Excessive production of airway mucus is a characteristic feature of many chronic inflammatory lung diseases. Although current pharmacological approaches to excessive mucus production are limited, glucocorticoids appear to be the most effective among a few useful drugs. The exact evidence for the effectiveness of glucocorticoids on mucus production has not been fully elucidated to date. The purpose of this study is to clarify the effect of dexamethasone on mucus production and mucin gene expression in a human pulmonary mucoepidermoid carcinoma cell line (NCI-H292). NCI-H292 cells produced hyaluronidase-resistant high-molecular-weight glycoconjugates (HMWG), which elute in the void volume on Sepharose CL-4B column chromatography. Dexamethasone significantly suppressed the basal production of [3H]glucosamine-or [3H]serine-labeled HMWG in NCI-H292 cells. In Northern blot analysis, dexamethasone attenuated steady-state mRNA levels of MUC-2 and MUC-5AC mucin genes. These data indicate that dexamethasone suppresses the basal production of HMWG and decreases steady-state mRNA levels of mucin genes in airway mucus-producing cancer cells.

Abnormal retention of v vF508 CFTR (cystic ¢brosis transmembrane conductance regulator) in the endoplasmic reticulum is a major cause of cystic ¢brosis (CF). We show that calnexin v v185^520 but not calnexin can partially reverse the mislocalization of v vF508 CFTR. This 256-amino acid protein has neither the transmembrane domain nor the P domain of calnexin. Calnexin v v185^520 interacted with CFTR directly, and was secreted into the extracellular compartment over time. Forty-eight hours after transfection into CHO cells, calnexin v v185^520 increased the conversion of immature v vF508 CFTR into mature v vF508 CFTR. In immortalized human CF cell lines expressing v vF508 CFTR, a halide e¥ux assay showed that calnexin v v185^520 partially restored CFTR function. These data indicate that calnexin v v185^520 may give a clue to develop the therapeutic way of cystic ¢brosis with v vF508 CFTR. ß

Abnormal regulation of airway mucus secretion may underlie many pulmonary diseases. The exact evidence for the involvement of intracellular signaling mechanisms in mucus secretion has not been fully elucidated to date. The purpose of this study is to clarify the involvement of protein kinase C in the secretion of high-molecular-weight glycoconjugates (HMWG) by hamster tracheal epithelial cells in culture, which elute in the void volume on Sepharose CL-4B column chromatography. HMWG were secreted by the cells cultured on the thick collagen gel, but not on the plastic plate. Two known activators of protein kinase C, 4 beta-phorbol 12 alpha-myristate 13-acetate (PMA) and 1-oleoyl-2-acetyl-sn-glycerol (OAG), stimulated HMWG secretion. In contrast, 4 alpha-phorbol 12,13-didecanoate, a biologically inactive phorbol, did not influence HMWG secretion. D-Sphingosine, an inhibitor of protein kinase C, suppressed the maximal PMA- (10(-8) M) and OAG- (200 microM) stimulated HMWG secretion. PMA induced protein kinase C translocation from cytosol to membrane. These data indicate that protein kinase C is involved in HMWG secretion in hamster tracheal epithelial cells in culture.

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We have examined the effects of pyridine derivatives on phosphatidylcholine secretion in primary cultures of rat type II pneumocytes. Of 12 pyridine derivatives, 4-aminopyridine, 4-dimethylaminopyridine and 4-pyrolidinopyridine had a stimulatory effect on phosphatidylcholine secretion, whereas other derivatives had little effect. The stimulatory effect of 4-aminopyridine was concentration- and time-dependent, and was inhibited by the acetoxymethyl ester of 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (3 microM), an intracellular Ca2+ chelator. In addition, the stimulatory effect of 4-aminopyridine was suppressed by W-7(N-(6-aminohexyl)-5-chloro-1-napthalene-sulphonamide)(10 microM), a calmodulin inhibitor, and sphingosine (10 microM) and staurosporine (0-1 microM), protein kinase C inhibitors. These results indicate that several pyridine derivatives stimulate phosphatidylcholine secretion in type II pneumocytes.