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 LTB4, PGE2, TNF‐α, IL‐6 and NO2− 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 μg ml−1) resulted in significant elevations of TNF‐α and NO2− 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 NO2− levels in BAL fluid. The lipoxygenase inhibitor AA‐861 (100 μg kg−1) partly inhibited the neutrophil influx in SEA‐treated rats without modifying the NO2− 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, PGE2, LTB4, TNF‐α and IL‐6.
British Journal of Pharmacology (2005) 146, 781–791. doi:
This study was undertaken to clarify the mechanisms by which C-fiber degeneration at neonatal stages exacerbates the inflammatory responses of rat airways. Rats were treated with capsaicin at neonatal stages and immunized with ovalbumin (OVA) at adult ages. Challenge of capsaicin-pretreated rats with OVA promoted a higher influx of neutrophils in bronchoalveolar lavage (BAL) fluid compared with the vehicle group. No significant differences were found for the other cell types. The increased adhesion of N-formyl-methionyl-leucyl-phenylalanine (fMLP; 0.1 M)-and phorbol myristate acetate (PMA; 1 M)-treated neutrophils to fibronectin-coated wells did not differ among vehicle-and capsaicin-pretreated rats. Additionally, fMLP (10 M), platelet-activating factor (0
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