Red cell metabolism

Biogenic metallic nanoparticles (Ag, TiO2, Fe) as potential fungicides for agriculture: are they safe for the freshwater mussel Anodontites trapesialis?

Silver (Ag), titanium dioxide (TiO₂), and iron (Fe) nanoparticles (NPs) synthesized using the fungus Trichoderma harzianum are effective against the agriculture pathogen Sclerotinia sclerotiorum. However, their effects should be evaluated in aquatic organisms, as agriculture practices can contaminate the aquatic environment. Thus, this work evaluated sublethal effects of acute exposure (24 h) to AgNP, TiO₂NP and FeNP, synthesized with T. harzianum, on the Neotropical freshwater bivalve Anodontites trapesialis, considering the hypothesis that suspension-feeding bivalves are susceptible to NPs toxicity. Individuals of A. trapesialis were divided into four groups (n = 8/group): a control group, kept in water only; a group exposed to AgNP; a group exposed to TiO₂NP; and a group exposed to FeNP. The bioaccumulation of Ag, Ti, and Fe was evaluated in the gills, hemolymph, mantle, digestive gland, and muscle (foot). Lipoperoxidation, activities of the glutathione S-transferase, catalase, and superoxide dismutase, and glycogen concentration were quantified in the gills, mantle, and digestive gland. Ions (Na⁺, K⁺, Cl^-, Ca²⁺, and Mg⁺²) and glucose concentrations were quantified in the hemolymph. Na⁺/K⁺-ATPase, H⁺-ATPase, Ca²⁺-ATPase, and carbonic anhydrase activities were assessed in the gills and mantle. Acetylcholinesterase activity was determined in the foot and adductor muscle. The mussels exposed to AgNP accumulated Ag in the gills, hemolymph, and foot, and showed a decrease in hemolymph concentrations of Na⁺ and Cl^-, which was associated with the action of Ag ion (Ag⁺). The exposures to TiO₂NP and FeNP led to the accumulation of Ti and Fe in the hemolymph, respectively, but did not promote additional effects. Accordingly, A. trapesialis showed bioaccumulation potential and susceptibility to AgNP, but was not susceptible to TiO₂NP and FeNP. Thus, the preferential agricultural use of TiO₂NP and FeNP over AgNP is highlighted.

From the Cradle to the Grave: The Role of Macrophages in Erythropoiesis and Erythrophagocytosis

Erythropoiesis is a highly regulated process where sequential events ensure the proper differentiation of hematopoietic stem cells into, ultimately, red blood cells (RBCs). Macrophages in the bone marrow play an important role in hematopoiesis by providing signals that induce differentiation and proliferation of the earliest committed erythroid progenitors. Subsequent differentiation toward the erythroblast stage is accompanied by the formation of so-called erythroblastic islands where a central macrophage provides further cues to induce erythroblast differentiation, expansion, and hemoglobinization. Finally, erythroblasts extrude their nuclei that are phagocytosed by macrophages whereas the reticulocytes are released into the circulation. While in circulation, RBCs slowly accumulate damage that is repaired by macrophages of the spleen. Finally, after 120 days of circulation, senescent RBCs are removed from the circulation by splenic and liver macrophages. Macrophages are thus important for RBCs throughout their lifespan. Finally, in a range of diseases, the delicate interplay between macrophages and both developing and mature RBCs is disturbed. Here, we review the current knowledge on the contribution of macrophages to erythropoiesis and erythrophagocytosis in health and disease.

Oxidative stress in β-thalassaemia and sickle cell disease

Sickle cell disease and β-thalassaemia are inherited haemoglobinopathies resulting in structural and quantitative changes in the β-globin chain. These changes lead to instability of the generated haemoglobin or to globin chain imbalance, which in turn impact the oxidative environment both intracellularly and extracellularly. The ensuing oxidative stress and the inability of the body to adequately overcome it are, to a large extent, responsible for the pathophysiology of these diseases. This article provides an overview of the main players and control mechanisms involved in the establishment of oxidative stress in these haemoglobinopathies.

Inborn defects in the antioxidant systems of human red blood cells

Red blood cells (RBCs) contain large amounts of iron and operate in highly oxygenated tissues. As a result, these cells encounter a continuous oxidative stress. Protective mechanisms against oxidation include prevention of formation of reactive oxygen species (ROS), scavenging of various forms of ROS, and repair of oxidized cellular contents. In general, a partial defect in any of these systems can harm RBCs and promote senescence, but is without chronic hemolytic complaints. In this review we summarize the often rare inborn defects that interfere with the various protective mechanisms present in RBCs. NADPH is the main source of reduction equivalents in RBCs, used by most of the protective systems. When NADPH becomes limiting, red cells are prone to being damaged. In many of the severe RBC enzyme deficiencies, a lack of protective enzyme activity is frustrating erythropoiesis or is not restricted to RBCs. Common hereditary RBC disorders, such as thalassemia, sickle-cell trait, and unstable hemoglobins, give rise to increased oxidative stress caused by free heme and iron generated from hemoglobin. The beneficial effect of thalassemia minor, sickle-cell trait, and glucose-6-phosphate dehydrogenase deficiency on survival of malaria infection may well be due to the shared feature of enhanced oxidative stress. This may inhibit parasite growth, enhance uptake of infected RBCs by spleen macrophages, and/or cause less cytoadherence of the infected cells to capillary endothelium.

Thiazole orange, a DNA-binding photosensitizer with flexible structure, can inactivate pathogens in red blood cell suspensions while maintaining red cell storage properties

BACKGROUND

Development of a robust pathogen reduction system for red cells (RBCs) utilizing photosensitive dyes has been constrained by hemolysis, usually mediated by reactive oxygen species emanating from dye free in solution as well as dye bound to the RBC membrane. The RBC binding properties of thiazole orange (TO), a flexible nucleic acid intercalating cyanine dye that predominantly acts as a photosensitizer only when bound, were assessed along with its virucidal, bactericidal, and light-induced hemolytic activities.

STUDY DESIGN AND METHODS

Leukodepleted 20% hematocrit RBCs suspended in Erythrosol (RAS-2) were oxygenated, inoculated with test organisms, incubated with TO, and illuminated. Control and treated samples were analyzed by appropriate assay. Identically prepared, but uncontaminated samples were phototreated, concentrated to 45% hematocrit, and assayed for potassium leakage, hemolysis, and ATP during storage.

RESULTS

Approximately 21 percent TO bound to RBCs. Phototreatment inactivated from 5.4 to 7.1 log(10) of 5 tested viruses and from 2.3 to greater than 7.0 log(10) of 8 tested bacteria. Phototreated RBCs exhibited only slightly increased hemolysis, moderately elevated potassium efflux, and similar levels of ATP compared to controls.

CONCLUSION

TO can photoinactivate several model viruses and pathogens in RBCs under conditions that produce limited hemolysis without the addition of quenchers or competitive inhibitors.

Oral L-glutamine therapy for sickle cell anemia: I. Subjective clinical improvement and favorable change in red cell NAD redox potential

Previously, we demonstrated that there is an increased utilization of glutamine by intact sickle red blood cells (RBC) in conjunction with nicotinamide adenine dinucleotide (NAD) metabolism in vitro. In this report, we describe the in vivo effect of L-glutamine supplementation on total NAD, nicotinamide adenine dinucleotide reduced (NADH), and NAD redox potential of sickle RBC. Seven adult sickle cell anemia patients participated in this study. The exclusion criteria were pregnancy, previous or current use of hydroxyurea, and transfusion within 3 months of initiation of the study. After proper consent, L-glutamine was started at a dose of 30 g/day administered orally. Fasting blood samples were drawn at baseline and after 4 weeks of therapy by routine phlebotomy for evaluation of RBC total NAD and NADH levels. We found significant changes in both the NADH level and NAD redox potential (ratio of NADH to NAD+ + NADH). NAD redox potential increased from 47.2 +/- 3.7% to 62.1 +/- 11.8% (P < 0.01). The NADH level increased from 47.5 +/- 6.3 to 72.1 +/- 15.1 nmol/ml RBC (P < 0.01). The total NAD level demonstrated an upward trend (from 101.2 +/- 16 to 116.4 +/- 14.7 nmol/ml RBC) but this was not statistically significant. Our data show that oral L-glutamine can significantly increase the NAD redox potential and NADH level in sickle RBC. These changes may decrease oxidative susceptibility of sickle RBC and result in clinical benefit.

Pyrimidine 5'-nucleotidase deficiency: studies of five cases in two Japanese families

Two new families with red cell pyrimidine 5'-nucleotidase (P5N) deficiencies were found in Japan. The enzyme activities were 4.8% in case 1 and 9.7% in case 2. The propositi showed characteristic hemolytic anemia with market basophilic stippling, increased reduced glutathione content and accumulation of pyrimidine nucleotides in the red cell. High Michaelis constants for cytidine monophosphate, normal thermostability, abnormal optimum pH in both cases, and normal electrophoretic mobility in case 1 and slower mobility in case 2 were shown, suggesting that the cause of P5N deficiency, at least in these cases, is due to the structural gene mutation.