title: Toll-like receptor-4-dependence of the lipopolysaccharide-mediated inhibition of osteoblast differentiation.
abstract: Bone fractures or bones subjected to open conduction and internal fixation are easily infected by bacteria; bacterial lipopolysaccharide (LPS) has been recognized as an important pathogenic factor affecting bone fracture healing. Therefore, the effect of LPS on bone metabolism is relevant for bone healing. In this study, we investigated the effect of LPS on the expression of Toll-like receptor (TLR)-4 (an LPS receptor) by using real-time quantitative PCR and western blotting. We also examined the regulatory role of LPS in osteoblast differentiation by measuring the ALP activity, matrix mineralization, and ALP, OCN, and Runx2 mRNA (essential factors affecting osteoblast differentiation) expression in LPS-treated mouse osteoblast MC3T3-E1 cells. We also evaluated the effect of TLR-4 on LPS-mediated inhibition of osteoblast differentiation using RNA interference. LPS promotes TLR-4 mRNA and protein expression in MC3T3-E1 cells (P < 0.05, P < 0.01 or P < 0.001), and inhibits osteoblast differentiation by downregulating matrix mineralization and ALP activity (P < 0.05, P < 0.01 or P < 0.001), and suppressing the expression ALP, OCN, and Runx2 mRNA in MC3T3-E1 cells (P < 0.05 or P < 0.01). Conversely, RNAi-mediated TLR-4 knockdown abrogates the LPS-mediated inhibition of osteoblast differentiation (P < 0.05 or P < 0.01). In summary, LPS was shown to inhibit osteoblast differentiation by suppressing the expression of ALP, OCN, and Runx2 in a TLR-4-dependent manner. The results of this study may provide insights into the signal pathway of LPS-induced bone loss or delayed bone fracture healing.
authors.affiliation: Department of Traumatology and Microsurgery, The Third Clinical College, Southern Medical University.|Department of Emergency, Inner Mongolia Hohhot No. 1 Hospital, Hohhot, Inner Mongolia, China.
authors.forename: Y H
authors.initials: YH
authors.lastname: Liu
authors.affiliation: Department of Traumatology and Microsurgery, The Third Clinical College, Southern Medical University.
authors.forename: D
authors.initials: D
authors.lastname: Huang
authors.affiliation: Department of Preclinical Medicine, Inner Mongolia Medical University, Hohhot, Inner Mongolia, China.
authors.forename: Z J
authors.initials: ZJ
authors.lastname: Li
authors.affiliation: Department of Preclinical Medicine, Inner Mongolia Medical University, Hohhot, Inner Mongolia, China.
authors.forename: X H
authors.initials: XH
authors.lastname: Li
authors.affiliation: Department of Preclinical Medicine, Inner Mongolia Medical University, Hohhot, Inner Mongolia, China.
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Emergency, Inner Mongolia Hohhot No. 1 Hospital, Hohhot, Inner Mongolia, China.
authors.forename: H P
authors.initials: HP
authors.lastname: Yang
authors.affiliation: Department of Emergency, Inner Mongolia Hohhot No. 1 Hospital, Hohhot, Inner Mongolia, China.
authors.forename: S P
authors.initials: SP
authors.lastname: Tian
authors.affiliation: Department of Thoracic Surgery, Inner Mongolia Hohhot No. 1 Hospital, Hohhot, Inner Mongolia, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Mao
authors.affiliation: Department of Emergency, Inner Mongolia Hohhot No. 1 Hospital, Hohhot, Inner Mongolia, China.
authors.forename: M F
authors.initials: MF
authors.lastname: Liu
authors.affiliation: Department of Orthopedics, No. 2 Hospital of Shanxi Medical University, Taiyuan, Shanxi, China.
authors.forename: Y F
authors.initials: YF
authors.lastname: Wang
authors.affiliation: Department of Traumatology and Microsurgery, The Third Clinical College, Southern Medical University.
authors.forename: Y
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Department of Traumatology and Microsurgery, The Third Clinical College, Southern Medical University.
authors.forename: X F
authors.initials: XF
authors.lastname: Han
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000096:biosynthesis; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D050659:Core Binding Factor Alpha 1 Subunit / Q000096:biosynthesis; D050723:Fractures, Bone / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D008070:Lipopolysaccharides / Q000008:administration & dosage; D008565:Membrane Proteins / Q000096:biosynthesis; D051379:Mice; D010006:Osteoblasts / Q000378:metabolism* / Q000473:pathology; D010012:Osteogenesis / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D051197:Toll-Like Receptor 4 / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C480020:Atrnl1 protein, mouse; D050659:Core Binding Factor Alpha 1 Subunit; D008070:Lipopolysaccharides; D008565:Membrane Proteins; D012333:RNA, Messenger; C493716:Runx2 protein, mouse; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4