Inhibition by licochalcone A, a novel flavonoid isolated from liquorice root, of IL-1beta-induced PGE2 production in human skin fibroblasts.

Licochalcone A, a novel flavonoid isolated from the root of Glycyrrhiza inflata, has been reported to exhibit anti-inflammatory activity in animal models. In this study, we examined the effect of licochalcone A on the production of chemical mediators such as prostaglandin (PG)E2 and cytokines by interleukin (IL)-1beta in human skin fibroblasts. Licochalcone A (IC50 15.0 nM) inhibited PGE2 production, but not IL-6 and IL-8 production, in response to IL-1beta. NS-398 (IC50 1.6 nM), a COX-2 selective inhibitor, also suppressed the PGE2 production. Furthermore, licochalcone A and NS-398 suppressed PGF(2alpha) production by IL-1beta. However, licochalcone A (1 microM) had no effect on increased levels of cyclooxygenase (COX)-2 mRNA and protein in cells. Dexamethasone (100 nM) not only inhibited PGE2, PGF(2alpha), IL-6 and IL-8 production but also strongly suppressed the expression of COX-2 mRNA and protein. Licochalcone A had no effect on COX-1-dependent PGE2 production, whereas indometacin (100 nM), a dual inhibitor of COX-1 and COX-2, was very effective. These results suggest that licochalcone A induces an anti-inflammatory effect through the inhibition of COX-2-dependent PGE2 production. Furthermore, it appears that the inhibitory effect of licochalcone A on PGE2 production in response to IL-1beta is quite different from that of the steroid.

Thrombin-stimulated proliferation of cultured human synovial fibroblasts through proteolytic activation of proteinase-activated receptor-1.

We examined the mechanism of thrombin on proliferation of synovial fibroblasts obtained from rheumatoid arthritis (RA). Thrombin concentration-dependently induced proliferation of synovial fibroblasts. Proliferation in response to thrombin (10 U/ml) was completely blocked by hirudin. TP367 and TP508, peptides corresponding to 2 noncatalytic regions of thrombin, failed to induce cell proliferation. Thrombin did not induce the production of basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF), and epidermal growth factor (EGF) in synovial fibroblasts. Expression of proteinase-activated receptor (PAR)-1 and PAR-3 mRNAs was observed in synovial fibroblasts. Thrombin and PAR-1 agonist peptide (AP), but not PAR-3 AP, induced intracellular calcium mobilization. PAR-1 AP induced cell proliferation whereas PAR-3 AP and PAR-4 AP had no effect on proliferation. Pertussis toxin (PTX), a Gialpha protein inhibitor; wortmannin, a PI (phosphatidylinositol) 3-kinase inhibitor; and PD98059, a specific MEK [mitogen-activated protein (MAK) kinase kinase] inhibitor, inhibited the thrombin-induced cell proliferation. Furthermore, the proliferation of synovial fibroblasts was suppressed by U-73122, a PLC (phospholipase C) inhibitor; 2-APB, an antagonist of InsP3 (inositol 1,4,5-triphosphate) receptor; and GF-109203X, a PKC (protein kinase C) inhibitor. These results suggest that thrombin induces the proliferation of RA synovial fibroblasts through the activation of PAR-1, leading to the PTX-sensitive G proteins - PI3 kinase pathway and PTX-insensitive G proteins - PLC (InsP3 receptor) Ca(2+)-PKC branch.

Synthesis and inhibitory effect of novel glycyrrhetinic acid derivatives on IL-1 beta-induced prostaglandin E(2) production in normal human dermal fibroblasts.

Olean-11,13(18)-dien-3beta,30-diol dihemiphthalate (3), which was derived from glycyrrhetinic acid (GA), has been reported to produce a potent of anti-inflammatory effect in in vivo assays. Using 3 as a lead compound, we attempted to synthesize some modified compounds which varied in the following; i) the position of a carboxyl group in the phthalate moiety, ii) the number of carboxyls attached to the benzoyl group, iii) conversion of benzene ring to another ring system, iv) the linkage form between the benzene ring and oleanene skeleton at position 3 and/or 30. These were screened for their inhibitory activity against interleukin-1 beta (IL-1 beta)-induced prostaglandin E(2) (PGE(2)) production in normal human dermal fibroblasts (NHDF). Although conversion of the ortho-carboxyl group of 3 into the meta-position or the para-position led to an increase in inhibitory activity, the elimination or increase of the carboxyl group resulted in loss of the inhibitory activity. Conversion of the ester bond to the amide bond at position 3 and/or 30 of 3 did not contribute to a significant increase in inhibitory activity. On the other hand, among the derivatives possessing an anthranilic acid moiety at position 30 of 3beta-O-acetyl-olean-11,13(18)-dien-30-oic acid (20), 3beta-hydroxy-30-nor-olean-11,13(18)-dien-20 beta-[N-(2-carboxyphenyl)]carboxamide (30) showed the most potent inhibitory activity (IC(50) 1.0 microM) in this series.