Disruption of mitochondrial membrane potential during apoptosis induced by PSC 833 and CsA in multidrug-resistant lymphoid leukemia.
Previous findings from our laboratory demonstrated that when used at low concentration (0.1 microg ml(-1)), CsA as well as its analog PSC 833 were able to revert the MDR phenotype, while at high concentration (1 microg ml(-1)) were able to induce apoptosis. CsA induced apoptosis in leukemia cell lines sensitive (LBR-) and resistant to vincristine (LBR-V160), and doxorubicin (LBR-D160), while PSC 833 only induced apoptosis in vincristine-resistant cell line (LBR-V160). In this work, we investigated mitochondrial-associated mechanisms during CsA- and PSC 833-induced apoptosis. Mitochondrial function was evaluated by recording changes in its transmembrane potential, cytochrome c release, and caspase activation cascade. Results showed that CsA- and PSC 833-induced apoptosis was associated with mitochondrial depolarization, through potentiometric measurements with JC-1 and DiOC(6) probes. Collapse of mitochondrial potential in these cell lines after CsA treatment was followed by cytochrome c release to the cytosol, reaching an increase of 2.61-fold in LBR-, 1.98-fold in LBR-V160, and 3.01-fold in the case of LBR-D160. However, in the case of PSC 833 treatment, induction of apoptosis in LBR-V160 was associated with mitochondrial depolarization followed by a lower cytochrome c release of 1.15-fold as compared with untreated cells. Caspase 3 activation was clearly observed in LBR-, LBR-V160, and LBR-D160 after CsA treatment, while in LBR-V160, PSC 833 was less effective inducing activation of this caspase. Neither caspase 6 nor 8 activity was observed in these three cell lines. Our results suggest that during CsA- and PSC 833-induced apoptosis, mitochondrial dysfunction occurs. This is mediated through mitochondrial events, associated with an evident decrease in DeltaPsi(m), cytochrome c release and caspase 3 activation.
Bustamante
Juanita
J
Catedra de Fisicoquimica, Facultad de Farmacia y Bioquimica, Universidad de Buenos Aires, 1113 Buenos Aires, Argentina. juanitab@ffyb.uba.ar
Caldas Lopes
Eloisi
E
Garcia
Mariana
M
Di Libero
Eugenia
E
Alvarez
Elida
E
Hajos
Silvia E
SE
D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000187:drug effects* / Q000378:metabolism; D016572:Cyclosporine / Q000494:pharmacology*; D003524:Cyclosporins / Q000494:pharmacology*; D018432:Drug Resistance, Multiple / Q000187:drug effects / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects; D005434:Flow Cytometry; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D007945:Leukemia, Lymphoid / Q000188:drug therapy* / Q000201:enzymology / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects*; D051379:Mice; D008807:Mice, Inbred BALB C; D008928:Mitochondria / Q000187:drug effects*; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D003524:Cyclosporins; D007166:Immunosuppressive Agents; D016572:Cyclosporine; D020169:Caspases; C070272:valspodar