Abstract:

Objective To investigate the therapeutic effects of Astragali Radix on the intestinal inflammation， intestinal barrier and intestinal flora in the rats with rhubarb-induced diarrhea，and to elucidate the possible mechanisms. Methods Fifty rats were randomly divided into control group， model group， positive control group （2.468 g·kg^－1 Shenlingbaizhu Powder）， low dose（1.35 g·kg^－1） of Astragali Radix group， and high dose（2.70 g·kg^－1） of Astragali Radix group，with 10 rats in each group. The rat diarrhea models were replicated by rhubarb gavage in combination with diet indiscipline.The body weights， fecal water contents and diarrhea scores of the rats in various groups were detected； HE staining was used to observe the pathomorphology of colon tissue of the rats in various groups， and Western blotting method was used to detect the expression levels of protease activated receptor-2（PAR-2），phosphorylated p38 （p-p38）， myosin light chain kinase （MLCK）， phosphorylated myosin light chain （p-MLC）， zonula occludens-1（ZO-1），Occludin，Toll-like receptor 4 （TLR4），tumor necrosis factor receptor-associated factor 6（TRAF6）， myeloid differentiation factor 88 （MyD88）， and nuclear factor-κB （NF-κB） proteins in colon tissue of the rats in various groups；the levels of motilin （MTL）， gastrin （GAS）， tumor necrosis factor-α （TNF-α）， interleukin-1β （IL-1β）， interleukin-6 （IL-6），interleukin-10 （IL-10），malondialdehyde （MDA），and secretory immunoglobulin A （SIgA） and the activities of superoxide dismutase （SOD） in serum of the rats in various groups were measured by enzyme linked immunosorbent assay（ELISA） method；16S r DNA gene sequencing was performed to analyze the intestinal flora of the rats in various groups. Results Compared with control group，the body weight of the rats in model group was significantly decreased（P<0.01）， the fecal water content and diarrhea score were significantly increased （P<0.01），and the levels of MTL and GAS in serum were significantly increased （P<0.01）； compared with model group，the body weights of the rats in positive control and low and high doses of Astragali Radix groups were significantly increased（P<0.01）， the fecal water contents and diarrhea scores were significantly decreased （P<0.01），and the levels of MTL and GAS in serum of the rats in were significantly decreased （P<0.01）. The HE staining results showed that compared with control group， the colonic epithelial mucosa of the rats in model group was damaged， with a large number of infiltrated inflammatory cells and disordered glands. Compared with model group， the mucosal structures of the epithelium in positive control and high dose of Astragali Radix groups were more regular， with less inflammatory cell infiltration and without obvious glandular disorder； the mucosal structure of the colonic epithelium in low dose of Astragali Radix group had slight mucosal damage， with partial inflammatory cell infiltration and more neatly arranged glands.The Western blotting results showed that compared with control group，the expression levels of PAR-2，MLCK，TLR4，TRAF6，MyD88，NF-κB，p-p38 and p-MLC proteins in colon tissue of the rats in model group were significantly increased （P<0.01），and the expression levels of ZO-1 and Occludin proteins in colon tissue of the rats in model group were significantly decreased （P<0.01）； compared with model group，the expression levels of PAR-2， MLCK， TLR4， TRAF6， MyD88， NF-κB，p-p38 and p-MLC proteins in colon tissue of the rats in positive control group，low dose of Astragali Radix group and high dose of Astragali Radix group were significantly decreased （P<0.05 or P<0.01）， and the expression levels of ZO-1 and Occludin proteins in colon tissue of the rats in positive control group， low dose of Astragali Radix group and high dose of Astragali Radix group were significantly increased （P<0.05 or P<0.01）.Compared with control group，the levels of TNF-α， IL-1β， IL-6 and MDA in serum of the rats in model group were significantly increased （P<0.01），the levels of IL-10， and SIgA in serum and the SOD activity of the rats were significantly decreased（P<0.01）； compared with model group， the levels of TNF-α， IL-1β， IL-6 and MDA in serum of the rats in positive control group， low dose of Astragali Radix group and high dose of Astragali Radix group were significantly decreased （P<0.01）， and the levels of IL-10 and SIgA in serum and the SOD activities were significantly increased （P<0.01）.At the level of phylum，the intestinal flora detection results showed that compared with control group， the abundance of Proteobacteria and Verrucomicrobia in model group was significantly increased （P<0.01）； compared with model group， the abundance of Proteobacteria and Verrucomicrobia in low and high doses of Astragali Radix groups was significantly decreased （P<0.01）， and the abundance of Epsilonbacteraeota in intestinal flora in high dose of Astragali Radix group was significantly increased （P<0.01）. Conclusion Astragali Radix has a therapeutic effect in the rhubarb-induced diarrhea model rats， and its mechanism may be related to inhibiting intestinal inflammation through TLR4/TRAF6/NF-κB signaling pathway， thereby repairing the intestinal barrier and restoring the composition of intestinal flora.

Key words: Astragali Radix, Intestinal barrier, Intestinal inflammation, Intestinal flora, Gram-negative bacillus