Mandal G, Wyllie S, Singh N, Sundar S, Fairlamb A H, Chatterjee M
Department of Pharmacology, Institute of Post Graduate Medical Education and Research, Kolkata, 244B Acharya JC Bose Road, Kolkata-700 020, India.
Parasitology. 2007 Nov;134(Pt 12):1679-87. doi: 10.1017/S0031182007003150. Epub 2007 Jul 5.
The current trend of antimony (Sb) unresponsiveness in the Indian subcontinent is a major impediment to effective chemotherapy of visceral leishmaniasis (VL). Although contributory mechanisms studied in laboratory-raised Sb-R parasites include an up-regulation of drug efflux pumps and increased thiols, their role in clinical isolates is not yet substantiated. Accordingly, our objectives were to study the contributory role of thiols in the generation of Sb unresponsiveness in clinical isolates. Promastigotes were isolated from VL patients who were either Sb responsive (n=2) or unresponsive (n=3). Levels of thiols as measured by HPLC and flow cytometry showed higher basal levels of thiols and a faster rate of thiol regeneration in Sb unresponsive strains as compared with sensitive strains. The effects of antimony on generation of reactive oxygen species (ROS) in normal and thiol-depleted conditions as also their H2O2 scavenging activity indicated that in unresponsive parasites, Sb-mediated ROS generation was curtailed, which could be reversed by depletion of thiols and was accompanied by a higher H2O2 scavenging activity. Higher levels of thiols in Sb-unresponsive field isolates from patients with VL protect parasites from Sb-mediated oxidative stress, thereby contributing to the antimony resistance phenotype.
印度次大陆目前出现的锑（Sb）无反应趋势是内脏利什曼病（VL）有效化疗的主要障碍。虽然在实验室培养的锑抗性（Sb-R）寄生虫中研究的促成机制包括药物外排泵的上调和硫醇增加，但它们在临床分离株中的作用尚未得到证实。因此，我们的目标是研究硫醇在临床分离株中产生锑无反应性的促成作用。从锑敏感（n = 2）或无反应（n = 3）的VL患者中分离前鞭毛体。通过高效液相色谱（HPLC）和流式细胞术测量的硫醇水平显示，与敏感菌株相比，锑无反应菌株的硫醇基础水平更高，硫醇再生速率更快。锑在正常和硫醇耗尽条件下对活性氧（ROS）生成的影响以及它们的过氧化氢清除活性表明，在无反应性寄生虫中，锑介导的ROS生成受到抑制，这可以通过硫醇耗尽来逆转，并伴随着更高的过氧化氢清除活性。VL患者的锑无反应现场分离株中较高水平的硫醇可保护寄生虫免受锑介导的氧化应激，从而导致锑抗性表型。
