DUAL INHIBITION OF CLASSICAL PKC-ALPHA AND PKC-BETA-ISOFORMS IN A PHARMACOLOGICAL AND DOUBLE KNOCK-OUT MOUSE APPROACH LEADS TO PROTECTION AGAINST DIABETIC NEPHROPATHY: 5A.04

Abstract

Both classical PKC isoforms, PKC-α and -β, have been implicated in the pathogenesis of diabetic microvascular diseases. We previously elucidated the specific role of these individual isoforms and revealed that activation of the PKC-β-isoform contributes to high-glucose-induced renal fibrosis whereas perlecan as well as nephrin and VEGF expression are regulated by a PKC-α-isoform-dependent signaling pathway leading to diabetic albuminuria. We now tested the hypothesis if deletion of both classical PKC isoforms is able to completely abolish the development of diabetic nephropathy in the streptozotocin-induced diabetic mouse model. We therefore studied distinct pharmacological approaches while inhibiting both classical PKC isoforms and validated the phenotype of nondiabetic and streptozotocin-induced diabetic homozygeous PKC-α/β double knock-out mice (PKC-α/β-/-) compared to appropriate 129/SV wild type mice. After 8 weeks of diabetes mellitus the high-glucose-induced renal and glomerular hypertrophy as well as the increased expression of extracellular matrix proteins such as collagen and fibronectin was abolished in the PKC-α/β-/- mice compared to WT controls. Furthermore, the high-glucose-induced expression of the profibrotic cytokine TGF-â1 was significantly diminished in the PKC-α/β-/- mice in comparison to diabetic WT mice. The loss of the basal membrane proteoglycan perlecan and the podocyte protein nephrin is prevented in the diabetic state in the PKC-α/β-/- mice. Furthermore, we were able to demonstrate, that a PKC-α/β inhibitor had a similar effect. In summary, blockade of the two prominent PKC isoforms α and β are able to prevent early diabetic nephropathy while inhibiting prosclerotic glomerular and tubulo-interstitial changes as well as the development of albuminuria. These results demonstrate that downregulation of the dual PKC-isoform activation in the diabetic state in vivo is a suitable therapeutic target in the prevention of diabetic microvascular complications such as diabetic nephropathy.