Nakajima A, Hakoda M, Yamanaka H, Kamatani N, Kashiwazaki S
Institute of Rheumatology, Tokyo Women's Medical College, Japan.
Ann Rheum Dis. 1996 Apr;55(4):237-42. doi: 10.1136/ard.55.4.237.
To define the mechanisms whereby methotrexate (MTX) manifests its effects in patients with rheumatoid arthritis.
T and B cells from peripheral blood and rheumatoid synovial tissues, synovial adherent cells, and the human fibrosarcoma cell line HT1080 and its mutant (defective in an enzyme in the nucleotide salvage pathway) were tested for clonal growth when cultured with MTX. Normal human fibroblasts and those with a deficiency in a salvage pathway were cultured with MTX in the presence or absence of purine and pyrimidine bases.
Clonal growth of T and B cells, but not synovial cells, was inhibited by clinically relevant concentrations of MTX. Slowly proliferating fibroblast lines were resistant to MTX, whereas their rapidly proliferating counterparts were not. However, mutant fibroblast lines deficient in a salvage pathway were sensitive to MTX despite slow proliferation. Similarly, while skin fibroblasts were resistant to MTX, germline mutant fibroblasts deficient in a salvage pathway were sensitive to small concentrations of MTX.
T and B lymphocytes, but not synovial cells, may be the target of MTX in vivo. Resistance to MTX may be associated with slow proliferation and the ability to synthesise nucleotides via salvage pathways. MTX can inhibit proliferation of even slowly growing cells by restricting the supply of nucleotides obtained via a salvage pathway, by removal of purine and pyrimidine bases, or by inducing a deficiency in a salvage pathway. It may be possible to manipulate the therapeutic effect of MTX by adjusting the amounts of purines and pyrimidines available to the cells in vivo.
明确甲氨蝶呤（MTX）在类风湿关节炎患者中发挥作用的机制。
检测外周血及类风湿滑膜组织中的T细胞和B细胞、滑膜贴壁细胞、人纤维肉瘤细胞系HT1080及其突变体（核苷酸补救途径中的一种酶存在缺陷）与MTX共同培养时的克隆生长情况。将正常人成纤维细胞和补救途径存在缺陷的成纤维细胞在有或无嘌呤及嘧啶碱基的情况下与MTX共同培养。
临床相关浓度的MTX可抑制T细胞和B细胞的克隆生长，但对滑膜细胞无此作用。增殖缓慢的成纤维细胞系对MTX有抗性，而增殖迅速的成纤维细胞系则无抗性。然而，补救途径存在缺陷的突变成纤维细胞系尽管增殖缓慢，但对MTX敏感。同样，皮肤成纤维细胞对MTX有抗性，而补救途径存在缺陷的种系突变成纤维细胞对低浓度的MTX敏感。
T淋巴细胞和B淋巴细胞而非滑膜细胞可能是MTX在体内的作用靶点。对MTX的抗性可能与增殖缓慢以及通过补救途径合成核苷酸的能力有关。MTX可通过限制经补救途径获得的核苷酸供应、去除嘌呤和嘧啶碱基或诱导补救途径缺陷来抑制即使是生长缓慢的细胞的增殖。通过调节体内细胞可利用的嘌呤和嘧啶量，有可能调控MTX的治疗效果。
