Action of Drugs on the Erythrocyte Membrane

Effective dielectric properties of biological cells: generalization of the spectral density function approach

We suggest an extension of the spectral density function approach to describe the complex dielectric response of suspensions of arbitrarily shaped particles having a thin shell, in particular, biological cells. The approach is shown to give analytical results in some simple but practically important cases. In the general case, for the 3-phase systems it reduces to determination of the spectral density function for the suspension of a certain kind. Prospects and limitations of the approach, as well as practical examples, are also considered.

Hemolysis and antihemolysis induced by amino acid-based surfactants

Surfactants have the special ability to interact with the lipid bilayer of cell membranes. The red blood cell is one of the most used cellular membrane models to study the mechanisms underlying surfactant-induced osmotic cell resistance. To increase our knowledge regarding the mechanisms of surfactant membrane interaction, we studied the action of five lysine-derivative anionic and three arginine-derivative cationic amino acid-based surfactants on hypotonic hemolysis. Results showed two different antihemolytic behaviors among amino acid-based surfactants, both related to the maximal protective concentration. How the physico-chemical properties and structure of these compounds determine the protection against hypotonic hemolysis is discussed in detail. We found a good correlation between the CMC and the concentrations resulting in maximum protection against hypotonic hemolysis for the cationic surfactants, but no correlation for the anionic surfactants. In the case of lysine derivative surfactants, which only differ in their counterions, the counterion is implicated in the differences in the antihemolytic potency and the hemolytic activities of this.

Changes in erythrocyte morphology induced by imipramine and chlorpromazine

Chlorpromazine (CPZ), a phenothiazine derivative, is a potent antipsychotic agent and imipramine (IP) is a widely used tricyclic antidepressant. The interaction between these molecules and erythrocyte membranes is of particular interest considering the role of these cells in the transport and release of these drugs at the central nervous system. In the present paper, we intend to study the effects of IP on erythrocyte membranes and to compare these effects with those of CPZ. Erythrocytes from adult Sprague-Dawley rats were incubated separately with different concentrations of IP or CPZ for lh at room temperature, fixed and stained by Giemsa. Changes in erythrocyte morphology were quantified by an image analysis system. The interaction of both drugs, CPZ and IP, with the erythrocyte membrane causes similar changes in cell shape. Increasing concentrations of both drugs induces the formation of stomatocytes, spherostomatocytes and spherocytes, because of an irreversible loss of area and volume, probably due to endovesiculation. Our results also show that the CPZ is more potent than IP.

Erythrocyte membrane modifying agents and the inhibition of Plasmodium falciparum growth: structure-activity relationships for betulinic acid analogues

The natural triterpene betulinic acid and its analogues (betulinic aldehyde, lupeol, betulin, methyl betulinate and betulinic acid amide) caused concentration-dependent alterations of erythrocyte membrane shape towards stomatocytes or echinocytes according to their hydrogen bonding properties. Thus, the analogues with a functional group having a capacity of donating a hydrogen bond (COOH, CH(2)OH, CONH(2)) caused formation of echinocytes, whereas those lacking this ability (CH(3), CHO, COOCH(3)) induced formation of stomatocytes. Both kinds of erythrocyte alterations were prohibitive with respect to Plasmodium falciparum invasion and growth; all compounds were inhibitory with IC(50) values in the range 7-28 microM, and the growth inhibition correlated well with the extent of membrane curvature changes assessed by transmission electron microscopy. Erythrocytes pre-loaded with betulinic acid or its analogues and extensively washed in order to remove excess of the chemicals could not serve as hosts for P. falciparum parasites. Betulinic acid and congeners can be responsible for in vitro antiplasmodial activity of plant extracts, as shown for Zataria multiflora Boiss. (Labiatae) and Zizyphus vulgaris Lam. (Rhamnaceae). The activity is evidently due to the incorporation of the compounds into the lipid bilayer of erythrocytes, and may be caused by modifications of cholesterol-rich membrane rafts, recently shown to play an important role in parasite vacuolization. The established link between erythrocyte membrane modifications and antiplasmodial activity may provide a novel target for potential antimalarial drugs.

Influence of band 3 protein absence and skeletal structures on amphiphile- and Ca(2+)-induced shape alterations in erythrocytes: a study with lamprey (Lampetra fluviatilis), trout (Onchorhynchus mykiss) and human erythrocytes

Amphiphiles which induce either spiculated (echinocytic) or invaginated (stomatocytic) shapes in human erythrocytes, and ionophore A23187 plus Ca(2+), were studied for their capacity to induce shape alterations, vesiculation and hemolysis in the morphologically and structurally different lamprey and trout erythrocytes. Both qualitative and quantitative differences were found. Amphiphiles induced no gross morphological changes in the non-axisymmetric stomatocyte-like lamprey erythrocyte or in the flat ellipsoidal trout erythrocyte, besides a rounding up at higher amphiphile concentrations. No shapes with large broad spicula were seen. Nevertheless, some of the 'echinocytogenic' amphiphiles induced plasma membrane protrusions in lamprey and trout erythrocytes, from where exovesicles were shed. In trout erythrocytes, occurrence of corrugations at the cell rim preceded protrusion formation. Other 'echinocytogenic' amphiphiles induced invaginations in lamprey erythrocytes. The 'stomatocytogenic' amphiphiles induced invaginations in both lamprey and trout erythrocytes. Surprisingly, in trout erythrocytes, some protrusions also occurred. Some of the amphiphiles hemolyzed lamprey, trout and human erythrocytes at a significantly different concentration/membrane area. Ionophore A23187 plus Ca(2+) induced membrane protrusions and sphering in human and trout erythrocytes; however, the lamprey erythrocyte remained unperturbed. The shape alterations in lamprey erythrocytes, we suggest, are characterized by weak membrane skeleton-lipid bilayer interactions, due to band 3 protein and ankyrin deficiency. In trout erythrocyte, the marginal band of microtubules appears to strongly influence cell shape. Furthermore, the presence of intermediate filaments and nuclei, additionally affecting the cell membrane shear elasticity, apparently influences cell shape changes in lamprey and trout erythrocytes. The different types of shape alterations induced by certain amphiphiles in the cell types indicates that their plasma membrane phospholipid composition differs.

Non-selective voltage-activated cation channel in the human red blood cell membrane

Using the patch-clamp technique, a non-selective voltage-activated Na+ and K+ channel in the human red blood cell membrane was found. The channel operates only at positive membrane potentials from about +30 mV (inside positive) onwards. For sodium and potassium ions, similar conductances of about 21 pS were determined. Together with the recently described K+(Na+)/H+ exchanger, this channel is responsible for the increase of residual K+ and Na+ fluxes across the human red blood cell membrane when the cells are suspended in low ionic strength medium.

Band 3, the anion exchanger of the erythrocyte membrane, is also a flippase

The transbilayer reorientation (flip-flop) of the long-chain amphiphilic anion DENSA (5-(N-decyl)aminonaphthalene-2-sulfonic acid) in the erythrocyte membrane was studied by fluorescence spectroscopy. DENSA intercalates into the membrane at a high membrane/water partition coefficient (3.2.10(5)) and rapidly reorients from the outer to the inner layer in a first order process (k = 0.11 min-1, 37 degrees C, pH 7.4) leading to a steady-state distribution inner:outer layer of about 30:70. The activation energy of the fully reversible and symmetric flip process is about 110 kJ/mol. DIDS and various other established covalent and non-covalent inhibitors of anion transport via the erythrocyte anion exchanger, band 3 (AE 1), suppress the flip to a minimum of about 30-35% of the control. The flip is also inhibited by Cl- with a half maximal inhibitory concentration equal to that required for the inhibition of the exchange flux of ordinary anions via band 3. These findings indicate the involvement of a band 3 mediated (DIDS-sensitive) component of the flip and a DIDS-insensitive one, possibly involving, at least to some extent, simple transbilayer 'diffusion'. This latter component is stimulated by diamide, an SH oxidant known to increase the permeability of the membrane lipid domain of the erythrocyte. Alcohols (butanol, hexanol) accelerate both flip components. Papain treatment, known to inhibit 'ordinary' anion exchange, accelerates both flip and flop. The results suggest that band 3 protein, besides being a conventional transporter of anions, can act as a flippase translocating anionic, membrane-intercalated amphiphiles approaching the transporter from the lipid domain. The flippase mode of operation of band 3 must, however, differ in its mechanism from the conventional exchange mode.

Involvement of cytoskeletal proteins in the barrier function of the human erythrocyte membrane. III. Permeability of spectrin-depleted inside-out membrane vesicles to hydrophilic nonelectrolytes. Formation of leaks by chemical or enzymatic modification of membrane proteins

Spectrin-depleted inside-out vesicles (IOV's) prepared from human erythrocyte membranes were characterized in terms of size, ground permeability to hydrophilic nonelectrolytes and their sensitivity to modification by SH reagents, DIDS and trypsin. IOV's proved to have the same permeability of their lipid domain to erythritol as native erythrocytes, in contrast to resealed ghosts (Klonk, S. and Deuticke, B. (1992) Biochim. Biophys. Acta 1106, 126-136 (Part I in this series)), which have a residual leak. On the other hand, IOV's have a slightly elevated permeability for mannitol and sucrose, nonelectrolytes which are almost (mannitol) or fully (sucrose) impermeant in the native membrane. These increased fluxes, which have a high activation energy and can be stimulated by phloretin, are, however, also much smaller than the corresponding leak fluxes observed in resealed ghosts. In view of these differences, formation of IOV's can be concluded to go along with partial annealing of barrier defects persisting in the erythrocyte membrane after preparation of resealed ghosts. Oxidation of SH groups of the IOV membrane by diamide produces an enhancement of permeability for hydrophilic nonelectrolytes which is much less pronounced than that induced by a similar treatment of erythrocytes or ghosts (Klonk, S. and Deuticke, B. (1992) Biochim. Biophys. Acta 1106, 126-136 (Part I in this series)). Moreover, proteolytic treatment of the vesicle membrane, although leading to a marked digestion of integral membrane proteins, only induces a minor, saturating increase of permeability, much lower than that in trypsinized resealed ghosts (Klonk, S. and Deuticke, B. (1992) Biochim. Biophys. Acta 1106, 137-142 (Part II of this series)). Since absence of the cytoskeletal proteins, spectrin and actin, is the major difference between IOV's and resealed ghosts, these results may be taken as further evidence for a dependence of the barrier properties of the erythrocyte membrane bilayer domain on its interaction with cytoskeletal elements. In contrast, these barrier properties seem to be rather insensitive to perturbations of integral proteins.

Influence of phloretin and alcohols on barrier defects in the erythrocyte membrane caused by oxidative injury and electroporation

Oxidative damage by diamide, periodate and oxygen-derived reactive species, but also exposure to electroporation induce in the erythrocyte membrane dynamic, presumably fluctuating, defects having the properties of aqueous holes with definable radii and selectivities. These leaks, which can be quantified by measuring tracer fluxes or rates of colloid-osmotic lysis, are here shown to be inhibited by phloretin and a small number of related phenol compounds (phenolphthalein, hydroxyacetophenones, nitrophenol), while a host of other 'membrane-active' agents is not effective in this respect. I50 values range from about 200 microM for phloretin and phenolphthalein to about 10 mM for 4-nitrophenol. Inhibition by phloretin is reversible, not competitive and not related in its extent to the extent of leakiness. In contrast, the enhancement of transbilayer mobility of amphiphilic lipid probes, which invariably goes along with leak formation of the type described, is not affected by phloretin. Aliphatic alcohols (hexanol, butanol) have an amplifying effect on leaks induced by oxidative damage but do not affect leaks induced by electroporation. The alcohol-amplified leaks maintain the properties of aqueous holes as indicated by a low activation energy of leak fluxes. Since both, inhibition and stimulation of leak fluxes do not go along with appreciable changes of the apparent radii of the aqueous holes, changes in the dynamics (opening and closing) of the defects are proposed to underly the effects of phloretin and alkanols. The membrane lipid domain is likely to be the site of the leaks and of their modulation.