Herbal remedy magnolol suppresses IL-6-induced STAT3 activation and gene expression in endothelial cells.
Magnolol (Mag), an active constituent isolated from the Chinese herb Hou p'u (Magnolia officinalis) has long been used to suppress inflammatory processes. Chronic inflammation is well known to be involved in vascular injuries such as atherosclerosis in which interleukin (IL)-6 may participate. Signal transducer and activator of transcription protein 3 (STAT3), a transcription factor involved in inflammation and the cell cycle, is activated by IL-6. In this study, we evaluated whether Mag can serve as an anti-inflammatory agent during endothelial injuries. The effects of Mag on IL-6-induced STAT3 activation and downstream target gene induction in endothelial cells (ECs) were examined. Pretreatment of ECs with Mag dose dependently inhibited IL-6-induced Tyr705 and Ser727 phosphorylation in STAT3 without affecting the phosphorylation of JAK1, JAK2, and ERK1/2. Mag pretreatment of these ECs dose dependently suppressed IL-6-induced promoter activity of intracellular cell adhesion molecule (ICAM)-1 that contains functional IL-6 response elements (IREs). An electrophoretic mobility shift assay (EMSA) revealed that Mag treatment significantly reduced STAT3 binding to the IRE region. Consistently, Mag treatment markedly inhibited ICAM-1 expression on the endothelial surface. As a result, reduced monocyte adhesion to IL-6-activated ECs was observed. Furthermore, Mag suppressed IL-6-induced promoter activity of cyclin D1 and monocyte chemotactic protein (MCP)-1 for which STAT3 activation plays a role. In conclusion, our results indicate that Mag inhibits IL-6-induced STAT3 activation and subsequently results in the suppression of downstream target gene expression in ECs. These results provide a therapeutic basis for the development of Mag as an anti-inflammatory agent for vascular disorders including atherosclerosis.
Chen
Shih-Chung
SC
Institute of Clinical Medicine, National Yang-Ming University and Division of Cardiovascular Medicine, Taipei Medical University-Wan-Fang Hospital, Taipei, Taiwan.
Chang
Ying-Ling
YL
Wang
Danny Ling
DL
Cheng
Jing-Jy
JJ
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D001713:Biphenyl Compounds / Q000494:pharmacology*; D015153:Blotting, Western; D002417:Cattle; D002448:Cell Adhesion / Q000187:drug effects; D002460:Cell Line; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000235:genetics; D019938:Cyclin D1 / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D024202:Electrophoretic Mobility Shift Assay; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics / Q000378:metabolism; D015850:Interleukin-6 / Q000494:pharmacology*; D017705:Lignans / Q000494:pharmacology*; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism*
D000894:Anti-Inflammatory Agents, Non-Steroidal; D001713:Biphenyl Compounds; D018932:Chemokine CCL2; D015850:Interleukin-6; D017705:Lignans; D011993:Recombinant Fusion Proteins; D050796:STAT3 Transcription Factor; C005498:magnolol; D018799:Intercellular Adhesion Molecule-1; D019938:Cyclin D1; D008156:Luciferases