Evaluation of the antioxidant effects of acid hydrolysates from Auricularia auricular polysaccharides using a Caenorhabditis elegans model

Caenorhabditis elegans is an important model organism for studying stress response mechanisms and identifying genetic pathways that influence longevity. The present study was designed to explore the in vivo-antioxidant potential and the probable mechanism of acid hydrolysates prepared from A. auricula polysaccharides (AAPHs-F) with the optimal acid hydrolysis conditions using Box-Behnken design, and C. elegans was used as a model organism. The effects of AAPHs-F on the locomotory behavior, lifespan, activities of antioxidant-related enzymes and levels of antioxidants in C. elegans were studied. In addition, the potential of AAPHs-F in up-regulating the expression of antioxidant-related genes in C. elegans, such as daf-16, skn-1, sod-1, sod-2 and sir-2.1, and the inhibition of cell apoptosis of C. elegans were also discussed. The results indicated that AAPHs-F could significantly increase the U-Turn frequency of nematodes, extend their lifespan, enhance antioxidant systems including superoxide dismutase (SOD) by 70.60%, catalase (CAT) by 73.45% and glutathione reductase (GR) by 258.68% (p < 0.01), increase the level of glutathione (GSH) by 110.22% (p < 0.01), and decrease the level of reactive oxygen species (ROS) and malondialdehyde (MDA) by 31.86% and 46.16% (p < 0.01), respectively. Quantitative real-time polymerase chain reaction (qRT-PCR) results showed that AAPHs-F could up-regulate mRNA expression levels of daf-16, skn-1, sir, sod-1 and sod-2 in wild-type C. elegans (>1.3 fold) when treated at a concentration of 0.1 mg mL(-1) (p < 0.05 or p < 0.01). AAPHs-F was concluded to be heteropolysaccharides composed of mannose, glucose and galactose with a molar ratio of 12.7 : 3.25 : 1. The molecular weight of AAPHs-F was determined to be 885.37 Da. Furthermore, AAPHs-F is mainly formed of (1 -> 3)-linked-alpha-d-glucopyranose, and carboxyl or acetamide is present in the molecule. In summary, our studies provide evidence that AAPHs-F helps improve the antioxidant defense system, and up-regulation of stress and longevity related genes suggests the possible involvement of these genes in the prevention of stress damage in C. elegans.