The working mechanism of bone resorption inhibitory protein induced by osteoclasts

牙周炎是一种由革兰氏阴性菌感染引起的慢性炎症性疾病，以牙槽骨吸收为特征。抑制骨吸收对牙周炎的治疗和预防至关重要。破骨细胞（OCL）是骨吸收的主要细胞，有关OCL分化的胞内信号通路的报道很多。如果我们能够控制这一信号通路，就有可能控制骨吸收。我们的合作者发现OCL抑制肽-1 （OIP-1/hSca）是一种新的OCL形成和骨吸收抑制剂，由OCL产生。OIP-1是OCL中一个独特的蛋白，能够单独抑制OCL的分化。我们本研究的主要目的是通过探讨OIP-1抑制OCL的机制，寻求其在牙周炎临床应用的可能性。我们使用周期依赖的逆转录聚合酶链反应（RT-PCR）分析表明，干扰素-γ (IFN-γ)强烈增强小鼠骨髓细胞和成骨细胞中OIP-1/hSca mRNA的表达。同样，白细胞介素(IL)-12也增强了OIP-1 mRNA的表达。为了确定OIP-1是否参与IFN-γ对OCL形成的抑制，我们测试了OIP-1 c肽特异性中和抗体抑制IFN-γ对小鼠巨噬细胞RAW 264.7细胞OCL样细胞分化的作用。抗oip -1 c肽特异性抗体部分中和IFN-γ对OCL分化的抑制作用。此外，OIP-1还能抑制RAW 264.7细胞的磷酸c- jun激酶活性。然而，OIP-1/hSca不影响这些细胞的NF-κB活化。Western blot分析进一步表明，OIP-1显著降低RAW 264.7细胞中TNF受体相关因子2 （TRAF-2）的表达。然而，OIP-1对这些细胞中TRAF-6的表达没有影响。这些数据表明，IFN-γ增强小鼠骨髓细胞和成骨细胞中OIP-1/hSca的表达，OIP-1通过抑制TRAF-2和p-c-Jun激酶活性来抑制OCL的形成。这些发现提示OIP-1可能抑制牙周炎患者的炎症性骨吸收

Periodontitis is a chronic inflammatory disease caused by infections with Gram-negative bacteria and characterized by alveolar bone resorption. It is very critical to inhibit bone resorption for treatment and prevention of periodontitis. The osteoclast (OCL) is the primary bone resorbing cell and there are many reports about intracellular signaling pathway related with OCL differentiation. It is possible to control bone resorption if we could manage this signaling pathway. Our collaborator identified OCL inhibitory peptide-1 (OIP-1/hSca) as a novel inhibitor of OCL formation and bone resorption that is produced by OCLs. OIP-1 is a unique protein from OCLs to be able to inhibit OCL differentiation by itself. Our main object of this study is to seek the possibility for clinical application of OIP-1 in periodontitis by expoloring the mechanism of this OCL inhibition. We used cycle-dependent reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, which demonstrated that interfer … More on-γ (IFN-γ) strongly enhanced OIP-1/hSca mRNA expression in mouse bone marrow cells and osteoblasts. Similarly, interleukin (IL)-12 also enhanced OIP-1 mRNA expression. To determine the participation of OIP-1 in IFN-γ inhibition of OCL formation, we tested the capacity of a neutralizing antibody specific to OIP-1 c-peptide to inhibit IFN-γ's effects on OCL-like cell differentiation of mouse macrophages, RAW 264.7 cells. Anti-OIP-1 c-peptide specific antibody partially neutralized IFN-γ inhibition of OCL differentiation. Furthermore, OIP-1 inhibited phospho-c-Jun (p-c-Jun) kinase activity in RAW 264.7 cells. However, OIP-1/hSca did not affect NF-κB activation hi these cells. Western blot analysis further demonstrated that OIP-1 significantly decreased TNF receptor associated factor 2 (TRAF-2) expression in RAW 264.7 cells. However, OIP-1 had no effect on TRAF-6 expression in these cells. These data show that IFN-γ enhances OIP-1/hSca expression in mouse bone marrow cells and osteoblasts, and that OIP-1 inhibits OCL formation through suppression of TRAF-2 and p-c-Jun kinase activity. These findings suggest the possibility by OIP-1 to inhibit inflammatory bone resorption in periodontitis Less