11-BETA-HYDROXYSTEROID DEHYDROGENASE-1 ACTIVITY AND GENE-EXPRESSION IN HUMAN ADIPOSE STROMAL CELLS - EFFECT ON AROMATASE-ACTIVITY

The biological activity of glucocorticoids in target tissues can be in fluenced by locally produced 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD), the enzyme responsible for the interconversion of cortisol and its inactive metabolite cortisone. In human adipose stromal cells, glucocorticoids are potent stimulators of the conversion of androgens to estrogens (aromatase activity). The present study was designed to determine whether 11 beta-HSD activity was present in human adipose st romal cells, and if changes in the activity of this enzyme could influ ence aromatase activity. 11 beta-HSD activity was determined by a radi ometric conversion assay in breast adipose tissue from six patients. I t was found that both dehydrogenase (cortisol to cortisone) and reduct ase (cortisone to cortisol) activities were present in all six subject s, and the reductase activity was always predominant. Carbenoxolone (C BX), a potent inhibitor of 11 beta-HSD, added to the culture medium at 50 and 200 mu M, resulted in 39 +/- 4% and 85 +/- 1% inhibition, resp ectively, of both reductase and dehydrogenase activity of 11 beta-HSD. To determine whether alterations in 11 beta-HSD could influence aroma tase activity, the effect of CBX (200 mu M) on cortisol- and cortisone -induced changes in the conversion of androstenedione to estrone was e xamined. CBX prevented the stimulatory effect of cortisone and minimal ly potentiated the stimulatory effect of cortisol on aromatase activit y, reflecting an inhibition of the local activation of cortisone and t he local metabolism of cortisol, respectively. In order to determine w hether the product of the 11 beta-HSD 1 gene was responsible for the o bserved 11 beta-HSD activity, total RNA extracts from these cells were subjected to Northern blot analysis using human 11 beta-HSD 1 cDNA as the probe. A single 1.8 11 beta-HSD 1 transcript was detected, and it s abundance was reduced by CBX. No 11 beta-HSD 2 mRNA was detected. Th e present results demonstrate that the 11 beta-HSD 1 gene is expressed and functional in human breast adipose stromal cells and that changes in 11 beta-HSD 1 activity result in alterations in aromatase activity . (C) 1997 Elsevier Science Ltd.