Dexamethasone increases airway epithelial cell neutral endopeptidase by enhancing transcription and new protein synthesis.
Neutral endopeptidase (NEP; also known as EC 3.4.24.11, CALLA) is a widely distributed membrane-bound enzyme that hydrolyzes many biologically important endogenous peptides. To evaluate the influence of glucocorticoids on airway epithelial cell NEP expression, we used the human airway epithelial cell line Calu-1. Cells, grown to confluency in Dulbecco's modified Eagle medium with 10% fetal bovine serum and penicillin-streptomycin, were incubated with different concentrations of dexamethasone or vehicle alone in the presence or absence of actinomycin D or cycloheximide for planned times. NEP activity was assayed at the end of treatment employing reverse-phase, high-pressure liquid chromatography. In some experiments, changes in NEP-specific mRNAs in the presence or absence of dexamethasone and/or the inhibitors were also evaluated by Northern blot analysis. We found that dexamethasone increased Calu-1 NEP activity in a dose- and time-dependent manner. Northern blot analysis indicated that NEP-specific mRNAs were also increased by dexamethasone. Furthermore, neither actinomycin D nor cycloheximide inhibited the increases in NEP activity and NEP-specific mRNAs caused by dexamethasone stimulation. We speculate, therefore, that dexamethasone increases NEP expression of these airway epithelial cells by enhancing transcription and new protein synthesis.
Lung Cell Biology Laboratories, Rush University, Chicago, IL 60612.
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D002294:Carcinoma, Squamous Cell; D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D003907:Dexamethasone / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004848:Epithelium / Q000187:drug effects; D006801:Humans; D008168:Lung / Q000187:drug effects*; D008175:Lung Neoplasms; D015260:Neprilysin / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics*; D014176:Protein Biosynthesis; D014158:Transcription, Genetic / Q000187:drug effects*; D014407:Tumor Cells, Cultured / Q000187:drug effects
D003609:Dactinomycin; D003907:Dexamethasone; D003513:Cycloheximide; D015260:Neprilysin