Ultrasound induces cyclooxygenase-2 expression through integrin, integrin-linked kinase, Akt, NF-kappaB and p300 pathway in human chondrocytes.
It has been shown that ultrasound (US) stimulation accelerates fracture healing in the animal models and in clinical studies. However, the precise molecular events generated by US in chondrocytes have not been clarified well. Here we found that US stimulation transiently increased the surface expression of alpha2, alpha5, beta1 or beta3 but not alpha3 or alpha4 integrins in human chondrocytes, as shown by flow cytometric analysis. US stimulation increased prostaglandin E(2) formation as well as the protein and mRNA levels of cyclooxygenase-2 (COX-2). At the mechanistic level, anti-integrin beta1 and beta3 antibodies or beta1 and beta3 integrin small interference RNA attenuated the US-induced COX-2 expression. Integrin-linked kinase (ILK) inhibitor (KP-392), Akt inhibitor, NF-kappaB inhibitor (PDTC) or IkappaB protease inhibitor (TPCK) also inhibited the potentiating action of US. US stimulation promotes kinase activity of ILK, phosphorylation of Akt. In addition, US stimulation also induces IKKalpha/beta phosphorylation, IkappaBalpha phosphorylation, IkappaBalpha degradation, p65 phosphorylation at Ser(276), p65 and p50 translocation from the cytosol to the nucleus, and kappaB-luciferase activity. The binding of p65 to the NF-kappaB element, as well as the recruitment of p300 and the enhancement of p50 acetylation on the COX-2 promoter was enhanced by US. Taken together, our results provide evidence that US stimulation increases COX-2 expression in chondrocytes via the integrin/ILK/Akt/NF-kappaB and p300 signaling pathway.
Hsu
Horng-Chaung
HC
Department of Orthopaedics, China Medical University Hospital, Taichung, Taiwan.
Fong
Yi-Chin
YC
Chang
Chih-Shiang
CS
Hsu
Chin-Jung
CJ
Hsu
Sheng-Feng
SF
Lin
Jaung-Geng
JG
Fu
Wen-Mei
WM
Yang
Rong-Sen
RS
Tang
Chih-Hsin
CH
D002478:Cells, Cultured; D019902:Chondrocytes / Q000201:enzymology*; D051546:Cyclooxygenase 2 / Q000096:biosynthesis*; D050881:E1A-Associated p300 Protein / Q000378:metabolism*; D004790:Enzyme Induction; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D008954:Models, Biological; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000235:genetics; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D015398:Signal Transduction; D014465:Ultrasonics; D000099200:Scaffold Protein ILK
D051546:Cyclooxygenase 2; D050881:E1A-Associated p300 Protein; D016023:Integrins; D016328:NF-kappa B; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D000099200:Scaffold Protein ILK; C496540:PTGS2 protein, human; C494360:EP300 protein, human