The Role of Eryptosis in the Pathogenesis of Renal Anemia: Insights From Basic Research and Mathematical Modeling

Red blood cells (RBC) are the most abundant cells in the blood. Despite powerful defense systems against chemical and mechanical stressors, their life span is limited to about 120 days in healthy humans and further shortened in patients with kidney failure. Changes in the cell membrane potential and cation permeability trigger a cascade of events that lead to exposure of phosphatidylserine on the outer leaflet of the RBC membrane. The translocation of phosphatidylserine is an important step in a process that eventually results in eryptosis, the programmed death of an RBC. The regulation of eryptosis is complex and involves several cellular pathways, such as the regulation of non-selective cation channels. Increased cytosolic calcium concentration results in scramblase and floppase activation, exposing phosphatidylserine on the cell surface, leading to early clearance of RBCs from the circulation by phagocytic cells. While eryptosis is physiologically meaningful to recycle iron and other RBC constituents in healthy subjects, it is augmented under pathological conditions, such as kidney failure. In chronic kidney disease (CKD) patients, the number of eryptotic RBC is significantly increased, resulting in a shortened RBC life span that further compounds renal anemia. In CKD patients, uremic toxins, oxidative stress, hypoxemia, and inflammation contribute to the increased eryptosis rate. Eryptosis may have an impact on renal anemia, and depending on the degree of shortened RBC life span, the administration of erythropoiesis-stimulating agents is often insufficient to attain desired hemoglobin target levels. The goal of this review is to indicate the importance of eryptosis as a process closely related to life span reduction, aggravating renal anemia.

Neutrophil Elastase Inhibitors and Chronic Kidney Disease

End-stage renal disease (ESRD), the last stage of chronic kidney disease (CKD), is characterized by chronic inflammation and oxidative stress. Neutrophils are the front line cells that mediate an inflammatory response against microorganisms as they can migrate, produce reactive oxygen species (ROS), secrete neutrophil serine proteases (NSPs), and release neutrophil extracellular traps (NETs). Serine proteases inhibitors regulate the activity of serine proteases and reduce neutrophil accumulation at inflammatory sites. This review intends to relate the role of neutrophil elastase in CKD and the effects of neutrophil elastase inhibitors in predicting or preventing inflammation.

Usefulness of Reticulocyte Parameters for Diagnosis of Hereditary Spherocytosis in Children

Innovations in laboratory equipment have enabled a widening of the spectrum of hematological parameters obtained from single measurements of peripheral blood samples, including reticulocyte parameters. The usefulness of reticulocytes indices to confirm the diagnosis of pediatric anemia was analyzed in this study. The study group consisted of 163 children, aged 1 month-17 years, with anemia. Complete blood count extended with an analysis of reticulocyte parameters were measured using a Beckman Coulter LH 750. The mean sphered corpuscular volume (MSCV) in the group of children with hereditary spherocytosis (HS) was 66.71 ± 8.45 fL, whereas in other anemic patients MSCV was 87.76 ± 11.22 fL, p < 0.0001. In HS children the average mean corpuscular volume of red blood cells was higher than the MSCV value, while an inverse correlation was observed in the group of children with other anemias, p < 0.0001. A significant difference was found between the ratio of absolute reticulocyte count and IRF fraction (Ret#/IRF)-0.6 ± 0.28 in the HS group and 0.23 ± 0.16 in the non-HS group, respectively. Our results suggest that analysis of reticulocyte parameters is useful in the diagnosis of anemia and should be included in the routine CBC analysis in anemic children.

Red blood cell abnormalities and the pathogenesis of anemia in end-stage renal disease

Anemia is the most common hematologic complication in end-stage renal disease (ESRD). It is ascribed to decreased erythropoietin production, shortened red blood cell (RBC) lifespan, and inflammation. Uremic toxins severely affect RBC lifespan; however, the implicated molecular pathways are poorly understood. Moreover, current management of anemia in ESRD is controversial due to the "anemia paradox" phenomenon, which underlines the need for a more individualized approach to therapy. RBCs imprint the adverse effects of uremic, inflammatory, and oxidative stresses in a context of structural and functional deterioration that is associated with RBC removal signaling and morbidity risk. RBCs circulate in hostile plasma by raising elegant homeostatic defenses. Variability in primary defect, co-morbidity, and therapeutic approaches add complexity to the pathophysiological background of the anemic ESRD patient. Several blood components have been suggested as biomarkers of anemia-related morbidity and mortality risk in ESRD. However, a holistic view of blood cell and plasma modifications through integrated omics approaches and high-throughput studies might assist the development of new diagnostic tests and therapies that will target the underlying pathophysiologic processes of ESRD anemia.

Genome-wide peripheral blood transcriptome analysis of Arab female lupus and lupus nephritis

Systemic lupus erythematosus (lupus) is a genetically heterogeneous autoimmune disorder with an obscure etiology. With 92-94% of human genes exhibiting alternative splicing, gaining insights to such events may lead to better diagnostics. Herein, we explored the genome-wide peripheral blood transcriptome of lupus and its severe form lupus-nephritis (LN) compared to healthy controls (HC). Age/gender/ethnically-matched Arab females were tested using high-density arrays and statistical analysis was carried out using appropriate software. Analysis revealed 15 splice variants that are differentially expressed between lupus/HC and 99 variants between LN/HC (p ≤ 0.05, SI> or ≤ 0.5, Benjamin Hochberg-False discovery rate correction). Comparison between LN/lupus revealed 7 variants that significantly differed in expression. Pathway analysis of differentially spliced-genes postulated 11 significant pathways in lupus and 12 in LN (p<0.05). Analysis of peripheral blood transcriptome possibly revealed signature causative genes that are alternatively spliced, signifying their clinical relevance. Present study is the first to reveal the significance of alternative variants in lupus and LN.

A role for the membrane proteome in human chronic kidney disease erythrocytes

The molecular basis of the reduced half-life of chronic kidney disease (CKD) erythrocytes is unclear. The erythrocyte membrane plays a key role in the erythrocyte mechanical properties and survival. The aim of the present work is to uncover erythrocyte membrane proteins whose expression could be altered in CKD. The erythrocyte membrane subproteome was analyzed by a non-biased approach where the whole set of proteins was simultaneously investigated by 2D fluorescence difference gel electrophoresis without preselection of potential targets. Proteins significantly altered in CKD were identified by mass spectrometry (MS) and results validation was performed by Western blot and confocal microscopy. Nine differentially expressed spots among healthy individuals, non-dialyzed CKD and erythropoietin/dialysis-treated CKD patients were identified by MS/MS corresponding to 5 proteins (beta-adducin, HSP71/72, tropomodulin-1, ezrin, and radixin). Ezrin and radixin were higher in dialyzed CKD patients than in the other 2 groups. Beta-adducin was increased in CKD patients (dialyzed or not). Three spots were normalized in patients on the dialysis/erythropoietin combination compared with non-dialyzed CKD. Among these, a spot corresponding to tropomodulin 1, was found to be of higher abundance in non-dialyzed CKD patients compared with controls or dialyzed CKD. In conclusion, this study identifies changes in erythrocyte membrane proteins in CKD, which may be relevant for the pathogenesis of red cell abnormalities in uremia.

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.