Quercetin Triggers Apoptosis of Lipopolysaccharide (LPS)-induced Osteoclasts and Inhibits Bone Resorption in RAW264.7 Cells
Quercetin Triggers Apoptosis of Lipopolysaccharide (LPS)-induced Osteoclasts and Inhibits Bone Resorption in RAW264.7 Cells
复制标题
DOI：
10.1159/000339052
复制
发表时间：
2012-01-01
影响因子：
--
通讯作者：
Du, Shi-xin
中科院分区：
文献类型：
--
作者：
Guo, Chun;Hou, Guo-qing;Du, Shi-xin
目的：栎素是一种存在于蔬菜中的黄酮类化合物，具有抗炎和潜在的抑制骨吸收的作用。到目前为止，槲皮素对内毒素诱导的破骨细胞生成的影响尚未见报道。在本研究中，我们评价了栎素对内毒素诱导的破骨细胞凋亡和骨吸收的影响。方法：将RAW264.7细胞分为未处理组、单用脂多糖处理组、脂多糖组和联合用药组。治疗后检测破骨细胞数、细胞活力、骨吸收和破骨细胞凋亡率。实时定量聚合酶链式反应(QPCR)检测破骨细胞相关基因的表达，包括抗酒石酸酸性磷酸酶(TRAP)、基质金属蛋白酶-9(MMP9)和组织蛋白酶K(CK)。Western blotting检测核因子受体激活剂-kappaB(RANK)、肿瘤坏死因子受体相关因子6(TRAF6)、环氧合酶-2(COX-2)、Bax、Bcl-2和丝裂原活化蛋白激酶(MAPKs)的蛋白水平。MAPK抑制剂可阻断MAPK信号转导通路。结果：脂多糖直接促进RAW264.7细胞向破骨细胞分化，上调RANK、TRAF6和COX-2的蛋白表达，而槲皮素则以剂量依赖的方式显著减少脂多糖诱导的破骨细胞数量。所有处理均未增加RAW264.7细胞的细胞毒性。槲皮素能抑制脂多糖诱导的成熟破骨细胞破骨细胞相关基因RANK、TRAF6和COX-2的基因表达和蛋白水平。在脂多糖诱导的成熟破骨细胞中，槲皮素有诱导细胞凋亡和抑制骨吸收活性的作用。此外，通过促进p38-MAPK、c-Jun氨基末端/应激激活蛋白激酶(JNK/SAPK)和Bax的磷酸化，促进细胞凋亡信号转导途径，抑制Bcl2的表达。结论：槲皮素可能通过阻断RANK信号通路，抑制破骨细胞相关基因的表达，从而抑制脂多糖诱导的破骨细胞骨吸收。栎素还通过激活MAPK凋亡信号通路促进脂多糖诱导的破骨细胞凋亡。这些发现表明，槲皮素可以作为治疗细菌诱导的骨吸收的潜在药物。版权所有(C)2012年，S.Karger AG，巴塞尔
Aims: Quercetin, a flavonoid present in vegetables, has anti-inflammatory properties and potential inhibitory effects on bone resorption. Up to date, the effect of quercetin on lipopolysaccharide (LPS)-induced osteoclastogenesis has not yet been reported. In the current study, we evaluated the effect of quercetin on LPS-induced osteoclast apoptosis and bone resorption. Methods: RAW264.7 cells were non-treated, treated with LPS alone, or treated with both LPS and quercetin. After treatment, the number of osteoclasts, cell viability, bone resorption and osteoclast apoptosis were measured. The expressions of osteoclast-related genes including tartrate-resistant acid phosphatase (TRAP), matrix metalloproteinase-9 (MMP-9) and cathepsin K (CK) were determined by real-time quantitative polymerase chain reaction (qPCR). Protein levels of receptor activator of nuclear factor-kappa B (RANK), tumor necrosis factor receptor-associated factor 6 (TRAF6), cyclooxygenase-2 (COX-2), Bax, Bcl-2 and mitogen-activated protein kinases (MAPKs) were measured using Western blotting assays. The MAPK signaling pathway was blocked by pretreatment with MAPK inhibitors. Results: LPS directly promoted osteoclast differentiation of RAW264.7 cells and upregulated the protein expression of RANK, TRAF6 and COX-2; while quercetin significantly decreased the number of LPS-induced osteoclasts in a dose-dependent manner. None of the treatments increased cytotoxicity in RAW264.7 cells. Quercetin inhibited mRNA expressions of osteoclast-related genes and protein levels of RANK, TRAF6 and COX-2 in LPS-induced mature osteoclasts. Quercetin also induced apoptosis and inhibited bone resorptive activity in LPS-induced mature osteoclasts. Furthermore, quercetin promoted the apoptotic signaling pathway including increasing the phosphorylation of p38-MAPK, c-Jun N-terminal kinases/stress-activated protein kinases (JNK/SAPK), and Bax, while inhibited Bcl-2 expression. Conclusions: Quercetin could suppress LPS-induced osteoclast bone resorption through blocking RANK signaling and inhibiting the expression of osteoclast-related genes. Quercetin also promoted LPS-induced osteoclast apoptosis via activation of the MAPK apoptotic signaling pathway. These findings suggest that quercetin could be of potential use as a therapeutic agent to treat bacteria-induced bone resorption. Copyright (c) 2012 S. Karger AG, Basel