Abstract
(R)-4-(3,4-Dihydro-8,8-dimethyl)-2H,8H-benzo[1,2-b:3,4-b′]dipyran-3yl)-1,3-benzenediol (glabridin), a flavonoid present in licorice extract, is known to have antimicrobial, anti-inflammatory, and cardiovascular protective activities. In the present study, we report the inhibitory effect of glabridin on nitric oxide (NO) production and inducible nitric oxide (iNOS) gene expression in murine macrophages. Glabridin attenuated lipopolysaccharide (LPS)-induced NO production in isolated mouse peritoneal macrophages and RAW 264.7 cells, a mouse macrophage-like cell line. Moreover, iNOS mRNA expression was also blocked by glabridin treatment in LPS-stimulated RAW 264.7 cells. Further study demonstrated that the LPS-induced nuclear factor (NF)-κB/Rel DNA binding activity and NF-κB/Rel-dependent reporter gene activity were significantly inhibited by glabridin in RAW 264.7 cells and that this effect was mediated through the inhibition of inhibitory factor-κB degradation and p65 nuclear translocation. Moreover, reactive oxygen species generation was also suppressed by glabridin treatment in RAW 264.7 cells. In contrast, the activity of mitogen-activated protein kinases was unaffected by glabridin treatment. In animal model, in vivo administration of glabridin increased the rate of survival of LPS-treated mice and inhibited LPS-induced increase in plasma concentrations of nitrite/nitrate and tumor necrosis factor-α. Collectively, these data suggest that glabridin inhibits NO production and iNOS gene expression by blocking NF-κB/Rel activation and that this effect was mediated, at least in part, by inhibiting reactive oxygen species generation. Furthermore, in vivo anti-inflammatory effect of glabridin suggests a possible therapeutic application of this agent in inflammatory diseases.
Footnotes
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This research was supported by a grant from the Korea Research Institute of Bioscience and Biotechnology Research Initiative Program.
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doi:10.1124/jpet.104.077107.
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ABBREVIATIONS: LPS, lipopolysaccharide; TNF-α, tumor necrosis factor-α; NO, nitric oxide; PGE2, prostaglandin E2; NOS, nitric-oxide synthase; iNOS, inducible NOS; NF-κB/Rel, nuclear factor-κB/Rel; IκB, inhibitory factor-κB; RT-PCR, reverse transcription-polymerase chain reaction; AP-1, activator protein-1; CAT, chloramphenicol acetyltransferase; SAPK, stress-activated protein kinase; JNK, c-Jun NH2-terminal kinase; ROS, reactive oxygen species; NOx, nitrite/nitrate; MAP, mitogen-activated protein; SP600125, anthra[1,9-cd]pyrazol-6(2H)-one; SB203580, 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole; PD98059, 2′-amino-3′-methoxyflavone; IKK, IκB kinase.
- Received September 2, 2004.
- Accepted November 9, 2004.
- The American Society for Pharmacology and Experimental Therapeutics
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