Antiinflammatory effect of Spirodela polyrhiza in RAW264.7 cells

Spirodela polyrhiza is widely used in Korean traditional medicine. We assessed the effects of S. polyrhiza extract (SPE) on the production of inflammatory mediators in lipopolysaccharide (LPS)-stimulated RAW264.7 cells and investigated some potential underlying mechanisms. RAW264.7 cells were subjected to 5, 10, 20, and 50µg/mL of SPE for 1h then treated with LPS for 24h. Production of namely nitric oxide (NO), prostaglandin E₂ (PGE₂) and cytokine levels were measured by the Griess reagent and ELISA, respectively. To investigate the underlying mechanisms of the anti-inflammatory activities of SPE, expression of nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and nuclear factor-kappa B (NF-κB) proteins were evaluated by western blot analysis. SPE treatment significantly inhibited the LPS-induced production of NO, PGE₂, interleukin (IL)-6 and tumor necrosis factor (TNF)-α and inhibited the expression of iNOS and COX-2 via attenuation of NF-κB p65 expression. These results indicate that the anti-inflammatory activity of SPE may be NF-κB p65 signaling.