title: Glucocorticoids differentially regulate expression of duodenal and renal calbindin-D9k through glucocorticoid receptor-mediated pathway in mouse model.
abstract: Dexamethasone (Dex) is a member of the glucocorticoids (GCs), and is broadly used as an anti-inflammatory medication. Continuous administration with GCs induces adverse effects and suffering in humans (i.e., osteoporosis) due to negative calcium balance derived from low re- and absorption in the duodenum and kidney. A cytosolic calcium-binding protein, calbindin-D9k (CaBP-9k), is dominantly expressed in the renal and intestinal tissues involved in calcium re- and absorption and plays an active role in calcium transport. In the present study, we employed adrenalectomized (ADX) and sham-treated (Sham) male mice to examine the effect of Dex on CaBP-9k gene expression in the duodenum and kidney. Dex significantly reduced the levels of duodenal CaBP-9k mRNA and protein, and it restored ADX-induced decrease in renal CaBP-9k protein compared with the level of Sham control. Dex treatment increased calcium and phosphate levels in the sera of both Sham and ADX mice. In a time course experiment, Dex significantly decreased duodenal CaBP-9k at the transcriptional and translational levels at 3 days, whereas it temporarily increased CaBP-9k mRNA and protein levels at 12 and 24 h. Altered CaBP-9k expression by Dex was completely reversed by mifepristone, an antagonist for the GC receptor (GR). In addition, duodenal CaBP-9k and GR were colocalized on the enterocyte (duodenocyte), supporting a role for GR in regulating CaBP-9k. In ovariectomized (OVX) and ADX female mice daily treated with Dex for 3 days, duodenal CaBP-9k was expressed at the same level as in male mice. Also, no cross-activity of progesterone and Dex on their receptors was observed. Taken together, these results indicate that mouse CaBP-9k gene may be regulated by Dex in a tissue-specific manner, and reduced duodenal CaBP-9k via the GR pathway may take part in negative calcium absorption of GC-induced osteoporosis, whereas renal CaBP-9k may not be involved in the regulation of calcium homeostasis.
authors.affiliation: Laboratory of Veterinary Biochemistry and Molecular Biology, College of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk, 361-763, Republic of Korea.
authors.forename: Geun-Shik
authors.initials: GS
authors.lastname: Lee
authors.forename: Kyung-Chul
authors.initials: KC
authors.lastname: Choi
authors.forename: Eui-Bae
authors.initials: EB
authors.lastname: Jeung
mesh_terms: D000818:Animals; D064026:Calbindins; D003907:Dexamethasone / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004386:Duodenum / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D005938:Glucocorticoids / Q000008:administration & dosage; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D023421:Models, Animal; D011965:Receptors, Glucocorticoid / Q000378:metabolism*; D064030:S100 Calcium Binding Protein G / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
chemical_list: D064026:Calbindins; D005938:Glucocorticoids; D011965:Receptors, Glucocorticoid; D064030:S100 Calcium Binding Protein G; C576506:S100G protein, human; C576507:S100g protein, mouse; D003907:Dexamethasone