Apolipoprotein E alters metabolism of AbetaPP in cells engaged in beta-amyloidosis

Canine smooth muscle cells (SMCs), cultured from amyloid-affected brain blood vessels accumulate Alzheimer amyloid-beta peptide (Abeta) intracellularly, either spontaneously or after treatment with apolipoprotein E (apoE). ApoE is codeposited with Abeta, which suggests that apoE participates in Abeta accumulation. We tested the hypothesis that apoE-induced accumulation of Abeta in SMCs is caused by an increased production of amyloid-beta precursor protein (AbetaPP) and/or its altered metabolism. We found that 24 hours of treatment with apoE3 or apoE4 induced intracellular accumulation of Abeta-immunoreactive deposits in SMCs but did not influence AbetaPP production and processing. The treatment with apoE3 or E4 for 3 days resulted in the following: increased Abeta-accumulation; reduced levels of secreted Abeta; increased production and cellular retention of mature AbetaPP770; and reduced culture growth, cell proliferation, and viability. ApoE4, but not apoE3, increased cellular levels of mRNA AbetaPP 770 (the main form produced in SMCs) about ninefold. ApoE3 stimulated production and cellular retention of endogenous apoE. We hypothesize that Abeta accumulation is triggered by apoE, which may bind and immobilize soluble Abeta produced in SMCs. The newly formed Abeta deposits may further accelerate Abeta accumulation by altering metabolism of AbetaPP.     

Oxidative protein damage in cells engaged in beta-amyloidosis is related to apoE genotype

The epsilon4 allele of apolipoprotein E (apoE) is a risk factor for Alzheimer's disease. The reduced antioxidant defense in epsilon4 carriers is suggested to contribute to beta-amyloidosis. We found that oxidative stress induced by treatment with Fe2+ ions raised more protein carbonyls in vascular smooth muscle cells isolated from human brains with apoE genotype epsilon4/epsilon4 than with 3epsilon/epsilon3 and epsilon3/epsilon4. Antioxidant vitamin E prevented formation of carbonyls but not in cells with genotype epsilon4/epsilon4. Treatment with Fe2+ ions induced cellular accumulation of amyloid-beta protein (Abeta)-immunoreactive material that co-localized with heme oxygenase, a marker of oxidative stress, and apoE. We hypothesize that the damage caused by oxidation in epsilon4/epsilon4 carriers facilitates development of beta-amyloidosis.     

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.     

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.     

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.     

A deficit in astroglial organization causes the impaired reactive sprouting in human apolipoprotein E4 targeted replacement mice

The epsilon4 allele of apolipoprotein (apo)E associates with an increased risk of developing Alzheimer's disease (AD) as well as an earlier age of onset. However, the exact mechanisms by which apoE4 confers such susceptibility is currently unknown. We used a human apoE targeted replacement (hE-TR) mouse model to investigate the allele-specific response to entorhinal cortex lesion (ECL). We observed a marked impairment in reactive sprouting in hE4 mice compared to hE3 mice. ApoE expression was similar between genotypes at days post-lesion (DPL) 2 and 14. Thirty days post-lesion, hE4 mice had more reactive astrocytes as well as a defective outward migration pattern of the astrocytes in the dentate gyrus. The expression of the anti-inflammatory cytokine IL-1ra was delayed in hE4 mice compared to hE3 mice. ApoE and beta-amyloid (Abeta) 1-40 accumulated at 30 DPL in hE4 mice. These results suggest that the presence of apoE4 delays the astroglial repair process and indirectly compromises synaptic remodeling.     

Association between apolipoprotein E epsilon4 allele and apathy in probable Alzheimer's disease

OBJECTIVE: There have been inconclusive results to date on the association between the Apolipoprotein E (ApoE) genotype and neuropsychiatric symptoms (NPS) in Alzheimer's disease (AD). We investigated whether ApoE epsilon4 allele is associated with NPS in probable AD. METHOD: Data for 197 subjects with probable AD were analysed. The Neuropsychiatric Inventory was used to evaluate the frequency and severity of NPS. Multiple logistic regression models were used to test the association between ApoE genotype and NPS in AD. RESULTS: The ApoE epsilon3/3 genotype was present in 52.3%, epsilon3/4 in 44.1%, and epsilon4/4 in 3.6% of patients. ApoE epsilon4 carriers showed a higher frequency of apathy than non-carriers. After multiple adjustments, the ApoE epsilon4 allele was significantly associated with apathy. CONCLUSION: Our results suggest a relationship between the ApoE epsilon4 allele and apathy in patients with AD.     

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.     

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.     

Effect of the apolipoprotein E epsilon4 allele on the efficacy and tolerability of galantamine in the treatment of Alzheimer's disease

OBJECTIVE: To investigate the effect of the apolipoprotein E (ApoE) epsilon4 allele on the efficacy and tolerability of galantamine treatment. METHODS: A total of 202 patients with mild to moderate Alzheimer's disease participated in a 16-week, prospective, multi-center, randomized, double-blind galantamine trial in a Korean population. Patients were assessed at baseline and after 4, 8 and 16 weeks of randomized treatment using the 11-item cognitive subscale of the Alzheimer's Disease Assessment Scale (ADAS-cog/11), the Clinician's Interview-Based Impression of Change plus Caregiver Input (CIBIC-plus), the Disability Assessment for Dementia Scale (DAD), the Behavioural Pathology in Alzheimer's Disease Rating Scale (BEHAVE-AD) and adverse events. ApoE genotypes were determined for all subjects. RESULTS: Of the 202 subjects, 115 carried at least one ApoE epsilon4 allele and 87 did not. In both ApoE epsilon4 carriers and ApoE epsilon4 noncarriers, significant improvements were detected relative to baseline on ADAS-cog/11, CIBIC-plus, DAD and BEHAVE-AD. ApoE epsilon4 noncarriers showed better improvement in mean total BEHAVE-AD score and mean psychosis (delusions and hallucinations) subscale score than ApoE epsilon4 carriers. The incidence of weight loss was significantly higher in ApoE epsilon4 carriers (n = 11; 9.6%) than in ApoE epsilon4 noncarriers (n = 1; 1.2%) during this 16-week study, even though 92% of patients who complained of weight loss completed this 16-week trial successfully. CONCLUSION: ApoE epsilon4 genotype does not affect galantamine-related improvements in cognition, global rating, function and behavior. Longer prospective studies with larger patient populations are required to confirm these new findings.     

The apolipoprotein E epsilon4 allele and the response to tacrine therapy in Alzheimer's disease.

The objective of our study was to evaluate the effects of the apolipoprotein E (ApoE) phenotype and gender on the response to tacrine treatment in Alzheimer's disease (AD). ApoE phenotyping was performed on 76 patients treated with tacrine for AD. This group comprised 33 ApoE epsilon4 allele carriers (epsilon4+) and 43 non-epsilon4 carriers (epsilon4-). Patients were treated blindly in relation to the ApoE phenotype, with incremental tacrine dosages ranging from 40 mg/day up to the highest dosage (160 mg) tolerated without side-effects. At least 6 weeks elapsed between each increase. Changes in the scores for the Alzheimer Disease Assessment Scale-Cognitive Component (ADAS-Cog) between baseline and each increment in dosage were assessed in the epsilon4- and epsilon4+ groups. The cut-off point for being considered as responsive to tacrine treatment was a 4-point decrease in the ADAS-Cog score. There was no tendency for the epsilon4- carriers to respond better than the epsilon4+ carriers. When patients were stratified by gender, no differences were found between the effects of the treatment on men and women. Consequently, these results do not support the hypothesis that the ApoE phenotype and gender are predictors of the response to tacrine in AD patients.     

Apolipoprotein E epsilon3 allele is not a risk factor of schizophrenia: a study of 314 Japanese patients

The association between apolipoprotein E (ApoE) alleles and schizophrenia has remained controversial. A recent report claiming that ApoE epsilon3 Taiwan Chinese carriers have an increased risk of schizophrenia prompted us to investigate the allele frequency in a large group of Japanese schizophrenic patients. Serum samples were obtained from 314 schizophrenic patients and 188 controls in Japan and examined using isoelectric focusing/immunoblotting. There were no significant differences in ApoE allele frequencies between schizophrenic patients and controls and in the odds ratios for schizophrenia among the epsilon2, epsilon3 and epsilon4 carriers. In contrast to the report from Taiwan, our findings and results of the majority of previous studies suggest no effects of ApoE alleles on the development of schizophrenia.     

Cholesterol is increased in the exofacial leaflet of synaptic plasma membranes of human apolipoprotein E4 knock-in mice

Inheritance of the apolipoprotein (apoE) epsilon4 allele is a risk factor for developing Alzheimer's disease (AD). The purpose of the present study was to determine effects of apoE-isoforms on the transbilayer distribution of cholesterol in synaptic plasma membranes (SPM) using mice expressing human apoE3 and apoE4. Total SPM cholesterol levels did not differ among the wild-type and apoE3 and apoE4 knock-in mice. However, a striking difference was observed in the transbilayer distribution of SPM cholesterol. ApoE4 knock-in mice showed an approximately 2-fold increase in exofacial leaflet cholesterol compared with apoE3 knock-in mice and wild-type mice. The results of this study suggest that pathogenic effects of apoE4 on AD development could be closely linked to alteration of cholesterol distribution in SPM.     

Apolipoprotein E: non-cognitive symptoms and cognitive decline in late onset Alzheimer's disease.

OBJECTIVES: To determine the association between the epsilon2 and epsilon4 alleles of apolipoprotein E (ApoE) and independent measures of cognitive decline and non-cognitive symptomatology in late onset Alzheimer's disease. METHODS: The frequency of the epsilon2 and epsilon4 alleles of ApoE and their association with measures of cognitive decline and non-cognitive symptomatology were assessed in a population based case register study of 164 patients with late onset Alzheimer's disease from the east Lambeth and south Southwark districts of south London. RESULTS: Analysis of a wide range of non-cognitive symptoms against ApoE epsilon4 genotype showed no significant association but a positive relation was found between ApoE epsilon2 genotype and depressive symptomatology (P = 0.004). No relation was found between measurements of cognitive decline and the presence of the ApoE epsilon4 allele. A trend for decreasing age at onset of 3 to 4 years in carriers of the ApoE epsilon4 allele was found, confirming earlier studies. CONCLUSION: Presence of the epsilon4 allele of ApoE is associated with an earlier age at onset but does not seem to be related to either a more severe psychopathology or a more rapid progression of the illness. The epsilon2 allele of ApoE is associated with depressive symptomatology in late onset Alzheimer's disease.     

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.     

Influence of apolipoprotein E epsilon4 genotype on brain tissue integrity in relapsing-remitting multiple sclerosis

BACKGROUND: Recent clinical and imaging studies have raised the hypothesis that patients with multiple sclerosis (MS) and the apolipoprotein E (ApoE) epsilon4 allele may have a more severe disease course than those without the ApoE epsilon4 allele. This seems to be related to more extensive tissue destruction and less efficient neuronal maintenance and repair in ApoE epsilon4 carriers. OBJECTIVE: To evaluate the influence of different ApoE genotypes on brain tissue integrity in patients with relapsing-remitting MS (RRMS). DESIGN: We determined the ApoE genotype in 76 RRMS patients. Conventional T1-, T2-, and proton density-weighted magnetic resonance (MR) images were obtained for each patient and in a group of demographically matched healthy control subjects. On conventional T1-weighted MR images, an automated analysis tool was used to obtain total brain volumes normalized for head size (NBVs). Total brain lesion load was estimated on proton density- and T2-weighted MR images. RESULTS: From the whole group of RRMS patients, we identified 18 with and 58 without the epsilon4 allele. Both patient groups were not significantly different in age, age of disease onset, clinical disability, and disease duration. Carriers of the epsilon4 allele showed significantly (P =.01) lower NBVs than controls and non-epsilon4 allele carriers. When a similar analysis was performed on only those patients with both very short disease duration and absence of clinical disability, NBV values were still significantly lower in RRMS patients with the epsilon4 allele than in those without it (P =.02) and in controls (P =.007). In contrast, RRMS patients with different ApoE genotypes did not show significant differences in values of total brain T2-weighted lesion volumes. CONCLUSIONS: The presence of significant NBV decreases only in the group of RRMS patients with the ApoE epsilon4 genotype provides new evidence that links ApoE epsilon4-related impaired mechanisms of cell repair and severe tissue destruction in MS. Results of the present study suggest that this negative influence of the ApoE epsilon4 genotype might be active from the earliest disease stages.     

Apolipoprotein E polymorphism in ischemic cerebrovascular diseases and vascular dementia patients in Taiwan

This study aims to clarify the association between apolipoprotein E gene (ApoE) polymorphism, ischemic cerebrovascular diseases (ICVD) and vascular dementia (VaD) in Taiwan Chinese. 277 patients with ICVD, 49 patients with probable VaD and 112 controls were recruited for this study. Distributions of ApoE epsilon4 carriers and allele frequencies were 28.5 and 14.5% for patients with ICVD, 20.4 and 10.2% for patients with VaD, whereas these values were 22.9 and 11.6% for controls. Distributions of ApoE epsilon2 carriers and allele frequencies were 10.1 and 5.2% for ICVD patients, 6.1 and 3.1% for VaD patients, but 12.5 and 8.0% for controls. There were no differences between ICVD patients and controls, or VaD patients and controls in their epsilon4 carriers. Those patients aged 65 and under, carrying the epsilon2 allele, had a lower risk of developing ICVD and VaD than did their counterparts. These findings suggest that ApoE epsilon4 plays no significant role in the development of ICVD and VaD, but that ApoE epsilon2 has a protective effect with regard to the development of ICVD and VaD for Taiwan Chinese below the age of 65.     

Apolipoprotein E polymorphism and acute ischemic stroke: a diffusion- and perfusion-weighted magnetic resonance imaging study.

Diffusion- and perfusion-weighted magnetic resonance imaging (MRI) was used to study the putative effects of apolipoprotein E (ApoE) polymorphism in stroke. Thirty-one patients with acute stroke, comparative for age and gender were scanned, nine of whom were ApoE allele epsilon 4 carriers. Initially, less than 24 hours from the onset of stroke, the epsilon 4 carriers had significantly smaller volumes of hypoperfusion on relative cerebral blood volume map (P = 0.001), and smaller infarct volumes (P = 0.008) compared with the noncarriers. By day 8, this difference in the infarct volumes had disappeared, suggesting relatively enhanced infarct growth. On average, the total infarct volume increased 145% of the initial infarct volume in the epsilon 4 carriers, and 84% in the noncarriers. There were strong correlations between the imaging findings and clinical status initially and with the outcome 3 months after the stroke in the epsilon 4 noncarriers, but, with a single exception at acute phase, a lack thereof in the epsilon 4 carriers. These patterns were virtually similar in a subgroup of patients with middle cerebral artery stroke. These data support the hypothesis of increased general vulnerability of the brain in the epsilon 4 carriers. Thus, the effects of ApoE polymorphism should be accounted for when interpreting diffusion- and perfusion-weighted MRI studies, particularly if predicting lesion growth.