Localization of 2 11β-OH Steroid Dehydrogenase Isoforms in Aortic Endothelial Cells

Abstract

11β-hydroxysteroid dehydrogenase (11β-HSD) is expressed in vascular smooth muscle cells (VSMC) but has not been reported to be present in vascular endothelial cells. This enzyme assists in regulating the cellular concentration of active endogenous glucocorticoids (GCs). We have observed that endothelium intact rat aortic rings express message for both Type 1 and Type 2 11β-HSD whereas primary cultures of VSMC express only mRNA for the Type I isoform. Since GCs diminish prostacyclin synthesis in endothelial cells, we hypothesized that 11β-HSD is present in vascular endothelial cells. In primary cultures of rat aortic endothelial (RAE) cells, mRNA from both isoforms of 11β-HSD could be detected by RT-PCR with higher levels of the Type 1 isoform. The oxo-reductase reaction “activating” 11-dehydro metabolites back to the parent steroid is the preferred enzyme direction (12:1 after a 120 minutes steroid incubation) in intact RAE cells. When RAE cells are grown in the presence of antisense oligonucleotides specific for Type 1 11β-HSD, oxo-reductase activity is decreased by approximately 50% but the dehydrogenase reaction, which inactivates endogenous GCs and is characteristic of the Type 2 isoform, is unaffected. Thus endothelial cells appear to express both isoforms of 11β-HSD; the Type 1 isoform dominates functioning in the oxo-reductase mode. Inhibition of the oxo-reductase reaction may lower the local concentrations of GC and indirectly allow for increased production of prostacyclin in endothelial cells.