Transgenic Nematodes Research Articles

Sweet tea (Rubus Suavissmus S. Lee) polysaccharides promote the longevity of Caenorhabditis elegans through autophagy-dependent insulin and mitochondrial pathways

The fine structure of sweet tea polysaccharide (STP-60a) has been characterized. However, the biological activity of STP-60a has not been extensively explored. This study aims to evaluate the anti-aging activity of STP-60a using Caenorhabditis elegans (C. elegans) as a model and to investigate the underlying molecular mechanism. 400 μg/mL of STP-60a increased the mean lifespan of C. elegans by 22.88%, reduced the lipofuscin content by 33.01%, and improved the survival rate under heat stress and oxidative stress by 32.33% and 27.63%, respectively. Further research in lifespan-related mutants revealed that STP-60a exerted anti-aging effects mainly through insulin and mitochondrial signaling pathways. Through qRT-PCR and microscopic imaging of transgenic nematodes, we found that 400 μg/mL of STP-60a increased the expression of daf-16, skn-1, and hsf-1 downstream of the insulin pathway by 1.68-fold, 1.88-fold, and 1.03-fold, respectively, and promoted the accumulation of daf-16 and skn-1 in the nucleus. STP-60a also significantly regulated the function of the mitochondrial respiratory chain and unfolded protein recovery system. Furthermore, STP-60a activated the autophagy level in C. elegans, and the mutation of daf-2 or clk-1 inhibited the upregulation of autophagy genes by STP-60a, suggesting that autophagy acted as an effector of the insulin and mitochondrial pathways during STP-60a antiaging.

Phytochemical Composition and Anti-Aging Activity of Butanol Extract of Hedyotis diffusa in Caenorhabditis elegans.

Hedyotis diffusa Willd. (H. diffusa), a kind of traditional Chinese medicine, has been evaluated to potential display antioxidant and anti-aging effects in vitro experiments. In this work, we investigated the effects on lifespan and stress resistance of the butanol extract from H. diffusa (NHD) in vivo using a Caenorhabditis elegans (C. elegans) model. The phytochemicals of NHD were identified by UPLC-ESI-qTOF-MS/MS method. NHD-treated wild-type N2 worms showed an increase in survival time under both normal and stress conditions. Meanwhile, NHD promoted the healthspan of nematodes by stimulating growth and development, reducing the deposition of age pigment, increasing the activities of superoxide dismutase (SOD) and glutathione peroxidase dismutase (GSH-Px), and decreasing the level of ROS without impairing fertility. Moreover, the upregulating of the expression of daf-16, gst-4, sod-3, hsp12.6 genes and the downregulating of the expression of daf-2 were involved in the NHD-mediated lifespan extension. Finally, the increasing of the expression of GST-4::GFP in CL2166 transgenic nematodes and the life-span-extending activity of NHD was completely abolished in daf-2 and daf-16 mutants further revealed that the potential roles for these genes in NHD-induced longevity in C. elegans. Collectively, our findings suggest that NHD may have an active effect in healthy aging and age-related diseases.

Zn-dependent β-amyloid Aggregation and its Reversal by the Tetrapeptide HAEE.

The pathogenesis of Alzheimer's disease (AD) is associated with the formation of cerebral amyloid plaques, the main components of which are the modified Aβ molecules as well as the metal ions. Aβ isomerized at Asp7 residue (isoD7-Aβ) is the most abundant isoform in amyloid plaques. We hypothesized that the pathogenic effect of isoD7-Aβ is due to the formation of zinc-dependent oligomers, and that this interaction can be disrupted by the rationally designed tetrapeptide (HAEE). Here, we utilized surface plasmon resonance, nuclear magnetic resonance, and molecular dynamics simulation to demonstrate Zn2+-dependent oligomerization of isoD7-Aβ and the formation of a stable isoD7-Aβ:Zn2+:HAEE complex incapable of forming oligomers. To demonstrate the physiological importance of zinc-dependent isoD7-Aβ oligomerization and the ability of HAEE to interfere with this process at the organismal level, we employed transgenic nematodes overexpressing human Aβ. We show that the presence of isoD7-Aβ in the medium triggers extensive amyloidosis that occurs in a Zn2+-dependent manner, enhances paralysis, and shortens the animals' lifespan. Exogenous HAEE completely reverses these pathological effects of isoD7-Aβ. We conclude that the synergistic action of isoD7-Aβ and Zn2+ promotes Aβ aggregation and that the selected small molecules capable of interrupting this process, such as HAEE, can potentially serve as anti-amyloid therapeutics.

Ursolic acid ameliorates amyloid β-induced pathological symptoms in Caenorhabditis elegans by activating the proteasome

BackgroundAmyloid β induces pathological symptoms in various neurodegenerative disorders. It is the hallmark of these neurodegenerative disorders, such as Alzheimer’s disease, and is reported to induce neurotoxicity leading to neuronal impairment. The continuous development of neurodegenerative disease accompanies pathological changes in amyloid β deposition in the brain. After amyloid β accumulates, the inadequate clearance of amyloid β further accelerates the development of events in the pathological cascade. In eukaryotes, the proteasome is responsible for the degradation of misfolded and damaged proteins to maintain proteostasis. Therefore, screening candidates that preserve proteasomal activity may promote amyloid β homeostasis, which is expected to provide new therapeutic opportunities for these neurodegenerative diseases. Ursolic acid, a natural triterpenoid, has prominent pharmacological antioxidant, anti-inflammatory, neuroprotective, and nontoxic activities. Here, we explored the protective effects of ursolic acid on amyloid β-induced pathological symptoms. MethodsThis study investigated the therapeutic potential of ursolic acid and its underlying molecular mechanisms using a Caenorhabditis elegans transgenic pathological model. ResultsIn our study, ursolic acid successfully repressed amyloid β-induced paralysis and hypersensitivity to serotonin in Caenorhabditis elegans. The levels of amyloid β monomers, oligomers, and deposits were decreased after treatment with ursolic acid in transgenic nematodes overexpressing human amyloid β; however, ursolic acid did not affect exogenous transgene transcription and expression levels. Ursolic acid transcriptionally enhanced the ubiquitin-proteasome system and augmented proteasome activity in vivo. However, the proteasome inhibitor MG132 abolished the therapeutic effect of ursolic acid on behavioral paralysis, and Parkinson’s disease-related-1 was required for the therapeutic effect of ursolic acid. ConclusionsOur study revealed that ursolic acid prevented amyloid β-induced proteotoxic stress, specifically by reducing the amount of amyloid β and increasing proteasome activity in vivo. Furthermore, the therapeutic effect of ursolic acid on transgenic nematodes expressing amyloid β depended on the increased activity of the proteasome. This work provides an essential supplement to the information on the pharmacological mechanism of ursolic acid.

Deer antler extracts reduce amyloid-beta toxicity in a Caenorhabditis elegans model of Alzheimer's disease

Ethnopharmacological relevanceVelvet antler extracts (VAE) are composed of a variety of active substances and growth factors, and have been reported to improve sleep quality and memory. Aim of the studyWe aimed to explore the protective effects and mechanism of action for VAE on Alzheimer's disease (AD) using a transgenic Caenorhabditis elegans model. Materials and methodsC. elegans were cultivated at 40% relative humidity on solid nematode growth medium (NGM) containing live E. coli (OP50) as the food source, with Strain N2 (normal) held at 20 °C and the CL4176s (transgenic) held at 16 °C. AD-like aggregation of Aβ peptide in the CL4176s strain is induced by lifting the temperature to 25 °C. Nematodes were treated with three types of VAEs and Resveratrol (positive control). Analyses included qRT-PCR for quantification of gene transcripts of interest; ELISA for measuring levels of amyloid-β protein; Thioflavin T fluorescent staining for localizing Aβ depositions; assays for reactive oxygen species (ROS) and superoxide dismutase activity (SOD). ResultsVAEs reduced β-amyloid peptide (Aβ) toxicity in the transgenic C. elegans model. An enzymatically-digested VAE (EDVAE) was superior to both a cold-water VAE (CWVAE) and a hot-water VAE (HWVAE) from the same velvet antler. EDVAE treatment reduced the severity of the Aβ-induced paralysis phenotype and decreased the amount of Aβ deposits in the AD model nematodes, and these effects were found to be significantly better than that of the positive control Resveratrol. In addition, EDVAE treatment reduced production of ROS (induced by Aβ), enhanced SOD activity, and elevated expression levels of antioxidant-related transcription factors, although it is not known whether these effects were achieved directly or indirectly. ConclusionEDVAE had a protective role in Aβ-induced toxicity in the transgenic AD nematodes, possibly through reducing accumulation of toxic Aβ and enhancing the ability of nematodes to resist oxidative stress. Thus, EDVAE has potential to be an effective treatment to relieve the symptoms of AD.

Alteration of mitochondrial homeostasis is an early event in a C. elegans model of human tauopathy.

Tauopathies are a group of progressive neurodegenerative disorders characterized by the presence of insoluble intracellular tau filaments in the brain. Evidence suggests that there is a tight connection between mitochondrial dysfunction and tauopathies, including Alzheimer’s disease. However, whether mitochondrial dysfunction occurs prior to the detection of tau aggregates in tauopathies remains elusive. Here, we utilized transgenic nematodes expressing the full length of wild type tau in neuronal cells and monitored mitochondrial morphology alterations over time. Although tau-expressing nematodes did not accumulate detectable levels of tau aggregates during larval stages, they displayed increased mitochondrial damage and locomotion defects compared to the control worms. Chelating calcium restored mitochondrial activity and improved motility in the tau-expressing larvae suggesting a link between mitochondrial damage, calcium homeostasis and neuronal impairment in these animals. Our findings suggest that defective mitochondrial function is an early pathogenic event of tauopathies, taking place before tau aggregation and undermining neuronal homeostasis and organismal fitness. Understanding the molecular mechanisms causing mitochondrial dysfunction early in tauopathy will be of significant clinical and therapeutic value and merits further investigation.

Synthesis of Novel Pinocembrin Amino Acid Derivatives and Their Antiaging Effect on Caenorhabditis elegans via the Modulating DAF-16/FOXO.

PurposePinocembrin is a dihydroflavonoid, which is widely found in several plant species. Although pinocembrin has good pharmacological activity, it has poor water solubility and low bioavailability. Therefore, we have modified the structure of pinocembrin with a combination of different amino acids to solve this problem. Moreover, the effect of the antiaging activity of them has not been explored. We aim to investigate the effect of pinocembrin and its amino acid derivatives on the aging of Caenorhabditis elegans.MethodsPinocembrin was spliced with different amino acids in order to obtain their corresponding derivatives. The preliminary research of pinocembrin and its amino acid derivatives on antiaging effect was studied by using the C. elegans model. Among all the compounds, the one shows the best antiaging effect was then studied on antiaging mechanism. The protective effect on nematodes under emergency conditions was explained by detecting the ROS content and sod-3p::GFP fusion protein expression in nematodes; the possible anti-aging mechanism of nematodes was determined by DAF-16 nuclear localization experiment and the survival curve of transgenic nematodes model under stress conditions.ResultsPb-3 showed the best effect on increasing tolerance to thermal and oxidative stress and reduce the accumulation of lipofuscin. In the assay of C. elegans, pb-3 reduced intracellular ROS accumulation. Application of pb-3 to the transgenic mutant TJ356 induced the translocation of the transcription factor DAF-16 from the cytosol to the nucleus, and modulated the expression of SOD-3 (downstream genes of daf-16), which regulates longevity in C. elegans. Moreover, pb-3 did not prolong the lifespan of daf-16, age-1, daf-2 and hsp16.2 mutants, suggesting that these genetic pathways are involved in mediating the antiaging effects of pb-3.ConclusionThe antioxidant and antiaging properties of pb-3 may involve in the DAF-16/FOXO transcription process. Pinocembrin amino acid derivatives might be a novel agent for antiaging therapy.

Chronic exposure to UV-aged microplastics induces neurotoxicity by affecting dopamine, glutamate, and serotonin neurotransmission in Caenorhabditis elegans

Microplastics are ubiquitous in all environments and exert toxic effects in various organisms. However, the neurotoxicity and underlying mechanisms of long-term exposure to MPs aged under UV radiation remain largely unclear. In this study, Caenorhabditis elegans was treated with 0.1–100 μg/L virgin and aged polystyrene microplastics (PS-MPs) for 10 d, with locomotion behavior, neuronal development, neurotransmitter content, and neurotransmission-related to gene expression as endpoints. Using locomotion behavior as an endpoint, chronic exposure to aged PS-MPs at low concentrations (1 μg/L) caused more severe neurotoxicity than that to virgin PS-MPs. In transgenic nematodes, exposure to 10–100 μg/L aged PS-MPs significantly influenced the fluorescence intensity and percentage of worms with neurodegeneration of dopaminergic, glutamatergic, and serotonergic neurons compared with control. Further investigations showed that the content of glutamate, serotonin, and dopamine was significantly influenced in nematodes chronically exposed to 100 μg/L of aged PS-MPs. Similarly, neurotransmission-related gene (e.g., eat-4, dat-1, and tph-1) expression was also altered in nematodes. These results indicate that aged PS-MPs exert neurotoxicity owing to their effects on dopamine, glutamate, and serotonin neurotransmission. This study provides insights into the underlying mechanisms and potential risks of PS-MPs after UV radiation.

Neuroprotective Effects of Palmatine via the Enhancement of Antioxidant Defense and Small Heat Shock Protein Expression in Aβ-Transgenic Caenorhabditis elegans.

Palmatine is a naturally occurring isoquinoline alkaloid that has been reported to display neuroprotective effects against amyloid-β- (Aβ-) induced neurotoxicity. However, the mechanisms underlying the neuroprotective activities of palmatine remain poorly characterized in vivo. We employed transgenic Caenorhabditis elegans models containing human Aβ1-42 to investigate the effects and possible mechanisms of palmatine-mediated neuroprotection. Treatment with palmatine significantly delayed the paralytic process and reduced the elevated reactive oxygen species levels in Aβ-transgenic C. elegans. In addition, it increased oxidative stress resistance without affecting the lifespan of wild-type C. elegans. Pathway analysis suggested that the differentially expressed genes were related mainly to aging, detoxification, and lipid metabolism. Real-time PCR indicated that resistance-related genes such as sod-3 and shsp were significantly upregulated, while the lipid metabolism-related gene fat-5 was downregulated. Further studies demonstrated that the inhibitory effects of palmatine on Aβ toxicity were attributable to the free radical-scavenging capacity and that the upregulated expression of resistance-related genes, especially shsp, whose expression was regulated by HSF-1, played crucial roles in protecting cells from Aβ-induced toxicity. The research showed that there were significantly fewer Aβ deposits in transgenic CL2006 nematodes treated with palmatine than in control nematodes. In addition, our study found that Aβ-induced toxicity was accompanied by dysregulation of lipid metabolism, leading to excessive fat accumulation in Aβ-transgenic CL4176 nematodes. The alleviation of lipid disorder by palmatine should be attributed not only to the reduction in fat synthesis but also to the inhibition of Aβ aggregation and toxicity, which jointly maintained metabolic homeostasis. This study provides new insights into the in vivo neuroprotective effects of palmatine against Aβ aggregation and toxicity and provides valuable targets for the prevention and treatment of AD.

Functional Modulators of Resilience to Age-Associated Dopaminergic Neurodegeneration in C. elegans

The societal costs of neurodegenerative diseases demand a sense of urgency and innovative strategies toward therapeutic intervention. We have exploited the experimental attributes of roundworm, C. elegans, as a model to expedite discovery of genetic and chemical modifiers of the age-dependent progressive neurodegeneration of dopaminergic neurons commonly associated with Parkinson’s disease (PD). Our model of transgenic nematodes overexpressing the misfolding-prone familial PD gene product, alpha-synuclein, has proven prescient in illuminating key aspects of PD pathology, including vesicular trafficking, autophagy, stress response, lipid dynamics, as well as the first evidence of endolysosomal function in effecting dopaminergic neurodegeneration. Subsequent chemical-genetic analyses reveal a mechanism whereby dopamine transport intersects with epigenetic control of gene expression through proteins functioning in endocytic regulation to modulate neuroprotection. We theorize this reflects a “tunable” nexus of gene-by-environmental regulation where dopamine levels, which impact alpha-synuclein misfolding, are coordinately controlled with epigenetic response to mediate resilience to age-dependent neurodegeneration.

Modeling neurodegeneration in Caenorhabditiselegans.

ABSTRACTThe global burden of neurodegenerative diseases underscores the urgent need for innovative strategies to define new drug targets and disease-modifying factors. The nematode Caenorhabditis elegans has served as the experimental subject for multiple transformative discoveries that have redefined our understanding of biology for ∼60 years. More recently, the considerable attributes of C. elegans have been applied to neurodegenerative diseases, including amyotrophic lateral sclerosis, Alzheimer's disease, Parkinson's disease and Huntington's disease. Transgenic nematodes with genes encoding normal and disease variants of proteins at the single- or multi-copy level under neuronal-specific promoters limits expression to select neuronal subtypes. The anatomical transparency of C. elegans affords the use of co-expressed fluorescent proteins to follow the progression of neurodegeneration as the animals age. Significantly, a completely defined connectome facilitates detailed understanding of the impact of neurodegeneration on organismal health and offers a unique capacity to accurately link cell death with behavioral dysfunction or phenotypic variation in vivo. Moreover, chemical treatments, as well as forward and reverse genetic screening, hasten the identification of modifiers that alter neurodegeneration. When combined, these chemical-genetic analyses establish critical threshold states to enhance or reduce cellular stress for dissecting associated pathways. Furthermore, C. elegans can rapidly reveal whether lifespan or healthspan factor into neurodegenerative processes. Here, we outline the methodologies employed to investigate neurodegeneration in C. elegans and highlight numerous studies that exemplify its utility as a pre-clinical intermediary to expedite and inform mammalian translational research.

Antioxidant Peptides from Sepia esculenta Hydrolyzate Attenuate Oxidative Stress and Fat Accumulation in Caenorhabditis elegans

The hydrolysate of golden cuttlefish (Sepia esculenta) was prepared by using papain, and then, it was further separated by ultrafiltration, gel filtration chromatography, and reverse-phase high-performance liquid chromatography (RP-HPLC). The peptide components of the active fraction were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and then two novel peptides, SeP2 (DVEDLEAGLAK, 1159.27 Da) and SeP5 (EITSLAPSTM, 1049.22 Da), were obtained and displayed significant alleviation effects on oxidative stress in Caenorhabditis elegans. Studies indicated that S. esculenta antioxidant peptides (SePs) increase superoxide dismutase (SOD) activity but reduce reactive oxygen species (ROS) and malondialdehyde (MDA) levelsin oxidation-damaged nematodes. Using transgenic CF1553 nematodes, the sod-3p::GFP expression in the worms treated with SePs was significantly higher than that of the control nematodes. Real-time PCR also demonstrated that the expression of stress-related genes such as sod-3 is up-regulated by SePs. Furthermore, studies showed that SePs could obviously decrease fat accumulation as well as reduce the elevated ROS and MDA levels in high-fat nematodes. Taken together, these results indicated that SePs are capable of the activation of antioxidant defense and the inhibition of free radicals and lipid peroxidation, play important roles in attenuating oxidative stress and fat accumulation in C. elegans, and might have the potential to be used in nutraceutical and functional foods.

Assessment of de novo Protein Synthesis Rates in Caenorhabditis elegans.

Maintaining a healthy proteome is essential for cell and organismal homeostasis. Perturbation of the balance between protein translational control and degradation instigates a multitude of age-related diseases. Decline of proteostasis quality control mechanisms is a hallmark of ageing. Biochemical methods to detect de novo protein synthesis are still limited, have several disadvantages and cannot be performed in live cells or animals. Caenorhabditis elegans, being transparent and easily genetically modified, is an excellent model to monitor protein synthesis rates by using imaging techniques. Here, we introduce and describe a method to measure de novo protein synthesis in vivo utilizing fluorescence recovery after photobleaching (FRAP). Transgenic animals expressing fluorescent proteins in specific cells or tissues are irradiated by a powerful light source resulting in fluorescence photobleaching. In turn, assessment of fluorescence recovery signifies new protein synthesis in cells and/or tissues of interest. Hence, the combination of transgenic nematodes, genetic and/or pharmacological interventions together with live imaging of protein synthesis rates can shed light on mechanisms mediating age-dependent proteostasis collapse.

Detoxification mechanisms of nickel sulfate in nematode Caenorhabditis elegans

Nickel is the most prevailing metal allergen with the highest sensitization rate among the “TOP 25” contact allergens and can affect about 15% of the human population. It is an essential trace metal in plants, animals, and humans. However, the environmental levels of nickel are considerably higher than what is needed for human life. Exposure to high levels of nickel can lead to skin allergies, lung fibrosis, and carcinogenesis. Few existing studies have closely examined the toxicity of nickel, let alone investigated the effective detoxification pathways. Here, we developed a high-throughput screening platform to comprehensively evaluate the nickel toxicity in wild-type C. elegans and explore the underlying detoxification mechanisms in transgenic nematodes. We demonstrated that nickel exerted multiple toxic effects on growth, brood size, feeding, and locomotion in C. elegans. Of which, brood size is the most sensitive endpoint. Nickel was found to first bind to phytochelatin (PC) after entering the worms’ body and this PC-Ni complex was further transported by the ABC transporter, CeHMT-1, into the coelomocytes for further detoxification. Our study also demonstrated that the high-throughput screening platform is a promising system for evaluation and investigation of the ecological risks of heavy metals.

Drug synergy as a strategy for compression of morbidity in a Caenorhabditis elegans model of Alzheimer's disease.

Alzheimer's disease (AD) is the most common cause of dementia worldwide. AD is a multifactorial disease with simultaneous occurrence of several connected pathological processes including mitochondrial dysfunction and impaired proteostasis. Most of these are also implicated in organismal aging per se. The presence of separable pathological conditions poses the opportunity to try combination treatments that target these different processes separately. This approach may provide an effective strategy to target AD; therefore, we investigated whether a combination of metformin (targeting mitochondria and energy metabolism) and lithium (targeting proteostasis) could result in synergistic benefits. In this perspective paper, we looked for benefits in lifespan and healthspan using a transgenic nematode strain, GRU102, which expresses pan-neuronal human amyloid-beta (Aβ). Individually, metformin and lithium extended the lifespan of both non-transgenic GRU101 controls and GRU102. Combination treatment using metformin and lithium did not result in any synergistic increase in GRU102 lifespan, but this treatment did result in a significant compression of morbidity when compared with each individual drug, resulting in relative and absolute extension of healthspan. Despite over-expressing pathogenic human Aβ in their neurons, GRU102 worms treated with the combination treatment enjoyed longer lifespans and significantly compressed morbidity, even compared with untreated non-transgenic animals. These findings suggest combination treatment as a strategy to compress morbidity, and highlight the distinction between healthspan and lifespan.

Nanopolystyrene-induced microRNAs response in Caenorhabditis elegans after long-term and lose-dose exposure

microRNAs (miRNAs) usually act post-transcriptionally to suppress the expression of many targeted genes. However, the response of miRNAs to nanoplastics is still unclear. We here employed Caenorhabditis elegans to investigate the response of miRNAs to 100 nm nanopolystyrene at a predicted environmental concentration (1 μg/L). After exposure from L1-larvae to adult day-3, we found that 7 miRNAs (4 down-regulated (mir-39, mir-76, mir-794, and mir-1830) and 3 up-regulated (mir-35, mir-38, and mir-354)) were dysregulated by nanopolystyrene. Expressions of these 7 miRNAs were dose-dependent in nematodes exposed to 1–100 μg/L nanopolystyrene. Among these 7 miRNAs, we found that only mir-35, mir-38, mir-76, mir-354, and mir-794 were involved in the regulation of response to nanopolystyrene based on phenotypic analysis of both transgenic strains and mutant nematodes. Overexpression of mir-35, mir-38, or mir-354 induced a resistance to nanopolystyrene toxicity, and overexpression of mir-76 or mir-794 induced a susceptibility to nanopolystyrene toxicity, which suggested that these 5 miRNAs mediated a protective response to nanopolystyrene. Gene ontology and KEGG analysis further implied that mir-35, mir-38, mir-76, mir-354, and mir-794 were associated with various biological processes and signaling pathways. Our results suggest the crucial role of a certain number of miRNAs in response to nanopolystyrene after long-term and low-dose exposure in organisms.

Genetic background modifies phenotypic and transcriptional responses in a C. elegans model of \u03b1-synuclein toxicity

BackgroundAccumulation of protein aggregates are a major hallmark of progressive neurodegenerative disorders such as Parkinson’s disease and Alzheimer’s disease. Transgenic Caenorhabditis elegans nematodes expressing the human synaptic protein α-synuclein in body wall muscle show inclusions of aggregated protein, which affects similar genetic pathways as in humans. It is not however known how the effects of α-synuclein expression in C. elegans differs among genetic backgrounds. Here, we compared gene expression patterns and investigated the phenotypic consequences of transgenic α-synuclein expression in five different C. elegans genetic backgrounds.ResultsTranscriptome analysis indicates that α-synuclein expression effects pathways associated with nutrient storage, lipid transportation and ion exchange and that effects vary depending on the genetic background. These gene expression changes predict that a range of phenotypes will be affected by α-synuclein expression. We confirm this, showing that α-synuclein expression delayed development, reduced lifespan, increased rate of matricidal hatching, and slows pharyngeal pumping. Critically, these phenotypic effects depend on the genetic background and coincide with the core changes in gene expression.ConclusionsTogether, our results show genotype-specific effects and core alterations in both gene expression and in phenotype in response to α-synuclein expression. We conclude that the effects of α-synuclein expression are substantially modified by the genetic background, illustrating that genetic background needs to be considered in C. elegans models of neurodegenerative disease.

Mitophagy inhibits amyloid-β and tau pathology and reverses cognitive deficits in models of Alzheimer's disease.

Accumulation of damaged mitochondria is a hallmark of aging and age-related neurodegeneration, including Alzheimer's disease (AD). The molecular mechanisms of impaired mitochondrial homeostasis in AD are being investigated. Here we provide evidence that mitophagy is impaired in the hippocampus of AD patients, in induced pluripotent stem cell-derived human AD neurons, and in animal AD models. In both amyloid-β (Aβ) and tau Caenorhabditis elegans models of AD, mitophagy stimulation (through NAD+ supplementation, urolithin A, and actinonin) reverses memory impairment through PINK-1 (PTEN-induced kinase-1)-, PDR-1 (Parkinson's disease-related-1; parkin)-, or DCT-1 (DAF-16/FOXO-controlled germline-tumor affecting-1)-dependent pathways. Mitophagy diminishes insoluble Aβ1-42 and Aβ1-40 and prevents cognitive impairment in an APP/PS1 mouse model through microglial phagocytosis of extracellular Aβ plaques and suppression of neuroinflammation. Mitophagy enhancement abolishes AD-related tau hyperphosphorylation in human neuronal cells and reverses memory impairment in transgenic tau nematodes and mice. Our findings suggest that impaired removal of defective mitochondria is a pivotal event in AD pathogenesis and that mitophagy represents a potential therapeutic intervention.

ApoE-associated modulation of neuroprotection from Aβ-mediated neurodegeneration in transgenic Caenorhabditis elegans.

ABSTRACTAllele-specific distinctions in the human apolipoprotein E (APOE) locus represent the best-characterized genetic predictor of Alzheimer's disease (AD) risk. Expression of isoform APOEε2 is associated with reduced risk, while APOEε3 is neutral and APOEε4 carriers exhibit increased susceptibility. Using Caenorhabditis elegans, we generated a novel suite of humanized transgenic nematodes to facilitate neuronal modeling of amyloid-beta peptide (Aβ) co-expression in the context of distinct human APOE alleles. We found that co-expression of human APOEε2 with Aβ attenuated Aβ-induced neurodegeneration, whereas expression of the APOEε4 allele had no effect on neurodegeneration, indicating a loss of neuroprotective capacity. Notably, the APOEε3 allele displayed an intermediate phenotype; it was not neuroprotective in young adults but attenuated neurodegeneration in older animals. There was no functional impact from the three APOE isoforms in the absence of Aβ co-expression. Pharmacological treatment that examined neuroprotective effects of APOE alleles on calcium homeostasis showed allele-specific responses to changes in ER-associated calcium dynamics in the Aβ background. Additionally, Aβ suppressed survival, an effect that was rescued by APOEε2 and APOEε3, but not APOEε4. Expression of the APOE alleles in neurons, independent of Aβ, exerted no impact on survival. Taken together, these results illustrate that C. elegans provides a powerful in vivo platform with which to explore how AD-associated neuronal pathways are modulated by distinct APOE gene products in the context of Aβ-associated neurotoxicity. The significance of both ApoE and Aβ to AD highlights the utility of this new pre-clinical model as a means to dissect their functional inter-relationship.This article has an associated First Person interview with the first author of the paper.

Novel Bioactive Peptides from Meretrix meretrix Protect Caenorhabditis elegans against Free Radical-Induced Oxidative Stress through the Stress Response Factor DAF-16/FOXO.

The hard clam Meretrix meretrix, which has been traditionally used as medicine and seafood, was used in this study to isolate antioxidant peptides. First, a peptide-rich extract was tested for its protective effect against paraquat-induced oxidative stress using the nematode model Caenorhabditis elegans. Then, three novel antioxidant peptides; MmP4 (LSDRLEETGGASS), MmP11 (KEGCREPETEKGHR) and MmP19 (IVTNWDDMEK), were identified and were found to increase the resistance of nematodes against paraquat. Circular dichroism spectroscopy revealed that MmP4 was predominantly in beta-sheet conformation, while MmP11 and MmP19 were primarily in random coil conformation. Using transgenic nematode models, the peptides were shown to promote nuclear translocation of the DAF-16/FOXO transcription factor, a pivotal regulator of stress response and lifespan, and induce the expression of superoxide dismutase 3 (SOD-3), an antioxidant enzyme. Analysis of DAF-16 target genes by real-time PCR reveals that sod-3 was up-regulated by MmP4, MmP11 and MmP19 while ctl-1 and ctl-2 were also up-regulated by MmP4. Further examination of daf-16 using RNA interference suggests that the peptide-increased resistance of C. elegans to oxidative stress was DAF-16 dependent. Taken together, these data demonstrate the antioxidant activity of M. meretrix peptides, which are associated with activation of the stress response factor DAF-16 and regulation of the antioxidant enzyme genes.