Ethyl pyruvate ameliorates experimental colitis in mice by inhibiting the HMGB1-Th17 and Th1/Tc1 responses

Ethyl pyruvate (EP), a simple lipophilic pyruvate ester, has demonstrated protective effects against murine colitis through inhibition the release of inflammatory factor high-mobility group protein box 1 (HMGB1). HMGB1 has been implicated in several autoimmune diseases by inducing Thl and Thl7 cells activation. This study was designed to investigate whether EP amelioration of murine colitis is related to the blocking of the HMGB1-Th17/Thl pathway. We induced murine colitis by intrarectal administration of 2, 4, 6-trinitrobenzene sulfonic acid (TNBS). Ethyl pyruvate was injected intraperitoneally once a day for 7days. One week after intrarectal challenge with TNBS, HMGB1, IL-17 and IFN-γ protein levels were remarkably increased following severe colon inflammation. Meanwhile, excessive infiltration of Th17 cells in colonic tissues, and an upregulated proportion of Th17 and Th1/Tc1 cells in the spleen and mesenteric lymph nodes (MLN) were found in the TNBS-treated group compared to the control group. Treatment with the HMGB1 inhibitor EP not only remarkably improved colon pathological damage, but also significantly reduced the number of Th17 cells in the local tissues of the colitis-induced mice. Furthermore, the percentage of Th1/Tc1 and Th17 cells in the spleen and MLN, as well as levels of serum IFN-γ and IL-17A, were all markedly decreased in the EP-treated group. Moreover, in vitro, our results showed that EP in a dose dependent manner inhibited HMGB1 release induced by LPS from CT26 cells (murine colon adenocarcinoma cell line). These results suggest that HMGB1 contributes to the development of murine colitis by promoting the Th17 and Th1/Tc1 responses, and that EP can significantly inhibit HMGB1-Th17 and Thl/Tc1 pathway activation, which may provide better protection to mice with TNBS-induced colitis.