Red Blood Cell Enzyme Research Articles

Prodrug activation in malaria parasites mediated by an imported erythrocyte esterase, acylpeptide hydrolase (APEH).

The continued emergence of antimalarial drug resistance highlights the need to develop new antimalarial therapies. Unfortunately, new drug development is often hampered by poor drug-like properties of lead compounds. Prodrugging temporarily masks undesirable compound features, improving bioavailability and target penetration. We have found that lipophilic diester prodrugs of phosphonic acid antibiotics, such as fosmidomycin, exhibit significantly higher antimalarial potency than their parent compounds (1). However, the activating enzymes for these prodrugs were unknown. Here, we show that an erythrocyte enzyme, acylpeptide hydrolase (APEH) is the major activating enzyme of multiple lipophilic ester prodrugs. Surprisingly, this enzyme is taken up by the malaria parasite, Plasmodium falciparum, where it localizes to the parasite cytoplasm and retains enzymatic activity. Using a novel fluorogenic ester library, we characterize the structure activity relationship of APEH, and compare it to that of P. falciparum esterases. We show that parasite-internalized APEH plays an important role in the activation of substrates with branching at the alpha carbon, in keeping with its exopeptidase activity. Our findings highlight a novel mechanism for antimicrobial prodrug activation, relying on a host-derived enzyme to yield activation at a microbial target. Mutations in prodrug activating enzymes are a common mechanism for antimicrobial drug resistance (2-4). Leveraging an internalized host enzyme would circumvent this, enabling the design of prodrugs with higher barriers to drug resistance.

Rare red cell enzymopathies in the Indian population: A comprehensive review

Red blood cell enzyme deficiencies are a rare category of hemolytic anaemia that typically present in children with varying degrees of hemolysis, indirect hyperbilirubinemia and splenomegaly. Glucose 6-phosphate dehydrogenase (G6PD) is the most common enzyme deficiency, followed by pyruvate kinase deficiency (PKD). This article aims to understand the pathophysiology of the rare enzymopathies due to deficiencies in the Embden-Meyerhoff pathway, glutathione metabolism, hexose monophosphate shunt and nucleotide metabolism pathway, and to study the incidence, clinical symptoms, diagnostic strategy, and management of enzyme deficiencies in the Indian patients. Most red blood cell (RBC) enzyme deficiencies are inherited in an autosomal recessive fashion except for G6PD, and phosphoglycerate kinase deficiency which has X-linked inheritance. Presentation depends on the representation of the enzyme on different tissues of the body, hence some enzyme deficiencies may present with neurological or muscular manifestations. In patients with suspected hemolytic anaemia, complete blood count and peripheral smear help in differentiating from hemoglobinopathies, etc. To clinch the diagnosis enzyme levels and genetic testing may be required. These tests guide antenatal diagnosis in subsequent pregnancies. Management of RBC enzymopathies depends on the predominant symptoms and severity of hemolysis. Patients with marked hemolysis require regular blood transfusions and hence appropriate chelation therapy. Hematopoeitic stem cell transplant is attempted in patients with severe spectrum with variable results. Newer drugs, including mitapivat have proven to be beneficial in adults with PKD and ongoing trials in children are showing promising results.

Proinflammatory activity of monocytes and activity of glutathione-dependent enzymes in red blood cells in women with depressive conditions

To search for possible connections between the anti-inflammatory activity of monocytes (PAM) and the activity of glutathione metabolic enzymes: glutathione reductase (GR) and glutathione-S-transferase (GT) in patients with depressive states (DS) within various mental pathologies, as well as between the studied biological parameters and clinical condition of patients. Sixty-one women, aged 18-56 years, with DC were examined before and after treatment. Symptom severity was assessed using the Positive and Negative Syndrome Scale (PANSS) and the Hamilton Depressive Symptom Rating Scale (HDRS-21). The control group included 23 women of the corresponding age without mental pathology. Biological parameters were assessed in the peripheral blood of patients and healthy people. Patients with a high level of PAM compared to the control (p<0.001) (subgroup 1, n=31) and with a low (at the control level) level (subgroup 2, n=30) were identified. In the subgroup 1, the values of GR and GT were significantly lower than in patients of subgroup 2 (p<0.05 and p<0.01, respectively). Negative correlations between the level of PAM before treatment and GR before and after treatment were revealed in patients who responded to treatment (r=-0.67; p=0.0041; r=-0.76; p=0.0001). The results may indicate the inverse relationship between the level of PAM and the activity of GR and GT, which are involved in the pathogenesis of DC, and can also serve as criteria for assessing the response of patients to treatment.

Current Status of Molecular Diagnosis of Hereditary Hemolytic Anemia in Korea.

Hereditary hemolytic anemia (HHA) is considered a group of rare hematological diseases in Korea, primarily because of its unique ethnic characteristics and diagnostic challenges. Recently, the prevalence of HHA has increased in Korea, reflecting the increasing number of international marriages and increased awareness of the disease. In particular, the diagnosis of red blood cell (RBC) enzymopathy experienced a resurgence, given the advances in diagnostic techniques. In 2007, the RBC Disorder Working Party of the Korean Society of Hematology developed the Korean Standard Operating Procedure for the Diagnosis of Hereditary Hemolytic Anemia, which has been continuously updated since then. The latest Korean clinical practice guidelines for diagnosing HHA recommends performing next-generation sequencing as a preliminary step before analyzing RBC membrane proteins and enzymes. Recent breakthroughs in molecular genetic testing methods, particularly next-generation sequencing, are proving critical in identifying and providing insight into cases of HHA with previously unknown diagnoses. These innovative molecular genetic testing methods have now become important tools for the management and care planning of patients with HHA. This review aims to provide a comprehensive overview of recent advances in molecular genetic testing for the diagnosis of HHA, with particular emphasis on the Korean context.

Biliverdin Reductase B Protects Against Primaquine Induced Hemolysis - Identification of a Novel Anti-Oxidant Pathway in Murine Erythrocytes

Background: Biliverdin Reductase B (BlvrB) is the fourth most abundant enzyme in red blood cells (RBCs) and is widely expressed in other tissues. In normal heme catabolism, porphyrin is converted to biliverdin-alpha (by hemoxygenase (HO)) and then reduced to bilirubin-alpha (by biliverdin reductase A (BlvrA)). Bilirubin-alpha is then glucuronidated and excreted. The large body of literature investigating heme metabolism, bilirubin-based pathologies, and the oxidative biology of bilirubin/biliverdin in adults focuses almost exclusively on BlvrA and the alpha isomers of biliverdin and bilirubin. However, porphyrin is a tetrapyrrole with 4 distinct meso-carbon bridges, each of which can be broken to generate a distinct biliverdin isomer (alpha, beta, gamma, or delta). Although HO is exquisitely specific for the alpha-bond (generating only biliverdin-alpha), chemical coupled oxidation of heme yields all four biliverdin isomers. BlvrB (and not BlvrA) can reduce each of non-alpha biliverdin isomers into their corresponding bilirubin isomers (bilirubin-beta is prevalent in neonatal jaundice and kernicterus). BlvrB also reduces flavins and additional quinone metabolites. Despite BlvrB's abundance and evolutionary conservation, its only known function is a subtle effect on hematopoietic lineage fate (megakaryocyte vs. erythroid). BlvrB has no known function in mature RBCs. We hypothesized that BlvrB plays an important antioxidant role that would only become obvious when other redundant anti-oxidant pathways were limited. Methods: A novel BlvrB knockout mouse was generated on a C57BL/6 background. A model of primaquine (PQ) induced oxidative hemolytic anemia in G6PD deficient mice was used as a clinically relevant scenario in which compromised antioxidant biology leads to treatment limiting pharmacotoxicity in RBCs. BlvrB-KO mice were crossed with two strains of mice that had murine G6PD replaced with either the A- deficient variant of human G6PD (hG6PD(A-)) or the non-deficient form of human G6PD (hG6PD(ND)). Four mouse strains (i.e., hG6PD(ND) and hG6PD(A-) mice with or without BlvrB deletion) received either a 4-day course of PQ or control PBS injections. Anemia was monitored by hematocrit (HCT). Reticulocyte count (RET) was monitored by flow cytometry as CD71+, thiazole orange+ erythrocytes. Peripheral blood was subjected to high resolution metabolomics to elucidate biochemical changes. Results: All mouse strains were healthy at baseline, with normal measured hematological parameters (i.e., Hct 40, RET 1.5%). No change in HCT or RET was observed in hG6PD(ND) or BlvrB-KOxhG6PD(ND) mice receiving PQ or in any strain receiving PBS. PQ induced hemolytic anemia in hG6PD(A-) mice, with an average HCT of 32.7 (18% drop) with RET of 3.1%. A significant exacerbation of PQ induced hemolysis was observed in BlvrB-KOxhG6PD(A-) mice that had an average HCT of 22.5 (44% drop) with RET of 5.3%. (n= 11 mice per group, p &amp;lt;0.001 between groups). Blood from PQ-treated hG6PD(A-)xBlvrBKO mice showed defective glycolysis at the level of glyceraldehyde 3-phosphate dehydrogenase, increased levels of multiple long-chain acylcarnitines, altered redox metabolism, and specific increases of hypoxanthine and sphingosine-1-phosphate (S1P). Three separate experiments were performed with similar results. Discussion: These data demonstrate that BlvrB deletion exacerbates oxidative injury and suggest that BlvrB provides a novel and hitherto undescribed antioxidant pathway in RBCs. Because approximately half a billion humans exhibit some form of G6PD deficiency, these data are also directly relevant to a large population of humans, which were modeled using hG6PD(A-) mice. These studies also define the metabolic lesion in peripheral blood. For example, GAPDH is well known to be highly sensitive to inactivation by oxidative damage, resulting in impaired glycolysis. Changes in hypoxanthine and S1P are known to be associated with decreased RBC function and survival. Finally, altered carnitine metabolism is associated with repair of lipid peroxidation in RBCs via the Lands Cycle. Although the mechanism by which BlvrB facilitates antioxidation is not yet clear, we hypothesize it involves redox cycling of non-alpha isomers of biliverdin and bilirubin. However, the mechanisms may be through reduction of flavins and/or other endogenous substrates. Ongoing studies are testing these hypotheses.

Characterizing Hereditary Hemolytic Anemias in a Hispanic Cohort Using Next Generation Sequencing

Background: Hereditary hemolytic anemias (HHA) are a heterogeneous group of nonimmune disorders characterized by increased red blood cell (RBC) destruction due to abnormalities of hemoglobin stability, defects of RBC metabolism, and disorders of RBC hydration. Although uncommon, they comprise important causes of anemia in children and adults by causing chronic or episodic hemolysis. Clinical, laboratory, and genetic heterogeneity characterize this group of disorders and make recognition challenging. The advent of next generation sequencing (NGS) has made accurate genetic diagnoses attainable, with an increasing number of studies reporting clinical utility in HHA. For patients with suspected HHA, multigene testing is available incorporating an NGS panel associated genes. However, there is limited data on the use of multigene NGS to characterize HHA in the Hispanic population. Herein, we describe results from NGS testing of a pilot cohort referred for HHA investigation to hematology clinics along the US/Mexico border. Methods: Pediatric and adult hematology clinics at Texas Tech University in El Paso, TX collaborated for testing on HHA referral and clinical case review. The diagnostic panel (AnemiaID/PerkinElmer/Revvity®) included 51 genes encoding RBC cytoskeletal proteins, membrane transporter, RBC enzymes, and certain bilirubin metabolism genes. The complete coding region, splice site junctions, and, where appropriate, deep intronic or regulatory regions were covered. Targeted gene capture and library construction for NGS were performed using a Whole Blood and Saliva kit and 150 base pair paired-end sequencing was done on Illumina® NGS systems at target average coverage of 80×. NGS output data were summarized descriptively for all patients and clinically correlated for diagnosis. Results: In this pilot cohort, 11 patients were tested during September 2022 to June 2023, age ranging 7-75 years, with females accounting for 64% of the group. Findings are reported in the Table below; Pathogenic variants leading to a definitive diagnosis were identified in 8 of 11 cases (73%). The most frequently mutated genes were SPTA1 followed by PIEZO1, SPTB, RHAG, GSR, SLC4A1 and TPI1. Approximately 58% of the mutations were reported as novel. Diagnoses included, most commonly, Hereditary Spherocytosis followed by Hereditary Pyropoikilocytosis and Congenital Dyserythropoietic Anemia. Compound heterozygosity leading to complex interactions was noted in 4 cases (36%), involving SPTA1 low expression alleles in trans (alpha-LELY and alpha-LEPRA) in 2 cases. Conclusion: Hereditary hemolytic anemia in the Hispanic population is characterized by complex molecular interactions and a high prevalence of novel mutations in RBC cytoskeleton/enzyme genes. NGS has clinical utility and should be considered for accurate diagnosis. Further research into the molecular basis and genetic spectrum of HHA in the Hispanic population is needed.

The Pyruvate Kinase (PK) Activator AG-946 Improves PK Properties and Red Blood Cell (RBC) Characteristics upon Ex Vivo treatment of RBCs from Patients with Myelodysplastic Syndromes

Background: Myelodysplastic syndromes (MDS) consist of a heterogenous group of clonal myeloid malignancies, characterized by dysplasia, ineffective hematopoiesis and cytopenias. MDS patients frequently suffer from anemia, directly affecting quality of life. The limited therapeutic options often do not result in the desired clinical improvement. Interestingly, in MDS the activity of the red blood cell (RBC) enzyme pyruvate kinase (PK), a key regulatory enzyme of glycolysis, may be decreased. The activation of PK via small molecules is hypothesized to be beneficial in a wide range of anemias. Currently, a phase 2a, open-label, proof of concept trial is running on the use of the PK activator AG-946 in low-risk MDS patients (NCT05490446). In light of these developments, we investigated the effect of ex vivo treatment of MDS RBCs with AG-946. Objectives: To evaluate RBC PK and cellular properties of patients with MDS, and to determine the effect of ex vivo treatment with the PK activator AG-946. Methods: Eleven low-risk non-transfusion dependent MDS patients and six healthy controls (HCs) were studied. Baseline PK activity and PK thermostability were measured in RBC lysates of purified RBCs, under V max conditions (phosphoenolpyruvate (PEP) 5mM final concentration). Hexokinase (HK) activity was included to relate PK activity to mean RBC age. Ex vivo treatment was performed by incubating MDS RBCs for 16 hours at 37 °C in presence or absence of the PK activator AG-946 (10μM or 5μM) using dimethylsulfoxide (DMSO) as a blank. Effect was assessed by measuring PK activity (using a final concentration of PEP 0.5mM) and levels of adenosine triphosphate (ATP) (LC-MS/MS). Functional RBC analysis was performed by osmotic gradient ektacytometry (Lorrca MaxSis). To investigate the effect on PK thermostability, RBC lysates were incubated with AG-946 (2μM or 1μM) or DMSO, after which residual PK activity was measured (PEP 0.5mM). The effect of AG-946 on erythroid development was studied using peripheral blood mononuclear cells, cultured in MethoCult TM H4434 medium for 14 days in the presence or absence of AG-946 (10μM or 625nM, DMSO as blank). Differences between conditions were determined using Unpaired T-test, ANOVA with Dunnett's test or Kruskal-Wallis with Dunn's test via GraphPad Prism. Results: Mean PK/HK ratio was significantly lower in RBCs from MDS patients compared to HCs (6.1 (SD 1.8) versus 10.5 (SD 1.5), p&amp;lt;0.001). Upon ex vivo treatment, PK activity significantly increased (independent of dosage) when compared to DMSO (10μM AG-946, mean increase 30% ( p&amp;lt;0.001); 5μM, 28% ( p&amp;lt;0.0001)) (Figure 1A). MDS RBCs displayed decreased PK thermostability at baseline under V max conditions (HCs 79% residual activity versus 68% in MDS, p&amp;lt;0.01). This was restored by ex vivo treatment with AG-946 (DMSO, 33% residual activity, 2μM AG-946, 85% ( p&amp;lt;0.0001); 1μM, 87% ( p&amp;lt;0.0001)). The increase in PK activity was accompanied by significantly increased ATP levels (N=10, DMSO, mean ATP 14.9 μg/mL RBC; 10μM AG-946, 21.0 μg/mL RBC ( p&amp;lt;0.01); 5μM, 21.1 μg/mL RBC ( p&amp;lt;0.01)) (Figure 1B). Functionally, RBC properties improved upon ex vivo treatment with AG-946 as reflected by the modest yet significant increase in O hyper, indicating improved hydration status (10μM AG-946, mean increase 2.3% ( p&amp;lt;0.001); 5μM, 2.9% ( p&amp;lt;0.0001)). To date, culture assays were performed in 8 patients; 3/8 showed an increase in the number of burst forming units-erythroid (BFU-Es) upon treatment with AG-946 when compared to DMSO. The percentual increases differed per patient: increase of 25% with 10μM AG946 and 150% with 625nM, increase of 40% (10μM) and 39% (625nM), and for the third an increase of 22% (10μM) and 39% (625nM). Conclusion: Our findings show that RBCs from MDS patients have decreased PK activity and thermostability. We demonstrate that ex vivo treatment with AG-946 increases PK activity and ATP levels and restores PK thermostability. Moreover, ex vivo treatment with AG-946 improves RBC hydration, suggesting that improved energy status directly improves RBC functional properties. The preliminary results of the culture assay could indicate that in certain patients, dyserythropoiesis may be ameliorated upon PK activation. To better understand the effects on erythropoiesis additional experiments are required. In conclusion, our data might support a rationale for the use of PK activators as a novel therapeutic option for MDS.

Prevalence of Glucose 6 Phosphate Dehydrogenase Deficiency in Population of Gujarat - Report of 9184 Cases

Background: All humans have the Glucose 6 phosphate dehydrogenase gene. Some people are born with a mutation of the Glucose 6 phosphate dehydrogenase gene. Most of these individuals are asymptomatic but may exhibit non-immune hemolytic anemia, even severe anemia in response to exposure to certain environmental triggers, most commonly, infection or exposure to certain foods like fava beans (favism), medications or chemicals. G6PD deficiency is an X-linked disorder that primarily affects males. Heterozygous females do not usually develop severe hemolytic anemia due to G6PD deficiency. This study destined to reveal the prevalence of G6PD deficiency in south Gujarat population. Methods: This is a retrospective case study designed to assess the prevalence of G6PD deficiency in gujarat population, for patient requesting G6PD test at multiple collection center of Desai metropolis laboratory pvt ltd. between January 2022 to May 2023. Glucose-6-phosphate dehydrogenase deficiency analysis was done by Methylene dye blue test (Arkray MBK) – Qualitative method. All G6PD deficient patient confirmed by G6PD-quantitative (Kinetic method). Results: Total 9180 patients (5790 male and 3394 female) were included in this study. They were subsequently categorized into various subgroups and analysed properly. The incidence of G6PD deficiency in the selected sample frame of cases was 3.69 %. In which 4.11% of G6PD deficient cases belong to the male while the rest 2.98 % belong to the female. Conclusion: Therefore, to conclude whenever clinical and hematological findings raise the suspicion of glucose 6 phosphate dehydrogenase deficiency, the disorder should be confirmed by quantitative/quantitative measurement of red blood cell enzyme activity in both male and female. There is also need for a large screening programme, especially in malaria endemic zones.

Molecular diagnosis of hereditary hemolytic anemias: Recent updates

AbstractHereditary hemolytic anemia (HHA) is a heterogeneous group of disorders due to genetically caused defects in red blood cell membrane structure, enzymes, heme and globin synthesis, erythroid proliferation, and differentiation. Traditionally, the diagnostic process is complex and includes a plethora of tests from routine to highly specialized ones. The inclusion of molecular testing has significantly improved the diagnostic yield. The value of molecular testing is broader than just rendering the correct diagnosis, as it may also guide therapeutic decisions. As more molecular modalities become available for clinical use, it is imperative to understand their benefits and disadvantages pertaining to the HHA diagnostics. Re‐evaluation of the traditional diagnostic workflow may also bring forth additional benefits. This review focuses on the current state of molecular testing for HHA.

GLUOSE 6-PHOSPHATE ISOMERASE DEFICIENCY: A RARE ENTITY

A young male presented to us with the chief complaints of jaundice, non-bilious vomiting and intermittent high-grade fever in the background of past history of recurrent blood transfusions.On examination, he had pallor, icterus with a massive non tender splenomegaly and his laboratory parameters were suggestive of indirect hyperbilirubinemia with low haptoglobin and elevated lactate dehydrogenase levels with reticulocytosis and erythroid hyperplasia on bone marrow aspiration. His Direct and indirect coombs test were negative.To rule out hemoglobinopathies, his hemoglobin electrophoresis was sent, which turned out to be normal. Hence, red blood cell membrane and enzyme studies were carried out which revealed Glucose-6-phosphate isomerase deficiency.

Clinical utility of targeted next-generation sequencing panel in routine diagnosis of hereditary hemolytic anemia: A national reference laboratory experience.

Hereditary hemolytic anemias (HHA) comprise a heterogeneous group of disorders resulting from defective red blood cell (RBC) cytoskeleton, RBC enzyme deficiencies, and hemoglobin (Hb) synthesis disorders such as thalassemia or sideroblastic anemia. Our hemolytic anemia diagnostic next-generation sequencing (NGS) panel includes 28 genes encoding RBC cytoskeletal proteins, membrane transporter, RBC enzymes, and certain bilirubin metabolism genes. The panel covers the complete coding region of these genes, splice junctions, and, wherever appropriate, deep intronic or regulatory regions are also included. Four hundred fifty-six patients with unexplained hemolytic anemia were evaluated using our NGS panel between 2015 and 2019. We identified pathogenic/likely pathogenic variants in 111/456 (24%) patients that were responsible for the disease phenotype (e.g., moderate to severe hemolytic anemia and hyperbilirubinemia). Approximately 40% of the mutations were novel. As expected, 45/456 (10%) patients were homozygous for the promoter polymorphism in the UGT1A1 gene, A(TA)7 TAA (UGT1A1*28). 8/45 homozygous UGT1A1*28 cases were associated with additional pathogenic mutations causing hemolytic anemia, likely exacerbating hyperbilirubinemia. The most common mutated genes were membrane cytoskeleton genes SPTA1, and SPTB, followed by PKLR. Complex interactions between SPTA1 low expression alleles, alpha-LELY and alpha-LEPRA alleles, and intragenic SPTA1 variants were associated with hereditary pyropoikilocytosis and autosomal recessive hereditary spherocytosis in 23/111 patients. Our results demonstrate that hemolytic anemia is underscored by complex molecular interactions of previously known and novel mutations in RBC cytoskeleton/enzyme genes, and therefore, NGS should be considered in all patients with clinically unexplained hemolytic anemia and in neonates with hyperbilirubinemia. Moreover, low expression alleles alpha-LELY and alpha-LEPRA should be included in all targeted HHA panels.

Elective Splenectomy for Haemolytic Anaemia: A Case Series

The spleen plays an important role in immune surveillance and haematopoiesis. Elective splenectomy is sometimes indicated for excessive cellular destruction (hypersplenism) or sequestration, lymphomatous or myeloid disease, or tumours. Hereditary haemolytic anaemias are disorders with a variety of causes, including red cell membrane defects, red blood cell enzyme disorders, congenital dyserythropoietic anaemias, thalassaemia syndromes, and haemoglobinopathies. Splenectomy is one of the therapeutic approaches in the management of haematological conditions. This is case series of 12 cases who underwent elective splenectomies for haemolytic anaemias in a tertiary care centre, over a period of one year. Out of the 12 patients, 10 patients were diagnosed to have Hereditary Spherocytosis (HS) and 2 patients were diagnosed with sickle cell anaemia. For all patients, preoperative blood transfusion was done to bring the Haemoglobin (Hb) above 9 g/dL for elective splenectomy. Among the 10 patients with HS, 6 patients had concomitant cholelithiasis for which cholecystectomy was done in the same sitting and three patients developed postoperative complication which was managed appropriately with no mortality and minimum morbidity. However, more detailed studies on this subset of patients are needed for the establishment of guidelines and optimal outcomes.

Congenital Disorders of Red Blood Cells.

See Bonus NeoBriefs videos and downloadable teaching slides Understanding the physiologic process of red blood cell development in utero and subsequent erythropoiesis in the neonate is crucial as this determines red blood cell structure and therefore function, which is vital to neonatal health. Infants frequently experience anemia, and special consideration must be given to the evaluation of these infants to determine the correct etiology. Traditionally, anemia is conceptualized in terms of inadequate red blood cell production, increased red blood cell destruction, or whole blood loss. This framework translates well to inherited red blood cell defects, which include genetic abnormalities in bone marrow productivity or structure of the red blood cell membrane, enzymes, or hemoglobin. This article highlights fetal and neonatal erythropoiesis and the underlying etiologies of the inherited red blood cell disorders, as well as reviews the appropriate diagnostic evaluation and next steps in management. It is imperative that neonatal clinicians remain informed about these disorders to enable early recognition and treatment, and ultimately to improve outcomes in affected infants.

Evaluation of Red Blood Cell Metabolism in Patients with Low-Risk Myelodysplastic Syndrome (LR-MDS): A Proof-of-Concept Study

Low risk myelodysplastic syndromes (MDS) show high clinical heterogeneity ranging from mild anemia with nearly normal performance status to life-threatening cytopenias, frequent hospitalization, and disability. Anemia occurs in 80%-85% of patients and therapeutic strategies are still very limited mainly consisting of of erythropoiesis stimulating agents and red blood cell (RBC) transfusion support. Starting from the working hypothesis that the defective maturation of hematopoietic precursors may dampen the "functionality" of MDS-RBCs, we aimed at evaluating RBC metabolic pathway in anemic patients with LR-MDS. We focused on the glycolytic pathway, which is the prominent metabolic cascade in RBCs and is currently targeted with allosteric stimulators of pyruvate kinase (PK) enzyme in clinical trials of PK deficiency, thalassemia, and sickle cell diseases, which are also marked by ineffective erythropoiesis like MDS. Sixty-six consecutive anemic patients (i.e. Hb<11 g/dL) diagnosed with MDS according to WHO 2016 classification that met IPSS-R criteria for very low, low, or intermediate-risk MDS were enrolled in the study. All patients were sampled for peripheral blood at least 4 weeks after the last RBC unit to reduce possible blood donor contamination. The determination of activities of the glycolytic RBC enzymes pyruvate kinase (PK) and hexokinase (HK) (the terminal and initial steps of the glycolytic pathway), and of ATP levels was performed by standard spectrophotometric method according to Beutler et al, 1984. 2,3 DPG determination was tested by AssayGenie Kit in a subgroup of patients. Ektacytometric analysis by LoRRca MaxSis (Laser-Assisted Optical Rotational Cell Analyzer, Mechatronics, NL) was also performed in a subgroup of patients. As shown in table 1, patients were mainly elderly males, and mostly belonged to IPSS low (78%) and IPSS-R very low/low groups (85%). Median levels of PK activity were 13.7 IU/gHb, with a wide range (7.5-35.9) and were reduced in 23 cases (35%; normal reference range 11.9-16.7 IU/gHb); median values of HK activity were 2.3 (0.8-8.1), increased in 60 patients (91%; normal reference range 0.78-1.32 IU/gHb). This resulted in an abnormally reduced PK/HK ratio (median 5.45, range 2-15) in 63 subjects (95%; (normal reference range calculated on 167 normal subjects: 11.55 - 17.65). To asses if impaired glycolysis may result in altered RBC deformability or in lack of energy, ATP levels, 2,3 DPG, and ektacytometric curve were evaluated. Median ATP levels were 3.4 mcM/gHb (1.3-6.5), reduced in 33/56 tested patients (59%; normal reference range 3.6-4.9 mcM/gHb), of whom 32 had simultaneous reduction of PK/HK activity ratio (figure 1), and 11 decreased PK activity. Concerning 2,3 DPG levels preliminarily analysed in a subgroup of patients, they were close to the upper limit of the normal range (median, 389 nM/gHb, 318-639). Osmoscan, performed in 10 patients did not show altered RBC deformability. Preliminary data show decreased glycolytic activity in RBCs from patients with LR-MDS highlighted by reduced PK activity in more than 1/3 of cases, and increased HK activity in almost all subjects. This results in reduced RBC ATP content in up to 2/3 of patients (possibly due to reduced production or to increased consumption) indicating an overall lack of energy in MDS-RBCs. The latter may be an interesting target for allosteric PK stimulators and warrants further investigations. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Galactose epimerase deficiency: lessons from the GalNet registry

BackgroundGalactose epimerase (GALE) deficiency is a rare hereditary disorder of galactose metabolism with only a few cases described in the literature. This study aims to present the data of patients with GALE deficiency from different countries included through the Galactosemia Network to further expand the existing knowledge and review the current diagnostic strategy, treatment and follow-up of this not well characterized entity.MethodsObservational study collecting medical data from December 2014 to April 2022 of 22 not previously reported patients from 14 centers in 9 countries. Patients were classified as generalized or non-generalized based on their genotype, enzyme activities in different tissues and/or clinical picture and professional judgment of the treating physician.ResultsIn total 6 patients were classified as generalized and 16 as non-generalized. In the generalized group, acute neonatal illness was reported in 3, cognitive and developmental delays were present in 5 and hearing problems were reported in 3. Four generalized patients were homozygous for the genetic variant NM_001008216.2:c.280G > A (p.Val94Met). In the non-generalized group, no clearly related symptoms were found. Ten novel genetic variants were reported in this study population.ConclusionThe phenotypic spectrum of GALE deficiency ranges from asymptomatic to severe. The generalized patients have a phenotype that is in line with the 9 described cases in the literature and prescribing dietary interventions is the cornerstone for treatment. In the non-generalized group, treatment advice is more difficult. To be able to offer proper counseling, in addition to red blood cell enzyme activity, genetic studies, transferrin glycoform analysis and enzymatic measurements in fibroblasts are recommended. Due to lack of facilities, additional enzymatic testing is not common practice in many centers nor a tailored long-term follow-up is performed.

EP420: Clinical utility of a 38-gene NGS panel in diagnosing patients with hemolytic anemia: A retrospective review of 435 cases

Hereditary hemolytic anemia (HHA) is a group of heterogeneous genetic conditions that are usually caused by pathogenic variants in genes encoding red blood cell (RBC) cytoskeleton proteins, RBC enzymes, and globins. In addition, congenital dyserythropoietic anemias (CDAs) typically present with a phenotype of hemolytic anemia. To utilize the advantages of next generation sequencing (NGS), a 38-gene panel was designed and incorporated in our clinical lab, encompassing 16 genes responsible for RBC membrane disorders, 14 genes responsible for RBC enzymopathies and 8 genes for CDAs.

EP331: Next-generation sequencing testing in identification and differential diagnosis of hereditary anemia due to erythrocyte membrane disorders, enzymopathies and related disorders

Our laboratory offers a hereditary anemia panel designed to use next generation sequencing genetic testing to help with the diagnosis of a series of anemia disorders. This panel focuses on red blood cell (RBC) membrane and enzyme disorders. Intrinsic erythrocyte membrane disorders include membrane structural defects leading to hereditary spherocytosis, hereditary elliptocytosis and hereditary ovalocytosis, and membrane transport function defects accounting for dehydrated hereditary stomatocytosis (aka hereditary xerocytosis) and overhydrated hereditary stomatocytosis.

Iron chelation therapy with deferiprone improves oxidative status and red blood cell quality and reduces redox-active iron in β-thalassemia/hemoglobin E patients.

The oxidative status of twenty-three β-thalassemia/hemoglobin E patients was evaluated after administration of 75mg/kg deferiprone (GPO-L-ONE®) divided into 3 doses daily for 12 months. Serum ferritin was significantly decreased; the median value at the initial and final assessments was 2842 and 1719ng/mL, respectively. Progressive improvement with significant changes in antioxidant enzyme activity, including plasma paraoxonase (PON) and platelet-activating factor acetylhydrolase (PAF-AH), and in antioxidant enzymes in red blood cells (glutathione peroxidase (GPx), catalase and superoxide dismutase (SOD)) were observed at 3-6months of treatment. The levels of total GSH in red blood cells were significantly increased at the end of the study. Improved red blood cell membrane integrity was also demonstrated using the EPR spin labeling technique. Membrane fluidity at the surface and hydrophobic regions of the red blood cell membrane was significantly changed after 12 months of treatment. In addition, a significant increase in hemoglobin content was observed (6.6±0.7 and 7.5±1.3g/dL at the initial assessment and at 6 months, respectively). Correlations were observed between hemoglobin content, membrane fluidity and antioxidant enzymes in red blood cells. The antioxidant activity of deferiprone may partly be explained by progressive reduction of redox active iron that catalyzes free radical reactions, as demonstrated by the EPR spin trapping technique. In conclusion, iron chelation therapy with deferiprone notably improved the oxidative status in thalassemia, consequently reducing the risk of oxidative-related complications. Furthermore, the improvement in red blood cell quality may improve the anemia situation in patients.

Red blood cell enzyme deficiencies presenting as neurological problems

Red blood cell enzyme deficiencies presenting as neurological problems

3,4-Dihydroxybenzaldehyde mitigates fluoride-induced cytotoxicity and oxidative damage in human RBC

BackgroundFluoride is an essential micronutrient that is needed for mineralization of bones and formation of dental enamel. It is a widely dispersed environmental pollutant and chronic exposure to it is toxic, resulting in malignancies and hematological damage in humans. Blood is a major and early target of environmental pollutants and toxicants like fluoride. Fluoride generates reactive oxygen species and free radicals which induce oxidative stress in target cells and mediate its toxic effects. The aim of this study was to determine the mitigating effect of plant antioxidant 3,4-dihydroxybenzaldehyde (DHB) on sodium fluoride (NaF) induced oxidative damage and cytotoxicity in isolated human red blood cells (RBC) MethodIsolated human RBC were treated with 0.5 mM NaF, in absence or presence of different concentrations of DHB (0.1–2.5 mM). Several biochemical parameters were analyzed in cell lysates and whole cells. ResultsTreatment of RBC with NaF increased the formation of reactive oxygen and nitrogen species. It oxidized thiols, proteins and lipids and generated their peroxidative products. Methemoglobin level, heme degradation and lipid peroxidation were increased but cellular antioxidant status declined significantly in NaF alone treated RBC, compared to the control. NaF inhibited antioxidant, membrane bound and glycolytic enzymes in RBC. However, prior incubation of RBC with DHB significantly attenuated the NaF-induced alterations in all these parameters in a DHB concentration-dependent manner. ConclusionThese results show that DHB mitigates NaF-induced oxidative damage in human RBC, probably because of its antioxidant character.