Systemic and local dexamethasone treatments prevent allergic eosinophilia in rats via distinct mechanisms

• Published in: European journal of pharmacology Vol. 368; no. 1; pp. 67 - 74
• Main Authors: Pasquale, Claudia P, Lima, Marcia C.R, Bandeira-Melo, Christianne, Cordeiro, Renato S.B, e Silva, Patrı́cia M.R, Martins, Marco A
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 26-02-1999; Elsevier
• Subjects: Allergens - adverse effects; Allergic pleurisy; Animals; Anti-Inflammatory Agents - pharmacology; Anti-Inflammatory Agents - therapeutic use; Biological and medical sciences; Blood eosinophilia; Bone Marrow Cells - cytology; Bone Marrow Cells - drug effects; Bones, joints and connective tissue. Antiinflammatory agents; Capillary Permeability - drug effects; Cell Degranulation - drug effects; Dexamethasone; Dexamethasone - pharmacology; Dexamethasone - therapeutic use; Eosinophil; Eosinophilia - chemically induced; Eosinophilia - prevention & control; Eosinophils - cytology; Eosinophils - drug effects; Female; Leukocyte Count - drug effects; Leukocytes, Mononuclear - drug effects; Leukocytes, Mononuclear - physiology; Male; Mast Cells - drug effects; Mast Cells - physiology; Medical sciences; Neutrophils - drug effects; Neutrophils - physiology; Ovalbumin - adverse effects; Pharmacology. Drug treatments; Pleurisy - chemically induced; Pleurisy - prevention & control; Rats; Rats, Wistar; Allergic pleurisy; Dexamethasone; Blood eosinophilia; Eosinophil; Immunopathology; Allergy; Corticosteroid; Intraperitoneal administration; Rat; Respiratory disease; Rodentia; Antiinflammatory agent; Intrapleural administration; Prevention; Vertebrata; Chemotherapy; Mammalia; Treatment; Animal; Pleurisy; Pleural disease; Mechanism of action
• ISSN: 0014-2999; 1879-0712
• DOI: 10.1016/S0014-2999(99)00010-2

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 μg/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.