Edelstein M P, Ozaki Y, Duch D S
Department of Medicinal Biochemistry, Wellcome Research Laboratories, Research Triangle Park, NC 27709.
J Immunol. 1989 Nov 1;143(9):2969-73.
Indoleamine 2,3-dioxygenase (IDO) is a flavin-dependent enzyme which uses superoxide anion as a cosubstrate to catalyze the decyclization of the pyrrole ring of L-tryptophan to form formylkynurenine. This enzyme is induced in some tumor cells after treatment with IFN-gamma. The mechanism of induction of IDO in tumor cells by IFN-gamma was studied in THP-1 human monocytic leukemia cells. Before the addition of IFN-gamma, no IDO could be detected in these cells. Treatment of THP-1 cells with IFN-gamma produced an induction of IDO, with peak activity occurring 72 to 96 h after addition of IFN-gamma. Because phorbol esters are known to induce many enzymes in cells, most likely through the activation of protein kinase C, the effects of PMA on the induction of IDO were determined. PMA potentiated the IFN-gamma-induced elevation of IDO, but by itself, was unable to induce enzyme activity. Maximum induction of IDO in the presence of PMA and IFN-gamma was obtained by preexposure of the cells to PMA for 48 h before the addition of IFN-gamma. Maximum induction of IDO after the addition of IFN-gamma occurred 24 to 48 h after addition of the cytokine to the culture medium. However, the induction of IDO does not appear to be potentiated through the activation of protein kinase C, because the addition of the protein kinase C inhibitor H-7 had no effect on the induction of IDO when the cells were exposed to PMA and IFN-gamma. Moreover, diacylglycerol was unable to replace PMA in these studies. Studies with cAMP and cGMP analogs suggest a role for these compounds in the regulation of IDO expression.
吲哚胺2,3-双加氧酶（IDO）是一种黄素依赖性酶，它利用超氧阴离子作为共底物来催化L-色氨酸吡咯环的脱环化反应，形成甲酰犬尿氨酸。在用γ-干扰素处理后，这种酶在一些肿瘤细胞中被诱导产生。在THP-1人单核细胞白血病细胞中研究了γ-干扰素诱导肿瘤细胞中IDO的机制。在添加γ-干扰素之前，在这些细胞中检测不到IDO。用γ-干扰素处理THP-1细胞可诱导IDO产生，添加γ-干扰素后72至96小时活性达到峰值。由于已知佛波酯可诱导细胞中的许多酶，很可能是通过激活蛋白激酶C，因此确定了佛波酯对IDO诱导的影响。佛波酯增强了γ-干扰素诱导的IDO升高，但它自身无法诱导酶活性。在添加γ-干扰素之前将细胞预先暴露于佛波酯48小时，可以在佛波酯和γ-干扰素共同作用下使IDO达到最大诱导。添加γ-干扰素后，IDO的最大诱导在将细胞因子添加到培养基中后24至48小时出现。然而，IDO的诱导似乎不是通过激活蛋白激酶C来增强的，因为当细胞暴露于佛波酯和γ-干扰素时，添加蛋白激酶C抑制剂H-7对IDO的诱导没有影响。此外，在这些研究中，二酰基甘油无法替代佛波酯。对环磷酸腺苷（cAMP）和环磷酸鸟苷（cGMP）类似物的研究表明这些化合物在IDO表达的调节中起作用。
