Mechanisms of glomerular injury: overview and relation with hemostasis.
The mechanisms of glomerular injury can be separated into nonimmunologically mediated glomerulonephritis (GN) such as diabetes, leading to glomerular hypertension and into immunologically mediated GN. The immunologically mediated GN may induce chronic glomerulopathy such as membranous GN or proliferative GN. The final pathway of these two types of GN is proteinuria and renal failure linked to glomerulosclerosis. In inflammatory GN, most of the mediators could be synthesized either by infiltrating cells or by resident glomerular cells. They include cytokines, lymphokines, complement activation, generation of superoxyde anions, arachidonic acid metabolites, and fibrin deposition. (a) We have investigated the interaction between isolated glomeruli and platelets and have demonstrated that lipidic and proteic extracts of glomeruli enhance thromboxane B2 platelet synthesis. This fact is related to the generation by isolated glomeruli of saturated fatty acids and tissue factor. (b) We investigated the interaction between rat isolated glomeruli and peritoneal macrophages. We have demonstrated that 12-HETE synthesized by isolated glomeruli induce macrophage prostaglandin synthesis which, in turn, inhibits the 12-HETE synthesis. (c) We have demonstrated, using human glomerular epithelial cells, that alpha-thrombin, the active form of thrombin, generated before fibrin formation, is able to induce cell proliferation and abolishes the profibrinolytic activity of these cells. In summary, the mechanisms of glomerular injury are complex, certainly acting by multiple pathways. So far, the mediators leading to proteinuria and renal failure after glomerular injury remain under investigation.