Antiinflammatory Effects of Orientin-2-O-Galactopyranoside on Lipopolysaccharide-Stimulated Microglia

Microglia activation-mediated neuroinflammation plays an important role in the pathogenesis of neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, and human immunodeficiency virus (HIV)-associated dementia. Inhibition of microglia activation may alleviate neurodegeneration under neuroinflammatory conditions. In the present study, we compared three flavone C-glycosides extracted from Trollius chinensis BUNGE using a cell-based assay to evaluate their antiinflammatory effects on microglial cells. The results showed that orientin-2 ''-O-galactopyranoside (OGA) significantly inhibited the production of nitric oxide and tumor necrosis factor (TNF)-alpha in lipopolysaccharide (LPS)-stimulated microglial cells. OGA also markedly inhibited the LPS-induced expression of TNF-alpha, interleukin-1 beta, inducible nitric oxide (NO) synthase, and cyclooxygenase-2, which was accompanied by suppression of the activation of nuclear factor (NF)-kappa B and the extracellular signal-regulated kinase (ERK) signal pathway. In addition, OGA decreased LPS-induced reactive oxygen species generation, which appears to be related to the activation of the NF-E2-related factor2 (NRF2)/ heme oxygenase-1 (HO-1) pathway in BV-2 microglial cells. Furthermore, OGA reduced the cytotoxicity of activated microglia toward HT-22 neuroblastoma cells in a co-culture system. Taken together, the present study demonstrated that the induction of HO-I-mediated inhibition of the NF-kappa B and ERK pathways contributes significantly to the antineuroinflammatory and neuroprotective effects elicited by OGA.