Immunomodulatory properties of Olea europaea leaf extract in intestinal inflammation

Scope: Extracts from olive (Olea europaea) leaves are used in Mediterranean traditional medicine as anti-inflammatory agents. They contain antioxidant phenolic compounds, such as oleuropeoside, which could be interesting for the treatment of inflammatory conditions associated with oxidative stress in humans, including inflammatory bowel disease. Methods and results: The anti-inflammatory effects of olive leaf extract (0.5–25 mg/kg) were studied in two mice models of colitis (DSS and DNBS). Olive leaf extract (0.1–100 μg/mL) immunomodulatory effects were also investigated in different cell types and in ex vivo organ cultures of mucosal explants of healthy donors and Crohn's disease (CD) patients. The extract showed effect in both colitis models reducing the expression of proinflammatory mediators (IL-1β, TNF-α, and iNOS), and improving the intestinal epithelial barrier integrity restoring the expression of ZO-1, MUC-2, and TFF-3. These effects were confirmed in vitro. Furthermore, it reduced the production of proinflammatory mediators (IL-1β, IL-6, IL-8, and TNF-α) in intestinal mucosal samples from CD patients. Conclusion: Olive leaf extract presented intestinal anti-inflammatory activity in colitis mouse models, maybe be related to its immunomodulatory properties and the capacity to restore the intestinal epithelial barrier. Besides, the extract could also regulate the activity of cells involved in the inflammatory response.