Anastasios Stavrou

Influenza Promotes Collagen Deposition via αvβ6-integrin Mediated Transforming Growth Factor β Activation

Background: The mechanism of influenza mediated TGFβ activation, and its role in pathogenesis is unclear. Results: H1N1 infection induced αvβ6-dependent TGFβ activity in iHBECs and increased epithelial cell death and collagen deposition in vivo. Conclusion: αvβ6 integrin-mediated TGFβ activation is involved in cell death and fibrogenesis following virus-induced epithelial injury. Significance: Viral infection may promote acute exacerbations of fibrotic lung disease. Influenza infection exacerbates chronic pulmonary diseases, including idiopathic pulmonary fibrosis. A central pathway in the pathogenesis of idiopathic pulmonary fibrosis is epithelial injury leading to activation of transforming growth factor β (TGFβ). The mechanism and functional consequences of influenza-induced activation of epithelial TGFβ are unclear. Influenza stimulates toll-like receptor 3 (TLR3), which can increase RhoA activity, a key event prior to activation of TGFβ by the αvβ6 integrin. We hypothesized that influenza would stimulate TLR3 leading to activation of latent TGFβ via αvβ6 integrin in epithelial cells. Using H1152 (IC50 6.1 μm) to inhibit Rho kinase and 6.3G9 to inhibit αvβ6 integrins, we demonstrate their involvement in influenza (A/PR/8/34 H1N1) and poly(I:C)-induced TGFβ activation. We confirm the involvement of TLR3 in this process using chloroquine (IC50 11.9 μm) and a dominant negative TLR3 construct (pZERO-hTLR3). Examination of lungs from influenza-infected mice revealed augmented levels of collagen deposition, phosphorylated Smad2/3, αvβ6 integrin, and apoptotic cells. Finally, we demonstrate that αvβ6 integrin-mediated TGFβ activity following influenza infection promotes epithelial cell death in vitro and enhanced collagen deposition in vivo and that this response is diminished in Smad3 knock-out mice. These data show that H1N1 and poly(I:C) can induce αvβ6 integrin-dependent TGFβ activity in epithelial cells via stimulation of TLR3 and suggest a novel mechanism by which influenza infection may promote collagen deposition in fibrotic lung disease.

Loss of epithelial Gq and G11 signaling inhibits TGFβ production but promotes IL-33–mediated macrophage polarization and emphysema

Signaling by Gq/11 is required for optimal TGFβ activation in the lung to prevent inflammation. Gq/11 signaling maintains healthy lungs Loss of signaling by the cytokine transforming growth factor–β (TGFβ) in mice results in emphysema-like symptoms, whereas excessive TGFβ signaling results in pulmonary fibrosis and ventilator-associated lung injury. G proteins of the Gq/11 and G12/13 families mediate the integrin-dependent activation and release of latent TGFβ from the epithelial cells. John et al. found that mice deficient in Gq/11, but not those deficient in G12/13, in lung epithelial cells had defective TGFβ activation and emphysema-like symptoms. In addition, the Gq/11-deficient mice had lung inflammation associated with increased amounts of the cytokine IL-33. However, the mice were protected from ventilator-induced injury. Together, these data suggest that Gq/11 signaling is required for optimal TGFβ activation in the lung and the prevention of inflammation. Heterotrimeric guanine nucleotide–binding protein (G protein) signaling links hundreds of G protein–coupled receptors with four G protein signaling pathways. Two of these, one mediated by Gq and G11 (Gq/11) and the other by G12 and G13 (G12/13), are implicated in the force-dependent activation of transforming growth factor–β (TGFβ) in lung epithelial cells. Reduced TGFβ activation in alveolar cells leads to emphysema, whereas enhanced TGFβ activation promotes acute lung injury and idiopathic pulmonary fibrosis. Therefore, precise control of alveolar TGFβ activation is essential for alveolar homeostasis. We investigated the involvement of the Gq/11 and G12/13 pathways in epithelial cells in generating active TGFβ and regulating alveolar inflammation. Mice deficient in both Gαq and Gα11 developed inflammation that was primarily caused by alternatively activated (M2-polarized) macrophages, enhanced matrix metalloproteinase 12 (MMP12) production, and age-related alveolar airspace enlargement consistent with emphysema. Mice with impaired Gq/11 signaling had reduced stretch-mediated generation of TGFβ by epithelial cells and enhanced macrophage MMP12 synthesis but were protected from the effects of ventilator-induced lung injury. Furthermore, synthesis of the cytokine interleukin-33 (IL-33) was increased in these alveolar epithelial cells, resulting in the M2-type polarization of alveolar macrophages independently of the effect on TGFβ. Our results suggest that alveolar Gq/11 signaling maintains alveolar homeostasis and likely independently increases TGFβ activation in response to the mechanical stress of the epithelium and decreases epithelial IL-33 synthesis. Together, these findings suggest that disruption of Gq/11 signaling promotes inflammatory emphysema but protects against mechanically induced lung injury.

Reduced Ets Domain-containing Protein Elk1 Promotes Pulmonary Fibrosis via Increased Integrin αvβ6 Expression

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease with high mortality. Active TGFβ1 is considered central to the pathogenesis of IPF. A major mechanism of TGFβ1 activation in the lung involves the epithelially restricted αvβ6 integrin. Expression of the αvβ6 integrin is dramatically increased in IPF. How αvβ6 integrin expression is regulated in the pulmonary epithelium is unknown. Here we identify a region in the β6 subunit gene (ITGB6) promoter acting to markedly repress basal gene transcription, which responds to both the Ets domain-containing protein Elk1 (Elk1) and the glucocorticoid receptor (GR). Both Elk1 and GR can regulate αvβ6 integrin expression in vitro. We demonstrate Elk1 binding to the ITGB6 promoter basally and that manipulation of Elk1 or Elk1 binding alters ITGB6 promoter activity, gene transcription, and αvβ6 integrin expression. Crucially, we find that loss of Elk1 causes enhanced Itgb6 expression and exaggerated lung fibrosis in an in vivo model of fibrosis, whereas the GR agonist dexamethasone inhibits Itgb6 expression. Moreover, Elk1 dysregulation is present in epithelium from patients with IPF. These data reveal a novel role for Elk1 regulating ITGB6 expression and highlight how dysregulation of Elk1 can contribute to human disease.

How is Europe positioned for a re-emergence of Schmallenberg virus?

Schmallenberg virus (SBV) caused a large scale epidemic in Europe from 2011 to 2013, infecting ruminants and causing foetal deformities after infection of pregnant animals. The main impact of the virus was financial loss due to restrictions on trade of animals, meat and semen. Although effective vaccines were produced, their uptake was never high. Along with the subsequent decline in new SBV infections and natural replacement of previously exposed livestock, this has resulted in a decrease in the number of protected animals. Recent surveillance has shown that a large population of naïve animals is currently present in Europe and that the virus is circulating at a low level. These changes in animal status, in combination with favourable conditions for insect vectors, may open the door to the re-emergence of SBV and another large scale outbreak in Europe. This review details the potential and preparedness for SBV re-emergence in Europe, discusses possible co-ordinated sentinel monitoring programmes for ruminant seroconversion and the presence of SBV in the insect vectors, and provides an overview of the economic impact associated with diagnosis, control and the effects of non-vaccination.

P144 Influenza infection affects the degree of fibrosis and apoptosis in the bleomycin mouse model

Introduction The bleomycin mouse mode can be used as a model of pulmonary fibrosis. The Influenza A virus can infects epithelial cells leading to cell death and injury. Acute exacerbations of Idiopathic Pulmonary Fibrosis (IPF) are characterised by epithelial cell apoptosis with unknown cause. The role of infection in acute exacerbations of IPF is unclear. The aim of this study is to investigate the effect of influenza infection on bleomycin-induced pulmonary fibrosis. Materials and Methods 60 U of bleomycin was instilled into lungs of 6–8 week old male C57Bl/6 mice. After 28 days mice were exposed intranasally with 10, 20 Units of influenza virus ‘x31’ or PBS, and lungs harvested 5 or 21 days later. Lung tissue harvested for mRNA analysis, histology and hydroxyproline levels. Animal studies were ethically reviewed and carried out in accordance with Animals (Scientific Procedures) Act 1986 and the GSK Policy on the Care, Welfare and Treatment of Animals. Results Influenza infection increased in lung collagen levels: COL1 mRNA but not COL3 was increased. There was also an increase in matrix deposition on Masson’s trichrome staining. There were increased hydroxyproline levels in influenza infected mice with fibrotic lungs due to bleomycin administration, compared with mice exposed only to bleomycin. Non-fibrotic, influenza- infected mice showed apoptosis on histological TUNEL staining. CCNA2 mRNA in influenza infected mice with fibrotic lungs was increased compared to fibrotic mice alone indicating an increase in epithelial apoptosis. Conclusion These data suggest that influenza infection may enhance the fibrotic response in the lung by promoting epithelial apoptosis and fibrogenesis.

S127 Influenza A and Poly(I:C) Induce α Vβ6-Integrin-Mediated TGFβ Activity in Human Epithelial Cells Via Stimulation of TLR3

People with chronic lung disease are more susceptible to influenza infection which may lead to exacerbation of pre-existing conditions such as fibrosis. Transforming growth factor-β (TGFβ) is a profibrotic cytokine, but its role during influenza infection remains unclear. Toll-like-receptor 3 is located on the endosomal membrane and binds dsRNA, an intermediate product from replicating ssRNAviruses such as influenza. TLR3 activation has been shown to increase RhoA activity, and we have previously shown that RhoA is a key intermediary inactivation of TGFβ by the αVβ6-integrin. Therefore, we hypothesised that influenza infection could stimulate TLR3 leading to activation of latent TGFβ via this integrin in epithelial cells. Immortalised human bronchial epithelial cells (iHBECs) were used in all experiments. To determine whether influenza virus (A/PR/8/34 H1N1), or poly (I:C) (20µg/ml) were able to activate TGFβ the following TGFβ activation assays were used; detection of phospho-smad2/3 in nuclear extracts of cell lysates by ELISA; analysis of TGFβ activity in cells transiently transfected with a TGFβ-sensitive reporterconstruct; and a co-culture of iHBECS with a TGFβ reporter cell line (TMLCs). To confirm the involvement of TLR3, cells were dual transfected with a TGFβ-sensitive reporter and a dominant negative TLR3 construct designed to prevent TLR3 signalling. The role of the RhoA-ROCK pathway, and αVβ6-integrin were investigated using the ROCK inhibitor H1152, and the αVβ6-integrin blocking antibody 6.3G9, respectively. H1N1 infection and poly(I:C) caused an increase in luciferase in iHBECs transiently transfected with a TGFβ reporter construct. Similarly, both H1N1 and poly(I:C) caused an increase in nuclear phospho-smad2/3 which could be blocked by 6.3G9 peaking at 4h. Both agents caused an increase in TGFβ as measured by a co-culture assay and this could be blocked by H1152 and 6.3G9 suggesting the involvement of ROCK, αVβ6-integrin and the requirement for cell-to-cell contact. Finally, arole for TLR3 in this process was confirmed in cells transfected with a dnTLR3 construct which lost the ability to activate TGFβ in response to poly(I:C) orH1N1. In conclusion, these data show that both influenza A and poly (I:C) lead to increased TGFβ activity in iHBECs. This supports the hypothesis that influenza A infection activates TGFβ via TLR3 and the αVβ6 integrin. These data suggest anovel mechanism by which influenza infection of epithelial cells may promoteairway and lung fibrosis.

S113 The influenza virus activates TGFß via an αVß6-integrin mediated pathway

Introduction and Objectives Idiopathic pulmonary fibrosis is a chronic progressive lung disease of unknown cause. Its pathogenesis is poorly understood but activation of latent TGFß on lung epithelium is an important factor. TGFß must be activated, as it is secreted in a latent complex with its propeptide, the latency associated peptide, and the avß6 integrin is a key activator in the lung. The Influenza A virus is a single-stranded segmented RNA virus that infects epithelial cells leading to cell death and injury. Toll-like receptors (TLRs) detect pathogens, such as influenza. TLR3 activation has been found to increase RhoA activity. We previously showed that RhoA is a key intermediary in avß6 integrin-mediated TGFß activation. The aim of this study is to investigate whether influenza can activate TGFß and stimulate TLR3 leading to activation of TGFß through the avß6 integrin in epithelial cells. Materials and Methods Immortalised human bronchial epithelial cells (iHBECs) were infected with influenza A (H2N3) virus at a multiplicity of infection 1 with, or without, the avß6 blocking antibody 6.3G9. iHBECs were also stimulated with the synthetic TLR3 ligand poly(I:C). TGFß activity was determined by: (1) immunoblotting for phosphorylated (phospho-) Smad2, and (2) Transformed mink lung cells (TMLC)-iHBEC cocultures. Infection efficiency was measured by Interferon ß mRNA levels by real-time qPCR. Results Infection with H2N3 and stimulation with poly(I:C) led to increase in phospho-smad2 and luciferase activity in coculture indicating increase in TGFß activation levels in a dose- and time-dependent manner. In both cases this was blocked with the addition of 6.3G9. qPCR data following infection showed increased IFNß1 and PAI-1, indicating the ability of the virus to infect the cells and activate TGFß. Conclusions Influenza infection and poly(I:C) activates TGFß in iHBECs in an avß6 integrin dependent manner. The data suggests a novel mechanism by which influenza infection of epithelial cells may promote lung fibrosis.