Antioxidant response is a protective mechanism against nutrient deprivation in C. elegans

Endogenous hydrogen peroxide positively regulates secretion of a gut-derived peptide in neuroendocrine potentiation of the oxidative stress response in C. elegans

The gut-brain axis mediates bidirectional signaling between the intestine and the nervous system and is critical for organism-wide homeostasis. Here we report the identification of a peptidergic endocrine circuit in which bidirectional signaling between neurons and the intestine potentiates the activation of the antioxidant response in C. elegans in the intestine. We identify a FMRF-amide-like peptide, FLP-2, whose release from the intestine is necessary and sufficient to activate the intestinal oxidative stress response by promoting the release of the antioxidant FLP-1 neuropeptide from neurons. FLP-2 secretion from the intestine is positively regulated by endogenous hydrogen peroxide (H2O2) produced in the mitochondrial matrix by sod-3/superoxide dismutase, and is negatively regulated by prdx-2/peroxiredoxin, which depletes H2O2 in both the mitochondria and cytosol. H2O2 promotes FLP-2 secretion through the DAG and calciumdependent protein kinase C family member pkc-2 and by the SNAP25 family member aex-4 in the intestine. Together, our data demonstrate a role for intestinal H2O2 in promoting inter-tissue antioxidant signaling through regulated neuropeptide-like protein exocytosis in a gut-brain axis to activate the oxidative stress response.

Neuronal MML-1/MXL-2 regulates systemic aging via glutamate transporter and cell nonautonomous autophagic and peroxidase activity

Accumulating evidence has demonstrated the presence of intertissue-communication regulating systemic aging, but the underlying molecular network has not been fully explored. We and others previously showed that two basic helix-loop-helix transcription factors, MML-1 and HLH-30, are required for lifespan extension in several longevity paradigms, including germlineless Caenorhabditis elegans. However, it is unknown what tissues these factors target to promote longevity. Here, using tissue-specific knockdown experiments, we found that MML-1 and its heterodimer partners MXL-2 and HLH-30 act primarily in neurons to extend longevity in germlineless animals. Interestingly, however, the downstream cascades of MML-1 in neurons were distinct from those of HLH-30. Neuronal RNA interference (RNAi)-based transcriptome analysis revealed that the glutamate transporter GLT-5 is a downstream target of MML-1 but not HLH-30. Furthermore, the MML-1-GTL-5 axis in neurons is critical to prevent an age-dependent collapse of proteostasis and increased oxidative stress through autophagy and peroxidase MLT-7, respectively, in long-lived animals. Collectively, our study revealed that systemic aging is regulated by a molecular network involving neuronal MML-1 function in both neural and peripheral tissues.

Pathogen infection induces specific transgenerational modifications to gene expression and fitness in Caenorhabditis elegans

How pathogen infection in a parental generation affects response in future generations to the same pathogen via epigenetic modifications has been the topic of recent studies. These studies focused on changes attributed to transgenerational epigenetic inheritance and how these changes cause an observable difference in behavior or immune response in a population. However, we questioned if pathogen infection causes hidden epigenetic changes to fitness that are not observable at the population level. Using the nematode Caenorhabditis elegans as a model organism, we examined the generation-to-generation differences in survival of both an unexposed and primed lineage of animals against a human opportunistic pathogen Salmonella enterica. We discovered that training a lineage of C. elegans against a specific pathogen does not cause a significant change to overall survival, but rather narrows survival variability between generations. Quantification of gene expression revealed reduced variation of a specific member of the TFEB lipophagic pathway. We also provided the first report of a repeating pattern of survival times over the course of 12 generations in the control lineage of C. elegans. This repeating pattern indicates that the variability in survival between generations of the control lineage is not random but may be regulated by unknown mechanisms. Overall, our study indicates that pathogen infection can cause specific phenotypic changes due to epigenetic modifications, and a possible system of epigenetic regulation between generations.

Tangeretin Supplementation Mitigates the Aging Toxicity Induced by Dietary Benzo[a]pyrene Exposure with Aberrant Proteostasis and Heat Shock Responses in Caenorhabditis elegans

Benzo[a]pyrene (BaP) is a common food contaminant that can impair organismal aging. Tangeretin (TAN) may mitigate aging toxicities as a dietary supplement. This study used Caenorhabditis elegans to investigate the effects of chronic exposure to BaP on aging and to determine whether TAN supplementation could alleviate BaP-induced toxicity. Early life exposure to BaP (10 μM) significantly inhibited growth by 5%, and exposure to 0.1 to 10 μM BaP impaired C. elegans motility, resulting in a 3.4-6.5% reduction in motility. Chronic exposure to BaP (10 μM) age-dependently aggravated aberrant protein aggregation (7% increase) and shortened the median lifespan of the worms from 20 to 16 days. In addition, BaP worsened the age-dependent decline in motility and pharyngeal pumping, as well as the accumulation of reactive oxygen species. Furthermore, exposure to BaP resulted in significantly higher relative transcript levels of approximately 1.8-2.0-fold for the hsp-16.1, hsp-16.2, hsp-16.49, and hsp-70 genes. Stressed worms exposed to BaP exhibited significantly lower survival under heat stress. Dietary TAN supplementation alleviated the BaP-induced decline in motility, pumping, and poly-Q accumulation and restored heat shock proteins' transcript levels. Our findings suggest that chronic BaP exposure adversely affects aging and that TAN exposure mitigates the BaP-induced aging toxicity.

Comparative Analysis of Muscle Atrophy During Spaceflight, Nutritional Deficiency and Disuse in the Nematode Caenorhabditis elegans

While spaceflight is becoming more common than before, the hazards spaceflight and space microgravity pose to the human body remain relatively unexplored. Astronauts experience muscle atrophy after spaceflight, but the exact reasons for this and solutions are unknown. Here, we take advantage of the nematode C. elegans to understand the effects of space microgravity on worm body wall muscle. We found that space microgravity induces muscle atrophy in C. elegans from two independent spaceflight missions. As a comparison to spaceflight-induced muscle atrophy, we assessed the effects of acute nutritional deprivation and muscle disuse on C. elegans muscle cells. We found that these two factors also induce muscle atrophy in the nematode. Finally, we identified clp-4, which encodes a calpain protease that promotes muscle atrophy. Mutants of clp-4 suppress starvation-induced muscle atrophy. Such comparative analyses of different factors causing muscle atrophy in C. elegans could provide a way to identify novel genetic factors regulating space microgravity-induced muscle atrophy.

Examining Sporadic Cancer Mutations Uncovers a Set of Genes Involved in Mitochondrial Maintenance

Mitochondria are key organelles for cellular health and metabolism and the activation of programmed cell death processes. Although pathways for regulating and re-establishing mitochondrial homeostasis have been identified over the past twenty years, the consequences of disrupting genes that regulate other cellular processes, such as division and proliferation, on affecting mitochondrial function remain unclear. In this study, we leveraged insights about increased sensitivity to mitochondrial damage in certain cancers, or genes that are frequently mutated in multiple cancer types, to compile a list of candidates for study. RNAi was used to disrupt orthologous genes in the model organism Caenorhabditis elegans, and a series of assays were used to evaluate these genes' importance for mitochondrial health. Iterative screening of ~1000 genes yielded a set of 139 genes predicted to play roles in mitochondrial maintenance or function. Bioinformatic analyses indicated that these genes are statistically interrelated. Functional validation of a sample of genes from this set indicated that disruption of each gene caused at least one phenotype consistent with mitochondrial dysfunction, including increased fragmentation of the mitochondrial network, abnormal steady-state levels of NADH or ROS, or altered oxygen consumption. Interestingly, RNAi-mediated knockdown of these genes often also exacerbated α-synuclein aggregation in a C. elegans model of Parkinson's disease. Additionally, human orthologs of the gene set showed enrichment for roles in human disorders. This gene set provides a foundation for identifying new mechanisms that support mitochondrial and cellular homeostasis.

Dithianon exposure induces dopaminergic neurotoxicity in Caenorhabditis elegans

Dithianon is a conventional broad-spectrum protectant fungicide widely used in agriculture, but its potential neurotoxic risk to animals remains largely unknown. In this study, neurotoxic effects of Dithianon and its underlying cellular and molecular mechanisms were investigated using the nematode, Caenorhabditis elegans, as a model system. Upon chronic exposure of C. elegans to Dithianon, dopaminergic neurons were found to be vulnerable, with significant degeneration in terms of structure and function in a concentration-dependent manner. In examining toxicity mechanisms, we observed significant Dithianon-induced increases in oxidative stress and mitochondrial fragmentation, both of which are often associated with cellular stress. The present study suggests that Dithianon exposure causes dopaminergic neurotoxicity in C. elegans, by inducing oxidative stress and mitochondrial dysfunction. These findings contribute to a better understanding of Dithianon's neurotoxic potential.

Exposure to multi-walled carbon nanotubes causes suppression in octopamine signal associated with transgenerational toxicity induction in C.elegans

Multi-walled carbon nanotube (MWCNT), a kind of carbon-based nanomaterials, has been extensively utilized in a variety of fields. In Caenorhabditis elegans, MWCNT exposure can result in toxicity not only at parental generation (P0-G) but also in the offspring. However, the underlying mechanisms remain still largely unknown. DAF-12, a transcriptional factor (TF), was previously found to be activated and involved in transgenerational toxicity control after MWCNT exposure. In this study, we observed that exposure to 0.1-10 μg/L MWCNTs caused the significant decrease in expression of tbh-1 encoding a tyramine beta-hydroxylase with the function to govern the octopamine synthesis, suggesting the inhibition in octopamine signal. After exposure to 0.1 μg/L MWCNT, the decrease in tbh-1 expression could be also detected in F1-G and F2-G. Moreover, in germline cells, the TF DAF-12 regulated transgenerational MWCNT toxicity by suppressing expression and function of TBH-1. Meanwhile, exposure to 0.1-10 μg/L MWCNTs induced the increase in octr-1 expression and the decrease in ser-6 expression. After exposure to 0.1 μg/L MWCNT, the increased octr-1 expression and the decreased ser-6 expression were further observed in F1-G and F2-G. Germline TBH-1 controlled transgenerational MWCNT toxicity by regulating the activity of octopamine receptors (SER-6 and OCTR-1) in offspring. Furthermore, in the offspring, SER-6 and OCTR-1 affected the induction of MWCNT toxicity by upregulating or downregulating the level of ELT-2, a GATA TF. Taken together, these findings suggested possible link between alteration in octopamine related signals and MWCNT toxicity induction in offspring in organisms.

Acute Toxicity Evaluation of Phosphatidylcholine Nanoliposomes Containing Nisin in Caenorhabditis elegans

Liposomes are among the most studied nanostructures. They are effective carriers of active substances both in the clinical field, such as delivering genes and drugs, and in the food industry, such as promoting the controlled release of bioactive substances, including food preservatives. However, toxicological screenings must be performed to ensure the safety of nanoformulations. In this study, the nematode Caenorhabditis elegans was used as an alternative model to investigate the potential in vivo toxicity of nanoliposomes encapsulating the antimicrobial peptide nisin. The effects of liposomes containing nisin, control liposomes, and free nisin were evaluated through the survival rate, lethal dose (LD₅₀), nematode development rate, and oxidative stress status by performing mutant strain, TBARS, and ROS analyses. Due to its low toxicity, it was not possible to experimentally determine the LD₅₀ of liposomes. The survival rates of control liposomes and nisin-loaded liposomes were 94.3 and 73.6%, respectively. The LD₅₀ of free nisin was calculated as 0.239 mg mL^-1. Free nisin at a concentration of 0.2 mg mL^-1 significantly affected the development of C. elegans, which was 25% smaller than the control and liposome-treated samples. A significant increase in ROS levels was observed after exposure to the highest concentrations of liposomes and free nisin, coinciding with a significant increase in catalase levels. The treatments induced lipid peroxidation as evaluated by TBARS assay. Liposome encapsulation reduces the deleterious effect on C. elegans and can be considered a nontoxic delivery system for nisin.

Structure and biological evaluation of Caenorhabditis elegans CISD-1/mitoNEET, a KLP-17 tail domain homologue, supports attenuation of paraquat-induced oxidative stress through a p38 MAPK-mediated antioxidant defense response

CISD-1/mitoNEET is an evolutionarily conserved outer mitochondrial membrane [2Fe-2S] protein that regulates mitochondrial function and morphology. The [2Fe-2S] clusters are redox reactive and shown to mediate oxidative stress in vitro and in vivo. However, there is limited research studying CISD-1/mitoNEET mediation of oxidative stress in response to environmental stressors. In this study, we have determined the X-ray crystal structure of Caenorhabditis elegans CISD-1/mitoNEET homologue and evaluated the mechanisms of oxidative stress resistance to the pro-oxidant paraquat in age-synchronized populations by generating C. elegans gain and loss of function CISD-1 models. The structure of the C. elegans CISD-1/mitoNEET soluble domain refined at 1.70-Å resolution uniquely shows a reversible disulfide linkage at the homo-dimeric interface and also represents the N-terminal tail domain for dimerization of the cognate kinesin motor protein KLP-17 involved in chromosome segregation dynamics and germline development of the nematode. Moreover, overexpression of CISD-1/mitoNEET in C. elegans has revealed beneficial effects on oxidative stress resistance against paraquat-induced reactive oxygen species generation, corroborated by increased activation of the p38 mitogen-activated protein kinase (MAPK) signaling cascade.

The p38 MAPK/PMK-1 Pathway Is Required for Resistance to Nocardia farcinica Infection in Caenorhabditis elegance

Nocardia farcinica is an opportunistic pathogen that causes nocardiosis primarily in patients with compromised immune systems. In this study, we used the genetically tractable organism Caenorhabditis elegans as a model to study the innate immune responses to N. farcinica infection. We found that unlike other pathogenic bacteria such as Pseudomonas aeruginosa and Staphylococcus aureus, N. farcinica failed to kill adult worms. In another words, adult worms exposed to N. farcinica exhibited a normal lifespan, compared with those fed the standard laboratory food bacterium Escherichia coli OP50. Interestingly, deletion of three core genes (pmk-1, nsy-1 and sek-1) in the p38 MAPK/PMK-1 pathway reduced the survival of worm exposure to N. farcinica, highlighting a crucial role of this pathway for C. elegans in resistance to N. farcinica. Furthermore, our results revealed that N. farcinica exposure up-regulated the level of PMK-1 phosphorylation. The activation of PMK-1 promoted nuclear translocation of a transcription factor SKN-1/Nrf2, which in turn mediated N. farcinica infection resistance in C. elegans. Our results provide an excellent example that the integrity of immune system is key aspect for counteract with pathogenesis of N. farcinica.

Ferritin-mediated iron detoxification promotes hypothermia survival in Caenorhabditis elegans and murine neurons

How animals rewire cellular programs to survive cold is a fascinating problem with potential biomedical implications, ranging from emergency medicine to space travel. Studying a hibernation-like response in the free-living nematode Caenorhabditis elegans, we uncovered a regulatory axis that enhances the natural resistance of nematodes to severe cold. This axis involves conserved transcription factors, DAF-16/FoxO and PQM-1, which jointly promote cold survival by upregulating FTN-1, a protein related to mammalian ferritin heavy chain (FTH1). Moreover, we show that inducing expression of FTH1 also promotes cold survival of mammalian neurons, a cell type particularly sensitive to deterioration in hypothermia. Our findings in both animals and cells suggest that FTN-1/FTH1 facilitates cold survival by detoxifying ROS-generating iron species. We finally show that mimicking the effects of FTN-1/FTH1 with drugs protects neurons from cold-induced degeneration, opening a potential avenue to improved treatments of hypothermia.

Strategies to improve cold resistance are of potential biomedical interest. Here the authors demonstrate that ferritin-mediated detoxification of iron, preventing the generation of reactive oxygen species, promotes cold survival in both Caenorhabditis elegans and cultured mammalian neurons.

A Lactobacilli diet that confers MRSA resistance causes amino acid depletion and increased antioxidant levels in the C. elegans host

Probiotic bacteria are increasingly popular as dietary supplements and have the potential as alternatives to traditional antibiotics. We have recently shown that pretreatment with Lactobacillus spp. Lb21 increases the life span of C. elegans and results in resistance toward pathogenic methicillin-resistant Staphylococcus aureus (MRSA). The Lb21-mediated MRSA resistance is dependent on the DBL-1 ligand of the TGF-β signaling pathway. However, the underlying changes at the metabolite level are not understood which limits the application of probiotic bacteria as timely alternatives to traditional antibiotics. In this study, we have performed untargeted nuclear magnetic resonance-based metabolic profiling. We report the metabolomes of Lactobacillus spp. Lb21 and control E. coli OP50 bacteria as well as the nematode-host metabolomes after feeding with these diets. We identify 48 metabolites in the bacteria samples and 51 metabolites in the nematode samples and 63 across all samples. Compared to the control diet, the Lactobacilli pretreatment significantly alters the metabolic profile of the worms. Through sparse Partial Least Squares discriminant analyses, we identify the 20 most important metabolites distinguishing probiotics from the regular OP50 food and worms fed the two different bacterial diets, respectively. Among the changed metabolites, we find lower levels of essential amino acids as well as increased levels of the antioxidants, ascorbate, and glutathione. Since the probiotic diet offers significant protection against MRSA, these metabolites could provide novel ways of combatting MRSA infections.

Oxidative Stress Protection by Canary Seed (Phalaris canariensis L.) Peptides in Caco-2 Cells and Caenorhabditis elegans

During oxidative stress, degenerative diseases such as atherosclerosis, Alzheimer’s, and certain cancers are likely to develop. Recent research on canary seed (Phalaris canariensis) peptides has demonstrated the high in vitro antioxidant potential. Thus, this study aimed to assess the cellular and in vivo antioxidant capacity of a low-molecular-weight (<3 kDa) canary seed peptide fraction (CSPF) using Caco-2 cells and the Caenorhabditis elegans model. The results show that the CSPF had no cytotoxicity effect on Caco-2 cells at any tested concentration (0.3−2.5 mg/mL). Additionally, the cellular antioxidant activity (CAA) of the CSPF was concentration-dependent, and the highest activity achieved was 80% by the CSPF at 2.5 mg/mL. Similarly, incubation with the CSPF significantly mitigated the acute and chronic oxidative damage, extending the lifespan of the nematodes by 88 and 61%, respectively. Furthermore, it was demonstrated that the CSPF reduced the accumulation of reactive oxygen species (ROS) to safe levels after sub-lethal doses of pro-oxidant paraquat. Quantitative real-time PCR revealed that the CSPF increased the expression of oxidative-stress-response-related gene GST-4. Overall, these results show that the CSPFs relied on GST-4 upregulation and scavenging of free radicals to confer oxidative stress protection and suggest that a CSPF can be used as a natural antioxidant in foods for health applications.

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.

N-γ-(L-glutamyl)-L-selenomethionine shows neuroprotective effects against Parkinson's disease associated with SKN-1/Nrf2 and TRXR-1 in Caenorhabditis elegans

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative disease, yet fundamental treatments for the disease remain sparse. Thus, the search for potentially efficacious compounds from medicinal plants that can be used in the treatment of PD has gained significant interest.

PURPOSE

In many medicinal plants, selenium is primarily found in an organic form. We investigated the neuroprotective potential of an organic form of selenium, N-γ-(L-glutamyl)-L-selenomethionine (Glu-SeMet) in a Caenorhabditis elegans PD model and its possible molecular mechanisms.

METHODS

We used a C. elegans pharmacological PD strain (BZ555) that specifically expresses green fluorescent protein (GFP) in dopaminergic neurons and a transgenic PD strain (NL5901) that expresses human α-synuclein (α-syn) in muscle cells to investigate the neuroprotective potential of Glu-SeMet against PD.

RESULTS

We found that Glu-SeMet significantly ameliorated 6-hydroxydopamine (6-OHDA)-induced dopaminergic neuron damage in the transgenic BZ555 strain, with corresponding improvements in slowing behavior and intracellular ROS levels. In addition, compared with clinical PD drugs (L-DOPA and selegiline), Glu-SeMet demonstrated stronger ameliorated effects on 6-OHDA-induced toxicity. Glu-SeMet also triggered the nuclear translocation of SKN-1/Nrf2 and significantly increased SKN-1, GST-4, and GCS-1 mRNA levels in the BZ555 strain. However, Glu-SeMet did not increase mRNA levels or ameliorate the damage to dopaminergic neurons when the BZ555 strain was subjected to skn-1 RNA interference (RNAi). Glu-SeMet also upregulated the mRNA levels of the selenoprotein TRXR-1 in both the BZ555 and BZ555; skn-1 RNAi strains and significantly decreased α-syn accumulation in the NL5901 strain, although this was not observed in the NL5901; trxr-1 strain.

CONCLUSION

We found that Glu-SeMet has a neuroprotective effect against PD in a C. elegans PD model and that the anti-PD effects of Glu-SeMet were associated with SKN-1/Nrf2 and TRXR-1. Glu-SeMet may thus have the potential for use in therapeutic applications or supplements to slow the progression of PD.

Autophagy and the Lysosomal System in Cancer

Autophagy and the lysosomal system, together referred to as the autophagolysosomal system, is a cellular quality control network which maintains cellular health and homeostasis by removing cellular waste including protein aggregates, damaged organelles, and invading pathogens. As such, the autophagolysosomal system has roles in a variety of pathophysiological disorders, including cancer, neurological disorders, immune- and inflammation-related diseases, and metabolic alterations, among others. The autophagolysosomal system is controlled by TFEB, a master transcriptional regulator driving the expression of multiple genes, including autophagoly sosomal components. Importantly, Reactive Oxygen Species (ROS) production and control are key aspects of the physiopathological roles of the autophagolysosomal system, and may hold a key for synergistic therapeutic interventions. In this study, we reviewed our current knowledge on the biology and physiopathology of the autophagolysosomal system, and its potential for therapeutic intervention in cancer.

Mining nematode protein secretomes to explain lifestyle and host specificity

Parasitic nematodes are highly successful pathogens, inflicting disease on humans, animals and plants. Despite great differences in their life cycles, host preference and transmission modes, these parasites share a common capacity to manipulate their host's immune system. This is at least partly achieved through the release of excretory/secretory proteins, the most well-characterized component of nematode secretomes, that are comprised of functionally diverse molecules. In this work, we analyzed published protein secretomes of parasitic nematodes to identify common patterns as well as species-specific traits. The 20 selected organisms span 4 nematode clades, including plant pathogens, animal parasites, and the free-living species Caenorhabditis elegans. Transthyretin-like proteins were the only component common to all adult secretomes; many other protein classes overlapped across multiple datasets. The glycolytic enzymes aldolase and enolase were present in all parasitic species, but missing from C. elegans. Secretomes from larval stages showed less overlap between species. Although comparison of secretome composition across species and life-cycle stages is challenged by the use of different methods and depths of sequencing among studies, our workflow enabled the identification of conserved protein families and pinpointed elements that may have evolved as to enable parasitism. This strategy, extended to more secretomes, may be exploited to prioritize therapeutic targets in the future.

Assessment and Validation of Globodera pallida as a Novel In Vivo Model for Studying Alzheimer's Disease

BACKGROUND

Whole transgenic or non-transgenic organism model systems allow the screening of pharmacological compounds for protective actions in Alzheimer's disease (AD).

AIM

In this study, a plant parasitic nematode, Globodera pallida, which assimilates intact peptides from the external environment, was investigated as a new potential non-transgenic model system of AD. Methods: Fresh second-stage juveniles of G. pallida were used to measure their chemosensory, perform immunocytochemistry on their neurological structures, evaluate their survival rate, measure reactive oxygen species, and determine total oxidized glutathione to reduced glutathione ratio (GSSG/GSH) levels, before and after treatment with 100 µM of various amyloid beta (Aβ) peptides (1-40, 1-42, 17-42, 17-40, 1-28, or 1-16). Wild-type N2 C. elegans (strain N2) was cultured on Nematode Growth Medium and directly used, as control, for chemosensory assays.

RESULTS

We demonstrated that: (i) G. pallida (unlike Caenorhabditis elegans) assimilates amyloid-β (Aβ) peptides which co-localise with its neurological structures; (ii) pre-treatment with various Aβ isoforms (1-40, 1-42, 17-42, 17-40, 1-28, or 1-16) impairs G. pallida's chemotaxis to differing extents; (iii) Aβ peptides reduced survival, increased the production of ROS, and increased GSSG/GSH levels in this model; (iv) this unique model can distinguish differences between different treatment concentrations, durations, and modalities, displaying good sensitivity; (v) clinically approved neuroprotective agents were effective in protecting G. pallida from Aβ (1-42) exposure. Taken together, the data indicate that G. pallida is an interesting in vivo model with strong potential for discovery of novel bioactive compounds with anti-AD activity.

Stress increases in exopher-mediated neuronal extrusion require lipid biosynthesis, FGF, and EGF RAS/MAPK signaling

In human neurodegenerative diseases, neurons can transfer toxic protein aggregates to surrounding cells, promoting pathology via poorly understood mechanisms. In Caenorhabditis elegans, proteostressed neurons can expel neurotoxic proteins in large, membrane-bound vesicles called exophers. We investigated how specific stresses impact neuronal trash expulsion to show that neuronal exopher production can be markedly elevated by oxidative and osmotic stress. Unexpectedly, we also found that fasting dramatically increases exophergenesis. Mechanistic dissection focused on identifying nonautonomous factors that sense and activate the fasting-induced exopher response revealed that DAF16/FOXO-dependent and -independent processes are engaged. Fasting-induced exopher elevation requires the intestinal peptide transporter PEPT-1, lipid synthesis transcription factors Mediator complex MDT-15 and SBP-1/SREPB1, and fatty acid synthase FASN-1, implicating remotely initiated lipid signaling in neuronal trash elimination. A conserved fibroblast growth factor (FGF)/RAS/MAPK signaling pathway that acts downstream of, or in parallel to, lipid signaling also promotes fasting-induced neuronal exopher elevation. A germline-based epidermal growth factor (EGF) signal that acts through neurons is also required for exopher production. Our data define a nonautonomous network that links food availability changes to remote, and extreme, neuronal homeostasis responses relevant to aggregate transfer biology.

Changes in metabolism and antioxidant systems during tropical diapause in the sunflower caterpillar Chlosyne lacinia (Lepidoptera: Nymphalidae)

Insect diapause shares many biochemical features with other states of metabolic depression, including the suppression of global metabolism, reorganization of metabolic pathways and improved stress resistance. However, little is known about the biochemical changes associated with the diapause phenotype in tropical insects. To investigate biochemical adaptations associated with tropical diapause, we measured the activities of metabolic and antioxidant enzymes, as well as glutathione levels, in the sunflower caterpillar Chlosyne lacinia at different times after initiation of diapause (<1, 20, 40, 60, and 120 days) and after arousal from diapause. Biochemical changes occurred early in diapausing animals, between the first 24 h and 20 days of diapause. Diapausing animals had reduced oxidative capacity associated with a decrease in the activities of peroxide-decomposing antioxidant enzymes. There was no sign of redox imbalance either during diapause or after recovery from diapause. Noteworthy, glutathione transferase and isocitrate dehydrogenase-NADP⁺ activities sharply increased in diapausing animals and stand out as diapause-associated proteins. The upregulation of these two enzymes ultimately indicate the occurrence of Preparation for Oxidative Stress in the tropical diapause of C. lacinia.

Oxidative Stress and Antioxidant Defense Mechanisms in Response to Starvation and Refeeding in the Intestine of Stellate Sturgeon (Acipenser stellatus) Juveniles from Aquaculture

Simple Summary

The stellate sturgeon (Acipenser stellatus) is a critically endangered species due to multiple causes including human impact, with its valuable roe being used for caviar production. As a consequence, it is intensively raised in aquaculture for both conservation and economical purposes. Food deprivation can occur in both natural and aquaculture environments due to specific conditions that impose food restrictions (such us extreme temperatures, deterioration of water quality, pathological manifestations). The purpose of this study was to investigate the physiological adaptability of stellate sturgeon under two starvation/refeeding regimes. Therefore, the study had two objectives: to assess the effects of an alternative feeding regime on oxidative stress biomarkers and to assess the antioxidant defense mechanisms in juveniles raised in aquaculture. The results showed that the starvation/refeeding regimes induced lipid peroxidation and an enhancement of antioxidant enzymes activities in the intestine of stellate sturgeon juveniles. To conclude, Acipenser stellatus proved to possess a potential to adapt to a starvation/refeeding regime, the most suitable being a 7-day starvation period followed by 21 days of refeeding. This regime could be useful to optimize the feeding practice in aquaculture production in order to increase the profitability of fish farming without affecting the stellate sturgeon juveniles.

Abstract

Acipenser stellatus is a critically endangered species due to the anthropic influence. It has been intensively captured for decades because of its high economic value, its roe being used in the caviar industry. Therefore, Acipenser stellatus is intensively raised in fish farms for both conservation and economical purposes. Aquaculture aims to optimize the feeding regime of juveniles in order to improve its profitability. The purpose of this study was to investigate if Acipenser stellatus can adapt to a starvation/refeeding regime by assessing the effects of this regime on oxidative stress biomarkers and antioxidant defense mechanisms in juveniles raised under aquaculture conditions. The juveniles were subjected to two regimes: a 7-day starvation period followed by 21 days of refeeding, respectively a 14-day starvation period followed by 21 days of refeeding. The results showed that both starvation/refeeding regimes induced an enhancement of antioxidant enzymes activities in the intestine of the juveniles. The oxidative damage was counteracted at the protein level. However, lipid peroxidation was significantly induced in the intestine of the juveniles subjected to 14/21-day starvation/refeeding regime. The 7/21-day starvation/refeeding regime proved to be more suitable for Acipenser stellatus and therefore, it could be useful to optimize the feeding practice in aquaculture production.

Starvation Responses Throughout the Caenorhabditiselegans Life Cycle

Caenorhabditis elegans survives on ephemeral food sources in the wild, and the species has a variety of adaptive responses to starvation. These features of its life history make the worm a powerful model for studying developmental, behavioral, and metabolic starvation responses. Starvation resistance is fundamental to life in the wild, and it is relevant to aging and common diseases such as cancer and diabetes. Worms respond to acute starvation at different times in the life cycle by arresting development and altering gene expression and metabolism. They also anticipate starvation during early larval development, engaging an alternative developmental program resulting in dauer diapause. By arresting development, these responses postpone growth and reproduction until feeding resumes. A common set of signaling pathways mediates systemic regulation of development in each context but with important distinctions. Several aspects of behavior, including feeding, foraging, taxis, egg laying, sleep, and associative learning, are also affected by starvation. A variety of conserved signaling, gene regulatory, and metabolic mechanisms support adaptation to starvation. Early life starvation can have persistent effects on adults and their descendants. With its short generation time, C. elegans is an ideal model for studying maternal provisioning, transgenerational epigenetic inheritance, and developmental origins of adult health and disease in humans. This review provides a comprehensive overview of starvation responses throughout the C. elegans life cycle.

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.

Effects of Phosphoethanolamine Supplementation on Mitochondrial Activity and Lipogenesis in a Caffeine Ingestion Caenorhabditis elegans Model

Caffeine intake is strongly linked to lipid metabolism. We previously reported the age-dependent physiological effects of caffeine intake in a Caenorhabditis elegans model. Since nutritional status can actively influence metabolism and overall health, in this study, we evaluated the effect of caffeine intake on lipid metabolism in adult-stage C. elegans. We found that, in C. elegans, fat storage and the level of phosphoethanolamine (PE) were significantly reduced with caffeine intake. In addition, mitochondrial activity decreased and mitochondrial morphology was disrupted, and the expression of oxidative stress response genes, hsp-6, gst-4, and daf-16, was induced by caffeine intake. Furthermore, the level of an energy metabolism sensor, phospho-AMP-activated protein kinase, was increased, whereas the expression of the sterol regulatory element binding protein gene and its target stearoyl-CoA desaturase genes, fat-5, -6, and -7, was decreased with caffeine intake. These findings suggest that caffeine intake causes mitochondrial dysfunction and reduces lipogenesis. Interestingly, these changes induced by caffeine intake were partially alleviated by PE supplementation, suggesting that the reduction in mitochondrial activity and lipogenesis is in part because of the low PE level, and proper dietary supplementation can improve organelle integrity.

Nematicidal activity of 5-iodoindole against root-knot nematodes

Multi-drug resistance in nematodes is a serious problem as lately several resistant phenotypes have emerged following the intermittent usage of synthetic nematicides. Contemporary research continues to focus on developing and/or repurposing small molecule inhibitors that are eco-friendly. Here, we describe the repurposing of the indole derivative, 5-iodoindole, as a nematicide for the root-knot nematode, Meloidogyne incognita. 5-Iodoindole effectively killed juveniles and freshly hatched juveniles by inducing multiple vacuole formation. Notably, at higher dosage (50 μg/mL), 5-iodoindole induced rapid juvenile death within 6 h. Microscopic analysis confirmed that the rapid death was due to the generation of reactive oxygen species (ROS). Computational docking attributed this ROS production to the antagonistic effect of 5-iodoindole on glutathione S-transferase (GST), which is known to play a critical role in the suppression of ROS in nematode models. Furthermore, 5-iodoindole also effectively reduced the gall formations and eggs masses of M. incognita on Solanum lycopersicum roots in pot experiments, and importantly it did not harm the physiological properties of the plant. Overall, the study provides valuable insights on the use of 5-iodoindole as an alternate measure to control root-knot nematodes. Overall, our findings suggest the efficacy of 5-iodoindole should be studied under field conditions.

Sestrins as a Therapeutic Bridge between ROS and Autophagy in Cancer

The regulation of Reactive Oxygen Species (ROS) levels and the contribution therein from networks regulating cell metabolism, such as autophagy and the mTOR-dependent nutrient-sensing pathway, constitute major targets for selective therapeutic intervention against several types of tumors, due to their extensive rewiring in cancer cells as compared to healthy cells. Here, we discuss the sestrin family of proteins—homeostatic transducers of oxidative stress, and drivers of antioxidant and metabolic adaptation—as emerging targets for pharmacological intervention. These adaptive regulators lie at the intersection of those two priority nodes of interest in antitumor intervention—ROS control and the regulation of cell metabolism and autophagy—therefore, they hold the potential not only for the development of completely novel compounds, but also for leveraging on synergistic strategies with current options for tumor therapy and classification/stadiation to achieve personalized medicine.

Loss of miR-83 extends lifespan and affects target gene expression in an age-dependent manner in Caenorhabditis elegans

MicroRNAs (miRNAs) are short non-coding RNAs that are involved in the post-transcriptional regulation of protein-coding genes. miRNAs modulate lifespan and the aging process in a variety of organisms. In this study, we identified a role of miR-83 in regulating lifespan of Caenorhabditis elegans. mir-83 mutants exhibited extended lifespan, and the overexpression of miR-83 was sufficient to decrease the prolonged lifespan of the mutants. We observed upregulation of the expression levels of a set of miR-83 target genes in young mir-83 mutant adults; while different sets of genes were upregulated in older mir-83 mutant adults. In vivo assays showed that miR-83 regulated expression of target genes including din-1, spp-9 and col-178, and we demonstrated that daf-16 and din-1 were required for the extension of lifespan in the mir-83 mutants. The regulation of din-1 by miR-83 during aging resulted in the differential expression of din-1 targets such as gst-4 and gst-10. In daf-2 mutants, the expression level of miR-83 was significantly reduced compared to wild-type animals. We identified a role for miR-83 in modulating lifespan in C. elegans and provided molecular insights into its functional mechanism.

Oxytocin-like signaling in ants influences metabolic gene expression and locomotor activity

Ants are emerging model systems to study cellular signaling because distinct castes possess different physiologic phenotypes within the same colony. Here we studied the functionality of inotocin signaling, an insect ortholog of mammalian oxytocin (OT), which was recently discovered in ants. In Lasius ants, we determined that specialization within the colony, seasonal factors, and physiologic conditions down-regulated the expression of the OT-like signaling system. Given this natural variation, we interrogated its function using RNAi knockdowns. Next-generation RNA sequencing of OT-like precursor knock-down ants highlighted its role in the regulation of genes involved in metabolism. Knock-down ants exhibited higher walking activity and increased self-grooming in the brood chamber. We propose that OT-like signaling in ants is important for regulating metabolic processes and locomotion.-Liutkevičiūtė, Z., Gil-Mansilla, E., Eder, T., Casillas-Pérez, B., Di Giglio, M. G., Muratspahić, E., Grebien, F., Rattei, T., Muttenthaler, M., Cremer, S., Gruber, C. W. Oxytocin-like signaling in ants influences metabolic gene expression and locomotor activity.

Glial loss of the metallo β-lactamase domain containing protein, SWIP-10, induces age- and glutamate-signaling dependent, dopamine neuron degeneration

Across phylogeny, glutamate (Glu) signaling plays a critical role in regulating neural excitability, thus supporting many complex behaviors. Perturbed synaptic and extrasynaptic Glu homeostasis in the human brain has been implicated in multiple neuropsychiatric and neurodegenerative disorders including Parkinson's disease, where theories suggest that excitotoxic insults may accelerate a naturally occurring process of dopamine (DA) neuron degeneration. In C. elegans, mutation of the glial expressed gene, swip-10, results in Glu-dependent DA neuron hyperexcitation that leads to elevated DA release, triggering DA signaling-dependent motor paralysis. Here, we demonstrate that swip-10 mutations induce premature and progressive DA neuron degeneration, with light and electron microscopy studies demonstrating the presence of dystrophic dendritic processes, as well as shrunken and/or missing cell soma. As with paralysis, DA neuron degeneration in swip-10 mutants is rescued by glial-specific, but not DA neuron-specific expression of wildtype swip-10, consistent with a cell non-autonomous mechanism. Genetic studies implicate the vesicular Glu transporter VGLU-3 and the cystine/Glu exchanger homolog AAT-1 as potential sources of Glu signaling supporting DA neuron degeneration. Degeneration can be significantly suppressed by mutations in the Ca2+ permeable Glu receptors, nmr-2 and glr-1, in genes that support intracellular Ca2+ signaling and Ca2+-dependent proteolysis, as well as genes involved in apoptotic cell death. Our studies suggest that Glu stimulation of nematode DA neurons in early larval stages, without the protective actions of SWIP-10, contributes to insults that ultimately drive DA neuron degeneration. The swip-10 model may provide an efficient platform for the identification of molecular mechanisms that enhance risk for Parkinson's disease and/or the identification of agents that can limit neurodegenerative disease progression.