Transforming growth factor beta enhances respiratory syncytial virus replication and tumor necrosis factor alpha induction in human epithelial cells

Concomitant inhibition of PI3K/mTOR signaling pathways boosts antiproliferative effects of lanreotide in bronchopulmonary neuroendocrine tumor cells

Introduction: Somatostatin analogues (SSAs) are commonly used in the treatment of hormone hypersecretion in neuroendocrine tumors (NETs), however the extent to which they inhibit proliferation is much discussed. Objective: We studied the antiproliferative effects of novel SSA lanreotide in bronchopulmonary NETs (BP-NETs). We focused on assessing whether pretreating cells with inhibitors for phosphatidylinositol 3-kinase (PI3K) and mammalian target for rapamycin (mTOR) could enhance the antiproliferative effects of lanreotide. Methods: BP-NET cell lines NCI-H720 and NCI-H727 were treated with PI3K inhibitor BYL719 (alpelisib), mTOR inhibitor everolimus and SSA lanreotide to determine the effect on NET differentiation markers, cell survival, proliferation and alterations in cancer-associated pathways. NT-3 cells, previously reported to express somatostatin receptors (SSTRs) natively, were used as control for SSTR expression. Results: SSTR2 was upregulated in NCI-H720 and NT-3 cells upon treatment with BYL719. Additionally, combination treatment consisting of BYL719 and everolimus plus lanreotide tested in NCI-H720 and NCI-H727 led to diminished cell proliferation in a dose-dependent manner. Production of proteins activating cell death mechanisms was also induced. Notably, a multiplexed gene expression analysis performed on NCI-H720 revealed that BYL719 plus lanreotide had a stronger effect on the downregulation of mitogens than lanreotide alone. Discussion/Conclusion: We report a widespread analysis of changes in BP-NET cell lines at the genetic/protein expression level in response to combination of lanreotide with pretreatment consisting of BYL719 and everolimus. Interestingly, SSTR expression reinduction could be exploited in therapeutic and diagnostic applications. The overall results of this study support the evaluation of combination-based therapies using lanreotide in preclinical studies to further increase its antiproliferative effect and ultimately facilitate its use in high-grade tumors.

Neuropilin 1 is an entry receptor for KSHV infection of mesenchymal stem cell through TGFBR1/2-mediated macropinocytosis

Kaposi's sarcoma-associated herpesvirus (KSHV) has been implicated in the pathogenesis of Kaposi's sarcoma (KS) and other malignancies. The cellular origin of KS has been suggested to be either mesenchymal stem cells (MSCs) or endothelial cells. However, receptor(s) for KSHV to infect MSCs remains unknown. By combining bioinformatics analysis and shRNA screening, we identify neuropilin 1 (NRP1) as an entry receptor for KSHV infection of MSCs. Functionally, NRP1 knockout and overexpression in MSCs significantly reduce and promote, respectively, KSHV infection. Mechanistically, NRP1 facilitated the binding and internalization of KSHV by interacting with KSHV glycoprotein B (gB), which was blocked by soluble NRP1 protein. Furthermore, NRP1 interacts with TGF-β receptor type 2 (TGFBR2) through their respective cytoplasmic domains and thus activates the TGFBR1/2 complex, which facilitates the macropinocytosis-mediated KSHV internalization via the small GTPases Cdc42 and Rac1. Together, these findings implicate that KSHV has evolved a strategy to invade MSCs by harnessing NRP1 and TGF-beta receptors to stimulate macropinocytosis.

RGD-binding integrins and TGF-β in SARS-CoV-2 infections - novel targets to treat COVID-19 patients?

The new coronavirus SARS‐CoV‐2 is a global pandemic and a severe public health crisis. SARS‐CoV‐2 is highly contagious and shows high mortality rates, especially in elderly and patients with pre‐existing medical conditions. At the current stage, no effective drugs are available to treat these patients. In this review, we analyse the rationale of targeting RGD‐binding integrins to potentially inhibit viral cell infection and to block TGF‐β activation, which is involved in the severity of several human pathologies, including the complications of severe COVID‐19 cases. Furthermore, we demonstrate the correlation between ACE2 and TGF‐β expression and the possible consequences for severe COVID‐19 infections. Finally, we list approved drugs or drugs in clinical trials for other diseases that also target the RGD‐binding integrins or TGF‐β. These drugs have already shown a good safety profile and, therefore, can be faster brought into a trial to treat COVID‐19 patients.

TGF-β1 signaling inhibit the in vitro apoptotic, infection and stimulatory cell response induced by influenza H1N1 virus infection on A549 cells

Influenza A virus (IAV) infection induces host cell responses that could derive in inflammatory and apoptotic response. In this respect, in multiple pathological situations, TGF-β1 has shown anti-inflammatory effect, but its role during IAV infection is poorly understood. Interestingly, recent profiling expression studies have suggested that the TGF-β1 pathway could be functionally related to the IAV infection's host response. To gain an understanding of the involvement of TGF-β1's signaling pathway during IAV infection, we compared different apoptotic proteins such as TNFR1, Fas ligand, XIAP, cIAP, among others proteins, and pro-inflammatory elements like IL-1β in the A549 cells during IAV infection (H1N1/NC/99), with and without 1 h of pre-treatment with TGF-β1. Pre-incubation with TGF-β1 significantly inhibited apoptosis and the presence of pro-apoptotic factors. Moreover, the relative abundance of immunodetected IAV M1 protein along 24 -h post-infection period was abridged, which correlated with a disminished infectious viral progeny Additionally, caspase 1 activation and increase of IL-1β induced by IAV infection was also reduced by TGF-β1 signaling activation. Whereas IAV infection increase of Smad-7 and, as consequence, partially inhibiting Smad2/3 phosphorylation, pre-treatment with TGF-β1 blocked IAV-dependent Smad7 induction and prevented Smad2/3 signaling shutdown. All these data suggest the role of TGF-β1 signaling pathway in the control of host cell response induced by the IAV infection and identify a potential clinical target to modulate acute cell death.

In well-differentiated primary human bronchial epithelial cells, TGF-1 and TGF-2 induce expression of furin

The COVID-19 pandemic is an ongoing threat to public health. Since the identification of COVID-19, the disease caused by SARS-CoV-2, no drugs have been developed to specifically target SARS-CoV-2. To develop effective and safe treatment options, a better understanding of cellular mechanisms underlying SARS-CoV-2 infection is required. To fill this knowledge gap, researchers require reliable experimental systems that express the host factor proteins necessary for the cellular entry of SARS-CoV-2. These proteins include the viral receptor, angiotensin-converting enzyme 2 (ACE2), and the proteases, transmembrane serine protease 2 (TMPRSS2) and furin. A number of studies have reported cell-type-specific expression of the genes encoding these molecules. However, less is known about the protein expression of these molecules. We assessed the suitability of primary human bronchial epithelial (HBE) cells maintained in an air-liquid interface (ALI) as an experimental system for studying SARS-CoV-2 infection in vitro. During cellular differentiation, we measured the expression of ACE2, TMPRSS2, and furin over progressive ALI days by reverse transcription-quantitative polymerase chain reaction (RT-qPCR), Western blot, and immunofluorescence staining. We also explored the effect of the fibrotic cytokine TGF-β on the expression of these proteins in well-differentiated HBE cells. Like ACE2, TMPRSS2 and furin proteins are localized in differentiated ciliated cells, as confirmed by immunofluorescence staining. These data suggest that well-differentiated HBE cells maintained in ALI are a reliable in vitro system for investigating cellular mechanisms of SARS-CoV-2 infection. We further identified that the profibrotic mediators, TGF-β1 and TGF-β2, increase the expression of furin, which is a protease required for the cellular entry of SARS-CoV-2.

The role of growth factor receptors in viral infections: An opportunity for drug repurposing against emerging viral diseases such as COVID-19?

Growth factor receptors are known to be involved in the process of viral infection. Many viruses not only use growth factor receptors to physically attach to the cell surface and internalize, but also divert receptor tyrosine kinase signaling in order to replicate. Thus, repurposing drugs that have initially been developed to target growth factor receptors and their signaling in cancer may prove to be a fast track to effective therapies against emerging new viral infections, including the coronavirus disease 19 (COVID-19).

Determining Immune and miRNA Biomarkers Related to Respiratory Syncytial Virus (RSV) Vaccine Types

Respiratory Syncytial Virus (RSV) causes serious respiratory tract illness and substantial morbidity and some mortality in populations at the extremes of age, i.e., infants, young children, and the elderly. To date, RSV vaccine development has been unsuccessful, a feature linked to the lack of biomarkers available to assess the safety and efficacy of RSV vaccine candidates. We examined microRNAs (miR) as potential biomarkers for different types of RSV vaccine candidates. In this study, mice were vaccinated with a live attenuated RSV candidate that lacks the small hydrophobic (SH) and attachment (G) proteins (CP52), an RSV G protein microparticle (GA2-MP) vaccine, a formalin-inactivated RSV (FI-RSV) vaccine or were mock-treated. Several immunological endpoints and miR expression profiles were determined in mouse serum and bronchoalveolar lavage (BAL) following vaccine priming, boost, and RSV challenge. We identified miRs that were linked with immunological parameters of disease and protection. We show that miRs are potential biomarkers providing valuable insights for vaccine development.

Regulatory cytokine function in the respiratory tract

The respiratory tract is an important site of immune regulation; required to allow protective immunity against pathogens, while minimizing tissue damage and avoiding aberrant inflammatory responses to inhaled allergens. Several cell types work in concert to control pulmonary immune responses and maintain tolerance in the respiratory tract, including regulatory and effector T cells, airway and interstitial macrophages, dendritic cells and the airway epithelium. The cytokines transforming growth factor β, interleukin (IL-) 10, IL-27, and IL-35 are key coordinators of immune regulation in tissues such as the lung. Here, we discuss the role of these cytokines during respiratory infection and allergic airway disease, highlighting the critical importance of cellular source and immunological context for the effects of these cytokines in vivo.

Surviving Deadly Lung Infections: Innate Host Tolerance Mechanisms in the Pulmonary System

Much research on infectious diseases focuses on clearing the pathogen through the use of antimicrobial drugs, the immune response, or a combination of both. Rapid clearance of pathogens allows for a quick return to a healthy state and increased survival. Pathogen-targeted approaches to combating infection have inherent limitations, including their pathogen-specific nature, the potential for antimicrobial resistance, and poor vaccine efficacy, among others. Another way to survive an infection is to tolerate the alterations to homeostasis that occur during a disease state through a process called host tolerance or resilience, which is independent from pathogen burden. Alterations in homeostasis during infection are numerous and include tissue damage, increased inflammation, metabolic changes, temperature changes, and changes in respiration. Given its importance and sensitivity, the lung is a good system for understanding host tolerance to infectious disease. Pneumonia is the leading cause of death for children under five worldwide. One reason for this is because when the pulmonary system is altered dramatically it greatly impacts the overall health and survival of a patient. Targeting host pathways involved in maintenance of pulmonary host tolerance during infection could provide an alternative therapeutic avenue that may be broadly applicable across a variety of pathologies. In this review, we will summarize recent findings on tolerance to host lung infection. We will focus on the involvement of innate immune responses in tolerance and how an initial viral lung infection may alter tolerance mechanisms in leukocytic, epithelial, and endothelial compartments to a subsequent bacterial infection. By understanding tolerance mechanisms in the lung we can better address treatment options for deadly pulmonary infections.

Safer approaches to therapeutic modulation of TGF-β signaling for respiratory disease

The transforming growth factor (TGF)-β cytokines play a central role in development and progression of chronic respiratory diseases. TGF-β overexpression in chronic inflammation, remodeling, fibrotic process and susceptibility to viral infection is established in the most prevalent chronic respiratory diseases including asthma, COPD, lung cancer and idiopathic pulmonary fibrosis. Despite the overwhelming burden of respiratory diseases in the world, new pharmacological therapies have been limited in impact. Although TGF-β inhibition as a therapeutic strategy carries great expectations, the constraints in avoiding compromising the beneficial pleiotropic effects of TGF-β, including the anti-proliferative and immune suppressive effects, have limited the development of effective pharmacological modulators. In this review, we focus on the pathways subserving deleterious and beneficial TGF-β effects to identify strategies for selective modulation of more distal signaling pathways that may result in agents with improved safety/efficacy profiles. Adverse effects of TGF-β inhibitors in respiratory clinical trials are comprehensively reviewed, including those of the marketed TGF-β modulators, pirfenidone and nintedanib. Precise modulation of TGF-β signaling may result in new safer therapies for chronic respiratory diseases.

TGF-β1 Suppresses the Type I IFN Response and Induces Mitochondrial Dysfunction in Alveolar Macrophages

TGF-β1 is a pleiotropic cytokine with an established role in fibrosis; however, the immunosuppressive effects of TGF-β1 are less characterized. Elevated levels of TGF-β1 are found in patients with acute and chronic lung diseases, and the underlying disease processes are exacerbated by respiratory viral infections. The alveolar macrophage is the first line of cellular defense against respiratory viral infections, and its response to infections is dependent on environmental cues. Using the mouse alveolar macrophage line, MH-S, and human CD14⁺ monocyte-derived macrophages, we examined the effects of TGF-β1 on the type I IFN antiviral response, macrophage polarization, and mitochondrial bioenergetics following a challenge with human respiratory syncytial virus (RSV). Our results showed that TGF-β1 treatment of macrophages decreased the antiviral and proinflammatory response, and suppressed basal, maximal, spare mitochondrial respiration, and mitochondrial ATP production. Challenge with RSV following TGF-β1 treatment further exacerbated mitochondrial dysfunction. The TGF-β1 and TGF-β1+RSV-treated macrophages had a higher frequency of apoptosis and diminished phagocytic capacity, potentially through mitochondrial stress. Disruption of TGF-β1 signaling or rescue of mitochondrial respiration may be novel therapeutically targetable pathways to improve macrophage function and prevent secondary bacterial infections that complicate viral respiratory infections.

TGFβ as a therapeutic target in cystic fibrosis

INTRODUCTION

Cystic fibrosis (CF) is a genetic disease characterized by progressive lung disease. Most CF therapies focus on treating secondary pulmonary complications rather than addressing the underlying processes inducing airway remodeling and ineffective response to infection. Transforming growth factor beta (TGFβ) is a cytokine involved in fibrosis, inflammation, and injury response as well as a genetic modifier and biomarker of CF lung disease. Targeting the TGFβ pathway has been pursued in other diseases, but the mechanism of TGFβ effects in CF is less well understood. Areas covered: In this review, we discuss CF lung disease pathogenesis with a focus on potential links to TGFβ. TGFβ signaling in lung health and disease is reviewed. Recent studies investigating TGFβ's impact in CF airway epithelial cells are highlighted. Finally, an overview of potential therapies to target TGFβ signaling relevant to CF are addressed. Expert opinion: The broad impact of TGFβ signaling on numerous cellular processes in homeostasis and disease is both a strength and a challenge to developing TGFβ dependent therapeutics in CF. We discuss the challenges inherent in developing TGFβ-targeted therapy, identifying appropriate patient populations, and questions regarding the timing of treatment. Future directions for research into TGFβ focused therapeutics are discussed.

In the Shadow of Fibrosis: Innate Immune Suppression Mediated by Transforming Growth Factor-β

Transforming growth factor-β (TGFB) regulates cell proliferation, differentiation, apoptosis, and matrix homeostasis and is intimately involved in fibrosis. TGFB expression is increased in fibrotic lung diseases, such as idiopathic pulmonary fibrosis, and in chronic inflammatory conditions, such as chronic obstructive pulmonary disease and asthma. In addition to exhibiting profibrotic activities, the protein exhibits profound immune-suppressive actions involving both innate and adaptive responses, but often this aspect of TGFB biology is overlooked. Recent investigations have demonstrated that TGFB causes wide-ranging immune suppression, including blunting of pivotal early innate IFN responses. These activities permit severe virus infections, often followed by secondary bacterial infections, which may last longer, with augmented inflammation, scarring, fibrosis, and loss of lung function. Strategies to oppose TGFB actions or to enhance IFN responses may help ameliorate the detrimental consequences of infection in patients with diseases characterized by TGFB overexpression, inflammation, and fibrosis.

Autophagy, TGF-β, and SMAD-2/3 Signaling Regulates Interferon-β Response in Respiratory Syncytial Virus Infected Macrophages

Human respiratory syncytial virus (RSV) is a lung tropic virus causing severe airway diseases including bronchiolitis and pneumonia among infants, children, and immuno-compromised individuals. RSV triggers transforming growth factor-β (TGF-β) production from lung epithelial cells and TGF-β facilitates RSV infection of these cells. However, it is still unknown whether RSV infected myeloid cells like macrophages produce TGF-β and the role of TGF-β if any during RSV infection of these cells. Our study revealed that RSV infected macrophages produce TGF-β and as a consequence these cells activate TGF-β dependent SMAD-2/3 signaling pathway. Further mechanistic studies illustrated a role of autophagy in triggering TGF-β production from RSV infected macrophages. In an effort to elucidate the role of TGF-β and SMAD-2/3 signaling during RSV infection, we surprisingly unfolded the requirement of TGF-β—SMAD2/3 signaling in conferring optimal innate immune antiviral response during RSV infection of macrophages. Type-I interferon (e.g., interferon-β or IFN-β) is a critical host factor regulating innate immune antiviral response during RSV infection. Our study revealed that loss of TGF-β—SMAD2/3 signaling pathway in RSV infected macrophages led to diminished expression and production of IFN-β. Inhibiting autophagy in RSV infected macrophages also resulted in reduced production of IFN-β. Thus, our studies have unfolded the requirement of autophagy—TGF-β—SMAD2/3 signaling network for optimal innate immune antiviral response during RSV infection of macrophages.

The genetic and epigenetic landscapes of the epithelium in asthma

Asthma is a global health problem with increasing prevalence. The airway epithelium is the initial barrier against inhaled noxious agents or aeroallergens. In asthma, the airway epithelium suffers from structural and functional abnormalities and as such, is more susceptible to normally innocuous environmental stimuli. The epithelial structural and functional impairments are now recognised as a significant contributing factor to asthma pathogenesis. Both genetic and environmental risk factors play important roles in the development of asthma with an increasing number of genes associated with asthma susceptibility being expressed in airway epithelium. Epigenetic factors that regulate airway epithelial structure and function are also an attractive area for assessment of susceptibility to asthma. In this review we provide a comprehensive discussion on genetic factors; from using linkage designs and candidate gene association studies to genome-wide association studies and whole genome sequencing, and epigenetic factors; DNA methylation, histone modifications, and non-coding RNAs (especially microRNAs), in airway epithelial cells that are functionally associated with asthma pathogenesis. Our aims were to introduce potential predictors or therapeutic targets for asthma in airway epithelium. Overall, we found very small overlap in asthma susceptibility genes identified with different technologies. Some potential biomarkers are IRAKM, PCDH1, ORMDL3/GSDMB, IL-33, CDHR3 and CST1 in airway epithelial cells. Recent studies on epigenetic regulatory factors have further provided novel insights to the field, particularly their effect on regulation of some of the asthma susceptibility genes (e.g. methylation of ADAM33). Among the epigenetic regulatory mechanisms, microRNA networks have been shown to regulate a major portion of post-transcriptional gene regulation. Particularly, miR-19a may have some therapeutic potential.

Human respiratory syncytial virus non-structural protein NS1 modifies miR-24 expression via transforming growth factor-β

Human respiratory syncytial virus (RSV) is a major health challenge in the young and elderly owing to the lack of a safe and effective vaccine and proven antiviral drugs. Understanding the mechanisms by which viral genes and proteins modulate the host response to infection is critical for identifying novel disease intervention strategies. In this study, the RSV non-structural protein NS1 was shown to suppress miR-24 expression during infection. Lack of NS1 was linked to increased expression of miR-24, whilst NS1 overexpression suppressed miR-24 expression. NS1 was found to induce Kruppel-like factor 6 (KLF6), a transcription factor that positively regulates the transforming growth factor (TGF)-b pathway to induce cell cycle arrest. Silencing of KLF6 led to increased miR-24 expression via downregulation of TGF-β. Treatment with exogenous TGF-β suppressed miR-24 expression and induced KLF6. Confocal microscopy showed co-localization of KLF6 and RSV NS1. These findings indicated that RSV NS1 interacts with KLF6 and modulates miR-24 expression and TGF-β, which facilitates RSV replication.

MIP-1α level in nasopharyngeal aspirates at the first wheezing episode predicts recurrent wheezing

BACKGROUND

Respiratory virus-induced wheezing, such as that induced by respiratory syncytial virus (RSV) and human rhinovirus, is an important risk factor for recurrent wheezing and childhood asthma. However, no biomarkers for predicting recurrent wheezing have been identified.

OBJECTIVE

We searched for predictors of recurrent wheezing using nasopharyngeal aspirates obtained from patients during the first wheezing episode who were hospitalized with an acute lower respiratory tract illness.

METHODS

We enrolled 82 infants during the first wheezing episode (median age, 5.0 months) who were hospitalized for acute lower respiratory tract illness between August 2009 and June 2012 and followed these patients for 2.5 years. Nasopharyngeal aspirates and blood samples were obtained on the first day of hospitalization. Viral genomes were identified by using RT-PCR and sequencing. Levels of 33 cytokines, tryptase, IgE, anti-RSV IgE, and anti-RSV IgG were measured by using ELISAs or the Bio-Plex multiplex assay. Predictors of recurrent wheezing were examined by using a stepwise logistic regression model with backward elimination.

RESULTS

Sixty percent of the patients experienced recurrent wheezing episodes. One or more viruses were detected in the nasopharynxes of 93% of the patients during the first wheezing episode. IFN-γ, IL-2, IL-9, MIP-1α, and MIP-1β levels were significantly higher among patients with recurrent wheezing than among those without recurrent wheezing (P < .05 or .01). The stepwise model demonstrated that the MIP-1α level (odds ratio, 7.72; 95% CI, 1.50-39.77; P = .015) was the strongest independent predictor of the occurrence of recurrent wheezing.

CONCLUSION

An increased MIP-1α level in nasopharyngeal aspirates from patients with acute respiratory symptoms during the first wheezing episode caused by viral infections might predict recurrent wheezing.

In vitro rapid clearance of infectious bursal disease virus in peripheral blood mononuclear cells of chicken lines divergent for antibody response might be related to the enhanced expression of proinflammatory cytokines

Infectious bursal disease (IBD) is an acute and highly contagious viral disease of young chickens caused by infectious bursal disease virus (IBDV). An effective way to control IBDV would be to breed chickens with a reduced susceptibility to IBDV infection. In the present work, we used chickens selected for high and low specific responses to sheep red blood cells (SRBC) (H and L, respectively) to assess the susceptibility of differential immune competent animals to IBDV infection. The peripheral blood mononuclear cells (PBMCs) of high SRBC line (HL) and low SRBC line (LL) were infected with IBDV and viral RNA loads were determined at different time post-IBDV infection. Chicken orthologues of the T helper 1 (Th1) cytokines, interferon-γ (IFN-γ) and interleukin-2 (IL-2); a Th2 cytokine, IL-10; a pro inflammatory cytokine, IL-6; the CCL chemokines, chCCLi2, chCCLi4 and chCCLi7; colony stimulating factor, GM-CSF; and a anti-inflammatory cytokine, transforming growth factor β-2 (TGFβ-2) were quantified. The expression of chCCLi2, chCCLi4 and chCCLi7 was significantly higher in L line as compared to H line. However, in H line the viral RNA loads were significantly lower than in L line. Therefore, the upregulated chemokines might be associated with the susceptibility to IBDV. The expression of IFN-γ, IL-2 and IL-6 was significantly higher in H line as compared to L line. We assume that the higher proinflammatory cytokines expression in H line might be related to the rapid clearance of virus from PBMCs. Significantly higher levels of IL-10 and TGFβ-2 mRNAs in L line might be related to the pathogenesis of IBDV. In conclusion, selection for antibody responses appears to influence the expression profiles of chemokines and cytokines against IBDV. Further, the selection for high SRBC response might improve the immuno-competence of chickens against IBDV.

Xiao-Qing-Long-Tang (Sho-seiryu-to) inhibited cytopathic effect of human respiratory syncytial virus in cell lines of human respiratory tract

ETHNOPHARMACOLOGICAL RELEVANCE

Xiao-Qing-Long-Tang (XQLT, TJ-19, Sho-seiryu-to, so-cheong-ryong-tang) has been used against acute airway diseases for thousands of year in ancient China. Most of the acute airway illnesses are caused by virus. However, without activity against influenza virus, XQLT has been questioned to manage respiratory tract viral infection. Nevertheless, XQLT might be active against airway viruses other than influenza. Human respiratory syncytial virus (HRSV) is one of the most common respiratory viral pathogens without effective management. However, it is unknown whether XQLT has anti-HRSV activity.

AIM OF THE STUDY

We tested the hypothesis that XQLT can effectively minimize HRSV-induced plaque formation in respiratory tract mucosal cell lines.

MATERIALS AND METHODS

Anti-HRSV activity of a hot water extract of XQLT was examined by plaque reduction assay in both human upper (HEp-2) and low (A549) respiratory tract cell lines. Its effects on syncytial formation and viral fusion (F) protein were examined directly by microscopy and by western blot, respectively. Ability of XQLT to stimulate IFN-β was evaluated by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Hot water extract of XQLT dose-dependently inhibited HRSV-induced plaque formation in both HEp-2 and A549 cells (P<0.0001), particularly when given before viral inoculation (p<0.0001). XQLT inhibited viral attachment (p<0.0001) and internalization (p<0.0001). 300μg/ml XQLT could decrease both the number and the size of HRSV-induced syncytium without clear effect on the production of viral F protein. XQLT could stimulate epithelial cells to secrete IFN-β before and after viral inoculation to counteract viral infection (p<0.0001).

CONCLUSIONS

XQLT is effective against HRSV infection on airway epithelia by preventing viral attachment, internalization, syncytial formation, and by stimulating interferon secretion.

Activation of TGF-β1 promoter by hepatitis C virus-induced AP-1 and Sp1: role of TGF-β1 in hepatic stellate cell activation and invasion

Our previous studies have shown the induction and maturation of transforming growth factor-beta 1 (TGF-β1) in HCV-infected human hepatoma cells. In this study, we have investigated the molecular mechanism of TGF-β1 gene expression in response to HCV infection. We demonstrate that HCV-induced transcription factors AP-1, Sp1, NF-κB and STAT-3 are involved in TGF-β1 gene expression. Using chromatin immunoprecipitation (ChIP) assay, we further show that AP-1 and Sp1 interact with TGF-b1 promoter in vivo in HCV-infected cells. In addition, we demonstrate that HCV-induced TGF-β1 gene expression is mediated by the activation of cellular kinases such as p38 MAPK, Src, JNK, and MEK1/2. Next, we determined the role of secreted bioactive TGF-β1 in human hepatic stellate cells (HSCs) activation and invasion. Using siRNA approach, we show that HCV-induced bioactive TGF-β1 is critical for the induction of alpha smooth muscle actin (α-SMA) and type 1 collagen, the markers of HSCs activation and proliferation. We further demonstrate the potential role of HCV-induced bioactive TGF-β1 in HSCs invasion/cell migration using a transwell Boyden chamber. Our results also suggest the role of HCV-induced TGF-β1 in HCV replication and release. Collectively, these observations provide insight into the mechanism of TGF-β1 promoter activation, as well as HSCs activation and invasion, which likely manifests in liver fibrosis associated with HCV infection.

Antiviral effect of cimicifugin from Cimicifuga foetida against human respiratory syncytial virus

Human respiratory syncytial virus (RSV) causes serious infection of the lower respiratory tract in children and an effective antiviral therapy against the viral pathogen remains unavailable. We previously demonstrated that the oriental medicinal plant, Cimicifuga foetida L. (C. foetida), possessed inhibitory activity against RSV. Since cimicifugin is a major constituent of C. foetida, we sought to examine in this study its anti-RSV effect on both the human upper (HEp-2) and lower (A549) respiratory tract cell lines. Results revealed that cimicifugin dose-dependently inhibited RSV-induced plaque formation in both HEp-2 and A549 cells (p < 0.0001), with a superior effect in the latter cell type (p < 0.0001). The antiviral activity of cimicifugin was time-dependent (p < 0.0001) and was most effective when cells were treated with the compound before viral inoculation. Additional experiments demonstrated that cimicifugin could inhibit viral attachment (p < 0.0001) and viral internalization (p < 0.0001). Furthermore, the drug could potentiate heparin's effect against attachment of RSV, particularly in A549 cells. Enzyme-linked immunosorbent assay (ELISA) analysis of antiviral cytokines induction revealed that cimicifugin could also stimulate epithelial cells to secrete IFN-β to counteract viral infection. Taken together, these results indicate that cimicifugin is an efficient antiviral agent against RSV infection. We suggest that cimicifugin might be useful for the management of RSV pathogenesis.

Transforming growth factor-beta promotes rhinovirus replication in bronchial epithelial cells by suppressing the innate immune response

Rhinovirus (RV) infection is a major cause of asthma exacerbations which may be due to a deficient innate immune response in the bronchial epithelium. We hypothesized that the pleiotropic cytokine, TGF-β, influences interferon (IFN) production by primary bronchial epithelial cells (PBECs) following RV infection. Exogenous TGF-β₂ increased RV replication and decreased IFN protein secretion in response to RV or double-stranded RNA (dsRNA). Conversely, neutralizing TGF-β antibodies decreased RV replication and increased IFN expression in response to RV or dsRNA. Endogenous TGF-β₂ levels were higher in conditioned media of PBECs from asthmatic donors and the suppressive effect of anti-TGF-β on RV replication was significantly greater in these cells. Basal SMAD-2 activation was reduced when asthmatic PBECs were treated with anti-TGF-β and this was accompanied by suppression of SOCS-1 and SOCS-3 expression. Our results suggest that endogenous TGF-β contributes to a suppressed IFN response to RV infection possibly via SOCS-1 and SOCS-3.

Cimicifuga foetida L. inhibited human respiratory syncytial virus in HEp-2 and A549 cell lines

Human respiratory syncytial virus (HRSV) causes serious pediatric infection of the lower respiratory tract without effective therapeutic modality. Sheng-Ma-Ge-Gen-Tang (SMGGT; Shoma-kakkon-to) has been proven to be effective at inhibiting HRSV-induced plaque formation, and Cimicifuga foetida is the major constituent of SMGGT. We tested the hypothesis that C. foetida effectively inhibited the cytopathic effects of HRSV by a plaque reduction assay in both human upper (HEp2) and lower (A549) respiratory tract cell lines. Its ability to stimulate anti-viral cytokines was evaluated by an enzyme-linked immunosorbent assay (ELISA). C. foetida dose-dependently inhibited HRSV-induced plaque formation (p < 0.0001) before and after viral inoculation, especially in A549 cells (p < 0.0001). C. foetida dose-dependently inhibited viral attachment (p < 0.0001) and could increase heparins effect on viral attachment. In addition, C. foetida time-dependently and dose-dependently (p < 0.0001) inhibited HRSV internalization. C. foetida could stimulate epithelial cells to secrete IFN-β to counteract viral infection. However, C. foetida did not stimulate TNF-α secretion. Therefore, C. foetida could be useful in managing HRSV infection. This is the first evidence to support that C. foetida possesses antiviral activity.

Expression analysis of immune response genes in fish epithelial cells following ranavirus infection

Ranaviruses (family Iridoviridae) are a growing threat to fish and amphibian populations worldwide. The immune response to ranavirus infection has been studied in amphibians, but little is known about the responses elicited in piscine hosts. In this study, the immune response and apoptosis induced by ranaviruses were investigated in fish epithelial cells. Epithelioma papulosum cyprini (EPC) cells were infected with four different viral isolates: epizootic haematopoietic necrosis virus (EHNV), frog virus 3 (FV3), European catfish virus (ECV) and doctor fish virus (DFV). Quantitative real-time PCR (qPCR) assays were developed to measure the mRNA expression of immune response genes during ranavirus infection. The target genes included tumour necrosis factor α (TNF-α), interleukin-1β (IL-1β), β2-microglobulin (β2M), interleukin-10 (IL-10) and transforming growth factor β (TGF-β). All ranaviruses elicited changes in immune gene expression. EHNV and FV3 caused a strong pro-inflammatory response with an increase in the expression of both IL-1β and TNF-α, whereas ECV and DFV evoked transient up-regulation of regulatory cytokine TGF-β. Additionally, all viral isolates induced increased β2M expression as well as apoptosis in the EPC cells. Our results indicate that epithelial cells can serve as an in vitro model for studying the mechanisms of immune response in the piscine host in the first stages of ranavirus infection.

Liu-He-Tang inhibited plaque formation by human respiratory syncytial virus infection in cell lines of the human respiratory tract

ETHNOPHARMACOLOGICAL RELEVANCE

Liu-He-Tang (LHT) has been used to treat adult respiratory tract infection with productive cough and fever for a thousand years in ancient China. Adults with respiratory tract infection of human respiratory syncytial virus (HRSV) can have symptoms similar to those managed by LHT. Therefore, LHT is supposed to be beneficial for adult HRSV infection. However, LHT does not have any antiviral activity to support its use against HRSV infection.

AIM OF THE STUDY

HRSV is the most important virus causing serious pediatric respiratory tract infections worldwide. HRSV also contributes considerably to respiratory tract illness in adults. There is no effective therapeutic modality against HRSV infection. In order to find readily available agents to manage adult HRSV infection, this study tested the hypothesis that LHT has antiviral activity against HRSV-induced cytopathy.

MATERIALS AND METHODS

Effect of the hot water extract of LHT on HRSV was tested by plaque reduction assay in both human upper (HEp-2) and low (A549) respiratory tract cell lines and also a human normal fibroblast cell line (WI-38). Ability of LHT to stimulate anti-viral cytokines was evaluated by enzyme-linked immunosorbent assay (ELISA).

RESULTS

LHT could dose-dependently inhibit HRSV-induced plaque formation (p < 0.0001), especially in A549 cell. 300 μg/ml LHT nearly abolished plaque formation in A549 cells. LHT was more effective when given before viral inoculation (p < 0.0001). LHT dose-dependently inhibited viral attachment (p < 0.0001). Besides, LHT could inhibit HRSV internalization both time-dependently and dose-dependently (p < 0.0001). Furthermore, LHT stimulated epithelial cells to secrete IFN-β and TNF-α to counteract HRSV infection before infection becomes established.

CONCLUSIONS

LHT has anti-HRSV activity that provides a basic support of its possible use in managing adult HRSV infection.

Krüppel-like factor 6 regulates transforming growth factor-β gene expression during human respiratory syncytial virus infection

Background

Human respiratory syncytial virus (RSV) infection is associated with airway remodeling and subsequent asthma development. Transforming growth factor-beta (TGF) plays a crucial role in asthma development. The mechanism regulating TGF gene expression during RSV infection is not known. Kruppel-like factor family of transcription factors are critical regulators of cellular/tissue homeostasis. Previous studies have shown that Kruppel-like factor 6 (KLF6) could function as a trans-activator of TGF gene; however, whether KLF members play a role during infection is unknown. In the current study we have evaluated the role of KLF6 during TGF expression in RSV infected cells.

Findings

Silencing KLF6 expression by shRNA led to drastic inhibition in TGF production during RSV infection, as assessed by ELISA analysis of medium supernatants. RT-PCR analysis revealed loss of TGF expression in KLF6 silenced cells. Chromatin-immunoprecipitation assay conducted with RSV infected cells showed binding of KLF6 protein to the TGF promoter during RSV infection. We further observed reduced RSV infectivity in KLF6 silenced cells and in cells incubated with TGF neutralizing antibody. In contrast, enhanced RSV infection was noted in cells incubated with purified TGF.

Conclusion

We have identified KLF6 as a key transcription factor required for trans-activation of TGF gene during RSV infection. Moreover, TGF production is required for efficient RSV infection and thus, KLF6 is also required for efficient RSV infection by virtue of KLF6 dependent TGF production during infection.

Sheng-Ma-Ge-Gen-Tang (Shoma-kakkon-to) inhibited cytopathic effect of human respiratory syncytial virus in cell lines of human respiratory tract

ETHNOPHARMACOLOGICAL RELEVANCE

Sheng-Ma-Ge-Gen-Tang (SMGGT; Shoma-kakkon-to) has been used against pediatric viral infection for thousands of year in ancient China. However, it is unknown whether SMGGT is effective against human respiratory syncytial virus (HRSV).

AIM OF THE STUDY

HRSV is a major pediatric viral pathogen of low respiratory tract infection without effective management. This study tested the hypothesis that SMGGT effectively inhibited cytopathy induced by HRSV.

MATERIALS AND METHODS

Effect of the crude extract of SMGGT on HRSV was tested by plaque reduction assay in both human upper (HEp-2) and low (A549) respiratory tract cell lines. Ability of SMGGT to stimulate anti-viral cytokines was evaluated by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Crude extract of SMGGT dose-dependently inhibited HRSV-induced plaque formation. The crude extract was more effective when given before viral infection (p<0.0001). It inhibited viral attachment dose-dependently (p<0.0001) and could increase heparin effect on viral attachment. Furthermore, it was synergistic with very low-dose heparin on viral attachment. In addition, the crude extract time-dependently and dose-dependently (p<0.0001) inhibited HRSV internalization into HEp-2 cells. Epithelial cells secrete IFN-β and TNF-α to counteract viral infection. The crude extract could stimulate epithelial cells to secrete these cytokines beforehand and become resistant to viral infection. It also stimulated IFN-β to defense HRSV after viral inoculation.

CONCLUSIONS

Sheng-Ma-Ge-Gen-Tang could be effective to manage HRSV infection in young children.

Hepatitis C virus-induced furin and thrombospondin-1 activate TGF-β1: role of TGF-β1 in HCV replication

In this study, we demonstrated the molecular mechanisms of TGF-β1 induction as well as proteolytic activation in HCV (JFH-1)-infected cells. Our studies showed the synthesis and secretion of TGF-β1 in HCV-infected cells which was reduced in the presence of Ca(2+) chelators, an inhibitor of mitochondrial Ca(2+) uptake, and antioxidants. We also showed that the expression of HCV NS proteins NS3/4A, and NS5A can induce TGF-β1 by cell-based luciferase assay. Furthermore, mutational analysis revealed that the functionally active protease domain of NS3 and N-terminus domain of NS5A are required for TGF-β1 activity. Using siRNA approach we demonstrated that HCV-induced furin and thrombospondin-1 (TSP-1) are involved in the proteolytic activation of TGF-β1. Our results also suggest that TGF-β1 positively regulates HCV RNA replication. Collectively, these observations provide insight into the mechanism of TGF-β1 activation, which likely manifest in liver fibrosis associated with hepatitis C infection.

Transforming growth factor beta is a major regulator of human neonatal immune responses following respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is a major cause of morbidity and mortality. Previous studies have suggested that T-cell responses may contribute to RSV immunopathology, which could be driven by dendritic cells (DCs). DCs are productively infected by RSV, and during RSV infections, there is an increase of DCs in the lungs with a decrease in the blood. Pediatric populations are particularly susceptible to severe RSV infections; however, DC responses to RSV from pediatric populations have not been examined. In this study, primary isolated DCs from cord blood and adult peripheral blood were compared after RSV infection. Transcriptional profiling and biological network analysis identified transforming growth factor beta (TGF-β) and associated signaling molecules as differentially regulated in the two age groups. TGF-β1 was decreased in RSV-infected adult-blood DCs but increased in RSV-infected cord blood DCs. Coculture of adult RSV-infected DCs with autologous T cells induced secretion of gamma interferon (IFN-γ), interleukin 12p70 (IL-12p70), IL-2, and tumor necrosis factor alpha (TNF-α). Conversely, coculture of cord RSV-infected DCs and autologous T cells induced secretion of IL-4, IL-6, IL-1β, and IL-17. Addition of purified TGF-β1 to adult DC-T-cell cocultures reduced secretion of IFN-γ, IL-12p70, IL-2, and TNF-α, while addition of a TGF-β chemical inhibitor to cord DC-T-cell cocultures increased secretion of IL-12p70. These data suggest that TGF-β acts as a major regulator of RSV DC-T-cell responses, which could contribute to immunopathology during infancy.

Cell cycle arrest by transforming growth factor beta1 enhances replication of respiratory syncytial virus in lung epithelial cells

Respiratory syncytial virus (RSV) is a common respiratory viral infection in children which is associated with immune dysregulation and subsequent induction and exacerbations of asthma. We recently reported that treatment of primary human epithelial cells (PHBE cells) with transforming growth factor beta (TGF-beta) enhanced RSV replication. Here, we report that the enhancement of RSV replication is mediated by induction of cell cycle arrest. These data were confirmed by using pharmacologic inhibitors of cell cycle progression, which significantly enhanced RSV replication. Our data also showed that RSV infection alone resulted in cell cycle arrest in A549 and PHBE cells. Interestingly, our data showed that RSV infection induced the expression of TGF-beta in epithelial cells. Blocking of TGF-beta with anti-TGF-beta antibody or use of a specific TGF-beta receptor signaling inhibitor resulted in rescue of the RSV-induced cell cycle arrest, suggesting an autocrine mechanism. Collectively, our data demonstrate that RSV regulates the cell cycle through TGF-beta in order to enhance its replication. These findings identify a novel pathway for upregulation of virus replication and suggest a plausible mechanism for association of RSV with immune dysregulation and asthma.

Transforming growth factor-beta enhances rhinovirus infection by diminishing early innate responses

Individuals with asthma are prone to viral and bacterial infections, and most asthma exacerbations have been linked to viruses, particularly rhinovirus. Excess transforming growth factor (TGF)-beta present in asthmatic airways may cause immune suppression, as well as transdifferentiate fibroblasts to myofibroblasts, thereby augmenting proinflammatory responses after rhinovirus infection. After rhinovirus infection we examined virus replication and host cell immune responses in airway fibroblasts in the presence of TGF-beta1 and in myofibroblasts. Primary culture fibroblasts were pretreated with TGF-beta1 or transdifferentiated into myofibroblasts, and then infected with rhinovirus. Viral replication, virus release, chemokine production, and interferon (IFN) responses were measured over 72 hours. Rhinovirus replication and virus release into supernatants were enhanced in fibroblasts incubated with TGF-beta1 and in fibroblasts obtained from patients with asthma. Myofibroblasts also showed more rhinovirus replication, and infected myofibroblasts produced excess neutrophil chemokines. Examination of innate responses revealed blunting of type I IFN reactions with dissociated viral RNA and IFN mRNA responses. Addition of type I IFN restituted antiviral responses, and the effect of TGF-beta1 appeared to be mediated via actions on IFN regulatory factor-3 pathways. These data demonstrate that TGF-beta1 mediates enhanced virus replication and proinflammatory responses in airway cells. TGF-beta may act as an endogenous immunosuppressant promoting virus replication and inflammation during the evolution of acute severe asthma associated with rhinovirus infection.

Viral infection in asthma

In bronchial asthma, respiratory virus infection involves several issues: 1) respiratory virus infection in infancy is a risk factor for, and may predispose to, the development of asthma later in life; 2) respiratory virus infection is associated with the acute exacerbation of bronchial asthma; and, 3) glucocorticosteroids (GC) are not adequate for controlling asthma-related symptoms upon respiratory virus infection. Various cells, inflammatory mediators and cytokines participate in the production of airway inflammation upon respiratory virus infection. Bronchial epithelial cells are a site of infection and replication of respiratory virus. They actively participate in the production of airway inflammation: 1) they produce various proinflammatory cytokines, chemokines and mediators; and, 2) they undergo apoptosis, thereby impairing the repair process. It is therefore important to understand the role of bronchial epithelial cells in the pathophysiology of bronchial asthma. In this review, the interaction between viral infection and asthma is discussed to elucidate the role of bronchial epithelial cells in viral infection.

HIV increases HCV replication in a TGF-beta1-dependent manner

BACKGROUND & AIMS

Human immunodeficiency virus (HIV) coinfection increases hepatitis C virus (HCV)-related progression of hepatic fibrosis, increases HCV persistence, and decreases response rates to interferon-based anti-HCV therapy. It has remained unclear how HIV, a nonhepatotropic virus, accelerates the progression of liver disease by HCV.

METHODS

We explored the possibility that circulating HIV and/or its proteins contribute to the pathogenesis of HCV through engagement of extracellular coreceptors on hepatocytes.

RESULTS

In this study, we found that inactivated HIV or gp120 increases HCV replication and enhances HCV-regulated transforming growth factor (TGF)-beta1 expression in both a replicon and an infectious model of HCV. This proviral effect of HIV and gp120 on HCV replication is neutralized by antibodies to CCR5 or CXCR4. However, HIV and gp120 did not alter type I interferon-mediated signaling in these HCV models, indicating that HIV regulates HCV replication through an alternative mechanism. Interestingly, we found that human TGF-beta1 also enhanced HCV replication. The effect of HIV on HCV replication was blocked by a neutralizing antibody to TGF-beta1, indicating that its effects on HCV replication are TGF-beta1 dependent.

CONCLUSIONS

These results suggest a novel mechanism by which HIV not only enhances HCV replication but also contributes to progression of hepatic fibrosis.

Understanding the mechanisms of viral induced asthma: new therapeutic directions

Asthma is a common and debilitating disease that has substantially increased in prevalence in Western Societies in the last 2 decades. Respiratory tract infections by respiratory syncytial virus (RSV) and rhinovirus (RV) are widely implicated as common causes of the induction and exacerbation of asthma. These infections in early life are associated with the induction of wheeze that may progress to the development of asthma. Infections may also promote airway inflammation and enhance T helper type 2 lymphocyte (Th2 cell) responses that result in exacerbations of established asthma. The mechanisms of how RSV and RV induce and exacerbate asthma are currently being elucidated by clinical studies, in vitro work with human cells and animal models of disease. This research has led to many potential therapeutic strategies and, although none are yet part of clinical practise, they show much promise for the prevention and treatment of viral disease and subsequent asthma.