MicroRNAs: new regulators of Toll-like receptor signalling pathways

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.

Cas9-mediated excision of proximal DNaseI/H3K4me3 signatures confers robust silencing of microRNA and long non-coding RNA genes

CRISPR/Cas9-based approaches have greatly facilitated targeted genomic deletions. Contrary to coding genes however, which can be functionally knocked out by frame-shift mutagenesis, non-coding RNA (ncRNA) gene knockouts have remained challenging. Here we present a universal ncRNA knockout approach guided by epigenetic hallmarks, which enables robust gene silencing even in provisionally annotated gene loci. We build on previous work reporting the presence of overlapping histone H3 lysine 4 tri-methylation (H3K4me3) and DNaseI hypersensitivity sites around the transcriptional start sites of most genes. We demonstrate that excision of this gene-proximal signature leads to loss of microRNA and lincRNA transcription and reveals ncRNA phenotypes. Exemplarily we demonstrate silencing of the constitutively transcribed MALAT1 lincRNA gene as well as of the inducible miR-146a and miR-155 genes in human monocytes. Our results validate a role of miR-146a and miR-155 in negative feedback control of the activity of inflammation master-regulator NFκB and suggest that cell-cycle control is a unique feature of miR-155. We suggest that our epigenetically guided CRISPR approach may improve existing ncRNA knockout strategies and contribute to the development of high-confidence ncRNA phenotyping applications.

The Role of MicroRNAs in Myeloid Cells during Graft-versus-Host Disease

The successful treatment of various hematologic diseases with allogeneic hematopoietic cell transplantation is often limited by the occurrence of graft-versus-host disease (GvHD). Several microRNAs (miRs) have recently been shown to impact the biology of GvHD by regulating pro- as well as anti-inflammatory target genes. There is increasing evidence that a single miR can have different effects by preferentially targeting certain genes depending on the cell type that the miR is analyzed in. This review will focus on the role of miRs in myeloid cells during the development of acute and chronic GvHD and autoimmune diseases. Because miRs act on the expression of multiple target genes and may thereby influence the immune system at different functional levels, they are potentially attractive targets for the modification of allogeneic immune responses using miR mimics and inhibitors.

Visfatin Promotes IL-6 and TNF-α Production in Human Synovial Fibroblasts by Repressing miR-199a-5p through ERK, p38 and JNK Signaling Pathways

Osteoarthritis (OA), an inflammatory form of arthritis, is characterized by synovial inflammation and cartilage destruction largely influenced by two key proinflammatory cytokines-interleukin-6 (IL-6) and tumor necrosis factor α (TNF-α). Notably, levels of visfatin (a proinflammatory adipokine) are elevated in patients with OA, although the relationship of visfatin to IL-6 and TNF-α expression in OA pathogenesis has been unclear. In this study, visfatin enhanced the expression of IL-6 and TNF-α in human OA synovial fibroblasts (OASFs) in a concentration-dependent manner and stimulation of OASFs with visfatin promoted phosphorylation of extracellular-signal-regulated kinase (ERK), p38, and c-Jun N-terminal kinase (JNK), while ERK, p38, and JNK inhibitors or siRNAs all abolished visfatin-induced increases in IL-6 and TNF-α production. Moreover, transfection with miR-199a-5p mimics reversed visfatin-induced increases in IL-6 and TNF-α production. Furthermore, we also found that visfatin-promoted IL-6 and TNF-α production is mediated via the inhibition of miR-199a-5p expression through the ERK, p38, and JNK signaling pathways. Visfatin may therefore be an appropriate target for drug intervention in OA treatment.

Toll-like receptor 2 activation implicated in oral squamous cell carcinoma development

Recent studies have revealed that Toll-like receptors (TLRs) are highly expressed and activated in many types of cancer. Physiologically, TLR2 recognizes bacteria and other microorganisms in the oral cavity; however, the role of TLR2 in oral squamous cell carcinoma (OSCC) is unclear. In this study, we demonstrated that TLR2 is highly expressed in OSCC in comparison with adjacent non-malignant tissue. TLR2 was also expressed in OSCC-derived cell lines, and its expression was activated by ligands derived from bacteria and mycoplasma. Furthermore, to elucidate the mechanism of OSCC progression via TLR2 signal transduction, we focused on microRNAs (miRNAs) that are induced by TLR2 activation. Interestingly, ligand activation of TLR2 induced the expression of miR-146a and we found that downregulation of caspase recruitment domain-containing protein 10 (CARD10) mRNA in OSCC-derived cell lines. Moreover, knockdown of CARD10 induced resistance to cisplatin-induced apoptosis in OSCC cells. These findings suggest that the activation of TLR2 by bacterial components can enhance the progression of OSCC and may be implicated in acquired resistance to cisplatin-induced apoptosis through regulation of the miR-146a pathway.

Prostate-specific PTen deletion in mice activates inflammatory microRNA expression pathways in the epithelium early in hyperplasia development

PTen loss is one of the most frequent events in prostate cancer both at the initiation stage and during late stage metastatic development. The mouse model of prostate-specific probasin-mediated Pten deletion leads to prostate intraepithelial neoplasia (PIN) leading to adenocarcinoma. Using this model, we analysed the miR and mRNA transcriptome profile of Pten^−/− PIN versus wild type age-matched prostate tissues and analysed the effects of Pten loss on miR expression in the early neoplastic process. At the PIN stage, Pten loss significantly changed the expression of over 20 miRNAs and over 4000 genes. The observed miR expression indicated a strong immunological cohort, which is seen in many human and mouse cancers and is thought to derive from infiltrating B and T immune cells. However, upon in situ hybridisation, these immunologically related miRs did not correlate with immune cell location, and emanated from the prostate epithelium itself and not from the associated immune cells present. Growing Pten^−/− prostate cells in culture showed that the overexpressed miRNAs seen in Pten^−/− were directly in response to the overactive PI3 kinase pathway and were in part responsible in reducing target gene expression levels. Inhibition of PI3 kinase downstream regulators, or re-introducing wild type Pten^cDNA reduced miR overexpression resulting in increased miR target gene expression. MiR inhibitors also showed this pattern, and synergised with an mTORC1 inhibitor. Overall, Pten deletion in the prostate epithelium activated a cohort of inflammation-related miRs usually associated with immune responses from B and T cells. These oncomiRs may then accelerate carcinogenesis.

Hyaluronic acid 35 normalizes TLR4 signaling in Kupffer cells from ethanol-fed rats via regulation of microRNA291b and its target Tollip

TLR4 signaling in hepatic macrophages is increased after chronic ethanol feeding. Treatment of hepatic macrophages after chronic ethanol feeding with small-specific sized hyaluronic acid 35 (HA35) normalizes TLR4 signaling; however, the mechanisms for HA35 action are not completely understood. Here we used Next Generation Sequencing of microRNAs to identify negative regulators of TLR4 signaling reciprocally modulated by ethanol and HA35 in hepatic macrophages. Eleven microRNAs were up-regulated by ethanol; only 4 microRNAs, including miR291b, were decreased by HA35. Bioinformatics analysis identified Tollip, a negative regulator of TLR4, as a target of miR291b. Tollip expression was decreased in hepatic macrophages from ethanol-fed rats, but treatment with HA35 or transfection with a miR291b hairpin inhibitor restored Tollip expression and normalized TLR4-stimulated TNFα expression. In peripheral blood monocytes isolated from patients with alcoholic hepatitis, expression of TNFα mRNA was robustly increased in response to challenge with lipopolysaccharide. Importantly, pre-treatment with HA35 reduced TNFα expression by more than 50%. Taken together, we have identified miR291b as a critical miRNA up-regulated by ethanol. Normalization of the miR291b → Tollip pathway by HA35 ameliorated ethanol-induced sensitization of TLR4 signaling in macrophages/monocytes, suggesting that HA35 may be a novel therapeutic agent in the treatment of ALD.

D-4F increases microRNA-124a and reduces neuroinflammation in diabetic stroke rats

D-4F is an apolipoprotein-A1 mimetic peptide that promotes anti-inflammatory effects. MicroRNA-124 is the most abundant brain-specific microRNA and has anti-inflammatory effects. In this study, we investigated the therapeutic efficacy and mechanisms of D-4F treatment of stroke in type one diabetes mellitus (T1DM) rats. Male Wistar rats were induced with T1DM, subjected to embolic middle cerebral artery occlusion and treated with PBS or D-4F (1 mg/kg i.p.) at 2, 24 and 48 hours after stroke (n=8/group). A battery of function tests, brain blood barrier (BBB) integrity, white matter changes and microRNA expression were evaluated in vivo and in vitro. D-4F treatment in T1DM-stroke rats significantly improves functional outcome, decreases BBB leakage, increases tight junction protein expression, decreases white matter damage and inflammatory factor expression, while increasing anti-inflammatory M2 macrophage polarization in the ischemic brain. D-4F significantly increases microRNA-124a expression, and decreases matrix metalloproteinase-9, tumor necrosis factor-α and toll-like receptor-4 gene expression in the ischemic brain, and in primary cortical neuronal and microglial cultures. Inhibition of microRNA-124 in cultured primary cortical neurons and microglia attenuates D-4F induced anti-inflammatory effects and M2 macrophage polarization. D-4F treatment of T1DM-stroke increases microRNA-124 expression, promotes anti-inflammatory effects and M2 macrophage polarization, which may contribute to D-4F-induced improvement in neurological function, and BBB and white matter integrity.

MicroRNA in gastrointestinal cell signalling

Our gut forms an important organ and its formation, functioning and homeostasis are maintained by several factors including cell signalling pathways and commensal microflora. These factors affect pathological, physiological and immunological parameters to maintain gut health and prevent its inflammation. Among these, different intracellular signalling pathways play an important role in regulating gut homeostasis. These pathways are in turn regulated by various microRNAs that play a key role in maintaining the balance between tolerance and inflammation. This review highlights the importance of various cell signalling pathways in modulating gut homeostasis and the role specific miRNAs play in their regulation.

Circulating MicroRNAs As Potential Biomarkers for Veterinary Infectious Diseases

MicroRNAs (miRNAs) are a kind of small non-coding RNA molecules that could regulate multiple biological pathways at posttranscriptional level. Over 2,000 miRNAs have so far been discovered in humans, and many of them are found to be linked to various kinds of diseases. Thus, miRNAs are being considered as clinical diagnostic and therapeutic targets. With the discovery of high stability of circulating miRNAs in various kinds of mammalian body fluids, the potential of circulating miRNAs as diagnostic/prognostic biomarkers of infectious diseases aroused great interest among researchers. As far as human diseases are concerned, some biomarkers based on circulating miRNAs have been progressed to clinical application. In veterinary fields, however, this concept is only beginning to come into view. In this review, we summarize an update of preclinical studies on using circulating miRNAs as diagnostic biomarkers to combat infectious diseases that affect domestic animals.

Integrated analysis of mRNA and viral miRNAs in the kidney of Carassius auratus gibelio response to cyprinid herpesvirus 2

MicroRNAs (miRNAs) are small, non-coding single stranded RNAs that play crucial roles in numerous biological processes. Vertebrate herpesviruses encode multiple viral miRNAs that modulate host and viral genes. However, the roles of viral miRNAs in lower vertebrates have not been fully determined. Here, we used high-throughput sequencing to analyse the miRNA and mRNA expression profiles of Carassius auratus gibelio in response to infection by cyprinid herpesvirus 2 (CyHV-2). RNA sequencing obtained 26,664 assembled transcripts, including 2,912 differentially expressed genes. Based on small RNA sequencing and secondary structure predictions, we identified 17 CyHV-2 encoded miRNAs, among which 14 were validated by stem-loop quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) and eight were validated by northern blotting. Furthermore, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of miRNAs-mRNA pairs revealed diverse affected immune signalling pathways, including the RIG-I-like receptor and JAK-STAT pathways. Finally, we presented four genes involved in RIG-I-like pathways, including host gene IRF3, RBMX, PIN1, viral gene ORF4, which are negatively regulated by CyHV-2 encoded miRNA miR-C4. The present study is the first to provide a comprehensive overview of viral miRNA-mRNA co-regulation, which might have a key role in controlling post-transcriptomic regulation during CyHV-2 infection.

Let's make microglia great again in neurodegenerative disorders

All of the common neurodegenerative disorders-Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and prion diseases-are characterized by accumulation of misfolded proteins that trigger activation of microglia; brain-resident mononuclear phagocytes. This chronic form of neuroinflammation is earmarked by increased release of myriad cytokines and chemokines in patient brains and biofluids. Microglial phagocytosis is compromised early in the disease process, obfuscating clearance of abnormal proteins. This review identifies immune pathologies shared by the major neurodegenerative disorders. The overarching concept is that aberrant innate immune pathways can be targeted for return to homeostasis in hopes of coaxing microglia into clearing neurotoxic misfolded proteins.

Toll-Like Receptor Function in Acute Wounds

Significance: Inflammation is an integral part of immune response and supports optimal wound healing in adults. Inflammatory cells such as neutrophils, macrophages, dendritic cells, lymphocytes, and mast cells produce important cytokines, chemokines, and growth factors. These immune cells interact with keratinocytes, fibroblasts, and endothelial cells (ECs), as well as the extracellular matrix within a complicated network that promotes and regulates wound healing. Aberrant and persistent inflammation may result in delayed wound healing, scar formation, or chronic wounds. Targeting the molecules involved in the inflammatory response may have great potential therapeutic value. Recent Advances and Critical Issues: Toll-like receptors (TLRs) are pattern recognition receptors that recognize pathogen-associated molecular patterns from microbes or danger-associated molecular patterns from damaged cells. The discovery of TLRs sheds new light on the mechanism by which the inflammatory or innate immune response is initiated in wound healing. Convincing evidence now shows that multiple types of cells, including infiltrating or resident inflammatory cells, keratinocytes, fibroblasts, and ECs, express specific types of TLRs. Experimental reduction of certain TLRs or treatment of wounds with TLR ligands has been shown to affect wound healing. A better understanding of the involvement of TLRs in the innate immune response during skin wound healing may suggest novel strategies to improve the quality of tissue repair. Future Directions: Despite the indisputable role of TLRs in regulating the immune response in acute wound healing, the functions of TLRs that are relevant to human wound healing and chronic wounds are poorly understood.

Toll-Like Receptor-4 Signaling Drives Persistent Fibroblast Activation and Prevents Fibrosis Resolution in Scleroderma

Significance: This review provides current overview of the emerging role of innate immunity in driving fibrosis, and preventing its resolution, in scleroderma (systemic sclerosis, SSc). Understanding the mechanisms of dysregulated innate immunity in fibrosis and SSc will provide opportunities for therapeutic interventions using novel agents and repurposed existing drugs. Recent Advances: New insights from genomic and genetic studies implicate components of innate immune signaling such as pattern recognition receptors (PRRs), downstream signaling intermediates, and endogenous inhibitors, in fibrosis in SSc. Recent studies distinguish innate immune signaling in tissue-resident myofibroblasts and bone marrow-derived immune cells and define their roles in the development and persistence of tissue fibrosis. Critical Issues: Activation of toll-like receptors (TLRs) and other PRR mechanisms occurs in resident nonimmune cells within injured tissue microenvironments. These cells respond to damage-associated molecular patterns (DAMPs), such as tenascin-C that are recognized as danger signals, and elicit matrix production, cytokine secretion, and myofibroblast transformation and survival. When these responses persist due to constitutive TLR activation or impaired termination by endogenous inhibitors, they interfere with fibrosis resolution. The genetic basis and molecular mechanisms of these phenomena in the context of fibrosis are under current investigation. Future Directions: Precise delineation of the pathogenic DAMPs, their interaction with TLRs and other PRRs, the downstream signaling pathways and transcriptional events, and the fibroblast-specific regulation and function of endogenous inhibitors of innate immunity, will form the foundation for innovative targeted therapies to block fibrosis by reestablishing balanced innate immune signaling in fibroblasts.

Neuroinflammatory targets and treatments for epilepsy validated in experimental models

A large body of evidence that has accumulated over the past decade strongly supports the role of inflammation in the pathophysiology of human epilepsy. Specific inflammatory molecules and pathways have been identified that influence various pathologic outcomes in different experimental models of epilepsy. Most importantly, the same inflammatory pathways have also been found in surgically resected brain tissue from patients with treatment-resistant epilepsy. New antiseizure therapies may be derived from these novel potential targets. An essential and crucial question is whether targeting these molecules and pathways may result in anti-ictogenesis, antiepileptogenesis, and/or disease-modification effects. Therefore, preclinical testing in models mimicking relevant aspects of epileptogenesis is needed to guide integrated experimental and clinical trial designs. We discuss the most recent preclinical proof-of-concept studies validating a number of therapeutic approaches against inflammatory mechanisms in animal models that could represent novel avenues for drug development in epilepsy. Finally, we suggest future directions to accelerate preclinical to clinical translation of these recent discoveries.

Association of MiR-146a Expression and Type 2 Diabetes Mellitus: A Meta-Analysis

Although deregulation of miR-146a has been reported in type 2 diabetes repeatedly, the direction of deregulation events (up or down) remained to be inconsistent in literatures. Therefore, in this study we performed a meta-analysis on the possible association between miR-146a expression levels and type 2 diabetes. A systematic literature searching of PubMed, ISI Web of Science and Google Scholar was performed up to the end of September 2016. Finally, a total of 12 studies including 344 diabetic patients and 316 controls were selected for meta-analysis. All statistical analysis was performed using the metafor package with R software. Moreover, publication bias was assessed by Egger’s and sensitivity analysis was applied on the meta-analysis. The results are presented as log10 odds ratios (logORs), 95% confidence intervals (CI) with relevant P values. The results revealed that miR-146a was downregulated in type 2 diabetes cases compared with normal subjects (P=0.01, logOR:-4.76, 95% CI:-8.41, -1.11). Furthermore, sub-group analysis showed that the association between miR-146a expression levels and type 2 diabetes in whole blood (P<0.001) and PBMCs (P<0.001) samples were significant. However, this association was not significant in the serum (P=0.67) and plasma (P=0.90) samples. Our finding suggests that miR-146a downregulation could be associated with type 2 diabetes susceptibility. Further investigations with larger sample size are required to evaluate this association in the type 2 diabetes pathogenesis.

MicroRNA 181b-3p and its target importin α5 regulate toll-like receptor 4 signaling in Kupffer cells and liver injury in mice in response to ethanol

Increased inflammatory signaling by Kupffer cells contributes to alcoholic liver disease (ALD). Here we investigated the impact of small, specific-sized hyaluronic acid of 35 kD (HA35) on ethanol-induced sensitization of Kupffer cells, as well as ethanol-induced liver injury in mice. Unbiased analysis of microRNA (miRNA) expression in Kupffer cells identified miRNAs regulated by both ethanol and HA35. Toll-like receptor 4 (TLR4)-mediated signaling was assessed in primary cultures of Kupffer cells from ethanol- and pair-fed rats after treatment with HA35. Female C57BL6/J mice were fed ethanol or pair-fed control diets and treated or not with HA35. TLR4 signaling was increased in Kupffer cells by ethanol; this sensitization was normalized by ex vivo treatment with HA35. Next generation sequencing of Kupffer cell miRNA identified miRNA 181b-3p (miR181b-3p) as sensitive to both ethanol and HA35. Importin α5, a protein involved in p65 translocation to the nucleus, was identified as a target of miR181b-3p; importin α5 protein was increased in Kupffer cells from ethanol-fed rats, but decreased by HA35 treatment. Overexpression of miR181b-3p decreased importin α5 expression and normalized lipopolysaccharide-stimulated tumor necrosis factor α expression in Kupffer cells from ethanol-fed rats. In a mouse model of ALD, ethanol feeding decreased miR181b-3p in liver and increased expression of importin α5 in nonparenchymal cells. Treatment with HA35 normalized these changes and also protected mice from ethanol-induced liver and intestinal injury.

CONCLUSION

miR181b-3p is dynamically regulated in Kupffer cells and mouse liver in response to ethanol and treatment with HA35. miR181b-3p modulates expression of importin α5 and sensitivity of TLR4-mediated signaling. This study identifies a miR181b-3p-importin α5 axis in regulating inflammatory signaling pathways in hepatic macrophages. (Hepatology 2017;66:602-615).

Inhibition of Toll-Like Receptor Signaling as a Promising Therapy for Inflammatory Diseases: A Journey from Molecular to Nano Therapeutics

The recognition of invading pathogens and endogenous molecules from damaged tissues by toll-like receptors (TLRs) triggers protective self-defense mechanisms. However, excessive TLR activation disrupts the immune homeostasis by sustained pro-inflammatory cytokines and chemokines production and consequently contributes to the development of many inflammatory and autoimmune diseases, such as systemic lupus erythematosus (SLE), infection-associated sepsis, atherosclerosis, and asthma. Therefore, inhibitors/antagonists targeting TLR signals may be beneficial to treat these disorders. In this article, we first briefly summarize the pathophysiological role of TLRs in the inflammatory diseases. We then focus on reviewing the current knowledge in both preclinical and clinical studies of various TLR antagonists/inhibitors for the prevention and treatment of inflammatory diseases. These compounds range from conventional small molecules to therapeutic biologics and nanodevices. In particular, nanodevices are emerging as a new class of potent TLR inhibitors for their unique properties in desired bio-distribution, sustained circulation, and preferred pharmacodynamic and pharmacokinetic profiles. More interestingly, the inhibitory activity of these nanodevices can be regulated through precise nano-functionalization, making them the next generation therapeutics or “nano-drugs.” Although, significant efforts have been made in developing different kinds of new TLR inhibitors/antagonists, only limited numbers of them have undergone clinical trials, and none have been approved for clinical uses to date. Nevertheless, these findings and continuous studies of TLR inhibition highlight the pharmacological regulation of TLR signaling, especially on multiple TLR pathways, as future promising therapeutic strategy for various inflammatory and autoimmune diseases.

Potential Roles of Exosomal MicroRNAs as Diagnostic Biomarkers and Therapeutic Application in Alzheimer's Disease

Exosomes are bilipid layer-enclosed vesicles derived from endosomes and are released from neural cells. They contain a diversity of proteins, mRNAs, and microRNAs (miRNAs) that are delivered to neighboring cells and/or are transported to distant sites. miRNAs released from exosomes appear to be associated with multiple neurodegenerative conditions linking to Alzheimer's disease (AD) which is marked by hyperphosphorylated tau proteins and accumulation of Aβ plaques. Exciting findings reveal that miRNAs released from exosomes modulate the expression and function of amyloid precursor proteins (APP) and tau proteins. These open up the possibility that dysfunctional exosomal miRNAs may influence AD progression. In addition, it has been confirmed that the interaction between miRNAs released by exosomes and Toll-like receptors (TLR) initiates inflammation. In exosome support-deprived neurons, exosomal miRNAs may regulate neuroplasticity to relieve neurological damage. In this review, we summarize the literature on the function of exosomal miRNAs in AD pathology, the potential of these miRNAs as diagnostic biomarkers in AD, and the use of exosomes in the delivery of miRNAs which may lead to major advances in the field of macromolecular drug delivery.

MicroRNA-148 as a negative regulator of the common TLR adaptor mediates inflammatory response in teleost fish

MicroRNAs are small endogenous noncoding RNAs implicating in the regulation of diverse biological processes, including proliferation, differentiation, cancer, apoptosis, and viral infections. MicroRNAs regulate gene expression by either mRNA degradation or inhibition of protein translation. Although microRNAs have emerged as important controller involved in regulation of inflammatory response, the microRNA-mediated regulatory mechanism remains less clear in teleost. Here, we report that miR-148 targets MyD88 and down-regulates its expression by inhibition protein translation rather than degradation mRNA in miiuy croaker. Additionally, we found that miR-148 was significantly upregulated in miiuy croaker after treated with Vibro harveyi, as well as LPS. Overexpression of miR-148 inhibited LPS-induced inflammatory cytokines production, such as IL-6 and IL-1β, which then avoid excessive inflammation response. miR-148 has also been identified to suppress NF-κB pathway through targeting and repressing MyD88 expression. Taken together, our findings indicate that miR-148 participates in bacteria-induced inflammatory response and act as a negative regulator for MyD88-mediated NF-κB signaling, which may clarify the mechanism of microRNAs for avoiding excessive inflammation in teleost fish.

MicroRNAs associated with inflammation in shoulder tendinopathy and glenohumeral arthritis

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

Downregulated Glia Interplay and Increased miRNA-155 as Promising Markers to Track ALS at an Early Stage

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease of unknown cause. Absence of specific targets and biomarkers compromise the development of new therapeutic strategies and of innovative tools to stratify patients and assess their responses to treatment. Here, we investigate changes in neuroprotective-neuroinflammatory actions in the spinal cord of SOD1 ^G93A mice, at presymptomatic and symptomatic stages to identify stage-specific biomarkers and potential targets. Results showed that in the presymptomatic stage, there are alterations in both astrocytes and microglia, which comprise decreased expression of GFAP and S100B and upregulation of GLT-1, as well as reduced expression of CD11b, M2-phenotype markers, and a set of inflammatory mediators. Reduced levels of Connexin-43, Pannexin-1, CCL21, and CX3CL1 further indicate the existence of a compromised intercellular communication. In contrast, in the symptomatic stage, increased markers of inflammation became evident, such as NF-κB/Nlrp3-inflammasome, Iba1, pro-inflammatory cytokines, and M1-polarizion markers, together with a decreased expression of M2-phenotypic markers. We also observed upregulation of the CX3CL1-CX3CR1 axis, Connexin-43, Pannexin-1, and of microRNAs (miR)-124, miR-125b, miR-146a and miR-21. Reduced motor neuron number and presence of reactive astrocytes with decreased GFAP, GLT-1, and GLAST further characterized this inflammatory stage. Interestingly, upregulation of miR-155 and downregulation of MFG-E8 appear as consistent biomarkers of both presymptomatic and symptomatic stages. We hypothesize that downregulated cellular interplay at the early stages may represent neuroprotective mechanisms against inflammation, SOD1 aggregation, and ALS onset. The present study identified a set of inflamma-miRNAs, NLRP3-inflammasome, HMGB1, CX3CL1-CX3CR1, Connexin-43, and Pannexin-1 as emerging candidates and promising pharmacological targets that may represent potential neuroprotective strategies in ALS therapy.

Altered MicroRNA Expression Is Responsible for the Pro-Osteogenic Phenotype of Interstitial Cells in Calcified Human Aortic Valves

BACKGROUND

The transition of aortic valve interstitial cells (AVICs) to myofibroblastic and osteoblast-like phenotypes plays a critical role in calcific aortic valve disease progression. Several microRNAs (miRs) are implicated in stem cell differentiation into osteoblast. We hypothesized that an epigenetic mechanism regulates valvular pro-osteogenic activity. This study examined miR profile in AVICs of calcified valves and identified miRs responsible for AVIC phenotypic transition.

METHODS AND RESULTS

AVICs were isolated from normal and diseased valves. The miR microarray analysis revealed 14 upregulated and 12 downregulated miRs in diseased AVICs. Increased miR-486 and decreased miR-204 levels were associated with higher levels of myofibroblastic biomarker α-smooth muscle actin and osteoblastic biomarkers runt-related transcription factor 2 (Runx2) and osterix (Osx). Cotransfection of miR-486 antagomir and miR-204 mimic in diseased AVICs reduced their ability to express Runx2 and Osx. The miR-486 mimic upregulated α-smooth muscle actin expression in normal AVICs through the protein kinase B pathway and moderately elevated Runx2 and Osx levels. Knockdown of α-smooth muscle actin attenuated Runx2 and Osx expression induced by miR-486. The miR-486 mimic and miR-204 antagomir synergistically promoted Runx2 and Osx expression and calcium deposition in normal AVICs and normal aortic valve tissue.

CONCLUSIONS

In AVICs of calcified valves, increased levels of miR-486 induce myofibroblastic transition to upregulate Runx2 and Osx expression and synergize with miR-204 deficiency to elevate cellular and valvular pro-osteogenic activity. These novel findings indicate that modulation of the epigenetic mechanism underlying valvular pro-osteogenic activity has therapeutic potential for prevention of calcific aortic valve disease progression.

Effect of age on pro-inflammatory miRNAs contained in mesenchymal stem cell-derived extracellular vesicles

Stem cells possess significant age-dependent differences in their immune-response profile. These differences were analysed by Next-Generation Sequencing of six age groups from bone marrow mesenchymal stem cells. A total of 9,628 genes presenting differential expression between age groups were grouped into metabolic pathways. We focused our research on young, pre-pubertal and adult groups, which presented the highest amount of differentially expressed genes related to inflammation mediated by chemokine and cytokine signalling pathways compared with the newborn group, which was used as a control. Extracellular vesicles extracted from each group were characterized by nanoparticle tracking and flow cytometry analysis, and several micro-RNAs were verified by quantitative real-time polymerase chain reaction because of their relationship with the pathway of interest. Since miR-21-5p showed the highest statistically significant expression in extracellular vesicles from mesenchymal stem cells of the pre-pubertal group, we conducted a functional experiment inhibiting its expression and investigating the modulation of Toll-Like Receptor 4 and their link to damage-associated molecular patterns. Together, these results indicate for the first time that mesenchymal stem cell-derived extracellular vesicles have significant age-dependent differences in their immune profiles.

MicroRNA-3570 Modulates the NF-κB Pathway in Teleost Fish by Targeting MyD88

The inflammatory response, a protective process to clear detrimental stimuli, constitutes the defense against infectious pathogens. However, excessive inflammation disrupts immune homeostasis, which may induce autoimmune and inflammatory diseases. In this study, we report that microRNA (miR)-3570 plays a negative role in the bacteria-induced inflammatory response of miiuy croaker. Upregulation of miR-3570 by Vibrio anguillarum and LPS inhibits LPS-induced inflammatory cytokine production, thus avoiding an excessive inflammation response. Evidence showed that miR-3570 targets MyD88 and posttranscriptionally downregulates its expression. Overexpression of miR-3570 in macrophages suppresses the expression of MyD88, as well as its downstream signaling of IL-1R-associated kinases 1 and 4 and TNFR-associated factor 6. These results suggest that miR-3570 plays a regulatory in the bacteria-induced inflammatory response through the MyD88-mediated NF-κB signaling pathway by targeting MyD88.

Inducible microRNA-214 contributes to the suppression of NF-κB-mediated inflammatory response via targeting myd88 gene in fish

Upon recognition of bacterial pathogens by pattern recognition receptors, cells are activated to produce pro-inflammatory cytokines and type I IFN by multiple signaling pathways. Every step of the process must be precisely regulated to prevent dysregulation. MicroRNAs (miRNAs) have been shown to be important regulators with profound effects on inflammatory response. Nevertheless, the miRNA-mediated regulatory mechanism remains unclear in fish species. Here, we addressed the role of miiuy croaker miR-214 in the bacteria triggered inflammatory response. miR-214 could significantly be up-regulated by Vibro harveyi and LPS stimulation. Up-regulating miR-214 subsequently inhibits the production of inflammatory cytokines by targeting myd88 to avoid excessive inflammation. Moreover, the negative regulatory mechanism of miR-214 has been demonstrated to be via the myd88-mediated NF-κB pathway. This is the first to focus on miR-214 acting as the negative regulator involved in the bacteria-triggered inflammatory response and thus may provide knowledge on the host-cell regulator responses to microbial infection.

Circulating microRNAs as Potential Biomarkers of Infectious Disease

microRNAs (miRNAs) are a class of small non-coding endogenous RNA molecules that regulate a wide range of biological processes by post-transcriptionally regulating gene expression. Thousands of these molecules have been discovered to date, and multiple miRNAs have been shown to coordinately fine-tune cellular processes key to organismal development, homeostasis, neurobiology, immunobiology, and control of infection. The fundamental regulatory role of miRNAs in a variety of biological processes suggests that differential expression of these transcripts may be exploited as a novel source of molecular biomarkers for many different disease pathologies or abnormalities. This has been emphasized by the recent discovery of remarkably stable miRNAs in mammalian biofluids, which may originate from intracellular processes elsewhere in the body. The potential of circulating miRNAs as biomarkers of disease has mainly been demonstrated for various types of cancer. More recently, however, attention has focused on the use of circulating miRNAs as diagnostic/prognostic biomarkers of infectious disease; for example, human tuberculosis caused by infection with Mycobacterium tuberculosis, sepsis caused by multiple infectious agents, and viral hepatitis. Here, we review these developments and discuss prospects and challenges for translating circulating miRNA into novel diagnostics for infectious disease.

Impact of Polyunsaturated Fatty Acids on miRNA Profiles of Monocytes/Macrophages and Endothelial Cells-A Pilot Study

Alteration of miRNAs and dietary polyunsaturated fatty acids (PUFAs) underlies vascular inflammation. PUFAs are known to be incorporated into the cell membrane of monocytes/macrophages or endothelial cells, the major cellular players of vascular diseases, thereby affecting cellular signal transduction. Nevertheless, there are no investigations concerning the PUFA impact on miRNA expression by these cells. With regard to the key role miRNAs play for overall cellular functionality, this study aims to elucidate whether PUFAs affect miRNA expression profiles. To this end, the monocyte/macrophage cell line RAW264.7 and the endothelial cell line TIME were enriched with either docosahexaenoic acid (DHA; n3-PUFA) or arachidonic acid (AA; n6-PUFA) until reaching a stable incorporation into the plasma membrane and, at least in part, exposed to an inflammatory milieu. Expressed miRNAs were determined by deep sequencing, and compared to unsupplemented/unstimulated controls. Data gained clearly show that PUFAs in fact modulate miRNA expression of both cell types analyzed regardless the presence/absence of an inflammatory stimulator. Moreover, certain miRNAs already linked to vascular inflammation were found to be affected by cellular PUFA enrichment. Hence, vascular inflammation appears to be influenced by dietary fatty acids, inter alia, via PUFA-mediated modulation of the type and amount of miRNAs synthesized by cells involved in the inflammatory process.

Exploring New Inflammatory Biomarkers and Pathways during LPS-Induced M1 Polarization

Identification of mediators triggering microglia activation and transference of noncoding microRNA (miRNA) into exosomes are critical to dissect the mechanisms underlying neurodegeneration. We used lipopolysaccharide- (LPS-) induced N9 microglia activation to explore new biomarkers/signaling pathways and to identify inflammatory miRNA (inflamma-miR) in cells and their derived exosomes. Upregulation of iNOS and MHC-II (M1-markers) and downregulation of arginase 1, FIZZ1 (M2-markers), and CX3CR1 (M0/M2 polarization) confirmed the switch of N9 LPS-treated cells into the M1 phenotype, as described for macrophages/microglia. Cells showed increased proliferation, activated TLR4/TLR2/NF-κB pathway, and enhanced phagocytosis, further corroborated by upregulated MFG-E8. We found NLRP3-inflammasome activation in these cells, probably accounting for the increased extracellular content of the cytokine HMGB1 and of the MMP-9 we have observed. We demonstrate for the first time that the inflamma-miR profiling (upregulated miR-155 and miR-146a plus downregulated miR-124) in M1 polarized N9 cells, noticed by others in activated macrophages/microglia, was replicated in their derived exosomes, likely regulating the inflammatory response of recipient cells and dissemination processes. Data show that LPS-treated N9 cells behave like M1 polarized microglia/macrophages, while providing new targets for drug discovery. In particular, the study yields novel insights into the exosomal circulating miRNA during neuroinflammation important for emerging therapeutic approaches targeting microglia activation.

Significant role for microRNA-21 affecting toll-like receptor pathway in primary graft dysfunction after human lung transplantation

BACKGROUND

MicroRNAs (miRNAs) were recently identified as modulators of immune responses after human lung transplantation (LTx). This study was undertaken to assess the contribution of miRNAs to the pathogenesis of primary graft dysfunction (PGD) after LTx.

METHODS

Of the 39 recipients, 14 (35.9%) developed Grade 3 PGD (i.e., severe PGD) within the first 72 hours of LTx. The remaining 25 recipients (64.1%) had Grade 2 or less PGD, and served as the control group. miRNAs were isolated from cells purified by bronchoalveolar lavage (BAL). Bioinformatic prediction and validation by luciferase reporter assays were performed to identify targets regulated by miR-21. Transfection of human monocytic cell line (THP-1) was conducted to determine miR-21's cellular function.

RESULTS

Pilot miRNA profiling of donor BAL samples before implantation in PGD (n = 6) revealed significant upregulation in 44 miRNAs and downregulation in 80 miRNAs compared with control (n = 6). Validation using a separate cohort demonstrated significant underexpression of miR-21 in patients with severe PGD. Furthermore, underexpression of miR-21 levels was negatively correlated with clinical PGD grades (Grade 2 PGD vs Grade 0 PGD: p = 0.042; Grade 3 PGD vs Grade 0 PGD: p = 0.004). Molecular analysis demonstrated that miR-21 targeted key components in the toll-like receptor (TLR) signaling pathway, including TLR4, IRAK3 and CXCL10. Further, incubation of THP-1 cells with cell-free BAL from severe PGD resulted in transactivation of inflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). In contrast, increased expression of miR-21 resulted in marked suppression of IL-1-β and TNF-α production.

CONCLUSIONS

Underexpression of miR-21 may lead to the development of severe PGD by activating key components of the TLR pathway.

Interleukin-8, CXCL1, and MicroRNA miR-146a Responses to Probiotic Escherichia coli Nissle 1917 and Enteropathogenic E. coli in Human Intestinal Epithelial T84 and Monocytic THP-1 Cells after Apical or Basolateral Infection

Bacterium-host interactions in the gut proceed via directly contacted epithelial cells, the host's immune system, and a plethora of bacterial factors. Here we characterized and compared exemplary cytokine and microRNA (miRNA) responses of human epithelial and THP-1 cells toward the prototype enteropathogenic Escherichia coli (EPEC) strain E2348/69 (O127:H6) and the probiotic strain Escherichia coli Nissle 1917 (EcN) (O6:K5:H1). Human T84 and THP-1 cells were used as cell culture-based model systems for epithelial and monocytic cells. Polarized T84 monolayers were infected apically or basolaterally. Bacterial challenges from the basolateral side resulted in more pronounced cytokine and miRNA responses than those observed for apical side infections. Interestingly, the probiotic EcN also caused a pronounced transcriptional increase of proinflammatory CXCL1 and interleukin-8 (IL-8) levels when human T84 epithelial cells were infected from the basolateral side. miR-146a, which is known to regulate adaptor molecules in Toll-like receptor (TLR)/NF-κB signaling, was found to be differentially regulated in THP-1 cells between probiotic and pathogenic bacteria. To assess the roles of flagella and flagellin, we employed several flagellin mutants of EcN. EcN flagellin mutants induced reduced IL-8 as well as CXCL1 responses in T84 cells, suggesting that flagellin is an inducer of this cytokine response. Following infection with an EPEC type 3 secretion system (T3SS) mutant, we observed increased IL-8 and CXCL1 transcription in T84 and THP-1 cells compared to that in wild-type EPEC. This study emphasizes the differential induction of miR-146a by pathogenic and probiotic E. coli strains in epithelial and immune cells as well as a loss of probiotic properties in EcN interacting with cells from the basolateral side.

miR-192 targeting IL-1RI regulates the immune response in miiuy croaker after pathogen infection in vitro and in vivo

Activation of innate and acquired immune responses is regulated by detailed mechanisms to control their onset and termination. MicroRNAs have been implicated as negative regulators controlling the diverse of biophysical and biochemical processes at the post-transcriptional level. However, the physiological roles of miRNAs in aquatic organisms are largely unclear. In this study, we explored the potential roles of mmi-miR-192 in regulating interleukin 1 receptor type I (IL-1RI) involved in immune and inflammatory response in miiuy croakers. This was further evaluated by negative expression profiles in both LPS exposure macrophages and Vibrio anguillarum challenged miiuy croaker. By means of promoter analysis, mmi-miR-192 was found to be an AP-1 dependent gene. Importantly, the dual luciferase reporter assay presented the regulation between mmi-miR-192 and IL-1RI. The result of miiuy croaker miR-192 reduced the wild-type IL-1RI but not the mutant one luciferase levels suggested that mmi-miR-192 modulated IL-1RI expression by directly targeting the 3'UTR of IL-1RI mRNA. Overall, our study revealed the mechanism that the miR-192-IL1RI pathway regulated bacteria infection in miiuy croakers.

Porphyromonas gingivalis-induced miR-132 regulates TNFα expression in THP-1 derived macrophages

Background

Periodontitis is a chronic inflammatory disease induced by periodontopathogens such as Porphyromonas gingivalis (P. gingivalis). MicroRNAs (miRNAs) are small single-stranded noncoding RNAs that regulate gene expression at the level of translation. MiRNAs have been reported to be involved in inflammatory processes. In this study, we examined the effects of P. gingivalis-induced inflammatory miRNAs expression on TNFα production in THP-1 derived macrophages.

Results

Porphyromonas gingivalis induced the expression of miR-132. P. gingivalis-induced miR-132 expression was significantly inhibited by TLR2/4 knock-down and NF-κB inhibitor. Additionally, miR-132 antagomir strongly repressed production of TNFα. The expression of NFE2L2 and NFAT5, the putative target genes of miR-132 involved in regulation of TNFα, decreased in response to P. gingivalis. Furthermore, miR-132 antagomir rescued P. gingivalis-induced suppression of NFE2L2 and NFAT5.

Conclusions

These results suggest that the induction of miR-132 by P. gingivalis can modulate the pathogenesis of periodontitis induced via regulatory expression of TNFα.

Resolvin D2 decreases TLR4 expression to mediate resolution in human monocytes

TLRs are critical for innate immunity, but excessive activation can lead to tissue damage and disease. Specialized proresolving mediators (SPMs), including resolvin D2 (RvD2), promote the active resolution of inflammation. How SPMs regulate early LPS signaling, including activation of TLR4, is unknown. We treated human THP-1 monocytic cells and primary human blood monocytes with RvD2 and LPS to evaluate modulation of TLRs. miRNA-146a overexpression and inhibition were used to dissect the mechanism of RvD2-mediated actions. We validated our studies using ELISAs for cytokines, PCR, Western blot analysis, and flow cytometry. Cells treated with 0.1% ethanol (control for RvD2) and/or PBS (control for LPS), and control microRNA mimics and inhibitors were used as controls. RvD2 reduced LPS-induced cytokines and TLR4 expression in human monocytes by up to 75%. In THP-1 cells, RvD2 reduced expression of TLR4, lymphocyte antigen 96 (MD-2), and downstream signals (MyD88, TRIF, and TAK1). These effects were partially mediated through RvD2 induction of microRNA-146a, and RvD2's actions were blocked by microRNA-146a inhibition. These new findings reveal the ability of RvD2 to reduce TLR4 expression and attenuate LPS-induced inflammation, providing a new area of SPM activity to investigate in this major area of therapeutic research.-Croasdell, A., Sime, P. J., Phipps, R. P. Resolvin D2 decreases TLR4 expression to mediate resolution in human monocytes.

miR-146a is essential for lipopolysaccharide (LPS)-induced cross-tolerance against kidney ischemia/reperfusion injury in mice

MicroRNA-146a is one of most important microRNAs involved in development of endotoxin tolerance via (toll-like receptors) TLRs/ NF-κB pathway. In this study, we sought to identify the mechanistic role of miR-146a in mediating the protective effect of lipopolysaccharide (LPS) pretreatment on kidney ischemia/reperfusion injury. A locked nucleic acid–modified anti-miR-146a given before LPS treatment knocked down miR-146a expression and completely negated LPS-mediated protection against kidney ischemia/reperfusion injury. Knockdown of miR-146a resulted in significantly higher histopathological scores for tubular damage, expression of proinflammatory cytokines and chemokines, and neutrophil and macrophage infiltration. Furthermore, knockdown of miR-146a greatly up-regulated the protein levels of IL-1 receptor-associated kinase (IRAK-1) and tumor-necrosis factor (TNF) receptor-associated factor 6 (TRAF6), which are known target genes of miR-146a, leading to activation of NF-κB. Finally, elevation of nuclear translocation of NF-κB p65/p50 and caspase-3 expression, degradation of cytosolic IkBα and BcL-xL, and substantially exacerbation of tubular cell apoptosis were inversely correlated with miR-146a expression. Taken together, our results identify that miR146a exerts a kidney protective effect through negative regulation of acute inflammatory response by suppressing NF-κB activation and proinflammatory genes expression.

Transition from inflammation to proliferation: a critical step during wound healing

The ability to rapidly restore the integrity of a broken skin barrier is critical and is the ultimate goal of therapies for hard-to-heal-ulcers. Unfortunately effective treatments to enhance healing and reduce scarring are still lacking. A deeper understanding of the physiology of normal repair and of the pathology of delayed healing is a prerequisite for the development of more effective therapeutic interventions. Transition from the inflammatory to the proliferative phase is a key step during healing and accumulating evidence associates a compromised transition with wound healing disorders. Thus, targeting factors that impact this phase transition may offer a rationale for therapeutic development. This review summarizes mechanisms regulating the inflammation-proliferation transition at cellular and molecular levels. We propose that identification of such mechanisms will reveal promising targets for development of more effective therapies.

Toll-like receptors and chronic inflammation in rheumatic diseases: new developments

In the past few years, new developments have been reported on the role of Toll-like receptors (TLRs) in chronic inflammation in rheumatic diseases. The inhibitory function of TLR10 has been demonstrated. Receptors that enhance the function of TLRs, and several TLR inhibitors, have been identified. In addition, the role of the microbiome and TLRs in the onset of rheumatic diseases has been reported. We review novel insights on the role of TLRs in several inflammatory joint diseases, including rheumatoid arthritis, systemic lupus erythematosus, gout and Lyme arthritis, with a focus on the signalling mechanisms mediated by the Toll-IL-1 receptor (TIR) domain, the exogenous and endogenous ligands of TLRs, and the current and future therapeutic strategies to target TLR signalling in rheumatic diseases.

Promoter-Specific Hypomethylation Correlates with IL-1β Overexpression in Tuberous Sclerosis Complex (TSC)

In tuberous sclerosis complex (TSC), overexpression of numerous genes associated with inflammation has been observed. Among different proinflammatory cytokines, interleukin-1β (IL-1β) has been shown to be significantly involved in epileptogenesis and maintenance of seizures. Recent evidence indicates that IL-1β gene expression can be regulated by DNA methylation of its promoter. In the present study, we hypothesized that hypomethylation in the promoter region of the IL-1β gene may underlie its overexpression observed in TSC brain tissue. Bisulfite sequencing was used to study the methylation status of the promoter region of the IL-1β gene in TSC and control samples. We identified hypomethylation in the promoter region of the IL-1β gene in TSC samples. IL-1β is overexpressed in tubers, and gene expression is correlated with promoter hypomethylation at CpG and non-CpG sites. Our results provide the first evidence of epigenetic modulation of the IL-1β signaling in TSC. Thus, strategies that target epigenetic alterations could offer new therapeutic avenues to control the persistent activation of interleukin-1β-mediated inflammatory signaling in TSC brain.

Immunomediated Pan-cancer Regulation Networks are Dominant Fingerprints After Treatment of Cell Lines with Demethylation

Pan-cancer studies are particularly relevant not only for addressing the complexity of the inherently observed heterogeneity but also for identifying clinically relevant features that may be common to the cancer types. Immune system regulations usually reveal synergistic modulation with other cancer mechanisms and in combination provide insights on possible advances in cancer immunotherapies. Network inference is a powerful approach to decipher pan-cancer systems dynamics. The methodology proposed in this study elucidates the impacts of epigenetic treatment on the drivers of complex pan-cancer regulation circuits involving cell lines of five cancer types. These patterns were observed from differential gene expression measurements following demethylation with 5-azacytidine. Networks were built to establish associations of phenotypes at molecular level with cancer hallmarks through both transcriptional and post-transcriptional regulation mechanisms. The most prominent feature that emerges from our integrative network maps, linking pathway landscapes to disease and drug-target associations, refers primarily to a mosaic of immune-system crosslinked influences. Therefore, characteristics initially evidenced in single cancer maps become motifs well summarized by network cores and fingerprints.

Modulation of endothelial function by Toll like receptors

Endothelial cells (EC) are able to actively control vascular permeability, coagulation, blood pressure and angiogenesis. Most recently, a role for endothelial cells in the immune response has been described. Therefore, the endothelium has a dual role controlling homeostasis but also being the first line for host defence and tissue damage repair thanks to its ability to mount an inflammatory response. Endothelial cells have been shown to express pattern-recognition receptors (PRR) including Toll-like receptors (TLR) that are activated in response to stimuli within the bloodstream including pathogens and damage signals. TLRs are strategic mediators of the immune response in endothelial cells but they also regulate the angiogenic process critical for tissue repair. Nevertheless, endothelial activation and angiogenesis can contribute to some pathologies. Thus, inappropriate endothelial activation, also known as endothelial dysfunction, through TLRs contributes to tissue damage during autoimmune and inflammatory diseases such as atherosclerosis, hypertension, ischemia and diabetes associated cardiovascular diseases. Also TLR induced angiogenesis is required for the growth of some tumors, atherosclerosis and rheumatoid arthritis, among others. In this review we discuss the importance of various TLRs in modulating the activation of endothelial cells and their importance in immunity to infection and vascular disease as well as their potential as therapeutic targets.

Toll-Like Receptors in Cystic Fibrosis: Impact of Dysfunctional microRNA on Innate Immune Responses in the Cystic Fibrosis Lung

Toll-like receptors (TLRs) are a class of pattern recognition receptors that are particularly expressed in the sentinel and epithelial cells in the body, including the lung. They are central players in the innate immune system in response to microbial infection, and are the triggers of a complex pathway network that both promotes the inflammatory response and influences the adaptive immune response. These pathways are transiently and finely tuned by cellular factors, including a cell's microRNA response program. MicroRNAs are small, non-coding RNAs that specifically regulate gene expression. In this article, we review the disease-specific microRNA regulatory network of cystic fibrosis, a debilitating and ultimately fatal disease and, specifically, its effect on TLR signalling.

Expression of microRNAs miR21, miR146a, and miR155 in tuberous sclerosis complex cortical tubers and their regulation in human astrocytes and SEGA-derived cell cultures

Tuberous sclerosis complex (TSC) is a genetic disease presenting with multiple neurological symptoms including epilepsy, mental retardation, and autism. Abnormal activation of various inflammatory pathways has been observed in astrocytes in brain lesions associated with TSC. Increasing evidence supports the involvement of microRNAs in the regulation of astrocyte-mediated inflammatory response. To study the role of inflammation-related microRNAs in TSC, we employed real-time PCR and in situ hybridization to characterize the expression of miR21, miR146a, and miR155 in TSC lesions (cortical tubers and subependymal giant cell astrocytomas, SEGAs). We observed an increased expression of miR21, miR146a, and miR155 in TSC tubers compared with control and perituberal brain tissue. Expression was localized in dysmorphic neurons, giant cells, and reactive astrocytes and positively correlated with IL-1β expression. In addition, cultured human astrocytes and SEGA-derived cell cultures were used to study the regulation of the expression of these miRNAs in response to the proinflammatory cytokine IL-1β and to evaluate the effects of overexpression or knockdown of miR21, miR146a, and miR155 on inflammatory signaling. IL-1β stimulation of cultured glial cells strongly induced intracellular miR21, miR146a, and miR155 expression, as well as miR146a extracellular release. IL-1β signaling was differentially modulated by overexpression of miR155 or miR146a, which resulted in pro- or anti-inflammatory effects, respectively. This study provides supportive evidence that inflammation-related microRNAs play a role in TSC. In particular, miR146a and miR155 appear to be key players in the regulation of astrocyte-mediated inflammatory response, with miR146a as most interesting anti-inflammatory therapeutic candidate.

Inhibitory Effects of JEUD-38, a New Sesquiterpene Lactone from Inula japonica Thunb, on LPS-Induced iNOS Expression in RAW264.7 Cells

We isolated JEUD-38, a new sesquiterpene lactone from Inula japonica Thunb. JEUD-38 dramatically attenuated lipopolysaccharide (LPS)-induced nitric oxide (NO) production. Consistent with this finding, the protein expression of inducible nitric oxide synthase (iNOS) was blocked by JEUD-38 in a concentration-dependent manner. To elucidate the mechanism, we examined the effect of JEUD-38 on LPS-stimulated nuclear factor-κB (NF-κB) nuclear translocation, inhibitory factor-κB (IκB) phosphorylation, and degradation. JEUD-38 reduced the translocation of p65, via abrogating IκB-α phosphorylation and degradation. In addition, JEUD-38 inhibited LPS-stimulated phosphorylation of mitogen-activated protein kinases (MAPKs) including extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK), and p38. Since iNOS as well as the upstream NF-κB and MAPKs are known to be closely involved in inflammation, these results suggest that JEUD-38 is a promising candidate for prevention and therapy of inflammatory diseases.

A Bioinformatics Approach to Prioritize Single Nucleotide Polymorphisms in TLRs Signaling Pathway Genes

It has been suggested that single nucleotide polymorphisms (SNPs) in genes involved in Toll-like receptors (TLRs) pathway may exhibit broad effects on function of this network and might contribute to a range of human diseases. However, the extent to which these variations affect TLR signaling is not well understood. In this study, we adopted a bioinformatics approach to predict the consequences of SNPs in TLRs network. The consequences of non-synonymous coding SNPs (nsSNPs) were predicted by SIFT, PolyPhen, PANTHER, SNPs&GO, I-Mutant, ConSurf and NetSurf tools. Structural visualization of wild type and mutant protein was performed using the project HOPE and Swiss PDB viewer. The influence of 5'-UTR and 3'- UTR SNPs were analyzed by appropriate computational approaches. Nineteen nsSNPs in TLRs pathway genes were found to have deleterious consequences as predicted by the combination of different algorithms. Moreover, our results suggested that SNPs located at UTRs of TLRs pathway genes may potentially influence binding of transcription factors or microRNAs. By applying a pathway-based bioinformatics analysis of genetic variations, we provided a prioritized list of potentially deleterious variants. These findings may facilitate the selection of proper variants for future functional and/or association studies.

Norcantharidin modulates miR-655-regulated SENP6 protein translation to suppresses invasion of glioblastoma cells

Norcantharidin (NCTD) is currently used as an anticancer drug for the treatment of some malignant cancers. However, whether it may have therapeutic effects on glioblastoma multiforme (GBM) remains unknown. Moreover, the underlying mechanisms have not been completely elucidated. Recently, SUMO-specific protease 6 (SENP6) has been shown as a tumor suppressor in some cancers. Nevertheless, whether it is involved in the pathogenesis of GBM has not been examined. Here, we studied the effects of NCTD on GBM cells. We found that NCTD dose-dependently increased SENP6 protein, but not messenger RNA (mRNA), in GBM cells, resulting in the suppression of cell invasion. Depletion of SENP6 in GBM cells significantly attenuated the NCTD-induced suppression of GBM cell invasion, while overexpression of SENP6 in GBM cells mimicked the effects of NCTD on cell invasion. Moreover, NCTD dose-dependently decreased the levels of microRNA-655 (miR-655), which bound to 3'-UTR of SENP6 mRNA to inhibit its translation. Overexpression of miR-655 decreased SENP6 in GBM cells, while depletion of miR-655 increased SENP6 protein in GBM cells. Taken together, our data demonstrates a previously unappreciated control of NCTD to suppress GBM cell invasion through modulation of miR-655-regulated SENP6 protein translation.

Chloroquine attenuates LPS-mediated macrophage activation through miR-669n-regulated SENP6 protein translation

Chloroquine (CQ) has been shown to inhibit Toll-like receptor 4 (TLR4)-mediated monocyte and macrophage activation induced by lipopolysaccharide (LPS). However, the underlying mechanisms have not been completely elucidated. Recently, SUMO-specific protease 6 (SENP6) has been reported to suppress LPS-induced activation of macrophages through deSUMOlation of NF-κB essential modifier (NEMO). Here, we studied whether this molecular pathway may also be involved in CQ/LPS model. We found that CQ dose-dependently increased SENP6 protein, but not mRNA, in mouse macrophages, RAW264.7 cells. Overexpression of SENP6 in RAW264.7 cells significantly decreased the LPS-induced release of pro-inflammatory proteins, TNF-α, IL-6 and IFN-γ, while depletion of SENP6 in RAW264.7 cells significantly increased these proteins. Moreover, in LPS-treated RAW264.7 cells, CQ dose-dependently decreased the levels of microRNA-669n (miR-669n), which bound to 3'-UTR of SENP6 mRNA to inhibit its translation. Overexpression of miR-669n decreased SENP6, resulting in increased production of TNF-α, IL-6 and IFN-γ in RAW264.7 cells, while depletion of miR-669n increased SENP6, resulting in decreased production of TNF-α, IL-6 and IFN-γ in RAW264.7 cells. In vivo, delivery of miR-669n plasmids augmented the effects of LPS, while delivery of antisense of miR-669n (as-miR-669n) plasmids abolished the effects of LPS. Taken together, our data demonstrate a previously unappreciated molecular control of LPS-induced macrophage activation by CQ, through miR-669n-regulated SENP6 protein translation.

Innate and adaptive immune response in stroke: Focus on epigenetic regulation

Inflammation and immune response play a pivotal role in the pathophysiology of ischemic stroke giving their contribution to tissue damage and repair. Emerging evidence supports the involvement of epigenetic mechanisms such as methylation, histone modification and miRNAs in the pathogenesis of stroke. Interestingly, epigenetics can influence the molecular events involved in ischemic injury by controlling the switch from pro- to anti-inflammatory response, however, this is still a field to be fully explored. The knowledge of epigenetic processes could to allow for the discovery of more sensitive and specific biomarkers for risk, onset, and progression of disease as well as further novel tools to be used in both primary prevention and therapy of stroke. Indeed, studies performed in vitro and in small animal models seem to suggest a neuroprotective role of HDAC inhibitors (e.g. valproic acid) and antagomir (e.g. anti-miR-181a) in ischemic condition by modulation of both immune and inflammatory pathways. Thus, the clinical implications of altered epigenetic mechanisms for the prevention of stroke are very promising but clinical prospective studies and translational approaches are still warranted.