In vitro quantification of dexamethasone-induced surfactant protein B expression in human lung cells

Objective: To determine whether the effect of a single 48-h exposure to dexamethasone in human lung cells is limited to 7-8 days. Study design: We used the NCI-H441 cell line, in which stability can be maintained beyond 7 days. The outcome was the stimulatory effect of dexamethasone on surfactant protein B (SP-B) gene transcription as expressed by SP-B mRNA accumulation. The experiment was conducted five times, in parallel with control. SP-B mRNA was determined at baseline, 48 h after dexamethasone exposure, and at 48-h intervals thereafter, up to 14 days, by quantitative reverse transcription polymerase chain reaction. Comparisons were made by the Mann-Whitney test. Results: In conditions of our experiment, the inductive profile of SP-B mRNA after exposure to dexamethasone demonstrated maximal stimulation at 48 h (13-fold over control). Subsequently, there was a decline in mRNA, with return to near control levels by day 8, suggesting reversibility of dexamethasone action. Conclusion: Our data support the view that the surfactant-inducing properties of corticosteroids are limited to 7-8 days.