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J Clin Invest. 2009 Oct;119(10):3024-34. doi: 10.1172/JCI38716. Epub 2009 Sep 21.

NF-kappaB p100 limits TNF-induced bone resorption in mice by a TRAF3-dependent mechanism.

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Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, 601 Elmwood Ave.,Rochester, NY 14642, USA.


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.

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