Antioxidant status and stress resistance in long- and short-lived lines of Drosophila melanogaster

"A comparison of thermal stress response between Drosophila melanogaster and Drosophila pseudoobscura reveals differences between species and sexes"

The environment is changing faster than anticipated due to climate change, making species more vulnerable to its impacts. The level of vulnerability of species is influenced by factors such as the degree and duration of exposure, as well as the physiological sensitivity of organisms to changes in their environments, which has been shown to vary among species, populations, and individuals. Here, we compared physiological changes in fecundity, critical thermalmaximum (CTmax), respiratory quotient (RQ), and DNA damage in ovaries in response to temperature stress in two species of fruit fly, Drosophila melanogaster (25 vs. 29.5 °C) and Drosophila pseudoobscura (20.5 vs. 25 °C). The fecundity of D. melanogaster was more affected by high temperatures when exposed during egg through adult development, while D. pseudoobscura was most significantly affected when exposed to high temperatures exclusively during egg through pupal development. Additionally, D. melanogaster males exhibited a decrease of CTmax under high temperatures, while females showed an increase of CTmax when exposed to high temperatures during egg through adult development. while D. pseudoobscura females and males showed an increased CTmax only when reared at high temperatures during egg through pupae development. Moreover, both species showed an acceleration in oogenesis and an increase in apoptosis due to heat stress. These changes can likely be attributed to key differences in the geographic range, thermal range, development time, and other different factors between these two systems. Through this comparison of variation in physiology and developmental response to thermal stress, we found important differences between species and sexes that suggest future work needs to account for these factors separately in understanding the effects of constant increased temperatures.

Phenotypic molecular features of long-lived animal species

One of the challenges facing science/biology today is uncovering the molecular bases that support and determine animal and human longevity. Nature, in offering a diversity of animal species that differ in longevity by more than 5 orders of magnitude, is the best 'experimental laboratory' to achieve this aim. Mammals, in particular, can differ by more than 200-fold in longevity. For this reason, most of the available evidence on this topic derives from comparative physiology studies. But why can human beings, for instance, reach 120 years whereas rats only last at best 4 years? How does nature change the longevity of species? Longevity is a species-specific feature resulting from an evolutionary process. Long-lived animal species, including humans, show adaptations at all levels of biological organization, from metabolites to genome, supported by signaling and regulatory networks. The structural and functional features that define a long-lived species may suggest that longevity is a programmed biological property.

Potentiation of paraquat toxicity by inhibition of the antioxidant defenses and protective effect of the natural antioxidant, 4-hydroxyisopthalic acid in Drosophila melanogaster

Exposure to pesticides such as paraquat (PQ) is known to induce oxidative stress-mediated damage, which is implicated in neurodegenerative diseases. The antioxidant enzymes are part of the endogenous defense mechanisms capable of protecting against oxidative damage, and down-regulation of these enzymes results in elevated oxidative stress. In this study, we have evaluated the protective action of 4-hydroxyisophthalic acid (DHA-I), a novel bioactive molecule from the roots of D. hamiltonii, against PQ toxicity and demonstrated the protective role of endogenous antioxidant enzymes under the condition of oxidative stress using Drosophila model. The activity of the major antioxidant enzymes, superoxide dismutase 1 (SOD1) and catalase, was suppressed either by RNAi-mediated post transcriptional gene silencing or chemical inhibition. With the decreased in vivo activity of either SOD1 or catalase, Drosophila exhibited hypersensitivity to PQ toxicity, demonstrating the essential role of antioxidant enzymes in the mechanism of defense against PQ-induced oxidative stress. Dietary supplementation of DHA-I increased the resistance of Drosophila depleted in either SOD1 or catalase to PQ toxicity. Enhanced survival of flies against PQ toxicity indicates the protective role of DHA-I against oxidative stress-mediated damage under the condition of compromised antioxidant defenses.

Drosophila as an emerging model organism for studies of food-derived antioxidants

Dietary supplementation with antioxidants provides health benefits by preventing diseases caused by oxidative stress and damage. Consequently, there has been growing interest in the study of antioxidative foods and their active ingredients. Oxidative stress and antioxidative responses are mechanistically conserved from Drosophila to mammals. Therefore, as a well-established model organism with a short life cycle and advantages of genetic manipulation, the fruit fly has been increasingly employed to assess functions of antioxidants in vivo. In this review, the antioxidative defense mechanisms, methods used and assays developed in Drosophila to evaluate antioxidant supplementation, are highlighted. The main manifestations of antioxidation include reduction of reactive species, up-regulation of endogenous antioxidants, inhibition on oxidative damage to biomacromolecules, enhanced resistance against oxidative stress and extension of lifespan, which are related to the activations of nuclear factor erythroid 2-related factor 2-antioxidant response element pathway and other adaptive responses. Moreover, the key considerations and future perspectives for the application of Drosophila models in the studies of food-derived antioxidants are discussed.

Towards understanding the evolutionary dynamics of mtDNA

Historically, mtDNA was considered a selectively neutral marker that was useful for estimating the population genetic history of the maternal lineage. Over time there has been an increasing appreciation of mtDNA and mitochondria in maintaining cellular and organismal health. Beyond energy production, mtDNA and mitochondria have critical cellular roles in signalling. Here we briefly review the structure of mtDNA and the role of the mitochondrion in energy production. We then discuss the predictions that can be obtained from quaternary structure modelling and focus on mitochondrial complex I. Complex I is the primary entry point for electrons into the electron transport system is the largest respiratory complex of the chain and produces about 40% of the proton flux used to synthesize ATP. A focus of the review is Drosophila's utility as a model organism to study the selective advantage of specific mutations. However, we note that the incorporation of insights from a multitude of systems is necessary to fully understand the range of roles that mtDNA has in organismal fitness. We speculate that dietary changes can illicit stress responses that influence the selective advantage of specific mtDNA mutations and cause spatial and temporal fluctuations in the frequencies of mutations. We conclude that developing our understanding of the roles mtDNA has in determining organismal fitness will enable increased evolutionary insight and propose we can no longer assume it is evolving as a strictly neutral marker without testing this hypothesis.

Cytoplasmic and Mitochondrial NADPH-Coupled Redox Systems in the Regulation of Aging

The reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) protects against redox stress by providing reducing equivalents to antioxidants such as glutathione and thioredoxin. NADPH levels decline with aging in several tissues, but whether this is a major driving force for the aging process has not been well established. Global or neural overexpression of several cytoplasmic enzymes that synthesize NADPH have been shown to extend lifespan in model organisms such as Drosophila suggesting a positive relationship between cytoplasmic NADPH levels and longevity. Mitochondrial NADPH plays an important role in the protection against redox stress and cell death and mitochondrial NADPH-utilizing thioredoxin reductase 2 levels correlate with species longevity in cells from rodents and primates. Mitochondrial NADPH shuttles allow for some NADPH flux between the cytoplasm and mitochondria. Since a decline of nicotinamide adenine dinucleotide (NAD⁺) is linked with aging and because NADP⁺ is exclusively synthesized from NAD⁺ by cytoplasmic and mitochondrial NAD⁺ kinases, a decline in the cytoplasmic or mitochondrial NADPH pool may also contribute to the aging process. Therefore pro-longevity therapies should aim to maintain the levels of both NAD⁺ and NADPH in aging tissues.

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

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

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

BACKGROUND

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

RESULTS

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

CONCLUSIONS

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

The naked mole-rat response to oxidative stress: just deal with it

SIGNIFICANCE

The oxidative stress theory of aging has been the most widely accepted theory of aging providing insights into why we age and die for over 50 years, despite mounting evidence from a multitude of species indicating that there is no direct relationship between reactive oxygen species (ROS) and longevity. Here we explore how different species, including the longest lived rodent, the naked mole-rat, have defied the most predominant aging theory.

RECENT ADVANCES

In the case of extremely long-lived naked mole-rat, levels of ROS production are found to be similar to mice, antioxidant defenses unexceptional, and even under constitutive conditions, naked mole-rats combine a pro-oxidant intracellular milieu with high, steady state levels of oxidative damage. Clearly, naked mole-rats can tolerate this level of oxidative stress and must have mechanisms in place to prevent its translation into potentially lethal diseases.

CRITICAL ISSUES

In addition to the naked mole-rat, other species from across the phylogenetic spectrum and even certain mouse strains do not support this theory. Moreover, overexpressing or knocking down antioxidant levels alters levels of oxidative damage and even cancer incidence, but does not modulate lifespan.

FUTURE DIRECTIONS

Perhaps, it is not oxidative stress that modulates healthspan and longevity, but other cytoprotective mechanisms that allow animals to deal with high levels of oxidative damage and stress, and nevertheless live long, relatively healthy lifespans. Studying these mechanisms in uniquely long-lived species, like the naked mole-rat, may help us tease out the key contributors to aging and longevity.

Age-induced perturbation in cell membrane phospholipid fatty acid profile of longevity-selected Drosophila melanogaster and corresponding control lines

Various compositions of fatty acids can produce cell membranes with disparate fluidity and propensity for oxidation. The latter characteristic, which can be evaluated via the peroxidation index (PI), has a fundamental role in the development of the "membrane-pacemaker theory" of aging. This study tried to evaluate differences between the membrane phospholipid fatty acid (PLFA) profile of longevity-selected (L) and corresponding control (C) lines of Drosophila melanogaster with age (3, 9, 14 and 19 days) and its consequences on phase transition temperature as a function of membrane fluidity. Despite an equal proportion of polyunsaturated fatty acids, PI and double bond index over all ages in both experimental groups, monounsaturated fatty acids showed significant variation with advancement of age in both L and C lines. A significant age-associated elevation of the unsaturation vs. saturation index in parallel with a gradual reduction of the mean melting point was observed in longevous flies. PLFA composition of the L vs. C lines revealed a dissimilarity in 3-day old samples, which was based on the positive loading of C(14:0) and C(18:3) as well as negative loading of C(18:0). The findings of this study are not in agreement with the principle of the "membrane pacemaker theory" linking PI and longevity. However, the physiochemical properties of PLFAs in longevity lines may retard the cells' senescence by maintaining optimal membrane functionality over time. Identical susceptibility to peroxidation of both types of lines underlines the involvement of other mechanisms in protecting the bio-membrane against oxidation, such as the reduced production of mitochondrial reactive oxygen species or improvement of the antioxidant defense system in longer-lived phenotypes. Concurrent assessments of these mechanisms in relation to cell membrane PLFA composition may clarify the cellular basis of lifespan in this species.

Modulation of methuselah expression targeted to Drosophila insulin-producing cells extends life and enhances oxidative stress resistance

Ubiquitously reduced signaling via Methuselah (MTH), a G-protein-coupled receptor (GPCR) required for neurosecretion, has previously been reported to extend life and enhance stress resistance in flies. Whether these effects are due to reduced MTH signalling in specific tissues remains unknown. We determined that reduced expression of mth targeted to the insulin-producing cells (IPCs) of the fly brain was sufficient to extend life and enhance oxidative stress resistance. Paradoxically, we discovered that overexpression of mth targeted to the same cells has similar phenotypic effects to reduced expression due to MTH's interaction with β-arrestin, which uncouples GPCRs from their G-proteins. We confirmed the functional relationship between MTH and β-arrestin by finding that IPC-targeted overexpression of β-arrestin alone mimics the longevity phenotype of reduced MTH signaling. As reduced MTH signaling also inhibits insulin secretion from the IPCs, the most parsimonious mechanistic explanation of its longevity and stress-resistance enhancement might be through reduced insulin/IGF signaling (IIS). However, examination of phenotypic features of long-lived IPC-mth modulated flies as well as several downstream IIS targets implicates enhanced activity of the JNK stress-resistance pathway more directly than insulin signaling in the longevity and stress-resistance phenotypes.

Healthy aging - insights from Drosophila

Human life expectancy has nearly doubled in the past century due, in part, to social and economic development, and a wide range of new medical technologies and treatments. As the number of elderly increase it becomes of vital importance to understand what factors contribute to healthy aging. Human longevity is a complex process that is affected by both environmental and genetic factors and interactions between them. Unfortunately, it is currently difficult to identify the role of genetic components in human longevity. In contrast, model organisms such as C. elegans, Drosophila, and rodents have facilitated the search for specific genes that affect lifespan. Experimental evidence obtained from studies in model organisms suggests that mutations in a single gene may increase longevity and delay the onset of age-related symptoms including motor impairments, sexual and reproductive and immune dysfunction, cardiovascular disease, and cognitive decline. Furthermore, the high degree of conservation between diverse species in the genes and pathways that regulate longevity suggests that work in model organisms can both expand our theoretical knowledge of aging and perhaps provide new therapeutic targets for the treatment of age-related disorders.

No evidence of elevated germline mutation accumulation under oxidative stress in Caenorhabditis elegans

Variation in rates of molecular evolution has been attributed to numerous, interrelated causes, including metabolic rate, body size, and generation time. Speculation concerning the influence of metabolic rate on rates of evolution often invokes the putative mutagenic effects of oxidative stress. To isolate the effects of oxidative stress on the germline from the effects of metabolic rate, generation time, and other factors, we allowed mutations to accumulate under relaxed selection for 125 generations in two strains of the nematode Caenorhabditis elegans, the canonical wild-type strain (N2) and a mutant strain with elevated steady-state oxidative stress (mev-1). Contrary to our expectation, the mutational decline in fitness did not differ between N2 and mev-1. This result suggests that the mutagenic effects of oxidative stress in C. elegans are minor relative to the effects of other types of mutations, such as errors during DNA replication. However, mev-1 MA lines did go extinct more frequently than wild-type lines; some possible explanations for the difference in extinction rate are discussed.

Molecular and structural antioxidant defenses against oxidative stress in animals

In this review, it is our aim 1) to describe the high diversity in molecular and structural antioxidant defenses against oxidative stress in animals, 2) to extend the traditional concept of antioxidant to other structural and functional factors affecting the "whole" organism, 3) to incorporate, when supportable by evidence, mechanisms into models of life-history trade-offs and maternal/epigenetic inheritance, 4) to highlight the importance of studying the biochemical integration of redox systems, and 5) to discuss the link between maximum life span and antioxidant defenses. The traditional concept of antioxidant defenses emphasizes the importance of the chemical nature of molecules with antioxidant properties. Research in the past 20 years shows that animals have also evolved a high diversity in structural defenses that should be incorporated in research on antioxidant responses to reactive species. Although there is a high diversity in antioxidant defenses, many of them are evolutionary conserved across animal taxa. In particular, enzymatic defenses and heat shock response mediated by proteins show a low degree of variation. Importantly, activation of an antioxidant response may be also energetically and nutrient demanding. So knowledge of antioxidant mechanisms could allow us to identify and to quantify any underlying costs, which can help explain life-history trade-offs. Moreover, the study of inheritance mechanisms of antioxidant mechanisms has clear potential to evaluate the contribution of epigenetic mechanisms to stress response phenotype variation.

Responses of Drosophila melanogaster to atypical oxygen atmospheres

We examined physiological phenotypes of Drosophila melanogaster in hypoxic to hyperoxic atmospheres. We performed measurements on life span or behavioural function in 5, 21, 40, 60, and 80% O(2), and combined this with literature data for 2% and 100% O(2). O(2) incubation resulted in a concentration-dependent reduction of life span in both hypoxia and hyperoxia, though different measures of life span were affected differently. We also examined how behavioural and metabolic functions were affected by exposure to hyperoxia (up to 60% O(2)). Climbing behaviour was measured as a fast (4 s) and slow (55 s) response in a negative geotaxis assay. In normoxia, both measures of climbing response declined exponentially until disappearing completely. Interestingly, survivorship was very high until the loss of climbing ability, after which it dropped rapidly. This pattern appeared accelerated in 40% O(2). However, while flies in 60% O(2) also apparently lost their fast climbing ability immediately prior to the drop in survivorship, they maintained considerable climbing ability over the longer trial. Metabolism, measured by CO(2) release, did not change with age in normoxic flies, but was significantly lower in flies exposed to hyperoxia, particularly as the flies aged. There was, however, a slight increase in water loss rate with age in normoxia, while in hyperoxia, water loss was reduced. Uniquely, the water loss rates of flies in 60% O(2) doubled immediately prior to the end of their life span. Because ageing results in generally irreversible functional declines, we examined if functional declines in hyperoxia (60% O(2)) were also irreversible, or whether some functioning could recover after a return to normoxia. After 7 days of recovery, water loss rates decreased, CO(2) exhalation slightly increased, and climbing ability was partially recovered. Therefore, the effect of O(2) on D. melanogaster function is non-linear, may be reversible, and may include unique phenotypes that arise at some O(2) concentrations, and not others.

Changed gene expression for candidate ageing genes in long-lived Bicyclus anynana butterflies

Candidate genes for the regulation of lifespan have emerged from studies that use mutants and genetically manipulated model organisms. However, it is rarely addressed whether these genes contribute to lifespan variation in populations of these species that capture natural standing genetic variation. Here, we explore expression variation in three candidate ageing genes, Indy, sod2, and catalase, in Bicyclus anynana, a butterfly with well understood ecology. We used lines established from natural populations and artificially selected for increased adult starvation resistance. They show a considerable increase in adult lifespan under both starvation and optimal food conditions. We measured adult butterflies of various ages, under a range of optimal and starvation diets, from two selected populations and one unselected control population. In all lines, Indy and catalase are up-regulated in response to starvation while this is not evident for sod2. Under starvation, Indy and catalase are up-regulated in, while this is not evident for sod2. Under optimal food conditions, Indy is down-regulated at a later age, with Indy expression showing relatively high inter-individual variation. We find differences between the selected lines and the unselected line. Under starvation conditions, expression is higher for catalase in one, and for sod2 in both selected lines. Importantly, sod2 expression is also higher in the selected populations under optimal food conditions. We conclude that sod2, but not Indy, is involved in the response to artificial selection for increased starvation resistance. The role of catalase is less clear because of the differences between the two selected lines. Moreover, sod2 appears to be a candidate gene that underpins the genetic correlation between starvation resistance and longevity. Our study indicates that some, but not all, genes identified through mutant screens in other organisms may underpin standing genetic variation for ageing-related traits in stocks of Bicyclus butterflies established from natural populations. Clearly, this needs to be investigated in other organisms as well, especially in the organisms to which mutants screens were applied. This information will narrow down the list of genes that underpin variation in lifespan and ageing in extant populations of organisms, and which may serve as candidate genes in humans.

Functional linkages for the pace of life, life-history, and environment in birds

For vertebrates, body mass underlies much of the variation in metabolism, but among animals of the same body mass, metabolism varies six-fold. Understanding how natural selection can influence variation in metabolism remains a central focus of Physiological Ecologists. Life-history theory postulates that many physiological traits, such as metabolism, may be understood in terms of key maturational and reproductive characteristics over an organism's life-span. Although it is widely acknowledged that physiological processes serve as a foundation for life-history trade-offs, the physiological mechanisms that underlie the diversification of life-histories remain elusive. Data show that tropical birds have a reduced basal metabolism (BMR), field metabolic rate, and peak metabolic rate compared with temperate counterparts, results consistent with the idea that a low mortality, and therefore increased longevity, and low productivity is associated with low mass-specific metabolic rate. Mass-adjusted BMR of tropical and temperate birds was associated with survival rate, in accordance with the view that animals with a slow pace of life tend to have increased life spans. To understand the mechanisms responsible for a reduced rate of metabolism in tropical birds compared with temperate species, we summarized an unpublished study, based on data from the literature, on organ masses for both groups. Tropical birds had smaller hearts, kidneys, livers, and pectoral muscles than did temperate species of the same body size, but they had a relatively larger skeletal mass. Direct measurements of organ masses for tropical and temperate birds showed that the heart, kidneys, and lungs were significantly smaller in tropical birds, although sample sizes were small. Also from an ongoing study, we summarized results to date on connections between whole-organism metabolism in tropical and temperate birds and attributes of their dermal fibroblasts grown in cell culture. Cells derived from tropical birds had a slower rate of growth, consistent with the hypothesis that these cells have a slower metabolism. We found that dermal fibroblasts from tropical birds resisted chemical agents that induce oxidative and non-oxidative stress better than do cells from temperate species, consistent with the hypothesis that birds that live longer invest more in self-maintenance such as antioxidant properties of cells.

Nrf2 signaling, a mechanism for cellular stress resistance in long-lived mice

Transcriptional regulation of the antioxidant response element (ARE) by Nrf2 is important for the cellular adaptive response to toxic insults. New data show that primary skin-derived fibroblasts from the long-lived Snell dwarf mutant mouse, previously shown to be resistant to many toxic stresses, have elevated levels of Nrf2 and of multiple Nrf2-sensitive ARE genes. Dwarf-derived fibroblasts exhibit many of the traits associated with enhanced activity of Nrf2/ARE, including higher levels of glutathione and resistance to plasma membrane lipid peroxidation. Treatment of control cells with arsenite, an inducer of Nrf2 activity, increases their resistance to paraquat, hydrogen peroxide, cadmium, and UV light, rendering these cells as stress resistant as untreated cells from dwarf mice. Furthermore, mRNA levels for some Nrf2-sensitive genes are elevated in at least some tissues of Snell dwarf mice, suggesting that the phenotypes observed in culture may be mirrored in vivo. Augmented activity of Nrf2 and ARE-responsive genes may coordinate many of the stress resistance traits seen in cells from these long-lived mutant mice.

Metabolic function in Drosophila melanogaster in response to hypoxia and pure oxygen

This study examined the metabolic response of Drosophila melanogaster exposed to O(2) concentrations ranging from 0 to 21% and at 100%. The metabolic rate of flies exposed to graded hypoxia remained nearly constant as O(2) tensions were reduced from normoxia to approximately 3 kPa. There was a rapid, approximately linear reduction in fly metabolic rate at P(O(2))s between 3 and 0.5 kPa. The reduction in metabolic rate was especially pronounced at P(O(2)) levels <0.5 kPa, and at a P(O(2)) of 0.1 kPa fly metabolic rate was reduced approximately 10-fold relative to normoxic levels. The metabolic rate of flies exposed to anoxia and then returned to normoxia recovered to pre-anoxic levels within 30 min with no apparent payment of a hypoxia-induced oxygen debt. Flies tolerated exposure to hypoxia and/or anoxia for 40 min with nearly 100% survival. Fly mortality increased rapidly after 2 h of anoxia and >16 h exposure was uniformly lethal. Flies exposed to pure O(2) for 24 h showed no apparent alteration of metabolic rate, even though such O(2) tensions should damage respiratory enzymes critical to mitochondria function. Within a few hours the metabolic rate of flies recovering from exposure to repeated short bouts of anoxia was the same as flies exposed to a single anoxia exposure.

Overexpression of methionine-R-sulfoxide reductases has no influence on fruit fly aging

Methionine sulfoxide reductases (Msrs) are enzymes that repair oxidized methionine residues in proteins. This function implicated Msrs in antioxidant defense and the regulation of aging. There are two known Msr types in animals: MsrA specific for the reduction of methionine-S-sulfoxide, and MsrB that catalyzes the reduction of methionine-R-sulfoxide. In a previous study, overexpression of MsrA in the nervous system of Drosophila was found to extend lifespan by 70%. Overexpression of MsrA in yeast also extended lifespan, whereas MsrB overexpression did so only under calorie restriction conditions. The effect of MsrB overexpression on lifespan has not yet been characterized in animal model systems. Here, the GAL4-UAS binary system was used to drive overexpression of cytosolic Drosophila MsrB and mitochondrial mouse MsrB2 in whole body, fatbody, and the nervous system of flies. In contrast to MsrA, MsrB overexpression had no consistent effect on the lifespan of fruit flies on either corn meal or sugar yeast diets. Physical activity, fecundity, and stress resistance were also similar in MsrB-overexpressing and control flies. Thus, MsrA and MsrB, the two proteins with similar function in antioxidant protein repair, have different effects on aging in fruit flies.

Genetic and environmental factors impact age-related impairment of negative geotaxis in Drosophila by altering age-dependent climbing speed

Age-related locomotor impairment in humans is important clinically because it is associated with several co-morbidities and increased risk of death. One of the hallmarks of age-related locomotor impairment in humans is a decrease in walking speed with age. Genetically tractable model organisms such as Drosophila are essential for delineating mechanisms underlying age-related locomotor impairment and age-related decreases in locomotor speed. Negative geotaxis, the ability of flies to move vertically when startled, is a common measure of locomotor behavior that declines with age in Drosophila. Toward further developing Drosophila as a model for age-related locomotor impairment, we investigated whether negative geotaxis reflects climbing or a combination of climbing and other behaviors such as flying and jumping. Additionally, we investigated whether locomotor speed in negative geotaxis assays declines with age in flies as found for walking speed in humans. We find that the vast majority of flies climb during negative geotaxis assays and that removal of hind legs, but not wings, impairs the behavior. We also find that climbing speed decreases with age in four wild type genetic backgrounds, in flies housed at different temperatures, and in control and long-lived flies harboring a mutation in OR83b. The decreases in climbing speed correlate with the age-related impairments in the distance climbed. These studies establish negative geotaxis in Drosophila as a climbing behavior that declines with age due to a decrease in climbing speed. Age-related decreases in locomotor speed are common attributes of locomotor senescence in flies and humans.

Working harder to stay alive: metabolic rate increases with age in Drosophila simulans but does not correlate with life span

The hypothesis that metabolic rate is inversely correlated with life span has long been debated. Another area of controversy has been the relationship between metabolic rate and aging. In most molecular studies key aspects of cellular metabolism have been shown to decline with age. Less attention has been focused on metabolic rate as an organism ages. We studied the survival of three Drosophila simulans fly lines and measured whole organism metabolic rate, mitochondrial DNA copy number and walking speed. Metabolic rate as assayed by CO(2) production did not correlate with median lifespan but increased by 0.43-1.14%/d. In contrast, mitochondrial DNA copy number decreased by 0.56-1.06%/d. Physical activity, as assayed by mean walking speed, did not change with age but was positively correlated with mitochondrial DNA copy number. One explanation for these data is that metabolic rate was increased, in the face of a reduced mitochondrial DNA copy number and capacity for oxidative metabolism, to maintain a constant bioenergetic demand (physical activity). Alternatively, metabolic rate may increase to provide energy for the repair of cellular damage or due to a shift in metabolic substrate use over time.

Life and death: metabolic rate, membrane composition, and life span of animals

Maximum life span differences among animal species exceed life span variation achieved by experimental manipulation by orders of magnitude. The differences in the characteristic maximum life span of species was initially proposed to be due to variation in mass-specific rate of metabolism. This is called the rate-of-living theory of aging and lies at the base of the oxidative-stress theory of aging, currently the most generally accepted explanation of aging. However, the rate-of-living theory of aging while helpful is not completely adequate in explaining the maximum life span. Recently, it has been discovered that the fatty acid composition of cell membranes varies systematically between species, and this underlies the variation in their metabolic rate. When combined with the fact that 1) the products of lipid peroxidation are powerful reactive molecular species, and 2) that fatty acids differ dramatically in their susceptibility to peroxidation, membrane fatty acid composition provides a mechanistic explanation of the variation in maximum life span among animal species. When the connection between metabolic rate and life span was first proposed a century ago, it was not known that membrane composition varies between species. Many of the exceptions to the rate-of-living theory appear explicable when the particular membrane fatty acid composition is considered for each case. Here we review the links between metabolic rate and maximum life span of mammals and birds as well as the linking role of membrane fatty acid composition in determining the maximum life span. The more limited information for ectothermic animals and treatments that extend life span (e.g., caloric restriction) are also reviewed.

Genetic variation for life span, resistance to paraquat, and spontaneous activity in unselected populations of Drosophila melanogaster: implications for transgenic rescue of life span

Genetic variation in adult life span, resistance to paraquat, resistance to DDT, and spontaneous flying activity were measured in 138 recombinant inbred lines of Drosophila melanogaster. We find that the phenotypic correlation between life span and resistance to an exogenous oxidizing agent is positive, though weak, and that there is little correlation between the two traits at the level of quantitative trait loci (QTLs). The sign of the life span-resistance correlation is haplotype-specific, suggesting a high degree of statistical interaction and dependence on genetic background. Because of the genotype-specificity in the relationship between life span and resistance phenotypes, interventions to extend life span by overexpression of antioxidant enzymes are likely to produce strain-specific results. These observations are in general agreement with the "genetic rescue" hypothesis of Sohal et al. [Sohal, R.S., Mockett, R.J., Orr, W.C., 2002. Mechanisms of aging: an appraisal of the oxidative stress hypothesis. Free Radic. Biol. Med. 33, 575-586.], though we emphasize that such statistical interaction is a normal feature of standing genetic variation, and does not imply that some genotypes are pathological. Ad hoc observation of spontaneous flying activity 5 days after emergence proved to be a much better predictor of life span than resistance to an exogenous oxidant in these populations.

Science of Cancer and Aging

This review provides an overview of a selection of the most pertinent molecular pathways that link cancer and aging and focuses on those where recent advances were most important. When organizing the bulk of information on this subject, I became aware of the fact that the most evident partition, namely, mechanisms that influence aging and mechanisms that influence cancer occurrence, is difficult to apply. Most mechanisms explaining the aging process are also those that influence carcinogenesis. Mechanisms that are described in tumor suppressor pathways are also contributors to the aging process. From an intuitive point of view, there are phenomena that have traditionally been contributed to aging others to cancer-inducing factors and they are presented herein.

Causative role of oxidative stress in a Drosophila model of Friedreich ataxia

Friedreich ataxia (FA), the most common form of hereditary ataxia, is caused by a deficit in the mitochondrial protein frataxin. While several hypotheses have been suggested, frataxin function is not well understood. Oxidative stress has been suggested to play a role in the pathophysiology of FA, but this view has been recently questioned, and its link to frataxin is unclear. Here, we report the use of RNA interference (RNAi) to suppress the Drosophila frataxin gene (fh) expression. This model system parallels the situation in FA patients, namely a moderate systemic reduction of frataxin levels compatible with normal embryonic development. Under these conditions, fh-RNAi flies showed a shortened life span, reduced climbing abilities, and enhanced sensitivity to oxidative stress. Under hyperoxia, fh-RNAi flies also showed a dramatic reduction of aconitase activity that seriously impairs the mitochondrial respiration while the activities of succinate dehydrogenase, respiratory complex I and II, and indirectly complex III and IV are normal. Remarkably, frataxin overexpression also induced the oxidative-mediated inactivation of mitochondrial aconitase. This work demonstrates, for the first time, the essential function of frataxin in protecting aconitase from oxidative stress-dependent inactivation in a multicellular organism. Moreover our data support an important role of oxidative stress in the progression of FA and suggest a tissue-dependent sensitivity to frataxin imbalance. We propose that in FA, the oxidative mediated inactivation of aconitase, which occurs normally during the aging process, is enhanced due to the lack of frataxin.

Increased Rheb-TOR signaling enhances sensitivity of the whole organism to oxidative stress

The accumulation of free radical damage to an organism over its lifespan can cause premature aging and disease including cancer, atherosclerosis and neurodegenerative disorders. The well-conserved Rheb-Target-of-rapamycin (TOR)-S6-kinase (S6K) signaling pathway regulates several cellular processes and has been shown to influence lifespan and diseases such as cancer and neurodegenerative disorders. Using adult Drosophila, we describe for the first time in metazoans that TOR activity can influence the stress response. We find that mildly increasing systemic Rheb-TOR-S6K signaling sensitizes the whole organism to oxidative stress and promotes senescence of locomotor activity with age. Furthermore, we find that S6K is required for increased Rheb-TOR signaling to sensitize the whole organism to oxidative stress and promote the senescence of locomotor activity. Interestingly, we also find that increasing Rheb-TOR signaling in muscle can increase the sensitivity of adults to oxidative stress. These data imply that pathological situations that increase TOR activity might perturb the ability of the whole organism to cope with stress causing disease progression and aging.

Comparison between the effects of aging and hyperoxia on glutathione redox state and protein mixed disulfides in Drosophila melanogaster

The main purpose of this study was to determine whether experimental enhancement of oxidative stress by exposure to hyperoxia is an appropriate model for the acceleration of the normal aging process or for establishing a causal association between oxidative stress and aging. Insect tissues are directly exposed to ambient air via the tracheolar invaginations and are thus highly susceptible to oxidative stress under hyperoxic conditions. Amounts of glutathione (GSH), glutathione disulfide (GSSG) and protein mixed disulfides (PrSSG) were compared under normoxic and 100% ambient oxygen in males of two different strains of Drosophila melanogaster (Oregon R (WT) and y w strains). The reason for using two different strains was to preclude the effects of genetic background and to determine whether variations in longevity of the two strains are associated with resistance to oxidative stress. Amounts of GSSG and PrSSG increased, whereas GSH:GSSG ratios declined as a function of age in both strains. Under hyperoxia, y w flies did not exhibit an increase in GSSG amount or a decline in GSH:GSSG ratio, whereas WT flies showed a decline in GSH:GSSG ratio only during the later part of hyperoxic exposure. In neither strain there was a progressive increase in PrSSG amount under hyperoxia. Results indicate that hyperoxia (100% oxygen) neither reproduces nor accelerates the pattern of alterations in glutathione redox state and PrSSG content observed during aging under normoxic conditions, although some other indicators of oxidative stress may be affected.

Resistance to oxidative stress induced by paraquat correlates well with both decreased and increased lifespan in Drosophila melanogaster

There is increasing support for the notion that genetic variation for lifespan, both within and between species, is correlated with variation in the efficiency of the free radical scavenging system and the ability to withstand oxidative stress. In Drosophila, resistance to dietary paraquat, a free radical generator, is often used as a measure of resistance to oxidative stress and is reported to give firm positive correlations with longevity. Recently it has been suggested that an increase in antioxidative defences in Drosophila only has a beneficial effect in relatively short-lived stocks. This implies that mechanisms of lifespan determination can be different in lines with different genetic constitution. Here we test if variation in resistance to dietary paraquat co-segregates with variation in lifespan in two sets of Drosophila melanogaster lines that were selected for decreased and increased virgin lifespan respectively. Flies of the short-lived lines show decreased resistance to paraquat compared to the control lines, indicating low resistance against oxidative stress. On the other hand, both males and females of the long-lived lines show, despite increased feeding rates on paraquat-supplemented food, no decreased survival compared to control lines. This shows that flies of the long-lived lines have increased paraquat resistance, but that this is masked by increased feeding rate, resulting in increased exposure to paraquat. This suggests that resistance to paraquat is a correlated response to selection on virgin lifespan over the entire genetic range.

Susceptibility of DNA to oxidative stressors in young and aging mice

The changes that accompany aging may be a result of oxidative damage to DNA that accumulates as a result of aging and age-related illnesses. Furthermore, a higher susceptibility is thought to be more common among elderly than young individuals. In the present study, we examined the severity of DNA damage caused by carbon tetrachloride (CCl4) and H2O2 in cells from young (2 month old) and older (14 month old) mice using both in vivo and in vitro exposures. CCl(4) is known to generate radical oxidative species (ROS) throughout its biotransformation in the liver. Therefore, 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxdGuo) was quantified in liver DNA obtained from young and older mice treated with CCl4. In addition, DNA single-strand breaks were measured by the Comet assay in primary lung fibroblasts cultured from young and older mice and treated in vitro with H2O2. Intracellular ROS production and mitochondrial enzyme activity were determined in parallel. 8-oxodGuo levels were significantly higher in older mouse liver DNA than younger, and increased significantly with CCl4 treatment. When the basal DNA damage was subtracted, the net damage was almost equal for both. In addition, untreated cells cultured from older mice had significantly greater levels of strand breaks than cells derived from young mice. H2O2 increased the level of damage in both cell cultures. Our findings indicate that the DNA damage observed in older animals probably results from the accumulation of endogenous damage with age, perhaps due to insufficient repair, which enhances the injury caused by exposure to the toxic agents.

Enhanced catabolism of mitochondrial superoxide/hydrogen peroxide and aging in transgenic Drosophila

The generation of superoxide anion radicals (O2*-) and hydrogen peroxide (H2O2) during mitochondrial respiration has been widely postulated to be causally linked to the aging process. The hypothesis that a specific enhancement of mitochondrial O2*-/H2O2 catabolism would delay age-associated physiological changes and extend the lifespan was tested by simultaneous overexpression of MnSOD (manganese superoxide dismutase) and catalase, ectopically targeted to the mitochondrial matrix of transgenic Drosophila melanogaster. The increased activities of these antioxidative enzymes resulted in a decrease of mitochondrial H2O2 release and enhancement of free methionine content. The MnSOD/mitochondrial catalase transgenic flies displayed an enhanced resistance to experimental oxidative stress, induced by dietary H2O2 administration or by exposure to 100% ambient oxygen. However, the lifespan of the flies was decreased, by up to 43%, and this effect coincided with (i) an overall decrease in physical fitness, as measured by the speed of walking, and (ii) an age-related decrease in mitochondrial state 3 (ADP-stimulated) respiration. These findings support the notion that mitochondrial O2*-/H2O2 production at physiological levels is essential for normal biological processes leading to the attainment of a normal lifespan.

Toward a unified theory of caloric restriction and longevity regulation

The diet known as calorie restriction (CR) is the most reproducible way to extend the lifespan of mammals. Many of the early hypotheses to explain this effect were based on it being a passive alteration in metabolism. Yet, recent data from yeast, worms, flies, and mammals support the idea that CR is not simply a passive effect but an active, highly conserved stress response that evolved early in life's history to increase an organism's chance of surviving adversity. This perspective updates the evidence for and against the various hypotheses of CR, and concludes that many of them can be synthesized into a single, unifying hypothesis. This has important implications for how we might develop novel medicines that can harness these newly discovered innate mechanisms of disease resistance and survival.

Oxidative damage, aging and anti-aging strategies

The last two decades brought remarkable insight into the nature of normal aging in multicellular organisms. However, we are still far away from realizing extension of maximum lifespan in humans. An important modulator of lifespan is oxidative damage induced by reactive species, such as reactive oxygen species (ROS). Studies from yeast, Caenorhabditis and Drosophila primarily focused on (1) reduced generation or (2) elimination of ROS but have two principal shortcomings: (1) dietary restriction and single gene mutations are often associated with physiological impairments and (2) overexpression of components of the antioxidant system extend lifetime only under stress-induced conditions. Recent results from Drosophila indicate the involvement of an endogenous repair and elimination system for oxidatively damaged proteins in the process of aging. This system includes methionine sulfoxide reductase A (MSRA) and the carbonyl reductase Sniffer, the protein-ubiquitin ligase Parkin and the chaperone Hsp22. In this review we summarize different anti-aging strategies and discuss a synergistic interaction between protection against free radicals and specific repair/elimination of oxidative damage in lifespan extension primarily using the model system Drosophila. To achieve lifespan extension, available experiments are often methodically grouped into (1) caloric restriction, (2) single gene mutation, and (3) overexpression of genes. Here we summarize different strategies by a more causal classification: (1) prevention of ROS generation, (2) reducing free ROS level, and (3) repair and elimination of ROS-damaged proteins.

Genetic approaches to study aging in Drosophila melanogaster

The process of aging can be described as a progressive decline in an organism's function that invariably results in death. This decline results from the activities of intrinsic genetic factors within an organism. The relative contributions of the biological and environmental components to senescence are hard to measure, however different strategies have been devised in Drosophila melanogaster to isolate and identify genetic influences on aging. These strategies include selective breeding, quantitative trait loci (QTL) mapping and single gene mutant analysis. Selective breeding effectively demonstrated a genetic, heritable component to aging while QTL mapping located regions within the Drosophila genome carrying loci that influence the aging process. Within the past decade, single gene mutant analysis has facilitated the identification of specific genes whose activities play a determinative role in Drosophila aging. This review will focus on the application of selective breeding, QTL mapping and single gene mutant analysis used in Drosophila to study aging as well as the results obtained through these strategies to date.

Functional senescence in Drosophila melanogaster

The fruit fly Drosophila melanogaster is one of the principal model organisms used for studying the biology of aging. Flies are well suited for such studies for a number of reasons. Flies develop to adulthood quickly, have a relatively short life span, and are inexpensive to house. Most of the fly genome has been sequenced, powerful genetic tools are available to manipulate it, and most fly genes have obvious homologues in mammals. While the majority of aging studies in flies have focused on regulation of life span, the fly is emerging as a powerful model system for investigating the biology that underlies age-related functional decline. Key to the use of flies in this way is the striking number of parallels between functional senescence in Drosophila and humans. Here, we review age-related functional declines in Drosophila, human correlates of these age-related declines, and common mechanisms that influence longevity and specific aspects of functional senescence in flies.

A life history model of somatic damage associated with resource acquisition: damage protection or prevention?

A resource acquisition-allocation model is developed to examine the trade-off between reproduction and somatic protection. Unlike previous studies, resource intake is not assumed to be constrained: instead, resource intake is free to vary, with increased intake being associated with an increased risk of somatic damage. This gives rise to an optimal resource intake as well as an optimal allocation strategy. This paper studies the relative importance of acquisition and allocation strategies in regulating acquisition-related mortality. Under the optimal allocation strategy mortality rate increases with age, in accordance with the disposable soma theory of aging. Contrary to the usual interpretation of the disposable soma theory, this increase in mortality can arise from an increase in the resource acquisition effort rather than a decrease in the resources allocated to protection. At early ages resource acquisition is found to be the primary path for regulating life history costs, whilst allocating resources to protection becomes more important later in life. Models for targeted and non-targeted damage repair are considered and the robustness of our results to the structure and parameterization of the model is discussed. The results from our models are discussed in light of published data. Resource acquisition is shown to be a potentially important mechanism for controlling somatic damage which deserves further study.

On the importance of fatty acid composition of membranes for aging

The membrane pacemaker theory of aging is an extension of the oxidative stress theory of aging. It emphasises variation in the fatty acid composition of membranes as an important influence on lipid peroxidation and consequently on the rate of aging and determination of lifespan. The products of lipid peroxidation are reactive molecules and thus potent damagers of other cellular molecules. It is suggested that the feedback effects of these peroxidation products on the oxidative stress experienced by cells is an important part of the aging process. The large variation in the chemical susceptibility of individual fatty acids to peroxidation coupled with the known differences in membrane composition between species can explain the different lifespans of species, especially the difference between mammals and birds as well as the body-size-related variation in lifespan within mammals and birds. Lifespan extension by calorie-restriction can also be explained by changes in membrane fatty acid composition which result in membranes more resistant to peroxidation. It is suggested that lifespan extension by reduced insulin/IGF signalling may also be mediated by changes in membrane fatty acid composition.

Evolutionary and mechanistic theories of aging

Senescence (aging) is defined as a decline in performance and fitness with advancing age. Senescence is a nearly universal feature of multicellular organisms, and understanding why it occurs is a long-standing problem in biology. Here we present a concise review of both evolutionary and mechanistic theories of aging. We describe the development of the general evolutionary theory, along with the mutation accumulation, antagonistic pleiotropy, and disposable soma versions of the evolutionary model. The review of the mechanistic theories focuses on the oxidative stress resistance, cellular signaling, and dietary control mechanisms of life span extension. We close with a discussion of how an approach that makes use of both evolutionary and molecular analyses can address a critical question: Which of the mechanisms that can cause variation in aging actually do cause variation in natural populations?

The role of oxidative damage and stress in aging

The Free Radical/Oxidative Stress Theory of Aging, which was first proposed in 1956, is currently one of the most popular explanations for how aging occurs at the biochemical/molecular level. However, most of the evidence in support of this theory is correlative, e.g., oxidative damage to various biomolecules increases with age, and caloric restriction, which increases life span and retards aging, reduces the age-related increase in oxidative damage to biomolecules. The most direct test of the Free Radical/Oxidative Stress Theory of Aging is to specifically alter the age-related increase in oxidative damage and determine how this alteration affects life span. For the first time, investigators can use genetically altered animals to test directly the role of oxidative damage in aging. In this manuscript, we critically review the past research in this area and discuss potential future research directions in testing the Free Radical/Oxidative Theory of Aging.

Testing the "rate of living" model: further evidence that longevity and metabolic rate are not inversely correlated in Drosophila melanogaster

In a recent study examining the relationship between longevity and metabolism in a large number of recombinant inbred Drosophila melanogaster lines, we found no indication of the inverse relationship between longevity and metabolic rate that one would expect under the classical "rate of living" model. A potential limitation in generalizing from that study is that it was conducted on experimental material derived from a single set of parental strains originally developed over 20 years ago. To determine whether the observations made with those lines are characteristic of the species, we studied metabolic rates and longevities in a second, independently derived set of recombinant inbred lines. We found no correlation in these lines between metabolic rate and longevity, indicating that the ability to both maintain a normal metabolic rate and have extended longevity may apply to D. melanogaster in general. To determine how closely our measurements reflect metabolic rates of flies maintained under conditions of life span assays, we used long-term, flow-through metabolic rate measurements and closed system respirometry to examine the effects of variables such as time of day, feeding state, fly density, mobility of the flies, and nitrogen knockout on D. melanogaster metabolic rate. We found that CO2 production estimated in individual flies accurately reflects metabolic rates of flies under the conditions used for longevity assays.

Thermal adaptation inDrosophila serrata under conditions linked to its southern border: Unexpected patterns from laboratory selection suggest limited evolutionary potential

To investigate the ability of Drosophila serrata to adapt to thermal conditions over winter at the species southern border, replicate lines from three source locations were held as discrete generations over three years at either 19 degrees C (40 generations) or temperatures fluctuating between 7 degrees C and 18 degrees C (20 generations). Populations in the fluctuating environment were maintained either with an adult 0 degrees C cold shock or without a shock. These conditions were expected to result in temperature-specific directional selection for increased viability and productivity under both temperature regimes, and reduced development time under the fluctuating-temperature regime. Selection responses of all lines were tested under both temperature regimes after controlling for carry-over effects by rearing lines in these environments for two generations. When tested in the 19 degrees C environment, lines evolving at 19 degrees C showed a faster development time and a lower productivity relative to the other lines, while cold shock reduced development time and productivity of all lines. When tested in the fluctuating environment, productivity of the 7-18 degrees C lines selected with a cold shock was relatively lower than that of lines selected without a shock, but this pattern was not observed in the other populations. Viability and body size as measured by wing length were not altered by selection or cold shock, although there were consistent effects of source population on wing length. These results provide little evidence for temperature-specific adaptation in D. serrata-although the lines had diverged for some traits, these changes were not consistent with a priori predictions. In particular, there was no evidence for life-history changes reflecting adaptation to winter conditions at the southern border. The potential for D. serrata to adapt to winter conditions may therefore be limited.

Delayed behavioural aging and altered mortality in Drosophila beta integrin mutants

The genetic basis for aging is being intensely investigated in a variety of model systems. Much of the focus in Drosophila has been on the molecular-genetic determinants of lifespan, whereas the molecular-genetic basis for age-related functional declines has been less vigorously explored. We evaluated behavioural aging and lifespan in flies harbouring loss-of-function mutations in myospheroid, the gene that encodes betaPS, a beta integrin. Integrins are adhesion molecules that regulate a number of cellular processes and developmental events. Their role in aging, however, has received limited attention. We report here that age-related declines in locomotor activity are ameliorated and that mean lifespan is increased in myospheroid mutants. The delayed functional senescence and altered mortality in myospheroid flies are independent of changes in body size, reproduction or stress resistance. Our data indicate that functional senescence and age-dependent mortality are influenced by beta integrins in Drosophila.