背景:牙周炎是一种常见的口腔疾病,在全球范围内患病率很高。神经表皮生长因子样蛋白1(Nell-1)最近被报道具有抗炎作用,可能是骨关节炎的候选药物。然而,其在牙周炎中的免疫治疗作用尚不清楚。因此,本研究从巨噬细胞极化的角度探讨Nell-1对牙周炎的影响,并分析其可能的作用机制。
方法:建立大鼠结扎诱导的实验性牙周炎模型,局部注射Nell-1(n=6/组)。使用Micro-CT分析体内牙周组织破坏和巨噬细胞极化,组织学分析,和westernblot.酶联免疫吸附试验用于评估血清炎性细胞因子。然后,用脂多糖(LPS)处理RAW264.7巨噬细胞,Nell-1和c-JunN末端激酶(JNK)抑制剂(SP600125)。RT-PCR,westernblot,和流式细胞术进一步分析了Nell-1对巨噬细胞极化的影响及其体外机制。
结果:Nell-1局部治疗可显着减轻牙周炎中牙槽骨和纤维的破坏,并上调牙周组织中M2/M1巨噬细胞的比例(P<0.05)。体外,浓度为200和500ng/mL的Nell-1能显著抑制LPS刺激的巨噬细胞M1相关炎症因子的表达,并增加M2相关标志物的表达,调节巨噬细胞表型转换为M2(P<0.05)。Nell-1也上调了JNK的mRNA和磷酸化JNK/JNK的相对蛋白水平(P<0.05)。此外,JNK抑制剂(SP600125)可逆转Nell-1对巨噬细胞极化的影响(P<0.05)。
结论:Nell-1可能通过JNK/MAPK信号通路调节M2/M1巨噬细胞的比例,随后减轻牙周炎引起的牙周组织的炎症和破坏。
BACKGROUND: Periodontitis is a common oral disease with high prevalence worldwide. Neural epidermal growth factor-like 1 protein (Nell-1) has recently been reported to have anti-inflammation effects and may be a drug candidate for osteoarthritis. However, its immunotherapeutic effects in periodontitis remain unknown. Therefore, this study aimed to investigate the effects of Nell-1 on periodontitis in terms of macrophage polarization and analyze its possible underlying mechanism.
METHODS: A rat ligation-induced experimental periodontitis model was established and locally injected with Nell-1 (n = 6/group). Periodontal tissue destruction and macrophage polarization in vivo were analyzed using micro-CT, histology analysis, and western blot. Enzyme-linked immunosorbent assay was used to evaluate serum inflammatory cytokines. Then, the RAW 264.7 macrophage cells were treated with lipopolysaccharide (LPS), Nell-1, and the c-Jun N-terminal kinases (JNK) inhibitor (SP600125). RT-PCR, western blot, and flow cytometry were performed to further analyze the effect of Nell-1 on macrophage polarization and the underlying mechanism in vitro.
RESULTS: Local treatment with Nell-1 significantly alleviated the destruction of alveolar bone and fibers in periodontitis, and upregulated the ratio of M2/M1 macrophages in periodontal tissues (P < 0.05). In vitro, Nell-1 at the concentrations of 200 and 500 ng/mL could significantly inhibit the expression of M1-related inflammatory factors in LPS-stimulated macrophages, and increase the expression of M2-related markers, regulating the macrophage phenotype switch into M2 (P < 0.05). The mRNA of JNK and relative protein level of phospho-JNK/JNK were also upregulated by Nell-1 (P < 0.05). Additionally, the JNK inhibitor (SP600125) could reverse the effect of Nell-1 on macrophage polarization (P < 0.05).
CONCLUSIONS: Nell-1 could modulate the ratio of M2/M1 macrophages possibly through the JNK/MAPK signaling pathway, subsequently attenuating the inflammation and destruction of periodontal tissues caused by periodontitis.