Graduate Institute of Clinical Dentistry, National Taiwan University, Taipei, Taiwan; Department of Dentistry, National Taiwan University Hospital, Taipei, Taiwan.
Department of Dentistry, National Taiwan University Hospital, Taipei, Taiwan; Department of Dentistry, School of Dentistry, College of Medicine, National Taiwan University, Taipei, Taiwan.
J Endod. 2020 Jan;46(1):65-73. doi: 10.1016/j.joen.2019.10.001. Epub 2019 Nov 18.
We have previously shown that intracanal metformin ameliorates apical periodontitis, partially by modulation of osteoblast apoptosis. The action of metformin on other cell types pertinent to the development of apical periodontitis needs to be examined. In the present study, we aimed to analyze whether its effects on the expression of inducible nitric oxide synthase (iNOS) and monocyte recruitment contribute to the therapeutic effect on apical periodontitis.
Lipopolysaccharide (LPS)-induced expression of iNOS in a human monocytic cell line, Mono-Mac-6, was assessed by Western blot. The amount of nitrite in culture medium was assessed to quantify nitric oxide (NO) production. C-C motif chemokine ligand-2 (CCL-2) synthesis was measured by enzyme-linked immunosorbent assay. Experimental apical periodontitis in rats was treated with root canal debridement with or without intracanal metformin medication. Lesion progression was assessed by conventional radiography and micro-computed tomographic imaging. Cellular expression of iNOS and the number of monocytes/macrophages were assessed by immunohistochemistry.
Metformin suppressed LPS-induced iNOS and NO production by monocytes. More importantly, metformin inhibited LPS-enhanced CCL-2 synthesis through modulation of the iNOS/NO pathway. Intracanal metformin reduced bone resorption associated with apical periodontitis and suppressed iNOS expression and monocyte recruitment.
Our results confirmed the therapeutic efficacy of intracanal metformin for apical periodontitis. Suppression of monocyte recruitment through modulation of iNOS expression and NO production is an important mechanism underlying the beneficial effect of metformin.
我们之前已经表明，根管内二甲双胍通过调节成骨细胞凋亡来改善根尖周炎。二甲双胍对与根尖周炎发展相关的其他细胞类型的作用需要进一步研究。本研究旨在分析其对诱导型一氧化氮合酶（iNOS）表达和单核细胞募集的影响是否有助于根尖周炎的治疗效果。
通过 Western blot 检测人单核细胞系 Mono-Mac-6 中 LPS 诱导的 iNOS 表达。通过酶联免疫吸附试验测量培养基中硝酸盐的含量来定量一氧化氮（NO）的产生。通过酶联免疫吸附试验测量 C-C 基序趋化因子配体-2（CCL-2）的合成。用根管清创术或联合根管内二甲双胍治疗大鼠实验性根尖周炎。通过常规放射照相术和微计算机断层扫描成像评估病变进展。通过免疫组织化学评估 iNOS 的细胞表达和单核细胞/巨噬细胞的数量。
二甲双胍抑制单核细胞中 LPS 诱导的 iNOS 和 NO 的产生。更重要的是，二甲双胍通过调节 iNOS/NO 途径抑制 LPS 增强的 CCL-2 合成。根管内二甲双胍可减少与根尖周炎相关的骨吸收，并抑制 iNOS 表达和单核细胞募集。
我们的研究结果证实了根管内二甲双胍治疗根尖周炎的疗效。通过调节 iNOS 表达和 NO 产生抑制单核细胞募集是二甲双胍有益作用的重要机制。
