Sereno D, Cavaleyra M, Zemzoumi K, Maquaire S, Ouaissi A, Lemesre J L
Laboratoire de Biologie Parasitaire, Centre ORSTOM, 34 032 Montpellier Cedex 1, France.
Antimicrob Agents Chemother. 1998 Dec;42(12):3097-102. doi: 10.1128/AAC.42.12.3097.
The mechanism(s) of activity of pentavalent antimony [Sb(V)] is poorly understood. In a recent study, we have shown that potassium antimonyl tartrate, a trivalent antimonial [Sb(III)], was substantially more potent than Sb(V) against both promastigotes and axenically grown amastigotes of three Leishmania species, supporting the idea of an in vivo metabolic conversion of Sb(V) into Sb(III). We report that amastigotes of Leishmania infantum cultured under axenic conditions were poorly susceptible to meglumine [Glucantime; an Sb(V)], unlike those growing inside THP-1 cells (50% inhibitory concentrations [IC50s], about 1.8 mg/ml and 22 microg/ml, respectively). In order to define more precisely the mode of action of Sb(V) agents in vivo, we first induced in vitro Sb(III) resistance by direct drug pressure on axenically grown amastigotes of L. infantum. Then we determined the susceptibilities of both extracellular and intracellular chemoresistant amastigotes to the Sb(V)-containing drugs meglumine and sodium stibogluconate plus m-chlorocresol (Pentostam). The chemoresistant amastigotes LdiR2, LdiR10, and LdiR20 were 14, 26, and 32 times more resistant to Sb(III), respectively, than the wild-type one (LdiWT). In accordance with the hypothesis described above, we found that intracellular chemoresistant amastigotes were resistant to meglumine [Sb(V)] in proportion to the initial level of Sb(III)-induced resistance. By contrast, Sb(III)-resistant cells were very susceptible to sodium stibogluconate. This lack of cross-resistance is probably due to the presence in this reagent of m-chlorocresol, which we found to be more toxic than Sb(III) to L. infantum amastigotes (IC50s, of 0.54 and 1.32 microg/ml, respectively). Collectively, these results were consistent with the hypothesis of an intramacrophagic metabolic conversion of Sb(V) into trivalent compounds, which in turn became readily toxic to the Leishmania amastigote stage.
五价锑[Sb(V)]的作用机制尚不清楚。在最近的一项研究中，我们发现酒石酸锑钾，一种三价锑化合物[Sb(III)]，对三种利什曼原虫的前鞭毛体和在无菌条件下培养的无鞭毛体的活性都比Sb(V)强得多，这支持了Sb(V)在体内代谢转化为Sb(III)的观点。我们报道，在无菌条件下培养的婴儿利什曼原虫无鞭毛体对葡甲胺[葡醛酯；一种Sb(V)]的敏感性较差，这与在THP-1细胞内生长的无鞭毛体不同（50%抑制浓度[IC50]分别约为1.8mg/ml和22μg/ml）。为了更精确地确定Sb(V)药物在体内的作用方式，我们首先通过对婴儿利什曼原虫在无菌条件下培养的无鞭毛体施加直接药物压力来诱导体外Sb(III)抗性。然后我们测定了细胞外和细胞内化学抗性无鞭毛体对含Sb(V)的药物葡甲胺和葡萄糖酸锑钠加间甲酚（喷他脒）的敏感性。化学抗性无鞭毛体LdiR2、LdiR10和LdiR20对Sb(III)的抗性分别比野生型（LdiWT）高14、26和32倍。根据上述假设，我们发现细胞内化学抗性无鞭毛体对葡甲胺[Sb(V)]的抗性与Sb(III)诱导抗性的初始水平成正比。相比之下，Sb(III)抗性细胞对葡萄糖酸锑钠非常敏感。这种交叉抗性的缺乏可能是由于该试剂中存在间甲酚，我们发现间甲酚对婴儿利什曼原虫无鞭毛体的毒性比Sb(III)更大（IC50分别为0.54和1.32μg/ml）。总的来说，这些结果与Sb(V)在巨噬细胞内代谢转化为三价化合物的假设一致，而三价化合物反过来对利什曼原虫无鞭毛体阶段很容易产生毒性。
