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Biomedical subjects

N K Isaev

Publications and source records attributed to N K Isaev.

At least 19 recordsLinked to original sources
PubMed2005

Reactive oxygen and nitrogen species: friends or foes?

Chemical and physiological functions of molecular oxygen and reactive oxygen species (ROS) and existing equilibrium between pools of pro-oxidants and anti-oxidants providing steady state ROS level vital for normal mitochondrial and cell functioning are reviewed. The presence of intracellular oxygen and ROS sensors is postulated and few candidates for this role are suggested. Possible involvement of ROS in the process of fragmentation of mitochondrial reticulum made of long mitochondrial filaments serving in the cell as "electric cables", as well as the role of ROS in apoptosis and programmed mitochondrial destruction (mitoptosis) are reviewed. The critical role of ROS in destructive processes under ischemia/reoxygenation and ischemic preconditioning is discussed. Mitochondrial permeability transition gets special consideration as a possible component of the apoptotic cascade, resulting in excessive "ROS-induced ROS release".

Animals↗
PubMed2005

Role of mitochondria in the mechanisms of glutamate toxicity.

Current data on glutamate-induced functional and morphological changes in mitochondria correlating with or being a result of their membrane potential changes are reviewed. The important role of Ca2+, Na+, and H+ in the potentiation of such changes is considered. It is assumed that glutamate-induced loss of mitochondrial potential is mediated by Ca2+ overload resulting in the induction of nonspecific permeability of the inner mitochondrial membrane.

Calcium↗
PubMed2002

Neuroprotective effects of the antifungal drug clotrimazole.

Pretreatment with 10 microM of the antifungal drug clotrimazole potently reduced the death of cultured rat cerebellar granule cells induced by oxygen/glucose deprivation, and the excitotoxic effect of glutamate on cultured hippocampal neurons and cerebellar granule cells. In patch-clamped hippocampal pyramidal neurons, 10-50 microM clotrimazole caused a decrease in the amplitude of N-methyl-D-aspartate (NMDA) receptor-mediated currents. Glutamate induced intracellular Ca(2+) overload, as measured by Fluo-3 confocal fluorescence imaging, while clotrimazole reduced Ca(2+) overload and promoted the recovery of intracellular calcium homeostasis after glutamate treatment. Using tetramethylrhodamine ethyl ester fluorescence as a marker of mitochondrial membrane potential we found that clotrimazole prevented the glutamate-induced loss of mitochondrial membrane potential. Our data provide evidence that the protective effect of clotrimazole against oxygen/glucose deprivation and excitotoxicity is due to the ability of this drug to partially block NMDA receptor-gated channel, thus causing both reduced calcium overload and lower probability of the mitochondrial potential collapse.

Animals↗
PubMed2001

Bifonazole modulates death of cultured cerebellar granular cells induced by glutamate and oxygen-glucose deprivation.

Treatment of cultured rat cerebellar granular cells with calmodulin antagonist bifonazole (10 mM) during oxygen-glucose deprivation or exposure to glutamate (75 mM) prevented neuronal death. However, addition of bifonazole after glutamate treatment promoted neuronal death. Calmodulin antagonists trifluoperazine and thioridazine had no protective effects, while thioridazine even potentiated the toxic effect of glutamate.

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

Neuroprotective properties of nootropic dipeptide GVS-111 in in vitro oxygen-glucose deprivation, glutamate toxicity and oxidative stress.

Argon anoxia and glucose deprivation were used for modeling of ischemic damage in the cultures of cerebellar granule cells. Protective effect of peptide piracetam analogue GVS-111 was demonstrated. GVS-111 prevented neurodegeneration induced by glutamate and oxidative stress. In contrast to GVS-111, piracetam did not attenuate neurocytotoxic effect of glutamate.

2-Amino-5-phosphonovalerate↗
PubMed1999

Induction of ischemic tolerance in rat cortical neurons by 3-nitropropionic acid: chemical preconditioning.

Sublethal ischemia leads to increased tolerance against subsequent ischemia. We investigated whether tolerance could also be elicited by mild respiratory-chain inhibition (chemical hypoxia) in a rat neuronal-cell enriched culture system. 3-Nitropropionic acid (3-NPA) caused a concentration-dependent inhibition of succinate-dehydrogenase. Two hours preconditioning with 3-NPA 24-48 h before oxygen-glucose deprivation (OGD) reduced neuronal damage morphologically and reduced lactate deydrogenase (LDH) release up to 72% compared to sham-treated sister cultures without 3-NPA. In an attempt to elucidate transcriptional mechanisms, we found no rapid translocation of the hypoxia-sensitive transcription factors N F-KB or hypoxia-inducible factor-I (HIF-I) at 3-NPA concentrations sufficient to trigger tolerance against OGD. In accordance to previous in vivo and brain slice data, we conclude that 3-NPA chemically induces tolerance against oxygen-glucose deprivation in vitro. However, the underlying mechanisms remain elusive.

Animals↗
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

Induction of tolerance in rat cortical neurons: hypoxic preconditioning.

Sublethal ischemia leads to increased tolerance against subsequent prolonged cerebral ischemia in vivo. In the present study we modeled preconditioning mechanisms in a neuronal-enriched culture. Damage was significantly reduced (up to 72%) with 1.5 h of oxygen-glucose deprivation 48-72 h before 3 h oxygen-glucose deprivation. Tolerance was also elicited by Na+-K+-ATPase inhibition. No damage was observed when astroglial or endothelial cells were exposed to hypoxia for 3 and 6 h, respectively. We conclude that hypoxic preconditioning is a robust neuronal phenomenon in vitro with a similar temporal pattern and selective cellular vulnerability as the ischemic tolerance phenomenon shown in vivo.

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↗