Antisense to Both 11β-Hsd1 and 2 Increase Glucocorticoid (GC) Activity in Vascular Tissue
GC’s amplify the pressor effects of catecholamines and Ang II in VSM. Thus, the level of vasoconstriction in vascular tissue can be influenced by local GC concentrations. GC’s are metabolized to their inactive 11-dehydro derivatives by the enzyme 11β-HSD which exists in at least two isoforms, 11β-HSD1 and 11β-HSD2. 11β-HSD2 is unidirectional, with only dehydrogenase activity (inactivating GC’s) while 11β-HSD1 is bi-directional, also possessing reductase activity and thus the ability to reactivate 11-dehydroGC’s back to the active parent steroid. The aim of the present study was to investigate the role of each isoform in the regulation of GC metabolism in vascular tissue. Aortic rings (2-3mm), from male SD rats, were incubated for 24 hrs in DMEM media with either corticosterone (B) or 11-dehydrocorticosterone (11-dehydroB)(10-8-10-7M) ± specific Antisense oligos (20 μg/ring) targeted against rat 11β-HSD1 or 11β-HSD2. The contractile responses to graded doses of phenylephrine (PE; 10-9 - 10-6 M)in individual rings were then measured. In aortic rings co-incubated with B and 11β-HSD2 Antisense, the contractile responses to PE were amplified 30-50% versus rings incubated with B + nonsense oligonicleotide (n = 21, p < 0.01). The co-incubation of aortic rings with B + 11β-HSD1 Antisense resulted in a 50% increase in the contractile responses to PE (n = 8, p<0.001). In parallel experiments, 11β-HSD2 Antisense caused a 25% reduction(n =16 aortic rings) and 11β-HSD1 Antisense a 12% reduction (n = 8 aortic rings)in the metabolism of B to 11-dehydroB. These results indicate that 11β-HSD1 and 11β-HSD2 are both important in the metabolism of GC’s in vascular tissue and hence in the regulation of vascular tone. Additionally, rat aortic rings incubated with 11-dehydroB have an increased contractile response to PE versus controls, an effect attenuated by 11β-HSD1 Antisense. This suggests 11-dehydroB is re-activated back to B by 11β-HSD1-reductase making this enzyme a target for possible antihypertensive therapies.