Increase in urinary leukotriene B4 glucuronide concentration in patients with aspirin-intolerant asthma after intravenous aspirin challenge

BACKGROUND: Aspirin challenge of aspirin-intolerant asthma (AIA) patients causes a significant increase in leukotriene E4 (LTE4) concentration in urine. However, knowledge on leukotriene B4 (LTB4) generation in patients with AIA is insufficient. Recent research has demonstrated that exogenously administered LTB4 is excreted as glucuronide into the urine in human healthy subjects. OBJECTIVE: The purpose of this study is to estimate urinary LTB4 glucuronide (LTBG) concentration in the clinically stable condition in healthy subjects and asthmatic patients and to investigate changes in urinary LTBG concentration in patients with AIA after aspirin challenge. METHODS: A provocation test was performed by intravenous aspirin challenge. After urine was hydrolysed by beta-glucuronidase, the fraction containing LTB4 was purified by high-performance liquid chromatography and LTB4 concentration was quantified by enzyme immunoassay. Urinary LTBG concentration was calculated as the difference between the concentration obtained with hydrolysis and that without hydrolysis. RESULTS: (1) After hydrolysis, the presence of urinary LTB4 was verified by gas chromatography-mass spectrometry-selected ion monitoring. (2) The urinary LTBG concentration was significantly higher in the asthmatic patients than in the healthy subjects (median, 5.37 pg/mg creatinine [range 1.2-13] vs. 3.32 pg/mg creatinine [range, 0.14-10.5], P = 0.0159). (3) The patients with AIA (n = 7), but not those with aspirin-tolerant asthma (n = 6), showed significant increases in LTBG and LTE4 excretions after aspirin challenge. (4) When the concentrations after aspirin challenge were analysed simultaneously, a significant linear correlation was observed between urinary LTBG concentration and urinary LTE4 concentration in patients with AIA (Spearman's rank correlation test, r = 0.817, P = 0.0003). CONCLUSION: LTBG is present in human urine, albeit at a concentration lower than urinary LTE4. In addition to a marked increase in cysteinyl-leukotriene production, aspirin challenge induced LTB4 production in AIA patients.     

Expression of 5-lipoxygenase and cyclooxygenase pathway enzymes in nasal polyps of patients with aspirin-intolerant asthma

In aspirin-intolerant subjects, adverse bronchial and nasal reactions to cyclooxygenase (COX) inhibitors are associated with over-production of cysteinyl-leukotrienes (cys-LTs) generated by the 5-lipoxygenase (5-LO) pathway. In the bronchi of patients with aspirin-intolerant asthma, we previously linked cys-LT over-production and aspirin hyper-reactivity with elevated immunoexpression in eosinophils of the terminal enzyme for cys-LT production, LTC4 synthase. We investigated whether this anomaly also occurs in the nasal airways of these patients. Immunohistochemical expression of 5-LO and COX pathway proteins was quantified in nasal polyps from 12 patients with aspirin-intolerant asthma and 13 with aspirin-tolerant asthma. In the mucosa of polyps from aspirin-intolerant asthmatic patients, cells immunopositive for LTC4 synthase were four-fold more numerous than in aspirin-tolerant asthmatic patients (p=0.04). There were also three-fold more cells expressing 5-LO (p=0.037), with no differences in 5-LO activating protein (FLAP), COX-1 or COX-2. LTC4 synthase-positive cell counts correlated exclusively with mucosal eosinophils (r=0.94, p<0.001, n=25). Co-localisation confirmed that five-fold higher eosinophil counts (p=0.007) accounted for the increased LTC4 synthase expression in polyps from aspirin-intolerant asthmatic patients, with no alterations in mast cells or macrophages. Within the epithelium, increased counts of eosinophils (p=0.006), macrophages (p=0.097), and mast cells (p=0.034) in aspirin-intolerant asthmatic polyps were associated only with 2.5-fold increased 5-LO-positive cells (p<0.05), while the other enzymes were not different. Our results indicate that a marked over-representation of LTC4 synthase in mucosal eosinophils is closely linked to aspirin intolerance in the nasal airway, as in the bronchial airways.     

Differential Contribution of the CysLTR1 Gene in Patients with Aspirin Hypersensitivity

In this study, we compared the roles of CysLT receptor type 1 (CysLTR1) and leukotriene C4 synthase (LTC4S) gene polymorphisms in two major aspirin-related allergic diseases, aspirin-intolerant asthma (AIA) and aspirin-induced chronic urticaria/angioedema (AICU). CysLTR1-634C>T and LTC4S-444A>C polymorphisms were genotyped and its functional effect on the promoter activity was compared. As in vivo functional study, changes of peripheral mRNA level of CysLTR1 were measured by real-time PCR before and after aspirin challenge. A significant association was found for the CysLTR1 promoter polymorphism and the AIA phenotype compared to AICU (P = 0.015). In U937 cells, the variant genotype reporter construct showed significantly higher promoter activity than the common genotype (P < 0.05). The CysLTR1 mRNA levels increased significantly after aspirin challenge in AIA patients (P = 0.013). In conclusion, the CysLTR1 polymorphism may contribute to develop to the AIA phenotype and be used as a genetic marker for differentiating two major aspirin hypersensitivity phenotypes.     

Effects of pranlukast on aspirin-induced bronchoconstriction: differences in chemical mediators between aspirin-intolerant and tolerant asthmatic patients.

BACKGROUND: Aspirin inhibits cyclooxygenase activity and modifies production of the arachidonate cascade in aspirin-induced asthma. The aim of the present study was to examine the effects of leukotriene (LT) receptor antagonist on aspirin challenge on eosinophil activity and chemical mediators released into the airway of asthmatic patients. METHODS: Aspirin oral provocation test was performed in aspirin-intolerant asthmatic patients (AIA; N = 7) and aspirin-tolerant asthmatic patients (ATA; N = 7). In AIA, LT receptor antagonist (pranlukast) was administered orally 2 hours before the test, and its inhibitory effects on sputum LTC4+C4, eosinophil cationic protein (ECP), eosinophil count, urinary LTE4/creatinine (Cr), 11-dehydrothromboxane (11-dhTX) B2/Cr, serum LTC4+D4, ECP, and peripheral blood eosinophil count were compared with the findings in ATA subjects. RESULTS: In AIA, aspirin induced an immediate reaction associated with increased urinary LTE4/Cr and sputum ECP and a fall in urinary 11-dhTXB2/Cr. Pranlukast inhibited the bronchial reaction and an increase in sputum ECP after threshold dosed of ASA, but failed to change aspirin-induced LT production in sputum and urine. In ATA, aspirin challenge was only associated with a fall in urinary 11-dhTXB2. CONCLUSIONS: Our results indicated that aspirin-induced asthma is associated with overproduction of LT with a shift to the 5-lipoxygenase series of the arachidonate cascade and that leukotriene receptor antagonist are useful for AIA through inhibition of production of LT and eosinophilic inflammation in the airway.     

A comparative study of eicosanoid concentrations in sputum and urine in patients with aspirin-intolerant asthma

BACKGROUND: Although many studies have assumed that the overproduction of cysteinyl- leukotrienes (cys-LTs) and an imbalance of arachidonic acid metabolism may be plausible causes for the pathogenesis of aspirin-intolerant asthma (AIA), there has been little experimental evidence to substantiate this notion in lower airways of patients with AIA. OBJECTIVES: The purpose of this study was to compare the eicosanoid concentrations in sputum and urine from patients with AIA. METHODS: The concentrations of sputum cys-LTs, prostaglandin E2 (PGE2), PGF2alpha, PGD2 and thromboxane B2 were measured to assess local concentrations of eicosanoids in patients with AIA and in those with aspirin-tolerant asthma (ATA). The concentrations of two urinary metabolites, leukotriene E4 (LTE4) and 9alpha11betaPGF2, were also measured to corroborate the relationship between the eicosanoid biosynthesis in the whole body and that in lower airways. RESULTS: The concentration of PGD2 in sputum was significantly higher in patients with AIA than in those with ATA (median, 5.3 pg/mL vs. 3.1 pg/mL, P < 0.05), but there was no significant difference in the concentration of the corresponding metabolite, 9alpha11betaPGF2, between the two groups. No differences were noted in the concentrations of other prostanoids in sputum between the two groups. The sputum cys-LT concentrations showed no differences between the two groups, in spite of the observation that the concentration of urinary LTE4 was significantly higher in patients with AIA than in those with ATA (median, 195.2 pg/mg-cre vs. 122.1 pg/mg-cre, P < 0.05). There was a significant correlation among the concentration of cys-LTs, the number of eosinophils and the concentration of eosinophil-derived neurotoxin (EDN) in sputum. CONCLUSION: The urinary concentration of LTE4 does not necessary reflect cys-LT biosynthesis in lower airways. A significantly higher concentration of PGD2 in sputum from patients with AIA suggests the possible ongoing mast cell activation in lower airways.     

Leukotriene C4 synthase promoter polymorphism in Japanese patients with aspirin-induced asthma

BACKGROUND: The A to C transversion in the promoter region of the gene encoding leukotriene C4 synthase (LTC4S) is proposed to be associated with the development of aspirin-induced asthma (AIA). OBJECTIVE: We investigated the frequency of the polymorphism in Japanese population and its association with clinical characteristics and cysteinyl leukotriene production. METHODS: Genotyping of LTC4S gene promoter was performed on 60 patients with AIA, 100 patients with aspirin-tolerant asthma (ATA), and 110 control subjects. We assessed the basal levels of urinary LTE4, the increment of urinary LTE4 on venous aspirin challenge, and LTC4S activity in peripheral blood eosinophils. RESULTS: The frequency of the variant C allele was significantly higher in patients with AIA (frequency of allele [q] = 0.192) than in patients with ATA (q = 0.110, P =.042). Variant C-allelic carriers experienced asthma at a significantly younger age (31.8 +/- 2.9 years [mean +/- SEM]) than wild-type A homozygotes (41.3 +/- 2.2 years, P =.007). Basal levels of LTE4 and the increment of urinary LTE4 on venous aspirin challenge did not show a difference between wild-type A homozygotes and variant C-allelic carriers. There was no relationship between the polymorphism and the LTC4S activity in eosinophils, although LTC4S activities were significantly higher in patients with AIA than in patients with ATA. CONCLUSION: Our findings reveal the lack of functionality of the polymorphism in the LTC4S gene, whereas this polymorphism might have some effect on the development of AIA, probably in linkage disequilibrium with another causatively important mutation.     

Possible involvement of mast-cell activation in aspirin provocation of aspirin-induced asthma

BACKGROUND: Although there is increasing evidence of the importance of cysteinyl leukotrienes (LT) as mediators of aspirin-induced bronchoconstriction in aspirin-sensitive asthma, the cellular origin of the LT is not yet clear. METHODS: Urinary concentrations of leukotriene E4 (LTE4), 11-dehydrothromboxane B2, 9alpha,11beta-prostaglandin F2, and Ntau-methylhistamine were measured during the 24 h following cumulative intravenous administration of increasing doses of lysine aspirin to asthmatic patients. In addition, the urinary concentrations of these metabolites were measured on 5 consecutive days in a patient who suffered an asthma attack after percutaneous administration of nonsteroidal anti-inflammatory drugs. RESULTS: In aspirin-induced asthma patients (AIA, n=10), the basal concentration of urinary LTE4, but not the other metabolites, was significantly higher than that in aspirin-tolerant asthma patients (ATA, n=10). After intravenous aspirin provocation, the AIA group showed a 13.1-fold (geometric mean) increase in excretion of LTE4 during the first 3 h, and 9alpha,11beta-prostaglandin F2 also increased in the AIA group during the first 0-3 h and the 3-6 h collection period. Ntau-methylhistamine excretion was also increased, but to a lesser degree. Administration of aspirin caused significant suppression of 11-dehydrothromboxane B2 excretion in both the AIA and ATA groups. When the percentage of maximum increase of each metabolite from the baseline concentrations was compared between the AIA group and the ATA group, a significantly higher increase in excretion of LTE4, 9alpha,11beta-prostaglandin F2, and Ntau-methylhistamine was observed in the AIA group than the ATA group. An increased excretion of LTE4 and 9alpha,11beta-prostaglandin F2 has been detected in a patient who suffered an asthma attack after percutaneous administration of nonsteroidal anti-inflammatory drugs. CONCLUSIONS: Considering that human lung mast cells are capable of producing LTC4, prostaglandin D2, and histamine, our present results support the concept that mast cells, at least, may participate in the development of aspirin-induced asthma.     

A moderate and unspecific release of cysteinyl leukotrienes by aspirin from peripheral blood leucocytes precludes its value for aspirin sensitivity testing in asthma

Aspirin-induced asthma (AIA) is a clinical syndrome related to cysteinyl leukotriene overproduction in airways. The confirmation of the diagnosis requires inconvenient provocation tests with acetyl salicylic acid (ASA). A study was performed to evaluate whether measurement in vitro of cysteinyl leukotrienes (cys-LTs) release by isolated peripheral blood leucocytes, stimulated with ASA, can be of use for diagnosis of AIA. A cellular allergen stimulation test, CAST, was adapted to measure leukotriene release from leucocytes of 32 aspirin-tolerant and 26 aspirin-intolerant asthmatics. The cells were stimulated with Lys-ASA, N-formyl-methionyl-leucyl-phenylalanine (fMLP), or both fMLP and Lys-ASA, in a buffer containing IL-3, and results compared with human leukaemia cell line (Hl-60) response to Lys-ASA. Cys-LTs were measured in cell supernatant fluids by ELISA. ASA had a rather week stimulatory effect on cys-LTs release in both groups of patients. Contrary to some previous studies, no significant differences were found between cys-LTs release by leucocytes from AIA and ATA, or by differentiated Hl-60 cells. Measurement of cysteinyl-leukotriene release by peripheral blood leucocytes pre-treated with aspirin has no value for diagnosis of AIA.     

Increased Generation of Leukotriene C4 from Eosinophils in Asthmatic Patients

Human eosinophils with a density of over 1.095 were isolated from peripheral blood by dextran sedimentation, centrifugation with Lymphoprep and density gradients with Percoll. After the cells (1 X 10(5)/ml) were incubated with 1 microgram/ml calcium ionophore A23187 for 20 min, leukotriene C4 (LTC4) content in the supernatant was measured by radioimmunoassay. The generation of LTC4 was significantly higher in the cells from extrinsic asthmatics (23.5 +/- 14.8 ng/10(6) cells, mean +/- SD, n = 26, P less than 0.01) and intrinsic asthmatics (24.6 +/- 20.6 ng/10(6) cells, n = 27, P less than 0.01 as compared with normal healthy subjects (8.3 +/- 7.7 ng/10(6) cells, n = 10). There was no significant difference in the generation of LTC4 between intrinsic and extrinsic asthmatics. These observations indicate that eosinophils from asthmatic patients have increased ability to release LTC4.     

Strategy for NSAID administration to aspirin-intolerant asthmatics in combination with PGE2 analogue: a theoretical approach

Aspirin-induced asthma (AIA) is a severe inflammatory disease, which affects aspirin-intolerant patients after ingestion of aspirin or other non-steroidal anti-inflammatory drugs (NSAIDs). In this article, a mathematical model describing arachidonic acid metabolism and its interaction with NSAIDs, is used to study the strategy for safe managing of NSAIDs to AIA patients. Three different AIA patient populations are taken into consideration. First, the values of aspirin and ibuprofen limiting doses that might induce symptoms of AIA are calculated and compared to experimentally observed threshold doses to enlighten which AIA patient population is susceptible to aspirin and ibuprofen. Second, the methodology of NSAID administration is studied on AIA populations susceptible to aspirin and ibuprofen by using 1,000 mg dose of aspirin and 200 or 400 mg dose of ibuprofen followed by PGE₂ analogue dosing. Our model results show that successive doses of PGE₂ analogue applied at appropriate time after aspirin or ibuprofen ingestion would enable administration of both NSAIDs to AIA patients. PGE₂ analogue doses and the corresponding times of their applications are calculated. The model is also used to estimate the duration of symptoms of AIA for different aspirin and ibuprofen doses.     

Deficiency of platelet lipoxygenase activity in myeloproliferative disorders

The myeloproliferative disorders are characterized by frequent bleeding and thrombotic complications, which have been attributed to abnormal platelet function. In 24 of 60 patients studied, reduced activity of the platelet lipoxygenase pathway for oxygenation of arachidonic acid was revealed by a new direct assay. This assay measured arachidonic acid-induced oxygen consumption in platelets preincubated with aspirin to block cyclooxygenase activity. Patients with secondary polycythemia or thrombocytosis had normal lipoxygenase activity . In the cells of seven of eight patients with lipoxygenase deficiency arachidonic acid induced increased synthesis of thromboxane, the major cyclooxygenase product. Nevertheless, patients with deficient lipoxygenase activity tended to have episodes of hemorrhage rather than thrombosis. Bleeding complications occurred in 67 per cent of patients with lipoxygenase deficiency, but in only 19 per cent of those with normal lipoxygenase activity (P less than 0.001). In contrast, 13 per cent of lipoxygenase-deficient patients, but 31 per cent of patients with other myeloproliferative disorders, had thromboembolic complications. Measurement of platelet lipoxygenase activity may be of diagnostic value in distinguishing myeloproliferative disorders from secondary thrombocytosis or polycythemia. Lipoxygenase deficiency may prove to be a useful natural model for investigating the role of lipoxygenase products in hemostasis.     

Sodium cromoglycate nebulized solution has an acute bronchodilative effect in patients with aspirin-intolerant asthma (AIA)]

Sodium cromoglycate (SCG) (Intal) is a well-known anti-allergic agent which protects against allergen- and exercise-induced bronchospasms. The effect has been recognized non-acute, unlike that of bronchodilators. However, we have found that some patients with aspirin-intolerant asthma (AIA) show significant improvement soon after a single inhalation of SCG nebulized solution. In this study, we investigated the acute bronchodilator effect of SCG given by nebulizer in adult asthmatics, especially compairing AIA with non-AIA (aspirin-tolerant asthma) patients. Twenty patients with AIA and 11 with non-AIA participated in the study. After performing spirometry on remission, they inhaled either SCG via a nebulizer or 4 ml of placebo in a randomized double-blind fashion. After inhalation, spirometry was performed every ten minutes for one hour. The placebo used was a saline solution of the same osmolarity as that of the SCG nebulized solution. Placebo inhalation provoked asthmatic attacks in five of the patients with AIA and one with non-AIA, but SCG did not. In the AIA group, twelve out of the twenty patients also had improved nasal symptoms soon after inhalation of SCG. Forced expiratory volume in one second (FEV1) was significantly improved 10 minutes after inhalation of SCG. Fifty minutes after SCG inhalation, the percent degree of FEV1 improvement was approximately 17%. However, FEV1 was significantly decreased by approximately 14% after inhalation of placebo. In the non-AIA group, FEV1 was not increased after inhalation of SCG. V25 was not changed after inhalation of SCG in AIA and non-AIA groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of inhalation aspirin challenge on exhaled nitric oxide in patients with aspirin-inducible asthma

BACKGROUND: A complex relationship between arachidonic acid metabolites and nitric oxide (NO) synthesis has been reported in asthma. The effects of inhaled aspirin on fractional exhaled NO (FENO) in patients with aspirin-tolerant (ATA) and aspirin-inducible (AIA) asthma compared with normal controls have been investigated. METHODS: The FENO was measured baseline, after saline and lysine-aspirin (L-ASA) bronchial challenge in 10 patients with ATA and in 10 patients with AIA [mean (PD(20)FEV(1) L-ASA): 14.7 +/- 12.7 mg], who had comparable age and baseline FEV(1). Ten healthy subjects served as controls. Sputum eosinophils were counted after saline and after L-ASA challenge in the two groups of asthmatics. RESULTS: Asthmatic patients had baseline FENO significantly higher than controls (29.7 +/- 6.8 vs 9.8 +/- 2.05 p.p.b. respectively, P < 0.0001). No difference was observed in methacholine PD(20)FEV(1) and baseline FENO between ATA and AIA patients. After L-ASA inhalation, FENO increased significantly only in patients with AIA, reaching the peak value 4 h after bronchoconstriction (from 31.1 +/- 6 to 43 +/- 4.8 p.p.b., P < 0.001), while no change was observed in patients with ATA and in controls. Sputum eosinophils increased significantly after L-ASA inhalation only in patients with AIA (from 8.1 +/- 2.7 to 11.1 +/- 2.8%, P < 0.005) and there was a significant relationship between the increase in sputum eosinophils and the increase in FENO after ASA challenge. CONCLUSION: Exhaled NO may indicate eosinophilic airway inflammation during ASA exposure in patients with ASA inducible asthma.     

Protection of leukotriene receptor antagonist against aspirin-induced bronchospasm in asthmatics

Purpose

Leukotriene receptor antagonists (LTRAs) are used to treat aspirin-intolerant asthma (AIA); however, the protective effects of long-term LTRA administration against aspirin-induced bronchospasm have not been evaluated.

Objectives

We investigated the efficacy of a 12-week treatment with a LTRA in protecting against aspirin-induced asthma in AIA patients.

Methods

Fifty-two adult patients with AIA underwent an aspirin challenge test just before administration of montelukast (10 mg/day) and just after 12 weeks of treatment. The protective effect was assessed as the disappearance of aspirin-induced bronchospasm after 12 weeks of treatment. The results were compared according to the patients'' clinical and physiological parameters.

Results

The decline in FEV1 following aspirin challenge was significantly reduced from 28.6±1.9% to 10.2±1.7% (P=0.0001) after 12 weeks of montelukast treatment. However, 14 subjects (30%) still showed a positive response (>15% decline in FEV1) to aspirin challenge. Grouping the subjects into good and poor responders according to post-treatment responses revealed that the pretreatment aspirin-induced FEV1 decline was significantly greater in the poor responders and that the triggering dose of aspirin and the induction time for a positive response were lower and shorter, respectively, in the poor responders. Histories of aspirin hypersensitivity and sinusitis were more prevalent among the poor responders than among the good responders.

Conclusions

Twelve weeks of treatment with montelukast protected against aspirin-induced bronchospasm in 70% of the AIA cases. A poor response was associated with more severe aspirin-induced bronchospasms before treatment and a history of aspirin hypersensitivity or sinusitis.

Clinical implications

A severe response to aspirin challenge may be a predictor of poor responsiveness to leukotriene antagonist treatment.     

Association analysis of C6 genetic variations and aspirin hypersensitivity in Korean asthmatic patients

There has been increasing evidence that genetic mechanisms contribute to the development of aspirin-intolerant asthma (AIA), a life-threatening disease. The complement component (C6) is a constituent of a biochemical cascade that has been implicated in airway epithelial damage and nasal polyposis, and therefore, may be a risk factor for AIA. To investigate the association between C6 variations and AIA in a Korean asthma cohort, 27 SNPs were selected for genotyping based on previously reported polymorphisms in the HapMap database. Genotyping was carried out using TaqMan assay, and five major haplotypes were obtained in 163 AIA cases and 429 aspirin-tolerant asthma (ATA) controls subjects. Genotype frequency distributions of C6 polymorphisms and haplotypes were analyzed using logistic and regression models. Subsequent analyses revealed a lack of association between C6 genetic variations and AIA. From the initial analyses, marginal associations of rs10512766 (p = 0.04 in co-dominant model) and rs4957374 (p = 0.05 in dominant model) with AIA did not reach the threshold of significance after multiple testing corrections; thus this study failed to find convincing evidence that variations in C6 gene influence the risk of AIA in a Korean population. However, these preliminary results may contribute to the etiology of aspirin hypersensitivity in Korean asthmatic patients.     

Clinical features of asthmatic patients with increased urinary leukotriene E4 excretion (hyperleukotrienuria): Involvement of chronic hyperplastic rhinosinusitis with nasal polyposis

BACKGROUND: The urinary leukotriene E4 (U-LTE4) concentration is significantly increased in patients with aspirin-intolerant asthma (AIA). However, the relationship between the clinicopathogenetic factors of asthma and the U-LTE4 concentration remains undetermined. OBJECTIVE: We sought to examine the clinical features of asthmatic patients with increased excretion levels of U-LTE4 (hyperleukotrienuria). METHODS: We measured the U-LTE4 concentrations in 137 asthmatic patients (including 64 patients with AIA) who were in clinically stable condition. A U-LTE4 concentration of 150 pg/mg creatinine or greater (mean U-LTE4 + 3 SDs of normal healthy control subjects) was indicative of hyperleukotrienuria. RESULTS: The basal concentration of U-LTE4 was significantly higher in the patients with AIA than in those with aspirin-tolerant asthma (ATA; median, 227.2 vs 90.3 pg/mg creatinine; P <.01). Compared with normal leukotrienuria in the patients with AIA, hyperleukotrienuria in the patients with AIA was associated with older age and decrease in pulmonary function. On the other hand, compared with normal leukotrienuria in the patients with ATA, hyperleukotrienuria in the patients with ATA was associated with severe asthma and chronic hyperplastic rhinosinusitis with nasal polyposis (CHRS/NP), which are well-known symptoms of the aspirin triad, as well as hypereosinophilia and anosmia. The patients with ATA with CHRS/NP excreted U-LTE4 at significantly high concentrations. There were significant decreases in the U-LTE4 concentrations before and after the sinus surgery in both the AIA and ATA groups (P <.05). CONCLUSION: Cysteinyl leukotrienes are not strictly associated with aspirin intolerance itself but rather with clinical features, such as CHRS/NP, that are similar to those seen in AIA. CHRS/NP might be involved in cysteinyl leukotriene overproduction in asthmatic patients.     

Aspirin-sensitive asthma: abnormal platelet response to drugs inducing asthmatic attacks. Diagnostic and physiopathological implications

The pathogenesis of aspirin-sensitive asthma remains unknown. Using a new model of platelet activation, initially described as a response of platelets to IgE antibody-dependent stimuli, this study was designed to test the hypothesis of a possible involvement of platelets in aspirin-sensitive asthma. Washed platelets from 35 aspirin-sensitive asthmatics showed an abnormal in vitro response to cyclooxygenase inhibiting nonsteroidal anti-inflammatory drugs (NSAIDs)--aspirin, indomethacin or flurbiprofen--characterized by the generation of a cytocidal supernatant and (14 patients explored) a burst of chemiluminescence; these drugs had no similar effect on platelets from 31 controls (p less than 0.0001). It was shown that the abnormal platelet response to NSAIDs was not mediated by IgE. In contrast to platelets, aspirin-sensitive asthmatic leukocytes generated neither cytocidal factors nor chemiluminescence in the presence of NSAIDs. Sodium salicylate and salicylamide, which, though structurally similar to aspirin, do not inhibit cyclooxygenase and are well tolerated by aspirin-sensitive asthmatics, did not activate their platelets to release cytocidal factors. Moreover, preincubation of platelets with sodium salicylate, salicylamide or prostaglandin endoperoxide PGH2, highly prevented their abnormal response to NSAIDs (greater than 80%; p less than 0.0001). Since several lipoxygenase inhibitors (NDGA, esculetin), including inhibitors of both cyclooxygenase and lipoxygenase (ETYA, BW755c), did not activate patient platelets and prevented the subsequent abnormal response to NSAIDs, it is suggested that the abnormal platelet activation by NSAIDs is not only the consequence of an inhibition of cyclooxygenase, but also involves generation of lipoxygenase metabolites of arachidonate. Besides, platelets from 4 aspirin-sensitive asthmatics undergoing aspirin desensitization were found to have completely lost their abnormal responsiveness to NSAIDs. These findings represent the first identification in aspirin-intolerant asthmatics of a specific abnormal cellular response to drugs inducing asthmatic attacks and open new perspectives into the pathogenesis, prevention and diagnosis of this disease. They also provide support to the concept of a role for platelets in asthma.     

Human bronchial epithelial cells express an active and inducible biosynthetic pathway for leukotrienes B4 and C4

BACKGROUND: Human bronchial epithelial cells synthesize cyclooxygenase and 15-lipoxygenase products, but the 5-lipoxygenase (5-LO) pathway that generates the leukotriene (LT) family of bronchoconstrictor and pro-inflammatory mediators is thought to be restricted to leucocytes. OBJECTIVE: We hypothesized that human bronchial epithelial cells (HBECs) express a complete and active 5-LO pathway for the synthesis of LTB4 and LTC4, either constitutively or after stimulation. METHODS: Flow cytometry, RT-PCR, Western blotting, enzyme immunoassays and reverse-phase high-performance liquid chromatography were used to investigate constitutive and stimulated expression of 5-LO pathway enzymes and the synthesis of LTs B4 and C4 in primary HBECs and in the 16-HBE 14o- cell line. RESULTS: Constitutive mRNA and protein expression for 5-LO, 5-LO-activating protein (FLAP), LTA4 hydrolase and LTC4 synthase were demonstrated in primary HBECs and in the 16-HBE 14o- cell line. In 16-HBE 14o- cells, treatment with calcium ionophore A23187, bradykinin or LPS up-regulated the expression of these enzymes. The up-regulation of 5-LO was blocked by the anti-inflammatory glucocorticoid dexamethasone. Human bronchial epithelial cells were shown to generate bioactive LTs, with primary HBECs generating 11-fold more LTC4 and five-fold more LTB4 than 16-HBE 14o- cells. LT production was enhanced by ionophore treatment and blocked by the FLAP inhibitor MK-886. CONCLUSIONS: Expression of an active and inducible 5-LO pathway in HBEC suggests that damaged or inflamed bronchial epithelium may synthesize LTs that contribute directly to bronchoconstriction and leucocytosis in airway inflammation.     

Effect of AA-861, a 5-Lipoxygenase Inhibitor, on Leukotriene Synthesis in Human Polymorphonuclear Leukocytes and on Cyclooxygenase and 12-Lipoxygenase Activities in Human Platelets

AA-861, a selective inhibitor of 5-lipoxygenase of arachidonic acid, was tested for ability to inhibit leukotriene C4 and leukotriene B4 synthesis in human polymorphonuclear leukocytes after calcium ionophore stimulation. AA-861 dose-dependently inhibited leukotriene B4 and leukotriene C4 generation in human polymorphonuclear leukocytes; the concentration required to inhibit generation by 50% (IC50) was 3 X 10(-7) M for leukotriene B4 and 1 X 10(-8) M for leukotriene C4. BW-755C inhibited the generation of leukotriene C4 with an IC50 of about 10(-5) M, indicating that AA-861 is about 1,000 times more potent than BW-755C. AA-861 did not affect the activity of either cyclooxygenase or 12-lipoxygenase at a concentration up to 10(-5) M in human platelets. AA-861 did not inhibit histamine release from human basophils. These results indicate that AA-861 selectively inhibits 5-lipoxygenase but not cyclooxygenase or 12-lipoxygenase in human specimens.