Radix Glycyrrhizae polysaccharide (GP), the most important component of Radix Glycyrrhizae, has been reported to have many immunopharmacological activities. However, the mechanism by which GP affects dendritic cells (DCs) has not been elucidated. In this study, we investigated the effect of GP on murine bone marrow-derived DCs and the potential pathway through which GP exerts this effect. Mononuclear cells (MNCs) were isolated from murine bone marrow and induced to become DCs by culturing with GM-CSF and IL-4. Six days later, DCs were divided into three groups: control group, GP group and LPS group. After 48 h of treatment, phenotypic figures and antigen uptake ability were determined by FACS analysis. The proliferation of DC-stimulated allogenic CD3+ T cells was detected by WST-1. IL-12 p70 and IFN-γ, which are secreted by DCs and CD3+ T cells respectively, were quantified by ELISA. Additionally, IL-12 p40 mRNA expression was determined by real-time PCR. Alterations in TLR4-related signaling pathways were examined by performing an antibody neutralization experiment. Treatment of DCs with GP resulted in the enhanced expression of the cell surface molecules CD80, CD86 and MHC I-A/I-E. GP also increased the production of IL-12 p70 by DCs in a time-dependent manner. The endocytosis of FITC-dextran by DCs was suppressed by GP administration. Furthermore, GP-treated DCs enhanced both the proliferation and IFN-γ secretion of allogenic CD3+ T cells. Finally, the effects of GP on DCs were partially reduced by using inhibitors of TLR4, NF-κB, p38 MAPK or JNK. In conclusion, GP can induce the maturation of DCs, and does so, in part, by regulating a TLR4-related signaling pathway.
据报道,甘草
多糖(GP)是甘草中最重要的成分,具有多种免疫药理活性。然而,GP 影响树突状细胞(DCs)的机制尚未阐明。在这项研究中,我们调查了 GP 对小鼠骨髓衍生 DC 的影响以及 GP 发挥这种作用的潜在途径。从小鼠骨髓中分离出单核细胞(MNCs),用 GM-CSF 和 I
L-4 培养诱导其成为 DCs。六天后,DCs 被分为三组:对照组、GP 组和 L
PS 组。处理 48 小时后,通过
FACS 分析测定表型和抗原摄取能力。用 W
ST-1 检测 DC 刺激的异源 CD3+ T 细胞的增殖情况。I
L-12 p70和IFN-γ分别由DC和CD3+ T细胞分泌,通过ELI
SA进行定量。此外,I
L-12 p40 mRNA 的表达也通过实时
PCR 进行了测定。通过
抗体中和实验检测了 TLR4 相关信号通路的变化。用 GP 处理 DC 会导致细胞表面分子 CD80、CD86 和
MHC I-A/I-E 的表达增强。GP 还以时间依赖性的方式增加了直流细胞产生的 I
L-12 p70。GP能抑制DC对FITC-
葡聚糖的内吞。此外,GP 处理的 DC 还能增强异源 CD3+ T 细胞的增殖和 IFN-γ 分泌。最后,使用 TLR4、NF-κB、p38
MAPK 或
JNK 抑制剂可部分降低 GP 对 DC 的影响。总之,GP 可诱导 DCs 成熟,而且部分是通过调节与 TLR4 相关的信号通路来实现的。