Skip Navigation
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

National Institute of Environmental Health Sciences

Use this QR code to view the newest version of this document
Use this QR code to view the newest version of this document

Your Environment. Your Health.

Publication Detail

Title: Cooperative role of NF-{kappa}B and poly(ADP-ribose) polymerase 1 (PARP-1) in the TNF-induced inhibition of PHEX expression in osteoblasts.

Authors: Majewski, Pawel M; Thurston, Robert D; Ramalingam, Rajalakshmy; Kiela, Pawel R; Ghishan, Fayez K

Published In J Biol Chem, (2010 Nov 05)

Abstract: Reduced bone mass is a common complication in chronic inflammatory diseases, although the mechanisms are not completely understood. The PHEX gene encodes a zinc endopeptidase expressed in osteoblasts and contributes to bone mineralization. The aim of this study was to determine the molecular mechanism involved in TNF-mediated down-regulation of Phex gene transcription. We demonstrate down-regulation of the Phex gene in two models of colitis: naive T-cell transfer and in gnotobiotic IL-10(-/-) mice. In vitro, TNF decreased expression of Phex in UMR106 cells and did not require de novo synthesis of a transrepressor. Transfecting UMR-106 cells with a series of deletion constructs of the proximal Phex promoter identified a region located within -74 nucleotides containing NF-κB and AP-1 binding sites. After TNF treatment, the RelA/p50 NF-κB complex interacted with two cis-elements at positions -70/-66 and -29/-25 nucleotides in the proximal Phex promoter. Inhibition of NF-κB signaling increased the basal level of Phex transcription and abrogated the effects of TNF, whereas overexpression of RelA mimicked the effect of TNF. We identified poly(ADP-ribose) polymerase 1 (PARP-1) binding immediately upstream of the NF-κB sites and showed that TNF induced poly(ADP-ribosyl)ation of RelA when bound to the Phex promoter. TNF-mediated Phex down-regulation was completely abrogated in vitro by PARP-1 inhibitor and overexpression of poly(ADP-ribose) glucohydrolase (PARG) and in vivo in PARP-1(-/-) mice. Our results suggest that NF-κB signaling and PARP-1 enzymatic activity cooperatively contribute to the constitutive and inducible suppression of Phex. The described phenomenon likely contributes to the loss of bone mass density in chronic inflammatory diseases, such as inflammatory bowel disease.

PubMed ID: 20817730 Exiting the NIEHS site

MeSH Terms: Animals; Calcification, Physiologic/genetics; Cell Line; Colitis/genetics; Colitis/metabolism; Colitis/pathology; Disease Models, Animal; Gene Expression Regulation, Enzymologic*; Germ-Free Life*; Humans; Interleukin-10/genetics; Interleukin-10/metabolism; Mice; Mice, Knockout; Osteoblasts/metabolism*; Osteoblasts/pathology; PHEX Phosphate Regulating Neutral Endopeptidase/biosynthesis*; PHEX Phosphate Regulating Neutral Endopeptidase/genetics; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerases/genetics; Poly(ADP-ribose) Polymerases/metabolism*; Response Elements/genetics; Transcription Factor RelA/genetics; Transcription Factor RelA/metabolism*; Tumor Necrosis Factor-alpha/metabolism*

Back
to Top