Inhibition of IFN-gamma-dependent antiviral airway epithelial defense by cigarette smoke.

Background: Although individuals exposed to cigarette smoke are more susceptible to respiratory infection, the effects of cigarette smoke on lung defense are incompletely understood. Because airway epithelial cell responses to type II interferon (IFN) are critical in regulation of defense against many respiratory viral infections, we hypothesized that cigarette smoke has inhibitory effects on IFN-gamma-dependent antiviral mechanisms in epithelial cells in the airway.

Methods: Primary human tracheobronchial epithelial cells were first treated with cigarette smoke extract (CSE) followed by exposure to both CSE and IFN-gamma.

Inhibition by cigarette smoke of nuclear factor-κB-dependent response to bacteria in the airway.

Although individuals exposed to cigarette smoke are more susceptible to respiratory infection, the effects of cigarette smoke on pulmonary defense are incompletely understood. Based on the observation that interactions between bacteria and host cells result in the expression of critical defense genes regulated by NF-κB, we hypothesized that cigarette smoke alters NF-κB function. In this study, primary human tracheobronchial epithelial cells were treated with cigarette smoke extract (CSE) and exposed to Haemophilus influenzae, and the effects of CSE on bacteria-induced signaling and gene expression were assessed.

Differential effects of cytokines and corticosteroids on toll-like receptor 2 expression and activity in human airway epithelia.

Background: The recognition of microbial molecular patterns via toll-like receptors (TLRs) is critical for mucosal defenses.

Methods: Using well-differentiated primary cultures of human airway epithelia, we investigated the effects of exposure of the cells to cytokines (TNF-alpha and IFN-gamma) and dexamethasone (dex) on responsiveness to the TLR2/TLR1 ligand Pam3CSK4. Production of IL-8, CCL20, and airway surface liquid antimicrobial activity were used as endpoints.

Ectodomain shedding of angiotensin converting enzyme 2 in human airway epithelia.

Angiotensin-converting enzyme 2 (ACE2) is a terminal carboxypeptidase and the receptor for the SARS and NL63 coronaviruses (CoV). Loss of ACE2 function is implicated in severe acute respiratory syndrome (SARS) pathogenesis, but little is known about ACE2 biogenesis and activity in the airways. We report that ACE2 is shed from human airway epithelia, a site of SARS-CoV infection.

Recognizing the importance of respiratory syncytial virus in chronic obstructive pulmonary disease.

Acute exacerbations of chronic obstructive pulmonary disease (COPD) are responsible for a large proportion of the health care dollar expenditure, morbidity, and mortality related to COPD. Respiratory infections are the most common cause of acute exacerbations, but recent evidence indicates that the importance of respiratory syncytial virus (RSV) infection in COPD is under-appreciated. Improved detection of RSV using techniques based on the polymerase chain reaction accounts for much of the increased recognition of the importance of this virus in COPD patients.

Cigarette smoke alters respiratory syncytial virus-induced apoptosis and replication.

Individuals exposed to cigarette smoke have a greater number and severity of viral infections, including respiratory syncytial virus (RSV) infections, than do nonsmokers, but the cellular mechanism is unknown. Our objective was to determine the mechanism by which cigarette smoke augments viral infection. We hypothesize that cigarette smoke causes necrosis and prevents virus-induced cellular apoptosis, and that this is associated with increased inflammation and viral replication.

Respiratory epithelial cells convert inactive vitamin D to its active form: potential effects on host defense.

The role of vitamin D in innate immunity is increasingly recognized. Recent work has identified a number of tissues that express the enzyme 1alpha-hydroxylase and are able to activate vitamin D. This locally produced vitamin D is believed to have important immunomodulatory effects.

Regulation of bacteria-induced intercellular adhesion molecule-1 by CCAAT/enhancer binding proteins.

Direct interaction between bacteria and epithelial cells may initiate or amplify the airway response through induction of epithelial defense gene expression by nuclear factor-kappaB (NF-kappaB). However, multiple signaling pathways modify NF-kappaB effects to modulate gene expression. In this study, the effects of CCAAT/enhancer binding protein (C/EBP) family members on induction of the leukocyte adhesion glycoprotein intercellular adhesion molecule-1 (ICAM-1) was examined in primary cultures of human tracheobronchial epithelial cells incubated with nontypeable Haemophilus influenzae.

Serial isolates of persistent Haemophilus influenzae in patients with chronic obstructive pulmonary disease express diminishing quantities of the HMW1 and HMW2 adhesins.

In patients with chronic obstructive pulmonary disease (COPD), the lower respiratory tract is commonly colonized by bacterial pathogens, including nontypeable Haemophilus influenzae. The H. influenzae HMW1 and HMW2 adhesins are homologous proteins that promote bacterial adherence to respiratory epithelium and are the predominant targets of the host immune response.

Human adenovirus modulates surfactant phospholipid trafficking.

Surfactant, highly enriched with phosphatidylcholine (PC), is secreted into the airspace by a classic apical secretory route, thereby maintaining lung stability. Herein, we show that adenoviral infection decreases surfactant PC in lungs by inhibiting its apical secretion and redirecting its export in alveolar cells by a basolateral route. These effects were not observed with replication-deficient adenovirus (Ad), specifically lacking early region 1 (E1) gene products.

Respiratory syncytial virus decreases p53 protein to prolong survival of airway epithelial cells.

Respiratory syncytial virus (RSV) is a clinically important pathogen. It preferentially infects airway epithelial cells causing bronchiolitis in infants, exacerbations in patients with obstructive lung disease, and life-threatening pneumonia in the immunosuppressed. The p53 protein is a tumor suppressor protein that promotes apoptosis and is tightly regulated for optimal cell growth and survival.

Inhibition of Jak1-dependent signal transduction in airway epithelial cells infected with adenovirus.

Adenoviral evolution has generated mechanisms to resist host cell defense systems, but the biochemical basis for evasion of multiple antiviral pathways in the airway by adenoviruses is incompletely understood. We hypothesized that adenoviruses modulate airway epithelial responses to type I interferons by altering the levels and activation of specific Janus family kinase-signal transducer and activator of transcription (JAK-STAT) signaling components. In this study, specific effects of adenovirus type 5 (AdV) on selected JAK-STAT signal transduction pathways were identified in human tracheobronchial epithelial cells, with focus on type I interferon-dependent signaling and gene expression.

Paracellular permeability restricts airway epithelial responses to selectively allow activation by mediators at the basolateral surface.

Respiratory pathogens and toxins often assault the lung from the airway lumen. Airway epithelia may initiate and amplify inflammation in response to these attacks, but under certain conditions confinement of inflammation to the airway lumen may be beneficial to the host. Accordingly, we hypothesized that airway epithelial polarity allows different responses to basolateral vs apical stimuli that may modulate inflammation.

Increased arylsulfatase B activity in cystic fibrosis cells following correction of CFTR.

Background: The genetic disorder cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, impairing its function as a regulated anion channel involved with fluid secretion across epithelial cells. However, the clinical manifestations of CF are not thoroughly explained by impaired CFTR function. Experimental data have demonstrated oversulfation of glycoconjugates synthesized by CF epithelial cells of lung, pancreas, and other organs, and increases in the glycosaminoglycans dermatan sulfate and chondroitin sulfate in cultured skin fibroblasts from patients with CF.

Nonstructural proteins of respiratory syncytial virus suppress premature apoptosis by an NF-kappaB-dependent, interferon-independent mechanism and facilitate virus growth.

The two nonstructural (NS) proteins NS1 and NS2 of respiratory syncytial virus (RSV) are abundantly expressed in the infected cell but are not packaged in mature progeny virions. We found that both proteins were expressed early in infection, whereas the infected cells underwent apoptosis much later. Coincident with NS protein expression, a number of cellular antiapoptotic factors were expressed or activated at early stages, which included NF-kappaB and phosphorylated forms of protein kinases AKT, phosphoinositide-dependent protein kinase, and glycogen synthase kinase.

Lethal infection of K18-hACE2 mice infected with severe acute respiratory syndrome coronavirus.

The severe acute respiratory syndrome (SARS), caused by a novel coronavirus (SARS-CoV), resulted in substantial morbidity, mortality, and economic losses during the 2003 epidemic. While SARS-CoV infection has not recurred to a significant extent since 2003, it still remains a potential threat. Understanding of SARS and development of therapeutic approaches have been hampered by the absence of an animal model that mimics the human disease and is reproducible.

Respiratory syncytial virus induces TLR3 protein and protein kinase R, leading to increased double-stranded RNA responsiveness in airway epithelial cells.

Respiratory syncytial virus (RSV) preferentially infects airway epithelial cells, causing bronchiolitis, upper respiratory infections, asthma exacerbations, chronic obstructive pulmonary disease exacerbations, and pneumonia in immunocompromised hosts. A replication intermediate of RSV is dsRNA. This is an important ligand for both the innate immune receptor, TLR3, and protein kinase R (PKR).

ACE2 receptor expression and severe acute respiratory syndrome coronavirus infection depend on differentiation of human airway epithelia.

Studies of patients with severe acute respiratory syndrome (SARS) demonstrate that the respiratory tract is a major site of SARS-coronavirus (CoV) infection and disease morbidity. We studied host-pathogen interactions using native lung tissue and a model of well-differentiated cultures of primary human airway epithelia. Angiotensin converting enzyme 2 (ACE2), the receptor for both the SARS-CoV and the related human respiratory coronavirus NL63, was expressed in human airway epithelia as well as lung parenchyma.

Respiratory syncytial virus nonstructural protein 2 specifically inhibits type I interferon signal transduction.

Human respiratory syncytial virus (RSV) inhibits type I interferon-induced gene expression by decreasing expression of signal transducer and activator of transcription (Stat)2. To identify the RSV protein that mediates effects on Stat2, airway epithelial cells were infected with vaccinia virus vectors that express single RSV proteins. Expression of RSV nonstructural (NS)2 protein alone was sufficient to decrease Stat2 levels.

Pyocyanin and its precursor phenazine-1-carboxylic acid increase IL-8 and intercellular adhesion molecule-1 expression in human airway epithelial cells by oxidant-dependent mechanisms.

Pseudomonas aeruginosa secretes numerous factors that alter host cell function and may contribute to disease pathogenesis. Among recognized virulence factors is the redox-active phenazine pyocyanin. We have recently demonstrated that the precursor for pyocyanin, phenazine-1-carboxylic acid (PCA), increases oxidant formation and alters gene expression in human airway epithelial cells.

A severe acute respiratory syndrome-associated coronavirus-specific protein enhances virulence of an attenuated murine coronavirus.

Most animal species that can be infected with the severe acute respiratory syndrome-associated coronavirus (SARS-CoV) do not reproducibly develop clinical disease, hindering studies of pathogenesis. To develop an alternative system for the study of SARS-CoV, we introduced individual SARS-CoV genes (open reading frames [ORFs]) into the genome of an attenuated murine coronavirus. One protein, the product of SARS-CoV ORF6, converted a sublethal infection to a uniformly lethal encephalitis and enhanced virus growth in tissue culture cells, indicating that SARS-CoV proteins function in the context of a heterologous coronavirus infection.

Haemophilus influenzae from patients with chronic obstructive pulmonary disease exacerbation induce more inflammation than colonizers.

Rationale: Airway infection with Haemophilus influenzae causes airway inflammation, and isolation of new strains of this bacteria is associated with increased risk of exacerbations in patients with chronic obstructive pulmonary disease (COPD).

Objective: To determine whether strains of H. influenzae associated with exacerbations cause more inflammation than strains that colonize the airways of patients with COPD.