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Inflammatory mechanisms underlying the rat pulmonary neutrophil influx induced by airway exposure to staphylococcal enterotoxin type A
Author(s) -
Desouza Ivani A,
FrancoPenteado Carla F,
Camargo Enilton A,
Lima Carmen S P,
Teixeira Simone A,
Muscará Marcelo N,
De Nucci Gilberto,
Antunes Edson
Publication year - 2005
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0706393
Subject(s) - lung , pathogenesis , dexamethasone , chemotaxis , inflammation , incubation , immunology , chemistry , medicine , endocrinology , receptor , biochemistry
Association between staphylococcal infection and pathogenesis of upper airways disease has been reported. This study aimed to investigate the mechanisms underlying the rat pulmonary inflammation induced by airway exposure to staphylococcal enterotoxin A (SEA). SEA (0.3–10 ng trachea −1 ) caused dose‐dependent neutrophil accumulation in BAL fluid, reaching maximal responses at 4 h (25‐fold increase for 3 ng trachea −1 ). Significant accumulation of both lymphocytes and macrophages in BAL fluid was also observed at 4 h (2.1‐ and 1.9‐fold increase, respectively, for 3 ng trachea −1 ). At later times (16 h), neutrophil counts in bone marrow (immature forms) and peripheral blood increased by 63 and 81%, respectively. SEA failed to directly induce chemotaxis and adhesion of isolated neutrophils. Analysis of mRNA expression for iNOS, COX‐2 and CINC‐2 in lung tissue showed an upregulation of these enzymes, which paralleled elevated levels of LTB 4 , PGE 2 , TNF‐ α , IL‐6 and NO 2 − in BAL fluid. Expression of CINC‐1 was unchanged, whereas CINC‐3 was reduced in SEA‐treated rats. Incubation of isolated alveolar macrophages with SEA (3 μ g ml −1 ) resulted in significant elevations of TNF‐ α and NO 2 − levels in the cell supernatants. Dexamethasone (0.5 mg kg −1 ), celecoxib (3 mg kg −1 ) and compound 1400 W (5 mg kg −1 ) markedly reduced SEA‐induced lung neutrophil influx and NO 2 − levels in BAL fluid. The lipoxygenase inhibitor AA‐861 (100 μ g kg −1 ) partly inhibited the neutrophil influx in SEA‐treated rats without modifying the NO 2 − levels. None of these treatments reduced the number of mononuclear cells in BAL fluid (except of dexamethasone, which abolished the increased lymphocyte counts). Our study shows that airways exposure to SEA results in marked neutrophil influx through mechanisms involving increased expressions of CINC‐2, iNOS and COX‐2, as well as enhanced production of NO, PGE 2 , LTB 4 , TNF‐ α and IL‐6.British Journal of Pharmacology (2005) 146 , 781–791. doi: 10.1038/sj.bjp.0706393