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In response to an inflammatory stimulus, arachidonic acid (AA), the main polyunsaturated fatty acid present in the phospholipid layer of cell membranes, is released and metabolized to a series of eicosanoids. These bioactive lipid mediators of inflammation arise physiologically through the action of the enzymes 5-lipoxygenase (5-LOX) and cyclooxygenases (constitutive COX-1 and inducible COX-2). It is believed that dual inhibition of 5-LOX and COXs may have a higher beneficial impact in the treatment of inflammatory disorders rather than the inhibition of each enzyme. With this demand for new dual-acting anti-inflammatory agents, a range of 2,3-diarylxanthones were tested through their ability to interact in the AA metabolism. In vitro anti-inflammatory activity was evaluated through the inhibition of 5-LOX-catalyzed leukotriene B 4 (LTB 4 ) formation in human neutrophils and inhibition of COX-1- and COX-2-catalyzed prostaglandin E 2 (PGE 2 ) formation in human whole blood. The results showed that some of the studied arylxanthones were able to prevent LTB 4 production in human neutrophils, in a concentration-dependent manner. The xanthone with a 2-catechol was the most active one (IC 50  ∼ 9 μM). The more effective arylxanthones in preventing COX-1-catalyzed PGE 2 production presented IC 50 values from 1 to 7 μM, exhibiting a structural feature with at least one non-substituted aryl group. All the studied arylxanthones were ineffective to prevent the formation of PGE 2 catalyzed by COX-2, up to the maximum concentration of 100 μM. The ability of the tested 2,3-diarylxanthones to interact with both 5-LOX and COX-1 pathways constitutes an important step in the research of novel dual-acting anti-inflammatory drugs.

Inflammation is a physiological response to tissue trauma or infection, but leukocytes, which are the effector cells of the inflammatory process, have powerful tissue remodelling capabilities. Thus, to ensure their precise localisation, passage of leukocytes from the blood into inflamed tissue is tightly regulated. Recruitment of blood borne neutrophils to the tissue stroma occurs during early inflammation. In this process, peptide agonists of the chemokine family are assumed to provide a chemotactic stimulus capable of supporting the migration of neutrophils across vascular endothelial cells, through the basement membrane of the vessel wall, and out into the tissue stroma. Here, we show that, although an initial chemokine stimulus is essential for the recruitment of flowing neutrophils by endothelial cells stimulated with the inflammatory cytokine tumour necrosis factor-alpha, transit of the endothelial monolayer is regulated by an additional and downstream stimulus. This signal is supplied by the metabolism of the omega-6-polyunsaturated fatty acid (n-6-PUFA), arachidonic acid, into the eicosanoid prostaglandin-D(2) (PGD(2)) by cyclooxygenase (COX) enzymes. This new step in the neutrophil recruitment process was revealed when the dietary n-3-PUFA, eicosapentaenoic acid (EPA), was utilised as an alternative substrate for COX enzymes, leading to the generation of PGD(3). This alternative series eicosanoid inhibited the migration of neutrophils across endothelial cells by antagonising the PGD(2) receptor. Here, we describe a new step in the neutrophil recruitment process that relies upon a lipid-mediated signal to regulate the migration of neutrophils across endothelial cells. PGD(2) signalling is subordinate to the chemokine-mediated activation of neutrophils, but without the sequential delivery of this signal, neutrophils fail to penetrate the endothelial cell monolayer. Importantly, the ability of the dietary n-3-PUFA, EPA, to inhibit this process not only revealed an unsuspected level of regulation in the migration of inflammatory leukocytes, it also contributes to our understanding of the interactions of this bioactive lipid with the inflammatory system. Moreover, it indicates the potential for novel therapeutics that target the inflammatory system with greater affinity and/or specificity than supplementing the diet with n-3-PUFAs., Competing Interests: The authors have declared that no competing interests exist.

Prostaglandins have wide-ranging effects in the body and are thought to be important mediators of inflammation. Cyclooxygenase (COX) plays a key regulatory role in prostaglandin synthesis, and occurs in both constitutive (COX-1) and inducible (COX-2) isoforms. COX-1 is thought to provide cytoprotective effects, whereas COX-2 is both inducible and the major isoform of inflammatory cells. Reduction of prostaglandin production by inhibition of cyclooxygenases appears to be the main mechanism of action of most non-steroidal anti-inflammatory drugs (NSAIDS). Here we present an animal model of COX-2 deficiency that was generated by gene targeting. Defects in null mice correlating with reduced viability included renal alterations, characteristic of renal dysplasia (100% penetrance), and cardiac fibrosis (50% penetrance). Female Cox-2-/- mice were infertile. COX-2 deficiency failed to alter inflammatory responses in several standard models, but striking mitigation of endotoxin-induced hepatocellular cytotoxicity was observed.

A quantitative method for testing antiinflammatory agents in beagles has been developed, based on measurement of paw inflammation induced by a local injection of carrageenin. Carrageenin [0.5 mL of 2% (wt/vol) in saline] was injected into the plantar region of the hindpaws of pentobarbital-anesthetized beagles. Paw pressure changes registered from a water-filled balloon held on the top of the paw by a light adhesive tape wrapping were monitored for 240 min. In control dogs given 0.5% (wt/vol) methylcellulose (10 mL/kg orally) just before carrageenin, paw pressure increased significantly (p less than 0.05) over eightfold, from 2.9 +/- 0.8 mm Hg (mean +/- SEM, n = 29 paws) at 75 min to 26.0 +/- 3.5 mmHg at 240 min. The increase in paw pressure was significantly inhibited by the cyclooxygenase inhibitors, ibuprofen, indomethacin, and orpanoxin, and partially inhibited by the lipoxygenase inhibitor, phenidone, administered orally before carrageenin injection. Thus this model, with further characterization, could provide a convenient, quantitative way of assessing the efficacy of nonsteroidal antiinflammatory agents in dogs.

TNF is a potent cytokine which can induce many of the pathological changes associated with inflammatory disease. In vitro studies have demonstrated that 5-lipoxygenase products promote the production of TNF by activated macrophages, suggesting that 5-lipoxygenase inhibitors may have therapeutic utility for the treatment of inflammatory conditions. A rat airpouch model of inflammation has been used to investigate the relationship between eicosanoid generation and TNF production in vivo. Injection of zymosan into the airpouch caused a time-dependent stimulation of TNF production which preceded leukotriene generation by at least 30 minutes. Injection of LPS into the airpouch also stimulated TNF production but not leukotriene generation. The selective 5-lipoxygenase inhibitors, ICI207968, A64077 and BWA4C, and the 5-lipoxygenase translocation inhibitor MK886, decreased leukotriene generation but enhanced TNF production. Taken together, these results do not support a role for 5-lipoxygenase products in the regulation of TNF production in vivo.

Research on the role of prostaglandins (PG) in inflammation has been divided along 2 lines of inquiry. One supposes that PG are proinflammatory, explaining why nonsteroidal antiinflammatory drugs (NSAID), which prevent conversion of arachidonic acid to stable PG through cyclooxygenase inhibition, exert their antiinflammatory effects. The other supposes that PG are antiinflammatory, explaining the reductions in inflammation produced by these substances in various experimental models of arthritis. A number of proinflammatory actions of PG have been identified, including vasodilatation and hyperalgesia. However, these activities are relatively modest and do not appear to account for the antiinflammatory effects of NSAID; indeed, mechanisms for these effects that do not depend on cyclooxygenase inhibition have been advanced. A number of potential mechanisms for antiinflammatory effects of PGE have been identified, including inhibition of neutrophil activation, O2 release and leukotriene B4 and cytokine production. It is likely that the availability of orally active PGE analogs will permit study leading to an integrated understanding of PG activity and an answer to the question whether such agents will prove useful in the treatment of chronic inflammatory diseases.

Arachidonic acid is a polyunsaturated fatty acid covalently bound in esterified form in the cell membranes of most body cells. Following irritation or injury, arachidonic acid is released and oxygenated by enzyme systems leading to the formation of an important group of inflammatory mediators, the eicosanoids. It is now recognised that eicosanoid release is fundamental to the inflammatory process. For example, the prostaglandins and other prostanoids, products of the cyclooxygenase enzyme pathway, have potent inflammatory properties and prostaglandin E2 is readily detectable in equine acute inflammatory exudates. The administration of nonsteroidal anti-inflammatory drugs results in inhibition of prostaglandin synthesis and this explains the mode of action of agents such as phenylbutazone and flunixin. Lipoxygenase enzymes metabolise arachidonic acid to a group of noncyclised eicosanoids, the leukotrienes, some of which are also important inflammatory mediators. They are probably of particular importance in leucocyte-mediated aspects of chronic inflammation. Currently available non-steroidal anti-inflammatory drugs, however, do not inhibit lipoxygenase activity. In the light of recent evidence, the inflammatory process is re-examined and the important emerging roles of both cyclo-oxygenase and lipoxygenase derived eicosanoids are explored. The mode of action of current and future anti-inflammatory drugs offered to the equine clinician can be explained by their interference with arachidonic acid metabolism.

Stimulated rabbit peritoneal polymorphonuclear leukocyte (PMN) preparations simultaneously produce prostaglandin-like material and mediators that induce metabolic alterations in experimental animals characteristic of the host's responses to inflammation. The alterations observed in rats include responses by: proteins, carbohydrates, hormones, trace metals, and total blood neutrophils. This study demonstrates a possible relationship between prostaglandins and PMN-derived substances that mediate plasma zinc depression, hepatic amino acid uptake, and increased numbers of blood neutrophils. Production of these mediators by stimulated-PMN preparations was prevented by 23 muM indomethacin or 93 muM aspirin. Conversely, morphine (2 mM or less) had no detrimental effect on production of these mediators, although, it consistently stimulated production of a substance stimulating total blood neutrophia. In addition, 2 muM prostaglandin E and F stimulated production of substances mediating hepatic amino acid uptake plasma zinc depression, respectively. At this concentration, neither prostaglandin significantly altered production of substances mediating increased numbers of total blood neutrophils. A partial-nitrogen atmosphere, dibutyryl cyclic analogs of AMP and GMP, or homogenization of the PMN had no effect on mediator production. The inhibitory effect of indomethacin and aspirin also was observed with PMN-homogenastes. These experimental observations suggest that prostaglandin synthesis has a function in production of mediators by stimulated-PMN preparations.

We have previously shown that production of plasminogen activator by inflammatory macrophages can be inhibited by immunomodulators of bacterial origin, especially LPS. In these experiments, the contribution of prostaglandins to this control was investigated. We examined the effect of two prostaglandin synthetase blockers, indomethacin and diclofenac. These drugs do not modify per se the production of plasminogen activator but they can partially prevent the inhibitory effect of LPS. Since restoration was not complete when plasminogen activator production was strongly inhibited, it is suggested that the immunomodulator acts through a mechanism involving more than one pathway only one of which would be mediated by prostaglandins.

A variety of steroidal and nonsteroidal antiinflammatory agents (NSAs) were compared for their effectiveness against a developing acute inflammatory reaction. Only BW 755C [3-amino-1-(m-trifluoromethyl)-phenyl-2-pyrazole] was immediately effective when administered 2 h after carrageenin, as the 3-h swelling was significantly reduced. Dexamethasone, a steroidal antiinflammatory agent, produced a delayed reduction. When administered at 2 h postcarrageenin, there was no effect at 3 h; but at 6 h, dexamethasone significantly reduced the swelling. In contrast, neither of the classic NSAs, aspirin or indomethacin, were effective when administered after the carrageenin. The results demonstrating a postcarrageenin effectiveness by BW 755C and dexamethasone are discussed as a possible reflection of an action on the lipoxygenase pathways of the arachidonic cascade that is not shared by the classic NSA.

Caffeine has been found to potentiate the acute anti-inflammatory activity of aspirin, indomethacin, and phenylbutazone, but not the activity of sodium salicylate or hydrocortisone, in the carrageenan pleurisy or hindlimb models of inflammation in the rat. The mobilization of inflammatory cells was not affected by aspirin in the presence or absence of caffeine. The mild analgesia produced by aspirin was confined to a hyperalgesic test in which this drug was able to reduce inflammation and concomitant hyperalgesia and thereby produce an "apparent" analgesic effect. This "apparent" analgesia produced by aspirin was potentiated by caffeine. The mechanism responsible for the potentiated anti-inflammatory and mild analgesic activity of aspirin remains unknown since caffeine did not alter the plasma salicylate levels or prostaglandin synthetase inhibition produced by aspirin.

Vasoprotective activity of COX inhibitors (diclofenac, piroxicam, indomethacin, aspirin) and of LOX inhibitors (nordihydroguaiaretic acid, propyl gallate, oxphaman) or of both (BW 755c) as well as of OFRS (mannitol, ethanol, thiourea, vitamin E) was investigated ex vivo in the isolated perfused hindlegs of the animals after in vivo u.v.-irradiation and antigen-provocation in mice and rats, respectively. The results show that vasodepression is mainly prevented by OFRS, antioxidants/LOX inhibitors and aspirin, but not by other COX inhibitors.

A method is described to examine the activity of potential antirheumatic drugs on the release and activity of lymphokines and interleukins in vitro, using human peripheral blood mononuclear cells and synovial cells. The enhancement of lymphocyte-mediated effects brought about by non-steroid anti-inflammatory drugs has been shown to be the result of inhibition of a prostaglandin negative-feedback mechanism. Since the underlying features of rheumatoid arthritis and related diseases are almost certainly brought about by mononuclear cell activation, their enhancement by non-steroid anti-inflammatory drugs might well have serious clinical implications. The possibility is discussed that aspirin-like drugs, administered in large doses to patients suffering slight joint pain, might well exacerbate, perpetuate or even initiate a chronic arthritic condition. We suggest that, as soon as the disease has been diagnosed, patients should be treated with a disease-modifying drug and, if necessary, an analgesic which does not inhibit cyclo-oxygenase.

An immune-complex-induced inflammatory reaction was elicited in the hamster cheek pouch microvasculature of ovalbumin (OA)-immunized animals by exposure to 1 or 100 micrograms/ml OA. The low antigen dose caused arteriolar constriction, transient platelet aggregation, and a reversible increase in vascular leakage at postcapillary venules. With the high antigen dose, the constriction and platelet aggregation were more pronounced and the vascular leakage was prolonged. This antigen dose also caused a massive PMNL accumulation in small venules, which coincided with the prolonged vascular leakage. Histamine was released in the reaction as pretreatment with mepyramine largely inhibited the leakage response to 1 microgram/ml OA. With 100 micrograms/ml OA, only the initial phase of vascular leakage was inhibited by mepyramine, leaving the prolonged vascular leakage and PMNL accumulation unaltered. Pretreatment with methylprednisolone 16-18 h prior to the experiments reduced both phases of vascular leakage as well as the PMNL accumulation. Pretreatment with the combined cyclo- and lipoxygenase inhibitors BW755C or nordihydroguaiaretic acid (NDGA) reduced the initial vasoconstriction induced with 100 micrograms/ml OA, thereby augmenting the initial vascular leakage. Despite this, the prolonged phase of vascular leakage was reduced in the NDGA-treated animals. Cyclooxygenase products were not found to play a crucial role in mediating the vascular response; on the contrary, indomethacin pretreatment slightly potentiated the vascular leakage induced by the low antigen dose.

Oxazolone-induced delayed hypersensitivity in mice produced swelling with concomitant increased tissue levels of leukotrienes and prostaglandins. Pharmacological agents were coapplied topically with oxazolone at the time of challenge in an attempt to modulate the immune-based inflammation. Dexamethasone inhibited both swelling and increases in eicosanoid levels. Indomethacin reduced prostaglandin levels but failed to inhibit swelling or reduce leukotriene levels. L-651,896 (2,3-dihydro-6-[3-(2-hydroxymethyl)phenyl-2-propenyl]-5-benzofuranol), a 5-lipoxygenase inhibitor, reduced leukotriene levels but did not reduce swelling or prostaglandin levels. A combination of indomethacin and L-651,896 reduced eicosanoid levels but did not reduce swelling. These data suggested that the reduction in tissue levels of 5-lipoxygenase or cyclooxygenase oxygenation products of arachidonic acid either singularly or together did not result in the concomitant reduction of the inflammation associated with oxazolone-induced delayed hypersensitivity.

Nonsteroidal antiinflammatory agents of several subgroups, regarding eicosanoid-producing enzyme inhibition, have been tested in vitro and in vivo. There was no overt correlation between cyclooxygenase and/or lipoxygenase inhibition in vitro and antiinflammatory effects. It is possible that eicosanoids do not play a key role as inflammatory mediators, i.e. that the course of the life-protecting inflammatory reaction is ensured by an ensemble of mediators, cellular events and further mechanisms of the whole living organism.

The enzymatic oxidation of arachidonic acid has been shown to yield potent pathological agents by two major pathways. Those of the prostaglandin (PG) pathway, particularly PGE2, have been implicated as inflammatory mediators for many years. The discovery and biological activities of thromboxane A2 and prostacyclin as well as a destructive oxygen-centered radical as additional products of this biosynthetic pathway now require these to be considered as potential inflammatory mediators. Like PGE2, their biosynthesis is prevented by nonsteroidal anti-inflammatory agents. More recently, the alternative metabolic route, the lipoxygenase pathway, has been shown to yield a new class of arachidonic acid oxygenation products, called the leukotrienes, which also appear to be important inflammatory mediators. Unlike the prostaglandins, some of which play important roles as biological regulators, the actions of the lipoxygenase products appear to be exclusively of a pathological nature.

The effects of a non-steroidal anti-inflammatory compound, ibuprofen, on experimentally-induced local oedema responses in rabbit skin were investigated. The accumulation of intravenously-injected 125I-albumin was used to measure oedema. Two peptides were used to increase microvascular permeability: C5a des Arg, whose action is dependent on circulating polymorphonuclear leukocytes, and bradykinin which acts directly on vascular endothelial cells. The peptides were injected intradermally together with either arachidonic acid or PGE2 to potentiate oedema formation. To study the cyclooxygenase inhibitory activity of ibuprofen, the effects of the mediators were potentiated by addition of arachidonic acid. To investigate whether the drug had effects independent of cyclo-oxygenase inhibition, PGE2 was used to potentiate responses. Both local and intravenous ibuprofen suppressed oedema induced by bradykinin + arachidonic acid and C5a des Arg + arachidonic acid, which is consistent with suppression of cyclo-oxygenase in the skin. Local ibuprofen had no effect on responses to bradykinin + PGE2 or C5a des Arg + PGE2. Intravenous ibuprofen had no significant effect on responses to bradykinin + PGE2 but, in contrast, had a marked inhibitory effect on responses to C5a des Arg + PGE2. It is concluded that, in addition to its known cyclo-oxygenase inhibitory activity, ibuprofen can inhibit inflammatory oedema at clinically-relevant doses by an action on circulating poly-morphonuclear leukocytes. These observations in vivo appear to be related to other observations on the effects of ibuprofen on polymorphonuclear leukocyte function in vitro and ex vivo. The observations described may also relate to the protective effects of ibuprofen on experimentally-induced myocardial infarction.

The history of the use of aspirin and salicylate is briefly reviewed, as are the many putative mediators of inflammation. The theory that aspirin-like drugs bring about their antiinflammatory effects through inhibition of prostaglandin biosynthesis is presented, in the light of other arachidonic acid products such as the leukotrienes. Evidence is presented that aspirin brings about its antiinflammatory effects (at least in the rat) after its conversion into salicylate. The selective inhibition of cyclooxygenase by the large group of aspirin-like non-steroid antiinflammatory drugs explains their therapeutic activity. The elucidation of other pathways of oxidative metabolism of arachidonic acid has revealed new targets for the development of drugs with potentially greater therapeutic activity in the treatment of inflammation, cardio-thrombotic diseases and asthma.

Inflammation is caused by release of chemicals from tissues and migrating cells. Most strongly implicated are the prostaglandins (PGs), leukotrienes (LTs), histamine, bradykinin, and, more recently, platelet-activating factor (PAF) and interleukin-1. Evidence for their involvement comes from studies with competitive antagonists for their receptors and inhibitors of their synthesis. H1 histamine antagonists are effective for hay fever and some skin allergies such as urticaria, which indicates the importance of histamine in these conditions. Symptoms of rheumatoid arthritis are alleviated by the aspirinlike anti-inflammatory drugs, which inhibit the cyclo-oxygenase enzyme and reduce synthesis of prostanoids. Corticosteroids prevent the formation of both PGs and LTs by causing the release of lipocortin, which by inhibition of phospholipase A2 reduces arachidonic acid release. They suppress the inflammation of rheumatoid arthritis and asthma. Currently, high doses of nonsedating H1 antihistamines and PAF antagonists are being tested for the treatment of allergic asthma.

The subcutaneous sponge implant model of acute inflammation in the rat has been evaluated as a suitable test system for evaluating the potential anti-inflammatory efficacy of 5-lipoxygenase inhibitors. The inflammatory parameters measured were exudate volume and leukocyte recruitment. Specific radioimmunoassays were used to measure (1) 5-lipoxygenase (LPO) and cyclo-oxygenase (CO) activity in exudate leukocytes stimulated ex vivo with A23187, and (2) the LTB4 and PGE2 content of inflammatory exudate. The NSAIDs flurbiprofen and indomethacin inhibited cell recruitment, exudate volume and CO activity with ED50S of approximately 1 mg per kg p.o. but failed to inhibit LPO activity at 10 mg per kg p.o. Nafazatrom (Bayer 6575), quercetin and NDGA, which inhibit LPO activity in vitro, were inactive against all parameters when dosed at 100 mg per kg p.o. The "mixed inhibitors" BW755C and phenidone were approximately equipotent inhibitors of LPO activity but BW755C was 10 times more potent than phenidone against CO activity. BW755C was also greater than 10 times more potent at inhibiting cell recruitment and exudate volume than phenidone suggesting that the anti-inflammatory efficacy of the mixed inhibitors reflect their potency against CO rather than LPO activity. Time course studies demonstrated that the inhibitor effects of BW755C and phenidone on leukocyte recruitment reflected a reduction in the PGE2 but not the LTB4 content of the inflammatory exudate. Polyester sponges soaked in high concentrations of LTB4 caused only a modest (2-fold) increase in leukocyte recruitment whilst physiological levels were inactive. The results taken together suggest that CO products make a major contribution to leukocyte recruitment in this model whilst the LPO product LTB4 has little role. This model therefore is of little value for evaluating the anti-inflammatory efficacy of 5-lipoxygenase inhibitors. Moreover, the rat would appear to be unsuitable for evaluating the role of LTB4 in acute inflammation.

The recurrence of allergic inflammation, as examined by exudate accumulation, infiltration of polymorphonuclear leukocytes into the exudate, edema formation, vascular permeability and prostaglandin E2 levels in the exudate, was induced by injecting the antigen, azobenzene arsonate-conjugated acetyl bovine serum albumin, into the capsule of the proliferative granulation tissue which had been formed by the first-time antigenic challenge injection into an air pouch in the dorsum of the sensitized rat. The recurrence of the allergic inflammation 4 and 24 h after the antigenic challenge was inhibited dose-dependently by treatment with cyclooxygenase inhibitors, suggesting the possible participation of cyclooxygenase products, especially prostaglandin E2. The difference in the allergic inflammatory responses induced by the first-time antigenic challenge and the second-time antigenic challenge was discussed from the viewpoint of chemical mediators.

Intravital microscopy and determination of in vivo histamine release revealed that the cyclooxygenase inhibitor indomethacin reduced antigen-induced vasodilation while enhancing plasma extravasation, leukocyte accumulation, and histamine release in cheek pouches of immunized hamsters. Topical application of prostaglandin E2 (PGE2, 30 nM) totally reversed the indomethacin-induced potentiation of the inflammatory reaction to antigen challenge and suppressed both the histamine release and plasma leakage also in the absence of indomethacin. On the other hand, PGE2, which per se caused vasodilation, markedly potentiated the postcapillary leakage of plasma induced by histamine or leukotriene C4, as well as the leukocyte activation and subsequent plasma extravasation evoked by leukotriene B4. Taken together, the data indicate that PGE2 reduced the antigen response by suppression of mediator release from the numerous mast cells present in the cheek pouch. Moreover, the PGE2-sensitive potentiation by indomethacin of the antigen response suggests that endogenous vasodilating prostaglandins (possibly PGE2) predominantly were anti-inflammatory.

The mechanism of the inhibitory action of cyclooxygenase inhibitors on leukocyte accumulation in the inflammatory locus was investigated in an allergic inflammation of the air pouch types in rats. Three kinds of cyclooxygenase inhibitors, indomethacin, diclofenac and tiaprofenic acid, caused not only inhibition of the vascular permeability response and leukocyte accumulation but also elevation of histamine levels in the exudate. These effects of indomethacin were all reversed by local administration of prostaglandin E2. Pyrilamine, an H1 antagonist, did not affect the anti-inflammatory actions of indomethacin. The H2 antagonists, cimetidine, ranitidine and famotidine, decreased the inhibitory effect of indomethacin on leukocyte accumulation without affecting the inhibitory action on vascular permeability. These results indicate that the inhibitory action of cyclooxygenase inhibitors on leukocyte accumulation is derived from their blocking effect against generation of PGE2 which works as an inhibitory factor on the production of histamine in the inflammatory tissues.

The rabbit hydronephrotic kidney (HNK) is a model of renal inflammation characterized by a marked increase in arachidonic acid metabolism that is temporally associated with an inflammatory cell influx into the injured tissue. The HNK exhibits an exaggerated elaboration of eicosanoids ex vivo in response to either bradykinin or the inflammatory cell agonist n-formyl-methionyl-leucyl-phenylalanine (fMLP) compared with the unobstructed contralateral kidney. To pharmacologically manipulate inflammatory cell influx into the HNK we administered ethoxyquin (200 mg/kg p.o.), a combined cyclooxygenase/lipoxygenase inhibitor, RS-5186 (10 mg/kg p.o.), a thromboxane synthase inhibitor or L-659,989 (5 mg/kg p.o.), a platelet activating factor antagonist, before and at various times during the development of hydronephrosis. Only ethoxyquin reduced inflammatory cell influx into the HNK and thereby prevented the enhancement of microsomal cyclooxygenase activity and attenuated the elaboration of eicosanoids ex vivo. Collectively, these results suggest a primary role of an eicosanoid, possibly leukotriene B4, but not thromboxane A2 or the chemotactic phospholipid, platelet activating factor, as a mediator of inflammatory cell influx resulting from ureter obstruction.

Administration of carrageenin or adjuvant to rats to induce inflammation produced increases in the plasma haptoglobin level. Simultaneously, there was an increase in the activity of the plasma inhibitor of prostaglandin E2 synthesis. Partially purified haptoglobin inhibited the microsomal over-all conversion of arachidonic acid to prostaglandin E2. The addition of the haptoglobin inhibited two heme-dependent reactions catalyzed by a purified enzyme of seminal vesicle microsome, i.e., the prostaglandin G2 synthesis from arachidonic acid and the conversion of prostaglandin G2 to H2. However, the plasma inhibitory activity was accounted for only partially by the haptoglobin contained in the plasma from treated rats.

Inflammation is an essential body immune system response against various infections and tissue injuries and maintains normal homeostasis. Alterations in inflammatory responses lead to multiple disorders like heart diseases, obesity, diabetes, cancer, stroke, and neurodegenerative disorders. Cyclooxygenases (COXs), the enzymes, exist in two isoforms (COX‐1 and COX‐2) that catalyze the rate‐determining step of prostaglandin biogenesis and play a significant role in inflammation. COX‐2 inhibitors, although effective anti‐inflammatory agents are considered to be highly unsafe for long‐term usage due to their possible side and adversative effects. Recently, fused‐thienopyrimidines have emerged as a privileged scaffold with excellent anti‐inflammatory potential. In the present review, we have emphasized the recent developments in the design and synthetic strategies of fused‐thienopyrimidine derivatives and their detailed structure‐activity‐relationship (SAR) studies. The primary goal of this review is to provide restructuring knowledge about this template, which could prove beneficial and valuable for chemists working in the anti‐inflammatory area. [ABSTRACT FROM AUTHOR]

Background: NSAIDs are well-established for treating pain, fever, and inflammation mainly by inhibiting inducible Cyclooxygenase 2 (COX-2) isoenzyme. However, most of the marketed NSAIDs non-selectively inhibit physiological COX-1 and exhibit adverse side effects like GI ulcers, renal toxicity, and platelet disorder. Moreover, cardiac side effects also led to the market withdrawal of some of the potential selective COX-2 inhibitors. Thus, several investigations are underway by researchers from academia and industry in search of safer and more effective COX-2 selective inhibitors devoid of existing side effects. Materials and Methods: In this work, four 2-substituted-5,6-dimethylthieno[2,3-d]pyrimidin-4(3H)-one derivatives (5,6,7,8 and 9) have been synthesized, purified, and characterized based on their physical and spectral data. These compounds were evaluated (in vitro) for their affinity and selectivity for human COX-2 enzyme against COX-1 isoenzyme using indomethacin as a positive control. Results and Discussion: Compound 5 with para fluorophenyl substituent was found to be the most potent, exhibiting better inhibition and selectivity towards COX-2 isoenzyme (IC50=42.19 M, SI=4.81) against COX-1 isoenzyme (IC50=202.96 M, SI=4.81) as compared to the other derivatives (6-8). Conclusion: The activity of compound 5 is promising compared to the non-selective drug indomethacin (IC50 COX-1=0.68 M, COX-2=18.3 M, SI=0.04). Therefore, compound 8 can be considered a lead molecule for further optimization to develop novel selective COX-2 inhibitors at nanomolar potency. [ABSTRACT FROM AUTHOR]

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Nonsteroidal anti‐inflammatory drugs (NSAIDs) inhibit the enzyme cyclooxygenase (COX), which forms prostaglandins involved in pain and inflammation. COX inhibitors have analgesic and anti‐inflammatory effects, but also increase risks for gastrointestinal ulcers, bleeding, and renal and cardiovascular adverse events. Identification of two isoforms of COX, COX‐1 and COX‐2, led to the development of selective COX‐2 inhibitors, which were launched as having fewer gastrointestinal side effects since gastroprotective prostaglandins produced via COX‐1 are spared. The balance between COX‐1 mediated prothrombotic thromboxane and COX‐2 mediated antithrombotic prostacyclin is important for thrombotic risk. An increased risk of suffering myocardial infarction and death with COX‐2 inhibitor treatment is well established from clinical trials and observational research. Rofecoxib (Vioxx) was withdrawn from the market for this reason, but the equally COX‐2 selective etoricoxib has replaced it in Europe but not in the United States. The "traditional" NSAID diclofenac is as COX‐2 selective as celecoxib and increases cardiovascular risk dose dependently. COX inhibitor dosages should be lower in osteoarthritis than in rheumatoid arthritis. Randomized trials comparing COX‐2 inhibitors with NSAIDs have exaggerated their gastrointestinal benefits by using maximal NSAID doses regardless of indication, and/or hidden the cardiovascular risk by comparing with COX‐2 selective diclofenac instead of low‐dose ibuprofen or naproxen. Observational studies show increased cardiovascular risks within weeks of treatment with COX‐2 inhibitors and high doses of NSAIDs other than naproxen, which is the safest alternative. COX inhibitors are symptomatic drugs that should be used intermittently at the lowest effective dosage, especially among individuals with an increased cardiovascular risk. [ABSTRACT FROM AUTHOR]

The cyclooxygenases COX-1 and COX-2 oxygenate arachidonic acid (AA) to prostaglandin H2 (PGH2). COX-2 also oxygenates the endocannabinoids 2-arachidonoylglycerol (2-AG) and arachidonoylethanolamide (AEA) to the corresponding PGH2 analogs. Both enzymes are targets of nonsteroidal anti-inflammatory drugs (NSAIDs), but NSAID-mediated COX inhibition is associated with gastrointestinal toxicity. One potential strategy to counter this toxicity is to also inhibit fatty acid amide hydrolase (FAAH), which hydrolyzes bioactive fatty acid ethanolamides (FAEs) into fatty acids and ethanolamine. Here, we investigated the mechanism of COX inhibition by ARN2508, an NSAID that inhibits both COXs and FAAH with high potency, target selectivity, and decreased gastrointestinal toxicity in mouse models, presumably due to its ability to increase levels of FAEs. A 2.27-Å-resolution X-ray crystal structure of the COX-2·(S)-ARN2508 complex reveals that ARN2508 adopts a binding pose similar to that of its parent NSAID flurbiprofen. However, ARN2508's alkyl tail is inserted deep into the top channel, an active site region not exploited by any previously reported NSAID. As for flurbiprofen, ARN2508's potency is highly dependent on the configuration of the α-methyl group. Thus, (S)-ARN2508 is more potent than (R)-ARN2508 for inhibition of AA oxygenation by both COXs and 2-AG oxygenation by COX-2. Also, similarly to (R)-flurbiprofen, (R)-ARN2508 exhibits substrate selectivity for inhibition of 2-AG oxygenation. Site-directed mutagenesis confirms the importance of insertion of the alkyl tail into the top channel for (S)-ARN2508's potency and suggests a role for Ser-530 as a determinant of the inhibitor's slow rate of inhibition compared with that of (S)-flurbiprofen.

Cyclooxygenase inhibitors are widely used in prescription. They are the choice of drugs worldwide. The drug naproxen, which is a propionic acid nonselective cyclooxygenase inhibitor, is still preferred in arthritis, osteoarthritis and gout. The drawback associated with this drug is that it causes nausea, vomiting or gastrointestinal upsets. The cause of gastrointestinal upset may be due to perforation of gastric mucosa or ulceration. To overcome this problem, this is associated with the free carboxylic group present on naproxen. Here the parent drug is modified using glycolic acid precursors with phytophenols. The phytophenols are known for their antioxidant properties and they also reduce ulceration. The glycolic acid spacer provides a single bond rotation that promotes excellent binding with the receptor. The different derivatives of naproxen were designed and screened by computational technique based on virtual screening against human cyclooxygenase-2 enzyme through Auto Dock. The identified derivatives were curtained through Lipinski’s rule of pharmacokinetics. The effective and innocuous molecule was identified. The identified derivative was synthesized, purified, characterized and pharmacological studies were done. The result obtained clearly indicating that there is a depiction in molecular docking and pharmacological studies. [ABSTRACT FROM AUTHOR]

The presence of AML1-ETO (RUNX1-CBF2T1), a fusion oncoprotein resulting from a t(8;21) chromosomal translocation, has been implicated as a necessary but insufficient event in the development of a subset of acute myeloid leukemias (AML). While AML1-ETO prolongs survival and inhibits differentiation of hematopoietic stem cells (HSC), other contributory events are needed for cell proliferation and leukemogenesis. We have postulated that specific tumor suppressor genes keep the leukemic potential of AML1-ETO in check. In studying del(9q), one of the most common concomitant chromosomal abnormalities with t(8;21), we identified the loss of an apparent tumor suppressor, TLE4, that appears to cooperate with AML1-ETO to confer a leukemic phenotype. This study sought to identify the molecular basis of this cooperation. We show that the loss of TLE4 confers proliferative advantage to leukemic cells, simultaneous with an upregulation of a pro- inflammatory signature mediated through aberrant increases in Wnt signaling activity. We further demonstrate that inhibition of cyclooxygenase (COX) activity partly reverses the pro-leukemic phenotype due to TLE4 knockdown, pointing towards a novel therapeutic approach for myeloid leukemia.

Non-steroidal anti-inflammatory drugs (NSAIDs) exert their pharmacological effects by inhibiting cyclooxygenase (COX)-1 and COX-2. Though widely prescribed for pain and inflammation, these agents have limited utility in chronic diseases due to serious mechanism-based adverse events such as gastrointestinal damage. Concomitant blockade of fatty acid amide hydrolase (FAAH) enhances the therapeutic effects of the NSAIDs while attenuating their propensity to cause gastrointestinal injury. This favorable interaction is attributed to the accumulation of protective FAAH substrates, such as the endocannabinoid anandamide, and suggests that agents simultaneously targeting COX and FAAH might provide an innovative strategy to combat pain and inflammation with reduced side effects. Here, we describe the rational design and structure-active relationship (SAR) properties of the first class of potent multitarget FAAH-COX inhibitors. A focused SAR exploration around the prototype 10r (ARN2508) led to the identification of achiral (18b) as well as racemic (29a-c and 29e) analogs. Absolute configurational assignment and pharmacological evaluation of single enantiomers of 10r are also presented. (S)-(+)-10r is the first highly potent and selective chiral inhibitor of FAAH-COX with marked in vivo activity, and represents a promising lead to discover novel analgesics and anti-inflammatory drugs.

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