Cyclosporin A-insensitive permeability transition in brain mitochondria: inhibition by 2-aminoethoxydiphenyl borate.
The mitochondrial permeability transition pore (PTP) may operate as a physiological Ca2+ release mechanism and also contribute to mitochondrial deenergization and release of proapoptotic proteins after pathological stress, e.g. ischemia/reperfusion. Brain mitochondria exhibit unique PTP characteristics, including relative resistance to inhibition by cyclosporin A. In this study, we report that 2-aminoethoxydiphenyl borate blocks Ca2+-induced Ca2+ release in isolated, non-synaptosomal rat brain mitochondria in the presence of physiological concentrations of ATP and Mg2+. Ca2+ release was not mediated by the mitochondrial Na+/Ca2+ exchanger or by reversal of the uniporter responsible for energy-dependent Ca2+ uptake. Loss of mitochondrial Ca2+ was accompanied by release of cytochrome c and pyridine nucleotides, indicating an increase in permeability of both the inner and outer mitochondrial membranes. Under these conditions, Ca2+-induced opening of the PTP was not blocked by cyclosporin A, antioxidants, or inhibitors of phospholipase A2 or nitric-oxide synthase but was abolished by pretreatment with bongkrekic acid. These findings indicate that in the presence of adenine nucleotides and Mg2+,Ca2+-induced PTP in non-synaptosomal brain mitochondria exhibits a unique pattern of sensitivity to inhibitors and is particularly responsive to 2-aminoethoxydiphenyl borate.
University of Maryland School of Medicine, Department of Anesthesiology, Baltimore, Maryland 21201, USA.
Christos
C
Chinopoulos
Anatoly A
AA
Starkov
Gary
G
Fiskum
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001865:Bongkrekic Acid / Q000494:pharmacology; D001896:Boron Compounds / Q000494:pharmacology*; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D016572:Cyclosporine / Q000494:pharmacology*; D003574:Cytochrome c Group / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D007425:Intracellular Membranes / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials; D008928:Mitochondria / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption; D010539:Permeability; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D051381:Rats; D017207:Rats, Sprague-Dawley; D013050:Spectrometry, Fluorescence; D013997:Time Factors
D000975:Antioxidants; D001896:Boron Compounds; D003574:Cytochrome c Group; D009243:NAD; D001865:Bongkrekic Acid; D016572:Cyclosporine; D000255:Adenosine Triphosphate; C109986:2-aminoethoxydiphenyl borate; D019001:Nitric Oxide Synthase; D010741:Phospholipases A; D054467:Phospholipases A2; D010100:Oxygen; D002118:Calcium