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.
Lang
Z
Z
Lung Cell Biology Laboratories, Rush University, Chicago, IL 60612.
Murlas
C G
CG
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