Uric acid increases erythrocyte aggregation: Implications for cardiovascular disease

New Onset Anemia, Worsened Plasma Creatinine Concentration, and Hyperviscosity in a Patient With a Monoclonal IgM Paraprotein

A 76-year-old female followed closely for five years with IgM monoclonal gammopathy of uncertain significance developed anemia, worsened plasma creatinine concentration, and markedly elevated serum viscosity. This case illustrates the scope of pathology that can be caused by elevated blood viscosity. Our patient's anemia was a homeostatic response to normalize systemic vascular resistance and resulted from activation of the systemic vascular resistance response. The elevated plasma creatinine resulted from decreased renal perfusion because of elevated blood viscosity. Recent insights in hemorheology (the study of blood flow) are discussed, namely the recent identification of preferential blood flow patterns and erythrocyte autoregulation of deformability. These insights confirm that blood viscosity is part of the "milieu intérieur."

TMEM16F mediated phosphatidylserine exposure and microparticle release on erythrocyte contribute to hypercoagulable state in hyperuricemia

The link between hyperuricemia (HUA) and the risk of venous thromboembolism (VTE) has been well established. However, the mechanisms of thrombus generation and the effect of HUA on procoagulant activity (PCA) of erythrocytes remain unclear no matter in uremia or hyperuricemia. Here, phosphatidylserine (PS) exposure, microparticles (MPs) release, cytosolic Ca2+, TMEM16F expression, reactive oxygen species (ROS) and lipid peroxidation of erythrocyte were detected by flow cytometer. PCA was assessed by coagulation time, purified coagulation complex and fibrin production assays. The fibrin formation was observed by scanning electron microscopy (SEM). We found that PS exposure, MPs generation, TMEM16F expression and consequent PCA of erythrocyte in HUA patients significantly increased compared to those in healthy volunteers. Furthermore, high UA induced PS exposure, and MPs release of erythrocyte in concentration and time-dependent manners in vitro, which enhanced the PCA of erythrocyte and was inhibited by lactadherin, a PS inhibitor. Additionally, using SEM, we also observed compact fibrin clots with highly-branched networks and thin fibers supported by red blood cells (RBCs) and RBC-derived MPs (RMPs). Importantly, we demonstrated UA enhanced the production of ROS and lipid peroxidation and reduced the generation of glutathione (GSH) of erythrocyte, which enhanced TMEM16F activity and followed PS externalization and RMPs formation. Collectively, these results suggest that Ca2+-dependent TMEM16F activation may be responsible for UA-induced PS exposure and MPs release of RBC, which thereby contribute to the prothrombotic risk in HUA.

Uric acid and uric acid/creatinine ratio and their correlations with the hemorheological determinants in subjects with subclinical carotid atherosclerosis

BACKGROUND AND OBJECTIVE

we have examined the concentration of serum uric acid and the serum uric acid/creatinine ratio as well as their correlations with the main determinants of the hemorheological profile in a group of subjects with subclinical carotid atherosclerosis.

METHODS

we evaluated the concentration of serum uric acid and the serum uric acid/creatine ratio in 43 men and 57 women [median age 66.00 (25)] with subclinical carotid atherosclerosis, subsequently divided according to the number of traditional cardiovascular risk factors and to the insulin resistance degree.

RESULTS

serum uric acid, but not the serum uric acid/creatinine ratio, results strongly influenced by the number of cardiovascular risk factors and by the insulin resistance degree. In the whole group and in the subgroups of subclinical carotid atherosclerosis subjects, serum uric acid and serum uric acid/creatinine ratio show significant correlation, besides with whole blood viscosity, with plasma viscosity and erythrocyte aggregation. The influence of the serum uric acid on the erythrocyte aggregability that is a part of the erythrocyte aggregation is to ascribe to the action carried out by serum uric acid on the erythrocyte zeta potential.

CONCLUSIONS

it is reasonable to think that the treatment of the asymptomatic or symptomatic hyperuricemia with the urate-lowering therapy that reduces the serum uric acid concentration may reflect on the hemorheological profile which role on the atherosclerotic cardiovascular disease is well known.

An assessment of the hemorheological profile in patients with subclinical carotid atherosclerosis divided in relation to the number of cardiovascular risk factors and different degrees of insulin resistance

We present a cohort of 100 subjects [43 men and 57 women; median age 66.00(25)] who were tested using carotid ultrasound to identify subclinical carotid atherosclerosis (SCA). We have evaluated the behaviour of whole blood viscosity (WBV) at high (450 s-1) and low (0.51 s-1) shear rates, plasma viscosity (450-1), hematocrit and mean erythrocyte aggregation. When compared to normal control subjects, using the Mann-Whitney test, we observed in SCA patients a significant increase in WBV only. The results were substantial after having divided the SCA subjects according to the cardiovascular risk factors (CRFs) and the degree of insulin resistance; the research was performed using two surrogate indexes such as TG/HDL-C and TyG. With the division carried out according to CRFs, employing the Kruskal-Wallis test, results show a significant increase in WBV (at high and low shear rates), in plasma viscosity, in erythrocyte aggregation and plasma fibrinogen level. Whereas by dividing them into the median of TG/HDL-C and TyG, we noticed a significant increase in WBV (at high and low shear rates) and in erythrocyte aggregation in the two groups with high TG/HDL-C ratio and with high TyG; having found an increased level of plasma fibrinogen in the latter. The data underlines the role of the main hemorheologic aspects in subclinical carotid atherosclerosis being closely correlated to the CRFs and different degrees of insulin resistance.

The Role of Blood Viscosity in Infectious Diseases

Blood viscosity is increased by elevated concentrations of acute phase reactants and hypergammaglobulinemia in inflammation. These increase blood viscosity by increasing plasma viscosity and fostering erythrocyte aggregation. Blood viscosity is also increased by decreased erythrocyte deformability, as occurs in malaria. Increased blood viscosity contributes to the association of acute infections with myocardial infarction (MI), venous thrombosis, and venous thromboembolism. It also increases vascular resistance, which decreases tissue perfusion and activates stretch receptors in the left ventricle, thereby initiating the systemic vascular resistance response. This compensates for the increased vascular resistance by vasodilation, lowering hematocrit, and decreasing intravascular volume. This physiological response causes the anemias associated with malaria, chronic inflammation, and other chronic diseases. Since tissue perfusion is inversely proportional to blood viscosity, anemia may be beneficial as it increases tissue perfusion when erythrocyte aggregating factors or erythrocytes with decreased deformability are present in the blood.

Phosphatidylserine on microparticles and associated cells contributes to the hypercoagulable state in diabetic kidney disease

Background

Relatively little is known about the role of phosphatidylserine (PS) in procoagulant activity (PCA) in patients with diabetic kidney disease (DKD). This study was designed to evaluate whether exposed PS on microparticles (MPs) and MP-origin cells were involved in the hypercoagulability in DKD patients.

Methods

DKD patients (n = 90) were divided into three groups based on urinary albumin excretion rate, defined as normoalbuminuria (No-A) (<30 mg/24 h), microalbuminuria (Mi-A) (30-299 mg/24 h) or macroalbuminuria (Ma-A) (>300 mg/24 h), and compared with healthy controls (n = 30). Lactadherin was used to quantify PS exposure on MPs and their original cells. Healthy blood cells (BCs) and human umbilical vein endothelial cells (HUVECs) were treated with 25, 5 or 2.5 mmol/L glucose as well as 3-12 mg/dL uric acid and cells were evaluated by clotting time and purified coagulation complex assays. Fibrin production was determined by turbidity. PS exposure and fibrin strands were observed using confocal microscopy.

Results

Using flow cytometry, we found that PS+ MPs (derived from platelets, erythrocytes, HUVECs, neutrophils, monocytes and lymphocytes) and BCs were significantly higher in patients than in controls. Furthermore, the number of PS+ MPs and BCs in patients with Ma-A was significantly higher than in patients with No-A. Similarly, we observed markedly elevated PS exposure on HUVECs cultured with serum from patients with Ma-A versus serum from patients with Mi-A or normoalbuminuria. In addition, circulating PS+ MPs cooperated with PS+ cells, contributing to markedly shortened coagulation time and dramatically increased FXa/thrombin generation and fibrin formation in each DKD group. Confocal microscopy images demonstrated colocalization of fibrin with PS on HUVECs. Moreover, blockade of exposed PS on MPs and cells with lactadherin inhibited PCA by ∼80%. In vitro, BCs and endothelial cells exposed more PS in hypoglycemia or hyperglycemia. Interestingly, reconstitution experiments showed that hypoglycemia-treated cells could be further activated or injured when recovery is obtained reaching hyperglycemia. Moreover, uric acid induced PS exposure on cells (excluding platelets) at concentrations >6 mg/dL. Linear regression analysis showed that levels of PS+ BCs and microparticles were positively correlated with uric acid and proteinuria, but negatively correlated with glomerular filtration rate.

Conclusions

Our results suggest that PS+ MPs and MP-origin cells play procoagulant roles in patients with DKD. Blockade of PS could become a novel therapeutic modality for the prevention of thrombosis in these patients.

Essential arterial hypertension patients present higher cell adhesion forces, contributing to fibrinogen-dependent cardiovascular risk

The increase of erythrocyte aggregation by high fibrinogen levels may be an indicator of cardiovascular risk. γ' fibrinogen variant has been considered as a possible player in enhancing aggregation. Here, we assessed, at the single-cell level, the influence of fibrinogen on erythrocyte aggregation in essential arterial hypertension. We also aimed at understanding how γ' fibrinogen is altered in this disease. Using atomic force microscopy (AFM), we show that the work and force necessary for erythrocyte-erythrocyte detachment is higher for patients than for healthy donors, with these parameters further increasing in both groups when higher fibrinogen concentrations are present. This can be associated with changes in blood flow, due to transient bridging of two erythrocytes by fibrinogen, representing an important cardiovascular risk factor. γ' fibrinogen can influence the increased risk in essential arterial hypertension, as we demonstrate that its levels are significantly increased in these patients' blood. Nevertheless, this cannot be the only cause for the changes observed in the AFM data.