Novel targets and drugs for the control of platyhelminth infections

描述(申请人提供)：扁虫(扁形线虫)引起的寄生虫感染在许多发展中国家是被忽视的疾病，是导致残疾、死亡和重大经济损失的主要原因。扁虫感染的大规模治疗依赖于一种可用的药物：吡喹酮，而耐药性的出现是一个迫在眉睫的威胁。识别新药，特别是如果它们通过不同的机制针对寄生虫，是最贫穷地区和国家公共卫生的一个重要目标。我们已经证明，扁虫寄生虫的氧化还原动态平衡和抗氧化防御完全依赖于一个单一的酶，硫氧还蛋白谷胱甘肽还原酶(TGR)。这种生化情景不同于宿主的生化情景，在宿主中存在相关但不同的途径。最近对血吸虫病的研究证实TGR是一种新的合理的药物靶点，并表明恶二唑N-氧化物作为血吸虫病的新药导向物具有很大的前景。在这个项目中，我们将寻找有效和特异的扁虫TGRS抑制剂，选择性地干扰扁虫的氧化还原动态平衡。在比较酶抑制试验中，我们将使用：i)一组来自绦虫和吸虫的重组TGR以及人重组硫氧还蛋白还原酶和TGR，以及一组已被确认为细粒棘球绦虫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(I)体外培养寄生虫的效果；以及(Ii)在啮齿动物模型中的效果。对于最佳的缓蚀剂，将对其抑制机理进行表征。将根据所获得的结果以及在电子对接和神经网络预测中进行系列扩展。此外，我们还将进一步研究TGRS的催化和调控作用。我们将研究：1)谷胱甘肽还原的机制；2)扁虫TGRS的谷胱甘肽还原活性；3)调节半胱氨酸(S)在TGR中的作用。这些生化研究将有助于药物的优化和设计。该项目解决了一个与乌拉圭和其他国家高度相关的重大全球卫生问题。 公共卫生相关性：由扁虫感染引起的被忽视的热带疾病与高发病率和高死亡率有关，对贫穷国家构成沉重负担。大规模治疗这些感染依赖于一种药物，人们有理由对出现抗药性寄生虫感到担忧，并迫切需要新药。我们提出了一种直接的方法来治疗扁虫感染，通过识别选择性干扰寄生虫的氧化还原动态平衡的药物。

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.