The Effect of Intranasal Administration of Gangliosides on the Viability of CA1 Hippocampal Neurons in Rat Two-Vessel Occlusion Model of Forebrain Ischemia/Reperfusion Injury.

Intranasal administration of total bovine brain gangliosides (6 mg/kg) to rats protected the CA1 hippocampal neurons from the death caused by two-vessel occlusion model (with hypotension) of forebrain ischemia/reperfusion injury. The immunohistochemical reaction of specific antibodies to marker proteins of activated microglia (Iba1) and astrocytes (GFAP) in hippocampal slices revealed the neuroprotective effect of exogenous gangliosides which can be mostly explained by their ability to suppress neuroinflammation and gliosis. The expression of neurotrophic factor BDNF in the CA1 region of hippocampus did not differ in sham-operated rats and animals exposed to ischemia/reperfusion. However, the administration of gangliosides increased the BDNF expression in both control and ischemic groups. The intranasal route of administration allows using lower concentrations of gangliosides preventing the death of hippocampal neurons.

Intranasal Administration of Insulin and Gangliosides Improves Spatial Memory in Rats with Neonatal Type 2 Diabetes Mellitus.

We analyzed the effects of intranasal administration of insulin (0.48 U/rat) and gangliosides (6 mg/kg) on spatial memory in rats with the neonatal model of the type 2 diabetes mellitus. The development of diabetes was verified by the glucose tolerance test. Insulin and gangliosides improved training and reversal training in diabetic rats in a modified version of Morris water maze test and reduced the time of finding the hidden platform. High effectiveness of intranasal administration of gangliosides to animals for the normalization of cognitive functions was shown for the first time. The effects of insulin and gangliosides were similar during training, but during reversal training, gangliosides were more effective. At the same time, intranasally administered insulin, unlike gangliosides, partially normalized glucose tolerance in rats with type 2 diabetes mellitus.

Insulin Increases Viability of Neurons in Rat Cerebral Cortex and Normalizes Bax/Bcl-2 Ratio under Conditions of Oxidative Stress.

We studied the protective effect of insulin in various concentrations and its effect on the Bax/ Bcl-2 ratio in neurons of rat cerebral cortex under conditions of oxidative stress. The protective effect of insulin was dose-dependent within the nanomolar range (1 nM<10 nM<100 nM). Preincubation with insulin in concentrations of 100 nM and 1 µM significantly increased Bcl-2 content in neurons in 5, 30, and 45 min and 1, 2, and 4 h after the start of cell exposure to H2O2. This prooxidant increased the Bax/Bcl-2 ratio in neurons to 141-164% in comparison with the control (100%); preincubation of neurons with insulin returned this ratio to normal.

Role of Protein Kinase Akt Activation in Protective Effect of Ganglioside GM1 on PC12 Cells Exposed to H2O2.

Micro- and nanomolar concentrations of ganglioside GM1 improved viability of neuronal PC12 cells under conditions of oxidative stress and reduced H2O2-induced ROS accumulation in these cells. These effects were more pronounced at micromolar concentrations. GM1 in concentrations of 100 nM and 10 µM significantly and substantially increased basal activity of protein kinase B (Akt) (the level of phosphorylated Akt form), but had virtually no effect on its expression in PC12 cells. In the presence of PI3K inhibitor LY294002 preventing protein kinase Akt activation, the protective effect of GM1 significantly decreased. These findings suggest that activation of protein kinase Akt by GM1 contributes to improvement of PC12 cell viability by this ganglioside.

[Antiapoptotic effect of gangliosides on PC12 cells exposed to bacterial lipopolysaccharide].

Lipopolysaccharide (LPS) from Escherichia coli of the 0111:B4 serotype was shown to exert the apoptotic effect on PC12 neuronal cells at concentrations of 0.1 and 0.125 mg/ml in DMEM (serum free medium). GD1a and GM1 gangliosides at a concentration of 100 µM were found to raise the PC12 cell viability and decrease the percentage of PC12 cells in the late apoptotic phase after exposure to LPS.

[Metabolic effects of ganglioside GM1 on PC12 cells at oxidative stress depend on modulation of activity of tyrosine kinase of trk receptor].

Evidence has been obtained that only GM1, but also other main brain gangliosides (GD1a, GD1b, and GT1b) increase viability of ells of the PC12 neuronal line submitted to action of H2O2. By the example of GM1 and GD1a, gangliosides have been shown to induce a protective effect when acting on PC12 cells under conditions of oxidative stress both at micro- and nanomolar concentrations that are physiological concentrations of gangliosides in cerebrospinal fluid. It has been shown for the first time that GM1 at nanomolar concentrations decrease the H2O2-induced formation of reactive oxygen species (ROS). It was found that in the presence of K-252a, an inhibitor of tyrosine kinase of Trk receptors, GM1 at concentrations of 10 microM and 10 nM lost the ability to increase viability of these cells under conditions of oxidative stress. The dependence of protective and metabolic effects of ganglioside GM 1 in PC 12 cells at action on them of H2O2 on modulation of activity of tyrosine kinase of Trk receptors (i. e., on the same signal system) agrees with concept of the essential role of the GM1 antioxidant effect in its increase of cell viability.

Α-tocopherol prevents ERK1/2 activation in PC12 cells under conditions of oxidative stress and its contribution to the protective effect.

Preincubation with 100 nM and 100 µM α-tocopherol for 18 h prevented long-term activation of extracellular signal-activated kinase (ERK1/2), induced by H2O2in PC12 cells. α-Tocopherol significantly reduced H2O2-induced death of PC12 cell, but its protective effect was significantly lower in the presence of ERK1/2 inhibitor. These data show that prevention of long-term activation of ERK1/2 by α-tocopherol contributes to the increase in viability of PC12 cells exposed to H2O2. This fact suggests that inhibition of ERK1/2 activity by α-tocopherol reduces neuronal cell death in the brain under conditions of oxidative stress in vivo.

[Protective effect of gangliosides against the toxic action of bacterial lipopolysaccharide of various serotypes on PC12 cells].

The effect of bacterial lipopolysaccharide (LPS) from E. coli on the viability of PC12 neuronal cell line was studied. LPS of 0111:B4 serotype and LPS of 055:B5 serotype were shown to have toxic effect on PC12 cells. But the toxic effect of LPS of 0127:B8 serotype was not revealed. Preincubation of PC12 cells with GM1 or GD1a gangliosides was found to diminish significantly the death of the cells and the formation of reactive oxygen species induced by LPS of 0111:B4 and 055:B5 serotypes in them. The protective effect of GM1 and GD1a was found not to depend on the presence of the inhibitor of Trk receptor tyrosine kinase in the medium, though activation of this protein kinase was previously shown to mediate the protective effect of gangliosides against the action of excitatory amino acids, pro-oxidants and other toxins on neurons and cells of neuronal cell lines. The protective effect of gangliosides against the LPS action on PC12 cells was similar to the effect of methyl-beta-cyclodextrin, which was shown to disturb cell membrane raft structure. The suggestion is put forward that the pronounced diminution of toxic effect of LPS on PC12 cells by gangliosides may be explained by the alteration of structural organization of lipid rafts caused by the incorporation of exogenous gangliosides in cell plasma membranes, which diminishes the translocation of TLR4 receptor into the rafts and their activation by LPS.

[Gangliosides GM1 and GD1a modulate inflammatory effect of bacterial lipopolysaccharide in epithelial cells].

It is known that exogenous gangliosides (GL) inhibit acute inflammatory signals in different cells induced by Escherichia coli lipopolysaccharide (LPS). Until now the mechanisms underlying their effect are unknown. We hypothesize that the anti-inflammatory effect of GL is caused by their ability to modify TLR4 translocation into the lipid rafts. To test this hypothesis, we studied the effect of exogenous GL on LPS-induced inflammatory reactions associated with increased nitric oxide and prostaglandin E2 (PGE2) production in epithelial cells isolated from the frog Rana temporia urinary bladder. It was shown that preincubation of cells with GM1 and GD1a in the concentration range from 100 nm to 50 µM reduced the effect of 25 µg/ml LPS E. coli on the increase of NO and PGE2 production. The effect of LPS was also eliminated in the presence of polymyxin B, capable to interact with lipid A in LPS molecule, which makes it inaccessible for binding to TLR4. The subcellular fractionation of epithelial cells in the sucrose density gradient in combination with immunoblotting revealed that LPS stimulates translocation of TLR4 into the lipid rafts in the cytoplasmic membrane. Preincubation of cells with GM1 or GD1a at concentration 20 µM completely eliminated the effect of LPS. A similar effect was revealed with 1 mM methyl-ß-cyclodextrin, a classical destructor of the lipid rafts. The results indicate the existence of a previously unknown mechanism of the anti-inflammatory effect of exogenous GL associated with their ability to interfere with LPS-induced translocation of TLR4 into the lipid rafts preventing LPS signal transduction. It is assumed that the observed effect of GL is based on their incorporation into cytoplasmic membrane and modification of the lipid rafts organization.

[Dependence of protective effect of alpha-tocopherol on its concentration and time of action on PC12 cell under conditions of oxidative stress].

At the short-term incubation (0.5 and 1.5 h) of cells of the PC12 neuronal line with alpha-tocopherol, its protective effect against the cytotoxic hydrogen peroxide action was increased with rise of its concentration in samples; the protection was practically absent at action of nanomolar antioxidant concentrations, but was well expressed at its micromolar concentrations. These data agree with the concept that alpha-tocopherol increases the cell living activity by reacting directly with free radicals, which leads to formation of the less reactive compounds deprived of non-paired electron. The evidence is obtained that at the long-term action on PC12 cells, alpha-tocopherol not only in micro-, but also in nanomolar concentrations increases statistically significantly the cell living activity under conditions of oxidative stress. As follows from the obtained data, an important role in realization of the alpha-tocopherol protective effect at the long-term incubation with it seems to be played by modulation by this antioxidant of activity of protein kinase activated by extracellular signaling, phosphatidylinosite 3-kinase, and protein kinase C.

[Antiapoptotic effect of alpha-tocopherol at micro- and nanomolar concentrations on cells of neuronal line PC12 according to data of flow cytometry].

By the method of flow cytometry it has been shown that alpha-tocopherol at micromolar concentrations produces antiapoptotic effect on the PC12 neuronal line cells exposed to the toxic agent hydrogen peroxide at various terms of incubation with it. At the same time, alpha-tocopherol at nanomolar concentrations had protective (antiapoptotic) effect only after the long (18 h) preincubation of the PC12 cells with it prior to exposure to hydrogen peroxide. This seems to indicate that the alpha-tocopherol effect at these concentrations is mediated by a signal transduction system.

[Role of tyrosine kinase of Trk-receptors in realization of antioxidant effect of ganglioside GM1 in PC12 cells].

Ganglioside GM1 has been shown to increase viability of PC12 cells at their induction of oxidative stress by hydrogen peroxide. However, in the presence of inhibitor of tyroxine kinase Trk-receptors K-252a this GM1 effect decreases or virtually disappears. To understand mechanism of the protective effect, there was studied action of H2O2, GM1, and inhibitor K-252a on formation of reactive oxygen species (ROS). It has been shown that ganglioside GM1 decreases significantly the H2O2-induced ROS accumulation in PC12 cells; however, in the presence of inhibitory of tyrosine kinase of Trk-receptors, this GM1 effect is not revealed. It has been found that inhibitors of each of protein kinases present at the signal realization stages following the stages of activation of tyrosine kinase Trk-receptors--Erk 1/2, PI3-kinases, and PKC, decreased the GM1 ability to reduce the H2O2-induced ROS accumulation, while in the combined use of inhibitors of these three protein kinases, the GM1 effect was completely absent. Thus, the ganglioside GM1 antioxidant effect on PC12 is mediated by activation of tyrosine kinase Trk-receptors and protein kinases perceiving signal from this enzyme.

[A decrease of neuroprotector effect of ganglioside GM1 on PC12 cells under conditions of oxidative stress in the presence of inhibitor of tyrosine kinase of Trk-receptors].

Effects of inhibitors of tyrosine kinases (K-252a, genistein) and of phospholipase A2 (bromophenacetyl bromide) on viability of PC12 cells are studied in the presence of hydrogen peroxide and ganglioside GM1. The degree of inhibition of hydrogen peroxide cytotoxic effect by ganglioside GM1 amounted to 52.8 +/- 4.3 %. However, in the presence in the medium of 0.1 and 1 microM inhibitors of tyrosine kinase of Trk-receptors (K-252a) it was as low as 32.7 +/- 6.5 % and 11.7 +/- 9.8 %, respectively. GM1 prevented Na+, K+-ATPase produced by H2O2, but in the presence of 1 microM K-252a this effect was practically not pronounced. In the presence of another inhibitor of tyrosine kinases--genistein, a tendency for a decrease of the GM1 protective effect was observed at its concentrations 0.1 and 1 microM, whereas at a higher concentration 10 microM genistein depressed the GM1 neuroprotective effect statistically significantly. It was found that inhibitor of phospholipase A2 bromophenacetyl bromide did not affect the action of GM1 aimed at increasing the viability of cells under action of hydrogen peroxide on them. It seems that this enzyme is not involved in the cascade of reactions participating in realization of the ganglioside protective effect. Thus, inhibitor of tyrosine kinase of Trk-receptors K-252 decreases or practically prevents the ganglioside GM1 neuroprotective effect of PC12 cells under stress conditions; the same ability is characteristic of genistein--an inhibitor of tyrosine kinases of the wider spectrum of action.

[PC12 cells transfected with human mutant gene causing one of Alzheimer's disease forms have a high sensitivity to oxidative stress].

Used in this work are PC12 cells transfected with human gene expressing amyloid precursor protein of beta-peptide and carrying the so-called "Swedish mutation" leading to the appearance of one Alzheimer's disease family forms. It has been shown that the PC12 cells transfected with this mutant gene, at action of various hydrogen peroxide concentrations, die to the significant greater degree than the used for comparison PC12 cells transfected with analogous human gene of the wild type or than vector-transfected cells. It has been found that ganglioside GM1 at micro- or nanomolar concentrations is able to increase viability of the PC12 cells transfected with the mutant gene causing a significant accumulation of endogenous amyloid beta-peptide. The obtained data confirm an important role of oxidative stress in injury and death of brain nerve cells in Alzheimer's disease.

[Effects of oxidative stress inducers, neurotoxins, and ganglioside GM1 on Na+, K+-ATPase in PC12 and brain synaptosomes].

To elucidate mechanism of ganglioside neuroprotection, it is important to study their metabolic effects, specifically of action on Na+, K+ -ATPase. It has been shown that under effect of oxidative stress inductors and neurotoxins an oxidative inactivation of this enzyme takes place in PC12 cells and brain cortex synaptosomes, this inactivation being able to be prevented or decreased by ganglioside GM1. Thus, for instance, 24 h after action of 1 mM H2O2, activity of Na+, K+ -ATPase in PC12 cells decreased more than twice. However, in the case of preincubation of the cells with ganglioside GM1 prior to the H2O2 action this enzyme activity did not differ statistically significantly from control. Ganglioside GM1 also was able to increase significantly the enzyme activity decreased by action on the PC12 cells of amyloid beta-peptide (AP) causing lesion of neurons in Alzheimer's disease and at low H202 concentrations. Experiments on brain cortex synaptosomes have established that not only antioxidants--alpha-tocopherol and superoxide dismutase--but also ganglioside GM1 prevent the glutamateproduced Na+, K+ -ATPase oxidative inactivation. The obtained data agree with a suggestion that the ganglioside neuroprotective effect at action on nerve cells of such toxins as Abeta, glutamate or reactive oxygen species is due to their ability to inhibit the free-radical reactions.

Different metabolic effects of ganglioside GM1 in brain synaptosomes and phagocytic cells.

The metabolic effects of ganglioside GM1 were found to be quite different in brain synaptosomes and phagocytic cells. Incubation of rat brain cortex synaptosomes with GM1 was shown to decrease the production of reactive oxygen species induced by Fe2+-H2O2 system and measured by chemiluminometric method in the presence of luminol. Gangliosides GM1, GD1a, and GT1b significantly diminished the induced accumulation of lipid peroxidation product in brain synaptosomes, but protein kinase inhibitor (polymyxin B) abolished this effect. Incubation with antioxidants or GM1 significantly diminished the increase of 45Ca2+ influx and oxidative inactivation of Na+,K+-ATPase in brain synaptosomes exposed to glutamate, the effect of GM1 was concentration-dependent in the range 10(-11)-10(-8) M. But the incubation of human neutrophils and mouse peritoneal macrophages with 10(-11)-10(-10) M GM1, on the contrary, increased several times the luminol-dependent chemiluminescence response of these cells to activation by low concentrations of 12-myristate-13-acetate phorbol ester. The opposite effects of GM1 in the nerve endings and phagocytic cells seem to be protective in both cases as the inhibition of reactive oxygen species production in the nerve cells may enhance their viability in damaged brain, while the intensification of their production in phagocytic cells may promote the resistance of organism to infection.