Hypoxia Inducible Factor-1α Directly Induces the Expression of Receptor Activator of Nuclear Factor-κB Ligand in MLO-Y4 Osteocytes
2
조회
0
다운로드
1
인용
0
참고문헌
키워드
초록
Osteocytes may function as mechanotransducers byregulating local osteoclastogenesis. Reduced availability ofoxygen, i.e. hypoxia, could occur during disuse, bonedevelopment, and fracture. Receptor activator of nuclearfactor-κB ligand (RANKL) is an osteoblast/stromal cellderived essential factor for osteoclastogenesis. The hypoxiainduced osteoclastogenesis via increased RANKL expressionin osteoblasts was demonstrated. Hypoxic regulation of geneexpression generally involves activation of thehypoxia-inducible factor (HIF) transcription pathway. In thepresent study, we investigated whether hypoxia regulatesRANKL expression in murine osteocytes and HIF-1αmediates hypoxia-induced RANKL expression bytransactivating RANKL promoter, to elucidate the role ofosteocyte in osteoclastogenesis in the context of hypoxiccondition. The expression levels of RANKL mRNA andprotein, as well as hypoxia inducible factor-1α (HIF-1α)protein, were significantly increased in hypoxic condition inMLO-Y4s. Constitutively active HIF-1α alone significantlyincreased the levels of RANKL expression in MLO-Y4sunder normoxic conditions, whereas dominant negativeHIF-1α blocked hypoxia-induced RANKL expression. Tofurther explore to find if HIF-1α directly regulates RANKLtranscription, a luciferase reporter assay was conducted. Hypoxia significantly increased RANKL promoter activity,whereas mutations of putative HIF-1α binding elements inRANKL promoter prevented this hypoxia-induced RANKLpromoter activity in MLO-Y4s. These results suggest thatHIF-1α mediates hypoxia-induced up-regulation of RANKLexpression, and that in osteocytes of mechanically unloadedbone, hypoxia enhances osteoclastogenesis, at least in part, viaan increased RANKL expression in osteocytes.
Abstract
Osteocytes may function as mechanotransducers byregulating local osteoclastogenesis. Reduced availability ofoxygen, i.e. hypoxia, could occur during disuse, bonedevelopment, and fracture. Receptor activator of nuclearfactor-κB ligand (RANKL) is an osteoblast/stromal cellderived essential factor for osteoclastogenesis. The hypoxiainduced osteoclastogenesis via increased RANKL expressionin osteoblasts was demonstrated. Hypoxic regulation of geneexpression generally involves activation of thehypoxia-inducible factor (HIF) transcription pathway. In thepresent study, we investigated whether hypoxia regulatesRANKL expression in murine osteocytes and HIF-1αmediates hypoxia-induced RANKL expression bytransactivating RANKL promoter, to elucidate the role ofosteocyte in osteoclastogenesis in the context of hypoxiccondition. The expression levels of RANKL mRNA andprotein, as well as hypoxia inducible factor-1α (HIF-1α)protein, were significantly increased in hypoxic condition inMLO-Y4s. Constitutively active HIF-1α alone significantlyincreased the levels of RANKL expression in MLO-Y4sunder normoxic conditions, whereas dominant negativeHIF-1α blocked hypoxia-induced RANKL expression. Tofurther explore to find if HIF-1α directly regulates RANKLtranscription, a luciferase reporter assay was conducted. Hypoxia significantly increased RANKL promoter activity,whereas mutations of putative HIF-1α binding elements inRANKL promoter prevented this hypoxia-induced RANKLpromoter activity in MLO-Y4s. These results suggest thatHIF-1α mediates hypoxia-induced up-regulation of RANKLexpression, and that in osteocytes of mechanically unloadedbone, hypoxia enhances osteoclastogenesis, at least in part, viaan increased RANKL expression in osteocytes.
참고문헌 (23)
- Wada T, "RANKL-RANK signaling in osteoclastogenesis and bone disease", Trends Mol Med, 12, pp.17~25 (2006)[DOI]
- Udagawa N, "Osteoblasts", stromal cells stimulate osteoclast activation through expression of osteoclast differentiation factor, Bone, pp.1999, 25[DOI]
- Lidan You, "Osteocytes as mechanosensors in the inhibition of bone resorption due to mechanical loading", Bone, 42(1), pp.172~179 (2008), Elsevier BV[DOI]
- E. SCHIPANI, "Hypoxia and HIF-1 in Chondrogenesis", Annals of the New York Academy of Sciences, 1068(1), pp.66~73 (2006), Wiley-Blackwell[DOI]
- Dodd JS, "Osteocyte hypoxia : a novel mechanotransduction pathway", Am J Physiol, 277, pp.598~602 (1999)
- Devakara R. Epari, "Pressure, oxygen tension and temperature in the periosteal callus during bone healing—An in vivo study in sheep", Bone, 43(4), pp.734~739 (2008), Elsevier BV[DOI]
- D.E Komatsu, "Activation of the transcription factor HIF-1 and its target genes, VEGF, HO-1, iNOS, during fracture repair", Bone, 34(4), pp.680~688 (2004), Elsevier BV[DOI]
- Brighton CT, "Oxygen tension of healing fractures in the rabbit", J Bone Joint Surg Am, 54, pp.323~332 (1972)
- Knowles HJ, "Hypoxia-inducible factor regulates osteoclast-mediated bone resorption : role of angiopoietin-like 4", FASEB J, 24, pp.4648~4659 (2010)
- Hyun-Jung Park, "Hypoxia Inducible Factor-1α Directly Induces then Expression of Receptor Activator of Nuclear Factor-κB Ligand in Periodontal Ligament Fibroblasts", Molecules and Cells, 31(6), pp.573~578 (2011), 한국분자세포생물학회
- Riddle RC, "Hypoxia-inducible factor-1α protein negatively regulates load-induced bone formation", J Biol Chem, 286, pp.44449~44456 (2011)
- Agnieszka Loboda, "HIF-1 and HIF-2 Transcription Factors - Similar but Not Identical", Molecules and Cells, 29(5), pp.435~442 (2010), 한국분자세포생물학회
- Stachurska A, "The new face of factors induced by hypoxia-HIF-1 and HIF-2and oxidative stress", Postepy biochemii, 56, pp.156~164 (2010)
- Arnett TR, "Hypoxia is a major stimulator of osteoclast formation and bone resorption", J Cell Physiol, 196, pp.2~8 (2003)
- Knowles HJ, "Acute hypoxia and osteoclast activity : a balance between enhanced resorption and increased apoptosis", J Pathol, 218, pp.256~264 (2009)
- Steinbach JP, "Inhibition of epidermal growth factor receptor signaling protects human malignant glioma cells from hypoxia-induced cell death", Cancer research, 64, pp.1575~1578 (2004)[DOI]
- Hamrick SE, "A role for hypoxia-inducible factor-1α in desferoxamine neuroprotection", Neurosci Lett, 379, pp.96~100 (2005)
- Yang-SookChun, "Oxygen-Dependent and -Independent Regulation of HIF-1alpha", Journal of Korean Medical Science, 17(5), pp.581~588 (2002), 대한의학회
- Chun YS, "A dominant-negative isoform lacking exons 11 and 12 of the human hypoxia-inducible factor-1α gene", Biochem J, 362, pp.71~79 (2002)
- Amarilio R, "HIF1α regulation of Sox9 is necessary to maintain differentiation of hypoxic prechondrogenic cells during early skeletogenesis", Development, 134, pp.3917~3928 (2007)
- Semenza GL, "Expression of hypoxia-inducible factor 1:mechanisms and consequences", Biochem Pharmacol, 59, pp.47~53 (2000)
- Wan C, "Activation of the hypoxia-inducible factor-1α pathway accelerates bone regeneration", Proc Natl Acad Sci U S A, 105, pp.686~691 (2008)
- Semenza GL, "Assignment of the hypoxia-inducible factor-1α gene to a region of conserved synteny on mouse chromosome 12 and human chromosome 14q", Genomics, 34, pp.437~439 (1996)