Inflammatory bowel disease is marked by mucosal infiltration with large numbers of neutrophils and by high levels of the lipoxygenase products leukotriene B4, 5-HETE, 12-HETE and 15-HETE. The goal of this project is to define the role of neutrophils and their lipoxygenase products in intestinal inflammation particularly as relates to inflammatory bowel disease.
The specific aims are: 1. We plan to manipulate the trinitrobenzylsulfonic (TNBS) acid model of chronic colitis in the rat with drugs and diets that alter the synthesis of cyclooxygenase and lipoxygenase products. Changes in the synthesis of lipoxygenase and cyclooxygenase products will be correlated with changes in histology. The role of lipoxygeanse products in inflammation will be defined by correlating changes in eicosanoid synthesis with changes on histology. 2. We will define the mechanism of neutrophil-induced killing of a human intestinal epithelial cell line, Caco2. The role of proteases and products of the respiratory burst in neutrophil killing of epithelial cells will be examined. The contribution of activated neutrophils to epithelial cell damage in intestinal inflammation will be assessed by treating the TNBS model of colitis with superoxide dismutase, catalase, and protease inhibitors. 3. We will define the effects of inflammatory mediators, particularly the lipoxygenase products, on intestinal epithelial cell lipid composition, membrane fluidity, and enzyme activities. Lipoxygenase products including 5-HETE, 12-HETE, and 15-HETE are present in inflammatory bowel disease mucosa. The HETEs are incorporated into membrane phospholipids in intestinal epithelial cells where they affect membrane biophysical properties and enzyme activities. The effects of the HETEs on membrane lipid composition, membrane fluidity, and enzyme activities will be assayed in CaCo2 cells, in inflammatory bowel disease, and in the TNBS model. This proposal is clinically relevant in that increasing our understanding of the role of neutrophils and their lipoxygenase products in intestinal inflammation should increase our understanding of the pathogenesis of inflammatory bowel disease and give insights into possible approaches for pharmacologic intervention by modulating the production of soluble mediators of inflammation.
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