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

Abstract

-Glucocorticoid (GC) metabolism by the 11␤-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 Ϫ7 M). By contrast, HSD1 protein was undetectable. We also show that the Dexmediated regulation of surfactant protein A is attenuated by inhibition of HSD2 activity. Furthermore, we demonstrate that unlike the inactive, 11-dehydro metabolite of cortisol (i.e., cortisone), the 11-dehydro metabolite of Dex, 11-dehydro-Dex, competes for binding to the GC receptor (GR) in human lung epithelial cells and retains GR agonist activity. Together, these data suggest that differences exist in the biological activities of the metabolites of cortisol and Dex.

11β-HSD1 reduces metabolic efficacy and adiponectin synthesis in hypertrophic adipocytes

“…In a separate experiment, differentiated 3T3L1 adipocytes at day 5 of culture were serum starved for 6 h to eliminate the influence of endogenous glucocorticoids that are present in FBS (Garbrecht et al 2006). Cells were then incubated with serum-free medium containing cortisone (Fig.…”

11-β Hydroxysteroid Dehydrogenase Type 2 in Human Adult and Fetal Lung and Its Regulation by Sex Steroids

“…Intact control and hormone-treated explants were washed with PBS and then incubated at 37°C in 1 mL of serum-free media that contained 1 nM 1,2,4-[ 3 H]-cortisol (41 Ci/mmol, American Radiolabeled Chemicals, St. Louis, MO) for 24 h on either d 1 (starting tissue) or d 6 (cultured explants). Labeled steroids were then isolated from the media and the production of tritiated cortisone was assessed via thin layer chromatography as previously described (12). HSD2 oxidase activity was determined by calculating the percent conversion of [ 3 H]-cortisol to [ 3 H]-cortisone.…”

“…Supernatant protein concentrations were quantified as described above. Immunoblotting was performed using a rabbit primary antibody specific for human HSD2 (2 g/mL) as previously described (12,19). HSD2 protein levels were normalized to ␤-actin levels, which were determined on membranes that were stripped and reprobed with a ␤-actin MAb (1:7500, Chemicon International, Temecula, CA).…”

“…Lung tissue was homogenized in 1 mL of TRIzol reagent (Invitrogen, Carlsbad, CA) and total RNA was isolated and quantified as described previously (12). RNA integrity was monitored by examining the ethidium bromide stained 28S and 18S rRNA bands after electrophoresis on agarose gels.…”

“…HSD2 mRNA and protein have been detected in human adult and fetal lung tissues, as well as in a number of human lung epithelial cell lines (12,13). In contrast, the oxidoreduction of cortisone to cortisol (suggestive of HSD1 activity) is negligible in intact cultured lung explants and undetectable in human fetal lung in vivo (11,14,15).…”