title: NF-kappaB p100 limits TNF-induced bone resorption in mice by a TRAF3-dependent mechanism.
abstract: TNF and RANKL mediate bone destruction in common bone diseases, including osteoarthritis and RA. They activate NF-kappaB canonical signaling directly in osteoclast precursors (OCPs) to induce osteoclast formation in vitro. However, unlike RANKL, TNF does not activate the alternative NF-kappaB pathway efficiently to process the IkappaB protein NF-kappaB p100 to NF-kappaB p52, nor does it appear to induce osteoclast formation in vivo in the absence of RANKL. Here, we show that TNF limits RANKL- and TNF-induced osteoclast formation in vitro and in vivo by increasing NF-kappaB p100 protein accumulation in OCPs. In contrast, TNF induced robust osteoclast formation in vivo in mice lacking RANKL or RANK when the mice also lacked NF-kappaB p100, and TNF-Tg mice lacking NF-kappaB p100 had more severe joint erosion and inflammation than did TNF-Tg littermates. TNF, but not RANKL, increased OCP expression of TNF receptor-associated factor 3 (TRAF3), an adapter protein that regulates NF-kappaB p100 levels in B cells. TRAF3 siRNA prevented TNF-induced NF-kappaB p100 accumulation and inhibition of osteoclastogenesis. These findings suggest that upregulation of TRAF3 or NF-kappaB p100 expression or inhibition of NF-kappaB p100 degradation in OCPs could limit bone destruction and inflammation-induced bone loss in common bone diseases.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, 601 Elmwood Ave.,Rochester, NY 14642, USA.
authors.forename: Zhenqiang
authors.initials: Z
authors.lastname: Yao
authors.forename: Lianping
authors.initials: L
authors.lastname: Xing
authors.forename: Brendan F
authors.initials: BF
authors.lastname: Boyce
mesh_terms: D000818:Animals; D001862:Bone Resorption / Q000378:metabolism*; D002478:Cells, Cultured; D006801:Humans; D007596:Joints / Q000033:anatomy & histology / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D052003:NF-kappa B p52 Subunit / Q000235:genetics / Q000378:metabolism*; D010010:Osteoclasts / Q000166:cytology / Q000502:physiology*; D053245:RANK Ligand / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D013234:Stem Cells / Q000166:cytology / Q000502:physiology; D048008:TNF Receptor-Associated Factor 3 / Q000235:genetics / Q000378:metabolism*
chemical_list: D052003:NF-kappa B p52 Subunit; D053245:RANK Ligand; D034741:RNA, Small Interfering; D048008:TNF Receptor-Associated Factor 3; C505689:Tnfsf11 protein, mouse