Age-related decreases in NAD(P)H and glutathione cause redox declines before ATP loss during glutamate treatment of hippocampal neurons.
Age-related glutamate excitotoxicity depends in an unknown manner on active mitochondria, which are key determinants of the cellular redox potential. Compared with embryonic and middle-aged neurons, old-aged rat hippocampal neurons have a lower resting reduced nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) and a lower redox ratio (NAD(P)H/flavin adenine nucleotide). Glutamate treatment resulted in an initial increase in NAD(P)H concentrations in all ages, followed by a profound calcium-dependent, age-related decline in NAD(P)H concentration and redox ratio. With complex I of the electron transport chain inhibited by rotenone, treatment with glutamate or ionomycin only resulted in the increase in NAD(P)H fluorescence. High-performance liquid chromatography analysis of adenine nucleotides in brain extracts showed 50% less nicotinamide adenine dinucleotide (NADH) and almost twice as much oxidized nicotinamide adenine dinucleotide, demonstrating a more oxidized ratio in old than middle-aged brain. Resting glutathione content also declined with age and further decreased with glutamate treatment without accompanying changes in adenosine triphosphate levels. We conclude that age does not affect production of NADH by dehydrogenases but that old-aged neurons consume more NADH and glutathione, leading to a catastrophic decline in redox ratio.
Parihar
Mordhwaj S
MS
Department of Medical Microbiology, Immunology and Cell Biology, Southern Illinois University School of Medicine, Springfield, Illinois 62794-9626, USA.
Kunz
Elizabeth A
EA
Brewer
Gregory J
GJ
D000255:Adenosine Triphosphate / Q000378:metabolism; D000375:Aging / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D042967:Electron Transport Complex I / Q000187:drug effects / Q000378:metabolism; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D018698:Glutamic Acid / Q000633:toxicity; D005978:Glutathione / Q000378:metabolism*; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009249:NADP / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats; D011916:Rats, Inbred F344
D005182:Flavin-Adenine Dinucleotide; D018698:Glutamic Acid; D009249:NADP; D000255:Adenosine Triphosphate; D042967:Electron Transport Complex I; D005978:Glutathione; D002118:Calcium