First Affiliated Hospital, Medical College of Shantou University, Shantou, Guangdong 515041, P.R. China.
Int J Mol Med. 2013 Aug;32(2):503-10. doi: 10.3892/ijmm.2013.1406. Epub 2013 Jun 5.
Bone degradation is a serious complication of chronic inflammatory diseases such as septic arthritis, osteomyelitis and infected orthopedic implant failure. At present, effective therapeutic treatments for lipopolysaccharide (LPS)-induced bone destruction are limited to antibiotics and surgical repair in chronic inflammatory diseases. The present study aimed to evaluate the mechanism of LPS on osteoclast differentiation and activation. RAW264.7 cells were non-induced, or induced by the receptor activator of nuclear factor-κB (RANK) ligand (RANKL) and macrophage-colony stimulating factor (M-CSF), and then treated with LPS. Following treatment, the number of osteoclasts and cell viability were measured. The expression of osteoclast-related genes including tartrate-resistant acid phosphatase (TRAP), matrix metalloproteinase-9 (MMP-9), cathepsin K (CK), carbonic anhydrase II (CAII) and cyclooxygenase-2 (COX-2) was determined by RT-PCR. Protein levels of RANK, tumor necrosis factor receptor-associated factor 6 (TRAF6), COX-2 and mitogen-activated protein kinases (MAPK) were measured using western blotting assays. LPS promoted osteoclast differentiation of RAW264.7 cells and differentiated osteoclasts. LPS significantly increased mRNA expression of osteoclast-related genes in RAW264.7 cells. Differentiated osteoclasts were treated with LPS (100 ng/ml) and the results showed a significantly increased mRNA expression of osteoclast-related genes and protein levels of RANK, TRAF6 and COX-2. Furthermore, LPS at 100 ng/ml significantly promoted the MAPK pathway including increasing the phosphorylation of c-Jun N-terminal kinases (JNK) and the phosphorylation of the extracellular signal-regulated kinase (ERK1/2). In conclusion, LPS promoted osteoclast differentiation and activation by enhancing RANK signaling and COX-2 expression. LPS also promoted osteoclast differentiation via activation of the JNK and ERK1/2 cell proliferation pathways.
骨降解是慢性炎症性疾病（如脓毒性关节炎、骨髓炎和感染性骨科植入物失败）的严重并发症。目前，针对脂多糖（LPS）诱导的骨破坏，有效的治疗方法仅限于抗生素和慢性炎症性疾病的手术修复。本研究旨在评估 LPS 对破骨细胞分化和激活的作用机制。RAW264.7 细胞未诱导或经核因子-κB 受体激活剂（RANKL）和巨噬细胞集落刺激因子（M-CSF）诱导后，用 LPS 处理。处理后，检测破骨细胞的数量和细胞活力。采用 RT-PCR 法检测破骨细胞相关基因包括抗酒石酸酸性磷酸酶（TRAP）、基质金属蛋白酶-9（MMP-9）、组织蛋白酶 K（CK）、碳酸酐酶 II（CAII）和环氧化酶-2（COX-2）的表达。采用 Western blot 法检测 RANK、肿瘤坏死因子受体相关因子 6（TRAF6）、COX-2 和丝裂原活化蛋白激酶（MAPK）的蛋白水平。LPS 促进 RAW264.7 细胞的破骨细胞分化和分化的破骨细胞。LPS 显著增加 RAW264.7 细胞中破骨细胞相关基因的 mRNA 表达。用 LPS（100ng/ml）处理分化的破骨细胞，结果显示破骨细胞相关基因的 mRNA 表达和 RANK、TRAF6 和 COX-2 的蛋白水平明显增加。此外，100ng/ml 的 LPS 显著促进了 MAPK 通路，包括增加 c-Jun N 端激酶（JNK）的磷酸化和细胞外信号调节激酶（ERK1/2）的磷酸化。总之，LPS 通过增强 RANK 信号和 COX-2 表达促进破骨细胞分化和激活。LPS 还通过激活 JNK 和 ERK1/2 细胞增殖通路促进破骨细胞分化。
