Eotaxin and monocyte chemotactic protein-4 mRNA expression in small airways of asthmatic and nonasthmatic individuals

Background: Although an eosinophilic infiltrate has been observed in the sm all airways of asthmatic individuals, the mechanisms responsible for cellul ar recruitment in the lung periphery remain to be clarified, Eotaxin and mo nocyte chemotactic protein (MCP)-4 are 2 eosinophil-associated chemokines s hown to be upregulated at sites of allergic inflammation. However, their ex pression within the small airways of asthmatic individuals remains to be el ucidated, Objective: We sought to determine the expression of eotaxin and,MCP-4 in th e peripheral airways and parenchyma of lungs of subjects vith asthma and to assess their relationship to the numbers of resident eosinophils. Methods: We examined surgically resected lung tissue from 6 asthmatic and 1 0 nonasthmatic subjects for the presence of eotaxin and MCP-4 mRNA. by in s itu hybridization, Chemokine mRNA expression was examined with respect to t he numbers of eosinophils within the airways, as detected by immunocytochem istry for major basic protein. Results: Numbers of chemokine mRNA-positive cells were significantly increa sed in the large and small airways of asthmatic subjects compared with nona sthmatic subjects, Although eotaxin and MCP-4 mRNA were widely expressed in the lungs of subjects with asthma, their expression was particularly evide nt within the bronchial epithelium and inflammatory cells. In the airways o f the asthmatic individuals, the expression of eotaxin mRNA was significant ly correlated to the numbers of eosinophils present. Conclusion: There is an increased expression of eotaxin and MCP-4 mRNA with in the peripheral airways of lungs of asthmatic subjects, suggesting that t hese chemokines contribute to the small airways and peripheral lung inflamm ation in asthma.