ABSTRACT
INTRODUCTION: High-mobility group box 1 (HMGB1) is a therapeutic target for sepsis. Glycyrrhizin (GL) is the aglycone of glycyrrhizin derived from licorice. We clarified the anti-inflammatory effects of GL. We explored the anti-HMGB1 effect of GL and elucidated its molecular mechanism, which will be of benefit for sepsis treatment. METHODS: We stimulated murine macrophage-like RAW 264.7 cells with lipopolysaccharide (LPS) and LPS + GL, then measured the expression and release of HMGB1. The expression of related signal transduction factors was detected. RESULTS: High-mobility group box 1 was distributed mainly in the nucleus with lower cytoplasmic levels in RAW 264.7 cells before LPS stimulation. After stimulation, cytoplasmic HMGB1 levels increased gradually, whereas in nuclear fluctuation a trend of HMGB1 expression was observed. Significant upregulation of HMGB1 mRNA occurred 12 h after LPS stimulation. Glycyrrhizin prevented the transfer of HMGB1 from the nucleus to the cytoplasm and inhibited upregulation of HMGB1 mRNA induced by LPS. Phospho-p38 mitogen-activated protein kinase and activated activating protein 1 increased significantly 8 h after LPS stimulation. Tumor necrosis factor α and interleukin 6 increased 4 h after LPS stimulation and peaked at 48 h, and HMGB1 increased at 8 h. The Toll-like receptor 4/MD2/nuclear factor κB signaling pathway was activated 4 h after LPS stimulation. Glycyrrhizin inhibited this pathway. CONCLUSIONS: Glycyrrhizin inhibited the expression and release of HMGB1 through blocking the p38 mitogen-activated protein kinase/activating protein 1 signaling pathway then inhibited the massive release of tumor necrosis factor α and interleukin 6.
Subject(s)
Glycyrrhizic Acid/chemistry , HMGB1 Protein/metabolism , Lipopolysaccharides/chemistry , Sepsis/drug therapy , Animals , Anti-Inflammatory Agents/chemistry , Cell Nucleus/metabolism , Cytoplasm/metabolism , Inflammation , Interleukin-6/metabolism , Mice , Microscopy, Fluorescence , RAW 264.7 Cells , Signal Transduction , Tumor Necrosis Factor-alpha/metabolism , p38 Mitogen-Activated Protein Kinases/metabolismABSTRACT
AIM: To elucidate the mechanism of ethyl pyruvate (EP) inhabit high mobility group protein B1 (HMGB1)expression and releasing in macrophage induced by lipopolysaccharide(LPS). METHODS: The murine macrophage-like cell line RAW264.7 cultured in vitro divided into LPS group and LPS+EP group. The expression of HMGB1 mRNA in cultured cell was determined by RT-PCR. The cytoplasmic and nuclear HMGB1 levels were detected by Western blot. The contents of HMGB1 and TNF-α and IL-6 protein in cultured cells supernatant were detected by ELISA. Immunocytochemistry and confocal laser-scanning microscopy were used to confirm the relocation and distribution of intracellular HMGB1 protein in RAW264.7 cells. RESULTS: HMGB1 mRNA expression in the LPS+EP group was significantly lower than in LPS alone, at 24, 36 and 48 hours. In the LPS+EP stimulation group, the cytoplasm stained weakly while the nuclear stain was stronger than that of the LPS group at the same time points. Both TNF-α and IL-6 levels in LPS+EP group were significantly lower than those in the LPS group at the same time points. EP also effectively prevented the release of HMGB1 protein. CONCLUSION: EP inhibits HMGB1 expression and release from LPS-stimulated macrophages.
