CYCLOSPORIN A (CyA) INDUCED ENDOTHELIAL CELL INJURY

The chronic administration of CyA to animals and humans to prevent graft rejection may induce renal arteriolar damage resembling hemolytic uremic syndrome (HUS). This is a syndrome of vascular damage with thrombotic occlusions of the microcirculation. Endothelial damage is considered the first event in the pathogenetic cascade leading to HUS. We have used bovine aortic endothelial cells in culture to address the issue of CyA-induced arteriolar damage. CyA-induced a time (1-24 hours) and dose (1-50 μM) dependent cell damage. CyA-induced injury was characterized by an early cell detachment followed by lysis as documented by the increase in LDH and Cr release. 1 μM CyA did not induce cell detachment and lysis was evident only after prolonged incubations. 10 and 50 μM CyA both induced marked cell detachment and lysis: lysis started 3 hours after incubation of endothelial cells with CyA and was maximal at the end of 24 hour incubation (LDH release, percent specific increase over control values: 10 μM CyA, 47%; 50 μM CyA, 70%; 51 Cr release, percent specific increase over control values: 10 μM CyA, 28%; 50 μM CyA, 34%). CyA-induced injury was associated with dose- and time-depedent increase in prostacyclin (PGI2) and thromboxane A2 (TxA2) release by endothelial cells exposed to 10 and 50 μM CyA. CyA-induced generation of PGI2 and TxA2 was inhibited when the incubations were carried-on in the presence of acetyl salicilic acid (500 μM). These studies indicate that CyA exerts a direct toxic effect on endothelial cells and might help to understand the pathogenesis of CyA-induced vascular damage.