Effects of Bletilla Striata Polysaccharide on Rat Ulcerative Colitis Model by Rebalancing Th1/Th2 and T17/Treg Subsets

Objective: Ulcerative colitis is an inflammatory disease that affects the lining of the colon and rectum. This study was to investigate the potential utility of Bletilla striata polysaccharide (BSP) for ulcerative colitis (UC) treatment and explore its immunoregulatory mechanisms. Methods: Male Wistar rats were assigned to four groups at a ratio of 1:1:1:1. The four groups of rats were treated with no intervention, 2,4,6-trinitrobenzenesulfonic acid (TNBS), high-performance liquid chromatography (HPLC)-purified BSP (60 mg/kg), sulfasalazine (100 mg/kg). Symptom severity was assessed. Flow cytometry and quantitative real-time polymerase Chain Reaction (qRT-PCR) were performed to assess T cell responses, including the proportions of cluster of differentiation 4 + (CD4 + ) T cells and particular cytokines. Autophagic markers microtubule-associated protein 1A/1B-light chain 3 (LC3) II and sequestosome 1 (p62), and granzyme (Grz)-related proteins, Granzyme M (GrzM), macrophage inflammatory protein 1 (MIP-1α) and macrophage migration inhibitory factor (MIF) were estimated by Western blot. Results: Significant elevations of T helper 1 (Th1) and Th17 and declines of Th2 and regulatory T cells (Treg) were observed in the UC group versus the controls ( p < 0.001). These alterations could be reversed significantly in UC rats treated with BSP, in contrast to UC group ( p < 0.001). T cell percentage alterations were validated by mRNA expression of cytokines associated to distinct T cell subgroups. BSP therapy resulted in increased LC3 II and decreased p62, as well as an increase in GrzM and MIP-1 and a decrease in MIF. Except for LC3 II, significant differences were observed in these protein levels from those in the UC group ( p < 0.001). Conclusion: BSP demonstrates great potential for UC management via rebalancing of Th1/Th2 and T17/Treg subsets. The study provides a certain theoretical basis for the treatment of UC with traditional Chinese medicine, but the results might be biased due to the small sample size, and future studies are required to further explore.