Erythrocyte Membrane Fluidity Research Articles

Effect of Hydroxymethylglutaryl-CoA Reductase Inhibitors on the Functional Properties of Erythrocyte Membranes

We studied 56 patients affected by primary hypercholesterolemia treated with placebo for 1 month and with simvastatin (20 mg/day) or pravastatin (20 mg/day) for 6 months during a double-blind clinical trial. At 1-month intervals we determined the following parameters in the serum: total and HDL cholesterol, triglycerides, and apolipoprotein A-1 and B. At the same time intervals we also determined the cholesterol and phospholipid concentration, the Na +/K + ATPase activity, and the fluidity of erythrocyte membranes. Our results demonstrated the following modifications in the erythrocyte membranes during simvastatin and pravastatin treatments: (1) an initial increase in cholesterol concentration and in cholesterol/phospholipid molar ratio, with a significant decrease only after 4 months; (2) a similar behavior of membrane fluidity, with an initial decrease and an elevation after 4 months; (3) an increase in the Na +/K + ATPase activity only after 4 months. We hypothesize that simvastatin and pravastatin not only inhibit the hepatic synthesis of cholesterol, but also modify the cholesterol exchange between plasma and the erythrocyte membrane.

Effect of Lowering Serum Cholesterol on Erythrocyte Membrane Fluidity

Effect of Lowering Serum Cholesterol on Erythrocyte Membrane Fluidity

A Fluorescence Polarization Assay of Erythrocyte Membrane Fluidity on the Abbott TDx Analyzer

Four fluorescein dye derivatives (attached to cholic acid, deoxycholic acid, lithocholic acid, and 5-cholenic acid-3β-ol) were studied as a means of detecting alterations in erythrocyte membrane fluidity. In addition, membrane fluidity using these novel dye derivatives was correlated to nonenzymatic glycation of erythrocyte membrane ghosts. These dyes have excitation and emission wavelengths suitable for analysis on an Abbott TDx analyzer. Both the lithocholic acid and the 5-cholenic acid-3β-ol fluorescein derivatives were capable of detecting erythrocyte membrane fluidity with an increase in polarization of approximately 34% over the range of glycation studied, and the fluidity was strongly correlated with the degree of glycation. The cholic acid and deoxycholic acid fluorescein derivatives were unable to enter the erythrocyte membrane since no alteration in fluorescence intensity or polarization was observed upon incubation with the membrane preparations. The results obtained indicate that the lithocholic acid and 5-cholenic acid-3β-oI fluorescein derivatives are potential new reagents for the development of routine assays for membrane fluidity on the Abbott TDx analyzer.

Action of dietary polyunsaturated fatty acids on the fluidity of erythrocyte and platelet membrane in NIDDM.

Action of dietary polyunsaturated fatty acids on the fluidity of erythrocyte and platelet membrane in NIDDM.

Effects of brazilin on lipid and phosphatidyl fatty acid composition of erythrocyte membrane in streptozotocin-induced diabetic rats

In diabetes, the abnormal increase of the membrane cholesterol/phospholipid ratio (C/PL) is considered to be the main reason for the decreased membrane fluidity, which then results in impaired erythrocyte deformability and subsequent microcirculatory disturbances. In this study, we examined the effects of brazilin on lipid and phosphatidyl fatty acid composition of erythrocyte membranes in streptozotocin induced diabetic rats. Treatment of brazilin (10 mg/kg or 100 mg/kg for 2 weeks, i.p) altered phospholipid and cholesterol contents in diabetic erythrocyte membranes. The C/PL ratio of brazilin treated groups decreased compared with that of diabetic control group while no change was observed in normal erythrocytes. In streptozotocin induced diabetic rats, alterations in phosphatidyl fatty acid composition of erythrocyte membranes were observed and brazilin could reverse these alterations. Arachidonic acid level retumed to a normal level while linoleic acid level remained unchanged by the treatment of brazilin. The results suggest that brazilin might increase erythrocyte membrane fluidity which plays a key role in regulating erythrocyte deformability, thereby it could exert positive effects on microcirculatory disturbances.

Changes of plasma lipids and erythrocyte membrane fluidity in psoriatic children.

Psoriasis has been associated with an abnormal plasma lipid metabolism, and changes of erythrocyte membrane lipid composition and fluidity have been shown in adult patients. To investigate whether the alterations of plasma lipids appear also in pediatric patients, we have studied plasma lipids and lipoproteins in 15 prepubertal children affected by mild-to-moderate psoriasis with respect to healthy controls. The patients showed higher levels of plasma total cholesterol (4.44 +/- 0.78 versus 4.03 +/- 0.58 mmol/L), a significant increase of cholesterol associated with HDL (1.39 +/- 0.26 versus 1.13 +/- 0.28 mmol/L, p = 0.02), and a significant decrease of the ratio LDL cholesterol to HDL cholesterol (1.73 +/- 0.6 versus 2.46 +/- 0.8, p = 0.02). By using fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene, we have shown a significant increase in fluidity in erythrocyte membrane of psoriatic children that was associated with a slight, but not significant, decrease in the cholesterol to protein ratio (422 +/- 127 versus 503 +/- 117 nmol/mg). No significant changes of phospholipid fatty acid composition have been shown, in disagreement with previous studies in adult patients. Our results support the relation between childhood psoriasis and plasma lipid changes, which are likely related to the slight compositional changes in erythrocytes. However, the observed abnormalities are expressed differently in children than in adults.

Changes induced by chlorpromazine and heat in erythrocyte membranes

1. 1. Chlorpromazine which is generally known as a tranquilizer, can be used to elucidate the role of membrane modification on the erythrocyte thermal properties. 2. 2. In this paper we examined the lipid fluidity of erythrocyte membranes and membrane protein conformational changes in cells pretreated with chlorpromazine and subsequently subjected to heating. 3. 3. The presence of drug before heating modified the response of erythrocytes to heat. 4. 4. These data show that low concentration of chlorpromazine protected pig erythrocytes from thermal haemolysis. Moreover, chlorpromazine at this concentration caused a modification of membrnes leading to induction of alterations in protein conformation.

Increased human erythrocyte sodium-lithium countertransport in hyperlipidaemic patients may indicate increased membrane lipid fluidity.

Erythrocyte sodium-lithium countertransport (SLC) activity, membrane fluidity, plasma triglyceride and cholesterol were measured in hyperlipidaemic patients and normal subjects. Fluidity was assessed by the fluorescence anisotropy (inversely related to fluidity) of the probes 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1,4-trimethylammonium-3,5-hexatriene (TMA-DPH). In a second group of patients the maximum velocity (Vmax) and external sodium affinity constant (km) of SLC was also measured. In the first group of patients, SLC activity was increased compared with the controls (0.279 +/- 0.019 vs. 0.213 +/- 0.013, P = 0.006) as was membrane fluidity in the deep hydrophobic regions (DPH anisotropy 0.211 +/- 0.0007 vs. 0.215 +/- 0.0011, P = 0.007). There was a strong correlation between SLC and DPH anisotropy (Rs = -0.72, P = < 0.001) which was due to the correlation between Vmax and DPH anisotropy (Rs = -0.90, P = < 0.001). Increases in Vmax of SLC in hyperlipidaemic patients may be due to differences in lipid organisation in the deep hydrophobic regions of the membrane which may affect the turnover rate of the transporter.

Impaired erythrocyte deformability and membrane fluidity in alcoholic liver disease: participation in disturbed hepatic microcirculation.

The erythrocyte deformability, membrane fluidity, mean corpuscular volume (MCV), and lipid compositions of erythrocyte membrane were investigated to evaluate the possible role in disturbed hepatic microcirculation in alcoholic liver disease. Erythrocyte deformability was assessed in 37 alcoholic patients and 20 normal subjects. Erythrocyte deformability determined by the filtration method was found to be decreased significantly in alcoholic patients. Erythrocyte membrane fluidity in alcoholic liver disease analysed by fluorescence recovery time after photobleaching was decreased significantly. The decrease of erythrocyte membrane fluidity in alcoholic patients correlated significantly with a decrease of erythrocyte deformability (r = -0.65, P < 0.02). The increased MCV in alcoholic liver disease also correlated with a decrease of erythrocyte deformability significantly (r = 0.652, P < 0.02). The lipid compositions of erythrocyte membrane were abnormal in alcoholic liver disease; the phosphatidylcholine:sphingomyelin ratio was increased (P < 0.001) and unsaturated:saturated fatty acid ratio was decreased (P < 0.01). We conclude that, in alcoholic liver disease, the decreased erythrocyte deformability was closely associated with changes of membrane fluidity and MCV. It was also associated with abnormalities of membrane lipid compositions. It is speculated that these abnormalities of erythrocytes result in further reduction of sinusoidal blood flow in alcoholic liver disease, and consequently disturb metabolic functions of the liver.

Red cell Ca2+ content (total and cytosolic) and erythrocyte membrane fluidity in several clinical conditions

Red cell Ca2+ content (total and cytosolic) and erythrocyte membrane fluidity in several clinical conditions

Thermal properties and fluidity of human erythrocyte membranes in diabetes mellitus.

Exposure of human erythrocytes to elevated temperatures induces a decrease in stability of the cell membrane. Thermally induced haemolysis of erythrocytes from patients with type 1 diabetes and from healthy control individuals was measured as a function of duration of exposure to heat between 48.0 and 54.0 degrees C. Results indicate that the thermosensitivity of erythrocytes from patients with type 1 diabetes is lower than for control individuals. Activation energies for lysis were similar for both control and 'diabetic' erythrocytes, being 298.3 and 287.7 kJ/mol, respectively. The steady-state fluorescence anisotropy measurement of TMA-DPH for each step of haemolysis was employed as a parameter characterizing membrane fluidity. We found that 'diabetic' erythrocyte membranes had significantly decreased fluidity. The relationship between fluidity and rate of haemolysis indicates that the rate-limiting step in the haemolysis reaction involves the rupturing of the membrane bilayer.

Effect of nimodipine on rheologic parameters in patients with chronic cerebrovascular disease

Sixteen patients with chronic cerebrovascular disease were treated with a monotherapeutic regimen of nimodipine 30 mg orally three times a day. At baseline and after 45 and 90 days of therapy, the patients' whole blood filterability, erythrocyte membrane fluidity, red blood cell membrane protein lateral mobility, and red blood cell Ca 2+ content (total and cytosolic) were evaluated. After 45 days, an increase in whole blood filterability and a decrease in the cytosolic red cell Ca 2+ content was seen. At the end of treatment, whole blood filterability, erythrocyte membrane fluidity, and red cell membrane protein lateral mobility had increased, compared with baseline values, while the total and cytosolic red cell Ca 2+ content had significantly decreased. These findings demonstrate that nimodipine not only influences red blood cell calcium but also acts on the macro- and microrheologic patterns.

Evaluation of blood esterases in Alzheimer's disease

The aim of this work was to evaluate a possible correlation between erythrocyte acetylcholinesterase activity (AChE) and membrane fluidity expressed by fluorescence polarization of--1,6--diphenyl 1,3,5--hexatriene (DPH). Blood samples of 34 Alzheimer's patients (18F and 16M) were obtained and haemoglobin concentration, haematocrit, plasma (butyrylcholinesterase, BuChE) and erythrocyte (AChE) esterase activities and fluorescence polarization after introduction of DPH in erythrocyte membrane have been determined. Results were compared with values obtained from blood samples of 34 apparently healthy volunteers with the same age variation (53-82 years). There was no correlation between AChE activity and fluorescence polarization in the control group nor in the patients' group. There was a significant negative correlation (r = -0.82; p < 0.001) between mean corpuscular hemoglobin concentration (MCHG) and erythrocyte acetylcholinesterase activity in Alzheimer's patients. This correlation suggests that any variation of internal globular viscosity (or MCHG) may indirectly affect AChE enzymatic activity and consequently contribute to the loss of interrelation between AChE activity and membrane lipid fluidity, verified in the present work. A biological marker for Alzheimer's disease diagnosis remains to be discovered.

Effect of mesoglycan on macrorheologic and microrheologic parameters

Whole blood filtration, mean erythrocyte aggregation, and erythrocyte membrane fluidity were examined in 10 patients with vascular atherosclerotic disease (VAD) and in 15 VAD patients with noninsulin-dependent diabetes mellitus (NIDDM) treated with mesoglycan (100 mg orally twice a day) for 30 days. The red cell membrane transverse fluidity gradient was evaluated in the VAD subjects, and the red cell membrane protein lateral mobility was measured in the VAD subjects with NIDDM. In both groups, mesoglycan treatment was responsible for an increase in erythrocyte membrane fluidity. This finding, which reflects an improvement in the dynamic properties of red cell membrane, assumes particular significance because this microrheologic parameter is always altered in VAD subjects, with or without NIDDM.

Membrane fluidity of platelets and erythrocytes in patients with Alzheimer's disease and the effect of small amounts of aluminium on platelet and erythrocyte membranes.

The membrane fluidity of platelet and erythrocyte membranes in 10 Alzheimer's disease patients and 9 age-matched controls was studied. The platelet membranes of patients with Alzheimer's disease were found to be significantly more fluid than those of controls (p less than 0.02). However, erythrocyte membranes of Alzheimer patients were less fluid (more viscous) than those of controls (p less than 0.05). On further investigation of platelet and erythrocyte membranes obtained from healthy volunteers, the fluidity was found to change with increasing aluminium concentrations. When aluminium ammonium sulphate (0.01-10 microM) was added to membrane suspensions, the fluidity of platelet membranes was increased, whereas the fluidity of erythrocyte membranes was decreased (i.e. the microviscosity was increased).

Changes in lipid composition of erythrocyte membranes with administration of S-adenosyl-L-methionine in chronic liver disease.

This study was undertaken to determine whether S-adenosyl-L-methionine (SAMe) changes the lipid composition and fluidity of erythrocyte membranes in chronic liver disease. SAMe was administered intravenously at a daily dose of 600 mg for 2 weeks to 10 patients; 6 patients with cirrhosis and four with primary biliary cirrhosis. The elevated free cholesterol to phospholipid molar (C/PL) ratio of the erythrocyte membranes of the patients (0.857 +/- 0.018) significantly decreased after the administration of SAMe (1 week, 0.823 +/- 0.021; 2 weeks, 0.823 +/- 0.013). In all of the four patients whose erythrocyte membrane fluidity was measured, fluidity improved with the administration of SAMe and correlated with the C/PL ratio of the membranes. These results suggest that SAMe decreases the C/PL ratio of erythrocyte membranes and thus improves membrane fluidity in chronic liver disease.

Effects of omega-3 fatty acid and vitamin E supplementation on erythrocyte membrane fluidity, tocopherols, insulin binding, and lipid composition in adult men

Dietary supplementation with an omega-3 fatty acid preparation (fish oil) together with pharmacologic doses of vitamin E increased both insulin binding and membrane fluidity in erythrocytes from human adult males. Supplementation with fish oil alone induced significant increases in the α- and γ-tocopherol contents of the red blood cell membranes. Forty healthy men were given controlled diets and supplements, which together provided 40% of energy from fat (polyunsaturated:monosaturated:saturated ratio of 0.8:1:1), 360 mg cholesterol/day, and a minimum of 22 mg α-tocopherol (αT)/day for three successive experimental periods of 10, 10, and 8 weeks, during which they were given capsules containing 15 g of a placebo oil/day, 15 g fish oil concentrate (FOC)/day, and 15 g fish oil + 200 IU αT (FOC + αT)/day, respectively. Erythrocyte ghost insulin binding (IB) and 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence-determined fluidity were significantly increased following the FOC + αT period, however FOC alone had no effect. At the end of each experimental period, IB values, as percentage bound/100 μg ghost protein at 4° C, were 0.96, 0.91, and 1.35, and DPH steady state fluorescence anisotropies were 0.311, 0.303, and 0.296, at 4° C, respectively. Small but statistically significant decreases in fluorescence lifetimes further indicated increased fluidity. FOC supplementation resulted in significantly lower membrane cholesterol:phospholipid ratios and increased membrane tocopherols despite daily vitamin E consumption of only 22 mg as in the placebo period. Membrane incorporation of n-3 fatty acids was, however, limited. Thus, dietary polyunsaturated fatty acids exerted substantial effects on erythrocyte membranes by affecting membrane contents of lipid molecules other than the fatty acids.

The role of endogenous Na+,K+-adenosine triphosphatase inhibitory factor in the regulation of membrane fluidity of erythrocytes in essential hypertension

To investigate the regulatory mechanisms of membrane functions in hypertension, we examined the relationship between endogenous Na+, K(+)-adenosine triphosphatase (ATPase) inhibitor (digitalis-like factor; DLF) and erythrocyte membrane fluidity in essential hypertension by means of an electron spin resonance (ESR) and spin labelling methods. Erythrocytes were obtained from patients with essential hypertension and normotensive subjects, and the ESR spectra for a fatty acid spin label agent (5-nitroxide stearate) incorporated into the erythrocyte membranes were studied. The DLF content in plasma was expressed as the inhibitory potency of dog kidney Na+, K(+)-ATPase activity in vitro. The values of outer hyperfine splitting and of order parameter in ESR spectra were significantly higher in hypertensive patients than in normotensive subjects. This finding shows that the erythrocyte membrane fluidity may be decreased in essential hypertension. The level of plasma DLF content was greater in hypertensive patients than in normotensive subjects and was significantly correlated with the decrease in erythrocyte membrane fluidity. These results suggest that the decrease in erythrocyte membrane fluidity may be partially dependent upon the increased plasma DLF content.

Alterations in erythrocyte membrane lipid composition and fluidity in primary lipoprotein lipase deficiency

Lipid composition of plasma lipoproteins and erythrocyte ghost membranes has been studied in 16 healthy normolipidaemic subjects and in 16 patients affected by primary lipoprotein lipase deficiency, resulting in severe chylomicronaemia and in cholesterol-depleted low-density lipoproteins and high-density lipoproteins. A significant decrease in membrane cholesterol/phospholipid ratio was observed in lipoprotein lipase deficient patients compared to controls (3.27 ± 0.33 vs. 3.95 ± 0.50, mean ± S.D.; P < 0.0001). There was also an increase in the erythrocyte membrane phosphatidylcholine/sphingomyelin ratio in lipoprotein lipase deficient patients compared to controls (1.53 ± 0.10 vs. 1.05 ± 0.13; P < 0.0001) due to a concurrent increase in phosphatidylcholine and decrease in sphingomyelin relative concentrations in these patients. Erythrocyte ghost membrane fluidity was determined by fluorescence anisotropy and found to be higher in membranes from lipoprotein lipase deficient patients. This increase in membrane fluidity can be attributed in part to changes in membrane cholesterol and phospholipid concentrations in response to abnormal plasma lipoprotein composition.

Lowered membrane fluidity of younger erythrocytes in diabetes

In vivo age-related changes in membrane fluidity of erythrocytes were investigated by a spin label method after fractionation of the cells by discontinuous density gradient centrifugation. Membrane fluidity was lower in older than in younger erythrocytes in both the normal and diabetic subjects. Cells from diabetic subjects showed a significantly lower level of membrane fluidity for all three age groups (younger, middle and older) than the corresponding cells from normal subjects. The magnitude of progression in the decrease in membrane fluidity in erythrocytes did not differ significantly between both groups of subjects. Both erythrocyte ATP and acetylcholinesterase activity declined, while glycosylated hemoglobin (HbA 1c) increased with cell age in both groups of subjects. The HbA 1c level in each corresponding fraction was higher in diabetic subjects than normal subjects, but was not correlated with membrane fluidity in either group. Neither the ATP level nor acetylcholinesterase activity in each corresponding fraction differed between groups. Membrane fluidity was significantly correlated with acetylcholinesterase activity in both normal and diabetic subjects. Our results indicate that decreased erythrocyte membrane fluidity in diabetic patients does not form gradually during their life span but develops soon after the cells enter the circulation or during their maturation in the bone marrow.