Protective Effects of Salvianolic Acid A against Dextran Sodium Sulfate-Induced Acute Colitis in Rats

Abstract

Salvianolic acid A (SAA) is an active phenolic acid derived from Salvia miltiorrhiza Bunge (Danshen). To explore whether SAA has a therapeutic effect against inflammatory bowel disease (IBD), an acute colitis model was induced in rats by administering 3% dextran sodium sulphate (DSS) for one week. SAA in doses of 4 and 8 mg/kg/day was given by tail vein injection during DSS administration. Both dosages of SAA ameliorated the colitis symptoms, with decreases observed in the disease activity index. A high dosage of SAA (8 mg/kg/day) promoted a longer colon length and an improved colonic tissue structure, compared with the DSS-treated rats not receiving SAA. SAA dose-dependently decreased colonic gene expression of pro-inflammatory cytokines (IL-1β, MCP-1 and IL-6). Moreover, a high dosage of SAA protected against DSS-induced damage to tight junctions (TJ) in the rats’ colons, by increasing TJ-related gene expression (ZO-1 and occuldin). Finally, using 16S rRNA phylogenetic sequencing, we found that SAA modulated gut microbiota imbalance during colitis by increasing the gut microbial diversity as well as selectively promoting some probiotic populations, including Akkermansia spp. Our study suggests that SAA is a promising candidate for the treatment of IBD.

Keywords: Salvia miltiorrhiza Bunge; dextran sodium sulphate; gut microbiota; inflammatory bowel disease; salvianolic acid A.

Figure 1

Chemical structure of salvianolic acid A (SAA).

Figure 2

Salvianolic acid A ameliorated DSS-induced acute colitis symptoms in rats. The rats were administered DSS (4%) in drinking water for seven days. The SAA low-dosage group (SAAL, 4 mg/kg/day i.v.) and SAA high-dosage group (SAAH, 8 mg/kg/day i.v.) were tail vein-injected with SAA until the end of the experiment. (A) Disease activity index (DAI) values were recorded daily. (B) Colon length was recorded and compared among the normal control (N), DSS, SAA low-dosage group (SAAL), and SAA high-dosage group (SAAH). The data shown are the means ± SD, and means with different letters are significantly different (p < 0.05); n = 8 rats per group in a single experiment (C) Representative hematoxylin and eosin (H&E)-stained distal colon sections. (D) The histologic scores of rats. The data represent the mean ± SD of eight rats per group.

Figure 3

Effects of salvianolic acid A on inflammatory gene expression in the colonic mucosa of rats after DSS-induced colitis. The rats’ distal colons were collected, and mRNA expression of TNF-α (A), IL-1β (B), IL-6 (C), and TGF-β (D) was quantified using real-time PCR. Fold changes are expressed as means ± SD (n = 8 for each group in a single experiment). Groups with different letters differ by a statistically significant margin (p < 0.05). N, normal control group; DSS, DSS colitis group; SAAL, SAA low-dosage group (SAAL, 4 mg/kg/day i.v.), and SAAH, SAA high-dosage group (SAAH, 8 mg/kg/day i.v.).

Figure 4

Effects of salvianolic acid A on the expression of genes coding for colonic tight junction proteins in DSS-induced-colitis rats. (A) The rats’ distal colons were collected, and mRNA expression of genes coding for the tight-junction proteins occludin (A) and ZO-1 (B) was quantified using real-time PCR. Fold changes are expressed as means ± SEM (n = 8 for each group in a single experiment). Groups with different letters differ by a statistically significant margin (p < 0.05).

Figure 5

Effects of SAA on gut microbial composition in DSS-induced-colitis rats in a single experiment. (A) Venn diagram showing overlapping operational taxonomic units (OTUs) identified in the intestinal microbiota in the normal control, DSS, and SAA groups. (B) Principal coordinates analysis (PCoA) plot of the gut microbiota based on weighted UniFrac metrics. (C) Structural comparison of intestinal microbiota between the three groups at the phyla level. (D) Hcluster analysis of the gene levels for the three experimental groups. (E) Heat map of the 20 most differentially abundant taxons in the three groups at the gene level.