Department of Experimental Medical Science, Lund University, Lund, Sweden.
Acta Odontol Scand. 2013 May-Jul;71(3-4):892-8. doi: 10.3109/00016357.2012.734415. Epub 2012 Nov 2.
Periodontal ligament (PDL) cells produce IL-6 upon stimulation with inflammation promoters, but the signaling pathways involved have not been characterized. This study investigates underlying mechanisms behind regulation of PDL cell IL-6 production by E. coli and P. gingivalis LPS.
Human PDL cells, endothelial cells and monocytes were stimulated with E. coli or P. gingivalis LPS in the presence or absence of pharmacological agents in order to disclose pathways involved in LPS signaling. Gene expression and cellular protein levels were assessed by quantitative real-time PCR and ELISA, respectively.
Stimulation with LPS from E. coli (1 µg/ml) for 24 h enhanced PDL cell IL-6 expression several fold, demonstrated both on transcript and protein levels, but P. gingivalis LPS (1-5 µg/ml) had no effect. TLR2 mRNA was more highly expressed than TLR4 transcript in PDL cells. Treatment with the non-selective nitric oxide synthase inhibitor L-NAME (100 µM) reduced E. coli LPS-induced PDL cell IL-6 by 30%, while neither aminoguanidine (10 µM), an inhibitor of inducible nitric oxide synthase, nor estrogen (17β-estradiol, 100 nM) influenced IL-6. Treatment with the glucocorticoid dexamethasone (1 µM) totally prevented the E. coli LPS-induced PDL cell IL-6. In endothelial cells, neither E. coli LPS nor P. gingivalis LPS promoted IL-6 production. In monocytes, serving as positive control, both E. coli and P. gingivalis LPS stimulated IL-6.
E. coli LPS but not P. gingivalis LPS stimulates PDL cell IL-6 production through a glucocorticoid-sensitive mechanism involving nitric oxide formation, probably via endothelial nitric oxide synthase.
牙周韧带（PDL）细胞在受到炎症促进剂刺激时会产生白细胞介素 6（IL-6），但参与其中的信号通路尚未得到阐明。本研究旨在探讨大肠杆菌和牙龈卟啉单胞菌 LPS 调控 PDL 细胞 IL-6 产生的潜在机制。
用大肠杆菌或牙龈卟啉单胞菌 LPS 刺激人牙周韧带细胞、内皮细胞和单核细胞，并在存在或不存在药理试剂的情况下，以揭示 LPS 信号通路中涉及的途径。通过实时定量 PCR 和 ELISA 分别评估基因表达和细胞蛋白水平。
用 1µg/ml 的大肠杆菌 LPS 刺激 24 小时可使 PDL 细胞 IL-6 的表达增加数倍，无论是在转录还是蛋白水平上均如此，但 1-5µg/ml 的牙龈卟啉单胞菌 LPS 则没有效果。与 TLR4 转录物相比，TLR2 mRNA 在 PDL 细胞中的表达更高。用非选择性一氧化氮合酶抑制剂 L-NAME（100µM）处理可使大肠杆菌 LPS 诱导的 PDL 细胞 IL-6 减少 30%，而诱导型一氧化氮合酶抑制剂氨基胍（10µM）或雌激素（17β-雌二醇，100nM）均不影响 IL-6。用糖皮质激素地塞米松（1µM）处理可完全阻止大肠杆菌 LPS 诱导的 PDL 细胞 IL-6。在内皮细胞中，大肠杆菌 LPS 和牙龈卟啉单胞菌 LPS 均不能促进 IL-6 的产生。在单核细胞中，作为阳性对照，大肠杆菌和牙龈卟啉单胞菌 LPS 均可刺激 IL-6 的产生。
大肠杆菌 LPS 而非牙龈卟啉单胞菌 LPS 通过糖皮质激素敏感的机制刺激 PDL 细胞 IL-6 产生，该机制涉及一氧化氮的形成，可能通过内皮型一氧化氮合酶。
