ABSTRACT
The lignan otobaphenol, (8R,8'R,7R)-4'-hydroxy-5'-methoxy-3,4-methylenedioxy-2',7,8,8'-neolignan, extracted from Virola Aff. Pavonis leaves, completely inhibits at a concentration of 2.5 micro M the Fe(3+)-ascorbate-induced lipoperoxidation of rat liver mitochondria that was determined by oxygen consumption and accumulation of thiobarbituric acid-reactive species. At 25 micro M, it delays the mitochondrial permeability transition induced by tert-butyl hydroperoxide or Ca(2+), substantially inhibits the state 3 respiration, does not affect the state 4 respiration and the ADP/O ratio (with succinate), diminishes the rate of Ca(2+) uptake by mitochondria, and delays the ruthenium red-insensitive uncoupler-induced release of the loaded Ca(2+). Dose-dependent delaying of the calcium-induced swelling of mitochondria in the presence of otobaphenol nonlinearly correlates with its 1,1-diphenyl-2-picrylhydrazyl free radical scavenging activity. At 75 micro M and higher, this lignan causes mitochondrial aggregation and is able to aggregate itself, without mitochondria. The formed aggregates of otobaphenol do not cause an aggregation of subsequently added mitochondria. Thus, otobaphenol seems to be a promising target to prevent the oxidative stress death of cells.
Subject(s)
Antioxidants/pharmacology , Mitochondria, Liver/drug effects , Mitochondria, Liver/metabolism , Phenols/pharmacology , Animals , Ascorbic Acid/antagonists & inhibitors , Ascorbic Acid/pharmacology , Biphenyl Compounds , Butylated Hydroxytoluene/pharmacology , Calcium/chemistry , Calcium/metabolism , Calcium/toxicity , Cell Membrane Permeability/drug effects , Ferric Compounds/antagonists & inhibitors , Ferric Compounds/pharmacology , Free Radical Scavengers/pharmacology , Intracellular Membranes/drug effects , Intracellular Membranes/metabolism , Intracellular Membranes/physiology , Lipid Peroxidation/drug effects , Male , Membrane Potentials/drug effects , Membrane Potentials/physiology , Mitochondrial Swelling/drug effects , NADP/metabolism , Oxidative Phosphorylation/drug effects , Oxygen Consumption/drug effects , Phenols/chemistry , Picrates/antagonists & inhibitors , Rats , Thiobarbituric Acid Reactive Substances/analysis , Thiobarbituric Acid Reactive Substances/metabolism , Time Factors , tert-Butylhydroperoxide/toxicityABSTRACT
It has been reported that dextrans diminish the intermembrane space of mitochondria, increase the number of contact sites between the inner and the outer mitochondrial membranes, decrease the outer membrane permeability to adenosine 5(')-diphosphate, and change the kinetic properties of mitochondrial kinases. In the present work the influence of dextran M40 (5% w/v) on the oxidoreductase activities of the inner and outer membranes of mitochondria, the interaction of cytochrome c with mitochondrial membranes, and the light scattering by rat liver mitochondria were studied. No influence of dextran on the release of cytochrome c from mitochondria or its interaction with mitochondrial membranes was observed. Decreases in the NADH-oxidase (to 80+/-2% of the control), NADH-cytochrome c reductase (to 26+/-2%), succinate-cytochrome c reductase (to 70+/-5%), and NADH-ferricyanide reductase (to 75+/-3%) activities induced by dextran, which may be due to the mitochondrial aggregation, were observed. The formation of aggregates was registered by light scattering, confirmed by light microscopy, and explained within the framework of the Gouy-Chapman theory of the electrical double layer. The observed mitochondrial aggregation seems to be useful also for understanding the mechanisms of mitochondrial condensation and perinuclear clustering during apoptosis.
