Glucocorticoid metabolism in the cardiac interstitium

11β-hydroxysteroid dehydrogenase activity in cardiac fibroblasts

Simon Slight, Venkataseshu K. Ganjam, Dan J. Nonneman, Karl Weber

Research output: Contribution to journalArticle

38 Citations (Scopus)

Abstract

The interstitial fibrosis seen in the heart and systemic organs in states of primary or secondary mineralocorticoid excess suggests that fibroblasts are responsive to mineralocorticoid. In vitro studies demonstrating increased fibroblast collagen synthesis in response to MC are consonant with this view. The nicotinamide-adenine dinucleotide phosphate+-dependent enzyme 11β-hydroxysteroid dehydrogenase converts the glucocorticoids corticosterone and cortisol to the inactive metabolites 11-dehydrocorticosterone and cortisone, respectively, conferring mineralocorticoid specificity to the cells within which it is active. We Investigated the presence of 11β-hydroxysteroid dehydrogenase in sonicates of cultured vascular endothelial cells and cardiac fibroblasts by incubating sonicates for 1 hour in the presence of 5 × 10-9 mol/L tritiated corticosterone or tritiated cortisol (1 μCi) and using reverse-phase high-performance liquid chromatography coupled to an on-line radioisotope detector for steroid separation and quantitation. Extracts of bovine endothelial cells showed no enzymatic activity with either substrate, whereas extracts of rat cardiac fibroblasts readily converted corticosterone to 11-dehydrocorticosterone, even in the absence of exogenous nicotinamide-adenine dinucleotide phosphate+ (10% conversion). When 5 × 10-4 mol/L nicotinamide-adenine dinucleotide phosphate+ was added to sonicated fibroblasts, conversion increased to 50%, corresponding to 12 pmol 11-dehydrocorticosterone formed/mg protein. Conversion of cortisol to cortisone was not observed in fibroblast or endothelial cell extracts. Significant levels of corticosterone to 11-dehydrocorticosterone conversion (0.14 pmol/106 cells/hour) were detected in intact fibroblasts, but no 11-dehydrogenation of corticosterone was observed in intact endothelial cells. Homogenates of rat heart also possessed high levels of 11β-hydroxysteroid dehydrogenase activity when incubated with corticosterone, effecting levels of conversion between 0.4 and 0.6 pmol/mg protein. Preincubation of intact fibroblasts for 24 hours with 10-7mol/L corticosterone before sonication and incubation with tritiated corticosterone doubled the conversion to 11-dehydrocorticosterone, indicating that 11β-hydroxysteroid dehydrogenase activity was inducible. Addition of classic 11β-hydroxysteroid dehydrogenase inhibitors (5 × 10-5 mol/L glycyrrhizic acid, glycyrrhetinic acid, or carbenoxolone) to fibroblast sonicates resulted in total inhibition of 11β-hydroxysteroid dehydrogenase activity. Thus in cardiac fibroblasts, unlike in vascular endothelial cells, 11β-hydroxysteroid dehydrogenase plays a significant role in modulating corticosterone available to steroid receptors and may thereby confer mineralocorticoid specificity to type I corticoid receptors in these mesenchymal cells.

Original languageEnglish (US)
Pages (from-to)180-187
Number of pages8
JournalThe Journal of Laboratory and Clinical Medicine
Volume122
Issue number2
StatePublished - Jan 1 1993
Externally publishedYes

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11-beta-Hydroxysteroid Dehydrogenases
Fibroblasts
Metabolism
Corticosterone
Glucocorticoids
Endothelial cells
Mineralocorticoids
Endothelial Cells
NADP
Hydrocortisone
Cortisone
Rats
Carbenoxolone
Glycyrrhetinic Acid
Glycyrrhizic Acid
Mineralocorticoid Receptors
Sonication
Steroid Receptors
High performance liquid chromatography
Reverse-Phase Chromatography

All Science Journal Classification (ASJC) codes

  • Pathology and Forensic Medicine

Cite this

Glucocorticoid metabolism in the cardiac interstitium : 11β-hydroxysteroid dehydrogenase activity in cardiac fibroblasts. / Slight, Simon; Ganjam, Venkataseshu K.; Nonneman, Dan J.; Weber, Karl.

In: The Journal of Laboratory and Clinical Medicine, Vol. 122, No. 2, 01.01.1993, p. 180-187.

Research output: Contribution to journalArticle

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abstract = "The interstitial fibrosis seen in the heart and systemic organs in states of primary or secondary mineralocorticoid excess suggests that fibroblasts are responsive to mineralocorticoid. In vitro studies demonstrating increased fibroblast collagen synthesis in response to MC are consonant with this view. The nicotinamide-adenine dinucleotide phosphate+-dependent enzyme 11β-hydroxysteroid dehydrogenase converts the glucocorticoids corticosterone and cortisol to the inactive metabolites 11-dehydrocorticosterone and cortisone, respectively, conferring mineralocorticoid specificity to the cells within which it is active. We Investigated the presence of 11β-hydroxysteroid dehydrogenase in sonicates of cultured vascular endothelial cells and cardiac fibroblasts by incubating sonicates for 1 hour in the presence of 5 × 10-9 mol/L tritiated corticosterone or tritiated cortisol (1 μCi) and using reverse-phase high-performance liquid chromatography coupled to an on-line radioisotope detector for steroid separation and quantitation. Extracts of bovine endothelial cells showed no enzymatic activity with either substrate, whereas extracts of rat cardiac fibroblasts readily converted corticosterone to 11-dehydrocorticosterone, even in the absence of exogenous nicotinamide-adenine dinucleotide phosphate+ (10{\%} conversion). When 5 × 10-4 mol/L nicotinamide-adenine dinucleotide phosphate+ was added to sonicated fibroblasts, conversion increased to 50{\%}, corresponding to 12 pmol 11-dehydrocorticosterone formed/mg protein. Conversion of cortisol to cortisone was not observed in fibroblast or endothelial cell extracts. Significant levels of corticosterone to 11-dehydrocorticosterone conversion (0.14 pmol/106 cells/hour) were detected in intact fibroblasts, but no 11-dehydrogenation of corticosterone was observed in intact endothelial cells. Homogenates of rat heart also possessed high levels of 11β-hydroxysteroid dehydrogenase activity when incubated with corticosterone, effecting levels of conversion between 0.4 and 0.6 pmol/mg protein. Preincubation of intact fibroblasts for 24 hours with 10-7mol/L corticosterone before sonication and incubation with tritiated corticosterone doubled the conversion to 11-dehydrocorticosterone, indicating that 11β-hydroxysteroid dehydrogenase activity was inducible. Addition of classic 11β-hydroxysteroid dehydrogenase inhibitors (5 × 10-5 mol/L glycyrrhizic acid, glycyrrhetinic acid, or carbenoxolone) to fibroblast sonicates resulted in total inhibition of 11β-hydroxysteroid dehydrogenase activity. Thus in cardiac fibroblasts, unlike in vascular endothelial cells, 11β-hydroxysteroid dehydrogenase plays a significant role in modulating corticosterone available to steroid receptors and may thereby confer mineralocorticoid specificity to type I corticoid receptors in these mesenchymal cells.",
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