MicroRNAs: new regulators of Toll-like receptor signalling pathways

Mesenchymal Stem Cell-derived Extracellular Vesicles for Skin Wound Healing

Skin is vulnerable to various external insults such as burn, severe injury, or inflammation, which necessitates a better strategy for wound repair. Mesenchymal stem cells (MSCs) can self-renew and differentiate into various supporting tissues including cartilage, bone, muscle, and adipose tissue. Along with their unique multipotent capacity, they secrete various paracrine mediators such as growth factors, cytokines, and membrane-enclosed particles called extracellular vesicles (EVs). Herein, we discussed the general traits of EVs such as cell-to-cell communicator, and highlighted the recent preclinical outcomes, with a focus on the application of MSC-derived EVs in wound repair. This chapter provides insights into developing novel strategies for skin wound healing in a cell-free manner.

Specific and selective induction of miR-124 in immune cells by the quinoline ABX464: a transformative therapy for inflammatory diseases

Inflammatory diseases are believed to develop as a result of dysregulated inflammatory responses to environmental factors on susceptible genetic backgrounds. Operating at the level of post-transcriptional gene regulation, miRNAs are a class of endogenous, small noncoding RNAs that can promote downregulation of protein expression by translational repression and/or mRNA degradation of target mRNAs involved in inflammation. MiR-124 is a crucial modulator of inflammation and innate immunity that could provide therapeutic restitution of physiological pathways lost in inflammatory diseases. A recently discovered small quinoline, ABX464, was shown to upregulate miR-124 in human immune cells. In vivo, in a proof-of-concept clinical study, ABX464 showed robust and consistent efficacy in ulcerative colitis (UC). In this review, we examine the current therapeutic options proposed for UC and discuss the drug candidate ABX464 in this context.

gga-miR-1603 and gga-miR-1794 directly target viral L gene and function as a broad-spectrum antiviral factor against NDV replication

As the causative agent of Newcastle disease (ND), Newcastle disease virus (NDV) has seriously restricted the development of the poultry industry. Previous research has shown that miRNAs, members of the small noncoding RNA family, are implicated in the regulation NDV replication through extensive interactions with host mRNAs, but whether miRNAs affect NDV replication by directly binding to the NDV antigenome remains unclear. In this study, potential Gallus gallus miRNAs targeting the antigenome of NDV were bioinformatically predicted using the online software RegRNA 2.0, and gga-miR-1603 and gga-miR-1794 were identified as targeting the viral L gene directly through dual-luciferase reporter assays. Sequence alignment analysis demonstrated that multiple genotypes of NDVs harbored highly conserved binding sites for gga-miR-1603 and gga-miR-1794 in the viral antigenome located at 8611–8634 nt and 14,490–14,514 nt, respectively. Meanwhile, we found that gga-miR-1603 and gga-miR-1794 negatively regulated the expression of viral L gene at both the RNA and protein levels, as well as viral replication in vitro. Furthermore, NDV infection had no effect on endogenous gga-miR-1603 and gga-miR-1794 expression in various avian cell lines. Overall, our present study demonstrated that gga-miR-1603 and gga-miR-1794 directly bind to the viral L gene to facilitate ts degradation and inhibit the replication of multiple genotypes of NDVs in vitro. These findings will provide us with important clues for antiviral therapy against NDV infection.

MicroRNAome: Potential and Veritable Immunomolecular Therapeutic and Diagnostic Baseline for Lingering Bovine Endometritis

The bovine endometrium is a natural pathogen invasion barrier of the uterine tissues' endometrial epithelial cells that can resist foreign pathogen invasion by controlling the inflammatory immune response. Some pathogens suppress the innate immune system of the endometrium, leading to prolonged systemic inflammatory response through the blood circulation or cellular degradation resulting in bovine endometritis by bacterial endotoxins. The microRNA (miRNA) typically involves gene expression in multicellular organisms in post-transcription regulation by affecting both the stability and the translation of messenger RNA. Accumulated evidence suggests that miRNAs are important regulators of genes in several cellular processes. They are a class of endogenous non-coding RNAs, which play pivotal roles in the inflammatory response of reproductive diseases. Studies confirmed that miRNAs play a key regulatory role in various inflammatory diseases by mediating the molecular mechanism of inflammatory cytokines via signal pathways. It implicates some miRNAs in the occurrence of bovine endometritis, resorting to regulating the activities of some inflammatory cytokines, chemokine, differentially expressed genes, and protein through modulating of specific cellular signal pathways functions. This review dwells on improving the knowledge of the role of miRNAs involvement in inflammatory response as to early diagnosis, control, and prevention of bovine endometritis and consequently enlighten on the molecular improvement of the genes coded by various differentially expressed miRNA through the need to adopt recent genetic technologies and the development of new pharmaceutical preparations.

The Therapeutic Potential of MicroRNAs in Cancer: Illusion or Opportunity?

The functional involvement of microRNAs in human neoplasia has raised in the last years an increasing interest in the scientific community toward the potential application in clinics as therapeutic tools. Indeed, the possibility to modulate their expression to re-establish a lost equilibrium and counteract tumor growth and dissemination, and/or to improve responsiveness to standard therapies, is promising and fascinating. However, several issues need to be taken into account such as factors related to miRNA stability in the blood, tissue penetration and potential off-target effects, which might affect safety, tolerability and efficacy of an miRNA-based therapy. Here we describe the most relevant challenges related to miRNA-based therapy, review the delivery strategies exploited to date and the on-going clinical trials.

In situ self-assembly of Au-antimiR-155 nanocomplexes mediates TLR3-dependent apoptosis in hepatocellular carcinoma cells

MicroRNA 155 (miRNA-155) is frequently dysregulated in hepatocellular carcinoma (HCC) and other cancer types. Toll-like receptor 3 (TLR3), a putative miR-155 target, plays a key role in liver pathophysiology, and its downregulation in HCC cells is associated with apoptosis evasion and poor outcomes. Herein, we examined the ability of in situ self-assembled Au-antimiR-155 nanocomplexes (Au-antimiRNA NCs) to activate TLR3 signaling in HCC cells. Gene expression analysis confirmed an inverse relationship between miR-155 and TLR3 expression in HCC samples, and marked upregulation of miR-155 was observed in HCC cells but not in normal L02 hepatocytes. RNA immunoprecipitation confirmed physical interaction between miR-155 and TLR3, while negative regulation of TLR3 expression by miR-155 was demonstrated by luciferase reporter assays. Au-antimiR-155 NCs were self-assembled within HepG2 HCC cells, but not within control L02 cells. They efficiently silenced miR-155, thereby inhibiting proliferation and migration and inducing apoptosis in HepG2 cells. Molecular analyses suggested these effects are secondary to TLR3 signaling mediating NF-κB transcription, caspase-8 activation, and interleukin-1β (IL-1β) release. Our results provide a basis for future studies examining the in vivo applicability of this novel Au-antimiRNA NCs delivery system to halt HCC progression by activating pro-apoptotic TLR3 signaling.

Identification of Ovine Serum miRNAs Following Bacterial Lipopolysaccharide Challenge

Host-pathogen interactions are complex and influenced by host genetic and epigenetic modifications. Recently, the significance of microRNAs (miRNAs) in pathogenic infection and the regulation of immune response has been highlighted. However, information on miRNAs' role in the course of inflammation is still very limited in small ruminants. The present study was intended to identify changes in the expression of circulatory miRNAs post-lipopolysaccharide (LPS)-challenge. In this study, young ewes (n = 18) were challenged with Escherichia coli LPS (400 ng/kg i.v.) and blood samples were collected for serum miRNA isolation at two-time points; prior to challenge (T0), and 4 h (T4) post-challenge, reflecting the peak cortisol response. A total of 91 miRNAs were profiled, including 84 miRNAs on a commercial ovine miRNA-PCR array, and seven individual miRNAs. Forty five miRNAs were differentially expressed (DE) with 35 being up-regulated (Fold regulation, FR > 2) and 10 being down-regulated (FR < 1, p < 0.05) at T4. Among the up-regulated miRNAs, 14 were significantly (p < 0.05) induced, including oar-miRs: 369-3p, 495-3p, 376a-3p, 543-3p, 668-3p, 329a-3p, 655-3p, 411a-5p, and 154a-3p, which were located on ovine chromosome 18 forming four miRNA clusters within 10 kb. The elevated miRNAs belonged to different functional classes, playing roles in activating the hypothalamic-pituitary-adrenal axis; increasing cell survival and differentiation; and inducing inflammatory responses and targeted PI3K-Akt and MAPK signaling and chemokine signaling pathways. In summary, these results reveal the dynamic nature of ovine serum miRNAs during LPS-induced stress and highlight the potential role of identified miRNA-clusters on chromosome 18 to understand the regulation of the acute-phase response. Some of these identified circulating miRNAs may also serve as stress biomarkers for livestock in the future.

Mechanistic Actions of microRNAs in Diabetic Wound Healing

Wound healing is a complex biological process that is impaired under diabetes conditions. Chronic non-healing wounds in diabetes are some of the most expensive healthcare expenditures worldwide. Early diagnosis and efficacious treatment strategies are needed. microRNAs (miRNAs), a class of 18-25 nucleotide long RNAs, are important regulatory molecules involved in gene expression regulation and in the repression of translation, controlling protein expression in health and disease. Recently, miRNAs have emerged as critical players in impaired wound healing and could be targets for potential therapies for non-healing wounds. Here, we review and discuss the mechanistic background of miRNA actions in chronic wounds that can shed the light on their utilization as specific wound healing biomarkers.

Kupffer Cells: Inflammation Pathways and Cell-Cell Interactions in Alcohol-Associated Liver Disease

Chronic alcohol consumption is linked to the development of alcohol-associated liver disease (ALD). This disease is characterized by a clinical spectrum ranging from steatosis to hepatocellular carcinoma. Several cell types are involved in ALD progression, including hepatic macrophages. Kupffer cells (KCs) are the resident macrophages of the liver involved in the progression of ALD by activating pathways that lead to the production of cytokines and chemokines. In addition, KCs are involved in the production of reactive oxygen species. Reactive oxygen species are linked to the induction of oxidative stress and inflammation in the liver. These events are activated by the bacterial endotoxin, lipopolysaccharide, that is released from the gastrointestinal tract through the portal vein to the liver. Lipopolysaccharide is recognized by receptors on KCs that are responsible for triggering several pathways that activate proinflammatory cytokines involved in alcohol-induced liver injury. In addition, KCs activate hepatic stellate cells that are involved in liver fibrosis. Novel strategies to treat ALD aim at targeting Kupffer cells. These interventions modulate Kupffer cell activation or macrophage polarization. Evidence from mouse models and early clinical studies in patients with ALD injury supports the notion that pathogenic macrophage subsets can be successfully translated into novel treatment options for patients with this disease.

MicroRNA-18a-5p mitigates oxygen-glucose-deprivation/reoxygenation-induced injury through suppression of TLRs/NF-κB signaling by targeting TLR8 in PC12 cells

This work aimed to assess the role of TLR8 in cerebral I/R injury and its in-depth pathogenesis. Bioinformatics analysis indicated that TLR8 was up-regulated in patients with ischemic stroke than that in healthy control, and miR-18a-5p was the upstream regulatory of TLR8. Then, the rat pheochromocytoma PC12 cells were exposed in oxygen-glucose-deprivation/reoxygenation (OGD/R) conditions to construct a model in vitro. The functional experiments indicated that OGD/R can decline the viability and elevate the apoptosis of PC12 cells, while up-regulation of miR-18a-5p can alleviate OGD/R-induced cell injury. Notably, overexpression of TLR8 reverses the miR-18a-5p-mediated protection on OGD/R-induced cells injury. Finally, we found that up-regulation of miR-18a-5p obviously declined the protein levels of TLR4 and TLR7 as well as the phosphorylation of NF-κB, while overexpression of TLR8 canceled the decrease caused by miR-18a-5p up-regulation. In summing, our results illustrated that miR-18a-5p/TLR8 axis can mitigate OGD/R-induced cells injury through TLRs and NF-κB pathway.

Acupuncture Attenuates Inflammation in Microglia of Vascular Dementia Rats by Inhibiting miR-93-Mediated TLR4/MyD88/NF-κB Signaling Pathway

BACKGROUND

It is widely accepted that inflammation may contribute to cognitive impairment in patients with vascular dementia (VD). Our prior clinical researches have reported that acupuncture can alleviate cognitive function in VD, but the underlying mechanisms are still unclear. The purpose of this research was to explore whether acupuncture alleviates cognitive impairment by suppressing the microRNA-93- (miR-93-) mediated Toll-like receptor (TLR) signaling pathway, which triggers inflammatory responses in the central nervous system.

METHODS

VD was established by permanent bilateral common carotid artery occlusion in male Wistar rats. Three days after operation, the rats began daily treatment with acupuncture for two weeks. The levels of miR-93, Toll-like receptors (TLR2 and TLR4), intracellular signaling molecules (myeloid differentiation factor 88 (MyD88) and nuclear factor-kappa B (NF-κB)), and inflammatory cytokines were subsequently detected. TLR4 colocalized with neurons, microglia, and astrocytes in the hippocampus was evaluated. Neuroinflammation and cognitive function were determined after intracerebroventricular injection of TLR4 antagonist TAK-242 or agonist lipopolysaccharide (LPS) with or without acupuncture.

RESULTS

We found that acupuncture notably repressed the expression of inflammatory cytokines in the hippocampus and plasma of VD rats. The expression of TLR4, but not TLR2, was markedly downregulated by acupuncture, accompanied by a decrease in miR-93 and MyD88/NF-κB signaling pathway activation. The overexpression of TLR4 in microglia, but not in astrocytes and neurons, was reversed by acupuncture. Furthermore, intracerebroventricular injection of TAK-242 had similar effects to acupuncture on inflammation and cognitive function, while LPS injection abolished the beneficial effects of acupuncture.

CONCLUSIONS

Taken together, these findings provide evidence that acupuncture attenuates cognitive impairment associated with inflammation through inhibition of the miR-93-mediated TLR4/MyD88/NF-κB signaling pathway in experimental VD. Acupuncture serves as a promising alternative therapy and may be an underlying TLR4 inhibitor for the treatment of VD.

Human urine-derived stem cells protect against renal ischemia/reperfusion injury in a rat model via exosomal miR-146a-5p which targets IRAK1

Rationale: Ischemia/reperfusion injury (IRI) is a major cause of acute kidney injury (AKI) that is associated with high morbidity and mortality, and for which specific treatments are lacking. In this study, we investigated the protective effect of human urine-derived stem cells (USCs) and their exosomes against IRI-induced AKI to explore the potential of these cells as a new therapeutic strategy.

Methods: USCs were derived from fresh human urine. Cell surface marker expression was analyzed by flow cytometry to determine the characteristics of the stem cells. Adult male Sprague-Dawley rats were used to generate a lethal renal IRI model. One dose of USCs (2×10⁶ cells/ml) or exosomes (20 µg/1 ml) in the experimental groups or saline (1 ml) in the control group was administered intravenously immediately after blood reperfusion. Blood was drawn every other day for measurement of serum creatinine (sCr) and blood urea nitrogen (BUN) levels. The kidneys were harvested for RNA and protein extraction to examine the levels of apoptosis and tubule injury. In vitro, the hypoxia-reoxygenation (H/R) model in human kidney cortex/proximal tubule cells (HK2) was used to analyze the protective ability of USC-derived exosomes (USC-Exo). Quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR), western blotting, superoxide dismutase activity, and malonaldehyde content analyses were used to evaluate oxidative stress in HK2 cells treated with USC-Exo after H/R. Exosomal microRNA sequencing techniques and bioinformatics analysis were used to search for enriched miRNAs in the exosomes and interacting genes. The interaction between miRNAs and the 3' untranslated region of the target gene was detected using a dual luciferase reporting system. The miRNA mimic and inhibitor were used to regulate the miRNA level in HK2 cells.

Results: Treatment with USCs led to reductions in the levels of sCr, BUN, and renal tubular cell apoptosis; inhibited the infiltration of inflammatory cells; and protected renal function in the rat IRI model. Additionally, USC-derived exosomes protected against IRI-induced renal damage. miR-146a-5p was the most abundant miRNA in exosomes obtained from the conditioned medium (CM) of USCs. miR-146a-5p targeted and degraded the 3'UTR of interleukin-1 receptor-associated kinase 1 (IRAK1) mRNA, subsequently inhibited the activation of nuclear factor (NF)-κB signaling, and protected HK2 cells from H/R injury. USC transplantation also upregulated miR-146a-5p expression, downregulated IRAK1 expression and inhibited nuclear translocation of NF-κB p65 in the kidney of the rat IRI model.

Conclusions: According to our experimental results, USCs could protect against renal IRI via exosomal miR-146a-5p, which could target the 3'UTR of IRAK1 and subsequently inhibit the activation of NF-κB signaling and infiltration of inflammatory cells to protect renal function. As a novel cell source, USCs represent a promising non-invasive approach for the treatment of IRI.

Microglia Susceptibility to Free Bilirubin Is Age-Dependent

Increased concentrations of unconjugated bilirubin (UCB), namely its free fraction (Bf), in neonatal life may cause transient or definitive injury to neurons and glial cells. We demonstrated that UCB damages neurons and glial cells by compromising oligodendrocyte maturation and myelination, and by activating astrocytes and microglia. Immature neurons and astrocytes showed to be especially vulnerable. However, whether microglia susceptibility to UCB is also age-related was never investigated. We developed a microglia culture model in which cells at 2 days in vitro (2DIV) revealed to behave as the neonatal microglia (amoeboid/reactive cells), in contrast with those at 16DIV microglia that performed as aged cells (irresponsive/dormant cells). Here, we aimed to unveil whether UCB-induced toxicity diverged from the young to the long-cultured microglia. Cells were isolated from the cortical brain of 1- to 2-day-old CD1 mice and incubated for 24 h with 50/100 nM Bf levels, which were associated to moderate and severe neonatal hyperbilirubinemia, respectively. These concentrations of Bf induced early apoptosis and amoeboid shape in 2DIV microglia, while caused late apoptosis in 16DIV cells, without altering their morphology. CD11b staining increased in both, but more markedly in 2DIV cells. Likewise, the gene expression of HMGB1, a well-known alarmin, as well as HMGB1 and GLT-1–positive cells, were enhanced as compared to long-maturated microglia. The CX3CR1 reduction in 2DIV microglia was opposed to the 16DIV cells and suggests a preferential Bf-induced sickness response in younger cells. In conformity, increased mitochondrial mass and NO were enhanced in 2DIV cells, but unchanged or reduced, respectively, in the 16DIV microglia. However, 100 nM Bf caused iNOS gene overexpression in 2DIV and 16DIV cells. While only arginase 1/IL-1β gene expression levels increased upon 50/100 nM Bf treatment in long-maturated microglia, MHCII/arginase 1/TNF-α/IL-1β/IL-6 (>10-fold) were upregulated in the 2DIV microglia. Remarkably, enhanced inflammatory-associated microRNAs (miR-155/miR-125b/miR-21/miR-146a) and reduced anti-inflammatory miR-124 were found in young microglia by both Bf concentrations, while remained unchanged (miR/21/miR-125b) or decreased (miR-155/miR-146a/miR-124) in aged cells. Altogether, these findings support the neurodevelopmental susceptibilities to UCB-induced neurotoxicity, the most severe disabilities in premature babies, and the involvement of immune-inflammation neonatal microglia processes in poorer outcomes.

Combination of TLR agonist and miR146a mimics attenuates ovalbumin-induced asthma

Background

microRNA-146a has been reported to be a regulator in the process of attenuating asthma by inhibiting Toll-like receptor 2 (TLR2) pathway. This study aimed to investigate how miR146a-inhibitor affect the symptom of asthma and the underlying mechanisms.

Methods

Ovalbumin (OVA)-induced allergic asthma mice model was established by intraperitoneal injection with 20 μg of OVA. Total cells and differential inflammatory cells in bronchoalveolar lavage fluid were counted by flow cytometry. The expression levels of molecules and cytokines in TLR2 signaling pathway were detected by Q-PCR and ELISA.

Results

miR146a-inhibitor attenuated OVA-induced allergic asthma by increasing Th1 cytokines in OVA-induced allergic asthma model, and the treatment of miR146a-inhibitor can reduce the inflammation caused by asthma, followed by the down-regulation of IL-5 and IL-13 in sorted ILC2. The inhibition of miR-146a significantly reduced symptoms of asthma model with TLR2-related molecules being up-regulated.

Conclusion

It was found that miR-146a is an important regulator in OVA-induced allergic asthma model, which can relieve symptoms of asthma through regulating TLR2 pathway. These findings provide a theoretical basis for solving asthma in clinical treatment.

Comprehensive Molecular Profiles of Functionally Effective MSC-Derived Extracellular Vesicles in Immunomodulation

Accumulating evidence indicates that mesenchymal stem/stromal cell-derived extracellular vesicles (MSC-EVs) exhibit immunomodulatory effects by delivering therapeutic RNAs and proteins; however, the molecular mechanism underlying the EV-mediated immunomodulation is not fully understood. In this study, we found that EVs from early-passage MSCs had better immunomodulatory potency than did EVs from late-passage MSCs in T cell receptor (TCR)- or Toll-like receptor 4 (TLR4)-stimulated splenocytes and in mice with ocular Sjögren's syndrome. Moreover, MSC-EVs were more effective when produced from 3D culture of the cells than from the conventional 2D culture. Comparative molecular profiling using proteomics and microRNA sequencing revealed the enriched factors in MSC-EVs that were functionally effective in immunomodulation. Among them, manipulation of transforming growth factor β1 (TGF-β1), pentraxin 3 (PTX3), let-7b-5p, or miR-21-5p levels in MSCs significantly affected the immunosuppressive effects of their EVs. Furthermore, there was a strong correlation between the expression levels of TGF-β1, PTX3, let-7b-5p, or miR-21-5p in MSC-EVs and their suppressive function. Therefore, our comparative strategy identified TGF-β1, PTX3, let-7b-5p, or miR-21-5p as key molecules mediating the therapeutic effects of MSC-EVs in autoimmune disease. These findings would help understand the molecular mechanism underlying EV-mediated immunomodulation and provide functional biomarkers of EVs for the development of robust EV-based therapies.

Alcoholic-Hepatitis, Links to Brain and Microbiome: Mechanisms, Clinical and Experimental Research

The following review article presents clinical and experimental features of alcohol-induced liver disease (ALD). Basic aspects of alcohol metabolism leading to the development of liver hepatotoxicity are discussed. ALD includes fatty liver, acute alcoholic hepatitis with or without liver failure, alcoholic steatohepatitis (ASH) leading to fibrosis and cirrhosis, and hepatocellular cancer (HCC). ALD is fully attributable to alcohol consumption. However, only 10-20% of heavy drinkers (persons consuming more than 40 g of ethanol/day) develop clinical ALD. Moreover, there is a link between behaviour and environmental factors that determine the amount of alcohol misuse and their liver disease. The range of clinical presentation varies from reversible alcoholic hepatic steatosis to cirrhosis, hepatic failure, and hepatocellular carcinoma. We aimed to (1) describe the clinico-pathology of ALD, (2) examine the role of immune responses in the development of alcoholic hepatitis (ASH), (3) propose diagnostic markers of ASH, (4) analyze the experimental models of ALD, (5) study the role of alcohol in changing the microbiota, and (6) articulate how findings in the liver and/or intestine influence the brain (and/or vice versa) on ASH; (7) identify pathways in alcohol-induced organ damage and (8) to target new innovative experimental concepts modeling the experimental approaches. The present review includes evidence recognizing the key toxic role of alcohol in ALD severity. Cytochrome p450 CYP2E1 activation may change the severity of ASH. The microbiota is a key element in immune responses, being an inducer of proinflammatory T helper 17 cells and regulatory T cells in the intestine. Alcohol consumption changes the intestinal microbiota and influences liver steatosis and liver inflammation. Knowing how to exploit the microbiome to modulate the immune system might lead to a new form of personalized medicine in ALF and ASH.

MicroRNA (miRNA): A New Dimension in the Pathogenesis of Antiphospholipid Syndrome (APS)

MicroRNAs (miRNAs) are single-stranded, endogenous RNA molecules that play a significant role in the regulation of gene expression as well as cell development, differentiation, and function. Recent data suggest that these small molecules are responsible for the regulation of immune responses. Therefore, they may act as potent modulators of the immune system and play an important role in the development of several autoimmune diseases. Antiphospholipid syndrome (APS) is an autoimmune systemic disease characterized by venous and/or arterial thromboses and/or recurrent fetal losses in the presence of antiphospholipid antibodies (aPLs). Several lines of evidence suggest that like other autoimmune disorders, miRNAs are deeply involved in the pathogenesis of APS, interacting with the function of innate and adaptive immune responses. In this review, we characterize miRNAs in the light of having a functional role in the immune system and autoimmune responses focusing on APS. In addition, we also discuss miRNAs as potential biomarkers and target molecules in treating APS.

Aberrant MicroRNAomics in Pulmonary Complications: Implications in Lung Health and Diseases

Over the last few decades, evolutionarily conserved molecular networks have emerged as important regulators in the expression and function of eukaryotic genomes. Recently, miRNAs (miRNAs), a large family of small, non-coding regulatory RNAs were identified in these networks as regulators of endogenous genes by exerting post-transcriptional gene regulation activity in a broad range of eukaryotic species. Dysregulation of miRNA expression correlates with aberrant gene expression and can play an essential role in human health and disease. In the context of the lung, miRNAs have been implicated in organogenesis programming, such as proliferation, differentiation, and morphogenesis. Gain- or loss-of-function studies revealed their pivotal roles as regulators of disease development, potential therapeutic candidates/targets, and clinical biomarkers. An altered microRNAome has been attributed to several pulmonary diseases, such as asthma, chronic pulmonary obstructive disease, cystic fibrosis, lung cancer, and idiopathic pulmonary fibrosis. Considering the relevant roles and functions of miRNAs under physiological and pathological conditions, they may lead to the invention of new diagnostic and therapeutic tools. This review will focus on recent advances in understanding the role of miRNAs in lung development, lung health, and diseases, while also exploring the progress and prospects of their application as therapeutic leads or as biomarkers.

MicroRNA-155 and microRNA-181a, via HO-1, participate in regulating the immunotoxicity of cadmium in the kidneys of exposed Cyprinus carpio

Cadmium (Cd) is a nonessential metal that is a contaminant in aquatic ecosystems. Cd can accumulate in aquatic animals, leading to detrimental effects in tissues, and Cd exposure can induce immunotoxicity in fish. MicroRNAs (miRNAs) play critical roles in immune responses, yet the participation of miRNAs in Cd-induced immunotoxicity remains poorly understood. The present study evaluated the effects of Cd exposure on the immune responses and the mRNAs and miRNAs expressions of immune-related genes in Cyprinus carpio (C. carpio). Then, microRNA-155 (miR-155) was overexpressed and microRNA-181a (miR-181a) was knocked down to determine which miRNA plays a key role in the immune response to Cd. The results showed that 0.5 mg/L Cd²⁺ significantly decreased the activity of alkaline phosphatase (AKP) and acid phosphatase (ACP) in the kidneys of C. carpio. Cd exposure upregulated the mRNA expressions of interleukin (IL)-1β, IL-8, nuclear factor-kappa B (NF-κB), tumour necrosis factor-α (TNF-α), and Toll-like receptor 4(TLR-4) and downregulated those of IL-10 and heme oxygenase-1 (HO-1) in C. carpio kidneys. Cd exposure also led to upregulation of miR-155 and miR-181a expressions. Furthermore, AKP and ACP activity in the kidneys was markedly changed after intraperitoneal injection of C. carpio with miR-155 agomir and miR-181a antagomir. All detected mRNA expressions were significantly decreased after injection of miR-155 agomir, and IL-10, NF-κB, TNF-α, and HO-1 mRNA expressions were markedly increased after injection of miR-181a antagomir. The results of this study demonstrate that Cd exposure can immunocompromise C. carpio by targeting HO-1 through miR-155 and miR-181a. This is the first study to reveal that Cd exposure induces immunotoxicity through miR-155 and miR-181a in the kidneys of C. carpio.

Interactions between immune response to fungal infection and microRNAs: The pioneer tuners

Due to their physiological and biological characteristics, numerous fungi are potentially emerging pathogens. Active dynamicity of fungal pathogens causes life-threatening infections annually impose high costs to the health systems. Although immune responses play crucial roles in controlling the fate of fungal infections, immunocompromised patients are at high risk with high mortality. Tuning the immune response against fungal infections might be an effective strategy for controlling and reducing the pathological damages. MicroRNAs (miRNAs) are known as the master regulators of immune response. These single-stranded tuners (18-23 bp non-coding RNAs) are endogenously expressed by all metazoan eukaryotes and have emerged as the master gene expression controllers of at least 30% human genes. In this review article, following the review of biology and physiology (biogenesis and mechanism of actions) of miRNAs and immune response against fungal infections, the interactions between them were scrutinised. In conclusion, miRNAs might be considered as one of the potential goals in immunotherapy for fungal infections. Undoubtedly, advanced studies in this field, further identifying of miRNA roles in governing the immune response, pave the way for inclusion of miRNA-related immunotherapeutic in the treatment of life-threatening fungal infections.

miRNAs Regulate Cytokine Secretion Induced by Phosphorylated S100A8/A9 in Neutrophils

The release of cytokines by neutrophils constitutes an essential process in the development of inflammation by recruiting and activating additional cells. Neutrophils are also able to secrete a complex of S100A8 and S100A9 proteins (S100A8/A9), which can amplify the general inflammatory state of the host and is involved in the pathogenesis of several chronic inflammatory diseases, such as rheumatoid arthritis (RA). S100A8/A9 have received renewed attention due to their susceptibility to several function-altering post-translational modifications. In that context, it has been recently demonstrated that only the phosphorylated form of S100A8/A9 (S100A8/A9-P) is able to induce the secretion of several cytokines in neutrophils. Here, we investigate the mechanism by which this post-translational modification of S100A8/A9 can regulate the extracellular activity of the protein complex and its impact on the inflammatory functions of neutrophils. We found that S100A8/A9-P are present in large amounts in the synovial fluids from RA patients, highlighting the importance of this form of S100A8/A9 complex in the inflammation process. Using miRNA-sequencing on S100A8/A9-P-stimulated differentiated HL-60 cells, we identified a dysregulation of miR-146a-5p and miR-155-5p expression through TRL4 signaling pathways. Our data reveal that overexpression of these miRNAs in neutrophil-like cells reduces S100A8/A9-P-mediated secretion of pro-inflammatory cytokines.

MicroRNA-182-3p negatively regulates cytokines expression by targeting TLR5M in orange-spotted grouper, Epinephelus coioides

Toll-like receptors (TLRs) as essential pattern recognition receptors in innate immunity, can recognize pathogens and trigger immune response to eliminate invading pathogens. MicroRNAs regulates multiple biological processes by suppressing mRNA translation or resulting in mRNA degradation. MiR-182 has previously been implicated in DNA repair, disease and cancer aspects. The potential role of miR-182-3p in TLR signaling pathway against pathogens is unclear. In this study, we found that the expression of miR-182-3p was up-regulated after Vibrio parahaemolyticus flagellin stimulation in grouper spleen (GS) cells, and negatively correlated with the expression of orange-spotted grouper (Epinephelus coioides) TLR5M (EcTLR5M). Then we found that miR-182-3p could directly target EcTLR5M by using bioinformatic analysis and dual-luciferase reporter assay. Dual-luciferase reporter assay also showed that miR-182-3p down-regulated the wild-type EcTLR5M 3'UTR in luciferase activity rather than the mutant group in HEK 293T cells. We further verified the effect of miR-182-3p on the activation of Nuclear factor-κB (NF-κB) signaling pathway, and found that miR-182-3p inhibitors significantly augmented flagellin-induced NF-κB phosphorylation. Additionally, we also demonstrated that the increased expression of miR-182-3p significantly suppressed the flagellin-induced EcTLR5M, pro-inflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) mRNA expression. And the endogenous miR-182-3p knockdown experiments reversely verified the regulatory effect of miR-182-3p. These results suggested that miR-182-3p post-transcriptionally controls EcTLR5M expression and thereby suppresses the expression of pro-inflammatory cytokines. This study is the first to demonstrate that miR-182-3p suppresses pro-inflammatory cytokines expression by regulating the TLR signaling pathway.

GABAAR α2-activated neuroimmune signal controls binge drinking and impulsivity through regulation of the CCL2/CX3CL1 balance

BACKGROUND AND PURPOSE

Toll-like receptors (TLRs) are a family of innate immune system receptors that respond to pathogen-derived and tissue damage-related ligands and are increasingly recognized for their impact on homeostasis and its dysregulation in the nervous system. TLR signaling participates in brain injury and addiction, but its role in the alcohol-seeking behavior, which initiates alcohol drinking, is still poorly understood. In this review, we discuss our findings designed to elucidate the potential contribution of the activated TLR4 signal located in neurons, on impulsivity and the predisposition to initiate alcohol drinking (binge drinking).

RESULTS

Our findings indicate that the TLR4 signal is innately activated in neurons from alcohol-preferring subjects, identifying a genetic contribution to the regulation of impulsivity and the alcohol-seeking propensity. Signal activation is through the non-canonical, previously unknown, binding of TLR4 to the α2 subunit of the γ-aminobutyric 2 acid A receptor (GABAAR α2). Activation is sustained by the stress hormone corticotrophin-releasing factor (CRF) and additional still poorly recognized ligand/scaffold proteins. Focus is on the effect of TLR4 signal activation on the balance between pro- and anti-inflammatory chemokines [chemokine (C-C motif) ligand 2 (CCL2)/chemokine (C-X3-C motif) ligand 1 (CX3CL1)] and its effect on binge drinking.

CONCLUSION

The results are discussed within the context of current findings on the distinct activation and functions of TLR signals located in neurons, as opposed to immune cells. They indicate that the balance between pro- and anti-inflammatory TLR4 signaling plays a major role in binge drinking. These findings have major impact on future basic and translational research, including the development of potential therapeutic and preventative strategies.

Cellular Responses to Exposure to Outdoor Air from the Chinese Spring Festival at the Air-Liquid Interface

The Spring Festival is the most important holiday in China. During this time, the levels of particulate matter (PM) as well as gaseous copollutants significantly increase because of the widespread enjoyment of fireworks. The expression patterns of microRNAs may serve as valuable signatures of exposure to environmental constituents. We exposed macrophages to the whole stream of outdoor air at the air-liquid interface aiming at closely approximating the physiological conditions and the inhalation situation in the lung. 58 miRNAs were up-regulated, and 68 miRNAs were down-regulated in the night of the New Year's Eve (exposure group E2N1) compared to filtered-air exposed control cells. The target genes of the up-regulated miRNAs were enriched in immunity- and inflammation-linked pathways, such as the TLR-NF-κB pathway. Compared to the E2N1 group, 29 miRNAs were up-regulated, and 23 miRNAs were down-regulated in the cells exposed to air from the daytime of the Chinese New Year with higher concentrations of particles, SO₂, and nitrogen oxide. The target genes of the up-regulated miRNAs were mostly enriched in apoptosis, adhesion, and junction-related pathways. These results preliminarily unravel part of the toxic mechanisms of air constituents and provide clues for discovering the main drivers of air pollution-induced disorders.

The Inducible microRNA-21 Negatively Modulates the Inflammatory Response in Teleost Fish via Targeting IRAK4

Eradication of bacterial infection requires timely and appropriate immune and inflammatory responses, but excessive induction of inflammatory cytokines can cause acute or chronic inflammatory disorders. Thus, various layers of negative regulators and mechanisms are needed to ensure maintenance of the homeostasis for the immune system. miRNAs are a family of small non-coding RNAs that emerged as significant and versatile regulators involved in regulation of immune responses. Recently, the molecular mechanisms of miRNA in host-pathogen interaction networks have been extensively studied in mammals, whereas the underlying regulatory mechanisms in fish are still poorly understood. In this study, we identify miR-21 as a negative regulator of the teleost inflammatory response. We found that lipopolysaccharide and Vibrio anguillarum significantly upregulated the expression of fish miR-21. Upregulated miR-21 suppresses LPS-induced inflammatory cytokine expression by targeting IL-1 receptor-associated kinase 4 (IRAK4), thereby avoiding excessive inflammatory responses. Furthermore, we demonstrated that miR-21 regulates inflammatory responses through NF-κB signaling pathways. The collective findings indicate that miR-21 plays a regulatory role in host-pathogen interactions through IRAK4-mediated NF-κB signaling pathway.

Aberrant Expression of Intracellular let-7e, miR-146a, and miR-155 Correlates with Severity of Depression in Patients with Major Depressive Disorder and Is Ameliorated after Antidepressant Treatment

Chronic inflammation and abnormalities in Toll-like receptor (TLR) signaling pathways are associated with major depressive disorder (MDD). Our previous work reported that impaired negative regulators for the TLR pathways are associated with MDD. This study aimed to assess the association between the severity of depression and the intracellular microRNAs that regulate TLR4 signaling in both peripheral blood mononuclear cells (PBMCs) and monocytes from MDD patients. The severity of MDD before and after antidepressant treatment was determined by the 17-item Hamilton Depression Rating Scale, and quantitative RT-PCR was used to measure the levels of intracellular regulatory microRNAs, including let-7e, miR-21-5p miR-145, miR-223, miR-146a, and miR-155, in PBMCs and monocytes isolated from 43 healthy controls and 84 patients with MDD before and after treatment with antidepressants. Assays of PBMCs showed that the levels of let-7e, miR-146a, and miR-155 were lower in MDD patients than in healthy controls and were significantly higher after than before treatment in the 69 patients who completed treatment with antidepressants for four weeks. Levels of miR-146a and miR-155 in monocytes were lower in MDD patients than in controls and were increased in the former after antidepressant treatment. Multiple linear regression analyses found that let-7e and miR-146a expression before treatment was inversely correlated with severity of depression, whereas miR-155 before treatment was directly correlated with severity of depression. These findings suggest that intracellular regulatory microRNAs which regulate TLR4 signaling are aberrantly expressed in patients with MDD and that these levels are ameliorated by antidepressant treatment.

A Review of Macrophage MicroRNAs' Role in Human Asthma

There is an imbalance in asthma between classically activated macrophages (M1 cells) and alternatively activated macrophages (M2 cells) in favor of the latter. MicroRNAs (miRNAs) play a critical role in regulating macrophage proliferation and differentiation and control the balance of M1 and M2 macrophage polarization, thereby controlling immune responses. Here we review the current published data concerning miRNAs with known correlation to a specific human macrophage phenotype and polarization, and their association with adult asthma. MiRNA-targeted therapy is still in the initial stages, but clinical trials are under recruitment or currently running for some miRNAs in other diseases. Regulating miRNA expression via their upregulation or downregulation could show potential as a novel therapy for improving treatment efficacy in asthma.

Regulating IRFs in IFN Driven Disease

The Interferon regulatory factors (IRFs) are a family of transcription factors that play pivotal roles in many aspects of the immune response, including immune cell development and differentiation and regulating responses to pathogens. Three family members, IRF3, IRF5, and IRF7, are critical to production of type I interferons downstream of pathogen recognition receptors that detect viral RNA and DNA. A fourth family member, IRF9, regulates interferon-driven gene expression. In addition, IRF4, IRF8, and IRF5 regulate myeloid cell development and phenotype, thus playing important roles in regulating inflammatory responses. Thus, understanding how their levels and activity is regulated is of critical importance given that perturbations in either can result in dysregulated immune responses and potential autoimmune disease. This review will focus the role of IRF family members in regulating type I IFN production and responses and myeloid cell development or differentiation, with particular emphasis on how regulation of their levels and activity by ubiquitination and microRNAs may impact autoimmune disease.

Circular RNA expression alterations in colon tissues of Crohn's disease patients

Genetic factors are crucial in the development of Crohn's disease (CD). Circular RNAs (circRNAs) are known to function as microRNA (miRNA) sponges and regulate a number of signalling pathways via circRNA‑miRNA interactions. As competing endogenous RNAs, the functions of circRNAs in CD should be investigated. In the present study, colon biopsy tissues were collected from ileocolon (L3)‑active CD patients and healthy controls. circRNA microarrays were performed with colon tissues from 3 CD patients and 3 controls. Subsequently, the candidate circRNAs were verified via reverse transcription‑quantitative polymerase chain reaction using colon tissues from a further 10 CD patients and 10 controls. Targeted miRNAs, genes and pathways of candidate circRNAs were predicted and analysed. Arraystar circRNA microarrays demonstrated that there were 163 upregulated circRNAs targeting 435 miRNAs and 55 downregulated circRNAs targeting 207 miRNAs (fold‑change >2 and P<0.01) in CD patients. As a candidate circRNA, hsa‑circRNA‑102685 was observed to putatively target hsa‑miR‑146b‑5p, hsa‑miR‑182‑5p and hsa‑miR‑146a‑5p. Furthermore, Kyoto Encyclopaedia of Genes and Genomes pathway analysis predicted that hsa‑circRNA‑102685 potentially participated in apoptosis, and in the Toll‑like receptor and p53 signalling pathways. Overall, the current study suggested that circRNA alterations serve an important role in the pathogenesis of CD. circRNAs, such as hsa‑circRNA‑102685, are involved in certain important signalling pathways of CD, and may be novel targets for diagnosis or treatment in this disease.

Circulating plasma microRNAs dysregulation and metabolic endotoxemia induced by a high-fat high-saturated diet

High-fat diet increase two to three times the plasma lipopolysaccharide (LPS) levels and induce subclinical inflammation. Diet can modify gene expression due to epigenetic processes related to MicroRNAs (miRNAs). MicroRNAs (miRNAs) play important role in the post-transcriptional mechanisms involved in regulation of expression of genes related to the inflammatory response. Also, diet can indirectly induce post-transcriptional regulation of gene expression by miRNAs, which may affect the risk for the development of chronic diseases.

OBJECTIVE

This study investigated the effect of high-fat high-saturated meal ingestion on plasma miRNA expression and LPS levels during the postprandial period in healthy women.

METHODS

An interventional study was carried out in which a high-fat breakfast (1067.45 kcal), composed mainly of saturated fatty acids (56 g), and 500 mL of water, was offered. Blood samples were collected at baseline and 1, 3 and 5 h after meal intake. The studied population consisted of healthy women (n = 11), aged between 20 and 40 years, and body mass index (BMI) between 18.5 and 25 kg/m². Plasma levels of lipid profile, cytokines, adhesion molecules, and LPS were measured at the 3 time points. A profile of 752 human plasma miRNA expression was analyzed by real-time PCR assay. These analyzes were performed for all blood collection time-points.

RESULTS

Expression profile analysis revealed 33 differentially expressed plasma circulating miRNAs compared to that of the control group. MiR-145-5p and miR-200 were differentially modulated in all time-points post meal consumption. In addition, there was a significant increase in plasma LPS, triglycerides, myristic and palmitic saturated fatty acids levels at the 3 time-points in comparison with the control basal levels. We also observed increased levels of the plasma tumor necrosis factor alpha (TNF-α) cytokine and the vascular cell adhesion molecule 1 (VCAM-1) levels after 5 h post meal ingestion.

CONCLUSION

Ingestion of high-fat high-saturated meal was able to induce metabolic endotoxemia and increase the expression of pro-inflammatory molecules such as TNF-alpha and VCAM-1, as well as modulating circulating miRNAs possibly controlling inflammatory and lipid metabolism proteins at the postprandial period.

Staphylococcus aureus: an underestimated factor in the pathogenesis of atopic dermatitis?

Atopic dermatitis is a common, recurrent pruritic dermatosis with a complex pathogenesis. It has been associated with disordered patterns of immunological response and impaired epithelial barrier integrity. These features predispose the patients to robust colonization of skin lesions by Staphylococcus aureus. Virulence factors of S. aureus (e.g. superantigens, α- and δ-toxin, protein A) have been shown to exacerbate and perpetuate the course of atopic dermatitis. Novel therapeutic options with potential for restoring natural microbiome composition are being elaborated and may enter clinical practice in the future.

The Inhibitory Role of M2000 (β-D-Mannuronic Acid) on Expression of Toll-like Receptor 2 and 4 in HT29 Cell Line

BACKGROUND/OBJECTIVES

Anti-inflammatory agents play a crucial role in controlling inflammatory diseases such as Inflammatory Bowel Disease (IBD) but their use is restricted due to their vast side effects. M2000 (β-D-mannuronic acid) is a new immunomodulatory drug. According to the capacity of M2000 in suppressing some molecules involved in Toll Like Receptors (TLRs) signaling and reducing oxidative stress we hypothesize that, this molecule may have a potential role in decreasing inflammatory responses in IBD. The aim of this study was to evaluate the cytotoxicity of M2000 and its effect on the gene expression of TLR2 and TLR4.

METHODS

HEK293 cell line was grown and divided into 96-well cell plate and MTT assay was performed. HT29 cells were cultured and treated with low and high doses of M2000. Total RNA was extracted and cDNA synthesized and quantitative real-time PCR was done to quantify the TLR2 and TLR4 mRNA expression.

RESULTS

We found that M2000 at the concentration of ≤ 1000µg/ml had no obvious cytotoxicity effect on the HEK293 cells. Also, low and high doses of M2000 could significantly down-regulate both TLR2 and TLR4 mRNA expression. Moreover, a significant reduction in gene expression of TLR2 and TLR4 in an inflammatory condition resulted in high doses of M2000 in the presence of LPS.

CONCLUSION

Our study which was conducted in colonic epithelial cell model, shows that M2000 can be considered as a new anti-inflammatory agent in IBD. However, more comprehensive experimental and clinical studies are required to recognize the molecular mechanism of M2000 and also its safety and efficacy.

Regulation of Endotoxin Tolerance and Compensatory Anti-inflammatory Response Syndrome by Non-coding RNAs

The onset and the termination of innate immune response must be tightly regulated to maintain homeostasis and prevent excessive inflammation, which can be detrimental to the organism, particularly in the context of sepsis. Endotoxin tolerance and compensatory anti-inflammatory response syndrome (CARS) describe a state of hypo-responsiveness characterized by reduced capacity of myeloid cells to respond to inflammatory stimuli, particularly those initiated by bacterial lipopolysaccharide (LPS). To achieve endotoxin tolerance, extensive reprogramming otherwise termed as “innate immune training”, is required that leads to both modifications of the intracellular components of TLR signaling and also to alterations in extracellular soluble mediators. Non-coding RNAs (ncRNAs) have been recognized as critical regulators of TLR signaling. Specifically, several microRNAs (miR-146, miR-125b, miR-98, miR-579, miR-132, let-7e and others) are induced upon TLR activation and reciprocally promote endotoxin tolerance and/or cross tolerance. Many other miRNAs have been also shown to negatively regulate TLR signaling. The long non-coding (lnc)RNAs (Mirt2, THRIL, MALAT1, lincRNA-21 and others) are also altered upon TLR activation and negatively regulate TLR signaling. Furthermore, the promotion or termination of myeloid cell tolerance is not only regulated by intracellular mediators but is also affected by other TLR-independent soluble signals that often achieve their effect via modulation of intracellular ncRNAs. In this article, we review recent evidence on the role of different ncRNAs in the context of innate immune cell tolerance and trained immunity, and evaluate their impact on immune system homeostasis.

Deep sequencing and miRNA profiles in alcohol-induced neuroinflammation and the TLR4 response in mice cerebral cortex

Alcohol abuse can induce brain injury and neurodegeneration, and recent evidence shows the participation of immune receptors toll-like in the neuroinflammation and brain damage. We evaluated the role of miRNAs as potential modulators of the neuroinflammation associated with alcohol abuse and the influence of the TLR4 response. Using mice cerebral cortex and next-generation sequencing (NGS), we identified miRNAs that were differentially expressed in the chronic alcohol-treated versus untreated WT or TLR4-KO mice. We observed a differentially expression of miR-183 Cluster (C) (miR-96/-182/-183), miR-200a and miR-200b, which were down-regulated, while mirR-125b was up-regulated in alcohol-treated WT versus (vs.) untreated mice. These miRNAs modulate targets genes related to the voltage-gated sodium channel, neuron hyperexcitability (Nav1.3, Trpv1, Smad3 and PP1-γ), as well as genes associated with innate immune TLR4 signaling response (Il1r1, Mapk14, Sirt1, Lrp6 and Bdnf). Functional enrichment of the miR-183C and miR-200a/b family target genes, revealed neuroinflammatory pathways networks involved in TLR4 signaling and alcohol abuse. The changes in the neuroinflammatory targets genes associated with alcohol abuse were mostly abolished in the TLR4-KO mice. Our results show the relationship between alcohol intake and miRNAs expression and open up new therapeutically targets to prevent deleterious effects of alcohol on the brain.

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.

Neuroinflammatory Nexus of Pediatric Epilepsy

A rapidly growing body of evidence supports the premise that neuroinflammation plays an important role in initiating and sustaining seizures in a range of pediatric epilepsies. Clinical and experimental evidence indicate that neuroinflammation is both an outcome and a contributor to seizures. In this manner, seizures that arise from an initial insult (e.g. infection, trauma, genetic mutation) contribute to an inflammatory response that subsequently promotes recurrent seizures. This cyclical relationship between seizures and neuroinflammation has been described as a 'vicious cycle.' Studies of human tissue resected for surgical treatment of refractory epilepsy have reported activated inflammatory and immune signaling pathways, while animal models have been used to demonstrate that key inflammatory mediators lead to increased seizure susceptibility. Further characterization of the molecular mechanisms involved in this cycle may ultimately enable the development of new therapeutic approaches for the treatment of epilepsy. In this brief review we focus on key inflammatory mediators that have become prominent in recent literature of epilepsy, including newly characterized microRNAs and their potential role in neuroinflammatory signaling.

Immune Regulation of Tissue Repair and Regeneration via miRNAs-New Therapeutic Target

The importance of immunity in tissue repair and regeneration is now evident. Thus, promoting tissue healing through immune modulation is a growing and promising field. Targeting microRNAs (miRNAs) is an appealing option since they regulate immunity through post-transcriptional gene fine-tuning in immune cells. Indeed, miRNAs are involved in inflammation as well as in its resolution by controlling immune cell phenotypes and functions. In this review, we first discuss the immunoregulatory role of miRNAs during the restoration of tissue homeostasis after injury, focusing mainly on neutrophils, macrophages and T lymphocytes. As tissue examples, we present the immunoregulatory function of miRNAs during the repair and regeneration of the heart, skeletal muscles, skin and liver. Secondly, we discuss recent technological advances for designing therapeutic strategies which target miRNAs. Specifically, we highlight the possible use of miRNAs and anti-miRNAs for promoting tissue regeneration via modulation of the immune system.

miR-155 is dispensable in monosodium urate-induced gouty inflammation in mice

BACKGROUND

The findings of a previous study by Jin et al. have shown that microRNA (miR)-155 was upregulated in patients with acute gouty arthritis and enhanced the proinflammatory cytokines. There is no direct evidence to support that miR-155 is indeed involved in monosodium urate (MSU)-induced inflammatory responses in vivo. The aim of this study was to investigate the role of miR-155 knock-out (KO) or knock-in (KI) mice in MSU-induced animal models to mimic acute gout.

METHODS

MiR-155 expression in cultured bone marrow-derived macrophages (BMDMs) from miR-155 KO, miR-155 KI, and wild-type (WT) mice treated with MSU crystals in vitro was detected by real-time quantitative polymerase chain reaction (qPCR). MiR-155 KO and WT mice were used to induce an acute gouty inflammatory response with MSU crystals including models of foot pad inflammation, ankle arthritis, air pouch inflammation, and peritonitis. Furthermore, the proinflammatory interleukin (IL)-1β levels in lavage fluids from air pouch and peritoneal cavity models were measured by enzyme-linked immunosorbent assay (ELISA), and tumor necrosis factor (TNF)-α production from BMDMs of miR-155 KI mice treated with MSU were measured by flow cytometry.

RESULTS

MiR-155 expression was quickly upregulated in BMDMs from WT mice following MSU treatment in vitro. In comparison with WT mice in vivo, the swelling index of miR-155 KO mice showed no significant difference in the murine foot pad and ankle arthritis models for the indicated different time points. There were similar changes in total cell numbers of lavage fluids in the air pouch and peritoneal cavity models between miR-155 KO and WT mice following MSU crystal injection. Moreover, the IL-1β levels of lavage fluids in the air pouch and peritonitis models from miR-155 KO mice were almost the same as those from WT mice. TNF-α levels were comparable from BMDMs treated with MSU crystals in vitro between miR-155 KI mice and WT mice.

CONCLUSIONS

MiR-155 is dispensable in MSU-induced gouty inflammation in mice. Deletion of miR-155 might not be an effective therapeutic approach to relieve the inflammation in acute gout.

Pre-Analytical Handling Conditions and Small RNA Recovery from Urine for miRNA Profiling

There are currently no standardized protocols for pre-analytical handling of urine to best preserve small RNA for miRNA profiling studies. miRNA is an attractive candidate as a potential biomarker because of the high level of stability in body fluids and its ability to be quantified on multiple high-throughput platforms. We present a comparison of small RNA recovery and stability in urine under alternate pre-analytical handling conditions and extend recommendations on what conditions optimize yield of miRNA from cell-free urine and urine extracellular vesicles (EVs). Using an affinity slurry for isolation of small RNA from urine, we found that urine samples held at room temperature (20°C) for up to 8 hours before processing yield the highest amounts of intact small RNAs from EVs. Some miRNA is lost from urine samples when held 2°C to 4°C and/or frozen before EV isolation, likely because of EV entrapment in uromodulin precipitates. However, we found that a simple 5-minute incubation of urine containing cold-induced precipitate at 37°C resolubilizes much of this precipitate and results in an increased recovery of EVs and miRNAs. Finally, small RNA integrity can be compromised when whole urine is held at 37°C for as little as 4 hours and is not conducive to efficient miRNA profiling.

The rs2910164 variant is associated with reduced miR-146a expression but not cytokine levels in patients with type 2 diabetes

PURPOSE

Previous reports have demonstrated that genetic variations in microRNAs regulome could affect microRNAs-mediated regulation. Therefore, in the present study we were aimed at (1) comparison of microRNA 146-a (miR-146a) peripheral blood mononuclear cells (PBMCs) and plasma levels between diabetic patients and controls, and (2) investigating the possible association of rs2910164 with miR-146a and its related target genes expression and also serum cytokine levels.

METHODS

The study population consisted of 60 subjects including 30 type 2 diabetes (T2D) patients and 30 controls with determined genotypes for rs2910164. The RNA expression levels were determined by real-time PCR. Moreover, TNF-α, IL-6, IL-10 and IL-1β serum levels were measured using ELISA method.

RESULTS

Our results showed that the miR-146a expression levels were significantly decreased in PBMCs (P = 0.004) and plasma (P = 0.008) samples of patients with T2D compared to healthy participants. In addition, we observed that IRAK1 mRNA expression-but not TLR4, TRAF6 and NFĸB-was significantly increased in patients with T2D compared to controls (P = 0.028). The relative expression levels of miR-146a in plasma and PBMCs samples of diabetic patients with the rs2910164 GG genotypes were significantly higher than that in CC (P < 0.05). Moreover, no significant differences were found in miR-146a targets and cytokine levels between the rs2910164 different genotypes.

CONCLUSION

Our study demonstrated that miR-146a circulating levels were significantly elevated in controls compared with T2D patients. In addition, we identified that rs2910164-C allele is associated with reduced expression levels of the miR-146a but not its mRNAs targets and cytokine levels in diabetic patients.

Nuclear PTEN enhances the maturation of a microRNA regulon to limit MyD88-dependent susceptibility to sepsis

Sepsis-induced organ damage is caused by systemic inflammatory response syndrome (SIRS), which results in substantial comorbidities. Therefore, it is of medical importance to identify molecular brakes that can be exploited to dampen inflammation and prevent the development of SIRS. We investigated the role of phosphatase and tensin homolog (PTEN) in suppressing SIRS, increasing microbial clearance, and preventing lung damage. Septic patients and mice with sepsis exhibited increased PTEN expression in leukocytes. Myeloid-specific Pten deletion in an animal model of sepsis increased bacterial loads and cytokine production, which depended on enhanced myeloid differentiation primary response gene 88 (MyD88) abundance and resulted in mortality. PTEN-mediated induction of the microRNAs (miRNAs) miR125b and miR203b reduced the abundance of MyD88. Loss- and gain-of-function assays demonstrated that PTEN induced miRNA production by associating with and facilitating the nuclear localization of Drosha-Dgcr8, part of the miRNA-processing complex. Reconstitution of PTEN-deficient mouse embryonic fibroblasts with a mutant form of PTEN that does not localize to the nucleus resulted in retention of Drosha-Dgcr8 in the cytoplasm and impaired production of mature miRNAs. Thus, we identified a regulatory pathway involving nuclear PTEN-mediated miRNA generation that limits the production of MyD88 and thereby limits sepsis-associated mortality.

MicroRNA regulation of Toll-like receptor signaling pathways in teleost fish

The innate immune system is the first line defense mechanism that recognizes, responds to, controls or eliminates invading pathogens. Toll-like receptors (TLRs) are a critical family of pattern recognition receptors (PRRs) tightly regulated by complex mechanisms involving many molecules to ensure a beneficial outcome in response to foreign invaders. MicroRNAs (miRNAs), a transcriptional and posttranscriptional regulator family in a wide range of biological processes, have been identified as new molecules related to the regulation of TLR-signaling pathways in immune responses. To date, at least 22 TLR types have been identified in more than a dozen different fish species. However, the functions and underlying mechanisms of miRNAs in the regulation of inflammatory responses related to the TLR-signaling pathway in fish is lacking. In this review, we summarize the regulation of miRNA expression profiles in the presence of TLR ligands or pathogen infections in teleost fish. We focus on the effects of miRNAs in regulating TLR-signaling pathways by targeting multiple molecules, including TLRs themselves, TLR-associated signaling proteins, and TLR-induced cytokines. An understanding of the relationship between the TLR-signaling pathways and miRNAs may provide new insights for drug intervention to manipulate immune responses in fish.

Mice with miR-146a deficiency develop severe gouty arthritis via dysregulation of TRAF 6, IRAK 1 and NALP3 inflammasome

BACKGROUND

MicroRNAs (miRNAs) serve as important regulators of inflammatory and immune responses and are implicated in several immune disorders including gouty arthritis. The expression of miR-146a is upregulated in the peripheral blood mononuclear cells of patients with inter-critical gout when compared to normouricemic and hyperuricemic controls and those patients with acute gout flares. However, the role of miR-146a in the development of gout remains unknown. Here, we used miR-146a knockout (KO) mice to test miR-146a function in a monosodium urate (MSU)-induced gouty arthritis model.

METHODS

The footpad or ankle joint of miR-146a KO and wild-type (WT) mice were injected with an MSU suspension to induce acute gouty arthritis. Bone marrow-derived macrophages (BMDMs) were stimulated with MSU and the gene expression of miR-146a; interleukin 1 beta (IL-1β); tumor necrosis factor-α (TNF-α); and the NACHT, LRR and PYD domains-containing protein 3 (NALP3) inflammasome was evaluated. TNF-α and IL-1β protein levels in BMDMs were assessed by fluorescence-activated cell sorting and western blot analyses. Gene and protein levels of TNF receptor-associated factor 6 (TRAF6) and IL-1 receptor-associated kinase (IRAK1), the targets of miR-146a, were also measured.

RESULTS

Significantly increased paw swelling and index and ankle joint swelling were observed in miR-146a KO mice compared to WT controls after MSU treatment. MiR-146a expression in BMDMs from WT mice was dramatically upregulated at 4 h following MSU stimulation. Additionally, the expression of IL-1β, TNF-α, and NALP3 was higher in BMDMs from miR-146a KO mice after exposure to MSU crystals compared to those from WT mice. Consistent with the observed gene expression, the IL-1β and TNF-α proteins were upregulated in miR-146a KO mice. Additionally quantitative RT-PCR and western blot demonstrated that TRAF6 and IRAK1 were dramatically upregulated in BMDMs from miR-146 KO mice compared to those from WT mice.

CONCLUSIONS

Collectively, these observations suggest that miR-146a provides negative feedback regulation of gouty arthritis development and lack of miR-146a enhances gouty arthritis via upregulation of TRAK6, IRAK-1, and the NALP3 inflammasome function.