title: NEMO-binding domain peptide promotes osteoblast differentiation impaired by tumor necrosis factor alpha.
abstract: Osteogenesis associated with persistent inflammation or infection exists in a broad range of conditions including rheumatoid arthritis and traumatic bone fracture. The poor outcomes of these conditions will benefit from more effective treatments. Here we investigated the molecular mechanisms and tested NEMO-binding domain peptide as a new approach of circumventing TNF-alpha inhibition of osteoblast differentiation. Our results showed: TNF-alpha markedly decreased BMP-2-induced alkaline phosphatase activity in the multipotent myoblast C2C12 cells in a dose dependent manner; stepwise experiments demonstrated that BMP-2-induced Smad1 activity was abrogated by addition of exogenous TNF-alpha or overexpression of NF-kappaB, and it was significantly elevated by overexpression of IkappaBalpha, an inhibitor of NF-kappaB; Western blotting showed that TNF-alpha markedly decreased the amount of phospho-Smad1 in BMP-2-activated C2C12 cells, but it did not alter Smad1 mRNA abundance as measured by real-time PCR; addition of a functional cell-permeable NEMO-binding domain (NBD) peptide antagonized NF-kappaB activity and ameliorated TNF-alpha inhibition of osteoblast differentiation. Taken together, our study reveals for the first time that NF-kappaB activation inhibits osteoblast differentiation by attenuating Smad1 activity and application of NBD peptide ameliorates this inhibitory effect. This could lead to new therapeutic drugs that circumvent the inflammatory inhibition of osteogenesis for treatment of traumatic open fractures with infection, rheumatoid arthritis and other bone loss disorders.
authors.affiliation: Department of Orthopedic Trauma, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China.
authors.forename: Wenfeng
authors.initials: W
authors.lastname: Li
authors.forename: Bin
authors.initials: B
authors.lastname: Yu
authors.forename: Mengmeng
authors.initials: M
authors.lastname: Li
authors.forename: Daming
authors.initials: D
authors.lastname: Sun
authors.forename: Yanjun
authors.initials: Y
authors.lastname: Hu
authors.forename: Ming
authors.initials: M
authors.lastname: Zhao
authors.forename: Cai-Bin
authors.initials: CB
authors.lastname: Cui
authors.forename: Shuxun
authors.initials: S
authors.lastname: Hou
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D006801:Humans; D051379:Mice; D032446:Myoblasts / Q000187:drug effects / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology*; D010012:Osteogenesis / Q000187:drug effects*; D010455:Peptides / Q000494:pharmacology*; D051898:Smad1 Protein / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors* / Q000494:pharmacology
chemical_list: D055396:Bone Morphogenetic Protein 2; C467063:NBD peptide, mouse; D016328:NF-kappa B; D010455:Peptides; D051898:Smad1 Protein; D014409:Tumor Necrosis Factor-alpha