American journal of respiratory cell and molecular biology
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Am. J. Respir. Cell Mol. Biol. · Feb 2009
Role of the cystic fibrosis transmembrane conductance channel in human airway smooth muscle.
Patients with cystic fibrosis (CF) suffer from asthma-like symptoms and gastrointestinal cramps, attributed to a mutation in the CF transmembrane conductance regulator (CFTR) gene present in a variety of cells. Pulmonary manifestations of the disease include the production of thickened mucus and symptoms of asthma, such as cough and wheezing. A possible alteration in airway smooth muscle (ASM) cell function of patients with CF has not been investigated. ⋯ The CFTR pharmacological blockers, glibenclamide and N-phenyl anthranilic acid, significantly reduced histamine-induced Ca(2+) release in non-CF cells, and similar results were obtained when CFTR expression was varied using antisense oligonucleotides. In conclusion, these data show that the CFTR channel is present in ASM cells, and that it modulates the release of Ca(2+) in response to contractile agents. In patients with CF, a dysfunctional CFTR channel could contribute to the asthma diathesis and gastrointestinal problems experienced by these patients.
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Am. J. Respir. Cell Mol. Biol. · Feb 2009
Epithelial sodium channel inhibition in primary human bronchial epithelia by transfected siRNA.
Na(+) absorption and Cl(-) secretion are in equilibrium to maintain an appropriate airway surface fluid volume and ensure appropriate mucociliary clearance. In cystic fibrosis, this equilibrium is disrupted by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene resulting in the absence of functional CFTR protein, which in turn results in deficient cAMP-dependent Cl(-) secretion and predominant Na(+) absorption. It has been suggested that down-regulation of the epithelial sodium channel, ENaC, might help to restore airway hydration and reverse the airway phenotype in patients with cystic fibrosis. ⋯ Transfection was performed by exposure to siRNA for 24 hours at the time of cell seeding on permeable support. By using primary human bronchial epithelial cells we demonstrate that (1) siRNA sequences complementary to ENaC subunits are able to reduce ENaC transcripts and Na(+) channel activity by 50 to 70%, (2) transepithelial fluid absorption decreases, and (3) these functional effects last at least 8 days. A decrease in ENaC mRNA results in a significant reduction of ENaC protein function and fluid absorption through the bronchial epithelium, indicating that an RNA interference approach may improve the airway hydration status in patients with cystic fibrosis.
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Am. J. Respir. Cell Mol. Biol. · Jan 2009
Role of small GTPases and alphavbeta5 integrin in Pseudomonas aeruginosa-induced increase in lung endothelial permeability.
Pseudomonas aeruginosa is an opportunistic pathogen that can cause severe pneumonia associated with airspace flooding with protein-rich edema in critically ill patients. The type III secretion system is a major virulence factor and contributes to dissemination of P. aeruginosa. However, it is still unknown which particular bacterial toxin and which cellular pathways are responsible for the increase in lung endothelial permeability induced by P. aeruginosa. ⋯ Finally, prior activation of the stress protein response or adenoviral gene transfer of the inducible heat shock protein Hsp72 also inhibited the damaging effects of P. aeruginosa on the barrier function of lung endothelium. Taken together, these results demonstrate the critical role of the RhoA/alphavbeta5 integrin pathway in mediating P. aeruginosa-induced lung vascular permeability. In addition, activation of the stress protein response with pharmacologic inhibitors of Hsp90 may protect lungs against P. aeruginosa-induced permeability changes.
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Am. J. Respir. Cell Mol. Biol. · Jan 2009
Overexpression of Sprouty 2 in mouse lung epithelium inhibits urethane-induced tumorigenesis.
Members of the Sprouty family encode novel proteins that are thought to function primarily as intracellular antagonists of the Ras-signaling pathway. Increased Ras signaling is a critical characteristic of human lung adenocarcinoma, the most common type of non-small cell lung cancer. Sprouty 2 is expressed in the lung epithelium, the tissue layer from which lung cancers arise. ⋯ Tumor diameter was also significantly smaller in Sprouty 2 overexpressors (0.85 mm +/- 0.03 versus 0.95 mm +/- 0.02, P = 0.005). Sprouty 2 overexpression did not alter Kras mutational frequencies in urethane-induced tumors, suggesting that the tumor-suppressing effect of Sprouty 2 overexpression acts at a stage after Kras mutation, perhaps by interfering with receptor tyrosine kinase-induced signaling. These results demonstrate that Sprouty 2 overexpression inhibited both tumor initiation and subsequent tumor growth.
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Am. J. Respir. Cell Mol. Biol. · Dec 2008
Down-regulated NF-E2-related factor 2 in pulmonary macrophages of aged smokers and patients with chronic obstructive pulmonary disease.
Pulmonary macrophages are one of the sources of various antioxidant and detoxification enzymes for which NF-E2-related factor 2 (Nrf2) is a key transcriptional factor. Although Nrf2 deficiency reportedly induces severe emphysema in mice exposed to cigarette smoke (CS), no reports have studied Nrf2 regulation in chronic obstructive pulmonary disease (COPD). In this study, Nrf2 activation in response to CS was evaluated in human alveolar macrophages, and age-related differences in CS-induced Nrf2 regulation in mouse alveolar macrophages were determined. ⋯ In mice, aging suppressed the CS-induced up-regulation of Nrf2 target genes, as well as Nrf2, in alveolar macrophages. Furthermore, the Nrf2 mRNA level was decreased in laser capture microdissection-retrieved macrophages obtained from subjects with COPD (n = 10) compared with control subjects (n = 10) (P = 0.001). In conclusion, CS induces Nrf2 activation in macrophages, and Nrf2 expression is decreased in the macrophages of older current smokers and patients with COPD.