Osthole Regulates Secretion of Pro-Inflammatory Cytokines and Expression of TLR2 and NF-κB in Normal Human Keratinocytes and Fibroblasts.

Introduction: Osthole (OST), an active compound isolated from Cnidium monnieri, is used in traditional Chinese medicine to treat a variety of human diseases. Although OST has a good therapeutic effect, the underlying mechanism of its action in inflammatory skin diseases in humans is still unknown. Purpose: The present study aimed to test the hypothesis that OST can be used as an herbal substance that minimizes skin inflammation and barrier dysfunction. In this study, histamine and LPS were used to induce inflammation in skin keratinocytes and fibroblasts to test whether OST can inhibit their responses. Methods: Cell migration was analyzed using a wound healing assay. Changes in cell monolayer integrity were assessed by the measurement of transepithelial electrical resistance. Secretion of IL-1ß, IL-6, IL-8, TNF-α, CCL2/MCP-1, CCL5/RANTES, and COX-2 was measured by ELISA, while expression of TLR2, NF-κB, and COX-2 was analyzed by qPCR. Results: OST decreased the level of IL-1ß, TNF-α, CCL2/MCP-1 and CCL5/RANTES, and expression of TLR2, NF-κB and COX-2 during histamine/LPS-induced inflammation in human keratinocytes and fibroblasts. OST also improved cell migration and cell barrier function. Conclusion: Our results suggest that OST suppresses inflammatory responses via regulation of IL-1ß, TNF-α, CCL2/MCP-1 and CCL5/RANTES secretion, and TLR2, and COX-2 expression.

Modulatory Effects of Osthole on Lipopolysaccharides-Induced Inflammation in Caco-2 Cell Monolayer and Co-Cultures with THP-1 and THP-1-Derived Macrophages.

Lipopolysaccharydes (LPS) are responsible for the intestinal inflammatory reaction, as they may disrupt tight junctions and induce cytokines (CKs) secretion. Osthole has a wide spectrum of pharmacological effects, thus its anti-inflammatory potential in the LPS-treated Caco-2 cell line as well as in Caco-2/THP-1 and Caco-2/macrophages co-cultures was investigated. In brief, Caco-2 cells and co-cultures were incubated with LPS to induce an inflammatory reaction, after which osthole (150-450 ng/mL) was applied to reduce this effect. After 24 h, the level of secreted CKs and changes in gene expression were examined. LPS significantly increased the levels of IL-1ß, -6, -8, and TNF-α, while osthole reduced this effect in a concentration-dependent manner, with the most significant decrease when a 450 ng/mL dose was applied (p < 0.0001). A similar trend was observed in changes in gene expression, with the significant osthole efficiency at a concentration of 450 ng/µL for IL1R1 and COX-2 (p < 0.01) and 300 ng/µL for NF-κB (p < 0.001). Osthole increased Caco-2 monolayer permeability, thus if it would ever be considered as a potential drug for minimizing intestinal inflammatory symptoms, its safety should be confirmed in extended in vitro and in vivo studies.