Cytoskeletal Involvement in Hypothermic Renal Preservation Injury

Abstract

Cytoskeletal degradation occurs in warm renal ischemia and reperfusion and during hypothermia. The purpose of this study was to determine cytoskeletal changes during cold storage preservation injury in renal tubules and to determine whether these changes contribute to the injury. Isolated canine renal proximal tubules or their primary epithelial cultures were cold-stored in University of Wisconsin solution and reperfused in vitro to simulate renal cold storage preservation injury. Assays for cytoskeletal protein degradation and viability together with biologically active cytoskeletal agents and molecular interventions were used to test this hypothesis. Progressively increasing the cold storage time of isolated renal tubules in University of Wisconsin solution caused proportional disassembly of both ezrin and Na/K adenosine triphosphatase proteins from their cytoskeletal attachments. The sublamellar structural protein, fodrin, was metabolized to products consistent with calpain hydrolysis during preservation. Time-dependent deterioration in tubule membrane function (organic cation transporter-1 transport activity) was observed during cold preservation, and this was mimicked in fresh tubules by chemically induced cytoskeletal disruption with cytochalasin-D treatment. Cold preservation decreased total tubulin content. Taxol slowed this loss by preventing tubulin depolymerization, which improved membrane function and tubule viability. The viability of primary renal epithelial cells was enhanced by overexpression of ezrin (transfection) and diminished with specific ezrin small interfering RNA knockdown during cold preservation injury. Hypothermic storage preservation causes disruption of key cytoskeletal elements in kidney tubules, which contributes causally to the injury at rewarming.