Induction of Oxidant Stress by Iron Available in Advanced Forms of Plasmodium Falciparum

Abstract

Oxidative stress has been incriminated as a deleterious factor in the development of malaria parasites. Various chemical reductones which can undergo cyclic oxidation and reduction, such as ascorbate have been shown to cause oxidative stress to red blood cells. This, naturally-occurring and redox-active compound, can induce the formation of active oxygen derived species, such as superoxide radicals (.O⁻₂), hydrogen peroxide (H₂O₂) and hydroxyl radical (OH.), The formation of the hydroxyl radical, the ultimate deleterious species, is mediated by the redox-active and available transition metals iron and copper in the Haber-Weiss reaction.

During the development of the parasite, hemoglobin is progressively digested and a concurrent release of high levels of iron-containing breakdown products takes place within the red blood cell. Indications for the progressive increase in redox-active iron during the growth of P. falciparum have been recently found in our lab: a) adventitious ascorbatc proved highly detrimental to the parasite when added to the mature forms. In contrast, if the parasitized erythrocytes were in the early phase following invasion, and only low levels of iron-containing structures had been liberated. then the observed effect was a small promotion of parasite development. b) erythrocytes containing mature parasites were more potent than erythrocytes containing ring forms as a source for redox-active iron in the acerbate-driven metal-mediated degradation of DNA. The addition of extracts from parasitized erythrocytes and ascorbate to DNA causcd a dose and time dependent DNA degradation. Non-infected erythrocytes had no effect. These findings could also propose that the parasite-dependent accumulation of redox-active forms of iron within the erythrocytes serve as a biological clock triggering the rupture of the red blood cell membrane at the right moment, when the parasite reaches its maturity.

Key Words:

• Plasmodium falciparum
• malaria
• iron
• oxidant stress
• free radicals.