Induction of mucin and MUC5AC expression by the protease activity of Aspergillus fumigatus in airway epithelial cells.

Allergic bronchopulmonary mycosis, characterized by excessive mucus secretion, airflow limitation, bronchiectasis, and peripheral blood eosinophilia, is predominantly caused by a fungal pathogen, Aspergillus fumigatus. Using DNA microarray analysis of NCI-H292 cells, a human bronchial epithelial cell line, stimulated with fungal extracts from A. fumigatus, Alternaria alternata, or Penicillium notatum, we identified a mucin-related MUC5AC as one of the genes, the expression of which was selectively induced by A. fumigatus. Quantitative RT-PCR, ELISA, and histochemical analyses confirmed an induction of mucin and MUC5AC expression by A. fumigatus extracts or the culture supernatant of live microorganisms in NCI-H292 cells and primary cultures of airway epithelial cells. The expression of MUC5AC induced by A. fumigatus extracts diminished in the presence of neutralizing Abs or of inhibitors of the epidermal growth factor receptor or its ligand, TGF-α. We also found that A. fumigatus extracts activated the TNF-α-converting enzyme (TACE), critical for the cleavage of membrane-bound pro-TGF-α, and its inhibition with low-molecular weight inhibitors or small interfering RNA suppressed the expression of MUC5AC. The protease activity of A. fumigatus extracts was greater than that of other fungal extracts, and treatment with a serine protease inhibitor, but not with a cysteine protease inhibitor, eliminated its ability to activate TACE or induce the expression of MUC5AC mRNA in NCI-H292. In conclusion, the prominent serine protease activity of A. fumigatus, which caused the overproduction of mucus by the bronchial epithelium via the activation of the TACE/TGF-α/epidermal growth factor receptor pathway, may be a pathogenetic mechanism of allergic bronchopulmonary mycosis.

Predictors of osteoporosis and vertebral fractures in patients presenting with moderate-to-severe chronic obstructive lung disease.

Bone mineral density (BMD) alone does not reliably predict osteoporotic fractures. The Fracture Risk Assessment Tool (FRAX) was developed to estimate the risk of fracture in the general population. This study was designed to identify predictors of osteoporosis and vertebral fractures in patients presenting with chronic obstructive pulmonary disease (COPD). We studied 85 patients (mean age = 75 years; 92% men) with moderate to very severe COPD. Osteoporosis and vertebral fractures were diagnosed with dual energy X-ray absorptiometric scan and vertebral X-rays, respectively. Patient characteristics, including age, gender, body mass index (BMI), and results of pulmonary function tests, chest computed tomography scan, blood and urinary biomarkers of bone turnover were recorded, and a FRAX score was calculated by a computer-based algorithm. Osteoporosis, defined as a T score < -2.5, found in 20 patients (24%), was associated with female gender, BMI, dyspnea scale, long-term oxygen therapy (LTOT), vital capacity (VC), emphysema score on computed tomography, measurements of serum and urinary biomarkers of bone turnover. Vertebral fractures, diagnosed in 29 patients (35%), were strongly correlated with age, LTOT, VC, and forced expiratory volume in 1 sec, treatment with oral corticosteroid or warfarin, and weakly associated with the presence of osteoporosis. There was no correlation between FRAX score and prevalence of vertebral fractures, suggesting that neither BMD alone nor FRAX score would predict the presence of vertebral fractures in COPD patients. A disease-specific algorithm to predict osteoporotic fractures is needed to improve the management of patients suffering from COPD.

Strain-specific phenotypes of airway inflammation and bronchial hyperresponsiveness induced by epicutaneous allergen sensitization in BALB/c and C57BL/6 mice.

BACKGROUND: Allergen sensitization through a disrupted skin barrier appears to play a prominent role in the development of atopic diseases, including allergic asthma. The role of the genetic background in immunological and physiological phenotypes induced by epicutaneous sensitization is undetermined. METHODS: BALB/c and C57BL/6 mice were sensitized either epicutaneously by patch application of ovalbumin (OVA) or systemically by intraperitoneal injection of OVA with alum before exposure to aerosolized OVA. The concentrations of OVA-specific immunoglobulin in serum and cytokines in bronchoalveolar lavage fluid (BALF) were measured by enzyme-linked immunosorbent assay. The severity of airway inflammation was evaluated by cell counts in BALF, and bronchial responsiveness to methacholine was measured by the flexiVent system. RESULTS: The production of OVA-specific IgG1 and IgE was greater in the epicutaneously sensitized BALB/c than C57BL/6 mice. In contrast, both eosinophilic airway inflammation and bronchial responsiveness to methacholine were more prominent in the C57BL/6 than in the BALB/c mice. The concentrations of interleukin-4 increased significantly in the BALF from C57BL/6 mice only. No between-strain differences were observed after intraperitoneal sensitization. CONCLUSIONS: The C57BL/6 mouse is a more appropriate model than the BALB/c mouse to study the relationship between skin barrier dysfunction and the pathogenesis of allergic asthma.