In vitro evidence that the anti-inflammatory effect of synthetic cinnamate-derived dienes is directly linked to a macrophage repolarization

The inflammatory process is a mammalian physiological reaction against infectious agents or injuries. Among the cells involved, the macrophages have a highlighted role during this process. Depending on the inflammatory context, they can polarize into pro- or anti-inflammatory profiles (M1 and M2). In this context, compounds derived from cinnamic acid have demonstrated strong evidence of anti-inflammatory activity; however, the mechanism responsible for this effect remains unclear. In this study, we investigated the anti-inflammatory activity of five cinnamate-derived dienes of synthetic origin. The compounds that did not demonstrate significant cytotoxicity were tested to assess anti-inflammatory activity (NOx) in RAW 264.7 cells stimulated with LPS. Then, the selected compound (diene 1) was evaluated as to its ability to inhibit the secretion of pro-inflammatory cytokines (IL-1 beta, TNF-alpha, INF-gamma, MCP-1, and IL-6) and increase the production of anti-inflammatory cytokines (IL-13, IL-4, and IL-10). Finally, diene 1 was able to reduce the expression of TLR4 and increase the phagocytic activity of the macrophages. Gathering these results together, we conclude that diene 1 showed an important anti-inflammatory effect, and this effect is linked to its immunomodulatory characteristic. Since the M1 markers were reduced at the same time, M2 markers were increased by the treatment of the macrophages with diene 1.