gamma-Mangostin inhibits inhibitor-kappaB kinase activity and decreases lipopolysaccharide-induced cyclooxygenase-2 gene expression in C6 rat glioma cells.

Abstract

We investigated the effect of gamma-mangostin purified from the fruit hull of the medicinal plant Garcinia mangostana on spontaneous prostaglandin E(2) (PGE(2)) genase release and inducible cyclooxy-2 (COX-2) gene expression in C6 rat glioma cells. An 18-h treatment with gamma-mangostin potently inhibited spontaneous PGE(2) release in a concentration-dependent manner with the IC(50) value of approximately 2 microM, without affecting the cell viability even at 30 microM. By immunoblotting and reverse-transcription polymerase chain reaction, we showed that gamma-mangostin concentration-dependently inhibited lipopolysaccharide (LPS)-induced expression of COX-2 protein and its mRNA, but not those of constitutive COX-1 cyclooxygenase. Because LPS is known to stimulate inhibitor kappaB (IkappaB) kinase (IKK)-mediated phosphorylation of IkappaB followed by its degradation, which in turn induces nuclear factor (NF)-kappaB nuclear translocation leading to transcriptional activation of COX-2 gene, the effect of gamma-mangostin on the IKK/IkappaB cascade controlling the NF-kappaB activation was examined. An in vitro IKK assay using IKK protein immunoprecipitated from C6 cell extract showed that this compound inhibited IKK activity in a concentration-dependent manner, with the IC(50) value of approximately 10 microM. Consistently gamma-mangostin was also observed to decrease the LPS-induced IkappaB degradation and phosphorylation in a concentration-dependent manner, as assayed by immunoblotting. Furthermore, luciferase reporter assays showed that gamma-mangostin reduced the LPS-inducible activation of NF-kappaB-and human COX-2 gene promoter region-dependent transcription. gamma-Mangostin also inhibited rat carrageenan-induced paw edema. These results suggest that gamma-mangostin directly inhibits IKK activity and thereby prevents COX-2 gene transcription, an NF-kappaB target gene, probably to decrease the inflammatory agent-stimulated PGE(2) production in vivo, and is a new useful lead compound for anti-inflammatory drug development.

• Authors: Keigo Nakatani, Tohru Yamakuni, Nobuhiko Kondo, Tsutomu Arakawa, Kenji Oosawa, Susumu Shimura, Hiroyasu Inoue, Yasushi Ohizumi
• Journal: Molecular pharmacology (Mol Pharmacol) Vol. 66 Issue 3 Pg. 667-74 (Sep 2004) ISSN: 0026-895X [Print] United States
• PMID: 15322259 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• I-kappa B Proteins
• Isoenzymes
• Lipopolysaccharides
• Membrane Proteins
• NF-kappa B
• RNA, Messenger
• Xanthones
• Cyclooxygenase 1
• Cyclooxygenase 2
• Prostaglandin-Endoperoxide Synthases
• Ptgs1 protein, rat
• Protein Serine-Threonine Kinases
• I-kappa B Kinase
• Dinoprostone
• mangostin

Topics

• Animals
• Brain Neoplasms
• Cyclooxygenase 1
• Cyclooxygenase 2
• Dinoprostone (metabolism)
• Drug Interactions
• Gene Expression (drug effects)
• Glioma
• I-kappa B Kinase
• I-kappa B Proteins (antagonists & inhibitors)
• Isoenzymes (biosynthesis, genetics, metabolism)
• Lipopolysaccharides (pharmacology)
• Male
• Membrane Proteins
• NF-kappa B (antagonists & inhibitors)
• Pain (chemically induced, drug therapy)
• Prostaglandin-Endoperoxide Synthases (biosynthesis, genetics, metabolism)
• Protein Serine-Threonine Kinases (physiology)
• RNA, Messenger (drug effects, metabolism)
• Rats
• Rats, Wistar
• Transcriptional Activation (drug effects)
• Tumor Cells, Cultured
• Xanthones (pharmacology, therapeutic use)