Abstract
Nostoc colonies have been used as food and medicine for centuries, and their main supporting matrix is polysaccharides, which help Nostoc cells resist various environmental stresses including oxidative stress. Here we isolated a polysaccharide, nostoglycan, from cultured Nostoc sphaeroides colonies and determined its physicochemical properties, which revealed a characteristic infrared absorption spectrum typical of polysaccharides and an amorphous morphology with rough surfaces. We also show that nostoglycan has strong moisture absorption and retention capacities and a high relative viscosity. Using Caenorhabditis elegans models, we then demonstrate that nostoglycan is capable of improving overall survival rate of the animals under increased oxidative stress caused by paraquat. Nostoglycan also reduces reactive oxygen species level, inhibits protein carbonyl formation and lipid peroxidation, and increases activities of superoxide dismutase and catalase in paraquat-exposed nematodes. As oxidative stress may drive tumor progression, we further demonstrate that nostoglycan can suppress the proliferation of several types of tumor cells and induce apoptosis of human lung adenocarcinoma A549 cells via caspase-3 activation. Together, our results yield important information on the physicochemical characteristics and demonstrate the antioxidant and anti-proliferative functions of nostoglycan, and thus provide an insight into its potential in food and health industries.
Highlights
Nostoc is a genus of nitrogen-fixing cyanobacteria that can form gelatinous colonies composed of filaments of moniliform cells in a range of environments
We first investigated the physicochemical properties of nostoglycan, a polysaccharide isolated from cultured N. sphaeroides colonies, and found that the polysaccharide has strong moisture absorption and retention capabilities and a high relative viscosity
We demonstrate that nostoglycan can increase survival rate, reduce reactive oxygen species (ROS) levels and protein carbonyl and MDA contents, and enhance superoxide dismutase (SOD) and CAT activities of C. elegans under increased oxidative stress induced by paraquat
Summary
Nostoc is a genus of nitrogen-fixing cyanobacteria that can form gelatinous colonies composed of filaments of moniliform cells in a range of environments. Nostoc colonies are commonly grown on soil surface and have developed a number of strategies to resist various environmental stresses, including extreme desiccation and intense solar ultraviolet radiation, both of which can stimulate ROS generation and induce oxidative damages [1,15,16]. The major adaptive strategies of Nostoc against desiccation, ultraviolet radiation, and other environmental conditions are closely associated with their abundant extracellular polysaccharides [1,4,15] These polysaccharides are shown to have beneficial effects such as complement-fixing and antioxidant activities [2,4,17]. We investigated the effect of nostoglycan on cell apoptosis and caspase-3 activation
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