Involvement of pyruvate on oxidative stress management in the microaerophilic protozoan parasite Giardia lamblia

Background: Giardia lamblia, a microaerophilic protozoon produces energy by fermentative metabolism. It is devoid of conventional mechanisms of oxidative stress management, including superoxide dismutase, catalase, peroxidase, and glutathione cycling, which are present in most eukaryotes. To protect and establish its pathogenesis within human gut it has to develop antioxidant defense strategies to grapple with elevated oxygen tensions, which are harmful for its survival. Methods: Intracellular reactive oxygen species (ROS) generation by Giardia suspension was monitored with the help of a dichlorodihydrofluoresceine diacetate based assay. Linoleic acid micelles were employed to investigate the lipid radical scavenging activity of pyruvate. In this study, we examined the effects of pyruvate addition during oxidative stress on DNA damage in Giardia. The pyruvate concentrations at different time points were measured during oxidative stress condition in Giardia. Results: Our results provide evidence that exogenously added pyruvate was also able to inhibit lipid peroxidation of stress Giardia and effects of pyruvate were concentration dependent but no inhibition of lipid peroxidation by pyruvate was observed in the micelle model. We have demonstrated trophozoites have the ability to regulate intracellular level of pyruvate during oxidative stress. Pyruvate recovers Giardia trophozoites from oxidative stress by decreasing the number of DNA breaks and might favor DNA repair. Conclusion: Our results clearly denote that pyruvate acts as a protector and a key regulatory factor of stressed Giardia lamblia.