Rationale: Chronic obstructive pulmonary disease is a leading cause of death worldwide, but its pathogenesis is not well understood. Previous studies have shown that airway surface dehydration in b-epithelial Na 1 channel (bENaC)-overexpressing mice caused a chronic lung disease with high neonatal pulmonary mortality and chronic bronchitis in adult survivors. Objectives: The aim of this study was to identify the initiating lesions and investigate the natural progression of lung disease caused by airway surface dehydration. Methods: Lung morphology, gene expression, bronchoalveolar lavage, and lung mechanics were studied at different ages in bENaCoverexpressing mice. Measurements and Main Results: Mucus obstruction in bENaCoverexpressing mice originated in the trachea in the first days of life and was associated with hypoxia, airway epithelial necrosis, and death. In surviving bENaC-overexpressing mice, mucus obstruction extended into the lungs and was accompanied by goblet cell metaplasia, increased mucin expression, and airway inflammation with transient perinatal increases in tumor necrosis factor-a and macrophages, IL-13 and eosinophils, and persistent increases in keratinocytederived cytokine (KC), neutrophils, and chitinases in the lung. bENaCoverexpressing mice also developed emphysema with increased lung volumes, distal airspace enlargement, and increased lung compliance.Conclusions: Our studies demonstrate that airway surface dehydration is sufficient to initiate persistent neutrophilic airway inflammation with chronic airways mucus obstruction and to cause transient eosinophilic airway inflammation and emphysema. These results suggest that deficient airway surface hydration may play a critical role in the pathogenesis of chronic obstructive pulmonary diseases of different etiologies and serve as a target for novel therapies.

Exposed to a diverse array of potentially noxious agents, the respiratory tract is protected by a highly developed innate defense system. Physiologically regulated epithelial ion and water transport coordinated with mucin secretion, beating cilia, and cough results in continuous flow of fluid and mucus over airway surfaces toward the larynx. This cleansing action is the initial and perhaps most quantitatively important innate defense mechanism. Repeated lung infections and eventual respiratory insufficiency characteristic of human cystic fibrosis (CF) and primary ciliary dyskinesia (PCD) illustrate the consequences of impaired mucus clearance. Altered mucus clearance likely contributes to the initiation, progression, and chronicity of other airway diseases characterized by inflammation and mucous secretory cell hyper/metaplasia that afflict millions worldwide, including chronic obstructive pulmonary disease (COPD). This review concisely discusses the pathophysiology of human diseases characterized by genetic defects that impair mucus clearance. It then explores animal models in which components of the mucus clearance system have been disrupted. These models firmly establish the importance of mucus clearance for respiratory health, and will help elucidate disease mechanisms and therapeutic strategies in CF, PCD and COPD.

Overexpression of the epithelial Na؉ channel ␤ subunit (Scnn1b gene, ␤ENaC protein) in transgenic (Tg) mouse airways dehydrates mucosal surfaces, producing mucus obstruction, inflammation, and neonatal mortality. Airway inflammation includes macrophage activation, neutrophil and eosinophil recruitment, and elevated KC, TNF-␣, and chitinase levels. These changes recapitulate aspects of complex human obstructive airway diseases, but their molecular mechanisms are poorly understood. We used genetic and pharmacologic approaches to identify pathways relevant to the development of Scnn1b-Tg mouse lung pathology. A irway epithelial overexpression of the epithelial Na ϩ channel ␤ subunit (␤ENaC protein, Scnn1b gene), driven by the Clara cell secretory protein (CCSP) 3 promoter in transgenic (Tg) mice, results in epithelial Na ϩ hyperabsorption, airway surface liquid (ASL) dehydration, impaired mucus clearance, airway inflammation, and early postnatal mortality (1). The Scnn1b-Tg mouse model recapitulates many features of cystic fibrosis (CF) and other human airway diseases associated with relative dehydration of airway surfaces (2), including chronic bronchitis (CB) and chronic obstructive pulmonary disease (COPD). At birth, the lungs of Scnn1b-Tg mice are morphologically normal, but they rapidly develop time-dependent abnormalities (3). Tracheal mucus obstruction is associated with neonatal mortality, and, in surviving mice, mucus plugging and mucous secretory cell (MuSC) metaplasia progressively extend into the intrapulmonary bronchi. The inflammatory infiltrate is characterized by enlarged/highly vacuolated macrophages, persistent neutrophilia associated with elevated KC, MIP-2, and TNF-␣, and transient eosinophilia with increased levels of IL-13 and eotaxin-1 (from 2 to 6 wk). YM1, YM2, and acidic mammalian chitinase, all associated with Th2-type inflammation in asthma and helmintic infection (4 -7), are also elevated in Scnn1b-Tg mice. Moreover, Scnn1b-Tg mice exhibit transient and spotty necrotic degeneration of Clara cells in the intrapulmonary airways, peaking at day 3 and being completely resolved by day 10, and early neonatal air-trapping that later results in emphysematous changes (3). As surviving Scnn1b-Tg mice age, lymphocytic aggregates similar to those described in the lungs of COPD patients (8) become more frequent, suggesting progressive development of

Rationale: High-mobility group box 1 (HMGB1) is a potent inflammatory mediator elevated in sepsis and rheumatoid arthritis, although its role in cystic fibrosis (CF) lung disease is unknown. Objectives: To determine whether HMGB1 contributes to CF lung inflammation, including neutrophil chemotaxis and lung matrix degradation. Methods: We used sputum and serum from subjects with CF and a Scnn1b-transgenic (Scnn1b-Tg) mouse model that overexpresses bepithelial Na 1 channel in airways and mimics the CF phenotype, including lung inflammation. Human secretions and murine bronchoalveolar lavage fluid (BALF) was assayed for HMGB1 by Western blot and ELISA. Neutrophil chemotaxis was measured in vitro after incubation with human neutrophils. The collagen fragment prolineglycine-proline (PGP) was measured by tandem mass spectroscopy. Measurements and Main Results: HMGB1 was detected in CF sputum at higher levels than secretions from normal individuals. Scnn1b-Tg mice had elevated levels of HMGB1 by Western blot and ELISA. We demonstrated that dose-dependent chemotaxis of human neutrophils stimulated by purified HMGB1 was partially dependent on CXC chemokine receptors and that this could be duplicated in CF sputum and BALF from Scnn1b-Tg mice. Neutralization by anti-HMGB1 antibody, in both the sputum and BALF-reduced chemotaxis, which suggested that HMGB1 contributed to the chemotactic properties of these samples. Intratracheal administration of purified HMGB1 induced neutrophil influx into the airways of mice and promoted the release of PGP. PGP was also elevated in Scnn1b-Tg mice and CF serum. Conclusions: HMGB1 expression contributes to pulmonary inflammation and lung matrix degradation in CF airway disease and deserves further investigation as a biomarker and potential therapeutic target.

The early onset of weaning in modern humans has been linked to the high nutritional demand of brain development that is intimately connected with infant physiology and growth rate. In Neanderthals, ontogenetic patterns in early life are still debated, with some studies suggesting an accelerated development and others indicating only subtle differences vs. modern humans. Here we report the onset of weaning and rates of enamel growth using an unprecedented sample set of three late (∼70 to 50 ka) Neanderthals and one Upper Paleolithic modern human from northeastern Italy via spatially resolved chemical/isotopic analyses and histomorphometry of deciduous teeth. Our results reveal that the modern human nursing strategy, with onset of weaning at 5 to 6 mo, was present among these Neanderthals. This evidence, combined with dental development akin to modern humans, highlights their similar metabolic constraints during early life and excludes late weaning as a factor contributing to Neanderthals’ demise.