Presence of pro-oxidants in plasma of patients suffering from falciparum malaria

Abstract

Haemolysis is the major cause of anaemia in acute Plasmodium falciparum malaria, destroying both parasitized and non-parasitized erythrocytes. Oxidative stress on erythrocytes is considered an important mechanism of haemolysis. Since non-parasitized erythrocytes are also destroyed, the extracellular environment of the erythrocyte may be a contributor to the oxidative stress. To examine the influence of extracellular factors on oxidative stress and haemolysis, baseline values of erythrocyte thio-barbituric acid-reactive substance (ETBAR) and haemolytic indices such as plasma haemoglobin and lactate dehydrogenase (LDH) were estimated in 19 children in Orissa (India) with acute P. falciparum malaria (haemoglobin level ⩽70 g/L). The indices were measured after incubating cross-matched isogroup adult control erythrocytes with patient's plasma, and patient's erythrocytes with adult control plasma both in presence of and in absence of t-butyl hydroperoxide (t-BHP). The procedure was repeated in the blood of 19 age- and sex-matched non-malarial children. Baseline plasma LDH, haemoglobin and ETBAR concentrations were significantly greater in malaria patients than non-malarial children ( P < 0·001 for all). Post-incubation values of ETBAR and plasma haemoglobin were significantly higher ( P < 0·05) when adult control erythrocytes were incubated with patient plasma, and plasma haemoglobin was significantly higher ( P < 0·05) in incubates of patient erythrocytes with adult control plasma, than their respective pre-incubation values when incubated in absence of t-BHP. These differences were not noticed in the incubates of non-malarial children with healthy adult control samples. When incubated in presence of t-BHP all the post-incubation values in the patients were significantly higher than their respective pre-incubation values and post-incubation values without t-BHP ( P < 0·001). In non-malarial control samples, only ETBAR concentration was higher than their respective pre-incubation and post-incubation values without t-BHP ( P < 0·01). All the values for post-incubation samples with t-BHP were significantly higher in patients than controls ( P < 0·001). In post-incubation samples of control erythrocytes and patient plasma in presence of t-BHP, ETBAR correlated inversely with pre-incubation haptoglobin values ( P < 0·001). Thus, plasma of acute malaria patients appears to contain pro-oxidants, which may contribute to extracellular oxidative stress on both parasitized and non-parasitized erythrocytes.