title: Hydrogen peroxide induces G2 cell cycle arrest and inhibits cell proliferation in osteoblasts.
abstract: Reactive oxygen species (ROSs) are involved in osteoporosis by inhibiting osteoblastic differentiation and stimulating osteoclastgenesis. Little is known about the role and how ROS controls proliferation of osteoblasts. Mammalian target of rapamycin, mTOR, is a central regulator of cell growth and proliferation. Here, we report for the first time that 5-200 microM hydrogen peroxide (H(2)O(2)) dose- and time-dependently suppressed cell proliferation without affecting cell viability in mouse osteoblast cell line, MC3T3-E1, and in human osteoblast-like cell line, MG63. Further study revealed that protein level of cyclin B1 decreased markedly and the percentage of the cells in G(2)/M phase increased about 2-4 fold by 200 microM H(2)O(2) treatment for 24-72 hr. A total of 0.5-5 mM of H(2)O(2) but not lower concentrations (5-200 microM) of H(2)O(2) inhibited mTOR signaling, as manifested by dephosphorylation of S6K (T389), 4E-BP1 (T37/46), and S6(S235/236) in MC3T3-E1 and MG63 cells. Rapamycin, which could inhibit mTOR signaling and cell proliferation, however, did not reduce the protein level of cyclin B1. In a summary, H(2)O(2) prevents cell proliferation of osteoblasts by down-regulating cyclin B1 and inducing G(2) cell cycle arrest. Inhibition of mTOR signaling by H(2)O(2) may not be involved in this process.
authors: Department of Cell Biology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China.
authors: Ming
authors: M
authors: Li
authors: Li
authors: L
authors: Zhao
authors: Jun
authors: J
authors: Liu
authors: An-Ling
authors: AL
authors: Liu
authors: Wei-Sen
authors: WS
authors: Zeng
authors: Shen-Qiu
authors: SQ
authors: Luo
authors: Xiao-Chun
authors: XC
authors: Bai
mesh_terms: D000818:Animals; D002453:Cell Cycle; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects*; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D015536:Down-Regulation; D016195:G2 Phase / Q000187:drug effects*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D051379:Mice; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects*; D011494:Protein Kinases / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases; D013997:Time Factors
chemical_list: C534699:CCNB1 protein, human; C534700:Ccnb1 protein, mouse; D019926:Cyclin B; D056744:Cyclin B1; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D011494:Protein Kinases; C546842:MTOR protein, human; C546843:mTOR protein, mouse; D058570:TOR Serine-Threonine Kinases