Protein Kinase C-δ Mediates Kidney Tubular Injury in Cold Storage-Associated Kidney Transplantation.

BACKGROUND: Kidney injury associated with cold storage is a determinant of delayed graft function and the long-term outcome of transplanted kidneys, but the underlying mechanism remains elusive. We previously reported a role of protein kinase C-delta (PKCdelta) in renal tubular injury during cisplatin nephrotoxicity and albumin-associated kidney injury, but whether PKCdelta is involved in ischemic or transplantation-associated kidney injury is unknown. METHODS: To investigate PKCdelta's potential role in injury during cold storage-associated transplantation, we incubated rat kidney proximal tubule cells in University of Wisconsin (UW) solution at 4 degrees C for cold storage, returning them to normal culture medium at 37 degrees C for rewarming. We also stored kidneys from donor mice in cold UW solution for various durations, followed by transplantation into syngeneic recipient mice. RESULTS: We observed PKCdelta activation in both in vitro and in vivo models of cold-storage rewarming or transplantation. In the mouse model, PKCdelta was activated and accumulated in mitochondria, where it mediated phosphorylation of a mitochondrial fission protein, dynamin-related protein 1 (Drp1), at serine 616. Drp1 activation resulted in mitochondrial fission or fragmentation, accompanied by mitochondrial damage and tubular cell death. Deficiency of PKCdelta in donor kidney ameliorated Drp1 phosphorylation, mitochondrial damage, tubular cell death, and kidney injury during cold storage-associated transplantation. PKCdelta deficiency also improved the repair and function of the renal graft as a life-supporting kidney. An inhibitor of PKCdelta, deltaV1-1, protected kidneys against cold storage-associated transplantation injury. CONCLUSIONS: These results indicate that PKCdelta is a key mediator of mitochondrial damage and renal tubular injury in cold storage-associated transplantation and may be an effective therapeutic target for improving renal transplant outcomes.