Anti-inflammatory constituents from Perovskia atriplicifolia.

CONTEXT: Perovskia atriplicifolia Benth (Labiantae) has long been used as a traditional herbal medicine for anti-inflammation in Pakistan; this prompted us to isolate anti-inflammatory compounds from this plant. OBJECTIVE: The objective of this study was to isolate and characterize the anti-inflammatory principles from Perovskia atriplicifolia. MATERIALS AND METHODS: The CHCl3-soluble fraction of the methanol extract of the whole plant on column chromatography yielded compounds 1-6. The anti-inflammatory potential of the compounds 1-6 was evaluated by Leukotriene C4 (LTC4) Release Assay which was performed according to the established protocol. LTC4 in the supernatant of each well was measured using an ELISA kit (Cayman Chemical Co., Ann Arbor, MI). RESULTS: The bioassay-guided phytochemical investigation of the CHCl3 soluble fraction of the methanol extract of Perovskia atriplicifolia furnished six compounds, abrotanone (1), abrotandiol (2), (+)-pinoresinol (3), (+)-syringaresinol (4), (+)-lariciresinol (5), and (+)-taxiresinol (6). The compounds (1-6) were evaluated for their inhibitory activities on LTC4 release. Among the tested compounds, (+)-taxiresinol (6) exhibited the most potent inhibition of LTC4 release with an IC50 value of 3.4 ± 0.09 µM followed by compounds 4, 5, 3, and 2 with an IC50 value ranging from 7.9 ± 0.04 to 17.2 ± 0.07 µM. Abrotanone (1) showed the lowest inhibition of LTC4 release with an IC50 value of 35.1 ± 0.05 µM (the positive control, zileuton, 0.77 ± 0.05 µM). CONCLUSION: Compounds 1-6 were found to possess inhibitory activity and seem to have potential therapeutic effect on inflammatory diseases.

Leukotriene C4 induces bronchoconstriction and airway vascular hyperpermeability via the cysteinyl leukotriene receptor 2 in S-hexyl glutathione-treated guinea pigs.

Cysteinyl leukotrienes act through G-protein-coupled receptors termed cysteinyl leukotriene 1 (CysLT1) and cysteinyl leukotriene 2 (CysLT2) receptors. However, little is known about the pathophysiological role of CysLT2 receptors in asthma. To elucidate the possible involvement of CysLT2 receptors in bronchoconstriction and airway vascular hyperpermeability, we have established a novel guinea pig model of asthma. In vitro study confirmed that CHO-K1 cells, expressing guinea pig CysLT2 and CysLT1 receptors are selectively stimulated by LTC4 and LTD4, respectively. However, when LTC4 was intravenously injected to guinea pigs, the resulting bronchoconstriction was fully abrogated by montelukast, a CysLT1 receptor antagonist, indicating rapid metabolism of LTC4 to LTD4 in the lung. We found that treatment with S-hexyl glutathione (S-hexyl GSH), an inhibitor of gamma-glutamyl transpeptidase, significantly increased LTC4 content and LTC4/(LTD4 plus LTE4) ratio in the lung. Under these circumstances, LTC4-induced bronchoconstriction became resistant to montelukast, but sensitive to Compound A, a CysLT2 receptor antagonist, depending on the dose of S-hexyl GSH. Combination with montelukast and Compound A completely abrogated this spasmogenic response. Additionally, we confirmed that LTC4 elicits airway vascular hyperpermeability via CysLT2 receptors in the presence of high dose of S-hexyl GSH as evidenced by complete inhibition of LTC4-induced hyperpermeability by Compound A, but not montelukast. These results suggest that CysLT2 receptors mediate bronchoconstriction and airway vascular hyperpermeability in guinea pigs and that the animal model used in this study may be useful to elucidate the functional role of CysLT2 receptors in various diseases, including asthma.

Modulation of basophils' degranulation and allergy-related enzymes by monomeric and dimeric naphthoquinones.

Allergic disorders are characterized by an abnormal immune response towards non-infectious substances, being associated with life quality reduction and potential life-threatening reactions. The increasing prevalence of allergic disorders demands for new and effective anti-allergic treatments. Here we test the anti-allergic potential of monomeric (juglone, menadione, naphthazarin, plumbagin) and dimeric (diospyrin and diosquinone) naphthoquinones. Inhibition of RBL-2H3 rat basophils' degranulation by naphthoquinones was assessed using two complementary stimuli: IgE/antigen and calcium ionophore A23187. Additionally, we tested for the inhibition of leukotrienes production in IgE/antigen-stimulated cells, and studied hyaluronidase and lipoxidase inhibition by naphthoquinones in cell-free assays. Naphthazarin (0.1 µM) decreased degranulation induced by IgE/antigen but not A23187, suggesting a mechanism upstream of the calcium increase, unlike diospyrin (10 µM) that reduced degranulation in A23187-stimulated cells. Naphthoquinones were weak hyaluronidase inhibitors, but all inhibited soybean lipoxidase with the most lipophilic diospyrin, diosquinone and menadione being the most potent, thus suggesting a mechanism of competition with natural lipophilic substrates. Menadione was the only naphthoquinone reducing leukotriene C4 production, with a maximal effect at 5 µM. This work expands the current knowledge on the biological properties of naphthoquinones, highlighting naphthazarin, diospyrin and menadione as potential lead compounds for structural modification in the process of improving and developing novel anti-allergic drugs.

Bioassay-guided identification of an anti-inflammatory prenylated acylphloroglucinol from Melicope ptelefolia and molecular insights into its interaction with 5-lipoxygenase.

A bioassay-guided investigation of Melicope ptelefolia Champ ex Benth (Rutaceae) resulted in the identification of an acyphloroglucinol, 2,4,6-trihydroxy-3-geranylacetophenone or tHGA, as the active principle inhibiting soybean 15-LOX. The anti-inflammatory action was also demonstrated on human leukocytes, where the compound showed prominent inhibitory activity against human PBML 5-LOX, with an IC(50) value of 0.42 µM, very close to the effect produced by the commonly used standard, NDGA. The compound concentration-dependently inhibited 5-LOX product synthesis, specifically inhibiting cysteinyl leukotriene LTC(4) with an IC(50) value of 1.80 µM, and showed no cell toxicity effects. The anti-inflammatory action does not seem to proceed via redox or metal chelating mechanism since the compound tested negative for these bioactivities. Further tests on cyclooxygenases indicated that the compound acts via a dual LOX/COX inhibitory mechanism, with greater selectivity for 5-LOX and COX-2 (IC(50) value of 0.40 µM). The molecular features that govern the 5-LOX inhibitory activity was thus explored using in silico docking experiments. The residues Ile 553 and Hie 252 were the most important residues in the interaction, each contributing significant energy values of -13.45 (electrostatic) and -5.40 kcal/mol (electrostatic and Van der Waals), respectively. The hydroxyl group of the phloroglucinol core of the compound forms a 2.56Å hydrogen bond with the side chain of the carboxylate group of Ile 553. Both Ile 553 and Hie 252 are crucial amino acid residues which chelate with the metal ion in the active site. Distorting the geometry of these ligands could be the reason for the inhibition activity shown by tHGA. The molecular simulation studies supported the bioassay results and served as a good model for understanding the way tHGA binds in the active site of human 5-LOX enzyme.

Luteolin-7-O-glucoside suppresses leukotriene C(4) production and degranulation by inhibiting the phosphorylation of mitogen activated protein kinases and phospholipase Cγ1 in activated mouse bone marrow-derived mast cells.

In this study, luteolin-7-O-glucoside (L7G), an herbal medicine isolated from Ailanthus altissima, inhibited 5-lipoxygenase (5-LOX)-dependent leukotriene C(4) (LTC(4)) production in bone marrow-derived mast cells (BMMCs) in a concentration-dependent manner with an IC(50) of 3.0 µM. To determine the action mechanism of L7G, we performed immunoblotting for cytosolic phospholipase A(2) (cPLA(2)) and mitogen-activated protein kinases (MAPKs) following c-kit ligand (KL)-induced activation of BMMCs with or without L7G. Inhibition of LTC(4) production by L7G was accompanied by a decrease in cPLA(2) phosphorylation, which occurred via the extracellular signal-regulated protein kinase-1/2 (ERK1/2) and p38 and c-Jun N-terminal kinase (JNK) pathways. In addition, L7G also attenuated mast cell degranulation in a dose-dependent manner (IC(50), 22.8 µM) through inhibition of phospholipase Cγ1 (PLCγ1) phosphorylation. Our results suggest that the anti-asthmatic activity of L7G may be mediated in part via the inhibition of LTC(4) generation and mast cell degranulation.

Effects of methyl gallate on arachidonic acid metabolizing enzymes: Cyclooxygenase-2 and 5-lipoxygenase in mouse bone marrow-derived mast cells.

Methyl gallate (MG) is a medicinal herbal product that is isolated from Paeonia lactiflora that inhibits cyclooxygenase-2 (COX-2) dependent phases of prostaglandin D2 (PGD2) generation in bone marrow-derived mast cells (BMMC) in a concentration-dependent manner with an IC50 values of 17.0 microM. This compound also found inhibited the COX-2-dependent conversion of the exogenous arachidonic acid to PGD2 in a dose-dependent manner with an IC50 values of 19.0 microM, using a COX enzyme assay kit. However, at concentrations up to 80 microM, MG did not inhibit COX-2 protein expression in BMMC, indicating that MG inhibits COX-2 activity directly. Furthermore, MG consistently inhibited the production of leukotriene C4 (LTC4) in a dose dependent manner, with an IC50 value of 5.3 microM. These results demonstrate that MG has a dual cyclooxygenase-2/5-lipoxygenase inhibitory activity, which might provide the basis for novel anti-inflammatory drugs.

Ginkgetin, a Biflavone from Ginko biloba leaves, inhibits cyclooxygenases-2 and 5-lipoxygenase in mouse bone marrow-derived mast cells.

Ginkgetin, a biflavone from Ginkgo biloba leaves, was previously reported to be a phospholipase A(2) inhibitor and this compound showed the potent antiarthritic activity in rat adjuvant-induced arthritis as well as analgesic activity. This investigation was carried out to find effects on cyclooxygenase-2 (COX-2) in vitro effect. Ginkgetin inhibits COX-2 dependent phases of prostaglandin D(2) (PGD(2)) generation in bone marrow-derived mast cells (BMMC) in a concentration-dependent manner with IC(50) values of 0.75 microM. Western blotting probed with specific anti-COX-2 antibodies showed that the decrease in quantity of the PGD(2) product was accompanied by a decrease in the COX-2 protein level. In addition, this compound consistently inhibited the production of leukotriene C(4) (LTC(4)) in a dose dependent manner, with an IC(50) value of 0.33 microM. These results demonstrate that ginkgetin has a dual cyclooxygenase-2/5-lipoxygenase inhibitory activity. Furthermore, this compound also inhibited degranulation reaction in a dose dependent manner, with an IC(50) value of 6.52 microM. Therefore, this compound might provide a basis for novel anti-inflammatory agents.

Antiinflammatory effect of tepoxalin: blood and synovial tissue studied in patients with knee arthrosis.

Our aim was to determine the amounts of eicosanoids in blood and synovial tissue of patients with knee arthrosis and to examine the effects of 2 doses of tepoxalin (50 mg twice, 200 mg twice), administered p.o. for 3.5 days. Concentrations of leukotriene B4 (LTB4, LTC4, and thromboxane B2 (TXB2) were measured in blood before and after oral administration of tepoxalin and release of prostaglandin E2 (PGE2), 6-keto-PGF1alpha, and LTC4 was measured in incubation media of synovial tissue, taken at surgery from patients treated with tepoxalin. Radioimmunoassay (RIA) was used to determine the levels of the eicosanoids. LT and TXB2 release was reduced by tepoxalin in both doses used. Under these conditions, PGE2, 6-keto-PGF1alpha, and LTC4 release from synovial tissue was detectable only after stimulation with calcium ionophore A23187. Washed synovial tissue, in which tepoxalin concentrations should be reduced, released higher amounts of all eicosanoids measured than directly incubated synovial tissue did. Pain after tepoxalin administration was significantly reduced. Relevant drug concentrations were detected in plasma and synovial fluid. Tepoxalin was well tolerated and had no marked adverse effects. At 400 mg, tepoxalin is a dual inhibitor of cyclooxygenase (CO) and 5-lipoxygenase (5-LO) in blood and synovial tissue.

Anti-allergic effect of tea-leaf saponin (TLS) from tea leaves (Camellia sinensis var. sinensis).

We investigated the anti-allergic effect of tea-leaf saponin (TLS), which was a mixture of saponins separated from the leaves of Camellia sinensis var. sinensis, in guinea pigs and rats. TLS (20-100 mg/kg) dose-dependently inhibited experimentally-induced asthma, and ID50 was 61.7 mg/kg. TLS (20-100 mg/kg) dose-dependently inhibited a 48 h homologous PCA (passive cutaneous anaphylaxis) reaction, and the inhibitory effect was similar to that of tranilast. TLS (1-100 microg/ml) also inhibited the release of antigen-induced leukotriene (LT) C4 from sensitized guinea pig lung samples in a dose-dependent fashion, but did not prevent histamine release. TLS (0.01-0.5 microg/ml) inhibited histamine release from rat peritoneal mast cells induced by compound 48/80. At higher concentrations, TLS elicited histamine release. These findings suggest that TLS may be a useful protective agent against clinical allergy, and that the inhibitory effects of TLS on mediator release are in some way related to its inhibitory effect on experimentally-induced asthma and PCA reaction.

Effects of stilbenes isolated from medicinal plants on arachidonate metabolism and degranulation in human polymorphonuclear leukocytes.

Studies were made on the effects of stilbene derivatives isolated from medicinal plants on arachidonate metabolism and degranulation in human polymorphonuclear leukocytes (PMN-L). Resveratrol (3,4',5-trihydroxystilbene) isolated from the roots of Reynoutria japonica was found to inhibit the 5-lipoxygenase products 5-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE), 5,12-dihydroxy-6,8,10,14-eicosatetraenoic acid (5,12-diHETE) and leukotriene C4(LTC4); its concentrations for 50% inhibition (IC50) were 8.90 x 10(-6) M, 6.70 x 10(-6) M and 1.37 x 10(-6) M, respectively. The IC50 of 5-HETE, 5,12-diHETE and LTC4 formations of synthetic 3,3',4-trihydroxystilbene were 5.90 x 10(-6) M, 6.30 x 10(-7) M and 8.80 x 10(-7) M, respectively. Moreover, they inhibited the release of lysosomal enzyme such as lysozyme and beta-glucuronidase induced by calcium ionophore A 23187 from human PMN-L at 10(-3)-10(-4) M.

Anti-inflammatory properties and inhibition of leukotriene C4 biosynthesis in vitro by flavonoid baicalein from Scutellaria baicalensis georgy roots.

Anti-inflammatory activity of baicalein (5,6,7-trioxyflavone-7-O-beta-D-glucuronide) was greater in the chronic inflammation model (rat adjuvant arthritis, ED50 = 120.6 mg/kg) than observed in the rat carrageenan-induced paw edema, ED50 > or = 200.0 mg/kg. A comparative study of the 5-lipoxygenase (5-LO) inhibitory activity of baicalein, BW 755 C, and hydroxamic acid arachidonate on leukotriene C4 (LTC4) biosynthesis by rat resident peritoneal macrophages stimulated with calcium ionophore (A 23186) showed that these drugs significantly inhibited LTC4 production, IC50: 9.5, 41.8, and 2.8 microM, respectively. This finding suggests that inhibition of the 5-LO pathway of arachidonic acid metabolism may be one of the mechanisms of baicalein's anti-inflammatory activity.