Ozone- and endotoxin-induced mucous cell metaplasias in rat airway epithelium: novel animal models to study toxicant-induced epithelial transformation in airways

A Scoping Analysis of Cathelicidin in Response to Organic Dust Exposure and Related Chronic Lung Illnesses

Over two billion people worldwide are exposed to organic dust, which can cause respiratory disorders. The discovery of the cathelicidin peptide provides novel insights into the lung’s response to organic dust; however, its role in the lung’s response to organic dust exposure and chronic lung diseases remains limited. We conducted a scoping review to map the current evidence on the role of cathelicidin LL-37/CRAMP in response to organic dust exposure and related chronic lung diseases: hypersensitivity pneumonitis (HP), chronic obstructive pulmonary disease (COPD) and asthma. We included a total of n = 53 peer-reviewed articles in this review, following the process of (i) a preliminary screening; (ii) a systematic MEDLINE/PubMed database search; (iii) title, abstract and full-text screening; (iv) data extraction and charting. Cathelicidin levels were shown to be altered in all clinical settings investigated; its pleiotropic function was confirmed. It was found that cathelicidin contributes to maintaining homeostasis and participates in lung injury response and repair, in addition to exerting a positive effect against microbial load and infections. In addition, LL-37 was found to sustain continuous inflammation, increase mucus formation and inhibit microorganisms and corticosteroids. In addition, studies investigated cathelicidin as a treatment modality, such as cathelicidin inhalation in experimental HP, which had positive effects. However, the primary focus of the included articles was on LL-37’s antibacterial effect, leading to the conclusion that the beneficial LL-37 activity has not been adequately examined and that further research is required.

Ameliorative Effect of Thymoquinone-Loaded PLGA Nanoparticles on Chronic Lung Injury Induced by Repetitive Intratracheal Instillation of Lipopolysaccharide in Rats

Thymoquinone (TQ), the active constituent of Nigella sativa, possesses several benefits in traditional and modern medicines. This study examined the effect of a single dose of Nano-TQ on chronic lung injury induced by repetitive intratracheal installation of lipopolysaccharide (LPS). Rats received LPS twice weekly for 8 weeks via intratracheal installation and a single dose of TQ-PLGA NPs on the day after the last dose of LPS. Six rats from each group were sacrificed after 8 and 10 weeks, and samples were collected for analysis. Repetitive intratracheal installation of LPS caused histopathological alterations, including partial or complete obstruction of the alveoli, interstitial edema, mild fibroblastic proliferation, fibrous strands besides lymphocytes and plasma infiltrations, suffered fetalization, bronchiectasis, hypertrophied arterioles, and others. Investigation of the ultrastructure revealed prominent necrotic pneumocytes with destructed chromatin and remnant of necrotic debris in the narrowing alveolar lumen in LPS-induced rats. TQ-PLGA NPs effectively ameliorated LPS-induced histopathological and ultrastructural alterations in the lung of rats. In addition, TQ-PLGA NPs significantly alleviated serum levels of IL-10 and TGF-β1 in LPS-induced rats. In conclusion, TQ-PLGA NPs prevented inflammation and tissue injury in the lungs of rats challenged with repetitive intratracheal installation of LPS. Therefore, TQ-PLGA NPs represent a promising candidate for the prevention of lung injury induced by LPS, pending further studies to determine its safety and exact protective mechanism.

Outdoor Air Pollution and New-Onset Airway Disease. An Official American Thoracic Society Workshop Report

Although it is well accepted that air pollution exposure exacerbates preexisting airway disease, it has not been firmly established that long-term pollution exposure increases the risk of new-onset asthma or chronic obstruction pulmonary disease (COPD). This Workshop brought together experts on mechanistic, epidemiological, and clinical aspects of airway disease to review current knowledge regarding whether air pollution is a causal factor in the development of asthma and/or COPD. Speakers presented recent evidence in their respective areas of expertise related to air pollution and new airway disease incidence, followed by interactive discussions. A writing committee summarized their collective findings. The Epidemiology Group found that long-term exposure to air pollution, especially metrics of traffic-related air pollution such as nitrogen dioxide and black carbon, is associated with onset of childhood asthma. However, the evidence for a causal role in adult-onset asthma or COPD remains insufficient. The Mechanistic Group concluded that air pollution exposure can cause airway remodeling, which can lead to asthma or COPD, as well as asthma-like phenotypes that worsen with long-term exposure to air pollution, especially fine particulate matter and ozone. The Clinical Group concluded that air pollution is a plausible contributor to the onset of both asthma and COPD. Available evidence indicates that long-term exposure to air pollution is a cause of childhood asthma, but the evidence for a similar determination for adult asthma or COPD remains insufficient. Further research is needed to elucidate the exact biological mechanism underlying incident childhood asthma, and the specific air pollutant that causes it.

Lung transcriptional profiling: insights into the mechanisms of ozone-induced pulmonary injury in Wistar Kyoto rats

Acute ozone-induced pulmonary injury and inflammation are well characterized in rats; however, mechanistic understanding of the pathways involved is limited. We hypothesized that acute exposure of healthy rats to ozone will cause transcriptional alterations, and comprehensive analysis of these changes will allow us to better understand the mechanism of pulmonary injury and inflammation. Male Wistar Kyoto rats (10-12 week) were exposed to air, or ozone (0.25, 0.5 or 1.0 ppm) for 4 h and pulmonary injury and inflammation were assessed at 0-h or 20-h (n = 8/group). Lung gene expression profiling was assessed at 0-h (air and 1.0 ppm ozone, n = 3-4/group). At 20-h bronchoalveolar lavage, fluid protein and neutrophils increased at 1 ppm ozone. Numerous genes involved in acute inflammatory response were up-regulated along with changes in genes involved in cell adhesion and migration, steroid metabolism, apoptosis, cell cycle control and cell growth. A number of NRF2 target genes were also induced after ozone exposure. Based on expression changes, Rela, SP1 and TP3-mediated signaling were identified to be mediating downstream changes. Remarkable changes in the processes of endocytosis provide the insight that ozone-induced lung injury and inflammation are likely initiated by changes in cell membrane components and receptors likely from oxidatively modified lung lining lipids and proteins. In conclusion, ozone-induced injury and inflammation are preceded by changes in gene targets for cell adhesion/migration, apoptosis, cell cycle control and growth regulated by Rela, SP1 and TP53, likely mediated by the process of endocytosis and altered steroid receptor signaling.

COPD in Nonsmokers: Reports from the Tunisian Population-Based Burden of Obstructive Lung Disease Study

Background

It’s currently well known that smoking and increasing age constitute the most important risk factors for chronic obstructive pulmonary disease (COPD). However, little is known about COPD among nonsmokers. The present study aimed to investigate prevalence, risk factors and the profiles of COPD among nonsmokers based on the Tunisian Burden of Obstructive Lung Disease (BOLD) study.

Methods

807 adults aged 40 years+ were randomly selected from the general population. We collected information about history of respiratory disease, risk factors for COPD and quality of life. Post-bronchodilator spirometry was performed for assessment of COPD. COPD diagnostic was based on the post-bronchodilator FEV₁/FVC ratio, according to the Global Initiative for Obstructive Lung Disease (GOLD) guidelines. The lower limit of normal (LLN) was determined as an alternative threshold for the FEV₁/FVC ratio.

Results and Conclusions

Among 485 nonsmokers, 4.7% met the criteria for GOLD grade I and higher COPD. These proportions were similar even when the LLN was used as a threshold. None of the nonsmokers with COPD reported a previous doctor diagnosis of COPD compared to 7.1% of smokers. Nonsmokers accounted for 45.1% of the subjects fulfilling the GOLD spirometric criteria of COPD. Nonsmokers were predominately men and reported more asthma problems than obstructed smokers. Among nonsmokers significantly more symptoms and higher co-morbidity were found among those with COPD. Increasing age, male gender, occupational exposure, lower body mass index and a previous diagnosis of asthma are associated with increased risk for COPD in nonsmokers. This study confirms previous evidence that nonsmokers comprise a substantial proportion of individuals with COPD. Nonsmokers with COPD have a specific profile and should, thus, receive far greater attention to prevent and treat chronic airway obstruction.

Rat lung response to ozone and fine particulate matter (PM2.5) exposures

Exposure to different ambient pollutants maybe more toxic to lung than exposure to a single pollutant. In this study, we discussed the inflammation and oxidative stress responses of rat lung caused by ozone and PM2.5 versus that of rats exposed to saline, ozone, or single PM2.5 . Wistar rats inhaled 0.8 ppm ozone or air for 4 h and then placed in air for 3 h following intratracheal instillation with 0, 0.2 (low dose), 0.8 (medium dose), 3.2 (high dose) mg/rat PM2.5 dissolved in sterile saline (0.25 mL/rat), repeated twice per week for 3 weeks, the cumulative doses of PM2.5 in animals were 1.2, 4.8, and 19.2 mg. Rats were sacrificed 24 h after the last (sixth) exposure. The collected bronchoalveolar lavage fluid (BALF) was analyzed for inflammatory cells and cytokines. Lung tissues were processed for light microscopic and transmission electron microscopic (TEM) examinations. Results showed that total cell number in BALF of PM2.5 -exposed groups were higher than control (p < 0.05). PM2.5 instillation caused dose-trend increase in tumor necrosis factor alpha (TNF-α), interleukin-6, lactate dehydrogenase, and total protein of BALF. Exposure to ozone alone only caused TNF-α significant change in above-mentioned indicators of lung injury. On the other hand, ozone could enhance PM2.5-induced inflammatory changes and pathological characters in rat lungs. SOD and GSH-Px activities in lung were reduced in PM2.5-exposed rats with and without prior ozone exposure compared to control. To determine whether the PM2.5 and ozone affect endothelium system, iNOS, eNOS, and ICAM-1 mRNA levels in lung were analyzed by real-time PCR. These data demonstrated that inflammation and oxidative stress were involved in toxicology mechanisms of PM2.5 in rat lung and ozone potentiated these effects induced by PM2.5. These results have implications for understanding the pulmonary effects induced by ozone and PM2.5.

Lifetime occupational exposure to dusts, gases and fumes is associated with bronchitis symptoms and higher diffusion capacity in COPD patients

BACKGROUND

Occupational exposure to dusts, gases and fumes has been associated with reduced FEV1 and sputum production in COPD patients. The effect of occupational exposure on other characteristics of COPD, especially those reflecting emphysema, has not been studied in these patients.

METHODS

We studied 338 patients hospitalized for a first exacerbation of COPD in 9 Spanish hospitals, obtaining full occupational history in a face-to-face interview; job codes were linked to a job exposure matrix for semi-quantitative estimation of exposure to mineral/biological dust, and gases/fumes for each job held. Patients underwent spirometry, diffusing capacity testing and analysis of gases in stable conditions. Quality of life, dyspnea and chronic bronchitis symptoms were determined with a questionnaire interview. A high- resolution CT scan was available in 133 patients.

RESULTS

94% of the patients included were men, with a mean age of 68(8.5) years and a mean FEV1% predicted 52 (16). High exposure to gases or fumes was associated with chronic bronchitis, and exposure to mineral dust and gases/fumes was associated with higher scores for symptom perception in the St. George's questionnaire. No occupational agent was associated with a lower FEV1. High exposure to all occupational agents was associated with better lung diffusion capacity, in long-term quitters. In the subgroup with CT data, patients with emphysema had 18% lower DLCO compared to those without emphysema.

CONCLUSIONS

In our cohort of COPD patients, high exposure to gases or fumes was associated with chronic bronchitis, and high exposure to all occupational agents was consistently associated with better diffusion capacity in long-term quitters.

Chronic Obstructive Pulmonary Disease in Never-Smoking Bricklayers

Background: Chronic obstructive pulmonary disease (COPD) due to occupational exposures remains an important public health problem taking significant toll on the global burden of the disease.Aim: In order to assess chronic prevalence and characteristics of COPD in bricklaying we performed a cross-sectional study including 47 never-smoking male bricklayers (aged 34 to 57 years) and an equal number of never-smoking male office workers studied as a control.Methods: Evaluation of examined subjects consisted of completion of a questionnaire, baseline spirometry, and bronchodilator reversibility testing.Results: We found higher prevalence of respiratory symptoms in bricklayers with significant difference for cough and phlegm. Majority of the chronic respiratory symptoms in bricklayers were work-related. The mean values of all measured spirometric parameters in bricklayers were significantly lower than in office workers. The prevalence of COPD was significantly higher in bricklayers than in office workers (14.9% vs. 4.3%, P = 0.034). COPD in both examined groups was close related to age over 45 years, while in bricklayers significant association was registered for duration of occupational exposure longer than 20 years and work-related respiratory symptoms.Conclusion: Our findings support data about relationship between occupational exposure to inorganic dust and fumes in construction workers and persistent airflow limitation.

A large scale gene-centric association study of lung function in newly-hired female cotton textile workers with endotoxin exposure

Background

Occupational exposure to endotoxin is associated with decrements in pulmonary function, but how much variation in this association is explained by genetic variants is not well understood.

Objective

We aimed to identify single nucleotide polymorphisms (SNPs) that are associated with the rate of forced expiratory volume in one second (FEV₁) decline by a large scale genetic association study in newly-hired healthy young female cotton textile workers.

Methods

DNA samples were genotyped using the Illumina Human CVD BeadChip. Change rate in FEV₁ was modeled as a function of each SNP genotype in linear regression model with covariate adjustment. We controlled the type 1 error in study-wide level by permutation method. The false discovery rate (FDR) and the family-wise error rate (FWER) were set to be 0.10 and 0.15 respectively.

Results

Two SNPs were found to be significant (P<6.29×10⁻⁵), including rs1910047 (P = 3.07×10⁻⁵, FDR = 0.0778) and rs9469089 (P = 6.19×10⁻⁵, FDR = 0.0967), as well as other eight suggestive (P<5×10⁻⁴) associated SNPs. Gene-gene and gene-environment interactions were also observed, such as rs1910047 and rs1049970 (P = 0.0418, FDR = 0.0895); rs9469089 and age (P = 0.0161, FDR = 0.0264). Genetic risk score analysis showed that the more risk loci the subjects carried, the larger the rate of FEV₁ decline occurred (P_trend = 3.01×10⁻¹⁸). However, the association was different among age subgroups (P = 7.11×10⁻⁶) and endotoxin subgroups (P = 1.08×10⁻²). Functional network analysis illustrates potential biological connections of all interacted genes.

Conclusions

Genetic variants together with environmental factors interact to affect the rate of FEV₁ decline in cotton textile workers.

Mucous hypersecretion and relationship to cough

A variety of foreign "invaders" such as viruses, bacteria and other particulates e.g., cigarette smoke, are inhaled, deposit on the airway surface and invade the "host." Mucins produced by the surface airway epithelium and by the submucosal glands are secreted into the airway lumen. Deposited particulates adhere to the mucus and are cleared via mucociliary transport and via cough. Mucins are major constituents of mucus, which is important in the clearance of inhaled materials. Normally, secreted mucus is cleared without symptoms or interference with lung function. However, in obstructive airway diseases such as COPD, asthma, and cystic fibrosis, excessive mucus is produced. Because of the prominence of mucous hypersecretion as a cause of cough, this discussion focuses on mechanisms regulating normal production of mucins and the mechanisms underlying exaggerated mucin secretion in chronic obstructive airway diseases. Mucins are produced by airway epithelial cells via a cascade of signals (the Epidermal Growth Factor Cascade) and secreted on the luminal epithelial surface, often in response to the deposition of inhaled irritants. Normally, only minimal amounts of mucins are secreted, which assist in clearance of the inhaled particulates. However, in disease, additional pathways are induced via positive feedback systems, which lead to mucous hypersecretion. In the large conducting airways, where cough receptors are concentrated, mucous hypersecretion causes stimulation of neural receptors that result in cough. However, in small airways (e.g., bronchioles), because of their small diameters, mucous hypersecretion leads to plugging of the airways. Because there are so many small airways, their plugging is difficult to detect early, and this locus is known as a "silent zone." In chronic obstructive airway diseases, plugging of small airways may persist and increase over time, finally resulting in severe airway obstruction. Different obstructive airway diseases induce inflammatory signaling (including mucous hypersecretion) via different stimuli, but often via similar signaling pathways. Application of present knowledge of signaling that occurs with mucous hypersecretion can lead to novel therapies for hypersecretion and cough induced in conducting airways and could prevent plugging in small airways that can lead to clinical deterioration and death.

Characterization of the lung epithelium of wild-type and TLR9(-/-) mice after single and repeated exposures to chicken barn air

Exposure to chicken barn air causes lung injury resulting in lower and upper respiratory symptoms in the poultry workers, and mechanisms of which are not fully understood. The lung injury can initiate modifications such as proliferation of the airway epithelial cells such as Clara cells, type II alveolar (T2) cells and mucus producing goblet cells as part of the innate immune response. Toll-like receptors (TLR) have been suggested to play a role in cell division and proliferation. To understand the effect of TLR9 on Clara cells, T2 and mucus-producing goblet cells, we quantified the numbers of these cells in the lungs of wild-type (WT) and TLR9(-/-) mice exposed to chicken barn air. The mice were exposed for either one day or five or 20 days for 8 h/day. Clara cells and T2 cells were labelled with antibodies, and the mucus cells were identified with Periodic-acid Schiff stain, and quantified in per unit tissue section area. The data show decrease in the number of Clara cells and increase in mucus-producing goblet cells after exposure to chicken barn air in both WT and TLR9(-/-) mice. Numbers of T2 cells increased and decreased in WT and TLR9(-/-) mice, respectively, after exposure to poultry barn air. These data show that exposure to chicken barn air can affect major lung epithelial cells, and allude to the role of TLR9 in regulation of some of these responses.

SERCA2 regulates non-CF and CF airway epithelial cell response to ozone

Calcium mobilization can regulate a wide range of essential functions of respiratory epithelium, including ion transport, ciliary beat frequency, and secretion of mucus, all of which are modified in cystic fibrosis (CF). SERCA2, an important controller of calcium signaling, is deficient in CF epithelium. We conducted this study to determine whether SERCA2 deficiency can modulate airway epithelial responses to environmental oxidants such as ozone. This could contribute to the pathogenesis of pulmonary exacerbations, which are important and frequent clinical events in CF. To address this, we used air-liquid interface (ALI) cultures of non-CF and CF cell lines, as well as differentiated cultures of cells derived from non-CF and CF patients. We found that ozone exposure caused enhanced membrane damage, mitochondrial dysfunction and apoptotic cell death in CF airway epithelial cell lines relative to non-CF. Ozone exposure caused increased proinflammatory cytokine production in CF airway epithelial cell lines. Elevated proinflammatory cytokine production also was observed in shRNA-mediated SERCA2 knockdown cells. Overexpression of SERCA2 reversed ozone-induced proinflammatory cytokine production. Ozone-induced proinflammatory cytokine production was NF-κB- dependent. In a stable NF-κB reporter cell line, SERCA2 inhibition and knockdown both upregulated cytomix-induced NF-κB activity, indicating importance of SERCA2 in modulating NF-κB activity. In this system, increased NF-κB activity was also accompanied by increased IL-8 production. Ozone also induced NF-κB activity and IL-8 release, an effect that was greater in SERCA2-silenced NF-κB-reporter cells. SERCA2 overexpression reversed cytomix-induced increased IL-8 release and total nuclear p65 in CFTR-deficient (16HBE-AS) cells. These studies suggest that SERCA2 is an important regulator of the proinflammatory response of airway epithelial cells and could be a potential therapeutic target.

Vanadium pentoxide (V(2)O(5)) induced mucin production by airway epithelium

Exposure to environmental pollutants has been linked to various airway diseases and disease exacerbations. Almost all chronic airway diseases such as chronic obstructive pulmonary disease and asthma are caused by complicated interactions between gene and environment. One of the major hallmarks of those diseases is airway mucus overproduction (MO). Excessive mucus causes airway obstruction and significantly increases morbidity and mortality. Metals are major components of environmental particulate matters (PM). Among them, vanadium has been suggested to play an important role in PM-induced mucin production. Vanadium pentoxide (V(2)O(5)) is the most common commercial source of vanadium, and it has been associated with occupational chronic bronchitis and asthma, both of which are MO diseases. However, the underlying mechanism is not entirely clear. In this study, we used both in vitro and in vivo models to demonstrate the robust inductions of mucin production by V(2)O(5). Furthermore, the follow-up mechanistic study revealed a novel v-raf-1 murine leukemia viral oncogene homolog 1-IKK-NF-κB pathway that mediated V(2)O(5)-induced mucin production. Most interestingly, the reactive oxygen species and the classical mucin-inducing epidermal growth factor receptor (EGFR)-MAPK pathway appeared not to be involved in this process. Thus the V(2)O(5)-induced mucin production may represent a novel EGFR-MAPK-independent and environmental toxicant-associated MO model. Complete elucidation of the signaling pathway in this model will not only facilitate the development of the treatment for V(2)O(5)-associated occupational diseases but also advance our understanding on the EGFR-independent mucin production in other chronic airway diseases.

An official American Thoracic Society public policy statement: Novel risk factors and the global burden of chronic obstructive pulmonary disease

RATIONALE

Although cigarette smoking is the most important cause of chronic obstructive pulmonary disease (COPD), a substantial proportion of COPD cases cannot be explained by smoking alone.

OBJECTIVES

To evaluate the risk factors for COPD besides personal cigarette smoking.

METHODS

We constituted an ad hoc subcommittee of the American Thoracic Society Environmental and Occupational Health Assembly. An international group of members was invited, based on their scientific expertise in a specific risk factor for COPD. For each risk factor area, the committee reviewed the literature, summarized the evidence, and developed conclusions about the likelihood of it causing COPD. All conclusions were based on unanimous consensus.

MEASUREMENTS AND MAIN RESULTS

The population-attributable fraction for smoking as a cause of COPD ranged from 9.7 to 97.9%, but was less than 80% in most studies, indicating a substantial burden of disease attributable to nonsmoking risk factors. On the basis of our review, we concluded that specific genetic syndromes and occupational exposures were causally related to the development of COPD. Traffic and other outdoor pollution, secondhand smoke, biomass smoke, and dietary factors are associated with COPD, but sufficient criteria for causation were not met. Chronic asthma and tuberculosis are associated with irreversible loss of lung function, but there remains uncertainty about whether there are important phenotypic differences compared with COPD as it is typically encountered in clinical settings.

CONCLUSIONS

In public health terms, a substantive burden of COPD is attributable to risk factors other than smoking. To prevent COPD-related disability and mortality, efforts must focus on prevention and cessation of exposure to smoking and these other, less well-recognized risk factors.

Review series: Occupational and environmental lung disease: Chronic obstructive pulmonary disease and the workplace

Chronic Obstructive Pulmonary Disease (COPD) is a progressive respiratory disease associated with increasing morbidity and mortality worldwide. Whilst tobacco smoking is the important cause, other cuases are regognised. This article discusses the contribution that harmful inhaled occupational exposures make to the overall burden of COPD, and goes on to discuss other aspects of the COPD workplace interface. Prevention is key. All healthcare professionals have a resposibility to consider workplace issues when dealing with their COPD patients.

Endogenous and exogenous thioredoxin 1 prevents goblet cell hyperplasia in a chronic antigen exposure asthma model

BACKGROUND

Goblet cell hyperplasia with mucus hypersecretion contribute to increased morbidity and mortality in bronchial asthma. We have reported that thioredoxin 1 (TRX1), a redox (reduction/oxidation)-active protein acting as a strong antioxidant, inhibits pulmonary eosinophilic inflammation and production of chemokines and Th2 cytokines in the lungs, thus decreasing airway hyperresponsiveness (AHR) and airway remodeling in mouse asthma models. In the present study, we investigated whether endogenous or exogenous TRX1 inhibits goblet cell hyperplasia in a mouse asthma model involving chronic exposure to antigen.

METHODS

We used wild-type Balb/c mice and Balb/c background human TRX1-transgenic mice constitutively overproducing human TRX1 protein in the lungs. Mice were sensitized 7 times (days 0 to 12) and then challenged 9 times with ovalbumin (OVA) (days 19 to 45). Every second day from days 18 to 44 (14 times) or days 35 to 45 (6 times), Balb/c mice were treated with 40 microg recombinant human TRX1 (rhTRX1) protein. Goblet cells in the lungs were examined quantitatively on day 34 or 45.

RESULTS

Goblet cell hyperplasia was significantly prevented in TRX1-transgenic mice in comparison with TRX1 transgene-negative mice. rhTRX1 administration during OVA challenge (days 18 to 44) significantly inhibited goblet cell hyperplasia in OVA-sensitized and -challenged wild-type mice. Moreover, rhTRX1 administration after the establishment of goblet cell hyperplasia (days 35 to 45) also significantly ameliorated goblet cell hyperplasia in OVA-sensitized and -challenged wild-type mice.

CONCLUSIONS

Our results suggest that TRX1 prevents the development of goblet cell hyperplasia, and also ameliorates established goblet cell hyperplasia.

Cyanobacterial megamolecule sacran efficiently forms LC gels with very heavy metal ions

We extracted the megamolecular polysaccharide sacran, which contains carboxylate and sulfate groups, from the jellylike extracellular matrix (ECM) of the cyanobacterium Aphanothece sacrum, which has mineral adsorption bioactivity. We investigated the gelation properties of sacran binding with various heavy metal ions. The sacran chain adsorbed heavier metal ions such as indium, rare earth metals, and lead ions more efficiently to form gel beads. In addition, trivalent metal ions adsorbed onto the sacran chains more efficiently than did divalent ions. The investigation of the metal ion binding ratio on sacran chains demonstrated that sacran adsorbed gadolinium trivalent ions more efficiently than indium trivalent ions. Gel bead formation may be closely correlated to the liquid-crystalline organization of sacran.

Alcian Blue and Pyronine Y histochemical stains permit assessment of multiple parameters in pulmonary disease models

Utilization of a combined Alcian Blue and Pyronine Y histochemical method for the assessment of multiple parameters in the respiratory tract of various species is described. Acidic mucins were deep blue (sialylated mucins), red (sulfated mucins), or variably purple (mixture of sialylated/sulfated mucins), and differential mucus production was readily detected in a murine respiratory syncytial virus vaccine model of pulmonary inflammation. Elastic fibers stained red in the walls of pulmonary arteries, connecting airways, alveolar septa, and subpleural interstitium. Mast cells had red to red-purple granular cytoplasmic staining. Nuclei were ubiquitously counterstained pale blue. Representative staining was detected in tissues from multiple species, including inbred mice, rats, ferrets, cats, dogs, sheep, and pigs. The fluorescent property of the stained tissues offers additional modalities with which to analyze tissue sections. This histochemical technique detects multiple critical parameters in routine paraffin sections of lung tissue, reduces the need for repeated serial sectioning and staining, and is cost-effective and simple to perform.

Enhanced goblet cell hyperplasia in HDC knockout mice with allergic airway inflammation

BACKGROUND

Histamine is known to have immunoregulatory roles in allergic reactions through histamine receptor 1 (H1R), H2R, H3R and H4R. However, its role in goblet cell hyperplasia in the airways of asthma patients is yet to be clarified.

OBJECTIVE

This study was designed to examine the role of histamine in goblet cell hyperplasia using histamine-deficient mice (Hdc-/- mice) with allergic airway inflammation.

METHODS

Wild-type and Hdc-/- C57BL/6 mice were sensitized with ovalbumin (OVA). After a 2-week exposure to OVA, goblet cell hyperplasia was evaluated. Cell differentials and cytokines in BALF were analyzed. The mRNA levels of MUC5AC and Gob-5 gene were determined quantitatively.

RESULTS

The number of eosinophils in BALF increased in both the sensitized wild-type mice and Hdc-/- mice with OVA inhalation. In addition, the numbers of alveolar macrophages and lymphocytes in BALF increased significantly in the sensitized Hdc-/- mice with OVA inhalation compared to the wild-type mice under the same conditions. The concentrations of Interleukin-4 (IL-4), IL-5, IL-13, Interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha) and IL-2 in the BALF all increased significantly in both groups compared to those exposed to saline. In particular, the concentration of TNF-alpha in the Hdc-/- mice exposed to OVA was significantly higher than that in the wild-type mice under the same conditions. The mRNA levels of Gob-5 and MUC5AC, and the ratio of the goblet cells in the airway epithelium significantly increased in Hdc-/- mice exposed to OVA compared to wild-type mice.

CONCLUSIONS

These results suggested that histamine may play a regulatory role in goblet cell hyperplasia in allergic airway inflammation.

Animal models of chronic obstructive pulmonary disease

The mechanisms involved in the genesis of chronic obstructive pulmonary disease (COPD) are poorly defined. This area is complicated and difficult to model because COPD consists of four separate anatomic lesions (emphysema, small airway remodeling, pulmonary hypertension, and chronic bronchitis) and a functional lesion, acute exacerbation; moreover, the disease in humans develops over decades. This review discusses the various animal models that have been used to attempt to recreate human COPD and the advantages and disadvantages of each. None of the models reproduces the exact changes seen in humans, but cigarette smoke-induced disease appears to come the closest, and genetically modified animals also, in some instances, shed light on processes that appear to play a role.

Progress in allergy signal research on mast cells: the role of histamine in goblet cell hyperplasia in allergic airway inflammation - a study using the Hdc knockout mouse

Although histamine is a central mediator in the immediate allergic reaction, its role in goblet cell hyperplasia in the airway of asthma is not completely understood. This study was designed to examine the role of histamine in goblet cell hyperplasia using histamine-deficient mice (Hdc(-/-) mice) with allergic airway inflammation. Wild-type and Hdc(-/-) C57BL/6 mice were sensitized with ovalbumin (OVA). After two-week exposure to OVA, goblet cell hyperplasia was evaluated. Cell differentials in BALF were analyzed. The mRNAs level of MUC5AC and Gob-5 gene were quantitatively determined. The number of eosinophils in BALF increased in both the wild-type mice and Hdc(-/-) mice; however, their ratio in Hdc(-/-) mice was significantly lower than that in the wild-type mice. The mRNA levels of Gob-5 and MUC5AC and the ratio of the goblet cells in the airway epithelium were significantly increased in Hdc(-/-) mice exposed to OVA compared to the wild-type mice under the same condition. These results suggested that histamine may play a regulatory role in goblet cell hyperplasia in allergic airway inflammation.

Role of epidermal growth factor receptor in maintaining airway goblet cell hyperplasia in rats sensitized to allergen

BACKGROUND

Stimulation of epidermal growth factor receptor (EGFR) induces airway goblet cell hyperplasia, but the role of this molecule in the maintenance of this pathologic change remains uncertain.

OBJECTIVE

To determine the mechanisms by which goblet cell hyperplasia is maintained in airway epithelium, we investigated EGFR-induced signalling pathways that lead to both mucin production and antiapoptosis in vitro. We also tested whether the inhibition of EGFR tyrosine kinase speeds reversal of established goblet cell hyperplasia to normal epithelial phenotype in vivo.

METHODS

MUC5AC production was measured by immunoassay, and antiapoptotic responses were determined by Bcl-2 expression and terminal deoxynucleotidyl transferase-mediated dUTP-biotin Nick End Labelling staining using NCI-H292 cells. The effect of an inhibitor of EGFR tyrosine kinase (AG1478) on goblet cell hyperplasia was also determined in rats sensitized with ovalbumin (OVA).

RESULTS

MUC5AC was constitutively expressed and few apoptotic cells were observed in NCI-H292 cells under non-stimulated condition. TGF-alpha increased MUC5AC and Bcl-2 expression, an effect that was prevented by inhibitors of EGFR tyrosine kinase (AG1478), MEK (PD98059), and NF-kappaB (CAPE). After the addition of TGF-alpha, AG1478 and an inhibitor of phosphatidylinositol 3 kinase/Akt (LY294002), but not PD98059, induced a marked apoptotic response, which was prevented by the caspase inhibitor Z-VAD fmk. Goblet cell hyperplasia and EGFR expression in airway epithelium were noted in the OVA-sensitized rats. Intratracheal instillation of AG1478 induced apoptosis of goblet cells, reverting the airway epithelium to normal epithelial phenotype.

CONCLUSION

These findings indicate that EGFR plays an important role in the maintenance of goblet cell hyperplasia. We speculate that inhibitors of the EGFR cascade might be an effective therapy of airway remodelling.

Time-dependent airway epithelial and inflammatory cell responses induced by influenza virus A/PR/8/34 in C57BL/6 mice

The present study examines the kinetics of airway epithelial remodeling and inflammation in the airways of C57BL/6J mice infected with influenza virus A/PR/8/34 (PR8). Mice were intranasally instilled with 50 plaque forming units (pfu) of virus or its respective vehicle, saline, and then were sacrificed at 3, 7, 10, 15, or 21 days postinfection (dpi). PR8 treatment resulted in airway epithelial cell regeneration as suggested by proliferating cell nuclear antigen (PCNA) positive staining at 7 and 10 dpi and mucous cell metaplasia (MCM) evident at 10, 15, and 21 dpi. PR8 treatment resulted in a classic pattern of inflammation observed in bronchoalveolar lavage fluid (BALF), in which neutrophils peaked at 3 and 7 dpi and monocytes, lymphocytes, and eosinophils peaked at 10 dpi before returning to background levels of detection. Chemokine (MCP-1) and cytokine (IL-6, TNF-alpha, IFN-gamma, IL-5, IL-4, and IL-9) levels peaked at 7 dpi in BALF. IL-13 levels were unaffected by PR8 treatment. Concurrent with inflammation, MUC5AC gene expression was markedly increased by PR8 treatment at 7 dpi. Collectively, the results of this study indicate that the onset of MCM in airway epithelium occurs during the remodeling process and persists after the inflammatory response has diminished.

Innate immune mucin production via epithelial cell surface signaling: relationship to allergic disease

PURPOSE OF REVIEW

Airway epithelial surface signaling is provided by epidermal growth factor receptor (EGFR) phosphorylation, resulting in innate immune responses. Here the focus is the EGFR cascades leading to immune mucin responses. The review is timely because recent discoveries implicate these pathways in multiple innate immune defenses in addition to mucin production.

RECENT FINDINGS

EGFR activation causes mucin production and inhibition prevents mucin production by multiple stimuli. The receptors and their epithelial-bound proligands are examined. Proteases cleave and release soluble ligand, which then activates EGFR. A surface metalloprotease, tumor necrosis factor alpha-converting enzyme (TACE), modulates proligand release (and thus EGFR activation). TACE is activated by reactive oxygen species, which can be produced by a novel molecule, dual oxidase-1, which provides reactive oxygen species for TACE cleavage. Upstream of dual oxidase-1 are epithelial receptors that receive messages from inhaled irritants and stimulate the dual oxidase-1-TACE-ligand-EGFR cascade.

SUMMARY

The EGFR surface signaling pathways are reviewed, with the focus on mucin production, involving human airway epithelial cultures and animal studies, including relevant studies of asthma in humans. Future studies may broaden the innate defenses and utilize these surface signaling pathways in various epithelia, with a variety of pathophysiologic stimuli, with the ultimate aim of examining these pathways in inflammatory diseases.

Chronic obstructive pulmonary disease (COPD) and occupational exposures

Chronic obstructive pulmonary disease (COPD) is one of the leading causes of morbidity and mortality in both industrialized and developing countries. Cigarette smoking is the major risk factor for COPD. However, relevant information from the literature published within the last years, either on general population samples or on workplaces, indicate that about 15% of all cases of COPD is work-related. Specific settings and agents are quoted which have been indicated or confirmed as linked to COPD. Coal miners, hard-rock miners, tunnel workers, concrete-manufacturing workers, nonmining industrial workers have been shown to be at highest risk for developing COPD. Further evidence that occupational agents are capable of inducing COPD comes from experimental studies, particularly in animal models. In conclusion, occupational exposure to dusts, chemicals, gases should be considered an established, or supported by good evidence, risk factor for developing COPD. The implications of this substantial occupational contribution to COPD must be considered in research planning, in public policy decision-making, and in clinical practice.

Persistent mucus accumulation: a consequence of delayed bronchial mucous cell apoptosis in RAO-affected horses?

This study examined the contribution of delayed apoptosis of bronchial mucous cells to mucus accumulation in equine recurrent airway obstruction (RAO). In pilot studies, Bcl-2, an apoptosis inhibitor, was detected in airway mucous cells of RAO-affected horses in remission and during acute disease, when most mucus was secreted. To study whether delayed apoptosis results in an increase in the number of mucous cells during disease recovery, six RAO-affected and six control horses were fed hay for 5 days to induce inflammation and then pellets for 7 days to partially resolve RAO before euthanasia. RAO-affected horses had more airway obstruction and luminal mucus than control horses under both management systems. At the time of euthanasia, RAO-affected horses had more inflammation and Bcl-2-positive bronchial mucous cells than control animals. In horses with >10 and <10 neutrophils per microliter of bronchoalveolar lavage fluid, >50% and <10% of mucous cells stained positive for Bcl-2, respectively. No differences in mucous cell number or amount of stored mucosubstance were observed between RAO-affected and control horses, but in RAO-affected animals, the amount of stored mucosubstance decreased as the number of neutrophils in bronchoalveolar lavage fluid increased. Because the number of mucous cells was similar in both groups of horses but only mucous cells of RAO-affected horses expressed Bcl-2 during recovery from acute disease, a conclusive role for Bcl-2 in prolonging bronchial mucous cell life could not be determined. Future studies are needed to compare horses that are kept in remission for prolonged periods when all mucous cells are fully developed.

Chronic cough due to occupational factors

Within the large variety of subtypes of chronic cough, either defined by their clinical or pathogenetic causes, occupational chronic cough may be regarded as one of the most preventable forms of the disease. Next to obstructive airway diseases such as asthma or chronic obstructive pulmonary disease, which are sometimes concomitant with chronic cough, this chronic airway disease gains importance in the field of occupational medicine since classic fiber-related occupational airway diseases will decrease in the future.

Apart from acute accidents and incidental exposures which may lead to an acute form of cough, there are numerous sources for the development of chronic cough within the workplace. Over the last years, a large number of studies has focused on occupational causes of respiratory diseases and it has emerged that chronic cough is one of the most prevalent work-related airway diseases. Best-known examples of occupations related to the development of cough are coal miners, hard-rock miners, tunnel workers, or concrete manufacturing workers.

As chronic cough is often based on a variety of non-occupational factors such as tobacco smoke, a distinct separation into either occupational or personally -evoked can be difficult. However, revealing the occupational contribution to chronic cough and to the symptom cough in general, which is the commonest cause for the consultation of a physician, can significantly lead to a reduction of the socioeconomic burden of the disease.

Occupational contribution to the burden of chronic obstructive pulmonary disease

OBJECTIVE

As a past recipient of the Jean Spencer Felton Award for Excellence in Scientific Writing from the Western Occupational and Environmental Medicine Association, it is truly an honor to contribute to this festschrift. What stands out in my mind about Dr Felton is that he loved to delve into the history of occupational medicine and tried to apply the lessons of that history to the modern practice of the discipline. He once wrote that "The name Ramazzini marks the beginning of society's concern with the well-being and physical and emotional health of its workers from the shops of the crafts to the offices of the executives." This review of a common disease for which an occupational contribution is too frequently ignored is offered in the spirit of both the father of modern occupational medicine and one of his 20th-century acolytes.

CONCLUSIONS

The biological plausibility of the capacity of occupational exposures to irritating dusts, gases, and fumes to cause chronic obstructive pulmonary disease (COPD) is high. Epidemiological evidence from both worker cohort and community studies supports an increased risk of COPD associated with such exposures. The occupational contribution to the burden of COPD is sufficiently great that preventive interventions are warranted.

Characterization of cigarette smoke-induced inflammatory and mucus hypersecretory changes in rat lung and the role of CXCR2 ligands in mediating this effect

Repetitive, acute inflammatory insults elicited by cigarette smoke (CS) contribute to the development of chronic obstructive pulmonary disease (COPD), a disorder associated with lung inflammation and mucus hypersecretion. Presently, there is a poor understanding of the acute inflammatory mechanisms involved in this process. The aims of this study were to develop an acute model to investigate temporal inflammatory changes occurring after CS exposure. Rats were exposed to whole body CS (once daily) generated from filtered research cigarettes. Initial studies indicated the generation of a neutrophilic/mucus hypersecreting lung phenotype in <4 days. Subsequent studies demonstrated that just two exposures to CS (15 h apart) elicited a robust inflammatory/mucus hypersecretory phenotype that was used to investigate mechanisms driving this response. Cytokine-induced neutrophil chemoattractants (CINCs) 1-3, the rat growth-related oncogene-alpha family homologs, and IL-1beta demonstrated time-dependent increases in lung tissue or lavage fluid over the 24-h period following CS exposure. The temporal changes in the neutrophil chemokines, CINCs 1-3, mirrored increases in neutrophil infiltration, indicative of a role in neutrophil migration. In addition, a specific CXCR2 antagonist, SB-332235, effectively inhibited CS-induced neutrophilia in a dose-dependent manner, supporting this conclusion. This modeling of the response of the rat airways to acute CS exposure indicates 1) as few as two exposures to CS will induce a phenotype with similarities to COPD and 2) a novel role for CINCs in the generation of this response. These observations represent a paradigm for the study of acute, repetitive lung insults that contribute to the development of chronic disease.

Ozone exposure enhances endotoxin-induced mucous cell metaplasia in rat pulmonary airways

Coexposure to different airborne pollutants can be more toxic to airway epithelium than an inhalation exposure to a single pollutant. We have previously reported that coexposure to ozone, the primary oxidant gas in photochemical smog, and unique inflammatory biogenic substances such as allergens or bacterial endotoxin, results in augmented epithelial and inflammatory responses in rat nasal airways (M. V. Fanucchi et al., 1998, Toxicol. Appl. Pharmacol. 152, 1-9; J. G. Wagner et al., 2002a, Toxicol. Sci.67, 284-294). In the present study, we investigated the toxic interaction of ozone and endotoxin on the respiratory epithelium in the pulmonary airways of laboratory rodents. F344 rats were intranasally instilled with 0, 2, or 20 microg endotoxin dissolved in sterile saline (150 microl/nasal passage). Six h after instillation rats were exposed to air or 1 ppm ozone for 8 h. One day later, endotoxin and ozone exposures were repeated. Three days after the last exposure, rats were sacrificed, the lungs were lavaged with saline, and the collected bronchoalveolar lavage fluid (BALF) was analyzed for inflammatory cells and secreted mucosubstances (mucin 5AC). Lung tissues were processed for light microscopic examination and morphometric analysis of numeric density of epithelial cell populations and volume densities of intraepithelial mucosubstances (IM). Conducting airways were microdissected and analyzed by quantitative RT-PCR to determine steady-state mucin gene (rMuc5AC) mRNA levels in respiratory epithelium. Endotoxin instillation caused a dose-dependent increase in BALF neutrophils that was further increased twofold in ozone-exposed rats given 20 microg endotoxin. Mucin glycoprotein 5AC was elevated in BALF from rats exposed to 20 microg, but not 2 microg endotoxin. Exposure to ozone alone did not cause mucus hypersecretion, but ozone potentiated mucus secretion in rats given 2 or 20 microg endotoxin. Airways of rats exposed to air or ozone alone had scant amounts of IM. Endotoxin instillation induced a dose-dependent increase in IM in airway epithelium that was significantly increased (twofold) in rats that were also exposed to ozone. Expression of rMuc5AC was induced in axial pulmonary airways by 2 and 20 microg endotoxin, and was increased further by ozone-exposure in rats instilled with 20 microg endotoxin. These data demonstrate that ozone exposure potentiates neutrophilic inflammation and mucus production and secretion elicited by a biogenic substance in rat pulmonary airways.

Effects of bacterial toxins on air-exposed cultured human respiratory sinus epithelium

The present study was designed to investigate the effects of the bacterial toxins lipopolysaccharide (LPS) and lipoteichoic acid (LTA) on air-exposed cultured human respiratory sinus epithelium. The morphological changes, proliferation, and differentiation of sphenoid sinus mucosa were examined after incubation with different LPS or LTA concentrations. Air-exposed cultured sinus mucosa differentiated from pseudostratified respiratory epithelium to squamous ciliated epithelium with few goblet cells. High concentrations of bacterial toxins induced a significant increase in mucus production and a decrease in ciliated cells. Ki67 immunostaining showed an increased cell proliferation after incubation with moderate levels of LPS or LTA. High concentrations of bacterial toxins, on the other hand, induced a decreased proliferation. Involucrin expression was clearly altered by incubation with high levels of bacterial toxins, indicating an increased degree of terminal differentiation. These results indicate that the bacterial toxins LPS and LTA both induce comparable dose-dependent morphological changes in sinus epithelium.

Occupational airways diseases from chronic low-level exposures to irritants

Short-term, high-level exposures to dusts, gases, mists, fumes, and smoke that are irritating to the respiratory tract are capable of inducing asthma, the so-called reactive airways dysfunction syndrome. Such exposures, however, do not occur frequently; chronic or recurrent exposures to lower levels of irritants are much more common. This article reviews the evidence that supports the concept that low-level exposures to respiratory tract irritants can contribute to the development of chronic obstructive pulmonary disease and asthma.

Secretoglobins SCGB3A1 and SCGB3A2 define secretory cell subsets in mouse and human airways

Clara cell secretory protein (CCSP) is expressed abundantly within the conducting airway epithelium and is thought to have immunoregulatory functions. Differences in the localization of CCSP between mouse and human airways led us to hypothesize that functional homologues of CCSP may compensate for the lack of CCSP expression in proximal airway locations. We previously identified an expressed sequence tag (W82219) whose expression is induced within Clara cells of CCSP knockout mice. Expressed sequence tag W82219 is distantly related to CCSP and represents a member of a new subfamily of secretoglobins (MmSCGB3A2). Another member of the mouse SCGB3 family (MmSCGB3A1) as well as human orthologues (HsSCGB3A1 and HsSCGB3A2) that possess structural homology to CCSP were identified, suggesting they may share common functional properties. SCGB3A1 messenger RNA localizes to a subset of SCGB3A2-expressing cells within bronchi of both mouse and neonatal human lungs. CCSP, SCGB3A1, and SCGB3A2 were decreased in airways of neonates with bronchopulmonary dysplasia and in mice after airway injury. We conclude that secretory cells of the conducting airway epithelium express distinct members of the secretoglobin family in a partially overlapping fashion. Altered expression of secretoglobins in airway disease may contribute to immunoregulatory perturbations commonly seen in chronic airway disease.

Mucin apoprotein expression in COPD

Mucins, which are complex glycoproteins that provide the viscoelastic properties of mucus that are essential for the protection of the airways, are characterized by a variable-number tandem repeats (VNTR) region that may undergo alternate splicing during transcription. Such transcripts may yield multiple proteins via diverse post-translational modifications involving glycosylation (within each VNTR). Fifteen distinct mucin genes have been identified, with several mapping to chromosomal clusters (ie, 7q22 and 11p15.5), possibly having evolved by gene duplication. The deduced protein sequences can be subdivided into both membrane-associated mucins and secreted mucins. Membrane-associated mucins consist of cytoplasmic, transmembrane, and extracellular domains. The membrane-associated mucins MUC1, MUC4, and MUC11 have been localized to the lung. In addition to VNTRs, secreted mucins possess repeated cysteine-rich D-domains (which are important in polymerization). Secreted mucins that are localized to the lung include MUC2 (in cells with and without secretory granules), MUC5AC (in surface and submucosal mucous cells), MUC5B and MUC8 (in submucosal mucous cells), and MUC7 (in submucosal serous cells). Currently, little is known about the regulation of mucins in COPD patients. Recent studies with acrolein and cigarette smoke have suggested that MUC5AC is inducible (accompanied by epidermal growth factor [EGF] ligand formation and the activation of EGF receptor-dependent pathways), whereas MUC5B is constitutively expressed (increasing through gland enlargement). Similarly, little is known about the genetic determinants that control mucus hypersecretion, but preliminary findings in animal models suggest that intrastrain differences in acrolein-induced mucin formation are amenable to genetic analysis. As our understanding of the functional genomics of mucin biology increases, further clinical targets and therapeutic strategies are likely to emerge.

Long-term intratracheal lipopolysaccharide exposure in mice results in chronic lung inflammation and persistent pathology

Lipopolysaccharide (LPS), a major proinflammatory glycolipid component of the gram-negative bacterial cell wall, is one of the agents ubiquitously present as contaminant on airborne particles, including air pollution, organic dusts, and cigarette smoke. Chronic exposure to significant levels of LPS is reported to be associated with the development and/or progression of many types of lung diseases, including asthma, chronic bronchitis, and progressive irreversible airflow obstruction, that are all characterized by chronic inflammatory processes in the lung. In the present study, pathologic effects of long-term LPS exposure to the lung were investigated in detail. To this end, a murine model in which mice were exposed to repeated intratracheal instillation of Escherichia coli LPS was developed. We show that long-term LPS instillation in mice results in persistent chronic pulmonary inflammation, characterized by peribronchial and perivascular lymphocytic aggregates (CD4(+), CD8(+), and CD19(+)), parenchymal accumulation of macrophages and CD8(+) T cells, and altered cytokine expression. Furthermore, airway and alveolar alterations such as mucus cell metaplasia, airway wall thickening, and irreversible alveolar enlargement accompanied the chronic inflammatory response. Interestingly, the observed inflammatory and pathologic changes mimic changes observed in human subjects with chronic inflammatory lung diseases, especially chronic obstructive pulmonary disease (COPD), suggesting that this murine model could be applicable to dissect the role of inflammation in the pathogenesis of these disease conditions.

Bcl-2 mediates sex-specific differences in recovery of mice from LPS-induced signs of sickness independent of IL-6

Chronic pulmonary diseases are more common in boys than in girls. Therefore, we investigated the differences in signs of sickness in male and female mice that were exposed to lipopolysaccharide (LPS) by intranasal instillation. Because apoptosis is important in the resolution of inflammation, we tested the hypothesis that reduced levels of Bcl-2, a regulator of apoptosis, may play a role in gender-specific differences in response to inflammation. Bcl-2 wild-type (+/+) female mice recovered from an LPS-induced drop in body temperature and loss in body weight significantly faster than male (+/+) mice. Female heterozygous (+/-) mice showed reduced Bcl-2 levels and exhibited a slower recovery than female (+/+) mice that was similar to the recovery pattern in male (+/+) and (+/-) mice. Interleukin-6 (IL-6) activity levels in the bronchoalveolar lavage fluid were higher in male than in female mice but were not different between (+/+) and (+/-) mice. We conclude that Bcl-2 plays a role in mediating the faster recovery of female (+/+) mice from LPS-induced signs of sickness independent of IL-6. These studies indicate that apoptotic mechanisms may be involved in gender-specific differences in chronic pulmonary diseases.

PAF mediates cigarette smoke-induced goblet cell metaplasia in guinea pig airways

Goblet cell metaplasia is an important morphological feature in the airways of patients with chronic airway diseases; however, the precise mechanisms that cause this feature are unknown. We investigated the role of endogenous platelet-activating factor (PAF) in airway goblet cell metaplasia induced by cigarette smoke in vivo. Guinea pigs were exposed repeatedly to cigarette smoke for 14 consecutive days. The number of goblet cells in each trachea was determined with Alcian blue-periodic acid-Schiff staining. Differential cell counts and PAF levels in bronchoalveolar lavage fluid were also evaluated. Cigarette smoke exposure significantly increased the number of goblet cells. Eosinophils, neutrophils, and PAF levels in bronchoalveolar lavage fluid were also significantly increased after cigarette smoke. Treatment with a specific PAF receptor antagonist, E-6123, significantly attenuated the increases in the number of airway goblet cells, eosinophils, and neutrophils observed after cigarette smoke exposure. These results suggest that endogenous PAF may play a key role in goblet cell metaplasia induced by cigarette smoke and that potential roles exist for inhibitors of PAF receptor in the treatment of hypersecretory airway diseases.

Bcl-2 in LPS- and allergen-induced hyperplastic mucous cells in airway epithelia of Brown Norway rats

Environmental toxins, infection, and allergens lead to a transient mucous cell hyperplasia (MCH) in airway epithelia; however, the mechanisms for reducing mucous cell numbers during recovery are largely unknown. This study investigated Bcl-2 expression in mucous cells induced by a neutrophilic or eosinophilic inflammatory response. Brown Norway rats intratracheally instilled with lipopolysaccharide (LPS) showed an inflammatory response characterized primarily by neutrophils. Secreted mucin was increased fourfold at 1 day, and the number of mucous cells was increased fivefold 2, 3, and 4 days post-LPS instillation compared with those in noninstilled rats. None of the mucous cells in non- or saline-instilled control animals expressed Bcl-2, whereas 20-30% of mucous cells were Bcl-2 positive 1 and 2 days post-LPS instillation. Brown Norway rats immunized and challenged with ovalbumin (OVA) for 2, 4, and 6 days showed an inflammatory response characterized primarily by eosinophils. Secreted mucin increased fivefold, and mucous cell number increased fivefold after 4 and 6 days of OVA exposure compared with water-immunized control rats challenged with OVA aerosols. Approximately 10-25% of mucous cells were Bcl-2 positive in OVA-immunized and -challenged rats. These data demonstrate Bcl-2 expression in hyperplastic mucous cells of Brown Norway rats regardless of the type of inflammatory response and indicate that apoptotic mechanisms may be involved in the resolution of MCHs.

Cross-species immunoreactivity of airway mucin as revealed by monoclonal antibodies directed against mucins from human, hamster, and rat

Airway mucin plays crucial role in host-defense and has been implicated in pathophysiology of various airway diseases including asthma and cystic fibrosis. The analysis of airway mucin has been hampered mostly by the lack of specific and efficient methods for the detection of mucin. Recent production of antibodies against airway mucin from several species and also the development of immunoassay procedures make it more efficient to study the airway mucin. However, the cross-species immunoreactivity of antibodies against airway mucin has not been clearly demonstrated and this prompted us to investigate the cross-species immunoreactivity of monoclonal antibodies against human (HM02), hamster (HTA), and rat airway mucin (RT03), which is three most widely used species in the study of mucin. All the monoclonal antibodies (MAbs) used in this study is IgM isotype and recognizes N-acetyl-galactosamine-linked carbohydrate core or backbone portion of airway mucin. In enzyme-linked immunoadsorbent assay (ELISA), Western blot, immunoprecipitation, and immunohistochemical staining experiments, it was demonstrated that human and hamster airway mucin showed strong cross-species immunoreactivity. However, rat airway mucin did not show any cross-species immunoreactivity against human and hamster airway mucin. Endotoxin-induced secretory cell metaplasia and hence the increase in mucin release from hamster airway mucin could be detected with antibodies against hamster and human airway mucin in vivo and in vitro. However, the same increase from rat airway could only be detected with antibody against rat airway mucin but not with antibodies against human and hamster airway mucin. In addition, the increase in mucin release from asthmatic patients could be detected with antibodies against human and hamster airway mucin but not with the antibody against rat airway mucin. The data from the present study implicates that the carbohydrate chain of human and hamster airway mucin, but not that of rat airway mucin, share common antigenic structure. In case of the interspecies use of the antibodies against airway mucin, it would be more desirable to clearly identify the cross-species immunoreactivity otherwise might lead to erroneous results.

Neutrophil-dependent and neutrophil-independent alterations in the nasal epithelium of ozone-exposed rats

Ozone induces epithelial hyperplasia and mucous cell metaplasia (MCM) in nasal transitional epithelium (NTE) of rats. A transient neutrophil influx accompanies upregulation of mucin messenger RNA (mRNA) before the onset of MCM. The present study was designed to examine the role of neutrophils in ozone-induced epithelial changes in the NTE of rats. Fourteen hours before inhalation exposure, male F344/N rats were injected intraperitoneally with antirat neutrophil antiserum to deplete circulating neutrophils, or were injected with normal (control) serum. Rats were then exposed to 0 ppm (filtered air) or 0.5 ppm ozone (8 h/d) for 1 or 3 d. Maxilloturbinates lined with NTE were analyzed to determine the epithelial labeling index; numeric densities of neutrophils, total epithelial cells, and mucous secretory cells; amount of stored intraepithelial mucosubstances; and steady-state ratMUC-5AC (mucin) mRNA levels. At 2 h after 3 d of exposure, rats treated with antiserum had 90% fewer circulating neutrophils than did rats treated with control serum. Antiserum-treated, ozone-exposed rats had 87% fewer infiltrating neutrophils than did control serum-treated, ozone-exposed rats. At 4 d after 3 d of exposure, antiserum-treated, ozone-exposed rats had 66% less stored intraepithelial mucosubstances and 58% fewer mucous cells in their NTE than did control serum-treated, ozone-exposed rats. Antiserum treatment had no effects on ozone-induced epithelial cell proliferation or mucin mRNA upregulation. The results of this study indicated that ozone-induced MCM was neutrophil-dependent, whereas ozone-induced epithelial cell proliferation and mucin gene upregulation were neutrophil-independent.

Monocyte inflammation augments acrolein-induced Muc5ac expression in mouse lung

Acrolein, an unsaturated aldehyde found in smog and tobacco smoke, can induce airway hyperreactivity, inflammation, and mucus hypersecretion. To determine whether changes in steady-state mucin gene expression (Muc2 and Muc5ac) are associated with inflammatory cell accumulation and neutrophil elastase activity, FVB/N mice were exposed to acrolein (3.0 parts/million; 6 h/day, 5 days/wk for 3 wk). The levels of Muc2 and Muc5ac mRNA were determined by RT-PCR, and the presence of Muc5ac protein was detected by immunohistochemistry. Total and differential cell counts were determined from bronchoalveolar lavage (BAL) fluid, and neutrophil elastase activity was measured in the BAL fluid supernatant. Lung Muc5ac mRNA was increased on days 12 and 19, and Muc5ac protein was detected in mucous granules and on the surface of the epithelium on day 19. Lung Muc2 mRNA was not detected at measurable levels in either control or exposed mice. Acrolein exposure caused a significant and persistent increase in macrophages and a rapid but transient increase in neutrophils in BAL fluid. Recoverable neutrophil elastase activity was not significantly altered at any time after acrolein exposure. To further examine the role of macrophage accumulation in mucin gene expression, additional strains of mice (including a strain genetically deficient in macrophage metalloelastase) were exposed to acrolein for 3 wk, and Muc5ac mRNA levels and macrophage accumulation were measured. The magnitude of macrophage accumulation coincided with increased Muc5ac mRNA levels, indicating that excessive macrophage accumulation augments acrolein-induced Muc5ac synthesis and secretion after repeated exposure. These findings support a role for chronic monocytic inflammation in the pathogenesis of mucus hypersecretion observed in chronic bronchitis.

Epidermal growth factor system regulates mucin production in airways

Goblet-cell hyperplasia is a critical pathological feature in hypersecretory diseases of airways. However, the underlying mechanisms are unknown, and no effective therapy exists. Here we show that stimulation of epidermal growth factor receptors (EGF-R) by its ligands, EGF and transforming growth factor alpha (TGFalpha), causes MUC5AC expression in airway epithelial cells both in in vitro and in vivo. We found that a MUC5AC-inducing epithelial cell line, NCI-H292, expresses EGF-R constitutively; EGF-R gene expression was stimulated further by tumor necrosis factor alpha (TNFalpha). EGF-R ligands increased the expression of MUC5AC at both gene and protein levels, and this effect was potentiated by TNFalpha. Selective EGF-R tyrosine kinase inhibitors blocked MUC5AC expression induced by EGF-R ligands. Pathogen-free rats expressed little EGF-R protein in airway epithelial cells; intratracheal instillation of TNFalpha induced EGF-R in airway epithelial cells, and subsequent instillation of EGF-R ligands increased the number of goblet cells, Alcian blue-periodic acid-Schiff staining (reflecting mucous glycoconjugates), and MUC5AC gene expression, whereas TNFalpha, EGF, or TGFalpha alone was without effect. In sensitized rats, three intratracheal instillations of ovalbumin resulted in EGF-R expression and goblet-cell production in airway epithelium. Pretreatment with EGF-R tyrosine kinase inhibitor, BIBX1522, prevented goblet-cell production both in rats stimulated by TNFalpha-EGF-R ligands and in an asthma model. These findings suggest potential roles for inhibitors of the EGF-R cascade in hypersecretory diseases of airways.

Clarithromycin suppresses proliferation of rat nasal epithelium exposed to endotoxin

A study was performed to elucidate the action of long-term macrolide therapy in chronic sinusitis. Clarithromycin (CAM) was administered orally once daily for 14 days. On the last 3 days, an endotoxin, lipopolysaccharide (LPS) was instilled intranasally. The extent of DNA synthesis acceleration was studied in both controls and pretreated animals by counting the number of 5-bromo-2'-deoxyuridine (BrdU)-labeled cells in the nasal transitional epithelium. Six hours after the final intranasal instillation of LPS, the number of BrdU-positive cells was significantly higher than control. Pretreatment with CAM for 2 weeks significantly inhibited this increase. Because similar results were obtained in neutrophil-depleted rats, LPS apparently promotes proliferation of the nasal epithelium in the absence of neutrophils: CAM-suppressed epithelial proliferation independently of the neutrophil count. Our results suggest that CAM inhibits LPS-induced increased rates of DNA synthesis by directly affecting the nasal epithelium. The mechanism by which macrolide therapy alleviates the signs and symptoms of chronic sinusitis might therefore involve suppression of inflammatory processes in the nasal and paranasal sinus epithelium.

Endotoxin potentiates ozone-induced mucous cell metaplasia in rat nasal epithelium

People are exposed to a combination of environmental pollutants throughout their lives. Repeated exposures of one common pollutant, ozone, have been reported to cause the development of mucous cell metaplasia in the nasal transitional epithelium (NTE) of rats. The present study was designed to test the hypothesis that exposure to bacterial endotoxin, another toxicant ubiquitous to the environment, potentiates this metaplastic response in rat NTE. Rats were exposed to 0 or 0.5 ppm ozone 8 h/day for 3 days. After ozone exposure, rats were intranasally instilled with saline containing 0 or 100 micrograms endotoxin once daily for 2 days. Rats were killed 6 h or 3 days after the last intranasal instillation. Nasal tissue was processed for light microscopy and image analysis, or for isolation of total RNA. Mucous cell metaplasia was not detected in air/endotoxin-exposed rats, was observed in ozone/saline-exposed rats, and was most severe in ozone/endotoxin-exposed rats. At 6 h after instillation, amounts of intraepithelial mucosubstances (IM) were 4-fold greater in NTE of ozone/endotoxin-exposed rats as compared to controls. These IM levels were similar to those of ozone/saline-exposed rats. Mucin-specific mRNA (rMuc-5AC) levels were elevated in all treatment groups at this timepoint. At 3 days after instillation, amounts of IM in ozone/endotoxin-exposed rats were 10-fold greater than in controls and 5-fold greater than in ozone/saline-exposed rats. rMuc-5AC mRNA levels remained elevated in the ozone/endotoxin-exposed rats. Despite the fact that bacterial endotoxin alone does not cause a phenotypic change in rat NTE, it can augment the mucous cell metaplasia induced by a previous exposure to ozone.

Expression of the Bcl-2 protein in nasal epithelia of F344/N rats during mucous cell metaplasia and remodeling

Exposure to ozone induces mucous cell metaplasia in rat airway epithelia. During the regeneration process, apoptotic mechanisms may be responsible for eliminating metaplastic cells. Therefore, the present study investigated expression of Bcl-2, a regulator of apoptosis, in ozone-induced mucous cell metaplasias. Adjacent metaplastic mucous cells in nasal airway epithelia that were exposed to ozone were heterogeneous in their expression of Bcl-2; some cells expressed high levels, whereas others expressed low levels or no Bcl-2. On Western blot analysis, Bcl-2 was detected in protein extracts from nasal epithelia of rats exposed to 0.5 ppm ozone for 1 mo but not in control rats exposed to filtered air. The number of metaplastic mucous cells in transitional epithelia of rat nasal airways was increased from 0 to about 200 after 3 and 6 mo of exposure to ozone; only 0 to 10 metaplastic mucous cells remained after a recovery period of 13 wk in rats exposed to ozone for 3 mo. The number of mucous cells of the respiratory epithelium lining the midseptum did not change after ozone exposure or recovery. The percentage of Bcl-2-positive cells lining the midseptum increased from 7 to 14% after a 3- and 6-mo ozone exposure, respectively. In transitional epithelia of the lateral wall and the nasoturbinates and maxilloturbinates, 35 to 55% of cells were Bcl-2-positive after a 1-mo exposure and 10 to 18% after both a 3- and a 6-mo exposure to ozone. Bcl-2 reactivity decreased to 0 to 8% after a recovery period of 13 wk. These observations suggest that Bcl-2 plays a role in the development and resolution of mucous cell metaplasias. This model may be useful in uncovering the role of Bcl-2 during the development and maintenance of metaplastic mucous cells. Disregulation of Bcl-2 expression may be responsible for the sustained mucous cell metaplasia in asthmatics or may allow cells to accumulate and become more susceptible to transformation leading to neoplasia.