Blood plasma metabolomics of children and adolescents with sickle cell anaemia treated with hydroxycarbamide: a new tool for uncovering biochemical alterations.

Sickle cell anaemia (SCA) is a debilitating genetic haemoglobinopathy predominantly affecting the disenfranchised strata of society in Africa and the Americas. The most common pharmacological treatment for this disease is the administration of hydroxycarbamide (HC) for which questions remain regarding its mechanism of action, efficacy and long-term toxicity specifically in paediatric individuals. A multiplatform metabolomics approach was used to assess the metabolome of plasma samples from a population of children and adolescents with SCA with and without HC treatment along with non-SCA individuals. Fifty-three metabolites were identified by ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS) and 1 H nuclear magnetic resonance (NMR) with a predominance of membrane lipids, amino acids and organic acids. The partial least-squares discriminant analysis (PLS-DA) analysis allowed a clear discrimination between the different studied groups, revealing clear effects of the HC treatment in the patients' metabolome including rescue of specific metabolites to control levels. Increased creatine/creatinine levels under HC treatment suggests a possible increase in the arginine pool and increased NO synthesis, supporting existing models for HC action in SCA. The metabolomics results extend the current knowledge on the models for SCA pathophysiology including impairment of Lands' cycle and increased synthesis of sphingosine 1-phosphate. Putative novel biomarkers are suggested.

Hydroxyurea treatment is associated with reduced degree of oxidative perturbation in children and adolescents with sickle cell anemia.

Sickle cell anemia (SCA) is the most common inherited hemolytic anemia worldwide. Here, we performed an exploratory study to investigate the systemic oxidative stress in children and adolescents with SCA. Additionally, we evaluated the potential impact of hydroxyurea therapy on the status of oxidative stress in a case-control study from Brazil. To do so, a panel containing 9 oxidative stress markers was measured in plasma samples from a cohort of 47 SCA cases and 40 healthy children and adolescents. Among the SCA patients, 42.5% were undertaking hydroxyurea. Multidimensional analysis was employed to describe disease phenotypes. Our results demonstrated that SCA is associated with increased levels of oxidative stress markers, suggesting the existence of an unbalanced inflammatory response in peripheral blood. Subsequent analyses revealed that hydroxyurea therapy was associated with diminished oxidative imbalance in SCA patients. Our findings reinforce the idea that SCA is associated with a substantial dysregulation of oxidative responses which may be dampened by treatment with hydroxyurea. If validated by larger prospective studies, our observations argue that reduction of oxidative stress may be a main mechanism through which hydroxyurea therapy attenuates the tissue damage and can contribute to improved clinical outcomes in SCA.

Hidden hearing loss in children and adolescents with sickle cell anemia.

OBJECTIVE: To evaluate the auditory system for hidden hearing loss (HHL) and its association with clinical variables and endothelial dysfunction (ED) in children and adolescents with sickle cell anemia (SCA). METHODS: Participants included 37 patients with stable SCA and 44 healthy controls (HC group) (aged 6-18 years) with hearing thresholds ≤ 20 dB (dB) were evaluated for pure tone audiometry, tympanometry, acoustic reflex, otoacoustic emission, and auditory evoked potentials. Laboratory analysis of the lipid profile, and C-reactive protein levels and endothelial function using ultrasonographic imaging of the brachial artery to assess flow-mediated dilation were performed. RESULTS: The SCA group presented with a higher rate of increased contralateral acoustic reflex thresholds, compared to those in the HC group at all frequencies and in both ears (p < 0.05). There were significant differences in the brainstem auditory evoked potentials between the SCA and HC groups. In the SCA group, the waves III and V latencies were increased (p = 0.006 and 0.004 respectively), and the I-III and I-V interpeak intervals were longer (p = 0.015 and 0.018 respectively) than those in the HC group. There was no association between the audiological measures and clinical and metabolic variables and sickle cell anemia complications including endothelial function and therapy. CONCLUSION: In conclusion, our findings suggest that damage in the auditory system in SCA patients can be present involving retrocochlear structures, causing functional deficits without deterioration of auditory sensitivity.

Sleep disorders and endothelial dysfunction in children with sickle cell anemia.

OBJECTIVE: We sought to assess sleep characteristics in children with sickle cell anemia (SCA) to investigate the possible association between sleep-related disorders and parameters of endothelial function. METHODS: Sleep Disturbance Scale for Children (SDSC) and endothelial function variables (flow-mediated dilatation using brachial artery ultrasound, cytokines) were compared in children with SCA and healthy children aged 6-18 years. RESULTS: Flow-mediated dilation (FMD) median (IQR) values were 10.1 (6.4; 14) vs 16.9 (12; 26.4), in the SCA and comparison groups (p = 0.001), respectively. Associations were found between difficulty initiating and maintaining sleep as well as IL-12p70 (rs = 0.3, p = 0.03) and IL-1b (rs = 0.4, p = 0.01); disorders of excessive sleepiness and TNF-a (rs = 0.3, p = 0.02), IL-6 (rs = 0.3, p = 0.03), e IL-17A (rs = 0.3, p = 0.04), and disorders of arousal with IL-6 (rs = 0.3, p = 0.04). Regarding SDSC subscales, the score for sleep breathing disorders was higher in the SCA group than in the comparison group [6.7 (3.4) vs. 5.2 (2.7), p = 0.04]. Sleep breathing disorders, disorders of excessive sleepiness and sleep hyperhidrosis scores were also higher among those SCA patients who were using hydroxyurea than those with SCA who were not using hydroxyurea [7.4 (3.9) vs. 5.9 (2.9); p = 0.026; 7.5 (3.5) vs. 6.9 (3); p = 0.028; 4.3 (3.1) vs. 3.9 (2.6); p = 0.044, respectively]. CONCLUSION: The SCA group presented higher sleep-disordered breathing scores and lower FMD values. Patients with SCA using hydroxyurea exhibited a higher frequency of scores on SDSC subscales. A positive correlation was found between SDSC subscales and cytokines.

Sensorineural hearing loss in children with sickle cell anemia and its association with endothelial dysfunction.

OBJECTIVES: To investigate the prevalence of sensorineural hearing loss (SNHL) in children and adolescents with sickle cell anemia (SCA) and its association with endothelial dysfunction (ED). METHODS: Fifty-two participants with stable SCA and 44 apparently healthy (AA genotype) participants aged 6-18 years were evaluated for pure tone audiometry and endothelial function using ultrasonographic imaging of the brachial artery to assess flow-mediated dilation (FMD). Laboratory analysis of the lipid profile and C-reactive protein levels was performed. RESULTS: In the SCA group, 15 (28.8%) patients presented with SNHL. The FMD values were reduced in the SCA with SNHL group compared with the SCA without SNHL and healthy groups. Logistic regression analysis showed that FMD was associated with SNHL independent of the lipid profile and SCA characteristics (odds ratio [95% confidence interval] = 0.614 [0.440-0.858]; p = 0.004). DISCUSSION: SNHL is a common complication in SCA; furthermore, this study identified a significant association between ED and SNHL. Damage to the vascular endothelium because of inflammation in SCA reduced blood flow in the inner ear. Thus, this circulatory disorder culminates in vaso-occlusive process and induces auditory disorders, such as SNHL.

Associations between endothelial dysfunction and clinical and laboratory parameters in children and adolescents with sickle cell anemia.

BACKGROUND: Hematological changes can drive damage of endothelial cells, which potentially lead to an early endothelial dysfunction in patients with sickle cell anemia (SCA). An association may exist between endothelial dysfunction and several clinical manifestations of SCA. The present study aims to evaluate the links between changes in endothelial function and clinical and laboratory parameters in children and adolescents with SCA. METHODS: This study included 40 children and adolescents with stable SCA as well as 25 healthy children; aged 6-18 years. All study subjects were evaluated for endothelial function using Doppler ultrasonography. In addition, a number of laboratory assays were performed, including reticulocyte and leukocyte counts as well as measurement of circulating levels of total bilirubin, C-reactive protein (CRP), glucose, lipoproteins and peripheral oxyhemoglobin saturation. These parameters were also compared between SCA patients who were undertaking hydroxyurea (HU) and those who were not. RESULTS: Flow-mediated vasodilation (FMD) values were found to be reduced in SCA patients compared with those detected in healthy controls. SCA individuals with lower FMD values exhibited higher number of hospital admissions due to vaso-occlusive events. Additional analyses revealed that patients who had decreased FMD values exhibited higher odds of acute chest syndrome (ACS) episodes. A preliminary analysis with limited number of individuals failed to demonstrate significant differences in FMD values between SCA individuals who were treated with HU and those who were not. CONCLUSIONS: Children and adolescents with SCA exhibit impaired endothelial function. Reductions in FMD values are associated with ACS. These findings underline the potential use of FMD as screening strategy of SCA patients with severe prognosis at early stages.

Association between endothelial dysfunction and otoneurological symptoms in children with sickle cell disease.

OBJECTIVE: To evaluate the association between endothelial dysfunction and otoneurological symptoms and vaso-occlusive phenomena in children with sickle cell disease (SCD). METHODS: Cross-sectional study with 54 children, aged between 6 and19 years of age, of whom 28 had genotype SS and 26 apparently healthy (AA genotype) whose parents or guardians, or the children themselves, filled out a questionnaire designed to assess their otoneurological symptoms. All the individuals were submitted assessment of endothelial function by flow-mediated dilation (FMD) percentage with reactive hyperemia of brachial artery Doppler. RESULTS: Otoneurological symptoms (tinnitus and/or vertigo) predominated in the SCD group (46.4 vs. 15.4%; p = 0.006). A negative correlation was observed between FMD percentage and time of evolution of vertigo SCD (r = -0.432; p = 0.022) and the linear regression analysis demonstrated that for every reduction in FMD percentage there was an increase in time of evolution of vertigo of 1.79 months (ß = -1.79; p = 0.022). The positive correlation between episodes of painful crisis and time of evolution of vertigo (r = 0.3; p = 0.04). DISCUSSION: The presence of vascular endothelial damage in the labyrinthine artery in patients with SCD is capable of compromising the semicircular canals, shown by clinical expression of otoneurological symptoms, such as vertigo. In the present study, an association was observed between endothelial dysfunction with otoneurological symptoms and otoneurological symptoms and vaso-occlusive phenomena in SCD.