11β-Hydroxysteroid dehydrogenase type 2 and the regulation of surfactant protein A by dexamethasone metabolites

Glucocorticoid (GC) metabolism by the 11β-hydroxysteroid dehydrogenase (HSD) system is an important prereceptor regulator of GC action. The HSD enzymes catalyze the interconversion of the endogenous, biologically active GC cortisol and its inactive 11-dehydro metabolite cortisone. The role of the HSD enzymes in the metabolism of synthetic GCs, such as dexamethasone (Dex), is more complex. The human lung is a classic GC-sensitive organ; however, the roles of the HSD enzymes (HSD1 and HSD2) in the human lung are poorly understood. In the present study, we examined the expression of the HSD enzymes in human adult and fetal lung tissues and the human lung epithelial cell line NCI-H441. We observed that human adult and fetal lung tissues, as well as H441 cells, express HSD2 protein and that it is upregulated by Dex (10−7 M). By contrast, HSD1 protein was undetectable. We also show that the Dex-mediated regulation of surfactant protein A is attenuated by inhibition of HSD2 activity. Furthermore, we demonstrate ...