Modeling neurodegeneration in Caenorhabditis elegans

Using Single-Cell RNA sequencing with Drosophila, Zebrafish, and mouse models for studying Alzheimer's and Parkinson's disease

Alzheimer's and Parkinson's disease are the most common neurodegenerative diseases, significantly affecting the elderly with no current cure available. With the rapidly aging global population, advancing research on these diseases becomes increasingly critical. Both disorders are often studied using model organisms, which enable researchers to investigate disease phenotypes and their underlying molecular mechanisms. In this review, we critically discuss the strengths and limitations of using Drosophila, zebrafish, and mice as models for Alzheimer's and Parkinson's research. A focus is the application of single-cell RNA sequencing, which has revolutionized the field by providing novel insights into the cellular and transcriptomic landscapes characterizing these diseases. We assess how combining animal disease modeling with high-throughput sequencing and computational approaches has advanced the field of Alzheimer's and Parkinson's disease research. Thereby, we highlight the importance of integrative multidisciplinary approaches to further our understanding of disease mechanisms and thus accelerating the development of successful therapeutic interventions.

Optogenetic induction of TDP-43 aggregation impairs neuronal integrity and behavior in Caenorhabditis elegans

BACKGROUND

Cytoplasmic aggregation of TAR DNA binding protein 43 (TDP-43) in neurons is one of the hallmarks of TDP-43 proteinopathy. Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) are closely associated with TDP-43 proteinopathy; however, it remains uncertain whether TDP-43 aggregation initiates the pathology or is a consequence of it.

METHODS

To demonstrate the pathology of TDP-43 aggregation, we applied the optoDroplet technique in Caenorhabditis elegans (C. elegans), which allows spatiotemporal modulation of TDP-43 phase separation and assembly.

RESULTS

We demonstrate that optogenetically induced TDP-43 aggregates exhibited insolubility similar to that observed in TDP-43 proteinopathy. These aggregates increased the severity of neurodegeneration, particularly in GABAergic motor neurons, and exacerbated sensorimotor dysfunction in C. elegans.

CONCLUSIONS

We present an optogenetic C. elegans model of TDP-43 proteinopathy that provides insight into the neuropathological mechanisms of TDP-43 aggregates. Our model serves as a promising tool for identifying therapeutic targets for TDP-43 proteinopathy.

Lacticaseibacillus casei IDCC 3451 alleviates cognitive and behavioral functions by reshaping the gut microbiome and regulating intestinal barrier integrity in chronic stress animal models

Lacticaseibacillus casei IDCC 3451 (3451) was evaluated for its effects on the gut-brain axis using Caenorhabditis elegans (C. elegans) and mouse models of stress and inflammation. In C. elegans, 3451 extended lifespans by 25 %, improved motility, and chemotaxis, enhanced survival under pathogen challenge, and reduced amyloid beta accumulation by 42 %. Transcriptomic profiling revealed upregulation of genes involved in neurotransmitter signaling and serine/threonine pathways. In the unpredictable chronic mild stress (UCMS) mouse model, 3451 administration increased the time spent in the center of the open field by 65 % and reduced immobility in the forced swim test by 32 %, indicating anxiolytic and antidepressant effects. Serum levels of aspartate aminotransferase (AST) and gamma-glutamyl transferase (GGT) were decreased by 18 % and 24 %, respectively. Additionally, 3451 restored the expressions of 5HT1AR, GABAR, and tight junction proteins, including ZO-1 and Claudin1. Metabolomic analysis showed increased glycine and decreased palmitic acid levels, associated with an increased abundance of Ruminococcus and Akkermansia. In the dextran sulfate sodium (DSS)-induced colitis model, 3451 reduced the disease activity index by 36 %, improved colon histology, increased goblet cell preservation, and upregulated ZO-1 and IL-10 expression. Threonine levels were also increased and correlated with a higher abundance of Coprococcus. These findings demonstrate that 3451 improved behavioral and intestinal outcomes through coordinated modulation of host signaling, metabolite production, and gut microbial composition, highlighting its therapeutic potential for managing IBD and neurobehavioral disorders.

Nicotinamide N-methyltransferase as a potential therapeutic target for neurodegenerative disorders: Mechanisms, challenges, and future directions

Neurodegenerative diseases (NDs), including Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD), are characterized by progressive neuronal loss and functional decline, posing significant global health challenges. Emerging evidence highlights nicotinamide N-methyltransferase (NNMT), a cytosolic enzyme regulating nicotinamide (NAM) methylation, as a pivotal player in NDs through its dual impact on epigenetic regulation and metabolic homeostasis. This review synthesizes current knowledge on NNMT's role in disease pathogenesis, focusing on its epigenetic modulation via DNA hypomethylation and histone modifications, alongside its disruption of NAD+ synthesis and homocysteine (Hcy) metabolism. Elevated NNMT activity depletes NAD+, exacerbating mitochondrial dysfunction and impairing energy metabolism, while increased Hcy levels drive oxidative stress, neuroinflammation, and aberrant protein aggregation (e.g., Aβ, tau, α-synuclein). Notably, NNMT overexpression in AD and PD correlates with neuronal hypomethylation and neurotoxicity, as observed in postmortem brain studies and transgenic models. Mechanistically, NNMT consumes S-adenosylmethionine (SAM), limiting methyl donor availability for DNA methyltransferases (DNMTs) and histone methyltransferases (HMTs), thereby altering gene expression patterns critical for neuronal survival. Concurrently, NNMT-mediated NAD+ depletion disrupts sirtuin activity (e.g., SIRT1) and mitochondrial biogenesis, accelerating axonal degeneration. Therapeutic strategies targeting NNMT, such as RNA interference (RNAi), small-molecule inhibitors and exercise therapy, show promise in preclinical models by restoring NAD+ levels and reducing Hcy toxicity. However, challenges persist in achieving cellular specificity, optimizing blood-brain barrier penetration, and mitigating off-target effects. This review underscores NNMT's potential as a multifactorial therapeutic target, bridging metabolic and epigenetic dysregulation in NDs. Future research should prioritize elucidating tissue-specific NNMT interactions, refining inhibitor pharmacokinetics, and validating translational efficacy in clinical trials. Addressing these gaps could pave the way for novel disease-modifying therapies to combat the rising burden of neurodegeneration.

Studying the mechanisms of neurodegeneration: C. elegans advantages and opportunities

Caenorhabditis elegans has been widely used as a model organism in neurodevelopment for several decades due to its simplicity, rapid growth, short life cycle, transparency, and rather simple genetics. It has been useful in modeling neurodegenerative diseases by the heterologous expression of the major proteins that form neurodegenerative-linked aggregates such as amyloid-β peptide, tau protein, and α-synuclein, among others. Furthermore, chemical treatments as well as the existence of several interference RNA libraries, transgenic worm lines, and the possibility of generating new transgenic strains create a magnificent range of possible tools to study the signaling pathways that could confer protection against protein aggregates or, on the contrary, are playing a detrimental role. In this review, we summarize the different C. elegans models of neurodegenerative diseases with a focus on Alzheimer's and Parkinson's diseases and how genetic tools could be used to dissect the signaling pathways involved in their pathogenesis mentioning several examples. Finally, we discuss the use of pharmacological agents in C. elegans models that could help to study these disease-associated signaling pathways and the powerful combinations of experimental designs with genetic tools. This review highlights the advantages of C. elegans as a valuable intermediary between in vitro and mammalian in vivo models in the development of potential new therapies.

Microbiological and toxicity analyses of the synthetic polymer polyhexamethylene guanidine hydrochloride against endodontic microorganisms

Failures in endodontic treatments are common due to microbial resistance in the pulp canal. The study evaluated the in vitro activity of polyhexamethylene guanidine hydrochloride (PHMGH) against endodontic strains, as well as in vivo toxicity. Using minimum inhibitory concentration and minimum bactericidal concentration techniques, PHMGH was effective against all microorganisms, even at low concentrations. At 50.0 µg/mL, it inhibited Enterococcus faecalis; furthermore, when compared to chlorhexidine (CLX), it demonstrated values 19 times lower against Candida albicans. The polymer's activity was also determined by agar diffusion, evaluating products A (calcium hydroxide - Ca(OH)2, as a reference), B (Ca(OH)2 combined with physiological solution, reference with a vehicle), C (PHMGH 6.25%), D (PHMGH 3.125%), E (PHMGH 1.5625%), F (PHMGH 0.78125%), G (PHMGH 6.25% and Ca(OH)2), H (PHMGH 3.125% and Ca(OH)2), I (PHMGH 1.5625% and Ca(OH)2), J (PHMGH 0.78125% and Ca(OH)2), and K (positive control, CLX 0.12%). Products containing PHMGH were more effective than the references against all strains, and C, D, and G were more effective than CLX against Peptostreptococcus anaerobius, Actinomyces naeslundii, and Actinomyces viscosus. According to the fractional inhibitory concentration index, the combination of PHMGH and CLX showed indifference for Peptostreptococcus anaerobius, Actinomyces naeslundii, Actinomyces viscosus and Escherichia coli, antagonism for Candida albicans, and synergy for Enterococcus faecalis. The toxicity of PHMGH at different concentrations was tested in Caenorhabditis elegans and did not show lethality in nematodes, with the LC50 observed only at the highest concentration (100 µg/mL) after two days of exposure. It is suggested that PHMGH exhibited antimicrobial activity against endodontic strains and low toxicity, raising expectations for new preventive and therapeutic products in endodontics.

Bio-orthogonal Glycan Imaging of Cultured Cells and Whole Animal C. elegans with Expansion Microscopy

Complex carbohydrates called glycans play crucial roles in regulating cell and tissue physiology, but how they map to nanoscale anatomical features must still be resolved. Here, we present the first nanoscale map of mucin-type O-glycans throughout the entirety of the Caenorhabditis elegans model organism. We constructed a library of multifunctional linkers to probe and anchor metabolically labeled glycans in expansion microscopy (ExM). A flexible strategy was demonstrated for the chemical synthesis of linkers with a broad inventory of bio-orthogonal functional groups, fluorophores, anchorage chemistries, and linker arms. Employing C. elegans as a test bed, metabolically labeled O-glycans were resolved on the gut microvilli and other nanoscale anatomical features. Transmission electron microscopy images of C. elegans nanoanatomy validated the fidelity and isotropy of gel expansion. Whole organism maps of C. elegans O-glycosylation in the first larval stage revealed O-glycan "hotspots" in unexpected anatomical locations, including the body wall furrows. Beyond C. elegans, we validated ExM protocols for nanoscale imaging of metabolically labeled glycans on cultured mammalian cells. Together, our results suggest the broad applicability of the multifunctional reagents for imaging glycans and other metabolically labeled biomolecules at enhanced resolutions with ExM.

Utilizing C. elegans Spermatogenesis and Fertilization Mutants as a Model for Human Disease

The nematode C. elegans is a proven model for identifying genes involved in human disease, and the study of C. elegans reproduction, specifically spermatogenesis and fertilization, has led to significant contributions to our understanding of cellular function. Approximately 70 genes have been identified in C. elegans that control spermatogenesis and fertilization (spe and fer mutants). This review focuses on eight genes that have human orthologs with known pathogenic phenotypes. Using C. elegans to study these genes has led to critical developments in our understanding of protein domain function and human disease, including understanding the role of OTOF (the ortholog of C. elegans fer-1) in hearing loss, the contribution of the spe-39 ortholog VIPAS39 in vacuolar protein sorting, and the overlapping functions of spe-26 and KLHL10 in spermatogenesis. We discuss the cellular function of both the C. elegans genes and their human orthologs and the impact that C. elegans mutants and human variants have on cellular function and physiology. Utilizing C. elegans to understand the function of the genes reviewed here, and additional understudied and undiscovered genes, represents a unique opportunity to understand the function of variants that could lead to better disease diagnosis and clinical decision making.

Assessment of developmental neurotoxicology-associated alterations in neuronal architecture and function using Caenorhabditis elegans

Few of the many chemicals that regulatory agencies are charged with assessing for risk have been carefully tested for developmental neurotoxicity (DNT). To speed up testing efforts, as well as to reduce the use of vertebrate animals, great effort is being devoted to alternate laboratory models for testing DNT. A major mechanism of DNT is altered neuronal architecture resulting from chemical exposure during neurodevelopment. Caenorhabditis elegans is a nematode that has been extensively studied by neurobiologists and developmental biologists, and to a lesser extent by neurotoxicologists. The developmental trajectory of the nervous system in C. elegans is easily visualized, normally entirely invariant, and fully mapped. Therefore, we hypothesized that C. elegans could be a powerful in vivo model to test chemicals for the potential to alter developmental patterning of neuronal architecture. To test whether this might be true, we developed a novel C. elegans DNT testing paradigm that includes exposure throughout development, examines all major neurotransmitter neuronal types for architectural alterations, and tests behaviors specific to dopaminergic, cholinergic, and glutamatergic functions. We used this paradigm to characterize the effects of early-life exposures to the developmental neurotoxicants lead, cadmium, and benzo(a)pyrene (BaP) on dopaminergic, cholinergic, and glutamatergic architecture. We also assessed whether exposures would alter neuronal specification as assessed by expression of reporter genes diagnostic of specific neurotransmitters. We identified no cases in which the apparent neurotransmitter type of the neurons we examined changed, but many in which neuronal morphology was altered. We also found that neuron-specific behaviors were altered during C. elegans mid-adulthood for populations with measured morphological neurodegeneration in earlier stages. The functional changes were consistent with the morphological changes we observed in terms of type of neuron affected. We identified changes consistent with those reported in the mammalian DNT literature, strengthening the case for C. elegans as a DNT model, and made novel observations that should be followed up in future studies.

A Comprehensive Review on Preclinical Alzheimer's Disease Models: Evaluating their Clinical Relevance

Alzheimer's disease (AD) is a neurological disorder that increases with age and must be treated immediately by worldwide healthcare systems. Internal neurofibrillary tau tangles and extracellular amyloid accumulation have been widely recognized as the primary causes of Alzheimer's disease. These degenerative age-related ailments are expected to proliferate exponentially as life expectancy rises. Experimental models of AD are essential for acquiring a deep knowledge of its pathogenesis and determining the viability of novel therapy options. Although there isn't a model that encompasses all the characteristics of real AD, these models are nonetheless highly helpful for the research of various modifications associated with it, even though they are only partially indicative of the disease circumstances being studied. Better knowledge of the advantages and disadvantages of each of the different models, as well as the use of more than one model to evaluate potential medications, would increase the effectiveness of therapy translation from preclinical research to patients. We outline the pathogenic characteristics and limitations of the main experimental models of AD in this review, including transgenic mice, transgenic rats, primates and non-primate models along with in-vitro cell culture models in humans. Additionally, it highlights the possible future of experimental modeling of AD and includes the co-morbid models.

Perillaldehyde alleviates polyQ-induced neurodegeneration through the induction of autophagy and mitochondrial UPR in Caenorhabditis elegans

Huntington's disease (HD) is a fatal neurodegenerative disease associated with autophagy disorder and mitochondrial dysfunction. Here, we identified therapeutic potential of perillaldehyde (PAE), a monoterpene compound obtained from Perilla frutescens (L.) Britt., in the Caenorhabditis elegans (C. elegans) model of HD, which included lifespan extension, healthspan improvement, decrease in polyglutamine (polyQ) aggregation, and preservation of mitochondrial network. Further analyses indicated that PAE was able to induce autophagy and mitochondrial unfolded protein reaction (UPRmt) activation and positively regulated expression of associated genes. In lgg-1 RNAi C. elegans or C. elegans with UPRmt-related genes knockdown, the effects of PAE treatment on polyQ aggregation or rescue polyQ-induced toxicity were attenuated, suggesting that its neuroprotective activity depended on autophagy and UPRmt. Moreover, we found that pharmacological and genetic activation of UPRmt generally protected C. elegans from polyQ-induced cytotoxicity. Finally, PAE promoted serotonin synthesis by upregulating expression of TPH-1, and serotonin synthesis and neurosecretion were required for PAE-mediated UPRmt activation and its neuroprotective activity. In conclusion, PAE is a potential therapy for polyQ-related diseases including HD, which is dependent on autophagy and cell-non-autonomous UPRmt activation.

The Effect of glna Loss on the Physiological and Pathological Phenotype of Parkinson's Disease C. elegans

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative disease. Glutamate(Glu) excitotoxicity is one of the main pathogenesis of PD. Glutaminase (Gls) is an enzyme primarily responsible for catalyzing the hydrolysis and deamidation of glutamine (Gln) to produce Glu and ammonia. Inhibiting the function of Gls may have a beneficial effect on the treatment of PD by reducing the production of Glu. The homologous gene of Gls in C. elegans is glna.

AIMS

To explore the effects of glna loss on physiological and pathological phenotype of PD C. elegans, and to provide new ideas and references for the research and treatment of PD.

MATERIALS & METHODS

We used PD C. elegans UA44 and QIN27 to detect development and lifespan, behavior, degeneration of dopaminergic neurons, lipid levels, ROS levels, expression levels of common amino acids.

RESULTS

Glna loss had no significant impact on the development and lifespan of PD C. elegans. Glna loss saved part of the decline of motor function, including the head thrash frequency and the body bend frequency, and the difference was significant. There was a trend of improvement in some motor behaviors, such as the ethanol avoidance experiment, while no improvement was observed in other experiments. Glna loss slowed down the degeneration of dopaminergic neurons. Glna loss increased the lipid levels and ROS levels in C. elegans. Glna loss decreased Glu content and increased Gln content in C. elegans.

DISCUSSION

The effect of glna loss on PD C. elegans may be the result of multiple factors, such as the tissue types of α-syn expression in C. elegans, the PD C. elegans model used, the adverse effects of glna loss on other systems, and the changes in ROS levels in C. elegans. The specific mechanisms causing these phenomena are still unclear and need to be further explored.

CONCLUSION

Glna loss has a certain protective effect on dopaminergic neurons in PD C. elegans, while the improvement effect on movement and behavior is limited.

Design, synthesis, and biological evaluation of tetrahydropyrimidine analogue as GSK-3β/Aβ aggregation inhibitor and anti-Alzheimer's agent

The complex nature of Alzheimer's disease (AD) etiopathology is among the principal hurdles to developing effective anti-Alzheimer agents. Tau pathology and Amyloid-β (Aβ) accumulation are hallmarks and validated therapeutic strategies of AD. GSK-3β is a serine/threonine kinase involved in tau phosphorylation. Its excessive activity also contributes to the production of Aβ plaques, making GSK-3β an attractive AD target. Taking this into account, In this article, we outline the design, synthesis, and biological validation of a focused library of 1,2,3,4-tetrahydropyrimidine based derivatives as inhibitors of GSK-3β, tau phosphorylation, and Aβ accumulation. The inhibitory activity of forty nine synthetic compounds was tested against GSK-3β and other AD-relevant kinases. The kinetic experiments revealed the mode of GSK-3β inhibition by the most potent compound 44. The in- vitro drug metabolism and pharmacokinetic studies were thereafter performed. The anti-aggregation activity of the most potent GSK-3β inhibitor was tested using AD transgenic Caenorhabditis elegans (C. elegans) strain CL2006 for quantification of Aβ plaques and BR5706 C. elegans strain for tau pathology evaluation. We then evaluated the blood-brain barrier permeability and got promising results. Therefore, we present compound 44 as a potential ATP-competitive GSK-3β inhibitor with good metabolism and pharmacokinetic profile, anti-aggregation properties for amyloid beta protein, and reduction in tau-phosphorylation levels. We recommend more investigation into compound 44-based small molecules as possible targets for AD disease-modifying treatments.

Nucleic acid aptamers protect against lead (Pb(II)) toxicity

Lead (Pb(II)) is a pervasive heavy metal toxin with many well-established negative effects on human health. Lead toxicity arises from cumulative, repeated environmental exposures. Thus, prophylactic strategies to protect against the bioaccumulation of lead could reduce lead-associated human pathologies. Here we show that DNA and RNA aptamers protect C. elegans from toxic phenotypes caused by lead. Reproductive toxicity, as measured by brood size assays, is prevented by co-feeding of animals with DNA or RNA aptamers. Similarly, lead-induced neurotoxicity, measured by behavioral assays, are also normalized by aptamer feeding. Further, cultured human HEK293 and primary murine osteoblasts are protected from lead toxicity by transfection with DNA aptamers. The osteogenic development, which is decreased by lead exposure, is maintained by prior transfection of lead-binding DNA aptamers. Aptamers may be an effective strategy for the protection of human health in the face of increasing environmental toxicants.

Transgenic expression of human cytochrome P450 2E1 in C. elegans and rat PC-12 cells sensitizes to ethanol-induced locomotor and mitochondrial effects

Chronic alcohol (ethanol) use is increasing in the United States and has been linked to numerous health issues in multiple organ systems including neurological dysfunction and diseases. Ethanol toxicity is mainly driven by the metabolite acetaldehyde, which is generated through three pathways: alcohol dehydrogenase (ADH2), catalase (CAT), and cytochrome P450 2E1 (CYP2E1). ADH2, while the main ethanol clearance pathway in the liver, is not expressed in the mammalian brain, resulting in CAT and CYP2E1 driving local metabolism of ethanol in the central nervous system. CYP2E1 is known to generate reactive metabolites and reactive oxygen species and localizes to the mitochondria (mtCYP2E1) and endoplasmic reticulum (erCYP2E1). We sought to understand the consequences of mtCYP2E1 and erCYP2E1 in the nervous system during acute ethanol exposure. To answer this question, we generated transgenic Caenorhabditis elegans roundworms expressing human CYP2E1 in the mitochondria, endoplasmic reticulum, or both and exposed them to ethanol. We found that at lower concentrations, wild-type and mtCYP2E1-expressing worms had a small but significant inhibition of locomotion, whereas the erCYP2E1-expressing worms showed protection from this inhibition. At higher doses, all strains had reduced locomotion, but the erCYP2E1-expressing worms recovered faster than wild-type controls. CYP2E1 expression, regardless of organellar targeting, reduced mitochondrial respiration in response to ethanol. Similarly, transgenic expression of CYP2E1 in either organelle in PC-12 rat neuronal cell lines sensitized them to ethanol-induced cell death. Together, these findings suggest that subcellular localization of CYP2E1 impacts behavioral effects of ethanol and should be further studied in the mammalian central nervous system.

Erucin, a Natural Isothiocyanate, Prevents Polyglutamine-Induced Toxicity in Caenorhabditis elegans via aak-2/AMPK and daf-16/FOXO Signaling

Several neurodegenerative diseases (NDDs), such as Huntington's disease, six of the spinocerebellar ataxias, dentatorubral-pallidoluysian atrophy, and spinobulbar muscular atrophy, are caused by abnormally long polyglutamine (polyQ) tracts. Natural compounds capable of alleviating polyQ-induced toxicity are currently of great interest. In this work, we investigated the modulatory effect against polyQ neurotoxic aggregates exerted by erucin (ERN), an isothiocyanate naturally present in its precursor glucoerucin in rocket salad leaves and in its oxidized form, sulforaphane (SFN), in broccoli. Using C. elegans models expressing polyQ in different tissues, we demonstrated that ERN protects against polyQ-induced toxicity and that its action depends on the catalytic subunit of AMP-activated protein kinase (aak-2/AMPKα2) and, downstream in this pathway, on the daf-16/FOXO transcription factor, since nematodes deficient in aak-2/AMPKα2 and daf-16 did not respond to the treatment, respectively. Although triggered by a different source of neurotoxicity than polyQ diseases, i.e., by α-synuclein (α-syn) aggregates, Parkinson's disease (PD) was also considered in our study. Our results showed that ERN reduces α-syn aggregates and slightly improves the motility of worms. Therefore, further preclinical studies in mouse models of protein aggregation are justified and could provide insights into testing whether ERN could be a potential neuroprotective compound in humans.

Use of Caenorhabditis elegans to Unravel the Tripartite Interaction of Kynurenine Pathway, UPRmt and Microbiome in Parkinson's Disease

The model organism Caenorhabditis elegans and its relationship with the gut microbiome are gaining traction, especially for the study of neurodegenerative diseases such as Parkinson's Disease (PD). Gut microbes are known to be able to alter kynurenine metabolites in the host, directly influencing innate immunity in C. elegans. While the mitochondrial unfolded protein response (UPRmt) was first characterized in C. elegans in 2007, its relevance in host-microbiome interactions has only become apparent in recent years. In this review, we provide novel insights into the current understanding of the microbiome-gut-brain axis with a focus on tripartite interactions between the UPRmt, kynurenine pathway, and microbiome in C. elegans, and explore their relationships for PD remediations.

Combined matrix-assisted laser desorption/ionisation-mass spectrometry imaging with liquid chromatography-tandem mass spectrometry for observing spatial distribution of lipids in whole Caenorhabditis elegans

RATIONALE

Matrix-assisted laser desorption/ionisation-mass spectrometry imaging (MALDI-MSI) is a powerful label-free technique for biomolecule detection (e.g., lipids), within tissue sections across various biological species. However, despite its utility in many applications, the nematode Caenorhabditis elegans is not routinely used in combination with MALDI-MSI. The lack of studies exploring spatial distribution of biomolecules in nematodes is likely due to challenges with sample preparation.

METHODS

This study developed a sample preparation method for whole intact nematodes, evaluated using cryosectioning of nematodes embedded in a 10% gelatine solution to obtain longitudinal cross sections. The slices were then subjected to MALDI-MSI, using a RapifleX Tissuetyper in positive and negative polarities. Samples were also prepared for liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis using an Exploris 480 coupled to a HPLC Vanquish system to confirm the MALDI-MSI results.

RESULTS

An optimised embedding method was developed for longitudinal cross-sectioning of individual worms. To obtain longitudinal cross sections, nematodes were frozen at -80°C so that all worms were rod shaped. Then, the samples were defrosted and transferred to a 10% gelatine matrix in a cryomold; the worms aligned, and the whole cryomold submerged in liquid nitrogen. Using MALDI-MSI, we were able to observe the distribution of lipids within C. elegans, with clear differences in their spatial distribution at a resolution of 5 μm. To confirm the lipids from MALDI-MSI, age-matched nematodes were subjected to LC-MS/MS. Here, 520 lipids were identified using LC-MS/MS, indicating overlap with MALDI-MSI data.

CONCLUSIONS

This optimised sample preparation technique enabled (un)targeted analysis of spatially distributed lipids within individual nematodes. The possibility to detect other biomolecules using this method thus laid the basis for prospective preclinical and toxicological studies on C. elegans.

The Citrus flavanone naringenin prolongs the lifespan in C. elegans and slows signs of brain aging in mice

Aging is one of the main risk factors for neurodegenerative disorders, which represent a global burden on healthcare systems. Therefore, identifying new strategies to slow the progression of brain aging is a compelling challenge. In this article, we first assessed the potential anti-aging effects of the Citrus flavanone naringenin (NAR), an activator of the enzyme sirtuin-1 (SIRT1), in a 3R-compliant and short-lived aging model (i.e., the nematode C. elegans). Then, we investigated the preventive effects of a 6-month treatment with NAR (100 mg/kg, orally) against brain aging and studied its mechanism of action in middle-aged mice. We demonstrated that NAR (100 μM) extends lifespan and improves healthspan in C. elegans. In the brain of middle-aged mice, NAR promotes the activity of metabolic enzymes (citrate synthase, cytochrome C oxidase) and increases the expression of the SIRT1 enzyme. Consistently, NAR up-regulates the expression of downstream antioxidant (Foxo3, Nrf2, Ho-1), anti-senescence (p16), and anti-inflammatory (Il-6, Il-18) markers. Our findings support NAR supplementation to slow the signs of brain aging.

Advanced Neural Functional Imaging in C. elegans Using Lab-on-a-Chip Technology

The ability to perceive and adapt to environmental changes is crucial for the survival of all organisms. Neural functional imaging, particularly in model organisms, such as Caenorhabditis elegans, provides valuable insights into how animals sense and process external cues through their nervous systems. Because of its fully mapped neural anatomy, transparent body, and genetic tractability, C. elegans serves as an ideal model for these studies. This review focuses on advanced methods for neural functional imaging in C. elegans, highlighting calcium imaging techniques, lab-on-a-chip technologies, and their applications in the study of various sensory modalities, including chemosensation, mechanosensation, thermosensation, photosensation, and magnetosensation. We discuss the benefits of these methods in terms of precision, reproducibility, and ability to study dynamic neural processes in real time, ultimately advancing our understanding of the fundamental principles of neural activity and connectivity.

A natural small molecule-mediated inhibition of alpha-synuclein aggregation leads to neuroprotection in Caenorhabditis elegans

Small molecules are being explored intensively for their applications as therapeutic molecules in the management of metabolic and neurological disorders. The natural small molecules can inhibit protein aggregation and underlying cellular pathogenesis of neurodegenerative diseases involving multi-factorial mechanisms of action. Certain natural small molecular inhibitors of pathogenic protein aggregation are highly efficient and have shown promising therapeutic potential. In the present study, Shikonin (SHK), a natural plant-based naphthoquinone has been investigated for its aggregation inhibition activity against α-synuclein (α-syn) and the neuroprotective potential in Caenorhabditis elegans (C. elegans). SHK significantly inhibited aggregation of α-syn at sub-stochiometric concentrations, delayed the linear lag phase and growth kinetics of seeded and unseeded α-syn aggregation. The binding of SHK to the C-terminus of α-syn maintained α-helical and disordered secondary structures with reduced beta-sheet content and complexity of aggregates. Further, in C. elegans transgenic PD models, SHK significantly reduced α-syn aggregation, improved locomotor activity and prevented dopaminergic (DA) neuronal degeneration, indicating the neuroprotective role of SHK. The present study highlights the potential of natural small molecules in the prevention of protein aggregation that may further be explored for their therapeutic efficacy in the management of protein aggregation and neurodegenerative diseases.

Investigating hormesis, aging, and neurodegeneration: From bench to clinics

Mitochondria-derived reactive oxygen species production at a moderate physiological level plays a fundamental role in the anti-aging signaling, due to their action as redox-active sensors for the maintenance of optimal mitochondrial balance between intracellular energy status and hormetic nutrients. Iron regulatory protein dysregulation, systematically increased iron levels, mitochondrial dysfunction, and the consequent oxidative stress are recognized to underlie the pathogenesis of multiple neurodegenerative diseases, such as Parkinson's disease and Alzheimer's disease. Central to their pathogenesis, Nrf2 signaling dysfunction occurs with disruption of metabolic homeostasis. We highlight the potential therapeutic importance of nutritional polyphenols as substantive regulators of the Nrf2 pathway. Here, we discuss the common mechanisms targeting the Nrf2/vitagene pathway, as novel therapeutic strategies to minimize consequences of oxidative stress and neuroinflammation, generally associated to cognitive dysfunction, and demonstrate its key neuroprotective and anti-neuroinflammatory properties, summarizing pharmacotherapeutic aspects relevant to brain pathophysiology.

JNK Signaling Positively Regulates Acute Ethanol Tolerance in C. elegans

Alcohol use disorder (AUD) is a chronic neurobehavioral condition characterized by a cycle of tolerance development, increased consumption, and reinstated craving and seeking behaviors during withdrawal. Understanding the intricate mechanisms of AUD necessitates reliable animal models reflecting its key features. Caenorhabditis elegans (C. elegans), with its conserved nervous system and genetic tractability, has emerged as a valuable model organism to study AUD. Here, we employ an ethanol vapor exposure model in Caenorhabditis elegans, recapitulating AUD features while maintaining high-throughput scalability. We demonstrate that ethanol vapor exposure induces intoxication-like behaviors, acute tolerance, and ethanol preference, akin to mammalian AUD traits. Leveraging this model, we elucidate the conserved role of c-jun N-terminal kinase (JNK) signaling in mediating acute ethanol tolerance. Mutants lacking JNK signaling components exhibit impaired tolerance development, highlighting JNK's positive regulation. Furthermore, we detect ethanol-induced JNK activation in C. elegans. Our findings underscore the utility of C. elegans with ethanol vapor exposure for studying AUD and offer novel insights into the molecular mechanisms underlying acute ethanol tolerance through JNK signaling.

Dendrite morphogenesis in Caenorhabditis elegans

Since the days of Ramón y Cajal, the vast diversity of neuronal and particularly dendrite morphology has been used to catalog neurons into different classes. Dendrite morphology varies greatly and reflects the different functions performed by different types of neurons. Significant progress has been made in our understanding of how dendrites form and the molecular factors and forces that shape these often elaborately sculpted structures. Here, we review work in the nematode Caenorhabditis elegans that has shed light on the developmental mechanisms that mediate dendrite morphogenesis with a focus on studies investigating ciliated sensory neurons and the highly elaborated dendritic trees of somatosensory neurons. These studies, which combine time-lapse imaging, genetics, and biochemistry, reveal an intricate network of factors that function both intrinsically in dendrites and extrinsically from surrounding tissues. Therefore, dendrite morphogenesis is the result of multiple tissue interactions, which ultimately determine the shape of dendritic arbors.

Exploiting the Unique Biology of Caenorhabditis elegans to Launch Neurodegeneration Studies in Space

The 21st century is likely to be the first century in which large-scale short- and long-term space missions become common. Accordingly, an ever-increasing body of research is focusing on understanding the effects of current and future space expeditions on human physiology in health and disease. Yet the complex experimental environment, the small number of participants, and the high cost of space missions are among the primary factors that hinder a better understanding of the impact of space missions on human physiology. The goal of our research was to develop a cost-effective, compact, and easy-to-manipulate system to address questions related to human health and disease in space. This initiative was part of the Ramon SpaceLab program, an annual research-based learning program designed to cultivate high school students' involvement in space exploration by facilitating experiments aboard the International Space Station (ISS). In the present study, we used the nematode Caenorhabditis elegans (C. elegans), a well-suited model organism, to investigate the effect of space missions on neurodegeneration-related processes. Our study specifically focused on the level of aggregation of Huntington's disease-causing polyglutamine stretch-containing (PolyQ) proteins in C. elegans muscles, the canonical system for studying neurodegeneration in this organism. We compared animals expressing PolyQ proteins grown onboard the ISS with their genetically identical siblings grown on Earth and observed a significant difference in the number of aggregates between the two populations. Currently, it is challenging to determine whether this effect stems from developmental or morphological differences between the cultures or is a result of life in space. Nevertheless, our results serve as a proof of concept and open a new avenue for utilizing C. elegans to address various open questions in space studies, including the effects of space conditions on the onset and development of neurodegenerative diseases.

Sink or swim: Does a worm paralysis phenotype hold clues to neurodegenerative disease?

Receiving a neurodegenerative disease (NDD) diagnosis, such as Alzheimer's disease, Parkinson's disease, Huntington's disease, or amyotrophic lateral sclerosis, is devastating, particularly given the limited options for treatment. Advances in genetic technologies have allowed for efficient modeling of NDDs in animals and brought hope for new disease-modifying medications. The complexity of the mammalian brain and the costs and time needed to identify and develop therapeutic leads limits progress. Modeling NDDs in invertebrates, such as the fruit fly Drosophila melanogaster and the nematode Caenorhabditis elegans, offers orders of magnitude increases in speed of genetic analysis and manipulation, and can be pursued at substantially reduced cost, providing an important, platform complement and inform research with mammalian NDD models. In this review, we describe how our efforts to exploit C. elegans for the study of neural signaling and health led to the discovery of a paralytic phenotype (swimming-induced paralysis) associated with altered dopamine signaling and, surprisingly, to the discovery of a novel gene and pathway whose dysfunction in glial cells triggers neurodegeneration. Research to date on swip-10 and its putative mammalian ortholog MBLAC1, suggests that a tandem analysis will offer insights into NDD mechanisms and insights into novel, disease-modifying therapeutics.

Penthorum chinense Pursh inhibits ferroptosis in cellular and Caenorhabditis elegans models of Alzheimer's disease

BACKGROUND

Ferroptosis, a unique type of cell death triggered by iron-dependent lipid peroxidation, plays a critical role in the pathogenesis of Alzheimer's disease (AD), a debilitating condition marked by memory loss and cognitive impairment due to the accumulation of beta-amyloid (Aβ) and hyperphosphorylated Tau protein. Increasing evidence suggests that inhibitors of ferroptosis could be groundbreaking in the treatment of AD.

METHOD

In this study, we established in vitro ferroptosis using erastin-, RSL-3-, hemin-, and iFSP1-induced PC-12 cells. Using MTT along with Hoechst/PI staining, we assessed cell viability and death. To determine various aspects of ferroptosis, we employed fluorescence probes, including DCFDA, JC-1, C11 BODIPY, Mito-Tracker, and PGSK, to measure ROS production, mitochondrial membrane potential, lipid peroxidation, mitochondrial morphology, and intracellular iron levels. Additionally, Western blotting, biolayer interferometry technology, and shRNA were utilized to investigate the underlying molecular mechanisms. Furthermore, p-CAX APP Swe/Ind- and pRK5-EGFP-Tau P301L overexpressing PC-12 cells, along with Caenorhabditis elegans (C. elegans) strains CL4176, CL2331, and BR5270, were employed to examine ferroptosis in AD models.

RESULTS

Here, we conducted a screening of our natural medicine libraries and identified the ethanol extract of Penthorum chinense Pursh (PEE), particularly its ethyl acetate fraction (PEF), displayed inhibitory effects on ferroptosis in cells. Specifically, PEF inhibited the generation of ROS, lipid peroxidation, and intracellular iron levels. Furthermore, PEF demonstrated protective effects against H2O2-induced cell death, ROS production, and mitochondrial damage. Mechanistic investigations unveiled PEF's modulation of intracellular iron accumulation, GPX4 expression and activity, and FSP1 expression. In p-CAX APP Swe/Ind and pRK5-EGFP-Tau P301L overexpressing PC-12 cells, PEF significantly reduced cell death, as well as ROS and lipid peroxidase production. Moreover, PEF ameliorated paralysis and slowing rate in Aβ and Tau transgenic C. elegans models, while inhibiting ferroptosis, as evidenced by decreased DHE intensity, lipid peroxidation levels, iron accumulation, and expression of SOD-3 and gst-4.

CONCLUSION

Our findings highlight the suppressive effects of PEF on ferroptosis in AD cellular and C. elegans models. This study helps us better understand how ferroptosis affects AD and emphasizes the potential of PCP as a candidate for AD intervention.

C. elegans: a prominent platform for modeling and drug screening in neurological disorders

INTRODUCTION

Human neurodevelopmental and neurodegenerative diseases (NDevDs and NDegDs, respectively) encompass a broad spectrum of disorders affecting the nervous system with an increasing incidence. In this context, the nematode C. elegans, has emerged as a benchmark model for biological research, especially in the field of neuroscience.

AREAS COVERED

The authors highlight the numerous advantages of this tiny worm as a model for exploring nervous system pathologies and as a platform for drug discovery. There is a particular focus given to describing the existing models of C. elegans for the study of NDevDs and NDegDs. Specifically, the authors underscore their strong applicability in preclinical drug development. Furthermore, they place particular emphasis on detailing the common techniques employed to explore the nervous system in both healthy and diseased states.

EXPERT OPINION

Drug discovery constitutes a long and expensive process. The incorporation of invertebrate models, such as C. elegans, stands as an exemplary strategy for mitigating costs and expediting timelines. The utilization of C. elegans as a platform to replicate nervous system pathologies and conduct high-throughput automated assays in the initial phases of drug discovery is pivotal for rendering therapeutic options more attainable and cost-effective.

Using C. elegans as a model for neurodegenerative diseases: Methodology and evaluation

Caenorhabditis elegans is a nematode that has been used as an animal model for almost 50years. It has primitive and simple tissues and organs, making it an ideal model for studying neurological pathways involved in neurodegenerative diseases like Alzheimer's disease (AD) and Parkinson's disease (PD). C. elegans has conserved neurological pathways and is able to mimic human diseases, providing valuable insights into the human disease phenotype. This methodological review presents current approaches to generate neurodegenerative-like models of AD and PD in C. elegans, and evaluates the experiments commonly used to validate the diseases. These experimental approaches include assessing survival, fertility, mobility, electropharyngeogram assays, confocal mitochondrial imaging, RNA extraction for qRT-PCR or RT-PCR, and rate of defecation. This review also summarizes the current knowledge acquired on AD and PD using the aforementioned experimental approaches. Additionally, gaps in knowledge and future directions for research are also discussed in the review.

Simple ammonium salt and sigma-1 receptor ligand dipentylammonium provides neuroprotective effects in cell culture and Caenorhabditis elegans models of Alzheimer's disease

The sigma-1 receptor (σ-1R), a chaperone protein located at the mitochondria-associated membrane (MAM) of the endoplasmic reticulum, can interact with and modify the signaling pathways of various proteins, thereby modulating many disease pathologies, including Alzheimer's disease (AD). The σ-1R ligand dipentylammonium (DPA) was analyzed for its anti-AD properties using PC12 cells (in vitro) and Caenorhabditis elegans (in vivo) models along with molecular docking (in silico) analysis. DPA at 1 and 10 µM concentrations was able to significantly potentiate NGF-induced neurite growth length by 137.7 ± 12.0 and 187.8 ± 16.4, respectively, when compared to the control 76.9 ± 7.4. DPA also regulated neurite damage caused by Aβ(25-35) treatment in differentiated PC12 cells by improving cell viability and neurite length. In C. elegans, DPA could significantly extend the median and maximum lifespan of Aβ transgenic strain CL2006 without impacting wild-type nematodes. Additionally, it could significantly reduce the paralysis phenotype of another Aβ transgenic strain, CL4176, thereby improving the overall health in AD pathogenesis. This effect depended on σ-1R, as DPA could not modulate the lifespan of σ-1R mutant TM3443. This was further confirmed using agonist PRE084 and antagonist BD1047, wherein the agonist alone could extend the lifespan of CL2006, while the antagonist suppressed the effect of DPA in CL2006. Interestingly, neither had an TM3443. Further, molecular docking analysis showed that DPA had a similar binding affinity as that of PRE084, BD1047 and pentazocine against the σ-1R receptor in humans and C. elegans, which collectively suggests the anti-AD properties of DPA.

Nucleic Acid Aptamers Protect Against Lead (Pb(II)) Toxicity

Lead (Pb(II)) is a pervasive heavy metal toxin with many well-established negative effects on human health. Lead toxicity arises from cumulative, repeated environmental exposures. Thus, prophylactic strategies to protect against the bioaccumulation of lead could reduce lead-associated human pathologies. Here we show that DNA and RNA aptamers protect C. elegans from toxic phenotypes caused by lead. Reproductive toxicity, as measured by brood size assays, is prevented by co-feeding of animals with DNA or RNA aptamers. Similarly, lead-induced behavioral anomalies are also normalized by aptamer feeding. Further, cultured human HEK293 and primary murine osteoblasts are protected from lead toxicity by transfection with DNA aptamers. The osteogenic development, which is decreased by lead exposure, is maintained by prior transfection of lead-binding DNA aptamers. Aptamers may be an effective strategy for the protection of human health in the face of increasing environmental toxicants.

Melatonin derivative 6a as a PARP-1 inhibitor for the treatment of Parkinson's disease

Both continuous oxidative stress and poly (ADP-ribose) polymerase 1 (PARP-1) activation occur in neurodegenerative diseases such as Parkinson's disease. PARP-1 inhibition can reverse mitochondrial damage and has a neuroprotective effect. In a previous study, we synthesized melatonin derivative 6a (MD6a) and reported that it has excellent antioxidant activity and significantly reduces α-synuclein aggregation in Caenorhabditis elegans; however, the underlying mechanism is largely unknown. In the present study, we revealed that MD6a is a potential PARP-1 inhibitor, leading to mammalian targe of rapamycin/heat shock factor 1 signaling downregulation and reducing heat shock protein 4 and 6 expression, thus helping to maintain protein homeostasis and improve mitochondrial function. Together, these findings suggest that MD6a might be a viable candidate for the prevention and treatment of Parkinson's disease.

C. elegans as a model to study mitochondrial biology and disease

Mitochondria perform a myriad of essential functions that ensure organismal homeostasis, including maintaining bioenergetic capacity, sensing and signalling the presence of pathogenic threats, and determining cell fate. Their function is highly dependent on mitochondrial quality control and the appropriate regulation of mitochondrial size, shape, and distribution during an entire lifetime, as well as their inheritance across generations. The roundworm Caenorhabditis elegans has emerged as an ideal model organism through which to study mitochondria. The remarkable conservation of mitochondrial biology has allowed C. elegans researchers to investigate complex processes that are challenging to study in higher organisms. In this review, we explore the key recent contributions of C. elegans to mitochondrial biology through the lens of mitochondrial dynamics, organellar removal, and mitochondrial inheritance, as well as their involvement in immune responses, various types of stress, and transgenerational signalling.

Exploring Caenorhabditis elegans as Parkinson's Disease Model: Neurotoxins and Genetic Implications

Parkinson's disease (PD) is the second most common neurodegenerative disease in the world, the first being Alzheimer's disease. Patients with PD have a loss of dopaminergic neurons in the substantia nigra of the basal ganglia, which controls voluntary movements, causing a motor impairment as a result of dopaminergic signaling impairment. Studies have shown that mutations in several genes, such as SNCA, PARK2, PINK1, DJ-1, ATP13A2, and LRRK2, and the exposure to neurotoxic agents can potentially increase the chances of PD development. The nematode Caenorhabditis elegans (C. elegans) plays an important role in studying the risk factors, such as genetic factors, aging, exposure to chemicals, disease progression, and drug treatments for PD. C. elegans has a conserved neurotransmission system during evolution; it produces dopamine, through the eight dopaminergic neurons; it can be used to study the effect of neurotoxins and also has strains that express human α-synuclein. Furthermore, the human PD-related genes, LRK-1, PINK-1, PDR-1, DJR-1.1, and CATP-6, are present and functional in this model. Therefore, this review focuses on highlighting and discussing the use of C. elegans an in vivo model in PD-related studies. Here, we identified that nematodes exposed to the neurotoxins, such as 6-OHDA, MPTP, paraquat, and rotenone, had a progressive loss of dopaminergic neurons, dopamine deficits, and decreased survival rate. Several studies have reported that expression of human LRRK2 (G2019S) caused neurodegeneration and pink-1, pdr-1, and djr-1.1 deletion caused several effects PD-related in C. elegans, including mitochondrial dysfunctions. Of note, the deletion of catp-6 in nematodes caused behavioral dysfunction, mitochondrial damage, and reduced survival. In addition, nematodes expressing α-synuclein had neurodegeneration and dopamine-dependent deficits. Therefore, C. elegans can be considered an accurate animal model of PD that can be used to elucidate to assess the underlying mechanisms implicated in PD to find novel therapeutic targets.

Bio-orthogonal Glycan Imaging of Culture Cells and Whole Animal C. elegans with Expansion Microscopy

Complex carbohydrates called glycans play crucial roles in the regulation of cell and tissue physiology, but how glycans map to nanoscale anatomical features must still be resolved. Here, we present the first nanoscale map of mucin-type O -glycans throughout the entirety of the Caenorhabditis elegans model organism. We construct a library of multifunctional linkers to probe and anchor metabolically labelled glycans in expansion microscopy (ExM), an imaging modality that overcomes the diffraction limit of conventional optical microscopes through the physical expansion of samples embedded in a polyelectrolyte gel matrix. A flexible strategy is demonstrated for the chemical synthesis of linkers with a broad inventory of bio-orthogonal functional groups, fluorophores, anchorage chemistries, and linker arms. Employing C. elegans as a test bed, we resolve metabolically labelled O -glycans on the gut microvilli and other nanoscale anatomical features using our ExM reagents and optimized protocols. We use transmission electron microscopy images of C. elegans nano-anatomy as ground truth data to validate the fidelity and isotropy of gel expansion. We construct whole organism maps of C. elegans O -glycosylation in the first larval stage and identify O -glycan "hotspots" in unexpected anatomical locations, including the body wall furrows. Beyond C. elegans , we provide validated ExM protocols for nanoscale imaging of metabolically labelled glycans on cultured mammalian cells. Together, our results suggest the broad applicability of the multifunctional reagents for imaging glycans and other metabolically labelled biomolecules at enhanced resolutions with ExM.

Graphical abstract

Simple models to understand complex disease: 10 years of progress from Caenorhabditis elegans models of amyotrophic lateral sclerosis and frontotemporal lobar degeneration

The nematode Caenorhabditis elegans are a powerful model system to study human disease, with numerous experimental advantages including significant genetic and cellular homology to vertebrate animals, a short lifespan, and tractable behavioral, molecular biology and imaging assays. Beginning with the identification of SOD1 as a genetic cause of amyotrophic lateral sclerosis (ALS), C. elegans have contributed to a deeper understanding of the mechanistic underpinnings of this devastating neurodegenerative disease. More recently this work has expanded to encompass models of other types of ALS and the related disease frontotemporal lobar degeneration (FTLD-TDP), including those characterized by mutation or accumulation of the proteins TDP-43, C9orf72, FUS, HnRNPA2B1, ALS2, DCTN1, CHCHD10, ELP3, TUBA4A, CAV1, UBQLN2, ATXN3, TIA1, KIF5A, VAPB, GRN, and RAB38. In this review we summarize these models and the progress and insights from the last ten years of using C. elegans to study the neurodegenerative diseases ALS and FTLD-TDP.

Amyotrophic Lateral Sclerosis Mechanism: Insights from the Caenorhabditis elegans Models

Amyotrophic Lateral Sclerosis (ALS) is a debilitating neurodegenerative condition characterized by the progressive degeneration of motor neurons. Despite extensive research in various model animals, the cellular signal mechanisms of ALS remain elusive, impeding the development of efficacious treatments. Among these models, a well-characterized and diminutive organism, Caenorhabditis elegans (C. elegans), has emerged as a potent tool for investigating the molecular and cellular dimensions of ALS pathogenesis. This review summarizes the contributions of C. elegans models to our comprehension of ALS, emphasizing pivotal findings pertaining to genetics, protein aggregation, cellular pathways, and potential therapeutic strategies. We analyze both the merits and constraints of the C. elegans system in the realm of ALS research and point towards future investigations that could bridge the chasm between C. elegans foundational discoveries and clinical applications.

Plate-Based Assays for the Characterization of Mitochondrial and Cellular Phenotypes

The mitochondria are essential to eukaryotic life, acting as key drivers of energy generation while also being involved in the regulation of many cellular processes including apoptosis, cell proliferation, calcium homeostasis, and metabolism. Mitochondrial diseases which disrupt these processes lead to a diverse range of pathologies and lack consistency in symptom presentation. In disease, mitochondrial activity and energy homeostasis can be adapted to cellular requirements, and studies using Dictyostelium and human lymphoblastoid cell lines have shown that such changes can be facilitated by the key cellular and energy regulators, TORC1 and AMPK. Fluorescence-based assays are increasingly utilized to measure mitochondrial and cell signalling function in mitochondrial disease research. Here, we describe a streamlined method for the simultaneous measurement of mitochondrial mass, membrane potential, and reactive oxygen species production using MitoTracker Green™ FM, MitoTracker Red™ CMXRos, and DCFH-DA probes. This protocol has been adapted for both Dictyostelium and human lymphoblastoid cell lines. We also describe a method for assessing TORC1 and AMPK activity simultaneously in lymphoblastoid cells. These techniques allow for the characterization of mitochondrial defects in a rapid and easy to implement manner.

Towards Understanding Neurodegenerative Diseases: Insights from Caenorhabditis elegans

The elevated occurrence of debilitating neurodegenerative disorders, such as amyotrophic lateral sclerosis (ALS), Huntington's disease (HD), Alzheimer's disease (AD), Parkinson's disease (PD) and Machado-Joseph disease (MJD), demands urgent disease-modifying therapeutics. Owing to the evolutionarily conserved molecular signalling pathways with mammalian species and facile genetic manipulation, the nematode Caenorhabditis elegans (C. elegans) emerges as a powerful and manipulative model system for mechanistic insights into neurodegenerative diseases. Herein, we review several representative C. elegans models established for five common neurodegenerative diseases, which closely simulate disease phenotypes specifically in the gain-of-function aspect. We exemplify applications of high-throughput genetic and drug screenings to illustrate the potential of C. elegans to probe novel therapeutic targets. This review highlights the utility of C. elegans as a comprehensive and versatile platform for the dissection of neurodegenerative diseases at the molecular level.

The effect of lipid metabolism on age-associated cognitive decline: Lessons learned from model organisms and human

Lipids are required as integral building blocks of cells to support cellular structures and functions. The intricate mechanisms underpinning lipid homeostasis are essential for the health and maintenance of the central nervous system. Here we summarize the recent advances in dissecting the effect of lipid metabolism on cognitive function and its age-associated decline by reviewing relevant studies ranging from invertebrate model organisms to mammals including human.

The million-molecule challenge: a moonshot project to rapidly advance longevity intervention discovery

Targeting aging is the future of twenty-first century preventative medicine. Small molecule interventions that promote healthy longevity are known, but few are well-developed and discovery of novel, robust interventions has stagnated. To accelerate longevity intervention discovery and development, high-throughput systems are needed that can perform unbiased drug screening and directly measure lifespan and healthspan metrics in whole animals. C. elegans is a powerful model system for this type of drug discovery. Combined with automated data capture and analysis technologies, truly high-throughput longevity drug discovery is possible. In this perspective, we propose the "million-molecule challenge", an effort to quantitatively assess 1,000,000 interventions for longevity within five years. The WormBot-AI, our best-in-class robotics and AI data analysis platform, provides a tool to achieve the million-molecule challenge for pennies per animal tested.

Chronic high-sugar diet in adulthood protects Caenorhabditis elegans from 6-OHDA-induced dopaminergic neurodegeneration

BACKGROUND

Diets high in saturated fat and sugar, termed "Western diets," have been associated with several negative health outcomes, including increased risk for neurodegenerative disease. Parkinson's disease (PD) is the second most prevalent neurodegenerative disease and is characterized by the progressive death of dopaminergic neurons in the brain. We build upon previous work characterizing the impact of high-sugar diets in Caenorhabditis elegans to mechanistically evaluate the relationship between high-sugar diets and dopaminergic neurodegeneration.

RESULTS

Adult high-glucose and high-fructose diets, or exposure from day 1 to 5 of adulthood, led to increased lipid content, shorter lifespan, and decreased reproduction. However, in contrast to previous reports, we found that adult chronic high-glucose and high-fructose diets did not induce dopaminergic neurodegeneration alone and were protective from 6-hydroxydopamine (6-OHDA) induced degeneration. Neither sugar altered baseline electron transport chain function and both increased vulnerability to organism-wide ATP depletion when the electron transport chain was inhibited, arguing against energetic rescue as a basis for neuroprotection. The induction of oxidative stress by 6-OHDA is hypothesized to contribute to its pathology, and high-sugar diets prevented this increase in the soma of the dopaminergic neurons. However, we did not find increased expression of antioxidant enzymes or glutathione levels. Instead, we found evidence suggesting downregulation of the dopamine reuptake transporter dat-1 that could result in decreased 6-OHDA uptake.

CONCLUSIONS

Our work uncovers a neuroprotective role for high-sugar diets, despite concomitant decreases in lifespan and reproduction. Our results support the broader finding that ATP depletion alone is insufficient to induce dopaminergic neurodegeneration, whereas increased neuronal oxidative stress may drive degeneration. Finally, our work highlights the importance of evaluating lifestyle by toxicant interactions.

Regulation of the proteostasis network by the neuronal system

The protein homeostasis (proteostasis) network is a nexus of molecular mechanisms that act in concert to maintain the integrity of the proteome and ensure proper cellular and organismal functionality. Early in life the proteostasis network efficiently preserves the functionality of the proteome, however, as the organism ages, or due to mutations or environmental insults, subsets of inherently unstable proteins misfold and form insoluble aggregates that accrue within the cell. These aberrant protein aggregates jeopardize cellular viability and, in some cases, underlie the development of devastating illnesses. Hence, the accumulation of protein aggregates activates different nodes of the proteostasis network that refold aberrantly folded polypeptides, or direct them for degradation. The proteostasis network apparently functions within the cell, however, a myriad of studies indicate that this nexus of mechanisms is regulated at the organismal level by signaling pathways. It was also discovered that the proteostasis network differentially responds to dissimilar proteotoxic insults by tailoring its response according to the specific challenge that cells encounter. In this mini-review, we delineate the proteostasis-regulating neuronal mechanisms, describe the indications that the proteostasis network differentially responds to distinct proteotoxic challenges, and highlight possible future clinical prospects of these insights.

Animal Models of Human Disease

The use of animal models of human disease is critical for furthering our understanding of disease mechanisms, for the discovery of novel targets for treatment, and for translational research. This Special Topic entitled "Animal Models of Human Disease" aimed to collect state-of-the-art primary research studies and review articles from international experts and leading groups using animal models to study human diseases. Submissions were welcomed on a wide range of animal models and pathologies, including infectious disease, acute injury, regeneration, cancer, autoimmunity, degenerative and chronic disease. Seven participating MDPI journals supported the Special Topic, namely: Biomedicines, Cells, Current Issues in Molecular Biology, Diagnostics, Genes, the International Journal of Molecular Sciences, and the International Journal of Translational Medicine. In total, 46 papers were published in this Special Topic, with 37 full length original research papers, 2 research communications and 7 reviews. These contributions cover a wide range of clinically relevant, translatable, and comparative animal models, as well as furthering understanding of fundamental sciences, covering topics on physiological processes, on degenerative, inflammatory, infectious, autoimmune, neurological, metabolic, heamatological, hormonal and mitochondrial disorders, developmental processes and diseases, cardiology, cancer, trauma, stress, and ageing.

Abl depletion via autophagy mediates the beneficial effects of quercetin against Alzheimer pathology across species

Alzheimer's disease is the most common age-associated neurodegenerative disorder and the most frequent form of dementia in our society. Aging is a complex biological process concurrently shaped by genetic, dietary and environmental factors and natural compounds are emerging for their beneficial effects against age-related disorders. Besides their antioxidant activity often described in simple model organisms, the molecular mechanisms underlying the beneficial effects of different dietary compounds remain however largely unknown. In the present study, we exploit the nematode Caenorhabditis elegans as a widely established model for aging studies, to test the effects of different natural compounds in vivo and focused on mechanistic aspects of one of them, quercetin, using complementary systems and assays. We show that quercetin has evolutionarily conserved beneficial effects against Alzheimer's disease (AD) pathology: it prevents Amyloid beta (Aβ)-induced detrimental effects in different C. elegans AD models and it reduces Aβ-secretion in mammalian cells. Mechanistically, we found that the beneficial effects of quercetin are mediated by autophagy-dependent reduced expression of Abl tyrosine kinase. In turn, autophagy is required upon Abl suppression to mediate quercetin's protective effects against Aβ toxicity. Our data support the power of C. elegans as an in vivo model to investigate therapeutic options for AD.

Cytochrome P450 and Epoxide Hydrolase Metabolites in Aβ and tau-induced Neurodegeneration: Insights from Caenorhabditis elegans

This study aims to uncover potent cytochrome P450 (CYP) and epoxide hydrolase (EH) metabolites implicated in Aβ and/or tau-induced neurodegeneration, independent of neuroinflammation, by utilizing Caenorhabditis elegans (C. elegans) as a model organism. Our research reveals that Aβ and/or tau expression in C. elegans disrupts the oxylipin profile, and epoxide hydrolase inhibition alleviates the ensuing neurodegeneration, likely through elevating the epoxy-to-hydroxy ratio of various CYP-EH metabolites. In addition, our results indicated that the Aβ and tau likely affect the CYP-EH metabolism of PUFA through different mechanism. These findings emphasize the intriguing relationship between lipid metabolites and neurodegenerations, in particular, those linked to Aβ and/or tau aggregation. Furthermore, our investigation sheds light on the crucial and captivating role of CYP PUFA metabolites in C. elegans physiology, opening up possibilities for broader implications in mammalian and human contexts.

Chronic high-sugar diet in adulthood protects Caenorhabditis elegans from 6-OHDA induced dopaminergic neurodegeneration

BACKGROUND

Diets high in saturated fat and sugar, termed western diets, have been associated with several negative health outcomes, including increased risk for neurodegenerative disease. Parkinson s Disease (PD) is the second most prevalent neurodegenerative disease and is characterized by the progressive death of dopaminergic neurons in the brain. We build upon previous work characterizing the impact of high sugar diets in Caenorhabditis elegans to mechanistically evaluate the relationship between high sugar diets and dopaminergic neurodegeneration.

RESULTS

Non-developmental high glucose and fructose diets led to increased lipid content and shorter lifespan and decreased reproduction. However, in contrast to previous reports, we found that non-developmental chronic high-glucose and high-fructose diets did not induce dopaminergic neurodegeneration alone and were protective from 6-hydroxydopamine (6-OHDA) induced degeneration. Neither sugar altered baseline electron transport chain function, and both increased vulnerability to organism-wide ATP depletion when the electron transport chain was inhibited, arguing against energetic rescue as a basis for neuroprotection. The induction of oxidative stress by 6-OHDA is hypothesized to contribute to its pathology, and high sugar diets prevented this increase in the soma of the dopaminergic neurons. However, we did not find increased expression of antioxidant enzymes or glutathione levels. Instead, we found evidence suggesting alterations to dopamine transmission that could result in decreased 6-OHDA uptake.

CONCLUSION

Our work uncovers a neuroprotective role for high sugar diets, despite concomitant decreases in lifespan and reproduction. Our results support the broader finding that ATP depletion alone is insufficient to induce dopaminergic neurodegeneration, whereas increased neuronal oxidative stress may drive degeneration. Finally, our work highlights the importance of evaluating lifestyle by toxicant interactions.

Synergetic effect of β-asarone and cannabidiol against Aβ aggregation in vitro and in vivo

Alzheimer's disease (AD) is a complex and multifactorial neurodegenerative disorder, and it is unlikely that any single drug or intervention will be very successful. The pathophysiology of Alzheimer's disease involves a range of complicated biological processes, including the accumulation of beta-amyloid protein and tau protein. Given the complexity of AD and amyloid accumulation, a combination of interventions remains to be further explored. Here, we investigated the potential of combining β-asarone and cannabidiol (CBD) as a treatment for AD. The study analyzed the combined effects of these two phytochemicals on beta-amyloid (Aβ) protein aggregation and toxicity in bulk solution, in cells as well as in C.elegans. We detailed the morphological and size changes of Aβ40 aggregates in the presence of β-asarone and cannabidiol. More importantly, the presence of both compounds synergistically inhibited apoptosis and downregulated relative gene expression in cells, and that it may also slow aging, decrease the rate of paralysis, enhance learning capacity, and boost autophagy activity in C.elegans. Our studies suggest that multiple drugs, like β-asarone and CBD, may be potentially developed as a medicinal adjunct in the treatment of AD, although further clinical trials are needed to determine the efficacy and safety of this combination treatment in humans.

A Reliable Method Based on Liquid Chromatography-Tandem Mass Spectrometry for the Simultaneous Quantification of Neurotransmitters in Caenorhabditis elegans

Neurotransmitters like dopamine (DA), serotonin (SRT), γ-aminobutyric acid (GABA) and acetylcholine (ACh) are messenger molecules that play a pivotal role in transmitting excitation between neurons across chemical synapses, thus enabling complex processes in the central nervous system (CNS). Balance in neurotransmitter homeostasis is essential, and altered neurotransmitter levels are associated with various neurological disorders, e.g., loss of dopaminergic neurons (Parkinson's disease) or altered ACh synthesis (Alzheimer's disease). Therefore, it is crucial to possess adequate tools to assess precise neurotransmitter levels, and to apply targeted therapies. An established in vivo model to study neurotoxicity is the model organism Caenorhabditis elegans (C. elegans), as its neurons have been well characterized and functionally are analogous to mammals. We have developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method including a sample preparation assuring neurotransmitter stability, which allows a simultaneous neurotransmitter quantification of DA, SRT, GABA and ACh in C. elegans, but can easily be applied to other matrices. LC-MS/MS combined with isotope-labeled standards is the tool of choice, due to its otherwise unattainable sensitivity and specificity. Using C. elegans together with our analytically validated and verified method provides a powerful tool to evaluate mechanisms of neurotoxicity, and furthermore to identify possible therapeutic approaches.

Mechanistic impacts of bacterial diet on dopaminergic neurodegeneration in a Caenorhabditis elegans α-synuclein model of Parkinson's disease

Failure of inherently protective cellular processes and misfolded protein-associated stress contribute to the progressive loss of dopamine (DA) neurons characteristic of Parkinson's disease (PD). A disease-modifying role for the microbiome has recently emerged in PD, representing an impetus to employ the soil-dwelling nematode, Caenorhabditis elegans, as a preclinical model to correlate changes in gene expression with neurodegeneration in transgenic animals grown on distinct bacterial food sources. Even under tightly controlled conditions, hundreds of differentially expressed genes and a robust neuroprotective response were discerned between clonal C. elegans strains overexpressing human alpha-synuclein in the DA neurons fed either one of only two subspecies of Escherichia coli. Moreover, this neuroprotection persisted in a transgenerational manner. Genetic analysis revealed a requirement for the double-stranded RNA (dsRNA)-mediated gene silencing machinery in conferring neuroprotection. In delineating the contribution of individual genes, evidence emerged for endopeptidase activity and heme-associated pathway(s) as mechanistic components for modulating dopaminergic neuroprotection.