Nimbolide Inhibits Nuclear Factor-κB Pathway in Intestinal Epithelial Cells and Macrophages, and Alleviates Experimental Colitis in Mice

Abstract

Introduction: Nimbolide is a limonoid extracted from neem tree (Azadirachta indica) that has antiinflammatory properties. The aim of this study was to investigate the effect of nimbolide on the nuclear factor-kappa B (NF-κB) pathway in intestinal epithelial cells (IECs), macrophages and in murine colitis models. Methods: The IEC cell-line COLO 205, the murine macrophage cell-line RAW 264.7 and peritoneal macrophages extracted from interleukin (IL)-10 deficient (IL-10-/-) mice were preconditioned with nimbolide or vehicle and then stimulated. The secretion of inflammatory cytokines (IL-6, IL-8, IL-12 and tumor necrosis factor-α) was examined by ELISA. Effects on the NF-κB pathway were evaluated by western blot of IκBα phosphorylation and electrophoretic mobility shift assay. Dextran sulfate sodium (DSS)-induced acute colitis model and chronic colitis model in IL-10-/- mice were used for in vivo experiments. Colitis was estimated by disease activity index (DAI) and histopathologic evaluation. Results: Nimbolide significantly suppressed the expression of inflammatory cytokines, and inhibited the phosphorylation of IκBα and the DNA-binding affinity of NF-κB in IECs and macrophages. Nimbolide was effective in both DSS-induced acute colitis and in IL-10-/- chronic colitis: It ameliorated weight loss, colon shortening, DAI score and histologic scores in DSS colitis. It also improved histopathologic scores in the chronic colitis of IL-10-/- mice. Staining for phosphorylated IκBα was significantly decreased in colon tissue after treatment with nimbolide in both models. Conclusions: Nimbolide inhibits NF-κB signaling in IECs and macrophages, and ameliorates experimental colitis in mice. Our results suggest nimbolide could be a potentially new treatment for inflammatory bowel disease.