Department of Orthodontics, University Hospital Regensburg, 93053 Regensburg, Germany.
Department of Conservative Dentistry and Periodontology, University Hospital Regensburg, 93053 Regensburg, Germany.
Int J Mol Sci. 2022 Nov 2;23(21):13397. doi: 10.3390/ijms232113397.
The concentration of melatonin is elevated during the night when patients mainly wear removable orthodontic appliances. Next to periodontal ligament fibroblasts and osteoblasts, macrophages react to mechanical strain with an increased expression of inflammatory mediators. Here, we investigated the impact of melatonin on RAW264.7 macrophages exposed to tensile or compressive strain occurring during orthodontic tooth movement in the periodontal ligament. Before exposure to mechanical strain for 4 h, macrophages were pre-incubated with different melatonin concentrations for 24 h, to determine the dependence of melatonin concentration. Afterwards, we performed experiments with and without mechanical strain, the most effective melatonin concentration (25 µM), and the melatonin receptor 2 (MT2) specific antagonist 4P-PDOT. The expression of inflammatory genes and proteins was investigated by RT-qPCR, ELISAs, and immunoblot. Both tensile and compressive strain increased the expression of the investigated inflammatory factors interleukin-1-beta, interleukin-6, tumor necrosis factor alpha, and prostaglandin endoperoxide synthase-2. This effect was inhibited by the addition of melatonin. Incubation with 4P-PDOT blocked this anti-inflammatory effect of melatonin. Melatonin had an anti-inflammatory effect on macrophages exposed to mechanical strain, independent of the type of mechanical strain. As inhibition was possible with 4P-PDOT, the MT2 receptor might be involved in the regulation of the observed effects.
褪黑素在夜间浓度升高，此时患者主要佩戴可摘式正畸矫治器。除牙周膜成纤维细胞和骨细胞外，巨噬细胞对机械应变的反应是增加炎症介质的表达。在这里，我们研究了褪黑素对暴露于牙周膜正畸牙齿移动过程中拉伸或压缩应变的 RAW264.7 巨噬细胞的影响。在将巨噬细胞暴露于机械应变 4 小时之前，用不同浓度的褪黑素预孵育 24 小时，以确定褪黑素浓度的依赖性。之后，我们进行了有和没有机械应变、最有效褪黑素浓度（25µM）以及褪黑素受体 2（MT2）特异性拮抗剂 4P-PDOT 的实验。通过 RT-qPCR、ELISA 和免疫印迹法研究了炎症基因和蛋白的表达。拉伸和压缩应变均增加了所研究的炎症因子白细胞介素-1β、白细胞介素-6、肿瘤坏死因子-α和前列腺素内过氧化物合酶-2 的表达。这种作用可被褪黑素抑制。用 4P-PDOT 孵育可阻断褪黑素的这种抗炎作用。褪黑素对暴露于机械应变的巨噬细胞具有抗炎作用，与机械应变的类型无关。由于用 4P-PDOT 进行抑制是可能的，因此 MT2 受体可能参与了观察到的效应的调节。
