The dementia of Alzheimer's disease (AD) is accompanied by accumulation of abnormal proteins in form of amyloid deposits in victims' brains. We hypothesize that these proteins are detrimental to surrounding brain cells and are a major cause of the symptoms seen in AD. To test this hypothesis in the living organism, we propose to express human amyloid components, specifically, different forms of mutated and non-mutated amyloid beta protein precursors (APP695, 751, 770) and the protease inhibitor alpha1- antichymotrypsin (ACT), in the brains of transgenic mice with the help of recombinant DNA constructs. CDNAS encoding these human proteins will be recombined with transgenic vectors (derived from the neuroA-specific enolase (NSE) gene and the glial fibrillary acidic protein (GFAP) gene) for the neuron-specific (NSE) or astrocyte-specific (GFAP) expression of foreign proteins in the brains of transgenic mice. These vectors are chosen because both neurons and astrocytes may function as a source of amyloid proteins in AD. The transgenes will be introduced into the germline of mice by microinjection of fertilized egg cells. Transgenic mice will be analyzed for the expression of the human CDNAS at the RNA and protein levels. The transgenic mouse model will be characterized by detailed neuropathologic and biochemical analysis. A battery of neurobehavioral tests will assess if overproduction of APP and/or ACT in the brains of the transgenic mice induces impairment of memory/learning or other forms of neurologic dysfunction. Behavioral abnormalities will be correlated with neuropathologic findings. If amyloid components are causative factors in the dementia of AD, inhibition of their formation, deposition or action should allow treatment of the disease. To help predict their usefulness in the treatment of AD, protease inhibitors, tachykinin agonists such as substance P, and other agents will be tested in the transgenic models for their ability to inhibit the structural and functional alterations induced by the overexpression of APP/ACT. The molecular mechanisms of drug actions and amyloid formation will be studied in vivo as well as in explant cultures of transgenic nervous tissue. This project will assess in vivo the role the following factors could play in the development of AD: i) different forms of APP, ii) an APP point mutation found in familial AD, iii) neuronal vs. astroglial processing of APP, and iv) protease inhibitors such as ACT. The transgenic models proposed should allow the efficient preclinical assessment of drugs aimed at different manifestations of AD and facilitate the development of new therapeutic and diagnostic strategies.
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