Effects of the vitamin E in catalase activities in hippocampus after status epilepticus induced by pilocarpine in Wistar rats

Inhibitory action of antioxidants (ascorbic acid or α-tocopherol) on seizures and brain damage induced by pilocarpine in rats

Temporal lobe epilepsy is the most common form of epilepsy in humans. Oxidative stress is a mechanism of cell death induced by seizures. Antioxidant compounds have neuroprotective effects due to their ability to inhibit free radical production. The objectives of this work were to comparatively study the inhibitory action of antioxidants (ascorbic acid or α-tocopherol) on behavioral changes and brain damage induced by high doses of pilocarpine, aiming to further clarify the mechanism of action of these antioxidant compounds. In order to determinate neuroprotective effects, we studied the effects of ascorbic acid (250 or 500 mg/kg, i.p.) and α-tocopherol (200 or 400 mg/kg, i.p.) on the behavior and brain lesions observed after seizures induced by pilocarpine (400 mg/kg, i.p., P400 model) in rats. Ascorbic acid or α-tocopherol injections prior to pilocarpine suppressed behavioral seizure episodes. These findings suggested that free radicals can be produced during brain damage induced by seizures. In the P400 model, ascorbic acid and α-tocopherol significantly decreased cerebral damage percentage. Antioxidant compounds can exert neuroprotective effects associated with inhibition of free radical production. These results highlighted the promising therapeutic potential of ascorbic acid and α-tocopherol in treatments for neurodegenerative diseases.

Oxidative stress mediates hippocampal neuron death in rats after lithium-pilocarpine-induced status epilepticus

Oxidative stress, which is defined as the over-production of free radicals, can dramatically alter neuronal function and has been linked to status epilepticus (SE). The pathological process and underlying mechanisms involved in the oxidative stress during SE are still not fully clear. In the current study, SE was induced in rats by lithium-pilocarpine administration. Our data show that hippocampal neuron death occurs at 6h and is sustained for 7 days after SE. The production of nitric oxide (NO) started to increase at 30 min and was evident at 6h and 7 days after SE, which coincided with increased expression of neuronal nitric oxide synthase (nNOS), inducible nitric oxide synthase (iNOS) and malondialdehyde (MDA) after SE, whereas, activated caspase-3 prominently appeared at 7 days after SE. Further, FK506, an immunosuppressant, partially rescued the neuron death and attenuated the expression of NO, nNOS, iNOS, MDA and activated caspase-3. Taken together, our study indicates that oxidative stress mediated hippocampal neuron death occurs prior to caspase-3 activation and that FK506 plays an important role in protecting hippocampal neurons during status epilepticus.

Mitochondria, oxidative stress, and temporal lobe epilepsy

Mitochondrial oxidative stress and dysfunction are contributing factors to various neurological disorders. Recently, there has been increasing evidence supporting the association between mitochondrial oxidative stress and epilepsy. Although certain inherited epilepsies are associated with mitochondrial dysfunction, little is known about its role in acquired epilepsies such as temporal lobe epilepsy (TLE). Mitochondrial oxidative stress and dysfunction are emerging as key factors that not only result from seizures, but may also contribute to epileptogenesis. The occurrence of epilepsy increases with age, and mitochondrial oxidative stress is a leading mechanism of aging and age-related degenerative disease, suggesting a further involvement of mitochondrial dysfunction in seizure generation. Mitochondria have critical cellular functions that influence neuronal excitability including production of adenosine triphosphate (ATP), fatty acid oxidation, control of apoptosis and necrosis, regulation of amino acid cycling, neurotransmitter biosynthesis, and regulation of cytosolic Ca(2+) homeostasis. Mitochondria are the primary site of reactive oxygen species (ROS) production making them uniquely vulnerable to oxidative stress and damage which can further affect cellular macromolecule function, the ability of the electron transport chain to produce ATP, antioxidant defenses, mitochondrial DNA stability, and synaptic glutamate homeostasis. Oxidative damage to one or more of these cellular targets may affect neuronal excitability and increase seizure susceptibility. The specific targeting of mitochondrial oxidative stress, dysfunction, and bioenergetics with pharmacological and non-pharmacological treatments may be a novel avenue for attenuating epileptogenesis.

Effects of ubiquinone on hydroperoxide concentration and antioxidant enzymatic activities in the rat hippocampus during pilocarpine-induced seizures

Recent researches have shown that antioxidant compounds may have certain neuroprotective effect against the neurotoxicity of seizures at cellular level. Ubiquinone (UQ), an antioxidant compound, exhibits a wide range of therapeutic effects that are attributed to its potent antioxidant capacity. The objective of the present study was to evaluate the neuroprotective effects of UQ in rats, against the observed oxidative stress during seizures induced by pilocarpine. Wistar rats were treated with either 0.9% saline (i.p., control group), UQ (5, 10 or 20 mg/kg, i.p., UQ5, UQ10 and UQ20 groups), pilocarpine (400 mg/kg, i.p., P400 group), or co-administration of pilocarpine with UQ group rats 30 min prior to UQ administration. After the treatments all groups were observed for 24 h. The antioxidant enzymatic activities as well as the hydroperoxide concentrations were measured using spectrophotometric methods and the results were analyzed. In pilocarpine group there was a significant increase in hydroperoxides concentration and glutathione peroxidase activity. However, no alteration was observed in superoxide dismutase and catalase activities. Antioxidant treatment significantly reduced the hydroperoxide content and increased the superoxide dismutase, catalase and glutathione peroxidase activities in rat hippocampus during seizures induced by pilocarpine. Our findings strongly support the hypothesis that oxidative stress in hippocampus occurs during seizures induced by pilocarpine, which indicates that brain damage induced by the oxidative process plays a crucial role in seizures pathogenic consequences. Our result also suggests that ubiquinone can exert significant neuroprotective effects that might be useful in the treatment of neurodegenerative diseases.

Cocaine-induced status epilepticus and death generate oxidative stress in prefrontal cortex and striatum of mice

Oxidative stress (OS) has been related to cocaine's actions and also to numerous nervous system pathologies, including seizures. The purpose of this work was to determine the alterations in glutathione (GSH) content, nitrite/nitrate and MDA levels after cocaine-induced toxicity. Male Swiss mice were injected (i.p.) with cocaine 90 mg/kg and observed during 1h. After this cocaine overdose some animals presented status epilepticus (SE) while some died after seizures. These animals were divided in two groups, SE and death. A group with an association of the antioxidant Vitamin E (Vit E, 400mg/kg, i.p.) plus Coc 90 (Vit E plus Coc 90) was undertaken to assess the neuroprotective effect of Vit E. Neurochemical analyses were carried out in prefrontal cortex (PFC) and striatum (ST). GSH levels increased only after cocaine-induced death in both areas studied. Cocaine-induced SE has increased nitrite/nitrate content in PFC and ST, while after death the increase was only in PFC. MDA (the lipid peroxidation marker) was elevated after SE and death in ST and only after death in PFC. Antioxidant treatment significantly reduced the GSH, nitrite/nitrate in ST and MDA levels. Only nitrite/nitrate content in PFC has not been decreased by Vit E pretreatment. The results relate that oxidative stress occurs after cocaine-induced toxicity mainly after death indicating that probably the increase of OS in the animal's brain leads to seizures and death, also showing a protective effect of Vit E in this process. Together with previous results this study contributes to the knowledge of cocaine-induced toxicity and possible in the near future to the use of antioxidants in the prevention of cocaine-induced CNS toxicity.

Oxidative stress in the hippocampus during experimental seizures can be ameliorated with the antioxidant ascorbic acid

Ascorbic acid has many nonenzymatic actions and is a powerful water-soluble antioxidant. It protects low density lipoproteins from oxidation and reduces harmful oxidants in the central nervous system. Pilocarpine-induced seizures have been suggested to be mediated by increases in oxidative stress. Current studies have suggested that antioxidant compounds may afford some level of neuroprotection against the neurotoxicity of seizures. The objective of the present study was to evaluate the neuroprotective effects of ascorbic acid (AA) in rats, against the observed oxidative stress during seizures induced by pilocarpine. Wistar rats were treated with 0.9% saline (i.p., control group), ascorbic acid (500 mg/kg, i.p., AA group), pilocarpine (400 mg/kg, i.p., pilocarpine group), and the association of ascorbic acid (500 mg/kg, i.p.) plus pilocarpine (400 mg/kg, i.p.), 30 min before of administration of ascorbic acid (AA plus pilocarpine group). After the treatments all groups were observed for 6h. The enzyme activities as well as the lipid peroxidation and nitrite concentrations were measured using spectrophotometric methods and the results compared to values obtained from saline and pilocarpine-treated animals. Protective effects of ascorbic acid were also evaluated on the same parameters. In pilocarpine group there was a significant increase in lipid peroxidation and nitrite level. However, no alteration was observed in superoxide dismutase and catalase activities. Antioxidant treatment significantly reduced the lipid peroxidation level and nitrite content as well as increased the superoxide dismutase and catalase activities in hippocampus of adult rats after seizures induced by pilocarpine. Our findings strongly support the hypothesis that oxidative stress in hippocampus occurs during seizures induced by pilocarpine, proving that brain damage induced by the oxidative process plays a crucial role in seizures pathogenic consequences, and also imply that a strong protective effect could be achieved using ascorbic acid.

Effects of lipoic acid on oxidative stress in rat striatum after pilocarpine-induced seizures

The relationship between free radical and scavenger enzymes has been found in the epilepsy and reactive oxygen species have been implicated in seizure-induced neurodegeneration. It has been suggested that pilocarpine-induced seizures is mediated by increases in oxidative stress. Current researches have suggested that antioxidant compounds may afford some level of neuroprotection against the neurotoxicity of seizures in cellular level. The objective of the present study was to evaluate the neuroprotective effects of lipoic acid (LA) in rats, against the observed oxidative stress during seizures induced by pilocarpine. Wistar rats were treated with 0.9% saline (i.p., control group), LA (20mg/kg, i.p., LA group), pilocarpine (400mg/kg, i.p., P400 group), and the association of LA (20mg/kg, i.p.) plus pilocarpine (400mg/kg, i.p.), 30 min before of administration of LA (LA plus P400 group). After the treatments all groups were observed for 1h. The enzyme activities as well as the lipid peroxidation and nitrite concentrations were measured using spectrophotometric methods and the results compared to values obtained from saline and pilocarpine-treated animals. Protective effects of LA were also evaluated on the same parameters. In P400 group there was a significant increase in lipid peroxidation, nitrite level and glutathione peroxidase (GPx) activity. However, no alteration was observed in superoxide dismutase (SOD) and catalase activities. Antioxidant treatment significantly reduced the lipid peroxidation level and nitrite content as well as increased the SOD, catalase and GPx activities in rat striatum after seizures. Our findings strongly support the hypothesis that oxidative stress in striatum occurs during seizures induced by pilocarpine, proving that brain damage induced by the oxidative process plays a crucial role in seizures pathogenic consequences, and also imply that strong protective effect could be achieved using LA.

Antioxidants and free radical scavengers do not consistently delay seizure onset in animal models of acute seizures

A number of herbal compounds with direct antioxidant activity slow the onset, or completely block, the occurrence of seizures. This increase in latency has been proposed to be due to the antioxidant activity. This hypothesis was directly tested by determining the effects of Trolox, a vitamin E analog, vitamin C, melatonin, and alpha-lipoic acid on the latency to acute seizures induced with pilocarpine, kainic acid, or subcutaneous pentylenetetrazol (PTZ) in adult rats. Trolox, vitamin C, and alpha-lipoic acid had significant anticonvulsant activity against pilocarpine, but there were no acute changes in reduced glutathione levels at 15 or 120 minutes. Other than reduced mortality with vitamin C in the PTZ model, none of the antioxidants had a significant effect against PTZ- or kainic acid-induced seizures. The lack of consistent anticonvulsant effect suggests that the antioxidant activity of the herbal preparations cannot account for the delay in seizure onset.

Vitamin C antioxidant effects in hippocampus of adult Wistar rats after seizures and status epilepticus induced by pilocarpine

Vitamin C (VIT C) is an exogenous antioxidant able to alter the brain oxidative stress. Antioxidant properties have been showed in seizures and status epilepticus (SE) induced by pilocarpine in adult rats. This present study was aimed at was investigating the VIT C effects on latency to first seizure, in percentage of seizures, mortality rate, as well as hippocampal lipid peroxidation levels and catalase activity after seizures and SE. The VIT C effects were investigated after the pretreatment with dose 250 mg/kg, i.p., 30 min before pilocarpine administration (400mg/kg, s.c., pilocarpine group (P400)). The VIT C increase the latency to first seizure and decrease the mortality rate and lipid peroxidation levels. In P400+VIT C and VIT C groups were observed an increase in hippocampal catalase activity. Our results suggests that the vitamin C can exert antioxidant and anticonvulsive effects in adult rats, suggesting that this vitamin can be able by reduction of lipid peroxidation content and increased of catalase enzymatic activity which cerebral compensatory mechanisms in free radical formation during SE.