Jiedu-Yizhi Formula Alleviates Neuroinflammation in AD Rats by Modulating the Gut Microbiota

Abstract

Background: The Jiedu-Yizhi formula (JDYZF) is a Chinese herbal prescription used to treat Alzheimer's disease (AD). It was previously confirmed that JDYZF can inhibit the expression of pyroptosis-related proteins in the hippocampus of AD rats and inhibit gut inflammation in AD rats. Therefore, it is hypothesized that JDYZF has a regulatory effect on the gut microbiota.

Methods: In this study, an AD rat model was prepared by bilateral hippocampal injection of Aβ _25-35 and AD rats received high, medium, and low doses of JDYZF orally for 8 weeks. The body weights of the AD rats were observed to assess the effect of JDYZF. The 16S rRNA sequencing technique was used to study the regulation of the gut microbiota by JDYZF in AD rats. Immunohistochemical staining was used to observe the expression levels of Caspase-1 and Caspase-11 in the hippocampus.

Results: JDYZF reduced body weight in AD rats, and this effect may be related to JDYZF regulating body-weight-related gut microbes. The 16S rRNA analysis showed that JDYZF increased the diversity of the gut microbiota in AD rats. At the phylum level, JDYZF increased the abundances of Bacteroidota and Actinobacteriota and decreased the abundances of Firmicutes, Campilobacterota, and Desulfobacterota. At the genus level, the abundances of Lactobacillus, Prevotella, Bacteroides, Christensenellaceae_R-7_group, Rikenellaceae_RC9_gut_group, and Blautia were increased and the abundances of Lachnospiraceae-NK4A136-group, Anaerobiospirillum, Turicibacter, Oscillibacter, Desulfovibrio, Helicobacter, and Intestinimonas were decreased. At the species level, the abundances of Lactobacillus johnsonii, Lactobacillus reuteri, and Lactobacillus faecis were increased and the abundances of Helicobacter rodentium and Ruminococcus_sp_N15.MGS-57 were decreased. Immunohistochemistry showed that JDYZF reduced the levels of Caspase-1- and Caspase-11-positive staining.

Conclusion: JDYZF has a regulatory effect on the gut microbiota of AD rats, which may represent the basis for the anti-inflammatory effect of JDYZF.

Figure 1

(a) Weight growth degree and trend of rats in each group; (b) the number of common and unique OTUs in each group and petal diagram; (c) the top 10 species in abundance at the genus level; (d) the top 10 species at the species level; (e) phylogenetic relationships of species at the genus level.

Figure 2

(a) Rarefaction curve; (b) species accumulation boxplot; (c) the boxplot of the Shannon index difference between groups; (d) three-dimensional PCoA map based on weighted UniFrac distance.

Figure 3

Phyla with significant differences in abundance at the phylum level in each group of rats. (a) p_Firmicutes; (b) p_Bacteroidota; (c) p_Unidentified_Bacteria; (d) p_Actinobacteriota; (e) p_Campilobacterota; (f) p_Desulfobacterota. Comparison between the groups: ^∗q < 0.05 and ^∗∗q < 0.01.

Figure 4

Genera with significant differences in abundance at the genus level in each group of rats. (a) g_lactobacillus; (b) g_bacteroides; (c) g_Lachnospiraceae-NK4A136-group; (d) g_Desulfovibrio; (e) g_Helicobacter; (f) g_Intestinimonas; (g) g_Prevotellaceae_Ga6A1_group; (h) g_prevotella; (i) g_Christensenellaceae_R-7_group; (j) g_Rikenellaceae_RC9_gut_group; (k) g_Anaerobiospirillum; (l) g_Turicibacter; (m) g_Oscillibacter; (n) g_Blautia; (o) g_Streptococcus. Comparison between the groups: ^∗q < 0.05 and ^∗∗q < 0.01.

Figure 5

Species with significant differences in abundance at the species level in each group of rats. (a) s_Lactobacillus_johnsonii; (b) s_Lactobacillus_reuteri; (c) s_Lactobacillus_faecis; (d) s_Helicobacter_rodentium; (e) s_Ruminococcus_sp_N15.MGS-57. Comparison between the groups: ^∗q < 0.05 and ^∗∗q < 0.01.

Figure 6

Histogram of the distribution of LDA values. The LDA score greater than 4 was regarded as the biomarker with the statistical difference between groups. The length of the histogram represents the effect size of the different species.

Figure 7

(a) Caspase-1 immunohistochemical staining and AOD levels in the hippocampus of rats in each group; (b) Caspase-11 immunohistochemical staining and AOD levels. ^∗∗p < 0.01, other groups are compared with the model group. ^#p < 0.05 and ^##p < 0.01, other groups are compared in pairs except for the model group.