Chan-Wei Yu

Curcumin-mediated lifespan extension in Caenorhabditis elegans

Curcumin is the active ingredient in the herbal medicine and dietary spice, turmeric (Curcuma longa). It has a wide range of biological activities, including anti-inflammatory, antioxidant, chemopreventive, and chemotherapeutic activities. We examined the effects of curcumin on the lifespan and aging in Caenorhabditis elegans, and found that it responded to curcumin with an increased lifespan and reduced intracellular reactive oxygen species and lipofuscin during aging. We analyzed factors that might influence lifespan extension by curcumin. We showed that lifespan extension by curcumin in C. elegans is attributed to its antioxidative properties but not its antimicrobial properties. Moreover, we showed that lifespan extension had effects on body size and the pharyngeal pumping rate but not on reproduction. Finally, lifespan tests with selected stress- and lifespan-relevant mutant strains revealed that the lifespan-extending phenotype was absent from the osr-1, sek-1, mek-1, skn-1, unc-43, sir-2.1, and age-1 mutants, whereas curcumin treatment prolonged the lifespan of mev-1 and daf-16 mutants. Our study has unraveled a diversity of modes of action and signaling pathways to longevity and aging with curcumin exposure in vivo.

Caenorhabditis elegans gcs-1 confers resistance to arsenic-induced oxidative stress

Gamma-glutamylcysteine synthetase (γ-GCS) catalyzes the first, rate-limiting step in the biosynthesis of glutathione (GSH). To evaluate the protective role of cellular GSH against arsenic-induced oxidative stress in Caenorhabditis elegans (C. elegans), we examined the effect of the C. elegans ortholog of GCS(h), gcs-1, in response to inorganic arsenic exposure. We have evaluated the responses of wild-type and gcs-1 mutant nematodes to both inorganic arsenite (As(III)) and arsenate (As(V)) ions and found that gcs-1 mutant nematodes are more sensitive to arsenic toxicity than that of wild-type animals. The amount of metal ion required to kill half of the population of worms falls in the order of wild-type/As(V)>gcs-1/As(V)> wild-type/As(III)>gcs-1/As(III). gcs-1 mutant nematodes also showed an earlier response to the exposure of As(III) and As(V) than that of wild-type animals. Pretreatment with GSH significantly raised the survival rate of gcs-1 mutant worms compared to As(III)- or As(V)-treated worms alone. These results indicate that GCS-1 is essential for the synthesis of intracellular GSH in C. elegans and consequently that the intracellular GSH status plays a critical role in protection of C. elegans from arsenic-induced oxidative stress.

In Vivo Antioxidant Activities of Essential Oils and Their Constituents from Leaves of the Taiwanese Cinnamomum osmophloeum

Cinnamomum osmophloeum Kaneh is an indigenous tree species in Taiwan. In this study, phytochemical characteristics and antioxidant activities of the essential oils and key constituents from the leaves of two C. osmophloeum clones were investigated. The two trees possess two chemotypes, which were classified as the cinnamaldehyde type and camphor type. We demonstrated that the essential oils from C. osmophloeum leaves exerted in vivo antioxidant activities in Caenorhabditis elegans. In addition, trans-cinnamaldehyde and D-(+)-camphor, which respectively represent the major compounds in the cinnamaldehyde-type and camphor-type trees, exerted significant in vivo antioxidant activities against juglone-induced oxidative stress in C. elegans. Moreover, expressions of antioxidative-related genes, including superoxide dismutase (SOD) and glutathione S-transferase (GST), were significantly induced by trans-cinnamaldehyde and D-(+)-camphor from C. osmophloeum leaves. Our results showed that the essential oils from C. osmophloeum leaves and their major compounds might have good potential for further development as nutraceuticals or antioxidant remedies.

Assessing the mechanisms controlling the mobilization of arsenic in the arsenic contaminated shallow alluvial aquifer in the blackfoot disease endemic area.

High levels of arsenic in groundwater and drinking water represent a major health problem worldwide. Drinking arsenic-contaminated groundwater is a likely cause of blackfoot disease (BFD) in Taiwan, but mechanisms controlling the mobilization of arsenic present at elevated concentrations within aquifers remain understudied. Microcosm experiments using sediments from arsenic contaminated shallow alluvial aquifers in the blackfoot disease endemic area showed simultaneous microbial reduction of Fe(III) and As(V). Significant soluble Fe(II) (0.23±0.03 mM) in pore waters and mobilization of As(III) (206.7±21.2 nM) occurred during the first week. Aqueous Fe(II) and As(III) respectively reached concentrations of 0.27±0.01 mM and 571.4±63.3 nM after 8 weeks. We also showed that the addition of acetate caused a further increase in aqueous Fe(II) but the dissolved arsenic did not increase. We further isolated an As(V)-reducing bacterium native to aquifer sediments which showed that the direct enzymatic reduction of As(V) to the potentially more-soluble As(III) in pore water is possible in this aquifer. Our results provide evidence that microorganisms can mediate the release of sedimentary arsenic to groundwater in this region and the capacity for arsenic release was not limited by the availability of electron donors in the sediments.

Phthalates Induce Neurotoxicity Affecting Locomotor and Thermotactic Behaviors and AFD Neurons through Oxidative Stress in Caenorhabditis elegans

Background Phthalate esters are ubiquitous environmental contaminants and numerous organisms are thus exposed to various levels of phthalates in their natural habitat. Considering the critical, but limited, research on human neurobehavioral outcomes in association with phthalates exposure, we used the nematode Caenorhabditis elegans as an in vivo model to evaluate phthalates-induced neurotoxicity and the possible associated mechanisms. Principal Findings Exposure to phthalates (DEHP, DBP, and DIBP) at the examined concentrations induced behavioral defects, including changes in body bending, head thrashing, reversal frequency, and thermotaxis in C. elegans. Moreover, phthalates (DEHP, DBP, and DIBP) exposure caused toxicity, affecting the relative sizes of cell body fluorescent puncta, and relative intensities of cell bodies in AFD neurons. The mRNA levels of the majority of the genes (TTX-1, TAX-2, TAX-4, and CEH-14) that are required for the differentiation and function of AFD neurons were decreased upon DEHP exposure. Furthermore, phthalates (DEHP, DBP, and DIBP) exposure at the examined concentrations produced elevated intracellular reactive oxygen species (ROS) in C. elegans. Finally, pretreatment with the antioxidant ascorbic acid significantly lowered the intracellular ROS level, ameliorated the locomotor and thermotactic behavior defects, and protected the damage of AFD neurons by DEHP exposure. Conclusions Our study suggests that oxidative stress plays a critical role in the phthalate esters-induced neurotoxic effects in C. elegans.

Caenorhabditis elegans expresses a functional ArsA

Because arsenic is the most prevalent environmental toxin, it is imperative that we understand the mechanisms of metalloid detoxification. In prokaryotes, arsenic detoxification is accomplished by chromosomal and plasmid‐borne operon‐encoded efflux systems. Bacterial ArsAu2003ATPase is the catalytic component of an oxyanion pump that is responsible for resistance to arsenite (As(III)) and antimonite (Sb(III)). Here, we describe the identification of a Caenorhabditis elegans homolog (asna‐1) that encodes the ATPase component of the Escherichia coli As(III) and Sb(III) transporter. We evaluated the responses of wild‐type and asna‐1‐mutant nematodes to various metal ions and found that asna‐1‐mutant nematodes are more sensitive to As(III) and Sb(III) toxicity than are wild‐type animals. These results provide evidence that ASNA‐1 is required for C.u2003elegans defense against As(III) and Sb(III) toxicity. A purified maltose‐binding protein (MBP)–ASNA‐1 fusion protein was biochemically characterized, and its properties compared with those of ArsAs. The ATPase activity of the ASNA‐1 protein was dependent on the presence of As(III) or Sb(III). As(III) stimulated ATPase activity by 2u2003±u20030.2‐fold, whereas Sb(III) stimulated it by 4.6u2003±u20030.15‐fold. The results indicate that As(III)‐ and Sb(III)‐stimulated ArsAu2003ATPase activities are not restricted to bacteria, but extend to animals, by demonstrating that the asna‐1 gene from the nematode, C.u2003elegans, encodes a functional ArsAu2003ATPase whose activity is stimulated by As(III) and Sb(III) and which is critical for As(III) and Sb(III) tolerance in the intact organism.

Curcumin-mediated oxidative stress resistance in Caenorhabditis elegans is modulated by age-1, akt-1, pdk-1, osr-1, unc-43, sek-1, skn-1, sir-2.1, and mev-1

Abstract Curcumin (diferuloylmethane), a pharmacologically active substance derived from turmeric, exhibits anti-inflammatory, anticarcinogenic, and antioxidant properties. We examined the modulation of oxidative-stress resistance and associated regulatory mechanisms by curcumin in a Caenorhabditis elegans model. Our results showed that curcumin-treated wild-type C. elegans exhibited increased survival during juglone-induced oxidative stress compared with the control treatment. In addition, curcumin reduced the levels of intracellular reactive oxygen species in C. elegans. Moreover, curcumin induced the expression of the gst-4 and hsp-16.2 stress response genes. Lastly, our findings from the mechanistic study in this investigation suggest that the antioxidative effect of curcumin is mediated via regulation of age-1, akt-1, pdk-1, osr-1, unc-43, sek-1, skn-1, sir-2.1, and mev-1. Our study elucidates the diverse modes of action and signaling pathways that underlie the antioxidant activity exhibited by curcumin in vivo.

Antioxidant Activity, Delayed Aging, and Reduced Amyloid-β Toxicity of Methanol Extracts of Tea Seed Pomace from Camellia tenuifolia

There is a growing interest in the exploitation of the residues generated by plants. This study explored the potential beneficial health effects from the main biowaste, tea seed pomace, produced when tea seed is processed. DPPH radical scavenging and total phenolic content assays were performed to evaluate the in vitro activities of the extracts. Caenorhabditis elegans was used as in vivo model to evaluate the beneficial health effects, including antioxidant activity, delayed aging, and reduced amyloid-β toxicity. Among all soluble fractions obtained from the extracts of tea seed pomace from Camellia tenuifolia, the methanol (MeOH)-soluble fraction has the best in vivo antioxidant activities. The MeOH-soluble extraction was further divided into six fractions by chromatography with a Diaion HP-20 column eluted with water/MeOH, and fraction 3 showed the best in vitro and in vivo antioxidant activities. Further analysis in C. elegans showed that the MeOH extract (fraction 3) of tea seed pomace significantly decreased intracellular reactive oxygen species, prolonged C. elegans lifespan, and reduced amyloid-β (Aβ) toxicity in transgenic C. elegans expressing human Aβ. Moreover, bioactivity-guided fractionation yielded two potent constituents from fraction 3 of the MeOH extract, namely, kaempferol 3-O-(2″-glucopyranosyl)-rutinoside and kaempferol 3-O-(2″-xylopyranosyl)-rutinoside, and both compounds exhibited excellent in vivo antioxidant activity. Taken together, MeOH extracts of tea seed pomace from C. tenuifolia have multiple beneficial health effects, suggesting that biowaste might be valuable to be explored for further development as nutraceutical products. Furthermore, the reuse of agricultural byproduct tea seed pomace also fulfills the environmental perspective.

Essential Oil Alloaromadendrene from Mixed-Type Cinnamomum osmophloeum Leaves Prolongs the Lifespan in Caenorhabditis elegans

Cinnamomum osmophloeum Kaneh. is an indigenous tree species in Taiwan. The present study investigates phytochemical characteristics, antioxidant activities, and longevity of the essential oils from the leaves of the mixed-type C. osmophloeum tree. We demonstrate that the essential oils from leaves of mixed-type C. osmophloeum exerted in vivo antioxidant activities on Caenorhabditis elegans. In addition, minor (alloaromadendrene, 5.0%) but not major chemical components from the leaves of mixed-type C. osmophloeum have a key role against juglone-induced oxidative stress in C. elegans. Additionally, alloaromadendrene not only acts protective against oxidative stress but also prolongs the lifespan of C. elegans. Moreover, mechanistic studies show that DAF-16 is required for alloaromadendrene-mediated oxidative stress resistance and longevity in C. elegans. The results in the present study indicate that the leaves of mixed-type C. osmophloeum and essential oil alloaromadendrene have the potential for use as a source for antioxidants or treatments to delay aging.

Arsenite exposure accelerates aging process regulated by the transcription factor DAF-16/FOXO in Caenorhabditis elegans.

Arsenic is a known human carcinogen and high levels of arsenic contamination in food, soils, water, and air are of toxicology concerns. Nowadays, arsenic is still a contaminant of emerging interest, yet the effects of arsenic on aging process have received little attention. In this study, we investigated the effects and the underlying mechanisms of chronic arsenite exposure on the aging process in Caenorhabditis elegans. The results showed that prolonged arsenite exposure caused significantly decreased lifespan compared to non-exposed ones. In addition, arsenite exposure (100 μM) caused significant changes of age-dependent biomarkers, including a decrease of defecation frequency, accumulations of intestinal lipofuscin and lipid peroxidation in an age-dependent manner in C. elegans. Further evidence revealed that intracellular reactive oxygen species (ROS) level was significantly increased in an age-dependent manner upon 100 μM arsenite exposure. Moreover, the mRNA levels of transcriptional makers of aging (hsp-16.1, hsp-16.49, and hsp-70) were increased in aged worms under arsenite exposure (100 μM). Finally, we showed that daf-16 mutant worms were more sensitive to arsenite exposure (100 μM) on lifespan and failed to induce the expression of its target gene sod-3 in aged daf-16 mutant under arsenite exposure (100 μM). Our study demonstrated that chronic arsenite exposure resulted in accelerated aging process in C. elegans. The overproduction of intracellular ROS and the transcription factor DAF-16/FOXO play roles in mediating the accelerated aging process by arsenite exposure in C. elegans. This study implicates a potential ecotoxicological and health risk of arsenic in the environment.