Effects of Rhei Undulati Rhizoma on lipopolysaccharide-induced neuroinflammation in vitro and in vivo

Neuroinflammation plays a critical role in the pathogenesis of degenerative brain diseases such as Alzheimer's disease and Parkinson's disease. Microglia are the major components of the brain immune system that regulate inflammatory processes. Activated microglia release pro-inflammatory factors and cytokines, resulting in neuronal cell death. We focused on inhibiting the activation of microglia from a stimulus as a strategy to search for neuroprotective drugs. Rhei Undulati Rhizoma (RUR) is traditionally used to treat various inflammatory disorders. In this study, we investigated whether RUR modulates inflammatory processes in lipopolysaccharide (LPS)-stimulated BV2 microglia cells and the mouse brain. RUR exerted anti-neuroinflammatory effects by inhibiting the production of nitric oxide and reactive oxygen species induced by LPS via the downregulation of transcription factors such as inducible nitric oxide synthase and cyclooxygenase-2 (COX-2) without causing cytotoxicity. RUR also regulated mitogen-activated protein kinase pathway by inhibiting phosphorylation of p38 and c-Jun N-terminal kinases and translocation of nuclear factor kappa B. Moreover, RUR attenuated LPS-induced glial activation and COX-2 expression in the substantia nigra and hippocampus of the mouse brain. These results indicate that RUR is a potential candidate to treat neurodegenerative diseases by regulating neuroinflammation.