Most forms of localized or generalized bone loss are due to NF-?B-mediated increased bone resorption and inadequate or decreased bone formation. Despite recent major advances, understanding of the mechanisms involved remains incomplete, therapeutic options are limited, and potential adverse effects of drugs limit patient compliance. NF-?B signaling positively regulates osteoclast (OC) formation, but it also inhibits osteoblast (OB) formation, and requires recruitment of TNF receptor-associated factors (TRAFs) to cytokine receptors to mediate downstream signaling. Thus, strategies to inhibit NF-?B or TRAF functions could reduce bone resorption and potentially increase formation. Despite these advances, there are no NF-?B inhibitors in clinical trials. We reported previously that TRAF3 (which generally works to inhibit NF-?B signaling) limits TNF-induced OC formation. In the current funding period, we extended these studies and generated mice with TRAF3 conditionally deleted in OC (LysM;traf3 cKO) and OB (Prx1;traf3 cKO) lineage cells. Our recently published and preliminary data show that expression of TRAF3 is required not only in OC, but also in OB lineage cells to maintain normal bone mass in mice as they age. Specifically, we have found that RANKL promotes TRAF3 ubiquitylation and degradation in OC precursors (OCPs) via autophagy, and the autophagy inhibitor, chloroquine (CQ), inhibits RANKL-induced OC formation and prevents PTH- and OVX-induced bone resorption in WT, but not in OC-Traf3 cKO mice. Prx1;traf3 cKO mice develop age-related bone loss with increased OC numbers and reduced bone formation. Bone marrow stromal cells (BMSCs) from Prx1;traf3 cKO mice express high levels of RANKL and have markedly decreased OB differentiation. TGF? reduces TRAF3 levels in OBs. These findings reveal novel and important roles for TRAF3 in OCs and OBs and suggest that inhibition of its degradation should prevent bone loss in a variety of clinical settins. In this competitive renewal, we plan to study the mechanisms whereby TRAF3 regulates osteoclast formation and inhibits osteoblast functions, and if inhibition of autophagic degradation of TRAF3 prevents bone loss by targeting both OCs and OBs. Our findings should identify TRAF3 as a new and important therapeutic target for preservation of bone mass and determine if CQ can prevent bone resorption and increase bone formation by inhibiting autophagy in bone cells.
Most humans develop bone loss as a result of aging, menopause, and inflammation caused by decreased activity of bone forming cells, called osteoblasts and increased activity of bone destroying cells, called osteoclasts. We propose to study the mechanisms whereby aging decreases osteoblast and increases osteoclast functions focusing on the role of TRAF3, a protein, which we have shown can promote osteoblast and inhibit osteoclast formation, and determine if we can alter TRAF3 levels in osteoblasts and osteoclasts to treat bone loss.
|Boyce, Brendan F; Li, Jinbo; Xing, Lianping et al. (2018) Bone Remodeling and the Role of TRAF3 in Osteoclastic Bone Resorption. Front Immunol 9:2263|
|Xiu, Yan; Dong, Qianze; Li, Qingchang et al. (2018) Stabilization of NF-?B-Inducing Kinase Suppresses MLL-AF9-Induced Acute Myeloid Leukemia. Cell Rep 22:350-358|
|Sun, Wen; Meednu, Nida; Rosenberg, Alexander et al. (2018) B cells inhibit bone formation in rheumatoid arthritis by suppressing osteoblast differentiation. Nat Commun 9:5127|
|Yao, Zhenqiang; Lei, Wei; Duan, Rong et al. (2017) RANKL cytokine enhances TNF-induced osteoclastogenesis independently of TNF receptor associated factor (TRAF) 6 by degrading TRAF3 in osteoclast precursors. J Biol Chem 292:10169-10179|
|Li, Xing; Sun, Wen; Li, Jinbo et al. (2017) Clomipramine causes osteoporosis by promoting osteoclastogenesis via E3 ligase Itch, which is prevented by Zoledronic acid. Sci Rep 7:41358|
|Wang, Wensheng; Wang, Hua; Zhou, Xichao et al. (2017) Lymphatic Endothelial Cells Produce M-CSF, Causing Massive Bone Loss in Mice. J Bone Miner Res 32:939-950|
|Sun, Wen; Zhang, Hengwei; Wang, Hua et al. (2017) Targeting Notch-Activated M1 Macrophages Attenuates Joint Tissue Damage in a Mouse Model of Inflammatory Arthritis. J Bone Miner Res 32:1469-1480|
|Zhang, Longze; Chang, Martin; Beck, Christopher A et al. (2016) Analysis of new bone, cartilage, and fibrosis tissue in healing murine allografts using whole slide imaging and a new automated histomorphometric algorithm. Bone Res 4:15037|
|Krieger, Nancy S; Yao, Zhenqiang; Kyker-Snowman, Kelly et al. (2016) Increased bone density in mice lacking the proton receptor OGR1. Kidney Int 89:565-73|
|Liang, Qianqian; Ju, Yawen; Chen, Yan et al. (2016) Lymphatic endothelial cells efferent to inflamed joints produce iNOS and inhibit lymphatic vessel contraction and drainage in TNF-induced arthritis in mice. Arthritis Res Ther 18:62|
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