Renal tubular epithelial cell death and cyclosporin A.

BACKGROUND The pathogenesis of chronic cyclosporin A (CsA) nephrotoxicity is largely unknown. In this study we examined whether CsA produces cell death through necrosis or apoptosis of either cultured human proximal tubular epithelial cells (PTEC) or the porcine tubular cell line LLC-PK(1). METHODS Primary isolates of human PTEC and LLC-PK(1) cells were treated for various time periods with CsA at concentrations of 0.01-100 microg/ml. Apoptosis was studied by the assessment of annexin binding and propidium iodide uptake, the measurement of cellular DNA content and cell cycle analysis, and by the evaluation of nuclear morphology. Cell death was studied by the trypan blue exclusion method. Hypoxic conditions were simulated through chemical ATP depletion. RESULTS In human PTEC, cell death was observed at CsA concentrations higher than 10 microg/ml; at these concentrations PTEC died as a result of necrosis and the toxicity of its vehicle Cremophore EL, and not as a result of CsA inducing apoptosis. The addition of cycloheximide to relieve a possible block in the apoptotic process had no effect on human PTEC, but did result in apoptosis of LLC-PK(1). In human PTEC, CsA did not augment cell death induced by chemical ATP depletion. CONCLUSIONS The results of this in vitro study do not support the hypothesis that CsA directly induces cell death of proximal tubular epithelial cells.