Erythrocyte deformability profile evaluated by laser diffractometry in patients with multiple myeloma: Re-examination of our cases.

BACKGROUND: Multiple myeloma is a complex pathology which represents about 10 % of all hematological neoplasms. It can often present changes in the hemorheological profile and, in relation to this last topic, our aim is to evaluate the hemorheological profile in a group of multiple myeloma patients, with reference to erythrocyte deformability. METHODS: We have examined the profile of the erythrocyte deformability in multiple myeloma enrolling 29 patients; this profile, expressed as elongation index at several shear stress, has been obtained using the diffractometric method. RESULTS: By comparing normal controls and MM patients, a significant decrease in erythrocyte deformability, especially at low shear stresses, but we did not observe any significant differences about this profile subdividing the whole group of MM patients according to the degree of bone marrow plasma cell infiltration, to the red blood cell distribution width and to the serum values of LDH. CONCLUSIONS: In this paper we have taken in consideration all the hypothesis for a possible explanation of the behaviour of this a reduced erythrocyte deformability in multiple myeloma. Erythrocyte deformability interferes with the physiological release of oxygen to tissues, with several clinical implications.

Microrheological disorders in patients with polycythemia vera suffered acute ischemic stroke.

The relevance of the study is determined by the fact that the combination of cerebrovascular disorders and myeloproliferative diseases requires the search for a predictive biomarker to improve outcomes. The aim of this article was to explore the meanings of microrheological disorders in patients with polycythemia vera (PV) who suffered an acute ischemic stroke (AIS). The study was carried out at the Research center of Neurology. We studied microrheological properties in 181 patients (aged 42-75 years). From the AIS developed in 68 (38%) patients with PV; 59 (32%) patients with AIS were without PV; 54 (30%) patients with PV did not suffer AIS. Microrheological disorders, first of all, the red blood cells (RBC) deformability correlated to AIS severity and its features in comorbid patients. The RBC deformability was dependent on the allelic load of the V617F mutation in the JAK2 gene. Additionally, it was found that RBC deformability perform diagnostic value in the acute phase of ischemic stroke as well as get predictive value for thrombotic complications development within 2 years after AIS in such patients. We suppose that in patients with PV an ischemic stroke and thrombosis would directly depend on the success of PV treatment. In turn, RBC deformability is applicable for some predictive models to late thrombosis development.

Red Blood Cell Morphodynamics in Patients with Polycythemia Vera and Stroke.

Polycythemia vera (PV) is a Ph-negative myeloproliferative neoplasm (MPN) which is characterized by erythrocytosis and a high incidence of thrombotic complications, including stroke. The study aimed to evaluate red blood cell (RBC) morphodynamic properties in PV patients and their possible association with stroke. We enrolled 48 patients with PV in this cross-sectional study, 13 of which have a history of ischemic stroke. The control group consisted of 90 healthy subjects. RBC deformability and aggregation analysis were performed using a laser-assisted optical rotational red cell analyzer. The following parameters were calculated: aggregation amplitude (Amp), RBC rouleaux formation time constant (Tf), time of formation of three-dimensional aggregates (Ts), aggregation index (AI), rate of complete disaggregation (y-dis), and the maximal elongation of RBC (EImax). Statistical analysis was performed with the R programming language. There were significant differences in RBCs morphodynamics features between patients with PV and the control group. Lower EImax (0.47 (0.44; 0.51) vs. 0.51 (0.47; 0.54), p < 0.001) and γ-dis (100 (100; 140) vs. 140 (106; 188) s-1, p < 0.001) along with higher amplitude (10.1 (8.6; 12.2) vs. 7.7 (6.6; 9.2), p < 0.001) was seen in patients with PV compared with control. A statistically significant difference between PV patients with and without stroke in aggregation amplitude was found (p = 0.03). A logistic regression model for stroke was built based on RBC morphodynamics which performed reasonably well (p = 0.01). RBC alterations may be associated with overt cerebrovascular disease in PV, suggesting a possible link between erythrocyte morphodynamics and increased risk of stroke.

Differential dielectroscopic data on the relation of erythrocyte membrane skeleton to erythrocyte deformability and flicker.

Two dielectric relaxations, ßsp (1.5 MHz) and γ1sp (7 MHz), have been detected on spectrin-based membrane skeleton (MS) of red blood cells (RBCs) using the plot of admittance changes at the spectrin denaturation temperature (Ivanov and Paarvanova in Bioelectrochemistry 110: 59-68, 2016, Electrochim Acta 317: 289-300, 2019a). In this study, we treated RBCs and RBC ghost membranes with agents that make membranes rigid and suppress membrane flicker, and studied the effect on ßsp and γ1sp relaxations. Diamide (diazene dicarboxylic acid bis-(N,N-dimethylamide)) (up to 0.85 mM), taurine mustard (tris(2-chloroethyl)amine) (up to 2 mM), known to specifically cross-link and stiffen spectrin, and glutaraldehyde (up to 0.044%) all inhibited the relaxations in RBC ghost membranes. Similar inhibition was obtained resealing RBC ghost membranes with 2,3-diphosphoglicerate (up to 15 mM), binding WGA (wheat germ agglutinin) (up to 0.025 mg/ml) to exofacial aspect of RBCs, incubating RBCs in hypotonic (200 mOsm) and hypertonic (600-900 mOsm) media and depleting RBCs of ATP. By contrast, concanavalin A (1 mg/ml) and DIDS (4,4'-diiso-thiocyanato stilbene-2,2'-disulfonic acid) (75 µM, pH 8.2), both known to bind specifically band 3 integral protein of RBCs without effect on RBC membrane rigidity, did not affect the relaxations. We conclude there might be a relation between the strength of dielectric relaxations on MS spectrin and the deformability and flicker of RBC membrane.

Myosin IIA interacts with the spectrin-actin membrane skeleton to control red blood cell membrane curvature and deformability.

The biconcave disk shape and deformability of mammalian RBCs rely on the membrane skeleton, a viscoelastic network of short, membrane-associated actin filaments (F-actin) cross-linked by long, flexible spectrin tetramers. Nonmuscle myosin II (NMII) motors exert force on diverse F-actin networks to control cell shapes, but a function for NMII contractility in the 2D spectrin-F-actin network of RBCs has not been tested. Here, we show that RBCs contain membrane skeleton-associated NMIIA puncta, identified as bipolar filaments by superresolution fluorescence microscopy. MgATP disrupts NMIIA association with the membrane skeleton, consistent with NMIIA motor domains binding to membrane skeleton F-actin and contributing to membrane mechanical properties. In addition, the phosphorylation of the RBC NMIIA heavy and light chains in vivo indicates active regulation of NMIIA motor activity and filament assembly, while reduced heavy chain phosphorylation of membrane skeleton-associated NMIIA indicates assembly of stable filaments at the membrane. Treatment of RBCs with blebbistatin, an inhibitor of NMII motor activity, decreases the number of NMIIA filaments associated with the membrane and enhances local, nanoscale membrane oscillations, suggesting decreased membrane tension. Blebbistatin-treated RBCs also exhibit elongated shapes, loss of membrane curvature, and enhanced deformability, indicating a role for NMIIA contractility in promoting membrane stiffness and maintaining RBC biconcave disk cell shape. As structures similar to the RBC membrane skeleton exist in many metazoan cell types, these data demonstrate a general function for NMII in controlling specialized membrane morphology and mechanical properties through contractile interactions with short F-actin in spectrin-F-actin networks.

Beneficial Effect of Quercetin on Erythrocyte Properties in Type 2 Diabetic Rats.

Diabetes mellitus is characterized by tissue oxidative damage and impaired microcirculation, as well as worsened erythrocyte properties. Measurements of erythrocyte deformability together with determination of nitric oxide (NO) production and osmotic resistance were used for the characterization of erythrocyte functionality in lean (control) and obese Zucker diabetic fatty (ZDF) rats of two age categories. Obese ZDF rats correspond to prediabetic (younger) and diabetic (older) animals. As antioxidants were suggested to protect erythrocytes, we also investigated the potential effect of quercetin (20 mg/kg/day for 6 weeks). Erythrocyte deformability was determined by the filtration method and NO production using DAF-2DA fluorescence. For erythrocyte osmotic resistance, we used hemolytic assay. Erythrocyte deformability and NO production deteriorated during aging-both were lower in older ZDF rats than in younger ones. Three-way ANOVA indicates improved erythrocyte deformability after quercetin treatment in older obese ZDF rats only, as it was not modified or deteriorated in both (lean and obese) younger and older lean animals. NO production by erythrocytes increased post treatment in all experimental groups. Our study indicates the potential benefit of quercetin treatment on erythrocyte properties in condition of diabetes mellitus. In addition, our results suggest potential age-dependency of quercetin effects in diabetes that deserve additional research.

Shear-thinning behaviour of blood in response to active hyperaemia: Implications for the assessment of arterial shear stress-mediated dilatation.

NEW FINDINGS: What is the central question of this study? Quantitative values of shear rate-specific blood viscosity and shear stress in the human macrovasculature in response to exercise hyperaemia are unknown. What is the main finding and its importance? Using the handgrip exercise model, we showed that an increase in brachial artery shear rate led to a decrease in blood viscosity, despite concomitant haemoconcentration. This shear-thinning behaviour of blood, secondary to increased erythrocyte deformability, blunted the expected increase in brachial artery shear stress based on shear rate prediction. Our data yield new insights into the magnitude and regulation of macrovascular blood viscosity and shear stress in physiological conditions of elevated metabolic demand and blood flow in humans. ABSTRACT: Blood viscosity is a well-known determinant of shear stress and vascular resistance; however, accurate quantitative assessments of shear rate-specific blood viscosity in the macrovasculature in conditions of elevated blood flow are inherently difficult, owing to the shear-thinning behaviour of blood. Herein, 12 men performed graded rhythmic handgrip exercise at 20, 40, 60 and 80% of their maximal workload. Brachial artery shear rate and diameter were measured via high-resolution Duplex ultrasound. Blood was sampled serially from an i.v. cannula in the exercising arm for the assessment of blood viscosity (cone-plates viscometer). We measured ex vivo blood viscosity at 10 discrete shear rates within the physiological range documented for the brachial artery in basal and exercise conditions. Subsequently, the blood viscosity data were fitted with a two-phase exponential decay, facilitating interpolation of blood viscosity values corresponding to the ultrasound-derived shear rate. Brachial artery shear rate and shear stress increased in a stepwise manner with increasing exercise intensity, reaching peak values of 940 ± 245 s-1 and 3.68 ± 0.92 Pa, respectively. Conversely, brachial artery shear rate-specific blood viscosity decreased with respect to baseline values throughout all exercise intensities by ∼6-11%, reaching a minimal value of 3.92 ± 0.35 mPa s, despite concomitant haemoconcentration. This shear-thinning behaviour of blood, secondary to increased erythrocyte deformability, blunted the expected increase in shear stress based on shear rate prediction. Consequently, the use of shear stress yielded a higher slope for the brachial artery stimulus versus dilatation relationship than shear rate. Collectively, our data refute the use of shear rate to infer arterial shear stress-mediated processes.

Effect of Hydrogen Sulfide on Deformability of Rat Erythrocytes.

The influence of a hydrogen sulfide donor NaHS (2×10-5-10-3 M) on the rat erythrocyte deformability was analyzed by laser diffractometry. NaHS (6×10-5 M) increased, while NaHS (10-3 M) reduced erythrocyte deformability. The effect of NaHS (6×10-5 M) was similar to that of NO donor sodium nitroprusside (SNP, 10-7 M). However, simultaneous use of NaHS (6×10-5 M) and SNP induced less pronounced changes in erythrocyte deformability than their individual application. It is likely H2S, similar to NO, is involved in the regulation of erythrocyte deformability in the microvascular bed.

Promotion of whole blood rheology after vitamin C supplementation: focus on red blood cells 1.

Hemorheological properties represent significant contributors in the pathogenesis of cardiovascular diseases. As plasma vitamin C is inversely associated with blood viscosity in humans, we aimed to characterize the effect of vitamin C supplementation on hemorheology with an emphasis on erythrocyte functions. Twenty young healthy volunteers were asked to take vitamin C (1000 mg per day) for 3 weeks. We observed beneficial effect of intervention on multiple hemorheological parameters: whole blood viscosity in the range of medium to high shear rates, Casson yield stress, complex viscosity, and storage and loss moduli. As erythrocyte properties play a significant role in hemorheology, we characterized their deformability, nitric oxide production, and sodium pump activity in erythrocyte membranes. We can conclude that observed promotion in whole blood rheology may be consequence of improved erythrocyte functionality as concerns their ability to pass through narrow capillaries of the microcirculation, nitric oxide production, and sodium pump activity. Parameters reflecting oxidative stress and antioxidant status in plasma were not affected by our intervention. As improvement in hemorheology may play an important role in cardioprotection, it would be challenging to investigate the vitamin C supplementation to patients suffering from microcirculatory disturbances and worsened organ perfusion in the case of cardiovascular diseases.

Impaired Blood Rheology in Pulmonary Arterial Hypertension.

BACKGROUND: Understanding of the pathophysiologic manifestations of pulmonary arterial hypertension (PAH) is still evolving. The aims of the present study were to determine the alterations in blood rheology, and to investigate the relationship between those alterations and laboratory parameters in PAH. METHODS: The study included 21 consecutive treatment-naive patients with PAH and 32 age and sex-matched healthy controls. Patients were categorised in class II (n=6), class III (n=13), and class IV (n=2). All subjects underwent right-heart catheterisation. Erythrocyte deformability and aggregation were measured by an ektacytometer. RESULTS: Haemodynamic variables were as follows: the mean right atrial pressure: 9.94±5.76mmHg; the average pulmonary vascular resistance: 5.66±3 WU; Fick cardiac index: 4.15±2.75l/min/m2; and mixed venous O2 saturation: 64.59±12.53%. The average 6-minute walk distance was 351.09±133.08m. Erythrocyte deformability measured at 0.95, 3.00, and 5.33Pa was significantly lower, erythrocyte aggregation index (AI) was higher, and aggregation half-time (t1/2) was lower in PAH. AI and fibrinogen were positively correlated with NT pro-BNP (AI-NT pro-BNP: r=0.579; fibrinogen-NT pro-BNP: r=0.591). t1/2 was negatively correlated with NT pro-BNP (t1/2-NT pro-BNP: r=-0.648). CONCLUSIONS: The increase in erythrocyte aggregation and the decrease in deformability may theoretically increase the flow resistance and may be of haemodynamic significance. The association between erythrocyte aggregation and NT pro-BNP may indicate that erythrocyte aggregation increases with disease progression. These alterations contribute to the understanding of the pathophysiology and could serve as markers of disease presence.

Epoetin beta pegol for treatment of anemia ameliorates deterioration of erythrocyte quality associated with chronic kidney disease.

BACKGROUND: Epoetin beta pegol (continuous erythropoietin receptor activator; C.E.R.A.) is currently widely used for the treatment of anemia associated with chronic kidney disease (CKD). Therapeutic control of anemia is assessed by monitoring haemoglobin (Hb) levels. However, certain qualitative aspects of erythrocytes are also impaired in CKD, including loss of deformability and shortened life-span. Therefore, monitoring Hb alone could potentially fail to reveal pathological changes in erythrocytes. Focusing on erythrocyte quality in CKD may lead to more effective anemia therapy with C.E.R.A. METHODS: A CKD rat model was induced by uninephrectomy followed by anti-Thy1.1 antibody injection. From 5 weeks after the operation, C.E.R.A. (0.6 µg/kg) or vehicle was administered every 2 weeks. Erythrocyte deformability was quantified with ektacytometry and erythrocyte turnover was estimated by biotin labeling. Intracellular calcium level was assessed by Fluo-3/AM. RESULTS: Erythrocyte deformability progressively declined in CKD rats. Furthermore, erythrocyte turnover in the circulation drastically accelerated in CKD rats. With administration of C.E.R.A. at a dose sufficient to adequately control Hb, deterioration of erythrocyte deformability and turnover in CKD rats were significantly improved. Intracellular calcium, which plays a pivotal role in the mediation of erythrocyte quality, was significantly increased in CKD and was normalized by C.E.R.A. CONCLUSION: C.E.R.A. treatment exerted a favorable effect not only on anemia but also on the improvement of erythrocyte quality. C.E.R.A. administered for the treatment of CKD-associated anemia may confer therapeutic benefits on erythrocytes.

Effect of cerium oxide on erythrocyte deformability in rat lower extremity ischemia reperfusion injury.

BACKGROUND: Cerium oxide is the oxide form of cerium, which has protective effects in ischemia reperfusion (I/R) injury. The purpose of our study was to look into the effects of this rare-earth metal on erythrocyte deformability in rat lower extremity I/R injury model. MATERIALS AND METHODS: We used 24 Wistar albino rats as subjects in our study. They were divided into 4 groups; randomized control group (group C; n = 6), cerium oxide group 0.5 mg.kg-1, intraperitoneal (group CO; n = 6), I/R group (group I/R; n = 6) and I/R group with cerium oxide 0.5 mg.kg-1 intraperitoneally (group I/R-CO; n = 6). Erythrocyte packs were prepared from heparinized blood samples and deformability measurements were performed. RESULTS: We obtained similar results from the control and I/R-CO groups (p = 0.158). The results in I/R group were evidently higher than those of the control, CO, and IR-CO groups (p < 0.0001, p < 0.0001, p = 0.001, respectively). CONCLUSION: We detected unfavorable effects of I/R on erythrocyte deformability, which may impair blood flow and hence tissue perfusion in infrarenal rat aorta. We also found that cerium oxide had beneficial effects by reversing undesirable effects of I/R. Further studies with larger volume are required to support our promising results (Fig. 1, Ref. 24).

Investigation of the effects of thymoquinone on erythrocyte deformability in sepsis treatment which created by cecal perforation in rat.

AIM: We aimed to study the effects of thymoquinone on erythrocyte deformability in an experimental model of sepsis given before or after the initiation of the sepsis model. METHOD: The animals were grouped as (n = 6) control, nigella sativa, sepsis, sepsis group with administration of nigella sativa before sepsis development and sepsis group with nigella sativa administration after sepsis development. Cecal ligation and puncture model (CLP) was used to induce sepsis in the animals. The thymoquinone was given 1 hour before or after the CLP in the study groups with a dose of 500 mg·kg(-1). Erythrocyte deformability and relative resistance was calculated. RESULT: Relative resistance was increased in the sepsis groups when compared to the control group (p < 0.0001). Deformability index was increased in the sepsis group when compared to the other groups (p < 0.0001 in all groups). Sepsis group with after nigella sativa groups deformability index was significantly different from the deformability index in control group (p = 0.002). The use of nigella sativa before the initiation of sepsis corrected the deformability index significantly and the results were comparable to the control group (p = 0.078). CONCLUSION: Thymoquinone administration before induction of CLP was observed to have protective effects on these alterations in CLP sepsis (Tab. 1, Fig. 1, Ref. 26).

Effects of dexmedetomidine and thymoquinone on erythrocyte deformability in lower limb ischemia reperfusion injury in streptozotocin-induced diabetic rats.

OBJECTIVE: In this study we aimed to evaluate the effect of dexmedetomidine and thymoquinone on erythrocyte deformability in lower limb ischaemia-reperfusion (IR) injury in streptozotocin-induced diabetic rats. MATERIAL AND METHODS: Thirty Wistar albino rats were equally divided into 5 groups (n = 6); randomized control group (Group C), diabetes control group (Group DC), DIR group (Group DIR), DIR group with thymoquinone 25 mg.kg‒1 intraperitoneally (Group DIRT) and Group DIR with dexmedetomidine 100 µg.kg‒1 intraperitoneally (Group DIRD). Erythrocyte packs were prepared from heparinized blood samples and deformability measurements were performed. RESULTS: IR significantly increased the relative resistance, a marker of erythrocyte deformability when compared to control group (p < 0.05). There were significant differences among the groups in comparisons with ANOVA test (p < 0.0001). Comparisons of the groups DIRD and DIRT revealed similar results (p = 0.824). The values of Group DIR were significantly higher than those of the control, DC, DIRD and DIRT groups (p < 0.0001, p = 0.001, p = 0.004, p = 0.002, respectively). The values of the DC, DIR, DIRD and DIRT groups were significantly higher than those of the control group (p < 0.0001, all). CONCLUSION: Erythrocyte deformability may cause more problems in microcirculation. Dexmedetomidine and thymoquinone may be useful in reducing the adverse effects of this type of injury (Fig. 1, Ref. 41).

HEMOGLOBIN A1c LEVEL HIGHER THAN 9.05% CAUSES A SIGNIFICANT IMPAIRMENT OF ERYTHROCYTE DEFORMABILITY IN DIABETES MELLITUS.

CONTEXT: Clinical studies demonstrated erythrocyte deformability (ED) is impaired in diabetic patients and described the correlations between HbA1c and ED. Few studies further investigated what an exact elevated HbA1c level linked to the impairment of ED in diabetes. OBJECTIVE: This study was to determine a cut-off point of HbA1c level leading to the impairment of ED in patients with diabetes. DESIGN: This was a retrospective observational study. ROC curve analysis was used to determine an optimal cut-off value of HbA1c for the increasing HSRV. SUBJECTS AND METHODS: In this study, 300 type 2 diabetic patients were enrolled. The whole blood viscosity was measured. High shear reductive viscosity (HSRV) was used to indirectly estimate ED. Based on the obtained cut-off value and glycemic control criteria for HbA1c, we divided all the cases into different groups to further confirm the accuracy of the cut-off value. RESULTS: In 300 patients, ROC curve illustrated that 9.05% was the optimal cut-off value as a predictor of the increasing HSRV. And higher odds ratio (OR) for significant decrease in ED was seen in the patients with HbA1c >9.05% compared to those with HbA1c≤9.05% (OR: 3.78, 95% CI: 2.08-6.87). HSRV increased significantly in patients with HbA1c level >9.05% in comparison to patients with HbA1c levels <6.5% between 6.5 and 8.0% and between 8.0 and 9.05%. CONCLUSION: ED decreased significantly in diabetic patients as soon as HbA1c level was higher than 9.05%.

Erythrocyte rheological properties but not whole blood and plasma viscosity are associated with severity of hypertension in older people.

OBJECTIVE: This study was carried out to determine whether changes in hemorheological parameters parallel the severity of essential hypertension. METHODS: A total of 198 older hypertensive patients were recruited and classified into 3 stages of hypertension according to the grading standard of hypertension. The whole blood viscosity (WBV) at various shear rates, plasma viscosity and erythrocyte rheology (including erythrocyte rigidity index, erythrocyte aggregation index and erythrocyte deformation index) were examined. RESULTS: Erythrocyte rheology paralleled the severity of essential hypertension and was significantly correlated to the average 24 h systolic blood pressure and diastolic blood pressure. Logistic analysis revealed that erythrocyte rigidity and the erythrocyte aggregation index were positively correlated with the severity of hypertension, while the erythrocyte deformation index was negatively correlated. No association was found between WBV, plasma viscosity and the severity of hypertension. CONCLUSION: The rheological properties of erythrocyte viscosity were correlated with the severity of hypertension in older people but the WBV and plasma viscosity were not.

Effect of apelin-13 on erythrocyte deformability during ischaemia-reperfusion injury of heart in diabetic rats.

OBJECTIVES: Erythrocyte deformability and plasma viscosity are of crucial importance for the perfusion of tissues and organs. The aim of this study was to evaluate the effect of apelin-13 on erythrocyte deformability during IR heart injury in diabetic rats. METHODS: Eighteen Wistar Albino rats were included in the study after streptozotocin (55 mg/kg) treatment for four weeks of observation for diabetes existence. The animals were randomly assigned to one of five experimental groups. In the Group C, DC (sham-control group) and DCA (sham-control group-apelin-13), the coronary artery was not occluded or re-perfused. In the Group DIR, a branch of the left coronary artery was occluded for 30 minutes followed by 90 minutes of re-perfusion to produce IR. In the Group DIRA, a branch of the left coronary artery was occluded for 30 minutes followed by 90 minutes of re-perfusion to produce IR, and apelin-13 was administrated via 10 µg.kg-1 IP route 30 minutes before ligating the left coronary artery.Deformability measurements were performed in erythrocyte suspensions containing Htc 5% in a PBS buffer. RESULTS: The deformability index was significantly increased in diabetic rats; however, it was similar in Group DC, DCA and DIRA. It was significantly increased in the Group DIR when compared to the Group C, DIRA, DCA and DC. The relative resistance was increased in IR models. CONCLUSION: Erythrocyte deformability was decreased in rats having diabetes and IR injury. This injury might lead to further problems in microcirculation. It was shown that apeline-13 may be useful in enhancing the adverse effects of this type of injury (Fig. 1, Ref. 35).

Erythrocyte deformability - A partner of the inflammatory response.

We aim to establish an in vivo animal model of acute inflammation using PAF (platelet activating factor) as inflammatory agent and to study the erythrocyte deformability changes induced by the inflammatory response. Counting the number of rolling and adherent neutrophils to endothelium after 2, 4 and 6h of intrascrotal injection of PAF we showed the induction of an inflammatory state. Blood samples are collected in order to measure the erythrocyte deformability and to quantify NO efflux from the red blood cells (RBCs). The results show an increased number of rolling and adherent neutrophils after 2h and 4h of inflammation as well as decreased values of erythrocyte deformability in the same time-points. This result is in line with the need of a low blood viscosity to the recruitment process that will improve leukocyte migration towards the endothelial wall. NO efflux from RBCs is also affected by the inflammatory response at the first hours of inflammation. This animal model demonstrates in vivo the association between an acute inflammatory response and the rheological properties of the blood, namely the RBCs deformability. For those reasons we consider this as an adequate model to study acute inflammatory responses as well as hemorheological parameters.

A Plasmodium falciparum S33 proline aminopeptidase is associated with changes in erythrocyte deformability.

Infection with the apicomplexan parasite Plasmodium falciparum is a major cause of morbidity and mortality worldwide. One of the striking features of this parasite is its ability to remodel and decrease the deformability of host red blood cells, a process that contributes to disease. To further understand the virulence of Pf we investigated the biochemistry and function of a putative Pf S33 proline aminopeptidase (PfPAP). Unlike other P. falciparum aminopeptidases, PfPAP contains a predicted protein export element that is non-syntenic with other human infecting Plasmodium species. Characterization of PfPAP demonstrated that it is exported into the host red blood cell and that it is a prolyl aminopeptidase with a preference for N-terminal proline substrates. In addition genetic deletion of this exopeptidase was shown to lead to an increase in the deformability of parasite-infected red cells and in reduced adherence to the endothelial cell receptor CD36 under flow conditions. Our studies suggest that PfPAP plays a role in the rigidification and adhesion of infected red blood cells to endothelial surface receptors, a role that may make this protein a novel target for anti-disease interventions strategies.

Diabetic foot disease is associated with reduced erythrocyte deformability.

The pathogenesis of diabetic foot disease is multifactorial and encompasses microvascular and macrovascular pathologies. Abnormal blood rheology may also play a part in its development. Using a cell flow analyser (CFA), we examined the association between erythrocyte deformability and diabetic foot disease. Erythrocytes from diabetic patients with no known microvascular complications (n = 11) and patients suffering from a diabetic foot ulcer (n = 11) were isolated and their average elongation ratio (ER) as well as the ER distribution curve were measured. Average ER was decreased in the diabetic foot patients compared with the patients with diabetes and no complications (1·64 ± 0·07 versus 1·71 ± 0·1; P = 0·036). A significant rise in the percentage of minimally deformable red blood cells RBCs in diabetic foot patients compared with the patients with no complications was observed (37·89% ± 8·12% versus 30·61% ± 10·17%; P = 0·039) accompanied by a significant decrease in the percentage of highly deformable RBCs (12·47% ± 4·43% versus 17·49% ± 8·17% P = 0·046). Reduced erythrocyte deformability may slow capillary flow in the microvasculature and prolong wound healing in diabetic foot patients. Conversely, it may be the low-grade inflammatory state imposed by diabetic foot disease that reduces erythrocyte deformability. Further study of the rheological changes associated with diabetic foot disease may enhance our understanding of its pathogenesis and aid in the study of novel therapeutic approaches.