Inborn defects in the antioxidant systems of human red blood cells

A novel stoploss mutation CYB5R3 c.906A>G(p.*302Trpext*42) involved in the pathogenesis of hereditary methemoglobinemia

Recessive congenital methemoglobinemia (RCM) is a hereditary autosomal disorder with an extremely low incidence rate. Here, we report a case of methemoglobinemia type I in a patient with congenital persistent cyanosis. The condition was attributed to a novel compound heterozygous mutation in CYB5R3, characterized by elevated methemoglobin levels (13.4 % of total hemoglobin) and undetectable NADH cytochrome b5 reductase (CYB5R3) activity. Whole-exome sequencing (WES) revealed two heterozygous mutations in CYB5R3: a previously reported pathogenic missense mutation c.611G>A(p.Cys204Tyr) inherited from the father, and a novel stop codon mutation c.906A>G(p.*302Trpext*42) from the mother, the latter mutation assessed as likely pathogenic according to ACMG guidelines. In cells overexpressing the CYB5R3 c.906A>G mutant construct, the CYB5R3 mRNA level was significantly lower than in cells overexpressing the wild-type (WT) CYB5R3 construct. However, there was no significant difference in protein expression levels between the mutant and WT constructs. Notably, an additional protein band of approximately 55 kDa was detected in the mutant cells. Immunofluorescence localization showed that, compared to wild-type CYB5R3, the subcellular localization of the CYB5R3 p.*302Trpext*42 mutant protein did not show significant changes and remained distributed in the endoplasmic reticulum and mitochondria. However, the c.906A>G(p.*302Trpext*42) mutation resulted in increased intracellular reactive oxygen species (ROS) levels and decreased NAD+/NADH ratio, suggesting impaired CYB5R3 function and implicating this novel mutation as likely pathogenic.

Late-onset refractory hemolytic anemia in siblings treated for methionine synthase reductase deficiency: A rare complication possibly prevented by hydroxocobalamin dose escalation?

Methionine synthase reductase deficiency (cblE) is a rare autosomal recessive inborn error of cobalamin metabolism caused by pathogenic variants in the methionine synthase reductase gene (MTRR). Patients usually exhibit early-onset bone marrow failure with pancytopenia including megaloblastic anemia. The latter can remain isolated or patients may present developmental delay and rarely macular dysfunction. Treatment mostly includes parenteral hydroxocobalamin to maximize the residual enzyme function and betaine to increase methionine concentrations and decrease homocysteine accumulation. We report herein 2 cblE siblings diagnosed in the neonatal period with isolated pancytopenia who, despite treatment, exhibited in adulthood hemolytic anemia (LDH >11 000 U/L, undetectable haptoglobin, elevated unconjugated bilirubin) which could finally be successfully treated by hydroxocobalamin dose escalation. There was no obvious trigger apart from a parvovirus B19 infection in one of the patients. This is the first report of such complications in adulthood. The use of LDH for disease monitoring could possibly be an additional useful biomarker to adjust hydroxocobalamin dosage. Bone marrow infection with parvovirus B19 can complicate this genetic disease with erythroblastopenia even in the absence of an immunocompromised status, as in other congenital hemolytic anemias. The observation of novel hemolytic features in this rare disease should raise awareness about specific complications in remethylation disorders and plea for hydroxocobalamin dose escalation.

Heme metabolism in nonerythroid cells

Heme is an iron-containing prosthetic group necessary for the function of several proteins termed "hemoproteins." Erythrocytes contain most of the body's heme in the form of hemoglobin and contain high concentrations of free heme. In nonerythroid cells, where cytosolic heme concentrations are 2 to 3 orders of magnitude lower, heme plays an essential and often overlooked role in a variety of cellular processes. Indeed, hemoproteins are found in almost every subcellular compartment and are integral in cellular operations such as oxidative phosphorylation, amino acid metabolism, xenobiotic metabolism, and transcriptional regulation. Growing evidence reveals the participation of heme in dynamic processes such as circadian rhythms, NO signaling, and the modulation of enzyme activity. This dynamic view of heme biology uncovers exciting possibilities as to how hemoproteins may participate in a range of physiologic systems. Here, we discuss how heme is regulated at the level of its synthesis, availability, redox state, transport, and degradation and highlight the implications for cellular function and whole organism physiology.

Detection of Transversions and Transitions in HBG2 Cis-Elements Associated with Sickle Cell Allele in Ghanaians

Short tandem repeats located 5' prime to the β-globin gene, have been observed to be in linkage disequilibrium with the HbS allele, and thought to affect the severity of sickle cell disease. Here, we report on new mutants within the HBG2 region that may impact sickle cell disease. To determine the cis-acting elements microsatellites, indels and single nucleotide polymorphisms (SNPs), within the HBG2 region by sequencing, in subjects with sickle cell disease. The case-control study was located at the Center for Clinical Genetics, Sickle cell unit, Korle-Bu Teaching Hospital. A questionnaire was used for demographic data and clinical information. Hematological profile (red blood cell, white blood cell, platelet, hemoglobin and mean corpuscular volume) were assessed in 83 subjects. A set of 45 samples comprising amplified DNA on the HBG2 gene from HbSS (22), HbSC (17) and 6 controls (HbAA) were sequenced. Differences in the microsatellite region between sickle cell disease (SCD) (HbSS and HbSC) genotypes and control subjects were identified by counting and assessed by Chi-square analysis. Red blood cells, hematocrit, platelets, white blood cells and hemoglobin indices differed in genotypic groups. HbSS subjects were affirmed to have severer hemolytic anemia than HbSC subjects. Two indels (T1824 and C905) were seen in both SS and SC genotypes. Two peculiar SNPs: G:T1860 (transition) and A:G1872 transversions were found within the HBG2 gene that were significantly associated with the HbSS genotype (Fisher's exact test, p = 0.006) and HbS allele respectively (Fisher's exact test, p = 0.006). Cis-acting elements in HbSS and HbSC were different and may contribute to the phenotype seen in the disease state.

Familial Psychomotor Delay of an Uncommon Cause: Type II Congenital Methemoglobinemia

Methemoglobinemia is due to oxidization of divalent ferro-iron of hemoglobin to ferri-iron of methemoglobin (MetHb) which is incapable of transferring oxygen to tissues. This disease may be acquired by intoxication with oxidizing agents or inherited with a mutation of CYB5R3, the gene coding for the methemoglobin reductase or cytochrome B5 reductase 3 responsible for the reduction of MetHb to hemoglobin. We report the case of 2 sisters aged respectively of 15 and 8 months. They were born to a second-degree consanguineous marriage with a history of precocious and unexplained deaths in 3 relatives. Both sisters presented neurological features including psychomotor retardation, microcephaly, and axial hypotonia. Cerebral magnetic resonance imaging revealed cerebral atrophy in both cases associated with hypoplasia of the corpus callosum in the younger child. The association of neurological disability, cyanosis, and hypoxemia prompted a search for methemoglobinemia, with MetHB levels respectively of 26% and 15.8%in the 2 sisters. Initial treatment was based on methylene blue, then ascorbic acid. The genetic study revealed a c.463+8G>C mutation of CYB5R3 confirming the diagnosis of methemoglobinemia type II. The diagnosis of methemoglobinemia, although rare, should be considered in the presence of psychomotor retardation with cyanosis and subacute onset hypoxemia, especially in the presence of a family history.

In vitro delayed response to dihydroartemisinin of malaria parasites infecting sickle cell erythocytes

BACKGROUND

Decreased efficacy of artemisinin-based combination therapy (ACT) for Plasmodium falciparum malaria has been previously reported in patients with sickle cell disease (SCD). The main purpose of this study was to investigate the in vitro susceptibility of isolates to dihydro-artemisinin (DHA) to provide a hypothesis to explain this treatment failure.

METHODS

Isolates were collected from patients attending health centres in Abidjan with uncomplicated P. falciparum malaria. The haemoglobin type has been identified and in vitro drug sensitivity tests were conducted with the ring stage assay and maturation inhibition assay.

RESULTS

134 isolates were obtained. Parasitaemia and haemoglobin levels at inclusion were lower in patients with haemoglobin HbSS and HbSC than in patients with normal HbAA. After ex vivo RSA and drug inhibition assays, the lowest rate of parasitic growth was found with isolates from HbAS red cells. Conversely, a significantly higher survival rate of parasites ranging from 15 to 34% were observed in isolates from HbSS. Isolates with in vitro reduced DHA sensitivity correlate with lower RBC count and haematocrit and higher parasitaemia at inclusion compared to those with isolates with normal DHA sensitivity. However, this decrease of in vitro sensitivity to DHA was not associated with Kelch 13-Propeller gene polymorphism.

CONCLUSION

This study highlights an in vitro decreased sensitivity to DHA, for isolates collected from HbSS patients, not related to the Pfkelch13 gene mutations. These results are in line with recent studies pointing out the role of the redox context in the efficacy of the drug. Indeed, SCD red cells harbour a highly different ionic and redox context in comparison with normal red cells. This study offers new insights into the understanding of artemisinin selective pressure on the malaria parasite in the context of haemoglobinopathies in Africa.

From Stress to Sick(le) and Back Again-Oxidative/Antioxidant Mechanisms, Genetic Modulation, and Cerebrovascular Disease in Children with Sickle Cell Anemia

Sickle cell anemia (SCA) is a genetic disease caused by the homozygosity of the HBB:c.20A>T mutation, which results in the production of hemoglobin S (HbS). In hypoxic conditions, HbS suffers autoxidation and polymerizes inside red blood cells, altering their morphology into a sickle shape, with increased rigidity and fragility. This triggers complex pathophysiological mechanisms, including inflammation, cell adhesion, oxidative stress, and vaso-occlusion, along with metabolic alterations and endocrine complications. SCA is phenotypically heterogeneous due to the modulation of both environmental and genetic factors. Pediatric cerebrovascular disease (CVD), namely ischemic stroke and silent cerebral infarctions, is one of the most impactful manifestations. In this review, we highlight the role of oxidative stress in the pathophysiology of pediatric CVD. Since oxidative stress is an interdependent mechanism in vasculopathy, occurring alongside (or as result of) endothelial dysfunction, cell adhesion, inflammation, chronic hemolysis, ischemia-reperfusion injury, and vaso-occlusion, a brief overview of the main mechanisms involved is included. Moreover, the genetic modulation of CVD in SCA is discussed. The knowledge of the intricate network of altered mechanisms in SCA, and how it is affected by different genetic factors, is fundamental for the identification of potential therapeutic targets, drug development, and patient-specific treatment alternatives.

Peroxiredoxins in erythrocytes: far beyond the antioxidant role

The red blood cells (RBCs) are essential to transport oxygen (O2) and nutrients throughout the human body. Changes in the structure or functioning of the erythrocytes can lead to several deficiencies, such as hemolytic anemias, in which an increase in reactive oxidative species generation is involved in the pathophysiological process, playing a significant role in the severity of several clinical manifestations. There are important lines of defense against the damage caused by oxidizing molecules. Among the antioxidant molecules, the enzyme peroxiredoxin (Prx) has the higher decomposition power of hydrogen peroxide, especially in RBCs, standing out because of its abundance. This review aimed to present the recent findings that broke some paradigms regarding the three isoforms of Prxs found in RBC (Prx1, Prx2, and Prx6), showing that in addition to their antioxidant activity, these enzymes may have supplementary roles in transducing peroxide signals, as molecular chaperones, protecting from membrane damage, and maintenance of iron homeostasis, thus contributing to the overall survival of human RBCs, roles that seen to be disrupted in hemolytic anemia conditions.

Prevalence and molecular analysis of glucose-6-phosphate dehydrogenase deficiency in Chin State, Myanmar

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is caused by X-linked recessive disorderliness. It induces severe anemia when a patient with G6PD deficiency is exposed to oxidative stress that occurs with administration of an antimalarial drug, primaquine. The distribution of G6PD deficiency remains unknown while primaquine has been used for malaria treatment in Myanmar. This study aimed to investigate the prevalence of G6PD deficiency and its variants in Chin State, Myanmar. Among 322 participants, 18 (11 males and 7 females) demonstrated a G6PD deficiency. Orissa variant was dominant in the molecular analysis. This would be related to neighboring Indian and Bangladeshi population, in which Orissa variant was also reported as the main mutation type. The screening test for G6PD deficiency before primaquine treatment appears to be important in Myanmar.

Oxidants and Antioxidants in the Redox Biochemistry of Human Red Blood Cells

Red blood cells (RBCs) are exposed to both external and internal sources of oxidants that challenge their integrity and compromise their physiological function and supply of oxygen to tissues. Autoxidation of oxyhemoglobin is the main source of endogenous RBC oxidant production, yielding superoxide radical and then hydrogen peroxide. In addition, potent oxidants from other blood cells and the surrounding endothelium can reach the RBCs. Abundant and efficient enzymatic systems and low molecular weight antioxidants prevent most of the damage to the RBCs and also position the RBCs as a sink of vascular oxidants that allow the body to maintain a healthy circulatory system. Among the antioxidant enzymes, the thiol-dependent peroxidase peroxiredoxin 2, highly abundant in RBCs, is essential to keep the redox balance. A great part of the RBC antioxidant activity is supported by an active glucose metabolism that provides reducing power in the form of NADPH via the pentose phosphate pathway. There are several RBC defects and situations that generate oxidative stress conditions where the defense mechanisms are overwhelmed, and these include glucose-6-phosphate dehydrogenase deficiencies (favism), hemoglobinopathies like sickle cell disease and thalassemia, as well as packed RBCs for transfusion that suffer from storage lesions. These oxidative stress-associated pathologies of the RBCs underline the relevance of redox balance in these anucleated cells that lack a mechanism of DNA-inducible antioxidant response and rely on a complex and robust network of antioxidant systems.

Ginseng polysaccharide attenuates red blood cells oxidative stress injury by regulating red blood cells glycolysis and liver gluconeogenesis

ETHNOPHARMACOLOGICAL RELEVANCE

Panax ginseng C.A. Mey (PG) is famous for "Qi-tonifying" effect, which has a medicinal history of more than 2 millennia. Modern pharmacology has confirmed that the "Qi-tonifying" effect of PG may be closely related to its pharmacological properties such as anti-oxidation, antineoplastic and treatment of cardiovascular disease. As one of the earliest cells affected by oxidative stress, RBCs are widely used in the diagnosis of diseases. Ginseng polysaccharide (GPS), is one of the major active components of PG, which plays an important role in resisting oxidative stress, affecting energy metabolism and other effects. However, the molecular mechanism explaining the "Qi-tonifying" effect of GPS from the perspective of RBCs oxidative damage has not been reported.

AIM OF THE STUDY

This study aimed to investigate the protective effect of GPS on oxidatively damaged RBCs using in vitro and in vivo models and explore the molecular mechanisms from the perspective of glycolysis and gluconeogenesis pathways. To provides a theoretical basis for the future research of antioxidant drugs.

MATERIALS AND METHODS

Established three different in vitro and in vivo research models: an in vitro model of RBCs exposed to hydrogen peroxide (H₂O₂) (40 mM), an in vivo model of RBCs from rats subjected to exhaustive swimming, and an in vitro model of BRL-3A cells exposed to H₂O₂ (25 μM). All three models were also tested in the presence of different concentrations of GPS.

RESULTS

The findings showed that GPS was the most potent antagonist of H₂O₂-induced hemolysis and redox inbalance in RBCs. In exhaustive exercise rats, GPS ameliorated RBVs hemolysis, including reducing whole-blood viscosity (WBV), improving deformability, oxygen-carrying and -releasing capacities, which was related to the enhancing of antioxidant capacity. Moreover, GPS promoted RBCs glycolysis in rats with exhaustive exercise by recovering the activities of glycolysis-related enzymes and increasing band 3 protein expression, thereby regulating the imbalance of energy metabolism caused by oxidative stress. Furthermore, we demonstrated that GPS improved antioxidant defense system, enhanced energy metabolism, and regulated gluconeogenesis via activating PPAR gamma co-activator 1 alpha (PGC-1α) pathway in H₂O₂-exposed BRL-3A cells. Mechanistically, GPS promoted glycolysis and protected RBCs from oxidative injury was partly dependent on the regulation of gluconeogenesis, as inhibition of gluconeogenesis by metformin (Met) attenuates the regulation of antioxidant enzymes and key enzymes of glycolytic by GPS in exhaustive exercise rats.

CONCLUSION

This study demonstrates that GPS protects RBCs from oxidative stress damage by promoting RBCs glycolysis and liver gluconeogenesis pathways. These results may contribute to the study of new RBCs treatments to boost antioxidant capacity and protect RBCs against oxidative stress.

Hemoglobin is an oxygen-dependent glutathione buffer adapting the intracellular reduced glutathione levels to oxygen availability

Fast changes in environmental oxygen availability translate into shifts in mitochondrial free radical production. An increase in intraerythrocytic reduced glutathione (GSH) during deoxygenation would support the detoxification of exogenous oxidants released into the circulation from hypoxic peripheral tissues. Although reported, the mechanism behind this acute oxygen-dependent regulation of GSH in red blood cells remains unknown. This study explores the role of hemoglobin (Hb) in the oxygen-dependent modulation of GSH levels in red blood cells. We have demonstrated that a decrease in Hb O₂ saturation to 50% or less observed in healthy humans while at high altitude, or in red blood cell suspensions results in rising of the intraerythrocytic GSH level that is proportional to the reduction in Hb O₂ saturation. This effect was not caused by the stimulation of GSH de novo synthesis or its release during deglutathionylation of Hb's cysteines. Using isothermal titration calorimetry and in silico modeling, we observed the non-covalent binding of four molecules of GSH to oxy-Hb and the release of two of them upon deoxygenation. Localization of the GSH binding sites within the Hb molecule was identified. Oxygen-dependent binding of GSH to oxy-Hb and its release upon deoxygenation occurred reciprocally to the binding and release of 2,3-bisphosphoglycerate. Furthermore, noncovalent binding of GSH to Hb moderately increased Hb oxygen affinity. Taken together, our findings have identified an adaptive mechanism by which red blood cells may provide an advanced antioxidant defense to respond to oxidative challenges immediately upon deoxygenation.

Effect of Near-Infrared Blood Photobiomodulation on Red Blood Cell Damage from the Extracorporeal Circuit during Hemodialysis In Vitro

The contact of blood with the bioincompatible membranes of the dialyzer, which is part of the extracorporeal circuit during hemodialysis (HD), causes upregulation of various cellular and non-cellular processes, including massive generation and release of reactive oxygen species (ROS), (which is one of the primary causes of anemia in chronic renal failure). We hypothesize that near-infrared (NIR) radiation possesses antioxidant properties and is considered to protect the red blood cell (RBC) membrane by enhancing its resilience to negative pressures. Our experimental setup consisted of an HD machine equipped with a dialyzer with a polyamide membrane; whole bovine blood was examined in vitro in blood-treated circulation. Blood samples were taken at 0, 5, 15, and 30 min during the HD therapy. We also assessed osmotic fragility, hematocrit, hemolysis, and oxidative stress as a concentration of reactive thiobarbituric acid substances (TBARS). Our results have shown that RBC membrane peroxidation increased significantly after 30 min of circulation, whereas the TBARS level in NIR-treated blood remained relatively steady throughout the experiment. The osmotic fragility of NIR-irradiated samples during dialysis was decreased compared to control samples. Our studies confirm that in vitro, blood photobiomodulation using NIR light diminishes oxidative damage during HD and can be considered a simultaneous pretreatment strategy for HD.

Redox Balance in β-Thalassemia and Sickle Cell Disease: A Love and Hate Relationship

β-thalassemia and sickle cell disease (SCD) are inherited hemoglobinopathies that result in both quantitative and qualitative variations in the β-globin chain. These in turn lead to instability in the generated hemoglobin (Hb) or to a globin chain imbalance that affects the oxidative environment both intracellularly and extracellularly. While oxidative stress is not among the primary etiologies of β-thalassemia and SCD, it plays a significant role in the pathogenesis of these diseases. Different mechanisms exist behind the development of oxidative stress; the result of which is cytotoxicity, causing the oxidation of cellular components that can eventually lead to cell death and organ damage. In this review, we summarize the mechanisms of oxidative stress development in β-thalassemia and SCD and describe the current and potential antioxidant therapeutic strategies. Finally, we discuss the role of targeted therapy in achieving an optimal redox balance.

The enzymatic function of the honorary enzyme: S-nitrosylation of hemoglobin in physiology and medicine

The allosteric transition within tetrameric hemoglobin (Hb) that allows both full binding to four oxygen molecules in the lung and full release of four oxygens in hypoxic tissues would earn Hb the moniker of 'honorary enzyme'. However, the allosteric model for oxygen binding in hemoglobin overlooked the essential role of blood flow in tissue oxygenation that is essential for life (aka autoregulation of blood flow). That is, blood flow, not oxygen content of blood, is the principal determinant of oxygen delivery under most conditions. With the discovery that hemoglobin carries a third biologic gas, nitric oxide (NO) in the form of S-nitrosothiol (SNO) at β-globin Cys93 (βCys93), and that formation and export of SNO to dilate blood vessels are linked to hemoglobin allostery through enzymatic activity, this title is honorary no more. This chapter reviews evidence that hemoglobin formation and release of SNO is a critical mediator of hypoxic autoregulation of blood flow in tissues leading to oxygen delivery, considers the physiological implications of a 3-gas respiratory cycle (O2/NO/CO2) and the pathophysiological consequences of its dysfunction. Opportunities for therapeutic intervention to optimize oxygen delivery at the level of tissue blood flow are highlighted.

Identification, analysis of deleterious SNPs of the human GSR gene and their effects on the structure and functions of associated proteins and other diseases

Hereditary glutathione reductase deficiency, caused by mutations of the GSR gene, is an autosomal recessive disorder characterized by decreased glutathione disulfide (GSSG) reduction activity and increased thermal instability. This study implemented computational analysis to screen the most likely mutation that might be associated with hereditary glutathione reductase deficiency and other diseases. Using ten online computational tools, the study revealed four nsSNPs among the 17 nsSNPs identified as most deleterious and disease associated. Structural analyses and evolutionary confirmation study of native and mutant GSR proteins using the HOPE project and ConSruf. HOPE revealed more flexibility in the native GSR structure than in the mutant structure. The mutation in GSR might be responsible for changes in the structural conformation and function of the GSR protein and might also play a significant role in inducing hereditary glutathione reductase deficiency. LD and haplotype studies of the gene revealed that the identified variations rs2978663 and rs8190955 may be responsible for obstructive heart defects (OHDs) and hereditary anemia, respectively. These interethnic differences in the frequencies of SNPs and haplotypes might help explain the unpredictability that has been reported in association studies and can contribute to predicting the pharmacokinetics and pharmacodynamics of drugs that make use of GSR.

Influenza Virus Down-Modulates G6PD Expression and Activity to Induce Oxidative Stress and Promote Its Replication

Influenza virus infection induces oxidative stress in host cells by decreasing the intracellular content of glutathione (GSH) and increasing reactive oxygen species (ROS) level. Glucose-6-phosphate dehydrogenase (G6PD) is responsible for the production of reducing equivalents of nicotinamide adenine dinucleotide phosphate (NADPH) that is used to regenerate the reduced form of GSH, thus restoring redox homeostasis. Cells deficient in G6PD display elevated levels of ROS and an increased susceptibility to viral infection, although the consequences of G6PD modulation during viral infection remain to be elucidated. In this study, we demonstrated that influenza virus infection decreases G6PD expression and activity, resulting in an increase in oxidative stress and virus replication. Moreover, the down regulation of G6PD correlated with a decrease in the expression of nuclear factor erythroid 2-related factor 2 (NRF2), a key transcription factor that regulates the expression of the antioxidant response gene network. Also down-regulated in influenza virus infected cells was sirtuin 2 (SIRT2), a NADPH-dependent deacetylase involved in the regulation of G6PD activity. Acetylation of G6PD increased during influenza virus infection in a manner that was strictly dependent on SIRT2 expression. Furthermore, the use of a pharmacological activator of SIRT2 rescued GSH production and NRF2 expression, leading to decreased influenza virus replication. Overall, these data identify a novel strategy used by influenza virus to induce oxidative stress and to favor its replication in host cells. These observations furthermore suggest that manipulation of metabolic and oxidative stress pathways could define new therapeutic strategies to interfere with influenza virus infection.

Melatonin: Regulation of Prion Protein Phase Separation in Cancer Multidrug Resistance

The unique ability to adapt and thrive in inhospitable, stressful tumor microenvironments (TME) also renders cancer cells resistant to traditional chemotherapeutic treatments and/or novel pharmaceuticals. Cancer cells exhibit extensive metabolic alterations involving hypoxia, accelerated glycolysis, oxidative stress, and increased extracellular ATP that may activate ancient, conserved prion adaptive response strategies that exacerbate multidrug resistance (MDR) by exploiting cellular stress to increase cancer metastatic potential and stemness, balance proliferation and differentiation, and amplify resistance to apoptosis. The regulation of prions in MDR is further complicated by important, putative physiological functions of ligand-binding and signal transduction. Melatonin is capable of both enhancing physiological functions and inhibiting oncogenic properties of prion proteins. Through regulation of phase separation of the prion N-terminal domain which targets and interacts with lipid rafts, melatonin may prevent conformational changes that can result in aggregation and/or conversion to pathological, infectious isoforms. As a cancer therapy adjuvant, melatonin could modulate TME oxidative stress levels and hypoxia, reverse pH gradient changes, reduce lipid peroxidation, and protect lipid raft compositions to suppress prion-mediated, non-Mendelian, heritable, but often reversible epigenetic adaptations that facilitate cancer heterogeneity, stemness, metastasis, and drug resistance. This review examines some of the mechanisms that may balance physiological and pathological effects of prions and prion-like proteins achieved through the synergistic use of melatonin to ameliorate MDR, which remains a challenge in cancer treatment.

Diagnosis and clinical management of enzymopathies

At least 16 genetically determined conditions qualify as red blood cell enzymopathies. They range in frequency from ultrarare to rare, with the exception of glucose-6-phosphate dehydrogenase deficiency, which is very common. Nearly all these enzymopathies manifest as chronic hemolytic anemias, with an onset often in the neonatal period. The diagnosis can be quite easy, such as when a child presents with dark urine after eating fava beans, or it can be quite difficult, such as when an adult presents with mild anemia and gallstones. In general, 4 steps are recommended: (1) recognizing chronic hemolytic anemia; (2) excluding acquired causes; (3) excluding hemoglobinopathies and membranopathies; (4) pinpointing which red blood cell enzyme is deficient. Step 4 requires 1 or many enzyme assays; alternatively, DNA testing against an appropriate gene panel can combine steps 3 and 4. Most patients with a red blood cell enzymopathy can be managed by good supportive care, including blood transfusion, iron chelation when necessary, and splenectomy in selected cases; however, some patients have serious extraerythrocytic manifestations that are difficult to manage. In the absence of these, red blood cell enzymopathies are in principle amenable to hematopoietic stem cell transplantation and gene therapy/gene editing.

Recommendations for diagnosis and treatment of methemoglobinemia

Methemoglobinemia is a rare disorder associated with oxidization of divalent ferro‐iron of hemoglobin (Hb) to ferri‐iron of methemoglobin (MetHb). Methemoglobinemia can result from either inherited or acquired processes. Acquired forms are the most common, mainly due to the exposure to substances that cause oxidation of the Hb both directly or indirectly. Inherited forms are due either to autosomal recessive variants in the CYB5R3 gene or to autosomal dominant variants in the globin genes, collectively known as HbM disease. Our recommendations are based on a systematic literature search. A series of questions regarding the key signs and symptoms, the methods for diagnosis, the clinical management in neonatal/childhood/adulthood period, and the therapeutic approach of methemoglobinemia were formulated and the relative recommendations were produced. An agreement was obtained using a Delphi‐like approach and the experts panel reached a final consensus >75% of agreement for all the questions.

The Role of RBC Oxidative Stress in Sickle Cell Disease: From the Molecular Basis to Pathologic Implications

Sickle cell disease (SCD) is an inherited monogenic disorder and the most common severe hemoglobinopathy in the world. SCD is characterized by a point mutation in the β-globin gene, which results in hemoglobin (Hb) S production, leading to a variety of mechanistic and phenotypic changes within the sickle red blood cell (RBC). In SCD, the sickle RBCs are the root cause of the disease and they are a primary source of oxidative stress since sickle RBC redox state is compromised due to an imbalance between prooxidants and antioxidants. This imbalance in redox state is a result of a continuous production of reactive oxygen species (ROS) within the sickle RBC caused by the constant endogenous Hb autoxidation and NADPH oxidase activation, as well as by a deficiency in the antioxidant defense system. Accumulation of non-neutralized ROS within the sickle RBCs affects RBC membrane structure and function, leading to membrane integrity deficiency, low deformability, phosphatidylserine exposure, and release of micro-vesicles. These oxidative stress-associated RBC phenotypic modifications consequently evoke a myriad of physiological changes involved in multi-system manifestations. Thus, RBC oxidative stress in SCD can ultimately instigate major processes involved in organ damage. The critical role of the sickle RBC ROS production and its regulation in SCD pathophysiology are discussed here.

Biochemical Evaluation of the Effects of Hydroxyurea in Vitro on Red Blood Cells

Hydroxyurea (HU) is a low-cost, low-toxicity drug that is often used in diseases, such as sickle cell anemia and different types of cancer. Its effects on the red blood cells (RBC) are still not fully understood. The in vitro effects of HU were evaluated on the biochemical parameters of the RBC from healthy individuals that were treated with 0.6 mM or 0.8 mM HU for 30 min and 1 h. After 30 min, there was a significant increase in almost all of the parameters analyzed in the two concentrations of HU, except for the pyruvate kinase (PK) activity. A treatment with 0.8 mM HU for 1 h resulted in a reduction of the levels of lipid peroxidation, Fe³⁺, and in the activities of some of the enzymes, such as glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G6PD), and PK. After the incubation for 1 h, the levels of H₂O₂, lipid peroxidation, reduced glutathione (GSH), enzymatic activity (hexokinase, G6PD, and superoxide dismutase (SOD) were reduced with the treatment of 0.8 mM HU when compared with 0.6 mM. The results have suggested that a treatment with HU at a concentration of 0.8 mM seemed to be more efficient in protecting against the free radicals, as well as in treating diseases, such as sickle cell anemia. HU appears to preferentially stimulate the pentose pathway over the glycolytic pathway. Although this study was carried out with the RBC from healthy individuals, the changes described in this study may help to elucidate the mechanisms of action of HU when administered for therapeutic purposes.

Antixoxidant Supplements versus Health Benefits of Brief/Intermittent Exposure to Potentially Toxic Physical or Chemical Agents

Although antioxidants can act locally to react with an oxidant, oral administration of "antioxidants" is quite useless in treating oxidative stress in tissues. Furthermore, it does not make sense to consider a vitamin as an antioxidant, but vitamin B3 leads to the in vivo formation of compounds that are essential for reducing this stress. A rigorous treatment of the subject indicates that to deal with oxidative stress, the most direct approach is to enhance the innate antioxidant mechanisms. The question is whether this is possible through daily activities. Diets can contain the necessary components for these mechanisms or may induce the expression of the genes involved in them. Another possibility is that pro-oxidant molecules in food increase the sensitivity and power of the detoxification pathways. This option is based on well-known DNA repair mechanisms after exposure to radiation (even from the Sun), or strong evidence of induction of antioxidant capacity after exposure to powerful pro-oxidants such as H₂O₂. More experimental work is required to test whether some molecules in food can increase the expression of antioxidant enzymes and/or improve antioxidant mechanisms. Identifying effective molecules to achieve such antioxidant power is critical to the food and nutraceutical industries. The potential of diet-based interventions to combat oxidative stress must be viewed from a new perspective.

Dosage Compensation in Females with X-Linked Metabolic Disorders

Through the use of new genomic and metabolomic technologies, our comprehension of the molecular and biochemical etiologies of genetic disorders is rapidly expanding, and so are insights into their varying phenotypes. Dosage compensation (lyonization) is an epigenetic mechanism that balances the expression of genes on heteromorphic sex chromosomes. Many studies in the literature have suggested a profound influence of this phenomenon on the manifestation of X-linked disorders in females. In this review, we summarize the clinical and genetic findings in female heterozygotic carriers of a pathogenic variant in one of ten selected X-linked genes whose defects result in metabolic disorders.

A Proposed Concept for Defective Mitophagy Leading to Late Stage Ineffective Erythropoiesis in Pyruvate Kinase Deficiency

Pyruvate kinase deficiency (PKD) is a rare congenital hemolytic anemia caused by mutations in the PKLR gene. Here, we review pathophysiological aspects of PKD, focusing on the interplay between pyruvate kinase (PK)-activity and reticulocyte maturation in the light of ferroptosis, an iron-dependent process of regulated cell death, and in particular its key player glutathione peroxidase 4 (GPX4). GPX4 plays an important role in mitophagy, the key step of peripheral reticulocyte maturation and GPX4 deficiency in reticulocytes results in a failure to fully mature. Mitophagy depends on lipid oxidation, which is under physiological conditions controlled by GPX4. Lack of GPX4 leads to uncontrolled auto-oxidation, which will disrupt autophagosome maturation and thereby perturb mitophagy. Based on our review, we propose a model for disturbed red cell maturation in PKD. A relative GPX4 deficiency occurs due to glutathione (GSH) depletion, as cytosolic L-glutamine is preferentially used in the form of α-ketoglutarate as fuel for the tricarboxylic acid (TCA) cycle at the expense of GSH production. The relative GPX4 deficiency will perturb mitophagy and, subsequently, results in failure of reticulocyte maturation, which can be defined as late stage ineffective erythropoiesis. Our hypothesis provides a starting point for future research into new therapeutic possibilities, which have the ability to correct the oxidative imbalance due to lack of GPX4.

Band 3 protein function and oxidative stress in erythrocytes

Band 3 protein (B3p), anion transporter, allows the HCO₃ ^- /Cl^- exchange across plasma membrane and plays an important role for erythrocytes homeostasis. In addition, B3p is linked to proteins cytoskeleton, thus contributing to cell shape and deformability, essential to erythrocytes adjustment within narrowest capillaries. Taking into account that erythrocytes are a suitable cell model to investigate the response of the oxidative stress effects, B3p functions, and specifically anion exchange capability, determining the rate constant for SO₄ ^2- uptake, has been considered. As, in the latter years, rising attention has been addressed to membrane transport system, and particularly to this protein, the present mini-review has been conceived to report the most recent knowledge about B3p, with specific regard to its functions in oxidative stress conditions, including oxidative stress-related diseases.

Hydroxyurea treatment is associated with reduced degree of oxidative perturbation in children and adolescents with sickle cell anemia

Sickle cell anemia (SCA) is the most common inherited hemolytic anemia worldwide. Here, we performed an exploratory study to investigate the systemic oxidative stress in children and adolescents with SCA. Additionally, we evaluated the potential impact of hydroxyurea therapy on the status of oxidative stress in a case–control study from Brazil. To do so, a panel containing 9 oxidative stress markers was measured in plasma samples from a cohort of 47 SCA cases and 40 healthy children and adolescents. Among the SCA patients, 42.5% were undertaking hydroxyurea. Multidimensional analysis was employed to describe disease phenotypes. Our results demonstrated that SCA is associated with increased levels of oxidative stress markers, suggesting the existence of an unbalanced inflammatory response in peripheral blood. Subsequent analyses revealed that hydroxyurea therapy was associated with diminished oxidative imbalance in SCA patients. Our findings reinforce the idea that SCA is associated with a substantial dysregulation of oxidative responses which may be dampened by treatment with hydroxyurea. If validated by larger prospective studies, our observations argue that reduction of oxidative stress may be a main mechanism through which hydroxyurea therapy attenuates the tissue damage and can contribute to improved clinical outcomes in SCA.

Glutathione-redox status on hydro alcoholic root bark extract of Premna integrifolia Linn in high fat diet induced atherosclerosis model

BACKGROUND

Premna integrifolia Linn. is a medicinal plant of an Ayurvedic importance and proved to have an anti-inflammatory, anti-diabetic, anti-microbial and hypo-lipidemic activity. Glutathione (GSH) redox status is an important parameter to assess the antioxidant activity of any neutraceuticals.

OBJECTIVE

In order to assess the anti-oxidant potential of hydro alcoholic extract (HAE) of P. integrifolia, this study was aimed to evaluate the GSH redox status in high fat diet induced experimental atherosclerosis.

MATERIALS AND METHODS

The present study comprises sixty Wistar rats and they were divided into six groups: the first group served as control, the second group was fed with high fat diet and the third, fourth and fifth groups were fed with high fat diet along with various concentrations of HAE of 200, 400 and 500 g/kg.b.wt respectively and the sixth group was administered high fat diet along with 10 mg/kg b.wt of atorvastatin for 30 days. GSH-dependent enzymes like GSH-peroxidase (GPx), GSH-reductase (GR) and glucose 6-phosphate dehydrogenase (G6PD) were estimated in hemolysate, kidney, heart and liver of experimental rats.

RESULTS

Analysis of GSH levels showed a significant decrease in hemolysate, heart and kidney (p < 0.05) and liver (p < 0.01) in high fat-fed rats when compared to control. Activities of GPx, GR and G6PD in hemolysate and heart (p < 0.001), liver and kidney (p < 0.05) in high fat-fed rats when compared to control. Dose-dependent increase was observed in rats treated with various concentrations of HAE.

CONCLUSION

The HAE of root bark of P. integrifolia is proved to have a protective role on antioxidant defense in high fat diet induced atherosclerosis model. As a whole P. integrifolia increases the GSH content in a dose-dependent manner and in turn altered the redox cycle.

Glucose-6-phosphate dehydrogenase deficiency genotypes and allele frequencies in the Kavango and Zambezi regions of northern Namibia

BACKGROUND

Namibia has made significant gains in the fight against malaria, with a target of elimination by 2023. We examined the genotype and allele frequencies of glucose-6-phosphate dehydrogenase (G6PD) deficiency to inform decisions on primaquine use, as we recently detected clusters of Plasmodium ovale curtisi in Kavango.

METHODS

A multistaged cross-sectional sampling method was used to enrol 212 children 2-9 y of age from schools and clinics in the Okavango and Zambezi regions of northern Namibia. Genotypes for the 202 G→A and 376 A→G mutations were assigned by polymerase chain reaction restriction fragment length polymorphism.

RESULTS

Of the 212 subjects enrolled, genotypes were available for 210, made up of 61 males and 149 females. G6PD-deficient males (hemizygotes) and females (homozygotes) constituted 3.27% (2/61) and 0.0% (0/149), respectively. Female heterozygotes (AA- and BA-) constituted 10.07% (15/149), while G6PD wild-type males (with A or B haplotype) and females (with AA, BB or AB haplotypes) consisted of 96.72% (59/61) and 89.93% (134/149), respectively. The A-, A and B allele frequencies were 0.0474, 0.3036 and 0.6490, respectively. Hardy-Weinberg equilibrium tests for female genotype frequencies did not show deviation (p=0.29).

CONCLUSIONS

The frequency of G6PD deficiency alleles in males in the Kavango and Zambezi regions of northern Namibia constitute 3.27%, a first report to inform policy on primaquine role out.

d-Galactose Decreases Anion Exchange Capability through Band 3 Protein in Human Erythrocytes

d-Galactose (d-Gal), when abnormally accumulated in the plasma, results in oxidative stress production, and may alter the homeostasis of erythrocytes, which are particularly exposed to oxidants driven by the blood stream. In the present investigation, the effect of d-Gal (0.1 and 10 mM, for 3 and 24 h incubation), known to induce oxidative stress, has been assayed on human erythrocytes by determining the rate constant of SO₄²⁻ uptake through the anion exchanger Band 3 protein (B3p), essential to erythrocytes homeostasis. Moreover, lipid peroxidation, membrane sulfhydryl groups oxidation, glycated hemoglobin (% A1c), methemoglobin levels (% MetHb), and expression levels of B3p have been verified. Our results show that d-Gal reduces anion exchange capability of B3p, involving neither lipid peroxidation, nor oxidation of sulfhydryl membrane groups, nor MetHb formation, nor altered expression levels of B3p. d-Gal-induced %A1c, known to crosslink with B3p, could be responsible for rate of anion exchange alteration. The present findings confirm that erythrocytes are a suitable model to study the impact of high sugar concentrations on cell homeostasis; show the first in vitro effect of d-Gal on B3p, contributing to the understanding of mechanisms underlying an in vitro model of aging; demonstrate that the first impact of d-Gal on B3p is mediated by early Hb glycation, rather than by oxidative stress, which may be involved on a later stage, possibly adding more knowledge about the consequences of d-Gal accumulation.

Donor glucose-6-phosphate dehydrogenase deficiency decreases blood quality for transfusion

BACKGROUNDGlucose-6-phosphate dehydrogenase (G6PD) deficiency decreases the ability of red blood cells (RBCs) to withstand oxidative stress. Refrigerated storage of RBCs induces oxidative stress. We hypothesized that G6PD-deficient donor RBCs would have inferior storage quality for transfusion as compared with G6PD-normal RBCs.METHODSMale volunteers were screened for G6PD deficiency; 27 control and 10 G6PD-deficient volunteers each donated 1 RBC unit. After 42 days of refrigerated storage, autologous 51-chromium 24-hour posttransfusion RBC recovery (PTR) studies were performed. Metabolomics analyses of these RBC units were also performed.RESULTSThe mean 24-hour PTR for G6PD-deficient subjects was 78.5% ± 8.4% (mean ± SD), which was significantly lower than that for G6PD-normal RBCs (85.3% ± 3.2%; P = 0.0009). None of the G6PD-normal volunteers (0/27) and 3 G6PD-deficient volunteers (3/10) had PTR results below 75%, a key FDA acceptability criterion for stored donor RBCs. As expected, fresh G6PD-deficient RBCs demonstrated defects in the oxidative phase of the pentose phosphate pathway. During refrigerated storage, G6PD-deficient RBCs demonstrated increased glycolysis, impaired glutathione homeostasis, and increased purine oxidation, as compared with G6PD-normal RBCs. In addition, there were significant correlations between PTR and specific metabolites in these pathways.CONCLUSIONBased on current FDA criteria, RBCs from G6PD-deficient donors would not meet the requirements for storage quality. Metabolomics assessment identified markers of PTR and G6PD deficiency (e.g., pyruvate/lactate ratios), along with potential compensatory pathways that could be leveraged to ameliorate the metabolic needs of G6PD-deficient RBCs.TRIAL REGISTRATIONClinicalTrials.gov NCT04081272.FUNDINGThe Harold Amos Medical Faculty Development Program, Robert Wood Johnson Foundation grant 71590, the National Blood Foundation, NIH grant UL1 TR000040, the Webb-Waring Early Career Award 2017 by the Boettcher Foundation, and National Heart, Lung, and Blood Institute grants R01HL14644 and R01HL148151.

Chlorogenic acid improves lipid membrane peroxidation and morphological changes in nitrite-induced erythrocyte model of methemoglobinemia

Nitrite salts are widely presented in food and their hazardous effects have been well documented. In this study, we evaluated the protective capacity of chlorogenic acid (CGA) against sodium nitrite (NaNO₂₎ -induced damage to rat erythrocytes. Two dosing regimens of CGA were undertaken to alleviate the erythrocyte injury induced by NaNO₂ . We examined the cell fragility, the level of methemoglobin and oxidative stress parameters of each treated group. In result, as compared to the CGA post-incubation, co-incubation of CGA with NaNO₂ decreased the content of advanced oxidation protein products. The protective capacity of CGA was superior to its remedial effect. We infer that the reaction of CGA and NaNO₂ may suppress the cytotoxicity of nitrite on erythrocytes and avoid the generation of oxidative stress induced by NaNO₂ . Our results suggest a novel diet strategy for preventing the adverse effects of nitrite in those people with exposure to nitrite. PRACTICAL APPLICATIONS: Nitrite is ubiquitous in our environment and can also be formed from nitrogenous compounds by microorganisms which exist in the soil, water, and saliva. Several researches have been performed to explore the protection of natural products on the toxic effects of Nitrite. In this study, exogenous chlorogenic acid (CGA) is able to avert the membrane damage, lipid peroxidation, and morphology in nitrite-induced erythrocytes. The protective capacity of CGA shows superior to the remediate effect of CGA against NaNO₂ caused damage to erythrocytes. These results suggest a novel diet strategy for preventing the adverse effects of NaNO₂ in those people with acute exposure to nitrite.

Ex Vivo Study of Laban's Role in Decreasing Hemolysis Crisis in G6PD-Deficient Patients

In spite of the vast nutritional and environmental benefits provided by fava bean (Vicia faba), the ingestion of vicine/convicine provokes an acute hemolytic anemia called favism in individuals with a glucose-6-phosphate dehydrogenase (G6PD) deficiency. The elimination of these glycosides is a goal that could be accomplished using different processing methods including bacteriological treatment. Laban as a good source of lactic acid bacteria was tested in an ex vivo assay on human blood samples in order to determine its capacity in decreasing the hemolysis crisis induced by the ingestion of fava beans. Results indicate a significant decrease in human blood cell hemolysis after the treatment of fava beans by Laban. This decrease in hemolysis was also correlated with the G6PD deficiency categorization. The highest hemolysis level (mean: 23.11 ± 0.76%) was observed in samples with G6PD activity between 10 and 30%, while the lowest hemolysis level (mean: 5.75 ± 0.64%) was observed in samples with G6PD activity more than 60%. This decrease was correlated with a high antioxidant capacity of Laban (51.61 ± 1.13% expressed by the percentage inhibition of DPPH radical). The counts of isolates from MRS and M17 culture plates were 6.75 ± 0.095 and 7.91 ± 0.061 log cfu ml^-1, respectively. In conclusion, the synergy between the antioxidant properties of Laban and the possible decrease of vicine and convicine concentrations by lactobacillus found in the fermented dairy products could explain the ability of Laban to reduce the hemolysis crisis ex vivo.

Natural Antioxidants Beneficial Effects on Anion Exchange through Band 3 Protein in Human Erythrocytes

Band 3 protein (B3p) exchanging Cl⁻ and HCO₃⁻ through erythrocyte membranes is responsible for acid balance, ion distribution and gas exchange, thus accounting for homeostasis of both erythrocytes and entire organisms. Moreover, since B3p cross links with the cytoskeleton and the proteins underlying the erythrocyte membrane, its function also impacts cell shape and deformability, essential to adaptation of erythrocyte size to capillaries for pulmonary circulation. As growing attention has been directed toward this protein in recent years, the present review was conceived to report the most recent knowledge regarding B3p, with specific regard to its anion exchange capability under in vitro oxidative conditions. Most importantly, the role of natural antioxidants, i.e., curcumin, melatonin and Mg²⁺, in preventing detrimental oxidant effects on B3p is considered.

The glucose-6-phosphate dehydrogenase Mahidol variant protects against uncomplicated Plasmodium vivax infection and reduces disease severity in a Kachin population from northeast Myanmar

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is one of the most common red cell disorders in the world. The aim of this study was to investigate whether the G6PD Mahidol variant and haplotype 1311 T/93C, which are prevalent in the Kachin ethnic population along the China-Myanmar border area, offer protection against Plasmodium vivax infection. Malaria was monitored in nine villages near the Laiza township, Kachin State, Myanmar, where 258 cases of uncomplicated P. vivax were identified in 2013-2017. From the same villages, 250 unrelated, malaria-free participants were recruited to serve as the control cohort. Quantitative enzyme activity analysis in 100 healthy individuals identified that both male hemizygotes and female heterozygotes of the G6PD Mahidol variant had on average ~40% lower enzyme activity relative to the wild-type individuals. Compared with the overall prevalence of 25.2% in the control cohort, the G6PD Mahidol variant had a significantly lower prevalence (7.0%) among the 258 vivax patients (P <  .0001, χ2 test). Logistic regression analysis of G6PD genotypes stratified by sex showed that the individuals with the Mahidol 487A allele had dramatically reduced odds of having acute vivax malaria (adjusted odds ratio = 0.213 for male 487A hemizygotes, P < .0001, and 0.248 for female 487GA heterozygotes, P < .001). Furthermore, both 487A hemizygous male and 487GA heterozygous female patients had significantly lower asexual parasitemias than the wild-type patients, suggesting a potential effect on alleviating disease severity. In contrast, the silent mutation haplotype 1311 T/93C was highly prevalent (49.6%) in the study population, but it was not associated with altered G6PD enzymatic activities nor did it seem to provide protection against vivax infection or disease severity. Taken together, this study provided evidence that the Mahidol G > A mutation offers protection against P. vivax infection and potentially reduces disease severity in a Kachin population.

Hormetic and Mitochondria-Related Mechanisms of Antioxidant Action of Phytochemicals

Antioxidant action to afford a health benefit or increased well-being may not be directly exerted by quick reduction-oxidation (REDOX) reactions between the antioxidant and the pro-oxidant molecules in a living being. Furthermore, not all flavonoids or polyphenols derived from plants are beneficial. This paper aims at discussing the variety of mechanisms underlying the so-called "antioxidant" action. Apart from antioxidant direct mechanisms, indirect ones consisting of fueling and boosting innate detox routes should be considered. One of them, hormesis, involves upregulating enzymes that are needed in innate detox pathways and/or regulating the transcription of the so-called vitagenes. Moreover, there is evidence that some plant-derived compounds may have a direct role in events taking place in mitochondria, which is an organelle prone to oxidative stress if electron transport is faulty. Insights into the potential of molecules able to enter into the electron transport chain would require the determination of their reduction potential. Additionally, it is advisable to know both the oxidized and the reduced structures for each antioxidant candidate. These mechanisms and their related technical developments should help nutraceutical industry to select candidates that are efficacious in physiological conditions to prevent diseases or increase human health.

Impaired antioxidant capacity causes a disruption of metabolic homeostasis in sickle erythrocytes

This study examined particularly relevant redox pathways such as glycolysis, pentose phosphate pathway (PPP), metHb reductase and nucleotide metabolism, in order to better address how sickle cells deal with redox metabolism disruption. We also investigated the generation of specific oxidative lesions, and the levels of an unexplored antioxidant that could act as a candidate biomarker for oxidative status in sickle cell anemia (SCA). We adopted rigorous exclusion criteria to obtain the studied groups, which were composed by 10 subjects without hemoglobinopathies and 10 SCA patients. We confirmed that sickle cells overwhelm the antioxidant defense system, leading to an impaired antioxidant capacity that significantly contributed to the increase in cholesterol oxidation (ChAld) and hemolysis. Among the antioxidants evaluated, ergothioneine levels decreased in SCA (two-fold). We found strong correlations of ergothioneine levels with other erythrocyte metabolism markers, suggesting its use as an antioxidant therapy alternative for SCA treatment. Moreover, we found higher activities of MetHb reductase, AChE, G6PDH, HXK, and LDH, as well as levels of NADPH, ATP and hypoxanthine in sickle cells. On this basis, we conclude that impaired antioxidant capacity leaves to a loss of glycolysis and PPP shifting mechanism control and further homeostasis rupture, contributing to a decreased lifespan of sickle cells.

Mitochondrial Toxicity of Azithromycin Results in Aerobic Glycolysis and DNA Damage of Human Mammary Epithelia and Fibroblasts

Mitochondria evolved from free-living bacteria via endocytosis within eukaryotic host cells millions of year ago. We hypothesized that antibiotics cause mammalian mitochondrial damage while causing bacterial lethality. Mitochondrial toxicity of azithromycin in human mammary epithelia MCF-12A and fibroblasts were tested by fluorescent and transmission electron microscopy. Gene expression and DNA damage were tested by real-time polymerase chain reaction (qPCR) and ELISA. We found azithromycin suppressed the mitochondrial membrane potential gradient of MCF-12A cells and fibroblasts. Ultrastructure exams showed that the antibiotic caused vacuolated and swollen mitochondria with disrupted cristae in MCF-12A cells and fibroblasts compared to the morphology of mitochondria in the cells without antibiotic treatment. Fluorescent microscopy also showed azithromycin-induced mitochondrial reactive oxygen species (ROS), superoxide, after 3 h of culture. The DNA oxidative damage product, 8-hydroxy-2’-deoxyguanosine (8-OHdG, significantly increased in the media after MCF-12A cells and fibroblasts were cultured in the media containing azithromycin for 24 h. Azithromycin upregulated gene expression of hypoxia inducible factor 1 alpha (HIF1a), glycolytic enzymes including hexokinase 2 (HK2), phosphofructokinase 1 (PFKM), pyruvate kinase muscle isozyme M2 (PKM2), and glucose transporters in MCF-12A cells and fibroblasts. Lactate production also increased in the culture media. After treatment with azithromycin, healthy MCF-12A and fibroblast cells increased aerobic glycolysis—the “Warburg Effect”—to generate energy. In summary, azithromycin caused mitochondrial toxicity, ROS overproduction, DNA oxidative damage, upregulation of the HIF1a gene, and aerobic glycolysis in healthy mammalian cells. Over-usage of antibiotics could contribute to tumorigenesis and neurodegeneration and aggravate existing mitochondria-associated diseases.

In silico study of peculiarities of metabolism of erythrocytes with glucosephosphate isomerase deficiency

Glucose phosphate isomerase (GPI) deficiency, the third most common cause of hereditary nonspherocytic hemolytic anemia, is associated with the mutation of the GPI gene. The results of the GPI deficiency are premature aging of erythrocytes, macrocytosis, reticulocytosis, minor splenomegaly, hyperbilirubinemia and hyperferritinemia, and hemolytic crisis under the influence of exogenous oxidants such as infections or drugs. Regarding the the lack of GPI correction drugs, the theoretical substantiation of supportive therapy based on system biology approaches that would allow the analysis of the relationships between numerical metabolic processes in a cell would be beneficial. The stoichiometric model of erythrocytes’ steady state metabolism, including the pathways of Embden-Meyerhof and pentose phosphate (PPP), purine metabolism cycles and glutathione synthesis, has been developed. To predict the redistribution of metabolic flows in erythrocytes under conditions of GPI deficiency, we used the flux balance analysis (FBA). In this approach, calculations of the elementary flux modes (EFMs) and the control-effective flux (CEF) have been performed. Using the CEF evaluation approach, effective profiles of enzymatic reactions depending on the degree of enzyme deficiency were obtained. It has been shown that these relationships can be the basis for future experimental studies. Analysis of the profiles of enzymatic reactions of metabolic networks suggests that erythrocytes are capable of metabolizing other substrates that contribute to overcoming the effects of energy stress in the case of enzymopathies. So, it is shown that erythrocytes can effectively use SAM and adenosine as alternative energy sources. It has been established that the GPI enzymopathy results in a decrease in the flow through the glycolysis and pentose phosphate pathway, resulting in a decrease in the content of such reducing agents as NADPH and GSH, ATP. The processes of the GSH synthesis from amino acids in the cell are shown to be suppressed. Decreased content of NADPH and GSH cause the premature aging of erythrocytes. The target therapeutic approaches that influence the behaviour of the metabolic network of erythrocytes are discussed.

Red Blood Cell Membrane Conductance in Hereditary Haemolytic Anaemias

Congenital haemolytic anaemias are inherited disorders caused by red blood cell membrane and cytoskeletal protein defects, deviant hemoglobin synthesis and metabolic enzyme deficiencies. In many cases, although the causing mutation might be known, the pathophysiology and the connection between the particular mutation and the symptoms of the disease are not completely understood. Thus effective treatment is lagging behind. As in many cases abnormal red blood cell cation content and cation leaks go along with the disease, by direct electrophysiological measurements of the general conductance of red blood cells, we aimed to assess if changes in the membrane conductance could be a possible cause. We recorded whole-cell currents from 29 patients with different types of congenital haemolytic anaemias: 14 with hereditary spherocytosis due to mutations in α-spectrin, β-spectrin, ankyrin and band 3 protein; 6 patients with hereditary xerocytosis due to mutations in Piezo1; 6 patients with enzymatic disorders (3 patients with glucose-6-phosphate dehydrogenase deficiency, 1 patient with pyruvate kinase deficiency, 1 patient with glutamate-cysteine ligase deficiency and 1 patient with glutathione reductase deficiency), 1 patient with β-thalassemia and 2 patients, carriers of several mutations and a complex genotype. While the patients with β-thalassemia and metabolic enzyme deficiencies showed no changes in their membrane conductance, the patients with hereditary spherocytosis and hereditary xerocytosis showed largely variable results depending on the underlying mutation.

Protective Effect of Dinitrosyl Iron Complexes with Glutathione in Red Blood Cell Lysis Induced by Hypochlorous Acid

Hypochlorous acid (HOCl), one of the major precursors of free radicals in body cells and tissues, is endowed with strong prooxidant activity. In living systems, dinitrosyl iron complexes (DNIC) with glutathione ligands play the role of nitric oxide donors and possess a broad range of biological activities. At micromolar concentrations, DNIC effectively inhibit HOCl-induced lysis of red blood cells (RBCs) and manifest an ability to scavenge alkoxyl and alkylperoxyl radicals generated in the reaction of HOCl with tert-butyl hydroperoxide. DNIC proved to be more effective cytoprotective agents and organic free radical scavengers in comparison with reduced glutathione (GSH). At the same time, the kinetics of HOCl-induced oxidation of glutathione ligands in DNIC is slower than in the case of GSH. HOCl-induced oxidative conversions of thiolate ligands cause modification of DNIC, which manifests itself in inclusion of other ligands. It is suggested that the strong inhibiting effect of DNIC with glutathione on HOCl-induced lysis of RBCs is determined by their antioxidant and regulatory properties.

Anticancer Thiosemicarbazones: Chemical Properties, Interaction with Iron Metabolism, and Resistance Development

SIGNIFICANCE

During the past decades, thiosemicarbazones were clinically developed for a variety of diseases, including tuberculosis, viral infections, malaria, and cancer. With regard to malignant diseases, the class of α-N-heterocyclic thiosemicarbazones, and here especially 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (Triapine), was intensively developed in multiple clinical phase I/II trials. Recent Advances: Very recently, two new derivatives, namely COTI-2 and di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC) have entered phase I evaluation. Based on the strong metal-chelating/metal-interacting properties of thiosemicarbazones, interference with the cellular iron (and copper) homeostasis is assumed to play an important role in their biological activity.

CRITICAL ISSUES

In this review, we summarize and analyze the data on the interaction of (α-N-heterocyclic) thiosemicarbazones with iron, with the special aim of bridging the current knowledge on their mode of action from chemistry to (cell) biology. In addition, we highlight the difference to classical iron(III) chelators such as desferrioxamine (DFO), which are used for the treatment of iron overload.

FUTURE DIRECTIONS

We want to emphasize that thiosemicarbazones are not solely removing iron from the cells/organism. In contrast, they should be considered as iron-interacting drugs influencing diverse biological pathways in a complex and multi-faceted mode of action. Consequently, in addition to the discussion of physicochemical properties (e.g., complex stability, redox activity), this review contains an overview on the diversity of cellular thiosemicarbazone targets and drug resistance mechanisms.

Antioxidant Defense Mechanisms in Erythrocytes and in the Central Nervous System

Differential antioxidant action is found upon comparison of organ/tissue systems in the human body. In erythrocytes (red blood cells), which transport oxygen and carbon dioxide through the circulatory system, the most important issue is to keep hemoglobin in a functional state that requires maintaining the haem group in ferrous (Fe²⁺) state. Conversion of oxidized Fe³⁺ back into Fe²⁺ in hemoglobin needs a special mechanism involving a tripeptide glutathione, glucose-6-phosphate dehydrogenase, and glucose and NADPH as suppliers of reducing power. Fava beans are probably a good resource to make the detox innate system more robust as the pro-oxidant molecules in this food likely induce the upregulation of members of such mechanisms. The central nervous system consumes more oxygen than the majority of human tissues, i.e., 20% of the body's total oxygen consumption and, therefore, it is exposed to a high level of oxidative stress. This fact, together with the progressive age-related decline in the efficiency of the antioxidant defense system, leads to neuronal death and disease. The innate mechanism operating in the central nervous system is not well known and seems different to that of the erythrocytes. The strategies of antioxidant intervention in brain will be reviewed here.

Formation primaquine-5,6-orthoquinone, the putative active and toxic metabolite of primaquine via direct oxidation in human erythrocytes

BACKGROUND

The activity and haemolytic toxicity associated with primaquine has been linked to its reactive metabolites. The reactive metabolites are thought to be primarily formed through the action of cytochrome P₄₅₀-mediated pathways. Human erythrocytes generally are not considered a significant contributor to drug biotransformation. As erythrocytes are the target of primaquine toxicity, the ability of erythrocytes to mediate the formation of reactive oxidative primaquine metabolites in the absence of hepatic enzymes, was evaluated.

METHODS

Primaquine and its enantiomers were incubated separately with human red blood cells and haemoglobin. Post-incubation analysis was performed with UPLC-MS/MS to identify products of biotransformation.

RESULTS

The major metabolite detected was identified as primaquine-5,6-orthoquinone, reflecting the pathway yielding putative active and haematotoxic metabolites of primaquine, which was formed by oxidative demethylation of 5-hydroxyprimaquine. Incubation of primaquine with haemoglobin in a cell-free system yielded similar results. It appears that the observed biotransformation is due to non-enzymatic processes, perhaps due to reactive oxygen species (ROS) present in erythrocytes or in the haemoglobin incubates.

CONCLUSION

This study presents new evidence that primaquine-5,6-orthoquinone, the metabolite of primaquine reflecting the oxidative biotransformation pathway, is generated in erythrocytes, probably by non-enzymatic means, and may not require transport from the liver or other tissues.

Prolonged erythrocyte auto-incubation as an alternative model for oxidant generation system

This study investigated the effects of incubation period and melatonin treatment on red blood cell (RBC) metabolism in an auto-incubation model of H₂O₂-induced oxidative stress. The study was carried out on three healthy adult donors by incubating RBCs in their own plasma at 37 °C, or under the influence of 1 mM H₂O₂ with and without 100 μM melatonin at different times (0, 1, 3 and 6 h). We assessed incubation period, treatment, as well as any interaction effects between these predictors on erythrocyte osmoregulation, hemolytic rate, oxidative stress markers, and adenylate nucleotide levels. We did not find any relevant effects of both incubation period and treatments on osmotic, antioxidant and adenylate parameters. On the other hand, hemolysis degree and biomolecule oxidation levels in the plasma increased over time, 3-fold and about 25%, respectively, regardless any treatment influence. H₂O₂ treatment more than doubled protein carbonyl groups, regardless time in plasma, and in a time-depending way in erythrocyte membrane extract, effects that were neutralized by melatonin treatment. Through multivariate analyses, we could expand the understanding of energy and redox metabolisms in the maintenance of cellular integrity and metabolic homeostasis. Another interesting observation was the 65-75% contribution of the oxidative lesion markers on hemolysis. Hence, these findings suggested a new and more intuitive RBC suspension model and reinforced the beneficial use of melatonin in human disorders.

Impact of glucose-6-phosphate dehydrogenase deficiency on dengue infection in Myanmar children

Glucose-6-phosphate dehydrogenase (G6PD) deficiency may affect the clinical presentation of dengue due to the altered redox state in immune cells. We aimed to determine the association between G6PD deficiency and severity of dengue infection in paediatric patients in Myanmar. A cross-sectional study was conducted among paediatric patients aged 2–13 years with dengue in Yankin Children Hospital, Myanmar. One hundred and ninety-six patients positive for dengue infection, as determined via PCR or ELISA, were enrolled. Dengue severity was determined according to the 2009 WHO classification guidelines. Spectrophotometric assays determined G6PD levels. The adjusted median G6PD value of males in the study population was used to define various cut-off points according to the WHO classification guidelines. G6PD genotyping for Mahidol, Kaiping and Mediterranean mutations was performed for 128 out of 196 samples by real-time multiplex PCR. 51 of 196 (26.0%) patients had severe dengue. The prevalence of G6PD phenotype deficiency (< 60% activity) in paediatric patients was 14.8% (29/196), specifically, 13.6% (14/103) in males and 16.2% (15/93) in females. Severe deficiency (< 10% activity) accounted for 7.1% (14/196) of our cohort, occurring 11.7% (12/103) in males and 2.2% (2/93) in females. Among 128 samples genotyped, the G6PD gene mutations were detected in 19.5% (25/128) of patients, with 20.3% (13/ 64) in males and 18.8% (12/64) in females. The G6PD Mahidol mutation was 96.0% (24/25) while the G6PD Kaiping mutation was 4.0% (1/25). Severe dengue was not associated with G6PD enzyme deficiency or presence of the G6PD gene mutation. Thus, no association between G6PD deficiency and dengue severity could be detected.

Trial registration: The study was registered following the WHO International Clinical Trials Registry Platform (WHO-ICTRP) on Thai Clinical Trials Registry (TCTR) website, registration number # TCTR20180720001

Hemolytic jaundice induced by pharmacological dose ascorbic acid in glucose-6-phosphate dehydrogenase deficiency: A case report

RATIONALE

Hemolysis induced by high dose ascorbic acid (AA) in patients with G6PD deficiency has been reported, but is rare. To our knowledge, this is the first reported case of a male with G6PD deficiency, coexpressed with cholecystolithiasis and cholecystitis, who developed extreme hemolysis and hyperbilirubinemia after receiving pharmacological doses ascorbic acid infusion.

PATIENT CONCERNS

A 27-year-old man history with glucose-6-phosphate dehydrogenase deficiency was admitted to our hospital because of cholecystolithiasis and cholecystitis. He appeared with scleral jaundice and very deep colored urine after receiving pharmacological doses ascorbic acid infusion.

DIAGNOSES

Clinical findings when combined with his medical history and various laboratory results confirmed the diagnosis as hemolysis and hyperbilirubinemia induced by ascorbic acid.

INTERVENTIONS

The patient was treated with steroids, hepatoprotective drugs, and folic acid in addition avoidance of agents with known hemolysis risk (such as vitamin C).

OUTCOMES

As a result, the patient's symptoms from hemolytic jaundice improved, hemoglobin remained stable, and the patient was discharged 11 days later.

LESSONS

Clinicians should bear in mind the possibility that vitamin C exposure may result in hemolysis in patients with G6PD deficiency, especially in those with known severe disease.

Membrane protein carbonylation of Plasmodium falciparum infected erythrocytes under conditions of sickle cell trait and G6PD deficiency

Deficiency of glucose-6-phosphate dehydrogenase (G6PD) and sickle cell trait (SCT) are described as the polymorphic disorders prevalent in erythrocytes. Both are considered the result of the selective pressure exerted by Plasmodium parasites over human genome, due to a certain degree of resistance to the clinical symptoms of severe malaria. There exist in both a prooxidant environment that favors the oxidative damage on membrane proteins, which probably is part of molecular protector mechanisms. Nevertheless, mechanisms are not completely understood at molecular level for each polymorphism yet, and even less if are commons for several of them. Here, synchronous cultures at high parasitemia levels of P. falciparum 3D7 were used to quantify oxidative damage in membrane proteins of erythrocytes with G6PD deficient and SCT. Carbonyl index by dot blot assay was used to calculate the variation of oxidative damage during the asexual phases. Besides, protein carbonylation profiles were obtained by Western blot and complemented with mass spectrometry using MALDI-TOF-TOF analysis. Erythrocytes with G6PD deficient and SCT showed higher carbonyl index values than control and similar profiles of carbonylated proteins; moreover, cytoskeletal and stress response proteins were identified as the main targets of oxidative damage. Therefore, both polymorphisms promote carbonylation on the same membrane proteins. Finally, these results allowed to reinforce the hypothesis of oxidative damage in erythrocyte membrane proteins as molecular mechanism of human adaptation to malaria infection.

Vitamin E deficiency in South Asian population and the therapeutic use of alpha-tocopherol (Vitamin E) for correction of anemia

Mild to moderate vitamin E deficiency because of inadequate consumption of vitamin E-rich foods and intestinal fat malabsorption is common in growing children, women of reproductive age and elderly South Asian population. Severe vitamin E deficiency may lead to peripheral and motor neurodegenerative diseases (e.g ataxia and motor skeletal myopathy), impaired immune response and free radical-induced hemolytic anemias. Vitamin E insufficiency and/or deficiency status in the general Pakistani population has not been sufficiently investigated. Moreover, there are challenges in determining vitamin E status in apparently healthy humans due to variations in their age, sources of consumed vitamin E and plasma lipid levels. Oxidative stress-induced reactive oxygen species have been shown to cause ineffective erythropoiesis and enhanced lysis of erythrocytes in some of the experimental animals and humans. Several studies on patients with various types of inherited hemolytic anemias, chronic renal disease, premature low birth infants and apparently healthy humans have shown that vitamin E might be therapeutically effective in the prevention and/ or treatment of anemia in these subjects.