Oral N-acetylcysteine reduces bleomycin-induced lung damage and mucin Muc5ac expression in rats.

Oxidative stress is involved in the pathogenesis of pulmonary fibrosis, therefore antioxidants may be of therapeutic value. Clinical work indicates that N-acetylcysteine (NAC) may be beneficial in this disease. The activity of this antioxidant was examined on bleomycin-induced lung damage, mucus secretory cells hyperplasia and mucin Muc5ac gene expression in rats. NAC (3 mmol x kg(-1) x day(-1)) or saline was given orally to Sprague-Dawley rats for 1 week prior to a single intratracheal instillation of bleomycin (2.5 U x kg(-1)) and for 14 days postinstillation. NAC decreased collagen deposition in bleomycin-exposed rats (hydroxyproline content was 4,257+/-323 and 3,200+/-192 microg x lung(-1) in vehicle- and NAC-treated rats, respectively) and lessened the fibrotic area assessed by morphometric analysis. The bleomycin-induced increases in lung tumour necrosis factor-alpha and myeloperoxidase activity were reduced by NAC treatment. The numbers of mucus secretory cells in airway epithelium, and the Muc5ac messenger ribonucleic acid and protein expression, were markedly augmented in rats exposed to bleomycin. These changes were significantly reduced in NAC-treated rats. These results indicate that bleomycin increases the number of airway secretory cells and their mucin production, and that oral N-acetylcysteine improved pulmonary lesions and reduced the mucus hypersecretion in the bleomycin rat model.     

Overexpressing mouse model demonstrates the protective role of Muc5ac in the lungs

MUC5AC, a major gel-forming mucin expressed in the lungs, is secreted at increased rates in response to infectious agents, implying that mucins exert a protective role against inhaled pathogens. However, epidemiological and pathological studies suggest that excessive mucin secretion causes airways obstruction and inflammation. To determine whether increased MUC5AC secretion alone produces airway obstruction and/or inflammation, we generated a mouse model overexpressing Muc5ac mRNA ∼20-fold in the lungs, using the rCCSP promoter. The Muc5ac cDNA was cloned from mouse lungs and tagged internally with GFP. Bronchoalveolar lavage fluid (BALF) analysis demonstrated an approximate 18-fold increase in Muc5ac protein, which formed high-molecular-weight polymers. Histopathological studies and cell counts revealed no airway mucus obstruction or inflammation in the lungs of Muc5ac-transgenic (Muc5ac-Tg) mice. Mucus clearance was preserved, implying that the excess Muc5ac secretion produced an “expanded” rather than more concentrated mucus layer, a prediction confirmed by electron microscopy. To test whether the larger mucus barrier conferred increased protection against pathogens, Muc5ac-Tg animals were challenged with PR8/H1N1 influenza viruses and showed significant decreases in infection and neutrophilic responses. Plaque assay experiments demonstrated that Muc5ac-Tg BALF and purified Muc5ac reduced infection, likely via binding to α2,3-linked sialic acids, consistent with influenza protection in vivo. In conclusion, the normal mucus transport and absence of a pulmonary phenotype in Muc5ac-Tg mice suggests that mucin hypersecretion alone is not sufficient to trigger luminal mucus plugging or airways inflammation/goblet cell hyperplasia. In contrast, increased Muc5ac secretion appears to exhibit a protective role against influenza infection.     

In vivo and in vitro effects of macrolide antibiotics on mucus secretion in airway epithelial cells

To examine the in vivo effects of macrolide antibiotics on mucus hypersecretion, we induced hypertrophic and metaplastic changes of goblet cells in rat nasal epithelium by intranasal instillation of ovalbumin (OVA) in OVA-sensitized rats and by intranasal LPS instillation. Oral administration of clarithromycin (CAM) (5-10 mg/kg) significantly inhibited OVA- and LPS-induced mucus production and neutrophil infiltration, whereas josamycin and ampicillin showed no effect. In vitro effects of macrolide antibiotics on airway epithelial cells were examined using NCI-H292 cells and human nasal epithelial cells cultured in air-liquid interface. Mucus secretion was evaluated by ELISA using anti-mucin monoclonal antibodies (anti-MUC5AC and HCS18). CAM and erythromycin significantly inhibited spontaneous and tumor necrosis factor-alpha (20 ng/ml)-induced mucus secretion from NCI-H292 cells at 10-6 to 10-7 M and from human nasal epithelial cells at 10-4 to 10-5 M. MUC5AC messenger RNA expression was also significantly inhibited. These results indicate that the 14-member macrolide antibiotics, CAM and erythromycin, exert direct inhibitory effects on mucus secretion from airway epithelial cells and that they may be useful for the treatment of mucus hypersecretion caused by allergic inflammation and LPS stimulation.     

水通道蛋白敲除对支气管哮喘小鼠气道黏蛋白谱表达的影响

目的 水通道蛋白5(aquaporin 5,AQP5)敲除对支气管哮喘(简称哮喘)小鼠气道黏蛋白(MUC)谱表达的影响.方法 用卵白蛋白致敏和激发制备AQP5敲除鼠的哮喘高分泌模型.用苏木精-伊红染色观察气道及血管周围炎性细胞浸润.阿辛兰-过碘酸雪夫检测显示气道上皮细胞总黏液分泌,免疫组织化学检测气道上皮MUC5AC,MUC5B,MUC2的表达情况.结果 哮喘小鼠气道和血管周围可见大量中性粒细胞,淋巴细胞和嗜酸粒细胞浸润,气道上皮有大量的紫红色中性黏液分布,其中以AQP5敲除鼠总黏液分布更多.免疫组织化学显示小鼠哮喘高分泌模型中MUC谱主要为MUC5AC和MUC5B,未见MUC2分布.与野生型哮喘小鼠比较,MUC5AC、MUC5B在AQP5敲除鼠中表达更丰富.结论 AQP5基因缺失可能使小鼠气道对过敏原的应激性提高,从而促进黏液高分泌.     

白细胞介素-13对人支气管上皮细胞SPDEF表达的影响及SPDEF在哮喘气道黏液高分泌中的作用

目的探讨白细胞介素(IL)-13对人支气管上皮细胞SPDEF表达的影响及SPDEF在哮喘气道黏液高分泌中的作用。方法将人原代支气管上皮细胞(NHBE细胞)分为对照组、IL-13组及IL-13+SPDEF siRNA组。培养28天后,收集NHBE细胞并提取总RNA,采用实时荧光定量聚合酶链反应检测NHBE细胞SPDEF、粘蛋白MUC5AC及MUC5B mRNA的表达水平,流式细胞术检测MUC5AC阳性细胞数量和免疫荧光强度,免疫荧光染色检测粘蛋白MUC5AC和MUC5B的表达水平。结果IL-13组NHBE细胞SPDEF和MUC5AC mRNA的表达水平、MUC5AC阳性细胞数量和免疫荧光强度均明显高于对照组(P<0.001),而MUC5B mRNA的表达水平明显低于对照组(P<0.05);IL-13+SPDEF siRNA组NHBE细胞SPDEF和MUC5AC mRNA的表达水平、MUC5AC阳性细胞数量和免疫荧光强度均明显低于IL-13组(P<0.001);IL-13+SPDEF siRNA组MUC5B mRNA的表达水平明显低于对照组(P<0.05)。IL-13组NHBE细胞MUC5AC的表达水平明显高于对照组和IL-13+SPDEF siRNA组,而MUC5B的表达水平低于对照组。结论IL-13可能通过诱导人支气管上皮细胞SPDEF上调,促进气道粘蛋白MUC5AC的高表达,引起哮喘气道黏液高分泌。     

Respiratory syncytial virus in allergic lung inflammation increases Muc5ac and gob-5

Respiratory syncytial virus (RSV) is associated with wheezing and childhood asthma. We previously reported that RSV infection prolongs methacholine-induced airway hyperresponsiveness in ovalbumin (OVA)-sensitized mice. In addition, allergically sensitized RSV-infected (OVA/RSV) mice had more abundant airway epithelial mucus production compared with OVA mice 14 days after infection, whereas there was almost no mucus in mice that were only RSV infected. We hypothesized that this increased mucus was associated with mucosal expression of Muc5ac, a mucus gene expression in airways, and gob-5, a member of the Ca(2)(+)-activated chloride channel family. By histochemical analysis, we found that there was significantly increased staining for gob-5 and Muc5ac in the airways of OVA/RSV mice compared with either OVA mice or allergically sensitized mice that were challenged with inactivated RSV, and virtually no detectable staining in the RSV group. These findings were confirmed by Western blot analysis. The increased mucus expression in the OVA/RSV group was associated with increased lung levels of interleukin-17, a factor known to stimulate airway mucin gene expression. The impact of virus infection combined with allergic inflammation on mucus production may partially explain the more severe disease and airway hyperresponsiveness associated with RSV in the setting of atopy.     

Role of Neutrophils in Mucus Hypersecretion in COPD and Implications for Therapy

Airway mucus hypersecretion is a serious and presently untreatable symptom of COPD. Over the past several years, emerging evidence has implicated epidermal growth factor receptor (EGFR) expression and activation in mucin production by airway epithelial (goblet) cells. Activated neutrophils recruited to the airways (and their secreted products) play several key roles in EGFR-dependent mucus hypersecretion: (i) activated neutrophils secrete tumor necrosis factor (TNF)-alpha, which induces EGFR expression in airway epithelial cells; (ii) activated neutrophils release reactive oxygen species, which activate EGFR; (iii) neutrophil elastase cleaves the EGFR proligand, pro-transforming growth factor (TGF)-alpha, releasing mature TGF alpha which activates EGFR in a ligand-dependent fashion; and (iv) neutrophil elastase causes potent goblet cell degranulation. The secretion of active products by neutrophils appears carefully regulated. The local release of neutrophil elastase requires close contact between the neutrophil and another cell, mediated by surface adhesion molecules, thus limiting proteolysis to the immediate pericellular environment. In the airway lumen, neutrophils undergo apoptosis and are cleared by macrophages without releasing their intracellular contents. In contrast, neutrophils that die by necrosis disgorge proteases and reactive oxygen species into the lumen. In COPD, conditions within the airway lumen promote neutrophil necrosis. It is concluded that neutrophil death via necrosis leads to the high concentrations of free neutrophil elastase and reactive oxygen species in the sputum of patients with airway neutrophilia and mucus hypersecretion. Inflammatory cells (neutrophils), molecules (neutrophil elastase and reactive oxygen species), signaling pathways (EGFR), and cellular processes (neutrophil necrosis) contribute to mucus hypersecretion in COPD, and are potential targets for therapy. Interventions that target EGFR, neutrophil elastase, and reactive oxygen species exist and can be evaluated as treatments for neutrophil-dependent mucus hypersecretion.     

Azithromycin, clarithromycin and telithromycin inhibit MUC5AC induction by Chlamydophila pneumoniae in airway epithelial cells

BackgroundAirway mucus hypersecretion is an important problem in chronic respiratory diseases including bronchial asthma. Chlamydophila pneumoniae is recently confirmed to be a pathogen in bronchial asthma, but the relationship between C. pneumoniae and mucus hypersecretion is uncertain. In this study, we examined whether C. pneumoniae induces MUC5AC mucin in airway epithelial cells. We also examined the effects of macrolide and ketolide antibiotics on the C. pneumoniae-induced mucus production.MethodsMUC5AC production in bronchial epithelial cells after stimulation with C. pneumoniae was analyzed by ELISA and quantitative RT-PCR. NF-κB and phosphorylated ERK were also analyzed. For inhibition study, cells were pretreated with azithromycin, clarithromycin and telithromycin before stimulation.ResultsC. pneumoniae dose-dependently induced MUC5AC production and gene expression. The ERK-NF-κB pathway was involved in C. pneumoniae-induced MUC5AC production. Macrolides and ketolides dose-dependently reduced C. pneumoniae-induced MUC5AC production. However, azithromycin was apparently less effective than the other antibiotics. Clarithromycin and telithromycin, but not azithromycin, reduced NF-κB activation.ConclusionsClarithromycin and telithromycin were thought to interfere with the signal pathways between ERK and NF-κB. These results suggest that airway mucus hypersecretion is one of the mechanisms of C. pneumoniae-induced bronchial asthma, and that macrolide and ketolide antibiotics represent a novel therapeutic intervention in these patients.     

气道黏液高分泌及其调节

正常情况下气道黏膜下腺体在MUC5B调控下分泌少量黏液,具有吸附吸入的微粒及病原菌等屏障作用;病理状态下存在黏液细胞增生、化生,黏液过度分泌导致气道狭窄.气道黏液高分泌的机制复杂,且针对高分泌目前缺乏有效治疗手段.新近研究显示,气道黏蛋白基因上调及其下游信号的激活是上述病理改变的基础.调控黏蛋白基因抑或成为未来治疗气道黏液高分泌的方向.     

白介素17在实验性支气管哮喘小鼠气道杯状细胞化生和黏液分泌中的作用

目的 观察经鼻滴人白介素17(interleukin-17,IL-17)对支气管哮喘(简称哮喘)小鼠气道杯状细胞表达Muc5ac黏蛋白的影响,探讨IL-17与哮喘黏液分泌的关系.方法 应用免疫组织化学法测定正常对照组、哮喘组、IL-17组及抗IL-17组肺组织黏蛋白Muc5ac的表达及应用AB-PAS染色观察支气管壁杯状细胞数量的差异.结果 Muc5ac蛋白阳性表达细胞均主要位于气道上皮,细胞胞浆呈棕黄色.与哮喘组相比,IL-17组黏蛋白Muc5ac表达量明显增加(P<0.01),抗IL-17组表达显著减少(P<0.01).AB-PAS染色结果同上.结论 IL-17具有增强哮喘小鼠气道黏液分泌的作用.     

水通道蛋白敲除对支气管哮喘小鼠气道黏蛋白谱表达的影响

目的水通道蛋白5（aquaporin5,AQP5）敲除对支气管哮喘（简称哮喘）小鼠气道黏蛋白（MUC）谱表达的影响。方法用卵白蛋白致敏和激发制备AQP5敲除鼠的哮喘高分泌模型。用苏木精-伊红染色观察气道及血管周围炎性细胞浸润。阿辛兰-过碘酸雪夫检测显示气道上皮细胞总黏液分泌,免疫组织化学检测气道上皮MUC5AC,MUC5B,MUC2的表达情况。结果哮喘小鼠气道和血管周围可见大量中性粒细胞,淋巴细胞和嗜酸粒细胞浸润,气道上皮有大量的紫红色中性黏液分布,其中以AQP5敲除鼠总黏液分布更多。免疫组织化学显示小鼠哮喘高分泌模型中MUC谱主要为MUC5AC和MUC5B,未见MUC2分布。与野生型哮喘小鼠比较,MUC5AC、MUC5B在AQP5敲除鼠中表达更丰富。结论AQP5基因缺失可能使小鼠气道对过敏原的应激性提高,从而促进黏液高分泌。     

蓝玉簪颗粒抑制慢性支气管哮喘小鼠气道黏液高分泌及Bcl-2表达

目的观察蓝玉簪颗粒对慢性支气管哮喘（简称哮喘）小鼠气道上皮杯状细胞化生及黏液高分泌的抑制作用并探讨其机制。方法32只BABL／C小鼠随机分成正常对照组（A组）、慢性哮喘模型组（B组）、蓝玉簪颗粒组（C组,0．33g生药／kg体质量）和地塞米松干预组（D组,2．0mg／kg体质量）,每组8只。卵白蛋白腹腔注射致敏并长期雾化吸入制备小鼠慢性哮喘模型。阿尔辛蓝-过碘酸-希夫（AB-PAS）染色观察气道上皮杯状细胞增生、黏液分泌情况,免疫组织化学半定量法测定气道壁Bcl-2含量。计算机图象分析软件测定气道壁Bcl-2、AB-PAS染色阳性面积和气道上皮层面积（Aep）与气道基底膜周径（Pbm）比值（如Aep／Pbm,Bcl-2／Pbm）等。结果B组小鼠气道上皮层增生,气道黏液分泌显著增加,气道壁Bcl-2表达增强;B组A昏PAS／Phm,Bcl-2／Pbm等值较C组均显著增高（P〈0．01）;B组和C组Aep／Pbm值比较差异有统计学意义（P〈0．01）,C组与D组比较差异无统计学意义;AB-PAS／Pbm与Bcl-2／Pbm呈显著正相关（r=0．671,P〈0．01）,Aep／Pbm与Bcb2表达也呈显著正相关（r=0．784,P〈0．001）。结论蓝玉簪颗粒可以抑制慢性哮喘小鼠气道上皮杯状细胞增殖和黏液高分泌,其部分机制可能通过抑制Bcl-2的表达实现。     

过氧化物酶体增殖物激活受体-γ及其配体在大鼠气道黏液高分泌中的作用

目的 探讨过氧化物酶体增殖物激活受体-γ(PPAR-γ)及其配体对气道黏液高分泌的作用及其机制.方法 应用随机数字表法将36只SD大鼠随机分为4组,其中生理盐水对照组(6只)雾化吸入生理盐水;罗格列酮对照组(6只)雾化吸入生理盐水,同时给予罗格列酮8 mg/kg灌胃;丙烯醛组(6只)雾化吸入丙烯醛3.0 mg/L,6 h/d,连续12 d;罗格列酮干预组根据不同剂量又分为低、中、高剂最组,每组各6只,在雾化吸入丙烯醛的同时分别给予2、4和8 mg/kg罗格列酮灌胃.采用HE染色及阿辛蓝-过碘酸雪夫染色法观察支气管肺组织的病理改变和气道黏液物质改变,应用实时荧光定量逆转录-PCR及免疫组织化学SP法检测黏蛋白5AC和PPAR-γ的表达水平.组间比较采用方差分析,两组比较采用q检验,相关性分析采用Pearson法.结果 丙烯醛组、生理盐水对照组及低、中、高剂量罗格列酮干预组气道黏液物质的相对着色而积分别为(60.2±9.3)%、(4.9±1.0)%、(53.3±8.5)%、(26.5±7.4)%和(12.5±3.7)%,组间比较差异有统计学意义(F=93.80,P＜0.01).黏蛋白5AC蛋白在丙烯醛组、生理盐水对照组及低、中、高剂量罗格列酮干预组表达的积分吸光度值分别为4339±453、1636±282、3996±346、3048±331和2376±343,组间比较差异有统计学意义(F=67.74,P＜0.01);PPAR-γ蛋白表达的积分吸光度值分别为1159±184、838±151、1272±189、1568±282和1872±270,组间比较差异有统计学意义(F=21.53,P＜0.01).丙烯醛组、生理盐水对照组及低、中、高剂量罗格列酮干预组黏蛋白5AC mRNA表达的相对拷贝数分别为35.3±10.0、2.2±0.7、30.5±10.2、18.6±5.3和10.8±2.6,组问比较差异有统计学意义(F=29.67,P＜0.01);PPAR-γ mRNA的相对拷贝数分别为7.8±1.9、2.0±0.6、9.8±2.8、18.6±5.3和31.6±8.9,组间比较差异有统计学意义(F=39.47,P＜0.01).丙烯醛组PPAR-γ蛋白水平与黏蛋白5AC mRNA表达呈负相关(r=-0.880,P＜0.01).结论 丙烯醛致气道黏液高分泌过程与PPAR-γ表达异常有关;PPAR-γ及其配体罗格列酮可以抑制丙烯醛诱导的气道黏液高分泌,其具体机制可能与下调黏蛋白5AC的表达有关.     

Understanding asthma pathophysiology.

Asthma is best described as a chronic disease that involves inflammation of the pulmonary airways and bronchial hyperresponsiveness that results in the clinical expression of a lower airway obstruction that usually is reversible. Physiologically, bronchial hyperresponsiveness is documented by decreased bronchial airflow after bronchoprovocation with methacholine or histamine. Other triggers that provoke airway obstruction include cold air, exercise, viral upper respiratory infection, cigarette smoke, and respiratory allergens. Bronchial provocation with allergen induces a prompt early phase immunoglobulin E (IgE)-mediated decrease in bronchial airflow (forced expiratory volume in 1 second) followed in many patients by a late-phase IgE-mediated reaction with a decrease in bronchial airflow for 4-8 hours. The gross pathology of asthmatic airways displays lung hyperinflation, smooth muscle hypertrophy, lamina reticularis thickening, mucosal edema, epithelial cell sloughing, cilia cell disruption, and mucus gland hypersecretion. Microscopically, asthma is characterized by the presence of increased numbers of eosinophils, neutrophils, lymphocytes, and plasma cells in the bronchial tissues, bronchial secretions, and mucus. Initially, there is recruitment of leukocytes from the bloodstream to the airway by activated CD4 T-lymphocytes. The activated T-lymphocytes also direct the release of inflammatory mediators from eosinophils, mast cells, and lymphocytes. In addition, the subclass 2 helper T-lymphocytes subset of activated T-lymphocytes produces interleukin (IL)-4, IL-5, and IL-13. IL-4 in conjunction with IL-13 signals the switch from IgM to IgE antibodies. The cross-linkage of two IgE molecules by allergen causes mast cells to degranulate, releasing histamine, leukotrienes, and other mediators that perpetuate the airway inflammation. IL-5 activates the recruitment and activation of eosinophils. The activated mast cells and eosinophils also generate their cytokines that help to perpetuate the inflammation. Regardless of the triggers of asthma, the repeated cycles of inflammation in the lungs with injury to the pulmonary tissues followed by repair may produce long-term structural changes ("remodeling") of the airways. This review will discuss in greater detail the relationships of inflammation and airway hyperresponsiveness to the pathophysiology of asthma.     

In silico cloning of mouse Muc5b gene and upregulation of its expression in mouse asthma model

Using a BLAST-searching approach, we identified a mouse expressed sequence tag (EST) clone (AA038672) showing great similarity to the 3' end of the human MUC5B gene. The clone was named "3pmmuc5b-1" after complete nucleotide sequencing (Genbank Accession, AF369933). A subsequent search of the mouse genome database with the 3pmmuc5b-1 sequence identified two overlapping genomic clones (AC020817 and AC020794) that contained the sequence of both 3pmmuc5b-1 and the mouse Muc5ac gene. Like their human homologs, the genomic order of the mouse Muc genes is 5'-Muc5ac-Muc5b-3'. These results suggest that the newly identified EST clone, 3pmmuc5b-1, is part of the 3' portion of the mouse Muc5b gene. In situ hybridization demonstrated that this putative mouse Muc5b message was expressed in a restricted manner in the sublingual gland region of the tongue and the submucosal gland region of the mouse trachea in a normal animal. However, the gene expression was greatly enhanced in airway surface epithelium and the submucosal gland region in ovalbumin-induced asthmatic mice. These results were consistent with previous studies of human airway tissues. We therefore conclude that this newly cloned mouse Muc5b gene could be used as a marker for studying aberrant mucin gene expression in mouse models of various airway diseases.     

Mechanisms of pathogenesis in allergic asthma: Role of interleukin‐23

Asthma is a chronic airway inflammatory disease characterized by intense leukocyte and eosinophilic infiltration accompanied by mucus hypersecretion and tissue hyperresponsiveness. Recent evidence suggests that T‐helper (Th)2 cells and their cytokine products orchestrate the pathology of asthma. In addition, Th17 cells are implicated in the pathogenesis of antigen‐induced airway inflammation. The Th17 related cytokine interleukin (IL)‐23 plays important roles in many immunological diseases, such as experimental autoimmune encephalomyelitis, rheumatoid arthritis, psoriasis and inflammatory bowel disease. Several reports describe the role of IL‐23 in the pathogenesis of allergic asthma in both human and mice. IL‐23 leads to neutrophil infiltration in the airway of asthmatic mice, which is characteristic of severe asthma resulting from Th17 development and subsequently IL‐17 secretion. IL‐23 can also promote eosinophil infiltration in the airway, which is a hallmark of allergic asthma. These studies suggest that IL‐23 could be a promoting factor in the development of allergic asthma and likewise would be a target for asthma therapy. In support of this view, trials of anti‐IL‐23 therapy have been attempted in human and mouse asthma models with encouraging outcomes. This review presents the role of IL‐23 in asthma according to recent clinical trials and animal model studies. The proposed mechanisms of IL‐23‐induced airway inflammation and the agents currently being tested that target IL‐23 related pathways are discussed.     

LPS-induced mucin expression in human sinus mucosa can be attenuated by hCLCA inhibitors

BACKGROUND: hCLCA1 is a member of the calcium-activated chloride channel family and is associated with disease-inducible mucus expression. Niflumic acid (NFA) and a closely related chemical structure are reported inhibitors of calcium-activated chloride channels and endotoxin-inducible mucus expression in the mouse. Therefore, we tested the hypothesis that hCLCA1 may be involved in lipopolysaccharide (LPS) induced mucin up-regulation in human airways. We also investigated the effect of NFA and MSI-2216 on LPS-induced mucin up-regulation. MATERIALS AND METHODS: Explanted human airways and the muco-epidermoid cell line Calu-3 were stimulated with LPS. Different concentrations of NFA or MSI-2216 were added to LPS-stimulated airway mucosa and Calu-3 cells. Expression of hCLCA1 and MUC5AC mRNA and protein was quantified in human airways using real-time PCR and PAS staining. In addition, immunohistochemistry was performed for quantification of inflammatory cells (lymphocytes, monocytes, eosinophils, and neutrophils) in the submucosa of the airways. Expression of hCLCA1 protein in Calu-3 cells was analysed by FACS. RESULTS: LPS significantly induced hCLCA1 and MUC5AC mRNA and protein expression in human airway mucosa (P < 0.05). NFA and MSI-2216 significantly decreased LPS-induced mucus expression in explanted airway mucosa in a dose-dependent manner (P < 0.05). In Calu-3 cells, LPS significantly increased hCLCA1 surface expression whereas intracellular expression was significantly decreased (P < 0.05). In Calu-3 cells, NFA and MSI-2216 also significantly reduced MUC5AC mRNA expression (P < 0.05). CONCLUSIONS: These data suggest that hCLCA1 may play a role in LPS-induced mucin expression in human airway mucosa. Calcium-activated chloride channel inhibitors significantly decreased LPS-induced mucus expression both ex vivo and in vitro . Therefore, blocking of hCLCA1 may offer a therapeutic approach to reduce bacterial-induced mucus hypersecretion.