Stimulation of PAI-1 in rabbit anti-GBM glomerulonephritis.

Abstract

It has previously been shown in human disease and animal models of glomerulonephritis (GN) that fibrin deposition is associated with a net reduction of glomerular fibrinolytic activity as a result of reduced expression of plasminogen activators and increased expression of plasminogen activator inhibitor type 1 (PAI-1). Conditioned media (CM) prepared from cultured glomeruli of normal rabbits and rabbits 24 (Day 1) and 96 (Day 4) h after induction of anti-GBM GN were compared for their effects on the synthesis of fibrinolytic molecules in human endothelial cells (EC). Only CM from Day 4 GN rabbits showed PAI-1 protein stimulatory activity of up to 148% (P<0.05; n = 3) above that of untreated EC. This was also seen at the mRNA level. Glomerulonephritis Day 4 CM showed significantly higher amounts of turnout necrosis factor (TNF) and thrombin and transforming growth factor-beta (TGF-beta) bioactivity in comparison to glomerular CM from normal rabbits. After high performance liquid chromatography (HPLC) of Day 4 GN CM, PAI-1 stimulatory activity was found to correlate with the presence of interleukin 1 (IL-1), TNF and TGF-beta. These results suggest a correlation between severity of anti-GBM GN in a rabbit model, increased PAI-1 synthesis and increased expression of TNF and TGF-beta. This may potentiate glomerular fibrin and extracellular matrix deposition in anti-GBM GN, leading to glomerular crescent formation and eventual renal failure.