The results indicate that H. influenzae strains isolated from patients during COPD exacerbations often induce more airway inflammation and likely have differences in virulence compared with colonizing strains. These findings support the concept that bacteria infecting the airway during COPD exacerbations mediate increased airway inflammation and contribute to decreased airway function.

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. We report in this work that PCA and pyocyanin increase expression of ICAM-1 both in vivo and in vitro. Moreover, phenazines enhanced cytokine-dependent increases in IL-8 and ICAM-1. Antioxidant intervention studies indicated both similarities and differences between PCA and pyocyanin. The thiol antioxidant N-acetyl cysteine, extracellular catalase, and inducible NO synthase inhibitors inhibited ICAM-1 and IL-8 increases in response to both phenazines. However, pyocyanin was significantly more sensitive to N-acetylcysteine inhibition. Interestingly, hydroxyl radical scavengers inhibited the response to pyocyanin, but not to PCA. These studies suggest that P. aeruginosa phenazines coordinately up-regulate chemokines (IL-8) and adhesion molecules (ICAM-1) by mechanisms that are, at least in part, oxidant dependent. However, results indicate that the mechanisms by which PCA and pyocyanin exert their effects are not identical, and not all antioxidant interventions are equally effective in inhibiting phenazine-mediated proinflammatory effects.

Many cell types in the airway express the adhesive glycoprotein for leukocytes intercellular adhesion molecule-1 (ICAM-1) constitutively and/or in response to inflammatory stimuli. In this study, we identified functions of ICAM-1 on airway epithelial cells in defense against infection with Haemophilus influenzae. Initial experiments using a mouse model of airway infection in which the bacterial inoculum was mixed with agar beads that localize inflammation in airways demonstrated that ICAM-1 expression was required for efficient clearance of H. influenzae. Airway epithelial cell ICAM-1 expression required few or no leukocytes, suggesting that epithelial cells could be activated directly by interaction with bacteria. Specific inhibition of ICAM-1 function on epithelial cells by orotracheal injection of blocking antibodies resulted in decreased leukocyte recruitment and H. influenzae clearance in the airway. Inhibition of endothelial cell ICAM-1 resulted in a similar decrease in leukocyte recruitment but did not affect bacterial clearance, indicating that epithelial cell ICAM-1 had an additional contribution to airway defense independent of effects on leukocyte migration. To assess this possibility, we used an in vitro model of neutrophil phagocytosis of bacteria and observed significantly greater engulfment of bacteria by neutrophils adherent to epithelial cells expressing ICAM-1 compared with nonadherent neutrophils. Furthermore, bacterial phagocytosis and killing by neutrophils after interaction with epithelial cells were decreased when a blocking antibody inhibited ICAM-1 function. The results indicate that epithelial cell ICAM-1 participates in neutrophil recruitment into the airway, but its most important role in clearance of H. influenzae may be assistance with neutrophil-dependent bacterial killing.

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. Using primary human airway epithelial cells differentiated at an air-liquid interface in culture, we found that responses to several cytokines required basolateral mediator application. In contrast, responses to Haemophilus influenzae occurred after either basolateral or apical interaction with airway epithelia. Experiments focused on IFN-γ receptor polarity confirmed its predominant basolateral location in cultured airway epithelia as well as in normal human airway tissue. Furthermore, physical and pharmacologic disruption of barrier function in airway epithelia allowed responses to apical application of IFN-γ and other cytokines. These in vitro studies directly correlated with experiments in mice in which an airway epithelial response to IFN-γ injected into the airway lumen was seen only after disruption of barrier function. The results indicate that airway epithelia with intact barrier function restrict inflammatory responses by limitation of cell activation through requiring interaction of selected mediators with the basolateral surface. However, loss of barrier integrity allows epithelial responses to these mediators if located in the airway lumen to amplify airway defenses.

Introduction: Chronic obstructive pulmonary disease (COPD) has been associated with lower airway, systemic, and, more recently, upper airway inflammation. The systemic component may be important through an association with increased cardiovascular comorbidity. While it is known that lower airway and systemic inflammation are increased at exacerbation of COPD (Ex)-COPD, it is not known whether the upper airway is involved at this time, nor how the upper airway, lower airway, and systemic compartments relate during such events. We investigated the relationships between systemic, upper airway, and lower airway inflammation at ExCOPD. Method: Serum, nasal wash, and sputum samples were obtained at 41 Ex in 41 subjects with COPD (mean [SD] age, 69.0 [7.7] yr; FEV 1 , 1.00 [0.43] L). We assayed leukocytes, IL-6, IL-8, myeloperoxidase (MPO), and CRP. Pre-Ex baseline samples were available in 21 patients. Results: In addition to increases in systemic and lower airway inflammation, Ex were associated with greater upper airway inflammation (nasal leukocytes and IL-6, stable vs. Ex: 4.08 vs. 4.41 log 10 cells/ml, p ϭ 0.04; 0.40 vs. 0.89 log 10 pg/ml, p ϭ 0.09). There were significant correlations between the lower airway and systemic, and lower and upper airway inflammation, but not between the upper airway and systemic compartments: sputum leukocytes with serum IL-6 and CRP (r ϭ 0.38, p ϭ 0.01; r ϭ 0.39, p ϭ 0.02) and sputum IL-8 with serum IL-6 (r ϭ 0.37, p ϭ 0.02). Sputum MPO correlated with nasal leukocytes, IL-6, IL-8, and MPO: (all r Ͼ 0.43, p Ͻ 0.01), and sputum leukocytes with nasal IL-6 (r ϭ 0.38, p ϭ 0.02). Similar relationships were observed in paired data for changes in sputum leukocytes with changes in serum IL-6 and CRP. Conclusion: ExCOPD are associated with pan-airway inflammation, but the systemic inflammatory response is related to the magnitude of the lower rather than upper airway inflammation. Conflict of Interest Statement : J.R.H. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript. W.R.P. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript. T.M.A.W. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript. G.C.D. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript. J.A.W. has received honoraria for lectures at meetings or attendance at Advisory Boards from the following companies: GlaxoSmithKline (GSK), Boehringer Ingelheim, Astra Zeneca, Bayer, and Aventis Pasteur. She has received research grants totaling approximately $600,000 from GSK for studies of COPD questionnaires, studies of COPD exacerbation time course, flow cytometric studies of the interaction of the upper and lower airway in COPD, study of time course of inflammatory markers at COPD exacerbation, analysis of long-term changes in airway and systemic inflammatory markers, clinical...

Infection by nontypable Haemophilus influenzae in the airway causes inflammation, and newly isolated strains of these bacteria are associated with an increased risk of disease exacerbation in patients with chronic obstructive pulmonary disease (COPD). In this study we questioned whether strains of H. influenzae associated with exacerbations cause greater inflammation than strains colonizing airways of COPD patients. Bacterial strains were obtained from COPD patients that underwent serial assessment of clinical status, sputum microbiology, and serum antibacterial antibody production. Exacerbation strains were defined as new isolates cultured during exacerbation of clinical symptoms with subsequent development of a homologous bactericidal antibody response. These strains were compared to colonization strains that were not associated with an increase in symptoms or new antibody production. We found that strains of H. influenzae associated with exacerbations caused more airway neutrophil recruitment than colonizer strains in an in vivo mouse model of airway infection. Experiments using an in vitro model of human primary airway epithelial cells revealed that exacerbation strains adhered significantly more to epithelial cells than colonizing strains. Exacerbating strains also induced greater release of interleukin-8 after interaction with airway epithelial cells, a response likely mediated by increased activation of both the nuclear factor-kappaB and p38 mitogen-activated protein kinase signaling pathways. The results indicate that H. influenzae isolated from patients with exacerbations of COPD induce more airway inflammation and likely have differences in virulence compared to colonizing strains. These findings support the concept that H. influenzae infecting the airway during COPD exacerbations mediate increased airway inflammation and contribute to decreased airway function.