Ha Hyunil, Kwak Han Bok, Lee Soo Woong, Jin Hye Mi, Kim Hyun-Man, Kim Hong-Hee, Lee Zang Hee
Department of Cell and Developmental Biology, College of Dentistry, Seoul National University, Seoul 110-749, Korea.
Exp Cell Res. 2004 Dec 10;301(2):119-27. doi: 10.1016/j.yexcr.2004.07.035.
RANKL, a member of tumor necrosis factor (TNF) superfamily, regulates the differentiation, activation, and survival of osteoclasts through binding to its cognate receptor, RANK. RANK can interact with several TNF-receptor-associated factors (TRAFs) and activates signaling molecules including Akt, NF-kappaB, and MAPKs. Although the transient elevation of reactive oxygen species (ROS) by receptor activation has been shown to act as a cellular secondary messenger, the involvement of ROS in RANK signaling pathways has been not characterized. In this study, we found that RANKL stimulated ROS generation in osteoclasts. Pretreatment of osteoclasts with the antioxidants N-acetyl-l-cystein and glutathione reduced RANKL-induced Akt, NF-kappaB, and ERK activation. The reduced NF-kappaB activity by antioxidants was associated with decreased IKK activity and IkappaBalpha phosphorylation. In contrast, antioxidants did not prevent TNF-alpha-induced Akt and NF-kappaB activation. Pretreatment with antioxidants also significantly reduced RANKL-induced actin ring formation, required for bone resorbing activity, and osteoclast survival. Taken together, our results suggest that ROS act as mediators in RANKL-induced signaling pathways and cellular events.
核因子κB受体活化因子配体（RANKL）是肿瘤坏死因子（TNF）超家族的成员之一，它通过与其同源受体RANK结合来调节破骨细胞的分化、活化和存活。RANK能与多种TNF受体相关因子（TRAFs）相互作用，并激活包括Akt、核因子κB（NF-κB）和丝裂原活化蛋白激酶（MAPKs）在内的信号分子。尽管已表明受体激活引起的活性氧（ROS）短暂升高可作为细胞第二信使，但ROS在RANK信号通路中的作用尚未明确。在本研究中，我们发现RANKL可刺激破骨细胞产生ROS。用抗氧化剂N-乙酰-L-半胱氨酸和谷胱甘肽预处理破骨细胞可降低RANKL诱导的Akt、NF-κB和细胞外信号调节激酶（ERK）活化。抗氧化剂使NF-κB活性降低与抑制性κB激酶（IKK）活性降低及IκBα磷酸化减少有关。相反，抗氧化剂并不能阻止肿瘤坏死因子-α（TNF-α）诱导的Akt和NF-κB活化。用抗氧化剂预处理还可显著减少RANKL诱导的骨吸收活性所需的肌动蛋白环形成及破骨细胞存活。综上所述，我们的结果表明ROS在RANKL诱导的信号通路和细胞事件中起介导作用。
