Dual artemisinin action combats resistance

总结 广泛的长期目标是优化关键的青蒿素和喹啉疟疾药物组合， 通过击败抗药性杀死恶性疟原虫。在当前耐药性持续存在的情况下， 部署药物，这项工作将量化血红素-青蒿素加合物的一种新的喹啉样作用机制， 确定与耐药水平相关的可逆或不可逆的血红素结晶抑制，并探索最佳的 血红素结晶抑制与喹啉-青蒿素组合杀灭寄生虫有关。初步数据验证 青蒿素的另一种作用机制是基于形成丰富的血红素-青蒿素加合物， 其以不可逆作用抑制血红素结晶。外源血红素-青蒿素加合物抑制青蒿素 环抗性突变体Kelch 13恶性疟原虫，具有低nM IC 50。实验方法采用 恶性疟原虫药物敏感和耐药寄生虫体外实验研究之间的协同作用， 用原子力显微镜对晶体生长的时间分辨原位观察获得的物理化学的认识 在不同的药物组合中。 该假说是通过双氢青蒿素（DHA， 大多数青蒿素类药物在体内的产物）使任何疟原虫分离株的滋养体敏感， 克服了青蒿素的轮状抗性。我们还假设，某些喹啉类化合物和 血红素-二氢青蒿素加合物（H-DHA）在杀死与血红素晶体抑制相关寄生虫方面是上级的， 以及分别与可逆/不可逆血红素晶体抑制的程度有关。为达致这些目标，我们会 三个具体目标：目标1。建立了外源as的抑制浓度和作用机制 以及生物活化的H-DHA在药物敏感和耐药疟原虫中的作用。目标二。确定可逆性或不可逆性 H-DHA血红素结晶抑制的体内和体外研究。目标3：确定抗疟喹啉类药物的双重组合 和H-DHA加合物增强，减弱，或不关心他们的伴侣对寄生虫的杀伤作用， 血红素结晶。 这项拟议的研究将量化青蒿素加合物代谢物杀死寄生虫的数量， 使滋养体阶段对青蒿素类药物敏感。这项工作也将告知基本知识 关于克服青蒿素耐药性的机制，血红素晶体生长的可逆性程度，以及 根据相互作用效果确定疟疾药物的最佳组合。

Summary The broad long-term goal is to optimize critical artemisinin and quinoline malaria drug combinations for maximum killing of the P. falciparum parasite by defeating resistance. In the setting of ongoing drug resistance to currently deployed drugs, this work will quantify a novel quinoline-like mechanism of action for the heme-artemisinin adducts, define reversible or irreversible heme crystal inhibition correlated to level of drug resistance, and explore optimum heme crystal inhibition related to parasite killing with quinoline-artemisinin combinations. Preliminary data validate an additional mechanism of action for the artemisinins based on formation of abundant heme-artemisinin adduct, which inhibits heme crystallization with irreversible action. Exogenous heme-artemisinin adducts inhibit artemisinin ring-resistant mutant Kelch13 P. falciparum parasites with low nM IC50s. The experimental approach employs the synergy between experimental investigations with P. falciparum drug-sensitive and resistant parasites in vitro and physicochemical insights obtained by time-resolved in situ observations of crystal growth by atomic force microscopy in the presence of different drug combinations. The hypothesis is that the inhibition of heme crystal formation by the heme adduct of dihydroartemisinin (DHA, the product of most artemisinin-class drugs in vivo) renders trophozoites of any Plasmodium isolate sensitive, which defeats the artemisinin ring-stage resistance. We also hypothesize that certain combinations of quinolines and heme-dihydroartemisinin adduct (H-DHA) are superior in killing of parasites correlated to heme crystal inhibition as well as separately to the degree of reversible/irreversible heme crystal inhibition. Towards these objectives, we will pursue three specific aims: Aim 1. Establish the inhibition concentrations and mechanism of action of exogenous as well as bio-activated H-DHA in drug sensitive and resistant Plasmodium. Aim 2. Establish reversibility or irreversibility of H-DHA heme crystal inhibition in vivo and in vitro. Aim 3. Establish if double combinations of antimalarial quinolines and H-DHA adducts enhance, weaken, or are indifferent to their partner’s action on parasite killing and the rate of hematin crystallization. This proposed research will quantify the amount of parasite killing by artemisinin adduct metabolites which renders trophozoite stages sensitive to the artemisinin drug class. The work will also inform fundamental knowledge regarding mechanisms to defeat artemisinin resistance, degree of reversibility of hematin crystal growth, and optimum combinations of malaria drugs based upon interaction effects.