11β-Hydroxysteroid dehydrogenase 1 activity and gene expression in human adipose stromal cells: Effect on aromatase activity

• Published in: The Journal of steroid biochemistry and molecular biology Vol. 60; no. 3; pp. 247 - 253
• Main Authors: Yang, K., Khalil, M.W., Strutt, B.J., Killinger, D.W.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.02.1997; Elsevier Science
• Subjects: Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Steroid hormones. Cholecalciferol derivatives; Vertebrates: endocrinology; Human; Adipose tissue; Enzymatic activity; Enzyme; 11β-Hydroxysteroid dehydrogenase; Oxidoreductases; Stromal cell; Estrogen synthase; Mammary gland; Gene expression
• ISSN: 0960-0760; 1879-1220
• DOI: 10.1016/S0960-0760(96)00187-2

The biological activity of glucocorticoids in target tissues can be influenced by locally produced 11β-hydroxysteroid dehydrogenase (11β-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 11β-HSD activity was present in human adipose stromal cells, and if changes in the activity of this enzyme could influence aromatase activity. 11β-HSD activity was determined by a radiometric conversion assay in breast adipose tissue from six patients. It was found that both dehydrogenase (cortisol to cortisone) and reductase (cortisone to cortisol) activities were present in all six subjects, and the reductase activity was always predominant. Carbenoxolone (CBX), a potent inhibitor of 11β-HSD, added to the culture medium at 50 and 200 μM, resulted in 39 ± 4% and 85 ± 1% inhibition, respectively, of both reductase and dehydrogenase activity of 11β-HSD. To determine whether alterations in 11β-HSD could influence aromatase activity, the effect of CBX (200 μM) on cortisol- and cortisone-induced changes in the conversion of androstenedione to estrone was examined. CBX prevented the stimulatory effect of cortisone and minimally potentiated the stimulatory effect of cortisol on aromatase activity, reflecting an inhibition of the local activation of cortisone and the local metabolism of cortisol, respectively. In order to determine whether the product of the 11β-HSD 1 gene was responsible for the observed 11β-HSD activity, total RNA extracts from these cells were subjected to Northern blot analysis using human 11β-HSD 1 cDNA as the probe. A single 1.8 11β-HSD 1 transcript was detected, and its abundance was reduced by CBX. No 11β-HSD 2 mRNA was detected. The present results demonstrate that the 11β-HSD 1 gene is expressed and functional in human breast adipose stromal cells and that changes in 11β-HSD 1 activity result in alterations in aromatase activity.