Metronidazole Induces the Metazoan Death of Giardia Trophozoites with the Aid of Pyruvate

Background: Metronidazole is the most common drug for the treatment of infectious agent Giardia. The trophozoites need to fight against the oxidative stress generated by metronidazole for their survival. It has been reported that trophozoites possesses several enzymes involved in response to oxidative stress like pyruvate-ferredoxin oxidoreductase, NADH oxidase, peroxiredoxin to combat the harsh condition. These enzyme systems generally act on the amitochondriate trophozoites to attenuate the reactive oxygen species generation which causes cytotoxicity but the actual mechanism of trophozoites death due to metronidazole treatment was still not clear. Methods: The present study aims to establish the effects of pyruvate in Giardia trophozoites exposed to metronidazole treatment. Intracellular reactive oxygen species (ROS) production by Giardia trophozoite suspension was monitored in the presence and absence of pyruvate with the help of a dichlorodihydrofluoresceine diacetate (H2DCFDA) based assay. In the present study, we have investigated the effects of pyruvate on DNA damage in the trophozoites during metronidazole stress. We have also looked into the expression levels of some genes to show their relevance to metronidazole stress. Results: The exogenously addition of physiologically relevant concentration of pyruvate was shown to elevate the rate of ROS generation in Giardia suspension under metronidazole stress. Our results provide evidence that exogenously added pyruvate have induced lipid peroxidation of stressed Giardia. Several known genes are modulated due to the exposure of metronidazole in trophozoites. Conclusion: These results suggest that pyruvate is the key regulatory metabolite that helps generation of different radicals to initiate apoptotic like death in Giardia trophozoites during metronidazole exposure.