LIPOXYGENASE PRODUCTS IN GLOMERULAR IMMUNE INJURY

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The presence of antigen-antibody complexes within the glomerulus is a common initiating mechanism in a wide variety of human glomerulopathies. While the site of formation of these complexes, the route(s) by which they gain access to the glomerulus, their localization, and the nature of the histopathologic reaction they elicit can vary considerably, the central role of the activated leukocyte in initiating and perpetuating pathogenetic events is well-established. A major consequence of PMN/macrophage activation is the release of potent pro-inflammatory oxygenated derivatives of arachidonic acid, in particular prostanoids, thromboxanes, and leukotrienes. Over the past seven years, evidence from our own work and that of other investigators has established enhanced glomerular synthesis, potent glomerular actions, and pathophysiologic relevance for 5- and 15-lipoxygenase (LO) products of arachidonic acid during inflammatory glomerular injury in the rat. More recently, we have obtained evidence that the intraglomerular synthesis of LO products may not be attributed solely to activated leukocytes, but involve the participation of indigenous glomerular cells. This appears to be particularly relevant in the capacity of these cells to effect the transcellular transformation of a key neutrophil/macrophage-derived metabolic intermediate, leukotriene A4, into potent pro-inflammatory eicosanoids. Analysis of the expression of arachidonate LO pathway enzymes in glomerular cells under normal and pathologic conditions is likely to provide significant insight toward understanding their potential roles in glomerular pathophysiology. Utilizing measurements of mRNA in cultured and freshly isolated glomerular cells, in situ hybridization for quantitation of mRNA in fresh tissue sections, and immunocytochemical localization and Western blot analysis of specific enzymes, we will examine the cellular localization and temporal regulation of arachidonate lipoxygenase enzymes gene transcription and translation during the course of glomerular immune injury. We will attempt a correlation of these measurements with end-product synthetic rates and, importantly, with the functional and histomorphologic sequelae of injury. Two representative models of glomerular disease will be studied: anti-glomerular basement membrane antibody-induced glomerulitis, and passive Heymann nephritis. The availability of cDNA clones and specific antibodies for all the major enzymes in these pathways, as well as highly sensitive and accurate analytic techniques for the detection and quantitation of their end-products, provides a unique opportunity to undertake this analysis with a reasonable chance for success.