Total flavonoids from Tetrastigma hemsleyanum ameliorates inflammatory stress in concanavalin A-induced autoimmune hepatitis mice by regulating Treg/Th17 immune homeostasis

Tetrastigma hemsleyanum, a rare and endangered medicinal plant, has attracted much attention due to its immunoregulatory and hepatoprotective activities. This study aimed to evaluate the anti-inflammatory effects and underlying mechanisms of total flavonoids from T. hemsleyanum(TFT)on Con A-induced hepatitis in mice. TFT (1, 2 and 4 g/kg) and a positive control drug bifendate (200 mg/kg) were administered intragastrically to mice once daily for 10 consecutive days. On the 10th day, the model autoimmune of hepatitis was established by intravenous injection of Con A (20 mg/kg) 1 h after drug administration. Liver injury was assessed by serum levels of alanine amino transferase (ALT and AST) and histopathology 8 h after Con A injection. The levels of pro-inflammatory Th17 cytokines (IL-17, IL-6) and anti-inflammatory Treg cytokines (IL-10, TGF-β1) in serum were evaluated by ELISA, the levels of Th17 and Treg cells infiltrated into spleen were investigated by flow cytometry methods, and hepatic tissue transcription factor Foxp3 and RORγt mRNA were determined using quantitative real-time PCR. Pretreatment with TFT and bifendate significantly reduced the serum levels of ALT and AST, and attenuated histopathological alterations in Con A-induced liver injury. With respect to samples treated with Con A alone, TFT and bifendate pretreatments differentially attenuated the increase of serum inflammatory factors interleukin (IL)-17 and IL-6 levels, the proportions of Th17 cells in spleen and the expression of RORγt in hepatic tissues. Meanwhile, TFT and bifendate pretreatments could enhance the percentage of Treg cells in spleen and the expression of Foxp3 in hepatic tissues, as well as the levels of transforming growth factor (TGF)-β1, IL-10 in serum. The anti-inflammatory effects of TFT was mediated by regulating Treg/Th17 immune homeostasis, which, therefore, suppressed the inflammatory immune response. This study provided scientific basis for the further researches and clinical applications of Tetrastigma hemsleyanum.