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.

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.

[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.

[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.

[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.

[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.

Gangliosides and neutral glycosphingolipids of normal tissue and oat cell carcinoma of human lung.

Concentration and composition of gangliosides and neutral glycosphingolipids of adult human lung, and lung small cell carcinoma were studied. The structures of the glycolipids were determined by quantitative component determination, enzymic degradation, permethylation and fast atom bombardment mass spectrometry. Adult human lung contained mainly gangliosides with lactosylceramide as the basic core, GM3, GD3 and GT3, and approx. equal proportions (10%) of gangliosides of the gangliotetraosyl- and lactotetraosylceramide series. 18 gangliosides with different carbohydrate moieties were identified: four of them were only found in the tumor tissue. The adult human lung contained 85 nmol (77-120) gangliosides and 140 nmol neutral glycosphingolipids per g wet weight. Globoside was the major neutral glycolipid and there were only minor amounts of glycolipids of the lactotetraose series. In small cell carcinoma tissue the concentration of neutral glycosphingolipids was approximately twice as high than in normal lung tissue, and there was a markedly larger concentration of both lactosylceramide and glycolipids of the lactotetraose series and fucose derivatives of these. The concentration of gangliosides varied between 202 and 415 nmol per g wet weight. Compared to normal lung tissue, the tumor tissue had a lower proportion of GD3, and a higher proportion of complex gangliosides, and they contained five tumor-associated gangliosides: Fuc-GM1, Fuc-GD1b, 3'-LM1, Fuc-3'-LM1 and 6'-nLM1.

Ganglioside-dependent factor, inhibiting lipid peroxidation in rat brain synaptosomes.

Preincubation of rat brain synaptosomes with GM1, GD1a or GT1b (10(-10)-10(-6) M), as well as with phorbol 12-myristate, 13-acetate (10(-10)-10(-6) M) was found to have dose dependent inhibitory effect on Fe(2+)-ascorbate induced lipid peroxidation, while penetrating analogue of c-AMP markedly decreased the inhibitory effect of these compounds. In liposomes made of lipids isolated from synaptosomal membranes the degree of inhibition of induced LPO by gangliosides was practically absent. The inhibitory effect of GM1 on lipid peroxidation could not be revealed after thermal denaturation of synaptosomes or after treatment with polymyxin B (inhibitor of lipid-dependent protein kinases). These results and some other data provide evidence for the existence of ganglioside-dependent factor inhibiting lipid peroxidation in brain tissue. It may be suggested to be a protein kinase modulated by gangliosides.

Study of brain and vascular plexus gangliosides in meningoencephalitis of various etiology.

The content of brain and vascular plexus gangliosides and their composition have been studied in 15 cases of meningoencephalitis of various etiology and degree of disease. The most pronounced decrease of ganglioside concentration was found in brain of children, who died from herpes virus infection. Decrease of ganglioside content was revealed in brain grey matter of patients with influenza virus or meningococcus infection, but not in cases of mycoplasma infection. These data provide evidence of nerve cell destruction due to meningoencephalitis of various etiology. The biochemical data obtained are in good agreement with the results of the brain of children infection by herpes virus (increase of GD1b content in grey matter). Ganglioside content in vascular plexes of patients with meningoencephalitis was found to be, on the contrary, much higher (ca 4 times) than in the controls. The higher the lesion of choroid plexes in meningoencephalitis is, the higher the ganglioside content in them is.

The effect of cold stress on ganglioside fatty acid composition and ganglioside-bound sialic acid content of rat brain subcellular fractions.

The effect of cold stress on the ganglioside fatty acid composition and sialic acid content of brain subcellular fractions and homogenate of rats was studied, the animals were kept in a cold room with 12h light-dark cycles at 3 and 10 degrees C for 2 weeks. (1) The rat brain homogenate, synaptosomes and myelin of rats exposed to 3 degrees C contained significantly higher amounts of ganglioside-bound sialic acid per mg of protein than these fractions of control rats kept at 23 degrees C; the differences were less pronounced in rats exposed to 10 degrees C. (2) A small, but significant, diminution of relative palmitic acid content and an increase of stearic acid content was found to take place in gangliosides from rat brain synaptosomes, synaptosomal plasma membranes and homogenate as a result of the exposure of animals to 3 degrees C and to a lesser extent to 10 degrees C. (3) The content of unsaturated fatty acids in gangliosides from brain subcellular fractions was approximately the same in cold exposed and control rats.

The use of antioxidants to prevent glutamate-induced derangement of calcium ion metabolism in rat cerebral cortex synaptosomes.

Glutamate is shown to induce increases in intracellular Ca2+ concentrations ([Ca2+]i), increases in 45Ca2+ influx, decreases in the activity of Na+,K+-ATPase activity, and activation of the Na+/Ca2+ exchanger in rat cerebral cortex synaptosomes. NMDA receptor antagonists virtually prevented these effects. Preincubation of synaptosomes with alpha-tocopherol, superoxide dismutase, and ganglioside GM1 normalized [Ca2+]i, 45Ca2+ influx, and Na+,K+-ATPase activity in rat cerebral cortex synaptosomes exposed to glutamate. Glutamate and GM1 activated the Na+/K+ exchanger, and their effects were additive. Calcium ions entering cerebral cortex nerve cells via NMDA receptors during exposure to high glutamate concentrations appeared to be only the trigger for the processes activating free-radical reactions. Activation of these reactions led to increases in Ca2+ influx into cells, decreases in Na+,K+-ATPase activity, and significant increases in [Ca2+]i, though this could be prevented by antioxidants and gangliosides.