INVESTIGADORES
LORES ARNAIZ Silvia
congresos y reuniones científicas
Título:
Characteristics of the permeability transition pore in brain cortex mitochondria.
Autor/es:
BUSTAMANTE, J.; LORES-ARNAIZ, S.
Lugar:
Buenos Aires
Reunión:
Simposio; Simposio-Workshop OXIDATIVE STRESS AND ANTIOXIDANTS.; 2009
Institución organizadora:
Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires.
Resumen:
Characteristics of the permeability
transition pore in brain cortex mitochondria
Juanita Bustamante and
Silvia Lores Arnaiz
Laboratory
of Free Radical Biology, School of Pharmacy and Biochemistry, University of
Buenos Aires, Junın 956, 1113 Buenos Aires, Argentina
Mitochondria
help to shape intracellular Ca2+ signalling by taking up cytosolic
Ca2+ through an uniporter located on the inner membrane. However,
their uptake capacity is finite, and when exceeded, mitochondrial Ca2+
efflux occurs rapidly by a change in the permeability of the mitochondrial
inner membrane resulting from the opening of a non-specific mega channel called
mitochondrial permeability transition pore or mitochondrial permeability
transition (MPT). In this work we studied the effect of high Ca2+ exposure
in the functions of non synaptic brain cortex mitochondria.. MPT was analysed
through its two main characteristics mitochondrial swelling and depolarization after a single pulse of 100 mM Ca2+ (corresponding to 400
nmol/mg protein). In these conditions, H2O2 and NO
production, mitochondrial respiratory function and the activity of the
monoamine oxidase (MAO), an outer mitochondrial membrane enzyme, were
determined. Energized organelles in the presence of 100 mM Ca2+, showed partial swelling
and depolarization, being maximal after addition of alamethicin. An impaired
respiratory function, with 47% increase in state 4 respiratory rate and 59%
decrease in state 3 respiratory rate was also observed after 100 mM Ca2+. Increased hydrogen
peroxide (H2O2) production was observed, being restored
after CsA pretreatment to those levels observed in untreated mitochondria. Additionally,
NO production was decreased by 51% and 73% after 3 and 7 min of 100 mM Ca2+ addition respectively and by 80% after alamethicin.
Similarly, marked decreases of 38% and 60% in MAO activity were observed 7
minutes after Ca2+ and alamethicin respectively as compared with
untreated mitochondria. Mitochondrial pretreatment with CsA, an inhibitor of
MPT, before 100 mM Ca2+, protect against calcium induced swelling, and restored NO
production and MAO activity to the levels observed in untreated mitochondria. We conclude that during Ca2+
or alamethicin induced swelling a marked increase
in H2O2 leads to a structurally
compromised mitochondria with disrupted antioxidant pathways, and that the
typical modulation of MAO activity and NO production could be closely related
with the topological alterations induced in the inner
and outer mitochondrial membranes during MPT.