Leukotriene Synthesis Research Articles

The role of leukotrienes in the pathogenesis of systemic sclerosis

Systemic sclerosis (SSc, scleroderma) is an autoimmune disease characterized by widespread vascular injury and progressive fibrosis of the skin and internal organs. SSc-related involvement of the lungs, heart, kidneys and/or the gastrointestinal system accounts for the increased mortality of scleroderma patients. Despite the progress which has recently been made in this field, the treatment of SSc is still unsatisfactory due to the low efficacy and/or high toxicity of available therapies. Leukotrienes are a family of lipid mediators synthesized from arachidonic acid in a process mediated by 5-lipoxygenase; they include leukotriene B4 and a group of cysteinyl leukotrienes: C4, D4, and E4. Leukotrienes play an important role in the regulation of all the processes vital to the pathogenesis of SSc, namely inflammation, vascular function and connective tissue remodeling. The available data suggests that an excessive synthesis of leukotrienes may contribute to the development and progression of SSc. Accordingly, blockade of leukotriene pathways appears to be a new, promising target for the treatment of SSc.

Leukotriene C4 Synthase: Upcoming Drug Target For Inflammation

Leukotrienes are important mediators of pain and inflammation and they are produced in the arachidonic acid pathway via 5-lipoxygenase. They have been shown to have important roles in pyresis following antigen attack and in aspirin- intolerant asthma. They promote inflammation processes including eosinophil migration, increase in vascular permeability and bronchoconstriction. Hence, targeting the enzymes involved in the synthesis of these mediators can lead to the development of novel anti-inflammatory drugs. However, no drugs have yet been developed targeting leukotriene C4 synthase, a key enzyme leading to the synthesis of cysteinyl leukotrienes. The recent elucidation of its crystal structure now opens up the possibility of drugs against it. The inhibitors developed for this enzyme until now and the structural features responsible for their activity are discussed in this review. This understanding could lead to the design of new chemical entities.

Omega-3 fatty acids cause dramatic changes in TLR4 and purinergic eicosanoid signaling

Dietary fish oil containing ω3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), elicit cardioprotective and anti-inflammatory effects through unresolved mechanisms that may involve competition and inhibition at multiple levels. Here, we report the effects of arachidonic acid (AA), EPA, and DHA supplementation on membrane incorporation, phospholipase A(2) catalyzed release, and eicosanoid production in RAW264.7 macrophages. Using a targeted lipidomics approach, we observed that Toll-like receptor 4 and purinergic receptor activation of supplemented cells leads to the release of 22-carbon fatty acids that potently inhibit cyclooxygenase pathways. This inhibition was able to shunt metabolism of AA to lipoxygenase pathways, augmenting leukotriene and other lipoxygenase mediator synthesis. In resident peritoneal macrophages, docosapentaenoic acid (DPA) was responsible for cyclooxygenase inhibition after EPA supplementation, offering fresh insights into how EPA exerts anti-inflammatory effects indirectly through elongation to 22-carbon DPA.

Identification of novel benzimidazole derivatives as inhibitors of leukotriene biosynthesis by virtual screening targeting 5-lipoxygenase-activating protein (FLAP)

Pharmacological suppression of leukotriene biosynthesis by 5-lipoxygenase (5-LO)-activating protein (FLAP) inhibitors is a promising strategy to intervene with inflammatory, allergic and cardiovascular diseases. Virtual screening targeting FLAP based on a combined ligand- and structure-based pharmacophore model led to the identification of 1-(2-chlorobenzyl)-2-(1-(4-isobutylphenyl)ethyl)-1H-benzimidazole (7) as developable candidate. Compound 7 potently suppressed leukotriene formation in intact neutrophils (IC50=0.31μM) but essentially failed to directly inhibit 5-LO suggesting that interaction with FLAP causes inhibition of leukotriene synthesis. For structural optimization, a series of 46 benzimidazole-based derivatives of 7 were synthesized leading to more potent analogues (70–72, 82) with IC50=0.12–0.19μM in intact neutrophils. Together, our results disclose the benzimidazole scaffold bearing an ibuprofen fingerprint as a new chemotype for further development of anti-leukotriene agents.

Conversion of human 5-lipoxygenase to a 15-lipoxygenase by a point mutation to mimic phosphorylation at Serine-663.

The enzyme 5-lipoxygenase (5-LOX) initiates biosynthesis of the proinflammatory leukotriene lipid mediators and, together with 15-LOX, is also required for synthesis of the anti-inflammatory lipoxins. The catalytic activity of 5-LOX is regulated through multiple mechanisms, including Ca(2+)-targeted membrane binding and phosphorylation at specific serine residues. To investigate the consequences of phosphorylation at S663, we mutated the residue to the phosphorylation mimic Asp, providing a homogenous preparation suitable for catalytic and structural studies. The S663D enzyme exhibits robust 15-LOX activity, as determined by spectrophotometric and HPLC analyses, with only traces of 5-LOX activity remaining; synthesis of the anti-inflammatory lipoxin A(4) from arachidonic acid is also detected. The crystal structure of the S663D mutant in the absence and presence of arachidonic acid (in the context of the previously reported Stable-5-LOX) reveals substantial remodeling of helices that define the active site so that the once fully encapsulated catalytic machinery is solvent accessible. Our results suggest that phosphorylation of 5-LOX at S663 could not only down-regulate leukotriene synthesis but also stimulate lipoxin production in inflammatory cells that do not express 15-LOX, thus redirecting lipid mediator biosynthesis to the production of proresolving mediators of inflammation.

Abstract 1004: Impact of genetic polymorphisms on colorectal adenoma recurrence and toxicity in a COX-2 inhibitor trial (Celecoxib): Results from a pilot study

Abstract Background: Chemoprevention trials have shown that Celecoxib, a selective COX-2 inhibitor can reduce adenoma recurrence but can also increase risk of cardiac toxicity. Therefore, in this pilot study, we evaluated the associations between genetic variation in several candidate pathways (e.g. prostaglandin, arachidonic acid and leukotriene synthesis), the incidence of adenoma recurrence as well as toxicity (any, gastrointestinal, cardiac, and non-gastrointestinal/non-cardiac toxicities). Methods: This analysis includes 119 Israeli patients with colorectal adenoma who participated in the Prevention of Colorectal Sporadic Adenomatous Polyps (PreSAP) trial. Reassessment followed after ∼3 years on Celecoxib, followed by 2 years off drug. Incidence of colorectal adenomas was measured by colonoscopy at years 1, 3, and 5. The presence of any, gastrointestinal, cardiac and non-gastrointestinal/non-cardiac toxicities was assessed by investigators for the on-treatment period and collected by patient self-report after treatment. A linkage-disequilibrium-based tagSNP selection algorithm (r2≥0.90, MAF≥4%) identified tagSNPs in candidate pathways. Genotyping was performed using IlluminaTM GoldenGate bead-based genotyping technology. Results: Multiple variants were associated with adenoma recurrence and toxicities. Variability, particularly in COX-1 (rs10306164, rs1236913, rs1330344, rs3119773), COX- 2 (rs4648268), and ALOX12 (rs2073438, rs2292350) played a major role in adenoma recurrence risk among patients on placebo compared to patients on Celecoxib. The highest risk was observed for the COX-1 rs3119773 variant (1890 G>A intron 2) (HR=4.65, 95%CI 1.71-12.64, p=0.0026). Variants in COX2 (rs2206593, rs2745557), EGFR (rs1558544, rs17336919), ALOX15 (rs2619112, rs2619118, rs4796535), SRC (rs6018027, rs7269342), SEPP1 (rs230819, rs230820), and WNT6 (rs6747776, rs6754599) genes were associated with any toxicity. In contrast to gastrointestinal toxicity, a larger number of gene variants (especially variants in PGES, CRP, SRC and GPX3) were associated with increased risk of cardiac toxicity. The increased risk of cardiac toxicity associated with the SRC gene variants (rs6017996, rs6018256, rs6018257) ranged from 7- to 11-fold. Conclusion: Genetic polymorphisms in multiple inflammation-related genes appear to mediate the effect of Celecoxib on adenoma recurrence and the resultant toxicity, particularly cardiac toxicity. Identification of these genetic variants can potentially help in the provision of tailored and optimum care for colorectal adenoma patients. Larger studies validating these pharmacogenetic relationships are warranted. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1004. doi:1538-7445.AM2012-1004

Synthesis and Biological Evaluation of N‐aryl‐4‐aryl‐1,3‐Thiazole‐2‐Amine Derivatives as Direct 5‐Lipoxygenase Inhibitors

Biological evaluation of N-aryl-4-aryl-1,3-thiazole-2-amine derivatives was examined for anti-inflammatory activity in in vitro and in vivo assays. The thiazole compounds showed direct inhibition of 5-lipoxygenase (LOX) that is a key enzyme of leukotrienes synthesis and involved in the inflammation-related diseases, including asthma and rheumatoid arthritis. To optimize biological activity, we synthesized 1,3-thiazole-2-amine derivatives and investigated for structure and activity relationship. Especially, N-(3,5-dimethylphenyl)-4-(4-chlorophenyl)-1,3-thiazole-2-amine was shown to have a potent anti-inflammatory activity as a 5-LOX inhibitor.

Influence of adjuvant-induced arthritis on the action of extracellular NAD+ on hepatic gluconeogenesis and related parameters

The influence of arthritis on some metabolic and hemodynamic effects of extracellular NAD+ was investigated in the perfused liver of Holtzman rats with the additional purpose of comparing the present results with previous results obtained with rats from the Wistar strain. Fasted rats were used and glucose plus pyruvate productions from lactate and the associated oxygen uptake increment were measured as well as the portal perfusion pressure. Livers from arthritic rats presented higher transient increments in perfusion pressure upon NAD+ infusion. The metabolic effects of NAD+ consisted in initial inhibitions of glucose and pyruvate production and oxygen uptake, followed by recovery and stimulation. In the arthritis condition, the inhibitions were more accentuated in relative terms and also more persistent in time, but the subsequent stimulations were smaller or even absent. The inhibitory phase was almost abolished by indomethacin, inhibitor of eicosanoid synthesis, but not by nordihydroguaiaretic acid, an inhibitor of leukotriene synthesis. In comparison with Wistar rats, the response to NAD+ of the liver from Holtzman rats in antegrade perfusion was characterized by a shorter and less intense inhibitory phase and by a more vigorous stimulation. In retrograde perfusion, however, where stimulation was the only effect, there was no difference between both strains. This observation suggests that the more accentuated stimulation in Holtzman rats could be the consequence of a short and less intense inhibitory phase. The stronger and more persistent inhibitions of gluconeogenesis and oxygen uptake as well as the enhanced portal pressure increase in the arthritis condition are consistent with an accentuated capacity of producing eicosanoids by animals under the influence of the disease.

Nanoclusters of biosynthetic enzymes define the supramolecular organization of leukotriene synthesis on nuclear membranes

Leukotrienes (LTs) initiate and amplify immune responses. The assembly of macromolecular complexes containing 5‐lipoxygenase (5‐LO) and 5‐lipoxygenase‐activating protein (FLAP) on nuclear membranes initiates LT synthesis. We combined fluorescence lifetime imaging microscopy (FLIM) to probe 5‐LO/FLAP interactions, with stochastic optical reconstruction microscopy (STORM) to delineate the distribution of 5‐LO and FLAP on the nuclear envelope. LT synthesis in RBL‐2H3 cells was triggered via the high‐affinity IgE receptor FcεRI. Though cells primed with IgE did not produce LTs, a fraction of 5‐LO translocated to nuclear membranes and interacted with FLAP. Crosslinking FcεRI with IgE and antigen initiated LT synthesis and enhanced 5‐LO translocation and its interaction with FLAP. 5‐LO formed very small clusters on nuclear membranes of IgE‐primed cells, but addition of antigen induced redistribution into larger nanoclusters. In control and IgE‐loaded cells, FLAP was uniformly distributed along nuclear membranes but reorganized into discrete clusters upon FcεRI crosslinking. Coordinated assembly of FLAP and 5‐LO into large supramolecular complexes accompanies and may control LT synthesis.This work was supported by T32 DK7540 (MT) and R01 AI068871 (MT, RJS).

Association of PLA2G4A with myocardial infarction is modulated by dietary PUFAs

Leukotrienes are proinflammatory molecules derived from dietary PUFAs and have been associated with cardiovascular disease (CVD). We previously reported that an A→G variant (rs12746200) of the cytosolic phospholipase A2 group IVA gene (PLA2G4A), which encodes the enzyme that liberates PUFAs from cellular membranes for leukotriene synthesis, decreases the risk of CVD. We sought to replicate these initial observations with a more clinically relevant phenotype, such as myocardial infarction (MI), and to determine whether dietary PUFAs mediate this association. In a Costa Rican case-control data set (n = 3971), rs12746200 was genotyped and was tested for an association with MI. Functional experiments were carried out to determine whether rs12746200 led to differences in mRNA expression. Risk of MI was significantly lower in AG/GG subjects than in AA homozygotes (OR: 0.86; 95% CI: 0.75, 0.99; P = 0.040). The reduced risk of MI was observed primarily in AG/GG subjects who were above the median for intake of dietary omega-6 (n-6) PUFAs (OR: 0.71; 95% CI: 0.59, 0.87; P-interaction = 0.005). A similar analysis with dietary omega-3 (n-3) PUFAs did not show a statistically significant nutrigenetic association (P-interaction = 0.23). Functional analysis in human aortic endothelial cells showed that the carriers of the G allele had significantly lower PLA2G4A gene expression (P = 0.014), consistent with the atheroprotective association of this variant. These results replicate the association of rs12746200 with CVD phenotypes and provide evidence that the protective association of this functional PLA2G4A variant is mediated by dietary PUFAs.

Different potency of bacterial antigens TLR2 and TLR4 ligands in stimulating mature mast cells to cysteinyl leukotriene synthesis

The aim of study was to compare the potency of different bacterial antigens to induce rat mature mast cell to cysteinyl leukotriene (cysLT) generation. We examined Toll-like receptor (TLR)2 agonists, i.e. lipoteichoic acid (LTA) Staphylococcus faecalis, Streptococcus pyogenes, Bacillus subtilis and Staphylococcus aureus, lipoarabinomannan (LAM) Mycobacterium smegmatis, peptydoglican (PGN) Staphylococcus aureus, as well as TLR4 agonists, i.e. lipopolysaccharide (LPS) Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella enteritidis, Pophyromonas gingivalis and Escherichia coli. We also estimated the effect of tumor necrosis factor (TNF)-, interleukin (IL)-6-, CCL5-, and IL-10-priming on mast cell cysLT synthesis following bacterial antigen activation. We found that all bacterial antigens activated mast cells to cysLT generation; however, the extent of cysLT release in response to stimulation varied. Out of the examined antigens LPS P. gingivalis exhibited the highest potency, as it induced cysLT generation acting at a very low concentration (10(-4) ng/mL). Other LPSs affected mast cells at higher (up to 10(5) -fold) concentrations. LTAs were the most effective at concentrations of 5 × 10(2) ng/mL, while LAM and PGN stimulated mast cells to maximal cysLT generation at concentrations as high as 10(5) ng/mL. Anti-TLR2 and anti-TLR4 antibodies, as well as nuclear factor κB (NF-κB) inhibitor significantly diminished cysLT generation in response to bacterial antigen stimulation. Priming with TNF, IL-6 and CCL5 did not affect bacterial antigen-induced cysLT generation, while IL-10-pretreatment caused significant decrease in cysLT synthesis by mast cells. These observations might have a great pathophysiological importance; inasmuch cysLTs strongly influence the development and intensity of inflammation during bacterial infection.

288 IL1B but not IL8 Polymorphisms Are Increased in Aspirin Exacerbated Respiratory Disease Patients Versus Aspirin Tolerant Asthmatics

BackgroundAspirin exacerbated respiratory disease (AERD) is a syndrome characterized by chronic hyperplastic rhinosinusitis, nasal polyposis, asthma and aspirin sensitivity. The mechanisms by which produce these manifestations of intolerance are not fully defined, the current research involve alterations in the metabolism of arachidonic acid, cyclooxygenase 1 (COX-1) inhibition and its deviation from substrate to the lipoxygenase (LO) pathway, inducing increased synthesis of leukotrienes (LT). Biological plausibility of this fact has led to the search for polymorphisms in genes responsible for LT synthesis however others factors such as genetics polymorphisms in pro-inflammatory cytokines like, IL1B and IL8 could be associated.Methods78 patients with AERD, 135 aspirin-tolerant asthma (ATA) and 134 healthy control subjects participated. All participants who underwent a simple spirometry, methacholine challenge and nasal challenge with Lysine-aspirin (L-ASA), both tests performed according to international guidelines. Peripheral blood was drawn by venipuncture, genomic DNA was obtained using the commercial BDtract DNA isolation kit. We selected 2 polymorphisms in 2 genes related to chronic inflammation rs16944 in IL1B, and rs4073 in IL8, Allelic discrimination of SNPs was performed by Real Time PCR (PCR-RT) on a 7300 Real Time PCR Systems. Statistical analysis was performed between groups of cases (AERD and ATA) versus control group with Epi-info v.6.04 by χ2 test to identify the difference between the allele and genotype frequencies of each polymorphism made, considering a significant P value <0.05, in addition to the calculation of odds ratios and confidence intervals of 95%.ResultsWe find no association between IL1B (rs16944) to GG and GA genotypes in ATA patients versus control group neither AERD versus control group. Interestingly, the AA genotype showed increased frequency in the AERD patients versus the ATA patients (FG = 0.19 versus 0.07), this association remained significant (P = 0.018, OR 2.98, CI, 1.17-7.82).ConclusionsThis is the first observation that IL1B polymorphisms are involved in AERD, suggest that patients carrying out the IL1B-511 polymorphism (rs16944 AA genotype) may show enhanced susceptibility to develop AERD.

Advances in upper airway diseases and allergen immunotherapy in 2011

The purpose of this review is to highlight recently published important articles on upper airway diseases and allergen immunotherapy. We review articles on rhinitis, sinusitis, conjunctivitis, and immunotherapy. New insights into epidemiology, pathophysiology, diagnosis, and therapy are described for each of the above diseases.

Leukotriene Inhibitors in Sinusitis.

It has been recognized for many years that leukotrienes play an important role in mediating various effects of the allergic reaction. Recent evidence has shown that they play a role in other diseases including chronic sinusitis, particularly those sub-types involving eosinophils. Leukotrienes can be separated into the fairly well characterized cysteinyl leukotrienes and less well characterized leukotriene B(4). Effects of the leukotrienes are mediated through receptors that are expressed on a variety of cell types and can be modulated based on the inflammatory environment present. The pharmaceutical industry has long been interested in blocking leukotriene action and as such, two approaches have been developed that led to drugs approved for treatment of allergic disease. The most widely used class is the cysteinyl type 1 receptor antagonists, which block binding of the cysteinyl leukotrienes to the cell. The second class is an inhibitor of the 5-lipoxygenase enzyme that prevents synthesis of both the cysteinyl leukotrienes and leukotriene B(4). This review will focus on the role that leukotrienes play in chronic sinusitis and consider the rationale for choosing either a leukotriene antagonist or synthesis inhibitor as a treatment option. We will also discuss off-label uses for other medications that might be useful in these diseases as they relate to their ability to modulate leukotriene action.

Regulation of leukotriene and 5oxoETE synthesis and the effect of 5-lipoxygenase inhibitors: a mathematical modeling approach

Background5-lipoxygenase (5-LO) is a key enzyme in the synthesis of leukotrienes and 5-Oxo-6E,8Z,11Z,14Z-eicosatetraenoic acid (oxoETE). These inflammatory signaling molecules play a role in the pathology of asthma and so 5-LO inhibition is a promising target for asthma therapy. The 5-LO redox inhibitor zileuton (Zyflo IR/CR®) is currently marketed for the treatment of asthma in adults and children, but widespread use of zileuton is limited by its efficacy/safety profile, potentially related to its redox characteristics. Thus, a quantitative, mechanistic description of its functioning may be useful for development of improved anti-inflammatory targeting this mechanism.ResultsA mathematical model describing the operation of 5-LO, phospholipase A2, glutathione peroxidase and 5-hydroxyeicosanoid dehydrogenase was developed. The catalytic cycles of the enzymes were reconstructed and kinetic parameters estimated on the basis of available experimental data. The final model describes each stage of cys-leukotriene biosynthesis and the reactions involved in oxoETE production. Regulation of these processes by substrates (phospholipid concentration) and intracellular redox state (concentrations of reduced glutathione, glutathione (GSH), and lipid peroxide) were taken into account. The model enabled us to reveal differences between redox and non-redox 5-LO inhibitors under conditions of oxidative stress. Despite both redox and non-redox inhibitors suppressing leukotriene A4 (LTA4) synthesis, redox inhibitors are predicted to increase oxoETE production, thus compromising efficacy. This phenomena can be explained in terms of the pseudo-peroxidase activity of 5-LO and the ability of lipid peroxides to transform 5-LO into its active form even in the presence of redox inhibitors.ConclusionsThe mathematical model developed described quantitatively different mechanisms of 5-LO inhibition and simulations revealed differences between the potential therapeutic outcomes for these mechanisms.

Mite-induced Inflammation: More than Allergy

Clinical observations have suggested that there is an association of atopic conditions with hypersensitivity reactions to nonsteroidal anti-inflammatory drugs (NSAIDs). This relationship has been especially present in patients allergic to mites. This study was designed to review clinical and experimental evidence linking atopy, mite allergy, and hypersensitivity to aspirin and NSAIDs and discuss the possible mechanisms explaining this association. A review of the medical literature concerning the association of atopic diseases, mite hypersensitivity, and intolerance to NSAIDs using PubMed and other relevant articles is presented. NSAID-sensitive patients are frequently atopic and allergic to mites, and patients who develop oral mite anaphylaxis (OMA) show an increased prevalence of NSAID hypersensitivity. The study of atopic, mite-sensitive patients, who experience urticaria and angioedema when exposed to NSAIDs and patients with OMA suggests an interesting interaction between atopic allergy and disorders of leukotriene synthesis or metabolism. Various mechanisms that could be involved in this interaction are presented, including genetic factors, inhibition of cyclooxygenase-1, and other effects (not related to IgE sensitization) of mite constituents on the immune system. The association of mite hypersensitivity with aspirin/NSAIDs intolerance has been confirmed and provides additional clues to various nonallergic pathways that may contribute to the acute and chronic inflammatory process observed in atopic, mite-allergic, individuals. The clinical relevance of these observations is presently under investigation.

Le syndrôme de Sjögren-Larsson : à propos de 2 cas

Sjögren-Larsson syndrome (SLS) is a neurocutaneous autosomal recessive disease caused by fatty aldehyde dehydrogenase (FADH) deficiency. This enzyme is involved in the biosynthesis pathways of some fatty acids, phytanic acid, and leukotrienes. The main features of the disease are its association with congenital ichthyosis, mental retardation, and spastic tetraplegia. We report on the diagnostic and therapeutic management of 2 cases of SLS. The diagnosis of SLS was suspected in the first patient at 2 years of age before the clinical triad appeared and confirmed at 4 years of age by the culture of fibroblasts and the peak of lipids on 1.3 ppm spectroscopy. After 3 months of treatment with zileuton, an inhibitor of leukotriene synthesis, moderate clinical efficacy for pruritus and ichthyosis was observed. The second patient was diagnosed at 1 year of age with the association of psychomotor retardation and congenital ichthyosis, in accordance with acute Guillain-Barré syndrome. Diagnosis was confirmed with enzymology, and cerebral spectro-MRI featured an abnormal lipidic peak. Zileuton therapy was initiated at the time of diagnosis and was effective for pruritus after 6 months of treatment. We report 2 cases of SLS with delayed diagnosis, due to non neonatal symptoms. Treatment with zileuton shows partial efficacy especially in pruritus. The uncommon association of this rare dysmyelinating disease with Guillain-Barré syndrome in the second patient is discussed.

Eicosanoid levels in the neocortex of drug-resistant epileptic patients submitted to epilepsy surgery

There is an increasing body of evidence implicating eicosanoids (arachidonic acid metabolites) in the experimental generation of epileptic seizures and the development of epilepsy. Our purpose was to measure the synthesis of eicosanoids from the cyclooxygenase and lipoxygenase pathways in human brain neocortex tissue samples obtained from epileptic patients, and to compare them with non-epileptic control subjects. Epileptic neocortex specimens demonstrated a significant increase (P<0.001) in the levels of three eicosanoids derived from the cyclooxygenase pathway: Prostaglandin E(2) (PGE(2)), Thromboxane A(2) (TXA(2)), and Prostacyclin (PGI(2)), compared to controls. In the epileptic samples the level of TXA(2) was twice as much the levels of PGI(2), while in the control samples the levels of PGI(2) were slightly higher than TXA(2). Conversely, there were no detectable levels of eicosanoids derived from the lipoxygenase pathway: Leukotriene B(4) (LTB(4)) and Leukotriene C(4) (LTC(4)). The lack of leukotrienes synthesis illustrates that COX pathway is dominant in neocortex of epileptic patients. Our human data are consistent with the results obtained in experimental animal models of epilepsy. The important increase in PGE(2) and TXA(2) suggests that selective inhibition of prostanoid synthesis or blockage of prostanoid receptors might provide novel antiepileptic strategies in human epilepsy.

The IL1B-511 Polymorphism (rs16944 AA Genotype) Is Increased in Aspirin-Exacerbated Respiratory Disease in Mexican Population

Aspirin exacerbated respiratory disease (AERD) is characterized by chronic hyperplastic rhinosinusitis, nasal polyposis, asthma, and aspirin sensitivity. The mechanisms which produce these manifestations of intolerance are not fully defined, current research focuses on cyclooxygenase 1 (COX-1) inhibition, metabolism of arachidonic acid, and the COX pathway to the lipoxygenase (LO) route, inducing increased synthesis of leukotrienes (LT). The biological plausibility of this model has led to the search for polymorphisms in genes responsible for proinflammatory cytokines synthesis, such as IL1B and IL8. We performed a genetic association study between IL8-251 (rs4073) and IL1B-511 (rs16944) polymorphisms in AERD, aspirin-tolerant asthma (ATA), and healthy control subjects. Using allelic discrimination by real-time PCR, we found statistically nonsignificant associations between AERD, ATA, and healthy control subjects for the GG and GA genotypes of IL1B (rs16944). Interestingly, the AA genotype showed an increased frequency in the AERD patients versus the ATA group (GF = 0.19 versus 0.07, p = 0.018, OR 2.98, and 95% CI 1.17–7.82). This is the first observation that IL1B polymorphisms are involved in AERD. Thus, future studies must investigate whether interleukin-1β is released in the airways of AERD patients and whether it relates to genetic polymorphisms in the IL1B gene.

Modulation of Mast Cell and Basophil Functions by Benzene Metabolites

Benzene is a carcinogenic compound used in industrial manufacturing and a common environmental pollutant mostly derived from vehicle emissions and cigarette smoke. Benzene exposure is associated with a variety of clinical conditions ranging from hematologic diseases to chronic lung disorders. Beside its direct toxicity, benzene exerts multiple effects after being converted to reactive metabolites such as hydroquinone and benzoquinone. Mast cells and basophils are primary effector cells involved in the development of respiratory allergies such as rhinitis and bronchial asthma and they play an important role in innate immunity. Benzene and its metabolites can influence mast cell and basophil responses either directly or by interfering with other cells, such as T cells, macrophages and monocytes, which are functionally connected to mast cells and basophils. Hydroquinone and benzoquinone inhibit the release of preformed mediators, leukotriene synthesis and cytokine production in human basophils stimulated by IgE- and non IgE-mediated agonists. Furthermore, these metabolites reduce IgE-mediated degranulation of mast cells and the development of allergic lung inflammation in rats. Both in vitro and in vivo studies indicate that benzene metabolites alter biochemical and functional activities of other immunocompetent cells and may impair immune responses in the lung. These inhibitory effects of benzene metabolites are primarily mediated by interference with early transduction signals such as PI3 kinase. Together, currently available studies indicate that benzene metabolites interfere by multiple mechanisms with the role of basophils and mast cells in innate immunity and in chronic inflammation in the lung.