Limonin: A triterpenoid exerts protective effect during lipopolysaccharide stimulated inflammation in BV2 microglial cells

Objectives: Neuroinflammation mediated by the reactive oxygen and nitrogen species (ROS and RNS, respectively) is responsible for the production of cytokines and chemokines in the central nervous system, which causes glial activation and associated pathology. Limonin is an oxygenated triterpenoid dilactone obtained from the families Rutaceae and Meliaceae. It exerts anticancer, antioxidant, antiviral, antinociceptive, and anti-inflammatory effects. In this study, we intended to analyze the anti-inflammatory and neuroprotective activities of limonin against neuroinflammation induced by lipopolysaccharide (LPS) in an in vitro model with BV2 immortalized murine microglial cells. Materials and Methods: Cytotoxicity of limonin was investigated via 3-(4,5-dimethylthiazolyl-2)-2,5-dipheniltetrazolium bromide tetrazol assay, and anti-inflammatory activity was assessed by analyzing the status of ROS, nitric oxide (NO), prostaglandin E2 (PGE2), interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α using ELISA. The expression of inducible nitric oxide synthase (iNOS), TNF-α, IL-1β, and Cyclooxygenase (COX-2) was studied through immunoblot analysis. Results: Our results showed that pretreatment of LPS-induced microglial cells with limonin appreciably prevented the formation of ROS and prevented the accretion of NO, PGE2, IL-1β, IL-6, and TNF-α. Furthermore, limonin pretreatment significantly reduced the expressions of iNOS and COX-2. Conclusion: Our results indicate that limonin inhibits inflammatory response through repressing the formation of ROS, accretion and discharge of cytokines, and activation of inflammatory mediators. Limonin can be used as a neuro-protecting agent.