MicroRNAs as New Regulators of Neutrophil Extracellular Trap Formation

Neutrophil microRNAs

Neutrophils are considered 'first-line defence' cells as they can be rapidly recruited to the site of the immune response. As key components of non-specific immune mechanisms, neutrophils use phagocytosis, degranulation, and formation of neutrophil extracellular traps (NETs) to fight pathogens. Recently, immunoregulatory abilities of neutrophils associated with the secretion of several mediators, including cytokines and extracellular vesicles (EVs) containing, among other components, microRNAs (miRNAs), have also been reported. EVs are small structures released by cells into the extracellular space and are present in all body fluids. Microvesicles show the composition and status of the releasing cell, its physiological state, and pathological changes. Currently, EVs have gained immense scientific interest as they act as transporters of epigenetic information in intercellular communication. This review summarises findings from recent scientific reports that have evaluated the utility of miRNA molecules as biomarkers for effective diagnostics or even as start-points for new therapeutic strategies in neutrophil-mediated immune reactions. In addition, this review describes the current state of knowledge on miRNA molecules, which are endogenous regulators of gene expression besides being involved in the regulation of the immune response.

microRNAs and thrombo-inflammation: relationship in sight

PURPOSE OF REVIEW

Thrombo-inflammation is a multifaceted pathologic process involving various cells such as platelets, neutrophils, and monocytes. In recent years, microRNAs have been consistently implicated as regulators of these cells.

RECENT FINDINGS

MicroRNAs play a regulatory role in several platelet receptors that have recently been identified as contributing to thrombo-inflammation and neutrophil extracellular trap (NET) formation. In addition, a growing body of evidence has shown that several intracellular and extracellular microRNAs directly promote NET formation.

SUMMARY

Targeting microRNAs is a promising therapeutic approach to control thrombosis in patients with both infectious and noninfectious inflammatory diseases. Future research efforts should focus on elucidating the specific roles of microRNAs in thrombo-inflammation and translating these findings into tangible benefits for patients.

miRNA-132-5p mediates a negative feedback regulation of IL-8 secretion through S100A8/A9 downregulation in neutrophil-like HL-60 cells

Background

Neutrophils are an important source of pro-inflammatory and immunomodulatory cytokines. This makes neutrophils efficient drivers of interactions with immune and non-immune cells to maintain homeostasis and modulate the inflammatory process by notably regulating the release of cytokines. Ca2+-dependent regulatory mechanism encompassing cytokine secretion by neutrophils are not still identified. In this context, we propose to define new insights on the role of Ca2+-binding proteins S100A8/A9 and on the regulatory role of miRNA-132-5p, which was identified as a regulator of S100A8/A9 expression, on IL-8 secretion.

Methods

Differentiated HL-60 cells, a human promyelocytic leukemia cell line that can be induced to differentiate into neutrophil-like cells, were used as a model of human neutrophils and treated with N- formyl-methionyl-leucyl-phenylalanine (fMLF), a bacterial peptide that activates neutrophils. shRNA knockdown was used to define the role of selected targets (S100A8/A9 and miRNA-132-5p) on IL-8 secretion.

Results and discussion

Different types of cytokines engage different signaling pathways in the secretion process. IL-8 release is tightly regulated by Ca2+ binding proteins S100A8/A9. miRNA-132-5p is up-regulated over time upon fMLF stimulation and decreases S100A8/A9 expression and IL-8 secretion.

Conclusion

These findings reveal a novel regulatory loop involving S100A8/A9 and miRNA-132-5p that modulates IL-8 secretion by neutrophils in inflammatory conditions. This loop could be a potential target for therapeutic intervention in inflammatory diseases.

miR-146a inhibits ovarian tumor growth in vivo via targeting immunosuppressive neutrophils and enhancing CD8+ T cell infiltration

Immunotherapies have emerged as promising strategies for cancer treatment. However, existing immunotherapies have poor activity in high-grade serous ovarian cancer (HGSC) due to the immunosuppressive tumor microenvironment and the associated low tumoral CD8+ T cell (CTL) infiltration. Through multiple lines of evidence, including integrative analyses of human HGSC tumors, we have identified miR-146a as a master regulator of CTL infiltration in HGSC. Tumoral miR-146a expression is positively correlated with anti-cancer immune signatures in human HGSC tumors, and delivery of miR-146a to tumors resulted in significant reduction in tumor growth in both ID8-p53-/- and IG10 murine HGSC models. Increasing miR-146a expression in tumors improved anti-tumor immune responses by decreasing immune suppressive neutrophils and increasing CTL infiltration. Mechanistically, miR-146a targets IL-1 receptor-associated kinase 1 and tumor necrosis factor receptor-associated factor 6 adaptor molecules of the transcription factor nuclear factor κB signaling pathway in ID8-p53-/- cells and decreases production of the downstream neutrophil chemoattractant, C-X-C motif chemokine ligand 1. In addition to HGSC, tumoral miR-146a expression also correlates strongly with CTL infiltration in other cancer types including thyroid, prostate, breast, and adrenocortical cancers. Altogether, our findings highlight the ability of miR-146a to overcome immune suppression and improve CTL infiltration in tumors.

Exosomal miR-127-5p from BMSCs alleviated sepsis-related acute lung injury by inhibiting neutrophil extracellular trap formation

Neutrophil extracellular traps (NETs) play an important role in sepsis-related acute lung injury (ALI). Bone marrow mesenchymal stem cells (BMSCs)-derived exosomes and miRNA are becoming promising agents for the treatment of ALI. The current study aimed to elucidate the mechanism by BMSCs-derived exosomes carrying miR-127-5p inhibiting to the formation of NETs in sepsis-related ALI. We successfully isolated exosomes from BMSCs and confirmed that miR-127-5p was enriched in the exosomes. ALI mice treated with BMSCs-derived exosomes histologically improved, and the release of NETs and inflammatory factors in lung tissue and peripheral blood of mice also decreased compared with LPS group, while the protective effect of exosomes was attenuated after the knockdown of miR-127-5p. Using dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay, we identified CD64 as a direct target of miR-127-5p. Meanwhile, BMSCs-derived exosomes can synergize with anti-CD64 mab in ALI mice to reduce tissue damage, inhibit the release of inflammatory factors and NETs formation. The synergistic effect of exosomes was attenuated when miR-127-5p was down-regulated. These findings suggest that exosomal miR-127-5p derived from BMSCs is a potential therapeutic agent for treatment of sepsis-induced ALI through reducing NETs formation by targeting CD64.

Role and Therapeutic Targeting Strategies of Neutrophil Extracellular Traps in Inflammation

Neutrophil extracellular traps (NETs) are large DNA reticular structures secreted by neutrophils and decorated with histones and antimicrobial proteins. As a key mechanism for neutrophils to resist microbial invasion, NETs play an important role in the killing of microorganisms (bacteria, fungi, and viruses). Although NETs are mostly known for mediating microbial killing, increasing evidence suggests that excessive NETs induced by stimulation of physical and chemical components, microorganisms, and pathological factors can exacerbate inflammation and organ damage. This review summarizes the induction and role of NETs in inflammation and focuses on the strategies of inhibiting NETosis and the mechanisms involved in pathogen evasion of NETs. Furthermore, herbal medicine inhibitors and nanodelivery strategies improve the efficiency of inhibition of excessive levels of NETs.

Exosomal miRNAs assist in the crosstalk between tumor cells and immune cells and its potential therapeutics

Exosomes are small extracellular vesicles that carry active substances (including proteins, lipids, and nucleic acids) and are essential for homeostasis and signal transmission. Recent studies have focused on the function of exosomal miRNAs in tumor progression. Researchers have expanded the use of exosomes and miRNAs as potential therapeutic tools and biomarkers to detect tumor progression. Immune cells, as an important part of the tumor microenvironment (TME), secrete a majority of exosome-derived miRNAs involved in the biological processes of malignancies. However, the underlying mechanisms remain unclear. Currently, there is no literature that systematically summarizes the communication of exosome-derived miRNAs between tumor cells and immune cells. Based on the cell specificity of exosome-derived miRNAs, this review provides the first comprehensive summary of the significant miRNAs from the standpoint of exosome sources, which are tumor cells and immune cells. Furthermore, we elaborated on the potential clinical applications of these miRNAs, attempting to propose existing difficulties and future possibilities in tumor diagnostics and therapy.

Long noncoding RNA SNHG16 regulates TLR4-mediated autophagy and NETosis formation in alveolar hemorrhage associated with systemic lupus erythematosus

BACKGROUND

Dysregulated long noncoding RNA (lncRNA) expression with increased apoptosis has been demonstrated in systemic lupus erythematosus (SLE) patients with alveolar hemorrhage (AH). SNHG16, a lncRNA, can enhance pulmonary inflammation by sponging microRNAs, and upregulate toll-like receptor 4 (TLR4) expression via stabilizing its mRNAs. TRAF6, a TLR4 downstream signal transducer, can induce autophagy and NETosis formation. In this study, we investigated whether SNHG16 could regulate TLR4-mediated autophagy and NETosis formation in SLE-associated AH.

METHODS

Expression of SNHG16, TLR4 and TRAF6 and cell death processes were examined in lung tissues and peripheral blood (PB) leukocytes from AH patients associated with SLE and other autoimmune diseases, and in the lungs and spleen from a pristane-induced C57BL/6 mouse AH model. SNHG16-overexpressed or -silenced alveolar and myelocytic cells were stimulated with lipopolysaccharide (LPS), a TLR4 agonist, for analyzing autophagy and NETosis, respectively. Pristane-injected mice received the intra-pulmonary delivery of lentivirus (LV)-SNHG16 for overexpression and prophylactic/therapeutic infusion of short hairpin RNA (shRNA) targeting SNHG16 to evaluate the effects on AH. Renal SNHG16 expression was also examined in lupus nephritis (LN) patients and a pristane-induced BALB/c mouse LN model.

RESULTS

Up-regulated SNHG16, TLR4 and TRAF6 expression with increased autophagy and NETosis was demonstrated in the SLE-AH lungs. In such patients, up-regulated SNHG16, TLR4 and TRAF6 expression was found in PB mononuclear cells with increased autophagy and in PB neutrophils with increased NETosis. There were up-regulated TLR4 expression and increased LPS-induced autophagy and NETosis in SNHG16-overexpressed cells, while down-regulated TLR4 expression and decreased LPS-induced autophagy and NETosis in SNHG16-silenced cells. Pristane-injected lung tissues had up-regulated SNHG16, TLR4/TRAF6 levels and increased in situ autophagy and NETosis formation. Intra-pulmonary LV-SNHG16 delivery enhanced AH through up-regulating TLR4/TRAF6 expression with increased cell death processes, while intra-pulmonary prophylactic and early therapeutic sh-SNHG16 delivery suppressed AH by down-regulating TLR4/TRAF6 expression with reduced such processes. In addition, there was decreased renal SNHG16 expression in LN patients and mice.

CONCLUSIONS

Our results demonstrate that lncRNA SNHG16 regulates TLR4-mediated autophagy and NETosis formation in the human and mouse AH lungs, and provide a therapeutic potential of intra-pulmonary delivery of shRNA targeting SNHG16 in this SLE-related lethal manifestation.

Cardiovascular complications of diabetes: role of non-coding RNAs in the crosstalk between immune and cardiovascular systems

Diabetes mellitus, a group of metabolic disorders characterized by high levels of blood glucose caused by insulin defect or impairment, is a major risk factor for cardiovascular diseases and related mortality. Patients with diabetes experience a state of chronic or intermittent hyperglycemia resulting in damage to the vasculature, leading to micro- and macro-vascular diseases. These conditions are associated with low-grade chronic inflammation and accelerated atherosclerosis. Several classes of leukocytes have been implicated in diabetic cardiovascular impairment. Although the molecular pathways through which diabetes elicits an inflammatory response have attracted significant attention, how they contribute to altering cardiovascular homeostasis is still incompletely understood. In this respect, non-coding RNAs (ncRNAs) are a still largely under-investigated class of transcripts that may play a fundamental role. This review article gathers the current knowledge on the function of ncRNAs in the crosstalk between immune and cardiovascular cells in the context of diabetic complications, highlighting the influence of biological sex in such mechanisms and exploring the potential role of ncRNAs as biomarkers and targets for treatments. The discussion closes by offering an overview of the ncRNAs involved in the increased cardiovascular risk suffered by patients with diabetes facing Sars-CoV-2 infection.

Inflammatory microRNAs in cardiovascular pathology: another brick in the wall

The regulatory role of microRNAs (miRNAs) is mainly mediated by their effect on protein expression and is recognized in a multitude of pathophysiological processes. In recent decades, accumulating evidence has interest in these factors as modulatory elements of cardiovascular pathophysiology. Furthermore, additional biological processes have been identified as new components of cardiovascular disease etiology. In particular, inflammation is now considered an important cardiovascular risk factor. Thus, in the present review, we will focus on the role of a subset of miRNAs called inflamma-miRs that may regulate inflammatory status in the development of cardiovascular pathology. According to published data, the most representative candidates that play functional roles in thromboinflammation are miR-21, miR-33, miR-34a, miR-146a, miR-155, and miR-223. We will describe the functions of these miRNAs in several cardiovascular pathologies in depth, with specific emphasis on the molecular mechanisms related to atherogenesis. We will also discuss the latest findings on the role of miRNAs as regulators of neutrophil extracellular traps and their impact on cardiovascular diseases. Overall, the data suggest that the use of miRNAs as therapeutic tools or biomarkers may improve the diagnosis or prognosis of adverse cardiovascular events in inflammatory diseases. Thus, targeting or increasing the levels of adequate inflamma-miRs at different stages of disease could help mitigate or avoid the development of cardiovascular morbidities.

microRNAs as biomarkers of risk of major adverse cardiovascular events in atrial fibrillation

Atrial fibrillation is a complex and multifactorial disease. Although prophylactic anticoagulation has great benefits in avoiding comorbidities, adverse cardiovascular events still occur and thus in recent decades, many resources have been invested in the identification of useful markers in the prevention of the risk of MACE in these patients. As such, microRNAs, that are small non-coding RNAs whose function is to regulate gene expression post-transcriptionally, have a relevant role in the development of MACE. miRNAs, have been investigated for many years as potential non-invasive biomarkers of several diseases. Different studies have shown their utility in the diagnosis and prognosis of cardiovascular diseases. In particular, some studies have associated the presence of certain miRNAs in plasma with the development of MACE in AF. Despite these results, there are still many efforts to be done to allow the clinical use of miRNAs. The lack of standardization concerning the methodology in purifying and detecting miRNAs, still provides contradictory results. miRNAs also have a functional impact in MACE in AF through the dysregulation of immunothrombosis. Indeed, miRNAs may be a link between MACE and inflammation, through the regulation of neutrophil extracellular traps that are a key element in the establishment and evolution of thrombotic events. The use of miRNAs as therapy against thromboinflammatory processes should also be a future approach to avoid the occurrence of MACE in atrial fibrillation.

Neutrophils in pancreatic cancer: Potential therapeutic targets

Pancreatic cancer is a digestive system malignancy and poses a high mortality worldwide. Traditionally, neutrophils have been thought to play a role in acute inflammation. In contrast, their importance during tumor diseases has been less well studied. Generally, neutrophils are recruited into the tumor microenvironment and exert inflammation and tumor-promoting effects. As an essential part of the tumor microenvironment, neutrophils play diverse roles in pancreatic cancer, such as angiogenesis, progression, metastasis and immunosuppression. Additionally, neutrophils can be a new potential therapeutic target in cancer. Inhibitors of cytokines, chemokines and neutrophil extracellular traps can exert antitumor effects. In this review, we describe the role of neutrophils in the development and progression of pancreatic cancer, discuss their potential as therapeutic targets, and aim to provide ideas for improving the prognosis of patients with this malignant tumor disease.

Dysregulated miRNAs network in the critical COVID-19: An important clue for uncontrolled immunothrombosis/thromboinflammation

Known as a pivotal immunohemostatic response, immunothrombosis is activated to restrict the diffusion of pathogens. This beneficial intravascular defensive mechanism represents the close interaction between the immune and coagulation systems. However, its uncontrolled form can be life-threatening to patients with the critical coronavirus disease 2019 (COVID-19). Hyperinflammation and ensuing cytokine storm underlie the activation of the coagulation system, something which results in the provocation of more immune-inflammatory responses by the thrombotic mediators. This vicious cycle causes grave clinical complications and higher risks of mortality. Classified as an evolutionarily conserved family of the small non-coding RNAs, microRNAs (miRNAs) serve as the fine-tuners of genes expression and play a key role in balancing the pro/anticoagulant and pro-/anti-inflammatory factors maintaining homeostasis. Therefore, any deviation from their optimal expression levels or efficient functions can lead to severe complications. Despite their extensive effects on the molecules and processes involved in uncontrolled immunothrombosis, some genetic agents and uncontrolled immunothrombosis-induced interfering factors (e.g., miRNA-single nucleotide polymorphysms (miR-SNPs), the complement system components, nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, and reactive oxygen species (ROS)) have apparently disrupted their expressions/functions. This review study aims to give an overview of the role of miRNAs in the context of uncontrolled immunothrombosis/thromboinflammation accompanied by some presumptive interfering factors affecting their expressions/functions in the critical COVID-19. Detecting, monitoring, and resolving these interfering agents mafy facilitate the design and development of the novel miRNAs-based therapeutic approaches to the reduction of complications incidence and mortality in patients with the critical COVID-19.

The Significance of Neutrophil Extracellular Traps in Colorectal Cancer and Beyond: From Bench to Bedside

Neutrophil extracellular traps (NETs), products of neutrophil death when exposed to certain stimuli, were first proposed as a type of response to bacterial infection in infectious diseases. Since then, extensive studies have discovered its involvement in other non-infectious inflammatory diseases including thromboembolism, autoimmune diseases, and cancer. Colorectal cancer (CRC) is one of the most common malignancies in the world. NET formation is closely associated with tumorigenesis, progression, and metastasis in CRC. Therefore, the application of NETs in clinical practice as diagnostic biomarkers, therapeutic targets, and prognostic predictors has a promising prospect. In addition, therapeutics targeting NETs are significantly efficient in halting tumor progression in preclinical cancer models, which further indicates its potential clinical utility in cancer treatment. This review focuses on the stimuli of NETosis, its pro-tumorigenic activity, and prospective clinical utility primarily in but not limited to CRC.

Bioinformatics analysis for identifying micro-RNAs, long noncoding RNAs, transcription factors, and immune genes regulatory networks in diabetic cardiomyopathy using an integrated bioinformatics analysis

OBJECTIVES

We identified functional genes and studied the underlying molecular mechanisms of diabetic cardiomyopathy (DCM) using bioinformatics tools.

METHODS

Original gene expression profiles were obtained from the GSE21610 and GSE112556 data sets. We used GEO2R to screen the differentially expressed genes (DEGs). Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed on DEGs. Protein-protein interaction (PPI) networks of DEGs were constructed using STRING and hub genes of signaling pathways were identified using Cytoscape. Aberrant hub gene expression was verified using The Cancer Genome Atlas data set.

RESULTS

The DEGs in DCM were mainly enriched in the nuclei and cytoplasm and involved in DCM and chemokine-related signaling pathways. In the PPI network, 32 nodes were chosen as hub nodes and an RNA interaction network was constructed with 517 interactions. The expression of key genes (JPIK3R1, CCR9, XIST, WDFY3.AS2, hsa-miR-144-5p, and hsa-miR-146b-5p) was significantly different between DCM and normal tissues.

CONCLUSIONS

The identified hub genes could be associated with DCM pathogenesis and could be used for treating DCM.

Current Understanding of the Neutrophil Transcriptome in Health and Disease

Neutrophils are key cells of the innate immune system. It is now understood that this leukocyte population is diverse in both the basal composition and functional plasticity. Underlying this plasticity is a post-translational framework for rapidly achieving early activation states, but also a transcriptional capacity that is becoming increasingly recognized by immunologists. Growing interest in the contribution of neutrophils to health and disease has resulted in more efforts to describe their transcriptional activity. Whilst initial efforts focused predominantly on understanding the existing biology, investigations with advanced methods such as single cell RNA sequencing to understand interactions of the entire immune system are revealing higher flexibility in neutrophil transcription than previously thought possible and multiple transition states. It is now apparent that neutrophils utilise many forms of RNA in the regulation of their function. This review collates current knowledge on the nuclei structure and gene expression activity of human neutrophils across homeostasis and disease, before highlighting knowledge gaps that are research priority areas.