression of cyp27b1 expression in peripheral B cells of patients with diabetes, which can be blocked by inhibition of miR-550a.

Effective experimental validation of miRNA targets using an improved linker reporter assay

miRNAs are small, non-coding RNAs that play critical roles in various cellular processes. Although there are several algorithms that can predict the potential candidate genes that are regulated by a miRNA, these algorithms require further experimental validation in order to demonstrate genuine targets of miRNAs. Moreover, most algorithms predict hundreds to thousands of putative target genes for each miRNA, and it is difficult to validate all candidates using the whole 3'-untranslated region (UTR) reporter assay. We report a fast, simple and efficient experimental approach to screening miRNA candidate targets using a 3'-UTR linker assay. Critically, the linker has only a short miRNA regulatory element sequence of approximately 22 base pairs in length and can provide a benefit for screening strong miRNA candidates for further validation using the whole 3'-UTR sequence. Our technique will provide a simplified platform for the high-throughput screening of miRNA target gene validation.

Increased microRNA-323-3p in IL-22/IL-17-producing T cells and asthma: a role in the regulation of the TGF-β pathway and IL-22 production

BACKGROUND

IL-22- and IL-17-producing T cells have important roles in allergic diseases. MicroRNAs (miRNAs) are posttranscriptional regulators of gene expression and modulate numerous biological processes. Little is known about the functions of miRNAs in IL-22/IL-17-producing T cells.

MATERIAL AND METHODS

IL-22- and IL-17-positive T cells were sorted from human peripheral blood mononuclear cells (PBMCs) by intracellular staining and dual-secretion assay. miRNA expression profiles were detected with TaqMan array microfluidic cards. T cells were transfected with miRNA mimics. Gene expression was analyzed using RT-qPCR and/or enzyme-linked immunosorbent assay in T-cell subsets and PBMCs from patients with asthma and atopic dermatitis.

RESULTS

The increased expression of miR-323-3p and noncoding RNA nc886 and reduced expression of miR-93, miR-181a, miR-26a, and miR-874 were detected in IL-22-producing T cells. The pathway analysis of the putative targets suggested that these differentially expressed miRNAs could impact the proliferation, differentiation, and effector functions of T cells. Further analyses showed the highest expression for miR-323-3p in IL-22- and IL-17-double-positive T cells and its capacity to suppress multiple genes from the transforming growth factor-β pathway and the production of IL-22 in T cells. An increased expression of miR-323-3p in PBMCs from patients with asthma and reverse correlation between miR-323-3p levels and IL-22 production in PBMCs cultured in T-cell growth conditions was observed.

CONCLUSIONS

Our data suggest that miR-323-3p acts in a negative feedback loop to control the production of IL-22 in IL-22/IL-17-producing T cells and might thus impact the T-cell responses in asthma.

New Insights into Regulatory T Cells: Exosome- and Non-Coding RNA-Mediated Regulation of Homeostasis and Resident Treg Cells

Regulatory T (Treg) cells are a group of cells that are heterogeneous in origin and in functional activity. Treg cells comprise a necessary balance to adaptive immune responses. As key regulators of self-tolerance, Treg cells have been involved in a series of pathologic processes and considered as therapeutic targets. Here, we summarize recent research regarding Treg cell origins and their functional classification, highlight the role of exosomes and non-coding RNA in modulating Treg cell homeostasis, and discuss the current understanding of resident Treg cells.

MicroRNA-146a Induces Lineage-Negative Bone Marrow Cell Apoptosis and Senescence by Targeting Polo-Like Kinase 2 Expression

OBJECTIVE

Lineage-negative bone marrow cells (lin- BMCs) are enriched in endothelial progenitor cells and mediate vascular repair. Aging-associated senescence and apoptosis result in reduced number and functionality of lin- BMCs, impairing their prorepair capacity. The molecular mechanisms underlying lin- BMC senescence and apoptosis are poorly understood. MicroRNAs (miRNAs) regulate many important biological processes. The identification of miRNA-mRNA networks that modulate the health and functionality of lin- BMCs is a critical step in understanding the process of vascular repair. The aim of this study was to characterize the role of the miR-146a-Polo-like kinase 2 (Plk2) network in regulating lin- BMC senescence, apoptosis, and their angiogenic capability.

APPROACH AND RESULTS

Transcriptome analysis in lin- BMCs isolated from young and aged wild-type and ApoE^-/- (apolipoprotein E) mice showed a significant age-associated increase in miR-146a expression. In silico analysis, expression study and Luciferase reporter assay established Plk2 as a direct target of miR-146a. miR-146a overexpression in young lin- BMCs inhibited Plk2 expression, resulting in increased senescence and apoptosis, via p16Ink4a/p19Arf and p53, respectively, as well as impaired angiogenic capacity in vitro and in vivo. Conversely, suppression of miR-146a in aged lin- BMCs increased Plk2 expression and rejuvenated lin- BMCs, resulting in decreased senescence and apoptosis, leading to improved angiogenesis.

CONCLUSIONS

(1) miR-146a regulates lin- BMC senescence and apoptosis by suppressing Plk2 expression that, in turn, activates p16Ink4a/p19Arf and p53 and (2) modulation of miR-146a or its target Plk2 may represent a potential therapeutic intervention to improve lin- BMC-mediated angiogenesis and vascular repair.

Retroviral Transduction of Helper T Cells as a Genetic Approach to Study Mechanisms Controlling their Differentiation and Function

Helper T cell development and function must be tightly regulated to induce an appropriate immune response that eliminates specific pathogens yet prevents autoimmunity. Many approaches involving different model organisms have been utilized to understand the mechanisms controlling helper T cell development and function. However, studies using mouse models have proven to be highly informative due to the availability of genetic, cellular, and biochemical systems. One genetic approach in mice used by many labs involves retroviral transduction of primary helper T cells. This is a powerful approach due to its relative ease, making it accessible to almost any laboratory with basic skills in molecular biology and immunology. Therefore, multiple genes in wild type or mutant forms can readily be tested for function in helper T cells to understand their importance and mechanisms of action. We have optimized this approach and describe here the protocols for production of high titer retroviruses, isolation of primary murine helper T cells, and their transduction by retroviruses and differentiation toward the different helper subsets. Finally, the use of this approach is described in uncovering mechanisms utilized by microRNAs (miRNAs) to regulate pathways controlling helper T cell development and function.

Reprogramming macrophage orientation by microRNA 146b targeting transcription factor IRF5

The regulation of macrophage orientation pathological conditions is important but still incompletely understood. Here, we show that IL-10 and Rag1 double knockout mice spontaneously develop colitis with dominant M1 macrophage phenotype, suggesting that IL-10 regulates macrophage orientation in inflammation. We demonstrate that IL-10 stimulation induced miR-146b expression, and that the expression of miR-146b was impaired in IL-10 deficient macrophages. Our data show that miR-146b targets IRF5, resulting in the regulation of macrophage activation. Furthermore, miR-146b deficient mice developed intestinal inflammation with enhanced M1 macrophage polarization. Finally, miR-146b mimic treatment significantly suppresses M1 macrophage activation and ameliorates colitis development in vivo. Collectively, the results suggest that IL-10 dependent miR-146b plays an important role in the modulation of M1 macrophage orientation.

•

Interleukin 10-induced miR-146b plays a critical role in the regulation of macrophage polarization and colitis development by targeting IRF5.

•

Treatment with miR-146b mimic significantly suppresses M1 macrophage activation and ameliorates colitis development.

Interleukin 10 and Interleukin receptor are clearly involved in the development of inflammatory bowel diseases and other inflammatory diseases. Notably, the mutation of Interleukin 10 and Interleukin 10 receptor are clearly correlated with inflammatory bowel diseases. In the present study we show that Interleukin 10-induced miR-146b plays a critical role in the regulation of macrophage polarization and colitis development by targeting IRF5. Treatment with miR-146b mimic significantly suppresses M1 macrophage activation and ameliorates colitis development. The results highlight the potent role of miR146b in the control of immune responses and pathogenesis of inflammatory diseases.

Circulating MicroRNAs in Graves' Disease in Relation to Clinical Activity

BACKGROUND

Understanding the roles of circulating microRNAs (miRNAs) can provide important and novel information regarding disease pathogenesis and a patient's clinical condition. Circulating miRNAs, such as exosomal miRNA, may regulate various bioactivities related to intercellular communication. However, the circulation of miRNAs in Graves' disease (GD) in relation to disease activity has never been elucidated. This study aimed to identify circulating miRNAs in GD in relation to disease activity and whether their exosomes play a role in the pathogenesis of GD.

METHODS

Circulating miRNAs were measured in serum obtained from seven intractable GD patients, seven GD patients in remission, and seven healthy controls using the miScript miRNA PCR Array. Altered miRNAs selected from array data were validated in 65 subjects. To investigate exosome biology, peripheral blood mononuclear cells (PBMCs) were incubated with exosomes isolated from the subjects' sera. mRNAs were quantified for cytokines using quantitative real-time polymerase chain reaction.

RESULTS

Circulating miR-23b-5p and miR-92a-39 were increased in GD patients in remission compared with intractable GD patients (p < 0.05). On the other hand, let-7g-3p and miR-339-5p were decreased in GD patients in remission compared with intractable GD patients (p < 0.05). Exosomes from intractable GD patients stimulated mRNA expression for IL-1β and TNF-α compared with GD patients in remission or healthy controls.

CONCLUSIONS

This study demonstrates that different levels of circulating miRNAs are associated with intractable GD. Moreover, serum exosomes of patients with intractable GD may activate immune cells, which may play an important role in GD pathogenesis.

Clonal selection versus clonal cooperation: the integrated perception of immune objects

Analogies between the immune and nervous systems were first envisioned by the immunologist Niels Jerne who introduced the concepts of antigen "recognition" and immune "memory". However, since then, it appears that only the cognitive immunology paradigm proposed by Irun Cohen, attempted to further theorize the immune system functions through the prism of neurosciences. The present paper is aimed at revisiting this analogy-based reasoning. In particular, a parallel is drawn between the brain pathways of visual perception and the processes allowing the global perception of an "immune object". Thus, in the visual system, distinct features of a visual object (shape, color, motion) are perceived separately by distinct neuronal populations during a primary perception task. The output signals generated during this first step instruct then an integrated perception task performed by other neuronal networks. Such a higher order perception step is by essence a cooperative task that is mandatory for the global perception of visual objects. Based on a re-interpretation of recent experimental data, it is suggested that similar general principles drive the integrated perception of immune objects in secondary lymphoid organs (SLOs). In this scheme, the four main categories of signals characterizing an immune object (antigenic, contextual, temporal and localization signals) are first perceived separately by distinct networks of immunocompetent cells.  Then, in a multitude of SLO niches, the output signals generated during this primary perception step are integrated by TH-cells at the single cell level. This process eventually generates a multitude of T-cell and B-cell clones that perform, at the scale of SLOs, an integrated perception of immune objects. Overall, this new framework proposes that integrated immune perception and, consequently, integrated immune responses, rely essentially on clonal cooperation rather than clonal selection.