Direct effect of Apoptosis inducers on rat Thymus mitochondrial functions

BUSTAMANTE, JOANITA; BRESIER, GERALDINE; DI LIBERO, EUGENIA; MONTI, NICOLAS; CARDILLO, ALEJANDRA BEATRIZ; BOVERIS, ALBERTO

Mar del Plata, Argentina

Congreso; South American Group For Free Radical Reaserch II Congress; 2001

Different studies demonstrate that mitochondrial functions are early altered after reached by apoptotic stimuli. In this study we analyze the direct effect of apoptosis inducers on thymus isolated mitochondria. It was observed that mitochondria permeability is affected by incubation with methylprednisolone, etoposide and thapsigargin which are able to induce rat thymocyte apoptosis. The three compounds caused an absorbance decrease that accompanies the permeability transition which was inhibited by CsA. Paralel experiments showed that after 20 min of mitochondrial swelling cytochrome c and GSH content was almost totally released in a cell-free system, also inhibited by CsA. A decrease of mitochondrial respiratory state 3, was closely associate with an increased mitochondrial NO production. The respiratory state 3 inhibition (using malate plus glutamate as a substrate) and the NO production induced by the three apoptosis inducers were dose dependent. The NO production was between 0.45 to 1.6 nmol/mg protein. Mitochondrial membrane potential (Äø m) was only decreased after 20 min of thapsigargin treatment. Mitochondrial swelling was accompanied by a lower mitochondrial respiration and increased NO production, facts closely related with cytochrome c release, after treatment with the three apoptosis inducers. Meanwhile depolarization, as observed by mitochondrial membrane potential (Äø m) decrease, was not correlated with swelling after methylprednisolone and etoposide treatment. This results indicate that the electrons transfer and permeability transition can be correlated with mitochondrial NO production. Meanwhile membrane potential due to proton pump activity seems to be independent from mitochondrial permeability transition.