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 st ructural transitions of membranes of human erythrocyte ghosts. The CHP homolysis was shown to cause: (a) reduction of the intensity of all s tructural transitions with the disappearance of B-1- 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 degrees C. All these changes occurred until the ratio Fe2+/CHP/membranes < 0.02:0.05:1 was reached, i.e., prior to th e moment of maximal level of TBA-RS in membrane ghosts. We interpret c hanges in the character of heat absorption by oxidized membranes as pe rturbations 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 f ormed by the msdB3. These perturbations are associated mainly with the decrease in the concentration of native protein in the domains becaus e of oxidative aggregation of proteins, as evidenced by SDS electropho resis of oxidized membranes. Preincubation of membranes with tocophero l did not block the aggregation of proteins in electrophoresis and the decrease in the intensity of structural transitions, whereas it block ed completely the formation of TBA-RS, changes in the thermogram slope and the sharp rise in the heat absorption above 72 degrees C, This pr oves that these processes are determined by the thermotropic propertie s of the oxidized lipid bilayer of membranes and also provides evidenc e that the degradation of PUFA of phospholipids modifies both the stru cture of protein domains and the physical properties of the lipid bila yer of membranes. (C) 1998 Elsevier Science B.V. All rights reserved.