Pulmonary arterial hypertension and left-sided heart disease in sickle cell disease: clinical characteristics and association with soluble adhesion molecule expression

Diagnosis and management of chronic thromboembolic pulmonary hypertension (CTEPH) in sickle cell disease: A review

Pulmonary hypertension in sickle cell disease (SCD) is a complex phenomenon resulting from multiple overlapping etiologies, including pulmonary vasoconstriction in the setting of chronic hemolytic anemia, diastolic dysfunction, and chronic thromboembolic disease. The presence of pulmonary hypertension of any cause in SCD confers a significant increase in mortality risk. Evidence to guide the management of patients with sickle cell disease and chronic thromboembolic pulmonary hypertension (CTEPH) is scant and largely the realm of case reports and small case series. Centered on a discussion of a complex young patient with hemoglobin hemoglobin SC who ultimately underwent treatment with pulmonary thromboendarterectomy, we review the available literature to guide management and discuss and overview of treatment of CTEPH in SCD, considering the unique considerations and challenges facing patients suffering from this multisystem disease.

A critical evaluation of crizanlizumab for the treatment of sickle cell disease

INTRODUCTION

P-selectin is a key adhesion molecule in the pathogenesis of sickle cell disease, including acute painful event(s). Many of the mediators activated in prototypical pain crisis are also involved in other complications seen in this population. Crizanlizumab is a monoclonal antibody approved in the US in 2019 for patients of all genotypes of sickle cell disease. By blocking P-selectin, it effectively prevents acute painful event(s) and has a manageable safety profile.

AREAS COVERED

In this review, we provide an overview of the (i) biology of P-selectin in sickle cell disease, (ii) various agents inhibiting P-selectin, (iii) pharmacology of crizanlizumab, (iv) preclinical and clinical data on crizanlizumab, and (v) its potential for other indications, ongoing studies, regulatory status, and cost issues. Further, we describe its position among other approved agents in sickle cell disease and project future directions as well.

EXPERT OPINION

Crizanlizumab holds great promise in modulating the natural history of sickle cell disease and may have pleotropic effects. Studies are ongoing to define its role in preventing other sickle cell-related complications, non-sickle cell inflammatory states, and thrombotic disorders.

End points for sickle cell disease clinical trials: renal and cardiopulmonary, cure, and low-resource settings

To address the global burden of sickle cell disease and the need for novel therapies, the American Society of Hematology partnered with the US Food and Drug Administration to engage the work of 7 panels of clinicians, investigators, and patients to develop consensus recommendations for clinical trial end points. The panels conducted their work through literature reviews, assessment of available evidence, and expert judgment focusing on end points related to patient-reported outcome, pain (non-patient-reported outcomes), the brain, end-organ considerations, biomarkers, measurement of cure, and low-resource settings. This article presents the findings and recommendations of the end-organ considerations, measurement of cure, and low-resource settings panels as well as relevant findings and recommendations from the biomarkers panel.

Cardiovascular Sequelae of Sickle Cell Disease

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

Identifying Clinical and Research Priorities in Sickle Cell Lung Disease. An Official American Thoracic Society Workshop Report

Background: Pulmonary complications of sickle cell disease (SCD) are diverse and encompass acute and chronic disease. The understanding of the natural history of pulmonary complications of SCD is limited, no specific therapies exist, and these complications are a primary cause of morbidity and mortality.Methods: We gathered a multidisciplinary group of pediatric and adult hematologists, pulmonologists, and emergency medicine physicians with expertise in SCD-related lung disease along with an SCD patient advocate for an American Thoracic Society-sponsored workshop to review the literature and identify key unanswered clinical and research questions. Participants were divided into four subcommittees on the basis of expertise: 1) acute chest syndrome, 2) lower airways disease and pulmonary function, 3) sleep-disordered breathing and hypoxia, and 4) pulmonary vascular complications of SCD. Before the workshop, a comprehensive literature review of each subtopic was conducted. Clinically important questions were developed after literature review and were finalized by group discussion and consensus.Results: Current knowledge is based on small, predominantly observational studies, few multicenter longitudinal studies, and even fewer high-quality interventional trials specifically targeting the pulmonary complications of SCD. Each subcommittee identified the three or four most important unanswered questions in their topic area for researchers to direct the next steps of clinical investigation.Conclusions: Important and clinically relevant questions regarding sickle cell lung disease remain unanswered. High-quality, multicenter, longitudinal studies and randomized clinical trials designed and implemented by teams of multidisciplinary clinician-investigators are needed to improve the care of individuals with SCD.

Doppler echocardiographic assessment of pulmonary artery pressure in children with sickle cell anaemia

Background

Pulmonary artery hypertension (PAH) is a known complication of patients with sickle cell disease (SCD). The prevalence of PAH has been reported to be high in children with SCD in developed countries. The mortality rate of patients with SCD who develop PAH is said to be 40% at 24 to 40 months after diagnosis. In Sub-Saharan Africa, particularly Nigeria, where the prevalence of SCD is high, there is a dearth of data on the prevalence of PAH in children with SCD. PAH may be a likely contributor to the unacceptably high mortality rate of children with SCD in Africa. The present study aimed to determine the pattern of pulmonary artery pressure in children with sickle cell anaemia (SCA) aged 1 to 12 years in their steady state using Doppler echocardiography in our environment.

Methods

Analytical, comparative and cross-sectional study. It was carried out at Lagos State University Teaching Hospital (LASUTH) over a period of seven months (31st August 2015 through 31st March 2016). A total of 400 children, aged 1 to 12 years were recruited following parental consent and assent. Two hundred children with SCA in steady state and 200 age and sex matched children with haemoglobin genotype AA who served as controls were studied. All subjects and controls had Doppler echocardiography performed on them by the author. PAH was defined as a pulmonary artery systolic pressure (PASP) of ≥30 mmHg at rest derived from the tricuspid regurgitant velocity (TRV) measured from Doppler echocardiography. This corresponds with TRV value of ≥2.5 m/s.

Results

The prevalence of PAH in children with SCA was 8% (n=16). None of the controls had PAH. The youngest subject with PAH was aged 2 years. The overall mean pulmonary artery pressure of children with SCA was significantly higher than that of controls (18.54±5.81 vs. 13.76±5.71 mmHg, P=0.000). The prevalence of PAH in children with SCA demonstrated an increase in trend with age.

Conclusions

The prevalence of PAH in children with SCA in steady state is high. This complication was noticed as early as the second year of life. It is recommended that all children with SCA should have periodic Doppler echocardiography for early detection of PAH.

Levels of Soluble Endothelium Adhesion Molecules and Complications among Sickle Cell Disease Patients in Ghana

BACKGROUND

Soluble adhesion molecules are involved in the gathering and joining of inflammatory cells to vascular endothelium. Therefore, they serve as potential markers of endothelial dysfunction in vascular diseases including sickle cell disease (SCD). In Ghana, there are scarcely any report on the levels of adhesion molecules among SCD patients. The current study aimed to determine plasma levels of ICAM-1, VCAM-1 and E-Selectin as markers of endothelial dysfunction in SCD patients in steady state, complications and controls.

METHODOLOGY

This was a cross-sectional study involving 60 HbAA controls, 46 HbSS steady state, 57 HbSS VOC, 18 HbSC VOC, 21 HbSS with leg ulcer and 11 HbSS with priapism. Blood samples were collected from all the study subjects (n = 213) and processed into plasma. The plasma levels of VCAM-1, ICAM-1 and E-Selectin concentrations of SCD patients and controls were measured using a double sandwich ELISA technique. Demographic information was also collected from the study subjects.

RESULTS

Levels of all soluble proteins (ICAM-1, VCAM-1 and E-Selectin) were significantly higher in HbSS steady-state patients compared to non-SCD controls (p < 0.001). Generally, SCD patients with complications had relatively higher levels of the soluble proteins compared to those in the steady-state. Of the SCD patients with complications, those with vaso-occlusion crisis (HbSS VOC) had relatively higher levels of ICAM-1, VCAM-1 and E-Selectin at (62.42 ng/mL &plusmn; 26.09), (634.99 ng/mL &plusmn; 324.31) and (236.77 ng/mL &plusmn; 114.40) respectively; Conclusion: Although levels of adhesion molecules were high in all the SCD patients with complications, those with vaso-occlusive crisis had higher levels. This might reflect an ongoing endothelial dysfunction in these patients. SCD patients with vaso-occlusive crisis presents with a more severe pathophysiology condition.

Early initiation of inhaled corticosteroids does not decrease acute chest syndrome morbidity in pediatric patients with sickle cell disease

Acute chest syndrome (ACS) is a leading cause of mortality in patients with sickle cell disease (SCD). Systemic corticosteroids decrease ACS severity, but the risk of readmission for vaso-occlusive crises (VOC) has limited their use. The efficacy of inhaled corticosteroids (ICS) as a safer alternative is currently unknown. An observational, historic cohort study compared patients with SCD with ACS who received ICS at admission (ICS) to those who did not (non-ICS). Outcome measures included rates of transfusion, oxygen requirement, BiPAP initiation, PICU transfer, intubation, readmission, hospital cost, and length of stay. One hundred twenty patients with SCD (55 non-ICS, 65 ICS) were included. A significantly higher proportion of the non-ICS group had bilateral infiltrates, but fewer had asthma. More children in the ICS group had BiPAP initiated, however transfer to the PICU, intubation, transfusion rates, oxygen requirement, hospital cost, length of stay, and readmission rates did not differ between groups. Regression analysis did not reveal any differences in outcomes, nor were outcomes changed when patients were separated based on the presence or absence of asthma. In this observational cohort study, ICS did not demonstrate a significant reduction in ACS morbidity, though ICS use should be studied in a prospective manner.

Inflammation and autoimmunity in pulmonary hypertension: is there a role for endothelial adhesion molecules? (2017 Grover Conference Series)

While pulmonary hypertension (PH) has traditionally not been considered as a disease that is directly linked to or, potentially, even caused by inflammation, a rapidly growing body of evidence has demonstrated the accumulation of a variety of inflammatory and immune cells in PH lungs, in and around the wall of remodeled pulmonary resistance vessels and in the vicinity of plexiform lesions, respectively. Concomitantly, abundant production and release of various inflammatory mediators has been documented in both PH patients and experimental models of PH. While these findings unequivocally demonstrate an inflammatory component in PH, they have fueled an intense and presently ongoing debate as to the nature of this inflammatory aspect: is it a mere bystander of or response to the actual disease process, or is it a pathomechanistic contributor or potentially even a trigger of endothelial injury, smooth muscle hypertrophy and hyperplasia, and the resulting lung vascular remodeling? In this review, we will discuss the present evidence for an inflammatory component in PH disease with a specific focus on the potential role of the endothelium in this scenario and highlight future avenues of experimental investigation which may lead to novel therapeutic interventions.

Adhesion Molecules: Master Controllers of the Circulatory System

This manuscript will review our current understanding of cellular adhesion molecules (CAMs) relevant to the circulatory system, their physiological role in control of vascular homeostasis, innate and adaptive immune responses, and their importance in pathophysiological (disease) processes such as acute lung injury, atherosclerosis, and pulmonary hypertension. This is a complex and rapidly changing area of research that is incompletely understood. By design, we will begin with a brief overview of the structure and classification of the major groups of adhesion molecules and their physiological functions including cellular adhesion and signaling. The role of specific CAMs in the process of platelet aggregation and hemostasis and leukocyte adhesion and transendothelial migration will be reviewed as examples of the complex and cooperative interplay between CAMs during physiological and pathophysiological processes. The role of the endothelial glycocalyx and the glycobiology of this complex system related to inflammatory states such as sepsis will be reviewed. We will then focus on the role of adhesion molecules in the pathogenesis of specific disease processes involving the lungs and cardiovascular system. The potential of targeting adhesion molecules in the treatment of immune and inflammatory diseases will be highlighted in the relevant sections throughout the manuscript.

Chronic Pulmonary Complications of Sickle Cell Disease

Sickle cell disease (SCD), the most common genetic hemolytic anemia worldwide, affects 250,000 births annually. In the United States, SCD affects approximately 100,000 individuals, most of African descent. Hemoglobin S (HbS) results from a glutamate-to-valine mutation of the sixth codon of the β-hemoglobin allele; the homozygous genotype (HbSS) is associated with the most prevalent and severe form of the disease. Other SCD genotypes include HbSC, composed of one HbS allele and one HbC (glutamate-to-lysine mutation) allele; and HbS-β-thalassemia(0) or HbS-β-thalassemia(+), composed of one HbS allele and one β-thalassemia allele with absent or reduced β-chain production, respectively. Despite advances in care, median survival remains in the fifth decade, due in large part to chronic complications of the disease. Chronic pulmonary complications in SCD are major contributors to this early mortality. Although our understanding of these conditions has improved much over the past 10 to 15 years, there remains no specific treatment for pulmonary complications of SCD. It is unclear whether conventional treatment regimens directed at non-SCD populations have equivalent efficacy in patients with SCD. This represents a critical research need. In this review, the authors review the state-of-the-art understanding of the following pulmonary complications of SCD: (1) pulmonary hypertension; (2) venous thromboembolic disease; (3) sleep-disordered breathing; (4) asthma and recurrent wheezing; and (5) pulmonary function abnormalities. This review highlights the advances as well as the knowledge gaps in this field to update clinicians and other health care providers and to garner research interest from the medical community.

Genetic diminution of circulating prothrombin ameliorates multiorgan pathologies in sickle cell disease mice

Sickle cell disease (SCD) results in vascular occlusions, chronic hemolytic anemia, and cumulative organ damage. A conspicuous feature of SCD is chronic inflammation and coagulation system activation. Thrombin (factor IIa [FIIa]) is both a central protease in hemostasis and a key modifier of inflammatory processes. To explore the hypothesis that reduced prothrombin (factor II [FII]) levels in SCD will limit vaso-occlusion, vasculopathy, and inflammation, we used 2 strategies to suppress FII in SCD mice. Weekly administration of FII antisense oligonucleotide "gapmer" to Berkeley SCD mice to selectively reduce circulating FII levels to ∼10% of normal for 15 weeks significantly diminished early mortality. More comprehensive, long-term comparative studies were done using mice with genetic diminution of circulating FII. Here, cohorts of FII(lox/-) mice (constitutively carrying ∼10% normal FII) and FII(WT) mice were tracked in parallel for a year following the imposition of SCD via hematopoietic stem cell transplantation. This genetically imposed suppression of FII levels resulted in an impressive reduction in inflammation (reduction in leukocytosis, thrombocytosis, and circulating interleukin-6 levels), reduced endothelial cell dysfunction (reduced endothelial activation and circulating soluble vascular cell adhesion molecule), and a significant improvement in SCD-associated end-organ damage (nephropathy, pulmonary hypertension, pulmonary inflammation, liver function, inflammatory infiltration, and microinfarctions). Notably, all of these benefits were achieved with a relatively modest 1.25-fold increase in prothrombin times, and in the absence of hemorrhagic complications. Taken together, these data establish that prothrombin is a powerful modifier of SCD-induced end-organ damage, and present a novel therapeutic target to ameliorate SCD pathologies.

The mechanistic basis of prostacyclin and its stable analogues in pulmonary arterial hypertension: Role of membrane versus nuclear receptors

Pulmonary arterial hypertension (PAH) is a progressive disease of distal pulmonary arteries in which patients suffer from elevated pulmonary arterial pressure, extensive vascular remodelling and right ventricular failure. To date prostacyclin (PGI2) therapy remains the most efficacious treatment for PAH and is the only approved monotherapy to have a positive impact on long-term survival. A key thing to note is that improvement exceeds that predicted from vasodilator testing strongly suggesting that additional mechanisms contribute to the therapeutic benefit of prostacyclins in PAH. Given these agents have potent antiproliferative, anti-inflammatory and endothelial regenerating properties suggests therapeutic benefit might result from a slowing, stabilization or even some reversal of vascular remodelling in vivo. This review discusses evidence that the pharmacology of each prostacyclin (IP) receptor agonist so far developed is distinct, with non-IP receptor targets clearly contributing to the therapeutic and side effect profile of PGI2 (EP3), iloprost (EP1), treprostinil (EP2, DP1) along with a family of nuclear receptors known as peroxisome proliferator-activated receptors (PPARs), to which PGI2 and some analogues directly bind. These targets are functionally expressed to varying degrees in arteries, veins, platelets, fibroblasts and inflammatory cells and are likely to be involved in the biological actions of prostacylins. Recently, a highly selective IP agonist, selexipag has been developed for PAH. This agent should prove useful in distinguishing IP from other prostanoid receptors or PPAR binding effects in human tissue. It remains to be determined whether selectivity for the IP receptor gives rise to a superior or inferior clinical benefit in PAH.

Hemoglobinopathies and sleep--The road less traveled

Sickle cell disease and thalassemia are common hereditary blood disorders associated with increased systemic inflammation, tissue hypoxia, endothelial dysfunction and end-organ damage, the latter accounting for the substantial morbidity and abbreviated lifespan associated with these conditions. Sleep perturbations in general, and sleep-disordered breathing in particular are also highly prevalent conditions and the mechanisms underlying their widespread end-organ morbidities markedly and intriguingly overlap with the very same pathways implicated in the hemoglobinopathies. However, little attention has been given to date to the potential contributing role of sleep disorders to sickle cell disease manifestations. Here, we comprehensively review the pathophysiological mechanisms and clinical manifestations linking disturbed sleep and hemoglobinopathies, with special emphasis on sickle cell disease. In addition to a broad summary of the available evidence, we identify many of the research gaps that require attention and future investigation, and provide the scientific contextual setting that should enable opportunities to investigate the intertwined pathophysiological mechanisms and clinical outcomes of sleep disorders and hemoglobinopathies.

Left ventricular rotational mechanics in Tanzanian children with sickle cell disease

Background

Sickle cell disease (SCD) is a common inherited hemoglobinopathy. Adults with SCD manifest both systolic and diastolic cardiac dysfunction, though the age of onset of dysfunction has not been defined. Left ventricular (LV) rotational mechanics have not been studied in children with SCD. The aim of this study was to investigate whether cardiac rotational mechanics differed between children with SCD and age-matched controls.

Methods

Basal and apical LV short-axis images were acquired prospectively in 213 patients with SCD (mean age, 14.1 ± 2.6 years) and 49 controls (mean age, 13.3 ± 2.8 years) from the Muhimbili Sickle Cohort in Dar es Salaam, Tanzania. The magnitude of basal and apical rotation, net twist angle, torsion, and untwist rate were obtained by two-dimensional speckle-tracking. The timing of events was normalized to aortic valve closure.

Results

Mean basal rotation was significantly lower in patients with SCD compared with controls (P = .012), although no difference was observed in apical rotation (P = .37). No statistically significant differences in torsion or net twist angle were detected. Rotation rate at the apex (P = .001) and base (P = .0004) were significantly slower in subjects with SCD compared with controls. Mean peak untwisting rate was also significantly slower in patients with SCD (P = .006). No associations were found between hemoglobin concentration and apical rotation, basal rotation, net twist, and torsion.

Conclusion

This study demonstrates alterations in LV rotational mechanics in children with SCD, including lower basal rotation, peak differential twist, and untwist rate. These abnormalities denote subclinical changes in LV systolic and diastolic performance in children with SCD. Future work may reveal an association between rotational metrics and long-term patient outcomes.

Pulmonary hypertension in sickle cell disease: diagnosis and management

The increased survival of patients with sickle cell disease (SCD) into adulthood is associated with an increased incidence of multiorgan dysfunction and a progressive systemic and pulmonary vasculopathy. The high prevalence of an elevated tricuspid regurgitant jet velocity and its association with an increased risk of death in adult patients is well established. However, there has been controversy regarding the prevalence of pulmonary hypertension (PH) and its association with mortality in SCD. Multiple recently published reports demonstrate that PH as diagnosed by right heart catheterization is common in adult SCD patients, with a prevalence of 6%–11%. Furthermore, PH is associated with an increased risk of death in SCD patients. In this chapter, we provide evidence for the high prevalence of PH in SCD and its association with mortality and make recommendations for its evaluation and management. Finally, we provide the rationale for screening for this life-threatening complication in adult patients with SCD.

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.

An official American Thoracic Society clinical practice guideline: diagnosis, risk stratification, and management of pulmonary hypertension of sickle cell disease

BACKGROUND

In adults with sickle cell disease (SCD), an increased tricuspid regurgitant velocity (TRV) measured by Doppler echocardiography, an increased serum N-terminal pro-brain natriuretic peptide (NT-pro-BNP) level, and pulmonary hypertension (PH) diagnosed by right heart catheterization (RHC) are independent risk factors for mortality.

METHODS

A multidisciplinary committee was formed by clinician-investigators experienced in the management of patients with PH and/or SCD. Clinically important questions were posed, related evidence was appraised, and questions were answered with evidence-based recommendations. Target audiences include all clinicians who take care of patients with SCD.

RESULTS

Mortality risk stratification guides decision making. An increased risk for mortality is defined as a TRV equal to or greater than 2.5 m/second, an NT-pro-BNP level equal to or greater than 160 pg/ml, or RHC-confirmed PH. For patients identified as having increased mortality risk, we make a strong recommendation for hydroxyurea as first-line therapy and a weak recommendation for chronic transfusions as an alternative therapy. For all patients with SCD with elevated TRV alone or elevated NT-pro-BNP alone, and for patients with SCD with RHC-confirmed PH with elevated pulmonary artery wedge pressure and low pulmonary vascular resistance, we make a strong recommendation against PAH-specific therapy. However, for select patients with SCD with RHC-confirmed PH who have elevated pulmonary vascular resistance and normal pulmonary capillary wedge pressure, we make a weak recommendation for either prostacyclin agonist or endothelin receptor antagonist therapy and a strong recommendation against phosphodiesterase-5 inhibitor therapy.

CONCLUSIONS

Evidence-based recommendations for the management of patients with SCD with increased mortality risk are provided, but will require frequent reassessment and updating.

Serum levels of soluble ICAM-1 in children with pulmonary artery hypertension

This prospective cross-sectional study attempted to determine both the usefulness of the serum intercellular adhesion molecule-1 (ICAM-1) as a biomarker for pulmonary artery hypertension secondary to congenital heart disease and the nature of this marker's association with catheter angiographic findings. Our study included a total of 70 male and female children, comprising 30 patients with both pulmonary artery hypertension and congenital heart disease, 20 patients with congenital heart disease alone, and 20 healthy control subjects. Levels of ICAM-1 in plasma samples from all groups were measured by the enzyme-linked immunosorbent assay method. Cardiac catheterization was also performed in all patients. The mean serum ICAM-1 levels in pediatric patients who had congenital heart disease with and without pulmonary artery hypertension were 349.6 ± 72.9 ng/mL and 312.3 ± 69.5 ng/mL, respectively (P=0.002). In healthy control subjects, the mean serum ICAM-1 level was 231.4 ± 60.4 ng/mL. According to the results of this study, the ICAM-1 level of the pulmonary artery hypertension group was significantly higher than those of the congenital heart disease group and the healthy control group. Correlation analysis showed that ICAM-1 level was correlated with systolic and mean pulmonary artery pressures (r=0.62, P=0.001; r=0.57, P=0.001)-which are 2 important values used in diagnosis of pulmonary artery hypertension. Moreover, receiver operating characteristic analysis yielded consistent results for the prediction of pulmonary artery hypertension. Therefore, we conclude that ICAM-1 has potential use as a biomarker for the diagnosis and follow-up of pulmonary artery hypertension.

Beyond the definitions of the phenotypic complications of sickle cell disease: an update on management

The sickle hemoglobin is an abnormal hemoglobin due to point mutation (GAG → GTG) in exon 1 of the β globin gene resulting in the substitution of glutamic acid by valine at position 6 of the β globin polypeptide chain. Although the molecular lesion is a single-point mutation, the sickle gene is pleiotropic in nature causing multiple phenotypic expressions that constitute the various complications of sickle cell disease in general and sickle cell anemia in particular. The disease itself is chronic in nature but many of its complications are acute such as the recurrent acute painful crises (its hallmark), acute chest syndrome, and priapism. These complications vary considerably among patients, in the same patient with time, among countries and with age and sex. To date, there is no well-established consensus among providers on the management of the complications of sickle cell disease due in part to lack of evidence and in part to differences in the experience of providers. It is the aim of this paper to review available current approaches to manage the major complications of sickle cell disease. We hope that this will establish another preliminary forum among providers that may eventually lead the way to better outcomes.

Pulmonary complications of sickle cell disease

Sickle cell disease (SCD) is a common monogenetic disorder with high associated morbidity and mortality. The pulmonary complications of SCD are of particular importance, as acute chest syndrome and pulmonary hypertension have the highest associated mortality rates within this population. This article reviews the pathophysiology, diagnosis, and treatment of clinically significant pulmonary manifestations of SCD, including acute chest syndrome, asthma, and pulmonary hypertension in adult and pediatric patients. Clinicians should be vigilant in screening and treating such comorbidities to improve patient outcomes.

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.

Ancestry of African Americans with sickle cell disease

The inheritance of genetic disease depends on ancestry that must be considered when interpreting genetic association studies and can provide insights when comparing traits in a population. We compared the genetic profiles of African Americans with sickle cell disease to those of Black Africans and Caucasian populations of European descent and found that they are less genetically admixed than other African Americans and have an ancestry similar to Yorubans, Mandenkas and Bantu.

Severe sickle cell anemia is associated with increased plasma levels of TNF-R1 and VCAM-1

Sickle cell anemia (SCA, HBB glu6val) is characterized by multiple complications and a high degree of phenotypic variability: some subjects have only sporadic pain crises and few acute hospitalizations, while others experience multiple serious complications, high levels of morbidity, and accelerated mortality [1]. The tumor necrosis factor-α (TNF-α) signaling pathway plays important roles in inflammation and the immune response; variation in this pathway might be expected to modify the overall severity of SCA through the pathway's effects on the vascular endothelium [2,3]. We examined plasma biomarkers of TNF-α activity and endothelial cell activation for associations with SCA severity in 24 adults (12 mild, 12 severe). Two biomarkers, tumor necrosis factor-α receptor-1 (TNF-R1) and vascular cell adhesion molecule-1 (VCAM-1) were significantly higher in subjects with severe SCA. Along with these biomarker differences, we also examined data from a genome-wide association study (GWAS) using SCA severity as a disease phenotype, and found evidence of genetic association between disease severity and a single nucleotide polymorphism (SNP) in VCAM1, which codes for VCAM-1, and several SNPs in ARFGEF2, a gene involved in TNF-R1 release [4].

High levels of placenta growth factor in sickle cell disease promote pulmonary hypertension

Pulmonary hypertension is associated with reduced nitric oxide bioavailability and early mortality in sickle cell disease (SCD). We previously demonstrated that placenta growth factor (PlGF), an angiogenic factor produced by erythroid cells, induces hypoxia-independent expression of the pulmonary vasoconstrictor endothelin-1 in pulmonary endothelial cells. Using a lentivirus vector, we simulated erythroid expression of PlGF in normal mice up to the levels seen in sickle mice. Consequently, endothelin-1 production increased, right ventricle pressures increased, and right ventricle hypertrophy and pulmonary changes occurred in the mice within 8 weeks. These findings were corroborated in 123 patients with SCD, in whom plasma PlGF levels were significantly associated with anemia, endothelin-1, and tricuspid regurgitant velocity; the latter is reflective of peak pulmonary artery pressure. These results illuminate a novel mechanistic pathway linking hemolysis and erythroid hyperplasia to increased PlGF, endothelin-1, and pulmonary hypertension in SCD, and suggest that strategies that block PlGF signaling may be therapeutically beneficial.

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

Background

Pulmonary hypertension and left ventricular diastolic dysfunction are complications of sickle cell disease. Pulmonary hypertension is associated with hemolysis and hypoxia, but other unidentified factors are likely involved in pathogenesis as well.

Design and Methods

Plasma concentrations of three angiogenic markers (fibroblast growth factor, platelet derived growth factor–BB [PDGF-BB], vascular endothelial growth factor [VEGF]) and seven inflammatory markers implicated in pulmonary hypertension in other settings were determined by Bio-Plex suspension array in 237 children and adolescents with sickle cell disease at steady state and 43 controls. Tricuspid regurgitation velocity (which reflects systolic pulmonary artery pressure), mitral valve E/Edti ratio (which reflects left ventricular diastolic dysfunction), and a hemolytic component derived from four markers of hemolysis and hemoglobin oxygen saturation were also determined.

Results

Plasma concentrations of interleukin-8, interleukin-10 and VEGF were elevated in the patients with sickle cell disease compared to controls (P≤0.003). By logistic regression, greater values for PDGF-BB (P = 0.009), interleukin-6 (P = 0.019) and the hemolytic component (P = 0.026) were independently associated with increased odds of elevated tricuspid regurgitation velocity while higher VEGF concentrations were associated with decreased odds (P = 0.005) among the patients with sickle cell disease. These findings, which are consistent with reports that PDGF-BB stimulates and VEGF inhibits vascular smooth muscle cell proliferation, did not apply to E/Etdi.

Conclusions

Circulating concentrations of angiogenic and pro-Inflammatory markers are altered in sickle cell disease children and adolescents with elevated tricuspid regurgitation velocity, a subgroup that may be at risk for developing worsening pulmonary hypertension. Further studies to understand the molecular changes in these children are indicated.

Relationship of erythropoietin, fetal hemoglobin, and hydroxyurea treatment to tricuspid regurgitation velocity in children with sickle cell disease

Hydroxyurea and higher hemoglobin F improve the clinical course and survival in sickle cell disease, but their roles in protecting from pulmonary hypertension are not clear. We studied 399 children and adolescents with sickle cell disease at steady state; 38% were being treated with hydroxyurea. Patients on hydroxyurea had higher hemoglobin concentration and lower values for a hemolytic component derived from 4 markers of hemolysis (P < or = .002) but no difference in tricuspid regurgitation velocity compared with those not receiving hydroxyurea; they also had higher hemoglobin F (P < .001) and erythropoietin (P = .012) levels. Hemoglobin F correlated positively with erythropoietin even after adjustment for hemoglobin concentration (P < .001). Greater hemoglobin F and erythropoietin each independently predicted higher regurgitation velocity in addition to the hemolytic component (P < or = .023). In conclusion, increase in hemoglobin F in sickle cell disease may be associated with relatively lower tissue oxygen delivery as reflected in higher erythropoietin concentration. Greater levels of erythropoietin or hemoglobin F were independently associated with higher tricuspid regurgitation velocity after adjustment for degree of hemolysis, suggesting an independent relationship of hypoxia with higher systolic pulmonary artery pressure. The hemolysis-lowering and hemoglobin F-augmenting effects of hydroxyurea may exert countervailing influences on pulmonary blood pressure in sickle cell disease.

Vasculopathy in sickle cell disease: Biology, pathophysiology, genetics, translational medicine, and new research directions

Sickle cell disease has been very well characterized as a single amino acid molecular disorder of hemoglobin leading to its pathological polymerization, with resulting red cell rigidity that causes poor microvascular blood flow, with consequent tissue ischemia and infarction. More recently, an independent spectrum of pathophysiology of blood vessel function has been demonstrated, involving abnormal vascular tone and activated, adhesive endothelium. These vasculopathic abnormalities are attributable to pathways involving hemolysis-associated defects in nitric oxide bioavailability, oxidative stress, ischemia-reperfusion injury, hemostatic activation, leukocytes and platelets. Vasculopathy of sickle cell disease has been implicated in the development of pulmonary hypertension, stroke, leg ulceration and priapism, particularly associated with hemolytic severity, and reported also in other severe hemolytic disorders. This vasculopathy might also play a role in other chronic organ dysfunction in patients with sickle cell disease. These pathways present novel targets for pharmacologic intervention, and several clinical trials are already under way. The authors present their perspectives of a workshop held at the National Institutes of Health in August 2008 on vasculopathy in sickle cell disease, along with meritorious future scientific questions on the topic of vascular complications of sickle cell disease.