Terminal Bronchiolar Epithelium Research Articles

Increased levels of FOXM1 transcription factor in bronchioalveolar stem cells promote epithelial cell repopulation in injured mouse airway

Bronchioalveolar stem cells (BASCs) have been shown to maintain the bronchiolar and alveolar epithelial cell renewal upon lung injury. Previously we have shown Foxm1 transcription factors plays essential roles in cellular proliferation, migration, differentiation and tumorigenesis. Conditional deletion of Foxm1 from mouse respiratory epithelium during initial stages of lung development inhibited lung maturation and caused respiratory failure after birth, while deletion of Foxm1 from adult lung airway epithelium reduced club cell proliferation after naphthalene‐induced lung injury. Here, we show that premature expression of transgenic FOXM1accelerated airway epithelial cell proliferation after naphthalene induced lung injury in CCSP‐rtTA/tetO‐FOXM1 mouse (C/FOXM1), which is associated with increased numbers of CC10 and Ki‐67 positive cells in terminal bronchiolar epithelium and bronchioalveolar duct junction (BADJ), the stem cell niche. Lineage tracing experiment showed that FOXM1 promotes proliferation of LacZ or Brainbow labelled naphthalene‐resistant CCSP expressing cells that differentiated into bronchiolar epithelium in healing processes. Co‐immunofluorescent staining showed an increased number of proSPCposCCSPpos BASCs were found in in BADJ of C/FOXM1 lungs, which consistent to result that an increased number of CD45neg CD31neg Sca‐1hi EpCAMhi bronchiolar stem cells in C/FoxM1 lungs by FASC analysis. Our results indicated that increased expression of FOXM1 contributes to the increases proliferation of lung stem/progenitor cells, and facilitates bronchiolar epithelium repair from acute lung injury.Support or Funding InformationNational Health Research Institute, Taiwan (NHRI‐EX106‐10309BC); Ministry of Science and Technology, Taiwan (MOST 105‐2628‐B‐007‐003‐MY3); and National Tsing Hua University, Taiwan (106J00X9V8) to I‐C.W.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Involvement of Igf1r in Bronchiolar Epithelial Regeneration: Role during Repair Kinetics after Selective Club Cell Ablation

Regeneration of lung epithelium is vital for maintaining airway function and integrity. An imbalance between epithelial damage and repair is at the basis of numerous chronic lung diseases such as asthma, COPD, pulmonary fibrosis and lung cancer. IGF (Insulin-like Growth Factors) signaling has been associated with most of these respiratory pathologies, although their mechanisms of action in this tissue remain poorly understood. Expression profiles analyses of IGF system genes performed in mouse lung support their functional implication in pulmonary ontogeny. Immuno-localization revealed high expression levels of Igf1r (Insulin-like Growth Factor 1 Receptor) in lung epithelial cells, alveolar macrophages and smooth muscle. To further understand the role of Igf1r in pulmonary homeostasis, two distinct lung epithelial-specific Igf1r mutant mice were generated and studied. The lack of Igf1r disturbed airway epithelial differentiation in adult mice, and revealed enhanced proliferation and altered morphology in distal airway club cells. During recovery after naphthalene-induced club cell injury, the kinetics of terminal bronchiolar epithelium regeneration was hindered in Igf1r mutants, revealing increased proliferation and delayed differentiation of club and ciliated cells. Amid airway restoration, lungs of Igf1r deficient mice showed increased levels of Igf1, Insr, Igfbp3 and epithelial precursor markers, reduced amounts of Scgb1a1 protein, and alterations in IGF signaling mediators. These results support the role of Igf1r in controlling the kinetics of cell proliferation and differentiation during pulmonary airway epithelial regeneration after injury.

Bromodeoxyuridine (BrdU)-label-retaining cells in mouse terminal bronchioles.

Adult male mice were continuously treated with bromodeoxyuridine (BrdU) for 1, 2, or 4 weeks by an osmotic pump. To detect BrdU-label-retaining cells (LRCs), putative progenitor/stem cells, other animals were continuously treated with BrdU for 2 weeks, and were then kept without any treatments for 2, 6, or 18 months. The lungs were fixed with 4% paraformaldehyde, and were paraffin-embedded. We observed terminal bronchioles with BrdU immunostaining alone or with BrdU immunostaining accompanying immunostaining for Clara cell secretory protein (CCSP), forkhead box protein J1 (FoxJ1), or calcitonin gene-related peptide (CGRP). The average incidences of BrdU-incorporated cells in the terminal bronchioles after 1, 2, and 4 weeks of continuous BrdU infusion were 6.2%, 11.9%, and 23.1%, respectively. Most BrdU-incorporated cells in these periods were CCSP-immunoreactive (91.7%, 91.3%, and 88.2%, respectively), which means progenitor function of Clara cells. FoxJ1-immunoreactive BrdU-incorporated cells were fewer (5.4%, 3.0%, 2.7%, respectively). The average incidences of BrdU-LRCs in the terminal bronchioles after 2, 6, and 18 months were 7.2%, 4.3, and 2.7%, respectively. Most BrdU-LRCs were CCSP-immunoreactive (91.0%, 92.7%, and 89.6%, respectively), and FoxJ1-immunoreactive BrdU-LRCs were fewer (6.0%, 5.7%, and 2.1%, respectively). CGRP-positive BrdU-incorporated cells were occasional. CGRP-positive BrdU-LRCs were detected in 17.6% of neuroepithelial bodies (NEBs) at 2 months, but disappeared at 6 months. BrdU-positive stem cell candidates, which locate at the brochiolo-alveolar duct junction or cover NEB, were few throughout this study. In conclusion, in the lungs treated only with BrdU, CCSP-immunoreactive cells are important to maintain homeostasis in the terminal bronchiolar epithelium.

CCAAT/Enhancer Binding Protein–α Regulates the Protease/Antiprotease Balance Required for Bronchiolar Epithelium Regeneration

Many transcription factors that regulate lung morphogenesis during development are reactivated to mediate repairs of the injured adult lung. We hypothesized that CCAAT/enhancer binding protein-α (C/EBPα), a transcription factor critical for perinatal lung maturation, regulates genes required for the normal repair of the bronchiolar epithelium after injury. Transgenic Cebpα(Δ/Δ) mice, in which Cebpa was conditionally deleted from Clara cells and Type II cells after birth, were used in this study. Airway injury was induced in mice by the intraperitoneal administration of naphthalene to ablate bronchiolar epithelial cells. Although the deletion of C/EBPα did not influence lung structure and function under unstressed conditions, C/EBPα was required for the normal repair of terminal bronchiolar epithelium after naphthalene injury. To identify cellular processes that are influenced by C/EBPα during repair, mRNA microarray was performed on terminal bronchiolar epithelial cells isolated by laser-capture microdissection. Normal repair of the terminal bronchiolar epithelium was highly associated with the mRNAs regulating antiprotease activities, and their induction required C/EBPα. The defective deposition of fibronectin in Cebpα(Δ/Δ) mice was associated with increased protease activity and delayed differentiation of FoxJ1-expressing ciliated cells. The fibronectin and ciliated cells were restored by the intratracheal treatment of Cebpα(Δ/Δ) mice with the serine protease inhibitor. In conclusion, C/EBPα regulates the expression of serine protease inhibitors that are required for the normal increase of fibronectin and the restoration of ciliated cells after injury. Treatment with serine protease inhibitor may aid in the recovery of injured bronchiolar epithelial cells, and prevent common chronic lung diseases.

Diverse Expression of Antioxidants and Inflammatory Chemokines in Terminal Bronchiolar Epithelium in Chronic Obstructive Pulmonary Disease

Diverse Expression of Antioxidants and Inflammatory Chemokines in Terminal Bronchiolar Epithelium in Chronic Obstructive Pulmonary Disease

Malignant Catarrhal Fever-like Disease in Sheep after Intranasal Inoculation with Ovine Herpesvirus-2

A malignant catarrhal fever (MCF)-like disease was induced experimentally in 3 sheep after aerosol inoculation with ovine herpesvirus-2 (OvHV-2). Each of 3 OvHV-2-negative sheep was nebulized with 2 ml of nasal secretions containing approximately 3.07 X 10(9) OvHV-2 DNA copies from a sheep experiencing an intensive viral-shedding episode. Ovine herpesvirus-2 DNA became detectable by polymerase chain reaction in the peripheral blood leukocytes of all 3 sheep within 3 days, and all 3 seroconverted between 6 and 8 days postinfection (PI). The sheep developed clinical signs, with copious mucopurulent nasal discharge and fever around 14 days PI. One of the 3 clinically affected sheep was euthanized at 18 days PI. Major lesions at necropsy were multifocal linear erosions and ulcers in mucosa of the cheeks, tongue, pharynx, and proximal esophagus and mild disseminated pneumonia. Microscopically, there was extensive moderate superficial histiocytic-lymphocytic rhinitis with epithelial dissociation and degeneration. Moderate multifocal histiocytic bronchointerstitial pneumonia was associated with loss of terminal bronchiolar epithelium. Lymphocytic vasculitis was present only in the lung. The remaining 2 sheep recovered clinically, approximately 25 days PI. The study revealed that clinical signs and lesions resembling MCF can develop when uninfected sheep are exposed to a high dose of aerosolized OvHV-2.

Calibration Study on Subchronic Inhalation Toxicity of Man-Made Vitreous Fibers in Rats

This 3-mo inhalation study investigated the biological effects of a special-purpose glass microfiber (E-glass microfiber), the stone wool fiber MMVF21, and a new high-temperature application fiber (calcium-magnesium-silicate fiber, CMS) in Wistar rats. Rats were exposed 6 h/day, 5 days/wk for 3 mo to fiber aerosol concentrations of approximately 15, 50, and 150 fibers/ml (fiber length >20 µm) for E-glass microfiber and MMVF21. For the CMS fiber only the highest exposure concentration was used. During a 3-mo postexposure period, recovery effects were studied. In the highest exposure concentration groups, gravimetric concentrations were 17.2 mg/m 3 for E-glass microfiber, 37 mg/m 3 for MMVF21, and 49.5 mg/m 3 for the CMS fiber. After 3 mo of exposure, lung retention of fibers longer than 20 µm per lung was 17 × 10 6 for E-glass microfiber, 5.7 × 10 6 for MMVF21, and 0.88 × 10 6 for CMS. After 3 mo of recovery the concentration of the long fiber fraction was decreased to 38.4%, 63.9%, and 3.0% compared to original lung burden for the E-glass microfiber, MMVF21, and CMS, respectively. Biological effects measured included inflammatory and proliferative potential, histopathology lesions, and the persistence of these effects over a recovery period of 3 mo. Generally, observed effects were higher for E-glass microfiber when compared to MMVF21. The following clear dose-dependent effects on E-glass microfiber and MMVF21 exposure were observed as main findings of the study: increase in lung weight, in measured biochemical parameters and polymorphonuclear leukocytes (PMN) in the bronchoalveolar lavage fluid (BALF), in cell proliferation (BrdU-response) of terminal bronchiolar epithelium, and in interstitial fibrosis. The values observed in the proliferation assay on the carcinogenic E-glass microfiber indicate that this assay has an important predictive value with regards to potential carcinogenicity. Surprisingly, for the biosoluble CMS fiber, fibrogenic potential was detected in this study. The results of the CMS exposure group indicate that effects may be dominated by the presence of nonfibrous particles and that fibrosis may not be a predictor of carcinogenic activity of fiber samples, if the fiber preparation contains a significant fraction of nonfibrous particles. In summary, this study demonstrates the importance of fiber dust contamination by granular components. For future subchronic studies a longer posttreatment observation period would be advisable.

P-655 Achaete-scute homologue-1 (ASH-1) enhances proliferation and resistance to apoptosis in the terminal bronchiolar epithelium in transgenic mice promoting brochiolization of the alveoli

P-655 Achaete-scute homologue-1 (ASH-1) enhances proliferation and resistance to apoptosis in the terminal bronchiolar epithelium in transgenic mice promoting brochiolization of the alveoli

Evaluation of potential modes of action of inhaled ethylbenzene in rats and mice.

Potential factors underlying the tumorigenic activity of ethylbenzene (EB) were examined in F344 rats and B6C3F1 mice inhaling 750 ppm EB vapor 6 h/day, 5 days/week, for one or four weeks. Target tissues (kidneys of rats and livers and lungs of mice) were evaluated for changes in organ weights, mixed function oxygenases (MFO), glucuronosyl transferase activities, S-phase DNA synthesis, apoptosis, alpha2u-globulin deposition, and histopathology. In male rats, kidney weight increases were accompanied by focal increases in hyaline droplets, alpha2u-globulin, degeneration, and S-phase synthesis in proximal tubules. In female rats, only decreased S-phase synthesis and MFO activities occurred. In mice, increased liver weights were accompanied by hepatocellular hypertrophy, mitotic figures, S-phase synthesis, and enzyme activities. S-phase synthesis rates in terminal bronchiolar epithelium were elevated and accompanied by loss of MFO activity. Exposure to a nontumorigenic level of 75 ppm for one week caused few changes. These data, considered with the general lack of EB genotoxicity, suggest a mode of tumorigenesis dependent upon increased cell proliferation and altered population dynamics in male rat kidney and mouse liver and lungs. A similar response in the kidneys of female rats appears to require a longer exposure period than was employed.

Calibration Study on Subchronic Inhalation Toxicity of Man-Made Vitreous Fibers in Rats

This 3-mo inhalation study investigated the biological effects of a special-purpose glass microfiber (E-glass microfiber), the stone wool fiber MMVF21, and a new high-temperature application fiber (calcium-magnesium-silicate fiber, CMS) in Wistar rats. Rats were exposed 6 h/day, 5 days/wk for 3 mo to fiber aerosol concentrations of approximately 15, 50, and 150 fibers/ml (fiber length >20 µm) for E-glass microfiber and MMVF21. For the CMS fiber only the highest exposure concentration was used. During a 3-mo postexposure period, recovery effects were studied. In the highest exposure concentration groups, gravimetric concentrations were 17.2 mg/m 3 for E-glass microfiber, 37 mg/m 3 for MMVF21, and 49.5 mg/m 3 for the CMS fiber. After 3 mo of exposure, lung retention of fibers longer than 20 µm per lung was 17 × 10 6 for E-glass microfiber, 5.7 × 10 6 for MMVF21, and 0.88 × 10 6 for CMS. After 3 mo of recovery the concentration of the long fiber fraction was decreased to 38.4%, 63.9%, and 3.0% compared to original lung burden for the E-glass microfiber, MMVF21, and CMS, respectively. Biological effects measured included inflammatory and proliferative potential, histopathology lesions, and the persistence of these effects over a recovery period of 3 mo. Generally, observed effects were higher for E-glass microfiber when compared to MMVF21. The following clear dose-dependent effects on E-glass microfiber and MMVF21 exposure were observed as main findings of the study: increase in lung weight, in measured biochemical parameters and polymorphonuclear leukocytes (PMN) in the bronchoalveolar lavage fluid (BALF), in cell proliferation (BrdU-response) of terminal bronchiolar epithelium, and in interstitial fibrosis. The values observed in the proliferation assay on the carcinogenic E-glass microfiber indicate that this assay has an important predictive value with regards to potential carcinogenicity. Surprisingly, for the biosoluble CMS fiber, fibrogenic potential was detected in this study. The results of the CMS exposure group indicate that effects may be dominated by the presence of nonfibrous particles and that fibrosis may not be a predictor of carcinogenic activity of fiber samples, if the fiber preparation contains a significant fraction of nonfibrous particles. In summary, this study demonstrates the importance of fiber dust contamination by granular components. For future subchronic studies a longer posttreatment observation period would be advisable.

The role of interleukin-6 in pulmonary inflammation and injury induced by exposure to environmental air pollutants.

This study was designed to examine the role of the cytokine interleukin-6 (IL-6) in environmental air pollutant-induced pulmonary inflammation, injury, and repair. IL-6 knockout (KO) mice and wild-type (WT) mice were exposed to filtered air; aged and diluted cigarette smoke (ADSS), a surrogate for environmental tobacco smoke; ozone; or ADSS followed by ozone (ADSS/ozone). The proportion of monocytes and neutrophils recovered by bronchoalveolar lavage (BAL) as well as the level of total protein in BAL fluid were significantly increased in both IL-6 KO and WT mice following exposure to ozone or to ADSS/ozone. However, bromodeoxyuridine (BrdU) labeling within terminal bronchiolar epithelium and proximal alveolar regions in IL-6 KO mice exposed to ozone or to ADSS/ozone was significantly reduced compared with IL-6 sufficient mice (WT). WT mice treated with IL-6 antibodies also demonstrated a reduction in BrdU cell labeling similar to that observed in IL-6 KO mice following exposure to ozone or ADSS/ozone. Clara cell secretory protein (CCSP) abundance, a marker of Clara cell maturation and function, was markedly reduced in the terminal bronchiolar epithelium of WT mice following exposure to ADSS and/or ozone, whereas CCSP abundance was unchanged in IL-6 KO mice. We conclude that endogenous IL-6 in mice plays a critical role in the progress of lung inflammation/injury, but CCSP may also play a role to protect the lungs of mice exposed to toxic air pollutants. Data from this study further suggest that IL-6 antibody treatment modalities may be a means to attenuate pulmonary inflammation and injury.

Terminal Bronchioles Harbor a Unique Airway Stem Cell Population That Localizes to the Bronchoalveolar Duct Junction

Cellular mechanisms contributing to renewal of terminal bronchioles remain poorly defined. Our previous studies identified pollutant-resistant Clara cell secretory protein (CCSP)-expressing stem cells that localize to the neuroepithelial body (NEB) and contribute to renewal of the proximal bronchiolar epithelium. However, activation of NEB-associated stem cells is unlikely to contribute to renewal of terminal bronchiolar epithelium because of the paucity of NEBs at this location. Goals of this study were to determine the location and properties of cells contributing to renewal of terminal bronchioles after Clara cell depletion. Pollutant-resistant CCSP-expressing cells were identified that localized to the bronchoalveolar duct junction (BADJ) and contribute to restoration of a phenotypically diverse epithelium. CCSP-expressing cells comprise the predominant proliferative population in initial terminal bronchiolar repair and include a population of label-retaining cells suggesting that they maintain characteristics of a stem cell population. Furthermore, immunohistochemical co-localization studies involving CCSP and the NEB-specific marker calcitonin gene-related peptide indicate that BADJ-associated CCSP-expressing stem cells function independently of NEB microenvironments. These studies identify a BADJ-associated, NEB-independent, CCSP-expressing stem cell population in terminal bronchioles and support the notion that regiospecific stem cell niches function to maintain epithelial diversity after injury.

ATTENUATION AND RECOVERY OF PULMONARY INJURY IN RATS FOLLOWING SHORT-TERM, REPEATED DAILY EXPOSURE TO OZONE

Controlled human and epidemiology studies have demonstrated that during repeated exposure to ozone (O 3) attenuation of lung function responses may occur. It is yet unknown whether inflammatory and biochemical effects in lower airways of humans, as observed upon single O 3 exposure, also show a diminutive response following repeated exposure to O 3. The aim of this study was to investigate inflammatory, permeability, and histopathological responses in lungs of rats following repeated daily O 3 exposure and to study the time course of attenuation and recovery of these effects using single O 3 challenges at various postexposure times. To aid in animal-to-human extrapolation, this study and a previously reported human study (Devlin et al., 1997) were designed with similar protocols. Wistar rats were exposed for 5 consecutive days to 0.4 ppm O 3 for 12 h/night. Subsequently, the time course of postexposure recovery was determined by a single challenge of 12 h to 0.4 ppm O 3 after a 5-, 10-, 15-, or 20-day recovery period. Broncho-alveolar lavage (BAL) examination and histopathology were performed 12 h after this O 3 challenge. To quantify the magnitude of the O 3 response, results were compared with a group exposed only once for 12 h to 0.4 ppm O 3 and sacrificed simultaneously. The results demonstrate that a single exposure of 0.4 ppm O 3 causes marked permeability and inflammatory responses in lower airways of rats, as evidenced by enhanced BAL fluid levels of proteins, fibronectin, interleukin (IL)-6, and inflammatory cells. However, 5 days of exposure to 0.4 ppm O 3 for 12 h/night resulted in a complete disappearance of these responses, resulting in BAL fluid values that were not different from those observed in unexposed controls. Postexposure analyses of pulmonary response to O 3 challenges demonstrated that these attenuated responses show a gradual recovery. The data indicate that with respect to BAL fluid levels of albumin, IL-6, and number of macrophages and neutrophils, the period for lung tissue to regain its full susceptibility and responsiveness to O 3 following a 5-day preexposure period is approximately 15-20 days. Remarkably, the total protein and fibronectin responses in BAL fluid still exhibited an attenuated response to an O 3 challenge at 20 days postexposure. Morphometry (number of BrdU-labeled cells in terminal bronchiolar epithelium, and number of alveolar macrophages) showed that after a recovery of 5-10 days following a 5-day preexposure the response to a challenge was identical to that after a single exposure. These results suggest that complete repair from lower airway inflammation caused by short-term, repeated exposure to O 3 may take longer than previously assumed.

Differentiation of ciliated cells in the terminal bronchioles of neonatal calves.

The bronchiolar ciliated cells are exquisitely sensitive to injury caused by infection or irritation of the airways. The mechanism by which bronchiolar ciliated cells are renewed following injury or during the normal course of differentiation is still debated. The present study aimed at recognizing the progenitor cell population for bronchiolar ciliated cells during early neonatal life of calves and to demonstrate the course of events occurs during its differentiation into ciliated cells. Scanning electron microscopy of the terminal bronchiolar epithelium revealed two distinct cell types namely ciliated and non-ciliated cells. Transmission electron microscopy revealed ciliated, non-ciliated (Clara), intermediate and basal cells. At least two categories of intermediate cells could be distinguished: intermediate cells with abundant glycogen and variable numbers of organelles; intermediate cells with little glycogen, large numbers of polyribosomes, and variable numbers of basal bodies. We conclude that: (1) both bronchiolar non-ciliated and basal cells serve as progenitors for the bronchiolar ciliated cells; (2) differentiation of ciliated cell from the non-ciliated one involves a transitional cell in which glycogen is lost, polyribosomes are synthesized before the synthesis of basal bodies and cilia.

Laser capture microdissection and real-time reverse transcriptase/ polymerase chain reaction of bronchiolar epithelium after bleomycin.

Terminal airways are affected in many lung diseases and toxic inhalations. To elucidate the changes in terminal airways in these diverse situations it will be helpful to profile and quantify gene expression in terminal bronchiolar epithelium. We used laser capture microdissection (LCM) to collect terminal bronchiolar epithelial cells from frozen sections of lungs of mice subjected to intratracheal bleomycin. The RNA from these cells was used for analysis of select messenger RNAs (mRNAs) by quantitative real-time polymerase chain reaction (PCR). In parallel, we used real-time PCR to analyze mRNAs in whole-lung homogenates prepared from other mice given intratracheal bleomycin. We found reductions of Clara cell-specific protein and keratinocyte growth factor receptor mRNAs in both terminal bronchiolar epithelium and whole-lung homogenates 7 d after bleomycin. In contrast, terminal bronchiolar epithelial transforming growth factor (TGF)-alpha mRNA was reduced but whole-lung TGF-alpha mRNA was not changed, whereas terminal bronchiolar epithelial epidermal growth factor (EGF) receptor mRNA was not changed but whole-lung EGF receptor was reduced. We conclude that LCM can isolate terminal bronchiolar epithelial cells for studies of cell-specific gene expression by quantitative real-time PCR, and that cell-specific gene expression in terminal bronchiolar epithelium is not necessarily reflected in analysis of whole-lung gene expression.

Cellular response in naphthalene-induced Clara cell injury and bronchiolar epithelial repair in mice

Clara cells, progenitors for bronchiolar epithelium, are also primary targets for metabolically activated pulmonary cytotoxicants and have an abundance of the cytochrome P-450 monooxygenases required for xenobiotic metabolism. To define the repair pattern after massive Clara cell injury, mice were treated with naphthalene, and lungs evaluated 1-14 days postinjury (DPI). Clara cells of terminal bronchioles were vacuolated and swollen 1 DPI, exfoliated 2 DPI, and resembled controls at 14 DPI. The volume fraction of vacuolated cells was highest 1 and 2 DPI and minimal at 5-7 DPI. The volume fraction of normal nonciliated cells decreased 40% at 1 DPI. Cell proliferation increased within epithelium and interstitium at 1 DPI, was maximal at 2 DPI, and at all other time points was similar to baseline levels. Expression of Clara cell differentiation markers was barely detectable in terminal bronchiolar epithelium at 1 and 2 DPI, clearly detectable at 4 DPI, and gradually returned to control levels at 5-14 DPI. We conclude that bronchiolar epithelial repair after naphthalene injury involves distinct phases of proliferation and differentiation, proliferation of cells that are not differentiated Clara cells, and interaction of multiple cell types including nontarget cells.

Acute Pulmonary Toxicity of Copper Gallium Diselenide, Copper Indium Diselenide, and Cadmium Telluride Intratracheally Instilled into Rats

Acute toxicity studies were conducted on copper gallium diselenide (CGS), copper indium diselenide (CIS), and cadmium telluride (CT), three novel compounds used in the photovoltaic and semiconductor industries. Female Sprague-Dawley rats (six rats/dose) were administered 0, 12, 25, 50, or 100 mg/kg body wt of CGS, CIS, or CT by intratracheal instillation. At 72 hr after treatment, body weight gain was significantly decreased in the 100 mg/kg CIS group and in all CT dose groups. Lung weights were increased in most chemical-treated rats, with CT causing the greatest increase. Total numbers of cells in bronchoalveolar lavage fluid (BALF) were significantly increased in treated rats and were greatest in the 100 mg/kg CIS group. Differential cell counts of BALF demonstrated a marked decrease in the percentage of alveolar macrophages and an increase in the percentage of polymorphonuclear leukocytes in all dose groups of all three chemicals. Slight to moderate increases in lactate dehydrogenase activity were observed in BALF from CGS- and CIS-treated rats; marked increases were observed in CT-treated rats. BALF protein was significantly increased in rats treated with CIS and CT. Microscopic examination revealed lymphoid hyperplasia in lungs of rats treated with all three chemicals. CT caused necrosis of the terminal bronchiolar epithelium and epithelium of the alveolar duct region with inflammation, prominent fibrin exudates, and type II cell hyperplasia. CGS and CIS also caused intraalveolar inflammation and type II cell hyperplasia, but did not cause the necrosis and fibrin exudate observed in lungs of CT-treated rats. Based on changes in lung weight, BALF indices, and histopathology, CT was the most toxic for the lung; CIS had intermediate toxicity and CGS was the least toxic. The solubilities of CGS and CIS were relatively low and similar at both pH levels and do not readily explain the observed differences in pulmonary toxicity. The solubility of CdTe was considerably greater than that of CGS and CIS and likely contributed to the greater toxicity of this compound.

Bauhinia purpurea lectin (BPA) binding of rat type I pneumocytes: Alveolar epithelial alterations after radiation-induced lung injury

In the rat lung, we found that the Bauhinia purpurea lectin (BPA) specifically binds to the type I alveolar epithelial cells and to the alveolar macrophages. Double label fluorescence employing FITC-coupled Maclura pomifera lectin (MPA) and bBPA-avidin-Texas Red showed that BPA binding was confined to type I cells. In addition, a minor staining of the luminal border of the terminal bronchiolar epithelium was found. The sequence of tissue injury following X-radiation was examined in rats. BPA is a suitable marker which indicates epithelial changes during the early stage of pneumonitis and the subsequent development of fibrosis.

Expression of the cyclin-dependent kinase cdk4 in perinatal and adult rat lung.

The identification of numerous cyclin-dependent kinases (cdk) and G1 cyclins suggests that cell cycle progression through G1/S may be controlled in a tissue-specific manner by various cdk/cyclin complexes. In situ hybridization was used to characterize expression of the cyclin-dependent kinase cdk4 in prenatal and postnatal rat lung and other tissues and to determine whether cdk4 expression is limited to proliferating cells, identified by BrdU incorporation and cdk1 mRNA expression. cdk4 co-localized with cdk1 in proliferating cells of both prenatal and postnatal lung and other tissues, consistent with an SPF function that is not tissue-specific. The distribution of cdk1 and cdk4 expression was identical in fetal rat tissues and was detected in lung parenchyma and throughout the airway. Pulmonary cell proliferation declined with increasing postnatal age and could be found only in focal areas of day 21 terminal and respiratory bronchiolar epithelium. Proliferation was undetectable in adult lung. Postnatal cdk4 expression was not restricted to cells expressing cdk1: cdk4 was evenly distributed in bronchiolar epithelium and was present throughout the airway and alveolar septae of day 21 lung. Expression of cdk4 was also maintained in adult bronchiolar epithelium. These studies demonstrate that although the expression of cdk1 is tightly correlated with proliferative capacity, the expression of cdk4 is not limited to proliferating cells, suggesting that cdk4 may have additional cell-specific functions unrelated to cell cycle progression.

Immunohistochemical localization of placental alkaline phosphatase, carcinoembryonic antigen, and cancer antigen 125 in normal and neoplastic human lung

Human placental alkaline phosphatase (HPLAP), carcinoembryonic antigen (CEA), and cancer antigen 125 (CA 125) were localized immunohistochemically in paraffin sections of normal lung tissue from 16 patients, using monoclonal antibodies and an indirect avidin-biotin-peroxidase staining procedure. HPLAP and CEA were present in epithelial cells of respiratory bronchioli and alveolar type I pneumocytes. CEA was also observed in the tracheal, bronchial, and bronchiolar epithelium. CA 125 was present in the tracheal, bronchial, bronchiolar, and terminal bronchiolar epithelium; in the tracheal and bronchial glands; and in the pleural mesothelium. Normal and hyperplastic type II pneumocytes were negative for HPLAP, CEA, and CA 125 but were histochemically positive for nonspecific alkaline phosphatase. Fetal lung tissue between 11 and 15 weeks of gestation was negative for HPLAP, CEA, and CA 125. The fetal tracheal and bronchial epithelium, tracheal glands, and pleural mesothelium were positive for CA 125. For ten malignant pulmonary tumors investigated, HPLAP staining was observed in five, CEA in nine, and CA 125 in seven. The localization of HPLAP, CEA, and CA 125 in apparently normal constituents of all pulmonary specimens is in disagreement with the concept that the expression of these substances in the lung is indicative of abnormal cellular activity.