Enhanced action of amphotericin B on Leishmania mexicana resulting from heat transformation
Enhanced action of amphotericin B on Leishmania mexicana resulting from heat transformation
复制标题
两性霉素 B 对热转化引起的墨西哥利什曼原虫的增强作用
DOI：
--
复制
发表时间：
1990
影响因子：
4.9
通讯作者：
J. Bolard
中科院分区：
文献类型：
--
作者：
H. Ramos;J. Milhaud;B. Cohen;J. Bolard
对多烯抗生素两性霉素 B (AmB) 对墨西哥利什曼原虫前鞭毛体在热转化为无鞭毛体样形式之前和之后的活力的影响进行了比较研究。通过使用核酸结合化合物溴化乙锭进行荧光分光光度法来追踪细胞死亡的动力学。研究发现，AmB 对利什曼原虫前鞭毛体的快速杀伤作用在其转化为无鞭毛体样形式后甚至更快。通过圆二色性对 AmB 与利什曼原虫膜的结合研究表明，热转化将其从非合作结合改为合作结合，减少了与膜结合的抗生素量。因此，溴化乙锭掺入转化细胞的速率增加与AmB结合量或膜中麦角甾醇量增加无关（热休克后麦角甾醇/磷脂比例小四倍）。外部水溶液中 Mg2+ 含量的增加能够阻止 AmB 诱导的溴化乙锭掺入利什曼原虫前鞭毛体，其程度（Ki = 13.8 mM）比进入热转化细胞（Ki = 64 mM）更大，表明热转化时利什曼原虫细胞表面发生显着变化。讨论了这些结果对于理解 AmB 对敏感生物体的作用机制的意义。
A comparative study of the effect of the polyene antibiotic amphotericin B (AmB) on the viability of Leishmania mexicana promastigotes before and after their transformation by heat into amastigotelike forms was carried out. The kinetics of cell death were followed by spectrofluorometry with the nucleic acid-binding compound ethidium bromide. It was found that the rapid killing effect that is exerted by AmB on Leishmania promastigotes was even faster after their transformation into amastigotelike forms. Binding studies of AmB to Leishmania membranes by circular dichroism indicated that heat transformation modified it from noncooperative to cooperative binding, decreasing the amount of antibiotic that bound to the membranes. Thus, the increased rate of ethidium bromide incorporation into transformed cells was not related either to the amount of AmB bound or to an increased amount of ergosterol in the membrane (the ergosterol/phospholipid ratio was four times smaller after heat shock). An increase in the Mg2+ content of the external aqueous solution was able to prevent the AmB-induced incorporation of ethidium bromide into Leishmania promastigotes to a greater extent (Ki = 13.8 mM) than it was into heat-transformed cells (Ki = 64 mM), suggesting that there were significant changes at the Leishmania cell surface on heat transformation. The significance of these results for understanding the mechanism of action of AmB on sensitive organisms is discussed.