Abstract
Osteoprotegerin (OPG), a secreted member of the tumor necrosis factor receptor superfamily, is a potent inhibitor of osteoclast formation and bone resorption. Because OPG functions physiologically as a locally generated (paracrine) factor, we used high-throughput screening to identify small molecules that enhance the activity of the promoter of the human OPG gene. We found three structurally unrelated compounds that selectively increased OPG gene transcription, OPG mRNA levels, and OPG protein production and release by osteoblastic cells. Structural analysis of one compound, a benzamide derivative, led to the identification of four related molecules, which are also OPG inducers. The most potent of these compounds, Cmpd 5 inhibited osteoclast formation and parathyroid hormone-induced calvarial bone resorption. In vivo, Cmpd 5 completely blocked resorptive activity (serum calcium, osteoclast number) in parathyroid hormone-treated rats. Furthermore, Cmpd 5 reduced the ability of a rat breast cancer to metastasize to bone. Finally, the compound also prevented bone loss in a rat adjuvant arthritis model. These results provide proof of the concept that low molecular weight compounds can enhance OPG production in ways that can result in effective therapies.
Footnotes
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↵1 Contributed equally to this manuscript.
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This project was supported by Eli Lilly and Company. These data were presented in abstract and oral form at the American Society for Bone and Mineral Research Annual Meeting, Sept. 19-23, 2003 in Minneapolis, MN.
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DOI: 10.1124/jpet.103.057893.
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ABBREVIATIONS: OPG, osteoprotegerin; TNF, tumor necrosis factor; RANK, receptor activator of nuclear factor κ B; RANKL, RANK ligand; β-gal, β-galactosidase; HDAC, histone deacetylase; PTH, parathyroid hormone; TGF-β, transforming growth factor beta; FBS, fetal bovine serum; DMSO, dimethyl sulfoxide; ELISA, enzyme-linked immunosorbent assay; PBS, phosphate-buffered saline; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; TRAP, tartrate-resistant acid phosphatase; PTX, parathyroidectomized; RLU, relative light units; Cmpd, compound; SV40, simian virus 40; MOPS, 3-(N-morpholino)propanesulfonic acid; SSC, standard saline citrate; 1,25(OH)2D3, 1,25-dihydroxyvitamin D3.
- Received July 30, 2003.
- Accepted December 31, 2003.
- The American Society for Pharmacology and Experimental Therapeutics
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