title: Comparison of the effects of betamethasone and dexamethasone on surfactant protein A mRNA expression in human lung cells.
abstract: OBJECTIVE
  While prenatal administration of synthetic corticosteroids stimulates both fetal lung development and expression of pulmonary surfactant, the specific effects may depend on the corticosteroid formulation used. We compared the dose-dependent effects of various concentrations of two synthetic corticosteroids, betamethasone and dexamethasone, on steady state levels of surfactant protein A (SP-A) mRNA in human lung cells.
  
  
  METHODS
  Cultured human NCI-H441 bronchoalveolar epithelial cells were exposed to varying concentrations of betamethasone or dexamethasone (10-7to 10-12M) for 48 h alone or in combination with dibutyryl cAMP (1 mM), which augments surfactant protein gene expression. RNA was harvested and SP-A mRNA levels were quantified by real-time quantitative reverse transcriptase polymerase chain reaction analysis. Results were compared using the Kruskal-Wallis test.
  
  
  RESULTS
  A dose-dependent modification in SP-A mRNA levels was demonstrated with both dexamethasone and betamethasone. Cells treated with cAMP expressed higher levels of SP-A mRNA than untreated cells. A biphasic curve in the SP-A mRNA response to corticosteroids was elicited only in the presence of cAMP: at lower concentrations (10-10through 10-12M), SP-A mRNA levels were upregulated, whereas at higher concentrations (10-7and 10-8M), SP-A mRNA levels were reduced. Dexamethasone was more effective than betamethasone in inducing these changes.
  
  
  CONCLUSIONS
  Our results support a biphasic effect on SP-A mRNA levels after exposure to corticosteroids in combination with cAMP. At higher corticosteroid concentrations, betamethasone is less inhibitory than dexamethasone on SP-A mRNA.
authors.affiliation: a Texas Perinatal Group , Austin , TX , USA.
authors.forename: Linda
authors.initials: L
authors.lastname: Fonseca
authors.affiliation: b Department of Pediatrics , University of Texas Medical School at Houston , Houston , TX , USA , and.
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Alcorn
authors.affiliation: c Department of Obstetrics and Gynecology , Baylor College of Medicine , Houston , TX , USA.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Ramin
authors.affiliation: c Department of Obstetrics and Gynecology , Baylor College of Medicine , Houston , TX , USA.
authors.forename: Alex C
authors.initials: AC
authors.lastname: Vidaeff
keywords: Antenatal corticosteroids; NCI-H441 cell line; surfactant protein A