Novel targets and drugs for the control of platyhelminth infections

描述（由申请人提供）：扁形虫（扁形动物）引起的寄生虫感染是一种被忽视的疾病，是许多发展中国家残疾、死亡和重大经济损失的主要原因。扁形虫感染的大规模治疗依赖于一种单一的药物：吡喹酮，而抗药性的出现是一个迫在眉睫的威胁。在最贫穷的地区和国家，确定新的药物，特别是如果它们通过不同的机制针对寄生虫，是公共卫生的一个重要目标。我们已经证明，氧化还原稳态和抗氧化防御的扁形虫寄生虫是完全依赖于一个单一的酶，硫氧还蛋白谷胱甘肽还原酶（TGR）。这种生化情况不同于宿主的生化情况，宿主有相关但不同的途径。近年来血吸虫病的研究证实TGR是一个新的合理的药物靶点，并显示恶二唑N-氧化物作为新的血吸虫病药物先导物具有很大的前景。在这个项目中，我们将确定有效的和具体的抑制剂，选择性地干扰扁形虫的氧化还原稳态。在比较性酶抑制试验中，我们将使用：用途：i）一组来自绦虫和吸虫（扁形动物寄生虫的两大类）的重组TGR以及人重组硫氧还蛋白还原酶和TGR，和ii）一组已被鉴定为细粒棘球绦虫TGR抑制剂的恶二唑N-氧化物和金配位化合物。我们将评估最佳抑制剂的作用：（i）使用培养的寄生虫进行体外试验;以及（ii）在啮齿动物模型中进行体内试验。对于最佳抑制剂，将表征抑制机制。系列扩展将进行基于所获得的结果和在硅片对接和神经网络预测。此外，我们还将进一步研究扁形动物TGR的催化和调控。我们将研究：i）谷胱甘肽还原的机制，ii）扁形虫TGR的脱谷胱甘肽化活性，和iii）调节性半胱氨酸在TGR中的作用。这些生化研究将有助于药物优化和设计。该项目涉及一个与乌拉圭和其他国家高度相关的重大全球健康问题。 公共卫生相关性：扁形虫感染引起的被忽视的热带疾病与高发病率和死亡率有关，给穷国造成沉重负担。对这些感染的大规模治疗依赖于单一药物，对抗药性寄生虫的出现存在合理的担忧，迫切需要新的药物。我们提出了一种直接的方法来治疗扁形虫感染，通过确定药物选择性干扰氧化还原稳态的寄生虫。

DESCRIPTION (provided by applicant): Parasitic infections caused by flatworms (platyhelminths) are neglected diseases and a major cause of disability, mortality and significant economic losses in many developing countries. Large-scale treatment of flatworm infections relies on a single drug available: praziquantel, and the emergence of drug resistance is an impending menace. The identification of novel drugs, in particular if they target the parasite by a different mechanism, is an important goal in public health in the poorest regions and countries. We have demonstrated that the redox homeostasis and antioxidant defenses of platyhelminth parasites are fully dependent on a single enzyme, thioredoxin glutathione reductase (TGR). This biochemical scenario differs from that of the host where there are related but distinct pathways. Recent studies in schistosomiasis validated TGR as a novel rational drug target, and have shown that oxadiazole N-oxides offer great promise as new drug leads for schistosomiasis. In this project, we will identify effective and specific inhibitors of platyhelminth TGRs, selectively disturbing flatworm redox homeostasis. In comparative enzymatic inhibition assays we will use: i) a panel of recombinant TGRs from tapeworms and flukes (the two major groups of platyhelminth parasites) as well as human recombinant thioredoxin reductases and TGR, and ii) a panel of oxadiazole N-oxides and gold coordination compounds already identified as inhibitors of Echinococcus granulosus TGR. We will assess the effect of best inhibitors (i) in vitro using cultured parasites; and (ii) in vivo in rodent models. For best inhibitors the mechanism of inhibition will be characterized. Series expansion will be carried out based on the results obtained and in silico docking and neural network predictions. In addition, we will further investigate catalysis and regulation of platyhelminth TGRs. We will study: i) the mechanism of glutathione reduction, ii) deglutathionylation activity of flatworm TGRs, and iii) the role of regulatory cysteine(s) in TGR. These biochemical studies will assist in drug optimization and design. The project addresses a significant global health problem, with high relevance to Uruguay and other countries. PUBLIC HEALTH RELEVANCE: Neglected tropical diseases caused by flatworm infections are associated with high morbidity and mortality and constitute a heavy burden to poor countries. Large-scale treatment of these infections relies on a single drug and there is justified concern regarding the emergence of drug-resistant parasites, and a pressing need for new drugs. We propose a straightforward approach to treat flatworm infections by identifying drugs selectively interfering with the redox homeostasis of the parasites.