title: Obatoclax regulates the proliferation and fusion of osteoclast precursors through the inhibition of ERK activation by RANKL.
abstract: Obatoclax, a pan-Bcl2 inhibitor, shows antitumor activities in various solid malignancies. Bcl2-deficient mice have shown the importance of Bcl2 in osteoclasts, as the bone mass of the mice was increased by the induced apoptosis of osteoclasts. Despite the importance of Bcl2, the effects of obatoclax on the proliferation and differentiation of osteoclast precursors have not been studied extensively. Here, we describe the anti-proliferative effects of obatoclax on osteoclast precursors and its negative role on fusion of the cells. Stimulation with low doses of obatoclax significantly suppressed the proliferation of osteoclast precursors in a dose-dependent manner while the apoptosis was markedly increased. Its stimulation was sufficient to block the activation of ERK MAP kinase by RANKL. The same was true when PD98059, an ERK inhibitor, was administered to osteoclast precursors. The activation of JNK1/2 and p38 MAP kinase, necessary for osteoclast differentiation, by RANKL was not affected by obatoclax. Interestingly, whereas the number of TRAP-positive mononuclear cells was increased by both obatoclax and PD98059, fused, multinucleated cells larger than 100 μm in diameter containing more than 20 nuclei were completely reduced. Consistently, obatoclax failed to regulate the expression of osteoclast marker genes, including c-Fos, TRAP, RANK and CtsK. Instead, the expression of DC-STAMP and Atp6v0d2, genes that regulate osteoclast fusion, by RANKL was significantly abrogated by both obatoclax and PD98059. Taken together, these results suggest that obatoclax down-regulates the proliferation and fusion of osteoclast precursors through the inhibition of the ERK1/2 MAP kinase pathway.
authors: Department of Biomedical Laboratory Science, College of Medical Sciences, Soonchunhyang University, Chungnam, 336-745, Korea.
authors: Ju Hee
authors: JH
authors: Oh
authors: Department of Biomedical Laboratory Science, College of Medical Sciences, Soonchunhyang University, Chungnam, 336-745, Korea.
authors: Jae Yoon
authors: JY
authors: Lee
authors: Department of Biomedical Laboratory Science, College of Medical Sciences, Soonchunhyang University, Chungnam, 336-745, Korea.
authors: Jin Hyeong
authors: JH
authors: Park
authors: Department of Biomedical Laboratory Science, College of Medical Sciences, Soonchunhyang University, Chungnam, 336-745, Korea.
authors: Jeong Hyeon
authors: JH
authors: No
authors: Department of Biomedical Laboratory Science, College of Medical Sciences, Soonchunhyang University, Chungnam, 336-745, Korea.
authors: Na Kyung
authors: NK
authors: Lee
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002459:Cell Fusion; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005419:Flavonoids / Q000494:pharmacology; D015870:Gene Expression; D020868:Gene Silencing; D007211:Indoles; D020935:MAP Kinase Signaling System; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008810:Mice, Inbred C57BL; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D010010:Osteoclasts / Q000502:physiology*; D011758:Pyrroles / Q000494:pharmacology*; D053245:RANK Ligand / Q000502:physiology*; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism
chemical_list: C499636:DC-STAMP protein, mouse; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007211:Indoles; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D011758:Pyrroles; D053245:RANK Ligand; C505689:Tnfsf11 protein, mouse; D048049:Extracellular Signal-Regulated MAP Kinases; C542312:Atp6v0d2 protein, mouse; D025262:Vacuolar Proton-Translocating ATPases; C520962:obatoclax; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one
keywords: ERK1/2 MAP kinase; fusion; obatoclax; osteoclast precursors; proliferation