title: Lipopolysaccharide (LPS) promotes osteoclast differentiation and activation by enhancing the MAPK pathway and COX-2 expression in RAW264.7 cells.
abstract: Bone degradation is a serious complication of chronic inflammatory diseases such as septic arthritis, osteomyelitis and infected orthopedic implant failure. At present, effective therapeutic treatments for lipopolysaccharide (LPS)-induced bone destruction are limited to antibiotics and surgical repair in chronic inflammatory diseases. The present study aimed to evaluate the mechanism of LPS on osteoclast differentiation and activation. RAW264.7 cells were non-induced, or induced by the receptor activator of nuclear factor-κB (RANK) ligand (RANKL) and macrophage-colony stimulating factor (M-CSF), and then treated with LPS. Following treatment, the number of osteoclasts and cell viability were measured. The expression of osteoclast-related genes including tartrate-resistant acid phosphatase (TRAP), matrix metalloproteinase-9 (MMP-9), cathepsin K (CK), carbonic anhydrase II (CAII) and cyclooxygenase-2 (COX-2) was determined by RT-PCR. Protein levels of RANK, tumor necrosis factor receptor-associated factor 6 (TRAF6), COX-2 and mitogen-activated protein kinases (MAPK) were measured using western blotting assays. LPS promoted osteoclast differentiation of RAW264.7 cells and differentiated osteoclasts. LPS significantly increased mRNA expression of osteoclast-related genes in RAW264.7 cells. Differentiated osteoclasts were treated with LPS (100 ng/ml) and the results showed a significantly increased mRNA expression of osteoclast-related genes and protein levels of RANK, TRAF6 and COX-2. Furthermore, LPS at 100 ng/ml significantly promoted the MAPK pathway including increasing the phosphorylation of c-Jun N-terminal kinases (JNK) and the phosphorylation of the extracellular signal-regulated kinase (ERK1/2). In conclusion, LPS promoted osteoclast differentiation and activation by enhancing RANK signaling and COX-2 expression. LPS also promoted osteoclast differentiation via activation of the JNK and ERK1/2 cell proliferation pathways.
authors.affiliation: First Affiliated Hospital, Medical College of Shantou University, Shantou, Guangdong 515041, P.R. China.
authors.forename: Guo-Qing
authors.initials: GQ
authors.lastname: Hou
authors.forename: Chun
authors.initials: C
authors.lastname: Guo
authors.forename: Guo-Hua
authors.initials: GH
authors.lastname: Song
authors.forename: Na
authors.initials: N
authors.lastname: Fang
authors.forename: Wen-Juan
authors.initials: WJ
authors.lastname: Fan
authors.forename: Xu-Dong
authors.initials: XD
authors.lastname: Chen
authors.forename: Lei
authors.initials: L
authors.lastname: Yuan
authors.forename: Zhen-Quan
authors.initials: ZQ
authors.lastname: Wang
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D008070:Lipopolysaccharides / Q000276:immunology / Q000494:pharmacology; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010010:Osteoclasts / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D010766:Phosphorylation; D053246:Receptor Activator of Nuclear Factor-kappa B / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D048029:TNF Receptor-Associated Factor 6 / Q000378:metabolism
chemical_list: D008070:Lipopolysaccharides; D053246:Receptor Activator of Nuclear Factor-kappa B; D048029:TNF Receptor-Associated Factor 6; D051546:Cyclooxygenase 2; D020928:Mitogen-Activated Protein Kinases