Products Of Cyclooxygenase Pathway Research Articles

Vaccination with celecoxib-treated dendritic cells improved cellular immune responses in an animal breast cancer model

PurposeProstaglandin E2 (PGE2), a product of cyclooxygenase (COX) pathway of arachidonic acid, exerts inhibitory impacts on dendritic cell (DC) activity to repress anti-tumor immune responses. Therefore, targeting COX during DC vaccine generation may enhance DC-mediated antitumor responses. We aimed to investigate the impacts of DC vaccine treated with celecoxib (CXB), a selective COX2 inhibitor, on some T cell-related parameters. Materials and methodsBreast cancer (BC) was induced in BALB/c mice, and then they received DC vaccine treated with lipopolysaccharide (LPS-mDCs), LPS with a 5 ​μM dose of CXB (LPS/CXB5-mDCs) and LPS with a 10 ​μM dose of CXB (LPS/CXB10-mDCs). The frequency of splenic Th1 and Treg cells and amounts of IFN-γ, IL-12 and TGF-β production by splenocytes, as well as, the expression of Granzyme-B, T-bet and FOXP3 in tumors were determined using flow cytometry, ELISA, and real-time PCR, respectively. ResultsCompared with untreated tumor group (T-control), treatment with LPS/CXB5-mDCs and LPS/CXB10-mDCs decreased tumor growth (P ​= ​0.009 and P ​< ​0.0001), escalated survival rate (P ​= ​0.002), increased the frequency of splenic Th1 cells (P ​= ​0.0872, and P ​= ​0.0155), increased the IFN-γ (P ​= ​0.0003 and P ​= ​0.0061) and IL-12 (P ​= ​0.001 and P ​= ​0.0009) production by splenocytes, upregulated T-bet (P ​= ​0.062 and P ​< ​0.0001) and Granzyme-B (P ​= ​0.0448 and P ​= ​0.4485), whereas decreased the number of Treg cells (P ​= ​0.0014, and P ​= ​0.0219), reduced the amounts of TGF-β production by splenocytes (P ​= ​0.0535 and P ​= ​0.0169), and reduced the expression of FOXP3 (P ​= ​0.0006 and P ​= ​0.0057) in comparison with T-control group. ConclusionsOur findings show that LPS/CXB-treated DC vaccine potently modulated antitumor immune responses in a mouse BC model.

Cyclooxygenase pathway mediates the inhibition of Na-glutamine co-transporter B0AT1 in rabbit villus cells during chronic intestinal inflammation.

In the mammalian intestine, glutamine assimilation by the absorptive villus cells is mediated by Na-glutamine co-transport, specifically by B0AT1. In a rabbit model of chronic intestinal inflammation, B0AT1 is inhibited secondary to a decrease in the number of co-transporters in the brush border membrane (BBM). This inhibition can be reversed by treatment with a broad-spectrum immune modulator such as glucocorticoid suggesting that immune inflammatory mediators may regulate B0AT1 during chronic intestinal inflammation. Arachidonic acid (AA) metabolites (AAM) are increased during chronic intestinal inflammation. However, whether AAM may regulate B0AT1 during chronic intestinal inflammation is unknown. Treatment of rabbits with ATK, to prevent the release of AAM reversed the inhibition of B0AT1. AAM are products of cyclooxygenase (COX) and/or lipoxygenase (LOX) pathways. Inhibition of COX with piroxicam, therefore reduction of prostaglandin formation in the chronically inflamed intestine, reversed the inhibition of B0AT1 to its normal levels. In contrast, inhibition of LOX with MK886, thus reduction of leukotriene formation during chronic enteritis, did not affect the inhibition of B0AT1. Kinetic studies showed that the mechanism of restoration of B0AT1 by ATK or piroxicam was secondary to the restoration of BBM co-transporter numbers. Western Blot analysis also demonstrated restoration of BBM B0AT1 co-transporter numbers. In conclusion, this study demonstrates that Na-glutamine co-transport mediated by B0AT1 in villus cells is regulated by prostaglandins rather than leukotrienes in the chronically inflamed intestine.

Possible Mechanism of Action of Mentha Arvensis in Cardiovascular Diseases

Mentha arvensis (MA) is traditionally used in hypertension and in patients with ischemic heart disease. The scientific rationale for its use is not known. In order to find a pharmacological basis of its use in traditional medicine we made three polarity based fraction from the crude extract of MA and investigated their effects on arachidonic acid metabolism. MA inhibited arachidonic acid metabolite thromboxane B2-a stable analogue of thromboxane-A2, formed via cyclooxygenase pathway and lipoxygenase product 1 and 12-hydroxyeicosatetraenoic acid formed via lipoxygenase pathway. More potent inhibition of thromboxane-B2 compared to lipoxygenase product 1 and 12-hydroxyeicosatetraenoic acid was observed and indicates MA might possess antiplatelet activity as thromboxane-B2 is one of the strongest proponents of platelet aggregation. When MA was investigated for antiplatelet activity, it was found to inhibit human platelet aggregation induced by arachidonic acid as well as by adenosine diphosphate and platelet activating factor while collagen-induced platelet aggregation was unaffected by MA. Since arachidonic acid-induced aggregation is mediated through thromboxane-A2, these results indicate that inhibition of platelet aggregation may be responsible for the observed beneficial effects of MA in patients with ischemic heart disease. Furthermore, MA was also effective in enhancing glutathione peroxidase activity, although it had no significant effect on superoxide dismutase activity. These activities were however, distributed throughout various fraction of MA.

The Lipid Mediator Protectin D1 Inhibits Influenza Virus Replication and Improves Severe Influenza

Influenza A viruses are a major cause of mortality. Given the potential for future lethal pandemics, effective drugs are needed for the treatment of severe influenza such as that caused by H5N1 viruses. Using mediator lipidomics and bioactive lipid screen, we report that the omega-3 polyunsaturated fatty acid (PUFA)-derived lipid mediator protectin D1 (PD1) markedly attenuated influenza virus replication via RNA export machinery. Production of PD1 was suppressed during severe influenza and PD1 levels inversely correlated with the pathogenicity of H5N1 viruses. Suppression of PD1 was genetically mapped to 12/15-lipoxygenase activity. Importantly, PD1 treatment improved the survival and pathology of severe influenza in mice, even under conditions where known antiviral drugs fail to protect from death. These results identify the endogenous lipid mediator PD1 as an innate suppressor of influenza virus replication that protects against lethal influenza virus infection.

Anaphylaxis of small arteries: putative role of nitric oxide and prostanoids

This study investigated possible implication of nitric oxide and prostanoids in anaphylactic reaction in small mesenteric and coronary arteries. MATERIAL AND METHODS. Isolated arteries from guinea pigs, sensitized with 0.5 mL of horse serum or sham-sensitized, were challenged with 1% of horse serum in vitro. Contractile responses of arteries (normalized diameter, 350-450 microm) were recorded by a small blood vessel wire myograph. For inhibition of the release of NO or prostanoids, vessels were pretreated with N(G)-nitro-L-arginine methyl ester (30 microM) or indomethacin (10 microM), respectively. RESULTS. Antigen challenge was followed by contraction of both coronary and mesenteric vessels. Two patterns of contraction were observed: 1) peak contraction - an immediate transient contraction of relatively high amplitude; this was the most common pattern; 2) biphasic: the initial peak contraction was followed by a slow growing contraction with low amplitude. Biphasic pattern was observed in 60% of the mesenteric vessels and 40% of the coronary vessels. Inhibition of NO synthase significantly increased the peak contraction in the coronary vessels and the second-phase contraction in the mesenteric vessels. Inhibition of cyclooxygenase caused a decrease in the peak and second-phase contraction of both the coronary and mesenteric vessels. CONCLUSIONS. Despite anaphylactic contraction, nitric oxide seems to be released from the endothelium following antigen challenge in the small coronary and mesenteric arteries. This may contribute to the development of hypotension during anaphylaxis. Prostanoids are playing a different role - the contracting products of cyclooxygenase pathway are important for the development of anaphylactic contraction of the small isolated arteries.

Polyunsaturated Fatty Acids and Inflammation: Therapeutic Potential in Rheumatoid Arthritis

The fatty acids of most relevance to inflammatory processes are the n-6 polyunsaturated fatty acid (PUFA) arachidonic acid, the precursor of inflammatory eicosanoids like prostaglandin E2 and leukotriene B4, and the n-3 PUFAs eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). EPA and DHA are found in oily fish and fish oils. Eicosanoids derived from the n-6 PUFA arachidonic acid play a role in rheumatoid arthritis (RA), and the efficacy of nonsteroidal antiinflammatory drugs in RA indicates the importance of pro-inflammatory cyclooxygenase pathway products of arachidonic acid in the pathophysiology of the disease. EPA and DHA inhibit arachidonic acid metabolism to inflammatory eicosanoids. EPA gives rise to eicosanoid mediators that are less inflammatory than those produced from arachidonic acid and both EPA and DHA give rise to resolvins that are anti-inflammatory and inflammation resolving. N- 3 PUFAs exert effects on other aspects of immunity relevant to RA like leukocyte chemotaxis, antigen presentation, T cell reactivity and inflammatory cytokine production. Fish oil has been shown to slow the development of arthritis in an animal model and to reduce disease severity. Randomised clinical trials have demonstrated a range of clinical benefits of fish oil in patients with RA including reducing pain, duration of morning stiffness and use of non-steroidal antiinflammatory drugs.

Session 3: Joint Nutrition Society and Irish Nutrition and Dietetic Institute Symposium on ‘Nutrition and autoimmune disease’ PUFA, inflammatory processes and rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease manifested by swollen and painful joints, bone erosion and functional impairment. The joint lesions are characterised by infiltration of T lymphocytes, macrophages and B lymphocytes into the synovium and by synovial inflammation involving eicosanoids, cytokines and matrix metalloproteinases. In relation to inflammatory processes, the main fatty acids of interest are the n-6 PUFA arachidonic acid, which is the precursor of inflammatory eicosanoids such as PGE2 and leukotriene B4, and the n-3 PUFA EPA and DHA, which are found in oily fish and fish oils. Eicosanoids derived from the n-6 PUFA arachidonic acid play a role in RA, and the efficacy of non-steroidal anti-inflammatory drugs in RA indicates the importance of pro-inflammatory cyclooxygenase pathway products of arachidonic acid in the pathophysiology of the disease. EPA and DHA inhibit arachidonic acid metabolism to inflammatory eicosanoids. EPA also gives rise to eicosanoid mediators that are less inflammatory than those produced from arachidonic acid and both EPA and DHA give rise to resolvins that are anti-inflammatory and inflammation resolving. In addition to modifying the lipid mediator profile, n-3 PUFA exert effects on other aspects of immunity relevant to RA such as antigen presentation, T-cell reactivity and inflammatory cytokine production. Fish oil has been shown to slow the development of arthritis in an animal model and to reduce disease severity. Randomised clinical trials have demonstrated a range of clinical benefits in patients with RA that include reducing pain, duration of morning stiffness and use of non-steroidal anti-inflammatory drugs.

Arachidonic acid influences intracellular calcium handling in human osteoblasts

The effect of arachidonic acid (AA) on intracellular Ca 2+ concentration ([Ca 2+] i) in human osteoblasts MG63 was studied. AA caused a concentration-dependent increase in [Ca 2+] i, mainly due to inward Ca 2+ transport from extracellular environment. Moreover, AA in Ca 2+ -free medium produced a small, transient increase of [Ca 2+] i, indicating that AA may also trigger Ca 2+ release from intracellular stores. Because the [Ca 2+] i response to AA was inhibited by the cyclooxygenase (COX) inhibitor indomethacin, we tested the effect of prostaglandins (PGs), products of COX pathway. PGs E1 and E2 caused an increase in [Ca 2+] i, which, however, was far lower than that obtained with AA. The [Ca 2+] i response to AA was not inhibited by nifedipine, suggesting that AA did not activate a voltage-dependent Ca 2+ channel. Our results indicate that AA could modulate [Ca 2+] i in MG63 human osteoblasts, where it may influence Ca 2+ transport across both plasma and endoplasmic membranes. Furthermore, they suggest that osteoblast activity may be modulated by AA.

PAR-2 activating peptide-induced stimulation of pregnant rat myometrium contractile activity partly involves the other membrane receptors

Objective To study if spontaneous contractions augmented by proteinase-activated receptor-2 (PAR-2)-activating peptide serine-leucine-isoleucine-glycine-arginine-leucine (SLIGRL) involve coactivation of membrane chemoceptors and are associated with expression of PAR-2 mRNA in non-pregnant and pregnant rat myometrium. Materials and methods Non-pregnant, mid-pregnant, and late pregnant rat uterine horn and small intestine segments were snap-frozen in liquid nitrogen to determine PAR-2 mRNA levels by real time polymerase chain reaction (PCR). Uterine rings were used for isometric tension recording. Effect of SLIGRL (0.1 mM) on spontaneous contractions before and after exposure to ibuprofen (cyclooxygenase inhibitor, 1.0 μM), SQ-29548 (thromboxane A 2 receptor inhibitor, 1.0 μM), ketotifen (histamine 1 receptor inhibitor, 10 μM), WEB-2170BS (platelet-activating factor (PAF) receptor inhibitor, 10 μM), atropine (muscarinic receptor inhibitor, 0.1 μM), or ketanserin (serotonin receptor inhibitor, 10 μM) were compared. Paired t-test and one-way ANOVA followed by Dunnett's or Newman–Keuls post hoc tests were used for statistical analysis when appropriate. Significance P < 0.05. Results The agents did not significantly affect time-associated decay in spontaneous contractile activity in any group of the tissues. Activation of spontaneous contractions induced by SLIGRL in non-pregnant rat myometrium did not involve coactivation of membrane chemoceptors, while in mid-pregnant rat myometrium coactivation of prostanoid, histamine, and serotonin receptors and in late pregnant rat myometrium coactivation of thromboxane receptors was noted. Expression of PAR-2 mRNA was similar in non-pregnant, mid-pregnant, and late pregnant rat myometrium. Conclusions Expression of PAR-2 in rat myometrium is not dependent on gestational age. Stimulation of PAR-2 is associated with production/release of cyclooxygenase pathway product(s) activating thromboxane/prostaglandin H2 receptors, partial involvement of histamine H1 receptors and serotonin receptors in midpregnancy and thromboxane A2/prostaglandin H2 receptors in late pregnancy.

Prostaglandins, not lipoxygenase products, mediate insect microaggregation reactions to bacterial challenge in isolated hemocyte preparations

Nodulation is the predominant cellular defense reaction to bacterial challenge in insects. Eicosanoids mediate several steps in the nodulation process, including formation of hemocyte microaggregations. Isolated hemocyte preparations synthesize and secrete eicosanoids, which mediate hemocytic immune reactions. Two major groups of eicosanoids are prostaglandins (products of cyclooxygenase pathways) and various products of lipoxygenase pathways. In this study, we test the hypothesis that prostaglandins, but not lipoxygenase products, mediate hemocyte microaggregation reactions in response to bacterial challenge. Our results indicate that isolated hemocyte preparations pretreated with the cyclooxygenase inhibitors indomethacin and naproxen yielded fewer microaggregates than untreated control groups (3.7×10 5 microaggregates/ml hemolymph vs. 11.0×10 5 microaggregates/ml hemolymph). These inhibitors influence hemocyte microaggregate formation in a dose–dependent manner in treatments ranging from 0 to 200 μM. The lipoxygenase inhibitors esculetin and caffeic acid did not impact the formation of microaggregates in this system. The influence of the phospholipase A 2 inhibitor dexamethasone was reversed by amending experimental (dexamethasone-treated) preparations with prostaglandin H 2, but not prostaglandin D 2, prostaglandin E 2, nor 5( S)-hydroperoxy-6E,8Z,11Z,14Z-eicosatetraenoic acid, a product of the lipoxygenase pathway. We infer that prostaglandins are the primary mediators of microaggregation reactions to bacterial challenge in insect hemocyte preparations.

Proteinase-activated receptor-2 activation induces uterine contractility in term pregnant rats that is not dependent on mast cell activation and cyclo-oxygenase products

Objectives: This study was undertaken to evaluate the effect of proteinase-activated receptor-2 (PAR-2) activation on the contractility of uterine tissues from term pregnant rats and the role of mast cells and prostaglandins in such an effect. Study Design: Uterine rings from pregnant (day 20-21) Sprague-Dawley rats were used for isometric tension recording in organ chamber experiments (Krebs solution, 5% carbon dioxide in air, 37°C, pH ~7.4). Responses to the PAR-2 activating peptide SLIGRL (serine-leucine-isoleucine-glycine-arginine-leucine), and to the inactive reverse peptide LRGILS (leucine-arginine-glycine-isoleucine-leucine-serine) were determined after pretreatments with compound 48/80, cromolyn, S[+]-chlorpheniramine maleate, cimetidine, combinations of histamine (H) receptor antagonists with cromolyn or ibuprofen and compared with vehicle. Results SLIGRL significantly augmented contractility of uterine tissues, and this response was not inhibited by compound 48/80, cromolyn, and ibuprofen, as well as by H1- and H2-receptor antagonists, alone or in combination with cromolyn. Conclusion: PAR-2 activation augments uterine contractility in tissues obtained from term pregnant rats, and this effect is independent of mast cell activation or cyclo-oxygenase pathway products. (Am J Obstet Gynecol 2003;188:1498-1503.)

Arachidonic acid increases intracellular calcium in erythrocytes

Recently, we have measured in erythrocytes a voltage-modulated and dihydropyridine-inhibited calcium influx. Since arachidonic acid and other polyunsaturated fatty acids influence the activities of most ion channels, we studied their effects on the erythrocyte Ca 2+ influx. It was measured on fresh erythrocytes, isolated from healthy donors, using the fluorescent dye Fura 2 as indicator of [Ca 2+] i. AA (5–50 μM) and EPA (20–30 μM) stimulated a concentration-dependent increase in [Ca 2+] i, deriving from extracellular calcium (1 mM), without affecting the intra- and extracellular pH and membrane voltage. The Ca 2+ influx rate varied from 0.5 to 3 nM Ca 2+/s in the presence of AA and from 0.9 to 1.7 nM Ca 2+/s with EPA. The Ca 2+ influx elicited by AA and EPA was not inhibited by dihydropyridines, while cyclooxygenase inhibitors were effective and PGE1 or PGE2 did not produce any effect. We conclude that AA could activate an erythrocyte voltage-independent Ca 2+ transport via an intermediate product of cyclooxygenase pathway; however, a direct interaction with the membrane lipid–protein cannot be excluded.

EFFECT OF ARACHIDONIC ACID METABOLIC INHIBITORS ON HYPOXIA/REOXYGENATION-INDUCED RENAL CELL INJURY

The present study was undertaken to examine the role of arachidonic acid (AA) metabolites in hypoxia/reoxygenation (H/R)-induced renal cell injury in rabbit renal cortical slices using AA metabolic inhibitors. Inhibitors of cyclooxygenase (indomethacin and diclofenac sodium) and lipoxygenase pathways (nordihydroguaiaretic acid, caffeic acid, and eicosapentaenoic acid) reduced H/R-induced LDH release in a dose-dependent manner, whereas an inhibitor of cytochrome P-450 monooxygenase pathway ethoxyresorufin was not effective. AA increased LDH release in control slices, and the effect was not altered by indomethacin and nordihydroguaiaretic acid. The protective effect of indomethacin was not affected by addition of PGE2, a main product of cyclooxygenase pathway in the kidney. H2O2-induced LDH release was prevented by inhibitors of lipoxygenase but not by inhibitors of cyclooxygenase and cytochrome P-450 monooxygenase H/R-induced LDH release was not altered by iron chelators, phenanthroline and deferoxamine, and a potent antioxidant, N,N,-diphenyl-p-phenylenediamine, suggesting that the H/R-induced cell injury is not attributed to a generation of reactive oxygen species. Morphological studies showed that H/R-induced structural changes including cell necrosis were significantly prevented by indomethacin.These results suggest that inhibitors of cyclooxygenase and lipoxy genase pathways exert a direct protective effect against the H/R-induced cell injury in renal tubules. Whether these effects are mediated by alterations of AA metabolic pathways is not certain.

Cyclooxygenase-2 up-regulation after FLAP transfection in human adenocarcinoma cell line HT29 cl.19A

Five-lipoxygenase-activating protein (FLAP) is usually described as an essential protein to activate the leukotriene (LTs) synthesis via the 5-lipoxygenase pathway. In the enterocyte model HT29 cl.19 A cell line, 5-lipoxygenase metabolism was found despite the lack of FLAP expression. Therefore HT29 cl.19A represents an original mammalian model to study FLAP-dependent leukotriene synthesis. In FLAP cDNA transfected HT29 cl.19 A cells, FLAP expression led to an increase in cyclooxygenase pathway products (mainly PGE 2) without an increase in 5-lipoxygenase metabolism. This increase in PGE 2 synthesis was associated with a cyclooxygenase-2 up-regulation in comparison to untransfected HT29 cl.19A cells. These results suggest a possible interaction between the two major pathways of arachidonic acid metabolism.

Role of free oxygen radicals and prostanoids in the pathogenesis of Henoch-Schönlein Purpura

The pathogenesis of Henoch-Schönlein Purpura (HSP) is still controversial. The aim of our study was to investigate the role of oxidative stress and cyclooxygenase (CO) pathway products in the pathogenesis of HSP. In order to investigate this, malondialdehyde (MDA) levels, indicating lipid peroxidation, prostaglandin E (PGE)-like activity as inflammatory mediator and vitamin E (vit-E) levels indicating anti-oxidant status were studied in a group of 10 children with HSP (five girls and five boys, aged 6–21 years, mean 10.7 years), both in the acute and recovery phase of the disease and in five age and sex-matched healthy children as a control group. The patients were also grouped into low and high clinical score groups. Plasma levels of MDA and PGE-like activity were significantly elevated in the active phase of HSP compared to the recovery phase. Vit-E levels were significantly reduced in the active phase compared to the recovery phase. The plasma levels of PGE-like activity of the patients obtained in the active phase were significantly higher than the levels of the control group, whereas the levels of the recovery phase were significantly lower than in the control group. No such difference between the controls and MDA and vit-E levels in the patient group was shown. No correlation between the clinical scores and the parameters studied could be found. Our findings indicate that oxidant stress and CO pathway products may play a role in the pathogenesis of HSP.

Inhibitory effect of indomethacin on tachyphylaxis in response to acetaldehyde-induced bronchoconstriction in patients with asthma

Background: Acetaldehyde, a main factor in alcohol-induced asthma, causes bronchoconstriction indirectly through histamine release; and tachyphylaxis in response to repeated inhalation of acetaldehyde is observed in patients with asthma. Objective: The study was designed to clarify the mechanism of tachyphylaxis in response to acetaldehyde-induced bronchoconstriction. Methods: We investigated the bronchial response to inhaled acetaldehyde in 10 patients with asthma who were treated with indomethacin in a double-blind, randomized, placebo-controlled, crossover fashion. Results: The mean acetaldehyde concentration causing a 20% fall in FEV 1 with placebo increased significantly from 13.0 mg/ml (geometric SEM = 0.115) to 31.1 mg/ml (geometric SEM = 0.069) over a period of 1 hour ( p < 0.01), whereas there was a slight but not significant tachyphylaxis during indomethacin treatment. The tachyphylactic effect, expressed as logarithmic value of the second PC 20 minus logarithmic value of the first PC 20, was significantly ( p < 0.05) reduced from 0.380 (0.066) with placebo treatment to 0.148 (0.094) with indomethacin treatment. Conclusion: These results suggest an important role of cyclooxygenase pathway products in decreased response to repeated inhalation of acetaldehyde in patients with asthma. (J Allergy Clin Immunol 1997;99:620-3.)

Effects of chronic treatment with carvedilol on abnormalities of endothelium-dependent relaxation and structure of endothelium in resistance arteries of SHRSP.

1. This study investigated the effects of chronic treatment with carvedilol, a beta-blocking agent with an alpha-blocking activity, on blood pressure, endothelium-dependent relaxation and the endothelial structure of the mesenteric resistance artery in stroke-prone spontaneously hypertensive rats (SHRSP). 2. Chronic treatment with carvedilol at a dose range of 30-120 mg/kg per day lowered systolic blood pressure of SHRSP from 234.9 +/- 3.3 to 198.7 +/- 3.1 mmHg at 16 weeks of age. 3. Acetylcholine-induced endothelium-dependent relaxation was impaired in the mesenteric artery from SHRSP and high concentrations of acetylcholine produced contractions. The impairment of the relaxation was abolished in the presence of indomethacin. Carvedilol treatment improved the impairment in the preparation from SHRSP. The structural abnormality of endothelium was observed in the preparation from SHRSP. The abnormality could be prevented by the antihypertensive treatment. 4. These results suggest that the impairment of endothelium-dependent relaxation in the preparation from SHRSP is due to the corelease of an endothelium-derived contracting factor which is considered to be a product of cyclo-oxygenase pathway of arachidonic acid cascade and that the impairment can be prevented by the antihypertensive treatment with carvedilol.

Platelet-activating factor stimulates eicosanoid production in cultured feline tracheal epithelial cells.

The effect of platelet-activating factor (PAF) on eicosanoid generation and release in cultured feline tracheal epithelial cells was investigated by measuring a wide range of lipoxygenase and cyclooxygenase pathway products. Subconfluent epithelial cell cultures were stimulated by PAF and eicosanoid production was determined by high performance liquid chromatography (HPLC) of [3H]-labeled arachidonic acid (AA) metabolites and by radioimmunoassay (RIA) following HPLC separation. The HPLC chromatograms revealed that PAF augmented the release of prostaglandin (PG)E2, PGF2 alpha, 12-hydroxyeicosatetraenoic acid (HETE), and AA. Among these eicosanoids, PGE2 predominated under baseline conditions and following PAF exposure. RIAs of the nonradiolabeled HPLC elution corresponding to various eicosanoid standards demonstrated that PAF increased the production of 6-keto-PGF1 alpha, thromboxane B2 (TXB2), PGD2, 5-HETE, and 15-HETE, as well as PGE2, PGF2 alpha, and 12-HETE. The PAF-induced eicosanoid augmentation was dose-dependent and occurred within 1 hour with a prompt decline following termination of PAF exposure. This stimulating effect of PAF on eicosanoid release was blocked by two PAF receptor antagonists, Ro 19-3704 and WEB 2086. The PAF-induced increase in eicosanoid release was similar in magnitude to the increase caused by calcium ionophore (Ca-ionophore) A23187, a potent known stimulus for eicosanoid release. Cells of different culture durations (3 and 6 days) showed similar capacity for eicosanoid production. We conclude that PAF stimulates the production of cyclooxygenase and lipoxygenase pathway products from airway epithelial cells via PAF receptors, and that these epithelium-derived eicosanoids may be responsible for some of the PAF-induced respiratory physiological and pathophysiological effects.

The skin as a model to study the pathogenesis of IgE-mediated acute and late-phase responses

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Eicosanoid production by human aortic endothelial cells in response to endothelin

Endothelial cells actively regulate their environment by secreting humoral substances, including endothelin-1 and a variety of eicosanoids, that have local actions. To elucidate interactions among these local mediators, we measured release of cyclooxygenase and lipoxygenase pathway products of arachidonate metabolism by human aortic endothelial cells after incubation with endothelin-1. Supernatants were collected, extracted, and fractionated using high-performance liquid chromatography. Radioimmunoassays for eicosanoids were performed on the appropriate fractions. After endothelin stimulation, production of the prostacyclin metabolite 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha), the thromboxane (Tx) metabolite TxB2, and prostaglandin E2 (PGE2) were increased (307 +/- 48, 320 +/- 91, and 315 +/- 74% of control, P < 0.05). Leukotriene B4 (LTB4) release was modestly increased (195 +/- 19% of control, P < 0.05). The release of 5-hydroxyeicosatetraenoic acid (5-HETE) was increased (300 +/- 57% of control, P < 0.05); production of 12-HETE and 15-HETE was unchanged. Production of eicosanoids peaked between 30 and 120 min. Preincubation with pertussis toxin prevented increased production of PGE2, LTB4, and 5-HETE after endothelin-1 stimulation; pretreatment with sphingosine had no effect. Interactions between endothelin and eicosanoids may be important components of the complex network that regulates vascular tone, coagulation, and inflammation at the local level.