title: AMP-activated protein kinase is involved in COX-2 expression in response to ultrasound in cultured osteoblasts.
abstract: It has been shown that ultrasound (US) stimulation accelerates fracture healing in the animal models and in clinical studies. Cyclooxygenase-2 (COX-2) is a crucial mediator in mechanically induced bone formation. AMP-activated protein kinase (AMPK) has reported to sense and regulate the cellular energy status in various cell types. Here we found that US-mediated COX-2 expression was attenuated by LKB1 and AMPKalpha1 small interference RNA (siRNA) in human osteoblasts. Pretreatment of osteoblasts with AMPK inhibitor (araA and compound C), p38 inhibitor (SB203580), NF-kappaB inhibitor (PDTC), IkappaB protease inhibitor (TPCK) and NF-kappaB inhibitor peptide also inhibited the potentiating action of US. US increased the kinase activity and phosphorylation of LKB1, AMPK and p38. Stimulation of osteoblasts with US activated IkappaB kinase alpha/beta (IKKalpha/beta), IkappaBalpha phosphorylation, IkappaBalpha degradation, p65 phosphorylation at Ser(276), p65 and p50 translocation from the cytosol to the nucleus, and kappaB-luciferase activity. US-mediated an increase of IKKalpha/beta activity, kappaB-luciferase activity and p65 and p50 binding to the NF-kappaB element was inhibited by araA, SB203580 and LKB1 siRNA. Our results suggest that US increased COX-2 expression in osteoblasts via the LKB1/AMPKalpha1/p38/IKKalphabeta and NF-kappaB signaling pathway.
authors.affiliation: Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan.
authors.forename: Chun-Han
authors.initials: CH
authors.lastname: Hou
authors.forename: Tzu-Wei
authors.initials: TW
authors.lastname: Tan
authors.forename: Chih-Hsin
authors.initials: CH
authors.lastname: Tang
mesh_terms: D000091162:AMP-Activated Protein Kinase Kinases; D055372:AMP-Activated Protein Kinases; D001483:Base Sequence; D002460:Cell Line; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D020672:I-kappa B Proteins / Q000378:metabolism; D008954:Models, Biological; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism; D010006:Osteoblasts / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction; D014162:Transfection; D014465:Ultrasonics; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D020672:I-kappa B Proteins; D009097:Multienzyme Complexes; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D034741:RNA, Small Interfering; D000072000:NF-KappaB Inhibitor alpha; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D017346:Protein Serine-Threonine Kinases; C109790:STK11 protein, human; D051550:I-kappa B Kinase; D048051:p38 Mitogen-Activated Protein Kinases; D000091162:AMP-Activated Protein Kinase Kinases; D055372:AMP-Activated Protein Kinases