Lysosomes participate in early steps of Tl(III)-mediateda apoptosis of PC12 cells

HANZEL, C. E.; VERSTRAETEN, S.V

Puerto Madryn, Chubut

Congreso; XLVI Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2010

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Previously, we demonstrated that the exposure of rat pheochromocytoma (PC12) cells to Tl(I) or Tl(III) (10-100 uM) decreased cell viability through the activation of mitochondrial (Tl(I) and Tl(III)), or extrinsic (Tl(III)) pathways of apoptosis. In the present work, we investigated if Tl(III) could be incorporated into cells following the route of iron uptake and damage lysosomes. Tl(III) caused a marked lysosomes acidification, effect that depended on serum or transferrin presence in the medium. Longer incubations (18 h) permanently damaged lysosomes, evidenced from the impairment of acridine orange uptake and the release of cathepsins B and D. Cathepsins mediated the cleavage of proapoptotic protein BID, involved in mitochondrial damage and in the triggering of the intrinsic pathway of apoptosis. Cells preincubation with pepstatin A (cathepsin D inhibitor) partially prevented Tl(III)-supported caspase 3 activation, effect that was not observed in cellspreincubated with E64d (cathepsin B inhibitor). Caspase 3 activation in Tl(I)-treated cells was not affected by these inhibitors. These experimental results support the role of lysosomal uptake ofTl(III) and its involvement in the early steps of Tl(III)-mediated PC12 cells apoptosis.