title: Fluid shear stress suppresses TNF-α-induced apoptosis in MC3T3-E1 cells: Involvement of ERK5-AKT-FoxO3a-Bim/FasL signaling pathways.
abstract: TNF-α is known to induce osteoblasts apoptosis, whereas mechanical stimulation has been shown to enhance osteoblast survival. In the present study, we found that mechanical stimulation in the form of fluid shear stress (FSS) suppresses TNF-α induced apoptosis in MC3T3-E1 cells. Extracellular signal-regulated kinase 5 (ERK5) is a member of the mitogen-activated protein kinase (MAPK) family that has been implicated in cell survival. We also demonstrated that FSS imposed by flow chamber in vitro leads to a markedly activation of ERK5, which was shown to be protective against TNF-α-induced apoptosis, whereas the transfection of siRNA against ERK5 (ERK5-siRNA) reversed the FSS-medicated anti-apoptotic effects. An initial FSS-mediated activation of ERK5 that phosphorylates AKT to increase its activity, and a following forkhead box O 3a (FoxO3a) was phosphorylated by activated AKT. Phosphorylated FoxO3a is sequestered in the cytoplasm, and prevents it from translocating to nucleus where it can increase the expression of FasL and Bim. The inhibition of AKT-FoxO3a signalings by a PI3K (PI3-kinase)/AKT inhibitor (LY294002) or the transfection of ERK5-siRNA led to the nuclear translocation of non-phosphorylated FoxO3a, and increased the protein expression of FasL and Bim. In addition, the activation of caspase-3 by TNF-α was significantly inhibited by aforementioned FSS-medicated mechanisms. In brief, the activation of ERK5-AKT-FoxO3a signaling pathways by FSS resulted in a decreased expression of FasL and Bim and an inhibition of caspase-3 activation, which exerts a protective effect that prevents osteoblasts from apoptosis.
authors.affiliation: The Second Hospital of Lanzhou University, #82 Cuiyingmen, Lanzhou, 730000 Gansu, China; Orthopaedics Key Laboratory of Gansu Province, Lanzhou, 730000 Gansu, China.
authors.forename: Geng
authors.initials: G
authors.lastname: Bin
authors.affiliation: The Second Hospital of Lanzhou University, #82 Cuiyingmen, Lanzhou, 730000 Gansu, China; Orthopaedics Key Laboratory of Gansu Province, Lanzhou, 730000 Gansu, China.
authors.forename: Zhang
authors.initials: Z
authors.lastname: Bo
authors.affiliation: The Second Hospital of Lanzhou University, #82 Cuiyingmen, Lanzhou, 730000 Gansu, China; Orthopaedics Key Laboratory of Gansu Province, Lanzhou, 730000 Gansu, China.
authors.forename: Wang
authors.initials: W
authors.lastname: Jing
authors.affiliation: The Second Hospital of Lanzhou University, #82 Cuiyingmen, Lanzhou, 730000 Gansu, China; Orthopaedics Key Laboratory of Gansu Province, Lanzhou, 730000 Gansu, China.
authors.forename: Jiang
authors.initials: J
authors.lastname: Jin
authors.affiliation: The Second Hospital of Lanzhou University, #82 Cuiyingmen, Lanzhou, 730000 Gansu, China; Orthopaedics Key Laboratory of Gansu Province, Lanzhou, 730000 Gansu, China.
authors.forename: Tan
authors.initials: T
authors.lastname: Xiaoyi
authors.affiliation: The Second Hospital of Lanzhou University, #82 Cuiyingmen, Lanzhou, 730000 Gansu, China; Orthopaedics Key Laboratory of Gansu Province, Lanzhou, 730000 Gansu, China.
authors.forename: Chen
authors.initials: C
authors.lastname: Cong
authors.affiliation: The Second Hospital of Lanzhou University, #82 Cuiyingmen, Lanzhou, 730000 Gansu, China; Orthopaedics Key Laboratory of Gansu Province, Lanzhou, 730000 Gansu, China.
authors.forename: An
authors.initials: A
authors.lastname: Liping
authors.affiliation: The Second Hospital of Lanzhou University, #82 Cuiyingmen, Lanzhou, 730000 Gansu, China; Orthopaedics Key Laboratory of Gansu Province, Lanzhou, 730000 Gansu, China.
authors.forename: Ma
authors.initials: M
authors.lastname: Jinglin
authors.affiliation: The Second Hospital of Lanzhou University, #82 Cuiyingmen, Lanzhou, 730000 Gansu, China; Orthopaedics Key Laboratory of Gansu Province, Lanzhou, 730000 Gansu, China.
authors.forename: Wang
authors.initials: W
authors.lastname: Cuifang
authors.affiliation: The Second Hospital of Lanzhou University, #82 Cuiyingmen, Lanzhou, 730000 Gansu, China; Orthopaedics Key Laboratory of Gansu Province, Lanzhou, 730000 Gansu, China.
authors.forename: Chen
authors.initials: C
authors.lastname: Yonggang
authors.affiliation: The Second Hospital of Lanzhou University, #82 Cuiyingmen, Lanzhou, 730000 Gansu, China; Orthopaedics Key Laboratory of Gansu Province, Lanzhou, 730000 Gansu, China. Electronic address: xiayayildey@163.com.
authors.forename: Xia
authors.initials: X
authors.lastname: Yayi
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D000072224:Bcl-2-Like Protein 11 / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D053222:Fas Ligand Protein / Q000378:metabolism*; D000071316:Forkhead Box Protein O3 / Q000378:metabolism*; D020868:Gene Silencing / Q000187:drug effects; D051379:Mice; D048054:Mitogen-Activated Protein Kinase 7 / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D012212:Rheology; D015398:Signal Transduction / Q000187:drug effects; D013314:Stress, Mechanical; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D000072224:Bcl-2-Like Protein 11; D053222:Fas Ligand Protein; D000071316:Forkhead Box Protein O3; C474033:FoxO3 protein, mouse; D034741:RNA, Small Interfering; D014409:Tumor Necrosis Factor-alpha; D051057:Proto-Oncogene Proteins c-akt; D048054:Mitogen-Activated Protein Kinase 7; D053148:Caspase 3
keywords: Bim; Extracellular signal-regulated kinase 5; FasL; Fluid shear stress; Forkhead box O 3a; Osteoblasts