This study was designed to discuss the effects of 3, 3'-diindolylmethane (DIM) on methionine-choline-deficient (MCD)-diet induced mouse nonalcoholic steatohepatitis (NASH) and the potential mechanisms. NASH mice were administrated with or without DIM at different concentrations for 8 weeks. Both the in-vivo and in-vitro effects of DIM on Treg/Th17 imbalance during NASH progression were analyzed. The in-vivo blocking of CD25 or IL-17 was performed to respectively deplete respective function of Treg or Th17 subset. Besides, with the assistance of AhR antagonist CH223191 and anti-TLR4 neutralizing antibody, we designed the in-vitro DIM-incubation experiments to discuss the roles of aryl hydrocarbon receptor (AhR) (CYP1A1, CYP1B1) and toll-like receptor 4 (TLR4) on DIM's effects when shifting Treg/Th17 imbalance. Notably, in NASH mouse models, DIM alleviated hepatic steatosis and inflammation, and shifted the Treg/Th17 imbalance from MCD diet-induced Th17 dominance to Treg dominance. In-vitro, DIM not only significantly up-regulated the mRNAs of Foxp3 (Treg-specific) in purified spleen CD4(+) T cells, but also enhanced the immunosuppressive function of these Treg cells. Besides, DIM significantly up-regulated the proteins of CYP1A1 and CYP1B1 whereas down-regulated those of TLR4 on CD4(+) T cells from MCD-diet mice. Moreover, blocking AhR attenuated while blocking TLR4 enhanced the effects of DIM when regulating Treg/Th17 imbalance. Conclusively, DIM could be used as a potential therapeutic candidate to treat NASH based on its dramatic induction of Treg dominance to alleviate intra-hepatic inflammation, suggesting us a clue that the dietary cruciferous vegetables (containing abundant DIM) might exist as a protective factor for patients with NASH-related liver diseases.
Keywords: 3, 3′-diindolylmethane; Aryl hydrocarbon receptor; Nonalcoholic steatohepatitis; Regulatory T cells; Th17 cells; Toll like receptor 4.
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