A bile acid-like steroid modulates Caenorhabditis elegans lifespan through nuclear receptor signaling

Photocatalytic Stereochemical Editing for the Concise Syntheses of (25S)-Δ7-Dafachronic Acid, Demissidine, and Smilagenin

Stereochemistry editing serves as an important tool to precisely adjust the desired stereochemical configuration of a molecule. In this study, enabled by photocatalytic stereochemical editing of tertiary C─H bonds of steroids, we have completed concise syntheses of (25S)-Δ7-dafachronic acid, demissidine, and smilagenin. The feasibility of regioselectively editing tertiary stereocenters with either very weak α-hydroxyl C─H bonds (in the synthesis of dafachronic acid), α-amino C─H bonds (in the synthesis of demissidine), or with varying steric hindrance (in the synthesis of smilagenin) has been successfully demonstrated.

Tauroursodeoxycholic acid targets HSP90 to promote protein homeostasis and extends healthy lifespan

As the elderly population expands, the pursuit of therapeutics to reduce morbidity and extend lifespan has become increasingly crucial. As an FDA-approved drug for chronic cholestatic liver diseases, tauroursodeoxycholic acid (TUDCA), a natural bile acid, offers additional health benefits beyond liver protection. Here, we show that TUDCA extends the lifespan and healthspan of C. elegans. Importantly, oral supplementation of TUDCA improves fitness in old mice, including clinically relevant phenotypes, exercise capacity and cognitive function. Consistently, TUDCA treatment drives broad transcriptional changes correlated with anti-aging characteristics. Mechanistically, we discover that TUDCA targets the chaperone HSP90 to promote its protein refolding activity. This collaboration further alleviates aging-induced endoplasmic reticulum (ER) stress and facilitates protein homeostasis, thus offering resistance to aging. In summary, our findings uncover new molecular links between an endogenous metabolite and protein homeostasis, and propose a novel anti-aging strategy that could improve both lifespan and healthspan.

Life history in Caenorhabditis elegans: from molecular genetics to evolutionary ecology

Life history is defined by traits that reflect key components of fitness, especially those relating to reproduction and survival. Research in life history seeks to unravel the relationships among these traits and understand how life history strategies evolve to maximize fitness. As such, life history research integrates the study of the genetic and developmental mechanisms underlying trait determination with the evolutionary and ecological context of Darwinian fitness. As a leading model organism for molecular and developmental genetics, Caenorhabditis elegans is unmatched in the characterization of life history-related processes, including developmental timing and plasticity, reproductive behaviors, sex determination, stress tolerance, and aging. Building on recent studies of natural populations and ecology, the combination of C. elegans' historical research strengths with new insights into trait variation now positions it as a uniquely valuable model for life history research. In this review, we summarize the contributions of C. elegans and related species to life history and its evolution. We begin by reviewing the key characteristics of C. elegans life history, with an emphasis on its distinctive reproductive strategies and notable life cycle plasticity. Next, we explore intraspecific variation in life history traits and its underlying genetic architecture. Finally, we provide an overview of how C. elegans has guided research on major life history transitions both within the genus Caenorhabditis and across the broader phylum Nematoda. While C. elegans is relatively new to life history research, significant progress has been made by leveraging its distinctive biological traits, establishing it as a highly cross-disciplinary system for life history studies.

Germline loss in C. elegans enhances longevity by disrupting adhesion between niche and stem cells

Ageing and fertility are intertwined. Germline loss extends the lifespan in various organisms, termed gonadal longevity. However, the original longevity signal from the somatic gonad remains poorly understood. Here, we focused on the interaction between germline stem cells (GSCs) and their niche, the distal tip cells (DTCs), to explore the barely known longevity signal from the somatic gonad in C. elegans. We found that removing germline disrupts the cell adhesions between GSC and DTC, causing a significant transcriptomic change in DTC through hmp-2/β-catenin and two GATA transcription factors, elt-3 and pqm-1 in this niche cell. Inhibiting elt-3 and pqm-1 in DTC suppresses gonadal longevity. Moreover, we further identified the TGF-β ligand, tig-2, as the cytokine from DTC upon the loss of germline, which evokes the downstream gonadal longevity signalling throughout the body. Our findings thus reveal the source of the longevity signalling in response to germline removal, highlighting the stem cell niche as a critical signalling hub in ageing.

Genome-wide RNA interference of the nhr gene family in barber's pole worm identified members crucial for larval viability in vitro

Nuclear hormone receptors (NHRs) are emerging target candidates against nematode infection and resistance. However, there is a lack of comprehensive information on NHR-coding genes in parasitic nematodes. In this study, we curated the nhr gene family for 60 major parasitic nematodes from humans and animals. Compared with the free-living model organism Caenorhabditis elegans, a remarkable contraction of the nhr family was revealed in parasitic species, with genetic diversification and conservation unveiled among nematode Clades I (10-13), III (16-42), IV (33-35) and V (25-64). Using an in vitro biosystem, we demonstrated that 40 nhr genes in a blood-feeding nematode Haemonchus contortus (clade V; barber's pole worm) were responsive to host serum and one nhr gene (i.e., nhr-64) was consistently stimulated by anthelmintics (i.e., ivermectin, thiabendazole and levamisole); Using a high-throughput RNA interference platform, we knocked down 43 nhr genes of H. contortus and identified at least two genes that are required for the viability (i.e., nhr-105) and development (i.e., nhr-17) of the infective larvae of this parasitic nematode in vitro. Harnessing this preliminary functional atlas of nhr genes for H. contortus will prime the biological studies of this gene family in nematode genetics, infection, and anthelmintic metabolism within host animals, as well as the promising discovery of novel intervention targets.

The 18S rRNA Methyltransferase DIMT-1 Regulates Lifespan in the Germline Later in Life

Ribosome heterogeneity has emerged as an important regulatory control feature for determining which proteins are synthesized, however, the influence of age on ribosome heterogeneity is not fully understood. Whether mRNA transcripts are selectively translated in young versus old cells and whether dysregulation of this process drives organismal aging is unknown. Here we examined the role of ribosomal RNA (rRNA) methylation in maintaining appropriate translation as organisms age. In a directed RNAi screen, we identified the 18S rRNA N6'-dimethyl adenosine (m6,2A) methyltransferase, dimt-1, as a regulator of C. elegans lifespan and stress resistance. Lifespan extension induced by dimt-1 deficiency required a functional germline and was dependent on the known regulator of protein translation, the Rag GTPase, raga-1, which links amino acid sensing to the mechanistic target of rapamycin complex (mTORC)1. Using an auxin-inducible degron tagged version of dimt-1, we demonstrate that DIMT-1 functions in the germline after mid-life to regulate lifespan. We further found that knock-down of dimt-1 leads to selective translation of transcripts important for stress resistance and lifespan regulation in the C. elegans germline in mid-life including the cytochrome P450 daf-9, which synthesizes a steroid that signals from the germline to the soma to regulate lifespan. We found that dimt-1 induced lifespan extension was dependent on the daf-9 signaling pathway. This finding reveals a new layer of proteome dysfunction, beyond protein synthesis and degradation, as an important regulator of aging. Our findings highlight a new role for ribosome heterogeneity, and specific rRNA modifications, in maintaining appropriate translation later in life to promote healthy aging.

The 18S rRNA Methyltransferase DIMT-1 Regulates Lifespan in the Germline Later in Life

Ribosome heterogeneity has emerged as an important regulatory control feature for determining which proteins are synthesized, however, the influence of age on ribosome heterogeneity is not fully understood. Whether mRNA transcripts are selectively translated in young versus old cells and whether dysregulation of this process drives organismal aging is unknown. Here we examined the role of ribosomal RNA (rRNA) methylation in maintaining appropriate translation as organisms age. In a directed RNAi screen, we identified the 18S rRNA N6'-dimethyl adenosine (m6,2A) methyltransferase, dimt-1, as a regulator of C. elegans lifespan and stress resistance. Lifespan extension induced by dimt-1 deficiency required a functional germline and was dependent on the known regulator of protein translation, the Rag GTPase, raga-1, which links amino acid sensing to the mechanistic target of rapamycin complex (mTORC)1. Using an auxin-inducible degron tagged version of dimt-1, we demonstrate that DIMT-1 functions in the germline after mid-life to regulate lifespan. We further found that knock-down of dimt-1 leads to selective translation of transcripts important for stress resistance and lifespan regulation in the C. elegans germline in mid-life including the cytochrome P450 daf-9, which synthesizes a steroid that signals from the germline to the soma to regulate lifespan. We found that dimt-1 induced lifespan extension was dependent on the daf-9 signaling pathway. This finding reveals a new layer of proteome dysfunction, beyond protein synthesis and degradation, as an important regulator of aging. Our findings highlight a new role for ribosome heterogeneity, and specific rRNA modifications, in maintaining appropriate translation later in life to promote healthy aging.

Decoding lifespan secrets: the role of the gonad in Caenorhabditis elegans aging

The gonad has become a central organ for understanding aging in C. elegans, as removing the proliferating stem cells in the germline results in significant lifespan extension. Similarly, when starvation in late larval stages leads to the quiescence of germline stem cells the adult nematode enters reproductive diapause, associated with an extended lifespan. This review summarizes recent advancements in identifying the mechanisms behind gonad-mediated lifespan extension, including comparisons with other nematodes and the role of lipid signaling and transcriptional changes. Given that the gonad also mediates lifespan regulation in other invertebrates and vertebrates, elucidating the underlying mechanisms may help to gain new insights into the mechanisms and evolution of aging.

Ganoderma lucidum methyl ganoderate E extends lifespan and modulates aging-related indicators in Caenorhabditis elegans

Methyl Ganoderate E (MGE) is a triterpenoid derived from Ganoderma lucidum (Reishi), an edible mushroom, commonly processed into food forms such as soups, drinks, culinary dishes, and supplements. MGE has been shown to inhibit 3T3-L1 murine adipocyte differentiation when combined with other G. lucidum triterpenes. However, the specific effect of MGE on biological processes remains unknown. In this study, we present the first evidence of MGE's anti-aging effect in Caenorhabditis elegans. Through our screening process using the UPRER regulation ability, we evaluated a library of 74 pure compounds isolated from G. lucidum, and MGE exhibited the most promising results. Subsequent experiments demonstrated that MGE extended the lifespan by 26% at 10 μg ml-1 through daf-16, hsf-1, and skn-1-dependent pathways. MGE also enhanced resistance to various molecular stressors, improved healthspan, increased fertility, and reduced the aggregation of alpha-synuclein and amyloid-beta. Transcriptome data revealed that MGE promoted processes associated with proteolysis and neural activity, while not promoting cell death processes. Collectively, our findings suggest that G. lucidum MGE could be considered as a potential anti-aging intervention, adding to the growing list of such interventions.

Bsep/Abcb11 knockout ameliorates Schistosoma mansoni liver pathology by reducing parasite fecundity

BACKGROUND AND AIMS

Schistosoma mansoni infection is one of the worldwide leading causes of liver fibrosis and portal hypertension. The objective of this study was to evaluate whether polyhydroxylated bile acids (BAs), known to protect mice from the development of acquired cholestatic liver injury, counteract S. mansoni-induced inflammation and fibrosis.

METHODS

Adult FVB/N wild type (WT) and Abcb11/Bsep-/- mice were infected with either 25 or 50 S. mansoni cercariae. Eight weeks post infection, effects on liver histology, serum biochemistry, gene expression profile of proinflammatory cytokines and fibrotic markers, hepatic hydroxyproline content and FACS analysis were performed.

RESULTS

Bsep-/- mice infected with S. mansoni showed significantly less hepatic inflammation and tendentially less fibrosis compared to infected WT mice. Despite elevated alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase levels in infected Bsep-/- mice, inflammatory cells such as M2 macrophages and Mac-2/galectin-3+ cells were reduced in these animals. Accordingly, mRNA-expression levels of anti-inflammatory cytokines (IL-4 and IL-13) were increased in Bsep-/- mice upon infection. Furthermore, infected Bsep-/- mice exhibited decreased hepatic egg load and parasite fecundity, consequently affecting the worm reproduction rate. This outcome could arise from elevated serum BA levels and lower blood pH in Bsep-/- mice.

CONCLUSIONS

The loss of Bsep and the resulting changes in bile acid composition and blood pH are associated with the reduction of parasite fecundity, thus attenuating the development of S. mansoni-induced hepatic inflammation and fibrosis.

piRNAs regulate a Hedgehog germline-to-soma pro-aging signal

The reproductive system regulates somatic aging through competing anti- and pro-aging signals. Germline removal extends somatic lifespan through conserved pathways including insulin and mammalian target-of-rapamycin signaling, while germline hyperactivity shortens lifespan through unknown mechanisms. Here we show that mating-induced germline hyperactivity downregulates piRNAs, in turn desilencing their targets, including the Hedgehog-like ligand-encoding genes wrt-1 and wrt-10, ultimately causing somatic collapse and death. Germline-produced Hedgehog signals require PTR-6 and PTR-16 receptors for mating-induced shrinking and death. Our results reveal an unconventional role of the piRNA pathway in transcriptional regulation of Hedgehog signaling and a new role of Hedgehog signaling in the regulation of longevity and somatic maintenance: Hedgehog signaling is controlled by the tunable piRNA pathway to encode the previously unknown germline-to-soma pro-aging signal. Mating-induced piRNA downregulation in the germline and subsequent Hedgehog signaling to the soma enable the animal to tune somatic resource allocation to germline needs, optimizing reproductive timing and survival.

Molecular Cloning and Characterization of a Fasciola gigantica Nuclear Receptor Subfamily 1 (FgNR1)

Fasciola gigantica, a giant liver fluke, causes tremendous loss to the livestock economy in several regions throughout the world. The situation of drug resistance has been emerging increasingly; therefore, novel drugs and drug targets need to be discovered. The adult F. gigantica inhabits the major bile ducts where bile salts accumulate—these are steroid-like molecules that mediate several physiological processes in organisms through interacting with their specific nuclear receptors. However, the molecular mechanism of the interaction in the parasitic organisms have not been clearly understood. In this study, putative nuclear receptor subfamily 1 of F. gigantica (FgNR1) was identified. Nucleotide and amino acid sequences of the FgNR1 homolog were obtained from the transcriptome of F. gigantica and predicted for properties and functions using bioinformatics. The full-length cDNA was cloned and expressed in the bacterial expression system and then used for immunization. Western analysis and immunolocalization suggested that FgNR1 could be detected in the crude worm antigens and was highly expressed in the caeca and testes of the adult parasite. Moreover, the bile could significantly activate the expression of FgNR1 in cultured parasites. Our results indicated that FgNR1 has high potential for the development of a novel anthelminthic drug in the future.

Gonadotropin-releasing hormone-like receptor 2 inversely regulates somatic proteostasis and reproduction in Caenorhabditis elegans

The quality control machinery regulates the cellular proteome to ensure proper protein homeostasis (proteostasis). In Caenorhabditis elegans, quality control networks are downregulated cell-nonautonomously by the gonadal longevity pathway or metabolic signaling at the onset of reproduction. However, how signals are mediated between the gonad and the somatic tissues is not known. Gonadotropin-releasing hormone (GnRH)-like signaling functions in the interplay between development and reproduction and have conserved roles in regulating reproduction, metabolism, and stress. We, therefore, asked whether GnRH-like signaling is involved in proteostasis collapse at the onset of reproduction. Here, we examine whether C. elegans orthologues of GnRH receptors modulate heat shock survival. We find that gnrr-2 is required for proteostasis remodeling in different somatic tissues during the transition to adulthood. We show that gnrr-2 likely functions in neurons downstream of the gonad in the gonadal-longevity pathway and modulate the somatic regulation of transcription factors HSF-1, DAF-16, and PQM-1. In parallel, gnrr-2 modulates egg-laying rates, vitellogenin production, and thus reproductive capacity. Taken together, our data suggest that gnrr-2 plays a GnRH-associated role, mediating the cross-talk between the reproduction system and the soma in the decision to commit to reproduction.

Steroid hormones of the octopus self-destruct system

Among all invertebrates, soft-bodied cephalopods have the largest central nervous systems and the greatest brain-to-body mass ratios, yet unlike other big-brained animals, cephalopods are unusually short lived.^1-5 Primates and corvids survive for many decades, but shallow-water octopuses, such as the California two-spot octopus (Octopus bimaculoides), typically live for only 1 year.^6,7 Lifespan and reproduction are controlled by the principal neuroendocrine center of the octopus: the optic glands, which are functional analogs to the vertebrate pituitary gland.^8-10 After mating, females steadfastly brood their eggs, begin fasting, and undergo rapid physiological decline, featuring repeated self-injury and leading to death.¹¹ Removal of the optic glands completely reverses this life history trajectory,¹⁰ but the signaling factors underlying this major life transition are unknown. Here, we characterize the major secretions and steroidogenic pathways of the female optic gland using mass spectrometry techniques. We find that at least three pathways are mobilized to increase synthesis of select sterol hormones after reproduction. One pathway generates pregnane steroids, known in other animals to support reproduction.^12-16 Two other pathways produce 7-dehydrocholesterol and bile acid intermediates, neither of which were previously known to be involved in semelparity. Our results provide insight into invertebrate cholesterol pathways and confirm a remarkable unity of steroid hormone biology in life history processes across Bilateria.

Oxysterols are potential physiological regulators of ageing

Delaying and even reversing ageing is a major public health challenge with a tremendous potential to postpone a plethora of diseases including cancer, metabolic syndromes and neurodegenerative disorders. A better understanding of ageing as well as the development of innovative anti-ageing strategies are therefore an increasingly important field of research. Several biological processes including inflammation, proteostasis, epigenetic, oxidative stress, stem cell exhaustion, senescence and stress adaptive response have been reported for their key role in ageing. In this review, we describe the relationships that have been established between cholesterol homeostasis, in particular at the level of oxysterols, and ageing. Initially considered as harmful pro-inflammatory and cytotoxic metabolites, oxysterols are currently emerging as an expanding family of fine regulators of various biological processes involved in ageing. Indeed, depending of their chemical structure and their concentration, oxysterols exhibit deleterious or beneficial effects on inflammation, oxidative stress and cell survival. In addition, stem cell differentiation, epigenetics, cellular senescence and proteostasis are also modulated by oxysterols. Altogether, these data support the fact that ageing is influenced by an oxysterol profile. Further studies are thus required to explore more deeply the impact of the "oxysterome" on ageing and therefore this cholesterol metabolic pathway constitutes a promising target for future anti-ageing interventions.

Characterization of the endogenous DAF-12 ligand and its use as an anthelmintic agent in Strongyloides stercoralis

A prevalent feature of Strongyloides stercoralis is a life-long and potentially lethal infection that is due to the nematode parasite's ability to autoinfect and, thereby, self-replicate within its host. Here, we investigated the role of the parasite's nuclear receptor, Ss-DAF-12, in governing infection. We identified Δ7-DA as the endogenous Ss-DAF-12 ligand and elucidated the hormone's biosynthetic pathway. Genetic loss of function of the ligand's rate-limiting enzyme demonstrated that Δ7-DA synthesis is necessary for parasite reproduction, whereas its absence is required for the development of infectious larvae. Availability of the ligand permits Ss-DAF-12 to function as an on/off switch governing autoinfection, making it vulnerable to therapeutic intervention. In a preclinical model of hyperinfection, pharmacologic activation of DAF-12 suppressed autoinfection and markedly reduced lethality. Moreover, when Δ7-DA was administered with ivermectin, the current but limited drug of choice for treating strongyloidiasis, the combinatorial effects of the two drugs resulted in a near cure of the disease.

CYP4V2 fatty acid omega hydroxylase, a druggable target for the treatment of metabolic associated fatty liver disease (MAFLD)

Fatty acids are essential in maintaining cellular homeostasis by providing lipids for energy production, cell membrane integrity, protein modification, and the structural demands of proliferating cells. Fatty acids and their derivatives are critical bioactive signaling molecules that influence many cellular processes, including metabolism, cell survival, proliferation, migration, angiogenesis, and cell barrier function. The CYP4 Omega hydroxylase gene family hydroxylate various short, medium, long, and very-long-chain saturated, unsaturated and polyunsaturated fatty acids. Selective members of the CYP4 family metabolize vitamins and biochemicals with long alkyl side chains and bioactive prostaglandins, leukotrienes, and arachidonic acids. It is uncertain of the physiological role of different members of the CYP4 omega hydroxylase gene family in the metabolic control of physiological and pathological processes in the liver. CYP4V2 is a unique member of the CYP4 family. CYP4V2 inactivation in retinal pigment epithelial cells leads to cholesterol accumulation and Bietti's Crystalline Dystrophy (BCD) pathogenesis. This commentary provides information on the role CYP4V2 has in metabolic syndrome and nonalcoholic fatty liver disease progression. This is accomplished by identifying its role in BCD, its control of cholesterol synthesis and lipid droplet formation in C. elegans, and the putative function in cardiovascular disease and gastrointestinal/hepatic pathologies.

miR-1 coordinately regulates lysosomal v-ATPase and biogenesis to impact proteotoxicity and muscle function during aging

Muscle function relies on the precise architecture of dynamic contractile elements, which must be fine-tuned to maintain motility throughout life. Muscle is also plastic, and remodeled in response to stress, growth, neural and metabolic inputs. The conserved muscle-enriched microRNA, miR-1, regulates distinct aspects of muscle development, but whether it plays a role during aging is unknown. Here we investigated Caenorhabditis elegans miR-1 in muscle function in response to proteostatic stress. mir-1 deletion improved mid-life muscle motility, pharyngeal pumping, and organismal longevity upon polyQ35 proteotoxic challenge. We identified multiple vacuolar ATPase subunits as subject to miR-1 control, and the regulatory subunit vha-13/ATP6V1A as a direct target downregulated via its 3'UTR to mediate miR-1 physiology. miR-1 further regulates nuclear localization of lysosomal biogenesis factor HLH-30/TFEB and lysosomal acidification. Our studies reveal that miR-1 coordinately regulates lysosomal v-ATPase and biogenesis to impact muscle function and health during aging.

Synthesis and biological activity of cyclopropyl Δ7-dafachronic acids as DAF-12 receptor ligands

The four cyclopropyl stereoisomers of Δ7-dafachronic acids were prepared from the bile acid hyodeoxycholic acid and employed as chemical tools to exploit the importance of the orientation and spatial disposition of the carboxyl tail and the C25-methyl group for the binding at the DAF-12 receptor. The synthesis route was based on (a) Walden inversion and stereoselective PtO₂-hydrogenation to convert the L-shaped 5β-cholanoid scaffold into the planar 5α-sterol intermediate; (b) two-carbon homologation of the side chain by Wittig and cyclopropanation reaction; and (c) formation of the 3-keto group and Δ7 double bond. The synthesized isomers were isolated and tested for their activity as DAF-12 ligands by AlphaScreen assays. Results showed a significant loss of potency and efficacy for all the four stereoisomers when compared to the parent endogenous ligand. Computational analysis has evidenced the configurational and conformational arrangement of both the carboxylic and the C25-methyl group of dafachronic acids as key structural determinants for DAF-12 binding and activation.

Lipid metabolism and lipid signals in aging and longevity

Lipids play crucial roles in regulating aging and longevity. In the past few decades, a series of genetic pathways have been discovered to regulate lifespan in model organisms. Interestingly, many of these regulatory pathways are linked to lipid metabolism and lipid signaling. Lipid metabolic enzymes undergo significant changes during aging and are regulated by different longevity pathways. Lipids also actively modulate lifespan and health span as signaling molecules. In this review, we summarize recent insights into the roles of lipid metabolism and lipid signaling in aging and discuss lipid-related interventions in promoting longevity.

miR-71 mediates age-dependent opposing contributions of the stress-activated kinase KGB-1 in Caenorhabditis elegans

Studying the evolutionary processes that shaped aging offers a path for understanding the causes of aging. The antagonistic pleiotropy theory for the evolution of aging proposes that the inverse correlation between age and natural selection strength allows positive selection of gene variants with early-life beneficial contributions to fitness despite detrimental late-life consequences. However, mechanistic understanding of how this principle manifests in aging is still lacking. We previously identified antagonistic pleiotropy in the function of the Caenorhabditis elegans JNK homolog KGB-1, which provided stress protection in developing larvae, but sensitized adults to stress and shortened their lifespan. To a large extent, KGB-1's contributions depended on age-dependent and opposing regulation of the stress-protective transcription factor DAF-16, but the underlying mechanisms remained unknown. Here, we describe a role for the microRNA miR-71 in mediating effects of KGB-1 on DAF-16 and downstream phenotypes. Fluorescent imaging along with genetic and survival analyses revealed age-dependent regulation of mir-71 expression by KGB-1-upregulation in larvae, but downregulation in adults-and showed that mir-71 was required both for late-life effects of KGB-1 (infection sensitivity and shortened lifespan), as well as for early life resistance to cadmium. While mir-71 disruption did not compromise development under protein-folding stress (known to depend on KGB-1), disruption of the argonaute gene alg-1, a central component of the microRNA machinery, did. These results suggest that microRNAs play a role in mediating age-dependent antagonistic contributions of KGB-1 to survival, with mir-71 playing a central role and additional microRNAs potentially contributing redundantly.

Cortisol promotes stress tolerance via DAF-16 in Caenorhabditis elegans

In this study, we studied the effects of cortisol and cortisone on the age-related decrease in locomotion in the nematode Caenorhabditis elegans and on the tolerance to heat stress at 35 °C and to oxidative stress induced by the exposure to 0.1% H₂O₂. Changes in mRNA expression levels of C. elegans genes related to stress tolerance were also analyzed. Cortisol treatment restored nematode movement following heat stress and increased viability under oxidative stress, but also shortened worm lifespan. Cortisone, a cortisol precursor, also restored movement after heat stress. Additionally, cortisol treatment increased mRNA expression of the hsp-12.6 and sod-3 genes. Furthermore, cortisol treatment failed to restore movement of daf-16-deficient mutants after heat stress, whereas cortisone failed to restore the movement of dhs-30-deficient mutants after heat stress. In conclusion, the results suggested that cortisol promoted stress tolerance via DAF-16 but shortened the lifespan, whereas cortisone promoted stress tolerance via DHS-30.

•

Cortisol promoted anti-aging, heat and oxidative stress tolerance but shorten life span

•Cortisone promoted anti-aging and heat stress tolerance

•Heat and oxidative stress tolerance induced by cortisol depended on DAF-16 and SKN-1, respectively.

•Cortisone was converted to cortisol via DHS-30

Targeting metabolic pathways for extension of lifespan and healthspan across multiple species

Metabolism plays a significant role in the regulation of aging at different levels, and metabolic reprogramming represents a major driving force in aging. Metabolic reprogramming leads to impaired organismal fitness, an age-dependent increase in susceptibility to diseases, decreased ability to mount a stress response, and increased frailty. The complexity of age-dependent metabolic reprogramming comes from the multitude of levels on which metabolic changes can be connected to aging and regulation of lifespan. This is further complicated by the different metabolic requirements of various tissues, cross-organ communication via metabolite secretion, and direct effects of metabolites on epigenetic state and redox regulation; however, not all of these changes are causative to aging. Studies in yeast, flies, worms, and mice have played a crucial role in identifying mechanistic links between observed changes in various metabolic traits and their effects on lifespan. Here, we review how changes in the organismal and organ-specific metabolome are associated with aging and how targeting of any one of over a hundred different targets in specific metabolic pathways can extend lifespan. An important corollary is that restriction or supplementation of different metabolites can change activity of these metabolic pathways in ways that improve healthspan and extend lifespan in different organisms. Due to the high levels of conservation of metabolism in general, translating findings from model systems to human beings will allow for the development of effective strategies for human health- and lifespan extension.

Polyunsaturated fatty acids and p38-MAPK link metabolic reprogramming to cytoprotective gene expression during dietary restriction

The metabolic state of an organism instructs gene expression modalities, leading to changes in complex life history traits, such as longevity. Dietary restriction (DR), which positively affects health and life span across species, leads to metabolic reprogramming that enhances utilisation of fatty acids for energy generation. One direct consequence of this metabolic shift is the upregulation of cytoprotective (CyTP) genes categorized in the Gene Ontology (GO) term of "Xenobiotic Detoxification Program" (XDP). How an organism senses metabolic changes during nutritional stress to alter gene expression programs is less known. Here, using a genetic model of DR, we show that the levels of polyunsaturated fatty acids (PUFAs), especially linoleic acid (LA) and eicosapentaenoic acid (EPA), are increased following DR and these PUFAs are able to activate the CyTP genes. This activation of CyTP genes is mediated by the conserved p38 mitogen-activated protein kinase (p38-MAPK) pathway. Consequently, genes of the PUFA biosynthesis and p38-MAPK pathway are required for multiple paradigms of DR-mediated longevity, suggesting conservation of mechanism. Thus, our study shows that PUFAs and p38-MAPK pathway function downstream of DR to help communicate the metabolic state of an organism to regulate expression of CyTP genes, ensuring extended life span.

A conserved mechanism of sirtuin signalling through steroid hormone receptors

SIRT1 and orthologous sirtuins regulate a universal mechanism of ageing and thus determine lifespan across taxa; however, the precise mechanism remains vexingly polemical. They also protect against many metabolic and ageing-related diseases by dynamically integrating several processes including autophagy, proteostasis, calorie restriction, circadian rhythmicity and metabolism. These sirtuins are therefore important drug targets particularly because they also transduce allosteric signals from sirtuin-activating compounds such as resveratrol into increased healthspan in evolutionarily diverse organisms. While many of these functions are apparently regulated by deacetylation, that mechanism may not be all-encompassing. Since gonadal signals have been shown to regulate ageing/lifespan in worms and flies, the present study hypothesized that these sirtuins may act as intermediary factors for steroid hormone signal transduction. Accordingly, SIRT1 and its orthologues, Sir2 and Sir-2.1, are shown to be veritable nuclear receptor coregulators that classically coactivate the oestrogen receptor in the absence of ligand; coactivation was further increased by 17β-oestradiol. Remarkably in response to the worm steroid hormone dafachronic acid, SIRT1 reciprocally coactivates DAF-12, the steroid receptor that regulates nematode lifespan. These results suggest that steroid hormones may co-opt and modulate a phyletically conserved mechanism of sirtuin signalling through steroid receptors. Hence, it is interesting to speculate that certain sirtuin functions including prolongevity and metabolic regulation may be mechanistically linked to this endocrine signalling pathway; this may also have implications for understanding the determinative role of gonadal steroids such as oestradiol in human ageing. At its simplest, this report shows evidence for a hitherto unknown deacetylation-independent mechanism of sirtuin signalling.

A Natural Mutational Event Uncovers a Life History Trade-Off via Hormonal Pleiotropy

Environmental signals often control central life history decisions, including the choice between reproduction and somatic maintenance. Such adaptive developmental plasticity occurs in the nematode Caenorhabditis elegans, where environmental cues govern whether larvae will develop directly into reproducing adults or arrest their development to become stress-resistant dauer larvae. Here, we identified a natural variant underlying enhanced sensitivity to dauer-inducing cues in C. elegans: a 92-bp deletion in the cis-regulatory region of the gene eak-3. This deletion reduces synthesis or activity of the steroid hormone dafachronic acid (DA), thereby increasing environmental sensitivity for dauer induction. Consistent with known pleiotropic roles of DA, this eak-3 variant significantly slows down reproductive growth. We experimentally show that, although the eak-3 deletion can provide a fitness advantage through facilitated dauer production in stressful environments, this allele becomes rapidly outcompeted in favorable environments. The identified eak-3 variant therefore reveals a trade-off in how hormonal responses influence both the pace of developmental timing and the way in which environmental sensitivity controls adaptive plasticity. Together, our results show how a single mutational event altering hormonal signaling can lead to the emergence of a complex life history trade-off.

Molecular Physiology of Bile Acid Signaling in Health, Disease, and Aging

Over the past two decades, bile acids (BAs) have become established as important signaling molecules that enable fine-tuned inter-tissue communication from the liver, their site of production, over the intestine, where they are modified by the gut microbiota, to virtually any organ, where they exert their pleiotropic physiological effects. The chemical variety of BAs, to a large extent determined by the gut microbiome, also allows for a complex fine-tuning of adaptive responses in our body. This review provides an overview of the mechanisms by which BA receptors coordinate several aspects of physiology and highlights new therapeutic strategies for diseases underlying pathological BA signaling.

The development of the dog heartworm is highly sensitive to sterols which activate the orthologue of the nuclear receptor DAF-12

Prevention therapy against Dirofilaria immitis in companion animals is currently threatened by the emergence of isolates resistant to macrocyclic lactone anthelmintics. Understanding the control over developmental processes in D. immitis is important for elucidating new approaches to heartworm control. The nuclear receptor DAF-12 plays a role in the entry and exit of dauer stage in Caenorhabditis elegans and in the development of free-living infective third-stage larvae (iL3) of some Clade IV and V parasitic nematodes. We identified a DAF-12 ortholog in the clade III nematode D. immitis and found that it exhibited a much higher affinity for dafachronic acids than described with other nematode DAF-12 investigated so far. We also modelled the DimDAF-12 structure and characterized the residues involved with DA binding. Moreover, we showed that cholesterol derivatives impacted the molting process from the iL3 to the fourth-stage larvae. Since D. immitis is unable to synthesize cholesterol and only completes its development upon host infection, we hypothesize that host environment contributes to its further molting inside the host vertebrate. Our discovery contributes to a better understanding of the developmental checkpoints of D. immitis and offers new perspectives for the development of novel therapies against filarial infections.

The road ahead for health and lifespan interventions

Aging is a modifiable risk factor for most chronic diseases and an inevitable process in humans. The development of pharmacological interventions aimed at delaying or preventing the onset of chronic conditions and other age-related diseases has been at the forefront of the aging field. Preclinical findings have demonstrated that species, sex and strain confer significant heterogeneity on reaching the desired health- and lifespan-promoting pharmacological responses in model organisms. Translating the safety and efficacy of these interventions to humans and the lack of reliable biomarkers that serve as predictors of health outcomes remain a challenge. Here, we will survey current pharmacological interventions that promote lifespan extension and/or increased healthspan in animals and humans, and review the various anti-aging interventions selected for inclusion in the NIA's Interventions Testing Program as well as the ClinicalTrials.gov database that target aging or age-related diseases in humans.

HLH-30/TFEB Is a Master Regulator of Reproductive Quiescence

All animals have evolved the ability to survive nutrient deprivation, and nutrient signaling pathways are conserved modulators of health and disease. In C. elegans, late-larval starvation provokes the adult reproductive diapause (ARD), a long-lived quiescent state that enables survival for months without food, yet underlying molecular mechanisms remain unknown. Here, we show that ARD is distinct from other forms of diapause, showing little requirement for canonical longevity pathways, autophagy, and fat metabolism. Instead it requires the HLH-30/TFEB transcription factor to promote the morphological and physiological remodeling involved in ARD entry, survival, and recovery, suggesting that HLH-30 is a master regulator of reproductive quiescence. HLH-30 transcriptome and genetic analyses reveal that Max-like HLH factors, AMP-kinase, mTOR, protein synthesis, and mitochondrial fusion are target processes that promote ARD longevity. ARD thus rewires metabolism to ensure long-term survival and may illuminate similar mechanisms acting in stem cell quiescence and long-term fasting.

A Molecular Basis for Reciprocal Regulation between Pheromones and Hormones in Response to Dietary Cues in C. elegans

Under stressful conditions, the early larvae of C. elegans enter dauer diapause, a non-aging period, driven by the seemingly opposite influence of ascaroside pheromones (ASCRs) and steroid hormone dafachronic acids (DAs). However, the molecular basis of how these small molecules engage in competitive crosstalk in coordination with insulin/IGF-1 signaling (IIS) remains elusive. Here we report a novel transcriptional regulatory pathway that seems to operate between the ASCR and DA biosynthesis under ad libitum (AL) feeding conditions or bacterial deprivation (BD). Although expression of the ASCR and DA biosynthetic genes reciprocally inhibit each other, ironically and interestingly, such dietary cue-mediated modulation requires the presence of the competitors. Under BD, induction of ASCR biosynthetic gene expression required DA, while ASCR suppresses the expression of the DA biosynthetic gene daf-36. The negative regulation of DA by ASCR was IIS-dependent, whereas daf-36 regulation appeared to be independent of IIS. These observations suggest that the presence of ASCR determines the IIS-dependency of DA gene expression regardless of dietary conditions. Thus, our work defines a molecular basis for a novel reciprocal gene regulation of pheromones and hormones to cope with stressful conditions during development and aging.

Nutrient Sensing and Response Drive Developmental Progression in Caenorhabditis elegans

In response to nutrient limitation, many animals, including Caenorhabditis elegans, slow or arrest their development. This process requires mechanisms that sense essential nutrients and induce appropriate responses. When faced with nutrient limitation, C. elegans can induce both short and long-term survival strategies, including larval arrest, decreased developmental rate, and dauer formation. To select the most advantageous strategy, information from many different sensors must be integrated into signaling pathways, including target of rapamycin (TOR) and insulin, that regulate developmental progression. Here, how nutrient information is sensed and integrated into developmental decisions that determine developmental rate and progression in C. elegans is reviewed.

A fln-2 mutation affects lethal pathology and lifespan in C. elegans

Differences in genetic background in model organisms can have complex effects on phenotypes of interest. We previously reported a difference in hermaphrodite lifespan between two wild-type lines widely used by C. elegans researchers (N2 hermaphrodite and male stocks). Here, using pathology-based approaches and genome sequencing, we identify the cause of this difference as a nonsense mutation in the filamin gene fln-2 in the male stock, which reduces early mortality caused by pharyngeal infection. We show how fln-2 variation explains previous discrepancies involving effects of sir-2.1 (sirtuin deacetylase) on ageing, and show that in a fln-2(+) background, sir-2.1 over-expression causes an FUDR (DNA synthesis inhibitor)-dependent reduction in pharyngeal infection and increase in lifespan. In addition we show how fln-2 variation confounds effects on lifespan of daf-2 (insulin/IGF-1 signalling), daf-12 (steroid hormone signalling), and eat-2 (putative dietary restriction). These findings underscore the importance of identifying and controlling genetic background variation.

Steroids originating from bacterial bile acid degradation affect Caenorhabditis elegans and indicate potential risks for the fauna of manured soils

Bile acids are steroid compounds from the digestive tracts of vertebrates that enter agricultural environments in unusual high amounts with manure. Bacteria degrading bile acids can readily be isolated from soils and waters including agricultural areas. Under laboratory conditions, these bacteria transiently release steroid compounds as degradation intermediates into the environment. These compounds include androstadienediones (ADDs), which are C₁₉-steroids with potential hormonal effects. Experiments with Caenorhabditis elegans showed that ADDs derived from bacterial bile acid degradation had effects on its tactile response, reproduction rate, and developmental speed. Additional experiments with a deletion mutant as well as transcriptomic analyses indicated that these effects might be conveyed by the putative testosterone receptor NHR-69. Soil microcosms showed that the natural microflora of agricultural soil is readily induced for bile acid degradation accompanied by the transient release of steroid intermediates. Establishment of a model system with a Pseudomonas strain and C. elegans in sand microcosms indicated transient release of ADDs during the course of bile acid degradation and negative effects on the reproduction rate of the nematode. This proof-of-principle study points at bacterial degradation of manure-derived bile acids as a potential and so-far overlooked risk for invertebrates in agricultural soils.

Dafachronic acid promotes larval development in Haemonchus contortus by modulating dauer signalling and lipid metabolism

Here, we discovered an endogenous dafachronic acid (DA) in the socioeconomically important parasitic nematode Haemonchus contortus. We demonstrate that DA promotes larval exsheathment and development in this nematode via a relatively conserved nuclear hormone receptor (DAF-12). This stimulatory effect is dose- and time-dependent, and relates to a modulation of dauer-like signalling, and glycerolipid and glycerophospholipid metabolism, likely via a negative feedback loop. Specific chemical inhibition of DAF-9 (cytochrome P450) was shown to significantly reduce the amount of endogenous DA in H. contortus; compromise both larval exsheathment and development in vitro; and modulate lipid metabolism. Taken together, this evidence shows that DA plays a key functional role in the developmental transition from the free-living to the parasitic stage of H. contortus by modulating the dauer-like signalling pathway and lipid metabolism. Understanding the intricacies of the DA-DAF-12 system and associated networks in H. contortus and related parasitic nematodes could pave the way to new, nematode-specific treatments.

In the present study, using an integrative multi-omics approach, we show that dafachronic acid (DA) plays a critical functional role in the developmental transition in larvae of the parasitic nematode Haemonchus contortus (barber’s pole worm) by modulating the dauer-like signalling pathway and lipid metabolism. The DA-DAF-12 signalling module in H. contortus provides a paradigm to explore its developmental and reproductive biology at the molecular level, to study physiochemical cross-talk between the parasite and its hosts, and to discover novel anthelmintic targets.

Aiweixin, a Traditional Uyghur Medicinal Formula, Extends the Lifespan of Caenorhabditis elegans

Aiweixin (AWX) is a traditional Uyghur medicine prescription, which has been used to treat senile diseases for a long time. We investigate whether the AWX extends the lifespan of Caenorhabditis elegans. The AWX decoction was the conventional product for clinical use. The wild-type Caenorhabditis elegans (N2) and mutational worms, daf-16(mu86), glp-1(e2141), daf-2(e1370), and eat-2(ad465), were applied for the lifespan analysis. We found that the lifespan of the N2 adults' worm received 0.005 and 0.01 volume of AWX/total volume was extended significantly, compared to the control without treatment of AWX. The AWX at 0.01 volume of AWX/total volume significantly prolonged the life of both mutational worms, daf-16 (mu86) and eat-2(ad465), but did not increase the lifespan of the mutational worms, daf-2(e1370) and glp-1(e2141). These results indicated that the AWX significantly extended the lifespan of wild-type nematodes, and the life extension effect of AWX was related to the germline longevity pathway and IIS signaling pathway but independent of DAF-16/FOXO.

The 7α-hydroxysteroid dehydratase Hsh2 is essential for anaerobic degradation of the steroid skeleton of 7α-hydroxyl bile salts in the novel denitrifying bacterium Azoarcus sp. strain Aa7

Bile salts are steroid compounds from the digestive tract of vertebrates and enter the environment via defecation. Many aerobic bile-salt degrading bacteria are known but no bacteria that completely degrade bile salts under anoxic conditions have been isolated so far. In this study, the facultatively anaerobic Betaproteobacterium Azoarcus sp. strain Aa7 was isolated that grew with bile salts as sole carbon source under anoxic conditions with nitrate as electron acceptor. Phenotypic and genomic characterization revealed that strain Aa7 used the 2,3-seco pathway for the degradation of bile salts as found in other denitrifying steroid-degrading bacteria such as Sterolibacterium denitrificans. Under oxic conditions strain Aa7 used the 9,10-seco pathway as found in, for example, Pseudomonas stutzeri Chol1. Metabolite analysis during anaerobic growth indicated a reductive dehydroxylation of 7α-hydroxyl bile salts. Deletion of the gene hsh2 _Aa7 encoding a 7-hydroxysteroid dehydratase led to strongly impaired growth with cholate and chenodeoxycholate but not with deoxycholate lacking a hydroxyl group at C7. The hsh2 _Aa7 deletion mutant degraded cholate and chenodeoxycholate to the corresponding C₁₉ -androstadienediones only while no phenotype change was observed during aerobic degradation of cholate. These results showed that removal of the 7α-hydroxyl group was essential for cleavage of the steroid skeleton under anoxic conditions.

Comparative bioinformatic analysis suggests that specific dauer-like signalling pathway components regulate Toxocara canis development and migration in the mammalian host

Background

Toxocara canis is quite closely related to Ascaris suum but its biology is more complex, involving a phase of arrested development (diapause or hypobiosis) in tissues as well as transplacental and transmammary transmission routes. In the present study, we explored and compared dauer-like signalling pathways of T. canis and A. suum to infer which components in these pathways might associate with, or regulate, this added complexity in T. canis.

Methods

Guided by information for Caenorhabditis elegans, we bioinformatically inferred and compared components of dauer-like signalling pathways in T. canis and A. suum using genomic and transcriptomic data sets. In these two ascaridoids, we also explored endogenous dafachronic acids (DAs), which are known to be critical in regulating larval developmental processes in C. elegans and other nematodes, by liquid chromatography-mass spectrometry (LC-MS).

Results

Orthologues of C. elegans dauer signalling genes were identified in T. canis (n = 55) and A. suum (n = 51), inferring the presence of a dauer-like signalling pathway in both species. Comparisons showed clear differences between C. elegans and these ascaridoids as well as between T. canis and A. suum, particularly in the transforming growth factor-β (TGF-β) and insulin-like signalling pathways. Specifically, in both A. suum and T. canis, there was a paucity of genes encoding SMAD transcription factor-related protein (daf-3, daf-5, daf-8 and daf-14) and insulin/insulin-like peptide (daf-28, ins-4, ins-6 and ins-7) homologues, suggesting an evolution and adaptation of the signalling pathway in these parasites. In T. canis, there were more orthologues coding for homologues of antagonist insulin-like peptides (Tc-ins-1 and Tc-ins-18), an insulin receptor substrate (Tc-ist-1) and a serine/threonine kinase (Tc-akt-1) than in A. suum, suggesting potentiated functional roles for these molecules in regulating larval diapause and reactivation. A relatively conserved machinery was proposed for DA synthesis in the two ascaridoids, and endogenous Δ4- and Δ7-DAs were detected in them by LC-MS analysis. Differential transcription analysis between T. canis and A. suum suggests that ins-17 and ins-18 homologues are specifically involved in regulating development and migration in T. canis larvae in host tissues.

Conclusion

The findings of this study provide a basis for functional explorations of insulin-like peptides, signalling hormones (i.e. DAs) and related nuclear receptors, proposed to link to development and/or parasite-host interactions in T. canis. Elucidating the functional roles of these molecules might contribute to the discovery of novel anthelmintic targets in ascaridoids.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3265-y) contains supplementary material, which is available to authorized users.

DAF-16/FOXO and HLH-30/TFEB function as combinatorial transcription factors to promote stress resistance and longevity

The ability to perceive and respond to harmful conditions is crucial for the survival of any organism. The transcription factor DAF-16/FOXO is central to these responses, relaying distress signals into the expression of stress resistance and longevity promoting genes. However, its sufficiency in fulfilling this complex task has remained unclear. Using C. elegans, we show that DAF-16 does not function alone but as part of a transcriptional regulatory module, together with the transcription factor HLH-30/TFEB. Under harmful conditions, both transcription factors translocate into the nucleus, where they often form a complex, co-occupy target promoters, and co-regulate many target genes. Interestingly though, their synergy is stimulus-dependent: They rely on each other, functioning in the same pathway, to promote longevity or resistance to oxidative stress, but they elicit heat stress responses independently, and they even oppose each other during dauer formation. We propose that this module of DAF-16 and HLH-30 acts by combinatorial gene regulation to relay distress signals into the expression of specific target gene sets, ensuring optimal survival under each given threat.

Regulation of Age-related Decline by Transcription Factors and Their Crosstalk with the Epigenome

Aging is a complex phenomenon, where damage accumulation, increasing deregulation of biological pathways, and loss of cellular homeostasis lead to the decline of organismal functions over time. Interestingly, aging is not entirely a stochastic process and progressing at a constant rate, but it is subject to extensive regulation, in the hands of an elaborate and highly interconnected signaling network. This network can integrate a variety of aging-regulatory stimuli, i.e. fertility, nutrient availability, or diverse stresses, and relay them via signaling cascades into gene regulatory events - mostly of genes that confer stress resistance and thus help protect from damage accumulation and homeostasis loss. Transcription factors have long been perceived as the pivotal nodes in this network. Yet, it is well known that the epigenome substantially influences eukaryotic gene regulation, too. A growing body of work has recently underscored the importance of the epigenome also during aging, where it not only undergoes drastic age-dependent changes but also actively influences the aging process. In this review, we introduce the major signaling pathways that regulate age-related decline and discuss the synergy between transcriptional regulation and the epigenetic landscape.

Emerging topics in C. elegans aging research: Transcriptional regulation, stress response and epigenetics

Key discoveries in aging research have been made possible with the use of model organisms. Caenorhabditis elegans is a short-lived nematode that has become a well-established system to study aging. The practicality and powerful genetic manipulations associated with this metazoan have revolutionized our ability to understand how organisms age. 25 years after the publication of the discovery of the daf-2 gene as a genetic modifier of lifespan, C. elegans remains as relevant as ever in the quest to understand the process of aging. Nematode aging research has proven useful in identifying transcriptional regulators, small molecule signals, cellular mechanisms, epigenetic modifications associated with stress resistance and longevity, and lifespan-extending compounds. Here, we review recent discoveries and selected topics that have emerged in aging research using this incredible little worm.

Endocannabinoids in Caenorhabditis elegans are essential for the mobilization of cholesterol from internal reserves

Proper cholesterol transport is crucial for the functionality of cells. In C. elegans, certain cholesterol derivatives called dafachronic acids (DAs) govern the entry into diapause. In their absence, worms form a developmentally arrested dauer larva. Thus, cholesterol transport to appropriate places for DA biosynthesis warrants the reproductive growth. Recently, we discovered a novel class of glycosphingolipids, PEGCs, required for cholesterol mobilization/transport from internal storage pools. Here, we identify other components involved in this process. We found that strains lacking polyunsaturated fatty acids (PUFAs) undergo increased dauer arrest when grown without cholesterol. This correlates with the depletion of the PUFA-derived endocannabinoids 2-arachidonoyl glycerol and anandamide. Feeding of these endocannabinoids inhibits dauer formation caused by PUFAs deficiency or impaired cholesterol trafficking (e.g. in Niemann-Pick C1 or DAF-7/TGF-β mutants). Moreover, in parallel to PEGCs, endocannabinoids abolish the arrest induced by cholesterol depletion. These findings reveal an unsuspected function of endocannabinoids in cholesterol trafficking regulation.

Ancylostoma ceylanicum infective third-stage larvae are activated by co-culture with HT-29-MTX intestinal epithelial cells

BACKGROUND

Human hookworm larvae arrest development until they enter an appropriate host. This makes it difficult to access the larvae for studying larval development or host-parasite interactions. While there are in vivo and in vitro animal models of human hookworm infection, there is currently no human, in vitro model. While animal models have provided much insight into hookworm biology, there are limitations to how closely this can replicate human infection. Therefore, we have developed a human, in vitro model of the initial phase of hookworm infection using intestinal epithelial cell culture.

RESULTS

Co-culture of the human hookworm Ancylostoma ceylanicum with the mucus-secreting, human intestinal epithelial cell line HT-29-MTX resulted in activation of infective third-stage larvae, as measured by resumption of feeding. Larvae were maximally activated by direct contact with fully differentiated HT-29-MTX intestinal epithelial cells. HT-29-MTX cells treated with A. ceylanicum larvae showed differential gene expression of several immunity-related genes.

CONCLUSIONS

Co-culture with HT-29-MTX can be used to activate A. ceylanicum larvae. This provides an opportunity to study the interaction of activated larvae with the human intestinal epithelium.

Lifespan Extension of Caenorhabditis elegans by Butyricicoccus pullicaecorum and Megasphaera elsdenii with Probiotic Potential

Butyricicoccus pullicaecorum and Megasphaera elsdenii inhabit the human intestine and have probiotic potential. The aim of this study was to evaluate the effects of B. pullicaecorum and M. elsdenii on the lifespan of Caenorhabditis elegans. They significantly (P < 0.05) extended the lifespan of C. elegans compared with Escherichia coli OP50, a standard food for the worm. Analysis of age-related biomarkers such as lipofuscin, body size, and locomotory activity showed that they retarded aging. They all failed to extend the lifespan of daf-12 or dbl-1 loss-of-function C. elegans mutants compared with E. coli OP50-fed worms. However, the increase in lifespan was observed in daf-16, jnk-1, pmk-1, and skn-1 mutants. Moreover, they increased the resistance of C. elegans to a human pathogen, Salmonella typhimurium. In conclusion, B. pullicaecorum and M. elsdenii extend the lifespan of C. elegans via the transforming growth factor-beta (TGF-β) pathway associated with anti-inflammatory processes in the innate immune system.

Cell cycle controls stress response and longevity in C. elegans

Recent studies have revealed a variety of genes and mechanisms that influence the rate of aging progression. In this study, we identified cell cycle factors as potent regulators of health and longevity in C. elegans. Focusing on the cyclin-dependent kinase 2 (cdk-2) and cyclin E (cye-1), we show that inhibition of cell cycle genes leads to tolerance towards environmental stress and longevity. The reproductive system is known as a key regulator of longevity in C. elegans. We uncovered the gonad as the central organ mediating the effects of cell cycle inhibition on lifespan. In particular, the proliferating germ cells were essential for conferring longevity. Steroid hormone signaling and the FOXO transcription factor DAF-16 were required for longevity associated with cell cycle inhibition. Furthermore, we discovered that SKN-1 (ortholog of mammalian Nrf proteins) activates protective gene expression and induces longevity when cell cycle genes are inactivated. We conclude that both, germline absence and inhibition through impairment of cell cycle machinery results in longevity through similar pathways. In addition, our studies suggest further roles of cell cycle genes beyond cell cycle progression and support the recently described connection of SKN-1/Nrf to signals deriving from the germline.