miR-9 enhances IL-2 production in activated human CD4+ T cells by repressing Blimp-1

Regulatory RNAs in immunosenescence

BACKGROUND

Immunosenescence is a multifactorial stress response to different intrinsic and extrinsic insults that cause immune deterioration and is accompanied by genomic or epigenomic perturbations. It is now widely recognized that genes and proteins contributing in the process of immunosenescence are regulated by various noncoding (nc) RNAs, including microRNAs (miRNAs), long ncRNAs, and circular RNAs.

AIMS

This review article aimed to evaluate the regulatore RNAs roles in the process of immunosenescence.

METHODS

We analyzed publications that were focusing on the different roles of regulatory RNAs on the several aspects of immunosenescence.

RESULTS

In the immunosenescence setting, ncRNAs have been found to play regulatory roles at both transcriptional and post-transcriptional levels. These factors cooperate to regulate the initiation of gene expression programs and sustaining the senescence phenotype and proinflammatory responses.

CONCLUSION

Immunosenescence is a complex process with pivotal alterations in immune function occurring with age. The extensive network that drive immunosenescence-related features are are mainly directed by a variety of regulatory RNAs such as miRNAs, lncRNAs, and circRNAs. Latest findings about regulation of senescence by ncRNAs in the innate and adaptive immune cells as well as their role in the immunosenescence pathways, provide a better understanding of regulatory RNAs function in the process of immunosenescence.

An Evaluation on the Role of Non-Coding RNA in HIV Transcription and Latency: A Review

The existence of latent cellular reservoirs is recognized as the major barrier to an HIV cure. Reactivating and eliminating "shock and kill" or permanently silencing "block and lock" the latent HIV reservoir, as well as gene editing, remain promising approaches, but so far have proven to be only partially successful. Moreover, using latency reversing agents or "block and lock" drugs pose additional considerations, including the ability to cause cellular toxicity, a potential lack of specificity for HIV, or low potency when each agent is used alone. RNA molecules, such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) are becoming increasingly recognized as important regulators of gene expression. RNA-based approaches for combatting HIV latency represent a promising strategy since both miRNAs and lncRNAs are more cell-type and tissue specific than protein coding genes. Thus, a higher specificity of targeting the latent HIV reservoir with less overall cellular toxicity can likely be achieved. In this review, we summarize current knowledge about HIV gene expression regulation by miRNAs and lncRNAs encoded in the human genome, as well as regulatory molecules encoded in the HIV genome. We discuss both the transcriptional and post-transcriptional regulation of HIV gene expression to align with the current definition of latency, and describe RNA molecules that either promote HIV latency or have anti-latency properties. Finally, we provide perspectives on using each class of RNAs as potential targets for combatting HIV latency, and describe the complexity of the interactions between different RNA molecules, their protein targets, and HIV.

Comparative transcriptomics reveals small RNA composition and differential microRNA responses underlying interferon-mediated antiviral regulation in porcine alveolar macrophages

Previous studies have shown that interferon-mediated antiviral activity is subtype-dependent. Using a whole transcriptome procedure, we aimed to characterize the small RNA transcriptome (sRNA-Seq) and specifically the differential microRNA (miRNA) responses in porcine alveolar macrophages (PAMs) upon antiviral activation during viral infection and interferon (IFN) stimulation. Data showed that near 90% of the qualified reads of sRNA were miRNAs, and about 10% of the other sRNAs included rRNA, snoRNA, snRNA, and tRNA in order of enrichment. As the majority of sRNA (>98%) were commonly detected in all PAM samples under different treatments, about 2% sRNA were differentially expressed between the different antiviral treatments. Focusing on miRNA, 386 miRNA were profiled, including 331 known and 55 novel miRNA sequences, of which most were ascribed to miRNA families conserved among vertebrates, particularly mammalian species. Of the miRNA profiles comparably generated across the different treatments, in general, significantly differentially expressed miRNA (SEM) demonstrated that: (1) the wild-type and vaccine strains of a porcine arterivirus (a.k.a., PRRSV) induced nearly reversed patterns of up- or down-regulated SEMs; (2) similar SEM patterns were found among the treatments by the vaccine strain and antiviral IFN-α1/-ω5 subtypes; and (3) the weak antiviral IFN-ω1, however, remarked a suppressive SEM pattern as to SEMs upregulated in the antiviral treatments by the vaccine and IFN-α1/-ω5 subtypes. Further articulation identified SEMs commonly or uniquely expressed in different treatments, and experimentally validated that some SEMs including miR-10b and particularly miR-9-1 acted significantly in regulation of differential antiviral reactions stimulated by different IFN subtypes. Therefore, this study provides a general picture of porcine sRNA composition and pinpoints key SEMs underlying antiviral regulation in PAMs correlated to a typical respiratory RNA virus in pigs.

Non-coding RNAs: Key players in T cell exhaustion

T cell exhaustion caused by continuous antigen stimulation in chronic viral infections and the tumor microenvironment is a major barrier to successful elimination of viruses and tumor cells. Although immune checkpoint inhibitors should reverse T cell exhaustion, shortcomings, such as off-target effects and single targets, limit their application. Therefore, it is important to identify molecular targets in effector T cells that simultaneously regulate the expression of multiple immune checkpoints. Over the past few years, non-coding RNAs, including microRNAs and long non-coding RNAs, have been shown to participate in the immune response against viral infections and tumors. In this review, we focus on the roles and underlying mechanisms of microRNAs and long non-coding RNAs in the regulation of T cell exhaustion during chronic viral infections and tumorigenesis. We hope that this review will stimulate research to provide more precise and effective immunotherapies against viral infections and tumors.

Regulatory roles of MicroRNA in shaping T cell function, differentiation and polarization

T lymphocytes are an integral component of adaptive immunity with pleotropic effector functions. Impairment of T cell activity is implicated in various immune pathologies including autoimmune diseases, AIDS, carcinogenesis, and periodontitis. Evidently, T cell differentiation and function are under robust regulation by various endogenous factors that orchestrate underlying molecular pathways. MicroRNAs (miRNA) are a class of noncoding, regulatory RNAs that post-transcriptionally control multiple mRNA targets by sequence-specific interaction. In this article, we will review the recent progress in our understanding of miRNA-gene networks that are uniquely required by specific T cell effector functions and provide miRNA-mediated mechanisms that govern the fate of T cells. A subset of miRNAs may act in a synergistic or antagonistic manner to exert functional suppression of genes and regulate pathways that control T cell activation and differentiation. Significance of T cell-specific miRNAs and their dysregulation in immune-mediated diseases is discussed. Exosome-mediated horizontal transfer of miRNAs from antigen presenting cells (APCs) to T cells and from one T cell to another T cell subset and their impact on recipient cell functions is summarized.

IgGs-Abzymes from the Sera of Patients with Systemic Lupus Erythematosus Hydrolyzed miRNAs

Background and Objectives

Systemic lupus erythematosus (SLE) is an inflammatory disease. The sera of SLE patients contain antibodies-abzymes hydrolyzing myelin basic protein (MBP), DNA, nucleotides, and oligosaccharides. The blood of SLE patients contains an increased amount of some specific miRNAs. This study aimed to analyze a possible hydrolysis of eight microRNAs found in the blood of SLE patients with high frequency by blood antibodies-abzymes.

Patients and Methods

Using affinity chromatography of the serum proteins of SLE patients and healthy donors on protein G-Sepharose and following FPLC gel filtration, electrophoretically homogeneous IgG preparations containing no impurities of canonical RNases were obtained. These preparations were used to analyze their activity in the hydrolysis of eight miRNAs.

Results

It was shown that SLE IgGs hydrolyze very efficiently four neuroregulatory miRNAs (miR-219-2-3p, miR-137, miR-219a-5p, and miR-9-5p) and four immunoregulatory miRNAs (miR-326, miR-21-3p, miR-155-5p, and miR-146a-3p). To demonstrate that the miRNAs hydrolysis is an intrinsic property of SLE IgGs, several rigid criteria were checked. Only some IgGs of healthy donors showed very weak, but reliably detectable activity in the hydrolysis miRNAs. The average activity of SLE patients IgGs according to median values is statistically significant 84.8-fold higher than that of healthy donors. The maximum and comparable average activity (RA) was observed in the hydrolysis of three miRAs: miR-9-5p, miR-155-5p, and miR-326. MiR-9-5p plays an important role in the development of lupus nephritis, while miR-326 activates the production of antibodies by B cells. The major and moderate specific sites of the hydrolysis of each miRNA were revealed. The hydrolysis of eight microRNAs was mostly site specific. Several SLE IgGs hydrolyzed some miRNAs demonstrating a combination of site-specific and non-specific splitting.

Conclusion

Since inflammatory processes in SLE are associated with the change in miRNAs expression, the decrease in their concentration due to hydrolysis by autoantibodies-abzymes may be important for SLE pathogenesis.

MicroRNA-9 Fine-Tunes Dendritic Cell Function by Suppressing Negative Regulators in a Cell-Type-Specific Manner

Dendritic cells, cells of the innate immune system, are found in a steady state poised to respond to activating stimuli. Once stimulated, they rapidly undergo dynamic changes in gene expression to adopt an activated phenotype capable of stimulating immune responses. We find that the microRNA miR-9 is upregulated in both bone marrow-derived DCs and conventional DC1s but not in conventional DC2s following stimulation. miR-9 expression in BMDCs and conventional DC1s promotes enhanced DC activation and function, including the ability to stimulate T cell activation and control tumor growth. We find that miR-9 regulated the expression of several negative regulators of transcription, including the transcriptional repressor Polycomb group factor 6 (Pcgf6). These findings demonstrate that miR-9 facilitates the transition of DCs from steady state to mature state by regulating the expression of several negative regulators of DC function in a cell-type-specific manner.

Cell-Mediated Immunity Generated in Response to a Purified Inactivated Vaccine for Dengue Virus Type 1

Dengue is a tropical disease transmitted by mosquitoes, and nearly half of the world’s population lives in areas where individuals are at risk of infection. Several vaccines for dengue are in development, including one which was recently licensed in several countries, although its utility is limited to people who have already been infected with one of the four dengue viruses. One major hurdle to understanding whether a dengue vaccine will work for everyone—before exposure—is the necessity of knowing which marker can be measured in the blood to signal that the individual has protective immunity. This report describes an approach measuring multiple different parts of immunity in order to characterize which signals one candidate vaccine imparted to a small number of human volunteers. This approach was designed to be able to be applied to any dengue vaccine study so that the data can be compared and used to inform future vaccine design and/or optimization strategies.

Dengue is the most prevalent arboviral disease afflicting humans, and a vaccine appears to be the most rational means of control. Dengue vaccine development is in a critical phase, with the first vaccine licensed in some countries where dengue is endemic but demonstrating insufficient efficacy in immunologically naive populations. Since virus-neutralizing antibodies do not invariably correlate with vaccine efficacy, other markers that may predict protection, including cell-mediated immunity, are urgently needed. Previously, the Walter Reed Army Institute of Research developed a monovalent purified inactivated virus (PIV) vaccine candidate against dengue virus serotype 1 (DENV-1) adjuvanted with alum. The PIV vaccine was safe and immunogenic in a phase I dose escalation trial in healthy, flavivirus-naive adults in the United States. From that trial, peripheral blood mononuclear cells obtained at various time points pre- and postvaccination were used to measure DENV-1-specific T cell responses. After vaccination, a predominant CD4⁺ T cell-mediated response to peptide pools covering the DENV-1 structural proteins was observed. Over half (13/20) of the subjects produced interleukin-2 (IL-2) in response to DENV peptides, and the majority (17/20) demonstrated peptide-specific CD4⁺ T cell proliferation. In addition, analysis of postvaccination cell culture supernatants demonstrated an increased rate of production of cytokines, including gamma interferon (IFN-γ), IL-5, and granulocyte-macrophage colony-stimulating factor (GM-CSF). Overall, the vaccine was found to have elicited DENV-specific CD4⁺ T cell responses as measured by enzyme-linked immunosorbent spot (ELISpot), intracellular cytokine staining (ICS), lymphocyte proliferation, and cytokine production assays. Thus, together with antibody readouts, the use of a multifaceted measurement of cell-mediated immune responses after vaccination is a useful strategy for more comprehensively characterizing immunity generated by dengue vaccines.

IMPORTANCE Dengue is a tropical disease transmitted by mosquitoes, and nearly half of the world’s population lives in areas where individuals are at risk of infection. Several vaccines for dengue are in development, including one which was recently licensed in several countries, although its utility is limited to people who have already been infected with one of the four dengue viruses. One major hurdle to understanding whether a dengue vaccine will work for everyone—before exposure—is the necessity of knowing which marker can be measured in the blood to signal that the individual has protective immunity. This report describes an approach measuring multiple different parts of immunity in order to characterize which signals one candidate vaccine imparted to a small number of human volunteers. This approach was designed to be able to be applied to any dengue vaccine study so that the data can be compared and used to inform future vaccine design and/or optimization strategies.

TGF-β1 increases viral burden and promotes HIV-1 latency in primary differentiated human bronchial epithelial cells

Combination antiretroviral therapy (cART) has increased the life expectancy of HIV patients. However, the incidence of non-AIDS associated lung comorbidities, such as COPD and asthma, and that of opportunistic lung infections have become more common among this population. HIV proteins secreted by the anatomical HIV reservoirs can have both autocrine and paracrine effects contributing to the HIV-associated comorbidities. HIV has been recovered from cell-free bronchoalveolar lavage fluid, alveolar macrophages, and intrapulmonary lymphocytes. We have recently shown that ex-vivo cultured primary bronchial epithelial cells and the bronchial brushings from human subjects express canonical HIV receptors CD4, CCR5 and CXCR4 and can be infected with HIV. Together these studies suggest that the lung tissue can serve as an important reservoir for HIV. In this report, we show that TGF-β1 promotes HIV latency by upregulating a transcriptional repressor BLIMP-1. Furthermore, we identify miR-9-5p as an important intermediate in TGF-β-mediated BLIMP-1 upregulation and consequent HIV latency. The transcriptionally suppressed HIV can be reactivated by common latency reactivating agents. Together our data suggest that in patients with chronic airway diseases, TGF-β can elevate the HIV viral reservoir load that could further exacerbate the HIV associated lung comorbidities.

Toxoplasma gondii: CD8 T Cells Cry for CD4 Help

Toxoplasma gondii, an apicomplexan parasite, is a pathogenic protozoan that can infect the central nervous system. In pregnant women, infection can result in congenital problems of the fetus, while in immunocompromised individual it can lead to severe neurological consequences. Although CD8 T cells play an important effector role in controlling the chronic infection, their maintenance is dependent on the critical help provided by CD4 T cells. In a recent study, we demonstrated that reactivation of the infection in chronically infected host is a consequence of CD8 T dysfunction caused by CD4 T cell exhaustion. Furthermore, treatment of chronically infected host with antigen-specific non-exhausted CD4 T cells can restore CD8 T cell functionality and prevent reactivation of the latent infection. The exhaustion status of CD4 T cells is mediated by the increased expression of the transcription factor BLIMP-1, and deletion of this molecule led to the restoration of CD4 T cell function, reversal of CD8 exhaustion and prevention of reactivation of the latent infection. In a recent study from our laboratory, we also observed an increased expression of miR146a levels by CD4 T cells from the chronically infected animals. Recent reports have demonstrated that microRNAs (especially miR146a) has a strong impact on the immune system of T. gondii infected host. Whether these molecules have any role in the BLIMP-1 up-regulation and dysfunctionality of these cells needs to be investigated.

Enhancing the pro-inflammatory anti-cancer T cell response via biomanufactured, secretome-based, immunotherapeutics

T lymphocytes play a critical role in the pro-inflammatory anti-cancer response; hence, significant pharmacologic efforts have been made to enhance the endogenous T cell response. Unfortunately, significant toxicity arises consequent to pan T cell activation. In contrast, the less robust T cell alloresponse has also demonstrated an anti-cancer effect, but poses an inherent risk of GvHD. To overcome the GvHD risk, an acellular pro-inflammatory agent (IA1) has been biomanufactured from the secretome of the allorecognition response. To assess IA1's immunomodulatory activity, T cell proliferation and differentiation were determined in vitro. The pro-inflammatory properties of the IA1 therapeutic were mediated by the miRNA-enriched fractions. Moreover, cross-species efficacy was observed consequent to the evolutionary conservation of miRNA. IA1 exerted no toxicity to resting PBMC but induced significant proliferation of resting CD3⁺ (CD4⁺ and CD8⁺) T cells and skewed the response towards a pro-inflammatory state (i.e., increased Teff:Treg ratio). Crucially, IA1-activated PBMC demonstrated a potent inhibition of cancer cell (HeLa and SH-4 melanoma) proliferation relative to the resting PBMC. The anti-proliferation effect of IA1-activated PBMC was noted within ˜12 h versus 4-5 days for resting cells. A second biomanufactured therapeutic (IA2; produced using HeLa cells) surprisingly demonstrated direct toxicity to cancer cells but was less effective than IA1 in inducing a cell-mediated response. This study demonstrates that miRNA-enriched therapeutics can be biomanufactured from the secretome and can induce a potent pro-inflammatory, anti-cancer, effect on resting lymphocytes.

MiRNAs and inflammatory bowel disease: An interesting new story

Inflammatory bowel disease (IBD), as a chronic and recurrent inflammatory disorder, is caused by a dysregulated and aberrant immune response to exposed environmental factors in genetically susceptible individuals. Despite huge efforts in determining the molecular pathogenesis of IBD, an increasing worldwide incidence of IBD has been reported. MicroRNAs (miRNAs) are a set of noncoding RNA molecules that are about 22 nucleotides long, and these molecules are involved in the regulation of the gene expression. By clarifying the important role of miRNAs in a number of diseases, their role was also considered in IBD; numerous studies have been performed on this topic. In this review, we attempt to summarize a number of studies and discuss some of the recent developments in the roles of miRNAs in the pathophysiology, diagnosis, and treatment of IBD.

Control of Immunoregulatory Molecules by miRNAs in T Cell Activation

MiRNA targeting of key immunoregulatory molecules fine-tunes the immune response. This mechanism boosts or dampens immune functions to preserve homeostasis while supporting the full development of effector functions. MiRNA expression changes during T cell activation, highlighting that their function is constrained by a specific spatiotemporal frame related to the signals that induce T cell-based effector functions. Here, we update the state of the art regarding the miRNAs that are differentially expressed during T cell stimulation. We also revisit the existing data on miRNA function in T cell activation, with a special focus on the modulation of the most relevant immunoregulatory molecules.

miR-9-5p in Nephrectomy Specimens is a Potential Predictor of Primary Resistance to First-Line Treatment with Tyrosine Kinase Inhibitors in Patients with Metastatic Renal Cell Carcinoma

Approximately 20–30% of patients with metastatic renal cell carcinoma (mRCC) in first-line treatment with tyrosine kinase inhibitors (TKIs) do not respond due to primary resistance to this drug. At present, suitable robust biomarkers for prediction of a response are not available. Therefore, the aim of this study was to evaluate a panel of microRNAs (miRNAs) in nephrectomy specimens for use as predictive biomarkers for TKI resistance. Archived formalin-fixed, paraffin embedded nephrectomy samples from 60 mRCC patients treated with first-line TKIs (sunitinib, n = 51; pazopanib, n = 6; sorafenib, n = 3) were categorized into responders and non-responders. Using the standard Response Evaluation Criteria in Solid Tumors, patients with progressive disease within 3 months after the start of treatment with TKI were considered as non-responders and those patients with stable disease and complete or partial response under the TKI treatment for at least 6 months as responders. Based on a miRNA microarray expression profile in the two stratified groups of patients, seven differentially expressed miRNAs were validated using droplet digital reverse-transcription quantitative real-time polymerase chain reaction (RT-qPCR) assays in the two groups. Receiver operating characteristic curve analysis and binary logistic regression of response prediction were performed. MiR-9-5p and miR-489-3p were able to discriminate between the two groups. MiR-9-5p, as the most significant miRNA, improved the correct prediction of primary resistance against TKIs in comparison to that of conventional clinicopathological variables. The results of the decision curve analyses, Kaplan-Meier analyses and Cox regression analyses confirmed the potential of miR-9-5p in the prediction of response to TKIs and the prediction of progression-free survival after the initiation of TKI treatment.

miRNA regulation of innate immunity

MicroRNAs (miRNAs) are small noncoding RNA and are pivotal posttranscriptional regulators of both innate and adaptive immunity. They act by regulating the expression of multiple immune genes, thus, are the important elements to the complex immune regulatory network. Deregulated expression of specific miRNAs can lead to potential autoimmunity, immune tolerance, hyper-inflammatory phenotype, and cancer initiation and progression. In this review, we discuss the contributory pathways and mechanisms by which several miRNAs influence the development of innate immunity and fine-tune immune response. Moreover, we discuss the consequence of deregulated miRNAs and their pathogenic implications.

Combinatorial regulation of a Blimp1 (Prdm1) enhancer in the mouse retina

The mouse retina comprises seven major cell types that exist in differing proportions. They are generated from multipotent progenitors in a stochastic manner, such that the relative frequency of any given type generated changes over time. The mechanisms determining the proportions of each cell type are only partially understood. Photoreceptors and bipolar interneurons are derived from cells that express Otx2. Within this population, Blimp1 (Prdm1) helps set the balance between photoreceptors and bipolar cells by suppressing bipolar identity in most of the cells. How only a subset of these Otx2+ cells decides to upregulate Blimp1 and adopt photoreceptor fate is unknown. To understand this, we investigated how Blimp1 transcription is regulated. We identified several potential Blimp1 retinal enhancer elements using DNase hypersensitivity sequencing. Only one of the elements recapitulated Blimp1 spatial and temporal expression in cultured explant assays and within the retinas of transgenic mice. Mutagenesis of this retinal Blimp1 enhancer element revealed four discrete sequences that were each required for its activity. These included highly conserved Otx2 and ROR (retinoic acid receptor related orphan receptor) binding sites. The other required sequences do not appear to be controlled by Otx2 or ROR factors, increasing the complexity of the Blimp1 gene regulatory network. Our results show that the intersection of three or more transcription factors is required to correctly regulate the spatial and temporal features of Blimp1 enhancer expression. This explains how Blimp1 expression can diverge from Otx2 and set the balance between photoreceptor and bipolar fates.

miR-34a and miR-9 are overexpressed and SIRT genes are downregulated in peripheral blood mononuclear cells of aging humans

Increased expression of sirtuins lowers the risk of age-related diseases, while their role in the regulation of longevity is not firmly established. Since aging is associated with immunosenescence, we tested whether sirtuin expression was modified in peripheral blood mononuclear cells (PBMC) in an age-related manner and whether this might result from altered expression of the selected miRNAs. The expression of seven SIRT genes and of SIRT1 mRNA-interacting miR-9, miR-34a, miR-132, and miR-199a-5p was evaluated by real-time PCR in PBMC originating from young (Y, n = 57, mean age 27 ± 4.3 years), elderly (E, n = 52, 65 ± 3.4 years), and long-lived (L, n = 56, 94 ± 3.5 years) individuals. Older age was associated with a decreased expression of the majority of the SIRT genes. Most severely affected were median expressions of SIRT1 ( P = 0.000001 for the whole studied group, Y vs. E: P < 0.000001, Y vs. L: P < 0.000001), and of SIRT3 ( P = 0.000001, Y vs. E: P = 0.000004, Y vs. L: P = 0.000028). Older age was also associated with the increased median expression of miR-34a ( P = 0.000001, Y vs. E: P = 0.001, Y vs. L: P = 0.000004) and of miR-9 ( P = 0.05, Y vs. L: P = 0.054). In functional studies, miR-9 interacted with the 3'UTR of SIRT1 mRNA. The SIRT1 mRNA level negatively correlated with the expression of miR-34a ( r = -0.234, P = 0.003). In conclusion, age-related decrease of SIRT1 expression in PBMC might in part result from overexpression of miR-34a and miR-9. In addition, the sustained expression of the SIRT genes in PBMC is not a prerequisite to longevity in humans but might be one of the reasons for the immune system dysfunction in the elderly. Impact statement High expression of sirtuins, particularly SIRT1, lowers the risk of age-related diseases and probably slows down the rate of aging; therefore, their sustained expression should be one of the features of longevity. However, in this work we show that in peripheral blood mononuclear cells (PBMC) of long-lived individuals, expression of majority of the SIRT genes is significantly lower than in cells of young study subjects. In long-lived individuals, downregulation of SIRT1 coexists with upregulation of SIRT1 mRNA-interacting miR-34a and miR-9, indicating the role of epigenetic drift in age-dependent deregulation of SIRT1 expression. Such constellation of SIRT1, miR-34a, and miR-9 expression in PBMC of successfully aging long-lived individuals indicates that, at least in these individuals, it is not a risk factor for morbidity and mortality. It might however affect the function of the immune system and, therefore, aging individuals can profit from interventions increasing the level of SIRT1.

New insights into Blimp-1 in T lymphocytes: a divergent regulator of cell destiny and effector function

B lymphocyte-induced maturation protein-1 (Blimp-1) serves as a master regulator of the development and function of antibody-producing B cells. Given that its function in T lymphocytes has been identified within the past decade, we review recent findings with emphasis on its role in coordinated control of gene expression during the development, differentiation, and function of T cells. Expression of Blimp-1 is mainly confined to activated T cells and is essential for the production of interleukin (IL)-10 by a subset of forkhead box (Fox)p3⁺ regulatory T cells with an effector phenotype. Blimp-1 is also required to induce cell elimination in the thymus and critically modulates peripheral T cell activation and proliferation. In addition, Blimp-1 promotes T helper (Th) 2 lineage commitment and limits Th1, Th17 and follicular helper T cell differentiation. Furthermore, Blimp-1 coordinates with other transcription factors to regulate expression of IL-2, IL-21 and IL-10 in effector T lymphocytes. In CD8⁺ T cells, Blimp-1 expression is distinct in heterogeneous populations at the stages of clonal expansion, differentiation, contraction and memory formation when they encounter antigens. Moreover, Blimp-1 plays a fundamental role in coordinating cytokine receptor signaling networks and transcriptional programs to regulate diverse aspects of the formation and function of effector and memory CD8⁺ T cells and their exhaustion. Blimp-1 also functions as a gatekeeper of T cell activation and suppression to prevent or dampen autoimmune disease, antiviral responses and antitumor immunity. In this review, we discuss the emerging roles of Blimp-1 in the complex regulation of gene networks that regulate the destiny and effector function of T cells and provide a Blimp-1-dominated transcriptional framework for T lymphocyte homeostasis.

HDAC inhibitor AR-42 decreases CD44 expression and sensitizes myeloma cells to lenalidomide

Multiple myeloma (MM) is a hematological malignancy of plasma cells in the bone marrow. Despite multiple treatment options, MM is inevitably associated with drug resistance and poor outcomes. Histone deacetylase inhibitors (HDACi's) are promising novel chemotherapeutics undergoing evaluation in clinical trials for the potential treatment of patients with MM. Although in preclinical studies HDACi's have proven anti-myeloma activity, but in the clinic single-agent HDACi treatments have been limited due to low tolerability. Improved clinical outcomes were reported only when HDACi's were combined with other drugs. Here, we show that a novel pan-HDACi AR-42 downregulates CD44, a glycoprotein that has been associated with lenalidomide and dexamethasone resistance in myeloma both in vitro and in vivo. We also show that this CD44 downregulation is in part mediated by miR-9–5p, targeting insulin-like growth factor 2 mRNA binding protein 3 (IGF2BP3), which directly binds to CD44 mRNA and increases its stability. Importantly, we also demonstrate that AR-42 enhances anti-myeloma activity of lenalidomide in primary MM cells isolated from lenalidomide resistant patients and in in vivo MM mouse model. Thus, our findings shed light on potential novel combinatorial therapeutic approaches modulating CD44 expression, which may help overcome lenalidomide resistance in myeloma patients.

miR-23a, miR-146a and miR-301a confer predisposition to Vogt-Koyanagi-Harada syndrome but not to Behcet's disease

Ninety-eight miRNAs are involved in the immune response. However, the genetic roles of these miRNAs remain unclear in Behcet's disease (BD) and Vogt-Koyanagi-Harada (VKH) syndrome. This study aimed to explore the association and functional roles of copy number variants (CNV) in several miRNAs with BD and VKH syndrome. Genotyping of CNVs was examined by TaqMan PCR. The expression of miR-23a, transfection efficiency and cytokine production were measured by real-time PCR, flow cytometry or ELISA. First, replication and combined studies for miR-23a, miR-146a and miR-301a demonstrated a similar association with VKH syndrome (Combined: P = 5.53 × 10(-8); P = 8.43 × 10(-31); P = 9.23 × 10(-8), respectively). No association of CNVs of the above mentioned miRNAs was observed in BD patients. mRNA expression of miR-23a showed a positive association with its copy numbers. Additionally, individuals with high copy number of miR-23a show an increased production of interleukin-6 (IL-6), but not IL-8 and monocyte chemoattractant protein-1 (MCP-1) by stimulated PBMCs. miR-23a transfected ARPE-19 cells modulated the production of IL-6 and IL-8, but not MCP-1. Our results suggest that CNVs of miR-146a, miR-23a and miR-301a confer susceptibility to VKH syndrome, but not to BD. The contribution of miR-23a to VKH syndrome may be mediated by increasing the production of IL-6.

Mutual interaction between BCL6 and microRNAs in T cell differentiation

The transcription factor B-cell CLL/lymphoma 6 (BCL6) and the regulatory factor microRNAs (miRNAs) are of great importance in the differentiation of T cell subsets. An increasing body of evidence has demonstrated that BCL6 and miRNAs can target one another and mutually adjust their expression in T cell subsets, such as T helper (Th)-2, Th17, CD8+ regulatory T (CD8+Treg) and T follicular helper (Tfh) cells. Here, we discuss the most recent advances and emerging concepts in how BCL6 and miRNAs regulate one another, and the effects of such mutual regulations on T cell subset differentiation.

Delivery of miR-155 to retinal pigment epithelial cells mediated by Burkitt's lymphoma exosomes

Exosomes are extracellularly secreted vesicles ranging from 40 to 100 nm in diameter that are thought to play important roles in intercellular communication. Exosomes contain numerous proteins, RNA, and lipids that can affect the status of recipient cells under various pathological conditions. MicroRNAs (miRNAs) are small non-coding RNAs that play a major role in post-transcriptional gene silencing by interacting with the 3'-untranslated regions of target genes. Epstein-Barr virus (EBV) has been reported to induce sustained elevation of cellular miRNAs such as miR-155. We hypothesized that miRNAs delivered by exosomes might affect the angiogenesis of retinal pigment epithelial (RPE) cells. Here, we demonstrated that co-culture of EBV-positive Burkitt's lymphoma (BL) cells (Raji) with retinal pigment epithelial (ARPE-19) cells increased the level of miR-155 in recipient cells whereas no major difference was detected for co-culture with EBV-negative BL cells (Ramos). Isolated Raji exosomes increased transcriptional and translational levels of VEGF-A in ARPE-19 cells, which was reversely correlated with von Hippel-Lindau expression. A human umbilical vein endothelial cell tube formation assay showed that delivery of ectopic miR-155 rendered ARPE-19 cells proangiogenic. Our results demonstrate that sustained accumulation of miR-155 mediated by exosomes might affect remote recipient cells such as retinal pigment epithelial cells.

MicroRNAs Signature in IL-2-Induced CD4+ T Cells and Their Potential Targets

MicroRNAs (miRNAs) are a class of small non-coding RNAs regulated gene expression at the post-transcriptional level. Many studies have investigated role of miRNAs in the biological processes such as proliferation, apoptosis, differentiation, and development. To evaluate role of miRNAs in proliferation and death of T cell, we performed miRNA profiling in activated CD4+ T cells after IL-2 induction and depletion. Proliferation rate of IL-2-induced cells was measured by MTT assay. Then quantitative RT-PCR arrays on 739 miRNAs revealed up- and down-regulation of 170 miRNAs in IL-2-induced CD4+ T cells relative to IL-2-depleted ones. In addition, in silico analysis predicted miRNA's potential targets in pathways such as JAK/STAT and PI3K pathways. JAK1 expression, a potential target of modulated miRNAs, was decreased in IL-2-depleted cells. This study suggests that clonal expansion is regulated by miRNAs in the absence or presence of IL-2 by targeting genes implicated in JAK/STAT and PI3K pathways.

Cross-regulation between cytokine and microRNA pathways in T cells

microRNA (miRNA) mediated regulation of protein expression has emerged as an important mechanism in T-cell physiology, from development and survival to activation, proliferation, and differentiation. One of the major classes of proteins involved in these processes are cytokines, which are both key input signals and major products of T-cell function. Here, we summarize the current data on the molecular cross-talk between cytokines and miRNAs: how cytokines regulate miRNA expression, and how specific miRNAs control cytokine production in T cells. We also describe the inflammatory consequences of deregulating the miRNA/cytokine axis in mice and humans. We believe this topical area will have key implications for immune modulation and treatment of autoimmune pathology.

miR-9 enhances the transactivation of nuclear factor of activated T cells by targeting KPNB1 and DYRK1B

The fast response to stimuli and subsequent activation of the nuclear factor of activated T cells (NFAT) signaling pathway play an essential role in human T cell functions. MicroRNAs (miRNAs) are increasingly implicated in regulation of numerous biological and pathological processes. In this study we demonstrate a novel function of miRNA-9 (miR-9) in regulation of the NFAT signaling pathway. Upon PMA-ionomycin stimulation, miR-9 was markedly increased, consistent with NFAT activation. Overexpression of miR-9 significantly enhanced NFAT activity and accelerated NFAT dephosphorylation and its nuclear translocation in response to PMA-ionomycin. Karyopherin-β1 (KPNB1, a nucleocytoplasmic transporter) and dual-specificity tyrosine phosphorylation-regulated kinase 1B (DYRK1B) were identified as direct targets of miR-9. Functionally, miR-9 promoted IL-2 production in stimulated human lymphocyte Jurkat T cells. Collectively, our data reveal a novel role for miR-9 in regulation of the NFAT pathway by targeting KPNB1 and DYRK1B.

MicroRNA modulation of key targets associated with T cell exhaustion in HIV-1 infection

PURPOSE OF REVIEW

The emergence of studies linking microRNAs (miRNAs), a species of small RNA molecules important in gene regulation, with HIV-1 infection has led to a better understanding of the complex molecular changes that occur following infection. We aim to discuss these changes and show how miRNAs may be involved with regulating key immunomodulatory molecules linked to T cell exhaustion at the post-transcriptional level.

RECENT FINDINGS

Blimp-1 is a recently described T cell exhaustion marker. Reduced levels of miR-9 have been shown to have a functional role in the higher levels of Blimp-1 in CD4 T cells from patients with HIV-1 infection. Reduced levels of let-7 miRNAs have been linked to higher levels of IL-10, again with potential pathophysiological significance in HIV-1 infection. The advent of deep sequencing technologies is allowing detection of virally derived miRNAs expressed at extremely low levels, although some controversy still exists.

SUMMARY

miRNAs have emerged as important players in the T cell dysfunction observed with HIV-1 infection. It is likely that they may emerge as novel markers of T cell dysfunction and provide potential targets for new therapeutics to reverse dysfunction.

Immuno-miRs: critical regulators of T-cell development, function and ageing

MicroRNAs (miRNAs) are instrumental to many aspects of immunity, including various levels of T-cell immunity. Over the last decade, crucial immune functions were shown to be regulated by specific miRNAs. These 'immuno-miRs' regulate generic cell biological processes in T cells, such as proliferation and apoptosis, as well as a number of T-cell-specific features that are fundamental to the development, differentiation and function of T cells. In this review, we give an overview of the current literature with respect to the role of miRNAs at various stages of T-cell development, maturation, differentiation, activation and ageing. Little is known about the involvement of miRNAs in thymic T-cell development, although miR-181a and miR-150 have been implicated herein. In contrast, several broadly expressed miRNAs including miR-21, miR-155 and miR-17~92, have now been shown to regulate T-cell activation. Other miRNAs, including miR-146a, show a more T-cell-subset-specific expression pattern and are involved in the regulation of processes unique to that specific T-cell subset. Importantly, differences in the miRNA target gene repertoires of different T-cell subsets allow similar miRNAs to control different T-cell-subset-specific functions. Interestingly, several of the here described immuno-miRs have also been implicated in T-cell ageing and there are clear indications for causal involvement of miRNAs in immunosenescence. It is concluded that immuno-miRs have a dynamic regulatory role in many aspects of T-cell differentiation, activation, function and ageing. An important notion when studying miRNAs in relation to T-cell biology is that specific immuno-miRs may have quite unrelated functions in closely related T-cell subsets.

Integration analysis of microRNA and mRNA expression profiles in human peripheral blood lymphocytes cultured in modeled microgravity

We analyzed miRNA and mRNA expression profiles in human peripheral blood lymphocytes (PBLs) incubated in microgravity condition, simulated by a ground-based rotating wall vessel (RWV) bioreactor. Our results show that 42 miRNAs were differentially expressed in MMG-incubated PBLs compared with 1 g incubated ones. Among these, miR-9-5p, miR-9-3p, miR-155-5p, miR-150-3p, and miR-378-3p were the most dysregulated. To improve the detection of functional miRNA-mRNA pairs, we performed gene expression profiles on the same samples assayed for miRNA profiling and we integrated miRNA and mRNA expression data. The functional classification of miRNA-correlated genes evidenced significant enrichment in the biological processes of immune/inflammatory response, signal transduction, regulation of response to stress, regulation of programmed cell death, and regulation of cell proliferation. We identified the correlation of miR-9-3p, miR-155-5p, miR-150-3p, and miR-378-3p expression with that of genes involved in immune/inflammatory response (e.g., IFNG and IL17F), apoptosis (e.g., PDCD4 and PTEN), and cell proliferation (e.g., NKX3-1 and GADD45A). Experimental assays of cell viability and apoptosis induction validated the results obtained by bioinformatics analyses demonstrating that in human PBLs the exposure to reduced gravitational force increases the frequency of apoptosis and decreases cell proliferation.

miRNAs and HIV: unforeseen determinants of host-pathogen interaction

Our understanding of the complexity of gene regulation has significantly improved in the last decade as the role of small non-coding RNAs, called microRNAs (miRNAs), has been appreciated. These 19-22 nucleotide RNA molecules are critical regulators of mRNA translation and turnover. The miRNAs bind via a protein complex to the 3' untranslated region (3' UTR) of mRNA, ultimately leading to mRNA translational inhibition, degradation, or repression. Although many mechanisms by which human immunodeficiency virus-1 (HIV-1) infection eventually induces catastrophic immune destruction have been elucidated, the important role that miRNAs play in HIV-1 pathogenesis is only now emerging. Accumulating evidence demonstrates that changes to endogenous miRNA levels following infection is important: in maintaining HIV-1 latency in resting CD4(+) T cells, potentially affect immune function via changes to cytokines such as interleukin-2 (IL-2) and IL-10 and may predict disease progression. We review the roles that both viral and host miRNAs play in different cell types and disease conditions that are important in HIV-1 infection and discuss how miRNAs affect key immunomodulatory molecules contributing to immune dysfunction. Further, we discuss whether miRNAs may be used as novel biomarkers in serum and the potential to modulate miRNA levels as a unique approach to combating this pathogen.

MiR-568 inhibits the activation and function of CD4⁺ T cells and Treg cells by targeting NFAT5

CD4(+) T cells play critical roles in orchestrating adaptive immune responses. Their activation and proliferation are critical steps that occur before they execute their biological functions. Despite the important role of this process, the underlying molecular events are not fully understood. MicroRNAs (miRNAs) have been shown to play important roles in lymphocyte development and function. However, the miRNAs that regulate T-cell differentiation, activation and proliferation are still largely unknown. In our previous study, using a miRNA array, we found that several miRNAs (including miR-202, 33b, 181c, 568 and 576) are differentially expressed between resting and activated CD4(+) T cells. In this study, we focused on the function of miR-568 during CD4(+) T-cell activation. We showed that the expression level of miR-568 decreased during the activation of T cells, including Jurkat cells and human peripheral blood CD4(+) T cells. When Jurkat or human peripheral blood CD4(+) T cells were transfected with miR-568 mimics, cell activation was significantly inhibited, as shown by the inhibited expression of activation markers such as CD25, CD69 and CD154; decreased IL-2 production; and inhibited cell proliferation. Using software predictions and confirmatory experiments, we demonstrated that nuclear factor of activated T cells 5 (NFAT5) is a target of miR-568. Treg cells are an important CD4(+) T-cell subpopulation, so we also evaluated the function of miR-568 in Treg-cell activation and differentiation. We showed that the miR-568 level decreased, while the NFAT5 protein level increased during CD4(+)CD25(+) Treg-cell activation, and the transfection of miR-568 mimics inhibited the NFAT5 expression, inhibited the production of both TGF-β and IL-10 and also inhibited the proliferation of Treg cells. Our further study showed that over-expression of miR-568 can inhibit Treg-cell differentiation and can inhibit the suppressive effect of these cells on effector cells. In addition, inhibition of NFAT5 by siRNA-mediated knockdown can inhibit the activation and differentiation of Treg cells. These findings reveal that miR-568 can inhibit the activation and function of both CD4(+) T cells and Treg cells by targeting NFAT5. Since miR-568 plays an important role in both CD4(+) T cells and Treg cells, these findings may provide leads for the development of novel treatments for human inflammatory and autoimmune diseases.

MicroRNA regulation of T-cell development

MicroRNAs are short, 19-24 nucleotide long, RNA molecules capable of regulating the longevity and, to a lesser extent, translation of messenger RNA (mRNA) species. The function of the microRNA network, and indeed, even that of individual microRNA species, can have profoundly different roles in even a single cell type as the microRNA/mRNA composition evolves. As the role of microRNA within T cells has come under increasing scrutiny, several distinct checkpoints have been demonstrated to have a particular reliance on microRNA regulation. MicroRNAs are arguably most important in T cells during the earliest and last stages in T-cell biology. The first stages of early thymic differentiation have a crucial reliance on the microRNA network, while later stages and peripheral homeostasis are largely, although not completely, microRNA-independent. The most profound effects on T cells are in the activation of effector and regulatory functions of conventional and regulatory T cells, where microRNA deficiency results in a near-complete loss of function. In this review, we focus on integrating the research on individual microRNA into a more global understanding of the function of the microRNA regulatory network in T cells.

MicroRNA-mediated regulation of T helper cell differentiation and plasticity

CD4(+) T helper (TH) cells regulate appropriate cellular and humoral immune responses to a wide range of pathogens and are central to the success of vaccines. However, their dysregulation can cause allergies and autoimmune diseases. The CD4(+) T cell population is characterized not only by a range of distinct cell subsets, such as TH1, TH2 and TH17 cells, regulatory T cells and T follicular helper cells--each with specific functions and gene expression programmes--but also by plasticity between the different TH cell subsets. In this Review, we discuss recent advances and emerging ideas about how microRNAs--small endogenously expressed oligonucleotides that modulate gene expression--are involved in the regulatory networks that determine TH cell fate decisions and that regulate their effector functions.

Control of HIV infection: escape from the shadow of Blimp-1

Prior murine studies have demonstrated the pivotal role that Blimp-1 has in the exhausted phenotype of T lymphocytes in chronic viral infection. In this issue of the European Journal of Immunology, Seddiki et al. [Eur. J. Immunol. 2013. 43: 510-520] demonstrate the applicability of this research to HIV infection. The authors do so by demonstrating differences in Blimp-1 expression between T lymphocytes isolated from patients with chronic active HIV versus those from long-term nonprogressors and showing that this is matched by differences in the cells' capacity to produce IL-2 and the level of expression of the inhibitory receptor PD-1. The data presented here suggest that this may relate to differential regulation of Blimp-1 by the micro RNA, mIR-9. These findings complement current murine work and fit squarely within the research priorities, as outlined by the International AIDS Society, for determining a cure for AIDS.

The role of T cell immunity in HIV-1 infection

The interplay between the T cell immune response and human immunodeficiency virus (HIV)-1 largely determines the outcome of infection. Typically, the virus overcomes the immune defences leading to a gradual decline in function that permits the development of disease. In recent years, a concerted effort in comparing T cell responses between 'controllers' and 'progressors' is beginning to identify the T cell subsets and factors that affect disease progression related to the effector functions of both CD4 and CD8 T cells. These efforts are providing opportunities for development of novel therapies and vaccines.

MicroRNA-155 regulates T cell proliferation through targeting GSK3β in cardiac allograft rejection in a murine transplantation model

Here we investigated the activity and regulation of miR-155 during cardiac allograft rejection (AR), and to examine the feasibility of using miR-155 as a biomarker of graft status. Expression of miR-155 in graft-infiltrating lymphocytes (GIL), T cells isolated from spleen (TFS), and lymphocytes separated from blood (LFB) was significantly increased during cardiac AR while GSK3β was downregulated in GIL and TFS. Inhibition of miR-155 impaired lymphocyte proliferation and enhanced the expression of GSK3β. Moreover, pharmacological inactivation of GSK3β resulted in rescue of the proliferative capability of T cells pretreated with a miR-155 inhibitor. Luciferase reporter assay confirmed that miR-155 interacted with the 3'-untranslated region (UTR) of GSK3β directly. In particular, the miR-155 in LFB can distinguish recipients with AR from syngeneic controls from POD 3 and later. The present study provides a better understanding of the pathophysiological process underlying cardiac AR progression.

Interleukin-2 at the crossroads of effector responses, tolerance, and immunotherapy

Interleukin-2 (IL-2) is a pleiotropic cytokine produced after antigen activation that plays pivotal roles in the immune response. Discovered as a T cell growth factor, IL-2 additionally promotes CD8(+) T cell and natural killer cell cytolytic activity and modulates T cell differentiation programs in response to antigen, promoting naïve CD4(+) T cell differentiation into T helper 1 (Th1) and T helper 2 (Th2) cells while inhibiting T helper 17 (Th17) and T follicular helper (Tfh) cell differentiation. Moreover, IL-2 is essential for the development and maintenance of T regulatory cells and for activation-induced cell death, thereby mediating tolerance and limiting inappropriate immune reactions. In this review, we focus on the molecular mechanisms and complex cellular actions of IL-2, its cooperative and opposing effects with other cytokines, and how both promoting and blocking the actions of IL-2 are being utilized in clinical medicine.

PRDM Proteins: Molecular Mechanisms in Signal Transduction and Transcriptional Regulation

PRDM (PRDI-BF1 and RIZ homology domain containing) protein family members are characterized by the presence of a PR domain and a variable number of Zn-finger repeats. Experimental evidence has shown that the PRDM proteins play an important role in gene expression regulation, modifying the chromatin structure either directly, through the intrinsic methyltransferase activity, or indirectly through the recruitment of chromatin remodeling complexes. PRDM proteins have a dual action: they mediate the effect induced by different cell signals like steroid hormones and control the expression of growth factors. PRDM proteins therefore have a pivotal role in the transduction of signals that control cell proliferation and differentiation and consequently neoplastic transformation. In this review, we describe pathways in which PRDM proteins are involved and the molecular mechanism of their transcriptional regulation.

miR-9 modulates the expression of interferon-regulated genes and MHC class I molecules in human nasopharyngeal carcinoma cells

The functions of miR-9 in some cancers are recently implicated in regulating proliferation, epithelial-mesenchymal transition (EMT), invasion and metastasis, apoptosis, and tumor angiogenesis, etc. miR-9 is commonly down-regulated in nasopharyngeal carcinoma (NPC), but the exact roles of miR-9 dysregulation in the pathogenesis of NPC remains unclear. Therefore, we firstly used miR-9-expressing CNE2 cells to determine the effects of miR-9 overexpression on global gene expression profile by microarray analysis. Microarray-based gene expression data unexpectedly demonstrated a significant number of up- or down-regulated immune- and inflammation-related genes, including many well-known interferon (IFN)-induced genes (e.g., IFI44L, PSMB8, IRF5, PSMB10, IFI27, PSB9_HUMAN, IFIT2, TRAIL, IFIT1, PSB8_HUMAN, IRF1, B2M and GBP1), major histocompatibility complex (MHC) class I molecules (e.g., HLA-B, HLA-C, HLA-F and HLA-H) and interleukin (IL)-related genes (e.g., IL20RB, GALT, IL7, IL1B, IL11, IL1F8, IL1A, IL6 and IL7R), which was confirmed by qRT-PCR. Moreover, the overexpression of miR-9 with the miRNA mimics significantly up- or down-regulated the expression of above-mentioned IFN-inducible genes, MHC class I molecules and IL-related genes; on the contrary, miR-9 inhibition by anti-miR-9 inhibitor in CNE2 and 5-8F cells correspondingly decreased or increased the aforementioned immune- and inflammation-related genes. Taken together, these findings demonstrate, for the first time, that miR-9 can modulate the expression of IFN-induced genes and MHC class I molecules in human cancer cells, suggesting a novel role of miR-9 in linking inflammation and cancer, which remains to be fully characterized.