Background. Caspase-3 plays a key role in apoptosis, but the involvement of apoptosis and caspase-3 in mediating long-term ischemia/reperfusion (I/R) and immunosuppressive injury are not fully defined. The present study was undertaken to investigate apoptosis and caspase-3 in a renal I/R injury rat model with or without immunosuppression. Methods. The right renal pedicle was clamped for 45 minutes and left nephrectomy was induced. Cyclosporin A (CsA), tacrolimus (Tac), rapamycin (Rap), or mycophenolate mofetil (MMF) were administered daily. Animals were killed at 16 weeks, and the levels of apoptosis (with in situ end-labeling fragmented DNA), caspase-3 protein (with immunohistochemistry, Western blotting, and activity assay), and messenger RNA (mRNA; with quantitative reverse-transcriptase polymerase chain reaction) were evaluated. Results. Kidneys with I/R injury showed increased apoptosis in tubular and interstitial areas compared with control kidneys. Tacrolimus, Rap, and MMF significantly reduced apoptosis, but CsA did not. Distribution of full-length caspase-3 widened in I/R–injured kidneys from normal distal tubules and collecting ducts to dilated proximal tubules and expanded interstitium, whereas active caspase-3 was mainly scattered in damaged tubules and interstitium. Active caspase-3 staining and 24-kDa active caspase-3 protein was enhanced in I/R–injured and CsA-treated kidneys, but decreased by Tac, Rap, and MMF. These results were also consistent with changes in caspase-3 activity. Although caspase-3 mRNA levels were significantly increased in uninephrectomy and I/R–injured kidneys, they were not significantly affected by the immunosuppressants. In addition, all changes detected were positively correlated with renal structure and function. Conclusion. Apoptosis and caspase-3 are not only involved in the long-term renal I/R injury, but also mediate the divergent effects of immunosuppression in this model.

Background. Ischemia-reperfusion injury (IRI) plays key roles in graft viability and posttransplantation function. Caspase-3 associated with apoptosis and inflammation is up-regulated by IRI. We propose that naked small interfering RNA (siRNA) targeting caspase-3 may prevent IRI and improve kidney preservation. Methods. Porcine kidneys were retrieved after 10-min warm ischemia and flushed with 500 mL hyperosmolar citrate. Caspase-3 siRNA was administered directly into the renal artery in hyperosmolar citrate solution (3 μg/ml) with the renal vein clamped and into autologous blood (0.15 μg/ml), both of which were stored for 24 hr on ice. The kidneys were reperfused with oxygenated autologous blood for 3 hr on an isolated organ perfusion system to assess renal function. Results. In the siRNA-treated group, the expression of 32-kDa caspase-3 precursor and 17-kDa active subunit was down-regulated by 30% and 56%, respectively, with 40% reduction in active caspase-3+ cells. Consequently, apoptotic cells in the renal cortex were significantly decreased by 47%, whereas inflammatory cells were only marginally reduced by 26%. Caspase-3 siRNA also doubled oxygen consumption and significantly neutralized perfusate pH. Renal blood flow was gradually increased from 5 min to 3 hr by caspase-3 siRNA and marginally improved at the end of 3-hr reperfusion by 45%. Conclusions. The administration of caspase-3 siRNA directly into the kidney and hemoperfusate during cold preservation improved IRI with reduced caspase-3 and apoptosis, and better renal oxygenation and acid-base homeostasis. This proof of principle experiment using a novel siRNA therapy in large animal organs provides valuable data for human kidney transplantation.

Erythropoietin (EPO) has been well recognized as a tissue protective agent by inhibiting apoptosis and inflammation. The tissue protective effect of EPO, however, only occurs at a high dosage, which may elicit severe side-effects at the meantime. Helix B surface peptide (HBSP), a novel peptide derived from the non-erythropoietic helix B of EPO, plays a specific role in tissue protection. We investigated effects of HBSP and the expression of its heterodimeric receptor, beta common receptor (βcR)/EPO receptor (), in a murine renal ischemia reperfusion (IR) injury model. HBSP significantly ameliorated renal dysfunction and tissue damage, decreased apoptotic cells in the kidney and reduced activation of caspase-9 and 3. The βcR/EPOR in the kidney was up-regulated by IR, but down-regulated by HBSP. Further investigation revealed that the expression and phosphorylation of Akt was dramatically enhanced by HBSP, but strongly reversed by wortmannin, the PI3K inhibitor. Wortmannin intervention improved βcR/EPOR expression, promoted caspase-9 and 3 activation, and increased active caspase-3 positive cells, while renal function and structure, and apoptotic cell counts scarcely changed. This result indicates a significant contribution of PI3K/Akt signaling pathway in the renoprotection of HBSP. The therapeutic effects of HBSP in this study suggest that HBSP could be a better candidate for renal protection.