洗心汤对D-半乳糖联合Aβ25-35诱导的AD模型大鼠结肠黏膜屏障及TLR4/NF-κB p65信号通路的影响OA

Objective:This study aims to investigate whether Xixintang could ameliorate cognitive dysfunction in an Alzheimer's disease(AD)rat model induced by D-galactose and β-amyloid(Aβ25-35),by means of repairing the colonic mucosal barrier,regulating the Toll-like receptor 4(TLR4)/nuclear factor-κB p65(NF-κB p65)signaling pathway,and intervening in the pathological process mediated by the gut-brain axis.Methods:Sixty specific pathogen-free(SPF)male Sprague-Dawley(SD)rats were randomly divided to five groups(n=12):A control group,a model group,a donepezil group,an Xixintang group,and a probiotic group.Except for those in the control group,rats in all other groups received daily intraperitoneal injections of D-galactose for six consecutive weeks.Subsequently,aggregated Aβ25-35 was injected stereotactically into the bilateral ventricles to establish the AD model.During the intervention periods,the rats in all groups were administered their respective drugs and normal saline by gavage.The Morris water maze test was used to assess the capacity for spatial learning and memory.Hematoxylin-eosin(HE)staining was employed to observe the histopathological changes in the colon tissues.Immunofluorescence was used to detect Aβ1-41 deposition in the hippocampal region and Mucin 2(MUC2)expression in the colonic mucosa.Western blot was performed to measure the protein expression levels of FFAR2,TLR4,NF-κB p65,occludin(OCLN),zonula occludens-1(ZO-1),and MUC2 in the colonic tissues.Enzyme-linked immunosorbent assay(ELISA)was used to determine the contents of interleukin-6(IL-6),tumor necrosis factor-α(TNF-α),serum amyloid A(SAA),and Aβ1-42 in the hippocampal region from the colonic tissues.The lipopolysaccharide(LPS)concentrations in colon tissues of rats were measured by using a dynamic chromogenic limulus assay.Results:Compared with those in the control group,the rats in the model group exhibited a significantly prolonged escape latency and a markedly shorter duration in the target quadrant(P＜0.01).The integrity of the colonic mucosal structure was compromised,with disordered gland arrangement and a reduced number of goblet cells.The Aβ1-42 deposition in the hippocampal region was significantly increased(P＜0.01).The protein expression levels of TLR4 and NF-κB p65 in colonic tissues were significantly upregulated(P＜0.01),while those of occludin and ZO-1 were downregulated(P＜0.01).The contents of inflammatory factors such as IL-6,TNF-α,and SAA were significantly elevated(P＜0.01),and the LPS level in the serum was markedly increased(P＜0.01).In comparison to those in the model group,the rats in the Xixintang group showed a significantly shortened escape latency and a prolonged duration in the target quadrant(P＜0.01).The colonic mucosal structure was ameliorated,with neat gland arrangement and an increased number of goblet cells.TheAβ1-42deposition in the hippocampal region was reduced(P＜0.01).The protein expressions of TLR4 and NF-κB p65 in the colon tissues were decreased(P＜0.05,P＜0.01),while the protein levels of occludin and ZO-1 were increased(P＜0.01).The contents of IL-6,TNF-α,and serum amyloid A(SAA)were decreased(P＜0.01),and the LPS level was reduced(P＜0.01).Conclusion:Xixintang can significantly ameliorate cognitive dysfunction of AD model rats,by means of restoring the colonic mucosal barrier structure,reducing cerebral Aβ deposition,and suppressing peripheral and central inflammatory response.Its mechanism of action may be closely associated with the suppression of the TLR4/NF-κB signaling pathway activation,reduction of endotoxin levels,and regulation of the gut-brain axis.