Role of membrane thermotropic properties on hypotonic hemolysis and hypertonic cryohemolysis of human red blood cells

Role of Membrane Components in Thermal Injury of Cells and Development of Thermotolerance

Exposure of cells to hyperthermia induces a transient resistance to subsequent heat treatment. The specific mechanisms responsible for hyperthermic cell killing and thermotolerance development are not well understood. It seems that heat may induce at least two different states of thermotolerance, of which one is dependent on protein synthesis. The expression of thermotolerance may include multiple cytoplasmic and membrane components. A number of studies have indicated that membranes play an important role in governing the thermal injury of cells. It seems, therefore, that heat denatured plasma membrane proteins may be a potential target for thermal stress and a trigger for the induction of thermotolerance. The localization of heat shock proteins in the plasma membrane and the suggestion of thermal resistance in enucleate erythrocytes support this suggestion. However, a direct relationship between the plasma membrane and hyperthermic killing or development of thermotolerance has not been found.

The effects of mitomycin-C and temperature on dynamical properties of human erythrocyte membrane

Alterations produced by mitomycin-C (hereafter MC) and temperature changes in human erythrocyte membrane molecular dynamics were studied, in vitro, by spin-labeling ESR technique. Erythrocyte cells were spin-labeled with 5- and 16-doxyl-stearic acids, 5- and 16-DSA, respectively, and membrane fluidity was quantified by measuring the changes in the order parameter (S), correlation time (tau), phase transition temperature and activation energies. Erythrocyte cells were first labeled with 5-DSA and 16-DSA at 37 degrees C for 10 min, then they were treated with MC of three different concentrations (2.5; 5 and 10 microM) for various time (0-300 min) at the same temperature. Experimental results indicate that treatment time and applied MC concentrations do not produce any significant reproducible changes in the spectral parameters. However, change in temperature was observed to alter significantly S and tau parameters that show biphasic character in the temperature range of 5-50 degrees C. Activation energy values of hydrocarbon chains above and below transition temperatures for untreated and MC-treated erythrocyte cells were also determined, and the effect of MC on these energy values were discussed.

Procaine incorporation into human erythrocyte membrane--a spin label study

The positioning of procaine among the components of human erythrocyte membranes was investigated by electron paramagnetic resonance (EPR) using several spin labelled molecules: fatty acids 5-, 12- and 16-doxyl-stearic acids (5DSA, 12DSA, 16DSA), procaine (SLP) and a quaternary ammonium salt (CAT4). It was proved that while procaine significantly modified EPR parameters of both CAT4 and 5DSA, it had no effect at the level of the twelfth or sixteenth carbon atom of the membrane lipid chains. Simultaneous incorporation of 5DSA and SLP and SLP in erythrocyte membranes revealed a shorter than 10 A distance between paramagnetic centers of 5DSA and SLP. It is inferred that procaine interacts with the membrane not only at lipid water interface, but also (at least) up to the fifth carbon atom of the hydrophobic tail of phopolipids. Procaine inclusion does not change the transition point (40 degrees C) at which a break appears in the temperature dependence of the erythrocyte volume, hence no strong interaction between the procaine and the cytoskeleton or the integral proteins responsible for this phase transition occurs. In the temperature domain of 25-42 degrees C, procaine seems to be freely diffusible within the membrane (Debye model can be applied).

Hypoxia-stimulated reduction of doxyl stearic acids in human red blood cells. Role of hemoglobin

Nitroxide free radicals are under active investigation for their potential use as metabolically responsive contrast agents in electron paramagnetic resonance and nuclear magnetic resonance imaging. The metabolism in human red blood cells of lipid-soluble nitroxides, doxyl stearic acids (DSA), has been investigated. We observed that under normoxia DSA were stable in red blood cells for at least 2 h, but hypoxia stimulated spin label reduction. Complete signal recovery after air or ferricyanide oxidation suggested the formation of hydroxylamine during hypoxia. DSA reduction was found to be dependent upon the position of the nitroxide ring in the fatty acid chain with the reduction rate higher when the -NO degree of the doxyl ring was closer to the fatty acid carboxylic end. The reduction kinetics of DSA with the doxyl ring nearest to the carboxylic end (5DSA) was bifasic. A rapid reduction of about half of the 5DSA was observed in the first hour and, thereafter, a slow reduction process become predominant. The slope of the slow reduction abruptly decreased below 5 microM, thus suggesting a concentration-dependent membrane-cytoplasm translocation of 5DSA. The reducing activity of the red blood cell (RBC) was completely recovered in the cell lysate. Under hypoxia, purified hemoglobin and myoglobin reduced 5DSA and a complete recovery of the signal was obtained after air reoxidation. Globin did not reduce 5DSA, while methemoglobin showed only a small reduction of 5DSA, thus suggesting that ferrous-heme was involved in the hypoxic reduction of DSA. both DSA localization and the characteristics of intracellular reductant (hemoglobin) are responsible for the high stability of DSA in the RBC.

The response of pig erythrocytes to thermal stress

The response of the pig erythrocytes exposed either to the action of a single temperature or to two different temperatures was investigated. The cells exposed to single heating indicated an increase of osmotic resistance with increasing temperature. The effect of two different temperatures depended on the time of incubation and the second temperature employed. In a step-up and step-down heating a sensitization to a second heating occurred during the first hours of incubation. We suggest that erythrocytes after prolonged incubation can adapt to thermal stress.

Thermal properties of red blood cells infected by malaria parasites

Three membrane thermotropic transitions at 8, 20, and 40 degrees C have been detected in human red blood cells (RBC) by using spin-labeled stearic acids. Red blood cells infected in vitro by Plasmodium falciparum showed the disappearance of the 8 degrees C transition and a lowering of the 40 degrees C transition to 32 degrees C. The disappearance of the 8 degrees C transition was observed in synchronized cultures of P. falciparum trophozoites as well as in mouse RBC infected in vivo by an asynchronous population of P. berghei. Furthermore, erythrocytes infected by P. falciparum showed an increase in the phosphorylation of protein 4.1. This protein was shown previously to be involved in the 8 degrees C transition, (T. Forte, T. L. Leto, M. Minetti, and V. T. Marchesi, Biochemistry 24, 7876-7880 (1985). Our results suggest that the malaria parasite invasion produces a disorganization of the protein 4.1-membrane interaction.

Critical temperatures for the interaction of free fatty acids with the erythrocyte membrane

Non-esterified long-chain fatty acids reduce the extent of hypotonic hemolysis at a certain low concentration range but cause hemolysis at higher concentrations. This biphasic behavior was investigated at different temperatures (0-37 degrees C) for lauric (12:0), myristic (14:0), palmitoleic (16:1), oleic (cis-18:1) and elaidic (trans-18:1) acids. The results are summarized as follows: (A) the fatty acids examined exhibit a high degree of specificity in their thermotropic behavior; (B) oleic acid protects against hypotonic hemolysis even at the highest concentrations, up to 15 degrees C, when it becomes hemolytic, but only in a limited concentration range; (C) elaidic acid does not affect the osmotic stability of erythrocytes up to 20 degrees C, when it starts protecting: above 30 degrees C, it becomes hemolytic at the highest concentrations; (D) palmitoleic acid is an excellent protecting agent at all temperatures in a certain concentration range, becoming hemolytic at higher concentrations; (E) lauric acid protects up to 30 degrees C and becomes hemolytic only above this temperature; (F) myristic acid exhibits an extremely unusual behavior at 30 and 37 degrees C by having alternating concentration ranges of protecting and hemolytic effects; (G) there is a common critical temperature for hemolysis at 30 degrees C for saturated and trans-unsaturated fatty acids; (H) the initial slope of Arrhenius plots of percent hemolysis at the concentration of maximum protection is negative for cis-unsaturated fatty acids and positive for saturated and trans-unsaturated fatty acids.

Involvement of erythrocyte skeletal proteins in the modulation of membrane fluidity by phenothiazines

The effects of phenothiazines (chlorpromazine, chlorpromazine sulfoxide, and trifluoperazine) and antimitotic drugs (colchicine and vinblastine) on the erythrocyte membrane have been investigated. Chlorpromazine and trifluoperazine induced a dose-dependent increase in the freedom of motion of stearic acid spin-labels bound to both intact erythrocytes and ghosts, but did not affect the freedom of motion of stearic acids bound to vesicles depleted of spectrin and actin or of ghosts resealed with anti-spectrin antibodies. Further, chlorpromazine and trifluoperazine were able to eliminate a protein 4.1 dependent membrane thermal transition detected by stearic acid spin-labels at 8.5 +/- 1.5 degrees C. Antimitotic drugs and chlorpromazine sulfoxide did not change either the freedom of motion of stearic acid spin-labels or the 8.5 degrees C membrane thermal transition. Results indicate the involvement of skeletal proteins as possible membrane target sites of biologically active phenothiazines and suggest that the control of stearic acid spin-label freedom of motion is mediated by the spectrin-actin network and the proteins that link the skeletal network to the membrane.

Cold shock hemolysis in human erythrocytes studied by spin probe method and freeze-fracture electron microscopy

When human erythrocytes are osmotically stressed or chemically treated, they hemolyze on cooling below 10 degrees C (called cold shock). We have studied the effects of osmotic stress and cooling on the state of membrane by the spin-probe method and freeze-fracture electron microscopy. At room temperature, the membrane fluidity detected by 12-doxyl stearate spin probe showed a steady decrease with osmolality in hypertonic NaCl solutions up to 900 mOsm/kg, above which it remained unchanged. In hypertonic sucrose solutions, the electron paramagnetic resonance spectra showed an additional pair of absorptions, indicating development of regions, in the membrane, further immobilized than in NaCl solutions. Mobility of a cholesterol analogue probe, androstane, did not show change by hypertonicity, but the spectral intensity dropped at 1,200 mOsm/kg, probably due to formation of loose aggregates in the cholesterol phase. On cooling the osmotically stressed cells in NaCl solution, the isotropic rotational correlation time vs. inverse temperature plot of 12-doxyl stearate probe exhibited a step-wise discontinuity at approximately 10 degrees C, suggestive of a drastic transition in the state of the membrane. At about the same temperature, the freeze-fracture pattern of osmotically stressed cells revealed the development of large wrinkles and aggregation of membrane particles, in contrast to the case of the cells in isotonicity. Significance of these findings in understanding cold shock hemolysis is discussed.