Physiological regulation of uteroglobin/CCSP expression

Sex-dependent regulation of mucin gene transcription and airway secretion and mechanics following intra-airway IL-13 in mice with conditional loss of club cell Creb1

Introduction: Interleukin 13 (IL-13) is an important effector molecule in allergic asthma. IL-13-mediated mucin hypersecretion requires conversion of secretoglobin-positive club cells into goblet cells through suppression of forkhead box A2 (FOXA2) and induction of SAM pointed domain containing ETS transcription factor (SPDEF). IL-13-mediated mucin hypersecretion may also include modulation of purinergic and muscarinic receptors that control basal and stimulated mucin secretion. We recently found that the transcription factor cAMP response element-binding protein (Creb1) inhibits FOXA2 and modulates mucus secretion in mice. Methods: We tested the hypothesis that loss of club cell Creb1 mitigates the pro-mucin effects of IL-13. We challenged male and female mice with conditional loss of club cell Creb1 and wild type littermates with intra-airway IL-13 or vehicle. We also studied human "club cell-like" NCI-H322 cells. Results: Loss of club cell Creb1 augmented IL-13-mediated increases in mRNA for the gel-forming mucins Muc5ac and Muc5b and prevented IL-13-mediated decreases in muscarinic 3 receptor (M3R) mRNA in male airways. In female airways, loss of club cell Creb1 reduced M3R mRNA and significantly blunted IL-13-mediated increases in purinergic receptor P2Y2 (P2ry2) mRNA but did not impact Muc5ac and Muc5b mRNA. Despite changes in mucins and secretion machinery, goblet cell density following cholinergic stimulation was not impacted by loss of club cell Creb1 in either sex. IL-13 treatment decreased basal airway resistance across sexes in mice with loss of club cell Creb1, whereas loss of club cell Creb1 augmented IL-13-mediated increases in airway elastance in response to methacholine. NCI-H322 cells displayed IL-13 signaling components, including IL-13Rα1 and IL-4Rα. Pharmacologic inhibition of CREB reduced IL-13Rα1 mRNA, whereas recombinant CREB decreased IL-4Rα mRNA. Application of IL-13 to NCI-H322 cells increased concentrations of cAMP in a delayed manner, thus linking IL-13 signaling to CREB signaling. Conclusion: These data highlight sex-specific regulation of club cell Creb1 on IL-13-mediated mucin hypersecretion and airway mechanics.

Club cell CREB regulates the goblet cell transcriptional network and pro-mucin effects of IL-1B

Introduction: Club cells are precursors for mucus-producing goblet cells. Interleukin 1β (IL-1B) is an inflammatory mediator with pro-mucin activities that increases the number of mucus-producing goblet cells. IL-1B-mediated mucin production in alveolar adenocarcinoma cells requires activation of the cAMP response element-binding protein (CREB). Whether the pro-mucin activities of IL-1B require club cell CREB is unknown. Methods: We challenged male mice with conditional loss of club cell Creb1 and wild type littermates with intra-airway IL-1B or vehicle. Secondarily, we studied human "club cell-like" H322 cells. Results: IL-1B increased whole lung mRNA of secreted (Mucin 5ac, Mucin 5b) and tethered (Mucin 1, Mucin 4) mucins independent of genotype. However, loss of club cell Creb1 increased whole lung mRNA of member RAS oncogene family (Rab3D), decreased mRNA of the muscarinic receptor 3 (M3R) and prevented IL-1B mediated increases in purinergic receptor P2Y, (P2ry2) mRNA. IL-1B increased the density of goblet cells containing neutral mucins in wildtype mice but not in mice with loss of club cell Creb1. These findings suggested that club cell Creb1 regulated mucin secretion. Loss of club cell Creb1 also prevented IL-1B-mediated impairments in airway mechanics. Four days of pharmacologic CREB inhibition in H322 cells increased mRNA abundance of forkhead box A2 (FOXA2), a repressor of goblet cell expansion, and decreased mRNA expression of SAM pointed domain containing ETS transcription factor (SPDEF), a driver of goblet cell expansion. Chromatin immunoprecipitation demonstrated that CREB directly bound to the promoter region of FOXA2, but not to the promoter region of SPDEF. Treatment of H322 cells with IL-1B increased cAMP levels, providing a direct link between IL-1B and CREB signaling. Conclusion: Our findings suggest that club cell Creb1 regulates the pro-mucin properties of IL-1B through pathways likely involving FOXA2.

Inactivation of FOXA2 by Respiratory Bacterial Pathogens and Dysregulation of Pulmonary Mucus Homeostasis

Forkhead box (FOX) proteins are transcriptional factors that regulate various cellular processes. This minireview provides an overview of FOXA2 functions, with a special emphasis on the regulation airway mucus homeostasis in both healthy and diseased lungs. FOXA2 plays crucial roles during lung morphogenesis, surfactant protein production, goblet cell differentiation and mucin expression. In healthy airways, FOXA2 exerts a tight control over goblet cell development and mucin biosynthesis. However, in diseased airways, microbial infections and proinflammatory responses deplete FOXA2 expression, resulting in uncontrolled goblet cell hyperplasia and metaplasia, mucus hypersecretion, and impaired mucociliary clearance of pathogens. Furthermore, accumulated mucus clogs the airways and creates a niche environment for persistent microbial colonization and infection, leading to acute exacerbation and deterioration of pulmonary function in patients with chronic lung diseases. Various studies have shown that FOXA2 inhibition is mediated through induction of antagonistic EGFR and IL-13R-STAT6 signaling pathways as well as through posttranslational modifications induced by microbial infections. An improved understanding of how bacterial pathogens inactivate FOXA2 may pave the way for developing therapeutics that preserve the protein's function, which in turn, will improve the mucus status and mucociliary clearance of pathogens, reduce microbial-mediated acute exacerbation and restore lung function in patients with chronic lung diseases.

CCSP G38A polymorphism environment interactions regulate CCSP levels differentially in COPD

Impaired airway homeostasis in chronic obstructive pulmonary disease (COPD) could be partly related to club cell secretory protein (CCSP) deficiency. We hypothesize that CCSP G38A polymorphism is involved and aim to examine the influence of the CCSP G38A polymorphism on CCSP transcription levels and its regulatory mechanisms. CCSP genotype and CCSP levels in serum and sputum were assessed in 66 subjects with stable COPD included in a 1-yr observational study. Forty-nine of them had an exacerbation. In an in vitro study, the impact on the CCSP promoter of 38G wild-type or 38A variant was assessed. BEAS-2B cells were transfected by either the 38G or 38A construct, in the presence/absence of cigarette smoke extract (CSE) or lipopolysaccharides (LPS). Cotransfections with modulating transcription factors, p53 and Nkx2.1, identified by in silico analysis by using ConSite and TFSEARCH were conducted. A allele carrier COPD patients had lower serum and sputum CCSP levels, especially among active smokers, and a decreased body mass index, airflow obstruction, dyspnea, and exercise capacity (BODE) score. In vitro, baseline CCSP transcription levels were similar between the wild and variant constructs. CSE decreased more profoundly the CCSP transcription level of 38A transfected cells. The opposite effect was observed with p53 cotransfection. LPS stimulation induced CCSP repression in 38A promoter transfected cells. Cotransfection with Nkx2.1 significantly activated the CCSP promoters irrespective of the polymorphism. Circulating CCSP levels are associated with smoking and the CCSP G38A polymorphism. CSE, LPS, and the Nkx2.1 and p53 transcription factors modulated the CCSP promoter efficiency. The 38A polymorphism exaggerated the CCSP repression in response to p53 and CSE.

Repair of naphthalene-induced acute tracheal injury by basal cells depends on β-catenin

OBJECTIVES

Little is known about the role of Wnt/β-catenin in postnatal airway homeostasis and basal cell function. This study aimed to investigate the role of Wnt signaling in the self-renewal of basal cells and the involvement of β-catenin in tracheal repair after naphthalene-induced injury.

METHODS

Mice were treated with naphthalene and injected with 4-hydroxytamoxifen. Injury and repair of the tracheal epithelium after naphthalene-mediated secretory cell depletion was assessed by a immunohistochemical study. The involvement of Wnt and β-catenin signaling in basal cell proliferation was investigated during in vitro expansion.

RESULTS

Immunohistochemical analysis of tracheal epithelium in wild-type mice showed a reduction in the number of Clara cell secretory protein (CCSP+) and forkhead box transcription factor (Fox-J1+) cells on days 2 to 5 after naphthalene-induced injury; this cell population was regenerated by day 10. After flush labeling, bromodeoxyuridine-positive (BrdU+) cells and Ki67+ cells were observed in tracheal epithelium on days 2 to 5 but not on days 10 and 21. Confocal microscopy visualizing K5+ and BrdU+ cells showed that Wnt3a promotes proliferation of K5+ cells. Immunohistochemical analysis of K5+ and CCSP+ in tracheal epithelial cells from wild-type littermate and K5-Cre-mediated β-catenin knock-out mice showed that on day 3, the number of CCSP+ cells was decreased in all mice. On day 10, CCSP+ cells were present in wild-type littermate mice but absent in conditional knock-out mice.

CONCLUSIONS

Basal cells serve as stem cells in the tracheal epithelium, regenerating and maintaining tracheal epithelial cells in a mouse model of tracheal injury. β-Catenin is required for proliferation and self-renewal of tracheal epithelial cells.

Chronic follicular bronchiolitis requires antigen-specific regulatory T cell control to prevent fatal disease progression

To study regulatory T (Treg) cell control of chronic autoimmunity in a lymphoreplete host, we created and characterized a new model of autoimmune lung inflammation that targets the medium and small airways. We generated transgenic mice that express a chimeric membrane protein consisting of hen egg lysozyme and a hemoglobin epitope tag under the control of the Clara cell secretory protein promoter, which largely limited transgene expression to the respiratory bronchioles. When Clara cell secretory protein-membrane hen egg lysozyme/hemoglobin transgenic mice were crossed to N3.L2 TCR transgenic mice that recognize the hemoglobin epitope, the bigenic progeny developed dense, pseudo-follicular lymphocytic peribronchiolar infiltrates that resembled the histological pattern of follicular bronchiolitis. Aggregates of activated IFN-γ- and IL-17A-secreting CD4(+) T cells as well as B cells surrounded the airways. Lung pathology was similar in Ifng(-/-) and Il17a(-/-) mice, indicating that either cytokine is sufficient to establish chronic disease. A large number of Ag-specific Treg cells accumulated in the lesions, and Treg cell depletion in the affected mice led to an interstitial spread of the disease that ultimately proved fatal. Thus, Treg cells act to restrain autoimmune responses, resulting in an organized and controlled chronic pathological process rather than a progressive disease.

Characterization of the cell of origin for small cell lung cancer

Small cell lung carcinoma (SCLC) is a neuroendocrine subtype of lung cancer that affects more than 200,000 people worldwide every year with a very high mortality rate. Here, we used a mouse genetics approach to characterize the cell of origin for SCLC; in this mouse model, tumors are initiated by the deletion of the Rb and p53 tumor suppressor genes in the lung epithelium of adult mice. We found that mouse SCLCs often arise in the lung epithelium, where neuroendocrine cells are located, and that the majority of early lesions were composed of proliferating neuroendocrine cells. In addition, mice in which Rb and p53 are deleted in a variety of non-neuroendocrine lung epithelial cells did not develop SCLC. These data indicate that SCLC likely arises from neuroendocrine cells in the lung.

Sexually dimorphic gene expression that overlaps maturation of type II pneumonocytes in fetal mouse lungs

BACKGROUND

In human, respiratory distress of the neonates, which occurs in prematurity, is prevalent in male. Late in gestation, maturation of type II pneumonocytes, and consequently the surge of surfactant synthesis are delayed in male fetuses compared with female fetuses. Although the presence of higher levels of androgens in male fetuses is thought to explain this sex difference, the identity of genes involved in lung maturation that are differentially modulated according to fetal sex is unknown. We have studied the sex difference in developing mouse lung by gene profiling during a three-day gestational window preceding and including the emergence of mature PTII cells (the surge of surfactant synthesis in the mouse occurs on GD 17.5).

METHODS

Total RNA was extracted from lungs of male and female fetal mice (gestation days 15.5, 16.5, and 17.5), converted to cRNA, labeled with biotin, and hybridized to oligonucleotide microarrays (Affymetrix MOE430A). Analysis of data was performed using MAS5.0, LFCM and Genesis softwares.

RESULTS

Many genes involved in lung maturation were expressed with no sex difference. Of the approximative 14,000 transcripts covered by the arrays, only 83 genes presented a sex difference at one or more time points between GDs 15.5 and 17.5. They include genes involved in hormone metabolism and regulation (i.e. steroidogenesis pathways), apoptosis, signal transduction, transcriptional regulation, and lipid metabolism with four apolipoprotein genes. Genes involved in immune functions and other metabolisms also displayed a sex difference.

CONCLUSION

Among these sexually dimorphic genes, some may be candidates for a role in lung maturation. Indeed, on GD 17.5, the sex difference in surfactant lipids correlates with the sex difference in pulmonary expression of apolipoprotein genes, which are involved in lipid transport. This suggests a role for these genes in the surge of surfactant synthesis. Our results would help to identify novel genes involved in the physiopathology of the respiratory distress of the neonates.

Induction of uteroglobin-related protein 2 (Ugrp2) gene expression by the Th2 cytokines IL-4 and IL-13

Uteroglobin-related proteins 1 and 2 (UGRP1 and -2) are thought to play important roles in inflammation and immunologic responses in the lung. In this study we demonstrate that IL-4 and IL-13 enhance Ugrp2 gene expression in the mouse transformed Clara cell line, mtCC, in a time- and dose-dependent manner. Addition of actinomycin D abrogated the IL-4- and IL-13-induced increase of Ugrp2 expression, demonstrating that this increase occurs at the transcriptional level. When mtCC cells were pretreated with IFN-gamma before the addition of IL-4 or IL-13, IL-4- and 13-induced Ugrp2 mRNA increase was markedly decreased. IL-4 and IL-13 induced phosphorylation of STAT6 in mtCC cells, which binds to the proximal STAT-binding element (SBE) in the Ugrp2 gene promoter, leading to transcriptional activation of this gene. Mutations of the proximal SBE abrogated the binding of activated STAT6 to this site and the IL-4-induced increase in Ugrp2 gene promoter activity. IFN-gamma-activated STAT1 binds to the same SBE in the Ugrp2 gene promoter to which STAT6 binds and decreases the binding of STAT6 to this site. Furthermore, an IL-4-induced increase in Ugrp2 expression was not observed in primary cultures of lung cells derived from STAT6-deficient mice. These results indicate that Ugrp2 expression is enhanced by IL-4 and IL-13 through STAT6 binding to the proximal SBE located in the Ugrp2 gene promoter.

PEA3, AP-1, and a unique repetitive sequence all are involved in transcriptional regulation of the breast cancer-associated gene, mammaglobin

The breast cancer-associated gene mammaglobin is a member of the secretoglobin protein family and has demonstrated its utility as a breast cancer marker. However, the transcriptional regulation of mammaglobin has not been well-characterized. In this report, we used luciferase reporter assays to identify the 200 bp directly 5' of the transcriptional start site as the minimal promoter region of mammaglobin. Sequence scanning indicated that two PEA3 transcription sites were possibly involved in mammaglobin transcription. By transfecting a PEA3 expression vector into breast cancer cell lines MDA-MB-415 and MCF-7, we determined that exogenous PEA3 was able to drive transcription. Mutational analysis indicated that each PEA3 site was functional. Our reporter system and electrophorectic mobility shift assays (EMSAs) also identified the involvement of a unique repetitive element in mammaglobin transcription. Finally, AP-1 was determined via luciferase assays to be involved in regulating non-PEA3 dependent transcription. Elucidating these cis-acting elements will impact our understanding of transcription of normal breast and breast cancer-associated genes.

Expression of epithelial sodium channel α-subunit mRNAs with alternative 5′-untranslated regions in the developing human lung

In preparation for birth, lung epithelia must switch from net fluid secretion, required for lung development, to net absorption, which prepares the lungs for postnatal gas exchange. The apical membrane amiloride-sensitive epithelial Na channel (ENaC) is the rate-limiting step for Na+ and fluid absorption. Expression of α-ENaC mRNA has been detected in human lung as early as the embryonic stage of development. However, humans express multiple transcripts for α-ENaC, containing differing 5′-untranslated regions (UTR) with unknown effects on protein translation, and different ontogenies for individual transcripts could provide a novel mechanism for developmental regulation of ENaC function. To assess the relative expression of the two most abundant α-ENaC transcripts (α-ENaC1 and α-ENaC2) during lung development, we performed nonradioactive in situ hybridization using probes specific to the alternative 5′-UTRs. Both transcripts were expressed throughout intrauterine lung development (8 to 40 wk gestation), and expression was localized to the surface epithelial cells of the conductive and respiratory airways in both ciliated cells and nonciliated Clara cells. α-ENaC mRNA expression was also identified in the serous cells of the submucosal glands surrounding the proximal airways. In the mature prenatal lung, subsets of alveolar type II (ATII) cells expressed one or both of the α-ENaC transcripts. Our observations demonstrate that a developmentally regulated switch between α-ENaC 5′-UTR variants is not the trigger by which the developing human lung becomes a fluid-absorbing organ at birth, that individual ATII cells express neither, one, or both of the α-ENaC transcripts, and that the overall expression is linked to epithelial cell differentiation and lung maturation.

FIZZ1 stimulation of myofibroblast differentiation

Bleomycin-induced pulmonary fibrosis is characterized by inflammation, emergence of myofibroblasts, and deposition of extracellular matrix. In an attempt to identify genes that may be involved in fibrosis, we used a 10,000 element (10 K) rat cDNA microarray to analyze the lung gene expression profiles in this model in the rat. Cluster analysis showed 628 genes were more than or equal to twofold up- or down-regulated, many of which were known to be involved in fibrosis. However, the most dramatic increase was observed with FIZZ1 (found in inflammatory zone; also known as RELM-alpha or resistin-like molecule-alpha), which was induced 17-fold to approximately 25-fold at the peak of expression. In situ hybridization analysis revealed FIZZ1 expression to localize primarily to alveolar and airway epithelium, which was confirmed in vitro by analysis of isolated type II alveolar epithelial cells. However FIZZ1 expression was not detected in isolated lung fibroblasts. Co-culture of FIZZ1-expressing type II cells with fibroblasts stimulated alpha-smooth muscle actin and type I collagen expression independent of transforming growth factor-beta. Transfection of a FIZZ1-expressing plasmid into fibroblasts or treatment with glutathione S-transferase-FIZZ1 fusion protein stimulated alpha-smooth muscle actin and collagen I production. These results suggest a novel role for FIZZ1 in myofibroblast differentiation in pulmonary fibrosis.

C/EBP transcription factors in the lung epithelium

During recent years, the biological roles of CCAAT/enhancer binding proteins (C/EBPs) in the lung have started to be uncovered. C/EBPs form a family within the basic region-leucine zipper class of transcription factors. In the lung epithelium C/EBPalpha, -beta, and -delta are expressed. Lung-specific target genes for these transcription factors include the surfactant proteins A and D, the Clara cell secretory protein, and the P450 enzyme CYP2B1. As more information is gathered, a picture is emerging in which C/EBPalpha has a role in regulating proliferation as well as differentiation-dependent gene expression, whereas C/EBPbeta and -delta, in addition to a partly overlapping role in regulating expression of differentiation markers, also seem to be involved in responses to injury and hormones.

Profile of gene expression induced by the tumour promotor TPA in murine epithelial cells

Malignant transformation of mouse skin by chemical carcinogens and tumour promoters, such as the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), is a multistage process that leads to squamous cell carcinoma (SCC) formation. In an effort to identify tumour-associated genes, we studied the influence of short-term TPA-treatment on the gene expression profile of murine skin. A comprehensive microarray with some 5,000 murine gene specific cDNA fragments was established and hybridised with pooled RNA derived from control and TPA-treated dorsal skin samples. Of these genes, 54 were up- and 35 were down-regulated upon TPA application. Additionally, we performed suppression subtractive hybridisation (SSH) with respective RNA pools to generate and analyse a cDNA library enriched for TPA-inducible genes. Expression data of selected genes were confirmed by quantitative real-time PCR and Northern blot analysis. Comparison of microarray and SSH data revealed that 26% of up-regulated genes identified by expression profiling matched with those present in the SSH library. Besides numerous known genes, we identified a large set of unknown cDNAs that represent previously unrecognised TPA-regulated genes in murine skin with potential function in tumour promotion. Additionally, some TPA-induced genes, such as Sprr1A, Saa3, JunB, Il4ralpha, Gp38, RalGDS and Slpi exhibit high basal level in advanced stages of skin carcinogenesis, suggesting that at least a subgroup of the identified TPA-regulated genes may contribute to tumour progression and metastasis.

Immunohistochemical analysis of Clara cell secretory protein expression in a transgenic model of mouse lung carcinogenesis

Immunohistochemical methods have been widely used to determine the histogenesis of spontaneous and chemically-induced mouse lung tumors. Typically, antigens for either alveolar Type II cells or bronchiolar epithelial Clara cells are studied. In the present work, the morphological and immunohistochemical phenotype of a transgenic mouse designed to develop lung tumors arising from Clara cells was evaluated. In this model, Clara cell-specific transformation is accomplished by directed expression of the SV40 large T antigen (TAg) under the mouse Clara cell secretory protein (CC10) promoter. In heterozygous mice, early lesions at 1 month of age consisted of hyperplastic bronchiolar epithelial cells. These progressed to adenoma by 2 months as proliferating epithelium extended into adjacent alveolar spaces. By 4 months, a large portion of the lung parenchyma was composed of tumor masses. Expression of constitutive CC10 was diminished in transgenic animals at all time points. Only the occasional cell or segment of the bronchiolar epithelium stained positively for CC10 by immunohistochemistry, and all tumors were found to be uniformly negative for staining. These results were corroborated by Western blotting, where CC10 was readily detectable in whole lung homogenate from nontransgenic animals, but not detected in lung from transgenic animals at any time point. Tumors were also examined for expression of surfactant apoprotein C (SPC), an alveolar Type II cell-specific marker, and found to be uniformly negative for staining. These results indicate that, in this transgenic model, expression of CC10, which is widely used to determine whether lung tumors arise from Clara cells, was reduced and subsequently lost during Clara cell tumor progression.

Transforming growth factor-beta inhibits pulmonary surfactant protein B gene transcription through SMAD3 interactions with NKX2.1 and HNF-3 transcription factors

Transforming growth factor-beta (TGF-beta) represses surfactant protein B (Sp-B) gene transcription through a mechanism that remains unknown. A homeodomain and a forkhead transcription factor, NKX2.1 and HNF-3, respectively, are known activators of Sp-B transcription. Because SMADs are the effectors of TGF-beta-induced gene activation, we examined the possibility that gene repression by TGF-beta may also occur through interactions of SMADs with NKX2.1 and HNF-3. We found that lung epithelial carcinoma H441 cells contain SMAD2/3 and -4, which localize to the nucleus in response to TGF-beta treatment. The activity of a transfected Sp-B promoter/reporter construct was reduced in a dose-dependent manner by TGF-beta. Cotransfection with a mutant, constitutively activated form of the Tgf-beta type I receptor repressed Sp-B promoter activity in the absence of TGF-beta ligand. Dominant negative mutants of Smads blocked the repressor activity of TGF-beta. SMAD3, but not SMAD2, mediated the repressor activity of TGF-beta on the Sp-B promoter. Mutations within a 70-base pair domain that includes binding sites for NKX2.1, hepatocyte nuclear factor 3 (HNF-3), or cAMP response element-binding protein (CREB) eliminated SMAD3-dependent repression of Sp-B transcription. Electrophoretic mobility shift analysis showed no evidence for direct binding of SMAD3 to the Sp-B promoter, and a DNA binding mutant of SMAD3 also repressed Sp-B, suggesting that direct DNA binding of SMAD3 may not be required. Using a mammalian two hybrid assay, we found physical and functional interactions between SMAD3 and both NKX2.1 and HNF-3. Also, a glutathione S-transferase-fused SMAD3 directly binds to in vitro synthesized NKX2.1 or HNF-3, demonstrating protein-protein interactions between SMAD3 and the two transcriptional factors. The DNA binding of NKX2.1 to Sp-B promoter was reduced in response to TGF-beta treatment, although expression of Nkx2.1 was not affected. We conclude that SMAD3 interactions with the positive regulators NKX2.1 and HNF-3 underlie the molecular basis for TGF-beta-induced repression of Sp-B gene transcription.

Mesenchymal-epithelial interactions in lung development and repair: are modeling and remodeling the same process?

We propose that lung morphogenesis and repair are characterized by complex cell-cell interactions of endodermal and mesodermal origin, leading to (or returning back to) an alveolar structure that can effectively exchange gases between the circulation and the alveolar space. We provide the developmental basis for cell/molecular control of lung development and disease, what is known about growth and transcription factors in normal and abnormal lung development, and how endodermal and mesodermal cell origins interact during lung development and disease. The global mechanisms that mediate mesenchymal-epithelial interactions and the plasticity of mesenchymal cells in normal lung development and remodeling provide a functional genomic model that may bring these concepts closer together. We present a synopsis followed by a vertical integration of the developmental and injury/repair mechanisms.

Glucocorticoids regulate the CCSP and CYP2B1 promoters via C/EBPbeta and delta in lung cells

Glucocorticoids have several important roles in the lung and play a key role in lung development and maturation. However, the specific molecular mechanisms of glucocorticoid action in lung are unclear. In this study, we have investigated two glucocorticoid-regulated genes expressed in the lung epithelium, the secretory protein CCSP, and the P450-enzyme CYP2B1. In transient transfections of lung epithelial cells, glucocorticoids increased expression from the CCSP and CYP2B1 promoters and we demonstrated that induction was dependent on the integrity of C/EBP-binding sites in both promoters. Electrophoretic mobility shift assays revealed increased DNA-binding of C/EBPbeta and C/EBPdelta after glucocorticoid treatment, which was not correlated to altered protein levels. The results of this study indicate a previously unknown role for C/EBP transcription factors in glucocorticoid signaling in the lung epithelium.