Department of Anesthesiology, Taipei Medical University and Hospital, Taipei 110, Taiwan.
J Nutr Biochem. 2011 Apr;22(4):351-9. doi: 10.1016/j.jnutbio.2010.03.002. Epub 2010 Jul 23.
Monocytes expressing toll-like receptor 4 (TLR4) play a major role in regulating the innate immune response and are involved in systemic inflammation. Previous studies have shown that Ginkgo biloba extract (GBE) may act as a therapeutic agent for some cardiovascular and neurological disorders. The objective of this study was to determine whether GBE could modulate immunity in human cells. The monocytic cell line THP-1 was used. Enzyme-linked immunosorbent assay results showed that lipopolysaccharide (LPS) induces the expression of monocyte chemotactic protein-1 (MIP-1), tumor necrosis factor-α, stromal cell-derived factor-1, and MIP-1α, and this induction may be repressed by GBE treatment due to TLR4 blockade. The Griess reagent assay and western blot analysis showed that GBE-mediated inhibition of TLR4 expression was associated with the activation of mitogen-activated protein kinase and production of nitric oxide (NO). Actinomycin D chase experiments demonstrated that GBE decreased the TLR4 mRNA stability in cells. Confocal microscopy and real-time polymerase chain reaction showed that GBE induced the expression of intracellular tristetraprolin (TTP). Transfection with TTP siRNA reversed the effects of GBE in naïve or TLR4-overexpressing cells. Treatment with SNAP (an NO donor) may increase intracellular TTP expression in cells. Immunoprecipitation analysis showed that GBE mediates TTP activation and increases the interaction of TTP with the 3' untranslated region (UTR) of TLR4 mRNA by regulating NO production. Our findings indicate that GBE could decrease the sensitivity of monocytes to LPS. Utilizing TTP to control TLR4 expression may be a promising approach for controlling systemic inflammation, and GBE may have potential applications in the clinical treatment of immune diseases.
单核细胞表达 Toll 样受体 4(TLR4)在调节先天免疫反应中起主要作用,并参与全身炎症反应。先前的研究表明,银杏叶提取物(GBE)可能作为一些心血管和神经疾病的治疗剂。本研究旨在确定 GBE 是否可以调节人细胞的免疫功能。使用单核细胞系 THP-1。酶联免疫吸附试验结果表明,脂多糖(LPS)诱导单核细胞趋化蛋白-1(MIP-1)、肿瘤坏死因子-α、基质细胞衍生因子-1 和 MIP-1α 的表达,而这种诱导可能由于 TLR4 阻断而被 GBE 治疗抑制。Griess 试剂测定和 Western blot 分析表明,GBE 介导的 TLR4 表达抑制与丝裂原活化蛋白激酶的激活和一氧化氮(NO)的产生有关。放线菌素 D 追踪实验表明,GBE 降低了细胞中 TLR4 mRNA 的稳定性。共聚焦显微镜和实时聚合酶链反应显示,GBE 诱导细胞内三丝氨酸磷酸酶(TTP)的表达。用 TTP siRNA 转染逆转了 GBE 在未处理或 TLR4 过表达细胞中的作用。用 SNAP(一种 NO 供体)处理可能会增加细胞内 TTP 的表达。免疫沉淀分析表明,GBE 通过调节 NO 的产生来介导 TTP 的激活并增加 TTP 与 TLR4 mRNA 3'非翻译区(UTR)的相互作用。我们的研究结果表明,GBE 可以降低单核细胞对 LPS 的敏感性。利用 TTP 控制 TLR4 表达可能是控制全身炎症的一种有前途的方法,GBE 可能在免疫性疾病的临床治疗中有潜在的应用。