leukotriene-c4 and Pleurisy

In addition to the well-recognized ability of prostaglandin D2 (PGD2) to regulate eosinophil trafficking, we asked whether PGD2 was also able to activate eosinophils and control their leukotriene C4 (LTC4)-synthesizing machinery. PGD2 administration to presensitized mice enhanced in vivo LTC4 production and formation of eosinophil lipid bodies-potential LTC4-synthesizing organelles. Immunolocalization of newly formed LTC4 demonstrated that eosinophil lipid bodies were the sites of LTC4 synthesis during PGD2-induced eosinophilic inflammation. Pretreatment with HQL-79, an inhibitor of PGD synthase, abolished LTC4 synthesis and eosinophil lipid body formation triggered by allergic challenge. Although PGD2 was able to directly activate eosinophils in vitro, in vivo PGD2-induced lipid body-driven LTC4 synthesis within eosinophils was dependent on the synergistic activity of endogenous eotaxin acting via CCR3. Our findings, that PGD2 activated eosinophils and enhanced LTC4 synthesis in vivo in addition to the established PGD2 roles in eosinophil recruitment, heighten the interest in PGD2 as a target for antiallergic therapies.

Topics: Adjuvants, Immunologic; Animals; Cells, Cultured; Chemokine CCL11; Chemokines, CC; Eosinophils; Female; Humans; Inflammation Mediators; Leukotriene C4; Lipids; Male; Mice; Pleurisy; Prostaglandin D2; Respiratory Hypersensitivity

Eosinophils are an important source of leukotriene (LT)C(4), which can be synthesized within lipid bodies-cytoplasmic organelles where eicosanoid formation may take place. Allergy-driven lipid body formation and function have never been investigated. Here, we studied the in vivo induction and role of lipid bodies within eosinophils recruited to sites of allergic inflammation. Using two murine models of allergic inflammation (asthma and pleurisy), we verified that parallel to the eosinophil influx, allergic challenge also induced lipid body formation within recruited eosinophils. Neutralizing antibodies to eotaxin/CCL11, RANTES/CCL5, or CCR3 partially inhibited lipid body formation within recruited eosinophils in the allergic pleurisy model. Likewise, intrapleural administration of RANTES or eotaxin also induced significant influx of eosinophils loaded with lipid bodies. By immunolabeling, we detected the presence of a key enzyme involved in the leukotriene metabolism-5-lipoxygenase-within eosinophil lipid bodies formed in vivo after allergen challenge. Furthermore, specific immunolocalization of newly formed LTC(4) demonstrated that lipid bodies were the sites of formation of this eicosanoid within infiltrating eosinophils. Therefore, allergic inflammation triggers in vivo formation of new lipid bodies within infiltrating eosinophils, a phenomenon largely mediated by eotaxin/RANTES acting via CCR3 receptors. Such in vivo allergen-driven lipid bodies function as intracellular compartments of LTC(4) synthesis.

Topics: Animals; Arachidonate 5-Lipoxygenase; Cell Compartmentation; Chemokine CCL11; Chemokine CCL5; Chemokines, CC; Chemotaxis, Leukocyte; Eosinophils; Female; Leukotriene C4; Lipid Metabolism; Lipids; Male; Mice; Mice, Inbred C57BL; Pleurisy; Respiratory Hypersensitivity; Signal Transduction

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.

Topics: Administration, Oral; Angiostrongylus; Animals; Anti-Inflammatory Agents, Non-Steroidal; Antigens, Helminth; Corticosterone; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Cyclooxygenase Inhibitors; Dinoprostone; Edema; Eosinophilia; Exudates and Transudates; Female; Hydroxyeicosatetraenoic Acids; Hypersensitivity; Injections, Intraperitoneal; Injections, Intravenous; Interleukin-5; Isoenzymes; Kinetics; Leukotriene C4; Lipoxins; Male; Misoprostol; Pleural Effusion; Pleurisy; Prostaglandin-Endoperoxide Synthases; Rats; Rats, Wistar; Strongylida Infections

The effect of fat-rich diets on the acute inflammatory response was examined. Male Wistar rats aged 21 days were fed, for 6 weeks, with a control diet (4% fat content), or a control diet supplemented with coconut or soybean oils (15% fat content). Carrageenan-induced paw oedema and pleurisy were evaluated. Prostaglandin (PG) E2 and leukotriene (LT) C4/D4 concentrations were determined in the pleural exudate (ELISA). Pleural samples were tested for their effect on cutaneous vascular permeability of control rats and the effect of a LTD4 receptor antagonist (L660-711; 10 mg/kg; i.v.) examined. Relative to controls, rats fed both fat-rich diets presented a significant reduction in protein leakage and oedema formation without affecting the number of migrating leukocytes. Production of LTC4/D4 in pleural exudate was significantly increased from 1.8 +/- 0.2 ng/ml in controls to 2.8 +/- 0.2 and 3.0 +/- 0.3 ng/ml in animals fed coconut and soybean oil enriched diets, respectively, without changes in PGE2 production. The activity of these samples on cutaneous vascular permeability was 50% reduced, returning to control values after treatment of testing animals with a LTD4 receptor antagonist. Rats fed fat-rich diets presented a reduced inflammatory response due, at least in part, to the LTC4/D4 mediated vasoconstrictor effect.

Topics: Acute-Phase Reaction; Animals; Capillary Permeability; Carrageenan; Coconut Oil; Dietary Fats; Dinoprostone; Edema; Enzyme-Linked Immunosorbent Assay; Exudates and Transudates; Hindlimb; Leukotriene Antagonists; Leukotriene C4; Leukotriene D4; Male; Plant Oils; Pleural Effusion; Pleurisy; Propionates; Quinolines; Rats; Rats, Wistar; Skin; Soybean Oil