Department of Orthodontics, Medical Faculty, University of Bonn, Welschnonnenstr. 17, 53111, Bonn, Germany.
Department of Integrated Oncology, Center for Integrated Oncology (CIO), University Hospital Bonn, Venusberg-Campus 1, 53127, Bonn, Germany.
Head Face Med. 2020 Nov 16;16(1):26. doi: 10.1186/s13005-020-00244-0.
Periodontal ligament (PDL) cells initiate local immune responses, similar to microglia regulating primary host defense mechanisms in neuroinflammatory events of the central nervous system. As these two cell types manifest similarities in their immunomodulatory behavior, this study investigated the thesis that the immunological features of PDL cells might be modulated by the endocannabinoid system, as seen for microglia.
A human PDL cell line and an Embryonic stem cell-derived microglia (ESdM) cell line were grown in n = 6 experimental groups each, incubated with cannabinoid receptor agonists arachidonoylethanolamine (AEA) (50 μM) or Palmitoylethanolamide (PEA) (50 μM) and challenged with centrifugation-induced inflammation (CII) for 6 and 10 h. Untreated samples served as controls. Quantitative real-time polymerase chain reaction was applied for gene expression analyses of inflammatory cytokines, cannabinoid receptors and ionized calcium binding adaptor molecule 1 (IBA-1). Microglia marker gene IBA-1 was additionally verified on protein level in PDL cells via immunocytochemistry. Proliferation was determined with a colorimetric assay (WST-1 based). Statistical significance was set at p < 0.05.
IBA-1 was inherently expressed in PDL cells both at the transcriptional and protein level. AEA counteracted pathological changes in cell morphology of PDL cells and microglia caused by CII, and PEA contrarily enhanced them. On transcriptional level, AEA significantly downregulated inflammation in CII specimens more than 100-fold, while PEA accessorily upregulated them. CII reduced cell proliferation in a time-dependent manner, synergistically reinforced by PEA decreasing cell numbers to 0.05-fold in PDL cells and 0.025-fold in microglia compared to controls.
PDL cells and microglia exhibit similar features in CII with host-protective effects for AEA through dampening inflammation and preserving cellular integrity. In both cell types, PEA exacerbated proinflammatory effects. Thus, the endocannabinoid system might be a promising target in the regulation of periodontal host response.
牙周韧带 (PDL) 细胞启动局部免疫反应，类似于小胶质细胞调节中枢神经系统神经炎症事件中的主要宿主防御机制。由于这两种细胞类型在其免疫调节行为上表现出相似性，因此本研究探讨了 PDL 细胞的免疫学特征可能受到内源性大麻素系统调节的假设，就像小胶质细胞一样。
将人牙周韧带细胞系和胚胎干细胞衍生的小胶质细胞 (ESdM) 细胞系分别在 n = 6 个实验组中培养，用大麻素受体激动剂花生四烯酰乙醇胺 (AEA)（50 μM）或棕榈酰乙醇酰胺 (PEA)（50 μM）孵育，并通过离心诱导的炎症 (CII) 孵育 6 和 10 小时。未处理的样本作为对照。采用实时定量聚合酶链反应分析炎症细胞因子、大麻素受体和离子钙结合接头分子 1 (IBA-1) 的基因表达。通过免疫细胞化学法在 PDL 细胞中进一步验证小胶质细胞标记基因 IBA-1 的蛋白水平。通过比色法 (基于 WST-1) 测定增殖。统计显著性设置为 p < 0.05。
IBA-1 在 PDL 细胞的转录和蛋白水平上均固有表达。AEA 拮抗了 CII 引起的 PDL 细胞和小胶质细胞形态的病理性变化，而 PEA 则相反地增强了这些变化。在转录水平上，AEA 使 CII 标本中的炎症显著下调超过 100 倍，而 PEA 则附加地上调了这些标本。CII 以时间依赖性方式降低细胞增殖，PEA 协同作用将 PDL 细胞中的细胞数减少到对照的 0.05 倍，将小胶质细胞中的细胞数减少到对照的 0.025 倍。
PDL 细胞和小胶质细胞在 CII 中表现出相似的特征，AEA 通过抑制炎症和维持细胞完整性发挥宿主保护作用。在这两种细胞类型中，PEA 加剧了促炎作用。因此，内源性大麻素系统可能是调节牙周宿主反应的有前途的靶点。
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