GM1 ganglioside attenuates convulsions and thiobarbituric acid reactive substances production induced by the intrastriatal injection of methylmalonic acid

Ganglioside GM1 and the Central Nervous System

GM1 is one of the major glycosphingolipids (GSLs) on the cell surface in the central nervous system (CNS). Its expression level, distribution pattern, and lipid composition are dependent upon cell and tissue type, developmental stage, and disease state, which suggests a potentially broad spectrum of functions of GM1 in various neurological and neuropathological processes. The major focus of this review is the roles that GM1 plays in the development and activities of brains, such as cell differentiation, neuritogenesis, neuroregeneration, signal transducing, memory, and cognition, as well as the molecular basis and mechanisms for these functions. Overall, GM1 is protective for the CNS. Additionally, this review has also examined the relationships between GM1 and neurological disorders, such as Alzheimer's disease, Parkinson's disease, GM1 gangliosidosis, Huntington's disease, epilepsy and seizure, amyotrophic lateral sclerosis, depression, alcohol dependence, etc., and the functional roles and therapeutic applications of GM1 in these disorders. Finally, current obstacles that hinder more in-depth investigations and understanding of GM1 and the future directions in this field are discussed.

The Neuroprotective Effect of GM-1 Ganglioside on the Amyloid-Beta-Induced Oxidative Stress in PC-12 Cells Mediated by Nrf-2/ARE Signaling Pathway

Alzheimer's disease (AD) is characterized by the accumulation of amyloid-β (Aβ) plaques, tau tangles, neuroinflammation, oxidative stress, and progressive memory deficits. Aβ deposition could exacerbate oxidative damage and cellular apoptosis. GM-1 ganglioside (GM-1) has previously been reported to exhibit neuroprotective effects in rodents and patients with AD. However, the substantial impacts and mechanism of GM-1 on Aβ-induced oxidative stress remain elusive. The present study used PC-12 pheochromocytoma cells treated with Aβ_25-35 peptide to construct the AD model in vitro. Aβ_25-35 administration alone inhibited cell viability and facilitated cell apoptosis in the range doses of 10 μM to 30 μM. At the same time, GM-1 supplementation promoted cell proliferation and rescued cell apoptosis in a dose-dependent fashion ranging from 5 to 30 μM. In parallel, GM-1 treatment alleviated Aβ-induced oxidative stress by increasing the level of antioxidant enzymes and decreasing the content of malondialdehyde (MDA). The nuclear factor-E2-related factor 2 (Nrf2) is a crucial mediator of antioxidant response. We reported herein that GM-1 could activate Nrf-2 in the PC-12 cells co-treated with Aβ_25-35, following with the activated expression of antioxidant response elements (ARE)-mediated antioxidant and detoxifying genes. Consistently, knock-down of Nrf-2 via siRNA abolished the beneficial decrease of Aβ-induced oxidative stress by GM-1 treatment, indicating that GM-1-improved oxidative stress was regulated by the Nrf-2 signaling pathway. Collectively, GM-1 could alleviate Aβ_25-35-induced oxidative damage mediated through the Nrf-2/ARE signaling pathway, which might be a potential agent for AD treatment.

Pathophysiology of propionic and methylmalonic acidemias. Part 2: Treatment strategies

Despite realizing increased survival rates for propionic acidemia (PA) and methylmalonic acidemia (MMA) patients, the current therapeutic regimen is inadequate for preventing or treating the devastating complications that still can occur. The elucidation of pathophysiology of these complications allows us to evaluate and rethink treatment strategies. In this review we display and discuss potential therapy targets and we give a systematic overview on current, experimental and unexplored treatment strategies in order to provide insight in what we have to offer PA and MMA patients, now and in the future. Evidence on the effectiveness of treatment strategies is often scarce, since none were tested in randomized clinical trials. This raises concerns, since even the current consensus on best practice treatment for PA and MMA is not without controversy. To attain substantial improvements in overall outcome, gene, mRNA or enzyme replacement therapy is most promising since permanent reduction of toxic metabolites allows for a less strict therapeutic regime. Hereby, both mitochondrial-associated and therapy induced complications can theoretically be prevented. However, the road from bench to bedside is long, as it is challenging to design a drug that is delivered to the mitochondria of all tissues that require enzymatic activity, including the brain, without inducing any off-target effects. To improve survival rate and quality of life of PA and MMA patients, there is a need for systematic (re-)evaluation of accepted and potential treatment strategies, so that we can better determine who will benefit when and how from which treatment strategy.

Methylmalonate Induces Inflammatory and Apoptotic Potential: A Link to Glial Activation and Neurological Dysfunction

Methylmalonic acid (MMA) accumulates in tissues in methylmalonic acidemia, a heterogeneous group of inherited childhood diseases characterized by neurological dysfunction, oxidative stress and neuroinflammation; it is associated with degeneration of striatal neurons and cerebral cortical atrophy. It is presently unknown, however, whether transient exposure to MMA in the neonatal period is sufficient to trigger inflammatory and apoptotic processes that lead to brain structural damage. Here, newborn mice were given a single intracerebroventricular dose of MMA at 12 hours after birth. Maze testing of 21- and 40-day-old mice showed that MMA-injected animals exhibited deficit in the working memory test but not in the reference test. MMA-injected mice showed increased levels of the reactive oxygen species marker 2',7'-dichlorofluorescein diacetate, tumor necrosis factor, interleukin-1β, caspases 1, 3, and 8, and increased acetylcholinesterase activity in the cortex, hippocampus and striatum. This was associated with increased astrocyte and microglial immunoreactivity in all brain regions. These findings suggest that transient exposure to MMA may alter the redox state and cause neuroinflammatory/apoptotic processes and glial activation during critical periods of brain development. Similar processes may underlie brain dysfunction and cognitive impairment in patients with methylmalonic acidemia.

Monosialoganglioside-Containing Nanoliposomes Restore Endothelial Function Impaired by AL Amyloidosis Light Chain Proteins

BACKGROUND

Light chain amyloidosis (AL) is associated with high mortality, especially in patients with advanced cardiovascular involvement. It is caused by toxicity of misfolded light chain proteins (LC) in vascular, cardiac, and other tissues. There is no treatment to reverse LC tissue toxicity. We tested the hypothesis that nanoliposomes composed of monosialoganglioside, phosphatidylcholine, and cholesterol (GM1 ganglioside-containing nanoliposomes [NLGM1]) can protect against LC-induced human microvascular dysfunction and assess mechanisms behind the protective effect.

METHODS AND RESULTS

The dilator responses of ex vivo abdominal adipose arterioles from human participants without AL to acetylcholine and papaverine were measured before and after exposure to LC (20 μg/mL) with or without NLGM1 (1:10 ratio for LC:NLGM1 mass). Human umbilical vein endothelial cells were exposed for 18 to 20 hours to vehicle, LC with or without NLGM1, or NLGM1 and compared for oxidative and nitrative stress response and cellular viability. LC impaired arteriole dilator response to acetylcholine, which was restored by co-treatment with NLGM1. LC decreased endothelial cell nitric oxide production and cell viability while increasing superoxide and peroxynitrite; these adverse effects were reversed by NLGM1. NLGM1 increased endothelial cell protein expression of antioxidant enzymes heme oxygenase 1 and NAD(P)H quinone dehydrogenase 1 and increased nuclear factor, erythroid 2 like 2 (Nrf-2) protein. Nrf-2 gene knockdown reduced antioxidant stress response and reversed the protective effects of NLGM1.

CONCLUSIONS

NLGM1 protects against LC-induced human microvascular endothelial dysfunction through increased nitric oxide bioavailability and reduced oxidative and nitrative stress mediated by Nrf-2-dependent antioxidant stress response. These findings point to a potential novel therapeutic approach for light chain amyloidosis.

2-Methylcitric acid impairs glutamate metabolism and induces permeability transition in brain mitochondria

Accumulation of 2-methylcitric acid (2MCA) is observed in methylmalonic and propionic acidemias, which are clinically characterized by severe neurological symptoms. The exact pathogenetic mechanisms of brain abnormalities in these diseases are poorly established and very little has been reported on the role of 2MCA. In the present work we found that 2MCA markedly inhibited ADP-stimulated and uncoupled respiration in mitochondria supported by glutamate, with a less significant inhibition in pyruvate plus malate respiring mitochondria. However, no alterations occurred when α-ketoglutarate or succinate was used as respiratory substrates, suggesting a defect on glutamate oxidative metabolism. It was also observed that 2MCA decreased ATP formation in glutamate plus malate or pyruvate plus malate-supported mitochondria. Furthermore, 2MCA inhibited glutamate dehydrogenase activity at concentrations as low as 0.5 mM. Kinetic studies revealed that this inhibitory effect was competitive in relation to glutamate. In contrast, assays of osmotic swelling in non-respiring mitochondria suggested that 2MCA did not significantly impair mitochondrial glutamate transport. Finally, 2MCA provoked a significant decrease in mitochondrial membrane potential and induced swelling in Ca(2+)-loaded mitochondria supported by different substrates. These effects were totally prevented by cyclosporine A plus ADP or ruthenium red, indicating induction of mitochondrial permeability transition. Taken together, our data strongly indicate that 2MCA behaves as a potent inhibitor of glutamate oxidation by inhibiting glutamate dehydrogenase activity and as a permeability transition inducer, disturbing mitochondrial energy homeostasis. We presume that 2MCA-induced mitochondrial deleterious effects may contribute to the pathogenesis of brain damage in patients affected by methylmalonic and propionic acidemias. We propose that brain glutamate oxidation is disturbed by 2-methylcitric acid (2MCA), which accumulates in tissues from patients with propionic and methylmalonic acidemias because of a competitive inhibition of glutamate dehydrogenase (GDH) activity. 2MCA also induced mitochondrial permeability transition (PT) and decreased ATP generation in brain mitochondria. We believe that these pathomechanisms may be involved in the neurological dysfunction of these diseases.

GM1 ganglioside activates ERK1/2 and Akt downstream of Trk tyrosine kinase and protects PC12 cells against hydrogen peroxide toxicity

Ganglioside GM1 at micro- and nanomolar concentrations was shown to increase the viability of pheochromocytoma PC12 cells exposed to hydrogen peroxide and diminish the accumulation of reactive oxygen species and oxidative inactivation of Na(+),K(+)-ATPase, the effects of micromolar GM1 being more pronounced than those of nanomolar GM1. These effects of GM1 were abolished by Trk receptor tyrosine kinase inhibitor and diminished by MEK1/2, phosphoinositide 3-kinase and protein kinase C inhibitors. Hydrogen peroxide activates Trk tyrosine kinase; Akt and ERK1/2 are activated downstream of this protein kinase. GM1 was found to activate Trk receptor tyrosine kinase in PC12 cells. GM1 (100 nM and 10 µM) increased the basal activity of Akt, but did not change Akt activity in cells exposed to hydrogen peroxide. Basal ERK1/2 activity in PC12 cells was increased by GM1 at a concentration of 10 µM, but not at nanomolar concentrations. Activation of ERK1/2 by hydrogen peroxide was enhanced by GM1 at a concentration of 10 µM and to a lesser extent at a concentration of 100 nM. Thus, the protective and metabolic effects of GM1 ganglioside on PC12 cells exposed to hydrogen peroxide appear to depend on the activation of Trk receptor tyrosine kinase and downstream activation of Akt and ERK1/2.

Disruption of redox homeostasis and brain damage caused in vivo by methylmalonic acid and ammonia in cerebral cortex and striatum of developing rats

Hyperammonemia is a common finding in children with methylmalonic acidemia and propionic acidemia, but its contribution to the development of the neurological symptoms in the affected patients is poorly known. Considering that methylmalonic acid (MMA) and propionic acid (PA) predominantly accumulate in these disorders, we investigated the effects of hyperammonemia induced by urease treatment in 30-day-old rats receiving an intracerebroventricular (ICV) injection of MMA or PA on important parameters of redox homeostasis in cerebral cortex and striatum. We evaluated glutathione (GSH) concentrations, sulfhydryl content, nitrate and nitrite concentrations, 2',7'-dichlorofluorescein (DCFH) oxidation, and the activity of antioxidant enzymes. MMA decreased GSH concentrations and sulfhydryl content and increased nitrate and nitrite concentrations in cerebral cortex and striatum from hyperammonemic rats, whereas MMA or ammonia per se did not alter these parameters. MMA plus hyperammonemia also decreased glutathione reductase activity in rat cerebral cortex, but did not affect catalase, superoxide dismutase and glutathione peroxidase activities, neither DCFH oxidation. Furthermore, ICV PA administration alone or combined with hyperammonemia did not alter any of the evaluated parameters. We also found that pre-treatment with antioxidants prevented GSH reduction and sulfhydryl oxidation, whereas N(ω)-nitro-L-arginine methyl ester (L-NAME) prevented the increased nitrate and nitrite concentrations provoked by MMA plus ammonia treatments. Histological alterations, including vacuolization, ischemic neurons, and pericellular edema, were observed in brain of hyperammonemic rats injected with MMA. The data indicate a synergistic effect of MMA and ammonia disturbing redox homeostasis and causing morphological brain abnormalities in rat brain.

L-carnitine supplementation as a potential antioxidant therapy for inherited neurometabolic disorders

In recent years increasing evidence has emerged suggesting that oxidative stress is involved in the pathophysiology of a number of inherited metabolic disorders. However the clinical use of classical antioxidants in these diseases has been poorly evaluated and so far no benefit has been demonstrated. l-Carnitine is an endogenous substance that acts as a carrier for fatty acids across the inner mitochondrial membrane necessary for subsequent beta-oxidation and ATP production. Besides its important role in the metabolism of lipids, l-carnitine is also a potent antioxidant (free radical scavenger) and thus may protect tissues from oxidative damage. This review addresses recent findings obtained from patients with some inherited neurometabolic diseases showing that l-carnitine may be involved in the reduction of oxidative damage observed in these disorders. For some of these diseases, reduced concentrations of l-carnitine may occur due to the combination of this compound to the accumulating toxic metabolites, especially organic acids, or as a result of protein restricted diets. Thus, l-carnitine supplementation may be useful not only to prevent tissue deficiency of this element, but also to avoid oxidative damage secondary to increased production of reactive species in these diseases. Considering the ability of l-carnitine to easily cross the blood-brain barrier, l-carnitine supplementation may also be beneficial in preventing neurological damage derived from oxidative injury. However further studies are required to better explore this potential.

Mitochondrial energy metabolism in neurodegeneration associated with methylmalonic acidemia

Methylmalonic acidemia is one of the most prevalent inherited metabolic disorders involving neurological deficits. In vitro experiments, animal model studies and tissue analyses from human patients suggest extensive impairment of mitochondrial energy metabolism in this disease. This review summarizes changes in mitochondrial energy metabolism occurring in methylmalonic acidemia, focusing mainly on the effects of accumulated methylmalonic acid, and gives an overview of the results found in different experimental models. Overall, experiments to date suggest that mitochondrial impairment in this disease occurs through a combination of the inhibition of specific enzymes and transporters, limitation in the availability of substrates for mitochondrial metabolic pathways and oxidative damage.

Experimental evidence that methylmalonic acid provokes oxidative damage and compromises antioxidant defenses in nerve terminal and striatum of young rats

Methylmalonic acidemia and propionic acidemia are organic acidemias biochemically characterized by predominant tissue accumulation of methylmalonic acid (MMA) and propionic acid (PA), respectively. Affected patients present predominantly neurological symptoms, whose pathogenesis is not yet fully established. In the present study we investigated the in vitro effects of MMA and PA on important parameters of lipid and protein oxidative damage and on the production of reactive species in synaptosomes from cerebrum of developing rats. Synaptosomes correspond to nerve terminals that have been used to investigate toxic properties of compounds on neuronal cells. The in vivo effects of intrastriatal injection of MMA and PA on the same parameters and on enzymatic antioxidant defenses, were also studied. MMA-induced in vitro and in vivo lipid peroxidation and protein oxidative damage. Furthermore, the lipid oxidative damage was attenuated or prevented, pending on the doses utilized, by the free radical scavengers α-tocopherol, melatonin and by the NMDA glutamate receptor antagonist MK-801, implying the involvement of reactive species and glutamate receptor activation in these effects. In addition, 2',7'-dichlorofluorescein diacetate oxidation was significantly increased in synaptosomes by MMA, reinforcing that reactive species generation is elicited by this organic acid. We also verified that glutathione peroxidase activity was inhibited by intrastriatal MMA injection. In contrast, PA did not induce any significant effect on all parameters examined in vitro and in vivo, implying a selective action for MMA. The present data demonstrate that oxidative stress is induced by MMA in vitro in nerve terminals and in vivo in striatum, suggesting the participation of neuronal cells in MMA-elicited oxidative damage.

Nitric oxide and potassium channels mediate GM1 ganglioside-induced vasorelaxation

Monosialotetrahexosylganglioside (GM1) is a glycosphingolipid present in most cell membranes that displays antioxidant and neuroprotective properties. It has been recently described that GM1 induces pial vessel vasodilation and increases NO( x ) content in cerebral cortex, which are fully prevented by the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME). However, it is not known whether GM1 relaxes larger vessels, as well as the mechanisms by which GM1 causes vasorelaxation. In this study, we demonstrate that GM1 (10, 30, 100, 300 microM, 1 and 3 mM) induces vascular relaxation determined by isometric tension studies in rat mesenteric artery rings contracted with 1 microM phenylephrine. The vasorelaxation induced by GM1 was abolished by endothelium removal, by incubation with L-NAME (1 microM), and partially inhibited by the blockade of potassium channels by 1 mM tetraethylammonium, 10 microM glibenclamide, by the soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-alpha]quinoxalin-1-one (10 microM), and by 50 nM charybdotoxin, a blocker of large and intermediate conductance calcium-activated potassium channels. Moreover, GM1-induced relaxation was not affected by apamin (50 nM), a small conductance calcium-activated potassium channel blocker. The results indicate that direct and indirect nitric oxide pathways play a pivotal role in vasorelaxation induced by GM1, which is mediated mainly by potassium channels activation. We suggest that vasodilation may underlie some of the biological effects of exogenous GM1 ganglioside.

Profiling of oxidative stress in patients with inborn errors of metabolism

Free radical formation resulting in oxidative stress is a hallmark of mitochondrial dysfunction. Indeed, oxidative stress has been demonstrated to be an underlying pathophysiologic process in various inborn errors of metabolism. Metabolic profiling of oxidative stress may provide a non-specific measure of disease activity that may further enable physicians to monitor disease. In the present study, we investigated two markers of oxidative damage in urinary samples from IEM subjects and controls: F-2 isoprostanes, a measure of lipid peroxidation and di-tyrosine, a measure of protein oxidation. We also determined urinary antioxidant activity in these samples. Subsets of IEM patients showed significantly higher levels of the damage markers isoprostanes and di-tyrosine. Of note, patients with cobalamin disorders (i.e., CblB and CblC) consistently had the highest levels of oxidative damage markers. Lower urine antioxidant capacity was seen in all subject categories, particularly cobalamin disorders and propionic acidemia. Longitudinal studies in subjects with MSUD showed good concordance between markers of oxidative damage and acute decompensation. Overall, quantifying oxidative stress offers a unique perspective to IEM. These measures may provide a means of addressing mitochondrial function in IEM and aid in the development of therapeutic targets and clinical monitoring in this diverse set of disorders.

Protective and antioxidative effects of GM1 ganglioside in PC12 cells exposed to hydrogen peroxide are mediated by Trk tyrosine kinase

GM1 ganglioside was found to increase the survival of PC12 cells exposed to H(2)O(2), its action was blocked by Trk tyrosine kinase inhibitor K-252a. Thus, the inhibition of H(2)O(2) cytotoxic action by GM1 constituted 52.8 +/- 4.3%, but in the presence of 1.0 microM K-252a it was only 11.7 +/- 10.8%, i.e. the effect of GM1 became insignificant. Exposure to GM1 markedly reduced the increased accumulation of reactive oxygen species (ROS) and diminished the inactivation of Na(+),K(+)-ATPase induced in PC12 cells by H(2)O(2), but in the presence of K-252a GM1 did not change these metabolic parameters. The inhibitors of extracellular signal-regulated protein kinase, phosphatidyl inositol 3-kinase and protein kinase C decreased the effects of GM1. A combination of these protein kinase inhibitors reduced inhibition of H(2)O(2) cytotoxic action by GM1 to the larger extent than each of the inhibitors and practically abolished the ability of GM1 to decrease H(2)O(2)-induced ROS accumulation. The protective and antioxidative effects of GM1 in PC12 cells exposed to H(2)O(2) appear to be mediated by activation of Trk receptor tyrosine kinase and the protein kinases downstream from this enzyme.

Monosialoganglioside Increases Catalase Activity in Cerebral Cortex of Rats

Monosialoganglioside (GM1) is a neuroprotective agent that has been reported to scavenge free radicals generated during reperfusion and to protect receptors and enzymes from oxidative damage. However, only a few studies have attempted to investigate the effects of GM1 on enzymatic antioxidant defenses of the brain. In the present study, we evaluate the effects of the systemic administration of GM1 on the activity of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px), and on spontaneous chemiluminescence and total radical-trapping potential (TRAP) in cerebral cortex of rats ex vivo. The effects of GM1 on CAT activity and spontaneous chemiluminescence in vitro were also determined. Animals received two injections of GM1 (50 mg/kg, i.p.) or saline (0.85% NaCl, i.p.) spaced 24 h apart. Thirty minutes after the second injection the animals were sacrificed and enzyme activities and spontaneous chemiluminescence and TRAP were measured in cell-free homogenates. GM1 administration reduced spontaneous chemiluminescence and increased catalase activity ex vivo, but had no effect on TRAP, SOD or GSH-Px activities. GM1, at high concentrations, reduced CATactivity in vitro. We suggest that the antioxidant activity of GM1 ganglioside in the cerebral cortex may be due to an increased catalase activity.

Methylmalonate-induced seizures are attenuated in inducible nitric oxide synthase knockout mice

Methylmalonic acidemias consist of a group of inherited neurometabolic disorders caused by deficiency of methylmalonyl-CoA mutase activity clinically and biochemically characterized by neurological dysfunction, methylmalonic acid (MMA) accumulation, mitochondrial failure and increased reactive species production. Although previous studies have suggested that nitric oxide (NO) plays a role in the neurotoxicity of MMA, the involvement of NO-induced nitrosative damage from inducible nitric oxide synthase (iNOS) in MMA-induced seizures are poorly understood. In the present study, we showed a decrease of time spent convulsing induced by intracerebroventricular administration of MMA (2 micromol/2 microL; i.c.v.) in iNOS knockout (iNOS(-/-)) mice when compared with wild-type (iNOS(+/+)) littermates. Visual analysis of electroencephalographic recordings (EEG) showed that MMA injection induced the appearance of high-voltage synchronic spike activity in the ipsilateral cortex which spreads to the contralateral cortex while quantitative electroencephalographic analysis showed larger wave amplitude during MMA-induced seizures in wild-type mice when compared with iNOS knockout mice. We also report that administration of MMA increases NOx (NO(2) plus NO(3) content) and 3-nitrotyrosine (3-NT) levels in a greater extend in iNOS(+/+) mice than in iNOS(-/-) mice, indicating that NO overproduction and NO-mediated damage to proteins are attenuated in iNOS knockout mice. In addition, the MMA-induced decrease in Na(+), K(+)-ATPase activity, but not in succinate dehydrogenase (SDH) activity, was less pronounced in iNOS(-/-) when compared with iNOS(+/+) mice. These results reinforce the assumption that metabolic collapse contributes for the secondary toxicity elicited by MMA and suggest that oxidative attack by NO derived from iNOS on selected target such as Na(+), K(+)-ATPase enzyme might represent an important role in this excitotoxicity induced by MMA. Therefore, these results may be of value in understating the pathophysiology of the neurological features observed in patients with methylmalonic acidemia and in the development of new strategies for treatment of these patients.

Creatine decreases convulsions and neurochemical alterations induced by glutaric acid in rats

Glutaric acidemia type I (GA-I) is an inherited metabolic disease characterized by striatal degeneration, seizures, and accumulation of glutaric acid (GA). Considering that GA impairs energy metabolism and induces reactive species generation, we investigated whether the acute administration of creatine, an amino acid with antioxidant and ergogenic properties, protects against the seizures and neurochemical alterations (inhibition of Na(+),K(+)-ATPase and increased protein carbonylation) induced by the intrastriatal injection of GA (4 micromol/striatum). We also investigated whether creatine protected against the GA-induced inhibition of glutamate uptake in vitro. Creatine administration (300 mg/kg, p.o.) decreased seizures (evidenced by electrographic changes), protein carbonylation and Na(+),K(+)-ATPase inhibition induced by GA. However, creatine, at a dose capable of fully preventing GA-induced protein carbonylation (50 and 150 mg/kg, p.o.), did not prevent convulsions and Na(+),K(+)-ATPase inhibition, suggesting that the anticonvulsant activity of creatine in this experimental model is not related to its antioxidant action. Creatine also protected against the GA-induced inhibition of l-[(3)H]glutamate uptake in synaptosomes, suggesting that creatine may reduce the deleterious effects of GA by maintaining glutamate uptake in the synaptic cleft. Therefore, considering that creatine significantly attenuates the deleterious effects of GA assessed by behavioral and neurochemical measures, it is plausible to propose the use of this amino acid as an adjuvant therapy in the management of glutaric acidemia.

GM1 ganglioside induces vasodilation and increases catalase content in the brain

Monosialoganglioside (GM1) is a glycosphingolipid present in most cell membranes that displays antioxidant and neuroprotective properties. GM1 increases catalase activity in cerebral cortices in vivo, but the mechanisms underlying this effect of GM1 are not known. In the current study we investigated the effect of GM1 (50 mg/kg, ip) on the content of hemoglobin and catalase activity of hippocampus, cortex, and striatum of rats. GM1 administration increased catalase activity and hemoglobin content in brain samples after 30 min, but had no effect on blood catalase activity. GM1-induced increase in catalase activity was abolished by brain perfusion with heparinized saline. Brain catalase activity in the absence of blood, estimated by regression analysis of data from perfused and nonperfused animals, was not altered by the systemic injection of GM1. Moreover, the addition of GM1 (30 or 100 microM) did not increase catalase activity in slices of cerebral cortex in situ, further suggesting that blood circulation is required for this effect. The GM1-induced vasodilation was confirmed in vivo, because the systemic injection of GM1 (50 mg/kg, ip) increased (1.2-1.6 times) the width of pial vessels.

Erythrocyte glutathione peroxidase activity and plasma selenium concentration are reduced in maple syrup urine disease patients during treatment

Maple syrup urine disease (MSUD) is an inherited disorder caused by a deficiency of the branched-chain alpha-keto acid dehydrogenase complex activity. In the present study we evaluated selenium levels in plasma from MSUD patients at diagnosis and under treatment and the activities of glutathione peroxidase, catalase and superoxide dismutase in erythrocytes from treated patients. We verified that MSUD patients present a significant selenium deficiency at diagnosis, which becomes more pronounced during treatment, as well as a decrease of erythrocyte glutathione peroxidase activity during treatment. In contrast, erythrocyte catalase and superoxide dismutase activities were not altered in these patients. Our present results suggest that the reduction of an important antioxidant enzyme activity may be partially involved in the pathomechanisms of this disorder and that plasma selenium levels must be corrected through dietary supplementation in MSUD patients.

Neuroprotective effect of ganglioside GM1 on the cytotoxic action of hydrogen peroxide and amyloid beta-peptide in PC12 cells

Ganglioside GM1 was shown to increase the viability of PC12 cells exposed to hydrogen peroxide or amyloid beta-peptide (Abeta(25-35)). The PC12 cells transfected with mutant gene (expressing APP(SW)) were found to be more sensitive to oxidative stress than the cells transfected with wild type gene (expressing APP(WT)) or vector-transfected cells, GM1 being effective in enhancing the viability of the cells transfected with mutant gene. The exposure to hydrogen peroxide or Abeta(25-35) results in a partial inactivation of Na(+),K(+)-ATPase in PC12 cells, H(2)O(2) increases MDA accumulation in these cells. But these effects could be partially prevented or practically abolished by GM1 ganglioside. In the presence of the inhibitor of tyrosine kinase of Trk receptors (K-252a) the protective and metabolic effects of GM1 on PC12 cells in conditions of oxidative stress caused by hydrogen peroxide are not observed or are markedly diminished.

The role of nitric oxide on the convulsive behavior and oxidative stress induced by methylmalonate: An electroencephalographic and neurochemical study

Methylmalonic acidemias consist of a group of inherited metabolic disorders caused by deficiency of methylmalonyl-CoA mutase activity and biochemically characterized by methylmalonate (MMA) accumulation, impairment mitochondrial oxidative metabolism and reactive species production. Preliminary studies with nitric oxide synthase (NOS) inhibitors have suggested that nitric oxide (NO) plays a role in the convulsant effect of MMA. However, definitive biochemical and electrophysiological evidence of the involvement of NO in the convulsions induced by MMA are lacking. In this study, we investigated whether the inhibition of NOS by 7-nitroindazole (7-NI, 3-60mg/kg, i.p.) altered the convulsions, protein oxidative damage, NO(x) (NO(2) plus NO(3)) production and Na(+),K(+)-ATPase activity inhibition induced by MMA. 7-NI decreased striatal NO(x) content, but increased seizures and protein carbonylation induced by MMA (6mumol/striatum). The intrastriatal injection of l-arginine (50nmol/0.5mul), but not of d-arginine (50nmol/0.5mul), increased striatal NO(x) content and protected against MMA-induced electroencephalographic seizures, striatal protein carbonylation and Na(+),K(+)-ATPase inhibition. Furthermore, l-arginine (50nmol/0.5mul) and MMA had no additive effect on NO(x) increase. These results are experimental evidence that endogenous NO plays a protective role in the convulsions and acute neurochemical alterations induced by this organic acid.

Effects of 3-nitropropionic acid administration on memory and hippocampal lipid peroxidation in sleep-deprived mice

Numerous studies have described memory deficits following sleep deprivation. There is also evidence that the absence of sleep increases brain oxidative stress. The present study investigates the effects of a pro-oxidant agent--3-nitropropionic acid (3-NP)--on hippocampal oxidative stress and passive avoidance performance of sleep-deprived mice. Mice were repeatedly treated i.p. with saline or 5 or 15 mg/kg 3-NP and sleep-deprived for 24 h by the multiple platform method--groups of 4-5 animals placed in water tanks, containing 12 platforms (3 cm in diameter) surrounded by water up to 1 cm beneath the surface or kept in their home cage (control groups). The results showed that: (1) neither a 24 h sleep deprivation period nor 3-NP repeated treatment alone were able to induce memory deficits and increased hippocampal lipid peroxidation; (2) this same protocol of sleep deprivation, combined with 15 mg/kg 3-NP repeated treatment, induced memory deficits and an increase in hippocampal lipid peroxidation. The results support the involvement of hippocampal oxidative stress in the memory deficits induced by sleep deprivation and the hypothesis that normal sleep would prevent oxidative stress.

Methylene blue prevents methylmalonate-induced seizures and oxidative damage in rat striatum

Methylene blue (MB) is a thiazine dye with cationic and lipophilic properties that acts as an electron transfer mediator in the mitochondria. Due to this metabolic improving activity and free radicals scavenging effects, MB has been used in the treatment of methemoglobinemia and ifosfamide-induced encephalopathy. Considering that methylmalonic acidemia consists of a group of inherited metabolic disorders biochemically characterized by impaired mitochondrial oxidative metabolism and reactive species production, we decided to investigate whether MB, protects against the behavioral and neurochemical alterations elicited by the intrastriatal injection of methylmalonate (MMA). In the present study we showed that intrastriatal injection of MB (0.015-1.5nmol/0.5microl) protected against seizures (evidenced by electrographic recording), protein carbonylation and Na(+),K(+)-ATPase inhibition ex vivo induced by MMA (4.5micromol/1.5microl). Furthermore, we investigated whether convulsions elicited by intrastriatal MMA administration are accompanied by striatal protein carbonyl content increase and changes in Na(+),K(+)-ATPase activity in rat striatum. The effect of MB (0.015-1.5nmol/0.5microl) and MMA (4.5micromol/0.5microl) on striatal NO(x) (NO(2) plus NO(3)) content was also evaluated. Statistical analysis revealed that the MMA-induced NO(x) content increase was attenuated by intrastriatal injection of MB and the duration of convulsive episodes correlated with Na(+),K(+)-ATPase inhibition, but not with MMA-induced total protein carbonylation. In view of that MB decreases MMA-induced neurotoxicity assessed by behavioral and neurochemical parameters, the authors suggest that MB may be of value to attenuate neurological deficits of methylmalonic acidemic patients.

GM1 ganglioside prevents seizures, Na+,K+-ATPase activity inhibition and oxidative stress induced by glutaric acid and pentylenetetrazole

Monosialoganglioside (GM1) is a glycosphingolipid that protects against some neurological conditions, such as seizures and ischemia. Glutaric acidemia type I (GA-I) is an inherited disease characterized by striatal degeneration, seizures, and accumulation of glutaric acid (GA). In this study, we show that GA inhibits Na+,K+-ATPase activity and increases oxidative damage markers (total protein carbonylation and thiobarbituric acid-reactive substances-TBARS) production in striatal homogenates from rats in vitro and ex vivo. It is also shown that GM1 (50 mg/kg, i.p., twice) protects against GA-induced (4 micromol/striatum) seizures, protein carbonylation, TBARS increase, and inhibition of Na+,K+-ATPase activity ex vivo. Convulsive episodes induced by GA strongly correlated with Na+,K+-ATPase activity inhibition in the injected striatum but not with oxidative stress marker measures. Muscimol (46 pmol/striatum), but not MK-801 (3 nmol/striatum) and DNQX (8 nmol/striatum) prevented GA-induced convulsions, increase of TBARS and protein carbonylation and inhibition of Na+,K+-ATPase activity. The protection of GM1 and muscimol against GA-induced seizures strongly correlated with Na+,K+-ATPase activity maintenance ex vivo. In addition, GM1 (50-200 microM) protected against Na+,K+-ATPase inhibition induced by GA (6 mM) but not against oxidative damage in vitro. GM1 also decreased pentylenetetrazole (PTZ)-induced (1.8 micromol/striatum) seizures, Na+,K+-ATPase inhibition, and increase of TBARS and protein carbonyl in the striatum. These data suggest that Na+,K+-ATPase and GABA(A) receptor-mediated mechanisms may play important roles in GA-induced seizures and in their prevention by GM1.

Effectiveness of creatine monohydrate on seizures and oxidative damage induced by methylmalonate

Methylmalonic acidemias are metabolic disorders caused by a severe deficiency of methylmalonyl CoA mutase activity, which are characterized by neurological dysfunction, including convulsions. It has been reported that methylmalonic acid (MMA) accumulation inhibits succinate dehydrogenase (SDH) and beta-hydroxybutyrate dehydrogenase activity and respiratory chain complexes in vitro, leading to decreased CO2 production, O2 consumption and increased lactate production. Acute intrastriatal administration of MMA also induces convulsions and reactive species production. Though creatine has been reported to decrease MMA-induced convulsions and lactate production, it is not known whether it also protects against MMA-induced oxidative damage. In the present study we investigated the effects of creatine (1.2-12 mg/kg, i.p.) and MK-801 (3 nmol/striatum) on the convulsions, striatal content of thiobarbituric acid reactive substances (TBARS) and on protein carbonylation induced by MMA. Moreover, we investigated the effect of creatine (12 mg/kg, i.p.) on the MMA-induced striatal creatine and phosphocreatine depletion. Low doses of creatine (1.2 and 3.6 mg/kg) protected against MMA-induced oxidative damage, but did not protect against MMA-induced convulsions. A high dose of creatine (12 mg/kg, i.p.) and MK-801 (3 nmol/striatum) protected against MMA-induced seizures (evidenced by electrographic recording), protein carbonylation and TBARS production ex vivo. Furthermore, acute creatine administration increased the striatal creatine and phosphocreatine content and protected against MMA-induced creatine and phosphocreatine depletion. Our results suggest that an increase of the striatal high-energy phosphates elicited by creatine protects not only against MMA-induced convulsions, but also against MMA-induced oxidative damage. Therefore, since NMDA antagonists are limited value in the clinics, the present results indicate that creatine may be useful as an adjuvant therapy for methylmalonic acidemic patients.

α-Tocopherol protects against pentylenetetrazol- and methylmalonate-induced convulsions

Increased excitatory amino acid transmission and decreased GABAergic inhibitory responses seem to be important mechanisms in the genesis of convulsions, where reactive oxygen species (ROS) have recently been suggested to play a critical role. Therefore, administration of antioxidants may be potentially beneficial for the treatment of convulsive states. In the current study we investigated the effect of the systemic Vitamin E administration, an antioxidant, on the convulsions and oxidative damage induced by two convulsant agents with different mechanisms of action: methylmalonic acid (MMA), which induces convulsions through energy depletion and secondary activation of glutamatergic mechanisms and ROS production and pentylenetetrazol (PTZ), which is a chemical convulsant that causes convulsions by blocking the GABAA receptor-coupled chloride ionophore. Adult male Wistar rats (270-300 g) were injected with vehicle (5% Tween 80 in 0.9% NaCl; 1 ml/kg, i.p.) or alpha-tocopherol (25, 75 or 225 mg/kg, i.p.), once a day for 7 days. On the seventh day of antioxidant treatment, the animals were injected with the antioxidant (or vehicle) and, 30 min later, they were intrastriatally injected with NaCl (9 micromol/2 microl) or with MMA (6 micromol/2 microl) or PTZ (3.26 mmicromol/2 microl). The animals were observed for the appearance of convulsive behavior and the striatal content of thiobarbituric acid-reactive substances (TBARS) and total protein carbonylation were determined. Intrastriatal injection of increasing amounts of PTZ and of MMA caused the appearance of convulsive behavior. PTZ- and MMA-induced convulsions, TBARS production and total protein carbonylation were attenuated by alpha-tocopherol in a dose-dependent manner.

Succinate causes oxidative damage through N-methyl-d-aspartate-mediated mechanisms

In this study we investigated whether succinate, the accumulating substrate in succinate dehydrogenase (SDH) deficiencies and SDH inhibitor intoxication, causes lipoperoxidation and protein carbonylation, and if NMDA receptors are involved in the succinate-induced oxidative damage. Adult male mice (30-40 g) received an intracerebroventricular injection of succinic acid (0.7, 1.0 and 1.7 micromol/5 microl) or 0.9% NaCl (5 microl) and had their exploratory behavior assessed in an open field for 10 min. Succinate (0.7 and 1.0 micromol/5 microl) decreased locomotor activity behavior and increased thiobarbituric acid reactive substances (TBARS) and protein carbonylation in the forebrain. Conversely, 1.7 micromol of succinate did not alter locomotor activity or oxidative damage parameters. The involvement of NMDA receptors in the succinate-induced increase of total protein carbonylation content and exploratory behavior inhibition was assessed by co-administrating MK-801 (7 nmol/2.5 microl icv), a noncompetitive NMDA receptor antagonist, with succinate (1 micromol/2.5 microl icv). The co-administration of MK-801 protected against succinate-induced increase of total protein carbonylation and decrease of locomotor activity. These results suggest the involvement of NMDA receptors in these effects of succinate, which may of particular relevance for succinate-accumulating conditions, such as SDH inhibitors intoxication and inherited SDH deficiencies.

Involvement of NO in the convulsive behavior and oxidative damage induced by the intrastriatal injection of methylmalonate

Acute intrastriatal administration of methylmalonic acid (MMA) induces convulsions through NMDA receptor-mediated mechanisms and increases production of end products of oxidative damage. Although it has been demonstrated that nitric oxide (NO) production increases with NMDA receptor stimulation and contributes to the oxidative damage observed in several neurodegenerative disorders, the role of NO in MMA-induced convulsions has not been investigated to date. In the present study we investigated the effects of the intrastriatal injection of N(omega)-nitro-L-arginine methyl ester (L-NAME: 10(-4) to 10(0) nmol/0.5 microl) on the convulsions and striatal protein carbonylation induced by the intrastriatal injection of MMA (4.5 micromol/1.5 microl). l-NAME (10(-3) to 10(-1)nmol) protected against MMA-induced convulsions and protein carbonylation ex vivo. These results suggest the involvement of NO in the convulsive behavior and protein carbonylation elicited by MMA.

The role of oxidative damage in the neuropathology of organic acidurias: insights from animal studies

Organic acidurias represent a group of inherited disorders resulting from deficient activity of specific enzymes of the catabolism of amino acids, carbohydrates or lipids, leading to tissue accumulation of one or more carboxylic (organic) acids. Patients affected by organic acidurias predominantly present neurological symptoms and structural brain abnormalities, of which the aetiopathogenesis is poorly understood. However, in recent years increasing evidence has emerged suggesting that oxidative stress is possibly involved in the pathology of some organic acidurias and other inborn errors of metabolism. This review addresses some of the recent developments obtained mainly from animal studies indicating oxidative damage as an important determinant of the neuropathophysiology of some organic acidurias. Recent data showing that various organic acids are capable of inducing free radical generation and decreasing brain antioxidant defences is presented. The discussion focuses on the relatively low antioxidant defences of the brain and the vulnerability of this tissue to reactive species. This offers new perspectives for potential therapeutic strategies for these disorders, which may include the early use of appropriate antioxidants as a novel adjuvant therapy, besides the usual treatment based on removing toxic compounds and using special diets and pharmacological agents, such as cofactors and L-carnitine.

Intrastriatal malonate administration induces convulsive behaviour in rats

Malonic acidaemia is an inborn error of metabolism that accumulates malonate, a competitive succinate dehydrogenase (SDH; EC 1.3.99.1) inhibitor. The present study investigated the behavioural effects of unilateral intrastriatal administration of malonate (0.6, 1.8 or 6 micromol) in adult male Wistar rats (n=10-13). Low doses of malonate (1.8 micromol) decreased exploratory activity and caused ipsiversive rotational behaviour. High doses of malonate (6 micromol) induced contralateral rotational behaviour and convulsive episodes. Malonate competitively inhibited SDH in mitochondrion-enriched fractions from striatum ( Ki=0.034+/-0.008 mmol/L). Interestingly, methylmalonate, which is a weaker SDH inhibitor than malonate (Ki=4.22+/-1.3 mmol/L), induced more convulsions than malonate at equimolar doses and did not cause ipsiversive rotational behaviour. It is suggested that the potency of SDH inhibition in vitro does not correlate positively with the convulsant potential of these inhibitors in vivo.

Ascorbate modulates pentylenetetrazol-induced convulsions biphasically

Ascorbate is an antioxidant vitamin that is found in high concentrations in the brain which seems to have neuroprotective properties in some experimental models of excitotoxic neurological disorders, including convulsive behavior and reactive species-related damage. In this study we tested whether ascorbate (30, 100 or 300 mg/kg, i.p.) protects against the convulsions, protein carbonylation and inhibition of Na(+),K(+)-ATPase activity induced by pentylenetetrazol (PTZ; 1.8 micromol/striatum), a classical convulsant agent that has been fairly used for the study of epilepsy and screening of new compounds with antiepileptic activity. The intrastriatal injection of PTZ caused convulsive behavior in a dose-dependent manner and an increase in the total protein carbonyl content of the injected striatum. However, duration of PTZ-induced convulsive episodes did not correlate with protein carbonyl content of the injected striatum. Ascorbate, at high doses (300 mg/kg), protected against PTZ-induced convulsions, protein carbonylation and inhibition of Na(+),K(+)-ATPase activity in the rat striatum, further suggesting a anticonvulsant and neuroprotective role for this vitamin. Conversely, intermediate doses of ascorbate (100 mg/kg) potentiated the duration of the convulsive episodes, but had no additive effects on protein carbonylation or Na(+),K(+)-ATPase activity inhibition induced by PTZ. Low doses of ascorbate (30 mg/kg) prevented PTZ-induced increase of total striatal carbonyl protein content, but did not alter PTZ-induced convulsions and Na(+),K(+)-ATPase activity inhibition. Collectively, these data indicate that the anticonvulsant activity of ascorbate is not related to its antioxidant action and support a dual role for this compound as a neuroprotective agent, since while it protects against PTZ-induced cellular oxidative damage, it has a biphasic effect on PTZ-induced convulsions.

Creatine protects against the convulsive behavior and lactate production elicited by the intrastriatal injection of methylmalonate

Methylmalonic acidemias are metabolic disorders caused by a severe deficiency of methylmalonyl-CoA mutase activity, which are characterized by neurological dysfunction, including convulsions. It has been reported that the accumulating metabolite, L-methylmalonic acid (MMA), inhibits succinate dehydrogenase leading to ATP depletion in vitro, and that the intrastriatal injection of MMA induces convulsions through secondary NMDA receptor stimulation. In this study we investigated the effect of creatine (1.2, 3.6 and 12.0 mg/kg, (i.p.), [DOSAGE ERROR CORRECTED] succinate (1.5 micromol/striatum) and MK-801 (3 nmol/striatum) on the convulsions and on the striatal lactate increase induced by MMA (4.5 micromol/striatum) in rats. The effect of creatine on the striatal phosphocreatine content and on MMA-induced phosphocreatine depletion was also evaluated. Creatine, succinate and MK-801 pretreatment decreased the number and duration of convulsive episodes and the lactate increase elicited by MMA. Creatine, but not succinate, prevented the convulsions and the lactate increase induced by the direct stimulation of NMDA receptors. Acute creatine administration increased the total striatal phosphocreatine content and prevented MMA-induced phosphocreatine depletion. Our results suggest that MMA increases lactate production through secondary NMDA receptor activation, and it is proposed that the anticonvulsant effect of creatine against MMA-induced convulsions may be due to an increase in the phosphocreatine content available for metabolic purposes.

Intrastriatal methylmalonic acid administration induces convulsions and TBARS production, and alters Na+,K+-ATPase activity in the rat striatum and cerebral cortex

PURPOSE

Methylmalonic acid (MMA) inhibits succinate dehydrogenase (SDH) and beta-hydroxybutyrate dehydrogenase activity in vitro. Acute intrastriatal administration of MMA induces convulsions through glutamatergic mechanisms probably involving primary adenosine triphosphate (ATP) depletion and free radical generation. In this study we investigated whether the intrastriatal administration of MMA causes lipoperoxidation and alteration in Na+, K+-ATPase activity ex vivo and characterized the electrographic changes elicited by the intrastriatal administration of this organic acid.

METHODS

MMA-induced lipoperoxidation, alterations in Na+, K+-ATPase activity and electrographic changes were measured by measuring total thiobarbituric acid-reacting substances and inorganic phosphate release by spectrophotometry, and by depth electrode recording, respectively.

RESULTS

We demonstrated that intrastriatal MMA (6 mmol) injection causes convulsive behavior and electrographically recorded convulsions that last approximately 2 h. Concomitant with the increase of thiobarbituric acid-reacting substances (TBARS) content, we observed a significant inhibition of Na+,K+-ATPase activity in the striatum, and activation of Na+,K+-ATPase activity in the ipsilateral cerebral cortex. Intrastriatal MMA injection increased the content of TBARS in the striatum measured 30 min (32.4 +/- 12.0%, compared with the noninjected contralateral striatum) and 3 h (39.7 +/- 5.1%, compared with the noninjected contralateral striatum) after MMA injection. TBARS content of the ipsilateral cerebral cortex increased after MMA injection at 30 min (42.1 +/- 6.0%) and 3 h (40.4 +/- 20.2%), and Na+,K+-ATPase activity in the ipsilateral cerebral cortex increased during ictal activity (113.8 +/- 18%) and returned to basal levels as electrographic convulsions vanished in the cortex. Interestingly, intrastriatal MMA administration induced a persistent decrease in Na+,K+-ATPase activity only in the injected striatum (44.9 +/- 8.1% at 30 min and 68.7 +/- 9.4 at 3 h).

CONCLUSIONS

These data suggest that MMA induces lipoperoxidation associated with Na+,K+-ATPase inhibition or activation, depending on the cerebral structure analyzed. It is suggested that Na+,K+-ATPase inhibition may play a primary role in generating MMA-induced convulsions.