Role of prostaglandin H synthase-2 in prostaglandin E2 formation in rat carrageenin-induced pleurisy

Phytoprostanes and phytofurans modulate COX-2-linked inflammation markers in LPS-stimulated THP-1 monocytes by lipidomics workflow

Inflammation is a fundamental pathophysiological process which occurs in the course of several diseases. The present work describes the capacity of phytoprostanes (PhytoPs) and phytofurans (PhytoFs) (plant oxylipins), present in plant-based foods, to modulate inflammatory processes mediated by prostaglandins (PGs, human oxylipins) in lipopolysaccharide (LPS)-stimulated THP-1 monocytic cells, through a panel of 21 PGs and PG's metabolites, analyzed by UHPLC-QqQ-ESI-MS/MS. Also, the assessment of the cytotoxicity of PhytoPs and PhytoFs on THP-1 cells evidenced percentages of cell viability higher than 90% when treated with up to 100 μM. Accordingly, 50 μM of the individual PhytoPs and PhytoFs 9-F_1t-PhytoP, 9-epi-9-F_1t-PhytoP, ent-16-F_1t-PhytoP, ent-16-epi-16-F_1t-PhytoP, ent-9-D_1t-PhytoP, 16-B₁-PhytoP, 9-L₁-PhytoP, ent-16(RS)-9-epi-ST-Δ¹⁴-10-PhytoF, ent-9(RS)-12-epi-ST-Δ¹⁰-13-PhytoF, and ent-16(RS)-13-epi-ST-Δ¹⁴-9-PhytoF were evaluated on their capacity to modulate the expression of inflammatory markers. The results obtained demonstrated the presence of 7 metabolites (15-keto-PGF_2α, PGF_2α, 11β-PGF_2α, PGE₂, PGD₂, PGDM, and PGF_1α) in THP-1 monocytic cells, which expression was significantly modulated when exposed to LPS. The evaluation of the capacity of the individual PhytoPs and PhytoFs to revert the modification of the quantitative profile of PGs induced by LPS revealed the anti-inflammatory ability of 9-F_1t-PhytoP, ent-9-D_1t-PhytoP, 16-B₁-PhytoP, 9-L₁-PhytoP, and ent-9(RS)-12-epi-ST-Δ¹⁰-13-PhytoF, as evidenced by their capacity to prevent the up-regulation of 15-keto-PGF_2α, PGF_2α, PGE₂, PGF_1α, PGDM, and PGD₂ induced by LPS. These results indicated that specific plant oxylipins can protect against inflammatory events, encouraging further investigations using plant-based foods rich in these oxylipins or enriched extracts, to identify specific bioactivities of the diverse individual molecules, which can be useful for nutrition and health in the frame of well-defined pathophysiological processes.

Inflammation and JNK's Role in Niacin-GPR109A Diminished Flushed Effect in Microglial and Neuronal Cells With Relevance to Schizophrenia

Schizophrenia is a neuropsychiatric illness with no single definitive aetiology, making its treatment difficult. Antipsychotics are not fully effective because they treat psychosis rather than the cognitive or negative symptoms. Antipsychotics fail to alleviate symptoms when patients enter the chronic stage of illness. Topical application of niacin showed diminished skin flush in the majority of patients with schizophrenia compared to the general population who showed flushing. The niacin skin flush test is useful for identifying patients with schizophrenia at their ultra-high-risk stage, and understanding this pathology may introduce an effective treatment. This review aims to understand the pathology behind the diminished skin flush response, while linking it back to neurons and microglia. First, it suggests that there are altered proteins in the GPR109A-COX-prostaglandin pathway, inflammatory imbalance, and kinase signalling pathway, c-Jun N-terminal kinase (JNK), which are associated with diminished flush. Second, genes from the GPR109A-COX-prostaglandin pathway were matched against the 128-loci genome wide association study (GWAS) for schizophrenia using GeneCards, suggesting that G-coupled receptor-109A (GPR109A) may have a genetic mutation, resulting in diminished flush. This review also suggests that there may be increased pro-inflammatory mediators in the GPR109A-COX-prostaglandin pathway, which contributes to the diminished flush pathology. Increased levels of pro-inflammatory markers may induce microglial-activated neuronal death. Lastly, this review explores the role of JNK on pro-inflammatory mediators, proteins in the GPR109A-COX-prostaglandin pathway, microglial activation, and neuronal death. Inhibiting JNK may reverse the changes observed in the diminished flush response, which might make it a good therapeutic target.

Ischaemia–Reperfusion Injury in the Isolated Haemoperfused Bovine Uterus: An In Vitro Model of Acute Inflammation

Following on from previous studies on dermal inflammation in the isolated perfused bovine udder, a new in vitro model of the isolated haemoperfused bovine uterus was established for studies on acute inflammatory reactions (for example, eicosanoid synthesis and regulation of cyclooxygenase-1 [COX-1] and COX-2) caused by ischaemia-reperfusion (I-R) injury. The organs and blood used in this study were obtained from a slaughterhouse. Within 2 hours of slaughter, uterine perfusion was re-established, by using a mixture of homologous blood and Tyrode solution (4:1). After equilibration, several deposits of arachidonic acid (5 mg and 0.1 mg) and arachidonylethanolamide (0.1 mg) were injected into the myometrial tissue. Tissue biopsies were taken from treated and untreated areas at 180 and 300 minutes after the onset of haemoperfusion, for measuring prostaglandin E(2) (PGE(2)) levels. In addition, the regulation of COX-1 and COX-2 mRNA was investigated by using the reverse transcriptase-polymerase chain reaction. Eicosanoid levels were determined by using an enzyme immunoassay (ELISA). Because both an increase in PGE(2) concentration and up-regulation of COX mRNA were observed, the inhibitory effects of dexamethasone, added to the perfusion medium, were studied. Dexamethasone caused a significant decrease in tissue PGE(2) production, but did not induce down-regulation of COX-2 mRNA. In conclusion, the isolated haemoperfused bovine uterus was introduced as an in vitro model of acute inflammation, induced by I-R injury. The suitability of the model for investigating anti-inflammatory substances was demonstrated. Use of the isolated haemoperfused bovine uterus in pharmacological research and drug screening may contribute to reducing the number of animals used for testing.

Effects of nimesulide, a selective COX-2 inhibitor, on cardiovascular function in 2 rat models of diabetes

Cyclooxygenase-2 (COX-2) has been found to be activated in diabetes. We investigated whether nimesulide (selective COX-2 inhibitor) alters cardiovascular responses to adrenaline in 2 rat models of diabetes. Wistar rats (5-week old) were continuously fed a normal or high-fructose diet (60% of caloric intake). At week 2, half of the rats in each diet regimen were given streptozotocin (STZ) (60 mg/kg, intravenously). At week 6, cardiovascular effects of adrenaline (6 and 16 × 10 mol·kg·min, intravenously) were measured in 4 groups of thiobutabarbital-anesthetized rats (control, fructose, STZ, and fructose-streptozotocin [F-STZ]) before and after the injection of nimesulide (3 mg/kg, intravenously). Both the STZ and F-STZ groups exhibited hyperglycemia and significantly (P < 0.05) reduced left ventricular contractility, mean arterial pressure, arterial and venous resistance, and mean circulatory filling pressure (index of venous tone) responses to adrenaline, relative to the control and fructose groups. Nimesulide did not affect responses in the control and fructose groups but increased the venous and, to a less extent, arterial constriction to adrenaline in both the groups of diabetic rats. The cardiac contractile responses, however, were not altered after nimesulide treatment. The results show that nimesulide partially restored arterial and venous constriction to adrenaline in rats with STZ- and F-STZ-induced diabetes.

Role of a histamine 4 receptor as an anti-inflammatory target in carrageenan-induced pleurisy in mice

The histamine 4 receptor (H4R) is expressed primarily on cells involved in inflammation and immune responses. Despite much research into inflammatory diseases, no drugs with favourable safety profiles are yet available for their treatment. The aim of the present study was to determine the potential anti-inflammatory effect of 4-methylhistamine (4-MeH) or JNJ77777120 (JNJ) and to explore the role of H4R in a mouse model of carrageenan (Cg) -induced pleurisy. A single dose of 4-MeH or JNJ (30 mg/kg) was administered intraperitoneally 1 hr before Cg administration. The results illustrate that both the numbers of CD4(+) , CD25(+) , CD4(+)  CD25(+) , GITR(+) , GITR(+)  IL-17A(+) -expressing T cells and the levels of T helper type 1 (Th1)/Th17 cytokines were markedly increased in both the Cg-treated and 4-MeH-treated groups, whereas the cytokines produced by Th2 cells were significantly decreased in the same groups. However, JNJ treatment significantly decreased both the number of T-cell subsets and GITR(+) , GITR(+)  IL-17A(+) -expressing T cells, and the production of Th1/Th17 cytokines. Further, JNJ up-regulated the expression of the Th2 cytokines. RT-PCR analysis revealed an increased expression of interleukin-1β, tumour necrosis factor-α, monocyte chemoattractant protein-1 and intercellular adhesion molecule-1 in the Cg-treated and 4-MeH-treated groups, which was reduced by treatment with JNJ in lung tissues. Moreover, histological examinations revealed anti-inflammatory effects of JNJ, whereas 4-MeH worsened Cg-induced inflammation. In conclusion, the results of the present work clearly indicate that JNJ possesses important anti-inflammatory properties that are increased in 4-MeH-treated mice, suggesting that H4R are involved in pleurisy and that JNJ has an anti-inflammatory effect in associated disease conditions.

Why do a wide variety of animals retain multiple isoforms of cyclooxygenase?

Cyclooxygenase (COX) has been cloned from the phyla Cnidaria, Mollusca, Arthropoda, and Chordata of the animal kingdom. Many organisms have multiple COX isoforms that have arisen from gene duplication. It is not well understood why there are multiple COX isoforms in the same organism, or when duplication of the COX gene occurred. Here, we summarize the current knowledge of the evolutionary history of COX in the animal kingdom and discuss the reasons why the multiple COX system has been retained so widely. The phylogenetic analysis suggests that all COX genes in animals may descend from a common ancestor and that the duplication of an ancestral COX gene might occur within each lineage after the divergence of the animal. In most instances, the expressions of multiple COX isoforms are separately regulated and these isoforms play different and important pathophysiological roles in each organism. This may be the reason why multiple COX isoforms are widely retained.

COX-2 expression in stromal fibroblasts self-limits their numbers in lymph node inflammatory responses

We previously reported the expression of cyclooxygenase (COX)-2 in draining lymph nodes during carrageenin-induced pleurisy of rats. Here, we analyzed histological and immunohistochemical characteristics of COX-2-expressing cells. After carrageenin administration into the pleural cavity of rats, parathymic lymph nodes were enlarged beginning at 8h and peaking from 24 to 48h. Lymphatic follicles disappeared 16h after injection, and numerous macrophages and fibroblasts were observed in the cortical region. COX-2-expressing cells in the cortical region showed characteristic dendritic processes from 16 to 48h and primarily co-localized with stromal fibroblastic reticular cell markers, α-smooth muscle actin (α-SMA), and desmin. Expression of α-SMA increased following COX-2 expression. Nimesulide, a COX-2 inhibitor, increased the dendritic processes of COX-2-expressing cells as well as expression of both COX-2 and α-SMA. These results suggest that COX-2-expressing cells may be stromal fibroblastic cells, which negatively self-regulate their proliferation and modulate tissue remodeling of draining lymph nodes at inflammatory sites.

Integrated analysis of COX-2 and iNOS derived inflammatory mediators in LPS-stimulated RAW macrophages pre-exposed to Echium plantagineum L. bee pollen extract

Oxidative stress and inflammation play important roles in disease development. This study intended to evaluate the anti-inflammatory and antioxidant potential of Echium plantagineum L. bee pollen to support its claimed health beneficial effects. The hydromethanol extract efficiently scavenged nitric oxide (^•NO) although against superoxide (O₂^•−) it behaved as antioxidant at lower concentrations and as pro-oxidant at higher concentrations. The anti-inflammatory potential was evaluated in LPS-stimulated macrophages. The levels of ^•NO and L-citrulline decreased for all extract concentrations tested, while the levels of prostaglandins, their metabolites and isoprostanes, evaluated by UPLC-MS, decreased with low extract concentrations. So, E. plantagineum bee pollen extract can exert anti-inflammatory activity by reducing ^•NO and prostaglandins. The extract is able to scavenge the reactive species ^•NO and O₂^•− and reduce markers of oxidative stress in cells at low concentrations.

Inhibitory effect of anethole in nonimmune acute inflammation

Anethole [1-methoxy-4-(1-propenyl)benzene] occurs naturally as a major component of the essential oil of star anise (Illicium verum Hook.f., family Illiciaceae), comprising more than 90 % of its volatile components. Studies showed that this substance has antioxidant, antibacterial, antifungal, and anesthetic properties. In this study, the anti-inflammatory properties of anethole in animal models of nonimmune acute inflammation such as croton oil-induced ear edema and carrageenan-induced pleurisy were investigated. The investigated parameters were edema formation, leukocyte migration, and inflammatory mediators involved. Oral administration of anethole at a dose of 250 and 500 mg/kg reduced both the volume of pleural exudates and the number of migrated leukocytes. Levels of nitric oxide (NO) and prostaglandins (PGE2) in the inflammatory exudate were reduced by treatment with anethole, but levels of tumor necrosis factor-α and interleukin-1β were not significantly altered. In ear edema, the oral treatment with anethole inhibited the formation of exudate and the activity of myeloperoxidase, but not after topical administration. These results suggest that the anethole may be effective in controlling some nonimmune acute inflammation-related disease, probably by an inhibitory action on production and/or release of PGE2 and NO.

Evaluation of soybean methanol fraction on acute inflammation

Soybeans have been of interest of researchers because of the presence of isoflavones, a subclass of flavonoids, which have demonstrated anti-inflammatory activity. The aim of this study was investigate the anti-inflammatory activity of the methanol fraction from soybean, which contains mainly isoflavone glucosides and malonylglucosides. The anti-inflammatory activity of the methanol fraction from soybean was studied using croton oil-induced mouse ear edema and carrageenan-induced pleurisy models. The methanol fraction inhibited the ear edema in a dose-dependent manner: 0.625 mg/kg by 44.23% (P<.05), 1.25 mg/kg by 60.68% (P<.01), and 2.5 mg/kg by 65.68% (P<.01). Myeloperoxidase enzyme activity was reduced at the dose of 2.5 mg/kg (64.79%, P<.05). No effects were seen on carrageenan-induced pleurisy at different doses of the methanol fraction (100 or 400 mg/kg). These results demonstrated that the methanol fraction containing conjugated isoflavones showed topical anti-inflammatory activity. There was no acute toxicity in Swiss mice after oral administration of the fraction, at doses of 1,000, 2,000, 3,000, and 4,000 mg/kg.

Hyperforin, an Anti-Inflammatory Constituent from St. John's Wort, Inhibits Microsomal Prostaglandin E(2) Synthase-1 and Suppresses Prostaglandin E(2) Formation in vivo

The acylphloroglucinol hyperforin (Hyp) from St. John's wort possesses anti-inflammatory and anti-carcinogenic properties which were ascribed among others to the inhibition of 5-lipoxygenase. Here, we investigated whether Hyp also interferes with prostanoid generation in biological systems, particularly with key enzymes participating in prostaglandin (PG)E₂ biosynthesis, i.e., cyclooxygenases (COX)-1/2 and microsomal PGE₂ synthase (mPGES)-1 which play key roles in inflammation and tumorigenesis. Similar to the mPGES-1 inhibitors MK-886 and MD-52, Hyp significantly suppressed PGE₂ formation in whole blood assays starting at 0.03–1 μM, whereas the concomitant generation of COX-derived 12(S)-hydroxy-5-cis-8,10-trans-heptadecatrienoic acid, thromboxane B₂, and 6-keto PGF_1α was not significantly suppressed up to 30 μM. In cell-free assays, Hyp efficiently blocked the conversion of PGH₂ to PGE₂ mediated by mPGES-1 (IC₅₀ = 1 μM), and isolated COX enzymes were not (COX-2) or hardly (COX-1) suppressed. Intraperitoneal (i.p.) administration of Hyp (4 mg kg⁻¹) to rats impaired exudate volume and leukocyte numbers in carrageenan-induced pleurisy associated with reduced PGE₂ levels, and Hyp (given i.p.) inhibited carrageenan-induced mouse paw edema formation (ED₅₀ = 1 mg kg⁻¹) being superior over indomethacin (ED₅₀ = 5 mg kg⁻¹). We conclude that the suppression of PGE₂ biosynthesis in vitro and in vivo by acting on mPGES-1 critically contributes to the anti-inflammatory efficiency of Hyp.

Effect of plant neutrophil elastase inhibitor on leucocyte migration, adhesion and cytokine release in inflammatory conditions

BACKGROUND AND PURPOSE

The serine and cysteine peptidase inhibitor, BbCI, isolated from Bauhinia bauhinioides seeds, is similar to the classical plant Kunitz inhibitor, STI, but lacks disulphide bridges and methionine residues. BbCI blocks activity of the serine peptidases, elastase (K(iapp) 5.3 nM) and cathepsin G (K(iapp) 160.0 nM), and the cysteine peptidase cathepsin L (K(iapp) 0.2 nM). These three peptidases play important roles in the inflammatory process.

EXPERIMENTAL APPROACH

We measured the effects of BbCI on paw oedema and on leucocyte accumulation in pleurisy, both induced by carrageenan. Leucocyte-endothelial cell interactions in scrotal microvasculature in Wistar rats were investigated using intravital microscopy. Cytokine levels in pleural exudate and serum were measured by elisa.

KEY RESULTS

Pretreatment of the animals with BbCI (2.5 mg·kg(-1)), 30 min before carrageenan-induced inflammation, effectively reduced paw oedema and bradykinin release, neutrophil migration into the pleural cavity. The number of rolling, adhered and migrated leucocytes at the spermatic fascia microcirculation following carrageenan injection into the scrotum were reduced by BbCI pretreatment. Furthermore, levels of the rat chemokine cytokine-induced neutrophil chemo-attractant-1 were significantly reduced in both pleural exudates and serum from animals pretreated with BbCI. Levels of interleukin-1β or tumour necrosis factor-α, however, did not change.

CONCLUSIONS AND IMPLICATIONS

Taken together, our data suggest that the anti-inflammatory properties of BbCI may be useful in investigations of other pathological processes in which human neutrophil elastase, cathepsin G and cathepsin L play important roles.

Anti-inflammatory effects of low molecular weight heparin derivative in a rat model of carrageenan-induced pleurisy

Low molecular weight heparin derivatives are characterized by low anti-coagulant activity and marked anti-inflammatory effects that allow for these molecules to be viewed as a new class of non-steroidal anti-inflammatory drugs (NSAIDs). We show here that K5NOSepiLMW, an O-sulphated heparin-like semi-synthetic polymer of the D-glucuronic acid-N-acetyleparoson disaccharide unit with low molecular weight, has marked anti-inflammatory effects in a rat model of acute inflammation, the carrageenan-induced pleurisy, commonly used to test NSAID efficacy. A 30-min. pre-treatment with K5NOSepiLMW (0.1, 0.5 and 1 mg/kg b.wt., given intrapleurally) attenuated the recruitment of leucocytes in the lung tissue and the pleural exudate, inhibited the induction of inducible nitric oxide synthase and cyclooxygenase-2 (COX-2), thereby abating the generation of nitric oxide and pro-inflammatory prostaglandins such as PgE(2) and PGF(1alpha), reduced the inflammation-induced nitroxidative lung tissue injury, as shown by tissue thiobarbituric acid-reactive substances and nitrotyrosine, and blunted the local generation of cytokines such as interleukin-1beta and tumour necrosis factor-alpha. All these parameters were markedly increased by intrapleural carrageenan in the absence of any pre-treatment. The anti-inflammatory action of K5NOSepiLMW is specific, as judged by the lack of therapeutic effects of B4/110, a biologically inactive cognate polysaccharide, given in the place of the authentic molecule. Moreover, K5NOSepiLMW showed similar effects as celecoxib (1 mg/kg b.wt), a COX-2 inhibitor and well-known NSAID. This study provides further insight into the mechanisms underlying the beneficial effects of heparin derivatives in inflammation and identifies K5NOSepiLMW as a novel, promising anti-inflammatory drug.

Anti-inflammatory effects of low molecular weight heparin derivative in a rat model of carrageenan-induced pleurisy

Low molecular weight heparin derivatives are characterized by low anti-coagulant activity and marked anti-inflammatory effects that allow for these molecules to be viewed as a new class of non-steroidal anti-inflammatory drugs (NSAIDs). We show here that K5NOSepiLMW, an O-sulphated heparin-like semi-synthetic polymer of the D-glucuronic acid-N-acetyleparoson disaccharide unit with low molecular weight, has marked anti-inflammatory effects in a rat model of acute inflammation, the carrageenan-induced pleurisy, commonly used to test NSAID efficacy. A 30-min. pre-treatment with K5NOSepiLMW (0.1, 0.5 and 1 mg/kg b.wt., given intrapleurally) attenuated the recruitment of leucocytes in the lung tissue and the pleural exudate, inhibited the induction of inducible nitric oxide synthase and cyclooxygenase-2 (COX-2), thereby abating the generation of nitric oxide and pro-inflammatory prostaglandins such as PgE(2) and PGF(1alpha), reduced the inflammation-induced nitroxidative lung tissue injury, as shown by tissue thiobarbituric acid-reactive substances and nitrotyrosine, and blunted the local generation of cytokines such as interleukin-1beta and tumour necrosis factor-alpha. All these parameters were markedly increased by intrapleural carrageenan in the absence of any pre-treatment. The anti-inflammatory action of K5NOSepiLMW is specific, as judged by the lack of therapeutic effects of B4/110, a biologically inactive cognate polysaccharide, given in the place of the authentic molecule. Moreover, K5NOSepiLMW showed similar effects as celecoxib (1 mg/kg b.wt), a COX-2 inhibitor and well-known NSAID. This study provides further insight into the mechanisms underlying the beneficial effects of heparin derivatives in inflammation and identifies K5NOSepiLMW as a novel, promising anti-inflammatory drug.

Contribution of the prostaglandin E2/E-prostanoid 2 receptor signaling pathway in abscess formation in rat zymosan-induced pleurisy

Abscess formation is a classic host response to infection by many pathogenic microorganisms. Here, we studied the role of prostaglandins (PGs) and their signal transduction in abscess formation. Zymosan was injected into the pleural cavity of rats. Expression of enzymes involved in PG synthesis, their receptors, and cytokines in exudate leukocytes and abscesses were analyzed by polymerase chain reaction, Western blotting, and immunohistochemistry. Treatment with ketorolac, a cyclooxygenase (COX)-1 inhibitor, or N-[2-cyclohexyloxy-4-nitrophenyl] methanesulfonamide (NS-398), a COX-2 inhibitor, reduced the size of abscesses and the number of cells recovered from the abscess. COX-2 was detected in leukocytes of the exudate and a marginal area of abscesses. Among detected terminal PG synthases, the major one was cytosolic PGE synthase. Membrane-bound PGE synthase (mPGES)-1 was detected in cells that were similar to the COX-2-expressing cells in morphology and localization. A high level of the E-prostanoid (EP)(2) receptor and a low level of the EP(4) receptor were detected. The expression pattern of the EP(2) receptor paralleled that of COX-2 and mPGES-1. 11,15-O-Dimethyl PGE(2) (ONO-AE1-259), an EP(2) receptor agonist, and rolipram, a phosphodiesterase type-4 inhibitor, reversed the effects of COX inhibitors on abscess formation. In contrast, 16-(3-methoxymethyl) phenyl-omega-tetranor-3,7-dithia PGE(1) (ONO-AE1-329), an EP(4) receptor agonist, did not reverse the effects of NS-398. Moreover, NS-398 reduced the mRNA levels in exudate leukocytes of some proinflammatory and fibrogenic cytokines, which was reversed by ONO-AE1-259. These results suggest that PGE(2) generated via COX-1 and COX-2 may interact with the EP(2) receptor and may up-regulate in cAMP-dependent fashion the production of cytokines that promote abscess formation.

Myrtucommulone from Myrtus communis exhibits potent anti-inflammatory effectiveness in vivo

Myrtucommulone (MC), a nonprenylated acylphloroglucinol contained in the leaves of myrtle (Myrtus communis), has been reported to suppress the biosynthesis of eicosanoids by inhibition of 5-lipoxygenase and cyclooxygenase-1 in vitro and to inhibit the release of elastase and the formation of reactive oxygen species in activated polymorphonuclear leukocytes. Here, in view of the ability of MC to suppress typical proinflammatory cellular responses in vitro, we have investigated the effects of MC in in vivo models of inflammation. MC was administered to mice intraperitoneally, and paw edema and pleurisy were induced by the subplantar and intrapleural injection of carrageenan, respectively. MC (0.5, 1.5, and 4.5 mg/kg i.p.) reduced the development of mouse carrageenan-induced paw edema in a dose-dependent manner. Moreover, MC (4.5 mg/kg i.p. 30 min before and after carrageenan) exerted anti-inflammatory effects in the pleurisy model. In particular, 4 h after carrageenan injection in the pleurisy model, MC reduced: 1) the exudate volume and leukocyte numbers; 2) lung injury (histological analysis) and neutrophil infiltration (myeloperoxidase activity); 3) the lung intercellular adhesion molecule-1 and P-selectin immunohistochemical localization; 4) the cytokine levels (tumor necrosis factor-alpha and interleukin-1beta) in the pleural exudate and their immunohistochemical localization in the lung; 5) the leukotriene B(4), but not prostaglandin E(2), levels in the pleural exudates; and 6) lung peroxidation (thiobarbituric acid-reactant substance) and nitrotyrosine and poly (ADP-ribose) immunostaining. In conclusion, our results demonstrate that MC exerts potent anti-inflammatory effects in vivo and offer a novel therapeutic approach for the management of acute inflammation.

Role of the cyclooxygenase 2-thromboxane pathway in 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced decrease in mesencephalic vein blood flow in the zebrafish embryo

Previously, we reported that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) evoked developmental toxicity required activation of aryl hydrocarbon receptor type 2 (AHR2), using zebrafish embryos. However, the downstream molecular targets of AHR2 activation are largely unknown and are the focus of the present investigation. TCDD induces cyclooxygenase 2 (COX2), a rate-limiting enzyme for prostaglandin synthesis in certain cells. In the present study, we investigated the role of the COX2-thromboxane pathway in causing a specific endpoint of TCDD developmental toxicity in the zebrafish embryo, namely, a decrease in regional blood flow in the dorsal midbrain. It was found that the TCDD-induced reduction in mesencephalic vein blood flow was markedly inhibited by selective COX2 inhibitors, NS-398 and SC-236, and by a general COX inhibitor, indomethacin, but not by a selective COX1 inhibitor, SC-560. Gene knock-down of COX2 by two different types of morpholino antisense oligonucleotides, but not by their negative homologs, also protected the zebrafish embryos from mesencephalic vein circulation failure caused by TCDD. This inhibitory effect of TCDD on regional blood flow in the dorsal midbrain was also blocked by selective antagonists of the thromboxane receptor (TP). Treatment of control zebrafish embryos with a TP agonist also caused a reduction in mesencephalic vein blood flow and it too was blocked by a TP antagonist, without any effect on trunk circulation. Finally, gene knock-down of thromboxane A synthase 1 (TBXS) with morpholinos but not by the morpholinos' negative homologs provided significant protection against TCDD-induced mesencephalic circulation failure. Taken together, these results point to a role of the prostanoid synthesis pathway via COX2-TBXS-TP in the local circulation failure induced by TCDD in the dorsal midbrain of the zebrafish embryo.

A novel model of pain sensation using superfused gastrosplenic omentum preparation of anesthetized rats

A pain model for screening analgesics was established in anesthetized rats. The omenta of urethane-anesthetized rats were exteriorized, fixed in a plastic chamber, and superfused with Tyrode solution. Administration of bradykinin (BK) in the chamber elicited the reflex hypertensive response (RHR). Modification of the RHR was tested by topical (in the chamber) or intravenous administration of drugs. The BK dose-response curve was shifted to the right by topical indomethacin. The RHR by BK was inhibited by topical application of a BK B(2) antagonist, (Thi(5,8)-D-Phe(7)-BK), a local anesthetic (2% carbocaine), and by intravenous administration of a ganglion blocker (hexamethonium) or an alpha-adrenergic blocker (dibenamine). The RHR by topical BK was almost completely inhibited by morphine and the suppression was largely reversed by naloxone. The RHR, induced by a threshold dose of BK and inhibited by indomethacin, was potentiated by pretreatment of the omentum with prostaglandin (PG) E(2) or PGI(2). PGE(2) was less potent, but the effect lasted longer than that of PGI(2). Topical administration of a non-acidic analgesic, mepirizole, inhibited the RHR by topical BK by only 20%, but intravenous mepirizole inhibited topical BK by 96.2%, indicating its major central action. This model may be useful for studying analgesics.

Interaction between cyclooxygenase (COX)-1- and COX-2-products modulates COX-2 expression in the late phase of acute inflammation

Prostanoid production depends on the activity of two cyclooxygenase (COX) isoforms. It is appreciated that COX-1 plays a role in physiological processes, whereas COX-2 acts in pathological conditions. However their roles, particularly roles of COX-1, have not yet been fully established in inflammation. Here, we examined the effects of COX inhibitors, having differential isoform selectivity, on the late phase of rat carrageenin-induced pleurisy to elucidate the role of COX-2 expressed in the draining lymph nodes and found substantial contribution of COX-1-product(s). Protein and mRNA of COX-2 were detectable with Western blotting analysis and reverse-transcription polymerase chain reaction (RT-PCR) analysis in parathymic lymph nodes, peaking at 48 h after induction of pleurisy. Microsomal prostaglandin E synthase (mPGES)-1 was detectable by immunohistochemical analysis in cells with dendritic processes, a morphological characteristic similar to that of COX-2 expressing cells. Although aspirin, indomethacin and a COX-1 inhibitor, ketorolac, significantly decreased the volume of pleural exudate, they did not affect the levels of COX-2 and mPGES-1 in the lymph node 24 h after induction of pleurisy. In contrast, COX-2 inhibitors, nimesulide and NS-398, had no effect on the exudate volume, but they increased the number of COX-2- and mPGES-1-expressing cells and extension of their dendritic processes with significant increase in the COX-2 level, which were antagonised by ketorolac. These results suggest that COX-2-expressing cells may negatively self-regulate their functions by producing PGE2 via mPGES-1: migration into the draining lymph node and their differentiation. Moreover, COX-1- and COX-2-derived prostanoids may play differential or sometimes antagonistic roles in the late phase of acute inflammation.

Anti-inflammatory effects of a triterpenoid isolated from Wilbrandia ebracteata Cogn

Wilbrandia ebracteata (WE), a Brazilian medicinal plant used in folk medicine for the treatment of rheumatic diseases, displays anti-inflammatory properties and constitutes a rich source of cucurbitacins and cucurbitacin-related compounds. The current study investigated the potential anti-inflammatory properties of Dihydrocucurbitacin B (DHCB), a cucurbitacin-derived compound isolated from roots of WE, in some in vivo and in vitro experimental models. Intraperitoneal treatment of mice with DHCB reduced both carrageenan-induced paw edema (0.3, 1 and 3 mg/kg caused inhibitions of 26, 44 and 56 % at 2 h after stimulation, respectively) and pleurisy (10 mg/kg inhibited leukocyte numbers and LTB(4) levels in the pleural fluid by 51 and 75% at 6 h after cavity challenge, respectively). In vitro, DHCB (up to 10 microg/mL) failed to modify LTB(4) production by human neutrophils or PGE(2) production by COS-7 cells transfected with COX-1, but PGE(2) production by COX-2 transfected COS-7 cells was markedly inhibited (by 72%). The levels of COX-1 or COX-2 proteins in IL-1alpha-stimulated NIH3T3 cells were unaffected by DHCB. The results corroborate the potential anti-inflammatory properties ascribed to W. ebracteata Cogn. in folk medicine and suggest that they might be attributed, at least in part, to the capacity of one of this plants main constituents, DHCB, to inhibit COX-2 activity (but not its expression) during inflammation.

Effect of combination of nitric oxide synthase and cyclooxygenase inhibitors on carrageenan-induced pleurisy in rats

In the present study, we examined the effects of L-nitroarginine methylester (L-NAME), a non-selective nitric oxide synthase (NOS) inhibitor, indomethacin (IND), a non-selective COX inhibitor and a combination of these agents (L-NAME+IND) on carrageenan-induced pleurisy in rats. Exudate volume, albumin leakage, leukocyte influx, exudate and plasma nitrite/nitrate (NO(x)) levels and exudate PGE(2) levels increased markedly 6 h after an intrapleural injection of 2% carrageenan. First, the effects of L-NAME and IND alone were investigated. L-NAME non-significantly reduced exudate volume by 26% at 10 mg/kg (i.p.), and significantly by 45% at 30 mg/kg. IND dose-dependently decreased the exudate volume at 0.3-10 mg/kg (p.o.) and the effect reached the maximal level at 1 mg/kg (33%). Second, the effects of L-NAME (10 mg/kg, i.p.), IND (1 mg/kg, p.o.) and L-NAME+IND were examined. L-NAME and IND alone at the dose employed significantly reduced the exudate volume and albumin levels by 21-26%. L-NAME but not IND tended to reduce the increased exudate and plasma NO(x) by 18% and 19%, respectively. IND but not L-NAME significantly reduced leukocyte numbers and PGE(2) levels in the exudates by 25% and 77%, respectively. L-NAME+IND significantly reduced exudate volume, albumin leakage, leukocyte number, PGE(2) and NO(x) by 43%, 41%, 31%, 80% and 37%, respectively. The inhibitory effects of L-NAME+IND on exudate volume, albumin leakage and NO(x) levels were greater than those of L-NAME and IND alone. In conclusion, a non-selective NOS inhibitor and COX inhibitor showed anti-inflammatory effects at the early phase of carrageenan-induced pleurisy, and a combination of both inhibitors had a greater effect than each alone probably via the potentiation of NOS inhibition. The simultaneous inhibition of NOS and COX could be a useful approach in therapy for acute inflammation.

Resident pleural macrophages are key orchestrators of neutrophil recruitment in pleural inflammation

RATIONALE

The role played by resident pleural macrophages in the initiation of pleural inflammation is currently unclear.

OBJECTIVE

To evaluate the role of resident pleural macrophages in the initiation of inflammation.

METHODS

We have used a conditional macrophage ablation strategy to determine the role of resident pleural macrophages in the regulation of neutrophil recruitment in a murine model of experimental pleurisy induced by the administration of carrageenan and formalin- fixed Staphylococcus aureus.

MEASUREMENTS AND MAIN RESULTS

Conditional macrophage ablation mice express the human diphtheria toxin receptor under the control of the CD11b promoter such that the administration of diphtheria toxin induces ablation of nearly 97% of resident macrophages. Ablation of resident pleural macrophages before the administration of carrageenan or S. aureus dramatically reduced neutrophil influx into the pleural cavity. In the carrageenan model, the reduction in neutrophil infiltration was associated with marked early reduction in the level of macrophage inflammatory protein 2 as well as reduced levels of various cytokines, including tumor necrosis factor alpha, interleukin 6, and interleukin 10. Adoptive transfer of nontransgenic macrophages partially restored neutrophil infiltration. We also stimulated macrophage-depleted and nondepleted pleural cell populations with carrageenan in vitro and determined the production of chemokines and cytokines. Chemokine and cytokine production was markedly reduced by macrophage depletion, reinforcing the role of resident pleural macrophages in the generation of mediators that initiate acute inflammation.

CONCLUSION

These studies indicate a critical role for resident pleural macrophages in sensing perturbation to the local microenvironment and orchestrating subsequent neutrophil infiltration.

Coupling between cyclooxygenases and terminal prostanoid synthases

Biosynthesis of prostanoids is regulated by three sequential enzymatic steps, namely phospholipase A2, cyclooxygenase (COX), and terminal prostanoid synthase. Recent evidence suggests that lineage-specific terminal prostanoid synthases, including prostaglandin (PG) E2, PGD2, PGF2alpha, PGI2, and thromboxane synthases, show distinct functional coupling with upstream COX isozymes, COX-1 and COX-2. This can account, at least in part, for segregated utilization of the two COX isozymes in distinct phases of PG-biosynthetic responses. In terms of their localization and COX preference, terminal prostanoid synthases are classified into three categories: (i) the perinuclear enzymes that prefer COX-2, (ii) the cytosolic enzyme that prefers COX-1, and (iii) the translocating enzyme that utilizes both COXs depending on the stimulus. Additionally, altered supply of arachidonic acid by phospholipase A2s significantly affects the efficiency of COX-terminal prostanoid synthase coupling. In this review, we summarize our recent understanding of the coupling profiles between the two COXs and various terminal prostanoid synthases.

Prostaglandin E Synthase, a Terminal Enzyme for Prostaglandin E2 Biosynthesis

Biosynthesis of prostanoids is regulated by three sequential enzymatic steps, namely phospholipase A2 enzymes, cyclooxygenase (COX) enzymes, and various lineagespecific terminal prostanoid synthases. Prostaglandin E synthase (PGES), which isomerizes COX-derived PGH2 specifically to PGE2, occurs in multiple forms with distinct enzymatic properties, expressions, localizations and functions. Two of them are membrane-bound enzymes and have been designated as mPGES-1 and mPGES-2. mPGES-1 is a perinuclear protein that is markedly induced by proinflammatory stimuli, is down-regulated by antiinflammatory glucocorticoids, and is functionally coupled with COX-2 in marked preference to COX-1. Recent gene targeting studies of mPGES-1 have revealed that this enzyme represents a novel target for anti-inflammatory and anti-cancer drugs. mPGES-2 is synthesized as a Golgi membrane-associated protein, and the proteolytic removal of the N-terminal hydrophobic domain leads to the formation of a mature cytosolic enzyme. This enzyme is rather constitutively expressed in various cells and tissues and is functionally coupled with both COX-1 and COX-2. Cytosolic PGES (cPGES) is constitutively expressed in a wide variety of cells and is functionally linked to COX-1 to promote immediate PGE2 production. This review highlights the latest understanding of the expression, regulation and functions of these three PGES enzymes.

Inhibition of 12- and 15-lipoxygenase activities and protection of human and tilapia low density lipoprotein oxidation by I-Tiao-Gung (Glycine tomentella)

I-Tiao-Gung, Glycine tomentella, has been used extensively as a traditional herbal medicine to relieve physical pain, but its bioactivity has not been studied systematically. Ninety-five percent ethanol extracts of G. tomentella (GT-E) showed antioxidant activity in human plasma by prolonging the lag phase (+Tlag) of Cu2+-induced LDL oxidation and were dose dependent. The +Tlag of LDL combined with 3.2 microg/mL GT-E was similar to that with 2.0 microM (ca. 0.5 microg/mL) Trolox. A similar inhibitory effect was found toward tilapia plasma LDL. In addition, GT-E inhibited tilapia thrombocyte (nucleated platelet) 5-, 12-, and 15-lipoxygenase (LOX). The IC50 values were 0.43, 0.72, and 0.42 microg/mL, respectively, whereas the IC50 values for nordihydroguaiaretic acid (NDGA) on 5-, 12-, and 15-LOX were 2.3, 1.6, and 1.7 microg/mL, respectively. The IC50 value for cyclooxygenase-2 (COX-2) inhibition by GT-E was 42.0 microg/mL, whereas the IC50 value by indomethacin as a positive control was 0.61 microLg/mL. The prevention of LDL oxidation and the dual inhibition of LOX and COX-2 are indicative of the possible roles of I-Tiao-Gung in antiatherosclerosis and anti-inflammation.

Identification and properties of parietal pleural afferents in rabbits

Although pain and dyspnoea are common symptoms in pleural diseases, there are few studies on the sensory innervation of the pleura. Using rabbits, after removal of all muscles in the intercostal space to be studied, we investigated the afferents of the internal intercostal nerve by applying to the internal thoracic wall pieces of gauze soaked in warmed (37 degrees C), buffered saline (mechanical stimulation) or solutions containing lactic acid, inflammatory mediators or capsaicin (chemical stimulation). The afferent conduction velocity ranged from 0.5 to 14 m s(-1). Most units (97%) were activated by mechanical stimulation of the pleura (local positive pressure range = 4.5-8.5 cmH2O) and we found a linear relationship between the discharge rate of afferents and the force applied to the thoracic wall. The majority of mechanosensitive units (70%) also responded to one or several chemical agents. Thus, the afferents were activated by lactic acid (49%) and/or a mixture of inflammatory mediators (50%). Local application of capsaicin elicited an initial increased or decreased background afferent activity in 57% of the afferents, a delayed decrease in firing rate being noted in some units initially activated by capsaicin. Capsaicin blocked the afferent response to a further application of inflammatory mediators but did not affect the mechanosensitive units. Thus, sensory endings connected with thin myelinated and unmyelinated fibres in the internal intercostal nerve detect the mechanical and chemical events of pleural diseases.

Local and systemic expression of inducible nitric oxide synthase in comparison with that of cyclooxygenase-2 in rat carrageenin-induced pleurisy

Expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) is up-regulated in response to inflammatory stimuli. To evaluate the extent to which local pleural inflammation involves additional site in the pleural cavity and elsewhere, we investigated the time course of the levels of iNOS and its product in the inflammatory and other sites, and compared those with a level of COX-2 in rat carrageenin-induced pleurisy. The exudate and plasma NOx levels rose, reaching peaks at 9 and 14 h, respectively. Both COX-2 and iNOS became detectable in exudate leukocytes, their levels reaching peaks at 3 and 9 h after irritation, respectively. COX-2 was detectable mainly in neutrophils, but iNOS was detectable in both neutrophils and mononuclear leukocytes. Furthermore, iNOS became detectable in neutrophils and mononuclear leukocytes in enlarged parathymic lymph nodes from 3h in addition to those in peripheral blood and Kupffer cells from 3 to 14 h, respectively. The gene product is also detectable in thymic large dendritic cells of pleurisy-induced rats as well as normal control rats. COX-2 became detectable in stellar dendritic cells of the enlarged draining lymph nodes from 14 h. Thus, these gene products were induced in the immediate proximity of regional lymph nodes, and even at a considerable distance of liver by the local inflammatory stimulus. Although their expression pattern was quite different from each other, these gene products were detectable in phagocytic cells.

Application of HPLC and HPTLC for the simultaneous determination of tizanidine and rofecoxib in pharmaceutical dosage form

Two methods are described for the simultaneous determination of tizanidine and rofecoxib in binary mixture. The first method was based on HPTLC separation of the two drugs followed by densitometric measurements of their spots at 311 nm. The separation was carried out on Merck HPTLC aluminium sheets of silica gel 60 F254 using toluene:methanol:acetone (7.5:2.5:1.0, v/v/v) as mobile phase. The linear regression analysis data was used for the regression line in the range of 10-100 and 100-1500 ng/spot for tizanidine and rofecoxib, respectively. The second method was based on HPLC separation of the two drugs on the reversed phase kromasil column [C18 (5 microm, 25 cm x 4.6 mm, i.d.)] at ambient temperature using a mobile phase consisting of phosphate buffer pH 5.5 and methanol (45:55, v/v). Flow rate was 1.0 ml/min with an average operating pressure of 180 kg/cm2. Quantitation was achieved with UV detection at 235 nm based on peak area with linear calibration curves at concentration ranges 10-200 and 100-2000 microg/ml for tizanidine and rofecoxib, respectively. Both methods have been successively applied to pharmaceutical formulation. No chromatographic interference from the tablet excipients was found. Both methods were validated in terms of precision, robustness, recovery and limits of detection and quantitation. The analysis of variance (ANOVA) and Student's t-test were applied to correlate the results of tizanidine and rofecoxib determination in dosage form by means of HPTLC and HPLC method.

Inhibitory effects of proanthocyanidins from Ribes nigrum leaves on carrageenin acute inflammatory reactions induced in rats

Background

The anti-inflammatory effects of proanthocyanidins (PACs), isolated from blackcurrant (Ribes nigrum L.) leaves, were analysed using carrageenin-induced paw oedema and carrageenin-induced pleurisy in rats.

Results

Pretreatment of the animals with PACs (10, 30, 60 and 100 mg/kg, i.p.) reduced paw oedema induced by carrageenin in a dose and time-dependent manner. PACs also inhibited dose-dependently carrageenin-induced pleurisy in rats. They reduced (A) lung injury, (B) pleural exudate formation, (C) polymorphonuclear cell infiltration, (D) pleural exudate levels of TNF-α, IL-1β and CINC-1 but did not affect IL-6 and IL-10 levels. They reduced (E) pleural exudate levels of nitrite/nitrate (NOx). In indomethacin treated rats, the volume of pleural exudate was low, its content in leukocytes and its contents in TNF-α, IL-1β, IL-6 and IL-10 but not in NOx were reduced. These data suggest that the anti-inflammatory properties of PACs are achieved through a different pattern from those of indomethacin.

Conclusion

These results suggest that the main mechanism of the anti-inflammatory effect of PACs mainly lies in an interference with the migration of the leukocytes. Moreover, PACs inhibited in vivo nitric oxide release.

Effect of methylguanidine in carrageenan-induced acute inflammation in the rats

In vitro and in vivo studies have demonstrated that methylguanidine, an inhibitor of nitric oxide synthase (NOS), is also able to reduce tumour necrosis factor-alpha (TNF-alpha) release. In the present study, we evaluated the anti-inflammatory potential of methylguanidine treatment in two models of acute inflammation (carrageenan-induced paw edema and pleurisy) where oxyradical, nitric oxide (NO) and prostaglandins play a crucial role in the inflammatory processes. Our data show that methylguanidine, given intraperitoneally at the dose of 30 mg/kg, inhibits the inflammatory response reducing significantly (P<0.05) paw swelling, pleural exudates formation, mononuclear cell infiltration and histological injury. Furthermore, our data suggests that there is a significant (P<0.05) reduction in the activity and expression both of the inducible NOS (iNOS) and of cyclooxygenase-2 in lung tissue of pleurisy model. Methylguanidine is also able to reduce the appearance of nitrotyrosine and of the nuclear enzyme poly(adenosine diphosphate [ADP]-ribose) synthase immunoreactivity in the inflamed lung tissues. Treatment with aminoguanidine, the reference drug, significantly reduced all the evaluated pro-inflammatory parameters in carrageenan-treated rats. Taken together, the present results demonstrate that methylguanidine exerts potent anti-inflammatory effects that could be, in part, related to an inhibition of the expression/activity of the iNOS and cyclooxygenase-2 and, another part, may be related to a reduction of TNF-alpha release.

Rosiglitazone, a ligand of the peroxisome proliferator-activated receptor-gamma, reduces acute inflammation

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily of ligand-activated transcription factors that are related to retinoid, steroid and thyroid hormone receptors. The PPAR-gamma receptor subtype appears to play a pivotal role in the regulation of cellular proliferation and inflammation. The thiazolidinedione rosiglitazone (Avandia) is a peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonist, that was recently approved by the Food and Drug Administration for treatment of type II diabetes mellitus. In the present study, we have investigated the effects of rosiglitazone in animal models of acute inflammation (carrageenan-induced paw oedema and carrageenan-induced pleurisy). We report here for the first time that rosiglitazone (given at 1, 3 or 10 mg/kg i.p. concomitantly with carrageenan injection in the paw oedema model, or at 3, 10 or 30 mg/kg i.p. 15 min before carrageenan administration in the pleurisy model) exerts potent anti-inflammatory effects (e.g. inhibition of paw oedema, pleural exudate formation, mononuclear cell infiltration and histological injury) in vivo. Furthermore, rosiglitazone reduced: (1) the increase in the staining (immunohistochemistry) for nitrotyrosine and poly (ADP-ribose) polymerase (PARP), (2) the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), intercellular adhesion molecules-1 (ICAM-1) and P-selectin in the lungs of carrageenan-treated rats. In order to elucidate whether the protective effect of rosiglitazone is related to activation of the PPAR-gamma receptor, we also investigated the effect of a PPAR-gamma antagonist, bisphenol A diglycidyl ether (BADGE), on the protective effects of rosiglitazone. BADGE (30 mg/kg i.p.) administered 30 min prior to treatment with rosiglitazone significantly antagonized the effect of the PPAR-gamma agonist and thus abolished the anti-inflammatory effects of rosiglitazone. We propose that rosiglitazone and other potent PPAR-gamma agonists may be useful in the therapy of inflammation.

Role of eicosanoids in structural degradation in osteoarthritis

PURPOSE OF REVIEW

Osteoarthritis is characterized mainly by degenerative changes in joint cartilage, ultimately resulting in loss of cartilage, and alterations in the subchondral bone. Osteoarthritis osteoblasts show a number of metabolic alterations that may interfere with normal cell metabolism and signaling, possibly leading to altered extracellular matrix composition. This review examines the role of eicosanoids in this structural degradation.

RECENT FINDINGS

Prostaglandins exert diverse modulatory roles in osteoarthritis, with prostaglandin E2 known to play an important role in inflammation. Prostaglandins and leukotriene B4 have been shown to regulate proinflammatory cytokine and interstitial collagenase synthesis in human osteoarthritis synovial membrane explants. Human osteoarthritis osteoblasts produce variable levels of prostaglandin E2 and leukotriene B4 compared with normal osteoblasts. Prostaglandin E2 levels can distinguish two types of patients with osteoarthritis: osteoblasts from one group produce low levels of prostaglandin E2 and interleukin-6, and the other shows an increase in production. In contrast, osteoarthritis osteoblasts that produce high levels of prostaglandin E2 produce low levels of leukotriene B4 and vice versa. This observation could be explained by the selective metabolism of arachidonic acid via the 5-lipoxygenase or cyclooxygenase pathways in osteoarthritis osteoblasts.

SUMMARY

Prostaglandins play a significant role not only in joint physiology, but also in the pathogenesis of joint disorders. In addition, it has been identified that osteoarthritis subchondral osteoblasts can synthesize leukotriene B4, indicating a role of leukotrienes in bone remodeling associated with osteoarthritis. A therapeutic intervention that blocks lipoxygenase/cyclooxygenase pathways, thereby inhibiting production of prostaglandins and leukotrienes, may therefore be very attractive for the treatment of osteoarthritis patients.

Concurrent evolution and resolution in an acute inflammatory model of rat carrageenin-induced pleurisy

Granulocyte apoptosis and subsequent clearance by phagocytes are critical for the resolution of inflammation. However, no studies have addressed how the resolution proceeds in the inflammatory site. We studied the time course of neutrophil apoptosis and the following ingestion by mononuclear leukocytes in rat carrageenin-induced pleurisy, detecting DNA fragmentation by the deoxyuridine triphosphate-biotin nick-end labeling (TUNEL) method, by acridine orange staining, and from the DNA ladder pattern on electrophoresis. Neutrophil accumulation started 3-5 h after carrageenin injection and then maintained a plateau until 24 h. Neutrophils decreased steeply between days 1 and 3. Mononuclear leukocytes started to accumulate at 5 h and reached a peak at day 2. TUNEL-positive bodies and acridine orange-positive bodies first became detectable in the cytoplasm of the mononuclear leukocytes from 24 h and 9 h, respectively. Both methods indicated that mononuclear leukocytes containing fragmented DNA increased rapidly on days 1 and 2 and reached a peak at day 3. The characteristic ladder pattern of neutrophil DNA was observed from 5 h. Tumor necrosis factor alpha was detectable on the start, and the levels of interleukin-10 and transforming growth factor-beta1 rose together with signs of neutrophil apoptosis and the following ingestion by mononuclear leukocytes. These results indicate that neutrophils start to undergo apoptosis just after the beginning of their accumulation in the inflammation site. Thus, evolution and resolution processes may proceed concurrently in acute inflammation.

Examination of rofecoxib solution decomposition under alkaline and photolytic stress conditions

Rofecoxib is a highly active and selective cyclo-oxygenase II inhibitor. A stability-indicating method for the assay of rofecoxib has been developed using reverse-phase high-performance liquid chromatography (HPLC). Stress testing of rofecoxib was conducted during the method development and validation. HPLC analysis of rofecoxib solutions stressed under alkaline and photolytic conditions revealed the presence of several degradates. Two main degradates were determined to be the cyclization product formed by photo-cyclization and the dicarboxylate formed by ring opening in the presence of base and oxygen. The identities of these degradates were confirmed by comparison of UV spectra and HPLC retention time with the independently synthesized products. The mechanistic pathways for the formation of these degradates are discussed. Further improvement of the HPLC method's ruggedness has been made based on these studies.

The cyclopentenone prostaglandin 15-deoxy-Delta(12,14)-prostaglandin J(2) attenuates the development of acute and chronic inflammation

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily of ligand-activated transcription factors that are related to retinoid, steroid, and thyroid hormone receptors. The PPAR-gamma receptor subtype seems to play a pivotal role in the regulation of cellular proliferation and inflammation. Recent evidence also suggests that the cyclopentenone prostaglandin (PG) 15-deoxyDelta(12,14)-PGJ(2) (15d-PGJ(2)), which is a metabolite of prostaglandin D(2), functions as an endogenous ligand for PPAR-gamma. We postulated that 15d-PGJ(2) would attenuate inflammation. In the present study, we have investigated the effects of 15d-PGJ(2) of acute and chronic inflammation (carrageenan-induced pleurisy and collagen-induced arthritis, respectively) in animal models. We report for the first time, to our knowledge, that 15d-PGJ(2) (given at 10, 30, or 100 microg/kg i.p. in the pleurisy model or at 30 microg/kg i.p every 48 h in the arthritis model) exerts potent anti-inflammatory effects (e.g., inhibition of pleural exudate formation, mononuclear cell infiltration, delayed development of clinical indicators, and histological injury) in vivo. Furthermore, 15d-PGJ(2) reduced the increase in the staining (immunohistochemistry) for nitrotyrosine and poly (ADP-ribose) polymerase and the expression of inducible nitric-oxide synthase and cyclooxygenase-2 in the lungs of carrageenan-treated mice and in the joints from collagen-treated mice. Thus, 15d-PGJ(2) reduces the development of acute and chronic inflammation. Therefore, the cyclopentenone prostaglandin 15d-PGJ(2) may be useful in the therapy of acute and chronic inflammation.

Protective effects of Celecoxib on lung injury and red blood cells modification induced by carrageenan in the rat

In the present study, we evaluated the effect of Celecoxib, a selective COX-2 inhibitor, in an acute model of lung injury induced by carrageenan administration in the rats. Injection of carrageenan into the pleural cavity of rats elicited an acute inflammatory response characterized by: fluid accumulation in the pleural cavity which contained a large number of polymorphonuclear neutrophils (PMNs) as well as an infiltration of PMNs in lung tissues and subsequent lipid peroxidation, and increased production of prostaglandin E(2) (PGE(2)), tumor necrosis factor alpha (TNFalpha), and interleukin-1beta. All parameters of inflammation were attenuated by Celecoxib. Furthermore, carrageenan induced an upregulation of the adhesion molecules ICAM-1 and P-selectin, as well as nitrotyrosine and poly(ADP-ribose) synthetase (PARS) as determined by immunohistochemical analysis of lung tissues. The degree of staining for the ICAM-1, P-selectin, nitrotyrosine and PARS was reduced by Celecoxib. These results clearly confirmed that COX-2 plays a critical role in the development of the inflammatory response by altering key components of the inflammatory cascade. Therefore, selective inhibitor of COX-2 such as Celecoxib, offers a therapeutic approach for the management of various inflammatory diseases.

Pyrrolidine dithiocarbamate attenuates the development of acute and chronic inflammation

The nuclear factor-kappaB (NF-kappaB) is a transcription factor which plays a pivotal role in the induction of genes involved in physiological processes as well as in the response to injury and inflammation. Dithiocarbamates are antioxidants which are potent inhibitors of NF-kappaB. We postulated that pyrrolidine dithiocarbamate (PDTC) would attenuate inflammation. In the present study we investigate the effects of PDTC in animal models of acute and chronic inflammation (carrageenan-induced pleurisy and collagen-induced arthritis). We report here for the first time that PDTC (given at 100, 30 or 10 mg kg(-1) i.p. in the pleurisy model or at 10 mg kg(-1) i.p. every 48 h in the arthritis model) exerts potent anti-inflammatory effects (e.g. significant reduction of (A) pleural exudate formation, (B) polymorphonuclear cell infiltration, (C) lipid peroxidation, (D) inducible nitric oxide synthase (iNOS) activity and nitric oxide production (E) plasma and pleural exudates levels of interleukin-1beta and tumour necrosis factor-alpha, (F) histological injury and (G) delayed development of clinical indicators). Furthermore, PDTC reduced immunohistochemical evidence of (A) formation of nitrotyrosine, (B) activation of poly (ADP-ribose) polymerase (PARP), (C) expression of iNOS and (D) expression of cyclo-oxygenase-2 (COX-2) in the lungs of carrageenan-treated mice and in the joints from collagen-treated mice. Additionally, Western blotting and immunohistochemical analysis of lung tissue revealed that PDTC prevented degradation of IKB-alpha and translocation of NF-kappaB from the cytoplasm into the nucleus. Taken together, our results clearly demonstrate that prevention of the activation of NF-kappaB by PDTC reduces the development of acute and chronic inflammation. Therefore, inhibition of NF-kappaB may represent a novel approach for the therapy of inflammation.

Difference in urinary 11-dehydro TXB2 and LTE4 excretion in patients with rheumatoid arthritis

Thromboxane and leukotrienes have been implicated in inflammation. However, the production level of these eicosanoids in patients with rheumatoid arthritis is still unclarified. In the present study, endogenous synthesis of thromboxane and cysteinyl leukotrienes in patients was investigated. The production of eicosanoids in patients is assessed by measuring stable urinary metabolites,11-dehydro thromboxane B2 and leukotriene E4, using gas chromatography/selected ion monitoring and liquid chromatography/tandem mass spectrometry. The level of urinary thromboxane in patients was significantly higher than that in healthy volunteers (P < 0.05). Furthermore, we investigated the effects of administered drugs on the production of these eicosanoids. The urinary thromboxane level of the untreated group (1630 +/- 613 pg/mg creatinine) was much higher than that of healthy volunteers (342 +/- 263 pg/mg creatinine). The level in the group receiving NSAID alone was similar to that in healthy volunteers, and the group receiving steroid alone showed slightly lower thromboxane levels than the untreated group. On the other hand, the leukotriene E4 level in patients (280 +/- 360 pg/mg creatinine) was also significantly higher than that in healthy volunteers (59 +/- 54 pg/mg creatinine, P < 0.05). In particular, the group receiving methotrexate (904 +/- 685 pg/mg creatinine) had higher leukotriene levels than not only healthy volunteers but also other medicated groups. These findings demonstrated that endogenous thromboxane and leukotriene production in patients with rheumatoid arthritis are enhanced, and the effects of medication on the production of these eicosanoids differed in thromboxane and leukotriene E4.

Coupling between cyclooxygenase, terminal prostanoid synthase, and phospholipase A2

We have recently shown that two distinct prostaglandin (PG) E(2) synthases show preferential functional coupling with upstream cyclooxygenase (COX)-1 and COX-2 in PGE(2) biosynthesis. To investigate whether other lineage-specific PG synthases also show preferential coupling with either COX isozyme, we introduced these enzymes alone or in combination into 293 cells to reconstitute their functional interrelationship. As did the membrane-bound PGE(2) synthase, the perinuclear enzymes thromboxane synthase and PGI(2) synthase generated their respective products via COX-2 in preference to COX-1 in both the -induced immediate and interleukin-1-induced delayed responses. Hematopoietic PGD(2) synthase preferentially used COX-1 and COX-2 in the -induced immediate and interleukin-1-induced delayed PGD(2)-biosynthetic responses, respectively. This enzyme underwent stimulus-dependent translocation from the cytosol to perinuclear compartments, where COX-1 or COX-2 exists. COX selectivity of these lineage-specific PG synthases was also significantly affected by the concentrations of arachidonate, which was added exogenously to the cells or supplied endogenously by the action of cytosolic or secretory phospholipase A(2). Collectively, the efficiency of coupling between COXs and specific PG synthases may be crucially influenced by their spatial and temporal compartmentalization and by the amount of arachidonate supplied by PLA(2)s at a moment when PG production takes place.

Microsomal prostaglandin E synthase is regulated by proinflammatory cytokines and glucocorticoids in primary rheumatoid synovial cells

The selective induction of PGE(2) synthesis in inflammation suggests that a PGE synthase may be linked to an inducible pathway for PG synthesis. We examined the expression of the recently cloned inducible microsomal PGE synthase (mPGES) in synoviocytes from patients with rheumatoid arthritis, its modulation by cytokines and dexamethasone, and its linkage to the inducible cyclooxygenase-2. Northern blot analysis showed that IL-1beta or TNF-alpha treatment induces mPGES mRNA from very low levels at baseline to maximum levels at 24 h. IL-1beta-induced mPGES mRNA was inhibited by dexamethasone in a dose-dependent fashion. Western blot analysis demonstrated that mPGES protein was induced by IL-1beta, and maximum expression was sustained for up to 72 h. There was a coordinated up-regulation of cyclooxygenase-2 protein, although peak expression was earlier. Differential Western blot analysis of the microsomal and the cytosolic fractions revealed that the induced expression of mPGES protein was limited to the microsomal fraction. The detected mPGES protein was catalytically functional as indicated by a 3-fold increase of PGES activity in synoviocytes following treatment with IL-1beta; this increased synthase activity was limited to the microsomal fraction. In summary, these data demonstrate an induction of mPGES in rheumatoid synoviocytes by proinflammatory cytokines. This novel pathway may be a target for therapeutic intervention for patients with arthritis.

Calpain inhibitor I reduces the development of acute and chronic inflammation

There is limited evidence that inhibition of the activity of the protease calpain I reduces inflammation. Here we investigate the effects of calpain inhibitor I in animal models of acute and chronic inflammation (carrageenan-induced pleurisy and collagen-induced arthritis). We report here for the first time that calpain inhibitor I (given at 5, 10, or 20 mg/kg i.p. in the pleurisy model or at 5 mg/kg i.p every 48 hours in the arthritis model) exerts potent anti-inflammatory effects (eg, inhibition of pleural exudate formation, mononuclear cell infiltration, delayed the development of the clinical signs and histological injury) in vivo. Furthermore, calpain inhibitor I reduced (1) the staining for nitrotyrosine and poly (ADP-ribose) polymerase (immunohistochemistry) and (2) the expression of inducible nitric oxide synthase and cyclooxygenase-2 in the lungs of carrageenan-treated rats and in joints from collagen-treated rats. Thus, prevention of the activation of calpain I reduces the development of acute and chronic inflammation. Inhibition of calpain I activity may represent a novel therapeutic approach for the therapy of inflammation.

Cloricromene, a coumarine derivative, protects against collagen-induced arthritis in Lewis rats

1. The aim of the present study was to investigate the effects of cloricromene, a coumarine derivative, in rats subjected to collagen-induced arthritis. 2. Collagen-induced arthritis (CIA) was induced in Lewis rats by an intradermal injection of 100 microl of the emulsion (containing 100 microg of bovine type II collagen) (CII) and complete Freund's adjuvant (CFA) at the base of the tail. On day 21, a second injection of CII in CFA was administered. 3. Lewis rats developed an erosive hind paw arthritis when immunized with CII in CFA. Macroscopic clinical evidence of CIA first appeared as peri-articular erythema and oedema in the hind paws. The incidence of CIA was 100% by day 27 in the CII challenged rats and the severity of CIA progressed over a 35-day period with radiographic evaluation revealing focal resorption of bone together with osteophyte formation in the tibiotarsal joint and soft tissue swelling. 4. The histopathology of CIA included erosion of the cartilage at the joint margins. Treatment of rats with cloricromene (10 mg kg(-1) i.p. daily) starting at the onset of arthritis (day 23), delayed the development of the clinical signs at days 24 - 35 and improved histological status in the knee and paw. 5. Immunohistochemical analysis for iNOS, COX-2, nitrotyrosine and for poly (ADP-ribose) synthetase (PARS) revealed a positive staining in inflamed joints from collagen-treated rats. The degree of staining for iNOS, COX-2, nitrotyrosine and PARS were markedly reduced in tissue sections obtained from collagen-treated rats, which had received cloricromene. 6. Radiographic signs of protection against bone resorption and osteophyte formation were present in the joints of cloricromene-treated rat. 7. This study provides the first evidence that cloricromene, a coumarine derivative, attenuates the degree of chronic inflammation and tissue damage associated with collagen-induced arthritis in the rat.

Coordinate up- and down-regulation of glutathione-dependent prostaglandin E synthase and cyclooxygenase-2 in A549 cells. Inhibition by NS-398 and leukotriene C4

Recently, a microsomal protein with 38% sequence identity to microsomal glutathione S-transferase 1 was shown to constitute an inducible, glutathione-dependent prostaglandin E synthase (PGES). To investigate the relationship between cyclooxygenase and PGES, a time-course study on protein expression was performed in A549 cells after treatment with interleukin-1beta. The result demonstrated a tandem expression of cyclooxygenase-2 and PGES. The observed induction of PGES protein correlated with microsomal PGES activity. No comparable PGES activity was observed in the absence of glutathione or in the cytosolic fraction. In addition, tumour necrosis factor-alpha was found to induce PGES in these cells. Dexamethasone was found to completely suppress the effect of both cytokines on PGES induction. We also describe a quantitative method, based on RP-HPLC with UV detection for the measurements of PGES activity. This method was used to screen potential PGES inhibitors. Several nonsteroidal anti-inflammatory drugs, stable prostaglandin H2 analogues and cysteinyl leukotrienes were screened for inhibition of PGES activity. NS-398, sulindac sulfide and leukotriene C4 were all found to inhibit PGES activity with IC50 values of 20 microM, 80 microM and 5 microM, respectively. In conclusion, it appears that PGES and cyclooxygenase-2 are functionally coupled in A549 cells and that a required coordinate expression of these enzymes allows for efficient biosynthesis of prostaglandin E2.

Molecular identification of cytosolic prostaglandin E2 synthase that is functionally coupled with cyclooxygenase-1 in immediate prostaglandin E2 biosynthesis

Here we report the molecular identification of cytosolic glutathione (GSH)-dependent prostaglandin (PG) E(2) synthase (cPGES), a terminal enzyme of the cyclooxygenase (COX)-1-mediated PGE(2) biosynthetic pathway. GSH-dependent PGES activity in the cytosol of rat brains, but not of other tissues, increased 3-fold after lipopolysaccharide (LPS) challenge. Peptide microsequencing of purified enzyme revealed that it was identical to p23, which is reportedly the weakly bound component of the steroid hormone receptor/hsp90 complex. Recombinant p23 expressed in Escherichia coli and 293 cells exhibited all the features of PGES activity detected in rat brain cytosol. A tyrosine residue near the N terminus (Tyr(9)), which is known to be critical for the activity of cytosolic GSH S-transferases, was essential for PGES activity. The expression of cPGES/p23 was constitutive and was unaltered by proinflammatory stimuli in various cells and tissues, except that it was increased significantly in rat brain after LPS treatment. cPGES/p23 was functionally linked with COX-1 in marked preference to COX-2 to produce PGE(2) from exogenous and endogenous arachidonic acid, the latter being supplied by cytosolic phospholipase A(2) in the immediate response. Thus, functional coupling between COX-1 and cPGES/p23 may contribute to production of the PGE(2) that plays a role in maintenance of tissue homeostasis.

Regulation of prostaglandin E2 biosynthesis by inducible membrane-associated prostaglandin E2 synthase that acts in concert with cyclooxygenase-2

Here we report the molecular identification of membrane-bound glutathione (GSH)-dependent prostaglandin (PG) E(2) synthase (mPGES), a terminal enzyme of the cyclooxygenase (COX)-2-mediated PGE(2) biosynthetic pathway. The activity of mPGES was increased markedly in macrophages and osteoblasts following proinflammatory stimuli. cDNA for mouse and rat mPGESs encoded functional proteins that showed high homology with the human ortholog (microsomal glutathione S-transferase-like 1). mPGES expression was markedly induced by proinflammatory stimuli in various tissues and cells and was down-regulated by dexamethasone, accompanied by changes in COX-2 expression and delayed PGE(2) generation. Arg(110), a residue well conserved in the microsomal GSH S-transferase family, was essential for catalytic function. mPGES was functionally coupled with COX-2 in marked preference to COX-1, particularly when the supply of arachidonic acid was limited. Increased supply of arachidonic acid by explosive activation of cytosolic phospholipase A(2) allowed mPGES to be coupled with COX-1. mPGES colocalized with both COX isozymes in the perinuclear envelope. Moreover, cells stably cotransfected with COX-2 and mPGES grew faster, were highly aggregated, and exhibited aberrant morphology. Thus, COX-2 and mPGES are essential components for delayed PGE(2) biosynthesis, which may be linked to inflammation, fever, osteogenesis, and even cancer.