A systematic review of known mechanisms of hydroxyurea-induced fetal hemoglobin for treatment of sickle cell disease

Controversies in the pathophysiology of leg ulcers in sickle cell disease

Patients with sickle cell disease (SCD) often experience painful vaso-occlusive crises and chronic haemolytic anaemia, as well as various acute and chronic complications, such as leg ulcers. Leg ulcers are characterized by their unpredictability, debilitating pain and prolonged healing process. The pathophysiology of SCD leg ulcers is not well defined. Known risk factors include male gender, poor social conditions, malnutrition and a lack of compression therapy when oedema occurs. Leg ulcers typically start with spontaneous pain, followed by induration, hyperpigmentation, blister formation and destruction of the epidermis. SCD is characterized by chronic haemolysis, increased oxidative stress and decreased nitric oxide bioavailability, which promote ischaemia and inflammation and consequently impair vascular function in the skin. This cutaneous vasculopathy, coupled with venostasis around the ankle, creates an ideal environment for local vaso-occlusive crises, which can result in the development of leg ulcers that resemble arterial ulcers. Following the development of the ulcer, healing is hindered as a result of factors commonly observed in venous ulceration, including venous insufficiency, oedema and impaired angiogenesis. All of these factors are modulated by genetic factors. However, our current understanding of these genetic factors remains limited and does not yet enable us to accurately predict ulceration susceptibility.

Consensus of the Brazilian Association of Hematology, Hemotherapy and Cellular Therapy (ABHH) and the Brazilian Ministry of Health - General management of blood and blood products on the tests necessary for the release of exceptional medicines for sickle cell disease

To date, hydroxyurea is the only effective and safe drug that significantly reduces morbidity and mortality of individuals with Sickle cell disease. Twenty years of real-life experience has demonstrated that hydroxyurea reduces pain attacks, vaso-occlusive events, including acute chest syndrome, the number and duration of hospitalizations and the need for transfusion. The therapeutic success of hydroxyurea is directly linked to access to the drug, the dose used and adherence to treatment which, in part, is correlated to the availability of hydroxyurea. This consensus aims to reduce the number of mandatory exams needed to access the drug, prioritizing the requesting physician's report, without affecting patient safety.

Successful quality improvement project to increase hydroxyurea prescriptions for children with sickle cell anaemia

Hydroxyurea (HU) is an effective but underused disease-modifying therapy for patients with sickle cell anaemia (SCA). EMBRACE SCD, a sickle cell disease treatment demonstration project, aimed to improve access to HU by increasing prescription (Rx) rates by at least 10% from baseline in children with SCA.The Model for Improvement was used as the quality improvement framework. HU Rx was assessed from clinical databases in three paediatric haematology centres. Children aged 9 months-18 years with SCA not on chronic transfusions were eligible for HU treatment. The health belief model was the conceptual framework to discuss with patients and promote HU acceptance. A visual aid showing erythrocytes under the effect of HU and the American Society of Hematology HU brochure were used as educational tools. At least 6 months after offering HU, a Barrier Assessment Questionnaire was given to assess reasons for HU acceptance and refusals. If HU was declined, the providers discussed with family again. We conducted chart audits to find missed opportunities to prescribe HU as one plan-do-study-act cycle.At initial measurement, 50.2% of 524 eligible patients had HU prescribed. During the testing and initial implementation phase, the mean performance after 10 data points was 53%. After 2 years, the mean performance was 59%, achieving an 11% increase in mean performance and a 29% increase from initial to the last measurement (64.8% HU Rx). During a 15-month period, 32.1% (N=168) of the eligible patients who were offered HU completed the barrier questionnaire with 19% (N=32) refusing HU, mostly based on not perceiving enough severity of their children's SCA or fearing side effects.Reviewing patient charts for missed opportunity of offering HU with feedback and evaluating the reasons of declining HU via a questionnaire were key components in increasing HU Rx in our population.

The Long Scientific Journey of Sirolimus (Rapamycin): From the Soil of Easter Island (Rapa Nui) to Applied Research and Clinical Trials on β-Thalassemia and Other Hemoglobinopathies

In this review article, we present the fascinating story of rapamycin (sirolimus), a drug able to induce γ-globin gene expression and increased production of fetal hemoglobin (HbF) in erythroid cells, including primary erythroid precursor cells (ErPCs) isolated from β-thalassemia patients. For this reason, rapamycin is considered of great interest for the treatment of β-thalassemia. In fact, high levels of HbF are known to be highly beneficial for β-thalassemia patients. The story of rapamycin discovery began in 1964, with METEI, the Medical Expedition to Easter Island (Rapa Nui). During this expedition, samples of the soil from different parts of the island were collected and, from this material, an antibiotic-producing microorganism (Streptomyces hygroscopicus) was identified. Rapamycin was extracted from the mycelium with organic solvents, isolated, and demonstrated to be very active as an anti-bacterial and anti-fungal agent. Later, rapamycin was demonstrated to inhibit the in vitro cell growth of tumor cell lines. More importantly, rapamycin was found to be an immunosuppressive agent applicable to prevent kidney rejection after transplantation. More recently, rapamycin was found to be a potent inducer of HbF both in vitro using ErPCs isolated from β-thalassemia patients, in vivo using experimental mice, and in patients treated with this compound. These studies were the basis for proposing clinical trials on β-thalassemia patients.

Interventions for chronic kidney disease in people with sickle cell disease

BACKGROUND

Sickle cell disease (SCD), one of the commonest severe monogenic disorders, is caused by the inheritance of two abnormal haemoglobin (beta-globin) genes. SCD can cause severe pain, significant end-organ damage, pulmonary complications, and premature death. Kidney disease is a frequent and potentially severe complication in people with SCD. Chronic kidney disease (CKD) is defined as abnormalities of kidney structure or function present for more than three months. Sickle cell nephropathy refers to the spectrum of kidney complications in SCD. Glomerular damage is a cause of microalbuminuria and can develop at an early age in children with SCD, with increased prevalence in adulthood. In people with sickle cell nephropathy, outcomes are poor as a result of the progression to proteinuria and chronic kidney insufficiency. Up to 12% of people who develop sickle cell nephropathy will develop end-stage renal disease. This is an update of a review first published in 2017.

OBJECTIVES

To assess the effectiveness of any intervention for preventing or reducing kidney complications or chronic kidney disease in people with sickle cell disease. Possible interventions include red blood cell transfusions, hydroxyurea, and angiotensin-converting enzyme inhibitors (ACEIs), either alone or in combination.

SEARCH METHODS

We searched for relevant trials in the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register, CENTRAL, MEDLINE, Embase, seven other databases, and two other trials registers.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing interventions to prevent or reduce kidney complications or CKD in people with SCD. We applied no restrictions related to outcomes examined, language, or publication status.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial eligibility, extracted data, assessed the risk of bias, and assessed the certainty of the evidence (GRADE).

MAIN RESULTS

We included three RCTs with 385 participants. We rated the certainty of the evidence as low to very low across different outcomes according to GRADE methodology, downgrading for risk of bias concerns, indirectness, and imprecision. Hydroxyurea versus placebo One RCT published in 2011 compared hydroxyurea to placebo in 193 children aged nine to 18 months. We are unsure if hydroxyurea compared to placebo reduces or prevents progression of kidney disease assessed by change in glomerular filtration rate (mean difference (MD) 0.58 mL/min /1.73 m2, 95% confidence interval (CI) -14.60 to 15.76; 142 participants; very low certainty). Hydroxyurea compared to placebo may improve the ability to concentrate urine (MD 42.23 mOsm/kg, 95% CI 12.14 to 72.32; 178 participants; low certainty), and may make little or no difference to SCD-related serious adverse events, including acute chest syndrome (risk ratio (RR) 0.39, 99% CI 0.13 to 1.16; 193 participants; low certainty), painful crisis (RR 0.68, 99% CI 0.45 to 1.02; 193 participants; low certainty); and hospitalisations (RR 0.83, 99% CI 0.68 to 1.01; 193 participants; low certainty). No deaths occurred in either trial arm and the RCT did not report quality of life. Angiotensin-converting enzyme inhibitors versus placebo One RCT published in 1998 compared an ACEI (captopril) to placebo in 22 adults with normal blood pressure and microalbuminuria. We are unsure if captopril compared to placebo reduces proteinuria (MD -49.00 mg/day, 95% CI -124.10 to 26.10; 22 participants; very low certainty). We are unsure if captopril reduces or prevents kidney disease as measured by creatinine clearance; the trial authors stated that creatinine clearance remained constant over six months in both groups, but provided no comparative data (very low certainty). The RCT did not report serious adverse events, all-cause mortality, or quality of life. Angiotensin-converting enzyme inhibitors versus vitamin C One RCT published in 2020 compared an ACEI (lisinopril) with vitamin C in 170 children aged one to 18 years with normal blood pressure and microalbuminuria. It reported no data we could analyse. We are unsure if lisinopril compared to vitamin C reduces proteinuria in this population: the large drop in microalbuminuria in both arms of the trial after only one month on treatment may have been due to an overestimation of microalbuminuria at baseline rather than a true effect. The RCT did not report serious adverse events, all-cause mortality, or quality of life.

AUTHORS' CONCLUSIONS

We are unsure if hydroxyurea improves glomerular filtration rate or reduces hyperfiltration in children aged nine to 18 months, but it may improve their ability to concentrate urine and may make little or no difference to the incidence of acute chest syndrome, painful crises, and hospitalisations. We are unsure if ACEI compared to placebo has any effect on preventing or reducing kidney complications in adults with normal blood pressure and microalbuminuria. We are unsure if ACEI compared to vitamin C has any effect on preventing or reducing kidney complications in children with normal blood pressure and microalbuminuria. No RCTs assessed red blood cell transfusions or any combined interventions to prevent or reduce kidney complications. Due to lack of evidence, we cannot comment on the management of children aged over 18 months or adults with any known genotype of SCD. We have identified a lack of adequately designed and powered studies, although we found four ongoing trials since the last version of this review. Only one ongoing trial addresses renal function as a primary outcome in the short term, but such interventions have long-term effects. Trials of hydroxyurea, ACEIs or red blood cell transfusion in older children and adults are urgently needed to determine any effect on prevention or reduction of kidney complications in people with SCD.

Role of microRNA in hydroxyurea mediated HbF induction in sickle cell anaemia patients

Hydroxyurea (HU) is found to be beneficial in sickle cell anaemia (SCA) patients, due to its ability to increase foetal haemoglobin (HbF), however, patients show a variable response. Differences in HbF levels are attributed to many factors; but, the role of miRNA in HbF regulation is sparsely investigated. In this study, we evaluated the effect of miRNA expression on HbF induction in relation to hydroxyurea therapy in 30 normal controls, 30 SCA patients at baseline, 20 patients after 3 and 6 months of hydroxyurea (HU) therapy. HbF levels were measured by HPLC. Total RNA and miRNA were extracted from CD71⁺ erythroid cells and the expression was determined using Taqman probes. The mean HbF level increased 7.54 ± 2.44 fold, after 3 months of HU therapy. After the HU therapy 8 miRNAs were significantly up-regulated while 2 were down-regulated. The increase in miR-210, miR16-1, and miR-29a expression and decrease in miR-96 expression were strongly associated with the HU mediated HbF induction. Post HU therapy, decreased miR-96 expression negatively correlate with HbF and γ-globin gene while increased expression of miR-210, miR-16-1 and miR-29a post HU therapy positively corelate with HbF and γ-globin gene. Thus, suggest that miR-210, miR-16-1 and miR-29a are positive regulator of γ-globin gene and miR-96 is negative regulator of γ-globin gene. The study suggests the role of miR-210, miR16-1, miR-29a, and miR-96 in γ-globin gene regulation leading to HbF induction. Identification of the relevant protein targets might be useful for understanding the HU mediated HbF induction.

Impact of Hydroxyurea Starting Dose on Pain Outcomes in Patients with Sickle Cell Disease

In patients with sickle cell disease, hydroxyurea decreases the number of pain crises experienced. This study aimed to evaluate the difference in pain outcomes between patients started on a guideline concordant, weight-based starting dose of at least 15 mg/kg/day of hydroxyurea and those not. The first prescription of hydroxyurea was the baseline date, follow-up was a visit 60-120 days after baseline. The primary outcome was the change in opioid prescribing between baseline and follow-up. 138 patients met inclusion criteria; of these, 55 were started on a guideline concordant dose of hydroxyurea. Greater white blood cell count (9.5 vs 12.0; p < 0.01) was statistically associated with subtherapeutic dosing. Greater actual body weight (68.0 vs 72.1 kg; p = 0.16) also appeared higher in the non-guideline concordant group. No statistically significant difference in opioid prescribing was observed between those started on a guideline concordant dose of hydroxyurea and those who were not. In the guideline concordant starting dose group, 42% had a reduction in pain scores at first follow up, compared to 35% with a non-guideline recommended starting dose. (p = 0.41). While this difference is in the direction that would be expected based on the guidelines, the difference does not appear to be clinically meaningful.

Cutaneous manifestations of sickle cell disease: an updated review

Sickle cell disease is a common and highly morbid genetic condition that is characterized by multi-system involvement, including numerous cutaneous manifestations. Persistent and recurrent leg ulceration has long been considered the dermatological hallmark of those with sickle cell disease, but there have been recent descriptions of associated infection with rare pathogens and episodes of liverdoid vasculopathy. Growing considerations for this population in the literature include cutaneous reactions to common treatments such as hydroxyurea and clinical management of the intersection between sickle cell disease and conditions like plaque psoriasis. Recent studies have also demonstrated an increased resistance to skin carcinogenesis for those with sickle cell disease through unclear mechanisms. However, though the body of knowledge regarding cutaneous manifestations and considerations of sickle cell disease is slowly expanding, it does not match the considerable disease and symptom burden faced by these patients. More research is needed to better delineate our understanding of these cutaneous manifestations of sickle cell disease to improve outcomes and further management.

The protective effect of the spleen in sickle cell patients. A comparative study between patients with asplenia/hyposplenism and hypersplenism

Sickle cell disease (SCD) is caused by a point mutation in the beta-globin gene. SCD is characterized by chronic hemolytic anemia, vaso-occlusive events leading to tissue ischemia, and progressive organ failure. Chronic inflammatory state is part of the pathophysiology of SCD. Patients with SCD have extremely variable phenotypes, from mild disease to severe complications including early age death. The spleen is commonly injured in SCD. Early splenic dysfunction and progressive spleen atrophy are common. Splenomegaly and hypersplenism can also occur with the loss of the crucial splenic function. Acute, life-threatening spleen-related complications in SCD are well studied. The association of laboratory parameters with the spleen status including hyposplenism, asplenia, and splenomegaly/hypersplenism, and their implication in vaso-occlusive crisis and long-term complications in SCD remain to be determined. We evaluated the association between the spleen status with clinical and laboratory parameters in 31 SCD patients: Group a) Patients with asplenia/hyposplenism (N = 22) (including auto-splenectomy and splenectomized patients) vs. Group b) patients with splenomegaly and or hypersplenism (N = 9). Laboratory studies included: Complete Blood Count, reticulocyte count, iron metabolism parameters, C Reactive Protein (CRP), Hb variant distribution, and D-dimer. Metabolic and morphological red blood cell (RBC) studies included: density gradient (by Percoll), glucose consumption, lactate release, and K⁺ leakage, fetal RBC (F-Cells) and F-Reticulocytes, annexinV+, CD71⁺, oxidative stress measured by GSH presence in RBC and finally Howell Jolly Bodies count were all analyzed by Flow Cytometry. Scanning electron microscopy analysis of RBC was also performed. Patients with asplenia/hyposplenism showed significantly higher WBC, platelet, Hematocrit, hemoglobin S, CRP, D-dimer, Gamma Glutamyl Transferase (GGT), cholesterol, transferrin, annexin V+ RBCs, CD71⁺ RBCs, together with a markedly lower F Reticulocyte levels in comparison with splenomegaly/hypersplenism patients. In summary, important differences were also found between the groups in the studied RBCs parameters. Further studies are required to elucidate the effect of the spleen including hyper and hypo-splenia on laboratory parameters and in clinical manifestations, vascular pathology, and long-term complications of SCD. The benefits and risks of splenectomy compared to chronic transfusion need to be evaluated in clinical trials and the standard approach managing hypersplenism in SCD patients should be re-evaluated.

Single Nucleotide Polymorphisms in XMN1-HBG2, HBS1L-MYB, and BCL11A and Their Relation to High Fetal Hemoglobin Levels That Alleviate Anemia

Anemia is a condition in which red blood cells and/or hemoglobin (Hb) concentrations are decreased below the normal range, resulting in a lack of oxygen being transported to tissues and organs. Those afflicted with this condition may feel lethargic and weak, which reduces their quality of life. The condition may be manifested in inherited blood disorders, such as thalassemia and sickle cell disease, whereas acquired disorders include aplastic anemia, chronic disease, drug toxicity, pregnancy, and nutritional deficiency. The augmentation of fetal hemoglobin (HbF) results in the reduction in clinical symptoms in beta-hemoglobinopathies. Several transcription factors as well as medications such as hydroxyurea may help red blood cells produce more HbF. HbF expression increases with the downregulation of three main quantitative trait loci, namely, the XMN1-HBG2, HBS1L-MYB, and BCL11A genes. These genes contain single nucleotide polymorphisms (SNPs) that modulate the expression of HbF differently in various populations. Allele discrimination is important in SNP genotyping and is widely applied in many assays. In conclusion, the expression of HbF with a genetic modifier is crucial in determining the severity of anemic diseases, and genetic modification of HbF expression may offer clinical benefits in diagnosis and disease management.

Isolation and Characterisation of Quercitrin as a Potent Anti-Sickle Cell Anaemia Agent from Alchornea cordifolia

Alchornea cordifolia Müll. Arg. (commonly known as Christmas Bush) has been used traditionally in Africa to treat sickle cell anaemia (a recessive disease, arising from the S haemoglobin (Hb) allele), but the active compounds are yet to be identified. Herein, we describe the use of sequential fractionation coupled with in vitro anti-sickling assays to purify the active component. Sickling was induced in HbSS genotype blood samples using sodium metabisulphite (Na2S2O5) or through incubation in 100% N2. Methanol extracts of A. cordifolia leaves and its sub-fractions showed >70% suppression of HbSS erythrocyte sickling. The purified compound demonstrated a 87.2 ± 2.39% significant anti-sickling activity and 93.1 ± 2.69% erythrocyte sickling-inhibition at 0.4 mg/mL. Nuclear magnetic resonance (NMR) spectra and high-resolution mass spectroscopy identified it as quercitrin (quercetin 3-rhamnoside). Purified quercitrin also inhibited the polymerisation of isolated HbS and stabilized sickle erythrocytes membranes. Metabolomic comparisons of blood samples using flow-infusion electrospray-high resolution mass spectrometry indicated that quercitrin could convert HbSS erythrocyte metabolomes to be like HbAA. Sickling was associated with changes in antioxidants, anaerobic bioenergy, and arachidonic acid metabolism, all of which were reversed by quercitrin. The findings described could inform efforts directed to the development of an anti-sickling drug or quality control assessments of A. cordifolia preparations.

Do Genetic Polymorphisms Affect Fetal Hemoglobin (HbF) Levels in Patients With Sickle Cell Anemia Treated With Hydroxyurea? A Systematic Review and Pathway Analysis

Hydroxyurea has long been used for the treatment of sickle cell anemia (SCA), and its clinical effectiveness is related to the induction of fetal hemoglobin (HbF), a major modifier of SCA phenotypes. However, there is substantial variability in response to hydroxyurea among patients with SCA. While some patients show an increase in HbF levels and an ameliorated clinical condition under low doses of hydroxyurea, other patients present a poor effect or even develop toxicity. However, the effects of genetic polymorphisms on increasing HbF levels in response to hydroxyurea in patients with SCA (Hb SS) have been less explored. Therefore, we performed a systematic review to assess whether single-nucleotide polymorphisms (SNPs) affect HbF levels in patients with SCA treated with hydroxyurea. Moreover, we performed pathway analysis using the set of genes with SNPs found to be associated with changes in HbF levels in response to hydroxyurea among the included studies. The systematic literature search was conducted on Medline/PubMed, EMBASE, Cochrane Central Register of Controlled Trials, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Scopus, and Web of Science. Seven cohort studies were included following our inclusion and exclusion criteria. From the 728 genetic polymorphisms examined in the included studies, 50 different SNPs of 17 genes were found to be associated with HbF changes in patients with SCA treated with hydroxyurea, which are known to affect baseline HbF but are not restricted to them. Enrichment analysis of this gene set revealed reactome pathways with the lowest adjusted p-values and highest combined scores related to VEGF ligand–receptor interactions (R-HSA-194313; R-HSA-195399) and the urea cycle (R-HSA-70635). Pharmacogenetic studies of response to hydroxyurea therapy in patients with SCA are still scarce and markedly heterogeneous regarding candidate genes and SNPs examined for association with HbF changes and outcomes, suggesting that further studies are needed. The reviewed findings highlighted that similar to baseline HbF, changes in HbF levels upon hydroxyurea therapy are likely to be regulated by multiple loci. There is evidence that SNPs in intron 2 of BCL11A affect HbF changes in response to hydroxyurea therapy, a potential application that might improve the clinical management of SCA.

Systematic Review Registration: (https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=208790).

Mechanisms of Hydroxyurea-Induced Cellular Senescence: An Oxidative Stress Connection?

Hydroxyurea (HU) is a water-soluble antiproliferative agent used for decades in neoplastic and nonneoplastic conditions. HU is considered an essential medicine because of its cytoreduction functions. HU is an antimetabolite that inhibits ribonucleotide reductase, which causes a depletion of the deoxyribonucleotide pool and dramatically reduces cell proliferation. The proliferation arrest, depending on drug concentration and exposure, may promote a cellular senescence phenotype associated with cancer cell therapy resistance and inflammation, influencing neighboring cell functions, immunosuppression, and potential cancer relapse. HU can induce cellular senescence in both healthy and transformed cells in vitro, in part, because of increased reactive oxygen species (ROS). Here, we analyze the main molecular mechanisms involved in cytotoxic/genotoxic HU function, the potential to increase intracellular ROS levels, and the principal features of cellular senescence induction. Understanding the mechanisms involved in HU's ability to induce cellular senescence may help to improve current chemotherapy strategies and control undesirable treatment effects in cancer patients and other diseases.

A novel index to evaluate ineffective erythropoiesis in hematological diseases offers insights into sickle cell disease

Not available.

Hydroxyurea Induces Bone Marrow Mesenchymal Stromal Cells Senescence and Modifies Cell Functionality In Vitro

Hydroxyurea (HU) is an antineoplastic agent that functions as an antimetabolite compound by inhibiting the ribonucleotide reductase. HU acts mainly as a cytostatic drug that through DNA replication stress may trigger a premature senescence-like cell phenotype, though its influence on bone marrow-derived mesenchymal stem/stromal cell (BMMSC) functions has not elucidated yet. Our results indicate that HU inhibits the growth of human BMMSC alongside senescence-like changes in both morphology and replicative potential, provokes cell cycle arrest at the S phase without affecting cellular viability and induces the expression of senescence-associated β-galactosidase and p16INK4. Moreover, HU-induced senescent BMMSC, although they did not change MSC markers expression, exhibited reduced capacity osteogenic and adipogenic differentiation. Conversely, HU treatment increased immunoregulatory functions of BMMSC compared with untreated cells and determined by T-cell proliferation. Interestingly, HU did not influence the capacity of BMMSC to induce monocytic myeloid-derived suppressor cells. Thus, these results suggest that HU improves the BMMSC functions on the T-cell inhibition and preserves their interaction with myeloid cell compartment. Mechanistically, BMMSC under HU treatment displayed a downregulation of mTOR and p38 MAPK signaling that may explain the reduced cell differentiation and increased immunomodulation activities. Together, the results obtained in this investigation suggest that HU by inducing senescence-like phenotype of BMMSC influences their cellular differentiation and immunoregulatory functions.

Hydroxyurea Induces Bone Marrow Mesenchymal Stromal Cells Senescence and Modifies Cell Functionality In Vitro

Hydroxyurea (HU) is an antineoplastic agent that functions as an antimetabolite compound by inhibiting the ribonucleotide reductase. HU acts mainly as a cytostatic drug that through DNA replication stress may trigger a premature senescence-like cell phenotype, though its influence on bone marrow-derived mesenchymal stem/stromal cell (BMMSC) functions has not elucidated yet. Our results indicate that HU inhibits the growth of human BMMSC alongside senescence-like changes in both morphology and replicative potential, provokes cell cycle arrest at the S phase without affecting cellular viability and induces the expression of senescence-associated β-galactosidase and p16INK4. Moreover, HU-induced senescent BMMSC, although they did not change MSC markers expression, exhibited reduced capacity osteogenic and adipogenic differentiation. Conversely, HU treatment increased immunoregulatory functions of BMMSC compared with untreated cells and determined by T-cell proliferation. Interestingly, HU did not influence the capacity of BMMSC to induce monocytic myeloid-derived suppressor cells. Thus, these results suggest that HU improves the BMMSC functions on the T-cell inhibition and preserves their interaction with myeloid cell compartment. Mechanistically, BMMSC under HU treatment displayed a downregulation of mTOR and p38 MAPK signaling that may explain the reduced cell differentiation and increased immunomodulation activities. Together, the results obtained in this investigation suggest that HU by inducing senescence-like phenotype of BMMSC influences their cellular differentiation and immunoregulatory functions.

The HBG2 rs7482144 (C > T) Polymorphism is Linked to HbF Levels but not to the Severity of Sickle Cell Anemia

Sickle cell anemia (SCA) is a severe disease characterized by anemia, acute clinical complications, and a relatively short life span. In this disease, abnormal hemoglobin makes the red blood cells deformed, rigid, and sticky. Fetal hemoglobin (HbF) is one of the key modulators of SCA morbidity and mortality. Interindividual HbF variation is a heritable trait that is controlled by polymorphism in genes linked and unlinked to the hemoglobin β gene (HBB). The genetic polymorphisms that determine HbF levels are known to ameliorate acute clinical events. About 190 well-characterized homozygous SCA patients were included in this study. Complete blood count (CBC), high-performance liquid chromatography (HPLC), and clinical investigations were obtained from patient's records. Severity scores were determined by using the combination of anemia, complications, total leucocyte count, and transfusion scores. HBG2 rs7482144 polymorphism was genotyped by using the polymerase chain reaction and restriction fragment length polymorphism. The association between HBG2 rs7482144 polymorphism and HbF levels as well as the disease severity of SCA were assessed. SCA patients carrying TT genotype were found to have higher HbF levels. In addition, SCA patients with increased severity showed significantly lower levels of hemoglobin, HbF, and hematocrit values. However, the genotypes of HBG2 rs7482144 polymorphism were not found to be associated with the risk of disease severity. In summary, this study demonstrated that HBG2 rs7482144 polymorphism is linked with HbF levels, but it does not affect disease severity. The sample sizes used and the pattern of association deduced from our small sample size prevents us from extrapolating our findings further.

Ineffective Erythropoiesis in β-Thalassaemia: Key Steps and Therapeutic Options by Drugs

β-thalassaemia is a rare genetic condition caused by mutations in the β-globin gene that result in severe iron-loading anaemia, maintained by a detrimental state of ineffective erythropoiesis (IE). The role of multiple mechanisms involved in the pathophysiology of the disease has been recently unravelled. The unbalanced production of α-globin is a major source of oxidative stress and membrane damage in red blood cells (RBC). In addition, IE is tightly linked to iron metabolism dysregulation, and the relevance of new players of this pathway, i.e., hepcidin, erythroferrone, matriptase-2, among others, has emerged. Advances have been made in understanding the balance between proliferation and maturation of erythroid precursors and the role of specific factors in this process, such as members of the TGF-β superfamily, and their downstream effectors, or the transcription factor GATA1. The increasing understanding of IE allowed for the development of a broad set of potential therapeutic options beyond the current standard of care. Many candidates of disease-modifying drugs are currently under clinical investigation, targeting the regulation of iron metabolism, the production of foetal haemoglobin, the maturation process, or the energetic balance and membrane stability of RBC. Overall, they provide tools and evidence for multiple and synergistic approaches that are effectively moving clinical research in β-thalassaemia from bench to bedside.

A comprehensive review of hydroxyurea for β-haemoglobinopathies: the role revisited during COVID-19 pandemic

Background

Hydroxyurea is one of the earliest drugs that showed promise in the management of haemoglobinopathies that include β-thalassaemia and sickle cell disease. Despite this, many aspects of hydroxyurea are either unknown or understudied; specifically, its usefulness in β-thalassaemia major and haemoglobin E β-thalassaemia is unclear. However, during COVID-19 pandemic, it has become a valuable adjunct to transfusion therapy in patients with β-haemoglobinopathies. In this review, we aim to explore the available in vitro and in vivo mechanistic data and the clinical utility of hydroxyurea in β-haemoglobinopathies with a special emphasis on its usefulness during the COVID-19 pandemic.

Main body

Hydroxyurea is an S-phase-specific drug that reversibly inhibits ribonucleoside diphosphate reductase enzyme which catalyses an essential step in the DNA biosynthesis. In human erythroid cells, it induces the expression of γ-globin, a fetal globin gene that is suppressed after birth. Through several molecular pathways described in this review, hydroxyurea exerts many favourable effects on the haemoglobin content, red blood cell indices, ineffective erythropoiesis, and blood rheology in patients with β-haemoglobinopathies. Currently, it is recommended for sickle cell disease and non-transfusion dependent β-thalassaemia. A number of clinical trials are ongoing to evaluate its usefulness in transfusion dependent β-thalassaemia. During the COVID-19 pandemic, it was widely used as an adjunct to transfusion therapy due to limitations in the availability of blood and logistical disturbances. Thus, it has become clear that hydroxyurea could play a remarkable role in reducing transfusion requirements of patients with haemoglobinopathies, especially when donor blood is a limited resource.

Conclusion

Hydroxyurea is a well-tolerated oral drug which has been in use for many decades. Through its actions of reversible inhibition of ribonucleoside diphosphate reductase enzyme and fetal haemoglobin induction, it exerts many favourable effects on patients with β-haemoglobinopathies. It is currently approved for the treatment of sickle cell disease and non-transfusion dependent β-thalassaemia. Also, there are various observations to suggest that hydroxyurea is an important adjunct in the treatment of transfusion dependent β-thalassaemia which should be confirmed by randomised clinical trials.

Therapeutic gene editing strategies using CRISPR-Cas9 for the β-hemoglobinopathies

With advancements in gene editing technologies, our ability to make precise and efficient modifications to the genome is increasing at a remarkable rate, paving the way for scientists and clinicians to uniquely treat a multitude of previously irremediable diseases. CRISPR-Cas9, short for clustered regularly interspaced short palindromic repeats and CRISPR-associated protein 9, is a gene editing platform with the ability to alter the nucleotide sequence of the genome in living cells. This technology is increasing the number and pace at which new gene editing treatments for genetic disorders are moving toward the clinic. The β-hemoglobinopathies are a group of monogenic diseases, which despite their high prevalence and chronic debilitating nature, continue to have few therapeutic options available. In this review, we will discuss our existing comprehension of the genetics and current state of treatment for β-hemoglobinopathies, consider potential genome editing therapeutic strategies, and provide an overview of the current state of clinical trials using CRISPR-Cas9 gene editing.

Generation of an immortalised erythroid cell line from haematopoietic stem cells of a haemoglobin E/β-thalassemia patient

The β-thalassemia syndromes are the most prevalent genetic disorder globally, characterised by reduced or absent β-globin chain synthesis. HbE/β-thalassemia is a subtype of β-thalassemia with extremely high frequency in Asia. Studying molecular defects behind β-thalassemia is severely impeded by paucity of material from patients and lack of suitable cell lines. Approaches to derive erythroid cells from induced pluripotent stem cells (iPSCs) created from patients are confounded by poor levels of erythroid cell expansion, aberrant or incomplete erythroid differentiation and foetal/embryonic rather than adult globin expression. In this study we generate an immortalised erythroid cell line from peripheral blood stem cells of a HbE/β-thalassemia patient. Morphological analysis shows the cells are proerythroblasts with some early basophilic erythroblasts, with no change in morphology over time in culture. The line differentiates along the erythroid pathway to orthochromatic erythroblasts and reticulocytes. Importantly, unlike iPSCs, the line maintains the haemoglobin profile of the patient's red blood cells. This is the first human cellular model for β-thalassemia providing a sustainable source of disease cells for studying underlying disease mechanisms and for use as drug screening platform, particularly for reagents designed to increase foetal haemoglobin expression as we have additionally demonstrated with hydroxyurea.

Epigenetic Reexpression of Hemoglobin F Using Reversible LSD1 Inhibitors: Potential Therapies for Sickle Cell Disease

Sickle cell disease (SCD) is caused by a single nucleotide polymorphism on chromosome 11 in the β-globin gene. The resulting mutant hemoglobin S (HbS) is a poor oxygen transporter and causes a variety of vascular symptoms and organ failures. At birth, the DRED epigenetic complex forms and silences the γ-globin gene, and fetal hemoglobin (HbF, 2 α-, and 2 γ-subunits) is replaced by adult HbA (α2β2) or HbS (α2βs 2) in SCD patients. HbF is a potent inhibitor of HbS polymerization, thus alleviating the symptoms of SCD. The current therapy, hydroxyurea (HU), increases γ-globin and the HbF content in sickle cells but is highly underutilized due to concern for adverse effects and other complications. The DRED complex contains the epigenetic eraser lysine-specific demethylase 1 (LSD1), which appears to serve as a scaffolding protein. Our recently discovered 1,2,4-triazole derivatives and cyclic peptide LSD1 inhibitors promote the upregulation of γ-globin production in vitro without significant toxicity. Herein, we demonstrate that these LSD1 inhibitors can be used to disrupt the DRED complex and increase the cellular HbF content in vitro and in vivo. This approach could lead to an innovative and effective treatment for SCD.

Understanding the structure and conformation of bovine hemoglobin in presence of the drug hydroxyurea: multi-spectroscopic studies supported by docking and molecular dynamics simulation

Binding interaction between the small antitumor drug Hydroxyurea (HU) and Bovine Hemoglobin (BHb) has been explored in details from multi-spectroscopic and computational studies. The formation of ground state complex between BHb and HU has been suggested from the electronic UV-Vis and steady-state fluorescence spectroscopic studies. The quenching in fluorescence of BHb in presence of HU at varied concentrations has been analyzed from the SV plots. Static type of quenching has been suggested from time-resolved fluorescence spectroscopic studies. Binding parameters associated with the BHb-HU complex have also been estimated from the temperature dependent fluorescence spectroscopic studies. Alterations in the micro-environment of the Tyr and Trp residues of BHb in presence of HU have been observed from the synchronous fluorescence measurement. The result obtained from CD spectroscopic measurements signify partial unfolding in the secondary structure of BHb due to binding with HU molecule. The experimental observations are supported by theoretical studies. Molecular docking and molecular dynamics simulations have been performed to investigate the structural stability and compactness of BHb in the binding interaction between BHb and HU. The interaction of BHb with HU is expected to provide fundamental insights towards understanding the therapeutic effectiveness of HU upon interaction with BHb used in chemo-, radio therpeutic procedures and also in the treatment of SCD.

Small molecule therapeutics to treat the β-globinopathies

PURPOSE OF REVIEW

The current review focuses on recent insights into the development of small molecule therapeutics to treat the β-globinopathies.

RECENT FINDINGS

Recent studies of fetal γ-globin gene regulation reveal multiple insights into how γ-globin gene reactivation may lead to novel treatment for β-globinopathies.

SUMMARY

We summarize current information regarding the binding of transcription factors that appear to be impeded or augmented by different hereditary persistence of fetal hemoglobin (HPFH) mutations. As transcription factors have historically proven to be difficult to target for therapeutic purposes, we next address the contributions of protein complexes associated with these HPFH mutation-affected transcription factors with the aim of defining proteins that might provide additional targets for chemical molecules to inactivate the corepressors. Among the enzymes associated with the transcription factor complexes, a group of corepressors with currently available inhibitors were initially thought to be good candidates for potential therapeutic purposes. We discuss possibilities for pharmacological inhibition of these corepressor enzymes that might significantly reactivate fetal γ-globin gene expression. Finally, we summarize the current clinical trial data regarding the inhibition of select corepressor proteins for the treatment of sickle cell disease and β-thalassemia.

Interventions for preventing silent cerebral infarcts in people with sickle cell disease

BACKGROUND

Sickle cell disease (SCD) is one of the commonest severe monogenic disorders in the world, due to the inheritance of two abnormal haemoglobin (beta globin) genes. SCD can cause severe pain, significant end-organ damage, pulmonary complications, and premature death. Silent cerebral infarcts are the commonest neurological complication in children and probably adults with SCD. Silent cerebral infarcts also affect academic performance, increase cognitive deficits and may lower intelligence quotient.

OBJECTIVES

To assess the effectiveness of interventions to reduce or prevent silent cerebral infarcts in people with SCD.

SEARCH METHODS

We searched for relevant trials in the Cochrane Library, MEDLINE (from 1946), Embase (from 1974), the Transfusion Evidence Library (from 1980), and ongoing trial databases; all searches current to 14 November 2019. We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register: 07 October 2019.

SELECTION CRITERIA

Randomised controlled trials comparing interventions to prevent silent cerebral infarcts in people with SCD. There were no restrictions by outcomes examined, language or publication status.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures.

MAIN RESULTS

We included five trials (660 children or adolescents) published between 1998 and 2016. Four of the five trials were terminated early. The vast majority of participants had the haemoglobin (Hb)SS form of SCD. One trial focused on preventing silent cerebral infarcts or stroke; three trials were for primary stroke prevention and one trial dealt with secondary stroke prevention. Three trials compared the use of regular long-term red blood cell transfusions to standard care. Two of these trials included children with no previous long-term transfusions: one in children with normal transcranial doppler (TCD) velocities; and one in children with abnormal TCD velocities. The third trial included children and adolescents on long-term transfusion. Two trials compared the drug hydroxyurea and phlebotomy to long-term transfusions and iron chelation therapy: one in primary prevention (children), and one in secondary prevention (children and adolescents). The quality of the evidence was moderate to very low across different outcomes according to GRADE methodology. This was due to trials being at high risk of bias because they were unblinded; indirectness (available evidence was only for children with HbSS); and imprecise outcome estimates. Long-term red blood cell transfusions versus standard care Children with no previous long-term transfusions and higher risk of stroke (abnormal TCD velocities or previous history of silent cerebral infarcts) Long-term red blood cell transfusions may reduce the incidence of silent cerebral infarcts in children with abnormal TCD velocities, risk ratio (RR) 0.11 (95% confidence interval (CI) 0.02 to 0.86) (one trial, 124 participants, low-quality evidence); but make little or no difference to the incidence of silent cerebral infarcts in children with previous silent cerebral infarcts on magnetic resonance imaging and normal or conditional TCDs, RR 0.70 (95% CI 0.23 to 2.13) (one trial, 196 participants, low-quality evidence). No deaths were reported in either trial. Long-term red blood cell transfusions may reduce the incidence of: acute chest syndrome, RR 0.24 (95% CI 0.12 to 0.49) (two trials, 326 participants, low-quality evidence); and painful crisis, RR 0.63 (95% CI 0.42 to 0.95) (two trials, 326 participants, low-quality evidence); and probably reduces the incidence of clinical stroke, RR 0.12 (95% CI 0.03 to 0.49) (two trials, 326 participants, moderate-quality evidence). Long-term red blood cell transfusions may improve quality of life in children with previous silent cerebral infarcts (difference estimate -0.54; 95% confidence interval -0.92 to -0.17; one trial; 166 participants), but may have no effect on cognitive function (least squares means: 1.7, 95% CI -1.1 to 4.4) (one trial, 166 participants, low-quality evidence). Transfusions continued versus transfusions halted: children and adolescents with normalised TCD velocities (79 participants; one trial) Continuing red blood cell transfusions may reduce the incidence of silent cerebral infarcts, RR 0.29 (95% CI 0.09 to 0.97 (low-quality evidence). We are very uncertain whether continuing red blood cell transfusions has any effect on all-cause mortality, Peto odds ratio (OR) 8.00 (95% CI 0.16 to 404.12); or clinical stroke, RR 0.22 (95% CI 0.01 to 4.35) (very low-quality evidence). The trial did not report: comparative numbers for SCD-related adverse events; quality of life; or cognitive function. Hydroxyurea and phlebotomy versus transfusions and chelation Primary prevention, children (121 participants; one trial) We are very uncertain whether switching to hydroxyurea and phlebotomy has any effect on: silent cerebral infarcts (no infarcts); all-cause mortality (no deaths); risk of stroke (no strokes); or SCD-related complications, RR 1.52 (95% CI 0.58 to 4.02) (very low-quality evidence). Secondary prevention, children and adolescents with a history of stroke (133 participants; one trial) We are very uncertain whether switching to hydroxyurea and phlebotomy has any effect on: silent cerebral infarcts, Peto OR 7.28 (95% CI 0.14 to 366.91); all-cause mortality, Peto OR 1.02 (95%CI 0.06 to 16.41); or clinical stroke, RR 14.78 (95% CI 0.86 to 253.66) (very low-quality evidence). Switching to hydroxyurea and phlebotomy may increase the risk of SCD-related complications, RR 3.10 (95% CI 1.42 to 6.75) (low-quality evidence). Neither trial reported on quality of life or cognitive function.

AUTHORS' CONCLUSIONS

We identified no trials for preventing silent cerebral infarcts in adults, or in children who do not have HbSS SCD. Long-term red blood cell transfusions may reduce the incidence of silent cerebral infarcts in children with abnormal TCD velocities, but may have little or no effect on children with normal TCD velocities. In children who are at higher risk of stroke and have not had previous long-term transfusions, long-term red blood cell transfusions probably reduce the risk of stroke, and other SCD-related complications (acute chest syndrome and painful crises). In children and adolescents at high risk of stroke whose TCD velocities have normalised, continuing red blood cell transfusions may reduce the risk of silent cerebral infarcts. No treatment duration threshold has been established for stopping transfusions. Switching to hydroxyurea with phlebotomy may increase the risk of silent cerebral infarcts and SCD-related serious adverse events in secondary stroke prevention. All other evidence in this review is of very low-quality.

Non-coding RNAs - A primer for the laboratory scientist

Advances in molecular genetics have identified several species of RNA that fail to translate - hence the non-coding RNAs. The two major groups within this class of nucleic acids are microRNAs (miRNA) and long non-coding RNAs (lncRNA). There is growing body of evidence supporting the view that these molecules have regulatory effect on both DNA and RNA. The objective of this brief review is to explain the molecular genetic of these molecules, to summarize their potential as mediators of disease, and to highlight their value as diagnostic markers and as tools in disease management.

Inpatient Ordering of Home Hydroxyurea by Residents for Hospitalized Patients With Sickle Cell Disease

BACKGROUND

Hydroxyurea is a well-established disease-modifying medication for sickle cell disease (SCD). At some institutions, hydroxyurea can only be ordered by "chemotherapy-certified" providers which may not include pediatric resident physicians.

METHODS

We conducted a survey of 39 American pediatric hospitals regarding their policy on resident hydroxyurea ordering for SCD. Our institution changed its policy in June 2016 to allow residents to order hydroxyurea for hospitalized patients with SCD who were already on hydroxyurea at home. We conducted a retrospective review of the medical records of a random sample of patients with SCD on hydroxyurea admitted the year before and the year after this policy change.

RESULTS

In our national survey, 51% of surveyed hospitals allowed residents to order hydroxyurea, 19% required a second signature, and 30% did not allow residents to order hydroxyurea. In our institutional study, patients after the policy change were significantly more likely to have received their home hydroxyurea by hospital day 1: before 62/90 (69%) versus after 105/119 (88%), P=0.0005. The proportion of patients who inappropriately received hydroxyurea was very low in both groups: before 1/91 (1%) versus after 3/126 (2%), P=0.64, with no serious adverse clinical events due to inappropriate hydroxyurea administration.

CONCLUSIONS

Considerable national variation in practice currently exists in regards to resident hydroxyurea ordering hospital policies. A policy allowing residents to order hydroxyurea significantly increased the likelihood of a patient receiving hydroxyurea while hospitalized with no significant increase in inappropriate hydroxyurea administration. Resident hydroxyurea ordering seems safe and beneficial.

Elevated levels of circulating invariant natural killer cell subsets are skewed toward Th2-like phenotype in children with sickle cell disease

Invariant natural killer T (iNKT) cells are being considered as potential targets for immunotherapeutic strategies in a variety of conditions including sickle cell disease (SCD). However, relatively little is known about the fate of iNKT cell subsets in children with SCD. Herein, quantitative and qualitative analyses of circulating iNKT cell subsets were carried out in 120 children in steady state and 30 healthy controls. Children with SCD displayed significantly elevated levels of circulating iNKT cell subsets with a preferential polarization toward Th2-like cells. The known SCD modifiers did not influence levels of iNKT cell subsets, except that children carrying the Bantu haplotype exhibited elevated levels of CD4iNKT cells, and to a lesser degree CD8iNKT cells. Collectively, these findings indicate that circulating iNKT cell subsets are significantly increased in children with SCD, and highlight the existence of imbalanced production of cytokines toward Th2-like phenotype, which seems to be associated with genetic polymorphisms.

Genetic Modifiers at the Crossroads of Personalised Medicine for Haemoglobinopathies

Haemoglobinopathies are common monogenic disorders with diverse clinical manifestations, partly attributed to the influence of modifier genes. Recent years have seen enormous growth in the amount of genetic data, instigating the need for ranking methods to identify candidate genes with strong modifying effects. Here, we present the first evidence-based gene ranking metric (IthaScore) for haemoglobinopathy-specific phenotypes by utilising curated data in the IthaGenes database. IthaScore successfully reflects current knowledge for well-established disease modifiers, while it can be dynamically updated with emerging evidence. Protein–protein interaction (PPI) network analysis and functional enrichment analysis were employed to identify new potential disease modifiers and to evaluate the biological profiles of selected phenotypes. The most relevant gene ontology (GO) and pathway gene annotations for (a) haemoglobin (Hb) F levels/Hb F response to hydroxyurea included urea cycle, arginine metabolism and vascular endothelial growth factor receptor (VEGFR) signalling, (b) response to iron chelators included xenobiotic metabolism and glucuronidation, and (c) stroke included cytokine signalling and inflammatory reactions. Our findings demonstrate the capacity of IthaGenes, together with dynamic gene ranking, to expand knowledge on the genetic and molecular basis of phenotypic variation in haemoglobinopathies and to identify additional candidate genes to potentially inform and improve diagnosis, prognosis and therapeutic management.

δ-Aminolevulinate induces fetal hemoglobin expression by enhancing cellular heme biosynthesis

Sickle cell disease (SCD) and β-thalassemia are inherited blood disorders caused by genetic defects in the β-globin gene on chromosome 11, producing severe disease in people worldwide. Induction of fetal hemoglobin consisting of two α-globin and two γ-globin chains ameliorates the clinical symptoms of both disorders. In the present study, we investigated the ability of δ-aminolevulinate (ALA), the heme precursor, to activate γ-globin gene expression as well as its effects on cellular functions in erythroid cell systems. We demonstrated that ALA induced γ-globin expression at both the transcriptional and protein levels in the KU812 erythroid cell line. Using inhibitors targeting two enzymes in the heme biosynthesis pathway, we showed that cellular heme biosynthesis was involved in ALA-mediated γ-globin activation. Moreover, the transcription factor NRF2 (nuclear factor [erythroid-derived 2]-like 2), a critical regulator of the cellular antioxidant response, was activated by ALA and contributed to mechanisms of γ-globin activation; ALA did not affect cell proliferation and was not toxic to cells. Subsequent studies demonstrated ALA-induced γ-globin activation in erythroid progenitors generated from normal human CD34+ stem cells. These data support future study to explore the potential of stimulating intracellular heme biosynthesis by ALA or similar compounds as a novel therapeutic strategy for treating SCD and β-thalassemia.

Impact statement

Inherited mutations in the β-globin-like genes result in the most common forms of genetic blood disease including sickle cell disease (SCD) and β-thalassemia worldwide. Therefore, effective inexpensive therapies that can be distributed widely are highly desirable. Currently, drug-mediated fetal hemoglobin (HbF) induction can ameliorate clinical symptoms of SCD and β-thalassemia and is the most effective strategy for developing new therapeutic options. In the current study, we confirmed that δ-Aminolevulinate (ALA), the precursor of heme, induces γ-globin expression at both the transcriptional and translational levels in primary human erythroid progenitors. Moreover, the results indicate activation of the transcription factor NRF2 (nuclear factor (erythroid-derived 2)-like 2) by ALA to enhance HbF expression. These data support future study to explore the potential of stimulating intracellular heme biosynthesis by ALA or similar compounds as a novel therapeutic strategy for treating SCD and β-thalassemia.

Nonmelanoma skin cancer associated with Hydroxyurea treatment: Overview of the literature and our own experience

Nonmelanoma skin cancer is the most common malignant tumor in the fair skin population, with each year several millions of diagnosed cases. Their most common risk factors are fair skin, a history of excessive ultraviolet light exposure, chronic inflammatory skin conditions, exposure to radiation, and contact with arsenic. Certain drugs can also be associated with a higher risk of nonmelanoma skin cancer. These include hydroxyurea, which acts as a metabolic inhibitor of ribonucleotide reductase and a potent nonalkylating myelosuppressive agent. It is used for the treatment of various myeloproliferative disorders, including chronic myeloid leukemia, polycythemia vera, and essential thrombocytopenia. Several publications describe an increased occurrence of skin manifestations following hydroxyurea treatment. A growing body of evidence indicates a possible role of hydroxyurea in skin cancer progression. In this review article, we summarize some relevant observations about the association of hydroxyurea and skin cancer, and we describe our own clinical experiences to provide up to date recommendations about the care of patients on hydroxyurea therapy.

Alpha Globin Gene Mutation: A Major Determinant of Hydroxyurea Response in Transfusion-Dependent HbE-β-Thalassaemia

Thalassaemias are the most common inherited autosomal recessive single gene disorders characterised by chronic hereditary haemolytic anaemia due to absence or reduced synthesis of one or more of the globin chains. Haemoglobin E (HbE)-β-thalassaemia is the genotype responsible for approximately one-half of all cases of severe β-thalassaemia worldwide. This study proposes to evaluate response of hydroxyurea in reducing transfusion requirements of severe HbE-β-thalassaemia patients, and its correlation with foetal haemoglobin (HbF) level and α-mutation. Hydroxyurea was started at a baseline dose in 82 transfusion-dependent HbE-β-thalassaemia patients. HbF levels and %F-cells were measured. β-Thalassaemia mutations and α-globin gene deletions and triplications were detected by amplification refractory mutation system (ARMS)-polymerase chain reaction (PCR) and Gap-PCR, respectively. Patients were categorised as good (41.5%), moderate (31.7%), and poor responders (26.8%) based on their decrease in transfusion requirements. Nine patients were excellent responders who became transfusion independent. The mean increase in HbF levels and %F-cells after therapy was correlated with decrease in transfusion requirements. Patients having a deletion of the α-globin gene were better responders. The response was proportional to the number of α-globin gene deletions. We conclude that hydroxyurea treatment decreases transfusion requirements, and the response correlates with α-globin gene deletions.

Hydroxyurea: Pattern of Use, Patient Adherence, and Safety Profile in Patients with Sickle Cell Disease in Oman

OBJECTIVES

Many barriers contribute to the underutilization of hydroxyurea (HU) in the treatment of sickle cell disease (SCD), and adherence to its use is often reported to be suboptimal. It is important to have information on the safety of HU in patients with SCD. Our study assessed the pattern of use, patients' adherence to medication, discontinuation of use, and safety of HU in patients with SCD.

METHODS

This cross-sectional study was conducted in the department of medicine of a referral hospital in Oman over five months and included a review of patient files and patient interview. Approval was obtained from the Regional Research and Ethics Committee of the A'Dakhiliyah Governorate and the hospital administration. The parameters were compared between groups using the chi-square test.

RESULTS

Of 298 patients studied, 128 (43.0%) had used HU at some points. The difference in the prevalence of HU use was statistically significant based only on age (p = 0.014), with younger patients more likely to be currently using HU or used HU in the past. The majority of patients were adherent (82.5%) based on self-reported adherence. The prevalence of discontinuation (temporary or permanent) of HU use was high (57.0%), and suspected adverse drug reaction (ADR) was the most common reason. Among those who had never used HU, 33.7% of patients had an indication for the initiation of HU. A quarter of patients who used HU developed a suspected ADR, with blood abnormalities being the commonest. The duration of HU use influenced ADR prevalence (p = 0.015).

CONCLUSIONS

Among the current users of HU, the majority of the patients were adherent based on self-reported medication adherence. The prevalence of discontinuation of HU use and instances of non-initiation of HU among those indicated were high. A larger study, ideally of a prospective nature, in various governorates of Oman, would provide a wider picture at the national level.

Sickling-preventive effects of rutin is associated with modulation of deoxygenated haemoglobin, 2,3-bisphosphoglycerate mutase, redox status and alteration of functional chemistry in sickle erythrocytes

Sickle cell anaemia is a hereditary disease branded by an upsurge in generation of ROS, irregular iron release and little or no antioxidant activity which can lead to cellular injuries due to oxidative stress resulting in severe symptoms including anaemia and pain. The disease is caused by a mutated version of the gene that helps make haemoglobin, the protein that carries oxygen in red blood cells. We used in silico and in vitro experiments to examine the antisickling effects of rutin for the first time by means of before and after induction approaches in sickle erythrocytes. Rutin was docked against deoxy-haemoglobin and 2,3-bisphosphoglycerate mutase, revealing binding energies (-27.329 and -25.614 kcal/mol) and Ki of 0.989μM and 0.990 μM at their catalytic sites through strong hydrophobic and hydrogen bond interactions. Sickling was thereafter, induced at 3 h with 2% metabisulphite. Rutin prevented sickling maximally at 12.3μM and reversed same at 16.4μM, by 78.5% and 69.9%, one-to-one. Treatment with rutin significantly (P < 0.05) reinvented the integrity of erythrocytes membrane as evident from the practical % haemolysis compared to induced erythrocytes. Rutin also significantly (P < 0.05) prevented and reversed lipid peroxidation relative to untreated. Likewise, GSH, CAT levels were observed to significantly (P < 0.05) increase with concomitant significant (P < 0.05) decrease in SOD activity based on administration of rutin after sickling induction approach. Furthermore, FTIR results showed that treatment with rutin favourably altered the functional chemistry, umpiring from shifts and functional groups observed. It can thus be deduced that, antisickling effects of rutin may be associated with modulation of deoxy-haemoglobin, 2,3-bisphosphoglycerate mutase, alteration of redox homeostasis and functional chemistry of sickle erythrocytes.

A novel, highly potent and selective phosphodiesterase-9 inhibitor for the treatment of sickle cell disease

The most common treatment for patients with sickle cell disease (SCD) is the chemotherapeutic hydroxyurea, a therapy with pleiotropic effects, including increasing fetal hemoglobin (HbF) in red blood cells and reducing adhesion of white blood cells to the vascular endothelium. Hydroxyurea has been proposed to mediate these effects through a mechanism of increasing cellular cGMP levels. An alternative path to increasing cGMP levels in these cells is through the use of phosphodiesterase-9 inhibitors that selectively inhibit cGMP hydrolysis and increase cellular cGMP levels. We have developed a novel, potent and selective phosphodiesterase-9 inhibitor (IMR-687) specifically for the treatment of SCD. IMR-687 increased cGMP and HbF in erythroid K562 and UT-7 cells and increased the percentage of HbF positive erythroid cells generated in vitro using a two-phase liquid culture of CD34⁺ progenitors from sickle cell blood or bone marrow. Oral daily dosing of IMR-687 in the Townes transgenic mouse SCD model, increased HbF and reduced red blood cell sickling, immune cell activation and microvascular stasis. The IMR-687 reduction in red blood cell sickling and immune cell activation was greater than that seen with physiological doses of hydroxyurea. In contrast to other described phosphodiesterase-9 inhibitors, IMR-687 did not accumulate in the central nervous system, where it would inhibit phosphodiesterase-9 in neurons, or alter rodent behavior. IMR-687 was not genotoxic or myelotoxic and did not impact fertility or fetal development in rodents. These data suggest that IMR-687 may offer a safe and effective oral alternative for hydroxyurea in the treatment of SCD.

Hydroxyurea-Induced miRNA Expression in Sickle Cell Disease Patients in Africa

Hydroxyurea (HU) is clinically beneficial in sickle cell disease (SCD) through fetal hemoglobin (HbF) induction; however, the mechanism of HU is not yet fully elucidated. Selected miRNAs have been associated with HU-induced HbF production. We have investigated differential HU-induced global miRNA expression in peripheral blood of adult SCD patients in patients from Congo, living in South Africa. We found 22 of 798 miRNAs evaluated that were differentially expressed under HU treatment, with the majority (13/22) being functionally associated with HbF-regulatory genes, including BCL11A (miR-148b-3p, miR-32-5p, miR-340-5p, and miR-29c-3p), MYB (miR-105-5p), and KLF-3 (miR-106b-5), and SP1 (miR-29b-3p, miR-625-5p, miR-324-5p, miR-125a-5p, miR-99b-5p, miR-374b-5p, and miR-145-5p). The preliminary study provides potential additional miRNA candidates for therapeutic exploration.

Sickle cell disease: Clinical presentation and management of a global health challenge

Sickle cell disease is an autosomal recessive, multisystem disorder, characterised by chronic haemolytic anaemia, painful episodes of vaso-occlusion, progressive organ failure and a reduced life expectancy. Sickle cell disease is the most common monogenetic disease, with millions affected worldwide. In well-resourced countries, comprehensive care programs have increased life expectancy of sickle cell disease patients, with almost all infants surviving into adulthood. Therapeutic options for sickle cell disease patients are however, still scarce. Predictors of sickle cell disease severity and a better understanding of pathophysiology and (epi)genetic modifiers are warranted and could lead to more precise management and treatment. This review provides an extensive summary of the pathophysiology and management of sickle cell disease and encompasses the characteristics, complications and current and future treatment options of the disease.

Whole-exome sequencing indicates FLG2 variant associated with leg ulcers in Brazilian sickle cell anemia patients

Although sickle cell anemia results from homozygosity for a single mutation at position 7 of the β-globin chain, the clinical aspects of this condition are very heterogeneous. Complications include leg ulcers, which have a negative impact on patients’ quality of life and are related to the severity of the disease. Nevertheless, the complex pathogenesis of this complication has yet to be elucidated. To identify novel genes associated with leg ulcers in sickle cell anemia, we performed whole-exome sequencing of extreme phenotypes in a sample of Brazilian sickle cell anemia patients and validated our findings in another sample. Our discovery cohort consisted of 40 unrelated sickle cell anemia patients selected based on extreme phenotypes: 20 patients without leg ulcers, aged from 40 to 61 years, and 20 with chronic leg ulcers. DNA was extracted from peripheral blood leukocytes and used for whole-exome sequencing. After the bioinformatics analysis, eight variants were selected for validation by Sanger sequencing and TaqMan® genotyping in 293 sickle cell anemia patients (153 without leg ulcers) from two different locations in Brazil. After the validation, Fisher’s exact test revealed a statistically significant difference in a stop codon variant (rs12568784 G/T) in the FLG2 gene between the GT and GG genotypes ( P = 0.035). We highlight the importance of rs12568784 in leg ulcer development as this variant of the FLG2 gene results in impairment of the skin barrier, predisposing the individual to inflammation and infection. Additionally, we suggest that the remaining seven variants and the genes in which they occur could be strong candidates for leg ulcers in sickle cell anemia.

Impact statement

To our knowledge, the present study is the first to use whole-exome sequencing based on extreme phenotypes to identify new candidate genes associated with leg ulcers in sickle cell anemia patients. There are few studies about this complication; the pathogenesis remains complex and has yet to be fully elucidated. We identified interesting associations in genes never related with this complication to our knowledge, especially the variant in the FLG2 gene. The knowledge of variants related with leg ulcer in sickle cell anemia may lead to a better comprehension of the disease’s etiology, allowing prevention and early treatment options in risk genotypes while improving quality of life for these patients.

Role of Genomic Biomarkers in Increasing Fetal Hemoglobin Levels Upon Hydroxyurea Therapy and in β-Thalassemia Intermedia: A Validation Cohort Study

Hemoglobinopathies exhibit a remarkable phenotypic diversity in terms of disease severity, while individual genetic background plays a key role in differential response to drug treatment. In the last decade, genomic variants in genes located within, as well as outside the human β-globin cluster have been shown to be significantly associated with Hb F increase, in relation to hydroxyurea (HU) therapy in patients with these diseases. Here, we aim to determine the effect of genomic variants located in genes, such as MAP3K5, ASS1, NOS2A, TOX, PDE7B, NOS1, FLT1 and ARG2, previously shown to modulate fetal hemoglobin (Hb F) levels in patients with β type hemoglobinopathies and reflecting disease severity and response to HU therapy in an independent cohort of Greek patients with these diseases. We recruited and genotyped 45 β-thalassemia patients (β-thal), either transfusion-dependent (TDT) or non transfusion-dependent (NTDT), 42 Hb S (HBB: c.20A>T)-β-thal compound heterozygotes, who were treated with HU, as well as 53 healthy individuals, all of Hellenic origin. Our study showed that genomic variants of the MAP3K5, NOS2A and ARG2 gene are associated with HU therapy efficacy in Hb S-β-thal compound heterozygotes. We have also shown that FLT1 and ARG2 genomic variants are associated with the mild phenotype of NTDT patients. Our findings provide evidence that MAP3K5, NOS2A, ARG2 and FLT1 genomic variants could be considered as genomic biomarkers to predict HU therapy efficacy in Hb S-β-thal compound heterozygotes and also to describe disease severity in patients with β type hemoglobinopathies.

Insight into the complex pathophysiology of sickle cell anaemia and possible treatment

Sickle cell anaemia (SCA) is the consequence of abnormal haemoglobin production due to an inherited point mutation in the β-globin gene. The resulting haemoglobin tetramer is poorly soluble when deoxygenated, and when this is prolonged, intracellular gelation of sickle haemoglobin occurs, followed by haemoglobin polymerisation. If many cycles of sickling and unsickling occur, the red cell membrane will be disrupted leading to haemolysis and vaso-occlusive events. Recent studies have also shown that leucocyte adhesion molecules and nitric oxide (NO) depletion are involved in endothelial damage. New insights in SCA pathophysiology and vascular biology have shown that cell-derived microparticle (MP) generation is also involved in the vaso-occlusion. Endothelial damage is perpetuated by impaired production or increased consumption of protective modulators such as protein C, protein S and NO. New therapeutic interventions should address these aspects of SCA pathogenesis. To date, the only US-FDA-approved therapy to prevent painful vaso-occulsive episodes is hydroxyurea that reduces haemoglobin polymerisation in sickle cells by increasing the production of foetal haemoglobin and L-glutamine. However, several new drugs have been tested in the last years in randomised clinical trials. We here report an update on the current status of knowledge on SCA.

New Therapeutic Options for the Treatment of Sickle Cell Disease

Sickle cell disease (SCD; ORPHA232; OMIM # 603903) is a chronic and invalidating disorder distributed worldwide, with high morbidity and mortality. Given the disease complexity and the multiplicity of pathophysiological targets, development of new therapeutic options is critical, despite the positive effects of hydroxyurea (HU), for many years the only approved drug for SCD. New therapeutic strategies might be divided into (1) pathophysiology-related novel therapies and (2) innovations in curative therapeutic options such as hematopoietic stem cell transplantation and gene therapy. The pathophysiology related novel therapies are: a) Agents which reduce sickling or prevent sickle red cell dehydration; b) Agents targeting SCD vasculopathy and sickle cell-endothelial adhesive events; c) Anti-oxidant agents. This review highlights new therapeutic strategies in SCD and discusses future developments, research implications, and possible innovative clinical trials.

Cell cycle shift from G0/G1 to S and G2/M phases is responsible for increased adhesion of calcium oxalate crystals on repairing renal tubular cells at injured site

Renal tubular cell injury can enhance calcium oxalate monohydrate (COM) crystal adhesion at the injured site and thus may increase the stone risk. Nevertheless, underlying mechanism of such enhancement remained unclear. In the present study, confluent MDCK renal tubular cell monolayers were scratched to allow cells to proliferate and repair the injured site. At 12-h post-scratch, the repairing cells had significant increases in crystal adhesion capacity and cell proliferation as compared to the control. Cell cycle analysis using flow cytometry demonstrated that the repairing cells underwent cell cycle shift from G0/G1 to S and G2/M phases. Cyclosporin A (CsA) and hydroxyurea (HU) at sub-toxic doses caused cell cycle shift mimicking that observed in the repairing cells. Crystal-cell adhesion assay confirmed the increased crystal adhesion capacity of the CsA-treated and HU-treated cells similar to that of the repairing cells. These findings provide evidence indicating that cell cycle shift from G0/G1 to S and G2/M phases is responsible, at least in part, for the increased adhesion of COM crystals on repairing renal tubular cells at the injured site.

Genetic determinants related to pharmacological induction of foetal haemoglobin in transfusion-dependent HbE-β thalassaemia

Thalassaemia are the most common inherited autosomal recessive single gene disorders characterized by chronic hereditary haemolytic anaemia due to the absence or reduced synthesis of one or more of the globin chains. Haemoglobin E-β thalassaemia is the genotype responsible for approximately one half of all severe beta-thalassaemia worldwide. This study proposes to evaluate the effect of various molecular parameters on the response of hydroxyurea. Hydroxyurea was started at an initial dose of 10 mg/kg of body weight/day on 110 transfusion-dependent HbE-β thalassaemia patients. HbF level was measured by HPLC analysis. β-Thalassaemia mutations, XmnI and five other SNPs, and α-globin gene deletions and triplications were detected by ARMS-PCR, RFLP-PCR and Gap-PCR, respectively. Based on the factors for evaluating hydroxyurea-response, 42 patients were responders as they showed an increment of Hb from a mean baseline value of 6.45 g/dl (± 0.70) to 7.78 g/dl (± 0.72) post-therapy. Based on increase in HbF above the median value (14.72%) post-therapy, 78 patients were found to be responders. All the 78 responders showed mean decrease in transfusion of 74.26% (± 8.32) with a maximum decrease of 98.43%. There was a significant correlation between decrease in transfusion and increase in HbF level for all 78 responders. XmnI polymorphism showed the strongest association (p < 0.0001) with increase in HbF levels and Hb levels. Patients with α-globin gene deletions were better responders. It was concluded that hydroxyurea treatment is effective in transfusion-dependent HbE-β thalassaemia patients and the response is best in patients having both XmnI polymorphism and α-deletion.

Pharmacoproteomics Profiling of Plasma From β-Thalassemia Patients in Response to Hydroxyurea Treatment

β-Thalassemia is a genetic disorder caused by defects in the β-globin gene resulting in the absence or reduced synthesis of adult hemoglobin (HbA). Hydroxyurea is an effective drug to increase fetal γ-globin (HbF) expression, replacing the missing adult β-globin. The mechanism of HbF induction by hydroxyurea and improvement in clinical symptoms are still poorly understood. In the present study we performed comparative analysis of plasma proteome in pre- and post-hydroxyurea-treated β-thalassemia major transfusion-dependent children (n = 10, mean age = 3.2 years) as well as responders versus nonresponders to hydroxyurea treatment. Plasma was collected before and after 6 months of hydroxyurea treatment, with patients subcategorized on the basis of their response to hydroxyurea. Among 400 identified proteins using a label-free quantitative proteomics approach, 28 proteins were found to be significantly different in pre- versus post-hydroxyurea-treated groups, with transferrin receptor protein-1 being most downregulated and hemopexin and haptoglobin the most upregulated proteins after treatment. In responder versus nonresponder comparison, 26 proteins were found to be differentially expressed, with carbonic anhydrase 1, hemoglobin subunit γ-1, and peroxiredoxin-2 showing the significant changes. The mechanism of hydroxyurea treatment in β-thalassemia patients appears to be complex, requiring a large sample size and a longer period of treatment to reveal its details.

Protective role of nimbolide against chemotherapeutic drug hydroxyurea induced genetic and oxidative damage in an animal model

Nimbolide is known to be an antioxidant found in neem plant. Hydroxyurea is a medication frequently used in sickle-cell disease, different cancers and HIV infection. The present study aimed to evaluate the adverse effect of HU and possible amelioration by nimbolide in Wistar rats. To test our hypothesis, we performed genotoxicity tests, biochemical assays, and histopathological studies. We observed that HU caused higher levels of genotoxicity in the treated animals. The observed genetic and oxidative damage might be due to the presence of reactive species as HU increased the level of the malondialdehyde-a biomarker of oxidative damage. Interestingly, co-treatment of animals with HU and nimbolide showed a lower level of damage. We conclude that nimbolide significantly protects the cells from the adverse effect of HU and could be considered as a potential adjuvant for the patients under HU therapy.

Loss of Wilms tumor 1 protein is a marker for apoptosis in response to replicative stress in leukemic cells

A remaining expression of the transcription factor Wilms tumor 1 (WT1) after cytotoxic chemotherapy indicates remaining leukemic clones in patients. We determined the regulation and relevance of WT1 in leukemic cells exposed to replicative stress and DNA damage. To induce these conditions, we used the clinically relevant chemotherapeutics hydroxyurea and doxorubicin. We additionally treated cells with the pro-apoptotic kinase inhibitor staurosporine. Our data show that these agents promote apoptosis to a variable extent in a panel of 12 leukemic cell lines and that caspases cleave WT1 during apoptosis. A chemical inhibition of caspases as well as an overexpression of mitochondrial, anti-apoptotic BCL2 family proteins significantly reduces the processing of WT1 and cell death in hydroxyurea-sensitive acute promyelocytic leukemia cells. Although the reduction of WT1 correlates with the pharmacological efficiency of chemotherapeutics in various leukemic cells, the elimination of WT1 by different strategies of RNA interference (RNAi) does not lead to changes in the cell cycle of chronic myeloid leukemia K562 cells. RNAi against WT1 does also not increase the extent of apoptosis and the accumulation of γH2AX in K562 cells exposed to hydroxyurea. Likewise, a targeted genetic depletion of WT1 in primary oviduct cells does not increase the levels of γH2AX. Our findings position WT1 as a downstream target of the apoptotic process that occurs in response to cytotoxic forms of replicative stress and DNA damage.