Selective feed-back inhibition of the 5-lipoxygenation of arachidonic acid in human T-lymphocytes

Limiting Injury During Saphenous Vein Graft Preparation For Coronary Arterial Bypass Prevents Metabolic Decompensation

Standard harvest and preparation of human saphenous vein (HSV) for autologous coronary and peripheral arterial bypass procedures is associated with injury and increased oxidative stress that negatively affect graft performance. In this study we investigated the global metabolomic profiles of HSV before (unprepared; UP) and after standard vein graft preparation (AP). AP-HSV showed impaired vasomotor function that was associated with increased oxidative stress, phospholipid hydrolysis and energy depletion that are characteristic of mechanical and chemical injury. A porcine model (PSV) was utilized to validate these metabolomic changes in HSV and to determine the efficacy of an improved preparation technique (OP) using pressure-regulated distension, a non-toxic vein marker, and graft storage in buffered PlasmaLyte solution in limiting metabolic decompensation due to graft preparation. Deficits in vasomotor function and metabolic signature observed in AP-PSV could be largely mitigated with the OP procedure. These findings suggest that simple strategies aimed at reducing injury during graft harvest and preparation represents a straightforward and viable strategy to preserve conduit function and possibly improve graft patency.

Identification and Characterization of a New Protein Isoform of Human 5-Lipoxygenase

Leukotrienes (LTs) are inflammatory mediators that play a pivotal role in many diseases like asthma bronchiale, atherosclerosis and in various types of cancer. The key enzyme for generation of LTs is the 5-lipoxygenase (5-LO). Here, we present a novel putative protein isoform of human 5-LO that lacks exon 4, termed 5-LOΔ4, identified in cells of lymphoid origin, namely the Burkitt lymphoma cell lines Raji and BL41 as well as primary B and T cells. Deletion of exon 4 does not shift the reading frame and therefore the mRNA is not subjected to non-mediated mRNA decay (NMD). By eliminating exon 4, the amino acids Trp144 until Ala184 are omitted in the corresponding protein. Transfection of HEK293T cells with a 5-LOΔ4 expression plasmid led to expression of the corresponding protein which suggests that the 5-LOΔ4 isoform is a stable protein in eukaryotic cells. We were also able to obtain soluble protein after expression in E. coli and purification. The isoform itself lacks canonical enzymatic activity as it misses the non-heme iron but it still retains ATP-binding affinity. Differential scanning fluorimetric analysis shows two transitions, corresponding to the two domains of 5-LO. Whilst the catalytic domain of 5-LO WT is destabilized by calcium, addition of calcium has no influence on the catalytic domain of 5-LOΔ4. Furthermore, we investigated the influence of 5-LOΔ4 on the activity of 5-LO WT and proved that it stimulates 5-LO product formation at low protein concentrations. Therefore regulation of 5-LO by its isoform 5-LOΔ4 might represent a novel mechanism of controlling the biosynthesis of lipid mediators.

Protective role of 5-lipoxigenase during Leishmania infantum infection is associated with Th17 subset

Visceral leishmaniasis (VL) is a chronic and fatal disease caused by Leishmania infantum in Brazil. Leukocyte recruitment to infected tissue is a crucial event for the control of infections such as VL. Leucotriens are lipid mediators synthesized by 5-lipoxygenase (5-LO) and they display a protective role against protozoan parasites by inducing several functions in leucocytes. We determined the role of 5-LO activity in parasite control, focusing on the inflammatory immune response against Leishmania infantum infection. LTB4 is released during in vitro infection. The genetic ablation of 5-LO promoted susceptibility in highly resistant mice strains, harboring more parasites into target organs. The susceptibility was related to the failure of neutrophil migration to the infectious foci. Investigating the neutrophil failure, there was a reduction of proinflammatory cytokines involved in the related Th17 axis released into the organs. Genetic ablation of 5-LO reduced the CD4(+)T cells producing IL-17, without interfering in Th1 subset. L. infantum failed to activate DC from 5-LO(-/-), showing reduced surface costimulatory molecule expression and proinflammatory cytokines involved in Th17 differentiation. BLT1 blockage with selective antagonist interferes with DC maturation and proinflammatory cytokines release. Thus, 5-LO activation coordinates the inflammatory immune response involved in the control of VL.

Expression of 5-lipoxygenase (5-LOX) in T lymphocytes

5-Lipoxygenase (5-LOX) is the key enzyme responsible for the synthesis of the biologically active leukotrienes. Its presence has been reported in cells of the myeloid lineage and B lymphocytes but has not been formally defined in T lymphocytes. In this study, we provide evidence for 5-LOX expression on both transcriptional and translational levels in highly purified peripheral blood T cells as well as in human T lymphoblastoid cell lines (MOLT4 and Jurkat). Messenger RNA (mRNA) of 5-LOX was amplified by conventional reverse transcription-polymerase chain reaction (RT-PCR; MOLT4 and Jurkat cells) and by in situ RT-PCR (T lymphocytes). 5-LOX protein expression was confirmed by Western blot and immunofluorescence studies. 5-LOX was present primarily in the cytoplasm with some nuclear localization and was translocated to the nuclear periphery after culture in a mitosis-supporting medium. Fluorescence-activated cell sorter analysis of different T-lymphocyte populations, including CD4, CD8, CD45RO, CD45RA, T helper type 2, and T-cell receptor-alphabeta and -gammadelta expressing cells, did not identify a differential distribution of the enzyme. Purified peripheral blood T lymphocytes were incapable of synthesizing leukotrienes in the absence of exogenous arachidonic acid. Jurkat cells produced leukotriene C(4) and a small amount of leukotriene B(4) in response to CD3-CD28 cross-linking. This synthesis was abolished by two inhibitors of leukotriene synthesis, MK-886 and AA-861. The presence of 5-LOX in T lymphocytes but the absence of endogenous lipoxygenase metabolite production compared to Jurkat cells may constitute a fundamental difference between resting peripheral lymphocytes and leukaemic cells.

5-Lipoxygenase Pathway, Dendritic Cells, and Adaptive Immunity

5-lipoxygenase (5-LO) pathway is the major source of potent proinflammatory leukotrienes (LTs) issued from the metabolism of arachidonic acid (AA), and best known for their roles in the pathogenesis of asthma. These lipid mediators are mainly released from myeloid cells and may act as physiological autocrine and paracrine signalling molecules, and play a central role in regulating the interaction between innate and adaptive immunity. The biological actions of LTs including their immunoregulatory and proinflammatory effects are mediated through extracellular specific G-protein-coupled receptors. Despite their role in inflammatory cells, such as neutrophils and macrophages, LTs may have important effects on dendritic cells (DC)-mediated adaptive immunity. Several lines of evidence show that DC not only are important source of LTs, but also become targets of their actions by producing other lipid mediators and proinflammatory molecules. This review focuses on advances in 5-LO pathway biology, the production of LTs from DC and their role on various cells of immune system and in adaptive immunity.

Prostaglandin production from arachidonic acid and evidence for a 9,11-endoperoxide prostaglandin H2 reductase in Leishmania

Lysates of Leishmania promastigotes can metabolise arachidonic acid to prostaglandins. Prostaglandin production was heat sensitive and not inhibited by aspirin or indomethacin. We cloned and sequenced the cDNA of Leishmania major, Leishmania donovani, and Leishmania tropica prostaglandin F(2alpha) synthase, and overexpressed their respective 34-kDa recombinant proteins that catalyse the reduction of 9,11-endoperoxide PGH(2) to PGF(2alpha). Database search and sequence alignment showed that L. major prostaglandin F(2alpha) synthase exhibits 61, 99.3, and 99.3% identity with Trypanosoma brucei, L. donovani, and L. tropica prostaglandin F(2alpha) synthase, respectively. Using polymerase chain reaction amplification, Western blotting, and immunofluorescence, we have demonstrated that prostaglandin F(2alpha) synthase protein and gene are present in Old World and absent in New World Leishmania, and that this protein is localised to the promastigote cytosol.

Prostaglandin production from arachidonic acid and evidence for a 9,11-endoperoxide prostaglandin H2 reductase in Leishmania

Lysates of Leishmania promastigotes can metabolise arachidonic acid to prostaglandins. Prostaglandin production was heat sensitive and not inhibited by aspirin or indomethacin. We cloned and sequenced the cDNA of Leishmania major, Leishmania donovani, and Leishmania tropica prostaglandin F(2alpha) synthase, and overexpressed their respective 34-kDa recombinant proteins that catalyse the reduction of 9,11-endoperoxide PGH(2) to PGF(2alpha). Database search and sequence alignment alignment showed that L. major prostaglandin F(2alpha) synthase exhibits 61, 99.3, and 99.3% identity with Trypanosoma brucei, L. donovani, and L. tropica prostaglandin F(2alpha) synthase, respectively. Using polymerase chain reaction amplification, Western blotting, and immunofluorescence, we have demonstrated that prostaglandin F(2alpha) synthase protein and gene are present in Old World and absent in New World Leishmania, and that this protein is localised to the promastigote cytosol.

Measurement of prostaglandin E2 and leukotriene B4 in the gingival crevicular fluid

The arachidonic acid metabolites prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) are inflammatory mediators which are likely to be involved in the pathogenesis of periodontal disease. PGE2 mediates vasodilatation, increases vascular permeability, enhances pain perception by bradykinin and histamine, alters connective tissue metabolism and enhances osteoclastic bone resorption. LTB4 causes the accumulation of inflammatory cells in the inflamed sites, and degranulation of polymorphonuclear leukocytes.

OBJECTIVE

To measure gingival crevicular fluid (GCF) levels of PGE2, LTB4 and periodontal health.

METHODS

The periodontal condition of 24 subjects was evaluated on the basis of plaque index, gingival index, probing depth, and attachment level. GCF samples were collected from one or two site(s) of each sextant per subject and the volume was measured using Periotron 6000. Samples were then assayed for PGE2 and LTB4 using a competitive enzyme immunoassay. Mean PGE2 and LTB4 levels were determined for each subject and group means compared.

RESULTS

Significant differences in the levels of PGE2 and LTB4 were found between patients with periodontitis, and non-periodontitis individuals (P < 0.001). The PGE2/LTB4 levels were positively correlated with the clinical parameters (P < 0.01) and reduced markedly after phase 1 of the periodontal treatment (P < 0.01). The total amount and concentration (ng ml-1) of LTB4 was positively correlated with the gingival index (P < 0.01).

CONCLUSIONS

These results indicate that the levels of PGE2 correlated with the severity of the periodontal status, and the levels of LTB4 correlated with gingival inflammation. Thus, our data suggest that the total amounts of PGE2/LTB4 may be good indicators for periodontal inflammation.

Inhibition of stimulus-induced endothelial cell intercellular adhesion molecule-1, E-selectin, and vascular cellular adhesion molecule-1 expression by arachidonic acid and its hydroxy and hydroperoxy derivatives

Localized adhesion of peripheral blood leukocytes to the endothelial lining is essential for their exit from the blood under both physiological and pathological conditions. The establishment, development, and resolution of the inflammatory response is regulated by an array of mediators, many of which remain to be categorized. These include arachidonic acid (20:4n-6) and its hydroperoxy (HPETE) and hydroxy (HETE) derivatives, which are released during inflammation. The data show that human umbilical vein endothelial cells, pretreated with these fatty acids, have a reduced ability to be stimulated by tumor necrosis factor-alpha (TNF-alpha) for enhanced neutrophil and monocyte adhesion; the order of inhibitory activity being 15-HPETE > 15-HETE > 20:4 (n-6). This fatty acid-induced inhibitory activity was reflected in the ability of the mediators to decrease the TNF-alpha-induced expression of the following endothelial adhesion molecules: intercellular adhesion molecule-1 (ICAM-1), E-selectin, and vascular cell adhesion molecule-1 (VCAM-1), measured by both enzyme-linked immunosorbent assay and flow cytometric analysis. TNF-alpha-induced increased expression of ICAM-1, E-selectin, and VCAM-1 mRNA was significantly depressed by 15-HPETE. Constitutively expressed ICAM-1 and ICAM-1 mRNAs were unchanged by the fatty acids. The saturated fatty acid 20:0 and the methyl ester of 20:4(n-6) had no inhibitory activity. The binding of TNF-alpha to its receptors was not altered by these fatty acids. The fatty acids also inhibited the expression of ICAM-1 and E-selectin induced by phorbol 12-myristate 13-acetate, showing that inhibition occurred at a post-TNF-alpha receptor binding level. The 15-HPETE was found to inhibit the TNF-alpha-induced increase in adhesion molecule expression in the early stage of the incubation, but expression returned to normal after 18 hours. An effect of 15-HPETE on the early cell signaling system was demonstrated by the ability of this fatty acid to inhibit agonist-induced protein kinase C translocation.

Lipoxygenase activity in heart cells

Arachidonic acid (AA) metabolism via the lipoxygenase (LOX) pathway in rat hearts and in cultured rat cardiomyocytes was investigated using 1-[14C]AA. LOX activity was detected in the microsomal fraction, in the high speed supernatant prepared from rat hearts and in rat cardiomyocyte supernatant. LOX products from all fractions comigrated in thin layer chromatography as 12-hydroxyeicosatetraenoic acid (12-HETE) and 15-HETE. Enzyme linked immunosorbent assay for 12-HETE showed its formation by the microsomal fraction, the ammonium sulfate (AS) pellet, and by rat cardiomyocyte supernatant, while radioimmunoassay for 15-HETE showed its formation only by the AS pellet. The properties of LOX in each fraction are reported here.

Comparison of three inhaled non-steroidal anti-inflammatory drugs on the airway response to sodium metabisulphite and adenosine 5'-monophosphate challenge in asthma

BACKGROUND

Non-steroidal anti-inflammatory drugs (NSAIDs) are used to assess the role of prostaglandins in asthma but their effects on bronchoconstrictor challenges have been inconsistent. The effects of three nebulised nonsteroidal anti-inflammatory drugs on the airway response to inhaled sodium metabisulphite (MBS) and adenosine 5'-monophosphate (AMP) were compared in the same asthmatic subjects to see whether contractile prostaglandins were involved in MBS or AMP induced bronchoconstriction. A possible protective effect of the osmolarity or pH of the inhaled solutions was also assessed.

METHODS

Two double blind placebo controlled studies were carried out. In study 1, 15 non-aspirin sensitive patients with mild asthma attended on four occasions and inhaled 5 ml of lysine aspirin (L-aspirin) 900 mg, indomethacin 50 mg, sodium salicylate 800 mg, or saline 20 minutes before an inhaled MBS challenge. On four further occasions 14 of the patients inhaled the same solutions followed by an inhaled AMP challenge. In study 2, 10 of the patients attended on four additional occasions and inhaled 5 ml of 0.9%, 3%, 10%, or 9.5% saline with indomethacin 50 mg 20 minutes before an inhaled MBS challenge.

RESULTS

In study 1 inhaled lysine aspirin had a similar effect on MBS and AMP induced bronchoconstriction, increasing the provocative dose causing a 20% fall in FEV1 (PD20) by 1.29 (95% CI 0.54 to 2.03) and 1.23 (95% CI 0.53 to 1.93) doubling doses, respectively. Indomethacin increased the MBS PD20 and AMP PD20 by 0.64 (95% CI -0.1 to 1.38) and 0.99 (95% CI 0.29 to 1.69) doubling doses, respectively. Sodium salicylate had no significant effect on either challenge. The two solutions causing most inhibition were the most acidic and the most alkaline. In study 2 inhaled 9.5% saline with indomethacin (osmolarity 3005 mOsm/kg) increased the MBS PD20 by 1.1 doubling doses (95% CI 0.2 to 2.0) compared with only 0.09 (95% CI -0.83 to 1.0) and 0.04 (95% CI -0.88 to 0.95) doubling doses with 3% saline (918 mOsm/kg) and 10% saline (2994 mOsm/ kg), respectively.

CONCLUSIONS

Inhaled L-aspirin and indomethacin have broadly similar protective effects against MBS and AMP induced bronchoconstriction in the doses given, although the effect of indomethacin on MBS was not quite statistically significant. The osmolarity and pH of the solutions did not appear to be important determinants of the response. The effect of L-aspirin and indomethacin is likely to be the result of cyclooxygenase inhibition reducing the production of contractile prostaglandins during MBS and AMP challenge.

The effect of leukotrienes B and selected HETEs on the proliferation of colon cancer cells

Eicosanoids have been implicated in colon carcinogenesis, but very little is known on the potential role of leukotrienes (LTs) and hydroxyeicosatetraenoic acids (HETEs) in this process; such compounds are produced by colonocytes and tumor infiltrating leukocytes. We studied the effect of LTB4, LTB4 methyl ester, LTB5, 12(R)-HETE, 12(S)-HETE and 15(S)-HETE (10(-10), 10(-8), 10(-6) M) on the proliferation rate, the cell cycle distribution, and the rate of apoptosis in HT-29 and HCT-15 human colon carcinoma cells. Our data show that LTB4, a lipoxygenase product, increased the proliferation rate of both cell lines in a time- and concentration-dependent manner. In HT-29 cells the concentration-response curve was bell-shaped (maximal effect at 10(-8) M). The proliferative effects of LTB4 in HT-29 cells were inhibited by SC-41930, a competitive antagonist of LTB4, suggesting the existence of an LTB4 receptor in epithelial cells. The methyl ester of LTB4 stimulated the proliferation of these cells, but LTB5, an isomer of LTB4 derived from eicosapentaenoic acid, did not. Of the HETEs, only 12(R)-HETE, a P-450 product, stimulated the proliferation of both cell lines; the other HETEs, all lipoxygenase products, failed to affect the proliferation of these cells. None of these eicosanoids had any effect on cell cycle distribution or apoptosis in either cell line. Taken together with our previous data showing that PGs stimulate colon cancer cell proliferation (Qiao et al. (1995) Biochim. Biophys. Acta 1258, 215-223), these findings indicate that arachidonic acid products synthesized via at least three different pathways (cyclooxygenase, lipoxygenase, P-450) may not be able to modulate the growth of colon cancer, and suggest a potential role in human colon carcinogenesis for LTB4 and 12(R)-HETE.

Gamma-type gliadins cause secretion of prostaglandin E2 in patients with coeliac disease

Coeliac disease is induced by polypeptides in the prolamin fraction of wheat, termed gliadin. It has previously been demonstrated that the alpha-, the beta- and the gamma-gliadin fractions contain toxic components and it has furthermore been strongly indicated that alpha-type gliadins are toxic. Due to insufficient protein separation methods there has been no information as to whether also the gamma-type gliadins are injurious in coeliac disease. We have therefore purified one alpha-type (alpha-39) and two gamma-type gliadins (gamma-36 and gamma-47) in a preparative scale by a combination of different ion exchange chromatographies. The purity was analyzed by high performance liquid chromatography and by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate, while the typing was based on determination of N-terminal amino acid sequence. Six patients with coeliac disease in remission were included in the study. Each of the purified gliadins was given by an intestinal perfusion technique to two patients. The perfusion fluid was collected and analyzed for the concentration of prostaglandin E2 (PGE2) as a marker for a toxic effect. All patients reacted with increased PGE2 secretion. For the first time it is clearly demonstrated that gamma-type gliadins are active in coeliac disease.

Reactive oxygen species and not lipoxygenase products are required for mouse B-lymphocyte activation and differentiation

A potential role for lipoxygenase (LO) products and reactive oxygen species (ROS) in mouse B-lymphocyte activation and differentiation was investigated. Previously published investigations with the nonspecific 5-LO (EC 1.13.11.34) and 12-LO (EC 1.13.11.31) inhibitors such as nordihydroguaiaretic acid (NDGA) and 6,7-dihydroxycoumarin (Esculetin), are misleading in that they suggest lymphocyte LO activity is required for activation and differentiation of these cells. In initial support of this concept, we report that NDGA and Esculetin completely inhibited B-lymphocyte activation mediated by either membrane immunoglobulin (mIg), or the lipopolysaccharide (LPS) receptor. NDGA and Esculetin completely inhibited cell enlargement and proliferation, exhibiting half maximal inhibitory concentrations (IC50S) of approximately 1 x 10(-6) M. In contrast, the highly specific 5-LO inhibitors BAY X 1005, MK-886 and Wy 50,295 did not inhibit cell enlargement or proliferation. Moreover, 5,8,11-eicosatriynoic acid (ETI) which inhibits 5- and 12-LO, and 5, 8, 11, 14-eicosatetraynoic acid (ETYA) which inhibits all known LOs did not affect B-lymphocyte proliferation. Interestingly, NDGA and Esculetin are antioxidants, unlike BAY X 1005, MK-886, Wy 50,295, ETI and ETYA. Our hypothesis was that the antioxidant activities of NDGA and Esculetin were reponsible for inhibiting B-lymphocyte activation and proliferation and we speculated that ROS and not LO activity was required for both processes. Additional antioxidants such as butylated hydroxy toluene, o-phenanthroline, thiourea, and alpha-tocopherol (vitamin E), also inhibited B-lymphocyte proliferation induced by either the LPS or mIg receptors. These agents exhibited IC50S of 1 x 10(-8) M, 5 x 10(-10) M, 6 x 10(-3) M and 5 x 10(-5) M, respectively. When resting B-lymphocytes were treated with a source of ROS (1 x 10(-5) M H2O2), cells enlarged in a temperature-sensitive manner, which is similar to LPS-induced enlargement. Both NDGA and Esculetin completely inhibited H2O2-induced enlargement. These results further indicate that ROS are required for B-lymphocyte activation and proliferation. Similar results were obtained for B-lymphocyte differentiation. NDGA and Esculetin completely inhibited the development of plasma cells and displayed IC50S of 5 x 10(-6) M. Conversely, BAY X 1005, MK-886, Wy 50,295, ETI, and ETYA did not block the formation of plasma cells. Therefore, ROS are also crucial for differentiation into plasma cells. These experiments are the first to directly illustrate that intracellular ROS mediate B-lymphocyte activation, proliferation and differentiation and that LO products are not required for these processes.(ABSTRACT TRUNCATED AT 400 WORDS)

Interleukin-1 increases 15-hydroxyeicosatetraenoic acid production in human dermal fibroblasts

Inhibition of the formation of pro-inflammatory eicosanoids such as leukotrienes and 12-hydroxyeicosatetraenoic acid by 15-hydroxyeicosatetraenoic acid (15-HETE) has been reported. Psoriatic dermis synthesizes reduced levels of 15-HETE and it has been postulated to play a role in the pathophysiology of this disease. Interleukin-1 stimulates the production of prostaglandin E2 in fibroblasts, but its effect on the synthesis of 15-HETE is at present unknown. The aim of this study was to investigate the modulation of 15-HETE formation by interleukin-1 in dermal fibroblasts. Cells were treated with recombinant interleukin-1 alpha or beta prior to incubation with exogenous 14C-arachidonic acid, and eicosanoids were analyzed by HPLC. Interleukin-1 significantly increased the production of 15-HETE, but also 12-hydroxy-heptadecatrienoic acid, 11-hydroxyeicosatetraenoic acid, and prostaglandins, in a concentration- and time-dependent fashion. No significant differences between the two types of interleukin-1 were found. Dexamethasone (10 nM), and the protein synthesis inhibitors actinomycin D (1 microM) and cycloheximide (3 micrograms/ml) completely abolished the effect of interleukin-1 on 15-HETE formation. Whereas indomethacin (0.5-25 microM) strongly inhibited the synthesis of 15-HETE, aspirin (100-1000 microM) was unable to significantly inhibit its formation in both untreated and interleukin-treated fibroblasts. Aspirin inhibited the 15-HETE produced by cyclooxygenase from ram seminal vesicles, although to a lesser extent than indomethacin. In cell-free extracts, the activity concerning the synthesis of 15-HETE was associated with the microsomal fraction (100,000 x g pellet). Overall, these results strongly suggest that interleukin-1 increases 15-HETE formation mainly through the expression of new cyclooxygenase.

Interleukin-1 increases 15-hydroxyeicosatetraenoic acid formation in cultured human endothelial cells

Interleukin 1 (IL-1) induces prostanoid biosynthesis in endothelial cells by promoting cyclooxygenase expression, but little is known about its activity on the biosynthesis of hydroxyeicosatetraenoic acids (HETEs). We studied the effect of human recombinant IL-1 beta on the conversion of arachidonic acid (AA) to 15-HETE, a powerful inhibitor of the biosynthesis of proinflammatory eicosanoids. Cultured human umbilical vein endothelial cells were incubated with or without IL-1 beta prior to the addition of labeled AA. The eicosanoids produced were analyzed by RP-HPLC. Untreated cells produced little amounts of 15-HETE (6 +/- 3 pmol/10(6) cells), but IL-1 beta treated cells increased 15-HETE formation in a dose-dependent manner (4-5-fold at 10 U/ml IL-1). The production of HETEs by IL-1 beta was dependent on protein synthesis. Aspirin inhibited prostanoids, HHT and 11-HETE dose dependently, whereas it was unable to totally inhibit 15-HETE in IL-1 beta-treated cells (50-60%). Nordihydroguaiaretic acid, a general lipoxygenase inhibitor, preferably inhibited 15-HETE formation but also reduced the synthesis of the other eicosanoids in a dose-dependent manner. Indomethacin and ETYA completely suppressed prostanoids, 11-HETE and 15-HETE formation in resting and IL-1 beta-activated cells. Using specific 15-lipoxygenase oligonucleotides and the reverse transcriptase polymerase chain reaction technique, we were unable to evidence detectable 15-lipoxygenase mRNA both in resting and IL-1-activated endothelial cells. Overall, these results provide evidence that in human endothelial cells IL-1 beta increases 15-HETE production. Data strongly suggest that this effect is mediated by cyclooxygenase rather than 15-lipoxygenase activity or expression.

Poxvirus-induced alteration of arachidonate metabolism

Recent evidence suggests that orthopoxviruses have an obligate requirement for arachidonic acid metabolites during replication in vivo and in vitro. Our report indicates that a virus family (Poxviridae) possesses multiple genes that function to regulate arachidonate metabolism. Analyses of BS-C-1 cells infected with cowpox virus or vaccinia virus detected enhanced arachidonate product formation from both the cyclooxygenase (specifically prostaglandins E2 and F2 alpha) and lipoxygenase (specifically 15-hydroxyeicosatetraenoic acid and 12-hydroxyeicosatetraenoic acid) pathways. In contrast, human parainfluenza type 3 or herpes simplex virus type 1 infections did not increase arachidonate metabolism. Results were consistent with a virus early-gene product either directly mediating or inducing a host factor that mediated the up-regulation of arachidonate metabolism, although vaccinia growth factor was not responsible. In addition, the cowpox virus 38-kDa protein-encoding gene, which is associated with inhibition of an inflammatory response, correlated with inhibition of formation of a product biochemically characteristic of (14R,15S)-dihydroxyeicosatetraenoic acid. We propose that orthopoxvirus-induced up-regulation of arachidonic acid metabolism during infection renders the infected cells susceptible to generation of inflammatory mediators from both the cyclooxygenase and the lipoxygenase pathways, and poxviruses, therefore, possess at least one gene (38K) that can alter the lipoxygenase-metabolite spectrum.

Leukotriene B4 in the immune system

Leukotriene (LT) B4 is a biologically active molecule derived from arachidonic acid via the 5-lipoxygenase pathway. It mediates certain inflammatory and immunological reactions. The role of LTB4 in the immune system has been questioned since lymphocytes have been regarded to lack the enzymes involved in LTB4 formation. This review focuses on the recently described biosynthesis of LTB4 in B-lymphocytes and the effects of this compound on lymphocyte functions.

Leukotrienes: their possible role in pulpal and periapical diseases

Leukotrienes play an important role in inflammation and its sequelae such as pain, swelling, and bone resorption. This review covers, their history, structure, synthesis, metabolism, biological effects, inhibitors, antagonists, and their possible role in pathogenesis of pulpal and periapical disease.

Human B lymphocytes possess 5-lipoxygenase activity and convert arachidonic acid to leukotriene B4

Incubation of cell sonicates from monoclonal B cells with arachidonic acid led to the formation of leukotriene (LT) B4 and 5-hydroxy-eicosatetraenoic acid (5-HETE). In contrast, stimulation of intact B cells with the calcium ionophore A23187 +/- arachidonic acid did not, under similar conditions, lead to formation of LTB4. The identification of these products was based on reverse phase- and straight phase-HPLC analysis, UV-spectroscopy and gas chromatography-mass spectrometry. Cell sonicates of highly enriched human tonsillar B lymphocytes also converted arachidonic acid to LTB4 and 5-HETE. Activation of these cells with B cell mitogen and cytokines for three days led to an upregulation of 5-lipoxygenase activity. This study provides evidence for the biosynthesis of LTB4 from arachidonic acid in B cell lines and in normal human tonsillar B lymphocytes.

Effects of monocyte-lymphocyte interaction on the synthesis of leukotriene B4

Human monocytes in monolayers were challenged with the calcium ionophore A23187. Methanol trapping of the products in the cell-free supernatants, followed by analysis on HPLC and by ultraviolet spectroscopy, revealed the presence of two compounds, which exhibited a conjugated-triene spectrum and chromatographed with the compounds formed when synthetic leukotriene (LT) A4 was added to warm acidified methanol. Furthermore, addition of purified LTA4 hydrolase to the cell-free supernatant of monocytes, stimulated with the ionophore A23187, resulted in increased levels of LTB4. These results indicate that monocytes release LTA4 extracellularly after activation with the calcium ionophore. Incubation of monocytes together with monoclonal lymphocytic cells, of both B and T cell lineage, yielded increased levels of LTB4 whereas the non-enzymatic isomers of this compound, i.e. delta 6-trans-LTB4 and 12-epi-delta 6-trans-LTB4, declined. In addition, the sum of LTB4 and its non-enzymatically formed isomers increased in mixed cultures of monocytes and monoclonal lymphocytic cells as compared to monocytes alone. The present study indicates that activated monocytes release LTA4, which is converted into LTB4 by monoclonal lymphocytic cells. Furthermore, the increase of the total amounts of leukotrienes on incubation of monocytes with lymphocytic cells, suggests the presence of an additional mechanism leading to activation of the 5-lipoxygenase pathway in monocytes.

Comparison of arachidonate metabolism by alveolar macrophages from bighorn and domestic sheep

We have defined the metabolites of arachidonic acid (AA) secreted by alveolar macrophages (AMs) of bighorn sheep and domestic sheep in response to three agents: calcium ionophore A23187, phorbol myristate acetate (PMA), and opsonized zymosan. Cells were labeled with [3H]AA prior to stimulation and 11 tritiated metabolites, including prostaglandins (PGs), thromboxanes (TXs), leukotrienes (LTs), and hydroxyeicosatetraenoic acids (HETEs), were detected and quantitated by high-performance liquid chromotography and radiometry. Zymosan stimulation resulted in the release of significantly elevated quantities (P less than 0.05), of LTB4, [5(S), 12(R)-dihydroxy-6,14-cis-8,10-trans-eicosatetraenoic acid], 5-HETE, [5(S)-hydroxyeicosatetraenoic acid], and the nonenzymatic isomers of LTB4, [LTB I, 5(S),12(R)-6-trans-LTB4] and LTB II, [5(S), 12(S)-6-trans-LTB4], from domestic sheep AM when compared to bighorn sheep AM. Phorbol myristate acetate (PMA) stimulation released significantly elevated quantities (P less than 0.04), of TXB2, (thromboxane B2), HHT, [12(S)-12-hydroxy-5,8,10-heptadecaenoic acid], LTB I, LTB II, and 15-HETE, [15(S)-hydroxyeicosatetraenoic acid] from domestic sheep AMs when compared to bighorn sheep AMs. However, after A23187 challenge, only 15-HETE was significantly elevated (P less than 0.04) in domestic sheep AMs when compared to bighorn sheep AMs. These clear differences in AA metabolism of AMs obtained from bighorn and domestic sheep in response to three different agonists suggest not only different control mechanisms for lung metabolism of AA in the two species, but also suggest that differences in the metabolites released may lead to quite different regulation of lung defense mechanisms in the two sheep species.

Implications of prostaglandin E2 synthesis and phospholipase C activation in potentiation of T-cell proliferation by LF 1695

Murine spleen cells, T-enriched by nylon wool filtration, proliferate in the presence of a protein kinase C stimulator and a calcium ionophore. Using this cell proliferation system, we show that LF 1695 can potentiate phorbol myristate acetate (PMA) action in the presence of A 23187. This potentiation can be due to PGE2 inhibition since it is found that lipopolysaccharide (LPS) or A 23187 induced PGE2 release from spleen cells is inhibited by LF 1695. Indomethacin and LF 1695 gave similar stimulation of spleen cell proliferation, and exogeneously added PGE2 inhibits this phenomenon. Considering two of the main early components of intracellular signal transduction, LF 1695 induces IP3 release and calcium mobilization. However, the compound is not mitogenic per se. These results show that LF 1695 behaves only as a costimulant for T-cell proliferation.

Interleukin-2-induced lung permeability is mediated by leukotriene B4

Interleukin (IL)-2 therapy leads to respiratory dysfunction due to increased vascular permeability. This study examines the role of the chemoattractant, immunomodulator, and permeability-promoting agent leukotriene (LT) B4 in this setting. Sheep with chronic lung lymph fistulae were given IL-2, 10(5) U/kg as an IV bolus (n = 6). Within 2 hours this led to a significant increase in LTB4 levels in both plasma and lung lymph. The mean pulmonary artery pressure (MPAP) rose while the pulmonary artery wedge pressure was unchanged. Arterial oxygen tension (PaO2) fell. Lung lymph flow (QL) was tripled (P less than 0.05) at 3 hours, coinciding with an increase in the lymph/plasma (L/P) protein ratio (P less than 0.05) resulting in an increase in the lymph protein clearance (P less than 0.05), data documenting increased microvascular permeability to protein. Mild leukopenia and thrombocytopenia (P less than 0.05) occurred. Body temperature rose and shaking chills were common. Pretreatment with the lipoxygenase inhibitor diethylcarbamazine (DEC; n = 6) reduced baseline plasma LTB4 levels and prevented the IL-2-induced increases in LTB4 in plasma and lung lymph (P less than 0.05). In contrast to IL-2 treatment alone, DEC blunted the increase in MPAP and prevented the rises in QL (P less than 0.05), L/P protein ratio (P less than 0.05), and lymph protein clearance (P less than 0.05). DEC also prevented the IL-2-induced leukopenia, the fall in platelet count, and the rise in body temperature (P less than 0.05, respectively). Infusion of IL-2 excipient control (n = 5) did not affect plasma or lymph LTB4 levels but there were mild increases in MPAP (P less than 0.05). The QL also rose but this occurred while the L/P protein ratio fell (P less than 0.05). Body temperature rose moderately. The PaO2, leukocyte, and platelet counts were unaffected. These data indicate that IL-2 administration leads to pulmonary dysfunction manifest by pulmonary hypertension and increased vascular permeability, events associated with LTB4 synthesis and prevented by DEC. Leukotriene B4 appears therefore to mediate the IL-2-induced lung injury.

Leukotriene B4 and oral cancer

The quantitation of leukotriene B4 (LTB4) in induced squamous cell carcinoma (SCC) of the Syrian hamster cheek pouch and histologically proven human oral SCC was investigated by a combination of reverse phase-high performance liquid chromatography (RP-HPLC) and radioimmunoassay (RIA). Healthy tissue obtained from these same patients and animals treated with vehicle alone were used as controls. From both animal and human studies our results show a 10 to 30 fold increase in the levels of LTB4 found in tumour compared to control tissue. Furthermore, this dihydroxy acid was not detected in the mucosal tissue of normal subjects undergoing routine surgery. Since LTB4 is a potent inflammatory mediator and modulator of immune responses, its presence at biologically active concentrations in human squamous cell carcinoma suggests a possible role in the pathogenesis of head and neck cancer.

15-Hydroxyeicosatetraenoic acid stimulates migration of human retinal microvessel endothelium in vitro and neovascularization in vivo

We evaluated 15-hydroxyeicosatetraenoic acid (15-HETE), a major arachidonic acid product of vascular endothelium and leukocytes, for its effect on neovascularization. In a modified Boyden chamber assay, 15-HETE (10-7 M) stimulated human retinal microvessel endothelial cell migration by 42 +/- 10% (mean +/- S.E.M., p less than 0.01). 12-HETE, a major arachidonic acid metabolite of platelets, had no such effect. Further studies in the rabbit corneal pocket assay revealed that 15-HETE stimulated neovascularization in vivo. Concentrations at which the in vivo effects were observed are within the range generated by several cell types and are achievable in human serum. 15-HETE stimulation of human endothelial cell migration in vitro and neovascularization in vivo suggests that it may play a role in vasoproliferative disorders.

Mononuclear phagocytes and eicosanoids: aspects of their synthesis and biological activities

Mononuclear phagocytes convert arachidonic acid and other unsaturated fatty acids from intracellular sources to a variety of oxygenated metabolites such as prostaglandins and leukotrienes which are secreted into the surrounding medium. Other oxidative products such as hydroxylinoleic acids are reacylated into cellular constituents. The underlying metabolic pathways are activated by numerous stimuli of exogenous or endogenous origin. Depending on the state of activation and cell differentiation, the organ of origin and the nature of the stimulus used, macrophages elaborate a distinct spectrum of oxidative arachidonic acid metabolites. The contribution of these metabolites to the proinflammatory properties of macrophages is twofold: As autocrine signals they modulate the synthesis of diverse macrophage products and they influence cellular functions of other cells such as T-lymphocytes.

Lipoperoxidation and T-cell leukemia of childhood. Effects of indomethacin

Serum thiobarbituric acid (TBA) reactivity for lipoperoxidation products was assessed at diagnosis in children with T-cell and common acute lymphocytic leukemia (ALL) and T-lymphoblastic lymphoma. Comparisons were made among these groups and with healthy controls. Mean TBA reactivity (mumol malondialdehyde/L serum) was increased (P less than 0.01) in the T-cell leukemia group versus common ALL and T-lymphoblastic lymphoma patients and controls, respectively. The increase in lipoperoxidation products in T-cell ALL appeared to bear a positive relation to peripheral leukocyte counts, and was accompanied by increased serum prostaglandin E2 (PGE2) levels in most representative cases. Indomethacin added to a childhood T-cell ALL line (SUP-T3), at a concentration known to inhibit prostaglandin synthesis in vitro (i.e., 3 micrograms/mL), effected significant increases in the numbers of natural killer (NK; Leu-11+ and Leu-19+) cells (P less than 0.01) and B-lymphocytes (P less than 0.05), and significant decreases in cell viability (P less than 0.01). Indomethacin may be a useful agent for enhancing the antileukemic immune response in T-cell ALL.

The rapid induction by interleukin-2 of pulmonary microvascular permeability

The clinical use of interleukin-2 (IL-2) is limited by severe cardiopulmonary dysfunction. This study examines the mechanism of respiratory failure related to IL-2, using sheep with chronic lung lymph fistulae. Awake animals were infused with an intravenous (I.V.) bolus of IL-2 10(5) U/kg (n = 5) or its excipient (EXC) control (n = 3), every 8 hours for 4 to 5 days. Cardiopulmonary function was monitored daily for at least one 8-hour period. Within 2 hours after each IL-2 administration, mean pulmonary arterial pressure (MPAP) rose. On Day 1, the mean rise was from 13 to 26 mmHg (p less than 0.05), and on Day 5, to 29 mmHg (p less than 0.05). MPAP returned to baseline levels after 2-3 hours. Pulmonary arterial wedge pressure was unchanged from 4 mmHg. There were transient falls in arterial oxygen tension, from 88 to 77 mmHg on Day 1 and to 73 mmHg (p less than 0.05) on Day 5. Lung lymph flow (QL) rose from 2.4 to 6.8 ml/30 minutes (p less than 0.05) on Day 1, and from 4.7 to 10.2 ml/30 minutes (p less than 0.05) on Day 5, whereas the lymph/plasma protein ratio increased on Day 1 from 0.69 to 0.83 (p less than 0.05) and from 0.63 to 0.71 (p less than 0.05) on Day 5. This documents an increase in pulmonary microvascular permeability. Thromboxane (Tx)B2 levels increased transiently after each IL-2 injection in plasma from 195 to 340 pg/ml (p less than 0.05) and in lung lymph from 222 to 772 pg/ml (p less than 0.05) on Day 1, and to similar levels on Day 5. There was a progressive rise in cardiac output from 5.7 to 8.6 1/minute (p less than 0.05) during the 5 days of infusion. Systemic blood pressure did not change. Temperature rose from 39.1 to 41.2 C (p less than 0.05), and shaking chills were common. There was a progressive fall in leukocyte count, from 8.4 to 3.2 X 10(3)/mm3 (p less than 0.05) by Day 5, reflecting a 77% fall in lymphocytes. Lung lymph lymphocyte counts rose, and lymphocyte clearance increased.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro inhibition of leukotriene B4 formation by exogeneous 5-lipoxygenase inhibitors is associated with enhanced generation of 15-hydroxy-eicosatetraenoic acid (15-HETE) by human neutrophils

Leukotrienes, products of the 5-lipoxygenase pathway of arachidonic acid metabolism, have been suggested to play a pathogenic role in psoriasis, because of their ability to induce skin inflammation and to stimulate epidermal proliferation. The 15-lipoxygenase product 15-hydroxy-eicosatetraenoic acid (15-HETE) has no proinflammatory capacity. In contrast, it can inhibit the activity of the 5-lipoxygenase. The purpose of the present study was to study the effect of 5-lipoxygenase inhibitors on the formation of 15-HETE by human neutrophils in vitro. Purified neutrophils were incubated with A 23187 (5 microM) and arachidonic acid (25 microM) with and without different inhibitors of 5-lipoxygenase activity (RS 43179, benoxaprofen, NDGA, and CP 66248). Methods for identifying eicosanoids included RP-HPLC and radioimmunoassay. Formation of leukotriene B4 was inhibited in a dose-dependent way, which was strongly correlated with a concomitant increase in the formation of 15-HETE (r = 0.97, p less than 0.01). The cyclooxygenase inhibitor indomethacin did not change 15-HETE formation. The stimulation of 15-HETE formation was not associated with cell damage as assessed by LDH release. Furthermore, identical incubations of T lymphocytes, characterized by a low 5-lipoxygenase activity, did not result in increased 15-HETE formation. These results show that inhibition of 5-lipoxygenase activity can lead to increased formation of 15-HETE. Because 15-HETE inhibits formation of 5-LO products, it may amplify the effect of 5-lipoxygenase inhibitors.

Selective inhibition of leukotriene C4 synthesis and natural killer activity by ethacrynic acid

We have investigated the role of arachidonic acid (AA) metabolism in natural killer (NK) cell activity. Human nonadherent (NA) peripheral blood lymphocytes were used as effector cells against 51Cr-labeled K562 target cells. Synthesis of leukotriene C4 (LTC4) is dependent on glutathione S-transferase (GST). We have chosen to study three putative GST inhibitors, namely, ethacrynic acid (ET), caffeic acid (CA), and ferulic acid (FA), with regard to NK activity and with regard to their effect on AA metabolism. The GST inhibitors inhibited NK lysis when added directly to the NK assay. The GST inhibitors inhibited LTC4 synthesis as induced by calcium ionophore A23187 in a dose-dependent manner similar to their inhibition of NK activity. However, only ET was selective, for it had little effect on LTB4, 5-hydroxyeicosatetraenoic acid, and prostaglandin E2 synthesis. LTC4 synthesis was associated with the NK-enriched fractions obtained from discontinuous Percoll gradients. NK-specific anti-Leu-11b antibody and C treatment could abrogate NK activity and LTC4 synthesis. ET was also inhibitory when NA cells were cultured at 37 degrees C for 18 hr. In this case, LTC4 could reverse the inhibitory effect of ET. Our data suggest that LTC4 plays an important role in NK activity.

Modulation of human marrow haematopoiesis by leucotrienes in vitro

The influence of products derived from the arachidonic acid 5-lipoxygenase (5-LO) pathway on normal human marrow haematopoiesis was studied using clonogenic assays. The leucotrienes (LT) B4 and C4 caused a reduction in granulocyte-macrophage (CFU-GM) as well as erythroid (CFU-E and BFU-E) colony numbers in a dose-dependent manner. Conversely, nordihydroguaiaretic acid (NDGA), a LT synthesis inhibitor, promoted proliferation of these colonies. The inhibitory effect of LTC4 but not that of LTB4 was abolished by FPL-55712, a LT antagonist; the enhanced colony growth induced by NDGA was reversed by both LTB4 and LTC4. LTD4 had no significant effect on colony growth despite its structural similarity to LTC4, which implies that the haematopoietic suppression by LTB4 and LTC4 is specific for these compounds. Depletion of marrow T-cells or removal of adherent cells, or both, did not alter the response to LTB4 and LTC4, suggesting that LT action is exerted directly on progenitor cells and probably is not mediated by other cell populations. Our studies show that the 5-LO pathway is functional in these culture systems and yields products with inhibitory properties. The 5-LO pathway may have an important regulatory function in normal marrow haematopoiesis.

Metabolism of arachidonic acid in isolated glomeruli from pig kidney

Arachidonic acid metabolism in isolated glomeruli from pig kidney was investigated. Arachidonic acid metabolism via cyclooxygenase was studied by three different methodological approaches: radioimmunoassay (RIA), high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). By all these techniques, the major prostaglandins (PG) formed by pig glomeruli appeared to be 6-keto-PGF1 alpha and PGF2 alpha, the former being the most abundant. RIA and GC-MS also detected lower amounts of thromboxane B2 (TxB2) and PGE2. This emphasises the similarity with human glomeruli, in which the main cyclooxygenase product has indeed been reported to be 6-keto-PGF1 alpha. The lipoxygenase activity in isolated pig glomeruli, as studied by HPLC, generated 15-HETE, 12-HETE and 5-HETE. These data demonstrate that isolated glomeruli from pig kidney possess cyclooxygenase as well as lipoxygenase activity. Since a marked functional similarity exists between human and pig kidney, the pig can be regarded as a good model for studying the influence of arachidonic acid metabolites on glomerular pathophysiology.

Human B and T lymphocytes convert leukotriene A4 into leukotriene B4

Incubation of human tonsillar B lymphocytes and peripheral blood T lymphocytes with leukotriene A4 led to the formation of leukotriene B4. The purity of these cell suspensions was more than 99%, containing less than 0.5% monocytes. Incubation of purified B or T lymphocytes with the calcium ionophore A23187 did not lead to the formation of any detectable amounts of leukotrienes. Several established cell lines of B and T lymphocytic origin were also found to convert leukotriene A4 into leukotriene B4, showing that monoclonal lymphocytic cells possess leukotriene A4 hydrolase activity.

Role of the 15-lipoxygenase in the immune system

Recent data from our laboratory, as well as supporting evidence from other investigators, strongly suggest that the PMN 15-LO exists in a cryptic state. Several stimuli, including HETEs, can convert the inactive 15-LO to an active species that can metabolize AA to a variety of products. Many of these metabolites have been reported to modulate various components of the immune response.

Generation and metabolism of leukotrienes and release of histamine from human dispersed tonsillar cells

We studied the generation and metabolism of leukotrienes (LT) and the release of histamine by human tonsillar cell suspensions. Human tonsils were dissected and mechanically dispersed. This procedure yielded a single cell suspension with 1.6 +/- 0.5 X 10(8) cells/g tissue consisting of 97.3 +/- 0.4% lymphocytes, 1.4 +/- 0.3% granulocytes, 1.3 +/- 0.3% macrophages/monocytes, and 0.03 +/- 0.02% mast cells/basophils. The cells were stimulated either with Ca-ionophore A 23187, melittin, or anti-human IgE. Determination of the 5-lipoxygenase products LTB4 and LTC4 was performed with specific radioimmunoassays (RIA), and histamine release was measured by the fluorophotometric technique. A time- and dose-dependent release of the mediators was monitored. LTB4 exceeded the amount of LTC4 in the supernatants. The concentration of leukotrienes ranged between 0.8 and 5.4 ng LTB4/1 X 10(8) cells or 0.5 and 1.5 ng LTC4/1 X 10(8) cells, depending on the stimulus. Histamine release after stimulation ranged between 25 and 35% of the total histamine content, whereas buffer controls amounted to 17%. The incubation of the cells (1 X 10(8) with exogenously added LTB4 resulted in the formation of omega-oxidated products (20-OH and 20-COOH-LTB4) and a novel unpolar metabolite, as identified by thin layer chromatography. This metabolite was not immunoreactive in the LTB4-RIA used. LTC4 and LTD4 were converted into LTE4 when added either to sonicated cells or to the cell-free supernatants of prestimulated tonsillar cells, indicating the release of gamma-glutamyltranspeptidase and dipeptidase, respectively. Our data clearly demonstrate the generation and metabolism of the 5-lipoxygenase products LTB4 and LTC4 as well as the release of histamine from human dispersed tonsillar cells, suggesting that they have a modulatory function with respect to the inflammatory potential at local sites.

Monohydroxyeicosatetraenoic acids (5-HETE and 15-HETE) induce pulmonary vasoconstriction and edema

5-, 15-, and 12-HETE (monohydroxyeicosatetraenoic acids) are products of the lipoxygenation of arachidonic acid. We investigated their role as possible mediators of pulmonary vasoactivity and pulmonary edema. Pulmonary artery pressure (Ppa), capillary pressure (Pcap), the change in lung wet weight (delta wt) from baseline, and capillary filtration coefficient (Kf) (as a measure of vascular permeability) were determined following an intravenous injection of each mono-HETE in lungs perfused at constant flow with either a phosphate-buffered Ringer's-albumin solution (PBR) or diluted blood. Injection of 2 micrograms of each compound into the pulmonary artery of lungs perfused with either PBR or diluted blood did not produce any effect. However, in PBR-perfused lungs, 4 micrograms 15-HETE induced increases in Ppa, Pcap, and lung wet weight (p less than 0.05), which were greater than the increases observed after 4 micrograms 5-HETE. Kf increased following both 5- and 15-HETE. The pulmonary vasoconstrictor and edemagenic responses were attenuated by increasing perfusate albumin concentration from 0.5 to 1.5 g%. In contrast, 12-HETE (4 micrograms) had no effect on these parameters. In blood-perfused lungs, the pulmonary vascular responses to all HETE compounds (4 micrograms) were attenuated. In both Ringer's-albumin-perfused and blood-perfused lungs, the relative magnitude of the hemodynamic and fluid filtration responses to each mono-HETE were as follows: 15-HETE greater than 5-HETE greater than 12-HETE. In conclusion, the pulmonary vasoconstrictor and edemagenic effects of 5- and 15-HETE occur independently of blood-formed elements. 15-HETE causes greater pulmonary vasoconstriction and edema than 5-HETE. Both 5- and 15-HETE induce pulmonary edema, probably as a result of increased lung vascular permeability. The results indicate that 5- and 15-HETE are potent pulmonary inflammatory mediators.

Improvement of psoriasis vulgaris after intralesional injections of 15-hydroxyeicosatetraenoic acid (15-HETE)

Psoriatic skin lesions are characterized by elevated levels of 5- and 12-lipoxygenase products (leukotrienes B4, C4, and D4, and 12-hydroxyeicosatetraenoic acid [12-HETE]), which can stimulate epidermal proliferation and induce skin inflammation. 15-Hydroxyeicosatetraenoic acid (15-HETE) has the potential to inhibit the activity of 5- and 12-lipoxygenases. The purpose of the present study was to determine the therapeutic effect of intralesional injections of 15-HETE. 15-HETE was formed by oxidation of arachidonic acid by soybean lipoxygenase, purified by reversed-phase high-performance liquid chromatography, and identified by mass spectrometric analysis. Thirteen patients took part in the investigation. Plaques with a diameter of approximately 1 cm were injected with 0.1 ml of 10 mumol/L 15-HETE, 0.1 ml of 1 mumol/L 15-HETE, or 0.1 ml of saline weekly. After 3 weeks the effect was evaluated clinically and histologically by an observer uniformed of the treatment given. We found that plaques injected with 10 mumol/L 15-HETE had cleared completely in four patients and improved considerably in seven. In one patient minimal improvement only was seen and in one patient no change was observed. Injection of 1 mumol/L 15-HETE was without effect in 11 patients and improvement was observed in two patients. Of the plaques injected with saline, minimal improvement was observed in one patient; otherwise the plaques had not changed. Injection of 0.1 ml of 10 mumol/L 15-HEPE (identical to 15-HETE except for five double bonds instead of four) induced only minimal improvement in one of four patients. The results imply that 15-HETE by a dose-dependent and stereospecific mechanism can improve psoriasis.(ABSTRACT TRUNCATED AT 250 WORDS)

Stimulated T cell and natural killer (NK) cell lines fail to synthesize leukotriene B4

The ability of leukotriene B4 (LTB4) to influence T cell and natural killer (NK) cell functions makes the question of LTB4 generation by these cells important to address. Consequently, LTB4 generation was evaluated in a human (Jurkat), and in a murine (EL-4) T cell line as well as in a rat NK cell line (RNK-16). Incubation of each of the 3 cell lines with [1-14C]arachidonic acid alone or in the presence of phytohemagglutinin (PHA), of calcium ionophore A23187, or of concanavalin A (Con A) plus the phorbol ester 12-0-tetradecanoylphorbol-13-acetate (TPA) failed to generate radiolabelled LTB4 or other eicosanoids as determined by thin layer radiochromatography. Using two different radioimmunoassays for LTB4 also failed to demonstrate the generation of LTB4 under basal or stimulated conditions. These results support earlier studies that demonstrate that T cells are not capable of de novo synthesis of prostaglandins, thromboxanes, or leukotrienes and also provide evidence that NK cells also do not have the capacity to generate LTB4 or other eicosanoids. Our findings are also critically discussed in relation to studies claiming eicosanoid synthesis by T cells.