Induction of immunomodulatory miR-146a and miR-155 in small intestinal epithelium of Vibrio cholerae infected patients at acute stage of cholera

Epigenetic changes induced by pathogenic Chlamydia spp

Chlamydia trachomatis, C. pneumoniae, and C. psittaci, the three Chlamydia species known to cause human disease, have been collectively linked to several pathologies, including conjunctivitis, trachoma, respiratory disease, acute and chronic urogenital infections and their complications, and psittacosis. In vitro, animal, and human studies also established additional correlations, such as between C. pneumoniae and atherosclerosis and between C. trachomatis and ovarian cancer. As part of their survival and pathogenesis strategies as obligate intracellular bacteria, Chlamydia spp. modulate all three major types of epigenetic changes, which include deoxyribonucleic acid (DNA) methylation, histone post-translational modifications, and microRNA-mediated gene silencing. Some of these epigenetic changes may be implicated in key aspects of pathogenesis, such as the ability of the Chlamydia spp. to induce epithelial-to-mesenchymal transition, interfere with DNA damage repair, suppress cholesterol efflux from infected macrophages, act as a co-factor in human papillomavirus (HPV)-mediated cervical cancer, prevent apoptosis, and preserve the integrity of mitochondrial networks in infected host cells. A better understanding of the individual and collective contribution of epigenetic changes to pathogenesis will enhance our knowledge about the biology of Chlamydia spp. and facilitate the development of novel therapies and biomarkers. Pathogenic Chlamydia spp. contribute to epigenetically-mediated gene expression changes in host cells by multiple mechanisms.

Modes of action and diagnostic value of miRNAs in sepsis

Sepsis is a clinical syndrome defined as a dysregulated host response to infection resulting in life-threatening organ dysfunction. Sepsis is a major public health concern associated with one in five deaths worldwide. Sepsis is characterized by unbalanced inflammation and profound and sustained immunosuppression, increasing patient susceptibility to secondary infections and mortality. microRNAs (miRNAs) play a central role in the control of many biological processes, and deregulation of their expression has been linked to the development of oncological, cardiovascular, neurodegenerative and metabolic diseases. In this review, we discuss the role of miRNAs in sepsis pathophysiology. Overall, miRNAs are seen as promising biomarkers, and it has been proposed to develop miRNA-based therapies for sepsis. Yet, the picture is not so straightforward because of the versatile and dynamic features of miRNAs. Clearly, more research is needed to clarify the expression and role of miRNAs in sepsis, and to promote the use of miRNAs for sepsis management.

Maintenance of gut barrier integrity after injury: Trust your gut microRNAs

The gastrointestinal (GI) tract is a highly dynamic structure essential for digestion, nutrient absorption, and providing an interface to prevent gut bacterial translocation. In order to maintain the barrier function, the gut utilizes many defense mechanisms including proliferation, apoptosis, and apical junctional complexes. Disruption of any of these parameters due to injury or disease could negatively impact the intestinal barrier function and homeostasis resulting in increased intestine inflammation, permeability, bacterial dysbiosis, and tissue damage. MicroRNAs are small noncoding RNA sequences that are master regulators of normal cellular homeostasis. These regulatory molecules affect cellular signaling pathways and potentially serve as candidates for providing a mechanism of impaired gut barrier integrity following GI-related pathologic conditions, ethanol exposure, or trauma such as burn injury. MicroRNAs influence cellular apoptosis, proliferation, apical junction complex expression, inflammation, and the microbiome. Due to their widespread functional affiliations, altered expression of microRNAs are associated with many pathologic conditions. This review explores the role of microRNAs in regulation of intestinal barrier integrity. The studies reviewed demonstrate that microRNAs largely impact intestine barrier function and provide insight behind the observed adverse effects following ethanol and burn injury. Furthermore, these studies suggest that microRNAs are excellent candidates for therapeutic intervention or for biomarkers to manage gut barrier integrity following trauma such as burn injury and other GI-related pathologic conditions.

Vibrio cholerae derived outer membrane vesicles modulate the inflammatory response of human intestinal epithelial cells by inducing microRNA-146a

The small intestinal epithelium of Vibrio cholerae infected patients expresses the immunomodulatory microRNAs miR-146a and miR-155 at acute stage of disease. V. cholerae release outer membrane vesicles (OMVs) that serve as vehicles for translocation of virulence factors including V. cholerae cytolysin (VCC). The aim was to investigate whether OMVs, with and/or without VCC-cargo could be responsible for induction of microRNAs in intestinal epithelial cells and thereby contribute to immunomodulation. Polarized tight monolayers of T84 cells were challenged with OMVs of wildtype and a VCC deletion mutant of the non-O1/non-O139 (NOVC) V. cholerae strain V:5/04 and with soluble VCC. OMVs, with and without VCC-cargo, caused significantly increased levels of miR-146a. Increase was seen already after 2 hours challenge with OMVs and persisted after 12 hours. Challenge with soluble VCC caused significant increases in interleukin-8 (IL-8), tumour necrosis factor-α (TNF-α), CCL20, IL-1β, and IRAK2 mRNA levels while challenge with OMVs did not cause increases in expression levels of any of these mRNAs. These results suggest that V. cholerae bacteria release OMVs that induce miR-146a in order to pave the way for colonization by reducing the strength of an epithelial innate immune defence reaction and also preventing inflammation in the mucosa that factors like VCC can evoke.

Extracellular Vesicles Mediate Mesenchymal Stromal Cell-Dependent Regulation of B Cell PI3K-AKT Signaling Pathway and Actin Cytoskeleton

Mesenchymal stromal cells (MSCs) are adult, multipotent cells of mesodermal origin representing the progenitors of all stromal tissues. MSCs possess significant and broad immunomodulatory functions affecting both adaptive and innate immune responses once MSCs are primed by the inflammatory microenvironment. Recently, the role of extracellular vesicles (EVs) in mediating the therapeutic effects of MSCs has been recognized. Nevertheless, the molecular mechanisms responsible for the immunomodulatory properties of MSC-derived EVs (MSC-EVs) are still poorly characterized. Therefore, we carried out a molecular characterization of MSC-EV content by high-throughput approaches. We analyzed miRNA and protein expression profile in cellular and vesicular compartments both in normal and inflammatory conditions. We found several proteins and miRNAs involved in immunological processes, such as MOES, LG3BP, PTX3, and S10A6 proteins, miR-155-5p, and miR-497-5p. Different in silico approaches were also performed to correlate miRNA and protein expression profile and then to evaluate the putative molecules or pathways involved in immunoregulatory properties mediated by MSC-EVs. PI3K-AKT signaling pathway and the regulation of actin cytoskeleton were identified and functionally validated in vitro as key mediators of MSC/B cell communication mediated by MSC-EVs. In conclusion, we identified different molecules and pathways responsible for immunoregulatory properties mediated by MSC-EVs, thus identifying novel therapeutic targets as safer and more useful alternatives to cell or EV-based therapeutic approaches.

Understanding how combinatorial targeting of TLRs and TNFR family costimulatory members promote enhanced T cell responses

INTRODUCTION

Due to the ability of pathogen-associated molecular patters and tumor necrosis factor receptor (TNFR) family costimulatory agonists to boost T cell responses, studies have combined Toll-like receptor (TLR) ligands with TNFR family costimulatory receptor agonists to induce impressive and long-lasting T cell responses. Although some studies have determined how these combinatorial vaccines promote enhanced T cell responses, much remains unknown about the mechanism used by these combinations to promote synergistic T cell responses - especially in settings of infectious diseases or cancer.

AREAS COVERED

In this review, we look in detail at the signaling pathways induced by combinatorial targeting of TLR and TNFR family costimulatory members that help them promote synergistic T cell responses. Understanding this can greatly aid the development of novel vaccine regimens that promote cellular immune responses, which is essential for treating certain infectious diseases and cancer.

EXPERT OPINION

Vaccines against some infectious diseases as well as therapeutic cancer vaccines require cellular immunity. Therefore, we evaluate here how signaling pathways induced by TLR ligand and costimulatory agonist combinations promote enhanced T cell responses during immunization with model antigens, viral pathogens, or tumor antigens. Once pathways that drive these combinatorial vaccines to boost T cell activation are identified, they can be incorporated in vaccines designed to target pathogens or cancer.

Integrated Lung and Tracheal mRNA-Seq and miRNA-Seq Analysis of Dogs with an Avian-Like H5N1 Canine Influenza Virus Infection

Avian-like H5N1 canine influenza virus (CIV) causes severe respiratory infections in dogs. However, the mechanism underlying H5N1 CIV infection in dogs is unknown. The present study aimed to identify differentially expressed miRNAs and mRNAs in the lungs and trachea in H5N1 CIV-infected dogs through a next-generation sequencing-based method. Eighteen 40-day-old beagles were inoculated intranasally with CIV, A/canine/01/Guangdong/2013 (H5N1) at a tissue culture infectious dose 50 (TCID₅₀) of 10⁶, and lung and tracheal tissues were harvested at 3 and 7 d post-inoculation. The tissues were processed for miRNA and mRNA analysis. By means of miRNA-gene expression integrative negative analysis, we found miRNA–mRNA pairs. Lung and trachea tissues showed 138 and 135 negative miRNA–mRNA pairs, respectively. One hundred and twenty negative miRNA–mRNA pairs were found between the different tissues. In particular, pathways including the influenza A pathway, chemokine signaling pathways, and the PI3K-Akt signaling pathway were significantly enriched in all groups in responses to virus infection. Furthermore, dysregulation of miRNA and mRNA expression was observed in the respiratory tract of H5N1 CIV-infected dogs and notably, TLR4 (miR-146), NF-κB (miR-34c) and CCL5 (miR-335), CCL10 (miR-8908-5p), and GNGT2 (miR-122) were found to play important roles in regulating pathways that resist virus infection. To our knowledge, the present study is the first to analyze miRNA and mRNA expression in H5N1 CIV-infected dogs; furthermore, the present findings provide insights into the molecular mechanisms underlying influenza virus infection.

Over-expression of miR-146b and its regulatory role in intestinal epithelial cell viability, proliferation, and apoptosis in piglets

BACKGROUND

Weaning stress affects the small intestine of piglets. MiR-146b is differentially expressed in suckling and weaned piglets. In this study, we evaluated the effects of miR-146b on cell viability, proliferation, and apoptosis in IPEC-J2 cells.

RESULTS

Transfection with miR-146b mimics successfully increased miR-146b levels by 1000× (P < 0.001). The over-expression of miR-146b significantly promoted the apoptosis (P < 0.01) of IPEC-J2 cells, with no significant effects on cell viability or proliferation. MiR-146b suppressed the luciferase activity of the miR-TLR4-wt by 57% compared with the negative control, while mutation of the miR-146b binding site significantly blocked the suppressive effect (P < 0.05). Western blot results showed that TLR4 levels decreased in IPEC-J2 cells transfected with miR-146b mimics (P < 0.05).

CONCLUSIONS

The over-expression of miR-146b promotes IPEC-J2 cell apoptosis. TLR4 is a direct target of miR-146b in IPEC-J2 cells.

REVIEWERS

This article was reviewed by Eugene Berezikov and Jan B Hoek.

An update: Epstein-Barr virus and immune evasion via microRNA regulation

Epstein-Barr virus (EBV) is an oncogenic virus that ubiquitously establishes life-long persistence in humans. To ensure its survival and maintain its B cell transformation function, EBV has developed powerful strategies to evade host immune responses. Emerging evidence has shown that microRNAs (miRNAs) are powerful regulators of the maintenance of cellular homeostasis. In this review, we summarize current progress on how EBV utilizes miRNAs for immune evasion. EBV encodes miRNAs targeting both viral and host genes involved in the immune response. The miRNAs are found in two gene clusters, and recent studies have demonstrated that lack of these clusters increases the CD4⁺ and CD8⁺ T cell response of infected cells. These reports strongly indicate that EBV miRNAs are critical for immune evasion. In addition, EBV is able to dysregulate the expression of a variety of host miRNAs, which influence multiple immune-related molecules and signaling pathways. The transport via exosomes of EBV-regulated miRNAs and viral proteins contributes to the construction and modification of the inflammatory tumor microenvironment. During EBV immune evasion, viral proteins, immune cells, chemokines, pro-inflammatory cytokines, and pro-apoptosis molecules are involved. Our increasing knowledge of the role of miRNAs in immune evasion will improve the understanding of EBV persistence and help to develop new treatments for EBV-associated cancers and other diseases.