Inflammation in sickle cell disease

Exploring the genetic mechanisms: SELP gene's contribution to alleviating vaso-occlusive crisis in sickle cell disease

Sickle cell disease is a catastrophic inflammatory disorder characterized by microvascular vaso-occlusion, leading to high morbidity and increased mortality. P-selectin, a cell adhesion molecule, plays a crucial role in the pathogenesis and severity of sickle cell disease. Its expression and binding with its ligand PSGL-1 is involved in various mechanisms that contribute to inflammation and immune response, resulting in complications in sickle cell disease. Preclinical data have verified the efficacy of P-Selectin inhibition in mitigating vaso-occlusive events and severity of disease. Currently clinical trials are ongoing to evaluate the safety and efficiency of P-Selectin-targeted therapies and concede the challenges and limitations associated with their use. Despite of its proven role in reducing severity in sickle cell disease, future research should focus on identifying other novel targets within the adhesion cascade and explore combination therapies. Conducting trials and addressing concerns about accessibility are crucial steps towards fully harnessing the potential of P selectin inhibitors as a groundbreaking treatment option. This review focuses on understanding the role of p selectin and its interactions with molecules involved in inflammation providing insights about the molecular etiology, pathophysiology, and potential therapeutic targets in sickle cell disease.

Optical Coherence Tomography Angiography of Macular Microangiopathy in Children With Sickle Cell Disease

In this study, we identified the presence of sickle cell maculopathy and determined correlations between hemolysis indicators and systemic and ocular manifestations in children with sickle cell disease (SCD). Thirty-three patients with SCD 5 to 18 years of age underwent optical coherence tomography angiography (OCTA) as part of a thorough eye examination. The hematological indices and clinical data (hemoglobin, fetal hemoglobin, mean corpuscular volume, and frequency of sickle cell-associated complications and therapy) were collected. The SCD group contained 33 patients (66 eyes), and the control group contained 36 healthy participants (72 eyes). The SCD group had significantly thinner parafoveal thickness ( P =0.041) and significantly smaller parafoveal volume ( P =0.041) than the controls. The SCD group had lower deep capillary plexus density than the controls ( P =0.029). The SCD group had significantly smaller flow areas than the controls ( P <0.001). The foveal avascular zone (FAZ) perimeter, foveal density, and FAZ area in the entire retina did not differ significantly between the groups ( P >0.05). The platelet level was negatively correlated with parafoveal and perifoveal thickness and density. OCTA detected early macular microvascular changes in children and adolescents with asymptomatic SCD.

Targeting ICAM1 to Ameliorate Vaso-Occlusion and Inflammation in Sickle Cell Disease

Sickle cell disease (SCD) is a hereditary disorder characterized by vaso-occlusion, inflammation, and tissue damage. Intercellular adhesion molecule 1 (ICAM-1) plays a crucial role in the pathophysiology of SCD by promoting the adhesion of sickle cells to the endothelium, contributing to vaso-occlusion and tissue damage. The ICAM-1 gene encodes a glycoprotein that interacts with lymphocyte function-associated antigen 1 (LFA-1) and macrophage 1-antigen (Mac-1) receptors, perpetuating inflammation, and oxidative stress. The NF-κB signaling pathway regulates ICAM-1 expression, which is elevated in patients with SCD, leading to increased endothelial cell activation and damage. Targeting ICAM-1 and its interactions with sickle cells and the endothelium has emerged as a potential therapeutic strategy for managing SCD. This review highlights the complex interplay between ICAM-1, sickle cells, and the endothelium, and discusses the potential of ICAM-1-targeted therapies for mitigating VOC and improving the quality of life for patients with SCD.

Role of endothelial dysfunction in sleep-disordered breathing in egyptian children with sickle cell disease

BACKGROUND

Endothelial dysfunction is an integral pathophysiologic mechanism in sickle cell disease (SCD), and can lead to many complications. Sleep-disordered breathing (SDB) is a SCD complication with diverse incidence and pathophysiology. This study aimed to determine the prevalence of SDB in children with SCD and to assess its relation to endothelial dysfunction.

METHODS

Sixty children with SCD and 60 healthy controls were enrolled. The levels of TNF-α, IL-6, and IL-17A were evaluated in the entire cohort using enzyme-linked immunosorbent assay (ELISA) kits. Polysomnography (PSG) was performed for all SCD patients after completion of the Pediatric Sleep Questionnaire (PSQ).

RESULTS

TNF-α, IL-6, and IL-17A levels were significantly greater in children with SCD than in controls (p-values < 0.001, < 0.001, and 0.006, respectively). The PSQ revealed symptoms suggestive of SDB in 50 children with SCD (83.3%), and PSG revealed obstructive sleep apnea (OSA) in 44 children with SCD (73.3%); 22 patients had mild OSA, and 22 had moderate-to-severe OSA according to the apnea-hypopnea index (AHI). TNF-α was significantly greater in SCD children who reported heavy or loud breathing, trouble breathing or struggle to breathe, and difficulty waking up in the morning (p-values = 0.002, 0.002, and 0.031, respectively). The IL-6 levels were significantly greater in SCD children who stopped growing normally (p-value = 0.002). The levels of IL-6 and IL-17A were significantly greater in SCD children with morning headaches (p-values = 0.007 and 0.004, respectively).

CONCLUSION

Children with SCD showed a high prevalence of SDB with significantly elevated levels of markers of endothelial function, highlighting the interplay of SDB and endothelial dysfunction in SCD.

Stroke without cerebral arteriopathy in sickle cell disease children: causes and treatment

Cerebral arteriopathy (CA) in children with sickle cell disease (SCD) is classically described as chronic stenosis of arteries in the anterior brain circulation, leading to ischemic stroke. Some studies have, however, reported strokes in children with SCD but without CA. In order to better understand the etiology and risk factors of these strokes, we retrospectively analyzed ischemic strokes occurring in a large cohort of children over a 13-year period. Between 2007 and 2020, 25 of 1,500 children with SCD had an ischemic stroke in our center. Among them, 13 (52%) had CA, described as anatomical arterial stenosis, while 12 (48%) did not. Patients with stroke without CA were older than patients with stroke attributed to SCD-CA (9.0 years old vs. 3.6 years old; P=0.008), and more frequently had SC genotype (25% vs. 0%, respectively). Their strokes more frequently involved the posterior circulation, with cerebellar involvement in 42%. Retained stroke etiologies in patients without typical SCD-related CA were reversible cerebral vasoconstriction syndrome, cerebral fat embolism, arterial thrombosis or thromboembolism, hyperviscosity, vasculitis in a context of infectious meningo-encephalitis, and severe hemodynamic failure. No recurrence was observed in the 24 months following stroke, even though 67% of the patients in this group were no longer receiving exchange transfusions. In conclusion, in a cohort of pediatric SCD patients with an efficient stroke screening strategy, half of the ischemic strokes that occurred were related to causes other than CA. They affected a different population of SCD children and systematic long-term transfusion programs may not be necessary in these cases.

Evaluation of anti-sickling effects of two varieties of Cajanus cajan (L.) Huth on sickle cell beta thalassemia

ETHNO-PHARMACOLOGICAL RELEVANCE

Globally, the prevalence of sickle cell disease is on the rise, with developing countries experiencing particularly alarming mortality rate compared to developed nations. The World Health Organization (WHO) and United Nations (UN) have acknowledged sickle cell disease as a significant global public health concern. Unfortunately, a cure for this condition is yet to be discovered, and existing allopathic treatments, while offering relief, come with serious side effects. In recent times, there has been a growing interest in exploring the potential of medicinal plants for treating sickle cell disease due to their content of secondary metabolites that may impact the disease's mechanisms. Cajanus cajan, a crucial grain legume in rain-fed agriculture in semi-arid tropics, has been traditionally used in folk medicine to manage various illnesses and is suggested to possess anti-sickling properties.

AIM OF THE STUDY

The present study investigated two varieties of C. cajan for their effectiveness in treating sickle cell beta thalassemia, a variant of sickle cell disease.

MATERIALS AND METHODS

The study was divided into four groups consisting of the untreated group (group 1), group treated with standard drug (group 2), group treated with white C. cajan (group 3) and group treated with brown C. cajan (group 4). The effects of the two variety of C. cajan were measured by polymerization test, reversibility test, osmotic fragility test, deoxygenation and beta globin synthesis test.

RESULT

The results revealed that both varieties of C. cajan demonstrated a reduction in polymerization rates, reversed sickled red blood cells, increased the oxygen affinity of Hb-S/β, elevated the Fe2+/Fe3+ ratio, and maintained the membrane stability of red blood cells. Notably, the white variety exhibited superior anti-sickling properties compared to the brown variety.

CONCLUSION

This suggests that this significant leguminous crop could be utilized for the treatment and management of sickling disorders, particularly in low-income countries where conventional treatments may be financially inaccessible to patients.

Comparative histological analysis of spleens in pediatric patients with hemolytic anemias: Insights into the pathophysiological mechanisms of spleen destruction in sickle cell anemia

While sickle cell anemia (SCA) and hereditary spherocytosis (HS) share common features of increased spleen erythrophagocytosis due to increased red blood cell (RBC) turnover, SCA is specifically characterized by susceptibility to infections. In this study, histological lesions in the spleens of pediatric patients with SCA were analyzed, in close correlation with past clinical history and comparatively to HS, healthy and transfused β-thalassemia patients (TDT). An evaluation of red pulp elementary lesions (red pulp fibrosis, iron deposition, number of Gandy-Gamna, and RBC trapping) combined into a severity score was established, as well as B-cell follicles analysis. Quantification on digitalized slides of iron deposition, RBC trapping, and red pulp fibrosis was additionally performed. Spleens from 22 children with SCA, eight with HS, eight with TDT, and three healthy controls (HC) were analyzed. Median age at splenectomy was not different between SCA and HS patients, 6.05 years (range: 4.5-16.0) versus 4.75 (range: 2.2-9.5). Marked heterogeneity was found in SCA spleens in contrast to other conditions. Contrary to previous reports, B-cell follicles were generally preserved in SCA. While RBC trapping was significantly increased in both SCA and HS (compared to TDT and HC), quantitative fibrosis and overall red pulp severity score were significantly increased in SCA spleens compared to other conditions. Moreover, there was an inverse correlation between quantitative fibrosis and number of B-cell follicles, linking these two compartments as well as spleen fibrosis to infectious susceptibility in SCA, potentially through impaired red pulp macrophage scavenging and B-cell subpopulations defects.

Exercise and training in sickle cell disease: Safety, potential benefits, and recommendations

Sickle cell disease (SCD) is a genetic disorder characterized by complex pathophysiological mechanisms leading to vaso-occlusive crisis, chronic pain, chronic hemolytic anemia, and vascular complications, which require considerations for exercise and physical activity. This review aims to elucidate the safety, potential benefits, and recommendations regarding exercise and training in individuals with SCD. SCD patients are characterized by decreased exercise capacity and tolerance. Acute intense exercise may be accompanied by biological changes (acidosis, increased oxidative stress, and dehydration) that could increase the risk of red blood cell sickling and acute clinical complications. However, recent findings suggest that controlled exercise training is safe and well tolerated by SCD patients and could confer benefits in disease management. Regular endurance exercises of submaximal intensity or exercise interventions incorporating resistance training have been shown to improve cardiorespiratory and muscle function in SCD, which may improve quality of life. Recommendations for exercise prescription in SCD should be based on accurate clinical and functional evaluations, taking into account disease phenotype and cardiorespiratory status at rest and in response to exercise. Exercise programs should include gradual progression, incorporating adequate warm-up, cool-down, and hydration strategies. Exercise training represents promising therapeutic strategy in the management of SCD. It is now time to move through the investigation of long-term biological, physiological, and clinical effects of regular physical activity in SCD patients.

Can we use biomarkers to identify those at risk of acute pain from sickle cell disease?

INTRODUCTION

Acute pain episodes, also known as vaso-occlusive crises (VOC), are a major symptom of sickle cell disease (SCD) and lead to frequent hospitalizations. The diagnosis of VOC can be challenging, particularly in adults with SCD, 50% of whom have chronic pain. Several potential biomarkers have been proposed for identifying individuals with VOC, including elevation above the baseline of various vascular growth factors, cytokines, and other markers of inflammation. However, none have been validated to date.

AREAS COVERED

We summarize prospective biomarkers for the diagnosis of acute pain in SCD, and how they may be involved in the pathophysiology of a VOC. Previous and current strategies for biomarker discovery, including the use of omics techniques, are discussed.

EXPERT OPINION

Implementing a multi-omics-based approach will facilitate the discovery of objective and validated biomarkers for acute pain.

Lumbar Fusions in Patients with Sickle Cell Disease: A Propensity-Matched Analysis of Postoperative Complications

OBJECTIVE

The present study compares postoperative outcomes between patients with and without sickle cell disease (SCD) undergoing 1-to 3-level lumbar spinal fusion for degenerative pathologies.

METHODS

Patients who underwent 1-to 3-level lumbar spinal fusion for degenerative pathologies from 2010 to 2021 were identified using the PearlDiver database. Patients were separated into 1) SCD and 2) non-SCD groups and were propensity-matched 1:1 for age, sex, Elixhauser Comorbidity Index, surgical approach, and various comorbidities. Complications were separately analyzed by single- and multilevel procedures using chi-squared and Mann-Whitney U testing.

RESULTS

Propensity-score matching identified 1934 SCD and non-SCD patients who underwent single-level fusion and 2094 SCD and non-SCD patients who underwent multilevel fusion. Across single-level fusions, those with SCD had a significantly higher risk of neurovascular compromise (P < 0.001), venous thromboembolism (P = 0.004), pneumonia (P = 0.032), urinary tract infections (P = 0.001), and greater postoperative opioid usage out to 12 months (P = 0.018). Across multilevel fusions, SCD carried higher risk for neurovascular compromise (P < 0.001), pneumonia (P = 0.010), and urinary tract infections (P < 0.001). All SCD patients had significantly higher opioid use at 1 month (P = 0.001) and at 6 months (P = 0.009) postoperatively.

CONCLUSIONS

Patients with SCD undergoing lumbar spinal fusion demonstrate higher risks for coagulopathic, ischemic, and infectious-related complications, as well as long-term postoperative opioid use. Awareness of the unique complication profile in SCD patients may help guide surgeons in refining perioperative management strategies to optimize outcomes in patients with SCD.

A critical review of therapeutic interventions in sickle cell disease: Progress and challenges

Sickle cell disease (SCD) is an autosomal recessive genetic disorder that occurs due to the point mutation in the β-globin gene, which results in the formation of sickle hemoglobin (HbS) in the red blood cells (RBCs). When HbS is exposed to an oxygen-depleted environment, it polymerizes, resulting in hemolysis, vaso-occlusion pain, and impaired blood flow. Still, there is no affordable cure for this inherited disease. Approved medications held promise but were met with challenges due to limited patient tolerance and undesired side effects, thereby inhibiting their ability to enhance the quality of life across various individuals with SCD. Progress has been made in understanding the pathophysiology of SCD during the past few decades, leading to the discovery of novel targets and therapies. However, there is a compelling need for research to discover medications with improved efficacy and reduced side effects. Also, more clinical investigations on various drug combinations with different mechanisms of action are needed. This review comprehensively presents therapeutic approaches for SCD, including those currently available or under investigation. It covers fundamental aspects of the disease, such as epidemiology and pathophysiology, and provides detailed discussions on various disease-modifying agents. Additionally, expert insights are offered on the future development of pharmacotherapy for SCD.

Evaluation of peripheral blood inflammatory biomarkers in sickle cell disease with and without retinopathy

BACKGROUND

The aim of this study was to evaluate the clinical significance of blood-cell associated inflammation markers in patients with sickle cell disease (SCD) and sickle cell retinopathy (SCR).

METHODS

Neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR), monocyte to lymphocyte ratio (MLR), systemic immune inflammation index (SIII), systemic inflammation response index (SIRI), systemic inflammation modulation index (SIMI) and aggregate systemic inflammation index (AISI) were calculated. This study included 45 healthy controls (Group 1) and 100 SCD (Group 2). Patients in Group 2 were then divided into two groups: without SCR (Group 3) and with SCR (Group 4), and patients with SCR (Group 4) were further divided into two groups: non-proliferative sickle cell retinopathy (NPSCR) (Group 5) and proliferative sickle cell retinopathy (PSCR) (Group 6).

RESULTS

The mean values for NLR, PLR, SIII, SIRI, AISI, and SIMI were significantly higher in Group 2 compared to Group 1 (p = 0.011 for NLR, p = 0.004 for SIII, and p < 0.001 for others). Furthermore, AISI and SIMI parameters demonstrated statistically significant discriminatory power to distinguish Group 5 from Group 6 (p = 0.0016 and p = 0.0006, respectively).

CONCLUSION

Given the critical role of inflammatory mechanisms in the pathogenesis of SCD and its related complications, the assessment of blood-cell-associated inflammatory markers may present a pragmatic and advantageous approach to the clinical oversight and therapeutic intervention of SCD.

The Association of Sickle-Cell Disorders With Diabetic Retinopathy: A Large Database Study

Purpose

To evaluate the association of sickle-cell disease (SCD) and sickle-cell trait (SCT) disease with diabetic retinopathy (DR) in patients with diabetes mellitus (DM).

Design

Population-based, retrospective cohort study utilizing data from the TriNetX Research Network, including 119 million patients across 80 health care organizations worldwide.

Participants

Diabetes mellitus patients (type 1 [T1DM] or 2 [T2DM]), with or without SCD and SCT, were included. Three cohorts were analyzed, including (1) DM patients without SCD, SCT, or sickle-cell/hemoglobin-C; (2) DM with SCD; and (3) DM with SCT.

Methods

All patients with DM were categorized into 3 cohorts based on the presence of SCD and SCT. Each cohort underwent 1:1 propensity score matching for demographics, blood glucose levels, hemoglobin A1C, and other relevant comorbidities.

Main Outcome Measures

Risk of DR in DM patients with and without SCD or SCT.

Results

There was no significant difference in the risk of any T1DR between those with and without SCD. However, for those with SCT, there was a notable twofold increased risk for T1-proliferative DR (PDR) (relative risk [RR]: 2.03; 95% confidence interval [CI]: 1.33-3.01). In contrast, there was an elevated risk for any T2DR in patients with SCD (RR: 1.50; 95% CI: 1.19-1.88), particularly due to higher PDR risks in T2DM patients (RR: 1.83; 95% CI: 1.29-2.60). The risk of mild to moderate T2DM non-PDR was also found to be higher in patients with SCT.

Conclusions

The risk of any DR was increased in T2DM patients with SCD or SCT, with increased risks for PDR in patients with SCT and T1DM. This indicates there may be a potential role of sickle-cell disorders in diabetic eye disease progression.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Genetic Modifiers of Stroke in Patients with Sickle Cell Disease-A Scoping Review

Sickle cell disease (SCD) clinically manifests itself with a myriad of complications. Stroke, both ischemic and hemorrhagic, as well as silent white matter changes, occurs at a relatively high prevalence. Understanding why and in whom stroke is most likely to occur is critical to the effective prevention and treatment of individuals with SCD. Genetic studies, including genome- and exome-wide association studies (GWAS and EWAS), have found several key modifiers associated with increased stroke/stroke risk in SCD via mechanisms including Hemoglobin F (HbF) modulation, inflammation, cellular adhesion, endothelial disruption, and hemolysis. We present a review on the modifiers that have most clearly demonstrated an association to date. More studies are needed to validate other potential polymorphisms and identify new ones. Incorporating gene-focused screenings in clinical care could provide avenues for more targeted, more effective, and less toxic prevention of stroke in this population. The data from this review will be used to inform the initial GWAS performed by the International Hemoglobinopathy Research Network (INHERENT) consortium.

Evaluating thromboprophylaxis in the sickle cell disease population: Navigating the evidence gap

Sickle cell disease (SCD) arises from beta-globin gene mutations, with global estimates indicating around 500 000 affected neonates in 2021. In the United States, it is considered rare, impacting fewer than 200 000 individuals. The key pathogenic flaw lies in mutant haemoglobin S, prone to polymerization under low oxygen conditions, causing erythrocytes to adopt a sickled shape. This leads to complications like vascular occlusion, haemolytic anaemia, inflammation and organ damage. Beyond erythrocyte abnormalities however, there is a body of literature highlighting the hypercoagulable state that is likely a contributor to many of the complications we see in SCD. The persistent activation of the coagulation cascade results in thromboembolic events, notably venous thromboembolism (VTE) which is independently associated with increased mortality in both adults and children with SCD. While the increased risk of VTE in the SCD population seems well established, there is a lack of guidelines for thromboprophylaxis in this population. This Wider Perspective will describe the hypercoagulable state and increased thrombosis risk in the SCD population, as well as advocate for the development of evidence-based guidelines to aid in the prevention of VTE in SCD.

Prevalence of Duffy null and its impact on hydroxyurea in young children with sickle cell disease in the United States

Consistent with studies showing a high prevalence of the Duffy null phenotype among healthy Black Americans, this retrospective study found that Duffy null was present in >75% of a young and contemporary cohort of children with sickle cell disease (SCD) in the United States. Despite the potential for this phenotype to impact absolute neutrophil counts, hydroxyurea (HU) dosing, and outcomes, it was not associated with being prescribed a lower HU dose or having increased acute SCD visits early in the HU treatment course. Future studies are needed to confirm these findings in older children with SCD.

Antioxidant supplementation for sickle cell disease

BACKGROUND

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

OBJECTIVES

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

SEARCH METHODS

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

SELECTION CRITERIA

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

DATA COLLECTION AND ANALYSIS

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

MAIN RESULTS

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

AUTHORS' CONCLUSIONS

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

Characterizing the Immature Immunophenotype of Sickle Cell Disease Monocytes

Sickle cell disease (SCD) is marked by episodic vaso-occlusive crisis (VOC). Recurrent VOC creates a pro-inflammatory state that induces phenotypic alterations in innate immune cells. Monocytes are of particular interest to VOC pathophysiology because they are especially malleable to inflammatory signaling. Indeed, inflammatory disease states such as chronic obstructive pulmonary disease (COPD), obesity and atherosclerosis are known to influence monocyte development and alter monocyte subpopulations. In this study, we describe SCD monocyte subsets by performing immunophenotypic flow cytometric, enzymatic, and morphologic analysis on peripheral blood. Herein, we add to the growing body of evidence suggesting aberrant monocyte populations underpin VOC pathophysiology. We found that SCD monocytes possess an immature phenotype as demonstrated by 1) decreased CD4 positivity (p < .01), 2) low α-naphthyl butyrate esterase (ANBE) expression, and 3) naïve morphologic features. We additionally found an increase in CD14+CD16-CD4- monocytes (p < .01), a subset associated with the impaired immune response of post-trauma patients. Interestingly, we also found a large proportion of CD14+CD4-HLA-DR- monocytes which, under normal circumstances, are exclusively found in neonates (p < .01). Finally, we report an increase in nonclassical monocytes (CD14dimCD16+), a subset recently shown to have a critical role in prevention and recovery from VOC.

Interplay between α-thalassemia and β-hemoglobinopathies: Translating genotype-phenotype relationships into therapies

α-Thalassemia represents one of the most important genetic modulators of β-hemoglobinopathies. During this last decade, the ongoing interest in characterizing genotype-phenotype relationships has yielded incredible insights into α-globin gene regulation and its impact on β-hemoglobinopathies. In this review, we provide a holistic update on α-globin gene expression stemming from DNA to RNA to protein, as well as epigenetic mechanisms that can impact gene expression and potentially influence phenotypic outcomes. Here, we highlight defined α-globin targeted strategies and rationalize the use of distinct molecular targets based on the restoration of balanced α/β-like globin chain synthesis. Considering the therapies that either increase β-globin synthesis or reactivate γ-globin gene expression, the modulation of α-globin chains as a disease modifier for β-hemoglobinopathies still remains largely uncharted in clinical studies.

Management of diabetes mellitus patients with sickle cell anemia: Challenges and therapeutic approaches

The coexistence of diabetes mellitus (DM) and sickle cell anemia (SCA) poses significant challenges in clinical management due to the complex interactions and overlapping complications associated with both conditions. Managing diabetes in individuals with SCA requires a comprehensive approach that addresses the unique physiological and pathological aspects of both diseases. This paper reviews the challenges encountered in the management of DM in patients with SCA and explores therapeutic strategies and approaches to optimize patient care. Challenges in the management of DM in individuals with SCA stem from several factors, including the impact of hemoglobin variants on glycemic control assessment, increased susceptibility to infections, altered immune response, and complications associated with both diseases. Moreover, the coexistence of SCA and DM heightens the susceptibility to infections due to compromised immune function, emphasizing the need for vigilant preventive measures, including vaccinations and close monitoring for infectious complications. Close collaboration among healthcare providers specializing in diabetes, hematology, and other relevant fields is crucial for developing comprehensive care plans. Individualized treatment strategies that balance glycemic control, pain management, and preventive care are essential to mitigate complications and optimize the overall health outcomes of patients with both DM and SCA. In conclusion, managing diabetes in the context of SCA necessitates a nuanced and patient-centered approach. By addressing the challenges and employing tailored therapeutic strategies, healthcare providers can improve the quality of life and health outcomes for individuals affected by both conditions.

Nitric oxide: A potential etiological agent for vaso-occlusive crises in sickle cell disease

Nitric oxide (NO), a vasodilator contributes to the vaso-occlusive crisis associated with the sickle cell disease (SCD). Vascular nitric oxide helps in vasodilation, controlled platelet aggregation, and preventing adhesion of sickled red blood cells to the endothelium. It decreases the expression of pro-inflammatory genes responsible for atherogenesis associated with SCD. Haemolysis and activated endothelium in SCD patients reduce the bioavailability of NO which promotes the severity of sickle cell disease mainly causes vaso-occlusive crises. Additionally, NO depletion can also contribute to the formation of thrombus, which can cause serious complications such as stroke, pulmonary embolism etc. Understanding the multifaceted role of NO provides valuable insights into its therapeutic potential for managing SCD and preventing associated complications. Various clinical trials and studies suggested the importance of artificially induced nitric oxide and its supplements in the reduction of severity. Further research on the mechanisms of NO depletion in SCD is needed to develop more effective treatment strategies and improve the management of this debilitating disease.

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.

Inflammation and autoimmunity are interrelated in patients with sickle cell disease at a steady-state condition: implications for vaso-occlusive crisis, pain, and sensory sensitivity

This study aimed to comprehensively analyze inflammatory and autoimmune characteristics of patients with sickle cell disease (SCD) at a steady-state condition (StSt) compared to healthy controls (HCs) to explore the pathogenesis of StSt and its impact on patients' well-being. The study cohort consisted of 40 StSt participants and 23 HCs enrolled between July 2021 and April 2023. StSt participants showed elevated white blood cell (WBC) counts and altered hematological measurements when compared to HCs. A multiplex immunoassay was used to profile 80 inflammatory cytokines/chemokines/growth factors in plasma samples from these SCD participants and HCs. Significantly higher plasma levels of 35 analytes were observed in SCD participants, with HGF, IL-18, IP-10, and MCP-2 being among the most significantly affected analytes. Additionally, autoantibody profiles were also altered, with elevated levels of anti-SSA/Ro60, anti-Ribosomal P, anti-Myeloperoxidase (MPO), and anti-PM/Scl-100 observed in SCD participants. Flow cytometric analysis revealed higher rates of red blood cell (RBC)/reticulocyte-leukocyte aggregation in SCD participants, predominantly involving monocytes. Notably, correlation analysis identified associations between inflammatory mediator levels, autoantibodies, RBC/reticulocyte-leukocyte aggregation, clinical lab test results, and pain crisis/sensitivity, shedding light on the intricate interactions between these factors. The findings underscore the potential significance of specific biomarkers and therapeutic targets that may hold promise for future investigations and clinical interventions tailored to the unique challenges posed by SCD. In addition, the correlations between vaso-occlusive crisis (VOC)/pain/sensory sensitivity and inflammation/immune dysregulation offer valuable insights into the pathogenesis of SCD and may lead to more targeted and effective therapeutic strategies.

Clinical Trial Registration

ClinicalTrials.gov, Identifier: NCT05045820.

Sickle Cell Disease Update: New Treatments and Challenging Nutritional Interventions

Sickle cell disease (SCD), a distinctive and often overlooked illness in the 21st century, is a congenital blood disorder characterized by considerable phenotypic diversity. It comprises a group of disorders, with sickle cell anemia (SCA) being the most prevalent and serious genotype. Although there have been some systematic reviews of global data, worldwide statistics regarding SCD prevalence, morbidity, and mortality remain scarce. In developed countries with a lower number of sickle cell patients, cutting-edge technologies have led to the development of new treatments. However, in developing settings where sickle cell disease (SCD) is more prevalent, medical management, rather than a cure, still relies on the use of hydroxyurea, blood transfusions, and analgesics. This is a disease that affects red blood cells, consequently affecting most organs in diverse manners. We discuss its etiology and the advent of new technologies, but the aim of this study is to understand the various types of nutrition-related studies involving individuals suffering from SCD, particularly in Africa. The interplay of the environment, food, gut microbiota, along with their respective genomes collectively known as the gut microbiome, and host metabolism is responsible for mediating host metabolic phenotypes and modulating gut microbiota. In addition, it serves the purpose of providing essential nutrients. Moreover, it engages in direct interactions with host homeostasis and the immune system, as well as indirect interactions via metabolites. Nutrition interventions and nutritional care are mechanisms for addressing increased nutrient expenditures and are important aspects of supportive management for patients with SCD. Underprivileged areas in Sub-Saharan Africa should be accompanied by efforts to define and promote of the nutritional aspects of SCD. Their importance is key to maintaining well-being and quality of life, especially because new technologies and products remain limited, while the use of native medicinal plant resources is acknowledged.

Understanding apoptosis in sickle cell anemia patients: Mechanisms and implications

Sickle cell anemia (SCA) is a hereditary blood disorder characterized by the presence of abnormal hemoglobin, leading to the formation of sickle-shaped red blood cells. While much research has focused on the molecular and cellular mechanisms underlying the pathophysiology of SCA, recent attention has turned to the role of apoptosis, or programmed cell death, in the disease progression. This review aims to elucidate the intricate mechanisms of apoptosis in SCA patients and explore its implications in disease severity, complications, and potential therapeutic interventions. Different research search engines such as PubMed central, Scopus, Web of Science, Google Scholar, ResearchGate, Academia Edu, etc were utilized in writing this paper. Apoptosis, a highly regulated cellular process, plays a crucial role in maintaining homeostasis by eliminating damaged or dysfunctional cells. In SCA, the imbalance between pro-apoptotic and anti-apoptotic signals contributes to increased erythrocyte apoptosis, exacerbating anemia and vaso-occlusive crises. Various factors, including oxidative stress, inflammation, and altered cell signaling pathways, converge to modulate the apoptotic response in SCA. Furthermore, the interaction between apoptotic cells and the vascular endothelium contributes to endothelial dysfunction, promoting the pathogenesis of vasculopathy and organ damage seen in SCA patients. In conclusion, unraveling the complexities of apoptosis in SCA provides valuable insights into the disease pathophysiology and offers novel avenues for therapeutic interventions.

A bone to pick-cellular and molecular mechanisms of bone pain in sickle cell disease

The bone is one of the most commonly affected organs in sickle cell disease (SCD). Repeated ischemia, oxidative stress and inflammation within the bone is largely responsible for promoting bone pain. As more individuals with SCD survive into adulthood, they are likely to experience a synergistic impact of both aging and SCD on their bone health. As bone health deteriorates, bone pain will likely exacerbate. Recent mechanistic and observational studies emphasize an intricate relationship between bone remodeling and the peripheral nervous system. Under pathological conditions, abnormal bone remodeling plays a key role in the propagation of bone pain. In this review, we first summarize mechanisms and burden of select bone complications in SCD. We then discuss processes that contribute to pathological bone pain that have been described in both SCD as well as non-sickle cell animal models. We emphasize the role of bone-nervous system interactions and pitfalls when designing new therapies especially for the sickle cell population. Lastly, we also discuss future basic and translational research in addressing questions about the complex role of stress erythropoiesis and inflammation in the development of SCD bone complications, which may lead to promising therapies and reduce morbidity in this vulnerable population.

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

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

Blood rheology and vascular function in sickle cell trait and sickle cell disease: From pathophysiological mechanisms to clinical usefulness

Sickle cell disease (SCD) is an autosomal recessive disorder. Although the molecular mechanisms at the origin of SCD have been well characterized, its clinical expression is highly variable. SCD is characterized by blood rheological abnormalities, increased inflammation and oxidative stress, and vascular dysfunction. Individuals with only one copy of the mutated β-globin gene have sickle cell trait (SCT) and are usually asymptomatic. The first part of this review focuses on the biological responses of SCT carriers during exercise and on the effects of combined SCT and diabetes on vascular function, several biomarkers and clinical complications. The second part of the review focuses on SCD and shows that the magnitude of red blood cell (RBC) rheological alterations is highly variable from one patient to another, and this variability reflects the clinical and hematological variability: patients with the less deformable RBCs have high hemolytic rate and severe anemia, and are prone to develop leg ulcers, priapism, cerebral vasculopathy, glomerulopathy or pulmonary hypertension. In contrast, SCD patients characterized by the presence of more deformable RBCs (but still rigid) are less anemic and may exhibit increased blood viscosity, which increases the risk for vaso-occlusive events. Several genetic and cellular factors may modulate RBC deformability in SCD: co-existence of α-thalassemia, fetal hemoglobin level, oxidative stress, the presence of residual mitochondria into mature RBCs, the activity of various non-selective cationic ion channels, etc. The last part of this review presents the effects of hydroxyurea and exercise training on RBC rheology and other biomarkers in SCD.

Association between trauma triage and time-to-vaso-occlusive events in patients with sickle cell disease after traumatic injury: a retrospective study

Introduction

Sickle cell disease (SCD) is associated with vaso-occlusive events (VOEs) that can lead to disease complications, including early mortality. Given that similar inflammatory responses characterize VOE and traumatic injury, injured patients with SCD may be vulnerable to acute complications. This study is the first to examine whether traumatic injury is associated with increased severity of future VOEs.

Methods

This cohort study was conducted using electronic health record data from an SCD clinic in Western Pennsylvania; 356 patients with SCD from January 2000 to July 2021 were identified via retrospective chart review. 55 patients were eligible based on continuous medical record data spanning 1 year preinjury and postinjury. Patients were sorted into three treatment groups based on injury management: (1) Neither triage to trauma team activation (TTA) nor inpatient admission (Early Discharge), (2) Triage but no inpatient admission (Triage Only), and (3) Triage and In-patient. Outcomes included time from injury to first VOE, annual VOE counts requiring an emergency department (ED) visit, and ED length of stay (LOS) for the first VOE after injury.

Results

Early Discharge individuals experienced a VOE event within 2.93 days of injury, significantly shorter time to event than Triage and In-patient individuals at 52.375 days and Triage Only individuals at 100.16 days (p=0.0058). No difference in annual VOE counts was noted postinjury across all groups. However, a significant increase in VOE LOS preinjury (16.1 hours) to postinjury (77.4 hours) was noted only for the Triage Only group (p=0.038). Cox regression model showed that shortened time to VOE events was marginally associated with TTA status (p=0.06).

Conclusion

Despite minimal changes in long-term VOE outcomes after injury, traumatic injuries may accelerate the time-to-VOE among the Early Discharge group. Therefore, future research is warranted to analyze whether the absence of postinjury triage assessment and intervention may cause unforeseen physiologic stressors contributing to VOE outcomes.

Level of evidence

Level IV: retrospective case-control study with three negative criteria.

Hypercoagulability in Sickle Cell Disease: A Thrombo-Inflammatory Mechanism

Sickle cell disease (SCD) is a group of inherited disorders characterized by the presence of abnormal hemoglobin S. Patients with SCD suffer from frequent episodes of anemia, chronic hemolysis, pain crisis, and vaso-occlusion. Additionally, SCD is associated with diverse and serious clinical complications, including thrombosis, which can lead to organ failure, increased morbidity, and eventually, mortality. SCD is known to be a hypercoagulable condition, and the cause of hypercoagulability is multifactorial, with the molecular basis of hemoglobin S being the main driver. The presence of hemoglobin S induces sickling of the RBCs and their subsequent hemolysis, as well as oxidative stress. Both of these processes can alter the hemostatic system, through the activation of platelets, coagulation system, and fibrinolysis, as well as depletion of coagulation inhibitors. These changes can also induce the formation of microvesicles and expression of tissue factor, leading to activation of WBCs, endothelial cell damage, and inflammatory response. Understanding the various factors that drive hypercoagulability as a thrombo-inflammatory mechanism in SCD can help provide explanations for the pathogenesis and other complications of the disease.

Le globule rouge drépanocytaire : données fonctionnelles

Sickle cell anemia is a genetic disorder that affects hemoglobin leading to the production of an abnormal hemoglobin, called HbS. HbS has the property to polymerize under deoxygenated conditions, causing a mechanical distortion of red blood cells; a phenomenon called sickling. These sickle red blood cells are more fragile and rigid, leading to chronic hemolytic anemia and painful vaso-occlusive crises, as well as chronic vascular complications that can affect many organs. The abnormal functional properties of these sickle red blood cells are responsible for a wide range of clinical expression of the disease. HbS polymerization can be influenced by many factors, such as the hydration state of the red blood cells or the affinity of hemoglobin for oxygen. Moreover, the rheological characteristics of red blood cells, including their deformability and aggregation properties, are associated with specific clinical phenotypes. The pro-inflammatory and pro-oxidant state, as well as the repeated polymerization of HbS, accelerate the senescence of sickle red blood cells, promoting the release of microparticles and contributing to vascular dysfunction. Patients' red blood cells also have molecular characteristics that promote their adhesion to the endothelium and other circulating cells, contributing to the onset of vascular complications. Massive intravascular hemolysis, due to increased erythrocyte fragility, is also responsible for chronic vascular complications. These different alterations are privileged therapeutic targets, leading to the emergence of new specific treatments. © 2023 Société nationale française de médecine interne (SNFMI). Published by Elsevier Masson SAS. All rights reserved.

Global analysis of suppressor mutations that rescue human genetic defects

BACKGROUND

Genetic suppression occurs when the deleterious effects of a primary "query" mutation, such as a disease-causing mutation, are rescued by a suppressor mutation elsewhere in the genome.

METHODS

To capture existing knowledge on suppression relationships between human genes, we examined 2,400 published papers for potential interactions identified through either genetic modification of cultured human cells or through association studies in patients.

RESULTS

The resulting network encompassed 476 unique suppression interactions covering a wide spectrum of diseases and biological functions. The interactions frequently linked genes that operate in the same biological process. Suppressors were strongly enriched for genes with a role in stress response or signaling, suggesting that deleterious mutations can often be buffered by modulating signaling cascades or immune responses. Suppressor mutations tended to be deleterious when they occurred in absence of the query mutation, in apparent contrast with their protective role in the presence of the query. We formulated and quantified mechanisms of genetic suppression that could explain 71% of interactions and provided mechanistic insight into disease pathology. Finally, we used these observations to predict suppressor genes in the human genome.

CONCLUSIONS

The global suppression network allowed us to define principles of genetic suppression that were conserved across diseases, model systems, and species. The emerging frequency of suppression interactions among human genes and range of underlying mechanisms, together with the prevalence of suppression in model organisms, suggest that compensatory mutations may exist for most genetic diseases.

Inflammation and autoimmunity are interrelated in patients with sickle cell disease at a steady-state condition: implications for vaso-occlusive crisis, pain, and sensory sensitivity

This study aimed to comprehensively analyze inflammatory and autoimmune characteristics of patients with sickle cell disease (SCD) at a steady-state condition (StSt) compared to healthy controls (HCs) to explore the pathogenesis of StSt and its impact on patients' well-being. The study cohort consisted of 40 StSt participants and 23 HCs enrolled between July 2021 and April 2023. StSt participants showed elevated white blood cell (WBC) counts and altered hematological measurements when compared to HCs. A multiplex immunoassay was used to profile 80 inflammatory cytokines/chemokines/growth factors in plasma samples from these SCD participants and HCs. Significantly higher plasma levels of 37 analytes were observed in SCD participants, with HGF, IL-18, IP-10, and MCP-2 being among the most significantly affected analytes. Additionally, autoantibody profiles were also altered, with elevated levels of anti-SSA/Ro60, anti-Ribosomal P, anti-Myeloperoxidase (MPO), and anti-PM/Scl-100 observed in SCD participants. Flow cytometric analysis revealed higher rates of red blood cell (RBC)/reticulocyte-leukocyte aggregation in SCD participants, predominantly involving monocytes. Notably, correlation analysis identified associations between inflammatory mediator levels, autoantibodies, RBC/reticulocyte-leukocyte aggregation, clinical lab test results, and pain crisis/sensitivity, shedding light on the intricate interactions between these factors. The findings underscore the potential significance of specific biomarkers and therapeutic targets that may hold promise for future investigations and clinical interventions tailored to the unique challenges posed by SCD. In addition, the correlations between vaso-occlusive crisis (VOC)/pain/sensory sensitivity and inflammation/immune dysregulation offer valuable insights into the pathogenesis of SCD and may lead to more targeted and effective therapeutic strategies.

Use of Compartmental Modeling and Retinol Isotope Dilution to Determine Vitamin A Stores in Young People with Sickle Cell Disease Before and After Vitamin A Supplementation

BACKGROUND

Suboptimal plasma retinol concentrations have been documented in US children with sickle cell disease (SCD) hemoglobin SS type (SCD-HbSS), but little is known about vitamin A kinetics and stores in SCD.

OBJECTIVES

The objectives were to quantify vitamin A total body stores (TBS) and whole-body retinol kinetics in young people with SCD-HbSS and use retinol isotope dilution (RID) to predict TBS in SCD-HbSS and healthy peers as well as after vitamin A supplementation in SCD-HbSS subjects.

METHODS

Composite plasma [13C10]retinol response data collected from 22 subjects with SCD-HbSS for 28 d after isotope ingestion were analyzed using population-based compartmental modeling ("super-subject" approach); TBS and retinol kinetics were quantified for the group. TBS was also calculated for the same individuals using RID, as well as for healthy peers (n = 20) and for the subjects with SCD-HbSS after 8 wk of daily vitamin A supplements (3.15 or 6.29 μmol retinol/d [900 or 1800 μg retinol activity equivalents/d]).

RESULTS

Model-predicted group mean TBS for subjects with SCD-HbSS was 428 μmol, equivalent to ∼11 mo of stored vitamin A; vitamin A disposal rate was 1.3 μmol/d. Model-predicted TBS was similar to that predicted by RID at 3 d postdosing (mean, 389 μmol; ∼0.3 μmol/g liver); TBS predictions at 3 compared with 28 d were not significantly different. Mean TBS in healthy peers was similar (406 μmol). RID-predicted TBS for subjects with SCD-HbSS was not significantly affected by vitamin A supplementation at either dose.

CONCLUSIONS

Despite differences in plasma retinol concentrations, TBS was the same in subjects with SCD-HbSS compared with healthy peers. Because 56 d of vitamin A supplementation at levels 1.2 to 2.6 times the Recommended Dietary Allowance did not increase TBS in these subjects with SCD-HbSS, further work will be needed to understand the effects of SCD on retinol metabolism. This trial was registered as NCT03632876 at clinicaltrials.gov.

Analysis of structural effects of sickle cell disease on brain vasculature of mice using three-dimensional quantitative phase imaging

Significance

Although the molecular origins of sickle cell disease (SCD) have been extensively studied, the effects of SCD on the vasculature-which can influence blood clotting mechanisms, pain crises, and strokes-are not well understood. Improving this understanding can yield insight into the mechanisms and wide-ranging effects of this devastating disease.

Aim

We aim to demonstrate the ability of a label-free 3D quantitative phase imaging technology, called quantitative oblique back-illumination microscopy (qOBM), to provide insight into the effects of SCD on brain vasculature.

Approach

Using qOBM, we quantitatively analyze the vasculature of freshly excised, but otherwise unaltered, whole mouse brains. We use Townes sickle transgenic mice, which closely recapitulate the pathophysiology of human SCD, and sickle cell trait mice as controls. Two developmental time points are studied: 6-week-old mice and 20-week-old mice. Quantitative structural and biophysical parameters of the vessels (including the refractive index (RI), which is linearly proportional to dry mass) are extracted from the high-resolution images and analyzed.

Results

qOBM reveals structural differences in the brain blood vessel thickness (thinner for SCD in particular brain regions) and the RI of the vessel wall (higher and containing a larger variation throughout the brain for SCD). These changes were only significant in 20-week-old mice. Further, vessel breakages are observed in SCD mice at both time points. The vessel wall RI distribution near these breaks, up to 350    μ m away from the breaking point, shows an erratic behavior characterized by wide RI variations. Vessel diameter, tortuosity, texture within the vessel, and structural fractal patterns are found to not be statistically different. As with vessel breaks, we also observe blood vessel blockages only in mice brains with SCD.

Conclusions

qOBM provides insight into the biophysical and structural composition of brain blood vessels in mice with SCD. Data suggest that the RI may be an indirect indicator of vessel rigidity, vessel strength, and/or tensions, which change with SCD. Future ex vivo and in vivo studies with qOBM could improve our understanding of SCD.

A Review of the Relationship between the Immune Response, Inflammation, Oxidative Stress, and the Pathogenesis of Sickle Cell Anaemia

Sickle cell anaemia (SCD) is a life-threatening haematological disorder which is predominant in sub-Saharan Africa and is triggered by a genetic mutation of the β-chain haemoglobin gene resulting in the substitution of glutamic acid with valine. This mutation leads to the production of an abnormal haemoglobin molecule called haemoglobin S (HbS). When deoxygenated, haemoglobin S (HbS) polymerises and results in a sickle-shaped red blood cell which is rigid and has a significantly shortened life span. Various reports have shown a strong link between oxidative stress, inflammation, the immune response, and the pathogenesis of sickle cell disease. The consequence of these processes leads to the development of vasculopathy (disease of the blood vessels) and several other complications. The role of the immune system, particularly the innate immune system, in the pathogenesis of SCD has become increasingly clear in recent years of research; however, little is known about the roles of the adaptive immune system in this disease. This review examines the interaction between the immune system, inflammation, oxidative stress, blood transfusion, and their effects on the pathogenesis of sickle cell anaemia.

Molecular and environmental contributors to neurological complications in sickle cell disease

Sickle cell disease (SCD) is an inherited hemoglobinopathy in which affected hemoglobin polymerizes under hypoxic conditions resulting in red cell distortion and chronic hemolytic anemia. SCD affects millions of people worldwide, primarily in Sub-Saharan Africa and the Indian subcontinent. Due to vaso-occlusion of sickled red cells within the microvasculature, SCD affects virtually every organ system and causes significant morbidity and early mortality. The neurological complications of SCD are particularly devastating and diverse, ranging from overt stroke to covert cerebral injury, including silent cerebral infarctions and blood vessel tortuosity. However, even individuals without evidence of neuroanatomical changes in brain imaging have evidence of cognitive deficits compared to matched healthy controls likely due to chronic cerebral hypoxemia and neuroinflammation. In this review, we first examined the biological contributors to SCD-related neurological complications and then discussed the equally important socioenvironmental contributors. We then discuss the evidence for neuroprotection from the two primary disease-modifying therapies, chronic monthly blood transfusions and hydroxyurea, and end with several experimental therapies designed to specifically target these complications.

Blockade of the mineralocorticoid receptor improves markers of human endothelial cell dysfunction and hematological indices in a mouse model of sickle cell disease

Increased endothelin-1 (ET-1) levels in patients with sickle cell disease (SCD) and transgenic mouse models of SCD contribute to disordered hematological, vascular, and inflammatory responses. Mineralocorticoid receptor (MR) activation by aldosterone, a critical component of the Renin-Angiotensin-Aldosterone-System, modulates inflammation and vascular reactivity, partly through increased ET-1 expression. However, the role of MR in SCD remains unclear. We hypothesized that MR blockade in transgenic SCD mice would reduce ET-1 levels, improve hematological parameters, and reduce inflammation. Berkeley SCD (BERK) mice, a model of severe SCD, were randomized to either sickle standard chow or chow containing the MR antagonist (MRA), eplerenone (156 mg/Kg), for 14 days. We found that MRA treatment reduced ET-1 plasma levels (p = .04), improved red cell density gradient profile (D50 ; p < .002), and increased mean corpuscular volume in both erythrocytes (p < .02) and reticulocytes (p < .024). MRA treatment also reduced the activity of the erythroid intermediate-conductance Ca2+ -activated K+ channel - KCa 3.1 (Gardos channel, KCNN4), reduced cardiac levels of mRNAs encoding ET-1, Tumor Necrosis Factor Receptor-1, and protein disulfide isomerase (PDI) (p < .01), and decreased plasma PDI and myeloperoxidase activity. Aldosterone (10-8  M for 24 h in vitro) also increased PDI mRNA levels (p < .01) and activity (p < .003) in EA.hy926 human endothelial cells, in a manner blocked by pre-incubation with the MRA canrenoic acid (1 μM; p < .001). Our results suggest a novel role for MR activation in SCD that may exacerbate SCD pathophysiology and clinical complications.

Description of a Colocated Comprehensive Care Model for People With Sickle Cell and Comorbid Pulmonary Disease

Comorbid pulmonary complications in people with sickle cell disease (pwSCD) are associated with high rates of morbidity and mortality, and poor access to care contributes to poor outcomes among this particularly high-risk pwSCD. Our purpose was to describe the population served and the resources required for hematology, pulmonary, nursing, respiratory therapy, social work, genetics, psychology, and school liaison providers to see these patients in an integrated clinic. We abstracted demographic, medication, clinical, and diagnostics data of the pwSCD seen at least once in this clinic from February 1, 2014 to December 10, 2020 from the electronic medical record and identified 145 unique pwSCD. Abnormal lung function and bronchodilator responsiveness were detected in 31% and 42% of participants respectively. Sleep abnormalities were found in over two-thirds of those screened and 65% had ≥1 previous acute chest syndrome episode. This clinic also allowed for direct provider communication and required relatively limited resources to serve a large number of severely affected pwSCD. Given the degree of abnormal respiratory variables detected and the limited resources required to implement this model, studies are warranted to evaluate whether it has the potential to improve outcomes in high-risk populations.

Impact of genotype on clinical course in sickle cell disease and the utility of neutrophil-lymphocyte ratio: a ten-year single-institution experience

BACKGROUND

Sickle cell disease (SCD) is a diverse group of blood disorders with significant global disease burden. Contemporary interest in the underlying inflammatory paradigm of SCD has emphasized the role of the neutrophil-lymphocyte ratio (NLR) as a prognostic inflammatory marker.

METHODS

We retrospectively reviewed 268 hospitalized patients with SCDs of different genotypes (HbSS, HbSβ0 thalassemia, HbSβ+ thalassemia, and HbSC), totaling 3329 hospital admissions over a 10-year period. Patients were stratified into SS/Sβ0 and Sβ+/SC groups for statistical analysis of parameters collected at steady state and at hospital admission.

RESULTS

At steady state, per unit increase of hemoglobin values was associated with reduced odds of ≥ 2 hospital admissions per year in SS/Sβ0 and Sβ+/SC groups; per unit increase in platelet count and white blood cell count was associated with increased odds only in the SS/Sβ0 group. The NLR had no association in either group. During admission, a cutoff of NLR = 3.5 discerned infection with a sensitivity of 60% and specificity of 57%. Performance improved when excluding patients on outpatient hydroxyurea therapy (cutoff of NLR = 3.5; sensitivity of 68% and specificity of 64%).

CONCLUSION

This study supports the utility of NLR as an accessible adjunctive clinical tool in SCD prognostication.

The Role of Antiplatelet in the Management of Sickle Cell Disease Patients

Sickle cell disease (SCD) is a genetic disorder characterized by abnormal hemoglobin, leading to red blood cell deformities and subsequent vaso-occlusive events. Platelet activation and adhesion play a significant role in the pathophysiology of SCD, contributing to the development of complications such as vaso-occlusive events, stroke, acute chest syndrome, and other manifestations. Antiplatelet therapy has emerged as a potential strategy to mitigate these complications by modulating the platelet function and reducing thrombotic events. This review article provides an overview of antiplatelet therapy's role in managing SCD patients. It discusses the pathophysiological abnormalities in the platelet function in SCD, the rationale for antiplatelet therapy, and the evidence supporting its use in various clinical scenarios. The article explores aspirin as the primary antiplatelet agent in SCD, including its mechanism of action, dosing considerations, and efficacy and safety data. Additionally, it highlights other antiplatelet agents, such as clopidogrel, prasugrel, ticagrelor, and emerging therapies under investigation. Clinical applications of antiplatelet therapy in primary and secondary prevention and the management of acute chest syndrome and other SCD complications are also discussed. Safety considerations are emphasized, including bleeding risk assessment, monitoring, and patient selection for antiplatelet therapy. Finally, the review highlights future research and clinical practice directions, including the development of novel antiplatelet agents, combination therapies, and the integration of antiplatelet therapy with other SCD treatments. Overall, this review provides a comprehensive understanding of the current role of antiplatelet therapy in SCD management, the challenges faced, and future directions for improving patient outcomes.

Macrophage metabolic rewiring improves heme-suppressed efferocytosis and tissue damage in sickle cell disease

Sickle cell disease (SCD) is hallmarked by an underlying chronic inflammatory condition, which is contributed by heme-activated proinflammatory macrophages. Although previous studies addressed heme ability to stimulate macrophage inflammatory skewing through Toll-like receptor4 (TLR4)/reactive oxygen species signaling, how heme alters cell functional properties remains unexplored. Macrophage-mediated immune cell recruitment and apoptotic cell (AC) clearance are relevant in the context of SCD, in which tissue damage, cell apoptosis, and inflammation occur owing to vaso-occlusive episodes, hypoxia, and ischemic injury. Here we show that heme strongly alters macrophage functional response to AC damage by exacerbating immune cell recruitment and impairing cell efferocytic capacity. In SCD, heme-driven excessive leukocyte influx and defective efferocytosis contribute to exacerbated tissue damage and sustained inflammation. Mechanistically, these events depend on heme-mediated activation of TLR4 signaling and suppression of the transcription factor proliferator-activated receptor γ (PPARγ) and its coactivator peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α). These changes reduce efferocytic receptor expression and promote mitochondrial remodeling, resulting in a coordinated functional and metabolic reprogramming of macrophages. Overall, this results in limited AC engulfment, impaired metabolic shift to mitochondrial fatty acid β-oxidation, and, ultimately, reduced secretion of the antiinflammatory cytokines interleukin-4 (IL-4) and IL-10, with consequent inhibition of continual efferocytosis, resolution of inflammation, and tissue repair. We further demonstrate that impaired phagocytic capacity is recapitulated by macrophage exposure to plasma of patients with SCD and improved by hemopexin-mediated heme scavenging, PPARγ agonists, or IL-4 exposure through functional and metabolic macrophage rewiring. Our data indicate that therapeutic improvement of heme-altered macrophage functional properties via heme scavenging or PGC1α/PPARγ modulation significantly ameliorates tissue damage associated with SCD pathophysiology.

Ellagic Acid Exerts Dual Action to Curb the Pathophysiological Manifestations of Sickle Cell Disease and Attenuate the Hydroxyurea-Induced Myelosuppression in Berkeley Mice

The use of adjuvant therapy is an attractive approach to manage sickle cell disease (SCD) symptomatically. The present study aimed to investigate the potential of ellagic acid as an adjuvant therapy with hydroxyurea (HU), a key drug for SCD with myelosuppressive toxic effects. A panel of experiments was performed using SCD patient's blood (ex vivo) and transgenic mice model of SCD (in vivo). Ellagic acid exhibited the following beneficial pharmacological actions: (a) potent anti-sickling, polymerization inhibitory, and inherent non-hemolytic activity; (b) pronounced action to abrogate HU-induced neutropenia and to improve key hematological parameters during SCD (RBC, Hb, platelet levels); (c) considerable action to foster vascular tone (L-proline); (d) marked attenuating effect against oxidative stress (nitrotyrosine, hypoxanthine, MDA, GSH); (e) substantial inhibitory role against inflammation (analgesic activity and regulation of hemin, TNF-α, IL-1β, NF-κB/IκBα); (f) remarkable outcome of declining vaso-occlusive crisis (P-selectin, ERK1/2); (g) notable shielding deed against elevated biochemical marker for organ toxicity (creatinine); (h) noticeably prevented histopathological alterations of the spleen. Additionally, the pharmacokinetic study results of HU in the presence and absence of ellagic acid using a mouse model demonstrate that ellagic acid could be safely co-administered with HU. Overall findings suggest that ellagic acid is a promising candidate for adjuvant therapy in SCD based on its own significant ability against SCD and potentiating capability of HU action via targeting improvement at the various stages of pathophysiological complications during SCD and minimizing HU-induced toxicological manifestations.

Co-expression of Foxp3 and Helios facilitates the identification of human T regulatory cells in health and disease

Foxp3 is regarded as the major transcription factor for T regulatory (Treg) cells and expression of Foxp3 is used to identify and quantitate Treg cells in mouse models. However, several studies have demonstrated that human CD4+ T conventional (Tconv) cells activated in vitro by T cell receptor (TCR) stimulation can express Foxp3. This observation has raised doubt as to the suitability of Foxp3 as a Treg marker in man. Helios, a member of the Ikaros gene family, has been shown to be expressed by 80-90% of human Foxp3+ Treg cells and can potentially serve as a marker of human Treg. Here, we confirm that Foxp3 expression is readily upregulated by Tconv upon TCR stimulation in vitro, while Helios expression is not altered. More importantly, we show that Foxp3 expression is not elevated by stimulation of hTconv in a humanized mouse model of graft versus host disease (GVHD) and in patients with a wide variety of acute and chronic inflammatory diseases including sickle cell disease, acute and chronic GVHD, systemic lupus erythematosus, as well as critical COVID-19. In all patients studied, an excellent correlation was observed between the percentage of CD4+ T cells expressing Foxp3 and the percentage expressing Helios. Taken together, these studies demonstrate that Foxp3 is not induced upon Tconv cell activation in vivo and that Foxp3 expression alone can be used to quantitate Treg cells in humans. Nevertheless, the combined use of Foxp3 and Helios expression provides a more reliable approach for the characterization of Treg in humans.

The inflammatory profiles of pulmonary alveolar macrophages and alveolar type 2 cells in SCD

The lung microenvironment plays a crucial role in maintaining lung homeostasis as well as the initiation and resolution of both acute and chronic lung injury. Acute chest syndrome (ACS) is a complication of sickle cell disease (SCD) like acute lung injury. Both the endothelial cells and peripheral blood mononuclear cells are known to secrete proinflammatory cytokines elevated during ACS episodes. However, in SCD, the lung microenvironment that may favor excessive production of proinflammatory cytokines and the contribution of other lung resident cells, such as alveolar macrophages and alveolar type 2 epithelial (AT-2) cells, to ACS pathogenesis is not completely understood. Here, we sought to understand the pulmonary microenvironment and the proinflammatory profile of lung alveolar macrophages (LAMs) and AT-2 cells at steady state in Townes sickle cell (SS) mice compared to control mice (AA). In addition, we examined lung function and micromechanics molecules essential for pulmonary epithelial barrier function in these mice. Our results showed that bronchoalveolar lavage (BAL) fluid in SS mice had elevated protein levels of pro-inflammatory cytokines interleukin (IL)-1β and IL-12 (p ⩽ 0.05) compared to AA controls. We showed for the first time, significantly increased protein levels of inflammatory mediators (Human antigen R (HuR), Toll-like receptor 4 (TLR4), MyD88, and PU.1) in AT-2 cells (1.4 to 2.2-fold) and LAM (17-21%) isolated from SS mice compared to AA control mice at steady state. There were also low levels of anti-inflammatory transcription factors (Nrf2 and PPARy) in SS mice compared to AA controls (p ⩽ 0.05). Finally, we found impaired lung function and a dysregulated composition of surfactant proteins (B and C). Our results demonstrate that SS mice at steady state had a compromised lung microenvironment with elevated expression of proinflammatory cytokines by AT-2 cells and LAM, as well as dysregulated expression of surfactant proteins necessary for maintaining the alveolar barrier integrity and lung function.

Molecular and cellular effects of in vivo chronic intravascular hemolysis and anti-inflammatory therapeutic approaches

Intravascular hemolysis (IVH) occurs in numerous inherited and acquired disorders, including sickle cell disease (SCD), malaria and sepsis. These diseases display unique symptoms, but often share complications, such as vasomotor dysfunction and pulmonary hypertension. Consequently, in vivo models are needed to study the effects of continuous intravascular hemolytic processes, independently of the molecular or extrinsic alteration that leads to erythrocyte destruction. We gave twice-weekly low-dose phenylhydrazine (LDPHZ) to C57BL/6 J mice for 4 weeks, and measured parameters indicative of anemia, hemoglobin-clearance pathways, inflammation and iron turnover, comparing these to those of a murine model of SCD, which displays associated IVH. LDPHZ administration provoked discreet anemia in mice and significant reticulocytosis, in association with hemoglobin/heme-clearance pathway protein depletion. Mice subjected to chronic hemolysis displayed elevated leukocyte counts and plasma levels of interleukin (IL)-1β, TNF-α, IL-6, soluble ICAM-1, endothelin-1 and anti-inflammatory IL-10, closely emulating alterations indicative of systemic inflammatory and endothelial activation in SCD, and confirming chronic IVH in itself as a serious complication. Discreet accelerations in hepatic and splenic iron turnover also occurred in LDPHZ mice, without alterations in liver damage markers. Examining the effects of two therapies on hemolysis-induced inflammation, the administration of hydroxyurea (and to a lesser extent, l-glutamine) significantly abrogated hemolytic inflammation in mice, without apparent inhibition of hemolysis. In conclusion, the isolation of chronic IVH, a common disease mechanism, using this model, may allow the study of hemolysis-specific sequelae at the cellular and systemic level, and the investigation of candidate agents that could potentially counter hemolytic inflammation.

Pathophysiological characterization of the Townes mouse model for sickle cell disease

A deeper pathophysiologic understanding of available mouse models of sickle cell disease (SCD), such as the Townes model, will help improve preclinical studies. We evaluated groups of Townes mice expressing either normal adult human hemoglobin (HbA), sickle cell trait (HbAS), or SCD (HbS), comparing younger versus older adults, and females versus males. We obtained hematologic parameters in steady-state and hypoxic conditions and evaluated metabolic markers and cytokines from serum. Kidney function was evaluated by measuring the urine protein/creatinine ratio and urine osmolality. In vivo studies included von Frey assay, non-invasive plethysmography, and echocardiography. Histopathological evaluations were performed in lung, liver, spleen, and kidney tissues. HbS mice displayed elevated hemolysis markers and white blood cell counts, with some increases more pronounced in older adults. After extended in vivo hypoxia, hemoglobin, platelet counts, and white blood cell counts decreased significantly in HbS mice, whereas they remained stable in HbA mice. Cytokine analyses showed increased TNF-alpha in HbS mice. Kidney function assays revealed worsened kidney function in HbS mice. The von Frey assay showed a lower threshold to response in the HbS mice than controls, with more noticeable differences in males. Echocardiography in HbS mice suggested left ventricular hypertrophy and dilatation. Plethysmography suggested obstructive lung disease and inflammatory changes in HbS mice. Histopathological studies showed vascular congestion, increased iron deposition, and disruption of normal tissue architecture in HbS mice. These data correlate with clinical manifestations in SCD patients and highlight analyses and groups to be included in preclinical therapeutic studies.

Management of Older Adults with Sickle Cell Disease: Considerations for Current and Emerging Therapies

People with sickle cell disease (SCD) are living longer than ever before, with the median survival increasing from age 14 years in 1973, beyond age 40 years in the 1990s, and as high as 61 years in recent cohorts from academic centers. Improvements in survival have been attributed to initiatives, such as newborn screening, penicillin prophylaxis, vaccination against encapsulated organisms, better detection and treatment of splenic sequestration, and improved transfusion support. There are an estimated 100,000 people living with SCD in the United States and millions of people with SCD globally. Given that the number of older adults with SCD will likely continue to increase as survival improves, better evidence on how to manage this population is needed. When managing older adults with SCD (defined herein as age ≥ 40 years), healthcare providers should consider the potential pitfalls of extrapolating evidence from existing studies on current and emerging therapies that have typically been conducted with participants at mean ages far below 40 years. Older adults with SCD have historically had little to no representation in clinical trials; therefore, more guidance is needed on how to use current and emerging therapies in this population. This article summarizes the available evidence for managing older adults with SCD and discusses potential challenges to using approved and emerging drugs in this population.