Loss of pH Control in Plasmodium falciparum Parasites Subjected to Oxidative Stress

The intraerythrocytic malaria parasite is susceptible to oxidative stress and this may play a role in the mechanism of action of some antimalarial agents. Here we show that exposure of the intraerythrocytic malaria parasite to the oxidising agent hydrogen peroxide results in a fall in the intracellular ATP level and inhibition of the parasite's V-type H(+)-ATPase, causing a loss of pH control in both the parasite cytosol and the internal digestive vacuole. In contrast to the V-type H(+)-ATPase, the parasite's digestive vacuole H(+)-pyrophosphatase is insensitive to hydrogen peroxide-induced oxidative stress. This work provides insights into the effects of oxidative stress on the intraerythrocytic parasite, as well as providing an alternative possible explanation for a previous report that light-induced oxidative stress causes selective lysis of the parasite's digestive vacuole.