Arachidonic acid-induced inflammation: inhibition by dual inhibitor of arachidonic acid metabolism, SK&F 86002

Anti-Inflammatory Activities of Arnica montana Planta Tota versus Flower Extracts: Analytical, In Vitro and In Vivo Mouse Paw Oedema Model Studies

Arnica montana is well known for its anti-inflammatory properties. While the anti-inflammatory activity of Arnica flowers (Arnicae flos) has been extensively studied, that of the whole plant (Arnicae planta tota) is less characterized. We compared the ability of Arnicae planta tota and Arnicae flos extracts to inhibit the pro-inflammatory NF-κB-eicosanoid pathway, using several in vitro and in vivo assays. We showed that Arnicae planta tota inhibited NF-κB reporter activation, with an IC₅₀ of 15.4 μg/mL (vs. 52.5 μg/mL for Arnicae flos). Arnicae planta tota also inhibited LPS-induced expression of ALOX5 and PTGS2 genes in human differentiated macrophages. ALOX5 and PTGS2 encode the 5-lipoxygenase (5-LO) and cyclooxygenase-2 (COX-2) enzymes that initialize the conversion of arachidonic acid into leukotrienes and prostaglandins, respectively. Arnicae planta tota inhibited 5-LO and COX-2 enzymatic activity in vitro and in human primary peripheral blood cells, with lower IC₅₀ compared to Arnicae flos. Finally, Arnicae planta tota applied topically reduced carrageenan-induced mouse paw oedema more efficiently than Arnicae flos. Altogether, Arnicae planta tota displayed a superior anti-inflammatory activity compared to Arnicae flos, suggesting that Arnicae-planta-tota-containing products might be more effective in alleviating the manifestations of acute inflammation than those based on Arnicae flos alone.

20-HETE is a pivotal endogenous ligand for TRPV1-mediated neurogenic inflammation in the skin

BACKGROUND AND PURPOSE

Transient receptor potential cation channel subfamily V member 1 (TRPV1) is localised to sensory C-fibres and its opening leads to membrane depolarization, resulting in neuropeptide release and neurogenic inflammation. However, the identity of the endogenous activator of TRPV1 in this setting is unknown. The arachidonic acid (AA) metabolites 12-hydroperoxyeicosatetraenoyl acid (12-HpETE) and 20-hydroxyeicosatetraenoic acid (20-HETE) have emerged as potential endogenous activators of TRPV1 however, whether these lipids underlie TRPV1-mediated neurogenic inflammation remains unknown.

EXPERIMENTAL APPROACH

we analysed human cantharidin-induced blister samples and inflammatory responses in TRPV1 transgenic mice.

KEY RESULTS

In a human cantharidin-blister model the potent TRPV1 activators 20-HETE but not 12-HETE (stable metabolite of 12-HpETE) correlated with AA levels. Similarly, in mice levels of 20-HETE (but not 12-HETE) and AA were strongly positively correlated within the inflammatory milieu. Furthermore, LPS-induced oedema formation and neutrophil recruitment were substantially and significantly attenuated by pharmacological block or genetic deletion of TRPV1 channels, inhibition of 20-HETE formation or SP receptor neurokinin 1 (NK₁ ) blockade. LPS treatment also increased cytochrome-P450 ώ-hydroxylase gene expression, the enzyme responsible for 20-HETE production.

CONCLUSIONS AND IMPLICATIONS

Taken together, our findings suggest that endogenously generated 20-HETE activates TRPV1 causing C-fibre activation and consequent oedema formation. These findings identify a novel pathway that may be useful in the therapeutics of diseases/conditions characterized by a prominent neurogenic inflammation, as in several skin diseases.

Topical Anti-Inflammatory Activity of Oil from Tropidurus hispidus (Spix, 1825)

Tropidurus hispidus has been used in traditional medicine in several regions of Northeastern Region of Brazil. Its medicinal use involves the treatment of diseases such as warts, sore throat, tonsillitis, chicken pox, varicella, measles, asthma, alcoholism, and dermatomycosis. The present study evaluated the topical anti-inflammatory activity of Tropidurus hispidus fat in treating ear edema in an animal model. Oil from T. hispidus (OTH) was evaluated on its effect against experimental inflammation in mice. OTH was extracted from body fat located in the ventral region of Tropidurus hispidus using hexane as a solvent. We used the model of mouse ear edema induced by phlogistic agents, croton oil (single and multiple applications), arachidonic acid, phenol, capsaicin, and histamine, applied into the right ears of animals pretreated with acetone (control), dexamethasone, or OTH. OTH inhibited the dermatitis induced by all noxious agents, except capsaicin. This effect may be related to the fatty acids present in OTH.

Synthesis and Biological Evaluation of N-Aryl-5-aryloxazol-2-amine Derivatives as 5-Lipoxygenase Inhibitors

We describe the synthesis and biological evaluation of N-aryl-5-aryloxazol-2-amine derivatives that are able to inhibit 5-lipoxygenase (5-LOX), a key enzyme of leukotriene synthesis, for the treatment of inflammation-related diseases including asthma and rheumatoid arthritis. A novel structural moiety containing oxazole was initially identified from a chemical library using an in vitro enzymatic and cell-based assay, and its synthesized oxazole derivatives were further examined to develop a structure-activity relationship (SAR). SAR analysis demonstrated that a hydroxyl or amino group at the p-position on N-phenyl was essential for the 5-LOX-inhibitory activities of the derivatives, and that other halogen and methyl group-substituted derivatives affected the potency, positively or negatively. As a result, derivatives selected through first-round screening were further optimized using a cell-based assay and an in vivo assay to develop a potent, selective 5-LOX inhibitor. A final hit exhibited an improved efficacy in arachidonic acid-induced ear edema when applied topically but not orally. Moreover, it showed the additional advantage of sustainable antiinflammatory activity over a reference compound, zileuton. Taken together, chemical entities bearing an oxazole scaffold could be promising as therapeutic drugs for the treatment of chronic inflammatory skin disorders.

Anti-inflammatory activity of animal oils from the Peruvian Amazon

ETHNOPHARMACOLOGICAL RELEVANCE

Animal oils and fats from the fishes Electrophorus electricus and Potamotrygon motoro, the reptiles Boa constrictor, Chelonoidis denticulata (Geochelone denticulata) and Melanosuchus niger and the riverine dolphin Inia geoffrensis are used as anti-inflammatory agents in the Peruvian Amazon. The aim of the study was to assess the topic anti-inflammatory effect of the oils/fats as well as to evaluate its antimicrobial activity and fatty acid composition.

MATERIALS AND METHODS

The oils/fats were purchased from a traditional store at the Iquitos market of Belen, Peru. The topic anti-inflammatory effect was evaluated by the mice ear edema induced by arachidonic acid (AA) and 12-O-tetradecanoylphorbol-13-acetate (TPA) at the dose of 3mg oil/ear. Indomethacine and nimesulide were used as reference anti-inflammatory drugs. The application resembles the traditional topical use of the oils. The antimicrobial effect of the oils/fats was assessed by the microdilution test against reference strains of Escherichia coli, Staphylococcus aureus and Salmonella enteritidis. The fatty acid composition of the oils/fats (as methyl esters) was determined by GC and GC-MS analysis after saponification.

RESULTS

All oils/fats showed topic anti-inflammatory activity, with better effect in the TPA-induced mice ear edema assay. The most active drugs were Potamotrygon motoro, Melanosuchus niger and Geochelone denticulata. In the AA-induced assay, the best activity was found for Potamotrygon motoro and Electrophorus electricus oil. The oil of Electrophorus electricus also showed a weak antimicrobial effect with MIC values of 250 µg/mL against Escherichia coli ATCC 25922 and Salmonella enteritidis-MI. The main fatty acids in the oils were oleic, palmitic and linoleic acids.

CONCLUSIONS

Topical application of all the oils/fats investigated showed anti-inflammatory activity in the mice ear edema assay. The effect can be related with the identity and composition of the fatty acids in the samples. This study gives support to the traditional use of animal oils/fats as ant-inflammatory agents in the Peruvian Amazon. However, new alternative should be encouraged due to the conservation status of several of the animal sources of the crude drugs.

Significance of arachidonic acid in ocular infections and inflammation

Innate immune responses in the cornea mainly play an important role to mobilize multiple interrelated pathways of corneal lipid, which involve in inflammatory corneal diseases. Signaling lipid mediators derived from arachidonic acid (AA) control cell proliferation, apoptosis, metabolism, and migration, are known as eicosanoids, phosphoinositides, sphingolipids, and fatty acids. Emerging evidences have highlighted the implication of lipid mediators in both injury and repair mechanisms in the cornea. Recently, the role of AA and its metabolites to induce proinflammatory mediators and inflammatory cell infiltration in the pathogen-infected cornea and to cause severe keratitis have been revealed. In this review, we focus on the novel roles of AA downstream signaling in the corneal inflammatory diseases and also the biological relevance of AA signaling in the therapeutic strategies for targeting sight-threatening diseases.

Seleno-auranofin (Et3PAuSe-tagl): synthesis, spectroscopic (EXAFS, 197Au Mössbauer, 31P, 1H, 13C, and 77Se NMR, ESI-MS) characterization, biological activity, and rapid serum albumin-induced triethylphosphine oxide generation

Seleno-auranofin (SeAF), an analogue of auranofin (AF), the orally active antiarthritic gold drug in clinical use, was synthesized and has been characterized by an array of physical techniques and biological assays. The Mössbauer and extended X-ray absorption fine structure (EXAFS) parameters of the solid compound demonstrate a linear P-Au-Se coordination environment at a gold(I) center, analogous to the structure of auranofin. The (31)P, (13)C, and (1)H NMR spectra of SeAF in chloroform solution closely resemble those of auranofin. The (77)Se spectrum consists of a singlet at 481 ppm, consistent with a metal-bound selenolate ligand. The absence of (2)J(PSe) coupling in the (31)P and (77)Se spectra may arise from dynamic processes occurring in solution or because the (2)J(PSe) coupling constants are smaller than the observed bandwidths. Electrospray ionization mass spectrometry (ESI-MS) spectra of SeAF in 50:50 methanol-water exhibited strong signals for [(Et(3)P)(2)Au](+), [(Et(3)PAu)(2)-mu-Se-tagl](+), and [Au(Se-tagl)(2)](-), which arise from ligand scrambling reactions. Three assays of the anti-inflammatory activity of SeAF allowed comparison to AF. SeAF exhibited comparable activity in the topically administered murine arachadonic acid-induced and phorbol ester-induced anti-inflammatory assays but was inactive in the orally administered carrageenan-induced assay in rats. However, in vivo serum gold levels were comparable in the rat, suggesting that differences between the in vivo metabolism of the two compounds, leading to differences in transport to the inflamed site, may account for the differential activity in the carrageenan-induced assay. Reactions of serum albumin, the principal transport protein of gold in the serum, demonstrated formation of AlbSAuPEt(3) at cysteine 34 and provided evidence for facile reduction of disulfide bonds at cysteine 34 and very rapid formation of Et(3)P=O, a known metabolite of auranofin.

Topical anti-inflammatory activity of body fat from the lizard Tupinambis merianae

AIM OF THE STUDY

Tupinambis merianae is one of the most frequently used animals in traditional medicine in Brazil as its body fat has many different therapeutic indications as a folk remedy. The present study evaluated the topical anti-inflammatory activity of Tupinambis merianae fat in treating ear edema in an animal model.

MATERIALS AND METHODS

Oil (OTM) was extracted from body fat located in the ventral region of Tupinambis merianae using hexane as a solvent. Ear edema provoked by the application of croton oil (single and multiple application), arachidonic acid, phenol and capsaicin to Swiss mice was used to evaluate the potential anti-inflammatory value of the topical use of OTM. Topical applications of these irritants were made to the right ears of animals that were pre-treated with a acetone (control), dexamethasone, or OTM.

RESULTS

Our results indicate that Tupinambis merianae fat demonstrates significant topical antiinflammatory activity that reduces inflammation related to ear edema caused by croton oil (single and multiple application), arachidonic acid, phenol. While the inflammation caused by capsaicin, OTM did not significantly reduce the edema.

CONCLUSION

This represents the first evidence of anti-inflammatory activity of Tupinambis merianae fat in in vivo models, confirming its usefulness in traditional medicine as a remedy for skin diseases (dermatitis). The fatty acids present in OTM most likely inhibit the response pathway of arachidonic acid and its metabolites, thus reducing the production of pro-inflammatory mediators.

L-selectin: an emerging player in chemokine function

The emigration of leukocytes across the blood-endothelium barrier and their subsequent transmigration through the interstitium is a complex process that is vital for maintaining the efficiency of the body's innate and adaptive immunity. The chemokines, a family of low-molecular-weight chemoattractant cytokines, are well recognized to be key players in this process. However, recent investigations have highlighted an important role played by the selectin family of adhesion molecules in enhancing chemokine functions. This review summarizes the in vitro and in vivo studies that support this growing notion. It discusses chemotaxis in the context of the phosphoinositide 3-kinase and p38 mitogen-activated protein kinase pathways, and their relation to several chemoattractants (i.e., interleukin-8, leukotriene-B(4), formyl-methionyl-leucyl-phenylalanine, keratinocyte-derived cytokine, and macrophage inflammatory protein-2), the possible role played by L-selectin, and finally how chemotaxis can be altered in different inflammatory settings, such as lipopolysaccharide-mediated endotoxemia or chronic vasculitis.

Role of p38 mitogen-activated protein kinase in chemokine-induced emigration and chemotaxis in vivo

It has been proposed that L-selectin engagement with ligand activates p38 mitogen-activated protein kinase (MAPK) and can impact on downstream events of leukocyte rolling, including adhesion, and emigration. Using a novel chemotactic assay in vivo, we visualized slow release of chemokine from an agarose gel positioned 350 microm from a postcapillary venule, which induced directed migration (chemotaxis) of neutrophils. In this system, keratinocyte-derived cytokine induced phosphorylation of p38 MAPK, which phosphorylated a downstream protein (ATF-2). This latter event was blocked by the concentration of p38 inhibitors used in this study. Mice were treated with two different p38 inhibitors: SKF86002 and SB203580. Neither inhibitor affected rolling or adhesion in microvessels. Intravenous treatment with SFK86002 (5, 10, and 20 mg/kg) 30 min before the inflammatory stimulus inhibited the total number of emigrated cells at a dose of 20 mg/kg (62%, p < 0.05), despite the presence of many adherent cells within the vessels. A similar inhibition was observed with 20 mg/kg of a second p38 inhibitor SB203580 (67%, p < 0.05). In addition to emigration, both p38 inhibitors impaired the ability of emigrated cells to migrate through the tissue toward the chemotactic stimulus. In fact, the majority of emigrated leukocytes in p38 inhibitor-treated animals remained within 50 microm of the venule. Superfusion of the tissue with SKF86002 (0.7 mM) to impact only on emigrated and not vascular leukocytes resulted in no impairment in emigration, but in a significant reduction in chemotaxis away from the vessel wall. Again, the majority of emigrated leukocytes remained within 50 microm of the blood vessel. Our results suggest that p38 does not affect rolling or adhesion, but that it is involved in leukocyte emigration and chemotaxis through interstitium in response to keratinocyte-derived cytokine in vivo.

Antiinflammatory activity of some extracts from plants used in the traditional medicine of north-African countries (II)

Aqueous, ethanol and chloroform extracts from Corrigiliola telephiifolia, Echinops spinosus, Kundmannia sicula, Tamarindus indica and Zygophyllum gaetulum were evaluated for antiinflammatory properties in mice (ear oedema induced by arachidonic acid) and rats (subplantar oedema induced by carrageenan) after topical or i.p. administration, respectively. Our results showed that all the plants exhibit antiinflammatory activity, since at least one extract from each plant was active in one of the experimental models. Whereas all the extracts of Corrigiliola telephiifolia and Echinops spinosus were highly active on all the experimental models assayed (values of inflammation inhibition well above 50%), poorer activity profiles were recorded in Kundmannia sicula, Tamarindus indica and Zygophyllum gaetulum. These results support the traditional uses for these plants but indicate that the active principles in the chloroform extracts are probably more active and/or are contained in larger concentrations than the principles in the polar extracts used in the traditional medicine of North-African countries.

Antiedematous effects of combination therapies with the leukotriene synthesis inhibitor BAY X 1005 in the archidonic acid-induced mouse ear inflammation test

The leukotriene synthesis inhibitor (LSI) BAY X 1005 was tested in the arachidonic acid (AA)-induced mouse ear inflammation test (AA-MEIT) alone and in combination with other representative anti-inflammatory compounds for antiedematous effects. When BAY X 1005 was used as a monotherapy, the ED50 (half-maximal effect) was observed at 5.1 mg/kg per os (p.o.) and at 0.8 microg for topical application. The maximal inhibition of edema formation was estimated to be 63% for p.o. application and 54% for topical application. Furthermore, experiments were carried out in which the animals were conditioned with a combination of the H1/5-HT receptor antagonists pyrilamine and methysergide in addition to treatment with BAY X 1005. This conditioning treatment alone, without BAY X 1005, resulted in a 45 +/- 13% reduction in edema formation. ED50 substance effects were observed at 5.3 mg/kg p.o. and at 0.02 microg per ear for topical application. The maximal inhibition of edema formation in the conditioned groups was 82% for the oral administration of BAY X 1005 and 72% for the topical application. To further characterize the antiinflammatory properties of BAY X 1005 in the conditioned and unconditioned AA-MEIT, BAY X 1005 was tested in combination with the nitric oxide (NO) synthase inhibitor L-NAME, with the cyclooxygenase inhibitor indomethacin, and in combination with both compounds. BAY X 1005 consistently exerted anti-inflammatory effects in the AA-MEIT. The effects of a combination of different inhibitors of inflammatory mediators were not simply additive in this model, as was demonstrated in the case of the combination of L-NAME and indomethacin where a smaller inhibition than with either substance alone was observed. In the conditioned model, a combination of BAY X 1005 with L-NAME or indomethacin, or with both compounds together was less effective than the monotherapy with BAY X 1005. Taken together, these data suggest that cyclooxygenase products and NO have little effect on edema formation in the conditioned and unconditioned AA-MEIT model and that their interaction with leukotrienes is of minor quantitative importance. Our results underline the complexity of the AA-MEIT model and provide a rationale for H1/5-HT-conditioning animals to compensate for peculiarities in the mouse-specific mediator spectrum and to recognize the importance of the leukotriene-specific inflammatory response.

(E)-3-[6-[[(2,6-dichlorophenyl)thio]methyl]-3-(2-phenylethoxy)-2- pyridinyl]-2-propenoic acid: a high-affinity leukotriene B4 receptor antagonist with oral antiinflammatory activity

An extensive structure-activity study based around the high-affinity leukotriene B4 (LTB4) receptor antagonist SB 201146 (1) led to the identification of (E)-3-[6-[[(2,6-dichlorophenyl)-thio]methyl]-3-(2-phenylethoxy)-2- pyridinyl]-2-propenoic acid (3). This compound displays high affinity for the human neutrophil LTB4 receptor (Ki = 0.78 nM), blocks LTB4-induced Ca2+ mobilization with an IC50 of 6.6 +/- 1.5 nM, and demonstrates potent oral and topical antiinflammatory activity in a murine model of dermal inflammation.

A useful method for differential evaluation of anti-inflammatory effects due to cyclooxygenase and 5-lipoxygenase inhibitions in mice

This study was performed to establish a useful method for monitoring the effects of inhibitors of 5-lipoxygenase (5-LO) and/or cyclooxygenase (CO) and for differential evaluation of these inhibitors. After oral dosing, CO inhibitors such as indomethacin (20-40 mg/kg) and ketoprofen (40-80 mg/kg), zileuton (5-LO inhibitor, 20-80 mg/kg) and MK886 (5-LO-activating-protein inhibitor, 640 mg/kg) potently suppressed arachidonic acid (AA, 0.25 mg)-induced ear edema in mice. Methysergide (serotonin antagonist, 20 mg/kg) showed a slight anti-edematous effect, while mepyramine (160 mg/kg) and bromelain (320 mg/kg) had no effect. The anti-edematous effects of indomethacin and ketoprofen were reduced by concomitant topical application of prostaglandin E2 (PGE2, 1 micrograms/ear), but not by concomitant intradermal application of leukotriene C4 (LTC4, 0.1 micrograms/ear). On the contrary, the anti-edematous effects of zileuton and MK886 were reduced by LTC4, but not by PGE2. Dual (5-LO and CO) inhibitors such as phenidone (80-160 mg/kg) and BW755C (40-80 mg/kg), which inhibited the biosynthesis of LTB4 13-15 times more potently than that of PGE2 in rat peritoneal exudate cells, also showed anti-edematous effects that were reduced by LTC4, but not by PGE2. These results suggest that the AA (0.25 mg)-induced ear edema in mice is mainly mediated by LTs and PGs and is suitable for evaluating inhibitors of 5-LO and/or CO, and that an application of LTC4 or PGE2 with AA is a useful method for differential evaluation of these inhibitors.

Pharmacological profile of a novel, orally active leukotriene B4 antagonist, SM-15178

SM-15178, a new hydroxyacetophenone derivative, was evaluated to determine its antiinflammatory activity and antagonistic activity against leukotriene B4 (LTB4). SM-15178 inhibited [3H]LTB4 binding to its receptors on human neutrophils (IC50 = 0.30 microM). It inhibited LTB4-induced chemotaxis of human neutrophils (IC50 = 0.72 microM) with little inhibitory effect against C5a or FMLP-induced chemotaxis at concentrations up to 30 microM. The compound alone did not cause human neutrophil chemotaxis at concentrations up to 10 microM. LTB4-induced chemotaxis of mouse and rat neutrophils and guinea pig eosinophils was also inhibited by the compound, with IC50 values of 0.55, 0.52, and 0.58 microM, respectively. In an in vivo study, SM-15178, given orally, significantly prevented LTB4-induced transient leukopenia. It also suppressed LTB4-induced bronchoconstriction in the guinea pig almost completely when given orally at a dose of 40 mg/kg. Furthermore, orally given SM-15178 suppressed arachidonic acid-induced neutrophil infiltration in mouse ears and Arthus reaction-induced paw edema in the mouse in a dose-dependent manner. These results suggest that SM-15178 is a selective and orally active LTB4 antagonist and that it might be effective for the treatment of some types of inflammatory diseases.

Effect of selective phosphodiesterase type IV inhibitor, rolipram, on fluid and cellular phases of inflammatory response

The antiinflammatory activity of rolipram, a selective inhibitor of the cyclic AMP-specific phosphodiesterase (PDE IV), was studied. Rolipram did not inhibit 5-lipoxygenase activity but did inhibit human monocyte production of leukotriene B4 (LTB4, IC50 3.5 microM). Likewise, murine mast cell release of leukotriene C4 and histamine was inhibited. In vivo, rolipram inhibited arachidonic acid-induced inflammation in the mouse, while the low Km-cyclic-GMP PDE inhibitor, zaprinast, did not inhibit. Rolipram had a modest effect on LTB4 production in the mouse, but markedly reduced LTB4-induced PMN infiltration. Beta-adrenergic receptor activation of adenylate cyclase was important for rolipram antiinflammatory activity since beta blockade abrogated arachidonic acid-induced inflammation. Thus, the antiinflammatory profile of rolipram is novel and may result from inhibition of PMN function and perhaps vasoactive amine release and leukotriene biosynthesis. These actions may be dependent upon endogenous beta-adrenergic activity and are likely mediated through inhibition of PDE IV.

Inhibition of CD44, CD45 and LFA-3 mediated cytokine release from human monocytes by SK&F 86002 and pentoxifylline

Compounds from two distinct pharmacological classes namely, SK&F 86002 and pentoxifylline, were examined for their effects on TNF alpha and IL-1 beta release by human monocytes stimulated with LPS or monoclonal antibodies to three cell surface glycoproteins, CD44, CD45 and LFA-3 (LFA-3 is also known as CD58). SK&F 86002, an inhibitor of 5-LO and CO in arachidonic acid metabolism, inhibited LPS-induced release of TNF alpha and IL-1 beta with an IC50 of 1 microM. At this dose, it also inhibited by > 50%, release of both cytokines induced by the three monoclonal antibodies. Pentoxifylline, a methylxanthine derivative with phosphodiesterase inhibitory activity, selectively inhibited LPS-induced TNF alpha release with an IC50 of 100 microM. TNF alpha and IL-1 beta release mediated by the monoclonal antibodies were inhibited by less than 30% in the presence of 100 microM pentoxifylline. These results suggest that (a) LPS induced cytokine release shares a common step with the physiologically relevant stimuli (involving cross-linking of cell surface receptors), and that this pathway is sensitive to inhibition by SK&F 86002 and, (b) SK&F 86002 is more potent than pentoxifylline in inhibiting TNF alpha and IL-1 beta release induced by both stimuli.

5-lipoxygenase inhibitors and their anti-inflammatory activities

A wide variety of agents have been reported as 5-LO inhibitors. The majority of the series appear to be lipophilic reducing agents, including phenols, partially saturated aromatics, and compounds containing heteroatom-heteroatom bonds. Many of these are not selective 5-LO inhibitors, but often affect CO and other LOs as well. In vivo systemic activity for many of these has been, in general, disappointing, probably because of poor bioavailability caused by lipophilicity and metabolic instability (oxidation, and conjugation of phenolic compounds). However, topically a number of agents have shown promise for skin inflammation, with Syntex's lonapalene the most advanced of these. Most results published to date appear more disappointing in the allergy/asthma field. More excitingly, a few structural types are selective 5-LO inhibitors which have shown systemic activity in vivo and in the clinic. Abbott's zileuton (136) appears to be one of the leading compounds in this category, along with other hydroxamates such as BW-A4C (129) from Burroughs-Wellcome. Recent selective non-reducing agents such as Wyeth-Ayerst's Wy-50,295 (143) and the similar ICI compounds such as ICI 216800 (145) also hold promise. The enantiospecific effects of (106) and (145) are especially interesting for the design of new inhibitors. If compounds like these validate the hypothesis that inhibition of 5-LO will have a significant anti-inflammatory effect, a redoubling of effort throughout the industry to find second- and third-generation selective agents may be expected. Part of the difficulty in interpreting and comparing the 5-LO literature is the plethora of test methods and activity criteria. As pointed out in the introduction, inhibition of product release from cells, often stimulated with A23187, has commonly been used to demonstrate 5-LO inhibition. However, this type of assay cannot be assumed to be diagnostic for 5-LO inhibition. Only if specificity for 5-LO product generation and (ideally) activity in cell-free enzymes is also shown should mechanistic interpretations be made. Recently, a new class of compounds was found at Merck which inhibited LT biosynthesis without inhibiting 5-LO, but apparently by a novel, specific mechanism. L-655,240 (169) and L-663,536 (MK-886) (170) were both active in human ISN, with IC50 values in the low micromolar range. Both also orally inhibited GPB (< 1 mg/kg). MK-886 was effective in Ascaris-induced asthma in squirrel monkeys, in rat carrageenan pleurisy, in rat Arthus pleurisy, and (topically) in guinea-pig ear oedema induced by A23187.(ABSTRACT TRUNCATED AT 400 WORDS)

Activation of the IL-1 gene in UV-irradiated mouse skin: association with inflammatory sequelae and pharmacologic intervention

The relationship between ultraviolet irradiation, interleukin-1 production, and inflammatory sequelae and the pharmacologic inhibition of these events was investigated in Balb/c mice exposed to ultraviolet irradiation from a bank of six Westinghouse FS40 sunlamps. The resulting edema (66% increase), inflammatory cell infiltration, and rise in the acute-phase reactant (fourfold) serum amyloid P component was preceded by the activation of the interleukin-1 beta gene and enhanced product formation. Administration of dexamethasone, which is known to inhibit interleukin-1 production, inhibited the inflammatory response to ultraviolet irradiation. Thus, production of interleukin-1 may be one of the initial events leading to the consequences of ultraviolet irradiation exposure.

Induction of plasma exudation and inflammatory cell infiltration by leukotriene C4 and leukotriene B4 in mouse peritonitis

Leukotriene induction of the fluid and cellular phases of the inflammatory response in the mouse was evaluated. Intraperitoneal injection of leukotriene C4 (LTC4 250 ng) led to dye extravasation but not polymorphonuclear leukocyte (PMN) infiltration, whereas injection of leukotriene B4 (LTB4 250 ng), led to PMN infiltration but not dye extravasation. The injection of both leukotrienes did not result in synergy. LTC4 did not appear to induce significant release or formation of chemotactic mediators, but the dye extravasation induced by LTC4 was inhibited by the vasoactive amine antagonist cyproheptadine and not by the eicosanoid inhibitors phenidone or naproxen. The response was markedly inhibited by the cytokine and eicosanoid inhibitors SK&F 86002 and SK&F 104493. PMN infiltration induced by LTB4 was not inhibited by SK&F 86002 or phenidone but was abrogated by colchicine treatment. LTB4 in this model did not appear to cause release or formation of vasoactive mediators. These leukotrienes appeared to be independent, complementary, and sufficient to mount a complete inflammatory response in the mouse.

Polymorphonuclear leukocyte infiltration into cerebral focal ischemic tissue: myeloperoxidase activity assay and histologic verification

Two different techniques were utilized to identify the infiltration of polymorphonuclear leukocytes (PMN) into cerebral tissue following focal ischemia: histologic analysis and a modified myeloperoxidase (MPO) activity assay. Twenty-four hours after producing permanent cortical ischemia by occluding and severing the middle cerebral artery of male spontaneously hypertensive rats, contralateral hemiparalysis and sensory-motor deficits were observed due to cerebral infarction of the frontal and parietal cortex. In hematoxylin-and-eosin-stained histologic sections, PMN, predominantly neutrophils, were identified at various stages of diapedesis from deep cerebral and meningeal vessels at the periphery of the infarct, into brain parenchyma. When MPO activity in normal brain tissue was studied initially, it could not be demonstrated in normal tissues extracted from non-washed homogenates. However, if tissue was homogenized in phosphate buffer (i.e., washed), MPO activity was expressed upon extraction. Utilizing this modified assay, MPO activity was significantly increased only in the infarcted cortex compared to other normal areas of the brain. This was observed in non-perfused animals and after perfusion with isotonic saline to remove blood constituents from the vasculature prior to brain removal. The increased PMN infiltration and MPO activity were not observed in forebrain tissue of sham-operated control rats. Also, MPO activity was not increased in the ischemic cortex of MCAO rats perfused immediately after middle cerebral artery occlusion, indicating that blood was not trapped in the ischemic area. By using a leukocyte histochemical staining assay, activity of peroxidases was identified within vascular-adhering/infiltrating PMN in the infarcted cortex 24 hr after focal ischemia. An evaluation of several blood components indicated that increased MPO activity was selective for PMN. The observed increase of approximately 0.3 U MPO/g wet weight ischemic tissue vs. nonischemic cerebral tissues probably reflects the increased vascular adherance/infiltration of approximately 600,000 PMN/g wet weight infarcted cortex 24 hr after focal ischemia. This combined biochemical and histological study strongly suggests that PMN adhere within blood vessels and infiltrate into brain tissue injured by focal ischemia and that the associated inflammatory response might contribute to delayed progressive tissue damage in focal stroke. This modified MPO assay is a useful, quantitative index of PMN that can be utilized to elucidate the potential deleterious consequences of neutrophils infiltrating into the central nervous system after cerebral ischemia, trauma, or other pro-inflammatory stimuli.

Extract and compounds obtained from Mandevilla velutina inhibit arachidonic acid-induced ear oedema in mice, but not rat stomach contraction

This study was designed to analyse the effect of crude extract (CE) and some pure compounds isolated from M. velutina on arachidonic acid (AA)-induced ear oedema in mice. The effect of these compounds on contractions in the rat stomach induced by AA and prostaglandin E2 (PGE2) was also investigated. The CE given orally to mice (50-400 mg/kg) 1h before inhibited the ear oedema in a dose-dependent manner, with a maximal inhibition (MI) of 56%. Given topically, compound MV8612 (200-600 mg/ear) isolated from this plant inhibited the oedema in a concentration-dependent manner with a MI of 66%, while compounds MV8608 and MV8610 (100-600 mg/ear) caused less inhibition, MI 29% and 39% respectively. Compound MV8612, given i.p. (3-30 mg/kg) 30 min before, also caused a dose-dependent inhibition of AA-induced ear oedema (MI of 60.5% compared with 28% and 49% for MV8608 and MV8610). Indomethacin (0.25-1.0 mg/ear) applied topically had no effect, but orally (1-10 mg/kg) gave MI of 66%. Phenidone given orally (10-100 mg/kg) gave a MI of 30% but it was very potent topically (0.5-2 mg/ear) (MI 66%). Nordihydroguaiaretic acid applied either topically (0.5-2.0 mg/ear) or orally (10-100 mg/kg) caused MI of 63% and 47%, respectively. BW 755C, orally (10-100 mg/kg), inhibited the AA-induced oedema in a dose-dependent manner (MI 48%), but was less effective when applied topically (0.25-1 mg/ear) (MI 32%). In the rat stomach preparation, compounds MV8608 and MV8612 (0.1-20 micrograms/ml) had no significant effect on contractions to AA or PGE2, while indomethacin (0.01-3 micrograms/ml) potently inhibited AA contraction, but had no effect on the PGE2 response. These results indicate that MV8608 and MV8612 exhibit both a topical and a systemic anti-inflammatory profile, presumably by a mechanism not related to inhibition of cyclooxygenase.

Assessment of myeloperoxidase activity in whole rat kidney

A method to quantitate myeloperoxidase (MPO) activity from rat whole kidney is described. Polymorphonuclear leukocyte (PMN) infiltration into tissue is a hallmark of acute inflammation. Historically, the degree of inflammation has been quantified by the identification and enumeration of PMNs histologically or by some other means. More recently, the enzyme activity of MPO, a marker enzyme for PMN, and freshly emigrated monocytes in many inflamed tissues has replaced these methods. The kidney, however, has been identified as a tissue from which MPO cannot be measured. Indeed, kidney homogenized by a standard extraction procedure was devoid of MPO activity. We modified the established methodology so that kidney was homogenized in 5 mM potassium phosphate buffer (PB) first and then centrifuged at 30,000 g for 30 min at 4 degrees C prior to extraction. The resulting 30,000 g pellets expressed MPO activity after suspending them in 50 mM PB containing 0.5% hexadecyltrimethylammoniumbromide (HTAB). Interference in the assay was observed with supernatants from control and inflamed kidney, which appeared to be due to kidney-derived material forming a complex with HTAB. After washing the pellets twice, we noted that their extracts exhibited greater activity, and interference from supernatants was abolished. Using this method, we observed that acutely inflamed kidneys from rats treated with sheep nephrotoxic immunoglobulin G (IgG) had significantly elevated MPO activity over kidneys from control rats. Thus, the described technique allows for the routine assay of MPO in kidney tissue.

The effect of leukotriene synthesis inhibitors on hamster periodontitis

The purpose of these experiments was to assess the role of the lipoxygenation products of arachidonic acid in hamster periodontitis. Phenidone and ketoconazole were used as inhibitors of leukotriene synthesis. In an established periodontitis, both drugs administered for 30 days induced a statistically significant decrease in PMNLs in the infiltrated connective tissue and around bacterial plaque within periodontal pockets. These changes were associated with a significant decrease in osteoclastic bone resorption. The results suggest that leukotrienes, and particularly leukotriene B4, are involved during hamster periodontitis and are responsible for PMNL infiltration of the periodontal pocket. The effects on bone are probably the consequence of the reduced inflammation resulting from the decrease in PMNL chemotaxis.

The effect of dual inhibitor, SK&F 86002, on helper T cell functions

SK&F 86002, a mixed cyclooxygenase-lipoxygenase inhibitor, was examined for its effects on helper T cell functions. The drug was found to inhibit concanavalin A-induced mitogenesis of splenic T cells (IC50 = 13 microns), the mixed lymphocyte response (IC50 = 16 microM), and proliferation of antigen specific T cells (cloned line, IC50 = 11 microM; uncloned line, IC50 = 13 microM). In contrast, another mixed cycloxygenase-lipoxygenase inhibitor, BW775c, did not have such effects at non-cytotoxic levels. These T cell functions are believed to be dependent on the effects of elaborated IL-1. SK&F 86002 has been shown to inhibit the production of mature IL-1 (IC50 = 1 microM), possibly accounting for the anti-inflammatory effects of the drug in rheumatoid arthritis models. In an in vivo model of contact sensitivity, SK&F 86002 was able to inhibit mouse footpad swelling, demonstrating additional anti-inflammatory activity. As an inhibitor of IL-1 synthesis or release, SK&F 86002 may be useful for the treatment of T cell-dependent inflammation.

Inhibition of inflammatory cell infiltration by bicyclic imidazoles, SK&F 86002 and SK&F 104493

The mode of action of the dual inhibitors of eicosanoid metabolism, SK&F 86002 and SK&F 104493 was evaluated on inflammatory cell infiltration induced in mice by carrageenan, monosodium urate crystals, and arachidonic acid. The results were compared to those seen with standard antiinflammatory compounds. Inflammatory cell infiltration was inhibited by SK&F 86002. SK&F 104493, colchicine, and phenidone but not naproxen. In vivo, PMN infiltration induced by LTB4 was inhibited by colchicine but not by SK&F 86002, SK&F 104493, or phenidone treatment. Similarly, in vitro chemotaxis to LTB4 was not inhibited by SK&F 86002. The 5-lipoxygenase inhibitors, SK&F 86002, SK&F 104493, and phenidone inhibited LTB4 production in vivo as well as inflammatory cell infiltration induced by arachidonic acid. The data are consistent with the suggestion that the bicyclic imidazoles inhibit PMN infiltration by virtue of inhibition of LTB4 production.

Inflammatory mediators of experimental colitis in rats

Colonic inflammation was induced in rats by intracolonic administration of 0.25 ml of 50% ethanol containing 30 mg of trinitrobenzene sulfonic acid (TNB). Control rats were treated with 0.25 ml of 50% ethanol or with 30 mg of TNB in 0.25 ml of saline. After 24 h, mucosal ulceration and hemorrhage were observed in TNB/ethanol-, 50% ethanol-, and to a lesser extent, in TNB/saline-treated rats. After 1 wk, mucosal damage was completely resolved in the 50% ethanol and TNB/saline-treated rats but the lesions in the TNB/ethanol-treated rats persisted and progressed to a chronic active inflammatory process after 3 wk. Myeloperoxidase activity was significantly elevated in mucosal scrapings from all treatment groups at all time intervals when macroscopic and microscopic mucosal injury was evident. Interleukin-1 was found to be the most sensitive indicator of mucosal inflammation, and its mucosal values correlated with myeloperoxidase activity. Leukotriene B4 was increased in control rats at 1 wk and in TNB/ethanol-treated rats at all time intervals. The maximal increase in leukotriene B4 was observed at 1 wk. Thromboxane B2 generation was reduced while platelet activating factor generation was not increased in TNB/ethanol-treated rats. These results indicate that in this TNB/ethanol model of gut inflammation, myeloperoxidase activity and interleukin-1 are reliable and sensitive indicators of colonic inflammation, and that thromboxane B2 is not involved in the acute lesions, whereas leukotriene B4 appears in the chronic active inflammatory response.

Evaluation of the effect of evan's blue and triphenyltetrazolium chloride dyes on myeloperoxidase activity in canine cardiac tissue

Myeloperoxidase (MPO) activity in postinfarction, dual-stained canine tissue in the presence of Evan's Blue (EB) and Triphenyltetrazolium chloride (TTC) was evaluated. Perfusion of EB and TTC allows quantification of the area of necrosis, area-at-risk of infarction and noninvolved, normal tissue postinfarction. EB in cardiac tissue has been reported to interfere with MPO activity used to measure polymorphonuclear leukocyte (PMN) infiltration, thus requiring that infarct size and MPO activity be measured in separate groups of animals. Admixtures of EB- or TTC-stained canine cardiac tissue extracts with MPO homogenates were found to have similar MPO activity. Addition of a constant amount of EB- or TTC-stained tissue to a standard curve of MPO activity failed to influence the concentration-activity relationship. Furthermore, EB in the presence of inflammatory cell infiltration in vivo in the mouse did not alter MPO activity. Thus, neither EB nor TTC significantly interfered with the measurement of MPO activity so that EB and/or TTC-stained tissue can be utilized to examine the role of PMN's in myocardial infarction.

Anti-inflammatory and peripheral analgesic activity of esculetin in vivo

Esculetin determined a reduction in oedema and granulocyte infiltration in the Croton oil ear test in vivo. The drug was able to inhibit Acethylcholine-writhing test and showed a LD50 of 1450 mg/kg i.p. and greater than 2000 mg/kg by mouth. In our experimental conditions, esculetin has an anti-inflammatory and analgesic effect.

Effect of inhibitors of eicosanoid metabolism in murine collagen-induced arthritis

The dual inhibitors of arachidonic acid metabolism, Smith Kline & French (SK&F) 86002, SK&F 104351, and phenidone; the corticosteroid, dexamethasone; and the selective cyclooxygenase inhibitors, ibuprofen, indomethacin, naproxen, and piroxicam were evaluated for their antiarthritic potency in the murine, collagen-induced arthritis model. The ability of these compounds to alter the severity of arthritic lesions and to reduce serum levels of the acute-phase reactant, serum amyloid P component (SAP) were monitored. Serum concentrations of SAP were found to correlate strongly (r = 0.985) with disease severity at day 35 postimmunization. Treatment with SK&F 86002, SK&F 104351, phenidone, or dexamethasone significantly reduced disease severity, as judged by clinical score (55%, 72%, 41%, and 45% inhibition, respectively) and SAP levels (62%, 94%, 52%, and 94% inhibition, respectively) in arthritic mice. This profile of activity was not shared by the selective cyclooxygenase inhibitors, which did not uniformly inhibit disease activity by both parameters. The results suggest that dual inhibitors of 5-lipoxygenase and cyclooxygenase may prove more effective than selective cyclooxygenase inhibitors as anti-arthritic agents.

Inhibition of monocyte IL-1 production by the anti-inflammatory compound, SK&F 86002

The effects of several anti-inflammatory/anti-arthritic drugs on the in vitro production of interleukin-1 (IL-1) by human monocytes were examined. SK&F 86002, a novel dihydroimidazo thiazoline which inhibits both 5-lipoxygenase- and cyclooxygenase-mediated arachidonate metabolism was shown to be a potent inhibitor of IL-1 production by LPS-stimulated human monocytes. The inhibition was dose-dependent (IC50 = 1.30 +/- 1 microM), reversible and was independent of the concentration or type of stimulus used. The compound also inhibited cell-associated IL-1 activity. The compound did not exert general inhibitory effects on such parameters as adherence, cytotoxic function and protein synthesis of the monocytes. Other cyclooxygenase and/or 5-lipoxygenase inhibitors of arachidonic acid metabolism tested, with the exception of nordihydroguaiaretic acid, were inactive in inhibiting monocyte IL-1 production suggesting that the inhibition of IL-1 production by 86002 may be dissociated from its inhibition of the fatty acid oxygenases. The inhibition of IL-1 production by SK&F 86002 adds another facet of drug action contributing to its spectrum of anti-inflammatory activities.

SK&F 86002: a structurally novel anti-inflammatory agent that inhibits lipoxygenase- and cyclooxygenase-mediated metabolism of arachidonic acid

The effects of SK&F 86002 [5-(4-pyridyl)-6 (4-fluorophenyl)-2,3-dihydroimidazo (2,1-b) thiazole] on the generation of eicosanoids in vitro and on inflammatory responses in vivo are described and compared to other non-steroidal anti-inflammatory drugs. SK&F 86002 inhibited prostaglandin H2 (PGH2) synthase activity (IC50 120 microM) as well as prostanoid production by rat basophilic leukemia (RBL-1) cells (IC50 70 microM) and its sonicate (IC50 100 microM) and human monocytes (IC50 1 microM). In addition, SK&F 86002 inhibited the generation of dihydroxyeicosatetraenoic acid (diHETE) and 5-hydroxyeicosatetraenoic acid (5-HETE) by a high speed supernatant fraction of RBL-1 cells (IC50 10 microM). Cellular production of 5-lipoxygenase products was inhibited by SK&F 86002 as measured by leukotriene B4 (LTB4) generation from human neutrophils (IC50 20 microM), leukotriene C4 (LTC4) generation by human monocytes (IC50 20 microM), and 5-HETE production by RBL-1 cells (IC50 40 microM). The in vivo profile of anti-inflammatory activity of SK&F 86002 supports the dual inhibition of arachidonate metabolism as indicated by its activity in inflammation models that are insensitive to selective cyclooxygenase inhibitors. The responses of arachidonic-acid-induced edema in the mouse ear and rat paw, as well as the cell infiltration induced by carrageenan in the mouse peritoneum and by arachidonic acid in the rat air pouch, were inhibited by SK&F 86002 and phenidone but not by the selective cyclooxygenase inhibitors naproxen and indomethacin.