An inhibitor of thrombin activated fibrinolysis inhibitor (TAFI) can reduce extracellular matrix accumulation in an in vitro model of glucose induced ECM expansion

Chronic kidney disease (CKD) is characterised by the pathological accumulation of extracellular matrix (ECM) proteins leading to progressive kidney scarring via glomerular and tubular basement membrane expansion. Increased ECM synthesis and deposition, coupled with reduced ECM breakdown contribute to the elevated ECM level in CKD. Previous pre-clinical studies have demonstrated that increased plasmin activity has a beneficial effect in the protein overload model of CKD. As plasmin activation is downregulated by the action of the Thrombin activated fibrinolytic inhibitor (TAFI), we tested the hypothesis that inhibition of TAFI might increase plasmin activity and reduce ECM accumulation in an in vitro model of glucose induced ECM expansion. Treatment of NRK52E tubular epithelial cells with increasing concentrations of glucose resulted in a 40% increase in TAFI activity, a 38% reduction in plasmin activity and a subsequent increase in ECM accumulation. In this model system, application of the previously reported TAFI inhibitor UK-396082 [(2S)-5-amino-2-[(1-n-propyl-1H-imidazol-4-yl)methyl]pentanoic acid] caused a reduction in TAFI activity, increased plasmin activity and induced a parallel decrease in ECM levels. In contrast, RNAi knockdown of plasmin resulted in an increase in ECM levels. The data presented here indicate that high glucose induces TAFI activity, inhibiting plasmin activation which results in elevated ECM levels in tubular epithelial cells. The results support the hypothesis that UK-396082 is able to reduce TAFI activity, normalising plasmin activity and preventing excess ECM accumulation suggesting that TAFI inhibition may have potential as an anti-scarring strategy in CKD.