Mortality In Drosophila Research Articles

Xanthohumol prolongs lifespan and decreases stress-induced mortality in Drosophila melanogaster

Aging is a significant risk factor that links to the genesis of human diseases. The capacity to scavenge free radicals and adapt to various stresses is essential for expanding living organisms' lifespan. The evidences on the promotion of longevity by dietary supplementation are growing. Drosophila or fruit fly is one of the most effective models for the evaluation of anti-aging compounds. Xanthohumol (XN) is a potential bioactive substance for the prevention and treatment of many diseases. The previous studies have reported its potent activities as antioxidant, anticancer, anti-inflammatory, antiviral, antibacterial antiplasmodial, and antiobesity. In this study, the effect of XN supplementation on the lifespan extension was investigated in Drosophila melanogaster. The effects of XN on the improvement of the recovery from cold and heat shock, the resistance to starvation stress, and free radical-induced oxidative stress in XN-treated flies were also evaluated. Results showed that supplementation with XN at 0.5 mg/mL diet extended the mean lifespan by 14.89%. This was consistent with a significant improvement of locomotor activity of the Drosophila fed with an XN-mixed diet compared with those fed with a control diet. XN supplementation significantly increased the antioxidant enzyme activities at both 25 and 40 days. Drosophila treated with XN exhibited increased survival after exposure to hydrogen peroxide and paraquat. Finally, XN supplementation improved the recovery from cold and heat shock, the resistance to starvation stress, and acetic acid-induced stress. The present study shows that dietary supplementation with XN revealed the longevity effect and ameliorated stress-induced mortality in Drosophila.

Neural dysfunction correlates with heat coma and CTmax in Drosophila but does not set the boundaries for heat stress survival.

When heated, insects lose coordinated movement followed by the onset of heat coma (critical thermal maximum, CTmax). These traits are popular measures to quantify interspecific and intraspecific differences in insect heat tolerance, and CTmax correlates well with current species distributions of insects, including Drosophila Here, we examined the function of the central nervous system (CNS) in five species of Drosophila with different heat tolerances, while they were exposed to either constant high temperature or a gradually increasing temperature (ramp). Tolerant species were able to preserve CNS function at higher temperatures and for longer durations than sensitive species, and similar differences were found for the behavioural indices (loss of coordination and onset of heat coma). Furthermore, the timing and temperature (constant and ramp exposure, respectively) for loss of coordination or complete coma coincided with the occurrence of spreading depolarisation (SD) events in the CNS. These SD events disrupt neurological function and silence the CNS, suggesting that CNS failure is the primary cause of impaired coordination and heat coma. Heat mortality occurs soon after heat coma in insects; to examine whether CNS failure could also be the proximal cause of heat death, we used selective heating of the head (CNS) and abdomen (visceral tissues). When comparing the temperature causing 50% mortality (LT50) of each body part versus that of the whole animal, we found that the head was not particularly heat sensitive compared with the abdomen. Accordingly, it is unlikely that nervous failure is the principal/proximate cause of heat mortality in Drosophila.

Dipteran toxicity assays for determining the oral insecticidal activity of venoms and toxins

The growing world population is placing an increasing demand on food production. In addition, abuse and misuse of chemical insecticides has led to the evolution of resistance in insect pests as well as environmental damage. Together, these developments have created a demand for new insecticidal compounds to facilitate global food production. Arachnid venom peptides provide an environmentally-friendly alternative as potential bioinsecticides given their advantages of being fully biodegradable, highly potent, and phyletically selective. However, the use of arachnid venom peptides as bioinsecticides has been questioned due to their presumed lack of oral toxicity. Thus, the aim of this work was to develop screens for oral insecticidal activity. Based on the high susceptibility of dipterans to venom peptides, fruit flies (Drosophila melanogaster) and sheep blowflies (Lucilia cuprina) were selected for screening 56 arachnid venoms. 71.4% of these venoms caused 50% or higher mortality in Drosophila, whereas 30.4% were lethal to blowflies at oral doses of 1 or 30 μg/fly, respectively. We used these assays to compare the oral and injection activity of four well-known spider venom peptides (Hv1a, Hv1c, Dc1a and Ta1a). Hv1c and Ta1a only showed weak or no oral activity in both species, while Hv1a and Dc1a showed higher oral activity in blowflies than Drosophila. Overall, we have established screens for oral toxicity in two dipteran insects. Our results indicate that oral insecticidal activity is more widespread in arachnid venoms than expected, and that some arachnid venoms and venom peptides exhibit phyletic differences in oral toxicity.

Nutritional geometry of paternal effects on embryo mortality.

Well-established causal links exist between maternal nutritional deficits and embryo health and viability. By contrast, environmental effects operating through the father that could influence embryo mortality have seldom been examined. Yet, ejaculates can require non-trivial resource allocation, and seminal plasma components are increasingly recognized to exert wide-ranging effects on females and offspring, so paternal dietary effects on the embryo should be expected. We test for effects of varying levels of protein (P), carbohydrate (C) and caloric load in adult male diet on embryo mortality in Drosophila melanogaster We demonstrate that macronutrient balance and caloric restriction exert significant effects, and that nutritional effects are more impactful when a prior mating has occurred. Once-mated males produced embryos with marginally elevated mortality under high-caloric densities and a 1 : 8 P : C ratio. In contrast, embryos produced by twice-mated males were significantly more likely to die under male caloric restriction, an outcome that may have resulted from shifts in ejaculate quality and/or epigenetic paternal effects. Body nutrient reserves were strongly and predictably altered by diet, and body condition, in turn, was negatively related to embryo mortality. Thus, sire nutritional history and resultant shifts in metabolic state predict embryo viability and post-fertilization fitness outcomes.

Exposure to Concentrated Ambient PM2.5 Shortens Lifespan and Induces Inflammation-Associated Signaling and Oxidative Stress in Drosophila.

Exposure to ambient PM 2.5 is associated with human premature mortality. However, it has not yet been toxicologically replicated, likely due to the lack of suitable animal models. Drosophila is frequently used in longevity research due to many incomparable merits. The present study aims to validate Drosophila models for PM 2.5 toxicity study through characterizing their biological responses to exposure to concentrated ambient PM 2.5 (CAP). The survivorship curve demonstrated that exposure to CAP markedly reduced lifespan of Drosophila. This antilongevity effect of CAP exposure was observed in both male and female Drosophila, and by comparison, the male was more sensitive [50% survivals: 20 and 48 days, CAP- and filtered air (FA)-exposed males, respectively; 21 and 40 days, CAP- and FA-exposed females, respectively]. Similar to its putative pathogenesis in humans, CAP exposure-induced premature mortality in Drosophila was also coincided with activation of pro-inflammatory signaling pathways including Jak, Jnk, and Nf-κb and increased systemic oxidative stress. Furthermore, like in humans and mammals, exposure to CAP significantly increased whole-body and circulating glucose levels and increased mRNA expression of Ilp2 and Ilp5 , indicating that CAP exposure induces dysregulated insulin signaling in Drosophila. Similar to effects on humans exposure to CAP leads to premature mortality likely through induction of inflammation-associated signaling, oxidative stress, and metabolic abnormality in Drosophila, strongly supporting that it can be a useful model organism for PM 2.5 toxicity study.

Impact of ERK activation on fly survival and Wolbachia-mediated protection during virus infection.

Elevated levels of reactive oxygen species (ROS) provide protection against virus-induced mortality in Drosophila. In addition to contributing to oxidative stress, ROS are known to activate a number of signalling pathways including the extracellular signal-regulated kinases (ERK) signalling cascade. It was recently shown that ERK signalling is important for resistance against viral replication and invasion in cultured Drosophila cells and the gut epithelium of adult flies. Here, using a Drosophila loss-of-function ERK (rolled) mutant we demonstrated that ERK is important for fly survival during virus infection. ERK mutant flies subjected to Drosophila C virus (DCV) oral and systemic infection were more susceptible to virus-induced mortality as compared with wild-type flies. We have demonstrated experimentally that ERK activation is important for fly survival during oral and systemic virus infection. Given that elevated ROS correlates with Wolbachia-mediated antiviral protection, we also investigated the involvement of ERK in antiviral protection in flies infected by Wolbachia. The results indicate that ERK activation is increased in the presence of Wolbachia but this does not appear to influence Wolbachia-mediated antiviral protection, at least during systemic infection.

Temporally distinct phosphorylations differentiate Tau-dependent learning deficits and premature mortality in Drosophila.

Abnormally phosphorylated Tau protein, the major component of neurofibrillary tangles, is critical in the pathogenesis of Alzheimer's disease and related Tauopathies. We used Drosophila to examine the role of key disease-associated phosphorylation sites on Tau-mediated neurotoxicity. We present evidence that the late-appearing phosphorylation on Ser(238) rather than hyperphosphorylation per se is essential for Tau toxicity underlying premature mortality in adult flies. This site is also occupied at the time of neurodegeneration onset in a mouse Tauopathy model and in damaged brain areas of confirmed Tauopathy patients, suggesting a similar critical role on Tau toxicity in humans. In contrast, occupation of Ser(262) is necessary for Tau-dependent learning deficits in adult Drosophila. Significantly, occupation of Ser(262) precedes and is required for Ser(238) phosphorylation, and these temporally distinct phosphorylations likely reflect conformational changes. Because sequential occupation of Ser(262) and Ser(238) is required for the progression from Tau-mediated learning deficits to premature mortality in Drosophila, they may also play similar roles in the escalating symptom severity in Tauopathy patients, congruent with their presence in damaged regions of their brains.

HIF-1α restricts NF-κB-dependent gene expression to control innate immunity signals.

Hypoxia and inflammation are intimately linked. It is known that nuclear factor κB (NF-κB) regulates the hypoxia-inducible factor (HIF) system, but little is known about how HIF regulates NF-κB. Here, we show that HIF-1α represses NF-κB-dependent gene expression. HIF-1α depletion results in increased NF-κB transcriptional activity both in mammalian cells and in the model organism Drosophila melanogaster. HIF-1α depletion enhances the NF-κB response, and this required not only the TAK-IKK complex, but also CDK6. Loss of HIF-1α results in an increased angiogenic response in mammalian cancer cells and increased mortality in Drosophila following infection. These results indicate that HIF-1α is required to restrain the NF-κB response, and thus prevents excessive and damaging pro-inflammatory responses.

Strong Dietary Restrictions Protect Drosophila against Anoxia/Reoxygenation Injuries

BackgroundReoxygenation of ischemic tissues is a major factor that determines the severity of cardiovascular diseases. This paper describes the consequences of anoxia/reoxygenation (A/R) stresses on Drosophila, a useful, anoxia tolerant, model organism.Methodology/Principal FindingsNewly emerged adult male flies were exposed to anoxic conditions (<1% O2) for 1 to 6 hours, reoxygenated and their survival was monitored.ResultsA/R stresses induced a transient increase in mortality which peaked at the time of reoxygenation. Then flies recovered low mortality rates similar to those of control flies. A/R induced mortality was strongly dependent on dietary conditions during the 48 h that preceded anoxia. Well fed flies were anoxia sensitive. Strong dietary restrictions and starvation conditions protected flies against A/R injuries. The tolerance to anoxia was associated to large decreases in glycogen, protein, and ATP contents. During anoxia, anoxia tolerant flies produced more lactate, less phosphate and they maintained more stable ATP levels than anoxia sensitive flies. Moderate dietary restrictions, which increased the longevity of normoxic flies, did not promote resistance to A/R stresses. Diet dependent A/R injuries were still observed in sima loss of function mutants and they were insensitive to dietary rapamycin or resveratrol. AICAR (5-aminoimidazole-4-carboxamide-1-beta-D-ribosefuranoside), an activator AMP kinase decreased A/R injuries. Mutants in the insulin signalling pathway were more anoxia tolerant in a fed state.Conclusion/SignificanceLong A/R stresses induce a transient increase in mortality in Drosophila. This mortality is highly dependent on dietary conditions prior to the stress. Strong dietary restrictions and starvation conditions protect flies against A/R injuries, probably by inducing a major remodelling of energy metabolism. The results also indicate that mechanistically different responses develop in response to dietary restrictions of different strengths. AMP kinase and the insulin signalling pathway are possible mediators of diet dependent anoxic tolerance in Drosophila.

Dynamics of the action of dFOXO on adult mortality in Drosophila

The insulin/insulin growth factor (IGF)-like signaling (IIS) pathway has a conserved role in regulating lifespan in Caenorhabditis elegans, Drosophila and mice. Extension of lifespan by reduced IIS has been shown in C. elegans to require the key IIS target, forkhead box class O (FOXO) transcription factor, DAF-16. dFOXO, the Drosophila DAF-16 orthologue, is also an IIS target, and its overexpression in adult fat body increases lifespan. In C. elegans, IIS acts exclusively during adulthood to determine adult survival. We show here, using an inducible overexpression system, that in Drosophila continuous dFOXO overexpression in adult fat body reduces mortality rate throughout adulthood. We switched the IIS status of the flies at different adult ages and examined the effects of these switches on dFOXO expression and mortality rates. dFOXO protein levels were switched up or down by the inducible expression system at all ages examined. If IIS status is reversed early in adulthood, similar to the effects of another intervention that reduces adult mortality in Drosophila, dietary restriction (DR), there is a complete switch of subsequent mortality rate to that of flies chronically exposed to the new IIS regime. At this age, IIS thus acts acutely to determine risk of death. Mortality rates continued to respond to a switch in IIS status up to 4 weeks of adult age, but not thereafter. However, unlike DR, as IIS status was altered at progressively later ages, mortality rates showed incomplete switching and responded with progressively smaller changes. These findings indicate that alteration of expression levels of dFOXO may have declining effects on IIS status with age, that there could be some process that prevents or lessens the physiological response to a switch in IIS status or that, unlike DR, this pathway regulates aging-related damage. The decreased mortality and increased lifespan of dFOXO overexpressing flies was uncoupled from any effect on female fecundity and from expression levels of Drosophila insulin-like peptides in the brain.

Dietary restriction, mortality trajectories, risk and damage

Restriction of food intake extends lifespan in evolutionarily diverse organisms, including mammals. Dietary restriction (DR) also delays the appearance of ageing-related damage and pathology and keeps organisms in a youthful state for longer. DR has hence been suggested to lower the rate of ageing. Analysis of mortality rates can be used to test this idea. During ageing, mortality rates in general increase, approximately exponentially. Lifespan can be extended either by a reduction in the rate of increase in mortality rate with age or a lowering of the initial rate of mortality. A reduction in the slope of a mortality trajectory has generally been taken to indicate that the rate of ageing has been lowered. Data on the effects of temperature on mortality in Drosophila are in accordance with this idea. Lowered temperature extends lifespan solely by lowering the slope of the mortality trajectory and flies with a hotter thermal history have permanently elevated death rates. In contrast, lowering of the initial rate of mortality has been taken to leave the rate of ageing unaffected. In Drosophila and in mice, but not in rats, DR extends lifespan by lowering the initial mortality rate. In Drosophila, the effect of DR is acute, and mortality rate switches rapidly between DR and control values with the corresponding changes in nutritional regime. DR in Drosophila therefore has no impact upon the rate of ageing. Possible mechanisms by which DR can both delay damage and pathology and yet act acutely to determine mortality rates are discussed. In rodents, some phenotypes associated with DR, including microarray profiles, show rapid switching with changed nutritional regime, pointing to potentially acute effects of DR in mammals.

Structured antedependence models for genetic analysis of repeated measures on multiple quantitative traits

Simultaneous analysis of correlated traits that change with time is an important issue in genetic analyses. Several methodologies have already been proposed for the genetic analysis of longitudinal data on single traits, in particular random regression and character process models. Although the latter proved, in most cases, to compare favourably to alternative approaches for analysis of single function-valued traits, they do not allow a straightforward extension to the multivariate case. In this paper, another methodology (structured antedependence models) is proposed, and methods are derived for the genetic analysis of two or more correlated function-valued traits. Multivariate analyses are presented of fertility and mortality in Drosophila and of milk, fat and protein yields in dairy cattle. These models offer a substantial flexibility for the correlation structure, even in the case of complex non-stationary patterns, and perform better than multivariate random regression models, with fewer parameters.

Dead Last

Yes, graying baby boomers, you can safely and naturally stop aging! Just live until your mid-90s and your body will quit decaying on its own! Few of us get that chance, but the question of why aging stops in the very old has nettled researchers for the last decade. Now, a study of fruit flies backs an evolutionary explanation and reveals that the age at which deterioration stops is more malleable than anyone expected. Far in the future, researchers might be able to halt human aging before people are too feeble to enjoy the extra time. Whoever said that life begins at 50 never read an actuarial table. By that milestone, an individual's risk of dying--a measure of physical decline--is about five times higher than a 20-year-old's and is rising fast. But for people who survive into their 90s, the mortality rate levels off. The fortunate oldsters apparently stop aging. The idea was controversial at first. "Ten years ago, I didn't believe this at all," says Michael Rose, an evolutionary biologist at the University of California, Irvine. But demographers have confirmed the plateaus in organisms as diverse as yeast and wasps. To explain the slowdown, some scientists back the "tough old bastard hypothesis," which ascribes the effect to inborn constitutional differences. Weaker individuals gradually perish, and by advanced ages, only the hardiest remain. Mathematical models of evolution suggest an alternative explanation. Natural selection dictates how fast organisms fall apart. Creatures grow decrepit because natural selection wanes with age, and mortality rates climb as the strength of natural selection falls (see "Aging Research Grows Up" ). Once an organism has reproduced for the last time, selection's strength reaches zero, and it might seem that aging should shift into overdrive. However, the evolutionary explanation predicts that death rates should level off and physical deterioration should cease. Rose and colleagues tested this explanation in fruit flies. It posits a close correspondence between the age of last reproduction and the age when mortality peaks--and that's what the researchers saw in four lines of flies. Although flies of different strains stopped laying eggs at different ages, in each strain the "break day" when death rates began to stabilize closely followed the end of breeding. The researchers then tried to shift the mortality pinnacle in late-reproducing flies whose break day came at 69 days of age. Rose and colleagues collected eggs only from mothers under the age of 15 days to form each succeeding generation. After 24 generations, the break day had slipped back to 48 days. "This is a fascinating result," says Kenneth Wachter, a demographer at the University of California, Berkeley, because the "onset of mortality plateaus evolves so quickly." The age when mortality levels off is changeable, says Rose, but don't expect these fly results to benefit humans soon. Sometime in the future, he predicts, researchers might know enough to halt aging earlier, say at 45 instead of 90. If scientists pull off that feat, saying that life begins at 50 will be more than a comforting fib. --Mitch Leslie; suggested by Donna Holmes M. R. Rose, M. D. Drapeau, P. G. Yazdi, K. H. Shah, D. B. Moise, R. R. Thakar, C. L. Rauser, L. D. Mueller, Evolution of late-life mortality in Drosophila melanogaster . Evolution 56 , 1982-1991 (2002). [Abstract] [Full Text]

The fractionation experiment: reducing heterogeneity to investigate age-specific mortality in Drosophila

Age-specific mortality rates decelerate at older ages in both genetically homogenous and heterogeneous populations of Drosophila. One explanation proposed for deceleration is population heterogeneity. This hypothesis suggests that a population consists of sub-populations that differ in mortality characteristics and that the deceleration is the result of selective survival of stronger individuals. Here we describe an experiment that fractionates populations into several sub-populations without changing the physiological characteristics of the post-fractionated populations. Through a careful process of selection of Drosophila eggs, larvae, pupae and adults, we attempt to reduce as much as possible the degree of pre-adult, environmentally induced heterogeneity among individuals of a genetically identical cohort. We then ask whether such cohorts, when compared to non-fractionated populations, exhibit a lesser degree of mortality deceleration at advanced ages. From a total of 106 fractionated and control populations, consisting of 51 331 individuals, 101 populations (93% of the fractionated populations and 100% of the control populations) exhibit a significant amount of mortality deceleration late in life. These observations suggest that environmental heterogeneity accrued during larval development is not a major factor contributing to mortality deceleration at older ages.

Age-specific properties of spontaneous mutations affecting mortality in Drosophila melanogaster.

An analysis of the effects of spontaneous mutations affecting age-specific mortality was conducted using 29 lines of Drosophila melanogaster that had accumulated spontaneous mutations for 19 generations. Divergence among the lines was used to estimate the mutational variance for weekly mortality rates and the covariance between weekly mortality rates at different ages. Significant mutational variance was observed in both males and females early in life (up to approximately 30 days of age). Mutational variance was not significantly different from zero for mortality rates at older ages. Mutational correlations between ages separated by 1 or 2 wk were generally positive, but they declined monotonically with increasing separation such that mutational effects on early-age mortality were uncorrelated with effects at later ages. Analyses of individual lines revealed several instances of mutation-induced changes in mortality over a limited range of ages. Significant age-specific effects of mutations were identified in early and middle ages, but surprisingly, mortality rates at older ages were essentially unaffected by the accumulation procedure. Our results provide strong evidence for the existence of a class of polygenic mutations that affect mortality rates on an age-specific basis. The patterns of mutational effects measured here relate directly to recently published estimates of standing genetic variance for mortality in Drosophila, and they support mutation accumulation as a viable mechanism for the evolution of senescence.

Effect of density on age-specific mortality in Drosophila: a density supplementation experiment.

Age-specific mortality rates were studied at two adult density levels in four inbred lines of Drosophila melanogaster. In experimental populations, adult densities were maintained at constant levels throughout the experiment by replacing dead flies with live, marked mutants. In control populations, densities declined naturally as the cohorts aged. For all experimental populations the best mortality model is the two-stage Gompertz model, with slower mortality acceleration at older ages. Flies in the experimental populations generally lived longer than flies in control populations, regardless of sex, genotype, or initial density level. The data demonstrate that deceleration of age-specific mortality rates at older ages is not caused by declining cohort densities. Mortality deceleration is a real phenomenon that raises serious questions about the evolution of senescence.