There is increasing evidence that infiltrating neutrophils and monocytes cause both structural and functional derangements in experimental and human glomerulonephritis. The biochemical mechanisms of this injury are unclear. We hypothesize that oxygen radicals, released by either infiltrating or resident glomerular cells, produce glomerular injury. Oxygen radicals can enhance injury by causing direct structural damage to the cells and by releasing mediators of the inflammatory process. Oxidant-induced release of arachidonic acid metabolites is well established and these autacoids have effects on glomerular function. We proposed both in vivo and in vitro studies to assess these potential mechanisms of oxidant-induced glomerular injury. Cultured glomerular mesangial and epithelial cells will be incubated with either an enzymatic source of oxygen radicals or with phorbol-stimulated neutrophils. We will measure synthesis of both cyclo-oxygenase and lipoxygenase products and cyclic nucleotide accumulation in both glomerular cell types. In similar incubations, we will assess cytotoxic potential of oxygen radicals by measurement of chromium-51 and lactate dehydrogenase release by the cultured cells. In in vivo studies, we will infuse intravenously the superoxide anion scavenger, superoxide dismutase, the hydrogen peroxide scavenger, catalase, and the hydroxyl radical scavenger, dimethyl sulfoxide, alone and in combination into rats with nephrotoxic serum nephritis. We will assess the effects of these scavengers on glomerular filtration rate, renal plasma flow, and glomerular morphology. Enhanced synthesis of glomerular arachidonate metabolites has been well demonstrated in this model of glomerulonephritis. However, the mechanisms of the enhanced thromboxane, prostaglandin, and 12-hydroxyeicosatetraenoic acid synthesis are unknown. We will study the effect of the infused scavengers on production of both cyclo-oxygenase and lipoxygenase products by isolated glomeruli. Platelet activating factor is a potent mediator of inflammation that is released by stimulated leukocytes and by renal tissue. Platelet activating factor stimulates a number of proinflammatory processes in neutrophils and macrophages. We will evaluate the capacity of stimulated cultured epithelial and mesangial cells to synthesize platelet activating factor and the effect of platelet activating factor on cyclic nucleotide accumulation, arachidonic acid metabolism and oxygen radical release in cultured glomerular cells.
