Augmentation of ischemia/reperfusion injury to endothelial cells by cyclosporin A

Ischemia/reperfusion (I/R) carries significant injury to endothelial cells in transplanted organs and is an important factor in chronic rejection. Immunosuppressive drugs, notably cyclosporin A (CyA) and FK506, can potentially augment this injury. Here, our goal was to determine the combined effects of I/R and CyA or FK506 on endothelial cells. Transformed mouse endothelial cells (SVEC 4-10) were subjected to ischemia or I/R for 2-24 hours by incubating cells in 100 per cent N₂ (ischemia) followed by 5 per cent CO₂ and 95 per cent O₂ (reperfusion) for 24 hours. In separate experiments, CyA or FK506 was added to cells subjected to ischemia or I/R. Nonviable cells were determined by Trypan blue exclusion assay. All experiments (done in triplicate) were analyzed by Student's r test. Increasing ischemia times resulted in a greater number of nonviable cells (2% nonviable cells at 0 hours and 57% at 24 hours of I/R). Addition of CyA significantly increased the number of nonviable cells when compared with the control (I/R only) group (P = 0.014). Interestingly, FK506 did not increase the percentage of nonviable cells compared with the control group (P = 0.2). Unlike FK506, CyA augments I/R injury to endothelial cells in vitro. These findings could be relevant in chronic rejection and transplantation.