A new approach for the development of the inhibitor on bone resorption: New drug development from the contact point between ligand and receptor.

破骨细胞的分化在骨吸收中发挥作用，需要NF-κB受体激活因子RANK与RANK配体的相互作用。由于这些分子分别保存TNF受体和TNF家族的成员，我们测试了TNF受体关键接触位点的肽模拟物（WP9QY）抑制RANK配体诱导的破骨细胞形成和激活的能力。WP9QY肽剂量依赖性地抑制小鼠共培养系统和RANK配体处理的骨髓细胞的破骨细胞生成，以及RANK配体诱导的离体破骨细胞的骨吸收。由于即使使用TNF受体缺陷小鼠的骨髓细胞也出现了对破骨细胞生成的抑制作用，因此认为这与TNF/TNF受体相互作用无关。此外，WP9QY还能抑制低钙喂养和卵巢切除引起的小鼠体内破骨细胞生成和骨质流失的增加。这些结果表明，TNFα与TNF受体(I)结构域3第一环之间的接触位点在RANK/RANK配体相互作用中至少部分保守，并且在诱导破骨细胞及其前体中RANK信号传导方面具有重要的功能。这种从配体/受体接触位点的晶体结构进行分子建模的策略可以为骨吸收抑制剂的药物开发开辟一个新时代。

The differentiation of osteoclasts, which play a role on bone resorption, requires the interaction of RANK (receptor activator of NF-κB) and RANK ligand. Since these molecules conserve members of the TNF receptor and TNF families, respectively, we tested the ability of a peptide mimic (WP9QY) of a critical contact site on the TNF receptor to inhibit RANK ligand-induced osteoclast formation and activation. The WP9QY peptide dose-dependently inhibited osteoclastogenesis in both the murine co-culture system and in RANK ligand-treated bone marrow cells, as well as RANK ligand-induced bone resorption by isolated osteoclasts. As the inhibitory effect on osteoclastogenesis even using the bone marrow cells from the TNF receptor deficient mice was appeared, it was suggested to be independent of TNF/TNF receptor interactions. Furthermore, WP9QY also prevented the increased in vivo osteoclastogenesis and bone loss induced in mice by a low calcium feeding and by the ovariectomy. These results suggest that the contact site between TNFα and the first loop of domain 3 of the TNF receptor (I) is at least partially conserved in the RANK/RANK ligand interaction and is functionally important for the induction of signaling from RANK in osteoclasts and their precursors. This strategy using a molecular modeling from the crystal structure of the ligand/receptor contact site could lead us a new age for drug development of the inhibitor on bone resorption.