The neuropathological features of Alzheimer's disease are characterized by the presence of insoluble amyloid deposits in the brain and cerebrovasculature, the intra-neuronal accumulation of abnormally phosphorylated and aggregated forms of tau, a microtubule binding protein and neuronal loss. Although the exact mechanisms producing these pathological changes remain unknown, the amyloid cascade hypothesis states that the peptides (A?) that make up amyloid deposits are the cause of the disease process. Despite numerous supportive studies, discrepancies between animal models of AD and humans with AD remain an obstacle for full acceptance of A? as the primary causal agent for AD. By altering the nitric oxide in mouse brain, we have generated a novel mouse model that provides unique insights into mouse-human differences. Our bigenic mouse models of AD increase the expression of human A? on a murine nitric oxide synthase 2 (NOS2) knockout background. The resulting phenotype is highly reminiscent of the pathology observed in humans with AD including high levels of A? peptides, tau hyperphosphorylation, tau redistribution and tau aggregation, neuronal loss and behavioral deficits. A primary advantage of the APPSw/NOS2-/- mouse is the formation of tau pathology from normal, not mutated tau AND the presence of significant neuronal loss. Thus, our model provides a unique opportunity to fully test the amyloid cascade hypothesis in vivo under conditions of chronic disease.
The first aim will confirm a pathological cascade in the APPSw/NOS2-/- mouse brain by measuring A?, tau pathology, neuronal loss and memory and learning in the APPSw/NOS2-/- mice brains at specific ages. To establish a direct, causal role for A? peptides in the cascade, we propose a) to reduce A? levels in the brains of APPSw/NOS2-/- mice by passive immunization and b) to increase A? levels in the brains of NOS2-/- mice using intrahippocampal injection of A? peptide mixtures.
The second aim will examine the role of NOS2. We propose a) to reduce brain iNOS protein using lentivirus delivery of small interfering RNA (shNOS2 lentivirus) b) to test the ability of NOS2 and NO replacement to alter the pathological cascade mediated by A?.
The third aim will examine a likely mechanism of NO's action, the regulation of caspase activity.

Public Health Relevance

This project will examine the role of A beta peptides derived from the amyloid precursor protein in generating the neuropathology associated with chronic neurodegenerative diseases such as Alzheimer's disease. The method used will involve the generation of a novel mouse model for potential therapeutic value and will provide a useful to tool to fully investigate therapeutics in the pre-clinical stage.

Agency
National Institute of Health (NIH)
Institute
National Institute on Aging (NIA)
Type
Research Project (R01)
Project #
5R01AG031124-03
Application #
8050053
Study Section
Special Emphasis Panel (ZRG1-MDCN-D (02))
Program Officer
Refolo, Lorenzo
Project Start
2009-04-01
Project End
2014-03-31
Budget Start
2011-04-01
Budget End
2012-03-31
Support Year
3
Fiscal Year
2011
Total Cost
$304,319
Indirect Cost
Name
Duke University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
044387793
City
Durham
State
NC
Country
United States
Zip Code
27705
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