Department of Orthodontics, National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing Key Laboratory of Digital Stomatology, Peking University School and Hospital of Stomatology, Haidian District, Beijing, China.
Central Laboratory, Peking University School and Hospital of Stomatology, Haidian District, Beijing, China.
J Dent Res. 2020 May;99(5):577-587. doi: 10.1177/0022034520910127. Epub 2020 Mar 31.
Periodontitis is a bacteria-driven inflammatory destructive disease that leads to attachment loss, bone resorption, and even tooth loss. Accumulating studies revealed that macrophages might play an nonnegligible role during the processes of periodontitis. However, the underlying mechanism remains largely unknown. In this study, we found novel Akt2/JNK1/2/c-Jun and Akt2/miR-155-5p/DET1/c-Jun signaling pathways that regulated the polarization of macrophages and altered periodontal inflammatory status. Through hematoxylin and eosin, immunostaining, and immunofluorescence staining of clinical specimens, a higher number of M1 phenotype macrophage infiltration was found in periodontitis than in normal controls. Flow cytometry and immunofluorescence showed that overexpression of Akt2 in RAW 264.7 cells induced M1 macrophage polarization and decreased M2 polarization, while knockdown of Akt2 exerted an opposite effect. Furthermore, overexpression of Akt2 activated the JNK pathway and then increased the release of proinflammatory mediators, while knockdown of Akt2 downregulated the above genes accordingly. Importantly, the macrophage polarization and the subsequent alteration of pathway molecules induced by overexpression of Akt2 could be rescued by Akt2 and JNK inhibitors. Moreover, JNK inhibition could facilitate M2 polarization of macrophages. In a mouse periodontitis model, the novel signaling pathway as well as clinical phenotype was further verified. Inhibition of Akt2 facilitated macrophage M2 polarization and rescued the bone loss due to periodontitis. Collectively, we identified novel Akt2/JNK1/2/c-Jun and Akt2/miR-155-5p/DET1/c-Jun signaling pathways that regulate macrophage polarization and highlight that Akt2 inhibition promotes M2 polarization of macrophages and can be a novel potential candidate in the treatment of periodontitis.
牙周炎是一种由细菌驱动的炎症破坏性疾病，导致附着丧失、骨吸收，甚至牙齿脱落。越来越多的研究表明，巨噬细胞在牙周炎的发生发展过程中可能发挥着不可忽视的作用。然而，其潜在的机制在很大程度上尚不清楚。在本研究中，我们发现了新的 Akt2/JNK1/2/c-Jun 和 Akt2/miR-155-5p/DET1/c-Jun 信号通路，这些信号通路调节巨噬细胞的极化，并改变牙周炎的炎症状态。通过对临床标本进行苏木精-伊红、免疫组化和免疫荧光染色，我们发现牙周炎患者组织中浸润的 M1 型巨噬细胞数量多于正常对照组。流式细胞术和免疫荧光实验显示，RAW 264.7 细胞中 Akt2 的过表达诱导 M1 型巨噬细胞极化，减少 M2 型极化，而 Akt2 的敲低则产生相反的效果。此外，Akt2 的过表达激活了 JNK 通路，进而增加了促炎介质的释放，而 Akt2 的敲低则相应地下调了上述基因。重要的是，Akt2 的过表达诱导的巨噬细胞极化和随后的通路分子变化可以被 Akt2 和 JNK 抑制剂挽救。此外，JNK 抑制可以促进巨噬细胞 M2 极化。在小鼠牙周炎模型中，进一步验证了新的信号通路和临床表型。Akt2 的抑制促进了巨噬细胞 M2 极化，挽救了因牙周炎导致的骨丢失。综上所述，我们确定了新的 Akt2/JNK1/2/c-Jun 和 Akt2/miR-155-5p/DET1/c-Jun 信号通路，这些信号通路调节巨噬细胞的极化，并表明 Akt2 抑制促进了巨噬细胞 M2 极化，有望成为治疗牙周炎的一种新的潜在候选药物。
