[Effects of dexamethasone on apoptosis of airway inflammatory cells in asthmatic guinea-pigs].

OBJECTIVE: Clearance of airway inflammatory cells is the key point of therapeutic effect in asthma. Apoptosis, a form of cell death, is thought to be critically important to promote the clearance of inflammatory cells and the resolution of inflammation. To investigate the effects of dexamethasone on apoptosis of airway inflammatory cells in asthma showed be very important. METHOD: Dexamethasone was used for the treatment of asthma model of guinea pigs set up by inhaling ovalbumin. Apoptotic cells were labelled with TdT-mediated dUTP nick end labeling(TUNEL) technique on formalin-fixed paraffin-embedded trachea and lung tissue sections. By way of immunohistochemistry, eosinophils were stained with EG2 antibody and T lymphocytes with CD3+, CD4+ and CD8+ antibodies on sections. RESULT: (1) The quantity of airway eosinophils and lymphocytes decreased in dexamethasone group, which could not be observed in the control one (P < 0.01). (2) Apoptotic index of lymphocytes was significantly elevated following dexamethasone treatment(P < 0.05). But no difference was found in the proportion of apoptotic eosinophils between these two groups. (3) The percentage of EG2 positive eosinophils and CD4+ positive lymphocytes decreased significantly following dexamethasone treatment. On the contrary, the number of CD8+ lymphocytes increased in dexamethasone group when compared with the control one (P < 0.05). CONCLUSION: (1) The quantity of airway eosinophils decreases following dexamethasone treatment in guinea-pigs asthma, and its mechanism may not be ascribed mainly to the apoptosis of eosinophils. (2) The number of lymphocytes, mainly CD4+, decreased following dexamethasone treatment in guinea-pig airways, and apoptosis may represent the mechanism that promotes the clearance of lymphocytes in asthma.