Suppression of B cell function by methotrexate and trimetrexate. Evidence for inhibition of purine biosynthesis as a major mechanism of action.
Suppression of B cell function by methotrexate and trimetrexate. Evidence for inhibition of purine biosynthesis as a major mechanism of action.
复制标题
甲氨蝶呤和三甲曲沙抑制 B 细胞功能。
作者：
G. Rosenthal;G. Weigand;D. Germolec;J. A. Blank;M. Luster
甲氨蝶呤（MTX）是一种广泛应用于治疗多种人类肿瘤的药物。与MTX不同，曲美曲沙（TMQ）是MTX的脂溶性喹唑啉衍生物，其不依赖于膜叶酸转运进入细胞。许多研究表明，MTX和最近的TMQ具有有效的免疫抑制特性。为了检查与抗叶酸剂对体液免疫的免疫调节作用相关的细胞事件，使用鼠B细胞成熟模型。在体外，MTX和TMQ减少了SRBC的抗体形成细胞的数量，以及IgM的产生。用抗Ig刺激的B细胞在加入任一药物后显示出[3 H]UdR掺入的剂量相关抑制，表明从头DNA合成减少。S期之前的B细胞活化事件也被两种抗叶酸剂抑制，如RNA合成的抑制所证明的。然而，无论是药物影响Ia Ag的表面表达，也不肌醇磷酸的积累。在10（-7）M MTX存在下，TdR的加入导致抗体形成细胞反应轻微增加，但不显著。然而，添加次黄嘌呤或腺嘌呤，而不是鸟嘌呤，导致完全恢复。定时添加显示，MTX抑制抗体反应的能力减弱，如果添加后48小时的文化，类似于逆转这种抑制介导的次黄嘌呤。LPS刺激的B淋巴细胞的细胞周期分析表明，这两种药物调制事件之前，以及在S期。目前的研究表明，虽然药物诱导的dTMP生物合成障碍可能是淋巴细胞增殖不足的原因，但抗叶酸诱导的嘌呤生物合成障碍是抗叶酸诱导的体液免疫抑制的主要机制。
Methotrexate (MTX) is a widely used drug in the treatment of a variety of human neoplasms. Trimetrexate (TMQ) is a lipid-soluble quinazoline derivate of MTX that, unlike MTX, is not dependent upon membrane folate transport for cellular entry. A number of studies have demonstrated that MTX and, more recently, TMQ possess potent immunosuppressive properties. To examine the cellular events associated with the immunomodulatory effects of anti-folates on humoral immunity, a murine B cell maturation model was used. In vitro, MTX and TMQ reduced the number of antibody-forming cells to SRBC, as well as IgM production. B cells stimulated with anti-Ig demonstrated a dose-related suppression in [3H]UdR incorporation after addition of either drug, suggestive of a decrease in de novo DNA synthesis. B cell activation events preceding S phase were also suppressed by both anti-folates, as evidenced by inhibition of RNA synthesis. However, neither drug affected surface expression of Ia Ag nor inositol phosphate accumulation. Addition of TdR caused a slight non-significant increase in the antibody-forming cell response in the presence of 10(-7) M MTX. However, addition of hypoxanthine or adenine, but not guanine, resulted in complete restoration. Timed addition revealed that the ability of MTX to suppress antibody responses was diminished if added after 48 h of culture, similar to the reversal of this suppression mediated by hypoxanthine. Cell cycle analysis of LPS-stimulated B lymphocytes demonstrated that both drugs modulated events preceding, as well as during, the S phase. The present studies suggest that although drug-induced impairments in dTMP biosynthesis may be responsible for deficient lymphoid proliferation, anti-folate-induced impairment in purine biosynthesis is a major mechanism in anti-folate-induced suppression of humoral immunity.