Intracellular signal transduction mechanisms of airway epithelial cells in allergic conditions

点击翻译按钮获取中文摘要

Recently, it is believed that epithelial cells play important roles in allergic conditions as in allergic rhinitis. We tried to elucidate the intracellular signal transduction mechanisms by which mediators have effects on functional changes in epithelial cells.1.Mechanism by which leukotrienes activate mucin gene transcriptionLeukotriene D_4 (LTD_4) has been shown to induce mucus secretion in the airway. However, nothing has previously been known about the effect of LTD_4 on mucin gene expression. Reporter gene assay was mainly used for analysis. We found that NF-κB is required for LTD_4-induced MUC2 gene transcription in a CysLT_1R-dependent manner. Taken together, our findings suggest that LTD_4 up-regulates MUC2 gene transcription via a signaling pathway involving CysLT_1R, G-protein, PKC, MEK, ERK and NF-κB.2.Mechanism by which thrombin increases permeability in epithelial cellsRecently, thrombin was reported to be increased in the airway of patients with asthma, and thrombin has b … More een shown to increase the permeability of endothelial cell monolayers. Therefore, we suspected that thrombin affects airway permeability. Calu-3 cell monolayers were established on microporous membranes of tissue culture cell inserts. We examined the effects of topically applied thrombin or thrombin receptor activating peptide (TRAP) on : (1) transepithelial permeability (luminal to serosal transfer) of radiolabeled mannitol and albumin, (2) changes in electrical resistance, and (3) actin fiber content as assessed by fluorescence microscopy. Compared with untreated control cultures, treatment of the monolayers for 24 h with thrombin or TRAP significantly decreased the electrical resistance and increased the permeability to mannitol and albumin. In addition, these treatments enhanced the appearance of actin stress fibers, and small gaps became visible at areas of cell-cell contact. Thrombin appears to increase epithelial permeability by receptor-mediated reorganization of the actin network in airway epithelial cells. This is likely to contribute to the impairment of the airway barrier function. Less