CaMKIIα mediates spermidine-induced memory enhancement in rats: A potential involvement of PKA/CREB pathway.

Memory consolidation is associated with the regulation of protein kinases, which impact synaptic functions and promote synaptogenesis. The administration of spermidine (SPD) has been shown to modulate major protein kinases associated with memory improvement, including the Ca2+-dependent protein kinase (PKC) and cAMP-dependent protein kinase (PKA), key players in the cAMP response element-binding protein (CREB) activation. Nevertheless, the initial mechanism underlying SPD-mediated memory consolidation remains unknown, as we hypothesize a potential involvement of the memory consolidation precursor, Ca2+/calmodulin-dependent protein kinase II-α (CaMKIIα), in this process. Based on this, our study aimed to investigate potential interactions among PKC, PKA, and CREB activation, mediated by CaMKIIα activation, in order to elucidate the SPD memory consolidation pathway. Our findings suggest that the post-training administration of the CaMKII inhibitor, KN-62 (0.25 nmol, intrahippocampal), prevented the memory enhancement induced by SPD (0.2 nmol, intrahippocampal) in the inhibitory avoidance task. Through western immunoblotting, we observed that phosphorylation of CaMKIIα in the hippocampus was facilitated 15 min after intrahippocampal SPD administration, resulting in the activation of PKA and CREB, 180 min after infusion, suggesting a possible sequential mechanism, since SPD with KN-62 infusion leads to a downregulation in CaMKIIα/PKA/CREB pathway. However, KN-62 does not alter the memory-facilitating effect of SPD on PKC, possibly demonstrating a parallel cascade in memory acquisition via PKA, without modulating CAMKIIα. These results suggest that memory enhancement induced by SPD administration involves crosstalk between CaMKIIα and PKA/CREB, with no PKC interaction.

Spermidine-induced improvement of memory consolidation involves PI3K/Akt signaling pathway.

Spermidine (SPD) is an endogenous polyamine that plays a facilitatory role in memory acquisition and consolidation. Memory consolidation occurs immediately after learning and again around 3-6 hours later. Current evidence indicates that the polyamine binding site at the NMDA receptor (NMDAr) mediates the effects of SPD on memory. While NMDAr activation increases brain-derived neurotrophic factor (BDNF) release, no study has investigated whether BDNF-activated signaling pathways, such as the phosphatidylinositol 3-kinase (PI3K)/Akt pathway play a role in SPD-induced improvement of memory consolidation. Therefore, the aim of the current study was to evaluate whether the TrkB receptor and the PI3K/Akt pathway are involved in the facilitatory effect of SPD on memory consolidation. Male Wistar rats were trained in the contextual conditioned fear task. SPD, ANA-12 (TrkB antagonist), and LY294002 (PI3K inhibitor) were administered immediately after training. The animals were tested 24 h after training. We found that SPD improved fear memory consolidation and that both ANA-12 and LY294002 prevented the facilitatory effect of SPD on memory. These results suggest that SPD-induced improvement of memory consolidation involves the activation of the TrkB receptor and PI3K/Akt pathway.

Nectandra grandiflora essential oil and its isolated sesquiterpenoids minimize anxiety-related behaviors in mice through GABAergic mechanisms.

Nectandra grandiflora Ness (Lauraceae) essential oil (EO) main constituent, the sesquiterpenoid (+)-dehydrofukinone (DHF), has sedative and anticonvulsant effects through GABAergic mechanisms. Other DHF-related sesquiterpenoids have been identified in the EO, such as, dehydrofukinone epoxide (DFX), eremophil-11-en-10-ol (ERM) and selin-11-en-4-α-ol (SEL). However, the neuronal effects of these compounds in mammals remain unknown. Therefore, the aim of this study was to evaluate the anxiolytic potential of the N. grandiflora EO and the isolated compounds in in mice. For this purpose, mice were administered orally with vehicle, 10, 30 or 100 mg/kg EO, DHF, DFX, ERM or SEL or 1 mg/kg diazepam. Locomotion and ethological parameters in the open field (OF) and elevated plus maze (EPM) were recorded. We also examined the effect of DFX, ERM and SEL on the membrane potential and calcium influx in synaptosomes, and the presence of the compounds in the cortical tissue using gas chromatography. EOs and isolated compounds reduced anxiety-related parameters in the EPM (open arms time and entries, end activity, head dipping) and OF (center time and entries, total rearing, unprotected rearing, sniffing, grooming) without alter ambulation or induce sedation. Flumazenil (2 mg/kg, i.p.) altered the anxiolytic-like effect of all treatments and vanished the DFX, ERM and SEL-induced changes in membrane potential. However, FMZ did not blocked the DFX-, ERM- and SEL-induced inhibition of calcium influx. Therefore, our results suggest that N. grandiflora EO and isolated compounds induced anxiolytic-like effect in mice due to positive modulation of GABAa receptors and/or inhibition of neuronal calcium influx.

Cyclooxygenase-2 inhibitors differentially attenuate pentylenetetrazol-induced seizures and increase of pro- and anti-inflammatory cytokine levels in the cerebral cortex and hippocampus of mice.

Seizures increase prostaglandin and cytokine levels in the brain. However, it remains to be determined whether cyclooxygenase-2 (COX-2) derived metabolites play a role in seizure-induced cytokine increase in the brain and whether anticonvulsant activity is shared by all COX-2 inhibitors. In this study we investigated whether three different COX-2 inhibitors alter pentylenetetrazol (PTZ)-induced seizures and increase of interleukin-1ß (IL-1ß), interleukin-6 (IL-6), interferon-γ (INF-γ), tumor necrosis factor-α (TNF-α) and interleukin-10 (IL-10) levels in the hippocampus and cerebral cortex of mice. Adult male albino Swiss mice received nimesulide, celecoxib or etoricoxib (0.2, 2 or 20mg/kg in 0.1% carboxymethylcellulose (CMC) in 5% Tween 80, p.o.). Sixty minutes thereafter the animals were injected with PTZ (50mg/kg, i.p.) and the latency to myoclonic jerks and to generalized tonic-clonic seizures were recorded. Twenty minutes after PTZ injection animals were killed and cytokine levels were measured. PTZ increased cytokine levels in the cerebral cortex and hippocampus. While celecoxib and nimesulide attenuated PTZ -induced increase of proinflammatory cytokines in the cerebral cortex, etoricoxib did not. Nimesulide was the only COX-2 inhibitors that attenuated PTZ-induced seizures. This effect coincided with an increase of IL-10 levels in the cerebral cortex and hippocampus, constituting circumstantial evidence that IL-10 increase may be involved in the anticonvulsant effect of nimesulide.

Modulation of learning and memory by natural polyamines.

Spermine and spermidine are natural polyamines that are produced mainly via decarboxylation of l-ornithine and the sequential transfer of aminopropyl groups from S-adenosylmethionine to putrescine by spermidine synthase and spermine synthase. Spermine and spermidine interact with intracellular and extracellular acidic residues of different nature, including nucleic acids, phospholipids, acidic proteins, carboxyl- and sulfate-containing polysaccharides. Therefore, multiple actions have been suggested for these polycations, including modulation of the activity of ionic channels, protein synthesis, protein kinases, and cell proliferation/death, within others. In this review we summarize these neurochemical/neurophysiological/morphological findings, particularly those that have been implicated in the improving and deleterious effects of spermine and spermidine on learning and memory of naïve animals in shock-motivated and nonshock-motivated tasks, from a historical perspective. The interaction with the opioid system, the facilitation and disruption of morphine-induced reward and the effect of polyamines and putative polyamine antagonists on animal models of cognitive diseases, such as Alzheimer's, Huntington, acute neuroinflammation and brain trauma are also reviewed and discussed. The increased production of polyamines in Alzheimer's disease and the biphasic nature of the effects of polyamines on memory and on the NMDA receptor are also considered. In light of the current literature on polyamines, which include the description of an inborn error of the metabolism characterized by mild-to moderate mental retardation and polyamine metabolism alterations in suicide completers, we can anticipate that polyamine targets may be important for the development of novel strategies and approaches for understanding the etiopathogenesis of important central disorders and their pharmacological treatment.

Commentary on Kaushik et al.: Prostaglandin D2 is crucial for seizure suppression and postictal sleep. Novel evidence supporting a role for prostanoid receptors in seizure control.

Accumulating clinical and experimental evidence suggests a role for prostaglandins (PGs) in epilepsy and isolated seizures. Prostaglandin levels are increased in the hippocampus of epileptic patients and in the cerebrospinal fluid of children with febrile seizures. Moreover, increased PGD2, PGE2 and PGF2α levels are found in the brain after chemically-induced seizures and in spontaneously epileptic mice. However, whether prostaglandins facilitate or decrease seizures has been a matter of debate in the literature. Both pro- and anticonvulsant activities have been described for most of prostaglandins, except for PGD2 and DP receptor agonists, for which a consistent anticonvulsant action has been reported. The study by Kaushik and colleagues elegantly extends this view by showing that hematopoietic PGD synthase (H-PGDS) and DP1 receptors are essential for seizure suppression and that lipocalin-type prostaglandin D synthase (L-PGDS)/PGD2/DP1 system regulates sleep that follows PTZ-induced seizures using knockout animals. This commentary discusses the experimental approach of the studies that have implicated prostaglandins and their receptors in seizures, the interesting approach and results of Kaushik and colleagues, and the challenges of considering PGD2 signaling as a therapeutic target in epilepsy.

Fish oil attenuates methylmalonate-induced seizures.

Methylmalonic acidemias are inherited metabolic disorders characterized by methylmalonate (MMA) accumulation and neurological dysfunction, including seizures. Dietary fatty acids are known as an important energy source and reduce seizure activity in selected acute animal models. This study investigated whether chronic treatment with fish oil or with oleic acid attenuates MMA-induced seizures and whether maintenance of Na(+),K(+)-ATPase activity was involved in such an effect. Adult male Wistar rats were given fish oil (85 mg/kg), oleic acid (85 mg/kg) or vehicle (0.42% aqueous Cremophor EL™, 4 mL/kg/body weight/day), p.o., for 75 days. On the 73th day a cannula was implanted in the right lateral ventricle with electrodes over the parietal cortex for EEG recording. On the 76th day the animals were injected with NaCl (2.5 µmol/2.5 µL, i.c.v.), or with MMA (2.5 µmol/2.5 µL, i.c.v.), and seizure activity was measured by electroencephagraphic (EEG) recording with concomitant behavior monitoring. The effect of prostaglandin E2 (PGE2) on Na(+),K(+)-ATPase activity of slices of cerebral cortex from NaCl-injected animals was determined. Fish oil increased the latency to MMA-induced tonic-clonic seizures, reduced the mean amplitude of ictal EEG recordings, and prevented PGE2-induced decrease of Na(+),K(+)-ATPase activity in cortical slices in vitro. Oleic acid decreased mean amplitude of ictal EEG recordings. The results support that fish oil decreases MMA-induced seizures. The decreased sensitivity of Na(+),K(+)-ATPase to the inhibitory effect of PGE2 in fish oil-treated animals may be related to the currently reported anticonvulsant activity.

N-Acetylcysteine prevents baker's-yeast-induced inflammation and fever.

OBJECTIVE AND DESIGN: To investigate whether N-acetylcysteine (NAC) alters baker's-yeast-induced fever and inflammation. MATERIAL OR SUBJECTS: Male Wistar rats (26-28 days old) injected with baker's yeast (135 mg/kg, intraperitoneal) or prostaglandin E(2) (300 ng/100 µL, intrathecal). TREATMENT: Rats were injected with NAC (500 mg/kg, subcutaneous, or 50 µg/100 µL, intrathecal) 1 h before, or 2 h after, pyrogen injection. METHODS: Rectal temperature changes induced by baker's yeast, PGE(2) and NAC were followed up over time. Four hours after baker's yeast injection, total leukocytes, protein, interleukin (IL)-1ß, tumor necrosis factor (TNF)-α and nonprotein thiol content were assessed in peritoneal lavage and hypothalamus. RESULTS: Systemic administration of NAC decreased leukocytes, protein, IL-1ß and TNF-α levels in peritoneal lavage, and decreased IL-1ß levels in the hypothalamus. The central administration of NAC prevented baker's-yeast-induced fever, but did not alter the febrile response elicited by prostaglandin E(2). CONCLUSION: These results suggest an anti-inflammatory and antipyretic role for NAC in yeast-induced peritonitis.

Hippocampal PKA/CREB pathway is involved in the improvement of memory induced by spermidine in rats.

Spermidine (SPD) is an endogenous polyamine that modulates N-methyl-D-aspartate (NMDA) receptor function, and has been reported to facilitate memory formation. In the current study we determined whether or not the PKA/CREB signaling pathway is involved in SPD-induced facilitation of memory of inhibitory avoidance task in adult rats. The post-training administration of the cAMP-dependent protein kinase (PKA) inhibitor, N-[2-bromocinnamylamino)ethyl]-5-isoquinoline sulfonamide [H-89, 0.5 ρmol intrahippocampal (ih)] or the antagonist of the NMDA receptor polyamine-binding site (arcaine, 0.02 nmol ih) with SPD (0.2 nmol ih) prevented memory improvement induced by SPD. Intrahippocampal administration of SPD (0.2 nmol) facilitated PKA and cAMP response element-binding protein (CREB) phosphorylation in the hippocampus 180 min, but not 30 min, after administration, and increased translocation of the catalytic subunit of PKA into the nucleus. Arcaine (0.02 nmol) and H-89 (0.5 ρmol) prevented the stimulatory effect of SPD on PKA and CREB phosphorylation. These results suggest that memory enhancement induced by the ih administration of SPD involves the PKA/CREB pathways in rats.

Spinal levels of nonprotein thiols are related to nociception in mice.

UNLABELLED: Oxidative stress markers are thought to be related to nociception. Because thiolic compounds are important antioxidants, we investigated the relationship between thiols, endogenous or exogenous, and nociception. Systemic or spinal, but not peripheral, administration of the exogenous thiolic compound N-acetyl-L-cysteine (NAC) reduced nociception induced by intraplantar capsaicin injection. Moreover, we detected an increase in lipid peroxidation and 3-nitrotyrosine and a decrease in nonprotein thiolic levels in the lumbar spinal cord of capsaicin-injected animals. All these effects were prevented by NAC treatment (i.p. and i.t.). Our findings confirm a role for the spinal cord in NAC actions because systemic NAC administration also reduced the nociception trigged by intrathecal injection of capsaicin. Moreover, adjuvant-induced arthritis, but not paw incision, also -decreases nonprotein thiol levels in the spinal cord. Similarly, NAC produced antinociception in adjuvant-treated animals, but not in paw-incised animals. Finally, we investigated the role of endogenous thiol compounds in the nociceptive process administrating buthionine-suphoxamine (BSO), an inhibitor of glutathione-synthesis. Intrathecal BSO treatment decreased nonprotein thiol levels in the spinal cord, as well as induced mechanical allodynia and chemical and thermal hyperalgesia. In conclusion, our results indicate a critical role for nonprotein thiols in nociception at the level of the spinal cord. PERSPECTIVE: The results presented here indicate that the loss of nonprotein thiols in the spinal cord is involved in pain development. Therefore, the administration of thiolic compounds or other strategies allow thiol levels to be maintained and could be a beneficial action in the therapy of painful conditions.

Diacerein decreases TNF-alpha and IL-1beta levels in peritoneal fluid and prevents Baker's yeast-induced fever in young rats.

OBJECTIVE: To investigate the effect of diacerein, an anti-inflammatory drug, on body temperature and protocols of fever induction in male Wistar rats. METHODS: The effect of diacerein (5.0 mg/kg, s.c.) on rectal temperature (T (R)) changes induced by Baker's yeast (0.135 g/kg, i.p.) and PGE(2) (10 ng/animal, i.t.) was evaluated. T (R) changes were recorded over time. The leukocyte count and TNF-alpha and IL-1beta content were evaluated in the peritoneal fluid by means of optical microscopy and enzyme immunoassay (ELISA kits), respectively. RESULTS: The administration of diacerein to febrile animals attenuated Baker's yeast-induced fever but did not alter prostaglandin E(2)-induced fever. Diacerein prevented the development of Baker's yeast-induced fever and significantly attenuated the increase in peritoneal leukocytes and decreased IL-1beta and TNF-alpha levels in peritoneal fluid. CONCLUSIONS: These data suggest that diacerein partially protects against Baker's yeast-induced fever and peritoneal leukocyte migration, and indicate that this effect appears to be due to inhibition of release of cytokines (such as TNF-alpha and IL-1beta).

Adaptation to oxidative challenge induced by chronic physical exercise prevents Na+,K+-ATPase activity inhibition after traumatic brain injury.

Physical exercise is likely to alter brain function and to afford neuroprotection in several neurological diseases. Although the favorable effects of physical exercise on traumatic brain injury (TBI) patients is well known, little information is available regarding the role of free radicals in the improvement induced by physical exercise in an experimental model of TBI induced by fluid percussion injury (FPI). Thus, we investigated whether 6 weeks of swimming training protects against oxidative damage (measured by protein carbonylation and thiobarbituric acid-reactive substances-TBARS) and neurochemical alterations represented by immunodetection of alpha subunit and activity of Na(+),K(+)-ATPase after FPI in cerebral cortex of rats. Statistical analysis revealed that physical training protected against FPI-induced TBARS and protein carbonylation increase. In addition, physical training was effective against Na(+),K(+)-ATPase enzyme activity inhibition and alpha(1) subunit level decrease after FPI. Pearson's correlation analysis revealed that the decrease in levels of catalytic alpha(1) subunit of Na(+),K(+)-ATPase induced FPI correlated with TBARS and protein carbonylation content increase. Furthermore, the effective protection exerted by physical training against FPI-induced free radical correlated with the immunocontent of the catalytic alpha(1) subunit maintenance. These data suggest that TBI-induced reactive oxygen species (ROS) generation decreases Na(+),K(+)-ATPase activity by decreasing the total number of enzyme molecules, and that physical exercise protects against this effect. Therefore, the effective protection of selected targets, such as Na(+),K(+)-ATPase induced by physical training, supports the idea that physical training may exert prophylactic effects on neuronal cell dysfunction and damage associated with TBI.

Prostaglandin E2 modulates Na+,K+-ATPase activity in rat hippocampus: implications for neurological diseases.

Prostaglandin E(2) (PGE(2)) is quantitatively one of the major prostaglandins synthesized in mammalian brain, and there is evidence that it facilitates seizures and neuronal death. However, little is known about the molecular mechanisms involved in such excitatory effects. Na(+),K(+)-ATPase is a membrane protein which plays a key role in electrolyte homeostasis maintenance and, therefore, regulates neuronal excitability. In this study, we tested the hypothesis that PGE(2) decreases Na(+),K(+)-ATPase activity, in order to shed some light on the mechanisms underlying the excitatory action of PGE(2). Na(+),K(+)-ATPase activity was determined by assessing ouabain-sensitive ATP hydrolysis. We found that incubation of adult rat hippocampal slices with PGE(2) (0.1-10 microM) for 30 min decreased Na(+),K(+)-ATPase activity in a concentration-dependent manner. However, PGE(2) did not alter Na(+),K(+)-ATPase activity if added to hippocampal homogenates. The inhibitory effect of PGE(2) on Na(+),K(+)-ATPase activity was not related to a decrease in the total or plasma membrane immunocontent of the catalytic alpha subunit of Na(+),K(+)-ATPase. We found that the inhibitory effect of PGE(2) (1 microM) on Na(+),K(+)-ATPase activity was receptor-mediated, as incubation with selective antagonists for EP1 (SC-19220, 10 microM), EP3 (L-826266, 1 microM) or EP4 (L-161982, 1 microM) receptors prevented the PGE(2)-induced decrease of Na(+),K(+)-ATPase activity. On the other hand, incubation with the selective EP2 agonist (butaprost, 0.1-10 microM) increased enzyme activity per se in a concentration-dependent manner, but did not prevent the inhibitory effect of PGE(2). Incubation with a protein kinase A (PKA) inhibitor (H-89, 1 microM) and a protein kinase C (PKC) inhibitor (GF-109203X, 300 nM) also prevented PGE(2)-induced decrease of Na(+),K(+)-ATPase activity. Accordingly, PGE(2) increased phosphorylation of Ser943 at the alpha subunit, a critical residue for regulation of enzyme activity. Importantly, we also found that PGE(2) decreases Na(+),K(+)-ATPase activity in vivo. The results presented here imply Na(+),K(+)-ATPase as a target for PGE(2)-mediated signaling, which may underlie PGE(2)-induced increase of brain excitability.

Swimming training prevents pentylenetetrazol-induced inhibition of Na+, K+-ATPase activity, seizures, and oxidative stress.

PURPOSE: In the present study we decided to investigate whether physical exercise protects against the electrographic, oxidative, and neurochemical alterations induced by subthreshold to severe convulsive doses of pentyltetrazole (PTZ). METHODS: The effect of swimming training (6 weeks) on convulsive behavior induced by PTZ (30, 45, and 60 mg/kg, i.p.) was measured and different electrographic electroencephalography (EEG) frequencies obtained from freely moving rats. After EEG recordings, reactive oxygen species (ROS) generation, nonprotein sulfhydryl (NPS), protein carbonyl, thiobarbituric acid-reactive substances (TBARS), superoxide dismutase (SOD), catalase (CAT), Na(+), K(+)-ATPase activity, and glutamate uptake were measured in the cerebral cortex of rats. RESULTS: We showed that physical training increased latency and attenuated the duration of generalized seizures induced by administration of PTZ (45 mg/kg). EEG recordings showed that physical exercise decreased the spike amplitude after PTZ administration (all doses). Pearson's correlation analysis revealed that protection of physical training against PTZ-induced seizures strongly correlated with NPS content, Na(+), K(+)-ATPase activity, and glutamate-uptake maintenance. Physical training also increased SOD activity, NPS content, attenuated ROS generation per se, and was effective against inhibition of Na(+), K(+)-ATPase activity induced by a subthreshold convulsive dose of PTZ (30 mg/kg). In addition, physical training protected against 2',7'-dichlorofluorescein diacetate (DCFH-DA) oxidation, TBARS and protein carbonyl increase, decrease of NPS content, inhibition of SOD and catalase, and inhibition glutamate uptake induced by PTZ. CONCLUSIONS: These data suggest that effective protection of selected targets for free radical damage, such as Na(+), K(+)-ATPase, elicited by physical training protects against the increase of neuronal excitability and oxidative damage induced by PTZ.

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.

Na+,K+-ATPase activity impairment after experimental traumatic brain injury: relationship to spatial learning deficits and oxidative stress.

Traumatic brain injury (TBI) is a devastating disease that commonly causes persistent mental disturbances and cognitive deficits. Although studies indicate that oxidative stress and functional deficits occurring after TBI are interrelated events, the knowledge of the mechanisms underlying the development of such cognitive deficits has been limited. Thus, in the present study, we investigated the effect of fluid percussion brain injury (FPI) on a spatial learning task and levels of oxidative stress markers, namely, protein carbonylation and thiobarbituric acid-reactive substances (TBARS) and Na+,K+-ATPase activity 1 or 3 months after FPI in rats. Statistical analysis revealed that FPI increased the scape latency and mean number of error in Barnes maze test 1 and 3 months after FPI. We also found that protein carbonylation and TBARS content increased in the parietal cortex 1 and 3 months after FPI. In addition, 3 months after FPI, protein carbonylation levels increased both in ipsilateral and contralateral cortices of FPI animals. Indeed, statistical analysis revealed a decrease in Na+,K+-ATPase activity in the cerebral cortex of 1 month FPI animals. Furthermore, the decrease in enzyme activity found 3 months was larger, when compared with 1 month after FPI. These results suggest that cognitive impairment following TBI may result, at least in part, from increase of two oxidative stress markers, protein carbonylation and TBARS that occurs concomitantly to a decrease in Na+,K+-ATPase activity.

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.

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.

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.

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.