Andrographolide derivative AL-1 ameliorates TNBS-induced colitis in mice: involvement of NF-кB and PPAR-γ signaling pathways

Andrographolide is a traditional herb medicine, widely used in Asia for conditions involving inflammation. The andrographlide-lipoic acid conjugate, AL-1, has been found being able to alleviate inflammation in our previous reports. Although the anti-inflammatory activity of AL-1 contributes to its cytoprotective effects, whether AL-1 can improve inflammatory bowel disease (IBD) and the underlying mechanisms of its action remain largely unknown. In this study, we investigated the anti-inflammatory effects of AL-1 in C57BL/6 mice with trinitrobenzenesulfonic acid (TNBS)-induced colitis. The body weight loss and length change of colon after TNBS instillation were more severe than those in normal mice. AL-1 treatment led to significant reductions in disease activity index (DAI), macroscopic score and colon mucosa damage index (CMDI) associated with TNBS administration. AL-1 inhibited the inflammatory response via lowering the level of inflammatory cytokines and myeloperoxidase (MPO) activity. AL-1 attenuated the expression of p-p65, p-IκBα and COX-2 in the colitis mice. The alleviation of colon injury by AL-1 treatment was also evidenced by the increased expression of PPAR-γ. These results indicated that AL-1 could protect intestinal tract from the injury induced by TNBS in mice, suggesting that AL-1 may have potential in treatment for IBD.