Inhibition of cigarette smoke-induced airway secretory cell hyperplasia by indomethacin, dexamethasone, prednisolone, or hydrocortisone in the rat

The Effect of Residential Environment on Respiratory Diseases and Pulmonary Function in Children from a Community in Jilin Province of China

Purpose

Respiratory disease is a major and increasingly global epidemic that has a great impact on humans, especially children. The purpose of this study was to identify environmental risk factors for respiratory diseases and pulmonary function in children.

Patients and Methods

A population-based, cross-sectional survey of respiratory diseases and environmental risk factors was conducted in Jilin Province, China. Complete questionnaire information was available for 2419 children, while adequate pulmonary function data were available for a subgroup of 627 children.

Results

Our study found that environmental risk factors for respiratory health in children were mainly concentrated indoors. After adjusting for demographic factors, insecticide exposure and passive smoking were risk factors for respiratory disease and industrial pollutant sources, insecticide exposure and the use of a fume exhauster may be independent risk factors for recurrent respiratory infections. The main fuel for cooking in the winter and passive smoking were the main influencing factors of pulmonary function indicators.

Conclusion

The primary risk factors differ in different respiratory diseases. Passive smoking remains a critical adverse factor for respiratory illness and pulmonary function in children, and it is important to reduce children’s exposure to passive smoking to increase pulmonary health. Insecticide exposure may be a neglected environmental risk factor, and further investigations are still needed to explore the relationship and mechanisms between insecticide exposure and children’s respiratory health.

Comprehensive overview of the structure and regulation of the glucocorticoid receptor

Glucocorticoids are among the most prescribed drugs worldwide for the treatment of numerous immune and inflammatory disorders. They exert their actions by binding to the glucocorticoid receptor (GR), a member of the nuclear receptor superfamily. There are several GR isoforms resulting from alternative RNA splicing and translation initiation of the GR transcript. Additionally, these isoforms are all subject to several transcriptional, post-transcriptional, and post-translational modifications, all of which affect the protein's stability and/or function. In this review, we summarize recent knowledge on the distinct GR isoforms and the processes that generate them. We also review the importance of all known transcriptional, post-transcriptional, and post-translational modifications, including the regulation of GR by microRNAs. Moreover, we discuss the crucial role of the putative GR-bound DNA sequence as an allosteric ligand influencing GR structure and activity. Finally, we describe how the differential composition and distinct regulation at multiple levels of different GR species could account for the wide and diverse effects of glucocorticoids.

Effects of passive smoking on adult nasal respiratory mucosa

OBJECTIVE

The present study aimed to investigate nasal mucosal changes in response to passive exposure to cigarette smoke.

STUDY DESIGN

The study included 20 women aged 35-51 years who were scheduled for non-rhinological surgical procedures, and who had at least 10 years' prolonged passive exposure to household cigarette smoke. During surgery, two 1-mm3 biopsies of nasal mucosa were taken from the lower border of the inferior turbinate. Specimens were processed and examined with light and transmission electron microscopy.

RESULTS

Examination of the nasal mucosa showed several histopathological changes. The severity of structural changes increased with duration of smoke exposure. No allergic or neoplastic changes were seen.

CONCLUSION

Passive exposure to cigarette smoke has a deleterious effect on the nasal respiratory mucosa. Prolonged passive smoke exposure may also induce other, significant changes not detected in the present study.

Effect of passive smoking on the ultrastructure of the nasal mucosa in children

OBJECTIVES/HYPOTHESIS

Passive exposure to cigarette smoke has been implicated in a number of respiratory childhood disorders. Most studies concerning smoking were directed to its carcinogenic effect on the lungs. However, the effects of smoking on nasal respiratory mucosa have not been widely studied. The aim of the present study was, therefore, to study the ultrastructural changes in the nasal mucosa of a pediatric population exposed to passive smoking.

STUDY DESIGN

The study included 20 children between the ages of 5 and 11 years, who were scheduled for tonsillectomy and at the same time had a positive history of prolonged exposure to household passive smoke. Another 10 children with a negative household smoking history were included as a control group. All children were nonatopic and with a negative family history of allergy. None of them had adenoids or infective rhinosinusitis.

METHODS

At the time of surgery, a 1-mm(3) biopsy was taken was taken from the lower border of the inferior turbinate. The specimens were processed and examined with electron microscopy

RESULTS

Examination of the nasal mucosa showed several ultrastructural changes. These included patchy loss of cilia, generalized loss of cilia, squamous metaplasia, hyperplasia of goblet cells and seromucinous acini, and vascular congestion. More severe changes were observed with longer passive exposures to cigarette smoke. The study did not disclose any evidence of ongoing allergic reaction or neoplastic transformations.

CONCLUSIONS

Children exposed to passive cigarette smoke may develop several structural changes in the respiratory nasal mucosa with subsequent negative effects on its ciliary activity and mucociliary function. As a result of these effects, defense mechanisms of the nose may be ruined or lost, and those children may develop persistent sinonasal infections. Exposure of these children to passive smoking for longer periods of time may also induce other significant changes that were not detected in the present study.

Persistent rhinitis and epithelial remodeling induced by cyclic ozone exposure in the nasal airways of infant monkeys

Children chronically exposed to high levels of ozone (O(3)), the principal oxidant pollutant in photochemical smog, are more vulnerable to respiratory illness and infections. The specific factors underlying this differential susceptibility are unknown but may be related to air pollutant-induced nasal alterations during postnatal development that impair the normal physiological functions (e.g., filtration and mucociliary clearance) serving to protect the more distal airways from inhaled xenobiotics. In adult animal models, chronic ozone exposure is associated with adaptations leading to a decrease in airway injury. The purpose of our study was to determine whether cyclic ozone exposure induces persistent morphological and biochemical effects on the developing nasal airways of infant monkeys early in life. Infant (180-day-old) rhesus macaques were exposed to 5 consecutive days of O(3) [0.5 parts per million (ppm), 8 h/day; "1-cycle"] or filtered air (FA) or 11 biweekly cycles of O(3) (FA days 1-9; 0.5 ppm, 8 h/day on days 10-14; "11-cycle"). The left nasal passage was processed for light microscopy and morphometric analysis. Mucosal samples from the right nasal passage were processed for GSH, GSSG, ascorbate (AH(2)), and uric acid (UA) concentration. Eleven-cycle O(3) induced persistent rhinitis, squamous metaplasia, and epithelial hyperplasia in the anterior nasal airways of infant monkeys, resulting in a 39% increase in the numeric density of epithelial cells. Eleven-cycle O(3) also induced a 65% increase in GSH concentrations at this site. The persistence of epithelial hyperplasia was positively correlated with changes in GSH. These results indicate that early life ozone exposure causes persistent nasal epithelial alterations in infant monkeys and provide a potential mechanism for the increased susceptibility to respiratory illness exhibited by children in polluted environments.

Effects of LTB4 receptor antagonism on pulmonary inflammation in rodents and non-human primates

Asthma, chronic obstructive pulmonary disease (COPD) and acute lung injury/acute respiratory distress syndrome (ALI/ARDS) are characterized by neutrophilic inflammation and elevated levels of leukotriene B4 (LTB4). However, the exact role of LTB4 pathways in mediating pulmonary neutrophilia and the potential therapeutic application of LTB4 receptor antagonists in these diseases remains controversial. Here we show that a novel dual BLT1 and BLT2 receptor antagonist, RO5101576, potently inhibited LTB4-evoked calcium mobilization in HL-60 cells and chemotaxis of human neutrophils. RO5101576 significantly attenuated LTB4-evoked pulmonary eosinophilia in guinea pigs. In non-human primates, RO5101576 inhibited allergen and ozone-evoked pulmonary neutrophilia, with comparable efficacy to budesonide (allergic responses). RO5101576 had no effects on LPS-evoked neutrophilia in guinea pigs and cigarette smoke-evoked neutrophilia in mice and rats. In toxicology studies RO5101576 was well-tolerated. Theses studies show differential effects of LTB4 receptor antagonism on neutrophil responses in vivo and suggest RO5101576 may represent a potential new treatment for pulmonary neutrophilia in asthma.

Airway and lung pathology due to mucosal surface dehydration in {beta}-epithelial Na+ channel-overexpressing mice: role of TNF-{alpha} and IL-4R{alpha} signaling, influence of neonatal development, and limited efficacy of glucocorticoid treatment

Overexpression of the epithelial Na(+) channel beta subunit (Scnn1b gene, betaENaC protein) in transgenic (Tg) mouse airways dehydrates mucosal surfaces, producing mucus obstruction, inflammation, and neonatal mortality. Airway inflammation includes macrophage activation, neutrophil and eosinophil recruitment, and elevated KC, TNF-alpha, and chitinase levels. These changes recapitulate aspects of complex human obstructive airway diseases, but their molecular mechanisms are poorly understood. We used genetic and pharmacologic approaches to identify pathways relevant to the development of Scnn1b-Tg mouse lung pathology. Genetic deletion of TNF-alpha or its receptor, TNFR1, had no measurable effect on the phenotype. Deletion of IL-4Ralpha abolished transient mucous secretory cell (MuSC) abundance and eosinophilia normally observed in neonatal wild-type mice. Similarly, IL-4Ralpha deficiency decreased MuSC and eosinophils in neonatal Scnn1b-Tg mice, which correlated with improved neonatal survival. However, chronic lung pathology in adult Scnn1b-Tg mice was not affected by IL-4Ralpha status. Prednisolone treatment ablated eosinophilia and MuSC in adult Scnn1b-Tg mice, but did not decrease mucus plugging or neutrophilia. These studies demonstrate that: 1) normal neonatal mouse airway development entails an IL-4Ralpha-dependent, transient abundance of MuSC and eosinophils; 2) absence of IL-4Ralpha improved neonatal survival of Scnn1b-Tg mice, likely reflecting decreased formation of asphyxiating mucus plugs; and 3) in Scnn1b-Tg mice, neutrophilia, mucus obstruction, and airspace enlargement are IL-4Ralpha- and TNF-alpha-independent, and only MuSC and eosinophilia are sensitive to glucocorticoids. Thus, manipulation of multiple pathways will likely be required to treat the complex pathogenesis caused by airway surface dehydration.

Corticosteroid therapy increases membrane-tethered while decreases secreted mucin expression in nasal polyps

BACKGROUND

Mucus hypersecretion is a hallmark of nasal polyposis (NP). Corticosteroids (CS) are first-line treatment for NP, decreasing their size and inflammatory component. However, their effect on mucin production is not well-understood. The aim of this (pilot) study was to investigate CS effect on mucin expression in NP.

METHODS

Patients were randomized in control (n = 9) and treatment (oral prednisone for 2 weeks and intranasal budesonide for 12 weeks; n = 23) groups. Nasal polyposis from nonasthmatic (NP; n = 13), aspirin-tolerant (NP-ATA; n = 11) and aspirin-intolerant (NP-AIA; n = 8) asthmatics were studied. Nasal polyposis biopsies were obtained before (w0) and after 2 (w2) and 12 (w12) weeks of CS treatment. Secreted (MUC5AC, MUC5B and MUC8) and membrane-tethered (MUC1, MUC4) mucins (immunohistochemistry) and goblet cells (Alcian blue-periodic acid Schiff) were quantified in both epithelium and glands. Rhinorrea and nasal obstruction were also assessed.

RESULTS

At w2, steroids increased MUC1 (from 70 to 97.5) and MUC4 (from 80 to 100) in NP-ATA patients' epithelium compared with baseline (w0). At w12, steroids decreased MUC5AC (from 40 to 5) and MUC5B (from 45 to 2.5) in NP-ATA patients' epithelium and glands, respectively, compared with baseline. No mucin presented significant changes in NP-AIA patients. MUC5AC and MUC5B expression correlated with goblet and mucous cell numbers, respectively, and MUC5AC also with rhinorrea score.

CONCLUSIONS

These results suggest: (i) CS up-regulate membrane (MUC1, MUC4) while down-regulate secreted (MUC5AC, MUC5B) mucins; (ii) there exists a link between secreted mucin expression and goblet cell hyperplasia; and (iii) NP from AIA may develop resistance to CS treatment.

Mechanisms of cigarette smoke-induced COPD: insights from animal models

Cigarette smoke-induced animal models of chronic obstructive pulmonary disease support the protease-antiprotease hypothesis of emphysema, although which cells and proteases are the crucial actors remains controversial. Inhibition of either serine or metalloproteases produces significant protection against emphysema, but inhibition is invariably accompanied by decreases in the inflammatory response to cigarette smoke, suggesting that these inhibitors do more than just prevent matrix degradation. Direct anti-inflammatory interventions are also effective against the development of emphysema, as are antioxidant strategies; the latter again decrease smoke-induced inflammation. There is increasing evidence for autoimmunity, perhaps directed against matrix components, as a driving force in emphysema. There is intriguing but controversial animal model evidence that failure to repair/failure of lung maintenance also plays a role in the pathogenesis of emphysema. Cigarette smoke produces small airway remodeling in laboratory animals, possibly by direct induction of fibrogenic growth factors in the airway wall, and also produces pulmonary hypertension, at least in part through direct upregulation of vasoactive mediators in the intrapulmonary arteries. Smoke exposure causes goblet cell metaplasia and excess mucus production in the small airways and proximal trachea, but these changes are not good models of either chronic bronchitis or acute exacerbations. Emphysema, small airway remodeling, pulmonary hypertension, and mucus production appear to be at least partially independent processes that may require different therapeutic approaches.

Mucin overproduction in chronic inflammatory lung disease

Mucus overproduction and hypersecretion are commonly observed in chronic inflammatory lung disease. Mucins are gel-forming glycoproteins that can be stimulated by a variety of mediators. The present review addresses the mechanisms involved in the upregulation of secreted mucins. Mucin induction by neutrophil elastase, bacteria, cytokines, growth factors, smoke and cystic fibrosis transmembrane conductance regulator malfunction are also discussed.

Respiratory tract mucin genes and mucin glycoproteins in health and disease

This review focuses on the role and regulation of mucin glycoproteins (mucins) in airway health and disease. Mucins are highly glycosylated macromolecules (> or =50% carbohydrate, wt/wt). MUC protein backbones are characterized by numerous tandem repeats that contain proline and are high in serine and/or threonine residues, the sites of O-glycosylation. Secretory and membrane-tethered mucins contribute to mucociliary defense, an innate immune defense system that protects the airways against pathogens and environmental toxins. Inflammatory/immune response mediators and the overproduction of mucus characterize chronic airway diseases: asthma, chronic obstructive pulmonary diseases (COPD), or cystic fibrosis (CF). Specific inflammatory/immune response mediators can activate mucin gene regulation and airway remodeling, including goblet cell hyperplasia (GCH). These processes sustain airway mucin overproduction and contribute to airway obstruction by mucus and therefore to the high morbidity and mortality associated with these diseases. Importantly, mucin overproduction and GCH, although linked, are not synonymous and may follow from different signaling and gene regulatory pathways. In section i, structure, expression, and localization of the 18 human MUC genes and MUC gene products having tandem repeat domains and the specificity and application of MUC-specific antibodies that identify mucin gene products in airway tissues, cells, and secretions are overviewed. Mucin overproduction in chronic airway diseases and secretory cell metaplasia in animal model systems are reviewed in section ii and addressed in disease-specific subsections on asthma, COPD, and CF. Information on regulation of mucin genes by inflammatory/immune response mediators is summarized in section iii. In section iv, deficiencies in understanding the functional roles of mucins at the molecular level are identified as areas for further investigations that will impact on airway health and disease. The underlying premise is that understanding the pathways and processes that lead to mucus overproduction in specific airway diseases will allow circumvention or amelioration of these processes.

Inhibition of endotoxin- and antigen-induced airway inflammation by fudosteine, a mucoactive agent

We evaluated the effect of a mucoactive agent (-)-(R)-2-amino-3-(3-hydroxypropylthio) propionic acid (fudosteine), on airway inflammation using endotoxin- and antigen-induced models. Time courses of growth related oncogene/cytokine-induced neutrophil chemoattractant-1 (GRO/CINC-1) production, neutrophil migration and goblet cell hyperplasia were examined in endotoxin-induced rat airway inflammation. GRO/CINC-1 in bronchoalveolar lavage fluid (BALF) increased in response to intratracheal instillation of endotoxin and peaked within 4 h. Neutrophils in BALF and goblet cells on trachea peaked 24 and 96 h after endotoxin instillation, respectively. Fudosteine significantly inhibited increases in GRO/CINC-1 at 10-100 mg/kg, and neutrophils and goblet cells at 30 and 100 mg/kg. These results suggest that inflammatory events including neutrophil chemoattractant production and neutrophil migration play important roles for goblet cell hyperplasia in endotoxin-induced airway inflammation, and fudosteine inhibits goblet cell hyperplasia by inhibiting GRO/CINC-1 production and/or neutrophil migration. Furthermore, fudosteine (100 mg/kg) inhibited ovalbumin-induced eosinophil infiltration into BALF, suggesting it attenuates asthmatic inflammation.

Eustachian tube goblet cell density during and after acute otitis media caused by Streptococcus pneumoniae: a morphometric analysis

BACKGROUND

Prior investigations have shown that the number of mucus-producing goblet cells in the middle ear mucosa is highly increased during and up to at least 6 months after experimental acute otitis media. This may, in conjunction with deteriorated eustachian tube function, predispose to subsequent development of secretory otitis media. One reason for the deteriorated tubal function after acute otitis media has been suggested to be an excessive accumulation of mucus secretions, blocking the tube and thereby clearance of the middle ear. This investigation determines the density of the mucus-producing goblet cells in the eustachian tube during and up to 6 months after experimental acute otitis media.

METHODS

Middle ear inoculation of Streptococcus pneumoniae in 25 rats. Groups of five animals, killed on Days 4, 8, 16, 90, and 180. Dissection and decalcification of the eustachian tube, followed by paraffin embedding and serial transverse sectioning, periodic acid-Schiff/Alcian blue staining and morphometric determination of the goblet cell density in every 20th section, using a light microscope.

RESULTS

The goblet cell density was increased on Day 8 and later in the tympanic orificium, in addition to the tympanic and midportion third of the tube. Increased goblet cell density was seen in the pharyngeal third on Days 8 and 16, whereas no changes were registered in the pharyngeal orificium. Pathologic intraepithelial glands formed after the infection and goblet cells were found in mucosal areas normally devoid of these.

CONCLUSIONS

The eustachian tube goblet cell density is increased during and up to 6 months after acute otitis media. Indicated excessive secretion of mucus by more goblet cells may contribute to the deteriorated eustachian tube function found after acute otitis media and thus predispose, sustain, or aggravate middle ear disease.

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.

Activation of epidermal growth factor receptors is responsible for mucin synthesis induced by cigarette smoke

Mucus hypersecretion from hyperplastic airway goblet cells is a hallmark of chronic obstructive pulmonary disease (COPD). Although cigarette smoking is thought to be involved in mucus hypersecretion in COPD, the mechanism by which cigarette smoke induces mucus overproduction is unknown. Here we show that activation of epidermal growth factor receptors (EGFR) is responsible for mucin production after inhalation of cigarette smoke in airways in vitro and in vivo. In the airway epithelial cell line NCI-H292, exposure to cigarette smoke upregulated the EGFR mRNA expression and induced activation of EGFR-specific tyrosine phosphorylation, resulting in upregulation of MUC5AC mRNA and protein production, effects that were inhibited completely by selective EGFR tyrosine kinase inhibitors (BIBX1522, AG-1478) and that were decreased by antioxidants. In vivo, cigarette smoke inhalation increased MUC5AC mRNA and goblet cell production in rat airways, effects that were prevented by pretreatment with BIBX1522. These effects may explain the goblet cell hyperplasia that occurs in COPD and may provide a novel strategy for therapy in airway hypersecretory diseases.

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.

Regulation of human airway mucins by acrolein and inflammatory mediators

Bronchitis, asthma, and cystic fibrosis, marked by inflammation and mucus hypersecretion, can be caused or exacerbated by airway pathogens or irritants including acrolein, an aldehyde present in tobacco smoke. To determine whether acrolein and inflammatory mediators alter mucin gene expression, steady-state mRNA levels of two airway mucins, MUC5AC and MUC5B, were measured (by RT-PCR) in human lung carcinoma cells (NCI-H292). MUC5AC mRNA levels increased after >/=0.01 nM acrolein, 10 microM prostaglandin E2 or 15-hydroxyeicosatetraenoic acid, 1.0 nM tumor necrosis factor-alpha (TNF-alpha), or 10 nM phorbol 12-myristate 13-acetate (a protein kinase C activator). In contrast, MUC5B mRNA levels, although easily detected, were unaffected by these agonists, suggesting that irritants and associated inflammatory mediators increase mucin biosynthesis by inducing MUC5AC message levels, whereas MUC5B is constitutively expressed. When transcription was inhibited, TNF-alpha exposure increased MUC5AC message half-life compared with control level, suggesting that transcript stabilization is a major mechanism controlling increased MUC5AC message levels. Together, these findings imply that irritants like acrolein can directly and indirectly (via inflammatory mediators) increase airway mucin transcripts in epithelial cells.

Induction, duration, and resolution of airway goblet cell hyperplasia in a murine model of atopic asthma: effect of concurrent infection with respiratory syncytial virus and response to dexamethasone

We recently described a murine model of atopic asthma in which a marked, extensive hyperplasia of airway goblet cells is induced by repeated challenge of ovalbumin (OA)-sensitized mice with intratracheally administered allergen (Am. J. Respir. Cell Mol. Biol. 1996;14:425-438). We report here the time course of the duration of this feature and of its spontaneous resolution in the absence of further allergen exposure. Induction of severe neutrophilic inflammation in the airways by repeated intratracheal administration of lipopolysaccharide failed to induce goblet cell hyperplasia (GCH) to as great a degree as that induced by allergen, suggesting that nonallergic inflammation is a relatively poor inducer of this phenotype change in mice. When a "subclinical" infection of the lungs with the human A2 strain of respiratory syncytial virus was superimposed on the model of atopic asthma, recruitment of monocytes and lymphocytes to the airways was enhanced and a discharge of goblet cell mucin contents was observed. This may partly explain the respiratory difficulty that typifies virally induced exacerbations of asthma in humans. Daily systemic treatment of sensitized mice with dexamethasone during the period of allergen challenge produced a dose-related suppression of developing GCH, while similar treatment during the period following the establishment of extensive hyperplasia induced an accelerated resolution toward a normal epithelial phenotype. These results confirm and extend the relevance of this model as a representation of the human disease.

Changes in mucosal goblet cell density in acute otitis media caused by non-typeable Haemophilus influenzae

The correlation between secretory otitis media and increased goblet cell density in the middle ear mucosa is well established. Previous studies have shown that a single episode of acute otitis media caused by Streptococcus pneumoniae is followed by increased goblet cell density for a period of at least 6 months, conceivably predisposing a subsequent development of secretory otitis media. In this study, 25 rat middle ears were inoculated with non-typeable Haemophilus influenzae in order to determine the effect on mucosal goblet cell density. Five rats were killed on days 4, 8, 16, 60 and 180 postinoculation, followed by dissection, staining and whole-mount embedding of the middle ear mucosae. The goblet cell density was determined in 24 well-defined localities. Compared with 25 normal middle ears, the goblet cell density was significantly increased in almost all localities, at all days on which the animals were killed. Thus, increased goblet cell density and enlargement of mucosal areas containing goblet cells persisted 6 months after the acute incident. The induced increase of goblet cell density was higher than the increase following inoculation of S. pneumoniae. We conclude that acute otitis media caused by non-typeable H. influenzae is followed by a longstanding increase in mucosal secretory capacity, likely to predispose a subsequent development of secretory otitis media.

Fluticasone propionate attenuates ozone-induced rhinitis and mucous cell metaplasia in rat nasal airway epithelium

Ozone (O3) is the principal oxidant pollutant in photochemical smog. Repeated exposures to O3 induces inflammation and mucous cell metaplasia in the nasal airways of laboratory animals. Our study was designed to determine the efficacy of a topical anti-inflammatory corticosteroid in preventing O3-induced rhinitis and mucous cell metaplasia in rat nasal epithelium. Male F344 rats were exposed to filtered air (0 ppm O3; air-controls) or 0.5 ppm O3, 8 h/day, for 3 or 5 days. Immediately before and after each exposure, rats received an intranasal instillation (50 microl/nasal passage) of a topical corticosteroid, fluticasone propionate (FP; 25 microg/nasal passage) or its vehicle only (0.01% ethanol in saline). Rats were killed 2 h after the third exposure (3-day exposure) or 3 days after the fifth exposure (5-day exposure) and nasal tissues were processed for light microscopy. Numeric densities of epithelial cells and neutrophils, and the amount of intraepithelial mucosubstances (IM) in the epithelium lining the maxilloturbinates were morphometrically determined. There were no significant differences in any measured parameter in air-exposed rats instilled with FP compared with air-exposed rats instilled with vehicle. Vehicle-treated rats exposed to ozone had neutrophilic rhinitis with 3.3- and 1.6-fold more intraepithelial neutrophils (3-day and 5-day exposure, respectively) and marked mucous cell metaplasia (5-day exposure only) with numerous mucous cells and approximately 60 times more IM in the nasal transitional epithelium compared with vehicle-treated air-controls. FP-treated rats exposed to ozone had minimal nasal inflammation (1.3-fold more intraepithelial neutrophils only after 3-day exposure) and minimal mucous cell metaplasia (5-fold more IM only after 5-day exposure) compared with vehicle-instilled, air-exposed rats. Results of this study indicate that FP-treatment is effective in attenuating not only O3-induced rhinitis (30-60% reduction) but also O3-induced mucous cell metaplasia (85% reduction) in rat nasal transitional epithelium. The cellular and molecular mechanisms involved in FP-induced attenuation of O3-induced nasal lesions remain to be determined.

Effects of indomethacin, dexamethasone, and erythromycin on endotoxin-induced intraepithelial mucus production of rat nasal epithelium

We produced hypertrophic and metaplastic changes of goblet cells in rat nasal respiratory epithelium by the intranasal instillation of endotoxin (ETN). In the present study, we examined in vivo effects of indomethacin (IND), dexamethasone (DEX), and erythromycin (EM) on intraepithelial mucus production using this animal model. Intraperitoneal injection of IND (2 to 4 mg/kg body weight x 4 days) or DEX (4 to 8 mg/kg body weight x 4 days) significantly inhibited intraepithelial mucus production induced after 3 days of ETN instillations. Intraperitoneal injection of EM (100 mg/kg body weight x 8 days), aminobenzylpenicillin (ABPC, 200 mg/kg body weight x 8 days), and cephalothin (CET, 200 mg/kg body weight x 8 days) also inhibited intraepithelial mucus production induced after 7 days of ETN instillations. When compared with ABPC and CET, EM had a greater inhibitory effect. These results indicate that ETN-induced intraepithelial mucus production can be inhibited by treatment with the anti-inflammatory drugs IND and DEX. Antibiotics such as EM, ABPC, and CET will also be effective, probably by preventing secondary bacterial infection, and EM has an additional inhibitory effect on intraepithelial mucus production.

The role of airway mucus in pulmonary toxicology

Airway mucus is a complex airway secretion whose primary function as part of the mucociliary transport mechanism is to to serve as renewable and transportable barrier against inhaled particulates and toxic agents. The rheologic properties necessary for this function are imparted by glycoproteins, or mucins. Some respiratory disease states, e.g., asthma, cystic fibrosis, and bronchitis, are characterized by quantitative and qualitative changes in mucus biosynthesis that contribute to pulmonary pathology. Similar alterations in various aspects of mucin biochemistry and biophysics, leading to mucus hypersecretion and altered mucus rheology, result from inhalation of certain air pollutants, such as ozone, sulfur dioxide, nitrogen dioxide, and cigarette smoke. The consequences of these pollutant-induced alterations in mucus biology are discussed in the context of pulmonary pathophysiology and toxicology.

Marked goblet cell hyperplasia with mucus accumulation in the airways of patients who died of severe acute asthma attack

To examine the changes in airways in bronchial asthma (BA) during an asthma attack causing death, we performed morphometric analysis of autopsied lungs from three outpatients who died of severe acute asthma attacks (group A) and compared these to five patients who died of non-status asthmaticus (group B). Controls (group NL) were four patients who died of diseases other than respiratory disorders. Area proportions of bronchial glands to bronchial wall (gland [percent]) and of goblet cells to total epithelial layer (goblet [percent]) and the intraluminal amount of mucus in the airways (MOR) were measured in a paraffin section. There were no significant differences in age, sex, smoking history, duration of BA history, and dosage of glucocorticoids received between groups A and B. Although both groups A and B showed significantly larger values of gland (percent) in the central airways and of inflammatory cell numbers in the airway walls than did group NL, no significant differences were observed between groups A and B. In contrast, markedly significant increases in goblet (percent) and in MOR were observed in group A compared to groups B and NL. These increases in group A were more dominant in the peripheral airway: 30-fold and threefold increases of group B in goblet (percent) and MOR, respectively. Furthermore, MOR significantly correlated with goblet (percent) in the peripheral airways (p less than 0.05). These findings suggest that a marked increase in goblet cells of the airways is a feature characteristic of patients with BA who die of a severe acute attack.

Parker B. Francis Lecture. Animal models of chronic airways injury

Airways SCM is induced by a wide variety of noxious agents that perturb but do not kill the epithelial cells. Discharge of mucus soon after first exposure to a noxious agent is frequently observed, but discharge of mucus may or may not be followed by development of SCM. Treatment with steroidal and nonsteroidal antiinflammatory agents protects against development of SCM in some models, such as tobacco smoke-induced SCM, but not in others, such as enzyme-induced SCM. In general, SCM regresses slowly or not at all spontaneously. Recovery of some models, such as tobacco smoke-induced SCM, is hastened by nonsteroidal antiinflammatory agents. Experimental protection against induction of enzyme-induced SCM by secretory leukocyte protease inhibitor, which is secreted by airways secretory cells, suggests that such protection may be the in vivo role of that antiprotease. The response of the airways to injury is heterogeneous, with patterns of response of the secretory cells varying according to agent, species, and longitudinal localization of epithelial cells in the airways. The longitudinal heterogeneity of response of secretory epithelial cells to injury is summarized in Table 1. Anatomic heterogeneity of epithelial cells may make a minor contribution to longitudinal variation in response of secretory cells to injury. Molecular heterogeneity of the cellular milieu seems the more likely explanation for this variation in cellular response.

Effects of a new compound (Zy 15850A) on cigarette smoke-induced bronchitis in the rat

The effect of 4H-4 phenylthieno-(3,2-C)-(1)-benzopyran-2-carboxylate (Zy 15850A) on mucous cell hyperplasia was examined in vivo using a well established rat model of cigarette smoke-induced bronchitis. Zy 15850A was given by gavage (25 mg/kg body weight) to male rats before and after sub-acute exposure (i.e. daily for 14 days) to an atmosphere of cigarette smoke (CS). CS significantly increased the thickness of the epithelium at three of the four sites studied in the trachea and in both of the intrapulmonary levels examined. CS increased the number of epithelial mucous cells in all intrapulmonary airways and also increased the mass of submucosal gland present in the larynx and upper trachea. Zy 15850A completely inhibited CS-induced increases in epithelial thickness in the upper trachea and the two intrapulmonary airway levels studied, and tended to inhibit CS-induced epithelial mucous cell hyperplasia in all the six intrapulmonary airway levels examined, with statistically significant inhibition in two. Zy 15850A had no inhibitory effect of the CS-induced enlargement of laryngo-tracheal submucosal glands. We conclude that, in the rat, the predominant inhibitory effect of Zy 15850A is on CS-induced epithelial thickening with weaker inhibitory effects on mucous cell hyperplasia and enlargement of submucosal glands. Zy 15850A is less effective than other mucoregulatory drugs or antiinflammatory agents we have tested in the same bronchitic model.

Hyperresponsiveness to tussive stimuli in cigarette smoke-exposed guinea-pigs: a role for capsaicin-sensitive, calcitonin gene-related peptide-containing nerves

Environmental pollutants may induce airway hyperresponsiveness to bronchonconstrictor stimuli, but if there is a concomitant change in other defensive reflexes, like the cough reflex, is not known. We have examined how two weeks' exposure to cigarette smoke influences airway sensitivity to inhaled irritants acting mainly through capsaicin-sensitive sensory neurons (citric acid, capsaicin) or rapidly adapting stretch receptors (cigarette smoke, histamine). Guinea-pigs were exposed, over a period of one hour, to cigarette smoke or room air, twice daily for 2 weeks. Twenty-four hours after the end of the smoke exposure coughing produced by nebulized citric acid (0.40 M) and capsaicin (30 microM) was enhanced 3.7 (P less than 0.001) and 2.5 (P less than 0.05) times, respectively, whereas the cigarette smoke-induced cough was unchanged. The enhanced responsiveness gradually returned to normal over a period of three weeks and was not mediated by cyclo-oxygenase products since it was not affected by indomethacin (3 mumols kg-1). In contrast, the broncho-constrictor responses to citric acid, capsaicin, cigarette smoke and histamine (0.70 mM) were not altered by inhalation of cigarette smoke. Smoke-exposed animals had a significantly (P less than 0.05) increased amount of calcitonin gene-related peptide-like material (CGRP, contained in capsaicin-sensitive sensory neurons) in tracheal tissue, suggesting that chronic irritation stimulates peptide synthesis. The amount of neuropeptide Y-like material (in autonomic motor nerves) in pulmonary tissue was not changed indicating some 'specificity' in the irritative effect of smoke. It is concluded that prolonged exposure to cigarette smoke produces a tussive hyperresponsiveness that seems to involve specifically capsaicin-sensitive, CGRP-containing sensory neurons mediating cough. The present data demonstrate the development of a 'sensory' hyperresponsiveness, separate from airway hyperresponsiveness to bronchoconstrictor agents.

Reversible pancreatic elastase-induced bronchial secretory cell metaplasia in the rat

Porcine pancreatic elastase (PPE) causes irreversible secretory cell metaplasia (SCM) in the intrapulmonary bronchi of hamsters. To determine whether this lesion can be induced in another rodent species, PPE was transorally instilled into the lungs of anesthetized rats. Saline-treated rats served as controls. Animals were killed 1 week, 3 weeks and 3 months after enzyme treatment and the lungs were inflation-fixed with 4% formalin/1% glutaraldehyde in 0.1 M Na cacodylate buffer at pH 7.4. Transverse sections from 3 intrapulmonary airway levels were embedded in paraffin and in glycol methacrylate. The secretory cell index (SCI) was determined from PAS-stained paraffin sections using a standardized scale of 0 to 4. There were no significant differences between SCI values of PPE-treated rats and saline-treated controls at any time point. Secretory cells in methacrylate sections were subclassified into S1, S2 and S3 cells on the basis of increasing amounts of PAS-positive intracellular granules. At one week, there was no effect of PPE on airway level I secretory cells, but significant increases in numbers of S2 and S3 cells were seen in level II and in S3 cells in level III. At 3 weeks, the number of S1 cells were increased in level I and S2 and S3 cells were increased in level III; level II secretory cells were unaffected. Level III secretory cells had returned to normal by 3 months. There were no significant differences between treatment groups in the total number of secretory cells (S1 + S2 + S3) at any airway level or time point examined.(ABSTRACT TRUNCATED AT 250 WORDS)

Regional difference in airway epithelial response to neutrophil elastase: tracheal secretory cells discharge and recover in hamsters that develop bronchial secretory-cell metaplasia

Human neutrophil elastase (HNE) causes secretory granule discharge and conversion of many Clara cells to mucous cells in hamster bronchi. We investigated whether the trachea responds to HNE in a similar manner because of its abundance of Clara cells. By light microscopy, the tracheal epithelium of animals exposed to a single intratracheal injection of HNE was normal at 21 days, although bronchial secretory-cell metaplasia (SCM) was present. An ultrastructural differential cell count showed no increase in the proportion of granulated secretory cells in HNE-treated animals at 8 and 21 days postinjection compared to saline or untreated controls. At 2 h, the percentage of granulated secretory cells was lower and that of granulated secretory cells was higher in HNE-treated animals than in controls. The HNE-treated animals had fewer secretory granules per cell profile and more surface undulation than controls. By 1 day, the differential cell count and number of granules per cell profile were normal. Saline did not affect the differential cell count or granule number at any time. Ultrastructural study of untreated trachea disclosed the same three types of Clara cell that are found in the bronchus, but their frequencies, with one exception, are significantly different in the two regions. We conclude that HNE acts as a secretagogue in both trachea and bronchus but that an amount of enzyme sufficient to cause bronchial SCM does not induce a similar lesion in trachea. Heterogeneity of Clara cell types in hamster airways may explain the regional variation in secretory-cell modulation by HNE.

The whole-mount method as a technique for measuring experimental changes in airway goblet cell number

The whole-mount staining method for mucous membranes was introduced as an experimental technique for measuring goblet cell density and for estimating the degree of goblet cell hyperplasia in the trachea of experimental animals. By this technique it was demonstrated that a single intratracheal instillation of lysed extract from human neutrophilic granulocytes in rats after 3 weeks caused a three-fold increase in the density of tracheal goblet cells as compared to control animals receiving saline. The increase is of 3-6 times greater magnitude than previously reported in similar experiments where the number of goblet cells was calculated from cross sections in a traditional manner. It was further shown that the increase in goblet cell density could be prevented if prednisone was given to the animals prior to and during the experiment. It is concluded that the whole-mount preparation method is a useful tool in the quantitation of airway goblet cells in experimental settings, and that it appears to be a more sensitive method than the traditionally used cross section techniques.

Dexamethasone reduces rat tracheal goblet cell hyperplasia produced by human neutrophil products

An experimental model leading to goblet cell hyperplasia was developed in order to examine the possible preventive effects of glucocorticosteroids. Human peripheral blood neutrophils were isolated and either freeze-thaw lysed or activated with serum opsonized zymosan. Supernatants from these neutrophil preparations were then instilled transorally into the tracheas of male Sprague-Dawley rats. After 7-35 days, the rats were sacrificed; the lower tracheas were excised, fixed in formalin, and stained with periodic acid-Schiff and alcian blue; and the goblet cells and total epithelial cells were counted. Supernatants from both lysed neutrophils and zymosan-activated neutrophils stimulated a 50% and 42% (respectively) increase in goblet cells after 3 weeks as compared to controls. Purified human neutrophil or porcine pancreatic elastase also caused goblet cell hyperplasia, while sham challenge, challenge with buffer, or challenge with lysates of human mononuclear cells failed to affect goblet cell number. The increase in goblet-cell number was maximal by three weeks and persisted through 35 days. Treatment of animals with glucocorticosteroids administered by the addition of dexamethasone to the drinking water (2 mg/l for 1 week followed by 0.2 mg/l for 2 weeks) ablated the goblet cell hyperplasia produced by neutrophil lysates or elastase alone. We conclude that goblet cell hyperplasia may be induced with insufflated neutrophil products and that this action can be inhibited by treatment with corticosteroids.

Oral N-acetylcysteine speeds reversal of cigarette smoke-induced mucous cell hyperplasia in the rat

We set out to determine whether or not the "mucolytic" drug N-acetylcysteine would speed the reversal of cigarette smoke-induced secretory-cell hyperplasia to normal, similar to that found previously for two nonsteroidal antiinflammatory drugs. Cigarette smoke alone significantly (p less than 0.01) increased the number of secretory cells in seven out of eight airway levels studied and maintained a significant increase in five of the levels at least 3 weeks after cessation of exposure. Treatment of rats with N-acetylcysteine, as 1% of their drinking water during the recovery period, reduced the time taken for secretory cell number to return to normal to between 4 days and 3 weeks, depending on airway level.

Inhibition by oral N-acetylcysteine of cigarette smoke-induced "bronchitis" in the rat

Specific pathogen-free rats were exposed to the cigarette smoke (CS) of 25 cigarettes daily for 14 days and concurrently given N-acetylcysteine (Nac) as 1% of their drinking water (average daily dose 973 mg/kg). The thickness of the epithelium was measured at four airway levels and the numbers of mucus-containing secretory cells, stained for neutral or acidic glycoprotein (NGP or AGP respectively), were counted in surface epithelium at eight airway levels. Cigarette smoke increased the thickness of the epithelium at three of the airway levels studied by between 37 and 72%. The number of secretory cells was increased at all airway levels distal to the upper trachea by between 102 and 421%. Secretory cells containing NGP were reduced in number but this was more than offset by a large increase in the number of secretory cells containing AGP at all airway levels. N-acetylcysteine inhibited CS-induced epithelial thickening. Nac also inhibited the CS-induced increase in the number of secretory cells with AGP, but had little effect on the CS-induced reduction in the number of cells with NGP. Thus, prophylactic oral N-acetylcysteine led to an overall inhibition of CS-induced mucous cell hyperplasia and epithelial hypertrophy. The results suggest a novel anti-inflammatory action for a drug with known mucolytic effects.

Indomethacin and flurbiprofen speed recovery of rat bronchial epithelium after exposure to cigarette smoke

The cigarette smoke-induced rat model of chronic bronchitis was used to study the time course of the return of cigarette smoke-induced secretory cell hyperplasia to the normal and the capacity of two non-steroidal anti-inflammatory drugs to speed this recovery. Cigarette smoke alone significantly increased (P less than 0.05) the number of secretory cells in all of the eight airway levels studied to between 52-225% above control values. After cessation of exposure, recovery was complete by 9 days in the trachea, between 10-21 days in 'proximal' intrapulmonary airways and 43-84 days in distal bronchioli. Indomethacin and flurbiprofen, given by intraperitoneal injection at 4 mg/kg body weight for 21 days of the recovery period, significantly reduced the time taken for recovery to between 4 and 9 days in intrapulmonary airways but had no effect in the trachea.