Superoxide dismutase mimetics elevate superoxide dismutase activity in vivo but do not retard aging in the nematode Caenorhabditis elegans

Redox regulation in lifespan determination

One of the major challenges that remain in the fields of aging and lifespan determination concerns the precise roles that reactive oxygen species (ROS) play in these processes. ROS, including superoxide and hydrogen peroxide, are constantly generated as byproducts of aerobic metabolism, as well as in response to endogenous and exogenous cues. While ROS accumulation and oxidative damage were long considered to constitute some of the main causes of age-associated decline, more recent studies reveal a signaling role in the aging process. In fact, accumulation of ROS, in a spatiotemporal manner, can trigger beneficial cellular responses that promote longevity and healthy aging. In this review, we discuss the importance of timing and compartmentalization of external and internal ROS perturbations in organismal lifespan and the role of redox regulated pathways.

Exploring the antioxidant activity of Fe(III), Mn(III)Mn(II), and Cu(II) compounds in Saccharomyces cerevisiae and Galleria mellonella models of study

Reactive oxygen species (ROS) are closely related to oxidative stress, aging, and the onset of human diseases. To mitigate ROS-induced damages, extensive research has focused on examining the antioxidative attributes of various synthetic/natural substances. Coordination compounds serving as synthetic antioxidants have emerged as a promising approach to attenuate ROS toxicity. Herein, we investigated the antioxidant potential of a series of Fe(III) (1), Mn(III)Mn(II) (2) and Cu(II) (3) coordination compounds synthesized with the ligand N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)[(3-chloro)(2-hydroxy)]-propylamine in Saccharomyces cerevisiae exposed to oxidative stress. We also assessed the antioxidant potential of these complexes in the alternative model of study, Galleria mellonella. DPPH analysis indicated that these complexes presented moderate antioxidant activity. However, treating Saccharomyces cerevisiae with 1, 2 and 3 increased the tolerance against oxidative stress and extended yeast lifespan. The treatment of yeast cells with these complexes decreased lipid peroxidation and catalase activity in stressed cells, whilst no change in SOD activity was observed. Moreover, these complexes induced the Hsp104 expression. In G. mellonella, complex administration extended larval survival under H2O2 stress and did not affect the insect's life cycle. Our results suggest that the antioxidant potential exhibited by these complexes could be further explored to mitigate various oxidative stress-related disorders.

Anti-Aging Drugs and the Related Signal Pathways

Aging is a multifactorial biological process involving chronic diseases that manifest from the molecular level to the systemic level. From its inception to 31 May 2022, this study searched the PubMed, Web of Science, EBSCO, and Cochrane library databases to identify relevant research from 15,983 articles. Multiple approaches have been employed to combat aging, such as dietary restriction (DR), exercise, exchanging circulating factors, gene therapy, and anti-aging drugs. Among them, anti-aging drugs are advantageous in their ease of adherence and wide prevalence. Despite a shared functional output of aging alleviation, the current anti-aging drugs target different signal pathways that frequently cross-talk with each other. At present, six important signal pathways were identified as being critical in the aging process, including pathways for the mechanistic target of rapamycin (mTOR), AMP-activated protein kinase (AMPK), nutrient signal pathway, silent information regulator factor 2-related enzyme 1 (SIRT1), regulation of telomere length and glycogen synthase kinase-3 (GSK-3), and energy metabolism. These signal pathways could be targeted by many anti-aging drugs, with the corresponding representatives of rapamycin, metformin, acarbose, nicotinamide adenine dinucleotide (NAD+), lithium, and nonsteroidal anti-inflammatory drugs (NSAIDs), respectively. This review summarized these important aging-related signal pathways and their representative targeting drugs in attempts to obtain insights into and promote the development of mechanism-based anti-aging strategies.

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.

Proteomic changes in various organs of Haemaphysalis longicornis under long-term starvation

Haemaphysalis longicornis (Neumann), a tick of public health and veterinary importance, spend the major part of their life cycle off-host, especially the adult host-seeking period. Thus, they have to contend with prolonged starvation. Here, we investigated the underlying molecular mechanism of tick starvation endurance in the salivary glands, midguts, ovaries, and Malpighian tubules of starved H. longicornis ticks using the data-independent acquisition quantitative proteomic approach to study the proteome changes. Essential synthases such as glutamate synthase, citrate synthase, and ATP synthase were up-regulated probably due to increased proteolysis and amino acid catabolism during starvation. The up-regulation of succinate dehydrogenase, ATP synthase, cytochrome c oxidase, and ADP/ATP translocase closely fits with an increased oxidative phosphorylation function during starvation. The differential expression of superoxide dismutase, glutathione reductase, glutathione S-transferase, thioredoxin, and peroxiredoxin indicated fasting-induced oxidative stress. The up-regulation of heat shock proteins could imply the activation of a protective mechanism that checks excessive protein breakdown during starvation stress. The results of this study could provide useful information about the vulnerabilities of ticks that could aid in tick control efforts.

Ticks are a common blood-sucking parasite, which spread many pathogens that cause serious diseases such as Lyme disease to people. Ixodid ticks can take up to three blood meals in their life. During the long process of waiting for their host in the wild, they have evolved a strong ability to tolerate hunger, which should not take more than a year. To study these tenacious molecular regulatory mechanisms, we conducted the DIA quantitative proteomics technology to perform large-scale protein quantitative research on various tissues of Haemaphysalis longicornis starved for a long time. Through the analysis of thousands of proteins produced by the performed research, the results showed that many proteins in the ticks starved for a long time had expressed quantitative changes such as the increased expression of some synthase enzymes. The large amount of data provided by this study can help to better understand the molecular mechanism of ticks’ long-term hunger tolerance. Although this study focuses on finding possible mechanisms for tick starvation resistance at the protein level, the current findings may well have a bearing on research about special activities such as ultra long-distance space travel in the dormant state of the human body in the future.

A Comprehensive Overview of the Complex Role of Oxidative Stress in Aging, The Contributing Environmental Stressors and Emerging Antioxidant Therapeutic Interventions

Introduction

Aging is a normal, inevitable, irreversible, and progressive process which is driven by internal and external factors. Oxidative stress, that is the imbalance between prooxidant and antioxidant molecules favoring the first, plays a key role in the pathophysiology of aging and comprises one of the molecular mechanisms underlying age-related diseases. However, the oxidative stress theory of aging has not been successfully proven in all animal models studying lifespan, meaning that altering oxidative stress/antioxidant defense systems did not always lead to a prolonged lifespan, as expected. On the other hand, animal models of age-related pathological phenotypes showed a well-correlated relationship with the levels of prooxidant molecules. Therefore, it seems that oxidative stress plays a more complicated role than the one once believed and this role might be affected by the environment of each organism. Environmental factors such as UV radiation, air pollution, and an unbalanced diet, have also been implicated in the pathophysiology of aging and seem to initiate this process more rapidly and even at younger ages.

Aim

The purpose of this review is to elucidate the role of oxidative stress in the physiology of aging and the effect of certain environmental factors in initiating and sustaining this process. Understanding the pathophysiology of aging will contribute to the development of strategies to postpone this phenomenon. In addition, recent studies investigating ways to alter the antioxidant defense mechanisms in order to prevent aging will be presented.

Conclusions

Careful exposure to harmful environmental factors and the use of antioxidant supplements could potentially affect the biological processes driving aging and slow down the development of age-related diseases. Maybe a prolonged lifespan could not be achieved by this strategy alone, but a longer healthspan could also be a favorable target.

Prevention of anticancer therapy-induced neurotoxicity: putting DNA damage in perspective

Chemotherapy-induced peripheral neuropathy (CIPN) is a severe side effect of conventional cancer therapeutics (cAT) that significantly impacts the quality of life of tumor patients. The molecular mechanisms of CIPN are incompletely understood and there are no effective preventive or therapeutic measures available to date. Here, we present a brief overview of the current knowledge about mechanisms underlying CIPN and discuss DNA damage-related stress responses as feasible targets for the prevention of CIPN. In addition, we discuss that the nematode Caenorhabditis elegans is a useful 3R-conform model organism to further elucidate molecular mechanisms of CIPN and to identify novel lead compounds protecting from cAT-triggered neuropathy.

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.

Specific collagens maintain the cuticle permeability barrier in Caenorhabditis elegans

Collagen-enriched cuticle forms the outermost layer of skin in nematode Caenorhabditis elegans. The nematode's genome encodes 177 collagens, but little is known about their role in maintaining the structure or barrier function of the cuticle. In this study, we found six permeability determining (PD) collagens. Loss of any of these PD collagens-DPY-2, DPY-3, DPY-7, DPY-8, DPY-9, and DPY-10-led to enhanced susceptibility of nematodes to paraquat (PQ) and antihelminthic drugs- levamisole and ivermectin. Upon exposure to PQ, PD collagen mutants accumulated more PQ and incurred more damage and death despite the robust activation of antioxidant machinery. We find that BLMP-1, a zinc finger transcription factor, maintains the barrier function of the cuticle by regulating the expression of PD collagens. We show that the permeability barrier maintained by PD collagens acts in parallel to FOXO transcription factor DAF-16 to enhance survival of insulin-like receptor mutant, daf-2. In all, this study shows that PD collagens regulate cuticle permeability by maintaining the structure of C. elegans cuticle and thus provide protection against exogenous toxins.

Pursuing the Elixir of Life: In Vivo Antioxidative Effects of Manganosalen Complexes

Manganosalen complexes are coordination compounds that possess a chelating salen-type ligand, a class of bis-Schiff bases obtained by condensation of salicylaldehyde and a diamine. They may act as catalytic antioxidants mimicking both the structure and the reactivity of the native antioxidant enzymes active site. Thus, manganosalen complexes have been shown to exhibit superoxide dismutase, catalase, and glutathione peroxidase activities, and they could potentially facilitate the scavenging of excess reactive oxygen species (ROS), thereby restoring the redox balance in damaged cells and organs. Initial catalytic studies compared the potency of these compounds as antioxidants in terms of rate constants of the chemical reactivity against ROS, giving catalytic values approaching and even exceeding that of the native antioxidative enzymes. Although most of these catalytic studies lack of biological relevance, subsequent in vitro studies have confirmed the efficiency of many manganosalen complexes in oxidative stress models. These synthetic catalytic scavengers, cheaper than natural antioxidants, have accordingly attracted intensive attention for the therapy of ROS-mediated injuries. The aim of this review is to focus on in vivo studies performed on manganosalen complexes and their activity on the treatment of several pathological disorders associated with oxidative damage. These disorders, ranging from the prevention of fetal malformations to the extension of lifespan, include neurodegenerative, inflammatory, and cardiovascular diseases; tissue injury; and other damages related to the liver, kidney, or lungs.

Production of YP170 Vitellogenins Promotes Intestinal Senescence in Caenorhabditis elegans

During aging, etiologies of senescence cause multiple pathologies, leading to morbidity and death. To understand aging requires identification of these etiologies. For example, Caenorhabditis elegans hermaphrodites consume their own intestinal biomass to support yolk production, which in later life drives intestinal atrophy and ectopic yolk deposition. Yolk proteins (YPs; vitellogenins) exist as three abundant species: YP170, derived from vit-1–vit-5; and YP115 and YP88, derived from vit-6. Here, we show that inhibiting YP170 synthesis leads to a reciprocal increase in YP115/YP88 levels and vice versa, an effect involving posttranscriptional mechanisms. Inhibiting YP170 production alone, despite increasing YP115/YP88 synthesis, reduces intestinal atrophy as much as inhibition of all YP synthesis, which increases life span. By contrast, inhibiting YP115/YP88 production alone accelerates intestinal atrophy and reduces life span, an effect that is dependent on increased YP170 production. Thus, despite copious abundance of both YP170 and YP115/YP88, only YP170 production is coupled to intestinal atrophy and shortened life span. In addition, increasing levels of YP115/YP88 but not of YP170 increases resistance to oxidative stress; thus, longevity resulting from reduced vitellogenin synthesis is not attributable to oxidative stress resistance.

Ecotoxicity of Caenorhabditis elegans following a step and repeated chronic exposure to tetrabromobisphenol A

To better understand the toxicity of tetrabromobisphenol A (TBBPA), its effects on the model nematode Caenorhabditis elegans were investigated. Following a step and repeated chronic exposure from L4-larvae to day-10 adult, physiology endpoints (growth and locomotion behaviors including head thrashes, body bends and pumping rate), biochemical endpoints (reactive oxygen species, superoxide dismutase activity, catalase activity), and molecular stress-related gene expression were tested at environmentally relevant concentrations of TBBPA (0.01-100 µg/L). The results showed that concentrations of TBBPA greater than 10 µg/L, clearly influenced the physiology behaviors (growth and locomotion endpoints). Under repeated exposure, C. elegans exhibited adaptive responses in head thrashes and pumping rate. Compared to toxicity evaluation following repeated chronic exposure, a significantly greater response was induced at the same concentration following a step chronic exposure. Reactive oxygen species production was significantly enhanced following a step and repeated TBBPA exposure at the concentrations of 1 and 10 µg/L, respectively. qRT-PCR showed that ctl-1, ctl-2, ctl-3 and sod-3 expression significantly increased, which was obviously correlated with physiological and biochemical behaviors under both treatment conditions according to Pearson correlation test analysis. sod-3 and ctl-2 mutations were more sensitive than the wild-type N2 under a step chronic TBBPA exposure at a level of 10 µg/L. Thus, chronic exposure to TBBPA induces an oxidative stress response in C. elegans, with ctl-2 and sod-3 playing a vital role in TBBPA-induced toxicity in nematodes.

Internal concentrations of perfluorobutane sulfonate (PFBS) comparable to those of perfluorooctane sulfonate (PFOS) induce reproductive toxicity in Caenorhabditis elegans

Perfluorobutane sulfonate (PFBS) is considered a less-toxic replacement for perfluorooctane sulfonate (PFOS), with multiple applications in industrial and consumer products. Previous studies comparing their toxicity generally used similar exposure levels, without taking internal concentrations into account. The current study compared the reproductive toxicity of PFOS and PFBS, at similar internal concentrations, to Caenorhabditis elegans (C. elegans). PFBS was much less bioaccumulative than PFOS. The 48-h median lethal concentrations (LC₅₀) for PFOS and PFBS were 1.4 μM (95% confidence interval [CI]: 1.1-1.6) and 794 μM (95% CI: 624-1009), respectively. Egg production and brood number of C. elegans decreased markedly following exposure to 0.1 μM PFOS or 1000 or 1500 μM PFBS. Germ-cell apoptosis and production of reactive oxygen species increased significantly following exposure to 2 μM PFOS or 500 or 1000 μM PFBS. Expression of the antioxidant genes sod-3, ctl-2, and gst-4 and the pro-apoptotic genes egl-1 and ced-13 was altered significantly following PFOS and PFBS exposure. These findings indicate that both chemicals exert reproductive toxicity in C. elegans, probably owing to germ-cell apoptosis resulting from elevated levels of reactive oxygen species. The vastly different exposure concentrations of PFBS and PFOS used in this study produced similar internal concentrations, leading to the reproductive toxicities observed.

The effects of ingestion of hormonal host factors on the longevity and insecticide resistance phenotype of the major malaria vector Anopheles arabiensis (Diptera: Culicidae)

Exogenous vertebrate-derived factors circulating in the blood have the capacity to modulate the biology of haematophagous insects. These include insulin, insulin growth factor 1 (IGF) and transforming growth factor β1 (TGFβ). The effects of the consumption of these three proteins were examined on laboratory strains of Anopheles arabiensis. SENN, an insecticide susceptible strain and SENN DDT, a resistant strain selected from SENN, were fed with host factor-supplemented sucrose. Adult longevity was measured and insecticide resistance phenotype over time was assessed by WHO bioassay. Detoxification and oxidative stress defence enzyme activity was assessed calorimetrically. Insulin supplementation augmented insecticide resistance in young adult mosquitoes. This effect was due to the hormonal nature of the protein, as heat-denatured insulin did not elicit the same response. In contrast, IGF and TGFβ consumption generally reduced the expression of insecticide resistance. Insulin ingestion significantly reduced longevity in the insecticide susceptible strain. IGF elicited the same response in the susceptible strain, while TGF consumption had no effect on either strain. Consumption of all factors significantly decreased Glutathione S-transferase activity and increased cytochrome P450 and superoxide dismutase activity. This suggests that the altered detoxification phenotype is mediated primarily by cytochrome P450 activity, which would result in an increase in oxidative stress. The increased superoxide dismutase activity suggests that this enzyme class alleviates the oxidative stress as opposed to glutathione-based redox systems. Oxidative stress responses play a crucial role in insecticide resistance and longevity. These data show that ingested hormonal factors can affect mosquito longevity and insecticide susceptibility, both of which are important characteristics in terms of malaria transmission and control.

2-SeCD treatment extends lifespan, improves healthspan and enhances resistance to stress in Caenorhabditis elegans

Aging is primarily caused by reactive oxygen species (ROS).

Caenorhabditis elegans as a model for understanding ROS function in physiology and disease

ROS (reactive oxygen species) are potentially damaging by-products of aerobic metabolism which, unchecked, can have detrimental effects on cell function. However, it is now widely accepted that, at physiological levels, certain ROS play important roles in cell signaling, acting as second messengers to regulate cell choices that contribute to the development, adaptation and survival of plants and animals. Despite important recent advances in the biochemical tools available to study redox-signaling, the molecular mechanisms underlying most of these responses remain poorly understood, particularly in multicellular organisms. As we will review here, C. elegans has emerged as a powerful animal model to elucidate these and other aspects of redox biology.

Mitochondrial ROS and the Effectors of the Intrinsic Apoptotic Pathway in Aging Cells: The Discerning Killers!

It has become clear that mitochondrial reactive oxygen species (mtROS) are not simply villains and mitochondria the hapless targets of their attacks. Rather, it appears that mitochondrial dysfunction itself and the signaling function of mtROS can have positive effects on lifespan, helping to extend longevity. If events in the mitochondria can lead to better cellular homeostasis and better survival of the organism in ways beyond providing ATP and biosynthetic products, we can conjecture that they act on other cellular components through appropriate signaling pathways. We describe recent advances in a variety of species which promoted our understanding of how changes of mtROS generation are part of a system of signaling pathways that emanate from the mitochondria to impact organism lifespan through global changes, including in transcriptional patterns. In unraveling this, many old players in cellular homeostasis were encountered. Among these, maybe most strikingly, is the intrinsic apoptotic signaling pathway, which is the conduit by which at least one class of mtROS exercise their actions in the nematode Caenorhabditis elegans. This is a pathway that normally contributes to organismal homeostasis by killing defective or otherwise unwanted cells, and whose various compounds have also been implicated in other cellular processes. However, it was a surprise that that appropriate activation of a cell killing pathway can in fact prolong the lifespan of the organism. In the soma of adult C. elegans, all cells are post-mitotic, like many of our neurons and possibly some of our immune cells. These cells cannot simply be killed and replaced when showing signs of dysfunction. Thus, we speculate that it is the ability of the apoptotic pathway to pull together information about the functional and structural integrity of different cellular compartments that is the key property for why this pathway is used to decide when to boost defensive and repair processes in irreplaceable cells. When this process is artificially stimulated in mutants with elevated mtROS generation or with drug treatments it leads to lifespan prolongations beyond the normal lifespan of the organism.

Mitochondrial reactive oxygen species: Do they extend or shorten animal lifespan?

Testing the predictions of the Mitochondrial Free Radical Theory of Ageing (MFRTA) has provided a deep understanding of the role of reactive oxygen species (ROS) and mitochondria in the aging process. However those data, which support MFRTA are in the majority correlative (e.g. increasing oxidative damage with age). In contrast the majority of direct experimental data contradict MFRTA (e.g. changes in ROS levels do not alter longevity as expected). Unfortunately, in the past, ROS measurements have mainly been performed using isolated mitochondria, a method which is prone to experimental artifacts and does not reflect the complexity of the in vivo process. New technology to study different ROS (e.g. superoxide or hydrogen peroxide) in vivo is now available; these new methods combined with state-of-the-art genetic engineering technology will allow a deeper interrogation of, where, when and how free radicals affect aging and pathological processes. In fact data that combine these new approaches, indicate that boosting mitochondrial ROS in lower animals is a way to extend both healthy and maximum lifespan. In this review, I discuss the latest literature focused on the role of mitochondrial ROS in aging, and how these new discoveries are helping to better understand the role of mitochondria in health and disease. This article is part of a Special Issue entitled 'EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2-6, 2016', edited by Prof. Paolo Bernardi.

Antioxidant activity in vitro and in vivo of the polysaccharides from different varieties of Auricularia auricula

In this study, five different kinds of polysaccharides (AAP1, AAP2, AAP3, AAP4, and AAP5) were extracted from different varieties ofAuricularia auriculathrough an alkali extraction process.

Antioxidant and neuroprotective potential of chitooligomers in Caenorhabditis elegans exposed to Monocrotophos

The objectives of this investigation were to establish the propensity of the chitooligomers (COS) to ameliorate neurodegeneration and oxidative stress in Caenorhabditis elegans induced by an organophosphorus insecticide, Monocrotophos (MCP). COS was prepared from α-chitosan by the enzymatic method using chitosanase and characterized by HPLC and electron spray ionization-TOF-(ESI-TOF)-MS. We exposed age synchronized L4 C. elegans worms (both wild type N2 and transgenic strain BZ555 (Pdat-1:GFP) to sublethal concentration of MCP (0.75mM) for 24h in the presence or absence of COS (0.2mM). The neuroprotective effect of COS was examined in N2 worms in terms of brood size, lifespan, egg laying, dopamine content, acetylcholinesterase and carboxylesterase activity and by direct visualization and quantification of degeneration of dopaminergic neurons in BZ555. Exposure to COS extended lifespan, normalized egg laying, increased brood size, decreased the dopaminergic neurodegeneration, increased the dopamine content and increased AChE and carboxylesterase activity in C. elegans treated with MCP. COS induced a significant decrease in reactive oxygen species and increased the reduced glutathione level as well as increased superoxide dismutase and catalase activity. Our findings demonstrate that COS significantly inhibits the dopaminergic neurodegeneration and associated physiological alterations induced by MCP in C. elegans by attenuating the oxidative stress as well.

Caenorhabditis elegans: What We Can and Cannot Learn from Aging Worms

SIGNIFICANCE

The nematode Caenorhabditis elegans is a widely used model organism for research into aging. However, nematodes diverged from other animals between 600 and 1300 million years ago. Beyond the intuitive impression that some aspects of aging appear to be universal, is there evidence that insights into the aging process of nematodes may be applicable to humans?

RECENT ADVANCES

There have been a number of results in nematodes that appear to contradict long-held beliefs about mechanisms and causes of aging. For example, ablation of several key antioxidant systems has often failed to result in lifespan shortening in C. elegans.

CRITICAL ISSUES

While it is clear that some central signaling pathways controlling lifespan are broadly conserved across large evolutionary distances, it is less clear to what extent downstream molecular mechanisms of aging are conserved. In this review we discuss the biology of C. elegans and mammals in the context of aging and age-dependent diseases. We consider evidence from studies that attempt to investigate basic, possibly conserved mechanisms of aging especially in the context of the free radical theory of aging. Practical points, such as the need for blinding of lifespan studies and for appropriate biomarkers, are also considered.

FUTURE DIRECTIONS

As data on the aging process(es) in different organisms increase, it is becoming increasingly clear that there are both conserved (public) and private aspects to aging. It is important to explore the dividing lines between these two aspects and to be aware of the large gray areas in-between.

Protective effect of Mn(III)-desferrioxamine B upon oxidative stress caused by ozone and acid rain in the Brazilian soybean cultivar Glycine max "Sambaiba"

This study aimed to investigate the effects of the Mn complex (Mn(III)-desferrioxamine B (MnDFB)) on oxidative stress in the Brazilian soybean cultivar Glycine max "Sambaiba" following exposure to ozone and acid rain. We determined the suitable dose of MnDFB to apply to G. max seedlings using a dose-response curve. The highest superoxide dismutase (SOD) activity and Mn content in leaves were found upon the application of 8 μM MnDFB. Thus, G. max seedlings pretreated with 8 μM MnDFB were individually exposed to ozone and acid rain simulated. Pretreatment with MnDFB reduced lipid peroxidation upon ozone exposure and increased SOD activity in leaves; it did not alter the metal content in any part of the plant. Conversely, following acid rain exposure, neither the metal content in leaves nor SOD enzyme activity were directly affected by MnDFB, unlike pH. Our findings demonstrated that exogenous MnDFB application before ozone exposure may modulate the MnSOD, Cu/ZnSOD, and FeSOD activities to combat the ROS excess in the cell. Here, we demonstrated that the applied dose of MnDFB enhances antioxidative defenses in soybean following exposure to acid rain and especially to ozone.

Identification of longevity, fertility and growth-promoting properties of pomegranate in Caenorhabditis elegans

BACKGROUND

Pomegranate (Punica granatum L.) is commonly consumed as fresh fruit and fruit juice. It is also used in the production of jam, wine, food coloring agent, and flavor enhancer.

OBJECTIVE

The aim of this study was to identify the possible longevity, fertility and growth promoting properties of different ethanolic extract concentrations of pomegranate in Caenorhabditis elegans, which is increasingly popular and has proven to be a very useful experimental model organism for aging studies as well as for testing antioxidants and other compounds for effects on longevity.

MATERIALS AND METHODS

In this study, five experimental groups (20, 10, 5, 2.5 and 1.25 mg pomegranate extract/mL and one control group) were used to determine the most effective dose of pomegranate in terms of longevity, fertility and growth parameters.

RESULTS

It was seen that, pomegranate extracts up to the concentration of 5 mg/mL, had the potential to promote for the longevity, formation of new generations, fertility of new generations and growth properties of C. elegans although higher concentrations significantly reduced these parameters.

CONCLUSION

these findings indicated that pomegranate could be used as a supplement to enhance longevity, fertility and growth rate for the other living organisms and human beings, but the dose should be carefully adjusted to avoid adverse effects.

Increased Akt signaling in the mosquito fat body increases adult survivorship

Akt signaling regulates diverse physiologies in a wide range of organisms. We examine the impact of increased Akt signaling in the fat body of 2 mosquito species, the Asian malaria mosquito Anopheles stephensi and the yellow fever mosquito Aedes aegypti. Overexpression of a myristoylated and active form of A. stephensi and Ae. aegypti Akt in the fat body of transgenic mosquitoes led to activation of the downstream signaling molecules forkhead box O (FOXO) and p70 S6 kinase in a tissue and blood meal-specific manner. In both species, increased Akt signaling in the fat body after blood feeding significantly increased adult survivorship relative to nontransgenic sibling controls. In A. stephensi, survivorship was increased by 15% to 45%, while in Ae. aegypti, it increased 14% to 47%. Transgenic mosquitoes fed only sugar, and thus not expressing active Akt, had no significant difference in survivorship relative to nontransgenic siblings. Expression of active Akt also increased expression of fat body vitellogenin, but the number of viable eggs did not differ significantly between transgenic and nontransgenic controls. This work demonstrates a novel mechanism of enhanced survivorship through increased Akt signaling in the fat bodies of multiple mosquito genera and provides new tools to unlock the molecular underpinnings of aging in eukaryotic organisms.

Preventive effect of safranal against oxidative damage in aged male rat brain

An imbalance between production of reactive oxygen species (ROS) and its elimination by antioxidant defense system in the body has been implicated for causes of aging and neurodegenerative diseases. This study was design to assess the changes in activities of antioxidant enzymes (superoxide dismutase (SOD), glutathione-S-transferase (GST), catalase), lipid peroxidation and reduced glutathione (GSH) levels in the brain of 2, 10 and 20 month old rats, and to determine the effect of safranal on the status of selected oxidative stress indices in the 10 and 20 month old rats. The aged rats (10 and 20 months) were given intraperitoneal injections of safranal (0.5 mg/kg day) daily for one month. The results of this study demonstrated that aging caused significant increase in the level of lipid peroxidation as well decrease in the GSH level and activities of SOD and GST in the brain of aging rats. The results of this study showed that safranal ameliorated the increased lipid peroxidation level as well as decreased GSH content of the brain of 10 and 20 month old rats. In addition, safranal treatment to the 20 month old rats, which restored the SOD and GST activities. In conclusion, safranal can be effective to protect susceptible aged brain from oxidative damage by increasing antioxidant defenses.

Endogenous ROS levels in C. elegans under exogenous stress support revision of oxidative stress theory of life-history tradeoffs

BACKGROUND

The oxidative stress theory of life-history tradeoffs states that oxidative stress caused by damaging free radicals directly underpins tradeoffs between reproduction and longevity by altering the allocation of energetic resources between these tasks. We test this theory by characterizing the effects of exogenous oxidative insult and its interaction with thermal stress and diet quality on a suite of life-history traits and correlations in Caenorhabditis elegans nematodes. We also quantify demographic aging rates and endogenous reactive oxygen species (ROS) levels in live animals.

RESULTS

Our findings indicate a tradeoff between investment in reproduction and antioxidant defense (somatic maintenance) consistent with theoretical predictions, but correlations between standard life-history traits yield little evidence that oxidative stress generates strict tradeoffs. Increasing oxidative insult, however, shows a strong tendency to uncouple positive phenotypic correlations and, in particular, to reduce the correlation between reproduction and lifespan. We also found that mild oxidative insult results in lower levels of endogenous ROS accompanied by hormetic changes in lifespan, demographic aging, and reproduction that disappear in combined-stress treatments--consistent with the oxidative stress theory of aging.

CONCLUSIONS

Our findings demonstrate that oxidative stress is a direct contributor to life-history trait variation and that traditional tradeoffs are not necessary to invoke oxidative stress as a mediator of relationships between life-history traits, supporting previous calls for revisions to theory.

Hydrogen sulfide is an endogenous regulator of aging in Caenorhabditis elegans

AIMS

To investigate the role of endogenous hydrogen sulfide (H2S) in the control of aging and healthspan of Caenorhabditis elegans.

RESULTS

We show that the model organism, C. elegans, synthesizes H2S. Three H2S-synthesizing enzymes are present in C. elegans, namely cystathionine γ lyase (CSE), cystathionine β synthetase, and 3-mercaptopyruvate transferase (MPST or 3-MST). Genetic deficiency of mpst-1 (3-MST orthologue 1), but not cth-2 (CSE orthologue), reduced the lifespan of C. elegans. This effect was reversed by a pharmacological H2S donor (GYY4137). GYY4137 also reduced detrimental age-dependent changes in a range of physiological indices, including pharyngeal contraction and defecation. Treatment of C. elegans with GYY4137 increased the expression of several age-related, stress response, and antioxidant genes, whereas MitoSOX Red fluorescence, indicative of reactive oxygen species generation, was increased in mpst-1 knockouts and decreased by GYY4137 treatment. GYY4137 additionally increased the lifespan in short-lived mev-1 mutants with elevated oxidative stress and protected wild-type C. elegans against paraquat poisoning. The lifespan-prolonging and health-promoting effects of H2S in C. elegans are likely due to the antioxidant action of this highly cell-permeable gas.

INNOVATION

The possibility that novel pharmacological agents based on the principle of H2S donation may be able to retard the onset of age-related disease by slowing the aging process warrants further study.

CONCLUSION

Our results show that H2S is an endogenous regulator of oxidative damage, metabolism, and aging in C. elegans and provide new insight into the mechanisms, which control aging in this model organism.

Simple biological systems for assessing the activity of superoxide dismutase mimics

SIGNIFICANCE

Half a century of research provided unambiguous proof that superoxide and species derived from it-reactive oxygen species (ROS)-play a central role in many diseases and degenerative processes. This stimulated the search for pharmaceutical agents that are capable of preventing oxidative damage, and methods of assessing their therapeutic potential.

RECENT ADVANCES

The limitations of superoxide dismutase (SOD) as a therapeutic tool directed attention to small molecules, SOD mimics, that are capable of catalytically scavenging superoxide. Several groups of compounds, based on either metal complexes, including metalloporphyrins, metallocorroles, Mn(II) cyclic polyamines, and Mn(III) salen derivatives, or non-metal based compounds, such as fullerenes, nitrones, and nitroxides, have been developed and studied in vitro and in vivo. Very few entered clinical trials.

CRITICAL ISSUES AND FUTURE DIRECTIONS

Development of SOD mimics requires in-depth understanding of their mechanisms of biological action. Elucidation of both molecular features, essential for efficient ROS-scavenging in vivo, and factors limiting the potential side effects requires biologically relevant and, at the same time, relatively simple testing systems. This review discuses the advantages and limitations of genetically engineered SOD-deficient unicellular organisms, Escherichia coli and Saccharomyces cerevisiae as tools for investigating the efficacy and mechanisms of biological actions of SOD mimics. These simple systems allow the scrutiny of the minimal requirements for a functional SOD mimic: the association of a high catalytic activity for superoxide dismutation, low toxicity, and an efficient cellular uptake/biodistribution.

SOD therapeutics: latest insights into their structure-activity relationships and impact on the cellular redox-based signaling pathways

SIGNIFICANCE

Superoxide dismutase (SOD) enzymes are indispensable and ubiquitous antioxidant defenses maintaining the steady-state levels of O2·(-); no wonder, thus, that their mimics are remarkably efficacious in essentially any animal model of oxidative stress injuries thus far explored.

RECENT ADVANCES

Structure-activity relationship (half-wave reduction potential [E1/2] versus log kcat), originally reported for Mn porphyrins (MnPs), is valid for any other class of SOD mimics, as it is dominated by the superoxide reduction and oxidation potential. The biocompatible E1/2 of ∼+300 mV versus normal hydrogen electrode (NHE) allows powerful SOD mimics as mild oxidants and antioxidants (alike O2·(-)) to readily traffic electrons among reactive species and signaling proteins, serving as fine mediators of redox-based signaling pathways. Based on similar thermodynamics, both SOD enzymes and their mimics undergo similar reactions, however, due to vastly different sterics, with different rate constants.

CRITICAL ISSUES

Although log kcat(O2·(-)) is a good measure of therapeutic potential of SOD mimics, discussions of their in vivo mechanisms of actions remain mostly of speculative character. Most recently, the therapeutic and mechanistic relevance of oxidation of ascorbate and glutathionylation and oxidation of protein thiols by MnP-based SOD mimics and subsequent inactivation of nuclear factor κB has been substantiated in rescuing normal and killing cancer cells. Interaction of MnPs with thiols seems to be, at least in part, involved in up-regulation of endogenous antioxidative defenses, leading to the healing of diseased cells.

FUTURE DIRECTIONS

Mechanistic explorations of single and combined therapeutic strategies, along with studies of bioavailability and translational aspects, will comprise future work in optimizing redox-active drugs.

Glucose feeding during development aggravates the toxicity of the organophosphorus insecticide Monocrotophos in the nematode, Caenorhabditis elegans

Several studies have demonstrated that high glucose feeding induced oxidative stress and apoptosis thereby affecting growth, fertility, aging and lifespan in Caenorhabditis elegans. Earlier studies from our laboratory had clearly established the propensity of monocrotophos, an OPI to alter the physiological and behavioral responses of C. elegans. The present study was aimed to investigate the effect of monocrotophos (MCP) on physiological/behavioral and biochemical responses in C. elegans that were maintained on high glucose diet. We exposed the worms through development to high glucose diet (2%) and then treated with sublethal concentrations of MCP (0.5, 0.75, 1.5mM). We measured the behavioral responses in terms of locomotion, physiological responses in terms of egg laying, brood size, lifespan; morphological alterations; and biochemical responses including glucose content. The worms exposed from egg stage through development to high glucose diet showed enhanced toxic outcome of MCP in terms of physiological, behavioral and biochemical responses. Our studies showed that C. elegans is a good model to study glucose-OPI interactive neurotoxicity since all the responses could be studied at ease in this organism and the outcome could be well extrapolated to those that one would expect in higher animals.

Novel interactions between mitochondrial superoxide dismutases and the electron transport chain

The processes that control aging remain poorly understood. We have exploited mutants in the nematode, Caenorhabditis elegans, that compromise mitochondrial function and scavenging of reactive oxygen species (ROS) to understand their relation to lifespan. We discovered unanticipated roles and interactions of the mitochondrial superoxide dismutases (mtSODs): SOD-2 and SOD-3. Both SODs localize to mitochondrial supercomplex I:III:IV. Loss of SOD-2 specifically (i) decreases the activities of complexes I and II, complexes III and IV remain normal; (ii) increases the lifespan of animals with a complex I defect, but not the lifespan of animals with a complex II defect, and kills an animal with a complex III defect; (iii) induces a presumed pro-inflammatory response. Knockdown of a molecule that may be a pro-inflammatory mediator very markedly extends lifespan and health of certain mitochondrial mutants. The relationship between the electron transport chain, ROS, and lifespan is complex, and defects in mitochondrial function have specific interactions with ROS scavenging mechanisms. We conclude that mtSODs are embedded within the supercomplex I:III:IV and stabilize or locally protect it from reactive oxygen species (ROS) damage. The results call for a change in the usual paradigm for the interaction of electron transport chain function, ROS release, scavenging, and compensatory responses.

A cytoprotective perspective on longevity regulation

There are many mechanisms of lifespan extension, including the disruption of insulin/insulin-like growth factor 1 (IGF-1) signaling, metabolism, translation, and feeding. Despite the disparate functions of these pathways, inhibition of each induces responses that buffer stress and damage. Here, emphasizing data from genetic analyses in Caenorhabditis elegans, we explore the effectors and upstream regulatory components of numerous cytoprotective mechanisms activated as major elements of longevity programs, including detoxification, innate immunity, proteostasis, and oxidative stress response. We show that their induction underpins longevity extension across functionally diverse triggers and across species. Intertwined with the evolution of longevity, cytoprotective pathways are coupled to the surveillance of core cellular components, with important implications in normal and aberrant responses to drugs, chemicals, and pathogens.

Xenohormetic and anti-aging activity of secoiridoid polyphenols present in extra virgin olive oil: a new family of gerosuppressant agents

Aging can be viewed as a quasi-programmed phenomenon driven by the overactivation of the nutrient-sensing mTOR gerogene. mTOR-driven aging can be triggered or accelerated by a decline or loss of responsiveness to activation of the energy-sensing protein AMPK, a critical gerosuppressor of mTOR. The occurrence of age-related diseases, therefore, reflects the synergistic interaction between our evolutionary path to sedentarism, which chronically increases a number of mTOR activating gero-promoters (e.g., food, growth factors, cytokines and insulin) and the "defective design" of central metabolic integrators such as mTOR and AMPK. Our laboratories at the Bioactive Food Component Platform in Spain have initiated a systematic approach to molecularly elucidate and clinically explore whether the "xenohormesis hypothesis," which states that stress-induced synthesis of plant polyphenols and many other phytochemicals provides an environmental chemical signature that upregulates stress-resistance pathways in plant consumers, can be explained in terms of the reactivity of the AMPK/mTOR-axis to so-called xenohormetins. Here, we explore the AMPK/mTOR-xenohormetic nature of complex polyphenols naturally present in extra virgin olive oil (EVOO), a pivotal component of the Mediterranean style diet that has been repeatedly associated with a reduction in age-related morbid conditions and longer life expectancy. Using crude EVOO phenolic extracts highly enriched in the secoiridoids oleuropein aglycon and decarboxymethyl oleuropein aglycon, we show for the first time that (1) the anticancer activity of EVOO secoiridoids is related to the activation of anti-aging/cellular stress-like gene signatures, including endoplasmic reticulum (ER) stress and the unfolded protein response, spermidine and polyamine metabolism, sirtuin-1 (SIRT1) and NRF2 signaling; (2) EVOO secoiridoids activate AMPK and suppress crucial genes involved in the Warburg effect and the self-renewal capacity of "immortal" cancer stem cells; (3) EVOO secoiridoids prevent age-related changes in the cell size, morphological heterogeneity, arrayed cell arrangement and senescence-associated β-galactosidase staining of normal diploid human fibroblasts at the end of their proliferative lifespans. EVOO secoiridoids, which provide an effective defense against plant attack by herbivores and pathogens, are bona fide xenohormetins that are able to activate the gerosuppressor AMPK and trigger numerous resveratrol-like anti-aging transcriptomic signatures. As such, EVOO secoiridoids constitute a new family of plant-produced gerosuppressant agents that molecularly "repair" the aimless (and harmful) AMPK/mTOR-driven quasi-program that leads to aging and aging-related diseases, including cancer.

Pharmacological lifespan extension of invertebrates

There is considerable interest in identifying small, drug-like compounds that slow aging in multiple species, particularly in mammals. Such compounds may prove to be useful in treating and retarding age-related disease in humans. Just as invertebrate models have been essential in helping us understand the genetic pathways that control aging, these model organisms are also proving valuable in discovering chemical compounds that influence longevity. The nematode Caenorhabditis elegans has numerous advantages for such studies including its short lifespan and has been exploited by a number of investigators to find compounds that impact aging. Here, we summarize the progress being made in identifying compounds that extend the lifespan of invertebrates, and introduce the challenges we face in translating this research into human therapies.

ROS in aging Caenorhabditis elegans: damage or signaling?

Many insights into the mechanisms and signaling pathways underlying aging have resulted from research on the nematode Caenorhabditis elegans. In this paper, we discuss the recent findings that emerged using this model organism concerning the role of reactive oxygen species (ROS) in the aging process. The accrual of oxidative stress and damage has been the predominant mechanistic explanation for the process of aging for many years, but reviewing the recent studies in C. elegans calls this theory into question. Thus, it becomes more and more evident that ROS are not merely toxic byproducts of the oxidative metabolism. Rather it seems more likely that tightly controlled concentrations of ROS and fluctuations in redox potential are important mediators of signaling processes. We therefore discuss some theories that explain how redox signaling may be involved in aging and provide some examples of ROS functions and signaling in C. elegans metabolism. To understand the role of ROS and the redox status in physiology, stress response, development, and aging, there is a rising need for accurate and reversible in vivo detection. Therefore, we comment on some methods of ROS and redox detection with emphasis on the implementation of genetically encoded biosensors in C. elegans.

Manipulation of in vivo iron levels can alter resistance to oxidative stress without affecting ageing in the nematode C. elegans

Iron-catalyzed generation of free radicals leads to molecular damage in vivo, and has been proposed to contribute to organismal ageing. Here we investigate the role of free iron in ageing in the nematode Caenorhabditis elegans. Media supplementation with Fe(III) increased free iron levels in vivo, as detected by continuous-wave electron paramagnetic resonance spectroscopy and elevated expression of the iron-sensitive reporter transgene pftn-1::gfp. Increased free iron levels caused elevated levels of protein oxidation and hypersensitivity to tert-butyl hydroperoxide (t-BOOH) given 9 mM Fe(III) or greater, but 15 mM Fe(III) or greater was required to reduce lifespan. Treatment with either an iron chelator (deferoxamine) or over-expression of ftn-1, encoding the iron sequestering protein ferritin, increased resistance to t-BOOH and, in the latter case, reduced protein oxidation, but did not increase lifespan. Expression of ftn-1 is greatly increased in long-lived daf-2 insulin/IGF-1 receptor mutants. In this context, deletion of ftn-1 decreased t-BOOH resistance, but enhanced both daf-2 mutant longevity and constitutive dauer larva formation, suggesting an effect of ferritin on signaling. These results show that high levels of iron can increase molecular damage and reduce lifespan, but overall suggest that iron levels within the normal physiological range do not promote ageing in C. elegans.

Clair D, Batinic-Haberle I. Manganese superoxide dismutase, MnSOD and its mimics

Increased understanding of the role of mitochondria under physiological and pathological conditions parallels increased exploration of synthetic and natural compounds able to mimic MnSOD - endogenous mitochondrial antioxidant defense essential for the existence of virtually all aerobic organisms from bacteria to humans. This review describes most successful mitochondrially-targeted redox-active compounds, Mn porphyrins and MitoQ(10) in detail, and briefly addresses several other compounds that are either catalysts of O(2)(-) dismutation, or its non-catalytic scavengers, and that reportedly attenuate mitochondrial dysfunction. While not a true catalyst (SOD mimic) of O(2)(-) dismutation, MitoQ(10) oxidizes O(2)(-) to O(2) with a high rate constant. In vivo it is readily reduced to quinol, MitoQH(2), which in turn reduces ONOO(-) to NO(2), producing semiquinone radical that subsequently dismutes to MitoQ(10) and MitoQH(2), completing the "catalytic" cycle. In MitoQ(10), the redox-active unit was coupled via 10-carbon atom alkyl chain to monocationic triphenylphosphonium ion in order to reach the mitochondria. Mn porphyrin-based SOD mimics, however, were designed so that their multiple cationic charge and alkyl chains determine both their remarkable SOD potency and carry them into the mitochondria. Several animal efficacy studies such as skin carcinogenesis and UVB-mediated mtDNA damage, and subcellular distribution studies of Saccharomyces cerevisiae and mouse heart provided unambiguous evidence that Mn porphyrins mimic the site and action of MnSOD, which in turn contributes to their efficacy in numerous in vitro and in vivo models of oxidative stress. Within a class of Mn porphyrins, lipophilic analogs are particularly effective for treating central nervous system injuries where mitochondria play key role. This article is part of a Special Issue entitled: Antioxidants and Antioxidant Treatment in Disease.

A significant component of ageing (DNA damage) is reflected in fading breeding colors: an experimental test using innate antioxidant mimetics in painted dragon lizards

A decade ahead of their time, von Schantz et al. united sexual selection and free radical biology by identifying causal links between deep-rooted physiological processes that dictate resistance to toxic waste from oxidative metabolism (reactive oxygen species, ROS), and phenotypic traits, such as ornaments. Ten years later, these ideas have still only been tested with indirect estimates of free radical levels (oxidative stress) subsequent to the action of innate and dietary antioxidants. Here, we measure net superoxide (a selection pressure for antioxidant production) and experimentally manipulate superoxide antioxidation using a synthetic mimetic of superoxide dismutase (SOD), Eukarion 134 (EUK). We then measure the toxic effect of superoxide in terms of DNA erosion and concomitant loss of male breeding coloration in the lizard, Ctenophorus pictus. Control males suffered more DNA damage than EUK males. Spectroradiometry showed that male coloration is lost in relation to superoxide and covaries with DNA erosion; in control males, these variables explained loss of color, whereas in EUK males, the fading of coloration was unaffected by superoxide and unrelated to DNA damage. Thus, EUK's powerful antioxidation removes the erosion effect of superoxide on coloration and experimentally verifies the prediction that colors reflect innate capacity for antioxidation.

Hormesis does not make sense except in the light of TOR-driven aging

Weak stresses (including weak oxidative stress, cytostatic agents, heat shock, hypoxia, calorie restriction) may extend lifespan. Known as hormesis, this is the most controversial notion in gerontology. For one, it is believed that aging is caused by accumulation of molecular damage. If so, hormetic stresses (by causing damage) must shorten lifespan. To solve the paradox, it was suggested that, by activating repair, hormetic stresses eventually decrease damage. Similarly, Baron Munchausen escaped from a swamp by pulling himself up by his own hair. Instead, I discuss that aging is not caused by accumulation of molecular damage. Although molecular damage accumulates, organisms do not live long enough to age from this accumulation. Instead, aging is driven by overactivated signal-transduction pathways including the TOR (Target of Rapamycin) pathway. A diverse group of hormetic conditions can be divided into two groups. "Hormesis A" inhibits the TOR pathway. "Hormesis B" increases aging-tolerance, defined as the ability to survive catastrophic complications of aging. Hormesis A includes calorie restriction, resveratrol, rapamycin, p53-inducing agents and, in part, physical exercise, heat shock and hypoxia. Hormesis B includes ischemic preconditioning and, in part, physical exercise, heat shock, hypoxia and medical interventions.

Significant damage-rescuing effects of wood vinegar extract in living Caenorhabditis elegans under oxidative stress

BACKGROUND

Wood vinegar (WV), a byproduct from the charcoal production process, has been reported to have excellent antioxidant capability by chemical examination. However, the biological effect of WV in living animals is still unknown. In this study, a simple model organism, the nematode Caenorhabditis elegans, was used as an in vivo system to assess the biological effects of wood vinegar through the development, lifespan, brood size, germline cell apoptosis and superoxide dismutase (SOD) level.

RESULTS

Wood vinegar extract (WVE) promoted the development, prolonged the lifespan and increased the brood size in reactive oxidative species (ROS)-sensitive mutant worms. WVE treatment rescued the effects of damage in germline cell apoptosis and SOD upregulation induced by paraquat, an ROS generator, to the control level. Additionally, WVE showed comparative ability in rescuing damage as compared with L-ascorbic acid and α-tocopherol.

CONCLUSION

WVE treatment exhibits a remedial/beneficial effect on ROS-sensitive mutant under normal cultural conditions and on wild-type worms under oxidative stress. ROS scavenging is involved in the damage-rescuing mechanism. This study will provide a basal biological and nutritional exploration for the use of WV as a functional food, and for the substitution of chemical antioxidants with side effects in food.

Increased life span from overexpression of superoxide dismutase in Caenorhabditis elegans is not caused by decreased oxidative damage

The superoxide free radical (O(2)(•-)) has been viewed as a likely major contributor to aging. If this is correct, then superoxide dismutase (SOD), which removes O(2)(•-), should contribute to longevity assurance. In Caenorhabditis elegans, overexpression (OE) of the major cytosolic Cu/Zn-SOD, sod-1, increases life span. But is this increase caused by enhanced antioxidant defense? sod-1 OE did not reduce measures of lipid oxidation or glycation and actually increased levels of protein oxidation. The effect of sod-1 OE on life span was dependent on the DAF-16/FoxO transcription factor (TF) and, partially, on the heat shock TF HSF-1. Similarly, overexpression of sod-2 (major mitochondrial Mn-SOD) resulted in life-span extension that was daf-16 dependent. sod-1 OE increased steady-state hydrogen peroxide (H(2)O(2)) levels in vivo. However, co-overexpression of catalase did not suppress the life-span extension, arguing against H(2)O(2) as a cause of longevity. sod-1 OE increased hsp-4 expression, suggesting increased endoplasmic reticulum (ER) stress. Moreover, longevity was partially suppressed by inactivation of ire-1 and xbp-1, mediators of the ER stress response. This suggests that high levels of SOD-1 protein may challenge protein-folding homeostasis, triggering a daf-16- and hsf-1-dependent stress response that extends life span. These findings imply that SOD overexpression increases C. elegans life span, not by removal of O(2)(•-), but instead by activating longevity-promoting transcription factors.

Extension of lifespan in C. elegans by naphthoquinones that act through stress hormesis mechanisms

Hormesis occurs when a low level stress elicits adaptive beneficial responses that protect against subsequent exposure to severe stress. Recent findings suggest that mild oxidative and thermal stress can extend lifespan by hormetic mechanisms. Here we show that the botanical pesticide plumbagin, while toxic to C. elegans nematodes at high doses, extends lifespan at low doses. Because plumbagin is a naphthoquinone that can generate free radicals in vivo, we investigated whether it extends lifespan by activating an adaptive cellular stress response pathway. The C. elegans cap‘n’collar (CNC) transcription factor, SKN-1, mediates protective responses to oxidative stress. Genetic analysis showed that skn-1 activity is required for lifespan extension by low-dose plumbagin in C. elegans. Further screening of a series of plumbagin analogs identified three additional naphthoquinones that could induce SKN-1 targets in C. elegans. Naphthazarin showed skn-1dependent lifespan extension, over an extended dose range compared to plumbagin, while the other naphthoquinones, oxoline and menadione, had differing effects on C. elegans survival and failed to activate ARE reporter expression in cultured mammalian cells. Our findings reveal the potential for low doses of naturally occurring naphthoquinones to extend lifespan by engaging a specific adaptive cellular stress response pathway.

Antioxidant Activities of the Pyroligneous Acid in Living Caenorhabditis Elegans

Pyroligneous acid (PA), obtained from charcoal production, has been reported excellent capability in antioxidant by chemical examination. However, the biological effect of PA in living animal is still unknown. In this study, a simple model organism, the nematodeCaenorhabditis elegans, was used as anin vivosystem to assess the biological effects of PA treatment. The worms were exposed to concentrated pyroligneous acid (CPA) and extraction (CPAE) thereof in a 0.5-5.0 mg/mL concentration and their brood size and germline cell apoptotisis were examined. The results showed that CPA and CPAE rescued the germline cell apoptosis induced by paraquat, a reactive oxygen species (ROS) generator. Additionally, CPA and CPAE did not show negative effect on the brood size and germline cell apoptosis in wild type at normal culture condition, suggesting safety of PA in living worms. To further scrutinize the antioxidant ability of PA, the apoptotic cell of germline induced by parapuat was assayed after treatment of 0.5 mg/mL CPA, CPAE, L-ascorbic acid and alpha-tocopherol. Treatment with CPAE or L-ascorbic acid could almost completely rescue the germline apoptosis to control level, indicating a potential material in food and biomedicine of PA.

Unraveling the biological roles of reactive oxygen species

Reactive oxygen species are not only harmful agents that cause oxidative damage in pathologies, they also have important roles as regulatory agents in a range of biological phenomena. The relatively recent development of this more nuanced view presents a challenge to the biomedical research community on how best to assess the significance of reactive oxygen species and oxidative damage in biological systems. Considerable progress is being made in addressing these issues, and here we survey some recent developments for those contemplating research in this area.