Hypoxia and inflammation in children with sickle cell disease: implications for hippocampal functioning and episodic memory

Simvastatin-Mediated Nrf2 Activation Induces Fetal Hemoglobin and Antioxidant Enzyme Expression to Ameliorate the Phenotype of Sickle Cell Disease

Sickle cell disease (SCD) is a pathophysiological condition of chronic hemolysis, oxidative stress, and elevated inflammation. The transcription factor Nrf2 is a master regulator of oxidative stress. Here, we report that the FDA-approved oral agent simvastatin, an inhibitor of hydroxymethyl-glutaryl coenzyme A reductase, significantly activates the expression of Nrf2 and antioxidant enzymes. Simvastatin also induces fetal hemoglobin expression in SCD patient primary erythroid progenitors and a transgenic mouse model. Simvastatin alleviates SCD symptoms by decreasing hemoglobin S sickling, oxidative stress, and inflammatory stress in erythroblasts. Particularly, simvastatin increases cellular levels of cystine, the precursor for the biosynthesis of the antioxidant reduced glutathione, and decreases the iron content in SCD mouse spleen and liver tissues. Mechanistic studies suggest that simvastatin suppresses the expression of the critical histone methyltransferase enhancer of zeste homolog 2 to reduce both global and gene-specific histone H3 lysine 27 trimethylation. These chromatin structural changes promote the assembly of transcription complexes to fetal γ-globin and antioxidant gene regulatory regions in an antioxidant response element-dependent manner. In summary, our findings suggest that simvastatin activates fetal hemoglobin and antioxidant protein expression, modulates iron and cystine/reduced glutathione levels to improve the phenotype of SCD, and represents a therapeutic strategy for further development.

Relations of hippocampal subfields atrophy patterns with memory and biochemical changes in end stage renal disease

End-stage renal disease (ESRD) results in hippocampal volume reduction, but the hippocampal subfields atrophy patterns cannot be identified. We explored the volumes and asymmetry of the hippocampal subfields and their relationships with memory function and biochemical changes. Hippocampal global and subfields volumes were derived from 33 ESRD patients and 46 healthy controls (HCs) from structural MRI. We compared the volume and asymmetric index of each subfield, with receiver operating characteristic curve analysis to evaluate the differentiation between ESRD and HCs. The relations of hippocampal subfield volumes with memory performance and biochemical data were investigated in ESRD group. ESRD patients had smaller hippocampal subfield volumes, mainly in the left CA1 body, left fimbria, right molecular layer head, right molecular layer body and right HATA. The right molecular layer body exhibited the highest accuracy for differentiating ESRD from HCs, with a sensitivity of 80.43% and specificity of 72.73%. Worse learning process (r = 0.414, p = 0.032), immediate recall (r = 0.396, p = 0.041) and delayed recall (r = 0.482, p = 0.011) was associated with left fimbria atrophy. The left fimbria volume was positively correlated with Hb (r = 0.388, p = 0.05); the left CA1 body volume was negatively correlated with Urea (r = - 0.469, p = 0.016). ESRD patients showed global and hippocampal subfields atrophy. Left fimbria atrophy was related to memory function. Anemia and Urea level may be associated with the atrophy of left fimbria and CA1 body, respectively.

Cognitive impairment caused by hypoxia: from clinical evidences to molecular mechanisms

Hypoxia is a state of reduced oxygen supply and excessive oxygen consumption. According to the duration of hypoxic period, it can be classified as acute and chronic hypoxia. Both acute and chronic hypoxia could induce abundant neurological deficits. Although there have been significant advances in the pathophysiological injuries, few studies have focused on the cognitive dysfunction. In this review, we focused on the clinical evidences and molecular mechanisms of cognitive impairment under acute and chronic hypoxia. Hypoxia can impair several cognitive domains such as attention, learning and memory, procession speed and executive function, which are similar in acute and chronic hypoxia. The severity of cognitive deficit correlates with the duration and degree of hypoxia. Recovery can be achieved after acute hypoxia, while sequelae or even dementia can be observed after chronic hypoxia, perhaps due to the different molecular mechanisms. Cardiopulmonary compensatory response, glycolysis, oxidative stress, calcium overload, adenosine, mitochondrial disruption, inflammation and excitotoxicity contribute to the molecular mechanisms of cognitive deficit after acute hypoxia. During the chronic stage of hypoxia, different adaptive responses, impaired neurovascular coupling, apoptosis, transcription factors-mediated inflammation, as well as Aβ accumulation and tau phosphorylation account for the neurocognitive deficit. Moreover, brain structural changes with hippocampus and cortex atrophy, ventricle enlargement, senile plaque and neurofibrillary tangle deposition can be observed under chronic hypoxia rather than acute hypoxia.

A Traditional Review of Sickle Cell Disease and the Associated Onset of Dementia: Hematological and Neurocognitive Crossroads

Sickle cell trait and disease are potential risk factors for dementia and cognitive dysfunction in African Americans, as are genetic variants. This illness affects around 300 million people globally. Due to its ability to defend against severe malaria, it represents an evolutionary survival advantage. It has been shown that sickle cell disease and trait are independent risk factors for the prevalence and incidence of albuminuria and chronic renal disease. Sickle cell anemia impairs cognitive performance in people with minimal or mild manifestations of the genetic blood disorder, owing mostly to its cerebrovascular implications. Similarly, various cerebral minor vascular disorders, such as silent cerebral infarcts, have been linked to the sickle cell trait, which is associated with impaired cognitive ability. It has been found that patients with sickle cell disease have a significantly decreased subcortical and cortical brain volume. Adults and children with sickle cell disease have been documented to have attention-related issues, particularly reduced sustained attention.

Analysis of hippocampal subfields in sickle cell disease using ultrahigh field MRI

Sickle cell disease (SCD) is an inherited hemoglobinopathy that causes organ dysfunction, including cerebral vasculopathy and neurological complications. Hippocampal segmentation with newer and advanced 7 Tesla (7T) MRI protocols has revealed atrophy in specific subregions in other neurodegenerative and neuroinflammatory diseases, however, there is limited evidence of hippocampal involvement in SCD. Thus, we explored whether SCD may be also associated with abnormalities in hippocampal subregions. We conducted 7T MRI imaging in individuals with SCD, including the HbSS, HbSC and HbS/beta thalassemia genotypes (n = 53), and healthy race and age-matched controls (n = 47), using a customized head coil. Both T1- and T2-weighted images were used for automatic segmentation of the hippocampal subfields. Individuals with SCD had, on average, significantly smaller volume of the region including the Dentate Gyrus and Cornu Ammonis (CA) 2 and 3 as compared to the control group. Other hippocampal subregions also showed a trend towards smaller volumes in the SCD group. These findings support and extend previous reports of reduced volume in the temporal lobe in SCD patients. Further studies are necessary to investigate the mechanisms that lead to structural changes in the hippocampus subfields and their relationship with cognitive performance in SCD patients.

Bright IDEAS problem-solving skills training for caregivers of children with sickle cell disease: A two-site pilot feasibility trial

BACKGROUND

Bright IDEAS problem-solving skills training (BI) is an evidence-based behavioral intervention that has been utilized extensively with caregivers of children recently diagnosed with cancer. Considerable evidence has shown that BI is acceptable to caregivers of children recently diagnosed with cancer, and improvements in problem-solving skills mediate reduced symptoms of distress.

PROCEDURES

A slightly modified version of BI was offered to caregivers of children with sickle cell disease (SCD) in a two-site pilot feasibility trial. BI was modified to reduce barriers to care, logistical challenges, and stigma associated with receiving behavioral health services. Our goal was to establish high rates of recruitment and retention among caregivers of children with SCD. Recruitment was acceptable (94%; N = 72) and retention reasonable (49%) across both sites with 35 caregivers successfully completing the BI program.

RESULTS

Results showed that caregivers of children with SCD, who successfully completed the BI program reported, significant improvements in problem-solving skills immediately and three months after intervention completion. Interestingly, initial levels of distress were low with few caregivers reporting clinically significant levels of distress; distress remained low over time.

CONCLUSIONS

Findings are discussed in the context of psychosocial screening and resilience of caregivers of children with SCD.

Ischemic sequelae and other vascular diseases

Although pediatric stroke is associated with higher survival rates compared with adult stroke, a substantial body of evidence indicates significant neuropsychologic morbidity in pediatric stroke survivors. Neuroplasticity does not guarantee good outcome in children. The general trends observed in the literature are reviewed as is the profile observed in common causes of pediatric stroke: congenital heart disease, moyamoya disease, and sickle cell disease. The neuropsychologic profile of pediatric stroke patients is heterogeneous due to the multiplicity of associated causes. Stroke in early infancy and large strokes are associated with cognitive impairment while more limited disorders, such as phasic deficit, are observed in childhood stroke. Executive dysfunction is common in pediatric stroke, but social interaction skills are usually preserved. Congenital heart disease and sickle cell disease are associated with global neuropsychologic dysfunction while cognition is usually preserved in moyamoya. Executive dysregulation is instead more frequently reported in this population. Further study of maladaptive processes after pediatric stroke will allow identification of predictors of functional and neuropsychologic outcomes and permit personalization of care.

Home Oxygen Therapy for Children. An Official American Thoracic Society Clinical Practice Guideline

Background: Home oxygen therapy is often required in children with chronic respiratory conditions. This document provides an evidence-based clinical practice guideline on the implementation, monitoring, and discontinuation of home oxygen therapy for the pediatric population.

Methods: A multidisciplinary panel identified pertinent questions regarding home oxygen therapy in children, conducted systematic reviews of the relevant literature, and applied the Grading of Recommendations, Assessment, Development, and Evaluation approach to rate the quality of evidence and strength of clinical recommendations.

Results: After considering the panel’s confidence in the estimated effects, the balance of desirable (benefits) and undesirable (harms and burdens) consequences of treatment, patient values and preferences, cost, and feasibility, recommendations were developed for or against home oxygen therapy specific to pediatric lung and pulmonary vascular diseases.

Conclusions: Although home oxygen therapy is commonly required in the care of children, there is a striking lack of empirical evidence regarding implementation, monitoring, and discontinuation of supplemental oxygen therapy. The panel formulated and provided the rationale for clinical recommendations for home oxygen therapy based on scant empirical evidence, expert opinion, and clinical experience to aid clinicians in the management of these complex pediatric patients and identified important areas for future research.

Higher executive abilities following a blood transfusion in children and young adults with sickle cell disease

Individuals with sickle cell disease (SCD) experience cognitive deficits; however, it remains unclear whether medical treatments for SCD improve cognition. Given that executive abilities are typically impaired in individuals with SCD, they were the focus of the current study. Our primary hypothesis was that executive abilities would be higher acutely soon after a blood transfusion in children and young adults with SCD. We used tests from the NIH Toolbox to assess executive abilities in 27 participants with SCD receiving chronic transfusion in comparison to 34 participants with SCD receiving hydroxyurea (HU) and 41 non-SCD demographically matched controls, all of whom were tested at two time points. Participants in the transfusion group completed cognitive testing within 3 days after a transfusion (soon after transfusion) and then within 3 days before their next transfusion (long after transfusion) over an interval of 3-7 weeks. We found that executive abilities were significantly poorer for the transfusion and HU groups than for the control group. In support of our primary hypothesis, executive abilities for the transfusion group were significantly better soon after a transfusion compared to long after a transfusion, χ² (1) = 17.8, P < .0001. Our results demonstrate that executive abilities were higher acutely following a blood transfusion. These findings have implications for daily functioning, medical decision making, and academic achievement in children and young adults with SCD.

Sickle cell trait and risk of cognitive impairment in African-Americans: The REGARDS cohort

BACKGROUND

Sickle cell anemia may be associated with cognitive dysfunction, and some complications of sickle cell anemia might affect those with sickle cell trait (SCT), so we hypothesized that SCT is a risk factor for cognitive impairment.

METHODS

The Reasons for Geographic and Racial Differences in Stroke (REGARDS) study enrolled a national cohort of 30,239 white and black Americans from 2003 to 7, who are followed every 6 months. Baseline and annual global cognitive function testing used the Six-Item Screener (SIS), a validated instrument (scores range 0-6; ≤ 4 indicates cognitive impairment). Participants with baseline cognitive impairment and whites were excluded. Logistic regression was used to calculate the association of SCT with incident cognitive impairment, adjusted for risk factors. Linear mixed models assessed multivariable-adjusted change in test scores on a biennially administered 3-test battery measuring learning, memory, and semantic and phonemic fluency.

FINDINGS

Among 7743 participants followed for a median of 7·1 years, 85 of 583 participants with SCT (14·6%) developed incident cognitive impairment compared to 902 of 7160 (12·6%) without SCT. In univariate analysis, the odds ratio (OR) of incident cognitive impairment was 1·18 (95% CI: 0·93, 1·51) for those with SCT vs. those without. Adjustment did not impact the OR. There was no difference in change on 3-test battery scores by SCT status (all p > 0·11).

INTERPRETATION

In this prospective cohort study of black Americans, SCT was not associated with incident cognitive impairment or decline in test scores of learning, memory and executive function.

FUNDING

National Institutes of Health, American Society of Hematology.

Integration of neuropsychology services in a sickle cell clinic and subsequent healthcare use for pain crises

Objective: Growing literature has documented the clinical utility of neuropsychological evaluations for predicting functional outcomes, including reduced healthcare service utilization, in a variety of clinical samples. The present study investigates the relationship between the integration of clinical neuropsychology services into an existing outpatient sickle cell clinic and frequency of emergency department (ED) visits and hospitalizations for pain crises. Method: Participants included 144 adults diagnosed with sickle cell disease (SCD) who either underwent neuropsychological evaluation (NP+), including interview, neuropsychological testing, and feedback, or treatment as usual (NP-). Medical records were reviewed for a two-year period, one year prior to study enrollment (pre-assessment) and one year post-study enrollment (post-assessment), to track the number of ED visits and hospitalizations related to sickle cell pain crises. Results: When examining pain crises ED visits prior to and following neuropsychological evaluation, there was a significant decrease in ED visits for the NP + group, but no change for the NP - group. No significant changes in pain crises hospitalizations were observed for the NP + and NP - groups. For the NP + group, the decreased incidence of pain crises ED visits and hospitalizations was associated with an estimated total cost savings of $994,821. Discussion: Results highlight that integration of neuropsychology services into an existing outpatient sickle cell clinic may reduce healthcare costs, particularly use of pain crises ED services, for adults with SCD.

Long-term cognitive and neuroanatomical stability in patients with anoxic amnesia: A Case Report

BACKGROUND

Anoxia can result in selective hippocampal damage with associated impairments in declarative memory. Whilst memory impairments and brain structures are thought to be stable, there are little data regarding the effects of ageing or change over time in patients with amnesia from anoxic brain injury.

METHODS

To assess change over time, we compared structural magnetic resonance imaging (MRI) with data obtained over ten years previously in two well-characterized patients with amnesia (JRW and RS) who experienced an anoxic brain injury. Six healthy, age-matched control participants were recruited to compare brain volumes with the patients at Time 2. Wechsler adult intelligence scale-revised and Wechsler memory scale-revised scores were compared to scores on the same tests administered 13 and 19 years prior.

RESULTS

Patients with amnesia had significantly smaller hippocampal volumes than controls, but comparable medial temporal lobe and ventricular volumes. Memory, intellectual function and brain volumes were stable over time.

CONCLUSION

Patients with an amnesia due to anoxia have memory impairments and smaller hippocampal volumes compared to controls; however, memory, intelligence and structural volumes remain stable over time. At ages 50 and 57, they do not appear to have early age-associated cognitive decline that is sometimes observed in patients with traumatic brain injury.

Cognitive functioning in children from Nigeria with sickle cell anemia

BACKGROUND

Cognitive impairment is a major neurological complication of sickle cell anemia (SCA) in the United States, but there are limited studies of cognitive impairment in Nigeria, the country with the highest SCA burden. We hypothesized that children from Nigeria with SCA have worse cognitive functioning than comparison children and explored the association between lower cognitive functioning and key laboratory demographic and socioeconomic variables among children with SCA.

PROCEDURE

We conducted a cross-sectional survey, supplemented by anthropomorphic and laboratory data, among a convenience sample of children from Nigeria with and without SCA. We administered the Wechsler Intelligence Scale for Children, Version IV. Our primary outcome measures included (1) estimated IQ (Est. IQ), (2) working memory (WM), and (3) processing speed (PS).

RESULTS

The sample included 56 children with SCA (mean age 9.20 [SD 2.75], 46.43% girls) and 44 comparison children (mean age 9.41 [SD 2.49], 40.91% girls). Children with SCA performed worse on Est. IQ (84.58 vs. 96.10, P = 0.006) and PS (86.69 vs 96.91, P = 0.009) than comparison children. There was no significant difference in WM between both groups. Factors associated with lower Est. IQ and PS among children with SCA included age, maternal education, weight-for-age Z scores, and height-for age Z scores.

CONCLUSION

In this small sample of children from Nigeria, we found worse cognitive functioning in children with SCA than in comparison children, and that sociodemographic and anthropomorphic factors were correlated with cognitive functioning.

Cognitive and behavior deficits in sickle cell mice are associated with profound neuropathologic changes in hippocampus and cerebellum

Strokes are perhaps the most serious complications of sickle cell disease (SCD) and by the fifth decade occur in approximately 25% of patients. While most patients do not develop strokes, mounting evidence indicates that even without brain abnormalities on imaging studies, SCD patients can present profound neurocognitive dysfunction. We sought to evaluate the neurocognitive behavior profile of humanized SCD mice (Townes, BERK) and to identify hematologic and neuropathologic abnormalities associated with the behavioral alterations observed in these mice. Heterozygous and homozygous Townes mice displayed severe cognitive deficits shown by significant delays in spatial learning compared to controls. Homozygous Townes also had increased depression- and anxiety-like behaviors as well as reduced performance on voluntary wheel running compared to controls. Behavior deficits observed in Townes were also seen in BERKs. Interestingly, most deficits in homozygotes were observed in older mice and were associated with worsening anemia. Further, neuropathologic abnormalities including the presence of large bands of dark/pyknotic (shrunken) neurons in CA1 and CA3 fields of hippocampus and evidence of neuronal dropout in cerebellum were present in homozygotes but not control Townes. These observations suggest that cognitive and behavioral deficits in SCD mice mirror those described in SCD patients and that aging, anemia, and profound neuropathologic changes in hippocampus and cerebellum are possible biologic correlates of those deficits. These findings support using SCD mice for studies of cognitive deficits in SCD and point to vulnerable brain areas with susceptibility to neuronal injury in SCD and to mechanisms that potentially underlie those deficits.

Prevention of Morbidity in sickle cell disease--qualitative outcomes, pain and quality of life in a randomised cross-over pilot trial of overnight supplementary oxygen and auto-adjusting continuous positive airways pressure (POMS2a): study protocol for a randomised controlled trial

BACKGROUND

Sickle cell anaemia (SCA) is an inherited disorder of haemoglobin. Patients experience long-term health care problems, affecting quality of life (QOL) including frequent acute pain, which is difficult to document in trials except as hospital admissions. Pilot data suggests that overnight respiratory support, either supplementary oxygen or auto-adjusting continuous positive airways pressure (APAP), is safe and may have clinical benefit. This pilot trial aims to determine which intervention is more acceptable to participants and whether there are other advantages of one over the other, e.g. in respiratory function or haematological parameters, before conducting the Phase 2 trial of overnight respiratory support funded by the National Institutes of Health Research.

METHODS/DESIGN

This is a pilot cross-over interventional trial with the order of interventions decided by simple randomization. Ten adults (age over 18 years) and 10 children (aged between 8 and 18 years) with homozygous sickle cell disease (haemoglobin SS, HbSS), recruited regardless of symptoms of sleep-disordered breathing, will undergo overnight pulse oximetry and will have two interventions, overnight oxygen and APAP, for a week each in randomised order with a washout week between interventions. Participants will complete online diaries via an iPad throughout the 29 days of the study and will complete QOL questionnaires and have measurement of haematology, biochemistry, spirometry and lung volumes (adults only) at 3 time points, at baseline and after each intervention, as well as in-depth semi-structured qualitative interviews after each intervention, carried out by an experienced psychologist. Both qualitative and statistical methods will be used to analyze the data. The primary outcome is qualitative data looking at participant experience from the transcribed interviews after each intervention. The participant's view on feasibility, acceptability and preference will specifically be explored. The QOL, laboratory and lung function data will be compared with baseline for each arm.

DISCUSSION

Patient and public involvement is an integral part of this trial and the key outcome is the qualitative result, which is dependent on obtaining good quality data to advise on participant feasibility, acceptability and preference. This is being addressed by using a standard interview. The development of a pain endpoint is another important outcome and collecting daily measurements is likely to be challenging. Research results will be used to inform design of the Phase 2 trial.

TRIAL REGISTRATION

ISRCTN46078697 18 July 2014.

Changes in the cornea related to sickle cell disease: a pilot investigation

PURPOSE

To investigate corneal structural changes (central corneal thickness, endothelial cell count, and cellular morphology) in patients with sickle cell disease (SCD).

METHODS

This prospective study included 56 patients with SCD and 50 age- and sex-matched healthy subjects without any eye disease aside from refractive errors. Endothelial cell density (ECD), percentage of hexagonality, and the coefficient of variation in cell size (CV) were measured using noncontact specular microscopy, and central corneal thickness (CCT) was measured by pachymetry.

RESULTS

The mean CCT value was 509.6 ± 20.7 μm in the study group and 520.8 ± 23.6 μm in the control group. The mean ECD, CV, and percentage of hexagonality values in the study group were 2712 ± 335 cells/mm², 34.5 ± 5.3%, and 57.2 ± 6.6%, respectively, and 3030 ± 247 cells/mm², 31.6 ± 5.0%, and 60.4 ± 6.9% in the control group, respectively. Endothelial cell density (p = 0.001), CCT (p = 0.011), CV (p = 0.005), and percentage of hexagonality values (p = 0.018) were significantly different between the study and control groups.

CONCLUSIONS

The results of the current study indicate that patients with SCD had considerable morphologic changes in the structure of the cornea when compared to healthy subjects.