miR-146a suppresses cellular immune response during Japanese encephalitis virus JaOArS982 strain infection in human microglial cells

Reduced miR-146a Promotes REG3A Expression and Macrophage Migration in Polymyositis and Dermatomyositis

Background: Growing evidence from studies elsewhere have illustrated that microRNAs (miRNAs) play important roles in polymyositis and dermatomyositis (PM/DM). However, little has been reported on their relationship with regenerating islet-derived protein 3-alpha (REG3A) as well as their associative roles in macrophage migration. Therefore, this study sought to establish the association between miR-146a and REG3A as well as investigate their functional roles in macrophage migration and PM/DM pathogenesis. Methods: Peripheral blood mononuclear cells (PBMCs) were isolated from PM/DM patients and healthy controls through density centrifugation. Macrophages were obtained from monocytes purified from PBMCs via differentiation before their transfection with miRNA or plasmids to investigate cell migration with transwell assay. An experimental autoimmune myositis murine model was used to investigate PM/DM. Real-time PCR and Western blot analysis were conducted to determine the expression levels of miR-146a, interferon gamma (IFN-γ), interleukin (IL)-17A, and REG3A. Results: The messenger RNA (mRNA) expression level of miR-146a markedly decreased, while the mRNA level of REG3A, IFN-γ, and IL-17A expression increased substantially in PBMCs from PM/DM patients compared with the healthy controls. The levels of IFN-γ and IL-17A in serum from PM/DM patients was much higher than the healthy controls. Immunohistochemistry analysis showed that REG3A expression increased in muscle tissues from patients. Consistent with clinical data, the mRNA expression level of miR-146a also decreased, whereas the mRNA and protein level of REG3A, IFN-γ, and IL-17A significantly increased in the muscle tissues of experimental autoimmune myositis mice. Moreover, miR-146a inhibited monocyte-derived macrophage migration, and REG3A promoted macrophage migration. In addition, IL-17A induced REG3A expression, while miR146a inhibited expression of REG3A in monocyte-derived macrophages from the PBMCs of the healthy donors. Notably, inhibition of macrophage migration by miR-146a was via the reduction in REG3A expression. Conclusions: Reduced miR-146a expression in PM/DM leads to increased REG3A expression that increases inflammatory macrophage migration, which may be a possible underlying mechanism of DM/PM pathogenesis.

Role of microRNAs in antiviral responses to dengue infection

Dengue virus (DENV) is the etiological agent of dengue fever. Severe dengue could be fatal and there is currently no effective antiviral agent or vaccine. The only licensed vaccine, Dengvaxia, has low efficacy against serotypes 1 and 2. Cellular miRNAs are post-transcriptional regulators that could play a role in direct regulation of viral genes. Host miRNA expressions could either promote or repress viral replications. Induction of some cellular miRNAs could help the virus to evade the host immune response by suppressing the IFN-α/β signaling pathway while others could upregulate IFN-α/β production and inhibit the viral infection. Understanding miRNA expressions and functions during dengue infections would provide insights into the development of miRNA-based therapeutics which could be strategized to act either as miRNA antagonists or miRNA mimics. The known mechanisms of how miRNAs impact DENV replication are diverse. They could suppress DENV multiplication by directly binding to the viral genome, resulting in translational repression. Other miRNA actions include modulation of host factors. In addition, miRNAs that could modulate immunopathogenesis are discussed. Major hurdles lie in the development of chemical modifications and delivery systems for in vivo delivery. Nevertheless, advancement in miRNA formulations and delivery systems hold great promise for the therapeutic potential of miRNA-based therapy, as supported by Miravirsen for treatment of Hepatitis C infection which has successfully completed phase II clinical trial.

The role of miR-146a in viral infection

Cellular microRNAs (miRNAs) were identified as a key player in the posttranscriptional regulation of cellular-genes regulatory pathways. They also emerged as a significant regulator of the immune response. In particular, miR-146a acts as an importance modulator of function and differentiation cells of the innate and adaptive immunity. It has been associated with disorder including cancer and viral infections. Given its significance in the regulation of key cellular processes, it is not surprising which virus infection have found ways to dysregulation of miRNAs. miR-146a has been identified in exosomes (exosomal miR-146a). After the exosomes release from donor cells, they are taken up by the recipient cell and probably the exosomal miR-146a is able to modulate the antiviral response in the recipient cell and result in making them more susceptible to virus infection. In this review, we discuss recent reports regarding miR-146a expression levels, target genes, function, and contributing role in the pathogenesis of the viral infection and provide a clue to develop the new therapeutic and preventive strategies for viral disease in the future.

Regulation of miRNAs as new tool for cutaneous vitality lesions demonstration in ligature marks in deaths by hanging

This study aims to demonstrate that the application of miRNA expression in forensic pathology, in cases of hanging, applying the method on skin samples. The proposed investigative protocol allowed us to highlight a different miRNA expression in the skin ligature marks of subjects who died by hanging compared to healthy skin control samples. The results obtained showed an increase in the expression of miRNAs recognized as regulators of the inflammatory response in skin lesions such as miR125a-5p and miR125b-5p. Furthermore, overexpression of additional miRNAs - miR214a-3p, miR128-3p, miR130a-3p, and miR92a-3p - with anti-inflammatory activity was highlighted. It was possible to document a statistical significance to control skin samples only for miR103a-3p (p < 0.05), miR214-3p and miR92a-3p (p < 0.01) The upregulation of miR222-3p and miR150-5p, respectively related to mast-cell activation and neutrophils after the application of traumatic stimuli supports the immunohistochemical data showed in literature. The diagnostic accuracy of miRNAs could expand the range of diagnostic tools available in the assessment of the vitality of a lesion.

High-Throughput MicroRNA Profiles of Permissive Madin-Darby Canine Kidney Cell Line Infected with Influenza B Viruses

Victoria and Yamagata lineages of influenza B viruses are globally circulating in seasonal epidemics. Madin–Darby canine kidney (MDCK) cells are permissive for viral isolation and vaccine manufacture. Nevertheless, the interplay between influenza B viruses and host microRNAs has not been investigated in this cell line. Therefore, the present study aims at high-throughput analysis of canine microRNA profile upon infection of influenza B viruses. Briefly, MDCK cells were infected with Victoria or Yamagata lineage at MOI of 0.01. After being harvested at 6, 12 and 24 h post infection, microRNAs were subjected to high-throughput sequencing based on MiSeq platform (Illumina). The results demonstrated that five microRNAs including cfa-miR-197, cfa-miR-215, cfa-miR361, cfa-miR-1841, and cfa-miR-1842 were overexpressed in both Victoria and Yamagata lineage infections. Interestingly, computational prediction showed that karyopherin alpha 6 (KPNA6) was targeted by cfa-miR-197 and cfa-miR-215. Moreover, the binding sites of both microRNAs were assessed by 3′-UTR reporter assay. The results showed that only cfa-miR-197 could bind to the target sites of KPNA6, leading to suppressing luciferase activity. Additionally, silencing of KPNA6 was confirmed by overexpression of cfa-miR-197. This study provides canine microRNA responses to seasonal influenza B viruses, suggesting that virus-mediated microRNAs might play crucial roles in host gene regulation.

Modulation of Type-I Interferon Response by hsa-miR-374b-5p During Japanese Encephalitis Virus Infection in Human Microglial Cells

Japanese Encephalitis virus (JEV) is a neurotropic ssRNA virus, belonging to the Flaviviridae family. JEV is one of the leading causes of the viral encephalitis in Southeast-Asian countries. JEV primarily infects neurons however, the microglial activation has been reported to further enhance the neuroinflammation and promote neuronal death. The PI3K/AKT pathway has been reported to play an important role in type-I interferon response via IRF3. Phosphatase and tensin homolog (PTEN), a negative regulator of PI3K/AKT pathway, participates in microglial polarization and neuroinflammation. The microRNAs are small non-coding endogenously expressed RNAs, which regulate the gene expression by binding at 3′ UTR of target gene. The human microglial cells were infected with JEV (JaOArS982 strain) and up-regulation of microRNA; hsa-miR-374b-5p was confirmed by qRT-PCR. The genes in PI3K/AKT pathway, over-expression and knock-down studies of hsa-miR-374b-5p with and without JEV infection were analyzed through immuno blotting. The regulatory role of hsa-miR-374b-5p on the expression of type-I interferon was determined by luciferase assays. JEV infection modulated the expression of hsa-miR-374b-5p and PI3K/AKT pathway via PTEN. The over-expression of hsa-miR-374b-5p suppressed the PTEN while up-regulated the AKT and IRF3 proteins, whereas, the knockdown rescued the PTEN expression and suppressed the AKT and IRF3 proteins. The modulation of hsa-miR-374b-5p regulated the type-I interferon response during JEV infection. In present study, we have shown the modulation of PTEN by hsa-miR-374b-5p, which regulated the PI3K/AKT/IRF3 axis in JEV infected microglial cells.

miR-146a promotes Borna disease virus 1 replication through IRAK1/TRAF6/NF-κB signaling pathway

BACKGROUND/AIMS

Borna disease virus 1 (BoDV-1) is a negative single-stranded RNA virus that is highly neurotropic. BoDV-1 infection can damage the central nervous system and cause inflammation. To survive in host cells, BoDV-1 must evade the host innate immune response. A previous study showed that miR-146a expression increased in neonatal rats infected with BoDV-1. miR-146a is a microRNA suggested to negatively regulate innate immune and inflammatory responses and antiviral pathways. Many groups have reported that its overexpression facilitates viral replication. However, it is unclear whether miR-146a is involved in escape from the host immune response during BoDV-1 infection.

METHODS

In this study, BoDV-1 was used to infect neonatal rats within 24 h of birth intracranially, as well as to infect human microglial cells (HMC3). miR-146a expression was analyzed by RT-qPCR. The TargetScanHuman database was used to find the target genes of miR-146a. A search of the binding sites of miR-146a and its target gene's 3'-untranslated region (3'UTR) was also performed using RNAhybrid software. The binding sites of miR-146a and the target gene's 3'UTR were detected by dual luciferase reporter assays. Overexpression and suppression studies of miR-146a were performed to determine its effect on BoDV-1 replication. The relative protein expression of members of the IRAK1/TRAF6/NF-κB signaling pathway was also evaluated by western blotting in HMC3.

RESULTS

After BoDV-1 infection of neurons in vivo and of HMC3 cells, miR-146a expression was significantly upregulated. miR-146a overexpression in HMC3 cells promoted viral replication, while its inhibition inhibited it. Through the TargetScanHuman database, we identified the target genes of anti-inflammatory miR-146a: IRAK1 and TRAF6. We also found that BoDV-1 could inhibit IRAK1 and TRAF6 expression in HMC3 cells. Moreover, we showed that the inhibition of IRAK1 and TRAF6 also led to decreases in the expression of P65 and phosphorylated P65 in the downstream NF-κB pathway. Subsequently, we confirmed the interaction of miR-146a with IRAK1 and TRAF6 by luciferase assay.

CONCLUSION

Our results suggest that miR-146a inhibits the IRAK1/TRAF6/NF-κB signaling pathway to facilitate BoDV-1 survival in host cells.

TRAF6 Plays a Proviral Role in Tick-Borne Flavivirus Infection through Interaction with the NS3 Protease

Tick-borne flaviviruses (TBFVs) can cause life-threatening encephalitis and hemorrhagic fever. To identify virus-host interactions that may be exploited as therapeutic targets, we analyzed the TBFV polyprotein in silico for antiviral protein-binding motifs. We obtained two putative tumor necrosis factor receptor-associated factor 6 (TRAF6)-binding motifs (TBMs) within the protease domain of the viral nonstructural 3 (NS3) protein. Here, we show that TBFV NS3 interacted with TRAF6 during infection and that TRAF6 supports TBFV replication. The proviral role of TRAF6 was not seen with mosquito-borne flaviviruses, consistent with the lack of conserved TBMs. Mutation of the second TBM within NS3 disrupted TRAF6 binding, coincident with reduced abundance of mature, autocatalytically derived form of the NS3 protease and significant virus attenuation in vitro. Our studies reveal insights into how flaviviruses exploit innate immunity for the purpose of viral replication and identify a potential target for therapeutic design.

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Langat virus (LGTV) NS3 protease interacts with TRAF6 during infection

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Tick-borne, unlike mosquito-borne, flaviviruses use TRAF6 for optimal replication

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E117A mutation of LGTV NS3 reduces TRAF6 binding and mature protease abundance

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LGTV with a mutated TRAF6-binding motif is attenuated in vitro

Evidence for Host Epigenetic Signatures Arising From Arbovirus Infections: A Systematic Review

Background: Arbovirus infections have steadily become a major pandemic threat. This study aimed at investigating the existence of host epigenetic markers arising from the principal arboviruses infections impacting on human health. We set to systematically review all published evidence describing any epigenetic modifications associated with infections from arboviruses, including, but not limited to, microRNAs, DNA methylation, and histone modifications. Methods: A comprehensive search was conducted using the electronic databases PubMed, Science Direct and Cochrane Library from inception to January 4th, 2018. We included reports describing original in vivo or in vitro studies investigating epigenetic changes related to arbovirus infections in either clinical subjects or human cell lines. Studies investigating epigenetic modifications related to the virus or the arthropod vector were excluded. A narrative synthesis of the findings was conducted, contextualizing comparative evidence from in vitro and in vivo studies. Results: A total of 853 unique references were identified and screened by two independent researchers. Thirty-two studies met the inclusion criteria and were reviewed. The evidence was centered mainly on microRNA and DNA methylation signatures implicated with secondary Dengue fever. Evidence for recent epidemic threats, such as the infections by Zika or Chikungunya viruses is still scant. Conclusions: Major epigenetic alterations found on arboviruses infections were miR-146, miR-30e and the Dicer complex. However, existing studies frequently tested distinct hypotheses resulting in a heterogeneity of methodological approaches. Whilst epigenetic signatures associated with arbovirus infections have been reported, existing studies have largely focused on a small number of diseases, particularly dengue. Validation of epigenetic signatures have an untapped potential, but concerted investigations are certainly required to deliver robust candidates of clinical utility for diagnosis, staging and prognosis of specific arboviral diseases.

MicroRNAs in Neuroinflammation: Implications in Disease Pathogenesis, Biomarker Discovery and Therapeutic Applications

The central nervous system can respond to threat via the induction of an inflammatory response. Under normal circumstances this response is tightly controlled, however uncontrolled neuroinflammation is a hallmark of many neurological disorders. MicroRNAs are small non-coding RNA molecules that are important for regulating many cellular processes. The ability of microRNAs to modulate inflammatory signaling is an area of ongoing research, which has gained much attention in recent years. MicroRNAs may either promote or restrict inflammatory signaling, and either exacerbate or ameliorate the pathological consequences of excessive neuroinflammation. The aim of this review is to summarize the mode of regulation for several important and well-studied microRNAs in the context of neuroinflammation, including miR-155, miR-146a, miR-124, miR-21 and let-7. Furthermore, the pathological consequences of miRNA deregulation during disorders that feature neuroinflammation are discussed, including Multiple Sclerosis, Alzheimer’s disease, Parkinson’s disease, Prion diseases, Japanese encephalitis, Herpes encephalitis, ischemic stroke and traumatic brain injury. There has also been considerable interest in the use of altered microRNA signatures as biomarkers for these disorders. The ability to modulate microRNA expression may even serve as the basis for future therapeutic strategies to help treat pathological neuroinflammation.

Chandipura virus changes cellular miRNome in human microglial cells

Chandipura virus (CHPV) is a neurotropic virus, known to cause encephalitis in humans. The microRNAs (miRNA/miR) play an important role in the pathogenesis of viral infection. The present study is focused on the role of miRNAs during CHPV (strain 1653514) infection in human microglial cells. The deep sequencing of CHPV-infected human microglial cells identified a total of 12 differentially expressed miRNA (DEMs). To elucidate the role of DEMs, the target gene prediction, Gene Ontology term (GO Term), pathway enrichment analysis, and miRNA-messenger RNA (mRNA) interaction network analysis was performed. The GO terms and pathway enrichment analysis provided 146 enriched genes; which were involved in interferon response, cytokine and chemokine signaling. Further, the WGCNA (weighted gene coexpression network analysis) of the enriched genes were discretely categorized into three modules (blue, brown, and turquoise). The hub genes in the blue module may correlate to CHPV induced neuroinflammation. Altogether, the miRNA-mRNA interaction network and WGCNA study revealed the following pairs, hsa-miR-542-3p and FAF1, hsa-miR-92a-1-5p and MYD88, and hsa-miR-3187-3p and TNFRSF21, which may contribute to neuroinflammation during CHPV infection in human microglial cells.

Dengue NS5 modulates expression of miR-590 to regulate ubiquitin-specific peptidase 42 in human microglia

Dengue virus (DENV), a member of Flaviviridae family, has become neurovirulent in humans after rapid geographical expansion. Host proteasomal machinery contains both ubiquitin ligases as well as deubiquitinases (DUBs), known to influence key cellular and biological functions. MicroRNA-mediated modulations of DUBs in case of DENV infections have not been explored yet. DENV propagation, MiRNA overexpression, miRNA knockdown, transfection, RT-PCR, luciferase assay, and western blotting have been used in this study to establish the interaction of miR-590 and USP42. DENV infection in human microglial cells resulted in downregulation of host DUB-USP42 in a dose-dependent manner and DENV-NS5 gene alone was found to be sufficient for this downregulation. miR-590 was upregulated upon NS5 overexpression in a dose-dependent manner. Downregulation of USP42 was observed with miR-590 overexpression. The specificity of this regulation was confirmed by miR-590 mimic and anti-miR transfections in microglial cells. miR-590 overexpression and knockdown affected the expression level of TRAF6 in indirect manner in microglial cells. The luciferase assay demonstrated the direct regulatory interaction between miR-590 and 3'UTR of USP42. These findings establish that DENV-NS5 protein can potentially modulate the host deubiquitinase protein USP42 expression via altering cellular miR-590 levels in human microglial cells.

Downregulation of miR-146a inhibits influenza A virus replication by enhancing the type I interferon response in vitro and in vivo

Albeit microRNAs (miRNAs) have become increasingly appreciated for their essential roles in innate immune responses to viral infections; however, it is unknown how host miRNAs regulate influenza A virus (IAV)-induced inflammation. The aim of our study was to investigate the role of miR-146a in IAV replication in vitro and in vivo. In vitro, we found miR-146a was significantly upregulated in A549 cells with IAV infection. Overexpression of miR-146a promoted IAV replication, while downregulation of miR-146a repressed replication. We found that miR-146a diminished type I interferon (IFN) responses by decreasing IFN-β production and IFN-stimulated gene (ISG) expression. Furthermore, we found the IFNs level and IAV replication regulated by miR-146a inhibitor was partially reversed by depletion of interferon receptor (IFNAR) 1 or 2. In addition, we found that miR-146a directly targets tumor necrosis factor receptor association factor 6 (TRAF6), which is involved in the production of type I IFN, and TRAF6 overexpression reversed the replication-promoting effect of miR-146a on IAV. In vivo, inhibition of miR-146a alleviated IAV-induced mice lung injury and promoted survival rates by promoting type I antiviral activities. It is, therefore, concluded that downregulation of miR-146a inhibits IAV replication by enhancing type I IFN response through its target gene TRAF6 in vitro and in vivo, suggesting miR-146a antagomir might be a potential therapeutic target during IAV infection.

Roles of microRNAs in T cell immunity: Implications for strategy development against infectious diseases

T cell immunity plays a vital role in pathogen infections. MicroRNA (miRNAs) are small, single-stranded noncoding RNAs that regulate T cell immunity by targeting key transcriptional factors, signaling proteins, and cytokines associated with T cell activation, differentiation, and function. The dysregulation of miRNA expression in T cells may lead to specific immune responses and can provide new therapeutic opportunities against various infectious diseases. Here, we summarize recent studies that focus on the roles of miRNAs in T cell immunity and highlight miRNA functions in prevalent infectious diseases. Additionally, we also provide insights into the functions of extracellular vesicle miRNAs and attempt to delineate the mechanism of miRNA sorting into extracellular vesicles and their immunomodulatory functions. Moreover, methodologies and strategies for miRNA delivery against infectious diseases are summarized. Finally, potential strategies for miRNA-based therapies are proposed.

The human microglial HMC3 cell line: where do we stand? A systematic literature review

Microglia, unique myeloid cells residing in the brain parenchyma, represent the first line of immune defense within the central nervous system. In addition to their immune functions, microglial cells play an important role in other cerebral processes, including the regulation of synaptic architecture and neurogenesis. Chronic microglial activation is regarded as detrimental, and it is considered a pathogenic mechanism common to several neurological disorders. Microglial activation and function have been extensively studied in rodent experimental models, whereas the characterization of human cells has been limited due to the restricted availability of primary sources of human microglia. To overcome this problem, human immortalized microglial cell lines have been developed. The human microglial clone 3 cell line, HMC3, was established in 1995, through SV40-dependent immortalization of human embryonic microglial cells. It has been recently authenticated by the American Type Culture Collection (ATCC®) and distributed under the name of HMC3 (ATCC®CRL-3304). The HMC3 cells have been used in six research studies, two of which also indicated by ATCC® as reference articles. However, a more accurate literature revision suggests that clone 3 was initially distributed under the name of CHME3. In this regard, several studies have been published, thus contributing to a more extensive characterization of this cell line. Remarkably, the same cell line has been used in different laboratories with other denominations, i.e., CHME-5 cells and C13-NJ cells. In view of the fact that "being now authenticated by ATCC®" may imply a wider distribution of the cells, we aimed at reviewing data obtained with the human microglia cell line clone 3, making the readers aware of this complicated nomenclature. In addition, we also included original data, generated in our laboratory with the HMC3 (ATCC®CRL-3304) cells, providing information on the current state of the culture together with supplementary details on the culturing procedures to obtain and maintain viable cells.

How to reprogram microglia toward beneficial functions

Microglia, brain cells of nonneural origin, orchestrate the inflammatory response to diverse insults, including hypoxia/ischemia or maternal/fetal infection in the perinatal brain. Experimental studies have demonstrated the capacity of microglia to recognize pathogens or damaged cells activating a cytotoxic response that can exacerbate brain damage. However, microglia display an enormous plasticity in their responses to injury and may also promote resolution stages of inflammation and tissue regeneration. Despite the critical role of microglia in brain pathologies, the cellular mechanisms that govern the diverse phenotypes of microglia are just beginning to be defined. Here we review emerging strategies to drive microglia toward beneficial functions, selectively reporting the studies which provide insights into molecular mechanisms underlying the phenotypic switch. A variety of approaches have been proposed which rely on microglia treatment with pharmacological agents, cytokines, lipid messengers, or microRNAs, as well on nutritional approaches or therapies with immunomodulatory cells. Analysis of the molecular mechanisms relevant for microglia reprogramming toward pro‐regenerative functions points to a central role of energy metabolism in shaping microglial functions. Manipulation of metabolic pathways may thus provide new therapeutic opportunities to prevent the deleterious effects of inflammatory microglia and to control excessive inflammation in brain disorders.

LncRNA, miRNA and lncRNA-miRNA interaction in viral infection

Noncoding RNAs (ncRNAs) are key components of the transcriptome and play an important role in both normal biological activity and pathological processes such as viral infection and tumorigenesis. LncRNAs and miRNAs are the most important elements of ncRNAs and function as vital regulatory elements. Their complex regulatory relationship has therefore attracted a lot of attention. In this review, we address the generation, classification, and regulatory mechanisms of lncRNAs and miRNAs in the interaction between virus and host, focusing on their mutual regulation in viral replication and pathogenesis. In-depth analysis of the underlying mechanisms will provide new information for the prevention of viral infections and development of antiviral drugs.

Epigenetics Control Microglia Plasticity

Microglia, resident immune cells of the central nervous system, fulfill multiple functions in the brain throughout life. These microglial functions range from participation in innate and adaptive immune responses, involvement in the development of the brain and its homeostasis maintenance, to contribution to degenerative, traumatic, and proliferative diseases; and take place in the developing, the aging, the healthy, or the diseased brain. Thus, an impressive level of cellular plasticity, appears as a requirement for the pleiotropic biological functions of microglia. Epigenetic changes, including histone modifications or DNA methylation as well as microRNA expression, are important modifiers of gene expression, and have been involved in cell phenotype regulation and reprogramming and are therefore part of the mechanisms regulating cellular plasticity. Here, we review and discuss the epigenetic mechanisms, which are emerging as contributors to this microglial cellular plasticity and thereby can constitute interesting targets to modulate microglia associated brain diseases, including developmental diseases, neurodegenerative diseases as well as cancer.

Increased serum microRNA-29b expression and bad recovery in Japanese encephalitis virus infected patients; A new component to improve the disease recovery

BACKGROUND

Japanese encephalitis virus (JEV) is a neurotropic mosquito-borne Flavivirus, mainly prevalent in Asia. It is the most important causative agent of acute viral encephalitis in humans. Recently, micro RNAs are discovered as a key regulator of inflammatory and immune responses in various diseases including neurological and viral infections. Thus, this study was proposed to check whether changes in cellular miRNA expression due to JE virus infection, can be detected in circulation which would be helpful in diagnosis and treatment.

METHODS

miRNAs (miR-29b and miR-146a) were analyzed in the serum of JEV infected patients using quantitative reverse transcription polymerase chain reaction (RT-qPCR).

RESULTS

miR-146a was found significantly decreased (p = 0.0008) in JEV infected patients as compared to healthy controls whereas miR-29b was significantly increased (p = 0.001) in JEV patients recovered with neurological sequelae when compared to those recovered without sequelae.

CONCLUSION

In conclusion, miRNA can be measured in serum. Studying microRNAs will provide novel information and help us to identify the components that can serve as biomarkers and can lead to new discovery in controlling disease recovery.

HIV-1-Induced miR-146a Attenuates Monocyte Migration by Targeting CCL5 in Human Primary Macrophages

MicroRNAs (miRNAs) are widely involved in immune regulation during virus infection. Several studies showed that the expression of miR-146a was increased in human immunodeficiency virus type I (HIV-1)-infected cells, but the definitive function of miR-146a in HIV-1 infection remains obscure. The production of chemokine (C-C motif) ligand 5 (CCL5) in macrophages has been reported to play an important role in HIV/AIDS-associated pathogenesis. In this study, we examined the effects of miR-146a on CCL5 regulation in HIV-1-infected macrophages. Gain and loss of function studies showed that CCL5 might be one of the miR-146a targets, as miR-146a mimic reduced, while miR-146a inhibitor increased CCL5 production in HIV-1-infected macrophages. In addition, we demonstrated that miR-146a reduced CCL5-induced monocyte migration. Our study provided evidence that miR-146a targets CCL5 3' untranslated regions, downregulates its release from macrophages, and affects monocyte migration consequently. These findings drew a novel layer of posttranscriptional control of the chemokine CCL5 by miR-146a during HIV infection, which might contribute to HIV pathogenesis.

Anti-Inflammatory MicroRNAs and Their Potential for Inflammatory Diseases Treatment

Inflammation is a complicated biological and pathophysiological cascade of responses to infections and injuries, and inflammatory mechanisms are closely related to many diseases. The magnitude, the complicated network of pro- and anti-inflammatory factors, and the direction of the inflammatory response can impact on the development and progression of various disorders. The currently available treatment strategies often target the symptoms and not the causes of inflammatory disease and may often be ineffective. Since the onset and termination of inflammation are crucial to prevent tissue damage, a range of mechanisms has evolved in nature to regulate the process including negative and positive feedback loops. In this regard, microRNAs (miRNAs) have emerged as key gene regulators to control inflammation, and it is speculated that they are fine-tune signaling regulators to allow for proper resolution and prevent uncontrolled progress of inflammatory reactions. In this review, we discuss recent findings related to significant roles of miRNAs in immune regulation, especially the potential utility of these molecules as novel anti-inflammatory agents to treat inflammatory diseases. Furthermore, we discuss the possibilities of using miRNAs as drugs in the form of miRNA mimics or miRNA antagonists.

MicroRNA-146a promotes red spotted grouper nervous necrosis virus (RGNNV) replication by targeting TRAF6 in orange spotted grouper, Epinephelus coioides

MicroRNA-146a (miR-146a) has been demonstrated to function as a negative regulator of cellular immune responses against pathogens in mammals, however, little information focused on its functions in lower vertebrates. In this study, we investigated the regulatory roles of orange spotted grouper, Epinephelus coioides miR-146a during red spotted grouper nervous necrosis virus (RGNNV) infection. During RGNNV infection in grouper spleen (GS) cells, the endogenous expression level of miR-146a and tumor necrosis factor receptor-associated factor 6 (TRAF6) significantly increased along with the infection time. Overexpression of miR-146a significantly facilitated viral infection, evidenced by the increased transcription of viral CP and RdRp genes, while miR-146a knockdown by specific inhibitors decreased RGNNV replication. Using pMIR-REPORT Luciferase system, we found that the 3' untranslated region (UTR) of grouper TRAF6 could be specifically targeted by miR-146a. Further studies showed that its downstream target gene pro-inflammatory cytokines, including TNF-α, IL-8 and IL-1β, were all significantly decreased in miR-146a mimic transfected cells, but increased in miR-146a inhibitors transfected cells during RGNNV infection. Thus, our results suggested and verified that holding the level of miR-146a exerted crucial roles in RGNNV infection through TRAF6-mediated inflammatory response.

Exploitation of microRNAs by Japanese Encephalitis virus in human microglial cells

JEV infection in CNS leads to the JE neuroinflammation. Children and old age individual have been reported to be more prone to JEV infection. MicroRNAs are endogenous, small non-coding RNAs, which regulate the gene expression. These are ∼22 nucleotide long, conserved RNA sequence that binds at the 3'UTR of a target mRNA and regulate the post-transcriptional gene expression. The role of microRNAs has been reported in several diseases like cancer, viral infection, neuro-degeneration, diabetes etc. In the present study, the human microglial cells were infected with JEV (JaOArS982). The control and infected samples were subject to microarray profiling for microRNA expression. The microarray profile yielded differentially expressed microRNAs from JEV infected samples. The microRNA gene targets, gene ontology, annotations, and pathways were identified through various bioinformatics tools. Additionally, the pathways were mostly found common to "ubiquitin mediated proteolysis," "cytokine signaling," "maintenance of barrier function/cell junctions," JAK/STAT pathway" "Toll-like receptor signaling," "Wnt-signaling," "adhesion molecules," "apoptosis," "endocytosis," "vesicle mediated transport" etc.

MiR-16-5p mediates a positive feedback loop in EV71-induced apoptosis and suppresses virus replication

Enterovirus 71 (EV71) is the predominant causative pathogen of hand-foot-and-mouth disease (HFMD). Contrary to other HFMD-causing enterovirus, EV71 can lead to severe neurological complications, even death. MicroRNAs (miRNAs) are small non-coding RNAs that constitute the largest family of gene regulators participating in numerous biological or pathological processes. We previously reported that miR-16-5p increases with severity of HFMD by investigating the expression patterns of host miRNAs in patients with HFMD. However, the mechanisms by which EV71 induces miR-16-5p expression are not clear, and the interaction between EV71 and miR-16-5p is not yet fully understood. Here, we confirmed EV71-induced expression of miR-16-5p both in vitro and in vivo and show that upregulation of miR-16-5p by EV71 infection may occur at the posttranscriptional level. Moreover, EV71-induced caspase activation facilitates the processing of pri-miR-16-1. We also revealed that miR-16-5p can promote EV71-induced nerve cells apoptosis through activating caspase-3. In addition, we found that miR-16-5p can inhibit EV71 replication. CCNE1 and CCND1, two important cell cycle regulators, play an important role in the suppression of EV71 replication by miR-16-5p. Therefore, miR-16-5p is a positive feedback regulator in EV71-induced apoptosis and a suppressor of virus replication. These results help in understanding the interaction network between miRNA and EV71 infection and provide a potential target for the development of antiviral therapy.

Molecular Mechanisms Modulating the Phenotype of Macrophages and Microglia

Macrophages and microglia play crucial roles during central nervous system development, homeostasis and acute events such as infection or injury. The diverse functions of tissue macrophages and microglia are mirrored by equally diverse phenotypes. A model of inflammatory/M1 versus a resolution phase/M2 macrophages has been widely used. However, the complexity of macrophage function can only be achieved by the existence of varied, plastic and tridimensional macrophage phenotypes. Understanding how tissue macrophages integrate environmental signals via molecular programs to define pathogen/injury inflammatory responses provides an opportunity to better understand the multilayered nature of macrophages, as well as target and modulate cellular programs to control excessive inflammation. This is particularly important in MS and other neuroinflammatory diseases, where chronic inflammatory macrophage and microglial responses may contribute to pathology. Here, we perform a comprehensive review of our current understanding of how molecular pathways modulate tissue macrophage phenotype, covering both classic pathways and the emerging role of microRNAs, receptor-tyrosine kinases and metabolism in macrophage phenotype. In addition, we discuss pathway parallels in microglia, novel markers helpful in the identification of peripheral macrophages versus microglia and markers linked to their phenotype.

miR-146a and miR-146b in the diagnosis and prognosis of papillary thyroid carcinoma

The present study investigated the relationship between the expression of miR-146a and miR-146b with the occurrence and prognosis of papillary thyroid carcinoma. Experiments in vitro were also used to explore the effect of the knocked down expression of the miRNAs on growth and migration of papillary thyroid carcinoma cells. A total of 73 patients with papillary thyroid carcinoma admitted to Yidu Central Hospital of Weifang from September 2013 to September 2015 were enrolled in the study. Carcinoma samples were obtained from each patient, and adjacent tissues were used as control samples to determine expression levels of miR-146a and miR146b by semi-quantitative RT-PCR. An analysis was conducted to find possible correlations between the miRNAs expression levels and clinicopathological features in the patients followed up for one year after diagnosis. Additionally, to examine the function of miR-146a and miR-146b on TPC-1 cells, the expression of miRNAs was knocked down using specific siRNAs. MTT and Transwell assays were used to evaluate cell proliferation and migration, respectively, in the miRNA cell lines. Finally, western blot analysis was used to analyze the expression of IRAK1 in PTC cancer cells. Our results showed that the expression levels of miR-146a and miR-146b in carcinoma tissues were significantly higher than the levels in cancer-free tissues (P<0.01). The relative expression levels of miR-146a and miR-146b in cancerous tissues could be associated with the pathological type and presence or absence of lymph node metastasis (P<0.05). Compared with the siRNA-control cell, MTT and Transwell assays showed that the cell growth and migration of TPC-1 cells were decreased in miR-146a and miR-146b low expression cells (P<0.01). Western blot analysis showed that the expression of IRAK1 in papillary thyroid carcinoma was higher than in adjacent tissue (P<0.01). Based on our findings, the expression of miR-146a and miR-146b correlates with the occurrence and prognosis of papillary thyroid carcinoma, and the expression levels of miR-146a and miR-146b seem to affect the cell proliferation and migration and regulate the expression of IRAK1 protein in cancer cells. Further studies are needed to validate our results to provide new targets for prevention and treatment of papillary thyroid carcinoma.

HTNV-induced upregulation of miR-146a in HUVECs promotes viral infection by modulating pro-inflammatory cytokine release

Increasing research has shown a link between viruses and miRNAs, such as miRNA-146a, in regulating virus infection and replication. In the current study, the association between miR-146a and hantaan virus (HTNV) infection in human umbilical vein endothelial cells (HUVECs) was investigated, with a focus on examining the expression of pro-inflammatory cytokines. The results showed that HTNV infection promoted the production of miR-146a in HUVECs and activated nuclear factor-κB (NF-κB) signaling, along with the upregulation of pro-inflammatory cytokines, including interleukin 8 (IL-8), C-C Motif Chemokine Ligand 5 (CCL5, also RANTES), interferon-inducible protein-10 (IP-10) and interferon beta (IFN-β). Moreover, miR-146a exhibited a negative regulatory effect on the NF-κB pathway. Accordingly, a miR-146a inhibitor increased the expression of IL-8, CCL5, IP-10 and IFN-β, whereas a miR-146a mimic reduced the levels of these cytokines. Consequently, exogenous transduction of miR-146a significantly enhanced HTNV replication in HUVEC cells. We also discovered that viral proteins (NP/GP) contributed to miR-146a expression via enhancement the activity of miR-146a promoter. In conclusion, these results imply the negative regulation of miR-146a on the production of HTNV-induced pro-inflammatory cytokines contributes to virus replication, which suggest that miR-146a may be regarded as a novel therapeutic target for HTNV infection.

Regulation of inflammation in Japanese encephalitis

Background

Uncontrolled inflammatory response of the central nervous system is a hallmark of severe Japanese encephalitis (JE). Although inflammation is necessary to mount an efficient immune response against virus infections, exacerbated inflammatory response is often detrimental. In this context, cells of the monocytic lineage appear to be important forces driving JE pathogenesis.

Main body

Brain-infiltrating monocytes, macrophages and microglia play a major role in central nervous system (CNS) inflammation during JE. Moreover, the role of inflammatory monocytes in viral neuroinvasion during JE and mechanisms of cell entry into the CNS remains unclear. The identification of cellular and molecular actors in JE inflammatory responses may help to understand the mechanisms behind excessive inflammation and to develop therapeutics to treat JE patients. This review addresses the current knowledge about mechanisms of virus neuroinvasion, neuroinflammation and therapeutics critical for JE outcome.

Conclusion

Understanding the regulation of inflammation in JE is challenging. Elucidation of the remaining open questions will help to the development of therapeutic approaches avoiding detrimental inflammatory responses in JE.

Viruses and miRNAs: More Friends than Foes

There is evidence that eukaryotic miRNAs (hereafter called host miRNAs) play a role in the replication and propagation of viruses. Expression or targeting of host miRNAs can be involved in cellular antiviral responses. Most times host miRNAs play a role in viral life-cycles and promote infection through complex regulatory pathways. miRNAs can also be encoded by a viral genome and be expressed in the host cell. Viral miRNAs can share common sequences with host miRNAs or have totally different sequences. They can regulate a variety of biological processes involved in viral infection, including apoptosis, evasion of the immune response, or modulation of viral life-cycle phases. Overall, virus/miRNA pathway interaction is defined by a plethora of complex mechanisms, though not yet fully understood. This article review summarizes recent advances and novel biological concepts related to the understanding of miRNA expression, control and function during viral infections. The article also discusses potential therapeutic applications of this particular host–pathogen interaction.

Enterovirus 71-induced has-miR-21 contributes to evasion of host immune system by targeting MyD88 and IRAK1

Enterovirus71(EV71), the etiological agent of hand-foot-and-mouth disease, has increasingly become a public health challenge around the world. Type I interferons (IFNs) are an important family of cytokines that regulate innate and adaptive immune responses to pathogens.These pathways are tightly regulated by the host to prevent an inappropriate cellular response, but viruses can modulate these pathways to proliferate and spread. In this study, we demonstrated that EV71 evades the immune surveillance system to proliferate by activating microRNA-21. We demonstrated that EV71 infection upregulates miR-21, which in turn suppresses EV71-triggered type I IFN production, thus promoting EV71 replication. Furthermore, we demonstrated that miR-21 targets the myeloid differentiation factor 88(MyD88) and interleukin-1 receptor-associated kinase 1(IRAK1), which are involved in EV71-induced type I IFN production.

miR-146a suppresses STAT3/VEGF pathways and reduces apoptosis through IL-6 signaling in primary human retinal microvascular endothelial cells in high glucose conditions

microRNA (miRNA) play critical roles in the pathological processes of diabetic retinopathy, including inflammatory responses, insulin signaling, and angiogenesis. In addition to their regulatory functions on gene expression, miRNA is considered as a potential therapeutic target, as well as a diagnostic marker for many diseases. Our understanding on the pathological mechanisms underlying diabetic retinopathy is still incomplete and additional investigations are required to develop novel therapeutic strategies. The aim of this study was to investigate our hypothesis that miR-146a plays a role in suppressing pro-inflammatory pathways, involving STAT3 and VEGF, through regulating IL-6 signaling to reduce apoptosis of human retinal endothelial cells (REC) in high glucose conditions. Human REC were cultured in normal (5mM) glucose or high glucose medium (25mM) for 3days. We performed transfections on REC with miRNA mimics (hsa-miR-146a-5p). Overexpression of miR-146a reduced IL-6 levels, STAT3 phosphorylation, and VEGF levels in REC cultured in high glucose. Cellular apoptosis was decreased in REC overexpressing miR-146a, as demonstrated by the inhibition of DNA fragmentation. More importantly, we demonstrated that the regulatory role of miR-146a on STAT3/VEGF and apoptosis was mediated by IL-6 receptor signaling in REC. Overall, we report that miR-146a suppressed IL-6 signaling, leading to reduced levels of STAT3 and VEGF in REC in high glucose conditions, leading to decreased apoptosis. The outcome suggests that miR-146a is a potential molecular target for inhibiting inflammation and apoptosis in the diabetic retina through the suppression of the IL-6-mediated STAT3/VEGF pathway.

miR-21 promotes dengue virus serotype 2 replication in HepG2 cells

Infection with the mosquito transmitted dengue virus (DENV) remains a significant worldwide public health problem. While the majority of infections are asymptomatic, infection can result in a range of symptoms. MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression through repression or degradation of mRNAs. To understand the contribution of miRNAs to DENV 2 replication, we screened a number of candidate miRNAs for variations in expression levels during DENV 2 infection of HepG2 (liver) cells. Seven miRNAs were identified as differentially expressed, and one, miR-21, was differentially expressed at all time points examined. Interestingly, miR-21 was also differentially regulated in DENV 2 infection under conditions of antibody dependent enhancement of infection, and in direct Zika virus infection, but not in DENV 4 infection. The role of miR-21 during DENV infection was further examined by treating HepG2 cells with an anti-miR-21 (AMO-21) before DENV infection. The results showed a significant reduction in DENV 2 production, clearly suggesting that miR-21 plays a key role in DENV 2 replication. To further confirm the role of miR-21 in DENV infection, a peptide nucleic acid-21 (PNA-21) construct with a nucleotide sequence complementary to AMO-21, was co-administered with AMO-21 as an AMO-21/PNA-21 complex followed by DENV 2 infection. The results showed that AMO-21 significantly reduced DENV 2 titer, PNA-21 significantly increased DENV 2 titer and the combined AMO-21/PNA-21 showed no difference from non-treated infection controls. Taken together, the results show that miR-21 promotes DENV 2 replication, and this mechanism could serve as a possible therapeutic intervention point.

Recent advances in Japanese encephalitis

Japanese encephalitis is a flaviviral disease that is endemic to the South, Southeast Asia, and Asia Oceania regions. Given that about 60% of the world’s population (about 7.4 billion) resides in this region (about 4.4 billion), this disease poses a significant threat to global health. Active vaccination campaigns conducted in endemic countries have led to a decrease in the number of reported cases over the years. In this article, we strive to briefly highlight recent advances in understanding the role of microRNAs in disease pathology, focus on providing brief summaries of recent clinical trials in the field of Japanese encephalitis therapeutics, and review the current prophylactic strategies.

Anti-NMDA Receptor Encephalitis and Vaccination

Anti-N-methyl-d-aspartate (Anti-NMDA) receptor encephalitis is an acute autoimmune neurological disorder. The cause of this disease is often unknown, and previous studies revealed that it might be caused by a virus, vaccine or tumor. It occurs more often in females than in males. Several cases were reported to be related to vaccination such as the H1N1 vaccine and tetanus/diphtheria/pertussis and polio vaccines. In this study, we reported an anti-NMDA receptor encephalitis case that may be caused by Japanese encephalitis vaccination. To investigate the association between anti-NMDA receptor encephalitis and vaccination, we analyzed the phylogenetic relationship of the microRNAs, which significantly regulate these vaccine viruses or bacteria, and the phylogenetic relationship of these viruses and bacteria. This reveals that anti-NMDA receptor encephalitis may be caused by Japanese encephalitis vaccination, as well as H1N1 vaccination or tetanus/diphtheria/pertussis and polio vaccinations, from the phylogenetic viewpoint.

Induction of Multiple miR-200/182 Members in the Brains of Mice Are Associated with Acute Herpes Simplex Virus 1 Encephalitis

Important roles of microRNAs (miRNAs) in regulating the host response during viral infection have begun to be defined. However, little is known about the functional roles of miRNAs within an in vivo acute viral encephalitis model. We therefore identified global changes in miRNA expression during acute herpes simplex virus type 1 (HSV-1) encephalitis (HSVE) in mice. We found that many of the highly upregulated miRNAs (miR-155, miR-146a and miR-15b) detected in HSV-1 infected brain tissue are known regulators of inflammation and innate immunity. We also observed upregulation of 7 members belonging to the related group of miRNAs, the miR-200 family and miR-182 cluster (miR-200/182). Using in situ hybridization, we found that these miRNAs co-localized to regions of the brain with severe HSVE-related pathology and were upregulated in various cell types including neurons. Induction was apparent but not limited to cells in which HSV-1 was detected by immunohistochemistry, suggesting possible roles of these miRNAs in the host response to viral-induced tissue damage. Bioinformatic prediction combined with gene expression profiling revealed that the induced miR-200/182 members could regulate the biosynthesis of heparan sulfate proteoglycans. Using luciferase assays, we found that miR-96, miR-141, miR-183 and miR-200c all potentially targeted the syndecan-2 gene (Sdc2), which codes for a cell surface heparan sulfate proteoglycan involved in HSV-1 cellular attachment and entry.

MicroRNA Regulation of RNA Virus Replication and Pathogenesis

microRNAs (miRNAs) are non-coding RNAs that regulate many processes within a cell by manipulating protein levels through direct binding to mRNA and influencing translation efficiency, or mRNA abundance. Recent evidence demonstrates that miRNAs can also affect RNA virus replication and pathogenesis through direct binding to the RNA virus genome or through virus-mediated changes in the host transcriptome. Here, we review the current knowledge on the interaction between RNA viruses and cellular miRNAs. We also discuss how cell and tissue-specific expression of miRNAs can directly affect viral pathogenesis. Understanding the role of cellular miRNAs during viral infection may lead to the identification of novel mechanisms to block RNA virus replication or cell-specific regulation of viral vector targeting.

Some RNA viruses possess miRNA-binding sites in a range of locations within the viral genome, including the 5′ and 3′ non-translated regions.

Host cell miRNAs can bind to RNA virus genomes, enhancing genome stability, repressing translation of the viral genome, or altering free miRNA levels within the cell.

miRNAs contribute to viral pathogenesis by promoting evasion of the host antiviral immune response, enhancing viral replication, or, potentially, altering miRNA-mediated host gene regulation.

RNA virus infection can lead to widespread changes in the host transcriptome by modulating cell-specific miRNA levels.

DNA damage response (DDR) and senescence: shuttled inflamma-miRNAs on the stage of inflamm-aging

A major issue in aging research is how cellular phenomena affect aging at the systemic level. Emerging evidence suggests that DNA damage response (DDR) signaling is a key mechanism linking DNA damage accumulation, cell senescence, and organism aging. DDR activation in senescent cells promotes acquisition of a proinflammatory secretory phenotype (SASP), which in turn elicits DDR and SASP activation in neighboring cells, thereby creating a proinflammatory environment extending at the local and eventually the systemic level. DDR activation is triggered by genomic lesions as well as emerging bacterial and viral metagenomes. Therefore, the buildup of cells with an activated DDR probably fuels inflamm-aging and predisposes to the development of the major age-related diseases (ARDs). Micro (mi)-RNAs - non-coding RNAs involved in gene expression modulation - are released locally and systemically by a variety of shuttles (exosomes, lipoproteins, proteins) that likely affect the efficiency of their biological effects. Here we suggest that some miRNAs, previously found to be associated with inflammation and senescence - miR-146, miR-155, and miR-21 - play a central role in the interplay among DDR, cell senescence and inflamm-aging. The identification of the functions of shuttled senescence-associated miRNAs is expected to shed light on the aging process and on how to delay ARD development.

Implications of non-coding RNAs in viral infections

The advances in RNA sequencing have unveiled various non-coding RNAs (ncRNAs), which modulate the gene expression. ncRNAs do not get translated into proteins. These include transfer RNAs, ribosomal RNAs, microRNA (miRNA), short interfering RNA, long non-coding RNA, piwi-interacting RNA and small nuclear RNA. ncRNAs regulate gene expression at various levels and control cellular machinery. miRNAs have been reported in plants, animals, several invertebrates and viruses. The miRNAs regulate the gene expression post-transcriptionally. Viral infection strongly influences the abundance and the distribution of miRNAs and other ncRNAs within the host cells. Viruses may encode their own miRNA, which help in the viral life cycle and other aspects of pathogenesis. Viruses are known to successfully modulate the expression pattern of ncRNAs. The ncRNA-based strategies adopted by viruses for their survival present a complex picture of host-virus interactions. Copyright © 2016 John Wiley & Sons, Ltd.

miR-124 attenuates Japanese encephalitis virus replication by targeting DNM2

Background

Japanese encephalitis virus (JEV) is a mosquito-borne flavivirus that causes acute viral encephalitis in humans. Pigs are important amplifier hosts of JEV. Emerging evidence indicates that host microRNAs (miRNAs) play key roles in modulating viral infection and pathogenesis. However, mechanistic studies delineating the roles of miRNAs in regulating host-JEV interactions remain scarce.

Results

In this study, we demonstrated that miR-124 inhibited JEV replication in porcine kidney epithelial PK15 cells. Furthermore, using bioinformatics tools, we identified dynamin2 (DNM2), a GTPase responsible for vesicle scission, as a target of miR-124. Small interfering RNA (siRNA) depletion studies inicated that dynamin2 was required for efficient JEV replication. We also demonstrated that upregulation of miR-124 expression corresponded to decreased expression of its target, DNM2, in the JEV-infected PK15 cells.

Conclusions

Overall, these results suggest the importance of miR-124 in modulating JEV replication and provide a scientific basis for using cellular miRNAs in anti-JEV therapies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-016-0562-y) contains supplementary material, which is available to authorized users.

Japanese Encephalitis Virus exploits the microRNA-432 to regulate the expression of Suppressor of Cytokine Signaling (SOCS) 5

Japanese encephalitis virus (JEV) is a plus strand RNA virus, which infects brain. MicroRNAs are regulatory non-coding RNAs which regulate the expression of various genes in cells. Viruses modulate the expression of various microRNAs to suppress anti-viral signaling and evade the immune response. SOCS (Suppressor of cytokine signalling) family of proteins are negative regulators of anti-viral Jak-STAT pathway. In this study, we demonstrated the regulatory role of SOCS5 in Jak-STAT signaling and its exploitation by JEV through a microRNA mediated mechanism. JEV infection in human brain microglial cells (CHME3) downregulated the expression of miR-432, and upregulated SOCS5 levels. SOCS5 was validated as a target of miR-432 by using 3'UTR clone of SOCS5 in luciferase vector along with miR-432 mimic. The overexpression of miR-432 prior to JEV infection enhanced the phosphorylation of STAT1 resulting into increased ISRE activity and cellular inflammatory response resulting into diminished viral replication. The knockdown of SOCS5 resulted into increased STAT1 phosphorylation and suppressed viral replication. JEV infection mediated downregulation of miR-432 leads to SOCS5 upregulation, which helps the virus to evade cellular anti-viral response. This study demonstrated that JEV utilizes this microRNA mediated strategy to manipulate cellular immune response promoting JEV pathogenesis.

A glance at subgenomic flavivirus RNAs and microRNAs in flavivirus infections

The family Flaviviridae comprises a wide variety of viruses that are distributed worldwide, some of which are associated with high rates of morbidity and mortality. There are neither vaccines nor antivirals for most flavivirus infections, reinforcing the importance of research on different aspects of the viral life cycle. During infection, cytoplasmic accumulation of RNA fragments mainly originating from the 3' UTRs, which have been designated subgenomic flavivirus RNAs (sfRNAs), has been detected. It has been shown that eukaryotic exoribonucleases are involved in viral sfRNA production. Additionally, viral and human small RNAs (sRNAs) have also been found in flavivirus-infected cells, especially microRNAs (miRNAs). miRNAs were first described in eukaryotic cells and in a mature and functional state present as single-stranded 18-24 nt RNA fragments. Their main function is the repression of translation through base pairing with cellular mRNAs, besides other functions, such as mRNA degradation. Canonical miRNA biogenesis involves Drosha and Dicer, however miRNA can also be generated by alternative pathways. In the case of flaviviruses, alternative pathways have been suggested. Both sfRNAs and miRNAs are involved in viral infection and host cell response modulation, representing interesting targets of antiviral strategies. In this review, we focus on the generation and function of viral sfRNAs, sRNAs and miRNAs in West Nile, dengue, Japanese encephalitis, Murray Valley encephalitis and yellow fever infections, as well as their roles in viral replication, translation and cell immune response evasion. We also give an overview regarding other flaviviruses and the generation of cellular miRNAs during infection.

MicroRNA-19b-3p Modulates Japanese Encephalitis Virus-Mediated Inflammation via Targeting RNF11

Japanese encephalitis virus (JEV) can invade the central nervous system and consequently induce neuroinflammation, which is characterized by profound neuronal cell damage accompanied by astrogliosis and microgliosis. Albeit microRNAs (miRNAs) have emerged as major regulatory noncoding RNAs with profound effects on inflammatory response, it is unknown how astrocytic miRNAs regulate JEV-induced inflammation. Here, we found the involvement of miR-19b-3p in regulating the JEV-induced inflammatory responsein vitroandin vivo The data demonstrated that miR-19b-3p is upregulated in cultured cells and mouse brain tissues during JEV infection. Overexpression of miR-19b-3p led to increased production of inflammatory cytokines, including tumor necrosis factor alpha, interleukin-6, interleukin-1β, and chemokine (C-C motif) ligand 5, after JEV infection, whereas knockdown of miR-19b-3p had completely opposite effects. Mechanistically, miR-19b-3p modulated the JEV-induced inflammatory response via targeting ring finger protein 11, a negative regulator of nuclear factor kappa B signaling. We also found that inhibition of ring finger protein 11 by miR-19b-3p resulted in accumulation of nuclear factor kappa B in the nucleus, which in turn led to higher production of inflammatory cytokines.In vivosilencing of miR-19b-3p by a specific antagomir reinvigorates the expression level of RNF11, which in turn reduces the production of inflammatory cytokines, abrogates gliosis and neuronal cell death, and eventually improves the survival rate in the mouse model. Collectively, our results demonstrate that miR-19b-3p positively regulates the JEV-induced inflammatory response. Thus, miR-19b-3p targeting may constitute a thought-provoking approach to rein in JEV-induced inflammation.

IMPORTANCE

Japanese encephalitis virus (JEV) is one of the major causes of acute encephalitis in humans worldwide. The pathological features of JEV-induced encephalitis are inflammatory reactions and neurological diseases resulting from glia activation. MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression posttranscriptionally. Accumulating data indicate that miRNAs regulate a variety of cellular processes, including the host inflammatory response under pathological conditions. Recently, a few studies demonstrated the role of miRNAs in a JEV-induced inflammatory response in microglia; however, their role in an astrocyte-derived inflammatory response is largely unknown. The present study reveals that miR-19b-3p targets ring finger protein 11 in glia and promotes inflammatory cytokine production by enhancing nuclear factor kappa B activity in these cells. Moreover, administration of an miR-19b-3p-specific antagomir in JEV-infected mice reduces neuroinflammation and lethality. These findings suggest a new insight into the molecular mechanism of the JEV-induced inflammatory response and provide a possible therapeutic entry point for treating viral encephalitis.

MicroRNA-27a Negatively Modulates the Inflammatory Response in Lipopolysaccharide-Stimulated Microglia by Targeting TLR4 and IRAK4

microRNA, a family of small non-coding RNA, plays significant roles in regulating gene expression, mainly via binding to the 3'-untranslated region of target genes. Although the role of miRNA in regulating neuroinflammation via the innate immune pathway has been studied, its role in the production of inflammatory mediators during microglial activation is poorly understood. In this study, we investigated the effect of miR-27a on lipopolysaccharide (LPS)-induced microglial inflammation. miR-27a expression was found to be rapidly decreased in microglia by real-time polymerase chain reaction (real-time PCR) after LPS stimulation. Over-expression of miR-27a significantly decreased the production of inflammatory cytokines, such as interleukin-6 (IL-6), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and nitric oxide (NO), whereas knockdown of miR-27a increased the expression of these inflammatory factors. We also demonstrated by loss- and gain-of-function studies that miR-27a directly suppressed the expression of toll-like receptor 4 (TLR4) and interleukin-1 receptor-associated kinase 4 (IRAK4)-a pivotal adaptor kinase in the TLR4/MyD88 signaling pathway-by directly binding their 3'-UTRs: knocking down TLR4 or IRAK4 in microglia significantly decreased TLR4 or IRAK4 expression and inhibited the downstream production of inflammatory mediators. Moreover, the inflammatory cytokines IL-6 and IL-1β were regulated by IRAK4, whereas TNF-α and NO were more dependent on TLR4 activation. Thus, miR-27a might regulate the LPS-induced production of inflammatory cytokines in microglia independently of TLR4 and IRAK4. Taken together, our results suggest that miR-27a is associated with microglial activation and the inflammatory response.

Transcriptional regulation of miR-15b by c-Rel and CREB in Japanese encephalitis virus infection

MicroRNAs (miRNAs) have been well known to play diverse roles in viral infection at the level of posttranscriptional repression. However, much less is understood about the mechanism by which miRNAs are regulated during viral infection. It is likely that both host and virus contain factors to modulate miRNA expression. Here we report the up-regulation of microRNA-15b (miR-15b) in vitro upon infection with Japanese encephalitis virus (JEV). Analysis of miR-15b precursor, pri-miR-15b and pre-miR-15b, suggest that the regulation occurs transcriptionally. Further, we identified the transcriptional regulatory region of miR-15b that contains consensus binding motif for NF-κB subunit c-Rel and cAMP-response element binding protein (CREB), which are known as transcription factor to regulate gene expression. By promoter fusion and mutational analyses, we demonstrated that c-Rel and CREB bind directly to the promoter elements of miR-15b, which are responsible for miR-15b transcription in response to JEV infection. Finally, we showed that pharmacological inhibition of ERK and NF-κB signaling pathway blocked induction of miR-15b in JEV infection, suggesting important roles of ERK and NF-κB pathway in the regulation of miR-15b gene. Therefore, our observations indicate that induced expression of miR-15b is modulated by c-Rel and CREB in response to JEV infection.

miR-146a Attenuates Inflammatory Pathways Mediated by TLR4/NF-κB and TNFα to Protect Primary Human Retinal Microvascular Endothelial Cells Grown in High Glucose

Pathological mechanisms underlying diabetic retinopathy are still not completely understood. Increased understanding of potential cellular pathways responsive to hyperglycemia is essential to develop novel therapeutic strategies for diabetic retinopathy. A growing body of evidence shows that microRNA (miRNA) play important roles in pathological mechanisms involved in diabetic retinopathy, as well as possessing potential as novel therapeutic targets. The hypothesis of this study was that miR-146a plays a key role in attenuating hyperglycemia-induced inflammatory pathways through reduced TLR4/NF-κB and TNFα signaling in primary human retinal microvascular endothelial cells (REC). We cultured human REC in normal (5 mM) glucose or transferred to high glucose medium (25 mM) for 3 days. Transfection was performed on REC with miRNA mimic (hsa-miR-146a-5p). Our results demonstrate that miR-146a expression was decreased in human REC cultured in high glucose. Overexpression of miR-146a using mimics reduced the levels of TLR4/NF-κB and TNFα in REC cultured in high glucose. Both MyD88-dependent and -independent signaling were decreased by miR-146a overexpression in REC in high glucose conditions. The results suggest that miR-146a is a potential therapeutic target for reducing inflammation in REC through inhibition of TLR4/NF-κB and TNFα. Our study will contribute to understanding of diabetic retinal pathology, as well as providing important clues to develop therapeutics for clinical applications.

MicroRNA transcriptome profiling of mice brains infected with Japanese encephalitis virus by RNA sequencing

Japanese encephalitis (JE) is a mosquito borne viral disease, caused by Japanese encephalitis virus (JEV) infection producing severe neuroinflammation in the central nervous system (CNS) with the associated disruption of the blood brain barrier. MicroRNAs (miRNAs) are a family of 21-24 nt small non-coding RNAs that play important post-transcriptional regulatory roles in gene expression and have critical roles in virus pathogenesis. We examined the potential roles of miRNAs in JEV-infected suckling mice brains and found that JEV infection changed miRNA expression profiles when the suckling mice began showing nervous symptoms. A total of 1062 known and 71 novel miRNAs were detected in JEV-infected group, accompanied with 1088 known and 75 novel miRNAs in mock controls. Among these miRNAs, one novel and 25 known miRNAs were significantly differentially expressed, including 18 up-regulated and 8 down-regulated miRNAs which were further confirmed by real-time PCR. Gene ontology (GO) and signaling pathway analysis of the predicted target mRNAs of the modulated miRNAs showed that they are correlated with the regulation of apoptosis, neuron differentiation, antiviral immunity and infiltration of mouse brain, and the validated targets of 12 differentially expressed miRNAs were enriched for the regulation of cell programmed death, proliferation, transcription, muscle organ development, erythrocyte differentiation, gene expression, plasma membrane and protein domain specific binding. KEGG analysis further reveals that the validated target genes were involved in the Pathways in cancer, Neurotrophin signaling pathway, Toll like receptor signaling pathway, Endometrial cancer and Jak-STAT signaling pathway. We constructed the interaction networks of miRNAs and their target genes according to GO terms and KEGG pathways and the expression levels of several target genes were examined. Our data provides a valuable basis for further studies on the regulatory roles of miRNAs in JE pathogenesis.

MicroRNA-33a-5p Modulates Japanese Encephalitis Virus Replication by Targeting Eukaryotic Translation Elongation Factor 1A1

Japanese encephalitis virus (JEV) is a typical mosquito-borne flavivirus responsible for acute encephalitis and meningitis in humans. However, the molecular mechanism for JEV pathogenesis is still unclear. MicroRNAs (miRNAs) are small noncoding RNAs that act as gene regulators. They are directly or indirectly involved in many cellular functions owing to their ability to target mRNAs for degradation or translational repression. However, how cellular miRNAs are regulated and their functions during JEV infection are largely unknown. In the present study, we found that JEV infection downregulated the expression of endogenous cellular miR-33a-5p. Notably, artificially transfecting with miR-33a-5p mimics led to a significant decrease in viral replication, suggesting that miR-33a-5p acts as a negative regulator of JEV replication. A dual-luciferase reporter assay identified eukaryotic translation elongation factor 1A1 (EEF1A1) as one of the miR-33a-5p target genes. Our study further demonstrated that EEF1A1 can interact with the JEV proteins NS3 and NS5 in replicase complex. Through this interaction, EEF1A1 can stabilize the components of viral replicase complex and thus facilitates viral replication during JEV infection. Taken together, these results suggest that miR-33a-5p is downregulated during JEV infection, which contributes to viral replication by increasing the intracellular level of EEF1A1, an interaction partner of JEV NS3 and NS5. This study provides a better understanding of the molecular mechanisms of JEV pathogenesis.

IMPORTANCE

MiRNAs are critical regulators of gene expression that utilize sequence complementarity to bind to and modulate the stability or translation efficiency of target mRNAs. Accumulating data suggest that miRNAs regulate a wide variety of molecular mechanisms in the host cells during viral infections. JEV, a neurotropic flavivirus, is one of the major causes of acute encephalitis in humans worldwide. The roles of cellular miRNAs during JEV infections are widely unexplored. The present study explores a novel role of miR-33a-5p as a negative regulator of JEV replication. We found EEF1A1 as a direct target of miR-33a-5p. We also demonstrated that EEF1A1 interacts with and stabilize the components of JEV replicase complex, which positively regulates JEV replication. These findings suggest a new insight into the molecular mechanism of JEV pathogenesis and provide a possible therapeutic entry point for viral encephalitis.

Human MicroRNA miR-532-5p Exhibits Antiviral Activity against West Nile Virus via Suppression of Host Genes SESTD1 and TAB3 Required for Virus Replication

West Nile virus (WNV) is a mosquito-transmitted flavivirus that naturally circulates between mosquitos and birds but can also infect humans, causing severe neurological disease. The early host response to WNV infection in vertebrates primarily relies on the type I interferon pathway; however, recent studies suggest that microRNAs (miRNAs) may also play a notable role. In this study, we assessed the role of host miRNAs in response to WNV infection in human cells. We employed small RNA sequencing (RNA-seq) analysis to determine changes in the expression of host miRNAs in HEK293 cells infected with an Australian strain of WNV, Kunjin (WNVKUN), and identified a number of host miRNAs differentially expressed in response to infection. Three of these miRNAs were confirmed to be significantly upregulated in infected cells by quantitative reverse transcription (qRT)-PCR and Northern blot analyses, and one of them, miR-532-5p, exhibited a significant antiviral effect against WNVKUN infection. We have demonstrated that miR-532-5p targets and downregulates expression of the host genes SESTD1 and TAB3 in human cells. Small interfering RNA (siRNA) depletion studies showed that both SESTD1 and TAB3 were required for efficient WNVKUN replication. We also demonstrated upregulation of mir-532-5p expression and a corresponding decrease in the expression of its targets, SESTD1 and TAB3, in the brains of WNVKUN -infected mice. Our results show that upregulation of miR-532-5p and subsequent suppression of the SESTD1 and TAB3 genes represent a host antiviral response aimed at limiting WNVKUN infection and highlight the important role of miRNAs in controlling RNA virus infections in mammalian hosts.

IMPORTANCE

West Nile virus (WNV) is a significant viral pathogen that poses a considerable threat to human health across the globe. There is no specific treatment or licensed vaccine available for WNV, and deeper insight into how the virus interacts with the host is required to facilitate their development. In this study, we addressed the role of host microRNAs (miRNAs) in antiviral response to WNV in human cells. We identified miR-532-5p as a novel antiviral miRNA and showed that it is upregulated in response to WNV infection and suppresses the expression of the host genes TAB3 and SESTD1 required for WNV replication. Our results show that upregulation of miR-532-5p and subsequent suppression of the SESTD1 and TAB3 genes represent an antiviral response aimed at limiting WNV infection and highlight the important role of miRNAs in controlling virus infections in mammalian hosts.