Root extract of Anacyclus pyrethrum ameliorates seizures, seizure-induced oxidative stress and cognitive impairment in experimental animals

In Ayurveda, Anacyclus pyrethrum has been used as a brain tonic. The present study evaluates the effect of hydroalcoholic extract of A. pyrethrum (HEAP) root against seizures, seizure-induced oxidative stress and cognitive impairment in experimental models of seizures. Male Wistar rats were used in the study. HEAP was administered in doses of 50, 100, 250, 500 in pentylenetetrazole (PTZ) model and 250, 500 and 1000 mg/kg in maximal electroshock (MES) model. Myoclonic jerk latency and generalized tonic clonic seizures (GTCS) were noted in PTZ whereas occurrence of tonic hind limb extension (THLE) was observed in MES seizures. Cognitive deficit was assessed using elevated plus maze and passive avoidance tests. Whole brain reduced glutathione, malondialdehyde levels and cholinesterase activity were measured. HEAP showed 50, 66.7, 83.3 and 100% protection at 50,100, 250 and 500 mg/kg, respectively against GTCS in PTZ induced seizures. In MES induced seizures, HEAP produced 16.7, 33.3 and 50% protection against THLE at 250, 500 and 1000 mg/kg, respectively. HEAP administration significantly prevented seizure induced oxidative stress and cognitive impairment in a dose-dependent manner. HEAP also normalized the decrease in cholinesterase activity caused by seizures. Thus, HEAP showed protective effect against seizures, seizure-induced oxidative stress and cognitive impairment in rats.     

Naringin ameliorates pentylenetetrazol-induced seizures and associated oxidative stress,inflammation, and cognitive impairment in rats: Possible mechanisms of neuroprotection

Oxidative stress and cognitive impairment are associated with PTZ-induced convulsions. Naringin is a bioflavonoid present in the grapefruit. It is a potent antioxidant, and we evaluated its effect on PTZ-induced convulsions. Rats were pretreated with normal saline, naringin (20, 40, and 80 mg/kg, i.p.), or diazepam (5 mg/kg, i.p.) 30 min prior to the administration of PTZ. The administration of PTZ induced myoclonic jerks and generalized tonic–clonic seizures (GTSs). We observed that naringin significantly prolonged the induction of myoclonic jerks dose-dependently. Naringin (80 mg/kg, i.p.) pretreatment protected all rats, and this protective effect was annulled by the GABA_A receptor antagonist, flumazenil. In addition, naringin reduced brain MDA and TNF-α levels and conserved GSH. The pretreatment also enhanced the performance of rats in the passive avoidance task. Our observations highlight the antioxidant, antiinflammatory, and anticonvulsant potential of naringin. Also, naringin modulates the GABA_A receptor to produce anticonvulsant effects and to ameliorate cognitive impairment.     

Coenzyme Q10 enhances the anticonvulsant effect of phenytoin in pilocarpine-induced seizures in rats and ameliorates phenytoin-induced cognitive impairment and oxidative stress

Conventional antiepileptic drugs fail to adequately control seizures and predispose to cognitive impairment and oxidative stress with chronic usage in a significant proportion of patients with epilepsy. Coenzyme Q10 (CoQ10), an antioxidant compound, exhibits a wide range of therapeutic effects that are attributed to its potent antioxidant capacity. To evaluate the neuroprotective effects of CoQ10 in rats against the observed oxidative stress during seizures induced by pilocarpine, and to study its interactions with the conventional antiepileptic drug phenytoin, two experiments were performed. Experiment 1 was conducted to test the effect of phenytoin, CoQ10, or both on seizure severity and oxidative markers in the pilocarpine model of epilepsy. Experiment 2 was conducted to test the effect of 2 weeks of chronic treatment with phenytoin, CoQ10, or both on oxidative markers and behavioral tests in rats. Overall, CoQ10 reduced the severity of pilocarpine-induced seizures and the severity of oxidative stress. Moreover, it potentiated the antiepileptic effects afforded by phenytoin treatment, with the potential safety and efficacy in ameliorating oxidative stress and cognitive impairment caused by chronic phenytoin therapy. Our findings strongly suggest that CoQ10 can be considered a safe and effective adjuvant to phenytoin therapy in epilepsy both to ameliorate seizure severity and to protect against seizure-induced oxidative damage by reducing the cognitive impairment and oxidative stress associated with chronic use of phenytoin.     

Animal models of epilepsy and experimental seizures

Animal models of epilepsy are essential for the search of new effective antiepileptic drugs. Moreover they may lead to the discovery of the basic neuronal dysfunction(s) which underlies human epilepsies. Animal epilepsies as well as experimental seizures are usually considered as valid models of human epilepsies when, and only when, the drugs which are effective in human epilepsies prevent seizures in animals. This, however, precludes finding new drugs for resistant epilepsies. Animal models of epilepsy can be classified as follows: (i) experimental seizures induced by convulsant drugs or by an electrical stimulation; (ii) reflex epilepsies; (iii) idiopathic epilepsies. Examples of animal models of epilepsy taken from each of these three classes are briefly reviewed. Seizures induced by convulsant drugs or by an electroshock are widely used as simple and rapid screening systems for new anticonvulsant compounds. Moreover, the use of chemical convulsants can lead to new hypotheses concerning the mechanisms underlying human epilepsies. Thus, one of the main arguments in favor of the GABAergic hypothesis of epilepsy is that GABA antagonists induce seizures which are readily counteracted by most antiepileptic drugs. Among the other models of experimentally induced seizures, the kindling model is usually considered, on the basis of its pharmacological characteristics, as a Grand Mal type epilepsy model. Thirty years after this model was first described, the exact modifications induced in the brain by the kindling procedure remain unknown. Various animal species exhibit reflex epilepsies. Myoclonic seizures can be induced by photic stimulation in Papio-papio baboons; tonic-clonic seizures can be induced by various auditory stimuli in certain strains of mice and rats; myoclonic and tonic-clonic seizures can be induced by a variety of environmental stimuli in the mongolian gerbil; photosensitive and febrile seizures have been described in fowl. Most antiepileptic drugs are effective in these reflex epilepsies. Alterations in several neurotransmitter systems have been reported in susceptible strains as compared to resistant strains, such as modifications in noradrenergic, serotoninergic, GABAergic or glutamatergic transmissions, but no single abnormal parameter can unequivocally be correlated to seizure susceptibility. Idiopathic epilepsy is not uncommon in dogs and the prevalence of the disease appears to be comparable to that observed in man. Grand Mal type epilepsy appears to be the most frequent type of epilepsy in dogs; little work has been devoted to the study of the neurochemical alterations which may underly the disease.     

Aminoguanidine alleviated MMA-induced impairment of cognitive ability in rats by downregulating oxidative stress and inflammatory reaction

Methylmalonic acidemia (MMA) is the most common organic acidemia in childhood. Many “treated” patients continued to display various degrees of mental retardation and psychomotor delay, which could be caused by brain damage from elevated oxidative stress. Aminoguanidine (AG), a synthetic antioxidant, was tested in a MMA rat model for its potential therapeutic effects on memory impairment. The effects of AG on MMA-induced cognitive impairment in Wistar rats were evaluated with Morris Water Maze. The levels of nerve cell apoptosis and microglial activation were investigated to illustrate the mechanisms of the improvement of cognition with AG treatment in MMA rats. To further explore the mechanism of neuroprotection induced by AG, several biomarkers including free radicals and inflammatory cytokines in the hippocampus were quantified. The results showed that the rats treated with AG exhibited better neurological behavior performances than MMA model rats. The AG-treated rats had a decreased level of apoptosis of the hippocampal neurons, which could be the structural basis of the observed neural behavior protection. In addition, AG treatment significantly inhibited the activation of microglia. The AG-treated rats had decreased levels of IL-1β, IL-6, TNF-α, NO, malonaldehyde and iNOS activities in the hippocampus. The level of glutathione and superoxide dismutase activity in the hippocampus of the AG-treated rats increased significantly. In conclusion, AG could alleviate the MMA-induced cognitive impairment via down-regulating of oxidative stress and inflammatory reaction and provide a basis as a therapeutic potential against MMA-induced cognitive impairment.     

Peripheral oxidative stress biomarkers in mild cognitive impairment and Alzheimer's disease

Oxidative stress has been associated with normal aging and Alzheimer's disease (AD). However, little is known about oxidative stress in mild cognitive impairment (MCI) patients who present a high risk for developing AD. The aim of this study was to investigate plasma production of the lipid peroxidation marker, malonaldehyde (MDA) and to determine, in erythrocytes, the enzymatic antioxidant activity of catalase, glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione S-transferase (GST) in 33 individuals with MCI, 29 with mild probable AD and 26 healthy aged subjects. GR/GPx activity ratio was calculated to better assess antioxidant defenses. The relationship between oxidative stress and cognitive performance was also evaluated by the Mini Mental State Examination (MMSE). AD patients showed higher MDA levels than both MCI and healthy elderly subjects. MCI subjects also exhibited higher MDA levels compared to controls. Catalase and GPx activity were similar in MCI and healthy individuals but higher in AD. GR activity was lower in MCI and AD patients than in healthy aged subjects. Additionally, GR/GPx ratio was higher in healthy aged subjects, intermediate in MCI and lower in AD patients. No differences in GST activity were detected among the groups. MMSE was negatively associated with MDA levels (r = -0.31, p = 0.028) and positively correlated with GR/GPx ratio in AD patients (r = 0.68, p < 0.001). MDA levels were also negatively correlated to GR/GPx ratio (r = -0.31, p = 0.029) in the AD group. These results suggest that high lipid peroxidation and decreased antioxidant defenses may be present early in cognitive disorders.     

美满霉素改善血管性痴呆大鼠认知功能损伤并抑制氧化应激

目的 观察美满霉素(minocycline)对血管性痴呆大鼠学习记忆功能和脑组织内皮型一氧化氮合酶(endothelial nitric oxide synthase,eNOS)、诱导型一氧化氮合酶(inducible nitric oxide synthase,iNOS)表达的影响,探讨美满霉素对血管性痴呆的脑保护作用的机制.方法 Wistar大鼠随机分为假手术组(S组)、痴呆模型组(M组)、美满霉素治疗组(MT组).RT-PCR和免疫组织化学法检测大鼠脑组织eNOS、iNOS的表达,行为学检测大鼠学习记忆功能的改变.结果 M组与S组行为学检查显示,M组大鼠有显著学习记忆障碍(P＜0.01),MT组与M组比较行为学检测结果显示,MT组大鼠学习记忆障碍有显著改善(P＜0.01).MT组iNOS表达较M组降低(P＜0.01),MT组eNOS表达较M组增高(P＜0.05);MT组eNOS、iNOS表达较S组增高(P＜0.01);M组eNOS、iNOS表达较S组显著增高(P＜0.01).结论 美满霉素能降低血管性痴呆大鼠脑组织iNOS表达,增强eNOS表达,抑制氧化应激反应,发挥脑保护作用.     

Intranasal pitavastatin attenuates seizures in different experimental models of epilepsy in mice

This study was carried out to evaluate the effect of intranasal pitavastatin (PVS) on pentylenetetrazole (PTZ)-induced seizures, increasing current electroshock (ICES) seizures, and status epilepticus in mice. Intranasal PVS, 0.5 and 1.0 mg/kg, showed significant increase in latency to PTZ-induced seizures and ICES seizure threshold compared to control; however, the effects were dose-dependent and were more significant at higher dose. Further, intranasal PVS (1.0 mg/kg) but not intravenous PVS (50.0 mg/kg) showed effective protection against PTZ-induced status epilepticus. No impairment in cognitive functions was observed following intranasal PVS (1.0 mg/kg), thus making it a prospective therapeutic approach for acute seizures and status epilepticus.     

Hydroxycitric acid ameliorates inlfammation and oxidative stress in mouse models of multiple sclerosis

Hydroxycitric acid (HCA) is derived primarily from the Garcinia plant and is widely used for its anti-in-lfammatory effects. Multiple sclerosis can cause an inlfammatory demyelination and axonal damage. In this study, to validate the hypothesis that HCA exhibits therapeutic effects on multiple sclerosis, we established female C57BL/6 mouse models of multiple sclerosis,i.e., experimental autoimmune encephalomyelitis, using Complete Freund’s Adjuvant (CFA) emulsion containing myelin oligodendrocyte glycoprotein (35–55). Treatment with HCA at 2 g/kg/d for 3 weeks obviously improved the symptoms of nerve injury of experimental autoimmune encephalomyelitis mice, decreased serum interleulin-6, tumor necrosis factor alpha, nitric oxide, and malondialdehyde levels, and increased superoxide dismutase and glutathione reduc-tase activities. hTese ifndings suggest that HCA exhibits neuroprotective effects on multiple sclerosis-caused nerve injury through ameliorating inlfammation and oxidative stress.     

Hydroxycitric acid ameliorates inflammation and oxidative stress in mouse models of multiple sclerosis

Hydroxycitric acid(HCA) is derived primarily from the Garcinia plant and is widely used for its anti-inflammatory effects. Multiple sclerosis can cause an inflammatory demyelination and axonal damage. In this study, to validate the hypothesis that HCA exhibits therapeutic effects on multiple sclerosis, we established female C57BL/6 mouse models of multiple sclerosis, i.e., experimental autoimmune encephalomyelitis,using Complete Freund's Adjuvant(CFA) emulsion containing myelin oligodendrocyte glycoprotein(35–55). Treatment with HCA at 2 g/kg/d for 3 weeks obviously improved the symptoms of nerve injury of experimental autoimmune encephalomyelitis mice, decreased serum interleulin-6, tumor necrosis factor alpha, nitric oxide, and malondialdehyde levels, and increased superoxide dismutase and glutathione reductase activities. These findings suggest that HCA exhibits neuroprotective effects on multiple sclerosis-caused nerve injury through ameliorating inflammation and oxidative stress.     

Decreased cerebral perfusion and oxidative stress result in acute and delayed cognitive impairment

Chronic cerebral hypoperfusion (CCH) is common in the pathogenesis of cognitive impairment, in which oxidative stress plays an important role. Here we describe an alternative rat model for CCH that involves two-stage, three-vessel occlusion (2s-3VO) and compare its effects with those of permanent bilateral occlusion (2VO) of the common carotid arteries. Real-time cerebral blood flow (CBF) during the surgery was monitored. Spatial learning and memory were tested with the Morris water maze, and oxidative damage was evaluated by measuring malondialdehyde (MDA) levels in both the hippocampus and cortex. We found that the CBF drop in the early stage of the 2s-3VO model was more modest than that in the 2VO model. Like 2VO rats, 2s-3VO rats showed impaired spatial learning and memory and increased MDA levels 8 weeks after surgery. Interestingly, when pooling observations from previous studies, we confirmed that oxidative damage appeared later than spatial learning and memory deficits but lasted longer than did cerebral hypoperfusion. Thus, the 2s-3VO model appears to be a suitable model for the study of CCH. Moreover, data support the notion that cognitive impairment in CCH rat models may be induced early by cerebral hypoperfusion early and in a later phase by oxidative stress.     

Spontaneous recurrent seizures in rats: An experimental model of partial epilepsy

Seizures induced by pilocarpine (PILO) have proven to be a useful procedure for investigating the basic mechanisms essential for generation, spread and motor expression of seizures in rodents. Here we report the long-term effects of PILO in rats. Following PILO (380 mg/kg, IP), 3 distinct phases were observed: 1) an acute period which lasted 1-2 days which corresponds to the pattern of repetitive seizures and status epilepticus; 2) a silent period (4-44 days) characterized by a progressive return to normal EEG and behavior; and 3) a period of recurrent seizures which started 5-45 days after PILO and lasted up to 120 days. These seizures lasted up to 50-60 sec, recurred 2-3 times per week and were more frequent during the light period of the light-dark cycle. These serial events offer a new method to induce spontaneous recurrent seizures in rats.     

Effects of a lyophilized aqueous extract of Feretia apodanthera Del. (Rubiaceae) on pentylenetetrazole-induced kindling,oxidative stress,and cognitive impairment in mice

Feretia apodanthera Del. (Rubiaceae) is extensively used in ethnomedicine in Cameroon and Nigeria for epilepsy, febrile convulsions, and rheumatic pains and for enhancing cognitive performance. The aim of the present study was to examine the effects of a lyophilized aqueous extract of F. apodanthera on the course of kindling development, kindling-induced learning deficit, oxidative stress markers, and cholinesterase activity in pentylenetetrazole (PTZ)-kindled mice. Pentylenetetrazole, 30 mg/kg, induced kindling in mice after 30.00 ± 1.67 days. The aqueous extract of F. apodanthera showed dose-dependent antiseizure effects. Feretia apodanthera (150–200 mg/kg) significantly increased the latency to myoclonic jerks, clonic seizures, and generalized tonic–clonic seizures. The extract also improved the seizure score and decreased the number of myoclonic jerks. Pentylenetetrazole kindling induced significant oxidative stress and cognitive impairment which were reversed by pretreatment with F. apodanthera in a dose-dependent manner. The significant decrease in cholinesterase activity observed in the PTZ-kindled mice was reversed by pretreatment with the F. apodanthera extract. The results indicated that pretreatment with the aqueous extract of F. apodanthera antagonizes seizures, oxidative stress, and cognitive impairment in PTZ-kindled mice. The aqueous extract of F. apodanthera also showed anxiolytic activities, but the inhibition of memory impairment was not attributed to the anxiolytic activities of the plant. These results thus suggest the potential of F. apodanthera as an adjuvant in epilepsy both to prevent seizures as well as to protect against seizure-induced oxidative stress and memory impairment.     

Cerebral hypoperfusion and cognitive impairment: the pathogenic role of vascular oxidative stress

Alzheimer's disease (AD) and vascular dementia (VaD) are the most frequent causes of cognitive impairment in the elderly. In the pathogenesis of cognitive impairment, the association of neurodegenerative and vascular factors indicates a major role of hemodynamic abnormalities including cerebral hypoperfusion. There is also ample evidence that oxidative stress of vascular origin leads to profound alterations in cerebrovascular regulation and is crucial to cerebrovascular dysfunction in a variety of conditions that result in chronic hypoperfusion of the brain. In rodents, experimental chronic cerebral hypoperfusion (CCH) can be initiated by occlusion of the major arterial supply. This way CCH brings about mitochondrial dysfunction and protein synthesis inhibition. These effects may destroy the balance of antioxidases and reactive oxygen species (ROS) and produce oxidative damage. At the same time, oxidative injury to vascular endothelial cell, glia, and neuron impairs vascular function and neurovascular coupling, which may result in a vicious cycle of further reduction of cerebral perfusion. In clinical cases of severe cognitive dysfunction, vascular risk factors are commonly present, while cerebral hypoperfusion is often associated with vascular oxidative damage. Thus we hypothesize that cerebral hypoperfusion is one of the key factors in the development of cognitive impairment, in which vascular oxidative stress plays a major role. The approaches against cerebrovascular dysfunction, combined with antioxidants and others, might make a promising contribution to the treatment of cognitive impairment.     

应激对高血压大鼠认知障碍的影响及其机制

目的 研究应激对高血压大鼠认知障碍的影响及机制.方法 62只大鼠被随机分为应激组与非应激组、对照组,前2组用双肾双夹法制作高血压模型大鼠,其中应激组再接受强迫游泳应激.应激10周后以跳台实 验测量大鼠的学习记忆能力,然后电镜下观察海马CA3区血管、神经元和突触结构的变化.结果 ①应激组大鼠血压较非应激组和对照组大鼠升高明显(P<0.05);②学习测验中,应激组跳台实验的错误次数和反应时间均高于非应激组和对照组(P<0.05);记忆测验中,应激组、非应激组和对照组的错误次数递减而潜伏期依次增加,两两差异均有统计学意义(P<0.05).③应激组的海马C3区突触曲率、活性区长度和突触后膜致密物质厚度较非应激组小(P<0.05).结论 应激可能是血管性认知障碍的危险因素之一.     

Effect of epilepsy, seizures and epileptiform EEG discharges on cognitive function

Patients with an established diagnosis of epilepsy were included in three groups on the basis of the absence (Group 2) or presence (Group 3) of epileptiform EEG discharges or subtle seizures (Group 4) during the cognitive assessment procedure. A separate age-matched non-epileptic control group (Group 1) was formed. Twenty-five patients were included in each of the four groups. Thus, a total of 100 patients were investigated. The patients were assessed with continuous 21-channel EEG and video-monitoring, combined with cognitive testing. The results show consistently lower performance on cognitive tests for Group 4, the group with subtle seizures. The difference with the control group was significant for the intelligence subtests and for the complex information processing test (p<0.05). No transient cognitive impairment was found. The results are discussed in the light of possible factors that may be responsible for the lower test-scores in the patients of Group 4: both the ictal effects of the seizures themselves, postictal effects and the effects of the epileptiform EEG discharges may have had an impact on cognitive performance. Finally the absence of evidence for transient cognitive impairment in a group with frequent epileptiform EEG discharges is discussed in detail.     

Hippocampal neuron loss in epilepsy and after experimental seizures

In this study, the hippocampus and its relationship to epilepsy is reviewed from a neuropathological point of view. The variability found in previous studies regarding the extent of the damage to neurons makes interpretation difficult. The aim of this study was to clarify the neuron loss by quantitation. The neuron density in the different H-fields of the pyramidal band and in the granule cell area has been determined throughout the hippocampi by means of light microscope and an ocular grid. The brains of 20 patients with epilepsy were studied. The type of epilepsy was verified from the case history and encephalographic recordings. The distribution of neuron loss was evaluated by statistical analyses of variance applied to the different means and related to the clinical assessments. The normal neuronal distribution was evaluated in 29 persons without any known cerebral disorders. In experimental studies, the changes in neuron density in relation to seizures were determined. 8 rats were studied after electroconvulsive seizures, elicited 3 times daily for 50 days. 10 animals served as controls. 20 gerbils of a seizure-sensitive strain with different types of seizures, 5 in each group, were the object of the second experimental study which also included a group of 5 gerbils of the seizure-resistant type. The aim of this part of the study was to illustrate the damage to the neurons in relation to different seizure types. The main result of the study of patients with epilepsy was that neuron loss occurs in all areas investigated. The severely affected areas were field H₃ and the granule cells. The neurons of field H₁ seemed to be damaged earlier in life, possibly due to hypoxia accompanying generalized convulsions. The study of the normal neuronal distribution in the hippocampus revealed a neuronal reduction of 20% in old age. This ageing phenomenon was taken into account when evaluating the pattern of neuron loss in the patients with epilepsy. No specific pattern of neuron loss characterized the different types of epilepsy. Neuron loss was related to generalized convulsions and increased throughout life with the duration of the disorder. The experimental studies of rats revealed that no neuron loss occurred as a result of generalized convulsions alone. In contrast, the pyramidal neurons of fields H₂ and H₃ were reduced in the gerbils with frequent generalized convulsions. However, the number of seizures was low, in comparison with the number of generalized convulsions in rats. The hypothesis is put forward that the neuron loss in the gerbils in this area, known for its high bursting activity, is due to seizure-activity which has been shown by others to occur interictally. It was thus suggested that seizure-activity even without clinical seizures might be responsible for neuron loss in the hippocampus also in man, in relation to epilepsy of a certain intensity and duration. The consequences of this with regard to prevention of the development of severe epilepsy after single and even minor seizures and the choice of treatment in the individual cases are considered and future projects are mentioned.