A role of Na+, K+ -ATPase in spatial memory deficits and inflammatory/oxidative stress after recurrent concussion in adolescent rats.

Sports-related concussions are particularly common during adolescence, and there is insufficient knowledge about how recurrent concussions in this phase of life alter the metabolism of essential structures for memory in adulthood. In this sense, our experimental data revealed that seven recurrent concussions (RC) in 35-day-old rats decreased short-term and long-term memory in the object recognition test (ORT) 30 days after injury. The RC protocol did not alter motor and anxious behavior and the immunoreactivity of brain-derived neurotrophic factor (BDNF) in the cerebral cortex. Recurrent concussions induced the inflammatory/oxidative stress characterized here by increased glial fibrillary acidic protein (GFAP), interleukin 1ß (IL 1ß), 4-hydroxynonenal (4 HNE), protein carbonyl immunoreactivity, and 2',7'-dichlorofluorescein diacetate oxidation (DCFH) levels and lower total antioxidant capacity (TAC). Inhibited Na+,K+-ATPase activity (specifically isoform α2/3) followed by Km (Michaelis-Menten constant) for increased ATP levels and decreased immunodetection of alpha subunit of this enzyme, suggesting that cognitive impairment after RC is caused by the inability of surviving neurons to maintain ionic gradients in selected targets to inflammatory/oxidative damage, such as Na,K-ATPase activity.

Ibuprofen intake increases exercise time to exhaustion: A possible role for preventing exercise-induced fatigue.

Although the intake of nonsteroidal anti-inflammatory drugs (NSAIDs) intake by athletes prevents soreness, little is known concerning their role in exercise performance. This study assessed the effects of ibuprofen intake on an exhaustive protocol test after 6 weeks of swimming training in rats. Animals were divided into sedentary and training groups. After training, animals were subdivided into two subsets: saline or ibuprofen. Afterwards, three repeated swimming bouts were performed by the groups. Ibuprofen (15 mg/kg) was administered once a day. Pain measurements were performed and inflammatory and oxidative stress parameters were assayed in cerebral cortex and gastrocnemius muscle. Training, ibuprofen administration, or both combined (P < 0.05; 211 ± 18s, 200 ± 31s, and 279 ± 23s) increased exercise time to exhaustion. Training decreased the acetylcholinesterase (AChE) activity (P < 0.05; 149 ± 11) in cerebral cortex. Ibuprofen intake decreased the AChE activity after exhaustive protocol test in trained and sedentary rats (P < 0.05; 270 ± 60; 171 ± 38; and 273 ± 29). It also prevented neuronal tumor necrosis factor-α (TNF-α) and interleukin (IL 1ß) increase. Fatigue elicited by this exhaustive protocol may involve disturbances of the central nervous system. Additive anti-inflammatory effects of exercise and ibuprofen intake support the hypothesis that this combination may constitute a more effective approach. In addition, ergogenic aids may be a useful means to prevent exercise-induced fatigue.

Contrasting effects of Na+, K+-ATPase activation on seizure activity in acute versus chronic models.

Epilepsy is a life-shortening brain disorder affecting approximately 1% of the worldwide population. Most epilepsy patients are refractory to currently available antiepileptic drugs (AEDs). Knowledge about the mechanisms underlying seizure activity and probing for new AEDs is fundamental to the discovery of new therapeutic strategies. Brain Na(+), K(+)-ATPase activity contributes to the maintenance of the electrochemical gradients underlying neuronal resting and action potentials as well as the uptake and release of neurotransmitters. Accordingly, a decrease of Na(+), K(+)-ATPase increases neuronal excitability and may predispose to appearing of seizure activity. In the present study, we tested the hypothesis that activation of Na(+), K(+)-ATPase activity with a specific antibody (DRRSAb) raised against a regulatory site in the α subunit would decrease seizure susceptibility. We found that incubation of hippocampal homogenates with DRRSAb (1 µM) increased total and α1 Na(+), K(+)-ATPase activities. A higher concentration (3 µM) increased total, α1 and α2/α3 Na(+), K(+)-ATPase activities. Intrahippocampal injection of DRRSAb decreased the susceptibility of post status epilepticus animals to pentylenetetrazol (PTZ)-induced myoclonic seizures. In contrast, administration of DRRSAb into the hippocampus of naïve animals facilitated the appearance of PTZ-induced seizures. Quantitative analysis of hippocampal electroencephalography (EEG) recordings revealed that DRRSAb increased the percentage of total power contributed by the delta frequency band (0-3 Hz) to a large irregular amplitude pattern of hippocampal EEG. On the other hand, we found no DRRSAb-induced changes regarding the theta functional state. Further studies are necessary to define the potential of Na(+), K(+)-ATPase activation as a new therapeutic approach for seizure disorders.

Involvement of oxidative stress in subacute toxicity induced by fumonisin B1 in broiler chicks.

Fumonisin B1 (FB1) is a mycotoxin produced by Fusarium spp. It has been reported to be a potential cause of liver cancer in rats and esophageal cancer in humans. The underlying mechanisms of FB1 toxicity are thought to be related to the inhibition of ceramide synthase, causing an accumulation of sphingosine (SO) and sphinganine (SA), which in turn may cause tissue functional impairment and the development of oxidative stress. Therefore, in this study, we investigate the effects of an FB1-contaminated diet on markers of oxidative stress in chick liver. A total of 24 male broiler chicks (Cobb 500) were fed a standard control diet or a diet contaminated with FB1 (100mg/kg) for 21 days, starting on postnatal day one. The feed and animals were weighed on days 0, 7, 14 and 21 to estimate the feed conversion ratio, and at 21 days, the liver weight and liver relative weight were determined. At the end of the experiment, samples of blood and liver were collected. The blood was used to quantify the SA/SO ratio, and the liver was used to determine the activity of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST); ascorbic acid levels (VitC), non-protein thiol (NPSH) levels and TBARS content were also determined. The FB1 diet increased the liver weight, liver relative weight, feed conversion and SA/SO ratio. Furthermore, hepatic TBARS levels, Vit C content and CAT activity were also increased. Conversely, the activities of SOD, GST and NPSH levels, in the liver were not altered by the mycotoxin-contaminated diet. In summary, we showed that subacute exposure of broiler chicks to FB1 induced liver oxidative stress concomitantly with SA/SO accumulation.

Convulsions induced by methylmalonic acid are associated with glutamic acid decarboxylase inhibition in rats: a role for GABA in the seizures presented by methylmalonic acidemic patients?

Methylmalonic acid (MMA) is an endogenous convulsing compound that accumulates in methylmalonic acidemia, an inborn error of the metabolism characterized by severe neurological dysfunction, including seizures. The mechanisms by which MMA causes seizures involves the activation of the N-methyl-D-aspartate (NMDA) receptors, but whether GABAergic mechanisms are involved in the convulsions induced by MMA is not known. Therefore, in the current study we investigated the involvement of GABAergic mechanisms in the convulsions induced by MMA. Adult rats were injected (i.c.v.) with muscimol (46 pmol/1 microl), baclofen (0.03, 0.1 and 0.3 micromol/1 microl), MK-801 (6 nmol/1 microl), pyridoxine (2 micromol/4 microl) or physiological saline (0.15 micromol/1 microl). After 30 min, MMA (0.3, 0.1 and 3 micromol/1 microl) or NaCl (6 micromol/1 microl, i.c.v.) was injected. The animals were immediately transferred to an open field and observed for the appearance of convulsions. After behavioral evaluation, glutamic acid decarboxylase (GAD) activity was determined in cerebral cortex homogenates by measuring the 14CO2 released from l-[14C]-glutamic acid. Convulsions were confirmed by electroencephalographic recording in a subset of animals. MMA caused the appearance of clonic convulsions in a dose-dependent manner and decreased GAD activity in the cerebral cortex ex vivo. GAD activity negatively correlated with duration of MMA-induced convulsions (r=-0.873, P<0.01), in an individual basis. Muscimol, baclofen, MK-801 and pyridoxine prevented MMA-induced convulsions, but only MK-801 and pyridoxine prevented MMA-induced GAD inhibition. These data suggest GABAergic mechanisms are involved in the convulsive action of MMA, and that GAD inhibition by MMA depends on the activation of NMDA receptors. While in this study we present novel data about the role of the GABAergic system in MMA-induced convulsions, the central role of NMDA receptors in the neurochemical actions of MMA is further reinforced since they seem to trigger GABAergic failure.

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 administration of 3-hydroxyglutaric acid induces convulsions and striatal lesions in rats.

Glutaryl-CoA dehydrogenase deficiency is an inherited neurometabolic disease complicated by precipitation of acute encephalopathic crises during a vulnerable period of brain development. These crises result in bilateral striatal damage and subsequently a dystonic dyskinetic movement disorder. In previous in vitro studies neuronal damage in this disease has been linked to an excitotoxic mechanism mediated in particular by one of the accumulating metabolites, 3-hydroxyglutaric acid. However, nothing is known about the in vivo effects of this organic acid. In the present study, we used a stereotaxic intrastriatal injection technique to investigate the behavioral and neurotoxic effects of 3-hydroxyglutaric acid exposure in rats. Here, we report that 3-hydroxyglutaric acid induced an increase in convulsion frequency and duration as determined by open field measurement. Nissl-stained coronal sections from treated rats revealed a pale lesion in the striatum following 3-hydroxyglutaric acid exposure. N-methyl-D-aspartate (NMDA) receptor blockade by MK-801 and stimulation of GABA(A) receptors by muscimol prevented the induction of convulsions and striatal damage by 3-hydroxyglutaric acid, whereas blockade of non-NMDA receptors by 6,7-dinitroquinoxaline-2,3-dione (DNQX) was not protective. We conclude that 3-hydroxyglutaric acid induces convulsions and striatal damage via initiation of an imbalance in the excitatory glutamatergic and the inhibitory GABAergic neurotransmission, resulting in an enhanced excitatory input in striatal neurons. These results support the hypothesis of NMDA receptor-mediated excitotoxic cell damage in glutaryl-CoA dehydrogenase deficiency and represent the basis for the development of new neuroprotective treatment strategies.

3-Methyl-5-hydroxy-5-trichloromethyl-1H-1-pyrazolcarboxyamide induces antinociception.

The antinociceptive action of a novel pyrazole-derived compound, 3-methyl-5-hydroxy-5-trichloromethyl-1H-1-pyrazolcarboxyamide (MPCA) was evaluated using the formalin and tail-immersion tests in mice. Anti-inflammatory activity was assessed by paw plethysmometry in adult rats using the carrageenin-induced paw edema test. Subcutaneous administration of MPCA (22, 66, and 200 mg/kg) induced a dose-dependent decrease in the time spent licking during the neurogenic and inflammatory phases of the formalin test, and preadministration of naloxone (1 mg/kg, sc) did not prevent MPCA-induced (200 mg/kg, sc) antinociception. Naloxone decreased the spontaneous locomotor activity of mice, while MPCA had no effect on locomotion. In contrast, administration of the opioid antagonist caused a significant increase in the locomotor behavior of mice previously injected with MPCA. MPCA was devoid of antinociceptive action by the tail-immersion test and of anti-inflammatory activity. Moreover, MPCA had no effect on the motor performance of mice in the rotarod test. These results suggest that MPCA induces antinociception in the neurogenic and inflammatory phases of the formalin test, an effect that does not involve opioid receptors.

Pharmacological evidence that alpha-ketoisovaleric acid induces convulsions through GABAergic and glutamatergic mechanisms in rats.

Neurological dysfunction is common in patients with maple syrup urine disease (MSUD). However, the mechanisms underlying the pathophysiology of this disorder are poorly known. In the present study we investigated the effect of intrastriatal administration of the alpha-keto acids accumulating in MSUD on the behavior of adult rats. After cannula placing, rats received unilateral intrastriatal injections of alpha-ketoisocaproic acid (KIC, 8 micromol), alpha-ketoisovaleric acid (KIV, 8 micromol), alpha-keto-beta-methylvaleric acid (KMV, 6 micromol) or NaCl. KIV elicited clonic convulsions in a dose-response manner, whereas KIC and KMV did not induce seizure-like behavior. Convulsions provoked by KIV were prevented by intrastriatal preadministration of muscimol (46 pmol) and MK-801 (3 nmol), but not by the preadministration of DNQX (8 nmol). These results indicate that among the keto acids that accumulate in MSUD, KIV is the only metabolite capable of causing convulsions in the present animal model and indicates that KIV is an important excitatory metabolite. Moreover, the participation of GABAergic and glutamatergic NMDA mechanisms in the KIV-induced convulsant behavior is suggested, since KIV-induced convulsions are attenuated by muscimol and MK-801. The authors suggest that KIV may play an important role in the convulsions observed in MSUD, and highlight its relevance to the understanding of the pathophysiology of the neurological dysfunction of MSUD patients.

Ascorbic acid and alpha-tocopherol attenuate methylmalonic acid-induced convulsions.

The effects of chronic administration of alpha-tocopherol or melatonin, or acute ascorbic acid administration on the convulsant action of methylmalonic acid (MMA) were investigated in adult male rats. Animals were chronically injected with alpha-tocopherol (40 mg kg(-1), i.p.), melatonin (5 mg kg(-1), i.p.) or vehicle for 7 days. Buffered MMA (6 micromol/2 microl) or NaCl (9 micromol/2 microl) was injected intrastriatally and the animals were observed for the appearance of clonic or tonic-clonic convulsions and rotational behavior. Ascorbic acid (100 mg kg(-1), s.c.) was administered 30 min before MMA injection. Alpha-tocopherol and ascorbic acid pretreatment decreased the duration of the convulsive episodes and the rotational behavior elicited by MMA. This study provides evidence that free radical generation may participate in the convulsant effects of methylmalonic acid.