Cellular and molecular mechanisms of aflatoxin B1-mediated neurotoxicity: The therapeutic role of natural bioactive compounds

Aflatoxin B1 (AFB1), a dietary toxin from the mold Aspergillus species, is well acknowledged to elicit extra-hepatic toxicity in both animals and humans. The neurotoxicity of AFB1 has become a global public health concern. Contemporary research on how AFB1 enters the brain to elicit neuronal dysregulation leading to noxious neurological outcomes has increased greatly in recent years. The current review discusses several neurotoxic outcomes and susceptible targets of AFB1 toxicity at cellular, molecular and genetic levels. Specifically, neurotoxicity studies involving the use of brain homogenates, neuroblastoma cell line IMR-32, human brain microvascular endothelial cells, microglial cells, and astrocytes, as well as mammalian and non-mammalian models to unravel the mechanisms associated with AFB1 exposure are highlighted. Further, some naturally occurring bioactive compounds with compelling therapeutic effects on AFB1-induced neurotoxicity are reviewed. In conclusion, available data from literature highlight AFB1 as a neurotoxin and its possible pathological contribution to neurological disorders. Further mechanistic studies aimed at discovering and developing effective therapeutics for AFB1 neurotoxicity is warranted.

Beta-caryophyllene mitigates the cognitive impairment caused by repeated exposure to aspartame in rats: Putative role of BDNF-TrKB signaling pathway and acetylcholinesterase activity

Aspartame (ASP) is a common sweetener, but studies show it can harm the nervous system, causing learning and memory deficits. β-caryophyllene (BCP), a natural compound found in foods, including bread, coffee, alcoholic beverages, and spices, has already described as a neuroprotector agent. Remarkably, ASP and BCP are commonly consumed, including in the same meal. Therefore, considering that (a) the BCP displays plenty of beneficial effects; (b) the ASP toxicity; and (c) that they can be consumed in the same meal, this study sought to investigate if the BCP would mitigate the memory impairment induced by ASP in rats and investigate the involvement of the brain-derived neurotrophic factor (BDNF)/ tropomyosin receptor kinase B (TrKB) signaling pathway and acetylcholinesterase (AChE) activity. Young male Wistar rats received ASP (75 mg/kg; i.g.) and/or BCP (100 mg/kg; i.p.) once daily, for 14 days. At the end of the treatment, the animals were evaluated in the open field and object recognition tests. The cerebral cortex and hippocampus samples were collected for biochemical and molecular analyses. Results showed that the BCP effectively protected against the cognitive damage caused by ASP in short and long-term memories. In addition, BCP mitigated the increase in AChE activity caused by ASP. Molecular insights revealed augmented BDNF and TrKB levels in the hippocampus of rats treated with BCP, indicating greater activation of this pathway. In conclusion, BCP protected against ASP-induced memory impairment. AChE activity and the BDNF/TrkB signaling pathway seem to be potential targets of BCP modulatory role in this study.

Intermittent Exposure to Aflatoxin B1 Did Not Affect Neurobehavioral Parameters and Biochemical Markers of Oxidative Stress

Aflatoxin B1 (AFB1) is the most common toxic mycotoxin that contaminates food. The treatment of its intoxication and the management of contaminations are a constant subject of health agendas worldwide. However, such efforts are not always enough to avoid population intoxication. Our objective was to investigate whether intermittent exposure to AFB1 would cause any impairment in biochemical and behavioral parameters, intending to simulate an irregular consumption. Male Wistar rats received four AFB1 administrations (250 μg/kg) by intragastric route separated by a 96-h interval. Toxicity was evaluated using behavioral tests (open field, object recognition, nest construction, marble burying, and splash test), biochemical markers of oxidative stress (cerebral cortex, hippocampus, liver, and kidneys), and plasma parameters of hepatic and renal functions. The intermittent exposure caused no modification in body weight gain as well as in organ weight. Both control and AFB1 groups presented similar profiles of behavior to all tests performed. Furthermore, AFB1 administrations alter neither antioxidant defenses nor markers of oxidation in all assayed tissues and in the plasma markers of hepatic and renal functions. Therefore, AFB1 intermittent administration did not cause its common damage from exposure to this toxicant, which must be avoided, and additional studies are required.

Repeated co-exposure to aflatoxin B1 and aspartame disrupts the central nervous system homeostasis: Behavioral, biochemical, and molecular insights

Several studies demonstrated the toxicity of aspartame (ASP) and aflatoxin B₁ (AFB₁ ) in preclinical models. Although the majority of these reports assessed the toxic effects of each substance separately, their concomitant exposure and hazardous consequences are scarce. Importantly, the deleterious effects at the central nervous system caused by ASP and AFB₁ co-exposure are rarely addressed. We evaluated if concomitant exposure to AFB₁ and ASP would cause behavioral impairment and alteration in oxidative status of the brain in male rats. Animals received once a day for 14 days AFB₁ (250 µg/kg, intragastric gavage [i.g.]), ASP (75 mg/kg, i.g.), or both substances (association). On day 14, they were subjected to behavioral evaluation, and biochemical and molecular parameters of oxidative status were measured in the cerebral cortex and hippocampus. In the open field test, AFB₁ and combination treatments modified the motor, exploratory, and grooming behavior. In the splash test, all treatments caused a reduction in grooming time compared to the control group. An increase in thiobarbituric acid-reactive substances content induced by AFB₁ and combination treatments was observed. The antioxidant defenses (vitamin C, nonprotein sulfhydryl, and ferric reducing antioxidant power) were impaired in all groups compared to control. Regarding molecular evaluation, mitochondrial superoxide dismutase-2 immunoreactivity decreased after AFB₁ or ASP exposition in the hippocampus. Thus, co-exposure to ASP and AFB₁ was potentially more toxic because it aggravated behavioral impairments and oxidative status disbalance in comparison to the groups that received only ASP or AFB₁ . Therefore, our data suggest that those substances caused a disruption in brain homeostasis.

Beneficial Effects of Rosmarinic Acid In Vitro and In Vivo Models of Epileptiform Activity Induced by Pilocarpine

Epilepsy is characterized by a predisposition to generate recurrent and spontaneous seizures; it affects millions of people worldwide. Status epilepticus (SE) is a severe type of seizure. In this context, screening potential treatments is very important. In the present study, we evaluated the beneficial effects of rosmarinic acid (RA) in pilocarpine-induced in vitro and in vivo models of epileptiform activity. Using an in vitro model in combined entorhinal cortex-hippocampal from Wistar rats we evaluated the effects of RA (10 µg/mL) on the lactate release and a glucose fluorescent analogue, 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose (2-NDBG), after incubation in high potassium aCSF supplemented or not with pilocarpine. In the in vivo model, SE was induced in male C57BL/6 mice by pilocarpine. At 1, 24, and 48 h after the end of SE mice were treated with RA (30 mg/kg/v.o.). We evaluated the neuromotor impairment by neuroscore tests and protein carbonyl levels in the cerebral cortex. In both in vitro models, RA was able to decrease the stimulated lactate release, while no effect on 2-NBDG uptake was found. RA has beneficial effects in models of epileptiform activity in vivo and in vitro. We found that RA treatment attenuated SE-induced neuromotor impairment at the 48 h timepoint. Moreover, post-SE treatment with RA decreased levels of protein carbonyls in the cerebral cortex of mice when compared to their vehicle-treated counterparts. Importantly, RA was effective in a model of SE which is relevant for the human condition. The present data add to the literature on the biological effects of RA, which could be a good candidate for add-on therapy in epilepsy.

Beta-caryophyllene attenuates short-term recurrent seizure activity and blood-brain-barrier breakdown after pilocarpine-induced status epilepticus in rats

BACKGROUND

Status epilepticus (SE) is a neurological life-threatening condition, resulting from the failure of the mechanisms responsible for seizure termination. SE is often pharmacoresistant and associated with significant morbidity and mortality. Hence, ceasing or attenuating SE and its consequences is of fundamental importance. Beta-caryophyllene is a functional CB2 receptor agonist and exhibit a good safety profile. Besides, it displays beneficial effects in several experimental conditions, including neuroprotective activity. In the present study we aimed to investigate the effects of beta-caryophyllene on pilocarpine-induced SE.

METHODS

Wistar rats were submitted to pilocarpine-induced SE and monitored for 24 hours by video and EEG for short-term recurrence of seizure activity (i.e. seizures occurring within 24 hours after termination of SE). Rats received beta-caryophyllene (100 mg/kg, ip) at 1, 8- and 16-hours after SE. Twenty-four hours after SE we evaluated sensorimotor response, neuronal damage (fluoro jade C staining) and serum albumin infiltration into brain parenchyma.

RESULTS

Beta-caryophyllene-treated animals presented fewer short-term recurrent seizures than vehicle-treated counterparts, suggesting an anticonvulsant effect after SE. Behavioral recovery from SE and the number of fluoro jade C positive cells in the hippocampus and thalamus were not modified by beta-caryophyllene. Treatment with beta-caryophyllene attenuated the SE-induced increase of albumin immunoreactivity in the hippocampus, indicating a protective effect against blood-brain-barrier breakdown.

CONCLUSIONS

Given the inherent difficulties in the treatment of SE and its consequences, present results suggest that beta-caryophyllene deserve further investigation as an adjuvant therapeutic strategy for SE.

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 1β (IL 1β), 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 α_2/3) followed by K_m (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.

Hepatic susceptibility to oxidative damage after repeated concomitant exposure to aspartame and aflatoxin B1 in rats

The potential interactions among food additives/contaminants and the consequences to biological systems is a topic that is rarely addressed in scientific literature. Thus, the current study investigated if the combined administration of ASP and AFB₁ would impair hepatic and renal oxidative status. Male Wistar rats received during 14 days once a day ASP (75 mg/Kg) and/or AFB₁ (250 µg/Kg) through intragastric route. At the end of experimental protocol, samples of liver and kidneys were collected for assessing biochemical markers of oxidative status. In the hepatic tissue, the treatment with a single substance (ASP or AFB₁) caused an increase in TBARS levels, and a reduction in non-enzymatic antioxidant defenses (Vit C and NPSH levels and FRAP test). In the kidneys, TBARS levels were increased only in the group that received ASP + AFB₁. The association reduced NPSH content, while the treatment with AFB₁ reduced the FRAP levels. GST and CAT activities were increased in all treatments. Overall, ASP and AFB1 association presented higher toxic effects to the tissues. To the best of our knowledge, this is the first study demonstrating that the associated use of both ASP and AFB1 induces more extensive injuries in comparison to the effects caused by each one alone. Therefore, these data demonstrated that concomitant exposure to ASP and AFB₁ potentiated their oxidative damage in hepatic tissue, suggesting that this organ is particularly sensitive to the toxic action induced by these substances.

Therapeutic potential of beta-caryophyllene against aflatoxin B1-Induced liver toxicity: biochemical and molecular insights in rats

Aflatoxin B₁ (AFB₁) is a mycotoxin highly toxic and carcinogenic to humans due to its potential to induce oxidative stress. The Beta-caryophyllene (BCP) have been highlighted for its broad spectrum of pharmacological effects. The present study aimed to investigate the beneficial effects of BCP against the susceptibility of hepatic and renal tissues to AFB₁ toxicity, in biochemical parameters to assess organ function, tissue oxidation, and the immunocontent of oxidative and inflammatory proteins. Male Wistar rats was exposed to AFB₁ (250 μg/kg, i.g.) and/or BCP (100 mg/kg, i.p.) for 14 successive days. It was found that exposure to AFB₁ did not change the measured renal toxicity parameters. Also, AFB₁ increased liver injury biomarkers (gamma glutamyl transferase and alkaline phosphatase) and reduced levels of non-enzymatic antioxidant defenses (ascorbic acid and non-protein thiol), however did not cause changes in the lipid peroxidation levels. Moreover, AFB₁ interfered in oxidative pathway regulated by Kelch-like ECH-associated protein (Keap1)/nuclear factor (erythroid-derived 2)-like 2 (Nrf2), overacting Glutathione-S-Transferase (GST) activity. Lastly, a main effect of AFB₁ on the total interleukin 1 beta (IL-1β) was observed. Remarkably, the associated treatment of AFB₁ + BCP improved altered liver parameters. In addition, BCP and AFB₁ + BCP groups showed an increase in the levels of inhibitor of nuclear factor kappa-B kinase subunit beta (IKKβ). Thus, these results indicated that BCP has potential protective effect against AFB₁ induced hepatotoxicity.

Inhibition of PACAP/PAC1/VPAC2 signaling impairs the consolidation of social recognition memory and nitric oxide prevents this deficit

Social recognition memory (SRM) forms the basis of social relationships of animals. It is essential for social interaction and adaptive behavior, reproduction and species survival. Evidence demonstrates that social deficits of psychiatric disorders such as autism and schizophrenia are caused by alterations in SRM processing by the hippocampus and amygdala. Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) and its receptors PAC1, VPAC1 and VPAC2 are highly expressed in these regions. PACAP is a pleiotropic neuropeptide that modulates synaptic function and plasticity and is thought to be involved in social behavior. PACAP signaling also stimulates the nitric oxide (NO) production and targets outcomes to synapses. In the present work, we investigate the effect of the infusion of PACAP-38 (endogenous neuropeptide and potent stimulator of adenylyl cyclase), PACAP 6-38 (PAC1/VPAC2 receptors antagonist) and S-Nitroso-N-acetyl-DL-penicillamine (SNAP, NO donor) in the CA1 region of the hippocampus and in the basolateral amygdala (BLA) on the consolidation of SRM. For this, male Wistar rats with cannulae implanted in CA1 or in BLA were subjected to a social discrimination paradigm, which is based on the natural ability of rodents to investigate unfamiliar conspecifics more than familiar one. In the sample phase (acquisition), animals were exposed to a juvenile conspecific for 1 h. Immediately, 60 or 150 min after, animals received one of different pharmacological treatments. Twenty-four hours later, they were submitted to a 5 min retention test in the presence of the previously presented juvenile (familiar) and a novel juvenile. Animals that received infusions of PACAP 6-38 (40 pg/side) into CA1 immediately after the sample phase or into BLA immediately or 60 min after the sample phase were unable to recognize the familiar juvenile during the retention test. This impairment was abolished by the coinfusion of PACAP 6-38 plus SNAP (5 μg/side). These results show that the blockade of PACAP/PAC1/VPAC2 signaling in the CA1 and BLA during a restricted post-acquisition time window impairs the consolidation of SRM and that the SNAP is able to abolish this deficit. Findings like this could potentially be used in the future to influence studies of psychiatric disorders involving social behavior.

Sustained glial reactivity induced by glutaric acid may be the trigger to learning delay in early and late phases of development: Involvement of p75NTR receptor and protection by N-acetylcysteine

Degeneration of striatal neurons and cortical atrophy are pathological characteristics of glutaric acidemia type I (GA-I), a disease characterized by accumulation of glutaric acid (GA). The mechanisms that lead to neuronal loss and cognitive impairment are still unclear. The purpose of this study was to verify if acute exposure to GA during the neonatal period is sufficient to trigger apoptotic processes and lead to learning delay in early and late period. Besides, whether N-acetylcysteine (NAC) would protect against impairment induced by GA. Pups mice received a dose of GA (2.5 μmol/ g) or saline, 12 hs after birth, and were treated with NAC (250 mg/kg) or saline, up to 21th day of life. Although GA exhibited deficits in the procedural and working memories in 21 and 40-day-old mice, NAC protected against cognitive impairment. In striatum and cortex, NAC prevented glial cells activation (GFAP and Iba-1), decreased NGF, Bcl-2 and NeuN, the increase of lipid peroxidation and PARP induced by GA in both ages. NAC protected against increased p75NTR induced by GA, but not in cortex of 21-day-old mice. Thus, we showed that the integrity of striatal and cortical pathways has an important role for learning and suggested that sustained glial reactivity in neonatal period can be an initial trigger for delay of cognitive development. Furthermore, NAC protected against cognitive impairment induced by GA. This work shows that early identification of the alterations induced by GA is important to avoid future clinical complications and suggest that NAC could be an adjuvant treatment for this acidemia.

Phenytoin-loaded lipid-core nanocapsules improve the technological properties and in vivo performance of fluidised bed granules

Lipid-core nanocapsules (LNCs) were recently reported by our group as a suitable binder system to produce fluidised bed granules. However, there is still a lack of knowledge about the influence of using these nanocarriers loaded with a drug on the properties of the granules and their in vivo performance. Therefore, this study was designed to produce innovative fluidised bed granules containing phenytoin-loaded LNCs (LNC_PHT) as a strategy to evaluate the influence of the presence of the drug-loaded nanocarriers on their in vitro and in vivo properties. Granules were produced using a mixture of maltodextrin and phenytoin (1:0.004 w/w) as substrate. They were prepared by fluid bed granulation using water or LNC_PHT as the liquid binder, affording good yields (73-82%) of granules with low moisture content (<5%). Granules prepared with LNC_PHT had larger mean size (122 μm) compared to maltodextrin primary particles (50 μm) due to the formation of solid bridges. Moreover, the use of LNC_PHT as the liquid binder improved their powder flow properties. The nanocarriers were recovered after aqueous dispersion (3.00 mg.mL^-1 of PHT) with a redispersibility close to 90%. After reconstitution in water, granules containing LNC_PHT showed an improved dissolution behaviour compared to those prepared without them. In addition, they showed a higher mucoadhesive effect due to a combined effect of the LNC_PHT and maltodextrin in the interactions with porcine intestinal mucosa. Regarding the in vivo studies, granules containing the combination of non-encapsulated PHT and PHT-loaded lipid-core nanocapsules increased the latency to seizures compared to placebo granules, showing effective anticonvulsant effect in mice. In conclusion, the use of drug-loaded nanocapsules as binder is an encouraging approach to produce fluidised bed mucoadhesive granules with improved technological properties and in vivo performance.

Neuroprotective effects of thromboxane receptor antagonist SQ 29,548 after pilocarpine-induced status epilepticus in mice

Thromboxane A₂ (TXA₂) is an important eicosanoid in the cardiovascular system, and increasing evidence suggests that TXA₂ receptors (TPs) and their ligands may constitute valuable tools for the development of neuroprotective drugs. However, the role of TPs on seizure-induced damage has not been investigated. Therefore, we evaluated the effects of SQ 29,548, a potent and selective TP antagonist-on neuromotor performance, neurodegeneration, reactive astrocytosis, and c-Fos protein immunoreactivity after pilocarpine-induced status epilepticus (SE) in mice. Adult C57BL/6 mice received intracerebroventricular SQ 29,548 injections 90 min and 24 h after pilocarpine-induced SE. We found that SQ 29,548 prevented the impairment of neuromotor performance (Neuroscore test) 48 h after pilocarpine-induced SE. Data analysis suggested the existence of two subgroups of SQ 29,548-treated post-SE animals. Eight out of 12 SQ 29,548-treated animals displayed Neuroscore values identical to those of vehicle-treated controls, and were considered SQ 29,548 responders. However, 4 out of 12 SQ 29,548-treated animals did not show any improvement in Neuroscore values, and were considered SQ 29,548 non-responders. Treatment with SQ 29,548 attenuated SE-induced increase in the number of FJC- or GFAP-positive cells in the hippocampus of SQ 29,548 responders. In addition, SQ 29,548 prevented the SE-elicited increase of c-Fos immunoreactivity in the hippocampus. In summary, our results suggest that the TP antagonist (SQ 29,548) improves neurological outcome after pilocarpine-induced SE in mice. The existence of SQ 29,548 responders and non-responders was suggested by results from the Neuroscore test. Additional studies are needed to understand the mechanisms underlying these findings, as well as the potential uses of TP antagonists in the treatment of seizure-induced damage.

The flavonoid chrysin protects against zearalenone induced reproductive toxicity in male mice

The mycotoxin zearalenone (ZEA) has strong estrogenic effects and elicits reproductive toxicity. Chrysin is a natural flavonoid found in many plant and has a broad range of pharmacological activities, including anticancer, antioxidant and anti-inflammatory. The present study aimed to investigate the potential protective effects of chrysin against ZEA toxicity. Mice received chrysin (5 or 20 mg/kg; i.g.) for ten days, and then received a single injection of ZEA (40 mg/kg). Two days thereafter, blood and testes were collected. ZEA decreased number and motility of sperm, plasma testosterone levels, enzymatic (glutathione peroxidase, glutathione reductase, glutathione-S-transferase) and non-enzimatic defenses (reduced glutathione). Moreover, ZEA increased 4-hydroxynonenal and 8-hydroxy-2'-deoxyguanosine levels, myeloperoxidase activity and levels of proinflammatory cytokines (interleukins-1β and 6, tumor necrosis factor alpha). ZEA also decreased levels of anti-inflammatory cytokine interleukin-10 and increased activity of caspases 3 and 9. Chrysin treatment increased the number and motility of sperm, testosterone levels, restored antioxidant defenses and reduced the inflammation and apoptosis process. In summary, chrysin attenuated the toxic effects caused by ZEA in blood and testes of mice, suggesting a potential preventive treatment against the deleterious effects of ZEA.

Ammonia role in glial dysfunction in methylmalonic acidemia

Hyperammonemia is a common finding in patients with methylmalonic acidemia. However, its contribution to methylmalonate (MMA)-induced neurotoxicity is poorly understood. The aim of this study was evaluate whether an acute metabolic damage to brain during the neonatal period may disrupt cerebral development, leading to neurodevelopmental disorders, as memory deficit. Mice received a single intracerebroventricular dose of MMA and/or NH₄Cl, administered 12 hs after birth. The maze tests showed that MMA and NH₄Cl injected animals (21 and 40 days old) exhibited deficit in the working memory test, but not in the reference memory test. Furthermore, MMA and NH₄Cl increased the levels of 2',7'-dichlorofluorescein-diacetate (DCF), TNF-α, IL-1β in the cortex, hippocampus and striatum of mice. MMA and NH₄Cl also increased glial proliferation in all structures. Since the treatment of MMA and ammonia increased cytokines levels, we suggested that it might be a consequence of the glial activation induced by the acid and ammonia, leading to delay in the developing brain and contributing to behavioral alterations. However, this hypothesis is speculative in nature and more studies are needed to clarify this possibility.

Na+, K+-ATPase Activating Antibody Displays in vitro and in vivo Beneficial Effects in the Pilocarpine Model of Epilepsy

Na⁺, K⁺-ATPase is an important regulator of brain excitability. Accordingly, compelling evidence indicates that impairment of Na⁺, K⁺-ATPase activity contributes to seizure activity in epileptic mice and human with epilepsy. In addition, this enzyme is crucial for plasma membrane transport of water, glucose and several chemical mediators, including glutamate, the major excitatory transmitter in the mammalian brain. Since glucose hypometabolism and increased glutamate levels occur in clinical and experimental epilepsy, we aimed the present study to investigate whether activation of Na⁺, K⁺-ATPase activity with specific antibody (DRRSAb) would improve glucose uptake and glutamate release in pilocarpine-treated mice. We found decreased uptake of the glucose fluorescent analog 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-il)amino]-2-desoxi-d-glucose (2-NBDG) in cerebral slices from pilocarpine-treated animals. Interestingly, decreased 2-NBDG uptake was not detected in DRRSAb-treated slices, suggesting a protective effect of the Na⁺, K⁺-ATPase activator. Moreover, DRRSAb prevented the increase in glutamate levels in the incubation media of slices from pilocarpine-treated mice. In addition, in vivo intrahippocampal injection of DRRSAb restored crossing activity of pilocarpine-treated mice in the open-field test. Overall, the present data further support the hypothesis that activation of the Na⁺, K⁺-ATPase is a promising therapeutic strategy for epilepsy.

Effect of atorvastatin on behavioral alterations and neuroinflammation during epileptogenesis

Temporal lobe epilepsy (TLE) is the most frequent and medically refractory type of epilepsy in humans. In addition to seizures, patients with TLE suffer from behavioral alterations and cognitive deficits. Poststatus epilepticus model of TLE induced by pilocarpine in rodents has enhanced the understanding of the processes leading to epilepsy and thus, of potential targets for antiepileptogenic therapies. Clinical and experimental evidence suggests that inflammatory processes in the brain may critically contribute to epileptogenesis. Statins are inhibitors of cholesterol synthesis, and present pleiotropic effects that include antiinflammatory properties. We aimed the present study to test the hypothesis that atorvastatin prevents behavioral alterations and proinflammatory state in the early period after pilocarpine-induced status epilepticus. Male and female C57BL/6 mice were subjected to status epilepticus induced by pilocarpine and treated with atorvastatin (10 or 100mg/kg) for 14days. Atorvastatin slightly improved the performance of mice in the open-field and object recognition tests. In addition, atorvastatin dose-dependently decreased basal and status epilepticus-induced levels of interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and interferon-γ (INF-γ) and increased interleukin-10 (IL-10) levels in the hippocampus and cerebral cortex. The antiinflammatory effects of atorvastatin were qualitatively identical in both sexes. Altogether, these findings extend the range of beneficial actions of atorvastatin and indicate that its antiinflammatory effects may be useful after an epileptogenic insult.

Subtle improvement of seizure susceptibility by atorvastatin treatment during epileptogenesis

BACKGROUND

The process by which a brain insult elicits epilepsy is termed epileptogenesis and it is characterized by numerous molecular and functional alterations. Statins are first-line drugs for hypercholesterolemia and related diseases, and display neuroprotective properties in clinical and experimental studies. Considering the importance in developing therapeutic strategies to prevent or modify epileptogenesis, we aimed the present study to test the hypothesis that atorvastatin modifies seizure susceptibility of mice after status epilepticus (SE).

METHODS

Male and female C57BL/6 mice were submitted to the pilocarpine-induced SE and then treated with atorvastatin (10 or 100mg/kg, once daily by gavage) for 14days. At days 7 and 14 post SE we evaluated the susceptibility of mice to the convulsant effects of a low dose of PTZ (30mg/kg). Cell loss in the hilus of dentate gyrus was evaluated by Giemsa staining.

RESULTS

Latencies to myoclonic jerks and to tonic-clonic seizures decreased between baseline (before SE) and days 7 and 14 after SE, confirming the development of seizure susceptibility. Atorvastatin protected against PTZ-induced tonic-clonic seizures in both sexes at day 14 post-SE. Protective effects were similar in both female and male mice, except that a high dose of atorvastatin was required for females (protection at 100mg/kg versus 10mg/kg in males). Giemsa staining did not reveal neuroprotective effects of atorvastatin.

CONCLUSIONS

Atorvastatin treatment during epileptogenesis had slight beneficial effects on seizure susceptibility. These seem not related to neuroprotection. Further studies are needed to determine the disease-modifying potential of atorvastatin in epilepsy.

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.

Rosmarinic acid is anticonvulsant against seizures induced by pentylenetetrazol and pilocarpine in mice

Epilepsy is a chronic neurological disease characterized by spontaneous recurrent seizures (SRS). Current anticonvulsant drugs are ineffective in nearly one-third of patients and may cause significant adverse effects. Rosmarinic acid is a naturally occurring substance which displays several biological effects including antioxidant and neuroprotective activity. Since oxidative stress and excitotoxicity play a role in the pathophysiology of seizures, we aimed the present study to test the hypothesis that rosmarinic acid displays anticonvulsant and disease-modifying effects. Female C57BL/6 mice received rosmarinic acid (0, 3, 10, or 30mg/kg; p.o.) 60min before the injection of pentylenetetrazol (PTZ, 60mg/kg; i.p.) or pilocarpine (300mg/kg, i.p.). Myoclonic and generalized tonic-clonic seizure latencies and generalized seizure duration were analyzed by behavioral and electroencephalographic (EEG) methods. The effect of acute administration of rosmarinic acid on mice behavior in the open-field, object recognition, rotarod, and forced swim tests was also evaluated. In an independent set of experiments, we evaluated the effect of rosmarinic acid (3 or 30mg/kg, p.o. for 14days) on the development of SRS and behavioral comorbidities in the pilocarpine post-status epilepticus (SE) model of epilepsy. Rosmarinic acid dose-dependently (peak effect at 30mg/kg) increased the latency to myoclonic jerks and generalized seizures in the PTZ model and increased the latency to myoclonic jerks induced by pilocarpine. Rosmarinic acid (30mg/kg) increased the number of crossings, the time at the center of the open field, and the immobility time in the forced swim test. In the chronic epilepsy model, treatment with rosmarinic acid did not prevent the appearance of SRS or behavioral comorbidities. In summary, rosmarinic acid displayed acute anticonvulsant-like activity against seizures induced by PTZ or pilocarpine in mice, but further studies are needed to determine its epilepsy-modifying potential.

Anticonvulsant activity of β-caryophyllene against pentylenetetrazol-induced seizures

Increasing evidence suggests that plant-derived extracts and their isolated components are useful for treatment of seizures and, hence, constitute a valuable source of new antiepileptic drugs with improved efficacy and better adverse effect profile. β-Caryophyllene is a natural bicyclic sesquiterpene that occurs in a wide range of plant species and displays a number of biological actions, including neuroprotective activity. In the present study, we tested the hypothesis that β-caryophyllene displays anticonvulsant effects. In addition, we investigated the effect of β-caryophyllene on behavioral parameters and on seizure-induced oxidative stress. Adult C57BL/6 mice received increasing doses of β-caryophyllene (0, 10, 30, or 100mg/kg). After 60 min, we measured the latencies to myoclonic and generalized seizures induced by pentylenetetrazole (PTZ, 60 mg/kg). We found that β-caryophyllene increased the latency to myoclonic jerks induced by PTZ. This result was confirmed by electroencephalographic analysis. In a separate set of experiments, we found that mice treated with an anticonvulsant dose of β-caryophyllene (100mg/kg) displayed an improved recognition index in the object recognition test. This effect was not accompanied by behavioral changes in the open-field, rotarod, or forced swim tests. Administration of an anticonvulsant dose of β-caryophyllene (100mg/kg) did not prevent PTZ-induced oxidative stress (i.e., increase in the levels of thiobarbituric acid-reactive substances or the decrease in nonprotein thiols content). Altogether, the present data suggest that β-caryophyllene displays anticonvulsant activity against seizures induced by PTZ in mice. Since no adverse effects were observed in the same dose range of the anticonvulsant effect, β-caryophyllene should be further evaluated in future development of new anticonvulsant drugs.

Fumonisin B1 facilitates seizures induced by pentylenetetrazol in mice

Fumonisin B1 (FB1) is a Fusarium spp. mycotoxin which constitutes a major public health issue because of its worldwide distribution and diversity of toxic effects.While the liver and kidney are considered the major target organs of FB1 toxicity in several species, evidence indicates that FB1 may be toxic to the brain. To further investigate the effects of FB1 on the central nervous system the present study aimed to test the hypothesis that acute FB1 exposure causes brain hyperexcitability and the potential underlying mechanisms. For these purposes, adult male C57BL/6 mice were injected with FB1 (8 mg/kg, i.p.) or its vehicle and 30 min thereafter received with a low dose of the classical convulsant pentylenetetrazol (PTZ, 30 mg/kg, i.p.) or its vehicle. After behavioral evaluation the cerebral cortex and the hippocampus were collected for analysis of Na(+),K(+)-ATPase activity, mitochondrial membrane potential (ΔΨm) and mitochondrial complex I and II activities. We found that FB1 reduced the latency for PTZ-induced myoclonic jerks and increased the number of these events. After exposure to FB1 total and α1 Na(+),K(+)-ATPase activities increased in cerebral cortex, whereas the same enzyme activities decreased in the hippocampus. Although no changes in mitochondrial complex I and II activities were found, acute exposure to FB1 increased ΔΨm in the cerebral cortex. Altogether, present results indicate that FB1 causes brain hyperexcitability in vivo, and that mitochondrial dysfunction may represent a potential underlying mechanism.

Evaluation of potential gender-related differences in behavioral and cognitive alterations following pilocarpine-induced status epilepticus in C57BL/6 mice

Together with pharmacoresistant seizures, the quality of life of temporal lobe epilepsy (TLE) patients is negatively impacted by behavioral comorbidities including but not limited to depression, anxiety and cognitive deficits. The pilocarpine model of TLE has been widely used to study characteristics of human TLE, including behavioral comorbidities. Since the outcomes of pilocarpine-induced TLE might vary depending on several experimental factors, we sought to investigate potential gender-related differences regarding selected behavioral alterations in C57BL6 mice. We found that epileptic mice, independent of gender, displayed increased anxiety-like behavior in the open-field test. In the object recognition test, epileptic mice, regardless of gender, showed a decreased recognition index at 24 (but not at 4) hours after training. On the other hand, no significant differences were found regarding mice learning and memory performance in the Barnes maze paradigm. Motor coordination and balance as assessed by the beam walk and rotarod tests were not impaired in epileptic mice of both genders. However, female mice, independent of epilepsy, performed the beam walk and rotarod tasks better than their male counterparts. We also found that only male epileptic mice displayed disturbed behavior in the forced swim test, but the mice of both genders displayed anhedonia-like behavior in the taste preference test. Lastly, we found that the extent of hilar cell loss is similar in both genders. In summary, both genders can be successfully employed to study behavioral comorbidities of TLE; however, taking the potential gender differences into account may help choose the more appropriated gender for a given task, which may be of value for the minimization of the number of animals used during the experiments.

Lycopene protects against acute zearalenone-induced oxidative, endocrine, inflammatory and reproductive damages in male mice

Male mice received lycopene for 10 days before a single oral administration of zearalenone (ZEA). After 48 h testes and blood were collected. Mice treated with lycopene/ZEA exhibited amelioration of the hematological changes. Lycopene prevented the reduction in the number and motility of spermatozoa and testosterone levels, indicating a protective effect in the testicular damage induced by ZEA. Lycopene was also effective in protecting against the decrease in glutathione-S-transferase, glutathione peroxidase, glutathione reductase and δ-aminolevulinic acid dehydratase activities caused by ZEA in the testes. Exposure of animals to ZEA induced modification of antioxidant and inflammatory status with increase of reduced glutathione (GSH) levels and increase of the oxidized glutathione, interleukins 1β, 2, 6, 10, tumor necrosis factor-α and bilirubin levels. Lycopene prevented ZEA-induced changes in GSH levels and inhibited the processes of inflammation, reducing the damage induced by ZEA. Altogether, our results indicate that lycopene was able to prevent ZEA-induced damage in the mice.

Long-term decrease in Na+,K+-ATPase activity after pilocarpine-induced status epilepticus is associated with nitration of its alpha subunit

Temporal lobe epilepsy (TLE) is the most common type of epilepsy with about one third of TLE patients being refractory to antiepileptic drugs. Knowledge about the mechanisms underlying seizure activity is fundamental to the discovery of new drug targets. 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. In the present study we tested the hypothesis that decreased Na(+),K(+)-ATPase activity is associated with changes in the alpha subunit phosphorylation and/or redox state. Activity of Na(+),K(+)-ATPase decreased in the hippocampus of C57BL/6 mice 60 days after pilocarpine-induced status epilepticus (SE). In addition, the Michaelis-Menten constant for ATP of α2/3 isoforms increased at the same time point. Nitration of the α subunit may underlie decreased Na(+),K(+)-ATPase activity, however no changes in expression or phosphorylation state at Ser(943) were found. Further studies are necessary define the potential of nitrated Na(+),K(+)-ATPase as a new therapeutic target for seizure disorders.

WITHDRAWN: Evaluation of potential gender-related differences in behavioral and cognitive alterations following pilocarpine-induced status epilepticus in C57BL/6 mice

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Lycopene treatment prevents hematological, reproductive and histopathological damage induced by acute zearalenone administration in male Swiss mice

Zearalenone (ZEA) is a mycotoxin commonly found as a contaminant in cereals. ZEA toxicity targets mainly the reproductive system, and oxidative stress plays an etiological role in its toxic effects. Therefore, the present study aimed to investigate the effect of lycopene, a potent carotenoid antioxidant, on markers of oxidative stress in liver, kidney and testes, and on reproductive, hematological and histopathological parameters after ZEA administration. Adult Swiss albino male mice received lycopene (20mg/kg, p.o.) for ten days before a single oral administration of ZEA (40mg/kg, p.o.), and 48h thereafter tissues (liver, kidney, testes and blood) were collected for biochemical, hematological and histological analyses. Lycopene prevented ZEA-induced changes in hematological parameters (increased number of leukocytes, segmented neutrophils, sticks, eosinophils and monocytes and decreased number of red blood cells (RBC), number of lymphocytes and platelets). Moreover, lycopene prevented the reduction in the number and motility of spermatozoa and the testicular tissue damage induced by ZEA. In addition, lycopene prevented the decrease in glutathione-S-transferase activity in kidney and testes and increased glutathione-S-transferase activity per se in the liver, kidneys and testes as well as superoxide dismutase activity in the liver. In summary, lycopene was able to prevent ZEA-induced acute toxic effects in male mice, suggesting that this antioxidant carotenoid may represent a promising prophylactic strategy against ZEA toxicity.

Atorvastatin withdrawal elicits oxidative/nitrosative damage in the rat cerebral cortex

Statins are inhibitors of the enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase, the rate-limiting step in cholesterol biosynthesis. Statins effectively prevent and reduce the risk of coronary artery disease through lowering serum cholesterol, and also exert anti-thrombotic, anti-inflammatory and antioxidant effects independently of changes in cholesterol levels. On the other hand, clinical and experimental evidence suggests that abrupt cessation of statin treatment (i.e. statin withdrawal) is associated with a deleterious rebound phenomenon. In fact, statin withdrawal increases the risk of thrombotic vascular events, causes impairment of endothelium-dependent relaxation and facilitates experimental seizures. However, evidence for statin withdrawal-induced detrimental effects to the brain parenchyma is still lacking. In the present study adult male Wistar rats were treated with atorvastatin for seven days (10mg/kg/day) and neurochemical assays were performed in the cerebral cortex 30 min (atorvastatin treatment) or 24h (atorvastatin withdrawal) after the last atorvastatin administration. We found that atorvastatin withdrawal decreased levels of nitric oxide and mitochondrial superoxide dismutase activity, whereas increased NADPH oxidase activity and immunoreactivity for the protein nitration marker 3-nitrotyrosine in the cerebral cortex. Catalase, glutathione-S-transferase and xanthine oxidase activities were not altered by atorvastatin treatment or withdrawal, as well as protein carbonyl and 4-hydroxy-2-nonenal immunoreactivity. Immunoprecipitation of mitochondrial SOD followed by analysis of 3-nitrotyrosine revealed increased levels of nitrated mitochondrial SOD, suggesting the mechanism underlying the atorvastatin withdrawal-induced decrease in enzyme activity. Altogether, our results indicate the atorvastatin withdrawal elicits oxidative/nitrosative damage in the rat cerebral cortex, and that changes in NADPH oxidase activity and mitochondrial superoxide dismutase activities may underlie such harmful effects.

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.

Involvement of hippocampal CAMKII/CREB signaling in the spatial memory retention induced by creatine

Although Creatine (Cr) and Phosphocreatine (PCr) systems play a key role in cellular energy and energy transport in neuronal cells, its implications for learning and memory are still controversial. Thus, we decided to investigate the involvement of cAMP-dependent protein kinase A (PKA), Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) and cAMP responsive element binding protein (CREB) in the spatial consolidation after an intrahippocampal injection of Cr. Statistical analysis revealed that Cr (2.5 nmol/hippocampus) (post-training) decreased the latency for escape and the mean number of errors on Barnes maze test. Post-training co-administration of the PKA inhibitor (H-89 25 ρmol/hippocampus) did not alter the facilitatory effect of Cr in this memory test. On the other hand, Cr-induced spatial retention was reverted by co-administration of the CaMKII inhibitor (STO-609 5 nmol/hippocampus). Neurochemical analysis revealed that intrahippocampal injection of Cr, when analyzed after 30 min rather than after 3 h, increased the levels of pCREB and pCaMKII but not pPKA levels. Statistical analysis also revealed that the post-training co-administration of STO-609 but not H-89 reversed the increase of pCREB levels induced by Cr. The results presented in this report suggest that intracellular CaMKII/CREB pathway plays a key role in the Cr-induced spatial retention. Thus, it is plausible to propose that Cr plays a putative role as a neuromodulator in the brain, and that at least some of its effects may be mediated by intracellular CaMKII/CREB pathway.

Exercise pre-conditioning reduces brain inflammation and protects against toxicity induced by traumatic brain injury: behavioral and neurochemical approach

Although the favorable effects of physical exercise in neurorehabilitation after traumatic brain injury (TBI) are well known, detailed pathologic and functional alterations exerted by previous physical exercise on post-traumatic cerebral inflammation have been limited. In the present study, it is showed that fluid percussion brain injury (FPI) induced motor function impairment, followed by increased plasma fluorescein extravasation and cerebral inflammation characterized by interleukin-1β, tumor necrosis factor-α (TNF-α) increase, and decreased IL-10. In addition, myeloperoxidase (MPO) increase and Na⁺,K⁺-ATPase activity inhibition after FPI suggest that the opening of blood-brain barrier (BBB) followed by neurtrophils infiltration and cerebral inflammation may contribute to the failure of selected targets leading to secondary damage. In fact, Pearson's correlation analysis revealed strong correlation of MPO activity increase with Na⁺,K⁺-ATPase activity inhibition in sedentary rats. Statistical analysis also revealed that previous running exercise (4 weeks) protected against FPI-induced motor function impairment and fluorescein extravasation. Previous physical training also induced IL-10 increase per se and protected against cerebral IL-1β, and TNF-α increase and IL-10 decrease induced by FPI. This protocol of physical training was effective against MPO activity increase and Na⁺,K⁺-ATPase activity inhibition after FPI. The present protection correlated with MPO activity decrease suggests that the alteration of cerebral inflammatory status profile elicited by previous physical training reduces initial damage and limits long-term secondary degeneration after TBI. This prophylactic effect may facilitate functional recovery in patients suffering from brain injury induced by 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.

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.

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.

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.