ABSTRACT
BACKGROUND AND PURPOSE: The guinea pig trachea (GPT) is commonly used in airway pharmacology. The aim of this study was to define the expression and function of EP receptors for PGE(2) in GPT as there has been ambiguity concerning their role. EXPERIMENTAL APPROACH: Expression of mRNA for EP receptors and key enzymes in the PGE(2) pathway were assessed by real-time PCR using species-specific primers. Functional studies of GPT were performed in tissue organ baths. KEY RESULTS: Expression of mRNA for the four EP receptors was found in airway smooth muscle. PGE(2) displayed a bell-shaped concentration-response curve, where the initial contraction was inhibited by the EP(1) receptor antagonist ONO-8130 and the subsequent relaxation by the EP(2) receptor antagonist PF-04418948. Neither EP(3) (ONO-AE5-599) nor EP(4) (ONO-AE3-208) selective receptor antagonists affected the response to PGE(2). Expression of COX-2 was greater than COX-1 in GPT, and the spontaneous tone was most effectively abolished by selective COX-2 inhibitors. Furthermore, ONO-8130 and a specific PGE(2) antibody eliminated the spontaneous tone, whereas the EP(2) antagonist PF-04418948 increased it. Antagonists of other prostanoid receptors had no effect on basal tension. The relaxant EP(2) response to PGE(2) was maintained after long-term culture, whereas the contractile EP(1) response showed homologous desensitization to PGE(2), which was prevented by COX-inhibitors. CONCLUSIONS AND IMPLICATIONS: Endogenous PGE(2), synthesized predominantly by COX-2, maintains the spontaneous tone of GPT by a balance between contractile EP(1) receptors and relaxant EP(2) receptors. The model may be used to study interactions between EP receptors.
Subject(s)
Dinoprostone/pharmacology , Muscle Contraction/drug effects , Muscle Tonus/drug effects , Muscle, Smooth/drug effects , Receptors, Prostaglandin E, EP1 Subtype/biosynthesis , Receptors, Prostaglandin E, EP2 Subtype/biosynthesis , Trachea/drug effects , Animals , Cyclooxygenase Inhibitors/pharmacology , Dinoprostone/physiology , Dose-Response Relationship, Drug , Guinea Pigs , Male , Organ Culture Techniques , RNA, Messenger/biosynthesis , Rats , Rats, Sprague-Dawley , Real-Time Polymerase Chain Reaction , Species SpecificityABSTRACT
BACKGROUND: A diagnosis of aspirin-intolerant asthma requires aspirin provocation in specialist clinics. Urinary leukotriene E(4) (LTE(4)) is increased in aspirin-intolerant asthma. A study was undertaken to investigate new biomarkers of aspirin intolerance by comparing basal levels of cysteinyl-leukotrienes (CysLTs) and leukotriene B(4) (LTB(4)) in saliva, sputum and ex vivo stimulated blood in subjects with aspirin-intolerant and aspirin-tolerant asthma. The effects of aspirin- and allergen-induced bronchoconstriction on leukotriene levels in saliva and ex vivo stimulated blood were also compared with the effects of the provocations on urinary mediators. METHODS: Induced sputum, saliva, urine and blood were obtained at baseline from 21 subjects with asthma. At a separate visit, 11 subjects showed a positive response to lysine-aspirin inhalation and 10 were aspirin tolerant. Saliva, blood and urine were also collected on the provocation day. Analyses of CysLTs and LTB(4) and the prostaglandin D(2) metabolite 9alpha,11beta-prostaglandin F(2) were performed and the fraction of exhaled nitric oxide was measured. RESULTS: Subjects with aspirin-intolerant asthma had higher exhaled nitric oxide levels and higher baseline levels of CysLTs in saliva, sputum, blood ex vivo and urine than subjects with aspirin-tolerant asthma. There were no differences in LTB(4) levels between the groups. Levels of urinary LTE(4) and 9alpha,11beta-prostaglandin F(2) increased after aspirin provocation whereas leukotriene levels in saliva and ex vivo stimulated blood did not increase. CONCLUSION: These findings support a global and specific increase in CysLT production in aspirin-intolerant asthma. Measurement of CysLTs in saliva has the potential to be a new and convenient non-invasive biomarker of aspirin-intolerant asthma.
Subject(s)
Anti-Inflammatory Agents, Non-Steroidal/adverse effects , Aspirin/adverse effects , Asthma/chemically induced , Cysteine/analysis , Drug Hypersensitivity/etiology , Leukotrienes/analysis , Adult , Biomarkers/analysis , Dinoprost/metabolism , Drug Hypersensitivity/metabolism , Female , Humans , Leukotriene B4/analysis , Male , Middle Aged , Saliva/chemistry , Sputum/chemistry , Uteroglobin/analysisABSTRACT
Leukotriene (LT)B4 in exhaled breath condensate (EBC) has been reported to be elevated in airway inflammation. The origin of leukotrienes in EBC is, however, not established. The aims of this study are to measure LTB4 levels in EBC collected in two challenges characterised by a strong neutrophilic airway inflammation and to compare LTB4 levels in EBC with levels in sputum and saliva. LTB4 and alpha-amylase were measured in EBC from 34 healthy subjects exposed in a pig confinement building or to a lipopolysaccharide provocation. These markers were also measured in induced sputum in 11 of the subjects. For comparison, LTB4 and alpha-amylase were measured in saliva from healthy subjects. Only four out of 102 EBC samples had detectable LTB4 (28-100 pg x mL(-1)). alpha-amylase activity was detected in the LTB4-positive samples. In contrast, LTB4 was detected in all examined sputum supernatants in the same study (median 1,190 pg x mL(-1)). The median LTB4 level in saliva was 469 pg x mL(-1). High levels of leukotriene B4 in saliva and the presence of leukotriene B4 in exhaled breath condensate only when alpha-amylase was detected, indicate that leukotriene B4 found in exhaled breath condensate is the result of saliva contamination. As leukotriene B4 was consistently present in sputum supernatants, exhaled breath condensate may be inappropriate for monitoring airway leukotriene B4.
