Anti-Parasitic Activity of Nucleoside Analogues against Leishmania tropica and Leishmania donovani.

开发具有选择性毒性的化疗药物的一种很有前途的方法是基于寄生虫与宿主细胞在结构或功能上的某些独特特征。利什曼原虫不能从头合成嘌呤，因此依赖于宿主的嘌呤来源。这种嘌呤回收酶和宿主与寄生虫相互转化途径的质性差异，为药物在寄生虫中的选择性毒性设计提供了合理的思路。我们发现3'-脱氧肌苷。碳环肌苷、7-去氮胞苷和3'-脱氧-3'-氟肌苷区对利什曼原虫原鞭毛菌有有效抑制作用，但对哺乳动物细胞的毒性明显降低。本实验采用含脂多糖的RPMI 1640培养基培养小鼠巨噬细胞J774.1。将贴壁细胞暴露于多诺瓦杆菌原毛菌中1天，并用药物处理。结果表明，肌苷类似物在体外对多诺瓦氏L. donovani无尾线虫具有一定的抑制作用。采用肌苷类似物（3′-脱氧肌苷、碳环肌苷、7-去氮胞苷和3′-脱氧-3′-氟肌苷）对感染多诺瓦杆菌的BALB/C小鼠进行治疗，评价其治疗效果。感染多诺瓦氏乳杆菌原鞭毛菌的小鼠分别给予5种不同剂量的药物，隔天给药。2周后制备肝脏印迹涂片，测定1000个肝细胞核表达为LDU的寄生虫载量。3′-脱氧肌苷100 mg/Kg静脉注射对多诺瓦氏杆菌感染小鼠的效果约为对照组的78%，环碳肌苷100 mg/Kg静脉注射对多诺瓦氏杆菌感染小鼠的效果为92%。7-去氮猪苷和3'-脱氧-3'-氟猪苷对感染小鼠也有效。

A promising approach for the development of chemotherapeutic agents possessing selective toxicity is the one based on certain unique features in structure or function of the parasite that differ from those of the host cells. Leishmania are incapable of synthesizing purine de novo and are thus dependent on the host for the source of performaed purine. This qualitative difference in the enzymes of purine salvage and interconversion pathway between host and parasite suggests a rational approach towards the design of agents selectivitgy toxic in the parasite. We found that 3'- deoxyinosine. carbocyclic inosine, 7-deazainosine and 3'-deoxy-3'-fluoroinosine area potent inhibitors of promastigotes of Leishmania but significantly less toxic mammalian cells.In the present experiments, J774.1, a mouse macrophage line, was cultured in RPMI 1640 medium containing lipopolysaccharide. The adherent cells were exposed to promastigotes of L. donovani for 1 day, and treated with the drug. The results indicate that inosine analogues are active against amastigotes of L. donovani in vitro.The BALB/C mice infected with L. donovani were treated with inosine analogues (3'- deoxyinosine, carbocyclic inosine, 7-deazainosine and 3'-deoxy-3'-fluoroinosine) for appraising those therapeutic effect. The mice infected with L. donovani promastigotes were treated with 5 different doses of each drug administered on alternative days. Two weeks after the impression smear of the liver was prepared to determine the parasite load which was expressed as LDU by 1000 hepatic cell nuclei. In the mice infected with L. donovani, 3'-deoxyinosine 100 mg/Kg I.V showed about 78 % effect as compared with control group, and carbocyclic inosine 100 mg/Kg I. V. showed 92 % effect. 7-Deazainosine and 3'-deoxy-3'-fluoroinosine were also effective against the infected mice.