title: Regulation of Vitamin D hydroxylases gene expression by 1,25-dihydroxyvitamin D3 and cyclic AMP in cultured human syncytiotrophoblasts.
abstract: Human placenta synthesizes and metabolizes 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)/calcitriol] through the activity of 25-hydroxyvitamin D(3)-1alpha-hydroxylase (CYP27B1) and 1,25(OH)(2)D(3)-24-hydroxylase (CYP24A1), the two key enzymes for Vitamin D metabolism. In this study, calcitriol rapidly generated intracellular cAMP accumulation in cultured human syncytiotrophoblast cells, which in turn enhanced hCG secretion, a marker of trophoblast endocrine activity. The effects of 1,25(OH)(2)D(3) upon the expression of CYP27B1 and CYP24A1 were also investigated. 1,25(OH)(2)D(3) and activators of the PKA signaling system decreased the expression of CYP27B1, whereas increased CYP24A1 gene transcription. The use of a selective inhibitor of PKA (H-89) prevented the effects of calcitriol on CYP27B1 gene and hCG secretion, but not on CYP24A1 transcription. Addition of ZK 159222, a Vitamin D receptor (VDR) antagonist, blocked the calcitriol-mediated upregulation of 24-hydroxylase gene expression but did not affect calcitriol-induced downregulation of CYP27B1 gene or hCG stimulation. In addition, our study also demonstrated a role of calcitonin on Vitamin D hydroxylases gene regulation in placenta. The overall data suggest that calcitriol downregulates CYP27B1 expression via a cAMP-dependent signaling pathway, whereas upregulates 24-hydroxylase gene expression through a VDR-dependent mechanism.
authors.affiliation: Department of Reproductive Biology, Instituto Nacional de Ciencias Médicas y Nutrición, Salvador Zubirán, Vasco de Quiroga No. 15, Tlalpan 14000, México D.F., Mexico.
authors.forename: Euclides
authors.initials: E
authors.lastname: Avila
authors.forename: Lorenza
authors.initials: L
authors.lastname: Díaz
authors.forename: David
authors.initials: D
authors.lastname: Barrera
authors.forename: Ali
authors.initials: A
authors.lastname: Halhali
authors.forename: Isabel
authors.initials: I
authors.lastname: Méndez
authors.forename: Leticia
authors.initials: L
authors.lastname: González
authors.forename: Ulrich
authors.initials: U
authors.lastname: Zuegel
authors.forename: Andreas
authors.initials: A
authors.lastname: Steinmeyer
authors.forename: Fernando
authors.initials: F
authors.lastname: Larrea
mesh_terms: D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase / Q000378:metabolism*; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D002117:Calcitriol / Q000494:pharmacology*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism / Q000502:physiology*; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D010920:Placenta / Q000201:enzymology; D018167:Receptors, Calcitriol; D013250:Steroid Hydroxylases / Q000378:metabolism; D014327:Trophoblasts / Q000201:enzymology* / Q000502:physiology; D065668:Vitamin D3 24-Hydroxylase; D014815:Vitamins / Q000494:pharmacology
chemical_list: D018167:Receptors, Calcitriol; D014815:Vitamins; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000242:Cyclic AMP; D013250:Steroid Hydroxylases; C585549:CYP24A1 protein, human; D065668:Vitamin D3 24-Hydroxylase; D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase; D002117:Calcitriol