This study aims to investigate the effect of Xixin Decoction on the T helper 17 cell(Th17)/regulatory T cell(Treg) ba-lance of intestinal mucosa and the expression of related transcription factors in the senescence-accelerated mouse-prone 8(SAMP8) model. Fifty 14-week male mice of SAMP8 were randomized by the random number table method into model group, probiotics group, and high-, medium-, and low-dose Xixin Decoction groups, with 10 mice in each group. Ten 14-week male mice of senescence-acce-lerated mouse-resistant 1(SAMR1) served as control group. After 10 weeks of feeding, the mice were administrated with correspon-ding drugs for 10 weeks. Morris water maze test was carried out to examine the learning and memory abilities of mice. Enzyme-linked immunosorbent assay(ELISA) was employed to determine the content of secretory immunoglobulin A(SIgA) in the intestinal mucosa, and flow cytometry to detect the percentage content of Th17 and Treg in the intestinal mucosa. Western blot was performed to determine the protein levels of retinoid-related orphan receptor gamma t(RORγt) and forkhead box p3(Foxp3) in the mouse colon tissue. Compared with control group, the escape latency of mice in model group was significantly prolonged(P<0.01), and the number of times of crossing the platform and the residence time in the target quadrant were significantly reduced within 60 s(P<0.01), intestinal mucosal SIgA content was significantly decreased(P<0.01), Th17 content was increased(P<0.05), Treg content was decreased(P<0.01), the expression of RORγt protein was increased and Foxp3 protein was decreased in colon(P<0.01). Compared with the model group, high-dose Xixin Decoction group improved the learning and memory ability(P<0.05 or P<0.01). Probiotics group and high-and medium-dose Xixin Decoction group increased the content of SIgA in intestinal mucosa(P<0.05 or P<0.01), decreased percentage content of Th17 and increased the percentage content of Treg in intestinal mucosa(P<0.05 or P<0.01). Furthermore, they down-regulated the protein level of RORγt and up-regulated the protein level of Foxp3 in the intestinal mucosa(P<0.01). In conclusion, Xixin Decoction may act on intestinal mucosal immune barrier, affect gut-brain information exchange, and improve the learning and memory ability of SAMP8 by promoting SIgA secretion and regulating the Th17/Treg balance and the expression of RORγt and Foxp3.
Keywords: Alzheimer′s disease; Th17/Treg balance; Xixin Decoction.