TNF-α mediates p38 MAP kinase activation and negatively regulates bone formation at the injured growth plate in rats
TNF-α mediates p38 MAP kinase activation and negatively regulates bone formation at the injured growth plate in rats
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DOI：
10.1359/jbmr.060410
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发表时间：
2006-07-01
影响因子：
6.2
通讯作者：
Xian, Cory J.
中科院分区：
文献类型：
--
作者：
Zhou, Fiona H.;Foster, Bruce K.;Xian, Cory J.
前言：肿瘤坏死因子-α在体外可抑制成骨细胞分化因子cbfa1的表达和成骨细胞的分化，但肿瘤坏死因子-α信号转导通路在骨折愈合过程中起重要作用。肿瘤坏死因子-α的作用。在受损生长板的骨修复中，软骨的作用尚不清楚。材料和方法：在接受肿瘤坏死因子-α抑制剂ENBREL或生理盐水对照的幼鼠模型中，检测了肿瘤坏死因子-α在p38丝裂原活化蛋白(MAP)激酶激活和随后的生长板损伤骨修复中的作用。用Western印迹分析和免疫组织化学方法检测p38的激活情况。术后第1天行生长板损伤部位炎性细胞计数，第8天测量修复组织比例，计数增殖性间充质细胞(n=6)。用定量RT-PCR方法检测损伤生长板中炎性细胞因子TNF-α、IL-1β、成纤维细胞生长因子-2、cbfa1和骨钙素的表达。用重组大鼠肿瘤坏死因子-α、ENBREL和p38抑制剂SB239063在原代培养的大鼠骨髓间充质细胞中检测肿瘤坏死因子-α信号对骨髓间充质细胞增殖、迁移和凋亡的影响，以及p38在这些过程中的调节作用。结果：在最初的炎症反应中，p38在损伤生长板被诱导激活，活化的p38免疫定位于损伤部位和邻近生长板的炎性细胞。此外，在用肿瘤坏死因子-α拮抗剂处理的大鼠中，p38的激活被阻断，这表明肿瘤坏死因子-α在p38的激活中起作用。而抑制肿瘤坏死因子-α并未改变损伤生长板的炎性浸润和IL-1β的表达，但在第8天减少了间充质的浸润和细胞的增殖及成纤维细胞生长因子-2的表达。在损伤生长板第8天，肿瘤坏死因子-α抑制增加了cbfa1和骨钙素的表达，并增加了损伤部位的骨小梁形成。肿瘤坏死因子-α与cbfa1的表达水平呈显著负相关，提示在该体内模型中，肿瘤坏死因子-α与cbfa1的表达呈负相关。结论：在损伤生长板的炎症反应中，肿瘤坏死因子-α激活了p38-MAPK，在生长板损伤部位和细胞培养中，肿瘤坏死因子-α-p38信号似乎是骨髓间充质细胞增殖和迁移所必需的。此外，肿瘤坏死因子信号通过抑制损伤部位的骨细胞分化和骨基质合成而抑制损伤生长板的骨形成。
Introduction: TNF-alpha inhibits expression of osteoblast differentiation factor cbfa1 and osteoblast differentiation in vitro and yet TNF-a signaling is essential for bone fracture healing. Roles of TNF-a. in the bony repair of injured growth plate cartilage are unknown.Materials and Methods: Roles of TNF-alpha in the activation of p38 mitogen activated protein (MAP) kinase and the subsequent bony repair of the injured growth plate were examined in young rats receiving the TNF-a inhibitor ENBREL or saline control. Activation of p38 was determined by Western blot analysis and immunohistochemistry. Inflammatory cell counts on day 1, measurements of repair tissue proportions, and counting of proliferative mesenchymal cells on day 8 at growth plate injury site were carried out (n = 6). Expression of inflammatory cytokines TNF-alpha and IL-1 beta, fibrogenic growth factor (FGF)-2, cbfa1, and bone protein osteocalcin at the injured growth plate was assessed by quantitative RT-PCR. Effects of TNF-alpha signaling on proliferation, migration, and apoptosis of rat bone marrow mesenchymal cells (rBMMCs) and the regulatory roles of p38 in these processes were examined using recombinant rat TNF-alpha, ENBREL, and the p38 inhibitor SB239063 in cultured primary rBMMCs.Results: p38 activation was induced in the injured growth plate during the initial inflammatory response, and activated p38 was immunolocalized in inflammatory cells at the injury site and in the adjacent growth plate. In addition, activation of p38 was blocked in rats treated with TNF-alpha antagonist, suggesting a role of TNF-alpha in p38 activation. Whereas TNF-alpha inhibition did not alter inflammatory infiltrate and expression of TNF-alpha and IL-1 beta at the injured growth plate on day 1, it reduced mesenchymal infiltrate and cell proliferation and FGF-2 expression on day 8. Consistently, TNF-alpha increased proliferation and migration of rBMMCs in vitro, whereas p38 inhibition reduced rBMMC proliferation and migration. At the injured growth plate on day 8, TNF-alpha inhibition increased expression of cbfa1 and osteocalcin and increased trabecular bone formation at the injury site. There was a significant inverse correlation between TNF-alpha and cbfa1 expression levels, suggesting a negative relationship between TNF-alpha and cbfa1 in this in vivo model.Conclusions: These observations suggest that TNF-alpha activates p38 MAP kinase during the inflammatory response at the injured growth plate, and TNF-alpha-p38 signaling seems to be required for marrow mesenchymal cell proliferation and migration at the growth plate injury site and in cell culture. Furthermore, TNF signaling has an inhibitory effect on bone formation at the injured growth plate by suppressing bone cell differentiation and bone matrix synthesis at the injury site.