EOSINOPHIL, EICOSANOID, BIOSYNTHESIS AND METABOLISM

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DESCRIPTION (Copied from Applicant Abstract): The pathogenesis of airways reactivity in asthma is thought to involve a complex interaction between multiple cells stimulated by a variety of mediators from cytokines to lipids derived from arachidonic acid called eicosanoids. The infiltration of eosinophils into the asthmatic lung has been thought to play a central role in allergic asthma and these cells have a diverse capacity for eicosanoid biosynthesis as well as being cells which respond to eicosanoids. The metabolism of arachidonic acid by the 5-lipoxygenase (5-LO) pathway leads to the formation of several different biologically active metabolites which include leukotrienes C4 and B4 which have been widely studied in terms of their role as mediating allergic reactions. In addition, 5-LO is thought to be involved in the formation of 5-oxo-eicosatetraenoic acid (5-oxo-ETE) which has been recently recognized as chemotactic factor for the human eosinophil and human neutrophil. Fundamental questions remain concerning the biosynthesis and metabolism of the 5-oxo-eicosanoids, in particular its synthesis by the eosinophil and macrophage. The results of preliminary investigations have identified for the first time the formation of 5-oxo-ETE in the lung through its appearance in bronchoalveolar lavage fluid of mice. Furthermore, studies of the metabolism of 5-oxo-ETE in the peritoneal macrophage has revealed the formation of an abundant metabolite which has also been found to be a potent chemotactic factor for the human eosinophil and neutrophil. This metaboilte is a unique glutathione product of 5-oxo-ETE and may likely itself be an important biologically active eicosanoid. Little is known about the formation of 5-oxo-ETE within cells or its metabolism. Since the eosinophil is abundant in the asthmatic airways, a major focus of this proposal will involve detail investigations of the biochemical pathways involved which can lead to the recruitment of eosinophils into the lung and the formation of critical lipid mediators relevant to the asthmatic airways. Highly sensitive mass spectrometric techniques will be employed to carry out these basic biochemical and pharmacological studies.