Caenorhabditis elegans OSR-1 regulates behavioral and physiological responses to hyperosmotic environments

Model biological systems demonstrate the inducibility of pathways that strongly reduce cryoprotectant toxicity

Cryoprotectant toxicity is a limiting factor for the cryopreservation of many living systems. We were moved to address this problem by the potential of organ vitrification to relieve the severe shortage of viable donor organs available for human transplantation. The M22 vitrification solution is presently the only solution that has enabled the vitrification and subsequent transplantation with survival of large mammalian organs, but its toxicity remains an obstacle to organ stockpiling for transplantation. We therefore undertook a series of exploratory studies to identify potential pretreatment interventions that might reduce the toxic effects of M22. Hormesis, in which a living system becomes more resistant to toxic stress after prior subtoxic exposure to a related stress, was investigated as a potential remedy for M22 toxicity in yeast, in the nematode worm C. elegans, and in mouse kidney slices. In yeast, heat shock pretreatment increased survival by 18-fold after exposure to formamide and by over 9-fold after exposure to M22 at 30 °C; at 0 °C and with two-step addition, treatment with 90% M22 resulted in 100% yeast survival. In nematodes, surveying a panel of pretreatment interventions revealed 3 that conferred nearly total protection from acute whole-worm M22-induced damage. One of these protective pretreatments (exposure to hydrogen peroxide) was applied to mouse kidney slices in vitro and was found to strongly protect nuclear and plasma membrane integrity in both cortical and medullary renal cells exposed to 75-100% M22 at room temperature for 40 min. These studies demonstrate for the first time that endogenous cellular defenses, conserved from yeast to mammals, can be marshalled to substantially ameliorate the toxic effects of one of the most toxic single cryoprotectants and the toxicity of the most concentrated vitrification solution so far described for whole organs.

Adenylosuccinate lyase deficiency affects neurobehavior via perturbations to tyramine signaling in Caenorhabditis elegans

Adenylosuccinate lyase deficiency is an ultrarare congenital metabolic disorder associated with muscle weakness and neurobehavioral dysfunction. Adenylosuccinate lyase is required for de novo purine biosynthesis, acting twice in the pathway at non-sequential steps. Genetic models can contribute to our understanding of the etiology of disease phenotypes and pave the way for development of therapeutic treatments. Here, we establish the first model to specifically study neurobehavioral aspects of adenylosuccinate lyase deficiency. We show that reduction of adsl-1 function in C. elegans is associated with a novel learning phenotype in a gustatory plasticity assay. The animals maintain capacity for gustatory plasticity, evidenced by a change in their behavior in response to cue pairing. However, their behavioral output is distinct from that of control animals. We link substrate accumulation that occurs upon adsl-1 deficiency to an unexpected perturbation in tyrosine metabolism and show that a lack of tyramine mediates the behavioral changes through action on the metabotropic TYRA-2 tyramine receptor. Our studies reveal a potential for wider metabolic perturbations, beyond biosynthesis of purines, to impact behavior under conditions of adenylosuccinate lyase deficiency.

Stress tolerance in entomopathogenic nematodes: Engineering superior nematodes for precision agriculture

Entomopathogenic nematodes (EPNs) are soil-dwelling parasitic roundworms commonly used as biocontrol agents of insect pests in agriculture. EPN dauer juveniles locate and infect a host in which they will grow and multiply until resource depletion. During their free-living stage, EPNs face a series of internal and environmental stresses. Their ability to overcome these challenges is crucial to determine their infection success and survival. In this review, we provide a comprehensive overview of EPN response to stresses associated with starvation, low/elevated temperatures, desiccation, osmotic stress, hypoxia, and ultra-violet light. We further report EPN defense strategies to cope with biotic stressors such as viruses, bacteria, fungi, and predatory insects. By comparing the genetic and biochemical basis of these strategies to the nematode model Caenorhabditis elegans, we provide new avenues and targets to select and engineer precision nematodes adapted to specific field conditions.

A germline-targeted genetic screen for xrn-2 suppressors identifies a novel gene C34C12.2 in Caenorhabditis elegans

XRN2 is an evolutionarily conserved 5'-to-3' exoribonuclease, which degrades or trims various types of RNA in the nucleus. Although XRN-2 is essential for embryogenesis, larval development and reproduction in Caenorhabditis elegans, relevant molecular pathways remain unidentified. Here we create a germline-specific xrn-2 conditional mutant and perform a mutagenesis screen for suppressors of sterility. Loss-of-function alleles of dpy-10, osr-1, ptr-6 and C34C12.2 genes are identified. Depletion of DPY-10, OSR-1 or PTR-6 increases expression of gpdh-1 that encodes a glycerol-3-phosphate dehydrogenase, thereby elevates glycerol accumulation to suppress sterility of the mutant. The C34C12.2 protein is predominantly localized in the nucleolus of germ cells and shows a similarity to Saccharomyces cerevisiae Net1, which is involved in rDNA silencing. Depletion of NRDE-2, a putative interacting partner of C34C12.2 and a component of the nuclear RNAi machinery, restores fertility to the xrn-2 conditional mutant. These results may help to identify an essential role of XRN-2 in germline development.

The Strongyloides bioassay toolbox: A unique opportunity to accelerate functional biology for nematode parasites

Caenorhabditis elegans is a uniquely powerful tool to aid understanding of fundamental nematode biology. While C. elegans boasts an unrivalled array of functional genomics tools and phenotype bioassays the inherent differences between free-living and parasitic nematodes underscores the need to develop these approaches in tractable parasite models. Advances in functional genomics approaches, including RNA interference and CRISPR/Cas9 gene editing, in the parasitic nematodes Strongyloides ratti and Strongyloides stercoralis provide a unique and timely opportunity to probe basic parasite biology and reveal novel anthelmintic targets in species that are both experimentally and therapeutically relevant pathogens. While Strongyloides functional genomics tools have progressed rapidly, the complementary range of bioassays required to elucidate phenotypic outcomes post-functional genomics remain more limited in scope. To adequately support the exploitation of functional genomic pipelines for studies of gene function in Strongyloides a comprehensive set of species- and parasite-specific quantitative bioassays are required to assess nematode behaviours post-genetic manipulation. Here we review the scope of the current Strongyloides bioassay toolbox, how established Strongyloides bioassays have advanced knowledge of parasite biology, opportunities for Strongyloides bioassay development and, the need for investment in tractable model parasite platforms such as Strongyloides to drive the discovery of novel targets for parasite control.

Nicandra physalodes Extract Exerts Antiaging Effects in Multiple Models and Extends the Lifespan of Caenorhabditis elegans via DAF-16 and HSF-1

The development of safe and effective therapeutic interventions is an important issue for delaying aging and reducing the risk of aging-related diseases. Chinese herbal medicines for the treatment of aging and other complex diseases are desired due to their multiple components and targets. Through screening for effects on lifespan of 836 Chinese herbal medicine extracts, Nicandra physalodes extract (HL0285) was found to exhibit lifespan extension activity in Caenorhabditis elegans (C. elegans). In further experiments, HL0285 improved healthspan, enhanced stress resistance, and delayed the progression of neurodegenerative diseases in C. elegans. Additionally, it ameliorated senescence in human lung fibroblasts (MRC-5 cells) and reversed liver function damage and reduced senescence marker levels in doxorubicin- (Dox-) induced aging mice. In addition, the longevity effect of HL0285 in C. elegans was dependent on the DAF-16 and HSF-1 signaling pathways, as demonstrated by the results of the mutant lifespan, gene level, and GFP level assays. In summary, we discovered that HL0285 had an antiaging effect in C. elegans, MRC-5 cells, and Dox-induced aging mice and deserves to be explored in the future studies on antiaging agents.

Dicarbonyl/L-xylulose reductase (DCXR) producing xylitol regulates egg retention through osmolality control in Caenorhabditis elegans

To support life, the osmolality of the cellular fluid is tightly regulated by various means, including osmolyte control. Dicarbonyl/L-xylulose reductase (DCXR) is a highly conserved enzyme reducing L-xylulose to xylitol, which serves as an effective osmolyte in various mammalian and human tissues such as lung epithelium, sperm, and lens. DHS-21 is the only DCXR ortholog in Caenorhabditis elegans, and DCXR null mutant worms accumulate eggs in the uterus. However, it has been unknown how and why the mutant worms impair egg retention. In this study, we tested whether the egg-retention in dhs-21 (jh129), the DCXR null mutant worm, is sensitive to changes in osmolarity. Low osmolality reverted the egg retention phenotype of dhs-21(jh129), while high osmolarity aggravated it. Also, knock-down of either one of osr-1, osm-7, or osm-11, osmoregulatory genes, also rescued egg-retention phenotypes of the null mutants. The study indicates that DCXR functions in fluid homeostasis by regulating cellular osmolality in C. elegans and provides insights into DCXR-involved clinical conditions, such as congenital cataracts and malfunctioning lung and kidney.

Caenorhabditis elegans DAF-16 regulates lifespan and immune responses to Cryptococcus neoformans and Cryptococcus gattii infections

Background

Cryptococcosis is a life-threatening infection is primarily caused by two sibling species Cryptococcus neoformans and Cryptococcus gattii. Several virulence-related factors of these cryptococci have been widely investigated in Caenorhabditis elegans, representing a facile in vivo model of host–pathogen interaction. While recent studies elucidated cryptococcal virulence factors, intrinsic host factors that affect susceptibility to infections by cryptococci remain unclear and poorly investigated.

Results

Here, we showed that defects in C. elegans insulin/insulin-like growth factor-1 (IGF-1) signaling (IIS) pathway influenced animal lifespan and mechanisms of host resistance in cryptococcal infections, which required the activation of aging regulator DAF-16/Forkhead box O transcription factor. Moreover, accumulation of lipofuscin, DAF-16 nuclear localization, and expression of superoxide dismutase (SOD-3) were elevated in C. elegans due to host defenses during cryptococcal infections.

Conclusion

The present study demonstrated the relationship between longevity and immunity, which may provide a possibility for novel therapeutic intervention to improve host resistance against cryptococcal infections.

Nematodes as Ghosts of Land Use Past: Elucidating the Roles of Soil Nematode Community Studies as Indicators of Soil Health and Land Management Practices

Soil health is a matter of growing concern because of its degradation due to unsustainable anthropogenic activities over the last few decades. It is maintained by interactions among the components of the soil food web commonly concentrated in the vicinity of the plant roots, called the rhizosphere. The soil food web is dominated by nematodes. They occupy various trophic positions because of their diverse feeding habits. The free-living forms are mainly dependent on soil bacteria and fungi for their nutrition, while the parasitic forms feed on plant roots. The population of these two groups is regulated by the activities of predatory nematodes which can be carnivorous or omnivorous. The soil nematodes thereby partake responsibilities in nutrient cycling, mineralization and decomposition pathways which, in turn, affects the aboveground productivity. This intricately connected food web structure is vulnerable to disturbances like increased soil salinity, acidity, nitrogen enrichment, tillage, crop rotations, fertilizers, pesticides, soil amendment techniques and heavy metal pollution. The effects are reflected by alterations in the abundance and diversity of soil nematodes belonging to various trophic groups. These alterations have been formulated into measurable indices like maturity index (MI), structure index (SI), enrichment index (EI) and channel index (CI). The faunal profile and metabolic footprints of soil nematodes are latest developments in the field of nematode community analyses. Though these indices cannot replace the conventional soil ecotoxicological assays, they can give added information about soil biology which can be utilized to design sustainable land use practices.

An extracellular matrix damage sensor signals through membrane-associated kinase DRL-1 to mediate cytoprotective responses in Caenorhabditis elegans

We and others previously identified circumferential bands of collagen named annular furrows as key components of a damage sensor in the cuticle of Caenorhabditis elegans that regulates cytoprotective genes. Mutation or loss of non-collagen secreted proteins OSM-7, OSM-8, and OSM-11 activate the same cytoprotective responses without obvious changes to the cuticle indicating that other extracellular proteins are involved. Here, we used RNAi screening to identify protein kinase DRL-1 as a key modulator of cytoprotective gene expression and stress resistance in furrow and extracellular OSM protein mutants. DRL-1 functions downstream from furrow disruption and is expressed in cells that induce cytoprotective genes. DRL-1 is not required for expression of cytoprotective genes under basal or oxidative stress conditions consistent with specificity to extracellular signals. DRL-1 was previously shown to regulate longevity via a 'Dietary Restriction-Like' state, but it functions downstream from furrow disruption by a distinct mechanism. The kinase domain of DRL-1 is related to mammalian MEKK3, and MEKK3 is recruited to a plasma membrane osmosensor complex by a scaffold protein. In C. elegans, DRL-1 contains an atypical hydrophobic C-terminus with predicted transmembrane domains and is constitutively expressed at or near the plasma membrane where it could function to receive extracellular damage signals for cells that mount cytoprotective responses.

The triterpenoid ursolic acid ameliorates stress in Caenorhabditis elegans by affecting the depression-associated genes skn-1 and prdx2

INTRODUCTION

Depression is one of the leading causes of death worldwide. Lower antioxidant concentrations and increased oxidative stress levels contribute to the development of depression. Effective and tolerable medications are urgently needed. Nrf2 and PRDX2 are promising targets in the treatment of oxidative stress and, therefore, promising for the development of novel antidepressants. Ursolic acid (UA), a natural triterpenoid found in various plants is known to exert neuroprotective and antioxidant effects. Skn-1 (which corresponds to human Nrf2) and prdx2 deficient mutants of the nematode Caenorhabditis elegans are suitable models to study the effect of UA on these targets. Additionally, stress assays are used to mimic stress or depressed state.

METHODS

We examined the antioxidant activity of UA in Caenorhabditis elegans wildtype and skn-1- and prdx2-deficient strains by H2DCF-DA and juglone assays as well as osmotic and heat stress assays. Additionally, we analyzed the binding of UA to human PRDX2 and Skn-1 proteins by molecular docking and microscale thermophoresis.

RESULTS

UA exerted strong antioxidant activities. Additionally, induction of stress resistance towards osmotic and heat stress was observed. qRT-PCR revealed that UA upregulated the gene expression of skn-1 and prdx2. Molecular docking studies supported these findings.

CONCLUSION

Our findings implicate that the strong antioxidant activity of UA may exert anti-depressive effects by its interaction with the Skn-1 transcription factor, which is part of a detoxification network, and the antioxidant PRDX2 protein, which protects the organism from the detrimental effects of radical oxygen species.

Red Cabbage Rather Than Green Cabbage Increases Stress Resistance and Extends the Lifespan of Caenorhabditis elegans

Many studies have demonstrated that cabbages possess various biological activities, and our previous studies confirmed that cyanidin-3-diglucoside-5-glucoside (CY3D5G), the major core of red cabbage anthocyanins, exhibited in vitro antioxidant activity. This study further investigated the protective effects of CY3D5G derivative from red cabbage juice (RCJ) on oxidative stress and lifespan in cells and Caenorhabditis elegans, green cabbage juice (GCJ) was used as control. RCJ rather than GCJ significantly improved cell viability and decreased lactate dehydrogenase release in H₂O₂-induced caco-2 cells. RCJ significantly increased survival during oxidative and heat stress and mean lifespan in C. elegans by 171.63% and 31.64%, and 28.16%, respectively, while GCJ treatment showed no significant effects (p < 0.05). These results might be attributed to significantly (p < 0.05) higher contents of total phenolics, ascorbic acid, glucosinolates, and anthocyanins in RCJ compared to those in GCJ. Additionally, both of them decreased autofluorescence and reproductive capacity, increased body length, but did not alter the intracellular ROS level. Prolonged lifespan by RCJ might require heat-shock transcription factor pathway, sirtuin signaling, and calmodulin kinase II pathway, independent of insulin/insulin-like growth factor-1 signaling pathway. RCJ showed promising antioxidant properties in caco-2 cells and C. elegans, which provided more information on the health benefits of cabbage.

G-Protein-Coupled Receptor SRBC-48 Protects against Dendrite Degeneration and Reduced Longevity Due to Infection

Increasing evidence suggests that deficient immune modulation and microbial infections underline neurodegeneration, but the mechanisms remain obscure. Here, we show that the G-protein-coupled receptor (GPCR) SRBC-48, which belongs to the class BC serpentine receptors, has a protective role in Caenorhabditis elegans dendrite degeneration caused by Pseudomonas aeruginosa infection. Our results indicate that SRBC-48 functions in a cell-autonomous manner in AWC neurons to protect against infection-associated dendrite degeneration. The absence of SRBC-48 results in a reduced lifespan caused by a pathogen infection early in life that induces dendrite degeneration. The decreased longevity in animals deficient in SRBC-48 is due to uncontrolled activation of immune genes, particularly those regulated by the FOXO family transcription factor DAF-16 that is part of the insulin/insulin-like growth factor (IGF)-1 receptor homolog DAF-2. These results reveal how an infection early in life can not only induce dendrite degeneration but also reduce lifespan.

Withanone Ameliorates Stress Symptoms in Caenorhabditis Elegans by Acting through Serotonin Receptors

INTRODUCTION

Depression is responsible for 800 000 deaths worldwide, a number that will rise significantly due to the COVID-19 pandemic. Affordable novel drugs with less severe side effects are urgently required. We investigated the effect of withanone (WN) from Withania somnifera on the serotonin system of wild-type and knockout Caenorhabditis elegans strains using in silico, in vitro, and in vivo methods.

METHODS

WN or fluoxetine (as positive control drug) was administered to wild-type (N2) and knockout C. elegans strains (AQ866, DA1814, DA2100, DA2109, and MT9772) to determine their effect on oxidative stress (Trolox, H₂DCFDA, and juglone assays) on osmotic stress and heat stress and lifespan. Quantitative real-time RT-PCR was applied to investigate the effect of WN or fluoxetine on the expression of serotonin receptors (ser-1, ser-4, ser-7) and serotonin transporter (mod-5). The binding affinity of WN to serotonin receptors and transporter was analyzed in silico using AutoDock 4.2.6.

RESULTS

WN scavenged ROS in wild-type and knockout C. elegans and prolonged their lifespan. WN upregulated the expression of serotonin receptor and transporter genes. In silico analyses revealed high binding affinities of WN to Ser-1, Ser-4, Ser-7, and Mod-5.

LIMITATIONS

Further studies are needed to prove whether the results from C. elegans are transferrable to mammals and human beings.

CONCLUSION

WN ameliorated depressive-associated stress symptoms by activating the serotonin system. WN may serve as potential candidate in developing new drugs to treat depression.

Induction of stress resistance and extension of lifespan in Chaenorhabditis elegans serotonin-receptor knockout strains by withanolide A

INTRODUCTION

Approximately 300 million people worldwide suffer from depression. The COVID-19 crisis may dramatically increase these numbers. Severe side effects and resistance development limit the use of standard antidepressants. The steroidal lactone withanolide A (WA) from Withania somnifera may be a promising alternative. Caenorhabditis elegans was used as model to explore WA's anti-depressive and anti-stress potential.

METHODS

C. elegans wildtype (N2) and deficient strains (AQ866, DA1814, DA2100, DA2109 and MT9772) were used to assess oxidative, osmotic or heat stress as measured by generation of reactive oxygen species (ROS), determination of lifespan, and mRNA expression of serotonin receptor (ser-1, ser-4, ser-7) and serotonin transporter genes (mod-5). The protective effect of WA was compared to fluoxetine as clinically established antidepressant. Additionally, WA's effect on lifespan was determined. Furthermore, the binding affinities and pKi values of WA, fluoxetine and serotonin as natural ligand to Ser-1, Ser-4, Ser-7, Mod-5 and their human orthologues proteins were calculated by molecular docking.

RESULTS

Baseline oxidative stress was higher in deficient than wildtype worms. WA and fluoxetine reduced ROS levels in all strains except MT9772. WA and fluoxetine prolonged survival times in wildtype and mutants under osmotic stress. WA but not fluoxetine increased lifespan of all heat-stressed C. elegans strains except DA2100. Furthermore, WA but not fluoxetine extended lifespan in all non-stressed C. elegans strains. WA also induced mRNA expression of serotonin receptors and transporters in wildtype and mutants. WA bound with higher affinity and lower pKi values to all C. elegans and human serotonin receptors and transporters than serotonin, indicating that WA may competitively displaced serotonin from the binding pockets of these proteins.

CONCLUSION

WA reduced stress and increased lifespan by ROS scavenging and interference with the serotonin system. Hence, WA may serve as promising candidate to treat depression.

Increased Stress Resistance and Lifespan in Chaenorhabditis elegans Wildtype and Knockout Mutants-Implications for Depression Treatment by Medicinal Herbs

Depression and anxiety disorders are widespread diseases, and they belong to the leading causes of disability and greatest burdens on healthcare systems worldwide. It is expected that the numbers will dramatically rise during the COVID-19 pandemic. Established medications are not sufficient to adequately treat depression and are not available for everyone. Plants from traditional medicine may be promising alternatives to treat depressive symptoms. The model organism Chaenorhabditis elegans was used to assess the stress reducing effects of methanol/dichlormethane extracts from plants used in traditional medicine. After initial screening for antioxidant activity, nine extracts were selected for in vivo testing in oxidative stress, heat stress, and osmotic stress assays. Additionally, anti-aging properties were evaluated in lifespan assay. The extracts from Acanthopanax senticosus, Campsis grandiflora, Centella asiatica, Corydalis yanhusuo, Dan Zhi, Houttuynia cordata, Psoralea corylifolia, Valeriana officinalis, and Withaniasomnifera showed antioxidant activity of more than 15 Trolox equivalents per mg extract. The extracts significantly lowered ROS in mutants, increased resistance to heat stress and osmotic stress, and the extended lifespan of the nematodes. The plant extracts tested showed promising results in increasing stress resistance in the nematode model. Further analyses are needed, in order to unravel underlying mechanisms and transfer results to humans.

Ursolic acid enhances stress resistance, reduces ROS accumulation and prolongs life span in C. elegans serotonin-deficient mutants

INTRODUCTION

Depression and anxiety disorders contribute to the global disease burden. Ursolic acid (UA), a natural compound present in many vegetables, fruits and medicinal plants, was tested in vivo for its effect on (1) enhancing resistance to stress and (2) its effect on life span.

METHODS

The compound was tested for its antioxidant activity in C. elegans. Stress resistance was tested in the heat and osmotic stress assay. Additionally, the influence on normal life span was examined. RT-PCR was used to assess possible serotonin targets.

RESULTS

UA prolonged the life span of C. elegans. Additionally, UA significantly lowered reactive oxygen species (ROS). Molecular docking studies, PCR analysis and microscale thermophoresis (MST) supported the results that UA acts through serotonin receptors to enhance stress resistance.

DISCUSSION

Considering the urgent need for new and safe medications in the treatment of depression and anxiety disorders, our results indicate that UA may be a promising new drug candidate.

The C. elegans Hypertonic Stress Response: Big Insights from Shrinking Worms

Cell volume is one of the most aggressively defended physiological set points in biology. Changes in intracellular ion and water concentrations, which are induced by changes in metabolism or environmental exposures, disrupt protein folding, enzymatic activity, and macromolecular assemblies. To counter these challenges, cells and organisms have evolved multifaceted, evolutionarily conserved molecular mechanisms to restore cell volume and repair stress induced damage. However, many unanswered questions remain regarding the nature of cell volume 'sensing' as well as the molecular signaling pathways involved in activating physiological response mechanisms. Unbiased genetic screening in the model organism C. elegans is providing new and unexpected insights into these questions, particularly questions relating to the hypertonic stress response (HTSR) pathway. One surprising characteristic of the HTSR pathway in C. elegans is that it is under strong negative regulation by proteins involved in protein homeostasis and the extracellular matrix (ECM). The role of the ECM in particular highlights the importance of studying the HTSR in the context of a live organism where native ECM-tissue associations are preserved. A second novel and recently discovered characteristic is that the HTSR is regulated at the post-transcriptional level. The goal of this review is to describe these discoveries, to provide context for their implications, and to raise outstanding questions to guide future research.

OSR1 phosphorylates the Smad2/3 linker region and induces TGF-β1 autocrine to promote EMT and metastasis in breast cancer

Oxidative stress-responsive kinase 1 (OSR1) plays a critical role in multiple carcinogenic signal pathways, and its overexpression has been found in various types of cancer; however, the pathophysiological role of OSR1 in breast cancer has not been evaluated. This study aims to elaborate on the role of OSR1 in breast cancer metastasis and the specific regulatory mechanism. Our results showed that OSR1 mRNA and protein were upregulated in both human breast cancer samples and cell lines. Moreover, phosphorylated OSR1 (p-OSR1) was an independent poor prognostic indicator in patients with breast cancer. OSR1 upregulation induced epithelial-to-mesenchymal transition (EMT) in normal and malignant mammary epithelial cells with the increasing metastatic capacity. In contrast, deleting OSR1 in aggressive breast cancer cells inhibited these phenotypes. OSR1 is the critical activator for transcription factors of EMT. Mechanistically, we found that OSR1 can directly interact and phosphorylate the linker region of Smad2 at Thr220 and Smad3 at Thr179. Phosphorylated Smad2/3 translocated into the nucleus to enhance transforming growth factor-β1 (TGF-β1) autocrine signalling and increase the transcription of EMT regulators. Importantly, interruption of the OSR1-Smad2/3-TGF-β1 signalling axis elicited a robust anti-EMT and anti-metastatic effect in vitro and in vivo. Taken together, we conclude that OSR1-mediated Smad2/3-TGF-β1 signalling promotes EMT and metastasis representing a promising therapeutic target in breast cancer treatment.

Non-Canonical Caspase Activity Antagonizes p38 MAPK Stress-Priming Function to Support Development

Recent studies have revealed non-canonical activities of apoptotic caspases involving specific modulation of gene expression, such as limiting asymmetric divisions of stem-like cell types. Here we report that CED-3 caspase negatively regulates an epidermal p38 stress-responsive MAPK pathway to promote larval development in C. elegans. We show that PMK-1 (p38 MAPK) primes animals for encounters with hostile environments at the expense of retarding post-embryonic development. CED-3 counters this function by directly cleaving PMK-1 to promote development. Moreover, we found that CED-3 and PMK-1 oppose each other to balance developmental and stress-responsive gene expression programs. Specifically, expression of more than 300 genes is inversely regulated by CED-3 and PMK-1. Analyses of these genes showed enrichment for epidermal stress-responsive factors, including the fatty acid synthase FASN-1, anti-microbial peptides, and genes involved in lethargus states. Our findings demonstrate a non-canonical role for a caspase in promoting development by limiting epidermal stress response programs.

Automated phenotyping of Caenorhabditis elegans embryos with a high-throughput-screening microfluidic platform

The nematode Caenorhabditis elegans has been extensively used as a model multicellular organism to study the influence of osmotic stress conditions and the toxicity of chemical compounds on developmental and motility-associated phenotypes. However, the several-day culture of nematodes needed for such studies has caused researchers to explore alternatives. In particular, C. elegans embryos, due to their shorter developmental time and immobile nature, could be exploited for this purpose, although usually their harvesting and handling is tedious. Here, we present a multiplexed, high-throughput and automated embryo phenotyping microfluidic approach to observe C. elegans embryogenesis after the application of different chemical compounds. After performing experiments with up to 800 embryos per chip and up to 12 h of time-lapsed imaging per embryo, the individual phenotypic developmental data were collected and analyzed through machine learning and image processing approaches. Our proof-of-concept platform indicates developmental lag and the induction of mitochondrial stress in embryos exposed to high doses (200 mM) of glucose and NaCl, while small doses of sucrose and glucose were shown to accelerate development. Overall, our new technique has potential for use in large-scale developmental biology studies and opens new avenues for very rapid high-throughput and high-content screening using C. elegans embryos.

Verapamil extends lifespan in Caenorhabditis elegans by inhibiting calcineurin activity and promoting autophagy

Previous evidence has revealed that increase in intracellular levels of calcium promotes cellular senescence. However, whether calcium channel blockers (CCBs) can slow aging and extend lifespan is still unknown. In this study, we showed that verapamil, an L-type calcium channel blocker, extended the Caenorhabditis elegans (C. elegans) lifespan and delayed senescence in human lung fibroblasts. Verapamil treatment also improved healthspan in C. elegans as reflected by several age-related physiological parameters, including locomotion, thrashing, age-associated vulval integrity, and osmotic stress resistance. We also found that verapamil acted on the α1 subunit of an L-type calcium channel in C. elegans. Moreover, verapamil extended worm lifespan by inhibiting calcineurin activity. Furthermore, verapamil significantly promoted autophagy as reflected by the expression levels of LGG-1/LC3 and the mRNA levels of autophagy-related genes. In addition, verapamil could not further induce autophagy when tax-6, calcineurin gene, was knocked down, indicating that verapamil-induced lifespan extension is mediated via promoting autophagy processes downstream of calcineurin. In summary, our study provided mechanistic insights into the anti-aging effect of verapamil in C. elegans.

Multiple sensory neurons mediate starvation-dependent aversive navigation in Caenorhabditis elegans

Processing and integrating multiple sensory inputs are essential for generating appropriate behavioral output, where sensory information of food is particularly important. The soil nematode Caenorhabditis elegans remembers salt concentrations that they have experienced under starvation conditions and learn to avoid them by monitoring current salt concentrations with the salt-sensory neuron called ASER. Here, we described how a sensory neuron pair that was not previously implicated, called ASG, plays a pivotal role in driving food-related navigation; sensory input to these 2 sensory neurons is required for navigation to avoid salt concentrations associated with starvation. Our results show how integrated sensory information determines the bias of turning behaviors to efficiently navigate toward food in starved worms.

Animals demonstrate flexible behaviors through associative learning based on their experiences. Deciphering the neural mechanisms for sensing and integrating multiple types of sensory information is critical for understanding such behavioral controls. The soil nematode Caenorhabditis elegans avoids salt concentrations it has previously experienced under starvation conditions. Here, we identify a pair of sensory neurons, the ASG neuron pair, which in cooperation with the ASER salt-sensing neuron generate starvation-dependent salt avoidance. Animals whose sensory input is restricted to only ASER failed to show learned avoidance due to inappropriately directed navigation behaviors. However, their navigation through a salt concentration gradient was improved by allowing sensory inputs to ASG in addition to ASER. Detailed behavioral analyses of these animals revealed that input from ASG neurons is required not only for controlling the frequency of initiating a set of sharp turns (called pirouettes) based on detected ambient salt concentrations but also adjusting the migration direction during pirouettes. Optogenetic activation of ASER by ChR2 induced turning behaviors in a salt concentration-dependent manner where presence of intact ASG was important for the starvation-dependent responses. Calcium imaging of the activity of ASG neurons in freely moving worms revealed that ASG is activated upon turning behavior. Our results indicate that ASG neurons cooperate with the ASER neuron to generate destination-directed reorientation in starvation-associated salt concentration avoidance.

p-Coumaric acid improves oxidative and osmosis stress responses in Caenorhabditis elegans

BACKGROUND

Stress-response pathways in Caenorhabditis elegans (C. elegans) were found to be closely related to human diseases and aging. Research on stress responses in C. elegans can therefore significantly facilitate understanding of related human diseases. p-Coumaric acid is present in peanuts, carrots, and garlic, and exerts many biological effects, however, its responses to various environmental stressors remain unknown. Thus, in the current study, we employed C. elegans as the in vivo animal model to examine the function of p-coumaric acid under various stressed conditions.

RESULTS

Treatment of C. elegans with p-coumaric acid resulted in a significant reduction in the intercellular reactive oxygen species levels, which suggests the in vivo antioxidant capacity of p-coumaric acid. Moreover, p-coumaric acid significantly increased the worms' survival under oxidative and osmosis stressed conditions but had no effect under normal or heat-stressed conditions. The increased oxidative resistance induced by p-coumaric acid was mediated by skn-1, an ortholog of the Nrf2 (nuclear factor erythroid 2-related factor 2) transcriptional factor. Downregulation of the osmosis regulatory gene, osr-1, might contribute to p-coumaric acids' effect on increased resistance to high osmolarity.

CONCLUSION

Taken together, our results suggest that p-coumaric acid, an antioxidant agent, ameliorated oxidative and osmosis stresses in C. elegans. © 2018 Society of Chemical Industry.

SIN-3 as a key determinant of lifespan and its sex dependent differential role on healthspan in Caenorhabditis elegans

Aging/senescence includes not just decline in lifespan but also etiologies of age associated morbidities which are inadequately understood. Extensive research has been undertaken to delineate the pathways and generate mutants with extended lifespan. However, little is known about the health status of these long lived mutants in the background of important genetic perturbations. Caenorhabditis elegans is one of the leading in vivo model organisms to study aging. Deletion of SIN-3, a transcription coregulator in C. elegans has been shown to reduce the lifespan of the mutant worms by half as compared to the wild-type and isogenic controls. The current study focuses on the effect of SIN-3 deletion on the healthspan of the worms. We find that not only are sin-3 mutants more susceptible to stress, but the overall stress intolerance and physiological decline is sex dependent. The severity of the phenotype is more pronounced in hermaphrodites as compared to the males carrying the same mutation with respect to the controls. The results further suggest that genetic perturbation along with the gender play an important role in determining the lifespan, healthspan and overall fitness of an organism.

Black tea increases hypertonic stress resistance in C. elegans

Here we identified that BTE (black tea extract), within the studied concentration range, is more effective than GTE (green tea extract) in protecting C. elegans against hypertonic stress, by enhancing survival after exposure to various salts, and alleviating suffered motility loss and body shrinkage. The mechanism of such protection may be due to the ability of black tea to induce the conserved WNK/GCK signaling pathway and down-regulation of the expression levels of nlp-29. Intriguingly, black tea does not relieve hypertonicity-induced protein damage. The findings implicate the potential health benefits of black tea consumed worldwide.

Antiageing properties of Damaurone D in Caenorhabditis elegans

Objectives

This study was conducted to evaluate the longevity potential of damaurone D (DaD), a component of the damask rose, in the animal model Caenorhabditis elegans.

Methods

To investigate the effect of DaD on the longevity, lifespan assay was carried out. Fluorescence intensity of transgenic mutants was quantified to test the expression levels of stress proteins. A genetic study using single gene knockout mutants was designed to determine the target genes of DaD.

Key findings

DaD prolonged the mean lifespan of wild-type nematodes by 16.7% under normal conditions and also improved their stress endurance under thermal, osmotic, and oxidative stress conditions. This longevity-promoting effect could be attributed to in vivo antioxidant capacity and its up-regulating effects on the expressions of stress-response proteins such as SOD-3 and HSP-16.2. In addition, DaD treatment attenuated food intake, body length, lipofuscin accumulation and age-dependent decline of motor ability. Gene-specific mutant studies showed the involvement of genes such as daf-2, age-1, and daf-16.

Conclusions

These results suggest that DaD has beneficial effects on the longevity, and thus it can be a valuable plant origin lead compound for the development of nutraceutical preparations targeting ageing and ageing-related diseases.

WNK1 kinase and its partners Akt, SGK1 and NBC-family Na+/HCO3- cotransporters are potential therapeutic targets for glioblastoma stem-like cells linked to Bisacodyl signaling

Glioblastoma is a highly heterogeneous brain tumor. The presence of cancer cells with stem-like and tumor initiation/propagation properties contributes to poor prognosis. Glioblastoma cancer stem-like cells (GSC) reside in hypoxic and acidic niches favoring cell quiescence and drug resistance. A high throughput screening recently identified the laxative Bisacodyl as a cytotoxic compound targeting quiescent GSC placed in acidic microenvironments. Bisacodyl activity requires its hydrolysis into DDPM, its pharmacologically active derivative. Bisacodyl was further shown to induce tumor shrinking and increase survival in in vivo glioblastoma models. Here we explored the cellular mechanism underlying Bisacodyl cytotoxic effects using quiescent GSC in an acidic microenvironment and GSC-derived 3D macro-spheres. These spheres mimic many aspects of glioblastoma tumors in vivo, including hypoxic/acidic areas containing quiescent cells. Phosphokinase protein arrays combined with pharmacological and genetic modulation of signaling pathways point to the WNK1 serine/threonine protein kinase as a mediator of Bisacodyl cytotoxic effect in both cell models. WNK1 partners including the Akt and SGK1 protein kinases and NBC-family Na⁺/HCO3⁻ cotransporters were shown to participate in the compound’s effect on GSC. Overall, our findings uncover novel potential therapeutic targets for combatting glioblastoma which is presently an incurable disease.

Endosome maturation factors Rabenosyn-5/VPS45 and caveolin-1 regulate ciliary membrane and polycystin-2 homeostasis

Primary cilium structure and function relies on control of ciliary membrane homeostasis, regulated by membrane trafficking processes that deliver and retrieve ciliary components at the periciliary membrane. However, the molecular mechanisms controlling ciliary membrane establishment and maintenance, especially in relation to endocytosis, remain poorly understood. Here, using Caenorhabditis elegans, we describe closely linked functions for early endosome (EE) maturation factors RABS-5 (Rabenosyn-5) and VPS-45 (VPS45) in regulating cilium length and morphology, ciliary and periciliary membrane volume, and ciliary signalling-related sensory behaviour. We demonstrate that RABS-5 and VPS-45 control periciliary vesicle number and levels of select EE/endocytic markers (WDFY-2, CAV-1) and the ciliopathy membrane receptor PKD-2 (polycystin-2). Moreover, we show that CAV-1 (caveolin-1) also controls PKD-2 ciliary levels and associated sensory behaviour. These data link RABS-5 and VPS-45 ciliary functions to the processing of periciliary-derived endocytic vesicles and regulation of ciliary membrane homeostasis. Our findings also provide insight into the regulation of PKD-2 ciliary levels via integrated endosomal sorting and CAV-1-mediated endocytosis.

An Intracellular Pathogen Response Pathway Promotes Proteostasis in C. elegans

Maintenance of protein homeostasis, or proteostasis, is crucial for organismal health. Disruption of proteostasis can lead to the accumulation of protein aggregates, which are associated with aging and many human diseases such as Alzheimer's disease [1-3]. Through analysis of the C. elegans host response to intracellular infection, we describe here a novel response pathway that enhances proteostasis capacity and appears to act in parallel to well-studied proteostasis pathways. These findings are based on analysis of the transcriptional response to infection by the intracellular pathogen Nematocida parisii [4]. The response to N. parisii is strikingly similar to the response to infection by the Orsay virus, another natural intracellular pathogen of C. elegans, and is distinct from responses to extracellular pathogen infection [4-6]. We have therefore named this common transcriptional response the intracellular pathogen response (IPR), and it includes upregulation of several predicted ubiquitin ligase complex components such as the cullin cul-6. Through a forward genetic screen we found pals-22, a gene of previously unknown function, to be a repressor of the cul-6/cullin gene and other IPR gene expression. Interestingly, pals-22 mutants have increased thermotolerance and reduced levels of stress-induced polyglutamine aggregates, likely due to upregulated IPR gene expression. We found the enhanced stress resistance of pals-22 mutants to be dependent on cul-6, suggesting that pals-22 mutants have increased activity of a CUL-6/cullin-containing ubiquitin ligase complex. pals-22 mutant phenotypes appear independent of the well-studied heat shock and insulin signaling pathways, indicating that the IPR is a distinct pathway that protects animals from proteotoxic stress.

Ethanol Stimulates Locomotion via a Gαs-Signaling Pathway in IL2 Neurons in Caenorhabditis elegans

Alcohol abuse is among the top causes of preventable death, generating considerable financial, health, and societal burdens. Paradoxically, alcohol...

Alcohol is a potent pharmacological agent when consumed acutely at sufficient quantities and repeated overuse can lead to addiction and deleterious effects on health. Alcohol is thought to modulate neuronal function through low-affinity interactions with proteins, in particular with membrane channels and receptors. Paradoxically, alcohol acts as both a stimulant and a sedative. The exact molecular mechanisms for the acute effects of ethanol on neurons, as either a stimulant or a sedative, however remain unclear. We investigated the role that the heat shock transcription factor HSF-1 played in determining a stimulatory phenotype of Caenorhabditis elegans in response to physiologically relevant concentrations of ethanol (17 mM; 0.1% v/v). Using genetic techniques, we demonstrate that either RNA interference of hsf-1 or use of an hsf-1(sy441) mutant lacked the enhancement of locomotion in response to acute ethanol exposure evident in wild-type animals. We identify that the requirement for HSF-1 in this phenotype was IL2 neuron-specific and required the downstream expression of the α-crystallin ortholog HSP-16.48. Using a combination of pharmacology, optogenetics, and phenotypic analyses we determine that ethanol activates a G_αs-cAMP-protein kinase A signaling pathway in IL2 neurons to stimulate nematode locomotion. We further implicate the phosphorylation of a specific serine residue (Ser322) on the synaptic protein UNC-18 as an end point for the G_αs-dependent signaling pathway. These findings establish and characterize a distinct neurosensory cell signaling pathway that determines the stimulatory action of ethanol and identifies HSP-16.48 and HSF-1 as novel regulators of this pathway.

An Aversive Response to Osmotic Upshift in Caenorhabditis elegans

Environmental osmolarity presents a common type of sensory stimulus to animals. While behavioral responses to osmotic changes are important for maintaining a stable intracellular osmolarity, the underlying mechanisms are not fully understood. In the natural habitat of Caenorhabditis elegans, changes in environmental osmolarity are commonplace. It is known that the nematode acutely avoids shocks of extremely high osmolarity. Here, we show that C. elegans also generates gradually increased aversion of mild upshifts in environmental osmolarity. Different from an acute avoidance of osmotic shocks that depends on the function of a transient receptor potential vanilloid channel, the slow aversion to osmotic upshifts requires the cGMP-gated sensory channel subunit TAX-2. TAX-2 acts in several sensory neurons that are exposed to body fluid to generate the aversive response through a motor network that underlies navigation. Osmotic upshifts activate the body cavity sensory neuron URX, which is known to induce aversion upon activation. Together, our results characterize the molecular and cellular mechanisms underlying a novel sensorimotor response to osmotic stimuli and reveal that C. elegans engages different behaviors and the underlying mechanisms to regulate responses to extracellular osmolarity.

Biphasic adaptation to osmotic stress in the C. elegans germ line

Cells respond to environmental stress in multiple ways. In the germ line, heat shock and nutritive stress trigger the assembly of large ribonucleoprotein (RNP) granules via liquid-liquid phase separation (LLPS). The RNP granules are hypothesized to maintain the quality of oocytes during stress. The goal of this study was to investigate the cellular response to glucose in the germ line and determine if it is an osmotic stress response. We found that exposure to 500 mM glucose induces the assembly of RNP granules in the germ line within 1 h. Interestingly, the RNP granules are maintained for up to 3 h; however, they dissociate after longer periods of stress. The RNP granules include processing body and stress granule proteins, suggesting shared functions. Based on several lines of evidence, the germ line response to glucose largely appears to be an osmotic stress response, thus identifying osmotic stress as a trigger of LLPS. Although RNP granules are not maintained beyond 3 h of osmotic stress, the quality of oocytes does not appear to decrease after longer periods of stress, suggesting a secondary adaptation in the germ line. We used an indirect marker of glycerol and observed high levels after 5 and 20 h of glucose exposure. Moreover, in gpdh-1;gpdh-2 germ lines, glycerol levels are reduced concomitant with RNP granules being maintained for an extended period. We speculate that increased glycerol levels may function as a secondary osmoregulatory adaptive response in the germ line, following a primary response of RNP granule assembly.

Neural Architecture of Hunger-Dependent Multisensory Decision Making in C. elegans

Little is known about how animals integrate multiple sensory inputs in natural environments to balance avoidance of danger with approach to things of value. Furthermore, the mechanistic link between internal physiological state and threat-reward decision making remains poorly understood. Here we confronted C. elegans worms with the decision whether to cross a hyperosmotic barrier presenting the threat of desiccation to reach a source of food odor. We identified a specific interneuron that controls this decision via top-down extrasynaptic aminergic potentiation of the primary osmosensory neurons to increase their sensitivity to the barrier. We also establish that food deprivation increases the worm's willingness to cross the dangerous barrier by suppressing this pathway. These studies reveal a potentially general neural circuit architecture for internal state control of threat-reward decision making.

Natural variability in Drosophila larval and pupal NaCl tolerance

The regulation of NaCl is essential for the maintenance of cellular tonicity and functionality, and excessive salt exposure has many adverse effects. The fruit fly, Drosophila melanogaster, is a good osmoregulator and some strains can survive on media with very low or high NaCl content. Previous analyses of mutant alleles have implicated various stress signaling cascades in NaCl sensitivity or tolerance; however, the genes influencing natural variability of NaCl tolerance remain for the most part unknown. Here, we use two approaches to investigate natural variation in D. melanogaster NaCl tolerance. We describe four D. melanogaster lines that were selected for different degrees of NaCl tolerance, and present data on their survival, development, and pupation position when raised on varying NaCl concentrations. After finding evidence for natural variation in salt tolerance, we present the results of Quantitative Trait Loci (QTL) mapping of natural variation in larval and pupal NaCl tolerance, and identify different genomic regions associated with NaCl tolerance during larval and pupal development.

Glycogen: A must have storage to survive stressful emergencies

Mechanisms of adaptation to acute changes in osmolarity are fundamental for life. When exposed to hyperosmotic stress, cells and organisms utilize conserved strategies to prevent water loss and maintain cellular integrity and viability. The production of glycerol is a common strategy utilized by the nematode Caenorhabditis elegans (C. elegans) and many other organisms to survive hyperosmotic stress. Specifically, the transcriptional upregulation of glycerol-3-phosphate dehydrogenase, a rate-limiting enzyme in the production of glycerol, has been previously implicated in many model organisms. However, what fuels this massive and rapid production of glycerol upon hyperosmotic stress has not been clearly elucidated. We have recently discovered an AMPK-dependent pathway that mediates hyperosmotic stress resistance in C. elegans. Specifically, we demonstrated that the chronic activation of AMPK leads to glycogen accumulation, which under hyperosmotic stress exposure, is rapidly degraded to mediate glycerol production. Importantly, we demonstrate that this strategy is utilized by flcn-1 mutant C. elegans nematodes in an AMPK-dependent manner. FLCN-1 is the worm homolog of the human renal tumor suppressor Folliculin (FLCN) responsible for the Birt-Hogg-Dubé neoplastic syndrome. Here, we comment on the dual role for glycogen in stress resistance: it serves as an energy store and a fuel for osmolyte production. We further discuss the potential utilization of this mechanism by organisms in general and by human cancer cells in order to survive harsh environmental conditions and notably hyperosmotic stress.

Context Specificity of Stress-activated Mitogen-activated Protein (MAP) Kinase Signaling: The Story as Told by Caenorhabditis elegans

Stress-associated p38 and JNK mitogen-activated protein (MAP) kinase signaling cascades trigger specific cellular responses and are involved in multiple disease states. At the root of MAP kinase signaling complexity is the differential use of common components on a context-specific basis. The roundwormCaenorhabditis eleganswas developed as a system to study genes required for development and nervous system function. The powerful genetics ofC. elegansin combination with molecular and cellular dissections has led to a greater understanding of how p38 and JNK signaling affects many biological processes under normal and stress conditions. This review focuses on the studies revealing context specificity of different stress-activated MAPK components inC. elegans.

Maintenance of Membrane Integrity and Permeability Depends on a Patched-Related Protein in Caenorhabditis elegans

Membrane integrity is critical for cell survival, defects of which cause pathological symptoms such as metabolic diseases. In this study, we used ethanol sensitivity of the nematode Caenorhabditis elegans to identify genetic factors involved in membrane integrity. InC. elegans, acute exposure to a high concentration (7% v/v) of ethanol changes membrane permeability, as measured by propidium iodide staining, and causes paralysis. We used the timing of complete paralysis as an indicator for alteration of membrane integrity in our genetic screen, and identified ptr-6 as a gene that confers ethanol resistance when mutated. PTR-6 is a patched-related protein and contains a sterol sensing domain. Inhibition of two PTR-encoding genes,ptr-15 and ptr-23, and mboa-1, encoding an Acyl Co-A: cholesterol acyltransferase homolog, restored ethanol sensitivity of the ptr-6 mutant, suggesting that these ptr genes and mboa-1 are involved in the maintenance of membrane integrity and permeability. Our results suggest that C. elegans can be used as a model system to identify factors involved in metabolic diseases and to screen for therapeutic drugs.

A Simple Light Stimulation of Caenorhabditis elegans

Response via noxious stimulus can be an important indicator of sensory neuron function and overall health of an organism. If the stimulation is quick and simple, and the animal can be rescued afterwards, such a method not only allows for assays pertaining to changed sensory ability after various treatments, but also increases the reliability of the statistical relationships that are established. This protocol demonstrates a stimulation assay in Caenorhabditis elegans, using blue light from common laboratory equipment: the fluorescent microscope. The nematode detects blue light using a set of amphid ciliary sensory neurons, and blue light is detrimental to its overall health after a prolonged exposure. However, under brief exposure, blue light stimulation provides a rapid and easy method for quantifying sensory functions and health without harming the animal.

FLCN and AMPK Confer Resistance to Hyperosmotic Stress via Remodeling of Glycogen Stores

Mechanisms of adaptation to environmental changes in osmolarity are fundamental for cellular and organismal survival. Here we identify a novel osmotic stress resistance pathway in Caenorhabditis elegans (C. elegans), which is dependent on the metabolic master regulator 5'-AMP-activated protein kinase (AMPK) and its negative regulator Folliculin (FLCN). FLCN-1 is the nematode ortholog of the tumor suppressor FLCN, responsible for the Birt-Hogg-Dubé (BHD) tumor syndrome. We show that flcn-1 mutants exhibit increased resistance to hyperosmotic stress via constitutive AMPK-dependent accumulation of glycogen reserves. Upon hyperosmotic stress exposure, glycogen stores are rapidly degraded, leading to a significant accumulation of the organic osmolyte glycerol through transcriptional upregulation of glycerol-3-phosphate dehydrogenase enzymes (gpdh-1 and gpdh-2). Importantly, the hyperosmotic stress resistance in flcn-1 mutant and wild-type animals is strongly suppressed by loss of AMPK, glycogen synthase, glycogen phosphorylase, or simultaneous loss of gpdh-1 and gpdh-2 enzymes. Our studies show for the first time that animals normally exhibit AMPK-dependent glycogen stores, which can be utilized for rapid adaptation to either energy stress or hyperosmotic stress. Importantly, we show that glycogen accumulates in kidneys from mice lacking FLCN and in renal tumors from a BHD patient. Our findings suggest a dual role for glycogen, acting as a reservoir for energy supply and osmolyte production, and both processes might be supporting tumorigenesis.

Abiotic stress does not magnify the deleterious effects of spontaneous mutations

Although the effects of deleterious alleles often are predicted to be greater in stressful environments, there is no theoretical basis for this prediction and the empirical evidence is mixed. Here we characterized the effects of three types of abiotic stress (thermal, oxidative and hyperosmotic) on two sets of nematode (Caenorhabditis elegans) mutation accumulation (MA) lines that differ by threefold in fitness. We compared the survival and egg-to-adult viability between environments (benign and stressful) and between fitness categories (high-fitness MA, low-fitness MA). If the environment and mutation load have synergistic effects on trait means, then the difference between the high and low-fitness MA lines should be larger in stressful environments. Although the stress treatments consistently decreased survival and/or viability, we did not detect significant interactions between fitness categories and environment types. In contrast, we did find consistent evidence for synergistic effects on (micro)environmental variation. The lack of signal in trait means likely reflects the very low starting fitness of some low-fitness MA lines, the potential for cross-stress responses and the context dependence of mutational effects. In addition, the large increases in the environmental variance in the stressful environments may have masked small changes in trait means. These results do not provide evidence for synergism between mutation and stress.

Neuronal responses to stress and injury in C. elegans

The nervous system plays critical roles in the stress response. Animals can survive and function under harsh conditions, and resist and recover from injuries because neurons perceive and respond to various stressors through specific regulatory mechanisms. Caenorhabditis elegans has served as an excellent model to discover fundamental mechanisms underlying the neuronal response to stress. The basic physiological processes that C. elegans exhibits under stress conditions are similar to those observed in higher organisms. Many molecular pathways activated by environmental and cellular stresses are also conserved. In this review, we summarize major findings in examining neuronal responses to hypoxia, oxidative stress, osmotic stress, and traumatic injury. These studies from C. elegans have provided novel insights into our understanding of neuronal responses to stress at the molecular, cellular, and circuit levels.

Black tea increased survival of Caenorhabditis elegans under stress

The present study examined the effects of black tea (Camellia sinensis) extracts (BTE) in Caenorhabditis elegans under various abiotic stressors. Results showed BTE increased nematode resistance to osmosis, heat, and UV irradiation treatments. However, BTE could not increase nematodes' lifespan under normal culture conditions and MnCl2-induced toxicity at concentrations we used. Further studies showed that BTE decreased reactive oxygen species and up-regulated some antioxidant enzymes, including GSH-PX, and genes, such as gsh-px and sod-3. However, only a slight extension in mev-1 mutants mean lifespan was observed without significance. These results indicated that the antioxidant activity of BTE might be necessary but not sufficient to protect against aging to C. elegans. Moreover, BTE increased the mRNA level of stress-response genes such as sir-2.1 and sek-1. Our finding demonstrated BTE might increase heat and UV stress resistance in a sir.2.1-dependent manner. Taken together, BTE enhanced stress resistance with multiple mechanisms in C. elegans.

Screening of odor-receptor pairs in Caenorhabditis elegans reveals different receptors for high and low odor concentrations

Olfactory systems sense and respond to various odorants. Olfactory receptors, which in most organisms are G protein (heterotrimeric guanine nucleotide-binding protein)-coupled receptors, directly bind volatile or soluble odorants. Compared to the genomes of mammals, the genome of the nematode Caenorhabditis elegans contains more putative olfactory receptor genes, suggesting that in nematodes there may be combinatorial complexity to the receptor-odor relationship. We used RNA interference (RNAi) screening to identify nematode olfactory receptors necessary for the response to specific odorants. This screening identified 194 candidate olfactory receptor genes linked to 11 odorants. Additionally, we identified SRI-14 as being involved in sensing high concentrations of diacetyl. Rescue and neuron-specific RNAi experiments demonstrated that SRI-14 functioned in ASH neurons, specific chemosensory neurons, resulting in avoidance responses. Calcium imaging revealed that ASH neurons responded to high diacetyl concentrations only, whereas another class of chemosensory neurons, AWA neurons, reacted to both low and high concentrations. Loss of SRI-14 function hampered ASH responses to high diacetyl concentrations, whereas loss of ODR-10 function reduced AWA responses to low odorant concentrations. Chemosensory neurons ectopically expressing SRI-14 responded to a high concentration of diacetyl. Thus, nematodes have concentration-dependent odor-sensing mechanisms that are segregated at the olfactory receptor and sensory neuron levels.

The C. elegans healthspan and stress-resistance assay toolkit

A wealth of knowledge on the genetic mechanisms that govern aging has emerged from the study of mutants that exhibit enhanced longevity and exceptional resilience to adverse environmental conditions. In these studies, lifespan has been an excellent proxy for establishing the rate of aging, but it is not always correlated with qualitative measures of healthy aging or 'healthspan'. Although the attributes of healthspan have been challenging to define, they share some universal features that are increasingly being incorporated into aging studies. Here we describe methods used to determine Caenorhabditis elegans healthspan. These include assessments of tissue integrity and functionality and resistance to a variety of biotic and abiotic stressors. We have chosen to include simple, rapid assays in this collection that can be easily undertaken in any C. elegans laboratory, and can be relied on to provide a preliminary but thorough insight into the healthspan of a population.

The GATA transcription factor/MTA-1 homolog egr-1 promotes longevity and stress resistance in Caenorhabditis elegans

Aging is associated with a large number of both phenotypic and molecular changes, but for most of these, it is not known whether these changes are detrimental, neutral, or protective. We have identified a conserved Caenorhabditis elegans GATA transcription factor/MTA-1 homolog egr-1 (lin-40) that extends lifespan and promotes resistance to heat and UV stress when overexpressed. Expression of egr-1 increases with age, suggesting that it may promote survival during normal aging. This increase in expression is dependent on the presence of the germline, raising the possibility that egr-1 expression is regulated by signals from the germline. In addition, loss of egr-1 suppresses the long lifespan of insulin receptor daf-2 mutants. The DAF-16 FOXO transcription factor is required for the increased stress resistance of egr-1 overexpression mutants, and egr-1 is necessary for the proper regulation of sod-3 (a reporter for DAF-16 activity). These results indicate that egr-1 acts within the insulin signaling pathway. egr-1 can also activate the expression of its paralog egl-27, another factor known to extend lifespan and increase stress resistance, suggesting that the two genes act in a common program to promote survival. These results identify egr-1 as part of a longevity-promoting circuit that changes with age in a manner that is beneficial for the lifespan of the organism.

Green Tea Extract Induces the Resistance of Caenorhabditis elegans against Oxidative Stress

Epidemiological studies on the effects of green tea consumption (Camellia sinensis) have demonstrated a reduction for the risk of age-related diseases. The investigation of the in vivo and in vitro antioxidant properties of an aqueous extract of green tea (GTE) was the aim of the current study. 2,2-Diphenyl-1-picrylhydrazyl (DPPH(•)) and superoxide anion radical (O₂(•-)) assays were used to estimate the GTE antioxidant activity. To investigate the protective effects of GTE against oxidative stress, wild-type N2 and transgenic strains (TJ374, hsp-16.2/GFP) of the model organism, Caenorhabditis elegans (C. elegans), were chosen. In the current study, the following catechins were identified by LC/ESI-MS: catechin, epicatechin, epicatechin gallate, gallocatechin, epigallocatechin and epigallocatechin gallate. GTE exhibited a free radical scavenging activity of DPPH(•) and O₂(•-) with IC50 8.37 and 91.34 µg/mL, respectively. In the C. elegans strain (TJ374, hsp-16.2/GFP), the expression of hsp-16.2/GFP was induced by a nonlethal dose of juglone, and the fluorescence density of hsp-16.2/GFP was measured. The hsp-16.2/GFP was reduced by 68.43% in the worms pretreated with 100 µg/mL GTE. N2 worms pretreated with 100 µg/mL GTE exhibited an increased survival rate of 48.31% after a lethal dose application of juglone. The results suggest that some green tea constituents are absorbed by the worms and play a substantial role to enhance oxidative stress resistance in C. elegans.

Açaí (Euterpe oleracea Mart.) modulates oxidative stress resistance in Caenorhabditis elegans by direct and indirect mechanisms

Açaí (Euterpe oleracea Mart.) has recently emerged as a promising source of natural antioxidants. Despite its claimed pharmacological and nutraceutical value, studies regarding the effects of açaí in vivo are limited. In this study, we use the Caenorhabditis elegans model to evaluate the in vivo antioxidant properties of açaí on an organismal level and to examine its mechanism of action. Supplementation with açaí aqueous extract (AAE) increased both oxidative and osmotic stress resistance independently of any effect on reproduction and development. AAE suppressed bacterial growth, but this antimicrobial property did not influence stress resistance. AAE-increased stress resistance was correlated with reduced ROS production, the prevention of sulfhydryl (SH) level reduction and gcs-1 activation under oxidative stress conditions. Our mechanistic studies indicated that AAE promotes oxidative stress resistance by acting through DAF-16 and the osmotic stress response pathway OSR-1/UNC-43/SEK-1. Finally, AAE increased polyglutamine protein aggregation and decreased proteasome activity. Our findings suggest that natural compounds available in AAE can improve the antioxidant status of a whole organism under certain conditions by direct and indirect mechanisms.