MAPK and SRC-kinases control EGR-1 and NF-kappa B inductions by changes in mechanical environment in osteoblasts.
Bone loss occurs in microgravity whereas an increase in bone mass is observed after skeletal loading. This tissue adaptation involves changes in osteoblastic proliferation and differentiation whose mechanisms remain largely unknown. In this context, we investigated the expression and the nuclear translocation of Egr-1 and NF-kappa B, in a simulated microgravity model (clinostat) and in a model of mechanical strain (Flexcell). We performed RT-PCR and immunocytochemistry analyses at baseline and up to 2 h after stimulation (a mitogenic regimen, 1% stretch, 0.05 Hz, 10 min, or clinorotation 50 rpm, 10 min) in osteoblastic ROS17/2.8 cells. Egr-1 induction as well as NF-kappa B nuclear translocation were activated by mechanical changes. PKC downregulation and COX1/2 inhibition did not alter these inductions. In contrast, ERK1/2, p38(MAPK) and src-kinases pathways were differentially involved in both models. Thus, we demonstrated that changes in the mechanical environment induced an activation of Egr-1 and NF-kappa B with specific kinetics and involved various transduction pathways including MAPKs and src-kinases. These could partially explain the later alterations of proliferation observed.
Granet
C
C
Laboratoire de Biologie et de Biochimie du Tissu Osseux LBBTO, INSERM E9901, Faculté de Médecine, 15 rue A. Paré, 42023 Saint-Etienne Cedex 2, France. lafagemh@univ-st-etienne.fr
Boutahar
N
N
Vico
L
L
Alexandre
C
C
Lafage-Proust
M H
MH
D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D051766:Early Growth Response Protein 1; D006801:Humans; D017874:Immediate-Early Proteins; D007700:Kinetics; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D010006:Osteoblasts / Q000378:metabolism*; D021381:Protein Transport; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D013314:Stress, Mechanical; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D018474:Weightlessness Simulation; D019061:src-Family Kinases / Q000502:physiology*
D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; C486110:Egr1 protein, rat; D017874:Immediate-Early Proteins; D016328:NF-kappa B; D012333:RNA, Messenger; D014157:Transcription Factors; D019061:src-Family Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases