Ethanol extract of Prunella vulgaris var. lilacina inhibits HMGB1 release by induction of heme oxygenase-1 in LPS-activated RAW 264.7 cells and CLP-induced septic mice

The ethanol extract of the flower of P. vulgaris var. lilacina (EEPV) has been used traditionally as an antiinflammatory agent in many countries. Inducers of heme oxygenase‐1 (HO‐1) reduce high mobility group box 1 (HMGB1), a late phase cytokine, in sepsis. Although EEPV has been used as an antiinflammatory agent, no report is available as to whether it modifies HMGB1 in sepsis due to HO‐1 induction. It was found that EEPV increased HO‐1 protein expression in RAW 264.7 cells, which was significantly inhibited by LY294002, but not PD98059, SB203580 or SP600125. In addition, EEPV activated NF‐E2‐related factor (Nrf2) to move from the cytosol to the nucleus, and EEPV‐induced HO‐1 and activation of ARE‐luciferase activity were significantly reduced by siNrf2 transfection and LY294002 but not SB203508. EEPV also significantly inhibited NF‐κB luciferase activity, and decreased both iNOS/NO and COX‐2/PGE₂ production in lipopolysaccharide (LPS)‐stimulated macrophages which was reversed by siHO‐1 RNA transfection. Importantly, EEPV inhibited HMGB1 release in LPS‐activated macrophages in a PI3K‐sensitive manner and reduced serum HMGB1 level and lung HMGB1 expression in cecal ligation and puncture (CLP)‐induced septic mice. It is concluded that EEPV induces HO‐1 expression through PI3K/Nrf2 signal pathways, which may be beneficial for the treatment of sepsis due to a reduction of HMGB1 release. Copyright © 2011 John Wiley & Sons, Ltd.