Sickle cell disease vasculopathy: a state of nitric oxide resistance

Arginine Therapy for Pain in Sickle Cell Disease: A Phase-2 Randomized, Placebo-Controlled Trial

We present a prospective randomized, placebo-controlled trial of intravenous arginine in patients 3-21 years hospitalized with sickle cell disease vaso-occlusive pain episodes (SCD-VOE) at two tertiary-care children's hospitals. Participants were randomized into 1 of 3 arms: Standard-dose (SD; 100 mg/kg/dose) every 8 h, Loading-dose (200 mg/kg followed by SD), or Placebo. The primary outcome was total parenteral opioid use (TPO). Secondary outcomes included time-to-crisis-resolution, pain scores, patient-reported outcomes (PROs), arginine bioavailability, and biomarkers of oxidative stress/mitochondrial function. Of 1548 patients screened, 108 were randomized (36 per study-arm; mean 12.6 ± 3.8 years, 52% female, and 65% hemoglobin-SS). This study did not meet its primary endpoint. TPO, time-to-crisis-resolution, pain scores, and PROs at discharge were similar across arms. Post hoc sensitivity analyses of children 5-16 years old demonstrated nearly double TPO utilization in those receiving placebo versus arginine (n = 87, p = 0.056), achieving significance in patients with plasma arginine < 60 μM. Arginine was low at presentation in 79% of patients (mean 50 ± 28 μM), and increased with arginine therapy (p < 0.001). Arginine bioavailability at VOE presentation inversely correlated with time-to-crisis-resolution (r = -0.39, p = 0.01) after placebo, an association eliminated by arginine supplementation (r = -0.04, p = 0.70). A dose-dependent increase in platelet-mitochondrial activity occurred after arginine versus no change after placebo (p < 0.001); plasma protein-carbonyl levels, a measure of oxidative stress, decreased after arginine therapy (p < 0.001) but increased in the placebo group (p = 0.02). SCD-VOE is associated with an acquired arginine deficiency that correlates with worse clinical outcomes. Arginine improved mitochondrial function and decreased oxidative stress compared to placebo, with clinically relevant opioid-sparing becoming significant in children with the lowest arginine concentration. TRIAL REGISTRATION: Registered with ClinicalTrials.gov (NCT02536170) in August 2015.

Disrupted homeostasis in sickle cells: Expanding the comprehension of metabolism adaptation and related therapeutic strategies

Sickle cell disease (SCD) is a hereditary hemolytic anemia associated with the alteration of the membrane composition of the sickle erythrocytes, the loss of glycolysis, dysregulation of the pyruvate phosphatase pathway, and changes in nucleotide metabolism of the sickle red blood cell (RBC). This review provides a comprehensive overview of the impact of the presence of Hb S, which leads to the disruption of the normal RBC metabolism. The intricate interplay between the redox and energetic balance in erythrocytic cells, where the glycolysis, pentose phosphate pathway, and methemoglobin reductase pathways are all altered in sickle RBC, is a key focus. Moreover, this review summarizes the current knowledge about the disease-modifying agents and their action mechanisms based on the sickle RBC alterations previously mentioned (i.e., their association with beneficial effects on the sickle cells' membrane, to their RBCs' energy metabolism, and to their oxidative status). Therefore, providing a comprehensive understanding of how sickle cells cope with the disruption of metabolic homeostasis and the most promising therapeutic agents able to ameliorate the various consequences of abnormal sickle RBC alterations.

Erectile Dysfunction and Oxidative Stress: A Narrative Review

Erectile dysfunction (ED) is a prevalent condition affecting male sexual health, characterized by the inability to achieve or maintain satisfactory erections. ED has a multifactorial pathogenesis in which psychological, hormonal, neurologic, cardiovascular, and lifestyle factors all contribute to a progressive decline of erectile function. A critical underlying mechanism involves oxidative stress (OS), an imbalance between reactive oxygen species (ROS) production and antioxidant defenses, which disrupts endothelial function, reduces nitric oxide (NO) bioavailability, and contributes to vascular dysfunction. This narrative review explores the interplay between OS and ED, focusing on the roles of ROS sources such as NADPH oxidase, xanthine oxidase, uncoupled nitric oxide synthase, and mitochondrial dysfunction. It examines the impact of OS on chronic conditions like hypertension, diabetes mellitus, hyperlipidemia, hypogonadism, and lifestyle factors like smoking and obesity, which exacerbate ED through endothelial and systemic effects. Emerging research underscores the potential of antioxidant therapies and lifestyle interventions to restore redox balance, improve endothelial function, and mitigate ED's progression. This review also highlights gaps in understanding the molecular pathways linking ROS to ED, emphasizing the need for further research to develop targeted therapeutic strategies.

Enhanced vasoconstriction in sickle cell disease is dependent on ETA receptor activation

Sickle cell disease (SCD) carries a significant risk for poor vascular health and vascular dysfunction. High levels of vascular reactive oxygen species (ROS) as well as elevated plasma endothelin-1 (ET-1), a potent vasoconstrictor with actions via the ETA receptor, are both common phenotypes in SCD. Alpha-1 adrenergic receptor activation is a major mediator of stress-induced vasoconstriction. However, the mechanism of the SCD enhanced vasoconstrictive response is unknown. We hypothesized that SCD induces enhanced alpha-1 adrenergic mediated vasoconstriction through the ET-1/ETA receptor pathway in arterial tissues. Utilizing humanized SCD (HbSS) and genetic control (HbAA) mice, alpha-1a, but not alpha-1b or alpha-1d, receptor expression was significantly greater in aortic tissue from HbSS mice compared to HbAA mice. Significantly enhanced vasoconstriction in aortic and carotid arterial segments were observed from HbSS mice compared with HbAA mice. Treatment with ambrisentan, a selective ETA receptor antagonist, and a ROS scavenger normalized the aortic vasoconstrictive response in HbSS mice. In a randomized translational study, patients with SCD were treated with placebo or ambrisentan for 3 months, with the treatment group showing an increase in the percent brachial arterial diameter. Taken together, these data suggest that the ETA receptor pathway interaction with the adrenergic receptor pathway contributes to enhanced aortic vasoconstriction in SCD. Findings indicate the potential of ETA antagonism as a therapeutic avenue for improving vascular health in SCD.

Clinical Insights into Sickle Cell Disease: A Comprehensive Multicenter Retrospective Analysis of Clinical Characteristics and Outcomes Across Different Age Groups

Background: Sickle cell disease (SCD) is a genetic hematological disorder associated with significant mortality and a range of complex complications that manifest differently across various age groups. Methods: This study aimed to evaluate the demographic, clinical, and laboratory characteristics of SCD patients in Taif City, Saudi Arabia, with a focus on variations among children, adolescents, adults, and middle-aged individuals. A multicenter retrospective cohort study included 129 patients with confirmed diagnosis of SCD between January 2018 to October 2023 and divided into 4 cohorts. The analysis compared hospital stay durations, admission rates, SCD complications, and medication usage. Results: Among the participants, 35 were children (27%), 18 adolescents (14%), 63 adults (49%), and 13 middle-aged individuals (10%). Clinical complications as splenic disease in children (34.3%) were more frequent compared to adolescents (5.6%) and adults (4.8%). Additionally, chronic kidney disease was more prevalent in middle-aged patients (15.4%). Pain was reported in 65.1% of patients, with vascular occlusive crises occurring in 41.1%. Treatment adherence varied, with children showing higher penicillin use (74.3%), while opioid usage was greater in middle-aged patients (76.9%). Conclusions: The findings underscore the necessity for age-specific management strategies in SCD. Further research with larger populations is suggested to enhance the understanding of disease progression and treatment efficacy across different age groups.

Prevalence and associated risk factors of myocardial ischemia in children living with sickle cell anemia in Lagos, Nigeria

Myocardial ischemia (MI) in children living with sickle cell anemia (SCA) is rarely reported. MI among children living with this disease could portend untoward outcomes on their quality of life and survival. This study evaluated the prevalence and associated risk factors of MI in children living with SCA during a vaso-occlusive crisis (VOC) compared with those with SCA who had no symptoms nor an MI in the past (those in "steady state") in Lagos, Nigeria. This comparative cross-sectional study was conducted over 10 months (between March and December 2019) among 250 children living with SCA aged 6 months-18 years (125 in VOC and 125 age and sex-matched controls in steady state). The assessment of MI was determined by measuring cardiac troponin T (cTnT) and electrocardiography (ECG). The prevalence of MI measuring cTnT alone in children with SCA during VOC and steady state was 42.4% and 23.2%, respectively. Comparatively, measuring ECG alone, the prevalence of MI in VOC and steady state was 40.8% and 20.8%, respectively. The prevalence of MI measuring cTnT and ECG in children with SCA in VOC and steady state was 38.4% and 20%, respectively. Older age, severity of pain, longer duration of illness, frequent crises per year, elevated white blood cells, and platelet count were significantly associated with MI in participants with SCA. However, with multivariate analysis, age, severity of pain, and elevated platelet counts remained significantly associated with the occurrence of MI. This study affirms the high prevalence of MI in children with SCA irrespective of the diagnostic criteria. Routine evaluation should be done in this cohort to avert MI-associated sequelae.

Oxidative Stress and Erectile Dysfunction: Pathophysiology, Impacts, and Potential Treatments

Erectile dysfunction (ED) is a prevalent condition affecting men's sexual health, with oxidative stress (OS) having recently been identified as a significant contributing causative factor. This narrative review aims to elucidate the role of OS in the pathophysiology of ED, focusing on impact, mechanisms, and potential therapeutic interventions. Key findings indicate that OS disrupts endothelial function and nitric oxide (NO) signaling, crucial for erectile function. Various sources of reactive oxygen species (ROS) and their detrimental effects on penile tissue are discussed, including aging, diabetes mellitus, hypertension, hyperlipidemia, smoking, obesity, alcohol consumption, psychological stress, hyperhomocysteinemia, chronic kidney disease, and sickle cell disease. Major sources of ROS, such as NADPH oxidase, xanthine oxidase, uncoupled endothelial NO synthase (eNOS), and mitochondrial electron transport, are identified. NO is scavenged by these ROS, leading to endothelial dysfunction characterized by reduced NO availability, impaired vasodilation, increased vascular tone, and inflammation. This ultimately results in ED due to decreased blood flow to penile tissue and the inability to achieve or maintain an erection. Furthermore, ROS impact the transmission of nitrergic neurotransmitters by causing the death of nitrergic neurons and reducing the signaling of neuronal NO synthase (nNOS), exacerbating ED. Therapeutic approaches targeting OS, including antioxidants and lifestyle modifications, show promise in ameliorating ED symptoms. The review underscores the need for further research to develop effective treatments, emphasizing the interplay between OS and vascular health in ED. Integrating pharmacological and non-pharmacological strategies could enhance clinical outcomes for ED patients, advocating for OS management in ED treatment protocols to improve patient quality of life.

Exploring the Impact of Naphthalene (Polycyclic Aromatic Hydrocarbons) on Anabas testudineus (Bloch) through Dose-Specific Bioenzymological Analysis

This study addresses the increasing concern about naphthalene, a polycyclic aromatic hydrocarbon (PAH), highlighting its growing threats to the environment and aquatic life. The research examines its impact on Anabas testudineus (Bloch) through a detailed dose-specific bioenzymological analysis. Experimental fish groups were exposed to T1 (0.71 mg/L) and T2 (1.42 mg/L) naphthalene concentrations, representing 25 and 50% of the LC50 value, respectively, over a 1-21 day period. Following the experiment, water samples underwent physicochemical analysis, while fish tissues were examined for diverse bioenzymological parameters. Among these parameters, aspirate aminotransferase (AST) and alanine aminotransferase (ALT) serve as crucial indicators for monitoring the physiological status of fish and addressing pollution induced by PAHs, especially naphthalene. Statistical significance was observed in morpho-pathological changes and erythrocyte alterations, particularly the presence of tear-drop appearance (Tr) positively interacting with swelled cells (Sc), vacuolated cells (Va), and sickle cells (Sk) (P < 0.05). These findings highlight tear-drop appearance (Tr) as a significant biomarker in response to naphthalene exposure. The observed changes in A. testudineus tissue bioenzymology, apoptosis, and erythrocytic alterations were exposure and dose-dependent. The research highlights the significance of overseeing and controlling PAH concentrations in aquatic ecosystems to ensure the well-being of A. testudineus (Bloch).

Sterile inflammation induces vasculopathy and chronic lung injury in murine sickle cell disease

Murine sickle cell disease (SCD) results in damage to multiple organs, likely mediated first by vasculopathy. While the mechanisms inducing vascular damage remain to be determined, nitric oxide bioavailability and sterile inflammation are both considered to play major roles in vasculopathy. Here, we investigate the effects of high mobility group box-1 (HMGB1), a pro-inflammatory damage-associated molecular pattern (DAMP) molecule on endothelial-dependent vasodilation and lung morphometrics, a structural index of damage in sickle (SS) mice. SS mice were treated with either phosphate-buffered saline (PBS), hE-HMGB1-BP, an hE dual-domain peptide that binds and removes HMGB1 from the circulation via the liver, 1-[4-(aminocarbonyl)-2-methylphenyl]-5-[4-(1H-imidazol-1-yl)phenyl]-1H-pyrrole-2-propanoic acid (N6022) or N-acetyl-lysyltyrosylcysteine amide (KYC) for three weeks. Human umbilical vein endothelial cells (HUVEC) were treated with recombinant HMGB1 (r-HMGB1), which increases S-nitrosoglutathione reductase (GSNOR) expression by ∼80%, demonstrating a direct effect of HMGB1 to increase GSNOR. Treatment of SS mice with hE-HMGB1-BP reduced plasma HMGB1 in SS mice to control levels and reduced GSNOR expression in facialis arteries isolated from SS mice by ∼20%. These changes were associated with improved endothelial-dependent vasodilation. Treatment of SS mice with N6022 also improved vasodilation in SS mice suggesting that targeting GSNOR also improves vasodilation. SCD decreased protein nitrosothiols (SNOs) and radial alveolar counts (RAC) and increased GSNOR expression and mean linear intercepts (MLI) in lungs from SS mice. The marked changes in pulmonary morphometrics and GSNOR expression throughout the lung parenchyma in SS mice were improved by treating with either hE-HMGB1-BP or KYC. These data demonstrate that murine SCD induces vasculopathy and chronic lung disease by an HMGB1- and GSNOR-dependent mechanism and suggest that HMGB1 and GSNOR might be effective therapeutic targets for reducing vasculopathy and chronic lung disease in humans with SCD.

Exploration de l’hémolyse associée à la drépanocytose et perspectives thérapeutiques spécifiques

Sickle Cell Anemia is a disease with a strong vascular tropism. Beyond anemia, the pathophysiological mechanisms responsible for hemolysis, directly affect both acute and chronic vascular damages, thus resulting in a systemic disease. Understanding the different types of hemolysis underline the need for novel specific biomarkers. Targeted therapeutic approaches for these pathophysiological pathways are necessary to improve Sickle Cell patients' prognosis. Finally, given its complexity, Sickle Cell Disease is often used as a "proof of concept" for other pathologies. It seems likely that the rapidly evolving knowledge in this field will also benefit other diseases. © 2023 Société nationale française de médecine interne (SNFMI). Published by Elsevier Masson SAS. All rights reserved.

Update on Treatment Options for Stuttering Priapism

Purpose of Review

There is a paucity of peer-reviewed evidence to guide medical management of stuttering priapism. The purpose of this review is to summarize the current understanding regarding the pathophysiology of priapism and management options for stuttering priapism.

Recent Findings

Conducting large-scale, randomized, placebo-controlled trials that elucidate the optimal treatment of stuttering priapism is challenging. Therefore, recent treatment guidelines are based upon small case series, retrospective studies, and expert opinions. Nonetheless, multiple compounds from various drug classes have shown promise in treating stuttering priapism, and a few pharmacotherapies such as Crizanlizumab are currently under active investigation.

Summary

Stuttering priapism is an under-investigated disorder with a complex pathophysiology. Currently, there is no wildly adopted universal therapeutic strategy. Further research is warranted to identify the appropriate treatment of stuttering priapism and to determine the long-term side effects of current pharmacotherapies.

Omega 3 fatty acids - Potential modulators for oxidative stress and inflammation in the management of sickle cell disease

OBJECTIVE

Sickle cell disease is characterized by clinical complications resulting in vaso-occlusive crisis with prominent attributes of oxidative stress, inflammation, and pain. Inflammation is an integral part of this disease which further exacerbates the pain during a crisis. Omega-3 fatty acids are known to possess anti-inflammatory and anti-aggregatory properties and assist in diminishing the slow physiological inactivation.

METHODS

A pilot nutritional interventional study was conducted wherein forty-three children with sickle cell disease aged 5-16 years were supplemented with omega-3 fatty acids for a period of six months. Analysis of oxidative stress, as well as inflammatory parameters, was done pre and post-supplementation.

RESULTS

Increased free oxygen radical transference values depicting free radical generation is enhanced in these patients along with a reduced antioxidant defense, as seen by decreased free oxygen radical defense values. Supplementation with omega-3 fatty acids for a period of six months significantly reduced the inflammatory marker homocysteine in all patients, whereas high sensitive C reactive protein was significantly reduced only in females of the age group 11-16years. Simultaneously a significant reduction in oxidative stress parameters with a concomitant increase of antioxidant defense was observed in all patients.

CONCLUSION

The authors' findings suggest the regulatory effects of omega-3 fatty acids as cellular activators in alleviating the complications due to sickle cell disease. Omega-3 fatty acids hold promise as future therapeutic candidates in patients with sickle cell disease.

Underutilized legumes, Cajanus cajan and Glycine max may bring about antisickling effect in sickle cell disease by modulation of redox homeostasis in sickled erythrocytes and alteration of its functional chemistry

The antisickling and anti-oxidative effect of the Cajanus cajan, Glycine max, and their blends were investigated in sickled erythrocytes. The powdered samples were analyzed for their nutritional and anti-nutritional constituents. Their aqueous extracts were analyzed for in vitro antioxidant activities. The extracts were incubated with sickled erythrocytes at 37°C for 6 hours and the antisickling effect examined via microscopic analysis. The blend was the most active and its incubated cells were subjected to anti-oxidative analysis which covers for GSH, SOD, catalase, and lipid peroxidation (LPO). Chemical functional group of the treated cells was analyzed with FTIR spectroscopy. The in silico binding of the predominant amino acid to hemoglobin was also investigated. An increased concentration of leucine was observed in the blend compared to that of C. cajan and G. max, respectively. Vitamins C, B6, and B9 were the only vitamins observed in the blend. Phytate and oxalate were present in all samples. All extracts displayed significant (p < .05) scavenging activities. Treatment with the blend exacerbated SOD and catalase activities as well as the GSH level, while suppressing LPO. FTIR analysis of the treated cells showed the presence of hydrophobic functional groups. Leucine was the predominant amino acid, and it showed a potent molecular interaction with HIS-87 residue of the alpha chain of 1HCO. C. cajan and G. max blend inhibited sickling activities of sickle erythrocytes, while concomitantly exacerbating their endogenous antioxidant enzymes activity and modification of the functional chemistry. PRACTICAL APPLICATIONS: Cajanus cajan and Glycine max are among the common underutilized legumes in Nigeria. Aside their nutritional properties, these legumes have been used from time immemorial for the treatment and management of various ailments. Sickle cell anemia is a class of hemoglobinopathy common in Sub-Saharan Africa. There have been concerns about its treatment owing to the increasing scourge of the disease coupled to the financial burden of its management. This study reports the ability of the potentials of the legumes to prevent sickling activities of sickled erythrocytes and the possible biochemical mechanism involved.

Metabolic Reprogramming in Sickle Cell Diseases: Pathophysiology and Drug Discovery Opportunities

Sickle cell disease (SCD) is a genetic disorder that affects millions of individuals worldwide. Chronic anemia, hemolysis, and vasculopathy are associated with SCD, and their role has been well characterized. These symptoms stem from hemoglobin (Hb) polymerization, which is the primary event in the molecular pathogenesis of SCD and contributes to erythrocyte or red blood cell (RBC) sickling, stiffness, and vaso-occlusion. The disease is caused by a mutation at the sixth position of the β-globin gene, coding for sickle Hb (HbS) instead of normal adult Hb (HbA), which under hypoxic conditions polymerizes into rigid fibers to distort the shapes of the RBCs. Only a few therapies are available, with the universal effectiveness of recently approved therapies still being monitored. In this review, we first focus on how sickle RBCs have altered metabolism and then highlight how this understanding reveals potential targets involved in the pathogenesis of the disease, which can be leveraged to create novel therapeutics for SCD.

Aphrodisiac Performance of Bioactive Compounds from Mimosa pudica Linn.: In Silico Molecular Docking and Dynamics Simulation Approach

Plants and their derived molecules have been traditionally used to manage numerous pathological complications, including male erectile dysfunction (ED). Mimosa pudica Linn. commonly referred to as the touch-me-not plant, and its extract are important sources of new lead molecules in drug discovery research. The main goal of this study was to predict highly effective molecules from M. pudica Linn. for reaching and maintaining penile erection before and during sexual intercourse through in silico molecular docking and dynamics simulation tools. A total of 28 bioactive molecules were identified from this target plant through public repositories, and their chemical structures were drawn using Chemsketch software. Graph theoretical network principles were applied to identify the ideal target (phosphodiesterase type 5) and rebuild the network to visualize the responsible signaling genes, proteins, and enzymes. The 28 identified bioactive molecules were docked against the phosphodiesterase type 5 (PDE5) enzyme and compared with the standard PDE5 inhibitor (sildenafil). Pharmacokinetics (ADME), toxicity, and several physicochemical properties of bioactive molecules were assessed to confirm their drug-likeness property. Molecular dynamics (MD) simulation modeling was performed to investigate the stability of PDE5–ligand complexes. Four bioactive molecules (Bufadienolide (−12.30 kcal mol⁻¹), Stigmasterol (−11.40 kcal mol⁻¹), Isovitexin (−11.20 kcal mol⁻¹), and Apigetrin (−11.20 kcal mol⁻¹)) showed the top binding affinities with the PDE5 enzyme, much more powerful than the standard PDE5 inhibitor (−9.80 kcal mol⁻¹). The four top binding bioactive molecules were further validated for a stable binding affinity with the PDE5 enzyme and conformation during the MD simulation period as compared to the apoprotein and standard PDE5 inhibitor complexes. Further, the four top binding bioactive molecules demonstrated significant drug-likeness characteristics with lower toxicity profiles. According to the findings, the four top binding molecules may be used as potent and safe PDE5 inhibitors and could potentially be used in the treatment of ED.

Attitudes and practices of unmarried adults towards sickle cell disease: emergent factors from a cross sectional study in Nigeria's capital

INTRODUCTION

Sickle cell disease is a genetic autosomal blood disorder that causes red blood cells to turn rigid and crescent shaped. The condition ultimately results to several complications leading to organ damage. This study aimed at assessing attitudes and practices of unmarried adults towards sickle cell disease.

METHODS

A cross sectional study was undertaken in the Nigerian Federal Capital Territory. Data were collected using a well-structured questionnaire. Descriptive and inferential statistics were undertaken.

RESULTS

Male and female participants were of a similar proportion as represented by 52% and 48%. The overall mean score for attitude towards sickle disease was 6.60 ± 2.583 (range; 0-11). A higher attitude score was observed among female participants (p = 0.012), older participants reported a better attitude towards sickle cell disease (p < 0.001), and level of education also influenced perception towards the disease (p < 0.001). Three-quarters of the participants (73.4%) supported the need for contextual legislation to prohibit marriage between two sickle cell carriers. More than one-tenth of the sample (14.4%) indicated that they would marry someone with sickle cell disease irrespective of their own genotype. Whilst two-thirds of the study participants (67.1%) indicated that they would prioritise sickle cell screening in their relationships, a third of them (33.3%) expressed a contrary standpoint.

CONCLUSION

Findings emanating from this research can guide Government and other critical Stakeholders in developing contextual policies and practices that will reduce the burden of sickle cell disorder.

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).

Human erythrocytes, nuclear factor kappaB (NFκB) and hydrogen sulfide (H2S) - from non-genomic to genomic research

Enucleated mature human erythrocytes possess NFĸBs and their upstream kinases. There is a negative correlation between eryptosis (cell death of erythrocytes) and the amount of NFĸB subunits p50 and Rel A (p65). This finding is based on the fact that young erythrocytes have the highest levels of NFĸBs and the lowest eryptosis rate, while in old erythrocytes the opposite ratio prevails. Human erythrocytes (hRBCs) effectively control the homeostasis of the cell membrane permeable anti-inflammatory signal molecule hydrogen sulfide (H2S). They endogenously produce H2S via both non-enzymic (glutathione-dependent) and enzymic processes (mercaptopyruvate sulfur transferase-dependent). They uptake H2S from diverse tissues and very effectively degrade H2S via methemoglobin (Hb-Fe3+)-catalyzed oxidation. Interestingly, a reciprocal correlation exists between the intensity of inflammatory diseases and endogenous levels of H2S. H2S deficiency has been observed in patients with diabetes, psoriasis, obesity, and chronic kidney disease (CKD). Furthermore, endogenous H2S deficiency results in impaired renal erythropoietin (EPO) production and EPO-dependent erythropoiesis. In general we can say: dynamic reciprocal interaction between tumor suppressor and oncoproteins, orchestrated and sequential activation of pro-inflammatory NFĸB heterodimers (RelA-p50) and the anti-inflammatory NFĸB-p50 homodimers for optimal inflammation response, appropriate generation, subsequent degradation of H2S etc., are prerequisites for a functioning cell and organism. Diseases arise when the fragile balance between different signaling pathways that keep each other in check is permanently disturbed. This work deals with the intact anti-inflammatory hRBCs and their role as guarantors to maintain the redox status in the physiological range, a basis for general health and well-being.

Deficient mitophagy pathways in sickle cell disease

Sickle cell disease (SCD) is characterised by chronic haemolysis and oxidative stress. Herein, we investigated 30 SCD patients and found 40% with elevated mitochondria levels (SS-mito⁺ ) in their mature red blood cells, while 60% exhibit similar mitochondria levels compared to the AA group (SS-mito^- ). The SS-mito⁺ patients are characterised by higher reticulocytosis and total bilirubin levels, lower foetal haemoglobin, and non-functional mitochondria. Interestingly, we demonstrated decreased levels of mitophagy inducers, PINK1 and NIX, and higher levels of HSP90 chaperone in their red cells. Our results highlighted for the first time an abnormal retention of mitochondria in SCD linked with mitophagy-related proteins.

The Worst Things in Life are Free: The Role of Free Heme in Sickle Cell Disease

Hemolysis is a pathological feature of several diseases of diverse etiology such as hereditary anemias, malaria, and sepsis. A major complication of hemolysis involves the release of large quantities of hemoglobin into the blood circulation and the subsequent generation of harmful metabolites like labile heme. Protective mechanisms like haptoglobin-hemoglobin and hemopexin-heme binding, and heme oxygenase-1 enzymatic degradation of heme limit the toxicity of the hemolysis-related molecules. The capacity of these protective systems is exceeded in hemolytic diseases, resulting in high residual levels of hemolysis products in the circulation, which pose a great oxidative and proinflammatory risk. Sickle cell disease (SCD) features a prominent hemolytic anemia which impacts the phenotypic variability and disease severity. Not only is circulating heme a potent oxidative molecule, but it can act as an erythrocytic danger-associated molecular pattern (eDAMP) molecule which contributes to a proinflammatory state, promoting sickle complications such as vaso-occlusion and acute lung injury. Exposure to extracellular heme in SCD can also augment the expression of placental growth factor (PlGF) and interleukin-6 (IL-6), with important consequences to enthothelin-1 (ET-1) secretion and pulmonary hypertension, and potentially the development of renal and cardiac dysfunction. This review focuses on heme-induced mechanisms that are implicated in disease pathways, mainly in SCD. A special emphasis is given to heme-induced PlGF and IL-6 related mechanisms and their role in SCD disease progression.

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

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

Interventions for treating leg ulcers in people with sickle cell disease

BACKGROUND

The frequency of skin ulceration makes an important contributor to the morbidity burden in people with sickle cell disease. Many treatment options are available to the healthcare professional, although it is uncertain which treatments have been assessed for effectiveness in people with sickle cell disease. This is an update of a previously published Cochrane Review.

OBJECTIVES

To assess the clinical effectiveness and harms of interventions for treating leg ulcers in people with sickle cell disease.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Haemoglobinopathies Trials Register. We searched LILACS (1982 to January 2020), ISI Web of Knowledge (1985 to January 2020), and the Clinical Trials Search Portal of the World Health Organization (January 2020). We checked the reference lists of all the trials identified. We also contacted those groups or individuals who may have completed relevant randomised trials in this area. Date of the last search of the Cochrane Cystic Fibrosis and Genetic Disorders Group's Haemoglobinopathies Trials Register: 13 January 2020; date of the last search of the Cochrane Wounds Group Trials Register: 17 February 2017.

SELECTION CRITERIA

Randomised controlled trials of interventions for treating leg ulcers in people with sickle cell disease compared to placebo or an alternative treatment.

DATA COLLECTION AND ANALYSIS

Two authors independently selected studies for inclusion. All three authors independently assessed the risk of bias of the included studies and extracted data. We used GRADE to assess the quality of the evidence.

MAIN RESULTS

Six studies met the inclusion criteria (198 participants with 250 ulcers). Each trial investigated a different intervention and within this review we have grouped these as systemic pharmaceutical interventions (L-cartinine, arginine butyrate, isoxsuprine) and topical pharmaceutical interventions (Solcoseryl® cream, arginine-glycine-aspartic acid (RGD) peptide dressing and topical antibiotics). No trials on non-pharmaceutical interventions were included in the review. All trials had an overall unclear or high risk of bias, and drug companies sponsored four of them. We were unable to pool findings due to the heterogeneity in outcome definitions, and inconsistency between the units of randomisation and analysis. Three interventions reported on the change in ulcer size (arginine butyrate, RGD peptide, L-cartinine). Of these, only arginine butyrate showed a reduction of ulcer size compared with a control group, mean reduction -5.10 cm² (95% CI -9.65 to -0.55), but we are uncertain whether this reduces ulcer size compared to standard care alone as the certainty of the evidence has been assessed as very low. Three trials reported on complete leg ulcer closure (isoxsuprine, arginine butyrate, RGD peptide matrix; very low quality of evidence). None reported a clinical benefit. No trial reported on: the time to complete ulcer healing; ulcer-free survival following treatment for sickle cell leg ulcers; quality of life measures; incidence of amputation or harms.

AUTHORS' CONCLUSIONS

Given the very low quality of the evidence identified in this updated Cochrane Review we are uncertain whether any of the assessed pharmaceutical interventions reduce ulcer size or result in leg ulcer closure in treated participants compared to controls. However, this intervention was assessed as having a high risk of bias due to inadequacies in the single trial report. Other included studies were also assessed as having an unclear or high risk of bias. The harm profile of the all interventions remains inconclusive.

Nitric oxide and sickle cell disease-Is there a painful connection?

Sickle cell disease is the most common hemoglobinopathy and affects millions worldwide. The disease is associated with severe organ dysfunction, acute and chronic pain, and significantly decreased life expectancy. The large body of work demonstrating that hemolysis results in rapid consumption of the endogenous vasodilator nitric oxide, decreased nitric oxide production, and promotion of vaso-occlusion provides the basis for the hypothesis that nitric oxide bioavailability is reduced in sickle cell disease and that this deficit plays a role in sickle cell disease pain. Despite initial promising results, large clinical trials using strategies to increase nitric oxide bioavailability in sickle cell disease patients yielded no significant change in duration or frequency of acute pain crises. Further, recent investigations showed that sickle cell disease patients and mouse models have elevated baseline levels of blood nitrite, a reservoir for nitric oxide formation and a product of nitric oxide metabolism, regardless of pain phenotype. These conflicting results challenge the hypotheses that nitric oxide bioavailability is decreased and that it plays a significant role in the pathogenesis in sickle cell disease acute pain crises. Conversely, a large body of work demonstrates that nitric oxide, as a neurotransmitter, has a complex role in pain neurobiology, contributes to the development of central sensitization, and can mediate hyperalgesia in inflammatory and neuropathic pain. These results support an alternative hypothesis: one proposing that altered nitric oxide signaling may contribute to the development of neuropathic and/or inflammatory pain in sickle cell disease through its role as a neurotransmitter.

Muscle structural, energetic and functional benefits of endurance exercise training in sickle cell disease

Sickle cell disease (SCD) patients display skeletal muscle hypotrophy, altered oxidative capacity, exercise intolerance and poor quality of life. We previously demonstrated that moderate-intensity endurance training is beneficial for improving muscle function and quality of life of patients. The present study evaluated the effects of this moderate-intensity endurance training program on skeletal muscle structural and metabolic properties. Of the 40 randomized SCD patients, complete data sets were obtained from 33. The training group (n = 15) followed a personalized moderate-intensity endurance training program, while the non-training (n = 18) group maintained a normal lifestyle. Biopsies of the vastus lateralis muscle and submaximal incremental cycling tests were performed before and after the training program. Endurance training increased type I muscle fiber surface area (P = .038), oxidative enzyme activity [citrate synthase, P < .001; β-hydroxyacyl-CoA dehydrogenase, P = .009; type-I fiber cytochrome c oxidase, P = .042; respiratory chain complex IV, P = .017] and contents of respiratory chain complexes I (P = .049), III (P = .005), IV (P = .003) and V (P = .002). Respiratory frequency, respiratory exchange ratio, blood lactate concentration and rating of perceived exertion were all lower at a given submaximal power output after training vs non-training group (all P < .05). The muscle content of proteins involved in glucose transport and pH regulation were unchanged in the training group relative to the non-training group. The moderate-intensity endurance exercise program improved exercise capacity and muscle structural and oxidative properties. This trial was registered at www.clinicaltrials.gov as #NCT02571088.

Decoding the role of SOD2 in sickle cell disease

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

Cardiovascular Sequelae of Sickle Cell Disease

Sickle cell disease (SCD) is one of the most common hereditary hemoglobinopathies worldwide. It is a multisystem disease that causes considerable patient morbidity. Despite advances in medical treatment, cardiopulmonary complications remain the most common cause of death in individuals with SCD. A growing body of evidence has shown that SCD results in a spectrum of cardiovascular complications through a variety of mechanisms, including chronic hemolysis, local tissue hypoxia, increased oxidative stress, and autonomic instability. Herein, we will examine the pathophysiology of sickle cell vasculopathy and discuss the spectrum of cardiovascular sequelae of the disease, while highlighting the impact of SCD on the cardiovascular health of the patients.

Effects of hypoxia-reoxygenation stimuli on renal redox status and nuclear factor erythroid 2-related factor 2 pathway in sickle cell SAD mice

NEW FINDINGS

What is the central question of this study? What are the effects of repeated subclinical vaso-occlusions on nuclear factor erythroid 2 related factor 2 (Nrf2) and oxidative stress balance regulation in the kidney of transgenic SAD mice? What is the main finding and its importance? In response to hypoxia-reoxygenation, nuclear Nrf2 protein expression decreased in the kidney of SAD mice while haem oxygenase transcripts were increased. This suggest that in SAD mice, other transcription factors than Nrf2 could be involved in renal antioxidant gene regulation in response to hypoxia-reoxygenation.

ABSTRACT

Hypoxia-reoxygenation (H/R) stress is known to increase oxidative stress in transgenic sickle mice and can cause organ failure. Here we described the effects of H/R on nuclear factor erythroid 2-related factor 2 (Nrf2) as a putative regulator of redox status in the kidneys of SAD mice investigating Nrf2-regulated antioxidant enzymes. Transgenic SAD mice and healthy C57Bl/6J mice were exposed to 4 h of hypoxia followed by various times of reoxygenation at ambient air (2 or 6 h). Regardless of the conditions (i.e. normoxia or H/R), SAD mice expressed higher renal oxidative stress levels. Nuclear Nrf2 protein expression decreased after 2 h post-hypoxia only in the medulla region of the kidney and only in SAD mice. Simultaneously, haem oxygenase transcripts were affected by H/R stimulus with a significant enhancement after 2 h post-hypoxia. Similarly, hypoxia inducible factor-1α staining increased after 2 h post-hypoxia in SAD mice in both cortex and medulla areas. Our data confirm that the kidneys are organs that are particularly sensitive to H/R stimuli in sickle cell SAD mice. Also, these results suggest an effect of the duration of recovery period (short vs. long) and specific responses according to kidney areas, medulla vs. cortex, on Nrf2 expression in response to H/R stimuli in SAD mice.

Antibiotics for treating osteomyelitis in people with sickle cell disease

BACKGROUND

Osteomyelitis (both acute and chronic) is one of the most common infectious complications in people with sickle cell disease. There is no standardized approach to antibiotic therapy and treatment is likely to vary from country to country. Thus, there is a need to identify the efficacy and safety of different antibiotic treatment approaches for people with sickle cell disease suffering from osteomyelitis. This is an update of a previously published Cochrane Review.

OBJECTIVES

To determine whether an empirical antibiotic treatment approach (monotherapy or combination therapy) is effective and safe as compared to pathogen-directed antibiotic treatment and whether this effectiveness and safety is dependent on different treatment regimens, age or setting.

SEARCH METHODS

We searched The Group's Haemoglobinopathies Trials Register, which comprises references identified from comprehensive electronic database searches and handsearching of relevant journals and abstract books of conference proceedings. We also searched the LILACS database (1982 to 20 October 2016), African Index Medicus (20 October 2016), ISI Web of Knowledge (20 October 2016) and clinical trials registries (19 September 2019).Date of most recent search of the Cochrane Cystic Fibrosis and Genetic Disorders Group's Haemoglobinopathies Trials Register: 18 September 2019.

SELECTION CRITERIA

We searched for published or unpublished randomised and quasi-randomised controlled trials.

DATA COLLECTION AND ANALYSIS

Each author intended to independently extract data and assess trial quality by standard Cochrane methodologies, but no eligible randomised controlled trials were identified.

MAIN RESULTS

This update was unable to find any randomised or quasi-randomised controlled trials on antibiotic treatment approaches for osteomyelitis in people with sickle cell disease.

AUTHORS' CONCLUSIONS

We were unable to identify any relevant trials on the efficacy and safety of the antibiotic treatment approaches for people with sickle cell disease suffering from osteomyelitis. Randomised controlled trials are needed to establish the optimum antibiotic treatment for this condition, however, we do not envisage further trials of this intervention will be conducted, and hence the review will no longer be regularly updated.

Antibiotics for treating acute chest syndrome in people with sickle cell disease

BACKGROUND

The clinical presentation of acute chest syndrome is similar whether due to infectious or non-infectious causes, thus antibiotics are usually prescribed to treat all episodes. Many different pathogens, including bacteria, have been implicated as causative agents of acute chest syndrome. There is no standardized approach to antibiotic therapy and treatment is likely to vary from country to country. Thus, there is a need to identify the efficacy and safety of different antibiotic treatment approaches for people with sickle cell disease suffering from acute chest syndrome. This is an update of a Cochrane Review first published in 2007, and most recently updated in 2015.

OBJECTIVES

To determine whether an empirical antibiotic treatment approach (used alone or in combination):1. is effective for acute chest syndrome compared to placebo or standard treatment;2. is safe for acute chest syndrome compared to placebo or standard treatment;Further objectives are to determine whether there are important variations in efficacy and safety:3. for different treatment regimens,4. by participant age, or geographical location of the clinical trials.

SEARCH METHODS

We searched The Group's Haemoglobinopathies Trials Register, which comprises references identified from comprehensive electronic database searches and handsearching of relevant journals and abstract books of conference proceedings. We also searched the LILACS database (1982 to 23 October 2017), African Index Medicus (1982 to 23 October 2017) and trial registries (23 October 2017).Date of most recent search of the Haemoglobinopathies Trials Register: 10 July 2019.

SELECTION CRITERIA

We searched for published or unpublished randomised controlled trials.

DATA COLLECTION AND ANALYSIS

Each author intended to independently extract data and assess trial quality by standard Cochrane methodologies, but no eligible randomised controlled trials were identified.

MAIN RESULTS

For this update, we were unable to find any randomised controlled trials on antibiotic treatment approaches for acute chest syndrome in people with sickle cell disease.

AUTHORS' CONCLUSIONS

This update was unable to identify randomised controlled trials on efficacy and safety of the antibiotic treatment approaches for people with sickle cell disease suffering from acute chest syndrome. While randomised controlled trials are needed to establish the optimum antibiotic treatment for this condition, we do not envisage further trials of this intervention will be conducted, and hence the review will no longer be regularly updated.

Serum levels of copper, zinc and disease severity scores in sickle cell disease patients in Benin City, Nigeria

BACKGROUND

Micronutrient deficiency is recognized in sickle cell anaemia (SCA) but it is not known for certain whether changes in zinc, copper and copper-to-zinc ratio are associated with Sickle cell disease severity scores.

OBJECTIVE

To compare serum levels of copper, zinc and copper-to-zinc ratio in SCA subjects with control group and correlate the variables with objective disease severity scores.

METHODS

Serum copper and zinc were determined in 100 SCA patients and 50 controls using kits supplied by Centronic, Germany. Unpaired Students't-test was used to compare the variables between SCA patients in steady clinical state, vaso-occlusive crisis and controls, while Spearman correlation coefficient was used to associate the parameters with disease severity scores.

RESULTS

Serum copper level was higher (P=0.008) in SCA patients than controls, while serum zinc level was lower (P<0.001) in SCA patients than controls. The copper/zinc ratio was higher (P<0.001) in SCA patients than controls. Significantly higher (P<0.001) copper and lower (P<0.001) zinc levels were observed in patients in vaso-occlusive crisis than in steady clinical state. Zinc correlated inversely (r=-0.2743; P=0.006) while copper-to-zinc ratio correlated positively with disease severity scores.

CONCLUSION

Copper-to-zinc ratio may be an indicator of disease severity in SCA patients.

Receptor for Advanced Glycation End Products Antagonism Blunts Kidney Damage in Transgenic Townes Sickle Mice

A large proportion of adult patients with sickle cell disease (SCD) develops kidney disease and is at a high risk of mortality. The contribution of advanced glycation end products and their receptor (AGE/RAGE) axis has been established in the pathogenesis of multiple kidney diseases. The aim of the present study was to determine the implication of RAGE in the development of SCD-related kidney complications in a mouse model of SCD, as this has never been investigated. 8-week-old AA (normal) and SS (homozygous SCD) Townes mice were treated with a specific RAGE antagonist (RAP) or vehicle (NaCl). After 3 weeks of treatment, red blood cell count, hematocrit, and hemoglobin levels were significantly higher in RAP-treated SS mice. Reticulocyte count and sickle cell count were reduced in RAP-SS compared to their NaCl-treated littermates. The lower NADPH oxidase activity in the kidney of RAP-treated mice compared to NaCl-treated mice suggests limited ROS production. RAP-treated SS mice had decreased NF-κB protein expression and activation as well as reduced TNF-α mRNA expression in the kidney. Glomerular area, interstitial fibrosis, tubular iron deposits, and KIM-1 protein expression were significantly reduced after RAP treatment. In conclusion, this study provides evidence supporting the pathogenic role of RAGE in kidney injuries in sickle cell mice.

Nitric Oxide-Independent Soluble Guanylate Cyclase Activation Improves Vascular Function and Cardiac Remodeling in Sickle Cell Disease

Sickle cell disease (SCD) is associated with intravascular hemolysis and oxidative inhibition of nitric oxide (NO) signaling. BAY 54-6544 is a small-molecule activator of oxidized soluble guanylate cyclase (sGC), which, unlike endogenous NO and the sGC stimulator, BAY 41-8543, preferentially binds and activates heme-free, NO-insensitive sGC to restore enzymatic cGMP production. We tested orally delivered sGC activator, BAY 54-6544 (17 mg/kg/d), sGC stimulator, BAY 41-8543, sildenafil, and placebo for 4-12 weeks in the Berkeley transgenic mouse model of SCD (BERK-SCD) and their hemizygous (Hemi) littermate controls (BERK-Hemi). Right ventricular (RV) maximum systolic pressure (RVmaxSP) was measured using micro right-heart catheterization. RV hypertrophy (RVH) was determined using Fulton's index and RV corrected weight (ratio of RV to tibia). Pulmonary artery vasoreactivity was tested for endothelium-dependent and -independent vessel relaxation. Right-heart catheterization revealed higher RVmaxSP and RVH in BERK-SCD versus BERK-Hemi, which worsened with age. Treatment with the sGC activator more effectively lowered RVmaxSP and RVH, with 90-day treatment delivering superior results, when compared with other treatments and placebo groups. In myography experiments, acetylcholine-induced (endothelium-dependent) and sodium-nitroprusside-induced (endothelium-independent NO donor) relaxation of the pulmonary artery harvested from placebo-treated BERK-SCD was impaired relative to BERK-Hemi but improved after therapy with sGC activator. By contrast, no significant effect for sGC stimulator or sildenafil was observed in BERK-SCD. These findings suggest that sGC is oxidized in the pulmonary arteries of transgenic SCD mice, leading to blunted responses to NO, and that the sGC activator, BAY 54-6544, may represent a novel therapy for SCD-associated pulmonary arterial hypertension and cardiac remodeling.

Noninvasive optical assessment of resting-state cerebral blood flow in children with sickle cell disease

Sickle cell disease (SCD) is a genetic blood disorder that has profound effects on the brain. Chronic anemia combined with both macro- and microvascular perfusion abnormalities that arise from stenosis or occlusion of blood vessels increased blood viscosity, adherence of red blood cells to the vascular endothelium, and impaired autoregulatory mechanisms in SCD patients all culminate in susceptibility to cerebral infarction. Indeed, the risk of stroke is 250 times higher in children with SCD than in the general population. Unfortunately, while transcranial Doppler ultrasound (TCD) has been widely clinically adopted to longitudinally monitor macrovascular perfusion in these patients, routine clinical screening of microvascular perfusion abnormalities is challenging with current modalities (e.g., positron emission tomography and magnetic resonance imaging) given their high-cost, requirement for sedation in children < 6 year, and need for trained personnel. We assess the feasibility of a low-cost, noninvasive optical technique known as diffuse correlation spectroscopy (DCS) to quantify an index of resting-state cortical cerebral blood flow (BFI) in 11 children with SCD along with 11 sex- and age-matched healthy controls. As expected, BFI was significantly higher in SCD subjects compared to healthy controls ( p < 0.001 ). Within SCD subjects, BFI was inversely proportional to resting-state arterial hemoglobin levels ( p = 0.012 ), consistent with expected anemia-induced compensatory vasodilation that aims to maintain adequate oxygen delivery to the tissue. Further, in a subset of patients measured with TCD ( n = 7 ), DCS-measured blood flow was correlated with TCD-measured blood flow velocity in middle cerebral artery ( R s = 0.68 ), although the trend was not statistically significant ( p = 0.11 ). These results are consistent with those of several previous studies using traditional neuroimaging techniques, suggesting that DCS may be a promising low-cost tool for assessment of tissue-level CBF in pediatric SCD.

Vascular TSP1-CD47 signaling promotes sickle cell-associated arterial vasculopathy and pulmonary hypertension in mice

Pulmonary hypertension (PH) is a leading cause of death in sickle cell disease (SCD) patients. Hemolysis and oxidative stress contribute to SCD-associated PH. We have reported that the protein thrombospondin-1 (TSP1) is elevated in the plasma of patients with SCD and, by interacting with its receptor CD47, limits vasodilation of distal pulmonary arteries ex vivo. We hypothesized that the TSP1-CD47 interaction may promote PH in SCD. We found that TSP1 and CD47 are upregulated in the lungs of Berkeley (BERK) sickling (Sickle) mice and patients with SCD-associated PH. We then generated chimeric animals by transplanting BERK bone marrow into C57BL/6J (n = 24) and CD47 knockout (CD47KO, n = 27) mice. Right ventricular (RV) pressure was lower in fully engrafted Sickle-to-CD47KO than Sickle-to-C57BL/6J chimeras, as shown by the reduced maximum RV pressure (P = 0.013) and mean pulmonary artery pressure (P = 0.020). The afterload of the sickle-to-CD47KO chimeras was also lower, as shown by the diminished pulmonary vascular resistance (P = 0.024) and RV effective arterial elastance (P = 0.052). On myography, aortic segments from Sickle-to-CD47KO chimeras showed improved relaxation to acetylcholine. We hypothesized that, in SCD, TSP1-CD47 signaling promotes PH, in part, by increasing reactive oxygen species (ROS) generation. In human pulmonary artery endothelial cells, treatment with TSP1 stimulated ROS generation, which was abrogated by CD47 blockade. Explanted lungs of CD47KO chimeras had less vascular congestion and a smaller oxidative footprint. Our results show that genetic absence of CD47 ameliorates SCD-associated PH, which may be due to decreased ROS levels. Modulation of TSP1-CD47 may provide a new molecular approach to the treatment of SCD-associated PH.

Sources of Vascular Nitric Oxide and Reactive Oxygen Species and Their Regulation

Nitric oxide (NO) is a small free radical with critical signaling roles in physiology and pathophysiology. The generation of sufficient NO levels to regulate the resistance of the blood vessels and hence the maintenance of adequate blood flow is critical to the healthy performance of the vasculature. A novel paradigm indicates that classical NO synthesis by dedicated NO synthases is supplemented by nitrite reduction pathways under hypoxia. At the same time, reactive oxygen species (ROS), which include superoxide and hydrogen peroxide, are produced in the vascular system for signaling purposes, as effectors of the immune response, or as byproducts of cellular metabolism. NO and ROS can be generated by distinct enzymes or by the same enzyme through alternate reduction and oxidation processes. The latter oxidoreductase systems include NO synthases, molybdopterin enzymes, and hemoglobins, which can form superoxide by reduction of molecular oxygen or NO by reduction of inorganic nitrite. Enzymatic uncoupling, changes in oxygen tension, and the concentration of coenzymes and reductants can modulate the NO/ROS production from these oxidoreductases and determine the redox balance in health and disease. The dysregulation of the mechanisms involved in the generation of NO and ROS is an important cause of cardiovascular disease and target for therapy. In this review we will present the biology of NO and ROS in the cardiovascular system, with special emphasis on their routes of formation and regulation, as well as the therapeutic challenges and opportunities for the management of NO and ROS in cardiovascular disease.

Intima-media thickness of the common femoral artery as a marker of leg ulceration in sickle cell disease patients

Leg ulceration is a debilitating chronic complication of sickle cell disease (SCD) the pathogenesis of which is yet to be fully elucidated. We hypothesized that SCD patients with histories of previous leg ulcers would have intima hyperplasia of the common femoral artery (CFA). We enrolled 44 SCD patients and 33 age-matched and sex-matched controls with hemoglobin AA. Anthropometric measurements, biochemical parameters, and sonographic intima-media thickness (IMT) of the CFA were determined. The median CFA IMT in SCD limbs with history of leg ulcers (SWLU) was 1.0 mm, whereas it was 0.7 mm in SCD limbs with no history of leg ulcer (SNLU) and 0.60 mm in controls (P < .001). Among the SNLU, 70.3% had CFA IMT <0.9 mm, whereas only 29.7% had CFA IMT ≥0.9 mm. Conversely, only 20.8% of SWLU had CFA IMT <0.9 mm, whereas the remaining 79.2% had CFA IMT ≥0.9 mm. All the controls had CFA IMT <0.9 mm. Binary logistic regression to determine the odds of having leg ulcer among SCD limbs with CFA IMT of ≥0.9 mm yielded an odds ratio of 9, indicating that SCD limbs with CFA IMT ≥0.9 mm had a 9 times greater risk of having leg ulcer compared with those with CFA IMT <0.9 mm. There is a significant increase in the CFA IMT of SCD limbs with ulcer compared with controls and SCD limbs without ulcer, suggesting that arterial vasculopathy plays a major role in the formation of these ulcers.

A potential therapeutic role for angiotensin-converting enzyme 2 in human pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a deadly disease with no cure. Alternate conversion of angiotensin II (AngII) to angiotensin-(1-7) (Ang-(1-7)) by angiotensin-converting enzyme 2 (ACE2) resulting in Mas receptor (Mas1) activation improves rodent models of PAH. Effects of recombinant human (rh) ACE2 in human PAH are unknown. Our objective was to determine the effects of rhACE2 in PAH.We defined the molecular effects of Mas1 activation using porcine pulmonary arteries, measured AngII/Ang-(1-7) levels in human PAH and conducted a phase IIa, open-label pilot study of a single infusion of rhACE2 (GSK2586881, 0.2 or 0.4 mg·kg^-1 intravenously).Superoxide dismutase 2 (SOD2) and inflammatory gene expression were identified as markers of Mas1 activation. After confirming reduced plasma ACE2 activity in human PAH, five patients were enrolled in the trial. GSK2586881 was well tolerated with significant improvement in cardiac output and pulmonary vascular resistance. GSK2586881 infusion was associated with reduced plasma markers of inflammation within 2-4 h and increased SOD2 plasma protein at 2 weeks.PAH is characterised by reduced ACE2 activity. Augmentation of ACE2 in a pilot study was well tolerated, associated with improved pulmonary haemodynamics and reduced markers of oxidant and inflammatory mediators. Targeting this pathway may be beneficial in human PAH.

Targeting βCys93 in hemoglobin S with an antisickling agent possessing dual allosteric and antioxidant effects

Sickle cell disease (SCD) is an inherited blood disorder caused by a β globin gene mutation of hemoglobin (HbS). The polymerization of deoxyHbS and its subsequent aggregation (into long fibers) is the primary molecular event which leads to red blood cell (RBC) sickling and ultimately hemolytic anemia. We have recently suggested that HbS oxidative toxicity may also contribute to SCD pathophysiology due to its defective pseudoperoxidase activity. As a consequence, a persistently higher oxidized ferryl heme is formed which irreversibly oxidizes "hotspot" residues (particularly βCys93) causing protein unfolding and subsequent heme loss. In this report we confirmed first, the allosteric effect of a newly developed reagent (di(5-(2,3-dihydro-1,4-benzodioxin-2-yl)-4H-1,2,4-triazol-3-yl)disulfide) (TD-1) on oxygen affinity within SS RBCs. There was a considerable left shift in oxygen equilibrium curves (OECs) representing treated SS cells. Under hypoxic conditions, TD-1 treatment of HbS resulted in an approximately 200 s increase in the delay time of HbS polymerization over the untreated HbS control. The effect of TD-1 binding to HbS was also tested on oxidative reactions by incrementally treating HbS with increasing hydrogen peroxide (H₂O₂) concentrations. Under these experimental conditions, ferryl levels were consistently reduced by approximately 35% in the presence of TD-1. Mass spectrometric analysis confirmed that upon binding to βCys93, TD-1 effectively blocked irreversible oxidation of this residue. In conclusion, TD-1 appears to shield βCys93 (the end point of radical formation in HbS) and when coupled with its allosteric effect on oxygen affinity may provide new therapeutic modalities for the treatment of SCD.

Haemoglobin oxygen saturation, leucocyte count and lactate dehydrogenase are predictors of elevated cerebral blood flow velocity in Nigerian children with sickle cell anaemia

BACKGROUND

Transcranial Doppler ultrasound (TCD) scan, which measures blood flow velocity through the time-averaged mean of maximum velocities (TAMMVs) in the internal carotid arteries and middle cerebral arteries, is a useful screening tool for predicting stroke risk in children with sickle cell anaemia (SCA).

AIM

To investigate which clinical and laboratory indices predict abnormal TCD velocity in children with SCA.

METHODS

Fifty-four SCA patients with normal TCD (TAMMV < 170 cm/s), classified as negative TCD (NTCD), and 93 patients with conditional and abnormal TCD velocities (TAMMV ≥ 170 cm/s) classified as positive TCD were recruited. The haemoglobin oxygen saturation, haematological variables, nitric oxide metabolites and lactate dehydrogenase activity of the patients were analysed.

RESULTS

The mean (SD) age was 7.16 (3.84) years (range 2-16). The median SpO₂ of the patients in the positive TCD group was significantly lower than that of the negative TCD group (p = 0.002). Multivariate logistic regression analysis indicated that the MCV [odds ratio (OR) 1.12, 95% confidence interval (CI) 1.04-1.22, p = 0.01)], MCH (OR 1.34, 95% CI 1.02-1.77, p = 0.04), leucocyte count (OR 1.26, 95% CI 1.07-1.49, p = 0.01) and lactate dehydrogenase (LDH) level (OR 1.00, 95% CI 1.00-1.01, p = 0.01) were independent predictors of high cerebral blood flow velocities.

CONCLUSIONS

These clinical and laboratory indices are characteristic of chronic hypoxia and severe anaemia and are predictors of abnormal cerebral blood flow velocity. They can be used to predict stroke risk in children with SCA when access to TCD screening is limited.

Vascular complications of sickle cell disease

Sickle cell disease (SCD) is a monogenetic disorder caused by a mutation in the β-globin gene HBB leading to polymerization of red blood cells causing damage to cell membranes, increasing its rigidity and intravascular hemolysis. Multiple lines of evidence suggest that SCD can be viewed as pan-vasculopathy associated with multiple mechanisms but driven by hemoglobin S polymerization. Here we review the pathophysiology, clinical manifestations and management strategies for cerebrovascular disease, pulmonary hypertension and renal disease associated with SCD. These "vascular phenotypes" reflect the systemic nature of the complications of SCD and are a major threat to the well-being of patients with the disorder.

Correlates of Pulmonary Function in Children with Sickle Cell Disease and Elevated Fetal Hemoglobin

OBJECTIVE

The current study was carried out to compare pulmonary function tests (PFTs) in pediatric Kuwaiti sickle cell disease (SCD) patients to age-matched normal controls and to investigate the association of PFTs with selected clinical and laboratory parameters. Subjects andMethods: There were 38 patients with SCD and 36 controls in the study. The patients were recruited from the Pediatric Hematology Clinics of Mubarak Al-Kabeer and Al-Amiri Hospitals, Kuwait, and were studied in steady state. The controls were healthy, non-sickle cell siblings of the patients. Forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), total lung capacity, and other PFT parameters were obtained using a constant-volume, variable-pressure, body plethysmograph. Hemoglobin, fetal hemoglobin, serum bilirubin, and lactate dehydrogenase were determined using standard methods.

RESULTS

The mean ages of the patients and controls were 10.5 ± 3.2 and 10.5 ± 3.5 years, respectively. The FEV1% predicted of 84.1 ± 15.4% among the patients was significantly lower than the 92.1 ± 11.8% in the controls (p = 0.003). The FVC% predicted was also significantly lower (p = 0.022) in the patients than in the controls, although the values were generally within the normal range. There was no association of FEV1 with pain phenotype, acute chest syndrome (ACS), or blood transfusions. Also, there was no significant correlation with reticulocytes, bilirubin, or lactate dehydrogenase.

CONCLUSIONS

In this study, changes in PFT, especially FEV1, developed early in the SCD patients. There was no demonstrable association with frequent vaso-occlusive crisis, ACS, and other variables. Hence, there is a need for follow-up studies with serial PFTs to identify vulnerable patients, who might need intervention to prevent early mortality.

Sickle cell disease: a malady beyond a hemoglobin defect in cerebrovascular disease

INTRODUCTION

Sickle cell disease (SCD) is a devastating monogenic disorder that presents as a multisystem illness and affects approximately 100,000 individuals in the United States alone. SCD management largely focuses on primary prevention, symptomatic treatment and targeting of hemoglobin polymerization and red blood cell sickling. Areas covered: This review will discuss the progress of SCD over the last few decades, highlighting some of the clinical (mainly cerebrovascular) and psychosocial challenges of SCD in the United States. In addition, focus will also be made on the evolving science and management of this inherited disease. Expert commentary: Until recently hydroxyurea (HU) has been the only FDA approved therapy for SCD. However, advancing understanding of SCD pathophysiology has led to multiple clinical trials targeting SCD related thrombo-inflammation, abnormal endothelial biology, increased oxidant stress and sickle cell mutation. Yet, despite advancing understanding, available therapies are limited. SCD also imposes great psychosocial challenges for the individual and the affected community, which has previously been under-recognized. This has created a pressing need for complementary adjuvant therapies with repurposed and novel drugs, in addition to the establishment of comprehensive clinics focusing on both the medical treatment and the psychosocial issues associated with SCD.

Pharmacogenomics of sickle cell disease: steps toward personalized medicine

Sickle cell disease (SCD) is a monogenetic disease but has a wide range of phenotypic expressions. Some of these differences in phenotype can be explained by genetic polymorphisms in the human globin gene. These polymorphisms can result in different responses to typical treatment, sometimes leading to inadequate therapeutics. Research is revealing more polymorphisms, and therefore, new targets for intervention to improve outcomes in SCD. This area of pharmacogenomics is continuing to develop. We provide a brief review of the current literature on pharmacogenomics in SCD and possible targets for intervention.

Associations between endothelial dysfunction and clinical and laboratory parameters in children and adolescents with sickle cell anemia

Background

Hematological changes can drive damage of endothelial cells, which potentially lead to an early endothelial dysfunction in patients with sickle cell anemia (SCA). An association may exist between endothelial dysfunction and several clinical manifestations of SCA. The present study aims to evaluate the links between changes in endothelial function and clinical and laboratory parameters in children and adolescents with SCA.

Methods

This study included 40 children and adolescents with stable SCA as well as 25 healthy children; aged 6–18 years. All study subjects were evaluated for endothelial function using Doppler ultrasonography. In addition, a number of laboratory assays were performed, including reticulocyte and leukocyte counts as well as measurement of circulating levels of total bilirubin, C-reactive protein (CRP), glucose, lipoproteins and peripheral oxyhemoglobin saturation. These parameters were also compared between SCA patients who were undertaking hydroxyurea (HU) and those who were not.

Results

Flow-mediated vasodilation (FMD) values were found to be reduced in SCA patients compared with those detected in healthy controls. SCA individuals with lower FMD values exhibited higher number of hospital admissions due to vaso-occlusive events. Additional analyses revealed that patients who had decreased FMD values exhibited higher odds of acute chest syndrome (ACS) episodes. A preliminary analysis with limited number of individuals failed to demonstrate significant differences in FMD values between SCA individuals who were treated with HU and those who were not.

Conclusions

Children and adolescents with SCA exhibit impaired endothelial function. Reductions in FMD values are associated with ACS. These findings underline the potential use of FMD as screening strategy of SCA patients with severe prognosis at early stages.

Pathways to pulmonary hypertension in sickle cell disease: the search for prevention and early intervention

INTRODUCTION

Pulmonary hypertension (PH) develops in a significant number of patients with sickle cell disease (SCD), resulting in increased morbidity and mortality. This review focuses on PH pathophysiology, risk stratification, and new recommendations for screening and treatment for patients with SCD. Areas covered: An extensive PubMed literature search was performed. While the pathophysiology of PH in SCD is yet to be fully deciphered, it is known that the etiology is multifactorial; hemolysis, hypercoagulability, hypoxemia, ischemic-reperfusion injury, oxidative stress, and genetic susceptibility all contribute in varying degrees to endothelial dysfunction. Hemolysis, in particular, seems to play a key role by inciting an imbalance in the regulatory axis of nitric oxide and arginine metabolism. Systematic risk stratification starting in childhood based on clinical features and biomarkers that enable early detection is necessary. Multi-faceted, targeted interventions, before irreversible vasculopathy develops, will allow for improved patient outcomes and life expectancy. Expert commentary: Despite progress in our understanding of PH in SCD, clinically proven therapies remain elusive and additional controlled clinical trials are needed. Prevention of disease starts in childhood, a critical window for intervention. Given the complex and multifactorial nature of SCD, patients will ultimately benefit from combination therapies that simultaneously targets multiple mechanisms.

Role of Exercise-Induced Oxidative Stress in Sickle Cell Trait and Disease

Sickle cell disease is a class of hemoglobinopathy in humans, which is the most common inherited disease in the world. Although complications of sickle cell disease start from polymerization of red blood cells during its deoxygenating phase, the oxidative stress resulting from the biological processes associated with this disease (ischaemic and hypoxic injuries, hemolysis and inflammation) has been shown to contribute to its pathophysiology. It is widely known that chronic exercise reduces oxidative stress in healthy people, mainly via improvement of antioxidant enzyme efficiency. In addition, recent studies in other diseases, as well as in sickle cell trait carriers and in a mouse model of sickle cell disease, have shown that regular physical activity could decrease oxidative stress. The purpose of this review is to summarize the role of oxidative stress in sickle cell disease and the effects of acute and chronic exercise on the pro-oxidant/antioxidant balance in sickle cell trait and sickle cell disease.