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

The impact of exercise training on the lipid peroxidation metabolomic profile and respiratory infection risk in older adults

Aging is associated with oxidative stress that may increase susceptibility to respiratory infections (RIs). We aimed to assess the impact of exercise training on the risk of RIs in older adults and on a targeted metabolomic profile of stress oxidative lipid peroxidation-related metabolites.

METHODS

In an 8-month clinical trial, 38 participants over 60 years of age were allocated to an exercise group (EG), in which participants underwent 90-min training sessions three times/week(n = 20), or a control group (CG), in which participants maintained daily physical activities(n = 18). Daily respiratory symptoms and RIs number and severity were collected. Serum by-products were assessed by comprehensive two-dimensional gas chromatography coupled to mass spectrometry with time of flight analyzer. Serum metabolomic profiling comprised 76 metabolites (alcohols, aldehydes, alkanes, and ketones). Principal components analysis and ANOVA-simultaneous component analysis were used to evaluate the metabolomic profile change.

RESULTS

The odds ratio of RIs for the EG was 2.0 CI 95% [0.2;25]. The incidence of RIs was 47% [23;70] in the EG vs. 44%[12;77] in the CG. The metabolomic profiling showed that alkanes and aldehydes classes differed between the EG and the CG before and after intervention. A calibration model showed a relation between the metabolites from four main classes (ketones, alcohols, alkanes and aldehydes) and the prediction of the number of RIs.

CONCLUSION

Moderate exercise training, in older adults, compared with no exercise in controls, did not show a difference in the risk of RIs. A pattern of lipid peroxidation was associated with the number of RIs.

Transcripts encoding free radical scavengers in human granulosa cells from primordial and primary ovarian follicles

PURPOSE

To study the presence and distribution of genes encoding free radical scavengers in human granulosa cells from primordial and primary ovarian follicles.

METHODS

A class comparison study on existing granulosa cell transcriptome from primordial (n = 539 follicles) and primary (n = 261) follicles donated by three women having ovarian tissue cryopreserved before chemotherapy was performed and interrogated.

RESULTS

In granulosa cells from primordial follicles, 30 genes were annotated 'mitochondrial dysfunction' including transcripts (PRDX5, TXN2) encoding enzymatic free radical scavengers peroxiredoxin 5 and thioredoxin 2. Several apoptosis regulation genes were noted (BCL2, CAS8, CAS9, AIFM1). In granulosa cells from primary follicles, mitochondrial dysfunction signalling pathway was annotated. High expression of transcripts encoding the free radical scavenger peroxiredoxin 3, as well as anti-apoptotic enzyme BCL2, was found. Interestingly, PARK7 encoding the deglycase (DJ-1) protein was expressed in granulosa cells from primary follicles. DJ-1 is implicated in oxidative defence and functions as a positive regulator of the androgen receptor and as a negative regulator of the phosphatidylinositol 3-kinase (PI3K)/phosphatase and tensin homolog (PTEN)/serine-threonine protein kinase (AKT) signalling pathway suppressor PTEN.

CONCLUSIONS

The results indicate extensive energy production and free radical scavenging in the granulosa cells of primordial follicles with potential implications for ovarian ageing, cigarette smoking, premature ovarian failure and polycystic ovarian syndrome. Furthermore, DJ-1 may be involved in androgen responsiveness and the regulation of follicle growth via PI3K/PTEN/AKT signalling pathway regulation in the granulosa cells of primary follicles. The involvement of mitochondrial free radical production in the age-related decline of competent oocytes is becoming apparent.

The subchronic exposure to malathion, an organophosphate pesticide, causes lipid peroxidation, oxidative stress, and tissue damage in rats: the protective role of resveratrol

The present study was planned to evaluate the protective role of resveratrol (Res) against subchronic malathion exposure in rats over four weeks. In total, 48 Wistar rats were used and divided equally into six groups. The groups were designed as the control group (received only a rodent diet and tap water), the corn oil group (0.5 ml corn oil by the oral route), and the malathion group (100 mg kg-1 day-1 by the oral route). Other three groups received malathion (100 mg kg-1 day-1) plus Res (5, 10, and 20 mg kg-1 day-1, respectively) by the oral route. Malathion increased malondialdehyde and 8-OHdG levels, whereas it decreased glutathione levels. Also, acetylcholinesterase, superoxide dismutase, and catalase activities were found to be low in the blood, liver, kidney, heart, and brain tissues. Biochemical parameters were not notably changed in all groups. In contrast, Res treatment inverted malathion-induced oxidative stress, lipid peroxidation, and activity of enzymes. Additionally, malathion-induced histopathological changes in the liver, kidney, heart, and brain were ameliorated by Res treatment. These results demonstrate that malathion increases oxidative stress and decreases the antioxidant status while Res has a protective function against malathion toxicity in rats.

Young and Especially Senescent Endothelial Microvesicles Produce NADPH: The Fuel for Their Antioxidant Machinery

In a previous study, we demonstrated that endothelial microvesicles (eMVs) have a well-developed enzymatic team involved in reactive oxygen species detoxification. In the present paper, we demonstrate that eMVs can synthesize the reducing power (NAD(P)H) that nourishes this enzymatic team, especially those eMVs derived from senescent human umbilical vein endothelial cells. Moreover, we have demonstrated that the molecules that nourish the enzymatic machinery involved in NAD(P)H synthesis are blood plasma metabolites: lactate, pyruvate, glucose, glycerol, and branched-chain amino acids. Drastic biochemical changes are observed in senescent eMVs to optimize the synthesis of reducing power. Mitochondrial activity is diminished and the glycolytic pathway is modified to increase the activity of the pentose phosphate pathway. Different dehydrogenases involved in NADPH synthesis are also increased. Functional experiments have demonstrated that eMVs can synthesize NADPH. In addition, the existence of NADPH in eMVs was confirmed by mass spectrometry. Multiphoton confocal microscopy images corroborate the synthesis of reducing power in eMVs. In conclusion, our present and previous results demonstrate that eMVs can act as autonomous reactive oxygen species scavengers: they use blood metabolites to synthesize the NADPH that fuels their antioxidant machinery. Moreover, senescent eMVs have a stronger reactive oxygen species scavenging capacity than young eMVs.

Redox Regulation of Homeostasis and Proteostasis in Peroxisomes

Peroxisomes are highly dynamic intracellular organelles involved in a variety of metabolic functions essential for the metabolism of long-chain fatty acids, d-amino acids, and many polyamines. A byproduct of peroxisomal metabolism is the generation, and subsequent detoxification, of reactive oxygen and nitrogen species, particularly hydrogen peroxide (H2O2). Because of its relatively low reactivity (as a mild oxidant), H2O2 has a comparatively long intracellular half-life and a high diffusion rate, all of which makes H2O2 an efficient signaling molecule. Peroxisomes also have intricate connections to mitochondria, and both organelles appear to play important roles in regulating redox signaling pathways. Peroxisomal proteins are also subject to oxidative modification and inactivation by the reactive oxygen and nitrogen species they generate, but the peroxisomal LonP2 protease can selectively remove such oxidatively damaged proteins, thus prolonging the useful lifespan of the organelle. Peroxisomal homeostasis must adapt to the metabolic state of the cell, by a combination of peroxisome proliferation, the removal of excess or badly damaged organelles by autophagy (pexophagy), as well as by processes of peroxisome inheritance and motility. More recently the tumor suppressors ataxia telangiectasia mutate (ATM) and tuberous sclerosis complex (TSC), which regulate mTORC1 signaling, have been found to regulate pexophagy in response to variable levels of certain reactive oxygen and nitrogen species. It is now clear that any significant loss of peroxisome homeostasis can have devastating physiological consequences. Peroxisome dysregulation has been implicated in several metabolic diseases, and increasing evidence highlights the important role of diminished peroxisomal functions in aging processes.

Purification and antioxidant activity of phycocyanin from Synechococcus sp. R42DM isolated from industrially polluted site

The cyanobacterium Synechococcus sp. R42DM, isolated from an industrially polluted site Vatva, Gujarat, India was recognized to produce phycocyanin (PC) as major phycobiliprotein. In present study, the combinatorial approach of chemical and physical methods i.e. Triton-X 100 treatment and ultra-sonication was designed for extraction of PC. From cell extract, the intact and functional-PC was purified up to purity 4.03 by ammonium sulphate fractionation and ion-exchange chromatography. The PC displayed considerable in vitro antioxidant and radical-scavenging activity. This PC was further noticed to scavenge intracellular-ROS and to increase tolerance against thermal and oxidative stress in Caenorhabditis elegans. Moreover, the PC was noticed to improve the physiological behaviour and longevity of C. elegans. In addition, the PC showed remarkable stability under physico-chemical stressors, which is desirable for their use in biomedical applications. In conclusion, present paper added up evidence in support of the prospective use of PC as an antioxidant nutraceutical.

Epigenetic factors Polycomb (Pc) and Suppressor of zeste (Su(z)2) negatively regulate longevity in Drosophila melanogaster

The process of aging is a hallmark of the natural life span of all organisms and individuals within a population show variability in the measures of age related performance. Longevity and the rate of aging are influenced by several factors such as genetics, nutrition, stress, and environment. Many studies have focused on the genes that impact aging and there is increasing evidence that epigenetic factors regulate these genes to control life span. Polycomb (PcG) and trithorax (trxG) protein complexes maintain the expression profiles of developmentally important genes and regulate many cellular processes. Here, we report that mutations of PcG and trxG members affect the process of aging in Drosophila melanogaster, with perturbations mostly associated with retardation in aging. We find that mutations in polycomb repressive complex (PRC1) components Pc and Su(z)2 increase fly survival. Using an inducible UAS-GAL4 system, we show that this effect is tissue-specific; knockdown in fat body, but not in muscle or brain tissues, enhances life span. We hypothesize that these two proteins influence life span via pathways independent of their PRC1 functions, with distinct effects on response to oxidative stress. Our observations highlight the role of global epigenetic regulators in determining life span.

Telomere length, sibling competition and development of antioxidant defense in wild house mice

Antioxidants and telomere length are potential biomarkers for individuals' exposure and ability to cope with environmental stressors. However, intraspecific variations in antioxidant alterations due to natural, life cycle related stress, have been rarely estimated. We investigated those changes in wild-derived house mice in a longitudinal study with natural sibling competition as a stressor. Blood was used for telomere length measurements at 8-weeks age and for several selected antioxidants at 8-weeks and 6-months age. Our results show that most of the antioxidants increase during that time, indicating that antioxidant-system continues to develop after early development and sexual maturation. In addition females had higher antioxidant-levels than males. Mice with longer telomeres had also higher superoxide dismutase-activity and more glutathione than mice with shorter telomeres, meaning that long telomeres are associated with better antioxidant defense at maturation and during later life. Sibling competition at early age affected superoxide dismutase-levels at 6-months, but only in females. Females, which were lighter than the average of the litter had low superoxide dismutase -activity in later adulthood, indicating delayed negative effect of sibling competition on antioxidant defense. Our results highlight that sex and developmental stage are crucial in intraspecific comparisons of the antioxidant status and its alterations.

Aromatic Regions Govern the Recognition of NADPH Oxidase Inhibitors as Diapocynin and its Analogues

Oxidative stress is related to the pathogenesis and progress of several human diseases. NADPH oxidase (NOX), and mainly the NOX2 isoform, produces superoxide anions (O₂^•- ). To date, it is known that NOX2 can be inhibited by preventing the assembly of its subunits, p47phox and p22phox. In this work, we analyzed the binding to NOX2 of the apocynin dimer, diapocynin (C1), a known NOX2 inhibitor, and of 18 designed compounds (C2-C19) which have chemical relationships to C1, by in silico methods employing a p47phox structure from the Protein Data Bank (PDB code: 1WLP). C1 and six of the designed compounds were recognized in the region where p22phox binds to p47phox and makes π-π interactions principally with W193, W263, and Y279, which form an aromatic-rich region. C8 was chosen as the best compound according to the in silico studies and was synthesized and evaluated in vitro. C8 was able to prevent the production of reactive oxygen species (ROS) similar to C1. In conclusion, targeting the aromatic region of p47phox through π-interactions is important for inhibiting NOX activity.

Sex as a determinant of age-related changes in rat spinal cord inflammation-oxidation state

To close the gap in our knowledge of sex influence on age-related changes in inflammation-oxidation state in spinal cord (SC) relevant to inflammation/oxidative-stress associated neuropathologies, 2-3 month-old (young) and 18-20 month-old (old) rats, exhibiting increased level of IL-6, a commonly used marker of inflamm-aging, were examined for inflammatory/redox status, and the underlying regulatory networks' molecules expression. With age, rat SC microglia became sensitized ("primed"), while SC tissue shifted towards mild inflammatory state, with increased levels of proinflammatory IL-1β (key marker of microglial systemic inflammation-induced neurotoxicity), which was more prominent in males. This, most likely, reflected age- and sex-related impairment in the expression of CX3CR1, the receptor for fractalkine (CX3CL1), the soluble factor which regulates microglial activation and diminishes production of IL-1β (central for fractalkine neuroprotection). Considering that (i) age-related changes in SC IL-1β expression were not followed by complementary changes in SC IL-6 expression, and (ii) the reversal in the direction of the sex bias in circulating IL-6 level and SC IL-1β expression, it seems obvious that there are tissue-specific differences in the proinflammatory cytokine profile. Additionally, old male rat SC exhibited greater oxidative damage than female, reflecting, most likely, their lower capacity to maintain the pro-oxidant-antioxidant balance. In conclusion, these findings, apart from highlighting the significance of sex for age-associated changes in SC inflammation-oxidation, may be relevant for understating sex differences in human inflammation/oxidative-stress related SC diseases, and consequently, for optimizing their prevention/therapy.

Phenotypes, antioxidant responses, and gene expression changes accompanying a sugar-only diet in Bactrocera dorsalis (Hendel) (Diptera: Tephritidae)

BACKGROUND

Diet composition (yeast:carbohydrate ratio) is an important determinant of growth, development, and reproduction. Recent studies have shown that decreased yeast intake elicits numerous transcriptomic changes and enhances somatic maintenance and lifespan, which in turn reduces reproduction in various insects. However, our understanding of the responses leading to a decrease in yeast ratio to 0% is limited.

RESULTS

In the present study, we investigated the effects of a sugar-only diet (SD) on the gene expression patterns of the oriental fruit fly, Bactrocera dorsalis (Hendel), one of the most economically important pests in the family Tephritidae. RNA sequencing analyses showed that flies reared on an SD induced significant changes in the expression levels of genes associated with specific metabolic as well as cell growth and death pathways. Moreover, the observed upregulated genes in energy production and downregulated genes associated with reproduction suggested that SD affects somatic maintenance and reproduction in B. dorsalis. As expected, we observed that SD altered B. dorsalis phenotypes by significantly increasing stress (starvation and desiccation) resistance, decreasing reproduction, but did not extend lifespan compared to those that received a normal diet (ND) regime. In addition, administration of an SD resulted in a reduction in antioxidant enzyme activities and an increase in MDA concentrations, thereby suggesting that antioxidants cannot keep up with the increase in oxidative damage induced by SD regime.

CONCLUSIONS

The application of an SD diet induces changes in phenotypes, antioxidant responses, and gene expressions in B. dorsalis. Previous studies have associated extended lifespan with reduced fecundity. The current study did not observe a prolongation of lifespan in B. dorsalis, which instead incurred oxidative damage. The findings of the present study improve our understanding of the molecular, biochemical, and phenotypic response of B. dorsalis to an SD diet.

Different effects of accelerated development and enhanced growth on oxidative stress and telomere shortening in amphibian larvae

Organisms react to environmental changes through plastic responses that often involve physiological alterations with the potential to modify life-history traits and fitness. Environmentally induced shifts in growth and development in species with complex life cycles determine the timing of transitions between subsequent life stages, as well as body condition at transformation, which greatly determine survival at later stages. Here we show that spadefoot toad larvae surviving pond drying and predators experienced marked alterations in growth and development, and in their fat reserves, oxidative stress, and relative telomere length. Tadpoles accelerated development but reduced growth and consumed more fat reserves when facing pond drying. However, oxidative stress was buffered by increased antioxidant enzyme activity, and telomeres remained unchanged. Predators caused opposite effects: they reduced larval density, hence relaxing competition and allowing faster development and enhanced growth of survivors. Tadpoles surviving predators metamorphosed bigger and had larger fat bodies, increasing their short-term survival odds, but showed signs of oxidative stress and had shorter telomeres. Developmental acceleration and enhanced growth thus seemed to have different physiological consequences: reduced fat bodies and body size compromise short-term survival, but are reversible in the long run, whereas telomere shortening is non-reversible and could reduce long-term survival.

Cigarette smoking is associated with amplified age-related volume loss in subcortical brain regions

BACKGROUND

Magnetic resonance imaging studies of cigarette smoking-related effects on human brain structure have primarily employed voxel-based morphometry, and the most consistently reported finding was smaller volumes or lower density in anterior frontal regions and the insula. Much less is known about the effects of smoking on subcortical regions. We compared smokers and non-smokers on regional subcortical volumes, and predicted that smokers demonstrate greater age-related volume loss across subcortical regions than non-smokers.

METHODS

Non-smokers (n=43) and smokers (n=40), 22-70 years of age, completed a 4T MRI study. Bilateral total subcortical lobar white matter (WM) and subcortical nuclei volumes were quantitated via FreeSurfer. In smokers, associations between smoking severity measures and subcortical volumes were examined.

RESULTS

Smokers demonstrated greater age-related volume loss than non-smokers in the bilateral subcortical lobar WM, thalamus, and cerebellar cortex, as well as in the corpus callosum and subdivisions. In smokers, higher pack-years were associated with smaller volumes of the bilateral amygdala, nucleus accumbens, total corpus callosum and subcortical WM.

CONCLUSIONS

Results provide novel evidence that chronic smoking in adults is associated with accelerated age-related volume loss in subcortical WM and GM nuclei. Greater cigarette quantity/exposure was related to smaller volumes in regions that also showed greater age-related volume loss in smokers. Findings suggest smoking adversely affected the structural integrity of subcortical brain regions with increasing age and exposure. The greater age-related volume loss in smokers may have implications for cortical-subcortical structural and/or functional connectivity, and response to available smoking cessation interventions.

3-NP-induced Huntington's-like disease impairs Nrf2 activation without loss of cardiac function in aged rats

Cardiovascular diseases (CVDs) are one of the leading causes of death in patients over 60years with Huntington's disease (HD). Here, we investigated if age-related oxidative stress (OS) is a relevant factor to develop cardiac damage in an in vivo model of striatal neurodegeneration induced by 3-nitropropionic acid (3-NP). We also evaluated the potential effect of tert-butylhydroquinone (tBHQ) to increase the Nrf2-regulated antioxidant response in hearts from adult and aged rats intoxicated with 3-NP. Our results showed that 3-NP-treatment did not induce cardiac dysfunction, neither in adult nor in aged rats. However, at the cellular level, adult animals showed higher susceptibility to 3-NP-induced damage than aged rats, which suggest that chronic oxidative stress ongoing during aging might have induced an hormetic response that probably prevented from further 3-NP damage. We also found that the oxidative unbalance concurs with unresponsiveness of the Nrf2-mediated antioxidant response in old animals.

The association between three major physiological stress systems and oxidative DNA and lipid damage

BACKGROUND

Increased activity of the three major physiological stress systems (immune-inflammatory system, hypothalamic-pituitary-adrenal-axis [HPA-axis], and autonomic nervous system [ANS]) is part of the pathophysiology of various somatic and psychiatric diseases. Oxidative damage is a key mechanism in both ageing and disease. Elucidating the relationship between these stress systems and oxidative damage would contribute to the understanding of the role of physiological stress in disease. This study therefore investigates associations between various measures of physiological stress and oxidative DNA (8-hydroxy-2'-deoxyguanosine, 8-OHdG) and lipid (F2-isoprostanes) damage.

METHODS

Plasma 8-OHdG and F2-isoprostanes were measured using LC-MS/MS in 2858 subjects (aged 18-65). Plasma inflammation markers, salivary cortisol and ANS markers (three for each stress system) were determined. Linear regression analyses were adjusted for sociodemographics, sampling factors and medication.

RESULTS

8-OHdG was positively associated with all inflammation markers (β=0.047-0.050, p<0.01), evening cortisol (β=0.073, p<0.001), and unexpectedly with low respiratory sinus arrhythmia (RSA) reflecting low ANS stress (β=0.073, p<0.001). F2-isoprostanes were associated with higher C-reactive protein (β=0.072, p<0.001), high ANS stress reflected in heart rate (β=0.064, p<0.001) and RSA (β=-0.076, p=0.001), but not with cortisol. Analyses investigating the cumulative impact of the stress systems demonstrated that the number of systems with ≥1 marker in the high risk quartile showed a positive linear trend with both 8-OHdG (p=0.030) and F2-isoprostanes (p=0.009).

CONCLUSION

This large-scale study showed that markers of inflammation, the HPA-axis and ANS are associated with oxidative DNA damage. Oxidative lipid damage is associated with inflammation and the ANS. Increased physiological stress across systems is associated with increasing oxidative damage in a dose-response fashion.

Signaling Networks Determining Life Span

The health of an organism is orchestrated by a multitude of molecular and biochemical networks responsible for ensuring homeostasis within cells and tissues. However, upon aging, a progressive failure in the maintenance of this homeostatic balance occurs in response to a variety of endogenous and environmental stresses, allowing the accumulation of damage, the physiological decline of individual tissues, and susceptibility to diseases. What are the molecular and cellular signaling events that control the aging process and how can this knowledge help design therapeutic strategies to combat age-associated diseases? Here we provide a comprehensive overview of the evolutionarily conserved biological processes that alter the rate of aging and discuss their link to disease prevention and the extension of healthy life span.

The Protective Effect of N-Acetylcysteine on Ionizing Radiation Induced Ovarian Failure and Loss of Ovarian Reserve in Female Mouse

Ionizing radiation may cause irreversible ovarian failure, which, therefore, calls for an effective radioprotective reagent. The aim of the present study was to evaluate the potential radioprotective effect of N-acetylcysteine (NAC) on ionizing radiation induced ovarian failure and loss of ovarian reserve in mice. Kun-Ming mice were either exposed to X-irradiation (4 Gy), once, and/or treated with NAC (300 mg/kg), once daily for 7 days before X-irradiation. We examined the serum circulating hormone levels and the development of ovarian follicles as well as apoptosis, cell proliferation, and oxidative stress 24 hours after X-irradiation. In addition, morphological observations on the endometrial luminal epithelium and the fertility assessment were performed. We found that NAC successfully restored the ovarian and uterine function, enhanced the embryo implantation, improved the follicle development, and altered the abnormal hormone levels through reducing the oxidative stress and apoptosis level in granulosa cells while promoting the proliferation of granulosa cells. In conclusion, the radioprotective effect of NAC on mice ovary from X-irradiation was assessed, and our results suggested that NAC can be a potential radioprotector which is capable of preventing the ovarian failure occurrence and restoring the ovarian reserve.

Environmental conditions can modulate the links among oxidative stress, age, and longevity

Understanding the links between environmental conditions and longevity remains a major focus in biological research. We examined within-individual changes between early- and mid-adulthood in the circulating levels of four oxidative stress markers linked to ageing, using zebra finches (Taeniopygia guttata): a DNA damage product (8-hydroxy-2'-deoxyguanosine; 8-OHdG), protein carbonyls (PC), non-enzymatic antioxidant capacity (OXY), and superoxide dismutase activity (SOD). We further examined whether such within-individual changes differed among birds living under control (ad lib food) or more challenging environmental conditions (unpredictable food availability), having previously found that the latter increased corticosterone levels when food was absent but improved survival over a three year period. Our key findings were: (i) 8-OHdG and PC increased with age in both environments, with a higher increase in 8-OHdG in the challenging environment; (ii) SOD increased with age in the controls but not in the challenged birds, while the opposite was true for OXY; (iii) control birds with high levels of 8-OHdG died at a younger age, but this was not the case in challenged birds. Our data clearly show that while exposure to the potentially damaging effects of oxidative stress increases with age, environmental conditions can modulate the pace of this age-related change.

Life-extending Dietary Restriction Reduces Oxidative Damage of Proteins in Grasshoppers but Does Not Alter Allocation of Ingested Nitrogen to Somatic Tissues

Dietary restriction (DR) extends life span and reduces reproduction in most animals. The disposable soma hypothesis suggests that this longevity is the result of reduced investment in reproduction and increased nutrient allocation to the soma, permitting an increase in cellular maintenance. To investigate the role of nutrient allocation upon life-extending DR, tissue-specific nitrogen allocation was tracked in grasshoppers (Romalea microptera) upon a full or restricted (60% of full) diet. In addition, carbonyl (oxidized protein) assays addressed tissue maintenance. To develop a labeled diet on which grasshoppers could thrive, hydroponically grown Romaine lettuce was enriched with 15N. This allowed quantification of nitrogen allocation upon a normal or restricted diet. There was a 50% decrease in reproductive investment upon DR. At the same time, relative allocation of 15N to the ovary did not change. Most important, relative allocation was similar between restricted and full diet grasshoppers for somatic tissues (ie, mandibular and femur muscle, dried hemolymph, gut, and fat body). Carbonyl assays of muscles, hemolymph, and gut revealed an overall reduction in protein oxidation upon DR. These data suggest that DR does not alter nutrient allocation but does reduce protein oxidation, an observation that is inconsistent with the basic predictions of the disposable soma hypothesis.

Insights into the biochemical defence and methylation of the solitary bee Osmia rufa L: A foundation for examining eusociality development

We examined age-related biochemical and histological changes in the fat bodies and hemolymph of Osmia rufa males and females. We analysed solitary bees during diapause, in October and in April; as well as the flying insects following diapause, in May and June. The trophocyte sizes, as well as the numbers of lipid droplets were the greatest at the beginning of diapause. Subsequently, they decreased along with age. Triglyceride and glucose concentrations systematically decreased in fat body cells but increased in the hemolymph from October to June. Concentrations/activities of (enzymatic and non-enzymatic) antioxidant and proteolytic systems, as well as phenoloxidase, aspartate aminotransferase, alanine aminotransferase and alkaline phosphatase levels were constant during the diapause, usually lower in the males than the females. Prior to the diapause/overwintering, the concentrations/activities of all the compounds were higher in the fat bodies than in the hemolymph. Later in the spring and in the summer, they increased in the hemolymph and on the body surfaces, while decreasing in the fat bodies. The global DNA methylation levels increased with age. Higher levels were always observed in the males than in the females. The study will promote better understanding of bee evolution and will be useful for the protection and management of solitary bees, with benefits to the environment and agriculture.

Associations of self-reported smoking, cotinine levels and epigenetic smoking indicators with oxidative stress among older adults: a population-based study

Tobacco smoking and oxidative stress (OS) are both related to a wide spectrum of adverse age-related health outcomes, but their association is not yet well-established. We examined the associations of self-reported smoking indicators, serum cotinine levels and smoking-related DNA methylation biomarkers with two urinary proxy markers of OS, 8-isoprostane (8-iso) and 8-hydroxy-2'-deoxyguanosine (8-oxodG), in two independent subsets of older adults recruited in Germany (discovery set: n = 978, validation set: n = 531). We obtained DNA methylation profiles in whole blood samples by Illumina Human Methylation450K Beadchip and measured the urinary levels of both OS markers using commercial ELISA kits. After controlling for potential confounders, current smoking, cumulative smoking exposure (pack-years) and serum cotinine levels (ng/ml) were strongly associated with 8-iso levels (p values <0.0001, 0.004 and 0.001, respectively). Of 151 previously identified smoking-related CpG sites, 71 loci were associated with 8-iso levels after correction for multiple testing (FDR < 0.05) in the validation phase and were designated as loci related to 8-iso levels defined OS. In addition, serum cotinine levels, cumulative smoking exposure and a smoking index (SI) based on the 71 identified loci manifested monotonic associations with 8-iso levels. However, we did not observe any associations between these smoking indicators and 8-oxodG levels. In conclusion, this study suggests that smoking-related epigenetic alterations are closely correlated with smoking-induced OS. The identified CpG sites could potentially be prognostic epigenetic markers of OS and OS-related health outcomes. Our findings and the underlying mechanisms should be followed up in further, preferably longitudinal studies.

Peroxiredoxin 6 overexpression attenuates lipopolysaccharide-induced acute kidney injury

Peroxiredoxin 6 (PRDX6) is a member of the PRDX family of antioxidant enzymes and correlated with inflammatory response. Therefore, we investigated the role of PRDX6 during lipopolysaccharide (LPS)-induced acute kidney injury. Both 3 months aged PRDX6-overexpressing transgenic mice (PRDX6 mice) and wild type (WT) mice had acute renal injury induced by intraperitoneal injection of LPS (10 mg/kg)., PRDX6 mice showed decreased mortality and renal injury following LPS challenge compared to WT mice. Furthermore, infiltration of macrophages, T-cells and neutrophils, and the number of apoptotic cells were more decreased by LPS treatment in PRDX6 mice than in WT mice. Because LPS induces reactive oxygen species (ROS) production which induces inflammation through c-Jun N-terminal Kinase (JNK) and p38 MAPK activation, we investigated ROS concentration and MAPK signaling pathway in the kidney of PRDX6 mice. As expected, LPS-induced oxidative stress was attenuated, and p38 MAPK and JNK activation was decreased in the kidney of PRDX6 mice. Inhibitory effect of PRDX6 on LPS-induced apoptosis and MAPK activation in the primary renal proximal tubular cells were overcome by treatment with PRDX6 inhibitor or hydrogen peroxide. These results suggest that PRDX6 overexpression inactivates p38 MAPK and JNK pathway through decrease LPS-induced ROS concentration in the kidney, resulting in inhibition of renal apoptosis and leukocyte infiltration and led to attenuation of LPS-induced acute kidney injury.

C-phycocyanin protects against low fertility by inhibiting reactive oxygen species in aging mice

Women over 35 have higher rates of infertility, largely due to deterioration of oocyte quality characterized by fragmentation, abnormal meiotic spindle-chromosome complexes, and oxidative stress. C-phycocyanin (PC) is a biliprotein enriched in Spirulina platensis that is known to possess antioxidant, anti-inflammatory, and radical-scavenging properties. D-galactose-induced aging acceleration in mice has been extensively used to study aging mechanisms and for pharmaceutical screening. In this study, adult female B6D2F/1 mice injected with D-galactose were used as a model to test the age-reversing effects of PC on degenerated reproductive ability. Our results show that PC can prevent oocyte fragmentation and aneuploidy by maintaining cytoskeletal integrity. Moreover, PC can reverse the expression of antioxidant genes, increase superoxide dismutase (SOD) activity and decrease methane dicarboxylic aldehyde (MDA) content, and normalize mitochondria distribution. PC exerts its benefit by inhibiting reactive oxygen species (ROS) production, which decreases apoptosis. Finally, we observe a significant increase in litter size after PC administration to D-galactose-induced aging mice. Our study demonstrates for the first time that D-galactose-induced impaired female reproductive capability can be partially rescued by the antioxidant effects of PC.

Association between heavy metal exposure and poor working memory and possible mediation effect of antioxidant defenses during aging

BACKGROUND

Inverse associations have been observed between memory performance and blood concentrations of cadmium (Cd) and lead (Pb). Low antioxidant cell activity has also been linked to decline in memory due to aging. However, it has not yet been established whether the heavy metal-memory relationship is mediated by differences in antioxidant activity.

METHODS

We examined Cd and Pb levels, as well as oxidative stress parameters, in blood samples from 125 older adults (age range 50-82years). The Counting Span Test (CST) was used to evaluate working memory capacity (WMC). The Monte Carlo Method for Assessing Mediation (MCMAM) was used to analyze the mediation role of antioxidant activity in the heavy metals-memory association.

RESULTS

High blood Cd (BCd) concentration alone, and in combination with elevated blood Pb (BPb) concentration, was associated with poor WMC (p≤0.001) and low enzymatic antioxidant defenses (p≥0.006). The variance in WMC accounted for by BCd or by BCd combine with BPb was 20.6% and 18.6%, respectively. The MCMAM revealed that the influence of BCd and BPb concentrations on WMC was mediated by low antioxidant capacity (confidence interval - CI: 0.072 to -0.064 for BCd; CI: -0.062 to -0.045 for BPb).

CONCLUSION

These findings showed Pb and Cd blood concentration in older adults, even at levels below the current recommended threshold, was negatively associated with WMC and that this relationship may be partly mediated by low antioxidant defenses. Knowledge on the environmental factors that negatively influence brain and cognition during aging can help inform public policy strategies to prevent and control the adverse effects of environmental contaminant exposure during aging.

Role of reactive oxygen species in age-related neuromuscular deficits

Although it is now clear that reactive oxygen species (ROS) are not the key determinants of longevity, a number of studies have highlighted the key role that these species play in age-related diseases and more generally in determining individual health span. Age-related loss of skeletal muscle mass and function is a key contributor to physical frailty in older individuals and our current understanding of the key areas in which ROS contribute to age-related deficits in muscle is through defective redox signalling and key roles in maintenance of neuromuscular integrity. This topical review will describe how ROS stimulate adaptations to contractile activity in muscle that include up-regulation of short-term stress responses, an increase in mitochondrial biogenesis and an increase in some catabolic processes. These adaptations occur through stimulation of redox-regulated processes that lead to the activation of transcription factors such as NF-κB, AP-1 and HSF1 which mediate changes in gene expression. They are attenuated during ageing and this appears to occur through an age-related increase in mitochondrial hydrogen peroxide production. The potential for redox-mediated cross-talk between motor neurons and muscle is also described to illustrate how ROS released from muscle fibres during exercise may help maintain the integrity of axons and how the degenerative changes in neuromuscular structure that occur with ageing may contribute to mitochondrial ROS generation in skeletal muscle fibres.

Long-term pre-treatment of antioxidant Ginkgo biloba extract EGb-761 attenuates cerebral-ischemia-induced neuronal damage in aged mice

Antioxidant activity has been attributed to the neuroprotective effects of Ginkgo biloba extract EGb-761 on brain disorders including ischemic stroke. It is suggested that oxidative stress implicates in neuron injuries during aging. However, whether or not EGb-761 could be used to treat age-related cerebral ischemia is unclear. In the present study, we directly studied the protective effects of EGb-761 in brain ischemia in the mice with different age. As expected, the recovery from brain damages was impaired in aged mice (24 months) in an animal model of middle cerebral artery occlusion (MCAO). Notably, a 12-month pretreatment of EGb-761 significantly ameliorated the ischemic injury of aged mice in a dose-dependent manner. The decreased stroke severity by EGb-761 was suggested by the reduced infarct volumes and brain edema, accompanied by alleviated oxidative stress. Additionally, we further explored the potential involvement of extra-cellular signal-regulated kinase (ERK) activation by MCAO in aged mice. ERK activation after MCAO was diminished by EGb-761, and this reduction may be mediated through an upregulation of phosphatase PP2A by EGb-761. These observations collectively support that natural antioxidant EGb-761 could be potentially exploited as an effective approach in treating neurological injury during aging.

Callogenesis and cell suspension establishment of tropical highland blackberry (Rubus adenotrichos Schltdl.) and its microscopic analysis

Blackberries are fruits produced worldwide, with 25 % of their production centered in Mexico, Central and South America. Tropical highland blackberry is a fruit that can potentially enhance human health, due to their high content in phenolic compounds, which include anthocyanins, phenolic acids, tannins (gallotannins and elagitannins) and flavonoids. Therefore, the overall aim of this study is the development of a callus induction protocol, the establishment of blackberry cell suspensions (Rubus adenotrichos Schltdl.) and their cell analysis through optical microscopy and TEM, for the potential production of phenolic compounds. In order to produce callogenesis, segments of blackberry leaves were disinfected and placed in different concentrations of 2,4-D and the control media (0; 0.5; 1.0; 1.5; 2.0; 2.5 and 3.0 mg/l of 2,4-D); obtaining the higher size of calli in the medium with 1.5 mg/l of 2,4-D. After this determination, and for this specific treatment, a growth curve was performed through the use of fresh and dry weight parameters, in order to identify each of the growth stages. Furthermore, the calli obtained from the 1.5 mg/l of 2,4-D treatment were placed in two different culture media (MS and MS supplemented with 1.5 mg/l of 2,4-D) in order to establish the cell suspensions and the growth curve. To the best treatment, the total polyphenols were also quantified. It was determined that the MS medium is ideal for the growth and disintegration of the cell suspensions, obtaining 0.0256 mg of gallic acid/g of fresh sample. Finally, a cell callus and cell suspension analysis was performed through OM and TEM, evidencing a higher hystological differentiation in the calli, as well as the observation of antioxidant storage in the plastids.

Nutrigenomics at the Interface of Aging, Lifespan, and Cancer Prevention

The percentage of elderly people with associated age-related health deterioration, including cancer, has been increasing for decades. Among age-related diseases, the incidence of cancer has grown substantially, in part because of the overlap of some molecular pathways between cancer and aging. Studies with model organisms suggest that aging and age-related conditions are manipulable processes that can be modified by both genetic and environmental factors, including dietary habits. Variations in genetic backgrounds likely lead to differential responses to dietary changes and account for some of the inconsistencies found in the literature. The intricacies of the aging process, coupled with the interrelational role of bioactive food components on gene expression, make this review a complex undertaking. Nevertheless, intriguing evidence suggests that dietary habits can manipulate the aging process and/or its consequences and potentially may have unprecedented health benefits. The present review focuses on 4 cellular events: telomerase activity, bioenergetics, DNA repair, and oxidative stress. These processes are linked to both aging and cancer risk, and their alteration in animal models by selected food components is evident.

Integrated High-Content Quantification of Intracellular ROS Levels and Mitochondrial Morphofunction

Oxidative stress arises from an imbalance between the production of reactive oxygen species (ROS) and their removal by cellular antioxidant systems. Especially under pathological conditions, mitochondria constitute a relevant source of cellular ROS. These organelles harbor the electron transport chain, bringing electrons in close vicinity to molecular oxygen. Although a full understanding is still lacking, intracellular ROS generation and mitochondrial function are also linked to changes in mitochondrial morphology. To study the intricate relationships between the different factors that govern cellular redox balance in living cells, we have developed a high-content microscopy-based strategy for simultaneous quantification of intracellular ROS levels and mitochondrial morphofunction. Here, we summarize the principles of intracellular ROS generation and removal, and we explain the major considerations for performing quantitative microscopy analyses of ROS and mitochondrial morphofunction in living cells. Next, we describe our workflow, and finally, we illustrate that a multiparametric readout enables the unambiguous classification of chemically perturbed cells as well as laminopathy patient cells.

BZLF1 Attenuates Transmission of Inflammatory Paracrine Senescence in Epstein-Barr Virus-Infected Cells by Downregulating Tumor Necrosis Factor Alpha

Recent studies have shown that inflammatory responses trigger and transmit senescence to neighboring cells and activate the senescence-associated secretory phenotype (SASP). Latent Epstein-Barr virus (EBV) infection induces increased secretion of several inflammatory factors, whereas lytic infections evade the antiviral inflammatory response. However, the changes in and roles of the inflammatory microenvironment during the switch between EBV life cycles remain unknown. In the present study, we demonstrate that latent EBV infection in EBV-positive cells triggers the SASP in neighboring epithelial cells. In contrast, lytic EBV infection abolishes this phenotype. BZLF1 attenuates the transmission of paracrine senescence during lytic EBV infection by downregulating tumor necrosis factor alpha (TNF-α) secretion. A mutant BZLF1 protein, BZLF1Δ207-210, that cannot inhibit TNF-α secretion while maintaining viral transcription, fails to block paracrine senescence, whereas a neutralizing antibody against TNF-α is sufficient to restore its inhibition. Furthermore, latent EBV infection induces oxidative stress in neighboring cells, while BZLF1-mediated downregulation of TNF-α reduces reactive oxygen species (ROS) levels in neighboring cells, and ROS scavengers alleviate paracrine senescence. These results suggest that lytic EBV infection attenuates the transmission of inflammatory paracrine senescence through BZLF1 downregulation of TNF-α secretion and alters the inflammatory microenvironment to allow virus propagation and persistence.

IMPORTANCE

The senescence-associated secretory phenotype (SASP), an important tumorigenic process, is triggered and transmitted by inflammatory factors. The different life cycles of Epstein-Barr virus (EBV) infection in EBV-positive cells employ distinct strategies to modulate the inflammatory response and senescence. The elevation of inflammatory factors during latent EBV infection promotes the SASP in uninfected cells. In contrast, during the viral lytic cycle, BZLF1 suppresses the production of TNF-α, resulting in the attenuation of paracrine inflammatory senescence. This finding indicates that EBV evades inflammatory senescence during lytic infection and switches from facilitating tumor-promoting SASP to generating a virus-propagating microenvironment, thereby facilitating viral spread in EBV-associated diseases.

Beyond Diabetes: Does Obesity-Induced Oxidative Stress Drive the Aging Process?

Despite numerous correlative data, a causative role for oxidative stress in mammalian longevity has remained elusive. However, there is strong evidence that increased oxidative stress is associated with exacerbation of many diseases and pathologies that are also strongly related to advanced age. Obesity, or increased fat accumulation, is one of the most common chronic conditions worldwide and is associated with not only metabolic dysfunction but also increased levels of oxidative stress in vivo. Moreover, obesity is also associated with significantly increased risks of cardiovascular disease, neurological decline and cancer among many other diseases as well as a significantly increased risk of mortality. In this review, we investigate the possible interpretation that the increased incidence of these diseases in obesity may be due to chronic oxidative stress mediating segmental acceleration of the aging process. Understanding how obesity can alter cellular physiology beyond that directly related to metabolic function could open new therapeutic areas of approach to extend the period of healthy aging among people of all body composition.

Reactive oxygen species derived from NADPH oxidase 1 and mitochondria mediate angiotensin II-induced smooth muscle cell senescence

Cellular senescence has emerged as an important player in both physiology and pathology. Excessive reactive oxygen species (ROS) is known to mediate cellular senescence. NADPH oxidases are major sources for ROS production in the vascular wall; the roles of different NADPH oxidase isoforms in cellular senescence remain unclear, however. We investigated the roles of two NADPH oxidase isoforms in mitochondrial dysfunction during angiotensin II (Ang II)-induced cellular senescence of human aortic vascular smooth muscle cells (VSMCs). Ang II (10(-7)M) stimulated ROS generation, exhibiting early increases between 30 and 60min and sustained increases between 24h and 72h, and induced VSMCs senescence after 48h or 72h treatment as assessed with senescence-associated β-galactosidase activity and the expression of two cell cycle inhibitors, p21 and p16. ROS scavengers and membrane-permeable catalase (catalase-PEG) reduced Ang II-stimulated cellular senescence. Furthermore, small interfering RNA (siRNA) of NADPH oxidase catalytic subunit Nox1, but not that of another isoform Nox4, inhibited Ang II-induced cellular senescence. Nox1 siRNA inhibited both early and sustained ROS increases induced by Ang II. In addition, a mitochondrial-specific antioxidant, mitoQ10, effectively inhibited Ang II-induced ROS increases and cellular senescence. Ang II decreased ATP synthesis and induced mitochondrial membrane depolarization, which were attenuated by pre-treating cells with Nox1 siRNA, mitoQ10 or catalase-PEG. The effect of Ang II on the mitochondrial regulator peroxisome-proliferator-activated receptor gamma coactivator-1α (PGC-1α) and its downstream genes was examined. Ang II stimulated S570 phosphorylation of PGC-1α with concomitant decreases in catalase and uncoupling protein-2 (UCP-2) levels between 12h and 72h, which were inhibited by Nox1 siRNA. Knockdown of both catalase and UCP-2 mimicked Ang II-induced VSMC senescence. These results suggested that Ang II-stimulated Nox1 activation mediates mitochondrial dysfunction, probably by decreasing PGC-1α activity and increasing mitochondrial oxidative stress, and leads to cellular senescence of VSMCs.

Effects of aluminum on the reduction of neural stem cells, proliferating cells, and differentiating neuroblasts in the dentate gyrus of D-galactose-treated mice via increasing oxidative stress

Aluminum (Al) accumulation increases with aging, and long-term exposure to Al is regarded as a risk factor for Alzheimer's disease. In this study, we investigated the effects of Al and/or D-galactose on neural stem cells, proliferating cells, differentiating neuroblasts, and mature neurons in the hippocampal dentate gyrus. AlCl₃ (40 mg/kg/day) was intraperitoneally administered to C57BL/6J mice for 4 weeks. In addition, vehicle (physiological saline) or D-galactose (100 mg/kg) was subcutaneously injected to these mice immediately after AlCl₃ treatment. Neural stem cells, proliferating cells, differentiating neuroblasts, and mature neurons were detected using the relevant marker for each cell type, including nestin, Ki67, doublecortin, and NeuN, respectively, via immunohistochemistry. Subchronic (4 weeks) exposure to Al in mice reduced neural stem cells, proliferating cells, and differentiating neuroblasts without causing any changes to mature neurons. This Al-induced reduction effect was exacerbated in D-galactose-treated mice compared to vehicle-treated adult mice. Moreover, exposure to Al enhanced lipid peroxidation in the hippocampus and expression of antioxidants such as Cu, Zn- and Mn-superoxide dismutase in D-galactose-treated mice. These results suggest that Al accelerates the reduction of neural stem cells, proliferating cells, and differentiating neuroblasts in D-galactose-treated mice via oxidative stress, without inducing loss in mature neurons.

Reactive oxygen species in sarcopenia: Should we focus on excess oxidative damage or defective redox signalling?

Physical frailty in the elderly is driven by loss of muscle mass and function and hence preventing this is the key to reduction in age-related physical frailty. Our current understanding of the key areas in which ROS contribute to age-related deficits in muscle is through increased oxidative damage to cell constituents and/or through induction of defective redox signalling. Recent data have argued against a primary role for ROS as a regulator of longevity, but studies have persistently indicated that aspects of the aging phenotype and age-related disorders may be mediated by ROS. There is increasing interest in the effects of defective redox signalling in aging and some studies now indicate that this process may be important in reducing the integrity of the aging neuromuscular system. Understanding how redox-signalling pathways are altered by aging and the causes of the defective redox homeostasis seen in aging muscle provides opportunities to identify targeted interventions with the potential to slow or prevent age-related neuromuscular decline with a consequent improvement in quality of life for older people.

Oxidative stress, thyroid dysfunction & Down syndrome

Down syndrome (DS) is one of the most common chromosomal disorders, occurring in one out of 700-1000 live births, and the most common cause of mental retardation. Thyroid dysfunction is the most typical endocrine abnormality in patients with DS. It is well known that thyroid dysfunction is highly prevalent in children and adults with DS and that both hypothyroidism and hyperthyroidism are more common in patients with DS than in the general population. Increasing evidence has shown that DS individuals are under unusual increased oxidative stress, which may be involved in the higher prevalence and severity of a number of pathologies associated with the syndrome, as well as the accelerated ageing observed in these individuals. The gene for Cu/Zn superoxide dismutase (SOD1) is coded on chromosome 21 and it is overexpressed (~50%) resulting in an increase of reactive oxygen species (ROS) due to overproduction of hydrogen peroxide (H₂O₂). ROS leads to oxidative damage of DNA, proteins and lipids, therefore, oxidative stress may play an important role in the pathogenesis of DS.

NPGPx (GPx7): a novel oxidative stress sensor/transmitter with multiple roles in redox homeostasis

NPGPx (GPx7) is a member of the glutathione peroxidase (GPx) family without any GPx activity. GPx7 displays a unique function which serves as a stress sensor/transmitter to transfer the signal to its interacting proteins by shuttling disulfide bonds in response to various stresses. In this review, we focus on the exceptional structural and biochemical features of GPx7 compared to other 7 family members and described how GPx7 regulates the diverse signaling targets including GRP78, PDI, CPEB2, and XRN2, and their different roles in unfolded protein response, oxidative stress, and non-targeting siRNA stress response, respectively. The phenotypes associated with GPx7 deficiency in mouse or human including ROS accumulations, highly elevated cancer incidences, auto-immune disorders, and obesity are also revealed in this paper. Finally, we compare GPx8 with GPx7, which shares the highest structural similarity but different biological roles in stress response. These insights have thus provided a more comprehensive understanding of the role of GPx7 in the maintenance of redox homeostasis.

Pyrroloquinoline quinone enhances the resistance to oxidative stress and extends lifespan upon DAF-16 and SKN-1 activities in C. elegans

Pyrroloquinoline quinone (PQQ) is linked to fundamental biological processes such as mitochondrial biogenesis and lipid metabolism. PQQ may also function as an essential micronutrient during animal development. Recent studies have shown the therapeutic potential of PQQ for several age-related diseases due to its antioxidant capacity. However, whether PQQ can promote longevity is unknown. Here, we investigate the effects of PQQ on oxidative stress resistance as well as lifespan modulation in Caenorhabditis elegans. We find that PQQ enhances resistance to oxidative stress and extends the lifespan of C. elegans at optimal doses. The underlying molecular mechanism involves the increased activities of the primary lifespan extension transcriptional factors DAF-16/FOXO, the conserved oxidative stress-responsive transcription factor SKN-1/Nrf2, and upregulation of daf-16, skn-1 downstream targets including sod-3, hsp16.2, gst-1 and gst-10. Our findings uncover a novel role of PQQ in longevity, supporting PQQ as a possible dietary supplement for overall health improvement.

The Role of Autophagy, Mitophagy and Lysosomal Functions in Modulating Bioenergetics and Survival in the Context of Redox and Proteotoxic Damage: Implications for Neurodegenerative Diseases

Redox and proteotoxic stress contributes to age-dependent accumulation of dysfunctional mitochondria and protein aggregates, and is associated with neurodegeneration. The free radical theory of aging inspired many studies using reactive species scavengers such as alpha-tocopherol, ascorbate and coenzyme Q to suppress the initiation of oxidative stress. However, clinical trials have had limited success in the treatment of neurodegenerative diseases. We ascribe this to the emerging literature which suggests that the oxidative stress hypothesis does not encompass the role of reactive species in cell signaling and therefore the interception with reactive species with antioxidant supplementation may result in disruption of redox signaling. In addition, the accumulation of redox modified proteins or organelles cannot be reversed by oxidant intercepting antioxidants and must then be removed by alternative mechanisms. We have proposed that autophagy serves this essential function in removing damaged or dysfunctional proteins and organelles thus preserving neuronal function and survival. In this review, we will highlight observations regarding the impact of autophagy regulation on cellular bioenergetics and survival in response to reactive species or reactive species generating compounds, and in response to proteotoxic stress.