Tetramethylpyrazine improves oxazolone-induced colitis by inhibiting the NF-κB pathway

Purpose: Tetramethylpyrazine (TMP) is an effective Chinese plant-derived medicine for colitis in the clinic, but the underlying molecular mechanisms of its use remain poorly understood. The purpose of this study was to investigate the mechanisms involved in its therapeutic action. Methods: A colitis mouse model was induced by oxazolone enema. TMP was administered at 80 mg/kg/day and sulphasalazine (SASP) was used as positive control and administered at 100 mg/kg/day for the treatment of colitis. On the fourth day after enema, mice were sacrificed. The inflammatory response was assessed by the disease activity index and histology. Colon mucosa was isolated and biochemically analyzed. In addition, in vitro studies were performed to evaluate the activity of TMP in Caco-2 cells. Results: Our results showed that TMP improved the colonic inflammatory status as evidenced by histological findings, as well as SASP. These effects were associated with a decrease in nucleus translocation of NF-κB. Paired with this inhibitive activity, there was a decrease in downstream signaling, such as C-MYC, iNOS and COX-2. In vitro assays revealed that TMP inhibited NF-κB translocation and its downstream production of inflammatory factors, such as TNF-α, IL-6 and IL-8, and that ROS production that was induced by LPS in Caco-2 cells. Conclusion: TMP improved the colitis induced by oxazoline, and its activity was associated with inhibition of NF-κB translocation, and subsequent inhibition of pro-inflammatory factor production and oxidative stress