Xie Yong, Ye Yi-Ping, Sun Hong-Xiang, Li Duo
College of Animal Sciences, Zhejiang University, Kaixuan Road 268, Hangzhou, Zheijiang 310029, China.
Vaccine. 2008 Jun 25;26(27-28):3452-60. doi: 10.1016/j.vaccine.2008.04.023. Epub 2008 May 1.
Platycodin D (PD), platycodin D3 (PD3), and platycoside E (PE) were the platycodigenin-type saponins isolated from the root of Platycodon grandiflorum. All shared a platycodigenin skeleton and the same sugar side chains attached to C-28 of the aglycone, only differ from one another by the number of glycosyl units in sugar moieties attached to C-3. To assess the potential contribution of the glycidic chains to the biological activities and elucidate the structure-activity relationships of the platycodigenin-type saponins, these three saponins were evaluated for their haemolytic activities and adjuvant potentials on the cellular and humoral immune responses of mice against ovalbumin (OVA). Among three saponins, the ranking of the haemolytic activity was PD>PD3>PE (P<0.001). PD and PD3 could significantly enhance mitogen- and OVA-induced splenocyte proliferation in the OVA-immunized mice (P<0.001). The order of increasing OVA-stimulated splenocyte proliferation was PD>PD3>PE (P<0.05, P<0.01, or P<0.001). The sera OVA-specific IgG, IgG1, IgG2a and IgG2b antibody levels in the OVA-immunized mice were significantly enhanced by PD and PD3. However, PE only significantly promoted the production of the sera OVA-specific IgG2a and IgG2b antibody in the OVA-immunized mice. Adjuvant potentials of PD on antibody responses were higher than those of PD3 and PE (P<0.05, P<0.01, or P<0.001). Meanwhile, PD also significantly enhanced the mRNA expression of cytokines IL-2, IFN-gamma, IL-4, and IL-10 and transcription factors T-bet and GATA-3 in mice splenocyte induced by Con A (P<0.05, P<0.01, or P<0.001). These results suggested that the number of sugar residues in the glycidic chains attached to C-3 of aglycone could affect the haemolytic and adjuvant activities of platycodigenin-type saponins, and that PD had immunological adjuvant activity, and simultaneously elicited a Th1 and Th2 immune response by regulating gene expression of Th1/Th2 cytokines and transcription factors.
桔梗皂苷D（PD）、桔梗皂苷D3（PD3）和桔梗皂苷E（PE）是从桔梗根中分离得到的桔梗皂苷元型皂苷。它们都具有桔梗皂苷元骨架，且在苷元的C-28位连接有相同的糖侧链，彼此之间仅在连接于C-3的糖部分的糖基单元数量上有所不同。为了评估糖苷链对生物活性的潜在贡献，并阐明桔梗皂苷元型皂苷的构效关系，对这三种皂苷在小鼠针对卵清蛋白（OVA）的细胞免疫和体液免疫反应中的溶血活性及佐剂潜力进行了评估。在这三种皂苷中，溶血活性的排序为PD>PD3>PE（P<0.001）。PD和PD3能显著增强OVA免疫小鼠中丝裂原和OVA诱导的脾细胞增殖（P<0.001）。OVA刺激的脾细胞增殖增加顺序为PD>PD3>PE（P<0.05、P<0.01或P<0.001）。PD和PD3显著提高了OVA免疫小鼠血清中OVA特异性IgG、IgG1、IgG2a和IgG2b抗体水平。然而，PE仅显著促进了OVA免疫小鼠血清中OVA特异性IgG2a和IgG2b抗体的产生。PD对抗体反应的佐剂潜力高于PD3和PE（P<0.05、P<0.01或P<0.001）。同时，PD还显著增强了刀豆蛋白A诱导的小鼠脾细胞中细胞因子IL-2、IFN-γ、IL-4和IL-10以及转录因子T-bet和GATA-3的mRNA表达（P<0.05、P<0.01或P<0.001）。这些结果表明，连接于苷元C-3的糖苷链中的糖残基数量可影响桔梗皂苷元型皂苷的溶血和佐剂活性，且PD具有免疫佐剂活性，并通过调节Th1/Th2细胞因子和转录因子的基因表达同时引发Th1和Th2免疫反应。
