Product Research Department, Fuji-Gotemba Research Laboratories, Chugai Pharmaceutical Co,, Ltd,, 1-135 Komakado, Gotemba, Shizuoka, 412-8513, Japan.
Arthritis Res Ther. 2012 Apr 30;14(2):R96. doi: 10.1186/ar3821.
Methotrexate (MTX) enters cells via the reduced folate carrier SLC19A1, suggesting that SLC19A1 is associated with the efficacy of MTX. We here examined the relationship between the efficacy of MTX and the expression of SLC19A1 in glucose 6-phosphate isomerase (GPI)-induced arthritis. We found that interleukin-6 (IL-6) regulated the expression of SLC19A1, so we studied the effect of a combination of MTX and anti-mouse IL-6 receptor antibody (MR16-1).
GPI-induced arthritis was induced by intradermal immunization with recombinant GPI. MTX was given from the first day of immunization. Mice were injected once with MR16-1 10 days after immunization. The levels of SLC19A1 mRNA in whole hind limbs and immune cells were measured. Synovial cells from arthritic mice were cultured with cytokines, and cell proliferation and gene expressions were measured.
MTX inhibited the development of GPI-induced arthritis; however, the efficacy of MTX gradually diminished. SLC19A1 expression in immunized mice with arthritis was lower than in intact mice; moreover, SLC19A1 expression in arthritic mice was further decreased when they were treated with MTX. IL-6 was highly expressed in whole hind limbs of arthritic mice. In an in vitro study using synovial cells from arthritic mice, IL-6 + soluble IL-6 receptor (sIL-6R) weakened the anti-proliferative effect of MTX and reduced SLC19A1 expression. Finally, although MR16-1 did not improve arthritis at all when administered on day 10, MTX in combination with MR16-1 more potently reduced the development of arthritis than did MTX alone. When used in combination with MTX, MR16-1 apparently reversed the decrease in SLC19A1 induced by MTX alone.
In the present study, we demonstrated for the first time that IL-6 reduced the efficacy of MTX by decreasing the expression of SLC19A1, which is important for MTX uptake into cells.
甲氨蝶呤（MTX）通过还原叶酸载体 SLC19A1 进入细胞，这表明 SLC19A1 与 MTX 的疗效有关。我们在此检查了 MTX 的疗效与葡萄糖 6-磷酸异构酶（GPI）诱导的关节炎中 SLC19A1 的表达之间的关系。我们发现白细胞介素 6（IL-6）调节 SLC19A1 的表达，因此我们研究了 MTX 与抗小鼠 IL-6 受体抗体（MR16-1）联合使用的效果。
通过皮内免疫重组 GPI 诱导 GPI 诱导的关节炎。从免疫第一天开始给予 MTX。免疫后 10 天，给小鼠注射一次 MR16-1。测量整个后肢和免疫细胞中 SLC19A1 mRNA 的水平。用细胞因子培养关节炎小鼠的滑膜细胞，并测量细胞增殖和基因表达。
MTX 抑制了 GPI 诱导的关节炎的发展；然而，MTX 的疗效逐渐减弱。患有关节炎的免疫小鼠的 SLC19A1 表达低于完整小鼠；此外，用 MTX 治疗时，关节炎小鼠的 SLC19A1 表达进一步降低。IL-6 在关节炎小鼠的整个后肢中高度表达。在使用来自关节炎小鼠的滑膜细胞的体外研究中，IL-6+可溶性 IL-6 受体（sIL-6R）减弱了 MTX 的抗增殖作用，并降低了 SLC19A1 的表达。最后，尽管在第 10 天给予 MR16-1 时根本没有改善关节炎，但 MTX 与 MR16-1 联合使用比单独使用 MTX 更有效地降低关节炎的发展。当与 MTX 联合使用时，MR16-1 明显逆转了 MTX 单独使用引起的 SLC19A1 减少。
在本研究中，我们首次证明 IL-6 通过降低 SLC19A1 的表达来降低 MTX 的疗效，这对 MTX 进入细胞很重要。
