Amma Owusu-Ansah

Complications Associated with Sickle Cell Trait: A Brief Narrative Review

Sickle cell trait occurs in approximately 300 million people worldwide, with the highest prevalence of approximately 30% to 40% in sub-Saharan Africa. Long considered a benign carrier state with relative protection against severe malaria, sickle cell trait occasionally can be associated with significant morbidity and mortality. Sickle cell trait is exclusively associated with rare but often fatal renal medullary cancer. Current cumulative evidence is convincing for associations with hematuria, renal papillary necrosis, hyposthenuria, splenic infarction, exertional rhabdomyolysis, and exercise-related sudden death. Sickle cell trait is probably associated with complicated hyphema, venous thromboembolic events, fetal loss, neonatal deaths, and preeclampsia, and possibly associated with acute chest syndrome, asymptomatic bacteriuria, and anemia in pregnancy. There is insufficient evidence to suggest an independent association with retinopathy, cholelithiasis, priapism, leg ulcers, liver necrosis, avascular necrosis of the femoral head, and stroke. Despite these associations, the average life span of individuals with sickle cell trait is similar to that of the general population. Nonetheless, given the large number of people with sickle cell trait, it is important that physicians be aware of these associations.

Nonhematopoietic Nrf2 dominantly impedes adult progression of sickle cell anemia in mice

The prevention of organ damage and early death in young adults is a major clinical concern in sickle cell disease (SCD). However, mechanisms that control adult progression of SCD during the transition from adolescence are poorly defined with no cognate prophylaxis. Here, we demonstrate in a longitudinal cohort of homozygous SCD (SS) mice a link between intravascular hemolysis, vascular inflammation, lung injury, and early death. Prophylactic Nrf2 activation in young SS mice stabilized intravascular hemolysis, reversed vascular inflammation, and attenuated lung edema in adulthood. Enhanced Nrf2 activation in endothelial cells in vitro concurred with the dramatic effect on vascular inflammation in the mice. BM chimeric SS mice lacking Nrf2 expression in nonhematopoietic tissues were created to dissect the role of nonerythroid Nrf2 in SCD progression. The SS chimeras developed severe intravascular hemolysis despite having erythroid Nrf2. In addition, they developed premature vascular inflammation and pulmonary edema and died younger than donor littermates with intact nonhematopoietic Nrf2. Our results reveal a dominant protective role for nonhematopoietic Nrf2 against tissue damage in both erythroid and nonerythroid tissues in SCD. Furthermore, we show that prophylactic augmentation of Nrf2-coordinated cytoprotection effectively impedes onset of the severe adult phenotype of SCD in mice.

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.

Triterpenoid inducers of Nrf2 signaling as potential therapeutic agents in sickle cell disease: a review

Sickle cell disease (SCD) is an inherited disorder of hemoglobin in which the abnormal hemoglobin S polymerizes when deoxygenated. This polymerization of hemoglobin S not only results in hemolysis and vasoocclusion but also precipitates inflammation, oxidative stress and chronic organ dysfunction. Oxidative stress is increasingly recognized as an important intermediate in these pathophysiological processes and is therefore an important target for therapeutic intervention. The transcription factor nuclear erythroid derived-2 related factor 2 (Nrf2) controls the expression of anti-oxidant enzymes and is emerging as a protein whose function can be exploited with therapeutic intent. This review article is focused on triterpenoids that activate Nrf2, and their potential for reducing oxidative stress in SCD as an approach to prevent organ dysfunction associated with this disease. A brief overview of oxidative stress in the clinical context of SCD is accompanied by a discussion of several pathophysiological mechanisms contributing to oxidative stress. Finally, these mechanisms are then related to current management strategies in SCD that are either utilized currently or under evaluation. The article concludes with a perspective on the potential of the various therapeutic interventions to reduce oxidative stress and morbidity associated with SCD.

Prevalence of relative systemic hypertension in adults with sickle cell disease in Ghana

Individuals with sickle cell disease particularly with the homozygous (SS) genotype historically have relatively low blood pressure. Nonetheless, they develop vasculopathy-associated organ dysfunction and the risk of organ dysfunction increases at blood pressures that are normal in the general population. This phenomenon is termed relative systemic hypertension (RSH) with a systolic blood pressure range of 120–139 mmHg, and diastolic blood pressure range of 70–89 mmHg. The significance of RSH lies in its association with renal insufficiency, pulmonary hypertension, stroke and propensity to progress to systemic hypertension. We conducted a retrospective chart review of 1,000 adults with sickle cell disease at the Ghana Institute of Clinical Genetics, to determine the prevalence of RSH in sickle cell disease in Ghana and associated complications. We found a high prevalence of RSH and hypertension with a relatively low frequency of renal insufficiency. Pulse pressure, a predictor of mortality, was higher in males of all ages. We anticipate that providing an estimate of the burden of RSH will heighten its recognition and clinical management among health care providers.

Sickle Cell Disease and Acute Chest Syndrome: Mechanisms and Pathogenenesis

Acute chest syndrome (ACS) is the major lung complication and leading cause of death in sickle cell disease (SCD). It is characterized by a rapid disease onset, pulmonary infiltration, hypoxemia, and several other clinical indications. Postmortem ACS lungs are characterized by histological evidence of alveolar capillary barrier disruption, fat emboli, and alveolar wall necrosis. Ischemia-reperfusion injury activation of invariant natural killer T lymphocytes is thought to heighten baseline pulmonary inflammation in SCD that may prime the lung for ACS development. Multiple factors, including hypoxia, infection, infarction, thrombosis, and fat emboli that are implicated in ACS pathogenesis are also associated with acute hemolysis. ACS is typically preceded by acute intravascular hemolysis, and the magnitude of anemia is linked to the severity of the lung injury. The heme hypothesis posits that the lung injury in ACS is caused by acute inflammation directly involving extracellular heme, a prototypical erythroid DAMP molecule released by hemolysis. In support of this model, the infusion of purified heme triggers a lethal acute lung injury in transgenic SCD mice that exhibit many of the characteristics of severe ACS. Additional experimental data indicate heme-induced ACS may involve vaso-occlusion and the release of neutrophil extracellular traps in the lung. Clinically, the risk of patients developing ACS is influenced by steady-state plasma concentrations of heme, and by polymorphisms in the gene encoding heme oxygenase-1, the rate-limiting heme degradation enzyme. Extracellular heme is therefore an ideal converging axis in the pathogenesis of ACS.

Assessment of Transition Readiness in Adolescents with Sickle Cell Disease and their Caretakers, A single institution experience: Kwarteng-Siaw M et al. Transition: Adolescents with Sickle Cell

AIM Sickle Cell Disease (SCD) is associated with high child mortality and birth incidence in sub-Saharan Africa. Improved SCD medical services in Ghana aims to enhance survival into adulthood, creating emerging need for transition from pediatric to adult care. Anticipating transition for adolescents with SCD, we sought to understand patient and caretaker perspectives on transition to adult care within Ghana. MATERIALS AND METHODS Structured interviews were conducted with a sample of patients ages 12–15 years and accompanying adults at Ghana’s Komfo Anokye Teaching Hospital Sickle Cell Clinic (KATH SCC) covering four areas: SCD medical knowledge, symptom self-management, psychosocial impact, and transition preparation. RESULTS In total, 46 children (mean age 13 years) paired with 46 adults were interviewed. Most children and caretakers had some knowledge about SCD and disease management. At least one-third lacked knowledge about SCD as an inherited condition. Youth were significantly more concerned about family burden and social stigmatization than adults. Most were unaware that patients are expected to switch care to adult medical providers by age 15 years, but were willing to transfer if needed. CONCLUSIONS Our clinic-based assessment at KATH SCC identified needs of adolescents and caretakers for education and counseling about disease, self-management, transition, family burden, and stigmatization. These findings provide insights into perspectives and educational gaps of families treated for SCD. Results suggest consideration of transition planning for adolescents with SCD and their caretakers in Ghana. Generalizability of our findings and practical methods to address needs for transition within Africa remain to be tested.

Organ damage in sickle cell disease study (ORDISS): protocol for a longitudinal cohort study based in Ghana

Introduction Sickle cell disease is highly prevalent in Africa with a significant public health burden. Nonetheless, morbidity and mortality in sickle cell disease that result from the progression of organ damage is not well understood. The Organ Damage in Sickle Cell Disease Study (ORDISS) is designed as a longitudinal cohort study to provide critical insight into cellular and molecular pathogenesis of chronic organ damage for the development of future innovative treatment. Methods and analysis ORDISS aims to recruit children aged 0–15 years who attend the Kumasi Centre for Sickle Cell Disease based at the Komfo Anokye Teaching Hospital in Kumasi, Ghana. Consent is obtained to collect blood and urine samples from the children during specified clinic visits and hospitalisations for acute events, to identify candidate and genetic markers of specific organ dysfunction and end-organ damage, over a 3 year period. In addition, data concerning clinical history and complications associated with sickle cell disease are collected. Samples are stored in biorepositories and analysed at the Kumasi Centre for Collaborative Research in Tropical Medicine, Ghana and the Centre for Translational and International Haematology, University of Pittsburgh, USA. Appropriate statistical analyses will be performed on the data acquired. Ethics and dissemination Research ethics approval was obtained at all participating sites. Results of the study will be submitted for publication in peer-reviewed journals, and the key findings presented at national and international conferences.