Continuous monitoring of hydroperoxide-induced peroxidation in human erythrocytes by low-level chemiluminescence

The antioxidant effect of free bilirubin on cumene-hydroperoxide treated human leukocytes

To examine the antioxidant effect of bilirubin (BR) on leukocyte, we treated leukocytes obtained from healthy subjects with an oxidant and various concentrations of BR. High concentrations of BR decreased thiobarbituric acid reactive substances (TBARS) and catalase activities, increased superoxide dismutase (SOD) activity, but had no effect on glutathione (GSH) concentration. Our results showed that under physiological conditions, BR has an antioxidant effect only in high concentrations.

The effect of bilirubin on lipid peroxidation and antioxidant enzymes in cumene hydroperoxide-treated erythrocytes

Recently, it has been suggested that bilirubin may act as a potent biological chain-breaking antioxidant. To observe the effects of free bilirubin on antioxidant reactions in cumene hydroperoxide-treated erythrocytes (15 g hemoglobin/dl), we added bilirubin at four different concentrations (0.5, 1, 5, and 10 mg/dl). We measured the thiobarbituric acid-reactive substance and reduced glutathione levels, and some antioxidant enzyme activities, namely superoxide dismutase, catalase, and glucose-6-phosphate dehydrogenase. Thiobarbituric acid-reactive substance and chemiluminescent signals decreased during the incubation. Superoxide dismutase activities also decreased but not as much as in the control group. Glucose-6-phosphate dehydrogenase activities and reduced glutathione levels increased, but catalase activities remained the same as the control group. Our results suggest that bilirubin--in the concentrations we have used--partially prevented the oxidant effects of cumene hydroperoxide.

The effect of oxidative stress on structural transitions of human erythrocyte ghost membranes

Differential scanning microcalorimetry was used to study the effect of oxidative stress induced by cumene hydroperoxide (CHP) and Fe2+ on structural transitions of membranes of human erythrocyte ghosts. The CHP homolysis was shown to cause: (a) reduction of the intensity of all structural transitions with the disappearance of B1- and D-transitions; (b) decrease in the enthalpy of oxidized membrane denaturation; (c) negative slope of thermograms; (d) anomalous growth of heat absorption by membranes above 72 degreesC. All these changes occurred until the ratio Fe2+/CHP/membranes<0.02:0.05:1 was reached, i.e., prior to the moment of maximal level of TBA-RS in membrane ghosts. We interpret changes in the character of heat absorption by oxidized membranes as perturbations in the structural organization and interactions inside the spectrin-actin-protein 4.1 domains, the spectrin-protein 4.2 domain, as well as inside the domain of spectrin-ankyrin-cdB3 and the domain formed by the msdB3. These perturbations are associated mainly with the decrease in the concentration of native protein in the domains because of oxidative aggregation of proteins, as evidenced by SDS electrophoresis of oxidized membranes. Preincubation of membranes with tocopherol did not block the aggregation of proteins in electrophoresis and the decrease in the intensity of structural transitions, whereas it blocked completely the formation of TBA-RS, changes in the thermogram slope and the sharp rise in the heat absorption above 72 degreesC. This proves that these processes are determined by the thermotropic properties of the oxidized lipid bilayer of membranes and also provides evidence that the degradation of PUFA of phospholipids modifies both the structure of protein domains and the physical properties of the lipid bilayer of membranes.

Inhibition of human erythrocyte (Na(+)-K+)ATPase by organic hydroperoxides and protection by ascorbic acid and butylated hydroxytoluene

1. The in vitro effects of cumene hydroperoxide and t-butyl hydroperoxide on intact human erythrocyte membrane (Na(+)-K+)ATPase activities have been studied. 2. (Na(+)-K+)ATPase activities on erythrocyte membranes decreased in agreement with the results of chemiluminescence experiments. 3. Our results demonstrated that the organic hydroperoxides inhibit the activity of (Na(+)-K+) ATPase enzyme and that the antioxidants used prevent this inhibition.

Increased resistance to oxidative stress in normal and glucose-6-phosphate dehydrogenase-deficient hemolysates in the presence of enzyme substrates

Erythrocytes and hemolysates from 10 normal and 10 glucose-6-phosphate dehydrogenase-deficient individuals were incubated with cumene hydroperoxide, and free radical-induced lipid peroxidation was monitored by chemiluminescence. Chemiluminescence intensities in erythrocytes of normal and deficient subjects were similar in the presence or absence of glucose-6-phosphate dehydrogenase substrates. Hemolysates of normal and deficient subjects also showed similar chemiluminescence in the absence of substrates. However, with the addition of substrates to the incubation medium, deficient hemolysates reached maximum chemiluminescence intensity within a shorter period, and maximum values were higher than in normal hemolysates. We believe this offers a new means of detection of glucose-6-phosphate dehydrogenase-deficient patients.