The effect of oxidative stress on accumulation of apolipoprotein E3 and E4 in a cell culture model of beta-amyloid angiopathy (CAA)

Apolipoprotein E (apoE) is a multifunctional molecule that is active during brain development, maintenance, and injury. Allele epsilon 4 of apoE is recognized as a risk factor for beta-amyloidosis, but the responsible mechanisms are not clear. Recently, we showed that vascular smooth muscle cells (SMCs) from epsilon 4/ epsilon 4 carriers are the most susceptible to oxidative protein damage that was associated with the appearance of apoE-Abeta-immunoreactive granules in cells. Here, we demonstrate that apoE4 is more readily accumulated in SMCs treated with ferrous ions than is apoE3. ApoE accumulated in lysosomes in the form of monomers, dimers, apoE-containing complexes, and apoE fragments. ApoE4 and apoE4-containing complexes persisted in SMCs longer than apoE3 and its complexes. Both isoforms of apoE stimulated formation of apoE-Abeta deposits and increased immobilization of iron in cultures treated with ferrous ions. The accumulation of apoE-Abeta deposits in lysosomes was associated with the appearance of lipid peroxidation products such as malondialdehyde and 4-hydroxynonenal-2-nonenal. The higher cellular accumulation of apoE4 than apoE3 in SMCs exposed to oxidative stress may facilitate development of beta-amyloid angiopathy that is more frequent in epsilon 4/ epsilon 4 carriers.     

Oxidative insults are associated with apolipoprotein E genotype in Alzheimer's disease brain

The epsilon4 allele of the apolipoprotein E gene (APOE) is associated with sporadic and familial late-onset Alzheimer's disease (AD). Oxidative stress is believed to play an important role in neuronal dysfunction and cell death in AD. We now provide evidence that in the hippocampus of AD, the level of thiobarbituric acid-reactive substances (TBARS) and the APOE genotype are linked. Within AD cases, the levels of TBARS were found to be higher among epsilon4 carriers while the apoE protein concentrations were lower. The relationship between the levels of TBARS and apoE proteins was corroborated by the results from the APOE-deficient mice, in which the levels of TBARS were higher than those in wild-type mice. Among AD cases, tissues from patients with the epsilon4 allele of APOE displayed lower activities of catalase and glutathione peroxidase and lower concentration of glutathione than tissues from patients homozygous for the epsilon3 allele of APOE. Together these data demonstrate that, in AD, the epsilon4 allele of APOE is associated with higher oxidative insults.     

APOE epsilon 3/ epsilon 4 heterozygotes have an elevated proportion of apolipoprotein E4 in cerebrospinal fluid relative to plasma,independent of Alzheimer's disease diagnosis

Inheritance of the apolipoprotein E (APOE) epsilon 4 allele is associated with an increased risk of Alzheimer's disease (AD). However, the risk of AD in APOE epsilon 3/ epsilon 4 heterozygotes is variable. We tested the hypothesis that the risk of AD in APOE epsilon 3/ epsilon 4 heterozygotes was linked to the relative levels of expression of apoE4 versus apoE3 protein. We measured the apoE4 isoform and total apoE using two specific enzyme-linked immunosorbent assay (ELISA) kits in three cohorts of plasma samples and two cohorts of cerebrospinal fluid samples from AD, mild cognitive impairment, and control subjects. The apoE4 ELISAs were specific as they did not detect apoE in APOE epsilon 3/epsilon 3 homozygotes and were comparable to the total apoE ELISAs in APOE epsilon 4/ epsilon 4 homozygotes. In APOE epsilon 3/ epsilon 4 individuals, the ratio of apoE4 to total apoE levels was 30-40% in plasma, suggesting a decreased production or an increased metabolism of apoE4 compared to apoE3. Surprisingly, the ratio in the CSF was reversed, with apoE4 accounting for 60-70% of the total apoE. The proportion of apoE4 in these cases did not vary by diagnosis, age of onset, or duration of AD. We conclude that the proportion of apoE4 in plasma is not predictive of AD risk in APOE epsilon 3/epsilon 4 individuals. However, the greater proportion of apoE4 in the cerebrospinal fluid suggests differential production or metabolism of the protein in the central nervous system (CNS), with the apoE4 isoform dominating.     

Effects of apolipoprotein E on the human immunodeficiency virus protein Tat in neuronal cultures and synaptosomes

Human immunodeficiency virus type 1 (HIV-1)-associated dementia is observed in 20-30% of patients with acquired immunodeficiency syndrome (AIDS). The epsilon4 allele of the apolipoprotein E (APOE) gene currently is thought to play a role as a risk factor for the development of HIV dementia. The HIV protein Tat is neurotoxic and binds to the same receptor as apoE, the low-density lipoprotein receptor-related protein (LRP). In this study, we investigated the role apoE plays in Tat toxicity. Synaptosomes from wild-type mice treated with Tat had increased reactive oxygen species (ROS), increased lipid and protein oxidation, and decreased mitochondrial membrane potential. Synaptosomes from APOE-knockout mice also had increased ROS, increased protein oxidation, and decreased mitochondrial membrane potential, but to a significantly lesser degree. Treatment of synaptosomes with heparinase and Tat increased Tat-induced oxidative stress, consistent with the notion of Tat requiring interaction with neuronal membranes to induce oxidative damage. Human lipidated apoE3 greatly protected neurons from Tat-induced toxicity, whereas human lipidated apoE4 showed no protection. We demonstrated that human apoE3 has antioxidant properties against Tat-induced toxicity. Taken together, the data suggest that murine apoE and human apoE4 act similarly and do not protect the cell from Tat-induced toxicity. This would allow excess Tat to remain outside the cell and interact with synaptosomal membranes, leading to oxidative stress and neurotoxicity, which could contribute to dementia associated with HIV. We show that the antioxidant properties of apoE3 greatly outweigh the competition for clearance in deterring Tat-induced oxidative stress.     

ApoE genotype in relation to AD and cholesterol: a study of 2,326 Chinese adults.

OBJECTIVE: To calculate the frequencies of apolipoprotein E (apoE) alleles in a large Chinese community sample and to compare the serum cholesterol levels of epsilon2, epsilon3, and epsilon4 carriers. BACKGROUND: In comparison with Western populations, a lower frequency of the apoE epsilon4 allele among the Chinese has been proposed as one factor for the lower prevalence of AD found in Chinese populations, but there are insufficient Chinese data on epsilon4 frequency that are based on large community samples. In addition, although Western studies have repeatedly found a lower cholesterol level in epsilon2 carriers and a higher cholesterol level in epsilon4 carriers in comparison with epsilon3 homozygotes, two Chinese studies have yielded inconsistent findings between them. METHODS: During the incidence phase of an epidemiologic survey of several neurologic disorders in a Chinese community, the authors took blood samples from 2,326 participants to determine the apoE genotypes and to measure cholesterol levels. RESULTS: The allelic frequencies of epsilon2, epsilon3, and epsilon4 were 11.8%, 76.4%, and 11.8% among 17 AD patients, and 7.8%, 84.1%, and 8.1% for the entire sample. The mean cholesterol level of the epsilon2 carriers was significantly lower, and that of the epsilon4 carriers significantly higher, than that of the epsilon3 homozygotes. CONCLUSIONS: The obtained epsilon4 rate of 8.1% is lower than most of the Western findings, and this may account in part for the lower prevalence of AD found among the Chinese. The associations between the apoE genotype and serum cholesterol level are similar between Chinese and white populations.     

Age-dependent association of apolipoprotein E genotypes with stroke subtypes in a Japanese rural population

BACKGROUND AND PURPOSE: The association between apolipoprotein E (apoE) polymorphisms and stroke has been controversial. These controversies may be due to inaccurate classification of stroke and differences in age ranges. We investigated the association between apoE genotypes and stroke subtypes (confirmed by CT or MRI findings) by case-control study in a Japanese rural population. METHODS: First-ever-stroke patients (n=322; cerebral infarction, n=201, intracerebral hemorrhage, n=84, and subarachnoid hemorrhage, n=37) aged 40 to 89 years were recruited from Hokuetsu Hospital, Japan. Healthy controls (n=1126) were selected from the general population in the same area. ApoE genotypes were determined by restriction fragment-length polymorphism analysis. RESULTS: Compared with apoE epsilon3/epsilon3 subjects, epsilon2 carriers had a 2-fold risk of cerebral infarction (OR 1.9, 95% CI 1.1 to 3.2). Among cerebral infarction patients, epsilon2 carriers had increased risks of cortical infarction (OR 2.4, 95% CI 1.3 to 4.6) (an anatomic subtype) and atherothrombosis (OR 3.9, 95% CI 1.7 to 9.0) and cardioembolism (OR 4.9, 95% CI 1.6 to 14.4) but not lacunar infarction (clinical subtypes). ApoE epsilon4 carriers had a 2. 5-fold risk of subarachnoid hemorrhage (OR 2.5, 95% CI 1.1 to 5.4). ApoE epsilon2/epsilon2 subjects had an increased risk of intracerebral hemorrhage (OR 4.4, 95% CI 1.0 to 19.7). ApoE epsilon3/epsilon4 subjects showed approximately 2-fold increased risk of atherothrombosis (OR 2.1, 95% CI 1.0 to 4.1) and intracerebral hemorrhage (OR 1.8, 95% CI 1.0 to 3.3). The association between epsilon2 and stroke was accentuated in subjects aged 70 years or older but not in those aged 40 to 69 years. CONCLUSIONS: Our study suggests that apoE epsilon2 is a risk factor for atherothrombosis, cardioembolism, and intracerebral hemorrhage, whereas epsilon4 is a risk factor for atherothrombosis, intracerebral hemorrhage, and subarachnoid hemorrhage. The occurrence of stroke may be affected by interaction between age and apoE gene polymorphisms.     

ApoE isoform affects LTP in human targeted replacement mice

Inheritance of the epsilon4 allele for apolipoprotein E (apoE) increases the risk of Alzheimer disease and memory impairment, whereas epsilon2 decreases these risks compared with the most common epsilon3 allele, but the mechanism for these effects is unknown. Long-term potentiation (LTP) is an experimentally induced increase in synaptic efficacy that models memory. Using hippocampal slices from wild type (WT), apoE knockout (apoE-KO), and targeted replacement mice expressing human apoE2, E3, or E4 (apoE-TR) we found that although all strains had comparable basal synaptic transmission, LTP was significantly greater in WT and apoE3-TR than in apoE-KO, apoE2-TR or apoE4-TR. This novel system may be used to investigate the mechanisms of apoE isoform dependent modulation of susceptibility to memory impairment.     

In situ detection of apolipoprotein E epsilon 4 in archival human brain

A monoclonal antibody specific to apolipoprotein E 4 (apoE4) was applied immunohistochemically to archival human brain tissue. The examined 30 cases comprised four epsilon/epsilon4, 10 epsilon3/epsilon4, one epsilon2/epsilon4, 10 epsilon3/epsilon3 and five epsilon2/epsilon3 genotypes. The anti apoE4 antibody visualized senile plaques, neurofibrillary tangles and reactive astrocytes, as well as serum in the blood vessels and vascular smooth muscle cells in the cases of epsilon4. Moreover, the staining intensity was stronger in the cases carrying the epsilon4 homozygosity than in those cases of epsilon4 heterozygosity. Specific immunoreactivity was not obtained in those cases not carrying the epsilon4 allele. This method will allow in situ detection of apoE epsilon4 and contribute to studies of the effect of epsilon4 on Alzheimer's disease.     

Involvement of apolipoprotein E in multiple sclerosis: absence of remyelination associated with possession of the APOE epsilon2 allele

Lipids are a major constituent of myelin and apolipoprotein E (apoE) plays a key role in lipid transport. We therefore hypothesized that apoE is involved in the processes of demyelination and remyelination. Furthermore as there is a biologically significant polymorphism in the APOE gene, the APOE genotype may influence the course of multiple sclerosis (MS). Specifically, as there is reduced affinity of the apoE E2 isoform for receptors on glial cells, we hypothesized that remyelination is impaired in individuals with the apoE epsilon2 allele. We determined the apoE genotypes of 71 archival cases of multiple sclerosis and 41 controls, reviewed the neurohistology, and performed apoE immunohistochemistry. ApoE immunoreactivity was increased in demyelinated areas compared with control white matter. ApoE immunostaining was markedly increased in areas of active demyelination, specifically in macrophages and astrocytes. The APOE allele frequencies of the cases of MS (epsilon2 = 0.06, epsilon3 = 0.8, epsilon4 = 0.13) resembled those of controls. Evidence of remyelination was identified in 25/ 71 MS cases (35%): in 25/64 patients (39%) without an epsilon2 allele and 0/7 (0%) patients with an epsilon2 allele (p < 0.05). In conclusion, we provide evidence that apoE is involved in the trafficking of lipid in MS and, although the number of cases with this allele was small, remyelination may be defective in patients with the APOE epsilon2 allele.     

Apolipoprotein C-I Expression in the Brain in Alzheimer's Disease

The H2 allele of apolipoprotein (apo) C-I is associated with Alzheimer's disease (AD). However, this association is potentially confounded by the linkage disequilibrium of H2 with the epsilon2 and epsilon4 alleles of apoE and of H1 with the epsilon3 allele. To establish plausibility for a direct role for apoC-I in AD, we compared apoC-I and apoE protein and mRNA levels in postmortem specimens of frontal cortex and hippocampus from AD patients with levels in nondemented controls. In H2-allelic individuals (usually also epsilon4 carriers), apoC-I mRNA levels were strikingly lower with AD (by 65%, P < 0.05), but apoC-I protein levels in AD were significantly higher (by 34%, P < 0.05). The opposite direction of the apoC-I mRNA and apoC-I protein level changes in AD in the epsilon4/H2 genotype may reflect decreased clearance of CNS lipoproteins associated with apoE4. In H1/H1 (usually epsilon3/epsilon3) individuals, both apoC-I protein and mRNA were lower in AD. ApoC-I protein levels in hippocampus were nearly twice those in frontal cortex. Immunohistochemistry of hippocampus revealed colocalization of apoC-I protein with the astrocytic marker GFAP. In addition, cultured human astrocytes expressed the mRNA for apoC-I. This study confirms apoC-I expression in the CNS and identifies astrocytes as the source of apoC-I. In addition, it has revealed differences in apoC-I expression based on site, genotype, and disease status that may reflect a role for apoC-I in the pathogenesis of AD.     

Apolipoprotein E genotypes and cognitive functions in healthy elderly persons

OBJECTIVES: We investigated whether apoE genotypes correlate with cognitive functions in clinically healthy persons. METHODS: In 1993 and 1995, we measured information processing speed, delayed free recall and semantic aspects of long-term memory in 227 men and 105 women aged 65 and over, a randomly selected subsample of the prospective Basel Study. Cardiovascular risk factors and education were assessed. RESULTS: E2 were more prevalent in old-old (>75 years, 23.5% vs. 15%) compared to E4 than in young-old (<75 years, 19.3% vs. 23.5%). Taking into account age and education, subjects with epsilon3/epsilon4 or epsilon4/epsilon4 alleles (E4) performed lowest in all 3 tests compared to those homozygous for epsilon3 (E3) or carriers of one or two epsilon2 alleles (E2) (reaction time P = 0.009, free recall P = 0.05, WAIS-R vocabulary P<0.05). In old-old there was a significant difference between E2 and E4 for reaction time (P = 0.02) and free recall (P<0.02) but not for vocabulary (P = 0.086). In all 3 groups there were no significant changes after 2 years. The subgroup with the genotype epsilon2/epsilon4 performed consistently best in the cognitive tests. Cholesterol was significantly increased in the E4 and E3 group compared to the E2 group. CONCLUSION: ApoE genotype correlates with cognitive performance. The increased prevalence of E2 in the old-old and the significantly lower plasma cholesterol levels suggest differential morbidity and mortality as important factors influencing the prevalence of cognitive disorders in late life.     

Apolipoprotein E polymorphism and central nervous system tumors: correlation with cell proliferation indices and clinical outcome

AIMS: This study was designed to determine whether the polymorphism of apolipoprotein E (apoE), one of the key regulatory proteins in cholesterol metabolism, is related to varying susceptibility to central nervous system (CNS) neoplasms, and to evaluate any possible interaction between this polymorphism and tumor cell proliferation or clinical outcome. METHODS AND RESULTS: 53 CNS tumors were selected. Follow-up and survival data were available for 36 patients. ApoE genotypes and cell proliferation indices (nucleolar organizer regions, MIB-1, PCNA, p53) were determined from paraffin-embedded tissue by standard methods. Each of the indices of cell proliferation correlated positively with tumor grade and negatively with duration of clinical follow-up and survival. There was a non-significant trend for apoE epsilon2 allele carriers to have high-grade tumors and apoE epsilon4 allele carriers to have low-grade tumors. Possession of apoE epsilon4 was associated with a more advanced age of disease presentation (p < 0.01) and a longer duration of follow-up (p < 0.04). No significant correlations were found between possession of either apoE epsilon2 or apoE epsilon4 alleles and indices of cell proliferation. CONCLUSIONS: These preliminary findings suggest that possession of apoE epsilon4 allele may correspond to a more favorable clinical course in terms of more advanced age of disease presentation, and longer duration of follow-up and survival in patients with CNS neoplasms.     

Apolipoprotein E polymorphism in German patients with frontotemporal degeneration

OBJECTIVES: The apolipoprotein E (apoE) polymorphism, designated as epsilon2, epsilon3, epsilon4, is a genetic risk factor associated with several forms of dementia. Inconclusive results have been reported in patients with frontotemporal degeneration which prompted this study of the apoE polymorphism in a German sample with frontotemporal degeneration. METHODS: the frequencies of the epsilon2 and epsilon4 alleles and the effect of these alleles on the age at onset in 52 patients with frontotemporal degeneration who underwent a thorough diagnostic examination and in 182 cognitively healthy age matched controls were assessed. Genotype comparisons between the groups were performed using multiple logistic regression analysis. Ages at onset according to the apoE genotype were compared by linear regression analysis. RESULTS: In patients with frontotemporal degeneration apoE epsilon2 and epsilon4 allele frequencies were 9.6% each, whereas the corresponding frequencies in controls were 9.6% and 9.9%, respectively. There was no significant difference in either epsilon2 or epsilon4 allele frequency between the groups. Age at onset was highest in patients with the epsilon2/epsilon3 genotype (61.3 years) followed by patients with the epsilon3/epsilon3 (58.3 years) and was lowest in patients with the epsilon3/epsilon4 genotype (56.4 years) but the differences failed to reach statistical significance. CONCLUSION: Allelic variants of the apoE gene do not modulate occurrence or age at onset in this sample of German patients with frontotemporal degeneration.     

Apolipoprotein E and beta-amyloid levels in the hippocampus and frontal cortex of Alzheimer's disease subjects are disease-related and apolipoprotein E genotype dependent.

The epsilon4 allele of apolipoprotein E (apoE) is associated with increased risk for the development of Alzheimer's disease (AD), possibly due to interactions with the beta-amyloid (Abeta) protein. The mechanism by which these two proteins are linked to AD is still unclear. To further assess their potential relationship with the disease, we have determined levels of apoE and Abeta isoforms from three brain regions of neuropathologically confirmed AD and non-AD tissue. In two brain regions affected by AD neuropathology, the hippocampus and frontal cortex, apoE levels were found to be decreased while Abeta(1-40) levels were increased. Levels of apoE were unchanged in AD cerebellum. Furthermore, levels of apoE and Abeta(1-40) were found to be apoE genotype dependent, with lowest levels of apoE and highest levels of Abeta(1-40) occurring in epsilon4 allele carriers. These results suggest that reduction in apoE levels may give rise to increased deposition of amyloid peptides in AD brain.     

Herpes simplex encephalitis: involvement of apolipoprotein E genotype

It was previously found that herpes simplex type 1 virus (HSV1) when present in the brain, is a risk factor for Alzheimer's disease in carriers of the type 4 allele of the gene for apolipoprotein E (apoE epsilon4), and apoE epsilon4 is a risk factor for herpes labialis. Whether a specific allele of the gene is involved in susceptibility to another disorder caused by HSV1-herpes simplex encephalitis (HSE)-has now been investigated. DNA was prepared from formalin-fixed, paraffin-embedded blocks of specimens from the brain or spleen of 14 United Kingdom patients with HSE, confirmed by necropsy, and from the CSF of seven United Kingdom clinical patients with HSV1 in their CSF detected by polymerase chain reaction (PCR). ApoE genotype of the DNA from blocks was determined by seminested PCR, and of the DNA from CSF by one step PCR, followed by restriction endonuclease digestion. The apoE allele frequencies were compared with values previously obtained for 238 normal people from the United Kingdom. The apoE epsilon2 allele frequency of the patients with HSE was 26%, significantly higher than the value of 7% for the normal subjects (OR=4.6, 95% confidence interval (95% CI) 2. 0-10.8). The apoE epsilon3 and epsilon4 allele frequencies did not differ significantly between the two groups. Thus, it seems that apoE epsilon2 is a risk factor for HSE.     

Longitudinal analysis of the effect of apolipoprotein E epsilon4 and education on cognitive performance in elderly subjects: the PAQUID study

BACKGROUND: The apolipoprotein E (apoE) epsilon4 allele has been shown to be a risk factor for dementia, but it is not clear to what extent apoE affects overall cognitive function in non-demented elderly subjects, or how this risk may be modified by gene-environment interactions. OBJECTIVE: To examine changes in cognitive function in elderly people as a function of the apoE epsilon4 phenotype. METHODS: A community based prospective cohort study of 600 non-demented subjects aged over 65 years living in Gironde (France) was analysed to evaluate change over time (seven years) in scores on the mini-mental state examination (MMSE). RESULTS: Age at cohort inception was negatively associated with cognitive performance for both epsilon4 carriers and non-carriers (p < 0.001). The evolution of MMSE scores differed as a function of age: scores remained stable among younger subjects but decreased over time in older subjects. The epsilon4 allele was shown to be significantly associated with lower cognitive performance at baseline (p = 0.02). The course of cognitive performance during the follow up was the same for both epsilon4 carriers and non-carriers. Lower educational level was associated with lower cognitive performance at baseline (p < 0.001) and the effect of an epsilon4 allele on cognitive performance disappeared after adjustment for education. When incident cases of dementia were excluded, the results were unchanged except for the course of the MMSE scores, which now remained stable over time in the older subjects. CONCLUSIONS: apoE epsilon4 carriers show decreased MMSE scores compared with epsilon4 non-carriers, but the effect of apoE on cognition disappears after adjustment for education. Non-demented elderly people maintain a stable cognitive performance regardless of their apoE phenotype.     

Pro-inflammatory cytokines modulate glial apolipoprotein E secretion

Alzheimer's disease (AD) is a neurological disorder characterized by plaques and an elevated immune response. Specifically, increased expression of interleukin (IL)-1 and tumour necrosis factor (TNF)-alpha, has been observed in AD cerebrospinal fluid and temporal brain tissue. Both of these immunomodulators were shown to carry genetic variants that increase the risk of developing AD. Studies have also established the apolipoprotein E (apoE) gene to be a risk factor for AD with epsilon4 carriers having been found to show lower levels of brain apoE. In the present study, treatment of primary rat mixed glial cell cultures with IL-1beta induced a significant increase in extracellular apoE protein. In contrast, treatment primary rat astrocyte and mixed glial cell cultures with TNF-alpha significantly reduced extracellular apoE protein levels. These results are consistent with the notion that elevated cytokine expression directly modulates immunosuppression and indirectly apoE-mediated neuronal remodeling.     

The apolipoprotein E epsilon 2 allele and decline in episodic memory

OBJECTIVES: The apolipoprotein E (apoE) epsilon 4 allele is related to decline in multiple cognitive domains, especially episodic memory, but the effect of the epsilon 2 allele on change in different forms of cognitive function has been difficult to establish. METHODS: Participants are from the Religious Orders Study. At baseline, they were at least 65 years old and free of clinical evidence of dementia. For up to eight years, they underwent annual clinical evaluations that included detailed cognitive function assessment from which previously established summary measures of episodic memory, semantic memory, working memory, perceptual speed, and visuospatial ability were derived. Growth curve models were used to assess change in each measure and its relation to apoE genotype, controlling for age, sex, education, and baseline level of cognition. Follow up data were available in 669 persons (98% of those eligible). We treated those with the epsilon 3/3 genotype as the reference group (n=425), which was contrasted with epsilon 2 ( epsilon 2/2, epsilon 2/3; n=86), and epsilon 4 ( epsilon 3/4, epsilon 4/4; n=158) subgroups. RESULTS: Rate of episodic memory change in the three subgroups significantly differed, with an average annual increase of 0.016 units in the epsilon 2 subgroup and annual decreases of 0.022 units in those with epsilon 3/3 and of 0.073 units in the epsilon 4 subgroup. The epsilon 2 subgroup did not differ from those with epsilon 3/3 in rate of decline in other cognitive systems. The epsilon 4 subgroup declined more rapidly than those with epsilon 3/3 in semantic memory and perceptual speed but not in working memory or visuospatial ability. CONCLUSION: Possession of one or more apoE epsilon 2 alleles is associated with reduced decline in episodic memory in older persons.     

Oxidized proteins in astrocytes generated in a hyperbaric atmosphere induce neuronal apoptosis

In the present study, we investigated the influence of the oxidative damage to astrocytes on neuronal cell survival using cultures of rat cerebral astrocytes and neurons. The exposure of astrocytes to hyperbaric oxygen induced a time-dependent apoptotic cell death, as observed by DNA ladder assessment. When astrocytes damaged by oxidative stress were cocultured with normal neurons from the cerebrum of a newborn rat, neuronal cell death was markedly induced, although normal astrocytes not subjected to hyperoxia cocultured with normal neurons showed no neuronal cell apoptosis. It was found that either the supernatant from the homogenate of astrocytes cultured in hyperbaric oxygen atmosphere or a protein mixture extracted from the supernatant induced neuronal cell death. The level of protein carbonyls, an index of protein oxidation analysis, in cultured astrocytes increased significantly with oxidative stress, and vitamin E inhibited the increase in the level of such oxidized proteins in astrocytes. Furthermore, a two-dimensional (2D) electrophoresis of a protein mixture extracted from the supernatant showed several changes in proteins. These results imply that reactive oxygen species (ROS) induced by oxidative stress attack astrocytes to induce oxidatively denatured proteins in the cells that act as a neurotoxic factor, and that vitamin E protects neurons by inhibiting astrocyte apoptosis caused by oxidative stress.     

Phosphorylation state of tau in the hippocampus of apolipoprotein E4 and E3 knock-in mice

The apolipoprotein E (apoE) epsilon 4 allele is associated with an increased risk of sporadic as well as late-onset familial Alzheimer's disease (AD). To accurately determine the isoform-specific effects of human apoE on AD-like phosphorylation of tau, hippocampi from human apoE knock-in (KI) mice were studied by quantitative immunoblotting. There was no significant difference in phosphorylation levels of tau at nine of the 13 epitopes, for six of eight tau kinases, or in protein levels of three tau phosphatases, between apoE3-KI and apoE4-KI mouse hippocampi. However, in apoE4-KI mice, phosphorylation of tau at Ser235 was increased to approximately 150%, that at Ser413 to approximately 140%, while that at Ser202/Thr205 and Thr205 were decreased to approximately 70%, and the protein level of tau protein kinase I/glycogen synthase kinase 3beta (TPKI/GSK3beta) was increased to approximately 120%, that of extracellular signal-regulated kinase 2 (ERK2) was increased to approximately 130%, compared with apoE3-KI mice.