Applying hormesis in aging research and therapy

Antiaging Strategies and Remedies: A Landscape of Research Progress and Promise

Aging is typified by a gradual loss of physiological fitness and accumulation of cellular damage, leading to deteriorated functions and enhanced vulnerability to diseases. Antiaging research has a long history throughout civilization, with many efforts put forth to understand and prevent the effects of aging. Multiple strategies aiming to promote healthy aging and extend the lifespan have been developed including lifestyle adjustments, medical treatments, and social programs. A multitude of antiaging medicines and remedies have also been explored. Here, we use data from the CAS Content Collection to analyze the publication landscape of recent research related to antiaging strategies and treatments. We review the recent advances and delineate trends in research headway of antiaging knowledge and practice across time, geography, and development pipelines. We further assess the state-of-the-art antiaging approaches and explore their correlations with age-related diseases. The landscape of antiaging drugs has been outlined and explored. Well-recognized and novel, currently evaluated antiaging agents have also been summarized. Finally, we review clinical applications of antiaging products with their development pipelines. The objective of this review is to summarize current knowledge on preventive strategies and treatment remedies in the field of aging, to outline challenges and evaluate growth opportunities, in order to further efforts to solve the problems that remain.

Hormesis defines the limits of lifespan

This commentary provides a novel synthesis of how biological systems adapt to a broad spectrum of environmental and age-related stresses that are underlying causes of numerous degenerative diseases and debilitating effects of aging. It proposes that the most fundamental, evolutionary-based integrative strategy to sustain and protect health is based on the concept of hormesis. This concept integrates anti-oxidant, anti-inflammatory and cellular repair responses at all levels of biological organization (i.e., cell, organ and organism) within the framework of biphasic dose responses that describe the quantitative limits of biological plasticity in all cells and organisms from bacteria and plants to humans. A major feature of the hormetic concept is that low levels of biological, chemical, physical and psychological stress upregulate adaptive responses that not only precondition, repair and restore normal functions to damaged tissues/organs but modestly overcompensate, reducing ongoing background damage, thereby enhancing health beyond that in control groups, lacking the low level "beneficial" stress. Higher doses of such stress often become counterproductive and eventually harmful. Hormesis is active throughout the life-cycle and can be diminished by aging processes affecting the onset and severity of debilitating conditions/diseases, especially in elderly subjects. The most significant feature of the hormetic dose response is that the limits of biological plasticity for adaptive processes are less than twice that of control group responses, with most, at maximum, being 30-60 % greater than control group values. Yet, these modest increases can make the difference between health or disease and living or dying. The quantitative features of these adaptive hormetic dose responses are also independent of mechanism. These features of the hormetic dose response determine the capacity to which systems can adapt/be protected, the extent to which biological performance (e.g., memory, resistance to injury/disease, wound healing, hair growth or lifespan) can be enhanced/extended and the extent to which synergistic interactions may occur. Hormesis defines the quantitative rules within which adaptive processes operate and is central to evolution and biology and should become transformational for experimental concepts and study design strategies, public health practices and a vast range of therapeutic strategies and interventions.

Cistanche deserticola Polysaccharide Reduces Inflammation and Aging Phenotypes in the Dermal Fibroblasts through the Activation of the NRF2/HO-1 Pathway

Dermal fibroblasts maintain the skin homeostasis by interacting with the epidermis and extracellular matrix. Their senescence contributes to functional defects in the skin related to aging. Therefore, there is an urgent need for novel therapeutic agents that could inhibit fibroblast senescence. In this study, we investigated the effects of Cistanche deserticola polysaccharide (CDP), a natural anti-inflammatory component, on the progression of senescence in human dermal fibroblasts. Normal human dermal fibroblasts (NHDFs) were cultured in passages, and highly senescent cells were selected as senescent cells. CDP treatment increased the cell proliferation in senescent NHDFs and decreased the proportion of senescence-associated-β-galactosidase-positive cells. The treatment suppressed the senescence-related secretory phenotype, and reactive oxygen species (ROS) production was reduced, alleviating H2O2-induced oxidative stress. CDP mitigated ROS formation via the nuclear factor erythroid 2-related factor/heme oxygenase-1 pathway in senescent cells and was involved in the suppression of upstream p-extracellular signal-regulated kinase. These results indicate that CDP is an antioxidant that can alleviate age-related inflammation and may be a useful compound for skin anti-aging.

Ginseng volatile oil prolongs the lifespan and healthspan of Caenorhabditis elegans

Ginseng volatile oil (GVO) is one of the main components of ginseng and has antibacterial and anti-inflammatory properties. In this study, gas chromatography-mass spectrometry (GC-MS) was applied to characterize GVO chemical composition, and 73 volatile components were detected from GVO. Caenorhabditis elegans was used as animal model to further elucidate the antioxidant and anti-aging effects of GVO in vivo. The results suggested that GVO significantly prolonged the lifespan of C. elegans and promoted its health without damaging its reproductive capacity. In addition, GVO increased the antioxidant capacity and survival rate of nematodes after heat shock. Transcriptional sequencing showed that autophagy-related genes atg-4.2, atg-7, lgg-2, and cyd-1 were up-regulated, and superoxide dismutase 1 (sod-1) expression was increased after GVO pretreatment. Considering the role of autophagy and antioxidant in aging, the expression of autophagy substrate P62 protein in BC12921 strain was analyzed and found to decrease by more than 50.00% after treatment with GVO. In addition, the lifespan of SOD-1 mutant nematodes was not significantly different from that of the control group. SOD activity and autophagy were activated, which is a clear expression of hormesis. All these results suggest that GVO prolongs the lifespan and healthspan of C. elegans, and its biological functions may be related to hormesis.

Handelin extends lifespan and healthspan of Caenorhabditis elegans by reducing ROS generation and improving motor function

Aging and aging-related disorders contribute to formidable socioeconomic and healthcare challenges. Several promising small molecules have been identified to target conserved genetic pathways delaying aging to extend lifespan and healthspan in many organisms. We previously found that extract from an edible and medicinal plant Chrysanthemum indicum L. (C. indicum L.) protect skin from UVB-induced photoaging, partially by reducing reactive oxygen species (ROS) generation. Thus, we hypothesized that C. indicum L. and its biological active compound may extend lifespan and health span in vivo. We find that both water and ethanol extracts from C. indicum L. extended lifespan of Caenorhabditis elegans, with better biological effect on life extending for ethanol extracts. As one of the major biological active compounds, handelin extended lifespan of C. elegans too. RNA-seq analysis revealed overall gene expression change of C. elegans post stimulation of handelin focus on several antioxidative proteins. Handelin significantly reduced ROS level and maintained the number and morphology of mitochondria. Moreover, handelin improveed many C. elegans behaviors related to healthspan, including increased pharyngeal pumping and body movement. Muscle fiber imaging analyses revealed that handelin maintains muscle architecture by stabilizing myofilaments. In conclusion, our present study finds a novel compound handelin, from C. indicum L., which bring about biologically beneficial effects by mild stress response, termed as hormetin, that can extend both lifespan and healthspan in vivo on C. elegans. Further study on mammal animal model of natural aging or sarcopenia will verify the potential clinical value of handelin.

Toxin-induced hormesis may restrain aging

Mild environmental stress might have beneficial effects in aging by activating maintenance and repair processes in cells and organs. These beneficial stress effects fit to the concept of hormesis. Prominent stressors acting in a hormetic way are physical exercises, fasting, cold and heat. This review will introduce some toxins, which have been found to induce hormetic responses in animal models of aging research. To highlight the molecular signature of these hormetic effects we will depict signaling pathways affected by low doses of toxins on cellular and organismic level. As prominent examples for signaling pathways involved in both aging processes as well as toxin responses, PI3K/Akt/mTOR- and AMPK-signal transduction will be described in more detail. Due to the striking overlap of signaling pathways mediating toxin induced responses and aging processes we propose considering the ability of low doses of toxins to slow down the rate of aging.

Resveratrol modulates response against acute inflammatory stimuli in aged mouse brain

With upcoming age, the capability to fight against harmful stimuli decreases and the organism becomes more susceptible to infections and diseases. Here, the objective was to demonstrate the effect of dietary resveratrol in aged mice in potentiating brain defenses against LipoPolySaccharide (LPS). Acute LPS injection induced a strong proinflammatory effect in 24-months-old C57/BL6 mice hippocampi, increasing InterLeukin (Il)-6, Tumor Necrosis Factor-alpha (Tnf-α), Il-1β, and C-X-C motif chemokine (Cxcl10) gene expression levels. Resveratrol induced higher expression in those cytokines regarding to LPS. Oxidative Stress (OS) markers showed not significant changes after LPS or resveratrol, although for resveratrol treated groups a slight increment in most of the parameters studies was observed, reaching signification for NF-kB protein levels and iNOS expression. However, Endoplasmic Reticulum (ER) stress markers demonstrated significant changes in resveratrol-treated mice after LPS treatment, specifically in eIF2α, BIP, and ATF4. Moreover, as described, resveratrol is able to inhibit the mechanistic Target of Rapamycin (mTOR) pathway and this effect could be linked to (eIF2α) phosphorylation and the increase in the expression of the previously mentioned proinflammatory genes as a response to LPS treatment in aged animals. In conclusion, resveratrol treatment induced a different cellular response in aged animals when they encountered acute inflammatory stimuli.

LPS alters pattern of sickness behavior but does not affect glutathione level in aged male rats

Behavioral symptoms of sickness, such as fever and motor activity are a coordinated set of changes that develop during infection. The aim of study was to compare the sickness behaviour (SB) in healthy old and young rats treated with pyrogenic dose of endotoxin and to check their glutathione level. Before experimentation male Wistar rats were selected according to standard body mass, motor activity, and white blood cells count. Intraperitoneal injection of lipopolysaccharide (LPS) from E. coli was used to provoke SB. The level of liver glutathione, interleukin (IL) -6, deep body temperature (Tb) and motor activity were measured. Glutathione level in old and young rats did not differ significantly. In both young and old rats LPS administration provoked fever (the mean value of Tb was 38.06 ± 0.01 °C in old rats, and 38.19 ± 0.06 °C in young rats). LPS injection affected night-time activity in both groups (12 h averages were 1.56 ± 0.40 counts in old LPS-treated rats vs 2.74 ± 0.53 counts in not-treated old rats and 3.44 ± 0.60 counts for young LPS-treated vs 4.28 ± 0.57 counts for young not-treated rats). The injection of LPS provoked an elevation of plasma IL-6 concentration (from values below the lowest detectable standard in not-treated groups of animals to 6322.82 ± 537.00 pg/mL in old LPS-treated rats and 7415.62 ± 451.88 pg/mL in young LPS-treated rats). Based on these data, we conclude that good health of aged rats prevents decrease in the glutathione level. Old rats are still able to develop SB in response to pyrogenic dose of LPS, although its components have changed pattern compared to young animals.

Genetics and pharmacology of longevity: the road to therapeutics for healthy aging

Aging can be defined as the progressive decline in tissue and organismal function and the ability to respond to stress that occurs in association with homeostatic failure and the accumulation of molecular damage. Aging is the biggest risk factor for human disease and results in a wide range of aging pathologies. Although we do not completely understand the underlying molecular basis that drives the aging process, we have gained exceptional insights into the plasticity of life span and healthspan from the use of model organisms such as the worm Caenorhabditis elegans and the fruit fly Drosophila melanogaster. Single-gene mutations in key cellular pathways that regulate environmental sensing, and the response to stress, have been identified that prolong life span across evolution from yeast to mammals. These genetic manipulations also correlate with a delay in the onset of tissue and organismal dysfunction. While the molecular genetics of aging will remain a prosperous and attractive area of research in biogerontology, we are moving towards an era defined by the search for therapeutic drugs that promote healthy aging. Translational biogerontology will require incorporation of both therapeutic and pharmacological concepts. The use of model organisms will remain central to the quest for drug discovery, but as we uncover molecular processes regulated by repurposed drugs and polypharmacy, studies of pharmacodynamics and pharmacokinetics, drug-drug interactions, drug toxicity, and therapeutic index will slowly become more prevalent in aging research. As we move from genetics to pharmacology and therapeutics, studies will not only require demonstration of life span extension and an underlying molecular mechanism, but also the translational relevance for human health and disease prevention.

Effect of Tai Chi versus walking on oxidative stress in Mexican older adults

It has recently been reported that the practice of Tai Chi reduces oxidative stress (OxS), but it is not clear whether walking or Tai Chi produces a greater antioxidant effect. The aim of the present study was to evaluate the effect of the practice of Tai Chi and walking on markers for OxS. We carried out a quasi-experimental study with 106 older adults between 60 and 74 years of age who were clinically healthy and divided into the following groups: (i) control group (n = 23), (ii) walking group (n = 43), and (iii) Tai Chi group (n = 31). We measured the levels of lipoperoxides (LPO), antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx), and total antioxidant status (TAS) pre- and post-intervention in all subjects. The data were subjected to a covariant analysis. We found lower levels of LPO in the Tai Chi group compared with the walking group (Tai Chi, 0.261 ± 0.02; walking, 0.331 ± 0.02; control, 0.304 ± 0.023 µmol/L; P = 0.05). Likewise, we observed significantly higher SOD activity and lower OxS-score in the Tai Chi group (P < 0.05). Our findings suggest that the practice of Tai Chi produces a more effective antioxidant effect than walking.

Tai chi diminishes oxidative stress in Mexican older adults

OBJECTIVE

To determine the effect of Tai Chi on oxidative stress in a population of elderly Mexican subjects.

DESIGN

It was carried out a quasi-experimental study with a sample of 55 healthy subjects randomly divided into two age-matched groups: (i) a control group with 23 subjects and (ii) an experimental group with 32 subjects. The experimental group received daily training in Tai Chi for 50 min.

MEASUREMENTS

It was measured before and after 6-month of exercise period: thiobarbituric acid reactive substances (TBARS), total antioxidant status (TAS), superoxide dismutase (SOD), and glutathione peroxidase (GPx).

RESULTS

It was found that the experimental group exhibited a statistically significant decrease in glucose levels, total cholesterol, low-density lipoprotein cholesterol (LDLC), and systolic blood pressure, as well as an increase in SOD and GPx activity and TAS compared with the control group (p < 0.05).

CONCLUSIONS

Our findings suggest that the daily practice of Tai Chi is useful for reducing OxS in healthy older adults.

Rationale and methods of discovering hormetins as drugs for healthy ageing

INTRODUCTION

Mild stress-induced hormesis is becoming increasingly attractive as an ageing interventional strategy and is leading to the discovery of hormesis-inducing compounds called hormetins. Almost 50 years of modern biogerontolgical research has established a clear framework regarding the biological basis of ageing and longevity, and it is now generally accepted that ageing occurs in spite of the presence of complex pathways of maintenance, repair and defense, and there is no 'enemy within.' This viewpoint makes modulation of ageing different from the treatment of one or more age-related diseases. A promising strategy to slow down ageing and prevent or delay the onset of age-related diseases is that of mild stress-induced hormesis by using hormetins.

AREAS COVERED

The article presents the rationale and a strategy for discovering novel hormetins as potential drugs for ageing intervention by elucidating multiple stress responses of normal human cells. Furthermore, it discusses the first steps in identifying prospective hormetin drugs and provides a recent example of successful product development, based on the ideas of hormesis and by following the strategy described here.

EXPERT OPINION

As a biomedical issue, the biological process of ageing underlies several major diseases, and although the optimal treatment of every disease, irrespective of age, is a social and moral necessity, preventing the onset of age-related diseases by intervening in the basic process of ageing is the best approach for achieving healthy ageing and for extending the healthspan.

Heat shocks enhance procollagen type I and III expression in fibroblasts in ex vivo human skin

BACKGROUND

The well-known characteristics of aging skin are the development of fine lines and wrinkles, but changes in skin tone, skin texture, thickness and moisture content are also aspects of aging. Rejuvenation of the skin aims at reversing the signs of aging and can be established in the epidermis as well as in the dermis. Aged dermis, in fact, has a degenerated collagen matrix. To regenerate this matrix, fibroblasts need to be stimulated into synthesizing new collagen.

AIMS

In this study, the effects of heat shocks of different temperatures on human dermal fibroblasts in ex vivo skin on the expression of procollagen 1, procollagen 3, heat shock protein (hsp)27, hsp47, and hsp70 are investigated.

MATERIALS AND METHODS

The heat shocks were applied on ex vivo skin samples by immersing the samples in heated phosphate-buffered saline of 45 °C or 60 °C. Metabolic activity was measured and at similar time points propidium-iodide-calceine staining was performed to establish cell viability. Quantitative polymerase chain reaction (qPCR) was performed after the heat shock to determine gene expression levels relative to the reference temperature. Furthermore, PicroSirius Red and hematoxylin stainings were performed to visualize the collagen network and the cells.

RESULTS

The skin samples were shown to be viable and metabolically active. Histology indicated that the heat shocks did not influence the structure of the collagen network or cell appearance. qPCR results showed that in contrast to the 45 °C heat shock the 60 °C heat shock resulted in significant upregulations of procollagen type I and III, hsp70 and hsp47.

CONCLUSION

A 60 °C, heat shock stimulates the human dermal fibroblasts in ex vivo skin to upregulate their procollagen type I and type III expression.

Effects of dietary restriction on mortality and age-related phenotypes in the short-lived fish Nothobranchius furzeri

The short-lived annual fish Nothobranchius furzeri shows extremely short captive life span and accelerated expression of age markers, making it an interesting model system to investigate the effects of experimental manipulations on longevity and age-related pathologies. Here, we tested the effects of dietary restriction (DR) on mortality and age-related markers in N. furzeri. DR was induced by every other day feeding and the treatment was performed both in an inbred laboratory line and a longer-lived wild-derived line. In the inbred laboratory line, DR reduced age-related risk and prolonged maximum life span. In the wild-derived line, DR induced early mortality, did not reduce general age-related risk and caused a small but significant extension of maximum life span. Analysis of age-dependent mortality revealed that DR reduced demographic rate of aging, but increased baseline mortality in the wild-derived strain. In both inbred- and wild-derived lines, DR prevented the expression of the age markers lipofuscin in the liver and Fluoro-Jade B (neurodegeneration) in the brain. DR also improved performance in a learning test based on conditioning (active avoidance in a shuttle box). Finally, DR induced a paradoxical up-regulation of glial fibrillary acidic protein in the brain.

Caloric restriction-induced life extension of rats and mice: a critique of proposed mechanisms

In 1935, Clive McCay and colleagues reported that decreasing the food intake of rats extends their life. This finding has been confirmed many times using rat and mouse models. The responsible dietary factor in rats is the reduced intake of energy; thus, this phenomenon is frequently referred to as caloric restriction. Although many hypotheses have been proposed during the past 74 years regarding the underlying mechanism, it is still not known. It is proposed that this lack of progress relates to the fact that most of these hypotheses have been based on a single underlying mechanism and that this is too narrow a focus. Rather, a broad framework is needed. Hormesis has been suggested as providing such a framework. Although it is likely that hormesis is involved in the actions of caloric restriction, it also is probably too narrowly focused. Based on currently available data, a provisional broad framework is presented depicting the complex of mechanisms that likely underlie the life-extending and other anti-aging actions of caloric restriction.

Principles and practice of hormetic treatment of aging and age-related diseases

Aging is characterized by stochastic accumulation of molecular damage, progressive failure of maintenance and repair, and consequent onset of age-related diseases. Applying hormesis in aging research and therapy is based on the principle of stimulation of maintenance and repair pathways by repeated exposure to mild stress. Studies on the beneficial biological effects of repeated mild heat shock on human cells in culture, and other studies on the anti-aging and life-prolonging effects of proxidants, hypergravity, irradiation and ethanol on cells and organisms suggest that hormesis as an antiaging and gerontomodulatory approach has a promising future. Its clinical applications include prevention and treatment of diabetes, cataract, osteoporosis, dementia and some cancers.

Hormetic effects of heavy metals in aquatic snails: is a little bit of pollution good?

Hormesis is the term to describe a stimulatory effects associated with a low dose of a potentially toxic substance or stress. We had anecdotal evidence of hormetic effects in some of our previous experiments concerning the influence of heavy metals on aquatic snail growth and recruitment. We therefore repeated a version of an earlier experiment but this time we expanded our low-dose treatments and increased our sample size. We also explored if metals had a hormetic effect on algae periphyton. We raised snails in outdoor mini-ecosystems containing lead, zinc, and cadmium-contaminated soil from an Environmental Protection Agency Superfund site in the Silver Valley of northern Idaho. The snails came from two sites. One population (Physella columbiana) has evolved for 120 years in the presence of heavy metals and one (Lymnaea palustris) has not. We found that P. columbiana exhibited hormesis with snails exposed to small amounts of metals exhibiting more reproduction and growth than snails not exposed to metals. Naturally occurring Oscillatoria algae also exhibited a hormetic effect of heavy metals but L. palustris did not display hormesis. Large doses negatively impacted all three species. Overall the levels of cadmium, lead, and zinc measured in the tissues of the snails were inversely correlated to the number of snails recruited into the tub populations. Only in comparisons of the lowest metal treatment to the control treatment is a positive effect detected. Indirect effects on competing species of snails, periphyton, and also fishermen, may be less favorable.

Electromagnetic field therapy delays cellular senescence and death by enhancement of the heat shock response

Hormesis may result when mild repetitive stress increases cellular defense against diverse injuries. This process may also extend in vitro cellular proliferative life span as well as delay and reverse some of the age-dependent changes in both replicative and non-replicative cells. This study evaluated the potential hormetic effect of non-thermal repetitive electromagnetic field shock (REMFS) and its impact on cellular aging and mortality in primary human T lymphocytes and fibroblast cell lines. Unlike previous reports employing electromagnetic radiation, this study used a long wave length, low energy, and non-thermal REMFS (50MHz/0.5W) for various therapeutic regimens. The primary outcomes examined were age-dependent morphological changes in cells over time, cellular death prevention, and stimulation of the heat shock response. REMFS achieved several biological effects that modified the aging process. REMFS extended the total number of population doublings of mouse fibroblasts and contributed to youthful morphology of cells near their replicative lifespan. REMFS also enhanced cellular defenses of human T cells as reflected in lower cell mortality when compared to non-treated T cells. To determine the mechanism of REMFS-induced effects, analysis of the cellular heat shock response revealed Hsp90 release from the heat shock transcription factor (HSF1). Furthermore, REMFS increased HSF1 phosphorylation, enhanced HSF1-DNA binding, and improved Hsp70 expression relative to non-REMFS-treated cells. These results show that non-thermal REMFS activates an anti-aging hormetic effect as well as reduces cell mortality during lethal stress. Because the REMFS configuration employed in this study can potentially be applied to whole body therapy, prospects for translating these data into clinical interventions for Alzheimer's disease and other degenerative conditions with aging are discussed.

Hormesis in aging

Hormesis in aging is represented by mild stress-induced stimulation of protective mechanisms in cells and organisms resulting in biologically beneficial effects. Single or multiple exposure to low doses of otherwise harmful agents, such as irradiation, food limitation, heat stress, hypergravity, reactive oxygen species and other free radicals have a variety of anti-aging and longevity-extending hormetic effects. Detailed molecular mechanisms that bring about the hormetic effects are being increasingly understood, and comprise a cascade of stress response and other pathways of maintenance and repair. Although the extent of immediate hormetic effects after exposure to a particular stress may only be moderate, the chain of events following initial hormesis leads to biologically amplified effects that are much larger, synergistic and pleiotropic. A consequence of hormetic amplification is an increase in the homeodynamic space of a living system in terms of increased defence capacity and reduced load of damaged macromolecules. Hormetic strengthening of the homeodynamic space provides wider margins for metabolic fluctuation, stress tolerance, adaptation and survival. Hormesis thus counter-balances the progressive shrinkage of the homeodynamic space, which is the ultimate cause of aging, diseases and death. Healthy aging may be achieved by hormesis through mild and periodic, but not severe or chronic, physical and mental challenges, and by the use of nutritional hormesis incorporating mild stress-inducing molecules called hormetins. The established scientific foundations of hormesis are ready to pave the way for new and effective approaches in aging research and intervention.

Glucose restriction extends Caenorhabditis elegans life span by inducing mitochondrial respiration and increasing oxidative stress

Increasing cellular glucose uptake is a fundamental concept in treatment of type 2 diabetes, whereas nutritive calorie restriction increases life expectancy. We show here that increased glucose availability decreases Caenorhabditis elegans life span, while impaired glucose metabolism extends life expectancy by inducing mitochondrial respiration. The histone deacetylase Sir2.1 is found here to be dispensable for this phenotype, whereas disruption of aak-2, a homolog of AMP-dependent kinase (AMPK), abolishes extension of life span due to impaired glycolysis. Reduced glucose availability promotes formation of reactive oxygen species (ROS), induces catalase activity, and increases oxidative stress resistance and survival rates, altogether providing direct evidence for a hitherto hypothetical concept named mitochondrial hormesis or "mitohormesis." Accordingly, treatment of nematodes with different antioxidants and vitamins prevents extension of life span. In summary, these data indicate that glucose restriction promotes mitochondrial metabolism, causing increased ROS formation and cumulating in hormetic extension of life span, questioning current treatments of type 2 diabetes as well as the widespread use of antioxidant supplements.

Prior Chronic in Vivo Glucocorticoid Excess Leads to an Anabolic Phenotype and an Extension of Cellular Life Span of Skin Fibroblasts in Vitro

Intense stress can be detrimental for tissue homeostasis and accelerates aging. On the other hand, repeated mild stresses can have beneficial and even life-prolonging effects. Hypersecretion of glucocorticoids (GCs) represents the major hormonal response to stress. However, besides its life-sustaining role, GC excess can promote a "catabolic" phenotype. Accordingly, we have studied the effect of long-lasting exposure to high GC levels in vivo on several parameters of tissue homeostasis, as well as cellular senescence, in cells removed from the high-GC milieu in vivo and then cultured in vitro. To this end, we have used human skin fibroblasts from (a) Cushing's syndrome patients that are characterized by chronic endogenous GC excess and (b) patients treated with exogenous GC administration. Interestingly, when Cushing's syndrome fibroblasts were cultured in vitro under standard conditions they express an "anabolic" phenotype, i.e., they restore their ability for collagen synthesis, secrete reduced levels of metalloproteases, and have an increased proliferative capacity and contractility. Furthermore, these cells exhibit a significant extension of their proliferative life span, while they respond better to exogenous stress by producing significantly higher levels of heat-shock protein-70 (HSP70). In addition, preliminary results with fibroblasts from patients subjected to chronic exogenous GC administration indicate that they express a similar behavior in vitro, at least with regard to the restoration of collagen expression. These data suggest that prior exposure to elevated GC concentrations is not associated with persisting adverse effects on fibroblasts and may also have a beneficial outcome in some aspects of cell physiology, including longevity in vitro.

Dietary restriction-induced life extension: a broadly based biological phenomenon

It is concluded that dietary restriction will extend the life of all species in the Animalia Kingdom, including the human species. This conclusion is based on the fact that hormesis is a component of the life-extending action and the other anti-aging effects of dietary restriction. It is also concluded that given the currently available database, it is not possible to predict the quantitative effect of dietary restriction on the human life span.

Heat-induced hormesis in longevity of two sibling Drosophila species

Previous work showed that mild-heat stress induces longevity hormesis in a model organism, D. melanogaster. Here we compared the possible heat-induced hormesis in longevity of other species of Drosophila, D. buzzatii and its sibling species D. koepferae, in a single-sex environment. Possible correlations between longevity and heat-stress resistance were also tested by measuring longevity, heat-knockdown resistance and the heat-induced Hsp70 expression for each species in a common environment. D. buzzatii was longer lived than D. koepferae at benign temperature. Knockdown resistance to heat stress was positively correlated to longevity within species. However, the shorter-lived species was more resistant to knockdown by heat stress than the longer-lived species. The heat-induced Hsp70 expression was similar between species. A heat-shock treatment (37 degrees C for 1 h at 4 days of age) extended mean longevity in the longer lived species but not in the shorter lived species. In D. koepferae, the demographic rate of senescence decreased but the baseline mortality rate increased by heat-shock, resulting in no extension of mean longevity. Sympatric populations of closely related species can be differentially sensitive to temperature and exhibit different patterns of 37 degrees C-induced hormesis in demographic senescence and longevity. The results also show that positive correlations between stress resistance and life span within species can shift in sign across closely related species. Finally, this study shows that heat-induced hormesis in longevity can be found across different Drosophila species, as hormetic effects are not limited to the previously studied D. melanogaster.

The unexpected anabolic phenotype and extended longevity of skin fibroblasts after chronic glucocorticoid excess

Intense stress can challenge tissue homeostasis and accelerate the ageing process. However, several lines of evidence indicate that repeated mild stresses can have beneficial and even life-prolonging effects. Hypersecretion of glucocorticoids (GC) represents the major hormonal response to stress. Besides its life-sustaining role, GC excess, usually due to several side-effects that promote a "catabolic" phenotype, can be detrimental for several tissues. Cushing's syndrome patients are characterized by chronic endogenous GC excess and consequently at the time of diagnosis they have an atrophic elderly-like skin. Interestingly, when Cushing's syndrome fibroblasts were removed from the high-GC milieu in vivo and cultured in vitro under standard conditions they express an "anabolic" phenotype, i.e. they restore their ability for collagen synthesis, they secrete reduced levels of metalloproteases (MMP-1 and MMP-2) and have an increased proliferative capacity and contractility. Furthermore, these cells exhibit a significant extension of their proliferative lifespan, while they respond better to exogenous stress by producing significantly higher levels of heat-shock protein-70 (HSP70). These results imply that long-term hypercortisolism in vivo can have beneficial consequences on fibroblast physiology in vitro.

Role of hormesis in life extension by caloric restriction

Caloric restriction (CR) markedly extends the life of rats, mice and several other species, and it also modulates age-associated physiological deterioration and delays the occurrence and/or slows progression of age-associated diseases. The level of CR that retards the aging processes is a low-intensity stressor, which enhances the ability of rats and mice of all ages to cope with intense stressors. CR thus exhibits a hormetic action in these species, and therefore it is hypothesized that hormesis plays a role in the life-extending and anti-aging actions of CR. Both the findings in support of this hypothesis and those opposing it are critically considered. However, it is likely that hormesis is not the only process contributing to CR-induced life extension. It is proposed that two general processes are involved in CR-induced life extension. One is the reduced endogenous generation of damaging agents, such as reactive oxygen species. The second is hormesis, which enhances processes that protect against the action of damaging agents and also promotes processes that repair the damage once it occurs.

Nutritional hormesis

OBJECTIVE

Hormesis, the biological and toxicological concept that small quantities have opposite effects from large quantities, is reviewed with emphasis on its relevance to nutrition.

RESULTS

Hormetic and other dose-response relationships are categorized, depicted, and discussed. Evidence for nutritional hormesis is presented for essential vitamin and mineral nutrients, dietary restriction, alcohol (ethanol), natural dietary and some synthetic pesticides, some herbicides, and acrylamide. Some of the different hormetic mechanisms that have been proposed are reviewed.

CONCLUSIONS

The credence and relevance of hormesis to nutrition are considered to be established. The roles of hormesis in nutritional research and in formulating nutritional guidelines are discussed.

SPONSORSHIP

The New York City Department of Health and Mental Hygiene.

Caloric restriction and aging: controversial issues

It has long been held that food restriction extends the life span of rodents and other species by decreasing caloric intake and slowing the rate of aging. Recent findings challenge these concepts. This review assesses these controversial issues. The conclusion is that caloric restriction underlies the life extension of rats, but not of Drosophila. Mortality characteristics show that food restriction slows the rate of aging of rats and, in some studies, of mice. However, in other mouse studies and in Drosophila, mortality characteristics have been interpreted as indicating that it delays the start but does not slow the rate of aging; the author believes that this interpretation is faulty. These differences in mortality responses to food restriction provide a potentially powerful tool for uncovering basic mechanisms underlying its life-prolonging action. A hypothesis is presented for use in the search for these mechanisms.

Calorie restriction mimetics: an emerging research field

When considering all possible aging interventions evaluated to date, it is clear that calorie restriction (CR) remains the most robust. Studies in numerous species have demonstrated that reduction of calories 30-50% below ad libitum levels of a nutritious diet can increase lifespan, reduce the incidence and delay the onset of age-related diseases, improve stress resistance, and decelerate functional decline. A current major focus of this research area is whether this nutritional intervention is relevant to human aging. Evidence emerging from studies in rhesus monkeys suggests that their response to CR parallels that observed in rodents. To assess CR effects in humans, clinical trials have been initiated. However, even if results from these studies could eventually substantiate CR as an effective pro-longevity strategy for humans, the utility of this intervention would be hampered because of the degree and length of restriction required. As an alternative strategy, new research has focused on the development of 'CR mimetics'. The objective of this strategy is to identify compounds that mimic CR effects by targeting metabolic and stress response pathways affected by CR, but without actually restricting caloric intake. For example, drugs that inhibit glycolysis (2-deoxyglucose), enhance insulin action (metformin), or affect stress signaling pathways (resveratrol), are being assessed as CR mimetics (CRM). Promising results have emerged from initial studies regarding physiological responses which resemble those observed in CR (e.g. reduced body temperature and plasma insulin) as well as protection against neurotoxicity (e.g. enhanced dopamine action and up-regulated neurotrophic factors). Ultimately, lifespan analyses in addition to expanded toxicity studies must be accomplished to fully assess the potential of any CRM. Nonetheless, this strategy clearly offers a very promising and expanding research endeavor.

Understanding and modulating ageing

Ageing is characterized by a progressive accumulation of molecular damage in nucleic acids, proteins and lipids. The inefficiency and failure of maintenance, repair and turnover pathways is the main cause of age-related accumulation of damage. Research in molecular gerontology is aimed at understanding the genetic and epigenetic regulation of survival and maintenance mechanisms at the levels of transcription, post-transcriptional processing, post-translational modifications, and interactions among various gene products. Concurrently, several approaches are being tried and tested to modulate ageing in a wide variety of organisms. The ultimate aim of such studies is to improve the quality of human life in old age and prolong the health-span. Various gerontomodulatory approaches include gene therapy, hormonal supplementation, nutritional modulation and intervention by free radical scavengers and other molecules. A recent approach is that of applying hormesis in ageing research and therapy, which is based on the principle of stimulation of maintenance and repair pathways by repeated exposure to mild stress. A combination of molecular, physiological and psychological modulatory approaches can realize "healthy ageing" as an achievable goal in the not-so-distant future.

Mild heat stress stimulates 20S proteasome and its 11S activator in human fibroblasts undergoing aging in vitro

Repeated mild heat shock (RMHS) has been shown to have several beneficial hormetic effects on human skin fibroblast undergoing aging in vitro. Because an age-related decline in proteasome activity is 1 of the reasons for the accumulation of abnormal proteins during aging, we have investigated the effects of RMHS on the 20S proteasome, which is the major proteolytic system involved in the removal of abnormal and oxidatively damaged proteins. Serially passaged human skin fibroblasts exposed to RMHS at 41 degrees C for 60 minutes twice a week had increased 3 proteasomal activities by 40% to 95% in early- and midpassage cultures. RMHS-treated cells also contained a 2-fold higher amount of the proteasome activator 11S, and the extent of the bound activator was double in early- and midpassage cells only. Furthermore, there was no difference in the content of the 19S proteasome regulator in the stressed and the unstressed cells. Therefore, RMHS-induced proteasome stimulation in early- and midpassage fibroblasts appears to be due to an induction and enhanced binding of 11S proteasome activators. In contrast to this, the proteasomal system in late-passage senescent cells appears to be less responsive to the stimulatory effects of mild heat shock.

Exercise and hormesis: oxidative stress-related adaptation for successful aging

The hormesis theory purports that biological systems respond with a bell-shaped curve to exposure to chemicals, toxins, and radiation. Here we extend the hormesis theory to include reactive oxygen species (ROS). We further suggest that the beneficial effects of regular exercise are partly based on the ROS generating capability of exercise, which is in the stimulation range of ROS production. Therefore, we suggest that exercise-induced ROS production plays a role in the induction of antioxidants, DNA repair and protein degrading enzymes, resulting in decreases in the incidence of oxidative stress-related diseases and retardation of the aging process.

Aging intervention, prevention, and therapy through hormesis

The phenomenon of hormesis is represented by mild stress-induced stimulation of maintenance and repair pathways resulting in beneficial effects for the cells and organisms. Anti-aging and life-prolonging effects of a wide variety of the so-called stressors, such as pro-oxidants, aldehydes, calorie restriction, irradiation, heat shock, and hypergravity, have been reported. Molecular mechanisms of hormesis due to different stresses are yet to be elucidated, but there are indications that relatively small individual hormetic effects become biologically amplified resulting in the collective significant improvement of cellular and organismic functions and survival. Accepting that some important issues with respect to establishing the optimal hormetic conditions still need to be resolved by future research, hormesis appears to be a promising and effective approach for modulating aging, for preventing or delaying the onset of age-related diseases, and for improving quality of life in old age.

Development of Calorie Restriction Mimetics as a Prolongevity Strategy

By applying calorie restriction (CR) at 30-50% below ad libitum levels, studies in numerous species have reported increased life span, reduced incidence and delayed onset of age-related diseases, improved stress resistance, and decelerated functional decline. Whether this nutritional intervention is relevant to human aging remains to be determined; however, evidence emerging from CR studies in nonhuman primates suggests that response to CR in primates parallels that observed in rodents. To evaluate CR effects in humans, clinical trials have been initiated. Even if evidence could substantiate CR as an effective antiaging strategy for humans, application of this intervention would be problematic due to the degree and length of restriction required. To meet this challenge for potential application of CR, new research to create "caloric restriction mimetics" has emerged. This strategy focuses on identifying compounds that mimic CR effects by targeting metabolic and stress response pathways affected by CR, but without actually restricting caloric intake. Microarray studies show that gene expression profiles of key enzymes in glucose (energy) handling pathways are modified by CR. Drugs that inhibit glycolysis (2-deoxyglucose) or enhance insulin action (metformin) are being assessed as CR mimetics. Promising results have emerged from initial studies regarding physiological responses indicative of CR (reduced body temperature and plasma insulin) as well as protection against neurotoxicity, enhanced dopamine action, and upregulated brain-derived neurotrophic factor. Further life span analyses in addition to expanded toxicity studies must be completed to assess the potential of any CR mimetic, but this strategy now appears to offer a very promising and expanding research field.

Mechanisms of Hormesis through Mild Heat Stress on Human Cells

In a series of experimental studies, it was shown that repetitive mild heat stress has antiaging hormetic effects on growth and various other cellular and biochemical characteristics of human skin fibroblasts undergoing aging in vitro. We have reported the hormetic effects of repeated challenge at the levels of maintenance of stress protein profile; reduction in the accumulation of oxidatively and glycoxidatively damaged proteins; stimulation of the proteasomal activities for the degradation of abnormal proteins; improved cellular resistance to ethanol, hydrogen peroxide, and ultraviolet-B rays; and enhanced levels of various antioxidant enzymes. Detailed analysis of the signal transduction pathways to determine alterations in the phosphorylation and dephosphorylation states of ERK, JNK, and p38 MAP kinases as a measure of cellular responsiveness to mild and severe heat stress is in progress. Furthermore, comparative studies using nonaging immortal cell lines, such as SV40-transformed human fibroblasts, spontaneous osteosarcoma cells, and telomerase-immortalized human bone marrow cells are also in progress for establishing differences in normal and cancerous cells for their responsiveness to mild and severe stresses.

Hormetic Mechanisms of Anti-Aging and Rejuvenating Effects of Repeated Mild Heat Stress on Human Fibroblasts in Vitro

The phenomenon of hormesis is represented by mild stress-induced stimulation of maintenance and repair pathways, resulting in beneficial effects for cells and organisms. We have reported that repeated mild heat stress (RMHS) has anti-aging hormetic effects on growth and various cellular and biochemical characteristics of human skin fibroblasts undergoing aging in vitro. These effects of RMHS include the maintenance of the stress protein profile, reduction in the accumulation of oxidatively and glycoxidatively damaged proteins, stimulation of the activities of the proteasome and its 11S activator, improvement in cellular resistance to ethanol, hydrogen peroxide, and ultraviolet rays, and increased antioxidative activity of the cells. We have also reported that RMHS prolongs the lifespan of Drosophila. Others have reported anti-aging and life prolonging effects of a wide variety of so-called stressors, such as pro-oxidants, aldehydes, calorie restriction, irradiation, heat shock, and hypergravity. Although molecular mechanisms of hormesis are yet to be elucidated, there are indications that relatively small hormetic effects become biologically amplified, resulting in significant improvement of cellular and organic functions and survival. Hormesis, therefore, can be an effective approach for modulating aging, for preventing or delaying the onset of age-related diseases, and for improving the quality of life in old age.

A pilot study of falls, fear of falling, activity levels and fall prevention actions in older people with polio

BACKGROUND AND AIMS

Polio survivors are ageing, and reporting new complications including falls. The aims of this study were: 1) to determine the frequency of falls, circumstances surrounding them, and the consequences of falls in older people who have polio; and 2) to investigate the range of fall prevention interventions undertaken to reduce the individual's risk of falling.

METHODS

A survey was conducted of members of the Eastern Polio Support Group of Victoria. Twenty-eight respondents (70%; 7 male, 21 female) had a mean age of 66 years and an average duration of 57 years since the onset of polio. The survey addressed demographic data, mobility, frequency and description of falls over the last 12 months, their consequences, and community services utilized. The Modified Falls Efficacy Scale (MFES) and Human Activity Profile (HAP) were also completed. Comparative data on the MFES and HAP were obtained from age- and gender-matched healthy community-dwelling older people.

RESULTS

Fourteen respondents (50%) reported one or more falls over the past 12 months, half reporting multiple falls. Two-thirds of falls occurred while walking. Of those who fell, 67% did not require medical attention. The highest percentage of injuries were bruises or grazes (44%), with one fracture reported. Sixty-one percent reported being fearful of falling, with an average MFES of 7.4 (+/-2.0), compared with the average of 9.7 (+/-0.5) for the age- and gender-matched controls (p<0.05). Only 5 of the respondents reported changing their level of activity as the result of a fall. A significant difference was identified on the Adjusted Activity Score (AAS) of the HAP between polio non-fallers (mean 56.3+/-19.1), polio fallers (mean 40.1+/-15.6) and age- and gender-matched controls (mean 73.5+/-10.3) (F2,46=25.5, p=0.000). The median number of fall prevention activities undertaken in the previous 12 months was one, 11 of the 28 respondents undertaking two or more. The most common interventions implemented were vision checks (42%) and review of medications by a doctor (25%).

CONCLUSIONS

A high rate of falling, fear of falling and low activity levels exist in older people with polio. There is a need for further research and clinical programs to reduce falls and injuries in this group.

Molecular mechanisms of anti-aging hormetic effects of mild heat stress on human cells

In a series of experimental studies we have shown that repetitive mild heat stress has anti-aging hormetic effects on growth and various other cellular and biochemical characteristics of human skin fibroblasts undergoing aging in vitro. We have reported the hormetic effects of repeated challenge at the levels of maintenance of stress protein profile; reduction in the accumulation of oxidatively and glycoxidatively damaged proteins; stimulation of the proteasomal activities for the degradation of abnormal proteins; improved cellular resistance to ethanol, hydrogenperoxide, and ultraviolet-B rays; and enhanced levels of various antioxidant enzymes. We are now undertaking a detailed analysis of the signal transduction pathways to determine alterations in the phosphorylation and dephosphorylation states of extracellular signal-related kinase, c-Jun terminal kinase and p38 MAP-kinases as a measure of cellular responsiveness to mild and severe heat stress. Furthermore, we are also undertaking comparative studies using non-aging immortal cell lines, such as SV40-transformed human fibroblasts, spontaneous osteosarcoma cells, and telomerase-immortalized human bone marrow cells for establishing differences in normal and cancerous cells with respect to their responsiveness to mild and severe stresses.

Early programming of adult longevity: demographic and experimental studies

It is supposed that longevity might be programmed by early life exposures. We had carried out demographic and experimental researches for the examination of the possibility of longevity programming. In demographic study, the recorded deaths in Kiev (Ukraine) between 1990 and 2000 (51,503 men and 50,131 women) were used. Age at death was strongly associated with month of birth. Subjects born in the middle of year (April-July) had the lowest longevity. Increasing longevity was observed with each successive birth-month in the second half of the year, with a peak longevity for births in December. To research of the mechanisms responsible for longevity programming, study of adult D. melanogaster DNA repair capacity after irradiation at the egg stage was carried out, using marker such as DNA strand breaks. Insects irradiated in low doses (0.50 and 0.75 Gy) had extended life span and increased stability to S1 nuclease treatment. The probable explanation of observed postponed effects might be the long-term modulation of certain (possibly repair) genes activity. We hypothesize that life-extending effects of different anti-aging treatments might be a consequence of their unspecific (hormetic) action, rather then specific (geroprotector) action on the some aging-related processes, and induction an "transcriptional reprogramming" may be a key mechanism of the longevity programming and artificial life extension.

Chronic in vivo exposure to glucocorticoids prolongs cellular lifespan: the case of Cushing's syndrome-patients' fibroblasts

Glucocorticoid (GC) hypersecretion constitutes the major hormonal response to stress. In an effort to investigate the impact of a long-lasting exposure to high GC levels in vivo on cellular longevity, we have studied the lifespan of skin fibroblasts from patients suffering from Cushing's syndrome, who are characterised by chronic endogenous GC excess. Interestingly, we have observed that these cells exhibit a significant increase in their proliferative lifespan when cultured in vitro, under standard conditions, compared to fibroblasts from normal donors. In parallel, these cells secrete lower levels of transforming growth factor-beta, known to be implicated in stress-induced premature senescence. Furthermore, they also exhibit an intense stress reaction (near 2-fold, compared to normal cells) in terms of heat-shock protein-70 induction. These results support the hypothesis that stress response may have beneficial consequences in cellular longevity, as well as in tissue homeostasis.

Mild stress-induced stimulation of heat-shock protein synthesis and improved functional ability of human fibroblasts undergoing aging in vitro

Repeated mild heat-shock (RMHS) treatment has anti-aging hormetic effects on human fibroblasts undergoing aging in vitro. Since heat and various other stresses induce the transcription and translation of heat-shock proteins (Hsp), it was investigated if RMHS treatment affected the basal levels of four major stress proteins Hsp27, 70, 90 and Hsc70. The basal levels of Hsp27, Hsc70, and Hsp70 increased significantly in late passage senescent cells, which is indicative of an adaptive response to cumulative intracellular stress during aging. RMHS increased the levels of these Hsp even in early passage young cells and were maintained high throughout their replicative lifespan. In comparison, the amount of Hsp90 decreased both with aging and RMHS treatment in vitro. However, whereas the difference in the levels of Hsp70 and Hsp90 was statistically significant, the levels of Hsp27 and Hsc70 were statistically similar in normal and RMHS-treated serially passaged cells. These alterations were accompanied by an improved functional and survival ability of the cells in terms of increased proteasomal activities, increased ability to decompose H(2)O(2), reduced accumulation of lipofuscin and enhanced resistance to ethanol, H(2)O(2) and UV-A radiation.