PubMed Health⌕ Search

Biomedical subjects

D B Zorov

Publications and source records attributed to D B Zorov.

At least 19 recordsLinked to original sources
PubMed2000

Reactive oxygen species (ROS)-induced ROS release: a new phenomenon accompanying induction of the mitochondrial permeability transition in cardiac myocytes.

We sought to understand the relationship between reactive oxygen species (ROS) and the mitochondrial permeability transition (MPT) in cardiac myocytes based on the observation of increased ROS production at sites of spontaneously deenergized mitochondria. We devised a new model enabling incremental ROS accumulation in individual mitochondria in isolated cardiac myocytes via photoactivation of tetramethylrhodamine derivatives, which also served to report the mitochondrial transmembrane potential, DeltaPsi. This ROS accumulation reproducibly triggered abrupt (and sometimes reversible) mitochondrial depolarization. This phenomenon was ascribed to MPT induction because (a) bongkrekic acid prevented it and (b) mitochondria became permeable for calcein ( approximately 620 daltons) concurrently with depolarization. These photodynamically produced "triggering" ROS caused the MPT induction, as the ROS scavenger Trolox prevented it. The time required for triggering ROS to induce the MPT was dependent on intrinsic cellular ROS-scavenging redox mechanisms, particularly glutathione. MPT induction caused by triggering ROS coincided with a burst of mitochondrial ROS generation, as measured by dichlorofluorescein fluorescence, which we have termed mitochondrial "ROS-induced ROS release" (RIRR). This MPT induction/RIRR phenomenon in cardiac myocytes often occurred synchronously and reversibly among long chains of adjacent mitochondria demonstrating apparent cooperativity. The observed link between MPT and RIRR could be a fundamental phenomenon in mitochondrial and cell biology.

Animals↗
PubMed2000

Inhibition of Na(+),K(+)-ATPase activity in cultured rat cerebellar granule cells prevents the onset of apoptosis induced by low potassium.

In cerebellar granule cells in culture, lowering of extracellular [K(+)] results in apoptotic death (D'Mello, S.R., Galli, C., Ciotti, T. and Calissano, P., Induction of apoptosis in cerebellar granule neurons by low potassium: inhibition of death by insulin-like growth factor I and cAMP, Proc. Natl. Acad. Sci. USA, 90 (1993) 10989-10993). In this model, we studied the influence of Na(+), K(+)-ATPase inhibition on apoptosis. We demonstrate that cell death (93+/-2 vs. 46+/-1.6%) as well as fragmentation of nuclear DNA induced by low extracellular potassium were prevented by addition of ouabain (0.1 mM), a specific inhibitor of the Na(+),K(+)-ATPase. Blockade of glutamatergic N-methyl-D-aspartate and alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors by 5-methyl-10,11-dihydro-5H-dibenzo(a,d)cyclohepten-5,10-imine hydrogen maleate (MK-801; 20 microM) and 6-Cyano-7-nitroquinoxaline-2,3-dione (CNQX; 50 microM) did not inhibit the protective effect of ouabain. 24 h treatment with ouabain also decreased cell death induced by Fe(2+)/ascorbic acid (74+/-2% to 49+/-3%). We speculate that ouabain pretreatment enhances the resistance against low [K(+)]-induced apoptosis independent of glutamate-receptor activation. Since this effect can be mimicked by a free-radical generating system, we suggest an antioxidative effect underlying ouabain-induced neuroprotection.

Adenosine Triphosphatases↗
PubMed2000

Virus-induced permeability transition in mitochondria.

Isolated rat liver mitochondria undergo permeability transition after supplementation with a suspension of tobacco mosaic virus. Four mitochondrial parameters proved the opening of the permeability transition pore in the inner mitochondrial membrane: increased oxygen consumption, collapse of the membrane potential, release of calcium ions from mitochondria, and high amplitude mitochondrial swelling. All virus-induced changes in mitochondria were prevented by cyclosporin A. These effects were not observed if the virus was treated with EGTA or disrupted by heating. Protein component of the virus particle in the form of 20S aggregate A-protein, or helical polymer, as well as supernatant of the heat-disrupted virus sample, had no effect on mitochondrial functioning. Electron microscopy revealed the direct interaction of the virus particles with isolated mitochondria. The possible role of the mitochondrial permeability transition pore in virus-induced apoptosis is discussed.

Animals↗
PubMed1999

Proteinaceous complexes from mitochondrial contact sites.

A Triton X-100 extract from rat brain mitochondria was obtained using low detergent/protein ratio. From this extract a proteinaceous complex was purified; its molecular weight was as high as 880 kD. The complex contained both hexokinase and creatine kinase activity. When incorporated into phospholipid bilayer membranes, the complex formed a channel whose activity was different than the channel activity of purified porin isolated either by adsorption chromatography or by dissociation from protein complexes. A ligand of the mitochondrial benzodiazepine receptor (Ro5-4864) in submicromolar concentrations had an apparent influence on the kinetic behavior of enzymatic coupling of hexokinase and creatine kinase. It is suggested that the 880-kD complex is formed by mitochondrial contact sites. The role of the isolated protein complex in the formation of nonspecific permeability in mitochondria is discussed.

Animals↗
PubMed1998

The permeability transition pore induced under anaerobic conditions in mitochondria energized with ATP.

The role of oxygen in the induction of mitochondrial permeability transitions was studied. Oxygen consumption, swelling, membrane potential and calcium transport were recorded simultaneously in isolated rat liver mitochondria. Oxygen depletion was accomplished by saturating the medium with N2 and allowing either mitochondrial respiration or glucose/glucose oxidase to consume the residual oxygen. Upon anaerobiosis, mitochondria were supplemented with 500 microM ATP to support succinate-driven membrane potential. Under these conditions, 100 microM Ca2+ induced cyclosporin A-sensitive permeability transitions. To eliminate the possible inhibition of permeability transition by high concentrations of adenine nucleotides, anaerobic mitochondria were also energized by the combination of 20 microM ADP and phosphoenolpyruvate/pyruvate kinase. These mitochondria also underwent Ca2+-induced permeability transition. Under both of these conditions, namely the addition of ATP as a single or through actions of pyruvate kinase, the respiratory components were totally reduced. Thus, oxygen is not a necessary factor for mitochondria to undergo permeability transitions.

Adenosine Triphosphate↗
PubMed1998

The lack of extracellular Na+ exacerbates Ca2+-dependent damage of cultured cerebellar granule cells.

Rhodamine 123 staining, light and electron microscopy were used to evaluate the ultrastructural and functional state of cultured cerebellar granule cells after short treatment with the solution where NaCl was substituted by sucrose (sucrose balance salt medium, SBSM). Cell exposure to SBSM for 20 min resulted in the fact that mitochondria in the neurons lost their ability to sequester rhodamine 123. This effect could be prevented by: (i) non-competitive N-methyl-D-aspartate (NMDA) receptor channel blocker, 10(-5) M MK-801; (ii) a competitive specific antagonist of NMDA glutamate receptors, 0.25 x 10(-3) M D,L-2-amino-7-phosphonoheptanoate (APH); (iii) 10(-3) M cobalt chloride; (iv) removal of Ca2+ from the medium. Low Na+ in the Ca2+-containing medium caused considerable mitochondrial swelling in granule cells. However, the same treatment in the absence of calcium ions in the medium abolished the deleterious effect of SBSM on the neuronal mitochondrial structure and functions. It is suggested that (i) the exposure of cultured cerebellar granule cells to SBSM leads to a release of endogenous glutamate from cells; (ii) Ca2+ ions potentially de-energizing neuronal mitochondria enter the neuron preferentially through the NMDA channels rather than through the Na+/Ca2+ exchanger; (iii) mitochondrial swelling in granule cells is highly Ca2+-dependent; (iv) cellular overload with sodium ions can activate mitochondrial Na+/Ca2+ exchanger and thus prevent permeability transition pore opening in mitochondria.

Animals↗
PubMed1997

The Ca2+ -induced pore opening in mitochondria energized by succinate-ferricyanide electron transport.

The oxygen dependence of the mitochondria permeability transition pore was under study in non-respiring rat liver mitochondria. Oxygen in the medium was depleted by saturation of the incubation medium with N2 and spontaneously by mitochondrial respiration followed by the addition of glucose/glucose oxidase. After the anaerobic state had been reached, ferricyanide has been added to support succinate-driven energization in the absence of oxygen. In the other set of the experiments KCN was added to block operation of the respiratory chain under aerobic conditions. Again, ferricyanide was added as an electron acceptor. Superoxide dismutase was added to trap superoxide anion radicals. Under either hypoxic conditions or in the presence of cyanide, calcium ions were shown to induce the permeability transition. The concentration of Ca2+ required was lower than under conditions of active respiration. In both cases, the transition was prevented by cyclosporine A.

Anaerobiosis↗
PubMed1997

Mitochondria revisited. Alternative functions of mitochondria.

This review explores the alternative functions of mitochondria inside the cell. In a general picture of mitochondrial functioning, the importance and uniqueness of these intrinsic functions make them irreplaceable by other intracellular compartments. Among these are, participation in apoptosis and cellular proliferation, regulation of the cellular redox state and level of second messengers, heme and steroid syntheses, production and transmission of a transmembrane potential, detoxication and heat production. In most of the listed functions, reactive oxygen species modulate a number of non-destructive cellular activities. Some of the mitochondrial functions are reviewed in detail.

Animals↗
PubMed1996

Neurotoxic glutamate treatment of cultured cerebellar granule cells induces Ca2+ -dependent collapse of mitochondrial membrane potential and ultrastructural alterations of mitochondria.

Rhodamine 123 staining and electron microscopy were used to reveal a correlation between the ultrastructural and functional state of cultured cerebellar granule cells after short glutamate treatment. Glutamate exposure (15 min, 100 microM) in Mg2+-free solution caused considerable ultrastructural alterations in a granule cell: clumping of the chromatin, swelling of the endoplasmic reticulum and mitochondria, and disruption of the mitochondrial cristae. After glutamate treatment, the mitochondria of the neurons lost their ability to sequester rhodamine 123. Both the N-methyl-D-aspartate receptor channel blocker MK-801 (30 microM) and cobalt chloride (2 mM) prevented the deteriorative effects of glutamate. These data suggest that glutamate-induced Ca2+ overload of the neurons can lead to non-specific permeability of the inner mitochondrial membrane, resulting in neuronal death.

Animals↗
PubMed1996

Mitochondrial damage as a source of diseases and aging: a strategy of how to fight these.

Some aspects of a defense against an oxidative stress are reviewed. All these aspects are focused on the necessity to defend mtDNA against damage. Protecting mechanisms involve the regulation of mitochondrial transport of nucleic acids, and the development of antioxygen defense as preventive measures. In the first case an exclusive role is supposed to play the mitochondrial benzodiazepine receptor and components, regulating the activity of its participants (mitochondrial porin and adenine nucleotide translocator). The possible transport of nucleic acids through Ca(2+)-dependent permeability transition pore, representing one of the functional states of mitochondrial benzodiazepine receptor, is put forth. Such mechanisms can also cover the genomic nuclear-mitochondrial exchange. The second aspect reviews the possible complex of measures to lower the harmful effect of oxygen. Among these measures are mild uncoupling, the opening of a permeability transition pore and cellular apoptosis as was recently suggested by Skulachev. Problems such as cellular aging and mitochondrial diseases, are discussed in light of the relevance to the problem of oxidative stress.

Aging↗
PubMed1996

[Stimulation of mitochondrial respiration, induced by laser irradiation in the presence of rhodamine dyes].

The effect of micromolar concentration of rhodamine 123 (methylrhodamine) and ethyl and amyl esters of unsubstituted rhodamine on oxygen consumption by rat liver mitochondria was studied under irradiation by an argon laser (488 and 514 nm). Irradiation of mitochondria in the presence of rhodamine stimulates their respiration. Light-induced stimulation of respiration is not inhibited by free radical scavenger ionol and by inhibitor of the permeability transition pore cyclosporine A. Stimulation of respiration by moderate doses of radiation is reversed in the dark. Increase in radiation dose resulted in only partial reversal of stimulated respiration in the dark. Rhodamine efficacy in stimulation of mitochondrial respiration depends on its structure (amyl > ethyl > methylrhodamine).

Animals↗
PubMed1996

[Mitochondrial transport of nucleic acids. Participation of the benzodiazepine receptor].

The models of mitochondrial transmembrane nucleic acid transfer are discussed. According to this hypothesis, mitochondria can exchange their nucleic acids by two possible mechanisms including either intermitochondrial fusion and fission or transmembrane transport. In the latter case, important roles for mitochondrial benzodiazepine receptor and factors that regulate activities of its components (mitochondrial porin and adenine nucleotide translocator) are suggested. Nucleic acids can be transported through a Ca(2+)-dependent pore that can be one of the functional states of mitochondrial exchange of genetic material. Problems like cellular aging, apoptosis, proliferation, mitochondrial diseases, multidrug resistance, intracellular traffic, and mitochondrial heredity are discussed considering an important role of mitochondrial benzodiazepine receptor in these processes.

Biological Transport↗
PubMed1995

Immunoelectron microscopic study of the distribution of porin on outer membranes of rat heart mitochondria.

The distribution of porin on the outer membranes of rat heart mitochondria has been studied by means of immunogold labelling with antibodies to the N-terminal part of the human protein. It was found that only a minority of isolated, unfixed mitochondria are labelled by these antibodies, with the gold particles frequently organized in threads or bands. Extensive immunogold labelling is frequently observed on regions of outer membranes stripped away from mitochondria and on regions separating two mitochondrial compartments whose cristae display different configurations (possibly representing two mitoplasts covered by a common outer membrane). Also, pairs of connected mitochondria are sometimes heavily labelled in the "neck" regions, which may represent the junctions involved in electrical communication between mitochondria in cardiac tissue.

Animals↗
PubMed1994

[Detection of porin in inter-mitochondrial contacts].

The binding of monoclonal antibodies (mAb) to the N-terminal part of VDAC with freshly isolated, unfixed rat heart mitochondria has been studied. It was established that mAb do not react with the main portion of the mitochondria. At the same time, successful binding to some of those was observed. Gold particles were organized, as a rule in three types of clusters: (i) thread-like clusters; (ii) small, irregularly shaped clusters, and (iii) big clusters covering the greater part of the mitochondrial surface. In the region of tight junctions between mitochondria, specific binding of mAb to mitochondrial VDAC, such as thread-like and small clusters, was found. In some cases, antibody clusters were localized in the region which separates two mitochondrial compartments differing in configuration of the cristae. When the outer mitochondrial membrane was partially stripped off, this membrane was extensively labelled by antibodies. It is concluded that the N-terminus of porin is localized on the inner surface of the outer mitochondrial membrane, so that some damage of the outer membrane appears to be required to allow the N-terminal porin antibody to contact the antigenic determinant. Such a damage is apparently more probable in the place of contacts of two mitochondria or two mitoplasts covered by the common outer membrane. In any case, the data obtained strongly suggest that porin is present in the junction region.

Animals↗