Currently, the Oxidative Stress (or Free Radical) Theory of Aging is the most popular explanation of how aging occurs at the molecular level. While data from studies in invertebrates (e.g., C. elegans and Drosophila) and rodents show a correlation between increased lifespan and resistance to oxidative stress (and in some cases reduced oxidative damage to macromolecules), direct evidence showing that alterations in oxidative damage/stress play a role in aging are limited to a few studies with transgenic Drosophila that overexpress antioxidant enzymes. Over the past eight years, our laboratory has conducted an exhaustive study on the effect of under- or overexpressing a large number and wide variety of genes coding for antioxidant enzymes. In this review, we present the survival data from these studies together. Because only one (the deletion of the Sod1 gene) of the 18 genetic manipulations we studied had an effect on lifespan, our data calls into serious question the hypothesis that alterations in oxidative damage/stress play a role in the longevity of mice.

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Target of rapamycin inhibition by rapamycin feeding has previously been shown to extend life in genetically heterogeneous mice. To examine whether it similarly affected mouse health, we fed encapsulated rapamycin or a control diet to C57BL/6Nia mice of both sexes starting at 19 months of age. We performed a range of health assessments 6 and 12 months later. Rapamycin feeding significantly reduced mTOR activity in most but not all tissues. It also reduced total and resting metabolic rate during the light (inactive) phase of the light:dark cycle in females only but had no effect on spontaneous activity or metabolism during the dark (active) phase of either sex. Males only had less fragmented sleep when fed rapamycin, whereas stride length and rotarod performance were improved in both sexes. Survival was also improved by this late-life rapamycin feeding, and some pathological lesions were delayed. We found no adverse health consequences associated with rapamycin treatment.

SummaryWe evaluated the effect of overexpressing antioxidant enzymes on the lifespans of transgenic mice that overexpress copper zinc superoxide dismutase (CuZnSOD), catalase, or combinations of either CuZnSOD and catalase or CuZnSOD and manganese superoxide dismutase (MnSOD). Our results show that the overexpression of these major antioxidant enzymes, which are known to scavenge superoxide and hydrogen peroxide in the cytosolic and mitochondrial compartments, is insufficient to extend lifespan in mice. Key words: aging; antioxidant enzymes; transgenic and knockout mice.The oxidative stress theory of aging offers a credible explanation of a molecular mechanism underlying the aging process. One of the most direct tests of the oxidative stress theory of aging has been to alter oxidative stress/damage and then determine how this alteration affects lifespan (e.g. to genetically manipulate the expression of antioxidant enzymes and observe the effects on lifespan). Based on studies to date, the effect of oxidative stress as a lifespan determinant has been dependent upon the type of animal model tested. Transgenic Drosophila overexpressing either CuZnSOD (Sun & Tower, 1999;Phillips et al ., 2000) or MnSOD (Sun et al ., 2002) have extended longevity.Although several studies have shown that overexpression of antioxidant enzymes in mice has a protective effect against oxidative stress, with a diminished accumulation of oxidative damage in macromolecules (Muller et al ., 2007), Huang et al . (2000) reported that transgenic mice overexpressing CuZnSOD (two-to five-fold increase) did not show any increase in lifespan (Huang et al ., 2000). In contrast, Schriner et al . (2005) targeted catalase to mitochondria and observed a 21% extension in the lifespan of transgenic mice.We studied the effects of CuZnSOD and catalase overexpression on lifespan, as well as the effects of combinations of CuZnSOD and catalase or CuZnSOD and MnSOD overexpression. Transgenic CuZnSOD and catalase mice were generated using large genomic segments of the human genes containing the intact genes with their endogenous promoter (Chen et al ., 2003). The MnSOD transgenic mice were generated by Dr Epstein's laboratory using the mouse Sod2 genomic fragment (Raineri et al ., 2001). These mice overexpress the expected enzymes, with increases of two-to four-fold in all tissues tested and no diminution of the expression of other major antioxidant enzymes (Raineri et al ., 2001;Chen et al ., 2003;Mele et al ., 2006). Fibroblast cell cultures derived from these mice were observed to be more resistant to oxidant stress (Mele et al ., 2006;Shan et al ., 2007). Figure 1 shows the survival curves of each single or double transgenic mouse strain compared to the wild type (WT) controls. Analysis of the survival curves by the log-rank test (Andersen et al ., 1993) showed no statistical differences in the survival curves between the WT mice and any of the transgenic mice. The survival data in Table 1 also show no significant differences in the mean, median, or 90% (when...

Cognitive dysfunction and memory loss are common features of Alzheimer's disease (AD). Abnormalities in the expression profile of immediate early genes that play a critical role in memory formation, such as the cAMP-response element binding protein (CREB), have been reported in the brains of AD patients. Here we show that amyloid-β (Aβ) accumulation, which plays a primary role in the cognitive deficits of AD, interferes with CREB activity. We further show that restoring CREB function via brain viral delivery of the CREB-binding protein (CBP) improves learning and memory deficits in an animal model of AD. Notably, such improvements occur without changes in Aβ and tau pathology, and instead are linked to an increased level of brain-derived neurotrophic factor. The resulting data suggest that Aβ-induced learning and memory deficits are mediated by alterations in CREB function, based on the finding that restoring CREB activity by directly modulating CBP levels in the brains of adult mice is sufficient to ameliorate learning and memory. Therefore, increasing CBP expression in adult brains may be a valid therapeutic approach not only for AD, but also for various brain disorders characterized by alterations in immediate early genes, further supporting the concept that viral vector delivery may be a viable therapeutic approach in neurodegenerative diseases.tangles | presenilin