Angiogenic and inflammatory markers of cardiopulmonary changes in children and adolescents with sickle cell disease

Circulating biomarkers associated with pediatric sickle cell disease

Introduction

Sickle cell disease (SCD) is a genetic blood disorder caused by a mutation in the HBB gene, which encodes the beta-globin subunit of hemoglobin. This mutation leads to the production of abnormal hemoglobin S (HbS), causing red blood cells to deform into a sickle shape. These deformed cells can block blood flow, leading to complications like chronic hemolysis, anemia, severe pain episodes, and organ damage. SCD genotypes include HbSS, HbSC (HbC is an abnormal variant of hemoglobin), and HbS/β-thalassemia. Sickle cell trait (SCT), HbAS, represents the carrier state, while other hemoglobin variants include HbCC, HbAC, and the normal HbAA. Over 7.5 million people worldwide live with SCD, with a high mortality rate in sub-Saharan Africa, including Ghana. Despite its prevalence, SCD is underdiagnosed and poorly managed, especially in children. Characterized by intravascular hemolysis, SCD leads to oxidative stress, endothelial activation, and systemic inflammation. Identifying circulating blood biomarkers indicative of organ damage and systemic processes is vital for understanding SCD and improving patient management. However, research on biomarkers in pediatric SCD is limited and few have been identified and validated. This study explores specific circulating biomarkers in pediatric SCD in Ghana (West Africa), hypothesizing that inflammatory and neuronal injury markers in children with SCD could predict disease outcomes.

Methods

Clinical data were collected from 377 children aged 3-8 years with various Hb genotypes, including SCD and SCT, at Korle-Bu Teaching Hospital in Accra, Ghana (2021-2022). A total of 80 age- and sex-matched subjects were identified. A cross-sectional study utilized a multiplexed immunoassay procedure to evaluate serum biomarkers, including cytokines, chemokines, vascular injury markers, systemic inflammation markers, cell-free heme scavengers, brain-derived neurotrophic factor (BDNF), and angiogenic factors.

Results

Elevated levels of BDNF, Ang-2, CXCL10, CCL11, TNF-α, IL-6, IL-10, IL12p40, ICAM-1, VCAM-1, Tie-2, and VEGFA were observed in HbSS subjects, correlating with hemoglobin level, leukocyte, and erythrocyte counts. Heme scavengers like HO-1, hemopexin, and haptoglobin also correlated with these parameters. ROC and AUC analyses demonstrated the potential of these biomarkers in predicting SCD outcomes.

Conclusion

These findings suggest that there are significant differences between biomarker expression among the different genotypes examined. We conclude that a predictive algorithm based on these biomarkers could be developed and validated through longitudinal assessment of within-genotype differences and correlation of the data with disease severity or outcomes. With such a tool one can enhance SCD management and improve patient outcomes. This approach may pave the way for personalized interventions and better clinical care for pediatric SCD patients.

Trimethylamine-N-oxide promotes osteoclast differentiation and oxidative stress by activating NF-κB pathway

BACKGROUND

Senile osteoporosis may be caused by an imbalance in intestinal flora and oxidative stress. Trimethylamine-N-oxide (TMAO), a metabolite of dietary choline dependent on gut microbes, has been found to be significantly increased in osteoporosis. However, the role of TMAO in bone loss during osteoporosis remains poorly understood. In this study, we examined the impact of TMAO on osteoclast differentiation and bone resorption in an in vitro setting.

METHODS

Osteoclast differentiation was induced by incubating RAW 264.7 cells in the presence of Receptor Activator for Nuclear Factor-κB Ligand (RANKL) and macrophage-stimulating factor (M-CSF). Flow cytometry, TRAP staining assay, CCK-8, and ELISA were employed to investigate the impact of TMAO on osteoclast differentiation and bone resorption activity in vitro. For mechanistic exploration, RT-PCR and Western blotting were utilized to assess the activation of the NF-κB pathway. Additionally, protein levels of secreted cytokines and growth factors were determined using suspension array technology.

RESULTS

Our findings demonstrate that TMAO enhances RANKL and M-CSF-induced osteoclast formation and bone resorption in a dose-dependent manner. Mechanistically, TMAO triggers the upregulation of the NF-κB pathway and osteoclast-related genes (NFATc1, c-Fos, NF-κB p65, Traf6, and Cathepsin K). Furthermore, TMAO markedly elevated the levels of oxidative stress and inflammatory factors.

CONCLUSIONS

In conclusion, TMAO enhances RANKL and M-CSF-induced osteoclast differentiation and inflammation in RAW 264.7 cells by activating the NF-κB signaling pathway. These findings offer a new rationale for further academic and clinical research on osteoporosis treatment.

Antiviral response and HIV-1 inhibition in sickle cell disease

Sickle cell disease (SCD) is characterized by hemolysis, vaso-occlusion, and ischemia. HIV-1 infection was previously shown to be suppressed in SCD PBMCs. Here, we report that HIV-1 suppression is attributed to the increased expression of iron, hypoxia, and interferon-induced innate antiviral factors. Inhibition of upregulated antiviral genes, HMOX-1, CDKN1A, and CH25H, increased HIV-1 replication in SCD PBMCs, suggesting their critical role in HIV-1 suppression. Levels of IFN-β were elevated in SCD patients. Sickle cell hemoglobin (HbS) treatment of THP-1-derived and primary monocyte-derived macrophages induced production of IFN-β, upregulated antiviral gene expression, and suppressed HIV-1 infection. Infection with mouse-adapted EcoHIV was suppressed in the SCD mice that also exhibited elevated levels of antiviral restriction factors. Our findings suggest that hemolysis and release of HbS leads to the induction of IFN-β production, induction of cellular antiviral state by the expression of iron and IFN-driven factors, and suppression of HIV-1 infection.

HIV-1 infection in sickle cell disease and sickle cell trait: role of iron and innate response

INTRODUCTION

Sickle cell disease (SCD), an inherited hemoglobinopathy, affects primarily African Americans in the U.S.A. In addition, about 15% African Americans carry sickle cell trait (SCT). Despite the risk associated with blood transfusions, SCD patients have lower risk of acquiring HIV-1 infection. SCT individuals might also have some protection from HIV-1 infection.

AREAS COVERED

Here, we will review recent and previous studies with the focus on molecular mechanisms that might underlie and contribute to the protection of individuals with SCD and SCT from HIV-1 infection. As both of these conditions predispose to hemolysis, we will focus our discussion on the effects of systemic and intracellular iron on HIV-1 infection and progression. We will also review changes in iron metabolism and activation of innate antiviral responses in SCD and SCT and their effects on HIV-1 infection.

EXPERT OPINION

Previous studies, including ours, showed that SCD might protect from HIV-1 infection. This protection is likely due to the upregulation of complex protein network in response to hemolysis, hypoxia and interferon signaling. These findings are important not only for HIV-1 field but also for SCD cure efforts as antiviral state of SCD patients may adversely affect lentivirus-based gene therapy efforts.

The gut microbiome in sickle cell disease: Characterization and potential implications

BACKGROUND

Sickle Cell Disease (SCD) is an inherited blood disorder that leads to hemolytic anemia, pain, organ damage and early mortality. It is characterized by polymerized deoxygenated hemoglobin, rigid sickle red blood cells and vaso-occlusive crises (VOC). Recurrent hypoxia-reperfusion injury in the gut of SCD patients could increase tissue injury, permeability, and bacterial translocation. In this context, the gut microbiome, a major player in health and disease, might have significant impact. This study sought to characterize the gut microbiome in SCD.

METHODS

Stool and saliva samples were collected from healthy controls (n = 14) and SCD subjects (n = 14). Stool samples were also collected from humanized SCD murine models including Berk, Townes and corresponding control mice. Amplified 16S rDNA was used for bacterial composition analysis using Next Generation Sequencing (NGS). Pairwise group analyses established differential bacterial groups at many taxonomy levels. Bacterial group abundance and differentials were established using DeSeq software.

RESULTS

A major dysbiosis was observed in SCD patients. The Firmicutes/Bacteroidetes ratio was lower in these patients. The following bacterial families were more abundant in SCD patients: Acetobacteraceae, Acidaminococcaceae, Candidatus Saccharibacteria, Peptostreptococcaceae, Bifidobacteriaceae, Veillonellaceae, Actinomycetaceae, Clostridiales, Bacteroidacbactereae and Fusobacteriaceae. This dysbiosis translated into 420 different operational taxonomic units (OTUs). Townes SCD mice also displayed gut microbiome dysbiosis as seen in human SCD.

CONCLUSION

A major dysbiosis was observed in SCD patients for bacteria that are known strong pro-inflammatory triggers. The Townes mouse showed dysbiosis as well and might serve as a good model to study gut microbiome modulation and its impact on SCD pathophysiology.

Urinary Kringle Domain-Containing Protein HGFL: A Validated Biomarker of Early Sickle Cell Anemia-Associated Kidney Disease

INTRODUCTION

Chronic kidney disease (CKD) is a prevalent complication of sickle cell anemia (SCA). Hyperfiltration that delayed detection of CKD is common in SCA patients. Identification of novel urinary biomarkers correlating with glomerular filtration rates may help to detect and predict progression of renal disease.

METHODS

Reanalysis of mass spectra of urinary samples obtained from University of Illinois at Chicago identified kringle domain-containing protein HGFL.

RESULTS

HGFL levels correlated with hyperfiltration, were significantly reduced at CKD stage 1 compared to stage 0, negatively correlated with progression of CKD and were suitable for differentiation of stage 1. Better prediction of CKD progression to stage 2 was observed for HGFL-based risk prediction compared to the estimated glomerular filtration rate (eGFR)-based prediction. Results from a Howard University patient cohort supported the utility of HGFL-based test for the differentiation of stage 1 of CKD.

CONCLUSION

Urinary HGFL may contribute additional information beyond eGFR and improve diagnosis of early-stage CKD in SCA patients.

Longitudinal effect of disease-modifying therapy on tricuspid regurgitant velocity in children with sickle cell anemia

Elevated tricuspid regurgitant velocity (TRV) ≥2.5 m/s is a predictor of disease severity in adults and children with sickle cell anemia (SCA), but how disease-modifying therapies (DMTs) affect this biomarker is incompletely understood. We investigated the effect of DMTs on TRV elevation in children. In a prospective single-center study, 204 subjects with HbSS or HbSβ0 thalassemia (mean age, 10.6 years; range, 5-18) had echocardiograms with assessment of TRV, with repeat evaluations after 2 years of observation. One-hundred and twelve participants received DMTs (hydroxyurea, n = 72; monthly erythrocyte transfusions, n = 40), 58 did not receive any DMT, and 34 were begun on hydroxyurea during this observation period. In the entire cohort, an increase in hemoglobin of 1.0 g/dL was associated with a 0.03-m/s decrease in TRV (P = .024), and a decrease in absolute reticulocyte count of 1.0 × 106/mL was associated with a 0.34-m/s decrease in TRV (P = .034). Compared with baseline, hydroxyurea exposure (continuous or newly started) was associated with an average 5% decline in mean TRV at the 2-year evaluation. Among participants newly started on hydroxyurea (mean treatment duration 1.2 ± 0.6 years), an increase in hemoglobin of 1.0 g/dL was associated with a 0.06-m/s decrease in TRV (P = .05). We conclude that hydroxyurea therapy may mitigate TRV elevation in children with SCA, possibly as a result of a reduction in hemolysis and improvement in anemia.

Vasculopathy in Sickle Cell Disease: From Red Blood Cell Sickling to Vascular Dysfunction

Sickle cell disease (SCD) is a hereditary disorder that leads to the production of an abnormal hemoglobin, hemoglobin S (HbS). HbS polymerizes in deoxygenated conditions, which can prompt red blood cell (RBC) sickling and leaves the RBCs more rigid, fragile, and prone to hemolysis. SCD patients suffer from a plethora of complications, ranging from acute complications, such as characteristic, frequent, and debilitating vaso-occlusive episodes to chronic organ damage. While RBC sickling is the primary event at the origin of vaso-occlusive processes, other factors that can further increase RBC transit times in the microcirculation may also be required to precipitate vaso-occlusive processes. The adhesion of RBC and leukocytes to activated endothelium and the formation of heterocellular aggregates, as well as increased blood viscosity, are among the mechanisms involved in slowing the progress of RBCs in deoxygenated vascular areas, favoring RBC sickling and promoting vascular occlusion. Chronic inflammatory processes and oxidative stress, which are perpetuated by hemolytic events and ischemia-reperfusion injury, result in this pan cellular activation and some acute events, such as stroke and acute chest syndrome, as well as chronic end-organ damage. Furthermore, impaired vasodilation and vasomotor hyperresponsiveness in SCD also contribute to vaso-occlusive processes. Treating SCD as a vascular disease in addition to its hematological perspective, the present article looks at the interplay between abnormal RBC physiology/integrity, vascular dysfunction and clinical severity in SCD, and discusses existing therapies and novel drugs in development that may ameliorate vascular complications in the disease. © 2021 American Physiological Society. Compr Physiol 11:1785-1803, 2021.

Cytokines, Chemokines, and Inflammation in Pulmonary Arterial Hypertension

According to the World Symposium Pulmonary Hypertension (WSPH) classification, pulmonary hypertension (PH) is classified into five categories based on etiology. Among them, Group 1 pulmonary arterial hypertension (PAH) disorders are rare but progressive and often, fatal despite multiple approved treatments. Elevated pulmonary arterial pressure in patients with WSPH Group 1 PAH is mainly caused by increased pulmonary vascular resistance (PVR), due primarily to sustained pulmonary vasoconstriction and excessive obliterative pulmonary vascular remodeling. Growing evidence indicates that inflammation plays a critical role in the development of pulmonary vascular remodeling associated with PAH. While the role of auto-immunity is unclear, infiltration of inflammatory cells in and around vascular lesions, including T- and B-cells, dendritic cells, macrophages, and mast cells have been observed in PAH patients. Serum and plasma levels of chemokines, cytokines, and autoantibodies are also increased in PAH patients; some of these circulating molecules are correlated with disease severity and survival. Preclinical experiments have reported a key role of the inflammation in PAH pathophysiology in vivo. Importantly, anti-inflammatory and immunosuppressive agents have further exhibited therapeutic effects. The present chapter reviews published experimental and clinical evidence highlighting the canonical role of inflammation in the pathogenesis of PAH and as a major target for the development of anti-inflammatory therapies in patients with PAH.

Association Between Nitric Oxide, Oxidative Stress, Eryptosis, Red Blood Cell Microparticles, and Vascular Function in Sickle Cell Anemia

Chronic hemolysis, enhanced oxidative stress, and decreased nitric oxide (NO) bioavailability promote vasculopathy in sickle cell anemia (SCA). Oxidative stress and NO are known to modulate eryptosis in healthy red blood cells (RBCs); however, their role in SCA eryptosis and their impact on the genesis of RBC-derived microparticles (RBC-MPs) remains poorly described. RBC-MPs could play a role in vascular dysfunction in SCA. The aims of this study were to evaluate the roles of oxidative stress and NO in eryptosis and RBC-MPs release, and to determine whether RBC-MPs could be involved in vascular dysfunction in SCA. Markers of eryptosis and oxidative stress, plasma RBC-MPs concentration and arterial stiffness were compared between SCA and healthy (AA) individuals. In-vitro experiments were performed to test: 1) the effects of oxidative stress (antioxidant: n-acetylcysteine (NAC); pro-oxidant: cumene hydroperoxide) and NO (NO donor: sodium nitroprusside (SNP); NO-synthase inhibitor (L-NIO)) on eryptosis, RBC deformability and RBC-MP genesis; 2) the effects of SCA/AA-RBC-MPs on human aortic endothelial cell (HAEC) inflammatory phenotype and TLR4 pathway. Eryptosis, RBC-MPs, oxidative stress and arterial stiffness were increased in SCA. NAC increased RBC deformability and decreased eryptosis and RBC-MPs release, while cumene did the opposite. SNP increased RBC deformability and limited eryptosis, but had no effect on RBC-MPs. L-NIO did not affect these parameters. Arterial stiffness was correlated with RBC-MPs concentration in SCA. RBC-MPs isolated directly from SCA blood increased adhesion molecules expression and the production of cytokines by HAEC compared to those isolated from AA blood. TLR4 inhibition alleviated these effects. Our data show that oxidative stress could promote eryptosis and the release of RBC-MPs that are potentially involved in macrovascular dysfunction in SCA.

High levels of proinflammatory cytokines IL-6 and IL-8 are associated with a poor clinical outcome in sickle cell anemia

Sickle cell anemia (SCA) pathophysiology is characterized by the activation of sickle red blood cells, reticulocytes, leukocytes, platelets, and endothelial cells, and with the expression of several inflammatory molecules. Therefore, it is conceivable that variations in levels of proinflammatory cytokines may act as a signaling of differential clinical course in SCA. Here, we evaluated the clinical impact of proinflammatory cytokines interleukin 1-β (IL-1β), interleukin 6 (IL-6), and interleukin 8 (IL-8) in 79 patients with SCA, followed in a single reference center from northeastern Brazil. The main clinical/laboratory data were obtained from patient interview and medical records. The proinflammatory markers IL-1β, IL-6, and IL-8 were evaluated by using commercially available enzyme-linked immunosorbent assay kits. According to levels of the proinflammatory markers, we observed that patients who had a higher frequency of VOC per year (P = 0.0236), acute chest syndrome (P = 0.01), leg ulcers (P = 0.0001), osteonecrosis (P = 0.0006), stroke (P = 0.0486), and priapism (P = 0.0347) had higher IL-6 levels compared with patients without these clinical complications. Furthermore, increased levels of IL-8 were found in patients who presented leg ulcers (P = 0.0184). No significant difference was found for IL-1β levels (P > 0.05). In summary, the present study emphasizes the role of inflammation in SCA pathophysiology, reveals an association of IL-8 levels and leg ulcer occurrence, and indicates that IL-6 levels can be used as a useful predictor for poor outcomes in SCA.

Sickle cell disease: at the crossroads of pulmonary hypertension and diastolic heart failure

Sickle cell disease (SCD) is caused by a single point mutation in the gene that codes for beta globin synthesis, causing haemoglobin polymerisation, red blood cell stiffening and haemolysis under low oxygen and pH conditions. Downstream effects include widespread vasculopathy due to recurring vaso-occlusive events and haemolytic anaemia, affecting all organ systems. Cardiopulmonary complications are the leading cause of death in patients with SCD, primarily resulting from diastolic heart failure (HF) and/or pulmonary hypertension (PH). HF in SCD often features biventricular cardiac hypertrophy and left ventricular (LV) diastolic dysfunction. Among HF cases in the general population, approximately half occur with preserved ejection fraction (HFpEF). The insidious evolution of HFpEF differs from the relatively acute evolution of HF with reduced ejection fraction. The PH of SCD has diverse origins, which can be pulmonary arterial (precapillary), pulmonary venous (postcapillary) or pulmonary thromboembolic. It is also appreciated that patients with SCD can develop both precapillary and postcapillary PH, with elevations in LV diastolic pressures, as well as elevations in transpulmonary pressure gradient and pulmonary vascular resistance. Regardless of the cause of PH in SCD, its presence significantly reduces functional capacity and increases mortality. PH that occurs in the presence of HFpEF is usually of postcapillary origin. This review aims to assemble what has been learnt from clinical and animal studies about the manifestation of PH-HFpEF in SCD, specifically the contributions of LV diastolic dysfunction and myocardial fibrosis, in an attempt to gain an understanding of its evolution.

Angiopoietin-2 as a Marker of Retinopathy in Children and Adolescents With Sickle Cell Disease: Relation to Subclinical Atherosclerosis

OBJECTIVES

Angiopoietin-2 (Ang-2) is a multifaceted cytokine that functions in both angiogenesis and inflammation. A proangiogenic state has been found in adults with sickle cell disease (SCD), mainly because of elevated Ang-2 levels. We determined Ang-2 level in 40 children and adolescents with SCD compared with 40 healthy controls and assessed its relation to retinopathy as well as carotid intimamedia thickness (CIMT).

METHODS

Hematologic profile, serum ferritin, and serum Ang-2 were measured. CIMT was assessed using high-resolution ultrasound. Fundus examination was performed followed by fundus fluorescein angiography. Optical coherence tomography angiography (OCTA) was used to find small vascular changes not clinically manifested.

RESULTS

Ang-2 levels and CIMT were significantly higher in SCD patients compared with controls. The incidence of nonproliferative retinopathy was 45%. SCD patients with retinopathy were older in age with a history of sickling crisis of >3 attacks per year and had a higher incidence of sickle cell anemia than sickle β-thalassemia. Ang-2 cutoff value 9000 pg/mL could significantly detect the presence of retinopathy among SCD patients with 100% sensitivity and specificity. Serum Ang-2 levels were positively correlated with HbS and CIMT. Logistic regression analysis revealed that Ang-2 and HbS significantly contribute to retinopathy among patients with SCD.

CONCLUSIONS

Elevated Ang-2 highlights the role of angiogenesis in the pathophysiology of SCD and may be considered a promising marker for screening of patients at risk of sickle retinopathy and vascular dysfunction.

Hypercoagulability in Pulmonary Hypertension

Pulmonary hypertension (PH) is divided into varied pathophysiological and etiologic groupings, as classified by the World Health Organization (WHO). Pulmonary arterial hypertension (PAH), which falls under WHO group 1 PH, is a progressive and potentially fatal disease characterized by a vasoconstrictive, proliferative, and thrombotic phenotype, which leads to increased pulmonary artery pressure, right heart failure, and death. Pathologically, in situ thromboses are found in the small distal pulmonary arteries. Dysregulation of coagulation, platelet function, and endothelial cells may contribute to a prothrombotic state. There is mixed evidence for the use of anticoagulation or antiplatelet therapy in PAH patients.

Inhaled steroids associated with decreased macrophage markers in nonasthmatic individuals with sickle cell disease in a randomized trial

Inhaled mometasone was shown to improve pain scores and decrease soluble vascular cell adhesion molecule (sVCAM) concentration in a randomized controlled trial of nonasthmatic patients with sickle cell disease. We sought to explore potential changes in systemic inflammation as a mechanism underlying this effect. Serum samples from 41 trial participants (15 placebo- and 26 mometasone-treated) were analyzed using a 92 inflammatory marker panel at baseline and after 8 weeks of mometasone therapy. Individual marker analysis and correlation analysis were conducted. Adjusted for age, the mometasone-treated group decreased the concentration of CXCL9, CXCL11, CD40, IL-10, and IL-18 relative to placebo-treated participants. Hierarchical clustering and correlation analysis identified additional evidence for a decrease in cytokines linking to macrophage signaling and migration. There was no statistically significant change in markers of asthma and allergy, indicating that the improvement was unlikely mediated by modulation of occult reactive airway disease. This analysis of inflammatory markers suggests that decrease in macrophage activity may be involved in the mediation of the clinical benefit seen with use of inhaled mometasone in nonasthmatic patients with sickle cell disease.Trial registration: clinicaltrials.gov identifier: NCT02061202.

Elevated Proangiogenic Markers are Associated with Vascular Complications within Ghanaian Sickle Cell Disease Patients

: Sickle cell disease (SCD) is an inherited blood disorder that can result in vasculopathy and end organ damage. Angiogenesis has been implicated as a key contributing factor to vascular mediated tissue injury in SCD. The relative plasma levels of angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2), and vascular endothelial growth factor (VEGF) greatly influence angiogenesis. Dysregulation of these growth factors, leading to a pro-angiogenic state in SCD patients, has been documented in the developed world but there is very little data in Africa. There is the need, therefore, for studies in Ghanaian SCD patients. The aim of this study was to assess plasma levels of Ang-1, Ang-2, and VEGF in homozygous (HbSS) SCD patients with or without complications and healthy controls (HbAA) in Ghana. The study was a case-control study involving 544 participants: 396 HbSS SCD patients and 148 HbAA healthy controls. The study was conducted at the Center for Clinical Genetics (Sickle Cell Clinic) and Accra Area Blood Centre for National Blood transfusion at the Korle-Bu Teaching Hospital, Accra, Ghana. The plasma levels of Ang-1, Ang-2, and VEGF of study participants were measured with a double sandwich enzyme-linked immunosorbent assay (ELISA) technique. Complete blood count (CBC) was measured with an autoanalyser. The mean plasma Ang-1, Ang-2, and VEGF were significantly higher in HbSS SCD patients with or without complications than healthy controls (p < 0.001). The Ang-2/Ang-1 ratio was significantly lower in the controls than the HbSS patients (p < 0.001). The Ang-2/Ang-1 ratio was higher in the HbSS patients with leg ulcers as compared with patients with other complications and healthy controls (p < 0.001). There were higher leucocyte counts in HbSS patients than healthy controls. Overall, there was elevated plasma levels of Ang-1, Ang-2, and VEGF in SCD patients. The higher Ang-2/Ang-1 plasma levels in patients with leg ulcers suggests a possible ongoing angiogenesis and response to inflammatory stimuli. The study provides a first report on plasma levels of angiopoietin-1, angiopoietin-2, and vascular endothelial growth factors in homozygous sickle cell disease patients in Ghana.

Inflammation in sickle cell disease

The primary β-globin gene mutation that causes sickle cell disease (SCD) has significant pathophysiological consequences that result in hemolytic events and the induction of the inflammatory processes that ultimately lead to vaso-occlusion. In addition to their role in the initiation of the acute painful vaso-occlusive episodes that are characteristic of SCD, inflammatory processes are also key components of many of the complications of the disease including autosplenectomy, acute chest syndrome, pulmonary hypertension, leg ulcers, nephropathy and stroke. We, herein, discuss the events that trigger inflammation in the disease, as well as the mechanisms, inflammatory molecules and cells that propagate these inflammatory processes. Given the central role that inflammation plays in SCD pathophysiology, many of the therapeutic approaches currently under pre-clinical and clinical development for the treatment of SCD endeavor to counter aspects or specific molecules of these inflammatory processes and it is possible that, in the future, we will see anti-inflammatory drugs being used either together with, or in place of, hydroxyurea in those SCD patients for whom hematopoietic stem cell transplants and evolving gene therapies are not a viable option.

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.

The role of inflammatory biomarkers in CHD-associated pulmonary hypertension in children

OBJECTIVE

The present study aims to identify the role of inflammatory markers such as C-reactive protein, interleukin-6, and fractalkine in CHD-associated pulmonary hypertension in children.

METHODS

This is a prospective review of 37 children with CHD-related pulmonary hypertension, 21 children with congenital heart defects, and 22 healthy children.

RESULTS

Serum C-reactive protein and interleukin-6 levels were significantly higher in the children with CHD-related pulmonary hypertension (respectively, p=0.049 and 0.026). Serum C-reactive protein concentrations correlated negatively with ejection fraction (r=-0.609, p=0.001) and fractional shortening (r=-0.452, p=0.007) in the pulmonary hypertension group. Serum fractalkine concentrations correlated negatively with ejection fraction (r=-0.522, p=0.002) and fractional shortening (r=-0.395, p=0.021) in the children with pulmonary hypertension. Serum interleukin-6 concentrations also correlated negatively with Qs (r=-0.572, p=0.021), positively with Rs (r=0.774, p=0.001), and positively with pulmonary wedge pressure (r=0.796, p=0.006) in the pulmonary hypertension group. A cut-off value of 2.2 IU/L for C-reactive protein was able to predict pulmonary hypertension with 77.5% sensitivity and 77.5% specificity. When the cut-off point for interleukin-6 concentration was 57.5 pg/ml, pulmonary hypertension could be predicted with 80% sensitivity and 75% specificity.

CONCLUSION

Inflammation is associated with the pathophysiology of pulmonary hypertension. The inflammatory markers C-reactive protein and interleukin-6 may have a role in the clinical evaluation of paediatric pulmonary hypertension related to CHDs.

Hydroxyurea treatment effect on children with sickle cell disease and obstructive sleep apnea

BACKGROUND

While hydroxyurea is the mainstay of treatment for many of the comorbidities associated with sickle cell disease, its effect on obstructive sleep apnea has not been fully investigated. The purpose of this project is to help characterize the effects of hydroxyurea on obstructive sleep apnea in children with sickle cell disease and determine its therapeutic role in the condition.

METHODS

Chart review was conducted on two pediatric patients with sickle cell disease who experienced resolution of obstructive sleep apnea following hydroxyurea administration.

RESULTS

After undergoing approximately 11 months of hydroxyurea therapy, sleep apnea symptoms improved and obstructive sleep apnea resolution was confirmed by repeat polysomnography in both cases. This resolution was largely secondary to a reduction in the obstructive component of the apnea hypopnea index, highlighting a previously unreported association.

CONCLUSIONS

As adenotonsillectomy is associated with significant risks in patients with sickle cell disease, it appears reasonable to consider a period of observation for improvement of obstructive sleep apnea following hydroxyurea administration rather than directly proceeding with surgery.

Increased iron export by ferroportin induces restriction of HIV-1 infection in sickle cell disease

The low incidence of HIV-1 infection in patients with sickle cell disease (SCD) and inhibition of HIV-1 replication in vitro under the conditions of low intracellular iron or heme treatment suggests a potential restriction of HIV-1 infection in SCD. We investigated HIV-1 ex vivo infection of SCD peripheral blood mononuclear cells (PBMCs) and found that HIV-1 replication was inhibited at the level of reverse transcription (RT) and transcription. We observed increased expression of heme and iron-regulated genes, previously shown to inhibit HIV-1, including ferroportin, IKBα, HO-1, p21, and SAM domain and HD domain-containing protein 1 (SAMHD1). HIV-1 inhibition was less pronounced in hepcidin-treated SCD PBMCs and more pronounced in the iron or iron chelators treated, suggesting a key role of iron metabolism. In SCD PBMCs, labile iron levels were reduced and protein levels of ferroportin, HIF-1α, IKBα, and HO-1 were increased. Hemin treatment induced ferroportin expression and inhibited HIV-1 in THP-1 cells, mimicking the HIV-1 inhibition in SCD PBMCs, especially as hepcidin similarly prevented HIV-1 inhibition. In THP-1 cells with knocked down ferroportin, IKBα, or HO-1 genes but not HIF-1α or p21, HIV-1 was not inhibited by hemin. Activity of SAMHD1-regulatory CDK2 was decreased, and SAMHD1 phosphorylation was reduced in SCD PBMCs and hemin-treated THP-1 cells, suggesting SAMHD1-mediated HIV-1 restriction in SCD. Our findings point to ferroportin as a trigger of HIV-1 restriction in SCD settings, linking reduced intracellular iron levels to the inhibition of CDK2 activity, reduction of SAMHD1 phosphorylation, increased IKBα expression, and inhibition of HIV-1 RT and transcription.

Albuminuria Is Associated with Endothelial Dysfunction and Elevated Plasma Endothelin-1 in Sickle Cell Anemia

Background

The pathogenesis of albuminuria in SCD remains incompletely understood. We evaluated the association of albuminuria with measures of endothelial function, and explored associations of both albuminuria and measures of endothelial function with selected biological variables (vascular endothelial growth factor [VEGF], endothelin-1 [ET-1], soluble fms-like tyrosine kinase-1 [sFLT-1], soluble vascular cell adhesion molecule-1 [soluble VCAM-1] and plasma hemoglobin).

Methods

Spot urine measurements for albumin-creatinine ratio (UACR) and 24-hour urine protein were obtained. Endothelial function was assessed using brachial artery ultrasound with measurements of flow-mediated dilation (FMD), nitroglycerin-mediated dilation (NTMD) and hyperemic velocity.

Results

Twenty three subjects with varying degrees of albuminuria were evaluated. UACR was significantly correlated with FMD (ρ = -0.45, p = 0.031). In univariate analysis, UACR was correlated with VEGF (ρ = -0.49; 95% CI: -0.75 –-0.1, p = 0.015), plasma hemoglobin (ρ = 0.50; 95% CI: 0.11–0.75, p = 0.013) and ET-1 (ρ = 0.40; 95% CI: -0.03–0.69, p = 0.06). Multivariable analysis showed significant associations of ET-1 (estimate: 455.1 [SE: 198.3], p = 0.02), VEGF (estimate: -1.1 [SE: 0.53], p = 0.04) and sFLT-1 (estimate: -1.14 [SE: 0.49], p = 0.02) with UACR. Only ET-1 (estimate: -8.03 [SE: 3.87], p = 0.04) was significantly associated with FMD in multivariable analyses. Finally, UACR was correlated with both 24-hour urine protein (ρ = 0.90, p < 0.0001) and urine aliquots for albumin-creatinine ratio obtained from the 24-hour urine collection (ρ = 0.97, p < 0.0001).

Conclusion

This study provides more definitive evidence for the association of albuminuria with endothelial dysfunction in SCD. Elevated circulating levels of ET-1 may contribute to SCD-related glomerulopathy by mediating endothelial dysfunction.

Inflammatory targets of therapy in sickle cell disease

Sickle cell disease (SCD) is a monogenic globin disorder characterized by the production of a structurally abnormal hemoglobin (Hb) variant Hb S, which causes severe hemolytic anemia, episodic painful vaso-occlusion, and ultimately end-organ damage. The primary disease pathophysiology is intracellular Hb S polymerization and consequent sickling of erythrocytes. It has become evident for more than several decades that a more complex disease process contributes to the myriad of clinical complications seen in patients with SCD with inflammation playing a central role. Drugs targeting specific inflammatory pathways therefore offer an attractive therapeutic strategy to ameliorate many of the clinical events in SCD. In addition, they are useful tools to dissect the molecular and cellular mechanisms that promote individual clinical events and for developing improved therapeutics to address more challenging clinical dilemmas such as refractoriness to opioids or hyperalgesia. Here, we discuss the prospect of targeting multiple inflammatory pathways implicated in the pathogenesis of SCD with a focus on new therapeutics, striving to link the actions of the anti-inflammatory agents to a defined pathobiology, and specific clinical manifestations of SCD. We also review the anti-inflammatory attributes and the cognate inflammatory targets of hydroxyurea, the only Food and Drug Administration-approved drug for SCD.

Pulmonary hypertension complicating multiple myeloma

Pulmonary hypertension (PH) is an infrequently reported complication of multiple myeloma (MM). PH has been more commonly associated with amyloidosis, myeloproliferative diseases, and the POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, skin changes) syndrome. PH in MM is typically mild to moderate and may be secondary to a variety of conditions, which include left ventricular dysfunction, high-output cardiac failure, chronic kidney disease, treatment-related toxicities, and precapillary involvement. We describe 3 patients with MM and severe PH. Each patient underwent right heart catheterization. All patients demonstrated elevated pulmonary pressures, transpulmonary gradients, and pulmonary vascular resistance. Each patient was ultimately treated with pulmonary vasodilator therapy with improvement in cardiopulmonary symptoms. Additional studies are needed to define the prevalence, prognosis, and pathogenesis of PH in this complex population and to help clarify who may benefit from targeted PH therapy.

Key endothelial cell angiogenic mechanisms are stimulated by the circulating milieu in sickle cell disease and attenuated by hydroxyurea

As hypoxia-induced inflammatory angiogenesis may contribute to the manifestations of sickle cell disease, we compared the angiogenic molecular profiles of plasma from sickle cell disease individuals and correlated these with in vitro endothelial cell-mediated angiogenesis-stimulating activity and in vivo neovascularization. Bioplex demonstrated that plasma from patients with steady-state sickle cell anemia contained elevated concentrations of pro-angiogenic factors (angiopoietin-1, basic fibroblast growth factor, vascular endothelial growth factor, vascular endothelial growth factor-D and placental growth factor) and displayed potent pro-angiogenic activity, significantly increasing endothelial cell proliferation, migration and capillary-like structure formation. In vivo neovascularization of Matrigel plugs was significantly greater in sickle cell disease mice than in non-sickle cell disease mice, consistent with an up-regulation of angiogenesis in the disease. In plasma from patients with hemoglobin SC disease without proliferative retinopathy, anti-angiogenic endostatin and thrombospondin-2 were significantly elevated. In contrast, plasma from hemoglobin SC individuals with proliferative retinopathy had a pro-angiogenic profile and more significant effects on endothelial cell proliferation and capillary formation than plasma from patients without retinopathy. Hydroxyurea therapy was associated with significant reductions in plasma angiogenic factors and inhibition of endothelial cell-mediated angiogenic mechanisms and neovascularization. Thus, individuals with sickle cell anemia or hemoglobin SC disease with retinopathy present a highly angiogenic circulating milieu, capable of stimulating key endothelial cell-mediated angiogenic mechanisms. Combination anti-angiogenic therapy to prevent the progression of unregulated neovascularization and associated manifestations in sickle cell disease, such as pulmonary hypertension, may be indicated; furthermore, the benefits and drawbacks of the potent anti-angiogenic effects of hydroxyurea should be clarified.

Morphine for the treatment of pain in sickle cell disease

Pain is a hallmark of sickle cell disease (SCD) and its treatment remains challenging. Opioids are the major family of analgesics that are commonly used for treating severe pain. However, these are not always effective and are associated with the liabilities of their own. The pharmacology and multiorgan side effects of opioids are rapidly emerging areas of investigation, but there remains a scarcity of clinical studies. Due to opioid-induced endothelial-, mast cell-, renal mesangial-, and epithelial-cell-specific effects and proinflammatory as well as growth influencing signaling, it is likely that when used for analgesia, opioids may have organ specific pathological effects. Experimental and clinical studies, even though extremely few, suggest that opioids may exacerbate existent organ damage and also stimulate pathologies of their own. Because of the recurrent and/or chronic use of large doses of opioids in SCD, it is critical to evaluate the role and contribution of opioids in many complications of SCD. The aim of this review is to initiate inquiry to develop strategies that may prevent the inadvertent effect of opioids on organ function in SCD, should it occur, without compromising analgesia.

Interleukin-1β and interleukin-6 gene polymorphisms are associated with manifestations of sickle cell anemia

Sickle cell anemia (SCA), a disorder characterized by both acute and chronic inflammation, exhibits substantial phenotypic variability. Interleukin-1 beta (IL-1β) and IL-6 are important in acute and chronic diseases, and their single nucleotide polymorphisms (SNPs) have been considered as predictors of prognosis in several inflammatory conditions. This study aims at exploring possible association of IL-1β and IL-6 SNPs as potential genetic modifiers and or predictors of SCA clinical and laboratory phenotypes. This cross-sectional study involved 107 SCA patients and 110 age, sex and ethnicity-matched healthy individuals. The SNPs were identified by PCR-RFLP for IL-1β (-511C>T and +3954C>T) and IL-6 (-597G>A and -174G>C) genes. Associations between these SNPs and the clinical and laboratory profiles of patients with SCA were then determined. Allelic and genotypic frequencies of IL-1β and IL-6 SNPs between patients with SCA and controls were similar and followed HWE. IL-1β +3954C>T SNP was associated with increased risk of osteonecrosis, elevated pulmonary arterial pressure and lower absolute reticulocyte count, while IL-6 -597G>A was associated with higher likelihood of retinopathy and leg ulcer. These data indicate that IL-1β and IL-6 gene SNPs are associated with SCA complications among Brazilian patients and may act as genetic predictors of SCA clinical heterogeneity.

Cellular, pharmacological, and biophysical evaluation of explanted lungs from a patient with sickle cell disease and severe pulmonary arterial hypertension

Pulmonary hypertension is recognized as a leading cause of morbidity and mortality in patients with sickle cell disease (SCD). We now report benchtop phenotyping from the explanted lungs of the first successful lung transplant in SCD. Pulmonary artery smooth muscle cells (PASMCs) cultured from the explanted lungs were analyzed for proliferate capacity, superoxide (O2 (•-)) production, and changes in key pulmonary arterial hypertension (PAH)-associated molecules and compared with non-PAH PASMCs. Upregulation of several pathologic processes persisted in culture in SCD lung PASMCs in spite of cell passage. SCD lung PASMCs showed growth factor- and serum-independent proliferation, upregulation of matrix genes, and increased O2 (•-) production compared with control cells. Histologic analysis of SCD-associated PAH arteries demonstrated increased and ectopically located extracellular matrix deposition and degradation of elastin fibers. Biomechanical analysis of these vessels confirmed increased arterial stiffening and loss of elasticity. Functional analysis of distal fifth-order pulmonary arteries from these lungs demonstrated increased vasoconstriction to an α1-adrenergic receptor agonist and concurrent loss of both endothelial-dependent and endothelial-independent vasodilation compared with normal pulmonary arteries. This is the first study to evaluate the molecular, cellular, functional, and mechanical changes in end-stage SCD-associated PAH.

Hypoxemia in sickle cell disease: significance and management

Hypoxemia is common in SCD and likely exacerbates SCD vasculopathy. Pulse oximeter correlation with arterial oxygen tension in patients with SCD may at times be poor and arterial blood gas confirmation is required in hypoxic patients. Supplemental oxygen should be administered for the correction of hypoxemia, which if untreated creates a risk of multi-organ failure. Transfusion and hydroxyurea can improve oxygen delivery to tissues and organs. The role of supplemental oxygen therapy in preventing or reversing SCD vasculopathy is controversial. Nitric oxide therapy for VOC pain has not fulfilled promise to date. On the other hand, lung distension (CPAP, incentive spirometry, PEP therapy) are promising treatments requiring further study.

Serum angiogenin level in sickle cell disease and beta thalassemia patients

INTRODUCTION

Angiogenesis has been investigated in different kinds of anemia. However, its role as a marker of angiogenesis has not been investigated in thalassemia or sickle cell disease (SCD).

OBJECTIVES

We aimed to investigate serum angiogenin level in children and adolescents with beta thalassemia or SCD and its relation to possible risk factors of angiogenesis.

MATERIALS AND METHODS

This study included; 32 β-thalassemia major (β-TM) patients aged 14.2 ± 3.8 years, 20 β-thalassemia intermedia (β-TI) patients aged 14.3 ± 4.8 years, 20 SCD patients aged 14.1 ± 2.4 years; 8 with (HbSS) and 12 with sickle thalassemia (HbS/β-thalassemia) and 35 age and sex-matched controls. Data collected regarding; age, sex, disease duration, blood transfusion frequency, transfusion index, chelation type and duration, CBC, Hb electrophoresis, serum ferritin and serum angiogenin level (by ELISA).

RESULTS

Angiogenin level was significantly higher in patients with SCD [250 (100-300) pg/mL] compared to β-TM [180 (140-230) pg/mL] and controls [89 (80-103) pg/mL] (P < .001) especially those with HbSS (P = .06). There was a significant negative correlation between serum angiogenin and age of patients, age of onset and duration of chelation in β-TM (P < .01, P < .001, P = .003) and β-TI (P = .009, P = .03, P < .001) and with serum ferritin in β-TI group (r = -0.573, P = .008). In SCD, angiogenin level was negatively correlated with both frequency of blood transfusion (r = -0.731, P < .001) and duration of hydroxyurea therapy (P = .017).

CONCLUSIONS

High angiogenin level detected among patients with SCD may be negatively influenced by regular blood transfusion and hydroxyurea therapy, while; early onset of chelation therapy may decrease angiogenin level in β-TM.

Hematological and Genetic Predictors of Daytime Hemoglobin Saturation in Tanzanian Children with and without Sickle Cell Anemia

Low hemoglobin oxygen saturation (SpO₂) is common in Sickle Cell Anemia (SCA) and associated with complications including stroke, although determinants remain unknown. We investigated potential hematological, genetic, and nutritional predictors of daytime SpO₂ in Tanzanian children with SCA and compared them with non-SCA controls. Steady-state resting pulse oximetry, full blood count, transferrin saturation, and clinical chemistry were measured. Median daytime SpO₂ was 97% (IQ range 94–99%) in SCA (N = 458), lower (P < 0.0001) than non-SCA (median 99%, IQ range 98–100%; N = 394). Within SCA, associations with SpO₂ were observed for hematological variables, transferrin saturation, body-mass-index z-score, hemoglobin F (HbF%), genotypes, and hemolytic markers; mean cell hemoglobin (MCH) explained most variability (P < 0.001, Adj r² = 0.09). In non-SCA only age correlated with SpO₂. α-thalassemia 3.7 deletion highly correlated with decreased MCH (Pearson correlation coefficient −0.60, P < 0.0001). In multivariable models, lower SpO₂ correlated with higher MCH (β-coefficient −0.32, P < 0.001) or with decreased copies of α-thalassemia 3.7 deletion (β-coefficient 1.1, P < 0.001), and independently in both models with lower HbF% (β-coefficient 0.15, P < 0.001) and Glucose-6-Phosphate Dehydrogenase genotype (β-coefficient −1.12, P = 0.012). This study provides evidence to support the hypothesis that effects on red cell rheology are important in determining SpO₂ in children with SCA. Potential mechanisms and implications are discussed.

Role of cellular iron and oxygen in the regulation of HIV-1 infection

Despite efficient antiretroviral therapy, eradication of HIV-1 infection is challenging and requires novel biological insights and therapeutic strategies. Among other physiological and environmental factors, intracellular iron greatly affects HIV-1 replication. Higher iron stores were shown to be associated with faster progression of HIV-1 infection and to inversely correlate with the survival of HIV-1 infected patients. Iron is required for several steps in the HIV-1 life cycle, including reverse transcription, HIV-1 gene expression and capsid assembly. Here, the authors present a comprehensive review of the molecular mechanisms involved in iron- and oxygen-mediated regulation of HIV-1 replication. We also propose key intracellular pathways that may be involved in regulating HIV-1 replication, via protein kinase complexes, CDK9/cyclin T1 and CDK 2/cyclin E, protein phosphatase-1 and other host factors.

Upper airway lymphoid tissue size in children with sickle cell disease

BACKGROUND

The prevalence of obstructive sleep apnea syndrome (OSAS) is higher in children with sickle cell disease (SCD) as compared with the general pediatric population. It has been speculated that overgrowth of the adenoid and tonsils is an important contributor.

METHODS

The current study used MRI to evaluate such an association. We studied 36 subjects with SCD (aged 6.9 ± 4.3 years) and 36 control subjects (aged 6.6 ± 3.4 years).

RESULTS

Compared with control subjects, children with SCD had a significantly smaller upper airway (2.8 ± 1.2 cm(3) vs 3.7 ± 1.6 cm(3), P < .01), and significantly larger adenoid (8.4 ± 4.1 cm(3) vs 6.0 ± 2.2 cm(3), P < .01), tonsils (7.0 ± 4.3 cm(3) vs 5.1 ± 1.9 cm(3), P < .01), retropharyngeal nodes (3.0 ± 1.9 cm(3) vs 2.2 ± 0.9 cm(3), P < .05), and deep cervical nodes (15.7 ± 5.7 cm(3) vs 12.7 ± 4.0 cm(3), P < .05). Polysomnography showed that 19.4% (seven of 36) of children with SCD had OSAS compared with 0% (zero of 20) of control subjects (P < .05) and that in children with SCD the apnea-hypopnea index correlated positively with upper airway lymphoid tissues size (r = 0.57, P < 001). In addition, children with SCD had lower arterial oxygen saturation nadir (84.3% ± 12.3% vs 91.2% ± 4.2%, P < .05), increased peak end-tidal CO(2) (53.4 ± 8.5 mm Hg vs 42.3 ± 5.3 mm Hg, P < .001), and increased arousals (13.7 ± 4.7 events/h vs 10.8 ± 3.8 events/h, P < .05).

CONCLUSIONS

Children with SCD have reduced upper airway size due to overgrowth of the surrounding lymphoid tissues, which may explain their predisposition to OSAS.

Plasma BDNF and PDGF-AA levels are associated with high TCD velocity and stroke in children with sickle cell anemia

Sickle cell anemia (SCA) associated cerebrovascular disease includes vascular remodeling, abnormal cerebral blood flow (CBF) and infarction. We studied the relationships between plasma brain derived neurotropic factor (BDNF), platelet derived growth factors (PDGF-AA and -AB/BB) and high trans-cranial Doppler (TCD) velocity, an indication of CBF velocity. Baseline plasma samples from 39 children (19 SCA with abnormal/high TCD [SATCD], 13 SCA with normal TCD [SNTCD] and 7 healthy non-SCA), were assayed for BDNF, PDGF-AA and -AB/BB plus 11 other cytokines. The sensitivity, specificity and usefulness of these biomarkers for stroke prediction was investigated. All subject groups were of similar age and gender distribution. Mean BDNF was significantly higher among SATCD than SNTCD (p=0.004) as was mean PDGF-AA (p=0.001). Similarly, mean PDGF-AA was higher among SCA subjects who developed stroke than those who did not (p=0.012). Elevated BDNF and PDGF-AA were good predictors of the presence of abnormally high CBF velocity and were both associated with severity of anemia. Elevated PDGF-AA predicted risk for stroke development. Stroke incidence and high TCD velocity were associated with elevated BDNF and PDGF-AA. These findings suggest a role for BDNF and PDGF-AA in the patho-physiological mechanism of cerebrovascular disease in SCA.

Proteinuria is associated with elevated tricuspid regurgitant jet velocity in children with sickle cell disease

BACKGROUND

Sickle cell disease (SCD) affects multiple organ systems. Complications of SCD such as pulmonary hypertension (PHT) and sickle cell nephropathy (SCN) are associated with an increased mortality. Both PHT and SCN have some common risk factors. In adults, PHT has been found to be associated with albuminuria, a manifestation of SCN. There is no data on this association in children. We conducted a study to determine if elevated pulmonary artery systolic pressures estimated on echocardiogram was associated with proteinuria in children with SCD.

METHODS

A detailed retrospective chart review was conducted on a cohort of sickle cell patients screened with echocardiograms from June 2005 to July 2010. Patients who had an initial screening echocardiogram and urine analysis within 1 year were included. Longitudinal data from all subsequent echocardiograms and urine analyses were collected.

RESULTS

Eighty-five patients were included. On initial echocardiograms 32.9% had an elevated tricuspid regurgitant jet velocity (TRV) ≥2.5 m/second. On follow up, in the 28 patients with elevated TRV, 49.27% of all repeat echocardiograms showed persistent elevation. In the 57 patients with normal baseline TRV, 73.6% of all repeat echocardiograms continued to have normal TRV. On initial screening 7.14% of patients with elevated TRV had proteinuria compared to 1.75% without elevated TRV. On follow up, 19.08% of repeat urinalysis had proteinuria in patients with elevated baseline TRV compared to 12.35% in patients with normal baseline TRV (P = 0.04).

CONCLUSIONS

Elevated TRV ≥ 2.5 m/second is significantly associated with proteinuria on longitudinal follow up in children with SCD.

Platelets in pulmonary hypertension: a causative role or a simple association?

PATHOPHYSIOLOGY OF PULMONARY ARTERIAL HYPERTENSION IS BASED ON THREE BASIC MECHANISMS: thrombotic pulmonary vascular lesions, vasoconstriction and vascular remodeling. Platelets are related to all of these mechanisms by their aggregation, production, storage and release of several mediators. The role of platelets is more prominent in some types of pulmonary arterial hypertension, including those which are secondary to inflammatory and infectious diseases, hemoglobinopathies, essential thrombocythemia, drugs, thromboembolism, and cardiac surgery. Most pulmonary antihypertensive drugs have a negative effect on platelets. In this review, the mechanisms of platelets association with pulmonary arterial hypertension, those types of pulmonary arterial hypertension with greatest platelet contribution to their pathophysiology, and the effects of pulmonary antihypertensive drugs on platelets are summarized.

Sickle cell disease is associated with decreased HIV but higher HBV and HCV comorbidities in U.S. hospital discharge records: a cross-sectional study

OBJECTIVE

Some studies suggest that HIV infection progresses slowly in patients with sickle cell disease (SCD). The authors aimed to determine the relationships between SCD and HIV infection.

METHODS

National Hospital Discharge Survey data from adult African-Americans in the period of 1997-2009 were analysed. The comorbidities of SCD with HIV infections in hospital discharges were analysed. Multiple logistic regression was used to test the association between SCD and HIV. For comparative purposes, the relationships of SCD with hepatitis B virus (HBV) and hepatitis C virus (HCV) were also assessed.

RESULTS

423,431 records were divided into two time periods 1997-2003 (53% of records) and 2004-2009 (47% of records). The frequency of HIV diagnosis was lower in patients with SCD (1.5% vs 3.3% in patients without SCD). In logistic regression, SCD diagnosis was associated with an OR of 0.24 (95% CI 0.18 to 0.32) for HIV diagnosis in the first period and with an OR of 0.31 (95% CI 0.22 to 0.42) in the second period. In contrast, SCD was associated with higher risk of HCV (OR=2.01, 95% CI 1.56 to 2.59 in the first period and OR=2.12, 95% CI 1.71 to 2.63 in the second period). SCD was also associated with a higher risk of HBV (OR=1.15, 95% CI 0.72 to 1.83 in the first period and OR=1.82, 95% CI 1.24 to 2.68 in the second period).

CONCLUSIONS

The lower risk of HIV comorbidity, but not HCV and HBV, with SCD is consistent with the possibility that SCD has a unique effect in altering the risk of HIV infection or progression. Investigation of how the haemolytic and immunological changes of SCD influence HIV might lead to new therapeutic or preventive approaches.

Elevated circulating angiogenic progenitors and white blood cells are associated with hypoxia-inducible angiogenic growth factors in children with sickle cell disease

We studied the number and function of angiogenic progenitor cells and growth factors in children aged 5–18 years without acute illness, 43 with Hemoglobin SS and 68 with normal hemoglobin. Hemoglobin SS subjects had at least twice as many mononuclear cell colonies and more circulating progenitor cell than Control subjects. Plasma concentrations of erythropoietin, angiopoietin-2, and stromal-derived growth factor (SDF)-1α were significantly higher in children with Hemoglobin SS compared to Control subjects. In a multivariate analysis model, SDF-1α concentration was found to be associated with both CPC number and total white blood cell count in the Hemoglobin SS group, suggesting that SDF-1α produced by ischemic tissues plays a role in mobilizing these cells in children with Hemoglobin SS. Despite having a higher number of angiogenic progenitor cells, children with Hemoglobin SS had slower migration of cultured mononuclear cells.

Inflammation in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterized by pulmonary vascular remodeling of the precapillary pulmonary arteries, with excessive proliferation of vascular cells. Although the exact pathophysiology remains unknown, there is increasing evidence to suggest an important role for inflammation. Firstly, pathologic specimens from patients with PAH reveal an accumulation of perivascular inflammatory cells, including macrophages, dendritic cells, T and B lymphocytes, and mast cells. Secondly, circulating levels of certain cytokines and chemokines are elevated, and these may correlate with a worse clinical outcome. Thirdly, certain inflammatory conditions such as connective tissue diseases are associated with an increased incidence of PAH. Finally, treatment of the underlying inflammatory condition may alleviate the associated PAH. Underlying pathologic mechanisms are likely to be "multihit" and complex. For instance, the inflammatory response may be regulated by bone morphogenetic protein receptor type 2 (BMPR II) status, and, in turn, BMPR II expression can be altered by certain cytokines. Although antiinflammatory therapies have been effective in certain connective-tissue-disease-associated PAH, this approach is untested in idiopathic PAH (iPAH). The potential benefit of antiinflammatory therapies in iPAH is of importance and requires further study.

Coronary artery dilation in sickle cell disease

OBJECTIVE

To evaluate the prevalence of coronary artery dilation in children with sickle cell disease (SCD).

STUDY DESIGN

This is a retrospective analysis performed in patients, between 10 and 19 years old, with SCD who underwent a routine transthoracic echocardiographic evaluation over a 20-month period. The left main, left anterior descending, and proximal right coronary artery diameters, as well as clinical and laboratory variables and other echocardiographic results were collected. Echocardiographic measurements were converted to z scores by using information from a large control population of normal children. Coronary artery ectasia (CAE) was defined as a coronary artery diameter z score ≥ 2. The patients with CAE were compared with those without CAE by using univariate and multivariate analyses.

RESULTS

Seventeen of 96 patients with SCD (17.7%) had CAE. There were no differences in sex, age, height, weight, body surface area, or genotype between those with and those without CAE. Patients with CAE had larger left ventricular end-diastolic dimension, shortening fraction, septal thickness, posterior wall thickness, mass, mass-to-volume ratio, and white blood cell count. Multivariate analysis revealed that the mass-to-volume ratio and elevated white blood cell count were associated with CAE.

CONCLUSION

CAE is common in SCD and is associated with left ventricular hypertrophy and inflammation.

Pulmonary artery pressure and iron deficiency in patients with upregulation of hypoxia sensing due to homozygous VHL(R200W) mutation (Chuvash polycythemia)

BACKGROUND

Patients with Chuvash polycythemia, (homozygosity for the R200W mutation in the von Hippel Lindau gene (VHL)), have elevated levels of hypoxia inducible factors HIF-1 and HIF-2, often become iron-deficient secondary to phlebotomy, and have elevated estimated pulmonary artery pressure by echocardiography. The objectives of this study were to provide a comprehensive echocardiographic assessment of cardiovascular physiology and to identify clinical, hematologic and cardiovascular risk factors for elevation of tricuspid regurgitation velocity in children and adults with Chuvash polycythemia.

DESIGN AND METHODS

This cross-sectional observational study of 120 adult and pediatric VHL(R200W) homozygotes and 31 controls at outpatient facilities in Chuvashia, Russian Federation included echocardiography assessment of pulmonary artery pressure (tricuspid regurgitation velocity), cardiac volume, and systolic and diastolic function, as well as hematologic and clinical parameters. We determined the prevalence and risk factors for elevation of tricuspid regurgitation velocity in this population and its relationship to phlebotomy.

RESULTS

The age-adjusted mean ± SE tricuspid regurgitation velocity was higher in VHL(R200W) homozygotes than controls with normal VHL alleles (2.5±0.03 vs. 2.3±0.05 m/sec, P=0.005). The age-adjusted left ventricular diastolic diameter (4.8±0.05 vs. 4.5±0.09 cm, P=0.005) and left atrial diameter (3.4±0.04 vs. 3.2±0.08 cm, P=0.011) were also greater in the VHL(R200W) homozygotes, consistent with increased blood volume, but the elevation in tricuspid regurgitation velocity persisted after adjustment for these variables. Among VHL(R200W) homozygotes, phlebotomy therapy was associated with lower serum ferritin concentration, and low ferritin independently predicted higher tricuspid regurgitation velocity (standardized beta=0.29; P=0.009).

CONCLUSIONS

Children and adults with Chuvash polycythemia have higher estimated right ventricular systolic pressure, even after adjustment for echocardiography estimates of blood volume. Lower ferritin concentration, which is associated with phlebotomy, independently predicts higher tricuspid regurgitation velocity (www.clinicaltrials.gov identifier NCT00495638).

Echocardiographic markers of elevated pulmonary pressure and left ventricular diastolic dysfunction are associated with exercise intolerance in adults and adolescents with homozygous sickle cell anemia in the United States and United Kingdom

BACKGROUND

Noninvasively assessed pulmonary pressure elevations and left ventricular (LV) diastolic dysfunction are associated with increased mortality in adults with sickle cell disease, but their relationship to exercise intolerance has not been evaluated prospectively.

METHODS AND RESULTS

Echocardiography, 6-minute walk distance, hemolytic rate, and serum concentrations of ferritin and erythropoietin were evaluated in a cohort of 483 subjects with homozygous hemoglobin S in the U.S. and U.K. Walk-Treatment of Pulmonary Hypertension and Sickle Cell Disease with Sildenafil Therapy (Walk-PHaSST) study. Tricuspid regurgitation velocity, which reflects systolic pulmonary artery pressure, was 2.7 to <3.0 m/s (mean±SD, 2.8±0.1) in 26% of the subjects and ≥3.0 m/s (mean±SD, 3.4±0.4) in 11%. The LV lateral E/e' ratio, which has been shown to reflect LV filling pressure in other conditions but has not been studied in sickle cell disease, was significantly higher in the groups with tricuspid regurgitation velocity ≥2.7 m/s. Increased hemolysis (P<0.0001), LV lateral E/e' ratio (P=0.0001), blood urea nitrogen (P=0.0002), and erythropoietin (P=0.002) were independently associated with an increased tricuspid regurgitation velocity. Furthermore, female sex (P<0.0001), older age (P<0.0001), LV lateral E/e' ratio (P=0.014), and tricuspid regurgitation velocity (P=0.019) were independent predictors of a shorter 6-minute walk distance.

CONCLUSIONS

Echocardiography-estimated elevated pulmonary artery systolic pressure and LV lateral E/e' ratio were independently associated with poor exercise capacity in a large cohort of patients with sickle cell anemia. Controlled trials investigating whether strategies to prevent or delay pulmonary hypertension and/or LV diastolic dysfunction will improve exercise capacity and long-term outcomes in sickle cell anemia should be considered. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique identifier: NCT00492531.

Predictors of osteoclast activity in patients with sickle cell disease

BACKGROUND

Bone changes are common in sickle cell disease, but the pathogenesis is not fully understood. Tartrate-resistant acid phosphatase (TRACP) type 5b is produced by bone-resorbing osteoclasts. In other forms of hemolytic anemia, increased iron stores are associated with osteoporosis. We hypothesized that transfusional iron overload would be associated with increased osteoclast activity in patients with sickle cell disease.

DESIGN AND METHODS

We examined tartrate-resistant acid phosphatase 5b concentrations in patients with sickle cell disease and normal controls of similar age and sex distribution at steady state. Serum tartrate-resistant acid phosphatase 5b concentration was measured using an immunocapture enzyme assay and plasma concentrations of other cytokines were assayed using the Bio-Plex suspension array system. Tricuspid regurgitation velocity, an indirect measure of systolic pulmonary artery pressure, was determined by echocardiography.

RESULTS

Tartrate-resistant acid phosphatase 5b concentrations were higher in 58 adults with sickle cell disease than in 22 controls (medians of 4.4 versus 2.4 U/L, respectively; P=0.0001). Among the patients with sickle cell disease, tartrate-resistant acid phosphatase 5b independently correlated with blood urea nitrogen (standardized beta=0.40, P=0.003), interleukin-8 (standardized beta=0.30, P=0.020), and chemokine C-C motif ligand 5 (standardized beta=-0.28, P=0.031) concentrations, but not with serum ferritin concentration. Frequent blood transfusions (>10 units in life time) were not associated with higher tartrate-resistant acid phosphatase 5b levels in multivariate analysis. There were strong correlations among tartrate-resistant acid phosphatase 5b, alkaline phosphatase and tricuspid regurgitation velocity (r>0.35, P<0.001).

CONCLUSIONS

Patients with sickle cell disease have increased osteoclast activity as reflected by serum tartrate-resistant acid phosphatase 5b concentrations. Our results may support a potential role of inflammation rather than increased iron stores in stimulating osteoclast activity in sickle cell disease. The positive relationships among tartrate-resistant acid phosphatase 5b, alkaline phosphatase and tricuspid regurgitation velocity raise the possibility of a common pathway in the pulmonary and bone complications of sickle cell disease.