Activated protein C ameliorates diabetic nephropathy by epigenetically inhibiting the redox enzyme p66 ^Shc

Abstract

The coagulation protease activated protein C (aPC) confers cytoprotective effects in various in vitro and in vivo disease models, including diabetic nephropathy. The nephroprotective effect may be related to antioxidant effects of aPC. However, the mechanism through which aPC may convey these antioxidant effects and the functional relevance of these properties remain unknown. Here, we show that endogenous and exogenous aPC prevents glomerular accumulation of oxidative stress markers and of the redox-regulating protein p66 Shc in experimental diabetic nephropathy. These effects were predominately observed in podocytes. In vitro, aPC inhibited glucose-induced expression of p66 Shc mRNA and protein in podocytes (via PAR-1 and PAR-3) and various endothelial cell lines, but not in glomerular endothelial cells. Treatment with aPC reversed glucose-induced hypomethylation and hyperacetylation of the p66 Shc promoter in podocytes. The hyperacetylating agent sodium butyrate abolished the suppressive effect of aPC on p66 Shc expression both in vitro and in vivo. Moreover, sodium butyrate abolished the beneficial effects of aPC in experimental diabetic nephropathy. Inhibition of p66 Shc expression and mitochondrial translocation by aPC normalized mitochondrial ROS production and the mitochondrial membrane potential in glucose-treated podocytes. Genetic ablation of p66 Shc compensated for the loss of protein C activation in vivo, normalizing markers of diabetic nephropathy and oxidative stress. These studies identify a unique mechanism underlying the cytoprotective effect of aPC. Activated PC epigenetically controls expression of the redox-regulating protein p66 Shc , thus linking the extracellular protease aPC to mitochondrial function in diabetic nephropathy.

SIRT4 overexpression protects against diabetic nephropathy by inhibiting podocyte apoptosis

“…This is consistent with the findings of Bock et al, who found that glucose impaired the MMP and increased ROS levels (31). However, in the present study, SIRT4 overexpression increased the MMP and reduced ROS levels in podocytes under hyperglycemic conditions, indicating that SIRT4 overexpression inhibits apoptosis by reducing the generation of ROS from mitochondrial sources in podocytes.…”

Activated Protein C Ameliorates Renal Ischemia-Reperfusion Injury by Restricting Y-Box Binding Protein-1 Ubiquitination

“…Several studies demonstrated a role of aPC in modulating mRNA expression by regulating transcription factor activity, mRNA stability, or through epigenetic mechanisms. 7,34,35 Within this study we establish that aPC additionally modulates protein stability via the ubiquitin-proteasome system. We show that aPC maintains the 50 kD form of full length YB-1 protein by decreasing the K48-linked YB-1 ubiquitination through an OTUB1-dependent mechanism.…”

“…5 Unlike thrombin, the anticoagulant serine protease activated protein C (aPC) is nephroprotective, ameliorating chronic 6,7 and acute 8,9 renal injury. The opposing effects of thrombin and aPC are largely controlled by thrombomodulin (TM).…”

Bidirectional Pathologic Effects of Thrombin

“…Low concentrations of thrombin are protective, whereas high concentrations lead to cell death in high-glucose culture. In many disease models, such as diabetic nephropathy, ischemia-reperfusion, and acute tubular injury, aPC signaling via EPCR and PAR1 reportedly restores renal function, protecting glomerular endothelial cells and renal tubular cells [55][56][57].…”