Cinnamic Acid Ameliorates Acetic Acid-induced Inflammatory Response through Inhibition of TLR-4 in Colitis Rat Model.

Background: Cinnamic acid, an active compound in cinnamon spp., has anti-inflammatory and antioxidant characteristics and is favorable in managing inflammatory bowel diseases.

Objectives: Evaluate cinnamic acid's effects on colitis in rats.

Methods: To induce colitis in experimental rats, excluding the sham group, a 4% intrarectal solution of acetic acid was administered. The rats were then given oral doses of cinnamic acid at 30, 45, and 90 mg/kg for two days. The animals were assessed for macroscopic and microscopic changes, and the levels of inflammatory mediators such as tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and myeloperoxidase (MPO) were measured using Eliza kits. Additionally, real-time PCR was performed to examine the gene level of toll-like receptor 4 (TLR-4) in the colon.

Results: Effective reduction of inflammation in acetic acid-induced colitis was achieved through Cinnamic acid administration at doses of 45 and 90 mg/kg. The decrease was achieved by inhibiting the activities of TNF-α, IL-6, and MPO while downregulating the expression of TLR-4. It is important to note that macroscopic and microscopic evaluations were significant in determining the effectiveness of cinnamic acid in reducing inflammation.

Conclusion: Downregulation of inflammatory cytokines and TLR-4 expression may contribute to cinnamic acid's anti-inflammatory effect.