Eicosanoid Generation Research Articles

Mechanisms of leukocyte lipid body formation and function in inflammation

An area of increasingly interest for the understanding of cell signaling are the spatio-temporal aspects of the different enzymes involved in lipid mediator generation (eicosanoid-forming enzymes, phospholipases and their regulatory kinases and phosphatases) and pools of lipid precursors. The compartmentalization of signaling components within discrete and dynamic sites in the cell is critical for specificity and efficiency of enzymatic reactions of phosphorilation, enzyme activation and function. We hypothesized that lipid bodies--inducible non-membrane bound cytoplasmic lipid domains--function as specialized intracellular sites of compartmentalization of signaling with major roles in lipid mediator formation within leukocytes engaged in inflammatory process. Over the past years substantial progresses have been made demonstrating that all enzymes involved in eicosanoid synthesis localize at lipid bodies and lipid bodies are distinct sites for eicosanoid generation. Here we will review our current knowledge on the mechanisms of formation and functions of lipid bodies pertinent to inflammation.

Antihistamines as Important Tools for Regulating Inflammation

Allergic disorders are characterized by typical symptoms and an infiltrate of cells, including Th2 lymphocytes, eosinophils and mast cells. Activated mast cell mediators cause the early appearance of symptoms, and cytokines induce a cascade of inflammatory events. Both resident and infiltrating cells are important sources of those mediators and cytokines which maintain and enhance the allergic inflammatory response. The predominant preformed mediator released by mast cells and basophils is histamine, which binds to specific cell receptors to produce its clinical effects. Therapeutic intervention in allergic disease has thus commonly focused on blocking the action of histamine. Ever since Arunlakshana demonstrated, in 1953, the ability of antihistamines to inhibit histamine release by mast cells, numerous studies have been conducted, both in vivo and in vitro , to determine the H1 antihistamines additional properties which contribute to their clinical efficacy in the treatment of allergic disease. It has been reported that some antihistamines can also regulate the expression and / or release of cytokines, chemokines, adhesion molecules, and or / inflammatory mediators. Such properties make these agents important tools for the continuous longterm regulation of both early and late-phase allergic reactions. It appears likely that antihistamines exert these antiinflammatory effects by means of both receptor-dependent and receptor-independent mechanisms. The receptordependent mechanisms seem to involve inhibition of the generation of NF-kB dependent cytokines and adhesion proteins. The latter mechanisms, which require higher drug concentrations, appear to include the release by inflammatory cells of pre-formed mediators, such as histamine and eosinophil proteins as well as eicosanoid generation and oxygen free radicals production. Herein, we review the current state of knowledge of the anti-inflammatory properties of antihistamines and their mechanisms.

Eicosanoid generation in the intertidal barnacle,Balanus perforatus—effect of season and reproductive status

The nature and quantity of the principal lipoxygenase (LO) products generated by the intertidal barnacle Balanus perforatus were examined at monthly intervals and their potential involvement in reproductive events was investigated. The main mono-hydroxy products generated were found to be formed through the action of an 8-lipoxygenase (8-LO) activity and were the mono-hydroxy fatty acids, 8-hydroxyeicosapentaenoic acid (HEPE) and 8-hydroxyeicosatetraenoic acid. Generation of these products was found to be correlated with the environmental seawater temperature, although no change in either 8-LO activity or the precursor fatty acid levels in total phospholipids was found with the time of the year. Changes in fatty acid composition measured in animals collected from summer and winter conditions were found to follow the pattern expected by homeoviscous adaptation of a cold-acclimated animal. Oogenesis was found to occur in August and was linked to a significant reduction in 8-HEPE generation. Spermatozoa were found to be present year-round in the seminal vesicles although the testes became atrophic during the winter months.

Effect of Cleome arabica leaf extract, rutin and quercetin on soybean lipoxygenase activity and on generation of inflammatory eicosanoids by human neutrophils

The effects of Cleome arabica leaf extract, rutin and quercetin on soybean lipoxygenase (Lox) activity and on calcium ionophore (A23187)-stimulated generation of the leukotriene B 4 and prostaglandin E 2 by human neutrophils were examined. The extract (25 μg/ml), rutin (25 μM) and quercetin (25 μM) inhibited LTB 4 synthesis at all concentrations of A23187 used. The extract at 1–100 μg/ml and rutin at 1–100 μM inhibited LTB 4 generation by neutrophils stimulated with 1 μM A23187 by about 50%. PGE 2 production in response to different concentrations of A23187 was affected in a biphasic manner by the extract and rutin. Quercetin at 1–100 μM caused concentration-dependent inhibition of LTB 4 and PGE 2 production. The extract, rutin and quercetin caused concentration-dependent inhibition of soybean Lox activity. These results indicate that rutin, quercetin and an extract of C. arabica containing these compounds inhibit Lox activity, consequently decreasing LTB 4 production. Thus, these compounds or extracts containing them may be beneficial for the treatment of inflammatory conditions, particularly those characterised by excessive leukotriene generation.

MITF Is Necessary for Generation of Prostaglandin D2 in Mouse Mast Cells

Mast cells generate eicosanoids that are linked to asthma and other inflammatory diseases. A basic-helix-loop-helix leucine zipper transcription factor termed MITF is essential for the development of mast cells. Although other substances also linked to inflammatory reactions (such as various proteases and serotonin) require MITF for their expression, the role of MITF in eicosanoid generation has not been studied. We examined eicosanoid generation in bone marrow-derived mast cells (BMMCs) of tg/tg mice that lack MITF. Most eicosanoids generated by BMMCs are either prostaglandin (PG) D2 or leukotriene C4. The former is synthesized via the cyclooxygenase pathway, whereas the latter is synthesized via the 5-lipoxygenase pathway. In response to stimulation with IgE and antigens, BMMCs of tg/tg mice synthesized leukotriene C4 normally. However, neither immediate nor delayed PGD2 production was detected in these BMMCs. This indicates that MITF is a transcription factor that specifically activates the cyclooxygenase pathway, but not the 5-lipoxygenase pathway. Significant decreases in expression of hematopoietic PGD2 synthase (hPGDS, a terminal synthase for PGD2) were observed at both mRNA and protein levels in tg/tg BMMCs. MITF transactivated the hPGDS gene via a CACCTG motif located in the promoter region. MITF appeared to be essential for generation of PGD2 by enhancing expression of the hPGDS gene in BMMCs.

Role of Group V Phospholipase A2 in Zymosan-induced Eicosanoid Generation and Vascular Permeability Revealed by Targeted Gene Disruption

Conclusions regarding the contribution of low molecular weight secretory phospholipase A2 (sPLA2) enzymes in eicosanoid generation have relied on data obtained from transfected cells or the use of inhibitors that fail to discriminate between individual members of the large family of mammalian sPLA2 enzymes. To elucidate the role of group V sPLA2, we used targeted gene disruption to generate mice lacking this enzyme. Zymosan-induced generation of leukotriene C4 and prostaglandin E2 was attenuated approximately 50% in peritoneal macrophages from group V sPLA2-null mice compared with macrophages from wild-type littermates. Furthermore, the early phase of plasma exudation in response to intraperitoneal injection of zymosan and the accompanying in vivo generation of cysteinyl leukotrienes were markedly attenuated in group V sPLA2-null mice compared with wild-type controls. These data provide clear evidence of a role for group V sPLA2 in regulating eicosanoid generation in response to an acute innate stimulus of the immune response both in vitro and in vivo, suggesting a role for this enzyme in innate immunity.

A novel role for phospholipase A2isoforms in the checkpoint control of acute inflammation

Acute inflammation can be considered in terms of a series of checkpoints where each phase of cellular influx, persistence, and clearance is controlled by endogenous stop and go signals. It is becoming increasingly apparent that in addition to initiating the inflammatory response, eicosanoids may also mediate resolution. This suggests there are two phases of arachidonic acid release: one at onset for the generation of proinflammatory eicosanoids and one at resolution for the synthesis of proresolving eicosanoids. What is unclear is the identity of the phospholipase (PLA2) isoforms involved in this biphasic release of arachidonic acid. We show here that type VI iPLA2 drives the onset of acute pleurisy through the synthesis of PGE2, LTB4, PAF, and IL-1beta. However, during resolution there is a switch to a sequential induction of first sPLA2 (types IIa and V) that mediates the release of PAF and lipoxin A4, which, in turn, are responsible for the subsequent induction of type IV cPLA2 that mediates the release of arachidonic acid for the synthesis of proresolving prostaglandins. This study is the first of its kind to address the respective roles of PLA2 isoforms in acute resolving inflammation and to identify type VI iPLA2 as a potentially selective target for the treatment of inflammatory diseases.

Resveratrol, a polyphenol found in grapes, suppresses oxidative damage and stimulates apoptosis during early colonic inflammation in rats

Oxidative stress, neutrophil infiltration, proinflammatory cytokines and eicosanoid generation are clearly involved in the pathogenesis of intestinal bowel disease. Resveratrol, a polyphenolic compound found in grapes and wine, has been shown to have anti-inflammatory, antioxidant, antitumour and immunomodulatory activities, however, its effects on experimental colitis remain unknown. We have investigated the effects of resveratrol on the colon injury caused by intracolonic instillation of trinitrobenzenesulphonic acid (TNBS) in rats. We determined the production of prostaglandin (PG)E 2 and PGD 2 in colon mucosa and the expression of cyclo-oxygenases (COX)-1 and -2 immunohistochemically. The inflammatory response was assessed by histology and myeloperoxidase activity, as an index of neutrophil infiltration. Interleukin-1β production, histological and histochemical analysis of the lesions were also carried out. Finally, since resveratrol has been found to modulate apoptosis we intended to elucidate its effects on colonic mucosa under early acute inflammatory conditions. Resveratrol (5–10 mg/kg/day) significantly reduced the degree of colonic injury, the index of neutrophil infiltration and the levels of the cytokine. Resveratrol did not revert the increased PGE 2 levels but produced a significant fall in the PGD 2 concentration. Compared with inflamed colon, no changes in staining for COX-1 were observed in colon of resveratrol and TNBS-treated rats. In contrast, COX-2 expression was decreased. Furthermore, resveratrol enhanced apoptosis compared with already high level induced by TNBS. In conclusion, resveratrol reduces the damage in experimentally induced colitis, alleviates the oxidative events and stimulates apoptosis.

Lysophosphatidic acid induces human mast cell activation in an IL-4-dependent manner

Rationale Lysophosphatidic acid (LPA) is a lipid constituent of human serum that functions as a signaling molecule through binding to 4 known G protein-coupled receptors, designated LPA1-4. LPA has previously been shown to act as a growth factor for human mast cells (hMCs) cultured under serum-free conditions. We now investigate the role of LPA in hMC activation. Methods hMCs were cultured from umbilical cord-derived mononuclear cells using serum-free medium with recombinant human stem cell factor, IL-6, IL-10, and supplemental LPA (5μM). Cells were primed with IL-4 (0.1-50 ng/mL) for up to 5 days. RT-PCR was performed to characterize LPA receptor expression. LPA-induced calcium flux was measured in Fura-2AM-loaded hMCs. For activation studies, hMCs were incubated with LPA (10-50μM) for 30 minutes to 6 hours. Histamine release, eicosanoids, and cytokine production were measured by ELISA. Kit (CD117) expression was measured by FACS analysis. Results mRNA encoding LPA1-4 are expressed by hMCs. LPA (20-50μM) induced calcium flux. LPA (10-50μM) induced MIP-1β production only in the presence of IL-4 priming. IL-4 enhanced MIP-1β generation in a dose-dependent manner, reaching 53 ± 13% (mean ± SEM, n=4) of the level produced by FcϵRI cross-link, compared with negligible levels in unprimed cells (p=0.04). In contrast, LPA did not induce hMC exocytosis or eicosanoid production. IL-4 priming significantly down-regulated Kit expression. Conclusions LPA induces cytokine generation by hMCs in an IL-4-dependent manner by a pathway that does not elicit exocytosis or eicosanoid generation.

Involvement of the mitogen-activated protein kinase cascade in peroxynitrite-mediated arachidonic acid release in vascular smooth muscle cells.

Eicosanoid production is reduced when the nitric oxide (NO.) pathway is inhibited or when the inducible NO synthase gene is deleted, indicating that the NO. and arachidonic acid pathways are linked. We hypothesized that peroxynitrite, formed by the reaction of NO. and superoxide anion, may cause signaling events leading to arachidonic acid release and subsequent eicosanoid generation. Western blot analysis of rat arterial smooth muscle cells demonstrated that peroxynitrite (100-500 microM) and 3-morpholinosydnonimine (SIN-1; 200 microM) stimulate phosphorylation of extracellular signal-regulated kinase (ERK), p38, and cytosolic phospholipase A(2) (cPLA(2)). We found that peroxynitrite-induced arachidonic acid release was completely abrogated by the mitogen-activated protein/ERK kinase (MEK) inhibitor U0126 and by calcium chelators. With the p38 inhibitor SB-20219, we demonstrated that peroxynitrite-induced p38 phosphorylation led to minor arachidonic acid release, whereas U0126 completely blocked p38 phosphorylation. Addition of arachidonic acid caused p38 phosphorylation, suggesting that arachidonic acid or its metabolites are responsible for p38 activation. KN-93, a specific inhibitor of Ca(2+)/calmodulin-dependent kinase II (CaMKII), revealed no role for this kinase in peroxynitrite-induced arachidonic acid release in our cell system. Together, these results show that in response to peroxynitrite the cell initiates the MEK/ERK cascade leading to cPLA(2) activation and arachidonic acid release. Thus studies investigating the role of the NO. pathway on eicosanoid production must consider the contribution of signaling pathways initiated by reactive nitrogen species. These findings may provide evidence for a new role of peroxynitrite as an important reactive nitrogen species in vascular disease.

Efficacy of recombinant granulocyte colony-stimulating factor (rhG-CSF) in experimental colitis.

Inflammatory bowel disease is associated with mucosal neutrophil recruitment and activatation, mediated in part by arachidonic acid metabolites. G-CSF attenuates the immune response to sepsis and ameliorates glycogen storage disease Ib-related colitis. These actions may be effected through the shedding of neutrophil adhesion molecules, or inhibition of proinflammatory mediator synthesis. Immune complex colitis was used to evaluate the effect of rhG-CSF on colonic mucosal inflammation, neutrophil recruitment and the generation of eicosanoids. Immune complex colitis was induced in White New Zealand rabbits. Animals were pretreated with rhG-CSF either 24 h before induction, or at induction, with dosages of 50 and 200 micrograms/kg. rhG-CSF caused a time- and dose-dependent neutrophilia in all animals. Pretreatment with rhG-CSF resulted in increased tissue myeloperoxidase levels, despite a histologically similar mucosal polymorphonuclear cell infiltrate between treated and control colitis groups. Leukotriene B4 (LTB4) and thromboxane B2 (TXB2) dialysis fluid levels were lower in treated animals, in particular in the groups receiving two doses (LTB4: both P < 0.01; TXB2: both P < 0.01. Prostaglandin E2 (PGE2) levels in dialysis fluid of the rhG-CSF-treated animals showed no difference from controls. In this model of experimental colitis, high-dose therapy with G-CSF resulted in a marked decrease of proinflammatory mediators, but mucosal generation of the protective PGE2 was preserved. These results suggest that prolonged high-dose therapy with G-CSF may have anti-inflammatory effects in colitis.

Differential effects of aspirin and misoprostol on 15-hydroxyeicosatetraenoic acid generation by leukocytes from aspirin-sensitive asthmatic patients

Background Although the mechanisms of aspirin-induced rhinosinusitis-asthma appear to be related to arachidonic acid abnormalities, only recently has a specific aspirin-triggered enhancement of 15-hydroxyeicosatetraenoic acid (15-HETE) generation in nasal polyp epithelial cells from aspirin-sensitive patients been demonstrated. Objective The aim of this study was to assess generation of 15-HETE and other eicosanoids by peripheral blood leukocytes (PBLs) from aspirin-sensitive and aspirin-tolerant asthmatic patients and modulation of 15-HETE generation by a prostaglandin (PG) E 1 analogue (misoprostol). Methods Twenty-four aspirin-sensitive patients with asthma-rhinosinusitis and 18 aspirin-tolerant asthmatic patients were studied, and eicosanoids released from PBLs were assessed by means of enzyme immunoassays. Results Unstimulated PBLs from aspirin-sensitive and aspirin-tolerant patients generated similar amounts of PGE 2, leukotriene C 4, and 15-HETE, but lipoxin A 4 release was significantly less in aspirin-sensitive patients (300 ± 70 pg/mL) in comparison with that seen in aspirin-tolerant patients (690 ± 100 pg/mL, P < .05). Cell incubation with 2, 20, or 200 μmol/L aspirin resulted in a dose-dependent increase in 15-HETE generation (mean change of +85%, +189%, and +284% at each aspirin concentration, respectively) only in aspirin-sensitive asthmatic patients. Naproxen stimulated 15-HETE generation in aspirin-sensitive asthmatic patients, but indomethacin or specific COX-2 inhibitors (NS-398 and celecoxib) did not affect 15-HETE release. A synthetic PGE 1 analogue (misoprostol) inhibited aspirin-induced 15-HETE release but enhanced 15-HETE generation by aspirin in leukocytes from aspirin-tolerant patients. After preincubation with misoprostol, aspirin induced a dose-dependent production of lipoxin A 4 in both groups. Conclusion PBLs from patients with aspirin-sensitive rhinosinusitis-asthma might be specifically triggered by aspirin to generate 15-HETE. Metabolism of 15-HETE is differentially regulated by misoprostol in aspirin-tolerant and aspirin-sensitive asthmatic patients.

Differential Effects of Aspirin and Misoprostol on 15-Hydroxyeicosatetraenoic Acid Generation by Leukocytes from Aspirin-Sensitive Asthmatic Patients

BackgroundAlthough the mechanisms of aspirin-induced rhinosinusitis-asthma appear to be related to arachidonic acid abnormalities, only recently has a specific aspirin-triggered enhancement of 15-hydroxyeicosatetraenoic acid (15-HETE) generation in nasal polyp epithelial cells from aspirin-sensitive patients been demonstrated.ObjectiveThe aim of this study was to assess generation of 15-HETE and other eicosanoids by peripheral blood leukocytes (PBLs) from aspirin-sensitive and aspirin-tolerant asthmatic patients and modulation of 15-HETE generation by a prostaglandin (PG) E1 analogue (misoprostol).MethodsTwenty-four aspirin-sensitive patients with asthma-rhinosinusitis and 18 aspirin-tolerant asthmatic patients were studied, and eicosanoids released from PBLs were assessed by means of enzyme immunoassays.ResultsUnstimulated PBLs from aspirin-sensitive and aspirin-tolerant patients generated similar amounts of PGE2, leukotriene C4, and 15-HETE, but lipoxin A4 release was significantly less in aspirin-sensitive patients (300 ± 70 pg/mL) in comparison with that seen in aspirin-tolerant patients (690 ± 100 pg/mL, P < .05). Cell incubation with 2, 20, or 200 μmol/L aspirin resulted in a dose-dependent increase in 15-HETE generation (mean change of +85%, +189%, and +284% at each aspirin concentration, respectively) only in aspirin-sensitive asthmatic patients. Naproxen stimulated 15-HETE generation in aspirin-sensitive asthmatic patients, but indomethacin or specific COX-2 inhibitors (NS-398 and celecoxib) did not affect 15-HETE release. A synthetic PGE1 analogue (misoprostol) inhibited aspirin-induced 15-HETE release but enhanced 15-HETE generation by aspirin in leukocytes from aspirin-tolerant patients. After preincubation with misoprostol, aspirin induced a dose-dependent production of lipoxin A4 in both groups.ConclusionPBLs from patients with aspirin-sensitive rhinosinusitis-asthma might be specifically triggered by aspirin to generate 15-HETE. Metabolism of 15-HETE is differentially regulated by misoprostol in aspirin-tolerant and aspirin-sensitive asthmatic patients.

Phospholipase A 2

Considerable progress has been made in characterizing the individual participant enzymes and their relative contributions in the generation of eicosanoids, lipid mediators derived from arachidonic acid, such as prostaglandins and leukotrienes. However, the role of individual phospholipase (PL) A 2 enzymes in providing arachidonic acid to the downstream enzymes for eicosanoid generation in biologic processes has not been fully elucidated. In this review, we will provide an overview of the classification of the families of PLA 2 enzymes, their putative mechanisms of action, and their role(s) in eicosanoid generation and inflammation.

STUDY OF THE NIGELLA SATIVAL OIL ON GASTRIC SECRETION AND GASTRIC MUCOSAL LESION INDUCED BY ORAL INDOMETHACIN IN ALBINO RATS

The black seed (Nigella sativa), a member of the Runuculaccae family, is an annual plant growing in countries bordering the Mediterranean sea (Jansen, 1981). It is one of the native plants that arc widely distributed in Egypt (Hashem and EI·Kiey, 1982). In Arabian folk medicine, the black seed and its constituents, especially oils, have been used for treatment of many diseases such as diabetes. hypertension, bronchial asthma and rheumatism (Hashem and El-Kiey, 1982). Moreover. Nigclla sativa seeds are digestive stimulants as well as carminative. diuretic, ami-hclmintic.antitumor activity (Hassan and EI-Dakhakhny, 1992). an immune modulating effect (El-Kadi et al., 1987) and cytoprotectivc effect on tissues exposed to cytotoxic agents (El-Kadl et at, 1987). It is reponed that the seeds contain fixed and volatile oils which contain thyrnoquinone (El-Dakhakhny, 1995). It has been reported that thymoquinone protects organs sgainst oxidative damage induced by a variety of free radical generating agents (EI-Tahir et at, 1993). It was reported also that thyrnoquinone has an anri-Inflammatory activity in rats and inhibits eicosanoids generation inleukocytes (Ligumsky et al., 1995) and non enzymatic peroxid.nion in brain phospholipid liposornes (Kolbasa et al., 1998). Thymoquinone reduces free radical generation especially hydroxyl radicals. These hydroxyl radicals arc known to playamajor role in the pathogenesis of gastric mucosal ulcer (Kolbasa et at, 1998).Indomethacin is widely used in treating many diseases as rheumatic diseases, gout and fevers. Many roxie and side effects can be seen due to the use or abuse of indomethacin, especially those related to the gastroimestinal tract due to its local irritant effect, that leads to gastric erosion and ulceration (Houghton et al., 1995). It is clear that Nigella sativa has a very low toxicity on oral administration (Zaoui et al., 2002). so the present work was done to study the ability of Nigella sativa oil as a cytoprotective agent against oxidative gastric mucosal damage induced by local irritanteffect of indomethacin in albino rats, Also, the study of the histological effect of indomethacin on gastric mucosa and effect of Nigella sativa oil on gastric mucosal lesion induced by indomethacin were studied.

Attenuation of glucocorticoid functions in an Anx-A1-/- cell line.

The Ca(2+)- and phospholipid-binding protein Anx-A1 (annexin 1; lipocortin 1) has been described both as an inhibitor of phospholipase A(2) (PLA(2)) activity and as a mediator of glucocorticoid-regulated cell growth and eicosanoid generation. Here we show that, when compared with Anx-A1(+/+) cells, lung fibroblast cell lines derived from the Anx-A1(-/-) mouse exhibit an altered morphology characterized by a spindle-shaped appearance and an accumulation of intracellular organelles. Unlike their wild-type counterparts, Anx-A1(-/-) cells also overexpress cyclo-oxygenase 2 (COX 2), cytosolic PLA(2) and secretory PLA(2) and in response to fetal calf serum, exhibit an exaggerated release of eicosanoids, which is insensitive to dexamethasone (10(-8)- 10(-6) M) inhibition. Proliferation and serum-induced progression of Anx-A1(+/+) cells from G(0)/G(1) into S phase, and the associated expression of extracellular signal-regulated kinase 2 (ERK2), cyclin-dependent kinase 4 (cdk4) and COX 2, is strongly inhibited by dexamethasone, whereas Anx-A1(-/-) cells are refractory to the drug. Loss of the response to dexamethasone in Anx-A1(-/-) cells occurs against a background of no apparent change in glucocorticoid receptor expression or sensitivity to non-steroidal anti-inflammatory drugs. Taken together, these observations suggest strongly that Anx-A1 functions as an inhibitor of signal-transduction pathways that lead to cell proliferation and may help to explain how glucocorticoids regulate these processes.

The activity against leukocyte eicosanoid generation of essential oil and polar fractions of Adesmia boronioides Hook.f.

The polar fractions (methanol and aqueous extract) and essential oil of Adesmia boronioides aerial parts were tested in vitro at concentrations of 15 and 50 microg/mL, for their effects on the COX and 5-LOX pathways of eicosanoid generation (TXB2, PGE2 and LTB4) in stimulated rat peritoneal leukocytes. Potent inhibition of LTB4 generation was displayed by the methanol extract and the essential oil, whereas the aqueous extract was essentially inactive. The methanol extract also caused potent inhibition of TXB2 generation but the essential oil and the aqueous extract were much less active. The effects on PGE2 production were much less striking, implying that the main effect is on thromboxane synthetase rather than on COX. Although the essential oil caused LDH release in leukocytes treated concurrently with ionophore, suggesting substantial toxicity to the cells, this extract did not affect cell viability according to the MTT test when incubated with the cells in the absence of ionophore. The two other extracts did not affect cell viability at the concentrations tested. It is concluded that Adesmia boronioides contains substance(s) that preferentially inhibit the 5-lipoxygenase activity of arachidonic acid metabolism and suggest that this may contribute to the antiinflammatory actions of extracts of this plant.

Inhibition of cyclooxygenases reduces complement-induced glomerular epithelial cell injury and proteinuria in passive Heymann nephritis.

In the passive Heymann nephritis (PHN) model of rat membranous nephropathy, complement induces glomerular epithelial cell injury and proteinuria, which is partially mediated by eicosanoids. Glomerular cyclooxygenase (COX)-1 and -2 are up-regulated in PHN and contribute to prostanoid generation. In the current study, we address the role of COX isoforms in proteinuria, using the nonselective COX inhibitor indomethacin and the COX-2-selective inhibitor 5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulphonyl)phenyl-2(5H)-furanone (DFU). Four groups of rats with PHN were treated twice daily, from day 7 through 14 with vehicle, 1 mg/kg DFU, 10 mg/kg DFU, or 2 mg/kg indomethacin. Vehicle-treated rats with PHN showed significant proteinuria on day 14 (163 +/- 15 mg/d, n = 19), compared with normal rats (10 +/- 4 mg/d, n = 3, p < 0.001). Treatment with DFU (1 or 10 mg/kg) reduced proteinuria significantly (by ~33%), compared with vehicle, but to a lesser extent than indomethacin (56% reduction). Glomerular eicosanoid generation was reduced significantly in the DFU and indomethacin groups, compared with vehicle. There were no significant differences among vehicle- or DFU-treated groups in [(3)H]inulin clearance, or in glomerular expression of COX-1 and -2. DFU did not affect the autologous immune response. In cultured rat glomerular epithelial cells, COX inhibition reduced complement-induced cytotoxicity, and this reduction was reversed by the thromboxane A(2) analog 9,11-dideoxy-9alpha,11alpha-methanoepoxyprostaglandin F(2alpha) (U46619). Thus, in experimental membranous nephropathy, selective inhibition of COX-2 reduces proteinuria, without adversely affecting renal function. However, inhibition of both COX-1 and -2 is required to achieve a maximum cytoprotective and antiproteinuric effect.

Cytosolic Phospholipase A2 Inhibitors as Therapeutic Agents for Neural Cell Injury

Cytosolic phospholipases A2 are a diverse group of enzymes with a growing number of members. These enzymes hydrolyze membrane glycerophospholipids into arachidonic acid and 1-acyl-lysophospholipids. Arachidonic acid and its metabolites (eicosanoids) play critical roles in the initiation and modulation of inflammation and oxidative stress. It is generally thought that the release of arachidonic acid by cytosolic phospholipase A2 is the rate-limiting step in the generation of eicosanoids. Neurological disorders, such as ischemia, spinal cord injury, and Alzheimers disease, are characterized by inflammatory reactions, oxidative stress, and increased cytosolic phospholipase A2 activity. Several cytosolic phospholipase A2 inhibitors were discovered recently. However, nothing is known about their neurochemical effects, mechanism of action, or toxicity in human or animal models of neurological disorders. Our recent studies have indicated that the use of cytosolic PLA2 inhibitors in kainic acid-induced toxicity model of neural injury can provide useful information on the beneficial effects of these compounds in brain tissue. Keywords: Cytosolic, Phospholipase, A2 Inhibitors, Neural Cell, eicosanoids, kainic acid, PLA2 inhibitors, neurochemical

Colonic anti-inflammatory mechanisms of conjugated linoleic acid

Conjugated linoleic acid (CLA) is a mixture of positional (e.g. 7,9; 9,11; 10,12; 11,13) and geometric ( cis or trans) isomers of octadecadienoic acid. This compound was first shown to prevent mammary carcinogenesis in murine models. Later investigations uncovered a number of additional health benefits, including decreasing atherosclerosis and inflammation while enhancing immune function. The mechanisms of action underlying these biological properties are not clearly understood. The aim of this review is to highlight recent advances in CLA research related to experimental inflammatory bowel disease. In addition, two possible mechanisms of action (i.e. endoplasmic and nuclear) were discussed in detail in the context of enteric inflammatory disorders. Conjugated linoleic acid was first implicated in down-regulating the generation of inducible eicosanoids (i.e. PGE 2 and LTB 4) involved in early micro-inflammatory events (endoplasmic). More recently, CLA has been shown to modulate the expression of genes regulated by peroxisome proliferator-activated receptors (PPARs; nuclear). In pigs, prolonged dietary CLA treatment stimulated the expression of PPAR-γ in the muscle. Thus, evidence supporting both mechanistic theories of CLA acting through eicosanoid synthesis and PPAR activity is available. The further understanding of the anti-inflammatory mechanisms of action of CLA may yield novel nutritional therapies for enteric inflammation.