Antioxidant and Oxidative Stress Inhibitory Activities of Tolypocladium sinense Polysaccharide

Objective: To explore the antioxidant activity of Tolypocladium sinense polysaccharide (TSP) in vitro and its inhibitory effect on apoptosis of mouse islet MIN6 cells which were suffered from oxidative stress-induced by hydrogen peroxide. Methods: The T. sinense polysaccharides was extracted by hot water extraction, and then the scavenging activities of superoxide anion radical ( \mathrmO_2^- ·), hydroxyl radical (·OH) and p-1,1-diphenylpicryl phenyl hydrazine radical (DPPH·) was determined. Oxidative stress of mouse islet MIN6 cells was induced by 200 μmol/L hydrogen peroxide (H₂O₂) and protected by high and low dose TSP (0.625, 0.156 mg/mL). The survival rate of MIN6 cells was determined by MTT method, and the cell morphology was observed by inverted microscope. The lactate dehydrogenase (LDH) level in culture medium, intracellular superoxide dismutase (SOD) activity and malondialdehyde (MDA) content were measured by kit. Apoptosis was detected by flow cytometry. The relative expressions of nuclear factor E2 related factor 2 (Nrf-2) and phosphorylated c-Jun N-terminal kinase (pJNK) were detected by Western Blot. Results: TSP had significant scavenging effect on three kinds of free radicals, and the results of cell experiment showed that compared with the hydrogen peroxide model group, the cell survival rate of high and low dose TSP group increased significantly (P<0.01, P<0.05), the number of suspension cells decreased significantly (P<0.01), the content of LDH in culture medium decreased significantly (P<0.01), and the rate of apoptosis decreased significantly (P<0.01, P<0.05). The level of intracellular SOD increased (P<0.01, P<0.05) and the content of MDA decreased significantly (P<0.01). The results of Western Blot showed that the expression of Nrf-2 in the high dose group was significantly higher than that in the model group (P<0.05), while the expression of pJNK in the high dose group and low dose group was significantly decreased (P<0.01, P<0.05). Conclusion: TSP has significant antioxidant activity, and can regulate the expression of Nrf-2 and pJNK to reduce apoptosis induced by oxidative stress.