Background: Tiaochang Xiaoyan tablet (TCXYT) is a traditional Chinese medicine prescription derived from the Xianglian pill, which is a traditional Chinese medicine for treating chronic dysentery recorded in the Taiping Huimin Heji Bureau [1078-1085]. For many years, TCXYT has been used to treat ulcerative colitis, however, its therapeutic mechanism is still unclear. In the present study, we used colonic lamina propria macrophages (LPM) and mouse-derived macrophage cell line RAW264.7 cells as the research objects, with the aim of exploring the therapeutic effects and mechanisms of TCXYT on colitis.
Methods: We used 2,4,6-trinitrobenzenesulfonic acid (TNBS) to induce a rat model of chronic colitis, and normal rats as the control. The disease activity index (DAI) and colonic histopathological changes of rats were used to evaluate the severity of colitis. Rats were divided into the control group; model group; high, middle-, and low-dose TCXYT group; and the hydroxychloroquine sulfate group. TCXYT was administered by gavage on the 3rd day after model replication and lasted for 7 days. The doses used for the high-, middle-, and low-dose TCXYT groups were 0.8, 0.4 and 0.2 g/kg, respectively. Enzyme-linked immunosorbent assay was used to detect the serum concentration of cytokines. Western blot was used to detect the expressions of Toll-like receptor 9 (TLR9), myeloid differentiation primary response 88 (MyD88), interleukin (IL) receptor-associated kinase (IRAK) 1, and IRAK4 in colonic LPM and RAW264.7 cells. Immunofluorescence was used to detect lysosomal activity. The chemical constituents of TCXYT were separated and identified based on Q-Orbitrap high resolution LC/MS data.
Results: TCXYT promoted the repair of colonic mucosal injury, attenuated inflammation, increased lysosome activity in macrophages, and decreased the DAI in rats with colitis compared with those in the model group. TCXYT decreased the serum concentrations of IL-1β and tumor necrosis factor-α (TNF-α), increased those of IL-4 and IL-10, and decreased the TLR9, MyD88, IRAK1, and IRAK4 protein levels in LPM and RAW264.7 cells compared to the model group.
Conclusions: TCXYT could ameliorate colon inflammation and CD11c+ macrophage infiltration in rats with chronic colitis. This effect may be mediated by activating lysosomes in macrophages by inhibiting the TLR9/MyD88/IRAK signaling pathway.
Keywords: Tiaochang Xiaoyan tablet (TCXYT); inflammation; lysosome; macrophages; ulcerative colitis.