title: Lipopolysaccharide (LPS) induces the apoptosis and inhibits osteoblast differentiation through JNK pathway in MC3T3-E1 cells.
abstract: Bone degradation is a serious complication of chronic inflammatory diseases such as septic arthritis, osteomyelitis, and infected orthopedic implant failure. Up to date, effective therapeutic treatments for bacteria-caused bone destruction are limited. In our previous study, we found that LPS promoted osteoclast differentiation and activity through activation of mitogen-activated protein kinases (MAPKs) pathway such as c-Jun N-terminal kinases (JNK) and extracellular signal regulated kinase (ERK1/2). The current study was to evaluate the mechanism of LPS on the apoptosis and osteoblast differentiation in MC3T3-E1 cells. MC3T3-E1 osteoblasts were non-treated, treated with LPS. After treatment, the cell viability, the activity of alkaline phosphatase (ALP) and caspase-3 were measured. The expressions of osteoblast-specific genes and Bax, Bcl-2, and caspase-3 were determined by real-time quantitative polymerase chain reaction (qPCR). Protein levels of Bax, Bcl-2, caspase-3, and phosphorylation of MAPKs were measured using Western blotting assays. The MAPK signaling pathway was blocked by pretreatment with JNK inhibitor SP600125. LPS treatment induced a significant decrease in cell metabolism, viability, and ALP activity in MC3T3-E1 cells. LPS also significantly decreased mRNA expressions of osteoblast-related genes in MC3T3-E1 cells. On the other hand, LPS significantly upregulated mRNA expressions and protein levels of Bax and caspase-3 as well as activation of caspase-3, whereas decreased Bcl-2 expression in MC3T3-E1 cells. Furthermore, LPS significantly promoted MAPK pathway including the phosphorylation of JNK and the phosphorylation of ERK1/2; moreover, pretreatment with JNK inhibitor not only attenuated both of phosphorylation-JNK and ERK1/2 enhanced by LPS in MC3T3-E1 cells, but also reversed the downregulated expressions of osteoblast-specific genes including ALP and BSP induced by LPS. In conclusion, LPS could induce osteoblast apoptosis and inhibit osteoblast differentiation via activation of JNK pathway.
authors.affiliation: Luohe Medical College, 148 Daxue Road, Luohe, 462002, Henan, People's Republic of China, guospring@126.com.
authors.forename: Chun
authors.initials: C
authors.lastname: Guo
authors.forename: Lei
authors.initials: L
authors.lastname: Yuan
authors.forename: Jian-guo
authors.initials: JG
authors.lastname: Wang
authors.forename: Fei
authors.initials: F
authors.lastname: Wang
authors.forename: Xu-Kai
authors.initials: XK
authors.lastname: Yang
authors.forename: Fu-hua
authors.initials: FH
authors.lastname: Zhang
authors.forename: Jin-ling
authors.initials: JL
authors.lastname: Song
authors.forename: Xu-yuan
authors.initials: XY
authors.lastname: Ma
authors.forename: Qi
authors.initials: Q
authors.lastname: Cheng
authors.forename: Guo-hua
authors.initials: GH
authors.lastname: Song
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D016723:Bone Remodeling / Q000187:drug effects*; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D051379:Mice; D010006:Osteoblasts / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism
chemical_list: C494827:Bax protein, mouse; D008070:Lipopolysaccharides; D047428:Protein Kinase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D051028:bcl-2-Associated X Protein; C482199:lipopolysaccharide, E coli O55-B5; C052617:Bcl2 protein, mouse; D048031:JNK Mitogen-Activated Protein Kinases; D000469:Alkaline Phosphatase; C505409:Casp3 protein, mouse; D053148:Caspase 3