Leukotriene Generation Research Articles

Effects of Pancreatic and Snake Venom Phospholipase A2 on the Generation of Leukotriene B4 and C4 by Human Leukocytes in Vitro

To investigate the effects of phospholipase A2 (PLA2) on leukotriene (LT) generation, we evaluated LTB4 and LTC4 production by human leukocytes after incubation with porcine pancreatic and snake venom PLA2. The pancreatic and venom PLA2 did not induce LTB4 and LTC4 generation by human leukocytes alone. However, both types of PLA2 promoted opsonized zymosan-induced LTB4 production in a dose-dependent manner (from 10(-10) to 10(-8) M), whereas they had no effect on opsonized zymosan-induced LTC4 generation. This promoting effect of pancreatic and venom PLA2 required Ca2+ in the incubation medium and was inhibited by mepacrine (10(-5) M). These findings suggest that increased production of PLA2 in combination with inflammatory stimuli such as endotoxin enhance LTB4 biosynthesis in acute pancreatitis.

Peroxynitrite-induced rat colitis—A new model of colonic inflammation

Background: Excessive production of nitric oxide, characteristic of inflamed states, may have deleterious effects through its facile conversion (in the presence of O2) to peroxynitrite, which promotes lipid and sulfhydryl oxidation. This study assessed the effect of peroxynitrite on the rat colon. Methods: Peroxynitrite was administered intrarectally to rats. One, 3,7, and 21 days after treatment, a distal colonic segment was isolated and tissue was obtained for histological evaluation and determination of myeloperoxidase activity and NOx, and eicosanoids generation. Results: Within 24 hours, the exposed segment was edematous and congested with occasional hemorrhagic mucosal ulceration. On day 7, the lumen was narrow; at day 21, there were signs of stenosis. Histological analysis showed transmucosal necrosis, acute inflammation, and exudative edema 24 hours after treatment. Surface re-epithelization and infiltration of granulation tissue were present at 1 week. Resolution of edema, mucin repletion, thickening of muscularis mucosa and propria, and fibrosis were observed at 3 weeks. Significant increase in NOx generation and myeloperoxidase and NO synthase activities were observed at 24 hours, whereas enhanced leukotriene generation was observed only at 21 days. Conclusions: Peroxynitrite-induced colonic inflammation provides a novel model of NO-related tissue injury and offers the opportunity to further explore the potential role of NO in the pathogenesis of inflammatory bowel disease.

Purification of human blood basophils and leukotriene C 4 generation following calcium ionophore stimulation

A simple method for purification of basophils from a relatively small volume of blood has been developed, which enables us to collect basophils with a purity of over 80%. Basophils were partially purified from 10∼20 ml of citrated whole blood using the discontinuous Percoll density gradient centrifugation technique and then contaminant cells were removed using monoclonal antibodies against CD2, CD19, CD14 and CD16. At the end of the procedure, basophils were >80% pure with lymphocytes accounting for most of the contaminating cells. When stimulated with anti-IgE or fMLP, histamine release from purified basophils was similar to that from mixed leukocytes. When highly purified basophils were challenged with calcium ionophore A23187, generation of leukotriene C 4 (LTC 4) was not significantly different between asthmatic patients and normal subjects ( 45.6 ± 22.6 vs 52.7 ± 25.6 ng 10 6 cells). Basophils were capable of generating LTC 4 in approximately the same quantities as eosinophils ( 46.5 ± 11.7 ng 10 6 cells, n = 3). Furthermore, it has been shown that incubation of basophils and eosinophils with calcium ionophore generates only small quantities of thromboxane B 2 (TXB 2).

MK 886, an antagonist of leukotriene generation, inhibits DNA synthesis in a subset of acute myeloid leukaemia cells

We have studied the actions of inhibitors of leukotriene generation on DNA synthesis (measured by 3H-thymidine incorporation) in blast cells from patients with acute myeloid leukaemia (AML). Cells from a subset only of these patients were sensitive to MK 886, a potent selective inhibitor of leukotriene synthesis. By contrast, DNA replication in cells from all of the patients was inhibited by nordihydroguiaretic acid (NDGA), a leukotriene synthesis inhibitor of lower selectivity. DNA synthesis in normal bone marrow cells and phytohaemagglutinin-stimulated lymphocytes was sensitive to NDGA but not to MK 886. The data suggest that NDGA inhibits DNA replication by a mechanism other than the abolition of leukotriene biosynthesis, but that DNA synthesis in a subset of AML cells may be dependent on the generation of lipoxygenase products, as indicated by sensitivity to MK 886.

Effect of intravenously infused eicosapentaenoic acid on the leukotriene generation in patients with active Crohn's disease A IKEHATA, N HIWATASHI, Y KINOUCHI, ET AL Tohoku University School of Medicine, Sendai, Japan

Nutrition in Clinical PracticeVolume 8, Issue 4 p. 185-185 Article Effect of intravenously infused eicosapentaenoic acid on the leukotriene generation in patients with active Crohn's disease A IKEHATA, N HIWATASHI, Y KINOUCHI, ET AL Tohoku University School of Medicine, Sendai, Japan Sheila Campbell, Sheila CampbellSearch for more papers by this author Sheila Campbell, Sheila CampbellSearch for more papers by this author First published: 01 August 1993 https://doi.org/10.1177/088453369300800408AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume8, Issue4August 1993Pages 185-185 RelatedInformation

Antioxidants impair the coupling of cell-surface ligand receptors to the inositol lipid signalling pathway in human T lymphocytes but not in jurkat T lymphoblastic leukemia cells. Evidence that leukotrienes are not involved in the coupling mechanism

Ligands including phytohaemagglutinin (PHA) and anti-CD3 monoclonal antibodies trigger the generation of inositol lipid-derived second messengers following their binding to cell-surface structures of human T lymphoid cells. Previous evidence has suggested that the generation of leukotrienes may play an intermediary role in coupling the ligation of T lymphoid cell-surface structures to the inositol lipid signalling system in these cells (A.R. Mire-Sluis et al. (1989) FEBS Lett. 258, 84–88). Here we have studied the actions of two novel selective leukotriene biosynthesis inhibitors, MK 886 and BW A4C and of two general lipid soluble antioxidants, butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) on this pathway. Neither MK 886 nor BW A4C abrogated stimulation of inositol lipid breakdown following PHA or anti CD3 treatment of T lymphocytes. By contrast, this pathway was inhibited by BHT and BHA. These observations, together with our failure to demonstrate the generation of lipoxygenase products following PHA stimulation of T lymphocytes, suggests that an antioxidant-sensitive step other than the generation of leukotrienes plays a critical role in coupling cell-surface receptors to the inositol lipid signalling system in these cells. By contrast none of these inhibitors abrogated ligand-stimulated inositol lipid signalling in Jurkat T acute lymphoblastic leukaemia cells. These results suggest a heterogeneity in the organization of the signal transduction machinery in lymphoid cells at different stages of differentiation.

Oxidized LDL-induced leukocyte/endothelium interaction in vivo involves the receptor for platelet-activating factor.

Leukocyte adhesion and subendothelial emigration, constant hallmarks of early atherogenesis, have been ascribed to the action of oxidized low-density lipoprotein (oxLDL). Using intravital fluorescence microscopy in the skinfold-chamber model in hamsters, we have previously shown that systemic administration of oxLDL stimulates leukocyte adhesion in vivo through a mechanism that depends on the generation and/or action of both leukotrienes and superoxide radicals. On the basis of the fact that oxygen radical-catalyzed peroxidation of phospholipids results in the generation of fragments with short sn2 residues, which besides authentic platelet-activating factor (PAF), activate the receptor for PAF on leukocytes and thereby induce leukocyte adhesion, we asked whether pretreatment of hamsters with a specific PAF receptor antagonist (WEB2170; 1 mg/kg of body weight IV, 10 minutes before oxLDL) attenuates leukocyte adhesion after injection of oxLDL (4 mg/kg of body weight IV, oxidized by 7.5 mumol/L Cu2+ for 18 hours at 37 degrees C). We demonstrate herein that in contrast to untreated control animals in which oxLDL elicited rolling and adhesion of circulating leukocytes to the endothelium of venules and arterioles, oxLDL-induced leukocyte adhesion was significantly attenuated in WEB2170-pretreated animals. These changes cannot be ascribed to alterations of microhemodynamic parameters and, hence, wall shear conditions. This finding indicates that oxLDL-induced leukocyte/endothelium interaction involves the PAF receptor, which may function both as a receptor for authentic PAF or for PAF-like lipids that are generated in a free radical-catalyzed peroxidation of phospholipids.

Neutrophil leukotriene generation and pulmonary dysfunction following abdominal aortic aneurysm repair: Gary A. Fantini, MD, Dominick Gadaleta, MD, Michael F. Silane, MD, and John M. Davis, MD, The New York Hospital-Cornell Medical Center and Cornell University Medical College, New York, N.Y.

Neutrophil leukotriene generation and pulmonary dysfunction following abdominal aortic aneurysm repair: Gary A. Fantini, MD, Dominick Gadaleta, MD, Michael F. Silane, MD, and John M. Davis, MD, The New York Hospital-Cornell Medical Center and Cornell University Medical College, New York, N.Y.

Differential activation of the endogenous leukotriene biosynthesis by two different preparations of granulocyte-macrophage colony-stimulating factor in healthy volunteers

Results from in vitro investigations and recent data obtained in patients with drug-induced cytopenia or myelodysplasia suggest that leukotrienes may be involved in mediating some of the actions of granulocyte-macrophage colony-stimulating factor (GM-CSF). In the present study, the possible role of leukotrienes was further characterized in 21 healthy individuals to avoid modification of response to GM-CSF by disease-specific variables. The effects of two different preparations of human recombinant GM-CSF, ie, glycosylated GM- CSF as expressed in a Chinese hamster ovary carcinoma (CHO) cell line and nonglycosylated GM-CSF obtained from Escherichia coli, were compared. GM-CSF was administered subcutaneously at a single dose of 0.7 nmol/kg body weight. Pharmacokinetic parameters and hematopoietic and adverse effects were monitored by blood analyses or physical examination, respectively. Leukotriene generation in vivo was evaluated by determination of leukotriene E4 and N-acetyl-leukotriene E4 in urine. After the injection of GM-CSF from E coli, serum concentrations increased and decreased more rapidly and reached a 2.3-fold higher maximum compared with GM-CSF from CHO. GM-CSF induced a biphasic change in leukocyte counts that proceeded considerably faster after the E coli preparation than after GM-CSF from CHO. The urinary leukotriene concentration increased 1.3- to 14-fold or 2.1- to 44-fold after the administration of GM-CSF from CHO or E coli, respectively. Urinary leukotriene concentrations correlated significantly with the maximum of basophil counts and correlated with the occurrence of some adverse reactions, ie, flu-like symptoms, bone pain, or dyspnoea. Our data confirm the conception that leukotrienes may play a significant role in GM-CSF action in vivo. They especially direct attention to the possible relevance of leukotrienes to untoward effects of GM-CSF treatment.

Differential Activation of the Endogenous Leukotriene Biosynthesis by Two Different Preparations of Granulocyte-Macrophage Colony-Stimulating Factor in Healthy Volunteers

Results from in vitro investigations and recent data obtained in patients with drug-induced cytopenia or myelodysplasia suggest that leukotrienes may be involved in mediating some of the actions of granulocyte-macrophage colony-stimulating factor (GM-CSF). In the present study, the possible role of leukotrienes was further characterized in 21 healthy individuals to avoid modification of response to GM-CSF by disease-specific variables. The effects of two different preparations of human recombinant GM-CSF, ie, glycosylated GM-CSF as expressed in a Chinese hamster ovary carcinoma (CHO) cell line and nonglycosylated GM-CSF obtained from Escherichia coli, were compared. GM-CSF was administered subcutaneously at a single dose of 0.7 nmol/kg body weight. Pharmacokinetic parameters and hematopoietic and adverse effects were monitored by blood analyses or physical examination, respectively. Leukotriene generation in vivo was evaluated by determination of leukotriene E4 and N-acetyl-leukotriene E4 in urine. After the injection of GM-CSF from E coli, serum concentrations increased and decreased more rapidly and reached a 2.3-fold higher maximum compared with GM-CSF from CHO. GM-CSF induced a biphasic change in leukocyte counts that proceeded considerably faster after the E coli preparation than after GM-CSF from CHO. The urinary leukotriene concentration increased 1.3- to 14-fold or 2.1- to 44-fold after the administration of GM-CSF from CHO or E coli, respectively. Urinary leukotriene concentrations correlated significantly with the maximum of basophil counts and correlated with the occurrence of some adverse reactions, ie, flu-like symptoms, bone pain, or dyspnoea. Our data confirm the conception that leukotrienes may play a significant role in GM-CSF action in vivo. They especially direct attention to the possible relevance of leukotrienes to untoward effects of GM-CSF treatment.

Sputum tumour necrosis factor-alpha and leukotriene concentrations in cystic fibrosis.

It is postulated that a vigorous host inflammatory response in the cystic fibrosis lung contributes to lung injury. Tumour necrosis factor-alpha (TNF-alpha) may play a part in that process and in the generation of leukotrienes. Therefore, the relationships between sputum TNF-alpha, leukotriene concentration, and lung function abnormalities in 16 children with cystic fibrosis were investigated. Each subject provided sputum samples and performed spirometry. TNF-alpha was measured by enzyme linked immunosorbent assay; individual leukotrienes were separated using high performance liquid chromatography and quantified by radioimmunoassay. The geometric mean concentration of TNF-alpha was 129.7 pg/ml and 95% confidence interval 48.2 to 348.3. Mean (SEM) leukotriene B4 (LTB4) was 97.8 (22.9) pmol/g and total cysteinyl leukotrienes were 60.9 (14.8) pmol/g. Mean (SD) forced expiratory volume in one second (FEV1) of the group was 53 (15)% of predicted and forced vital capacity (FVC) was 65 (14)% of predicted. There was a significant positive correlation between TNF-alpha and both LTB4 and the total cysteinyl leukotriene sputum content. An inverse relationship existed between TNF-alpha and FEV1 and FVC. Moreover, a negative correlation was observed between sputum LTB4 and FEV1 and FVC. These results suggest that TNF-alpha and the leukotrienes may participate in the airways inflammation and airflow obstruction observed in cystic fibrosis subjects and support the hypothesis that TNF-alpha upregulates the 5-lipoxygenase pathway in vivo.

Effect of 5-lipoxygenase inhibitors on in situ LTB4 biosynthesis following calcium ionophore stimulation in the rat pleural cavity.

The intrapleural injection of carrageenan in the rat induces exudate formation, cellular influx and leukotriene generation in the pleural cavity. We have demonstrated that the inflammatory response (exudate volume, and LTB4 levels) is increased in situ by the intrapleural administration of calcium ionophore A 23187 (100 nmol/rat) at 4, 16, 24, 48, and 72 h after the injection of carrageenan and that the A 23187-induced increase is dose-dependent. The oral administration of A-64077 and MK-886, two 5-lipoxygenase inhibitors (5-LOIs), at 10 mg/kg causes marked decreases in LTB4 release at the above-mentioned time intervals. However, A 23187-induced augmented exudate formation is not affected by the treatment with 5-LOIs. The results suggest that the use of 5-LOIs to inhibit LTB4 biosynthesis may be beneficial in various LTB4-dependent pathological conditions.

Evidence that endogenous generation of leukotrienes does not regulate proliferation of malignant hemopoietic cell lines

The proliferation of malignant hemopoietic cell lines is inhibited by antagonists of 5-lipoxygenase, suggesting that the endogenous generation of leukotrienes via the action of this enzyme may play some role in the proliferation of these cells (Snyder D. S., Castro R. & Desforges J. F. (1989), Expl Hemat. 17, 6). Here we have confirmed that the lipoxygenase inhibitors piriprost, nordihydroguiaretic acid and BW755C decreased DNA synthesis and proliferation of leukemic cell lines. However, the concentrations of these drugs required for half-maximal inhibition of proliferation were significantly greater than their ic 50 values for 5-lipoxygenase inhibition. We therefore studied the actions of two novel, potent lipoxygenase inhibitors, BWA4C and MK886, on proliferation (as measured by estimating the number of viable, trypan blue-excluding cells) and DNA synthesis (measured by the incorporation of radiolabeled thymidine) in the leukemia cell lines HL60, K562 and Jurkat. Neither parameter was affected by concentrations of these drugs which were shown in parallel studies to substantially inhibit leukotriene generation in whole blood. The data show that endogenous leukotriene generation does not play a significant role in the regulation of proliferation of these leukemic cell lines and suggest that conclusions about leukotriene involvement in the control of cellular metabolic pathways based on the use of lipoxygenase inhibitors should be re-assessed.

Dietary omega-3 polyunsaturated fatty acids inhibit phosphoinositide formation and chemotaxis in neutrophils.

Earlier studies demonstrated that dietary omega-3 polyunsaturated fatty acid (PUFA) supplementation attenuates the chemotactic response of neutrophils and the generation of leukotriene (LT) B4 by neutrophils stimulated with calcium ionophore; however, the mechanisms and relationship of these effects were not examined. Neutrophils and monocytes from eight healthy individuals were examined before and after 3 and 10 wk of dietary supplementation with 20 g SuperEPA daily, which provides 9.4 g eicosapentaenoic acid (EPA) and 5 g docosahexaenoic acid. The maximal neutrophil chemotactic response to LTB4, assessed in Boyden microchambers, decreased by 69% after 3 wk and by 93% after 10 wk from prediet values. The formation of [3H]inositol tris-phosphate (IP3) by [3H]inositol-labeled neutrophils stimulated by LTB4 decreased by 71% after 3 wk (0.033 +/- 0.013% [3H] release, mean +/- SEM) and by 90% after 10 wk (0.011 +/- 0.011%) from predict values (0.114 +/- 0.030%) as quantitated by beta-scintillation counting after resolution on HPLC. LTB4-stimulated neutrophil chemotaxis and IP3 formation correlated significantly (P < 0.0001); each response correlated closely and negatively with the EPA content of the neutrophil phosphatidylinositol (PI) pool (P = 0.0003 and P = 0.0005, respectively). Neither the affinities and densities of the high and low affinity LTB4 receptors on neutrophils nor LTB4-mediated diglyceride formation changed appreciably during the study. Similar results were observed in neutrophils activated with platelet-activating factor (PAF). The summed formation of LTB4 plus LTB5 was selectively inhibited in calcium ionophore-stimulated neutrophils and was also inhibited in zymosan-stimulated neutrophils. The inhibition of the summed formation of LTB4 plus LTB5 in calcium ionophore-stimulated neutrophils and in zymosan-stimulated neutrophils did not correlate significantly with the EPA content of the PI pool. The data indicate that dietary omega-3 PUFA supplementation inhibits the autoamplification of the neutrophil inflammatory response by decreasing LTB4 formation through the inactivation of the LTA epoxide hydrolase and independently by inhibiting LTB4- (and PAF) stimulated chemotaxis by attenuating the formation of IP3 by the PI-selective phospholipase C. This is the initial demonstration that dietary omega-3 PUFA supplementation can suppress signal transduction at the level of the PI-specific phospholipase C in humans.

Mobilization of different arachidonate pools and their roles in the generation of leukotrienes and free arachidonic acid during immunologic activation of mast cells.

Immunologic activation of mast cells leads to the mobilization of arachidonic acid (AA) from membrane phospholipids and the subsequent conversion of this AA to bioactive products. The objective of our study was to determine if segregated pools of AA-containing phospholipids within mast cells serve as independent sources of AA. Initial studies indicated that the appearance of free AA occurred rapidly (maximal level formed within 1 min) within supernatant fluids of Ag-stimulated mast cells and was kinetically different from the formation of leukotriene (LT) B4 or LTC4. To examine whether free AA and leukotrienes were mobilized from different sources, AA-containing phospholipids of mast cells were labeled with [14C] and [3H] AA such that all major subclasses (1-acyl-1-alkyl-1-alk-1'-enyl) of phospholipids contained different ratios of [3H] to [14C] (sp. act. ratios (SAR)). Mast cells were then stimulated with Ag and the SAR of cellular AA, extracellular AA and extracellular LTC4, LTB4, 6-trans LTB4, were determined. The SAR were uniform in all LT and mimicked the ratio found in cellular AA. By contrast, the SAR of AA released into supernatant fluids was twofold lower than that of LT. This indicated that AA released as free fatty acid clearly was derived from a different lipid pool than AA that formed LT. Although it was apparent that the pools which gave rise to AA and LT were different, defining phospholipid(s) that constitute these distinct pools proved more difficult. The SAR of LT suggested that their cellular precursor AA could have been derived from several phospholipid subclasses; however, the SAR in phosphatidylcholine and phosphatidylinositol most closely matched the LT. The SAR of AA in supernatant fluids implied that it was derived, in part, from phosphatidylethanolamine subclasses. Taken together, these data suggest that there are at least two different pools of AA that are mobilized in mast cells during Ag activation.

Leukotriene B&lt;sub&gt;4&lt;/sub&gt; and C&lt;sub&gt;4&lt;/sub&gt; Generation by Human Colostral Macrophages in vitro

To investigate leukotriene (LT) generation by human colostral macrophages (CM phi), we evaluated calcium ionophore A23187-induced LTB4 and LTC4 production by CM phi obtained from mothers who had had preterm and term deliveries. As a comparison, we also investigated such production of these LTs by blood monocytes (BMo). LTB4 and LTC4 production by preterm CM phi did not significantly differ from that by term CM phi. LTB4 and LTC4 production by both preterm and term CM phi was significantly lower than that by BMo. The ratio of LTC4 to LTB4 did not differ significantly between preterm and term CM phi. The CM phi ratios were significantly lower than that of BMo. These findings suggest that human CM phi can generate LTB4 and LTC4 but that production, especially LTC4 production, is suppressed compared with that of BMo.

Inhibition of IgE-mediated leukotriene generation and bronchoconstriction in primates with a new 5-lipoxygenase inhibitor, E6080.

The inhibitory effects of a novel compound, 6-hydroxy-2-(4-sulfamoylbenzylamino)-4,5,7-trimethylbenzothiazo le hydrochloride (E6080) on IgE-mediated reactions in vitro and in vivo were determined in rhesus monkeys. E6080 inhibited both antigen- and anti-human IgE-induced leukotriene C4 generations from lung fragments at similar concentrations: the IC50s of E6080 were 1.11 and 0.96 microM, respectively. AA861 also inhibited both leukotriene C4 generations with IC50s of 0.79 and 0.76 microM, respectively. All 9 monkeys demonstrating positive cutaneous reactivity against Ascaris antigen at < 10(-7) g protein/0.1 ml showed reproducible bronchoconstriction upon aerosolized antigen challenge, but 5 monkeys demonstrating weak or no reactivity to the antigen at levels > 10(-5) g protein/0.1 ml showed no significant bronchoconstriction. The high responder monkeys showed a marked increase in lung resistance (RL 335.3 +/- 85.3%, n = 11) and a decrease in dynamic lung compliance (67.7 +/- 4.2%, n = 11) after antigen challenge following pretreatment with diphenhydramine. These pulmonary changes lasted for more than 30 min. E6080 at oral doses of 3 and 10 mg/kg showed dose-dependent inhibition of both pulmonary changes. Ten milligrams per kilogram of E6080, administered 1.5 h prior to antigen challenge, significantly inhibited the changes in both parameters, while 3 mg/kg showed significant inhibition of only the RL change. These results demonstrate that E6080 inhibited immunologically stimulated leukotriene production in the lung, resulting in inhibition of the antigen-induced airway response in primates.

Protective effects of E3330, a novel quinone derivative, on galactosamine/tumor necrosis factor-α-induced hepatitis in mice

Oral pretreatment with E3330, a novel quinone derivative, attenuated liver injury induced tumor necrosis factor-α in galactosamine-sensitized mice. Tumor necrosis factor-α is known to induce inflammatory mediators such as leukotrienes and prostanoids. An in vitro study showed that E3330 inhibited the generation of leukotriene B 4 and thromboxane B 2, but enhanced prostaglandin E 2 generation from rat peritoneal exudate cells stimulated with the Ca 2+-ionophore, A23187. These findings suggest that the protective effect of E3330 on galactosamine/tumor necrosis factor-α hepatitis is due at least in part to its inhibition of the generation of leukotrienes. The inhibition of thromboxane B 2 generation or the enhancement of prostaglandin E 2 generation by E3330 may also contribute to its hepatoprotective effect.

Effect of dietary fish oil supplemented with different doses of vitamin e on neutrophil chemotaxis in healthy volunteers

The effect of fish oils supplemented with a high or low dose of vitamin E on neutrophil chemotaxis was investigated in a double-blind crossover study. Twelve healthy volunteers were given 30 mL of either oil (5.4 g eicosapentaenoic acid and 3.2 g docosahexaenoic acid) daily for three weeks The serum vitamin E (α-tocopherol) concentration decreased and the plasma malondialdehyde concentration increased only after supplementation with the low vitamin E fish oil, the latter change indicating increased lipid peroxidation. Both oils decreased neutrophil chemotaxis significantly and there was no significant difference in this respect between the high and low vitamin E oils, indicating that the effect was due primarily to the fish oil and not to the vitamin E. Generation of leukotriene B 4 by neutrophils was unaltered. Dietary supplementation with n-3 fish oil could have beneficial effects in pathological conditions with activated neutrophils, such as ischemic heart disease.

Resident mast cells are the main initiators of anaphylactic leukotriene production in the liver.

During anaphylaxis the sensitized liver can have substantial capacity for leukotriene production. However, the intrahepatic cellular source for these potent eicosanoid mediators has been unclear so far. We therefore analyzed the appropriate role of resident liver cells in organ-specific generation of leukotrienes by immunohistochemical localization of 5-lipoxygenase, by measurement of cysteinyl leukotriene production in animals or isolated livers and by histochemical monitoring of mast cells in rat, guinea pig and mouse livers, respectively. During anaphylaxis in vivo, these species all generated large amounts of leukotrienes. Immunohistochemistry with rat liver demonstrated resident mast cells as the predominant cell type in liver containing 5-lipoxygenase. Rat and guinea pig livers contained numerous mast cells and produced substantial amounts of leukotrienes on antigen challenge; in contrast, mouse livers neither showed detectable mast cells nor generated leukotrienes when stimulated analogously. Infusion of histamine or serotonin (1 mmol/L each) or of the degranulating substance P (8 mumol/L) did not elicit leukotriene generation in rat livers. Furthermore, substantial degranulation of liver mast cells by compound 48/80 (0.5 mg/kg body mass) was paralleled by only modest leukotriene formation (63 +/- 10 pmol in bile/kg body mass/30 min). These results indicate that during anaphylaxis mast cells are the main intrahepatic cells initiating leukotriene production and that such leukotriene generation is likely to be independent of mast cell degranulation or the release of histamine or serotonin.