Glomerular arachidonate lipoxygenation in rat nephrotoxic serum nephritis.

Abstract

Arachidonate lipoxygenation to monohydroxylated eicosatetraenoic acids (HETE) was studied in rat nephrotoxic serum nephritis (NSN). A single infusion of nephrotoxic serum enhanced conversion of V3Hiarachidonic acid (pH]C20:4) to 13H112-HETE in glomeruli isolated from nephritic rats compared with controls. The percent conversion of IHiarachidonic acid was 1.95±0.2% in control glomeruli and 14.2±2% in nephritic glomeruli 2 d after induction of disease. No significant changes in the conversion of V3H1C20:4 to PHM5-, 8-, and 9-HETE were noted. Extraction of glomerular HETE by alkaline hydrolysis, to evaluate possible reacylation of HETE after their production, confirmed the presence of 12-HETE and did not provide evidence of 5-HETE synthesis. Increased glomerular 12-HETE synthesis in nephritic rats was also demonstrated by high pressure liquid chromatography-UV detection and by 12-HETE radioimmunoassay. The enhanced glomerular 12-HETE synthesis commenced as early as 3-5 h after administration of nephrotoxic serum and peaked at day 2 with 10-fold enhancement of 12-HETE production. Increments of glomerular 12-HETE persisted on day 7 and returned toward control levels by day 14. Platelet depletion, induced by antiplatelet antisera, did not decrease glomerular 12-HETE synthesis in NSN, thereby eliminating platelets as the cellular origin of 12-HETE. Glomerular epithelial and mesangial cells are the most likely sources of enhanced 12-lipoxygenase activity. The enhanced arachidonate 12-lipoxygenation in glomerular immune injury could have important proinflammatory effects in the evolution of glomerulonephritis since 12-HETE has important effects on leukocyte function.

Eicosanoids, Mesangial Contraction, and Intracellular Signal Transduction.

“…Lipooxygenase metabolites of AA also have potent effects on vascular smooth muscle and chemotactic properties on leukocytes (Hammarstrom 1983;Lewis and Austen 1984). Leukotrienes (LT) are abundantly produced by leukocytes and possibly resident cells in certain forms of experimental glomerulonephritis (Lianos et al 1985;Stork et al 1986). Mesangial cells are a potential target for LT, as the glomerulus expresses specific binding sites for LTC4 (Ballermann et al 1985), and contraction of the mesangium may play a role in the renal response to intravenous infusion of LTC4 in the rat (Rosenthal and Pace-Asciak 1983; Badr et al 1984).…”

Synthesis of hydroxyeicosatetraenoic acids and leukotrienes in rat nephrotoxic serum glomerulonephritis. Role of anti-glomerular basement membrane antibody dose, complement, and neutrophiles.

“…Augmented synthesis of 12-HETE, prostaglandins and was observed whether serum thromboxane A2 begins later (3 h) and is maintained (TxB2, a with RPMI was employed. 12-HETE) throughout the period of study of the disease (4,6).…”

“…Arachidonate lipoxygenation has also been demonstrated in isolated rat glomeruli which synthesize primarily 1 2-HETE when stimulated by the phospholipase activator, cationophore A23 187 (3). Enhanced lipoxygenation of exogenous arachidonate was observed in experimental antiglomerular basement membrane (GBM) antibody-induced glomerulonephritis in the rat with increased levels of immunoassayable 12-HETE detected in isolated glomeruli over a 14-d period (4). In these studies proteinuric doses of anti-GBM immune serum were employed and glomerular 1 2-HETE synthesis was found to be independent of glomerular platelet infiltration (4).…”

“…Enhanced lipoxygenation of exogenous arachidonate was observed in experimental antiglomerular basement membrane (GBM) antibody-induced glomerulonephritis in the rat with increased levels of immunoassayable 12-HETE detected in isolated glomeruli over a 14-d period (4). In these studies proteinuric doses of anti-GBM immune serum were employed and glomerular 1 2-HETE synthesis was found to be independent of glomerular platelet infiltration (4). The glomerular pathology in this model ofexperimental glomerulonephritis presents a spectrum of lesions including mild to severe proliferation of endogenous glomerular cells (mesangial, resident macrophages) and injury and exfoliation of endothelial cells (5).…”

Studies on the mechanism of omega-hydroxylation of platelet 12-hydroxyeicosatetraenoic acid (12-HETE) by unstimulated neutrophils.

“…Recently it was demonstrated in animal models that glomerular immune injury is accompanied by increased 12-HETE synthesis (2) and that 12-HETE enhances epidermal cell proliferation (3). Additional autacoid functions of 12-HETE include chemotaxis for human neutrophils in vitro (4) and in vivo (5), chemokinesis for smooth muscle cells (6), and enhancement of mononuclear procoagulant activity (7).…”