Aging in a very short-lived nematode

Climate change effects on terrestrial parasitic nematodes: Where are the knowledge gaps?

Climate change is expected to affect parasitic nematodes and hence possibly parasite-host dynamics and may have far-reaching consequences for animal health, livestock production, and ecosystem functioning. However, there has been no recent overview of current knowledge to identify how studies could contribute to a better understanding of terrestrial parasitic nematodes under changing climates. Here we screened almost 1,400 papers to review 57 experimental studies on the effects of temperature and moisture on hatching, development, survival, and behaviour of the free-living stages of terrestrial parasitic nematodes with a direct life cycle in birds and terrestrial mammals. Two major knowledge gaps are apparent. First, research should study the temperature dependency curves for hatching, development, and survival under various moisture treatments to test the interactive effect of temperature and moisture. Second, we specifically advocate for more studies that investigate how temperature, and its interaction with moisture, affect both vertical and horizontal movement of parasitic nematodes to understand infection risks. Overall, we advocate for more field experiments that test environmental effects on life-history traits and behaviour of parasitic nematodes in their free-living stages under natural and realistic circumstances. We also encourage studies to expand the range of used hosts and parasitic nematodes because 66% of results described in the available studies use sheep and cattle as hosts and 32% involve just three nematode species. This new comprehension brings attention to understudied abiotic impacts on terrestrial parasitic nematodes and will have broader implications for livestock management, wildlife conservation, and ecosystem functioning in a rapidly warming climate.

Gliadin nanoparticles for oral administration of bioactives: Ex vivo and in vivo investigations

This study aims to provide a thorough characterization of Brij O2-stabilized gliadin nanoparticles to be used for the potential oral administration of various compounds. Different techniques were used in order to evaluate their physico-chemical features and then in vivo studies in rats were performed for the investigation of their biodistribution and gastrointestinal transit profiles. The results showed that the gliadin nanoparticles accumulated in the mucus layer of the bowel mucosa and evidenced their ability to move along the digestive systems of the animals. The incubation of the nanosystems with Caenorhabditis elegans, used as an additional in vivo model, confirmed the intake of the particles and evidenced their presence along the entire gastrointestinal tract of these nematodes. The gliadin nanoparticles influenced neither the egg-laying activity of the worms nor their metabolism of lipids up to 10 μg/mL of nanoformulation. The systems decreased the content of the age-related lipofuscin pigment in the nematodes in a dose-dependent manner, demonstrating a certain antioxidant activity. Lastly, dihydroethidium staining showed the absence of oxidative stress upon incubation of the worms together with the formulations, confirming their safe profile. This data paves the way for the future application of the proposed nanosystems regarding the oral delivery of various bioactives.

Grifola frondosa (Maitake) Extract Reduces Fat Accumulation and Improves Health Span in C. elegans through the DAF-16/FOXO and SKN-1/NRF2 Signalling Pathways

In recent years, food ingredients rich in bioactive compounds have emerged as candidates to prevent excess adiposity and other metabolic complications characteristic of obesity, such as low-grade inflammation and oxidative status. Among them, fungi have gained popularity for their high polysaccharide content and other bioactive components with beneficial activities. Here, we use the C. elegans model to investigate the potential activities of a Grifola frondosa extract (GE), together with the underlying mechanisms of action. Our study revealed that GE represents an important source of polysaccharides and phenolic compounds with in vitro antioxidant activity. Treatment with our GE extract, which was found to be nongenotoxic through a SOS/umu test, significantly reduced the fat content of C. elegans, decreased the production of intracellular ROS and aging–lipofuscin pigment, and increased the lifespan of nematodes. Gene expression and mutant analyses demonstrated that the in vivo anti-obesity and antioxidant activities of GE were mediated through the daf-2/daf-16 and skn-1/nrf-2 signalling pathways, respectively. Taken together, our results suggest that our GE extract could be considered a potential functional ingredient for the prevention of obesity-related disturbances.

Bioactive extracts from persimmon waste: influence of extraction conditions and ripeness

In this work, a bioactive persimmon extract was produced from discarded fruits. A central composite design was used to evaluate the effect of different extraction parameters and ripeness stages of persimmon fruits on the total phenolic content and antioxidant activity of the resulting extracts. Significantly greater phenolic contents were obtained from immature persimmon (IP) fruits. The optimum IP extract with the conditions set by the experimental design was industrially up-scaled and its composition and functional properties were evaluated and compared with those obtained under lab-scale conditions. Both extracts contained significant protein (>20%) and phenolic contents (∼11-27 mg GA/g dry extract) and displayed significant antiviral activity against murine norovirus and hepatitis A virus. Moreover, the extract showed no toxicity and significantly reduced the fat content and the cellular ageing of Caenorhabditis elegans (C. elegans) without affecting the worm development. These effects were mediated by down-regulation of fat-7, suggesting an anti-lipogenic activity of this extract.

Phenolic Compounds Reduce the Fat Content in Caenorhabditis elegans by Affecting Lipogenesis, Lipolysis, and Different Stress Responses

Supplementation with bioactive compounds capable of regulating energy homeostasis is a promising strategy to manage obesity. Here, we have screened the ability of different phenolic compounds (myricetin, kaempferol, naringin, hesperidin, apigenin, luteolin, resveratrol, curcumin, and epicatechin) and phenolic acids (p-coumaric, ellagic, ferulic, gallic, and vanillic acids) regulating C. elegans fat accumulation. Resveratrol exhibited the strongest lipid-reducing activity, which was accompanied by the improvement of lifespan, oxidative stress, and aging, without affecting worm development. Whole-genome expression microarrays demonstrated that resveratrol affected fat mobilization, fatty acid metabolism, and unfolded protein response of the endoplasmic reticulum (UPRER), mimicking the response to calorie restriction. Apigenin induced the oxidative stress response and lipid mobilization, while vanillic acid affected the unfolded-protein response in ER. In summary, our data demonstrates that phenolic compounds exert a lipid-reducing activity in C. elegans through different biological processes and signaling pathways, including those related with lipid mobilization and fatty acid metabolism, oxidative stress, aging, and UPR-ER response. These findings open the door to the possibility of combining them in order to achieve complementary activity against obesity-related disorders.

The genome ofStrongyloidesspp. gives insights into protein families with a putative role in nematode parasitism

Parasitic nematodes are important and abundant parasites adapted to live a parasitic lifestyle, with these adaptations all aimed at facilitating their survival and reproduction in their hosts. The recently sequenced genomes of fourStrongyloidesspecies, gastrointestinal parasites of humans and other animals, alongside transcriptomic and proteomic analysis of free-living and parasitic stages of their life cycles have revealed a number of protein families with a putative role in their parasitism. Many of these protein families have also been associated with parasitism in other parasitic nematode species, suggesting that these proteins may play a fundamental role in nematode parasitism more generally. Here, we review key protein families that have a putative role inStrongyloides’ parasitism – acetylcholinesterases, astacins, aspartic proteases, prolyl oligopeptidases, proteinase inhibitors (trypsin inhibitors and cystatins), SCP/TAPS and transthyretin-like proteins – and the evidence for their key, yet diverse, roles in the parasitic lifestyle.

Germline organization in Strongyloides nematodes reveals alternative differentiation and regulation mechanisms

Nematodes of the genus Strongyloides are important parasites of vertebrates including man. Currently, little is known about their germline organization or reproductive biology and how this influences their parasitic life strategies. Here, we analyze the structure of the germline in several Strongyloides and closely related species and uncover striking differences in the development, germline organization, and fluid dynamics compared to the model organism Caenorhabditis elegans. With a focus on Strongyloides ratti, we reveal that the proliferation of germ cells is restricted to early and mid-larval development, thus limiting the number of progeny. In order to understand key germline events (specifically germ cell progression and the transcriptional status of the germline), we monitored conserved histone modifications, in particular H3Pser10 and H3K4me3. The evolutionary significance of these events is subsequently highlighted through comparisons with six other nematode species, revealing underlying complexities and variations in the development of the germline among nematodes.

Time till death affects spider mobility and web-building behavior during web construction in an orb-web spider

It is well known that age influences organism mobility. This was demonstrated in vertebrates (such as mammals and birds) but has been less studied in invertebrates with the exception of Drosophila and the nematode Caenorhabditis elegans. Here we studied the influence of age on the mobility of the orb-weaving spider Zygiella x-notata during web construction. The orb-web is a good model because it has a characteristic geometrical structure and video tracking can be used to easily follow the spider’s movements during web building. We investigated the influence of age (specifically chronological age, life span, and time till death) on different parameters of spider mobility during the construction of the capture spiral (distance traveled, duration of construction, spider velocity, spider movement, and spider inactivity) with a generalized linear model (GLM) procedure adjusted for the spider mass. The results showed that neither chronological age, nor life span affected the mobility parameters. However, when the time till death decreased, there was a decrease in the distance traveled, the duration of the construction of the capture spiral, and the spider movement. The spider velocity and the time of inactivity were not affected. These results could be correlated with a decrease in the length of the silky thread deposited for the construction of the capture spiral. Spiders with a shorter time till death built smaller web using less silk. Thus, our study suggests strongly that time till death affects spider mobility during web construction but not the chronological age and thus may be a good indicator of senescence.

Strongyloides ratti and S. venezuelensis - rodent models of Strongyloides infection

Strongyloides spp. are common parasites of vertebrates and two species, S. ratti and S. venezuelensis, parasitize rats; there are no known species that naturally infect mice. Strongyloides ratti and S. venezuelensis overlap in their geographical range and in these regions co-infections appear to be common. These species have been widely used as tractable laboratory systems in rats as well as mice. The core biology of these two species is similar, but there are clear differences in aspects of their within-host biology as well as in their free-living generation. Phylogenetic evidence suggests that S. ratti and S. venezuelensis are the result of two independent evolutionary transitions to parasitism of rats, which therefore presents an ideal opportunity to begin to investigate the basis of host specificity in Strongyloides spp.

Caenorhabditis elegans as model system in pharmacology and toxicology: effects of flavonoids on redox-sensitive signalling pathways and ageing

Flavonoids are secondary plant compounds that mediate diverse biological activities, for example, by scavenging free radicals and modulating intracellular signalling pathways. It has been shown in various studies that distinct flavonoid compounds enhance stress resistance and even prolong the life span of organisms. In the last years the model organism C. elegans has gained increasing importance in pharmacological and toxicological sciences due to the availability of various genetically modified nematode strains, the simplicity of modulating genes by RNAi, and the relatively short life span. Several studies have been performed demonstrating that secondary plant compounds influence ageing, stress resistance, and distinct signalling pathways in the nematode. Here we present an overview of the modulating effects of different flavonoids on oxidative stress, redox-sensitive signalling pathways, and life span in C. elegans introducing the usability of this model system for pharmacological and toxicological research.

Phenotypic plasticity in nematodes: Evolutionary and ecological significance

Model systems, including C. elegans, have been successfully studied to understand the genetic control of development. A genotype's phenotype determines its evolutionary fitness in natural environments, which are typically harsh, heterogeneous and dynamic. Phenotypic plasticity, the process by which one genome can produce different phenotypes in response to the environment, allows genotypes to better match their phenotype to their environment. Phenotypic plasticity is rife among nematodes, seen both as differences among life-cycles stages, perhaps best exemplified by parasitic nematodes, as well as developmental choices, such as shown by the C. elegans dauer/non-dauer developmental choice. Understanding the genetic basis of phenotypically plastic traits will probably explain the function of many genes whose function still remains unclear. Understanding the adaptive benefits of phenotypically plastic traits requires that we understand how plasticity differs among genotypes, and the effects of this in diverse, different environments.

Macroparasite life histories

Parasites and parasitism is common. Worm macroparasites have evolved life-history traits that allow them to successfully transmit between spatially and temporally separated patches of host resource and to survive within these environments. Macroparasites have common life-history strategies to achieve this, but these general themes are modified in a myriad of ways related to the specific biology of their hosts. Parasite life histories are also dynamic, responding to conditions inside and outside of hosts, and they continue to evolve, especially in response to our attempts to control them and the harm that they cause.

The effect of dichloroacetate on health- and lifespan in C. elegans

Aging is associated with increased vulnerability to chronic, degenerative diseases and death. Strategies for promoting healthspan without necessarily affecting lifespan or aging rate have gained much interest. The mitochondrial free radical theory of aging suggests that mitochondria and, in particular, age-dependent mitochondrial decline play a central role in aging, making compounds that affect mitochondrial function a possible strategy for the modulation of healthspan and possibly the aging rate. Here we tested such a "metabolic tuning" approach in nematodes using the mitochondrial modulator dichloroacetate (DCA). We explored DCA as a proof-of-principle compound to alter mitochondrial parameters in wild-type animals and tested whether this approach is suitable for reducing reactive oxygen species (ROS) production and for improving organismal health- and lifespan. In parallel, we addressed the potential problem of operator bias by running both unblinded and blinded lifespan studies. We found that DCA treatment (1) increased ATP levels without elevating oxidative protein damage and (2) reduced ROS production in adult C. elegans. DCA treatment also significantly prolonged nematode health- and lifespan, but did not strongly impact mortality doubling time. Operator blinding resulted in considerably smaller lifespan-extending effects of DCA. Our data illustrate the promise of a "metabolic tuning" intervention strategy, emphasize the importance of mitochondria in nematode aging and highlight operator bias as a potential confounder in lifespan studies.

Transcript profiles of long- and short-lived adults implicate protein synthesis in evolved differences in ageing in the nematode Strongyloides ratti

The nematode Strongyloides ratti shows remarkable phenotypic plasticity in ageing, with parasitic adults living at least 80-times longer than free-living adults. Given that long- and short-lived adults are genetically identical, this plasticity is likely to be due to differences in gene expression. To try and understand how this inter-morph difference in longevity evolved, we compared gene expression in long- and short-lived adults. DNA microarray analysis of long- and short-lived adults identified 32 genes that were up-regulated in long-lived adults, and 96 genes up-regulated in short-lived adults. Strikingly, 38.5% of the genes expressed more in the short-lived morph are predicted to encode ribosomal proteins, compared with only 9% in the long-lived morph. Among the 32 longevity-associated genes there was very little enrichment of genes linked to cellular maintenance. Overall, we have therefore observed a negative correlation between expression of ribosomal protein genes and longevity in S. ratti. Interestingly, engineered reduction of expression of ribosomal protein genes increases lifespan in the free-living nematode Caenorhabditis elegans. Our study therefore suggests that differences in levels of protein synthesis could contribute to evolved differences in animal longevity.

Mixed pulmonary infection with Strongyloides stercoralis and Blastomyces dermatitidis

We report the first case of mixed pulmonary infection with Strongyloides stercoralis and Blastomyces dermatitidis. Histopathology from the lung biopsy showed structures consistent with B. dermatitidis and S. stercoralis. A parasitology exam from a bronchi alveolar lavage yielded an immature rhabditiform larva and female worm. Fungal cultures grew B. dermatitidis.

Extraordinary plasticity in aging in Strongyloides ratti implies a gene-regulatory mechanism of lifespan evolution

Aging evolves as the result of weakened selection against late-acting deleterious alleles due, for example, to extrinsic mortality. Comparative studies of aging support this evolutionary theory, but details of the genetic mechanisms by which lifespan evolves remain unclear. We have studied aging in an unusual nematode, Strongyloides ratti, to gain insight into the nature of these mechanisms, in this first detailed examination of aging in a parasitic nematode. S. ratti has distinct parasitic and free-living adults, living in the rat small intestine and the soil, respectively. We have observed reproductive and demographic aging in parasitic adults, with a maximum lifespan of 403 days. By contrast the maximum lifespan of free-living adults is only 5 days. Thus, the two adults of S. ratti have evolved strikingly different rates of aging. Parasitic nematode species are frequently longer-lived than free-living species, presumably reflecting different extrinsic mortality rates in their respective niches. Parasitic and free-living female S. ratti are morphologically different, yet genetically identical. Thus, the 80-fold difference in their lifespans, the greatest plasticity in aging yet reported, must largely reflect evolved differences in gene expression. This suggests that interspecific differences in lifespan may evolve via similar mechanisms.

Caenorhabditis elegans as a screening tool for the endothelial cell-derived putative aging-related proteins detected by proteomic analysis

Endothelial cells go through progressive pathophysiologic modification as cellular senescence progresses. In vitro, endothelial cell senescence is accompanied by failure of proliferation and by perturbations in gene and protein expressions. Moreover, this cellular senescence in culture has been proposed to reflect processes that occur in the organism in vivo and free radical theory is accepted to be the most plausible explanation for this process. We have screened proteins involved in both cellular senescence and reactive oxygen species induced condition using 2-D gel analysis and found that ubiquitin carboxyl terminal hydrolase L1, peroxyredoxin 2, peroxyredoxin 4, fatty acid binding proteins (FABPs), and 5'-AMP-activated protein kinase beta-1 subunit were candidate aging-related proteins. To evaluate in vivo function of these proteins, Caenorhabditis elegans (C. elegans) knock-down system using RNA interference was applied. Aging-specific expression of lipofucsin and the lifespan of knocked-down C. elegans were observed to assess the outcome. Interestingly, the inhibition of the genes led to short lifespan and earlier accumulation of lipofucsin with increasing age when compared with the wild type. These results suggest that the above genes may be related to cellular senescence process in determining the longevity in C. elegans and that gene inactivation renders animals susceptible to oxidative stress.

Beyond the evolutionary theory of ageing, from functional genomics to evo-gero

By the mid 1970s, the mechanisms by which ageing can evolve had a secure theoretical basis in population genetics. Here, we discuss how subsequent evolutionary work has focussed on testing and extending this theory, and on attempting to integrate it with other emerging facets of the biology of ageing, such as genetic studies of long-lived mutants and of phenotypic plasticity in ageing, such as in response to nutritional status. We also describe how functional genomic studies are providing new insights into the evolutionary forces shaping genome evolution and lifespan control. Future challenges include understanding the biochemistry of longevity and how its failure generates ageing and associated diseases, and the determination of the genetic basis of lifespan evolution and the great plasticity that it displays.

Parastrongyloides trichosuri, a nematode parasite of mammals that is uniquely suited to genetic analysis

Commonly studied nematode parasites have not proven amenable to simple genetic analyses and this has significantly reduced the available research options. We introduce here a nematode parasite of mammals, Parastrongyloides trichosuri, which has features uniquely suited for genetic analysis. This parasite has the capacity to undergo multiple reproductive cycles as a free-living worm and thereby amplify the numbers of its infective L3s in faeces. Culture conditions are presented that permit facile laboratory maintenance of this worm for >90 free-living life cycles (to date) without the need for re-entry into a permissive host. Even after long maintenance as a free-living worm, culture conditions can be manipulated to favour development of infective L3 worms, which remain able to successfully infect their marsupial hosts. The switch to infective L3 development is triggered by a secreted factor contained in culture medium conditioned by multiple generations of free-living worm culture. It is simple to perform single pair crosses with P. trichosuri to carry out Mendelian genetics in the laboratory and this has been done multiple times with sibling pairs to generate highly inbred lines. Lines of worms can readily be cryopreserved and recovered. Over 7000 expressed sequence tags have been produced from cDNAs at different life cycle stages and used to identify single nucleotide polymorphisms and microsatellites as genetic markers. Free-living worms live only a few days on average while the patency of parasitic infections can last for several months. Since we show this is not the result of re-infection, we conclude that parasitic worms have a lifespan capacity at least 20-30 times longer than their free-living counterparts. We discuss how it should be possible to exploit these unique features of P. trichosuri as a model for future studies that explore the genetic basis of longevity and parasitism.

What are the effects of maternal and pre-adult environments on ageing in humans, and are there lessons from animal models?

An open issue in research on ageing is the extent to which responses to the environment during development can influence variability in life span in animals, and the health profile of the elderly in human populations. Both affluence and adversity in human societies have profound impacts on survivorship curves, and some of this effect may be traceable to effects in utero or in infancy. The Barker Hypothesis that links caloric restriction in very early life to disruptions of glucose-insulin metabolism in later life has attracted much attention, as well as some controversy, in medical circles. It is only rarely considered by evolutionary biologists working on phenotypic plasticity, or by biogerontologists studying model organisms such as C. elegans or Drosophila. One crucial mechanism by which animals can respond in an adaptive manner to adverse conditions, for example in nutrition or infection, during development is phenotypic plasticity. Here we begin with a discussion of adaptive plasticity in animals before asking what such phenomena may reveal of relevance to rates of ageing in animals, and in humans. We survey the evidence for effects on adult ageing of environmental conditions during development across mammalian and invertebrate model organisms, and ask whether evolutionary conserved mechanisms might be involved. We conclude that the Barker Hypothesis is poorly supported and argue that more work in human populations should be integrated with multi-disciplinary studies of ageing-related phenomena in experimental populations of different model species that are subjected to nutritional challenges or infections during pre-adult development.