ORIGINAL CONTRIBUTION. Deposition of -Amyloid Subtypes 40 and 42 Differentiates Dementia With Lewy Bodies From Alzheimer Disease

ORIGINAL CONTRIBUTION Deposition of -Amyloid Subtypes 40 and 42 Differentiates Dementia With Lewy Bodies From Alzheimer Disease Carol F. Lippa, MD; Kazuharu Ozawa, PhD; David M. A. Mann, PhD; Kazuhiro Ishii, MD; Thomas W. Smith, MD; Shigeki Arawaka, MD; Hiroshi Mori, PhD Background: Alterations in the metabolism of the amyloid precursor protein and the formation of -amyloid (A ) plaques are associated with neuronal death in Alzheimer disease (AD). The plaque subtype A x-42 occurs as an early event, with A x-40 plaques forming at a later stage. In dementia with Lewy bodies (DLB), an increase in the amount of cortical A occurs without severe cortical neuronal losses. Objective: To advance our understanding of the natural history of A in neurodegenerative diseases. Design: We evaluated the expression of A x-40 and A 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 A plaques were more numerous in patients with DLB than in controls in most brain regions, although the A x-42 plaque subtype was predominant in both conditions. Overall, A x-42 plaque density was similar in patients with DLB and those with AD, but A x-40 plaques were more numerous in persons with AD than in those with DLB. The ratio of A x-40 to A x-42 plaques was significantly reduced in persons with DLB compared with patients with AD. Conclusions: The A 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 A plaque subtypes in DLB is distinguishable from that in AD. Arch Neurol. 1999;56:1111-1118 From the Department of Neurology, MCP-Hahnemann University, Philadelphia, Pa (Dr Lippa); Department of Neuroscience, Osaka City University Medical School, Aebnoku, Japan (Drs Ozawa, Ishii, Arawaka, and Mori) Division of Molecular Pathology, Department of Pathological Sciences, University of Manchester, Manchester, England (Dr Mann); and Division of Neuropathology, Department of Pathology, University of Massachusetts Medical Center, Worcester (Dr Smith). THE MOLECULAR basis of neuronal degeneration in Alzheimer disease (AD) is not fully understood, but recentattention 1-14 hasfocused on the importance of the role of differentlength -amyloid (A ) peptides. Because there is an increased amount of the subtype A x-42, but not of A x-40, 9 in presymptomatic patients with genetic forms of AD, including Down syndrome and presenilin 1 AD, A x-42 deposition is considered 12 an early event in the AD process, with A x-40 plaques occurring later. Both A subtypes are presentinthebrainsofolderpatientswithdown syndrome and in patients with AD. 9,13-15 The biological factors associated with the accumulation of the different A subtypes in degenerative diseases are not well understood. Brain specimens from patients with familial AD, however, show greater amounts of A x-42 than do those from patients with sporadic AD. 13-15 Compared with that in patients with sporadic AD, the ratio of A x-42 to A x-40 is also increased in patients with AD with mutations of the amyloid precursor protein (APP) on chromosome 21 and presenilin 1 mutations on chromosome 14. 13-15 Recent evidence 16,17 suggests that intraneuronal organelles are important in the A cascade and in the formation of the A subtypes. The subtypes A x-42 and A x-40 are formed in the endoplasmic reticulum and the Golgi apparatus, respectively. 16,17 Despite these major breakthroughs, the biological trigger for the A cascade is unknown. Also unknown is whether the process of A formation from APP involves an identical biochemical sequence of events in all A -forming diseases. The study of A in other degenerative diseases may advance our understanding of the role of A in AD and in neuronal degeneration. Dementia with Lewy bodies (DLB) is an increasingly recognized 18-21 subtype of dementia. Although DLB frequently occurs concurrently with AD changes, many patients have pure DLB. 22 In patients with DLB not meeting 1111

PARTICIPANTS AND METHODS PATIENTS WITH DLB We examined the brains of 19 patients (mean age, 75.0 years at death) (Table 1) who met consensus pathological criteria 27 for transitional or neocortical DLB. Specimens from 12 patients were obtained from the Neurology Brain Bank, MCP- HahnemannUniversity, Philadelphia, Pa, andspecimensfrom 7 patients were obtained from the Department of Pathological Sciences University of Manchester, Manchester, England. Neurons were identified as containing Lewy bodies if inclusions had the morphologic appearance of a Lewy body and a nucleuswaspresent. Caseswereidentifiedusinghematoxylineosin stains and confirmed using ubiquitin and -synuclein immunohistochemicalstains. ThisgroupofpatientshadavaryingnumberofdiffuseA PsshownbyA immunohistochemical techniques and silver stains (described later). The brain specimens lacked other notable neuropathological features; inparticular,theydidnotcontaincorticalneurofibrillarytangles. All had infrequent plaques by criteria of the consortium on DLBinternationalworkshop, 28 andbraakstages 29 rangedfrom I to IV. Most would be categorized as having a low likelihood that their dementia is caused by AD. 30 No patients with DLB met criteria of the National Institute on Aging and the Reagan Institute Working Group on Diagnostic Criteria for the Neuropathological Assessment of Alzheimer s Disease 30 for a high likelihood that dementia was related to AD. Although parkinsonism developed in some patients, all patients with DLB had dementia as the first symptom. No other notable neurologic diagnoses were identified. The mean duration of disease was 7.6 years, and all patients but 1 MCP-Hahnemann University case had advanced dementia, were in nursing homes, and required assistance for all activities before death. The other patient had moderate disease severity at death. The disease severity was not known for the 7 patients from the University of Manchester. PATIENTS WITH AD We examined brain specimens from 10 patients from MCP- Hahnemann University, Philadelphia, who met clinical criteria of the National Institute of Neurological Disorders and Stroke and the Alzheimer s Disease and Related Disorders Association 31 for possible or probable AD. All had frequent neuritic plaque scores according to criteria of the Consortium to Establish a Registry for Alzheimer s Disease 28 and Braak 29 stages V or VI. All met criteria of the National Institute on Aging Reagan Institute Working Group 30 for a high likelihood that their dementia was related to AD. All patients lacked intracortical or nigral Lewy bodies. The mean age was 74.5 years at death. The mean disease duration was slightly longer in patients with AD (9.5 years) than in those with DLB, but these differences were not significant (P =.29). All except 1 patient died with advanced disease. This patient had moderately severe manifestations of the disease at death. None had significant concurrent neurologic diagnoses. CONTROL SUBJECTS We examined brain tissue from 17 control subjects who died without significant dementia or neuropathologic diagnoses. Cognitive status was confirmed by medical records review. The mean age at death was 75.9 years. Braak 29 stages were I or II, and staging according to the consortium on DLB international workshop 28 showed that neuritic plaques were infrequent. None had cortical or nigral Lewy bodies. GENOTYPING Genotyping for APOE was performed on brain tissue using a polymerase chain reaction protocol. 32 NEUROPATHOLOGIC METHODS We obtained coronal sections of the middle frontal gyrus, medial temporal lobe (CA1 and CA3 sectors of the hippocampus and parahippocampal gyrus [PHG]) at the level of the lateral geniculate nucleus, and cerebellar hemisphere lateral to the dentate gyrus. Tissue blocks were embedded in paraffin and cut to a thickness of 6 µm. ANTIBODY PREPARATION AND STAINING Sections were stained with antibodies directed against A x-40 (6A; monoclonal, 1:1000 dilution) and A x-42 (11C; monoclonal, 1:1000 dilution). Both antibodies produced using standard methods are C-terminal specific. Briefly, BALB/c mice (Japan SLC, Shizuoka, Japan) were immunized with the synthetic peptides with the sequence of either CVGGVV or CGVVIT, which corresponded to A 36-40 or A 38-42. The aminoterminal cysteine was added to the synthetic peptides for conjugation with keyhole limpet hemocyanin (Wako Chemicals, Osaka, Japan). Afterseveralimmunizations, spleen lymphocytes from the immunized mice were fused with myeloma cells to generate the hybridoma. Following 2 limited dilution series, we screened the 2 monoclonal antibodies 6A and 11C for specificity by enzyme-linked immunosorbent assays using relevant synthetic peptides 14 and Western blot analysis (Figure 1). Western blot specimens included 001, a rabbit polyclonal antibody against the A 1-42 peptide, and a monoclonal antibody (2Fi) directed against A 18-28, in addition to the 6A and 11C antibodies. These antibodies recognize both A x-40 and A x-42 species. A total of 100 ng of peptides was used for each lane. Sodium dodecyl sulfate polyacrylamide gel electrophoresis was carried out under reducing conditions on all specimens, and proteins on gels were transferred on PVDF membrane (Hybond-P, Amersham Life Sciences, United Kingdom). The membrane was blocked with 3% gelatin and incubated with the monoclonal pathological criteria for AD, A plaque (A P) deposition in the cortex is often increased compared with that in agematched controls. 23 In patients with DLB, however, cortical neuronal loss is minimal. 24-26 Differences in A x-40 and A x-42 formation between AD and DLB suggest that the biochemical processes that lead to A formation may differ. To address this issue, we examine the relationship between DLB, AD, normal aging, and the different lengths of A. RESULTS A P DENSITIES Microscopic examination in affected regions showed that the A antibodies detected A Ps in regions consistent with their known distribution in AD. The subtype A x-42 was common in all patients with AD and all patients with DLB except 1 but was more variable in controls. The same brain 1112

antibody, followed by the horseradish peroxidase conjugated second antibody. The color was developed with 4-chloro-1-naphthol. The protein concentration was quantitated by measuring the absorption at 562 nm using an assay kit (BCA, Pierce, Rockford, Ill). In addition, each antibody was examined for the appropriate pattern of immunoreactivity using immunohistochemical technique on paraffin sections of brain from patients with AD. We used the biotinstreptavidin technique with diaminobenzidine and a light hematoxylin counterstain. All sections were pretreated with formic acid. Tissue designated negative control included adjacent sections where nonimmune serum replaced the primary antibodies. Tissue designated positive control included the cerebral cortex of patients with advanced AD known to have an abundance of both A x-40 and A x-42. QUANTITATIVE METHODS All A data were obtained by 2 observers (C.F.L. and Brendan O Connell) who were blinded to the subjects diagnosis during data acquisition. We obtained data from the middle frontal gyrus, the hippocampal CA1 and CA3 regions, the PHG, and the cerebellar hemisphere. To make our data comparable to those of other A studies, we measured A P densities and calculated the percentage of area with A (amyloid burden) from the field with the maximal A P deposition within each region of interest. 8,14 For density data, all A Ps at least as large as a small neuron were counted at a magnification of 10. Each field was 3.5 mm 2. Densities in each region of interest were expressed as the number per square millimeter. To determine the amyloid burden, we used a previously described sampling procedure 33 but captured images using a digital camera (SenSys; Photometrics Ltd, Munich, Germany) attached to a light microscope (Precision Instrument Division, Olympus Corporation, Lake Success, NY). The percentage of each field stained by A was calculated using a semiautomated computer program (Image-Pro; Media Cybernetics, Silver Spring, Md) and sampling 0.6-mm 2 fields. For each specimen, the A x-40 :A x-42 ratio was calculated in each region using both A sampling methods. STATISTICAL ANALYSIS Data were analyzed using an analysis of variance. Data differences that were significant at the P.05 level were further analyzed using the Tukey-Kramer method to determine which groups differed from each other. This method adjusts the P value to allow for multiple comparisons. Table 1. Clinical Features of 29 Patients With Dementia and 17 Control Subjects* Patient or Control No./Sex/Age, y Duration, y Disease Severity APOE Genotype Patients With DLB 1/M/75 5 3 3/3 2/M/73 10 3 3/3 3/M/75 3 2 3/4 4/M/73 10 3 3/3 5/M/72 3 3 3/4 6/M/81 NA NA 3/3 7/F/70 NA NA 3/3 8/F/58 15 3 2/4 9/F/84 10 3 2/4 10/M/82 10 3 3/3 11/M/70 11 3 3/3 12/M/87 8 3 2/3 13/M/72 12 NA 3/4 14/M/66 5 NA 4/4 15/M/62 11 NA 3/3 16/M/73 3 NA 3/3 17/M/79 2 NA 4/4 18/M/88 6 NA 3/4 19/F/85 1 NA 4/4 Patients With AD 20/F/54 10 3 3/3 21/M/69 15 2 2/4 22/F/74 10 3 3/3 23/F/82 10 3 4/4 24/M/69 10 3 3/3 25/M/72 8 3 3/3 26/M/80 13 3 3/4 27/F/76 7 3 3/4 28/F/76 9 3 3/4 29/F/63 11 3 4/4 Control Subjects 30/F/68 0 0 NA 31/M/62 0 0 3/3 32/M/73 0 0 3/3 33/F/83 0 0 3/3 34/F/84 0 0 3/3 35/M/82 0 0 3/3 36/M/91 0 0 3/3 37/M/81 0 0 3/3 38/M/61 0 0 3/3 39/F/88 0 0 3/3 40/M/59 0 0 3/3 41/F/71 0 0 3/3 42/M/67 0 0 3/4 43/M/76 0 0 NA 44/M/67 0 0 3/3 45/M/91 0 0 NA 46/F/87 0 0 NA *Age is age at death, and duration refers to total disease duration. Disease severity score is as follows: 1 = mild symptoms; 2 = moderate symptoms, living at home, requires supervision; and 3 = severe symptoms, requires assistance for all activities of daily living at death. DLB indicates dementia with Lewy bodies; AD, Alzheimer disease; and NA, not available. regions were preferentially affected in all groups, with the greatest number of A Ps in the frontal cortex, the fewest number in the PHG (CA sectors), and the lowest number in the cerebellum. In patients with DLB, A x-42 plaques sometimes appeared smaller and more irregular than those observed in patients with AD. As expected, our A x-40 antibody stained fewer A Ps than the A x-42 antibody. Overall, A x-40 was rare in control specimens and those from patients with DLB and variable in patients with AD. In addition to A P, patients with AD showed A x-40 immunostaining of meningeal and intraparenchymal blood vessels. When A x-40 densities were compared (Table 2), overall differences were significant between control specimens (Figure 2, A), specimens from patients with DLB (Figure 2, C) and those from patients with AD (Figure 2, E) in all regions except the cerebellum. The F scores 1113

kd 44 28.8 18.5 14.4 5.8 2.9 β001 2F 11 C 6 A M a b M a b M a b M a b Figure 1. Western blot analysis showing the specificity of the 6A and 11C antibodies. Lanes labeled M indicate molecular weight markers; a, A x-40 ; and b, A x-42. The first 2 blots were stained by the rabbit polyclonal antibody against A 1-42 ( 001) and a monoclonal antibody against A 18-28 (2F) that recognizes both A x-40 and A x-42. This demonstrates that 6A recognizes A x-40 but not A x-42 and that 11C recognizes A x-42 but not A x-40 ;6Aand 11C do not cross-react. revealed that the group with AD had greater A x-40 plaque densities than either the DLB group or the control group. In the cerebellum, statistical analysis was not possible because A x-40 was absent in both the control group and the group with DLB (no variance within groups). Overall, the A x-40 burden (percentage of cortex with A x-40 immunoreactivity) paralleled A x-40 density data, with A x-40 densities being less in controls and patients with DLB than in patients with AD. These differences reached significance in all regions except the cerebellum. The A x-42 plaque densities showed overall differences among controls (Figure 2, B), patients with DLB (Figure 2, D), and patients with AD (Figure 2, F), with the groups with DLB and AD showing greater densities of A x-42 plaques than controls. In the frontal gyrus, CA3, and PHG, significant differences were observed among the 3 groups, with the group with DLB having A x-42 plaque densities intermediate between those of the group with AD and controls. In the CA1 region, the control group had significantly fewer plaques than either of the other 2 groups. Differences between patients with AD and Table 2. Plaque Density and Burden of -Amyloid (A ) Subtypes in Postmortem Brain Tissue From Patients With Dementia and Controls* Group Variable AD DLB Controls F Score P Middle Frontal Gyrus A x-40 31.52 1.43 1.61 11.81.001 A x-42 94.30 59.88 28.20 13.57.001 A x-40 3.39 0.17 0.14 8.10.001 A x-42 7.70 5.19 2.99 8.89.001 CA3 of Hippocampus A x-40 7.43 0.24 0.09 10.18.001 A x-42 14.68 6.29 0.64 4.26.02 A x-40 1.49 0.04 0.01 9.93.001 A x-42 2.33 0.74 0.05 4.13.02 CA1 of Hippocampus A x-40 10.91 1.40 0.28 20.21.001 A x-42 28.94 15.08 2.57 10.06.001 A x-40 1.68 0.16 0.03 11.38.001 A x-42 2.41 1.17 0.26 9.36.001 Parahippocampal Gyrus A x-40 20.11 1.33 1.52 6.65.003 A x-42 76.89 40.97 15.51 22.72.001 A x-40 2.66 0.20 0.20 6.20.005 A x-42 6.46 3.31 1.39 12.20.001 Cerebellar Hemisphere A x-40 1.92 0 0...... A x-42 5.38 0.14 0.09 12.48.001 A x-40 0.06 0 0...... A x-42 0.48 0.01 0.01 8.10.001 *AD indicates Alzheimer disease; DLB, dementia with Lewy bodies; and ellipses, data not calculable. 1114

A B C D E F 30 µm Figure 2. Photomicrographs of sections of frontal lobe from control subjects (A and B), patients with dementia with Lewy bodies (DLB) (C and D), and patients with Alzheimer disease (AD) (E and F) after immunohistochemical staining for A x-40 (A, C, and E) and A x-42 (B, D, and F) (original magnification, 10). The A x-40 plaques are almost nonexistent in control subjects (A) and patients with DLB (C) but are numerous in those with AD (E). The A x-42 plaques are numerous in patients with DLB (D) and those with AD (F) but rare in control subjects (B). those with DLB were not significant in CA1. In the cerebellum, the group with AD showed greater densities than the group with DLB or the control group. The A x-42 burden also showed overall differences among the 3 groups. The control group showed a lower burden than the group with DLB, and the group with DLB showed less A x-42 than the group with AD in all regions except the cerebellum, where the group with AD had greater A x-42 burden than either of the other groups. The A x-40 :A x-42 ratio in all regions was significantly greater in the group with AD than in either the group with DLB or controls, whether density or amyloid burden was assessed (Figure 3 and Table 3). The A x-40 :A x-42 ratio of the group with DLB was sometimes less than that of the control group, although these differences did not reach significance because of the small amount of A x-40 in each group. In the cerebellum, ratios were 1.0 for the group with DLB and the control group and approached 0 for the group with AD because A x-40 plaques are exceedingly rare in the cerebellum, even in persons with advanced AD. APOE GENOTYPE In most regions, patients with DLB (n = 9) and those with AD (n = 6) with the APOE 4 allele had similar densities and percentage of area with A P deposition compared with those lacking this allele (n = 9 and n = 4, respec- 1115

tively). In the control group, only 1 subject had the APOE 4 allele. In patients with DLB, differences between groups with and without APOE 4 varied, reaching significance in the PHG, where A x-40 densities were 23.7/mm 2 and 58.7/mm 2, respectively (t 1 = 2.809, P =.01). In patients with AD, the APOE genotype influenced A x-40 deposition more consistently, with mean A x-40 densities consistently greater in the group with AD with the 4 allele than in those without the 4 allele. These differences in A x-40 deposition reached significance in sections from the CA1 and the PHG (4.86/mm 2 and 16.97/mm 2 [t = 2.726, P =.03] vs 1.54/mm 2 and 18.68/mm 2 [t = 2.377, P =.04], respectively). The presence of A x-42 was not associated with increased A P deposition. Aβ Plaques, No./mm 2 Aβ40:Aβ42 Ratio 120 100 80 60 40 20 0 1.0 0.8 0.6 0.4 0.2 0 A B Aβ x-40 Aβ x-42 Aβ x-40 Aβ x-42 Aβ x-40 Aβ x-42 DLB AD Control DLB AD Disease Group Control Figure 3. Graphs demonstrating the density of -amyloid (A ) subtypes A x-40 and A x-42 plaques (A) and the ratio of A x-40 to A x-42 (B) in the frontal lobe from the different patient groups and control subjects. Whether density or ratio data are used, control subjects and patients with dementia with Lewy bodies (DLB) show minimal A x-40 densities, whereas patients with Alzheimer disease (AD) show varying amounts of A x-40 deposition. The deposition of A x-42 is high in patients with DLB and those with AD and lower in control subjects. The A x-40 :A x-42 ratio is less in patients with DLB than in those with AD. COMMENT We confirmed previous reports that patients with DLB, those with AD, and control subjects have A Ps. We extend this finding by determining that the pattern of A P deposition differs between those with DLB and AD in all brain regions examined. In patients with DLB, A x-40 plaque densities were less than the densities in patients with AD. The A x-42 plaque densities were nearly as great in patients with DLB as they were in those with AD. Therefore, the A x-40 :A x-42 ratio was less in patients with DLB than that in patients with AD. Also, the specimens of brain from patients with DLB lacking significant neuritic degeneration and severe neuronal losses contain increased densities of A Ps compared with age-matched controls. The pattern of A P deposition, however, is similar in normal aging and in patients with DLB, with almost all A Ps being composed of A x-42 ;A x-40 plaques were nearly nonexistent. Why the A x-40 :A x-42 ratio in patients with DLB differs from that in patients with AD is unknown. Our observation that A x-40 densities in patients with DLB are less than those in patients with AD suggests that differences may occur between these 2 conditions in APP metabolism. We found no evidence to support the notion, however, that regional differences exist in the susceptibility to A P formation in these 2 conditions because the regional distribution of A P of both subtypes was similar in patients with AD and those with DLB. For example, in both conditions, the lowest density of A Ps (of either subtype) was found in the cerebellum, followed by the CA hippocampal subregions. The largest number of both A x-40 and A x-42 plaques was found in the cerebral cortex in patients with DLB and those with AD. Furthermore, the differences in A x-40 :A x-42 ratios between patients with AD and those with DLB are not limited to specific brain regions. The APOE genotype affects the likelihood of AD developing. Persons carrying the APOE 4 allele are more likely to acquire AD, and symptoms are more likely to develop at an earlier age 34,35 than in those lacking this allele. In patients with AD, APOE affects the deposition of A x-40 and not A x-42. 36 Our data from patients with AD confirm this trend. In our study, however, the effect of the APOE genotype was less marked in patients with DLB Table 3. Ratios of Densities and Burdens of -Amyloid (A ) Subtypes in Brain Tissue* Region of Brain Group FC CA3 CA1 PHG CBM A x-40 :A x-42 Ratios Based on Densities Control 0.06 0.09 0.09 0.08 0.00 AD 0.34 0.45 0.39 0.30 0.01 DLB 0.03 0.04 0.08 0.03 0.00 A x-40 :A x-42 Ratios Based on Amyloid Burden Control 0.05 0.14 0.09 0.13 0.00 AD 0.46 0.58 0.67 0.42 0.03 DLB 0.04 0.05 0.08 0.06 0.00 *FC indicates middle frontal gyrus; CA3 and CA1, sectors of hippocampus; PHG, parahippocampal gyrus; CBM, cerebellar hemisphere; AD, Alzheimer disease; and DLB, dementia with Lewy bodies. 1116

than in those with AD. The overall poor relationship between the APOE genotype and A in individual patients with DLB may be due to the paucity of A x-40 plaques in those with DLB. When group trends are examined, however, the frequency of the 4 allele and the number of A x-40 plaques are lower in the group with DLB than in the group with AD. Therefore, our data do not contradict the hypothesis that APOE principally affects A x-40. The relationship between in vivo neurotoxicity and A subtypes remains unknown. We postulate that the subtype of A deposited may be related to neuronal cell death. Many investigators think that A x-42 is the more toxic and aggressive form of A because brain tissue from patients with early-onset AD (from both presenilin 1 and APP mutations) shows a reduced ratio of A x-40 : A x-42. 13-15 Patients with AD who have both presenilin 1 and APP have more severe neuronal losses and at an earlier age than comparable patients with late-onset AD. 24,25,33 Our data are more compatible with the hypothesis that A x-42 is benign and that A x-40 (or the intraneuronal processes that contribute to A x-40 formation) is more strongly associated with neuronal degeneration. A previous study 26 reported that cortical neuronal loss is small in patients with DLB compared with the severe losses seen in those with AD. If A x-42 exerts a major, direct neurotoxic effect, we would expect to find much lower levels of A x-42 in the brain specimens of patients with DLB. Our immunohistochemical data from patients with DLB suggest that neuronal degeneration may occur after a threshold of A x-40 is reached. Any effect from differences in the aminoterminal of A cannot be addressed by this study because the antibodies we used were specific only for the carboxyterminal. The factors determining the relative proportion of A x-40 to A x-42 formed at the time of the metabolic breakdown of APP are not well understood. The subtypes A x-40 and A x-42 are both produced in the neuron during the metabolic degradation of APP. 16,17 Cell culture studies by Hartmann et al 16 and Cook et al 17 suggest that A x-42 synthesis occurs in the endoplasmic reticulum, whereas A x-40 is produced at a more distal point in the Golgi apparatus. Further characterization of these intraneuronal events will be important for our understanding of the role of A in neuronal degeneration. Recently, endoplasmic reticulum associated A protein (ERAB) has been shown 37 to bind A x-42 in patients with AD. This protein may be crucial to the pathogenesis of AD because ERAB is overexpressed in the brain of patients with AD. In addition, cell culture studies show that the toxic effect of A on neurons is reduced when ERAB is blocked and increased when ERAB is overexpressed. The levels of ERAB in patients with DLB have not been determined. Because increased ERAB levels are associated with increased A neurotoxicity, however, ERAB may not be increased in patients with DLB as neuronal losses in such patients are small. Dickson et al 23 have termed patients with DLB with diffuse A P deposition as having pathological aging. Although the patients with DLB in this study do not meet consensus criteria 30 for a high likelihood that their symptoms were due to AD, it could be argued that the increased amount of A indicates that they are in an early stage of the AD process and thus had incipient AD. Our data cannot determine whether A deposition is fundamentally different between patients with AD and those with DLB or whether plaque formation is in an earlier stage of AD, particularly because our patients with DLB had slightly shorter disease durations than the group with AD. Another study 38 of A P deposition in patients with DLB that examined frontal cortex showed a similar trend. The near absence, however, of A x-40 in patients with A x-42 densities approaching those of patients with AD suggests that the events leading to A deposition in patients with AD and those with DLB may differ. Further study of factors determining which APP metabolite is formed in patients with DLB, those with AD, and as a result of normal aging may advance our understanding of the natural history of APP and A in neurodegenerative diseases. Accepted for publication December 11, 1998. This study was supported in part by grant 13623 from the National Institute on Aging, Bethesda, Md, and the Robert Potamkin Fund (Dr Lippa). We acknowledge Brendan O Connell for assistance with data acquisition, the Joseph and Kathleen Bryan Brain Bank at Duke University Medical Center, Durham, NC, which is supported by grant AG05128 from the National Institute on Aging and Glaxo Wellcome Inc, Research Triangle Park, NJ. We also acknowledge the Grant in Aid for Scientific Research on Priority Area (Dr Mori). Reprints: Carol F. Lippa, MD, Department of Neurology, MCP-Hahnemann University, 3300 Henry Ave, Philadelphia, PA 19129 (e-mail: lippa@auhs.edu). REFERENCES 1. Mann DMA. The pathogenesis and progression of the pathological changes of Alzheimer s disease. Ann Med. 1989;21:133-136. 2. Jarrett JT, Berger EP, Lansbury PT Jr. The C-terminus of the protein is critical in amyloidogenesis. Ann N Y Acad Sci. 1993;695:144-148. 3. Barrow CJ, Zagorski MG. Solution structures of peptide and its constituent fragments: relation to amyloid deposition. Science. 1991;253:179-182. 4. Mori H, Takio K, Ogawara M, Selkoe D. Mass spectrometry of purified amyloid protein in Alzheimer s disease. J Biol Chem. 1992;267:17082-17086. 5. Miller DL, Papayannopoulos IA, Styles J, et al. Peptide compositions of the cerebrovascular and senile plaque core amyloid deposits of Alzheimer s disease. Arch Biochem Biophys. 1993;301:41-52. 6. Selkoe DJ. Alzheimer s disease: a central role for amyloid. J Neuropathol Exp Neurol. 1994;53:438-447. 7. Tamaoka A, Kondo T, Odaka A, et al. Biochemical evidence for the long-tail form (A 1-42/43 ) of amyloid protein as a seed molecule in cerebral deposits of Alzheimer s disease. Biochem Biophys Res Commun. 1994;205:834-842. 8. Iwatsubo T, Odaka A, Suzuki N, Mizusawa H, Nukina N, Ihara Y. Visualization of A 42(43) and A 40 in senile plaques with end-specific A monoclonals: evidence that an initially deposited species is A 42(43). Neuron. 1994;13: 45-53. 9. Iwatsubo T, Mann DMA, Odaka A, Suzuki N, Ihara Y. Amyloid protein (A ) deposition: A 42(43) precedes A 40 in Down syndrome. Ann Neurol. 1995;37:294-299. 10. Mann DM, Iwatsubo T, Cairns NJ, et al. Amyloid protein (A ) deposition in chromosome 14-linked Alzheimer s disease: predominance of A 42(43). Ann Neurol. 1996;40:149-156. 11. Lemere CA, Lopera F, Kosik KS, et al. The E280A presenilin 1 Alzheimer mutation produces increased A 42 deposition and severe cerebellar pathology. Nat Med. 1996;2:1146-1150. 12. Lippa CF, Nee LE, Mori H, St George-Hyslop PH. A -42 deposition precedes other changes in PS-1 Alzheimer s disease [letter]. Lancet. 1998;352:1117-1118. 13. Mann DM, Iwatsubo T, Ihara Y, et al. Predominant deposition of amyloid- 42 1117

(43) in plaques in cases of Alzheimer s disease and hereditary cerebral hemorrhage associated with mutations in the amyloid precursor protein gene. Am J Pathol. 1996;148:1257-1266. 14. Suzuki N, Cheung TT, Cai XD, et al. An increased percentage of long amyloid protein secreted by familial amyloid protein precursor ( APP717) mutants. Science. 1994;264:1336-1340. 15. Song XH, Suzuki N, Bird T, et al. Plasma amyloid protein (A ) ending at A 42 (43) is increased in carriers of familial AD (FAD) linked to chromosome 14 [abstract]. Soc Neurosci Abstr. 1995;2:1501. 16. Hartmann T, Bieger SC, Bruhl B, et al. Distinct sites of intracellular production for Alzheimer s disease A 40/42 amyloid peptides. Nat Med. 1997;3:1016-1020. 17. Cook DG, Forman MS, Sung JC, et al. Alzheimer s A (1-42) is generated in the endoplasmic reticulum/intermediate compartment of NT2N cells. Nat Med. 1997; 3:1021-1023. 18. Dickson DW, Ruan D, Crystal H, et al. Hippocampal degeneration differentiates diffuse Lewy body disease (DLBD) from Alzheimer s disease: light and electron microscopic immunocytochemistry of CA2-3 neurites specific to DLBD. Neurology. 1991;41:1402-1409. 19. Hansen L, Salmon D, Galasko D, et al. The Lewy body variant of Alzheimer s disease: a clinical and pathological entity. Neurology. 1990;40:1-8. 20. Perry RH, Irving D, Blessed G, Fairbairn A, Perry EK. Senile dementia of Lewy body type: a clinically and neuropathologically distinct type of Lewy body dementia in the elderly. J Neurol Sci. 1990;95:119-139. 21. Lennox G, Lowe J, Morrell K, Landon M, Mayer RJ. Anti-ubiquitin immunocytochemistry is more sensitive than conventional techniques in the detection of diffuse Lewy body disease. J Neurol Neurosurg Psychiatry. 1989;52:67-71. 22. Kosaka K. Diffuse Lewy body disease in Japan. J Neurol. 1990;237:197-204. 23. Dickson DW, Crystal H, Mattiace LA, et al. Diffuse Lewy body disease: light and electron microscopic immunocytochemistry of senile plaques. Acta Neuropathol (Berl). 1989;78:572-584. 24. Lippa CF, Smith TW, Swearer JM. Alzheimer s disease and Lewy body disease: a comparative clinicopathological study [published correction appears in Ann Neurol. 1994;35:380]. Ann Neurol. 1994;35:81-88. 25. Lippa CF, Pulaski-Salo D, Dickson DW, Smith TW. Alzheimer s disease, Lewy body disease and aging: a comparative study of the perforant pathway. J Neurol Sci. 1997;147:161-166. 26. Gomez-Isla T, Growdon W, McNamara M, Growdon JH, Hyman BT. Diffuse Lewy body dementia: quantitative neuropathological studies and APOE genotyping [abstract]. Neurology. 1997;48(suppl):A140. 27. McKeith IG, Galasko D, Kosaka K, et al. Consensus guidelines for the clinical and pathologic diagnosis of dementia with Lewy bodies (DLB): report of the consortium on DLB international workshop. Neurology. 1996;46:1113-1124. 28. Mirra SS, Heyman A, McKeel D, et al. The Consortium to Establish a Registry for Alzheimer s Disease (CERAD), II: standardization of the neuropathologic assessment of Alzheimer s disease. Neurology. 1991;41:479-486. 29. Braak H, Braak E. Staging of Alzheimer s disease-related neurofibrillary changes. Neurobiol Aging. 1995;16:271-284. 30. National Institute on Aging and Reagan Institute Working Group on Diagnostic Criteria for the Neuropathological Assessment of Alzheimer s Disease. Consensus recommendations for the postmortem diagnosis of Alzheimer disease. Neurobiol Aging. 1997;18(suppl):S1-S3. 31. McKhann G, Drachman DA, Folstein M, Katzman R, Price D, Stadlan EM. Clinical diagnosis of Alzheimer s disease: report of the NINCDS-ADRDA Work Group under the auspices of Department of Health and Human Services Task Force on Alzheimer s Disease. Neurology. 1984;34:939-944. 32. Wenham PR, Price WH, Blandell G. Apolipoprotein E genotyping by one-stage PCR [letter]. Lancet. 1991;337:1158-1159. 33. Lippa CF, Saunders AM, Smith TW, et al. Familial and sporadic Alzheimer s disease: neuropathology cannot exclude a final common pathway. Neurology. 1996; 46:406-412. 34. Schmechel DE, Saunders AM, Strittmatter WJ, et al. Increased amyloid -peptide deposition in cerebral cortex as a consequence of apolipoprotein E genotype in late-onset Alzheimer disease. Proc Natl Acad Sci USA.1993;90:9649-9653. 35. Mann DM, Iwatsubo T, Pickering-Brown SM, Owen F, Saido TC, Perry RH. Preferential deposition of amyloid protein (A ) in the form of A 40 in Alzheimer s disease is associated with a gene dosage effect of the apolipoprotein E 4 allele. Neurosci Lett. 1997;221:81-84. 36. Gearing M, Mori H, Mirra SS. A -peptide length and apolipoprotein E genotype in Alzheimer s disease. Ann Neurol. 1996;39:395-399. 37. Yan SD, Fu J, Soto C, et al. An intracellular protein that binds amyloid- peptide and mediates neurotoxicity in Alzheimer s disease. Nature. 1997;389:689-695. 38. Mann DMA, Brown SM, Owen F, Baba M, Iwatsubo T. Amyloid protein (A ) deposition in dementia with Lewy bodies: predominance of A 42(43) and paucity of A 40 compared with sporadic Alzheimer s disease. Neuropathol Appl Neurobiol. 1998;24:187-194. 1118