Regulation of surfactant protein gene transcription

A promoterless AAV6.2FF-based lung gene editing platform for the correction of surfactant protein B deficiency

Surfactant protein B (SP-B) deficiency is a rare genetic disease that causes fatal respiratory failure within the first year of life. Currently, the only corrective treatment is lung transplantation. Here, we co-transduced the murine lung with adeno-associated virus 6.2FF (AAV6.2FF) vectors encoding a SaCas9-guide RNA nuclease or donor template to mediate insertion of promoterless reporter genes or the (murine) Sftpb gene in frame with the endogenous surfactant protein C (SP-C) gene, without disrupting SP-C expression. Intranasal administration of 3 × 1011 vg donor template and 1 × 1011 vg nuclease consistently edited approximately 6% of lung epithelial cells. Frequency of gene insertion increased in a dose-dependent manner, reaching 20%-25% editing efficiency with the highest donor template and nuclease doses tested. We next evaluated whether this promoterless gene editing platform could extend survival in the conditional SP-B knockout mouse model. Administration of 1 × 1012 vg SP-B-donor template and 5 × 1011 vg nuclease significantly extended median survival (p = 0.0034) from 5 days in the untreated off doxycycline group to 16 days in the donor AAV and nuclease group, with one gene-edited mouse living 243 days off doxycycline. This AAV6.2FF-based gene editing platform has the potential to correct SP-B deficiency, as well as other disorders of alveolar type II cells.

Molecular Impact of Conventional and Electronic Cigarettes on Pulmonary Surfactant

The alveolar epithelium is covered by a non-cellular layer consisting of an aqueous hypophase topped by pulmonary surfactant, a lipo-protein mixture with surface-active properties. Exposure to cigarette smoke (CS) affects lung physiology and is linked to the development of several diseases. The macroscopic effects of CS are determined by several types of cell and molecular dysfunction, which, among other consequences, lead to surfactant alterations. The purpose of this review is to summarize the published studies aimed at uncovering the effects of CS on both the lipid and protein constituents of surfactant, discussing the molecular mechanisms involved in surfactant homeostasis that are altered by CS. Although surfactant homeostasis has been the topic of several studies and some molecular pathways can be deduced from an analysis of the literature, it remains evident that many aspects of the mechanisms of action of CS on surfactant homeostasis deserve further investigation.

Staphylococcus aureus Lung Infection Results in Down-Regulation of Surfactant Protein-A Mainly Caused by Pro-Inflammatory Macrophages

Pneumonia is the leading cause of hospitalization worldwide. Besides viruses, bacterial co-infections dramatically exacerbate infection. In general, surfactant protein-A (SP-A) represents a first line of immune defense. In this study, we analyzed whether influenza A virus (IAV) and/or Staphylococcus aureus (S. aureus) infections affect SP-A expression. To closely reflect the situation in the lung, we used a human alveolus-on-a-chip model and a murine pneumonia model. Our results show that S. aureus can reduce extracellular levels of SP-A, most likely attributed to bacterial proteases. Mono-epithelial cell culture experiments reveal that the expression of SP-A is not directly affected by IAV or S. aureus. Yet, the mRNA expression of SP-A is strongly down-regulated by TNF-α, which is highly produced by professional phagocytes in response to bacterial infection. By using the human alveolus-on-a-chip model, we show that the down-regulation of SP-A is strongly dependent on macrophages. In a murine model of pneumonia, we can confirm that S. aureus decreases SP-A levels in vivo. These findings indicate that (I) complex interactions of epithelial and immune cells induce down-regulation of SP-A expression and (II) bacterial mono- and super-infections reduce SP-A expression in the lung, which might contribute to a severe outcome of bacterial pneumonia.

Clinical significance of thyroid hormone and antibodies in patients with idiopathic interstitial pneumonia

Background

Hypothyroidism was recently reported to be common and to predict mortality in patients with idiopathic pulmonary fibrosis (IPF). In addition, a high prevalence of hypothyroidism was shown in patients with idiopathic pleuroparenchymal fibroelastosis. However, in idiopathic interstitial pneumonia (IIP), a clinical significance of thyroid function has not been clarified in detail. The goal of this study was to investigate the clinical significance of thyroid function and the presence of thyroid antibodies in IIP.

Methods

We have reviewed IIP patients, and analyzed the positivity of thyroid antibodies at first. Next, the relationship of clinical characteristics with thyroid function and the positivity of thyroid antibodies was analyzed. Lastly, the positivity of thyroid antibodies and other autoantibodies was evaluated.

Results

In IIP patients, thyroglobulin and thyroid peroxidase antibodies were positive in 17 and 16%, respectively, and 22% of patients had either or both antibodies. Subclinical and/or overt hypothyroidism was confirmed in 7% of IIP patients. The free thyrotropin level had a significant positive correlation with vital capacity and a significant negative correlation with the C-reactive protein and surfactant protein-A levels, and erythrocyte sedimentation ratio (ESR). In addition, autoantibodies suggestive of connective tissue diseases (CTDs) were positive in more than two thirds of IIP patients with the thyroid antibody, and the positive rate of antinuclear and proteinase-3 anti-neutrophil cytoplasmic antibodies was significantly higher in IIP patients with thyroid antibodies than those without the antibodies.

Conclusions

Although thyroid dysfunction is not frequent, thyroid hormones and thyroid antibodies are possibly involved in the pathogenesis of IIP and their evaluation may be clinically useful to identify the clinical phenotype of IIP with autoimmune features.

Survival analyses and immunohistochemical study of primary signet ring cell carcinoma of the lung adenocarcinoma

Background

The clinicopathological features, immunohistochemical (IHC) characteristics and survival outcomes of primary lung adenocarcinoma with signet ring cells (LAdSRCs) component were analyzed.

Methods

A retrospective analysis of primary LAdSRCs consecutively collected from 2010 to 2014 was performed and compared with lung adenocarcinoma (ADC). We investigated the survival outcomes and the expression of cytokeratin 7 (CK7), CK20, thyroid transcription factor-1 (TTF-1) and villin in these 35 cases of primary LAdSRCs.

Results

We identified 1,715 patients in total, 35 (2.0%) of whom had signet ring cell (SRC) component. Excepting for 2 cases without IHC information, a CK profile (CK7+/CK20-) were identified in 69.7% (23/33) of LAdSRC; 22 (66.7%) of 33 LAdSRCs exhibited positive TTF-1 expression, but no other TTF-1 positive was found in signet ring cell carcinoma (SRCC) of other organs, and villin was not identified in these 33 cases. Age, sex, tumor size, surgery resection, smoking history, tumor stage, nodal stage, predominant histology subtype, pathology and adjuvant therapy were all significant predictors of relapse-free survival (RFS) and overall survival (OS) in univariable analysis. Compared to lung ADC, the lung ADCs with SRC component had an inferior prognosis. In multivariable analysis, sex, tumor size, tumor stage, nodal stage, predominant histology subtype and adjuvant therapy were still significant predictors for both RFS and OS while the pathology [RFS: hazard ratio (HR), 0.918; 95% confidence interval (CI), 0.581-1.492; P=0.712; OS: HR, 1.392; 95% CI, 0.820-2.364; P=0.221, respectively] was not.

Conclusions

Univariable analysis revealed primary LAdSRC is a rare ADC subtype with a worse prognosis compared with ADC. The high percentage expression of TTF-1 and immunostaining profiles CK7+/CK20- in primary LAdSRC is significant to identify the source of SRCCs.

Double knock-out of Hmga1 and Hipk2 genes causes perinatal death associated to respiratory distress and thyroid abnormalities in mice

The serine–threonine kinase homeodomain-interacting protein kinase 2 (HIPK2) modulates important cellular functions during development, acting as a signal integrator of a wide variety of stress signals, and as a regulator of transcription factors and cofactors. We have previously demonstrated that HIPK2 binds and phosphorylates High-Mobility Group A1 (HMGA1), an architectural chromatinic protein ubiquitously expressed in embryonic tissues, decreasing its binding affinity to DNA. To better define the functional role of HIPK2 and HMGA1 interaction in vivo, we generated mice in which both genes are disrupted. About 50% of these Hmga1/Hipk2 double knock-out (DKO) mice die within 12 h of life (P1) for respiratory failure. The DKO mice present an altered lung morphology, likely owing to a drastic reduction in the expression of surfactant proteins, that are required for lung development. Consistently, we report that both HMGA1 and HIPK2 proteins positively regulate the transcriptional activity of the genes encoding the surfactant proteins. Moreover, these mice display an altered expression of thyroid differentiation markers, reasonably because of a drastic reduction in the expression of the thyroid-specific transcription factors PAX8 and FOXE1, which we demonstrate here to be positively regulated by HMGA1 and HIPK2. Therefore, these data indicate a critical role of HIPK2/HMGA1 cooperation in lung and thyroid development and function, suggesting the potential involvement of their impairment in the pathogenesis of human lung and thyroid diseases.

Autophagy is required for lung development and morphogenesis

Bronchopulmonary dysplasia (BPD) remains a major respiratory illness in extremely premature infants. The biological mechanisms leading to BPD are not fully understood, although an arrest in lung development has been implicated. The current study aimed to investigate the occurrence of autophagy in the developing mouse lung and its regulatory role in airway branching and terminal sacculi formation. We found 2 windows of epithelial autophagy activation in the developing mouse lung, both resulting from AMPK activation. Inhibition of AMPK-mediated autophagy led to reduced lung branching in vitro. Conditional deletion of beclin 1 (Becn1) in mouse lung epithelial cells (Becn1Epi-KO), either at early (E10.5) or late (E16.5) gestation, resulted in lethal respiratory distress at birth or shortly after. E10.5 Becn1Epi-KO lungs displayed reduced airway branching and sacculi formation accompanied by impaired vascularization, excessive epithelial cell death, reduced mesenchymal thinning of the interstitial walls, and delayed epithelial maturation. E16.5 Becn1Epi-KO lungs had reduced terminal air sac formation and vascularization and delayed distal epithelial differentiation, a pathology similar to that seen in infants with BPD. Taken together, our findings demonstrate that intrinsic autophagy is an important regulator of lung development and morphogenesis and may contribute to the BPD phenotype when impaired.

Expression of surfactant protein B is dependent on cell density in H441 lung epithelial cells

Background

Expression of surfactant protein (SP)-B, which assures the structural stability of the pulmonary surfactant film, is influenced by various stimuli, including glucocorticoids; however, the role that cell-cell contact plays in SP-B transcription remains unknown. The aim of the current study was to investigate the impact of cell-cell contact on SP-B mRNA and mature SP-B expression in the lung epithelial cell line H441.

Methods

Different quantities of H441 cells per growth area were either left untreated or incubated with dexamethasone. The expression of SP-B, SP-B transcription factors, and tight junction proteins were determined by qPCR and immunoblotting. The influence of cell density on SP-B mRNA stability was investigated using the transcription inhibitor actinomycin D.

Results

SP-B mRNA and mature SP-B expression levels were significantly elevated in untreated and dexamethasone-treated H441 cells with increasing cell density. High cell density as a sole stimulus was found to barely have an impact on SP-B transcription factor and tight junction mRNA levels, while its stimulatory ability on SP-B mRNA expression could be mimicked using SP-B-negative cells. SP-B mRNA stability was significantly increased in high-density cells, but not by dexamethasone alone.

Conclusion

SP-B expression in H441 cells is dependent on cell-cell contact, which increases mRNA stability and thereby potentiates the glucocorticoid-mediated induction of transcription. Loss of cell integrity might contribute to reduced SP-B secretion in damaged lung cells via downregulation of SP-B transcription. Cell density-mediated effects should thus receive greater attention in future cell culture-based research.

Hyperoxia treatment of TREK-1/TREK-2/TRAAK-deficient mice is associated with a reduction in surfactant proteins

We previously proposed a role for the two-pore domain potassium (K2P) channel TREK-1 in hyperoxia (HO)-induced lung injury. To determine whether redundancy among the three TREK isoforms (TREK-1, TREK-2, and TRAAK) could protect from HO-induced injury, we now examined the effect of deletion of all three TREK isoforms in a clinically relevant scenario of prolonged HO exposure and mechanical ventilation (MV). We exposed WT and TREK-1/TREK-2/TRAAK-deficient [triple knockout (KO)] mice to either room air, 72-h HO, MV [high and low tidal volume (TV)], or a combination of HO + MV and measured quasistatic lung compliance, bronchoalveolar lavage (BAL) protein concentration, histologic lung injury scores (LIS), cellular apoptosis, and cytokine levels. We determined surfactant gene and protein expression and attempted to prevent HO-induced lung injury by prophylactically administering an exogenous surfactant (Curosurf). HO treatment increased lung injury in triple KO but not WT mice, including an elevated LIS, BAL protein concentration, and markers of apoptosis, decreased lung compliance, and a more proinflammatory cytokine phenotype. MV alone had no effect on lung injury markers. Exposure to HO + MV (low TV) further decreased lung compliance in triple KO but not WT mice, and HO + MV (high TV) was lethal for triple KO mice. In triple KO mice, the HO-induced lung injury was associated with decreased surfactant protein (SP) A and SPC but not SPB and SPD expression. However, these changes could not be explained by alterations in the transcription factors nuclear factor-1 (NF-1), NKX2.1/thyroid transcription factor-1 (TTF-1) or c-jun, or lamellar body levels. Prophylactic Curosurf administration did not improve lung injury scores or compliance in triple KO mice.

Roles of Thyroid Transcription Factor 1 in Lung Cancer Biology

Thyroid transcription factor 1 (TTF-1 or NKX2-1) is a transcription factor of fundamental importance in driving lung maturation and morphogenesis. In the last decade, scientists began to appreciate the functional roles of TTF-1 in lung tumorigenesis. This movement was triggered by the discoveries of genetic alterations of TTF-1 in the form of gene amplification in lung cancer. Many downstream target genes of TTF-1 relevant to the lung cancer biology of TTF-1 have been documented. One of the most surprising findings was that TTF-1 may exhibit either pro- or antitumorigenic activities, an outcome with the complexity exceeding the original anticipation purely based on the fact that TTF-1 undergoes gene amplification in lung cancer. In the coming decade, we believe, we will witness additional surprises as the research exploring the cancer roles of TTF-1 progresses.

Co-infection of H9N2 subtype avian influenza virus and infectious bronchitis virus decreases SP-A expression level in chickens

Chicken surfactant protein A (cSP-A) is a collectin believed to play an important role in antiviral immunity. However, cSP-A expression in the respiratory tract of chickens after viral co-infection remains unclear. The aim of this study was the detection and characterization of cSP-A in co-infected chickens. For this purpose, four-week-old specific pathogen-free (SPF) chickens were divided into five groups and inoculated intranasally with H9N2 subtype avian influenza virus (AIV), infectious bronchitis virus (IBV), or Newcastle disease virus (NDV). Chickens were sacrificed at three days post inoculation, and the lung, trachea, and air sac samples were taken to determine histological changes and expression levels of cSP-A mRNA and cSP-A protein. The cSP-A mRNA and its protein were detected separately using real-time quantitative reverse transcriptional polymerase chain reaction (qRT-PCR), a sandwich enzyme-linked immunosorbent assay (S-ELISA), and an immunohistochemistry assay (IHC). In comparison, for the PBS group as the negative group and the NDV-infected group as the positive group, the histological changes showed that the lesions of the AIV+ IBV co-infected group were more serious compared to the AIV-infected group and the IBV-infected group. Consequently, the expression level of cSP-A in the AIV+IBV co-infected group significantly decreased when compared to the AIV-infected group and the IBV-infected group by qRT-PCR, ELISA, and IHC analysis. The mechanism of the downregulation of SP-A expression level will be addressed in future.

Evolution, Development, and Function of the Pulmonary Surfactant System in Normal and Perturbed Environments

Surfactant lipids and proteins form a surface active film at the air-liquid interface of internal gas exchange organs, including swim bladders and lungs. The system is uniquely positioned to meet both the physical challenges associated with a dynamically changing internal air-liquid interface, and the environmental challenges associated with the foreign pathogens and particles to which the internal surface is exposed. Lungs range from simple, transparent, bag-like units to complex, multilobed, compartmentalized structures. Despite this anatomical variability, the surfactant system is remarkably conserved. Here, we discuss the evolutionary origin of the surfactant system, which likely predates lungs. We describe the evolution of surfactant structure and function in invertebrates and vertebrates. We focus on changes in lipid and protein composition and surfactant function from its antiadhesive and innate immune to its alveolar stability and structural integrity functions. We discuss the biochemical, hormonal, autonomic, and mechanical factors that regulate normal surfactant secretion in mature animals. We present an analysis of the ontogeny of surfactant development among the vertebrates and the contribution of different regulatory mechanisms that control this development. We also discuss environmental (oxygen), hormonal and biochemical (glucocorticoids and glucose) and pollutant (maternal smoking, alcohol, and common "recreational" drugs) effects that impact surfactant development. On the adult surfactant system, we focus on environmental variables including temperature, pressure, and hypoxia that have shaped its evolution and we discuss the resultant biochemical, biophysical, and cellular adaptations. Finally, we discuss the effect of major modern gaseous and particulate pollutants on the lung and surfactant system.

Oncolytic adenovirus targeting cyclin E overexpression repressed tumor growth in syngeneic immunocompetent mice

Background

Clinical trials have indicated that preclinical results obtained with human tumor xenografts in mouse models may overstate the potential of adenovirus (Ad)-mediated oncolytic therapies. We have previously demonstrated that the replication of human Ads depends on cyclin E dysregulation or overexpression in cancer cells. ED-1 cell derived from mouse lung adenocarcinomas triggered by transgenic overexpression of human cyclin E may be applied to investigate the antitumor efficacy of oncolytic Ads.

Methods

Ad-cycE was used to target cyclin E overexpression in ED-1 cells and repress tumor growth in a syngeneic mouse model for investigation of oncolytic virotherapies.

Results

Murine ED-1 cells were permissive for human Ad replication and Ad-cycE repressed ED-1 tumor growth in immunocompetent FVB mice. ED-1 cells destroyed by oncolytic Ads in tumors were encircled in capsule-like structures, while cells outside the capsules were not infected and survived the treatment.

Conclusion

Ad-cycE can target cyclin E overexpression in cancer cells and repress tumor growth in syngeneic mouse models. The capsule structures formed after Ad intratumoral injection may prevent viral particles from spreading to the entire tumor.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1731-x) contains supplementary material, which is available to authorized users.

Thyroid Disease Is Prevalent and Predicts Survival in Patients With Idiopathic Pulmonary Fibrosis

BACKGROUND

A significant minority of patients with idiopathic pulmonary fibrosis (IPF) display features of autoimmunity without meeting the criteria for overt connective tissue disease. A link between IPF and other immune-mediated processes, such as hypothyroidism (HT), has not been reported. In this investigation, we aimed to determine whether HT is associated with IPF and if outcomes differ between patients with IPF with and without HT.

METHODS

A retrospective case-control analysis was conducted. Of 311 patients referred to the University of Chicago Interstitial Lung Disease Center with an initial diagnosis of IPF, 196 met the inclusion criteria and were included in the final analysis. Each case was matched 1:1 by age, sex, and race to a control subject with COPD.

RESULTS

HT was identified in 16.8% of cases and 7.1% of control subjects (OR, 2.7; 95% CI, 1.31-5.54; P = .01). Among patients with IPF, HT was associated with reduced survival time (P < .001) and was found to be an independent predictor of mortality in multivariable Cox regression analysis (hazard ratio, 2.12; 95% CI, 1.31-3.43; P = .002). A secondary analysis of two IPF clinical trial datasets supports these findings.

CONCLUSIONS

HT is common among patients with IPF, with a higher prevalence than in those with COPD and the general population. The presence of HT also predicts mortality in IPF, a finding that may improve future prognostication models. More research is needed to determine the biologic link between IPF and HT and how the presence of thyroid disease may influence disease progression.

Application of Immunohistochemistry in Thyroid Pathology

Context

Accurate classification of follicular-patterned thyroid lesions is not always an easy task on routine surgical hematoxylin-eosin–stained or cytologic fine-needle aspiration specimens. The diagnostic challenges are partially due to differential diagnostic criteria that are often subtle and subjective. In the past decades, tremendous advances have been made in molecular gene profiling of tumors and diagnostic immunohistochemistry, aiding in diagnostic accuracy and proper patient management.

Objective

To evaluate the diagnostic utility of the most commonly studied immunomarkers in the field of thyroid pathology by review of the literature, using the database of indexed articles in PubMed (US National Library of Medicine) from 1976–2013.

Data Sources

Literature review, authors' research data, and personal practice experience.

Conclusions

The appropriate use of immunohistochemistry by applying a panel of immunomarkers and using a standardized technical and interpretational method may complement the morphologic assessment and aid in the accurate classification of difficult thyroid lesions.

Neuregulin-ErbB4 signaling in the developing lung alveolus: a brief review

Lung immaturity is the major cause of morbidity and mortality in premature infants, especially those born <28 weeks gestation. Proper lung development from 23-28 weeks requires coordinated cell proliferation and differentiation. Infants born at this age are at high risk for respiratory distress syndrome (RDS), a lung disease characterized by insufficient surfactant production due to immaturity of the alveoli and its constituent cells in the lung. The ErbB4 receptor and its stimulation by neuregulin (NRG) plays a critical role in surfactant synthesis by alveolar type II epithelial cells. In this review, we first provide an introduction to normal human alveolar development, followed by a discussion of the neuregulin and ErbB4-mediated mechanisms regulating alveolar development and surfactant production.

Pro-surfactant protein B as a biomarker for lung cancer prediction

PURPOSE

Preliminary studies have identified pro-surfactant protein B (pro-SFTPB) to be a promising blood biomarker for non-small-cell lung cancer. We conducted a study to determine the independent predictive potential of pro-SFTPB in identifying individuals who are subsequently diagnosed with lung cancer.

PATIENTS AND METHODS

Pro-SFTPB levels were measured in 2,485 individuals, who enrolled onto the Pan-Canadian Early Detection of Lung Cancer Study by using plasma sample collected at the baseline visit. Multivariable logistic regression models were used to evaluate the predictive ability of pro-SFTPB in addition to known lung cancer risk factors. Calibration and discrimination were evaluated, the latter by an area under the receiver operating characteristic curve (AUC). External validation was performed with samples collected in the Carotene and Retinol Efficacy Trial (CARET) participants using a case-control study design.

RESULTS

Adjusted for age, sex, body mass index, personal history of cancer, family history of lung cancer, forced expiratory volume in one second percent predicted, average number of cigarettes smoked per day, and smoking duration, pro-SFTPB (log transformed) had an odds ratio of 2.220 (95% CI, 1.727 to 2.853; P < .001). The AUCs of the full model with and without pro-SFTPB were 0.741 (95% CI, 0.696 to 0.783) and 0.669 (95% CI, 0.620 to 0.717; difference in AUC P < .001). In the CARET Study, the use of pro-SFPTB yielded an AUC of 0.683 (95% CI, 0.604 to 0.761).

CONCLUSION

Pro-SFTPB in plasma is an independent predictor of lung cancer and may be a valuable addition to existing lung cancer risk prediction models.

Amplification of steroid-mediated SP-B expression by physiological levels of caffeine

Factors positively influencing surfactant homeostasis in general and surfactant protein B (SP-B) expression in particular are considered of clinical importance regarding an improvement of lung function in preterm infants. The objective of this study was to identify effects of physiological levels of caffeine on glucocorticoid-mediated SP-B expression in vitro and in vivo. Levels of SP-B and pepsinogen C were quantified by quantitative real-time RT-PCR or immunoblotting in NCI-H441 cells daily exposed to caffeine and/or dexamethasone (DEX). In vivo, SP-B expression was analyzed in bronchoalveolar lavage (BAL) of preterm sheep exposed to antenatal DEX and/or postnatal caffeine. If DEX and caffeine were continuously present, SP-B mRNA and protein levels were increased for up to 6 days after induction (P < 0.05). Additionally, caffeine enhanced SP-B mRNA expression in DEX-pretreated cells (P < 0.05). Moreover, caffeine amplified DEX-induced pepsinogen C mRNA expression (P < 0.05). After short-term treatment with caffeine in vivo, only slightly higher SP-B levels could be detected in BAL of preterm sheep following antenatal DEX, combined with an increase of arterial oxygen partial pressure (P < 0.01). Our data demonstrated that the continuous presence of caffeine in vitro is able to amplify DEX-mediated SP-B expression. In contrast, short-term improvement of lung function in vivo is likely to be independent of altered SP-B transcription and translation. An impact of caffeine on release of surfactant reservoirs from lamellar bodies could, however, quickly affect SP-B content in BAL, which has to be further investigated. Our findings indicate that caffeine is able to amplify main effects of glucocorticoids that result from changes in surfactant production, maturation, and release.

ErbB4 is an upstream regulator of TTF-1 fetal mouse lung type II cell development in vitro

TTF-1 is an important transcription factor in lung development and lung disease and is essential for lung cell differentiation, specifically surfactant protein (Sftp) expression. The molecular mechanisms that drive the expression and transcriptional control of TTF-1 are not fully understood. In the fetal lung, ErbB4 functions as a transcriptional co-factor and regulates the timely onset of fetal Sftp expression. We speculate that ErbB4 is an upstream regulator of TTF-1 and regulates Sftpb expression via this pathway in alveolar type II cells. Neuregulin-induced ErbB4 and TTF-1 signaling interactions were studied by co-immunoprecipitation and confocal microscopy. Overexpression of ErbB4 and TTF-1 was analyzed in its effect on cell viability, Sftpb expression, TTF-1 expression, and Sftpb and TTF-1 promoter activity. The effect of ErbB4 deletion and ErbB4 nuclear translocation on TTF-1 expression was studied in primary fetal type II epithelial cells, isolated from transgenic HER4(heart(-/-)) mice. ErbB4 ligand neuregulin induces ErbB4 and TTF-1 co-precipitation and nuclear colocalization. Combined ErbB4 and TTF-1 overexpression inhibits cell viability, while promoting Sftpb expression more than single overexpression of each protein. NRG stimulates TTF-1 expression in ErbB4-overexpressing epithelial cells, while this effect is absent in ErbB4-depleted cells. In primary fetal type II cells, ErbB4 nuclear translocation is critical for its regulation of TTF-1-induced Sftpb upregulation. TTF-1 overexpression did not overcome this important requirement. We conclude that ErbB4 is a critical upstream regulator of TTF-1 in type II epithelial cells and that this interaction is important for Sftpb regulation.

Synergistic effect of caffeine and glucocorticoids on expression of surfactant protein B (SP-B) mRNA

Administration of glucocorticoids and caffeine is a common therapeutic intervention in the neonatal period, but possible interactions between these substances are still unclear. The present study investigated the effect of caffeine and different glucocorticoids on expression of surfactant protein (SP)-B, crucial for the physiological function of pulmonary surfactant. We measured expression levels of SP-B, various SP-B transcription factors including erythroblastic leukemia viral oncogene homolog 4 (ErbB4) and thyroid transcription factor-1 (TTF-1), as well as the glucocorticoid receptor (GR) after administering different doses of glucocorticoids, caffeine, cAMP, or the phosphodiesterase-4 inhibitor rolipram in the human airway epithelial cell line NCI-H441. Administration of dexamethasone (1 µM) or caffeine (5 mM) stimulated SP-B mRNA expression with a maximal of 38.8±11.1-fold and 5.2±1.4-fold increase, respectively. Synergistic induction was achieved after co-administration of dexamethasone (1 mM) in combination with caffeine (10 mM) (206±59.7-fold increase, p<0.0001) or cAMP (1 mM) (213±111-fold increase, p = 0.0108). SP-B mRNA was synergistically induced also by administration of caffeine with hydrocortisone (87.9±39.0), prednisolone (154±66.8), and betamethasone (123±6.4). Rolipram also induced SP-B mRNA (64.9±21.0-fold increase). We detected a higher expression of ErbB4 and GR mRNA (7.0- and 1.7-fold increase, respectively), whereas TTF-1, Jun B, c-Jun, SP1, SP3, and HNF-3α mRNA expression was predominantly unchanged. In accordance with mRNA data, mature SP-B was induced significantly by dexamethasone with caffeine (13.8±9.0-fold increase, p = 0.0134). We found a synergistic upregulation of SP-B mRNA expression induced by co-administration of various glucocorticoids and caffeine, achieved by accumulation of intracellular cAMP. This effect was mediated by a caffeine-dependent phosphodiesterase inhibition and by upregulation of both ErbB4 and the GR. These results suggested that caffeine is able to induce the expression of SP-transcription factors and affects the signaling pathways of glucocorticoids, amplifying their effects. Co-administration of caffeine and corticosteroids may therefore be of benefit in surfactant homeostasis.

Lung adenocarcinoma originates from retrovirus infection of proliferating type 2 pneumocytes during pulmonary post-natal development or tissue repair

Jaagsiekte sheep retrovirus (JSRV) is a unique oncogenic virus with distinctive biological properties. JSRV is the only virus causing a naturally occurring lung cancer (ovine pulmonary adenocarcinoma, OPA) and possessing a major structural protein that functions as a dominant oncoprotein. Lung cancer is the major cause of death among cancer patients. OPA can be an extremely useful animal model in order to identify the cells originating lung adenocarcinoma and to study the early events of pulmonary carcinogenesis. In this study, we demonstrated that lung adenocarcinoma in sheep originates from infection and transformation of proliferating type 2 pneumocytes (termed here lung alveolar proliferating cells, LAPCs). We excluded that OPA originates from a bronchioalveolar stem cell, or from mature post-mitotic type 2 pneumocytes or from either proliferating or non-proliferating Clara cells. We show that young animals possess abundant LAPCs and are highly susceptible to JSRV infection and transformation. On the contrary, healthy adult sheep, which are normally resistant to experimental OPA induction, exhibit a relatively low number of LAPCs and are resistant to JSRV infection of the respiratory epithelium. Importantly, induction of lung injury increased dramatically the number of LAPCs in adult sheep and rendered these animals fully susceptible to JSRV infection and transformation. Furthermore, we show that JSRV preferentially infects actively dividing cell in vitro. Overall, our study provides unique insights into pulmonary biology and carcinogenesis and suggests that JSRV and its host have reached an evolutionary equilibrium in which productive infection (and transformation) can occur only in cells that are scarce for most of the lifespan of the sheep. Our data also indicate that, at least in this model, inflammation can predispose to retroviral infection and cancer.

The predominant expression of hepatocyte nuclear factor 4α (HNF4α) in thyroid transcription factor-1 (TTF-1)-negative pulmonary adenocarcinoma

AIMS

To investigate TTF-1-negative pulmonary adenocarcinoma, focusing upon mucin production and the expression of hepatocyte nuclear factor-4α (HNF4α).

MATERIALS AND METHODS

Two hundred and sixty-two cases of pulmonary adenocarcinoma were examined histologically and immunohistochemically; TTF-1 was expressed in 222 cases (84.7%), and 40 cases (15.3%) were negative. Among TTF-1-negative cases there were 31 mucinous-type tumours, and HNF4α, MUC5AC and MUC2 were expressed in 34 cases (85%), 29 cases (72.5%) and four cases (10%), respectively. In contrast, their expression was rare in TTF-1-positive tumours. A statistically inverse correlation was confirmed between the expression of TTF-1 and that of HNF4α and MUC5AC.

CONCLUSION

Most TTF-1-negative pulmonary adenocarcinomas are mucinous lesions with the predominant expression of HNF4α and MUC5AC.

A systems approach to mapping transcriptional networks controlling surfactant homeostasis

Background

Pulmonary surfactant is required for lung function at birth and throughout life. Lung lipid and surfactant homeostasis requires regulation among multi-tiered processes, coordinating the synthesis of surfactant proteins and lipids, their assembly, trafficking, and storage in type II cells of the lung. The mechanisms regulating these interrelated processes are largely unknown.

Results

We integrated mRNA microarray data with array independent knowledge using Gene Ontology (GO) similarity analysis, promoter motif searching, protein interaction and literature mining to elucidate genetic networks regulating lipid related biological processes in lung. A Transcription factor (TF) - target gene (TG) similarity matrix was generated by integrating data from different analytic methods. A scoring function was built to rank the likely TF-TG pairs. Using this strategy, we identified and verified critical components of a transcriptional network directing lipogenesis, lipid trafficking and surfactant homeostasis in the mouse lung.

Conclusions

Within the transcriptional network, SREBP, CEBPA, FOXA2, ETSF, GATA6 and IRF1 were identified as regulatory hubs displaying high connectivity. SREBP, FOXA2 and CEBPA together form a common core regulatory module that controls surfactant lipid homeostasis. The core module cooperates with other factors to regulate lipid metabolism and transport, cell growth and development, cell death and cell mediated immune response. Coordinated interactions of the TFs influence surfactant homeostasis and regulate lung function at birth.

A study of immunohistochemical differential expression in pulmonary and mammary carcinomas

The risk of developing a second primary cancer is increased in patients with breast cancer, and the lung is one of the major sites involved. Moreover, the lung is the major metastatic site for breast cancers. A distinction between metastatic breast cancer and primary lung cancer can be histologically difficult, and both show an overlapping CK7+/CK20- immunoprofile in a majority of cases. The degree of difficulty increases with poorly differentiated tumors. We investigated differential expressions of TTF-1, Napsin A, surfactant apoprotein A, estrogen receptor, GATA-3, mammaglobin, and GCDFP-15 immunostains in 197 pulmonary carcinomas (158 adenocarcinomas, 39 squamous) and 115 invasive mammary carcinomas (91 ductal, 24 lobular type). In mammary carcinomas, estrogen receptor, GATA-3, mammaglobin, and GCDFP-15 were expressed in 74, 72, 64, and 62%, respectively, whereas TTF-1, Napsin A, and surfactant apoprotein A were all negative. The expressions were diffuse in estrogen receptor and GATA-3, and variable in mammaglobin and GCDFP-15. For a combination of estrogen receptor/mammaglobin or GATA-3/mammaglobin, 83% of mammary carcinomas were positive, and the detection rate was not improved by using all three markers. All lung squamous cell carcinomas were negative for all markers studied. TTF-1, Napsin A, and surfactant apoprotein A were positive in 80, 77, and 45% of pulmonary adenocarcinomas. None of the TTF-1-negative tumors expressed surfactant apoprotein A. GCDFP-15 was focally expressed in 2.5% of pulmonary adenocarcinomas, and estrogen receptor was focally expressed in one case (1.2%) of pulmonary adenocarcinoma. When metastasis from breast cancer is suspected in the lung, a combination of either estrogen receptor/mammaglobin or GATA-3/mammaglobin as breast markers, and a combination of TTF-1 and Napsin A as lung markers may be helpful for differentiating between the two. Caution should be taken in the interpretation of GCDFP-15 due to its occasional expression in pulmonary adenocarcinomas.

Intrauterine growth restriction delays surfactant protein maturation in the sheep fetus

Pulmonary surfactant is synthesized by type II alveolar epithelial cells to regulate the surface tension at the air-liquid interface of the air-breathing lung. Developmental maturation of the surfactant system is controlled by many factors including oxygen, glucose, catecholamines, and cortisol. The intrauterine growth-restricted (IUGR) fetus is hypoxemic and hypoglycemic, with elevated plasma catecholamine and cortisol concentrations. The impact of IUGR on surfactant maturation is unclear. Here we investigate the expression of surfactant protein (SP) A, B, and C in lung tissue of fetal sheep at 133 and 141 days of gestation (term 150 +/- 3 days) from control and carunclectomized Merino ewes. Placentally restricted (PR) fetuses had a body weight <2 SD from the mean of control fetuses and a mean gestational Pa(O(2)) <17 mmHg. PR fetuses had reduced absolute, but not relative, lung weight, decreased plasma glucose concentration, and increased plasma cortisol concentration. Lung SP-A, -B, and -C protein and mRNA expression was reduced in PR compared with control fetuses at both ages. SP-B and -C but not SP-A mRNA expression and SP-A but not SP-B or -C protein expression increased with gestational age. Mean gestational Pa(O(2)) was positively correlated with SP-A, -B, and -C protein and SP-B and -C mRNA expression in the younger cohort. SP-A and -B gene expression was inversely related to plasma cortisol concentration. Placental restriction, leading to chronic hypoxemia and hypercortisolemia in the carunclectomy model, results in significant inhibition of surfactant maturation. These data suggest that IUGR fetuses are at significant risk of lung complications, especially if born prematurely.

Lung organogenesis

Developmental lung biology is a field that has the potential for significant human impact: lung disease at the extremes of age continues to cause major morbidity and mortality worldwide. Understanding how the lung develops holds the promise that investigators can use this knowledge to aid lung repair and regeneration. In the decade since the "molecular embryology" of the lung was first comprehensively reviewed, new challenges have emerged-and it is on these that we focus the current review. Firstly, there is a critical need to understand the progenitor cell biology of the lung in order to exploit the potential of stem cells for the treatment of lung disease. Secondly, the current familiar descriptions of lung morphogenesis governed by growth and transcription factors need to be elaborated upon with the reinclusion and reconsideration of other factors, such as mechanics, in lung growth. Thirdly, efforts to parse the finer detail of lung bud signaling may need to be combined with broader consideration of overarching mechanisms that may be therapeutically easier to target: in this arena, we advance the proposal that looking at the lung in general (and branching in particular) in terms of clocks may yield unexpected benefits.

Ablation of lung epithelial cells deregulates FGF-10 expression and impairs lung branching morphogenesis

Epithelial-mesenchymal interactions are essential for tissue patterning during organogenesis. Distal lung epithelium and its adjacent mesenchyme comprise the epithelial-mesenchymal signaling unit that regulates lung branching morphogenesis. Tissue recombination experiments have demonstrated the importance of mesenchymal signals in inducing lung epithelial differentiation and branching, but the role of the epithelium in regulating mesenchymal signals has not been well characterized. Using transgenic mice, we ablated distal lung epithelial cells during lung development by inducing the expression of a constitutively active proapoptotic Bax protein under the surfactant protein C (SP-C) promoter. We found that epithelial cell ablation results in impaired lung branching morphogenesis, which progresses to emphysematous airspaces in the adults. Mesenchymal expression of fibroblast growth factor 10 (Fgf-10), whose strict spatial and temporal expression is critical for proper lung branching morphogenesis, is disrupted and loses its localized pattern. Interestingly, the expression of sonic hedgehog (Shh), an epithelial gene known to modulate Fgf-10 expression, is unchanged, indicating the existence of other distal epithelial signals that regulate mesenchymal Fgf-10expression. We propose that distal SP-C expressing lung epithelial cells provide essential signals for the downregulation of Fgf-10 expression in the distal mesenchyme during lung development. 292:123-130, 2009. (c) 2008 Wiley-Liss, Inc.

Lineage-Specific Dependency of Lung Adenocarcinomas on the Lung Development Regulator TTF-1

Emerging evidence, although currently very sparse, suggests the presence of "lineage-specific dependency" in the survival mechanisms of certain cancers. TTF-1 has a decisive role as a master regulatory transcription factor in lung development and in the maintenance of the functions of terminal respiratory unit (TRU) cells. We show that a subset of lung adenocarcinoma cell lines expressing TTF-1, which presumably represent those derived from the TRU lineage, exhibit marked dependence on the persistent expression of TTF-1. The inhibition of TTF-1 by RNA interference (RNAi) significantly and specifically induced growth inhibition and apoptosis in these adenocarcinoma cell lines. Furthermore, a fraction of TTF-1-expressing tumors and cell lines displayed an increase in the gene dosage of TTF-1 in the analysis of 214 patients with non-small-cell lung cancer, including 174 adenocarcinomas, showing a tendency of higher frequency of increased gene copies at metastatic sites than at primary sites (P=0.07, by two-sided Fisher's exact test). These findings strongly suggest that in addition to the development and maintenance of TRU lineages in normal lung, sustained TTF-1 expression may be crucial for the survival of a subset of adenocarcinomas that express TTF-1, providing credence for the lineage-specific dependency model.

Epidermal growth factor receptor mutations in lung cancers

In 2004, two groups reported somatic mutations in the gene for the epidermal growth factor receptor (EGFR) in patients with non-small cell lung cancer (NSCLC), which were highly correlated with the clinical response to the anticancer drug, gefitinib. Since then, a tremendous amount of knowledge has accumulated, and sheds light on significant oncological properties as well as the clinical relevance of this mutation, which could be applicable to other malignancies. The EGFR mutations are distributed throughout the kinase domain, but a deletion in exon 19 and the point mutation L858R in exon 21 account for approximately 90%, which confer a greater response to gefitinib treatment, compared with other types of EGFR mutations. These EGFR mutations in the tyrosine kinase domain are seldom acquired in cancers of the other organs and the mutations preferentially involve a subset of lung cancers, which are clinicopathologically characterized by female sex, non-smoking, adenocarcinoma histology and East Asian ethnicity. In Japan, the EGFR mutations are detected in approximately 30% of overall NSCLC and approximately 40% of surgically resected adenocarcinomas. The morphological features of adenocarcinomas harboring the mutations were reported to be frequent in those with bronchioloalveolar features, but it is suggested that the cellular lineage of the putative original cells of the cancers refines the subset more clearly. In the present study the current knowledge of EGFR mutations is reviewed, insights from which raise many further questions, and thus suggest new directions for future research.

Ectopic expression of C/EBPalpha in the lung epithelium disrupts late lung development

The lung develops from the endoderm through a process of branching morphogenesis. This process is highly active during the pseudoglandular stage of lung development and continues into the canalicular stage, resulting in the formation of terminal sacs. CCAAT/enhancer binding proteins (C/EBPs) are transcription factors regulating central aspects of differentiation and proliferation. We report here the developmental expression of C/EBPalpha, -beta, and -delta in the lung. C/EBPalpha exhibits a dynamic expression pattern and is first detected during the late pseudoglandular stage. At this stage, expression is observed in a subset of epithelial cells in the distal parts of the branching tubules. The expression of C/EBPalpha is confined to nonproliferating cells. To examine the role of C/EBPalpha in lung development, we generated transgenic mice ectopically expressing C/EBPalpha in the lung epithelium using the human surfactant protein C promoter. Lungs from these mice were of normal size but exhibited a phenotype characterized by fewer and larger developing epithelial tubules, indicating that the branching process was affected. No effects on overall proliferation or cellular differentiation were observed. When this phenotype was compared with that of mice carrying a targeted mutation of the Cebpa gene, the Cebpa-/- mice exhibited a similar developmental phenotype. In conclusion, our results show a role for C/EBPalpha in lung development and suggest a function in the later stages of lung branching morphogenesis.

Tracheal occlusion in fetal rats alters expression of mesenchymal nuclear transcription factors without affecting surfactant protein expression

BACKGROUND/PURPOSE

Mesenchymal nuclear transcription factors (MNTF) are involved in lung development and maturation and regulate surfactant protein (SP) expression. Prolonged (>2 weeks) fetal tracheal occlusion (TO) has been shown to accelerate lung growth and inhibit pulmonary surfactant synthesis. The effects of TO on SP expression and MNTF, however, have not been formally assessed. The objectives of this study were to evaluate the effects of short-term (3 days) TO on normal lung growth and protein expression of pulmonary MNTF involved in SP synthesis.

METHODS

At E19 (term, 22 days), 2 fetuses per time-dated Sprague-Dawley rats underwent either TO (n = 23) or a sham (n = 22) operation. Lungs were harvested 72 hours post surgery. Pulmonary SP-A; SP-B; SP-C messenger RNA (mRNA) expression; and SP-A and SP-B, Hoxb5, thyroid transcription factor 1, and retinoic X receptor-alpha protein expression were analyzed.

RESULTS

Lung weight was significantly increased by TO (TO 0.32 +/- 0.02g vs SHAM 0.14 +/- 0.01 g; P < .001), resulting in 123% increase of the lung-to-body-weight ratio. No difference of SP-A-mRNA (177 +/- 4.3 TO vs 169 +/- 4.4 SHAM; P = .25), SP-B-mRNA (87.7 +/- 0.2 TO vs 87.4 +/- 0.02 SHAM; P = .33), and SP-C-mRNA (186.5 +/- 3.2 TO vs 183.2 +/- 2.7 SHAM; P = .45) expression was found. Surfactant protein A (175.6 +/- 25.3 TO vs 192.5 +/- 19.8 SHAM; P = .59) and SP-B (163.4 +/- 5.2 TO vs 166.8 +/- 9.3 SHAM; P = .75) protein expression were similar in both groups; however, Hoxb5 (70.3 +/- 18.9 TO vs 130.6 +/- 5.1 SHAM; P = .02) and thyroid transcription factor 1 (102.6 +/- 19 TO vs 181.1 +/- 6.3 SHAM; P = .007) expression were significantly decreased. Retinoic X receptor-alpha expression tended to be increased by TO (171.9 +/- 6.0 TO vs 155.4 +/- 6.7 SHAM; P = .06).

CONCLUSIONS

Short-term TO late in gestation induces rapid lung growth. Surfactant protein-mRNA and protein expression are not significantly altered. Thyroid transcription factor 1 and Hoxb5 are down-regulated by TO, suggesting that duration and timing of occlusion are important in balancing the effects of TO on lung growth vs lung maturation.

PARP-2 Interacts with TTF-1 and Regulates Expression of Surfactant Protein-B

Thyroid transcription factor 1 (TTF-1/Nkx-2.1) plays a critical role in lung morphogenesis and regulates the expression of lung-specific genes, including the surfactant proteins required for pulmonary function after birth. The activity of TTF-1 is influenced by its interactions with other transcription factors and coactivators, including CBP/p300 and SRC-1. In this study, we have identified poly(ADP-ribose) polymerases (PARP-2 and PARP-1) as TTF-1 interacting proteins that influence its transcriptional activity. Endogenous PARP-2 was coimmunoprecipitated from transformed mouse lung epithelial cell (MLE15) extracts with TTF-1 and was identified by mass spectrometry. PARP-1 and Ku70/Ku80 were also coimmunoprecipitated from the cell extracts with TTF-1. The E domain of PARP-2 interacted via the C-terminal domain of TTF-1. Both PARP-1 and PARP-2 enhanced the activity of the promoter of surfactant protein-B (Sftpb gene) but not other surfactant proteins in vitro. PARP-2 was selectively expressed in epithelial cells of the conducting and peripheral lung tubules of the fetal mouse lung from embryonic day 12.5 and was detected in bronchial epithelial cells in the adult lung at cellular sites consistent with that of surfactant protein B. PARP-2 and PARP-1 interact with TTF-1 and regulate the expression of surfactant protein B, a protein required for lung function.

Alveolar epithelial cell differentiation and surfactant protein expression after mild preterm birth in sheep

As the transition to extrauterine life at birth alters the proportions of type I and II alveolar epithelial cells (AECs), our aim was to determine the effect of mild preterm birth on AECs and surfactant protein (SP) gene expression. Preterm lambs were born at approximately 133 d of gestational age (DGA); controls were born at term (approximately 147 DGA). Lungs were collected from preterm lambs at term-equivalent age (TEA; approximately 2 wk after preterm birth) and 6 wk post-TEA. Control lung tissue was collected from fetuses (at 132 DGA), as well as from lambs at approximately 6 h (normal term) and 2, 6, and 8 wk of postnatal age (PNA). In controls, the proportion of type I AECs decreased from 65.1 +/- 3.9% at term to 50.9 +/- 3.3%, while the proportion of type II AECs increased from 33.7 +/- 3.9% to 48.5 +/- 3.3% at 6 wk PNA. At 2 wk after preterm birth, the proportions of type I and II AECs were similar in preterm lambs compared to 132-d fetal levels and term controls but differed from control values at 2 wk PNA; differences between control and preterm lambs persisted at 8 wk PNA. At approximately 2 wk after preterm birth, SP-A and SP-B, but not SP-C, mRNA levels were significantly reduced in preterm lambs compared with term controls, but these differences did not persist at 2 and 6 wk PNA. We conclude that mild preterm birth alters the normal postnatal changes in type I and II cell proportions but does not severely affect SP gene expression.

In vivo and in vitro analysis of factor binding sites in Jaagsiekte sheep retrovirus long terminal repeat enhancer sequences: roles of HNF-3, NF-I, and C/EBP for activity in lung epithelial cells

Jaagsiekte sheep retrovirus (JSRV) is the causative agent of ovine pulmonary adenocarcinoma, a contagious lung cancer of sheep that arises from type II pneumocytes and Clara cells of the lung epithelium. Studies of the tropism of this virus have been hindered by the lack of an efficient system for viral replication in tissue culture. To map regulatory regions important for transcriptional activation, an in vivo footprinting method that couples dimethyl sulfate treatment and ligation-mediated PCR was performed in murine type II pneumocyte-derived MLE-15 cells infected with a chimeric Moloney murine leukemia virus driven by the JSRV enhancers (DeltaMo+JS Mo-MuLV). In vivo footprints were found in the JSRV enhancers in two regions previously shown to be important for JSRV long terminal repeat (LTR) activity: a binding site for the lung-specific transcription factor HNF-3beta and an E-box element in the distal enhancer adjacent to an NF-kappaB-like binding site. In addition, in vivo footprints were detected in two downstream motifs likely to bind C/EBP and NF-I. Mutational analysis of a JSRV LTR reporter construct (pJS21luc) revealed that the C/EBP binding site is critical for LTR activity, while the putative NF-I binding element is less important; elimination of these sites resulted in 70% and 40% drops in LTR activity, respectively. Electrophoretic mobility shift assays using nuclear extracts from MLE-15 murine Clara cell-derived mtCC1-2 cells with probes corresponding to the NF-I or C/EBP sites revealed several complexes. Antiserum directed against NF-IA, C/EBPalpha, or C/EBPbeta supershifted the corresponding protein-DNA complexes, indicating that these isoforms, which are also important for the expression of several cellular lung-specific genes, may be important for JSRV expression in lung epithelial cells.

Primary rat alveolar epithelial cells for use in biotransformation and toxicity studies

The alveolar epithelium may function as a barrier for airborne xenobiotics, and in vitro models mimicking this barrier are useful for metabolism and toxicity studies. To gain insight into the metabolic competence of alveolar epithelial cells (AECs), we investigated transcript expression of 10 different cytochrome P450 monooxygenases as well as expression of surfactant proteins A to D. We also investigated gene expression of the transcription factors PCNA, TTF-1, HNF3beta , GATA-6, C/EBPalpha and C/EBPdelta which drive, at least in part, development and differentiation of alveolar epithelium. We further studied the metabolism of testosterone, a substrate for cytochrome P450 (CYP) monooxygenases, in cultures of AECs. Essentially, medium supplementation with 5% rat serum, as opposed to 10% FCS, promoted a high level of differentiation, as judged by the mRNA expression of CYP monooxygenases, e.g. 1A1, 1A2, 2B1 and 2J3, the expression of the surfactant proteins A, B, and C, the immunohistochemical staining for surfactant protein C, and staining for alkaline phosphatase activity. Further, AECs, when cultured in the presence of 5% rat serum, promoted metabolic competence, as evidenced by the fingerprinting of individual testosterone metabolites. We thus characterized AECs in culture and found these respiratory epithelial cells to express an array of differentiation markers and showed these cultures to be metabolically competent under optimized culture conditions.

Iroquois genes influence proximo-distal morphogenesis during rat lung development

Lung development is a highly regulated process directed by mesenchymal-epithelial interactions, which coordinate the temporal and spatial expression of multiple regulatory factors required for proper lung formation. The Iroquois homeobox (Irx) genes have been implicated in the patterning and specification of several Drosophila and vertebrate organs, including the heart. Herein, we investigated whether the Irx genes play a role in lung morphogenesis. We found that Irx1-3 and Irx5 expression was confined to the branching lung epithelium, whereas Irx4 was not expressed in the developing lung. Antisense knockdown of all pulmonary Irx genes together dramatically decreased distal branching morphogenesis and increased distention of the proximal tubules in vitro, which was accompanied by a reduction in surfactant protein C-positive epithelial cells and an increase in beta-tubulin IV and Clara cell secretory protein positive epithelial structures. Transmission electron microscopy confirmed the proximal phenotype of the epithelial structures. Furthermore, antisense Irx knockdown resulted in loss of lung mesenchyme and abnormal smooth muscle cell formation. Expression of fibroblast growth factors (FGF) 1, 7, and 10, FGF receptor 2, bone morphogenetic protein 4, and Sonic hedgehog (Shh) were not altered in lung explants treated with antisense Irx oligonucleotides. All four Irx genes were expressed in Shh- and Gli(2)-deficient murine lungs. Collectively, these results suggest that Irx genes are involved in the regulation of proximo-distal morphogenesis of the developing lung but are likely not linked to the FGF, BMP, or Shh signaling pathways.

Congenital diaphragmatic hernia, tracheal occlusion, thyroid transcription factor-1, and fetal pulmonary epithelial maturation

Congenital diaphragmatic hernia (CDH) occurs in ∼1:2,500 human births and has high morbidity and mortality rates, primarily due to pulmonary hypoplasia and pulmonary hypertension. Tracheal occlusion (TO), in experimental animals, distends lungs and increases lung growth and alveolar type I cell maturation but decreases surfactant components and reduces alveolar type II cell density. We examined effects of CDH and CDH+TO on lung growth and maturation in fetal rats. To induce CDH, we administered nitrofen (100 mg) to dams at 9.5 days of gestation. We compared lungs from fetuses with CDH, CDH+TO, and those exposed to nitrofen without CDH. CDH decreased lung wet weight bilaterally ( P < 0.0001) and DNA content in lung ipsilateral to CDH ( P < 0.05). CDH+TO significantly increased lung wet weights bilaterally; DNA content was intermediate between CDH and NC. To evaluate effects on the distal pulmonary epithelium, we examined surfactant mRNA and protein levels, type I and II cell-specific markers (RTI40 and RTII70, respectively), and transcriptional regulator thyroid transcription factor-1 (TTF-1). Decreased lung distension (due to CDH) increased SP-C mRNA and TTF-1 protein expression and reduced RTI40 ( P < 0.05 for all). Increased lung distension (due to CDH+TO) reduced expression of SP mRNAs and pro-SP-C and TTF-1 proteins and enhanced expression of RTI40 (mRNA and protein; P < 0.05 for all). We conclude that CDH+TO partially reverses effects of CDH; it corrects the pulmonary hypoplasia and restores type I cell differentiation but adversely affects SP expression in type II cells. These effects may be mediated through changes in TTF-1 expression.

EGFR Mutation Is Specific for Terminal Respiratory Unit Type Adenocarcinoma

We have previously reported that terminal-respiratory-unit (TRU) type adenocarcinoma is a distinct subset of lung adenocarcinoma in terms of molecular pathway for carcinogenesis and phenotypic profiles. This type of cancer shows TRU features, characterized by distinct cellular morphology and the expression of TTF-1 and surfactant proteins. Recently, two groups published novel mutations of the epidermal growth factor receptor (EGFR) that are closely associated with clinical response to gefitinib. The clinicopathologic features of gefitinib responders overlap with those of TRU-type adenocarcinoma, and the characteristics of TRU are likely to correspond to the bronchioloalveolar features reported as a predictor of gefitinib response. We therefore examined the characteristics of EGFR-mutated pulmonary adenocarcinomas with special reference to TRU-type adenocarcinoma. EGFR mutation was detected in 97 of 195 adenocarcinomas, 91 of 149 TRU-type adenocarcinomas and 6 of 46 tumors of other types. Conversely, 91 of 97 EGFR-mutated adenocarcinomas were categorized as TRU-type adenocarcinomas. This type-specific involvement was confirmed by logistic regression model. In addition, EGFR mutation was detected in some cases of atypical adenomatous hyperplasia, a preinvasive lesion of TRU-type adenocarcinoma. These findings further confirm that TRU-type-adenocarcinoma is a distinct adenocarcinoma subset in which a particular molecular pathway is involved.

Overexpression of lunatic fringe does not affect epithelial cell differentiation in the developing mouse lung

The Notch/Notch-ligand pathway regulates cell fate decisions and patterning in various tissues. Several of its components are expressed in the developing lung, suggesting that this pathway is important for airway cellular patterning. Fringe proteins, which modulate Notch signaling, are crucial for defining morphogenic borders in several organs. Their role in controlling cellular differentiation along anterior-posterior axis of the airways is unknown. Herein, we report the temporal-spatial expression patterns of Lunatic fringe (Lfng) and Notch-regulated basic helix-loop-helix factors, Hes1 and Mash-1, during murine lung development. Lfng was only expressed during early development in epithelial cells lining the larger airways. Those epithelial cells also expressed Hes1, but at later gestation Hes1 expression was confined to epithelium lining the terminal bronchioles. Mash-1 displayed a very characteristic expression pattern. It followed neural crest migration in the early lung, whereas at later stages Mash-1 was expressed in lung neuroendocrine cells. To clarify whether Lfng influences airway cell differentiation, Lfng was overexpressed in distal epithelial cells of the developing mouse lung. Overexpression of Lfng did not affect spatial or temporal expression of Hes1 and Mash-1. Neuroendocrine CGRP and protein gene product 9.5 expression was not altered by Lfng overexpression. Expression of proximal ciliated (β-tubulin IV), nonciliated ( CCSP), and distal epithelial cell ( SP-C, T1α) markers also was not influenced by Lfng excess. Overexpression of Lfng had no effect on mesenchymal cell marker (α-sma, vWF, PECAM-1) expression. Collectively, the data suggest that Lunatic fringe does not play a significant role in determining cell fate in fetal airway epithelium.

Changes in pulmonary surfactant function and composition in bleomycin-induced pneumonitis and fibrosis

Bleomycin is a widely accepted cancer drug but may induce life-threatening interstitial lung disease in a subset of patients. We evaluated the effect of bleomycin administration on pulmonary surfactant function and composition in rabbit lungs. In order to obtain a uniform response to bleomycin, aerosol technology was employed for bronchoalveolar delivery of 1.8 U/kg b.w. bleomycin. On days 4, 8, 16, 24, 32, and 64 after challenge, bronchoalveolar lavages were performed. Sham-aerosolized rabbits served as controls. In the early acute respiratory distress syndrome (ARDS)-like post-bleomycin period (4-16 days), marked loss of surface activity of the large surfactant aggregate (LA) fraction of surfactant was noted. In parallel, reduced percentages of LA, but only minor changes in surfactant apoproteins (SP)-A, SP-B, and SP-C, were encountered. Analysis of the surfactant lipid profile showed impressively enhanced cholesterol and significantly decreased phosphatidylglycerol (PG) levels. The relative content of dipalmitoyl-PC (DPPC) was slightly increased, and a several-fold increase within the 1-O-alkyl-2-acyl subclass of PC was observed. During the prolonged fibroproliferative period, a highly significant downregulation of SP-B and SP-C levels was observed. This was paralleled by an upregulation of the total extracellular phospholipid pool, with a far-reaching normalization of the (phospho)-lipid profile. The biophysical surfactant function never fully normalized within the 64-day observation period. In conclusion, bleomycin caused marked abnormalities of pulmonary surfactant, with the profile of changes being different between the early ARDS and the late fibrotic phase.

Nuclear factor I/thyroid transcription factor 1 interactions modulate surfactant protein C transcription

Surfactant protein C (SP-C; Sftpc) gene expression is restricted to pulmonary type II epithelial cells. The proximal SP-C promoter region contains critical binding sites for nuclear factor I (NFI) and thyroid transcription factor 1 (TTF-1; also called Nkx2.1). To test the hypothesis that NFI isoforms interact with TTF-1 to differentially regulate SP-C transcription, we performed transient transfection assays in JEG-3 cells, a choriocarcinoma cell line with negligible endogenous NFI or TTF-1 activity. Cotransfection of NFI family members with TTF-1 induced synergistic activation of the SP-C promoter that was further enhanced by p300. TTF-1 directly interacts with the conserved DNA binding and dimerization domain of all NFI family members in coimmunoprecipitation and mammalian two-hybrid experiments. To determine whether SP-C expression is regulated by NFI in vivo, a chimeric fusion protein containing the DNA binding and dimerization domain of NFI-A and the Drosophila engrailed transcriptional repression domain (NFIen) was conditionally expressed in mice under control of a doxycycline-inducible transgene. Induction of NFIen in a subset of type II cells inhibited SP-C gene expression without affecting expression of TTF-1 in doxycycline-treated double-transgenic mice. Taken together, these findings support the hypothesis that NFI family members interact with TTF-1 to regulate type II cell function.

Epithelial plasma cell granuloma-like tumors of the lungs. A hitherto unrecognized tumor

We present two cases of benign pulmonary epithelial tumors located in the middle lobes of the lungs. The patients were women of 56 and 36 years of age. The tumors were morphologically similar to plasma cell granuloma. At the tumor periphery, the lesion cells formed thin organoid rows of cells and vague trabeculae, disclosing morphologically their epithelial nature. In addition, the tumors strongly stained immunohistochemically with antibodies to cytokeratins, TTF-1 and EMA, and they were negative for immunoglobulin kappa and lambda light chains. We are not aware of similar tumors described in the literature, and we suggest the name "epithelial plasma cell granuloma-like tumors" for these lesions.

Envelope-induced cell transformation by ovine betaretroviruses

Ovine betaretroviruses include Jaagsiekte sheep retrovirus (JSRV) and enzootic nasal tumor virus (ENTV). JSRV and ENTV represent a unique class of oncogenic retroviruses that induce tumors of the respiratory tract. JSRV and ENTV are highly related but induce different diseases. Expression of the JSRV envelope (Env) induces transformation of rodent fibroblasts in vitro and phosphorylation of Akt, a central player in the phosphatidylinositol 3-kinase (PI-3K)/Akt signal transduction pathway. However, little information is available on the molecular biology of ENTV. In this study, we initially assessed whether the ENTV Env has the same properties as the homologous JSRV protein. We performed entry and interference assays using retroviral vectors pseudotyped with either the JSRV or the ENTV Env and sheep choroid plexus cells, choroid plexus cells stably expressing the JSRV Env protein, human 293T cells, mouse NIH 3T3 cells, or NIH 3T3 cells expressing human hyaluronidase 2 (HYAL2), the cellular receptor for JSRV. The results obtained indicated that ENTV and JSRV share the same receptor in sheep cells and that they can use human HYAL2 as a cellular receptor in mouse cells. The ENTV Env induces transformation of rodent fibroblasts in vitro. As with the JSRV Env, the tyrosine at position 590 is critical for ENTV Env-induced cell transformation, and Akt is phosphorylated in ENTV Env-transformed cells but not in the parental cell lines. Thus, ovine betaretroviruses share a common mechanism of cell transformation. We further investigated the relevance of Akt activation in cells transformed by ovine betaretroviruses. A PI-3K inhibitor blocked Akt phosphorylation in JSRV Env-transformed cells, suggesting a possible involvement of PI-3K in JSRV and ENTV Env-induced cell transformation. In addition, phosphorylated Akt was detected in a cell line derived from a lung tumor of a sheep with naturally occurring ovine pulmonary adenocarcinoma.

Human surfactant protein B promoter in transgenic mice: temporal, spatial, and stimulus-responsive regulation

Surfactant protein B (SP-B) is a developmentally and hormonally regulated lung protein that is required for normal surfactant function. We generated transgenic mice carrying the human SP-B promoter (-1,039/+431 bp) linked to chloramphenicol acetyltransferase (CAT). CAT activity was high in lung and immunoreactive protein localized to alveolar type II and bronchiolar epithelial cells. In addition, thyroid, trachea, and intestine demonstrated CAT activity, and each of these tissues also expressed low levels of SP-B mRNA. Developmental expression of CAT activity and SP-B mRNA in fetal lung were similar and both increased during explant culture. SP-B mRNA but not CAT activity decreased during culture of adult lung, and both were reduced by transforming growth factor (TGF)-beta(1). Treatment of adult mice with intratracheal bleomycin caused similar time-dependent decreases in lung SP-B mRNA and CAT activity. These findings indicate that the human SP-B promoter fragment directs tissue- and lung cell-specific transgene expression and contains cis-acting elements involved in regulated expression during development, fetal lung explant culture, and responsiveness to TGF-beta and bleomycin-induced lung injury.

Increased expression of thyroid transcription factor-1 (TTF-1) in respiratory epithelial cells inhibits alveolarization and causes pulmonary inflammation

Thyroid transcription factor-1 (TTF-1), a member of the Nkx2 family of homeodomain-containing transcription factors, is expressed in the epithelium of the lung. TTF-1 is a critical regulator of transcription for the surfactant proteins (SP) A, B, and C and is essential for lung morphogenesis. Sites and levels of TTF-1 expression vary during lung morphogenesis and following injury. In order to determine the role of TTF-1 in lung formation, transgenic mice were generated in which TTF-1 was expressed in respiratory epithelial cells of wild-type and Ttf1 null mutant (-/-) mice, using the lung-specific SP-C promoter. The SP-C-Ttf1 transgene did not rescue the severe pulmonary hypoplasia characteristic of the Ttf1 (-/-) mice. Increased expression of TTF-1, however, caused dose-dependent alterations in postnatal lung morphology of wild-type mice. Modest overexpression of TTF-1 caused type II cell hyperplasia and increased the cellular content of SP-B. In contrast, higher expression levels of TTF-1 disrupted alveolar septation, causing emphysema. In mice with the highest transgene expression, TTF-1 caused severe inflammation, pulmonary fibrosis, respiratory failure, and death, associated with eosinophil infiltration and increased expression of eotaxin and IL-6. Increased expression of TTF-1 altered alveolarization and caused chronic pulmonary inflammation, demonstrating that precise regulation of TTF-1 is critical for homeostasis in the postnatal lung.