Effects of Ginkgo biloba extract (EGb 761) and quercetin on lipopolysaccharide-induced signaling pathways involved in the release of tumor necrosis factor-α

Teri L. Wadsworth, Tasha L. McDonald, Dennis Koop

Research output: Contribution to journalArticle

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Abstract

Administration of bacterial lipopolysaccharide (LPS) to laboratory animals and cultured macrophages induces tumor necrosis factor-α (TNF-α), a pro-inflammatory cytokine. Pretreatment with Ginkgo biloba extract (EGb 761) inhibited the in vivo production of TNF-α (measured by ELISA) after challenge with LPS. To begin to understand the mechanism of this inhibition, we evaluated the in vitro effects of EGb 761 and its flavonoid component, quercetin, on LPS-treated RAW 264.7 macrophages. Pretreatment with EGb 761 or quercetin concentration-dependently inhibited TNF-α release, as measured by the L929 fibroblast assay. Northern blotting demonstrated that quercetin inhibited LPS-induced TNF-α mRNA, but did not alter its half-life. Activation of mitogen-activated protein kinases (MAPKs) and the redox-sensitive transcription factors, nuclear factor-κB (NF-κB) and activator protein 1 (AP-1), are key events in the signal transduction pathways mediating TNF-α induction. Phosphorylation of extracellular signal-related kinases 1 and 2 (ERK 1/2), p38 MAPK, and Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK), members of the MAPK family, was analyzed by western blotting. Our results suggest that quercetin is unique in its ability to inhibit TNF-α transcription by inhibiting the phosphorylation and activation of JNK/SAPK and, therefore, suppressing AP-1-DNA binding [assessed by electrophoretic mobility shift analysis (EMSA)]. Results from western analysis, EMSA, and transient transfections suggest that EGb 761 diminishes LPS-induced NF-κB but has no effect on LPS-induced TNF-α transcription. Both EGb 761 and quercetin inhibited ERK1/2 phosphorylation and p38 MAPK activity, which are important in the post-transcriptional regulation of TNF-α mRNA.

Original languageEnglish (US)
Pages (from-to)963-974
Number of pages12
JournalBiochemical Pharmacology
Volume62
Issue number7
DOIs
StatePublished - Oct 1 2001

Fingerprint

Quercetin
Lipopolysaccharides
Tumor Necrosis Factor-alpha
Phosphorylation
Electrophoretic mobility
Phosphotransferases
Macrophages
Transcription Factor AP-1
p38 Mitogen-Activated Protein Kinases
Transcription
Heat-Shock Proteins
Mitogen-Activated Protein Kinases
Protein Kinases
Chemical activation
Signal transduction
Messenger RNA
Ginkgo biloba extract 761
Laboratory Animals
Fibroblasts
Flavonoids

Keywords

  • EGb 761
  • Macrophage
  • MAPK
  • Quercetin
  • TNF-α

ASJC Scopus subject areas

  • Pharmacology

Cite this

Effects of Ginkgo biloba extract (EGb 761) and quercetin on lipopolysaccharide-induced signaling pathways involved in the release of tumor necrosis factor-α. / Wadsworth, Teri L.; McDonald, Tasha L.; Koop, Dennis.

In: Biochemical Pharmacology, Vol. 62, No. 7, 01.10.2001, p. 963-974.

Research output: Contribution to journalArticle

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