In a healthy human, the airway mucus forms a thin, protective liquid layer covering the surface of the respiratory tract. It comprises a complex blend of mucin, multiple antibacterial proteins, metabolic substances, water, and electrolytes. This mucus plays a pivotal role in the lungs' innate immune system by maintaining airway hydration and capturing airborne particles and pathogens. However, heightened mucus secretion in the airway can compromise ciliary clearance, obstruct the respiratory tract, and increase the risk of pathogen colonization and recurrent infections. Consequently, a thorough exploration of the mechanisms driving excessive airway mucus secretion is crucial for establishing a theoretical foundation for the eventual development of targeted drugs designed to reduce mucus production. Across a range of lung diseases, excessive airway mucus secretion manifests with unique characteristics and regulatory mechanisms, all intricately linked to mucin. This article provides a comprehensive overview of the characteristics and regulatory mechanisms associated with excessive airway mucus secretion in several prevalent lung diseases.
Humans ; Mucus/metabolism* ; Mucins/physiology* ; Lung Diseases/metabolism* ; Respiratory Mucosa/metabolism* ; Pulmonary Disease, Chronic Obstructive/physiopathology* ; Asthma/physiopathology* ; Cystic Fibrosis/physiopathology* ; Mucociliary Clearance/physiology*

OBJECTIVETo investigate the effect of annexin A2 (AnxA2) on epithelial growth factor receptor (EGFR)/nuclear factor-κB (NF-κB) signal transduction and mucin expression in human airway epithelial H292 cells treated with Mycoplasma pneumoniae (MP).

METHODSH292 cells were divided into control group, MP group, NC-siRNA+MP group, and AnxA2 siRNA+MP group. The cells in the MP group were incubated with 5 μg/mL MP antigen for 2 hours. The cells in the NC-siRNA+MP and AnxA2 siRNA+MP groups were transfected with NC-siRNA and AnxA2 siRNA for 24 hours, followed by MP antigen stimulation for 2 hours. The MTT method was used to measure cell viability; quantitative real-time PCR was used to measure the mRNA expression of AnxA2; Western blot was used to measure the protein expression of AnxA2, phosphorylated EGFR (p-EGFR), and phosphorylated p65 NF-κB (p-p65 NF-κB); ELISA was used to measure the secretion of mucin 5AC (MUC5AC) and mucin 5B (MUC5B).

RESULTSThe MP and NC-siRNA+MP groups had lower cell viability than the control group (P<0.05). The AnxA2 siRNA+MP group had higher cell viability than the MP and NC-siRNA+MP groups and lower cell viability than the control group (P<0.05). The MP and NC-siRNA+MP groups had significantly higher mRNA and protein expression of AnxA2 than the AnxA2 siRNA+MP group (P<0.05). Compared with the control group, the MP and NC-siRNA+MP groups had significant increases in the protein expression of p-EGFR, p-p65 NF-κB, MUC5AC, and MUC5B (P<0.05); the AnxA2 siRNA+MP group had lower protein expression than the MP and NC-siRNA+MP groups, but higher protein expression than the control group (P<0.05).

CONCLUSIONSAnxA2 is involved in the airway lesion induced by MP antigen via mediating EGFR/NF-κB signaling activation and mucin expression in human airway epithelial cells.

Annexin A2 ; physiology ; Bronchi ; physiology ; Cells, Cultured ; Epithelial Cells ; microbiology ; Humans ; Mucins ; analysis ; Mycoplasma pneumoniae ; pathogenicity ; NF-kappa B ; physiology ; Receptor, Epidermal Growth Factor ; physiology ; Signal Transduction ; physiology

Biomedical Research ; trends ; Breast Neoplasms ; metabolism ; Female ; Humans ; Mucins ; physiology ; Neoplasm Proteins ; physiology

PURPOSE: Recent discoveries suggest that aberrant DNA methylation provides cancer cells with advanced metastatic properties. However, the precise regulatory mechanisms controlling metastasis genes and their role in metastatic transformation are largely unknown. To address epigenetically-regulated gene products involved in ovarian cancer metastasis, we examined the mechanisms regulating mucin 13 (MUC13) expression and its influence on aggressive behaviors of ovarian malignancies. MATERIALS AND METHODS: We injected SK-OV-3 ovarian cancer cells peritoneally into nude mice to mimic human ovarian tumor metastasis. Overexpression of MUC13 mRNA was detected in metastatic implants from the xenografts by expression microarray analysis and quantitative reverse-transcription polymerase chain reaction (qRT-PCR). The DNA methylation status within the MUC13 promoter region was determined using bisulfite sequencing PCR and quantitative methylation-specific PCR. We evaluated the effects of exogenous MUC13 on cell invasion and migration using in vitro transwell assays. RESULTS: MUC13 mRNA expression was up-regulated, and methylation of specific CpG sites within the promoter was reduced in the metastatic implants relative to those in wild-type SK-OV-3 cells. Addition of a DNA methyltransferase inhibitor to SK-OV-3 cells induced MUC13 expression, thereby implying epigenetic regulation of MUC13 by promoter methylation. MUC13 overexpression increased migration and invasiveness, compared to control cells, suggesting aberrant up-regulation of MUC13 is strongly associated with progression of aggressive behaviors in ovarian cancer. CONCLUSION: We provide novel evidence for epigenetic regulation of MUC13 in ovarian cancer. We suggest that the DNA methylation status within the MUC13 promoter region may be a potential biomarker of aggressive behavior in ovarian cancer.
Animals ; Cell Line, Tumor ; *DNA Methylation ; Epigenesis, Genetic ; Female ; *Gene Expression Regulation, Neoplastic ; Heterografts/metabolism ; Humans ; Mice ; Mice, Nude ; Mucins/*genetics/metabolism/physiology ; Neoplasm Invasiveness/genetics ; Ovarian Neoplasms/genetics/*metabolism/pathology ; RNA, Messenger/metabolism

Vasoactive intestinal peptide (VIP) is a neuropeptide with potent bronchodilator, immunomodulator, and anti-inflammatory properties, and thus has biological properties capable of counteracting all major features of the asthmatic response. However, the effect of VIP on bronchial mucin secretion remains unclear. In order to observe the influence of VIP on bronchial mucin, the present study was designed to observe the correlation between VIP and total bronchial mucin changes under different time of ozone stress in rat lung. Sixty-four Sprague-Dawley rats were used in the experiment. Under different time of ozone stress, VIP content in lung homogenate was analyzed by radioimmunoassay, and changes in total bronchial mucin in the lung were analyzed by calculating the goblet cell hyperplasia ratio and the epithelial cell mucus occupying ratio from the periodic acid-Schiff reaction (PAS) staining. The results showed that, at early stage of respiratory tract injury, VIP did not change significantly, while the total bronchial mucin secretion increased; with the development of damage, the secretion of VIP increased by compensation, followed by a decrease in total bronchial mucin; with further injury, the numbers of pulmonary endocrine VIP positive nerve fibers and endocrine cells decreased, but bronchial mucin volume gradually increased. It is concluded that the secretion of VIP is negatively correlated with the secretion of bronchial mucin during the development of inflammation.
Animals ; Inflammation ; pathology ; Lung ; physiology ; physiopathology ; Mucins ; physiology ; Ozone ; adverse effects ; Rats, Sprague-Dawley ; Vasoactive Intestinal Peptide ; physiology

Animals ; Aquaporin 5 ; physiology ; Cytokines ; physiology ; Gene Expression Regulation ; Humans ; Intracellular Signaling Peptides and Proteins ; physiology ; Membrane Proteins ; physiology ; Mucins ; genetics ; Mucus ; secretion ; Myristoylated Alanine-Rich C Kinase Substrate ; Pulmonary Disease, Chronic Obstructive ; metabolism ; Respiratory Mucosa ; secretion ; Signal Transduction

BACKGROUNDChronic obstructive pulmonary disease (COPD) is usually complicated with mucus overproduction in airway. Recently the increased expression of the human calcium-activated chloride channel 1 (CaCC(1)) was found to play an important role in mucus overproduction in the asthmatic airways. To investigate the relationship of CaCC(1) and mucus overproduction in the airway of Chinese patients with COPD, the expressions of CaCC(1), MUC5AC and mucus in bronchial tissues were examined.

METHODSBronchial tissues were obtained from fiberoptic bronchoscopy and bronchial biopsy in West China Hospital from April to July in 2004. Twenty-five patients were diagnosed as the patients with COPD overproduction, and other 20 were the control subjects. The expressions of CaCC(1), MUC5AC and mucin in bronchial tissues were detected by reverse transcriptase-polymerase chain reaction (RT-PCR), in situ hybridization with digoxigenin (DIG)-labeled RNA probe, immunohistochemical and alcian blue-periodic acid Schiff (AB-PAS) staining, respectively.

RESULTSCompared with the control group, the stronger expressions of CaCC(1) were further detected throughout the bronchial tissues from patients with COPD (P < 0.01). Furthermore, the stronger expressions of the CaCC(1) mRNA were related to the severity of airflow obstruction. Samples from COPD showed a stronger staining for MUC5AC than those in control subjects (P < 0.01) and AB-PAS staining revealed more mucins in COPD patients' submucosal gland comparing with that in control subjects (P < 0.01). Expression levels of the CaCC(1) mRNA were respectively negatively correlated with the patients' forced expiratory volume in one second (FEV(1))/forced vital capacity (FVC) data, FEV(1)% predicted data, V(50)% predicted data, V(25)% predicted data (r = -0.43, r = -0.43, r = -0.35, r = -0.36, P < 0.01, P < 0.01, P < 0.05, P < 0.05). While the expression levels of the CaCC(1) mRNA were well correlated with the expression levels of the MUC5AC mRNA of airway epithelium and the PAS-AB stained area of submucosal glands (r = 0.39, r = 0.46, P < 0.05, P < 0.01). Expression levels of the MUC5AC mRNA were negatively correlated with the patients' FEV(1)/FVC data (P = 0.01), FEV(1)% pred data (P = 0.01), V(50)% predicted data, V(25)% predicted data (r = -0.53, r = -0.53, r = -0.48, r = -0.43, P < 0.01, P < 0.01, P < 0.01, P < 0.01). While the expression levels of the MUC5AC mRNA were well correlated with the positively PAS-AB stained area of submucosal gland (P < 0.05), and the correlation coefficients were 0.43.

CONCLUSIONThese results suggest that the stronger gene expression of CaCC(1) exists, complicated with mucus overproduction in the airway of Chinese patients with COPD.

Adult ; Aged ; Bronchi ; metabolism ; Chloride Channels ; genetics ; Female ; Forced Expiratory Volume ; Gene Expression Regulation ; Humans ; Male ; Middle Aged ; Mucin 5AC ; Mucins ; genetics ; Mucus ; physiology ; Pulmonary Disease, Chronic Obstructive ; metabolism ; physiopathology ; RNA, Messenger ; analysis ; Vital Capacity

Interleukin 1 beta (IL-1 beta), a proinflammatory cytokine, is related with inflammatory diseases and it up-regulates MUC2 gene expression and mucin secretion. This study was designed to investigate the signal transduction pathway of the IL-1 beta-mediated MUC2 gene expression and mucin secretion in human airway epithelial cells. In cultured human airway NCI-H292 epithelial cells, the steady state of the mRNA level of MUC2 gene expression and mucin secretion induced by IL-1 were determined by reverse transcriptase-polymerase chain reaction (RT-PCR), enzyme immunoassay, and immunoblot analysis. To observe the signal pathway of the IL-1 beta-mediated MUC2 gene expression and mucin secretion, we used several specific inhibitors. PD98059 (MEK/ERK inhibitor) suppressed IL-1 beta-mediated MUC2 gene expression and mucin secretion, while SB203580 (p38 inhibitor) did not. Ro31-8220 (PKC inhibitor) inhibited IL-1 beta-mediated MUC2 gene expression and mucin secretion. It inhibited ERK phosphorylation, but did not inhibit p38 phosphorylation. LY294002 (PI3K inhibitor) also suppressed MUC2 expression, but did not inhibit any MAPKs phosphorylation. These results suggest that the IL-1 -mediated MUC2 gene expression and mucin secretion in NCI-H292 cells are regulated through activation of the PKC-MEK/ERK pathway, and that PI3K is also involved in the IL-1 beta-mediated MUC2 gene expression and mucin secretion.
1-Phosphatidylinositol 3-Kinase/*metabolism ; Cell Line ; Chromones/pharmacology ; Dose-Response Relationship, Drug ; Enzyme Activation ; Enzyme Inhibitors/pharmacology ; Epithelium/*enzymology ; Flavonoids/pharmacology ; Humans ; Imidazoles/pharmacology ; Immunoassay ; Immunoblotting ; Indoles/pharmacology ; Interleukin-1/metabolism/*physiology ; Lung/cytology/*metabolism ; MAP Kinase Signaling System ; Mitogen-Activated Protein Kinase Kinases/*metabolism ; Morpholines/pharmacology ; Mucin-2 ; Mucins/*biosynthesis/metabolism ; Phosphorylation ; Protein Kinase C/*metabolism ; Protein Structure, Tertiary ; Pyridines/pharmacology ; Reverse Transcriptase Polymerase Chain Reaction ; Signal Transduction ; Time Factors