Clonal hematopoiesis and acquired genetic abnormalities of the red cell: An historical review

Several syndromes affecting the red cell that mimic those induced by germline mutations may result from a somatic mutation that accompanies a myeloid malignancy. These syndromes are most notable in cases of myelodysplastic syndrome, but they are not limited to any one category of myeloid neoplasm. Their occurrence in males exceed the male predominance that is evident in myeloid neoplasms. The syndromes include disorders of globin chain synthesis (α- and β-thalassemia), heme synthesis (erythropoietic porphyria and erythropoietic uroporphyria), red cell membrane structure (elliptocytosis and spherocytosis), red cell enzyme activity (pyruvate kinase deficiency, glucose-6-phosphate dehydrogenase deficiency) and lowered expression of red cell ABO blood group antigens. This historical review describes the path to uncovering these acquired syndromes and their causal somatic mutations, where known. These syndromes often go unrecognized because of the dominant concern of the primary neoplasm. They may add to the healthcare needs of the patient.

Acquired elliptocytosis in chronic myeloid neoplasms: An enigmatic relationship to acquired red cell membrane protein and genetic abnormalities

Nineteen reports of 41 cases of acquired red cell elliptocytosis associated with a chronic myeloid neoplasm are described. Although the majority of cases have an abnormality of the long arm of chromosome 20, del(q20), several cases do not. Moreover, in one case a specific qualitative abnormality of red cell protein band 4.1(4.1R) was reported; however, several subsequent cases could find no abnormality of a red cell membrane protein or found a different abnormality, usually quantitative. Thus, this striking red cell phenotypic feature, acquired elliptocytosis, seen in myelodysplastic syndrome and other chronic myeloproliferative diseases, closely simulating the red cell phenotype of hereditary elliptocytosis, has an unexplained genetic basis, presumably as the result of an acquired mutation(s) in some chronic myeloid neoplasms.

Fyn specifically Regulates the activity of red cell glucose-6-phosphate-dehydrogenase

Fyn is a tyrosine kinase belonging to the Src family (Src-Family-Kinase, SFK), ubiquitously expressed. Previously, we report that Fyn is important in stress erythropoiesis. Here, we show that in red cells Fyn specifically stimulates G6PD activity, resulting in a 3-fold increase enzyme catalytic activity (k_cat) by phosphorylating tyrosine (Tyr)-401. We found Tyr-401 on G6PD as functional target of Fyn in normal human red blood cells (RBC), being undetectable in G6PD deficient RBCs (G6PD-Mediterranean and G6PD-Genova). Indeed, Tyr-401 is located to a region of the G6PD molecule critical for the formation of the enzymatically active dimer. Amino acid replacements in this region are mostly associated with a chronic hemolysis phenotype. Using mutagenesis approach, we demonstrated that the phosphorylation status of Tyr401 modulates the interaction of G6PD with G6P and stabilizes G6PD in a catalytically more efficient conformation. RBCs from Fyn^-/-mice are defective in G6PD activity, resulting in increased susceptibility to primaquine-induced intravascular hemolysis. This negatively affected the recycling of reduced Prx2 in response to oxidative stress, indicating that defective G6PD phosphorylation impairs defense against oxidation. In human RBCs, we confirm the involvement of the thioredoxin/Prx2 system in the increase vulnerability of G6PD deficient RBCs to oxidation. In conclusion, our data suggest that Fyn is an oxidative radical sensor, and that Fyn-mediated Tyr-401 phosphorylation, by increasing G6PD activity, plays an important role in the physiology of RBCs. Failure of G6PD activation by this mechanism may be a major limiting factor in the ability of G6PD deficient RBCs to withstand oxidative stress.

Rapid Identification of Biallelic SPTB Mutation in a Neonate with Severe Congenital Hemolytic Anemia and Liver Failure

Heterozygous pathogenic variants in SPTB cause autosomal dominant hereditary spherocytosis, an important cause of neonatal nonimmune hemolytic anemia. Biallelic mutations are rarely reported, all with severe neonatal presentation. We describe rapid (68 h) genomic diagnosis of homozygous β-spectrin deficiency in a newborn with severe transfusion-dependent hemolytic anemia, conjugated hyperbilirubinemia, and progressive liver failure. Trio whole-exome sequencing identified a novel biallelic SPTB variant (c.6119C>T; p.Thr2040Ile) located in the critical spectrin repeat region. Pretransfusion blood film showed marked spherocytosis including microspherocytes and nucleated erythrocytes, and eosin-5-maleimide (E5M) staining was markedly reduced, supporting pathogenicity. Both asymptomatic heterozygous parents demonstrated mildly reduced E5M staining, with occasional spherocytes and elliptocytes. Early molecular diagnosis facilitated hypertransfusion to suppress ineffective erythropoiesis and reverse hepatic dysfunction. This report broadens the genotypic and phenotypic spectrum of spectrin deficiency and highlights the utility of rapid genomic testing in facilitating early diagnosis and informing targeted therapy in critically ill patients.

Red Cell Transfusions in the Genomics Era

Red cell genotyping has become widely available and now contributes to support transfusion of patients with hematologic diseases. This technology has facilitated the immunohematologic approach to antibody prevention, detection and identification. Donors, particularly rare donors, are most efficiently screened and identified by red cell genotyping. In transfused patients with challenging serologic reactivity, antibodies are more reliably identified when molecular typing information is available. Red cell genotyping of both donors and patients augments the selection of blood components. This technology, serving at the core of a real-time database inventory, is resulting in blood supply efficiencies. However, there is limited published evidence on the extent to which red cell genotyping has translated into improved clinical outcomes. Red cell alloimmunized patients may benefit the most in enhanced safety. For patients with antibodies to high-prevalence antigens, other than Rh, blood centers realized supply-chain efficiencies in the past decade. Prospective clinical trials and cost-effectiveness studies would contribute to further clarifying the optimal role of molecular testing in providing transfusion support for patients with hematologic diseases.

Plasma peroxiredoxin changes and inflammatory cytokines support the involvement of neuro-inflammation and oxidative stress in Autism Spectrum Disorder

BACKGROUND

It has been established that children with Autism Spectrum Disorders (ASD) are affected by oxidative stress, the origin of which is still under investigation. In the present work, we evaluated inflammatory and pro-oxidant soluble signature in non-syndromic ASD and age-matched typically developing (TD) control children.

METHODS

We analyzed leukocyte gene expression of inflammatory cytokines and inflammation/oxidative-stress related molecules in 21 ASD and 20 TD children. Moreover, in another-comparable-group of non-syndromic ASD (N = 22) and TD (N = 21) children, we analyzed for the first time the protein expression of the four members of the antioxidant enzyme family of peroxiredoxins (Prx) in both erythrocyte membranes and in plasma.

RESULTS

The gene expression of IL6 and of HSP70i, a stress protein, was increased in ASD children. Moreover, gene expression of many inflammatory cytokines and inflammation/oxidative stress-related proteins correlated with clinical features, and appeared to be linked by a complex network of inter-correlations involving the Aryl Hydrocarbon Receptor signaling pathway. In addition, when the study of inter-correlations within the expression pattern of these molecules was extended to include the healthy subjects, the intrinsic physiological relationships of the inflammatory/oxidative stress network emerged. Plasma levels of Prx2 and Prx5 were remarkably increased in ASD compared to healthy controls, while no significant differences were found in red cell Prx levels.

CONCLUSIONS

Previous findings reported elevated inflammatory cytokines in the plasma of ASD children, without clearly pointing to the presence of neuro-inflammation. On the other hand, the finding of microglia activation in autoptic specimens was clearly suggesting the presence of neuro-inflammation in ASD. Given the role of peroxiredoxins in the protection of brain cells against oxidative stress, the whole of our results, using peripheral data collected in living patients, support the involvement of neuro-inflammation in ASD, and generate a rational for neuro-inflammation as a possible therapeutic target and for plasma Prx5 as a novel indicator of ASD severity.

Transfusion as a Palliative Strategy

PURPOSE OF REVIEW

The palliative care population is a complex and heterogeneous one. While transfusion therapy is a readily available intervention for many patients, inadequate knowledge for accurately identifying which patient subsets at end-of-life will benefit from a transfusion, along with an unclear understanding of the magnitude of attendant risks of transfusion in those receiving palliative care, complicates the risk-benefit assessment of this therapy. In this brief review, the current literature surrounding transfusion of red cells and platelets in the palliative care patient population will be reviewed and recommendations provided.

RECENT FINDINGS

Benefits of transfusion therapy include subjective relief of fatigue and dyspnea, and improved sense of wellness, amongst other findings. However, these responses are not durable and there are currently no validated, objective metrics that correlate with symptomatic improvements. It is clear that transfusion-associated adverse reactions are underestimated in those receiving palliative care, with reaction rates similar to the general patient population. Additionally, based on the high mortality rates reported soon after transfusion, the impact of these blood components must be considered as an exacerbating or causative factor of mortality when evaluating declining condition or death. Hematinics are rarely assessed in anemic palliative care patients or, when measured, are often not corrected. The decision to transfuse palliative care patients is multifactorial, and benefits, risks, patient wishes, blood component inventories, and alternatives to transfusion should all be considered. There are many unknowns regarding transfusion in palliative care. Critical next steps for optimizing blood component therapy in this population include high-quality trials that help to identify validated measures of objective functional changes that parallel patient-reported outcomes and subsets of patients receiving end-of-life care that will most likely be positively impacted by transfusion therapy.

Indications for red cell transfusions in pediatric patients

Red cell transfusions are amongst the most common therapeutic procedures in seriously ill children, particularly in the inpatient setting. This is despite the fact that there is no evidence base for most clinical settings, with the exception of patients with hemoglobinopathies, particularly thalassemia and sickle cell anemia. Obviously exsanguinating hemorrhage and life threatening anemia are urgent indications for which no other therapeutic approach is currently available. Most transfusions are, however, given prophylactically to prevent the complications of hypoxia or hemodynamic stability, based upon expert opinion and a faith in the oxygen carrying capacity and beneficial hemodynamic properties of transfused red cells. The question confronting current day pediatric practice is to what extent transfused red cells prevent adverse events, other than in thalassemia and sickle cell anemia, as opposed to causing them. Do transfusions of red cells prevent organ failure, stroke, etc. or not? There is epidemiologic evidence in the adult randomized trial literature that liberal red cell transfusion likely causes more such adverse events than it prevents. The relevance of such studies to children, particularly neonates, is uncertain. Randomized trials in critically ill neonates have yielded little to no evidence that liberal red cell transfusion is beneficial, but the data are not definitive. In critically ill older children the data suggest there is no benefit to liberal red cell transfusion, but the indications for red cell transfusion are uncertain. Most practitioners would agree that combining laboratory data such hemoglobin/hematocrit with clinical indications for transfusions (evidence of end organ hypoxia such as tachycardia, shortness of breath, etc.) is the only viable strategy at present, until more definitive randomized trial data are available.

Time-restricted feeding influences immune responses without compromising muscle performance in older men

OBJECTIVE

This study examined the effect of 12 wk of time-restricted feeding (TRF) on complete blood cell counts, natural killer cells, and muscle performance in 20- and 50-year-old men.

METHODS

Forty active and healthy participants were randomly divided into young experimental, young control, aged experimental, and aged control group. Experimental groups participated in TRF. Before (P1) and after (P2) TRF, participants performed a maximal exercise test to quantify muscle power. Resting venous blood samples were collected for blood count calculation.

RESULTS

No changes were identified in muscle power in all groups after TRF (P > 0.05). At P1, red cells, hemoglobin, and hematocrit were significantly higher in young participants compared with elderly participants (P < 0.05). At P2, this age effect was not found in red cells between the young experimental group and the aged experimental group (P > 0.05). At P1, white blood cells and neutrophils were significantly higher in young participants compared with elderly participants (P < 0.05). At P2, only neutrophils decreased significantly (P < 0.05) in experimental groups without significant (P > 0.05) difference among them. Lymphocytes decreased significantly in the aged experimental group at P2 (P < 0.05), whereas NKCD16⁺ and NKCD56⁺ decreased significantly in experimental groups at P2 (P < 0.05). TRF had no effect on CD3, CD4⁺, and CD8⁺ levels (P > 0.05).

CONCLUSION

TRF decreases hematocrit, total white blood cells, lymphocytes, and neutrophils in young and older men. TRF may be effective in preventing inflammation by decreasing natural killer cells. As such, TRF could be a lifestyle strategy to reduce systemic low-grade inflammation and age-related chronic diseases linked to immunosenescence, without compromising physical performance.

Molecular and expression analysis of the Allograft inflammatory factor 1 (AIF-1) in the coelomocytes of the common sea urchin Paracentrotus lividus

Allograft inflammatory factor 1 (AIF-1) is a highly conserved gene involved in inflammation, cloned and characterized in several evolutionary distant animal species. Here, we report the molecular identification, characterization and expression of AIF-1 from the common sea urchin Paracentrotus lividus. In this species, AIF-1 encodes a predicted 151 amino acid protein with high similarity to vertebrate AIF-1 proteins. Immunocytochemical analyses on coelomocytes reveal localization of the AIF-1 protein in amoebocytes (perinuclear cytoplasmic zone) and red sphaerulocytes (inside granules), but not in vibratile cells and colorless sphaerula cells. The significant increase of AIF-1 expression (mRNA and protein) found in the coelomocytes of the sea urchin after Gram + bacterial challenge suggests the involvement of AIF-1 in the inflammatory response. Our analysis on P. lividus AIF-1 contributes to elucidate AIF-1 function along the evolutionary scale and consolidate the key evolutionary position of echinoderms throughout metazoans with respect to the common immune paths.

Does Erythropoietin Regulate TRPC Channels in Red Blood Cells?

BACKGROUND

Cation channels play an essential role in red blood cells (RBCs) ion homeostasis. One set of ion channels are the transient receptor potential channels of canonical type (TRPC channels). The abundance of these channels in primary erythroblasts, erythroid cell lines and RBCs was associated with an increase in intracellular Ca2+ upon stimulation with Erythropoietin (Epo). In contrast two independent studies on Epo-treated patients revealed diminished basal Ca2+ concentration or reduced phosphatidylserine exposure to the outer membrane leaflet.

METHODS

To resolve the seemingly conflicting reports we challenged mature human and mouse RBCs of several genotypes with Epo and Prostaglandin E2 (PGE2) and recorded the intracellular Ca2+ content. Next Generation Sequencing was utilised to approach a molecular analysis of reticulocytes.

RESULTS/CONCLUSIONS

Our results allow concluding that Epo and PGE2 regulation of the Ca2+ homeostasis is distinctly different between murine and human RBCs and that changes in intracellular Ca2+ upon Epo treatment is a primary rather than a compensatory effect. In human RBCs, Epo itself has no effect on Ca2+ fluxes but inhibits the PGE2-induced Ca2+ entry. In murine mature RBCs functional evidence indicates TRPC4/C5 mediated Ca2+ entry activated by Epo whereas PGE2 leads to a TRPC independent Ca2+ entry.

Developing new pharmacotherapeutic approaches to treating sickle-cell disease

Survival for patients with SCD has been prolonged by improvements in supportive care, including vaccinations, antibiotic prophylaxis, and overall medical management, including tra nsfusion. However, there remains only one approved, partially effective drug for sickle cell disease-hydroxyurea (hydroxycarbamide). The world desperately needs better ways of both treating and preventing the recurrent painful vaso-occlusive episodes pathognomonic of sickle cell disease as well as the end-organ damage that still leads inexorably to severely shortened life expectancies throughout the world. Based on accumulating knowledge about how the abnormal red blood cells of sickle cell disease cause the double scourge of acute painful episodes and progressive end-organ damage, both pharmaceutical enterprises and individual investigators are now pursuing multiple new avenues for treating sickle cell disease. As a result, many compounds are in active development, both in preclinical models as well as in phase I, II, and III clinical trials. These agents target many pathophysiologic processes thought to be critical in sickle cell disease, including the chemical and physical behavior of haemoglobin S, cell adhesion, coagulation pathways, platelet activation, inflammatory pathways, and upregulation of haemoglobin F expression. In addition, recent explorations of the genetic variations that predispose to certain types of sickle cell disease-related tissue injury, such as stroke or nephropathy, are expected to lead to identification of drugs targeting the pathways uncovered by such work. Thus, the next five to ten years holds a promise of new treatments for sickle cell disease.

Transfusion Medicine

Transfusion of various blood components can provide relief from symptomatic anemia and reduce the bleeding risks associated with low platelet counts or presence of coagulopathy. Blood components are collected from volunteer donors and processed into separate components to maximize efficient utilization of a scarce resource while also providing maximum clinical benefit. Tests including blood type and screening for clinically significant alloantibodies increase the likelihood of successful transfusion. Risks of transfusion include hypersensitivity and hemolytic transfusion reactions, transfusion-related acute lung injury, transfusion-associated circulatory overload, and transmission of infection. Indications for transfusion are reviewed along with various products available for transfusion.

Hepcidin/Ferritin Quotient Helps to Predict Spontaneous Recovery from Iron Loss following Blood Donation

BACKGROUND

Iron supplementation is generally recommended for blood donors even though there are inter-individual differences in iron homeostasis.

METHODS

Ferritin levels of repeat donors were compared with first-time donors, retrospectively. Prospectively, we tested 27 male repeat donors for the following parameters at the day of blood donation as well as 1, 3, 7, 10, and 56 days thereafter: ferritin, hepcidin, transferrin, transferrin receptor, hemoglobin, erythropoietin, reticulocytes, hemoglobin in reticulocyte, twisted gastrulation protein homolog 1, and growth differentiation factor-15.

RESULTS

56 days after blood donation, donors' average ferritin dropped to 55% (range 30-100%) compared to the initial value. Of all tested parameters hepcidin showed the highest and most significant changes beginning 1 day after donation and lasting for the whole period of 56 days. Along with ferritin, there was a high variation in hepcidin levels indicating inter-individual differences in hepcidin response to iron loss. Donors with a hepcidin/ferritin quotient < 0.3 regained 60% of their initial ferritin after 56 days, while those with a quotient ≥ 0.3 reached less than 50%.

CONCLUSION

As hepcidin appears to integrate erythropoietic and iron-loading signals, clinical measurement of hepcidin (together with the hepcidin-ferritin ratio) may become a useful indicator of erythropoiesis and iron kinetics.

Cation Homeostasis in Red Cells From Patients With Sickle Cell Disease Heterologous for HbS and HbC (HbSC Genotype)

Sickle cell disease (SCD) in patients of HbSC genotype is considered similar, albeit milder, to that in homozygous HbSS individuals--but with little justification. In SCD, elevated red cell cation permeability is critical as increased solute loss causes dehydration and encourages sickling. Recently, we showed that the KCl cotransporter (KCC) activity in red cells from HbSC patients correlated significantly with disease severity, but that in HbSS patients did not. Two transporters involved in red cell dehydration, the conductive channels Psickle and the Gardos channel, behaved similarly in red cells from the two genotypes, but were significantly less active in HbSC patients. By contrast, KCC activity was quantitatively greater in HbSC red cells. Results suggest that KCC is likely to have greater involvement in red cell dehydration in HbSC patients, which could explain its association with disease severity in this genotype. This work supports the hypothesis that SCD in HbSC patients is a distinct disease entity to that in HbSS patients. Results suggest the possibility of designing specific treatments of particular benefit to HbSC patients and a rationale for the development of prognostic markers, to inform early treatment of children likely to develop more severe complications of the disease.

The novel role of peroxiredoxin-2 in red cell membrane protein homeostasis and senescence

Peroxiredoxin-2 (Prx2), a typical two-cysteine peroxiredoxin, is the third most abundant protein in red cells. Although progress has been made in the functional characterization of Prx2, its role in red cell membrane protein homeostasis is still under investigation. Here, we studied Prx2(-/-) mouse red cells. The absence of Prx2 promotes (i) activation of the oxidative-induced Syk pathway; (ii) increased band 3 Tyr phosphorylation, with clustered band 3; and (iii) increased heat shock protein (HSP27 and HSP70) membrane translocation. This was associated with enhanced in vitro erythrophagocytosis of Prx2(-/-) red cells and reduced Prx2(-/-) red cell survival, indicating the possible role of Prx2 membrane recruitment in red cell aging and in the clearance of oxidized hemoglobin and damaged proteins through microparticles. Indeed, we observed an increased release of microparticles from Prx2(-/-) mouse red cells. The mass spectrometric analysis of erythroid microparticles found hemoglobin chains, membrane proteins, and HSPs. To test these findings, we treated Prx2(-/-) mice with antioxidants in vivo. We observed that N-acetylcysteine reduced (i) Syk activation, (ii) band 3 clusterization, (iii) HSP27 membrane association, and (iv) erythroid microparticle release, resulting in increased Prx2(-/-) mouse red cell survival. Thus, we propose that Prx2 may play a cytoprotective role in red cell membrane protein homeostasis and senescence.

Neonatal transfusion

Neonates and particularly preterm neonates are frequent recipients of large volumes of blood products relative to their size. Good quality evidence for transfusion practice in this patient group has been lacking but is now increasing. Triggers for red cell transfusion are now better defined, with on-going trials of platelet transfusions likely to yield similar evidence. Transfusion is now extremely safe, but complications such as transfusion associated acute lung injury (TRALI) and transfusion associated circulatory overload (TACO) are likely to be under recognised, particularly in the sick extremely preterm neonate with respiratory symptoms. This review summarises the rationale and current practice with regard to blood component therapy. Background data on component specifications and hazards of transfusion are provided. Indications for transfusion of specific products including red cells, platelets, and plasma are discussed, and their use is illustrated by case examples.

Altered red cell and platelet adhesion in hemolytic diseases: Hereditary spherocytosis, paroxysmal nocturnal hemoglobinuria and sickle cell disease

OBJECTIVES

Intravascular hemolysis may have important pathophysiological consequences, such as the induction of cellular adhesion and vasculopathy. We compared the adhesive properties of red cells (RBC) and platelets in hereditary spherocytosis (HS), paroxysmal nocturnal hemoglobinuria (PNH) and sickle cell disease (SCD) patients.

DESIGN AND METHODS

The adhesion of RBC and platelets, from patients and healthy subjects, was determined using static adhesion assays. RBC surface markers were characterized by flow cytometry and lactate dehydrogenase (LDH), plasma hemoglobin (pHb) and TNF-α were assayed in serum/plasma samples.

RESULTS

pHb levels were elevated in all three hemolytic diseases, indicating the incidence of intravascular hemolysis. RBC adhesion and TNF-α were augmented in HS and SCD, but not in PNH. Reticulocyte counts were raised in the three diseases, but were higher in HS and SCD than in PNH; high expressions of CD71, CD36 and CD49d were observed on SCD RBC, while CD71 alone was increased on HS and PNH RBC. Splenectomy was associated with reversals of increased pHb, RBC adhesion, reticulocytes, RBC marker expression and inflammation in HS. In contrast, platelet adhesion was elevated in SCD and PNH, but not HS. Platelet adhesion correlated significantly with serum LDH, but not pHb, in the hemolytic disease cohort; interestingly, LDH did not correlate with reticulocytes or pHb levels.

CONCLUSIONS

Results indicate that extravascular, rather than intravascular, hemolysis (and ensuing RBC production) may contribute to elevations in RBC adhesive properties in HS and SCD, while mechanisms peculiar to each disease may augment platelet adhesion in SCD and PNH.

STUDY OF WEAK D PHENOTYPE IN HETEROGENEOUS POPULATION

Weak D is the current phenotypic term used to denote a weakened expression of Rhesus (Rh) D antigen on red cells due to a quantitative or qualitative difference in Rh antigen. The present study was undertaken from January 1986 to August 1997. Out of a total of 5042 Rh D confirmation tests 22 (0.43%) weak D phenotypes were detected. Fifteen (68.3%) weak D phenotypes were from blood group O. Five (22.7%) from blood group A and one (4.5%) each from blood group B and AB. There were 15 males and 7 females. There were no cases of haemolytic disease of the newborn or Rh incompatibility.