23. Tools for Research on the Genetics and Proteomics of Aging. Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by impairment of cognitive functions and by beta amyloid plaques in cerebral cortex and hippocampus. Because of the challenges in identifying and obtaining presymptomatic human AD brains, we investigated an established amyloid precursor protein (APP) transgenic mice line (Tg2576) for gene expression profiles at ages long before (2 months), immediately before (5-6 months), and after (18 months) the appearance of amyloid plaque pathology and cognitive impairment. We employed cDNA microarray techniques and measured mRNA levels of the cerebral cortex in APP transgenic and wild-type mice at each time point for 11,400 genes. Our preliminary screening of gene expression in APP mice compared to age-matched wild-type mice revealed that at 2 months of age, up-regulated genes are associated mainly with mitochondrial energy metabolism and oxidative stress, and these same genes are progressively up-regulated in 5- and 18-month-old APP mice. We confirmed these results by Northern blot and real-time PCR analyses. Based on these preliminary results, we hypothesize that impairment of mitochondrial energy metabolism is an early cellular event in the progression of AD in APP mice. Currently, our laboratory is testing this hypothesis by treating APP mice and age-matched wild-type mice with mitochondrial antioxidants such as lipoic acid, melatonin and co-enzyme Q10 to determine whether mitochondrial antioxidants can rescue cognitive deficits, reduce mRNA expression, and compensate for biochemical enzymes in mitochondrial energy metabolism. Ultimately, successful agents may be used as clinical trials in AD patients. However, global screening of gene expression for routine detection of gene expression in APP mice after treatment with antioxidants is very expensive. To reduce the cost of global screening of mouse genes for mRNA expression, we propose to develop custom cDNA microarrays for AD transgenic mice. The objective of this research proposal is to develop custom cDNA microarrays for AD transgenic mice. In the present study, we propose to develop high-sensitivity, low-density mitochondrial, oxidative damage and inflammatory response related cDNA microarrays in mice. These custom cDNA microarrays will be instrumental in continuing our studies on the dysfunction of gene expression before and after treatment with mitochondrial antioxidants in APP mice. The outcome of this proposed investigation will be useful in screening several mitochondrial antioxidants in AD transgenic mouse models as pre-clinical trials of AD patients.
