[Effects of epidermal growth factor receptor on airway inflammation in a rat asthmatic model].

OBJECTIVE: To explore the possible roles of epidermal growth factor receptor (EGFR) in the process of acute and chronic airway inflammation in a rat asthmatic model. METHODS: Forty-five Sprague-Dawley (SD) rats were randomly divided into control groups (subgroups A1, A2, A4), asthmatic groups (subgroups B1, B2, B4) and treatment groups (subgroups C1, C2, C4), with 5 mice in each subgroup. Mice in the asthmatic and treatment groups were exposed to OVA challenge for 1 week, 2 weeks and 4 weeks. Rats in the treatment groups received intraperitoneal injection of a tyrosine kinase inhibitor Genistein (Rongli China) with the dose of 20 mg/kg 1 hour before OVA exposure. Total cell counts and cell differentials in bronchoalveolar lavage fluid (BALF) were performed. A semi-quantified method of airway inflammation score was used to evaluate airway inflammation by hematoxylin-eosin (HE) staining. Expression of EGFR and tyrosine phosphorylation (EGFR activation) in airway epithelium at different times of OVA exposure were evaluated by immunohistochemical and immunofluorescence. All data were expressed as mean +/- SD. One-way ANOVA was used for comparison between 2 groups and post-hoc multiple comparisons of means were performed by using Least Significant Difference. RESULTS: (1) The total cell counts and cell differentials in the BALF of subgroups B1, B2 and B4 were higher than those of subgroups A1, A2 and A4. The total cell counts and eosinophils (EOS) in the BALF of subgroups C1, C2, and C4 [Total cells (48 +/- 6) x 10(5), (51 +/- 9) x 10(5), (57 +/- 12) x 10(5); EOS (2.5 +/- 0.5) x 10(5), (2.7 +/- 0.6) x 10(5), (2.6 +/- 0.5) x 10(5), respectively] decreased significantly as compared to those of subgroups B1, B2 and B4 [Total cells (70 +/- 10) x 10(5), (88 +/- 8) x 10(5), (72 +/- 10) x 10(5); EOS (5.6 +/- 0.8) x 10(5), (6.6 +/- 0.6) x 10(5), (4.3 +/- 0.4) x 10(5)], all P < 0.05. There was no significant difference in the counts of neutrophils and lymphocytes in BALF between the treatment groups and the asthmatic groups. The count of epithelial cells in group C1 [(2.5 +/- 0.5) x 10(5)] was lower than that in group B1[(4.9 +/- 0.7) x 10(5)], q = 4.671, P < 0.05. But that in group C4[(5.7 +/- 1.2) x 10(5)] was higher than that in group B4 [(4.3 +/- 0.4) x 10(5)], q = 4.012, P < 0.05. (2) The airway inflammation score in group C4(3.6 +/- 0.6) was less than that in group B4(5.1 +/- 0.6), q = 4.923, P < 0.05. The scores of group C1 and C2 were less than those of group B1 and B2, but the differences did not reach statistical significance. (3) The expression of EGFR and tyrosine phosphorylation in airway epithelium of the OVA sensitized subgroups were increased statistically as compared to the control subgroups (all P < 0.05). Genistein decreased tyrosine phosphorylation of EGFR in subgroups C1, C2 and C4[(3.12 +/- 0.24), (3.00 +/- 0.28), (2.69 +/- 0.54)] as compared to subgroups B1, B2 and B4[(3.69 +/- 0.43), (3.57 +/- 0.29), (4.46 +/- 0.47), respectively] (all P < 0.05). (4) There were positive correlations between expression and activation of EGFR in airway epithelium and total cell counts, EOS counts, neutrophil and lymphocyte counts in BALF, and airway inflammation scores (all P < 0.05). CONCLUSIONS: EGFR is involved in airway inflammation of asthmatic rats. Tyrosine kinase inhibitor Genistein inhibits acute and chronic airway inflammation in the asthmatic model.