Effects of Prothrombin on Podocytopathy and Proteinuria in Glomerular Disease.

Background: Chronic kidney disease (CKD) is a leading cause of death, its progression is driven by glomerular podocyte injury and loss, manifesting as proteinuria. Proteinuria includes loss of coagulation zymogens, cofactors, and inhibitors resulting in a hypercoagulable state characterized by enhanced thrombin generation. Both CKD and proteinuria significantly increase the risk of thromboembolic disease. Meanwhile, anticoagulant medications (which antagonize thrombin and thereby prevent thromboembolism) have been shown to reduce proteinuria in rats and thrombin has been shown to injure cultured human and rat podocytes. We thus aimed to directly determine the influence of circulating prothrombin, the zymogen precursor of thrombin, on glomerular pathobiology. We hypothesized that (pro)thrombin drives podocytopathy, podocytopenia, and proteinuria.

Methods: Glomerular proteinuria was induced with puromycin aminonucleoside in rats. Prothrombin was either knocked down using an antisense oligonucleotide targeting prothrombin mRNA or elevated by serial intravenous prothrombin protein infusions, previously established methods to model hypo- and hyper-prothrombinemia, respectively. After 10 days plasma prothrombin levels were determined, kidneys were examined for (pro)thrombin co-localization to podocytes, histology, and electron microscopy. Podocytopathy, podocytopenia, proteinuria, and plasma albumin were measured.

Results: Antisense oligonucleotide-mediated prothrombin knockdown significantly reduced prothrombin colocalization to podocytes, tubular injury, podocyte foot process effacement, podocytopathy, and proteinuria along with improved plasma albumin in the puromycin aminonucleoside glomerular disease model. In contrast, elevated prothrombin levels significantly increased podocytopathy and proteinuria. Podocytopenia was significantly improved in hypo-prothrombinemic vs. hyper-prothrombinemic rats.

Conclusions: Thrombin generation is enhanced by glomerular proteinuria and thrombin injures conditionally immortalized podocytes in vitro. In the present study, prothrombin knockdown ameliorated in vivo podocyte injury and improved podocyte function in the rat puromycin aminonucleoside-induced glomerular disease model whereas hyper-prothrombinemia exacerbated podocyte injury and diminished podocyte function.