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Pittsburgh compound-B does not detect cotton wool plaques in PS-1 mutation carriers
Poster Presentations: P1
P1-110
SPACE-LIKE RADIATION CAUSES ACCELERATED COGNITIVE IMPAIRMENT AND INCREASED ALZHEIMER’S-LIKE PATHOLOGY IN CRND8 APP TRANSGENIC MICE
Xinglong Wang1, Wenzhang Wang1, Gemma Casadesus1, HyoungGon Lee1, Xiongwei Zhu1, 1Case Western Reserve University, Cleveland, Ohio, United States. Contact e-mail: [email protected] Background: Detrimental effects of space irradiation on the central nervous system have been known for some time and emerging evidence support a potential risk for Alzheimer disease (AD) as a valid concern for long duration space exploration. However, our understanding of the effect of space radiation on neuronal function remains limited and few studies have been conducted to investigate the effect of spaceradiation exposure on the onset and progress of AD and the underlying mechanisms. Methods: As an AD mouse model, CRND8 mouse overexpressing FAD-causing APP mutations were exposed to 56Fe (600Mev/u) and 28Si (300Mev/u) at 0.5 and 2Gy at 3 and 6 months of age and brain tissues harvested for pathology analysis after behavioral tests were performed at various time post-irradiation. To obtain mechanistic insights, we compared difference between primary hippocampal neurons from CRND8 transgenic mouse as a cell model for AD to neurons from their littermate controls in response to 56Fe or 28Si at 0.1, 0.5 and 2 Gy and studied at various post-irradiation times by immunocytochemistry and immunoblot analysis for various parameters including cell death, cell cycle, oxidative stress, APP processing, tau phosphorylation, mitochondrial function and synaptic changes. Results: CRND8 mice demonstrated accelerate decrease in cognitive function measured by novel object recognition and contextual fear conditioning 6 months after exposure to 56Fe and 28Si at both 0.5Gy and 2Gy. Indeed, increased amyloid pathology in both hippocampus and cortex was also apparent in irradiated CRND8 mice. The quantitative analysis of golgi stain-impregnated segments of apical dendritic branches of the CA1 pyramidal neurons revealed that exposure to 56Fe and 28Si caused significant reduction in spine numbers. There was a dose-dependent increase in DNA damage and oxidative stress as well as synaptic dysfunction, tau phosphorylation and cell death in either 56Fe- or 28Si-exposed WT neurons. Importantly, APP neurons demonstrated significantly higher abnormalities in all these parameters measured. Conclusions: Overall, our study demonstrated that space-like irradiation can increase AD-type deficits in AD mouse model which may have implications in long term space travel to Mars with accumulative irradiation dose exceeding certain levels.
P1-111
PITTSBURGH COMPOUND-B DOES NOT DETECT COTTON WOOL PLAQUES IN PS-1 MUTATION CARRIERS
Milos Ikonomovic1, Eric Abrahamson1, Julie Price1, Chester Mathis1, William Klunk1, 1University of Pittsburgh, Pittsburgh, Pennsylvania, United States. Contact e-mail: [email protected] Background: In Alzheimer’s disease (AD), [C-11]PiB retention in vivo is believed to reflect amounts of compact (cored/neuritic) plaques consisting of fibrillar amyloid-b (Ab). However, in familial AD with presenilin-1 (PS-1) mutations, PiB retention is most prominent in the striatum which contains exclusively diffuse Ab plaques, and moderate in neocortical regions containing both compact and diffuse Ab plaques. Therefore the relationship between PiB binding and diffuse plaques remains unclear. In this study, we explored the interaction of a highly fluorescent PiB derivative (6-CN-PiB) with striatal and neocortical plaques of various morphologies. Methods: Consecutive thin paraffin sections of caudate, frontal and temporal cortices, and cerebellum were assessed for Ab immunohistochemistry (mab 4G8) and histology with hematoxylin/eosin (H&E), 6-CN-PiB, and a highly fluorescent Congo red derivative (X-34) in two PS-1 mutation (A426P) cases compared to three sporadic AD cases. Results: In the neocortex of all cases, both 6-CN-PiB and X-34 labeled compact Ab plaques brightly, and diffuse Ab plaques
P191
weakly. The only exception were cotton wool plaques (CWP) in familial AD; in these large Ab-immunoreactive plaques, easily identified in H&E preparations, prominent X-34 labeling indicated their beta-sheet structure but 6-CN-PiB fluorescence was not above background levels. Diffuse Ab-immunoreactive, X-34-positive and 6-CN-PiB-negative plaques were also observed in the cerebellum of both familial and sporadic AD cases. Striatal diffuse Ab plaques were labeled moderately with 6-CN-PiB and X-34, similar in familial and sporadic AD except for greater striatal plaque load in familial AD. Conclusions: The current histological study provides a high resolution examination of the interaction between PiB and diffuse Ab plaques, particularly the CWP type, in PS-1 mutation carriers. Besides cerebellar diffuse Ab plaques, CWP are the second plaque type not detected using 6-CN-PiB histology. The possibility that the difference in CWP labeling between X-34 and 6CN-PiB is due to differences in their fluorescence intensities is unlikely considering that these dyes showed comparable labeling of striatal diffuse plaques as well as neocortical diffuse and compact plaques. The apparent beta-sheet structure of CWPs, demonstrated using X-34, suggests that a unique tertiary structure or a unique combination of modified Ab species may prevent their detection using PiB.
P1-112
ABERRANT EXPRESSION OF THE ASTROCYTE GLUTAMATE TRANSPORTER EAAT2 OCCURS IN EARLY-STAGE ALZHEIMER’S DISEASE AND PRECEDES HIPPOCAMPAL SYNAPTIC LOSS
James Meabon1, Kole Meeker2, Bertrand R. Huber1, Randy Woltjer3, David Cook1, 1VA Medical Center, Seattle, Washington, United States; 2 University of Washington, Seattle, Washington, United States; 3Oregon Health & Science University, Portland, Oregon, United States. Contact e-mail: [email protected] Background: Synaptically released glutamate is cleared mostly by astrocytic glutamate transporters. This function of astrocytes is crucial for regulating spatial and temporal synaptic specificity. In the hippocampus, greater than 80% of synaptically-released glutamate is taken up by the astrocytic glutamate transporter EAAT2, also known as GLT-1. To examine the role of A b in astrocyte dysfunction we investigated the impact of A b 1-42 exposure on the morphological integrity of EAAT2-positive astrocytes in acute hippocampal slices. To address the potential significance of astrocytic dysfunction in AD we examined EAAT2 expression in the hippocampus of mild cognitively impaired (MCI) and late-stage AD patients. Methods: Confocal microscopy was performed on hippocampi from normal subjects, subjects with a clinical dementia rating (CDR) ¼ 0.5 (intended to approximate mild cognitive impairment), and AD subjects. Hippocampal slices were prepared from C57BL6 mouse brains (P14-21) using standard methods and were incubated for 30 minutes with 500nM synthetic human Ab 4. Results: Ab 1-42 exposure induced rapid (approx. 30 min) re-sculpturing of astrocytic morphology in hippocampal slices that was evidenced by reduced process length (p<0.001) and reduced branching (p<0.05). This increase in astrocyte dysmorphology produced micro-domains where PSD95-positive synaptic puncta appeared separated from EAAT2-positive astrocytic processes. EAAT2 immunostaining of normal, CDR¼0.5, and AD hippocampus revealed markedly similar astrocytic dysmorphology in both MCI and AD cases that was evidenced by loss of fine EAAT2-positive distal astrocyte processes, aberrant accumulation of EAAT2 in astrocyte cell bodies, and distinct micro-domains of EAAT2 loss in fields that were immuno-positive for both PSD95 and GFAP. In hilus significant loss of EAAT2 immunostaining in CDR¼0.5 patients (p<0.034) and AD patients (p<0.019) preceded loss of PSD95 in CDR¼0.05 patients (nonsignificant) and AD patients (p<0.001) compared to controls. Conclusions: Ab 1-42 -induces astrocyte dysmorphology and mislocalization of EAAT2. Markedly similar astrocytic dysmorphology was observed in early and latestage AD suggesting that AD pathogenesis may involve a form of early occurring synaptic neglect arising from disorganized glial/synapse morphologic associations. This may leave synapses increasingly isolated from efficient access to critical clearance functions and other forms of metabolic and trophic support that is provided by astrocytes.
P1-110
SPACE-LIKE RADIATION CAUSES ACCELERATED COGNITIVE IMPAIRMENT AND INCREASED ALZHEIMER’S-LIKE PATHOLOGY IN CRND8 APP TRANSGENIC MICE
Xinglong Wang1, Wenzhang Wang1, Gemma Casadesus1, HyoungGon Lee1, Xiongwei Zhu1, 1Case Western Reserve University, Cleveland, Ohio, United States. Contact e-mail: [email protected] Background: Detrimental effects of space irradiation on the central nervous system have been known for some time and emerging evidence support a potential risk for Alzheimer disease (AD) as a valid concern for long duration space exploration. However, our understanding of the effect of space radiation on neuronal function remains limited and few studies have been conducted to investigate the effect of spaceradiation exposure on the onset and progress of AD and the underlying mechanisms. Methods: As an AD mouse model, CRND8 mouse overexpressing FAD-causing APP mutations were exposed to 56Fe (600Mev/u) and 28Si (300Mev/u) at 0.5 and 2Gy at 3 and 6 months of age and brain tissues harvested for pathology analysis after behavioral tests were performed at various time post-irradiation. To obtain mechanistic insights, we compared difference between primary hippocampal neurons from CRND8 transgenic mouse as a cell model for AD to neurons from their littermate controls in response to 56Fe or 28Si at 0.1, 0.5 and 2 Gy and studied at various post-irradiation times by immunocytochemistry and immunoblot analysis for various parameters including cell death, cell cycle, oxidative stress, APP processing, tau phosphorylation, mitochondrial function and synaptic changes. Results: CRND8 mice demonstrated accelerate decrease in cognitive function measured by novel object recognition and contextual fear conditioning 6 months after exposure to 56Fe and 28Si at both 0.5Gy and 2Gy. Indeed, increased amyloid pathology in both hippocampus and cortex was also apparent in irradiated CRND8 mice. The quantitative analysis of golgi stain-impregnated segments of apical dendritic branches of the CA1 pyramidal neurons revealed that exposure to 56Fe and 28Si caused significant reduction in spine numbers. There was a dose-dependent increase in DNA damage and oxidative stress as well as synaptic dysfunction, tau phosphorylation and cell death in either 56Fe- or 28Si-exposed WT neurons. Importantly, APP neurons demonstrated significantly higher abnormalities in all these parameters measured. Conclusions: Overall, our study demonstrated that space-like irradiation can increase AD-type deficits in AD mouse model which may have implications in long term space travel to Mars with accumulative irradiation dose exceeding certain levels.
P1-111
PITTSBURGH COMPOUND-B DOES NOT DETECT COTTON WOOL PLAQUES IN PS-1 MUTATION CARRIERS
Milos Ikonomovic1, Eric Abrahamson1, Julie Price1, Chester Mathis1, William Klunk1, 1University of Pittsburgh, Pittsburgh, Pennsylvania, United States. Contact e-mail: [email protected] Background: In Alzheimer’s disease (AD), [C-11]PiB retention in vivo is believed to reflect amounts of compact (cored/neuritic) plaques consisting of fibrillar amyloid-b (Ab). However, in familial AD with presenilin-1 (PS-1) mutations, PiB retention is most prominent in the striatum which contains exclusively diffuse Ab plaques, and moderate in neocortical regions containing both compact and diffuse Ab plaques. Therefore the relationship between PiB binding and diffuse plaques remains unclear. In this study, we explored the interaction of a highly fluorescent PiB derivative (6-CN-PiB) with striatal and neocortical plaques of various morphologies. Methods: Consecutive thin paraffin sections of caudate, frontal and temporal cortices, and cerebellum were assessed for Ab immunohistochemistry (mab 4G8) and histology with hematoxylin/eosin (H&E), 6-CN-PiB, and a highly fluorescent Congo red derivative (X-34) in two PS-1 mutation (A426P) cases compared to three sporadic AD cases. Results: In the neocortex of all cases, both 6-CN-PiB and X-34 labeled compact Ab plaques brightly, and diffuse Ab plaques
P191
weakly. The only exception were cotton wool plaques (CWP) in familial AD; in these large Ab-immunoreactive plaques, easily identified in H&E preparations, prominent X-34 labeling indicated their beta-sheet structure but 6-CN-PiB fluorescence was not above background levels. Diffuse Ab-immunoreactive, X-34-positive and 6-CN-PiB-negative plaques were also observed in the cerebellum of both familial and sporadic AD cases. Striatal diffuse Ab plaques were labeled moderately with 6-CN-PiB and X-34, similar in familial and sporadic AD except for greater striatal plaque load in familial AD. Conclusions: The current histological study provides a high resolution examination of the interaction between PiB and diffuse Ab plaques, particularly the CWP type, in PS-1 mutation carriers. Besides cerebellar diffuse Ab plaques, CWP are the second plaque type not detected using 6-CN-PiB histology. The possibility that the difference in CWP labeling between X-34 and 6CN-PiB is due to differences in their fluorescence intensities is unlikely considering that these dyes showed comparable labeling of striatal diffuse plaques as well as neocortical diffuse and compact plaques. The apparent beta-sheet structure of CWPs, demonstrated using X-34, suggests that a unique tertiary structure or a unique combination of modified Ab species may prevent their detection using PiB.
P1-112
ABERRANT EXPRESSION OF THE ASTROCYTE GLUTAMATE TRANSPORTER EAAT2 OCCURS IN EARLY-STAGE ALZHEIMER’S DISEASE AND PRECEDES HIPPOCAMPAL SYNAPTIC LOSS
James Meabon1, Kole Meeker2, Bertrand R. Huber1, Randy Woltjer3, David Cook1, 1VA Medical Center, Seattle, Washington, United States; 2 University of Washington, Seattle, Washington, United States; 3Oregon Health & Science University, Portland, Oregon, United States. Contact e-mail: [email protected] Background: Synaptically released glutamate is cleared mostly by astrocytic glutamate transporters. This function of astrocytes is crucial for regulating spatial and temporal synaptic specificity. In the hippocampus, greater than 80% of synaptically-released glutamate is taken up by the astrocytic glutamate transporter EAAT2, also known as GLT-1. To examine the role of A b in astrocyte dysfunction we investigated the impact of A b 1-42 exposure on the morphological integrity of EAAT2-positive astrocytes in acute hippocampal slices. To address the potential significance of astrocytic dysfunction in AD we examined EAAT2 expression in the hippocampus of mild cognitively impaired (MCI) and late-stage AD patients. Methods: Confocal microscopy was performed on hippocampi from normal subjects, subjects with a clinical dementia rating (CDR) ¼ 0.5 (intended to approximate mild cognitive impairment), and AD subjects. Hippocampal slices were prepared from C57BL6 mouse brains (P14-21) using standard methods and were incubated for 30 minutes with 500nM synthetic human Ab 4. Results: Ab 1-42 exposure induced rapid (approx. 30 min) re-sculpturing of astrocytic morphology in hippocampal slices that was evidenced by reduced process length (p<0.001) and reduced branching (p<0.05). This increase in astrocyte dysmorphology produced micro-domains where PSD95-positive synaptic puncta appeared separated from EAAT2-positive astrocytic processes. EAAT2 immunostaining of normal, CDR¼0.5, and AD hippocampus revealed markedly similar astrocytic dysmorphology in both MCI and AD cases that was evidenced by loss of fine EAAT2-positive distal astrocyte processes, aberrant accumulation of EAAT2 in astrocyte cell bodies, and distinct micro-domains of EAAT2 loss in fields that were immuno-positive for both PSD95 and GFAP. In hilus significant loss of EAAT2 immunostaining in CDR¼0.5 patients (p<0.034) and AD patients (p<0.019) preceded loss of PSD95 in CDR¼0.05 patients (nonsignificant) and AD patients (p<0.001) compared to controls. Conclusions: Ab 1-42 -induces astrocyte dysmorphology and mislocalization of EAAT2. Markedly similar astrocytic dysmorphology was observed in early and latestage AD suggesting that AD pathogenesis may involve a form of early occurring synaptic neglect arising from disorganized glial/synapse morphologic associations. This may leave synapses increasingly isolated from efficient access to critical clearance functions and other forms of metabolic and trophic support that is provided by astrocytes.