High molecular weight of polysaccharides from Hericium erinaceus against amyloid beta-induced neurotoxicity

Background: Hericium erinaceus (HE) is a well-known mushroom in traditional Chinese food and medicine. HE extracts from the fruiting body and mycelia not only exhibit immunomodulatory, antimutagenic and antitumor activity but also have neuroprotective properties. Here, we purified HE polysaccharides (HEPS), composed of two high molecular weight polysaccharides (1.7 x 10(5) Da and 1.1 x 10(5) Da), and evaluated their protective effects on amyloid beta (A beta)-induced neurotoxicity in rat pheochromocytoma PC12 cells. Methods: HEPS were prepared and purified using a 95 % ethanol extraction method. The components of HEPS were analyzed and the molecular weights of the polysaccharides were determined using high-pressure liquid chromatography (HPLC). The neuroprotective effects of the polysaccharides were evaluated through a 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay and an MTT assay and by quantifying reactive oxygen species (ROS) and mitochondrial membrane potentials (MMP) of A beta-induced neurotoxicity in cells. Result: Our results showed that 250 mu g/ml HEPS was harmless and promoted cell viability with 1.2 mu M A beta treatment. We observed that the free radical scavenging rate exceeded 90 % when the concentration of HEPS was higher than 1 mg/mL in cells. The HEPS decreased the production of ROS from 80 to 58 % in a dose-dependent manner. Cell pretreatment with 250 mu g/mL HEPS significantly reduced A beta-induced high MMPs from 74 to 51 % and 94 to 62 % at 24 and 48 h, respectively. Finally, 250 mu g/mL of HEPS prevented A beta -induced cell shrinkage and nuclear degradation of PC12 cells. Conclusion: Our results demonstrate that HEPS exhibit antioxidant and neuroprotective effects on A beta-induced neurotoxicity in neurons.