title: Glycyrrhetinic acid-induced apoptosis in thymocytes: impact of 11beta-hydroxysteroid dehydrogenase inhibition.
abstract: It has been proposed that glycyrrhetinic acid (GA) enhances endogenous glucocorticoid (GC) action by suppressing the metabolism of the steroid. We show here that marked involution of the thymus occurred within 24 h of a single intraperitoneal administration of GA in mice. Thymocytes from mice treated with GA exhibited DNA cleavage and mitochondrial transmembrane potential disruption, as demonstrated with agarose gel electrophoresis and flow cytometric analysis. Immunocytochemical staining revealed that CD4(+)CD8(+) double positive cells markedly decreased after GA treatment. In contrast to GA in vivo, GA in vitro did not induce apoptosis of cultured thymocytes. These findings suggest that the apoptosis-inducing effect of GA on thymocytes is due to its indirect action. Because GA has been known to inhibit 11beta-hydroxysteroid dehydrogenase (11beta-HSD), we measured the enzyme activity in major organs and endogenous corticosterone concentration after GA treatment. The results showed a significant decrease of 11beta-HSD activity (P < 0.0001) and an increase in serum corticosterone concentration (P < 0.005). We concluded that the inhibition of hepatic 11beta-HSD activity by GA has a serious effect on GC metabolism, which results in a significant elevation of systemic GC levels. Apoptosis of thymocytes occurred as a consequence of the elevation in the level of endogenous corticosterone.
authors.affiliation: Department of Clinical Pharmacology, School of Pharmacy, Tokyo University of Pharmacy and Life Science, Hachioji, Tokyo 192-0392, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Horigome
authors.forename: A
authors.initials: A
authors.lastname: Horigome
authors.forename: M
authors.initials: M
authors.lastname: Homma
authors.forename: T
authors.initials: T
authors.lastname: Hirano
authors.forename: K
authors.initials: K
authors.lastname: Oka
mesh_terms: D042842:11-beta-Hydroxysteroid Dehydrogenases; D000818:Animals; D017209:Apoptosis; D003345:Corticosterone / Q000097:blood; D006034:Glycyrrhetinic Acid / Q000494:pharmacology*; D006913:Hydroxysteroid Dehydrogenases / Q000037:antagonists & inhibitors*; D066298:In Vitro Techniques; D008099:Liver / Q000201:enzymology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009929:Organ Size / Q000187:drug effects; D009994:Osmolar Concentration; D013950:Thymus Gland / Q000033:anatomy & histology / Q000166:cytology / Q000187:drug effects* / Q000502:physiology
chemical_list: D006913:Hydroxysteroid Dehydrogenases; D042842:11-beta-Hydroxysteroid Dehydrogenases; D006034:Glycyrrhetinic Acid; D003345:Corticosterone