Induction of apoptosis by a ribosome-inactivating protein from Agrostemma githago is associated with down-regulation of anti-apoptotic bcl-2 protein expression.

Agrostin is a type 1 ribosome-inactivating protein (RIP) isolated from the seeds of Agrostemma githago. 3[H]-thymidine incorporation in human leukemic HL-60 cells was significantly reduced after incubation with agrostin showing that the RIP was inhibitory on the cell proliferation. Results from flow cytometric studies illustrated that apoptosis was induced by agrostin, which was associated with activation of endonucleases and DNA fragmentation of the leukemic cells. Anti-apoptotic bcl-2 protein level was also reduced by agrostin showing that the associated apoptotic pathway might involve down-regulation of the intracellular bcl-2 protein level.