Oxidative stress in sickle cell disease; pathophysiology and potential implications for disease management

Gene-environmental influence of space and microgravity on red blood cells with sickle cell disease

A fundamental question in human biology and for hematological disease is how do complex gene-environment interactions lead to individual disease outcome? This is no less the case for sickle cell disease (SCD), a monogenic disorder of Mendelian inheritance, both clinical course, severity, and treatment response, is variable amongst affected individuals. New insight and discovery often lie between the intersection of seemingly disparate disciplines. Recently, opportunities for space medicine have flourished and have offered a new paradigm for study. Two recent Nature papers have shown that hemolysis and oxidative stress play key mechanistic roles in erythrocyte pathogenesis during spaceflight. This paper reviews existing genetic and environmental modifiers of the sickle cell disease phenotype. It reviews evidence for erythrocyte pathology in microgravity environments and demonstrates why this may be relevant for the unique gene-environment interaction of the SCD phenotype. It also introduces the hematology and scientific community to methodological tools for evaluation in space and microgravity research. The increasing understanding of space biology may yield insight into gene-environment influences and new treatment paradigms in SCD and other hematological disease phenotypes.

A pharmacokinetic-pharmacodynamic analysis of l-glutamine for the treatment of sickle cell disease: Implications for understanding the mechanism of action and evaluating response to therapy

The mechanisms of action of l-glutamine for the treatment of sickle cell disease (SCD) are not well understood and there are no validated clinical biomarkers to assess response. We conducted a three-week, dose-ascending trial of glutamine and measured the pharmacokinetic (PK) exposure parameters, peak concentration (Cmax) and area under the curve (AUC). We used a panel of biomarkers to investigate the pharmacodynamics (PD) of glutamine and studied PK-PD relationships. There was no plasma accumulation of glutamine, glutamate, arginine or other amino acids over time, but modestly improved arginine bioavailability was observed. In standard analysis by dose levels over time, there were no measurable effects on blood counts, viscosity, ektacytometry or reactive oxygen species (ROS). In PK-PD analysis, however, higher glutamine exposure (Cmax or AUC) was associated with increased whole blood viscosity and cellular dehydration, yet also with higher haemoglobin concentration, increased haematocrit-to-viscosity ratio, decreased reticulocyte ROS, improved RBC deformability and decreased point of sickling. This novel PK-PD analysis identified biomarkers reflecting the positive and negative effects of glutamine, helping to elucidate its mechanisms of action in SCD. PK-optimized dosing to achieve glutamine exposure (AUC or Cmax) that is associated with salutary biological effects should be studied to support its therapeutic use.

Red Blood Cells as Therapeutic Target to Treat Sickle Cell Disease

Significance: Sickle cell disease (SCD) is the most common inherited diathesis affecting mostly underserved populations globally. SCD is characterized by chronic pain and fatigue, severe acute painful crises requiring hospitalization and opioids, strokes, multiorgan damage, and a shortened life span. Symptoms may appear shortly after birth, and, in less developed countries, most children with SCD die before attaining age 5. Hematopoietic stem cell transplant and gene therapy offer a curative therapeutic approach, but, due to many challenges, are limited in their availability and effectiveness for a majority of persons with SCD. A critical unmet need is to develop safe and effective novel targeted therapies. A wide array of drugs currently undergoing clinical investigation hold promise for an expanded pharmacological armamentarium against SCD. Recent Advances: Hydroxyurea, the most widely used intervention for SCD management, has improved the survival in the Western world and more recently, voxelotor (R-state-stabilizer), l-glutamine, and crizanlizumab (anti-P-selectin antibody) have been approved by the Food and Drug Administration (FDA) for use in SCD. The recent FDA approval emphasizes the need to revisit the advances in understanding the core pathophysiology of SCD to accelerate novel evidence-based strategies to treat SCD. The biomechanical breakdown of erythrocytesis, the core pathophysiology of SCD, is associated with intrinsic factors, including the composition of hemoglobin, membrane integrity, cellular volume, hydration, andoxidative stress. Critical Issues and Future Directions: In this context, this review focuses on advances in emerging nongenetic interventions directed toward the therapeutic targets intrinsic to sickle red blood cells (RBCs), which can prevent impaired rheology of RBCs to impede disease progression and reduce the sequelae of comorbidities, including pain, vasculopathy, and organ damage. In addition, given the intricate pathophysiology of the disease, it is unlikely that a single pharmacotherapeutic intervention will comprehensively ameliorate the multifaceted complications associated with SCD. However, the availability of multiple drug options affords the opportunity for individualized therapeutic regimens tailored to specific SCD-related complications. Furthermore, it opens avenues for combination drug therapy, capitalizing on distinct mechanisms of action and profiles of adverse effects.

Antioxidant supplementation for sickle cell disease

BACKGROUND

Sickle cell disease (SCD) refers to a group of genetic disorders characterized by the presence of an abnormal haemoglobin molecule called haemoglobin S (HbS). When subjected to oxidative stress from low oxygen concentrations, HbS molecules form rigid polymers, giving the red cell the typical sickle shape. Antioxidants have been shown to reduce oxidative stress and improve outcomes in other diseases associated with oxidative stress. Therefore, it is important to review and synthesize the available evidence on the effect of antioxidants on the clinical outcomes of people with SCD.

OBJECTIVES

To assess the effectiveness and safety of antioxidant supplementation for improving health outcomes in people with SCD.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search date was 15 August 2023.

SELECTION CRITERIA

We included randomized and quasi-randomized controlled trials comparing antioxidant supplementation to placebo, other antioxidants, or different doses of antioxidants, in people with SCD.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data, assessed the risk of bias and certainty of the evidence, and reported according to Cochrane methodological procedures.

MAIN RESULTS

The review included 1609 participants in 26 studies, with 17 comparisons. We rated 13 studies as having a high risk of bias overall, and 13 studies as having an unclear risk of bias overall due to study limitations. We used GRADE to rate the certainty of evidence. Only eight studies reported on our important outcomes at six months. Vitamin C (1400 mg) plus vitamin E (800 mg) versus placebo Based on evidence from one study in 83 participants, vitamin C (1400 mg) plus vitamin E (800 mg) may not be better than placebo at reducing the frequency of crisis (risk ratio (RR) 1.18, 95% confidence interval (CI) 0.64 to 2.18), the severity of pain (RR 1.33, 95% CI 0.40 to 4.37), or adverse effects (AE), of which the most common were headache, nausea, fatigue, diarrhoea, and epigastric pain (RR 0.56, 95% CI 0.31 to 1.00). Vitamin C plus vitamin E may increase the risk of SCD-related complications (acute chest syndrome: RR 2.66, 95% CI 0.77 to 9.13; 1 study, 83 participants), and increase haemoglobin level (median (interquartile range) 90 (81 to 96) g/L versus 93.5 (84 to 105) g/L) (1 study, 83 participants) compared to placebo. However, the evidence for all the above effects is very uncertain. The study did not report on quality of life (QoL) of participants and their caregivers, nor on frequency of hospitalization. Zinc versus placebo Zinc may not be better than placebo at reducing the frequency of crisis at six months (rate ratio 0.62, 95% CI 0.17 to 2.29; 1 study, 36 participants; low-certainty evidence). We are uncertain whether zinc is better than placebo at improving sickle cell-related complications (complete healing of leg ulcers at six months: RR 2.00, 95% CI 0.60 to 6.72; 1 study, 34 participants; very low-certainty evidence). Zinc may be better than placebo at increasing haemoglobin level (g/dL) (MD 1.26, 95% CI 0.44 to 1.26; 1 study, 36 participants; low-certainty evidence). The study did not report on severity of pain, QoL, AE, and frequency of hospitalization. N-acetylcysteine versus placebo N-acetylcysteine (NAC) 1200 mg may not be better than placebo at reducing the frequency of crisis in SCD, reported as pain days (rate ratio 0.99 days, 95% CI 0.53 to 1.84; 1 study, 96 participants; low-certainty evidence). Low-certainty evidence from one study (96 participants) suggests NAC (1200 mg) may not be better than placebo at reducing the severity of pain (MD 0.17, 95% CI -0.53 to 0.87). Compared to placebo, NAC (1200 mg) may not be better at improving physical QoL (MD -1.80, 95% CI -5.01 to 1.41) and mental QoL (MD 2.00, 95% CI -1.45 to 5.45; very low-certainty evidence), reducing the risk of adverse effects (gastrointestinal complaints, pruritus, or rash) (RR 0.92, 95% CI 0.75 to 1.14; low-certainty evidence), reducing the frequency of hospitalizations (rate ratio 0.98, 95% CI 0.41 to 2.38; low-certainty evidence), and sickle cell-related complications (RR 5.00, 95% CI 0.25 to 101.48; very low-certainty evidence), or increasing haemoglobin level (MD -0.18 g/dL, 95% CI -0.40 to 0.04; low-certainty evidence). L-arginine versus placebo L-arginine may not be better than placebo at reducing the frequency of crisis (monthly pain) (RR 0.71, 95% CI 0.26 to 1.95; 1 study, 50 participants; low-certainty evidence). However, L-arginine may be better than placebo at reducing the severity of pain (MD -1.41, 95% CI -1.65 to -1.18; 2 studies, 125 participants; low-certainty evidence). One participant allocated to L-arginine developed hives during infusion of L-arginine, another experienced acute clinical deterioration, and a participant in the placebo group had clinically relevant increases in liver function enzymes. The evidence is very uncertain whether L-arginine is better at reducing the mean number of days in hospital compared to placebo (MD -0.85 days, 95% CI -1.87 to 0.17; 2 studies, 125 participants; very low-certainty evidence). Also, L-arginine may not be better than placebo at increasing haemoglobin level (MD 0.4 g/dL, 95% CI -0.50 to 1.3; 2 studies, 106 participants; low-certainty evidence). No study in this comparison reported on QoL and sickle cell-related complications. Omega-3 versus placebo Very low-certainty evidence shows no evidence of a difference in the risk of adverse effects of omega-3 compared to placebo (RR 1.05, 95% CI 0.74 to 1.48; 1 study, 67 participants). Very low-certainty evidence suggests that omega-3 may not be better than placebo at increasing haemoglobin level (MD 0.36 g/L, 95% CI -0.21 to 0.93; 1 study, 67 participants). The study did not report on frequency of crisis, severity of pain, QoL, frequency of hospitalization, and sickle cell-related complications.

AUTHORS' CONCLUSIONS

There was inconsistent evidence on all outcomes to draw conclusions on the beneficial and harmful effects of antioxidants. However, L-arginine may be better than placebo at reducing the severity of pain at six months, and zinc may be better than placebo at increasing haemoglobin level. We are uncertain whether other antioxidants are beneficial for SCD. Larger studies conducted on each comparison would reduce the current uncertainties.

Simvastatin-Mediated Nrf2 Activation Induces Fetal Hemoglobin and Antioxidant Enzyme Expression to Ameliorate the Phenotype of Sickle Cell Disease

Sickle cell disease (SCD) is a pathophysiological condition of chronic hemolysis, oxidative stress, and elevated inflammation. The transcription factor Nrf2 is a master regulator of oxidative stress. Here, we report that the FDA-approved oral agent simvastatin, an inhibitor of hydroxymethyl-glutaryl coenzyme A reductase, significantly activates the expression of Nrf2 and antioxidant enzymes. Simvastatin also induces fetal hemoglobin expression in SCD patient primary erythroid progenitors and a transgenic mouse model. Simvastatin alleviates SCD symptoms by decreasing hemoglobin S sickling, oxidative stress, and inflammatory stress in erythroblasts. Particularly, simvastatin increases cellular levels of cystine, the precursor for the biosynthesis of the antioxidant reduced glutathione, and decreases the iron content in SCD mouse spleen and liver tissues. Mechanistic studies suggest that simvastatin suppresses the expression of the critical histone methyltransferase enhancer of zeste homolog 2 to reduce both global and gene-specific histone H3 lysine 27 trimethylation. These chromatin structural changes promote the assembly of transcription complexes to fetal γ-globin and antioxidant gene regulatory regions in an antioxidant response element-dependent manner. In summary, our findings suggest that simvastatin activates fetal hemoglobin and antioxidant protein expression, modulates iron and cystine/reduced glutathione levels to improve the phenotype of SCD, and represents a therapeutic strategy for further development.

Haematopoietic stem cell health in sickle cell disease and its implications for stem cell therapies and secondary haematological disorders

Gene modification of haematopoietic stem cells (HSCs) is a potentially curative approach to sickle cell disease (SCD) and offers hope for patients who are not eligible for allogeneic HSC transplantation. Current approaches require in vitro manipulation of healthy autologous HSC prior to their transplantation. However, the health and integrity of HSCs may be compromised by a variety of disease processes in SCD, and challenges have emerged in the clinical trials of gene therapy. There is also concern about increased susceptibility to haematological malignancies during long-term follow up of patients, and this raises questions about genomic stability in the stem cell compartment. In this review, we evaluate the evidence for HSC deficits in SCD and then discuss their potential causation. Finally, we suggest several questions which need to be addressed in order to progress with successful HSC manipulation for gene therapy in SCD.

Sickle Cell Disease: From Genetics to Curative Approaches

Sickle cell disease (SCD) is a monogenic blood disease caused by a point mutation in the gene coding for β-globin. The abnormal hemoglobin [sickle hemoglobin (HbS)] polymerizes under low-oxygen conditions and causes red blood cells to sickle. The clinical presentation varies from very severe (with acute pain, chronic pain, and early mortality) to normal (few complications and a normal life span). The variability of SCD might be due (in part) to various genetic modulators. First, we review the main genetic factors, polymorphisms, and modifier genes that influence the expression of globin or otherwise modulate the severity of SCD. Considering SCD as a complex, multifactorial disorder is important for the development of appropriate pharmacological and genetic treatments. Second, we review the characteristics, advantages, and disadvantages of the latest advances in gene therapy for SCD, from lentiviral-vector-based approaches to gene-editing strategies.

Emerging Therapies for the Management of Pain and Vaso-Occlusive Crises in Patients With Sickle Cell Disease: A Systematic Review of Randomized Controlled Trials

Sickle cell disease (SCD) is an inherited disorder that impairs red blood cells (RBCs) and disrupts the delivery of oxygen to tissues. There is currently no cure. Symptoms can appear as early as six months of age and include anemia, acute episodes of pain, swelling, infections, delayed growth, and vision problems. A growing number of therapies are being investigated for reducing these episodes of pain, also known as vaso-occlusive crises (VOCs). The research literature evidence, however, currently includes far more approaches that have not shown superiority versus placebo than ones that have been proven effective. The purpose of this systematic review is to evaluate the body of randomized controlled trials (RCTs) to determine the quality of support for and against the use of a variety of current and emerging therapies for treading SCD VOCs. Several important new papers have emerged since previous systematic reviews with similar objectives were published. This review was conducted according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines and focused on PubMed exclusively. Only RCTs were sought, and no other filters, except for a five-year historical timeline cut-off, were used. Of the 46 publications that were returned in response to the query, 18 were ultimately accepted as meeting the pre-established inclusion criteria. The Cochrane risk-of-bias tool was utilized as a quality assessment measure, and the GRADE (Grading of Recommendations, Assessment, Development, and Evaluations) framework was used to assess the certainty of the evidence. Among the included publications, five out of 18 featured positive results with superiority and statistical significance versus placebo for either reduction in pain score or number/duration of VOCs. The approaches featured therapies ranging from de novo molecules to currently available drugs approved for other indications to naturally occurring metabolites such as amino acids and vitamins. A single therapy, arginine, was supported for both clinical endpoints: pain score reduction and shortened VOC duration. Currently, two therapies are approved by the United States Food and Drug Administration (FDA) and are commercially available (crizanlizumab, ADAKVEO and L-glutamine, Endari). All other therapies are investigational only in nature. Several studies included measurement of biomarker endpoints as well as clinical outcomes. Generally, beneficial outcomes related to improving biomarker levels did not also translate into statistically significant reduction of pain scores or number/duration of VOCs. While measuring biomarkers may contribute to the understanding of pathophysiology, it does not appear to directly offer predictive value toward treatment success clinically. It can be concluded that there exists a specific opportunity to design, fund, and execute investigations that both compare emerging and existing therapies versus one another and compare combinational therapies versus placebo.

Effects of l-arginine supplementation in patients with sickle cell disease: A systematic review and meta-analysis of clinical trials

Background and Aims

Previous studies have shown that supplementation of some amino acids such as l-arginine or its precursors could exert beneficial effects in patients with sickle cell disease (SCD). The objective of this study is to systematically review the literature to assess the effect of arginine administration on the clinical and paraclinical parameters of patients with SCD.

Methods

Four online databases of PubMed, Web of Sciences, Scopus, and Embase were selected for systematic search. Eligible studies were clinical trials that evaluated the effect of arginine usage in patients with SCD. Effects sizes were calculated using weighted mean difference (WMD) and Hedge's g and they were pooled using random-effects modeling with Hartung-Knapp adjustment. Additional analyses were also conducted.

Results

Twelve studies containing detail of 399 patients with SCD were found to be eligible. The data synthesis showed that l-arginine significantly increased the level of NO metabolites (Hedge's g: 1.50, 0.48-1.82, I 2: 88%) and hemoglobin F (WMD: 1.69%, 0.86-2.52, I 2: 0%) and significantly decreased systolic blood pressure (WMD: -8.46 mmHg, -15.58 to -1.33, I 2: 53%) and aspartate transaminase (Hedge's g: -0.49, -0.73 to -0.26, I 2: 0%). However, there were no significant effects on hemoglobin, reticulocyte, malondialdehyde and diastolic blood pressure, and alanine transaminase.

Conclusion

Our meta-analysis showed that l-arginine use for SCD could be beneficial, increase hemoglobin F and exert blood pressure-lowering and hepatoprotective properties. However, for a firm conclusion and widespread use of  l-arginine for these patients, more studies are needed.

Keap1-Nrf2 Heterodimer: A Therapeutic Target to Ameliorate Sickle Cell Disease

Sickle cell disease (SCD) is a monogenic inheritable disease characterized by severe anemia, increased hemolysis, and recurrent, painful vaso-occlusive crises due to the polymerization of hemoglobin S (HbS)-generated oxidative stress. Up until now, only four drugs are approved for SCD in the US. However, each of these drugs affects only a limited array of SCD pathologies. Importantly, curative therapies, such as gene therapy, or hematopoietic stem cell transplantation are not available for every patient because of their high costs, availability of donor matching, and their serious adverse effects. Therefore, there is an unmet medical need for novel therapeutic strategies that target broader SCD sequelae. SCD phenotypic severity can be alleviated by increasing fetal hemoglobin (HbF) expression. This results in the inhibition of HbS polymerization and thus sickling, and a reduction in oxidative stress. The efficacy of HbF is due to its ability to dilute HbS levels below the threshold required for polymerization and to influence HbS polymer stability in RBCs. Nuclear factor-E2-related factor 2 (Nrf2)/Kelch-like ECH-associated protein-1 (Keap1)-complex signaling is one of the most important cytoprotective signaling controlling oxidative stress. Nrf2 is present in most organs and, after dissociation from Keap1, it accumulates in the cytoplasm, then translocates to the nucleus where it binds to the antioxidant response element (ARE) sequences and increases the expression of various cytoprotective antioxidant genes. Keeping this in mind, various researchers have proposed a role of multiple agents, more importantly tert-Butylhydroquinone (tBHQ), curcumin, etc., (having electrophilic properties) in inhibiting keap1 activity, so that Nrf2 can translocate to the nucleus to activate the gamma globin gene, thus maintaining alpha-hemoglobin-stabilizing protein (AHSP) and HbF levels. This leads to reduced oxidative stress, consequently minimizing SCD-associated complications. In this review, we will discuss the role of the Keap-1–Nrf2 complex in hemoglobinopathies, especially in SCD, and how this complex might represent a better target for more effective treatment options.

Emerging drug targets for sickle cell disease: shedding light on new knowledge and advances at the molecular level

INTRODUCTION

In sickle cell disease (SCD), a single amino acid substitution at β6 of the hemoglobin (Hb) chain replaces glutamate with valine, forming HbS instead of the normal adult HbA. Loss of a negative charge, and the conformational change in deoxygenated HbS molecules, enables formation of HbS polymers. These not only distort red cell morphology but also have other profound effects so that this simple etiology belies a complex pathogenesis with multiple complications. Although SCD represents a common severe inherited disorder with life-long consequences, approved treatments remain inadequate. Hydroxyurea is currently the most effective, with a handful of newer treatments, but there remains a real need for novel, efficacious therapies.

AREAS COVERED

This review summarizes important early events in pathogenesis to highlight key targets for novel treatments.

EXPERT OPINION

A thorough understanding of early events in pathogenesis closely associated with the presence of HbS is the logical starting point for identification of new targets rather than concentrating on more downstream effects. We discuss ways of reducing HbS levels, reducing the impact of HbS polymers, and of membrane events perturbing cell function, and suggest using the unique permeability of sickle cells to target drugs specifically into those more severely compromised.

Effects of hydroxyurea on skeletal muscle energetics and force production in a sickle cell disease murine model

Hydroxyurea (HU) is commonly used as a treatment for patients with sickle cell disease (SCD) to enhance fetal hemoglobin production. This increased production is expected to reduce anemia (which depresses oxygen transport) and abnormal Hb content alleviating clinical symptoms such as vaso-occlusive crisis and acute chest syndrome. The effects of HU on skeletal muscle bioenergetics in vivo are still unknown. Due to the beneficial effects of HU upon oxygen delivery, improved skeletal muscle energetics and function in response to a HU treatment have been hypothesized. Muscle energetics and function were analyzed during a standardized rest-exercise-recovery protocol, using ³¹P-magnetic resonance spectroscopy in Townes SCD mice. Measurements were performed in three groups of mice: one group of 2-mo-old mice (SCD_2m, n = 8), another one of 4-mo-old mice (SCD_4m, n = 8), and a last group of 4-mo-old mice that have been treated from 2 mo of age with HU at 50 mg/kg/day (SCD_4m-HU, n = 8). As compared with SCD_2m mice, SCD_4m mice were heavier and displayed a lower acidosis. As lower specific forces were developed by SCD_4m compared with SCD_2m, greater force-normalized phosphocreatine consumption and oxidative and nonoxidative costs of contraction were also reported. HU-treated mice (SCD_4m-HU) displayed a significantly higher specific force production as compared with untreated mice (SCD_4m), whereas muscle energetics was unchanged. Overall, our results support a beneficial effect of HU on muscle function.NEW & NOTEWORTHY Our results highlighted that force production decreases between 2 and 4 mo of age in SCD mice thereby indicating a decrease of muscle function during this period. Of interest, HU treatment seemed to blunt the observed age effect given that SCD_4m-HU mice displayed a higher specific force production as compared with SCD_4m mice. In that respect, HU treatment would help to maintain a higher capacity of force production during aging in SCD.

Central Retinal Artery Occlusion in a Young Patient With a Hidden Unusual Sickle Cell Trait

Sickle cell trait is considered a benign condition. Ophthalmic manifestations are infrequent but can result in significant visual deterioration. We present a case of a 33-year-old male, not known to have any medical illnesses, who presented to the ophthalmological emergency room complaining of a sudden onset of painless and profound left eye vision loss for 12 hours. The patient denied any medication use, past eye trauma, or surgery. On detailed ophthalmologic examination, the best-corrected visual acuity (BCVA) was 20/20 in the right eye and hand movement in the left eye. Dilated fundus examination of the left eye showed a central retinal artery occlusion (CRAO) with pale, white retinal swelling and a macular cherry-red spot. Fundus fluorescein angiography showed delayed arterial filling with persistently reduced macular perfusion. CRAO was diagnosed in an otherwise healthy young male. Systemic workup was negative except for protein electrophoresis, which showed sickle cell trait, and HbA1C was 7.8%. Later, atrophic macular changes with a pale optic disc were observed, and BCVA was reduced to light perception. CRAO in young patients amounts to diverse causes, which require extensive systemic workup. In addition, the concurrence of the sickle cell trait with diabetes mellitus might have a role in CRAO development.

Knowledge and awareness of sickle cell disease: a cross sectional study amongst unmarried adults in Nigeria's capital city

Sickle cell disease is a genetic disorder characterised by the tendency of haemoglobin to polymerise and deform red blood cells to a sickle or crescent shape; this consequently results in vaso-occlusive condition. A better knowledge and awareness about sickle cell disease amongst the population can help reduce its prevalence. This study aimed at assessing awareness and knowledge of unmarried adults in Nigeria's capital. A cross sectional survey was undertaken amongst unmarried individuals residing in the Federal Capital Territory. Questionnaires were administered to participants using convenience sampling strategy. Data were analysed using Statistical Package for Social Sciences version 25. Descriptive and inferential statistical analyses were carried out. A total of 1423 questionnaires were completed and returned, response rate was 83.71%, male participants were in the majority as indicated by 52% of the sample, and the dominant age group was 21 to 30 years (47.90%). Almost all the study participants (92.50%), have heard about sickle cell disease. Knowledge about sickle cell disease was average, as mean score for all the participants was 9.01 ± 3.18, with a range of 0 to 17. Some misconceptions were observed, for instance some participants believed that bacterial or viral infections could cause sickle cell disease. Male participants had a higher knowledge score compared to females (p < 0.001), and older participants were more knowledgeable about sickle cell disease (p < 0.001). This study identified that knowledge gaps exist about sickle cell disease. Emergent findings can underpin government, policymakers' and stakeholders' contextual strategies to prevent sickle cell through public health enlightenment and other relevant means.

Role of Oxidative Stress and the Protective Effect of Fermented Papaya Preparation in Sickle Cell Disease

Fermented papaya preparation (FPP) is the source of antioxidants that may help in reducing the complications associated with oxidative stress and may improve the quality of life in sickle cell disease patients. In this study, we assessed the in vitro effect of FPP on sickled red blood cells (RBCs) using oxidative stress markers and observed that FPP has the potential to reduce the oxidative stress. Scanning electron microscopy (SEM) and eosin 5' malaemide (E5'M) dye test showed that FPP protects red cell morphology against the oxidative stress. Liquid chromatography mass spectrometry (LCMS) analysis of FPP suggests the presence of essential amino acids, vitamin D3, and its derivatives. Fermented papaya preparation can be of benefit either in reducing oxidative stress parameters or in preventing pathophysiological events in the sickle cell disease patients.

Antioxidant-Rich Nutraceutical as a Therapeutic Strategy for Sickle Cell Disease

Sickle cell disease (SCD) is a genetically inherited disease in which the "SS" individual possesses two copies of the abnormal beta-globin gene. This disease is one of the most dominant genetic diseases in the world. SCD is marked by the propensity of red cell hemoglobin to polymerize and distort the red cell from a biconcave disk shape into a sickle shape, resulting in a typical vaso-occlusive episode and accelerated hemolysis. Plants are rich sources of bioactive compounds that are promising anti-sickling agents to scavenge free radicals, thereby ensuring oxidative balance. The current review highlights the potential therapeutic benefits of antioxidant-rich nutraceutical in the treatment and management of sickle cell disease. The anti-sickling potential of nutraceutical is attributed to the presence of antioxidant bioactive chemicals such as alkaloids, polyphenols, vitamins, and minerals, which acts as scavengers of free radicals that prevent oxidative damage of the hemoglobin and prevent hemolysis, facilitating longer erythrocyte lifespan. The challenges of current therapies for SCD and future directions are also discussed.KEY TEACHING POINTSSickle cell disease is a genetically inherited disease in which SS individuals possess two copies of the abnormal beta-globin gene.Oxidative stress contributes to the pathophysiology of secondary dysfunction in sickle cell patients.Antioxidants can play a vital role in maintaining a balance between oxidant and antioxidant defense systems.Nutraceutical rich in antioxidants such as alkaloids, polyphenols, vitamins, and minerals is potential therapeutic agents for sickle cell disease.An antioxidant-rich nutraceutical may act to reduce vaso-occlusive crises.

Cardiovascular consequences of sickle cell disease

Sickle cell disease (SCD) is an inherited blood disorder caused by a single point mutation within the beta globin gene. As a result of this mutation, hemoglobin polymerizes under low oxygen conditions causing red blood cells to deform, become more adhesive, and increase in rigidity, which affects blood flow dynamics. This process leads to enhanced red blood cell interactions with the endothelium and contributes to vaso-occlusion formation. Although traditionally defined as a red blood cell disorder, individuals with SCD are affected by numerous clinical consequences including stroke, painful crisis episodes, bone infarctions, and several organ-specific complications. Elevated cardiac output, endothelium activation along with the sickling process, and the vaso-occlusion events pose strains on the cardiovascular system. We will present a review of the cardiovascular consequences of sickle cell disease and show connections with the vasculopathy related to SCD. We will also highlight biophysical properties and engineering tools that have been used to characterize the disease. Finally, we will discuss therapies for SCD and potential implications on SCD cardiomyopathy.

Barbosa F, Fleury M. Predictive Equations Overestimated the Rest Energy Expenditure by Indirect Calorimetry in Adults with Sickle Cell Disease

Background: Traditionally, hypermetabolism is described in sickle cell disease (SCD). Despite this, few studies have compared rest energy expenditure (REE) with estimated by predictive equations (EEE) in the assessment of adults with SCD. Aims:  To compare REE values determined by indirect calorimetry (IC) with that EEE in adults with SCD. Subjects and Methods: A cross-sectional observational study was performed with 46 individuals over 34 years old in the treatment from two reference centers for SCD located in the city of Rio de Janeiro, Brazil. The dual-energy X-ray absorptiometry (DXA) and IC  were used to assess BC and REE, respectively. Blood levels were measured to assess hemolytic and protein markers. Pearson’s correlation test was used in the univariate correlation. The Intraclass Correlation Coefficient (ICC) and the Bland-Altman analysis were used in the comparison between EEE and IC. P-values ≤ 0.05 were considered statistically significant. Results: Most participants were from the female sex, Hb SS genotype (80.4%) and with black color (52.2%). The mean age was 50 years old. Weight (r= 0.469; p=0,001), LM (r = 0.631; p=0.000), BMC (r = 0.508; p=0.000) and CRP(r=0.319; p = 0.002) correlated positively with the REE. There was no linear correlation between makers of hemolysis with REE. The REE was overestimated in the EEE when compared to IC (p<0.001). Conclusions: The prediction equations developed for healthy populations are not accurate enough to determine the energy requirements and more studies are needed to better understand how REE role in middle-aged and elderly adults with SCD.

A pH-stable, mucin based nanoparticle system for the co-delivery of hydrophobic and hydrophilic drugs

Biopolymer-based drug carriers are commonly used for the development of safe delivery systems. However, biopolymer-based systems are often highly sensitive to the acidic pH levels in the stomach and release most of their cargo before they have reached their point of destination. Such premature drug release combined with the resulting high dose requirements is not cost-efficient and comes with the risk of unwanted side effects on non-target tissues/organs. This problem can be mitigated by the mucin-based drug carriers developed here, which exhibit good stability at acidic pH levels as proven by dynamic light scattering and enzymatic degradation tests with pepsin. In addition, the mucin-based particles can deliver hydrophobic and hydrophilic drugs simultaneously, which is demonstrated both with experiments performed under in vitro sink conditions and with drug transport tests involving eukaryotic cells as targets. As photo-induced cross-links covalently stabilize those particles, they can release their payload over time in a sustained manner. The drug carrier system introduced here combines good stability with high drug encapsulation efficiency and very good biocompatibility and thus may be valuable for a broad spectrum of applications in biological settings.

Effects of Hydroxyurea on Skeletal Muscle Energetics and Function in a Mildly Anemic Mouse Model

Hydroxyurea (HU) is a ribonucleotide reductase inhibitor most commonly used as a therapeutic agent in sickle cell disease (SCD) with the aim of reducing the risk of vaso-occlusion and improving oxygen transport to tissues. Previous studies suggest that HU may be even beneficial in mild anemia. However, the corresponding effects on skeletal muscle energetics and function have never been reported in such a mild anemia model. Seventeen mildly anemic HbAA Townes mice were subjected to a standardized rest-stimulation (transcutaneous stimulation)-protocol while muscle energetics using 31Phosphorus magnetic resonance spectroscopy and muscle force production were assessed and recorded. Eight mice were supplemented with hydroxyurea (HU) for 6 weeks while 9 were not (CON). HU mice displayed a higher specific total force production compared to the CON, with 501.35 ± 54.12 N/mm3 and 437.43 ± 57.10 N/mm3 respectively (+14.6%, p &lt; 0.05). Neither the total rate of energy consumption nor the oxidative metabolic rate were significantly different between groups. The present results illustrated a positive effect of a HU chronic supplementation on skeletal muscle function in mice with mild anemia.

Resveratrol-nitric oxide donor hybrid effect on priapism in sickle cell and nitric oxide-deficient mouse

Background

Children and adult with sickle cell disease (SCD) display priapism associated with low nitric oxide (NO) bioavailability and oxidative stress in penis.

Aim

This study aimed to evaluate the effects of hybrid compound RVT-FxMe, derived from resveratrol bearing a NO-donor subunit, on two murine model that display priapism phenotype, SCD transgenic mice and endothelial NO synthase gene-deficient (eNOS^-/-) mice.

Methods

Wild-type, SCD, and eNOS^-/- mice were treated with RVT-FxMe (25 mg/kg/d, 2 weeks).

Outcomes

Hematological parameters, concentration-response curves to acetylcholine (ACh) and sodium nitroprusside (SNP), as well as to electrical field stimulation (EFS), were obtained in mice corpus cavernosum strips.

Results

Corpus cavernosum relaxations to SNP and EFS were increased in eNOS^-/- group, which were normalized by RVT-FxMe treatment. SCD mice exhibited an excessive CC relaxant response induced by ACh, EFS and SNP RVT-FxMe treatment did not change the increased relaxant responses to ACh, EFS and SNP in corpus cavernosum from SCD group.

Clinical translation

Excess of plasma hemoglobin in SCD may interfere in pharmacological activity of NO donors compounds.

Strength/Limitations

While mechanistic data with promising potential is showed, the current study is not without limitations. RVT-FxMe effects in the mid- and long-term warrant complementary studies.

Conclusion

Treatment with RVT-FxMe reversed the enhanced NO-cGMP-mediated CC relaxations in eNOS^-/- mice, but not in SCD mice; it is likely that excess of plasma hemoglobin in SCD mice act to inactivate NO before it reaches soluble guanylyl cyclase, avoiding restoration of NO bioavailability in penis.

Functional foods: promising therapeutics for Nigerian Children with sickle cell diseases

Sickle cell disease (SCD), also known as sickle cell anemia (SCA) is one of the structural hemoglobinopathies that occurs due to a single nucleotide mutation from GAG to GTG, which changes the amino acid of a β-globin chain of hemoglobin (Hb) from glutamate to valine. This singular mutation results to disorderliness in red blood cells (RBCs) with advent of changes in RBC morphology and other pathological conditions. In the 1980s, intermittent red blood cell transfusions, opioids, and penicillin prophylaxis were the only available therapy for SCA and were commonly reserved for acute, life threatening complications. So far, the US Food and Drug Administration (FDA) has granted a total of four drugs approval for the prophylaxis and treatment of the clinical complications of SCD. Due to limitations (adherence, safety, adverse effects) of existing therapies in the prophylaxis and treatment of SCD complications in Nigerian children and their inaccessibility to approved drugs, the present study discusses the therapeutic effects of readily available functional food as one of the therapies or an adjunct therapy to tackle the sickle cell crisis in Nigerian Children.

Impact of Superoxide Dismutase Genetic Polymorphism (SOD2 Val16Ala) and Superoxide Dismutase Level on Disease Severity in a Cohort of Egyptian Sickle Cell Disease Patients

Background

Oxidative stress plays a pivotal role in the pathophysiology of sickle cell disease (SCD) and its associated disease complications. Superoxide Dismutases (SODs) are protective enzymes against oxidative stress. SOD2 deficiency results in the accumulation of oxidized red cell proteins, increased rate of hemoglobin oxidation, decreased red cell membrane deformability, and subsequently decreased red cells survival.

Objective

The current study was designed to determine the effect of SOD2 Val16Ala gene polymorphism (rs4880) on SOD2 level and their possible impact on SCD disease severity in a cohort of Egyptian SCD patients.

Methods

Genotyping SOD2 Val16Ala polymorphism by TaqMan allelic discrimination assay for hundred SCD patients and a hundred age-sex matched healthy controls revealed the genotypic and allelic frequencies of the studied polymorphism in the SCD patients were close to that of the controls.

Results

Serum SOD2 level was significantly lower in those having the polymorphic genotypes (p=0.005). SOD2 level inversely correlates with the annual rate of hospitalization (r=-0.023, p= 0.038).

Conclusion

SOD2 Val16Ala polymorphism was associated with low serum SOD2 level that may predict disease severity.

Advances in the Management of Sickle Cell Disease: New Concepts and Future Horizons

Sickle cell disease is a chronic and life-limiting disorder. Approximately 100,000 Americans are affected with sickle cell disease with most being African Americans. Newborn screening for sickle cell is available in the United States, leading to early detection and management of the disease beginning in infancy. According to the 2014 National Heart, Lung, and Blood Institute sickle cell disease guidelines, supportive care has been primary management of sickle cell disease, with hydroxyurea being the only FDA-approved, disease-modifying pharmacotherapy available and allogeneic hematopoietic stem cell transplant the only cure. Since 2017, three new disease-modifying therapies have been approved by the FDA: L-glutamine, crizanlizumab, and voxelotor. This review will discuss pertinent trials, dosing, interactions, side effects, access, cost, and their role in sickle cell management.

Body composition, energy expenditure, and markers of hemolysis in adults with sickle cell disease

Background: Historically, malnutrition is described in individuals with SCD. However, more recent studies have shown a change in the profile of the nutritional status and distribution of body composition of SCD patients, mainly adult individuals. Aims: To assess the body composition (BC), resting energy expenditure (REE), and the biomarkers of hemolysis in adults with sickle cell disease (SCD). Subjects and Methods: A cross-sectional observational study was performed with 64 individuals over 39 years old in the treatment from two reference centers for SCD located in the city of Rio de Janeiro, Brazil. The dual-energy X-ray absorptiometry (DXA) and indirect calorimetry were used to assess BC and REE, respectively. Blood levels of hemoglobin, reticulocytes, lactate dehydrogenase (LDH), leukocytes, platelets, total and direct bilirubin, total protein, and albumin were measured to assess the hemolysis and protein status. The descriptive and inferential analysis was composed of the different methods (one-way ANOVA with the multiple comparison test of Tukey, Student t-test, and Pearson's correlation coefficient). Were considered statistically significant when the p-values were ≤ 0.05. Results: Most participants with SCD were female sex, colored (brown/black), and mean age of 51.2 years old. The obesity prevalence was 70.7% according to the body fat (BF%), with a major mean among women (p < 0.0001). Men had a higher mean of lean mass (LM) (p=0.0005) and fat-free mass (FFM) (p=0.0007). There was no difference for REE in comparing the genotypes (p= 0.53), and genders (p=0.075). The hemolysis markers (LDH, reticulocytes, and TB) correlated inversely with BMI (p=0.013), FM (p=0.022), and FFM (p=0.034). Conclusions: The important change observed in body composition in people with sickle cell disease was characterized by a high percentage of fat body and a decrease in lean mass. The hemolysis markers LDH, reticulocytes, and BT correlated inversely with BMI, FM, and FFM indicating that high levels of hemolysis may affect nutritional status, without influencing the REE. Keywords: sickle cell disease, body composition, fat mass, fat-free mass, energy expenditure, hemolysis.

Pharmacodynamic of rocuronium in sickle cell patients

BACKGROUND

Sickle cell disease is the most widespread genetic disease in the world. The chronic organ damage due to this disease could lead to variability of responses to the anaesthetic drugs. We analysed the pharmacodynamics response of rocuronium to sickle cell patients.

METHODS

We observed and compared the onset time and clinical duration (time to recovery first twitch) of 0.6 mg kg^-1 of rocuronium using a TOFscan® monitor, as well as the time before the first incremental dose (time to recovery second twitch), in a group of 22 homozygous sickle cell patients and a group of 23 controls, all programmed for laparoscopic surgical procedures.

RESULTS

The onset time of rocuronium was longer in sickle cell patients [mean ± SD (extremes)], [6.3 ± 2.1 (1.8-10) min] than in the control group [2.5 ± 0.6 (1.4-3.5) min] (P < 0.01). The clinical duration was shorter in sickle cell patients [19.2 ± 7.1 (13-41) min] when compared to the control group [28.9 ± 6.9 (21-48) min] (P < 0.01). The time before the first incremental dose was shorter in the sickle cell patients group [27.7 ± 7.9 (19-49) min] compared to the control group [39.9 ± 8.7 (30-56) min] (P < 0.01).

CONCLUSION

The onset time and duration of action of rocuronium was significantly shorter in patients with sickle cell disease versus the general population.

How I approach disease-modifying therapy in children with sickle cell disease in an era of novel therapies

Finally,after decades of stagnation, the therapeutic landscape for sickle cell disease (SCD) is changing with an increasing number of novel therapeutics. Hydroxyurea remains the primary disease-modifying therapy and, when started early in life with maintenance of an optimal dose, can reduce many SCD-related complications. To complement hydroxyurea, there are a growing number of pharmacologic options with additional efforts focused on the development and optimization of curative therapies. Here, we review current treatment options and provide recommendations as to how to approach the treatment of children and adolescents within this evolving therapeutic landscape to allow for full and healthy lives.

Multiple inducers of endothelial NOS (eNOS) dysfunction in sickle cell disease

A characteristic aspect of the robust, systemic inflammatory state in sickle cell disease is dysfunction of endothelial nitric oxide synthase (eNOS). We identify 10 aberrant endothelial cell inputs, present in the specific sickle context, that are known to have the ability to cause eNOS dysfunction. These are: endothelial arginase depletion, asymmetric dimethylarginine, complement activation, endothelial glycocalyx degradation, free fatty acids, inflammatory mediators, microparticles, oxidized low density lipoproteins, reactive oxygen species, and Toll‐like receptor 4 signaling ligands. The effect of true eNOS dysfunction on clinical testing using flow‐mediated dilation can be simulated by two known examples of endothelial dysfunction mimicry (hemoglobin consumption of NO; and oxidation of smooth muscle cell soluble guanylate cyclase). This lends ambiguity to interpretation of such clinical testing. The presence of these multiple perturbing factors argues that a therapeutic approach targeting only a single injurious endothelial input (or either example of mimicry) would not be sufficiently efficacious. This would seem to argue for identifying therapeutics that directly protect eNOS function or application of multiple therapeutic approaches.

Investigation of the relationship between periodontal and systemic inflammation in children with Sickle Cell Disease: A case- control study

Periodontal diseases are chronic inflammatory diseases and tissue destruction increases with oxidative stress in periodontal tissues. Periodontal diseases are associated with systemic diseases such as diabetes, cardio-vascular diseases and rheumatoid arthritis by means of systemic inflammation. Sickle cell disease (SCD) is a chronic inflammatory disease in which vaso-occlusive crisis and endothelial dysfunction are present. It is not known whether the chronic systemic inflammation seen in SCD affect periodontal tissues. The aim of this study was to investigate the relationship between periodontal and systemic inflammation in children with SCD. Forty-three children with SCD and 43 healthy children were included in the study. Physical, dental and periodontal statuses were examined, blood and saliva samples were taken. Levels of pro-inflammatory and oxidative stress mediators in serum and saliva were evaluated. The periodontal findings of the groups were similar. The majority of the subjects in both groups had gingival inflammation. In SCD group, significantly higher serum high sensitive C-reactive protein (Hs-CRP), interleukin (IL)-6, IL-8, tumor necrosis factor (TNF)-α, total oxidant status (TOS), nitric oxide (NO) and salivary IL-6 were observed (p < 0.05). There were positive correlations between salivary IL-6 levels and serum Hs-CRP levels (r = 0.303, p < 0.05). In addition; it was determined that salivary IL-6, TNF-α and NO levels were increased 3-6 times in children with a history of painful crisis or acute chest syndrome compared to children who had never had a painful crisis or acute chest syndrome. Although, observed oral health status was similar in both groups, salivary cytokine levels were increased in children with SCD. The higher salivary cytokine levels may be associated with chronic systemic inflammation and vaso-occlusion observed in children with SCD.

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.

Mitochondrial reactive oxygen species scavenging attenuates thrombus formation in a murine model of sickle cell disease

BACKGROUND

Sickle cell disease (SCD) is characterized by hemolysis-associated platelet dysfunction that leads to increased risk of thrombosis and plays a role in the high morbidity and mortality of the disease. The mechanisms by which hemolysis induces platelet activation remain unclear. We recently demonstrated that patients with SCD showed increased platelet mitochondrial reactive oxygen species (mtROS) production that correlates with markers of hemolysis and platelet activation. Experiments in isolated platelets demonstrated that mtROS stimulated platelet activation. However, the role of hemolysis-induced mtROS in thrombus formation in vivo remains unclear.

OBJECTIVES

Here, we hypothesize that scavenging of mtROS attenuates the propensity for thrombosis in mouse models of hemolysis.

METHODS

We used models of hemolysate infusion into wildtype mice as well as the Berkley transgenic mouse model of SCD, a chronic mode of hemolysis, to test the effect of hemolysis on platelet mtROS production and thrombosis.

RESULTS

We show that infusion of hemolysate in wildtype mice induces platelet mtROS production and decreases time to vessel occlusion in a model of ferric chloride-induced carotid artery thrombosis. Increased mtROS and propensity for thrombosis was also observed in the Berkley transgenic mouse model of SCD. Notably, treatment with mtROS scavengers decreased platelet mtROS levels and attenuated the propensity for thrombus formation in both models.

CONCLUSIONS

These data demonstrate that mtROS significantly contribute to the mechanism of hemolysis-induced thrombosis in vivo and suggest a potential role for mitochondrially targeted antioxidant therapy in hemolysis and SCD-related thrombosis.

Mn porphyrins as a novel treatment targeting sickle cell NOXs to reverse and prevent acute vaso-occlusion in vivo

In sickle cell disease (SCD), adhesion of sickle red blood cells (SSRBCs) and activated leukocytes in inflamed venules affects blood rheology, causing vaso-occlusive manifestations and vital reduction in microvascular blood flow. Recently, we found that NADPH oxidases (NOXs) create a vicious feedback loop within SSRBCs. This positive feedback loop mediates SSRBC adhesion to the endothelium. We show for the first time the therapeutic effectiveness of the redox-active manganese (Mn) porphyrins MnTnBuOE-2-PyP5+ (MnBuOE; BMX-001) and MnTE-2-PyP5+ (MnE; BMX-010, AEOL10113) to treat established vaso-occlusion in a humanized sickle mouse model of an acute vaso-occlusive crisis using intravital microscopy. These Mn porphyrins can suppress SSRBC NOX activity. Subcutaneous administration of only 1 dose of MnBuOE or MnE at 0.1 to 2 mg/kg after the inflammatory trigger of vaso-occlusion, or simultaneously, reversed and reduced leukocyte and SSRBC adhesion, diminished leukocyte rolling, restored blood flow, and increased survival rate. Furthermore, MnBuOE and MnE administered to sickle mice subcutaneously at 0.1 to 1 mg/kg for 28 days (except on weekends) did not exacerbate anemia, which seemed to be due to downregulation of both SSRBC reactive oxygen species production and exposure of the eryptotic marker phosphatidylserine. In addition, Mn porphyrins ameliorated leukocytosis, venous blood gases, endothelial activation, and organ oxidative damage. Our data suggest that Mn porphyrins, likely by repressing NOX-mediated adhesive function of SSRBCs and activated leukocytes, could represent a novel, safe therapeutic intervention to treat or prevent the establishment of acute pain crises. These NOX-targeted antioxidants merit further assessment in SCD clinical trials.

Red blood cell mannoses as phagocytic ligands mediating both sickle cell anaemia and malaria resistance

In both sickle cell disease and malaria, red blood cells (RBCs) are phagocytosed in the spleen, but receptor-ligand pairs mediating uptake have not been identified. Here, we report that patches of high mannose N-glycans (Man_5-9GlcNAc₂), expressed on diseased or oxidized RBC surfaces, bind the mannose receptor (CD206) on phagocytes to mediate clearance. We find that extravascular hemolysis in sickle cell disease correlates with high mannose glycan levels on RBCs. Furthermore, Plasmodium falciparum-infected RBCs expose surface mannose N-glycans, which occur at significantly higher levels on infected RBCs from sickle cell trait subjects compared to those lacking hemoglobin S. The glycans are associated with high molecular weight complexes and protease-resistant, lower molecular weight fragments containing spectrin. Recognition of surface N-linked high mannose glycans as a response to cellular stress is a molecular mechanism common to both the pathogenesis of sickle cell disease and resistance to severe malaria in sickle cell trait.

Hemolysis inhibits humoral B-cell responses and modulates alloimmunization risk in patients with sickle cell disease

Red blood cell alloimmunization remains a barrier for safe and effective transfusions in sickle cell disease (SCD), but the associated risk factors remain largely unknown. Intravascular hemolysis, a hallmark of SCD, results in the release of heme with potent immunomodulatory activity, although its effect on SCD humoral response, specifically alloimmunization, remains unclear. Here, we found that cell-free heme suppresses human B-cell plasmablast and plasma cell differentiation by inhibiting the DOCK8/STAT3 signaling pathway, which is critical for B-cell activation, as well as by upregulating heme oxygenase 1 (HO-1) through its enzymatic byproducts, carbon monoxide and biliverdin. Whereas nonalloimmunized SCD B cells were inhibited by exogenous heme, B cells from the alloimmunized group were nonresponsive to heme inhibition and readily differentiated into plasma cells. Consistent with a differential B-cell response to hemolysis, we found elevated B-cell basal levels of DOCK8 and higher HO-1-mediated inhibition of activated B cells in nonalloimmunized compared with alloimmunized SCD patients. To overcome the alloimmunized B-cell heme insensitivity, we screened several heme-binding molecules and identified quinine as a potent inhibitor of B-cell activity, reversing the resistance to heme suppression in alloimmunized patients. B-cell inhibition by quinine occurred only in the presence of heme and through HO-1 induction. Altogether, these data suggest that hemolysis can dampen the humoral B-cell response and that B-cell heme responsiveness maybe a determinant of alloimmunization risk in SCD. By restoring B-cell heme sensitivity, quinine may have therapeutic potential to prevent and inhibit alloimmunization in SCD patients.

Polymorphisms of the receptor for advanced glycation end products as vasculopathy predictor in sickle cell disease

BACKGROUND

The genetic variants of the receptor for advanced glycation end products (RAGE) gene have been associated with vascular disease risk. The objective of this work was to explore the association of three single-nucleotide polymorphisms (SNPs) of RAGE gene (374T/A, 429T/C, and G82S) with vascular complications in SCD.

METHODS

The study was conducted on 40 children with SCD and 40 healthy children served as controls. All participants were genotyped for the three studied RAGE polymorphisms by polymerase chain reaction (PCR).

RESULTS

Regarding 374T/A polymorphism, the frequency of TA, TT genotypes and T allele were higher in patients (p < 0.001). T allele was associated with higher incidence of sickling crisis and stroke (p < 0.05). In the subgroup analyses of 429T/C polymorphism, an association between C allele and SCD vascular complications was observed (p < 0.05). Concerning the frequency of G82S genotypes of RAGE, GG variant was detected in 39 (97.5%) of the patients, as compared with 40 (100%) of controls (p = 0.3). A regression analysis proved that HbS%, serum ferritin, and the -374T and 429C alleles were significant independent predictors of frequent sickling episodes (p < 0.05).

CONCLUSIONS

The C allele of -429T/C and T allele of 374T/A RAGE polymorphisms may be considered as predictors for vascular dysfunction in SCD.

IMPACT

The C allele of -429T/C and T allele of 374T/A RAGE polymorphisms may be considered as predictors for vascular dysfunction in SCD patients. To our knowledge, our study is the first exploring the association of three single-nucleotide polymorphisms of RAGE gene (374T/A, 429T/C, and G82S) with vascular complications in SCD. Early identification of patients carrying these genetic variants might be of great importance not only to identify subjects at risk of vasculopathy but also to direct them to RAGE-targeted treatments.

Trends in Sickle Cell Disease-Related Mortality in the United States, 1979 to 2017

STUDY OBJECTIVE

We provide an updated assessment of trends in sickle cell disease (SCD)-related mortality, a significant source of mortality in the United States among black persons, using 1979 to 2017 US mortality data.

METHODS

SCD-related deaths were identified with International Classification of Diseases codes. Because SCD-related death is rare in other races, the analysis focused on black decedents. Age-specific and average annual SCD-related death rates were calculated. Causes of death codes were categorized into 20 groups relevant to SCD outcomes. SCD-related deaths were compared with non-SCD-related deaths after matching on race, sex, age group, and year of death.

RESULTS

There were 25,665 SCD-related deaths reported among blacks in the United States from 1979 through 2017. During that period, the annual SCD-related death rate declined in children and increased in adults, and the median age at death increased from 28 to 43 years. Acute causes of death, such as infection and cerebrovascular complications, were more common in younger age groups. Chronic complications were more common in adults. SCD-related deaths were more likely to be related to acute cardiac, pulmonary, and cerebrovascular complications; acute infections; and chronic cardiac and pulmonary complications and renal disorders; and less likely to be related to drug overdose and chronic infections than non-SCD-related deaths.

CONCLUSION

These data indicate SCD-related deaths are now more likely to be related to chronic complications of the disease than to acute complications. More research regarding prevention and treatment of chronic complications of SCD is necessary because persons with SCD are living longer.

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.

Effects of hydroxyurea on cytotoxicity, inflammation and oxidative stress markers in neutrophils of patients with sickle cell anemia: dose-effect relationship

Introduction

Although the efficacy of hydroxyurea (HU) in inhibiting erythrocyte sickling has been well demonstrated, the action of this drug on human neutrophils and the mechanism by which it improves the manifestations of the disease have not been studied thoroughly. We aimed to investigate the cell viability, along with inflammatory and oxidative markers in the neutrophils of sickle cell anemia (SCA) patients and the effects of HU therapy on these cells, by evaluating the dose-responsiveness.

Methods

In the present study, 101 patients (45 men and 56 women, aged 18–69 years) with SCA were divided into groups according to the use or not of HU: the SS group (without HU treatment, n = 47) and the SSHU group (under HU treatment, n = 54). The SSHU group was further stratified into subgroups according to the daily dose of the drug that patients already used: SSHU - 0.5 g (n = 19); SSHU - 1 g (n = 26) and SSHU - 1.5–2 g (n = 9). A control group (AA) comprised 50 healthy individuals. Neutrophils isolated from whole blood were analyzed using Trypan Blue, monoiodotyrosine (MTT) and lactate dehydrogenase (LDH) toxicity assays. Myeloperoxidase (MPO), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) activities and concentrations of interleukin 10 (IL-10), tumor necrosis factor alpha (TNF-α) and malonaldehyde (MDA) were also measured.

Results

Neutrophils from SCA patients showed membrane fragility and a significant decrease in cell viability when analyzed by Trypan Blue (p < 0.05), MTT (p < 0.001) and LDH (p = 0.011), compared to the AA group. Levels of inflammatory (MPO, TNF-α, and IL-10) and oxidative markers (SOD, GSH-Px, and MDA) were also altered (p < 0.05) in these cells, showing a significant difference in the SSHU-1g and SSHU - 1.5–2 g groups, compared to the SS group. Treatment with HU reverted the levels of all markers to concentrations similar to those in healthy individuals in a positive dose-effect relationship.

Conclusion

The HU did not generate a cytotoxic effect on neutrophils in SCA patients, but it modulated their oxidative and inflammatory mechanisms, promoting cytoprotection with a positive dose-effect.

Decoding the role of SOD2 in sickle cell disease

Sickle cell disease (SCD) is an inherited hemoglobinopathy caused by a single point mutation in the β-globin gene. As a consequence, deoxygenated hemoglobin polymerizes triggering red blood cell sickling and hemolysis, vaso-occlusion, and ischemia/reperfusion. Allied to these pathologies is the overproduction of reactive oxygen species driven by hemoglobin Fenton chemistry and peroxidase reactions as well as by secondary activation of vascular oxidases, including NAD(P)H oxidase and xanthine oxidase. In addition, hypoxia, produced by sickle red blood cell occlusion, disrupts mitochondrial metabolism and generates excess superoxide through electron leak from the mitochondrial respiratory chain. Superoxide dismutase 2 (SOD2) is a mitochondrial-specific antioxidant enzyme that dismutates superoxide to hydrogen peroxide, which is then converted to water by catalase and glutathione peroxidase. In SCD, the antioxidant defense system is significantly diminished through decreased expression and activity levels of antioxidant enzymes, including superoxide dismutase, catalase, and glutathione peroxidase. From a translational perspective, genetic variants including a missense variant in SOD2 (valine to alanine at position 16) are present in 45% of people with African ancestry and are associated with increased sickle complications. While it is known that there is an imbalance between oxidative species and antioxidant defenses in SCD, much more investigation is warranted. This review summarizes our current understanding of antioxidant defense systems in SCD, particularly focused on SOD2, and provides insight into challenges and opportunities as the field moves forward.

Dapsone Hydroxylamine, an Active Metabolite of Dapsone, Can Promote the Procoagulant Activity of Red Blood Cells and Thrombosis

Dapsone hydroxylamine (DDS-NHOH), N-hydroxylated metabolite of a sulfonamide antibiotic, dapsone, is responsible for various adverse effects of dapsone that include methemoglobinemia, hemolytic anemia, and thrombosis. However, the mechanism underlying DDS-NHOH-induced thrombosis remains unclear. Here, we demonstrated that DDS-NHOH, but not dapsone, could increase prothrombotic risks through inducing the procoagulant activity of red blood cells (RBCs). In freshly isolated human RBCs in vitro, sub-hemolytic concentrations of DDS-NHOH (10-50 μM) increased phosphatidylserine (PS) exposure and augmented the formation of PS-bearing microvesicles (MV). Reactive oxygen species (ROS) generation and the subsequent dysregulation of enzymes maintaining membrane phospholipid asymmetry were found to induce the procoagulant activity of DDS-NHOH. Dapsone hydroxylamine also accelerated thrombin generation and enhanced RBC self-aggregation and adherence of RBCs to endothelial cells in vitro. Most importantly, both the single dose of 50 or 100 mg/kg (i.p.) DDS-NHOH and repeated doses of 10 mg/kg per day (i.p.) for 4 days increased thrombus formation in rats (six rats per dose) in vivo, substantiating a potential prothrombotic risk of DDS-NHOH. Collectively, these results demonstrated the central role of RBC procoagulant activity induced by DDS-NHOH in the thrombotic risk of dapsone.

NRF2 mediates γ-globin gene regulation through epigenetic modifications in a β-YAC transgenic mouse model

IMPACT STATEMENT

Sickle cell disease is an inherited hemoglobin disorder that affects over 100,000 people in the United States causing high morbidity and early mortality. Although new treatments were recently approved by the FDA, only one drug Hydroxyurea induces fetal hemoglobin expression to inhibit sickle hemoglobin polymerization in red blood cells. Our laboratory previously demonstrated the ability of the NRF2 activator, dimethyl fumarate to induce fetal hemoglobin in the sickle cell mouse model. In this study, we investigated molecular mechanisms of γ-globin gene activation by NRF2. We observed the ability of NRF2 to modulate chromatin structure in the human β-like globin gene locus of β-YAC transgenic mice during development. Furthermore, an NRF2/TET3 interaction regulates γ-globin gene DNA methylation. These findings provide potential new molecular targets for small molecule drug developed for treating sickle cell disease.

Hydroxyurea Scavenges Free Radicals and Induces the Expression of Antioxidant Genes in Human Cell Cultures Treated With Hemin

The excessive release of heme during hemolysis contributes to the severity of sickle cell anemia (SCA) by exacerbating hemoglobin S (HbS) autoxidation, inflammation and systemic tissue damage. The present study investigated the effect of hydroxyurea (HU) on free radical neutralization and its stimulation of antioxidant genes in human peripheral blood mononuclear cells (PBMC) and human umbilical vein endothelial cells (HUVEC) in the presence or absence of hemin. HU (100 and 200 μM) significantly reduced the production of intracellular reactive oxygen species (ROS) induced by hemin at 70 μM in HUVEC. HUVECs treated with HU+hemin presented significant increases in nitric oxide (NO) production in culture supernatants. HU alone or in combination with hemin promoted the induction of superoxide dismutase-1 (SOD1) and glutathione disulfide-reductase (GSR) in HUVECs and PBMCs, and glutathione peroxidase (GPX1) in PBMCs. Microarray analysis performed in HUVECs indicated that HU induces increased expression of genes involved in the antioxidant response system: SOD2, GSR, microsomal glutathione S-transferase (MGST1), glutathione S-transferase mu 2 (GSTM2), carbonyl reductase 1 (CBR1) and klotho B (KLB). Significant increases in expression were observed in genes with kinase activity: protein kinase C beta (PRKCB), zeta (PRKCZ) and phosphatidylinositol-4-phosphate 3-kinase catalytic subunit type 2 beta (PIK3C2B). HU also induced a significant increase in expression of the gene p62/sequestosome (p62/SQSTM1) and a significant decrease in the expression of the transcriptional factor BACH1 in HUVECs. Upstream analysis predicted the activation of Jun, miR-155-5p and mir-141-3p. These results suggest that HU directly scavenges free radicals and induces the expression of antioxidant genes via induction of the Nrf2 signaling pathway.

Sickle cell disease as a vascular disorder

INTRODUCTION

In sickle cell disease (SCD), hemoglobin S (HbS) red blood cells (RBCs) are characteristically deformed and inflexible. Often breaking down in the circulation, they exhibit increased adhesive properties with the endothelium and activated neutrophils and platelets, increasing the risk of occlusion of the microcirculation. SCD is categorized into two sub-phenotypes: hyperhemolytic, associated with priapism, leg ulcers, pulmonary hypertension, and stroke, and high hemoglobin/viscosity, which may promote vaso-occlusion-associated pain, acute chest syndrome, and osteonecrosis.

AREAS COVERED

The sub-phenotypes are not completely distinct. Hemolysis may trigger vaso-occlusion, contributing to vascular complications. Targeting P-selectin, a key mediator of cross-talk between hyperhemolysis and vaso-occlusion, may be beneficial for vascular and vaso-occlusion-associated complications. English-language articles from PubMed on the topic of SCD and vaso-occlusive crises (VOCs) were reviewed from 1 January 2000 to 1 January 2019 using the search terms 'sickle cell disease,' 'vaso-occlusive crises,' and 'selectin.'

EXPERT OPINION

Besides targeting P-selectin, other strategies to counter VOCs and RBC sickling are being pursued. These include platelet inhibition to counter aggregation, intercellular adhesion, and thrombosis during VOCs; gene therapy to correct the homozygous missense mutation in the β-globin gene, causing polymerization of HbS; L-glutamine, possibly reducing oxidative stress in sickled RBCs; and fetal hemoglobin inducers.

Ambient air pollution and sickle cell disease-related emergency department visits in Atlanta, GA

BACKGROUND

Sickle cell disease (SCD) is an inherited, autosomal recessive blood disorder, among the most prevalent genetic diseases, globally. While the genetic and hemolytic dynamics of SCD have been well-characterized, the etiology of SCD-related pathophysiological processes is unclear. Although limited, observational evidence suggests that environmental factors, including urban air pollution, may play a role.

OBJECTIVES

We assessed whether daily ambient air pollution concentrations are associated with corresponding emergency department (ED) visit counts for acute SCD exacerbations in Atlanta, Georgia, during a 9-year (2005-2013) period. We also examined heterogeneity in response by age and sex.

METHODS

ED visit data were from 41 hospitals in the 20-county Atlanta, GA area. Associations between daily air pollution levels for 8 urban air pollutants and counts of SCD related ED visits were estimated using Poisson generalized linear models.

RESULTS

We observed positive associations between pollutants generally indicative of traffic emissions and corresponding SCD ED visits [e.g., rate ratio of 1.022 (95% CI: 1.002, 1.043) per interquartile range increase in carbon monoxide]. Age stratified analyses indicated stronger associations with traffic pollutants among children (0-18 years), as compared to older age strata. Associations involving other pollutants, including ozone and particulate matter and for models of individuals >18 years old, were consistent a null hypothesis of no association.

DISCUSSION

This analysis represents the first North American study to examine acute risk among individuals with SCD to urban air pollution and provide evidence of urban air pollution, especially from traffic sources, as a trigger for acute exacerbations. These findings are consistent with a hypothesis that biological pathways, including several centrally associated with oxidative stress, may contribute towards enhanced susceptibility in individuals with SCD.

Relationship between Higher Atherogenic Index of Plasma and Oxidative Stress of a Group of Patients Living with Sickle Cell Anemia in Cameroon

Dyslipidemia is highly prevalent in sickle cell anemia (SCA) patients and is one of the major risk factors for cardiovascular diseases induced by oxidative stress in Africa. The aim of this research was to investigate the correlation between higher atherogenic index of plasma (API) and oxidative stress in a group of patients living with SCA in Cameroon. Methods. A group of 85 homozygote SS patients (male and female) were enrolled at the Central hospital of Yaounde in Cameroon between May and October 2017. After informed consent through the signature of a consent form was obtained, the plasma was collected to determine the lipid profile while the lysate solution of RBC was used to explore some markers of oxidative stress using spectrophotometric methods. Results. Among the 85 patients included in our study, the mean age was 30 ± 5 years and the female to male ratio was 0.97. The majority of the patients (52-81%) had dyslipidaemia, and 22.4% of the patients demonstrated a higher level of atherogenic index of plasma. The patients with a higher level of total cholesterol (TC) (>240 mg/dl) and low-density lipoprotein (LDL-C) (>159 mg/dl) had at least 1,334 fold of malondialdeheyde (MDA) concentration than those with normal level. Also in the same patients, the higher atherogenic plasmatic index (API) significantly (p < 0.05) increased with the concentration of MDA. Except HDL-C, the other parameters of lipid profile had significant (p < 0.05) correlation with reduced glutathione (GsH) and total antioxidant capacity (TAC). The significant (p < 0.05) and linear regression was found between the increased MDA and higher API. Conclusion. Dyslipidemia increases oxidative stress and higher API which leads to coronary vascular disease in patients with SCA.