Impairment Of Erythrocyte Deformability Research Articles

Lipid Domains at the Plasma Membrane of Red Blood Cells: Organization and Involvement in Deformation

Erythrocytes are highly deformable cells that go through capillaries eight times-narrower than their diameter to deliver oxygen throughout the body. This deformability is linked to erythrocytes specific features such as their biconcave shape, their highly regulated hemoglobin concentration and the strong anchorage of their membrane to the underlying cytoskeleton. Based on our recent evidence for submicrometric lipid domains upon labeling of cholesterol and polar lipids (sphingomyelin, phosphatidylcholine, ganglioside GM1) in erythrocyte outer plasma membrane leaflet, we here explore the mapping of lipid domains in erythrocytes at resting state and under deformation. Thanks to differential properties between cholesterol- and polar lipid-enriched domains (curvature association, lipid order, temperature dependence, cholesterol content dependence) and partial spatial dissociation, we suggest the coexistence of at least two types of lipid domains at the erythrocyte surface at resting state: those enriched in cholesterol and preferentially associated with high-curvature membranes and those mostly enriched in phosphatidylcholine and ganglioside GM1 and associated with low-curvature membranes. Biophysical properties of these domains are currently explored by atomic force microscopy and force correlation spectroscopy. Lipid domains abundance, composition and biophysical properties are differentially modulated by (i) impairment of erythrocyte deformability (energy depletion, modulation of anchorage to the cytoskeleton by pharmacological and genetic approaches), (ii) simulation of deformation (calcium channel activation, stretching in silicon chambers) and (iii) simulation of shape restoration after deformation (stimulation of calcium efflux). Indeed, high-curvature cholesterol-enriched domains gather under deformation while low-curvature domains become enriched in sphingomyelin and lose some of their ganglioside GM1 enrichment. We hypothesize that cholesterol-enriched domains can help to stabilize high curvature membranes during deformation while polar lipid-enriched domains, especially those enriched in sphingomyelin, are involved into calcium balance regulation during or after deformation. This hypothesis is under investigation.

Early hemorheological changes in a porcine model of intravenously given E. coli induced fulminant sepsis.

The pathophysiology of hemorheological and microcirculatory disturbances in septic process -mostly during the early hours- still not clarified in all the details, yet. In anesthetized pigs living E. coli (ATCC 25922 strain) was administered intravenously with an increasing concentration and the animals were observed for 8 hours. Before the intervention and in every 2 hours arterial (cannulated femoral artery) and venous (cannulated external jugular vein) blood samples were collected for hemorheological laboratory tests: blood and plasma viscosity, ESR, leukocyte anti-sedimentation rate, erythrocyte deformability (together with osmoscan parameters) and erythrocyte aggregation (using light-transmission and laser back-scattering methods) Control animals were stable over the 8-hour anesthesia, while septic animals died by the 6th hours in a fulminant sepsis. Over the experimental period, the tendency of impairment in erythrocyte deformability (together with osmotic gradient ektacytometry parameters) and the controversial decreasing of erythrocyte aggregation values (declining all aggregation index values, elongating t1/2) were well detected in this porcine model during the early hours (4- 6) of fulminant sepsis. The in vitro effect of these bacteria on erythrocytes' micro-rheological parameter was similar: decreasing red blood cell deformability and lowering aggregation. Further studies are needed to clarify the early micro-rheological changes of bacteremia and the developing sepsis.

Impaired deformability of circulating erythrocytes obtained from nondiabetic hypertensive patients: investigation by a nickel mesh filtration technique.

IntroductionHypertension is associated with microcirculatory disturbance, and erythrocyte deformability is a major determinant of the microcirculation. However, impairment of erythrocyte deformability in hypertensive patients in relation to antihypertensive treatment is unclear. The present study aimed to investigate this impairment in hypertensive patients under treatment using a highly sensitive and quantitative nickel mesh filtration technique.MethodsDeformability was evaluated by filterability, defined as the flow rate of a hematocrit-adjusted erythrocyte suspension relative to that of saline under a specific filtration pressure in a pressure-flow curve obtained by continuous filtration. Baseline characteristics of hypertensive patients (n = 101) and age-matched normotensive subjects (n = 14) were obtained from medical records, and diabetic patients were excluded.ResultsErythrocyte deformability in the hypertensive group was significantly (p = 0.010) lower (87.8 ± 2.2 %) than that of the normotensive group (89.4 ± 1.7 %) and inversely proportional (r = −0.303, p = 0.002) to the mean blood pressure (BP) measured on blood sampling for the filtration study. Stepwise multiple regression analysis demonstrated that this impairment was mostly attributable to the mean BP (p = 0.001), whereas current smoking and episodes of stroke or coronary artery disease were not contributors.DiscussionThese findings indicate that erythrocyte deformability is impaired in the hypertensive patients, which depends on the current BP control rather than target organ damage.

The Effects of Electromagnetic Fields Generated from 1800 MHz Cell Phones on Erythrocyte Rheological Parameters and Zinc Level in Rats

The aim of this study was to investigate the effects of the electromagnetic field generated from the 1800 MHz radiofrequency radiation (EF) on erythrocyte rheological parameters and erythrocyte zinc levels. Twenty-four male Wistar Albino rats were randomly grouped as follows: 1) two control groups and 2) study groups: i) Group A: EF exposed group (2.5 h/day for 30 days, the phone on stand-by), and ii) Group B: EF exposed group (2.5 min/day for 30 days, the phone ringing in silent mode). At the end of the experimental period erythrocyte rheological parameters such as erythrocyte deformability and aggregation were determined by an ectacytometer. Erythrocyte zinc level, which affects hemorheological parameters, was also measured by atomic absorption spectrophotometer. Erythrocyte deformability was decreased in both study groups but the decrease in group A was not statistically significant. Exposure to EF did not have any significant effect on erythrocyte aggregation. On the other hand, erythrocyte zinc level was significantly reduced in both study groups. Exposure to EF may have decreased tissue oxygenation due to reduced erythrocyte deformability. Decrease in erythrocyte zinc level may have caused the impairment in erythrocyte deformability.

Impaired deformability of erythrocytes in diabetic rat and human: investigation by the nickel-mesh-filtration technique

Comprehensive research to quantify the deformability of erythrocytes in diabetic animals and humans has been lacking. The objective of this study was to compare the impairment of erythrocyte deformability in diabetic rats and patients by use of the same rheologic method. Deformability was investigated in streptozotocin-induced diabetic rats and diabetic patients, by using the highly sensitive and quantitative nickel-mesh-filtration technique. Erythrocyte filterability (whole-cell deformability) was defined as flow rate of hematocrit-adjusted erythrocyte suspension relative to that of saline (%). Hematological and biochemical data for diabetic rats did not differ from those for age-matched control rats except for hyperglycemia and malnutrition. Erythrocyte filterability for diabetic rats was significantly lower than that for control rats (69.4 ± 10.1%, n = 8, compared with 83.1 ± 4.2%, n = 8; p < 0.001). Likewise, erythrocyte filterability for diabetic patients was significantly impaired compared with that for controls (87.6 ± 3.4%, n = 174, compared with 88.6 ± 2.1%, n = 51; p = 0.046). Stepwise multiple regression analysis revealed that this impairment was mostly attributable to associated obesity (BMI, p = 0.029) and glycemic stress (HbA1c(JDS), p = 0.046). We therefore conclude that erythrocyte filterability is commonly impaired in diabetic rats and in humans. Moreover, metabolic risk accumulation further impairs erythrocyte filterability, resulting in derangement of the microcirculation.

Redistribution of intestinal microcirculatory oxygenation during acute hemodilution in pigs.

Acute normovolemic hemodilution (ANH) compromizes intestinal microcirculatory oxygenation; however, the underlying mechanisms are incompletely understood. We hypothesized that contributors herein include redistribution of oxygen away from the intestines and shunting of oxygen within the intestines. The latter may be due to the impaired ability of erythrocytes to off-load oxygen within the microcirculation, thus yielding low tissue/plasma Po(2) but elevated microcirculatory hemoglobin oxygen (HbO(2)) saturations. Alternatively, oxygen shunting may also be due to reduced erythrocyte deformability, hindering the ability of erythrocytes to enter capillaries. Anesthetized pigs underwent ANH (20, 40, 60, and 90 ml/kg hydroxyethyl starch; ANH group: n = 10; controls: n = 5). We measured systemic and mesenteric perfusion. Microvascular intestinal oxygenation was measured independently by remission spectrophotometry [microcirculatory HbO(2) saturation (muHbO(2))] and palladium-porphyrin phosphorescence quenching [microcirculatory oxygen pressure in plasma/tissue (muPo(2))]. Microcirculatory oxygen shunting was assessed as the disparity between mucosal and mesenteric venous HbO(2) saturation (HbO(2)-gap). Erythrocyte deformability was measured as shear stress-induced cell elongation (LORCA difractometer). ANH reduced hemoglobin concentration from 8.1 to 2.2 g/dl. Relative mesenteric perfusion decreased (decreased mesenteric/systemic perfusion fraction). A paralleled reduction occurred in mucosal muHbO(2) (68 +/- 2 to 41 +/- 3%) and muPo(2) (28 +/- 1 to 17 +/- 1 Torr). Thus the proposed constellation indicative for oxygen off-load deficits (sustained muHbO(2) at decreased muPo(2)) did not develop. A twofold increase in the HbO(2)-gap indicated increasing intestinal microcirculatory oxygen shunting. Significant impairment in erythrocyte deformability developed during ANH. We conclude that reduced intestinal oxygenation during ANH is, in addition to redistribution of oxygen delivery away from the intestines, associated with oxygen shunting within the intestines. This shunting appears to be not primarily caused by oxygen off-load deficit but rather by oxygen/erythrocytes bypassing capillaries, wherein a potential contributor is impaired erythrocyte deformability.

Cation-osmotic Haemolysis in Patients with Retinal Vein Occlusion

The purpose of this work was to use a new technique to assess erythrocyte deformability in patients with retinal vein occlusion. Erythrocyte microrheology changes were measured by cation-osmotic haemolysis (COH) in healthy donors and in patients with both central (n= 6) and branch (n= 16) retinal vein occlusion up to 12 months after the occlusion. The patient group consisted of five patients with ischaemic and 17 with oedematous vein occlusion. The control group consisted of the same number of age-, sex- and risk factor (hypertension)-matched donors. In patients with retinal vein occlusion, COH was significantly decreased compared to the control group. The decrease was most marked at low and high concentrations of incubating media where the differences reached high statistical significance (p<0.01–0.001). In our previous experiments we showed that COH and erythrocyte deformability (ED) are closely related and that COH reflects basic information about erythrocyte deformability. Thus, decreased COH in patients with retinal vein occlusion points to reduced ED in comparison with the control group. We, therefore, assume that impairment in ED together with other microrheological abnormalities contributes to the pathophysiology of changes in patients with retinal vein occlusion.

The required dose of erythropoietin during renal anaemia treatment is related to the degree of impairment in erythrocyte deformability.

Renal anaemia is rapidly corrected by recombinant human erythropoietin (rHuEpo) therapy, but the dose required varies greatly. Since impaired erythrocyte deformability may be one factor contributing to the development of renal anaemia, the interrelationship between that variable and the rHuEpo requirement was examined. Twenty-five patients treated with hemodialysis and rHuEpo for at least 6 months were included in the study. The Hb value had been stable and the rHuEpo dose unchanged the last two months. Using a rotational viscometer, the fluidity of erythrocytes, separated from plasma and re-suspended in isotonic buffered saline to a standardized haematocrit, was taken as a measure of erythrocyte deformability. The average weekly dose of s.c. epoetin alpha was 186 +/- 93 U/kg body weight (range 56-370). The dose was correlated to the reticulocyte fraction (R = 0.69, P = 0.0001). When the rHuEpo dose was used as dependent variable and blood haemoglobin concentration, serum (S) albumin, S ferritin, S aluminium, S PTH, S urea, Kt/V/week, erythrocyte fluidity, and plasma viscosity were used as independent variables in a stepwise multiple regression analysis, only erythrocyte fluidity remained significantly negatively correlated to the rHuEpo dose (R = 0.5, P = 0.01). Despite a tendency towards higher doses of rHuEpo in patients with a C-reactive protein concentration exceeding 20 mg/l, the Hb was lower in these patients. We conclude that the interindividual differences in bone marrow response to rHuEpo were small in these patients. Impaired erythrocyte deformability and inflammation seem to be factors associated with increased rHuEpo requirement.