Elucidating the aryl hydrocarbon receptor antagonism from a chemical-structural perspective.

The aryl hydrocarbon receptor (AhR) plays an important role in several biological processes such as reproduction, immunity and homoeostasis. However, little is known on the chemical-structural and physicochemical features that influence the activity of AhR antagonistic modulators. In the present report, in vitro AhR antagonistic activity evaluations, based on a chemical-activated luciferase gene expression (AhR-CALUX) bioassay, and an extensive literature review were performed with the aim of constructing a structurally diverse database of contaminants and potentially toxic chemicals. Subsequently, QSAR models based on Linear Discriminant Analysis and Logistic Regression, as well as two toxicophoric hypotheses were proposed to model the AhR antagonistic activity of the built dataset. The QSAR models were rigorously validated yielding satisfactory performance for all classification parameters. Likewise, the toxicophoric hypotheses were validated using a diverse set of 350 decoys, demonstrating adequate robustness and predictive power. Chemical interpretations of both the QSAR and toxicophoric models suggested that hydrophobic constraints, the presence of aromatic rings and electron-acceptor moieties are critical for the AhR antagonism. Therefore, it is hoped that the deductions obtained in the present study will contribute to elucidate further on the structural and physicochemical factors influencing the AhR antagonistic activity of chemical compounds.

In vitro and in vivo effects of Ranunculus peltatus subsp. baudotii methanol extract on models of eicosanoid production and contact dermatitis.

Ranunculus (Crowfoot) species are numerous and they are all reputed to be counter-irritants and are used in several topical conditions. In order to study the pharmacological mechanisms of action underlying this popular use, a methanol extract of Ranunculus peltatus was tested in vitro in various assays involving eicosanoid and human elastase release by intact cells as well as in vivo, with models of delayed-type hypersensitivity (DTH) contact dermatitis. The extract proved to be a selective inhibitor of the cyclooxygenase-1 pathway, producing the total inhibition of 12-(S)-HHTrE release at 200 microg/mL, while leaving both 5-lipoxygenase and 12-lipoxygenase activities unaffected at the same dose. The n-hexane, chloroform and ethyl acetate fractions of the crude methanol extract inhibited LTB(4) release by intact rat peritoneal neutrophils, but more polar fractions were inactive and did not increase the 5-LOX activity as seen previously for extracts of other Ranunculus species. In the in vivo models, the methanol extract reduced the dinitrofluorobenzene (DNFB)-induced oedema by 40%, but failed to inhibit the oedema brought on by oxazolone. The results agree with the age-old assertion that Water Crowfoot species can be used as a topical antiinflammatory remedy without the prominent irritant action that accompanies the application of non-aquatic Ranunculus species.

Effects of plant alkylphenols on cytokine production, tyrosine nitration and inflammatory damage in the efferent phase of contact hypersensitivity.

BACKGROUND AND PURPOSE: The phenolic compounds isoprenylhydroquinone glucoside (IHG), 3,5-dicaffeoylquinic acid (DCA), and its methyl ester (DCE) have previously been shown to inhibit both contact hypersensitivity (CHS) and peroxynitrite reactivity. The present work seeks to establish a relationship between the anti-inflammatory effect and the release of cytokines and tyrosine nitration in skin. EXPERIMENTAL APPROACH: Murine CHS was developed by means of sensitization and challenge with dinitrofluorobenzene (DNFB) or oxazolone. Ear swelling was measured 24 and 96 h after challenge. Interleukin (IL)-1beta, IL-4, and tumour necrosis factor (TNF)-alpha were measured by ELISA; and the expression of inducible nitric oxide synthase (iNOS) was detected by Western blotting. Histological samples were analysed for 3-nitrotyrosine. KEY RESULTS: In the oxazolone model, DCE reduced the 24 h swelling by 54% whereas the effect of DCA was lower (40% inhibition). All the test compounds reduced IL-1beta values 24 h after challenge with DNFB or oxazolone, DCE particularly inhibited IL-4 production (74% and 78%, respectively; P<0.01). Tyrosine nitration was also markedly reduced by DCE. In general, the test compounds limited the presence of polymorphonuclear (PMN) leukocytes in the skin. CONCLUSIONS AND IMPLICATIONS: These results suggest that the effect of 3,5-dicaffeoylquinic esters on CHS is associated with a decrease in the production of interleukins, but not with the inhibition of iNOS expression. Moreover, esterification of the carboxyl group at C-1 enhanced protection against tyrosine nitration in the skin.

Demethylnobiletin inhibits delayed-type hypersensitivity reactions, human lymphocyte proliferation and cytokine production.

BACKGROUND AND PURPOSE: Our aim was to examine the effect of demethylnobiletin on various experimental models of delayed-type hypersensitivity (DTH) reactions and to determine its influence on the mediators and enzymes involved in these reactions. EXPERIMENTAL APPROACH: DTH was induced in mice by oxazolone, dinitrofluorobenzene (DNFB) and sheep red blood cells (SRBC). The effect of demethylnobiletin on the ensuing DTH was studied, especially in relation to oedema formation, cell infiltration and tissue damage. Its activity on different mediators implicated in DTH reactions was also determined and its effect on nitric oxide synthase (NOS)-2 analysed. Finally, its influence on T lymphocyte proliferation, apoptosis and caspase 3 activity was tested. KEY RESULTS: DTH reactions were all reduced by demethylnobiletin. The experimental results suggest that the compound may act by reducing cell infiltration and by suppressing mediators such as interleukin-2 (IC50=1.63 microM), interleukin-4 (IC50=2.76 microM), tumour necrosis factor-alpha (IC50=0.66 microM), interferon-gamma (IC50=1.35 microM), and interleukin-1 beta (46% at 2.5 microM) and by concomitantly increasing the production of the anti-inflammatory cytokine, interleukin-10. In addition, while demethylnobiletin affected nitric oxide production, it did not modify NOS-2 expression. Finally, demethylnobiletin inhibited proliferation of T cells and induced their apoptosis. CONCLUSIONS AND IMPLICATIONS: Demethylnobiletin decreased DTH reactions induced by various agents. This finding, along with the fact that the compound has a low toxicity and exhibits several other interesting properties, could pave the way for other structurally related citroflavonoids to be used as pharmacological agents in complementary therapies.

Anti-inflammatory profile of dehydrocostic acid, a novel sesquiterpene acid with a pharmacophoric conjugated diene.

Sesquiterpene acids are natural products that, in contrast with the thoroughly studied sesquiterpene lactones, have received little pharmacological attention. A good source of this class of compounds is Inula viscosa (Asteraceae), a plant with documented anti-inflammatory effects. The present paper gives the results of our investigations on the biochemical mechanisms involved in the anti-inflammatory activity of one such compound, dehydrocostic acid. The most salient findings were that in vitro dehydrocostic acid inhibits leukotriene B(4) production (IC(50)=22 microM), elastase activity (IC(50)=43 microM) and bee venom phospholipase A(2) activity (IC(50)=17 microM). Furthermore, this sesquiterpenoid was effective on some models of acute edema induced by PLA(2) and 12-O-tetradecanoylphorbol 13-acetate (TPA) Comparison of these data with that known for ilicic acid firmly suggests that the presence of a semiplanar ring A is essential for an improved inhibitory activity on inflammatory mediators.

Effect of selected triterpenoids on chronic dermal inflammation.

The activity of four natural triterpenoids on a 12-O-tetradecanoylphorbol-13-acetate multiple-dose model of skin chronic inflammation was studied. Erythrodiol and ursolic acid were significantly effective. The most important features concerning structure-activity relationship and previous data on the effect of these triterpenoids on other inflammatory conditions are discussed.

Anti-inflammatory glycoterpenoids from Scrophularia auriculata.

The activity of the four glycoterpenoids: two saponins, verbascosaponin A and verbascosaponin, and two iridoids, scropolioside A and scrovalentinoside, isolated from Scrophularia auriculata ssp. pseudoauriculata, were studied in different models of acute and chronic inflammation. Both saponins significantly inhibited the mouse paw edema induced by carrageenan and ear edema induced by single and multiple doses of 12-O-tetradecanoylphorbol 13-acetate (TPA). Verbascosaponin A showed a potency twice as high as that of indomethacin in the acute TPA model. Verbascosaponin A and scropolioside A were active after a long latency period against ethyl phenylpropiolate edema, as are glucocorticoids. When the putative corticoid-like mechanism of the two compounds was studied, verbascosaponin A activity was notably reduced by the mRNA synthesis inhibitor, actinomycin D, while the effect of scropolioside A was partially interfered with by the anti-glucocorticoid drugs used. Both iridoids were active on the delayed type hypersensitivity reaction. They significantly reduced the inflammatory lesion and suppressed the cellular infiltration.

Oleanonic acid, a 3-oxotriterpene from Pistacia, inhibits leukotriene synthesis and has anti-inflammatory activity.

One of the best known bioactive triterpenoids is oleanolic acid, a widespread 3-hydroxy-17-carboxy oleanane-type compound. In order to determine whether further oxidation of carbon 3 affects anti-inflammatory activity in mice, different tests were carried out on oleanolic acid and its 3-oxo-analogue oleanonic acid, which was obtained from Pistacia terebinthus galls. The last one showed activity on the ear oedema induced by 12-deoxyphorbol-13-phenylacetate (DPP), the dermatitis induced by multiple applications of 12-O-tetradecanoyl-13-acetate (TPA) and the paw oedemas induced by bradykinin and phospholipase A2. The production of leukotriene B4 from rat peritoneal leukocytes was reduced by oleanonic acid with an IC50 of 17 microM. Negligible differences were observed in the response of both triterpenes to DPP, bradykinin, and phospholipase A2, while oleanonic acid was more active on the dermatitis by TPA and on the in vitro leukotriene formation. In conclusion, the presence of a ketone at C-3 implies an increase in the inhibitory effects on models related to 5-lipoxygenase activity and on associated in vivo inflammatory processes.

Anti-phospholipase A2 and anti-inflammatory activity of Santolina chamaecyparissus.

The activity of the Santolina chamaecyparissus methanol extract was tested against the phospholipase A2 (PLA2)-induced mouse paw edema and in vitro inhibition of PLA2 activity. After fractionation, only the dichloromethane extract was active against the PLA2 in vitro test. In addition, it reduced the edema induced by arachidonic acid, and by 12-O-tetradecanoylphorbol-13-acetate in a multidose test. After chromatography on silicagel and gel filtration on Sephadex, and using an in vitro anti-PLA2 assay-guided process, we have isolated and identified from the dichloromethane extract the flavone nepetin and four sesquiterpenes.

On the activity of trifluoperazine and palmitoylcarnitine in mice: delayed hypersensitivity models.

The effect of pre- and post-challenge treatments with trifluoperazine and palmitoylcarnitine, two protein kinase C (PKC) inhibitors characterised by their interaction with the phospholipid enzyme cofactor, on the inflammation caused by delayed hypersensitivity (DTH) to dinitrofluorobenzene (DNFB) and sheep red blood cells (SRBC) in mice is reported. The activity of dexamethasone and two immunosuppressors, azathioprine and methotrexate, is also evaluated. The effectiveness of pre-treatment with each of the test drugs diminished when the DNFB challenge dose increased, whereas trifluoperazine and azathioprine were more active when administered after the challenge at the high DNFB dose. Trifluoperazine, which is also a calmodulin-antagonist, was the more effective of the PKC inhibitors tested on DNFB-DTH (39% and 59% inhibition swelling 24 and 96 h after challenge, respectively). SRBC-DTH was sensitive only to the action of the drugs given after challenge. In this test, PKC inhibitors showed a moderate effect, in the same range as methotrexate, whereas dexamethasone suppressed the reaction. The ability of trifluoperazine in inhibiting cutaneous DTH reaction, depending on the treatment schedule and the hapten challenge dose, has been determined.

In vivo anti-inflammatory activity of saponins from Bupleurum rotundifolium.

Seven oleanane-type triterpene saponins were isolated from the methanolic extract of the aerial parts of Bupleurum rotundifolium. They were identified on the basis of their spectral data as 3-O-[alpha-L-rhamnopyranosyl (1-->2)-beta-D-glucopyranosyl (1-->2)-beta-D-glucopyranosyl]-28-O-[beta-D-glucopyranosyl (1-->2)-beta-D-glucopyranosyl] echinocystic acid (saponin 1), 3-O-[alpha-L-rhamnopyranosyl (1-->2)-beta-D-glucopyranosyl (1-->2)-beta-D-fucopyranosyl] 11-methoxy-primulagenin A (saponin 2), rotundioside E (saponin 3), rotundioside F (saponin 4), 3beta-sulfate, 28-O-[beta-D-glucopyranosyl (1-->6)-beta-D-glucopyranosyl (1-->2)-beta-D-glucopyranosyl (1-->2)-beta-D-glucopyranosyl] ester of primulagenin A (saponin 5), rotundioside C (saponin 6) and 3-O-[alpha-L-rhamnopyranosyl (1-->2)-beta-D-glucopyranosyl (1-->2)-beta-D-fucopyranosyl] 11-methoxy-16beta,21alpha,28-trihydroxyolean-12-ene (saponin 7). All these saponins proved to be effective against TPA-induced ear edema in mice. Their ID50 were determined to be 248, 288, 128, 99 and 297 nmol/ear for saponin 1, 2, 3, 4 and 6, respectively. Saponins 3 and 6 were also active on a TPA multiple-dose model of skin chronic inflammation.

In vivo activity of pseudoguaianolide sesquiterpene lactones in acute and chronic inflammation.

The pseudoguaianolide sesquiterpene lactones 4-alpha-O-acetyl-pseudoguaian-6beta-olide (1), hymenin (2), ambrosanolide (3), tetraneurin A (4), parthenin (5), hysterin (6) and confertdiolide (7) were evaluated for their ability to affect the inflammation responses induced by different agents. All the compounds showed activity against the 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced mouse ear edema. The ethyl phenylpropiolate (EPP)-induced mouse ear edema was inhibited by compounds 3, 5 and 7. However, when sesquiterpene-lactones were assayed on the arachidonic acid (AA)-induced mouse ear edema, none of them were active. The only sesquiterpene lactone orally active against the paw mouse edema induced by carrageenan was 7, which gave a 46% edema inhibition after 3 h. On the other hand, compounds 3, 5 and 7 reduced the serotonin-induced paw edema in mice, although compound 7 was inactive in presence of cycloheximide. In addition, the sesquiterpene lactones were assayed against the chronic inflammation induced by repeated application of TPA on mouse ear. Confertdiolide was the most active compound; it reduced the edema by 87% and had a more moderate effect against the leukocyte recruitment (36% reduction in myeloperoxidase (MPO) levels). A histological study of ear the samples treated with 7 presented no detectable morphological lesions such as those treated with dexamethasone. On the oxazolone-induced delayed type hypersensitivity (DTH) only compounds 4 and 5 were active 24 h after the challenge. Compound 5 affected polymorphonuclear leukocyte infiltration (69% reduction in MPO levels). The results suggest that the especial chemical structure and spatial conformation of confertdiolide may facilitate its anti-inflammatory effect.

Influence of traditional Chinese anti-inflammatory medicinal plants on leukocyte and platelet functions.

The enzymes 5-lipoxygenase and elastase are therapeutic targets in dermatological disorders such as psoriasis. Fifteen extracts from traditional Chinese medicinal plants used to treat topical inflammations were screened for their inhibitory effect on lipoxygenase, cyclooxygenase and elastase activity in intact leukocytes and platelets. Astragalus membranaceus, Forsythia suspensa and Poria cocos inhibited 5-lipoxygenase, with IC50 values of 141, 80 and 141 microg mL(-1), respectively. The latter two species, along with Angelica dahurica and Angelica pubescens, also inhibited elastase (IC50 values of 80, 123, 68 and 93 microg mL(-1), respectively), while A. pubescens, Atractylodes macrocephala, Lentinus edodes, Rehmannia glutinosa and Paeonia lactiflora selectively inhibited 12-(S)-HHTrE production, a valid marker of cyclooxygenase activity. The inhibition of phospholipase A(2) activity by P. cocos is discussed. Dehydrotumulosic and pachymic acids, which have been isolated from P. cocos, were shown to inhibit leukotriene B(4) release. The results indicate that both P. cocos and F. suspensa are potentially valuable species in the management of skin pathologies involving chronic inflammation.

Anti-inflammatory effects of South American Tanacetum vulgare.

In recent years the role of phenolic compounds and sesquiterpene lactones, particularly parthenolide, in the anti-migraine and anti-inflammatory effects of Tanacetum parthenium (Asteraceae) has attracted much attention. However, the closely-related cosmopolitan species T. vulgare has remained outside the mainstream of research in this field. After treating the aerial parts of T. vulgare with dichloromethane and methanol, and applying conventional column and thin-layer chromatographic techniques, it was possible to isolate from the moderately lipophilic fractions the principles responsible for the anti-inflammatory activity of this plant against the mouse-ear oedema induced by 12-O-tetradecanoylphorbol 13-acetate. These were identified by ultraviolet and nuclear magnetic resonance spectroscopy as parthenolide (93% oedema inhibition at 0.5 mg/ear, ID50 (dose of drug inhibiting the oedema by 50%) = 0.18 micromol/ear) and the methoxyflavones jaceosidin (80% oedema inhibition at 0.5 mg/ear, ID50 = 0.50 micromol/ear), eupatorin, chrysoeriol and diosmetin. Because in molar terms the potency of parthenolide was nearly three times greater than that of the most active of the flavones and because it is obtained from the plant in considerably larger amounts, the flavonoids must only be partially responsible, and to a minor extent, for the observed in-vivo anti-inflammatory local effect.

Inhibitory effects of Santolina chamaecyparissus extracts against spasmogen agonists.

Several extracts of Santolina chamaecyparissus ssp. squarrosa antagonized in a concentration-dependent way the contractions of rat duodenum, guinea-pig ileum, rat vas deferens and rat uterus as induced by acetylcholine, histamine, noradrenaline, oxytocin and serotonin. Polar extracts were less active than apolar extracts, and it was necessary to assay the former at higher concentrations. Only the lyophilized aqueous extract produced a slight hypotensive effect when given intravenously at 150 mg/kg to urethananesthetized rats.

Pharmacological approach to the pro- and anti-inflammatory effects of Ranunculus sceleratus L.

Ranunculus sceleratus is a widespread species with unique toxicological and pharmacological activities. The present study seeks to assess this species' ability, both in vitro and in vivo, to modulate processes involved in inflammations. To this end, different extracts from the aerial parts of the plant were tested in several models of acute inflammation induced by tetradecanoylphorbol acetate (TPA), arachidonic acid (AA), and carrageenan, as well as in two models of delayed hypersensitivity induced by oxazolone and dinitrofluorobencene (DNFB). The extracts were also assayed in models of eicosanoid and elastase release by intact cells. When tested in vivo, all of the extracts showed anti-inflammatory or neutral effects. In vitro, non-polar extracts of this species were able to inhibit eicosanoid production, whereas polar extracts enhanced the synthesis of 5(S)-HETE, LTB(4) and 12(S)-HHTrE. The hypothesis of a "counter-irritant" mechanism of action has thus been proposed and is also discussed herein.

Dual inhibition of cyclooxygenase-1 and 5-lipoxygenase by aerial part of Bupleurum fruticescens methanol extract.

The effect of the methanol extract from aerial parts of Bupleurum fruticescens on the release of eicosanoids and hydrolytic enzymes was determined on in vitro cell systems. The extract had a significant effect on 5-lipoxygenase (5-LOX) activity, inhibiting both LTB4 and 5(S)-HETE production with IC50 values of 112 microg/ml and 95 microg/ml, respectively. At concentrations of 200 microg/ml, the extract also inhibited cyclooxygenase-1 (90%) and elastase activities (54%). The 12-LOX activity in intact platelets was not affected; a fact, which suggests that phospholipase A2 (PLA2) activity, is not modified by the extract.

Topical anti-inflammatory activity of some Asian medicinal plants used in dermatological disorders.

The topical anti-inflammatory activity of extracts from Cassia angustifolia, Rheum palmatum, Coptis chinensis, Phellodendron amurense and Scutellaria baicalensis, plants used in traditional East Asian medicine against different skin disorders, was studied. Though in different degree, all the extracts significantly inhibited the edema induced by 12-O-tetradecanoylphorbol-13-acetate (TPA), in both single or multiple application, oxazolone, and arachidonic acid (AA). None of the extracts inhibited in vitro the activity of phospholipase A(2) (PLA(2)) from Naja naja.

Topical anti-inflammatory lignans from Haplophyllum hispanicum.

The present paper reports the results of the methanol extract of Haplophyllum hispanicum Spach on single or repeated local 12-O-tetradecanoylphorbol acetate (TPA) administration and in the oxazolone-induced contact-delayed hypersensitivity mouse ear edemas. Two topical anti-inflammatory aryl naphthalide lignans were isolated from the active fractions of the methanol extract. They were identified by spectroscopic methods, including 13C NMR and heteronuclear multiple bond correlation (HMBC), as diphyllin acetyl apioside and tuberculation. The former was the most active on acute TPA edema with a ID50 of 0.27 mumol/ear.

Shikonin promotes intestinal wound healing in vitro via induction of TGF-ß release in IEC-18 cells.

The intestinal barrier is a complex system with a dynamic structure that is designed for the maintenance of homeostasis in healthy individuals. Ulcerative colitis, one of the main manifestations of inflammatory bowel disease, is characterized by an inadequate and delayed wound healing. Shikonin, the active principle in the root of Lithospermum erythrorhizon, has demonstrated its ability to attenuate dextran sulfate sodium-induced ulcerative colitis in mice. Moreover, the root of L. erythrorhizon has been used in traditional Chinese medicine for treatment of burns, anal ulcers, hemorrhoids and skin wounds. However, the effect of shikonin on intestinal wound healing is unknown. Using an in vitro model for wound healing, we observed that shikonin enhances cell migration of intestinal epithelial cells through a mechanism that involves TGF-ß1 induction. The combination of shikonin's anti-inflammatory activity together with its wound-healing properties makes it a great potential therapeutic agent for the treatment of injury associated with intestinal inflammation.