Fukushima Hidefumi, Jimi Eijiro, Okamoto Fujio, Motokawa Wataru, Okabe Koji
Department of Physiological Science and Molecular Biology, Fukuoka Dental College, Fukuoka, 814-0193, Japan.
Bone. 2005 Feb;36(2):267-75. doi: 10.1016/j.bone.2004.09.011.
Periodontitis, an inflammatory disorder of the supporting tissue of teeth, is one of the most common infectious diseases in humans. Periodontal pathogens promote inflammatory cytokines such as interleukin-1 (IL-1) and prostaglandin E2 (PGE2), resulting in alveolar bone destruction. In the present study, we examined the cellular and molecular mechanisms of IL-1-induced osteoclastogenesis using a coculture system of human periodontal ligament (PDL) cells and mouse spleen cells. IL-1alpha induced tartrate-resistant acid phosphatase positive (TRAP+) cell formation in a dose-dependent manner. IL-1alpha up-regulated receptor activator of NF-kappaB ligand (RANKL) and down-regulated osteoprotegerin (OPG) mRNA expression in PDL cells. The addition of cell-permeable PKI, an inhibitor of the cAMP/PKA signaling pathway, to the cocultures 8 h after the IL-1alpha stimulation inhibited IL-1alpha-induced TRAP+ cell formation. IL-1alpha-induced TRAP+ cell formation was completely blocked by either NS398, a selective inhibitor of cyclooxygenase (COX)-2, or PD98059, a specific inhibitor of extracellular signal-regulated kinase (ERK). Pretreatment with NS398 and PD98059 also inhibited both the up-regulation of RANKL and the down-regulation of OPG expression by IL-1alpha in PDL cells. IL-1alpha activated ERK phosphorylation and PD98059 greatly inhibited both COX-2 mRNA expression and PGE(2) production induced by IL-1alpha in PDL cells. In contrast, NEMO binding domain (NBD) peptide, a specific inhibitor of NF-kappaB signaling, did not affect COX2, RANKL, or OPG mRNA expression induced by IL-1alpha. These results suggest that IL-1alpha stimulates osteoclast formation by increasing the expression level of RANKL versus OPG via ERK-dependent PGE2 production in PDL cells.
牙周炎是牙齿支持组织的一种炎症性疾病，是人类最常见的传染病之一。牙周病原体可促进炎性细胞因子如白细胞介素-1（IL-1）和前列腺素E2（PGE2）的产生，导致牙槽骨破坏。在本研究中，我们使用人牙周膜（PDL）细胞和小鼠脾细胞的共培养系统，研究了IL-1诱导破骨细胞生成的细胞和分子机制。IL-1α以剂量依赖性方式诱导抗酒石酸酸性磷酸酶阳性（TRAP+）细胞形成。IL-1α上调PDL细胞中核因子κB受体激活剂配体（RANKL）的表达，并下调骨保护素（OPG）mRNA的表达。在IL-1α刺激8小时后，向共培养物中添加细胞可渗透的PKI（一种cAMP/PKA信号通路抑制剂）可抑制IL-1α诱导的TRAP+细胞形成。IL-1α诱导的TRAP+细胞形成被环氧合酶（COX）-2的选择性抑制剂NS398或细胞外信号调节激酶（ERK）的特异性抑制剂PD98059完全阻断。用NS398和PD98059预处理也可抑制IL-1α在PDL细胞中对RANKL的上调和对OPG表达的下调。IL-1α激活ERK磷酸化，PD98059可显著抑制IL-1α在PDL细胞中诱导的COX-2 mRNA表达和PGE2产生。相反，NF-κB信号通路的特异性抑制剂NEMO结合域（NBD）肽不影响IL-1α诱导的COX2、RANKL或OPG mRNA表达。这些结果表明，IL-1α通过在PDL细胞中依赖ERK的PGE2产生增加RANKL相对于OPG的表达水平，从而刺激破骨细胞形成。
