Iyer Jitesh P, Kaprakkaden Anees, Choudhary Manohar L, Shaha Chandrima
National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India.
Mol Microbiol. 2008 Apr;68(2):372-91. doi: 10.1111/j.1365-2958.2008.06154.x. Epub 2008 Feb 26.
Leishmania donovani, the causative agent of visceral leishmaniasis, uses a cascade of enzymes that include cytosolic tryparedoxin peroxidase (cTXNPx) for detoxification of peroxides, an event pivotal for survival of digenic parasites living in two disparate biological environments. In this study, we observed an increase in promastigote cTXNPx levels after exposure to H(2)O(2) and this group did not show any cell death; however, exposure to a combination of H(2)O(2) and nitric oxide resulted in significant reduction of cTXNPx levels accompanied by high cell death. The protective relationship between higher levels of cTXNPx and survival was further substantiated by the improved ability of L. donovani promastigotes overexpressing cTXNPx to withstand exposure to H(2)O(2) and nitric oxide combination as compared with vector transfectants. In addition, cTXNPx transfectants demonstrated increased virulence, causing higher parasite burden in macrophages as compared with vector transfectants. Interestingly, the cTXNPx transfectants as promastigotes or amastigotes were resistant to clearance by the anti-leishmanial drug antimony, suggesting a cTXNPx link to drug response. Mechanistically, cTXNPx overexpression was protective against changes in Ca(2+) homeostasis but not against mitochondrial hyperpolarization brought about by exposure to H(2)O(2) and nitric oxide. Therefore, this study provides a link between cTXNPx expression to survival, virulence and drug response in L. donovani.
杜氏利什曼原虫是内脏利什曼病的病原体，它利用一系列酶（包括胞质型锥虫硫氧还蛋白过氧化物酶（cTXNPx））来清除过氧化物，这一过程对于生活在两种不同生物环境中的双基因寄生虫的生存至关重要。在本研究中，我们观察到前鞭毛体暴露于H₂O₂后cTXNPx水平升高，且该组未出现任何细胞死亡；然而，暴露于H₂O₂和一氧化氮的组合会导致cTXNPx水平显著降低，并伴有高细胞死亡率。与载体转染子相比，过表达cTXNPx的杜氏利什曼原虫前鞭毛体耐受H₂O₂和一氧化氮组合暴露的能力增强，进一步证实了较高水平的cTXNPx与生存之间的保护关系。此外，与载体转染子相比，cTXNPx转染子表现出更强的毒力，在巨噬细胞中导致更高的寄生虫负荷。有趣的是，作为前鞭毛体或无鞭毛体的cTXNPx转染子对抗利什曼药物锑的清除具有抗性，这表明cTXNPx与药物反应有关。从机制上讲，cTXNPx的过表达对Ca²⁺稳态的变化具有保护作用，但对暴露于H₂O₂和一氧化氮引起的线粒体超极化没有保护作用。因此，本研究揭示了cTXNPx表达与杜氏利什曼原虫的生存、毒力和药物反应之间的联系。
