Behavioral dysfunction, brain oxidative stress, and impaired mitochondrial electron transfer in aging mice

Abstract

Behavioral dysfunction, brain oxidative stress, and impaired mitochondrial electron transfer in aging mice. Am J Physiol Regulatory Integrative Comp Physiol 282: R985-R992, 2002; 10.1152/ajpregu.00537.2001.-Behavioral tests, tightrope success, and exploratory activity in a T maze were conducted with male and female mice for 65 wk. Four groups were defined: the lower performance slow males and slow females and the higher performance fast males and fast females. Fast females showed the longest life span and the highest performance, and slow males showed the lowest performance and the shortest life span. Oxidative stress and mitochondrial electron transfer activities were determined in brain of young (28 wk), adult (52 wk), and old (72 wk) mice in a crosssectional study. Brain thiobarbituric acid reactive substances (TBARS) were increased by 50% in old mice and were ϳ15% higher in males than in females and in slow than in fast mice. Brain Cu,Zn-superoxide dismutase (SOD) activity was increased by 52% and Mn-SOD by 108% in old mice. The activities of mitochondrial enzymes NADH-cytochrome c reductase, cytochrome oxidase, and citrate synthase were decreased by 14-58% in old animals. The cumulative toxic effects of oxyradicals are considered the molecular mechanism of the behavioral deficits observed on aging. neuromuscular impairment; NADH-cytochrome c reductase BOTH AGING AND AGE-ASSOCIATED neurodegeneration are related to the development of behavioral impairments; consequently, decreased performances in neuromuscular coordination and exploratory tests are considered markers of neurological aging (15). The life span of rodent strains was found inversely related to the intensity of their behavioral and neuroendocrine responses to stress, this type of evidence suggesting a genetic linkage between the quality of response to stress, the performance in behavioral tests, the rate of age-dependent neurodegeneration, and life span (12,13,19).The likely molecular candidates responsible for the neuromuscular deficits are oxidizing free radicals and the consequent oxidative stress they generate. The free radical theory of aging, understood as the decline of biological function on time, is complemented with the concept that life span is a consequence of oxygen toxicity at 20 kPa O 2 (18, 21). When the free radical theory of aging (21) is focused in mitochondria, it becomes more attractive as the mitochondrial hypothesis of aging (22,30,37 • that act as intermediates and, among others, the stable products of the oxidation of unsaturated fatty acids, proteins, and DNA. Thiobarbituric acid reactive substances (TBARS), protein carbonyls, and 8-hydroxy-deoxyguanosine (8-OH-dG) are the usual markers of oxidative stress as byproducts of free radical-mediated oxidation of cell components. The first aim of this study, in accordance with the mitochondrial hypothesis of aging, was to assess oxidative stress and mitochondrial electron transfer in aging animals. The second aim was to establish the relationships between oxidative stress mar...

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Is defective electron transport at the hub of aging?

“…The scattergrams presented are the result in the main of imprecise assay protocols and complex II not being activated prior to assay (see above). A similar disparity between the age-related declines of complex I and IV activities was evident in mouse brain (Navarro et al, 2002), where the losses in 18-month-old animals amounted to 40% and 15%, respectively, relative to complex II activity, which remained constant. As an indication of increasing oxidative stress, thiobarbituric acid reactive substances (50%), cytoplasmic SOD (52%) and matrix SOD (108%) had all increased.…”

“…Respiratory chain complexes in mitotic tissues such as liver and kidney from a variety of species seem not to decline with age (Sugiyama et al, 1993;Barazzoni et al, 2000;Kwong & Sohal, 2000;Navarro et al, 2002). In cell culture both human fibroblasts (Martinez et al, 1991) and rat hepatocytes (Hagen et al, 1997) have been shown to develop distinct populations judged on the basis of membrane potential and replicative ability.…”

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