The effects of dihydroartemisinin on Giardia lamblia morphology and cell cycle in vitro.

Several anti-Giardia drugs, such as metronidazole, tinidazole, mebendazole, albendazole and furazolidone, are usually effective but have severe side effects and potential toxicity. An urgent need exists for more effective and less toxic agents that can act against this protozoan. For this purpose, the effects of dihydroartemisinin (DHA) on Giardia lamblia were investigated in vitro. Axenically grown G. lamblia trophozoites were treated with DHA (LD(50) = 200 microg/mL) at different time intervals. The morphological and ultrastructural changes of the treated trophozoites were observed by both light and transmission electron microscopy (TEM). Changes in the cell cycle of the treated cells were observed by flow cytometry. By light microscopy, we observed that DHA-treated trophozoites were detached from the wall of the culture tube and shown bradypraxia and bubbles in the dorsal and ventral surfaces. Ultrastructural observations by TEM revealed that DHA promoted modifications of the cell shape, pronounced dorsal vesiculation, plasma membrane blebbing, disaggregation of ribosomes, depletion of cytoplasmic matrix and heavy deposition of electron-dense precipitates on the cytoplasm and nucleus. The main changes observed in the treated group included the following: (1) trophozoites were rounder in shape and the endoplasmic reticulum was dilated, (2) enlarged trophozoites contained lamella structures and deformed nuclei, (3) trophozoites displayed dissolved cytoplasm with large vacuole spaces or decreased cytoplasmic volume, (4) adhesive disc bubbles or the lamella structures of cytoplasm were clearly observed, and (5) cell division was arrested. Using microscopy and cytometry techniques, we demonstrate that changes in G. lamblia morphology and cell cycle state were induced by DHA.