An integrated view of oxidative stress in aging: basic mechanisms, functional effects, and pathological considerations

Senescent peritoneal mesothelial cells promote ovarian cancer cell adhesion: the role of oxidative stress-induced fibronectin

Adhesion of ovarian cancer cells to the peritoneal mesothelium is a key step in the malignant progression of the disease. In an in vitro study, we showed that the adherence of ovarian cancer cells (of the OVCAR-3, SKOV-3, and A2780 cell lines) to senescent human omentum-derived peritoneal mesothelial cells (HOMCs) was greater than to early passage cells. The process was mediated primarily by the increased interaction of the alpha5beta1 integrin on cancer cells with HOMC-associated fibronectin (FN). In comparison with early passage HOMCs, senescent cells exhibited increased FN mRNA expression levels and produced significantly more FN. To assess the effect of senescence-associated oxidative stress on FN release, HOMCs were rendered senescent by exposure to an oxidant, tert-butyl hydroperoxide. Treatment with tert-butyl hydroperoxide resulted in a significant increase in HOMC FN mRNA and protein expression levels. The effect of oxidative stress on FN synthesis was found to be mediated by transforming growth factor-beta1, whose signaling pathway was controlled at upstream and downstream levels by p38 MAPK. The activity of p38 MAPK increased markedly in senescent HOMCs. Treatment of HOMCs with antioxidants significantly attenuated senescence-associated increases in p38 MAPK activity, production of both transforming growth factor-beta1 and FN, and ovarian cancer cell adhesion. These data indicate that oxidative stress that accompanies senescence may increase FN production by HOMCs and thus facilitate binding and dissemination of ovarian cancer cells.

Estrogen and mechanisms of vascular protection

Estrogen has antiinflammatory and vasoprotective effects when administered to young women or experimental animals that appear to be converted to proinflammatory and vasotoxic effects in older subjects, particularly those that have been hormone free for long periods. Clinical studies have raised many important questions about the vascular effects of estrogen that cannot easily be answered in human subjects. Here we review cellular/molecular mechanisms by which estrogen modulates injury-induced inflammation, growth factor expression, and oxidative stress in arteries and isolated vascular smooth muscle cells, with emphasis on the role of estrogen receptors and the nuclear factor-kappaB (NFkappaB) signaling pathway, as well as evidence that these protective mechanisms are lost in aging subjects.

Multiple measures of functionality exhibit progressive decline in a parallel, stochastic fashion in Drosophila Sod2 null mutants

Oxidative damage has been proposed as an important factor in the progression of pathological and non-pathological age-related functional declines. Here, we examine functional deterioration in short-lived flies mutant for the mitochondrial antioxidant Manganese Superoxide Dismutase (Sod2). We find that the decline of several functional measures of aging occurs, in an accelerated fashion, in Sod2 mutants. Olfactory behavior, locomotor ability and cardiac performance were all seen to decline rapidly in Sod2 mutants. On average, functional declines in Sod2 mutants occur in a pattern similar to that seen in late-life Drosophila with a normal complement of Sod2. In longitudinal experiments, however, we find that functional failures occur in every possible sequence in Sod2 mutants. Significantly, failure of these functional measures is not irreversible, as spontaneous functional recovery was sometimes observed. These findings support a model where ROS-related damage strikes at multiple organ systems in parallel, rather than a "chain of dominos" model, in which primary organ failure contributes to the deterioration of further organ systems.

Aging augments mitochondrial susceptibility to heat stress

The pathophysiology of aging is accompanied by a decline in tolerance to environmental stress. While mitochondria are primary suspects in the etiology of aging, little is known about their ability to tolerate perturbations to homeostasis in older organisms. To investigate the role of mitochondria in the increased susceptibility to heat stress that accompanies aging, young and old Fischer 344 rats underwent a heat stress protocol known to elicit exaggerated cellular damage with aging. At either 2 or 24 h after heat stress, livers were removed from animals, and hepatic mitochondria were isolated. Electron microscopy revealed extensive morphological damage to mitochondria from young and, to a greater extent, old rats after heat stress. There was also a significant loss of cytochrome c from old, but not young, mitochondria and a persistent increase in 4-hydroxynonenal-modified proteins in old vs. young mitochondria exposed to heat stress. Electron paramagnetic resonance measurements of superoxide indicate greater superoxide production from mitochondria of old compared with young animals and suggest that mitochondrial integrity was altered during heat stress. The mitochondrial stress response, which functions to correct stress-induced damage to mitochondrial proteins, was also blunted in old rats. Delayed and reduced levels of heat shock protein 60 (Hsp60), the main inducible mitochondrial stress protein, were observed in old compared with young mitochondria after heat stress. Additionally, the amount of Hsp10 protein increased in young, but not old, rat liver mitochondria after hyperthermic challenge. Taken together, these data suggest that mitochondria in old animals are more vulnerable to incurring and less able to repair oxidative damage that occurs in response to a physiologically relevant heat stress.

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

BACKGROUND

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation.

REVIEW

We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation).The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible.This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, since in some circumstances (especially the presence of poorly liganded iron) molecules that are nominally antioxidants can actually act as pro-oxidants. The reduction of redox stress thus requires suitable levels of both antioxidants and effective iron chelators. Some polyphenolic antioxidants may serve both roles.Understanding the exact speciation and liganding of iron in all its states is thus crucial to separating its various pro- and anti-inflammatory activities. Redox stress, innate immunity and pro- (and some anti-)inflammatory cytokines are linked in particular via signalling pathways involving NF-kappaB and p38, with the oxidative roles of iron here seemingly involved upstream of the IkappaB kinase (IKK) reaction. In a number of cases it is possible to identify mechanisms by which ROSs and poorly liganded iron act synergistically and autocatalytically, leading to 'runaway' reactions that are hard to control unless one tackles multiple sites of action simultaneously. Some molecules such as statins and erythropoietin, not traditionally associated with anti-inflammatory activity, do indeed have 'pleiotropic' anti-inflammatory effects that may be of benefit here.

CONCLUSION

Overall we argue, by synthesising a widely dispersed literature, that the role of poorly liganded iron has been rather underappreciated in the past, and that in combination with peroxide and superoxide its activity underpins the behaviour of a great many physiological processes that degrade over time. Understanding these requires an integrative, systems-level approach that may lead to novel therapeutic targets.

Bringing the bedside to the bench, and then to the community: a prospectus for intervention research in late-life anxiety disorders

BACKGROUND

Anxiety disorders are highly prevalent in elderly persons, and they are associated with functional impairment, poorer quality of life, and adverse long-term consequences such as cognitive decline. Intervention research in late-life anxiety disorders (LLAD) lags behind where it ought to be. Research in cognitive neuroscience, aging, and stress intersects in LLAD and provides the opportunity to develop innovative interventions to prevent chronic anxiety and its consequences in this age group.

METHODS

This paper evaluates gaps in the evidence base for treatment of LLAD and synthesizes recent research in cognitive neuroscience, basic behavioral science, stress, and aging.

RESULTS

We examine three intervention issues in LLAD: (1) prevention; (2) acute treatment; and (3) pre-empting adverse consequences. We propose combining randomized controlled trials (RCTs) with mechanistic biobehavioral methodologies as an optimal approach for developing novel, optimized, and personalized treatments. Additionally, we examine three barriers in the field of LLAD research: (1) How do we measure anxiety?; (2) How do we raise awareness?; (3) How will we ensure our research is applicable to underserved populations (particularly minority groups)?

CONCLUSIONS

This prospectus outlines approaches for intervention research that can reduce the morbidity of LLAD.

Base excision repair of oxidative DNA damage and association with cancer and aging

Aging has been associated with damage accumulation in the genome and with increased cancer incidence. Reactive oxygen species (ROS) are produced from endogenous sources, most notably the oxidative metabolism in the mitochondria, and from exogenous sources, such as ionizing radiation. ROS attack DNA readily, generating a variety of DNA lesions, such as oxidized bases and strand breaks. If not properly removed, DNA damage can be potentially devastating to normal cell physiology, leading to mutagenesis and/or cell death, especially in the case of cytotoxic lesions that block the progression of DNA/RNA polymerases. Damage-induced mutagenesis has been linked to various malignancies. The major mechanism that cells use to repair oxidative damage lesions, such as 8-hydroxyguanine, formamidopyrimidines, and 5-hydroxyuracil, is base excision repair (BER). The BER pathway in the nucleus is well elucidated. More recently, BER was shown to also exist in the mitochondria. Here, we review the association of BER of oxidative DNA damage with aging, cancer and other diseases.

Maternally transmitted milk containing recombinant human catalase provides protection against oxidation for mouse offspring during lactation

Catalase plays an important role in protecting organisms against oxidative damage caused by reactive oxygen species (ROS) by degrading surplus hydrogen peroxide. Addition of exogenous catalase can alleviate injuries caused by ROS. Thus, production of human catalase through genetic engineering will meet the increasing therapeutic demand for this enzyme. In this study, we successfully expressed the recombinant gene in mouse mammary gland, and biologically active human catalase was secreted into the milk of the transgenic mice. The peroxisomal targeting sequence (PTS) within the catalase gene had no significant negative effect on the secretion of the recombinant protein. Intake of the transgenic milk by the pups was found to decrease lipid peroxidation, increase the total superoxide dismutase (T-SOD) activity in the brain, and enhance the total antioxidative capacity (T-AOC) of brain, liver, and serum. To our knowledge, this is the first example of efficient production of biologically active human catalase in the milk of transgenic animals. Our study suggests that scaled-up production in transgenic farm animals would yield sufficient human catalase for biomedical research and clinical therapies.

Replicative senescence induced by Romo1-derived reactive oxygen species

Persistent accumulation of DNA damage induced by reactive oxygen species (ROS) is proposed to be a major contributor toward the aging process. Furthermore, an increase in age-associated ROS is strongly correlated with aging in various species, including humans. Here we showed that the enforced expression of the ROS modulator 1 (Romo1) triggered premature senescence by ROS production, and this also contributed toward induction of DNA damage. Romo1-derived ROS was found to originate in the mitochondrial electron transport chain. Romo1 expression gradually increased in proportion to population doublings of IMR-90 human fibroblasts. An increase in ROS production in these cells with high population doubling was blocked by the Romo1 knockdown using Romo1 small interfering RNA. Romo1 knockdown also inhibited the progression of replicative senescence. Based on these results, we suggest that age-related ROS levels increase, and this contributes to replicative senescence, which is directly associated with Romo1 expression.

The oxidative stress theory of aging: embattled or invincible? Insights from non-traditional model organisms

Reactive oxygen species (ROS), inevitable byproducts of aerobic metabolism, are known to cause oxidative damage to cells and molecules. This, in turn, is widely accepted as a pivotal determinant of both lifespan and health span. While studies in a wide range of species support the role of ROS in many age-related diseases, its role in aging per se is questioned. Comparative data from a wide range of endotherms offer equivocal support for this theory, with many exceptions and inconclusive findings as to whether or not oxidative stress is either a correlate or a determinant of maximum species lifespan. Available data do not support the premise that metabolic rate and in vivo ROS production are determinants of lifespan, or that superior antioxidant defense contributes to species longevity. Rather, published studies often show either a negative associate or lack of correlation with species longevity. Furthermore, many long-living species such as birds, bats and mole-rats exhibit high levels of oxidative damage even at young ages. Similarly genetic manipulations altering expression of key antioxidants do not necessarily show an impact on lifespan, even though oxidative damage levels may be affected. While it is possible that these multiple exceptions to straightforward predictions of the free radical theory of aging all reflect species-specific, "private" mechanisms of aging, the preponderance of contrary data nevertheless present a challenge to this august theory. Therefore, contrary to accepted dogma, the role of oxidative stress as a determinant of longevity is still open to question.

Growth hormone and heart failure: oxidative stress and energetic metabolism in rats

Several evidences point for beneficial effects of growth hormone (GH) in heart failure (HF). Taking into account that HF is related with changes in myocardial oxidative stress and in energy generation from metabolic pathways, it is important to clarify whether GH increase or decrease myocardial oxidative stress and what is its effect on energetic metabolism in HF condition. Thus, this study investigated the effects of two different doses of GH on energetic metabolism and oxidative stress in myocardium of rats with HF. Male Wistar rats (n=25) were submitted to aortic stenosis (AS). The HF was evidenced by tachypnea and echocardiographic criteria around 28 weeks of AS. The rats were then randomly divided into three groups: (HF) with HF, treated with saline (0.9% NaCl); (HF-GH1), treated with 1 mk/kg/day recombinant human growth hormone (rhGH), and (HF-GH2) treated with 2 mg/kg/day rhGH. GH was injected, subcutaneously, daily for 2 weeks. A control group (sham; n=12), with the same age of the others rats was evaluated to confirm data for AS. HF had lower IGF-I (insulin-like growth factor-I) than sham-operated rats, and both GH treatments normalized IGF-I level. HF-GH1 animals had lower lipid hydroperoxide (LH), LH/total antioxidant substances (TAS) and glutathione-reductase than HF. Glutathione peroxidase (GSH-Px), hydroxyacyl coenzyme-A dehydrogenase, lactate dehydrogenase(LDH) were higher in HF-GH1 than in HF. HF-GH2 compared with HF, had increased LH/TAS ratio, as well as decreased oxidized glutathione and LDH activity. Comparing the two GH doses, GSH-Px, superoxide dismutase and LDH were lower in HF-GH2 than in HF-GH1. In conclusion, GH effects were dose-dependent and both tested doses did not aggravate the heart dysfunction. The higher GH dose, 2 mg/kg exerted detrimental effects related to energy metabolism and oxidative stress. The lower dose, 1mg/kg GH exerted beneficial effects enhancing antioxidant defences, reducing oxidative stress and improving energy generation in myocardium of rats with heart failure.

Modulating an oxidative-inflammatory cascade: potential new treatment strategy for improving glucose metabolism, insulin resistance, and vascular function

Type 2 diabetes is a result of derangement of homeostatic systems of metabolic control and immune defense. Increases in visceral fat and organ adipose, environmental factors and genetic predisposition create imbalances of these homeostatic mechanisms, ultimately leading to a condition in which the oxidative environment cannot be held in check. A significant imbalance between the production of reactive oxygen species and antioxidant defenses, a condition called to oxidative stress, ensues, leading to alterations in stress-signalling pathways and potentially end-organ damage. Oxidative stress and metabolic inflammation upregulate the expression pro-inflammatory cytokines, including tissue necrosis factor alpha, monocyte chemoattractant protein-1 and interleukin-6, as well as activating stress-sensitive kinases, such as c-Jun N-terminal kinase (JNK), phosphokinase C isoforms, mitogen-activated protein kinase and inhibitor of kappa B kinase. The JNK pathway (specifically JNK-1) appears to be a regulator that triggers the oxidative-inflammation cascade that, if left unchecked, can become chronic and cause abnormal glucose metabolism. This can lead to insulin resistance and dysfunction of the vasculature and pancreatic beta-cell. The series of events set in motion by the interaction between metabolic inflammation and oxidative stress constitutes an 'oxidative-inflammatory cascade', a delicate balance driven by mediators of the immune and metabolic systems, maintained through a positive feedback loop. Modulating an oxidative-inflammation cascade may improve glucose metabolism, insulin resistance and vascular function, thereby slowing the development and progression to cardiovascular diseases and type 2 diabetes.

Progeric effects of catalase inactivation in human cells

Peroxisomes generate hydrogen peroxide, a reactive oxygen species, as part of their normal metabolism. A number of pathological situations exist in which the organelle's capacity to degrade the potentially toxic oxidant is compromised. It is the peroxidase, catalase, which largely determines the functional antioxidant capacity of the organelle, and it is this enzyme that is affected in aging, in certain diseases, and in response to exposure to specific chemical agents. To more tightly control the enzymatic activity of peroxisomal catalase and carefully document the effects of its impaired action on human cells, we employed the inhibitor 3-amino-1,2,4-triazole. We show that by chronically reducing catalase activity to approximately 38% of normal, cells respond in a dramatic manner, displaying a cascade of accelerated aging reactions. Hydrogen peroxide and related reactive oxygen species are produced, protein and DNA are oxidatively damaged, import into peroxisomes and organelle biogenesis is corrupted, and matrix metalloproteinases are hyper-secreted from cells. In addition, mitochondria are functionally impaired, losing their ability to maintain a membrane potential and synthesize reactive oxygen species themselves. These latter results suggest an important redox-regulated connection between the two organelle systems, a topic of considerable interest for future study.

Chronic exposure to 50Hz magnetic fields causes a significant weakening of antioxidant defence systems in aged rat brain

Several studies suggest that extremely low-frequency magnetic fields (ELF-MFs) may enhance the free radical endogenous production. It is also well known that one of the unavoidable consequences of ageing is an overall oxidative stress-based decline in several physiological functions and in the general resistance to stressors. On the basis of these assumptions, the aim of this study was to establish whether the ageing process can increase susceptibility towards widely present ELF-MF-mediated pro-oxidative challenges. To this end, female Sprague-Dawley rats were continuously exposed to a sinusoidal 50 Hz, 0.1 mT magnetic field for 10 days. Treatment-induced changes in the major antioxidant protection systems and in the neurotrophic support were investigated, as a function of the age of the subjects. All analyses were performed in brain cortices, due to the high susceptibility of neuronal cells to oxidative injury. Our results indicated that ELF-MF exposure significantly affects anti-oxidative capability, both in young and aged animals, although in opposite ways. Indeed, exposed young individuals enhanced their neurotrophic signalling and anti-oxidative enzymatic defence against a possible ELF-MF-mediated increase in oxygen radical species. In contrast, aged subjects were not capable of increasing their defences in response to ELF-MF treatment but, on the contrary, they underwent a significant decrease in the major antioxidant enzymatic activities. In conclusion, our data seem to suggest that the exposure to ELF-MFs may act as a risk factor for the occurrence of oxidative stress-based nervous system pathologies associated with ageing.

Ginsenoside Rg1 delays tert-butyl hydroperoxide-induced premature senescence in human WI-38 diploid fibroblast cells

Tert-butyl hydroperoxide (t-BHP), an analog of hydroperoxide, induced characteristic changes of senescence in human diploid fibroblasts WI-38 cells. It was reported that ginsenoside Rg1, an active ingredient of ginseng, ameliorated learning deficits in aged rats. The present study was aimed to investigate whether ginsenoside Rg1 can delay the premature senescence of WI-38 cells induced by t-BHP and to explore the underlying molecular mechanisms. First, Rg1 pretreatment markedly reversed senescent morphological changes in WI-38 cells induced by t-BHP. Second, t-BHP treatment alone resulted in an increase in the protein levels of P16 and P21, and a decline in intracellular adenosine 5'-triphosphate (ATP) level and mitochondrial complex IV activity. Ginsenoside Rg1 pretreatment had significant effects of attenuating these changes. These data indicate that ginsenoside Rg1 has an anti-aging effect on t-BHP-induced premature senescence in WI-38 cells. This effect may be mediated by regulating cell cycle proteins and enhancing mitochondrial functioning.

Age and disease-related structural changes in the retinal pigment epithelium

As the retinal pigment epithelium (RPE) ages, a number of structural changes occur, including loss of melanin granules, increase in the density of residual bodies, accumulation of lipofuscin, accumulation of basal deposits on or within Bruch's membrane, formation of drusen (between the basal lamina of the RPE and the inner collagenous layer of Bruch's membrane), thickening of Bruch's membrane, microvilli atrophy and disorganization of the basal infoldings. Although these changes are well known, the basic mechanisms involved in them are frequently poorly understood. These age-related changes progress slowly and vary in severity in different individuals. These changes are also found in age-related macular degeneration (AMD), a late onset disease that severely impacts the RPE, but they are much more pronounced than during normal aging. However, the changes in AMD lead to severe loss of vision. Given the many supporting functions which the RPE serves for the retina, it is important to decipher the age-related changes in this epithelium in order to understand age-related changes in vision.

Telomere attrition due to infection

BACKGROUND

Telomeres--the terminal caps of chromosomes--become shorter as individuals age, and there is much interest in determining what causes telomere attrition since this process may play a role in biological aging. The leading hypothesis is that telomere attrition is due to inflammation, exposure to infectious agents, and other types of oxidative stress, which damage telomeres and impair their repair mechanisms. Several lines of evidence support this hypothesis, including observational findings that people exposed to infectious diseases have shorter telomeres. Experimental tests are still needed, however, to distinguish whether infectious diseases actually cause telomere attrition or whether telomere attrition increases susceptibility to infection. Experiments are also needed to determine whether telomere erosion reduces longevity.

METHODOLOGY/PRINCIPAL FINDINGS

We experimentally tested whether repeated exposure to an infectious agent, Salmonella enterica, causes telomere attrition in wild-derived house mice (Mus musculus musculus). We repeatedly infected mice with a genetically diverse cocktail of five different S. enterica strains over seven months, and compared changes in telomere length with sham-infected sibling controls. We measured changes in telomere length of white blood cells (WBC) after five infections using a real-time PCR method. Our results show that repeated Salmonella infections cause telomere attrition in WBCs, and particularly for males, which appeared less disease resistant than females. Interestingly, we also found that individuals having long WBC telomeres at early age were relatively disease resistant during later life. Finally, we found evidence that more rapid telomere attrition increases mortality risk, although this trend was not significant.

CONCLUSIONS/SIGNIFICANCE

Our results indicate that infectious diseases can cause telomere attrition, and support the idea that telomere length could provide a molecular biomarker for assessing exposure and ability to cope with infectious diseases.

Long flights and age affect oxidative status of homing pigeons (Columba livia)

Flying is an energy demanding activity that imposes several physiological challenges on birds, such as increase in energy expenditure. Evidence from sports medicine shows that exhausting exercise may cause oxidative stress. Studies on avian flight have so far considered several blood parameters, such as uric acid, corticosteroids, or circulating free fatty acids, but only one study has analysed markers of oxidative stress in flying birds. In this study, we evaluated, for the first time, how different flight efforts affect the oxidative status using homing pigeons (Columba livia) as a model species. Two groups of pigeons flew for around 60 and 200 km, respectively. Pigeons that flew for 200 km had a 54% increase in oxidative damage as measured by serum reactive oxygen metabolites (ROMs), a 19% drop in total serum antioxidant capacity (OXY) and an 86% increase of oxidative stress (ROMs/OXYx1000). Older pigeons depleted more serum antioxidants regardless of the release distance. Among pigeons that flew the longer distance, heavier ones depleted less serum antioxidants. The results of the study suggest that long flights may cause oxidative stress, and that older individuals may experience higher physiological demands.

Cellular and molecular characterization of oxidative stress in olfactory epithelium of Harlequin mutant mouse

Oxidative stress in the olfactory system is a major factor associated with age-related olfactory impairment, although the mechanisms by which this occurs are not completely understood. The Harlequin mutant mouse (Hq/Y), which carries an X-linked recessive mutation in the Aifm1 gene, is a model of progressive oxidative stress-induced neurodegeneration in the cerebellum and retina. To determine whether the Hq/Y mutant mouse is a suitable model of oxidative stress-associated olfactory aging, we investigated cellular and molecular changes in the olfactory epithelium (OE) and olfactory bulb (OB) of 6-month-old male Hq/Y mice compared to those in sex-matched littermate controls (+/Y) and in age- and sex-matched C57BL/6 mice. Immunoreactivity for apoptosis-inducing factor, the protein product of Aifm1, was localized in mature olfactory sensory neurons (mOSNs) in +/Y mice but was rarely detected in Hq/Y mice. Hq/Y mice also exhibited increased lipofuscin autofluorescence and increased immunoreactivity for an oxidative DNA/RNA damage marker in mOSNs and in mitral/tufted cells in the OB and an increased number of cleaved caspase-3 immunoreactive apoptotic cells in the OE. Microarray analysis demonstrated that Aifm1 expression was down-regulated by 80% in the OE of Hq/Y mice compared to that in +/Y mice. Most significantly, regulated genes were classified into functional categories of cell signaling/apoptosis/cell cycle, oxidative stress/aging, and cytoskeleton/extracellular matrix/transport-associated. Analysis with EASE software indicated that the functional categories significantly overrepresented in Hq/Y mice included up-regulated mitochondrial genes and down-regulated cytoskeletal organization- and neurogenesis-related genes. Our results strongly support the Hq/Y mutant mouse being a novel model for mechanistic studies of oxidative stress-associated olfactory aging.

Dysregulation of hepatic iron with aging: implications for heat stress-induced oxidative liver injury

Environmental heat stress is associated with an age-related increase in hepatic oxidative damage and an exaggerated state of oxidative stress. The purpose of this investigation was to evaluate the regulation of hepatic iron after heat stress. A secondary aim was to determine a potential role for iron in heat stress-induced liver injury. Hyperthermia-induced alterations in hepatic iron were evaluated in young (6 mo) and old (24 mo) Fischer 344 rats by exposing them to a two-heat stress protocol. Livers were harvested at several time points after the second heating and assayed for labile and nonheme iron. In the control condition, there was no difference in labile iron between age groups. Both labile iron and storage iron were not altered by hyperthermia in young rats, but both were increased immediately after heating in old rats. To evaluate a role for iron in liver injury, hepatic iron content was manipulated in young and old rats, and then both groups were exposed to heat stress. Iron administration to young rats significantly increased hepatic iron content and ferritin but did not affect markers of lipid peroxidation under control conditions or after heat stress. In old rats, iron chelation with deferoxamine prevented the increase in nonheme iron, labile iron, ferritin, and lipid peroxidation after heat stress. These results suggest that iron may play a role in hepatic injury after hyperthermia. Thus, dysregulation of iron may contribute to the gradual decline in cellular and physiological function that occurs with aging.

Aging results in increased autophagy of mitochondria and protein nitration in rat hepatocytes following heat stress

The natural breakdown of cells, tissues, and organ systems is a significant consequence of aging and is at least partially caused by a decreased ability to tolerate environmental stressors. Based on quantitative ultrastructural analysis using transmission electron microscopy and computer imaging, we show significant differences in hepatocyte morphology between young and old rats during a 48-hr recovery period following a 2-day heat stress protocol. Mitochondrial injury was greater overall in old compared with young rats. Autophagy was observed in both young and old rats, with autophagy greater overall in old compared with young hepatocytes. Lipid peroxidation and protein nitration were evaluated by localization and quantification of 4-hydroxy-2-nonenal (4-HNE)-modified protein adducts and 3-nitrotyrosine (3-NT) levels, respectively. Levels of 3-NT but not 4-HNE-protein adducts were significantly elevated in hepatocytes of old rats in comparison with young at 90 min after heat stress, suggesting a major role for reactive nitrogen species in the pathology observed at this time point. These results show a differential response of hepatocyte mitochondria to heat stress with aging, as well as greater levels of both autophagic and nitrative damage in old vs young hepatocytes. This manuscript contains online supplemental material at http://www.jhc.org. Please visit this article online to view these materials.

PGAM5 tethers a ternary complex containing Keap1 and Nrf2 to mitochondria

Eukaryote cells balance production of reactive oxygen species (ROS) with levels of anti-oxidant enzyme activity to maintain cellular redox homeostasis. Mitochondria are a major source of ROS, while many anti-oxidant genes are regulated by the Nrf2 transcription factor. Keap1, a redox-regulated substrate adaptor for a cullin-based ubiquitin ligase, targets Nrf2 for proteosome-mediated degradation and represses Nrf2-dependent gene expression. We have previously identified a member of the phosphoglycerate mutase family, PGAM5, as a Keap1-binding protein. In this report, we demonstrate that PGAM5 is targeted to the outer membrane of mitochondria by an N-terminal mitochondrial-localization sequence. Furthermore, we provide evidence that PGAM5 forms a ternary complex containing both Keap1 and Nrf2, in which the dimeric Keap1 protein simultaneously binds both PGAM5 and Nrf2 through their conserved E(S/T)GE motifs. Knockdown of either Keap1 or PGAM5 activates Nrf2-dependent gene expression. We suggest that this ternary complex provides a molecular framework for understanding how nuclear anti-oxidant gene expression is regulated in response to changes in mitochondrial function(s).

A combination of genomic approaches reveals the role of FOXO1a in regulating an oxidative stress response pathway

BACKGROUND

While many of the phenotypic differences between human and chimpanzee may result from changes in gene regulation, only a handful of functionally important regulatory differences are currently known. As a first step towards identifying transcriptional pathways that have been remodeled in the human lineage, we focused on a transcription factor, FOXO1a, which we had previously found to be up-regulated in the human liver compared to that of three other primate species. We concentrated on this gene because of its known role in the regulation of metabolism and in longevity.

METHODOLOGY

Using a combination of expression profiling following siRNA knockdown and chromatin immunoprecipitation in a human liver cell line, we identified eight novel direct transcriptional targets of FOXO1a. This set includes the gene for thioredoxin-interacting protein (TXNIP), the expression of which is directly repressed by FOXO1a. The thioredoxin-interacting protein is known to inhibit the reducing activity of thioredoxin (TRX), thereby hindering the cellular response to oxidative stress and affecting life span.

CONCLUSIONS

Our results provide an explanation for the repeated observations that differences in the regulation of FOXO transcription factors affect longevity. Moreover, we found that TXNIP is down-regulated in human compared to chimpanzee, consistent with the up-regulation of its direct repressor FOXO1a in humans, and with differences in longevity between the two species.

Cellular and molecular aspects of ovarian follicle ageing

It is well established that age-related decline of the biological capacity of a woman to reproduce is primarily related to the poor developmental potential of her gametes. This renders female ageing the most significant determinant of success in IVF. Starting with a reference picture of the main molecular and cellular failures of aged oocytes, granulosa cells and follicular microenvironment, this review focuses on age-related biochemical mechanisms underlying these changes. According to the most relevant concept of ageing, age-associated malfuction results from physiological accumulation of irreparable damage to biomolecules as an unavoidable side effect of normal metabolism. More than a decade after the free radical theory of ovarian ageing, biological and clinical research supporting the involvement of oxidative injuries in follicle ageing is discussed. Looking for the aetiology of oxidative stress, we consider the effect of ageing on ovarian and follicular vascularization. Then, we propose a potential role of advanced glycation end-products known to be involved in the physiological ageing of most tissues and organs. We conclude that future investigation of age-related molecular damage in the different ovarian components will be imperative in order to evaluate the possibility to save or rescue the developmental potential of aged oocytes.

Attenuation of senescence-induced oxidative exacerbations in aged rat brain by (-)-epigallocatechin-3-gallate

Aging is a complex biological phenomenon which involves free radicals and oxidative stress. Brain is more susceptible and vulnerable to oxidative damage due to its high-polyunsaturated fatty acid content and high rate of aerobic metabolism. Since the antioxidant defense system is diminished during aging, antioxidant supplementation might be a protective strategy against age-associated oxidative damage. The present study evaluates the antioxidant potential of (-)-epigallocatechin-3-gallate (EGCG), a major polyphenol present in green tea against age-associated oxidative damage in rat brain. Male albino rats of Wistar strain were used in the study. Group I (young) and Group II (aged) rats received saline alone orally for 30 days. Group III (young) and Group IV (aged) rats received EGCG (2mg/kg body weight/day) orally for 30 days. Antioxidant status and oxidative damage were assessed. EGCG brought about an augmentation in the activities of enzymic antioxidants like superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glucose-6-phosphate dehydrogenase and improved the non-enzymic antioxidants like tocopherol, ascorbic acid and glutathione. EGCG ameliorated the malondialdehyde and protein carbonyl levels. Thus, EGCG has emerged out as a good antioxidant neutraceutical and a neuroprotective agent in alleviating the age-associated oxidative damage in aged rat brain.

Oxidative stress is associated with greater mortality in older women living in the community

OBJECTIVES

To determine whether oxidative stress, as implied by oxidative damage to proteins, is associated with greater mortality in older women living in the community.

DESIGN

Longitudinal.

SETTING

Women's Health and Aging Study I, Baltimore, Maryland.

PARTICIPANTS

Seven hundred forty-six moderately to severely disabled women, aged 65 and older, with baseline measures of serum protein carbonyls.

MEASUREMENTS

Serum protein carbonyls, which consist of chemically stable aldehyde and ketone groups produced on protein side chains when they are oxidized, were measured using enzyme-linked immunosorbent assay. Multivariate logistic regression was used to adjust for potential confounders.

RESULTS

During 5 years of follow-up, 202 (27.1%) participants died. Geometric mean serum protein carbonyls were 0.091 nmol/mg in women who died and 0.083 nmol/mg in those who survived (P=.02). Log(e) protein carbonyls (nmol/mg) were associated with greater risk of mortality (hazards ratio=1.34, 95% confidence interval=1.01-1.79, P=.04) in a multivariate Cox proportional hazards model adjusting for age, current smoking, and body mass index.

CONCLUSION

Greater oxidative stress, as indicated by elevated serum protein carbonyl concentrations, was associated with greater risk of death in older women living in the community who were moderately to severely disabled. Prevention of oxidative stress may reduce the risk of mortality.

DNA damage, cellular senescence and organismal ageing: causal or correlative?

Cellular senescence has long been used as a cellular model for understanding mechanisms underlying the ageing process. Compelling evidence obtained in recent years demonstrate that DNA damage is a common mediator for both replicative senescence, which is triggered by telomere shortening, and premature cellular senescence induced by various stressors such as oncogenic stress and oxidative stress. Extensive observations suggest that DNA damage accumulates with age and that this may be due to an increase in production of reactive oxygen species (ROS) and a decline in DNA repair capacity with age. Mutation or disrupted expression of genes that increase DNA damage often result in premature ageing. In contrast, interventions that enhance resistance to oxidative stress and attenuate DNA damage contribute towards longevity. This evidence suggests that genomic instability plays a causative role in the ageing process. However, conflicting findings exist which indicate that ROS production and oxidative damage levels of macromolecules including DNA do not always correlate with lifespan in model animals. Here we review the recent advances in addressing the role of DNA damage in cellular senescence and organismal ageing.

Oxidative stress reduces transintestinal transports and (Na+, K+) -ATPase activity in rat jejunum

Because oxidative stress is a component of gastrointestinal injury, we investigated the effect of H(2)O(2) on transintestinal transport using isolated rat jejunum incubated in vitro. Millimolar concentrations of H(2)O(2) inhibited all the tested parameters without inducing any cytotoxic effect. Electrophysiological experiments indicated that H(2)O(2) decreases significantly both short circuit current and transepithelial electrical potential difference without affecting transepithelial resistance. The possibility that H(2)O(2) could influence (Na+, K+) -ATPase activity was explored using isolated basolateral membranes. Besides H(2)O(2), free radicals (O(2)(*-), HO*) were generated using different iron-dependent and independent systems; (Na+, K+) -ATPase activity was inhibited after membrane exposure to all ROS tested. The inhibition was prevented by allopurinol, superoxide dismutase or desferrioxamine. Western blot analysis showed a decreased expression of the alpha(1)-subunit of (Na+, K+) -ATPase. We conclude that H(2)O(2) may be a modulator of jejunal ion and water transport by multiple mechanisms, among which a significant inhibition of the basolateral (Na+, K+) -ATPase.

Assessment of paraoxonase activity and lipid peroxidation levels in diabetic and senile subjects suffering from cataract

OBJECTIVES

The purpose of this study was to evaluate antioxidant effect of paraoxonase 1 activity and malondialdehyde (MDA) levels as a marker of oxidative stress in patients suffering from cataract due to diabetes and aging.

DESIGN AND METHODS

One hundred cataract patients (senile and diabetic) and age- and sex-matched controls were studied. Paraoxonase 1 and arylesterase activities in plasma samples were measured using paraoxon and phenylacetate as substrates, respectively. The magnitude of lipid peroxidation was established by measuring plasma MDA and oxidized low-density lipoprotein (ox LDL) levels. One-way ANOVA was employed for analysis of results.

RESULTS

We observed significantly lower plasma paraoxonase and arylesterase activities in senile and diabetic cataractous patients as compared to respective controls (p<0.001). Plasma MDA and ox LDL levels were found to be higher in patients suffering from cataract (p<0.001).

CONCLUSIONS

The results of present study suggest that the observed decrease in PON1 activity may be due to increase in oxidative stress. It can be concluded that lower paraoxonase activity could contribute to the higher risk of cataract formation.

Oxidative stress, chronic disease, and muscle wasting

Underlying the pathogenesis of chronic disease is the state of oxidative stress. Oxidative stress is an imbalance in oxidant and antioxidant levels. If an overproduction of oxidants overwhelms the antioxidant defenses, oxidative damage of cells, tissues, and organs ensues. In some cases, oxidative stress is assigned a causal role in disease pathogenesis, whereas in others the link is less certain. Along with underlying oxidative stress, chronic disease is often accompanied by muscle wasting. It has been hypothesized that catabolic programs leading to muscle wasting are mediated by oxidative stress. In cases where disease is localized to the muscle, this concept is easy to appreciate. Transmission of oxidative stress from diseased remote organs to skeletal muscle is thought to be mediated by humoral factors such as inflammatory cytokines. This review examines the relationship between oxidative stress, chronic disease, and muscle wasting, and the mechanisms by which oxidative stress acts as a catabolic signal.

Possible involvement of oxidative stress in salivary gland of patients with Sjogren's syndrome

OBJECTIVE

To determine the involvement of oxidative stress in the salivary gland of patients with Sjogren's syndrome (SS).

METHODS

Oxidative damage to the gland was measured by 8-hydroxy-2'-deoxyguanosine (8-OHdG) and hexanoyl-lysine (HEL) using the SS saliva. In addition, lactate dehydrogenase (LDH) and mitochondrial glutamic-oxaloacetic transaminase (m-GOT), both general markers for cell damage, were also analyzed.

RESULTS

Increased levels of 8-OHdG and HEL were found in the saliva of SS patients, but not in that of patients with other salivary gland dysfunction or of healthy individuals. Levels of LDH and m-GOT were significantly correlated with 8-OHdG and HEL levels, respectively. Furthermore, the increased levels of 8-OHdG and HEL were also correlated in the SS saliva.

CONCLUSION

These findings suggested the involvement of oxidative stress in glandular tissue destruction in SS. It was indicated that the detection of 8-OHdG and HEL in the saliva may become a useful tool for the diagnosis of SS.

RCAN1 (DSCR1) increases neuronal susceptibility to oxidative stress: a potential pathogenic process in neurodegeneration

Oxidative stress (OS) underlies neuronal dysfunction in many neurodegenerative disorders. Regulator of Calcineurin 1 (RCAN1 or DSCR1) is a dose-sensitive gene whose overexpression has been linked to Down syndrome (DS) and Alzheimer's disease (AD) neuropathology and to the response of cells to stress stimuli. Here, we show that RCAN1 mRNA and protein expression are sensitive to OS in primary neurons, and we evaluate the involvement of RCAN1 dosage in neuronal death induced by OS. We find that Rcan1(-/-) neurons display an increased resistance to damage by H(2)O(2), which can be reverted by RCAN1 overexpression or by exogenous inhibitors of calcineurin. Although increased intracellular Ca(2+) concentration is an important factor in OS-mediated cell death, our results show that Ca(2+) loading after exposure to H(2)O(2) was similar in Rcan1(+/+) and Rcan1(-/-) neurons. Our data further suggest that CaN and NFAT signaling protect against OS in both Rcan1(+/+) and Rcan1(-/-) neurons. To explain the observed differential vulnerability, we therefore propose a mechanism downstream of H(2)O(2)-mediated Ca(2+) entry, involving calcineurin-NFAT signaling. These findings highlight the importance of RCAN1 gene dosage in the modulation of cell survival and death pathways and suggest that changes in the amount of RCAN1 could represent an important mechanism for regulating susceptibility to neurodegeneration, especially in DS and AD.

Antioxidative action of royal jelly in the yeast cell

Royal jelly is a bee product, secreted from the hypopharingeal and mandibular glands of worker bees. There are many reports on pharmacological activities of royal jelly in experimental animals, but there are few about its antioxidative properties connected to aging. The aim of the work was to investigate the antioxidative action of royal jelly in the cell of the yeast Saccharomyces cerevisiae as a model organism. Yeast was cultivated in YEPD medium enriched with different concentrations of royal jelly like 1, 2 and 5 g/L. Yeast growth was monitored by measuring optical density. At different time points cell energy metabolic activity was measured using the cell energy metabolism indicator resazurin, and 2',7'-dichlorofluorescein was applied to estimate intracellular oxidation. Additionally, protein profile of cell extract was analyzed by 2-D electrophoresis. Results showed that royal jelly decreased intracellular oxidation in a dose dependent manner. Additionally it affected growth and cell energy metabolic activity in a growth phase dependent manner. Protein profile analysis showed that royal jelly in the cell does not act only as a scavenger of reactive oxygen species, but it also affects protein expression. Differentially expressed proteins were identified.

Ischemia-reperfusion and cardioprotection: a delicate balance between reactive oxygen species generation and redox homeostasis

Ischemia-reperfusion injury of the myocardium has long been a subject of intense research. Cardiac preconditioning, an associated phenomenon, has also been critically investigated over the past two decades. Although the biochemistry of ischemia-reperfusion and its association with oxidative metabolism has long been established, recent studies have further revealed a more intricate role of a number of reactive oxygen-nitrogen species in those processes. Emerging evidence suggests that an elaborate network of enzymes (and other biomolecules) dedicated to the generation, utilization, and diminution of reactive oxygen-nitrogen species maintains the redox homeostasis in the myocardium, and any perturbation of its status has distinctive effects. It thus appears that while excessive generation of reactive species leads to cellular injury, their regulated generation may cause transient and reversible modifications of cellular proteins leading the transmission of intracellular signals with specific effects. Taken together, generation of reactive oxygen-nitrogen species in the myocardium plays a nodal role in mediating both ischemic injury and cardioprotection.