Disease modifying drugs targeting β-amyloid

At this time there are no effective methods to alter the disease course in Alzheimer's disease. All FDA approved interventions are for symptomatic relief only. However, it is an exciting time as many agents in development have theorhetical potential to impact the disease course. This review discusses some of the agents that have been in clinical trials, particularly those that affect amyloid processing. Some agents have failed while others still provide hope. Since amyloid is the peptide most closely linked to disease pathogenesis, it is possible that some of the anti-amyloid agents will impact the disease progression in a meaningful way.

DLB and PDD boundary issues: Diagnosis, treatment, molecular pathology, and biomarkers

For more than a decade, researchers have refined criteria for the diagnosis of dementia with Lewy bodies (DLB) and at the same time have recognized that cognitive impairment and dementia occur commonly in patients with Parkinson disease (PD). This article addresses the relationship between DLB, PD, and PD with dementia (PDD). The authors agreed to endorse "Lewy body disorders" as the umbrella term for PD, PDD, and DLB, to promote the continued practical use of these three clinical terms, and to encourage efforts at drug discovery that target the mechanisms of neurodegeneration shared by these disorders of alpha-synuclein metabolism. We concluded that the differing temporal sequence of symptoms and clinical features of PDD and DLB justify distinguishing these disorders. However, a single Lewy body disorder model was deemed more useful for studying disease pathogenesis because abnormal neuronal alpha-synuclein inclusions are the defining pathologic process common to both PDD and DLB. There was consensus that improved understanding of the pathobiology of alpha-synuclein should be a major focus of efforts to develop new disease-modifying therapies for these disorders. The group agreed on four important priorities: 1) continued communication between experts who specialize in PDD or DLB; 2) initiation of prospective validation studies with autopsy confirmation of DLB and PDD; 3) development of practical biomarkers for alpha-synuclein pathologies; 4) accelerated efforts to find more effective treatments for these diseases.

Office of Rare Diseases neuropathologic criteria for corticobasal degeneration

A working group supported by the Office of Rare Diseases of the National Institutes of Health formulated neuropathologic criteria for corticobasal degeneration (CBD) that were subsequently validated by an independent group of neuropathologists. The criteria do not require a specific clinical phenotype, since CBD can have diverse clinical presentations, such as progressive asymmetrical rigidity and apraxia, progressive aphasia, or frontal lobe dementia. Cortical atrophy, ballooned neurons, and degeneration of the substantia nigra have been emphasized in previous descriptions and are present in CBD, but the present criteria emphasize tau-immunoreactive lesions in neurons, glia, and cell processes in the neuropathologic diagnosis of CBD. The minimal pathologic features for CBD are cortical and striatal tau-positive neuronal and glial lesions, especially astrocytic plaques and thread-like lesions in both white matter and gray matter, along with neuronal loss in focal cortical regions and in the substantia nigra. The methods required to make this diagnosis include histologic stains to assess neuronal loss, spongiosis and ballooned neurons, and a method to detect tau-positive neuronal and glial lesions. Use of either the Gallyas silver staining method or immunostains with sensitive tau antibodies is acceptable. In cases where ballooned neurons are sparse or difficult to detect, immunostaining for phospho-neurofilament or alpha-B-crystallin may prove helpful. Methods to assess Alzheimer-type pathology and Lewy body pathology are necessary to rule out other causes of dementia and Parkinsonism. Using these criteria provides good differentiation of CBD from other tauopathies, except frontotemporal dementia and Parkinsonism linked to chromosome 17, where additional clinical or molecular genetic information is required to make an accurate diagnosis.

Beta-amyloid, neuronal death and Alzheimer's disease

Alzheimer's disease (AD) is a common neurodegenerative disease that affects cognitive function in the elderly. Large extracellular beta-amyloid (Abeta) plaques and tau-containing intraneuronal neurofibrillary tangles characterize AD from a histopathologic perspective. However, the severity of dementia in AD is more closely related to the degree of the associated neuronal and synaptic loss. It is not known how neurons die and synapses are lost in AD; the current review summarizes what is known about this issue. Most evidence indicates that amyloid precursor protein (APP) processing is central to the AD process. The Abeta in plaques is a metabolite of the APP that forms when an alternative (beta-secretase and then gamma-secretase) enzymatic pathway is utilized for processing. Mutations of the APP gene lead to AD by influencing APP metabolism. One leading theory is that the Abeta in plaques leads to AD because Abeta is directly toxic to the adjacent neurons. Other theories advance the notion that neuronal death is triggered by intracellular events that occur during APP processing or by extraneuronal preplaque Abeta oligomers. Some investigators speculate that in many cases there is a more general disorder of protein processing in neurons that leads to cell death. In the later models, Abeta plaques are a byproduct of the disease process, rather than the direct cause of neuronal death. A direct correlation between Abeta plaque burden and neuronal (or synaptic) loss should occur in AD if Abeta plaques cause AD through a direct toxic effect. However, histopathologic studies indicate that the correlation between Abeta plaque burden and neuronal (or synaptic) loss is poor. We conclude that APP processing and Abeta formation is important to the AD process, but that neuronal alterations that underlie symptoms of AD are not due exclusively to a direct toxic effect of the Abeta deposits that occur in plaques. A more general problem with protein processing, damage due to the neuron from accumulation of intraneuronal Abeta or extracellular, preplaque Abeta may also be important as underlying factors in the dementia of AD.

Alpha-synuclein in familial Alzheimer disease: epitope mapping parallels dementia with Lewy bodies and Parkinson disease

BACKGROUND

Alpha-synuclein is a major component of Lewy bodies (LBs) in Parkinson disease and dementia with LBs and of glial cytoplasmic inclusions in multiple system atrophy. However, epitope mapping for alpha-synuclein is distinctive in different neurodegenerative diseases. The reasons for this are poorly understood but may reflect fundamental differences in disease mechanisms.

OBJECTIVE

To investigate the alpha-synuclein epitope mapping properties of LBs in familial Alzheimer disease.

DESIGN AND SETTING

We compared LBs in familial Alzheimer disease with those in synucleinopathies by probing 6 brains of persons with familial Alzheimer disease using a panel of antibodies to epitopes spanning the alpha-synuclein protein. Results were compared with data from brains of persons with Parkinson disease, dementia with LBs, and multiple system atrophy.

RESULTS

The brains of persons with familial Alzheimer disease showed consistent staining of LBs with all antibodies, similar to Parkinson disease and dementia with LBs but different from alpha-synuclein aggregates that occurred in multiple system atrophy.

CONCLUSIONS

These data suggest that the epitope profiles of alpha-synuclein in LBs are similar, regardless of whether the biological trigger is related to synuclein or a different genetic pathway. These findings support the hypothesis that the mechanism of alpha-synuclein aggregation is the same within cell types but distinctive between cell types.

Frontotemporal dementia: report of a familial case

The authors describe a 49-year-old woman (R.K.) who presented with one year of progressive frontal lobe dysfunction, including signs of expressive aphasia. Signs of parkinsonism were absent until late in the clinical course. Neuropsychologic testing and neuroimaging studies are described. The patient died at age 55, after 7 years of symptoms. Family history was remarkable for a mother who died at the age of 45, after experiencing 7 years of progressive aphasia. R.K.'s brain showed asymmetric frontotemporal atrophy, which was more severe on the left side. Histopathologic analysis was remarkable for numerous tau-positive neurons with some classic-appearing Pick bodies and many ballooned neurons. Tau-positive glial cells were also present. The authors suggest that the abnormal tau aggregates are related to the symptoms experienced by affected members of this family.

Inherited Alzheimer's disease PS-1 olfactory function: a 10-year follow-up study

This study was undertaken to evaluate smell tests as a clinical marker for identifying mutation carrier status and determining the clinical diagnosis of presenilin-1 Alzheimer's disease (AD) in family members of those afflicted with the disease. Ten years ago, we gave the self-administered, 40-question scratch and sniff University of Pennsylvania Smell Identification Test to 18 at-risk family members, individuals with dominantly-inherited Alzheimer's disease. Testing results were normal 10 years ago except in the case of one individual who had smoked three packs of cigarettes a day for more than 23 years. Four subjects tested in 1990 are now afflicted with Alzheimer's disease, including the smoker. The smell test in 1990 did not demonstrate predictive capabilities before clinical conversion to dementia. At follow-up, two subjects were too impaired to take the test. Two "converted" from normal smell function to abnormal function with a wide range in score. Study findings indicate that the smell test is too variable a measure to be used as a reliable test for predicting or verifying a diagnosis of presenilin-1 Alzheimer's disease.

JNK activation is associated with intracellular beta-amyloid accumulation

c-Jun has been implicated in the pathogenesis of Alzheimer's disease (AD), but the upstream cascade leading to c-Jun activation in AD is not known. Activation of c-Jun N-terminal kinase (JNK) is obviously a candidate for the upstream event. We tested this possibility focusing on PS1-linked AD. First, we observed that JNK is actually activated in cerebral neurons of PS1-linked AD patients, using immunohistochemistry and Western blot analyses with anti-activated JNK antibodies. We analyzed the relationship between beta-amyloid (beta A) and JNK activation by using aged transgenic mice overexpressing mutant (M146L) PS1 and human AD brains. The mice showed no neuronal loss but a very few diffuse beta A deposits, corresponding to the early stage of PS1-linked AD brain. Some neurons were reactive for anti-beta A antibodies in the cerebral cortex. Interestingly, JNK activation was observed in neurons showing intracellular beta A immunoreactivity in transgenic mice. Association between intracellular beta A and JNK activation was confirmed in cortical neurons of sporadic and PS1-linked AD patients. Furthermore, introduction of beta A peptides into the primary culture cortical neurons induced JNK activation and cell death. Collectively, these results suggested that intracellular beta A accumulation might trigger JNK activation leading to neuronal death.

Frontotemporal dementia with novel tau pathology and a Glu342Val tau mutation

It is unclear how tau gene mutations cause frontotemporal dementia (FTD) with parkinsonism linked to chromosome 17 (FTDP-17), but those in exon 10 (E10) or the following intron may be pathogenic by altering E10 splicing, perturbing the normal 1:1 ratio of four versus three microtubule-binding repeat tau (4R:3R tau ratio) and forming tau inclusions. We report on a 55-year old woman with frontotemporal dementia and a family history of FTDP-17 in whom we found a novel E12 (Glu342Val) tau gene mutation, prominent frontotemporal neuron loss, intracytoplasmic tau aggregates, paired helical tau filaments, increased 4R tau messenger RNA, increased 4R tau without E2 or E3 inserts, decreased 4R tau with these inserts, and a 4R:3R tau ratio greater than 1 in gray and white matter. Thus, this novel Glu342Val mutation may cause FTDP-17 by unprecedented mechanisms that alter splicing of E2, E3, and E10 to preferentially increase 4R tau without amino terminal inserts and promote aggregation of tau filaments into cytopathic inclusions.

Brain expression of presenilins in sporadic and early-onset, familial Alzheimer's disease

BACKGROUND

Mutations in the presenilin proteins cause early-onset, familial Alzheimer's disease (FAD).

MATERIALS AND METHODS

We characterized the cellular localization and endoproteolysis of presenilin 2 (PS2) and presenilin 1 (PS1) in brains from 25 individuals with presenilin-mutations causing FAD, as well as neurologically normal individuals and individuals with sporadic Alzheimer's disease (AD).

RESULTS

Amino-terminal antibodies to both presenilins predominantly decorated large neurons. Regional differences between the broad distributions of the two presenilins were greatest in the cerebellum, where most Purkinje cells showed high levels of only PS2 immunoreactivity. PS2 endoproteolysis in brain yielded multiple amino-terminal fragments similar in size to the PS1 amino-terminal fragments detected in brain. In addition, two different PS2 amino-terminal antibodies also detected a prominent 42 kDa band that may represent a novel PS2 form in human brain. Similar to PS1 findings, neither amino-terminal nor antiloop PS2 antibodies revealed substantial full-length PS2 in brain. Immunocytochemical examination of brains from individuals with the N141I PS2 mutation or eight different PS1 mutations, spanning the molecule from the second transmembrane domain to the large cytoplasmic loop domain, revealed immunodecoration of no senile plaques and only neurofibrillary tangles in the M139I PS1 mutation stained with PS1 antibodies.

CONCLUSIONS

Overall presenilin expression and the relative abundance of full-length and amino-terminal fragments in presenilin FAD cases were similar to control cases and sporadic AD cases. Thus, accumulation of full-length protein or other gross mismetabolism of neither PS2 nor PS1 is a consequence of the FAD mutations examined.

Familial Alzheimer's disease: site of mutation influences clinical phenotype

Alzheimer's disease (AD) is caused by multiple genetic and/or environmental etiologies. Because differences in the genetically determined pathogenesis may cause differences in the phenotype, we examined age at onset and age at death in 90 subjects with dominantly inherited AD due to different mutations (amyloid precursor protein, presenilin-1, and presenilin-2 genes). We found that among patients with dominantly inherited AD, genetic factors influence both age at onset and age at death.

AMY plaques in familial AD: comparison with sporadic Alzheimer's disease

OBJECTIVE

To assess AMY expression in familial AD (FAD).

BACKGROUND

The discovery of nonbeta-amyloid (Abeta), plaque-like deposits composed of a 100-kd protein (AMY) in sporadic AD (SAD) brains prompted us to determine whether these plaques (AMY plaques) also occur in AD due to mutations of the presenilin-1 (PS-1), presenilin-2 (PS-2), or the amyloid precursor protein (APP) genes.

METHODS

We used immunohistochemistry and confocal laser scanning microscopy to probe the brains of 22 patients with FAD (13 with PS-1, 5 with PS-2, and 4 with APP mutations) and 14 patients with SAD.

RESULTS

AMY plaques were present in all SAD and FAD brains, including an FAD/PS-1 brain from an individual with preclinical disease. The morphology of AMY plaques in SAD and FAD brains was indistinguishable, but they differed from Abeta deposits because AMY plaques lacked an immunoreactive core. AMY plaques sometimes colocalized with Abeta(x-42) deposits, but they did not colocalize with Abeta(x-40) plaque cores in either SAD or FAD brains. The percent of cortical area occupied by AMY was greater in FAD than in SAD brains (mean percent area = 9.8% and 5.9%, t = 2.487, p = 0.018). In particular, APP and PS-1 cases had more AMY deposition than PS-2 or SAD cases (12.9%, 10.5%, 6.2% in APP, PS-1, and PS-2 AD).

CONCLUSIONS

AMY plaques are consistently present in familial AD due to presenilin-1 (PS-1), PS-2, and amyloid precursor protein mutations, and they can begin to accumulate before the emergence of dementia.

Familial Alzheimer's disease: genetic influences on the disease process (Review)

Alzheimer's disease (AD) has both genetic and environmental etiologies. Genetic causes include presenilin (PS) mutations on chromosomes 1 and 14, and amyloid precursor protein (APP) mutations on chromosome 21. At least two susceptibility genes also exist. In this review phenotypic differences in AD groups are described and possible differences in the mechanism(s) by which AD mutations lead to dementia are reviewed. Clinical, pathological and biochemical phenotypes distinguish AD cases with different etiologies. For example, age-at-onset and age-at-death between PS-1, PS-2, APP and sporadic AD groups differ. Also, some forms of AD are associated with more Abeta deposition others, and some AD groups have morphologically distinct Abeta deposits or other unique histopathologic features. APP-related AD mutations always occur within the Abeta portion of the APP gene, adjacent to sites where alpha-, beta- and gamma-secretase breakdown pathways operate in the expressed protein. These mutations alter APP metabolism leading to increased Abeta production. It is unknown if other AD groups are subject to identical changes in APP metabolism. Activation of apoptosis pathways, more general defects in protein transport or metabolism, differential regulation of tau kinases or other factors may also be important. Overall, data support the notion that differences occur in the disease process in etiologically distinct AD groups.

Deposition of beta-amyloid subtypes 40 and 42 differentiates dementia with Lewy bodies from Alzheimer disease

BACKGROUND

Alterations in the metabolism of the amyloid precursor protein and the formation of beta-amyloid (Abeta) plaques are associated with neuronal death in Alzheimer disease (AD). The plaque subtype Abeta(x-42) occurs as an early event, with Abeta(x-40) plaques forming at a later stage. In dementia with Lewy bodies (DLB), an increase in the amount of cortical Abeta occurs without severe cortical neuronal losses.

OBJECTIVE

To advance our understanding of the natural history of Abeta in neurodegenerative diseases.

DESIGN

We evaluated the expression of Abeta(x-40) and Abeta(x-42) in DLB using monoclonal antibodies and immunohistochemical techniques in 5 brain regions. The data were compared with those elicited with normal aging and from patients with AD.

SETTING AND PATIENTS

A postmortem study involving 19 patients with DLB without concurrent neuritic degeneration, 10 patients with AD, and 17 aged persons without dementia for control subjects.

RESULTS

The Abeta plaques were more numerous in patients with DLB than in controls in most brain regions, although the Abeta(x-42) plaque subtype was predominant in both conditions. Overall, Abeta(x-42) plaque density was similar in patients with DLB and those with AD, but Abeta(x-40) plaques were more numerous in persons with AD than in those with DLB. The ratio of Abeta(x-40) to Abeta(x-42) plaques was significantly reduced in persons with DLB compared with patients with AD.

CONCLUSIONS

The Abeta plaques were more numerous in patients with DLB than persons with normal aging, but the plaque subtypes were similar. The relative proportion of the 2 Abeta plaque subtypes in DLB is distinguishable from that in AD.

Dementia with Lewy bodies: choline acetyltransferase parallels nucleus basalis pathology

The biological substrate underlying the reduced cortical choline acetyltransferase (ChAT) in dementia with Lewy bodies (DLB) is incompletely understood. We compared cortical ChAT levels with Lewy body densities and neuronal loss in the nucleus basalis of Meynert (nbM) and cerebral cortex in six DLB, seven Alzheimer's disease (AD), and six control cases. We found greater neuronal loss in the nbM in DLB compared to AD (U = 9.500, p = 0.049). Mean ChAT levels in the cortex were lower in dementia patients than controls (t = 17.500, p = 0.001), and DLB cases had slightly lower ChAT levels than AD cases, but this difference was not significant (t = -0.332, p = 0.746). Overall, cortical ChAT levels correlated inversely with neuronal loss in the nbM (Spearman rank correlation coefficient = -0.53). The correlation between ChAT level and the combined factor of nbM LBs and neuronal loss was -0.59. A similar correlation between ChAT level and the combined factor of nbM neurofibrillary tangles and neuronal loss was -0.72. The correlation between ChAT and the combined factor of nbM LBs and neuronal loss was -0.81 when AD cases were excluded from the analysis. Local cortical pathology was not related to ChAT level. We conclude that neuronal loss and Lewy body formation in the nbM may contribute to the reduction in cortical ChAT in DLB.

Antibodies to alpha-synuclein detect Lewy bodies in many Down's syndrome brains with Alzheimer's disease

Immunohistochemical examination of 20 Down's syndrome brains, using antibodies to alpha-, beta-, and gamma-synuclein, demonstrated many alpha-synuclein-positive Lewy bodies and dystrophic neurites in 50% of amygdala samples from Down's syndrome brains with Alzheimer's disease. Similar lesions were less common in other regions of these brains, none of which contained beta-synuclein or gamma-synuclein abnormalities. Thus, alpha-synuclein-positive Lewy bodies and neuritic processes frequently occur with Alzheimer's disease in Down's syndrome brains.

Alzheimer's disease in 22 twin pairs--13-year follow-up: hormonal, infectious and traumatic factors

We obtained follow-up data on 22 sets of twins where at least one twin had Alzheimer's disease (AD). The concordance rate for monozygotic twins (n = 17 pairs) was 59%, whereas that for dizygotic twins was 40%. In our series 8 monozygotic twins had hysterectomies; all had AD. The twins with hysterectomies also had a tendency to develop AD at an earlier age than their co-twin. Five twins with serious systemic infection developed AD, and they tended to have earlier onset than their corresponding twin. We found no strong evidence that head injury predisposed to AD.

Lewy bodies contain altered alpha-synuclein in brains of many familial Alzheimer's disease patients with mutations in presenilin and amyloid precursor protein genes

Missense mutations in the alpha-synuclein gene cause familial Parkinson's disease (PD), and alpha-synuclein is a major component of Lewy bodies (LBs) in sporadic PD, dementia with LBs (DLB), and the LB variant of Alzheimer's disease (AD). To determine whether alpha-synuclein is a component of LBs in familial AD (FAD) patients with known mutations in presenilin (n = 65) or amyloid precursor protein (n = 9) genes, studies were conducted with antibodies to alpha-, beta-, and gamma-synuclein. LBs were detected with alpha- but not beta- or gamma-synuclein antibodies in 22% of FAD brains, and alpha-synuclein-positive LBs were most numerous in amygdala where some LBs co-localized with tau-positive neurofibrillary tangles. As 12 (63%) of 19 FAD amygdala samples contained alpha-synuclein-positive LBs, these inclusions may be more common in FAD brains than previously reported. Furthermore, alpha-synuclein antibodies decorated LB filaments by immunoelectron microscopy, and Western blots revealed that the solubility of alpha-synuclein was reduced compared with control brains. The presence of alpha-synuclein-positive LBs was not associated with any specific FAD mutation. These studies suggest that insoluble alpha-synuclein aggregates into filaments that form LBs in many FAD patients, and we speculate that these inclusions may compromise the function and/or viability of affected neurons in the FAD brain.

TGF-beta receptors-I and -II immunoexpression in Alzheimer's disease: a comparison with aging and progressive supranuclear palsy

The transforming growth factor-betas (TGF-betas) influence cell survival, and TGF-beta2 shows increased immunoexpression in neurofibrillary tangle-bearing neurons and reactive glia in Alzheimer's disease (AD) and progressive supranuclear palsy (PSP). We compared immunohistochemical expression of TGF-beta type I (RI) and type II (RII) receptors in eight patients with AD, eight controls and three cases of progressive supranuclear palsy. Mild intraneuronal immunoreactivity for the RI receptor was observed in all cases. Intraneuronal TGF-beta RII receptor immunoexpression was more common in all groups, and its frequency did not differ between groups. We observed increased immunoreactivity for both RI and RII subtypes in reactive glia in the AD frontal cortex (RI: U = 0.5, p = 0.002; and RII: U = 9.000, p = 0.006) and parahippocampal gyrus (RI: U = 9.500, p = 0.013; RII: U = 14.5, p = 0.05) compared to control cases. We conclude that TGF-beta RI and II immunoreactivity is increased in reactive glia in AD and progressive supranuclear palsy, and RI immunoreactivity may occasionally be increased in neurons in cases with advanced AD.

The medial temporal lobe in dementia with Lewy bodies: a comparative study with Alzheimer's disease

The usefulness of determining medial temporal lobe (MTL) size in differentiating Alzheimer's disease (AD) from other dementia subtypes is unknown. We compared the cross-sectional areas of the MTLs in histological sections from the brains of 18 patients with dementia with Lewy bodies (DLB) but lacking AD changes, 24 DLB patients with concurrent AD pathology, 20 pure AD cases, and 18 age-matched control cases. Duration and severity of disease were comparable between groups. When data for cross-sectional area were expressed as percentages of the average control area, DLB MTLs were significantly larger than either AD or DLB/AD MTLs at rostral levels (86 +/- 16%, 54 +/- 17%, and 66 +/- 23% of control areas, respectively). At caudal levels, DLB MTLs were larger than AD MTLs (80 +/- 20%, 59 +/- 21%, and 77 +/- 26% of control areas in DLB, AD, and DLB/AD, respectively). MTL cross-sectional area often approaches normal in pure DLB, even when disease duration is prolonged and symptoms are end stage. In contrast, a greatly reduced MTL area mitigates against the diagnosis of DLB, unless there are concurrent AD changes.

Transforming growth factor-betas in neurodegenerative disease

Transforming growth factors-betas (TGF-betas), a family of multifunctional peptide growth factors, affect cells of the central nervous system (CNS). The three mammalian TGF-beta isoforms, TGF-betas 1, 2 and 3, are expressed in adult human brain. Since neuronal degeneration is a defining feature of CNS degenerative diseases, TGF-beta may be important because it can influence neuronal survival. In vitro TGF-beta promotes survival of rat spinal cord motoneurons and dopaminergic neurons. In addition to direct effects on neuronal survival, TGF-beta treatment of cultured astrocytes induces a reactive phenotype. Thus, TGF-beta may also normalize the extracellular matrix environment in degenerative diseases. The expression of TGF-betas change in response to neuronal injury. TGF-beta 1 expression increases in astrocytes and microglia in animal models of cerebral ischemia, while TGF-beta 2 expression increases in activated astroglial cells in human neurodegenerative diseases. TGF-betas protect neurons from a variety of insults. TGF-beta maintains survival of chick telencephalic neurons made hypoxic by treatment with cyanide and decreases the area of infarction when administered in animal models of cerebral ischemia. In vitro TGF-beta protects neurons from damage induced by treatment with beta-amyloid peptide, FeSO4 (induces production of reactive oxygen species), Ca2+ ionophores, glutamate, glutamate receptor agonists and MPTP (toxic for dopaminergic neurons). TGF-beta maintains mitochondrial potential and Ca2+ homeostasis and inhibits apoptosis in neurons. TGF-beta does not prevent neuronal degeneration in a rat model of Parkinson's disease and has yet to be tested in newly developed transgenic mouse models of Alzheimer's disease. TGF-beta is a potent neuroprotective agent which may affect the pathogenesis of neurodegenerative diseases of the CNS.

Alzheimer's disease, Lewy body disease and aging: a comparative study of the perforant pathway

The relationship between Alzheimer's disease (AD) and Lewy body disease (LBD) is poorly understood. In AD there is severe loss of neurons comprising the perforant pathway. To assess perforant pathway integrity in pure LBD we compared neuronal counts in layer II of the entorhinal cortex (ERC) in 11 cases of pure LBD that did not meet CERAD pathologic criteria for AD with ERC neuronal counts from seven AD cases with a similar disease duration and six cognitively normal individuals. We counted cell bodies/island in layer II of the ERC using formalin-fixed, paraffin-embedded, tau/cresyl violet-stained sections at the level of the rostral-most body of the hippocampus. There was marked variability in neuronal counts among cases in the LBD group; LBD data overlapped with data from both normal and AD groups. Overall, perforant pathway perikaryal counts in LBD differed significantly from those in AD, but not from those in aged normals (mean perikarya/island = 30.09 +/- 8.95, 7.57 +/- 6.08, and 38.83 +/- 8.98, respectively; F = 26.131, P < 0.001). The percent of remaining neurons bearing neurofibrillary tangles in LBD also overlapped with AD and control groups (16.17 = 13.85%, 87.86 +/- 11.81%, and 24.36 +/- 13.30% of remaining neurons, respectively, F = 65.62, P < 0.001). We conclude that although perforant pathway neuronal loss may occur in LBD, it is more often milder and more variable than that seen in AD.

Apolipoprotein E-epsilon 2 and Alzheimer's disease: genotype influences pathologic phenotype

To determine whether apolipoprotein E epsilon 2 (APOE-epsilon 2) affects neuropathology in aging and Alzheimer's disease (AD), we compared beta-amyloid plaque (A beta P) and neurofibrillary tangle densities, neuropil thread formation, and amyloid angiopathy in five APOE-epsilon 2/3 AD patients, five APOE-epsilon 3/3 AD patients, five APOE-epsilon control patients, and five APOE-epsilon 3/3 control patients. We examined the (frontal and parietal) neocortex, hippocampus, entorhinal cortex, and cerebellum and found A beta P densities to be lower (t = 3.121, p = 0.011) in the cortex of APOE-epsilon 2/3 AD patients than in APOE-epsilon 3/3 AD patients. Amyloid angiopathy was also less in APOE-epsilon 2/3 patients than in APOE-3/3 patients (U = 4.500, p = 0.027). Control APOE-epsilon 2/3 brains had little AD-related pathology; even our 102-year-old control case showed few A beta Ps compared with the elderly APOE-epsilon 3/3 cases. The APOE-epsilon 2/3 genotype may influence pathologic phenotype in some aged normal and AD populations.

Inducible nitric oxide synthase in tangle-bearing neurons of patients with Alzheimer's disease

In Alzheimer's disease (AD), affected neurons accumulate beta amyloid protein, components of which can induce mouse microglia to express the high-output isoform of nitric oxide synthase (NOS2) in vitro. Products of NOS2 can be neurotoxic. In mice, NOS2 is normally suppressed by transforming growth factor beta 1 (TGF-beta 1). Expression of TGF-beta 1 is decreased in brains from AD patients, a situation that might be permissive for accumulation of NOS2. Accordingly, we investigated the expression of NOS2 in patients with AD, using three monospecific antibodies: a previously described polyclonal and two new monoclonal antibodies. Neurofibrillary tangle-bearing neurons and neuropil threads contained NOS2 in brains from each of 11 AD patients ranging in age from 47 to 81 years. NOS2 was undetectable in brains from 6 control subjects aged 23-72 years, but was expressed in small amounts in 3 control subjects aged 77-87 years. Thus, human neurons can express NOS2 in vivo. The high-output pathway of NO production may contribute to pathogenesis in AD.

Familial and sporadic Alzheimer's disease: neuropathology cannot exclude a final common pathway

Whether all etiologic forms of Alzheimer's disease (AD) share a final common pathway is a major issue. We determined the severity and regional distribution of neuronal loss, amyloid plaques, neuritic plaques (NPs), and neurofibrillary tangles (NFTs), and calculated the ratio of neuronal loss to NPs and NFTs in brains of 19 familial AD (FAD) patients with linkage to chromosome 14, six AD patients with mutations of chromosome 21 (codon 717 of the beta-amyloid percursor protein gene), and 11 sporadic AD (SAD) patients. There was no difference in the pattern of distribution of the various pathologic features or in the ratio of neuronal loss to NPs or NFTs in any AD group. However, FAD groups could be distinguished from SAD by the greater severity and the lack of influence of apolipoprotein E genotype on pathology. These differences may reflect differences in age at onset rather than different etiopathologic mechanisms. The similarity of pathologic findings in the different AD groups provides evidence for a final common pathophysiologic pathway in AD.

Transforming growth factor-beta: neuronal and glial expression in CNS degenerative diseases

We have previously shown that the brains of patients with Alzheimer's disease (AD) express transforming growth factor (TGF)-beta 2 in neurofibrillary tangle (NFT)-bearing neurons and reactive astrocytes. The present study was undertaken to determine whether other neurodegenerative diseases were also associated with an alteration of the TGF-beta's. The immunohistochemical expression of TGF-beta 1, -2 and -3 was assessed in the brains of patients with progressive supranuclear palsy (n = 2), amyotrophic lateral sclerosis (n = 3), Lewy body disease (n = 5), Parkinson's disease (n = 1), Shy-Drager syndrome (n = 1), Pick's disease (n = 3), lobar atrophy (n = 1), and corticobasal degeneration (n = 2). Our results were compared to norms for controls (n = 8). We found expression of TGF-beta 2 in both NFT bearing neurons and tangle-bearing glial cells in progressive supranuclear palsy and in neurons with age-related NFT formation. Widespread staining of reactive astrocytes for TGF-beta 2 was observed in all degenerative diseases. TGF-beta 1 and -3 staining was not selectively altered in these diseases. We conclude that induction of TGF-beta 2 may be an intrinsic part of the processes that underlie NFT formation and reactive gliosis in a variety of neurodegenerative diseases.

Apolipoprotein E epsilon 4 allele and the lifetime risk of Alzheimer's disease. What physicians know, and what they should know

BACKGROUND

Published studies now show a clear association between Alzheimer's disease (AD) and the apolipoprotein E epsilon 4 allele (APOE* epsilon 4). The clinical value of this information to estimate a healthy individual's lifetime risk of AD has not been well delineated. Physicians dealing with AD may not know either the lifetime risk of developing AD or the effect of the APOE genotype on this risk. Because the lifetime risk of AD depends in part on life expectancy, and available figures on APOE are not population based, a computation is necessary to derive risk estimates useful to physicians.

OBJECTIVES

To estimate the lifetime risk of AD and the effect of APOE genotype information on that risk and to assess the knowledge of these risks among physicians who manage patients with dementia.

DESIGN

Estimation of risk of AD and survey of physician awareness. The lifetime risk of developing AD without APOE genotype information was first computed for 65-year-olds from existing epidemiologic studies of age-related AD incidence and an actuarial life-table analysis. Using this computed a priori risk of AD and published studies of APOE genotypes in individuals with and without AD, we used a Bayesian analysis to determine the risk of developing AD, with and without an APOE* epsilon 4 allele, for unaffected 65-year-olds. To assess physician knowledge of the lifetime risk of AD and the effect of APOE genotyping on the risk, 50 neurologists, internists, geriatricians, geriatric psychiatrists, and family physicians who manage patients with dementia were randomly selected to participate in a questionnaire-driven telephone survey.

RESULTS

In a person with no family history of AD, the epidemiologic/actuarial lifetime risk of AD is approximately 15%. Based on a Bayesian calculation and published APOE data, the lifetime risk of AD is 29% for individuals with one APOE* epsilon 4 allele and it is 9% if no APOE* epsilon 4 allele is present. Physician awareness survey results were as follows: 42% of physicians correctly estimated the approximate lifetime risk of AD; of these, only one third were moderately sure of their response. Only three physicians correctly estimated the change in risk given the APOE* epsilon 4 genotype; only one of these was at least moderately sure.

CONCLUSIONS

Determining the APOE* epsilon 4 status of healthy adults with no family history of AD approximately doubles (for the epsilon 4 allele) or reduces by 40% (for the non-epsilon 4 allele) the uninformed lifetime risk of developing AD. Even with an APOE* epsilon 4 allele, the lifetime risk remains below 30%. Most physicians managing patients with AD do not know the lifetime risk of AD, and very few know how APOE* epsilon 4 status modifies the risk. These clinically relevant risk figures should be more widely disseminated among physicians.

Altered expression of transforming growth factor-beta in Alzheimer's disease

We compared immunohistochemical expression of the transforming growth factor-betas (TGF-beta 1, TGF-beta 2, and TGF-beta 3) using brain tissue from patients with nondominantly inherited Alzheimer's disease (NDAD) (n = 9), autosomal dominantly inherited Alzheimer's disease with linkage to 14q24.3 (FAD-14) (n = 4), and cognitively normal controls (n = 10) to determine whether their pathologic changes are associated with an altered distribution of the TGF-betas. We found increased expression of TGF-beta 2 in large, tangle-bearing neurons with widespread staining of glia in NDAD and FAD-14 patients compared with control cases. This result was confirmed with sandwich ELISA assays of brain tissue, which showed TGF-beta 2 levels in AD and NDAD to average 3.2 times the average level of control cases. Despite proximity of TGF-beta 1 and TGF-beta 3 to the sites of susceptibility loci on chromosomes 19 and 14, we did not find that TGF-beta 1 and TGF-beta 3 were selectively altered in any AD subtypes. However, selective induction of TGF-beta 2 may occur in NDAD and FAD-14.

Familial Alzheimer's disease and cortical Lewy bodies: is there a genetic susceptibility factor?

The reason for the occurrence of Lewy body disease (LBD) in Alzheimer's disease (AD) patients is unknown. If brains from etiologically different AD groups differ in their tendency to develop cortical Lewy bodies, the concurrence of LBD in AD patients may be a manifestation of the AD process in specific AD subsets. To address this issue, we counted cortical Lewy bodies in AD patients with genetic abnormalities on chromosome 14 (n = 19), and chromosome 21 (n = 3), sporadic AD (n = 27), Down's syndrome (n = 1) and control (n = 26) patients. Cortical Lewy bodies were occasionally present in AD patients with long-duration disease in most of the above AD subgroups, but were not present in any of our age-matched control cases. We suggest that cortical Lewy body formation may be an intrinsic part of the late pathologic changes of AD regardless of etiology and that it is not specific to any of the AD subtypes studied.

Ki-67 immunoreactivity in Alzheimer's disease and other neurodegenerative disorders

Cell cycle-associated nuclear proteins may have more specialized functions in the adult nervous system in addition to those directly associated with cell proliferation, as suggested by a recent study showing that neurofibrillary tangles (NFT) and dystrophic neurites in Alzheimer's disease (AD) are immunoreactive for the proliferation-associated antigen p105. To further investigate this hypothesis, we studied the expression of another proliferation-associated antigen, Ki-67, in the brains of patients with AD and other neurodegenerative disorders. Formalin-fixed, paraffin-embedded sections from autopsy cases of AD, Down's syndrome with dementia and AD pathology (DS/AD), Pick's disease (PiD), progressive supranuclear palsy (PSP), Lewy body disease (LBD), Parkinson's disease (PD), corticobasal degeneration (CBD), and young and aged normal brains, and from two surgically resected gangliogliomas were immunostained using antibodies to Ki-67 (MIB-1 clone equivalent) and tau (tau). Ki-67 staining was performed following antigen retrieval by microwave heating. Ki-67 labeled NFT that were observed in the AD, DS/AD, PiD, PSP, LBD, and PD cases, one aged normal brain, and one ganglioglioma. Ki-67 generally labeled fewer NFT compared to tau. Pick bodies, ballooned neurons (Pick cells) in CBD and PiD, and nigral corticobasal inclusions in CBD were immunoreactive for tau but not Ki-67. Neither antibody labeled cortical or subcortical Lewy bodies. Our findings suggest that Ki-67 may be involved in the pathogenesis of neurofibrillary degeneration in AD, other neurodegenerative disorders, normal aging, and neoplasms such as ganglioglioma. We postulate a possible role for Ki-67 in the production of the abnormally phosphorylated tau protein that leads to the formation of paired helical filaments within susceptible neurons.

Role of the dorsomedial nucleus of the thalamus in Alzheimer's disease

It is not known whether changes in the thalamus play a role in the memory loss or dementia of Alzheimer's disease (AD), although trauma, infarction, and hemorrhage to the thalamus, particularly the dorsomedial nucleus (DMN), can cause these cognitive changes. To determine the pathologic changes in the DMN in AD, we examined the DMN in 16 cases of AD and 7 age-matched controls, with quantitative assessments of the total neuronal population and synaptic density, Alz-50-positive neurons, neurofibrillary tangles (NFT), and senile plaques (SP). We examined sections after staining with cresyl violet, a silver stain, and immunocytochemical staining for Alz-50 and synapsin I. Stereologic analysis demonstrated a mean loss of 29% of DMN neurons in AD and a synaptic density decrease of 21%. Alz-50 staining and NFT were present in all AD cases but in none of the controls. Senile plaques were 52 times more frequent in the DMN in AD than in the age-matched controls. The large variation in pathologic changes among our AD cases suggests that neuronal losses and other pathology in the DMN in AD may contribute to the total brain burden of pathology resulting in dementia in some AD patients, but not in others.

Apolipoprotein E genotype and Lewy body disease

To determine whether apolipoprotein E (APOE) genotype affects neuropathology in Lewy body disease (LBD), we examined 18 cases of LBD that did not have concurrent Alzheimer's disease by the CERAD criteria. We obtained APOE genotypes, determined diffuse beta-amyloid plaque (A beta P) and Lewy body densities in multiple brain regions, and graded the intensity of CA2-3 ubiquitin-positive neurites, vacuolar change, nigral pathology, amyloid angiopathy, and subpial amyloid deposition. The APOE allele frequencies were as follows: epsilon 2, 0.14 +/- 0.07; epsilon 3, 0.64 +/- 0.08; and epsilon 4, 0.22 +/- 0.03. The mean A beta P density was lower in APOE epsilon 3/3 cases (14.5 A beta Ps per mm2) than in the groups with the APOE epsilon 2 (67.0) or APOE epsilon 4 (46.6) alleles. This difference was due largely to the difference between A beta P density in the APOE epsilon 2 group and the APOE epsilon 3/3 group (F = 5.525, p < 0.02). CA2-3 neuritic degeneration was greater in those with the APOE epsilon 4 allele than in those with the APOE epsilon 3/3 genotype (grade = 1.9 +/- 1.3 versus 0.938 +/- 0.9; Kruskal-Wallis test statistic = 6.962, p < 0.05). These data are consistent with the hypothesis that APOE genotype may affect neuropathology in LBD.

Alzheimer's disease and Lewy body disease: a comparative clinicopathological study

The exact nature of the relationship between Lewy body disease and Alzheimer's disease (AD) is unknown. To investigate this, we compared cases of pure Lewy body disease, mixed Lewy body disease with AD, and pure AD to see what pathological features were shared and how they differed. We counted neurons, Lewy bodies, diffuse and neuritic senile plaques, neurofibrillary tangles, and neuropil threads in the frontal and medial temporal cortex and hippocampus from 5 autopsied cases of Lewy body disease (without AD histopathology), 7 with combined Lewy body disease and AD, 6 with AD, and 5 age-matched normal control subjects. Average neuronal counts in the cases with Lewy body disease were indistinguishable from those of control subjects, but higher than those for AD and combined Lewy body disease and AD. Diffuse plaque densities were similar in all disease forms. Neuritic senile plaques, neurofibrillary tangles, and neuropil threads were numerous in AD and combined Lewy body disease and AD, but sparse or absent in Lewy body disease and controls. Pure Lewy body disease and AD appear to be distinct clinicopathological entities except for the common feature of diffuse plaques in both disorders.

Vascular amyloid deposition in Alzheimer's disease. Neither necessary nor sufficient for the local formation of plaques or tangles

OBJECTIVE

To determine the relationship between vascular beta-amyloid (beta A4) and senile plaques (SPs) and neurofibrillary tangles (NFTs).

DESIGN

We counted vascular amyloid deposition with SP and NFT density in the medial temporal lobe (CA1 plus the subiculum) and the cerebellum.

PATIENTS

The brains of seven patients with Alzheimer's disease and of three age-matched nondemented control subjects were studied.

RESULTS

In Alzheimer's disease, the density of beta A4-laden blood vessels was significantly higher in the cerebellum than in CA1 plus the subiculum. Conversely, the densities of SPs and NFTs were much greater in the CA1 plus the subiculum than in the cerebellum.

CONCLUSIONS

This study indicates that local vascular beta A4 deposition is not directly correlated with SP and NFT densities. Deposition of beta A4 in blood vessel walls may not be instrumental in the formation of SPs and/or NFTs in the brain.

Cortical tubers demonstrate reduced immunoreactivity for synapsin I

To evaluate the effects of tuberous sclerosis (TS) on cortical synaptic organization, we analyzed synaptic densities within cortical tubers from the brains of two TS patients using a polyclonal antibody directed against synapsin I, a synaptic terminal-specific protein. The synaptic densities of the tubers and adjacent histologically normal cortex were obtained by determining optical densities using an IBAS (Zeiss) image analysis system. The tubers showed abnormally low levels of synapsin I compared with the normal cortex. The data suggest that cortical tubers do not contain a normal complement of synapses. This may reflect focal underdevelopment of normal cortical-cortical connections. Altered afferent cortical projections may also contribute to synaptic loss in cortical tubers.

The indusium griseum in Alzheimer's disease: an immunocytochemical study

The immunocytochemical features of the indusium griseum (IG) were compared with the corresponding hippocampus in 5 patients with Alzheimer's disease (AD) and 5 age-matched nondemented individuals using antibodies against beta-amyloid, the A68 protein (Alz-50 antibody), tau, ubiquitin and synapsin I. beta-Amyloid-positive plaques were prominent in the AD hippocampus but were not present in the IG. Numerous Alz-50, tau and ubiquitin-positive neurofibrillary tangles and dystrophic neurites were observed in the AD hippocampus but were infrequent in the IG. Synapsin I immunoreactivity was significantly reduced in both the AD hippocampus and the AD IG when compared to age-matched patients. These findings suggest that the IG may be resistant to factors that trigger production of abnormal AD-associated proteins. Loss of synaptic input alone may not account for the AD-associated changes in the hippocampus since synaptic depletion was seen in both the hippocampus and the unaffected AD IG.

Alzheimer's disease and aging: effects on perforant pathway perikarya and synapses

The hippocampal perforant pathway originates in the entorhinal cortex (ERC) and terminates in the outer molecular layer of the dentate gyrus (DG). To compare the effects of normal aging and Alzheimer's disease (AD) on the elements of the perforant pathway, we compared relative perikaryal numbers (determined by counting cell bodies and estimating volumes) in layer II of the ERC with synaptic quantities (estimated from immunoreactivity for the synaptic terminal protein synapsin I and DG volume) in the molecular layer of the DG. The brains of 5 young and 9 elderly cognitively normal individuals, and of 9 AD patients were studied. In normal aging we found a significant age-related decline in perikaryal numbers in the ERC without demonstrable synaptic loss in the DG. In AD there was marked and equivalent, (or proportional) reduction in both ERC perikaryal numbers and DG synapses. These data suggest that in normal aging remaining neurons may continue to support a full array of synapses, perhaps due to mechanisms such as axonal sprouting, synaptic enlargement, or synaptic ingrowth. In AD, however, the accelerated neuronal loss may overwhelm such compensatory mechanisms or alternatively, independent synaptic and perikaryal losses may occur.

Architecture of the suprachiasmatic nuclei in BALB/c and C57BL/6 inbred mouse strains

Quantitative values representing the length, girth, volume, shape, and cell counts of the suprachiasmatic nuclei (SCN) were measured in BALB/cByJ and C57BL/6J inbred mouse strains, which exhibit a large interstrain difference in the free-running period of their circadian locomotor rhythms. There were no differences in the gross architectural features of the SCN in these two strains.

Immunocytochemical study of ballooned neurons in cortical degeneration with neuronal achromasia

We studied the immunocytochemical characteristics of the ballooned neurons (BN) in three patients with cortical degeneration with neuronal achromasia (CDNA) using antibodies to phosphorylated neurofilaments (PNF), tau, Alz-50, ubiquitin, beta (A4) amyloid, and glial fibrillary acidic protein. All BN exhibited intense perikaryal staining for PNF protein. Most BN and some normal-appearing neurons also stained for ubiquitin and Alz-50. The BN did not immunostain for tau protein, and none of the cases had tau-reactive neocortical neurofibrillary tangles or Pick bodies. One case had occasional senile plaques that stained for beta amyloid; no case had amyloid angiopathy. Our findings suggest that the pathophysiologic basis of the cortical degeneration in CDNA involves an alteration of neuronal cytoskeletal metabolism affecting neurofilament and possibly microtubular proteins in conjunction with activation of the ubiquitin proteolytic system.

Primary progressive aphasia with focal neuronal achromasia

We describe the clinical, radiologic, neuropsychological, and neuropathologic features of a 69-year-old man with a 3-year history of progressive transcortical expressive aphasia. Neuropsychological testing showed progressive dysfunction of expressive language. Neuropathologic examination demonstrated focal cortical degeneration involving the left superior frontal gyrus, with swollen achromasic neurons and no evidence of Alzheimer's disease, Pick's disease, Creutzfeldt-Jakob disease, Lewybody disease, or other dementing disorders. This case adds to the known heterogeneity of the underlying pathology of patients with primary progressive aphasia.

Lobar atrophy with pontine neuronal chromatolysis ("ballooned" neurons)

A 64-year-old man developed progressive dementia over a period of 11 years. Postmortem examination showed severe atrophy of the temporal lobes of the brain with extensive neuronal loss and a remarkable alteration of the neuronal perikaryon--the "ballooned" neuron--restricted to the nuclei of the basis pontis. No neuritic plaques, neurofibrillary tangles, or Pick bodies were seen.

Corticonigral degeneration with neuronal achromasia. A clinicopathologic study of two cases

We describe the clinical and neuropathological features of two patients having corticonigral degeneration with neuronal achromasia (CND). Both patients had cognitive decline and movement disorders. Magnetic resonance (MR) scans showed cortical atrophy, which in one case was most prominent in the parasylvian region, and ventricular enlargement in both cases. Neuropathological examination revealed swollen achromasic neurons within the cerebral cortex and marked neuronal loss in the substantia nigra. No Pick bodies, Lewy bodies, histologic changes of Alzheimer's disease, or spongiform change were present in either case. The diagnosis of CND should be considered in patients with complex movement disorders, with or without abnormalities in cognitive function.

The indusium griseum: is it involved in Alzheimer's disease?

The histopathology of the indusium griseum (IG), a displaced hippocampal anlage, was studied in five patients with Alzheimer's disease (AD) and five controls. In the AD group, the IG had occasional neurons with granulovacuolar change (GVD) and rare Hirano bodies (HB), but no senile plaques (SP), neurofibrillary tangles (NFT), or neurons staining for phosphorylated neurofilament antigen. There was a slight but not statistically significant diminution of neurons within the IG. In all AD cases, the hippocampus showed abundant AD-associated histopathology. In the control cases, only rare neurons with GVD were present in the IG. These findings indicate that although single neurons within the IG may show some of the cytologic changes seen in the hippocampal neurons in normal aging and AD, IG neurons do not express the full range and severity of histopathologic abnormalities characteristic of AD. This suggests that factors other than selective vulnerability of neurons of hippocampal origin might be operating to induce the neuropathologic picture of AD.