Ultrastructural and proapoptotic-like effects of kaempferol in Giardia duodenalis trophozoites and bioinformatics prediction of its potential protein target

Abstract

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.

Key words:
kaempferol; Giardia duodenalis; aldose reductase; reactive oxygen species; apoptosis-like