| Background: Polysaccharide is a traditional Chinese medicine commonly used in China,which has the effect of tonifying the liver and kidneys and prolonging life.It contains chemical substances such as polysaccharides,steroidal saponins and flavonoids.Among them,Polygonatum sibiricmu polysaccharides(PSP)is one of the main constituents of Polysaccharide,which has anti-tumour,immune modulating,antioxidant damage,anti-inflammatory and anti-ageing effects.Studies have shown that Polygonatum sibiricmu polysaccharides can improve neurological inflammation,alleviate oxidative stress and improve memory and cognitive function.The majority of the concoction methods used in the preparation of Polysaccharide are "nine steams and nine dryings",which is a traditional concoction method used to change the taste of the herb and enhance the biological activity,absorption rate and efficacy of the drug.As raw Polysaccharide has a strong numbing taste,when taken raw,the mouth and tongue become numb and the throat is irritated,so the earliest concoction is to remove the irritation and facilitate long-term preservation.However,whether the structural properties of the Polygonatum sibiricmu polysaccharides change after "long steaming" and the effect of "long steaming" PSPs on the improvement of learning memory in D-gal-induced mice have not yet been studied and the mechanism of action is not yet clear.Objective: This study aimed to evaluate the effects of steaming process on physicochemical properties of PSP and determine their effects on aging-related memory impairment.Methods: Polygonatum sibiricum rhizome was undergone “nine steams and nine dryings” process and PSPs with different steaming times were abstracted.Thereafter,the physicochemical properties were qualified by Fourier transform infrared spectroscopy spectra,particle size analyzer,p H meter and X-ray polycrystalline powder diffractometer.The antioxidant activities of PSPs were evaluated by flow cytometer method in D-galinduced HT-22 cell model.The effects of PSPs(PSP0,PSP5 and PSP9)on memory was evaluated using D-gal-induced mice model and finally,the action mechanisms were determined from the prospective of cell death,oxidative stress,inflammation and synaptic functions.Results: 1.The structure of the Polygonatum sibiricmu polysaccharides was changed by steaming: the p H value of the Polygonatum sibiricmu polysaccharides increased with the increase of the number of concoction treatments;the FTIR spectra showed that the polysaccharides had similar main chains and substituents,and the Polygonatum sibiricmu polysaccharides with different concoction times were all acidic polysaccharides containing galacturonic acid.X-Ray diffraction showed that the crystalline state of the polysaccharide was not destroyed by the concoction treatment,and that the polysaccharide was an amorphous polymer,not a polymer with sub-microcrystalline and amorphous coexistence.This property can be used to test the purity of the Polygonatum sibiricmu polysaccharides;the characterization of the polysaccharide charge shows that the concoction PSPs have a large negative charge,which can be used to prepare stable concoction PSPs mixed solutions or colloids.2.The fluorescence intensity of DCFH-DA in D-gal treated HT-22 cells was significantly higher than that of the control group compared to the normal group.Compared with the model group,the fluorescence intensity of DCFH-DA was significantly lower in the concoction PSPs group,in which the antioxidant capacity of PSP1 was lower than that of PSP0.After that,the antioxidant capacity of Polygonatum sibiricmu polysaccharides increased as the number of concoction treatments increased.These results suggest that the concoction PSPs inhibited D-gal-induced cytoplasmic ROS production in HT-22 cells.3.Subcutaneous injection of D-gal impaired the learning and memory in mice,and all PSP0,PSP5 and PSP9 could significantly ameliorate the behavioral impairment of Dgal-injured mice,in which PSP5 showed the optimal effect.Meanwhile,PSP5 also demonstrated the best effect on preventing cell death in hippocampal DG,CA1,and CA3 regions.Additionally,PSP5 had the optimal effect to rescue synaptic injury in D-galtreated mice.Compared with control group,the expression of activity-regulated cytoskeletal protein(Arc),postsynaptic density protein 95(PSD95),N-methyl-Daspartate receptor(NMDAR)subunits(Glu N2 A,p-Glu N2 B,Glu N2B),α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptor(AMPAR)subunits(Glu A1,Glu A2),nuclear factor-erythroid factor 2-related factor 2(Nrf2)and heme oxygenase-1(HO-1)decreased,while the expression of apoptosis-associated speck like protein(ASC)and NOD-like receptor protein 3(NLRP3)increased in D-gal-treated mice.However,those abnormal protein expressions were improved following treatment with steamed PSPs.Conclusion: 1.Concoction changed the structural properties of the Polygonatum sibiricmu polysaccharides aurantium,which improved the antioxidant capacity of PSPs and the ability to improve learning and memory impairment,and PSP5 compared to PSP0.PSP5 compared to PSP0 or PSP9 could improve the memory dysfunction.2.PSP5 could better improve D-gal-induced learning and memory impairment,possibly by preventing oxidative stress and reducing inflammation,thus protecting synaptic plasticity and neuronal damage through the Nrf2/HO-1 signalling pathway.This study provides a potential molecular mechanism for the application of steamed polysaccharides in the prevention of ageing-related memory dysfunction. |
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