Polymerization Of Hemoglobin Research Articles

Hydroxyurea reduces the levels of the fetal globin gene repressors ZBTB7A/LRF and BCL11A in erythroid cells in vitro

Abstract Objectives Hydroxyurea (HU) is the most widely used therapy for adults and children with sickle cell disease (SCD). It is believed to act largely by inducing the transcription of fetal γ-globin genes to generate fetal hemoglobin (HbF), which inhibits the pathological polymerization of sickle hemoglobin (HbS). The mechanisms by which hydroxyurea elevates HbF are unclear. We explored the hypothesis that hydroxyurea induces HbF expression by inhibiting the expression of 2 γ-globin gene repressors, BCL11A and ZBTB7A (also known as LRF), which normally bind the γ-globin gene promoters to inhibit their expression after birth. Methods We treated immortalized murine erythroleukemia cells and normal human donor CD34+ hematopoietic stem and progenitor cell-derived erythroblasts with hydroxyurea and measured the effects on globin, BCL11A and ZBTB7A protein and mRNA expression. Results Treating murine erythroleukemia cells or human CD34+ hematopoietic stem and progenitor cell-derived erythroblasts with hydroxyurea reduced the protein levels of BCL11A and ZBTB7A compared to the vehicle-treated control. BCL11A mRNA levels were reduced in both cell types upon hydroxyurea treatment. However, ZBTB7A mRNA levels were only reduced in human CD34+ hematopoietic stem and progenitor cell-derived erythroblasts. Conclusions Hydroxyurea can act in erythroid cells to reduce the levels and activity of two direct fetal γ-globin transcriptional repressors with accompanying de-repression of the γ-globin genes and induction of HbF, which may explain the mechanism of action leading to amelioration of symptoms in SCD patients treated with this drug.

Effects of GBT1118, a voxelotor analog, on bone disease in sickle cell disease mice

We assessed the effect of GBT1118, a sickle hemoglobin polymerization inhibitor on bone loss in humanized sickle cell disease (SCD) mice. Healthy control (Ctrl) 4-months-old female and male mice were fed Vehicle-chow for 2-months, while SCD mice were fed Vehicle-chow or GBT1118-chow. By micro-CT, GBT1118 significantly increased femur metaphyseal trabecular thickness (Tb.Th) and tissue mineral density (TMD), and significantly decreased trabecular spacing in female SCD mice. In SCD male mice, there was significant reduction in epiphyseal trabecular bone volume fraction (BV/TV), Tb.Th and TMD and GBT1118 significantly increased BV/TV and TMD but not Tb.Th. A significant decrease in cortical area fraction in SCD female mice was rescued by GBT1118 but not SCD males. Markedly decreased mineralized femur trabeculae in SCD females and males was partially rescued by GBT1118. Bone histomorphometry of femurs demonstrated significantly decreased bone formation parameters and increased bone resorption parameters in SCD mice of both sex that were rescued by GBT1118. Significant alteration in bone and hypoxia related genes of SCD mice of both sexes were differentially modulated by GBT1118. We conclude that "a sickle hemoglobin polymerization inhibitor" might be efficacious in improving some parameters of SCD bone loss.

LC-MS/MS Analysis of crude Flavonoid Compounds from <i>Justicia secunda</i> from Democratic Republic of the Congo and evaluation of their antisickling Activity

<i>Justicia secunda</i> Vahl (Acanthaceae) is a tropical herbaceous plant traditionally used by indigenous peoples of the Democratic Republic of the Congo (DRC) to treat symptoms associated with sickle cell disease (SCD), a genetic condition with life-threatening complications. Given the lack of side-effect-free drugs, alternative herbal therapies that can reduce or reverse red blood cell sickling may serve as safe and effective treatments. The primary objective of this study is to conduct a phytochemical screening of crude flavonoids extracted from <i>J. secunda</i> using LC-ESI/MS/MS. <i>J. secunda</i> extracts were evaluated for their phytoconstituents and anti-sickling properties. The anti-sickling properties were assessed through reverse sickling estimation, polymerization and oxidation inhibition, and osmotic fragility assays. Fractionation of the methanol extract and chemical profiling were performed by flash chromatography and high-performance thin-layer chromatography analysis respectively. Characterization and identification of the crude flavonoids were done using chromatography and spectroscopy methods. Chemical screening of crude flavonoids revealed the presence of 12 flavonoid O-glycosides based on one flavonol (methoxy-kaempferol) and two flavones (luteolin and apigenin). The crude flavonoid extracts demonstrated maximum reversal of sickled red blood cells (91.9 ± 0.8%), significant inhibition of hemoglobin polymerization (77.8 ± 7.6%) and hemoglobin S auto-oxidation (96.3 ± 0.2), and provided maximum protection of red blood cells against hyperhemolysis. The results validate the traditional use of <i>J. secunda</i> and identify potential compounds for the development of novel anti-sickling agents.

A Systematic Review of Medicinal Plants and Their Compounds Validated as Agents for the Management of Sickle Cell Disease

Some plants used in traditional medicine to manage sickle cell disease have been validated pharmacologically to ascertain their anti-sickling properties. However, there is no global systematic review of the evidence in support of their use for sickle cell management. This research aimed to conduct a systematic review of the pharmacological evidence to highlight species, genera, and some phytochemicals which could be primed for novel anti-sickling medications. The Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines were used. Articles in English, published from 2000 to 2022 were included in the analysis. The literature search covered 411 publications of which 82 were found to be eligible. More than half (53.65%) of the articles were published from 2016 to 2022. Anti-sickling research from Africa accounted for 86.58% of the publications, with more than half coming from Nigeria, 12.20% from Asia and only 1.22% from Europe. The Fabaceae, Euphorbiaceae, and Annonaceae were the top three plant families whereas Zanthoxylum and Terminalia were the most reported genera. Carica papaya and Terminalia catappa were the most reported species. Sickling reversal ( n = 33/82) and hemoglobin polymerization studies ( n = 29/82) were the most reported assays. Benzoic acid derivatives, butyl stearate, ellagic acid derivatives, and some pentacyclic triterpenoids were the only plant derived compounds validated for anti-sickling activities. A total of 117 plant species with anti-sickling activities were documented. Studies on secondary metabolites with anti-sickling properties to serve as scaffolds for novel drug development for sickle cell management were limited.

Changes in indicators of cerebral metabolic stress following treatment with voxelotor in children and adolescents with sickle cell anemia

AbstractVoxelotor is a small molecule that reduces the polymerization of sickle hemoglobin by increasing its affinity for oxygen. In patients with sickle cell anemia, it has been postulated that increasing hemoglobin‐oxygen affinity could limit oxygen offloading from hemoglobin, causing an increase in cerebral metabolic stress. To investigate this hypothetical concern, we used multimodal brain imaging to define the effects of voxelotor on cerebral blood flow and oxygen extraction. We followed four patients for 2–5 months during and/or after voxelotor therapy. This study showed no observable increase in cerebral blood flow or oxygen extraction fraction during treatment.

Voxelotor (GBT440) in pediatric sickle cell disease: A review

Sickle cell disease (SCD) was first described in 1910 in African Americans, and the mutant hemoglobin S (HbS) was identified by electrophoresis in 1948. Sickle cell disease is the first genetic disease to be molecularly defined - a single point mutation in the β-globin gene (GAG→GTG) results in substitution of valine for glutamic acid at amino acid residue 7 (including the starting methionine). Pharmacological intervention to correct the defect at a molecular/protein level has proven complex. The only established curative therapy is hematopoietic stem cell transplantation, with recent gene therapy approvals providing hope for the same. Herein, we discuss voxelotor, a drug designed to reverse the hemoglobin polymerization defect caused by the β7Glu > Val substitution in the hemoglobin molecule.

EE243 Targeted Literature Review of Cost-Effectiveness Analyses in Sickle Cell Disease: Identifying the Optimal Modeling Approach for Therapies Targeting Sickle Hemoglobin Polymerization

EE243 Targeted Literature Review of Cost-Effectiveness Analyses in Sickle Cell Disease: Identifying the Optimal Modeling Approach for Therapies Targeting Sickle Hemoglobin Polymerization

Metabolic blood profile and response to treatment with the pyruvate kinase activator mitapivat in patients with sickle cell disease.

Mitapivat is an investigational, oral, small-molecule allosteric activator of pyruvate kinase (PK). PK is a regulatory glycolytic enzyme that is key in providing the red blood cell (RBC) with sufficient amounts of adenosine triphosphate (ATP). In sickle cell disease (SCD), decreased 2,3-DPG levels increase the oxygen affinity of hemoglobin, thereby preventing deoxygenation and polymerization of sickle hemoglobin. The PK activator mitapivat has been shown to decrease levels of 2,3-DPG and increase levels of ATP in RBCs in patients with SCD. In this phase 2, investigator-initiated, open-label study (https://www.clinicaltrialsregister.eu/ NL8517; EudraCT 2019-003438-18), untargeted metabolomics was used to explore the overall metabolic effects of 8-week treatment with mitapivat in the dose-finding period. In total, 1773 unique metabolites were identified in dried blood spots of whole blood from ten patients with SCD and 42 healthy controls (HCs). The metabolic phenotype of patients with SCD revealed alterations in 139/1773 (7.8%) metabolites at baseline when compared to HCs (false discovery rate-adjusted p < 0.05), including increases of (derivatives of) polyamines, purines, and acyl carnitines. Eight-week treatment with mitapivat in nine patients with SCD altered 85/1773 (4.8%) of the total metabolites and 18/139 (12.9%) of the previously identified altered metabolites in SCD (unadjusted p < 0.05). Effects were observed on a broad spectrum of metabolites and were not limited to glycolytic intermediates. Our results show the relevance of metabolic profiling in SCD, not only to unravel potential pathophysiological pathways and biomarkers in multisystem diseases but also to determine the effect of treatment.

Revolutionary breakthrough: FDA approves CASGEVY, the first CRISPR/Cas9 gene therapy for sickle cell disease.

Sickle cell disease (SCD) is a hereditary hemoglobinopathy resulting from a β-globin chain mutation that causes abnormal hemoglobin (HbS) polymerization and leads to severe complications. Current treatment options primarily focus on symptom management, with limited curative potential. Recently, Casgevy, the first CRISPR/Cas9-based gene therapy for SCD, has received breakthrough FDA approval. Clinical trials have shown that Casgevy administered to patients aged older than or equal to 12 years enables precise modifications in hematopoietic stem cells, resulting in elevated fetal hemoglobin (HbF) levels and a significant reduction in vaso-occlusive events. Unlike conventional treatments, this therapy offers a curative approach and eliminates the need for recurrent transfusions and transplants, thereby improving the quality of life of patients with SCD. Casgevy has emerged as a beacon of hope for SCD patients and signifies a potential paradigm shift in SCD management due to its safety, curative potential, and transformative impact, positioning it as a groundbreaking intervention. Nevertheless, ethical considerations surrounding CRISPR technology and regulatory frameworks must be addressed to ensure responsible application and equitable access to this one-time gene editing therapy. As the authors celebrate this scientific advancement, sustained interdisciplinary collaboration and ethical scrutiny are essential to navigating the evolving landscape of CRISPR technology in medicine. This review aims to provide a detailed insight into the application of Casgevy, challenges associated with its application, future prospects of this therapy, and its comparison with existing treatment options for SCD.

Diastolic blood pressure in hemorrhagic shock, the disregarded parameter

The management of trauma and hemorrhagic shock (T/HS) is a critical aspect of emergency medicine and trauma care. The use of whole blood for fluid resuscitation is considered the gold standard when available because it provides a balanced combination of red blood cells, plasma, and clotting factors. However, whole blood is not always readily available, and alternative options must be considered. In such cases, various fluid replacements and vasoactive drugs can be used to help stabilize patients with T/HS. The goal of our study was to compare several fluid therapies and vasoactive drugs for blood pressure stabilization after T/HS. Male Wistar rats (±400g) were subjected to laparotomy and hypotension (a mean arterial blood pressure (MAP) of 35-40mmHg) was induced by blood withdrawal for 90 min. Following the hypotensive period, animals were resuscitated with candidate solutions and/or vasoactive drugs in an effort to increase MAP to at least 60mmHg for 120min. Lactated Ringers (LR) with 5% dextrose was used as control fluid and in combination with vasopressors; whole blood resuscitation was considered the positive control. Among the studied medications, only vasopressin (60.0mmHg*) and resveratrol (60.2mmHg*) were able to achieve the target MAP. (Packed) red blood cells (70.4mmHg***), polymerized hemoglobin (74.4mmHg***), and whole blood (84.4mmHg****) increased MAP closer to baseline levels. While all of the groups studied were capable of restoring systolic pressure not significantly different from to baseline (SHAM =108.5mmHg), the inability to recover MAP was almost exclusively due to low diastolic arterial pressure (DAP). Using the SHAM DAP as reference (65.2mmHg) and the LR-reperfusion group as control (31.7mmHg), there was no increase in effcacy upon addition of angiotensin II (25.4mmHg), phenylephrine (27.9mmHg), vasopressin (37.8mmHg), L-NAME (35.7mmHg), resveratrol (41.1mmHg), sphingosine-1-phosphate (33.0mmHg), or naloxone (31.8mmHg). There was a similar lack of effcacy found using different fluid therapies: Hetastarch increased DAP to only 33.9mmHg, and 10% Albumin (41.0mmHg), and plasma (38.6mmHg) were only slightly superior to control. Only oxygen-carrying solutions were able to increase DAP: polymerized hemoglobin (55.7mmHg***), red blood cells (55.5mmHg***), and whole blood (67.8mmHg***). These findings underscore the complexity of T/HS management and the challenges in restoring and maintaining perfusing blood pressure, e.g. MAP, in these situations. This study provides valuable insights into the comparative effectiveness of various resuscitative approaches, shedding light on potential strategies to enhance outcomes after T/HS. Many shock studies often concentrate only on mean arterial pressure, potentially overlooking a crucial aspect of hemorrhage resuscitation—low diastolic pressure. Our study emphasizes that low diastolic pressure constitutes the primary component contributing to low MAP after reperfusion in T/HS. This result is likely associated with inadequate oxygen availability to the tissues, as only oxygen carriers, such as polymerized hemoglobin, red blood cells, and whole blood were capable of improving DAP. Future therapies should be directed towards preferentially improving DBP as an approach to achieving optimal hemodynamics after T/HS.(*p&lt;0.05, **p&lt;0.01, ***p&lt;0.001, ****p&lt;0.0001 compared to LR control). Department of Defense Award W81XWH-17-2-0047. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Metabolic Reprogramming of Human Macrophages by Sickle Cell Hemoglobin

BACKGROUND: Sickle cell disease is caused by a single nucleotide mutation in the β-globin gene, resulting in the substitution of valine for glutamic acid, polymerization of hemoglobin and sickling of red blood cells (RBCs) under low oxygen conditions causing chronic hemolysis, and organs damage. SCA is characterized by the presence of cell-free plasma hemoglobin. Organ damage is associated with chronic inflammation and pro-inflammatory macrophages phenotype. Typically, anti-inflammatory response is elicited by the phagocytosis of senescent RBCs and cell-free hemoglobin. We have demonstrated that treatment of human macrophages with sickle cell hemoglobin (HbS) leads to lysosome accumulation, autophagy activation, and pro-inflammatory phenotype. The propensity of mutant HbS to polymerize under low pH may promote lysosomal HbS polymer accumulation, hindering degradation, and inducing macrophage differentiation towards a pro-inflammatory state. The differentiation of macrophages into specific phenotypes is associated with significant metabolic reprogramming. HYPOTHESIS: We hypothesize that the uptake of HbS by human macrophages induces their metabolic reprogramming via mitochondrial remodeling. METHODS: Human THP-1 cells were differentiated into macrophages with PMA and treated with either purified HbS or normal hemoglobin (HbA). Mitochondria were detected with MitoTrackerTM Green FM dye, and mitochondrial ROS (mtROS) level was detected by Mito SOX Red Kit. Transmission electron microscopy imaging was performed at Talos 200X transmission electron microscope. EPView (Olympus) software was used for the structure analysis. Total RNA was isolated by Trizol and sequenced on an Illumina® NextSeq 500. Comparisons between treatments were conducted using Gene Set Enrichment Analysis (GSEA). RESULTS: Immunofluorescent staining demonstrated accumulation of mitochondria after treatment with HbS compared to untreated (ctrl) or HbA-treated macrophages. Electron microscopy revealed an increase in the number and size of mitochondria. In 25 random microphotographs of cytoplasm, we detected 51 mitochondria in control, 79 in HbA treated and, 96 in HbS treated macrophages. The mitochondria volume and cristae size were significantly increased in macrophages treated with HbS. There was no increase in mtROS production in HbS treatment compared to ctrl. As expected, HbA treatment reduced mtROS production. The mitochondrial gene set (242 genes) was the second most enriched GSEA set in HbS-treated compared to HbA-treated macrophages. The larger mitochondrial size may be associated with a reduction of fission or an increase in fusion. We did not find differences in the expression of mitochondrial fission and fusion genes between HbS and HbA-treated macrophages. The increase in the mitochondrial size and cristae size may also be associated with increased oxidative phosphorylation. We found significant enrichment of genes responsible for oxidative phosphorylation in the HbS-treated macrophages. We did not find significant differences in the expression of glycolysis genes. CONCLUSION: Treatment of human macrophages with HbS significantly increases the number and volume of mitochondria, size of the cristae, and oxidative phosphorylation without upregulation of mtROS production and reduction of glycolysis. This work was supported by NIH Research Grants SC1HL150685, P50HL118006, and R01HL125005. We thank Drs. Castle Raley and Keith Crandall, George Washington University SPH Genomics Core, for sequencing and guidance in data analysis; Dr. Christine Brantner, GW Nanofabrication and Imaging Center, for TEM imaging. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A framework of computer vision-enhanced microfluidic approach for automated assessment of the transient sickling kinetics in sickle red blood cells.

The occurrence of vaso-occlusive crisis greatly depends on the competition between the sickling delay time and the transit time of individual sickle cells, i.e., red blood cells (RBCs) from sickle cell disease (SCD) patients, while they are traversing the circulatory system. Many drugs for treating SCD work by inhibiting the polymerization of sickle hemoglobin (HbS), effectively delaying the sickling process in sickle cells (SS RBCs). Most previous studies on screening anti-sickling drugs, such as voxelotor, rely on in vitro testing of sickling characteristics, often conducted under prolonged deoxygenation for up to 1 hour. However, since the microcirculation of RBCs typically takes less than 1 minute, the results of these studies may be less accurate and less relevant for in vitro-in vivo correlation. In our current study, we introduce a computer vision-enhanced microfluidic framework designed to automatically capture the transient sickling kinetics of SS RBCs within a 1-min timeframe. Our study has successfully detected differences in the transient sickling kinetics between vehicle control and voxelotor-treated SS RBCs. This approach has the potential for broader applications in screening anti-sickling therapies.

Iron restriction in sickle cell disease: When less is more.

Primum non nocere! Can iron deficiency, an abnormality that causes anemia, benefit people with sickle cell disease (SCD) who already have an anemia? The published literature we review appears to answer this question in the affirmative: basic science considerations, animal model experiments, and noncontrolled clinical observations all suggest a therapeutic potential of iron restriction in SCD. This is because SCD's clinical manifestations are ultimately attributable to the polymerization of hemoglobin S (HbS), a process strongly influenced by intracellular HbS concentration. Even small decrements in HbS concentration greatly reduce polymerization, and iron deficiency lowers erythrocyte hemoglobin concentration. Thus, iron deficiency could improve SCD by changing its clinical features to those of a more benign anemia (i.e., a condition with fewer or no vaso-occlusive events). We propose that well-designed clinical studies be implemented to definitively determine whether iron restriction is a safe and effective option in SCD. These investigations are particularly timely now that pharmacologic agents are being developed, which may directly reduce red cell hemoglobin concentrations without the need for phlebotomies to deplete total body iron.

The influence of voxelotor on cerebral blood flow and oxygen extraction in pediatric sickle cell disease

AbstractVoxelotor is an inhibitor of sickle hemoglobin polymerization that is used to treat sickle cell disease. Although voxelotor has been shown to improve anemia, the clinical benefit on the brain remains to be determined. This study quantified the cerebral hemodynamic effects of voxelotor in children with sickle cell anemia (SCA) using noninvasive diffuse optical spectroscopies. Specifically, frequency-domain near-infrared spectroscopy combined with diffuse correlation spectroscopy were used to noninvasively assess regional oxygen extraction fraction (OEF), cerebral blood volume, and an index of cerebral blood flow (CBFi). Estimates of CBFi were first validated against arterial spin–labeled magnetic resonance imaging (ASL-MRI) in 8 children with SCA aged 8 to 18 years. CBFi was significantly positively correlated with ASL-MRI–measured blood flow (R2 = 0.651; P = .015). Next, a single-center, open-label pilot study was completed in 8 children with SCA aged 4 to 17 years on voxelotor, monitored before treatment initiation and at 4, 8, and 12 weeks (NCT05018728). By 4 weeks, both OEF and CBFi significantly decreased, and these decreases persisted to 12 weeks (both P < .05). Decreases in CBFi were significantly correlated with increases in blood hemoglobin (Hb) concentration (P = .025), whereas the correlation between decreases in OEF and increases in Hb trended toward significance (P = .12). Given that previous work has shown that oxygen extraction and blood flow are elevated in pediatric SCA compared with controls, these results suggest that voxelotor may reduce cerebral hemodynamic impairments. This trial was registered at www.ClinicalTrials.gov as #NCT05018728.

Disease-Modifying Therapies for Sickle Cell Disease-An Overview.

Sickle cell disease refers to a group of inherited blood disorders in which hemoglobin polymerization leads to hemolysis and vaso-occlusion. This causes a myriad of complications during a patient's life span, ranging from anemia, infections, and acute and chronic pain to stroke and multiorgan dysfunction. Although there have been dramatic improvements in childhood survival thanks to improved supportive care with penicillin prophylaxis, immunizations, and improved transfusion practices, there was a dearth of disease-modifying therapies, with hydroxyurea being the only medication for >20 years. Here, we discuss the newer therapies for sickle cell disease that have emerged in recent years. [Pediatr Ann. 2024;53(2):e52-e55.].

Using linear dichroism to measure the participation of fetal hemoglobin in sickle hemoglobin polymerization

Using linear dichroism to measure the participation of fetal hemoglobin in sickle hemoglobin polymerization

Biophysical chemistry behind sickle cell anemia and the mechanism of voxelotor action

Sickle cell anemia disease has been a great challenge to the world in the present situation. It occurs only due to the polymerization of sickle hemoglobin (HbS) having Pro–Val–Glu typed mutation, while the polymerization does not occur in normal hemoglobin (HbA) having Pro–Glu–Glu peptides. It is also well confirmed that the oxygenated HbS (OHbS) does not participate in the polymerization, while the deoxygenated HbS (dHbS) does, which causes the shape of red blood cells sickled. After polymerization, the blood has a low oxygen affinity. Keeping this fact into consideration, only those drugs are being synthesized that stabilize the OHbS structure so that the polymerization of HbS can be stopped. The literature data showed no systematic description of the changes occurring during the OHbS conversion to dHbS before polymerization. Hence, an innovative reasonable study between HbA and HbS, when they convert into their deoxygenated forms, was done computationally. In this evaluation, physiochemical parameters in HbA/HbS before and after deoxygenation were studied and compared deeply. The computationally collected data was used to understand the abnormal behaviour of dHbS arising due to the replacement of Glu6 with Val6. Consequently, during the presented computational study, the changes occurring in HbS were found opposite/abnormal as compared to HbA after the deoxygenation of both. The mechanism of Voxelotor (GBT-440) action to stop the HbS polymerization was also explained with the help of computationally collected data. Besides, a comparative study between GBT-440 and another suggested drug was also done to know their antisickling strength. Additionally, the effect of pH, CO, CO2, and 2,3-diphosphoglycerate (2,3-DPG) on HbS structure was also studied computationally.

Pharmacologic Therapies in Beta Hemoglobinopathies: Fetal Globin Gene Induction in the First Molecular Diseases

Beta hemoglobinopathies and thalassemias are caused by diverse molecular mutations of the βA globin chains and modulated by polymorphisms. These are important disorders in medical history, as they became prevalent globally in regions where P. falciparum malaria was endemic. Heterozygous or carrier states conferred a survival advantage; however, doubly heterozygous or homozygous states cause severe hemolytic anemia and multi-organ complications. These disorders are somewhat unique in that all humans have alternate genes for fetal globin chains, which are expressed in fetal life but are silenced on a developmental clock in infancy. An established approach to ameliorating conditions of abnormal adult globin genes is to reactivate, or increase expression, of the endogenous fetal globin genes to replace the missing protein chains in beta thalassemias or inhibit polymerization of hemoglobin S and reduce the red cell abnormalities. This review provides a high-level overview of cell and molecular mechanisms that mediate fetal to adult globin gene switching and pharmacologic therapies that can reactivate fetal globin through different actions. Intermittent or metronomic dosing regimens have overcome challenges of undesirable off-target effects by agents that cause erythroid cell growth arrest. Multiple pharmacologic candidates reactivate or increase the expression of fetal globin protein and proportions of red blood cells containing HbF (F-cells). Hydroxyurea maintains high levels of HbF if begun in infancy, with some decline in mid-childhood. It elicits lower responses in HbF in adult patients, but still has broad clinical benefit in reducing many complications. However, many adult patients do not tolerate optimal hydroxyurea dosing due to cytopenias. Parenterally administered therapies with differing molecular actions, such as demethylating agents and histone deacetylase inhibitors, have shown proof-of-principle in reactivating HbF. Orally bioavailable candidates with complementary molecular mechanisms are in trials. Combining fetal globin-inducing agents with other therapies with complementary mechanisms, such as recombinant erythropoietin that promotes the survival of red blood cells and therapeutics that promote erythroid cell metabolism, should have additive effects. These pharmaceutical candidates offer great clinical potential and global feasibility for ameliorating these serious diseases.

Management of Acute Sickle Cell Disease Pain.

Pain is a common complication of sickle cell disease. Sickle cell pain can often be effectively managed by pediatricians in outpatient and hospital settings. Acute pain management should be initiated quickly. Patients need to be evaluated for sickle cell complications and other causes of pain. Nonsteroidal anti-inflammatory drugs and opioids are the mainstay of pain treatment, but additional therapies include hydration, local pain control, muscle relaxants, and nonpharmacologic approaches. Healthy lifestyle habits and good behavioral and mental health are important for preventing and coping with sickle cell disease pain. Disease-modifying therapies, such as hydroxyurea, can help prevent sickle hemoglobin polymerization and acute pain episodes. Because sickle cell disease largely affects people who are racialized minorities in the United States, health-care providers need to be aware of how their own personal biases may affect care of these patients.

Differential sensitivity to hypoxia enables shape-based classification of sickle cell disease and trait blood samples at point of care.

Red blood cells (RBCs) become sickle-shaped and stiff under hypoxia as a consequence of hemoglobin (Hb) polymerization in sickle cell anemia. Distinguishing between sickle cell disease and trait is crucial during the diagnosis of sickle cell disease. While genetic analysis or high-performance liquid chromatography (HPLC) can accurately differentiate between these two genotypes, these tests are unsuitable for field use. Here, we report a novel microscopy-based diagnostic test called ShapeDx™ to distinguish between disease and trait blood in less than 1 h. This is achieved by mixing an unknown blood sample with low and high concentrations of a chemical oxygen scavenger and thereby subjecting the blood to slow and fast hypoxia, respectively. The different rates of Hb polymerization resulting from slow and fast hypoxia lead to two distinct RBC shape distributions in the same blood sample, which allows us to identify it as healthy, trait, or disease. The controlled hypoxic environment necessary for differential Hb polymerization is generated using an imaging microchamber, which also reduces the sickling time of trait blood from several hours to just 30 min. In a single-blinded proof-of-concept study conducted on a small cohort of clinical samples, the results of the ShapeDx™ test were 100% concordant with HPLC results. Additionally, our field studies have demonstrated that ShapeDx™ is the first reported microscopy test capable of distinguishing between sickle cell disease and trait samples in resource-limited settings with the same accuracy as a gold standard test.