title: Vitamin-D receptor agonist calcitriol reduces calcification in vitro through selective upregulation of SLC20A2 but not SLC20A1 or XPR1.
abstract: Vitamin D deficiency (hypovitaminosis D) causes osteomalacia and poor long bone mineralization. In apparent contrast, hypovitaminosis D has been reported in patients with primary brain calcifications ("Fahr's disease"). We evaluated the expression of two phosphate transporters which we have found to be associated with primary brain calcification (SLC20A2, whose promoter has a predicted vitamin D receptor binding site, and XPR1), and one unassociated (SLC20A1), in an in vitro model of calcification. Expression of all three genes was significantly decreased in calcifying human bone osteosarcoma (SaOs-2) cells. Further, we confirmed that vitamin D (calcitriol) reduced calcification as measured by Alizarin Red staining. Cells incubated with calcitriol under calcifying conditions specifically maintained expression of the phosphate transporter SLC20A2 at higher levels relative to controls, by RT-qPCR. Neither SLC20A1 nor XPR1 were affected by calcitriol treatment and remained suppressed. Critically, knockdown of SLC20A2 gene and protein with CRISPR technology in SaOs2 cells significantly ablated vitamin D mediated inhibition of calcification. This study elucidates the mechanistic importance of SLC20A2 in suppressing the calcification process. It also suggests that vitamin D might be used to regulate SLC20A2 gene expression, as well as reduce brain calcification which occurs in Fahr's disease and normal aging.
authors.affiliation: Department of Biomedical Sciences - Quillen College of Medicine, East Tennessee State University, Johnson City, USA.|Keizo Asami Laboratory - Federal University of Pernambuco, Recife-PE, Brazil.
authors.forename: M P
authors.initials: MP
authors.lastname: Keasey
authors.affiliation: Keizo Asami Laboratory - Federal University of Pernambuco, Recife-PE, Brazil.
authors.forename: R R
authors.initials: RR
authors.lastname: Lemos
authors.affiliation: Department of Biomedical Sciences - Quillen College of Medicine, East Tennessee State University, Johnson City, USA.
authors.forename: T
authors.initials: T
authors.lastname: Hagg
authors.affiliation: Keizo Asami Laboratory - Federal University of Pernambuco, Recife-PE, Brazil.|Neuropsychiatry Department - Federal University of Pernambuco, Recife-PE, Brazil.
authors.forename: J R M
authors.initials: JR
authors.lastname: Oliveira
mesh_terms: D001205:Ascorbic Acid / Q000494:pharmacology; D064113:CRISPR-Cas Systems; D002114:Calcinosis / Q000235:genetics* / Q000473:pathology*; D002117:Calcitriol / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects; D045744:Cell Line, Tumor; D055785:Gene Knockdown Techniques; D005994:Glycerophosphates / Q000494:pharmacology; D006801:Humans; D008954:Models, Biological; D028061:Phosphate Transport Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018167:Receptors, Calcitriol / Q000819:agonists* / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000235:genetics* / Q000378:metabolism; D011991:Receptors, Virus / Q000235:genetics* / Q000378:metabolism; D050611:Sodium-Phosphate Cotransporter Proteins, Type III / Q000235:genetics* / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics*; D000089842:Xenotropic and Polytropic Retrovirus Receptor
chemical_list: D005994:Glycerophosphates; D028061:Phosphate Transport Proteins; D012333:RNA, Messenger; D018167:Receptors, Calcitriol; D043562:Receptors, G-Protein-Coupled; D011991:Receptors, Virus; C493586:SLC20A1 protein, human; C493589:SLC20A2 protein, human; D050611:Sodium-Phosphate Cotransporter Proteins, Type III; C000715267:XPR1 protein, human; D000089842:Xenotropic and Polytropic Retrovirus Receptor; D002117:Calcitriol; D001205:Ascorbic Acid; C031463:beta-glycerophosphoric acid