5,7-dihydroxy-3,4,6-trimethoxyflavone inhibits the inflammatory effects induced by Bacteroides fragilis enterotoxin via dissociating the complex of heat shock protein 90 and I kappaB alpha and I kappaB kinase-gamma in intestinal epithelial cell culture.
Enterotoxin produced by enterotoxigenic Bacteroides fragilis (BFT) has been associated with mucosal inflammation and diarrhoeal diseases. In this study, the anti-inflammatory molecular mechanism of 5,7-dihydroxy-3,4,6-trimethoxyflavone (eupatilin) was characterized in an HT-29 intestinal epithelial cell line stimulated with BFT. Pre-treatment of HT-29 cells with eupatilin decreased the production significantly of both interleukin (IL)-8 and prostaglandin E(2) induced by BFT in a dose-dependent manner. BFT-activated nuclear factor-kappaB (NF-kappaB) signals in HT-29 cells and pretreatment with eupatilin suppressed NF-kappaB activation that resulted in the significant inhibition of IL-8 and cyclo-oxygenase-2 expression. BFT-induced phosphorylation of both I kappaB alpha and I kappaB kinase (IKK) signals was prevented in eupatilin-pretreated HT-29 cells. Transfection of siRNA for IKK-alpha and IKK-beta decreased the production of IL-8 and prostaglandin E(2); however, the transfection of IKK-beta siRNA showed a more significant reduction of BFT-induced I kappaB alpha phosphorylation compared with that of IKK-alpha siRNA. In addition, herbimycin A, a specific inhibitor of heat shock protein 90 (Hsp90), decreased the BFT-induced activation of IKK and NF-kappaB, suggesting that Hsp90 is associated with a pathway of IKK-NF-kappaB-IL-8/cyclo-oxygenase-2 gene signalling. Furthermore, eupatilin dissociated the complex between Hsp90 and IKK-gamma in BFT-stimulated HT-29 cells. These results suggest that eupatilin can suppress the NF-kappaB signalling pathway by targeting the Hsp90-IKK-gamma complex in intestinal epithelial cells and may attenuate BFT-induced inflammatory responses.
Kim
J M
JM
Department of Microbiology, Hanyang University College of Medicine, Seoul, Korea. jungmogg@hanyang.ac.kr
Lee
D H
DH
Kim
J S
JS
Lee
J Y
JY
Park
H-G
HG
Kim
Y-J
YJ
Oh
Y-K
YK
Jung
H C
HC
Kim
S I
SI
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D001441:Bacteroides fragilis; D054426:Chemokine CXCL2 / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D004768:Enterotoxins / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000276:immunology / Q000378:metabolism*; D005419:Flavonoids / Q000494:pharmacology*; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D019073:HT29 Cells; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D020672:I-kappa B Proteins / Q000378:metabolism; D007082:Ileum; D047468:Immunoprecipitation; D016209:Interleukin-8 / Q000276:immunology; D007413:Intestinal Mucosa / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000893:Anti-Inflammatory Agents; D054426:Chemokine CXCL2; C404915:Cxcl2 protein, mouse; D004768:Enterotoxins; D005419:Flavonoids; D018841:HSP90 Heat-Shock Proteins; D020672:I-kappa B Proteins; D016209:Interleukin-8; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C000606205:Nfkbia protein, mouse; D000072000:NF-KappaB Inhibitor alpha; C104803:santin; C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2; D051550:I-kappa B Kinase