Multi-Step Regulation of the TLR4 Pathway by the miR-125a~99b~let-7e Cluster

Extracellular vesicles are key players in mesenchymal stem cells' dual potential to regenerate and modulate the immune system

MSCs are used for treatment of inflammatory conditions or for regenerative purposes. MSCs are complete cells and allogenic transplantation is in principle possible, but mostly autologous use is preferred. In recent years, it was discovered that cells secrete extracellular vesicles. These are active budded off vesicles that carry a cargo. The cargo can be miRNA, protein, lipids etc. The extracellular vesicles can be transported through the body and fuse with target cells. Thereby, they influence the phenotype and modulate the disease. The extracellular vesicles have, like the MSCs, immunomodulatory or regenerative capacities. This review will focus on those features of extracellular vesicles and discuss their dual role. Besides the immunomodulation, the regeneration will concentrate on bone, cartilage, tendon, vessels and nerves. Current clinical trials with extracellular vesicles for immunomodulation and regeneration that started in the last five years are highlighted as well. In summary, extracellular vesicles have a great potential as disease modulating entity and treatment. Their dual characteristics need to be taken into account and often are both important for having the best effect.

A glimpse into let-7e roles in human disorders; friend or foe?

MicroRNAs (miRNAs) have been linked to abnormal expression and regulation in a number of diseases, including cancer. Recent studies have concentrated on miRNA Let-7e's significance in precision medicine for cancer screening and diagnosis as well as its prognostic and therapeutic potential. Differential let-7e levels in bodily fluids have the possibility to enable early detection of cancer utilizing less-invasive techniques, reducing biopsy-related risks. Although Let-7e miRNAs have been described as tumor suppressors, it is crucial to note that there exists proof to support their oncogenic activity in vitro and in in vivo. Let-7e's significance in chemo- and radiation treatment decisions has also been demonstrated. Let-7e can also prevent the synthesis of proinflammatory cytokines in a number of degenerative disorders, including musculoskeletal and neurological conditions. For the first time, an overview of the significance of let-7e in the prevention, detection, and therapy of cancer and other conditions has been given in the current review. Additionally, we focused on the specific molecular processes that underlie the actions of let-7e, more particularly, on malignant cells.

Identification of Important Genes Associated with the Development of Atherosclerosis

Atherosclerosis is one of the most important medical problems due to its prevalence and significant contribution to the structure of temporary and permanent disability and mortality. Atherosclerosis is a complex chain of events occurring in the vascular wall over many years. Disorders of lipid metabolism, inflammation, and impaired hemodynamics are important mechanisms of atherogenesis. A growing body of evidence strengthens the understanding of the role of genetic and epigenetic factors in individual predisposition and development of atherosclerosis and its clinical outcomes. In addition, hemodynamic changes, lipid metabolism abnormalities, and inflammation are closely related and have many overlapping links in regulation. A better study of these mechanisms may improve the quality of diagnosis and management of such patients.

Targeted delivery of miR125a-5p and human Factor VIII attenuates molecular mediators of hemophilic arthropathy

Hemophilic arthropathy (HA) due to repeated bleeding into the joint cavity is a major cause of morbidity in patients with hemophilia. The molecular mechanisms contributing to this condition are not well characterized. MicroRNAs (miRs) are known to modulate the phenotype of multiple joint diseases such as osteoarthritis (OA) and rheumatoid arthritis (RA). Since miR125a is known to modulate disease progression in OA and RA, we performed a targeted screen of miR125a-5p and its target genes in a murine model of chronic HA. A digital PCR analysis demonstrated significant downregulation of miR125a-5p (2-fold vs control joint). Further molecular evaluation revealed elevated expression of the immunological markers STAT1 (7.6-fold vs control joint) and TRAF6 (10.6 fold vs control joint), which are direct targets of miR125a-5p. We then studied the impact of targeted overexpression of miR125a-5p using an Adeno-associated virus (AAV) vector in modulating the molecular mediators of HA. AAV5-miR125a vectors were administered intra-articularly either alone or in combination with a low dose of AAV8-based human factor 8 (F8) gene in a murine model of HA. We observed significantly increased expression of miR125a-5p in AAV5-miR125a administered mice (~12 fold vs injured joint) or in combination with AAV8-F8 vectors (~44 fold vs injured joint). The activity assay revealed ~17 %-20 % FVIII levels in mice that received low dose liver-directed F8 gene therapy. Further immunohistochemical analysis, demonstrated a decrease in inflammatory markers (STAT1 and TRAF6) and cartilage-degrading matrix metalloproteinases (MMPs) 3, 9, 13 in the joints of treated animals. These data highlight the crucial role of miR125a-5p in the development of HA.

Role of miR‑let‑7c‑5p/c‑myc signaling axis in the committed differentiation of leukemic THP‑1 cells into monocytes/macrophages

In a preliminary experiment, it was found that c-myc expression was decreased following the differentiation of THP-1 cells into monocytes/macrophages induced by phorbol 12-myristate 13 acetate (PMA) + lipopolysaccharide (LPS) + interferon (IFN)-γ. The expression of miR-let-7c-5p was then found to be elevated by cross-sectional analysis using TargetScan and PubMed and differential microarray analysis. The present study aimed to investigate the role of the miR-let-7c-5p/c-myc signaling axis in the committed differentiation of THP-1 leukemic cells into monocytes/macrophages induced by PMA + LPS + IFN-γ. Human THP-1 leukemic cells were induced to differentiate into monocytes/macrophages by PMA + LPS + IFN-γ. Following induction for 48 h, the growth density of the THP-1 cells was observed directly under an inverted microscope, cell proliferation was measured using Cell Counting Kit-8 assay and the cell cycle and the expression of differentiation-related antigens (CD11b and CD14) were measured using flow cytometry. The mRNA expression of miR-let-7c-5p and c-myc was detected using reverse transcription-quantitative PCR and the protein expression of c-myc was detected using western blot analysis. Dual luciferase reporter gene analysis was used to detect the targeted binding of miR-let-7c-5p on the 3'UTR of c-myc. The relative expression of miR-let-7c-5p and c-myc genes in THP-1 cells induced by PMA + LPS + IFN-γ was found to be up- and downregulated respectively, and expression of miR-let-7c-5p was negatively correlated with the expression of c-myc gene. Dual luciferase reporter gene assays confirmed that miR-let-7c-5p targeted the 3'UTR of c-myc and inhibited luciferase activity. Following transfection with miR-let-7c-5p mimics, the expression of c-myc was markedly downregulated and the proliferative ability of the THP-1 cells was decreased, while the expression rate of CD11b and CD14 was significantly increased. The rescue experiment revealed that the effects of miR-let-7c-5p mimics on the proliferation and differentiation of THP-1 cells were attenuated by transfection with c-myc overexpression vector. Together, the findings of the present study demonstrated that miR-let-7c-5p can target the 3'UTR region of c-myc and that the miR-let-7c-5p/c-myc signaling axis is one of the critical pathways involved in the directional differentiation of leukemic cells into monocytes/macrophages.

MicroRNAs in Macrophages: Regulators of Activation and Function

Macrophages are sentinels of the innate immune system that maintain tissue homeostasis and contribute to inflammatory responses. Their broad scope of action depends on both functional heterogeneity and plasticity. Small noncoding RNAs called microRNAs (miRNAs) contribute to macrophage function as post-transcriptional inhibitors of target gene networks. Genetic and pharmacologic studies have uncovered genes regulated by miRNAs that control macrophage cellular programming and macrophage-driven pathology. miRNAs control proinflammatory M1-like activation, immunoregulatory M2-like macrophage activation, and emerging macrophage functions in metabolic disease and innate immune memory. Understanding the gene networks regulated by individual miRNAs enhances our understanding of the spectrum of macrophage function at steady state and during responses to injury or pathogen invasion, with the potential to develop miRNA-based therapies. This review aims to consolidate past and current studies investigating the complexity of the miRNA interactome to provide the reader with a mechanistic view of how miRNAs shape macrophage behavior.

Distinct non-coding RNA cargo of extracellular vesicles from M1 and M2 human primary macrophages

Macrophages are important antigen presenting cells which can release extracellular vesicles (EVs) carrying functional cargo including non-coding RNAs. Macrophages can be broadly classified into M1 'classical' and M2 'alternatively-activated' macrophages. M1 macrophages have been linked with inflammation-associated pathologies, whereas a switch towards an M2 phenotype indicates resolution of inflammation and tissue regeneration. Here, we provide the first comprehensive analysis of the small RNA cargo of EVs from human M1 and M2 primary macrophages. Using small RNA sequencing, we identified several types of small non-coding RNAs in M1 and M2 macrophage EVs including miRNAs, isomiRs, tRNA fragments, piRNA, snRNA, snoRNA and Y-RNA fragments. Distinct differences were observed between M1 and M2 EVs, with higher relative abundance of miRNAs, and lower abundance of tRNA fragments in M1 compared to M2 EVs. MicroRNA-target enrichment analysis identified several gene targets involved in gene expression and inflammatory signalling pathways. EVs were also enriched in tRNA fragments, primarily originating from the 5' end or the internal region of the full length tRNAs, many of which were differentially abundant in M1 and M2 EVs. Similarly, several other small non-coding RNAs, namely snRNAs, snoRNAs and Y-RNA fragments, were differentially enriched in M1 and M2 EVs; we discuss their putative roles in macrophage EVs. In conclusion, we show that M1 and M2 macrophages release EVs with distinct RNA cargo, which has the potential to contribute to the unique effect of these cell subsets on their microenvironment.

Understanding fibrosis pathogenesis via modeling macrophage-fibroblast interplay in immune-metabolic context

Fibrosis is a progressive biological condition, leading to organ dysfunction in various clinical settings. Although fibroblasts and macrophages are known as key cellular players for fibrosis development, a comprehensive functional model that considers their interaction in the metabolic/immunologic context of fibrotic tissue has not been set up. Here we show, by transcriptome-based mathematical modeling in an in vitro system that represents macrophage-fibroblast interplay and reflects the functional effects of inflammation, hypoxia and the adaptive immune context, that irreversible fibrosis development is associated with specific combinations of metabolic and inflammatory cues. The in vitro signatures are in good alignment with transcriptomic profiles generated on laser captured glomeruli and cortical tubule-interstitial area, isolated from human transplanted kidneys with advanced stages of glomerulosclerosis and interstitial fibrosis/tubular atrophy, two clinically relevant conditions associated with organ failure in renal allografts. The model we describe here is validated on tissue based quantitative immune-phenotyping of biopsies from transplanted kidneys, demonstrating its feasibility. We conclude that the combination of in vitro and in silico modeling represents a powerful systems medicine approach to dissect fibrosis pathogenesis, applicable to specific pathological conditions, and develop coordinated targeted approaches.

Extracellular Vesicle Associated miRNAs Regulate Signaling Pathways Involved in COVID-19 Pneumonia and the Progression to Severe Acute Respiratory Corona Virus-2 Syndrome

Background

Extracellular vesicles (EVs) are mediators of cell-to-cell communication in inflammatory lung diseases. They function as carriers for miRNAs which regulate mRNA transcripts and signaling pathways after uptake into recipient cells. We investigated whether miRNAs associated with circulating EVs regulate immunologic processes in COVID-19.

Methods

We prospectively studied 20 symptomatic patients with COVID-19 pneumonia, 20 mechanically ventilated patients with severe COVID-19 (severe acute respiratory corona virus-2 syndrome, ARDS) and 20 healthy controls. EVs were isolated by precipitation, total RNA was extracted, profiled by small RNA sequencing and evaluated by differential gene expression analysis (DGE). Differentially regulated miRNAs between groups were bioinformatically analyzed, mRNA target transcripts identified and signaling networks constructed, thereby comparing COVID-19 pneumonia to the healthy state and pneumonia to severe COVID-19 ARDS.

Results

DGE revealed 43 significantly and differentially expressed miRNAs (25 downregulated) in COVID-19 pneumonia when compared to controls, and 20 miRNAs (15 downregulated) in COVID-19 ARDS patients in comparison to those with COVID-19 pneumonia. Network analysis for comparison of COVID-19 pneumonia to healthy controls showed upregulated miR-3168 (log2FC=2.28, p_adjusted<0.001), among others, targeting interleukin-6 (IL6) (25.1, 15.2 - 88.2 pg/ml in COVID-19 pneumonia) and OR52N2, an olfactory smell receptor in the nasal epithelium. In contrast, miR-3168 was significantly downregulated in COVID-19 ARDS (log2FC=-2.13, p_adjusted=0.003) and targeted interleukin-8 (CXCL8) in a completely activated network. Toll-like receptor 4 (TLR4) was inhibited in COVID-19 pneumonia by miR-146a-5p and upregulated in ARDS by let-7e-5p.

Conclusion

EV-derived miRNAs might have important regulative functions in the pathophysiology of COVID-19: CXCL8 regulates neutrophil recruitment into the lung causing epithelial damage whereas activated TLR4, to which SARS-CoV-2 spike protein binds strongly, increases cell surface ACE2 expression and destroys type II alveolar cells that secrete pulmonary surfactants; both resulting in pulmonary-capillary leakage and ARDS. These miRNAs may serve as biomarkers or as possible therapeutic targets.

Alternative activation of macrophages by prostacyclin synthase ameliorates alcohol induced liver injury

Alcoholic liver disease (ALD) is a major cause of chronic liver disease worldwide. Macrophages exhibit different functional states and are classified as classically activated (M1) and alternatively activated (M2) macrophages. However, the mechanisms that govern M1/M2 polarization in chronic ALD remain to be elucidated. Prostacyclin (PGI2) synthase (PTGIS) is an enzyme of the prostaglandin pathway which catalyzes the conversion of Prostaglandin H2 (PGH2) to PGI2. PTGIS has anti-inflammatory properties. However, the function of PTGIS in ALD has not yet been determined. In this study, we demonstrated that PTGIS was downregulated in ALD and forced PTGIS expression in vivo using recombinant adeno-associated viral vector-packed PTGIS overexpression plasmid, which alleviated the inflammatory response and suppressed the macrophage M1 phenotype in mice. Loss- and gain-of function-experiments demonstrated that forced PTGIS expression inhibited the macrophage switch to the M1 phenotype and promoted M2 polarization. Furthermore, we identified the genes regulated by PTGIS through RNA-sequencing (RNA-seq) analysis. Gene ontology and KEGG pathway analyses showed that PTGIS regulates many genes involved in the immune response and is enriched in the Janus kinase/signal transducers and activators of transcription (JAK/STAT) signal transduction pathway, which plays an important role in regulating macrophage polarization. The proteins interacting with JAKs were predicted using the STRING database. The overlap between the RNA-seq and the STRING database was interleukin-6; this indicated that it was involved in macrophage polarization regulated by JAK/STAT signaling. We further explored the microRNAs that could regulate the expression of PTGIS through TargetScan. The results of luciferase assay illustrated that the expression of PTGIS was regulated by miR-140-3p.1. These results imply that PTGIS plays a pivotal role in ALD, partly by influencing macrophage polarization.

DGCR8 deficiency impairs macrophage growth and unleashes the interferon response to mycobacteria

The mycobacterial cell wall glycolipid trehalose-6,6-dimycolate (TDM) activates macrophages through the C-type lectin receptor MINCLE. Regulation of innate immune cells relies on miRNAs, which may be exploited by mycobacteria to survive and replicate in macrophages. Here, we have used macrophages deficient in the microprocessor component DGCR8 to investigate the impact of miRNA on the response to TDM. Deletion of DGCR8 in bone marrow progenitors reduced macrophage yield, but did not block macrophage differentiation. DGCR8-deficient macrophages showed reduced constitutive and TDM-inducible miRNA expression. RNAseq analysis revealed that they accumulated primary miRNA transcripts and displayed a modest type I IFN signature at baseline. Stimulation with TDM in the absence of DGCR8 induced overshooting expression of IFNβ and IFN-induced genes, which was blocked by antibodies to type I IFN. In contrast, signaling and transcriptional responses to recombinant IFNβ were unaltered. Infection with live Mycobacterium bovis Bacille Calmette-Guerin replicated the enhanced IFN response. Together, our results reveal an essential role for DGCR8 in curbing IFNβ expression macrophage reprogramming by mycobacteria.

MicroRNA-99 family in cancer and immunity

The microRNA (miR)-99 family comprising miR-99a, miR-99b, and miR-100 is an evolutionarily conserved family with existence dating prior to the bilaterians. Members are typically oncogenic in leukemia while their functional roles in other cancers alternate between that of a tumor suppressor and a tumor promoter. Targets of the miR-99 family rank in the lists of oncogenes and tumor suppressors, thereby illustrating the dual role of this miR family as oncogenic miRs (oncomiRs) and tumor suppressing miRs (TSmiRs) in different cellular contexts. In addition to their functional roles in cancers, miR-99 family is implicated in the modulation of macrophage inflammatory responses and T-cell subsets biology, thereby exerting critical roles in the maintenance of tissue homeostasis, establishment of peripheral tolerance as well as resolution of an inflammatory reaction. Here, we review emerging knowledge of this miR family and discuss remaining concerns linked to their activities. A better dissection of the functional roles of miR-99 family members in cancer and immunity will help in the development of novel miR-99-based therapeutics for the treatment of human cancer and immune-related diseases. This article is categorized under: RNA in Disease and Development > RNA in Disease.

Modulation of microRNA processing by 5-lipoxygenase

The miRNA biogenesis is tightly regulated to avoid dysfunction and consequent disease development. Here, we describe modulation of miRNA processing as a novel noncanonical function of the 5-lipoxygenase (5-LO) enzyme in monocytic cells. In differentiated Mono Mac 6 (MM6) cells, we found an in situ interaction of 5-LO with Dicer, a key enzyme in miRNA biogenesis. RNA sequencing of small noncoding RNAs revealed a functional impact, knockout of 5-LO altered the expression profile of several miRNAs. Effects of 5-LO could be observed at two levels. qPCR analyses thus indicated that (a) 5-LO promotes the transcription of the evolutionarily conserved miR-99b/let-7e/miR-125a cluster and (b) the 5-LO-Dicer interaction downregulates the processing of pre-let-7e, resulting in an increase in miR-125a and miR-99b levels by 5-LO without concomitant changes in let-7e levels in differentiated MM6 cells. Our observations suggest that 5-LO regulates the miRNA profile by modulating the Dicer-mediated processing of distinct pre-miRNAs. 5-LO inhibits the formation of let-7e which is a well-known inducer of cell differentiation, but promotes the generation of miR-99b and miR-125a known to induce cell proliferation and the maintenance of leukemic stem cell functions.

Prognostic Impact of let-7e MicroRNA and Its Target Genes in Localized High-Risk Intestinal GIST: A Spanish Group for Research on Sarcoma (GEIS) Study

MicroRNAs (miRNAs) are small non-coding RNAs that negatively regulate gene expression at the post-transcriptional level, and they have been described as being associated with tumor prognosis. Here, miRNA profiling was planned to explore new molecular prognostic biomarkers in localized intestinal high-risk GIST. Paraffin tumor blocks of 14 and 86 patients were used in the discovery and expansion sets, respectively. GeneChip miRNA v3.0 was employed to identify the miRNAs differentially expressed between relapsed and non-relapsed patient samples, which were validated in the expansion set, by qRT-PCR. RT2 Profiler PCR Array was used for the screening of let-7e targets. Expression levels were correlated with relapse-free survival and overall survival. In the discovery set, 39 miRNAs were significantly deregulated, let-7e and miR-550 being the most underexpressed and overexpressed miRNAs in the relapsed group, respectively. In the expansion set, the underexpression of let-7e or the overexpression of 4 of its target genes (ACVR1B, CASP3, COL3A1, and COL5A2) were statistically associated with worse relapse-free survival. The expression of let-7e and 4 of its target genes are potential prognostic biomarkers in high-risk localized intestinal GIST. The expression of these genes is a potential molecular tool useful for a more accurate prognosis in this subset of GIST patients.

microRNAs Shape Myeloid Cell-Mediated Resistance to Cancer Immunotherapy

Immunotherapy with immune checkpoint inhibitors can achieve long-term tumor control in subsets of patients. However, its effect can be blunted by myeloid-induced resistance mechanisms. Myeloid cells are highly plastic and physiologically devoted to wound healing and to immune homeostasis maintenance. In cancer, their physiological activities can be modulated, leading to an expansion of pro-inflammatory and immunosuppressive cells, the myeloid-derived suppressor cells (MDSCs), with detrimental consequences. The involvement of MDSCs in tumor development and progression has been widely investigated and MDSC-induced immunosuppression is acknowledged as a mechanism hindering effective immune checkpoint blockade. Small non-coding RNA molecules, the microRNAs (miRs), contribute to myeloid cell regulation at different levels, comprising metabolism and function, as well as their skewing to a MDSC phenotype. miR expression can be indirectly induced by cancer-derived factors or through direct miR import via extracellular vesicles. Due to their structural stability and their presence in body fluids miRs represent promising predictive biomarkers of resistance, as we recently found by investigating plasma samples of melanoma patients undergoing immune checkpoint blockade. Dissection of the miR-driven involved mechanisms would pave the way for the identification of new druggable targets. Here, we discuss the role of these miRs in shaping myeloid resistance to immunotherapy with a special focus on immunosuppression and immune escape.

MicroRNAs: At the Interface of Metabolic Pathways and Inflammatory Responses by Macrophages

Macrophages are key cells of the innate immune system with functional roles in both homeostatic maintenance of self-tissues and inflammatory responses to external stimuli, including infectious agents. Recent advances in metabolic research have revealed that macrophage functions rely upon coordinated metabolic programs to regulate gene expression, inflammation, and other important cellular processes. Polarized macrophages adjust their use of nutrients such as glucose and amino acids to meet their changing metabolic needs, and this in turn supports the functions of the activated macrophage. Metabolic and inflammatory processes have been widely studied, and a crucial role for their regulation at the post-transcriptional level by microRNAs (miRNAs) has been identified. miRNAs govern many facets of macrophage biology, including direct targeting of metabolic regulators and inflammatory pathways. This review will integrate emerging data that support an interplay between miRNAs and metabolism during macrophage inflammatory responses, highlighting critical miRNAs and miRNA families. Additionally, we will address the implications of these networks for human disease and discuss emerging areas of research in this field.

Lack of TLR4 modifies the miRNAs profile and attenuates inflammatory signaling pathways

TLR4 is a member of the toll-like receptors (TLR) immune family, which are activated by lipopolysaccharide, ethanol or damaged tissue, among others, by triggering proinflammatory cytokines release and inflammation. Lack of TLR4 protects against inflammatory processes and neuroinflammation linked with several neuropathologies. By considering that miRNAs are key post-transcriptional regulators of the proteins involved in distinct cellular processes, including inflammation, this study aimed to assess the impact of the miRNAs profile in mice cortices lacking the TLR4 response. Using mice cerebral cortices and next-generation sequencing (NGS), the findings showed that lack of TLR4 significantly reduced the quantity and diversity of the miRNAs expressed in WT mice cortices. The results also revealed a significant down-regulation of the miR-200 family, while cluster miR-99b/let-7e/miR-125a was up-regulated in TLR4-KO vs. WT. The bioinformatics and functional analyses demonstrated that TLR4-KO presented the systematic depletion of many pathways closely related to the immune system response, such as cytokine and interleukin signaling, MAPK and ion Channels routes, MyD88 pathways, NF-κβ and TLR7/8 pathways. Our results provide new insights into the molecular and biological processes associated with the protective effects of TLR-KO against inflammatory damage and neuroinflammation, and reveal the relevance of the TLR4 receptors response in many neuropathologies.

Transcriptomic microRNA Profiling of Dendritic Cells in Response to Gut Microbiota-Secreted Vesicles

The interconnection between nutrients, metabolites and microbes is a key factor governing the healthy/pathological status of an individual. Thus, microbiota-based research is essential in order to better understand human health and nutrition. Gut bacteria release membrane vesicles (MVs) as an intercellular communication mechanism that allows the direct delivery of factors that prime the host’s innate immune system. We have previously shown that MVs from intestinal E. coli activate dendritic cells (DCs) in a strain-specific manner. To gain insights into the regulatory mechanisms involved, here, we have used an RNA deep sequencing approach to identify differentially expressed miRNAs (microRNAs) in DCs which are challenged by the MVs of the probiotic Nissle 1917 (EcN) or the commensal ECOR12. MicroRNAs are post-transcriptional regulatory mediators that permit the fine tuning of signaling pathways. This approach allowed the identification of a common set of miRNAs which are modulated by MVs from both strains and miRNAs which are differentially expressed in response to EcN or ECOR12 MVs. Based on the differential expression of the target genes and subsequent validation experiments, we correlated some of the selected miRNAs with the reported cytokine profile and specific T cell responses. As far as we know, this is the first study to analyze the regulation of miRNAs in DCs by MVs released by gut microbiota.

Dicer up-regulation by inhibition of specific proteolysis in differentiating monocytic cells

Dicer is a ribonuclease III enzyme in biosynthesis of miRNAs, regulators of gene expression involved in macrophage differentiation. We found a specific truncation of Dicer in monocytic cells resulting from apparently constitutive cleavage by a serine protease. Inhibition of this proteolytic truncation, which occurred during macrophage differentiation in presence of TLR ligands or prostaglandin E₂, up-regulates full-length Dicer and promotes miR biosynthesis. Regulation of transcription of pri-miRNA is one mode to regulate biosynthesis of mature miRNA. Inhibition of constitutive proteolysis of Dicer, as described here, provides a second layer of regulation, at the level of miRNA processing. Our data provide insights to Dicer and miRNAs in macrophage polarization/differentiation, a key process in the innate immune response.

Dicer is a ribonuclease III enzyme in biosynthesis of micro-RNAs (miRNAs). Here we describe a regulation of Dicer expression in monocytic cells, based on proteolysis. In undifferentiated Mono Mac 6 (MM6) cells, full-length Dicer was undetectable; only an ∼50-kDa fragment appeared in Western blots. However, when MM6 cells were treated with zymosan or LPS during differentiation with TGF-β and 1,25diOHvitD3, full-length Dicer became abundant together with varying amounts of ∼170- and ∼50-kDa Dicer fragments. Mass spectrometry identified the Dicer fragments and showed cleavage about 450 residues upstream from the C terminus. Also, PGE₂ (prostaglandin E2) added to differentiating MM6 cells up-regulated full-length Dicer, through EP2/EP4 and cAMP. The TLR stimuli strongly induced miR-146a-5p, while PGE₂ increased miR-99a-5p and miR-125a-5p, both implicated in down-regulation of TNFα. The Ser protease inhibitor AEBSF (4-[2-aminoethyl] benzene sulfonyl fluoride) up-regulated full-length Dicer, both in MM6 cells and in primary human blood monocytes, indicating a specific proteolytic degradation. However, AEBSF alone did not lead to a general increase in miR expression, indicating that additional mechanisms are required to increase miRNA biosynthesis. Finally, differentiation of monocytes to macrophages with M-CSF or GM-CSF strongly up-regulated full-length Dicer. Our results suggest that differentiation regimens, both in the MM6 cell line and of peripheral blood monocytes, inhibit an apparently constitutive Dicer proteolysis, allowing for increased formation of miRNAs.

An Anti-inflammatory microRNA Signature Distinguishes Group 3 Innate Lymphoid Cells From Natural Killer Cells in Human Decidua

Innate lymphoid cells (ILCs) are a heterogeneous subset of lymphocytes deeply implicated in the innate immune responses to different pathogens, in lymphoid organogenesis and in the maintenance of tissue homeostasis. Group 3 innate lymphoid cells (ILC3) have been detected in human decidua, where they play a role in the early inflammatory phase favoring implantation and tissue remodeling as well as in the subsequent regulatory phase preventing fetal rejection and supporting neoangiogenesis. A balance between inflammation and immune tolerance is required to maintain pregnancy, thus maternal immune system must be controlled by finely tuned mechanisms. microRNAs (miRNAs) are small non-coding RNAs with important regulatory roles in immune cells, but their function in decidual ILC3 (dILC3) and in decidual NK (dNK) cells is still undefined. Here, we examined the miRNome by microarray in these cells during the first trimester of pregnancy and compared with miRNA profiles of peripheral blood NK (pbNK) cells from pregnant women. We show that distinct miRNA profiles could clearly distinguish dILC3 from NK cells. Correlation analyses revealed that dNK and pbNK miRNome profiles are more similar to each other as compared to dILC3. In particular, we identified 302 and 279 mature miRNAs differentially expressed in dILC3 as compared to dNK and pbNK, respectively. The expression of miR-574-3p and the miR-99b/let-7e/miR-125a miRNA cluster resulted the most increased in dILC3. Remarkably, gene ontology analysis and pathway enrichments of miRNA targets revealed an involvement of these miRNAs in the promotion of anti-inflammatory responses. In agreement to this finding, we also found a higher expression of the anti-inflammatory miR-146a-5p in dILC3 with respect to NK cells. Overall, our data identified specific miRNA signatures distinguishing dILC3, dNK, and pbNK cells. Our data suggest the existence of a tight epigenetic control mediated by miRNAs in dILC3, potentially acting as a brake to prevent exaggerated inflammatory responses and to maintain the immune homeostasis in the early phases of pregnancy.

Diversity, Mechanisms, and Significance of Macrophage Plasticity

Macrophages are a diverse set of cells present in all body compartments. This diversity is imprinted by their ontogenetic origin (embryonal versus adult bone marrow-derived cells); the organ context; by their activation or deactivation by various signals in the contexts of microbial invasion, tissue damage, and metabolic derangement; and by polarization of adaptive T cell responses. Classic adaptive responses of macrophages include tolerance, priming, and a wide spectrum of activation states, including M1, M2, or M2-like. Moreover, macrophages can retain long-term imprinting of microbial encounters (trained innate immunity). Single-cell analysis of mononuclear phagocytes in health and disease has added a new dimension to our understanding of the diversity of macrophage differentiation and activation. Epigenetic landscapes, transcription factors, and microRNA networks underlie the adaptability of macrophages to different environmental cues. Macrophage plasticity, an essential component of chronic inflammation, and its involvement in diverse human diseases, most notably cancer, is discussed here as a paradigm.

Functional analysis of RPS27 mutations and expression in melanoma

Next-generation sequencing has enabled genetic and genomic characterization of melanoma to an unprecedent depth. However, the high mutational background plus the limited depth of coverage of whole-genome sequencing performed on cutaneous melanoma samples make the identification of novel driver mutations difficult. We sought to explore the somatic mutation portfolio in exonic and gene regulatory regions in human melanoma samples, for which we performed targeted sequencing of tumors and matched germline DNA samples from 89 melanoma patients, identifying known and novel recurrent mutations. Two recurrent mutations found in the RPS27 promoter associated with decreased RPS27 mRNA levels in vitro. Data mining and IHC analyses revealed a bimodal pattern of RPS27 expression in melanoma, with RPS27-low patients displaying worse prognosis. In vitro characterization of RPS27-high and RPS27-low melanoma cell lines, as well as loss-of-function experiments, demonstrated that high RPS27 status provides increased proliferative and invasive capacities, while low RPS27 confers survival advantage in low attachment and resistance to therapy. Additionally, we demonstrate that 10 other cancer types harbor bimodal RPS27 expression, and in those, similarly to melanoma, RPS27-low expression associates with worse clinical outcomes. RPS27 promoter mutation could thus represent a mechanism of gene expression modulation in melanoma patients, which may have prognostic and predictive implications.

MicroRNAs in Inflammatory Heart Diseases and Sepsis-Induced Cardiac Dysfunction: A Potential Scope for the Future?

Background: MicroRNAs (miRNAs) are small, single-stranded RNA sequences that regulate gene expression on a post-transcriptional level. In the last few decades, various trials have investigated the diagnostic and therapeutic potential of miRNAs in several disease entities. Here, we provide a review of the available evidence on miRNAs in inflammatory heart diseases (myocarditis, endocarditis, and pericarditis) and sepsis-induced cardiac dysfunction. Methods: Systematic database research using the PubMed and Medline databases was conducted between July and September 2019 using predefined search terms. The whole review was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Results: In total, 131 studies were screened, 96 abstracts were read, and 69 studies were included in the review. Discussion: In the future, circulating miRNAs could serve as biomarkers for diagnosis and disease monitoring in the context of inflammatory heart diseases and sepsis-induced cardiac dysfunction. Considering the promising results of different animal models, certain miRNAs could also emerge as novel therapeutic approaches in this setting.

Profiling circulating microRNAs in serum of Fasciola gigantica-infected buffalo

Circulating miRNAs are stably existed in serum and plasma and can serve as a novel class of biomarkers for the diagnosis of helminthic infection. Fasciola gigantica, the causative agents of fascioliasis, live in the liver of in humans and ruminants, especially cattle, goat and sheep. In this study, a total of 121 host circulating miRNAs were differentially expressed (2 ≥ fold change, p < 0.05), of which 44 miRNAs were up-regulated and 77 miRNAs were significantly down-regulated. Consistent with the sequencing data, qRT-PCR results showed that the expression levels of bta-miR-21-5p and bta-miR-23a were elevated gradually and bta-miR-125a was decreased gradually at the F. gigantica infection time points. Four F. gigantica-specific miRNAs, including three known miRNAs (fgi-miR-87, fgi-miR-71, and fgi-miR-124), and one novel miRNA (novel miR-1) were identified in the sera of F. gigantica-infected buffaloes. Further analyses demonstrated that two parasite-derived miRNAs (fgi-miR-87 and fgi-miR-71) were specifically detected in sera of F. gigantica-infected buffaloes. These findings will be helpful to understand the roles of circulating miRNAs in host-parasite interaction and to potentiate serum miRNAs as diagnostic targets for F. gigantica.

Regulation of Eicosanoid Pathways by MicroRNAs

Over the last years, many microRNAs (miRNAs) have been identified that regulate the formation of bioactive lipid mediators such as prostanoids and leukotrienes. Many of these miRNAs are involved in complex regulatory circuits necessary for the fine-tuning of biological functions including inflammatory processes or cell growth. A better understanding of these networks will contribute to the development of novel therapeutic strategies for the treatment of inflammatory diseases and cancer. In this review, we provide an overview of the current knowledge of miRNA regulation in eicosanoid pathways with special focus on novel miRNA functions and regulatory circuits of leukotriene and prostaglandin biosynthesis.

miRNAs Involved in M1/M2 Hyperpolarization Are Clustered and Coordinately Expressed in Alcoholic Hepatitis

The innate immune system, including monocytes/macrophages, is critical to the progression of alcoholic liver disease (ALD). In response to chronic ethanol, Kupffer cells, the resident macrophage of livers, and peripheral monocytes become sensitized to bacterial lipopolysaccharides (LPS), express more pro-inflammatory cytokines and exhibit macrophage M1/M2 hyperpolarization. Since miRNAs play an important role in the regulation of M1/M2 polarization, we hypothesized that miRNAs regulating macrophage polarization would be dysregulated after chronic ethanol consumption. miRNA sequencing data from Kupffer cells isolated from rats fed an ethanol diet vs. control diet and qPCR data from PBMCs isolated from alcoholic hepatitis (AH) patients and healthy controls were used to assess the role of miRNAs in macrophage hyperpolarization in ALD. Differential expression analyses revealed 40 misregulated miRNAs in Kupffer cells from the chronic ethanol-fed rats compared to pair-fed controls. Nine of these miRNAs are known to be associated with macrophage polarization and consist of a mixture of M1- and M2-associated miRNAs, indicative of hyperpolarization. Twenty-three of the 40 differentially expressed miRNAs were localized to miRNA clusters throughout the genome. Correlation analyses revealed that miRNAs in three of these clusters were co-regulated and located within antisense non-coding RNAs. Similar to Kupffer cells from ethanol-fed rats, M1 and M2 polarization markers, as well as sensitivity to LPS, were elevated in PBMCs from AH patients compared to healthy controls. These increases were associated with an up-regulation of polarization-associated miRNAs, including miR-125a-5p, a miRNA associated with hyperpolarization. miR-125a-5p is clustered in the genome with other miRNAs inside a host gene, Spaca6, which was also upregulated in PBMCs, as well as isolated monocytes, from AH patients. Finally, correlation analyses revealed co-regulation of human polarization-associated miRNA clusters. While expression of polarization-associated miRNAs in clusters was upregulated in AH compared to healthy controls, co-regulation of the miRNAs within a cluster was independent of disease state. Together, these results reveal that global changes in miRNA regulation are associated with polarization phenotypes in Kupffer cells from rat after chronic ethanol as well as in PBMCs from patients with AH. Importantly, polarization-associated miRNAs were localized to coordinately regulated clusters.

A Review of Macrophage MicroRNAs' Role in Human Asthma

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

MicroRNAs as Molecular Switches in Macrophage Activation

The efficacy of macrophage- mediated inflammatory response relies on the coordinated expression of key factors, which expression is finely regulated at both transcriptional and post-transcriptional level. Several studies have provided compelling evidence that microRNAs play pivotal roles in modulating macrophage activation, polarization, tissue infiltration, and resolution of inflammation. In this review, we highlight the essential molecular mechanisms underlying the different phases of inflammation that are targeted by microRNAs to inhibit or accelerate restoration to tissue integrity and homeostasis. We further review the impact of microRNA-dependent regulation of tumor-associated macrophages and the relative implication for tumor biology.