Yoshihiro Konno1, Rick Moore, Nobuhiro Kamiya, Masahiko Negishi. 1. Pharmacogenetics Section, Laboratory of Reproductive and Developmental Toxicology, National Institute of Environmental Health Sciences, National Institutes of Health, North Carolina 27709, USA.
Abstract
OBJECTIVE: We previously found that the lack of nuclear xenobiotic receptor, PXR, decreases femoral bone mineral density (BMD) in Pxr-/- mice. Our present study aims to elucidate the inherited phenotype that correlates with the decreased BMD and to identify the PXR-regulated gene that may link with this phenotype. METHODS: Pxr+/+ and Pxr-/- mice were used to measure the serum levels of inorganic phosphate (Pi), calcium and vitamin D3. Real time PCR and western blots were used to determine the intestinal and renal expressions of Pi and calcium transporters and various other genes involved in bone homeostasis. Cell-based reporter and gel shift assays were performed to characterize the promoter of the identified PXR-regulated gene. RESULTS: In both Pxr-/- male and female mice, lumbar, sternum, and skull were all also found to have decreased their BMD values. Serum Pi levels, but not calcium levels, are attenuated in Pxr-/- mice, exhibiting a phenotype of hypophosphatemia. Among the members of the Na/Pi contransporter family, only the SLC34A2 mRNA and protein are repressed in Pxr-/- mice. PXR can directly activate the transcription of the SLC34A2 gene through an ER6 motif on its promoter. CONCLUSION: Pxr-/- mice show the inherited phenotype of hypophosphatemia. The lack of PXR results in a severe repression of the Na/Pi cotransporter NaPi-IIb/Npt2b (SLC34A2), thus leading Pxr-/- males and females to develop a type of hypophosphatemia.
OBJECTIVE: We previously found that the lack of nuclear xenobiotic receptor, PXR, decreases femoral bone mineral density (BMD) in Pxr-/- mice. Our present study aims to elucidate the inherited phenotype that correlates with the decreased BMD and to identify the PXR-regulated gene that may link with this phenotype. METHODS:Pxr+/+ and Pxr-/- mice were used to measure the serum levels of inorganic phosphate (Pi), calcium and vitamin D3. Real time PCR and western blots were used to determine the intestinal and renal expressions of Pi and calcium transporters and various other genes involved in bone homeostasis. Cell-based reporter and gel shift assays were performed to characterize the promoter of the identified PXR-regulated gene. RESULTS: In both Pxr-/- male and female mice, lumbar, sternum, and skull were all also found to have decreased their BMD values. Serum Pi levels, but not calcium levels, are attenuated in Pxr-/- mice, exhibiting a phenotype of hypophosphatemia. Among the members of the Na/Pi contransporter family, only the SLC34A2 mRNA and protein are repressed in Pxr-/- mice. PXR can directly activate the transcription of the SLC34A2 gene through an ER6 motif on its promoter. CONCLUSION:Pxr-/- mice show the inherited phenotype of hypophosphatemia. The lack of PXR results in a severe repression of the Na/Pi cotransporter NaPi-IIb/Npt2b (SLC34A2), thus leading Pxr-/- males and females to develop a type of hypophosphatemia.
Authors: Matthew C Salanga; Nadja R Brun; Rene D Francolini; John J Stegeman; Jared V Goldstone Journal: Toxicol Sci Date: 2020-03-01 Impact factor: 4.849