2,5-dihydroxyacetophenone isolated from Rehmanniae Radix Preparata inhibits inflammatory responses in lipopolysaccharide-stimulated RAW264.7 macrophages

Rehmanniae Radix Preparata, the steamed root of Rehmannia glutinosa Libosch, has been widely used for the treatment of inflammatory conditions in Oriental medicines. In this study we evaluated the effects of 2,5-dihydroxyacetophenone (DHAP) isolated from Rehmanniae Radix Preparata on inflammatory responses in lipopolysaccharide (LPS)-stimulated RAW264.7 mouse macrophages. LPS-stimulated RAW264.7 cells were used to investigate the anti-inflammatory activity of DHAP on the production of inflammatory mediators such as nitric oxide (NO), inducible NO Synthase (iNOS), tumor necrosis factor-α (TNF-α), and interleukin (IL)-6. DHAP significantly inhibited NO production via the suppression of iNOS expression and significantly decreased levels of the pro-inflammatory cytokines TNF-α and IL-6 via the down-regulation of their mRNA expression in LPS-stimulated RAW264.7 cells. DHAP potently inhibited the phosphorylation of extracellular signal-related kinase (ERK) 1/2 and the nuclear translocation of nuclear factor-κB (NF-κB) p65 in LPS-stimulated cells. These results indicate that DHAP inhibits the production of inflammatory mediators in activated macrophages by blocking the ERK1/2 and NF-κB signaling pathways. Our results suggest that DHAP from Rehmanniae Radix Preparata has anti-inflammatory activity in activated macrophages, raising the possibility that this compound has a therapeutic potential for inflammatory conditions.