Update on the oxidative stress theory of aging: does oxidative stress play a role in aging or healthy aging?

[Oxidative stress and longevity; a case-control study]

INTRODUCTION

Human longevity is a complex issue influenced by genetic and environmental factors. Oxidative stress (OE) could play an important role in this process. Succesful aging could be related with the organism ability facing OE. In the present study we compared malondialdehyde (MDA) and oxidized proteins (OP) plasma levels, in elderly people older than 97 years and 70-80 years old, to better understand the effects of OE on human longevity.

MATERIAL AND METHODS

Population-based case control study. We considered as cases patients who were born and live on la Ribera county in Valencia (Spain) older than 97 years old and who accepted to participate in the study. Controls were from the same poblational base, chosen randomly, and 70-80 years old. We made a descriptive analysis of sociodemographic, clinic and functional variables; an odds ratio (OR) estimation of being centenarian by OP and MDA quartiles; and a tendency analysis by Mantel-Haenszel test.

RESULTS

Twenty eight cases and 31 controls were included. Functional state and robust percentage were worse in cases. MDA (1,44±0,45 vs 1,84±0,59, p=0,005), and OP (64,29±15,73 vs. 76,52±13,44, p=0,002) levels, were significantly lower in cases. The OR of being centenarian in lower/higher quartile were 3,8 for MDA and 5,7 for OP, with a Mantel-Haenszel signification of 0,029 and 0,044 respectively.

CONCLUSIONS

In our study OE level were lower in centenarians than in younger elderly, and the lower the OE grade, the higher were the likelihood of being centenarian.

Caloric restriction and the aging process: a critique

The main objective of this review is to provide an appraisal of the current status of the relationship between energy intake and the life span of animals. The concept that a reduction in food intake, or caloric restriction (CR), retards the aging process, delays the age-associated decline in physiological fitness, and extends the life span of organisms of diverse phylogenetic groups is one of the leading paradigms in gerontology. However, emerging evidence disputes some of the primary tenets of this conception. One disparity is that the CR-related increase in longevity is not universal and may not even be shared among different strains of the same species. A further misgiving is that the control animals, fed ad libitum (AL), become overweight and prone to early onset of diseases and death, and thus may not be the ideal control animals for studies concerned with comparisons of longevity. Reexamination of body weight and longevity data from a study involving over 60,000 mice and rats, conducted by a National Institute on Aging-sponsored project, suggests that CR-related increase in life span of specific genotypes is directly related to the gain in body weight under the AL feeding regimen. Additionally, CR in mammals and "dietary restriction" in organisms such as Drosophila are dissimilar phenomena, albeit they are often presented to be the very same. The latter involves a reduction in yeast rather than caloric intake, which is inconsistent with the notion of a common, conserved mechanism of CR action in different species. Although specific mechanisms by which CR affects longevity are not well understood, existing evidence supports the view that CR increases the life span of those particular genotypes that develop energy imbalance owing to AL feeding. In such groups, CR lowers body temperature, rate of metabolism, and oxidant production and retards the age-related pro-oxidizing shift in the redox state.

Oxidative stress markers and all-cause mortality at older age: a population-based cohort study

BACKGROUND

The free radical/oxidative stress theory of aging has recently received much attention but the association of oxidative stress markers with all-cause mortality was not yet assessed in humans.

METHODS

We measured derivatives of reactive oxygen metabolites (d-ROM) as a proxy for the reactive oxygen species concentration and total thiol levels (TTL) as a proxy for the redox control status in 2,932 participants of a population-based cohort study from Germany.

RESULTS

The median age of the population was 70 years and 120 (4.1%) study participants died during a mean follow-up of 3.3 years. Compared with the bottom tertiles, the top tertiles of d-ROM and TTL concentrations were both associated with all-cause mortality in models adjusted for age, sex, education, smoking, physical activity, and alcohol consumption (hazard ratios and 95% confidence intervals: 1.63 [1.01; 2.63] and 0.68 [0.53; 0.87], respectively). Adding diseases, the inflammatory marker C-reactive protein or a cumulative somatic morbidity index did not alter the results for TTL. However, the association of d-ROM and mortality was attenuated and no longer statistically significant after adding C-reactive protein and the somatic morbidity index to the model.

CONCLUSIONS

This study adds epidemiological evidence to the free radical/oxidative stress theory of aging. Both d-ROM and TTL were associated with mortality at older age. For TTL, this association was independent of baseline health status. Inflammation and higher general morbidity could be intermediate states on the pathway from high d-ROM levels to mortality. This hypothesis should to be explored by future studies with repeated measurements.

Oxidative stress in pregnancy and fertility pathologies

Oxidative stress designates the state of imbalance between reactive oxygen species (ROS) production and antioxidant levels. In a healthy placenta, there is an increase in ROS production, due to formation of new tissues and inherent metabolism, but this is balanced by higher levels of antioxidants. However, this balance is lost in some situations, with a consequent increase in oxidative stress levels. Oxidative stress has been implicated in several placental disorders and pregnancy pathologies. The present review intends to summarize what is known about the relationship between oxidative stress and well-known pregnancy disorders.

Mitochondrial reactive oxygen species (ROS) in animal cells: relevance to aging and normal physiology

In animal mitochondria, the four electron reduction of molecular oxygen to produce water at respiratory complex IV is the terminal step in substrate oxidation. However, respiratory complexes I, II, and III can participate in the single electron reduction of oxygen to produce the radical species superoxide. This progenitor reactive oxygen species (ROS) participates in a number of reactions that generate other ROS. These molecules may react with, and damage, intracellular macromolecules, leading to cellular dysfunction. Mitochondrial ROS production is often considered from this perspective of macromolecular damage and is central to the “oxidative damage theory of aging”, which suggests the accumulation of oxidative damage in animal cells underlies the aging phenotype and limits lifespan. In this review, we discuss some experimental results accumulated over the past decade that are inconsistent with this theory. A limitation of the theory is that it presupposes mitochondrial ROS are inherently harmful. However, it is increasingly apparent that some basic cellular functions are physiologically regulated by normal levels of mitochondrial ROS. For example, cell growth and division, the apoptotic pathway, and mitochondrial fusion–fission dynamics all appear to be redox-regulated by mitochondrial ROS and perhaps the matrix manganese superoxide dismutase (MnSOD). Therefore, it is less clear how the balance between ROS regulation of normal cellular activities and ROS-mediated macromolecular damage is maintained and how this relates to aging and longevity in animals.

Causes and Consequences of Age-Related Changes in DNA Methylation: A Role for ROS?

Recent genome-wide analysis of C-phosphate-G (CpG) sites has shown that the DNA methylome changes with increasing age, giving rise to genome-wide hypomethylation with site‑specific incidences of hypermethylation. This notion has received a lot of attention, as it potentially explains why aged organisms generally have a higher risk of age-related diseases. However, very little is known about the mechanisms that could cause the occurrence of these changes. Moreover, there does not appear to be a clear link between popular theories of aging and alterations in the methylome. Some of the most fruitful of these theories attribute an important role to reactive oxygen species, which seem to be responsible for an increase in oxidative damage to macromolecules, such as DNA, during the lifetime of an organism. In this review, the connection between changes in DNA methylation and these reactive oxygen species is discussed, as well as the effect of these changes on health. Deeper insights into the nature, causes and consequences of the aging methylome might provide a deeper understanding of the molecular mechanisms of aging and eventually contribute to the development of new diagnostic and therapeutic tools.

Revisiting an age-old question regarding oxidative stress

Significant advances in maintaining health throughout life can be made through a clear understanding of the fundamental mechanisms that regulate aging. The Oxidative Stress Theory of Aging (OSTA) is probably the most well studied mechanistic theory of aging and suggests that the rate of aging is controlled by accumulation of oxidative damage. To directly test the OSTA, aging has been measured in several lines of mice with genetic alterations in the expression of enzymatic antioxidants. Under its strictest interpretation, these studies do not support the OSTA, as modulation of antioxidant expression does not generally affect mouse life span. However, the incidence of many age-related diseases and pathologies is altered in these models, suggesting that oxidative stress does significantly influence some aspects of the aging process. Further, oxidative stress may affect aging in disparate patterns among tissues or under various environmental conditions. In this review, we summarize the current literature regarding aging in antioxidant mutant mice and offer several interpretations of their support of the OSTA.

Litter size manipulation in laboratory mice: an example of how proteomic analysis can uncover new mechanisms underlying the cost of reproduction

Background

Life history theories predict that investment in current reproduction comes at a cost for future reproduction and survival. Oxidative stress is one of the best documented mechanisms underlying costs of reproduction to date. However, other, yet to be described molecular mechanisms that play a short term role during reproduction may explain the negative relationships underlying the cost of reproduction. To identify such new mechanisms, we used a global proteomic determination of liver protein profiles in laboratory adult female mice whose litter size had been either reduced or enlarged after birth. This litter size manipulation was expected to affect females by either raising or decreasing their current reproductive effort. At the same time, global parameters and levels of oxidative stress were also measured in all females.

Results

Based on plasma analyses, females with enlarged litters exhibited increased levels of oxidative stress at the date of weaning compared to females with reduced litters, while no significant difference was found between both the latter groups and control females. None of the liver proteins related to oxidative balance were significantly affected by the experimental treatment. In contrast, the liver protein profiles of females with enlarged and reduced litters suggested that calcium metabolism and cell growth regulation were negatively affected by changes in the number of pup reared.

Conclusions

Plasma oxidative stress levels in reproductive mice revealed that the degree of investment in reproduction can actually incur a cost in terms of plasmatic oxidative stress, their initial investment in reproduction being close to maximum and remaining at a same level when the energy demand of lactation is reduced. Liver proteomic profiles in reproductive females show that hepatic oxidative stress is unlikely to be involved in the cost of reproduction. Reproductive females rather exhibited liver protein profiles similar to those previously described in laboratory ageing mice, thus suggesting that hepatic cell pro-ageing processes may be involved in the cost of reproduction. Overall, our data illustrate how a proteomic approach can unravel new mechanisms sustaining life-history trade-offs, and reproduction costs in particular.

Amelioration of reproduction-associated oxidative stress in a viviparous insect is critical to prevent reproductive senescence

Impact of reproductive processes upon female health has yielded conflicting results; particularly in relation to the role of reproduction-associated stress. We used the viviparous tsetse fly to determine if lactation, birth and involution lead to damage from oxidative stress (OS) that impairs subsequent reproductive cycles. Tsetse females carry an intrauterine larva to full term at each pregnancy cycle, and lactate to nourish them with milk secretions produced by the accessory gland ( = milk gland) organ. Unlike most K-strategists, tsetse females lack an apparent period of reproductive senescence allowing the production of 8-10 progeny over their entire life span. In a lactating female, over 47% of the maternal transcriptome is associated with the generation of milk proteins. The resulting single larval offspring weighs as much as the mother at birth. In studying this process we noted an increase in specific antioxidant enzyme (AOE) transcripts and enzymatic activity at critical times during lactation, birth and involution in the milk gland/fat body organ and the uterus. Suppression of superoxide dismutase (sod) decreased fecundity in subsequent reproductive cycles in young mothers and nearly abolished fecundity in geriatric females. Loss of fecundity was in part due to the inability of the mother to produce adequate milk to support larval growth. Longevity was also impaired after sod knockdown. Generation of OS in virgin females through exogenous treatment with hydrogen peroxide at times corresponding to pregnancy intervals reduced survival, which was exacerbated by sod knockdown. AOE expression may prevent oxidative damage associated with the generation of nutrients by the milk gland, parturition and milk gland breakdown. Our results indicate that prevention of OS is essential for females to meet the growing nutritional demands of juveniles during pregnancy and to repair the damage that occurs at birth. This process is particularly important for females to remain fecund during the latter portion of their lifetime.

Lifespan effects of simple and complex nutraceutical combinations fed isocalorically to mice

Present data suggest that the consumption of individual dietary supplements does not enhance the health or longevity of healthy rodents or humans. It might be argued that more complex combinations of such agents might extend lifespan or health-span by more closely mimicking the complexity of micronutrients in fruits and vegetables, which appear to extend health-span and longevity. To test this hypothesis we treated long-lived, male, F1 mice with published and commercial combinations of dietary supplements and natural product extracts, and determined their effects on lifespan and health-span. Nutraceutical, vitamin or mineral combinations reported to extend the lifespan or health-span of healthy or enfeebled rodents were tested, as were combinations of botanicals and nutraceuticals implicated in enhanced longevity by a longitudinal study of human aging. A cross-section of commercial nutraceutical combinations sold as potential health enhancers also were tested, including Bone Restore®, Juvenon®, Life Extension Mix®, Ortho Core®, Ortho Mind®, Super K w k2®, and Ultra K2®. A more complex mixture of vitamins, minerals, botanical extracts and other nutraceuticals was compounded and tested. No significant increase in murine lifespan was found for any supplement mixture. Our diverse supplement mixture significantly decreased lifespan. Thus, our results do not support the hypothesis that simple or complex combinations of nutraceuticals, including antioxidants, are effective in delaying the onset or progress of the major causes of death in mice. The results are consistent with epidemiological studies suggesting that dietary supplements are not beneficial and even may be harmful for otherwise healthy individuals.

Influence on longevity of blueberry, cinnamon, green and black tea, pomegranate, sesame, curcumin, morin, pycnogenol, quercetin, and taxifolin fed iso-calorically to long-lived, F1 hybrid mice

Phytonutrients reportedly extend the life span of Caenorhabditis elegans, Drosophila, and mice. We tested extracts of blueberry, pomegranate, green and black tea, cinnamon, sesame, and French maritime pine bark (Pycnogenol and taxifolin), as well as curcumin, morin, and quercetin for their effects on the life span of mice. While many of these phytonutrients reportedly extend the life span of model organisms, we found no significant effect on the life span of male F1 hybrid mice, even though the dosages used reportedly produce defined therapeutic end points in mice. The compounds were fed beginning at 12 months of age. The control and treatment groups were iso-caloric with respect to one another. A 40% calorically restricted and other groups not reported here did experience life span extension. Body weights were un-changed relative to controls for all but two supplemented groups, indicating most supplements did not change energy absorption or utilization. Tea extracts with morin decreased weight, whereas quercetin, taxifolin, and Pycnogenol together increased weight. These changes may be due to altered locomotion or fatty acid biosynthesis. Published reports of murine life span extension using curcumin or tea components may have resulted from induced caloric restriction. Together, our results do not support the idea that isolated phytonutrient anti-oxidants and anti-inflammatories are potential longevity therapeutics, even though consumption of whole fruits and vegetables is associated with enhanced health span and life span.

Increased oxidative stress response in granulocytes from older patients with a hip fracture may account for slow regeneration

Proximal femur fracture, a typical fracture of the elderly, is often associated with morbidity, reduced quality of life, impaired physical function and increased mortality. There exists evidence that responses of the hematopoietic microenvironment to fractures change with age. Therefore, we investigated oxidative stress markers and oxidative stress-related MAPK activation in granulocytes from the young and the elderly with and without fractured long bones. Lipid peroxidation levels were increased in the elderly controls and patients. Aged granulocytes were more sensitive towards oxidative stress induced damage than young granulocytes. This might be due to the basally increased expression of SOD-1 in the elderly, which was not further induced by fractures, as observed in young patients. This might be caused by an altered MAPK activation. In aged granulocytes basal p38 and JNK activities were increased and basal ERK1/2 activity was decreased. Following fracture, JNK activity decreased, while ERK1/2 and p38 activities increased in both age groups. Control experiments with HL60 cells revealed that the observed p38 activation depends strongly on age. Summarizing, we observed age-dependent changes in the oxidative stress response system of granulocytes after fractures, for example, altered MAPK activation and SOD-1 expression. This makes aged granulocytes vulnerable to the stress stimuli of the fracture and following surgery.

Ovarian aging-like phenotype in the hyperandrogenism-induced murine model of polycystic ovary

There are prominently similar symptoms, effectors, and commonalities in the majority of characteristics between ovarian aging and polycystic ovarian syndrome (PCOS). Despite the approved role of oxidative stress in the pathogenesis of PCOS and aging, to our knowledge, the link between the PCO(S) and aging has not been investigated yet. In this study we investigated the possible exhibition of ovarian aging phenotype in murine model of PCO induced by daily oral administration of letrozole (1 mg/kg body weight) for 21 consecutive days in the female Wistar rats. Hyperandrogenization showed irregular cycles and histopathological characteristics of PCO which was associated with a significant increase in lipid peroxidation (LPO) and reactive oxygen species (ROS) and decrease in total antioxidant capacity (TAC) in serum and ovary. Moreover, serum testosterone, insulin and tumor necrosis factor-alpha (TNF-α) levels, and ovarian matrix metalloproteinase-2 (MMP-2) were increased in PCO rats compared with healthy controls, while estradiol and progesterone diminished. Almost all of these findings are interestingly found to be common with the characteristics identified with (ovarian) aging showing that hyperandrogenism-induced PCO in rat is associated with ovarian aging-like phenotypes. To our knowledge, this is the first report that provides evidence regarding the phenomenon of aging in PCO.

Early life hormetic treatments decrease irradiation-induced oxidative damage, increase longevity, and enhance sexual performance during old age in the Caribbean fruit fly

Early life events can have dramatic consequences on performance later in life. Exposure to stressors at a young age affects development, the rate of aging, risk of disease, and overall lifespan. In spite of this, mild stress exposure early in life can have beneficial effects on performance later in life. These positive effects of mild stress are referred to as physiological conditioning hormesis. In our current study we used anoxia conditioning hormesis as a pretreatment to reduce oxidative stress and improve organismal performance, lifespan, and healthspan of Caribbean fruit flies. We used gamma irradiation to induce mild oxidative damage in a low-dose experiment, and massive oxidative damage in a separate high-dose experiment, in pharate adult fruit flies just prior to adult emergence. Irradiation-induced oxidative stress leads to reduced adult emergence, flight ability, mating performance, and lifespan. We used a hormetic approach, one hour of exposure to anoxia plus irradiation in anoxia, to lower post-irradiation oxidative damage. We have previously shown that this anoxic-conditioning treatment elevates total antioxidant capacity and lowers post-irradiation oxidative damage to lipids and proteins. In this study, conditioned flies had lower mortality rates and longer lifespan compared to those irradiated without hormetic conditioning. As a metric of healthspan, we tracked mating both at a young age (10 d) and old age (30 d). We found that anoxia-conditioned male flies were more competitive at young ages when compared to unconditioned irradiation stressed male flies, and that the positive effects of anoxic conditioning hormesis on mating success were even more pronounced in older males. Our data shows that physiological conditioning hormesis at a young age, not only improves immediate metrics of organismal performance (emergence, flight, mating), but the beneficial effects also carry into old age by reducing late life oxidative damage and improving lifespan and healthspan.

Green tea drinking improves erythrocytes and saliva oxidative status in the elderly

We have previously shown that green tea (GT) drinking combined with vitamin E supplementation reduced plasma protein carbonyls and increased erythrocytes catalase activity in exercising healthy elderly. In the present study we set out to investigate the antioxidative effects of GT drinking in an aging population. We performed an interventional, crossover, controlled prospective trial with 35 healthy elderly subjects (mean age 67.3±4.8 years), supplemented with four daily placebo maltodextrin "tea-bags" for 12 weeks, followed by four 1.5 g daily GT bags for another 12 weeks. Data were obtained at baseline, at the end of the placebo period, and at the end of the GT intervention period. We found that GT did not alter erythrocyte catalase activity. However, it provided protection against 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH)-induced oxidative hemolysis which declined by 10.2% (p<0.001). No changes were observed in saliva oral peroxidase enzymes. Nonetheless, saliva total antioxidant capacity increased by 42.0% (p<0.01). Plasma oxidative products, such as protein carbonyls, lipid peroxides and thiobarbituric acid reactive substances (TBARS) were stable throughout the intervention period. We conclude that four daily cups of GT are well tolerated in elderly free living subjects. Our results demonstrate that both erythrocyte resistances to oxidation and saliva antioxidant capacity are improved by GT drinking. The clinical implications of these oxidation modifications require further research.

A genetic program theory of aging using an RNA population model

Aging is a common characteristic of multicellular eukaryotes. Copious hypotheses have been proposed to explain the mechanisms of aging, but no single theory is generally acceptable. In this article, we refine the RNA population gene activating model (Lv et al., 2003) based on existing reports as well as on our own latest findings. We propose the RNA population model as a genetic theory of aging. The new model can also be applied to differentiation and tumorigenesis and could explain the biological significance of non-coding DNA, RNA, and repetitive sequence DNA. We provide evidence from the literature as well as from our own findings for the roles of repetitive sequences in gene activation. In addition, we predict several phenomena related to aging and differentiation based on this model.

Role of antioxidant enzymes in redox regulation of N-methyl-D-aspartate receptor function and memory in middle-aged rats

Overexpression of superoxide dismutase 1 (SOD1) in the hippocampus results in age-dependent impaired cognition and altered synaptic plasticity suggesting a possible model for examining the role of oxidative stress in senescent neurophysiology. However, it is unclear if SOD1 overexpression involves an altered redox environment and a decrease in N-methyl-D-aspartate receptor (NMDAR) synaptic function reported for aging animals. Viral vectors were used to express SOD1 and green fluorescent protein (SOD1 + GFP), SOD1 and catalase (SOD1 + CAT), or GFP alone in the hippocampus of middle-aged (17 months) male Fischer 344 rats. We confirm that SOD1 + GFP and SOD1 + CAT reduced lipid peroxidation indicating superoxide metabolites were primarily responsible for lipid peroxidation. SOD1 + GFP impaired learning, decreased glutathione peroxidase activity, decreased glutathione levels, decreased NMDAR-mediated synaptic responses, and impaired long-term potentiation. Co-expression of SOD1 + CAT rescued the effects of SOD1 expression on learning, redox measures, and synaptic function suggesting the effects were mediated by excess hydrogen peroxide. Application of the reducing agent dithiolthreitol to hippocampal slices increased the NMDAR-mediated component of the synaptic response in SOD1 + GFP animals relative to animals that overexpress SOD1 + CAT indicating that the effect of antioxidant enzyme expression on NMDAR function was because of a shift in the redox environment. The results suggest that overexpression of neuronal SOD1 and CAT in middle age may provide a model for examining the role of oxidative stress in senescent physiology and the progression of age-related neurodegenerative diseases.

Glutathione peroxidase-1 deficiency potentiates dysregulatory modifications of endothelial nitric oxide synthase and vascular dysfunction in aging

Recently, we demonstrated that gene ablation of mitochondrial manganese superoxide dismutase and aldehyde dehydrogenase-2 markedly contributed to age-related vascular dysfunction and mitochondrial oxidative stress. The present study has sought to investigate the extent of vascular dysfunction and oxidant formation in glutathione peroxidase-1-deficient (GPx-1(-/-)) mice during the aging process with special emphasis on dysregulation (uncoupling) of the endothelial NO synthase. GPx-1(-/-) mice on a C57 black 6 (C57BL/6) background at 2, 6, and 12 months of age were used. Vascular function was significantly impaired in 12-month-old GPx-1(-/-) -mice as compared with age-matched controls. Oxidant formation, detected by 3-nitrotyrosine staining and dihydroethidine-based fluorescence microtopography, was increased in the aged GPx-1(-/-) mice. Aging per se caused a substantial protein kinase C- and protein tyrosine kinase-dependent phosphorylation as well as S-glutathionylation of endothelial NO synthase associated with uncoupling, a phenomenon that was more pronounced in aged GPx-1(-/-) mice. GPx-1 ablation increased adhesion of leukocytes to cultured endothelial cells and CD68 and F4/80 staining in cardiac tissue. Aged GPx-1(-/-) mice displayed increased oxidant formation as compared with their wild-type littermates, triggering redox-signaling pathways associated with endothelial NO synthase dysfunction and uncoupling. Thus, our data demonstrate that aging leads to decreased NO bioavailability because of endothelial NO synthase dysfunction and uncoupling of the enzyme leading to endothelial dysfunction, vascular remodeling, and promotion of adhesion and infiltration of leukocytes into cardiovascular tissue, all of which was more prominent in aged GPx-1(-/-) mice.

Antioxidant capacity responsible for a hypocholesterolemia is independent of dietary cholesterol in adult rats fed rice protein

Dietary cholesterol and aging are major risk factors to accelerate oxidation process for developing hypercholesterolemia. The major aim of this study is to elucidate the effects of rice protein on cholesterol level and oxidative stress in adult rats fed with and without cholesterol. After 2 weeks of feeding, hepatic and plasma contents of cholesterol, reduced glutathione (GSH), oxidized glutathione (GSSG), malondialdehyde (MDA) and protein carbonyl (PCO) were measured. In liver, total antioxidative capacity (T-AOC), activities of antioxidant enzymes (total superoxide dismutase, T-SOD; catalase, CAT), glutathione metabolizing enzyme activities and gene expression levels (γ-glutamylcysteine synthetase, γ-GCS; glutathione reductase, GR; glutathione peroxidase, GPx) were determined. Under cholesterol-free/enriched dietary condition, T-AOC, activities of T-SOD and CAT, glutathione metabolism related enzymes' activities and mRNA levels (γ-GCS, GR and GPx) were effectively stimulated by rice proteins as compared to caseins. Compared with caseins, rice proteins significantly increased hepatic and plasma GSH contents, whereas hepatic and plasma accumulations of MDA, PCO and GSSG were significantly reduced by rice protein-feedings. As a result, the marked reductions of cholesterol in the plasma and in the liver were observed in adult rats fed rice proteins with and without cholesterol. The present study demonstrates that the hypocholesterolemic effect of rice protein is attributable to inducing antioxidative response and depressing oxidative damage in adult rats fed cholesterol-free/enriched diets. Results suggest that the antioxidant capability involved in the hypocholesterolemic action exerted by rice protein is independent of dietary cholesterol during adult period.

Oxidative damage and cellular defense mechanisms in sea urchin models of aging

The free radical, or oxidative stress, theory of aging proposes that the accumulation of oxidative cellular damage is a major contributor to the aging process and a key determinant of species longevity. This study investigates the oxidative stress theory in a novel model for aging research, the sea urchin. Sea urchins present a unique model for the study of aging because of the existence of species with tremendously different natural life spans, including some species with extraordinary longevity and negligible senescence. Cellular oxidative damage, antioxidant capacity, and proteasome enzyme activities were measured in the tissues of three sea urchin species: short-lived Lytechinus variegatus, long-lived Strongylocentrotus franciscanus, and Strongylocentrotus purpuratus, which has an intermediate life span. Levels of protein carbonyls and 4-hydroxynonenal measured in tissues (muscle, nerve, esophagus, gonad, coelomocytes, ampullae) and 8-hydroxy-2'-deoxyguanosine measured in cell-free coelomic fluid showed no general increase with age. The fluorescent age pigment lipofuscin, measured in muscle, nerve, and esophagus, increased with age; however, it appeared to be predominantly extracellular. Antioxidant mechanisms (total antioxidant capacity, superoxide dismutase) and proteasome enzyme activities were maintained with age. In some instances, levels of oxidative damage were lower and antioxidant activity higher in cells or tissues of the long-lived species compared to the short-lived species; however, further studies are required to determine the relationship between oxidative damage and longevity in these animals. Consistent with the predictions of the oxidative stress theory of aging, the results suggest that negligible senescence is accompanied by a lack of accumulation of cellular oxidative damage with age, and maintenance of antioxidant capacity and proteasome enzyme activities may be important mechanisms to mitigate damage.

Manipulating reproductive effort leads to changes in female reproductive scheduling but not oxidative stress

The trade-off between reproductive investment and lifespan is the single most important concept in life-history theory. A variety of sources of evidence support the existence of this trade-off, but the physiological costs of reproduction that underlie this relationship remain poorly understood. The Free Radical Theory of Ageing suggests that oxidative stress, which occurs when there is an imbalance between the production of damaging Reactive Oxygen Species (ROS) and protective antioxidants, may be an important mediator of this trade-off. We sought to test this theory by manipulating the reproductive investment of female mice (Mus musculus domesticus) and measuring the effects on a number of life history and oxidative stress variables. Females with a greater reproductive load showed no consistent increase in oxidative damage above females who had a smaller reproductive load. The groups differed, however, in their food consumption, reproductive scheduling and mean offspring mass. Of particular note, females with a very high reproductive load delayed blastocyst implantation of their second litter, potentially mitigating the costs of energetically costly reproductive periods. Our results highlight that females use strategies to offset particularly costly periods of reproduction and illustrate the absence of a simple relationship between oxidative stress and reproduction.

Comparative effect of Piper betle, Chlorella vulgaris and tocotrienol-rich fraction on antioxidant enzymes activity in cellular ageing of human diploid fibroblasts

Background

Human diploid fibroblasts (HDFs) undergo a limited number of cellular divisions in culture and progressively reach a state of irreversible growth arrest, a process termed cellular ageing. Even though beneficial effects of Piper betle, Chlorella vulgaris and tocotrienol-rich fraction (TRF) have been reported, ongoing studies in relation to ageing is of interest to determine possible protective effects that may reverse the effect of ageing. The aim of this study was to evaluate the effect of P. betle, C. vulgaris and TRF in preventing cellular ageing of HDFs by determining the activity of antioxidant enzymes viz.; catalase, superoxide dismutase (SOD) and glutathione peroxidase.

Methods

Different passages of HDFs were treated with P. betle, C. vulgaris and TRF for 24 h prior to enzymes activity determination. Senescence-associated beta-galactosidase (SA β-gal) expression was assayed to validate cellular ageing.

Results

In cellular ageing of HDFs, catalase and glutathione peroxidase activities were reduced, but SOD activity was heightened during pre-senescence. P. betle exhibited the strongest antioxidant activity by reducing SA β-gal expression, catalase activities in all age groups, and SOD activity. TRF exhibited a strong antioxidant activity by reducing SA β-gal expression, and SOD activity in senescent HDFs. C. vulgaris extract managed to reduce SOD activity in senescent HDFs.

Conclusion

P. betle, C. vulgaris, and TRF have the potential as anti-ageing entities which compensated the role of antioxidant enzymes in cellular ageing of HDFs.

Copper-zinc superoxide dismutase deficiency impairs sperm motility and in vivo fertility

Oxidative stress, overproduction of reactive oxygen species (ROS) in relation to defence mechanisms, is considered to be a major cause of male infertility. For protection against the deleterious effects of ROS, animals have a variety of enzymatic antioxidants that reduce these molecules to less reactive forms. The physiological role of these antioxidants in vivo has been explored extensively through genetic inhibition of gene expression; surprisingly, many of these animals remain fertile in spite of increased oxidative stress. Copper-zinc superoxide dismutase-deficient (Sod1(-/-)) male mice are one such example for which in vivo fertility has been repeatedly reported as normal, although examination of fertility has consisted of simply pairing animals of the same strain and checking for litters. This is a fairly low criterion by which to assess fertility. Herein, we show that Sod1-deficient males have zero fertilisation success in sperm competition trials that pit them against wild-type males of an otherwise identical genetic background and are almost completely infertile when mated singly with females of a different genotype. We also show that various aspects of sperm motility and function are impaired in Sod1-deficient mice. Testing the breeding capabilities of mice under more ecologically relevant conditions and with females of different genotypes may help reveal additional physiological causes of infertility.

A botanical containing freeze dried açai pulp promotes healthy aging and reduces oxidative damage in sod1 knockdown flies

Superoxide dismutase 1 (SOD1), a critical enzyme against oxidative stress, is implicated in aging and degenerative diseases. We previously showed that a nutraceutical containing freeze-dried açai pulp promotes survival of flies fed a high-fat diet or sod1 knockdown flies fed a standard diet. Here, we investigated the effect of açai supplementation initiated at the early or late young adulthood on lifespan, physiological function, and oxidative damage in sod1 knockdown flies. We found that Açai supplementation extended lifespan even when started at the age of 10 days, which is the time shortly before the mortality rate of flies accelerated. Life-long açai supplementation increased lifetime reproductive output in sod1 knockdown flies. Our molecular studies indicate that açai supplementation reduced the protein levels of genes involved in oxidative stress response, cellular growth, and nutrient metabolism. Açai supplementation also affected the protein levels of ribosomal proteins. In addition, açai supplementation decreased the transcript levels of genes involved in oxidative stress response and gluconeogenesis, while increasing the transcript levels of mitochondrial biogenesis genes. Moreover, açai supplementation reduced the level of 4-hydroxynonenal-protein adducts, a lipid peroxidation marker. Our findings suggest that açai supplementation promotes healthy aging in sod1-deficient flies partly through reducing oxidative damage, and modulating nutrient metabolism and oxidative stress response pathways. Our findings provide a foundation to further evaluate the viability of using açai as an effective dietary intervention to promote healthy aging and alleviate symptoms of diseases with a high level of oxidative stress.

Thyroid hormone signaling and homeostasis during aging

Studies in humans and in animal models show negative correlations between thyroid hormone (TH) levels and longevity. TH signaling is implicated in maintaining and integrating metabolic homeostasis at multiple levels, notably centrally in the hypothalamus but also in peripheral tissues. The question is thus raised of how TH signaling is modulated during aging in different tissues. Classically, TH actions on mitochondria and heat production are obvious candidates to link negative effects of TH to aging. Mitochondrial effects of excess TH include reactive oxygen species and DNA damage, 2 factors often considered as aging accelerators. Inversely, caloric restriction, which can retard aging from nematodes to primates, causes a rapid reduction of circulating TH, reducing metabolism in birds and mammals. However, many other factors could link TH to aging, and it is these potentially subtler and less explored areas that are highlighted here. For example, effects of TH on membrane composition, inflammatory responses, stem cell renewal and synchronization of physiological responses to light could each contribute to TH regulation of maintenance of homeostasis during aging. We propose the hypothesis that constraints on TH signaling at certain life stages, notably during maturity, are advantageous for optimal aging.

Gender and longevity: why do men die earlier than women? Comparative and experimental evidence

Sex differences in lifespan exist world-wide, with women outliving men by more than a decade in some countries. The gender gap is not a uniquely human phenomenon; most sexually reproducing species examined show sex differences in patterns of ageing, yet a comprehensive explanation does not exist. Here, we discuss how ageing responds to natural selection on traits that arise as a consequence of sexuality. Sexual dimorphisms in vertebrates are mediated by sex-steroids, such as androgens and oestrogens, and we examine their regulation of biological processes that can affect ageing and lifespan. The sexes can respond differently to dietary restriction and altered activity of nutrient-sensing pathways, with females showing a greater plasticity for life extension. We suggest that the cross-regulation of steroid hormone and nutrient-sensing signalling pathways is a promising process for further study in understanding the biological basis for the gender gap.

Prolonged lifespan with enhanced exploratory behavior in mice overexpressing the oxidized nucleoside triphosphatase hMTH1

The contribution that oxidative damage to DNA and/or RNA makes to the aging process remains undefined. In this study, we used the hMTH1-Tg mouse model to investigate how oxidative damage to nucleic acids affects aging. hMTH1-Tg mice express high levels of the hMTH1 hydrolase that degrades 8-oxodGTP and 8-oxoGTP and excludes 8-oxoguanine from both DNA and RNA. Compared to wild-type animals, hMTH1-overexpressing mice have significantly lower steady-state levels of 8-oxoguanine in both nuclear and mitochondrial DNA of several organs, including the brain. hMTH1 overexpression prevents the age-dependent accumulation of DNA 8-oxoguanine that occurs in wild-type mice. These lower levels of oxidized guanines are associated with increased longevity and hMTH1-Tg animals live significantly longer than their wild-type littermates. Neither lipid oxidation nor overall antioxidant status is significantly affected by hMTH1 overexpression. At the cellular level, neurospheres derived from adult hMTH1-Tg neural progenitor cells display increased proliferative capacity and primary fibroblasts from hMTH1-Tg embryos do not undergo overt senescence in vitro. The significantly lower levels of oxidized DNA/RNA in transgenic animals are associated with behavioral changes. These mice show reduced anxiety and enhanced investigation of environmental and social cues. Longevity conferred by overexpression of a single nucleotide hydrolase in hMTH1-Tg animals is an example of lifespan extension associated with healthy aging. It provides a link between aging and oxidative damage to nucleic acids.

Mice with heterozygous deficiency of manganese superoxide dismutase (SOD2) have a skin immune system with features of "inflamm-aging"

Dendritic cells (DC) are central in regulating skin immunity. Immunosenescence is associated with a chronic inflammatory state. Little is known about the contribution of DC to "inflamm-aging". When determining langerhans cell (LC) numbers, we found a 60 % reduction of LC in aged epidermis. Reactive oxygen species(ROS) are linked with aging. The mitochondrial manganese superoxide dismutase (SOD2) is in the first line of antioxidant defense. We investigated the function of DC from SOD2 heterozygous mice (SOD2+/-) and found that at 4 months of age LC numbers are not altered, but activated LC have impaired expression of MHC-II and CD44. Immature SOD2+/- DC produced increased proinflammatory IL-6 and chemokines CXCL1 and CXCL2. Upon challenge SOD2+/- DC accumulated ROS. When activating SOD2+/- DC by LPS they less efficiently upregulated MHC-II, CD86 and CD44. Surprisingly, in vivo contact hypersensitivity (CHS) was enhanced in SOD2+/- mice although SOD2+/- DC were less potent in stimulating wt T cells. However, SOD2+/- T cells showed increased proliferation, even when stimulated with SOD2+/- DC, possibly explaining the increased CHS. Our findings suggest that SOD2 is a molecular candidate in the regulation of "inflamm-aging" conveying both immunosuppressive and proinflammatory signals through alteration of DC and T cell functions.

Life-extending ovariectomy in grasshoppers increases somatic storage, but dietary restriction with an equivalent feeding rate does not

Reduced diet or reduced reproduction each extends lifespan in many animals. It is often thought that reduced reproduction and reduced diet may act through the same mechanisms. In grasshoppers, ovariectomy extends lifespan and reduces feeding to a level similar to that used for life extension by dietary restriction, further suggesting mechanistic overlap. Here, we measure the feeding rate of ovariectomized grasshoppers and, by manipulating feeding levels, create a sham-operated & dietary restricted group with matched daily feeding. Both groups show ~25% increased survivorship near the median age of mortality for fully fed and reproductive controls. Ovariectomy results in a doubling of fat body mass and hemolymph volume in comparison to both a feeding-matched dietary restriction group and a sham-operated & fully fed control, which do not differ from each other. Total anti-oxidant activity in the hemolymph and the skeletal muscle was unchanged upon ovariectomy or dietary restriction, so it does not appear to be a major factor in lifespan extension. Next, we measured mitochondrial counts using qPCR to determine mitochondrial cytochrome-b concentrations relative to nuclear (genomic) beta-actin. Mitochondrial counts in the ovariectomized group were lower than sham-operated and fully fed controls but not than the dietary restriction group. Last, in the fat body, transcript levels of hexamerin-90 (a hemolymph storage protein) were affected by neither ovariectomy nor dietary restriction. Hence, ovariectomy resulted in large magnitude increases in organismal storage. The matched-fed dietary restricted group differed from the ovariectomized group only in organismal storage, and not in any of the cellular parameters measured here. This study suggests that longevity via ovariectomy has distinct physiological mechanisms from longevity via dietary restriction in grasshoppers that are independent of daily feeding rate, particularly for protein and fat storage.

The role of oxidative stress in nervous system aging

While oxidative stress is implicated in aging, the impact of oxidative stress on aging in the peripheral nervous system is not well understood. To determine a potential mechanism for age-related deficits in the peripheral nervous system, we examined both functional and morphological changes and utilized microarray technology to compare normal aging in wild-type mice to effects in copper/zinc superoxide dismutase-deficient (Sod1(-/-)) mice, a mouse model of increased oxidative stress. Sod1(-/-) mice exhibit a peripheral neuropathy phenotype with normal sensory nerve function and deficits in motor nerve function. Our data indicate that a decrease in the synthesis of cholesterol, which is vital to myelin formation, correlates with the structural deficits in axons, myelin, and the cell body of motor neurons in the Sod1(+/+) mice at 30 months and the Sod1(-/-) mice at 20 months compared with mice at 2 months. Collectively, we have demonstrated that the functional and morphological changes within the peripheral nervous system in our model of increased oxidative stress are manifested earlier and resemble the deficits observed during normal aging.

Study of antioxidative effects and anti-inflammatory effects in mice due to low-dose X-irradiation or radon inhalation

Low-dose irradiation induces various stimulating effects, especially activation of the biological defense system including antioxidative and immune functions. Oxidative stress induced by reactive oxygen species (ROS) can cause cell damage and death and can induce many types of diseases. This paper reviews new insights into inhibition of ROS-related diseases with low-dose irradiation or radon inhalation. X-irradiation (0.5 Gy) before or after carbon tetrachloride (CCl4) treatment inhibits hepatopathy in mice. X-irradiation (0.5 Gy) before ischemia-reperfusion injury or cold-induced brain injury also inhibits edema. These findings suggest that low-dose X-irradiation has antioxidative effects due to blocking the damage induced by free radicals or ROS. Moreover, radon inhalation increases superoxide dismutase activity in many organs and inhibits CCl4-induced hepatic and renal damage and streptozotocin-induced type I diabetes. These findings suggest that radon inhalation also has antioxidative effects. This antioxidative effect against CCl4-induced hepatopathy is comparable to treatment with ascorbic acid (vitamin C) at a dose of 500 mg/kg weight, or α-tocopherol (vitamin E) treatment at a dose of 300 mg/kg weight, and is due to activation of antioxidative functions. In addition, radon inhalation inhibits carrageenan-induced inflammatory paw edema, suggesting that radon inhalation has anti-inflammatory effects. Furthermore, radon inhalation inhibits formalin-induced inflammatory pain and chronic constriction injury-induced neuropathic pain, suggesting that radon inhalation relieves pain. Thus, low-dose irradiation very likely activates the defense systems in the body, and therefore, contributes to preventing or reducing ROS-related injuries, which are thought to involve peroxidation.

Croix C, Sowa G, Pola E, Robbins PD, Kang J, Niedernhofer LJ, Wipf P, Vo NV. Mitochondrial-derived reactive oxygen species (ROS) play a causal role in aging-related intervertebral disc degeneration

Oxidative damage is a well-established driver of aging. Evidence of oxidative stress exists in aged and degenerated discs, but it is unclear how it affects disc metabolism. In this study, we first determined whether oxidative stress negatively impacts disc matrix metabolism using disc organotypic and cell cultures. Mouse disc organotypic culture grown at atmospheric oxygen (20% O(2)) exhibited perturbed disc matrix homeostasis, including reduced proteoglycan synthesis and enhanced expression of matrix metalloproteinases, compared to discs grown at low oxygen levels (5% O(2)). Human disc cells grown at 20% O(2) showed increased levels of mitochondrial-derived superoxide anions and perturbed matrix homeostasis. Treatment of disc cells with the mitochondria-targeted reactive oxygen species (ROS) scavenger XJB-5-131 blunted the adverse effects caused by 20% O(2). Importantly, we demonstrated that treatment of accelerated aging Ercc1(-/Δ) mice, previously established to be a useful in vivo model to study age-related intervertebral disc degeneration (IDD), also resulted in improved disc total glycosaminoglycan content and proteoglycan synthesis. This demonstrates that mitochondrial-derived ROS contributes to age-associated IDD in Ercc1(-/Δ) mice. Collectively, these data provide strong experimental evidence that mitochondrial-derived ROS play a causal role in driving changes linked to aging-related IDD and a potentially important role for radical scavengers in preventing IDD.

Peroxisome degradation in mammals: mechanisms of action, recent advances, and perspectives

Peroxisomes are remarkably dynamic organelles that participate in a diverse array of cellular processes, including the metabolism of lipids and reactive oxygen species. In order to regulate peroxisome function in response to changing nutritional and environmental stimuli, new organelles need to be formed and superfluous and dysfunctional organelles have to be selectively removed. Disturbances in any of these processes have been associated with the etiology and progression of various congenital neurodegenerative and age-related human disorders. The aim of this review is to critically explore our current knowledge of how peroxisomes are degraded in mammalian cells and how defects in this process may contribute to human disease. Some of the key issues highlighted include the current concepts of peroxisome removal, the peroxisome quality control mechanisms, the initial triggers for peroxisome degradation, the factors for dysfunctional peroxisome recognition, and the regulation of peroxisome homeostasis. We also dissect the functional and mechanistic relationship between different forms of selective organelle degradation and consider how lysosomal dysfunction may lead to defects in peroxisome turnover. In addition, we draw lessons from studies on other organisms and extrapolate this knowledge to mammals. Finally, we discuss the potential pathological implications of dysfunctional peroxisome degradation for human health.

Gene expression changes in response to aging compared to heat stress, oxidative stress and ionizing radiation in Drosophila melanogaster

Gene expression changes in response to aging, heat stress, hyperoxia, hydrogen peroxide, and ionizing radiation were compared using microarrays. A set of 18 genes were up-regulated across all conditions, indicating a general stress response shared with aging, including the heat shock protein (Hsp) genes Hsp70, Hsp83 and l(2)efl, the glutathione-S-transferase gene GstD2, and the mitochondrial unfolded protein response (mUPR) gene ref(2)P. Selected gene expression changes were confirmed using quantitative PCR, Northern analysis and GstD-GFP reporter constructs. Certain genes were altered in only a subset of the conditions, for example, up-regulation of numerous developmental pathway and signaling genes in response to hydrogen peroxide. While aging shared features with each stress, aging was more similar to the stresses most associated with oxidative stress (hyperoxia, hydrogen peroxide, ionizing radiation) than to heat stress. Aging is associated with down-regulation of numerous mitochondrial genes, including electron-transport-chain (ETC) genes and mitochondrial metabolism genes, and a sub-set of these changes was also observed upon hydrogen peroxide stress and ionizing radiation stress. Aging shared the largest number of gene expression changes with hyperoxia. The extensive down-regulation of mitochondrial and ETC genes during aging is consistent with an aging-associated failure in mitochondrial maintenance, which may underlie the oxidative stress-like and proteotoxic stress-like responses observed during aging.

Medicinal plants for renal injury prevention

It has been estimated that about 20% of men and 25% of women between the ages of 65 and 74 have some degrees of chronic kidney. This complication is attributed to oxidative stress. Oxidative stress is an important factor contributing to kidney damage by increasing production of oxidants, particularly insufficiency of endogenous antioxidant defense system. Medicinal plants antioxidants are able to ameliorate oxidative induced kidney damage by reduction of lipid peroxidation and enhancement of scavenging ability of antioxidant defense system. Supplementation of medicinal plants antioxidants might be considered important remedies to abrogate pathology of oxidative stress induced kidney damage, however, single antioxidants do not act the same and might not be beneficial.

Exceptionally old mice are highly resistant to lipoxidation-derived molecular damage

Membrane unsaturation plays an important role in the aging process and the determination of inter-species animal longevity. Furthermore, the accumulation of oxidation-derived molecular damage to cellular components particularly in the nervous and immune systems over time leads to homeostasis loss, which highly influences age-related morbidity and mortality. In this context, it is of great interest to know and discern the degree of membrane unsaturation and the steady-state levels of oxidative damage in both physiological systems from long-lived subjects. In the present work, adult (28 ± 4 weeks), old (76 ± 4 weeks) and exceptionally old (128 ± 4 weeks) BALB/c female mice were used. Brain and spleen were analysed for membrane fatty acid composition and specific markers of protein oxidation, glycoxidation and lipoxidation damage, i.e. glutamic semialdehyde, aminoadipic semialdehyde, carboxyethyl-lysine, carboxymethyl-lysine and malondialdehyde-lysine, by gas chromatography-mass spectrometry. The results showed significantly lower peroxidizability index in brain and spleen from exceptionally old animals when compared to old specimens. The higher membrane resistance to lipid peroxidation and lower lipoxidation-derived molecular damage found in exceptionally old animals was associated with a significantly lower desaturase activity and peroxisomal β-oxidation. Protein oxidation markers in brain and spleen from adult and exceptionally old animals showed similar levels, which were higher in old mice. In addition, the higher levels of the glycoxidation-derived marker observed in exceptionally old animals, as well as in adult mice, could be considered as a good indicator of a better bioenergetic state of these animals when compared to the old group. In conclusion, low lipid oxidation susceptibility and maintenance of adult-like protein lipoxidative damage could be key mechanisms for longevity achievement.

Oxidative stress activates a specific p53 transcriptional response that regulates cellular senescence and aging

Oxidative stress is a determining factor of cellular senescence and aging and a potent inducer of the tumour-suppressor p53. Resistance to oxidative stress correlates with delayed aging in mammals, in the absence of accelerated tumorigenesis, suggesting inactivation of selected p53-downstream pathways. We investigated p53 regulation in mice carrying deletion of p66, a mutation that retards aging and confers cellular resistance and systemic resistance to oxidative stress. We identified a transcriptional network of ~200 genes that are repressed by p53 and encode for determinants of progression through mitosis or suppression of senescence. They are selectively down-regulated in cultured fibroblasts after oxidative stress, and, in vivo, in proliferating tissues and during physiological aging. Selectivity is imposed by p66 expression and activation of p44/p53 (also named Delta40p53), a p53 isoform that accelerates aging and prevents mitosis after protein damage. p66 deletion retards aging and increases longevity of p44/p53 transgenic mice. Thus, oxidative stress activates a specific p53 transcriptional response, mediated by p44/p53 and p66, which regulates cellular senescence and aging.

A review of oxidative stress in acute kidney injury: protective role of medicinal plants-derived antioxidants

Acute kidney injury (AKI) is the common clinical syndrome which is associated with increased morbidity and mortality. The severity extends from less to more advanced spectrums which link to biological, physical and chemical agents. Oxidative stress (OS)-related AKI has demonstrated the increasing of reactive oxygen species (ROS) and reactive nitrogen species (RNS) and the decreasing of endogenous antioxidants. Medicinal plants-derived antioxidants can be ameliorated oxidative stress-related AKI through reduction of lipid peroxidation (LPO) and enhancement of activities and levels of endogenous antioxidants. Therefore, medicinal plants are good sources of exogenous antioxidants which might be considered the important remedies to ameliorate pathological alterations in oxidative stress-related AKI.

Oxidative stress and the ageing endocrine system

Ageing is a process characterized by a progressive decline in cellular function, organismal fitness and increased risk of age-related diseases and death. Several hundred theories have attempted to explain this phenomenon. One of the most popular is the 'oxidative stress theory', originally termed the 'free radical theory'. The endocrine system seems to have a role in the modulation of oxidative stress; however, much less is known about the role that oxidative stress might have in the ageing of the endocrine system and the induction of age-related endocrine diseases. This Review outlines the interactions between hormones and oxidative metabolism and the potential effects of oxidative stress on ageing of endocrine organs. Many different mechanisms that link oxidative stress and ageing are discussed, all of which converge on the induction or regulation of inflammation. All these mechanisms, including cell senescence, mitochondrial dysfunction and microRNA dysregulation, as well as inflammation itself, could be targets of future studies aimed at clarifying the effects of oxidative stress on ageing of endocrine glands.

Obsolete ideas and logical confusions can be obstacles for biogerontology research

Some misconceptions can be an obstacle for biogerontology research. These misconceptions can be classified in two categories: (1) obsolete ideas in biology, for example "aging has a universal cause" and "living beings are like machines", and (2) conceptual and logical confusions, such as "longevity is not dependent on other life-history traits", "between-groups variability allows to infer conclusions about individual variability", and "the burden of the proof lies with the opponents to the hypothesis". This opinion article describes these problems in the hope it will help to overcome them.

Evaluation of in vitro antioxidant effect of new mono and diselenides

This study was designed to examine the antioxidant activity in vitro of novel mono- and diselenide compounds. We compared whether the formation of p-methyl-selenol from compounds 1-phenyl-3-(p-tolylselanyl)propan-2-amine (C1) and 1,2-dip-tolyldiselenide (C4) and o-methoxy-selenol from compounds 1-(2-methoxyphenylselanyl)-3-phenylpropan-2-amine (C2) and 1,2-bis(2-methoxyphenyl)diselenide (C3) may be involved in their antioxidant effects. The compounds were tested against Fe(II) and sodium nitroprusside (SNP)-induced lipid peroxidation in rat brain and liver homogenates. Likewise, the antioxidant capacity of the compounds was assessed by their ability to decolorize the DPPH radical as well as the Fe(II) chelating assay through the reduction of molybdenum(VI) (Mo6+) to molybdenum(V) (Mo5+). This colorimetric assay was also used to quantify thiol peroxidase (GPx) and oxidase activity and thioredoxin reductase (TrxR) activity. The results showed that the novel selenide compounds inhibit the thiobarbituric acid reactive species (TBARS) induced by different pro-oxidants, but the monoselenides effects were significant only at concentrations higher than the concentrations of the diselenides. Similarly, the total antioxidant activity was higher in the diselenides. Moreover, GPx and TrxR activity was only observed for the diselenides, which indicates that these compounds are more stable selenol molecules than monoselenides.

Time line of redox events in aging postmitotic cells

The precise roles that oxidants play in lifespan and aging are still unknown. Here, we report the discovery that chronologically aging yeast cells undergo a sudden redox collapse, which affects over 80% of identified thiol-containing proteins. We present evidence that this redox collapse is not triggered by an increase in endogenous oxidants as would have been postulated by the free radical theory of aging. Instead it appears to be instigated by a substantial drop in cellular NADPH, which normally provides the electron source for maintaining cellular redox homeostasis. This decrease in NADPH levels occurs very early during lifespan and sets into motion a cascade that is predicted to down-regulate most cellular processes. Caloric restriction, a near-universal lifespan extending measure, increases NADPH levels and delays each facet of the cascade. Our studies reveal a time line of events leading up to the system-wide oxidation of the proteome days before cell death.

DOI:http://dx.doi.org/10.7554/eLife.00306.001

While most animals experience a physiological decline as they age, the underlying cause of this decline is not fully understood. According to the free radical theory of aging, chemicals known as reactive oxygen species build up in the body and then cause damage to various components within cells, including DNA and proteins. These species, which include hydrogen peroxide and peroxynitrite, can cause substantial oxidative damage. However, while there is definitely a relationship between aging and reactive oxygen species, it remains possible that oxidative damage is a byproduct of aging rather than the cause of it.

In the past researchers have measured the carbonylation of proteins (that is, the oxidation of certain amino acids in proteins) as a proxy for damage caused by reactive oxygen species, but this method has a number of shortcomings. More recently, it has become possible to quantify the oxidation state of cysteine, an amino acid that contains sulfur, in proteins using a technique based on mass spectrometry. Building on previous work in which they used this technique to measure the oxidation state of 300 proteins in vivo in the yeast Saccharomyces cerevisiae, Brandes et al. have now determined how the oxidation state of these proteins changes over the lifespan of S. cerevisiae, which is a popular model system for analyzing aging in cells that are in a high metabolic state but are no longer dividing. This made it possible to identify protein targets that might—as a result of changes in their oxidation state caused by reactive oxygen species—contribute to the physiological alterations observed in aging organisms. It was also possible to establish a clear connection between the onset and extent of oxidative stress and lifespan.

Brandes et al. discovered that several days before the yeast cells died, they underwent a sudden and global ‘redox collapse’ in which ∼80% of the 300 proteins being studied experienced an increase in their oxidation state (i.e., they lost electrons). This event was preceded by a large drop in the level of NADPH, a coenzyme that, by being a source of electrons, helps to counterbalance the removal of electrons by reactive oxygen species within cells. The drop in the concentration of NADPH occurred very early in the life cycle of the yeast, and set in motion a series of events that down-regulated most cellular processes. Intriguingly, these findings are consistent with the effect of caloric restriction, a condition that is known to extend the lifespan of animals. Caloric restriction increases cellular NADPH and delays the down-regulation of cellular processes.

Brandes et al. propose that the underlying cause of aging is not the accumulation of reactive oxygen species: rather, these results suggest that aging is caused by a sudden and substantial decrease in available NADPH, which means that cells cannot maintain a stable oxidation state. If borne out by further work, these findings could have a significant impact on how we think about the aging process, and could require researchers to rethink how they study aging.

DOI:http://dx.doi.org/10.7554/eLife.00306.002

The effect of resveratrol on lifespan depends on both gender and dietary nutrient composition in Drosophila melanogaster

Resveratrol, a polyphenolic compound, has been shown to extend lifespan in different organisms. Emerging evidence suggests that the prolongevity effect of resveratrol depends on dietary composition. However, the mechanisms underlying the interaction of resveratrol and dietary nutrients in modulating lifespan remain elusive. Here, we investigated the effect of resveratrol on lifespan of Drosophila melanogaster fed diets differing in the concentrations of sugar, yeast extract, and palmitic acid representing carbohydrate, protein, and fat, respectively. Resveratrol at up to 200 μM in diets did not affect lifespan of wild-type female flies fed a standard, restricted or high sugar-low protein diet, but extended lifespan of females fed a low sugar-high protein diet. Resveratrol at 400 μM extended lifespan of females fed a high-fat diet. Lifespan extension by resveratrol was associated with downregulation of genes in aging-related pathways, including antioxidant peroxiredoxins, insulin-like peptides involved in insulin-like signaling and several downstream genes in Jun-kinase signaling involved in oxidative stress response. Furthermore, resveratrol increased lifespan of superoxide dismutase 1 (sod1) knockdown mutant females fed a standard or high-fat diet. No lifespan extension by resveratrol was observed in wild-type and sod1 knockdown males under the culture conditions in this study. Our results suggest that the gender-specific prolongevity effect of resveratrol is influenced by dietary composition and resveratrol promotes the survival of flies by modulating genetic pathways that can reduce cellular damage. This study reveals the context-dependent effect of resveratrol on lifespan and suggests the importance of dietary nutrients in implementation of effective aging interventions using dietary supplements.

Ageing-induced decrease in cardiac mitochondrial function in healthy rats

It is widely recognized that mitochondrial dysfunction is a key component of the multifactorial process of ageing. The effects of age on individual components of mitochondrial function vary across species and strains. In this study we investigated the oxygen consumption, the mitochondrial membrane potential (Δψ), the sensitivity of mitochondrial permeability transition pore (mPTP) to calcium overload, and the production of reactive oxygen species (ROS) in heart mitochondria isolated from old compared with adult healthy Sprague-Dawley rats. Respirometry studies and Δψ measurements were performed with an Oxygraph-2k equipped with a tetraphenylphosphonium electrode. ROS production and calcium retention capacity were measured spectrofluorimetrically. Our results show an important decline for all bioenergetic parameters for both complex I and complex II supported-respiration, a decreased Δψ in mitochondria energized with complex I substrates, and an increased mitochondrial ROS production in the old compared with the adult group. Mitochondrial sensitivity to Ca²⁺-induced mPTP opening was also increased in the old compared with the adult animals. Moreover, the protective effect of cyclosporine A on mPTP opening was significantly reduced in the old group. We conclude that healthy ageing is associated with a decrease in heart mitochondria function in Sprague-Dawley rats.

The modulation of the oxidative stress response in chondrocytes by Wip1 and its effect on senescence and dedifferentiation during in vitro expansion

Obtaining a sufficient number of cells ex vivo for tissue regeneration, which are appropriate for cartilage repair, requires improved techniques for the continuous expansion of chondrocytes in a manner that does not change their innate characteristics. Rapid senescence or dedifferentiation during in vitro expansion results in loss of chondrocyte phenotype and the formation of fibrous cartilage replacement tissue, rather than hyaluronic cartilage, after transplantation. As demonstrated in the current study, wild-type p53-inducible phosphatase (Wip1), a well-established stress modulator, was highly expressed in early-passage chondrocytes, but declined rapidly during in vitro expansion. Stable Wip1-expressing chondrocytes generated by microporation were less susceptible to the onset of senescence and dedifferentiation, and were more resistant to oxidative stress. The increased resistance of Wip1 chondrocytes to oxidative stress was due to modulation of p38 mitogen-activated protein kinase (MAPK) activity. Importantly, chondrocytes expressing Wip1 maintained their innate chondrogenic properties for a longer period of time, resulting in improvements in cartilage regeneration after transplantation. Chondrocytes from Wip1 knockout (Wip1(-/-)) mice were defective in cartilage regeneration compared with those from wild-type mice. Thus, Wip1 expression represents a potentially useful mechanism by which a chondrocyte phenotype can be retained during in vitro expansion through modulation of cellular stress responses.

Assessing senescence in Drosophila using video tracking

Senescence is associated with changes in gene expression, including the upregulation of stress response- and innate immune response-related genes. In addition, aging animals exhibit characteristic changes in movement behaviors including decreased gait speed and a deterioration in sleep/wake rhythms. Here, we describe methods for tracking Drosophila melanogaster movements in 3D with simultaneous quantification of fluorescent transgenic reporters. This approach allows for the assessment of correlations between behavior, aging, and gene expression as well as for the quantification of biomarkers of aging.