Redox Balance & Drug Development in Schistosoma mansoni

描述（申请人提供）：血吸虫病是一种重要的热带人类寄生虫病。尽管使用了有效的抗血吸虫药物，但估计仍有2亿人感染，2000万人患有严重的疾病症状，每年有28万人死于血吸虫病。此外，随着药物的使用，传播率略有变化，并且有证据表明抗药性寄生虫的发展。由于目前没有合适的替代疗法，因此迫切需要开发新的抗β-内酰胺酶体药物。在本申请中，我们建议将重点放在寄生虫的生化氧化还原机制作为抗寄生虫药物开发的新靶点。血吸虫在其最终宿主和中间宿主中必须能够在免疫和自身产生的活性氧化合物的存在下存活，并为许多关键的酶途径提供二硫键还原当量。在大多数生物体中存在两个提供氧化防御和还原能力的平行系统，一个基于谷胱甘肽，另一个基于硫氧还蛋白。我们最近的研究结果表明，曼氏血吸虫有根本不同的氧化还原机制，从他们的哺乳动物宿主。蠕虫中不存在两种关键的氧化还原酶，谷胱甘肽还原酶和硫氧还蛋白还原酶。相反，这些活动被发现在一个单一的蛋白质硫氧还蛋白-谷胱甘肽还原酶（TGR）。我们已经表明，TGR是一种重要的寄生虫蛋白，抑制TGR会导致寄生虫死亡。在研究计划中，我们将：（1）基于我们已经鉴定的先导化合物合成潜在的TGR抑制剂，并确定它们对寄生虫和宿主酶的相对抑制活性以及它们对培养的蠕虫和哺乳动物细胞的毒性，（2）发展TGR催化机制的假说，这将进一步发展TGR抑制剂，（3）确定适合TGR结晶的条件并确定其三维结构以用于药物精制。由于二硫键氧化还原平衡的寄生虫体是集中在一个单一的关键氧化还原酶，是从根本上不同的主机机制，我们建议在利用这种寄生虫途径作为一个有前途的目标，合理的药物设计。

DESCRIPTION (provided by applicant): Schistosomiasis is an important tropical parasitic human disease. Although an effective anti-schistosome drug is in use, it is estimated that 200 million people remain infected, 20 million individuals suffer severe disease symptoms, and 280,000 people die annually from schistosomiasis. Furthermore, transmission rates have changed a little with the use of the drug and there is evidence for the development of drug resistant parasites. Because there is currently no suitable alternative therapy available there is an urgent need for the development of novel antischistosomal agents. In this application we propose to focus on parasite biochemical redox mechanisms as novel targets for antischistosomal drug development. Schistosomes in their definitive and intermediate hosts must be able to survive in the presence of both immune and self generated reactive oxygen compounds and provide disulfide reducing equivalents for a number of critical enzymatic pathways. Two parallel systems to provide oxidative defense and reducing power occur in most organisms, one based on glutathione and the other based on thioredoxin. Our recent results indicate that Schistosoma mansoni has fundamentally different redox mechanisms from their mammalian host. Entirely absent from worms are two key redox enzymes, glutathione reductase and thioredoxin reductase. Instead, these activities are found together in a single protein thioredoxin-glutathione reductase (TGR). We have shown that TGR is an essential parasite protein and that inhibition of the TGR leads to parasite death. In the research proposal we will: (1) synthesize potential TGR inhibitors based on lead compounds we have already identified and determine their relative inhibitory activity against parasite and host enzymes and their toxicity to cultured worms and mammalian cells, (2) develop an hypothesis for the catalytic mechanism of TGR, which will further the development of TGR inhibitors and, (3) define conditions suitable for the crystallization of TGR and determine its 3D structure for drug refinement. Because disulfide redox balance in schistosomes is centered on a single key redox enzyme and is fundamentally different from host mechanisms we propose in exploit this parasite pathway as a promising target for rational drug design.