Yeon Sook Chi

Effect of wogonin, a plant flavone from Scutellaria radix, on the suppression of cyclooxygenase-2 and the induction of inducible nitric oxide synthase in lipopolysaccharide-treated RAW 264.7 cells.

Plant flavonoids show anti-inflammatory activity both in vitro and in vivo. Some flavonoids, such as flavone derivatives, have been reported previously to inhibit nitric oxide (NO) production by suppressing inducible nitric oxide synthase (iNOS) expression. In this investigation, the effects of wogonin, a potent inhibitor of NO production among the flavonoids tested, on cyclooxygenase-2 (COX-2) induction and activity were elucidated further in connection with iNOS, using a mouse macrophage cell line, RAW 264.7. Wogonin inhibited NO and prostaglandin E(2) (PGE(2)) production from lipopolysaccharide-induced RAW cells with IC(50) values of 31 and 0.3 microM, respectively. When added after the induction of iNOS and COX-2, wogonin inhibited the formation of PGE(2) (IC(50) = 0.8 microM), but not the production of NO. Wogonin inhibited COX-2 activity directly (IC(50) = 46 microM) from the homogenate of aspirin-pretreated RAW cells, as determined by measuring [(14)C]PGE(2) formation from [(14)C]arachidonic acid. However, it did not inhibit iNOS or phospholipase A(2) activity. Western blotting showed that wogonin suppressed the induction of both iNOS and COX-2. Prednisolone also suppressed the induction of iNOS and COX-2. Whereas RU-486 (a steroid receptor antagonist) reversed the suppressive activity of prednisolone, it did not affect the suppressive activity of wogonin, suggesting that the suppressive activity of wogonin is not mediated by binding to a steroid receptor. Results from the present study demonstrated that wogonin is a direct COX-2 inhibitor, as well as an inhibitor of iNOS and COX-2 induction. Wogonin may be a potential agent for use in the treatment of inflammatory diseases.

Effects of naturally occurring prenylated flavonoids on enzymes metabolizing arachidonic acid: Cyclooxygenases and lipoxygenases

Prenylated flavonoids are chemical entities having an isoprenyl, a geranyl, a 1,1-dimethylallyl, and/or a lavandulyl moiety as part of their flavonoid backbone structure. In this study, the effects of 19 naturally occurring prenylated flavonoids, isolated from medicinal plants, on cyclooxygenase (COX)-1 and COX-2 and on 5-lipoxygenase (5-LOX) and 12-LOX were investigated using [14C]arachidonic acid as a substrate. The homogenates of bovine platelets and polymorphonuclear leukocytes were used as COX-1, 12-LOX, and 5-LOX enzyme sources; the homogenate of aspirin-pretreated lipopolysaccharide-induced RAW 264.7 cells was used for the COX-2 enzyme source. Among the 19 prenylated flavonoids, morusin, kuwanon C, sanggenon B, sanggenon D and kazinol B inhibited COX-2 activity (ic(50) = 73-100 microM), but the potencies were far less than that of NS-398 (ic(50) = 2.9 microM). In contrast, many prenylated flavonoids, such as kuraridin, kuwanon C and sophoraisoflavanone A, inhibited COX-1 activity. Of the COX-1 inhibiting prenylated flavonoids, kuraridin, kurarinone, and sophoraflavanone G, all having a C-8 lavandulyl moiety, showed potent activity (ic(50) = 0.1 to 1 microM) comparable to that of indomethacin (ic(50) = 0.7 microM). Most of the prenylated flavonoids tested inhibited 5-LOX activity with ic(50) values ranging from 0.09 to 100 microM. Of these, only kuwanon C, papyriflavonol A and sophoraflavanone G showed inhibitory activity against 12-LOX at low concentration ranges (ic(50) = 19-69 microM) comparable to that of NDGA (ic(50) = 2.6 microM). Our results suggest that the position and the nature of the prenyl substitution greatly influence in vitro biological activities of these molecules.

Effects of wogonin, a plant flavone from Scutellaria radix, on skin inflammation: in vivo regulation of inflammation-associated gene expression

Flavonoids from plant origin show anti-inflammatory activity in vitro and in vivo. In addition to inhibition of inflammation-associated enzymes, such as cyclooxygenases (COX) and lipoxygenases, they have been found to regulate the expression of inflammation-associated proteins from in vitro experiments. In order to prove in vivo behavior and the potential for beneficial use against inflammatory skin disorders, the effect of wogonin (5,7-dihydroxy-8-methoxyflavone) on in vivo expression of several inflammation-associated genes was examined in the intact as well as in the inflamed mouse skin by reverse transcriptase-polymerase chain reaction analysis. When applied topically on the intact skin, only a high dose treatment of wogonin (1000 microg/ear/3 days) slightly increased COX-1 and fibronectin mRNA. On the other hand, wogonin at the doses of 250-1000 microg/ear/3 days potently lowered mRNA levels of COX-2 and tumor necrosis factor-alpha with less effect on intercellular adhesion molecule-1 and interleukin-1beta in a sub-chronic skin inflammation model of tetradecanoylphorbol-13-acetate-induced ear edema (multiple treatment). The decrease of prostaglandin E(2) concentration (27.3-34.3%) was concomitantly observed in the wogonin-treated groups. A similar effect was also observed in an acute inflammation model of arachidonic acid-induced ear edema. From the present study, wogonin was proved to differentially regulate the expression of inflammation-associated genes in vivo and to become a useful therapeutic agent for skin inflammatory diseases mainly due to its modulation of the expression of proinflammatory molecules.

Effects of sophoraflavanone G, a prenylated flavonoid from Sophora flavescens, on cyclooxygenase-2 and in vivo inflammatory response.

Previously, several prenylated flavonoids having a C-8 lavandulyl moiety were found to inhibit cyclooxygenase-1 (COX-1) as well as 5-lipoxygenase (5-LOX), and sophoraflavanone G was the most potent inhibitor against these eicosanoid generating enzymes among 19 prenylated flavonoids tested. In this investigation, effects of sophoraflavanone G on COX-2 induction from RAW 264.7 cells andin vivo inflammatory response were studied. Sophoraflavanone G inhibited prostaglandin E2 (PGE2) production from lipopolysaccharide (LPS)-treated RAW cells by COX-2 down-regulation at 1-50 uM. Other prenylated flavonoids including kuraridin and sanggenon D also down-regulated COX-2 induction at 10-25 uM, while kurarinone and echinoisoflavanone did not. In addition, sophoraflavanone G showedin vivo anti-inflammatory activity against mouse croton oil-induced ear edema and rat carrageenan paw edema via oral (2-250 mg/kg) or topical administration (10-250 ug/ear). Although the potencies of inhibition were far less than that of a reference drug, prednisolone, this compound showed higher antiinflammatory activity when applied topically, suggesting a potential use for several eicosanoidrelated skin inflammation such as atopic dermatitis.

Effects of the chestnut inner shell extract on the expression of adhesion molecules, fibronectin and vitronectin, of skin fibroblasts in culture.

The inner shell of the chestnut (Castanea crenata S. et Z., Fagaceae) has been used as an anti-wrinkle/skin firming agent in East Asia, and preliminary experiments have found that a 70% ethanol extract from this plant material can prevent cell detachment of skin fibroblasts from culture plates. In order to examine the molecular mechanisms underlying this phenomenon, its effects on the expression of adhesion molecules, such as fibronectin and vitronectin, were investigated using the mouse skin fibroblast cell line, NIH/3T3. Using fixed-cell ELISA, Western blotting and immunofluorescence cell staining, it was clearly demonstrated that the chestnut inner shell extract enhanced the expression of the cell-associated fibronectin and vitronectin. Scoparone (6,7-dimethoxycoumarin), isolated from the extract, also possessed similar properties. These findings suggest that the enhanced expression of the adhesion molecules may be one of the molecular mechanisms for how the chestnut inner shell extract preventing cell detachment and may be also responsible for its anti-wrinkle/skin firming effect.

Synthesis and PGE2 Inhibitory Activity of Vinylated and Allylated Chrysin Analogues

Vinylated and allylated chrysin analogues were prepared as congeners of prenylated flavonoids and evaluated their anti-inflammatory activity. 8-Substituted chrysin analogues were prepared from 2’-hydroxy-3’-iodo-4’,6’-dimethoxyacetophenone in 3 steps. 3-Allylated chrysin analogues were prepared from chrysin in 3 steps. Synthesized chrysin analogues (4, 5 and8) showed moderate inhibitory activities of PGE2 production from LPS-induced RAW 264.7 cells.