MicroRNA-155 regulates host immune response to postviral bacterial pneumonia via IL-23/IL-17 pathway

miR-155 promotes Th17 differentiation by targeting FOXP3 to aggravate inflammation in MRSA pneumonia

BACKGROUND

Previous researches have clarified that miR-155 is increased in methicillin-resistant Staphylococcus aureus (MRSA) pneumonia, and modulates Th9 differentiation. Like Th9 cells, Th17 cells were also a subset of CD4+ T cells and involved in MRSA pneumonia progression. This work aimed to investigate the role and mechanism of miR-155 in Th17 differentiation.

METHODS

Bronchoalveolar lavage fluid (BALF) was collected from children with MRSA pneumonia and bronchial foreign bodies. MRSA-infected murine model was established followed by collecting BALF and lung tissues. qRT-PCR, ELISA and flow cytometry were performed to examine the mRNA expression and concentration of IL-17 and the number of Th17 cells in above samples. HE and ELISA were used to evaluate inflammatory responses in lung. Furthermore, CD4+ T cells were isolated from BALF of children for in vitro experiments. After treatments with miR-155 mimic/inhibitor, the roles of miR-155 in Th17/IL-17 regulation were determined. The downstream of miR-155 was explored by qRT-PCR, western blotting, dual luciferase reporter analysis and RIP assay.

RESULTS

The levels of IL-17 and the proportion of Th17 cells were increased in children with MRSA pneumonia. A similar pattern was observed in MRSA-infected mice. On the contrary, IL-17 neutralization abolished the activation of Th17/IL-17 induced by MRSA infection. Furthermore, IL-17 blockade diminished the inflammation caused by MRSA. In vitro experiments demonstrated miR-155 positively regulated IL-17 expression and Th17 differentiation. Mechanistically, FOXP3 was a direct target of miR-155. miR-155 inhibited FOXP3 level via binding between FOXP3 and Argonaute 2 (AGO2), the key component of RNA-induced silencing complex (RISC). FOXP3 overexpression reversed elevated IL-17 levels and Th17 differentiation induced by miR-155.

CONCLUSIONS

miR-155 facilitates Th17 differentiation by reducing FOXP3 through interaction of AGO2 and FOXP3 to promote the pathogenesis of MRSA pneumonia. IL-17 blockade weakens the inflammation due to MRSA, which provides a nonantibiotic treatment strategy for MRSA pneumonia.

STAT3 Deficiency Alters the Macrophage Activation Pattern and Enhances Matrix Metalloproteinase 9 Expression during Staphylococcal Pneumonia

Staphylococcus aureus is a significant cause of morbidity and mortality in pulmonary infections. Patients with autosomal-dominant hyper-IgE syndrome due to STAT3 deficiency are particularly susceptible to acquiring staphylococcal pneumonia associated with lung tissue destruction. Because macrophages are involved in both pathogen defense and inflammation, we investigated the impact of murine myeloid STAT3 deficiency on the macrophage phenotype in vitro and on pathogen clearance and inflammation during murine staphylococcal pneumonia. Murine bone marrow-derived macrophages (BMDM) from STAT3 LysMCre+ knockout or Cre- wild-type littermate controls were challenged with S. aureus, LPS, IL-4, or vehicle control in vitro. Pro- and anti-inflammatory responses as well as polarization and activation markers were analyzed. Mice were infected intratracheally with S. aureus, bronchoalveolar lavage and lungs were harvested, and immunohistofluorescence was performed on lung sections. S. aureus infection of STAT3-deficient BMDM led to an increased proinflammatory cytokine release and to enhanced upregulation of costimulatory MHC class II and CD86. Murine myeloid STAT3 deficiency did not affect pathogen clearance in vitro or in vivo. Matrix metalloproteinase 9 was upregulated in Staphylococcus-treated STAT3-deficient BMDM and in lung tissues of STAT3 knockout mice infected with S. aureus. Moreover, the expression of miR-155 was increased. The enhanced inflammatory responses and upregulation of matrix metalloproteinase 9 and miR-155 expression in murine STAT3-deficient as compared with wild-type macrophages during S. aureus infections may contribute to tissue damage as observed in STAT3-deficient patients during staphylococcal pneumonia.

MicroRNAs in infectious diseases: potential diagnostic biomarkers and therapeutic targets

MicroRNAs (miRNAs) are conserved, short, non-coding RNAs that play a crucial role in the post-transcriptional regulation of gene expression. They have been implicated in the pathogenesis of cancer and neurological, cardiovascular, and autoimmune diseases. Several recent studies have suggested that miRNAs are key players in regulating the differentiation, maturation, and activation of immune cells, thereby influencing the host immune response to infection. The resultant upregulation or downregulation of miRNAs from infection influences the protein expression of genes responsible for the immune response and can determine the risk of disease progression. Recently, miRNAs have been explored as diagnostic biomarkers and therapeutic targets in various infectious diseases. This review summarizes our current understanding of the role of miRNAs during viral, fungal, bacterial, and parasitic infections from a clinical perspective, including critical functional mechanisms and implications for their potential use as biomarkers and therapeutic targets.

Memory Th17 cell-mediated protection against lethal secondary pneumococcal pneumonia following influenza infection

Streptococcus pneumoniae (Sp) frequently causes secondary pneumonia after influenza A virus (IAV) infection, leading to high morbidity and mortality worldwide. Concomitant pneumococcal and influenza vaccination improves protection against coinfection but does not always yield complete protection. Impaired innate and adaptive immune responses have been associated with attenuated bacterial clearance in influenza virus-infected hosts. In this study, we showed that preceding low-dose IAV infection caused persistent Sp infection and suppression of bacteria-specific T-helper type 17 (Th17) responses in mice. Prior Sp infection protected against subsequent IAV/Sp coinfection by improving bacterial clearance and rescuing bacteria-specific Th17 responses in the lungs. Furthermore, blockade of IL-17A by anti-IL-17A antibodies abrogated the protective effect of Sp preinfection. Importantly, memory Th17 responses induced by Sp preinfection overcame viral-driven Th17 inhibition and provided cross-protection against different Sp serotypes following coinfection with IAV. These results indicate that bacteria-specific Th17 memory cells play a key role in providing protection against IAV/Sp coinfection in a serotype-independent manner and suggest that a Th17-based vaccine would have excellent potential to mitigate disease caused by coinfection. IMPORTANCE Streptococcus pneumoniae (Sp) frequently causes secondary bacterial pneumonia after influenza A virus (IAV) infection, leading to increased morbidity and mortality worldwide. Current pneumococcal vaccines induce highly strain-specific antibody responses and provide limited protection against IAV/Sp coinfection. Th17 responses are broadly protective against Sp single infection, but whether the Th17 response, which is dramatically impaired by IAV infection in naïve mice, might be effective in immunization-induced protection against pneumonia caused by coinfection is not known. In this study, we have revealed that Sp-specific memory Th17 cells rescue IAV-driven inhibition and provide cross-protection against subsequent lethal coinfection with IAV and different Sp serotypes. These results indicate that a Th17-based vaccine would have excellent potential to mitigate disease caused by IAV/Sp coinfection.

RNA2Immune: A Database of Experimentally Supported Data Linking Non-coding RNA Regulation to The Immune System

Non-coding RNAs (ncRNAs), such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), have emerged as important regulators of the immune system and are involved in the control of immune cell biology, disease pathogenesis, as well as vaccine responses. A repository of ncRNA-immune associations will facilitate our understanding of ncRNA-dependent mechanisms in the immune system and advance the development of therapeutics and prevention for immune disorders. Here, we describe a comprehensive database, RNA2Immune, which aims to provide a high-quality resource of experimentally supported database linking ncRNA regulatory mechanisms to immune cell function, immune disease, cancer immunology, and vaccines. The current version of RNA2Immune documents 50,433 immune-ncRNA associations in 42 host species, including (1) 6690 ncRNA associations with immune functions involving 31 immune cell types; (2) 38,672 ncRNA associations with 348 immune diseases; (3) 4833 ncRNA associations with cancer immunology; and (4) 238 ncRNA associations with vaccine responses involving 26 vaccine types targeting 22 diseases. RNA2Immune provides a user-friendly interface for browsing, searching, and downloading ncRNA-immune system associations. Collectively, RNA2Immune provides important information about how ncRNAs influence immune cell function, how dysregulation of these ncRNAs leads to pathological consequences (immune diseases and cancers), and how ncRNAs affect immune responses to vaccines. RNA2Immune is available at http://bio-bigdata.hrbmu.edu.cn/rna2immune/home.jsp.

Exploring the Role of a Novel Interleukin-17 Homolog from Invertebrate Marine Mussel Mytilus coruscus in Innate Immune Response: Is Negative Regulation by Mc-Novel_miR_145 the Key?

Interleukin-17 (IL-17) represents a class of proinflammatory cytokines involved in chronic inflammatory and degenerative disorders. Prior to this study, it was predicted that an IL-17 homolog could be targeted by Mc-novel_miR_145 to participate in the immune response of Mytilus coruscus. This study employed a variety of molecular and cell biology research methods to explore the association between Mc-novel_miR_145 and IL-17 homolog and their immunomodulatory effects. The bioinformatics prediction confirmed the affiliation of the IL-17 homolog with the mussel IL-17 family, followed by quantitative real-time PCR assays (qPCR) to demonstrate that McIL-17-3 was highly expressed in immune-associated tissues and responded to bacterial challenges. Results from luciferase reporter assays confirmed the potential of McIL-17-3 to activate downstream NF-κb and its targeting by Mc-novel_miR_145 in HEK293 cells. The study also produced McIL-17-3 antiserum and found that Mc-novel_miR_145 negatively regulates McIL-17-3 via western blotting and qPCR assays. Furthermore, flow cytometry analysis indicated that Mc-novel_miR_145 negatively regulated McIL-17-3 to alleviate LPS-induced apoptosis. Collectively, the current results showed that McIL-17-3 played an important role in molluscan immune defense against bacterial attack. Furthermore, McIL-17-3 was negatively regulated by Mc-novel_miR_145 to participate in LPS-induced apoptosis. Our findings provide new insights into noncoding RNA regulation in invertebrate models.

Enhanced Therapeutic Efficacy of Immunostimulatory CpG-ODN by Silencing SOCS-1 with Polysaccharide/miR-155 Complexes

For the induction of antigen-specific immune responses, adjuvants as well as antigens are essential. CpG-ODN is a potent agonist of toll-like receptor 9 (TLR9) and is known as an adjuvant to induce cellular immune responses. We previously developed a therapeutic oligonucleotide delivery system based on the formation of a complex between schizophyllan (SPG), a kind of β-1,3-glucan, and poly(dA), which actively delivered CpG-ODN to antigen-presenting cells (APCs) in the draining lymph nodes and induced antigen-specific immune responses. However, unfortunately, the signaling pathway of TLR9 is negatively regulated by an intracellular protein called suppressor of cytokine signaling-1 (SOCS-1), which suppresses the adjuvant effect of CpG-ODN. To solve this, we focused on microRNA-155 (miR-155), which regulates innate and autoimmune processes by targeting SOCS-1. In this study, we proposed a strategy of combining miR-155 and CpG-ODN, each complexed with SPG (denoted as SPG/miR-155 and SPG/CpG, respectively), to induce a more potent immune response. As a result, we showed that the efficient delivery of miR-155 to APCs by a complex form could induce much more potent cellular immune responses than SPG/CpG alone. Furthermore, the mice treated with the combination of SPG/miR-155 and SPG/CpG showed a long delay in tumor growth occurrence and improved survival after tumor inoculation. These results indicate the possibility of therapeutic strategies for cancer.

Myeloid miR-155 plays a limited role in antibacterial defense during Klebsiella-derived pneumosepsis and is dispensable for lipopolysaccharide- or Klebsiella-induced inflammation in mice

MicroRNA-155 (miR-155) plays a crucial role in regulating host inflammatory responses during bacterial infection. Previous studies have shown that constitutive miR-155 deficiency alleviates inflammation while having varying effects in different bacterial infection models. However, whether miR-155 in myeloid cells is involved in the regulation of inflammatory and antibacterial responses is largely elusive. Mice with myeloid cell specific miR-155 deficiency were generated to study the in vitro response of bone marrow-derived macrophages (BMDMs), alveolar macrophages (AMs) and peritoneal macrophages (PMs) to lipopolysaccharide (LPS), and the in vivo response after intranasal or intraperitoneal challenge with LPS or infection with Klebsiella (K.) pneumoniae via the airways. MiR-155-deficient macrophages released less inflammatory cytokines than control macrophages upon stimulation with LPS in vitro. However, the in vivo inflammatory cytokine response to LPS or K. pneumoniae was not affected by myeloid miR-155 deficiency. Moreover, bacterial outgrowth in the lungs was not altered in myeloid miR-155-deficient mice, but Klebsiella loads in the liver of these mice were significantly higher than in control mice. These data argue against a major role for myeloid miR-155 in host inflammatory responses during LPS-induced inflammation and K. pneumoniae-induced pneumosepsis but suggest that myeloid miR-155 contributes to host defense against Klebsiella infection in the liver.

The role of serum circulating microbial toxins in severity and cytokine storm of COVID positive patients

The emergence of Coronavirus disease 2019 (Covid-19) is a global problem nowadays, causing health difficulty with increasing mortality rates, which doesn't have a verified treatment. SARS-CoV-2 infection has various pathological and epidemiological characteristics, one of them is increased amounts of cytokine production, which in order activate an abnormal unrestricted response called "cytokine storm". This event contributes to severe acute respiratory distress syndrome (ARDS), which results in respiratory failure and pneumonia and is the great cause of death associated with Covid-19. Endotoxemia and the release of bacterial lipopolysaccharides (endotoxins) from the lumen into the bloodstream enhance proinflammatory cytokines. SARS-CoV-2 can straightly interplay with endotoxins via its S protein, leading to the extremely elevating release of cytokines and consequently increase the harshness of Covid-19. In this review, we will discuss the possible role of viral-bacterial interaction that occurs through the transfer of bacterial products such as lipopolysaccharide (LPS) from the intestine into the bloodstream, exacerbating the severity of Covid-19 and cytokine storms.

PI3K/AKT-mediated autophagy inhibition facilitates mast cell activation to enhance severe inflammatory lung injury in influenza A virus- and secondary Staphylococcus aureus-infected mice

Influenza A virus infection causes considerable morbidity and mortality each year globally, and secondary bacterial infection further exacerbates the severity and fatality of the initial viral infection. Mast cells have substantial roles in protecting the respiratory tract mucosa, while their role in viral and bacterial co-infection remains unclear. The present study revealed that secondary Staphylococcus aureus infection significantly aggravated the activation of mast cells during the initial H1N1 infection both in vivo and in vitro, which was closely related to the increased inflammatory lung injury and mortality. Meanwhile, the secondary S. aureus infection suppressed autophagy and promoted inflammatory mediators released by mast cells through activating the PI3K/Akt signaling pathway. Blocking PI3K/Akt pathway by LY294002, an inhibitor of Akt phosphorylation, could rescue autophagy and inhibit the release of inflammatory mediators. Furthermore, based on the influenza A viral and secondary bacterial infected mice model, we showed that the combination of LY294002 and antiviral drug oseltamivir could effectively reduce the inflammatory damage and pro-inflammatory cytokines releasing in lungs, recovering body weight loss and improving the survival rate from the co-infections. In conclusion, secondary bacterial infection can inhibit autophagy and stimulate mast cell activation through the PI3K/Akt pathway, which might explain why secondary bacterial infection would cause severe and fatal consequences following an initial influenza A viral infection.

Cytokines and microRNAs in SARS-CoV-2: What do we know?

The coronavirus disease 2019 (COVID-19) pandemic constitutes a global health emergency. Currently, there are no completely effective therapeutic medications for the management of this outbreak. The cytokine storm is a hyperinflammatory medical condition due to excessive and uncontrolled release of pro-inflammatory cytokines in patients suffering from severe COVID-19, leading to the development of acute respiratory distress syndrome (ARDS) and multiple organ dysfunction syndrome (MODS) and even mortality. Understanding the pathophysiology of COVID-19 can be helpful for the treatment of patients. Evidence suggests that the levels of tumor necrosis factor alpha (TNF-α) and interleukin (IL)-1 and IL-6 are dramatically different between mild and severe patients, so they may be important contributors to the cytokine storm. Several serum markers can be predictors for the cytokine storm. This review discusses the cytokines involved in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, focusing on interferons (IFNs) and ILs, and whether they can be used in COVID-19 treatment. Moreover, we highlight several microRNAs that are involved in these cytokines and their role in the cytokine storm caused by COVID-19.

Biology of lung macrophages in health and disease

Tissue-resident alveolar and interstitial macrophages and recruited macrophages are critical players in innate immunity and maintenance of lung homeostasis. Until recently, assessing the differential functional contributions of tissue-resident versus recruited macrophages has been challenging because they share overlapping cell surface markers, making it difficult to separate them using conventional methods. This review describes how scRNA-seq and spatial transcriptomics can separate these subpopulations and help unravel the complexity of macrophage biology in homeostasis and disease. First, we provide a guide to identifying and distinguishing lung macrophages from other mononuclear phagocytes in humans and mice. Second, we outline emerging concepts related to the development and function of the various lung macrophages in the alveolar, perivascular, and interstitial niches. Finally, we describe how different tissue states profoundly alter their functions, including acute and chronic lung disease, cancer, and aging.

Ursolic acid represses influenza A virus-triggered inflammation and oxidative stress in A549 cells by modulating the miR-34c-5p/TLR5 axis

BACKGROUND

Ursolic acid (UA) is a pentacyclic triterpenoid compound with a wide range of anti-tumor, anti-inflammatory, hypotensive and other pharmacological effects. Here, the biological roles and regulatory mechanisms of UA in influenza A virus (IAV)-treated A549 cells were investigated.

METHOD

The cytotoxic impacts of UA on A549 cells with or without IAV treatment were determined using MTT and LDH assays. The inflammatory responses and oxidative stress of IAV-treated A549 cells were measured by RT-qPCR, ELISA, DCFH-DA probe, and colorimetric assays. A dual luciferase assay was carried out to validate the molecular interaction between miR-34c-5p and TLR5. Promoter methylation was detected by MSP experiment. Methylation-related proteins were quantified by western blot. Virus replication was assessed by TCID50 and western blot assays.

RESULTS

UA significantly ameliorated IAV-triggered cell injury and inflammatory response, virus replication and oxidative stress by elevating cell viability, ROS level and the activities of SOD and GSH-Px but reducing the LDH, MDA, and TCID50 values and the expression of virus-related proteins (NP) and cytokines (TNF-α, IL-1β, IL-6, and IL-18). Moreover, UA promoted miR-34c-5p expression by repressing DNMTs-mediated methylation. TLR5 was verified to be a direct target of miR-34c-5p and could be downregulated by UA. Rescue experiments revealed that silencing miR-34c-5p diminished the regulatory roles of UA in IAV-treated A549 cells.

CONCLUSION

Our data elucidated that UA attenuated IAV-triggered inflammatory responses and oxidative stress in A549 cells by regulating the miR-34c-5p/TLR5 axis, suggesting that UA plays a protective role in IAV-induced pneumonia.

The current landscape of microRNAs (miRNAs) in bacterial pneumonia: opportunities and challenges

MicroRNAs (miRNAs), which were initially discovered in Caenorhabditis elegans, can regulate gene expression by recognizing cognate sequences and interfering with the transcriptional or translational machinery. The application of bioinformatics tools for structural analysis and target prediction has largely driven the investigation of certain miRNAs. Notably, it has been found that certain miRNAs which are widely involved in the inflammatory response and immune regulation are closely associated with the occurrence, development, and outcome of bacterial pneumonia. It has been shown that certain miRNA techniques can be used to identify related targets and explore associated signal transduction pathways. This enhances the understanding of bacterial pneumonia, notably for "refractory" or drug-resistant bacterial pneumonia. Although these miRNA-based methods may provide a basis for the clinical diagnosis and treatment of this disease, they still face various challenges, such as low sensitivity, poor specificity, low silencing efficiency, off-target effects, and toxic reactions. The opportunities and challenges of these methods have been completely reviewed, notably in bacterial pneumonia. With the continuous improvement of the current technology, the miRNA-based methods may surmount the aforementioned limitations, providing promising support for the clinical diagnosis and treatment of "refractory" or drug-resistant bacterial pneumonia.

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.

Understanding microRNAs in the Context of Infection to Find New Treatments against Human Bacterial Pathogens

The development of RNA-based anti-infectives has gained interest with the successful application of mRNA-based vaccines. Small RNAs are molecules of RNA of <200 nucleotides in length that may control the expression of specific genes. Small RNAs include small interference RNAs (siRNAs), Piwi-interacting RNAs (piRNAs), or microRNAs (miRNAs). Notably, the role of miRNAs on the post-transcriptional regulation of gene expression has been studied in detail in the context of cancer and many other genetic diseases. However, it is also becoming apparent that some human miRNAs possess important antimicrobial roles by silencing host genes essential for the progress of bacterial or viral infections. Therefore, their potential use as novel antimicrobial therapies has gained interest during the last decade. The challenges of the transport and delivery of miRNAs to target cells are important, but recent research with exosomes is overcoming the limitations in RNA-cellular uptake, avoiding their degradation. Therefore, in this review, we have summarised the latest developments in the exosomal delivery of miRNA-based therapies, which may soon be another complementary treatment to pathogen-targeted antibiotics that could help solve the problem caused by multidrug-resistant bacteria.

Bacterial and viral infections and related inflammatory responses in chronic obstructive pulmonary disease

In chronic obstructive pulmonary disease (COPD) patients, bacterial and viral infections play a relevant role in worsening lung function and, therefore, favour disease progression. The inflammatory response to lung infections may become a specific indication of the bacterial and viral infections. We here review data on the bacterial-viral infections and related airways and lung parenchyma inflammation in stable and exacerbated COPD, focussing our attention on the prevalent molecular pathways in these different clinical conditions. The roles of macrophages, autophagy and NETosis are also briefly discussed in the context of lung infections in COPD. Controlling their combined response may restore a balanced lung homeostasis, reducing the risk of lung function decline. KEY MESSAGE Bacteria and viruses can influence the responses of the innate and adaptive immune system in the lung of chronic obstructive pulmonary disease (COPD) patients. The relationship between viruses and bacterial colonization, and the consequences of the imbalance of these components can modulate the inflammatory state of the COPD lung. The complex actions involving immune trigger cells, which activate innate and cell-mediated inflammatory responses, could be responsible for the clinical consequences of irreversible airflow limitation, lung remodelling and emphysema in COPD patients.

MicroRNA-155 and antiviral immune responses

The microRNA, miR-155 regulates both adaptive and innate immune responses. In viral infections, miR-155 can affect both innate immunity (interferon response, natural killer cell activity, and macrophage polarization) and adaptive immunity (including generation of anti-viral antibodies, CD8⁺ cytotoxic T lymphocytes, Th17, Th2, Th1, Tfh and Treg cells). In many viral infections, the proper and timely regulation of miR-155 expression is critical for the induction of an effective anti-virus immune response and viral clearance without any harmful immunopathologic consequences. MiR-155 may also exert pro-viral effects, mainly through the inhibition of the anti-viral interferon response. Thus, dysregulated expression of miR-155 can result in virus persistence and disruption of the normal response to viral infections. This review provides a thorough discussion of the role of miR-155 in immune responses and immunopathologic reactions during viral infections, and highlights its potential as a therapeutic target.

MiR-155 regulates Th9 differentiation in children with methicillin-resistant Staphylococcus aureus pneumonia by targeting SIRT1

Th9 is a subset of CD4⁺ T cells that mainly secrete IL-9. Th9/IL-9 participates in immune response during Staphylococcus aureus and methicillin-resistant Staphylococcus aureus pneumonia (MRSA) infection. Here, we collected bronchoalveolar lavage fluid (BALF) from 30 children with MRSA pneumonia (MRSA group) and 10 children with bronchial foreign bodies (Control group). RT-PCR, ELISA and flow cytometry were used to detect the expression of miR-155 and IL-9 in BALF and the number of Th9 cells. CD4⁺ T cells isolated from BALF of MRSA and Control group were transfected with miR-155 mimic or inhibitor, and then induced Th9 cell differentiation. The results showed that the expression of miR-155 and IL-9 were significantly increased in BALF and Th9 cell of MRSA group, as well as the number of Th9 cells. miR-155 mimic upregulated IL-9 mRNA expression, IL-9 secretion and increased number of Th9 cells. On the contrary, miR-155 inhibitor inhibited IL-9 mRNA expression, IL-9 secretion and decreased number of Th9 cells. The dual luciferase assays demonstrated miR-155 can target binding to SIRT1 3'UTR. Moreover, overexpression of SIRT1 could reverse the effect of miR-155 mimic on IL-9 expression level, Th9 cell number and transcription factors PU.1 and IRF4 expression. In conclusion, miR-155 regulates Th9 differentiation in children with MRSA by targeting SIRT1.

Down-regulation of miR-155 inhibits inflammatory response in human pulmonary microvascular endothelial cells infected with influenza A virus by targeting sphingosine-1-phosphate receptor 1

Background:

Endothelial cells play a key role in the cytokine storm caused by influenza A virus. MicroRNA-155 (miR-155) is an important regulator in inflammation. Its role in the inflammatory response to influenza A infection, however, has yet to be elucidated. In this study, we explored the role as well as the underlying mechanism of miR-155 in the cytokine production in influenza A-infected endothelial cells.

Methods:

Human pulmonary microvascular endothelial cells (HPMECs) were infected with the influenza A virus strain H1N1. The efficiency of H1N1 infection was confirmed by immunofluorescence. The expression levels of proinflammatory cytokines and miR-155 were determined using real-time polymerase chain reaction. A dual-luciferase reporter assay characterized the interaction between miR-155 and sphingosine-1-phosphate receptor 1 (S1PR1). Changes in the target protein levels were determined using Western blot analysis.

Results:

MiR-155 was elevated in response to the H1N1 infection in HPMECs (24 h post-infection vs. 0 h post-infection, 3.875 ± 0.062 vs. 1.043 ± 0.013, P = 0.001). Over-expression of miR-155 enhanced inflammatory cytokine production (miR-155 mimic vs. negative control, all P < 0.05 in regard of cytokine levels) and activation of nuclear factor kappa B in infected HPMECs (miR-155 mimic vs. negative control, P = 0.004), and down-regulation of miR-155 had the opposite effect. In addition, S1PR1 was a direct target of miR-155 in the HPMECs. Inhibition of miR-155 enhanced the expression of the S1PR1 protein. Down-regulation of S1PR1 decreased the inhibitory effect of the miR-155 blockade on H1N1-induced cytokine production and nuclear factor kappa B activation in HPMECs.

Conclusion:

MiR-155 maybe modulate influenza A-induced inflammatory response by targeting S1PR1.

Extracellular Vesicle Associated Non-Coding RNAs in Lung Infections and Injury

Extracellular vesicles (EVs) refer to a heterogenous population of membrane-bound vesicles that are released by cells under physiological and pathological conditions. The detection of EVs in the majority of the bodily fluids, coupled with their diverse cargo comprising of DNA, RNA, lipids, and proteins, have led to the accumulated interests in leveraging these nanoparticles for diagnostic and therapeutic purposes. In particular, emerging studies have identified enhanced levels of a wide range of specific subclasses of non-coding RNAs (ncRNAs) in EVs, thereby suggesting the existence of highly selective and regulated molecular processes governing the sorting of these RNAs into EVs. Recent studies have also illustrated the functional relevance of these enriched ncRNAs in a variety of human diseases. This review summarizes the current state of knowledge on EV-ncRNAs, as well as their functions and significance in lung infection and injury. As a majority of the studies on EV-ncRNAs in lung diseases have focused on EV-microRNAs, we will particularly highlight the relevance of these molecules in the pathophysiology of these conditions, as well as their potential as novel biomarkers therein. We also outline the current challenges in the EV field amidst the tremendous efforts to propel the clinical utility of EVs for human diseases. The lack of published literature on the functional roles of other EV-ncRNA subtypes may in turn provide new avenues for future research to exploit their feasibility as novel diagnostic and therapeutic targets in human diseases.

Critical role of microRNAs in host and influenza A (H1N1) virus interactions

As a type of non-coding RNA, microRNAs are considered to be a new regulator in viral infections. Influenza A (H1N1) virus infection is a serious threat to human health. There is growing evidence supporting that microRNAs play important roles in various cellular infection stages and host antiviral response during H1N1 infection. Some microRNAs defend against H1N1 invasion, while others may promote viral replication. MicroRNAs are implicated in the host-viral interactions and serve versatile functions in it. In this review, we focus on the innate immune response and virus replication regulated by microRNAs during H1N1 infection. MicroRNAs can influence H1N1 virus replication by directly binding to viral compositions and through host cellular pathways. Moreover, microRNAs are involved in multiple antiviral response, including production of interferons (IFNs), retinoic acid-inducible gene I (RIG-I) signaling pathway, immune cells development and secretion, activation of nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB). Furthermore, these regulatory effects of microRNAs suggest its potential clinical significance. In addition, another non-coding RNA, lncRNA, are also mentioned in the review, which can regulate innate immune response and influence virus replication during H1N1 infection as well.

miR-122 promotes virus-induced lung disease by targeting SOCS1

Virus-induced respiratory tract infections are a major health burden in childhood, and available treatments are supportive rather than disease modifying. Rhinoviruses (RVs), the cause of approximately 80% of common colds, are detected in nearly half of all infants with bronchiolitis and the majority of children with an asthma exacerbation. Bronchiolitis in early life is a strong risk factor for the development of asthma. Here, we found that RV infection induced the expression of miRNA 122 (miR-122) in mouse lungs and in human airway epithelial cells. In vivo inhibition specifically in the lung reduced neutrophilic inflammation and CXCL2 expression, boosted innate IFN responses, and ameliorated airway hyperreactivity in the absence and in the presence of allergic lung inflammation. Inhibition of miR-122 in the lung increased the levels of suppressor of cytokine signaling 1 (SOCS1), which is an in vitro-validated target of miR-122. Importantly, gene silencing of SOCS1 in vivo completely reversed the protective effects of miR-122 inhibition on RV-induced lung disease. Higher miR-122 expression in nasopharyngeal aspirates was associated with a longer time on oxygen therapy and a higher rate of treatment failure in 87 infants hospitalized with moderately severe bronchiolitis. These results suggest that miR-122 promotes RV-induced lung disease via suppression of its target SOCS1 in vivo. Higher miR-122 expression was associated with worse clinical outcomes, highlighting the potential use of anti-miR-122 oligonucleotides, successfully trialed for treatment of hepatitis C, as potential therapeutics for RV-induced bronchiolitis and asthma exacerbations.

MicroRNA-4485 ameliorates severe influenza pneumonia via inhibition of the STAT3/PI3K/AKT signaling pathway

The present study aimed to explore the potential roles and mechanism of microRNA-4485 (miR-4485) in severe influenza pneumonia. miR-4485 expression was detected in patients with severe H1N1 pneumonia using quantitative PCR. Furthermore, the effects of aberrantly expressed miR-4485 on H1N1-infected A549 cells were investigated using Cell Counting Kit-8, terminal deoxynucleotidyl transferase dUTP nick end labeling, western blotting and (ELISA) assays. Furthermore, the regulatory relationships between miR-4485 and the STAT3-mediated PI3K/AKT/mTOR signaling pathway were explored using a luciferase reporter and rescue assay. MiR-4485 expression was downregulated following H1N1 infection and in patients with H1N1 pneumonia. In addition, miR-4485 alleviated H1N1-induced A549 cell injury by promoting cell viability and the production of cytokines, as well as reducing apoptosis in A549 cells. Furthermore, STAT3 was revealed to be a target gene of miR-4485. Additionally, STAT3 silencing reversed the protective effects of miR-4485 knockdown on H1N1-induced cell injury via inhibition of the PI3K/AKT/mTOR signaling pathway. In conclusion, miR-4485 inhibited H1N1-induced severe pneumonia in A549 cells by targeting STAT3 via the PI3K/AKT/mTOR signaling pathway.

miR-26a-5p mediates TLR signaling pathway by targeting CTGF in LPS-induced alveolar macrophage

To explore the regulation mechanism of miR-26a-5p and connective tissue growth factor (CTGF) in lipopolysaccharide (LPS)-induced alveolar macrophages, which is a severe pneumonia cell model. MH-S cells were grouped into Normal group, Model group, negative control (NC) group, miR-26a-5p mimic group, oe-CTGF group, miR-26a-5p mimic + oe-CTGF group. The expression level of miR-26a-5p, CTGF and Toll-like receptor (TLR) signaling related molecules (TLR2, TLR4 and nuclear factor-κB p65) were detected by qRT-PCR and WB, respectively. The cell viability and apoptosis rate were detected by methyl thiazolyl tetrazolium (MTT) and flow cytometry, respectively. Compared with the Normal group, the expression level of miR-26a-5p was significantly decreased, while CTGF protein level was significantly increased in the Model group. Compared with the Model group, MH-S cells with miR-26a-5p overexpression showed enhanced cell viability, decreased apoptosis rate, declined expression level of TLR signaling related molecules and reduced level of tumor necrosis factor-α (TNF-α), interleukin (IL) 6 (IL-6) and IL-1β, while those with CTGF overexpression had an opposite phenotype. In conclusion, miR-26a-5p can inhibit the expression of CTGF and mediate TLR signaling pathway to inhibit the cell apoptosis and reduce the expression of proinflammatory cytokines in alveolar macrophages which is a cell model of severe pneumonia.

DsRNA induction of microRNA-155 disrupt tight junction barrier by modulating claudins

Background

The impaired barrier function of the airway epithelium due to RNA virus infection is closely related to the development and exacerbation of allergic airway inflammation.

Objective

In this study, we investigated the roles of microRNAs on the mechanisms of double-stranded RNA (dsRNA)-induced epithelial barrier dysfunction.

Methods

16HBE14o- human bronchial epithelial cells were grown to confluence on Transwell inserts and exposed to poly-I:C. We studied epithelial barrier function by measuring transepithelial electrical resistance and paracellular flux of fluorescent markers and structure of tight junctions by immunofluorescence microscopy.

Results

Poly-I:C treated 16HBE14o- cells increased paracellular permeability. Knockdown of Toll-like receptor 3 and TRIF abrogated these effects. The expression of microRNA-155 (miR-155) was increased by poly-I:C in dose-dependent manner. Transfection of mir155 mimics into 16HBE14o- cells increased permeability and inhibited tight junction formation. Transfection of miR-155 inhibitor suppressed poly-I:C-induced barrier disruption. Poly-I:C treatment significantly decreased the expression of claudin members—claudin-1, -3, -4, -5, -9, -11, -16, -18 and -19. Transfection of miR-155 mimics showed similar changing expression pattern of claudin members with those of poly-I:C treatment.

Conclusion

These results suggest that RNA virus infection can impair the epithelial barrier disruption mechanism by down-regulation of claudin members through the induction of miR-155.

miR-495 targets ROCK1 to inhibit lipopolysaccharides-induced WI-38 cells apoptosis and inflammation

Pneumonia is an inflammatory disease with leading mortality rate in children. It has been well established that microRNAs (miRNAs) have been regarded as critical regulator in acute lung injury. We intended to explore the effect and underlying mechanism of miR-495 on lipopolysaccharides (LPS)-induced WI-38 cells. Here, we first found that miR-495 was downregulated in serum of patients with acute stage pneumonia. To establish cell model of acute pneumonia, WI-38 cells were treated with 20 μg/mL LPS, and qRT-PCR analysis also confirmed the downregulation of miR-495 in LPS-induced WI-38 cells. Data from MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) and flow cytometry assays showed that the decreased cell viability and induced cell apoptosis by LPS treatment were also reversed by miR-495 over-expression. Moreover, miR-495 inhibited expression of associated inflammatory factors, which were induced by LPS treatment. Second, ROCK1 (rho-associated, coiled-coil-containing protein kinase 1) was identified as functional target gene of miR-495, whose expression was decreased by miR-495. Mechanically, combination of miR-495 and ROCK1 over-expression reversed the influence of miR-495 on LPS-induced inflammation, viability, and apoptosis. In conclusion, our findings indicated that miR-495 inhibited LPS-induced inflammation injury and apoptosis in WI-38 cells via targeting ROCK1, which would shed light on therapeutic schedule in acute pneumonia.

miR‑155 inhibition represents a potential valuable regulator in mitigating myocardial hypoxia/reoxygenation injury through targeting BAG5 and MAPK/JNK signaling

Increasing evidence has indicated that miR-155 is closely associated with apoptosis, which may protect the myocardium and diminish the infarct area in myocardial ischemia reperfusion injury (IRI). In addition, studies have revealed that miR-155 serves a leading role in promoting fibroblast inflammation, cardiac dysfunction and other aspects of myocardial injury. The present study aimed to uncover the function and potential biological mechanism of miR-155 in myocardial IRI. The rat H9c2 myocardial cells was treated with hypoxia/reoxygenation (H/R) to simulate IRI in vitro. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to detect the expression levels of miR-155 mRNA. Cell Counting Kit-8 and flow cytometry assays and western blot analysis were applied to determine the biological behaviors of the H/R-treated cells. The association between miR-155 and BAG family molecular chaperone regulator 5 (BAG5) was predicted by bioinformatics software and was confirmed by dual luciferase assay. RT-qPCR and western blot analysis were used to analyze the expression of BAG5. The key proteins involved in mitogen-activated protein kinase (MAPK)/JNK signaling pathway were detected by western blot analysis. The data from the RT-qPCR assay indicated that the expression of miR-155 was markedly upregulated in the H/R model, and that downregulation of miR-155 may promote cell proliferation and inhibit cell apoptosis, and vice versa. BAG5, which was downregulated in the H/R model, was confirmed as a target of miR-155 and negatively modulated by miR-155. The key proteins involved in MAPK/JNK signaling, which were highly expressed in the H/R model, were suppressed by treatment with the miR-155 inhibitor, and overexpression of BAG5 promoted the protective effect of miR-155 inhibition on cell injury caused by H/R. In addition, the expression patterns of hypoxia-inducible factor 1-α and von Hippel-Lindau were altered following different treatments. Taken together, the data from the present study indicated that miR-155 inhibition represented a potential treatment strategy to improve myocardial H/R injury, which may be associated with targeting BAG5 and inhibition of the MAPK/JNK pathway.

Effects of AntagomiRs on Different Lung Diseases in Human, Cellular, and Animal Models

INTRODUCTION

MiRNAs have been shown to play a crucial role among lung cancer, pulmonary fibrosis, tuberculosis (TBC) infection, and bronchial hypersensitivity, thus including chronic obstructive pulmonary disease (COPD) and asthma. The oncogenic effect of several miRNAs has been recently ruled out. In order to act on miRNAs turnover, antagomiRs have been developed.

MATERIALS AND METHODS

The systematic review was conducted under the PRISMA guidelines (registration number is: CRD42019134173). The PubMed database was searched between 1 January 2000 and 30 April 2019 under the following search strategy: (((antagomiR) OR (mirna antagonists) OR (mirna antagonist)) AND ((lung[MeSH Terms]) OR ("lung diseases"[MeSH Terms]))). We included original articles, published in English, whereas exclusion criteria included reviews, meta-analyses, single case reports, and studies published in a language other than English.

RESULTS AND CONCLUSIONS

A total of 68 articles matching the inclusion criteria were retrieved. Overall, the use of antagomiR was seen to be efficient in downregulating the specific miRNA they are conceived for. The usefulness of antagomiRs was demonstrated in humans, animal models, and cell lines. To our best knowledge, this is the first article to encompass evidence regarding miRNAs and their respective antagomiRs in the lung, in order to provide readers a comprehensive review upon major lung disorders.

CCR2 mediates increased susceptibility to post-H1N1 bacterial pneumonia by limiting dendritic cell induction of IL-17

Post influenza bacterial pneumonia is associated with significant mortality and morbidity. Dendritic cells (DCs) play a crucial role in host defense against bacterial pneumonia, but their contribution to post influenza-susceptibility to secondary bacterial pneumonia is incompletely understood. WT and CCR2^-/- mice were infected with 100 plaque forming units (pfu) H1N1 intranasally alone or were challenged on day 5 with 7 × 10⁷ colony forming units (cfu) methicillin-resistant Staphylococcus aureus intratracheally. WT mice express abundant CCL2 mRNA and protein post-H1N1 alone or dual infection. CCR2^-/- mice had significantly higher survival as compared to WT mice, associated with significantly improved bacterial clearance at 24 and 48 h (10-fold and 14-fold, respectively) post bacterial challenge. There was robust upregulation of IL-23 and IL-17 as well as downregulation of IL-27 expression in CCR2^-/- mice following sequential infection as compared to WT mice, which was also associated with significantly greater accumulation of CD103⁺ DC. Finally, WT mice treated with a CCR2 inhibitor showed improved bacterial clearance in association with similar cytokine profiles as CCR2^-/- mice. Thus, CCR2 significantly contributes to increased susceptibility to bacterial infection after influenza pneumonia likely via altered dendritic cell responses and thus, CCR2 antagonism represents a potential therapeutic strategy.

MiR-24 inhibits inflammatory responses in LPS-induced acute lung injury of neonatal rats through targeting NLRP3

Inflammation plays an important role in the development of acute lung injury (ALI) in preterm infants. Despite the critical role of microRNA in inflammatory response, little is known about its function in ALI. In this study, we investigate the role of MicroRNA-24 (miR-24) in lipopolysaccharide (LPS) induced neonatal rats ALI and its potential mechanism. LPS was used to induce ALI neonatal animal model. miR-24 expression in the lung tissues of LPS-challenged neonatal rats was detected by qPCR. Proinflammatory factors, including tumor necrosis factor-alpha (TNF-α), IL-1β, IL-18 in the bronchoalveolar lavage fluid and lung tissues of LPS-challenged neonatal rats were measured by qRT-PCR and western blot, respectively. The mRNA levels of surfactant protein A (SP-A) and D (SP-D) was measured by qRT-PCR. Direct binding of miR-24 and pyrin domain-containing 3(NLRP3) were determined by dual luciferase assay. The levels of NLRP3, apoptosis-associated speck-like protein containing a C‑terminal caspase recruitment domain (ASC) and caspase-1 protein expression were detected by immunohistochemistry (IHC) staining and western blot, respectively. Our data indicated that LPS-induced lung injury in neonatal rats and resulted in significant downregulated of miR-24 expression. Overexpression of miR-24 significantly reduced LPS-induced lung damage and decreased the release of proinflammatory cytokine TNF-α, IL-6, IL-1β and SP-A, SP-D expression induced by LPS. In addition, miR-24 inhibited the expression of NLRP3 by directly targeting to the CDS region of NLRP3 mRNA. Furthermore, miR-24 overexpression attenuated lung inflammation and deactivated the NLRP3/caspase-1/IL-1β pathway in LPS-challenged neonatal rats. These data show that miR-24 alleviated inflammatory responses in LPS-induced ALI via targeting NLRP3.

miRNAs reshape immunity and inflammatory responses in bacterial infection

Pathogenic bacteria cause various infections worldwide, especially in immunocompromised and other susceptible individuals, and are also associated with high infant mortality rates in developing countries. MicroRNAs (miRNAs), small non-coding RNAs with evolutionarily conserved sequences, are expressed in various tissues and cells that play key part in various physiological and pathologic processes. Increasing evidence implies roles for miRNAs in bacterial infectious diseases by modulating inflammatory responses, cell penetration, tissue remodeling, and innate and adaptive immunity. This review highlights some recent intriguing findings, ranging from the correlation between aberrant expression of miRNAs with bacterial infection progression to their profound impact on host immune responses. Harnessing of dysregulated miRNAs in bacterial infection may be an approach to improving the diagnosis, prevention and therapy of infectious diseases.

Changes in production of tiny cellular RNAs in response to bacterial infection could guide the development of better diagnostics and therapies. MicroRNAs regulate other genes by binding to messenger RNA strands and controlling their translation into proteins. Xikun Zhou, Min Wu and colleagues of the University of North Dakota have now reviewed current knowledge about how microRNA levels shift during infection with various bacterial pathogens. These microRNAs can modulate the immune response as well as pathways that influence metabolic activity and cell survival. Increasing studies have indicated that shifts in microRNA levels in response to different infections could provide a potential bacterial ‘fingerprint’ for achieving accurate diagnosis. With deeper insight into how different microRNAs influence infection, it might one day day become possible to target these molecules with ‘antisense’ or ‘agonist’ drugs that modulate their activity.

MK2 mediates macrophage activation and acute lung injury by regulating let-7e miRNA

MAPK-activated protein kinase 2 (MK2) plays a critical role in the development of inflammation. However, the modulatory mechanisms in macrophage activation and acute lung injury (ALI) have not been completely defined. Here, we reported that MK2-deficient mice (MK2^-/-) protected against sepsis-induced ALI. In response to lipopolysaccharide (LPS) challenge, MK2^-/- mice and myeloid cell-specific MK2 conditional knockout mice (MK2^Lyz2-KO) exhibited attenuated inflammatory response, especially producing fewer amounts of tumor necrosis factor-α (TNF-α), interleukin (IL)-6, and macrophage inflammatory protein 2 (MIP-2). LPS treatment in vitro resulted in reduced cytokine expression in MK2^-/- bone marrow-derived macrophages (BMDMs). Furthermore, we found that LPS-induced microRNA lethal-7e ( let-7e) expression was significantly increased in MK2^-/- macrophages. Transfection of let-7e antagomirs into MK2^-/- BMDM rescued LPS-induced expression of TNF-α, IL-6, and MIP-2. In contrast, transfection of let-7e mimics into MK2^+/+BMDM decreased cytokine expression. Meanwhile, LPS-induced phosphorylation of cAMP response element-binding (CREB) protein, a substrate of MK2, was downregulated in MK2^-/- BMDMs. Lin28, an inhibitory molecule of let-7, was significantly reduced in MK2^-/- macrophages. Our results suggested that MK2 boosts LPS-induced macrophage activation and ALI via increasing activation of CREB and consequently, the expression of Lin28 and downregulation of let-7e.

IL-17 in the lung: the good, the bad, and the ugly

The IL-17 family of cytokines has emerged over the last two decades as a pleiotropic group of molecules that function in a wide variety of both beneficial and detrimental (pathological) processes, mainly in mucosal barrier tissue. The beneficial effects of IL-17 expression are especially important in the lung, where exposure to foreign agents is abundant. IL-17A plays an important role in protection from both extracellular bacteria and fungi, as well as viruses that infect cells of the mucosal tracts. IL-17 coregulated cytokines, such as IL-22, are involved in maintaining epithelial cell homeostasis and participate in epithelial cell repair/regeneration following inflammatory insults. Thus, the IL-17/IL-22 axis is important in both responding to, and recovering from, pathogens. However, aberrant expression or overexpression of IL-17 cytokines contributes to a number of pathological outcomes, including asthma, pneumonitis, and generation or exacerbation of pulmonary fibrosis. This review covers the good, bad, and ugly aspects of IL-17 in the lung.

Influenza virus infection alters ion channel function of airway and alveolar cells: mechanisms and physiological sequelae

The cystic fibrosis transmembrane conductance regulator (CFTR) and the amiloride-sensitive epithelial sodium channels (ENaC) are located in the apical membranes of airway and alveolar epithelial cells. These transporters play an important role in the regulation of lung fluid balance across airway and alveolar epithelia by being the conduits for chloride (Cl^-) and bicarbonate ([Formula: see text]) secretion and sodium (Na⁺) ion absorption, respectively. The functional role of these channels in the respiratory tract is to maintain the optimum volume and ionic composition of the bronchial periciliary fluid (PCL) and alveolar lining fluid (ALF) layers. The PCL is required for proper mucociliary clearance of pathogens and debris, and the ALF is necessary for surfactant homeostasis and optimum gas exchange. Dysregulation of ion transport may lead to mucus accumulation, bacterial infections, inflammation, pulmonary edema, and compromised respiratory function. Influenza (or flu) in mammals is caused by influenza A and B viruses. Symptoms include dry cough, sore throat, and is often followed by secondary bacterial infections, accumulation of fluid in the alveolar spaces and acute lung injury. The underlying mechanisms of flu symptoms are not fully understood. This review summarizes our present knowledge of how influenza virus infections alter airway and alveolar epithelial cell CFTR and ENaC function in vivo and in vitro and the role of these changes in influenza pathogenesis.

Virus-Bacteria Interactions: An Emerging Topic in Human Infection

Bacteria and viruses often occupy the same niches, however, interest in their potential collaboration in promoting wellness or disease states has only recently gained traction. While the interaction of some bacteria and viruses is well characterized (e.g., influenza virus), researchers are typically more interested in the location of the infection than the manner of cooperation. There are two overarching types of bacterial-virus disease causing interactions: direct interactions that in some way aid the viruses, and indirect interactions aiding bacteria. The virus-promoting direct interactions occur when the virus exploits a bacterial component to facilitate penetration into the host cell. Conversely, indirect interactions result in increased bacterial pathogenesis as a consequence of viral infection. Enteric viruses mainly utilize the direct pathway, while respiratory viruses largely affect bacteria in an indirect fashion. This review focuses on some key examples of how virus-bacteria interactions impact the infection process across the two organ systems, and provides evidence supporting this as an emerging theme in infectious disease.

Influenza Casts a Lung Shadow

This commentary highlights the article by Pociask et al that provides new insights into the lingering effects of influenza infection.

Epigenetic and Transcriptomic Regulation of Lung Repair during Recovery from Influenza Infection

Seasonal and pandemic influenza is a cause of morbidity and mortality worldwide. Most people infected with influenza virus display mild-to-moderate disease phenotypes and recover within a few weeks. Influenza is known to cause persistent alveolitis in animal models; however, little is known about the molecular pathways involved in this phenotype. We challenged C57BL/6 mice with influenza A/PR/8/34 and examined lung pathologic processes and inflammation, as well as transcriptomic and epigenetic changes at 21 to 60 days after infection. Influenza induced persistent parenchymal lung inflammation, alveolar epithelial metaplasia, and epithelial endoplasmic reticulum stress that were evident after the clearance of virus and resolution of morbidity. Influenza infection induced robust changes in the lung transcriptome, including a significant impact on inflammatory and extracellular matrix protein expression. Despite the robust changes in lung gene expression, preceding influenza (21 days) did not exacerbate secondary Staphylococcus aureus infection. Finally, we examined the impact of influenza on miRNA expression in the lung and found an increase in miR-155. miR-155 knockout mice recovered from influenza infection faster than controls and had decreased lung inflammation and endoplasmic reticulum stress. These data illuminate the dynamic molecular changes in the lung in the weeks after influenza infection and characterize the repair process, identifying a novel role for miR-155.

Role of MicroRNA in the Lung's Innate Immune Response

The immune response to respiratory pathogens must be robust enough to defend the host yet properly constrained such that inflammation-induced tissue damage is avoided. MicroRNA (miRNA) are small noncoding RNA which posttranscriptionally influence gene expression. In this review, we discuss recent experimental evidence of the contribution of miRNA to the lung's response to bacterial and viral pathogens.

Role of microRNA-155 in the liver

MicroRNAs (miRNAs) are a class of endogenous non-coding small RNAs of 22 nucleotides in length that are found in most eukaryotes. Although miRNAs are highly evolutionally conserved, they show temporal and tissue specificity. They transcriptionally and posttranscriptionally regulate gene expression by completely or imperfectly base pairing with the 3' untranslated region (3'-UTR) of target mRNAs and modulate cell proliferation, apoptosis and differentiation. MicroRNA-155 (miR-155) is a typical representative miRNA, and abnormal expression or dysfunction of miR-155 function not only affects the development of inflammation and autoimmune diseases, but also plays an important role in tumor proliferation and apoptosis. In recent years, it has been found that miR-155 plays an important role in the differentiation, morphology and function of the liver, and is associated with the development, diagnosis and treatment of liver diseases.