A synergistic effect of albumin and fibrinogen on immunoglobulin-induced red blood cell aggregation

Forces of interaction of red blood cells and endothelial cells at different concentrations of fibrinogen: Measurements with laser tweezers in vitro

Blood microrheology depends on the constituents of blood plasma, the interaction between blood cells resulting in red blood cell (RBC) and platelets aggregation, and adhesion of RBC, platelets and leukocytes to vascular endothelium. The main plasma protein molecule -actuator of RBC aggregation is fibrinogen. In this paper the effect of interaction between the endothelium and RBC at different fibrinogen concentrations on the RBC microrheological properties was investigated in vitro. Laser tweezers were used to measure the RBC-endothelium interaction forces. It was shown for the first time that the interaction forces between RBC and endothelium are comparable with the RBC aggregation forces, they increase with fibrinogen concentration and reach the saturation level of about 4 pN at the concentration of 4 mg/ml. These results are important for better understanding the mechanisms of RBC and endothelium interaction and developing the novel therapeutic protocols of the microrheology correction in different pathologies.

Role of Plasma Membrane at Dielectric Relaxations and Intermembrane Interaction in Human Erythrocytes

Dielectric relaxations at 1.4 MHz (β_sp) and 9 MHz (γ1_sp) on the erythrocyte spectrin network were studied by dielectric spectroscopy using dense suspensions of erythrocytes and erythrocyte ghost membranes, subjected to extraction with up to 0.2% volume Triton-X-100. The step-wise extraction of up to 60% of membrane lipids preserved γ1_sp and gradually removed β_sp-relaxation. On increasing the concentration up to 100 mM of NaCl at either side of erythrocyte plasma membranes, the β_sp-relaxation was linearly enhanced, while the strength of γ1_sp-relaxation remained unchanged. In media with NaCl between 100 and 150 mM β_sp-relaxation became slightly inhibited, while γ1_sp-relaxation almost disappeared, possibly due to the decreased electrostatic repulsion allowing erythrocytes to come into closer contact. When these media contained, at concentrations 10-30 mg/mL dextran (MW 7 kDa), polyethylene glycol or polyvinylpyrrolidone (40 kDa), or albumin or homologous plasma with equivalent concentration of albumin, the γ1_sp-relaxation was about tenfold enhanced, while β_sp-relaxation was strengthened or preserved. The results suggest the Maxwell-Vagner accumulation of ions on the lipid bilayer as an energy source for β_sp-relaxation. While β_sp-relaxation appears sensitive to erythrocyte membrane deformability, γ1_sp-relaxation could be a sensitive marker for the inter-membrane interactions between erythrocytes.

Determination of the erythrocyte sedimentation rate using the hematocrit-corrected aggregation index and mean corpuscular volume

BACKGROUND

Determination of the erythrocyte sedimentation rate (ESR) by measurement of erythrocyte aggregation is an alternative to the Westergren method and can be performed rapidly. However, its principle is opaque and the ESR values obtained can deviate from Westergren method values (WG ESR) due to hematocrit. Furthermore, WG ESR is affected by particle size, but no studies have examined the effect of individual mean corpuscular volumes (MCVs).

METHODS

Simultaneous measurement of the erythrocyte aggregation index (AI) over a 5-s interval and determination of the complete blood count in 80 μL blood from 203 patients were performed (hematocrit, 21.4%-52.3%; MCV, 62.7-114.1 fL). ESR values were calculated with the hematocrit-corrected AI (HAI) for comparison with WG ESR. We improved the calculation formula by using MCV.

RESULTS

The sedimentation velocity of a single erythrocyte in the samples agreed well with an exponential function of HAI. ESR values calculated using HAI showed excellent correlation with WG ESR (r = 0.899, p < 0.001; Bland-Altman analysis: bias 2.76, limits of agreement (LOA) -24.5 to 30.0), but the difference between the calculated ESR and WG ESR increased with decreasing MCV. Calculation of ESR considering both HAI and MCV eliminated the MCV-dependent deviation and improved the correlation with WG ESR (r = 0.920, p < 0.001, bias -2.17, LOA -24.6 to 20.3).

CONCLUSION

Calculation using HAI and MCV can rapidly provide ESR values that are highly correlated with WG ESR in clinical specimens over a wide range of hematocrit and MCV values.

Albumin effect on hemorheological parameters in patients with liver transplant

BACKGROUND

Liver transplantation is a life-saving treatment in end-stage liver failure. Hemorheological features as blood fluidity and red blood cell aggregation may alter effective tissue perfusion, graft function and hemodynamic variables.

OBJECTIVE

The aim of the study is to investigate effect of albumin infusion on red blood cell deformability and aggregation, blood viscosity and hemodynamics in liver transplant patients.

METHODS

Seventeen live or cadaveric donors were included in this prospective study. Hemorheological and hemodynamic measurements were performed in order to evaluate the effects of albumin infusion in perioperative period.

RESULTS

Erythrocyte aggregation was significantly reduced 90 minutes after albumin infusion (p < 0.01). Mean blood viscosity revealed significant decrease at 20 rpm and 50 rpm after 90 minutes of albumin infusion (p < 0.05). Plasma viscosity decreased significantly compared to the value before albumin infusion at 20 rpm (p < 0.05). Albumin replacement improved hemodynamic variables in patients with low blood pressure and cardiac index measurements (p > 0.05).

CONCLUSIONS

Human albumin infusion led to decrease in whole blood and plasma viscosities, red blood cell aggregation and induced blood pressure and cardiac index elevation in perioperative liver transplant patients. Determination of hemodynamic and hemorheological effects of human albumin replacement in various patient populations may serve beneficial clinical data.

Erythrocyte aggregation in sudden flow arrest is linked to hyperthermia, hypoxemia, and band 3 availability

BACKGROUND

Erythrocyte aggregation is a phenomenon that is commonly found in several pathological disease states: stroke, myocardial infarction, thermal burn injury, and COVID-19. Erythrocyte aggregation is characterized by rouleaux, closely packed stacks of cells, forming three-dimensional structures. Healthy blood flow monodisperses the red blood cells (RBCs) throughout the vasculature; however, in select pathological conditions, involving hyperthermia and hypoxemia, rouleaux formation remains and results in occlusion of microvessels with decreased perfusion.

OBJECTIVES

Our objective is to address the kinetics of rouleaux formation with sudden cessation of flow in variable temperature and oxygen conditions.

METHODS

RBCs used in this in vitro system were obtained from healthy human donors. Using a vertical stop-flow system aligned with a microscope, images were acquired and analyzed for increased variation in grayscale to indicate increased aggregation. The onset of aggregation after sudden cessation of flow was determined at proscribed temperatures (37-49°C) and oxygen (0%, 10%), and in the presence and absence of 4, 4'-Diisothiocyano-2,2'-stilbenedisulfonic acid (DIDS). Both autologous and homologous plasma were tested.

RESULTS

RBCs in autologous plasma aggregate faster and with a higher magnitude with both hyperthermia and hypoxemia. Preventing deoxyhemoglobin from binding to band 3 with DIDS (dissociates the cytoskeleton from the membrane) fully blocks aggregation. Further, RBC aggregation magnitude is greater in autologous plasma.

CONCLUSIONS

We show that the C-terminal domain of band 3 plays a pivotal role in RBC aggregation. Further, aggregation is enhanced by hyperthermia and hypoxemia.

Problems of Red Blood Cell Aggregation and Deformation Assessed by Laser Tweezers, Diffuse Light Scattering and Laser Diffractometry

This study aims to highlight the problems with implementing optical techniques (laser tweezers, diffuse light scattering and laser diffractometry) in clinical hemorheological practice. We provide the feasibility of these techniques to assess microrheological effects of various molecular mechanisms affecting RBC aggregation and deformability. In particular, we show that they allow assessment of changes in RBC aggregation in whole blood samples both on the level of single cells and on the level of large ensembles of cells. Application of these methods allows for studying the mechanisms of RBC aggregation because they are sensitive to changes in the medium which surrounds the RBC (i.e., blood plasma, serum or model solutions of blood plasma proteins) and to changes in the cellular properties of RBCs (i.e., effects on the cell membrane due to glycoprotein inhibition).

Determination of red blood cell adhesion to vascular endothelial cells: A critical role for blood plasma

Red blood cell (RBC) adhesion to vascular endothelial cells (EC) is considered a potent effector of circulatory disorders, and its enhancement is implicated in the pathophysiology of numerous conditions, mainly hemoglobinopathies. The actual RBC/EC interaction is determined by both cellular and plasmatic factors, and the differentiation between them is essential for understanding its physiological implications. Yet, RBC/EC adhesion has been studied predominantly in protein-free media. To explore the plasma contribution to RBC/EC adhesion, we examined the adhesion of human RBC to human vascular endothelial cells in the presence of fresh frozen plasma (FFP) and compared it to that in a protein-free phosphate-buffered saline (PBS). RBC from blood samples freshly-collected from five healthy donors and from fifteen units of packed RBC units were used. The same FFP sample was used in all measurements. In FFP, the RBC form strongly adherent aggregates, which are dispersed as the shear stress (τ) increases to 3.0 Pa, and even at 5.0 Pa a large portion of the RBC are still adherent. In PBS, the RBC are singly dispersed and their adhesion becomes insignificant already at τ = 0.5 Pa. No cross-correlation was found between the adhesion in PBS vs. that in FFP at the same τ. However, in both media, under conditions that form singly dispersed adherent RBC, an inverse correlation between RBC/EC adhesion in PBS vs. that in FFP was observed. This study clearly implies that for understanding the physiological relevance of RBC/EC adhesion it should be determined in plasma.

The Role of RBC Oxidative Stress in Sickle Cell Disease: From the Molecular Basis to Pathologic Implications

Sickle cell disease (SCD) is an inherited monogenic disorder and the most common severe hemoglobinopathy in the world. SCD is characterized by a point mutation in the β-globin gene, which results in hemoglobin (Hb) S production, leading to a variety of mechanistic and phenotypic changes within the sickle red blood cell (RBC). In SCD, the sickle RBCs are the root cause of the disease and they are a primary source of oxidative stress since sickle RBC redox state is compromised due to an imbalance between prooxidants and antioxidants. This imbalance in redox state is a result of a continuous production of reactive oxygen species (ROS) within the sickle RBC caused by the constant endogenous Hb autoxidation and NADPH oxidase activation, as well as by a deficiency in the antioxidant defense system. Accumulation of non-neutralized ROS within the sickle RBCs affects RBC membrane structure and function, leading to membrane integrity deficiency, low deformability, phosphatidylserine exposure, and release of micro-vesicles. These oxidative stress-associated RBC phenotypic modifications consequently evoke a myriad of physiological changes involved in multi-system manifestations. Thus, RBC oxidative stress in SCD can ultimately instigate major processes involved in organ damage. The critical role of the sickle RBC ROS production and its regulation in SCD pathophysiology are discussed here.

Assessment of Fibrinogen Macromolecules Interaction with Red Blood Cells Membrane by Means of Laser Aggregometry, Flow Cytometry, and Optical Tweezers Combined with Microfluidics

An elevated concentration of fibrinogen in blood is a significant risk factor during many pathological diseases, as it leads to an increase in red blood cells (RBC) aggregation, resulting in hemorheological disorders. Despite the biomedical importance, the mechanisms of fibrinogen-induced RBC aggregation are still debatable. One of the discussed models is the non-specific adsorption of fibrinogen macromolecules onto the RBC membrane, leading to the cells bridging in aggregates. However, recent works point to the specific character of the interaction between fibrinogen and the RBC membrane. Fibrinogen is the major physiological ligand of glycoproteins receptors IIbIIIa (GPIIbIIIa or αIIββ3 or CD41/CD61). Inhibitors of GPIIbIIIa are widely used in clinics for the treatment of various cardiovascular diseases as antiplatelets agents preventing the platelets’ aggregation. However, the effects of GPIIbIIIa inhibition on RBC aggregation are not sufficiently well studied. The objective of the present work was the complex multimodal in vitro study of the interaction between fibrinogen and the RBC membrane, revealing the role of GPIIbIIIa in the specificity of binding of fibrinogen by the RBC membrane and its involvement in the cells’ aggregation process. We demonstrate that GPIIbIIIa inhibition leads to a significant decrease in the adsorption of fibrinogen macromolecules onto the membrane, resulting in the reduction of RBC aggregation. We show that the mechanisms underlying these effects are governed by a decrease in the bridging components of RBC aggregation forces.

Unit-to-unit variability in the deformability of red blood cells

BACKGROUND

In blood banking practice, the storage duration is used as the primary criterion for inventory management, and usually, the packed red blood cells (PRBC) units are supplied primarily according to first-in-first-out (FIFO) principle. However, the actual functionality of individual PRBC units is mostly ignored. One of the main features of the RBCs not accounted for under this approach is the deformability of the red cells, i.e., their ability to affect the recipients' blood flow. The objective of the study was to analyze unit-to-unit variability in the deformability of PRBCs during their cold storage.

METHODS

RBC samples were obtained from twenty leukoreduced PRBC units, stored in SAGM. The deformability of cells was monitored from the day of donation throughout 42 days. RBC deformability was determined using the computerized cell flow-properties analyzer (CFA) based on cell elongation under a shear stress of 3.0 Pa, expressed by the elongation-ratio (ER). The image analysis determines the ER for each cell and provides the ER distribution in the population of 3000-6000 cells.

RESULTS

The deformability of freshly-collected RBCs exhibited marked variability already on the day of donation. We also found that the aging curve of PRBC deformability varies significantly among donors.

SIGNIFICANCE

The present study has demonstrated that storage duration is only one of the factors, and seemingly not even the major one, affecting the PRBCs functionality. Therefore, the FIFO approach is not sufficient for assessing the potential transfusion outcome, and the PRBC functionality should be determined explicitly for each unit.

Oxidative Stress and Thrombosis during Aging: The Roles of Oxidative Stress in RBCs in Venous Thrombosis

Mid-life stage adults are at higher risk of developing venous thrombosis (VT)/thromboembolism (VT/E). Aging is characterized by an overproduction of reactive oxygen species (ROS), which could evoke a series of physiological changes involved in thrombosis. Here, we focus on the critical role of ROS within the red blood cell (RBC) in initiating venous thrombosis during aging. Growing evidence has shifted our interest in the role of unjustifiably unvalued RBCs in blood coagulation. RBCs can be a major source of oxidative stress during aging, since RBC redox homeostasis is generally compromised due to the discrepancy between prooxidants and antioxidants. As a result, ROS accumulate within the RBC due to the constant endogenous hemoglobin (Hb) autoxidation and NADPH oxidase activation, and the uptake of extracellular ROS released by other cells in the circulation. The elevated RBC ROS level affects the RBC membrane structure and function, causing loss of membrane integrity, and decreased deformability. These changes impair RBC function in hemostasis and thrombosis, favoring a hypercoagulable state through enhanced RBC aggregation, RBC binding to endothelial cells affecting nitric oxide availability, RBC-induced platelet activation consequently modulating their activity, RBC interaction with and activation of coagulation factors, increased RBC phosphatidylserine exposure and release of microvesicles, accelerated aging and hemolysis. Thus, RBC oxidative stress during aging typifies an ultimate mechanism in system failure, which can affect major processes involved in the development of venous thrombosis in a variety of ways. The reevaluated concept of the critical role of RBC ROS in the activation of thrombotic events during aging will help identify potential targets for novel strategies to prevent/reduce the risk for VT/E or VT/E recurrences in mid-life stage adults.

The Relationship Between Aggregation and Deformability of Red Blood Cells in Health and Disease

The molecular organization of the membrane of the red blood cell controls cell morphology and function and is thereby a main determinant of red blood cell homeostasis in the circulation. The role of membrane organization is prominently reflected in red blood cell deformation and aggregation. However, there is little knowledge on whether they are controlled by the same membrane property and if so, to what extent. To address the potential interdependence of these two parameters, we measured deformation and aggregation in a variety of physiological as well as pathological conditions. As a first step, we correlated a number of deformability and aggregation parameters in red blood cells from healthy donors, which we obtained in the course of our studies on red blood cell homeostasis in health and disease. This analysis yielded some statistically significant correlations. Also, we found that most of these correlations were absent in misshapen red blood cells that have an inborn defect in the interaction between the membrane and the cytoskeleton. The observations suggest that deformability and aggregation share at least one common, membrane-related molecular mechanism. Together with data obtained after treatment with various agents known to affect membrane organization in vitro, our findings suggest that a phosphorylation-controlled interaction between the cytoskeleton and the integral membrane protein band 3 is part of the membrane-centered mechanism that plays a role in deformability as well as aggregation.

Potential Diagnostic Hemorheological Indexes for Chronic Kidney Disease in Patients With Type 2 Diabetes

Many studies have demonstrated that an alteration in hemorheological properties is closely correlated with diabetic microcirculatory diseases. However, most of these studies have been limited to animal studies or used a small number of clinical samples, due to a lack of effective point-of-care (POC) devices to measure such properties within clinical environments. Owing to recent developments in microfluidic technology, several hemorheological POC devices have been designed that allow for the possibility of conducting extensive clinical studies using hemorheological measurements. Here, we reviewed recent clinical studies of diabetic kidney disease (DKD) associated with hemorheological parameters. We found that RBC deformability alone did not show a significant difference according to the degree of DKD, whereas critical shear stress (CSS) was found to be closely related to the ratio of albumin to creatinine and glomerular filtration rate. We also reviewed studies that alteration of hemorheological properties are associated with the development of DKD, which showed that CSS could be considered as a potential index to diagnose other diabetic complications as well as DKD.

Nitric oxide releasing vascular catheters for eradicating bacterial infection

The interaction of blood proteins with an implant surface is not only a fundamental phenomenon but is also key to several important medical complications. Plasma proteins binding on the surface of intravascular catheters can promote bacterial adhesion leading to the risk of local and systemic complications such as catheter-related blood infections (CRBIs). The incidences of CRBIs in the United States amount to more than 250,000 cases/year with an attributable mortality of up to 35% and an annual healthcare expenditure of $2.3 billion approximately. This demands the development of truly nonthrombogenic and antimicrobial catheters. In the present study, catheters were fabricated by incorporating a nitric oxide (NO) donor molecule, S-nitroso-N-acetyl-penicillamine (SNAP) in a hydrophobic medical grade polymer, Elasteon-E2As. NO offers antithrombotic and antibacterial attributes without promoting drug resistance and cytotoxicity. E2As-SNAP catheters were first coated with fibrinogen, a blood plasma protein plays a key role in clot formation and eventual bacterial adhesion to the implant surface. The suitability of the catheters for biomedical applications was tested in vitro for contact angle, NO release kinetics, inhibition of bacteria, and absence of cytotoxicity toward mammalian cells. The highly hydrophobic catheters released NO in the physiological range that inhibited >99% bacterial viability on fibrinogen-coated catheters in a 24 h study. No toxic response of E2As-SNAP catheters leachate was observed using a standard cytotoxicity assay with mouse fibroblast cells. Overall, the results showed that the E2As-SNAP catheters can inhibit viable bacteria even in the presence of blood proteins without causing a cytotoxic response. The fundamentals of this study are applicable to other blood-contacting medical devices as well. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2849-2857, 2018.

Significantly increased low shear rate viscosity, blood elastic modulus, and RBC aggregation in adults following cardiac surgery

Open heart surgeries are common for treating ischemic and heart valve disease. During cardiac surgery, cardiopulmonary bypass (CPB) can temporarily take over the function of heart and lungs. However, elevated red blood cell (RBC) aggregation may lead to the common side-effects such as microinfarction. We investigated blood physical properties changes and the correlation between blood microstructure, viscoelastic response and biochemical changes following surgery with CPB. We examined shear-rate dependent blood viscosity, elasticity and RBC aggregate size in the pre-surgery disease state, post-surgery state and long-term recovery state of cardiac surgical patients. Within a week following surgery, the patient hematocrit was significantly lower due to CPB. Despite lower RBC concentration, the RBC aggregate shape became larger and more rounded, which is correlated to the elevated plasma fibrinogen related to systemic inflammatory response. During the same period, the hematocrit-adjusted low shear rate viscosity increased significantly, as did the yield stress, indicating more solid-like behavior for blood. Six months to one year later, all the physical and biochemical properties measured returned to baseline.

Optical tweezers study of red blood cell aggregation and disaggregation in plasma and protein solutions

Kinetics of optical tweezers (OT)-induced spontaneous aggregation and disaggregation of red blood cells (RBCs) were studied at the level of cell doublets to assess RBC interaction mechanics. Measurements were performed under in vitro conditions in plasma and fibrinogen and fibrinogen + albumin solutions. The RBC spontaneous aggregation kinetics was found to exhibit different behavior depending on the cell environment. In contrast, the RBC disaggregation kinetics was similar in all solutions qualitatively and quantitatively, demonstrating a significant contribution of the studied proteins to the process. The impact of the study on assessing RBC interaction mechanics and the protein contribution to the reversible RBC aggregation process is discussed.

Intravenous immune globulin and thromboembolic adverse events in patients with hematologic malignancy

In patients with hypogammaglobulinemia secondary to chronic lymphocytic leukemia (CLL) or multiple myeloma (MM), intravenous immune globulin (IVIg) may be administered to reduce the risk of infection. Since 2013, IVIg products have carried a boxed safety warning about the risk of thromboembolic events (TEEs), with TEEs reported in 0.5% to 15% of patients treated with IVIg. In this retrospective cohort study of older patients with CLL or MM identified from the Surveillance, Epidemiology, and End Results-Medicare Linked Database, we assessed rates of clinically serious TEEs in 2724 new users of IVIg and a propensity-matched comparison group of 8035 nonusers. For the primary end point, arterial TEE, we observed a transient increased risk of TEE during the day of an IVIg infusion and the day afterward (hazard ration = 3.40; 95% confidence interval [CI]: 1.25, 9.25); this risk declined over the remainder of the 30-day treatment cycle. When considered in terms of absolute risk averaged over a 1-year treatment period, the increase in risk attributable to IVIg was estimated to be 0.7% (95% CI: -0.2%, 2.0%) compared with a baseline risk of 1.8% for the arterial TEE end point. A statistically nonsignificant risk increase of 0.3% (95% CI: -0.4%, 1.5%) compared with a baseline risk of 1.1% was observed for the venous TEE end point. Further research is needed to establish the generalizability of these results to patients receiving higher doses of IVIg for other indications.

Managing patients with side effects and adverse events to immunoglobulin therapy

Immunoglobulin therapy has not only served as a lifesaving approach for the prevention and treatment of infections in primary and secondary immunodeficiency diseases, but has also been used as an immunomodulatory agent for autoimmune and inflammatory disorders and to provide passive immunity for some infectious diseases. Most of the adverse effects associated with immunoglobulin therapy are mild, transient and self-limiting. However, serious side effects also occur. Therefore, to minimize the adverse events of immunoglobulin therapy, specialist review of patient clinical status and immunoglobulin products, in addition to selection of appropriate treatment strategy for the management of patients with associated side effects and adverse events, are crucial.

Fibrinogen, red blood cells, and factor XIII in venous thrombosis

Cardiovascular disease is the leading cause of death and disability worldwide. Among cardiovascular causes of death, venous thrombosis (VT) is ranked third most common in the world. Venous thrombi have high red blood cell and fibrin content; however, the pathophysiologic mechanisms that contribute to venous thrombus composition and stability are still poorly understood. This article reviews biological, biochemical, and biophysical contributions of fibrinogen, factor XIII, and red blood cells to VT, and new evidence suggesting interactions between these components mediate venous thrombus composition and size.

Deep Venous Thrombosis with Pulmonary Embolism Related to IVIg Treatment: A Case Report and Literature Review

IVIg therapy has potentially been related to arterial and venous therapy. We performed an Ovid review focusing on IVIg and thrombotic events. While a few case reports were reviewed case series and case control studies were particularly reviewed in relation to thrombotic events. Outcomes demonstrate a correlation between underlying cardiovascular risk factors with predominately arterial events which typically occurred within 4–24 hours of infusion. While venous events occurred less commonly they were associated with traditional risk factors and occurred later, typically, 1–7 days following infusion of IVIg. Potential causation of thrombotic events was discussed.

Role of red blood cell flow behavior in hemodynamics and hemostasis

The primary role of red blood cells (RBCs) is to transport oxygen to the tissues, which is performed predominantly in the blood capillaries. However, RBCs have unique flow-affecting properties that play a key role in blood flow in all blood vessel types and sizes. While RBCs as oxygen carriers have been studied extensively, their hemodynamic function has been examined less comprehensively. This review aims to bridge this gap, focusing on the role of RBC flow properties in hemodynamics, hemostasis and thrombosis.

Behaviour of human erythrocyte aggregation in presence of autologous lipoproteins

The aim of this work was to evaluate in vitro the effect of autologous plasma lipoprotein subfractions on erythrocyte tendency to aggregate. Aliquots of human blood samples were enriched or not (control) with their own HDL-C, LDL-C, or VLDL-C fractions obtained from the same batch by density gradient ultracentrifugation. Plasma osmolality and erythrocyte aggregation index (EAI) were determined. Blood aliquots enriched with LDL-C and HDL-C showed significant higher EAI than untreated aliquots, whereas enrichment with VLDL-C does not induce significant EAI changes. For the same range of lipoprotein concentrations expressed as percentage of osmolality variation, the EAI variation was positive and higher in presence of HDL-C than upon enrichment with LDL-C (P < 0.01). Particle size, up to LDL diameter values, seems to reinforce erythrocyte tendency to aggregate at the same plasma osmolality (particle number) range of values.

Erythrocyte aggregation as a cause of slow flow in patients of acute coronary syndromes

BACKGROUND

There are multiple lines of evidence to suggest the role of erythrocyte aggregation (EA) in microcirculatory dysfunction during conditions of very slow flow. Such conditions might develop in the myocardium of patients with acute coronary syndromes (ACS).

METHODS

EA as a function of shear stress was evaluated by using a cell flow properties analyzer (CFA) in a cohort of 91 ACS patients and in 36 patients with non specific chest pain or heart failure at the time of cardiac catheterization.

RESULTS

The ACS group included 34 patients with acute myocardial infarction and 57 patients with unstable angina. In addition, we examined 36 patients who underwent angiography for non specific chest pain or heart failure. A significant (r=0.44, p<0.0005) correlation was found between the concentration of fibrinogen and the average aggregate size (AAS) only when using conditions of very slow flow and applying relatively low (0.15 dyn/cm(2)) shear stress in the ACS group. This correlation decreased and became insignificant when applying shear stress forces of 1 dyn/cm(2) and more. This correlation was nonsignificant for all the 5 shear stress forces (between 0.15 and 4 dyn/cm(2)) in the samples obtained from the non-ACS group.

CONCLUSION

Erythrocytes that are suspended in autologous plasma obtained from patients with ACS tend to aggregate in conditions of very slow flow. These findings might be detrimental in terms of microcirculatory flow in ACS patients and might open new therapeutic options such as the use of low dose thrombolysis following PCI.

Cerebral sinus thrombosis following IV immunoglobulin therapy of immune thrombocytopenia purpura

We present a pediatric patient treated with high dose intravenous immunoglobulin (IVIG) for acute immune thrombocytopenic purpura (ITP), who developed cerebral sinus thrombosis in the absence of any identifiable hypercoagulable state. This report describes the successful management of this rare complication in this challenging setting. This report shows IVIG induced cerebral sinus thrombosis in ITP.

Haemolytic activity of polyamidoamine dendrimers and the protective role of human serum albumin

We have examined the haemolytic activity of polyamidoamine dendrimers. Haemolysis increased in a generation- and concentration-dependent manner. Moreover, the longer the incubation time, the greater the amount of haemoglobin released. When human serum albumin (HSA) was present in the incubation buffer, the extent of haemolysis decreased. This protective effect may be due to the high affinity of dendrimers for proteins: dendrimers that interact with HSA are unable to disrupt the membrane to the same extent as free dendrimers. The presence of HSA makes the buffer more relevant to physiological conditions. The results of this study suggest that the actual haemotoxicity of dendrimers in vivo is lower than is observed in vitro .

Increased strength of erythrocyte aggregates in blood of patients with inflammatory bowel disease

BACKGROUND

Increased strength of red blood cell (RBC) aggregates are present during the acute inflammatory response and contribute to erythrocyte aggregation and may lead to microvascular dysfunction. Inflammatory bowel diseases (IBDs) are characterized by damage to the bowel wall. This damage may be at least partially attributed to microvascular ischemia caused by enhanced erythrocyte aggregation. The aim of this study was to evaluate the strength of RBC aggregates in the blood of patients with IBD.

METHODS

The strengths of RBC aggregates were characterized by integrative RBC aggregation parameters, determined by measuring of RBC aggregation as a function of shear stress. The results are represented as the area under the curve (AUC) of aggregate size plotted against shear stress. For each patient, dynamic aggregation and disaggregation of RBC were recorded and analyzed according to the RBC aggregate size distribution at the different shear stresses. Aggregation indices were correlated with disease activity and inflammatory biomarkers.

RESULTS

We examined 53 IBD patients and 63 controls. IBD patients had significantly elevated concentrations of inflammation-sensitive proteins and aggregation parameters. The strength of large aggregates, represented by AUC for large fraction aggregates, among patients (15.2 +/- 18.6) was double that of controls (7 +/- 10.9) (P = 0.006). The strength of large aggregates correlated with disease activity (r = 0.340; P < 0.001) with concentration of fibrinogen (r = 0.575; P < 0.001) and with concentration of high sensitivity C-reactive protein (r = 0.386; P < 0.001).

CONCLUSIONS

The strength of RBC aggregates is increased in patients with IBD and correlates with the intensity of the acute phase response. This could contribute to bowel damage in these diseases.

Myocardial infarction during intravenous immunoglobulin infusion in a 65-year-old man with common variable immunodeficiency and subsequent successful repeated administration

BACKGROUND

Intravenous immunoglobulin (IVIG) may cause thromboembolic events. Although such events are usually associated with large IVIG doses administered to treat neurologic diseases, thromboembolic events may also occur with standard immunodeficiency doses.

OBJECTIVE

We describe a 65-year-old man with common variable immunodeficiency (CVID) who experienced angina and myocardial infarction with IVIG infusion.

METHODS

The patient's electronic medical record was reviewed.

RESULTS

The patient developed substernal chest pain during a scheduled 40-g (400-mg/kg) infusion. The infusion was discontinued, and a cardiac evaluation was initiated. The patient was found to have elevated troponin T and creatine kinase MB levels, signifying cardiac injury. Heart catheterization revealed severe vessel disease, and surgical revascularization was subsequently performed. Three weeks after revascularization, an IVIG dose of 200 mg/kg was cautiously readministered. This dose was increased in 2 weeks to 300 mg/kg, which was tolerated every 3 to 4 weeks without any adverse thrombotic events in the subsequent 12 months.

CONCLUSIONS

This case demonstrates not only angina and myocardial infarction associated with IVIG infusion in a patient with CVID but also the successful reinitiation of IVIG infusion after surgical revascularization. This case also underscores the importance of caution with IVIG infusion in patients with CVIDand known coronary artery disease.

Blood banking-induced alteration of red blood cell flow properties

BACKGROUND

Blood banking procedures are associated with damage to red blood cell (RBC) membranes, which can impair their flow properties, namely, their deformability, aggregability, and adherence to endothelial cells (ECs) and thus possibly introducing a circulatory risk to recipients. This study was undertaken to comprehensively explore the effect of cold storage and gamma irradiation on RBC flow properties.

STUDY DESIGN AND METHODS

RBC flow properties were monitored as a function of shear stress with a computerized cell flow properties analyzer. Because we had previously studied storage effect on RBC aggregability (Transfusion 1999;39:277-81), here we determined the storage effect on RBC adherence and deformability, by measuring them before (control) and during storage. Gamma irradiation effect on RBC aggregability, adherence, and deformability was determined before (control) and after irradiation.

RESULTS

Cold storage significantly elevated the number of adherent RBCs and the strength of their interaction with ECs, and was marked by decreased RBC deformability as early as 2 weeks into the storage period. The elevation of RBC-EC interaction was well correlated with translocation of phosphatidylserine to the RBC surface. Gamma irradiation induced an immediate and marked increase in the number of rigid cells, but did not affect RBC adherence and aggregability.

CONCLUSION

RBC flow properties appear to be especially sensitive to cold storage and gamma irradiation because they are impaired long before the expiration date. Because impaired RBC flow properties facilitate circulatory disorders, the potential circulatory risk of transfusion RBC with blood banking-impaired rheology should be considered.

Lipid contribution to the affinity of antigen association with specific antibodies conjugated to liposomes

Immunoliposomes, directed to clinically relevant cell-surface molecules with antibodies, antibody fragments or peptides, are used for site-specific diagnostic evaluation or delivery of therapeutic agents. We have developed intrinsically echogenic liposomes (ELIP) covalently linked to fibrin(ogen)-specific antibodies and Fab fragments for ultrasonic imaging of atherosclerotic plaques. In order to determine the effect of liposomal conjugation on the molecular dynamics of fibrinogen binding, we studied the thermodynamic characteristics of unconjugated and ELIP-conjugated antibody molecules. Utilizing radioimmunoassay and enzyme-linked immunosorbent assay protocols, binding affinities were derived from data obtained at three temperatures. The thermodynamic functions DeltaH(o) , DeltaG(o) and DeltaS(o) were determined from van't Hoff plots and equations of state. The resultant functions indicated that both specific and nonspecific associations of antibody molecules with fibrinogen occurred through a variety of molecular interactions, including hydrophophic, ionic and hydrogen bonding mechanisms. ELIP conjugation of antibodies and Fab fragments introduced a characteristic change in both DeltaH(o) and DeltaS(o) of association, which corresponded to a variable contribution to binding by phospholipid gel-liquid crystal phase transitions. These observations suggest that a reciprocal energy transduction, affecting the strength of antibody-antigen binding, may be a singular characteristic of immunoliposomes, having utility for optimization and further development of the technology.

The role of albumin in fluid and electrolyte balance

Albumin plays an important role in maintaining homeostasis within the body and depends on the cell membrane and the transport mechanism, including diffusion, osmosis, filtration, and active transport. The dissolved proteins, which are the only substances that do not penetrate the pores of the capillary membrane, are responsible for the osmotic pressure of the capillary membrane. Approximately 75% of the total colloid osmotic pressure is related to albumin.

Venous and arterial thrombosis following administration of intravenous immunoglobulins

Thrombotic events are an increasingly recognized complication of treatment with intravenous immunoglobulins (IVIg). We aimed to define clinical characteristics, risk factors and outcome for venous thrombosis as opposed to arterial thrombosis following administration of IVIg. Six patients with post-IVIg venous thrombosis were identified at our institution. In addition, a review of the literature revealed 65 reported cases. Arterial thrombosis (stroke and myocardial infarction) was four times more common than venous thrombosis (deep vein thrombosis and pulmonary embolism). The incidence rate was estimated at 0.15-1.2% per treatment course, but the large increase in reported cases in 2003 suggests that the true incidence may be significantly greater. The following differences were found between arterial and venous events: arterial thrombosis occurred early after IVIg administration (49% within 4 h, 77% within 24 h) and was associated with advanced age and atherosclerotic vascular disease; venous thrombosis occurred later (54% more than 24 h after IVIg administration) and was associated with factors contributing to venous stasis (obesity and immobility). Thirteen patients died (mortality 20%), 11 of whom had arterial thrombosis. In conclusion, IVIg-associated thrombosis is more common than previously recognized, and is associated with significant mortality. The different characteristics of arterial and venous events may reflect different pathophysiological mechanisms. A better understanding of these mechanisms should aid in defining a risk-benefit ratio for the individual patient.

Intravenous immunoglobulin-associated arterial and venous thrombosis; report of a series and review of the literature

BACKGROUND

To date, the prevalence of intravenous immunoglobulin (IvIg)-related thrombotic complications has not been evaluated in patients with autoimmune disorders followed up in Departments of Internal Medicine.

OBJECTIVES

To assess prevalence and characteristics of IvIg-related thrombotic complications in patients with autoimmune disorders receiving IvIg therapy; to evaluate the predictive factors for onset of IvIg-related thrombotic manifestation in patients, and to detect patients at risk for these types of complications.

PATIENTS AND METHODS

The medical records of 46 patients with autoimmune disorders who were given IvIg therapy at our Department of Internal Medicine between January 2002 and December 2004 were reviewed.

RESULTS

Among the 46 patients, nine exhibited IvIg-associated severe complications (19.6%). Six patients (13%) developed IvIg-related thrombotic complications. Thrombotic complications frequently occurred during IvIg infusion (50%), although they were also observed within 1-8 days following IvIg infusion in other patients. IvIg-related thrombotic complications consisted of: deep venous thrombosis or pulmonary embolism (n = 3), myocardial infarction (n = 2) and stroke (n = 1). The outcome of thrombotic complications was favourable in all patients, after appropriate therapy institution. Older age, history of associated arterial hypertension and hypercholesterolaemia were more common in the group of patients with IvIg-related thrombotic complications.

CONCLUSIONS

Our study demonstrates that IvIg-related thrombotic arterial/venous complications are not uncommon in patients with autoimmune disorders (13% of patients). Nevertheless, patients, who are followed up in Departments of Internal Medicine often have concomitant disorders placing them at increased risk to develop IvIg-related thrombotic complications; the latter may also explain the high rate of IvIg-related thrombosis in our cohort. Our series further indicates that patients should be monitored closely for these types of adverse events during the whole period of IvIg therapy, as thrombotic manifestations occurred in patients who had received multiple IvIg infusions without exhibiting complications. In addition, our results suggest that it is questionable to initiate IvIg therapy in patients presenting with predictive factors of thrombotic complications; in this subgroup of patients, IvIg should be prescribed cautiously, after re-weighing risk-benefit considerations.

Plasma dependent reduction in red blood cell aggregation after dextran sulfate low-density lipoprotein apheresis--implications for rheological studies

Red blood cell (RBC) aggregation is increased in familial hypercholesterolemia, and is reduced significantly after low density lipoprotein (LDL) apheresis. The purpose of the present study was to clarify whether this reduction depends on changes in plasma composition, RBC membrane properties, or both. RBC aggregation was determined in a computerized cell flow-properties analyzer, before and after LDL apheresis. We compared RBC aggregation in autologous plasma with aggregation in a plasma-free standard solution (0.5% of dextran 500 kDa) to define the separate contributions of plasma and cellular properties to the observed RBC aggregation. RBC aggregation in autologous plasma was reduced by 35.5% after LDL apheresis (P=0.01) but was not significantly affected when measured in dextran 500. This suggests that LDL apheresis attenuated RBC aggregation by altering plasma composition rather than RBC membrane properties. These results are relevant to the understanding of hemorheological changes which follow therapeutic apheresis in hypercholesterolemic patients.

Enhanced Erythrocyte Aggregation in Clinically Diagnosed Pelvic Inflammatory Disease

OBJECTIVE

Enhanced erythrocyte aggregation, revealed using a simple bedside test, has been found recently in several inflammatory conditions. The diagnosis of pelvic inflammatory disease (PID) is at times difficult because of the vague symptoms and signs, but is crucial because even mild PID can have future reproductive consequences. Our objective was to determine the degree of erythrocyte aggregation in PID. The demonstration of an increase in aggregation could be of additive value in cases in which the diagnosis is difficult.

STUDY DESIGN

A prospective case-control study was conducted. Fifteen consecutive women diagnosed clinically as having PID based on Centers for Disease Control and Prevention criteria, and 15 matched controls were enrolled. Blood samples were drawn for hematologic indices, C-reactive protein, fibrinogen levels, and red cell aggregation. We studied the degree of red cell aggregation using a simple slide test and image analysis. The variable measured was the erythrocyte percent (EP), equivalent to the slide area covered by erythrocytes.

RESULTS

Erythrocyte percent was 59.6 +/- 4.2 and 80.0 +/- 3.6 for the study group and controls, respectively (P <0.001). A significant difference was noted also for the other hematologic and biochemical markers of inflammation between patients and the controls.

CONCLUSIONS

We conclude that the degree of erythrocyte aggregation is increased in PID. Its simplicity, rapidity, and low cost should be further evaluated as a diagnostic tool in the context of this frequent disease.

Automatic 3-dimensional visualization of peripheral blood slides: a new approach for the detection of infection/inflammation at the point of care

CONTEXT

The identification and quantitation of the intensity of the acute-phase response at the point of care might be of clinical relevance.

OBJECTIVE

To report the possibility of automatic screening of unstained peripheral blood slides by using a 3-dimensional image analysis system.

DESIGN

Peripheral venous blood was obtained from children with acute inflammation/infection and examined by an automatic 3-dimensional image analyzer to detect the number of white blood cells as well as to reveal the degree of erythrocyte aggregation, a marker of the humoral phase response.

RESULTS

We included 66 children with acute bacterial infections and 59 with nonbacterial inflammation/infection; mean ages of the 2 groups were 4.3 +/- 3.9 years and 4.2 +/- 3.7 years, respectively (P = .91). The percentages of correct classifications based on discriminant analysis in predicting between bacterial and nonbacterial inflammation/infection were 61.3% by using the white blood cell count, 64.5% by using the percentage of granulocytes, 61.6% by using the degree of erythrocyte aggregation, and 59.2% by using the number of leukocytes counted on the unstained slides. The results of the receiver-operated characteristic curve analysis yielded an area under the curve of 0.714 (P < .001) for the number of granulocytes, 0.699 (P < .001) for the white blood cell count, 0.685 (P < .001) for the number of leukocytes on the slides, and 0.685 (P = .001) for the degree of erythrocyte aggregation. The correlation between the number of leukocytes by the electronic cell analyzer and the number of cells counted on the slides was highly significant (r = 0.85, P < .001).

CONCLUSIONS

It is feasible to use an automatic 3-dimensional image analyzer to reveal the different intensities of the acute-phase response between a group of children with an acute bacterial infection and another with nonbacterial inflammation/infection. These findings might be relevant for potential application at the point of care.

Inflammation-related erythrocyte aggregation in patients with inflammatory bowel disease

Chronic inflammation is associated with increased erythrocyte adhesiveness/aggregation. This might have deleterious effects on the microcirculatory flow and tissue oxygenation. We aimed to determine the degree of erythrocyte adhesiveness/aggregation in the peripheral blood of individuals with inflammatory bowel disease (IBD). Fifty-two patients (24 women and 28 men) with ulcerative colitis (UC) at a mean age of 44.0+/-16.8 years and 96 patients (44 women and 52 men) with Crohn's disease (CD) at a mean age of 38.0+/-15.5 years, with various degrees of disease activity, were matched to normal controls. A simple slide test and image analysis were used to determine the degree of erythrocyte adhesiveness/aggregation. CD activity index (CDAI) was determined in patients with CD, while clinical colitis activity index was applied for patients with UC. A significant (P < 0.0005) increment in the degree of erythrocyte adhesiveness/aggregation was noted in both groups of IBD patients compared with matched control groups. This increment was evident even in individuals with a low index of disease activity and during remission. The highly significant correlation with the concentrations of fibrinogen suggests that the degree of erythrocyte adhesiveness/aggregation is an inflammation-related phenomenon. An enhanced state of erythrocyte adhesiveness/aggregation was noted in the peripheral blood of patients with IBD. This might have a deleterious effect on intestinal microcirculatory flow and tissue oxygenation.

Association of components of the metabolic syndrome with the appearance of aggregated red blood cells in the peripheral blood. An unfavorable hemorheological finding

BACKGROUND

Components of the metabolic syndrome are associated with low-grade inflammation. This can be accompanied by the synthesis of sticky proteins and erythrocyte aggregation.

METHODS

The degree of erythrocyte aggregation was evaluated by a simple slide test and image analysis along with other markers of the acute-phase response, including the white blood cell count (WBCC), erythrocyte sedimentation rate (ESR), fibrinogen and high sensitivity C-reactive protein (hs-CRP) concentrations. Patients were categorized in four groups according to the absence or presence of 1, 2 and 3 or more components of the metabolic syndrome.

RESULTS

We examined a total of 1447 individuals (576 women and 871 men) who gave their informed consent for participation. A significant cardiovascular risk factors, age and hemoglobin adjusted correlation was noted between the degree of erythrocyte aggregation and the number of components of the metabolic syndrome (r = 0.17, p < 0.0005). This correlation was better than that observed for clottable fibrinogen (r = 0.13 p < 0.0005), for ESR (r = 0.11 p < 0.0005) or WBCC (r = 0.13 p < 0.0005). A somewhat better correlation was noted for hs-CRP (r = 0.26 p < 0.0005).

CONCLUSIONS

The multiplicity of components of the metabolic syndrome is associated with enhanced erythrocyte aggregation, probably related to the presence of multiple adhesive macromolecules in the peripheral blood. The enhanced aggregation might contribute to capillary slow flow, tissue deoxygenation as well as vasomotor tone changes in the presence of multiple components of this syndrome.

The red blood cell and vascular function in health and disease

Nitric oxide (NO) is widely accepted as a central regulator of vascular tone and a vast array of other cardiovascular signaling mechanisms. An emerging player in these mechanisms is hemoglobin (Hb), an erythrocytic protein that serves as the archetypical model for an allosteric protein. Specifically, red blood cells (RBC) are suggested to be integral in matching blood flow to tissue oxygen demands. The mechanisms proposed involve the ability of Hb to sense changes in oxygen concentrations and coupling this process to modulating vascular NO levels. The molecular basis of these mechanisms remains under investigation, but is clearly diverse and discussed in this article from the basis of the blood flow responses to hypoxia. Another emerging theme in RBC biology is the role of these cells during inflammatory disease in which disease processes promote the interaction of vascular NO and the RBC. This is exemplified in hemolytic diseases, in which released Hb has drastic affects on vascular homeostasis mechanisms. Additionally, it is becoming evident that RBC express numerous molecules that mediate interactions with the extracellular matrix and cellular mediators of inflammation. The functional implications for such interactions remain unclear but highlight potential roles of the RBC in modulating inflammatory disease.

Flow-resistant red blood cell aggregation in morbid obesity

OBJECTIVE

Enhanced red blood cell (RBC) aggregation has an adverse effect on microcirculatory blood flow and tissue oxygenation. It has been previously shown that obesity is associated with increased RBC aggregation. The objectives of the present study were to further characterize obesity-related RBC aggregation and to examine whether the enhanced aggregation is a plasma- or cellular-dependent process.

METHODS

Obese (body mass index (BMI)=40+/-6.3 kg/m2, n=22) and nonobese (BMI=24+/-3.4 kg/m2, n=18) individuals were evaluated for inflammation markers and aggregation parameters. Aggregation parameters were derived from the distribution of RBC population into aggregate sizes, and from the variation of the distribution as a function of flow-derived shear stress, using a cell flow properties analyzer. To differentiate plasmatic from cellular factors, we determined the aggregation in the presence of autologous plasma or dextran-500 kDa and calculated the plasma factor (PF) in the obese group. PF ranges from 0 to 1. When the PF=1, the aggregation is all due to plasmatic factors, when PF=0, the altered aggregation depends entirely on cellular factors, whereas 0<PF<1 reflects the joint contribution of cellular and plasmatic factors.

RESULTS

Obese subjects had relatively larger aggregates that were more resistant to dispersion by flow. The calculated PF in the obese group was 0.9, indicating a pronounced contribution of plasma to RBC aggregation in obesity.

DISCUSSION

Our results suggest that obese individuals present pathological plasma-dependent RBC aggregation, which is probably triggered by plasma macromolecules associated with the inflammatory response. These findings impact the future attempts to develop strategies aimed at attenuation of the enhanced RBC aggregation in obese individuals.

Rheological determinants in patients with Gaucher disease and internal inflammation

The purpose of this study was to determine whether the inflammatory response in patients with Gaucher disease (GD) is accompanied by enhanced adhesiveness/aggregation of both red and white blood cells. Sixty patients with GD and matched controls were included. The degree of erythrocyte and leukocyte adhesiveness/aggregation was determined by using a simple slide test and image analysis. Patients with GD had significantly elevated concentrations of fibrinogen (328 vs. 262 mg/dl, P < 0.0001) and accelerated erythrocyte sedimentation rates (27 vs. 13 mm/H, P < 0.005). This was accompanied by a significantly enhanced degree of erythrocyte (75 vs. 85, P < 0.0001) and leukocyte (3.5 vs. 1.3, P < 0.002) adhesiveness/aggregation. The low-grade, smoldering, and subclinical internal inflammation in individuals with GD is accompanied by an increased degree of erythrocyte and leukocyte adhesiveness/aggregation. These findings might have rheological consequences in terms of microcirculatory slow flow and tissue hypoxemia.