Hypoxia inducible factor-1α directly induces the expression of receptor activator of nuclear factor-κB ligand in periodontal ligament fibroblasts
During orthodontic tooth movement, local hypoxia and enhanced osteoclastogenesis are observed in the compression side of periodontal tissues. The receptor activator of nuclear factor-κB ligand (RANKL) is an osteoblast/stromal cell-derived factor that is essential for osteoclastogenesis. In this study, we examined the effect of hypoxia on RANKL expression in human periodontal ligament fibroblasts (PDLFs) to investigate the relationship between local hypoxia and enhanced osteoclastogenesis in the compression side of periodontal tissues. Hypoxia significantly enhanced the levels of RANKL mRNA and protein as well as hypoxia inducible factor-1α (HIF-1α) protein in PDLFs. Constitutively active HIF-1α alone significantly increased the levels of RANKL expression in PDLFs under normoxic conditions, whereas dominant negative HIF-1α blocked hypoxia-induced RANKL expression. To investigate further whether HIF-1α directly regulates RANKL transcription, a luciferase reporter assay was performed using the reporter vector containing the RANKL promoter sequence. Exposure to hypoxia or overexpression of constitutively active HIF-1α significantly increased RANKL promoter activity, whereas dominant negative HIF-1α blocked hypoxia-induced RANKL promoter activity. Furthermore, mutations of putative HIF-1α binding elements in RANKL promoter prevented hypoxia-induced RANKL promoter activity. The results of chromatin immunoprecipitation showed that hypoxia or constitutively active HIF-1α increased the DNA binding of HIF-1α to RANKL promoter. These results suggest that HIF-1α mediates hypoxia-induced up-regulation of RANKL expression and that in compression side periodontal ligament, hypoxia enhances osteoclastogenesis, at least in part, via an increased RANKL expression in PDLFs.
Keywordshypoxia hypoxia inducible factor-1α periodontal ligament fibroblasts RANK Ligand
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- Clauss, M., Weich, H., Breier, G., Knies, U., Rockl, W., Waltenberger, J., and Risau, W. (1996). The vascular endothelial growth factor receptor Flt-1 mediates biological activities. Implications for a functional role of placenta growth factor in monocyte activation and chemotaxis. J. Biol. Chem. 271, 17629–17634.PubMedCrossRefGoogle Scholar
- Kitase, Y., Yokozeki, M., Fujihara, S., Izawa, T., Kuroda, S., Tanimoto, K., Moriyama, K., and Tanaka, E. (2009). Analysis of gene expression profiles in human periodontal ligament cells under hypoxia: the protective effect of CC chemokine ligand 2 to oxygen shortage. Arch. Oral Biol. 54, 618–624.PubMedCrossRefGoogle Scholar
- Matsumoto, Y., Tanaka, K., Hirata, G., Hanada, M., Matsuda, S., Shuto, T., and Iwamoto, Y. (2002). Possible involvement of the vascular endothelial growth factor-Flt-1-focal adhesion kinase pathway in chemotaxis and the cell proliferation of osteoclast precursor cells in arthritic joints. J. Immunol. 168, 5824–5831.PubMedGoogle Scholar
- Nishijima, Y., Yamaguchi, M., Kojima, T., Aihara, N., Nakajima, R., and Kasai, K. (2006). Levels of RANKL and OPG in gingival crevicular fluid during orthodontic tooth movement and effect of compression force on releases from periodontal ligament cells in vitro. Orthod. Craniofac. Res. 9, 63–70.PubMedCrossRefGoogle Scholar
- Semenza, G.L., Jiang, B.H., Leung, S.W., Passantino, R., Concordet, J.P., Maire, P., and Giallongo, A. (1996). Hypoxia response elements in the aldolase A, enolase 1, and lactate dehydrogenase A gene promoters contain essential binding sites for hypoxia-inducible factor 1. J. Biol. Chem. 271, 32529–32537.PubMedCrossRefGoogle Scholar
- Shirakura, M., Tanimoto, K., Eguchi, H., Miyauchi, M., Nakamura, H., Hiyama, K., Tanaka, E., Takata, T., and Tanne, K. (2010). Activation of the hypoxia-inducible factor-1 in overloaded temporomandibular joint, and induction of osteoclastogenesis. Biochem. Biophys. Res. Commun. 393, 800–805.PubMedCrossRefGoogle Scholar
- Udagawa, N., Takahashi, N., Jimi, E., Matsuzaki, K., Tsurukai, T., Itoh, K., Nakagawa, N., Yasuda, H., Goto, M., Tsuda, E., et al. (1999). Osteoblasts/stromal cells stimulate osteoclast activation through expression of osteoclast differentiation factor/RANKL but not macrophage colony-stimulating factor: receptor activator of NF-kappa B ligand. Bone 25, 517–523.PubMedCrossRefGoogle Scholar
- Wan, C., Gilbert, S.R., Wang, Y., Cao, X., Shen, X., Ramaswamy, G., Jacobsen, K.A., Alaql, Z.S., Eberhardt, A.W., Gerstenfeld, L.C., et al. (2008). Activation of the hypoxia-inducible factor-1alpha pathway accelerates bone regeneration. Proc. Natl. Acad. Sci. USA 105, 686–691.PubMedCrossRefGoogle Scholar