RESUMO
BACKGROUND AND PURPOSE: Prostaglandin (PG) D(2) has emerged as a key mediator of allergic inflammatory pathologies and, particularly, PGD(2) induces leukotriene (LT) C(4) secretion from eosinophils. Here, we have characterized how PGD(2) signals to induce LTC(4) synthesis in eosinophils. EXPERIMENTAL APPROACH: Antagonists and agonists of DP(1) and DP(2) prostanoid receptors were used in a model of PGD(2) -induced eosinophilic inflammation in vivo and with PGD(2) -stimulated human eosinophils in vitro, to identify PGD(2) receptor(s) mediating LTC(4) secretion. The signalling pathways involved were also investigated. KEY RESULTS: In vivo and in vitro assays with receptor antagonists showed that PGD(2) -triggered cysteinyl-LT (cysLT) secretion depends on the activation of both DP(1) and DP(2) receptors. DP(1) and DP(2) receptor agonists elicited cysLTs production only after simultaneous activation of both receptors. In eosinophils, LTC(4) synthesis, but not LTC(4) transport/export, was activated by PGD(2) receptor stimulation, and lipid bodies (lipid droplets) were the intracellular compartments of DP(1) /DP(2) receptor-driven LTC(4) synthesis. Although not sufficient to trigger LTC(4) synthesis by itself, DP(1) receptor activation, signalling through protein kinase A, did activate the biogenesis of eosinophil lipid bodies, a process crucial for PGD(2) -induced LTC(4) synthesis. Similarly, concurrent DP(2) receptor activation used Pertussis toxin-sensitive and calcium-dependent signalling pathways to achieve effective PGD(2) -induced LTC(4) synthesis. CONCLUSIONS AND IMPLICATIONS: Based on pivotal roles of cysLTs in allergic inflammatory pathogenesis and the collaborative interaction between PGD(2) receptors described here, our data suggest that both DP(1) and DP(2) receptor antagonists might be attractive candidates for anti-allergic therapies.
Assuntos
Leucotrieno C4/biossíntese , Prostaglandina D2/metabolismo , Receptores Imunológicos/metabolismo , Receptores de Prostaglandina/metabolismo , Animais , Cálcio/metabolismo , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Cisteína/metabolismo , Eosinófilos/metabolismo , Humanos , Leucotrienos/metabolismo , Masculino , Camundongos , Toxina Pertussis/farmacologia , Antagonistas de Prostaglandina/farmacologia , Receptores Imunológicos/agonistas , Receptores Imunológicos/antagonistas & inibidores , Receptores de Prostaglandina/agonistas , Receptores de Prostaglandina/antagonistas & inibidores , Transdução de Sinais/efeitos dos fármacosRESUMO
Tissue eosinophilia prevention represents one of the primary targets to new anti-allergic therapies. As lipoxin A4 (LXA4) and aspirin-triggered 15-epi-LXA4 (ATL) are emerging as endogenous "stop signals" produced in distinct pathologies including some eosinophil-related pulmonary disorders, we evaluated the impact of in situ LXA4/ATL metabolically stable analogues on allergen-induced eosinophilic pleurisy in sensitized rats. LXA4/ATL analogues dramatically blocked allergic pleural eosinophil influx, while concurrently increasing circulating eosinophilia, inhibiting the earlier edema and neutrophilia associated with allergic reaction. The mechanisms underlying this LXA4/ATL-driven allergic eosinophilia blockade was independent of mast cell degranulation and involved LXA4/ATL inhibition of both IL-5 and eotaxin generation, as well as platelet activating factor action. These findings reveal LXA4/ATL as a novel class of endogenous anti-allergic mediators, capable of preventing local eosinophilia.
Assuntos
Alérgenos/imunologia , Antialérgicos/farmacologia , Anti-Inflamatórios não Esteroides/farmacologia , Aspirina/administração & dosagem , Movimento Celular/imunologia , Eosinófilos/imunologia , Ácidos Hidroxieicosatetraenoicos/farmacologia , Lipoxinas , Animais , Anti-Inflamatórios não Esteroides/administração & dosagem , Anti-Inflamatórios não Esteroides/metabolismo , Inibição de Migração Celular , Movimento Celular/efeitos dos fármacos , Relação Dose-Resposta Imunológica , Eosinofilia/imunologia , Eosinofilia/patologia , Eosinófilos/efeitos dos fármacos , Feminino , Ácidos Hidroxieicosatetraenoicos/administração & dosagem , Ácidos Hidroxieicosatetraenoicos/metabolismo , Masculino , Ovalbumina/administração & dosagem , Ovalbumina/imunologia , Pleurisia/imunologia , Pleurisia/patologia , Pleurisia/prevenção & controle , Ratos , Ratos WistarRESUMO
In noninfected rats, challenge with allergen following local IgE sensitization induced a pleurisy marked by intense protein exudation that plateaued from 30 min to 4 h after challenge, reducing thereafter. Infection of rats with Angiostrongylus costaricensis induced a 5-fold increase in blood eosinophil numbers by 25 days postinfection, whereas the numbers of eosinophils in the pleural cavity ranged from normal to a weak increase. In infected rats, identically sensitized, challenge with Ag induced a much shorter duration of pleural edema with complete resolution by 4 h, but no change in the early edema response. In parallel, infection increased the number of eosinophils recovered from the pleural cavity at 4 h, but not at 30 min, following allergen challenge. Pretreatment with IL-5 (100 IU/kg, i.v.) also increased eosinophil numbers in blood and, after allergen challenge, shortened the duration of the pleural edema and increased pleural eosinophil numbers. There were increases in the levels of both PGE2 and lipoxin A4 (LXA4) in pleural exudate. Selective cyclooxygenase (COX)-2 inhibitors, NS-398, meloxicam, and SC-236, did not alter pleural eosinophilia, but reversed the curtailment of the edema in either infected or IL-5-pretreated rats. Pretreatment of noninfected animals with the PGE analogue, misoprostol, or two stable LXA4 analogues did not alter the magnitude of pleural exudation response, but clearly shortened its duration. These results indicate that the early resolution of allergic pleural edema observed during A. costaricensis infection coincided with a selective local eosinophilia and seemed to be mediated by COX-2-derived PGE2 and LXA4.
Assuntos
Angiostrongylus/imunologia , Dinoprostona/fisiologia , Edema/terapia , Eosinofilia/enzimologia , Ácidos Hidroxieicosatetraenoicos/fisiologia , Hipersensibilidade/terapia , Isoenzimas/metabolismo , Lipoxinas , Prostaglandina-Endoperóxido Sintases/metabolismo , Infecções por Strongylida/enzimologia , Administração Oral , Animais , Anti-Inflamatórios não Esteroides/metabolismo , Anti-Inflamatórios não Esteroides/farmacologia , Antígenos de Helmintos/administração & dosagem , Corticosterona/sangue , Ciclo-Oxigenase 2 , Inibidores de Ciclo-Oxigenase 2 , Inibidores de Ciclo-Oxigenase/administração & dosagem , Dinoprostona/metabolismo , Edema/enzimologia , Edema/patologia , Edema/fisiopatologia , Eosinofilia/patologia , Eosinofilia/fisiopatologia , Exsudatos e Transudatos/efeitos dos fármacos , Exsudatos e Transudatos/enzimologia , Feminino , Ácidos Hidroxieicosatetraenoicos/metabolismo , Hipersensibilidade/enzimologia , Hipersensibilidade/patologia , Hipersensibilidade/fisiopatologia , Injeções Intraperitoneais , Injeções Intravenosas , Interleucina-5/administração & dosagem , Isoenzimas/farmacologia , Cinética , Leucotrieno C4/metabolismo , Masculino , Misoprostol/administração & dosagem , Derrame Pleural/enzimologia , Derrame Pleural/metabolismo , Derrame Pleural/patologia , Derrame Pleural/prevenção & controle , Pleurisia/enzimologia , Pleurisia/patologia , Pleurisia/fisiopatologia , Prostaglandina-Endoperóxido Sintases/farmacologia , Ratos , Ratos Wistar , Infecções por Strongylida/patologia , Infecções por Strongylida/fisiopatologiaRESUMO
1. Bradykinin is suggested to play a role in the pathophysiology of several acute and chronic diseases, including allergic disorders such as asthma. In the present study, we have investigated the importance of bradykinin in mediating allergic inflammation in rats. 2. To this end we have tested the effects of the B2 receptor antagonists Hoe 140, FR173657 or FR172357 on the pleural inflammatory response triggered by intrapleural (i.pl.) injection of allergen (ovalbumin, 12 microg cavity(-1)) in 14 day-actively sensitized Wistar rats. Analysis of the pleural fluid effluent revealed a sequence of mast cell-dependent inflammatory events, including early protein exudation and neutrophilia and late pleural eosinophil influx. 3. Local treatment with Hoe 140 (0.1 and 1 microg cavity(-1)), FR173657 (1 and 10 microg cavity(-1)) or FR172357 (1 and 10 microg cavity(-1)) inhibited dose-dependently allergen-induced mast cell activation with impairment of pleural plasma leakage, neutrophil accumulation and late eosinophil influx. 4. Moreover, the B2 receptor antagonists also dose-dependently inhibited the allergic like inflammatory pleurisy triggered by bradykinin (50 microg cavity(-1)), which is characterized by acute mast cell degranulation, protein leakage and pleural eosinophil infiltration. 5. Taken together, our findings provide substantial evidence to suggest that bradykinin acting on its B2 receptors play a critical role in mediating allergic mast cell-dependent inflammation in rats, and suggest that B2 receptor antagonists may be useful therapeutically to control allergic dysfunction.
Assuntos
Alérgenos/farmacologia , Antialérgicos/farmacologia , Antagonistas dos Receptores da Bradicinina , Bradicinina/análogos & derivados , Exsudatos e Transudatos/metabolismo , Leucócitos/efeitos dos fármacos , Quinolinas/farmacologia , Animais , Bradicinina/farmacologia , Degranulação Celular/efeitos dos fármacos , Exsudatos e Transudatos/efeitos dos fármacos , Feminino , Liberação de Histamina/efeitos dos fármacos , Masculino , Mastócitos/efeitos dos fármacos , Fator de Ativação de Plaquetas/farmacologia , Pleurisia/imunologia , Pleurisia/metabolismo , Proteínas/metabolismo , Ratos , Receptor B2 da Bradicinina , p-Metoxi-N-metilfenetilamina/farmacologiaRESUMO
We have studied the effect of local and systemic treatment with dexamethasone for prevention of the pleural eosinophilia triggered by allergen in actively sensitised Wistar rats. Parallel changes in blood and marrow eosinophil numbers were assessed for comparison. The intrapleural (i.pl.) injection of ovalbumin into ovalbumin-sensitised animals led to a long-lasting pleural fluid eosinophilia which peaked from 24 to 72 h post-challenge. At these time points, there was a significant 2- to 3-fold increase in the blood eosinophil numbers, whereas the bone marrow number of mature eosinophils remained unaltered. Systemic treatment with dexamethasone (0.05-0.5 mg/kg, i.p.) abolished the pleural and blood eosinophilia observed 24 and 48 h post-challenge, also causing a significant reduction in marrow eosinophil numbers. Despite being unable to alter blood and bone marrow eosinophil numbers, the local i.pl. administration of dexamethasone (2.5-10 microg/cavity) inhibited dose dependently the allergen-induced pleural eosinophil influx at 24 h but not at 48 h post-challenge. This treatment also shortened the time course of eosinophil accumulation in the pleural space from the 48 h time point on. We conclude that the effect of systemic but not of local treatment with dexamethasone on allergen-induced eosinophil recruitment is well correlated with the inhibition of eosinophil production in bone marrow. In contrast, low amounts of dexamethasone injected into the pleural space seem to affect locally eosinophil recruitment and survival.
Assuntos
Anti-Inflamatórios/farmacologia , Dexametasona/farmacologia , Eosinofilia/prevenção & controle , Pleurisia/prevenção & controle , Alérgenos/efeitos adversos , Animais , Anti-Inflamatórios/uso terapêutico , Células da Medula Óssea/citologia , Células da Medula Óssea/efeitos dos fármacos , Permeabilidade Capilar/efeitos dos fármacos , Degranulação Celular/efeitos dos fármacos , Dexametasona/uso terapêutico , Eosinofilia/induzido quimicamente , Eosinófilos/citologia , Eosinófilos/efeitos dos fármacos , Feminino , Contagem de Leucócitos/efeitos dos fármacos , Leucócitos Mononucleares/efeitos dos fármacos , Leucócitos Mononucleares/fisiologia , Masculino , Mastócitos/efeitos dos fármacos , Mastócitos/fisiologia , Neutrófilos/efeitos dos fármacos , Neutrófilos/fisiologia , Ovalbumina/efeitos adversos , Pleurisia/induzido quimicamente , Ratos , Ratos WistarRESUMO
The eosinophilic response has been identified as a key alteration in the pathogenesis of asthma and other allergic diseases. A close-correlation between disease severity and eosinophilia, and the eosinophil ability to provide toxic and pro-inflammatory agents are the major elements supporting the interpretation that there is indeed a causal relationship between these phenomena. Nevertheless, controversy still persists since some studies have clearly demonstrated that eosinophil infiltration is not necessarily accompanied by tissue damage or hyperresponsiveness. In addition, there are some examples in the literature in which such alterations are not modified following abrogation of eosinophil influx. In this review it will be argued, based on a model of IgE-dependent pleurisy, that eosinophil infiltration can be associated with down-regulation of allergic inflammatory response. The potential mechanism by which eosinophils could be acting as a immunomodulatory cells in this particular system will also be assessed.
Assuntos
Asma/fisiopatologia , Eosinófilos/fisiologia , Hipersensibilidade/imunologia , Inflamação/imunologia , Animais , Eosinofilia , Imunoglobulina E , Pleurisia , Prostaglandinas , RatosRESUMO
1. Recent evidence has implicated eosinophils in the inhibition of allergen-induced rat pleurisy, but the mechanism of this negative modulation is not completely understood. This study was undertaken in order to define the potential role of prostaglandins in this phenomenon. 2. Wistar rats were actively sensitized by subcutaneous injection of a mixture of ovalbumin and AI(OH)3 and challenged with an intrapleural (i.pl.) injection of ovalbumin (12 micrograms/cavity) 14 days later. 3. Analysis of the pleural fluid effluent revealed a massive mast cell degranulation and plasma protein extravasation 4 h post-challenge. We confirmed that concurrently with selective pleural fluid eosinophilia caused by platelet-activating factor (PAF), the pleural cavity became hyporesponsive to allergen-induced protein exudation and to the parallel reduction in the number of intact mast cells. 4. These hyporesponsive animals presented a significant augmentation in the pleural effluent level of prostaglandin E2 (PGE2), which increased with increasing numbers of eosinophils in the pleural cavity. Furthermore, pretreatment with either indomethacin or aspirin failed to modify allergen-induced exudation but reversed the exudatory hyporesponsiveness associated with eosinophil recruitment. 5. Allergic exudation was clearly down-regulated by the following pretreatments: (i) PGE2 (10 micrograms/cavity, i.pl.) plus rolipram (40 micrograms/cavity, i.pl.), (ii) misoprostol (200 micrograms kg-1, p.o.) or (iii) dibutyryl cyclic AMP (80 micrograms/cavity, i.pl.). 6. We conclude that prostaglandins may be implicated in the eosinophil-mediated inhibition of allergic pleurisy, probably acting via cyclic AMP signalling pathway activation.
Assuntos
Dinoprostona/farmacologia , Regulação para Baixo/fisiologia , Eosinófilos/metabolismo , Hipersensibilidade/metabolismo , Pleurisia/metabolismo , Animais , Aspirina/farmacologia , Feminino , Indometacina/farmacologia , Masculino , Ratos , Ratos WistarRESUMO
Eosinophils are supposed to play a critical role in the pathology of several allergic diseases because after activation they can release toxic and proinflammatory agents. In this study we have investigated whether IgE-mediated rat pleurisy could be affected by an ongoing pleural eosinophilic inflammatory response. IgE-passively sensitized rats were challenged with an intrapleural (i.pl.) injection of allergen (dinitrophenylated bovine serum albumin, 1 microgram/cavity) and exudation assessed by measuring the amount of protein extravasated into the pleural cavity within 4 h. We have confirmed that lipopolysaccharide (LPS) stimulation (250 ng/cavity i.pl.) was followed by a marked pleural neutrophilia, apparent at 3 h, which was followed by an eosinophil accumulation noted within 48-72 h postchallenge. We have also confirmed that a boiled sample of LPS pleural washing (LPS-PW, 200 microliters i.pl.) caused selective eosinophilia in recipient rats. Pleural exudation remained unaltered when the allergenic challenge was performed 3 h after LPS in a condition of intense pleural fluid neutrophilia. In contrast, this was significantly reduced (P < .001) when the challenge occurred 72 h after LPS or 24 h after LPS-PW in selective pleural fluid eosinophilia. In another series of experiments repeated daily i.pl. injections of platelet-activating factor (PAF; 1 microgram/cavity) resulted in a progressive increase in eosinophil number recovered from the pleural cavity. The values were 1.2 +/- 0.2, 3.0 +/- 0.2, and 5.8 +/- 0.5 x 10(6) eosinophils/cavity (mean +/- SEM) after 0, 1, and 4 injections, respectively. Allergen challenge performed after 0, 1, or 4 PAF stimulations led to pleural protein levels of 88.6 +/- 5.7, 33.7 +/- 0.7, and 19.4 +/- 2.3 mg/cavity, respectively, indicating that the allergic pleurisy is inhibited in a manner dependent on the magnitude of eosinophil accumulation. Furthermore, the impairment of PAF-induced eosinophil accumulation by cetirizine (30 mg/kg i.p.) restored the exudatory response. Exudation triggered by compound 48/80 (25 micrograms/cavity), histamine (200 micrograms/cavity), or 5-hydroxytryptamine (100 micrograms/cavity) was not affected by four previous PAF daily injections. The findings indicate that allergen-induced exudation is selectively down-regulated in the eosinophil-enriched pleural space of rats, a suppression that increased with increasing eosinophil number and disappeared after chemical impairment of the eosinophilia.