Thymol reduces acetic acid-induced inflammatory response through inhibition of NF-kB signaling pathway in rat colon tissue.

AIM: The aim of the present study was to evaluate the anti-inflammatory effect of thymol in acetic acid-induced rat colitis through inhibiting the NF-κB signaling pathway.

METHODS: Colitis was induced by intra-rectal administration of 2 mL of diluted acetic acid (4%) solution using a flexible plastic rubber catheter in Wistar rats. Colitis was induced on the first day and all treatments were applied 5 days after the induction of colitis. Thymol was dissolved in 0.2% tween 80 in saline and administered orally at doses of 10, 30, and 100 mg/kg per day. Macroscopic and histopathologic investigations were done. The expression of myeloperoxidase (MPO) and tumor necrosis factor-α (TNF-α) was determined by immunohistochemistry (IHC) assay. The protein expression level of pNF-κB p65 was measured by the Western blot technique.

RESULTS: Treatment with thymol reduced mucosal and histological damages compared to the acetic acid group. Our results showed that thymol markedly inhibited the production of MPO and TNF-α in the colon tissue of the acetic acid-induced group. In addition, thymol decreased acetic acid-induced up-regulation of pNFκB p65 protein.

CONCLUSIONS: The results of our study suggest that thymol exerts an anti-inflammatory effect in acetic acid-induced rat colitis by inhibiting the NF-κB signaling pathway and downregulating TNF-α and MPO expressions.