Division of Oral Pathopharmacology, Department of Developmental and Reconstructive Medicine, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki 852-8588, Japan.
J Cell Biochem. 2012 Feb;113(2):486-98. doi: 10.1002/jcb.23372.
The differentiation of osteoclasts is regulated by several essential cytokines, such as receptor activator of nuclear factor κB ligand (RANKL) and macrophage colony-stimulating factor. Recently, high mobility group box 1 (HMGB1), a chromatin protein, also has been identified as one of these osteoclast differentiation cytokines. However, the molecular mechanisms that control HMGB1 release from osteoclast precursor cells are not known. Here, we report that RANKL-induced suppression of heme oxygenase-1 (HO-1), a heme-degrading enzyme, promotes HMGB1 release during osteoclastogenesis. In contrast, induction of HO-1 with hemin or curcumin in bone marrow-derived macrophages or RAW-D murine osteoclast precursor cells inhibited osteoclastogenesis and suppressed HMGB1 release. Since an inhibitor for p38 mitogen-activated protein kinase (MAPK) prevented the RANKL-mediated HO-1 suppression and extracellular release of HMGB1, these effects were p38 MAPK-dependent. Moreover, suppression of HO-1 in RAW-D cells by RNA interference promoted the activation of caspase-3 and HMGB1 release, whereas overexpression of HO-1 inhibited caspase-3 activation as well as HMGB1 release. Furthermore, these effects were regulated by redox conditions since antioxidant N-acetylcysteine abolished the HO-1/HMGB1/caspase-3 axis. These results suggest that RANKL-dependent HO-1 suppression leads to caspase-3 activation and HMGB1 release during osteoclastogenesis.
破骨细胞的分化受几种重要细胞因子的调节，如核因子κB 受体激活剂配体（RANKL）和巨噬细胞集落刺激因子。最近，高迁移率族蛋白 B1（HMGB1），一种染色质蛋白，也被鉴定为这些破骨细胞分化细胞因子之一。然而，控制破骨细胞前体细胞中 HMGB1 释放的分子机制尚不清楚。在这里，我们报告 RANKL 诱导的血红素加氧酶-1（HO-1）抑制，一种血红素降解酶，在破骨细胞发生过程中促进 HMGB1 释放。相比之下，用血红素或姜黄素诱导骨髓来源的巨噬细胞或 RAW-D 鼠破骨细胞前体细胞中的 HO-1 抑制破骨细胞发生并抑制 HMGB1 释放。由于 p38 丝裂原活化蛋白激酶（MAPK）的抑制剂可防止 RANKL 介导的 HO-1 抑制和 HMGB1 的细胞外释放，因此这些作用依赖于 p38 MAPK。此外，RAW-D 细胞中 HO-1 的 RNA 干扰抑制可促进 caspase-3 的激活和 HMGB1 的释放，而过表达 HO-1 可抑制 caspase-3 的激活以及 HMGB1 的释放。此外，这些作用受氧化还原条件的调节，因为抗氧化剂 N-乙酰半胱氨酸可消除 HO-1/HMGB1/caspase-3 轴。这些结果表明，RANKL 依赖性 HO-1 抑制导致破骨细胞发生过程中的 caspase-3 激活和 HMGB1 释放。
