The aqueous extract from Toona sinensis leaves inhibits microglia‐mediated neuroinflammation

The leaves of Toona sinensis, a well‐known traditional oriental medicine, have been prescribed for the treatment of enteritis and infection. Recently, aqueous extracts of Toona sinensis leaves (TSL‐1) have demonstrated many biological effects both in vitro and in vivo. In the central nervous system, microglial activation and their proinflammatory responses are considered an important therapeutic strategy for neuroinflammatory disorders such as cerebral ischemia, Alzheimer's disease, and Parkinson's disease. The present study attempted to validate the effect of TSL‐1 on microglia‐mediated neuroinflammation stimulated by lipopolysaccharide (LPS). As inflammatory parameters, the production of nitric oxide (NO), inducible NO synthase, and tumor necrosis factor‐α were evaluated. Our results demonstrate that TSL‐1 suppresses LPS‐induced NO production, tumor necrosis factor‐α secretion, and inducible NO synthase protein expression in a concentration‐dependent manner, without causing cytotoxicity. In addition, the inhibitory effects of TSL‐1 in LPS‐stimulated BV‐2 microglia were extended to post‐treatment suggesting the therapeutic potential of TSL‐1. Therefore, this work provides the future evaluation of the role of TSL‐1 in the treatment of neurodegenerative diseases by inhibition of inflammatory mediator production in activated microglia.