Erythrocyte membrane abnormalities in Duchenne muscular dystrophy monitored by saturation transfer electron paramagnetic resonance spectroscopy

Lipid fluidity and composition of the erythrocyte membrane from healthy dogs and Labrador retrievers with hereditary muscular dystrophy

Erythrocyte membranes and their liposomes were prepared from clinically normal dogs and Labrador retrievers with hereditary muscular dystrophy. The "static" and "dynamic" components of fluidity of each membrane were then assessed by steady-state fluorescence polarization techniques using limiting hindered fluorescence anisotropy and order parameter values of 1,6-diphenyl-1,3,5-hexatriene (DPH) and fluorescence anisotropy values of DL-2-(9-anthroyl)-stearic acid and DL-12-(9-anthroyl)-stearic acid, respectively. Membrane lipids were extracted and analyzed by thin-layer chromatography and gas chromatography. The results of these studies demonstrated that the lipid fluidity of erythrocyte membranes, and their liposomes, prepared from dystrophic dogs were found to possess significantly lower "static and dynamic components of fluidity" than control counterparts. Analysis of the composition of membranes from dystrophic dogs revealed a higher ratio of saturated fatty acyl chain/unsaturated chains (w/w) and lower double-bond index. Alterations in the fatty acid composition such as decrease in levels of linoleic (18:2) and arachidonic (20:4) acids and increase in palmitic (16:0) and stearic (18:0) acids were also observed in the membranes of dystrophic animals. These associated fatty acyl alterations could explain, at least in part, the differences in membrane fluidity between dystrophic and control dogs.

Halothane induced disorder of red cell membranes of subjects susceptible to malignant hyperthermia

Membrane fluidity of red blood cells drawn from malignant hyperthermic pigs and humans was studied using spin-probes and electron paramagnetic resonance technique. The order parameter and rotational correlation time were determined with 12-doxylstearate and 16-doxylstearate, respectively. It was found that halothane decreased both parameters, but that the decrease of these parameters in subjects susceptible to malignant hyperthermia was much greater than that in normal subjects. The differences were most pronounced at 3 mM halothane. A possibility of using blood for a non-invasive screening for malignant hyperthermia is discussed.

Duchenne muscular dystrophy: pathogenetic aspects and genetic prevention

Duchenne muscular dystrophy (DMD) is the most common sex linked lethal disease in man (one case in about 4000 male live births). The patients are wheelchair bound around the age of 8-10 years and usually die before the age of 20 years. The mutation rate, estimated by different methods and from different population studies, is in the order of 7 X 10(-5), which is higher than for any other X-linked genetic disease. Moreover, unlike other X linked diseases such as hemophilia A or Lesh-Nyhan's disease, there seems to be no sex difference for the mutation rates in DMD. Several observations of DMD in girls bearing X-autosomal translocations and linkage studies on two X chromosomal DNA restriction fragment length polymorphisms indicate that the DMD locus is situated on the short arm of the X chromosome, between Xp11 and Xp22. It may be of considerable length, and perhaps consisting of actively coding and non-active intervening DNA sequences. Thus unequal crossing over during meiosis in females could theoretically account for a considerable proportion of new mutations. However, there is no structurally or functionally abnormal protein known that might represent the primary gene product, nor has any pathogenetic mechanism leading to the observed biochemical and histological alterations been elucidated. Among the numerous pathogenetic concepts the hypothesis of a structural or/and functional defect of the muscular plasma membrane is still the most attractive. It would explain both the excess of muscular constituents found in serum of patients and carriers, such as creatine kinase (CK), as well as the excessive calcium uptake by dystrophic muscle fibres, which, prior to necrosis, could lead to hypercontraction, rupture of myofilaments in adjacent sarcomeres and by excessive Ca uptake to mitochondrial damage causing crucial energy loss. The results of studies on structural and functional membrane abnormalities in cells other than muscle tissue, e.g., erythrocytes, lymphocytes and cultured fibroblasts, indicate that the DMD mutation is probably demonstrable in these tissues. However, most of the findings are still difficult to reproduce or even controversial. DMD is an incurable disease; therefore most effort, in research as well as in practical medicine, is concentrated upon its prevention.(ABSTRACT TRUNCATED AT 400 WORDS)

Erythrocyte membrane glycerophospholipid organization is normal in multiple sclerosis

The phospholipid composition of erythrocyte membranes from patients with multiple sclerosis (MS) was found to be normal, in agreement with previous reports. The transbilayer asymmetry of the glycerophospholipids in MS red cells was probed using bee venom phospholipase A2 and was also found not to be significantly different from normal. Abnormal membrane glycerophospholipid organisation is therefore not involved in the increased red cell size, osmotic fragility, and electrophoretic mobility associated with MS.

Modification of cell membrane composition by dietary lipids and its implications for atherosclerosis

Dietary lipids can modify the properties of cell membranes, including membrane fluidity and membrane permeability. The saturation and isomerization of dietary fatty acids may affect the pattern of fatty acids acylated to glycerol in phospholipids. Oxidized sterols may affect membrane properties directly by their insertion in the membrane or indirectly through their effects on lipid metabolism. The flow of calcium and other nutrients into the cells appears to be a major property affected by those changes in lipid composition of membranes and may be important in the onset of atherosclerosis. The factors that alter the character of the lipids in cell membranes should receive increased study in both in vitro and in vivo systems to clarify their role in diseases processes.

A protein anomaly in erythrocyte membranes of patients with Duchenne muscular dystrophy

Raman spectroscopic comparisons of erythrocyte membranes from 20 patients with Duchenne muscular dystrophy and 8 age-matched controls indicate a prominent and consistent protein anomaly in the patient samples. This was apparent in the following: (a) CH-stretching signals from control membranes reveal a thermotropic transition at 15.6 degrees C, attributable to a protein/lipid phase that is lacking in dystrophic membranes. (b) CH-stretching signals from control membranes also show a protein transition at 39 degrees C [pH 7.4] that is shifted to 45 degrees in dystrophic membranes. (c) A reduction in pH to 5.7 shifts this transition from 39 degrees C to 7 degrees C in normal membranes and from 45 degrees C to 24 degrees C in dystrophic membranes. (d) The Amide I/Amide III regions indicate a significant proportion of beta-structured peptide in dystrophic but not normal membranes. (e) Analysis of tyrosine signals indicates greater polar exposure of tyrosine hydroxyl groups in dystrophic vs normal membranes. All of the differences between dystrophic and normal membranes are highly significant (P less than 0.001).

The distribution of inside-out and right-side-out erythrocyte membrane vesicles in Duchenne progressive muscular dystrophy

In ten cases of Duchenne muscular dystrophy, the distribution of erythrocyte ghost vesicles in dextran 110 gradient was examined. When compared with controls a greater number of inside-out vesicles was observed. It is suggested that the tendency to form abnormally oriented vesicles could result from structural abnormalities of the erythrocyte membranes.

Fluidity properties and liquid composition of erythrocyte membranes in Chediak-Higashi syndrome

We have earlier shown through electron spin resonance (ESR) studies of leukocytes that membranes of cells from both Chediak-Higashi syndrome (CHS) mice and humans have abnormally high fluidity. We have extended our studied to erythrocytes. Erythrocytes were labeled with the nitroxide-substituted analogue of stearic acid, 2-(3-carboxypropyl)-4,4-dimethyl-2-tridecyl-3-oxazolidinyloxyl, and ESR spectra were obtained. Order parameter, S, at 23 degrees C, was 0.661 and 0.653 for erythrocytes of normal and CHS mice (P less than 0.001). S was 0.684 for normal human erythrocytes and 0.675 (P less than 0.001) for CHS erythrocytes at 25 degrees C. Because S varies inversely to fluidity, these results indicate that CHS erythrocytes tend to have higher fluidity than normal. In vitro treatment of both mice and human CHS erythrocytes with 10 mM ascorbate returned their membrane fluidity to normal. We prepared erythrocyte ghosts and extracted them with CHCl3:CH3OH (2:1). Gas-liquid chromatography analysis showed a greater number of unsaturated fatty acids for CHS. The average number of double bonds detected in fatty acids for mice on a standard diet was 1.77 for normal and 2.02 for CHS (P less than 0.04); comparison of human erythrocytes from one normal control and one CHS patient showed a similar trend. Our results suggest that an increased proportion of unsaturated fatty acids may contribute to increased fluidity of CHS erythrocytes. Our observation that both leukocytes and erythrocytes of CHS have abnormal fluidity indicates that CHS pathophysiology may relate to a general membrane disorder.

Spin-label studies of the lipid and protein components of erythrocyte membranes. A comparison of electron paramagnetic resonance and saturation transfer electron paramagnetic resonance methods

We have used both a protein spin label and a lipid spin probe to study some of the slow motions of proteins and of lipids, respectively, in intact erythrocyte membranes. Three electron paramagnetic resonance (EPR) methods, conventional (V1) EPR, second harmonic out-of-phase absorption saturation transfer (ST) EPR (V'2), and first harmonic out-of-phase dispersion ST EPR (U'1) were used to compare the experimental methods and spectral sensitivities with different kinds of molecular motions in human erythrocyte membranes under different experimental conditions. The results show that the V'2 display is relatively more sensitive to the protein motion, while the U'1 display appears more sensitive to the lipid motions, and the V'2 display is substantially more convenient to obtain than the U'1 display.

Electron paramagnetic resonance and saturation transfer electron paramagnetic resonance studies on erythrocytes from goats with and without heritable myotonia

Erythrocytes from myotonic goats, an animal model of heritable myotonia, and normal goats were studied using electron paramagnetic resonance (EPR) and saturation transfer electron paramagnetic resonance (ST-EPR) spin labeling techniques. Three fatty acid spin labels with the nitroxide moiety at progressively greater distances from the carboxyl group were used to monitor different regions within the erythrocyte membrane. Since spin labels have been shown to induce hemolytic and morphologic alterations in erythrocytes, conditions for minimizing these alterations were first defined by hemolysis studies and scanning electron microscopy. Using these defined conditions for our studies we observed no significant differences in any of the EPR or ST-EPR parameters for normal and myotonic goat erythrocytes with any of the fatty acid spin labels used. Our results do not support the theory that myotonia is the result of a generalized membrane defect characterized by increased membrane fluidity as determined by fatty acid spin labels.

Biochemistry of muscle membranes in Duchenne muscular dystrophy

In Duchenne muscular dystrophy, as in other genetic diseases, there must be a biochemical abnormality. This fundamental genetic fault has not been identified, but several indirect lines of evidence suggest that the surface membranes of skeletal muscle are affected. The biochemical evidence implies abnormal egress of soluble enzymes and other proteins from muscle, abnormal permeability, and altered properties of membrane-bound enzymes. As a result of the presumed genetic abnormality, functional properties are altered, and impaired regulation of intracellular calcium content could be responsible for the hallmarks of the disease--progressive weakness and degeneration of muscle. The evidence is by no means conclusive, however, and some of it is contradictory. Technical advances must be made before isolated membranes can be characterized biochemically. Other theories are also being evaluated.

Red cell membrane protein phosphorylation in hemolytic anemias and muscular dystrophies

We review our current understanding of membrane phosphorylation in normal and abnormal erythrocytes. The major phosphoproteins in red blood cell (RBC) membranes are spectrin (band 2), bands 3, 2.1, and 4.5, and glycophorin A. At least two protein kinases can be distinguished on the basis of their stimulation by cyclic AMP and salt; they are present both in the membrane and in the cytosol. Analysis of the conflicting data on endogenous membrane-protein phosphorylation in abnormal RBCs indicates a considerable variability of phosphorylation rates which largely depends on the manner of preparation of ghosts and enzyme assay conditions. This variability reflects differences in the partitioning of protein kinases between the membrane and cytosol, the specificity and accessibility of membrane-protein substrates, and reaction kinetics. We select examples of data from several hemolytic anemias to illustrate that precautions are needed to interpret abnormalities of membrane-protein phosphorylation properly; we discuss possible new methodological approaches.

Red blood cell alterations in muscular dystrophy: the role of lipids

Biochemical, morphologic, and biophysical studies support the concept that the red blood cell (RBC) membrane is altered in both myotonic muscular dystrophy (MyD) and Duchenne muscular dystrophy (DMD). These studies have not identified a primary metabolic defect that would explain the various alterations of membrane properties. Since the lipid milieu of the membrane affects most membrane properties, it has been extensively investigated in MyD and DMD. Although some studies have suggested specific lipid abnormalities, no reproducible alterations have been reported in the major lipid constituents of the RBC membrane in these disorders. These findings suggest that major alterations of the predominant membrane lipids are not involved in these diseases. Furthermore, studies of the RBC membrane do not provide definitive statements as to the inborn error of metabolism, whether proteins or lipid constituents are primarily affected, or even whether the described alterations are intrinsic to the membrane or are secondary to some circulating factors. Nevertheless, RBCs have proved useful in demonstrating the involvement of the plasma membrane in muscle disorders and should be important in defining how such membrane perturbations affect transport mechanisms.

Physical probes of biological membranes in studies of the muscular dystrophies

This review deals with recent physical approaches to the study of biomembranes. First, current concepts of the structure and dynamic organization of biological membranes are considered. The theoretical basis and practical application of various physical probe techniques are then discussed with specific reference to their usefulness in studies of these membranes. Particular emphasis is given to electron spin resonance and fluorescence techniques and to the potential difficulties encountered in their use and interpretation. Finally, reports applying these physical probes to various aspects of the human muscular dystrophies are reviewed and our current information in this area is summarized.

Partition coefficients of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO0 in erythrocyte lipids in multiple sclerosis

Electron spin resonance (ESR) was used in a search for a possible generalized membrane defect underlying myelin instability in multiple sclerosis (MS). In contrast to most ESR studies of biological membranes, a small, nonelectrolyte spin label, TEMPO, was chosen; its partition coefficient was determined in extracted erythrocyte lipids from MS patients and normal controls. No differences were observed the advantages and limitations of TEMPO in comparison with lipid spin labels as probes for the study of biological membranes are discussed.

Erythrocyte spectrofluorometric abnormalities in Duchenne patients and carriers. A new approach to carrier detection

Duchenne muscular dystrophy (DMD) is a disorder whose pathogenesis is attributed, according to the most recent theories, to generalized membrane abnormalities, including red cell membrane. The study of erythrocyte ghosts in patients affected by DMD showed alterations in ion transport and in various enzymatic activities. Employing a spectrofluorometric method using 1-anilino-8-naphthalene sufonate (1.8-ANS) we have tried to characterize the erythrocyte ghosts of DMD patients, definite DMD carriers and normal controls, matched for age and sex. We found an increase of membrane polarity in DMD and definite DMD-carrier erythrocyte ghosts. Using this new method we were able to: - confirm by means of a different technique the previous observations of many authors on erythrocyte ghost alterations in DMD - find a new technique useful in detecting the DMD carriers. It is noteworthy that in such a way the detection rate of definite DMD carriers was higher than with the CPK test.

Evidence for an altered physical state of membrane proteins in erythrocytes in Friedreich's ataxia

Electron spin resonance, scanning electron microscopic, and SDS-polyacrylamide gel electrophoretic studies of erythrocytes in Friedreich's ataxia have been performed. No alteration in the physical state of membrane lipids, in morphology, or in the staining profile of erythrocytes in Friedreich's ataxia could be demonstrated. An altered conformation and/or organization of proteins in erythrocyte membranes in this disorder was suggested by spin labeling studies (P less than 0.025), favoring the possibility of a generalized membrane abnormality in Friedreich's ataxia. These findings are discussed in relation to other inherited neurological diseases where similar studies have been performed.

Role of intracellular calcium in promoting muscle damage: a strategy for controlling the dystrophic condition

It is suggested that various muscle diseases and examples of experimentally-induced muscle damage arise because of a high calcium level in the myoplasm. When [Ca2+]i is raised experimentally in amphibian or mammaliam muscle by treatment with A23187 or caffeine, myofilament degradation follows quickly. Such a rapid action suggests the involvement of a sequence of proteolytic activity that is stimulated by a rise in [Ca2+]i. Ca2+ might either trigger protease activity directly or indirectly, or promote the release of lysosomal enzymes. A high [Ca2+]i in dystrophic muscle is believed to be the resultant of a sequence of events that is summarized in the figure. Suggestions are presented for different ways in which the steady-state position of [Ca2+]i might ultimately be controlled for the clinical amelioration of some dystrophic conditions.

Large-scale rotational motions of proteins detected by electron paramagnetic resonance and fluorescence

Direct spectroscopic measurements of rotational motions of proteins and large protein segments are crucial to understanding the molecular dynamics of protein function. Fluorescent probes and spin labels attached to proteins have proved to be powerful tools in the study of large-scale protein motions. Fluorescence depolarization and conventional electron paramagnetic resonance (EPR) are applicable to the study of rotational motions in the nanosecond-to-microsecond time range, and have been used to demonstrate segmental flexibility in an antibody and in myosin. Very slow rotational motions, occurring in the microsecond-to-millisecond time range, are particularly important in supramolecular assemblies, where protein motions are restricted by association with other molecules. Saturation transfer spectroscopy (ST-EPR), a recently developed electron paramagnetic resonance (EPR) technique that permits the detection of rotational correlation times as long as 1 ms, has been used to detect large-scale rotational motions of spin-labeled proteins in muscle filaments and in membranes, providing valuable insights into energy transduction mechanisms in these assemblies.