title: ERK5 signalling pathway is essential for fluid shear stress-induced COX-2 gene expression in MC3T3-E1 osteoblast.
abstract: Bone cells respond to various mechanical stimuli including fluid shear stress (FSS) in vitro. Induction of cyclooxygenase-2 (COX-2) is thought to be important for the anabolic effects of mechanical loading. Recently, extracellular-signal-regulated kinase 5 (ERK5) has been found to be involved in multiple cellular processes. However, the relationship between ERK5 and the induction of COX-2 is still unknown. Here, we investigated the potential involvement of ERK5 in the response of pre-osteoblastic MC3T3-E1 cells upon FSS. MC3T3-E1 cells were subjected to 12 dyn/cm(2) FSS. Then, we established a ERK5 small interfering RNA (siRNA) transfected cell line using the MC3T3-E1 cells. After the successful transfection confirmed by real-time reverse transcription-polymerase chain reaction and Western blotting, the expression of COX-2, cAMP response element-binding protein (CREB), and nuclear factor kappa B cells (NF-κB) were assayed for downstream effectors of activated ERK5 under FSS by Western blotting. Our results showed that FSS could stimulate COX-2 activity, and induce the phosphorylation of ERK5, CREB, and NF-κB. When the MC3T3-E1 cells were transfected using siRNA before exposure to FSS, COX-2 activity was suppressed, and the phosphorylation of CREB and NF-κB was significantly downregulated. In summary, we demonstrated that ERK5 pathway is essential in the induction of COX-2 gene.
authors.affiliation: Department of Orthopaedics, Second Hospital of Lanzhou University, No. 82 Cuiyingmen, Chengguan District, Lanzhou, Gansu, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Jiang
authors.forename: Liang-gong
authors.initials: LG
authors.lastname: Zhao
authors.forename: Yuan-jun
authors.initials: YJ
authors.lastname: Teng
authors.forename: Shao-long
authors.initials: SL
authors.lastname: Chen
authors.forename: Li-ping
authors.initials: LP
authors.lastname: An
authors.forename: Jing-ling
authors.initials: JL
authors.lastname: Ma
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.forename: Ya-yi
authors.initials: YY
authors.lastname: Xia
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D004790:Enzyme Induction; D051379:Mice; D048054:Mitogen-Activated Protein Kinase 7 / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D041681:NIH 3T3 Cells; D010006:Osteoblasts / Q000201:enzymology*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D015398:Signal Transduction; D013312:Stress, Physiological
chemical_list: D016328:NF-kappa B; C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2; D048054:Mitogen-Activated Protein Kinase 7