What does mucin have to do with lung disease?

MUC5AC concentrations in lung lavage fluids are associated with acute lung injury after cardiac surgery

Heart surgery may be complicated by acute lung injury and adult respiratory distress syndrome. Expression and release of mucins MUC5AC and MUC5B in the lungs has been reported to be increased in acute lung injury. The aim of our study was to [1] investigate the perioperative changes of MUC5AC, MUC5B and other biomarkers in mini-bronchoalveolar lavage (minBAL), and [2] relate these to clinical outcomes after cardiac surgery. In this prospective cohort study in 49 adult cardiac surgery patients pre- and post-surgery non-fiberscopic miniBAL fluids were analysed for MUC5AC, MUC5B, IL-8, human neutrophil elastase, and neutrophils. All measured biomarkers increased after surgery. Perioperative MUC5AC-change showed a significant negative association with postoperative P/F ratio (p = 0.018), and a positive association with ICU stay (p = 0.027). In conclusion, development of lung injury after cardiac surgery and prolonged ICU stay are associated with an early increase of MUC5AC as detected in mini-BAL.

Qufeng Xuanbi Formula inhibited benzo[a]pyrene-induced aggravated asthma airway mucus secretion by AhR/ROS/ERK pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Excessive secretion of airway mucus may be an important pathological factor of air pollution-induced acute asthma attacks. Treatment of airway mucus hypersecretion improves asthma aggravated by air pollutants. Qufeng Xuanbi Formula (QFXBF) has been used to treat asthma for more than 30 years. However, whether QFXBF inhibits asthmatic mucus secretion exacerbated by air pollutants has not yet been established.

AIM OF THE STUDY

This study aimed to evaluate the effect of QFXBF on airway mucus secretion and the mechanism of action in an air pollutant benzo[a]pyrene (BaP)-induced mouse model of aggravated asthma.

MATERIALS AND METHODS

Ovalbumin (OVA) and BaP co-exposure were used to establish the aggravated asthma model. The average enhanced pause (Penh), serum OVA-specific IgE, and changes in lung histopathology were determined. 16HBE cells exposed to BaP, treatment with QFXBF, arylhydrocarbon receptor (AhR) signal antagonist SR1, reactive oxygen species (ROS) antagonist NAC, or extracellular signal-regulated kinase (ERK1/2) signal antagonist U0126 were established to investigate the effect of QFXBF on BaP-induced mucus secretion and its target. The mRNA and protein expression levels of MUC5AC in the lung tissue and 16HBE cells were examined. We also studied the effect of QFXBF on ROS production. Finally, the protein expression of AhR, phospho-extracellular signal-regulated kinases (p-ERK1/2), and ERK1/2 in 16HBE cells and lung tissues was determined by western blotting.

RESULTS

Administration of QFXBF significantly alleviated the pathological symptoms, including Penh, serum OVA-specific IgE, and changes in lung histopathology in a BaP-induced mouse model of aggravated asthma. QFXBF inhibited MUC5AC expression in asthmatic mice and 16HBE cells exposed to BaP. ROS production, AhR expression, and ERK1/2 phosphorylation were significantly increased in BaP-induced asthmatic mice and 16HBE cells. Signaling pathway inhibitors StemRegenin 1 (SR1), NAC, and U0126 significantly inhibitedBaP-induced MUC5AC expression in 16HBE cells. SR1 reversed Bap-induced ROS production and ERK activation, and NAC inhibited Bap-induced ERK activation. In addition, QFXBF regulated AhR signaling, inhibited ROS production, reversed ERK activation, and downregulated mucus secretion to improve asthma aggravated by air pollutant BaP.

CONCLUSIONS

QFXBF can ameliorate mucus secretion in BaP-induced aggravated asthmatic mice and 16HBE cells, and the specific mechanism may be related to the inhibition of the AhR/ROS/ERK signaling pathway.

Antiviral Activity of Cell Membrane-Bound Amphiphilic Polymers

We demonstrate that cholesterol-modified polyethylene glycol has antiviral activity, exerted by anchoring to plasma membranes and sterically inhibiting viruses from entering cells. These polymers distribute sparsely on cell membranes even at binding saturation. However, the polymers have sufficient elastic repulsion energy to repel various kinds of viruses with sizes larger than the mean distances between anchored polymers, including SARS-CoV-2 pseudoparticles. Our strategy can be applied to protect the epithelium from viruses. When these polymers are applied to the epithelium, they localize on the apical surface due to the tight junction barriers, resulting in surface-only coating. Therefore, these polymers can prevent the entry of viruses into cells of the epithelium with minimal disturbance to lateral cell-cell interactions and organizations.

Expression of MUC-2, MUC-6, NAPE-PLD, IL-6 and IL-13 in Healthy and Metaplastic Bronchial Epithelium

Background: The normal tissue structure of the respiratory system is necessary to provide adequate protection of the airways and lungs. Prolonged exposure to trigger factors can result in adaptive mechanism activation and lead to the development of chronic pulmonary diseases or even dysplastic changes. Materials and methods: Respiratory system material with a pseudostratified ciliated epithelium was obtained from 12 patients (aged 16 to 95), and material with a stratified squamosa epithelium was obtained from six patients (aged 23 to 93). Routine staining was performed, and an immunohistochemistry was conducted for MUC-2, MUC-6, NAPE-PLD, IL-6 and IL-13. Results: Inflammatory processes were not detected in any of the specimens. A number of correlations were identified, with the most important being a strong positive correlation for IL-13 between the alveolar epithelium and alveolar macrophages and a strong positive correlation for IL-6 between the alveolar epithelium and alveolar macrophages in the stratified squamous epithelium group. We also detected a statistically significant difference in IL-6 in alveolar macrophages. Conclusions: There were no signs of dysplastic changes in either group. Increased secretion of IL-13 in the stratified squamous epithelium group shows its involvement in metaplastic changes in the bronchial epithelium. The secretion of atypical factors by hyaline cartilage demonstrates its plasticity and adaptability.

Pretreatment Methods for Human Nasopharyngeal Swabs to Increase the Signal to Noise Ratio of High Sensitivity Immunoassays

Mucous samples collected through nasopharyngeal (NP) swabs are considered gold standard specimens for the detection of respiratory pathogens. Matrices of these highly viscous samples often cause significant background noises in immunoassays, especially immunoassays with high sensitivity. We demonstrated such nonspecific background signals in both a chemiluminescence enzyme-linked immunosorbent assay (ELISA) and a novel highly sensitive immunoassay called Microbubbling SARS-CoV-2 Antigen Assay (MSAA). We developed and demonstrated the effectiveness of two quick sample pretreatment methods, filtration and preadsorption, to decrease nonspecific signals and increase the signal-to-noise ratio (SNR). Using these pretreatment methods, the SNR (at 3.6 × 10⁴ copies/mL of inactivated SARS-CoV-2) was increased by 42.4-fold (95% CI 41.0-43.8) and 67.1-fold (95% CI 57.9-76.3) in the MSAA, and 1.3-fold (95% CI 0.9-1.7) and 1.8-fold (95% CI 1.6-2.0) in the chemiluminescence ELISA assay. Sample pretreatment methods developed in this study are broadly adaptable for the development of immunoassays for highly viscous samples.

Advances in MUC1-Mediated Breast Cancer Immunotherapy

Breast cancer (BRCA) is the leading cause of death from malignant tumors among women. Fortunately, however, immunotherapy has recently become a prospective BRCA treatment with encouraging achievements and mild safety profiles. Since the overexpression and aberrant glycosylation of MUC1 (human mucin) are closely associated with BRCA, it has become an ideal target for BRCA immunotherapies. In this review, the structure and function of MUC1 are briefly introduced, and the main research achievements in different kinds of MUC1-mediated BRCA immunotherapy are highlighted, from the laboratory to the clinic. Afterward, the future directions of MUC1-mediated BRCA immunotherapy are predicted, addressing, for example, urgent issues in regard to how efficient immunotherapeutic strategies can be generated.

Therapeutic implementation in arterial thrombosis with pulmonary administration of fucoidan microparticles containing acetylsalicylic acid

Several antithrombotic drugs are available to treat cardiovascular diseases due to its high mortality and morbidity worldwide. Despite these, severe adverse effects that can lead to treatment withdrawal have been described, highlighting the importance of new therapies. Thus, this work describes the development of fucoidan microparticles containing acetylsalicylic acid (MP/F4M) for pulmonary delivery and in vitro, ex vivo, and in vivo evaluation. Microparticles were prepared via spray-drying and characterized in vitro (mucoadhesive properties, coagulation time, platelet aggregation, adhesion, and hemolysis) followed by ex vivo platelet aggregation, in vivo arterial thrombosis, and hemorrhagic profile. The formulation physicochemical characterization showed suitable characteristics along with delayed drug release, increased breathable particle fraction, and high washability resistance as well as antiplatelet activity and enhanced platelet adhesion in vitro. In in vivo assays, MP/F4M protected against arterial thrombosis, without changes in the hemorrhagic profile. Finally, no lung changes were observed after prolonged pulmonary administration, whereas isolated ASA led to an inflammatory response. In conclusion, pulmonary administration of fucoidan microparticles with an antiplatelet drug may be an alternative therapy to treat cardiovascular diseases, opening the field for different formulations.

Benzo(a)pyrene induces MUC5AC expression through the AhR/mitochondrial ROS/ERK pathway in airway epithelial cells

OBJECTIVES

Benzo(a)pyrene (BaP) is a ubiquitous air pollutants, and BaP exposure leads to a risk of respiratory diseases. The oversecretion of airway mucus and high expression of mucin 5AC (MUC5AC) are associated with common respiratory disorders caused by air pollution. We aimed to investigate the effect of BaP on MUC5AC expression, especially the mechanisms by which BaP induces MUC5AC gene expression.

METHODS

The human airway epithelial cell NCI-H292 was used to test the effects of BaP on the expression of MUC5AC in vitro. MUC5AC mRNA and protein expression were assessed with real-time quantitative PCR, immunochemistry, and western blotting. A luciferase assay was conducted to detect the activity of the promoter. The total cellular ROS and mitochondrial ROS were measured by corresponding probes. Small-interfering RNAs were used for gene silencing. AhR-overexpressing cell lines were constructed by transfection with AhR overexpression lentivirus.

RESULTS

We found that BaP stimulation upregulated the MUC5AC mRNA and protein levels and activated the ERK pathway. Suppressing ERK with U0126 (an ERK inhibitor) or knocking down ERK with siRNA decreased BaP-induced MUC5AC expression. The luciferase activity transfected with the MUC5AC promoter and cAMP-response element (CRE) was increased after BaP treatment, whereas CREB siRNA suppressed the BaP-induced overexpression of MUC5AC. In addition, BaP increased mitochondrial ROS production, and Mito-TEMP, a mitochondrial ROS inhibitor, inhibited BaP-induced MUC5AC expression and ERK activation. BaP increased the mRNA levels of CYP1A1 and CYP1B1, while Alizarin, a CYP1s inhibitor, suppressed the effects of BaP, including the MUC5AC overexpression, ERK activation and mitochondrial ROS generation. BaP induced the translocation of aryl hydrocarbon receptor (AhR) from the cytoplasm to the nucleus. SiRNA-mediated knockdown or chemical inhibition of AhR decreased the BaP-induced expression of MUC5AC, while the overexpression of AhR significantly enhanced the BaP-induced expression of MUC5AC. ITE, an endogenous AhR ligand, also upregulated the mRNA and protein expression of MUC5AC. Furthermore, resveratrol treatment inhibited the BaP-induced MUC5AC overexpression, AhR translocation, mitochondrial ROS production and ERK pathway activation.

CONCLUSION

Here, we highlighted the crucial role of AhR/mitochondrial ROS/ERK pathway activation in BaP-induced MUC5AC overexpression and identified resveratrol as a promising drug to reduce BaP-induced MUC5AC overexpression.

Chloroquine and hydroxychloroquine for combating COVID-19: Investigating efficacy and hypothesizing new formulations using Bio/chemoinformatics tools

Chloroquine (CQ) and hydroxychloroquine (HCQ) are undergoing several clinical trials for evaluating their efficacy and safety as antiviral drugs. Yet, there is still a great debate about their efficacy in combating COVID-19. This study aimed to evaluate the feasibility of intranasal and/or pulmonary administration of CQ/HCQ for COVID-19 using Bio/chemoinformatics tools. We, hereby, hypothesize the success of the intranasal and the pulmonary routes through a gelatin matrix to overcome several challenges related to CQ and HCQ pharmacodynamics and pharmacokinetics properties and to increase their local concentrations at the sites of initial viral entry while minimizing the potential side effects. Molecular docking on the gelatin-simulated matrix demonstrated high loading values and a sustained release profile. Moreover, the docking on mucin as well as various receptors including Angiotensin-converting enzyme 2 (ACE-2), heparin sulphate proteoglycan and Phosphatidylinositol binding clathrin assembly protein (PICALM), which are expressed in the lung and intranasal tissues and represent initial sites of attachment of the viral particles to the surface of respiratory cells, has shown good binding of CQ and HCQ to these receptors. The presented data provide an insight into the use of a novel drug formulation that needs to be tested in adequately powered randomized controlled clinical trials; aiming for a sustained prophylaxis effect and/or a treatment strategy against this pandemic viral infection.

Influence of silica particles on mucociliary structure and MUC5B expression in airways of C57BL/6 mice

Purpose: Impaired mucociliary clearance is an initial characteristic of recurrent cough, respiratory infection and chronic respiratory diseases. It has been demonstrated that prolonged inhalation of respirable silica particles results in a variety of pulmonary diseases, but whether the mucociliary system is involved in this process is unclear. This study aims to evaluate the effects of silica particles on mucociliary structure and MUC5B production in respiratory tract.Materials and Methods: C57BL/6 mice were administered with 2.5 mg silica particles through a single intratracheal instillation. The changes of mucociliary structure and MUC5B expression in trachea was evaluated by HE and AB-PAS staining, transmission electron microscopy and immunohistochemistry on days 1, 7, 28 and 84 post-exposure.Results: The mucociliary structure of airway epithelium was obviously impaired by silica particles, showing disordered, shortened or partially lost cilia on the surface, increased mucus in mucous layer and submucosal glands from day 7 to day 84. A variety of ultrastructural abnormalities were discovered in silica-exposed airway cilia, including absence of central pair microtubules, disorganized microtubules and clusters of axoneme on day 1 and 7. The numbers of ciliary axonemes and basal bodies in ciliated epithelial cells were significantly decreased, whereas the proportion of abnormal axonemes was gradually increased with exposure to silica particles (P < 0.05). In addition, silica particles significantly decreased MUC5B expression on the surface of airway epithelium on day 28 and 84, but obviously increased its production in submucosal glands from day 1 to day 84 (P < 0.01).Conclusions: Silica particles could lead to ultrastructural defects in airway cilia, mucus hypersecretion and altered MUC5B expression in trachea, indicating that impaired mucociliary structure and altered MUC5B production might participate in the development of silica-related respiratory diseases.

MUC1 Mucin: A Putative Regulatory (Checkpoint) Molecule of T Cells

T lymphocytes are at the center of inducing an effective adaptive immune response and maintaining homeostasis. T cell responses are initiated through interactions between antigen presenting cells (APCs) and T cells. The type and strength of signals delivered through the T cell receptor (TCR) may modulate how the cells respond. The TCR-MHC (T cell receptor-major histocompatibility complex molecules) complex dictates the specificity, whereas co-stimulatory signals induced by interaction of various accessory cell surface molecules strengthen and optimize T cell responses. Multiple immune regulatory mechanisms brought about by co-inhibitory molecules expressed on T cells play a key role in orchestrating successful and non-damaging immunity. These co-inhibitory molecules are also referred to as initiators of immune check-points or co-inhibitory pathways. Knowledge of co-inhibitory pathways associated with activated T lymphocytes has allowed a better understanding of (a) the inflammatory and anti-inflammatory processes associated with infectious diseases and autoimmune diseases, and (b) mechanisms by which tumors evade immune attack. Many of these regulatory pathways are non-redundant and function in a highly concerted manner. Targeting them has provided effective approaches in treating cancer and autoimmune diseases. For this reason, it is valuable to identify any co-inhibitory molecules that affect these pathways. MUC1 mucin (CD227) has long been known to be expressed by epithelial cells and overexpressed by a multitude of adenocarcinomas. As long ago as 1998 we made a surprising discovery that MUC1 is also expressed by activated human T cells and we provided the first evidence of the role of MUC1 as a novel T cell regulator. Subsequent studies from different laboratories, as well as ours, supported an immuno-regulatory role of MUC1 in infections, inflammation, and autoimmunity that corroborated our original findings establishing MUC1 as a novel T cell regulatory molecule. In this article, we will discuss the experimental evidence supporting MUC1 as a putative regulatory molecule or a “checkpoint molecule” of T cells with implications as a novel biomarker and therapeutic target in chronic diseases such as autoimmunity, inflammation and cancer, and possibly infections.

Pollen-derived adenosine is a necessary cofactor for ragweed allergy

BACKGROUND

Ragweed (Ambrosia artemisiifolia) is a strong elicitor of allergic airway inflammation with worldwide increasing prevalence. Various components of ragweed pollen are thought to play a role in the development of allergic responses. The aim of this study was to identify critical factors for allergenicity of ragweed pollen in a physiological model of allergic airway inflammation.

METHODS

Aqueous ragweed pollen extract, the low molecular weight fraction or the major allergen Amb a 1 was instilled intranasally on 1-11 consecutive days, and allergic airway inflammation was evaluated by bronchoalveolar lavage, lung histology, serology, gene expression in lung tissue, and measurement of lung function. Pollen-derived adenosine was removed from the extract enzymatically to analyze its role in ragweed-induced allergy. Migration of human neutrophils and eosinophils toward supernatants of ragweed-stimulated bronchial epithelial cells was analyzed.

RESULTS

Instillation of ragweed pollen extract, but not of the major allergen or the low molecular weight fraction, induced specific IgG1 , pulmonary infiltration with inflammatory cells, a Th2-associated cytokine signature in pulmonary tissue, and impaired lung function. Adenosine aggravated ragweed-induced allergic lung inflammation. In vitro, human neutrophils and eosinophils migrated toward supernatants of bronchial epithelial cells stimulated with ragweed extract only if adenosine was present.

CONCLUSIONS

Pollen-derived adenosine is a critical factor in ragweed-pollen-induced allergic airway inflammation. Future studies aim at therapeutic strategies to control these allergen-independent pathways.

MUC5B promoter polymorphisms and risk of coal workers' pneumoconiosis in a Chinese population

Coal workers' pneumoconiosis (CWP) is characterized by fibrosing nodular lesions that eventually develop into progressive pulmonary fibrosis. Genetic variations have been recognized to be involved in the multi-factorial susceptibility to CWP, and MUC5B is a candidate lung fibrosis susceptibility gene. In the present study, we investigated possible genetic associations between three single nucleotide polymorphisms in MUC5B promoter region and CWP in a case-control study including 686 CWP patients and 680 controls. Genotyping was carried out by TaqMan method. Only rs2672794 allele and genotype frequencies distributions were significantly different between CWP patients and controls (P = 0.017 and 0.046 for allele and genotype, respectively). The MUC5B rs2672794 CC genotype was associated with a significantly increased risk of CWP, compared with the TT genotype. Moreover, individuals with TC/CC genotype had an obviously increased risk of CWP than those with TT genotype, particularly among subgroups of dust exposure <27 years and smokers. This is the first report showing an association between the MUC5B rs2672794 polymorphism and CWP, and our results suggest that MUC5B rs2672794 CC genotype could increase the risk of CWP. Further studies are warranted to confirm our findings.

The Effects of Eucheuma cottonii on Signaling Pathway Inducing Mucin Synthesis in Rat Lungs Chronically Exposed to Particulate Matter 10 (PM10) Coal Dust

This study was aimed at investigating the effects of Eucheuma cottonii (EC) in oxidative stress and the signaling for mucin synthesis in rat lungs chronically exposed to coal dust. Coal dust with concomitant oral administration of ethanolic extract of EC at doses of 150 (EC₁₅₀) or 300 mg/kg BW (EC₃₀₀) compared to exposed to PM₁₀ coal dust at doses of 6.25 (CD_6.25), 12.5 (CD_12.5), or 25 mg/m³ (CD₂₅) (an hour daily for 6 months) and nonexposure group (control). The malondialdehyde (MDA), epidermal growth factor (EGF), transforming growth factor (TGF)-α, epidermal growth factor receptor (EGFR), and MUC5AC levels were determined in the lung. The administration of EC₃₀₀ significantly (p < 0.05) reduced the MDA levels in groups exposed to all doses of coal dust compared to the respective coal dust-exposed nonsupplemented groups. Although not statistically significant,EC reduced the EGF levels and EGFR expressions in CD_12.5 and CD₂₅ groups and decreased the TGF-α, level and MUC5AC expression in CD₂₅ group compared to the respective coal dust-exposed nonsupplemented groups. EC was able to decrease oxidative stress and was also able to decrease signaling for mucin synthesis, at least a part, via reducing the ligand in chronic coal dust exposure.

Pathobiological implications of MUC4 in non-small-cell lung cancer

INTRODUCTION

Altered expression of MUC4 plays an oncogenic role in various cancers, including pancreatic, ovarian, and breast. This study evaluates the expression and role of MUC4 in non-small-cell lung cancer (NSCLC).

METHODS

We used a paired system of MUC4-expressing (H292) and MUC4-nonexpressing (A549) NSCLC cell lines to analyze MUC4-dependent changes in growth rate, migration, and invasion using these sublines. We also evaluated the alterations of several tumor suppressor, proliferation, and metastasis markers with altered MUC4 expression. Furthermore, the association of MUC4 expression (by immunohistochemistry) in lung cancer samples with patient survival was evaluated.

RESULTS

MUC4-expressing lung cancer cells demonstrated a less proliferative and metastatic phenotype. Up-regulation of p53 in MUC4-expressing lung cancer cells led to the accumulation of cells at the G2/M phase of cell cycle progression. MUC4 expression attenuated Akt activation and decreased the expression of Cyclins D1 and E, but increased the expression of p21 and p27. MUC4 expression abrogated cancer cell migration and invasion by altering N- & E-cadherin expression and FAK phosphorylation. A decrease in MUC4 expression was observed with increasing tumor stage (mean composite score: stage I, 2.4; stage II, 1.8; stage III, 1.4; and metastatic, 1.2; p = 0.0093). Maximal MUC4 expression was associated with a better overall survival (p = 0.042).

CONCLUSION

MUC4 plays a tumor-suppressor role in NSCLC by altering p53 expression in NSCLC. Decrease in MUC4 expression in advanced tumor stages also seems to confirm the novel protective function of MUC4 in NSCLC.

Fetal exposure of rhesus macaques to bisphenol a alters cellular development of the conducting airway by changing epithelial secretory product expression

BACKGROUND

Bisphenol A (BPA) exposure early in life results in organizational changes in reproductive organs, but the effect of BPA on conducting airway cellular maturation has not been studied. Late gestation is characterized by active differentiation of secretory cells in the lung epithelium.

OBJECTIVE

We evaluated the hypothesis that BPA exposure disrupts epithelial secretory cell development in the fetal conducting airway of the rhesus macaque.

METHODS

We exposed animals to BPA during either the second (early term) or the third (late term) trimester. There were four treatment groups: a) sham control early term, b) sham control late term, c) BPA early term (BPA-early), and d) BPA late term (BPA-late). Because cellular maturation occurs nonuniformly in the lung, we defined mRNA and protein expression by airway level using microdissection.

RESULTS

BPA exposure of the dam during late term significantly accelerated secretory cell maturation in the proximal airways of the fetus; both Clara cell secretory protein (CCSP) and MUC5AC/5B mRNA and protein expression increased.

CONCLUSIONS

BPA exposure during late gestation accelerates secretory cell maturation in the proximal conducting airways. We identified a critical window of fetal susceptibility for BPA effects on lung epithelial cell maturation in the third trimester. This is of environmental health importance because increases in airway mucins are hallmarks of a number of childhood lung diseases that may be affected by BPA exposure.

EPS-I polysaccharide protects Mycoplasma pulmonis from phagocytosis

Few mycoplasmal polysaccharides have been described and little is known about their role in pathogenesis. The infection of mice with Mycoplasma pulmonis has been utilized in many in vivo and in vitro studies to gain a better understanding of host-pathogen interactions during chronic respiratory infection. Although alveolar macrophages have a primary role in host defence, M. pulmonis is killed inefficiently in vitro. One antiphagocytic factor produced by the mycoplasma is the family of phase- and size-variable Vsa lipoproteins. However, bacteria generally employ multiple strategies for combating host defences, with capsular polysaccharide often having a key role. We show here that mutants lacking the EPS-I polysaccharide of M. pulmonis exhibit increased susceptibility to binding and subsequent killing by alveolar macrophages. These results give further insight into how mycoplasmas are able to avoid the host immune system and sustain a chronic infection.

Acrolein - a pulmonary hazard

Acrolein is a respiratory irritant that can be generated during cooking and is in environmental tobacco smoke. More plentiful in cigarette smoke than polycyclic aromatic hydrocarbons (PAH), acrolein can adduct tumor suppressor p53 (TP53) DNA and may contribute to TP53-mutations in lung cancer. Acrolein is also generated endogenously at sites of injury, and excessive breath levels (sufficient to activate metalloproteinases and increase mucin transcripts) have been detected in asthma and chronic obstructive pulmonary disease (COPD). Because of its reactivity with respiratory-lining fluid or cellular macromolecules, acrolein alters gene regulation, inflammation, mucociliary transport, and alveolar-capillary barrier integrity. In laboratory animals, acute exposures have lead to acute lung injury and pulmonary edema similar to that produced by smoke inhalation whereas lower concentrations have produced bronchial hyperreactivity, excessive mucus production, and alveolar enlargement. Susceptibility to acrolein exposure is associated with differential regulation of cell surface receptor, transcription factor, and ubiquitin-proteasome genes. Consequent to its pathophysiological impact, acrolein contributes to the morbidly and mortality associated with acute lung injury and COPD, and possibly asthma and lung cancer.

Regulation of PMA-induced MUC5AC expression by heparin in human bronchial epithelial cells

Mucus hypersecretion is a major pathophysiologic feature in chronic inflammatory airway diseases. Oxidative stress plays a pivotal role in this process. Recent studies have found that heparin has antioxidant effects which can reduce free radical damage. Here, we hypothesized that heparin has some influence on the expression of mucin 5AC (MUC5AC) induced by phorbol myristate acetate (PMA) in a bronchial epithelial cell line (HBE16), also we have investigated the potential mechanism involved in the process. We found that ROS, the mRNA of Duox1, EGFR and MUC5AC, as well as the protein levels of Duox1, p-EGFR, EGFR, and MUC5AC in the PMA group were significantly increased when compared with the control group (all P < 0.01). After pretreatment with heparin however, there was a significant decrease in ROS levels, the mRNA of Duox1, EGFR, and MUC5AC, and the protein levels of Duox1, p-EGFR, EGFR, and MUC5AC, when compared with the PMA group (all P < 0.01). MUC5AC protein in the supernatant was inhibited in a dose-dependent manner by heparin. Pretreatment with DMTU resulted in a significant decrease in ROS content, the mRNA of Duox1, EGFR, and MUC5AC as well as the protein levels of Duox1, p-EGFR, EGFR, and MUC5AC when compared with the PMA group (all P < 0.01). When cells were pretreated with both heparin and DMTU, there was a further reduction in ROS content, the mRNA of Duox1, EGFR, and MUC5AC as well as the protein levels of Duox1, p-EGFR, EGFR, and MUC5AC, when compared with either the PMA group, heparin group, or DMTU group (all P < 0.01). Our results show that PMA can induce MUC5AC expression by activation of the Duox1-ROS-TACE-TGF-α-EGFR signaling pathway. Heparin can decrease the level of Duox1, ROS production and block the PMA-induced activation of EGFR, thus inhibiting the overexpression of mucin MUC5AC in a dose-dependent manner. In addition to reducing ROS production, heparin may also inhibit the expression of MUC5AC through other signal mechanisms.

The extracellular signal-regulated kinase mitogen-activated protein kinase/ribosomal S6 protein kinase 1 cascade phosphorylates cAMP response element-binding protein to induce MUC5B gene expression via D-prostanoid receptor signaling

Mucus hypersecretion is a prominent feature of respiratory diseases, and MUC5B is a major airway mucin. Mucin gene expression can be affected by inflammatory mediators, including prostaglandin (PG) D(2,) an inflammatory mediator synthesized by hematopoietic PGD synthase (H-PGDS). PGD(2) binds to either D-prostanoid receptor (DP1) or chemoattractant receptor homologous molecule expressed on T-helper type 2 cells (CRTH2). We investigated the mechanisms by which PGD(2) induces MUC5B gene expression in airway epithelial cells. Western blot analysis showed that H-PGDS was highly expressed in nasal polyps. Similar results were obtained for PGD(2) expression. In addition, we could clearly detect the expressions of both H-PGDS and DP1 in nasal epithelial cells but not CRTH2. We demonstrated that PGD(2) increased MUC5B gene expression in normal human nasal epithelial cells as well as in NCI-H292 cells in vitro. S5751, a DP1 antagonist, inhibited PGD(2)-induced MUC5B expression, whereas a CRTH2 antagonist (OC0459) did not. These data suggest that PGD(2) induced MUC5B expression via DP1. Pretreatment with extracellular signal-regulated kinase (ERK) inhibitor (PD98059) blocked both PGD(2)-induced ERK mitogen-activated protein kinase (MAPK) activation and MUC5B expression. Proximity ligation assays showed direct interaction between RSK1 and cAMP response element-binding protein (CREB). Stimulation with PGD(2) caused an increase in intracellular cAMP levels, whereas intracellular Ca(2+) did not have such an effect. PGD(2)-induced MUC5B mRNA levels were regulated by CREB via direct interaction with two cAMP-response element sites (-921/-914 and -900/-893). Finally, we demonstrated that PGD(2) can induce MUC5B overproduction via ERK MAPK/RSK1/CREB signaling and that DP1 receptor may have suppressive effects in controlling MUC5B overproduction in the airway.

Nerve growth factor localization in the nasal mucosa of patients with persistent allergic rhinitis

BACKGROUND AND OBJECTIVES

Nerve growth factor (NGF) and NGF receptors have been shown to be expressed by structural and infiltrating inflammatory cells in the human allergic bronchial mucosa and conjunctiva. In the nose, a positive immunostaining for NGF was recently reported in biopsies of subjects undergoing surgery for refractory nasal obstruction. This study was aimed at studying by immunohistochemistry NGF expression and localization in the nasal mucosa from subjects with moderate/severe persistent allergic rhinitis and natural allergen exposure.

METHODS

Immunostaining for NGF, tryptase and eosinophil cationic protein was performed in human nasal turbinate sections of 25 patients affected by persistent allergic rhinitis and sensitization to Dermatophagoides pteronyssinus.

RESULTS

NGF was consistently expressed in the epithelium and in the submucosa of allergic rhinitic subjects, preferentially localized in eosinophils and mast cells. A strong NGF immunostaining was found in mucous cells of the epithelial lining and in the submucosal glands.

CONCLUSIONS

As previously shown for allergic asthma and allergic conjunctivitis, NGF is also detectable in the nasal mucosa of patients with persistent allergic rhinitis. The preferential NGF localization in mucous cells of the epithelial lining and in the submucosal glands suggests a possible role for NGF in modulating secretion in allergic rhinitis and possibly other allergic diseases.

Role of mechanical stress in regulating airway surface hydration and mucus clearance rates

Effective clearance of mucus is a critical innate airway defense mechanism, and under appropriate conditions, can be stimulated to enhance clearance of inhaled pathogens. It has become increasingly clear that extracellular nucleotides (ATP and UTP) and nucleosides (adenosine) are important regulators of mucus clearance in the airways as a result of their ability to stimulate fluid secretion, mucus hydration, and cilia beat frequency (CBF). One ubiquitous mechanism to stimulate ATP release is through external mechanical stress. This article addresses the role of physiologically relevant mechanical forces in the lung and their effects on regulating mucociliary clearance (MCC). The effects of mechanical forces on the stimulating ATP release, fluid secretion, CBF, and MCC are discussed. Also discussed is evidence suggesting that airway hydration and stimulation of MCC by stress-mediated ATP release may play a role in several therapeutic strategies directed at improving mucus clearance in patients with obstructive lung diseases, including cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD).

Quantification of mucin gene expression in tracheobronchial epithelium of healthy dogs and dogs with chronic bronchitis

OBJECTIVE

To develop a real-time PCR assay for the quantification of mucin gene expression in tracheobronchial brushing specimens from dogs and compare mucin gene expression in specimens from dogs with naturally occurring chronic bronchitis with that in specimens from healthy dogs.

ANIMALS

7 healthy dogs and 5 dogs with chronic bronchitis.

PROCEDURES

Primers that were designed to span the predicted intron-exon boundaries of a canine MUC5AC-like gene were used to develop a real-time PCR assay for quantification of expression of that gene. Total mRNA was isolated from tracheobronchial brushing specimens obtained from dogs with and without bronchitis during anesthesia; MUC5AC-like gene expression in those samples was quantified by use of the real-time PCR assay.

RESULTS

The PCR assay was sensitive and specific for the target sequence, the predicted amino acid sequence of which had greatest homology with human, porcine, and rat MUC5AC. The assay was able to quantify the target over a wide dynamic range. Dogs with chronic bronchitis had a 3.0-fold increase in the quantity of MUC5AC-like mRNA, compared with healthy dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

The ability to measure mucin gene expression from tracheobronchial brushing specimens collected from client-owned dogs during routine bronchoscopy should prove to be a useful tool for the study of bronchitis in dogs and expand the usefulness of airway inflammation in dogs as a model for bronchitis in humans.

Regulation of MUC5AC expression by NAD(P)H:quinone oxidoreductase 1

Neutrophil elastase (NE), a potent neutrophil inflammatory mediator, increases MUC5AC mucin gene expression through undefined pathways involving reactive oxygen species. To determine the source of NE-generated reactive oxygen species, we used pharmacologic inhibitors of oxidoreductases to test whether they blocked NE-regulated MUC5AC mRNA expression. We found that dicumarol, an inhibitor of the NADP(H):quinone oxidoreductase 1 (NQO1), inhibited MUC5AC mRNA expression in A549 lung adenocarcinoma cells and primary normal human bronchial epithelial cells. We further tested the role of NQO1 in mediating NE-induced MUC5AC expression by inhibiting NQO1 expression using short interfering RNA (siRNA). Transfection with siRNA specific for NQO1 suppressed NQO1 expression and significantly abrogated MUC5AC mRNA expression. NE treatment caused lipid peroxidation in A549 cells; this effect was inhibited by pretreatment with dicumarol, suggesting that NQO1 also regulates oxidant stress in A549 cells after NE exposure. NE exposure increased NQO1 protein and activity levels; NQO1 expression and activity were limited to the cytosol and did not translocate to the plasma membrane. Our results indicate that NQO1 has an important role as a key mediator of NE-regulated oxidant stress and MUC5AC mucin gene expression.

The characterisation of mucin in a mature ovarian teratoma occurring in an eight year old patient

INTRODUCTION

The presence of MUC5AC (M1 antigen) and MUC6 have previously been found in ovarian mucinous cyst. We characterized the mucins in the crude mucus and tissue of a mature ovarian teratoma in an 8 year old girl.

MATERIALS AND METHODS

Mucins were purified from crude mucus by density gradient ultra-centrifugation in CsCl and analysed by gel-filtration and SDS-PAGE analysis. Mucin identification and expression was by western blotting and immunohistochemistry.

RESULTS

Histology showed a tumour with solid and cystic areas, with the cysts lined by colonic and respiratory mucosae. Equal volumes of 'sol' and 'gel' phases of approximately 10.0 ml of crude mucus were obtained. Gel filtration and SDS-PAGE analyses suggested that the mucin was mainly of the large polymeric type which dissociated upon reduction of disulphide bonds with DTT. The colonic and respiratory epithelia predominantly expressed acidic mucin of the sialated and sulphated types respectively. MUC1 and MUC1c were expressed exclusively in respiratory epithelium, MUC2 and some MUC6 (focal) in the colonic tissue and MUC5AC in both tissues. Western blotting confirmed the presence of MUC2, MUC5AC and MUC5B in the secreted gel. Serine, threonine and proline made up the bulk of the amino acids in the sample.

DISCUSSION

Ovarian teratoma produced a highly viscous mucus secretion in which the mucin was largely polymeric and of the MUC2, MUC5AC and MUC5B type. The respiratory component of the teratoma expressed MUC1 and MUC1c and the colonic components of the teratoma expressed MUC2 and some MUC6. MUC5AC was expressed in both components.

Effect of pro-inflammatory stimuli on mucin expression and inhibition by secretory leucoprotease inhibitor

Stimuli-induced expression of certain mucin genes has been demonstrated to occur as a result of ligand-dependent activation of the epidermal growth factor receptor (EGFR). In particular, MUC5AC expression can be induced by cigarette-smoke, neutrophil elastase and lipopolysaccharide (LPS) following activation of tumour necrosis factor alpha-converting enzyme. We now show that a large of number of stimuli relevant to the cystic fibrosis lung - neutrophil elastase, LPS, Pam3Cys-Ser-(Lys)4 Hydrochloride (a lipopeptide analogue), CpG DNA (which mimics bacterial DNA) and cystic fibrosis bronchoalveolar lavage fluid - can activate MUC1 and 2 expression as well as MUC5AC expression in lung epithelial cells via an EGFR-dependent mechanism. In addition, we demonstrate that the immunomodulatory anti-protease, secretory leucoprotease inhibitor, can inhibit stimuli-induced MUC1, 2 and 5AC expression via a mechanism that is primarily dependent on the inhibition of transforming growth factor type alpha release. Therefore, mucin gene expression, induced by cystic fibrosis respiratory stimuli, can be inhibited by secretory leucoprotease inhibitor indicating its potential importance as an anti-mucin agent in cystic fibrosis and other chronic lung diseases characterized by mucus hypersecretion.

Differential Muc2 and Muc5ac secretion by stimulated guinea pig tracheal epithelial cells in vitro

BACKGROUND

Mucus overproduction is a characteristic of inflammatory pulmonary diseases including asthma, chronic bronchitis, and cystic fibrosis. Expression of two mucin genes, MUC2 and MUC5AC, and their protein products (mucins), is modulated in certain disease states. Understanding the signaling mechanisms that regulate the production and secretion of these major mucus components may contribute significantly to development of effective therapies to modify their expression in inflamed airways.

METHODS

To study the differential expression of Muc2 and Muc5ac, a novel monoclonal antibody recognizing guinea pig Muc2 and a commercially-available antibody against human MUC5AC were optimized for recognition of specific guinea pig mucins by enzyme-linked immunosorbent assay (ELISA), Western blot, and immunohistochemistry (IHC). These antibodies were then used to analyze expression of Muc2 and another mucin subtype (likely Muc5ac) in guinea pig tracheal epithelial (GPTE) cells stimulated with a mixture of pro-inflammatory cytokines [tumor necrosis factor-alpha (TNF-alpha), interleukin 1beta (IL-1beta), and interferon- gamma (IFN-gamma)].

RESULTS

The anti-Muc2 (C4) and anti-MUC5AC (45M1) monoclonal antibodies specifically recognized proteins located in Muc2-dominant small intestinal and Muc5ac-dominant stomach mucosae, respectively, in both Western and ELISA experimental protocols. IHC protocols confirmed that C4 recognizes murine small intestine mucosal proteins while 45M1 does not react. C4 and 45M1 also stained specific epithelial cells in guinea pig lung sections. In the resting state, Muc2 was recognized as a highly expressed intracellular mucin in GPTE cells in vitro. Following cytokine exposure, secretion of Muc2, but not the mucin recognized by the 45M1 antibody (likely Muc5ac), was increased from the GPTE cells, with a concomitant increase in intracellular expression of both mucins.

CONCLUSION

Given the tissue specificity in IHC and the differential hybridization to high molecular weight proteins by Western blot, we conclude that the antibodies used in this study can recognize specific mucin subtypes in guinea pig airway epithelium and in proteins from GPTE cells. In addition, Muc2 is highly expressed constitutively, modulated by inflammation, and secreted differentially (as compared to Muc5ac) in GPTE cells. This finding contrasts with expression patterns in the airway epithelium of a variety of mammalian species in which only Muc5ac predominates.

Regulation of mucin expression: mechanistic aspects and implications for cancer and inflammatory diseases

Mucins are large multifunctional glycoproteins whose primary functions are to protect and lubricate the surfaces of epithelial tissues lining ducts and lumens within the human body. Several lines of evidence also support the involvement of mucins in more complex biological processes such as epithelial cell renewal and differentiation, cell signaling, and cell adhesion. Recent studies have uncovered the role of select mucins in the pathogenesis of cancer, underscoring the importance of a detailed knowledge about mucin biology. Under normal physiological conditions, the production of mucins is optimally maintained by a host of elaborate and coordinated regulatory mechanisms, thereby affording a well-defined pattern of tissue-, time-, and developmental state-specific distribution. However, mucin homeostasis may be disrupted by the action of environmental and/or intrinsic factors that affect cellular integrity. This results in an altered cell behavior that often culminates into a variety of pathological conditions. Deregulated mucin production has indeed been associated with numerous types of cancers and inflammatory disorders. It is, therefore, crucial to comprehend the underlying basis of molecular mechanisms controlling mucin production in order to design and implement adequate therapeutic strategies for combating these diseases. Herein, we discuss some physiologically relevant regulatory aspects of mucin production, with a particular emphasis on aberrations that pertain to pathological situations. Our views of the achievements, the conceptual and technical limitations, as well as the future challenges associated with studies of mucin regulation are exposed.

The role of airway epithelium and blood neutrophils in the inflammatory response in cystic fibrosis

Cystic fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene, which accounts for the cAMP-modulated chloride conductance of airway epithelial cells. CFTR also regulates other membrane proteins like the negative regulation of the amiloride-sensitive epithelial sodium channel (ENaC). Mutations in the CFTR gene lead to hyperabsorption of sodium chloride and a reduction in the periciliary salt and water content which leads to impaired mucociliary clearance. It seems that a lack of functional CFTR leads to abnormal function of the NF-kappaB pathway in submucosal gland cells, causing an increased production of pro-inflammatory cytokines and the chemokine IL-8, and a pro-inflammatory environment. CFTR is also expressed in neutrophils and several neutrophil functions like cytokine production, migration, phagocytosis and apoptosis seem altered in CF. In this review we describe the role of airway epithelium and blood neutrophils in the viscious circle of inflammation and infection seen in CF.

Innate host defense of the lung: effects of lung-lining fluid pH

Lung-lining fluid (LLF) is a primary constituent of the pulmonary host defense system. It is distributed continuously throughout the respiratory tract but is heterogeneous regarding its chemistry and physiology between the conducting airways and alveoli. The conducting airways are lined with airway surface liquid (ASL), a mucus gel-aqueous sol complex that interacts functionally with epithelial cilia as the mucociliary escalator. The alveoli are lined with alveolar subphase fluid (AVSF) and pulmonary surfactant. AVSF sterility is maintained in part by the phagocytic activity of resident alveolar macrophages. Normal ASL and AVSF are both more acidic than blood plasma. However, the details of acid-base regulation differ between the two media. Appreciable transepithelial acid-base flux is possible across the airway epithelium, whereas the alveolar epithelium is relatively impermeable to transepithelial acid-base flux. Moreover, one must consider the influence of resident macrophages on AVSF pH. Resident macrophages occupy a sizable fraction of AVSF by volume and are a substantial source of metabolic H+. The buffering capacities of ASL and AVSF probably are largely due to secreted peptides (e.g., ASL mucins and AVSF surfactant proteins). Acid-base exchange between the extracellular hydrophase and intracellular buffering systems of resident macrophages represents an additional buffer pool for AVSF. The pH of ASL and AVSF can be depressed by disease or inflammation. Low pH is predicted to suppress microbe clearance from the airways and alveoli, increase pathogen survival in both regions, and alter mediator release by resident macrophages and recruited leukocytes thereby increasing the propensity for bystander cell injury. Overall, ASL/AVSF pH is expected to be a major determinant of lung host defense responses.

Differential regulation of MUC5AC/Muc5ac and hCLCA-1/mGob-5 expression in airway epithelium

This study demonstrates that the two biomarkers, MUC5AC/ Muc5ac and hCLCA1/Gob5, which are frequently associated with surface mucous/goblet cells in asthmatic airways, are differentially regulated. Intratracheal instillation of IL-13 (0.5 mug/mouse lung) elicited 8- and 110-fold induction of Muc5ac and Gob5 messages, respectively, within 24 h in wild-type mouse lung, whereas these inductions were abrogated in Stat6 knockout mice. The induction of MUC5AC/Muc5ac message could not be duplicated in vitro with primary tracheobronchial epithelial (TBE) cells derived from wild-type mice or humans, despite significant inductions still seen for hCLCA1/Gob5. Further studies with JAK inhibitors and STAT6 signaling showed active signaling of the JAK/STAT6 pathway in these primary TBE cultures by IL-13 in the regulation of hCLCA1 expression. Dual immunofluorescent staining with antibodies specific to MUC5AC and hCLCA1 revealed a differential nature of the expression of these two biomarkers by distinct cell types of primary TBE cultures. Finally, MUC5AC expression could be elevated by a bacterial product, peptidoglycan, without any induction of hCLCA1. Thus, these results suggest that the two biomakers of the metaplastic airway mucous cell type are differentially regulated by JAK/STAT6-dependent and -independent pathways.

Immunofluorescence assay for detection of the nucleocapsid antigen of the severe acute respiratory syndrome (SARS)-associated coronavirus in cells derived from throat wash samples of patients with SARS

An antigen detection assay for severe acute respiratory syndrome (SARS) coronavirus was established in this study by an indirect immunofluorescence test, which utilized cells derived from throat wash samples of patients with SARS and a rabbit serum that recognized the nucleocapsid protein of SARS-associated coronavirus (SARS-CoV) but not that of other human coronavirus tested. It detected SARS-CoV in 11 of 17 (65%) samples from SARS patients as early as day 2 of illness but in none of the 10 samples from healthy controls. Compared with other diagnostic modalities for detecting SARS-CoV, this assay is simpler, more convenient, and economical. It could be an alternative for early and rapid diagnosis, should SARS return in the future.

A549 lung epithelial cells grown as three-dimensional aggregates: alternative tissue culture model for Pseudomonas aeruginosa pathogenesis

A three-dimensional (3-D) lung aggregate model was developed from A549 human lung epithelial cells by using a rotating-wall vessel bioreactor to study the interactions between Pseudomonas aeruginosa and lung epithelial cells. The suitability of the 3-D aggregates as an infection model was examined by immunohistochemistry, adherence and invasion assays, scanning electron microscopy, and cytokine and mucoglycoprotein production. Immunohistochemical characterization of the 3-D A549 aggregates showed increased expression of epithelial cell-specific markers and decreased expression of cancer-specific markers compared to their monolayer counterparts. Immunohistochemistry of junctional markers on A549 3-D cells revealed that these cells formed tight junctions and polarity, in contrast to the cells grown as monolayers. Additionally, the 3-D aggregates stained positively for the production of mucoglycoprotein while the monolayers showed no indication of staining. Moreover, mucin-specific antibodies to MUC1 and MUC5A bound with greater affinity to 3-D aggregates than to the monolayers. P. aeruginosa attached to and penetrated A549 monolayers significantly more than the same cells grown as 3-D aggregates. Scanning electron microscopy of A549 cells grown as monolayers and 3-D aggregates infected with P. aeruginosa showed that monolayers detached from the surface of the culture plate postinfection, in contrast to the 3-D aggregates, which remained attached to the microcarrier beads. In response to infection, proinflammatory cytokine levels were elevated for the 3-D A549 aggregates compared to monolayer controls. These findings suggest that A549 lung cells grown as 3-D aggregates may represent a more physiologically relevant model to examine the interactions between P. aeruginosa and the lung epithelium during infection.

Reevaluating gel-forming mucins' roles in cystic fibrosis lung disease

The existence of mucus plugs, containing mucins, bacteria, and neutrophils, blocking the lower airways in the lung of cystic fibrosis (CF) patients has raised the possibility that production of "abnormal" mucins is a critical characteristic of this disease. The molecular nature, if any, of this abnormality is unknown. Recent studies suggest that CF lung disease progression is characterized by an early phase in which airway surface liquid (ASL) increased dehydration is accompanied by altered pH and levels of reduced glutathione (GSH). In a later phase, bacterial infection and neutrophil invasion lead to increased ASL of concentrations myeloperoxidase and hypochlorous acid (HOCl). Independent studies indicate that gel-forming mucins, the key components of airway mucus, form disulfide-linked polymers through a pH-dependent, likely self-catalyzed mechanism. In this article, we present the hypothesis that increased mucus concentration (dehydration) and altered pH, and levels of GSH, myeloperoxidase, and/or HOCl result in the extracellular formation of additional interchain bonds among airway mucins. These novel interactions would create an atypical mucin network with abnormal viscoelastic and adhesive properties.

Reduced airway inflammation and remodeling in parallel with mucin 5AC protein expression decreased by s-carboxymethylcysteine, a mucoregulant, in the airways of rats exposed to sulfur dioxide

BACKGROUND

Human obstructive airway diseases are histopathologically characterized by inflammatory cell infiltration, goblet cell hyperplasia, and mucus hypersecretion in airways. We prepared a rat model of airway injury by exposure of sulfur dioxide (SO2) and then evaluated the effects of S-carboxymethylcysteine (S-CMC), a mucoregulant.

METHODS

Rats were exposed to SO2 gas for 44 days and orally given S-CMC at 250 mg/kg, twice daily, from 21 to 44 days of exposure for histopathological and immunohistochemical evaluation.

RESULTS

SO2 exposure induced inflammatory cell infiltration and mucus cell increase in rat airways. S-CMC treatment significantly decreased this inflammatory cell infiltration in proximal and peripheral airways. Morphometrically, SO2 exposure significantly increased the number of Alcian blue (pH 2.5)- and periodic acid-Schiff (AB/PAS)-positive cells in rat airways (11.8 x 10(-2) cell/nuclear profiles per micrometer basement membrane) compared to normal rat airways (1.6 x 10(-2) cell/nuclear profiles per micrometer basement membrane). S-CMC treatment significantly decreased the number of AB/PAS-positive cells (4.4 x 10(-2) cell/nuclear profiles per micrometer basement membrane, p < 0.01 vs. SO2-exposed rats). Immunohistochemically, SO2 exposure increased the expression of mucin 5AC (MUC5AC) protein in the airway epithelium of rats, but S-CMC treatment inhibited the increase.

CONCLUSIONS

The increased mucus cells and MUC5AC protein expression seem associated with SO2-induced airway inflammation in rats. The fact that S-CMC suppresses airway inflammation and the increase in mucus cells and MUC5AC protein expression suggests that this mucoregulant may be advantageous in the treatment of inflammatory airway diseases with goblet cell hyperplasia.

Pulmonary mucus: Pediatric perspective

Airway mucus hypersecretion is a clinical feature of a number of childhood diseases, including asthma and bronchitis-associated conditions. However, compared with adults, there is relatively scarce information concerning mucus pathophysiology in respiratory diseases in children. The available evidence indicates many similarities between adult and childhood respiratory hypersecretory conditions, including goblet-cell hyperplasia and submucosal gland hypertrophy, and airway mucus plugging in asthma. Consequently, it is likely that treatments that are effective in adults would be effective in children. Numerous therapeutic targets are linked to the pathophysiology of airway mucus hypersecretion in experimental models and adults with respiratory disease. Whether or not these same targets are relevant in children is for the most part unclear. These targets include the inflammatory cells mediating the inflammatory response that generates the hypersecretory phenotype, and highly specific cellular elements such as epidermal growth factor receptor tyrosine kinase and calcium-activated chloride (CACL) channels. Identification of these factors is linked with the development of different classes of pharmacotherapeutic molecules directed at these targets. Compounds with a broader spectrum of anti-inflammatory activity are likely to be more effective than compounds with restricted activity. However, certain highly specific targets, such as human CACL1 channels, appear to be strongly associated with the development of an airway hypersecretory phenotype. Data from current clinical trials in adults with blockers of these specific targets are awaited with great interest. The hope is that, if effective, pediatric trials with these compounds could be initiated with a view to alleviation of the clinical impact of airway mucus hypersecretion in children. A significant challenge to the therapeutic progression of these new compounds is effective delivery to the airways in children, with the research effort into development of new compounds matched by advances in inhaler design.

Stimulation of airway mucin gene expression by interleukin (IL)-17 through IL-6 paracrine/autocrine loop

Mucus hypersecretion and persistent airway inflammation are common features of various airway diseases, such as asthma, chronic obstructive pulmonary disease, and cystic fibrosis. One key question is: does the associated airway inflammation in these diseases affect mucus production? If so, what is the underlying mechanism? It appears that increased mucus secretion results from increased mucin gene expression and is also frequently accompanied by an increased number of mucous cells (goblet cell hyperplasia/metaplasia) in the airway epithelium. Many studies on mucin gene expression have been directed toward Th2 cytokines such as interleukin (IL)-4, IL-9, and IL-13 because of their known pathophysiological role in allergic airway diseases such as asthma. However, the effect of these cytokines has not been definitely linked to their direct interaction with airway epithelial cells. In our study, we treated highly differentiated cultures of primary human tracheobronchial epithelial (TBE) cells with a panel of cytokines (interleukin-1alpha, 1beta, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15, 16, 17, 18, and tumor necrosis factor alpha). We found that IL-6 and IL-17 could stimulate the mucin genes, MUC5B and MUC5AC. The Th2 cytokines IL-4, IL-9, and IL-13 did not stimulate MUC5AC or MUC5B in our experiments. A similar stimulation of MUC5B/Muc5b expression by IL-6 and IL-17 was demonstrated in primary monkey and mouse TBE cells. Further investigation of MUC5B expression demonstrated that IL-17's effect is at least partly mediated through IL-6 by a JAK2-dependent autocrine/paracrine loop. Finally, evidence is presented to show that both IL-6 and IL-17 mediate MUC5B expression through the ERK signaling pathway.