Proteinase 3 drives murine diabetic kidney disease by mediating caspase-3-dependent apoptosis of podocytes

INTRODUCTION: Podocytes play a pivotal role in maintaining homeostasis of the glomerular filtration barrier. Podocyte loss represents a critical event that contributes to the development of diabetic kidney disease (DKD). Nonetheless the key mediators and mechanisms underlying DKD-associated podocyte death remain poorly characterized. Proteinase 3 (PR3) is a serine protease with selective high abundance in myeloid cells and pleiotropic effects on the regulation of innate immunity. METHODS: An experimental DKD model was induced by a combination strategy of uninephrectomy, intraperitoneal injection of streptozocin, and feeding of a high-fat diet in global or podocyte-specific PR3 knockout mice and their controls. Mouse primary podocytes lacking PR3 or conditionally immortalized murine podocytes overexpressing PR3 were incubated with high glucose to trigger apoptosis. Adeno-associated viruses expressing the serine protease inhibitor elafin were injected locally into mouse kidney to inhibit kidney PR3. RESULTS: PR3 abundance in the kidney was markedly increased, predominantly in podocytes, in mouse models of DKD. Global or podocyte-specific genetic ablation of PR3 significantly attenuated severe proteinuria, mesangial matrix expansion, and podocyte injury in diabetic mice. Mechanistically, the lysates from mouse primary podocytes with high glucose-elicited PR3 enrichment and enhanced enzymatic activity induced cleavage of procaspase-3 and triggered podocyte apoptosis that was substantially alleviated in the presence of genetic ablation or pharmacological inhibition of PR3. Adenovirus-mediated overexpression of PR3 markedly potentiated caspase-3 cleavage and cell apoptosis in conditionally immortalized murine podocytes. In contrast, a lack of PR3 protected against adriamycin-induced podocytopathy in mice, further confirming PR3 as a driving force of podocyte injury. Therapeutically, kidney overexpression of elafin significantly attenuated podocyte loss and other DKD-like traits in mice. CONCLUSIONS: Our results demonstrate that podocyte-derived PR3 induces caspase-3 cleavage to mediate podocyte apoptosis, thereby potentiating DKD progression, suggesting that pharmacological intervention of podocyte-derived PR3 may represent a promising therapeutic strategy for DKD.