EphB4/TNFR2/ERK/MAPK 信号通路构成了一个信号轴，介导 TNF-α 对成骨分化的正向作用。

EphB4/ TNFR2/ERK/MAPK signaling pathway comprises a signaling axis to mediate the positive effect of TNF-α on osteogenic differentiation.

机构信息

Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Department of Endodontics, School of Stomatology, Shandong University, No. 44-1 Wenhua Road West, Jinan, Shandong Province, China.

Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Department of Periodontology, School of Stomatology, Shandong University, No. 44-1 Wenhua Road West, Jinan, Shandong Province, China.

出版信息

BMC Mol Cell Biol. 2020 Apr 16;21(1):29. doi: 10.1186/s12860-020-00273-2.

BACKGROUND

Low concentrations of tumor necrosis factor-alpha (TNF-α) and its receptor TNFR2 are both reported to promote osteogenic differentiation of osteoblast precursor cells. Moreover, low concentrations of TNF-α up-regulate the expression of EphB4. However, the molecular mechanisms underlying TNF-α-induced osteogenic differentiation and the roles of TNFR2 and EphB4 have not been fully elucidated.

RESULTS

The ALP activity, as well as the mRNA and protein levels of RUNX2, BSP, EphB4 and TNFR2, was significantly elevated in MC3T3-E1 murine osteoblast precursor cells when stimulated with 0.5 ng/ml TNF-α. After TNFR2 was inhibited by gene knockdown with lentivirus-mediated shRNA interference or by a neutralizing antibody against TNFR2, the pro-osteogenic effect of TNF-α was partly reversed, while the up-regulation of EphB4 by TNF-α remained unchanged. With EphB4 forward signaling suppressed by a potent inhibitor of EphB4 auto-phosphorylation, NVP-BHG712, TNF-α-enhanced expressions of TNFR2, BSP and Runx2 were significantly decreased. Further investigation into the signaling pathways revealed that TNF-α significantly increased levels of p-JNK, p-ERK and p-p38. However, only the p-ERK level was significantly inhibited in TNFR2-knockdown cells. In addition, the ERK pathway inhibitor, U0126 (10 μM), significantly reversed the positive effect of TNF-α on the protein levels of RUNX2 and BSP.

CONCLUSIONS

The EphB4, TNFR2 and ERK/MAPK signaling pathway comprises a signaling axis to mediate the positive effect of TNF-α on osteogenic differentiation.

背景

低浓度的肿瘤坏死因子-α（TNF-α）及其受体 TNFR2 均被报道可促进成骨前体细胞的成骨分化。此外，低浓度的 TNF-α可上调 EphB4 的表达。然而，TNF-α诱导成骨分化的分子机制以及 TNFR2 和 EphB4 的作用尚未完全阐明。

结果

当用 0.5ng/ml TNF-α刺激 MC3T3-E1 鼠成骨前体细胞时，碱性磷酸酶（ALP）活性以及 RUNX2、BSP、EphB4 和 TNFR2 的 mRNA 和蛋白水平均显著升高。用慢病毒介导的 shRNA 干扰或 TNFR2 的中和抗体抑制 TNFR2 后，TNF-α的促成骨作用部分逆转，而 TNF-α对 EphB4 的上调作用保持不变。用 EphB4 正向信号的强力抑制剂 NVP-BHG712 抑制 EphB4 自动磷酸化后，TNF-α增强的 TNFR2、BSP 和 Runx2 表达显著降低。进一步研究信号通路发现，TNF-α显著增加了 p-JNK、p-ERK 和 p-p38 的水平。然而，只有在 TNFR2 敲低细胞中，ERK 通路抑制剂 U0126（10μM）才显著抑制了 TNFR2 表达。