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P2‐251: Age‐related changes in NAD+ metabolism in the brain of aged Wister rats: Relevance for Alzheimer's disease
Author(s) -
Braidy Nady,
Guillemin Gilles,
Mansour Hussein,
Chan-Ling Tailoi,
Grant Ross
Publication year - 2010
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2010.05.1301
Subject(s) - nad+ kinase , oxidative stress , intracellular , lipid peroxidation , biochemistry , nicotinamide adenine dinucleotide , poly adp ribose polymerase , dna damage , biology , chemistry , microbiology and biotechnology , dna , enzyme , polymerase
Background: Aging is characterised by elevated levels of oxidative stress. DNA damage and reduced energy production are hallmarks of this degenerative process. Nicotinamide adenine dinucleotide (NAD+) provides a link between energy production, resistance to stress and longevity. NAD+ serves as a redox carrier, and as a substrate for the NAD-dependent DNA nick sensor poly(ADP-ribose) polymerase (PARP), and the Sirtuins, a family of transcription regulators that play crucial roles in cellular resistance to stress and increased lifespan. Methods: We examined age associated effects on intracellular NAD+ metabolism in selected brain regions in female wistar rats. Formation of protein carbonyls were detected using oand m-tyrosine assay using GC/MS. Lipid peroxidation was observed using western blotting for the detection of 4-hydroxynonenal protein expression. DNA damage and SIRT1 activity were measured using well established flourometric assays. Intracellular NAD+, NADH levels, and PARP activities were measured spectrophotometrically using well established assays. Results: Our results are the first to show a significant decline in intracellular NAD+ levels and NAD:NADH ratio after 12 and 24 months of age compared to young 3 month old rats, in parallel with an increase in lipid peroxidation, and increased formation of protein carbonyls and decline in total antioxidant capacity in the cortex, brainstem, hippocampus and cerebellum. We also found elevated levels of phosphorylated H2AX levels, a measure of DNA damage, in these same brain regions. Reduced mitochondrial complex I activity was also observed in aged rats, suggesting an accumulation of NADH and enhanced potential for production of free radicals by Fenton chemistry. A strong positive correlation was found between oxidative stress, PARP activity, ADP-ribose polymers and NAD+ depletion suggesting a role for NAD+ as a longevity assurance factor. While decreased Sirt1 activity was observed in response to NAD+ depletion, our observed moderate over-expression of Sirt1 may be a response to retard aging and confer resistance to oxidative stress in the brain. Conclusions: Chronic oxidative stress may lead to significant depletion of cellular NAD+ levels. Therefore, therapeutic targets aimed at promoting cellular NAD+ anabolism may prove efficacious in the protection of age-dependent cellular damage, in general, and in neurodegenerative diseases such as Alzheimer’s disease.