Thrombin-Induced Podocyte Injury Is Protease-Activated Receptor Dependent

Abstract

Nephrotic syndrome is characterized by massive proteinuria and injury of specialized glomerular epithelial cells called podocytes. Studies have shown that, whereas low-concentration thrombin may be cytoprotective, higher thrombin concentrations may contribute to podocyte injury. We and others have demonstrated that plasma thrombin generation is enhanced during nephrosis, suggesting that thrombin may contribute to nephrotic progression. Moreover, nonspecific thrombin inhibition has been shown to decrease proteinuria in nephrotic animal models. We thus hypothesized that thrombin contributes to podocyte injury in a protease-activated receptor-specific manner during nephrosis. Here, we show that specific inhibition of thrombin with hirudin reduced proteinuria in two rat nephrosis models, and thrombin colocalized with a podocyte-specific marker in rat glomeruli. Furthermore, flow cytometry immunophenotyping revealed that rat podocytes express the protease-activated receptor family of coagulation receptors High-concentration thrombin directly injured conditionally immortalized human and rat podocytes. Using receptor-blocking antibodies and activation peptides, we determined that thrombin-mediated injury depended upon interactions between protease-activated receptor 3 and protease-activated receptor 4 in human podocytes, and between protease-activated receptor 1 and protease-activated receptor 4 in rat podocytes. Proximity ligation and coimmunoprecipitation assays confirmed thrombin-dependent interactions between human protease-activated receptor 3 and protease-activated receptor 4, and between rat protease-activated receptor 1 and protease-activated receptor 4 in cultured podocytes. Collectively, these data implicate thrombinuria as a contributor to podocyte injury during nephrosis, and suggest that thrombin and/or podocyte-expressed thrombin receptors may be novel therapeutic targets for nephrotic syndrome.

Single cell transcriptomics identifies focal segmental glomerulosclerosis remission endothelial biomarker

“…Thus, inhibition of aPC by A2M may block the protective role of aPC. In addition, repression of aPC is known to enhance thrombin generation (41), and Kerlin and colleagues recently have shown that thrombin injures podocytes (42). A2M-mediated inhibition of aPC-mediated podocyte protection may simultaneously enhance thrombin-mediated podocyte injury.…”

Pharmacological PAR‐1 inhibition reduces blood glucose levels but does not improve kidney function in experimental type 2 diabetic nephropathy

“…Both control-and vorapaxar-treated BTBR ob/ob mice showed significant podocyte loss compared with nondiabetic BTBR WT mice, suggesting that vorapaxar treatment does not affect podocyte apoptosis or survival in this particular model. This is interesting, as thrombin is known to affect podocyte apoptosis (11).…”

“…As podocyte loss is an important hallmark of albuminuria, and PAR-1 has previously been described to facilitate both cytoprotective and disruptive signaling in podocytes (10)(11)(12), we next assessed the number of podocytes by WT1 immunostaining. As expected, podocyte numbers were significantly reduced in BTBR ob/ob mice as compared with BTBR WT mice, but vorapaxar treatment did not affect podocyte loss (Fig.…”

Nephrin as a biomarker of sickle cell glomerulopathy in Malawi

“…33 It is suggested that thrombin may contribute to progression of proteinuria in animal models of nephrotic syndrome. 34 The role of coagulation activation in SCD pathophysiology is highlighted by a recent study which showed that genetic reduction in prothrombin levels in sickle mice not only resulted in decreased levels of thrombin-antithrombin complexes and D-dimer, but also produced significant reductions in renal complications, including albuminuria, compared with wild type sickle mice. 35 In light of these previous reports, the negative association between D-dimer and both NCR and UACR was surprising and unexpected.…”