Is the oxidative stress theory of aging dead?

Effects of age on oxidative stress and locomotion in the pollinator, Megachile rotundata

Despite numerous aging studies, the relationship between oxidative stress, aging, and decline in functions such as locomotion is still debated. Insects offer a promising model for analyzing the relationship between oxidative stress and aging, because they exhibit vast differences in lifespan that may be affected by the environment, social factors, levels of activity, and aging interventions. In this study, we explore the effects of aging on oxidative stress and locomotion using the pollinator, Megachile rotundata, a species that is very mobile and active in the adult stage. Across the adult lifespan of M. rotundata, we assessed changes in walking, flight, oxidative damage, and antioxidant defenses. Our results suggest that M. rotundata experience age-related declines in flight, but not walking. Additionally, we found that oxidative damage and antioxidant capacity initially increase with age and physical activity, but then levels are maintained. Overall, these data show that M. rotundata, like some other organisms, may not perfectly follow the free radical theory of aging.

Short lifespan is one's fate, long lifespan is one's achievement: lessons from Daphnia

Studies of longevity rely on baseline life expectancy of reference genotypes measured in standardized conditions. Variation among labs, protocols, and genotypes makes longevity intervention studies difficult to compare. Furthermore, extending lifespan under suboptimal conditions or that of a short-lived genotype may be of a lesser theoretical and translational value than extending the maximal possible lifespan. Daphnia is becoming a model organism of choice for longevity research complementing data obtained on traditional models. In this study, we report longevity of several genotypes of a long-lived species D. magna under a variety of protocols, aiming to document the highest lifespan, factors reducing it, and parameters that change with age and correlate with longevity. Combining longevity data from 25 experiments across two labs, we report a strong intraspecific variation, moderate effects of group size and medium composition, and strong genotype-by-environment interactions with respect to food level. Specifically, short-lived genotypes show no caloric restriction (CR) effect, while long-lived ones expand their lifespan even further under CR. We find that the CR non-responsive clones show little correlation between longevity and two measures of lipid peroxidation. In contrast, the long-lived, CR-responsive clones show a positive correlation between longevity and lipid hydroperoxide abundance, and a negative correlation with MDA concentration. This indicates differences among genotypes in age-related accumulation and detoxification of LPO products and their effects on longevity. Our observations support the hypothesis that a long lifespan can be affected by CR and levels of oxidative damage, while genetically determined short lifespan remains short regardless.

Molecular and cellular consequences of mitochondrial DNA double-stranded breaks

Mitochondria are subcellular organelles essential for life. Beyond their role in producing energy, mitochondria govern various physiological mechanisms, encompassing energy generation, metabolic processes, apoptotic events, and immune responses. Mitochondria also contain genetic material that is susceptible to various forms of damage. Mitochondrial double-stranded breaks (DSB) are toxic lesions that the nucleus repairs promptly. Nevertheless, the significance of DSB repair in mammalian mitochondria is controversial. This review presents an updated view of the available research on the consequences of mitochondrial DNA DSB from the molecular to the cellular level. We discuss the crucial function of mitochondrial DNA damage in regulating processes such as senescence, integrated stress response, and innate immunity. Lastly, we discuss the potential role of mitochondrial DNA DSB in mediating the cellular consequences of ionizing radiations, the standard of care in treating solid tumors.

Restricting bioenergetic efficiency enhances longevity and mitochondrial redox capacity in Drosophila melanogaster

Mitochondria are essential for survival and as such, impairments in organelle homeostasis significantly accelerate age-related morbidity and mortality. Here, we determined the contribution of bioenergetic efficiency to life span and health span in Drosophila melanogaster utilizing the mitochondrial uncoupler BAM15. Life span was determined in flies fed a normal diet (ND) or high fat diet (HFD) supplemented with vehicle or BAM15. Locomotor function was determined by negative geotaxis assay in middle-aged flies fed vehicle or BAM15 under ND or HFD conditions. Redox capacity (high-resolution respirometry/fluorometry), citrate synthase (enzyme activity), mtDNA content (qPCR), gene expression (qPCR), and protein expression (western blot) were assessed in flight muscle homogenates of middle-aged flies fed vehicle or BAM15 ND. The molar ratio of H2O2 and O2 (H2O2:O2) in a defined respiratory state was calculated as a measure of redox balance. BAM15 extended life span by 9% on ND and 25% on HFD and improved locomotor activity by 125% on ND and 53% on HFD. Additionally, BAM15 enhanced oxidative phosphorylation capacity supported by pyruvate + malate, proline, and glycerol 3-phosphate. Concurrently, BAM15 enhanced the mitochondrial H2O2 production rate, reverse electron flow from mitochondrial glycerol-3-phosphate dehydrogenase (mGPDH) to Complex I, mGPDH, and Complex I without altering the H2O2:O2 ratio. BAM15 upregulated transcriptional signatures associated with mitochondrial function and fitness as well as antioxidant defense. BAM15-mediated restriction of bioenergetic efficiency prolongs life span and health span in Drosophila fed a ND or HFD. Improvements in life span and health span in ND were supported by synergistic enhancement of muscular redox capacity.

MANIPULATING MITOCHONDRIAL REACTIVE OXYGEN SPECIES ALTERS SURVIVAL IN UNEXPECTED WAYS IN A DROSOPHILA MODEL OF NEURODEGENERATION

Reactive oxygen species (ROS) are associated with aging and neurodegeneration, but the significance of this association remains obscure. Here, using a Drosophila model of age-related neurodegeneration, we probe this relationship in the pathologically relevant tissue, the brain, by quantifying three specific mitochondrial ROS and manipulating these redox species pharmacologically. Our goal is to ask whether pathology-associated changes in redox state are detrimental for survival, whether they may be beneficial responses, or whether they are simply covariates of pathology that do not alter viability. We find, surprisingly, that increasing mitochondrial H2O2 correlates with improved survival. We also find evidence that drugs that alter the mitochondrial glutathione redox potential modulate survival primarily through the compensatory effects they induce rather than through their direct effects on the final mitochondrial glutathione redox potential per se. We also find that the response to treatment with a redox-altering drug varies dramatically depending on the age at which the drug is administered, the duration of the treatment, and the genotype of the individual receiving the drug. These data have important implications for the design and interpretation of studies investigating the effect of redox state on health and disease as well as on efforts to modify the redox state to achieve therapeutic goals.

Decoding lifespan secrets: the role of the gonad in Caenorhabditis elegans aging

The gonad has become a central organ for understanding aging in C. elegans, as removing the proliferating stem cells in the germline results in significant lifespan extension. Similarly, when starvation in late larval stages leads to the quiescence of germline stem cells the adult nematode enters reproductive diapause, associated with an extended lifespan. This review summarizes recent advancements in identifying the mechanisms behind gonad-mediated lifespan extension, including comparisons with other nematodes and the role of lipid signaling and transcriptional changes. Given that the gonad also mediates lifespan regulation in other invertebrates and vertebrates, elucidating the underlying mechanisms may help to gain new insights into the mechanisms and evolution of aging.

Trioxidized cysteine in the aging proteome mimics the structural dynamics and interactome of phosphorylated serine

Aging is the primary risk factor for the development of numerous human chronic diseases. On a molecular level, it significantly impacts the regulation of protein modifications, leading to the accumulation of degenerative protein modifications (DPMs) such as aberrant serine phosphorylation (p-Ser) and trioxidized cysteine (t-Cys) within the proteome. The altered p-Ser is linked to abnormal cell signaling, while the accumulation of t-Cys is associated with chronic diseases induced by oxidative stress. Despite this, the potential cross-effects and functional interplay between these two critical molecular factors of aging remain undisclosed. This study analyzes the aging proteome of wild-type C57BL/6NTac mice over 2 years using advanced proteomics and bioinformatics. Our objective is to provide a comprehensive analysis of how t-Cys affects cell signaling and protein structure in the aging process. The results obtained indicate that t-Cys residues accumulate in the aging proteome, interact with p-Ser interacting enzymes, as validated in vitro, and alter their structures similarly to p-Ser. These findings have significant implications for understanding the interplay of oxidative stress and phosphorylation in the aging process. Additionally, they open new venues for further research on the role(s) of these protein modifications in various human chronic diseases and aging, wherein exacerbated oxidation and aberrant phosphorylation are implicated.

Mitochondria-Targeted Catalase Does Not Suppress Development of Cellular Senescence during Aging

Cellular senescence is a complex stress response marked by stable proliferative arrest and the secretion of biologically active molecules collectively known as the senescence-associated secretory phenotype (SASP). Mitochondria-derived reactive oxygen species (ROS) have been implicated in aging and age-related processes, including senescence. Stressors that increase ROS levels promote both senescence and the SASP, while reducing mitochondrial ROS or mitochondria themselves can prevent senescence or the SASP. Mitochondrially targeted catalase (mCAT), a transgene that reduces mitochondrial levels of ROS, has been shown to extend the lifespan of murine models and protect against the age-related loss of mitochondrial function. However, it remains unclear whether mCAT can prevent senescence or the SASP. In this study, we investigated the impact of mCAT on senescence in cultured cells and aged mice in order to discover if the lifespan-extending activity of mCAT might be due to the reduction in senescent cells or the SASP. Contrary to expectations, we observed that mCAT does not reduce markers of senescence or the SASP in cultured cells. Moreover, mCAT does not prevent the accumulation of senescent cells or the development of the SASP in adipose tissue from aged mice. These results suggest that mitochondrial ROS may not always play a causal role in the development of senescence during natural aging and underscore the need for a nuanced understanding of the intricate relationship between mitochondrial ROS and cellular senescence.

Enhanced ROS Production in Mitochondria from Prematurely Aging mtDNA Mutator Mice

An increase in mitochondrial DNA (mtDNA) mutations and an ensuing increase in mitochondrial reactive oxygen species (ROS) production have been suggested to be a cause of the aging process ("the mitochondrial hypothesis of aging"). In agreement with this, mtDNA-mutator mice accumulate a large amount of mtDNA mutations, giving rise to defective mitochondria and an accelerated aging phenotype. However, incongruously, the rates of ROS production in mtDNA mutator mitochondria have generally earlier been reported to be lower - not higher - than in wildtype, thus apparently invalidating the "mitochondrial hypothesis of aging". We have here re-examined ROS production rates in mtDNA-mutator mice mitochondria. Using traditional conditions for measuring ROS (succinate in the absence of rotenone), we indeed found lower ROS in the mtDNA-mutator mitochondria compared to wildtype. This ROS mainly results from reverse electron flow driven by the membrane potential, but the membrane potential reached in the isolated mtDNA-mutator mitochondria was 33 mV lower than that in wildtype mitochondria, due to the feedback inhibition of succinate oxidation by oxaloacetate, and to a lower oxidative capacity in the mtDNA-mutator mice, explaining the lower ROS production. In contrast, in normal forward electron flow systems (pyruvate (or glutamate) + malate or palmitoyl-CoA + carnitine), mitochondrial ROS production was higher in the mtDNA-mutator mitochondria. Particularly, even during active oxidative phosphorylation (as would be ongoing physiologically), higher ROS rates were seen in the mtDNA-mutator mitochondria than in wildtype. Thus, when examined under physiological conditions, mitochondrial ROS production rates are indeed increased in mtDNA-mutator mitochondria. While this does not prove the validity of the mitochondrial hypothesis of aging, it may no longer be said to be negated in this respect. This paper is dedicated to the memory of Professor Vladimir P. Skulachev.

Open Genes-a new comprehensive database of human genes associated with aging and longevity

The Open Genes database was created to enhance and simplify the search for potential aging therapy targets. We collected data on 2402 genes associated with aging and developed convenient tools for searching and comparing gene features. A comprehensive description of genes has been provided, including lifespan-extending interventions, age-related changes, longevity associations, gene evolution, associations with diseases and hallmarks of aging, and functions of gene products. For each experiment, we presented the necessary structured data for evaluating the experiment's quality and interpreting the study's findings. Our goal was to stay objective and precise while connecting a particular gene to human aging. We distinguished six types of studies and 12 criteria for adding genes to our database. Genes were classified according to the confidence level of the link between the gene and aging. All the data collected in a database are provided both by an API and a user interface. The database is publicly available on a website at https://open-genes.org/.

The role of Caenorhabditis elegans in the discovery of natural products for healthy aging

Covering: 2012 to 2023The human population is aging. Thus, the greatest risk factor for numerous diseases, such as diabetes, cancer and neurodegenerative disorders, is increasing worldwide. Age-related diseases do not typically occur in isolation, but as a result of multi-factorial causes, which in turn require holistic approaches to identify and decipher the mode of action of potential remedies. With the advent of C. elegans as the primary model organism for aging, researchers now have a powerful in vivo tool for identifying and studying agents that effect lifespan and health span. Natural products have been focal research subjects in this respect. This review article covers key developments of the last decade (2012-2023) that have led to the discovery of natural products with healthy aging properties in C. elegans. We (i) discuss the state of knowledge on the effects of natural products on worm aging including methods, assays and involved pathways; (ii) analyze the literature on natural compounds in terms of their molecular properties and the translatability of effects on mammals; (iii) examine the literature on multi-component mixtures with special attention to the studied organisms, extraction methods and efforts regarding the characterization of their chemical composition and their bioactive components. (iv) We further propose to combine small in vivo model organisms such as C. elegans and sophisticated analytical approaches ("wormomics") to guide the way to dissect complex natural products with anti-aging properties.

Upstream migrant sea lamprey (Petromyzon marinus) show signs of increasing oxidative stress but maintain aerobic capacity with age

Following the parasitic juvenile phase of their life cycle, sea lamprey (Petromyzon marinus) mature into a reproductive but rapidly aging and deteriorating adult, and typically die shortly after spawning in May or June. However, pre-spawning upstream migrant sea lamprey can be maintained for several months beyond their natural lifespan when held in cold water (∼4-8 °C) under laboratory conditions. We exploited this feature to investigate the interactions between senescence, oxidative stress, and metabolic function in this phylogenetically ancient fish. We investigated how life history traits and mitochondria condition, as indicated by markers of oxidative stress (catalase activity, lipid peroxidation) and aerobic capacity (citrate synthase activity), changed in adult sea lamprey from June to December after capture during their upstream spawning migration. Body mass but not liver mass declined with age, resulting in an increase in hepatosomatic index. Both effects were most pronounced in males, which also tended to have larger livers than females. Lamprey experienced greater oxidative stress with age, as reflected by increasing activity of the antioxidant enzyme catalase and increasing levels of lipid peroxidation in liver mitochondrial isolates over time. Surprisingly, the activity of citrate synthase also increased with age in both sexes. These observations implicate mitochondrial dysfunction and oxidative stress in the senescence of sea lamprey. Due to their unique evolutionary position and the technical advantage of easily delaying the onset of senescence in lampreys using cold water, these animals could represent an evolutionary unique and tractable model to investigate senescence in vertebrates.

Signatures of Extreme Longevity: A Perspective from Bivalve Molecular Evolution

Among Metazoa, bivalves have the highest lifespan disparity, ranging from 1 to 500+ years, making them an exceptional testing ground to understand mechanisms underlying aging and the evolution of extended longevity. Nevertheless, comparative molecular evolution has been an overlooked approach in this instance. Here, we leveraged transcriptomic resources spanning 30 bivalve species to unravel the signatures of convergent molecular evolution in four long-lived species: Margaritifera margaritifera, Elliptio complanata, Lampsilis siliquoidea, and Arctica islandica (the latter represents the longest-lived noncolonial metazoan known so far). We applied a comprehensive approach-which included inference of convergent dN/dS, convergent positive selection, and convergent amino acid substitution-with a strong focus on the reduction of false positives. Genes with convergent evolution in long-lived bivalves show more physical and functional interactions to each other than expected, suggesting that they are biologically connected; this interaction network is enriched in genes for which a role in longevity has been experimentally supported in other species. This suggests that genes in the network are involved in extended longevity in bivalves and, consequently, that the mechanisms underlying extended longevity are-at least partially-shared across Metazoa. Although we believe that an integration of different genes and pathways is required for the extended longevity phenotype, we highlight the potential central roles of genes involved in cell proliferation control, translational machinery, and response to hypoxia, in lifespan extension.

AAV1.NT-3 gene therapy in the SOD1KO mouse model of accelerated sarcopenia

BACKGROUND

Sarcopenia, an age-related loss of muscle mass, is a critical factor that affects the health of the older adults. The SOD1KO mouse is deficient of Cu/Zn superoxide dismutase, used as an accelerated aging model. We previously showed that NT-3 improves muscle fibre size by activating the mTOR pathway, suggesting a potential for attenuating age-related muscle loss. This study assessed the therapeutic efficacy of AAV1.NT-3 in this accelerated aging model.

METHODS

Twelve 6 months old SOD1KO mice were injected intramuscularly with a 1 × 1011 vg dose of AAV1.tMCK.NT-3, and 13 age-matched SOD1KO mice were used as controls. The treatment effect was evaluated using treadmill, rotarod and gait analyses as well as histological studies assessing changes in muscle fibre, and fibre type switch, in tibialis anterior, gastrocnemius, and triceps muscles, and myelin thickness by calculating G ratio in sciatic and tibial nerves. Molecular studies involved qPCR experiments to analyse the expression levels of mitochondrial and glycolysis markers and western blot experiments to assess the activity of mTORC1 pathway.

RESULTS

Treatment resulted in a 36% (154.9 vs. 114.1; P < 0.0001) and 76% increase (154.3 vs. 87.6; P < 0.0001) in meters ran, with treadmill test at 3 and 6 months post gene delivery. In addition, the treated cohort stayed on rotarod 30% (52.7 s vs. 40.4 s; P = 0.0095) and 54% (50.4 s vs. 32.7 s; P = 0.0007) longer, compared with untreated counterparts at 3 and 6 months post injection. Gait analysis, performed at endpoint, showed that stride width was normalized to wild type levels (29.3 mm) by an 11% decrease, compared with untreated cohort (28.6 mm vs. 32.1 mm; P = 0.0014). Compared with wild-type, SOD1KO mice showed 9.4% and 11.4% fibre size decrease in tibialis anterior and gastrocnemius muscles, respectively, which were normalized to wild type levels with treatment. Fibre diameter increase was observed prominently in FTG fibre type. G ratio analysis revealed hypomyelination in the tibial (0.721) and sciatic (0.676) nerves of SOD1KO model, which was reversed in the NT-3 cohort (0.646 and 0.634, respectively). Fibre size increase correlated with the increase in the p-S6 and p-4E-BP1 levels, and in the glycolysis markers in tibialis anterior. Alterations observed in the mitochondrial markers were not rescued with treatment. Overall, response to NT-3 was subdued in gastrocnemius muscle.

CONCLUSIONS

This study shows that AAV1.NT-3 gene therapy protected SOD1KO mouse from accelerated aging effects functionally and histologically. We further confirmed that NT-3 has potential to activate the mTOR and glycolytic pathways in muscle.

Urgent needs of caregiving in ageing populations with Alzheimer's disease and other chronic conditions: Support our loved ones

The ageing process begins at birth. It is a life-long process, and its exact origins are still unknown. Several hypotheses attempt to describe the normal ageing process, including hormonal imbalance, formation of reactive oxygen species, DNA methylation & DNA damage accumulation, loss of proteostasis, epigenetic alterations, mitochondrial dysfunction, senescence, inflammation, and stem cell depletion. With increased lifespan in elderly individuals, the prevalence of age-related diseases including, cancer, diabetes, obesity, hypertension, Alzheimer's, Alzheimer's disease and related dementias, Parkinson's, and other mental illnesses are increased. These increased age-related illnesses, put tremendous pressure & burden on caregivers, family members, and friends who are living with patients with age-related diseases. As medical needs evolve, the caregiver is expected to experience an increase in duties and challenges, which may result in stress on themselves, and impact their own family life. In the current article, we assess the biological mechanisms of ageing and its effect on body systems, exploring lifestyle and ageing, with a specific focus on age-related disorders. We also discussed the history of caregiving and specific challenges faced by caregivers in the presence of multiple comorbidities. We also assessed innovative approaches to funding caregiving, and efforts to improve the medical system to better organize chronic care efforts, while improving the skill and efficiency of both informal and formal caregivers. We also discussed the role of caregiving in end-of-life care. Our critical analysis strongly suggests that there is an urgent need for caregiving in aged populations and support from local, state, and federal agencies.

Impact of air pollution on cardiovascular aging

The world population is aging rapidly, and by some estimates, the number of people older than 60 will double in the next 30 years. With the increase in life expectancy, adverse effects of environmental exposures start playing a more prominent role in human health. Air pollution is now widely considered the most detrimental of all environmental risk factors, with some studies estimating that almost 20% of all deaths globally could be attributed to poor air quality. Cardiovascular diseases are the leading cause of death worldwide and will continue to account for the most significant percentage of non-communicable disease burden. Cardiovascular aging with defined pathomechanisms is a major trigger of cardiovascular disease in old age. Effects of environmental risk factors on cardiovascular aging should be considered in order to increase the health span and reduce the burden of cardiovascular disease in older populations. In this review, we explore the effects of air pollution on cardiovascular aging, from the molecular mechanisms to cardiovascular manifestations of aging and, finally, the age-related cardiovascular outcomes. We also explore the distinction between the effects of air pollution on healthy aging and disease progression. Future efforts should focus on extending the health span rather than the lifespan.

The Relationship between Lifespan of Marine Bivalves and Their Fatty Acids of Mitochondria Lipids

Marine bivalves belonging to the Mytilidae and Pectinidae Families were used in this research. The specific objectives of this study were: to determine the Fatty Acids (FAs) of mitochondrial gill membranes in bivalves with different lifespans, belonging to the same family, and to calculate their peroxidation index; to compare the levels of ROS generation, malondialdehyde (MDA), and protein carbonyls in the mitochondria of gills, in vitro, during the initiation of free-radical oxation; to investigate whether the FAs of mitochondria gill membranes affect the degree of their oxidative damage and the maximum lifespan of species (MLS). The qualitative membrane lipid composition was uniform in the studied marine bivalves, regardless of their MLS. In terms of the quantitative content of individual FAs, the mitochondrial lipids differed significantly. It is shown that lipid matrix membranes of the mitochondria of long-lived species are less sensitive to in vitro-initiated peroxidation compared with the medium and short-lived species. The differences in MLS are related to the peculiarities of FAs of mitochondrial membrane lipids.

Unraveling effects of anti-aging drugs on C. elegans using liposomes

Liposome-mediated delivery is a possible means to overcome several shortcomings with C. elegans as a model for identifying and testing drugs that retard aging. These include confounding interactions between drugs and the nematodes' bacterial food source and failure of drugs to be taken up into nematode tissues. To explore this, we have tested liposome-mediated delivery of a range of fluorescent dyes and drugs in C. elegans. Liposome encapsulation led to enhanced effects on lifespan, requiring smaller quantities of compounds, and enhanced uptake of several dyes into the gut lumen. However, one dye (Texas red) did not cross into nematode tissues, showing that liposomes cannot ensure the uptake of all compounds. Of six compounds previously reported to extend lifespan (vitamin C, N-acetylcysteine, glutathione (GSH), trimethadione, thioflavin T (ThT), and rapamycin), this effect was reproduced for the latter four in a condition-dependent manner. For GSH and ThT, antibiotics abrogated life extension, implying a bacterially mediated effect. With GSH, this was attributable to reduced early death from pharyngeal infection and associated with alterations of mitochondrial morphology in a manner suggesting a possible innate immune training effect. By contrast, ThT itself exhibited antibiotic effects. For rapamycin, significant increases in lifespan were only seen when bacterial proliferation was prevented. These results document the utility and limitations of liposome-mediated drug delivery for C. elegans. They also illustrate how nematode-bacteria interactions can determine the effects of compounds on C. elegans lifespan in a variety of ways.

Evolutionarily Conserved Role of Thioredoxin Systems in Determining Longevity

Thioredoxin and thioredoxin reductase are evolutionarily conserved antioxidant enzymes that protect organisms from oxidative stress. These proteins also play roles in redox signaling and can act as a redox-independent cellular chaperone. In most organisms, there is a cytoplasmic and mitochondrial thioredoxin system. A number of studies have examined the role of thioredoxin and thioredoxin reductase in determining longevity. Disruption of either thioredoxin or thioredoxin reductase is sufficient to shorten lifespan in model organisms including yeast, worms, flies and mice, thereby indicating conservation across species. Similarly, increasing the expression of thioredoxin or thioredoxin reductase can extend longevity in multiple model organisms. In humans, there is an association between a specific genetic variant of thioredoxin reductase and lifespan. Overall, the cytoplasmic and mitochondrial thioredoxin systems are both important for longevity.

Zearalenone induces the senescence of cardiovascular cells in vitro and in vivo

Zearalenone is a contaminant in food and feed products. It has been reported that zearalenone could lead to serious damage to health. So far, it is unclear whether zearalenone could lead to cardiovascular aging-related injury. For this, we assessed the effect of zearalenone on cardiovascular aging. Cardiomyocyte cell lines and primary coronary endothelial cells were used as two cell models in vitro experiments, and Western-blot, indirect immunofluorescence, and flow cytometry were performed to study the effect of zearalenone on cardiovascular aging. Experimental results indicated zearalenone treatment increased Sa-β-gal positive cell ratio, and the expression of senescence markers (p16 and p21) was significantly upregulated. Additionally zearalenone upregulated the inflammation and oxidative stress in cardiovascular cells. Furthermore, the effect of zearalenone on cardiovascular aging was also evaluated in vivo, and the results indicated that zearalenone treatment also led to the aging of myocardial tissue. These findings suggest that zearalenone could lead to cardiovascular aging-related injury. Furthermore, we also preliminarily explored the potential effect of zeaxanthin (which is a powerful antioxidant) on zearalenone-caused aging-related damage in vitro cell model, and found that zeaxanthin could alleviate zearalenone-induced aging-related damage. Collectively, the most important finding of the current work is that zearalenone could lead to cardiovascular aging. Next in importance, we also found that zeaxanthin could partially alleviate zearalenone-induced cardiovascular aging in vitro, indicating that zeaxanthin can be used as a drug or functional food to treat cardiovascular damage caused by zearalenone.

Effects of Fisetin, a Plant-Derived Flavonoid, on Response to Oxidative Stress, Aging, and Age-Related Diseases in Caenorhabditis elegans

Fisetin (3,3',4',7-tetrahydroxyflavone), a flavonoid abundant in various fruits and vegetables, including apple, strawberry, and onion, shows several beneficial effects such as anti-oxidant, anti-inflammatory, and anti-tumor effects. The free radical theory of aging suggests that age-related accumulation of oxidative damage is the major cause of aging and that decreasing cellular oxidative stress can regulate aging. Here, we investigated the effects of dietary supplementation with fisetin on the stress response, aging, and age-related diseases. Fisetin reduced the cellular ROS levels and increased the resistance to oxidative stress. However, the response to UV irradiation was not affected by fisetin. Both the mean and maximum lifespans were significantly extended by fisetin; lifespan extension by fisetin was accompanied by reduced fertility as a trade-off. Age-related decline in motility was also delayed by supplementation with fisetin. Amyloid beta-induced toxicity was markedly decreased by fisetin, which required DAF-16 and SKN-1. Reduced motility induced by a high-glucose diet was completely recovered by supplementation with fisetin, which was dependent on SKN-1. Using a Parkinson's disease model, we showed that degeneration of dopaminergic neurons was significantly inhibited by treatment with fisetin. Genetic analysis revealed that lifespan extension by fisetin was mediated by DAF-16-induced stress response and autophagy. These findings support the free radical theory of aging and suggest that fisetin can be a strong candidate for use in novel anti-aging anti-oxidant nutraceuticals.

Mitochondrial function and nutrient sensing pathways in ageing: enhancing longevity through dietary interventions

Ageing is accompanied by alterations in several biochemical processes, highly influenced by its environment. It is controlled by the interactions at various levels of biological hierarchy. To maintain homeostasis, a number of nutrient sensors respond to the nutritional status of the cell and control its energy metabolism. Mitochondrial physiology is influenced by the energy status of the cell. The alterations in mitochondrial physiology and the network of nutrient sensors result in mitochondrial damage leading to age related metabolic degeneration and diseases. Calorie restriction (CR) has proved to be as the most successful intervention to achieve the goal of longevity and healthspan. CR elicits a hormetic response and regulates metabolism by modulating these networks. In this review, the authors summarize the interdependent relationship between mitochondrial physiology and nutrient sensors during the ageing process and their role in regulating metabolism.

Oxysterols are potential physiological regulators of ageing

Delaying and even reversing ageing is a major public health challenge with a tremendous potential to postpone a plethora of diseases including cancer, metabolic syndromes and neurodegenerative disorders. A better understanding of ageing as well as the development of innovative anti-ageing strategies are therefore an increasingly important field of research. Several biological processes including inflammation, proteostasis, epigenetic, oxidative stress, stem cell exhaustion, senescence and stress adaptive response have been reported for their key role in ageing. In this review, we describe the relationships that have been established between cholesterol homeostasis, in particular at the level of oxysterols, and ageing. Initially considered as harmful pro-inflammatory and cytotoxic metabolites, oxysterols are currently emerging as an expanding family of fine regulators of various biological processes involved in ageing. Indeed, depending of their chemical structure and their concentration, oxysterols exhibit deleterious or beneficial effects on inflammation, oxidative stress and cell survival. In addition, stem cell differentiation, epigenetics, cellular senescence and proteostasis are also modulated by oxysterols. Altogether, these data support the fact that ageing is influenced by an oxysterol profile. Further studies are thus required to explore more deeply the impact of the "oxysterome" on ageing and therefore this cholesterol metabolic pathway constitutes a promising target for future anti-ageing interventions.

Deletions of the cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE) genes, involved in the control of hydrogen sulfide biosynthesis, significantly affect lifespan and fitness components of Drosophila melanogaster

The gasotransmitter hydrogen sulfide (H₂S) is an important biological mediator, playing an essential role in many physiological and pathological processes. It is produced by transsulfuration - an evolutionarily highly conserved pathway for the metabolism of sulfur-containing amino acids methionine and cysteine. Cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE) enzymes play a central role in cysteine metabolism and H₂S production. Here we investigated the fitness components (longevity, stress resistance, viability of preimaginal stages, and reproductive function parameters) in D. melanogaster lines containing deletions of the CBS and CSE genes. Surprisingly, in most tests, CSE deletion improved, and CBS worsened the fitness. Lines with deletion of both CBS and CSE demonstrated better stress resistance and longevity than lines with single CBS deletion. At the same time, deletion of both CBS and CSE genes causes more serious disturbances of reproductive function parameters than single CBS deletion. Thus, a complex interaction of H₂S-producing pathways and cellular stress response in determining the lifespan and fitness components of the whole organism was revealed.

The Unfolded Protein Responses in Health, Aging, and Neurodegeneration: Recent Advances and Future Considerations

Aging and age-related neurodegeneration are both associated with the accumulation of unfolded and abnormally folded proteins, highlighting the importance of protein homeostasis (termed proteostasis) in maintaining organismal health. To this end, two cellular compartments with essential protein folding functions, the endoplasmic reticulum (ER) and the mitochondria, are equipped with unique protein stress responses, known as the ER unfolded protein response (UPR^ER) and the mitochondrial UPR (UPR^mt), respectively. These organellar UPRs play roles in shaping the cellular responses to proteostatic stress that occurs in aging and age-related neurodegeneration. The loss of adaptive UPR^ER and UPR^mt signaling potency with age contributes to a feed-forward cycle of increasing protein stress and cellular dysfunction. Likewise, UPR^ER and UPR^mt signaling is often altered in age-related neurodegenerative diseases; however, whether these changes counteract or contribute to the disease pathology appears to be context dependent. Intriguingly, altering organellar UPR signaling in animal models can reduce the pathological consequences of aging and neurodegeneration which has prompted clinical investigations of UPR signaling modulators as therapeutics. Here, we review the physiology of both the UPR^ER and the UPR^mt, discuss how UPR^ER and UPR^mt signaling changes in the context of aging and neurodegeneration, and highlight therapeutic strategies targeting the UPR^ER and UPR^mt that may improve human health.

Small-Molecule Mn Antioxidants in Caenorhabditis elegans and Deinococcus radiodurans Supplant MnSOD Enzymes during Aging and Irradiation

Denham Harman's oxidative damage theory identifies superoxide (O₂^•-) radicals as central agents of aging and radiation injury, with Mn²⁺-dependent superoxide dismutase (MnSOD) as the principal O₂^•--scavenger. However, in the radiation-resistant nematode Caenorhabditis elegans, the mitochondrial antioxidant enzyme MnSOD is dispensable for longevity, and in the model bacterium Deinococcus radiodurans, it is dispensable for radiation resistance. Many radiation-resistant organisms accumulate small-molecule Mn²⁺-antioxidant complexes well-known for their catalytic ability to scavenge O₂^•-, along with MnSOD, as exemplified by D. radiodurans. Here, we report experiments that relate the MnSOD and Mn-antioxidant content to aging and oxidative stress resistances and which indicate that C. elegans, like D. radiodurans, may rely on Mn-antioxidant complexes as the primary defense against reactive oxygen species (ROS). Wild-type and ΔMnSOD D. radiodurans and C. elegans were monitored for gamma radiation sensitivities over their life spans while gauging Mn²⁺-antioxidant content by electron paramagnetic resonance (EPR) spectroscopy, a powerful new approach to determining the in vivo Mn-antioxidant content of cells as they age. As with D. radiodurans, MnSOD is dispensable for radiation survivability in C. elegans, which hyperaccumulates Mn-antioxidants exceptionally protective of proteins. Unexpectedly, ΔMnSOD mutants of both the nematodes and bacteria exhibited increased gamma radiation survival compared to the wild-type. In contrast, the loss of MnSOD renders radiation-resistant bacteria sensitive to atmospheric oxygen during desiccation. Our results support the concept that the disparate responses to oxidative stress are explained by the accumulation of Mn-antioxidant complexes which protect, complement, and can even supplant MnSOD. IMPORTANCE The current theory of cellular defense against oxidative damage identifies antioxidant enzymes as primary defenders against ROS, with MnSOD being the preeminent superoxide (O₂^•-) scavenger. However, MnSOD is shown to be dispensable both for radiation resistance and longevity in model organisms, the bacterium Deinococcus radiodurans and the nematode Caenorhabditis elegans. Measured by electron paramagnetic resonance (EPR) spectroscopy, small-molecule Mn-antioxidant content was shown to decline in unison with age-related decreases in cell proliferation and radioresistance, which again are independent of MnSOD presence. Most notably, the Mn-antioxidant content of C. elegans drops precipitously in the last third of its life span, which links with reports that the steady-state level of oxidized proteins increases exponentially during the last third of the life span in animals. This leads us to propose that global responses to oxidative stress must be understood through an extended theory that includes small-molecule Mn-antioxidants as potent O₂^•--scavengers that complement, and can even supplant, MnSOD.

N-Acetyl-Cysteine: Modulating the Cysteine Redox Proteome in Neurodegenerative Diseases

In the last twenty years, significant progress in understanding the pathophysiology of age-associated neurodegenerative diseases has been made. However, the prevention and treatment of these diseases remain without clinically significant therapeutic advancement. While we still hope for some potential genetic therapeutic approaches, the current reality is far from substantial progress. With this state of the issue, emphasis should be placed on early diagnosis and prompt intervention in patients with increased risk of neurodegenerative diseases to slow down their progression, poor prognosis, and decreasing quality of life. Accordingly, it is urgent to implement interventions addressing the psychosocial and biochemical disturbances we know are central in managing the evolution of these disorders. Genomic and proteomic studies have shown the high molecular intricacy in neurodegenerative diseases, involving a broad spectrum of cellular pathways underlying disease progression. Recent investigations indicate that the dysregulation of the sensitive-cysteine proteome may be a concurrent pathogenic mechanism contributing to the pathophysiology of major neurodegenerative diseases, opening new therapeutic opportunities. Considering the incidence and prevalence of these disorders and their already significant burden in Western societies, they will become a real pandemic in the following decades. Therefore, we propose large-scale investigations, in selected groups of people over 40 years of age with decreased blood glutathione levels, comorbidities, and/or mild cognitive impairment, to evaluate supplementation of the diet with low doses of N-acetyl-cysteine, a promising and well-tolerated therapeutic agent suitable for long-term use.

The hyperfunction theory: An emerging paradigm for the biology of aging

The process of senescence (aging) is predominantly determined by the action of wild-type genes. For most organisms, this does not reflect any adaptive function that senescence serves, but rather evolutionary effects of declining selection against genes with deleterious effects later in life. To understand aging requires an account of how evolutionary mechanisms give rise to pathogenic gene action and late-life disease, that integrates evolutionary (ultimate) and mechanistic (proximate) causes into a single explanation. A well-supported evolutionary explanation by G.C. Williams argues that senescence can evolve due to pleiotropic effects of alleles with antagonistic effects on fitness and late-life health (antagonistic pleiotropy, AP). What has remained unclear is how gene action gives rise to late-life disease pathophysiology. One ultimate-proximate account is T.B.L. Kirkwood's disposable soma theory. Based on the hypothesis that stochastic molecular damage causes senescence, this reasons that aging is coupled to reproductive fitness due to preferential investment of resources into reproduction, rather than somatic maintenance. An alternative and more recent ultimate-proximate theory argues that aging is largely caused by programmatic, developmental-type mechanisms. Here ideas about AP and programmatic aging are reviewed, particularly those of M.V. Blagosklonny (the hyperfunction theory) and J.P. de Magalhães (the developmental theory), and their capacity to make sense of diverse experimental findings is assessed.

Role of the mtDNA Mutations and Mitophagy in Inflammaging

Ageing is an unavoidable multi-factorial process, characterised by a gradual decrease in physiological functionality and increasing vulnerability of the organism to environmental factors and pathogens, ending, eventually, in death. One of the most elaborated ageing theories implies a direct connection between ROS-mediated mtDNA damage and mutations. In this review, we focus on the role of mitochondrial metabolism, mitochondria generated ROS, mitochondrial dynamics and mitophagy in normal ageing and pathological conditions, such as inflammation. Also, a chronic form of inflammation, which could change the long-term status of the immune system in an age-dependent way, is discussed. Finally, the role of inflammaging in the most common neurodegenerative diseases, such as Alzheimer’s and Parkinson’s, is also discussed.

The KEAP1-NRF2 System in Healthy Aging and Longevity

Aging is inevitable, but the inherently and genetically programmed aging process is markedly influenced by environmental factors. All organisms are constantly exposed to various stresses, either exogenous or endogenous, throughout their lives, and the quality and quantity of the stresses generate diverse impacts on the organismal aging process. In the current oxygenic atmosphere on earth, oxidative stress caused by reactive oxygen species is one of the most common and critical environmental factors for life. The Kelch-like ECH-associated protein 1-NFE2-related factor 2 (KEAP1-NRF2) system is a critical defense mechanism of cells and organisms in response to redox perturbations. In the presence of oxidative and electrophilic insults, the thiol moieties of cysteine in KEAP1 are modified, and consequently NRF2 activates its target genes for detoxification and cytoprotection. A number of studies have clarified the contributions of the KEAP1-NRF2 system to the prevention and attenuation of physiological aging and aging-related diseases. Accumulating knowledge to control stress-induced damage may provide a clue for extending healthspan and treating aging-related diseases. In this review, we focus on the relationships between oxidative stress and aging-related alterations in the sensory, glandular, muscular, and central nervous systems and the roles of the KEAP1-NRF2 system in aging processes.

The Nitrate-Nitrite-Nitric Oxide Pathway on Healthy Ageing: A Review of Pre-clinical and Clinical Data on the Impact of Dietary Nitrate in the Elderly

We are living longer. Are we living healthier? As we age, cellular and molecular damage reshape our physiological responses towards environmental and endogenous stimuli. The free radical theory of ageing has been proposed long before ageing has been considered a “scientific discipline” and, since then, has been discussed and upgraded as a major contributor to aberrant ageing. Assuming that ageing results merely from the accumulation of oxidative modifications of biomolecules is not only a simplistic and reductive view of such a complex and dynamic process, but also free radicals and related oxidants are now considered pivotal signalling molecules. The fine modulation of critical signalling pathways by redox compounds demands a novel approach to tackle the role of free radicals in ageing. Nitric oxide (^⋅NO) is a paradigmatic example given its biological functions in cardiovascular, neurologic and immune systems. In addition to the canonical ^⋅NO synthesis by a family of enzymes, nitrate from green leafy vegetables, is reduced to nitrite in the oral cavity which is further reduced to ^⋅NO in the stomach. Boosting this nitrate-nitrite-NO pathway has been shown to improve gastrointestinal, cardiovascular, metabolic and cognitive performance both in humans and in animal models of disease. In the elderly, nitrate-derived ^⋅NO has been shown improve several physiological functions that typically decline during ageing. In this paper, the role of nitrate and derived nitrogen oxides will be discussed while reviewing pre-clinical and clinical data on the cardiovascular, neuronal, musculoskeletal and metabolic effects of nitrate during healthy ageing.

Redox Dysregulation in Aging and COPD: Role of NOX Enzymes and Implications for Antioxidant Strategies

With a rapidly growing elderly human population, the incidence of age-related lung diseases such as chronic obstructive pulmonary disease (COPD) continues to rise. It is widely believed that reactive oxygen species (ROS) play an important role in ageing and in age-related disease, and approaches of antioxidant supplementation have been touted as useful strategies to mitigate age-related disease progression, although success of such strategies has been very limited to date. Involvement of ROS in ageing is largely attributed to mitochondrial dysfunction and impaired adaptive antioxidant responses. NADPH oxidase (NOX) enzymes represent an important enzyme family that generates ROS in a regulated fashion for purposes of oxidative host defense and redox-based signalling, however, the associations of NOX enzymes with lung ageing or age-related lung disease have to date only been minimally addressed. The present review will focus on our current understanding of the impact of ageing on NOX biology and its consequences for age-related lung disease, particularly COPD, and will also discuss the implications of altered NOX biology for current and future antioxidant-based strategies aimed at treating these diseases.

Oklahoma Nathan Shock Aging Center - assessing the basic biology of aging from genetics to protein and function

The Oklahoma Shock Nathan Shock Center is designed to deliver unique, innovative services that are not currently available at most institutions. The focus of the Center is on geroscience and the development of careers of young investigators. Pilot grants are provided through the Research Development Core to junior investigators studying aging/geroscience throughout the USA. However, the services of our Center are available to the entire research community studying aging and geroscience. The Oklahoma Nathan Shock Center provides researchers with unique services through four research cores. The Multiplexing Protein Analysis Core uses the latest mass spectrometry technology to simultaneously measure the levels, synthesis, and turnover of hundreds of proteins associated with pathways of importance to aging, e.g., metabolism, antioxidant defense system, proteostasis, and mitochondria function. The Genomic Sciences Core uses novel next-generation sequencing that allows investigators to study the effect of age, or anti-aging manipulations, on DNA methylation, mitochondrial genome heteroplasmy, and the transcriptome of single cells. The Geroscience Redox Biology Core provides investigators with a comprehensive state-of-the-art assessment of the oxidative stress status of a cell, e.g., measures of oxidative damage and redox couples, which are important in aging as well as many major age-related diseases as well as assays of mitochondrial function. The GeroInformatics Core provides investigators assistance with data analysis, which includes both statistical support as well as analysis of large datasets. The Core also has developed number of unique software packages to help with interpretation of results and discovery of new leads relevant to aging. In addition, the Geropathology Research Resource in the Program Enhancement Core provides investigators with pathological assessments of mice using the recently developed Geropathology Grading Platform.

The hoverfly and the wasp: A critique of the hallmarks of aging as a paradigm

With the goal of representing common denominators of aging in different organisms López-Otín et al. in 2013 described nine hallmarks of aging. Since then, this representation has become a major reference point for the biogerontology field. The template for the hallmarks of aging account originated from landmark papers by Hanahan and Weinberg (2000, 2011) defining first six and later ten hallmarks of cancer. Here we assess the strengths and weaknesses of the hallmarks of aging account. As a checklist of diverse major foci of current aging research, it has provided a useful shared overview for biogerontology during a time of transition in the field. It also seems useful in applied biogerontology, to identify interventions (e.g. drugs) that impact multiple symptomatic features of aging. However, while the hallmarks of cancer provide a paradigmatic account of the causes of cancer with profound explanatory power, the hallmarks of aging do not. A worry is that as a non-paradigm the hallmarks of aging have obscured the urgent need to define a genuine paradigm, one that can provide a useful basis for understanding the mechanistic causes of the diverse aging pathologies. We argue that biogerontology must look and move beyond the hallmarks to understand the process of aging.

The role of mitochondria dysfunction and hepatic senescence in NAFLD development and progression

Senescence is a crucial player in several metabolic disorders and chronic inflammatory diseases. Recent data prove the involvement of hepatocyte senescence in the development of NAFLD (non-alcoholic fatty liver disease). As the main energy and ROS (reactive oxygen species) producing organelle, mitochondria play the central role in accelerated senescence and diseases development. In this review, we focus on the role of regulation of mitochondrial Ca²⁺ homeostasis, NAD+/NADH ratio, UPR^mt (mitochondrial unfolded protein response), phospholipids and fatty acid oxidation in hepatic senescence, lifespan and NAFLD disease susceptibility. Additionally, the involvement of mitochondrial and nuclear mutations in lifespan-modulation and NAFLD development is discussed. While nuclear and mitochondria DNA mutations and SNPs (single nucleotide polymorphisms) can be used as effective diagnostic markers and targets for treatments, advanced age should be considered as an independent risk factor for NAFLD development.

Sensory and memory processing in old female and male Wistar rat brain, and its relationship with the cortical and hippocampal redox state

The brain is one of the most sensitive organs damaged during aging due to its susceptibility to the aging-related oxidative stress. Hence, in this study, the sensory nerve pathway integrity and the memory were evaluated and related to the redox state, the antioxidant enzymes function, and the protein oxidative damage in the brain cortex (Cx) and the hippocampus (Hc) of young (4-month-old) and old (24-month-old) male and female Wistar rats. Evoked potentials (EP) were performed for the auditory, visual, and somatosensory pathways. In both males and females, the old rat groups' latencies were larger in almost all waves when compared to the young same-sex animals. The novel object test was performed to evaluate memory. The superoxide dismutase and catalase antioxidant activity, as well as the protein oxidative damage, and the redox state were evaluated. Magnetic resonance (MR) imaging was used to obtain the diffusion tensor imaging, and the brain volume, while MR spectroscopy was used to obtain the brain metabolite concentrations (glutamine, glutamate, Myo-inositol, N-acetyl-aspartate, creatine) in the Cx and the Hc of young and old females. Our data suggest that, although there are limited variations regarding memory and nerve conduction velocity by sex, the differences concerning the redox status might be important to explain the dissimilar reactions during brain aging between males and females. Moreover, the increment in Myo-inositol levels in the Hc of old rats and the brain volume decrease suggest that redox state alterations might be correlated to neuroinflammation during brain aging.

Thiol-based redox-active proteins as cardioprotective therapeutic agents in cardiovascular diseases

Thiol-based redox compounds, namely thioredoxins (Trxs), glutaredoxins (Grxs) and peroxiredoxins (Prxs), stand as a pivotal group of proteins involved in antioxidant processes and redox signaling. Glutaredoxins (Grxs) are considered as one of the major families of proteins involved in redox regulation by removal of S-glutathionylation and thereby reactivation of other enzymes with thiol-dependent activity. Grxs are also coupled to Trxs and Prxs recycling and thereby indirectly contribute to reactive oxygen species (ROS) detoxification. Peroxiredoxins (Prxs) are a ubiquitous family of peroxidases, which play an essential role in the detoxification of hydrogen peroxide, aliphatic and aromatic hydroperoxides, and peroxynitrite. The Trxs, Grxs and Prxs systems, which reversibly induce thiol modifications, regulate redox signaling involved in various biological events in the cardiovascular system. This review focuses on the current knowledge of the role of Trxs, Grxs and Prxs on cardiovascular pathologies and especially in cardiac hypertrophy, ischemia/reperfusion (I/R) injury and heart failure as well as in the presence of cardiovascular risk factors, such as hypertension, hyperlipidemia, hyperglycemia and metabolic syndrome. Further studies on the roles of thiol-dependent redox systems in the cardiovascular system will support the development of novel protective and therapeutic strategies against cardiovascular diseases.

The AGE Presents Introduction to Geroscience video lecture series

The AGE Presents Introduction to Geroscience video lecture series is a collection of high-quality didactic video lectures and associated teaching materials focused on foundational topics in aging biology. The videos are made freely available on YouTube and are targeted toward an audience familiar with concepts learned in the first year of a college undergraduate biology/biomedical major. Members of the American Aging Association also receive the original lecture slides and lecture notes, with additional course materials to be developed in the future. We expect that these lectures will enhance understanding of geroscience among the general public while also providing tools that educators can use in the classroom for high school, undergraduate, and graduate level curricula.

Mitophagy and Oxidative Stress: The Role of Aging

Mitochondrial dysfunction is a hallmark of aging. Dysfunctional mitochondria are recognized and degraded by a selective type of macroautophagy, named mitophagy. One of the main factors contributing to aging is oxidative stress, and one of the early responses to excessive reactive oxygen species (ROS) production is the induction of mitophagy to remove damaged mitochondria. However, mitochondrial damage caused at least in part by chronic oxidative stress can accumulate, and autophagic and mitophagic pathways can become overwhelmed. The imbalance of the delicate equilibrium among mitophagy, ROS production and mitochondrial damage can start, drive, or accelerate the aging process, either in physiological aging, or in pathological age-related conditions, such as Alzheimer’s and Parkinson’s diseases. It remains to be determined which is the prime mover of this imbalance, i.e., whether it is the mitochondrial damage caused by ROS that initiates the dysregulation of mitophagy, thus activating a vicious circle that leads to the reduced ability to remove damaged mitochondria, or an alteration in the regulation of mitophagy leading to the excessive production of ROS by damaged mitochondria.

Supplementation with phosphatidylethanolamine confers anti-oxidant and anti-aging effects via hormesis and reduced insulin/IGF-1-like signaling in C. elegans

Phosphatidylethanolamine is a major component of phospholipids with both structural and metabolic functions in cells. Previous studies have revealed that phosphatidylethanolamine can modulate autophagy with a protective effect against age-related diseases. We examined the effect of dietary supplementation with phosphatidylethanolamine on stress response and aging in Caenorhabditis elegans. Phosphatidylethanolamine increased resistance to oxidative stress without effect on heat stress or ultraviolet irradiation. Both mean and maximum lifespans were significantly increased by phosphatidylethanolamine while fertility was reduced as a trade-off. Age-related decline of muscle function was delayed in animals treated with phosphatidylethanolamine. Supplementation with phosphatidylethanolamine suppressed toxic effect of amyloid β and high-glucose diet. Increased ROS levels and induction of stress-responsive genes after dietary supplementation with phosphatidylethanolamine suggest that anti-oxidative stress and anti-aging effects of phosphatidylethanolamine might be though hormesis. Genetic analysis using long-lived mutants and knockdown by RNAi revealed that the lifespan-extending effect of phosphatidylethanolamine overlapped with that of reduced insulin/IGF-1-like signaling and required DAF-16, a downstream transcription factor known to regulate the expression of many stress-responsive genes. These findings indicate that phosphatidylethanolamine has anti-oxidative stress and anti-aging activities with its underlying mechanisms involving hormesis and reduced insulin/IGF-1-like signaling in C. elegans.

Downregulation of DUOX1 function contributes to aging-related impairment of innate airway injury responses and accelerated senile emphysema

Aging is associated with a gradual loss of lung function due to increased cellular senescence, decreased regenerative capacity, and impaired innate host defense. One important aspect of innate airway epithelial host defense to nonmicrobial triggers is the secretion of alarmins such as IL-33 and activation of type 2 inflammation, which were previously found to depend on activation of the NADPH oxidase (NOX) homolog DUOX1, and redox-dependent signaling pathways that promote alarmin secretion. Here, we demonstrate that normal aging of C57BL/6J mice resulted in markedly decreased lung innate epithelial type 2 responses to exogenous triggers such as the airborne allergen Dermatophagoides pteronyssinus, which was associated with marked downregulation of DUOX1, as well as DUOX1-mediated redox-dependent signaling. DUOX1 deficiency was also found to accelerate age-related airspace enlargement and decline in lung function but did not consistently affect other features of lung aging such as senescence-associated inflammation. Intriguingly, observations of age-related DUOX1 downregulation and enhanced airspace enlargement due to DUOX1 deficiency in C57BL/6J mice, which lack a functional mitochondrial nicotinamide nucleotide transhydrogenase (NNT), were much less dramatic in C57BL/6NJ mice with normal NNT function, although the latter mice also displayed impaired innate epithelial injury responses with advancing age. Overall, our findings indicate a marked aging-dependent decline in (DUOX1-dependent) innate airway injury responses to external nonmicrobial triggers, but the impact of aging on DUOX1 downregulation and its significance for age-related senile emphysema development was variable between different C57BL6 substrains, possibly related to metabolic alterations due to differences in NNT function.

Oxidative stress and senescence in social insects: a significant but inconsistent link?

The life-prolonging effects of antioxidants have long entered popular culture, but the scientific community still debates whether free radicals and the resulting oxidative stress negatively affect longevity. Social insects are intriguing models for analysing the relationship between oxidative stress and senescence because life histories differ vastly between long-lived reproductives and the genetically similar but short-lived workers. Here, we present the results of an experiment on the accumulation of oxidative damage to proteins, and a comparative analysis of the expression of 20 selected genes commonly involved in managing oxidative damage, across four species of social insects: a termite, two bees and an ant. Although the source of analysed tissue varied across the four species, our results suggest that oxidative stress is a significant factor in senescence and that its manifestation and antioxidant defenses differ among species, making it difficult to find general patterns. More detailed and controlled investigations on why responses to oxidative stress may differ across social species may lead to a better understanding of the relations between oxidative stress, antioxidants, social life history and senescence. This article is part of the theme issue 'Ageing and sociality: why, when and how does sociality change ageing patterns?'

An energetics perspective on geroscience: mitochondrial protonmotive force and aging

Mitochondria are organelles that provide energy to cells through ATP production. Mitochondrial dysfunction has long been postulated to mediate cellular declines that drive biological aging. Many well-characterized hallmarks of aging may involve underlying energetic defects that stem from loss of mitochondrial function with age. Why and how mitochondrial function declines with age is an open question and one that has been difficult to answer. Mitochondria are powered by an electrochemical gradient across the inner mitochondrial membrane known as the protonmotive force (PMF). This gradient decreases with age in several experimental models. However, it is unclear if a diminished PMF is a cause or a consequence of aging. Herein, we briefly review and define mitochondrial function, we summarize how PMF changes with age in several models, and we highlight recent studies that implicate PMF in aging biology. We also identify barriers that must be addressed for the field to progress. Emerging technology permits more precise in vivo study of mitochondria that will allow better understanding of cause and effect in metabolic models of aging. Once cause and effect can be discerned more precisely, energetics approaches to combat aging may be developed to prevent or reverse functional decline.

Accelerated Aging and Age-Related Diseases (CVD and Neurological) Due to Air Pollution and Traffic Noise Exposure

The World Health Organization estimates that only approximately 25% of diversity in longevity is explained by genetic factors, while the other 75% is largely determined by interactions with the physical and social environments. Indeed, aging is a multifactorial process that is influenced by a range of environmental, sociodemographic, and biopsychosocial factors, all of which might act in concert to determine the process of aging. The global average life expectancy increased fundamentally over the past century, toward an aging population, correlating with the development and onset of age-related diseases, mainly from cardiovascular and neurological nature. Therefore, the identification of determinants of healthy and unhealthy aging is a major goal to lower the burden and socioeconomic costs of age-related diseases. The role of environmental factors (such as air pollution and noise exposure) as crucial determinants of the aging process are being increasingly recognized. Here, we critically review recent findings concerning the pathomechanisms underlying the aging process and their correlates in cardiovascular and neurological disease, centered on oxidative stress and inflammation, as well as the influence of prominent environmental pollutants, namely air pollution and traffic noise exposure, which is suggested to accelerate the aging process. Insight into these types of relationships and appropriate preventive strategies are urgently needed to promote healthy aging.

Geroprotective potential of genetic and pharmacological interventions to endogenous hydrogen sulfide synthesis in Drosophila melanogaster

Endogenous hydrogen sulfide (H₂S) is a gasotransmitter with a wide range of physiological functions. Aging is accompanied by disruption of H₂S homeostasis, therefore, interventions to the processes of H₂S metabolism to maintain its balance may have geroprotective potential. Here we demonstrated the additive geroprotective effect of combined genetic and pharmacological interventions to the hydrogen sulfide biosynthesis system by overexpression of cystathionine-β-synthase and cystathionine-γ-lyase genes and treatment with precursors of H₂S synthesis cysteine (Cys) and N-acetyl-L-cysteine (NAC). The obtained results suggest that additive effects of genetic and pharmacological interventions to H₂S metabolism may be associated with the complex interaction between beneficial action of H₂S production and prevention of adverse effects of excess H₂S production by Cys and NAC treatment.

The goal of geroscience is life extension

Although numerous drugs seemingly extend healthspan in mice, only a few extend lifespan in mice and only one does it consistently. Some of them, alone or in combination, can be used in humans, without further clinical trials.

Thioredoxin - a magic bullet or a double-edged sword for mammalian aging?

After the discovery of thioredoxin as a reductant for many important enzymes in the early 1960s, biological roles of thioredoxin in pathophysiology have been examined using various species and experimental models, e.g., yeast, invertebrates, rodents, and humans. A large number of studies demonstrated that thioredoxin plays an essential role to maintain a reduced cellular environment and possesses many beneficial effects by maintaining cellular/organ functions and against diseases. However, an important question that remains to be answered is whether thioredoxin could attenuate aging by reducing oxidative damage and changing cellular redox state, which alters redox-sensitive signaling pathways. To address this important question, we have been conducting aging studies with transgenic and knockout mice, and transgenic rats to examine whether the upregulation or downregulation of thioredoxin alters lifespan and age-related pathology. Aging studies conducted by our laboratory and others revealed that the roles of thioredoxin on pathophysiology seem to be more complex than our initial expectations as a potential magic bullet to solve the issues with age. Recent studies indicate that thioredoxin could have both beneficial and potentially deleterious effects on aging and age-related diseases. To critically evaluate the biological effects of thioredoxin on aging and age-related diseases, studies require further consideration to assess additional factors, e.g. levels of thioredoxin in different cellular compartments, different effects in each cell/tissue/organ, physiological aging vs. pathology, and/or at different life stages.

Proteasome activator PA200 maintains stability of histone marks during transcription and aging

The epigenetic inheritance relies on stability of histone marks, but various diseases, including aging-related disorders, are usually associated with alterations of histone marks. Whether and how the proteasome is responsible for maintaining the histone marks during transcription and aging remain unclear. The core histones can be degraded by the atypical proteasome, which contains the proteasome activator PA200, in an acetylation-dependent manner during somatic DNA damage response and spermiogenesis. Methods: By utilizing a substitute of methionine to label proteins metabolically, we analyzed histone degradation genome-wide by sequencing the DNA fragments following pulse-chase assays. The genome-wide RNA-sequencing analysis was performed to analyze transcription and chromatin-immunoprecipitation (ChIP)-sequencing was used for analyses of histone marks. The experimental models included gene-manipulated cells (including both mouse and yeast), mouse liver, and mice. Results: Degradation of H4 or the transcription-coupled histone variant H3.3 could be suppressed by deletion of PA200 or its yeast ortholog Blm10. The histone deacetylase inhibitor accelerated the degradation rates of H3, while the mutations of the putative acetyl-lysine-binding region of PA200 abolished histone degradation in the G1-arrested cells. Deletion of PA200 dramatically altered deposition of the active transcriptional hallmarks (H3K4me3 and H3K56ac) and transcription, especially during cellular aging. Furthermore, deletion of PA200 or Blm10 accelerated cellular aging. Notably, the PA200-deficient mice displayed a range of aging-related deteriorations, including immune malfunction, anxiety-like behavior and shorter lifespan. Conclusion: PA200 promotes the transcription-coupled degradation of the core histones, and plays an important role in maintaining the stability of histone marks during transcription and aging.