A central pathophysiologic characteristic of asthma is the recruitment of eosinophils into the lungs, followed by their activation and release of proinflammatory mediators. An improved understanding of the mechanism involved in this response is therefore of great relevance to asthma pathogenesis and the development of new therapeutics. The objective of this proposal is to further elucidate the molecular mechanism for preferential recruitment and activation of eosinophils and basophils in asthma. Exciting new information implicates cytokines, C-C chemokines, and adhesion molecules in these processes. We will test the hypothesis that cytokines that activate eosinophils and basophils (such as IL-3, IL-5 and GM-CSF) and those that induce their migration and accumulation (such as C-C chemokines) alter the expression and/or function of integrin adhesion molecules. In particular, preliminary results suggest that these chemokines alter integrin function in a reciprocal manner, upregulating beta2 integrin function while downregulating beta1 integrin function. We will use well-established assays of cell activation, adhesion, chemotaxis and transendothelial migration to examine the regulation of integrin-dependent responses by chemokines and cytokines. Emphasis will be placed on three newly identified eosinophil- and bsophil-activie C-C chemokines (monocyte chemotactic protein-4 (MCP-4). Ckbeta6, and monocyte-derived chemokine (MDC), ad one novel member of the beta2 integrin family. Alpha d beta2 integrin. Activation epitope- specific mAb will be used to monitor expression of activated beta1 and beta2 integrins, and pharmacologic agents will be used to define the intracellular mechanisms controlling integrin function. Based on preliminary data suggesting that eosinophils and basophils express alpha d beta2 integrin, we will delineate stimuli, that alter intracelluar and cell surfact levels of beta2 integrins, including alpha d beta2. Since preliminary results also suggest selective modulation of alpha d beta2 and Mac-1, we will determine the location of intracellular pools of alpha d and CD11b using immunoelectron microscopy. Additional experiments will characterize the functional ligand(s) for alpha d beta2 on these cells . Finally, in vivo studies will use endobronchial allergen challenge to determine whether integrin function is altered in eosinophils and basophils recruited into the airways during experimental allergic inflammatory responses in the lun. This approach will also be used to test the hypothesis that the above- mentioned novel chemokines are generated in the airways after allergen challenge. Levels of MCP-4, MDC and CK beta6 mRNA and protein will be measured in airway samples and the cellular sources fo the chemokines will be determined. Additional experiments will analyze the airways of normals, allergic rhinitics and allergic asthmatics of varying degrees of asthma severity for the presence of chemokine protein and mRNA in airways brushings and biopsies. It is anticipated that the proposed studies will lead to an improved understanding of the pathogenesis of asthma. We believe that the combined use of both in vitro and in vivo models uniquely positions us to assess the relevance of cellular and molecular processes to human allergic diseases.
