The Neuroprotective Effects Of Chinese Bavberry Leaves Proanthocyanidins And Its Mechanism

Chinese bayberry(Myrica rubra Sieb.et Zucc.)is an important fruit of China with more than 2000 year of cultivation history,Chinese bayberry leaves are evergreen and contain high content of proanthocyanidins(PAs).PAs in Chinese bayberry leaves(BLPs)contain unique epigallocatechin-3-O-gallate(EGCG)as its terminal unit and most of its extension units.What's more,its mDP(-6.7)is much lower than grape seed proanthocyanidin(GSPA),PAs from cranberry and apple.On top of that,it has been reported to exhibit antioxidant,antimicrobial,anti-obesity,anti-cancer,and anti-inflammatory activities.In the present study,the neuroprotective effects of two type of BLPs,the Sephadex-LH20 purified BLPs(SPBLPs)and the ultrasound degraded BLPs(UDBLPs)with EGCG as positive control were investigated based on A(3 model.Moreover,the potential function and possible mechanism was identified to inhibit A? fibrillization,structural transformation and neurotoxicity both in vitro and in vivo.The results are revealed as follows:1.Both BLPs could interfere with self-aggregated A? and form a complex,therefore,inhibit A? fibrillogenesis,A? morphology and A? secondary structure transformation with dose-dependent manners.In addition,the change of thermodynamic function reveals that the BLPs with a lower mDP has a more intimate binding with A?.To be specific,from molecular docking simulation,they could target to A? with specific binding sites,varying from different mDP.The lower mDP of BLPs is closer to the N-terminal region and the core hydrophobic region HHQK sequence,besides the complex they formed is also more stable.2.Both BLPs could inhibit oligomer A?-induced cytotoxicity and affect the survival of SH-SY5Y cells,at the same time,the neuroprotective effect of UDBLPs is much stronger than SPBLPs.In the AP-induced cytotoxicity model,the neuroprotective effect reached its maximum at a dose of 20 ?g/mL for both BLPs in the A?-induced cytotoxicity model.Western blot analysis showed that BLPs could up-regulate the ratio of Bcl-2 to Bax and down-regulate the expression of caspase-3 downstream,which further blocked the apoptosis of SH-SY5Y cells induced by A? oligomer.3.Animal experiments reveal that after the UDBLPs,GSPA and EGCG drug treatment for 2 months in APP/PSN transgenetic mice,Morris water maze test revealed that BLPs can significantly improve the learning and spatial memory levels of APP/PSN mice.Immunohistochemistry and Western blotting showed that the area and size of the senile plaques in the parietal lobe,hippocampus and temporal lobe were significantly reduced,compared with the blank control group.At the same time,BLPs could reduce A? protein expression in the hippocampus and cortex.Moreover,the neuroprotective effect of BLPs is better than grape seed proanthocyanidin(GSPA).This study provided deep insight into the inhibitory effects of BLPs with different mDP on A?,and ultrasonic degradation of BLPs can improve its neuroprotection,therefore,BLPs might be developed as a novel type of functional food to prevent Alzheimer's disease(AD).