A basic research on anti-oxidant system of Plasmodium falciparum for its suitability as targets for anti-malarial chemotherapy: In special relation to the parasite peroxiredoxins as the drug targets.

我们证明了人恶性疟原虫的2-半胱氨酸过氧化还蛋白(2-Cys Prx)可以作为寄生虫硫氧还蛋白系统的末端过氧化物酶。2-Cys Prx-Null寄生虫系对超氧化物和一氧化氮的敏感性高于野生型。这些发现表明，2-Cys PRX保护寄生虫细胞免受氧化和亚硝化应激的影响。实时定量逆转录聚合酶链式反应检测到2-Cys Px基因在红内期的组成性表达，表明其在寄生虫的抗氧化防御机制中起重要作用。2-Cys Px蛋白在鼠疟原虫约氏疟原虫红内期的表达谱相似。此外，这种Prx蛋白在啮齿动物疟疾寄生虫的昆虫阶段(受精卵、卵子和子孢子)中也有表达。相比之下，该寄生虫的1-Cys Prx mRNA在滋养体晚期表现出阶段特异性表达。在啮齿动物疟疾寄生虫中证实了滋养体特异性的PRX蛋白在红细胞内和昆虫阶段的表达。高表达1-Cys Prx的寄生虫对氯喹的敏感性较低，氯喹增加了寄生虫细胞的血红素负担。重组的1-Cys PRX蛋白能够在体外处理谷胱甘肽诱导的血红素降解产生的ROS。滋养体是血红蛋白代谢活跃的阶段，在滋养体中发现了Prx蛋白的高表达，这表明这种Prx与血红素来源的ROS有关。进一步研究阐明Prx蛋白在疟疾寄生虫中的这种作用可能为将这些蛋白用作疟疾化疗的替代靶点铺平道路。

We demonstrated that the 2-Cys peroxiredoxin (2-Cys Prx) from the human malaria parasite P. falciparum can act as a terminal peroxidase of the parasite thioredoxin system. The 2-Cys Prx-null parasite line was more sensitive to superoxide and nitric oxide than wildtype. These findings suggest that the 2-Cys Prx protects the parasite cells from oxidative and nitrosative stresses. A constitutive expression of the 2-Cys Px mRNA, which was depicted by real-time quantitative reverse transcriptase PCR in the intraerythrocytic stage, indicated its fundamental roles in the parasite's antioxidat defense mechanism. The 2-Cys Px protein showed similar expression profile in the intraerythrocytic stage of rodent malaria parasite, P. yoelii. In addition, this Prx protein was expressed in the insect stage (zygote, ookinete and sporozoite) of the rodent malaria parasite.In contrast, the parasite's 1-Cys Prx mRNA showed a stage-specific expression at the late trophozoite. The trophozoite-specific expression of the Prx protein during the intraerythrocytic and insect stages was confirmed in the rodent malaria parasite. The 1-Cys Prx-overexpressing parasite was less susceptible to chloroquine, which increases heme burden to the parasite cell. The recombinant 1-Cys Prx protein can deal with reactive oxygen species (ROS), emerged from glutathione-induced heme degradation in vitro. An elevated expression of the Prx protein seen in the trophozoite, the stage with active hemoglobin metabolism, suggests an association of this Prx with heme-derived ROS.Further studies to elucidate such roles of Prx proteins in the malaria parasite may pave the way to utilize the proteins as an alternative targets for the malaria chemotherapy.