Improve Red Blood Cell Deformability Research Articles

Voxelotor and Red Blood Cell Pyruvate Kinase Activator Affect Clot Strength in Sickle Cell Disease

Introduction: Sickle cell disease (SCD) is a common genetic red blood cell (RBC) disorder that results from a single substitution of valine for glutamic acid in the β-globin gene, resulting in sickle hemoglobin (HbSS). Under hypoxia, HbS polymerizes and forms fibers within the RBCs, thus making the cells rigid, deformed, and sickle-shaped [1]. Deformed RBCs influence the compactness and dynamics of blood clots [2]. In addition, people with SCD are susceptible to thrombophilia [2,3,4]. Recently, there has been a heightened interest in ameliorating SCD using RBCs pyruvate kinase (PKR) activators, which increase ATP and decrease 2,3 DPG, resulting in increased oxygen affinity and improved RBCs deformability [5]. Voxelotor is also an oxygen affinity-modifying drug, recently FDA-approved. Voxelotor delays deoxy-HbSS formation, preventing in vitro HbSS polymerization and RBC sickling, thus improving RBC deformability [6]. The in vitro impact of PKR activators and Voxelotor on blood clotting in clinical samples from people with SCD has not been examined. Here we use a microfluidic dielectric sensor, termed ClotChip ® [7,8], to investigate the effects of Voxelotor and a PKR activator on the clotting time and clot strength of samples from people with SCD. Methods: Venous blood samples were collected in sodium-citrate from subjects with homozygous HbSS and healthy volunteers (HbAA) under an IRB-approved protocol. ClotChip ® microsensors were fabricated as previously described [7]. Blood samples were centrifuged at 200 g for 10 min. Plasma and buffy coats were removed and stored at 4 °Cfor 6 hours. Isolated, washed RBCs were then re-suspended in PBS at 20% hematocrit and then mixed with 67 mg/mL of Voxelotor (GBT440; Selleckchem) to a final concentration of 600 µM (in DMSO) or a PKR activator (PKR activator 3; MedChem Express) at 10 mM (in DMSO) and incubated at 37 °Cfor 6 hours. For controls, HbSS- or HbAA-containing RBCs at 20% hematocrit were mixed with PBS containing 0.5% v/v DMSO and incubated at 37 °C for 6 hours. After incubation, HbSS+Vox, HbSS+PKR, and control samples were centrifuged at 500 g for 10 min to remove PBS. Each sample's plasma was used to reconstitute RBCs at 20% hematocrit. CaCl 2 was added to the samples to induce coagulation, and the samples were injected into the ClotChip ® microfluidic sensors. An Agilent 4294A impedance analyzer was used to obtain the ClotChip ® readout curve defined as the temporal variation of the normalized real part of blood dielectric permittivity at 1 MHz (see Figure 1A). Based on our previous studies [7,8], the time to reach a permittivity peak (T peak) parameter was taken to indicate the clotting time, whereas the maximum change in permittivity after the peak (ΔƐ r,max) parameter was taken to indicate the clot strength. Data are reported as mean ± standard deviation (SD). Results: We analyzed the ClotChip ® T peak and ΔƐ r,max readout parameters for HbSS (n=11), HbSS+Vox (n=11), HbSS+PKR (n=11), and HbAA control (n=8) samples ( Figure 1B). The clot strength was ~50% higher in HbAA than HbSS (HbAA vs. HbSS: p= 0.001, Mann-Whitney test). However, when the SCD samples were treated with Voxelotor, the clot strength was observed to increase by ~10% (HbSS vs. HbSS+Vox, p=0.01, Paired t-test). Treatment with a PKR activator increased the clot strength by ~30% (HbSS vs. HbSS+PKR, p=0.003, Figure 1B). A significant difference was observed in the clotting time between HbAA vs. HbSS (p=0.001) but treatment with Voxelotor or a PKR activator did not change the clotting time for HbSS (HbSS vs. HbSS+Vox, p=0.43; HbSS vs. HbSS+ PKR, p=0.29) ( Figure 1B). (p values were determined using a non-parametric Mann-Whitney test and paired t-test). Discussion : We found that treatment of HbS-containing RBCs with a PKR activator or voxelotor improves clot strength but not clotting time. PKR activators improved the strength of the clot significantly more than Voxelotor. Patients with SCD had a faster clotting time than healthy participants, which agrees with earlier researchers on hypercoagulability in SCD [4]. These data suggest that HbS polymerization and RBC health affect clot characteristics but not clot kinetics in SCD. Further investigations may be required to relate RBC deformability, which is well-known to impact SCD pathophysiology, to blood clotting and venous thromboembolism.

Low-Dose Dietary Fish Oil Improves RBC Deformability without Improving Post-Transfusion Recovery in Mice.

Long-chain polyunsaturated fatty acids (LC-PUFAs) are important modulators of red blood cell (RBC) rheology. Dietary LC-PUFAs are readily incorporated into the RBC membrane, improving RBC deformability, fluidity, and hydration. Female C57BL/6J mice consumed diets containing increasing amounts of fish oil (FO) ad libitum for 8 weeks. RBC deformability, filterability, and post-transfusion recovery (PTR) were evaluated before and after cold storage. Lipidomics and lipid peroxidation markers were evaluated in fresh and stored RBCs. High-dose dietary FO (50%, 100%) was associated with a reduction in RBC quality (i.e., in vivo lifespan, deformability, lipid peroxidation) along with a reduced 24 h PTR after cold storage. Low-dose dietary FO (6.25-12.5%) improved the filterability of fresh RBCs and reduced the lipid peroxidation of cold-stored RBCs. Although low doses of FO improved RBC deformability and reduced oxidative stress, no improvement was observed for the PTR of stored RBCs. The improvement in RBC deformability observed with low-dose FO supplementation could potentially benefit endurance athletes and patients with conditions resulting from reduced perfusion, such as peripheral vascular disease.

Rheological Impact of GBT1118 Cessation in a Sickle Mouse Model.

In sickle cell disease (SCD), higher whole blood viscosity is a risk factor for vaso-occlusive crisis, avascular necrosis, and proliferative retinopathy. Blood viscosity is strongly impacted by hemoglobin (Hb) levels and red blood cell (RBC) deformability. Voxelotor is a hemoglobin S (HbS) polymerization inhibitor with anti-sickling properties that increases the Hb affinity for oxygen, thereby reducing HbS polymerization. In clinical trials, voxelotor increased Hb by an average of 1g/dl, creating concern that this rise in Hb could increase viscosity, particularly when the drug was cleared. To investigate this potential rebound hyperviscosity effect, we treated SCD mice with GBT1118, a voxelotor analog, and stopped the treatment to determine the effect on blood viscosity and RBC deformability under a range of oxygen concentrations. GBT1118 treatment increased Hb, improved RBC deformability by increasing the elongation index under normoxic (EImax) and hypoxic conditions (EImin), and decreased the point of sickling (PoS) without increasing blood viscosity. The anti-sickling effects and improvement of RBC deformability balanced the effect of increased Hb such that there was no increase in blood viscosity. Forty-eight hours after ceasing GBT1118, Hb declined from the rise induced by treatment, viscosity did not increase, and EImin remained elevated compared to control animals. Hb and PoS were not different from control animals, suggesting a return to native oxygen affinity and clearance of the drug. RBC deformability did not return to baseline, suggesting some residual rheological improvement. These data suggest that concerns regarding viscosity rise above pre-treatment levels upon sudden cessation of voxelotor are not warranted.

FT-4202, an oral PKR activator, has potent antisickling effects and improves RBC survival and Hb levels in SCA mice

Sickle cell anemia (SCA) results from an abnormal sickle hemoglobin (HbS). HbS polymerizes upon deoxygenation, resulting in red blood cell (RBC) sickling and membrane damage that cause vaso-occlusions and hemolysis. Sickle RBCs contain less adenosine triphosphate and more 2,3-diphosphoglycerate than normal RBCs, which allosterically reduces hemoglobin (Hb) oxygen (O2) affinity (ie, increases the partial pressure of oxygen at which hemoglobin is 50% saturated with oxygen [P50]), potentiating HbS polymerization. Herein, we tested the effect of investigational agent FT-4202, an RBC pyruvate kinase (PKR) activator, on RBC sickling and membrane damage by administering it to Berkeley SCA mice. Two-week oral FT-4202 administration was well tolerated, decreasing HbS P50 to levels similar to HbA and demonstrating beneficial biological effects. In FT-4202–treated animals, there was reduced sickling in vivo, demonstrated by fewer irreversibly sickled cells, and improved RBC deformability, assessed at varying shear stress. Controlled deoxygenation followed by reoxygenation of RBCs obtained from the blood of FT-4202–treated mice showed a shift in the point of sickling to a lower partial pressure of oxygen (pO2). This led to a nearly 30% increase in RBC survival and a 1.7g/dL increase in Hb level in the FT-4202–treated SCA mice. Overall, our results in SCA mice suggest that FT-4202 might be a potentially useful oral antisickling agent that warrants investigation in patients with SCA.

Standardized microfluidic assessment of red blood cell-mediated microcapillary occlusion: Association with clinical phenotype and hydroxyurea responsiveness in sickle cell disease.

We present a standardized in vitro microfluidic assay and Occlusion Index (OI) for the assessment of red blood cell (RBC)-mediated microcapillary occlusion and its clinical associations in sickle cell disease (SCD). Red blood cell mediated microcapillary occlusion represented by OI and its clinical associations were assessed for seven subjects with hemoglobin-SC disease (HbSC), 18 subjects with homozygous SCD (HbSS), and five control individuals (HbAA). We identified two sub-populations with HbSS based on the OI distribution. HbSS subjects with relatively higher OIs had significantly lower hemoglobin levels, lower fetal hemoglobin (HbF) levels, and lower mean corpuscular volume (MCV), but significantly higher serum lactate dehydrogenase levels and absolute reticulocyte counts, compared to subjects with HbSS and lower OIs. HbSS subjects who had relatively higher OIs were more likely to have had a concomitant diagnosis of intrapulmonary shunting (IPS). Further, lower OI associated with hydroxyurea (HU) responsiveness in subjects with HbSS, as evidenced by significantly elevated HbF levels and MCV. We demonstrated that RBC-mediated microcapillary occlusion and OI associated with subject clinical phenotype and HU responsiveness in SCD. The presented standardized microfluidic assay may be useful for evaluating clinical phenotype and assessing therapeutic outcomes in SCD, including emerging targeted and curative treatments that aim to improve RBC deformability and microcirculatory health.

FT-4202, an Allosteric Activator of Pyruvate Kinase-R, Demonstrates Proof of Mechanism and Proof of Concept after a Single Dose and after Multiple Daily Doses in a Phase 1 Study of Patients with Sickle Cell Disease

FT-4202, an Allosteric Activator of Pyruvate Kinase-R, Demonstrates Proof of Mechanism and Proof of Concept after a Single Dose and after Multiple Daily Doses in a Phase 1 Study of Patients with Sickle Cell Disease

An Adaptive, Randomized, Placebo-Controlled, Double-Blind, Multi-Center Study of Oral FT-4202, a Pyruvate Kinase Activator in Patients with Sickle Cell Disease (PRAISE)

An Adaptive, Randomized, Placebo-Controlled, Double-Blind, Multi-Center Study of Oral FT-4202, a Pyruvate Kinase Activator in Patients with Sickle Cell Disease (PRAISE)

Rheological Impact of GBT1118 Cessation in a Sickle Mouse Model

Background: In sickle cell disease (SCD), elevated blood viscosity is a risk factor for vaso-occlusive crisis (VOC). Blood viscosity is influenced by hemoglobin (Hb) levels, red blood cell (RBC) deformability, density, and aggregation. Voxelotor is an HbS polymerization inhibitor that increases the Hb affinity for oxygen and reduces sickling. In human subjects, voxelotor significantly increases Hb levels. A rise in Hb due to voxelotor does not increase blood viscosity the way a similar increase in unmodified HbS would. However, voxelotor transiently modifies HbS, raising concern that if voxelotor was stopped suddenly, the drug induced extra HbS would revert to its unmodified state, causing a significant rise in blood viscosity and increasing the risk of VOC. This effect could continue until the drug induced Hb is eliminated by hemolysis. To investigate this, we treated a sickle mouse model with GBT1118, a voxelotor analog. We then stopped the treatment and determined the effect on whole blood viscosity, the hematocrit-to-viscosity ratio (HVR), a measure of oxygen carrying capacity, and RBC deformability. As GBT1118 has a half-life of 14 hours in SCD mouse, we measured the post-drug effect 48 hours after drug withdrawal. Methods: Ten Townes HbSS mice were fed control chow, 10 were fed chow containing GBT1118 for 7 days, 10 were fed GBT1118 chow for 7 days, and then returned to control chow for 48 hours. RBC deformability was measured by oxygen gradient ektacytometry (Lorrca with Oxygenscan, RR Mechatronics). Blood viscosity was measured with a cone and plate viscometer (Brookfield DVII+). Hb was measured via ADVIA (Siemens). Results: Treatment with GBT1118 significantly increased Hb without increasing blood viscosity. HVR was increased at both 45 s-1 and 225 s-1 shear rates (Figure 1). GBT1118 treatment also improved RBC deformability under both normoxic (EImax) and hypoxic conditions (EImin). Point of sickling (PoS) was reduced, indicating that treated RBC tolerated lower oxygen concentrations before sickling (Figure 2). When the drug was withdrawn for 48 hours, compared to control animals, 1) Hb declined rapidly (7.1 g/dL in control feed, 13.1 g/dL in treated mice compared to 9.0 g/dL after 48 hours off treatment, P<0.001); 2) viscosity did not increase compared to control feed (at shear rate 45 s-1, 12.8 cP after treatment compared to 11.4 cP in control cohort; at shear rate 225 s-1,10.8 cP after treatment compared to 10.3 cP in controls); 3) HVR returned to baseline (at shear rate 45 s-1, 4.5 after treatment compared to 3.6 in controls; at shear rate 225 s-1, 6.6 after treatment compared to 4 cP in controls), 4) EImin remained elevated (0.16 in controls compared to 0.32 after 48 hours off treatment, P<0.001); 5) Elmax and PoS were not significantly different. Conclusions: The GBT1118-treated sickle mouse had a significant rise in Hb and improvement in PoS and deformability. Forty-eight hours after removing the analog compound, Hb dropped markedly, and the PoS was not different from control animals, suggesting a return to native oxygen affinity and clearance of the drug. Interestingly, deformability (EImin) did not return to baseline, suggesting some residual rheological improvement occurred in the red cell population that did not dissipate when the drug was cleared. These data suggest that potential concerns regarding viscosity rising above pre-treatment levels upon sudden cessation of voxelotor are not warranted. This may be due to retained improvement in red cell rheology after voxelotor is stopped combined with rapid return to baseline Hb levels. Further study in patients treated with voxelotor may be needed to determine if voxelotor produces additional benefits, such as reduction in oxidative stress, that outlive its presence in the red cell. Disclosures Pochron: Global Blood Therapeutics: Current Employment, Current equity holder in publicly-traded company. Oksenberg:Global Blood Therapeutics: Current Employment, Current equity holder in publicly-traded company. Sheehan:Global Blood Therapeutics: Research Funding; Emmaus: Research Funding; Novartis: Research Funding.

Ischemic Preconditioning Enhances Performance and Erythrocyte Deformability of Responders.

This pilot study aimed to evaluate the differential effects of a remote ischemic preconditioning (rIPC) manoeuvre on performance and red blood cell (RBC) deformability compared to a sham control and a placebo setting. Ten male subjects performed three test settings in a single-blind, crossover, and randomized control design. All settings started with 20 min of rest and were followed by 4 cycles of occlusion/reperfusion consisting of 5 min each. During rIPC and placebo, the cuff pressure was inflated to 200 mmHg and 120 mmHg, respectively. During the sham control setting, 10 mmHg pressure was applied. All tests were followed by a cycle exercise with lactate diagnostics. Power at 2 and 4 mmol/l lactate thresholds were calculated. RBC deformability was measured before and after the respective manoeuvre. Results showed that no effect resulted from any manoeuvre on performance values or RBC deformability. But 6 subjects showed a higher power at the 2 mmol/l threshold, and 5 subjects exerted higher power at the 4 mmol/l threshold when the rIPC manoeuvre preceded the exercise. In these responsive subjects, RBC deformability also improved. Hence, rIPC effects are much influenced by the subjects' responsiveness, and improved RBC deformability might contribute to enhanced performance in responsive subjects.

Speed Modulation of the HeartWare HVAD to Assess In Vitro Hemocompatibility of Pulsatile and Continuous Flow Regimes in a Rotary Blood Pump.

Although rotary blood pumps (RBPs) sustain life, blood exposure to continuous supra-physiological shear stress induces adverse effects (e.g., thromboembolism); thus, pulsatile flow in RBPs represents a potential solution. The present study introduced pulsatile flow to the HeartWare HVAD using a custom-built controller and compared hemocompatibility biomarkers (i.e., platelet aggregation, concentrations for ADAMTS13, von Willebrand factor (vWf), and free-hemoglobin in plasma (pfHb), red blood cell (RBC) deformability, and RBC-nitric oxide synthase(NOS) activity) between continuous and pulsatile flow in a blood circulation loop over 5 h. The HeartWare HVAD was operated using a custom-built controller, atcontinuous speed (3282 rev/min) or in a pulsatile mode (mean speed = 3273 rev/min, amplitude = 430 rev/min, frequency = 1 Hz) to generate a blood flow rate of 5.0 L/min, HVAD differential pressure of 90 mm Hg for continuous flow and 92 mm Hg for pulsatile flow, and systolic and diastolic pressures of 121/80 mm Hg. For bothflow regimes, the current study found; (i) ADP- and collagen-induced platelet aggregation, and ADAMTS13 concentration significantly decreased after 5 h (P < 0.01; P < 0.05), (ii) ristocetin-induced platelet aggregation significantly increased after 45 min (P < 0.05), (iii) vWf concentration did not significantly differ at any time point, (iv) pfHb significantly increased after 5 h (P < 0.01), (v) RBC deformability improved during the continuous flow regime (P < 0.05) but not during pulsatile flow, and (vi) RBC-NOS activity significantly increased during continuous flow (15 min), and pulsatile flow (5 h; P < 0.05). The current study demonstrated: (i) speed modulation does not improve hemocompatibility of the HeartWare HVAD based on no observable differences being detected for routine biomarkers, and (ii) the time-course for increased RBC-NOS activity observed during continuous flow mayhave improved RBC deformability.

Regulation of red blood cell deformability is independent of red blood cell-nitric oxide synthase under hypoxia.

The aim was to study impacts of mild to severe hypoxia on human red blood cell (RBC)-nitric oxide synthase (NOS)-dependent NO production, protein S-nitrosylation and deformability.Ambient air oxygen concentration of 12 healthy subjects was step-wisely reduced from 20.95% to 16.21%, 12.35%, 10% and back to 20.95%. Additional in vitro experiments involved purging of blood (±sodium nitrite) with gas mixtures corresponding to in vivo intervention.Vital and hypoxia-associated parameters showed physiological adaptation to changing demands. Activation of RBC-NOS decreased with increasing hypoxia. RBC deformability, which is influenced by RBC-NOS activation, decreased under mild hypoxia, but surprisingly increased at severe hypoxia in vivo and in vitro. This was causatively induced by nitrite reduction to NO which increased S-nitrosylation of RBC α- and β-spectrins -a critical step to improve RBC deformability. The addition of sodium nitrite prevented decreases of RBC deformability under hypoxia by sustaining S-nitrosylation of spectrins suggesting compensatory mechanisms of non-RBC-NOS-produced NO.The results first time indicate a direct link between maintenance of RBC deformability under severe hypoxia by non-enzymatic NO production because RBC-NOS activation is reduced. These data improve our understanding of physiological mechanisms supporting adequate blood and, thus, oxygen supply to different tissues under severe hypoxia.

Varied Walking Dose In Women With Type 2 Diabetes: Heart Rate Variability And Hemorheology Responses

Type 2 diabetes accelerates and exacerbates the age-related decline in heart rate variability (HRV) and impairment of hemorheology. While exercise training is one of the cornerstone therapies for managing type 2 diabetes, little is known about the optimum dose of exercise training for the improvement of HRV and/or hemorheology. PURPOSE: To investigate HRV and hemorheology adaptations to 12 wk of varied-dose treadmill walking in women aged 65-74 yr with type 2 diabetes. METHODS: Fifteen subjects with uncomplicated type 2 diabetes (Age: 69 ± 2 yr; BMI: 30 ± 5 kg·m-2; VO2peak: 20.3 ± 3.1 ml·kg-1·min-1) were randomly allocated into two exercise training groups (Group 1: 2 x 60 min·wk-1 or Group 2: 4 x 30 min·wk-1). The exercise program was 12 wk and the exercise intensity was set and adjusted every 6 wk to equal 100% of each individual’s gas-exchange threshold. Time domain indices of HRV included i. the standard deviation of RR intervals (SDNN) ii. the square root of the mean of squared differences between successive intervals (RMSSD). Frequency domain indices of HRV included: log-transformed low and high frequency (lnLF and lnHF, respectively) power. Red blood cell (RBC) aggregation was measured in plasma and a standard aggregating solution (3% dextran 70 kDa), and RBC deformability was determined via ektacytometry. Dependent variables were measured before (wk -6 and 0), during (wk 6) and after (wk 12) the walking program. RESULTS: Twelve weeks of exercise training significantly improved VO2peak, time to exhaustion, and the gas-exchange threshold (p < 0.05), independent of exercise group. While exercise training did not improve glycemic control, high-density lipoprotein concentration increased by 7.5% for both groups (p = 0.01). Exercise training reduced RBC aggregation in plasma by -6.6% and in dextran-70 by -12.2% (p < 0.05), and improved RBC deformability by 3.4% (p < 0.05) for both groups. No change in HRV was observed for Group 1, whereas SDNN, RMSSD and lnHF power were improved in Group 2 (p < 0.05). CONCLUSIONS: These results suggest that the accumulated weekly exercise duration may be the most important training component for the prescription of exercise in older women with type 2 diabetes. Exercise frequency should be considered, however, when prescribing exercise to improve HRV.

Effects of different resuscitation fluids on the rheologic behavior of red blood cells, blood viscosity and plasma viscosity in experimental hemorrhagic shock

Background Hemorrhagic shock is associated with severe rheological abnormalities. We hypothesized that in the setting of hemorrhagic shock, resuscitation can alter hemorheological characteristics dramatically, and different fluids cause different effects. The aim of this study was to investigate whether the type of fluid administered has an impact on hemorheological characteristics at the early stage of resuscitation in a rodent model of hemorrhagic shock. Methods Animals were randomized into five groups: (1) sham hemorrhage (SHAM); (2) shock and sham resuscitation (SHOCK); (3) shock and resuscitation with normal saline 32 ml/kg (NS); (4) shock and resuscitation with 7.5% hypertonic saline 4 ml/kg (HS); (5) shock and resuscitation with 7.5% hypertonic saline/6% Dextran 70 4 ml/kg (HSD). Hemorheological characteristics were measured at 60 min after resuscitation. Results Results showed that NS resuscitation deteriorated red blood cell (RBC) deformability compared with the SHOCK group. The HS group showed improved RBC deformability compared with the NS group, although the differences were not statistically significant. There were significant improvements of RBC deformability at all shear rates in the HSD group compared with the NS group. Whole blood and plasma viscosities decreased significantly in the SHOCK group compared with the SHAM group. At shear rates of 60 and 150 s −1, the NS group decreased whole blood viscosity compared with the SHOCK group. The HSD group showed elevated plasma viscosity compared with the SHOCK, NS and HS groups. Conclusion These results suggested that at the early stage of hemorrhagic shock resuscitation, hypertonic–hyperoncotic resuscitation could improve RBC deformability compared with isotonic crystalloid resuscitation. Dextran 70 could elevate plasma viscosity to nearly baseline level. These effects of hypertonic–hyperoncotic resuscitation could be beneficial to maintain microcirculation.

Effect of sulfite on red blood cell deformability ex vivo and in normal and sulfite oxidase-deficient rats in vivo

The effect of sulfite, a widely used food additive, on red blood cell deformability ex vivo and in vivo was investigated. Ex vivo experiments were conducted in human blood exposed to sulfite (5, 10 and 20 mM). In vivo experiments were carried out in sulfite oxidase-competent (SOXC) and sulfite oxidase-deficient (SOXD) rats. In the in vivo experiments, sulfite was administered in the form of sodium metabisulfite (Na(2)S(2)O(5), 25 mg/kg/day) via drinking water. Vitamin E dissolved in olive oil at a dose of 50 mg/kg was administered by gastric gavages. Red blood cell (RBC) deformability was determined at various fluid shear stresses using an ektacytometer. Ex vivo sulfite exposure to RBC did not affect RBC deformability. In the in vivo experiments, although RBC deformability was not affected by sulfite treatment in SOXD rats, it was found to be significantly increased in SOXC rats. Vitamin E treatment in combination with sulfite caused impairment in RBC deformability in both SOXC and SOXD rats. We suggest that sulfite needs to be oxidized in order to improve RBC deformability.

Evaluation of Red Blood Cell Deformability and Uterine Blood Flow in Pregnant Women with Preeclampsia or IUGR and Reduced Uterine Blood Flow Following the Intravenous Application of Magnesium

Objective: Red blood cell (RBC) deformability is one of the factors determining microcirculation. In preeclampsia (PE) and some cases of intrauterine growth restriction (IUGR), RBC deformability and, consequently, microcirculation appear to be impaired. Magnesium sulfate is administered to reduce the risk of seizures in PE. The aim of our study was to detect the effect of 24‐hour intravenous (IV) magnesium on RBC deformability and on uterine artery blood flow in pregnant patients with preeclampsia or IUGR and pathologic uterine blood flow. Methods: Magnesium IV (1 g/h) was administered to 25 pregnant women with reduced uterine blood flow for a period of at least 24 hours. The RBC deformability was measured by laser diffractoscopy, blood volume flow was measured by uterine artery Doppler. Measurements were taken before the start of magnesium therapy and 24 h later. Magnesium plasma levels were measured at the same time. Results: High plasma levels of magnesium improve RBC deformability from E = 0,109 (SD ± 0.023) to E = 0.115 (SD ± 0.021) after 24 h IV magnesium (p = 0.043). There is no correlation of E to the plasma magnesium level either before or after 24 h magnesium treatment. Blood volume flow in the uterine arteries increased significantly from 5.09 mL/s (SD ± 3.03) to 10.02 mL/s (SD ± 5.86) after 24 h magnesium (p = 0.0002). The differences in the resistance index do not significantly differ from 0 (p = 0.46). Conclusion: A high IV dosage of magnesium over a period of 24 hours dilates the uterine arteries of pregnant women with PE and/or IUGR, reduces uterine blood flow, and improves the deformability of RBC. Both parameters enhance the oxygen supply to the fetus, a critical parameter in these pregnancies. Thus magnesium might not only be effective as phrophylaxis against seizures but also in cases of IUGR with a reduced uterine blood flow. The clinically observed beneficial effect of magnesium in PE could be due to the improved blood supply for the fetus.

The Effects of KBT-3022, a New Anti-platelet Agent, on Hemorheological Properties in Guinea Pigs

Using guinea pigs, a study was conducted on the effects of KBT-3022, a new anti-platelet agent, on hemorheological properties in various tests including blood filterability, blood viscosity, shear stress-induced red blood cell (RBC) deformability and contents of ATP and 2,3-diphosphoglycerate (2,3-DPG). Oral administration of KBT-3022 at 1 and 10 mg/kg significantly increased blood filterability, and significantly reduced blood viscosity at 10 mg/kg without changing the hematocrit, plasma fibrinogen concentration or plasma viscosity. KBT-3022 (10 mg/kg, p.o.) improved RBC deformability in response to shear stress, which was evoked by passing the blood through a thin tube. This dose of KBT-3022 also increased the contents of ATP and 2,3-DPG in RBC. These findings indicate that KBT-3022 may reduce blood viscosity as a sequel to improvement of RBC deformability through direct action on RBC. The increase in the intracellular levels of ATP and 2,3-DPG was considered to be involved in this improvement of hemorheological properties. These hemorheological effects of KBT-3022 appear to be promising for the treatment of patients with ischemic vascular disease.

Linoleate-Rich Triacylglycerol inPanax pseudo-ginsengImproves Erythrocyte Deformabilityin vitro

With Reid's filtration techniques as a bioassay for evaluating red blood cell (RBC) deformability, we purified from Panax pseudo-ginseng an active component that improved the deformability of calcium-loaded RBC. NMR and mass spectrometric studies showed that the purified substance was a triacylglycerol (TG) with linoleic acid as the major fatty acid residue in the esterified positions of glycerol. The mechanism for this TG to improve RBC deformability could be a modification of membrane fluidity rather than a competitive antagonism with calcium ion.

Effect of triacylglycerols on erythrocyte deformability in vitro

With Reid's filtration technique as a bioassay for evaluating red blood cell (RBC) deformability, we found that tripalmitolein, triolein and trilinolein improved the deformability of calcium-loaded RBC while glycerol, linoleic acid, dilinoleoyl phosphatidyl choline, trilpalmitin, tristearin, trilinolenin and triarachidonin did not. Maximal effect of tripalmitolein, triolein and trilinolein was achieved at 10 −9, 10 −10 and 10 −8 M respectively. We propose that only those triacylglycerols which contain fatty acids with one or two double bonds could modify RBC membrane fluidity and improve RBC deformability.

The etiopathogenesis of premenstrual syndrome as a consequence of altered blood rheology: a new hypothesis

The multisystem symptoms of premenstrual syndrome (PMS), the variable nature of their occurrence and their relatively rapid disappearance with the onset of bleeding are highly suggestive of a systemic factor as the causal agent of the disorder. Reports of increased blood viscosity and enhanced red blood cell (RBC) hydration provide a basis for proposing that PMS is the consequence of an aberration of the change in blood viscosity which occurs in the third week of the normal menstrual cycle. The seriousness of the viscosity-impaired capillary blood flow will be greatest in organs and capillary beds with the smallest capillaries. Such an assumption implies that those women who suffer from PMS will be individuals whose capillaries are smaller in size than non-sufferers. The frequency of occurrence of fluid retention as a symptom suggests that the specific etiologic agent could be a reduction in RBC deformability as a consequence of impaired linoleic acid metabolism or high levels of noradrenaline or hypothyroidism or combinations of the three factors. If poorly deformable RBCs are involved then the use of agents such as evening primrose oil or fish oil to improve RBC deformability could ameliorate the symptoms of PMS. It is speculated that similar changes in RBC deformability should occur at other times of hormonal change. Health problems occurring during pregnancy, or after parturition, or after cessation of ovarian function might be caused by or exacerbated by reduced RBC deformability.