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PubMed2000

Polymorphonuclear integrins, membrane fluidity, and cytosolic Ca(2+) content after activation in essential hypertension.

The purpose of this research was to obtain further information about the role of polymorphonuclear leukocytes in essential hypertension. These cells could be involved in the pathogenesis of organ injury. Thirty subjects (14 men and 16 women) with essential hypertension were enrolled. In these subjects we determined, at baseline and after in vitro activation with 4-phorbol 12-myristate 13-acetate and N:-formyl-methionyl-leucyl-phenylalanine, the polymorphonuclear leukocyte membrane fluidity, obtained by labeling the cells with 1-[4-(trimethylamino)phenyl]-6-phenyl-1,3, 5-hexatriene, cytosolic Ca(2+) concentration, obtained by marking the cells with Fura 2-AM, and integrin pattern (CD11a, CD11b, CD11c, and CD18), by using the indirect immunofluorescence with a flow cytometer. At baseline there was no difference in membrane fluidity between normal subjects and hypertensives, whereas hypertensives showed an increase in cytosolic Ca(2+) content and an increase of the phenotypical expression of CD11a, CD11b, and CD18. In normal subjects and in hypertensives, after activation, no variation was found in membrane fluidity and cytosolic Ca(2+) content. In normal subjects, after activation, we observed a significant increase of the expression of all adhesion molecules, whereas in hypertensives we found an increase of the expression of CD11b, CD11c, and CD18 but also a decrease of CD11a. The behavior of the polymorphonuclear leukocyte integrin profile may have several explanations, and in particular, the trend of CD11a after chemotactic activation may be related to its cleavage or to an altered integrin phosphorylation/dephosphorylation balance hypothetically present in this clinical condition.

Adult↗
PubMed1988

Abnormal membrane fluidity and acetylcholinesterase activity in erythrocytes from insulin-dependent diabetic patients.

An alteration in the enzymatic properties of the erythrocyte membrane acetylcholinesterase (AchE) and Na+,K+-ATPase has been described in experimental diabetes mellitus. We studied erythrocyte membrane fluidity and AchE and Na+,K+-ATPase activities in 15 insulin-dependent diabetic patients and 11 normal subjects. Fluidity was assessed by fluorescence polarization, using 1,6-diphenyl-1,3,5-hexatriene as a probe, and AchE and Na+,K+-ATPase activities were measured enzymatically. We found a significant increase in the enzymatic activity of AchE and a change in its enzymatic properties in diabetic patients compared with those in normal subjects. AchE activity correlated inversely with membrane fluorescence polarization, which was decreased in the diabetic patients, indicating an increase in membrane fluidity. Na+,K+-ATPase activity was reduced in the diabetic patients and correlated positively with the fluorescence polarization values. We hypothesize that the abnormal dynamic properties of the erythrocyte membrane may play a major role in determining the described change in enzymatic activity.

Acetylcholinesterase↗
PubMed1990

A compensatory mechanism improving red cell membrane fluidity in hemodialysed patients.

A fluorescence polarization technique with 1,6-diphenyl 1,3,5-hexatriene as a fluorescent probe was used to determine the fluidity of red cell membranes from hemodialysed patients before and after dialysis. After dialysis, there was a decrease in fluidity and activation energy values revealed a significantly changed distribution. The membrane lipid composition showed a significant increase in cholesterol after dialysis (p less than 0.001) and a significant reduction in saturated fatty acids (p less than 0.01) with an increase in unsaturated fatty acids (p less than 0.05). A compensatory mechanism could be suggested involving a reduction of saturated fatty acids in response to the increase in the cholesterol/phospholipid ratio. This could lead to an optimization of membrane fluidity.

Adult↗
PubMed2002

Sex differences in p-aminohippuric acid transport in rat kidney: role of membrane fluidity and expression of OAT1.

Sex differences in the kinetic parameters of p-aminohippuric acid (PAH) transport in brush border (BBMV) and basolateral (BLMV) membrane vesicles from kidney cortex have been observed. Membrane fluidity of BBMV was higher in females as compared with male rats as indicated by anisotropy values (0.1897 +/- 0.0010 vs. 0.2003 +/- 0.0014, p < 0.05, for females and males respectively). Membrane fluidity of BLMV were similar in both sexes. Western blot studies revealed that OAT1 protein in female BLMV was present at only 40% of level found in BLMV from male rats. The lower expression of OAT1 in BLMV in association with the higher BBMV fluidity (which may affect the affinity of PAH transporter in this membrane domain) observed in females may be responsible, at least in part, for the gender difference described in renal PAH secretion.

Alkaline Phosphatase↗
PubMed2000

Acute ischemic stroke : polymorphonuclear leukocyte membrane fluidity and cytosolic Ca(2+) concentration at baseline and after chemotactic activation.

BACKGROUND AND PURPOSE: Several reports have considered the role of systemic leukocytes in acute ischemic stroke (AIS). Initially, greater attention was focused on the leukocyte count and subsequently on their adhesiveness, aggregation, rheology, and activation. The aim of this study was the evaluation of certain polymorphonuclear leukocyte (PMN) parameters, reflecting their rheology and activation, in subjects with AIS. METHODS: In a group of 19 subjects with AIS and in a control group of 18 subjects with asymptomatic vascular atherosclerotic disease, we evaluated the PMN membrane fluidity and cytosolic Ca(2+) concentration at baseline and after in vitro chemotactic activation with 4-phorbol 12-myristate 13-acetate (PMA) and N-formyl-methionyl-leucyl-phenylalanine (fMLP). RESULTS: From the obtained data, it is evident that at baseline only PMN membrane fluidity distinguishes control subjects from AIS subjects. After PMN activation with PMA and fMLP, prolonged for 5 and 15 minutes, we found an increase in PMN cytosolic Ca(2+) concentration and a decrease in PMN membrane fluidity only in subjects with AIS. CONCLUSIONS: These findings emphasize that in subjects with AIS a functional alteration of systemic PMN cells is clearly expressed during chemotactic activation, although the mechanism of this abnormality is not yet explained.

Acute Disease↗
PubMed1990

[Importance of membrane fluidity determination].

Translational motions of lipids and proteins and molecular motions within the lipid hydrocarbon chains of biological membranes can be approached by spectroscopic methods. The electron spin resonance (ESR) spectra of spin labels bound on proteins or grafted on fatty acids and incorporated into biological membranes undergo characteristic changes which may be resolved in terms of modifications of membrane environment. However, the method is still scarcely used in routine clinical studies. In contrast, fluorescence methods such as intermolecular excimers or fluorescence polarization might join the ranks of routine analyses. The labeling of lipid compartments with fluorescent probes and the study of their spectroscopic properties give informations on the cohesion of their immediate environment. Polyenic molecules (DPH and TMA-DPH) which are located in different lipid compartments characterize deep and superficial areas of cell membrane, respectively. A set of probes in which a 9-anthroyloxy group is attached to different positions of a long chain fatty acid provides a means of measuring a fluidity gradient into membrane bilayer. Thus, these fluorescence methods which are simple and rapid represent a semi-quantitative approach of the so called "membrane fluidity". Modifications in membrane fluidity can control the expression of proteins, receptors exposed on cell surface and alter functional properties of cells. Moreover, pathological processes can also be related to fluidity modifications. In particular, in hypertension and vascular diseases, a decrease in membrane fluidity has been shown in platelets and red cells. Nevertheless, further investigations combining biophysical, biochemical and immunological methods are needed to determine the exact relations between membrane fluidity, classical rheological properties and cell functions.

Biophysical Phenomena↗
PubMedDate not supplied

Cholesterol modulation of membrane fluidity and ecto-nucleotide triphosphatase activity in human normal and CLL lymphocytes.

Lymphocytes isolated from the peripheral blood of patients with chronic lymphocytic leukemia (CLL) and from healthy donors were studied for membrane fluidity and lipid phase separation. The degree of fluidity of the surface membrane lipids was estimated by fluorescence polarization analysis using the probe 1,6-diphenyl-1,3,5-hexatriene (DPH) embedded in the lipid core of the surface membrane of intact cells. CLL lymphocytes showed a more fluid lipid bilayer in their plasma membrane than normal lymphocytes. Treatment of both groups of lymphocytes with cholesteryl hemisuccinate (CHS) complexed with PVP and BSA resulted in rigidification of cell membranes. A lipid thermotropic transition temperatures was observed at 23.6 + 1.1 degree in normal lymphocytes and 16.3 + 1.0 degree in CLL lymphocytes, which rose to 32.3 + 1.3 degree in normal and was abolished in CLL lymphocytes after treatment with CHS. "Compound lipid fluidizer" reduced the thermotropic transition temperature to 17.5 + 1.0 degree and 15.1 + 0.9 degree in normal and CLL lymphocytes, respectively. A statistically significant increase (p less than 0.01) in the specific activity of the ecto-ATPase was observed in CLL lymphocytes as compared to normal cells. A dramatic increase of the ecto-ATPase activity was also observed when normal lymphocytes were treated with 0.05-0.5 mM CHS. The biological significance of these results is discussed in terms of modifications in the lipid-protein interactions in lymphocyte plasma membrane induced by CHS and the implications in the proliferation of leukemic cells.

Adenosine Triphosphatases↗
PubMed2001

Relationship between age-related increases in rat liver lipid peroxidation and bile canalicular plasma membrane fluidity.

Aging is associated with increased cellular levels of lipid peroxides and reactive oxygen species. This increase in the radical species may affect membrane fluidity and consequently membrane functions. We attempted to determine whether age-related increases in lipid peroxide and reactive oxygen species levels affect the annular fluidity of the bile canalicular plasma membrane in young (2-3 weeks old), adult (20 weeks old) and old (100 weeks old) rats. Hepatic levels of lipid peroxides measured with thiobarbituric acid reactive substances (TBARS), reactive oxygen species and reduced glutathione were significantly higher in the old rats than in the young and adult rats. Arachidonic acid (AA) levels increased and docosahexaenoic acid (DHA) levels decreased in the isolated canalicular plasma membrane of the old rats, and the ratio of DHA to AA thus decreased significantly with rat aging. Hepatic TBARS levels correlated negatively with molar ratios of DHA to AA. The annular fluidity of the bile canalicular plasma membrane decreased significantly in the old rats compared with that in the young and adult rats. These results suggest that the age-related decrease in DHA content of the bile canalicular plasma membrane and the molar ratio of DHA to AA may be associated with age-related deterioration of membrane annular fluidity.

Aging↗
PubMed1981

Mechanism of the concanavalin A-induced change of membrane fluidity of chicken erythrocytes.

When chicken erythrocytes labeled with a stearic acid derivative spin label was treated with concanavalin A (Con A), ESR spectra showed a change in the peaks due to the labels in membrane lipids, indicating an increase of membrane lipid fluidity. Addition of Con A increased the fluidity rapidly. This change was reversible only up to 30 min after adding Con A, and thereafter it gradually became irreversible. However, if the erythrocytes were treated with cytochalasin B and methyl alpha-D-mannoside, a complete return of fluidity to the normal level could be observed at any stage after the binding of Con A. The observation of freeze-fracture replicas of erythrocyte membranes by transmission electron microscopy also showed that the redistribution of intramembranous particles gradually became irreversible after exposure to Con A. These results suggest that the microfilament-like system, which modulates the distribution of cell surface receptors for Con A, participates in the modulation of membrane fluidity. Phospholipid methylation of chicken erythrocyte membrane was stimulated immediately after the binding of Con A. A methyltransferase inhibitor, 5'-deoxy-5'-S-isobutyl adenosine, abolished the increase of membrane fluidity within the first 10 min and also that occurring later than 60 min after adding Con A, but it was without effect on the elevated fluidity found between 20 and 60 min. Removal of extracellular Ca2+ had an inhibitory effect on the lasting increase of fluidity. These results suggest that the first increase of membrane fluidity by Con A may be caused by phospholipid methylation, while the second increase may depend on the rearrangement of Con A receptor glycoproteins through cross-linking wit Con A. The irreversible part of the membrane fluidity increase probably depends on Ca2+ influx, phospholipid methylation, and peripheral membrane proteins which constitute the microfilament-like system at the membrane inner surface.

Animals↗
PubMed1982

Interferon inhibits Sendai virus-induced cell fusion: an effect on cell membrane fluidity.

Interferon can affect several cellular functions, in addition to its antiviral activity. We report here that pretreatment of human cells with homologous interferon significantly inhibits cell fusion induced by Sendai virus and that this refractory state is accompanied by a decrease in cell plasma membrane fluidity. Multinucleate cell formation induced by beta-propiolactone-inactivated Sendai virus in human fibroblast cells (a system in which fusion results from an interaction of the viral glycoprotein with the cell membrane) was inhibited by more than 90% after addition of human interferon for 18-24 hr. This inhibition could be neutralized by antiserum to interferon. Furthermore, inhibitor studies with cycloheximide and actinomycin D clearly indicated that synthesis of protein and RNA is necessary to establish the resistant state. To determine whether the inhibition of Sendai virus-induced cell fusion resulted from interferon-induced changes at the cell plasma membrane, experiments were carried out using the fluorescence probe 1,6-diphenyl-1,3,5-hexatriene, which is capable of sensing molecular motions in the hydrocarbon core of the bilayer structure. A significant decrease in the membrane fluidity of interferon-treated cells was observed. It is likely, therefore, that the inhibitory effect on Sendai virus-induced cell fusion observed in interferon-treated cells results from an increased rigidity of the target cell membrane.

Cell Fusion↗
PubMed1995

beta-Amyloid peptide decreases membrane fluidity.

The beta-amyloid peptide-25-35 (beta A25-35) decreases the fluidity of mouse brain membranes in a concentration-depending fashion. First effects were already seen at a beta A25-35 concentration of 100 nmol/1. beta-Amyloid peptide(1-40) was similarly active. beta A25-35 also decreases the fluidity of human lymphocyte membranes and of membranes from the cortex, hippocampus, striatum, and cerebellum of the rat, although the effects in the rat cerebellum are only weak. Scrambled beta A25-35 when investigated under similar conditions showed no effects on membrane fluidity. It is suggest that the effect on cellular calcium-signalling but also the neurotoxic properties of beta-amyloid might be the result of its concentration depending effects on membrane properties.

Amino Acid Sequence↗
PubMedDate not supplied

Expression of proliferation and differentiation antigens in response to modulation of membrane fluidity in chronic lymphocytic leukemia lymphocytes.

Isolated lymphocytes from patients with chronic lymphocytic leukemia (CLL) and from healthy controls were investigated for cell membrane fluidity and lipid phase separation. Expression of surface immunoglobulins, OKB7 and HLA-DR antigen, transferrin and interleukin-2 receptor was determined in relation to modulation of membrane lipid composition in each individual case. Structural and functional changes of membrane lipids and impaired lipid-protein interactions could be demonstrated in CLL lymphocytes. However, there is no simple correlation of membrane fluidity and receptor expression. This interaction poses a complex physicochemical problem, which must consider the original structural and functional state of the lipid bilayer. Disturded lipid-protein interactions are discussed in terms of defective transmembrane signalling and cell-cell interaction, allowing uncoupling of the leukemic cell from the network of growth and differentiation factors.

Antigens, Differentiation↗
PubMed2006

Docosahexaenoic acid-induced protective effect against impaired learning in amyloid beta-infused rats is associated with increased synaptosomal membrane fluidity.

In the present study, we investigated the relationship between the docosahexaenoic acid (DHA)-induced protection of learning deficit of amyloid beta(1-40)-infused Alzheimer's disease (AD) model rats and changes in synaptosomal plasma membrane fluidity of the cerebral cortex. Synaptosomal membrane lateral and rotational fluidity were measured using pyrene excimer spectroscopy and fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH), respectively. Avoidance learning ability, as assessed by a two-way active avoidance paradigm, decreased significantly in the AD model rats. Pyrene-determined annular/non-annular fluidity ratio and the DPH-determined bulk fluidity of the synaptosomal plasma membrane decreased in the amyloid beta(1-40)-infused rats. Oral pre-administration of DHA (300 mg/kg per day for 12 weeks) significantly increased both lateral and rotational fluidity. The synaptosomal membrane DHA content increased and the cholesterol to phospholipid molar ratio and lipid peroxidation decreased. The annular to non-annular fluidity ratio of the synaptic plasma membrane was positively correlated with total avoidance learning. The present results indicate that DHA-induced alterations in synaptic plasma membrane fluidity may contribute to the synaptic plasma membrane-related functions that constitute avoidance learning-related memory in amyloid beta(1-40)-infused rats.

Alzheimer Disease↗
PubMed1977

Electron spin resonance studies of an animal model of human congenital myotonia: increased erythrocyte membrane fluidity in rats with 20,25-diazacholesterol-induced myotonia.

Electron spin resonance experiments have been performed on erythrocyte membranes from rats with myotonia induced by treatment with 20,25-diazacholesterol. The results suggest that erythrocyte membranes in this animal model of human congenital myotonia possess a highly significantly increased surface membrane fluidity compared to that of controls. Alterations in the physical state of membrane proteins were not apparent. These findings, also present in human congenital myotonia [Butterfield, Chesnut, Roses & Appel, 1976, Nature (London) 263:159; Butterfield, 1977 (Submitted for publication)], strengthen the concepts that increased membrane fluidity is associated with the presence of myotonia and that congenital myotonia may be a diffuse membrane disease.

Amino Acids, Sulfur↗
PubMed1987

Increased membrane fluidity of erythrocytes in a case with malignant hyperthermia.

In a case with malignant hyperthermia (MH), membrane fluidity of erythrocytes was studied by electron spin resonance (ESR)-spin labeling technique. The measurement was made with samples obtained during and after pyrexic crisis until full recovery. The results indicated that membrane fluidity increased during pyrexic crisis and that these changes were serially restored. As the physicochemical characteristics of the erythrocyte membrane resemble those of cellular and cell organella membrane, it was concluded that membrane composition and configuration might have been altered pathophysiologically during the crisis of MH in our case.

Journal Article↗
PubMed1991

Effect of salt and membrane fluidity on fluorophore motions of a gramicidin C derivative.

We have used fluorescence spectroscopy to investigate the effect of salt and membrane fluidity on the rotational motion of a 5-(dimethylamino)naphthalene-1-sulfonyl (dansyl) derivative of gramicidin C (dansyl-gC) in dimyristoylphosphatidylcholine bilayers, under conditions where the peptide is a formyl-NH to formyl-NH terminal dimer, and in octyl glucoside micelles, where the peptide is an intertwined helical dimer. Energy-transfer experiments showed no changes in either conformation or dimer aggregation under the conditions explored here (15-40 degrees C, 1-350 bar, 0-0.33 M Mg2+, and 0-1 M Na+). The addition of permeable (Na+) or nonpermeable (Mg2+) ions did not affect the temperature or pressure behavior of dansyl rotation. However, fluorescence lifetime measurements indicated an increase in solvent accessibility in the presence of sodium. In bilayers, the temperature dependence of the fluorescence polarization and lifetime shows strong interactions between the dansyl residue and the peptide, and at no time did the dansyl motions become solvent controlled as has been observed for aqueous solvent peptides [Scarlata, S. F., Rholam, M., & Weber, G. (1984) Biochemistry 23, 6789]. In micelles, the change in rotational motion with temperature followed solvent expansion, showing that in this case the dansyl residue does not associate extensively with the peptide. Our results indicate that because of the extensive coupling between the dansyl residue and the rest of the peptide, membrane fluidity does not play a major role in controlling side-chain motions.

Amino Acid Sequence↗
PubMed1985

Macrophage phagocytosis and membrane fluidity in mice: the effect of age and dietary protein.

Male C57BL/6NNia mice were used to investigate the effects of age and dietary protein intake on Fc and C3b receptor-mediated phagocytosis and on membrane fluidity. Six-month-old (adult) and 24-month-old (aged) mice were fed a 6% or 25% protein diet for 3, 5, or 6 weeks at which time thioglycollate elicited peritoneal macrophages were isolated. Both binding of IgG-coated sheep red blood cells to the macrophages and ingestion via the Fc-receptor were identical in all 4 groups after 3 and 6 weeks of feeding but were decreased at 5 weeks in the aged animals fed 6% protein. Phagocytosis via the C3b receptor was not depressed in either age group fed the low protein diet; it was, however, augmented significantly in the aged animals fed the 25% protein diet for 5 and 6 weeks. Membrane fluidity of the plasma membrane outer hemileaflet was monitored with an impermeant fluorescent probe. No changes were observed between adult and aged mice maintained up to 6 weeks on the diets.

Aging↗
PubMed1988

Changes of lymphocyte membrane fluidity in rheumatoid arthritis: a fluorescence polarisation study.

Fluorescence polarisation of 1,6-diphenyl-1,3,5-hexatriene was used to study the lymphocyte membrane in rheumatoid arthritis. The increase of polarisation value in the patients (n = 27) compared with healthy controls (n = 32) suggests a decrease of membrane fluidity. Moreover, erythrocyte sedimentation rate (ESR) and plasma fibrinogen concentrations were positively correlated with lymphocyte fluorescence polarisation values (r = 0.66 and r = 0.76 respectively). The results suggest that the changes in lymphocyte membrane fluidity could be involved in the pathogenetic mechanism of rheumatoid arthritis.

Adult↗