Molecular mechanism of human leukemia Jurkat T-cell apoptosis induced by plant trypsin inhibitors

TRONCOSO, MARÍA F.; BIRON, VERÓNICA A.; LONGHI, SILVIA A.; RETEGUI, LILIA A. AND WOLFENSTEIN-TODEL CARLOTA.

Pinamar, Buenos Aires, Argentina.

Congreso; Reunión Científica de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB); 2005

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

Plants constitute an important source of compounds which can induce apoptosis in a variety of cells. Previously, we reported the isolation of a trypsin inhibitor from Peltophorum dubium seeds (PDTI). This inhibitor, as well as soybean trypsin inhibitor (SBTI), has lectin-like properties and triggers rat lymphoma cell apoptosis. In the present study, we demonstrate that PDTI and SBTI induce human leukemia Jurkat cell death. Induction of apoptosis was confirmed by flow citometry after propidium iodide labeling, showing a significant increase of the sub G0/G1 fraction. To understand the mechanism of apoptosis, we evaluated caspases involvement and showed caspases-3 and -8 activation by PDTI or SBTI treatment. Consistent with these results, pan caspase inhibitor and caspase-8 inhibitor protected Jurkat cells from apoptosis. However, there was no caspase-9 activation, confirmed by the failure of caspase-9 inhibitor to prevent cell death. We detected a moderate decrease of mitochondrial membrane potential but no significant release of cytochrome c from mitochondria. These results suggest that the intrinsic mitochondrial pathway is not predominant in the apoptotic process. On the other hand, we observed the recruitment of Fas-associated death domain (FADD) to the cell membrane indicating the involvement of this adaptor protein in PDTI- and SBTI-induced apoptosis in Jurkat cells.