Protein Kinase C-<i>δ</i> Mediates Kidney Tubular Injury in Cold Storage-Associated Kidney Transplantation.

Abstract

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-<i>δ</i> (PKC<i>δ</i>) in renal tubular injury during cisplatin nephrotoxicity and albumin-associated kidney injury, but whether PKC<i>δ</i> is involved in ischemic or transplantation-associated kidney injury is unknown. To investigate PKC<i>δ</i>'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°C for cold storage, returning them to normal culture medium at 37°C for rewarming. We also stored kidneys from donor mice in cold UW solution for various durations, followed by transplantation into syngeneic recipient mice. We observed PKC<i>δ</i> activation in both <i>in vitro</i> and <i>in vivo</i> models of cold-storage rewarming or transplantation. In the mouse model, PKC<i>δ</i> 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 PKC<i>δ</i> in donor kidney ameliorated Drp1 phosphorylation, mitochondrial damage, tubular cell death, and kidney injury during cold storage-associated transplantation. PKC<i>δ</i> deficiency also improved the repair and function of the renal graft as a life-supporting kidney. An inhibitor of PKC<i>δ</i>, <i>δ</i>V1-1, protected kidneys against cold storage-associated transplantation injury. These results indicate that PKC<i>δ</i> 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.