摘要目的:探讨人牙周膜干细胞（human periodontal ligament stem cell，HPDLSC）经低剂量脂多糖作用后，对巨噬细胞促炎因子表达的影响及其机制。方法:培养原代HPDLSC，并以磷酸盐缓冲液（phosphate buffer saline，PBS）、100 μg/L或10 mg/L 脂多糖处理48 h，收集各自条件培养基（conditioned medium，CM），分别与人单核白血病细胞（human monocyte leukemic cell，THP-1）源性巨噬细胞共培养48 h，对应实验分组为PBS处理的HPDLSC条件培养基（PBS-treated HPDLSC-derived CM，CM-C）组、低剂量脂多糖处理的HPDLSC条件培养基（low dose lipopolysaccharide-treated HPDLSC-derived CM，CM-L）组和高剂量脂多糖处理的HPDLSC条件培养基（high dose lipopolysaccharide-treated HPDLSC-derived CM，CM-H）组。实时荧光定量PCR检测各组巨噬细胞促炎因子相关基因白介素（interleukin，IL）-6、IL-8、IL-12、肿瘤坏死因子-α（tumor necrosis factor-α，TNF-α）mRNA表达；CM-C、CM-L组核因子E2相关因子2 ［nuclear factor （erythroid-derived 2）-like 2，NRF2］及其下游抗氧化基因谷氨酸半胱氨酸连接酶催化亚基（glutamate-cysteine ligase catalytic subunit，GCLC）、还原型烟酰胺腺嘌呤二核苷酸（磷酸）：醌氧化还原酶1［NAD（P）H quinone dehydrogenase 1，NQO1］及血红素加氧酶1（heme oxygenase 1，HO-1）mRNA的表达。同时以蛋白质免疫印迹法检测CM-C和CM-L组巨噬细胞胞质与胞核NRF2蛋白、GCLC及HO-1蛋白表达；2′，7′-二氯荧光素探针检测CM-C和CM-L组巨噬细胞内活性氧水平，以平均荧光强度（mean fluorescent intensity，MFI）表征结果。结果:CM-H组巨噬细胞内促炎因子IL-6、IL-8、IL-12及TNF-α mRNA表达（2.332±0.594、3.601±0.639、2.120±0.677、2.468±0.236）均较CM-C组（1.000±0.321、1.000±0.151、1.000±0.059、1.000±0.095）显著上调（ P<0.05）；而CM-L组巨噬细胞内IL-6、IL-12及TNF-α mRNA表达（0.056±0.002、0.215±0.024、0.567±0.071）均较CM-C组（1.000±0.209、1.000±0.220、1.000±0.220）显著下调（ P<0.05）。在mRNA水平，NRF2表达在CM-L组（1.864±0.198）较CM-C组（1.000±0.094）显著上调（ P<0.05）；在蛋白水平，CM-L组巨噬细胞胞质及胞核NRF2表达（1.175±0.104、1.308±0.082）均较CM-C组（1.000±0.025、1.000±0.049）显著升高（ P<0.05）。CM-L组巨噬细胞NRF2下游抗氧化基因GCLC、NQO1 mRNA表达（1.786±0.278、1.444±0.078）均较CM-C组（1.000±0.139、1.000±0.226）显著上调（ P<0.05），且CM-L组GCLC、HO-1蛋白水平（1.159±0.036、1.412±0.075）均显著高于CM-C组（1.000±0.050、1.000±0.013）（ P<0.05）。同时CM-L组巨噬细胞活性氧水平（MFI：123 419±1 302）较CM-C组（MFI：139 193±1 241）显著降低（ P<0.05）。 结论:低剂量脂多糖可以诱导HPDLSC激活巨噬细胞NRF2信号通路调控氧化应激反应，下调巨噬细胞促炎因子表达。

abstractsObjective:To investigate the effect of low dose lipopolysaccharide (LPS)-treated human periodontal ligament stem cells (HPDLSC) on the expression of macrophage pro-inflammatory factors and the mechanism involved.Methods:The primary HPDLSCs were obtained from healthy third molar periodontal ligament tissue. Phosphate buffer saline (PBS), 100 μg/L or 10 mg/L of LPS were used to treat HPDLSCs for 48 h, and their conditioned media were respectively co-cultured with THP-1-derived macrophages for 48 h. The corresponding experimental groups were PBS-treated HPDLSC-derived conditioned medium (CM-C) group, low dose LPS-treated HPDLSC-derived conditioned medium (CM-L) group, and high dose LPS-treated HPDLSC-derived conditioned medium (CM-H) group. Quantitative real-time PCR was performed to explore the mRNA expressions of macrophage interleukin (IL)-6, IL-8, IL-12, tumor necrosis factor-α (TNF-α) in the CM-C, CM-L and CM-H groups, and the expressions of nuclear factor (erythroid-derived 2)-like 2 (NRF2), glutamate-cysteine ligase catalytic subunit (GCLC), NAD(P)H quinone dehydrogenase 1 (NQO1) and heme oxygenase 1 (HO-1) in the CM-C and CM-L groups. Meanwhile, Western blotting was used to detect the change of nuclear and cytoplasmic NRF2 and the levels of GCLC and HO-1 in the CM-C and CM-L groups. The 2′, 7′-dichlorofluorescein probe was adopted to detect the reactive oxygen species (ROS) levels of macrophages in the CM-C and CM-L groups and the data were characterized by the mean fluorescent intensity (MFI).Results:The mRNA expressions of macrophage pro-inflammatory factors IL-6, IL-8, IL-12 and TNF-α in the CM-H group (2.332±0.594, 3.601±0.639, 2.120±0.677 and 2.468±0.236) were significantly upregulated compared with those in the CM-C group (1.000±0.321, 1.000±0.151, 1.000±0.059 and 1.000±0.095) ( P<0.05); while the relative mRNA levels of IL-6, IL-12 and TNF-α in the CM-L group (0.056±0.002, 0.215±0.024 and 0.567±0.071) were much lower than those in the CM-C group (1.000±0.209, 1.000±0.220 and 1.000±0.220) ( P<0.05). At the mRNA level, the expression of NRF2 was significantly increased in the CM-L group (1.864±0.198) compared with that in the CM-C group (1.000±0.094) ( P<0.05). At the protein level, the cytoplasmic NRF2 and nuclear NRF2 were increased in CM-L group (1.175±0.104 and 1.308±0.082) compared with those in the CM-C group (1.000±0.025 and 1.000±0.049) ( P<0.05). Furthermore, the antioxidative genes, i.e. GCLC and NQO1, localized in NRF2 downstream, were significantly upregulated in the CM-L group (1.786±0.278 and 1.444±0.078) compared with the CM-C group (1.000±0.139 and 1.000±0.226) ( P<0.05). The protein levels of GCLC and HO-1 were augmented in the CM-L group (1.159±0.036 and 1.412±0.075) in contrast with those in the CM-C group (1.000±0.050 and 1.000±0.013) ( P<0.05). In addition, the MFI in the CM-L group (123 419±1 302) was significantly lower than that in the CM-C group (139 193±1 241) ( P<0.05). Conclusions:Low-dose LPS-treated HPDLSCs could regulate oxidative stress response through activating the NRF2 signaling pathway of macrophages and further downregulating the expressions of macrophage pro-inflammatory factors.