New insight into Ginseng root polysaccharide GRP-E1F2 on prodynorphin inhibition to delay senescence-associated neuroaging via modulating cellular senescence

Neuroaging is one of the most distinct signs of aging, which promotes mild cognitive impairment (MCI) and various neurodegenerative diseases. Previous studies have indicated that Panax ginseng C. A. Mey. (ginseng) root polysaccharides have positive effects against senescence and nerve damage. However, its structure and role in delaying senescence-associated neuroaging have not been comprehensively studied. Therefore, this research characterized the structural features of a ginseng root polysaccharide (GRP-E1F2) and the potential mechanism underlying its anti-neurodegeneration effect against senescence-related function and pathological damage. GRP-E1F2 is a neutral polysaccharide with 11.688 kDa molecular weight, which was isolated from the ginseng roots. In this study, NMR, HPLC, FT-IR, and methylation analyses were performed to identify the physiochemical characteristics of GRP-E1F2, which provided its repetitive unit structures. The in vivo experiments revealed that GRP-E1F2 prolonged the lifespan and mitigated senescence-related symptoms including aggregation of lipofuscin and ROS, as well as the antioxidant enzyme inactivation in aging animals (C. elegans and mice). Furthermore, tert-butyl hydroperoxide (tBHP) induced senescent cells indicated that GRP-E1F2 treated has beneficial anti-aging effects. Moreover, the transgenic C. elegans expressing GFP in D-type gamma-aminobutyric acid (GABA)-positive neurons and mice indicated that GRP-E1F2 reduced neuronal morphological abnormalities and reversed aging-induced cognitive deficits, indicating the anti-neuroaging effects of GRP-E1F2. Mechanistically, GRP-E1F2 downregulates cellular senescence in aging brains and cell models, which was indicated by senescence-associated β-galactosidase (SA-β-gal) activity, marker protein p53, p21, phospho-histone H2A.X, and senescence-associated secretory phenotype (SASP). In addition, RNA-seq, RT-qPCR, and immunofluorescence assays revealed that GRP-E1F2 down-regulated mRNA and protein levels of prodynorphin (Pdyn) in aging models. Moreover, the p53 activator and overexpression vectors of Pdyn were employed to determine the pharmacological mechanism of GRP-E1F2 in reducing Pdyn expressions to delay neuroaging by inhibiting the cellular senescence signaling pathway. This research provides theoretical support and experimental evidence for the clinical application of ginseng root polysaccharides against senescence-associated neuroaging, promoting the modern development of traditional medicines from natural polysaccharides.