gamma-Mangostin inhibits inhibitor-kappaB kinase activity and decreases lipopolysaccharide-induced cyclooxygenase-2 gene expression in C6 rat glioma cells.
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.
Nakatani
Keigo
K
Department of Pharmaceutical Molecular Biology, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan.
Yamakuni
Tohru
T
Kondo
Nobuhiko
N
Arakawa
Tsutomu
T
Oosawa
Kenji
K
Shimura
Susumu
S
Inoue
Hiroyasu
H
Ohizumi
Yasushi
Y
D000818:Animals; D001932:Brain Neoplasms; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D015232:Dinoprostone / Q000378:metabolism; D004347:Drug Interactions; D015870:Gene Expression / Q000187:drug effects*; D005910:Glioma; D051550:I-kappa B Kinase; D020672:I-kappa B Proteins / Q000037:antagonists & inhibitors*; D007527:Isoenzymes / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008297:Male; D008565:Membrane Proteins; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D010146:Pain / Q000139:chemically induced / Q000188:drug therapy; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015533:Transcriptional Activation / Q000187:drug effects; D014407:Tumor Cells, Cultured; D044004:Xanthones / Q000494:pharmacology* / Q000627:therapeutic use
D020672:I-kappa B Proteins; D007527:Isoenzymes; D008070:Lipopolysaccharides; D008565:Membrane Proteins; D016328:NF-kappa B; D012333:RNA, Messenger; D044004:Xanthones; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; C496513:Ptgs1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051550:I-kappa B Kinase; D015232:Dinoprostone; C021053:mangostin