Isolation of a Hypomorphic skn-1 Allele That Does Not Require a Balancer for Maintenance

Sulforaphane Exposure Prevents Cadmium-Induced Toxicity and Mitochondrial Dysfunction in the Nematode Caenorhabditis elegans by Regulating the Insulin/Insulin-like Growth Factor Signaling (IIS) Pathway

Cadmium (Cd) is a heavy metal that is highly toxic to humans and animals. Its adverse effects have been widely associated with mitochondrial alterations. However, there are not many treatments that target mitochondria. This study aimed to evaluate the impact of sulforaphane (SFN) pre-exposure against cadmium chloride (CdCl2)-induced toxicity and mitochondrial alterations in the nematode Caenorhabditis elegans (C. elegans), by exploring the role of the insulin/insulin-like growth factor signaling pathway (IIS). The results revealed that prior exposure to SFN protected against CdCl2-induced mortality and increased lifespan, body length, and mobility while reducing lipofuscin levels. Furthermore, SFN prevented mitochondrial alterations by increasing mitochondrial membrane potential (Δψm) and restoring mitochondrial oxygen consumption rate, thereby decreasing mitochondrial reactive oxygen species (ROS) production. The improvement in mitochondrial function was associated with increased mitochondrial mass and the involvement of the daf-16 and skn-1c genes of the IIS signaling pathway. In conclusion, exposure to SFN before exposure to CdCl2 mitigates toxic effects and mitochondrial alterations, possibly by increasing mitochondrial mass, which may be related to the regulation of the IIS pathway. These discoveries open new possibilities for developing therapies to reduce the damage caused by Cd toxicity and oxidative stress in biological systems, highlighting antioxidants with mitochondrial action as promising tools.

Cytosolic Ribosomal Protein Haploinsufficiency affects Mitochondrial Morphology and Respiration

The interplay between ribosomal protein composition and mitochondrial function is essential for sustaining energy homeostasis. Precise stoichiometric production of ribosomal proteins is crucial to maximize protein synthesis efficiency while reducing the energy costs to the cell. However, the impact of this balance on mitochondrial ATP generation, morphology and function remains unclear. Particularly, the loss of a single copy ribosomal protein gene is observed in Mendelian disorders like Diamond Blackfan Anemia and is common in somatic tumors, yet the implications of this imbalance on mitochondrial function and energy dynamics are still unclear. In this study, we investigated the impact of haploinsufficiency for four ribosomal protein genes implicated in ribosomopathy disorders (rps-10, rpl-5, rpl-33, rps-23) in Caenorhabditis elegans and corresponding reductions in human lymphoblast cells. Our findings uncover significant, albeit variably penetrant, mitochondrial morphological differences across these mutants, alongside an upregulation of glutathione transferases, and SKN-1 dependent increase in oxidative stress resistance, indicative of increased ROS production. Specifically, loss of a single copy of rps-10 in C. elegans led to decreased mitochondrial activity, characterized by lower energy levels and reduced oxygen consumption. A similar reduction in mitochondrial activity and energy levels was observed in human leukemia cells with a 50% reduction in RPS10 transcript levels. Importantly, we also observed alterations in the translation efficiency of nuclear and mitochondrial electron transport chain components in response to reductions in ribosomal protein genes' expression in both C. elegans and human cells. This suggests a conserved mechanism whereby the synthesis of components vital for mitochondrial function are adjusted in the face of compromised ribosomal machinery. Finally, mitochondrial membrane and cytosolic ribosomal components exhibited significant covariation at the RNA and translation efficiency level in lymphoblastoid cells across a diverse group of individuals, emphasizing the interplay between the protein synthesis machinery and mitochondrial energy production. By uncovering the impact of ribosomal protein haploinsufficiency on the translation efficiency of electron transport chain components, mitochondrial physiology, and the adaptive stress responses, we provide evidence for an evolutionarily conserved strategy to safeguard cellular functionality under genetic stress.

Peroxiredoxin 2 is required for the redox mediated adaptation to exercise

Exercise generates a site-specific increase in Reactive Oxygen Species (ROS) within muscle that promotes changes in gene transcription and mitochondrial biogenesis, required for the beneficial adaptive response. We demonstrate that Peroxiredoxin 2 (Prdx2), an abundant cytoplasmic 2-Cys peroxiredoxin, is required for the adaptive hormesis response to physiological levels of H₂O₂ in myoblasts and following exercise in C. elegans. A short bolus addition of H₂O₂ increases mitochondrial capacity and improves myogenesis of cultured myoblasts, this beneficial adaptive response was suppressed in myoblasts with decreased expression of cytoplasmic Prdxs. Moreover, a swimming exercise protocol in C. elegans increased mitochondrial content, fitness, survival and longevity in wild type (N2) worms. In contrast, prdx-2 mutant worms had decreased fitness, disrupted mitochondria, reduced survival and lifespan following exercise. Global proteomics following exercise identified distinct changes in the proteome of N2 and prdx-2 mutants. Furthermore, a redox proteomic approach to quantify reversible oxidation of specific Cysteine residues revealed a more reduced redox state in the non-exercised prdx-2 mutant strain that become oxidized following exercise. In contrast, specific Cys residues from regulatory proteins become more reduced in the N2 strain following exercise, establishing the key regulatory role of PRDX-2 in a redox signalling cascade following endogenous ROS generation. Our results demonstrate that conserved cytoplasmic 2-Cys Peroxiredoxins are required for the beneficial adaptive response to a physiological redox stress.

Distinct designer diamines promote mitophagy, and thereby enhance healthspan in C. elegans and protect human cells against oxidative damage

Impaired mitophagy is a primary pathogenic event underlying diverse aging-associated diseases such as Alzheimer and Parkinson diseases and sarcopenia. Therefore, augmentation of mitophagy, the process by which defective mitochondria are removed, then replaced by new ones, is an emerging strategy for preventing the evolvement of multiple morbidities in the elderly population. Based on the scaffold of spermidine (Spd), a known mitophagy-promoting agent, we designed and tested a family of structurally related compounds. A prototypic member, 1,8-diaminooctane (VL-004), exceeds Spd in its ability to induce mitophagy and protect against oxidative stress. VL-004 activity is mediated by canonical aging genes and promotes lifespan and healthspan in C. elegans. Moreover, it enhances mitophagy and protects against oxidative injury in rodent and human cells. Initial structural characterization suggests simple rules for the design of compounds with improved bioactivity, opening the way for a new generation of agents with a potential to promote healthy aging.

Distinct mechanisms underlie H2O2 sensing in C. elegans head and tail

Environmental oxidative stress threatens cellular integrity and should therefore be avoided by living organisms. Yet, relatively little is known about environmental oxidative stress perception. Here, using microfluidics, we showed that like I2 pharyngeal neurons, the tail phasmid PHA neurons function as oxidative stress sensing neurons in C. elegans, but display different responses to H₂O₂ and light. We uncovered that different but related receptors, GUR-3 and LITE-1, mediate H₂O₂ signaling in I2 and PHA neurons. Still, the peroxiredoxin PRDX-2 is essential for both, and might promote H₂O₂-mediated receptor activation. Our work demonstrates that C. elegans can sense a broad range of oxidative stressors using partially distinct H₂O₂ signaling pathways in head and tail sensillae, and paves the way for further understanding of how the integration of these inputs translates into the appropriate behavior.

Cold shock induces a terminal investment reproductive response in C. elegans

Challenges from environmental stressors have a profound impact on many life-history traits of an organism, including reproductive strategy. Examples across multiple taxa have demonstrated that maternal reproductive investment resulting from stress can improve offspring survival; a form of matricidal provisioning when death appears imminent is known as terminal investment. Here we report a reproductive response in the nematode Caenorhabditis elegans upon exposure to acute cold shock at 2 °C, whereby vitellogenic lipid movement from the soma to the germline appears to be massively upregulated at the expense of parental survival. This response is dependent on functional TAX-2; TAX-4 cGMP-gated channels that are part of canonical thermosensory mechanisms in worms and can be prevented in the presence of activated SKN-1/Nrf2, the master stress regulator. Increased maternal provisioning promotes improved embryonic cold shock survival, which is notably suppressed in animals with impaired vitellogenesis. These findings suggest that cold shock in C. elegans triggers terminal investment to promote progeny fitness at the expense of parental survival and may serve as a tractable model for future studies of stress-induced progeny plasticity.

A PTEN variant uncouples longevity from impaired fitness in Caenorhabditis elegans with reduced insulin/IGF-1 signaling

Insulin/IGF-1 signaling (IIS) regulates various physiological aspects in numerous species. In Caenorhabditis elegans, mutations in the daf-2/insulin/IGF-1 receptor dramatically increase lifespan and immunity, but generally impair motility, growth, and reproduction. Whether these pleiotropic effects can be dissociated at a specific step in insulin/IGF-1 signaling pathway remains unknown. Through performing a mutagenesis screen, we identified a missense mutation daf-18(yh1) that alters a cysteine to tyrosine in DAF-18/PTEN phosphatase, which maintained the long lifespan and enhanced immunity, while improving the reduced motility in adult daf-2 mutants. We showed that the daf-18(yh1) mutation decreased the lipid phosphatase activity of DAF-18/PTEN, while retaining a partial protein tyrosine phosphatase activity. We found that daf-18(yh1) maintained the partial activity of DAF-16/FOXO but restricted the detrimental upregulation of SKN-1/NRF2, contributing to beneficial physiological traits in daf-2 mutants. Our work provides important insights into how one evolutionarily conserved component, PTEN, can coordinate animal health and longevity.

Biogenic amine neurotransmitters promote eicosanoid production and protein homeostasis

Metazoans use protein homeostasis (proteostasis) pathways to respond to adverse physiological conditions, changing environment, and aging. The nervous system regulates proteostasis in different tissues, but the mechanism is not understood. Here, we show that Caenorhabditis elegans employs biogenic amine neurotransmitters to regulate ubiquitin proteasome system (UPS) proteostasis in epithelia. Mutants for biogenic amine synthesis show decreased poly-ubiquitination and turnover of a GFP-based UPS substrate. Using RNA-seq and mass spectrometry, we found that biogenic amines promote eicosanoid production from poly-unsaturated fats (PUFAs) by regulating expression of cytochrome P450 monooxygenases. Mutants for one of these P450s share the same UPS phenotype observed in biogenic amine mutants. The production of n-6 eicosanoids is required for UPS substrate turnover, whereas accumulation of n-6 eicosanoids accelerates turnover. Our results suggest that sensory neurons secrete biogenic amines to modulate lipid signaling, which in turn activates stress response pathways to maintain UPS proteostasis.

An NRF2 Perspective on Stem Cells and Ageing

Redox and metabolic mechanisms lie at the heart of stem cell survival and regenerative activity. NRF2 is a major transcriptional controller of cellular redox and metabolic homeostasis, which has also been implicated in ageing and lifespan regulation. However, NRF2's role in stem cells and their functioning with age is only just emerging. Here, focusing mainly on neural stem cells, which are core to adult brain plasticity and function, we review recent findings that identify NRF2 as a fundamental player in stem cell biology and ageing. We also discuss NRF2-based molecular programs that may govern stem cell state and function with age, and implications of this for age-related pathologies.

The transcription factor SKN-1 and detoxification gene ugt-22 alter albendazole efficacy in Caenorhabditis elegans

Parasitic nematodes infect over 1/4 th of the human population and are a major burden on livestock and crop production. Benzimidazole class anthelmintics are widely used to treat infections, but resistance is a widespread problem. Mutation of genes encoding the benzimidazole target β-tubulin is a well-established mechanism of resistance, but recent evidence suggests that metabolism of the drugs may also occur. Our objective was to investigate contributions of the detoxification-response transcription factor SKN-1 to anthelmintic drug resistance using C. elegans. We find that skn-1 mutations alter EC₅₀ of the common benzimidazole albendazole in motility assays by 1.5–1.7 fold. We also identify ugt-22 as a detoxification gene associated with SKN-1 that influences albendazole efficacy. Mutation and overexpression of ugt-22 alter albendazole EC₅₀ by 2.3–2.5-fold. The influence of a nematode UGT on albendazole efficacy is consistent with recent studies demonstrating glucose conjugation of benzimidazoles.