Change of Th17/Treg cells in experimental colitis mice and the protective effect of mica

Objective To investigate the role of Th17/Treg cells in colitis through observing the change of Foxp3/ROR-γt in TNBS-induced experimental colitis mice, and to explore the protective effect and possible mechanism of mica. Methods Thirty male BALB/C mice of clean grade were randomly divided into control group, model group and mica group with 10 mice in each group. Mice of model group and mica group were initiated by intra-rectal administration of TNBS to establish the model. From the first day after model establishment, the control group and model group received intra-rectal administration with normal saline for 3 days; the mica group received intra-rectal administration with mica for 3 days. Then all the mice were killed and specimens were taken. Gross and histological damage of colon in mice were observed. Expressions of ROR-γt, Foxp3, IL-17A, IL-10 in colon tissues were examined by RT-qPCR, immunohistochemistry, and ELISA. Results Mice in model group presented as follows: curled and lazy; DAI scores significantly increased; colonic canal was thick and short; colonic mucosa was sporadic hyperaemia, erosion, and multiple ulcers; histopathology of colonic mucosa showed ulcers and necrosis, lots of inflammatory cells in mucosa and submucosa. Compared with model group, obviously decreased DAI scores, macroscopic and histological damage score were observed in mica group (all P<0.05) . Compared with control group, expressionsof ROR-γt, Foxp3, IL-17A, IL-10 in model group were all higher (all P<0.05) , while the ratio of Foxp3/ROR-γt was obviously decreased (P= 0.012) . Compared with model group, expressions of ROR-γt, IL-17A was obviously decreased (all P<0.05) , expression of Foxp3, IL-10 was obviously increased (all P<0.05) , while the ratio of Foxp3/ROR-γt obviously increased in mica group (P= 0.00) . Pearson analysis showed the ratio of Foxp3/ROR-γt was positively correlated with IL-10 expression (r= 0.72, P= 0.03) and negatively correlated with IL-17A expression (r=-0.67, P= 0.05) . Conclusions The Th17/Treg cells and inflammation-related cytokines are imbalances in TNBS-induced ulcerative colitis mice. Mica has a protective effect on ulcerative colitis mice, which can adjust the imbalance of Th17/Treg cells, up-regulate the expression of IL-10, inhibit the expression of IL-17A and ameliorate the inflammation reaction. Key words: Inflammatory bowel diseases; Thelper 17 cells; Regulatory T cells; IL-17A; IL-10; Mica