Effect of amyloid β-peptide on permeability transition pore:: A comparative study

A potentially central factor in neurodegeneration is the permeability transition pore (PTP). Because of the tissue-specific differences in pore properties, we directly compared isolated brain and liver mitochondria responses to the neurotoxic Abeta peptides. For this purpose, the following parameters were examined: mitochondrial membrane potential (Deltapsim), respiration, swelling, ultrastructural morphology, and content of cytochrome c. Both peptides, Abeta(25-35) (50 muM) and Abeta(1-40) (2 muM), had a similar toxicity, exacerbating the effects of Ca2+, although, per se, they did not induce (PTP). In liver mitochondria, Abeta led to a drop in Deltapsim and potentiated matrix swelling and disruption induced by Ca2+. In contrast, brain mitochondria, exposed to the same conditions, demonstrated a higher capacity to accumulate Ca2+ before the Deltapsim drop and a slight increase of mitochondrial swelling compared with liver mitochondria. Furthermore, mitochondrial respiratory state 3 was depressed in the presence of Abeta, whereas state 4 was unaltered, resulting in an uncoupling of respiration. In both types of mitochondria, Abeta did not affect the content of cytochrome c. The Deltapsim drop was reversed when Ca2+ was removed by EGTA or when ADP plus oligomycin was present. Pretreatment with cyclosporin A or ADP plus oligomycin prevented the deleterious effects promoted by Abetaand/or Ca2+. It can be concluded that brain and liver mitochondria show a different susceptibility to the deleterious effect of Abeta peptide, brain mitochondria being more resistant to the potentiation by Abeta of Ca2+-induced PTP. (C) 2002 Wiley-Liss, Inc.