Dumont F J, Kastner C A
Department of Immunology Research, Merck Research Laboratories, Rahway, New Jersey 07065.
J Cell Physiol. 1994 Jul;160(1):141-53. doi: 10.1002/jcp.1041600117.
Transforming growth factor beta 1 (TGF-beta 1) is a multifunctional cytokine whose potent immunomodulatory activity is well documented. To explore the mechanisms of this activity we examined the effect of TGF-beta 1 on the production of IFN-gamma measured at the mRNA and protein levels in the YAC-1 T cell lymphoma. In previous studies, this model proved useful to characterize the mode of action of the immunosuppressant rapamycin (RAP). Here, we found that when induced by IL-1 or IL-1 + PMA, the production of IFN-gamma is suppressed by both TGF-beta 1 (ED50 = 1.9 pM) and RAP (ED50 = 0.2 nM). In contrast, when induced by the calcium ionophore ionomycin, in the absence or in the presence of PMA, this production is enhanced up to 10-fold by TGF-beta 1 (ED50 = 1.8 pM) and 1.5-3-fold by RAP. Therefore, in YAC-1 cells, TGF-beta 1 exerts opposite effects on IFN-gamma production depending on the mode of activation, and these effects parallel those of RAP. To further analyze the mode of action of TGF-beta 1 in this system, we used okadaic acid (OA), an inhibitor of serine/threonine protein phosphatases. Treatment with OA rendered the expression of IFN-gamma mRNA induced by IL-1 insensitive to TGF-beta 1 or RAP, indicating that activation of a phosphatase may play a role in the suppressive effect of both agents. However, OA did not prevent the augmentation of ionomycin-mediated induction of IFN-gamma mRNA by either TGF-beta 1 or RAP. Hence, the up-regulation of IFN-gamma production by TGF-beta 1 and RAP may involve a different biochemical mechanism than that mediating their suppressive action. These observations also favor the hypothesis that the two agents act on the same regulatory pathways. This was further supported by the finding that TGF-beta 1 and RAP modulate IFN-gamma production in an additive rather than synergistic fashion. However, their effects could be dissociated in mutants of YAC-1 cells selected for resistance to the inhibition of IL-1-mediated IFN-gamma induction by RAP. Moreover, the IFN-gamma modulatory action of RAP in YAC-1 cells was accompanied by an antiproliferative effect, whereas TGF-beta 1 failed to alter the growth of these cells. Therefore, the immunomodulatory action of TGF-beta 1 may result from the disruption of biochemical processes related to, although distinct from, those affected by RAP.
转化生长因子β1（TGF-β1）是一种多功能细胞因子，其强大的免疫调节活性已有充分记载。为了探究这种活性的机制，我们检测了TGF-β1对YAC-1 T细胞淋巴瘤中干扰素-γ（IFN-γ）在mRNA和蛋白水平产生的影响。在先前的研究中，该模型被证明有助于表征免疫抑制剂雷帕霉素（RAP）的作用模式。在此，我们发现，当由白细胞介素-1（IL-1）或IL-1 +佛波酯（PMA）诱导时，IFN-γ的产生受到TGF-β1（半数有效剂量[ED50]=1.9皮摩尔）和RAP（ED50 = 0.2纳摩尔）的抑制。相比之下，当由钙离子载体离子霉素诱导时，无论有无PMA存在，这种产生都会被TGF-β1（ED50 = 1.8皮摩尔）增强至10倍，被RAP增强1.5至3倍。因此，在YAC-1细胞中，TGF-β1根据激活方式对IFN-γ的产生发挥相反的作用，且这些作用与RAP的作用相似。为了进一步分析TGF-β1在该系统中的作用模式，我们使用了冈田酸（OA），一种丝氨酸/苏氨酸蛋白磷酸酶的抑制剂。用OA处理使IL-1诱导的IFN-γ mRNA表达对TGF-β1或RAP不敏感，表明磷酸酶的激活可能在这两种药物的抑制作用中起作用。然而，OA并不能阻止TGF-β1或RAP对离子霉素介导的IFN-γ mRNA诱导的增强作用。因此，TGF-β1和RAP对IFN-γ产生的上调作用可能涉及与介导它们抑制作用不同的生化机制。这些观察结果也支持了这两种药物作用于相同调节途径的假说。这一点进一步得到以下发现的支持：TGF-β1和RAP以相加而非协同的方式调节IFN-γ的产生。然而，在为抵抗RAP对IL-1介导的IFN-γ诱导的抑制作用而选择的YAC-1细胞突变体中，它们的作用可以被区分开来。此外，RAP在YAC-1细胞中对IFN-γ的调节作用伴随着抗增殖作用，而TGF-β1未能改变这些细胞的生长。因此，TGF-β1的免疫调节作用可能源于与RAP所影响的生化过程相关但不同的生化过程的破坏。
