Apolipoprotein E polymorphism: survival and neurological outcome after cardiopulmonary resuscitation

Neurodevelopmental Outcomes in Tetralogy of Fallot: A Systematic Review

BACKGROUND

Tetralogy of Fallot (TOF) represents between 7 and 10% of the total cases of congenital heart defects (CHD) and is estimated to be the most common cyanotic CHD, requiring medical or surgical intervention within the first year of life. Current advances in prenatal screening and fetal echocardiography led to increased rates of prenatal diagnosis of TOF. Furthermore, improvements in initial medical care, surgical repair, and long-term care are associated with excellent long-term survival until adulthood. Consequently, issues of morbidity have come under the spotlight, specifically neurodevelopmental and psychiatric adverse outcomes, which affect the quality of life of TOF survivors.

METHOD

This study is a systematic review of English articles, using PUBMED and applying the following search terms, Tetralogy of Fallot, neurodevelopment, autism, cerebral palsy, attention-deficit hyperactivity disorder. Data were extracted by two authors.

RESULTS

Most researchers suggest that TOF survivors score lower in neurodevelopmental tests than healthy populations of the same age and are in danger of neurodevelopmental impairments. Furthermore, it is suggested that TOF adolescents show higher rates of psychiatric disorders.

CONCLUSIONS

The neurodevelopment of TOF survivors is not intensively studied. Existing studies in TOF survivors focus on different developmental aspects, using different evaluation methods and thus making conclusions for either one of the four aspects of neurodevelopment (executive function, cognition, and adaptive function, speech-language and motor function, or neuropsychiatric domain). The poor outcomes of these isolated studies indicate the need for future research as well as for continuous neuropsychological assessment and close monitoring of children and adolescents with TOF.

Neurodevelopmental outcomes of children with congenital heart disease: A review

Congenital heart defects are the most common birth anomaly affecting approximately 1% of births. With improved survival in this population, there is enhanced ability to assess long-term morbidities including neurodevelopment. There is a wide range of congenital heart defects, from those with minimal physiologic consequence that do not require medical or surgical intervention, to complex structural anomalies requiring highly specialized medical management and intricate surgical repair or palliation. The impact of congenital heart disease on neurodevelopment is multifactorial. Susceptibility for adverse neurodevelopment increases with advancing severity of the defect with initial risk factors originating during gestation. Complex structural heart anomalies may pre-dispose the fetus to abnormal circulatory patterns in utero that ultimately impact delivery of oxygen rich blood to the fetal brain. Thus, the brain of a neonate born with complex congenital heart disease may be particularly vulnerable from the outset. That vulnerability is compounded during the newborn period and through childhood, as this population endures a myriad of medical and surgical interventions. For each individual patient, these factors are likely cumulative and synergistic with progression from fetal life through childhood. This review discusses the spectrum of risk factors that may impact neurodevelopment in children with congenital heart disease, describes current recommendations and practices for neurodevelopmental follow-up of children with congenital heart disease and reviews important neurodevelopmental trends in this high risk population.

Genetic Variation and Neuroplasticity: Role in Rehabilitation After Stroke

BACKGROUND AND PURPOSE

In many neurologic diagnoses, significant interindividual variability exists in the outcomes of rehabilitation. One factor that may impact response to rehabilitation interventions is genetic variation. Genetic variation refers to the presence of differences in the DNA sequence among individuals in a population. Genetic polymorphisms are variations that occur relatively commonly and, while not disease-causing, can impact the function of biological systems. The purpose of this article is to describe genetic polymorphisms that may impact neuroplasticity, motor learning, and recovery after stroke.

SUMMARY OF KEY POINTS

Genetic polymorphisms for brain-derived neurotrophic factor (BDNF), dopamine, and apolipoprotein E have been shown to impact neuroplasticity and motor learning. Rehabilitation interventions that rely on the molecular and cellular pathways of these factors may be impacted by the presence of the polymorphism. For example, it has been hypothesized that individuals with the BDNF polymorphism may show a decreased response to neuroplasticity-based interventions, decreased rate of learning, and overall less recovery after stroke. However, research to date has been limited and additional work is needed to fully understand the role of genetic variation in learning and recovery.

RECOMMENDATIONS FOR CLINICAL PRACTICE

Genetic polymorphisms should be considered as possible predictors or covariates in studies that investigate neuroplasticity, motor learning, or motor recovery after stroke. Future predictive models of stroke recovery will likely include a combination of genetic factors and other traditional factors (eg, age, lesion type, corticospinal tract integrity) to determine an individual's expected response to a specific rehabilitation intervention.

Child apolipoprotein E gene variants and risk of cerebral palsy: estimation from case-parent triads

OBJECTIVE

To use case-parent triad data to investigate if cerebral palsy (CP) is associated with variants of the APOE gene, the rs59007384 SNP of the TOMM40 gene or combined haplotypes of the two genes.

STUDY DESIGN

DNA was analyzed in buccal swabs from 235 children with CP, their parents and a sibling. The relative risks (RR) with 95% confidence intervals (CI) that the children would have a distribution of APOE genotypes, rs59007384 variants or combined haplotypes deviating from Mendelian inheritance were estimated.

RESULTS

Children with CP were more likely than expected to carry the APOEε3 allele (RR 7.5; CI: 0.99-53.7 for heterozygotes and 10.3; CI: 1.4-79.6 for homozygotes), and to have the haplotype of APOEε3 and rs59007384 G (RR 2.4; CI: 1-5.7 for heterozygotes, RR 3.7; CI: 1.4-9.5 for homozygotes) whereas the distribution was as expected for rs59007384 alone. In the subgroup analyses the findings were confined to children born preterm. Among siblings the distribution of these genes was as expected according to Mendelian inheritance.

CONCLUSION

We speculate that children with APOEε2/APOEε4 alleles are more likely to die following cerebral injury in utero, resulting in a higher than expected proportion of children with CP carrying the APOEε3 allele.

Apolipoprotein E genotype and outcome in infants with hypoxic-ischemic encephalopathy

BACKGROUND

Adults with the apolipoprotein E (APOE) gene alleles e4 and e2 are at high risk of poor neurological outcome after brain injury. The e4 allele has been associated with cerebral palsy (CP), and the e2 allele has been associated with worse neurological outcome with congenital heart disease. This study was done to test the hypothesis that the APOE genotype is associated with outcome among neonates who survive after hypoxic-ischemic encephalopathy (HIE).

METHODS

We conducted a cohort study of infants who survived HIE and had 18-22 mo standardized neurodevelopmental evaluations to assess associations between disability and the APOE genotypes e3/e3, e4/-, and e2/-.

RESULTS

A total of 139 survivors were genotyped. Of these, 86 (62%) were of the e3/e3, 41 (29%) were of the e4/-, and 14 (10%) were of the e2/- genotypes. One hundred and twenty-nine infants had genotype and follow-up data; 26% had moderate or severe disabilities. Disability prevalence was 30 and 19% among those with and without the e3/e3 genotype, 25 and 26% among those with and without the e2 allele, and 18 and 29% among those with and without the e4 allele, respectively. None of the differences were statistically significant. CP prevalence was also similar among genotype groups.

CONCLUSION

Disability was not associated with the APOE genotype in this cohort of HIE survivors.

The influence of Apolipoprotein E genotype on regional pathology in Alzheimer's disease

Background

Carriers of the ApoE ϵ4 allele are at a greater risk for developing Alzheimer’s disease (AD) and those who do develop AD tend to have a much greater neuropathological disease burden. Although several studies have shown significant differences in AD pathology among ϵ4 carriers and non-carriers, few have characterized these differences in terms of brain region and neuropathological score frequency.

Methods

566 pathologically-confirmed AD cases who were followed prospectively with antemortem dementia diagnoses (312 ApoE ϵ4 carriers and 254 ApoE ϵ4 non-carriers) were compared on the frequencies of neuropathological frequency scores (none, sparse, moderate, frequent) among several different brain regions (frontal, temporal, parietal, hippocampal, and entorhinal) using the CERAD scoring system. Pathology score frequencies were analyzed by carrier status (ϵ4 carrier vs. ϵ4 non-carrier) and by genotype (2/3, 3/3, 2/4, 3/4, 4/4). Both analyses investigated pathology score frequencies among different brain regions (frontal, temporal, parietal, hippocampal, and entorhinal).

Results

ϵ4 carriers had a significantly lower age at death (p <0.001) and significantly higher Braak scores (p <0.001) than ϵ4 non-carriers. Genotype comparison revealed that plaque and tangle pathologies increased in the following pattern, 2/3<3/3<2/4<3/4<4/4, for several brain regions. When stratified by age and ApoE ϵ4 carrier status, ϵ4 carriers tended to have significantly more frequent scores across most cortical areas. However, non-carriers age 90 and older tended to have greater plaque pathology than carriers. For tangle pathology, ϵ4 carriers tended to have significantly more “frequent” scores than non-carriers, except for the hippocampal and entorhinal areas in individuals age 90 and older.

Conclusions

ApoE ϵ4 carriers had a significantly higher percentage of “frequent” scores for plaques and tangles when compared to ApoE ϵ4 non-carriers for several brain regions. However, ϵ4 non-carriers age 90 and older tended to have less plaque and tangle pathology in certain brain regions. These results demonstrate that AD pathology may manifest itself differently based on ApoE genotype and suggest that ApoE carriers and non-carriers may have different patterns of AD neuropathology location and density.

Significance of apolipoprotein E in subarachnoid hemorrhage: neuronal injury, repair, and therapeutic perspectives--a review

Subarachnoid hemorrhage (SAH) strikes individuals at a young age with devastating neurologic consequences. Classic formulations that correlate complications and outcome with clinical variables do not explain all the heterogeneity that is usually found in clinical practice. The role of genetic predisposition has recently been investigated. Particular attention has been paid to the apolipoprotein E (APOE) genotype that encodes for a polymorphic protein existing as 3 isoforms (apoE2, apoE3, apoE4), products of alleles E2, E3, and E4 at a single gene locus. ApoE is produced by astrocytes and exerts complex neuroprotective functions that make it a hub of the biochemical network of SAH. The neuroprotective effectiveness of the apoE4 isoform is reduced with respect to the others and this has made the E4 allele a risk factor candidate. Recently published observational studies and meta-analyses suggested that the APOE genotype may strongly improve the usual predictive model with the possibility of optimizing clinical decisions according to the individual's needs. Furthermore, the clinical results, together with new biological insights, suggest that SAH may be a possible candidate for the ongoing research on apoE-based neuroprotective therapy. This article reviews the clinical studies, analyzes their methodology, and surveys the biological links between the physiopathology of SAH and apoE and the possible prospects.

Does the apolipoprotein epsilon 4 allele predispose varsity athletes to concussion? A prospective cohort study

OBJECTIVE

To determine the association between the apolipoprotein epsilon 4 allele and concussion. We hypothesized that apolipoprotein epsilon 4 carriers may be more likely to sustain a concussion.

DESIGN

Prospective cohort study.

SETTING

University of Toronto varsity athletics.

PARTICIPANTS

Included 318 of 822 collegiate student athletes who participated in University of Toronto varsity sports from September 2002 to April 2006.

ASSESSMENT OF RISK FACTORS

The presence of apolipoprotein epsilon 4 was described dichotomously after genotyping blood samples collected from participants.

MAIN OUTCOME MEASUREMENTS

Concussions were identified by sport-medicine professionals present on the sidelines using on-field assessment forms. All concussion diagnoses were verified by a sports medicine physician. Survival analysis was used to determine the association between apolipoprotein epsilon 4 and first concussion.

RESULTS

The unadjusted hazard ratio for concussion in the apolipoprotein epsilon 4 carriers was 1.18 (95% CI: 0.52, 2.69) compared to noncarriers. Adjustment for sex, weight, height, and team type resulted in a hazard ratio of 1.06 (95% CI: 0.41, 2.72), indicating little effect from confounding factors.

CONCLUSIONS

There is no important association between carrying the apolipoprotein epsilon 4 allele and sustaining a concussion. At this time, we do not recommend preseason genetic testing for varsity athletes as a mechanism for targeting prevention strategies.

Apolipoprotein E genotype and traumatic brain injury in children--association with neurological outcome

OBJECTIVE

To determine whether the presence of Apolipoprotein E epsilon4 genotype (ApoE epsilon4) is associated with outcomes of traumatic brain injury in children.

MATERIALS AND METHODS

The ApoE genotype was examined in the group of 70 pediatric patients who suffered from traumatic brain injury. The group consists of 48 boys and 22 girls, and the most frequent was the E3 isoform of ApoE. Polymerase chain reaction/restriction fragment length polymorphism method was used for the ApoE genotype assessment. The severity of trauma was assessed by Glasgow Coma Scale and graded into three categories. The presence of focal neurology signs, comparing the admission and dimission status, and duration of hospital care were observed. The neurological outcome after 1 year was assessed by Glasgow Outcome Scale. Trauma severity was compared with the neurological outcome, according to different ApoE genotypes. For statistical processing, t test, nonparametric Wilcoxon test, Fisher, and chi(2) tests were used.

CONCLUSION

Our results suggest the association between the ApoE genotype and outcome of traumatic brain injury in children. Patients with ApoE epsilon4 genotype were more likely to have severe clinical symptomatology and unfavorable neurological outcome after traumatic brain injury compared to significantly better outcome with other ApoE genotype.

Apolipoprotein E and neurological disease: therapeutic potential and pharmacogenomic interactions

The apolipoprotein E (apoE) polymorphism is emerging as a uniquely important genetic modifier that affects functional outcome from both acute and chronic neurological injuries. Recent attention has focused on common denominator mechanisms by which apoE might affect brain injury and/or brain repair responses in clinically diverse diseases. Although endogenous apoE likely serves several adaptive functions in the injured CNS, there is growing evidence that its effect on modifying brain inflammatory responses and providing protection from excitotoxic injury may be central to its protective properties. A more complete understanding of the role that apoE plays in the injured brain has led to novel therapeutic strategies for both acute and chronic neurological disease.

Apolipoprotein E epsilon4 allele and outcomes of traumatic spinal cord injury

BACKGROUND/OBJECTIVE

To test the hypothesis that apolipoprotein E (APOE) polymorphisms are associated with outcomes after spinal cord injury (SCI).

METHODS

Retrospective cohort study, from rehabilitation admission to discharge.

PARTICIPANTS

Convenience sample of 89 persons with cervical SCI (C3-C8) treated from 1995 through 2003. Median age was 30 years (range 14-70); 67 were male (75%) and 83 were white (93%).

MAIN OUTCOME MEASURES

American Spinal Injury Association (ASIA) motor and sensory scores, ASIA Impairment Scale (AIS), time from injury to rehabilitation admission, and length of stay (LOS) in rehabilitation.

RESULTS

Subjects with an APOE epsilon4 allele (n = 15; 17%) had significantly less motor recovery during rehabilitation than did individuals without an epsilon4 allele (median 3.0 vs 5.5; P < 0.05) and a longer rehabilitation LOS (median 106 vs 89 days; P = 0.04), but better sensory-pinprick recovery (median 5.0 vs 2.0; P= 0.03). There were no significant differences by APOE epsilon4 allele status in sensory-light touch recovery, likelihood of improving AIS Grade, or time from injury to rehabilitation admission.

CONCLUSIONS

APOE epsilon4 allele was associated with differences in neurological recovery and longer rehabilitation LOS. Genetic factors may be among the determinants of outcome after SCI and warrant further study.

Apolipoprotein E genotype and traumatic brain injury in children--association with neurological outcome

OBJECTIVE

To determine whether the presence of Apolipoprotein E epsilon4 genotype (ApoE epsilon4) is associated with outcomes of traumatic brain injury in children.

MATERIALS AND METHODS

The ApoE genotype was examined in the group of 70 pediatric patients who suffered from traumatic brain injury. The group consists of 48 boys and 22 girls, and the most frequent was the E3 isoform of ApoE. Polymerase chain reaction/restriction fragment length polymorphism method was used for the ApoE genotype assessment. The severity of trauma was assessed by Glasgow Coma Scale and graded into three categories. The presence of focal neurology signs, comparing the admission and dimission status, and duration of hospital care were observed. The neurological outcome after 1 year was assessed by Glasgow Outcome Scale. Trauma severity was compared with the neurological outcome, according to different ApoE genotypes. For statistical processing, t test, nonparametric Wilcoxon test, Fisher, and chi(2) tests were used.

CONCLUSION

Our results suggest the association between the ApoE genotype and outcome of traumatic brain injury in children. Patients with ApoE epsilon4 genotype were more likely to have severe clinical symptomatology and unfavorable neurological outcome after traumatic brain injury compared to significantly better outcome with other ApoE genotype.

Apolipoprotein E modifies the CNS response to injury via a histamine-mediated pathway

Recent evidence demonstrates that apolipoprotein E (apoE) influences the central nervous system (CNS) response to both acute and chronic injury. To address the mechanisms by which apoE influences neurological disease, we examined differential gene expression in the brains of apoE transgenic mice after closed head injury. Apart from confirming the knockout of apoE, the largest differential gene expression occurred for the interleukin-9 receptor (IL-9R), which was > 100-fold up-regulated in apoE-deficient versus wild-type mice. We observed a similar pattern of posttraumatic IL-9R up-regulation in APOE4 targeted replacement mice as compared with their APOE3 counterparts. This difference in gene expression was associated with increased neuronal protein expression of IL-9R in E4 animals compared with E3 as demonstrated by immunohistochemistry. The consequence of IL-9R binding in mast cells is the induction of proliferation and differentiation. This indirectly favors degranulation and release of histamine and inflammatory mediators, which have previously been demonstrated to exacerbate secondary neuronal injury. We found that apoE-deficient animals had increased levels of systemic histamine after injury and that pre-treatment with antihistamines improved functional outcomes in apoE-deficient but not wild-type animals after head injury. These results suggest that apoE modifies secondary neuronal injury caused by histamine release and are consistent with previous observations that apoE affects the CNS inflammatory response in an isoform-specific manner.

Neurodevelopmental outcomes following congenital heart surgery

Advances in both surgical techniques and perioperative care have led to improved survival outcomes in infants and children undergoing surgery for complex congenital heart disease. An awareness is emerging that early and late neurological morbidities complicate the outcome of these operations. Adverse neurological outcomes after neonatal and infant cardiac surgery are related to both fixed and modifiable mechanisms. Fixed factors include many variables specific to the individual patient, including genetic predisposition, gender, race, socioeconomic status, and in utero central nervous system development. Modifiable factors include not only intraoperative variables (cardiopulmonary bypass, deep hypothermic circulatory arrest, and hemodilution) but also such variables as hypoxemia, hypotension, and low cardiac output. The purpose of this review is to examine these mechanisms as they relate to available outcome data.

Apolipoprotein E4 polymorphism as a genetic predisposition to delirium in critically ill patients

OBJECTIVE

To test for an association between apolipoprotein E (APOE) genotypes and duration of intensive care unit delirium.

DESIGN

Prospective, observational cohort study.

SETTING

A 541-bed, community-based teaching hospital.

PATIENTS

Fifty-three mechanically ventilated intensive care unit patients.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

All patients were managed with standardized sedation and ventilator weaning protocols as part of an ongoing clinical trial and were evaluated prospectively for delirium with the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU). DNA was extracted from whole blood samples obtained on enrollment, and APOE genotype was determined using polymerase chain reaction followed by restriction enzyme digestion by investigators blinded to the clinical information. Delirium occurred in 47 (89%) patients at some point during the intensive care unit stay. Of the 53 patients, 12 (23%) had an APOE4 allele (APOE4+) and 41 (77%) had only APOE2 or APOE3 alleles (APOE4-). APOE4+ patients were younger (53.2 +/- 21.9 vs. 65.4 +/- 13.4, p = .08) and less often admitted for pneumonia (0% vs. 29.3%, p = .05) compared with APOE4- patients, yet they had a duration of delirium that was twice as long: median (interquartile range), 4 (3, 4.5) vs. 2 (1, 4) days (p = .05). No other clinical outcomes were significantly different between the APOE4+ and APOE4- patients. Using multivariable regression analysis to adjust for age, admission diagnosis of sepsis or acute respiratory distress syndrome or pneumonia, severity of illness, and duration of coma, the presence of APOE4 allele was the strongest predictor of delirium duration (odds ratio, 7.32; 95% confidence interval, 1.82-29.51, p = .005).

CONCLUSIONS

APOE4 allele represents the first demonstrated genetic predisposition to longer duration of delirium in humans.

An apolipoprotein E-based therapeutic improves outcome and reduces Alzheimer's disease pathology following closed head injury: evidence of pharmacogenomic interaction

Apolipoprotein E (apoE) modifies glial activation and the CNS inflammatory response in an isoform-specific manner. Peptides derived from the receptor-binding region of apoE have been demonstrated to maintain the functional activity of the intact protein, and to improve histological and functional deficits after closed head injury. In the current study, APOE2, APOE3, and APOE4 targeted replacement (TR) mice expressing the human apoE protein isoforms (apoE2, apoE3 and apoE4) were used in a clinically relevant model of closed head injury to assess the interaction between the humanized apoE background and the therapeutic apoE mimetic peptide, apoE(133-149). Treatment with the apoE-mimetic peptide reduced microglial activation and early inflammatory events in all of the targeted replacement animals and was associated with histological and functional improvement in the APOE2TR and APOE3TR animals. Similarly, brain beta amyloid protein (Abeta)(1-42) levels were increased as a function of head injury in all of the targeted replacement mice, while treatment with apoE peptide suppressed Abeta(1-42) levels in the APOE2TR and APOE3TR animals. These results suggest a pharmacogenomic interaction between the therapeutic effects of the apoE mimetic peptide and the human apoE protein isoforms. Furthermore, they suggest that administration of apoE-mimetic peptides may serve as a novel therapeutic strategy for the treatment of acute and chronic neurological disease.

Association of APOE e4 and cerebrovascular pathology in traumatic brain injury

BACKGROUND

Previous studies have found the e4 allele of the apolipoprotein E gene (APOE e4) is associated with an unfavourable outcome after head injury, but this has not been related to specific pathological features.

OBJECTIVES

This study tested the postulate that head injured patients with APOE e4, amounting to approximately a third of the population, are selectively predisposed to one or more of the different pathological features that constitute the response to traumatic brain injury (TBI), and that this underlies the association of APOE e4 with poor clinical outcome.

METHODS

Included in the study were 239 fatal cases of TBI (1987-1999) for which APOE genotypes were determined from archival tissue. For each case, specific pathological features of trauma were recorded by researchers blinded to the APOE e4 status. Of the 239 cases examined, 83 (35%) were APOE e4 carriers and 156 (65%) were non-carriers.

RESULTS

Possession of APOE e4 was associated with a greater incidence of moderate or severe contusions (42% v 30% for carriers versus e4 non-carriers; p = 0.05) and there was a trend towards a greater incidence of severe ischaemic brain damage (54% v 42%; p = 0.08). Significant differences were not noted between the other pathological features examined.

CONCLUSIONS

Possession of APOE e4 is associated with a greater incidence of moderate/severe contusional injury and severe ischaemic brain damage in fatal cases of TBI. This may be relevant to the relatively poor outcome from traumatic brain injury in patients with APOE e4 identified in clinical studies.

Intrathecal administration of a novel apoE-derived therapeutic peptide improves outcome following perinatal hypoxic–ischemic injury

Perinatal hypoxic-ischemic brain injury remains a significant clinical problem for which there remains no adequate therapeutic intervention. Apolipoprotein E (apoE) is a 299 amino acid protein that has been demonstrated to modify functional recovery following acute ischemic and traumatic brain injury. The aim of the current study was to evaluate whether administration of an apoE-derived peptide could reduce CNS injury in a rodent model of perinatal hypoxia and ischemia. We found that intrathecal delivery of an apoE-mimetic peptide caused a significant reduction in post-ischemic brain necrosis, as reflected by decreased reduction in ipsilateral brain weight 7 days following hypoxic-ischemic injury. These results suggest that administration of an apoE-derived therapeutic peptide represents a novel therapeutic strategy in the clinical setting of perinatal hypoxic-ischemic injury.

A novel therapeutic derived from apolipoprotein E reduces brain inflammation and improves outcome after closed head injury

Although apolipoprotein E4 (APOE4) was initially identified as a susceptibility gene for the development of Alzheimer's disease, the presence of the APOE4 allele is also associated with poor outcome after acute brain injury. One mechanism by which apoE may influence neurological outcome is by downregulating the neuroinflammatory response. Because it does not readily cross the blood-brain barrier, the apoE holoprotein has limited therapeutic potential. We demonstrate that a single intravenous injection of a small peptide derived from the apoE receptor binding region crosses the blood-brain barrier and significantly improves histological and functional outcomes after traumatic brain injury (TBI). The development of an apoE-based intervention represents a novel therapeutic strategy in the management of acute brain injury.

There is no evidence of an association in children and teenagers between the apolipoprotein E epsilon4 allele and post-traumatic brain swelling

Traumatic brain injury (TBI) is an important cause of mortality and disability in children and teenagers. A particular feature of the neuropathology at post-mortem is brain swelling. The cause of the swelling in some cases is not known, while in others it is associated with traumatic axonal injury or hypoxia. Apolipoprotein E (APOE) epsilon4 allele is known to be an important genetic determinant of outcome in children after TBI. We hypothesized a relationship between possession of APOEepsilon4 and diffuse traumatic brain swelling. A total of 165 cases aged between 2 and 19 years were identified from the department's tissue archive. APOE genotype was determined by polymerase chain reaction (PCR) in 106 cases. Bilateral swelling was present in 44 cases (11 with APOEepsilon4), unilateral swelling in 25 cases (7 with APOEepsilon4) and in 36 cases (9 with APOEepsilon4) there was no evidence of brain swelling. There was no significant relationship between possession of APOEepsilon4 and the presence of cerebral swelling (chi(2) = 0.09, df = 2, P = 0.96). The 95% confidence interval for difference in proportions with swelling in those with and without the APOE epsilon4 is -19% to 22%. Thus, a significant relationship was not found between diffuse brain swelling and possession of APOEepsilon4, and in this cohort of patients there was an identifying cause of the brain swelling in all cases.

[Gene polymorphism in intensive care patients. Is the course of disease predetermined?]

Die enormen Fortschritte der molekularbiologischen Grundlagenforschung haben unser Verständnis der pathophysiologischen Mechanismen von Erkrankungen entscheidend vorangetrieben. Die große interindividuelle Variabilität von Krankheitsverläufen in der Intensivmedizin lässt sich häufig nicht allein durch bekannte Risikofaktoren erklären. Vielmehr scheint auch der Genotyp des einzelnen Patienten Inzidenz, Verlauf und Mortalität schwerster Krankheitsbilder zu verändern. Im Rahmen von Genassoziationsstudien wurde eine Vielzahl genetischer Polymorphismen untersucht, die in der Intensivmedizin eine Rolle spielen könnten. Beeinflusst werden neben Entzündungsreaktionen [z. B. Tumor-Nekrose-Faktor- (TNF-)α, Interleukin- (Il-)10] auch spezifische Infektionserkrankungen (Pneumonie, Meningitis), Sepsis oder „acute respiratory distress syndrome“ (ARDS) ebenso wie die Letalität schwerst traumatisierter Patienten [Polytrauma, Schädel-Hirn-Trauma (SHT)]. Die weitere Identifizierung solcher Allo- und Haplotypen kann nicht nur erklären, warum intensivmedizinische Patienten unterschiedlich auf vergleichbare Therapien ansprechen, sondern möglicherweise auch mittels verbesserter Risikostratifizierung und an den Genotyp des einzelnen Patienten angepasster Therapie zu einer Verringerung von Morbidität und Mortalität beitragen.

Alterations in cerebrospinal fluid apolipoprotein E and amyloid beta-protein after traumatic brain injury

There is evidence that apolipoprotein E (apoE) and amyloid beta-protein (Abeta), which are implicated in the pathology of chronic neurodegenerative disorders, are involved in the response of the brain to acute injury; however, human in vivo evidence is sparse. We conducted a prospective observational study to determine the magnitude and time-course of alterations in cerebrospinal fluid (CSF) apoE and Abeta concentrations after traumatic brain injury (TBI), and the relationship of these changes to severity of injury and clinical outcome. Enzyme linked immunosorbant assay (ELISA) was used to assay apoE, Abeta(1-40) and Abeta(1-42) in serial CSF samples from 13 patients with TBI and 13 controls. CSF S100B and tau were assayed as surrogate markers of brain injury. There was a significant decrease in CSF apoE (p < 0.001) and Abeta (p< 0.001) after TBI contrasting the observed elevation in CSF S100B (p < 0.001) and tau (p < 0.001) concentration. There was significant correlation (r = 0.67, p = 0.01) between injury severity and the decrease in Abeta(1-40) concentration after TBI. In vivo, changes in apoE and Abeta concentration occur after TBI and may be important in the response of the human brain to injury.

Apolipoprotein E genotype and neurodevelopmental sequelae of infant cardiac surgery

BACKGROUND

There has been increasing recognition of adverse neurodevelopmental sequelae in some children after repair of congenital heart defects. Even among children with the same cardiac defect, significant interindividual variation exists in developmental outcome. Polymorphisms of apolipoprotein E have been identified as a risk factor for worse neurologic recovery after central nervous system injury.

METHODS

A single-institution prospective study of patients <or=6 months of age undergoing cardiopulmonary bypass for repair of congenital heart defects was undertaken to evaluate the association between apolipoprotein E genotype and postoperative neurodevelopmental dysfunction. Developmental outcomes were evaluated at 1 year of age by using the Bayley Scales of Infant Development.

RESULTS

One-year evaluation was performed in 244 patients. After adjustment for preoperative and postoperative covariates-including gestational age, age at operation, sex, race, socioeconomic status, cardiac defect, and use of deep hypothermic circulatory arrest-the apolipoprotein E epsilon2 allele was associated with a worse neurologic outcome as assessed by the Psychomotor Developmental Index of the Bayley Scales of Infant Development (P =.036). Patients with the apolipoprotein E epsilon2 allele had approximately a 7-point decrease in the Psychomotor Developmental Index.

CONCLUSIONS

Apolipoprotein E epsilon2 allele carriers had significantly lower Psychomotor Development Index scores at 1 year of age after infant cardiac surgery. The effect was independent of ethnicity, socioeconomic status, cardiac defect, and use of deep hypothermic circulatory arrest. An effect of the apolipoprotein E epsilon4 allele was not detected. Genetic polymorphisms that decrease neuroresiliency and impair neuronal repair after central nervous system injury are important risk factors for neurodevelopmental dysfunction after infant cardiac surgery.

Remodeling of cerebrospinal fluid lipoprotein particles after human traumatic brain injury

The association between possession of the APOE epsilon4 allele and unfavourable outcome after traumatic brain injury (TBI) suggests that the apolipoprotein E protein (apoE) plays a key role in the response of the human brain to injury. ApoE is known to regulate cholesterol metabolism in the periphery through its action as a ligand for receptor mediated uptake of lipoprotein particles (Lps). Greater understanding of cholesterol metabolism in the human central nervous system may identify novel treatment strategies applicable to acute brain injury. We report findings from the analysis of lipoproteins in the cerebrospinal fluid (CSF) of patients with TBI and non-injured controls, testing the hypothesis that remodeling of CSF lipoproteins reflects the response of the brain to TBI. CSF Lps were isolated from the CSF of controls and patients with severe TBI by size exclusion chromatography, and the lipoprotein fractions analysed for cholesterol, phospholipid, apoAI, and apoE. There was a marked decrease in apoE containing Lps in the TBI CSF compared to controls (p=0.002). After TBI there was no significant decrease in apoAI containing CSF Lps (CSF LpAI), but the apoAI resided on smaller sized particles than in control CSF. There was a population of very small sized Lps in TBI CSF, which were associated with the increased cholesterol (p=0.0001) and phospholipid (p=0.040) seen after TBI. The dramatic loss of apoE containing Lps from the CSF, and the substantial increase in CSF cholesterol, support the concept that apoE and cholesterol metabolism are intimately linked in the context of acute brain injury. Treatment strategies targeting CNS lipid transport, required for neuronal sprouting and synaptogenesis, may be applicable to traumatic brain injury.

Protective effect of apolipoprotein E-mimetic peptides on N-methyl-D-aspartate excitotoxicity in primary rat neuronal-glial cell cultures

Apolipoprotein E (apoE) is a 34-kD protein with multiple biological properties. Recent clinical and preclinical observations implicate a role for apoE in modifying the response of the brain to focal and global ischemia. One mechanism by which apoE might exert these effects is by reducing glutamate-induced excitotoxic neuronal injury associated with ischemic insults. We demonstrate that human recombinant apoE confers a mild neuroprotective effect in primary neuronal-glial cultures exposed to 100 microM N-methyl-D-aspartate. Furthermore, a peptide derived from the receptor-binding region of apoE (residues 133-149) maintained a significant helical population as assessed by circular dichroism, and completely suppressed the neuronal cell death and calcium influx associated with N-methyl-D-aspartate exposure. Neuroprotection was greatest when the peptide was added concurrently with N-methyl-D-aspartate; however, a significant protection was observed when peptide was preincubated and washed off prior to N-methyl-D-aspartate exposure. These results suggest that one mechanism by which apoE may modify the CNS response to ischemia is by partially blocking glutamate excitotoxicity. Moreover, small peptide fragments derived from the receptor-binding region of apoE have enhanced bioactivity compared with the intact holoprotein, and may represent a novel therapeutic strategy for the treatment of brain ischemia.

Cerebrospinal fluid apolipoprotein E concentration decreases after traumatic brain injury

The APOE epsilon4 allele has been associated with unfavorable outcome after several types of acute brain injury, yet the biological mechanisms underlying this observation are poorly understood. Postmortem and experimental brain injury studies suggest the presence of increased amounts of apolipoprotein E (apoE) within the neuropil after acute brain injury. We assayed the concentration of apolipoprotein E in the cerebrospinal fluid (CSF) of non-injured controls and patients with traumatic brain injury (TBI) to determine whether differences exist, and if these differences correlate with injury severity and clinical outcome. CSF apoE and S100B, a marker of injury severity, were measured by enzyme linked immunosorbant assay. CSF was sampled from 27 traumatic brain injury patients (mean age 32, median 25, range 16-65 years) within 3 days of injury, and 28 controls (mean age 40, median 37, range 19-73 years). The TBI patients all had a Glasgow Coma Score (GCS) of less than eight (i.e., severe head injury). Clinical outcome was determined using the Glasgow Outcome Score (GOS). The average concentration of apoE in the CSF of controls was 12.4 mg/L (95% CI: 10.5-14.3 mg/L) and in TBI patients was 3.7 mg/L (95% CI: 2.1-4.1 mg/L; Mann-Whitney: p < 0.0001). In contrast, the concentration of S100B in the CSF of TBI patients was significantly higher than that of controls (Mann-Whitney: p < 0.0001). We speculate that apoE is retained within the parenchyma of the central nervous system in response to injury where in view of previous data, it may have a protective role.

Endocytic pathway alterations in human hippocampus after global ischemia and the influence of APOE genotype

Apolipoprotein epsilon4 (apoE, protein; APOE, gene) allele is the most important genetic risk factor for development of Alzheimer's disease and is also associated with poor outcome after brain injury. Although the mechanisms underlying this susceptibility are currently unknown, recent experimental evidence suggests that APOE genotype may influence activity in the endocytic pathway of neurons. This study determined whether alterations in the endocytic pathway occurred in medial temporal lobe sections after brain injury because of cardiorespiratory arrest and whether these alterations were influenced by APOE genotype. Antibodies to two proteins involved in endocytosis, rabaptin-5 and rab4, were used as markers of endocytic pathway activity. Alterations in immunoreactivity were examined in medial temporal lobe sections in the postmortem brain of patients who experienced an episode of global ischemia and in controls. After global ischemia there was a marked increase in immunoreactivity of both endocytic markers, rabaptin-5 and rab4, in neurons, and to a lesser extent in glia compared to controls. Furthermore, possession of an APOE epsilon4 allele was associated with specific alterations in the endocytic pathway. After global ischemia, there was no influence of APOE genotype on the extent of rabaptin-5 immunoreactivity. However, there was a statistically significant influence of APOE genotype on the extent of rab4 immunoreactivity in response to global ischemia. These results indicate marked alterations in the endocytic pathway after global ischemia that are dependent on APOE genotype. This may underlie the important influence of APOE genotype on brain injury and disease.

Apolipoprotein E protects against NMDA excitotoxicity

Preclinical and clinical evidence implicates a role for endogenous apolipoprotein E in modifying the response of the brain to focal and global ischemia. To investigate whether apoE modulates the neuronal response to glutamate excitotoxicity, we exposed primary neuronal glial cultures and a neuronal cell line to biologically relevant concentrations of apolipoprotein E prior to NMDA exposure. In both of these paradigms, apolipoprotein E exerted partial protective effects. At neuroprotective concentrations, however, apolipoprotein E failed to block NMDA-induced calcium influx to the same magnitude as the NMDA receptor antagonist MK-801. These results suggest that one mechanism by which apolipoprotein E modifies the central nervous system response to ischemia may be by reducing glutamate-induced excitotoxicity.

Apolipoproteins and aging: emerging mechanisms

One of the goals of modern medicine is to foster successful aging. In order to age successfully, one must accomplish two things: first, survive; and second, survive with good health and a sharp mind. In this discussion of apolipoproteins and aging, the focus will be on apolipoprotein E (apoE), a protein with three common isoforms, which has a large impact on longevity and successful aging. One variant of apoE (E4) is associated with increased risk for heart disease, stroke and Alzheimer's disease (AD). In addition, some of the potential mechanisms for the observed effects of apoE on aging will be discussed.