The effect and mechanism of stilbene glycosides on improving neuronal injury in Alzheimer's disease rats by regulating ASK/MKK7/JNK pathway

Objective:To investigate the mechanism of action of tetrahydroxy stilbene glycosides(TSG)in ameliorating neuronal damage in Alzheimer's disease rats by regulating MKK7 and JNK kinases.Methods:A total of 24-month-old 42 SD rats were randomly selected for the experiment in 7 groups:normal group,sham-operated group,model group,positive drug group,low,medium and high dose TSG group at 0.033 g/kg,0.1 g/kg,0.3 g/kg.The Model Group and the TSG groups were established by stereotaxic Aβ25-35 solution.After 28 days,the model rats were selected by passive avoidance test.After screening,each dosage group of TSG and positive drug group was given intragastrically according to the corresponding dosage,and the experiment was carried out after 28 days.The pathological changes of hippocampal CA1 region were observed by tissue staining,and the amount of MKK7 and JNK proteins and the expression content of MKK7 and JNK mRNA by histochemical method of protein,and qRTPCR assay.Results:(1)He staining observation:Compared with the normal group and the sham-operated group,the number of nerve cells in the model group decreased and arranged irregularly,the cell membrane shrank,and the nucleus deformed and dissolved.The number of neurons in the positive drug group and TSG Group also increased significantly,the order is also relatively well.(2)From the results of the Tunel staining experiments:the positive apoptotic cells in the model group were higher than control group and sham-operated group,positive drug group and TSG drugs group was significantly smaller than that in the model group(P<0.05).(3)Compared with the control group and the Virtual Operation Group,the MKK7 and JNK protein concentrations in the brain of the model group were increased(P<0.05)by data analysis of immunohistochemistry:Compared with the model group,the protein expression of positive drug and TSG each dose group were reduced(P<0.05).(4)The results of QRTPCR data showed that the levels of MKK7 and JNK mRNA in the brain tissue of the model group were increased compared with the normal group and sham-operated groups(P<0.05).Conclusion:Stilbene glycoside has a certain effect on neuronal injury and repair which may be related to the changes of mRNA transcription and protein expression of MKK7 and JNK kinases.

In situ absorption and metabolism of stilbene glycoside in rat

Stilbene glycoside(TSG)has been shown to have many beneficial properties.It is therefore essential to understand the absorption and metabolism of TSG in detail.We determined the recovery of TSG and its metabolites(TSG sulfate/glucuronides)in rat gastric contents,gastric mucosa,portal vein plasma,celiac arterial plasma,bile,and urine after administration of 15 mg of TSG in 0.5 mL physiological saline or incubation for 20 min in situ in the stomach of rats.Within 20 min,(64.0±9.8)% of the administered TSG disappeared from the stomach;later,TSG was recovered in both free and conjugated forms in plasma and bile,but not in urine.On the other hand,only free TSG was detected in the gastric contents and mucosa;it was also detected in the portal vein plasma as(48.1±3.5)% of the total TSG(all forms of TSG).However,the proportion of free TSG in the celiac arterial plasma and bile decreased to 4%-10%.In addition,the proportion of free TSG to total TSG in the liver microsome incubation mixture after TSG was incubated in liver microsome at 37 ℃ for 30 min was very low [(10.6 ± 2.6)%].These results indicate that TSG could be quickly absorbed from the rat stomach,conjugated in liver and excreted in bile.Such novel information would be helpful for the use of TSG as a beneficial natural product which may improve its proposed efficacy in preventing chronic diseases.

Hypoglycemic effects of naturally processed Polygonum multiflorum extract in KK CgAy/J mice and its mechanism of action

In 2021,there are approximately 537 million adults ageing 20-79 years affected by diabetes worldwide and the number is rising rapidly,hence it is important to manage and control diabetes mellitus and its associated complications.Food is one of the key factors in preventing and combating diseases such as diabetes.Both as a food and an herbal medicine,Polygonum multiflorum(PM)has been used as an anti-aging tonic,for hair darkening in traditional Chinese medicine for several centuries.The recent research effort of PM has been focused on antioxidant,anti-ageing and anti-tumor properties.In the present study,we utilized the traditional processing of harvested raw PM,and identified several stilbene components and then evaluated the potential anti-diabetic effects of the processed PM extract(PME).PME(0.075%)was given to diabetic mice(KK CgAy/J)in drinking water and after 7 weeks,PME-treated mice had significantly lower glucose levels than mice in the diabetic control group(P<0.01).The mechanism was explored with ELISA and Western blotting and results suggested that the effect was through maintainingβ-cell function.

Effect of TSG on tau phosphorylation via GSK-3βpathway

Objective:To observe how TSG interferes with Tau phosphorylation in Aβ25-35 induced dementia model via GSK-3βpathway.Methods:Thirty-six male SD rats aged 24 months were randomly divided into control group,sham group,model group,low-dose,medium-dose and high-dose of TSG groups(TSG,0.033,0.1,0.3g·kg^(-1)),with 6 rats in each group.Model group and TSG dose groups were injected Aβ25-35 into hippocampus by brain stereoscopic locator to induce dementia model(sham group was injected with equal volume of normal saline).Six SD rats of the same age were selected as normal group.14d after modeling by Aβ25-35,the rats was given TSG by gavage.once A day in each group for 4 weeks.After 4 weeks of treatment with TSG,HE staining was used to observe the structural changes of nerve cells in brain tissue,IHC was used to observe the expression of PKC and PKA protein in brain tissue,real-time PCR was used to observe the mRNA expressions of GSK-3β,PKA,PI3K,PKB and PKC,and Western blot was used to observe the expression of GSK-3β,P-tau,PI3K and PKB protein in hippocampus.Results:Compared with normal group,the number of nerve cells in model group was less,and the arrangement was sparse and disordered.The expression of PI3K,PKB mRNA were significantly decrease(P<0.01),the expression of GSK-3β,PKA mRNA was go up(P<0.05),the exPression of PKC mRNA was decreased(P<0.05),the protein expression level of PKC(P<0.01),PI3K(P<0.05)and PKB(P<0.01)were decreased,the expression levels of PKC protein in hippocampus and cortex were significantly decreased(P<0.01),the expression levels of PKA protein in hippocampus and cortex were go up(P<0.05).Compared with model group,the number of nerve cells in each administration group increased to a certain extent,the expression levels of P-tau,GSK-3βand PKA protein and mRNA were significantly decrease(P<0.05,P<0.01),the expression levels of PI3K,PKB and PKC protein and mRNA were significantly up-regulated(P<0.05,P<0.01).Conclusion:TSG can regulate GSK-3β,PI3K,PKC,PKB and PKA in the hippocampus of Aβ25-35 induced dementia model.By regulating the expression of these factors,the hyperphosphorylation of Tau protein can be inhibited and the phenomenon of hyperphosphorylation of Tau protein can be improved.