CYCLOSPORINE-A, AN IMMUNOSUPPRESSIVE DRUG, INDUCES PROGRAMMED CELL-DEATH IN RAT C6 GLIOMA-CELLS BY A MECHANISM THAT INVOLVES THE AP-1 TRANSCRIPTION FACTOR

Cyclosporin A (CsA) is a clinically important immunosuppressive drug w idely used to prevent graft rejection following organ or bone marrow t ransplantation. Although there are reports of serious neurologic alter ations associated with the use of the drug, the precise mechanism of i ts action on the CNS still remains unknown. We studied the effects of CsA on the growth of C6 glioma cells. We found that CsA inhibits the g rowth of C6 glioma cells in a dose-dependent manner and induces morpho logical changes such as shrinkage of the cell body and loss of extensi ons followed by cell death. The analysis of DNA from CsA-treated cells revealed a ladder-like pattern of fragmented DNA. Acridine orange sta ining showed the occurrence of apoptotic changes in nuclear morphology . Apoptotic morphological alterations were prevented by the treatment with cycloheximide. Altogether, our findings suggest that the CsA-indu ced cell death of C6 glioma cells bears all the features characteristi c of programmed cell death. We also observed a significant increase in the DNA-binding activity of AP-1 during CsA-induced apoptosis. The AP -1 induction preceded the appearance of apoptotic, morphological chang es and was accounted for by an increase in the expression of c-Jun pro tein. The occurrence of increased levels of AP-1 complex and c-Jun pro tein during CsA-induced programmed cell death suggests its involvement in the induction of apoptosis.