OBJECTIVETo study the effect of dexamethasone on airway morphology and on the expression of angiopoietin-1 (Ang-1) and its tyrosine kinase receptor Tie-2 in the airway of asthmatic rats.

METHODSForty-five Sprague-Dawley rats were randomly divided into control, asthmatic, and dexamethasone-treated asthmatic groups. Asthma was induced by repeated sensitization and challenge with ovalbumin in the latter two groups. The dexamethasone intervention group received an intraperitonea injection of dexamethasone (2 mg/kg) before asthma challenge. Immunohistochemistry was used to measure the expression of Ang-1 and Tie-2 in the airway. Airway thickness was estimated by a computerized digital image analyzer.

RESULTSAirway thickness in the asthmatic group (33.9333+/-8.3791 micro m2/micro m) increased significantly compared with that in the control group (21.1333+/-2.7740 micro m2/micro m) (P<0.01). The dexamethasone intervention group also showed increased thickness of the airway (27.4000 +/- 4.6105 micro m2/micro m) compared with the control group (P<0.01), but the airway thickness in the dexamethasone intervention group was significantly reduced compared with that in the untreated asthmatic group (P<0.01). The expression of Ang-1 (103.9487+/-8.2914 vs 76.0320+/-3.7728; P<0.01) and Tie-2 (99.2307+/-8.1913 vs 75.3153+/-3.7321; P<0.01) in the airway increased significantly in the asthmatic group compared to controls. The expression of Ang-1 and Tie-2 in the airway of the dexamethasone intervention group (90.6180+/-5.2339 and 86.6633+/-3.7321, respectively) was statistically higher than that in the control group (P<0.01) but statistically lower than that in the untreated asthmatic group (P<0.01). Ang-1 and Tie-2 expression in the airway was positively correlated with the thickness of airway (r(Ang)-1=0.719r(Tie)-2=0.746P<0.01). There was also a positive correlation between Ang-1 and Tie-2 expression (r=0.742P<0.01).

CONCLUSIONSThe expression of Ang-1 and Tie-2 in the airway increased in asthmatic rats and was positively correlated with the thickness of the airway. Ang-1 and Tie-2 may participate in the process of airway remodeling in asthma. Dexamethasone can decrease the expression of Ang-1 and Tie-2 in the airway and relieve the changes of airway morphology.