BACKGROUND Kaempferol (KPF) is a flavonoid with antiparasitic activity including experimental giardiasis which mechanism of action is unknown. OBJECTIVE To analyse the cytotoxic effects of KPF on Giardia duodenalis trophozoites and to identify a likely parasite target of this compound. METHODS We used inhibitory concentrations of KPF (IC25, IC50 and IC100) and albendazole (ABZ) as reference drug. The ultrastructure of the trophozoites was analysed by transmission electron microscopy (TEM) whilst apoptosis/necrosis, production of reactive oxygen species (ROS) and cell cycle progression were assessed by flow cytometry (FCM) and confocal laser microscopy (CLM). Ligand-protein docking analyses were carried out using KPF structure from a drug library and crystal structure of a G. duodenalis aldose reductase (GdAldRed) homolog. RESULTS KPF provoked appearance of perinuclear and periplasmic spaces devoid of cytosolic content and multilamellar structures. KPF induced proapoptotic death associated with partial arrest in the S phase without ROS production. Bioinformatics approaches predicted that GdAldRed is a viable KPF target (ΔG = -7.09 kCal/mol), exhibiting 92% structural identity and a similar coupling pattern as its human homolog. CONCLUSIONS KPF exerted a proapoptotic effect on G. duodenalis trophozoites involving partial interruption of DNA synthesis without oxidative stress or structure damage to chromatin and cytoskeletal structures. GdAldRed is a likely target underlying its antigiardial activity.

中文翻译：

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山奈酚对十二指肠贾第鞭毛虫滋养体的超微结构和促凋亡作用及其潜在蛋白质靶标的生物信息学预测


背景技术山奈酚(KPF)是一种具有抗寄生虫活性的类黄酮，包括实验性贾第鞭毛虫病，其作用机制尚不清楚。目的 分析 KPF 对十二指肠贾第鞭毛虫滋养体的细胞毒性作用，并确定该化合物可能的寄生虫靶标。方法采用抑菌浓度的KPF（IC25、IC50和IC100）和阿苯达唑（ABZ）作为对照药。通过透射电子显微镜（TEM）分析滋养体的超微结构，同时通过流式细胞术（FCM）和共焦激光显微镜（CLM）评估细胞凋亡/坏死、活性氧（ROS）的产生和细胞周期进展。使用药物库中的 KPF 结构和十二指肠球菌醛糖还原酶 (GdAldRed) 同系物的晶体结构进行配体-蛋白质对接分析。结果 KPF 引发了缺乏胞质内容物和多层结构的核周和周质空间的出现。 KPF 诱导促凋亡死亡，与 S 期部分停滞相关，且不产生 ROS。生物信息学方法预测 GdAldRed 是一个可行的 KPF 靶点 (ΔG = -7.09 kCal/mol)，与其人类同源物表现出 92% 的结构同一性和相似的耦合模式。结论 KPF 对十二指肠球菌滋养体发挥促凋亡作用，涉及部分中断 DNA 合成，而没有氧化应激或对染色质和细胞骨架结构的结构损伤。 GdAldRed 可能是其抗贾德活性的目标。