2-Butoxytetrahydrofuran and Palmitic Acid from Holothuria scabra Enhance C. elegans Lifespan and Healthspan via DAF-16/FOXO and SKN-1/NRF2 Signaling Pathways

Extracts from a sea cucumber, Holothuria scabra, have been shown to exhibit various pharmacological properties including anti-oxidation, anti-aging, anti-cancer, and anti-neurodegeneration. Furthermore, certain purified compounds from H. scabra displayed neuroprotective effects against Parkinson's and Alzheimer's diseases. Therefore, in the present study, we further examined the anti-aging activity of purified H. scabra compounds in a Caenorhabditis elegans model. Five compounds were isolated from ethyl acetate and butanol fractions of the body wall of H. scabra and characterized as diterpene glycosides (holothuria A and B), palmitic acid, bis (2-ethylhexyl) phthalate (DEHP), and 2-butoxytetrahydrofuran (2-BTHF). Longevity assays revealed that 2-BTHF and palmitic acid could significantly extend lifespan of wild type C. elegans. Moreover, 2-BTHF and palmitic acid were able to enhance resistance to paraquat-induced oxidative stress and thermal stress. By testing the compounds' effects on longevity pathways, it was shown that 2-BTHF and palmitic acid could not extend lifespans of daf-16, age-1, sir-2.1, jnk-1, and skn-1 mutant worms, indicating that these compounds exerted their actions through these genes in extending the lifespan of C. elegans. These compounds induced DAF-16::GFP nuclear translocation and upregulated the expressions of daf-16, hsp-16.2, sod-3 mRNA and SOD-3::GFP. Moreover, they also elevated protein and mRNA expressions of GST-4, which is a downstream target of the SKN-1 transcription factor. Taken together, the study demonstrated the anti-aging activities of 2-BTHF and palmitic acid from H. scabra were mediated via DAF-16/FOXO insulin/IGF and SKN-1/NRF2 signaling pathways.

Network analysis in aged C. elegans reveals candidate regulatory genes of ageing

Ageing is a biological process guided by genetic and environmental factors that ultimately lead to adverse outcomes for organismal lifespan and healthspan. Determination of molecular pathways that are affected with age and increase disease susceptibility is crucial. The gene expression profile of the ideal ageing model, namely the nematode Caenorhabditis elegans mapped with the microarray technology initially led to the identification of age-dependent gene expression alterations that characterize the nematode's ageing process. The list of differentially expressed genes was then utilized to construct a network of molecular interactions with their first neighbors/interactors using the interactions listed in the WormBase database. The subsequent network analysis resulted in the unbiased selection of 110 candidate genes, among which well-known ageing regulators appeared. More importantly, our approach revealed candidates that have never been linked to ageing before, thus suggesting promising potential targets/ageing regulators.

Holothuria scabra extracts possess anti-oxidant activity and promote stress resistance and lifespan extension in Caenorhabditis elegans

Holothuria scabra is a sea cucumber that is mostly found in the Indo-Pacific region including Thailand. Extracts from many sea cucumbers possess pharmacological activities proposed to benefit human health. In this study, we investigated the anti-oxidant and anti-ageing activities of extracts from H. scabra by using Caenorhabditis elegans as a model organism. Parts of H. scabra were solvent-extracted and divided into nine fractions including whole body-hexane (WBHE), whole body-ethyl acetate (WBEA), whole body-butanol (WBBU), body wall-hexane (BWHE), body wall-ethyl acetate (BWEA), body wall-butanol (BWBU), viscera-hexane (VIHE), viscera-ethyl acetate (VIEA), and viscera-butanol (VIBU). All fractions of the extracts were tested for anti-oxidant activities by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays and for anti-ageing effects by lifespan assays using C. elegans as a model. The results showed anti-oxidant properties in all fractions with the highest activity shown by the DPPH assay in WBBU (EC₅₀ = 3.12 ± 0.09 mg/ml), and by the ABTS assay in WBHE (EC₅₀ = 0.31 ± 0.10 mg/ml). In lifespan assays the highest anti-ageing effect was detected in WBBU- and BWEA-treated C. elegans with increased mean lifespans of 8.12% and 4.77%, respectively. Furthermore, WBBU and BWEA-treated C. elegans exhibited significantly higher resistance against heat shock and paraquat-induced oxidative stresses than controls. By using LC-MS/MS, both extracts were characterized to contain triterpene glycosides as the main bioactive components. To explore mechanisms of H. scabra extracts on longevity and stress resistance, worms with genetic mutations in anti-ageing pathways were analyzed and showed that WBBU and BWEA did not prolong the lifespan of daf-16, age-1, sir-2.1, jnk-1, sek-1, and osr-1 mutants, suggesting that these genetic pathways are involved in mediating the anti-ageing effects of the H. scabra extracts. Moreover, WBBU and BWEA enhanced the nuclear translocation of the FoxO/DAF-16 transcription factor, and increased mRNA expression of this gene and its downstream targets sod-3, hsp12.3, and hsp16.2. In conclusion, this study strongly demonstrates anti-oxidant and anti-ageing properties of H. scabra extracts containing triterpene glycosides, which, in the C. elegans model, may be mediated via the insulin/IGF-1 signaling (IIS)-DAF-16 pathway.

Measuring oxidative stress resistance of Caenorhabditis elegans in 96-well microtiter plates

Oxidative stress, which is the result of an imbalance between production and detoxification of reactive oxygen species, is a major contributor to chronic human disorders, including cardiovascular and neurodegenerative diseases, diabetes, aging, and cancer. Therefore, it is important to study oxidative stress not only in cell systems but also using whole organisms. C. elegans is an attractive model organism to study the genetics of oxidative stress signal transduction pathways, which are highly evolutionarily conserved. Here, we provide a protocol to measure oxidative stress resistance in C. elegans in liquid. Briefly, ROS-inducing reagents such as paraquat (PQ) and H2O2 are dissolved in M9 buffer, and solutions are aliquoted in the wells of a 96 well microtiter plate. Synchronized L4/young adult C. elegans animals are transferred to the wells (5-8 animals/well) and survival is measured every hour until most worms are dead. When performing an oxidative stress resistance assay using a low concentration of stressors in plates, aging might influence the behavior of animals upon oxidative stress, which could lead to an incorrect interpretation of the data. However, in the assay described herein, this problem is unlikely to occur since only L4/young adult animals are being used. Moreover, this protocol is inexpensive and results are obtained in one day, which renders this technique attractive for genetic screens. Overall, this will help to understand oxidative stress signal transduction pathways, which could be translated into better characterization of oxidative stress-associated human disorders.