Molecular Basis for Antioxidant Enzymes in Mediating Copper Detoxification in the Nematode Caenorhabditis elegans

Abstract

Antioxidant enzymes play a major role in defending against oxidative damage by copper. However, few studies have been performed to determine which antioxidant enzymes respond to and are necessary for copper detoxification. In this study, we examined both the activities and mRNA levels of SOD, CAT, and GPX under excessive copper stress in Caenorhabditis elegans, which is a powerful model for toxicity studies. Then, taking advantage of the genetics of this model, we assessed the lethal concentration (LC50) values of copper for related mutant strains. The results showed that the SOD, CAT, and GPX activities were significantly greater in treated groups than in controls. The mRNA levels of sod-3, sod-5, ctl-1, ctl-2, and almost all gpx genes were also significantly greater in treated groups than in controls. Among tested mutants, the sod-5, ctl-1, gpx-3, gpx-4, and gpx-6 variants exhibited hypersensitivity to copper. The strains with SOD or CAT over expression were reduced sensitive to copper. Mutations in daf-2 and age-1, which are involved in the insulin/insulin-like growth factor-1 signaling pathway, result in reduced sensitivity to stress. Here, we showed that LC50 values for copper in daf-2 and age-1 mutants were significantly greater than in N2 worms. However, the LC50 values in daf-16;daf-2 and daf-16;age-1 mutants were significantly reduced than in daf-2 and age-1 mutants, implying that reduced copper sensitivity is influenced by DAF-16-related functioning. SOD, CAT, and GPX activities and the mRNA levels of the associated copper responsive genes were significantly increased in daf-2 and age-1 mutants compared to N2. Additionally, the activities of SOD, CAT, and GPX were greater in these mutants than in N2 when treated with copper. Our results not only support the theory that antioxidant enzymes play an important role in copper detoxification but also identify the response and the genes involved in these processes.

Pyrroloquinoline-Quinone Suppresses Liver Fibrogenesis in Mice

“…The supernatant lysates of liver tissues or primary cells were used to determine the activity of antioxidant enzymes. Glutathione peroxidase (GSH-Px) activity was detected according to the DTNB (5,5'-Dithiobis-(2-nitrobenzoic acid)) method [ 25 ], and one unit of GSH-Px activity is defined as the net amount of the enzyme capable of hydrolyzing 1 μmol of GSH per minute at 37°C [ 26 ]. Superoxide dismutase (SOD) was evaluated by the xanthine oxidase method [ 25 ], and one unit of SOD activity is defined as the amount of enzyme in each milliliter of the reaction solution at 50% SOD inhibition at 37°C [ 26 ].…”

Hydrostatic pressure and temperature affect the tolerance of the free-living marine nematode Halomonhystera disjuncta to acute copper exposure

“…Changes in hydrostatic pressure lead to a shift in biochemical reaction rates and in the fluidity of membranes (Brown and Thatje, 2014;Pradillon and Gaill, 2007) which may in turn affect uptake rates of copper from the environment. Copper toxicity is mainly caused by accumulation of oxidative damage resulting from reactive oxygen species in the cells, and organisms may respond to this by enhancing antioxidant enzyme expression (Song et al, 2014). This, however, will increase basal metabolic rate and may have consequences for the energy allocation of the organisms (Sokolova and Lannig, 2008).…”

Hydrogen extends Caenorhabditis elegans longevity by reducing reactive oxygen species

“…It is thus evident that hydrogen is more effective than other antiaging drugs. In addition, age-1 mutants were more resistant to copper than wild-type worms and revealed an increased capacity for antioxidant enzyme activity and expression during copper treatment [27]. Ins-18, with a C peptide, antagonizes daf-2, and a high gene dosage of ins-18 induces dauer arrest in wild-type animals at 26˚C and enhances dauer arrest in daf-2(e1365) at 20˚C [28].…”

“…SOD plays an important role in the balance between oxidation and antioxidation and is closely related to the occurrence and development of many diseases [29]. Sod-5 is necessary for copper detoxification, and other genes also play a role in copper detoxification [27]. The mRNA expression levels of sod-1, sod-2, sod-3 and sod-5 were upregulated under 0.25 mM phoxim treatment, especially sod-3 and sod-5, which increased >10-and 70-fold, respectively [30].…”