TLR2 Activation Limits Rhinovirus-Stimulated CXCL-10 by Attenuating IRAK-1-Dependent IL-33 Receptor Signaling in Human Bronchial Epithelial Cells.

Airway epithelial cells are the major target for rhinovirus (RV) infection and express proinflammatory chemokines and antiviral cytokines that play a role in innate immunity. Previously, we demonstrated that RV interaction with TLR2 causes ILR-associated kinase-1 (IRAK-1) depletion in both airway epithelial cells and macrophages. Further, IRAK-1 degradation caused by TLR2 activation was shown to inhibit ssRNA-induced IFN expression in dendritic cells. Therefore, in this study, we examined the role of TLR2 and IRAK-1 in RV-induced IFN-ß, IFN-λ1, and CXCL-10, which require signaling by viral RNA. In airway epithelial cells, blocking TLR2 enhanced RV-induced expression of IFNs and CXCL-10. By contrast, IRAK-1 inhibition abrogated RV-induced expression of CXCL-10, but not IFNs in these cells. Neutralization of IL-33 or its receptor, ST2, which requires IRAK-1 for signaling, inhibited RV-stimulated CXCL-10 expression. In addition, RV induced expression of both ST2 and IL-33 in airway epithelial cells. In macrophages, however, RV-stimulated CXCL-10 expression was primarily dependent on TLR2/IL-1R. Interestingly, in a mouse model of RV infection, blocking ST2 not only attenuated RV-induced CXCL-10, but also lung inflammation. Finally, influenza- and respiratory syncytial virus-induced CXCL-10 was also found to be partially dependent on IL-33/ST2/IRAK-1 signaling in airway epithelial cells. Together, our results indicate that RV stimulates CXCL-10 expression via the IL-33/ST2 signaling axis, and that TLR2 signaling limits RV-induced CXCL-10 via IRAK-1 depletion at least in airway epithelial cells. To our knowledge, this is the first report to demonstrate the role of respiratory virus-induced IL-33 in the induction of CXCL-10 in airway epithelial cells.

Nod-like receptor X-1 is required for rhinovirus-induced barrier dysfunction in airway epithelial cells.

UNLABELLED: Barrier dysfunction of airway epithelium may increase the risk for acquiring secondary infections or allergen sensitization. Both rhinovirus (RV) and polyinosinic-polycytidilic acid [poly(I·C)], a double-stranded RNA (dsRNA) mimetic, cause airway epithelial barrier dysfunction, which is reactive oxygen species (ROS) dependent, implying that dsRNA generated during RV replication is sufficient for disrupting barrier function. We also demonstrated that RV or poly(I·C)-stimulated NADPH oxidase 1 (NOX-1) partially accounts for RV-induced ROS generation. In this study, we identified a dsRNA receptor(s) contributing to RV-induced maximal ROS generation and thus barrier disruption. We demonstrate that genetic silencing of the newly discovered dsRNA receptor Nod-like receptor X-1 (NLRX-1), but not other previously described dsRNA receptors, abrogated RV-induced ROS generation and reduction of transepithelial resistance (R(T)) in polarized airway epithelial cells. In addition, both RV and poly(I·C) stimulated mitochondrial ROS, the generation of which was dependent on NLRX-1. Treatment with Mito-Tempo, an antioxidant targeted to mitochondria, abolished RV-induced mitochondrial ROS generation, reduction in R(T), and bacterial transmigration. Furthermore, RV infection increased NLRX-1 localization to the mitochondria. Additionally, NLRX-1 interacts with RV RNA and poly(I·C) in polarized airway epithelial cells. Finally, we show that NLRX-1 is also required for RV-stimulated NOX-1 expression. These findings suggest a novel mechanism by which RV stimulates generation of ROS, which is required for disruption of airway epithelial barrier function. IMPORTANCE: Rhinovirus (RV), a virus responsible for a majority of common colds, disrupts the barrier function of the airway epithelium by increasing reactive oxygen species (ROS). Poly(I·C), a double-stranded RNA (dsRNA) mimetic, also causes ROS-dependent barrier disruption, implying that the dsRNA intermediate generated during RV replication is sufficient for this process. Here, we demonstrate that both RV RNA and poly(I·C) interact with NLRX-1 (a newly discovered dsRNA receptor) and stimulate mitochondrial ROS. We show for the first time that NLRX-1 is primarily expressed in the cytoplasm and at the apical surface rather than in the mitochondria and that NLRX-1 translocates to mitochondria following RV infection. Together, our results suggest a novel mechanism for RV-induced barrier disruption involving NLRX-1 and mitochondrial ROS. Although ROS is necessary for optimal viral clearance, if not neutralized efficiently, it may increase susceptibility to secondary infections and alter innate immune responses to subsequently inhaled pathogens, allergens, and other environmental factors.

Neonatal rhinovirus induces mucous metaplasia and airways hyperresponsiveness through IL-25 and type 2 innate lymphoid cells.

BACKGROUND: Early-life human rhinovirus infection has been linked to asthma development in high-risk infants and children. Nevertheless, the role of rhinovirus infection in the initiation of asthma remains unclear. OBJECTIVE: We hypothesized that, in contrast to infection of mature BALB/c mice, neonatal infection with rhinovirus promotes an IL-25-driven type 2 response, which causes persistent mucous metaplasia and airways hyperresponsiveness. METHODS: Six-day-old and 8-week-old BALB/c mice were inoculated with sham HeLa cell lysate or rhinovirus. Airway responses from 1 to 28 days after infection were assessed by using quantitative PCR, ELISA, histology, immunofluorescence microscopy, flow cytometry, and methacholine responsiveness. Selected mice were treated with a neutralizing antibody to IL-25. RESULTS: Compared with mature mice, rhinovirus infection in neonatal mice increased lung IL-13 and IL-25 production, whereas IFN-γ, IL-12p40, and TNF-α expression was suppressed. In addition, the population of IL-13-secreting type 2 innate lymphoid cells (ILC2s) was expanded with rhinovirus infection in neonatal but not mature mice. ILC2s were the major cell type secreting IL-13 in neonates. Finally, anti-IL-25 neutralizing antibody attenuated ILC2 expansion, mucous hypersecretion, and airways responsiveness. CONCLUSIONS: These findings suggest that early-life viral infection could contribute to asthma development by provoking age-dependent, IL-25-driven type 2 immune responses.

Rhinovirus-induced macrophage cytokine expression does not require endocytosis or replication.

Rhinovirus (RV) is responsible for the majority of virus-induced asthma exacerbations. We showed previously that RV infection of ovalbumin-sensitized and -challenged BALB/c mice induces production of type 2 cytokines from M2-polarized macrophages. In the present study, we sought to determine the mechanism of RV-induced cytokine expression. We infected bone marrow-derived macrophages (BMMs) from BALB/c mice with RV serotype 1B, a minor group virus that infects mouse cells. Selected cultures were pretreated with IL-4, a type 2 cytokine increased in allergic asthma. RV infection of untreated cells increased messenger RNA and protein expression of the M1 cytokines TNF-α, CXCL1, and IL-6 but failed to induce expression of the M2 cytokines CCL22 and CCL24. Cells pretreated with IL-4 showed decreased expression of M1 cytokines but increased expression of Ym-1, Arg-1 (M2 markers), CCL22, and CCL24. Infection with ultraviolet (UV)-irradiated, replication-deficient RV elicited similar cytokine responses, suggesting that the outcome is replication independent. Consistent with this, viral RNA copy number did not increase in RV-treated BMMs or bronchoalveolar macrophages. RV-induced cytokine expression was not affected when cells were pretreated with cytochalasin D, suggesting that viral endocytosis is not required for the response. Finally, RV-induced cytokine expression and viral attachment were abolished in BMMs from myeloid differentiation factor 88 and Toll-like receptor (TLR)2 KO mice, suggesting a specific requirement of TLR2. We conclude that RV elicits a proinflammatory cytokine response in BMMs through a cell-surface-mediated, TLR2-dependent mechanism that does not require viral endocytosis or replication.

Combined exposure to cigarette smoke and nontypeable Haemophilus influenzae drives development of a COPD phenotype in mice.

BACKGROUND: Cigarette smoke (CS) is the major etiologic factor of chronic obstructive pulmonary disease (COPD). CS-exposed mice develop emphysema and mild pulmonary inflammation but no airway obstruction, which is also a prominent feature of COPD. Therefore, CS may interact with other factors, particularly respiratory infections, in the pathogenesis of airway remodeling in COPD. METHODS: C57BL/6 mice were exposed to CS for 2 h a day, 5 days a week for 8 weeks. Mice were also exposed to heat-killed non-typeable H. influenzae (HK-NTHi) on days 7 and 21. One day after the last exposure to CS, mice were sacrificed and lung inflammation and mechanics, emphysematous changes, and goblet cell metaplasia were assessed. Mice exposed to CS or HK-NTHi alone or room air served as controls. To determine the susceptibility to viral infections, we also challenged these mice with rhinovirus (RV). RESULTS: Unlike mice exposed to CS or HK-NTHi alone, animals exposed to CS/HK-NTHi developed emphysema, lung inflammation and goblet cell metaplasia in both large and small airways. CS/HK-NTHi-exposed mice also expressed increased levels of mucin genes and cytokines compared to mice in other groups. CS/HK-NTHi-exposed mice infected with RV demonstrated increased viral persistence, sustained neutrophilia, and further increments in mucin gene and chemokine expression compared to other groups. CONCLUSIONS: These findings indicate that in addition to CS, bacteria may also contribute to development of COPD, particularly changes in airways. Mice exposed to CS/HK-NTHi are also more susceptible to subsequent viral infection than mice exposed to either CS or HK-NTHi alone.

Macrophage activation state determines the response to rhinovirus infection in a mouse model of allergic asthma.

BACKGROUND: The mechanisms by which viruses cause asthma exacerbations are not precisely known. Previously, we showed that, in ovalbumin (OVA)-sensitized and -challenged mice with allergic airway inflammation, rhinovirus (RV) infection increases type 2 cytokine production from alternatively-activated (M2) airway macrophages, enhancing eosinophilic inflammation and airways hyperresponsiveness. In this paper, we tested the hypothesis that IL-4 signaling determines the state of macrophage activation and pattern of RV-induced exacerbation in mice with allergic airways disease. METHODS: Eight week-old wild type or IL-4 receptor knockout (IL-4R KO) mice were sensitized and challenged with OVA and inoculated with RV1B or sham HeLa cell lysate. RESULTS: In contrast to OVA-treated wild-type mice with both neutrophilic and eosinophilic airway inflammation, OVA-treated IL-4R KO mice showed increased neutrophilic inflammation with few eosinophils in the airways. Like wild-type mice, IL-4R KO mice showed OVA-induced airway hyperreactivity which was further exacerbated by RV. There was a shift in lung cytokines from a type 2-predominant response to a type 1 response, including production of IL-12p40 and TNF-α. IL-17A was also increased. RV infection of OVA-treated IL-4R KO mice further increased neutrophilic inflammation. Bronchoalveolar macrophages showed an M1 polarization pattern and ex vivo RV infection increased macrophage production of TNF-α, IFN-γ and IL-12p40. Finally, lung cells from OVA-treated IL-4R KO mice showed reduced CD206+ CD301+ M2 macrophages, decreased IL-13 and increased TNF-α and IL-17A production by F4/80+, CD11b+ macrophages. CONCLUSIONS: OVA-treated IL-4R KO mice show neutrophilic airway inflammation constituting a model of allergic, type 1 cytokine-driven neutrophilic asthma. In the absence of IL-4/IL-13 signaling, RV infection of OVA-treated mice increased type 1 cytokine and IL-17A production from conventionally-activated macrophages, augmenting neutrophilic rather than eosinophilic inflammation. In mice with allergic airways inflammation, IL-4R signaling determines macrophage activation state and the response to subsequent RV infection.

Neonatal rhinovirus infection induces mucous metaplasia and airways hyperresponsiveness.

Recent studies link early rhinovirus (RV) infections to later asthma development. We hypothesized that neonatal RV infection leads to an IL-13-driven asthma-like phenotype in mice. BALB/c mice were inoculated with RV1B or sham on day 7 of life. Viral RNA persisted in the neonatal lung up to 7 d postinfection. Within this time frame, IFN-α, -ß, and -γ peaked 1 d postinfection, whereas IFN-λ levels persisted. Next, we examined mice on day 35 of life, 28 d after initial infection. Compared with sham-treated controls, virus-inoculated mice demonstrated airways hyperresponsiveness. Lungs from RV-infected mice showed increases in several immune cell populations, as well as the percentages of CD4-positive T cells expressing IFN-γ and of NKp46/CD335(+), TCR-ß(+) cells expressing IL-13. Periodic acid-Schiff and immunohistochemical staining revealed mucous cell metaplasia and muc5AC expression in RV1B- but not sham-inoculated lungs. Mucous metaplasia was accompanied by induction of gob-5, MUC5AC, MUC5B, and IL-13 mRNA. By comparison, adult mice infected with RV1B showed no change in IL-13 expression, mucus production, or airways responsiveness 28 d postinfection. Intraperitoneal administration of anti-IL-13 neutralizing Ab attenuated RV-induced mucous metaplasia and methacholine responses, and IL-4R null mice failed to show RV-induced mucous metaplasia. Finally, neonatal RV increased the inflammatory response to subsequent allergic sensitization and challenge. We conclude that neonatal RV1B infection leads to persistent airways inflammation, mucous metaplasia, and hyperresponsiveness, which are mediated, at least in part, by IL-13.

Elastase/LPS-exposed mice exhibit impaired innate immune responses to bacterial challenge: role of scavenger receptor A.

Nontypeable Haemophilus influenzae (NTHi) is an important bacterial pathogen associated with lower respiratory tract colonization and with acute exacerbations and disease progression in chronic obstructive pulmonary disease (COPD). Why the immune system fails to eliminate NTHi and the exact contribution of the organism to COPD progression are not well understood, in part because we lack an animal model that mimics all aspects of COPD. For this study, we used an established murine model that exhibits typical features of COPD. Elastase/LPS-exposed mice infected with NTHi showed persistence of bacteria up to 5 days after infection, whereas mice exposed to elastase, LPS, or PBS cleared all bacteria by 3 days. Elastase/LPS-exposed mice also showed sustained lung neutrophilic inflammation, goblet cell metaplasia, airway hyperresponsiveness, and progression of emphysema at 15 days after infection. Alveolar macrophages isolated from elastase/LPS-exposed mice showed impaired bacterial phagocytosis, reduced expression of MARCO and of mannose receptor, and absent expression of scavenger receptor-A (SR-A). Neutralization of SR-A significantly decreased phagocytosis of NTHi by normal alveolar macrophages. Our results suggest that elastase/LPS-exposed mice show impaired bacterial clearance and sustained lung inflammation. Lack of SR-A expression may, in part, be responsible for impaired phagocytosis of bacteria by alveolar macrophages of elastase/LPS-exposed mice. These data validate the suitability of elastase/LPS model for investigating NTHi pathogenesis and progression of disease in COPD.

Susceptibility to viral infections in chronic obstructive pulmonary disease: role of epithelial cells.

PURPOSE OF REVIEW: The aim is to understand how airway epithelial cells with compromised innate defense mechanisms enhance susceptibility to respiratory virus infections in chronic obstructive pulmonary disease (COPD). RECENT FINDINGS: Exacerbations associated with respiratory viruses are more severe and increase disease severity in COPD. Airway epithelial cells cultured from COPD patients show excessive innate immune response to viral infection and higher viral load compared with normal cells. SUMMARY: Airway epithelial cells are the first line of defense in the lung and are equipped with several lines of innate defense mechanisms to fight against invading pathogens including viruses. Under normal conditions, mucociliary and barrier functions of airway epithelial cells prevent virus binding and entry into the cells. Virus-infected airway epithelial cells also express various cytokines, which recruit and activate innate and adaptive immune cells ultimately controlling the infection and tissue damage. In COPD however, compromised mucociliary and barrier functions may increase virus binding and allow virus entry into airway epithelial cells. Virus-infected COPD airway epithelial cells also show disproportionate cytokine expression leading to inappropriate recruitment and activation of innate and adaptive immune cells. COPD airway epithelial cells also show defective antiviral responses. Such defects in innate defense mechanisms may increase susceptibility to viral infections and disease severity in COPD.

Efficacy of bacteriophage therapy in a model of Burkholderia cenocepacia pulmonary infection.

The therapeutic potential of bacteriophages (phages) in a mouse model of acute Burkholderia cenocepacia pulmonary infection was assessed. Phage treatment was administered by either intranasal inhalation or intraperitoneal injection. Bacterial density, macrophage inflammatory protein 2 (MIP-2), and tumor necrosis factor alpha (TNF-alpha) levels were significantly reduced in lungs of mice treated with intraperitoneal phages (P < .05). No significant differences in lung bacterial density or MIP-2 levels were found between untreated mice and mice treated with intranasal phages, intraperitoneal ultraviolet-inactivated phages, or intraperitoneal lambda phage control mice. Mock-infected mice treated with phage showed no significant increase in lung MIP-2 or TNF-alpha levels compared with mock-infected/mock-treated mice. We have demonstrated the efficacy of phage therapy in an acute B. cenocepacia lung infection model. Systemic phage administration was more effective than inhalational administration, suggesting that circulating phages have better access to bacteria in lungs than do topical phages.

Quercetin prevents progression of disease in elastase/LPS-exposed mice by negatively regulating MMP expression.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is characterized by chronic bronchitis, emphysema and irreversible airflow limitation. These changes are thought to be due to oxidative stress and an imbalance of proteases and antiproteases. Quercetin, a plant flavonoid, is a potent antioxidant and anti-inflammatory agent. We hypothesized that quercetin reduces lung inflammation and improves lung function in elastase/lipopolysaccharide (LPS)-exposed mice which show typical features of COPD, including airways inflammation, goblet cell metaplasia, and emphysema. METHODS: Mice treated with elastase and LPS once a week for 4 weeks were subsequently administered 0.5 mg of quercetin dihydrate or 50% propylene glycol (vehicle) by gavage for 10 days. Lungs were examined for elastance, oxidative stress, inflammation, and matrix metalloproteinase (MMP) activity. Effects of quercetin on MMP transcription and activity were examined in LPS-exposed murine macrophages. RESULTS: Quercetin-treated, elastase/LPS-exposed mice showed improved elastic recoil and decreased alveolar chord length compared to vehicle-treated controls. Quercetin-treated mice showed decreased levels of thiobarbituric acid reactive substances, a measure of lipid peroxidation caused by oxidative stress. Quercetin also reduced lung inflammation, goblet cell metaplasia, and mRNA expression of pro-inflammatory cytokines and muc5AC. Quercetin treatment decreased the expression and activity of MMP9 and MMP12 in vivo and in vitro, while increasing expression of the histone deacetylase Sirt-1 and suppressing MMP promoter H4 acetylation. Finally, co-treatment with the Sirt-1 inhibitor sirtinol blocked the effects of quercetin on the lung phenotype. CONCLUSIONS: Quercetin prevents progression of emphysema in elastase/LPS-treated mice by reducing oxidative stress, lung inflammation and expression of MMP9 and MMP12.

Microarray analysis identifies defects in regenerative and immune response pathways in COPD airway basal cells.

BACKGROUND: Airway basal cells are specialised stem cells and regenerate airway epithelium. Airway basal cells isolated from patients with COPD regenerate airway epithelium with an abnormal phenotype. We performed gene expression analysis to gain insights into the defective regenerative programme in COPD basal cells. METHODS: We conducted microarray analysis and compared COPD versus normal basal cells to identify differentially regulated genes (DEGs) and the enriched biological pathways. We determined the correlation of DEGs with cell polarisation and markers of ciliated and goblet cells. HOXB2 was knocked down in 16HBE14o- cells and monitored for polarisation of cells. HOXB2 expression in the lung sections was determined by immunofluorescence. RESULTS: Comparison of normal and COPD basal cell transcriptomic profiles highlighted downregulation of genes associated with tissue development, epithelial cell differentiation and antimicrobial humoral response. Expression of one of the tissue development genes, HOXB2 showed strong correlation with transepithelial resistance and this gene was downregulated in COPD basal cells. Knockdown of HOXB2, abrogated polarisation of epithelial cells in normal cells. Finally, HOXB2 expression was substantially reduced in the bronchial epithelium of COPD patients. CONCLUSIONS: Defect in gene signatures involved in tissue development and epithelial differentiation were implicated in COPD basal cells. One of the tissue developmental genes, HOXB2, is substantially reduced in bronchial epithelium of COPD patients. Since HOXB2 contributes to airway epithelial cell polarisation, we speculate that reduced expression of HOXB2 in COPD may contribute to abnormal airway epithelial regeneration in COPD.

FOXO3a regulates rhinovirus-induced innate immune responses in airway epithelial cells.

Forkhead transcription factor class O (FOXO)3a, which plays a critical role in a wide variety of cellular processes, was also found to regulate cell-type-specific antiviral responses. Airway epithelial cells express FOXO3a and play an important role in clearing rhinovirus (RV) by mounting antiviral type I and type III interferon (IFN) responses. To elucidate the role of FOXO3a in regulating antiviral responses, we generated airway epithelial cell-specific Foxo3a knockout (Scga1b1-Foxo3a-/-) mice and a stable FOXO3a knockout human airway epithelial cell line. Compared to wild-type, Scga1b1-Foxo3a-/- mice show reduced IFN-α, IFN-ß, IFN-λ2/3 in response to challenge with RV or double-stranded (ds)RNA mimic, Poly Inosinic-polycytidylic acid (Poly I:C) indicating defective dsRNA receptor signaling. RV-infected Scga1b1-Foxo3a-/- mice also show viral persistence, enhanced lung inflammation and elevated pro-inflammatory cytokine levels. FOXO3a K/O airway epithelial cells show attenuated IFN responses to RV infection and this was associated with conformational change in mitochondrial antiviral signaling protein (MAVS) but not with a reduction in the expression of dsRNA receptors under unstimulated conditions. Pretreatment with MitoTEMPO, a mitochondrial-specific antioxidant corrects MAVS conformation and restores antiviral IFN responses to subsequent RV infection in FOXO3a K/O cells. Inhibition of oxidative stress also reduces pro-inflammatory cytokine responses to RV in FOXO3a K/O cells. Together, our results indicate that FOXO3a plays a critical role in regulating antiviral responses as well as limiting pro-inflammatory cytokine expression. Based on these results, we conclude that FOXO3a contributes to optimal viral clearance and prevents excessive lung inflammation following RV infection.

Rhinovirus and COPD airway epithelium.

Chronic Obstructive Pulmonary Disease (COPD) is characterized by irreversible airflow limitation. It is a global disease and expected to be the third leading cause of death. Respiratory exacerbations are associated with increased mortality and morbidity in this patient population. Respiratory viruses were isolated from at least 30 to 50% of the infectious respiratory COPD exacerbations with rhinovirus being most commonly isolated pathogen. Although rhinovirus does not cause airway epithelial damage like influenza and other respiratory viruses, it may further impair innate immunity of airway epithelium, which is the first line of defense in the lungs. This may increase susceptibility to secondary bacterial infections leading to progression of lung disease. Currently, there arc no therapies available to treat rhinovirus infection in COPD and therefore understanding the mechanisms underlying RV pathogenesis in COPD is essential to identify molecular target to develop new therapeutic strategies. Quercetin, a plant polyphenol, which modulates innate immunity and effectively blocks viral replication may be useful in treating rhinovirus associated COPD exacerbations.

Differential responses to rhinovirus- and influenza-associated pulmonary exacerbations in patients with cystic fibrosis.

RATIONALE: The mechanism by which viruses cause exacerbations of chronic airway disease and the capacity of patients with cystic fibrosis (CF) to respond to viral infection are not precisely known. OBJECTIVES: To determine the antiviral response to infection in patients with CF. METHODS: Sputum was collected from patients with CF with respiratory exacerbation. Viruses were detected in multiplex polymerase chain reaction (PCR)-based assays. Gene expression of 84 antiviral response genes was measured, using a focused quantitative PCR gene array. MEASUREMENTS AND MAIN RESULTS: We examined 36 samples from 23 patients with respiratory exacerbation. Fourteen samples tested virus-positive and 22 virus-negative. When we compared exacerbations associated with rhinovirus (RV, n = 9) and influenza (n = 5) with virus-negative specimens, we found distinct patterns of antiviral gene expression. RV was associated with greater than twofold induction of five genes, including those encoding the monocyte-attracting chemokines CXCL10, CXCL11, and CXCL9. Influenza was associated with overexpression of 20 genes, including those encoding the cytokines tumor necrosis factor and IL-12; the kinases MEK, TBK-1, and STAT-1; the apoptosis proteins caspase-8 and caspase-10; the influenza double-stranded RNA receptor RIG-I and its downstream effector MAVS; and pyrin, an IFN-stimulated protein involved in influenza resistance. CONCLUSIONS: We conclude that virus-induced exacerbations of CF are associated with immune responses tailored to specific infections. Influenza induced a more potent response consisting of inflammation, whereas RV infection had a pronounced effect on chemokine expression. As far as we are aware, this study is the first to compare specific responses to different viruses in live patients with chronic airway disease.

Repair and Remodeling of airway epithelium after injury in Chronic Obstructive Pulmonary Disease.

COPD is thought to develop as a result of chronic exposure to cigarette smoke, occupational or other environmental hazards and it comprises both airways and parenchyma. Acute infections or chronic colonization of airways with bacteria may also contribute to development and/or progression of COPD lung disease. Airway epithelium is the primary target for the inhaled environmental factors and pathogens. The repetitive injury as a result of chronic exposure to environmental factors may result in persistent activation of pathways involved in airway epithelial repair, such as epithelial to mesenchymal transition, altered migration and proliferation of progenitor cells, and abnormal redifferentiation leading to airway remodeling. Development of model systems which mimics chronic airways disease as observed in COPD is required to understand the molecular mechanisms underlying the abnormal airway epithelial repair that are specific to COPD and to also develop novel therapies focused on airway epithelial repair.

Barrier function of airway tract epithelium.

Airway epithelium contributes significantly to the barrier function of airway tract. Mucociliary escalator, intercellular apical junctional complexes which regulate paracellular permeability and antimicrobial peptides secreted by the airway epithelial cells are the three primary components of barrier function of airway tract. These three components act cooperatively to clear inhaled pathogens, allergens and particulate matter without inducing inflammation and maintain tissue homeostasis. Therefore impairment of one or more of these essential components of barrier function may increase susceptibility to infection and promote exaggerated and prolonged innate immune responses to environmental factors including allergens and pathogens resulting in chronic inflammation. Here we review the regulation of components of barrier function with respect to chronic airways diseases.

Quercetin inhibits rhinovirus replication in vitro and in vivo.

Rhinovirus (RV), which is responsible for the majority of common colds, also causes exacerbations in patients with asthma and chronic obstructive pulmonary disease. So far, there are no drugs available for treatment of rhinovirus infection. We examined the effect of quercetin, a plant flavanol on RV infection in vitro and in vivo. Pretreatment of airway epithelial cells with quercetin decreased Akt phosphosphorylation, viral endocytosis and IL-8 responses. Addition of quercetin 6h after RV infection (after viral endocytosis) reduced viral load, IL-8 and IFN responses in airway epithelial cells. This was associated with decreased levels of negative and positive strand viral RNA, and RV capsid protein, abrogation of RV-induced eIF4GI cleavage and increased phosphorylation of eIF2α. In mice infected with RV, quercetin treatment decreased viral replication as well as expression of chemokines and cytokines. Quercetin treatment also attenuated RV-induced airway cholinergic hyperresponsiveness. Together, our results suggest that quercetin inhibits RV endocytosis and replication in airway epithelial cells at multiple stages of the RV life cycle. Quercetin also decreases expression of pro-inflammatory cytokines and improves lung function in RV-infected mice. Based on these observations, further studies examining the potential benefits of quercetin in the prevention and treatment of RV infection are warranted.

Cable pili and the associated 22 kDa adhesin contribute to Burkholderia cenocepacia persistence in vivo.

BACKGROUND: Infection by Burkholderia cenocepacia in cystic fibrosis (CF) patients is associated with poor clinical prognosis. Previously, we demonstrated that one of the highly transmissible strains, BC7, expresses cable pili and the associated 22 kDa adhesin, both of which contribute to BC7 binding to airway epithelial cells. However, the contribution of these factors to induce inflammation and bacterial persistence in vivo is not known. METHODOLOGY/PRINCIPAL FINDINGS: Wild-type BC7 stimulated higher IL-8 responses than the BC7 cbl and BC7 adhA mutants in both CF and normal bronchial epithelial cells. To determine the role of cable pili and the associated adhesin, we characterized a mouse model of B. cenocepacia, where BC7 are suspended in Pseudomonas aeruginosa alginate. C57BL/6 mice were infected intratracheally with wild-type BC7 suspended in either alginate or PBS and were monitored for lung bacterial load and inflammation. Mice infected with BC7 suspended in PBS completely cleared the bacteria by 3 days and resolved the inflammation. In contrast, mice infected with BC7 suspended in alginate showed persistence of bacteria and moderate lung inflammation up to 5 days post-infection. Using this model, mice infected with the BC7 cbl and BC7 adhA mutants showed lower bacterial loads and mild inflammation compared to mice infected with wild-type BC7. Complementation of the BC7 cblS mutation in trans restored the capacity of this strain to persist in vivo. Immunolocalization of bacteria revealed wild-type BC7 in both airway lumen and alveoli, while the BC7 cbl and BC7 adhA mutants were found mainly in airway lumen and peribronchiolar region. CONCLUSIONS AND SIGNIFICANCE: B. cenocepacia suspended in alginate can be used to determine the capacity of bacteria to persist and cause lung inflammation in normal mice. Both cable pili and adhesin contribute to BC7-stimulated IL-8 response in vitro, and BC7 persistence and resultant inflammation in vivo.