INHIBITION OF DIHYDROOROTATE DEHYDROGENASE BY THE IMMUNOSUPPRESSIVE AGENT LEFLUNOMIDE
INHIBITION OF DIHYDROOROTATE DEHYDROGENASE BY THE IMMUNOSUPPRESSIVE AGENT LEFLUNOMIDE
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DOI：
10.1016/0006-2952(95)00255-x
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发表时间：
1995-09-07
影响因子：
5.8
通讯作者：
LOU, L
中科院分区：
文献类型：
--
作者：
GREENE, S;WATANABE, K;LOU, L
来氟米特[HWA 486或RS-34821，5-甲基-N-（4-三氟甲基苯基）-4-异恶唑甲酰亚胺]是一种有效治疗类风湿性关节炎的免疫抑制剂。尽管具有临床潜力，但其作用机制尚未阐明。最近的研究表明，来氟米特可能会干扰嘧啶核苷酸的代谢。在我们的研究中，来氟米特的活性代谢产物RS-61980（A77 1726，2-羟基亚乙基-氰基乙酸-4-三氟甲基苯胺）对人T淋巴母细胞瘤细胞系（A3.01）具有细胞抑制作用。尿苷能完全克服对细胞生长的抑制作用。其他核苷，胞苷，腺苷和鸟苷，没有克服该化合物的效果。由于尿苷是UMP补救合成的前体，因此我们认为RS-61980可能抑制UMP合成的从头途径。使用人细胞，检测了催化从头UMP生物合成的六种酶对RS-61980的敏感性。RS-61980仅抑制其中一种酶二氢乳清酸脱氢酶（DHODH，EC 1.3.3.1），Ki值为2.7 +/- 0.7 μ M。其他五种酶没有受到影响。对底物二氢乳清酸和辅酶Q的抑制表现出混合型动力学。这些结果表明来氟米特作用的分子靶点是DHODH。其免疫调节活性可能与抑制增殖淋巴细胞UMP合成有关。
Leflunomide [HWA 486 or RS-34821, 5-methyl-N-(4-trifluoromethylphenyl)-4-isoxazole carboximide] is an immunosuppressive agent effective in the treatment of rheumatoid arthritis. In spite of its clinical potential, its mechanism of action has not been elucidated. Recent studies suggest that leflunomide may interfere with the metabolism of pyrimidine nucleotides. In our studies, the active metabolite of leflunomide, RS-61980 (A77 1726, 2-hydroxyethylidene-cyanoacetic acid-4-trifluoromethyl anilide), was cytostatic towards a human T-lymphoblastoma cell line (A3.01). The inhibition of growth could be overcome completely by uridine. The other nucleosides, cytidine, adenosine and guanosine, did not overcome the effect of the compound. Since uridine is a precursor for the salvage synthesis of UMP, we propose that RS-61980 may be inhibiting the de novo pathway of UMP synthesis. Using human cells, the six enzymes catalyzing de novo UMP biosynthesis were tested for their sensitivity towards RS-61980. Only one of the enzymes, dihydroortate dehydrogenase (DHODH, EC 1.3.3.1) was inhibited by RS-61980 with a K-i value of 2.7 +/- 0.7 mu M. The other five enzymes were not affected. The inhibition exhibited mixed-type kinetics towards both substrates, dihydroorotic acid and coenzyme Q. These results suggest that the molecular target of leflunomide action is DHODH. The immunomodulating activity may be related to the inhibition of UMP synthesis in proliferating lymphocytes.