The surfactant protein A (SP-A) gene was disrupted by homologous recombination in embryonic stem cells that were used to generate homozygous SP-A-deficient mice. SP-A mRNA and protein were not detectable in the lungs

Goblet cell hyperplasia and mucous hypersecretion contribute to the pathogenesis of chronic pulmonary diseases including cystic fibrosis, asthma, and chronic obstructive pulmonary disease. In the present work, mouse SAM pointed domain-containing ETS transcription factor (SPDEF) mRNA and protein were detected in subsets of epithelial cells lining the trachea, bronchi, and tracheal glands. SPDEF interacted with the C-terminal domain of thyroid transcription factor 1, activating transcription of genes expressed selectively in airway epithelial cells, including Sftpa, Scgb1a1, Foxj1, and Sox17. Expression of Spdef in the respiratory epithelium of adult transgenic mice caused goblet cell hyperplasia, inducing both acidic and neutral mucins in vivo, and stainined for both acidic and neutral mucins in vivo. SPDEF expression was increased at sites of goblet cell hyperplasia caused by IL-13 and dust mite allergen in a process that was dependent upon STAT-6. SPDEF was induced following intratracheal allergen exposure and after Th2 cytokine stimulation and was sufficient to cause goblet cell differentiation of Clara cells in vivo.

Surfactant protein D (SP-D

To determine the role of surfactant protein-A(SP-A) in antiviral host defense, mice lacking SP-A (SP-A -/-) were produced by targeted gene inactivation. SP-A -/-and control mice (SP-A +/+ ) were infected with respiratory syncytial virus (RSV) by intratracheal instillation. Pulmonary infiltration after infection was more severe in SP-A -/-than in SP-A +/+ mice and was associated with increased RSV plaque-forming units in lung homogenates. Pulmonary infiltration with polymorphonuclear leukocytes was greater in the SP-A -/-mice. Levels of proinflammatory cytokines tumor necrosis factor-α and interleukin-6 were enhanced in lungs of SP-A -/-mice. After RSV infection, superoxide and hydrogen peroxide generation was deficient in macrophages from SP-A -/-mice, demonstrating a critical role of SP-A in oxidant production associated with RSV infection. Coadministration of RSV with exogenous SP-A reduced viral titers and inflammatory cells in the lung of SP-A -/-mice. These findings demonstrate that SP-A plays an important host defense role against RSV in vivo.

Cis-acting elements determining lung epithelial cell-selective transcription of the murine surfactant protein A (SP-A) gene were identified between nucleotide positions -255 and -57. This region of the murine SP-A gene contained nucleotide sequences consistent with thyroid transcription factor-1 (TTF-1) binding motifs. An SP-A-CAT plasmid containing the TTF-1 binding sites was transcriptionally active in mouse lung epithelial (MLE-15) cells but not in HeLa, 3T3, or H441 cells. However, transcription of the SP-A-CAT construct was activated after cotransfection of HeLa cells with a vector expressing recombinant TTF-1, pCMV-TTF-1. Recombinant TTF-1 homeodomain protein bound to four distinct binding sites located between nucleotides -166 to -117 [corrected]. Proteins in nuclear extracts of MLE-15 cells bound TTF-1 binding sites and were supershifted by TTF-1 antibody. Mutations of three of the TTF-1 binding sites in this region reduced expression of the SP-A-CAT construct in transfected MLE-15 cells and reduced transactivation in HeLa cells. TTF-1 interacts with complex protein/DNA binding sites located in the 5'-flanking region of the murine SP-A gene enhancing lung epithelial cell-specific expression in vitro.

To determine the role of surfactant protein-A (SP-A) in host defense, the murine SP-A locus was targeted by homologous recombination to produce mice lacking SP-A. SP-A-/- and wild-type mice were infected with mucoid Pseudomonas aeruginosa by intratracheal instillation. Pulmonary bacterial loads were greater in SP-A-/- than in wild-type mice, with increased numbers of mucoid P. aeruginosa in lung homogenates at 6 and 24 h after infection. Pulmonary infiltration with polymorphonuclear leukocytes (PMN) was similar in both groups; however, an earlier influx of PMN into the lung occurred in the SP-A-/- mice. The number of bacteria phagocytosed by alveolar macrophages was decreased in the SP-A-/- mice at 1 h after infection. Superoxide-radical generation by PMN was similar for the SP-A-/- and wild-type mice, but nitrite levels were increased in SP-A-/- mice. Concentrations of tumor necrosis factor-alpha, interleukin-6, and macrophage inflammatory protein-2 (proinflammatory cytokines) were greater in bronchoalveolar lavage fluid at 2 h after infection in SP-A-/- mice. SP-A plays an important role in the pathogenesis of mucoid P. aeruginosa infection in the lung in vivo by enhancing macrophage phagocytosis and clearance of bacteria, and by modifying the inflammatory response.

ATP-dependent chromatin remodeling activities function to manipulate chromatin structure during gene regulation. One of the ways in which they do this is by altering the positions of nucleosomes along DNA. Here we provide support for the ability of these complexes to move nucleosomes into positions in which DNA is unraveled from one edge. This is expected to result in the loss of histone-DNA contacts that are important for retention of one H2A/H2B dimer within the nucleosome. Consistent with this we find that several chromatin remodeling complexes are capable of catalyzing the exchange of H2A/H2B dimers between chromatin fragments in an ATP-dependent reaction. This provides eukaryotes with additional means by which they may manipulate chromatin structure.

Surfactant protein-A (SP-A) gene-targeted mice clear group B streptococcus (GBS) from the lungs at a slower rate than wild-type mice. To determine mechanisms by which SP-A enhances pulmonary clearance of GBS, the role of SP-A in binding and phagocytosis of GBS was assessed in SP-A (-/-) mice infected with GBS in the presence and absence of exogenous SP-A. Coadministration of GBS with exogenous SP-A decreased GBS colony counts in lung homogenates of SP-A (-/-) mice. SP-A bound to GBS in a calcium-dependent manner. Although pulmonary infiltration with macrophages was not altered in SP-A (-/-) versus wild-type mice after GBS infection, the number of alveolar macrophages with phagocytosed bacteria was lower in the SP-A (-/-) mice than in the wild-type mice. When SP-A was coadministered with GBS, phagocytosis was significantly increased. Oxygen radical production by alveolar macrophages from SP-A (-/-) mice infected with GBS was decreased compared with wild-type controls and was increased when SP-A (-/-) mice were infected in the presence of exogenous SP-A. Superoxide (SO) radical generation was deficient in macrophages from SP-A (-/-) mice. SP-A plays an important role in GBS clearance in vivo, mediated in part by binding to and enhancing GBS phagocytosis and by increasing SO production by alveolar macrophages.