MicroRNAs: Fine Tuners of Monocyte Heterogeneity

Detection of microRNAs expression signatures in vitreous humor of intraocular tuberculosis

BACKGROUND

MicroRNA (miRNA) expression analysis has been shown to provide them as biomarkers in several eye diseases and has a regulatory role in pathogenesis. However, miRNA expression analysis in the vitreous humor (VH) of intraocular tuberculosis (IOTB) is not studied. Thus, we aim to find miRNA expression signatures in the VH of IOTB patients to identify their regulatory role in disease pathogenesis and to find them as potential biomarkers for IOTB.

METHODS AND RESULTS

First, we profiled miRNAs in VH of three IOTB and three Macular hole (MH) samples as controls through small-RNA deep sequencing using Illumina Platform. In-house bioinformatics analysis identified 81 dysregulated miRNAs in IOTB. Further validation in VH of IOTB (n = 15) compared to MH (n = 15) using Real-Time quantitative PCR (RT-qPCR) identified three significantly upregulated miRNAs, hsa-miR-150-5p, hsa-miR-26b-5p, and hsa-miR-21-5p. Based on the miRNA target prediction, functional network analysis, and RT-qPCR analysis of target genes, the three miRNAs downregulating WNT5A, PRKCA, MAP3K7, IL7, TGFB2, IL1A, PRKCB, TNFA, and TP53 genes involving MAPK signaling pathway, PI3K-AKT signaling pathway, WNT signaling pathway, Cell cycle, TGF-beta signaling pathway, Long-term potentiation, and Sphingolipid signaling pathways, have a potential role in disease pathogenesis. The ROC analysis of RT-qPCR data showed that hsa-miR-150-5p with AUC = 0.715, hsa-miR-21-5p with AUC = 0.789, and hsa-miR-26b-5p with AUC = 0.738; however, the combination of hsa-miR-21-5p and hsa-miR-26b-5p with AUC = 0.796 could serve as a potential biomarker for IOTB.

CONCLUSIONS

This study provides the first report on miRNA expression signatures detected in VH for IOTB pathogenesis and also provides a potential biomarker for IOTB.

Peripheral blood mononuclear cells expression of miR-200c, miR-125b, miR-27b, miR-203, and miR-155 in patients with significant or insignificant coronary artery stenosis

Coronary artery disease (CAD) is one of the principal causes of death worldwide. Among several predisposing factors, inflammation and inflammatory genes play a significant role in disease pathogenesis. Inflammatory microRNAs, small noncoding RNAs involved in regulating inflammation, are promising candidates for understanding pathogenesis of CAD and developing diagnostic biomarkers. The aim of the study was to evaluate the alteration of miR-200c, miR-125b, miR-27b, miR-203 and, miR-155 in patients suffering from coronary artery stenosis and insignificant coronary artery stenosis compared to healthy subjects. In this study we compared expressions of five inflammatory miRNAs in peripheral blood mononuclear cells (PBMCs) of 72 patients suffering significant coronary artery stenosis (CAD), 74 individuals without coronary artery disease and 30 individuals with insignificant coronary artery stenosis (ICAD). After blood collection, PBMCs were isolated and RNA was extracted. Gene expression levels were assessed by SYBR green based real-time PCR. Statistical analysis was performed using R program. Expression levels of miR-200c, miR-203, and miR-155 were lower in subjects with ICAD than that in CAD patients and subjects of the control group. MiR-125b was downregulated in CAD and ICAD groups compared to the control group. PBMC miR-27b was upregulated in the CAD group as compared to the ICAD and control groups. Receiver operating characteristic curve analysis verified potential of three miRNAs in separating subjects with ICAD from CAD patients and healthy individuals. In conclusion, this original investigation suggested that altered expression of these five miRNAs may serve as a novel diagnostic biomarker discriminating clinical presentations of coronary artery diseases.

Monocyte heterogeneity in cardiovascular disease

Monocytes circulate the vasculature at steady state and are recruited to sites of inflammation where they differentiate into macrophages (MФ) to replenish tissue-resident MФ populations and engage in the development of cardiovascular disease (CVD). Monocytes display considerable heterogeneity, currently reflected by a nomenclature based on their expression of cluster of differentiation (CD) 14 and CD16, distinguishing CD14++CD16- classical (cMo), CD14++CD16+ intermediate (intMo) and CD14+CD16++ non-classical (ncMo) monocytes. Several reports point to shifted subset distributions in the context of CVD, with significant association of intMo numbers with atherosclerosis, myocardial infarction, and heart failure. However, clear indications of their causal involvement as well as their predictive value for CVD are lacking. As recent high-parameter cytometry and single-cell RNA sequencing (scRNA-Seq) studies suggest an even higher degree of heterogeneity, better understanding of the functionalities of these subsets is pivotal. Considering their high heterogeneity, surprisingly little is known about functional differences between MФ originating from monocytes belonging to different subsets, and implications thereof for CVD pathogenesis. This paper provides an overview of recent findings on monocyte heterogeneity in the context of homeostasis and disease as well as functional differences between the subsets and their potential to differentiate into MФ, focusing on their role in vessels and the heart. The emerging paradigm of monocyte heterogeneity transcending the current tripartite subset division argues for an updated nomenclature and functional studies to substantiate marker-based subdivision and to clarify subset-specific implications for CVD.

MicroRNAs in inflammasomopathies

microRNAs (miRNAs) are small non-coding RNA sequences that negatively regulate the expression of protein-encoding genes at the post-transcriptional level. They play a role in the regulation of inflammatory responses by controlling the proliferation and activation of immune cells and their expression is disrupted in several immune-mediated inflammatory disorders. Among these, autoinflammatory diseases (AID) are a group of rare hereditary disorders caused by abnormal activation of the innate immune system and characterized by recurrent fevers. Major groups of AID are inflammasomopathies, which are associated with hereditary defects in the activation of inflammasomes, cytosolic multiprotein signaling complexes regulating IL-1 family cytokine maturation and pyroptosis. The study of the role of miRNAs in AID is only recently emerging and remains scarce in inflammasomopathies. In this review, we describe the AID and inflammasomopathies, and the current knowledge on the role of miRNAs in disease processes.

The generation, activation, and polarization of monocyte-derived macrophages in human malignancies

Macrophages are immune cells that originate from embryogenesis or from the differentiation of monocytes. They can adopt numerous phenotypes depending on their origin, tissue distribution and in response to different stimuli and tissue environment. Thus, in vivo, macrophages are endowed with a continuum of phenotypes that are rarely strictly pro-inflammatory or anti-inflammatory and exhibit a broad expression profile that sweeps over the whole polarization spectrum. Schematically, three main macrophage subpopulations coexist in human tissues: naïve macrophages also called M0, pro-inflammatory macrophages referred as M1 macrophages, and anti-inflammatory macrophages also known as M2 macrophages. Naïve macrophages display phagocytic functions, recognize pathogenic agents, and rapidly undergo polarization towards pro or anti-inflammatory macrophages to acquire their full panel of functions. Pro-inflammatory macrophages are widely involved in inflammatory response, during which they exert anti-microbial and anti-tumoral functions. By contrast, anti-inflammatory macrophages are implicated in the resolution of inflammation, the phagocytosis of cell debris and tissue reparation following injuries. Macrophages also play important deleterious or beneficial roles in the initiation and progression of different pathophysiological settings including solid and hematopoietic cancers. A better understanding of the molecular mechanisms involved in the generation, activation and polarization of macrophages is a prerequisite for the development of new therapeutic strategies to modulate macrophages functions in pathological situations.

Modulation of Monocyte Response by Microrna-15b/106a/374a During Antibody-mediated Rejection in Kidney Transplantation

BACKGROUND

Increasing evidence suggest that microRNAs are involved in the physiopathology of acute or chronic renal disease. In kidney transplantation, as key regulators of cellular homeostasis, microRNAs may be involved in the regulation of immune cell function and the allograft response. Here, we investigated the change in circulating microRNA expression profile and their involvement in the profound transcriptional changes associated with antibody-mediated rejection (ABMR).

METHODS

Blood samples were collected at the time of the 710 kidney allograft biopsies at 4 European transplant centers. Messenger RNA and microRNA profiling analyses were performed in a discovery-to-validation study within 3 independent cohorts encompassing N = 126, N = 135, and N = 416 patients, respectively.

RESULTS

Compared with samples with no ABMR, 14 microRNAs were significantly decreased in ABMR samples. Among them, expression levels of microRNA-15b, microRNA-106a, and microRNA-374a gradually decreased with the severity of ABMR lesions. From their in silico-predicted target genes, a high proportion proved to be significantly upregulated in the paired transcriptomic analysis. Gene ontology analyses of microRNA-15b/-106a/-374a suggested enrichment in myeloid-related pathways, which was further refined by in silico and ex vivo transcriptomic analyses, showing a specific origin from classical CD14 + monocytes. Finally, human CD14 + monocytes were subjected to transduction by antago-microRNAs to mimic ABMR pathology. MicroRNA-15b/-106a/-374a impairment resulted in cellular activation with an increased expression of CD69, CRIM1, IPO7, and CAAP1, direct and common targets of the 3 microRNAs.

CONCLUSIONS

Together, our data provide new insights into circulating microRNAs as markers and key players in ABMR, and they suggest monocyte involvement in this process.

Monocyte exposure to fine particulate matter results in miRNA release: A link between air pollution and potential clinical complication

Chronic exposure to PM_2.5 contributes to the pathogenesis of numerous disorders, although the underlying mechanisms remain unknown. The study investigated whether exposure of human monocytes to PM_2.5 is associated with alterations in miRNAs. Monocytes were exposed in vitro to PM_2.5 collected during winter and summer, followed by miRNA isolation from monocytes. Additionally, in 140 persons chronically exposed to air pollution, some miRNA patterns were isolated from serum seasonally. Between-season differences in chemical PM_2.5 composition were observed. Some miRNAs were expressed both in monocytes and in human serum. MiR-34c-5p and miR-223-5p expression was more pronounced in winter. Bioinformatics analyses showed that selected miRNAs were involved in the regulation of several pathways. The expression of the same miRNA species in monocytes and serum suggests that these cells are involved in the production of miRNAs implicated in the development of disorders mediated by inflammation, oxidative stress, proliferation, and apoptosis after exposure to PM_2.5.

Defining the Role of Monocytes in Sjögren's Syndrome

Sjögren's syndrome is one of the most prevalent autoimmune diseases after rheumatoid arthritis, with a preference for middle age, and is characterised by exocrine glandular involvement leading to xerostomia and xerophthalmia. It can have systemic implications with vascular, neurological, renal, and pulmonary involvement, and in some cases, it may evolve to non-Hodgkin's lymphoma. For a long time, B- and T-lymphocytes have been the focus of research and have been considered key players in Sjögren's syndrome pathogenesis and evolution. With the development of new technologies, including omics, more insights have been found on the different signalling pathways that lead to inflammation and activation of the immune system. New evidence indicates that a third actor linking innate and adaptive immunity plays a leading role in the Sjögren's syndrome play: the monocyte. This review summarises the recent insights from transcriptomic, proteomic, and epigenetic studies that help us to understand more about the Sjögren's syndrome pathophysiology and redefine the involvement of monocytes in this disease.

Osteoclast-like stromal giant cells in breast cancer likely belong to the spectrum of immunosuppressive tumor-associated macrophages

Background: Breast cancer with osteoclast-like stromal giant cells (OSGC) is an exceedingly rare morphological pattern of invasive breast carcinoma. The tumor immune microenvironment (TIME) of these tumors is populated by OSGC, which resemble osteoclasts and show a histiocytic-like immunophenotype. Their role in breast cancer is unknown. The osteoclast maturation in the bone is regulated by the expression of cytokines that are also present in the TIME of tumors and in breast cancer tumor-associated macrophages (TAMs). TAMs-mediated anti-tumor immune pathways are regulated by miRNAs akin to osteoclast homeostasis. Here, we sought to characterize the different cellular compartments of breast cancers with OSGC and investigate the similarities of OSGC with tumor and TIME in terms of morphology, protein, and miRNA expression, specifically emphasizing on monocytic signatures.

Methods and Results: Six breast cancers with OSGC were included. Tumor-infiltrating lymphocytes (TILs) and TAMs were separately quantified. The different cellular populations (i.e., normal epithelium, cancer cells, and OSGC) were isolated from tissue sections by laser-assisted microdissection. After RNA purification, 752 miRNAs were analyzed using a TaqMan Advanced miRNA Low-Density Array for all samples. Differentially expressed miRNAs were identified by computing the fold change (log2Ratio) using the Kolmogorov-Smirnov test and p values were corrected for multiple comparisons using the false discovery rate (FDR) approach. As a similarity analysis among samples, we used the Pearson test. The association between pairs of variables was investigated using Fisher exact test. Classical and non-classical monocyte miRNA signatures were finally applied. All OSGC displayed CD68 expression, TILs (range, 45–85%) and high TAMs (range, 35–75%). Regarding the global miRNAs profile, OSGC was more similar to cancer cells than to non-neoplastic ones. Shared deregulation of miR-143-3p, miR-195-5p, miR-181a-5p, and miR-181b-5p was observed between OSGC and cancer cells. The monocyte-associated miR-29a-3p and miR-21-3p were dysregulated in OSGCs compared with non-neoplastic or breast cancer tissues.

Conclusion: Breast cancers with OSGC have an activated TIME. Shared epigenetic events occur during the ontogenesis of breast cancer cells and OSGC but the innumophenotype and miRNA profiles of the different cellular compartmens suggest that OSGC likely belong to the spectrum of M2 TAMs.

The Role of miRNA in Regulating the Fate of Monocytes in Health and Cancer

Monocytes represent a heterogeneous population of blood cells that provide a link between innate and adaptive immunity. The unique potential of monocytes as both precursors (e.g., of macrophages) and effector cells (as phagocytes or cytotoxic cells) makes them an interesting research and therapeutic target. At the site of a tumor, monocytes/macrophages constitute a major population of infiltrating leukocytes and, depending on the type of tumor, may play a dual role as either a bad or good indicator for cancer recovery. The functional activity of monocytes and macrophages derived from them is tightly regulated at the transcriptional and post-transcriptional level. This review summarizes the current understanding of the role of small regulatory miRNA in monocyte formation, maturation and function in health and cancer development. Additionally, signatures of miRNA-based monocyte subsets and the influence of exogenous miRNA generated in the tumor environment on the function of monocytes are discussed.

RelA/MicroRNA-30a/NLRP3 signal axis is involved in rheumatoid arthritis via regulating NLRP3 inflammasome in macrophages

NLRP3 inflammasome plays an important role in the pathogenesis of rheumatoid arthritis (RA). However, the post-transcriptional regulation of NLRP3 expression by miRNA in synovial macrophages is still not well understood. The aim of the study is to elucidate the mechanisms of RA with the focus on miRNAs mediated post-transcriptional regulation of the NLRP3 inflammasome. Here, we used NLRP3-deficient mice (NLRP3^KO) to cross with TNFα-transgenic mice (TNF^TG) to generate NLRP3^KO/TNF^TG mice, and compared their joint phenotypes with those of their TNF^TG and wild-type (WT) littermates at 5 months of age. In comparison to WT mice, articular bone volume and cartilage area are decreased, whereas inflammed area, eroded surface, ALP+ osteoblast number, TRAP+ osteoclast number, and the areas of RelA+F4/80+, Caspase-1+F4/80+, IL-1β+F4/80+ synoviocytes are increased in the TNF^TG mice. Knockout of NLRP3 ameliorates joint inflammation and bone damage in TNF^TG mice. Further, in TNFα-primed BMDMs, RelA positively regulates NLRP3 expression, but negatively regulates miR-30a. Additionally, miR-30a negatively mediates NLRP3 expression by directly binding to its 3' UTR, suggesting a miR-30a-mediated feedforward loop acting on NLRP3. Finally, intra-articular injection of AAV-miR-30a inhibits NLRP3 inflammasome activation, reduces joint inflammation, and attenuates bone damage in TNF^TG mice. Thus, RelA/miR-30a/NLRP3 signal axis is involved in RA through regulating NLRP3 Inflammasome in macrophages.

miR profile in pagetic osteoclasts: from large-scale sequencing to gene expression study

Paget's disease of bone (PDB) is characterized by excessive and disorganized bone remodeling, in which bone-resorbing osteoclasts play a key role. We investigated microRNA (miR) expression in osteoclasts derived from the blood of 40 PDB patients and 30 healthy controls. By deep sequencing, a preliminary analysis identified differentially expressed miRs in a discovery cohort of 9 PDB patients and 9 age and sex-matched healthy controls. Six mature miRs, miR-29b1-3p, miR-15b-5p, miR-181a-5p, let-7i-3p, miR-500b-5p, and miR-1246, were found to be significantly decreased in pagetic overactive osteoclasts. The differential expression of the miRs was confirmed by the analysis of a larger independent cohort using qPCR. In an integrative network biology analysis of the miR candidates, we identified strong validated interactions between the miRs and some pathways, primarily apoptosis, and major osteoclast signaling pathways including PI3K/Akt, IFNγ, or TGFβ, as well as c-Fos, a transcription factor, and MMP-9, a metalloprotease. In addition, other genes like CCND2, CCND1, WEE1, SAMHD1, and AXIN2 were revealed in this network of interactions. Our results enhance the understanding of osteoclast biology in PDB; our work may also provide fresh perspectives on the research or therapeutic development of other bone diseases. KEY MESSAGES: miR profile in overactive osteoclasts from patients with Paget's disease of bone. Six mature miRs were significantly decreased in pagetic osteoclasts vs controls. miRs of interest: let7i-3p, miR-15b-5p, -29b1-3p, -181a-5p, -500b-5p, and -1246. Target genes and enriched pathways highlight the importance of apoptotic pathways.

Monocyte and Macrophage miRNA: Potent Biomarker and Target for Host-Directed Therapy for Tuberculosis

The end TB strategy reinforces the essentiality of readily accessible biomarkers for early tuberculosis diagnosis. Exploration of microRNA (miRNA) and pathway analysis opens an avenue for the discovery of possible therapeutic targets. miRNA is a small, non-coding oligonucleotide characterized by the mechanism of gene regulation, transcription, and immunomodulation. Studies on miRNA define their importance as an immune marker for active disease progression and as an immunomodulator for innate mechanisms, such as apoptosis and autophagy. Monocyte research is highly advancing toward TB pathogenesis and biomarker efficiency because of its innate and adaptive response connectivity. The combination of monocytes/macrophages and their relative miRNA expression furnish newer insight on the unresolved mechanism for Mycobacterium survival, exploitation of host defense, latent infection, and disease resistance. This review deals with miRNA from monocytes, their relative expression in different disease stages of TB, multiple gene regulating mechanisms in shaping immunity against tuberculosis, and their functionality as biomarker and host-mediated therapeutics. Future collaborative efforts involving multidisciplinary approach in various ethnic population with multiple factors (age, gender, mycobacterial strain, disease stage, other chronic lung infections, and inflammatory disease criteria) on these short miRNAs from body fluids and cells could predict the valuable miRNA biosignature network as a potent tool for biomarkers and host-directed therapy.

miR-181a Mediates Inflammatory Gene Expression After Intracerebral Hemorrhage: An Integrated Analysis of miRNA-seq and mRNA-seq in a Swine ICH Model

Intracerebral hemorrhage (ICH) is a severe neurological disorder with no proven treatment. Inflammation after ICH contributes to clinical outcomes, but the relevant molecular mechanisms remain poorly understood. In studies of peripheral leukocyte counts and mRNA-sequencing (mRNA-seq), our group previously reported that monocytes and Interleukin-8 (IL-8) were important contributors to post-ICH inflammation. microRNA (miRNA) are powerful regulators of gene expression and promising therapeutic targets. We now report findings from an integrated analysis of miRNA-seq and mRNA-seq in peripheral blood mononuclear cells (PBMCs) from a swine ICH model. In 10 pigs, one PBMC sample was collected immediately prior to ICH induction and a second 6 h later; miRNA-seq and mRNA-seq were completed for each sample. An aggregate score calculation determined which miRNA regulated the differentially expressed mRNA. Networks of molecular interactions were generated for the combined miRNA/target mRNA. A total of 227 miRNA were identified, and 46 were differentially expressed after ICH (FDR < 0.05). The anti-inflammatory miR-181a was decreased post-ICH, and it was the most highly connected miRNA in the miRNA/mRNA bioinformatic network analysis. miR-181a has interconnected pathophysiology with IL-8 and monocytes; in prior studies, we found that IL-8 and monocytes contributed to post-ICH inflammation and ICH clinical outcome, respectively. miR-181a was a significant mediator of post-ICH inflammation and is promising for further study, including as a potential therapeutic target. This investigation also demonstrated feasible methodology for miRNA-seq/mRNA-seq analysis in swine that is innovative, and with unique challenges, compared with transcriptomics research in more established species.

Age-related differences in monocyte DNA methylation and immune function in healthy Kenyan adults and children

BACKGROUND

Age-related changes in adaptive and innate immune cells have been associated with a decline in effective immunity and chronic, low-grade inflammation. Epigenetic, transcriptional, and functional changes in monocytes occur with aging, though most studies to date have focused on differences between young adults and the elderly in populations with European ancestry; few data exist regarding changes that occur in circulating monocytes during the first few decades of life or in African populations. We analyzed DNA methylation profiles, cytokine production, and inflammatory gene expression profiles in monocytes from young adults and children from western Kenya.

RESULTS

We identified several hypo- and hyper-methylated CpG sites in monocytes from Kenyan young adults vs. children that replicated findings in the current literature of differential DNA methylation in monocytes from elderly persons vs. young adults across diverse populations. Differentially methylated CpG sites were also noted in gene regions important to inflammation and innate immune responses. Monocytes from Kenyan young adults vs. children displayed increased production of IL-8, IL-10, and IL-12p70 in response to TLR4 and TLR2/1 stimulation as well as distinct inflammatory gene expression profiles.

CONCLUSIONS

These findings complement previous reports of age-related methylation changes in isolated monocytes and provide novel insights into the role of age-associated changes in innate immune functions.

Specific MiRNAs in naïve T cells associated with Hepatitis C Virus-induced Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common type of cancer and the second leading cause of cancer-associated mortality worldwide. Hepatitis C virus (HCV) infection is the primary cause of hepatic fibrosis and cirrhosis, which in turn, notably increase the risk of developing HCC. The systematic immune response plays a vital role in protecting eukaryotic cells from exogenous antigens. In the present study, to determine the association between T cells and miRNAs in HCV-induced HCC (HCV-HCC), bulk mRNA and miRNA sequencing data from HCV-HCC tissues were combined, along with single-cell RNA sequencing (RNA-seq) data from T cells. Deconvoluted bulk RNA-seq data and miRNA profiles enabled the identification of naive CD4+ T cell-associated miRNAs, which may help to elucidate the underlying mechanism of the anti-HCV immune response. Using bulk RNA-seq data, the current analysis presents a feasible method for assessing the relationship between miRNAs and cell components, providing valuable insights into the effects of T cell-associated miRNAs in HCV-HCC.

Monocyte Transmodulation: The Next Novel Therapeutic Approach in Overcoming Ischemic Stroke?

The immune response following neuroinflammation is a vital element of ischemic stroke pathophysiology. After the onset of ischemic stroke, a specialized vasculature system that effectively protects central nervous system tissues from the invasion of blood cells and other macromolecules is broken down within minutes, thereby triggering the inflammation cascade, including the infiltration of peripheral blood leukocytes. In this series of processes, blood-derived monocytes have a significant effect on the outcome of ischemic stroke through neuroinflammatory responses. As neuroinflammation is a necessary and pivotal component of the reparative process after ischemic stroke, understanding the role of infiltrating monocytes in the modulation of inflammatory responses may offer a great opportunity to explore new therapies for ischemic stroke. In this review, we discuss and highlight the function and involvement of monocytes in the brain after ischemic injury, as well as their impact on tissue damage and repair.

A comprehensive review on miR-146a molecular mechanisms in a wide spectrum of immune and non-immune inflammatory diseases

MicroRNAs (miRNAs) are single-strand endogenous and non-coding RNA molecules with a length of about 22 nucleotides, which regulate genes expression, through modulating the translation and stability of their target mRNAs. miR-146a is one of the most studied miRNAs, due to its central role in immune system homeostasis and control of the innate and acquired immune responses. Accordingly, abnormal expression or function of miR-146a results in the incidence and progression of immune and non-immune inflammatory diseases. Its deregulated expression pattern and inefficient function have been reported in a wide spectrum of these illnesses. Based on the existing evidence, this miRNA qualifies as an ideal biomarker for diagnosis, prognosis, and activity evaluation of immune and non-immune inflammatory disorders. Moreover, much attention has recently been paid to therapeutic potential of miR-146a and several researchers have assessed the effects of different drugs on expression and function of this miRNA at diverse experimental, animal, besides human levels, reporting motivating results in the treatment of the diseases. Here, in this comprehensive review, we provide an overview of miR-146a role in the pathogenesis and progression of several immune and non-immune inflammatory diseases such as Rheumatoid arthritis, Systemic lupus erythematosus, Inflammatory bowel disease, Multiple sclerosis, Psoriasis, Graves' disease, Atherosclerosis, Hepatitis, Chronic obstructive pulmonary disease, etc., discuss about its eligibility for being a desirable biomarker for these disorders, and also highlight its therapeutic potential. Understanding these mechanisms underlies the selecting and designing the proper therapeutic targets and medications, which eventually facilitate the treatment process.

Human Monocyte Subset Distinctions and Function: Insights From Gene Expression Analysis

Monocytes are a highly plastic innate immune cell population that displays significant heterogeneity within the circulation. Distinct patterns of surface marker expression have become accepted as a basis for distinguishing three monocyte subsets in humans. These phenotypic subsets, termed classical, intermediate and nonclassical, have also been demonstrated to differ in regard to their functional properties and disease associations when studied in vitro and in vivo. Nonetheless, for the intermediate monocyte subset in particular, functional experiments have yielded conflicting results and some studies point to further levels of heterogeneity. Developments in genetic sequencing technology have provided opportunities to more comprehensively explore the phenotypic and functional differences among conventionally-recognized immune cell subtypes as well as the potential to identify novel subpopulations. In this review, we summarize the transcriptomic evidence in support of the existence of three separate monocyte subsets. We also critically evaluate the insights into subset functional distinctions that have been garnered from monocyte gene expression analysis and the potential utility of such studies to unravel subset-specific functional changes which arise in disease states.

Epigenetics in non-classical monocytes support their pro-inflammatory gene expression

Non-classical human monocytes are characterized by high-level expression of cytokines like TNF, but the mechanisms involved are elusive. We have identified miRNAs and CpG-methylation sites that are unique to non-classical monocytes, defined via CD14 and CD16 expression levels. For down-regulated miRNAs that are linked to up-regulated mRNAs the dominant gene ontology term was intracellular signal transduction. This included down-regulated miRNA-20a-5p and miRNA-106b-5p, which both are linked to increased mRNA for the TRIM8 signaling molecule. Methylation analysis revealed 16 hypo-methylated CpG sites upstream of 14 differentially increased mRNAs including 2 sites upstream of TRIM8. Consistent with a positive role in signal transduction, high TRIM8 levels went along with high basal TNF mRNA levels in non-classical monocytes. Since cytokine expression levels in monocytes strongly increase after stimulation with toll-like-receptor ligands, we have analyzed non-classical monocytes (defined via slan expression) after stimulation with lipopolysaccharide (LPS). LPS-stimulated cells continued to have low miRNA-20a and miRNA-106b and high TRIM8 mRNA levels and they showed a 10-fold increase in TNF mRNA. These data suggest that decreased miRNAs and CpG hypo-methylation is linked to enhanced expression of TRIM8 and that this can contribute to the increased TNF levels in non-classical human monocytes.