Subclinical ischaemic episodes during the steady state of sickle cell anaemia

Body composition analysis using dual-energy x-ray absorptiometry in an Egyptian pediatric sickle cell disease cohort

BACKGROUND

Growth failure is commonly encountered in sickle cell disease (SCD). Tissue compartment growth and development are subsequently likely to be altered in such patients.

OBJECTIVE

We aimed to analyze body composition in an Egyptian pediatric SCD cohort using dual-energy x-ray absorptiometry (DEXA), one of the most comprehensive and noninvasive assessment methods available.

METHODS

Forty children with SCD ≤18 years and 40 healthy youngsters age- and gender-matched were enrolled. Patients' demographic, clinical, and laboratory parameters were obtained from their archived files. All patients and controls were subjected to body composition assessment using a MedixDR-Whole Body DEXA System.

RESULTS

In SCD patients; weight and height relative to age Z scores were significantly lower (p < .001), total body lean was significantly higher (p = .006), and total body fat percentage was lower, yet the difference was not statistically significant (p = .09). There were no statistically significant variations in bone mineral density or content, basal metabolic rate, subcutaneous adipose tissue, android/gynoid fat ratio, and visceral adipose tissue. There were no significant gender disparities between SCD patients and controls.

CONCLUSION

Faltering growth in children with SCD should be addressed with a multidisciplinary approach including nutritional support, correction of anemia, and proper medical care. Body composition parameters assessed using DEXA were comparable between cases and controls apart from total body lean. Further clinical studies are needed with multicenter cooperation and a larger sample size to assess the usefulness of DEXA as an assessment tool for body composition in children with SCD.

Thrombin activatable fibrinolysis inhibitor plasma levels and TAFI Thr325Ile genetic polymorphism in a cohort of Egyptian sickle cell disease patients and impact on disease severity

BACKGROUND

Thrombin is a critical protease modulating thrombosis as well as inflammation, which are one of the main pathophysiological mechanisms in sickle vasculopathy, and its levels were reported to be high in sickle cell disease (SCD). The thrombin-thrombomodulin complex activates the TAFI inhibitor of fibrinolysis, which acts by reducing plasmin affinity for its substrate thus hindering fibrinolysis.

OBJECTIVE

We aimed to determine the influence of the Thr325Ile single nucleotide polymorphism (SNP) on TAFI antigen levels and potential effects on the severity of SCD in a cohort of Egyptian patients.

METHODS

Genotyping of Thr325lle polymorphism using Taq-Man SNP genotyping assay and TAFI level measurement using an enzyme-linked immunosorbent assay were performed for 80 SCD patients (45 homozygous HbSS, 16 S/β0 and 19 Sβ+) as well as 80 age- and gender-matched healthy control subjects.

RESULTS

Plasma TAFI levels were higher in SCD patients with Thr325Ile polymorphism, yet the difference was not statistically significant (p = .204). SCD patients with polymorphic genotypes had a greater number of hospital admissions (p = .03). Ten patients with acute chest syndrome had the homozygous polymorphic genotype (GG), and all patients with pulmonary hypertension had the polymorphic genotype (six were homozygous [GG] and five were heterozygous [GA]). Patients with SCD complicated with pulmonary hypertension showed significantly higher plasma TAFI levels (p = .044).

CONCLUSION

The analysis of Thr325Ile polymorphisms combined with plasma TAFI levels suggests that the analyzed SNP could influence plasma TAFL levels and SCD disease severity and hospitalization rates, which could be predictors for complex disease.

Assessment of hypoxemia among young adults with sickle cell anaemia in steady state in southwestern Nigeria: a crosssectional study

OBJECTIVES

Hypoxia is a known feature of sickle cell anaemia (SCA) which results from chronic anaemia and recurrent vaso-occlusive crisis (VOC) which can cause tissue ischaemia that leads to an end organ damage. The hallmark of SCA is chronic anaemia and recurrent vaso-occlusive crisis. The aim of this study is to compare the oxygen saturation of sickle cell anaemic individuals with the normal haemoglobin type (Hb AA) control and also to determine the prevalence of hypoxemia among SCA.

RESULTS

Two-hundred and twenty-two (136 Hb SS and 86 Hb AA) participated in the study. The mean ± SD of age (years), oxygen saturation (%) and pulse rate (bpm) of participants with sickle cell anaemia and Hb AA control were 21.85 ± 3.04 and 22.14 ± 3.18 (t = 0.701, p = 0.436), 95.21 ± 3.02 and 98.07 ± 0.81 (t=-8.598, p < 0.0001) and 77.10 ± 9.28 and 73.16 ± 8.52 (t = 3.173, p = 0.002) respectively. The prevalence of hypoxemia among SCA participants was 47.1%. Prevalence of hypoxemia in males with SCA was 60.9% while 39.1% of the females had hypoxemia.

Blood pressure and electrocardiographic profile of children with sickle cell anaemia in steady-state and vaso-occlusive crisis

Objective

To compare the cardiovascular features of patients with sickle cell anaemia (SCA) in steady-state with those in vaso-occlusive crisis (VOC) at the Wesley Guild Hospital (WGH).

Design

A descriptive cross-sectional, matched, case-control study among children with SCA at the WGH, a tertiary health facility in southwest Nigeria.

Setting

The participants were recruited from the children's emergency unit and paediatric haematology clinic of the WGH.

Participants

Consisted of 93 children with VOC (cases) and 93 age and sex-matched in steady state (controls), aged 5 - 15 years.

Main outcome measures

Cardiovascular parameters, including pulse rate, blood pressure, and electrocardiographic profile, were assessed and compared using the appropriate statistical tests.

Results

The mean (SD) age of the cases and controls were 8.8 (3.2) years and 9.0 (3.1) years, respectively (p= 0.106). There was no significant difference in the mean height of the groups. The mean pulse rate, diastolic, systolic, and mean arterial pressures were significantly higher in the cases than in the controls. A significantly higher proportion of the cases than the controls also had a higher frequency of heart blocks, prolonged QTc interval, ST elevation or depression, and T wave abnormality (p = 0.018, 0.039, 0.041, 0.009, respectively). The prevalence of chamber enlargements was not significantly different between the two groups.

Conclusion

Cardiovascular dysfunction is worse during VOC when compared with steady state. Physicians should look for these dysfunctions in SCA children with VOC to reduce mortality from the disease.

Funding

None declared.

Clinical Utilities of Electrocardiography in the Diagnosis of Myocardial Ischemia in Children With Sickle Cell Anemia: Correlation With Serum Cardiac Troponin I

BACKGROUND

Sickle cell anemia (SCA) is associated with recurrent vaso-occlusive crisis (VOC) and the risk of myocardial ischemia (MI). This study investigated the utility of electrocardiography (ECG) and cardiac troponin I (cTnI) in diagnosing MI during VOC.

MATERIALS AND METHODS

Children with SCA 5 to 15 years of age in VOC (patients) and age-matched and sex-matched steady-state controls were studied. Their ECG and cTnI levels were measured at contact and after 4 to 6 weeks.

RESULTS

One hundred eighty-six children (93 patients and 93 controls) were studied. The mean (SD) ages of the patients and controls were 8.8 (3.2) and 9.0 (3.1) years, respectively. The mean MI score was significantly higher for the patients, 1.7 (1.2), than the controls, 1.3 (1.0), P=0.002. A significantly higher proportion of the patients, 18 (19.4%), also had significant ischemia compared with the controls, 8 (8.6%), P=0.016. The median (interquartile range) serum cTnI level was significantly higher in the patients than the controls, P=0.006. All 7 of the patients with elevated cTnI had VOC. No significant correlation was found between MI score and cTnI in both groups.

CONCLUSIONS

cTnI is elevated and ECG features of MI worsen during VOC. Longitudinal studies to investigate their evolvement over time are advocated.

Haematological Profile of Children With Sickle Cell Anaemia in Steady State

Introduction

Sickle cell anaemia (SCA) is an inherited, autosomal recessive condition that results from a mutation in the β-globin gene. Vascular occlusion is the underlying mechanism behind a myriad of complications encountered. This vascular occlusion is primarily caused by the increased tendency of red blood cells (RBC) to adhere to the vascular endothelium, and the activation of platelets and total leucocyte count (TLC), hence the need for a steady-state haematological profile in these patients.

Method

This was a cross-sectional study conducted over four months at a sickle cell clinic. Haemoglobin (Hb) concentration, haematocrit, platelet, TLC, mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) of the subjects were recorded and analysed.

Results

Ninety-nine subjects aged 1-18 years were recruited for the study. There were 53 (53.5%) males. Leucocytosis was seen in 80 (80.8%), anaemia in 99 (100%), and thrombocytosis in 30 (30.3%) patients. The mean Hb, TLC and platelets were 7.9 ± 1.3g/dl, 14.3 ± 4.5 x 10³/mm³ and 391.5 ± 182.6 x 10³/mm³ respectively. Mean MCV, MCH and MCHC were 81.3 ± 7.1 fl, 28.6 ± 2.9 pg and 35.2 ± 1.7 g/dl respectively. Children aged one to four years had the highest TLC (p=0.002) but the lowest mean Hb and platelet (p=0.094 and 0.06) respectively. The mean MCV, MCH and MCHC were lowest in children aged one to four years (p=0.047, 0.001 and 0.001).

Conclusion

Anaemia, leucocytosis and thrombocytosis are characteristics features of children with SCA, especially in male and younger subjects. Although Iron markers are generally normal in children with SCA, those under the age of five years tend to have lower values.

Investigation of Lipid Profile and Clinical Manifestations in SCA Children

Introduction

Clinical complications in sickle cell anemia (SCA) are heterogeneous and involve several molecules. It has been suggested that SCA individuals present a dyslipidemic phenotype and that lipid parameters are associated with severe clinical complications, such as pulmonary hypertension. We sought to investigate associations between lipid parameters and clinical manifestations, as well as other laboratory parameters in a population of pediatric SCA patients.

Methods

Our cross-sectional evaluation included 126 SCA patients in steady state and who were not undergoing lipid-lowering therapy. Hematological and biochemical parameters were characterized, and previous clinical manifestations were investigated.

Results

Total cholesterol and low-density lipoprotein cholesterol (LDL-C) levels were increased in patients with a previous history of pneumonia, which also positively correlated with HbS levels. Decreased LDL-C levels were also associated with leg ulcers and anemia. Elevated high-density lipoprotein cholesterol (HDL-C) levels were associated with pain crises, increased viscosity, and decreased hemolysis. Several studies have determined that lipids play a role in the vascular impairment seen in SCA, which was corroborated by our findings.

Conclusions

In sum, our results suggest that total cholesterol, HDL-C, and LDL-C levels are associated with hemolysis and anemia markers and, most importantly, with clinical complications related to vasculopathy in SCA.

Methylene tetrahydrofolate reductase gene mutation in sickle cell anaemia patients in Lagos, Nigeria

Introduction

The significant causes of mortality among individuals with sickle cell anaemia (SCA) such as acute chest syndrome and cerebrovascular disease are related to vascular occlusion. Polymorphisms of the methylene tetrahydrofolate reductase (MTHFR) gene in persons with sickle cell anaemia have been suggested as a potential risk for vaso-occlusive events, with the C677T and A1298C polymorphisms being the commonest. This study therefore aimed to establish the pattern of MTHFR C677T and A1298C gene mutations among adults with HbSS phenotype attending the Haematology Clinic in Lagos State University Teaching Hospital Lagos, Nigeria.

Methods

A cross-sectional study was done among SCA patients attending the Haematology Clinic of the Lagos State University Teaching Hospital (LASUTH), using age and sex matched HbAA controls. DNA extraction and gene analysis were done. The selective amplification of a particular segment of the DNA by polymerase chain reaction (PCR) was done and subsequent digestion of the amplified MTHFR gene into its various fragments.

Results

The overall prevalence of the C677T mutation among participants was 19.3% (37 of 192), while the prevalence of A1298C was 15% (29 of 192).

Conclusion

The prevalence of MTHFR C677T was higher than A1298C mutations among sickle cell anaemia subjects.

The Inflammatory Response to Surgery in Sickle Cell Disease Patients Undergoing Cholecystectomy

Background and Objectives:

Patients with sickle cell anemia (SCA) may have elevated inflammatory markers in health, and this may be heightened after open operations. The inflammatory response of patients with SCA after minimally invasive surgeries has not been fully explored.

Patients and Methods:

Consecutive patients with SCA and with hemoglobin AA (HbAA) undergoing laparoscopic cholecystectomy for acute cholecystitis were recruited into the study. Blood samples were taken before induction of anesthesia (0-h); at 4, 12, 24, and 48 h; and on postoperative day 7. Samples were analyzed for serum C-reactive protein and interleukin (IL)-1 through IL-18.

Results:

Twenty-three patients, including 9 with SCA and 14 with HbAA, were recruited with 4 cases performed by open laparotomy. At 0-h, proinflammatory IL-1 levels (6.1 versus 4.8) and C-reactive protein levels (32.5 versus 26.6) were higher in patients with hemoglobin SS (HbSS) than in patients with HbAA, respectively. Over time, inflammatory markers were generally higher at each time-point for patients with HbSS compared with patients with HbAA for both proinflammatory and anti-inflammatory cytokines, rising immediately after surgery and up to 48 hours, then returning to baseline by postoperative day 7. There was a higher mean IL-1 level across all time-points in the HbSS group than in the HbAA group (P = .04).

Conclusion:

This exploratory study found an enhanced inflammatory response to cholecystectomy in patients with SCA compared with patients with HbAA. Minimally invasive surgical strategies for this patient group may help to mediate this response.

Serum homocysteine and disease severity in sickle cell anemia patients in Lagos

Purpose: Hypercoagulability in sickle cell anemia (SCA) may be responsible for the increased development of vascular occlusion in certain organs as well as acute pain episodes. The causes of hypercoagulability in SCA are multifactorial and include raised homocysteine levels. This study, therefore, aimed to determine serum homocysteine levels in SCA patients in steady state and to correlate its levels with SCA disease severity. Patients and Methods: This was a cross-sectional study done among SCA patients in steady state attending the Haematology Clinic of the Lagos State University Teaching Hospital (LASUTH). Matched age and sex HbAA controls were also recruited. Serum homocysteine of each participant was done with enzyme-linked immunosorbent assay and disease severity score assessed in every SCA patient using clinical and laboratory parameters. Results: The mean value for homocysteine in the study group (SCA patients) was 19.80±19.75 µmol/L whilst that of the control group was 9.16±4.29 µmol/L. Thirty-nine out of 96 (46.6%) SCA patients had elevated homocysteine levels (>15 µmol/L) whilst all 96 participants in the control group had normal homocysteine levels. The difference in the means in the two groups was statistically significant with p=0.001. Majority (62.5%) of the SCA patients had a mild disease (severity score ≤3). There was a significant correlation between serum homocysteine levels and disease severity scores with p=0.04; χ2=4.04. Conclusion: Homocysteine levels were significantly higher in HbSS patients compared with matched HbAA controls and showed a positive correlation with disease severity scores in the SCA patients.

Studies on the effect of a nutritious vegetable, Telfairia occidentalis, on HbSS blood

Medicinal plants have been used traditionally in Africa, especially Nigeria, in the management of sickle cell disorder (SCD) whose treatment has been mainly palliative. The antisickling properties of ethanol extract of Telfairia occidentalis Hook, F. (TO) (Family Cucurbitaceae) leaf was tested in vitro at concentrations 1, 2, 4, 8 and 16 mg/mL using inhibitory and reversal models. Nitrogen gas was used to induce hypoxia for 1 h. The effect of TO on red cell density and cell membrane were also determined. The methanol sub fraction of TO extract was subjected to GC/MS to identify some of the active compounds. The TO gave antisickling activities of 78.84 ± 1.34% inhibition and 95.4 ± 0.81% reversal, which are significantly (p < 0.05) higher than that of Ciklavit^®. The TO extract gave a change in density of 17.83 ± 0.77% and a dose dependent activity on RBC membrane. Methyl 9-cis 11- trans-octadecadienoate; 1, 4- benzenedicarboxylic acid; 9, 12-octadecadienoic acid (Linoleic acid); and hexadecanoic acid methyl ester (palmitic acid); were identified from TO ethanol leaf extract for the first time using GC/MS. This study authenticated the ethnomedicinal claims of the use of T. occidentalis in the management of sickle cell disorder.

Correlating transcranial arterial Doppler velocities with haematologic parameters and haemolytic indices of Nigerian children with sickle cell anaemia

Introduction

Cerebral vasculopathy, elevated transcranial Doppler velocities and stroke are linked to excessive intravascular haemolysis in sickle cell anaemia. This study determined the prevalence and pattern of abnormal blood flow velocities in children with sickle cell anaemia from Northern Nigeria using transcranial Doppler and to correlate transcranial Doppler velocities with haematological and biochemical markers of haemolysis.

Methods

Full blood count, reticulocyte count, fetal haemoglobin and some selected biochemical markers of haemolysis of 100 children with sickle cell anaemia were determined at steady state. The time-averaged mean of maximal velocities in four major intracranial blood vessels was measured using non-imaging transcranial Doppler, which were then classified according to the stroke prevention in sickle cell disease trial protocol. A simple linear correlation between time-averaged mean of maximal velocities in the four major intracranial vessels as the dependent variable and haematological and biochemical markers of haemolysis as independent variables was also determined at the significance level of 0.05.

Results

Abnormal transcranial Doppler velocities, classified as high risk, were found in 3% of the studied patients; 11% had intermediate risk while 84% had standard risk. Most high velocities were detected in the middle cerebral artery. The time-averaged mean of maximal velocities of middle cerebral artery positively correlated with total white blood cell count, absolute neutrophil count, platelet count, reticulocyte count, serum lactate dehydrogenase and total bilirubin, while it was negatively correlated with haematocrit and fetal haemoglobin levels.

Conclusion

Our study showed low prevalence of abnormal transcranial Doppler velocities and low prevalence is unrelated to low markers of haemolysis in our study population.

Subclinical myocardial injury during vaso-occlusive crisis in pediatric sickle cell disease

Acute painful crisis is the most frequent complication of sickle cell disease (SCD) in children. Recurrent vaso-occlusion may be associated with cardiac injury. The study aimed to assess silent myocardial injuries for sickle cell children during acute painful crisis by measuring serum level of troponin I and galectin-3. The study included 87 participates; study group (n = 44) sickle cell children presented at Jeddah hospitals in Saudi Arabia by painful crisis or acute illness as fever or cough (2017-2018). The controls were healthy children (n = 43). Demographic and history data were collected from the cases. Troponin I and galectin-3 were measured. Galectin-3 values were higher among cases with significant difference when compared to controls (7.5 ± 3.1 versus 3.2 ± 1.6, < 0.001). Galectin-3 at a cutoff > 5.1 ng/ml, the sensitivity was 88.64 and specificity was 88.37. Galectin-3 levels were higher for the pain crisis subgroup in comparison to acute illness group with significant difference (r 0.551*, p < 0.001*⁾. Galectin-3 values were higher among troponin-positive cases with significant difference (p = 0.046) to troponin-negative cases.Conclusion: Positive results of troponin I and high levels of galectin-3 in sickle cell children during acute painful crisis were potent indicators for subclinical myocardial injury. What is Known: • The hallmark of sickle cell disease is recurrent episodes of vaso-occlusive crisis which had deleterious effects on many organs. • Cardiac changes in pediatric sickle cell disease whether structural or functional are mainly attributed to chronic anemia and or pulmonary hypertension. What is New: • The observed positive results of cardiac troponin I and high values of galectin-3 in sickle cell children during vaso-occlusive crisis are strong indicator of myocardial ischemia and ongoing cardiac fibrosis respectively. • The observed correlation between biological markers (positive troponin and high galectin-3) could be an indication of subclinical cardiac injury.

GlycA is not a useful biomarker of inflammation in sickle cell disease

INTRODUCTION

Sickle cell disease (SCD) is a multisystemic disorder, the pathology being driven by recurrent inflammation particularly during a vaso-occlusive crisis. GlycA, a composite measure of protein glycation, is a sensitive biomarker for disorders associated with vascular inflammation. We determined the utility of GlycA as a biomarker of inflammation in SCD.

METHODS

Stored plasma samples from patients with SCD recruited to two clinical studies were analyzed. One study encompasses 488 patient samples with SCD (HbSS, HbSβ⁰ and HbSC) at steady state and 52 race-matched, healthy controls. The other study included paired plasma samples during steady state and acute pain crisis from (HbSS) patients with SCD. Plasma GlycA was measured using a proton NMR on the Vantera^® Clinical Analyzer. We performed analysis comparing patients with SCD, healthy controls, and paired samples analysis.

RESULTS

The mean plasma GlycA level was lower in SCD compared with healthy controls (324.6 ± 70.4 μmol/L vs. 386.3 ± 74.6 μmol/L, P < 0.0001). Within the same patient, mean plasma GlycA during acute pain crisis was lower than steady state, although the difference was not significant (300.5 ± 36.3 μmol/L vs 314.2 ± 34.8 μmol/L, P = 0.020). Plasma GlycA correlated inversely with serum LDH (P = 0.009).

CONCLUSION

GlycA is not a suitable biomarker of inflammation in SCD. We surmise that its signal is confounded by hemolysis leading to a depletion of haptoglobin, one of the major plasma proteins included in the composite NMR signal. Hemolysis is further exacerbated during an acute pain crisis, hence the lower GlycA levels in crisis compared to steady state.

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

BACKGROUND

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Pulmonary hypertension in Nigerian adults with sickle cell anemia

Background

Sickle cell anemia (SCA) is the commonest hemoglobinopathy and is associated with high morbidity and mortality. Pulmonary hypertension (PH) is reported to play a significant role in this regard. There is very limited literature on PH in SCA in Nigeria.

Objectives

The objectives of this study were to determine the prevalence of Doppler-derived PH in SCA, assess its influence on exercise capacity, and determine the correlates and predictors of measures of estimated pulmonary pressure.

Methods

A total of 92 SCA subjects had echocardiography and 6-minute self-paced walking exercise. PH was diagnosed by Doppler echocardiography on finding a tricuspid regurgitant velocity (TRV) of ≥2.5 m/s. The pulmonary flow profile was also assessed to estimate mean pulmonary arterial pressure (MPAP).

Results

Doppler-derived PH was detected in 23.9% of adults with SCA. The 6-minute walking distance (6MWD) was significantly lower in SCA adults with PH than in those without PH (380.33 ± 63.17 m vs 474.28 ± 76.74 m; p = 0.014). TRV and estimated MPAP had a significant inverse correlation with the 6MWD (r = −0.442; p < 0.001 and r = −0.571; p < 0.001, respectively).

Conclusion

PH as derived by Doppler is common in Nigerian adults with SCA and has a significantly negative influence on exercise capacity. Screening for PH should be encouraged to optimize management and thus improve their quality of life and life expectancy.

Crises in Sickle Cell Disease

In spite of significant strides in the treatment of sickle cell disease (SCD), SCD crises are still responsible for high morbidity and early mortality. While most patients initially seek care in the acute setting for a seemingly uncomplicated pain episode (pain crisis or vaso-occlusive crisis), this initial event is the primary risk factor for potentially life-threatening complications. The pathophysiological basis of these illnesses is end-organ ischemia and infarction combined with the downstream effects of hemolysis that results from red blood cell sickling. These pathological changes can occur acutely and lead to a dramatic clinical presentation, but are frequently superimposed over a milieu of chronic vasculopathy, immune dysregulation, and decreased functional reserve. In the lungs, acute chest syndrome is a particularly ominous lung injury syndrome with a complex pathogenesis and potentially devastating sequelae, but all organ systems can be affected. It is, therefore, critical to understand the SCD patients' susceptibility to acute complications and their risk factors so that they can be recognized promptly and managed effectively. Blood transfusions remain the mainstay of therapy for all severe acute crises. Recommendations and indications for the safest and most efficient implementation of transfusion strategies in the critical care setting are therefore presented and discussed, together with their pitfalls and potential future therapeutic alternatives. In particular, the importance of extended phenotypic red blood cell matching cannot be overemphasized, due to the high prevalence of severe complications from red cell alloimmunization in SCD.

Bayesian analyses demonstrate tissue blood volume is not decreased during acute sickle cell pain episodes: A preliminary study

BACKGROUND

Pain is the most common complication of Sickle Cell Disease (SCD). Tissue oximetry properties in SCD during steady state and acute pain are not well described.

METHODS

This was a cross sectional study of tissue oximetry properties in individuals with SCD during steady state, acute pain and healthy controls without SCD. A novel tissue oximetry device was used to better account for tissue pigmentation interference. We hypothesized that during acute SCD pain, blood volume to painful areas would be at least 10% less than steady state. Bayesian analyses of the data (with flat piors) were planned a priori because of the small projected sample size.

RESULTS

The sample included 14 individuals (4 during crisis, 5 steady state, and 5 controls). In individuals with SCD, blood volume to the lower back was higher during crisis (0.18% of tissue volume vs. 0.14% ). Bayesian analyses yielded a 3% probability that our hypothesis (that blood volume would decrease by 10% ) was correct.

CONCLUSIONS

During acute SCD pain, blood volume to painful areas is not decreased. Bayesian analyses were useful for interpretation of small sample data and may have utility in early phase trials for rare diseases.

Ischemia-reperfusion injury in sickle cell anemia: relationship to acute chest syndrome, endothelial dysfunction, arterial vasculopathy, and inflammatory pain

Ischemia-reperfusion (I/R) physiology, also called reperfusion injury, instigates vascular and tissue injury in human disease states. This review describes why sickle cell anemia should be conceptualized in this fashion and how I/R physiology explains the genesis of characteristic aspects of vascular pathobiology and clinical disease in sickle cell anemia. The nature of I/R and its relevance to sickle cell anemia are discussed, with an emphasis on the acute chest syndrome, endothelial dysfunction with aberrant vasoregulation, circle of Willis vasculopathy, and inflammatory pain. Viewing sickle disease from this perspective elucidates defining pathophysiology and identifies a host of novel potential therapeutic targets.

Cardiac autonomic dysfunction in sickle cell anaemia and its correlation with QT parameters

Background:

Abnormalities of QT parameters together with cardiac autonomic neuropathy (CAN) confer significant risks of cardiac morbidity and mortality in patients with diabetes mellitus. We questioned whether or not CAN influences occurrence of QT interval prolongation and dispersion in patients with sickle cell anaemia (SCA).

Materials and Methods:

Forty stable adult sickle cell patients with 44 healthy haemoglobin AA controls were studied. Baseline electrocardiograms were obtained and cardiovascular autonomic function tests were performed using standard protocols.

Results:

Mean corrected QT (QTc) in sickle cell patients was significantly higher (P = 0.001) than the mean of controls. Similarly, mean QT dispersion (QTcd) was higher (P = 0.001) in the former than in the latter. Mean QTc in patients with CAN was longer than patients with normal autonomic function (461 ± 26 ms versus 411 ± 23 ms), P = 0.001 (OR of 17.1, CI 3.48–83.71). Similarly, QTcd was higher (P = 0.001) in patients with CAN than those with normal cardiac autonomic function. Positive correlations were found between CAN with QTc and QTcd (r = 0.604, P = 0.001, r = 0.523, P = 0.001, respectively).

Conclusion:

CAN is a risk factor for abnormalities of QT parameters in SCA and both may be harbinger for cardiac death.

Utility of plasma transferrin receptor, ferritin and inflammatory markers in children with sickle cell disease

BACKGROUND

Soluble transferrin receptor (sTfR) is generally unaffected by inflammatory status, whereas ferritin increases along with acute-phase proteins. The utility of these iron biomarkers in relation to inflammatory markers in children with sickle cell disease (SCD) with differing grades of severity is unclear.

OBJECTIVES

To describe iron biomarker profiles and inflammatory responses in relation to disease severity in children with SCD.

METHODS

This cross-sectional study describes plasma levels of sTfR, ferritin, C-reactive protein (CRP) and serum amyloid A (SAA) among 102 Yemeni children with SCD in relation to clinical profiles and disease severity.

RESULTS

Median (IQR) sTfR was 58·5 mg/L (38-81), and concentration was positively correlated with reticulocyte count (r = +0·31, P = 0·002) and splenic enlargement (r = +0·20, P = 0·04), and was negatively correlated with Hb (r = -0·28, P = 0·004). Subcategories of children in a steady state were identified using ferritin and CRP cut-off values to discriminate iron status. In children in a steady state, the prevalence of iron deficiency was 25%, iron repletion 48% and marginal or normal status 27%. Ferritin concentration correlated positively with Hb and 23% of iron-deficient children had severe anaemia. CRP and SAA were increased in the steady state and were higher with acute disease complications (P<0·05 and <0·001, respectively). There was no association between sTfR or sTfR-ferritin index and inflammatory markers or disease severity score.

CONCLUSION

In SCD, elevated sTfR is related to hypererythropoietic activity and does not correlate with inflammatory status or disease severity. Iron deficiency prevalence was estimated to be 25%. A classification of iron status is proposed.

The role of infection in the pathogenesis of vaso-occlusive crisis in patients with sickle cell disease

Sickle cell disease (SCD) is characterized by recurrent vaso-occlusive crisis (VOC). Patients with SCD have impaired immunity and are thus predispose to infections. The vast majority of SCD patients live in underdeveloped nations with high prevalence and transmission rates of infections. This makes the SCD patients prone to infections, which frequently precipitate VOC. We reviewed the role of infection in the pathogenesis of VOC, taking into consideration all potential mechanisms from previous studies and hypothetical perspectives. The potential mechanisms through which infections may lead to VOC involve several pathological changes including pneumonitis, pyrexia, acute phase reaction, hypercoagulability, neutrophilia, eosinophilia, thrombocytosis, bronchospasm, red cell cytopathic and membrane changes, auto-antibodies mediated red cell agglutination and opsonization, diarrhoea and vomiting, which may act singly or in concert to cause red cell sickling. These changes can induce sickling directly or indirectly through their adverse effects on Hb oxygenation and polymerization, hydration, blood viscosity, red cell metabolism, procoagulant activation, intercellular adherence and aggregation, culminating in VOC. There is therefore the need to ameliorate the burden of infection on SCD through immunization, prophylactic and therapeutic use of antimicrobials, barrier protection and vector control in communities with high prevalence of SCD.

A pilot study of the short-term use of simvastatin in sickle cell disease: effects on markers of vascular dysfunction

Sickle cell disease (SCD) is characterized by progressive vascular injury and its pathophysiology is strikingly similar to that of atherosclerosis. Statins decrease inflammation and improve endothelial function in cardiovascular disease, but their effect in SCD is not known. In this pilot study, we examined the safety and effect of short-term simvastatin on biomarkers of vascular dysfunction in SCD. We treated 26 SCD patients with simvastatin, 20 or 40 mg/d, for 21 d. Plasma nitric oxide metabolites (NOx), C-reactive protein (CRP), interleukin-6 (IL-6), vascular cell adhesion molecule-1 (VCAM-1), tissue factor (TF) and vascular endothelial growth factor (VEGF) were analyzed and responses to simvastatin were compared between the two treatment groups. Simvastatin increased NOx levels by 23% in the low-dose (P =0·01) and 106% in the moderate-dose (P =0·01) groups, and by 52% overall (P=0·0008). CRP decreased similarly in both dose groups and by 68% overall (P =0·02). Levels of IL-6 decreased by 50% (P=0·04) and 71% (P<0·05) in the low- and moderate-dose groups, respectively. Simvastatin had no effect on VEGF, VCAM1 or TF. Simvastatin was well-tolerated and safe. Our preliminary findings showing a dose-related effect of simvastatin on levels of NOx, CRP and IL-6 suggest a potential therapeutic role for simvastatin in SCD.

Hematological indices of sickle cell anaemia patients with pulmonary tuberculosis in northern Nigeria

Nigeria has the fourth highest prevalence of TB and the highest prevalence of Sickle cell anaemia (SCA) in the world. SCA patients have impaired immunity and are vulnerable to TB. Hence, we studied the haematological indices of SCA patients with TB in Nigeria. A total of 23 SCA patients with TB were studied in parallel with equal number of age and sex matched SCA patients without TB. SCA patients with TB had significantly lower haematocrit, higher level of circulating sickle cells (CSCs) and similar level of reticulocyte count in comparison to patients without TB. SCA patients with TB had significantly higher mean WBC count associated with higher frequency of neutrophilia in comparison to those without TB. Monocytosis and eosinopenia were exclusively found in SCA patients with TB at frequencies of 52% and 65% respectively. Lymphocyte and basophil counts were normal in all patients with and without TB. Mean platelet counts were high in both patient groups but the frequency of thrombocytosis was significantly higher in patients with TB. SCA patients with TB had significantly higher mean ESR than their counterparts without the infection. The findings of this study revealed that TB in SCA patients was associated with rising level of CSCs, falling level of haematocrit, sub-optimal reticulocytosis, neutrophilia, monocytosis, thrombocytosis, eosinopenia and rising level of ESR. Hence, SCA patients presenting with these haematological indices should be investigated for TB.

Apolipoprotein A-I and serum amyloid A plasma levels are biomarkers of acute painful episodes in patients with sickle cell disease

BACKGROUND

Acute painful episodes are the clinical hallmark of sickle cell disease and have been linked to morbidity and mortality in the sickle cell population.

DESIGN AND METHODS

We undertook exploratory proteomic studies on paired plasma samples collected from a cohort of 26 adult sickle cell patients during steady state and on the first day of an acute painful episode. We screened for changes in abundance of specific protein peaks via surface-enhanced laser desorption/ionization time of flight mass spectrometry (SELDI-TOF MS), and confirmed the identify of candidate protein peaks by specific immunoassays.

RESULTS

The levels of hemoglobin, hematocrit, total protein, and albumin were lower and the levels of lactate dehydrogenase and absolute reticulocytes higher during acute painful episodes than during the steady state. Surface-enhanced laser desorption/ionization time of flight mass spectrometry spectral analysis consistently showed a mass-to-charge peak at 11.7 kDa with elevated intensities during acute painful episodes, which correlated significantly with the serum amyloid A immunoassay. Serum amyloid A levels were significantly elevated during acute painful episodes, especially in four patients with marked end-organ complications of such episodes. A second, recurring peak, less abundant during acute painful episodes, was present at 28.1 kDa; this peak was correlated significantly with immunoassay measurements of apolipoprotein A1.

CONCLUSIONS

On the average, plasma serum amyloid A rises and apolipoprotein AI falls during acute painful episodes. The serum amyloid A/apolipoprotein AI ratio increased in 81% of the patients during acute painful episodes, potentially making it a useful objective marker of such episodes. We propose that these protein alterations, known to contribute to endothelial dysfunction in other settings, might do likewise acutely in acute painful episodes and present a new target for therapeutic intervention in sickle cell disease. (ClincalTrials.gov Identifier: NCT00081523).

Pattern of serum cytokine expression and T-cell subsets in sickle cell disease patients in vaso-occlusive crisis

The pathogenesis of sickle vaso-occlusive crisis (VOC) in sickle cell disease (SCD) patients involves the accumulation of rigid sickle cells and the stimulation of an ongoing inflammatory response, as well as the stress of infections. The immune response, via cytokine imbalances and deregulated T-cell subsets, also has been proposed to contribute to the development of VOC. In this study, a panel of high-sensitivity cytokine kits was used to investigate cytokines in the sera of SCD patients in VOC. The results were compared primarily with those for stable SCD patients and secondarily with those for normal healthy people who served as controls. The cytokines studied included interleukin-2 (IL-2), IL-4, and IL-10. Lymphocyte subsets of patients with VOC were also studied and were compared with those of both control groups (20 stable patients without crisis [SCD group] and 20 normal healthy controls [NHC]). The VOC group was notable for remarkably elevated levels of IL-4, among the three cytokines tested, compared with those for the SCD and NHC groups. Patients with VOC also differed from stable SCD patients and NHC by having notably lower IL-10 levels, as well as the lowest ratio of CD4(+) to CD8(+) T cells (0.7). The patterns of the proinflammatory cytokine IL-2 did not differ between VOC and stable SCD patients, but NHC had significantly lower IL-2 levels than both the VOC and SCD groups. Our results demonstrate coexisting levels, both high and low, of TH1- and TH2-type cytokines, as well as diminished levels of T-cell subsets in VOC. These results are discussed in an effort to better understand the importance of the immune system profile in the pathogenesis of sickle cell VOC. Since the possibility that a cytokine imbalance is implicated in the pathogenesis of sickle cell crisis has been raised, our results should prompt further investigation of the host immune response in terms of TH1 and TH2 balance in sickle cell crisis.

Small Bowel Ischemia in a Sickle Cell Patient

We report a case of small bowel ischemia secondary to sickle cell disease. Acute bowel ischemia is an uncommon presentation of patients with sickle cell disease. Historically, only a handful of cases have been reported. We also provide a summary of the literature relevant to sickle cell patients with acute bowel ischemia.

Energy expenditure, inflammation, and oxidative stress in steady-state adolescents with sickle cell anemia

Sickle cell anemia (HbSS) is characterized by hypermetabolism, chronic inflammation, and increased oxidative stress, but the relationship between these factors is undefined. In this study, we examined indicators of inflammatory process and markers of oxidative damage and their impact on resting energy expenditure (REE) in stable HbSS adolescents (n = 35) and healthy controls carrying normal hemoglobin genotype (HbAA) (n = 39). C-reactive protein (CRP), white blood cell (WBC) count, and proinflammatory cytokines were measured as markers of inflammation and 2,3-dinor-5,6-dihydro-15-F2t-isoprostane (F2-IsoPM) as a marker of oxidative stress. REE was measured by indirect calorimetry. WBC counts (11.90 +/- 5.3 x10/muL versus 5.6 +/- 1.9 x10/muL; p < 0.001), serum CRP (9.1 +/- 11.0 mug/mL versus 0.4 +/- 0.7 mug/mL; p < 0.001) and serum IL-8 (7.5 +/- 4.4 pg/mL versus 5.5 +/- 4.8 pg/mL; p = 0.011) were higher in HbSS than HbAA, suggesting an anti-inflammatory response in HbSS. Higher urinary F2-IsoPM in HbSS (1.2 +/- 0.4 versus 0.7 +/- 0.3 ng/mg creatinine; p < 0.001) indicates increased oxidative stress. Fat free mass (FFM), hemoglobin (Hgb), interleukin (IL)-8, and F2-IsoPM were independent predictors of REE in HbSS (overall r = 0.778; p < 0.001). Low-grade inflammation and increased oxidative stress are present in adolescents with HbSS in the absence of acute crisis, and their markers are correlated with elevated REE.

Abnormal pulmonary function in adults with sickle cell anemia

RATIONALE

Pulmonary complications of sickle cell anemia (Hb-SS) commonly cause morbidity, yet few large studies of pulmonary function tests (PFTs) in this population have been reported.

OBJECTIVES

PFTs (spirometry, lung volumes, and diffusion capacity for carbon monoxide [DLCO]) from 310 adults with Hb-SS were analyzed to determine the pattern of pulmonary dysfunction and their association with other systemic complications of sickle cell disease.

METHODS

Raw PFT data were compared with predicted values. Each subject was subclassified into one of five groups: obstructive physiology, restrictive physiology, mixed obstructive/restrictive physiology, isolated low DLCO, or normal. The association between laboratory data of patients with decreased DLCO or restrictive physiology and those of normal subjects was assessed by multivariate linear regression.

MEASUREMENTS AND MAIN RESULTS

Normal PFTs were present in only 31 of 310 (10%) patients. Overall, adults with Hb-SS were characterized by decreased total lung capacities (70.2 +/- 14.7% predicted) and DLCO (64.5 +/- 19.9%). The most common PFT patterns were restrictive physiology (74%) and isolated low DLCO (13%). Decreased DLCO was associated with thrombocytosis (p = 0.05), with hepatic dysfunction (elevated alanine aminotransferase; p = 0.07), and a trend toward renal dysfunction (elevated blood urea nitrogen and creatinine; p = 0.05 and 0.07, respectively).

CONCLUSIONS

Pulmonary function is abnormal in 90% of adult patients with Hb-SS. Common abnormalities include restrictive physiology and decreased DLCO. Decreased DLCO may indicate more severe sickle vasculopathy characterized by impaired hepatic and renal function.

Plasma levels of tissue factor and soluble E-selectin in sickle cell disease: relationship to genotype and to inflammation

BACKGROUND

Microvascular occlusion, the pathophysiological hallmark of sickle cell disease (SCD), is a complex multifactorial process with alterations in coagulation, endothelial function and inflammation. However, relationships between these process in the two most common genotypes, HbSS and HbSC, are unknown. We hypothesized differences in the hypercoagulable state [as assessed by tissue factor (TF), fibrinogen and D-dimer], endothelial function [markers soluble E-selectin (sE-sel) and von Willebrand factor (vWf)], and inflammation [markers interleukin-6 (IL-6) and high-sensitivity C-reactive protein (hsCRP)] in these two SCD genotypes. Citrated plasma TF, sE-sel, vWf, fibrinogen and fibrin D-dimer, and serum IL-6 and hsCRP (enzyme-linked immunosorbent assay/Clauss) were measured in 64 patients with SCD (27 with HbSS disease) and 42 AA subjects matched for age and ethnic origin. TF (P = 0.0014), sE-sel (P = 0.001) and, as expected, vWf, D-dimer, and hsCRP (all P < or = 0.01), but not fibrinogen or IL-6, were raised in the SCD patients compared with the AA subjects. However, only vWf and, as expected, D-dimer (all P < or = 0.01) were higher in HbSS disease than in HbSC disease. Raised plasma TF and sE-sel in SCD compared with HbAA subjects may contribute to the increased risk of thrombotic disease in this group. Raised vWf in HbSS compared with HbSC may be important in determining pathophysiology in these two genotypes. Positive correlations between IL-6 and TF in both HbSC and HbSS disease leads us to speculate that inflammation may be important in coagulation activation in these patients, or vice versa. However, lack of correlation of sE-sel with inflammatory markers implies that other mechanisms are responsible for increased levels of this marker of endothelial activation.

Differential gene expression in pulmonary artery endothelial cells exposed to sickle cell plasma

Clinical variability in sickle cell disease (SCD) suggests a role for extra-erythrocytic factors in the pathogenesis of vasoocclusion. We hypothesized that endothelial cell (EC) dysfunction, one possible modifier of disease variability, results from induction of phenotypic changes by circulating factors. Accordingly, we analyzed gene expression in cultured human pulmonary artery ECs (HPAEC) exposed to plasma from 1) sickle acute chest syndrome (ACS) patients, 2) SCD patients at steady state, 3) normal volunteers, and 4) serum-free media, using whole genome microarrays (U133A-B GeneChip, Affymetrix). Data were analyzed by Bayesian analysis of differential gene expression (BADGE). Differential expression was defined by the probability of >1.5 fold change in signal intensity greater than 0.999 and a predicted score of 70-100, measured by cross-validation. Compared with normal plasma, plasma from SCD patients (steady state) resulted in differential expression of 50 genes in HPAEC. Of these genes, molecules involved in cholesterol biosynthesis and lipid transport, the cellular stress response, and extracellular matrix proteins were most prominent. Another 58 genes were differentially expressed in HPAEC exposed to plasma from ACS patients. The pattern of altered gene expression suggests that plasma from SCD patients induces an EC phenotype which is anti-apoptotic and favors cholesterol biosynthesis. An altered EC phenotype elicited by SCD plasma may contribute to the pathogenesis of sickle vasoocclusion.

Proinflammatory cytokines and the hypermetabolism of children with sickle cell disease

Sickle cell anemia (HbSS) includes chronic inflammation, but the origin is unclear. We hypothesized that in stable HbSS patients the inflammation was associated with hypermetabolism. We compared selected hypermetabolic and key immunomodulator indicators in HbSS versus control children and examined associations between measures of hypermetabolism and inflammation. Twelve fasting asymptomatic HbSS children 6-12 years and 9 controls matched for age, gender and fat mass (FM) were studied. Proportional reticulocyte count (retic%) and resting energy expenditure (REE) represented hypermetabolism, and C-reactive protein (CRP) indicated inflammation. Proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6), chemokine monocyte chemoattractant protein-1 (MCP-1), and energy balance cytokine leptin were measured. Methods were indirect calorimetry, enzyme-linked immunosorbent assay, and radioimmunoassay. Statistical analysis included simple correlation and regression analysis. REE (51 +/- 6 vs. 43 +/- 12 kcal/kg per fat-free mass (FFM), mean +/- SD), retic% (12 +/- 4 vs. 0.7 +/- 0.3%), CRP (5 +/- 3 vs. 0.3 +/- 0.4 mg/liter), and IL-6 (71 +/- 40 vs. 20 +/- 7 pg/ml) were significantly higher for HbSS than controls (P < 0.05). Conversely, leptin (0.1 +/- 0.1 vs. 2 +/- 1 microg/liter per kgFM) and MCP-1 (34 +/- 5 vs. 41 +/- 4 pg/ml) were significantly lower for the HbSS subjects (P < 0.01). TNF-alpha was not significantly different. There were no significant associations between REE or retic% and any cytokine measured. However, CRP was significantly associated with REE in HbSS (r = 0.8, P = 0.003) and an important predictor of REE/FFM. We provide new evidence for low circulating levels of inflammatory chemokine MCP-1 in stable HbSS children, confirm mostly low cytokine levels, inflammation, and hypermetabolism and demonstrate association of hypermetabolism with inflammation via CRP but not via cytokines.

Vitamin A status, hospitalizations, and other outcomes in young children with sickle cell disease

OBJECTIVE

To determine the relation of serum vitamin A status to growth, nutritional and hematologic status, and to the number of hospitalizations in children with sickle cell disease-SS (homozygous for the S allele, SCD-SS).

STUDY DESIGN

Children (2-9.9 years of age) with SCD-SS were assessed for serum retinol, hemoglobin, hematocrit, reticulocyte count, height, weight, body mass index, and recalled dietary intake. Vitamin A status was defined on the basis of serum retinol concentration as suboptimal (<30 microg/dL) and normal (> or =30 microg/dL). Hospitalizations were determined for 1 year after vitamin A assessment.

RESULTS

Mean serum retinol was 26.7 +/- 6.8 microg/dL in 66 subjects (39 girls) and was suboptimal in 66% of children. Compared with those with normal status, children with suboptimal vitamin A had significantly lower body mass index z score (-0.7 +/- 1.0 vs -0.1 +/- 0.6) and hemoglobin (7.9 +/- 1.1 vs 8.5 +/- 1.1), and hematocrit (23.3 +/- 3.0 vs 25.1 +/- 3.8) and significantly more hospitalizations (2.8 +/- 2.0 vs 0.7 +/- 0.8). After adjusting for age and sex, suboptimal vitamin A status was associated with a 10-fold increased risk for hospitalization (OR, 10.5; 95% CI, 2.3, 48.6) and with increased pain (OR,5.3; 95% CI, 1.3, 21.6) and fever episodes (OR, 6.4; 95% CI, 1.7, 24.9) requiring hospitalization.

CONCLUSIONS

Suboptimal vitamin A status was prevalent in US children with SCD-SS and was associated with increased hospitalizations and poor growth and hematologic status.

Silent brain infarcts in adult Kuwaiti sickle cell disease patients

Although overt stroke is a common complication of sickle cell disease (SCD), its incidence is very low in Kuwaiti patients. On the other hand, the prevalence of silent brain infarcts, which is reported to be about 17-20% in American patients, has not been documented in adult Kuwaiti patients. This is a 1-year study of consecutive, asymptomatic SCD patients seen in the hematology clinic of Mubarak Al-Kabeer Hospital. Patients with a past history of seizure or any other neurological abnormality were excluded. The patients' charts were reviewed for frequency of hospitalizations, any documented complications, and steady-state CBC. MRI was done with a 1.5-Tesla unit with super-conducting magnet. T1- and T2-weighted sagittal and axial sections and proton-density axial images were obtained in 5-mm-thick sections. Thirty-five patients were studied, made up of 25 SS and 10 Sbeta(0)Thal, aged between 17 and 44 years, with a mean age of 26.9 +/- 9.3 years. MRI findings consistent with infarcts were found in 7 (20.0%) patients-6 SS and 1 Sbeta(0)thal-with a mean age of 31.8 +/- 8.2 years, which was significantly higher (P < 0.05) than the mean age of the unaffected group (25.1 - 9.0 years). There were also no differences in the mean Hb, Hb F, or any other hematological parameter in the two groups. Among the affected 6 SS, 2 had co-existent alpha-thal trait. It is interesting that, while silent infarcts are prevalent in young American patients, it is in the older age group that they occur in Kuwaiti patients. Further studies are needed to investigate the factors modulating this heterogeneity.

Oral citrulline as arginine precursor may be beneficial in sickle cell disease: early phase two results

L-Arginine may be a conditionally essential amino acid in children and adolescents with sickle cell disease, particularly as required substrate in the arginine-nitric oxide pathway for endogenous nitrovasodilation and vasoprotection. Vasoprotection by arginine is mediated partly by nitric oxide-induced inhibition of endothelial damage and inhibition of adhesion and activation of leukocytes. Activated leukocytes may trigger many of the complications, including vasoocclusive events and intimal hyperplasias. High blood leukocyte counts during steady states in the absence of infection are significant laboratory risk factors for adverse complications. L-Citrulline as precursor amino acid was given orally twice daily in daily doses of approximately 0.1 g/kg in a pilot Phase II clinical trial during steady states in four homozygous sickle cell disease subjects and one sickle cell-hemoglobin C disease patient (ages 10-18). There soon resulted dramatic improvements in symptoms of well-being, raised plasma arginine levels, and reductions in high total leukocyte and high segmented neutrophil counts toward or to within normal limits. Continued L-citrulline supplementation in compliant subjects continued to lessen symptomatology, to maintain plasma arginine concentrations greater than control levels, and to maintain nearly normal total leukocyte and neutrophil counts. Side effects or toxicity from citrulline were not experienced. Oral L-citrulline may portend very useful for palliative therapy in sickle cell disease. Placebo-controlled, long-term trials are now indicated.

Reperfusion injury pathophysiology in sickle transgenic mice

Reperfusion of tissues after interruption of their vascular supply causes free-radical generation that leads to tissue damage, a scenario referred to as “reperfusion injury.” Because sickle disease involves repeated transient ischemic episodes, we sought evidence for excessive free-radical generation in sickle transgenic mice. Compared with normal mice, sickle mice at ambient air had a higher ethane excretion (marker of lipid peroxidation) and greater conversion of salicylic acid to 2,3-dihydroxybenzoic acid (marker of hydroxyl radical generation). During hypoxia (11% O2), only sickle mice converted tissue xanthine dehydrogenase to oxidase. Only the sickle mice exhibited a further increase in ethane excretion during restitution of normal oxygen tension after 2 hours of hypoxia. Only the sickle mice showed abnormal activation of nuclear factor–κB after exposure to hypoxia-reoxygenation. Allopurinol, a potential therapeutic agent, decreased ethane excretion in the sickle mice. Thus, sickle transgenic mice exhibit biochemical footprints consistent with excessive free-radical generation even at ambient air and following a transient induction of enhanced sickling. We suggest that reperfusion injury physiology may contribute to the evolution of the chronic organ damage characteristic of sickle cell disease. If so, novel therapeutic approaches might be of value.

Reperfusion injury pathophysiology in sickle transgenic mice

Reperfusion of tissues after interruption of their vascular supply causes free-radical generation that leads to tissue damage, a scenario referred to as “reperfusion injury.” Because sickle disease involves repeated transient ischemic episodes, we sought evidence for excessive free-radical generation in sickle transgenic mice. Compared with normal mice, sickle mice at ambient air had a higher ethane excretion (marker of lipid peroxidation) and greater conversion of salicylic acid to 2,3-dihydroxybenzoic acid (marker of hydroxyl radical generation). During hypoxia (11% O2), only sickle mice converted tissue xanthine dehydrogenase to oxidase. Only the sickle mice exhibited a further increase in ethane excretion during restitution of normal oxygen tension after 2 hours of hypoxia. Only the sickle mice showed abnormal activation of nuclear factor–κB after exposure to hypoxia-reoxygenation. Allopurinol, a potential therapeutic agent, decreased ethane excretion in the sickle mice. Thus, sickle transgenic mice exhibit biochemical footprints consistent with excessive free-radical generation even at ambient air and following a transient induction of enhanced sickling. We suggest that reperfusion injury physiology may contribute to the evolution of the chronic organ damage characteristic of sickle cell disease. If so, novel therapeutic approaches might be of value.

Tumor necrosis factor-alpha is undetectable in the plasma of SS patients with elevated Hb F

Steady-state sickle cell disease (SCD) patients may have increased plasma levels of acute phase reactants and pro-inflammatory cytokines because of subclinical inflammation. We have estimated TNF-alpha levels in the plasma and in supernatants following peripheral blood mononuclear cell (PBMC) activation with phytohemagglutinin (PHA) in a group of Kuwaiti SCD patients using ELISA. The group consisted of 28 SS, 8 Sbeta-thal, and 2 SD patients all in steady state; 5 SS patients were studied during 7 episodes of painful crisis. The subjects were aged 2 to 16 years, with a mean of 7.3 +/- 3.5 years. The beta(S)-globin gene cluster haplotype, alpha-tha1 status, and spleen function were determined in the SS group using standard techniques. Most (82%) were homozygous for the Saudi Arabia/India haplotype and had elevated Hb F levels ranging from 15% to 35%. There were 24 controls (Hb AA or AS), of whom 14 were healthy and 10 were acutely ill at the time of the study. None of the children with SCD (either in steady state or crisis) had detectable plasma TNF-alpha, but four controls (3 acutely ill and one healthy) had levels ranging from 61.7 to 249.8 pg/mL. Following PHA stimulation most subjects responded with high levels of TNF-alpha, with the median level among the steady-state SS patients being significantly higher than that in the controls (both the acutely ill or healthy). It therefore appears that because of the mild disease among our Arab SS children, TNF-alpha is not detectable in their plasma in steady state; these children, however, had a significantly higher response than controls following PBMC activation.

Antiphospholipid antibodies, proteins C and S, and coagulation changes in sickle cell disease

The significance, interactions, and sources of coagulation abnormalities and their relationship to clinical severity and painful episodes in sickle cell disease are not clear. To evaluate this, we have examined various measures of coagulation in 37 patients with sickle cell disease (20 patients with HbSS disease and 17 patients with HbSC disease). Measurements have included isotypes of antiphospholipid antibodies (IgG, IgM, IgA) to specific phospholipids; proteins C (activity, total antigen) and S (activity, total and free antigen); measures of coagulation activation (prothrombin fragment 1.2, thrombin-antithrombin, fibrinopeptide A, d-dimers); indicators of clinical severity; and studies obtained during steady states and painful episodes. Results in HbSS disease showed that antiphospholipid antibodies were increased, with IgG phosphatidylserine showing the highest and most frequently increased levels (37% of patients). Protein C (activity) and protein S (activity, total, free antigen) were decreased (P<.01), and all measures of coagulation activation were increased (P<.001). In HbSC disease, antiphospholipid antibodies were normal, protein C (activity) and protein S (free antigen) were decreased (P<.001), and all measures of coagulation activation were increased (P<.02). A strong correlation was observed in HbSS disease between IgG-PS and d-dimers. Moderate correlations occurred between protein C activity and thrombin-antithrombin and fibrinopeptide A, between protein S activity and prothrombin fragment 1.2 and d-dimers, and between protein C and protein S activity. In HbSC disease, moderate and fewer correlations occurred. Significant differences between HbSS disease and HbSC disease were observed in aPLs, proteins C and S, and measures of coagulation activation. Measurements during steady states and during painful episodes were not significantly different. We conclude that the antiphospholipid antibody IgG-PS may contribute to coagulation activation in HbSS disease and that IgG-PS, protein C, and protein S relate to each other and jointly to measures of coagulation activation. The increased level of IgG-PS in HbSS disease most likely reflects exposure of the procoagulant phosphatidylserine on the surfaces of red cell-shed vesicles and sickle red cells, which would further affect coagulation activation. The significant differences in coagulation measures between HbSS disease and HbSC disease are consistent with differences in clinical severity between the diseases. The development of painful episodes does not appear to be related to the coagulation changes.

Sickle Cell Anemia as a Possible State of Enhanced Anti-Apoptotic Tone: Survival Effect of Vascular Endothelial Growth Factor on Circulating and Unanchored Endothelial Cells

The biologic processes of apoptosis and angiogenesis are linked in endothelial biology because some endothelial cell growth factors also exert anti-apoptotic effects. We studied whether apoptosis is occurring in circulating endothelial cells (CEC) that have lost the survival signals derived from anchorage to extracellular matrix. Consistent with this expectation, 64% ± 16% of CEC from normal donors showed evidence of apoptosis (by morphology and TdT-mediated dUTP nick end labeling [TUNEL] assay). However, only 30% ± 15% (P &lt; .001 v normal) of CEC from donors with sickle cell anemia were apoptotic. Vascular endothelial growth factor (VEGF) levels were significantly (P = .001) higher in plasma of sickle donors (120.1 ± 81.4 pg/mL) than that of normal donors (37.6 ± 34.6 pg/mL), and there was an inverse correlation between VEGF and CEC apoptosis (r = .612,P = .001). Consistent with stimulation by VEGF, CEC from sickle donors exhibited increased expression of vβ3. In vitro experiments showed that VEGF inhibits apoptosis for cultured endothelial cells that are kept unanchored and not allowed to re-establish attachment to extracellular matrix, thus demonstrating that VEGF provides survival signals independent of its ability to promote matrix reattachment. These data suggest the hypothesis that sickle cell anemia is a state of enhanced anti-apoptotic tone for endothelial cells. If true, this has implications for disease pathobiology, particularly the development of neovascularizing retinopathy.

Sickle Cell Anemia as a Possible State of Enhanced Anti-Apoptotic Tone: Survival Effect of Vascular Endothelial Growth Factor on Circulating and Unanchored Endothelial Cells

The biologic processes of apoptosis and angiogenesis are linked in endothelial biology because some endothelial cell growth factors also exert anti-apoptotic effects. We studied whether apoptosis is occurring in circulating endothelial cells (CEC) that have lost the survival signals derived from anchorage to extracellular matrix. Consistent with this expectation, 64% ± 16% of CEC from normal donors showed evidence of apoptosis (by morphology and TdT-mediated dUTP nick end labeling [TUNEL] assay). However, only 30% ± 15% (P < .001 v normal) of CEC from donors with sickle cell anemia were apoptotic. Vascular endothelial growth factor (VEGF) levels were significantly (P = .001) higher in plasma of sickle donors (120.1 ± 81.4 pg/mL) than that of normal donors (37.6 ± 34.6 pg/mL), and there was an inverse correlation between VEGF and CEC apoptosis (r = .612,P = .001). Consistent with stimulation by VEGF, CEC from sickle donors exhibited increased expression of vβ3. In vitro experiments showed that VEGF inhibits apoptosis for cultured endothelial cells that are kept unanchored and not allowed to re-establish attachment to extracellular matrix, thus demonstrating that VEGF provides survival signals independent of its ability to promote matrix reattachment. These data suggest the hypothesis that sickle cell anemia is a state of enhanced anti-apoptotic tone for endothelial cells. If true, this has implications for disease pathobiology, particularly the development of neovascularizing retinopathy.

Acute phase proteins and interleukins in steady state sickle cell disease

To identify a possible acute phase response during the steady state of sickle cell disease, we estimated the serum alterations of acute phase proteins, beta2-microglobulin (beta2M), kappa and lambda light chains, interleukins (ILs) and tumor necrosis factor-alpha (TNFalpha) in 21 patients. Increased concentrations of C-reactive protein (CRP) were found in 5 patients, alpha-1-acid-glycoprotein (AGP) in 3, alpha-1-antitrypsin (AAT) in 8, ceruloplasmin (CER) in 2, alpha-2-macroglobulin (AMG) in 14 and decreased haptoglobin (HPT) and transferrin (TFR) in 11 and 9, respectively. Increased beta2M was found in 10 patients and kappa and lambda light chains in 11. IL-1beta, IL-2, IL-4, IL-10 and TNFalpha were not detected in any of the patients. However, significantly increased values of IL-6 and sIL-2r were found. This study has demonstrated increased serum levels of some of the acute phase proteins in patients during the steady state of sickle cell disease. This may be a result of a subclinical vaso-occlusion which in turn leads to a covert inflammatory response. Cytokines, and in particular IL-6, produced after this response, seem to be responsible for the high levels of acute phase proteins in the steady state of this disease.

Whole Blood Tissue Factor Procoagulant Activity Is Elevated in Patients With Sickle Cell Disease

We developed a simple assay for the measurement of tissue factor procoagulant activity (TF PCA) in whole blood samples that avoids the need for mononuclear cell isolation. This method combines convenience of sample collection and processing with a high degree of sensitivity and specificity for TF. Using this method, we have determined that TF PCA is detectable in whole blood samples from normal individuals, which is itself a novel observation. Essentially all PCA could be shown to be localized in the mononuclear cell fraction of blood. Compared with controls, whole blood TF levels were significantly (P &lt; .000001) elevated in patients with sickle cell disease (SCD), regardless of the subtype of hemoglobinopathy (SS or SC disease). No significant difference in TF PCA was observed between patients in pain crisis compared with those in steady-state disease. Because TF functions as cofactor in the proteolytic conversion of FVII to FVIIa in vitro, it was expected that an increase in circulating TF PCA would lead to an increased in vivo generation of FVIIa. On the contrary, FVIIa levels were actually decreased in the plasma of patients with SCD. Plasma TF pathway inhibitor (TFPI) antigen levels were normal in SCD patients, suggesting that accelerated clearance of FVIIa by the TFPI pathway was not responsible for the reduced FVIIa levels. We propose that elevated levels of circulating TF PCA may play an important role in triggering the activation of coagulation known to occur in patients with SCD. Because TF is the principal cellular ligand for FVIIa, it is possible that increased binding to TF accounts for the diminished plasma FVIIa levels.

Whole Blood Tissue Factor Procoagulant Activity Is Elevated in Patients With Sickle Cell Disease

We developed a simple assay for the measurement of tissue factor procoagulant activity (TF PCA) in whole blood samples that avoids the need for mononuclear cell isolation. This method combines convenience of sample collection and processing with a high degree of sensitivity and specificity for TF. Using this method, we have determined that TF PCA is detectable in whole blood samples from normal individuals, which is itself a novel observation. Essentially all PCA could be shown to be localized in the mononuclear cell fraction of blood. Compared with controls, whole blood TF levels were significantly (P < .000001) elevated in patients with sickle cell disease (SCD), regardless of the subtype of hemoglobinopathy (SS or SC disease). No significant difference in TF PCA was observed between patients in pain crisis compared with those in steady-state disease. Because TF functions as cofactor in the proteolytic conversion of FVII to FVIIa in vitro, it was expected that an increase in circulating TF PCA would lead to an increased in vivo generation of FVIIa. On the contrary, FVIIa levels were actually decreased in the plasma of patients with SCD. Plasma TF pathway inhibitor (TFPI) antigen levels were normal in SCD patients, suggesting that accelerated clearance of FVIIa by the TFPI pathway was not responsible for the reduced FVIIa levels. We propose that elevated levels of circulating TF PCA may play an important role in triggering the activation of coagulation known to occur in patients with SCD. Because TF is the principal cellular ligand for FVIIa, it is possible that increased binding to TF accounts for the diminished plasma FVIIa levels.

Increased circulating levels of soluble HLA class I heterodimers in patients with sickle cell disease

This study examined the presence of a persistent state of low-grade inflammation in sickle cell anemia patients by measuring circulating sHLA-I heterodimers and C-reactive protein during the steady state and after recent crises. Thirty-nine pediatric sickle hemoglobinopathy patients were studied during the steady state and 11 patients were evaluated within 1 month of a painful crisis. A disease severity score was generated for each patient, and soluble HLA-I (sHLA-I) and C-reactive protein levels were determined. Soluble HLA-I was significantly elevated in 55% of the steady-state group and in 36% of the recent-crisis group. The percentage of patients with elevated sHLA-I differed in the various disease subgroups in the steady state: 46% of Hb SS patients, 70% of Hb SC patients, 75% of Hb S beta-thal patients, and 20% of Hb SSF patients. Steady-state and recent-crisis sHLA-I levels were not significantly different. C-reactive protein levels were elevated in 11% of steady-state patients and in 9% of recent-crisis patients. Soluble HLA-I levels did not correlate with C-reactive protein levels or disease severity score, age, hemoglobin, reticulocyte count, platelet count, or white cell count. These results show that the majority of sickle hemoglobinopathy patients have elevated sHLA-I levels during the steady state and after recent crisis, suggesting the presence of chronic inflammation during the steady state.