Tao X, Davis L S, Hashimoto K, Lipsky P E
Harold C Simmons Arthritis Research Center, University of Texas Southwestern Medical Center, Dallas, USA.
J Pharmacol Exp Ther. 1996 Jan;276(1):316-25.
T2, an extract of Tripterygium wilfordii Hook F, has been reported to be effective in the treatment of a variety of autoimmune diseases, including rheumatoid arthritis. Previous studies have shown that T2 inhibited mitogen- or antigen-induced proliferation of human peripheral blood T cells and B cells, IL-2 production by T cells and Ig production by B cells. In contrast, T2 did not affect monocyte functions, such as IL-1 production and antigen presentation. The current studies sought to localize the immunosuppressive action of T2 more precisely. Results show that T2 prevented [3H]-uridine uptake by mitogen-stimulated T cells and arrested them in the early GI phase of the cell cycle. The inhibitory effects of T2 could be partially overcome by costimulating PHA activated T cells with PMA and completely nullified by costimulation with PMA plus a monoclonal antibody to CD28. Moreover, T2 had no effect on expression of IL-2R or the transferrin receptor (CD71), but inhibited production of a number of cytokines, including IL-2 and IFN-gamma by activated T cells. T2 suppressed IL-2 mRNA levels, but not IL-2R mRNA levels, in activated T cells. T2-mediated inhibition reflected suppression of IL-2 gene transcription as indicated by suppression of the expression of a reporter gene driven by the IL-2 promoter. T2 had little inhibitory effect on either IL-2 gene expression or cell cycle progression when added after initial mitogenic stimulation, indicating that an early step in the cascade of activation events was inhibited. However, initial activation events including protein tyrosine phosphorylation, the generation of diacylglycerol, IP3, and the translocation of protein kinase C were not inhibited by T2. Moreover, T2 did not inhibit the phosphatase activity of calcineurin. These results have localized the effect of T2 to a step in the T cell activation cascade after initial second messenger generation, tyrosine phosphorylation and protein kinase activation, but before IL-2 gene transcription.
雷公藤多苷（T2）是雷公藤（Tripterygium wilfordii Hook F）的提取物，据报道它对包括类风湿性关节炎在内的多种自身免疫性疾病有效。先前的研究表明，T2可抑制有丝分裂原或抗原诱导的人外周血T细胞和B细胞增殖、T细胞产生白细胞介素-2（IL-2）以及B细胞产生免疫球蛋白（Ig）。相比之下，T2不影响单核细胞功能，如IL-1产生和抗原呈递。目前的研究旨在更精确地定位T2的免疫抑制作用。结果显示，T2可阻止有丝分裂原刺激的T细胞摄取[3H] - 尿苷，并使它们停滞在细胞周期的早期G1期。用佛波酯（PMA）共刺激PHA激活的T细胞可部分克服T2的抑制作用，而用PMA加抗CD28单克隆抗体共刺激则可完全消除这种抑制作用。此外，T2对IL-2受体或转铁蛋白受体（CD71）的表达没有影响，但可抑制活化T细胞产生多种细胞因子，包括IL-2和干扰素-γ（IFN-γ）。在活化T细胞中，T2可抑制IL-2 mRNA水平，但不抑制IL-2R mRNA水平。T2介导的抑制作用反映为IL-2基因转录的抑制，这可通过抑制由IL-2启动子驱动的报告基因的表达来表明。当初始有丝分裂原刺激后添加T2时，它对IL-2基因表达或细胞周期进程几乎没有抑制作用，这表明激活事件级联反应的早期步骤受到了抑制。然而，包括蛋白酪氨酸磷酸化、二酰基甘油、肌醇三磷酸（IP3）的产生以及蛋白激酶C的转位等初始激活事件并未被T2抑制。此外，T2不抑制钙调神经磷酸酶的磷酸酶活性。这些结果已将T2的作用定位在初始第二信使产生、酪氨酸磷酸化和蛋白激酶激活之后，但在IL-2基因转录之前的T细胞激活级联反应中的一个步骤上。
