Membrane Lipid Alterations in Hemoglobinopathies

Catalase, Glutathione Peroxidase, and Peroxiredoxin 2 in Erythrocyte Cytosol and Membrane in Hereditary Spherocytosis, Sickle Cell Disease, and β-Thalassemia

Catalase (CAT), glutathione peroxidase (GPx), and peroxiredoxin 2 (Prx2) can counteract the deleterious effects of oxidative stress (OS). Their binding to the red blood cell (RBC) membrane has been reported in non-immune hemolytic anemias (NIHAs). Our aim was to evaluate the relationships between CAT, GPx, and Prx2, focusing on their role at the RBC membrane, in hereditary spherocytosis (HS), sickle cell disease (SCD), β-thalassemia (β-thal), and healthy individuals. The studies were performed in plasma and in the RBC cytosol and membrane, evaluating OS biomarkers and the enzymatic activities and/or the amounts of CAT, GPx, and Prx2. The binding of the enzymes to the membrane appears to be the primary protective mechanism against oxidative membrane injuries in healthy RBCs. In HS (unsplenectomized) and β-thal, translocation from the cytosol to the membrane of CAT and Prx2, respectively, was observed, probably to counteract lipid peroxidation. RBCs from splenectomized HS patients showed the highest membrane-bound hemoglobin, CAT, and GPx amounts in the membrane. SCD patients presented the lowest amount of enzyme linkage, possibly due to structural changes induced by sickle hemoglobin. The OS-induced changes and antioxidant response were different between the studied NIHAs and may contribute to the different clinical patterns in these patients.

Lipid and hemolysis parameters predicting acute chest syndrome in adulthood with sickle cell disease

Sickle cell disease (SCD) is a lifelong blood disorder affecting approximately 100,000 people in the United States and is one of the most common monogenic diseases. A serious complication of SCD is acute chest syndrome (ACS). ACS is a condition with a high rate of morbidity and mortality. The aim of the study was to assess hemolysis and lipid parameters in a cohort of confirmed SCD patients to predict ACS development in the following year.Standard lipid were performed (triglycerides, total cholesterol, high-density cholesterol, low-density cholesterol) panel to calculate of non-HDL-C, large buoyant LDL cholesterol (lbLDL-C) and small dense LDL cholesterol (sdLDL-C) with Sampson equation. Hemolysis and hematologic parameters were also evaluated.Among 91 patients included between September 2018 and June 2021, thirty-seven patients had history of ACS and 6 patients developed ACS during following year. In unadjusted logistic regression, total bilirubin was associated with ACS occurrence (RR: 1.2 [1.05-1.51] p = 0.013). Concerning lipid profile, non-HDL-C (RR: 0.87 [0.0.67-0.99] p = 0.04) and sdLDL-C (RR: 0.78 [0.49-0.96] p = 0.03) were associated with ACS occurrence decrease. C-reactive protein was associated with ACS occurrence (RR: 1.27 [1.065-1.85] p = 0.011).Based on these findings, this study demonstrated that several biomarker easily available can be used at steady state to predict ACS in the following year. The validation of these results are required to ensure the reproducibility of the findings.

The significance of antiglobulin (Coombs) test reactivity in patients with COVID-19

Previous case reports have described patients with COVID-19-associated autoimmune hemolytic anemia (AIHA), and cold agglutinin disease (CAD) which is characterized by a positive direct antiglobulin (DAT) or "Coombs" test, yet the mechanism is not well understood. To investigate the significance of Coombs test reactivity among COVID-19 patients, we conducted a retrospective study on hospitalized COVID-19 patients treated at NMC Royal Hospital between 15 April and 30 May 2020. There were 27 (20%) patients in the Coombs-positive group and 108 (80%) in the Coombs-negative group. The cold agglutinin titer was examined in 22 patients due to symptoms suggestive of cold agglutinin disease, and all tested negative. We demonstrated a significant association with reactive Coombs test results in univariate analysis through clinical findings such as ICU admission rate, the severity of COVID-19, and several laboratory findings such as CRP, D-dimer, and hemoglobin levels lactate dehydrogenase, and RDW-CV. However, only hemoglobin levels and disease severity had a statistically significant association in multivariate analysis. A possible explanation of COVID-19-associated positive Coombs is cytokine storm-induced hyperinflammation, complement system activation, alterations of RBCs, binding of SARS-CoV-2 proteins to hemoglobin or its metabolites, and autoantibody production. Coombs-positive patients were tested for hemolysis using indirect bilirubin, consumed haptoglobin, and/or peripheral smear that ruled out any evidence of hemolysis. Understanding this etiology sheds new light on RBC involvement as a pathophysiological target for SARS-CoV-2 by interfering with their function; consequently, therapies capable of restoring RBC function, such as erythrocytapheresis, could be repurposed for the treatment of worsening severe and critical COVID-19.

Complement in sickle cell disease and targeted therapy: I know one thing, that I know nothing

Sickle cell disease (SCD) is a common inherited clinical syndrome, characterized by the presence of hemoglobin S. Anemia, susceptibility to infections and episodes of vaso-occlusive crisis (VOC) are among its features. Since SCD complications (VOC or delayed hemolytic transfusion reaction/DHTR) lead to significant morbidity and mortality, a number of studies have addressed their pathophysiology Although SCD pathophysiology has been mainly attributed to the interaction between sickle cells and neutrophils, platelets or endothelial cells in small vessels leading to hemolysis, the role of complement activation has been increasingly investigated. Importantly, complement inhibition with eculizumab has shown beneficial effects in DHTR. Given the unmet clinical need of novel therapeutics in SCD, our review summarizes current understanding of (a) complement system for the clinician, (b) complement activation in SCD both in asymptomatic state and severe clinical manifestations, (c) probable underlying mechanisms of complement activation in SCD, and (d) new therapeutic perspective of complement inhibition.

Whole-blood PUFA and associations with markers of nutritional and health status in acutely malnourished children in Cambodia

OBJECTIVE

To measure fatty acid composition, particularly whole-blood PUFA content, in acutely malnourished children and identify associations with markers of nutritional and health status.

DESIGN

PUFA were assessed in dried blood spots obtained from a cross-sectional study. Nutritional and health status were assessed by anthropometry, haemoglobinopathies, inflammation and blood counts.

SETTING

Cambodia.

PARTICIPANTS

The study was conducted with 174 children aged 0·5-18 years with acute malnutrition.

RESULTS

Among total fatty acids (FA), the relative percentage of total PUFA was 20 % FA, with 14 % of the children having very low PUFA (mead acid (MA):arachidonic acid (AA) >0·02, n-6 docosapentaenoic acid:DHA >0·2 and total n-6:n-3 PUFA >10·5). Wasting was not associated with any PUFA. Stunting and low height were consistently positively associated with total PUFA and positively with n-6 PUFA. Height was positively associated with n-3 long-chain PUFA (LCPUFA). The presence of haemoglobinopathies or inflammation was positively associated with MA:AA, but not total PUFA. Elevated blood platelet counts were positively correlated with linoleic acid and appeared to be influenced by anaemia (P = 0·010) and inflammation (P = 0·002). Monocyte counts were high during inflammation (P = 0·052) and correlated positively with n-6 LCPUFA and n-3 LCPUFA.

CONCLUSIONS

Children with acute malnutrition or stunting had low PUFA, while elevated platelets and monocytes were associated with high PUFA. In acutely malnourished children, inflammation could lead to elevated blood cell counts resulting in increased whole-blood PUFA which does not reflect dietary intake or nutritional status.

Enhanced phosphocholine metabolism is essential for terminal erythropoiesis

Red cells contain a unique constellation of membrane lipids. Although much is known about regulated protein expression, the regulation of lipid metabolism during erythropoiesis is poorly studied. Here, we show that transcription of PHOSPHO1, a phosphoethanolamine and phosphocholine phosphatase that mediates the hydrolysis of phosphocholine to choline, is strongly upregulated during the terminal stages of erythropoiesis of both human and mouse erythropoiesis, concomitant with increased catabolism of phosphatidylcholine (PC) and phosphocholine as shown by global lipidomic analyses of mouse and human terminal erythropoiesis. Depletion of PHOSPHO1 impaired differentiation of fetal mouse and human erythroblasts, and, in adult mice, depletion impaired phenylhydrazine-induced stress erythropoiesis. Loss of PHOSPHO1 also impaired phosphocholine catabolism in mouse fetal liver progenitors and resulted in accumulation of several lipids; adenosine triphosphate (ATP) production was reduced as a result of decreased oxidative phosphorylation. Glycolysis replaced oxidative phosphorylation in PHOSPHO1-knockout erythroblasts and the increased glycolysis was used for the production of serine or glycine. Our study elucidates the dynamic changes in lipid metabolism during terminal erythropoiesis and reveals the key roles of PC and phosphocholine metabolism in energy balance and amino acid supply.

Sickle cell disease

Sickle cell disease (SCD) is a group of inherited disorders caused by mutations in HBB, which encodes haemoglobin subunit β. The incidence is estimated to be between 300,000 and 400,000 neonates globally each year, the majority in sub-Saharan Africa. Haemoglobin molecules that include mutant sickle β-globin subunits can polymerize; erythrocytes that contain mostly haemoglobin polymers assume a sickled form and are prone to haemolysis. Other pathophysiological mechanisms that contribute to the SCD phenotype are vaso-occlusion and activation of the immune system. SCD is characterized by a remarkable phenotypic complexity. Common acute complications are acute pain events, acute chest syndrome and stroke; chronic complications (including chronic kidney disease) can damage all organs. Hydroxycarbamide, blood transfusions and haematopoietic stem cell transplantation can reduce the severity of the disease. Early diagnosis is crucial to improve survival, and universal newborn screening programmes have been implemented in some countries but are challenging in low-income, high-burden settings.

Pathways to pulmonary hypertension in sickle cell disease: the search for prevention and early intervention

INTRODUCTION

Pulmonary hypertension (PH) develops in a significant number of patients with sickle cell disease (SCD), resulting in increased morbidity and mortality. This review focuses on PH pathophysiology, risk stratification, and new recommendations for screening and treatment for patients with SCD. Areas covered: An extensive PubMed literature search was performed. While the pathophysiology of PH in SCD is yet to be fully deciphered, it is known that the etiology is multifactorial; hemolysis, hypercoagulability, hypoxemia, ischemic-reperfusion injury, oxidative stress, and genetic susceptibility all contribute in varying degrees to endothelial dysfunction. Hemolysis, in particular, seems to play a key role by inciting an imbalance in the regulatory axis of nitric oxide and arginine metabolism. Systematic risk stratification starting in childhood based on clinical features and biomarkers that enable early detection is necessary. Multi-faceted, targeted interventions, before irreversible vasculopathy develops, will allow for improved patient outcomes and life expectancy. Expert commentary: Despite progress in our understanding of PH in SCD, clinically proven therapies remain elusive and additional controlled clinical trials are needed. Prevention of disease starts in childhood, a critical window for intervention. Given the complex and multifactorial nature of SCD, patients will ultimately benefit from combination therapies that simultaneously targets multiple mechanisms.

Fatty acids composition in erythrocyte membranes of athletes after one and after a series of whole body cryostimulation sessions

Whole body cryotherapy (WBC) is a treatment often used by athletes as part of biological renewal. Despite the large interest in this form therapy there is still a lack of information on the effects of WBC on the concentration of fatty acids in erythrocyte membranes. Our study aimed at comparing the fatty acids (FA) composition of erythrocyte membranes of athletes after one session and after a series of sessions of whole body cryostimulation. In our study small changes in the level of total cholesterol (decrease) were observed 24 h after a single session. After the twelfth session of whole body cryostimulation, the level of saturated fatty acids (SFA), mainly palmitic acid (C16:0) and n-3 fatty acid eicosapentaenoic (EPA, C20:5n-3) increased almost two-times fold in the red blood cell membranes. The level of n-6 polyunsaturated fatty acids (PUFA n-6), mainly gamma-linolenic acid (C18:3n-6) as well as trans fatty acids (elaidic acid) decreased in the erythrocyte membranes from men after a series of session in a cryochamber, when compared to the control sample. The n-3/n-6 FA ratio in the erythrocyte membranes was higher after twelfth session in a cryochamber in comparison to the control sample. The data obtained during our study will be important for further research regarding the biochemistry of lipids in men after sessions of whole body cryostimulation.

Hypoxia-mediated impaired erythrocyte Lands' Cycle is pathogenic for sickle cell disease

Although Lands' cycle was discovered in 1958, its function and cellular regulation in membrane homeostasis under physiological and pathological conditions remain largely unknown. Nonbiased high throughput metabolomic profiling revealed that Lands' cycle was impaired leading to significantly elevated erythrocyte membrane lysophosphatidylcholine (LysoPC) content and circulating and erythrocyte arachidonic acid (AA) in mice with sickle cell disease (SCD), a prevalent hemolytic genetic disorder. Correcting imbalanced Lands' cycle by knockdown of phospholipase 2 (cPLA2) or overexpression of lysophosphatidycholine acyltransferase 1 (LPCAT1), two key enzymes of Lands' cycle in hematopoietic stem cells, reduced elevated erythrocyte membrane LysoPC content and circulating AA levels and attenuated sickling, inflammation and tissue damage in SCD chimeras. Human translational studies validated SCD mouse findings and further demonstrated that imbalanced Lands' cycle induced LysoPC production directly promotes sickling in cultured mouse and human SCD erythrocytes. Mechanistically, we revealed that hypoxia-mediated ERK activation underlies imbalanced Lands' cycle by preferentially inducing the activity of PLA2 but not LPCAT in human and mouse SCD erythrocytes. Overall, our studies have identified a pathological role of imbalanced Lands' cycle in SCD erythrocytes, novel molecular basis regulating Lands' cycle and therapeutic opportunities for the disease.

Getting to the Outer Leaflet: Physiology of Phosphatidylserine Exposure at the Plasma Membrane

Phosphatidylserine (PS) is a major component of membrane bilayers whose change in distribution between inner and outer leaflets is an important physiological signal. Normally, members of the type IV P-type ATPases spend metabolic energy to create an asymmetric distribution of phospholipids between the two leaflets, with PS confined to the cytoplasmic membrane leaflet. On occasion, membrane enzymes, known as scramblases, are activated to facilitate transbilayer migration of lipids, including PS. Recently, two proteins required for such randomization have been identified: TMEM16F, a scramblase regulated by elevated intracellular Ca(2+), and XKR8, a caspase-sensitive protein required for PS exposure in apoptotic cells. Once exposed at the cell surface, PS regulates biochemical reactions involved in blood coagulation, and bone mineralization, and also regulates a variety of cell-cell interactions. Exposed on the surface of apoptotic cells, PS controls their recognition and engulfment by other cells. This process is exploited by parasites to invade their host, and in specialized form is used to maintain photoreceptors in the eye and modify synaptic connections in the brain. This review discusses what is known about the mechanism of PS exposure at the surface of the plasma membrane of cells, how actors in the extracellular milieu sense surface exposed PS, and how this recognition is translated to downstream consequences of PS exposure.

The effect of erythrocyte membranes from diabetic and hypercholesterolemic individuals on human carbonic anhydrase II activity

CONTEXT

Erythrocyte membranes regulate many enzyme activities, including carbonic anhydrase II (CA II). Membrane fluidity is associated with alterations in protein function and protein-protein interactions.

OBJECTIVE

The purpose of this study was to show the human CA II (hCA II) activity regulation by human erythrocyte membranes from diabetic and hypercholesterolemic subjects.

MATERIALS AND METHODS

Erythrocyte membranes were obtained from diabetic, hypercholesterolemic, and healthy subjects. hCA II activity was measured using the electrometric method.

RESULTS

hCA II activity was increased in vitro by membranes from both diabetic and hypercholesterolemic patients, with hypercholesterolemic membranes exhibiting a greater increase.

CONCLUSION

Changes in membrane composition may affect the erythrocyte membranes' capacity to increase in vitro hCA II activity.

The hypercoagulable status in common Mediterranean β-thalassaemia mutations trait

INTRODUCTION

The coagulation activation in β-thalassaemia is multifactorial and most likely a consequence of the exposure of phosphatidylserine (PS) on RBCs surface. The degree of PS exposure and procoagulant activity of RBCs in β-thalassaemia trait (BTT) subjects carrying common Mediterranean mutations were assessed.

METHODS

Eighty BTT subjects carrying common Mediterranean mutations (β+, n = 53 and β0 , n = 27) and sixty healthy subjects served as controls were studied. Plasma prothrombin fragment 1+2 (F1+2), percentage of PS expression on RBCs membrane, clotting times of modified thromboplastin generation test (MTGT) and modified partial thromboplastin with kaolin (MPTTK) were estimated.

RESULTS

The percentage of annexin V positive RBCs and plasma F1+2 had a significant increase and MTGT had a significant decrease in BTT subjects versus controls and in β0 group versus β+ group. MPTTK was significantly shorter in BTT subjects than controls, but no significant deference between BTT subjects. The percentage of annexin V positive RBCs showed a significant negative correlation with haemoglobin level, MTGT and MPTTK, and a significant positive correlation with plasma F1+2.

CONCLUSION

BTT subjects may have a risk of hypercoagulable state particularly in β0 genotype. Measurement of PS exposure on RBCs and the plasma F1+2 is useful to evaluate hypercoagulability state.

Erythrocytic phosphatidylserine exposure and hemostatic alterations in β-thalassemia intermediate patients

INTRODUCTION

Hypercoagulable state is one of the common findings in beta-thalassemia intermedia (β-TI), particularly in splenectomized patients, with infrequent blood transfusion. Abnormality of the red blood cells (RBC) membrane due to oxidative damage is suggestive of possible etiologies. Membrane lipid peroxidation increases the exposure of phosphatidylserine (PS) that plays a role in the activation of coagulation factors V and X, subsequently initiating thrombosis. Our aim of this study was to find the probable correlation of the alteration of the PS on the RBC outer membrane with the hypercoagulable state in the β-TI patients.

MATERIALS AND METHODS

Our cross-sectional study was conducted on 39 splenectomized β-TI patients and 38 age-matched healthy controls. The mean age was 37 years. Analysis of the PS exposure on the RBCs was performed by fluorescein isothiocyanate (FITC) conjugated AV protein. Measurement of the coagulation factors X, V and antithrombin III (AT-III) was performed. We also checked the D-dimer levels. Analysis was performed by SPSS16.

RESULTS

Fluorescence of FITC-Annexin V labeling on patients RBCs were higher than healthy controls; (2.8 ± 2.2%) of the patients versus (0.4 ± 0.18%) in the control group and was statistically significant (P < 0.05). Mean levels of factor X and AT-III of the patients as compared with the control group decreased and showed significant difference (P < 0.05).

CONCLUSIONS

Circulation of thalassemic RBCs, which abnormally possess PS on RBC membrane outer surface, suggests the possibility of the gradual consumption of the coagulation factors in the presence of a chronic coagulability state.

Effect of lead on lipid peroxidation, phospholipids composition, and methylation in erythrocyte of human

Lead (Pb) is one of the most abundant heavy metals on earth considered as number one environmental persistent toxin and health hazard affecting millions of people in all age groups. After entering bloodstream, 99% of Pb is accumulated in erythrocytes and causes poisoning. Toxic Pb effects on erythrocytes membrane's composition of phosphatidyl serine (PS), phosphatidyl ethanolamine (PE), phosphatidyl choline (PC), and sphingomyelin (SM), and phospholipids transmethylation were determined. Lipid peroxidation in Pb-exposed erythrocytes was evaluated as malondialdehyde (MDA) formation in presence of Fe and vitamin E to understand severity of Pb toxicity and its mitigation. Pb (0.5-5.0 μM) degraded PS (12 to 31%, P < 0.05-0.001) and elevated SM (19-51%, P < 0.05-0.001). Composition of PC and PE were diminished (22%) and elevated (29%), respectively, with higher Pb exposure (5.0 μM, P < 0.001). Pb toxicity suppressed (P < 0.001) transmethylation of phospholipids in membranes (34, 41, and 50%, respectively, with 0.5, 2.5, and 5.0 μM). Pb-induced dose-related MDA production (P < 0.05-0.001) in erythrocytes was obtained, which was accentuated in presence of Fe (P < 0.05-0.001). The vitamin E mitigated (P < 0.05-0.01) the severity of Pb-induced lipid peroxidation. The ratio PS/SM showed maximum change of -27 (P < 0.01), -30 (P < 0.01), and -54% (P < 0.001), respectively at 0.5, 2.5, and 5.0 μM Pb exposures. Ratios PC/SM and PS/PE were at the second, whereas PE/PS at the third order. The study suggests that the mechanisms underlying distortion of compositional phospholipids, inhibition of transmethylation, and exasperated phospholipid peroxidative damage are the active phenomena of Pb toxicity in erythrocytes.

A two-event in vitro model of acute chest syndrome: the role of secretory phospholipase A2 and neutrophils

BACKGROUND

Acute chest syndrome (ACS) in sickle cell disease is associated with elevation of secretory phospholipase A(2) (sPLA(2) ). We hypothesize that sPLA(2) cleaves membrane lipids from sickled red blood cells (RBCs) causing PMN-mediated endothelial cell injury (ECI) as the second event in a two-event model.

METHODS

Whole blood was collected from children when in steady state or daily during admissions for vaso-occlusive pain (VOC) or ACS. The plasma and RBCs were separated, sPLA(2) levels were measured, and the RBCs were incubated with sPLA(2) . Plasma and lipids, extracted from the plasma or the supernatant of sPLA(2) -treated RBCs, were assayed for PMN priming activity and used as the second event in a model of PMN-mediated ECI. Phosphatidylserine (PS) surface expression on RBCs was quantified by flow cytometry.

RESULTS

Increased sPLA(2) -IIa levels were associated with ACS. SPLA(2) -liberated lipids from VOC and the plasma, plasma lipids and sPLA(2) -liberated lipids from ACS primed PMNs and caused PMN-mediated ECI (P < 0.01). RBCs from VOC had increased in PS surface expression versus steady state.

CONCLUSIONS

ACS plasma and lipids and sPLA(2) -released lipids from RBCs during VOC or ACS induce PMN-mediated ECI. VOC elicited increases in PS surface expression providing a membrane substrate for sPLA(2) lysis of sickle RBCs.

Risk factors and mortality associated with an elevated tricuspid regurgitant jet velocity measured by Doppler-echocardiography in thalassemia: a Thalassemia Clinical Research Network report

An elevated tricuspid regurgitant jet velocity (TRV) is associated with hemolysis and early mortality in sickle cell disease, yet risk factors, clinical parameters, and mortality associated with this biomarker in thalassemia are poorly defined. This report summarizes the prevalence of an elevated TRV in 325 patients screened by Doppler echocardiography in the Thalassemia Clinical Research Network. A documented TRV was reported in 148 of 325 (46%) of patients. Average age was 25.9 years (range, 5-56 years) and 97% were transfusion-dependent. Mean TRV was 2.3 ± 0.4 m/s (range, 0.2-3.5 m/s). An abnormal TRV ≥ 2.5 m/s was identified in 49 of 148 (33%) of patients with a documented TRV, 5% (8/148), with a TRV ≥ 3.0 m/s, suggesting significant PH risk. Older age was strongly associated with a high TRV; however, 16% of children had a TRV ≥ 2.5 m/s. A history of splenectomy, hepatitis C, smoking, or high white blood cell count was associated with TRV elevation. In summary, an elevated TRV is noted in one-third of transfusion-dependent thalassemia patients with a documented value and develops in both children and adults. Age, splenectomy, hepatitis C, and smoking are significant univariate risk factors, with splenectomy surfacing as the dominant risk factor over time. Mortality was low in this cohort. Prospective longitudinal studies are needed. This study is registered at http://www.clinicaltrials.gov as NCT00661804.

Inhibition of cation channels in human erythrocytes by spermine

In erythrocytes, spermine concentration decreases gradually with age, which is paralleled by increases of cytosolic Ca²+ concentration, with subsequent cell shrinkage and cell membrane scrambling. Cytosolic Ca²+ was estimated from fluo-3 fluorescence, cell volume from forward scatter, cell membrane scrambling from annexin V binding and cation channel activity with whole-cell patch-clamp in human erythrocytes. Extracellular spermine exerted a dual effect on erythrocyte survival. At 200 μM spermine blunted the increase of intracellular Ca²+, cell shrinkage and annexin V binding following 48 h exposure of cells at +37 °C. In contrast, short exposure (10-30 min) of cells to 2 mM spermine was accompanied by increased cytosolic Ca²+ and annexin binding. Intracellular addition of spermine at subphysiological concentration (0.2 μM) significantly decreased the conductance of monovalent cations (Na+, K+, NMDG+) and of Ca²+. Moreover, spermine (0.2 μM) blunted the stimulation of voltage-independent cation channels by Cl⁻ removal. Spermine (0.2 and 200 μM) added to the extracellular bath solution similarly inhibited the cation conductance in Cl⁻-containing bath solution. The effect of 0.2 μM spermine, but not the effect of 200 μM, was rapidly reversible. Acute addition (250 μM) of a naphthyl acetyl derivative of spermine (200 μM) again significantly decreased basal cation conductance in NaCl bath solution and inhibited voltage-independent cation channels. Spermine is a powerful regulator of erythrocyte cation channel cytosolic Ca²+ activity and, thus, cell survival.

Temperature sensitivity of suicidal erythrocyte death

BACKGROUND

Fever and hyperthermia are frequently associated with anaemia. Under most clinical conditions, they are considered to be two mutually independent clinical consequences of a common cause. The present study explored the possibility that anaemia results from temperature-sensitive suicidal erythrocyte death or eryptosis. Eryptosis is characterised by cell shrinkage and cell membrane scrambling with phosphatidylserine (PS) exposure at the erythrocyte surface. It is triggered by increase in the cytosolic Ca(2+) activity on the one hand and by ceramide formation on the other.

MATERIAL AND METHODS

Annexin V-binding was utilised to disclose PS exposure, forward scatter to analyse cell volume, Fluo 3 fluorescence to estimate cytosolic Ca(2+) activity, binding of fluorescent antibodies to determine ceramide abundance and a luciferin/luciferase-based assay to measure the cytosolic ATP concentration.

RESULTS

Graded increases in temperature from 37 to 41 degrees C decreased the forward scatter and stimulated annexin V-binding of human erythrocytes. The effect was accompanied by increased cytosolic Ca(2+) activity, decrease of the cellular ATP content and a moderate rise in ceramide formation. The effect of hyperthermia on annexin V-binding was significantly blunted by the leukotriene receptor CysLT1 antagonist cinalukast (1 microM).

CONCLUSIONS

Hyperthermia stimulates Ca(2+) entry into erythrocytes leading to cell shrinkage and PS exposure. As PS-exposing erythrocytes are rapidly cleared from circulating blood, the eryptosis during hyperthermia may cause anaemia.

Delayed hemolytic transfusion reaction in sickle cell disease patients: evidence of an emerging syndrome with suicidal red blood cell death

BACKGROUND

Delayed hemolytic transfusion reaction (DHTR) is a life-threatening complication in sickle cell disease (SCD) characterized by recurrence of disease complications, recipient red blood cell (RBC) destruction, and frequently no detectable antibody. Phosphatidylserine (PS) exposure signs suicidal RBC death or eryptosis and is involved in vasoocclusive crisis (VOC).

STUDY DESIGN AND METHODS

Transfusion was monitored in 48 SCD patients for up to 20 days. PS exposure was evaluated in vivo on patient RBCs (PS-RBCs) at five time points and in vitro after incubation of donor RBCs with pretransfusion plasma.

RESULTS

Three VOC patients displayed DHTR with recurrent SCD features and no detectable antibody in two cases. In vitro, PS-RBC percentage was significantly increased by incubating donor RBCs with pretransfusion plasma samples from DHTR patients with no detectable antibody. No such increase was observed with samples from other patients. This result indicates that donor RBCs may be damaged by the environment of SCD patients, increasing the physiologic clearance of apoptotic RBCs. In vivo, PS-RBC percentage increased in all three cases after destruction of transfused RBCs, indicating that DHTR induces PS-RBCs and, possibly, subsequent VOC and autologous RBC destruction.

CONCLUSION

This study clearly demonstrates that DHTR can occur in the absence of detectable antibody. In these cases, a mechanism of excessive eryptosis is proposed.

Lipidomics of the red cell in diagnosis of human disorders

Applications of tandem mass spectrometry in the field of lipid clinical chemistry are considered. Haemato-logical and biochemical advantages are presented favoring the choice of red blood cell membranes as a starting material in a wide variety of biomedical fields. Practical considerations are discussed with respect to methods of sampling, storage, and lipid extraction of red blood cells. The chapter describes the capabilities of a direct infusion of raw lipid extracts in the electro-spray ionization source compared with the more sophisticated method of high-performance liquid chromatography coupled with hybrid tandem mass spectrometry. Both methods have been evaluated and have been shown to be suitable for diagnosis and/or monitoring for a variety of human disorders.

Delayed Hemolytic Transfusion Reaction in Sickle Cell Disease Patients: Evidence of An Emerging Syndrome with Suicidal Erythrocyte Death

Background: Delayed hemolytic transfusion reaction (DHTR) is a life-threatening complication in sickle cell disease (SCD). Some features are characteristic: destruction of both donor and recipient red blood cells (RBCs), hemolysis exacerbation by further transfusions, recurrence of SCD complications, reported cases without demonstrable RBC antibodies. We carried out a prospective study to clarify mechanisms of DHTR without demonstrable antibody and associated features. In this matter, we considered that study of phosphatidylserine exposure (PS) was important as PS-exposure signed eryptosis or suicidal erythrocyte death1, a process of membrane shedding leading to clearance of apoptotic erythrocytes by macrophages through their PS-receptors.

Patients and methods: 48 SCD patients were included. Transfusion occurred for different SCD indications. Adverse events were monitored. Analyses were performed at 5 time points (day 0 and around days 1, 5, 10 and 20 post-transfusion) including hemolysis parameters, % of HbA and HbS, and research of antibodies against RBCs by antibody-screening in plasma and eluate, cross-matching between donor RBCs and both plasma and eluate, direct antiglobulin test with anti-IgG, IgM, IgA, C3d/C3b (DAT). Amount of PS-RBCs was determined by flow cytometry as Annexin V-positive RBCs, in vivo, on patient samples and in vitro, on healthy blood donor RBCs previously incubated 48H in the J0 plasma of the patients.

Results and discussion: Transfusion outcome was known for all patients, 31 patients could be completely studied at the biological level. Three patients experienced DHTR, confirmed by complete disappearance of HbA at days 13, 7 and 10 respectively and by biological parameters of hemolysis. Two cases occurred without demonstrable antibody, in the third case, RBC antibodies could not be eliminated as DAT became positive with IgG. In vivo, a significant fold increase of PS-RBCs was observed for the 3 DHTR patients around day 10 (3.74±2.0, p=0.009) and day 17 (4.85±1.4, p=0.007). This result shows that DHTR, with no consideration of the mechanism, is a risk factor for recurrence of SCD complications as PS-RBCs are involved in vaso-occlusive crisis (VOC)2. In vitro, PS-RBCs % increases significantly (p&lt;0.01) after incubation of donor RBCs into J0 plasma of the 15 patients transfused for VOC (12.8±9.9%) compared with J0 plasma of patients transfused for other indications (4.7±4.6%). The increase is significantly higher (p&lt;0.05) with plasma of the 2 VOC patients who experienced DHTR without demonstrable antibody (37.1±6.7%) compared with other transfused VOC patients. This result indicates that transfused RBCs can suffer from the in vivo environment of SCD patients who encountered VOC and their survival be compromised by enhancing the normal physiological clearance of apoptotic RBCs.

Conclusion: In this study, we clearly demonstrate that DHTR can occur without demonstrable antibody. Based on PS-exposure results, we propose the following scenario of DHTR features: RBCs transfused in a high oxidative stress environment (VOC) suffer from accelerated eryptosis. Hemolysis reaction of transfused RBCs promotes a cascade of events that increases release of oxidative stress mediators and more destruction of autologous RBCs that are already fragile. A further transfusion will trigger a new wave of hemolysis with amplified consequences. The only way to stop the loop is to stop transfusion. It remains to determine the mediators which accelerate eryptosis of transfused RBCs in order to propose the adapted prevention such as cytoprotective drugs.

Mechanisms of vasculopathy in sickle cell disease and thalassemia

Many mechanisms contribute to the complex pathophysiology of sickle cell disease (SCD), with dysfunction of the vascular endothelium as a unifying theme. Specifically, hemolysis-associated low arginine and nitric oxide (NO) bioavailability, amplified by NO synthase uncoupling, elevated arginase activity, superoxide production, oxidative stress, accumulation of arginine analogs such as asymmetric dimethylarginine, ischemia-reperfusion injury, inflammation, apolipoprotein A-1 depletion, and a hypercoagulable state are significant mechanisms contributing to endothelial dysfunction. Genetic polymorphisms also influence disease severity. Clearly the variable spectrum of disease is the consequence of multiple events and genetic susceptibility that go beyond the occurrence of a single amino acid substitution in the beta globin chain of hemoglobin. Recent studies begin to demonstrate overlap among these seemingly unrelated processes. Impaired NO bioavailability represents the central feature of endothelial dysfunction, and is a common denominator in the pathogenesis of vasculopathy in SCD. The consequences of decreased NO bioavailability include endothelial cell activation, upregulation of the potent vasoconstrictor endothelin-1, vasoconstriction, platelet activation, increased tissue factor, and activation of coagulation, all of which ultimately translate into the clinical manifestations of SCD. Evidence supporting vasculopathy subphenotypes in SCD, including pulmonary hypertension, priapism, cutaneous leg ulceration, and stroke, will be reviewed and relevance to other hemolytic disorders including the thalassemia syndromes will be considered.