Current Advances on Different Kinases Involved in Tau Phosphorylation, and Implications in Alzheimers Disease and Tauopathies

Hyperphosphorylation and accumulation of tau in neurons (and glial cells) is one the main pathologic hallmarks in Alzheimer's disease (AD) and other tauopathies, including Pick's disease (PiD), progressive supranuclear palsy, corticobasal degeneration, argyrophilic grain disease and familial frontotemporal dementia and parkinsonism linked to chromosome 17 due to mutations in the tau gene (FTDP-17-tau). Hyperphosphorylation of tau is regulated by several kinases that phosphorylate specific sites of tau in vitro. GSK-3-immunoprecipitated sarcosyl-insoluble fractions in AD have the capacity to phosphorylate recombinant tau. In addition, GSK-3 phosphorylated at Ser9, that inactivates GSK-3, is found in the majority of neurons with neurofibrillary tangles and dystrophic neurites of senile plaques in AD, and in Pick bodies and other phospho-tau-containing neurons and glial cells in other tauopathies. Increased expression of active kinases, including stress-activated kinase, c-Jun N-terminal kinase (SAPK/JNK) and kinase p38 has been found in brain homogenates in all the tauopathies. Strong active SAPK/JNK and p38 immunoreactivity has been observed restricted to neurons and glial cells containing hyperphosphorylated tau, as well as in dystrophic neurites of senile plaques in AD. Moreover, SAPK/JNK- and p38-immunoprecipitated sub-cellular fractions enriched in abnormal hyperphosphorylated tau have the capacity to phosphorylate recombinant tau and c-Jun and ATF-2 which are specific substrates of SAPK/JNK and p38 in AD and PiD. Interestingly, increased expression of phosphorylated (active) SAPK/JNK and p38 and hyperphosphorylated tau containing neurites have been observed around betaA4 amyloid deposits in the brain of transgenic mice (Tg 2576) carrying the double APP Swedish mutation. These findings suggest that betaA4 amyloid has the capacity to trigger the activation of stress kinases which, in turn, phosphorylate tau in neurites surrounding amyloid deposits. Complementary findings have been reported from the autopsy of two AD patients who participated in an amyloid-beta immunization trial and died during the course of immunization-induced encephalitis. The neuropathological examination of the brain showed massive focal reduction of amyloid plaques but not of neurofibrillary degeneration. Activation of SAPK/JNK and p38 were reduced together with decreased tau hyperphosphorylation of aberrant neurites in association with decreased amyloid plaques in both Tg2576 mice and human brains. These findings support the amyloid cascade hypothesis of tau phosphorylation mediated by stress kinases in dystrophic neurites of senile plaques but not that of neurofibrillary tangles and neuropil threads in AD.

Serum insulin-like growth factor I regulates brain amyloid-beta levels

Levels of insulin-like growth factor I (IGF-I), a neuroprotective hormone, decrease in serum during aging, whereas amyloid-beta (Abeta), which is involved in the pathogenesis of Alzheimer disease, accumulates in the brain. High brain Abeta levels are found at an early age in mutant mice with low circulating IGF-I, and Abeta burden can be reduced in aging rats by increasing serum IGF-I. This opposing relationship between serum IGF-I and brain Abeta levels reflects the ability of IGF-I to induce clearance of brain Abeta, probably by enhancing transport of Abeta carrier proteins such as albumin and transthyretin into the brain. This effect is antagonized by tumor necrosis factor-alpha, a pro-inflammatory cytokine putatively involved in dementia and aging. Because IGF-I treatment of mice overexpressing mutant amyloid markedly reduces their brain Abeta burden, we consider that circulating IGF-I is a physiological regulator of brain amyloid levels with therapeutic potential.

Serum insulin-like growth factor I regulates brain amyloid-beta levels

Levels of insulin-like growth factor I (IGF-I), a neuroprotective hormone, decrease in serum during aging, whereas amyloid-beta (Abeta), which is involved in the pathogenesis of Alzheimer disease, accumulates in the brain. High brain Abeta levels are found at an early age in mutant mice with low circulating IGF-I, and Abeta burden can be reduced in aging rats by increasing serum IGF-I. This opposing relationship between serum IGF-I and brain Abeta levels reflects the ability of IGF-I to induce clearance of brain Abeta, probably by enhancing transport of Abeta carrier proteins such as albumin and transthyretin into the brain. This effect is antagonized by tumor necrosis factor-alpha, a pro-inflammatory cytokine putatively involved in dementia and aging. Because IGF-I treatment of mice overexpressing mutant amyloid markedly reduces their brain Abeta burden, we consider that circulating IGF-I is a physiological regulator of brain amyloid levels with therapeutic potential.

MRI measures of entorhinal cortex vs hippocampus in preclinical AD

BACKGROUND

MRI measures of the entorhinal cortex and the hippocampus have been used to predict which nondemented individuals with memory problems will progress to meet criteria for AD on follow-up, but their relative accuracy remains controversial.

OBJECTIVES

To compare MRI measures of the entorhinal cortex and the hippocampus for predicting who will develop AD.

METHODS

MRI volumes of the entorhinal cortex and the hippocampus were obtained in 137 individuals comprising four groups: 1) individuals with normal cognition both at baseline and after 3 years of follow-up (n = 28), 2) subjects with memory difficulty but not dementia both at baseline and after 3 years of follow-up (n = 73), 3) subjects with memory difficulty at baseline who were diagnosed with probable AD within 3 years of follow-up (n = 21), and 4) patients with mild AD at baseline (n = 16).

RESULTS

Measures of both the entorhinal cortex and the hippocampus were different for each of the pairwise comparisons between the groups (p < 0.001) and were correlated with tests of memory (p < 0.01). However, the volume of the entorhinal cortex differentiated the subjects from those destined to develop dementia with considerable accuracy (84%), whereas the measure of the hippocampus did not.

CONCLUSION

These findings are consistent with neuropathologic data showing substantial involvement of the entorhinal cortex in the preclinical phase of AD and suggest that, as the disease spreads, atrophic change develops within the hippocampus, which is measurable on MRI.

The human DIMINUTO/DWARF1 homolog seladin-1 confers resistance to Alzheimer's disease-associated neurodegeneration and oxidative stress

In Alzheimer's disease (AD) brains, selected populations of neurons degenerate heavily, whereas others are frequently spared from degeneration. To address the cellular basis for this selective vulnerability of neurons in distinct brain regions, we compared gene expression between the severely affected inferior temporal lobes and the mostly unaffected fronto-parietal cortices by using an mRNA differential display. We identified seladin-1, a novel gene, which was downregulated in large pyramidal neurons in vulnerable regions in AD but not control brains. Seladin-1 is a human homolog of the DIMINUTO/DWARF1 gene described in plants and Caenorhabditis elegans. Its sequence shares similarities with flavin-adenin-dinucleotide (FAD)-dependent oxidoreductases. In human control brain, seladin-1 was highly expressed in almost all neurons. In PC12 cell clones that were selected for resistance against AD-associated amyloid-beta peptide (Abeta)-induced toxicity, both mRNA and protein levels of seladin-1 were approximately threefold higher as compared with the non-resistant wild-type cells. Functional expression of seladin-1 in human neuroglioma H4 cells resulted in the inhibition of caspase 3 activation after either Abeta-mediated toxicity or oxidative stress and protected the cells from apoptotic cell death. In apoptotic cells, however, endogenous seladin-1 was cleaved to a 40 kDa derivative in a caspase-dependent manner. These results establish that seladin-1 is an important factor for the protection of cells against Abeta toxicity and oxidative stress, and they suggest that seladin-1 may be involved in the regulation of cell survival and death. Decreased expression of seladin-1 in specific neurons may be a cause for selective vulnerability in AD.

Endocytic pathway abnormalities precede amyloid beta deposition in sporadic Alzheimer's disease and Down syndrome: differential effects of APOE genotype and presenilin mutations

Endocytosis is critical to the function and fate of molecules important to Alzheimer's disease (AD) etiology, including the beta protein precursor (betaPP), amyloid beta (Abeta) peptide, and apolipoprotein E (ApoE). Early endosomes, a major site of Abeta peptide generation, are markedly enlarged within neurons in the Alzheimer brain, suggesting altered endocytic pathway (EP) activity. Here, we show that neuronal EP activation is a specific and very early response in AD. To evaluate endocytic activation, we used markers of internalization (rab5, rabaptin 5) and recycling (rab4), and found that enlargement of rab5-positive early endosomes in the AD brain was associated with elevated levels of rab4 immunoreactive protein and translocation of rabaptin 5 to endosomes, implying that both endocytic uptake and recycling are activated. These abnormalities were evident in pyramidal neurons of the neocortex at preclinical stages of disease when Alzheimer-like neuropathology, such as Abeta deposition, was restricted to the entorhinal region. In Down syndrome, early endosomes were significantly enlarged in some pyramidal neurons as early as 28 weeks of gestation, decades before classical AD neuropathology develops. Markers of EP activity were only minimally influenced by normal aging and other neurodegenerative diseases studied. Inheritance of the epsilon4 allele of APOE, however, accentuated early endosome enlargement at preclinical stages of AD. By contrast, endosomes were normal in size at advanced stages of familial AD caused by mutations of presenilin 1 or 2, indicating that altered endocytosis is not a consequence of Abeta deposition. These results identify EP activation as the earliest known intraneuronal change to occur in sporadic AD, the most common form of AD. Given the important role of the EP in Abeta peptide generation and ApoE function, early endosomal abnormalities provide a mechanistic link between EP alterations, genetic susceptibility factors, and Abeta generation and suggest differences that may be involved in Abeta generation and beta amyloidogenesis in subtypes of AD.

Description of microcolumnar ensembles in association cortex and their disruption in Alzheimer and Lewy body dementias

The cortex of the brain is organized into clear horizontal layers, laminae, which subserve much of the connectional anatomy of the brain. We hypothesize that there is also a vertical anatomical organization that might subserve local interactions of neuronal functional units, in accord with longstanding electrophysiological observations. We develop and apply a general quantitative method, inspired by analogous methods in condensed matter physics, to examine the anatomical organization of the cortex in human brain. We find, in addition to obvious laminae, anatomical evidence for tightly packed microcolumnar ensembles containing approximately 11 neurons, with a periodicity of about 80 microm. We examine the structural integrity of this new architectural feature in two common dementing illnesses, Alzheimer disease and dementia with Lewy bodies. In Alzheimer disease, there is a dramatic, nearly complete loss of microcolumnar ensemble organization. The relative degree of loss of microcolumnar ensembles is directly proportional to the number of neurofibrillary tangles, but not related to the amount of amyloid-beta deposition. In dementia with Lewy bodies, a similar disruption of microcolumnar ensemble architecture occurs despite minimal neuronal loss. These observations show that quantitative analysis of complex cortical architecture can be applied to analyze the anatomical basis of brain disorders.

Use of structural magnetic resonance imaging to predict who will get Alzheimer's disease

We used magnetic resonance imaging (MRI) measurements to determine whether persons in the prodromal phase of Alzheimer's disease (AD) could be accurately identified before they developed clinically diagnosed dementia. Normal subjects (n = 24) and those with mild memory difficulty (n = 79) received an MRI scan at baseline and were then followed annually for 3 years to determine which individuals subsequently met clinical criteria for AD. Patients with mild AD at baseline were also evaluated (n = 16). Nineteen of the 79 subjects with mild memory difficulty "converted" to a diagnosis of probable AD after 3 years of follow-up. Baseline MRI measures of the entorhinal cortex, the banks of the superior temporal sulcus, and the anterior cingulate were most useful in discriminating the status of the subjects on follow-up examination. The accuracy of discrimination was related to the clinical similarity between groups. One hundred percent (100%) of normal subjects and patients with mild AD could be discriminated from one another based on these MRI measures. When the normals were compared with the individuals with memory impairments who ultimately developed AD (the converters), the accuracy of discrimination was 93%, based on the MRI measures at baseline (sensitivity = 0.95; specificity = 0.90). The discrimination of the normal subjects and the individuals with mild memory problems who did not progress to the point where they met clinical criteria for probable AD over the 3 years of follow-up (the "questionables") was 85% and the discrimination of the questionables and converters was 75%. The apolipoprotein E genotype did not improve the accuracy of discrimination. The specific regions selected for each of these discriminations provides information concerning the hierarchical fashion in which the pathology of AD may affect the brain during its prodromal phase.

Donepezil therapy in clinical practice: a randomized crossover study

OBJECTIVE

To determine the efficacy of donepezil hydrochloride for the treatment of Alzheimer disease in patients drawn from clinical practice.

DESIGN

Two-center, randomized, placebo-controlled, double-masked crossover study.

SETTING

Memory disorders units at Massachusetts General and Brigham and Women's hospitals, Boston.

PATIENTS

Sixty individuals (30 men and 30 women; mean +/- SD age, 75.0+/-9.5 years) with probable Alzheimer disease and scores of 20 or less on the information-memory-concentration subscale of the Blessed Dementia Scale.

INTERVENTIONS

Placebo wash-in, followed in randomized sequence by (1) donepezil hydrochloride therapy, 5 mg/d, for 6 weeks, followed by placebo washout for 6 weeks and (2) placebo treatment for 6 weeks.

PRIMARY OUTCOME MEASURE

Change in Alzheimer's Disease Assessment Scale cognitive subscale scores from the beginning to the end of the two 6-week treatment periods.

RESULTS

Among patients completing treatment and testing for both periods (n = 48), subscale scores improved (mean +/- SEM) 2.17+/-0.98 points (95% confidence interval, 0.20-4.10 points) during donepezil therapy relative to placebo therapy (P = .04). Scores returned toward baseline within 3 weeks of drug washout. There was no associated change in caregiver-rated global impression (donepezil vs placebo: proportion improved, 0.24 vs 0.22; proportion worsened, 0.27 vs 0.35; P = .34) or on specific tests of explicit memory or verbal fluency. Contrary to studies with tacrine, the presence of the apolipoprotein E epsilon4 allele did not predict donepezil treatment failure. Most common adverse events related to donepezil therapy were nausea (5 patients), diarrhea (3 patients), and agitation (3 patients). Serious events possibly related to drug use were seizure, pancreatitis, and syncope (1 patient each).

CONCLUSION

This independent confirmation of data from phase 3 trials suggests that donepezil therapy modestly improves cognition in patients with Alzheimer disease who are encountered in clinical practice.

Risperidone treatment of behavioral disturbances in outpatients with dementia

The authors retrospectively assessed the effectiveness and side effects of risperidone used to treat behavioral disturbances in elderly outpatients with dementia. In 41 patients treated with risperidone 1.8 +/- 1.4 mg/day, there was complete suppression of the target symptom in 15%, partial response in 41%, and no response in 44%. Risperidone appeared equally effective in treating agitation and psychosis. New or worsening extrapyramidal side effects (EPS) occurred in 32%, associated with longer duration of treatment and possibly with concomitant use of serotonergic anti-depressants. Risperidone was a useful adjunct in the treatment of agitation and psychosis in outpatients with dementia but was limited by EPS in about one-third of patients.

Abeta associated neuropil changes: correlation with neuronal loss and dementia

Although genetic studies clearly implicate beta-amyloid peptide (Abeta) as a pathogenic agent in Alzheimer disease (AD), it is puzzling that the total amount of Abeta immunoreactivity does not correlate closely with neuronal loss or degree of dementia. We hypothesized that Abeta deposits could vary in the extent to which they disrupt the neuropil, and that the degree to which this occurs might then correlate with the degree of dementia. We used 3 dimensional triple immunofluorescent confocal microscopy to examine the fine structural relationships between Abeta deposits and neurites in their vicinity. In non-demented elderly, Abeta deposits were porous structures with numerous normal appearing processes coursing through them. In AD, dendrites within Abeta deposits, compared with dendrites in the surrounding neuropil, were likely to have decreased SMI32 immunoreactivity and increased Alz-50 immunoreactivity. We found that the degree to which Abeta deposits disrupt the neuropil, as assessed by local loss of SMI32 immunoreactivity, correlates closely with the amount of neuronal loss and with duration of dementia. These observations support the hypothesis that a subset of Abeta deposits contribute directly to neural system failure in AD.

Genetic association of an alpha2-macroglobulin (Val1000lle) polymorphism and Alzheimer's disease

alpha2-Macroglobulin (A2M) is a proteinase inhibitor found in association with senile plaques (SP) in Alzheimer's disease (AD). A2M has been implicated biochemically in binding and degradation of the amyloid beta (Abeta) protein which accumulates in SP. We studied the relationship between Alzheimer's disease and a common A2M polymorphism, Val1000 (GTC)/Ile1000 (ATC), which occurs near the thiolester active site of the molecule. In an initial exploratory data set (90 controls and 171 Alzheimer's disease) we noted an increased frequency of the G/G genotype from 0.07 to 0.12. We therefore tested the hypothesis that the G/G genotype is over-represented in Alzheimer's disease in an additional independent data set: a group of 359 controls and 566 Alzheimer's disease patients. In the hypothesis testing cohort, the G/G genotype increased from 0.07 in controls to 0.12 in Alzheimer's disease (P < 0.05, Fisher's exact test). The odds ratio for Alzheimer's disease associated with the G/G genotype was 1.77 (1.16-2.70, P < 0.01) and in combination with APOE4 was 9.68 (95% CI 3.91-24.0, P < 0.001). The presence of the G allele was associated with an increase in Abeta burden in a small series. The A2M receptor, A2M-r/LRP, is a multifunctional receptor whose ligands include apolipoprotein E and the amyloid precursor protein. These four proteins have each been genetically linked to Alzheimer's disease, suggesting that they may participate in a common disease pathway.

Apolipoprotein E genotype and deposits of Abeta40 and Abeta42 in Alzheimer disease

OBJECTIVE

To examine the differential deposition of amyloid beta (Abeta) peptide isoforms Abeta40 and Abeta42 in the Alzheimer disease (AD) brain in relation to the apolipoprotein E (APOE) genotype.

BACKGROUND

The APOE epsilon4 genotype is an inherited risk factor for AD and is associated with increased deposition of Abeta protein in the cerebral cortex. Previous data from familial AD due to mutations in presenilin 1 and presenilin 2 genes and the amyloid precursor protein suggest that the long form of Abeta peptide, Abeta42, is selectively increased in these circumstances. Herein, we examine whether APOE genotype influenced the species of Abeta peptide deposited.

DESIGN AND METHODS

The amount of Abeta40, Abeta42, and total Abeta deposited in immunostained temporal lobe tissue of 28 cases of AD of known APOE genotype was determined.

RESULTS

Individuals with the APOE epsilon4 genotype (APOE epsilon4/4) were associated with both increased Abeta40 (P<.05) and Abeta42 (P<.05) compared with individuals without the APOE epsilon4/4 genotype.

CONCLUSION

Our results differ from the data from AD due to mutations in presenilin 1 and presenilin 2 genes and the amyloid precursor protein and suggest that the APOE epsilon4 genotype mediates increased Abeta deposition by a mechanism that differs from that found in other genetic causes of AD.

Nigral and cortical Lewy bodies and dystrophic nigral neurites in Parkinson's disease and cortical Lewy body disease contain alpha-synuclein immunoreactivity

A mutation in the alpha-synuclein gene has recently been linked to some cases of familial Parkinson's disease (PD). We characterized the expression of this presynaptic protein in the midbrain, striatum, and temporal cortex of control, PD, and dementia with Lewy bodies (DLB) brain. Control brain showed punctate pericellular immunostaining. PD brain demonstrated alpha-synuclein immunoreactivity in nigral Lewy bodies, pale bodies and abnormal neurites. Rare neuronal soma in PD brain were immunoreactive for alpha-synuclein. DLB cases demonstrated these findings as well as alpha-synuclein immunoreactivity in cortical Lewy bodies and CA2-3 neurites. These results suggest that, even in sporadic cases, there is an early and direct role for alpha-synuclein in the pathogenesis of PD and the neuropathologically related disorder DLB.

Lack of association of a polymorphism in the low-density lipoprotein receptor-related protein gene with Alzheimer disease

BACKGROUND

The apolipoprotein E epsilon 4 (ApoE epsilon 4) allele is associated with an increased risk for development of Alzheimer disease (AD). We hypothesized that polymorphisms in proteins that interact with ApoE also might have an impact on the likelihood of AD developing. We examined a polymorphism in the gene for the low-density lipoprotein receptor-related protein (LRP), because LRP is a major ApoE receptor in the brain that also mediates binding and degradation of secreted Kunitz protease inhibitor forms of amyloid precursor protein.

SUBJECTS AND DESIGN

The LRP genotypes in 2 groups were studied. The first group consisted of 130 patients with probable or definite AD (mean +/- SD age, 78.2 +/- 8.9 years) and 64 nondemented, control subjects (mean +/- SD age, 81.7 +/- 12.3 years) who were primarily the spouses of the patients. The second group consisted of individuals from a population-based, epidemiologic study, including 38 cognitively impaired individuals (mean +/- SD age, 79.9 +/- 4.1 years) and 93 nondemented controls (mean +/- SD age, 78.7 +/- 4.4 years). Finally, 22 brains with a neuropathological diagnosis of AD were evaluated for neuronal loss, beta-amyloid deposition, and neurofibrillary tangle number and compared with the LRP genotype.

RESULTS

No genetic disequilibrium in LRP allele frequencies between controls and patients with AD or cognitive impairment was observed. No interaction between the ApoE epsilon 4 and LRP genotypes was observed in patients with AD. Moreover, the LRP genotype did not correlate with degree of neuronal loss, beta-amyloid deposition, or neurofibrillary tangle number in individuals examined using quantitative neuropathological techniques.

CONCLUSION

This LRP gene polymorphism is not linked with the pathophysiological changes of AD.

Epidemiological, clinical, and neuropathological study of apolipoprotein E genotype in Alzheimer's disease

Our studies of the APOE genotype in AD confirm a strong association of the epsilon 4 allele with development of AD and a decreased risk associated with epsilon 2. From a clinical/neuropathological perspective, the major effects of APOE epsilon 4 are to lower the age of onset and to increase the amount of A beta deposit in the brain. Neither rate of progression nor number of neurofibrillary tangles were affected. We also carried out a longitudinal population-based assessment of the APOE genotype to determine the risk for developing cognitive impairment of someone in the general population based on APOE genotype. APOE epsilon 4 carried about 1.4-fold increased risk, and APOE epsilon 2 about 1.7-fold decreased risk. Thus, inheritance of APOE epsilon 4 is a major biological risk factor for AD, but it has limited utility as a prognostic indicator for development of dementia in an individual.

Apolipoprotein E genotype does not influence rates of cognitive decline in Alzheimer's disease

BACKGROUND

Inheritance of the apolipoprotein E (apoE) epsilon 4 allele is a risk factor for developing Alzheimer's disease (AD) and is associated with a lower age of dementia onset. The purpose of this study was to determine whether apoE genotypes differentially influence the course of cognitive decline in AD dementia.

METHODS

We administered nine cognitive tests that assessed explicit memory, attention, language, visuospatial function, frontal-lobe function, and logical reasoning abilities to 66 probable AD patients every 6 to 24 months over a span of up to 5.5 years. We identified apoE genotype by a PCR-based method; there were 16 patients with epsilon 3/3, 34 with epsilon 3/4, and 16 with epsilon 4/4. Using regression statistical methods, we computed the change in performance for each test for each patient over time. We then analyzed the mean change in each test in patients grouped according to apoE genotype.

RESULTS

For the AD patients as a group, performance on all cognitive tests declined significantly over time, but the rate of decline did not vary significantly across apoE genotypes on any cognitive test. Specifically, the rate of cognitive decline was not faster in patients with an epsilon 4 allele than in those with epsilon 3/3.

CONCLUSIONS

These results indicate that the mechanism placing individuals with an epsilon 4 allele at risk for developing AD does not influence the rate of cognitive decline. These observations imply that the influence of apoE epsilon 4 either precedes or occurs at an early point in the AD disease process.

A newly identified polymorphism in the apolipoprotein E enhancer gene region is associated with Alzheimer's disease and strongly with the epsilon 4 allele

Apolipoprotein E allele 4 (apoE epsilon 4) is a major risk factor for late-onset AD. Inheritance of this allele is associated with an earlier age of onset of dementia in individuals with AD. It is unknown whether other polymorphisms in the apoE gene may influence the effect of apoE epsilon 4 on AD. We screened portions of the promoter enhancer element and of the apoE receptor binding domain for other polymorphisms that could affect risk of AD. In particular, a C/G polymorphism at position +113 of the apoE mRNA in the apoE intron 1 enhancer element (IE1) has been recently identified. We found no other polymorphisms. We studied the relationship of the two alleles of the IE1 polymorphism with AD and found an apparent association between IE1 G and AD (n = 94; p = 0.0515). However, the IE1 G allele is also closely associated with apoE epsilon 4 (p < 0.0001). When the presence of apoE epsilon 4 is covaried, the association between the IE1 G allele and AD is no longer statistically significant (odds ratio = 1.29, 95% confidence interval: 0.44, 3.78). In contrast, epsilon 4 is still highly associated with AD when IE1 G is controlled for (odds ratio = 5.91, 95% confidence interval: 3.29, 10.63). Furthermore, there is no significant association between the age of onset of dementia and the inheritance of the G allele. We believe that the apparent association between IE1 G and AD is a consequence of the association between the epsilon 4 and IE1 G alleles.

Apolipoprotein E and cognitive change in an elderly population

The apolipoprotein E (apoE) epsilon 4 allele is overrepresented, and the apoE epsilon 2 allele underrepresented, in Alzheimer's disease. To assess the risk of cognitive impairment in individuals with these genotypes in the general population, we studied a population-based sample of 1,899 individuals 65 years and older as a follow-up to the Iowa 65+ Rural Health Study. Multiple regression and logistic regression analyses demonstrated significant effects of apoE epsilon 4 and apoE epsilon 2 in predicting performance on a delayed recall task over a 4- to 7-year period. The magnitude of this effect was, however, fairly modest, with odds ratios for developing impairment of approximately 1.37 (95% confidence interval: 1.007, 1.850; p = 0.045) for apoE epsilon 4 and 0.53 (95% confidence interval: 0.368, 0.777; p = 0.001) for apoE epsilon 2. These effects were more pronounced in women than men. Importantly, 85% of elderly apoE E4/4 individuals (average age, 81) scored in the unimpaired range on a screening mental status test. Thus, many individuals reach old age without cognitive impair- ment despite inheritance of one or two apoE epsilon 4 alleles. This suggests that apoE genotyping will have limited utility as a diagnostic or prognostic indicator of cognitive decline in individuals.

Clinical and neuropathological correlates of apolipoprotein E genotype in Alzheimer's disease. Window on molecular epidemiology

Inheritance of the apolipoprotein E (apo E) epsilon 4 allele has recently been found to be associated with Alzheimer's disease. We have studied the clinical and neuropathological correlates of apolipoprotein E genotype in a large group of Alzheimer's patients. The primary influence on clinical presentation is a shift towards earlier age of onset in individuals who have the apo E epsilon 4 gene: no change in clinical course was observed. In neuropathological studies, we find that the major influence of apo E epsilon 4 is on increased A beta deposition. These results led to a model of the biological interaction between the apo E protein and Alzheimer's disease.

Clinical and pathological correlates of apolipoprotein E epsilon 4 in Alzheimer's disease

Inheritance of the apolipoprotein E (apoE) epsilon 4 allele is associated with a high likelihood of developing Alzheimer's disease (AD). The pathophysiologic basis of this genetic influence is unknown. We reasoned that understanding the influence of apoE epsilon 4 on the clinical course and neuropathological features of AD may provide tests of potential mechanisms. We carried out a prospective longitudinal study to compare the age of onset, duration, and rate of progression of 359 AD patients to apoE genotype. Thirty-one of the individuals who died during the study were available for quantitative neuropathological evaluation. Statistically unbiased stereological counts of neurofibrillary tangles (NFTs) and A beta deposits were assessed in a high-order association cortex, the superior temporal sulcus. Analysis of clinical parameters compared with apoE genotype showed that the epsilon 4 allele is associated with an earlier age of onset but no change in rate of progression of dementia. Quantitative neuropathological assessment revealed that NFTs were strongly associated with clinical measures of dementia duration and severity but not with apoE genotype. A beta deposition, by contrast, was not related to clinical features but was elevated in association with apoE epsilon 4. These results indicate that apoE epsilon 4 is associated with selective clinical and neuropathological features of AD and support hypotheses that focus on an influence of apoE epsilon 4 on amyloid deposition.

Apolipoprotein E epsilon 4 and cerebral hemorrhage associated with amyloid angiopathy

Cerebral amyloid angiopathy (CAA) is characterized by cerebrovascular deposition of the amyloid beta-peptide, leading to intracerebral hemorrhage in severe cases. Other than rare familial cases, the only identified risks for CAA are advancing age and accompanying Alzheimer's disease. We tested whether the apolipoprotein E epsilon 4 (apoE epsilon 4) allele was associated with CAA and hemorrhage and whether this association was independent of Alzheimer's disease. The apoE epsilon 4 genotype was determined without knowledge of the pathology for 93 postmortem cases systematically graded for severity of CAA and for 15 patients with CAA-associated intracerebral hemorrhage. We found a significant and independent effect of the apoE genotype in both cohorts. Among the postmortem cases, the presence of apoE epsilon 4 increased the odds ratio for moderate or severe CAA by 2.9-fold, relative to cases without epsilon 4; two copies of epsilon 4 increased the odds ratio 13.1-fold. In the cohort of CAA-associated cerebral hemorrhages, the apoE epsilon 4 allele frequency was 0.40, significantly greater than the control frequency of 0.14. The increase in CAA remained even after controlling for the presence of Alzheimer's disease, suggesting that apoE epsilon 4 is a risk factor for CAA and CAA-related hemorrhage, independent of its association with Alzheimer's disease.