The red blood cell deformability in patients suffering from end stage renal failure on hemodialysis or continuous ambulatory peritoneal dialysis

Vitamin E‑coated dialyzer alleviates erythrocyte deformability dysfunction in patients with end‑stage renal disease undergoing hemodialysis

Patients with end-stage renal disease (ESRD) are characterized by augmented oxidative stress (OS) due to the imbalance between the generation of increased concentrations of oxidative molecules and decreased antioxidant capacity. Vitamin E-coated dialyzer membranes (VEMs) have previously been reported to alleviate the imbalance of redox metabolism in patients with ESRD undergoing hemodialysis (HD); however, their effect on the deformability of red blood cells (RBCs) remains unknown. In the present study, 48 patients with ESRD undergoing HD were enrolled and randomly assigned into two groups: HD with VEMs (VEM group; n=24) and HD with polysulfone dialyzer membranes (PM group; n=24), and another 24 healthy volunteers served as the control group. The present study investigated the morphological changes and deformability of RBCs in patients with ESRD and healthy volunteers. The concentration of serum vitamin E, the parameters of antioxidant stress and OS, and the degree of oxidative phosphorylation and clustering of anion exchanger 1 (Band 3) in RBCs were measured. The results obtained suggested that VEM treatment markedly ameliorated the abnormalities of RBC morphology and deformability in patients with ESRD undergoing HD. Mechanistic studies showed that VEM treatment led to a marked improvement in the concentration of serum vitamin E, which was positively associated with the restored antioxidant capacity, and decreased oxidative phosphorylation and clustering of Band 3 in RBCs of patients with ESRD undergoing HD. Taken together, the results of the present study have demonstrated that VEM treatment effectively restored the imbalance of redox metabolism, and improved the oxidative phosphorylation and clustering of Band 3 in RBCs of patients with ESRD undergoing HD via delivering vitamin E, which may alleviate the abnormal morphological and mechanical properties of RBCs. These findings are anticipated to be useful with respect to improving the nursing care and cure rate of patients with ESRD.

Microfluidic assessment of red blood cell mediated microvascular occlusion

Abnormal red blood cell (RBC) deformability contributes to hemolysis, thrombophilia, inflammation, and microvascular occlusion in various circulatory diseases. A quantitative and objective assessment of microvascular occlusion mediated by RBCs with abnormal deformability would provide valuable insights into disease pathogenesis and therapeutic strategies. To that end, we present a new functional microfluidic assay, OcclusionChip, which mimics two key architectural features of the capillary bed in the circulatory system. First, the embedded micropillar arrays within the microchannel form gradient microcapillaries, from 20 μm down to 4 μm, which mimic microcapillary networks. These precisely engineered microcapillaries retain RBCs with impaired deformability, such that stiffer RBCs occlude the wider upstream microcapillaries, while less stiff RBCs occlude the finer downstream microcapillaries. Second, the micropillar arrays are coupled with two side passageways, which mimic the arteriovenous anastomoses that act as shunts in the capillary bed. These side microfluidic anastomoses prevent microchannel blockage, and enable versatility and testing of clinical blood samples at near-physiologic hematocrit levels. Further, we define a new generalizable parameter, Occlusion Index (OI), which is an indicative index of RBC deformability and the associated microcapillary occlusion. We demonstrate the promise of OcclusionChip in diverse pathophysiological scenarios that result in impaired RBC deformability, including mercury toxin, storage lesion, end-stage renal disease, malaria, and sickle cell disease (SCD). Hydroxyurea therapy improves RBC deformability and increases fetal hemoglobin (HbF%) in some, but not all, treated patients with SCD. HbF% greater than 8.6% has been shown to improve clinical outcomes in SCD. We show that OI associates with HbF% in 16 subjects with SCD. Subjects with higher HbF levels (HbF > 8.6%) displayed significantly lower OI (0.88% ± 0.10%, N = 6) compared with those with lower HbF levels (HbF ≤ 8.6%) who displayed greater OI (3.18% ± 0.34%, N = 10, p < 0.001). Moreover, hypoxic OcclusionChip assay revealed a significant correlation between hypoxic OI and subject-specific sickle hemoglobin (HbS) level in SCD. OcclusionChip enables versatile in vitro assessment of microvascular occlusion mediated by RBCs in a wide range of clinical conditions. OI may serve as a new parameter to evaluate the efficacy of treatments improving RBC deformability, including hemoglobin modifying drugs, anti-sickling agents, and genetic therapies.

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.

Association between serum hepcidin-25 and primary resistance to erythropoiesis-stimulating agents in chronic kidney disease: a secondary analysis of the HERO trial

BACKGROUND

Pentoxifylline has been shown to increase haemoglobin levels in patients with chronic kidney disease (CKD) and erythropoietin-stimulating agent (ESA)-hyporesponsive anaemia in the Handling Erythropoietin Resistance with Oxpentifylline multicentre double-blind, randomized controlled trial. The present sub-study evaluated the effects of pentoxifylline on the iron-regulatory hormone hepcidin in patients with ESA-hyporesponsive CKD.

METHODS

This sub-study included 13 patients in the pentoxifylline arm (400 mg daily) and 13 in the matched placebo arm. Hepcidin-25 was measured by ultra performance liquid chromatography/quadrupole time-of-flight mass spectrometry following isolation from patient serum. Serum hepcidin-25, serum iron biomarkers, haemoglobin and ESA dosage were compared within and between the two groups.

RESULTS

Hepcidin-25 concentration at 4 months adjusted for baseline did not differ significantly in pentoxifylline versus placebo treated patients (adjusted mean difference (MD) -7.9 nmol, P = 0.114), although the difference between the groups mean translated into a >25% reduction of circulating hepcidin-25 due to pentoxifylline compared with the placebo baseline. In paired analysis, serum hepcidin-25 levels were significantly decreased at 4 months compared with baseline in the pentoxifylline group (-5.47 ± 2.27 nmol/l, P < 0.05) but not in the placebo group (2.82 ± 4.29 nmol/l, P = 0.24). Pentoxifylline did not significantly alter serum ferritin (MD 55.4 mcg/l), transferrin saturation (MD 4.04%), the dosage of ESA (MD -9.93 U/kg per week) or haemoglobin concentration (MD 5.75 g/l).

CONCLUSION

The reduction of circulating hepcidin-25 due to pentoxifylline did not reach statistical significance; however, the magnitude of the difference suggests that pentoxifylline may be a clinically and biologically meaningful modulator of hepcidin-25 in dialysis of patients with ESA-hyporesponsive anaemia.

Alterations of erythrocyte rheology and cellular susceptibility in end stage renal disease: Effects of peritoneal dialysis

In this study, we investigated the effects of peritoneal dialysis on hemorheological and hematological parameters and their relations with oxidant and antioxidant status of uremic patients. Hemorheological parameters (erythrocyte deformability, erythrocyte aggregation, osmotic deformability, blood and plasma viscosity) were measured in patients with renal insufficiency undergoing peritoneal dialysis (PD) and volunteers. Erythrocyte deformability, osmotic deformability and aggregation in both autologous plasma and 3% dextran 70 were measured by laser diffraction ektacytometry. Enzyme activities of glutathione peroxidase, superoxide dismutase and catalase were studied in erythrocytes; lipid peroxidation was studied by measuring the amount of malondialdehyde in both erythrocytes and plasma samples. Blood viscosity at native hematocrit was significantly lower in PD patients at all measured shear rates compared to controls, but it was high in PD patients at corrected (45%) hematocrit. Erythrocyte deformability did not show any difference between the two groups. Osmotic deformability was significantly lower in PD patients compared to controls. Aggregation index values were significantly high in PD patients in plasma Catalase and glutathione peroxidase activities in erythrocytes were decreased in PD patients whereas superoxide dismutase activity was increased compared to controls. Malondialdehyde was significantly increased in erythrocytes and plasma samples of PD patients which also shows correlations with aggregation parameters. It has been concluded that erythrocytes in PD patients are more prone to aggregation and this tendency could be influenced by lipid peroxidation activity in patient's plasma. These results imply that uremic conditions, loss of plasma proteins and an increased risk of oxidative stress because of decreasing levels of antioxidant enzymes affect erythrocyte rheology during peritoneal dialysis. This level of distortion may have crucial effects, impairing the blood flow dynamics and causing inadequate microcirculatory perfusion.

Circulating growth arrest-specific protein 6 levels are associated with erythropoietin resistance in hemodialysis patients

Growth arrest-specific protein 6 (Gas6) works synergistically with erythropoietin (EPO) to increase the proliferation and maturation of erythroblasts. However, the role of Gas 6 levels on EPO resistance in hemodialysis (HD) patients remains unclear. Therefore, the objective of this study was the first to examine the correlation between plasma Gas6 levels and EPO resistance in HD patients. We enrolled 134 HD patients and 85 healthy individuals. The HD patients were divided into 2 groups: 98 non-EPO-resistant patients and 36 EPO-resistant patients. Plasma levels of Gas6, interleukin 6 (IL-6), high-sensitivity C-reactive protein (hs-CRP), and albumin were quantified. Compared with non-EPO-resistant patients, EPO-resistant patients had elevated plasma concentrations of Gas6 (15.4 ± 3.3 vs. 13.7 ± 3.2 ng/mL, P = 0.006), IL-6 (3.1 ± 3.1 vs. 2.1 ± 1.5 pg/mL, P = 0.009), and hs-CRP (12.7 ± 25.2 vs. 4.5 ± 5.5 mg/L, P = 0.002). In EPO-resistant HD patients, plasma Gas6 levels were negatively correlated with albumin levels (r = −0.388, P < 0.021). Elevated Gas6 levels are associated with EPO resistance in HD patients. Also, EPO resistance is related to inflammation and malnutrition. Thus, circulating Gas6 levels could be used as the potential marker in HD patients with EPO resistance.

Early utilization of hypertonic peritoneal dialysate and subsequent risks of non-traumatic amputation among peritoneal dialysis patients: a nationwide retrospective longitudinal study

BACKGROUND

The hemodialysis (HD) population has a particularly high incidence of amputation, which is likely associated with decreased tissue oxygenation during HD. However, information about the risk factors leading to amputation in peritoneal dialysis (PD) patients is limited. Here, we have investigated the association between the use of hypertonic peritoneal dialysate (HPD) and subsequent amputation in PD patients.

METHODS

Based on the data from the Taiwan National Health Insurance research database, this observational cohort study enrolled 203 PD patients who had received HPD early during treatment and had not undergone amputation and 296 PD controls who had not undergone amputation. Subjects were followed through until the end of 2009 and the event rates of new non-traumatic amputation were compared between groups.

RESULTS

The incidence of amputation was 3 times higher for the HPD cohort than for the comparison cohort (23.68 vs. 8.01 per 1000 person-years). The hazard ratio (HR) for this group, estimated using a multivariable Cox model, was 2.48 (95% confidence interval [CI] = 1.06-5.79). The HR for patients with both diabetes and early adoption of HPD increased to 44.34 (95% CI = 5.51-357.03), compared to non-HPD non-diabetic PD controls.

CONCLUSION

Early utilization of HPD in PD patients is associated with increasing risk of amputation; this risk considerably increases for those with concomitant diabetes.

Oxidative stress-associated shape transformation and membrane proteome remodeling in erythrocytes of end stage renal disease patients on hemodialysis

This study was designed to evaluate the oxidative stress status of erythrocytes and its association with cellular ultrastructure and membrane proteome modifications in patients with end stage renal disease (ESRD) on hemodialysis (HD). For that purpose, we studied red blood cells' (RBCs) modifications in twelve non-diabetic ESRD patients that were responsive in erythropoietin therapy. Intracellular ROS levels were measured by fluorometry, RBCs ultra-structure was examined by electron microscopy, while the membrane proteome by electrophoresis and immunoblotting. Compared to the healthy subjects, the uremic RBCs exhibited significantly increased ROS accumulation. Dialysis partially ameliorated the basal ROS levels but triggered cellular sensitivity to exogenous oxidative stimuli. Common membrane modifications involved loss, aggregation, fragmentation and carbonylation of critical components as well as over-expression of stress markers. HD significantly contributed to membrane proteome remodeling, especially for aquaporin-1, peroxiredoxin-2 and ubiquitinated proteins. The intracellular redox status and the closely associated membrane modifications seemed to be related to membrane instability, loss of surface area through vesiculation, echinocytosis and stomatocytosis. Our data evinced a network of interactions among the uremic toxins, the RBCs membrane composition and the cellular shape modifications in ESRD, which is developed around a core of oxidative provocations and cellular responses.

Effect of Hemodialysis on the Content of Fatty Acids in Monolayers of Erythrocyte Membranes in Patients with Chronic Renal Failure

Lipid metabolism disorders are found in patients with chronic renal failure (CRF). Changes in the content of fatty acids of the phospholipid fraction of erythrocyte membranes can lead to changes in the rheological properties. The objective of our study was to assess the effect of hemodialysis on the composition of fatty acids in two fractions of phospholipids: sphingomyelin (SPH, representative of the external monolayer) and phosphatidylethanolamine (PE, representative of the internal monolayer). Venous blood was drawn from patient with CRF before and after the HD procedure. Lipids from the erythrocyte stroma were extracted using the Rose and Oklander method and then were separated into phospholipid fractions using thin-layer chromatography (TLC). PE and SPH fractions were extracted, and the fatty acid profile was determined using gas chromatography (Perkin Elmer 8400; RTx 2330 column; length: 105 m). In the phospholipid fractions tested, a high content of saturated FA with a medium carbon chain (C 16:0 to C 18:2) and a long carbon chain such as C 24:0, C 24:1; C 22:6; and C 26:0 was found. The HD procedure affected the FA profile in the fractions tested. The proportion of saturated and unsaturated long-chain FA (above 18 C) increased in PE. However, the content of medium-chain FA C 16:0 to C 18:1 decreased. A significant decrease in the content of the majority of long-chain FA could be noted in SPH. The ratio of unsaturated (U) to saturated (S) fatty acids in the SPH fraction increased. Hemodialysis has a significant effect on the content of fatty acids in the PE and SPH fractions of erythrocyte membranes in patients with CRF.

Does glucose in dialysis fluid protect erythrocytes in patients with chronic renal failure?

BACKGROUND/AIMS

The aim of this study was to assess the multifaceted influence of glucose present in dialyzing fluid on erythrocytes of patients with chronic renal failure (CRF) undergoing regular hemodialysis.

METHODS

A group of 44 subjects with CRF undergoing regular hemodialysis was studied. Two tests were used: osmotic fragility and resistance to the hemolytic agent saponin. The total content of isoprostane 8-iso-prostaglandin F2alpha type III (8-iPF2alpha-III) in plasma and erythrocyte's membrane were determined by the ELISA method.

RESULTS

The presence of glucose in the dialysate is associated with lower intravascular hemolysis markers and high total 8-iPF2alpha-III concentrations in plasma.

CONCLUSION

The presence of glucose in dialyzing fluid could protect erythrocytes. It limits hemolysis in patients with CRF, but, on the other hand, increases the oxidative processes. This kind of treatment along with other therapeutic intervention such as administration of antioxidants (e.g. alpha-tocopherol, ascorbic acid, N-acetylcysteine) could improve the condition of erythrocytes and outcome in CRF.