Searched for: person:wisnit01
Ex - vivo magnetic resonance imaging of beta - amyloid plaques in transgenic AD mice [Meeting Abstract]
Tang, C.; Hajianpour, A.; Aguinaldo, G.; Ho, L.; Pasinetti, G.; Hof, P. R.; Perl, D. P.; Sadowski, M.; Wisniewski, T.
According to the amyloid hypothesis, it is the progressive accumulation of beta-amyloid that leads to a cascade of neurodegenerative processes in Alzheimer's disease (AD). Thus, current strategies for diagnosis and treatment evaluation rely on the ability to accurately quantify beta-amyloid burden. It has previously been shown that beta-amyloid plaques can be imaged using Magnetic Resonance Microscopy (MRM) at 40mum isotropic resolution in ex vivo human samples of the hippocampus. Transgenic (Tg) mice have been generated for research as beta-amyloidosis models. Plaque sizes range can from 5mum to 200mum, with an average diameter of approximately 25mum. In the present study, we used high resolution MRM to explore the feasibility of visualizing beta-amyloid plaque deposits in the brain of Tg2576 mice carrying the Swedish mutation of APP. We obtained T2 weighted 3D whole brain MRM data at 20mum and 25mum isotropic resolution. MRM images were compared with histological data to confirm that the signal seen on MRM corresponded to actual beta-amyloid plaque deposits. We conclude that MRM is a practical and useful assay for imaging beta-amyloid plaques with diameters as small as 20mum. These results will aid in the interpretation of MRI data gathered from in-vivo scans of mice, including scans wherein contrast agents are employed. This MRI technique can be easily applied to whole brain plaque quantification studies and for the purpose of studying treatment strategies using mouse models of AD, and may further be extended to in vivo studies tracking amyloid deposit formation and maturation throughout the animals life span
BIOSIS:PREV200400205607
ISSN: 1558-3635
CID: 97617
in vivo magnetic resonance imaging of amyloid plaques in AD model mice [Meeting Abstract]
Wisniewski, T.; Sigurdsson, E. M.; Wadghiri, Y. Z.; Sadowski, M.; Scholtzova, H.; Tang, C. Y.; Aguilnaldo, G.; Duff, K.; Turnbull, D. H.
Amyloid deposition in Alzheimer's disease (AD) occurs many years before cognitive impairment. Brain imaging techniques targeting plaques will have an important diagnostic value and may help in identifying individuals in preclinical stages of AD. Magnetic resonance imaging (MRI) has a much higher resolution than positron enhanced tomography (PET) imaging and, therefore, is a more sensitive method to detect amyloid plaques. In our initial proof-of-concept studies (Magnetic Resonance in Medicine, in press), we utilized Abeta1-40 peptide, labeled with gadolinium or monocrystalline iron oxide nanoparticles (MION). When either of these ligands is injected in vivo systemically with mannitol to transiently open the blood-brain-barrier, we are able to image ex vivo the majority of Abeta plaques in Tg mice. Using Gd labeled Abeta1-40 and in vivo muMRI, we can also detect a substantial percentage of amyloid lesions. There is a high correlation between the numerical density of Abeta plaques detected by muMRI and by immunohistochemistry. Clinical use of Abeta1-40 is not feasible because it may add to the plaque burden. As a safer approach, we are using gadolinium labeled K6Abeta1-30, a non-toxic Abeta derivative with low propensity to form beta-sheet, while maintaining high affinity for Abeta. Our initial findings indicate that this compound has a similar effect as gadolinium labeled Abeta1-40 in allowing in vivo detection of amyloid plaques in Tg mice. We are currently exploring various ways to enhance the uptake of this compound into the brain. This approach may lead to a diagnostic MRI method to detect Abetaplaques in AD patients
BIOSIS:PREV200400196138
ISSN: 1558-3635
CID: 97618
Immunization approaches for the treatment of prion disease
Wisniewski, Thomas; Sy, Man-Sun; Sadowski, Marcin; Kascsak, Richard J.; Kascsak, Regina; Carp, Richard; Goni, Fernando; Sigurdsson, Einar
BIOSIS:PREV200300192522
ISSN: 0028-3878
CID: 97619
Immunization with amyloid - beta derivatives improves cognition while provoking a weak antibody response [Meeting Abstract]
Knudsen, E. L.; Wisniewski, T.; Quartermain, D.; Sage, D.; Scholtzova, H.; Frangione, B.; Sigurdsson, E. M.
We have reported that an amyloid-beta derivative, K6Abeta1-30-NH2 reduces amyloid burden in mice to a similar extent as previously shown for Abeta1-42 (Am J Pathol 159:439-47,2001). This derivative may be a safer alternative to Alzheimer's vaccination with Abeta1-42 because it has a low beta-sheet content while maintaining the main antigenic sites of Abeta. To determine the in vivo effect of other derivatives with similar in vitro properties, we immunized Tg2576 mice with Abeta1-30-NH2, in which amino acids 18 and 19 were substituted with glutamate (Abeta1-30E18E19). In a parallel study, mice were immunized with K6Abeta1-30E18E19. Freund's adjuvant was used to allow a comparison with our findings with K6Abeta1-30-NH2. Antibody titers were detectable, but much lower than we had observed for K6Abeta1-30-NH2 or Abeta1-42, indicating that the central hydrophobic region of Abeta may have an epitope important for modulating humoral response. Cognitive performance was assessed in a radial arm maze before sacrifice at 19-21 months. Control Tg mice had more errors than their wild-type littermates (p<0.01), and the Abeta1-30E18E19-treated mice (p<0.05). Mice receiving K6Abeta1-30E18E19 also performed better than their Tg controls (p<0.05). Histologically, no difference was observed in brain amyloid plaque burden in 6E10 stained brain sections from the Abeta1-30E18E19-vaccinated mice, compared to vehicle treated mice. Furthermore, amyloid burden did not correlate with cognitive performance. Analysis of plaque burden in the K6Abeta1-30E18E19-immunized mice is underway, as well as measurements of brain levels of Abeta to determine if these values will provide a better correlation with cognitive performance. A robust antibody response and a diminished plaque burden may not be necessary for a therapeutic effect of Abeta derived vaccines
BIOSIS:PREV200400194897
ISSN: 1558-3635
CID: 97630
Copper modulates prion infectivity [Meeting Abstract]
Sigurdsson, E. M.; Brown, D.; Alim, M. A.; Scholtzova, H.; Carp, R.; Meeker, H. C.; Prelli, F.; Frangione, B.; Wisniewski, T.
The prion protein (PrP) is a copper binding protein; however, the role of copper in prion infection is unclear. Under some conditions copper facilitates refolding of denatured PrPSc into a protease resistant and infectious form. Hence copper may enhance the infectivity of the prion protein. To determine the feasibility of copper targeted therapy for prion disease, we treated mice (n=10 per group) with d-penicillamine (d-PEN; 100 mg/kg, i.p.), immediately following scrapie inoculation (139A strain, i.p.). Subsequent drug injections were daily, five days per week. d-PEN delayed the onset of prion disease in the mice (p=0.002). The effect was more pronounced at the 1000-fold dilution of agent (d-PEN=179 +- 3 days, VEH=165 +- 4, p=0.006), but a trend for a delay was observed at the 10-fold dilution (d-PEN=153 +- 2, VEH=146 +- 3, p=0.1). As expected, d-PEN reduced brain copper levels (p<0.01) by 26% (10-fold dil.; p=0.04) and 32% (1000-fold dil.; p=0.02), compared to control animals. Brain levels of iron and zinc were not reduced. To further support the notion that the therapeutic effect of d-PEN was mediated through its copper chelating properties, brain homogenates from terminally ill 139A infected mice were incubated with copper and d-PEN. Following a 72 h incubation, copper sulfate increased aggregation of the prion protein in a dose dependent manner, resulting in an enhanced resistance to proteinase K. This effect was counteracted by co-incubation with d-PEN. These findings support the proposed in vivo effect of d-PEN in delaying the onset of prion disease in these mice. Copper chelator-based therapy may benefit those incubating prion disease but this approach may be more effective at higher doses and/or in a multi-targeted combinational therapy
BIOSIS:PREV200400202959
ISSN: 1558-3635
CID: 97631
Longitudinal cerebrospinal fluid tau load increases in mild cognitive impairment
de Leon, M J; Segal, S; Tarshish, C Y; DeSanti, S; Zinkowski, R; Mehta, P D; Convit, A; Caraos, C; Rusinek, H; Tsui, W; Saint Louis, L A; DeBernardis, J; Kerkman, D; Qadri, F; Gary, A; Lesbre, P; Wisniewski, T; Poirier, J; Davies, P
Cross-sectional cerebrospinal fluid (CSF) levels of tau and amyloid (A) beta (beta) are of diagnostic importance for Alzheimer's disease (AD) and mild cognitive impairment (MCI). However, most longitudinal studies of tau fail to demonstrate progression. Because predominantly brain-derived proteins such as tau, have higher ventricle to lumbar ratios, we hypothesized that adjusting for the ventricular enlargement of AD would correct for the dilution of tau, and improve detection of longitudinal change. Abeta which is not exclusively brain derived, shows a ratio <1, and no benefit was expected from adjustment. In a 1 year longitudinal study of eight MCI and ten controls, we examined CSF levels of hyperphosphorylated (P) tau231, Abeta40, and Abeta42. In cross-section, MCI patients showed elevated Ptau231 and Abeta40 levels, and greater ventricular volumes. Longitudinally, only after adjusting for the ventricular volume and only for Ptau231, were increases seen in MCI. Further studies are warranted on mechanisms of tau clearance and on using imaging to interpret CSF studies
PMID: 12429378
ISSN: 0304-3940
CID: 39372
A safer vaccine for Alzheimer's disease?
Sigurdsson, Einar M; Wisniewski, Thomas; Frangione, Blas
Recent reports indicate that amyloid-beta (Abeta) vaccine-based therapy for Alzheimer's disease (AD) may be on the horizon. There are, however, concerns about the safety of this approach. Immunization with Abeta1-42 may not be appropriate in humans because it crosses the blood-brain barrier, can seed fibril formation, and is highly fibrillogenic. Abeta1-42 fibrils can in turn cause inflammation and neurotoxicity. This issue is of a particular concern in the elderly who often do not mount an adequate immune response to vaccines. Our findings show that vaccination with nonamyloidogenic/nontoxic Abeta derivative may be a safer therapeutic approach to impede the progression of Abeta-related histopathology in AD. Although the site of action of the anti-Abeta antibodies has been suggested to be within the brain, peripheral clearance of Abeta may have a greater role in reducing cerebral amyloid plaques in these animals and eventually in AD patients. Antibodies in general are predominantly found outside the central nervous system (CNS) and will, therefore, primarily clear systemic Abeta compared to brain Abeta. This disruption of the equilibrium between central and peripheral Abeta should then result in efflux of Abeta out of the brain, and subsequent removal of plaques. Abeta therapy can be targeted to the periphery, which may result in fewer CNS side effects, such as inflammation. Future Abeta derived vaccines should include T(h) epitopes, carriers and/or lipid moieties to enhance antibody production in the elderly, the population predominantly affected by AD
PMID: 12470795
ISSN: 0197-4580
CID: 32918
Molecular targeting of Alzheimer's amyloid plaques for contrast-enhanced magnetic resonance imaging
Poduslo, Joseph F; Wengenack, Thomas M; Curran, Geoffry L; Wisniewski, Thomas; Sigurdsson, Einar M; Macura, Slobodon I; Borowski, Bret J; Jack, Clifford R Jr
Smart molecular probes for both diagnostic and therapeutic purposes are expected to provide significant advances in clinical medicine and biomedical research. We describe such a probe that targets beta-amyloid plaques of Alzheimer's disease and is detectable by magnetic resonance imaging (MRI) because of contrast imparted by gadolinium labeling. Three properties essential for contrast enhancement of beta-amyloid plaques on MRI exist in this smart molecular probe, putrescine-gadolinium-amyloid-beta peptide: (1) transport across the blood-brain barrier following intravenous injection conferred by the polyamine moiety, (2) binding to plaques with molecular specificity by putrescine-amyloid-beta, and (3) magnetic resonance imaging contrast by gadolinium. MRI was performed on ex vivo tissue specimens at 7 T at a spatial resolution approximating plaque size (62.5 microm(3)), in order to prove the concept that the probe, when administered intravenously, can selectively enhance plaques. The plaque-to-background tissue contrast-to-noise ratio, which was precisely correlated with histologically stained plaques, was enhanced more than nine-fold in regions of cortex and hippocampus following intravenous administration of this probe in AD transgenic mice. Continuing engineering efforts to improve spatial resolution are underway in MRI, which may enable in vivo imaging at the resolution of individual plaques with this or similar contrast probes. This could enable early diagnosis and also provide a direct measure of the efficacy of anti-amyloid therapies currently being developed
PMID: 12505424
ISSN: 0969-9961
CID: 62132
Infectivity of amyloid diseases
Sigurdsson, Einar M; Wisniewski, Thomas; Frangione, Blas
To date, transmissibility of amyloid diseases has not been thoroughly investigated. Although only some of these conformational disorders are considered infectious, all amyloid diseases could be infectious under certain conditions. For transmissibility, endogenous expression of an amyloidogenic peptide required, as well as the presence of an inoculum that is rich in amyloid fibrils and/or their precursors. Notably, administration of one type of amyloid might result in deposition of a different amyloid. Various cofactors could be essential for transmission - some might chaperone the amyloid peptides and/or fibrils, thereby directly facilitating their propagation; others might indirectly stabilize and/or increase levels of conformers with a high beta-sheet content. It is possible that these chaperones are induced by inflammation, which itself can lead to secondary amyloidosis. Thus, amyloid-related therapeutic approaches should not be based on administration of amyloidogenic peptides in conjunction with an inflammatory stimulus, such as in a recently halted clinical trial for Alzheimer's disease
PMID: 12223307
ISSN: 1471-4914
CID: 32920
Immunization treatment approaches in Alzheimer's and prion diseases
Wisniewski, Thomas; Sigurdsson, Einar M
There is growing realization that many neurodegenerative conditions have the same underlying pathogenetic mechanism: a change in protein conformation, where the beta-sheet content is increased. In Alzheimer's disease (AD), amyloid deposition in the form of neuritic plaques and congophilic angiopathy is driven by the conversion of normal soluble amyloid beta (sAbeta) to Abeta plaques, whereas in the prionoses the critical event is the conversion of normal prion protein, PrP(C), to PrP(Sc). This common theme in the pathogenesis of these disorders and the extracellular localization of the accumulating abnormal protein make them highly amenable to therapeutic approaches based on experimental manipulation of protein conformation and clearance. Different approaches under development include drugs that affect the processing of the precursor proteins, enhance clearance of the amyloidogenic protein, and inhibit or prevent the conformation change. Particularly interesting are recent studies of immune system activation, which appear to increase the clearance of the disease-associated protein. These immunologically based approaches are highly effective in animal models of these disorders, and in these model systems are associated with no obvious side effects. In transgenic mice with AD-related pathology, immunization has also been shown to prevent age-related cognitive impairment. However, the first clinical trial of this approach in AD patients was associated with unacceptable toxicity. These immune-based treatment approaches have great potential as rational therapies for this devastating group of disorders, but additional development is needed before they can be safely applied to humans
PMID: 12169219
ISSN: 1528-4042
CID: 32923