Protective effects of idebenone and alpha-tocopherol on beta-amyloid-(1-42)-induced learning and memory deficits in rats: implication of oxidative stress in beta-amyloid-induced neurotoxicity in vivo

Exposure to As-, Cd-, and Pb-mixture induces Aβ, amyloidogenic APP processing and cognitive impairments via oxidative stress-dependent neuroinflammation in young rats

Environmental pollutants act as risk factors for Alzheimer's disease (AD), mainly affecting the aging population. We investigated early manifestations of AD-like pathology by a mixture of arsenic (As), cadmium (Cd), and lead (Pb), reported to impair neurodevelopment. We treated rats with As+Cd+Pb at their concentrations detected in groundwater of India, ie, 0.38, 0.098, and 0.22 ppm or 10 times of each, respectively, from gestation-05 to postnatal day-180. We identified dose-dependent increase in amyloid-beta (Aβ) in frontal cortex and hippocampus as early as post-weaning. The effect was strongly significant during early-adulthood, reaching levels comparable to an Aβ-infused AD-like rat model. The metals activated the proamyloidogenic pathway, mediated by increase in amyloid precursor protein (APP), and subsequent beta secretase (BACE) and presenilin (PS)-mediated APP-processing. Investigating the mechanism of Aβ-induction revealed an augmentation in oxidative stress-dependent neuroinflammation that stimulated APP expression through interleukin-responsive-APP-mRNA 5'-untranslated region. We then examined the effects of individual metals and binary mixtures in comparison with the tertiary. Among individual metals, Pb triggered maximum induction of Aβ, whereas individual As or Cd had a relatively non-significant effect on Aβ despite enhanced APP, owing to reduced induction of BACE and PS. Interestingly, when combined the metals demonstrated synergism, with a major contribution by As. The synergistic effect was significant and consistent in tertiary mixture, resulting in the augmentation of Aβ. Eventually, increase in Aβ culminated in cognitive impairments in the young rats. Together, our data demonstrate that exposure to As+Cd+Pb induces premature manifestation of AD-like pathology that is synergistic, and oxidative stress and inflammation dependent.

Idebenone and neuroprotection: antioxidant, pro-oxidant, or electron carrier?

Ubiquinone, commonly called coenzyme Q10 (CoQ), is a lipophilic electron carrier and endogenous antioxidant found in all cellular membranes. In the mitochondrial inner membrane it transfers electrons to complex III of the electron transport chain. The short chain CoQ analogue idebenone is in clinical trials for a number of diseases that exhibit a mitochondrial etiology. Nevertheless, evidence that idebenone ameliorates neurological symptoms in human disease is inconsistent. Although championed as an antioxidant, idebenone can also act as a pro-oxidant by forming an unstable semiquinone at complex I. The antioxidant function of idebenone is critically dependent on two-electron reduction to idebenol without the creation of unstable intermediates. Recently, cytoplasmic

NAD(P)H

quinone oxidoreductase 1 (NQO1) was identified as a major enzyme catalyzing idebenone reduction. While reduction allows idebenone to act as an antioxidant, evidence also suggests that NQO1 enables idebenone to shuttle reducing equivalents from cytoplasmic NAD(P)H to mitochondrial complex III, bypassing any upstream damage to the electron transport chain. In this mini-review we discuss how idebenone can influence mitochondrial function within the context of cytoprotection. Importantly, in the brain NQO1 is expressed primarily by glia rather than neurons. As NQO1 is an inducible enzyme regulated by oxidative stress and the nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway, optimizing NQO1 expression in appropriate cell types within a specific disease context may be key to delivering on idebenone's therapeutic potential.

How dependent is synaptic plasticity on microglial phenotype?

Microglia are particularly plastic cells which can be shifted from their resting state by numerous factors and adopt distinct phenotypes. The cells are multifunctional, though their main role is probably maintenance of homoeostasis. Resting cells are responsible for surveillance, whereas activation induces the cells to adopt neuroprotective or neurodetrimental roles, which are anti-inflammatory or pro-inflammatory respectively. The evidence indicates that activated cells with a pro-inflammatory phenotype predominate in neurodegenerative diseases and models of neurodegeneration and that this may significantly contribute to the deteriorating neuronal function. This question is considered in this review, in particular in the context of animal models of Alzheimer's disease (AD). This article is part of a Special Issue entitled 'Neuroimmunology and Synaptic Function'.

Effect of dietary supplementation of dates in Alzheimer's disease APPsw/2576 transgenic mice on oxidative stress and antioxidant status

Oxidative stress may play a key role in Alzheimer's disease (AD) neuropathology. Changes in the oxidative stress, antioxidants, and membrane-bound enzymes were investigated in the cerebral cortex and hippocampus of AD transgenic mice model after long-term dietary supplementation of date palm fruits from Oman. The 4-month-old mice with double Swedish APP mutation (APPsw/Tg2576) were purchased from Taconic Farm, NY, USA; mice were fed two different doses of dates (such as 4 and 2%) or control diet for 15 months and then assessed for the influence of diet on oxidative stress. Significant increase in oxidative stress in terms of enhanced levels of lipid peroxidation (LPO) and protein carbonyls and parallel decrease in the activity of antioxidant enzymes were observed in control diet-treated Tg2576 AD mice. Dates (4 and 2%) treated APPsw/Tg2576 AD mice exhibited significantly attenuated oxidative damage, evidenced by decreased LPO and protein carbonyl levels and restoration in the activities of the antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, glutathione, and glutathione reductase). The activities of membrane-bound enzymes (Na(+), K(+)-ATPase and acetyl cholinesterase) were altered in control diet-treated APPsw/Tg2576 AD mice brain regions. Meanwhile, both the percentages of date supplementation were able to restore the activity of enzymes to comparable values observed in controls. In summary, we have shown that chronic dietary supplementation of date palm fruits grown in Oman showed possible beneficial effects concomitant with oxidative stress reduction and increased antioxidant enzymes in AD transgenic mice model. These results warrant further exploration of how anti-reactive oxygen species properties of dates offer such beneficial effects on the AD-like brain.

Fingolimod increases brain-derived neurotrophic factor levels and ameliorates amyloid β-induced memory impairment

Alzheimer's disease is a progressive neurodegenerative disorder. Amyloid β, a neurotoxic protein, causes disruption of hippocampal synaptic plasticity, and induces cognitive impairment in Alzheimer's disease. We previously revealed that fingolimod, a new oral immunosuppressant used to treat multiple sclerosis, ameliorates oligomeric amyloid β-induced neuronal damage via up-regulation of neuronal brain-derived neurotrophic factor (BDNF). Here, we showed that oral administration of fingolimod ameliorated the impairment in object recognition memory and associative learning in mice injected with amyloid β. This effect was associated with restoration of normal BDNF expression levels in the cerebral cortices and hippocampi, suggesting that neuroprotection was mediated by up-regulation of neuronal BDNF levels. Therefore, fingolimod may provide therapeutic effects in patients with Alzheimer's disease.

Effects of specific multi-nutrient enriched diets on cerebral metabolism, cognition and neuropathology in AβPPswe-PS1dE9 mice

Recent studies have focused on the use of multi-nutrient dietary interventions in search of alternatives for the treatment and prevention of Alzheimer's disease (AD). In this study we investigated to which extent long-term consumption of two specific multi-nutrient diets can modulate AD-related etiopathogenic mechanisms and behavior in 11-12-month-old AβPPswe-PS1dE9 mice. Starting from 2 months of age, male AβPP-PS1 mice and wild-type littermates were fed either a control diet, the DHA+EPA+UMP (DEU) diet enriched with uridine monophosphate (UMP) and the omega-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), or the Fortasyn® Connect (FC) diet enriched with the DEU diet plus phospholipids, choline, folic acid, vitamins and antioxidants. We performed behavioral testing, proton magnetic resonance spectroscopy, immunohistochemistry, biochemical analyses and quantitative real-time PCR to gain a better understanding of the potential mechanisms by which these multi-nutrient diets exert protective properties against AD. Our results show that both diets were equally effective in changing brain fatty acid and cholesterol profiles. However, the diets differentially affected AD-related pathologies and behavioral measures, suggesting that the effectiveness of specific nutrients may depend on the dietary context in which they are provided. The FC diet was more effective than the DEU diet in counteracting neurodegenerative aspects of AD and enhancing processes involved in neuronal maintenance and repair. Both diets elevated interleukin-1β mRNA levels in AβPP-PS1 and wild-type mice. The FC diet additionally restored neurogenesis in AβPP-PS1 mice, decreased hippocampal levels of unbound choline-containing compounds in wild-type and AβPP-PS1 animals, suggesting diminished membrane turnover, and decreased anxiety-related behavior in the open field behavior. In conclusion, the current data indicate that specific multi-nutrient diets can influence AD-related etiopathogenic processes. Intervention with the FC diet might be of interest for several other neurodegenerative and neurological disorders.

Nitrone-based therapeutics for neurodegenerative diseases: their use alone or in combination with lanthionines

The possibility of free radical reactions occurring in biological processes led to the development and employment of novel methods and techniques focused on determining their existence and importance in normal and pathological conditions. For this reason the use of nitrones for spin trapping free radicals became widespread in the 1970s and 1980s, when surprisingly the first evidence of their potent biological properties was noted. Since then widespread exploration and demonstration of the potent biological properties of phenyl-tert-butylnitrone (PBN) and its derivatives took place in preclinical models of septic shock and then in experimental stroke. The most extensive commercial effort made to capitalize on the potent properties of the PBN-nitrones was for acute ischemic stroke. This occurred during 1993-2006, when the 2,4-disulfonylphenyl PBN derivative, called NXY-059 in the stroke studies, was shown to be safe in humans and was taken all the way through clinical phase 3 trials and then was deemed to be ineffective. As summarized in this review, because of its excellent human safety profile, 2,4-disulfonylphenyl PBN, now called OKN-007 in the cancer studies, was tested as an anti-cancer agent in several preclinical glioma models and shown to be very effective. Based on these studies this compound is now scheduled to enter into early clinical trials for astrocytoma/glioblastoma multiforme this year. The potential use of OKN-007 in combination with neurotropic compounds such as the lanthionine ketamine esters is discussed for glioblastoma multiforme as well as for various other indications leading to dementia, such as aging, septic shock, and malaria infections. There is much more research and development activity ongoing for various indications with the nitrones, alone or in combination with other active compounds, as briefly noted in this review.

Impact of a multi-nutrient diet on cognition, brain metabolism, hemodynamics, and plasticity in apoE4 carrier and apoE knockout mice

Lipid metabolism and genetic background together strongly influence the development of both cardiovascular and neurodegenerative diseases like Alzheimer's disease (AD). A non-pharmacological way to prevent the genotype-induced occurrence of these pathologies is given by dietary behavior. In the present study, we tested the effects of long-term consumption of a specific multi-nutrient diet in two models for atherosclerosis and vascular risk factors in AD: the apolipoprotein ε4 (apoE4) and the apoE knockout (apoE ko) mice. This specific multi-nutrient diet was developed to support neuronal membrane synthesis and was expected to contribute to the maintenance of vascular health. At 12 months of age, both genotypes showed behavioral changes compared to control mice and we found increased neurogenesis in apoE ko mice. The specific multi-nutrient diet decreased anxiety-related behavior in the open field, influenced sterol composition in serum and brain tissue, and increased the concentration of omega-3 fatty acids in the brain. Furthermore, we found that wild-type and apoE ko mice fed with this multi-nutrient diet showed locally increased cerebral blood volume and decreased hippocampal glutamate levels. Taken together, these data suggest that a specific dietary intervention has beneficial effects on early pathological consequences of hypercholesterolemia and vascular risk factors for AD.

A novel melatonin agonist Neu-P11 facilitates memory performance and improves cognitive impairment in a rat model of Alzheimer' disease

Previous studies have shown that melatonin is implicated in modulating learning and memory processing. Melatonin also exerts neuroprotective activities against Aβ-induced injury in vitro and in vivo. Neu-P11 (piromelatine, N-(2-(5-methoxy-1H-indol-3-yl)ethyl)-4-oxo-4H-pyran-2-carboxamide) is a novel melatonin (MT1/MT2) receptor agonist and a serotonin 5-HT1A/1D receptor agonist recently developed for the treatment of insomnia. In the present study we firstly investigated whether Neu-P11 and melatonin enhance memory performance in the novel object recognition (NOR) task in rats, and then assessed whether Neu-P11 and melatonin improve neuronal and cognitive impairment in a rat model of Alzheimer' disease (AD) induced by intrahippocampal Aβ(1-42) injection. The results showed that a single morning or afternoon administration of Neu-P11 enhanced object recognition memory measured at 4 or 24h after training. Melatonin was effective in the memory facilitating effects only when administered in the afternoon. Further results showed that intrahippocampal Aβ(1-42) injection resulted in hippocampal cellular loss, as well as decreased learning ability and memory in the Y maze and NOR tasks in rats. Neu-P11 but not melatonin attenuated cellular loss and cognitive impairment in the rat AD model. The current data suggest that Neu-P11 may serve as a novel agent for the treatment of AD.

Neuropeptide S enhances memory and mitigates memory impairment induced by MK801, scopolamine or Aβ₁₋₄₂ in mice novel object and object location recognition tasks

Neuropeptide S (NPS), the endogenous ligand of NPSR, has been shown to promote arousal and anxiolytic-like effects. According to the predominant distribution of NPSR in brain tissues associated with learning and memory, NPS has been reported to modulate cognitive function in rodents. Here, we investigated the role of NPS in memory formation, and determined whether NPS could mitigate memory impairment induced by selective N-methyl-D-aspartate receptor antagonist MK801, muscarinic cholinergic receptor antagonist scopolamine or Aβ₁₋₄₂ in mice, using novel object and object location recognition tasks. Intracerebroventricular (i.c.v.) injection of 1 nmol NPS 5 min after training not only facilitated object recognition memory formation, but also prolonged memory retention in both tasks. The improvement of object recognition memory induced by NPS could be blocked by the selective NPSR antagonist SHA 68, indicating pharmacological specificity. Then, we found that i.c.v. injection of NPS reversed memory disruption induced by MK801, scopolamine or Aβ₁₋₄₂ in both tasks. In summary, our results indicate that NPS facilitates memory formation and prolongs the retention of memory through activation of the NPSR, and mitigates amnesia induced by blockage of glutamatergic or cholinergic system or by Aβ₁₋₄₂, suggesting that NPS/NPSR system may be a new target for enhancing memory and treating amnesia.

Protective effect of cyanidin 3-O-glucoside on beta-amyloid peptide-induced cognitive impairment in rats

Alzheimer's disease (AD) is a neurodegenerative disorder that results in cognitive impairment. It has been proposed that deposits of beta-amyloid (Aβ) form the cores of the plaque and, subsequently, induce the activation of GSK-3β and the hyperphosphorylation of tau, resulting in cognitive impairment. Oxidative stress has been proposed to be an important factor in the pathogenesis of AD. Cyanidin 3-O-glucoside (Cy3G) is a neuroprotective antioxidant. However, the effects of Cy3G on cognition are unclear. In this paper, we show that Cy3G is protective against the Aβ-induced impairment of learning and memory, but has no effect on normal learning and memory. Moreover, we found that Gy3G attenuated the Aβ-induced tau hyperphosphorylation and GSK-3β hyperactivation observed in AD. Taken together, these results demonstrated that Cy3G can rescue the cognitive impairments that are induced by Aβ via the modulation of GSK-3β/tau, suggesting a potential therapeutic role of Cy3G in AD.

Therapeutic approaches to age-associated neurocognitive disorders

The United Nations projects that the number of individuals with dementia in developed countries alone will be approximately 36,7 million by the year 2050. International recognition of the significant emotional and economic burden of Alzheimer's disease has been matched by a dramatic increase in the development of pharmacological and nonpharmacological approaches to this illness in the past decade. Changing demographics have underscored the necessity to develop similar approaches for the remediation of the cognitive impairment associated with more benign syndromes, such as mild cognitive impairment (MCI) and age-associated cognitive decline (AACD). The present article aims to provide an overview of the most current therapeutic approaches to age-associated neurocognitive disorders. Additionally, it discusses the conceptual and methodological issues that surround the design, implementation, and interpretation of such approaches.

Akebia Saponin D attenuates amyloid β-induced cognitive deficits and inflammatory response in rats: involvement of Akt/NF-κB pathway

Neuroinflammatory responses caused by amyloid β(Aβ) play an important role in the pathogenesis of Alzheimer's disease (AD). Aβ is known to be directly responsible for the activation of glial cells and induction of apoptosis. Akebia Saponin D (ASD) is extracted from a traditional herbal medicine Dipsacus asper Wall, which has been shown to protect against ibotenic acid-induced cognitive deficits and cell death in rats. In this study, we investigated the in vivo protective effect of ASD on learning and memory impairment induced by bilateral intracerebroventricular injections of Aβ1-42 using Morris water and Y-maze task. Furthermore, the anti-inflammatory activity and neuroprotective effect of ASD was examined with methods of histochemistry and biochemistry. These data showed that oral gavage with ASD at doses of 30, 90 and 270 mg/kg for 4 weeks exerted an improved effect on cognitive impairment. Subsequently, the ASD inhibited the activation of glial cells and the expression of tumor necrosis factor (TNF)-α, interleukin-1 beta (IL-1β) and cyclooxygenase-2 (COX-2) in rat brain. Moreover, ASD afforded beneficial actions on inhibitions of Akt and IκB kinase (IKK) phosphorylations, as well as nuclear factor κB (NF-κB) activation induced by Aβ1-42. These results suggest that ASD may be a potential agent for suppressing both Alzheimer's disease-related neuroinflammation and memory system dysfunction.

The phosphodiesterase-4 inhibitor rolipram reverses Aβ-induced cognitive impairment and neuroinflammatory and apoptotic responses in rats

β-amyloid (Aβ) peptides play an important role in cognition deficits, neuroinflammation, and apoptosis observed in Alzheimer's disease (AD). Activation of cyclic AMP (cAMP) signalling enhances memory and inhibits inflammatory and apoptotic responses. However, it is not known whether inhibition of phosphodiesterase-4 (PDE4), a critical controller of intracellular cAMP concentrations, affects AD-associated neuroinflammatory and apoptotic responses and whether these responses contribute to deficits of memory mediated by cAMP signalling. We addressed these issues using memory tests and neurochemical measures. Specifically, rats microinfused with aggregated Aβ25-35 (10 μg/side) into bilateral CA1 subregions displayed deficits in learning ability and memory, as evidenced by decreases in escape latency during acquisition trials and exploratory activities in the probe trial in the water-maze task and 24-h retention in the passive avoidance test. These effects were reversed by rolipram (0.1, 0.25 and 0.5 mg/kg.d i.p.), a prototypic PDE4 inhibitor, in a dose-dependent manner. Interestingly, Aβ25-35-treated rats also displayed decreases in expression of phosphorylated cAMP response-element binding protein (pCREB) and Bcl-2, but increases in expression of NF-κB p65 and Bax in the hippocampus; these effects were also reversed by rolipram in a dose-dependent manner. Similar neurochemical results were observed by replacing Aβ25-35 with Aβ1-42, a full-length amyloid peptide that quickly forms toxic oligomers. These results suggest that PDE4 inhibitors such as rolipram may reverse Aβ-induced memory deficits at least in part via the attenuation of neuronal inflammation and apoptosis mediated by cAMP/CREB signalling. PDE4 could be a target for treatment of memory loss associated with AD.

Therapeutic Effect of Yi-Chi-Tsung-Ming-Tang on Amyloid β-Induced Alzheimer's Disease-Like Phenotype via an Increase of Acetylcholine and Decrease of Amyloid β

Alzheimer's disease (AD) is an irreversible neurodegenerative disorder characterized by amyloid accumulation, neuronal death, and cognitive impairments. Yi-Chi-Tsung-Ming-Tang (YCTMT) is a traditional Chinese medicine and has never been used to enhance cognitive function and treat neurodegenerative disorders such as senile dementia. Whether YCTMT has a beneficial role in improving learning and memory in AD patients remains unclear. The present study showed that oral administration of YCTMT ameliorated amyloid-β- (Aβ₁₋₄₀) injection-induced learning and memory impairments in rats, examined using passive avoidance and Morris water-maze tests. Immunostaining and Western Blot results showed that continuous Aβ₁₋₄₀ infusion caused amyloid accumulation and decreased acetylcholine level in hippocampus. Oral administration of medium and high dose of YCTMT 7 days after the Aβ₁₋₄₀ infusion decreased amyloid accumulation area and reversed acetylcholine decline in the Aβ₁₋₄₀-injected hippocampus, suggesting that YCTMT might inhibit Aβ plague accumulation and rescue reduced acetylcholine expression. This study has provided evidence on the beneficial role of YCTMT in ameliorating amyloid-induced AD-like symptom, indicating that YCTMT may offer an alternative strategy for treating AD.

Palmitoylethanolamide protects against the amyloid-β25-35-induced learning and memory impairment in mice, an experimental model of Alzheimer disease

Alzheimer disease (AD) is the most common form of neurodegenerative dementia. Amyloid-β deposition, neurofibrillary tangle formation, and neuro-inflammation are the major pathogenic mechanisms that in concert lead to memory dysfunction and decline of cognition. Palmitoylethanolamide (PEA) is the naturally occurring lipid amide between palmitic acid and ethanolamine. Despite its clear role in inflammation and pain control, only limited in vitro evidence exist about a role for PEA in neurodegenerative diseases. Here we describe the neuroprotective activities of PEA in mice injected intracerebroventricularly with amyloid-β 25-35 (Ab25-35) peptide (9 nmol). We used spatial and non-spatial memory tasks to evaluate learning and memory dysfunctions. Ab25-35 injection significantly impaired spontaneous alternation performances, water maze spatial reference and working-like memory, and novel object recognition test. PEA was administered once a day (3-30 mg/kg, subcutaneously), starting 3 h after Ab25-35, for 1 or 2 weeks. PEA reduced (10 mg/kg) or prevented (30 mg/kg) behavioral impairments induced by Ab25-35 injection. PEA failed to rescue memory deficits induced by Ab25-35 injection in peroxisome proliferator-activated receptor-α (PPAR-α) null mice. GW7647 (2-(4-(2-(1-cyclohexanebutyl)-3-cyclohexylureido)ethyl)phenylthio)-2-methylpropionic acid; 5 mg/kg per day), a synthetic PPAR-α agonist, mimicked the effect of PEA. Acute treatment with PEA was ineffective. According with the neuroprotective profile of PEA observed during behavioral studies, experimental molecular and biochemical markers induced by Ab25-35 injection, such as lipid peroxidation, protein nytrosylation, inducible nitric oxide synthase induction, and caspase3 activation, were reduced by PEA treatment. These data disclose novel findings about the therapeutic potential of PEA, unrevealing a previously unknown therapeutic possibility to treat memory deficits associated with AD.

Matrix metalloproteinases contribute to neuronal dysfunction in animal models of drug dependence, Alzheimer's disease, and epilepsy

Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) remodel the pericellular environment by regulating the cleavage of extracellular matrix proteins, cell surface components, neurotransmitter receptors, and growth factors that mediate cell adhesion, synaptogenesis, synaptic plasticity, and long-term potentiation. Interestingly, increased MMP activity and dysregulation of the balance between MMPs and TIMPs have also been implicated in various pathologic conditions. In this paper, we discuss various animal models that suggest that the activation of the gelatinases MMP-2 and MMP-9 is involved in pathogenesis of drug dependence, Alzheimer's disease, and epilepsy.

Neuronal and vascular oxidative stress in Alzheimer's disease

The brain is a highly metabolically active organ producing large amounts of reactive oxygen species (ROS). These ROS are kept in check by an elaborate network of antioxidants. Although ROS are necessary for signaling and synaptic plasticity, their uncontrolled levels cause oxidation of essential macromolecules such as membrane lipids, nucleic acids, enzymes and cytoskeletal proteins. Indeed, overproduction of ROS and/or failure of the antioxidant network lead to neuronal oxidative stress, a condition associated with not only aging but also Alzheimer's disease (AD). However, the specific source of excessive ROS production has not yet been identified. On one hand, amyloid beta (Aβ) has been extensively shown to act as an oxidant molecule. On the other hand, oxidative stress has been shown to precede and exacerbate Aβ pathology. This review will address the involvement of oxidative stress in the context of neuronal as well as vascular dysfunction associated with AD.

The effects of idebenone on mitochondrial bioenergetics

We have studied the effects of idebenone on mitochondrial function in cybrids derived from one normal donor (HQB17) and one patient harboring the G3460A/MT-ND1 mutation of Leber's Hereditary Optic Neuropathy (RJ206); and in XTC.UC1 cells bearing a premature stop codon at aminoacid 101 of MT-ND1 that hampers complex I assembly. Addition of idebenone to HQB17 cells caused mitochondrial depolarization and NADH depletion, which were inhibited by cyclosporin (Cs) A and decylubiquinone, suggesting an involvement of the permeability transition pore (PTP). On the other hand, addition of dithiothreitol together with idebenone did not cause PTP opening and allowed maintenance of the mitochondrial membrane potential even in the presence of rotenone. Addition of dithiothreitol plus idebenone, or of idebenol, to HQB17, RJ206 and XTC.UC1 cells sustained membrane potential in intact cells and ATP synthesis in permeabilized cells even in the presence of rotenone and malonate, and restored a good level of coupled respiration in complex I-deficient XTC.UC1 cells. These findings demonstrate that idebenol can feed electrons at complex III. If the quinone is maintained in the reduced state, a task that in some cell types appears to be performed by dicoumarol-sensitive NAD(P)H:quinone oxidoreductase 1 [Haefeli et al. (2011) PLoS One 6, e17963], electron transfer to complex III may allow reoxidation of NADH in complex I deficiencies.

Cognitive impairments in adult mice with constitutive inactivation of RIP140 gene expression

Receptor-interacting protein 140 (RIP140) is a negative transcriptional coregulator of nuclear receptors such as estrogen, retinoic acid or glucocorticoid receptors. Recruitment of RIP140 results in an inhibition of target gene expression through different repressive domains interacting with histone deacetylases or C-terminal binding proteins. In this study, we analyzed the role of RIP140 activity in memory processes using RIP140-deficient transgenic mice. Although the RIP140 protein was clearly expressed in the brain (cortical and hippocampus areas), the morphological examination of RIP140(-/-) mouse brain failed to show grossly observable alterations. Using male 2-month-old RIP140(-/-) , RIP140(+/-) or RIP140(+/+) mice, we did not observe any significant differences in the open-field test, rotarod test and in terms of spontaneous alternation in the Y-maze. By contrast, RIP140(-/-) mice showed long-term memory deficits, with an absence of decrease in escape latencies when animals were tested using a fixed platform position procedure in the water maze and in the passive avoidance test. Noteworthy, RIP140(-/-) mice showed decreased swimming speed, suggesting swimming alterations that may in part account for the marked alterations measured in the water maze. Moreover, RIP140(+/-) and RIP140(-/-) mice showed a significant increase in immobility time in the forced swimming test as compared with wild-type animals. These observations showed that RIP140 gene depletion results in learning and memory deficits as well as stress response, bringing to light a major role for this transcriptional coregulator in the neurophysiological developmental mechanisms underlying cognitive functions.

Antioxidants prevent memory deficits provoked by chronic variable stress in rats

Learning and memory deficits occur in depression and other stress related disorders. Although the pathogenesis of cognitive impairment after stress has not been fully elucidated, factors such as oxidative stress and neurotrophins are thought to play possible roles. Here we investigated the effect of treatment with vitamin E (40 mg/kg) and vitamin C (100 mg/kg) on the effects elicited by chronic variable stress on rat performance in Morris water maze. Brain-derived neurotrophic factor (BDNF) immunocontent was also evaluated in hippocampus of rats. Sixty-day old Wistar rats were submitted to different stressors for 40 days (stressed group). Half of stressed group received administration of vitamins once a day, during the period of stress. Chronically stressed rats presented a marked decrease in reference memory in the water maze task as well as a reduced efficiency to find the platform in the working memory task. Rats treated with vitamins E and C had part of the above effects prevented, suggesting the participation of oxidative stress in such effects. The BDNF levels were not altered in hippocampus of stressed group when compared to controls. Our findings lend support to a novel therapeutic strategy, associated with these vitamins, to the cognitive dysfunction observed in depression and other stress related diseases.

Punica granatum protects against oxidative stress in PC12 cells and oxidative stress-induced Alzheimer's symptoms in mice

Alzheimer's disease (AD) is a progressive degenerative brain disorder that is characterized by neuronal loss, neurofibrillary tangles, and the abnormal deposition of senile plaque and amyloid β peptide (Aβ). The brains of AD patients are under intense oxidative stress. The overproduction of Aβ leads to Aβ-associated free radical oxidative stress. In this study, the antioxidative and neuronal protective effects of Punica granatum extract were investigated against oxidative stress-induced cytotoxicity in PC12 cells. The ethanol extracts of P. granatum protected PC12 cells from hydrogen peroxide (H₂O₂-induced oxidative stress. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction assays revealed a significant increase in cell viability when oxidatively stressed PC12 cells were treated with the P. granatum extract. To examine the effects of P. granatum on Aβ₁₋₄₂-induced learning and memory impairment in mice, in vivo behavioral tests were performed. Treatment with the extract of P. granatum increased step-through latency in mice injected with Aβ₁₋₄₂. The results of this study suggest that the ethanol extract of P. granatum mitigated H₂O₂-induced oxidative stress in PC12 cells. In addition, the extract inhibited neuronal cell death caused by Aβ-induced oxidative stress and Aβ-induced learning and memory deficiency.

Reactive oxygen species in the regulation of synaptic plasticity and memory

The brain is a metabolically active organ exhibiting high oxygen consumption and robust production of reactive oxygen species (ROS). The large amounts of ROS are kept in check by an elaborate network of antioxidants, which sometimes fail and lead to neuronal oxidative stress. Thus, ROS are typically categorized as neurotoxic molecules and typically exert their detrimental effects via oxidation of essential macromolecules such as enzymes and cytoskeletal proteins. Most importantly, excessive ROS are associated with decreased performance in cognitive function. However, at physiological concentrations, ROS are involved in functional changes necessary for synaptic plasticity and hence, for normal cognitive function. The fine line of role reversal of ROS from good molecules to bad molecules is far from being fully understood. This review focuses on identifying the multiple sources of ROS in the mammalian nervous system and on presenting evidence for the critical and essential role of ROS in synaptic plasticity and memory. The review also shows that the inability to restrain either age- or pathology-related increases in ROS levels leads to opposite, detrimental effects that are involved in impairments in synaptic plasticity and memory function.

Idebenone inhibition of glutamate release from rat cerebral cortex nerve endings by suppression of voltage-dependent calcium influx and protein kinase A

The present study was aimed at investigating the effect and the possible mechanism of idebenone on endogenous glutamate release in nerve terminals of rat cerebral cortex (synaptosomes). Idebenone inhibited the release of glutamate that was evoked by exposing synaptosomes to the K(+) channel blocker 4-aminopyridine (4-AP), and this phenomenon was concentration dependent. Inhibition of glutamate release by idebenone was prevented by chelating extracellular Ca(2+), or by the vesicular transporter inhibitor bafilomycin A1, but was insensitive to DL-threo-beta-benzyl-oxyaspartate, a glutamate transporter inhibitor. Idebenone decreased the depolarization-induced increase in the cytosolic free Ca(2+) concentration ([Ca(2+)](C)),whereas it did not alter the resting synaptosomal membrane potential or 4-AP-mediated depolarization. The inhibitory effect of idebenone on evoked glutamate release was prevented by blocking the Ca(v)2.2 (N-type) and Ca(v)2.1 (P/Q-type) channels, but not by blocking intracellular Ca(2+) release or Na(+)/Ca(2+) exchange. Furthermore, the idebenone effect on 4-AP-evoked Ca(2+) influx and glutamate release was completely abolished by the protein kinase A (PKA) inhibitors, H89 and KT5720. On the basis of these results, it was concluded that idebenone inhibits glutamate release from rat cortical synaptosomes and this effect is linked to a decrease in [Ca(2+)](C) contributed by Ca(2+) entry through presynaptic voltage-dependent Ca(2+) channels and to the suppression of PKA signaling cascade.

Synthesis and evaluation of arylquinones as BACE1 inhibitors, β-amyloid peptide aggregation inhibitors, and destabilizers of preformed β-amyloid fibrils

BACE1 activity, inhibition of Aβ aggregation, and disaggregation of preformed Aβ fibrils constitute the three major targets in the development of small-molecule lipophilic new drugs for the treatment of Alzheimer's disease (AD). Quinones are widely distributed among natural products and possess relevant and varied biological activities including antitumor and antibiotic, inhibition of HIV-1 reverse transcriptase, antidiabetic, or COX-inhibition, among others. We report herein the interaction of several arylquinones and their derivatives with the amyloidogenic pathway of the amyloid precursor protein processing. Our studies put forward that these compounds are promising candidates in the development of new drugs which are effective simultaneously towards the three major targets of AD.

Prolonged treatment with vitamins C and E separately and together decreases anxiety-related open-field behavior and acoustic startle in hooded rats

Adult male and female hooded rats (about 110 days old) consumed vitamins C and E separately and combined together in their drinking water and were assessed for anxiety approximately 50 and then 80 days later in an open field and an acoustic startle apparatus. They were tested when 160+ days old, and then again at 190+ days. For both testing ages combined, the vitamins and their combination increased open-field ambulation and occupancy of the four center squares of the apparatus, while also accordingly decreasing occupancy of the four corners. Treatment with vitamins C and E separately and combined together also decreased acoustic startle amplitude. While there were several significant overall sex and testing age differences, there was no evidence that the vitamin treatment effects were dependent on the operation of either variable. There was also no evidence of synergism between vitamins C and E in their effects. It was suggested that decreases in anxiety produced by the vitamins may have arisen from their antioxidant properties, attenuation of cortisol activity or some as yet undetermined effects on anxiety-related brain structures and neurotransmitters.

Dietary antioxidants and long-term risk of dementia

BACKGROUND

The Rotterdam Study previously found that higher dietary intakes of vitamins E and C related to lower risk of dementia and Alzheimer disease (AD) over 6 years of follow-up.

OBJECTIVE

To study consumption of major dietary antioxidants relative to long-term risk of dementia.

DESIGN

Population-based prospective cohort study.

SETTING

The Rotterdam Study in the Netherlands.

PARTICIPANTS

A total of 5395 participants, 55 years and older, who were free of dementia and provided dietary information at study baseline.

MAIN OUTCOME MEASURES

Incidence of dementia and AD, based on internationally accepted criteria, relative to dietary intake of vitamin E, vitamin C, beta carotene, and flavonoids.

RESULTS

During a mean follow-up period of 9.6 years, dementia developed in 465 participants, of whom 365 were diagnosed as having AD. In multivariate models adjusted for age, education, apolipoprotein E epsilon4 genotype, total energy intake, alcohol intake, smoking habits, body mass index, and supplement use, higher intake of vitamin E at study baseline was associated with lower long-term risk of dementia (P = .02 for trend). Compared with participants in the lowest tertile of vitamin E intake, those in the highest tertile were 25% less likely to develop dementia (hazard ratio, 0.75; 95% confidence interval, 0.59-0.95 with adjustment for potential confounders). Dietary intake levels of vitamin C, beta carotene, and flavonoids were not associated with dementia risk after multivariate adjustment (P > .99 for trend for vitamin C and beta carotene and P = .60 for trend for flavonoids). Results were similar when risk for AD was specifically assessed.

CONCLUSION

Higher intake of foods rich in vitamin E may modestly reduce long-term risk of dementia and AD.

Mice knock out for the histone acetyltransferase p300/CREB binding protein-associated factor develop a resistance to amyloid toxicity

p300/CREB binding protein-associated factor (PCAF) regulates gene expression by acting through histone acetylation and as a transcription coactivator. Although histone acetyltransferases were involved in the toxicity induced by amyloid-beta (Abeta) peptides, nothing is known about PCAF. We here analyzed the sensitivity of PCAF knockout (KO) mice to the toxic effects induced by i.c.v. injection of Abeta(25-35) peptide, a nontransgenic model of Alzheimer's disease. PCAF wild-type (WT) and KO mice received Abeta(25-35) (1, 3 or 9 nmol) or scrambled Abeta(25-35) (9 nmol) as control. After 7 days, Abeta(25-35) toxicity was measured in the hippocampus of WT mice by a decrease in CA1 pyramidal cells and increases in oxidative stress, endoplasmic reticulum stress and induction of apoptosis. Memory deficits were observed using spontaneous alternation, water-maze learning and passive avoidance. Non-treated PCAF KO mice showed a decrease in CA1 cells and learning alterations. However, Abeta(25-35) injection failed to induce toxicity or worsen the deficits. This resistance to Abeta(25-35) toxicity did not involve changes in glutamate or acetylcholine systems. Examination of enzymes involved in Abeta generation or degradation revealed changes in transcription of presenilins, activity of neprilysin (NEP) and an absence of Abeta(25-35)-induced regulation of NEP activity in PCAF KO mice, partly due to an altered expression of somatostatin (SRIH). We conclude that PCAF regulates the expression of proteins involved in Abeta generation and degradation, thus rendering PCAF KO insensitive to amyloid toxicity. Modulating acetyltransferase activity may offer a new way to develop anti-amyloid therapies.

Potential future neuroprotective therapies for neurodegenerative disorders and stroke

The cellular mechanisms underlying neuronal loss and neurodegeneration have been an area of interest in the last decade. Although neurodegenerative diseases such as Alzheimer disease, Parkinson disease, and Huntington disease each have distinct clinical symptoms and pathologies, they all share common mechanisms such as protein aggregation, oxidative injury, inflammation, apoptosis, and mitochondrial injury that contribute to neuronal loss. Although cerebrovascular disease has different causes from the neurodegenerative disorders, many of the same common disease mechanisms come into play following a stroke. Novel therapies that target each of these mechanisms may be effective in decreasing the risk of disease, abating symptoms, or slowing down their progression. Although most of these therapies are experimental, and require further investigation, a few seem to offer promise.

The role of nutrition in Alzheimer's disease: epidemiological evidence

The prevalence of Alzheimer's disease (AD) increases exponentially with age but there is limited knowledge of the modifiable risk factors for AD. However, there is growing evidence for possible dietary risk factors in the development of AD and cognitive decline with age, such as antioxidant nutrients, fish, dietary fats, and B-vitamins. Numerous animal and laboratory studies have shown that antioxidant nutrients can protect the brain from oxidative and inflammatory damage, but there are limited data available from epidemiological studies. There is more substantial epidemiological evidence from a number of recent studies that demonstrate a protective role of omega-3 fatty acids, such as docosahexaenoic acid, in AD and cognitive decline. This review will focus on epidemiological evidence investigating the relationship between nutrition and AD, focusing particularly on the roles of dietary fats and antioxidants.

Matrix metalloprotease-9 inhibition improves amyloid beta-mediated cognitive impairment and neurotoxicity in mice

In Alzheimer's disease (AD), the expression of matrix metalloproteases (MMPs), which are capable of degrading extracellular matrix proteins, is increased in the brain. Previous studies with cultured glial cells have demonstrated that amyloid beta (Abeta) protein can induce the expression of MMPs, which could be involved in the degradation of Abeta. In the present study, we investigated the role of MMP-2 and MMP-9 in cognitive impairment induced by the injection of Abeta in mice. The intracerebroventricular injection of Abeta25-35, Abeta1-40, and Abeta1-42, but not Abeta40-1, transiently increased MMP-9, but not MMP-2, activity and protein expression in the hippocampus. Immunohistochemistry revealed the expression of MMP-9 to be increased in both neurons and glial cells in the hippocampus after Abeta treatment. The Abeta-induced cognitive impairment in vivo as well as neurotoxicity in vitro was significantly alleviated in MMP-9 homozygous knockout mice and by treatment with MMP inhibitors. These results suggest the increase in MMP-9 expression in the hippocampus to be involved in the development of cognitive impairment induced by Abeta1-40. Thus, specific inhibitors of MMP-9 may have therapeutic potential for the treatment of AD. Our findings suggest that, as opposed to expectations based on previous findings, MMP-9 plays a causal role in Abeta-induced cognitive impairment and neurotoxicity.

Peroxiredoxin II preserves cognitive function against age-linked hippocampal oxidative damage

Reactive oxygen species (ROS), routinely produced in biological reactions, contribute to both normal aging and age-related decline in cognitive function. However, little is known regarding the involvement of specific antioxidants in the underlying mechanism(s). Here, we examined if peroxiredoxin II (Prx II) scavenges intracellular ROS that cause age-dependent mitochondrial decay in hippocampal CA1 pyramidal neurons and subsequent impairment of learning and memory. Age-dependent mitochondrial ROS generation and long-term potentiation (LTP) decline were more prominent in hippocampal neurons in Prx II(-/-) than in wild-type mice. Additionally, Prx II(-/-) mice failed to activate synaptic plasticity-related cellular signaling pathways involving CREB, CaMKII, and ERK, or to maintain functional integrity of their mitochondria. Dietary vitamin E alleviated Prx II deficiency-related deficits, including mitochondrial decay and CREB signaling, resulting in restoration of the abrupt cognitive decline in aged Prx II(-/-) mice. These results suggest that Prx II help maintain hippocampal synaptic plasticity against age-related oxidative damage.

The rat as an animal model of Alzheimer's disease

As a disease model, the laboratory rat has contributed enormously to neuroscience research over the years. It has also been a popular animal model for Alzheimer's disease but its popularity has diminished during the last decade, as techniques for genetic manipulation in rats have lagged behind that of mice. In recent years, the rat has been making a comeback as an Alzheimer's disease model and the appearance of increasing numbers of transgenic rats will be a welcome and valuable complement to the existing mouse models. This review summarizes the contributions and current status of the rat as an animal model of Alzheimer's disease.

Very-high-dose alpha-tocopherol supplementation increases blood pressure and causes possible adverse central nervous system effects in stroke-prone spontaneously hypertensive rats

Tocopherols and tocotrienols constitute the vitamin E family. Although alpha-tocotrienol is the most neuroprotective form of vitamin E proved to be effective against stroke, alpha-tocopherol is the most abundant in nature and is used most often for disease prevention/treatment. A recent metaanalysis of human studies suggested that alpha-tocopherol supplementation increases all-cause mortality. Therefore, we investigated the effects of alpha-tocopherol ( approximately 44 mg/kg body weight; equivalent to 2,600 mg/human/day) on the central nervous system (CNS) of stroke-prone spontaneously hypertensive rats (SHRSP). SHRSP treated with high dose alpha-tocopherol had significantly higher blood pressure than untreated controls fed a basal diet that contained approximately 4 mg tocopherols/kg body weight, but neither group experienced a change in degree of lipid peroxidation in serum or CNS tissue. Biochemical/immunohistochemical analyses demonstrated that expressions of phosphorylated neurofilament H protein, glial fibrillary acidic protein and cathepsin D in the CNS tissue were significantly enhanced in alpha-tocopherol-supplemented rats, whereas expressions of SOD2 and Bcl-xL were diminished in response to alpha-tocopherol supplementation. Similarly, the frequency of cathepsin D-positive cells, corresponding mostly to microglial cells, was significantly increased in alpha-tocopherol-supplemented rats. Alpha-tocopherol supplementation also increased the number of lysosomes and lipofuscin granules in perikarya of both hippocampal pyramidal and Purkinje cells. Furthermore, alpha-tocopherol supplementation increased the frequency of glial filaments and lipofuscin granules in astrocytes and lysosomes in microglial cells that were frequently occupied with phagocytosed inclusion structures. The present results are the first to suggest that a very high dose of alpha-tocopherol supplementation increases blood pressure in SHRSP rats and influences the CNS tissue in a manner that seems adverse.

Ameliorative effect of 1,2-benzenedicarboxylic acid dinonyl ester against amyloid beta peptide-induced neurotoxicity

Amyloid beta peptide (Abeta)-induced oxidative stress may be linked to neurodegenerative disease. Ethanol extracts of Rosa laevigata protected PC12 cells from hydrogen peroxide-induced oxidative stress. (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) reduction assays revealed a significant increase in cell viability when oxidatively stressed PC12 cells were treated with R. laevigata extract. The effect of R. laevigata on oxidative stress-induced cell death was further investigated by lactate dehydrogenase release assays and trypan blue exclusion assays. Administration of 1,2-benzenedicarboxylic acid dinonyl ester from R. laevigata extract to mice infused with Abeta significantly reversed learning and memory impairment in behavioural tests. After behavioural testing, the mice were sacrificed and brains were collected for the examination of lipid peroxidation, catalase activity and acetylcholinesterase (AchE) activity. These results suggest that 1,2-benzenedicarboxylic acid dinonyl ester from R. laevigata extract may be able to reduce Abeta-induced neurotoxicity, possibly by reducing oxidative stress. Therefore, R. laevigata extract may be useful for the prevention of oxidative stress-induced neurodegenerative disorders.

Mitochondrial approaches for neuroprotection

A large body of evidence from postmortem brain tissue and genetic analysis in humans and biochemical and pathological studies in animal models (transgenic and toxin) of neurodegeneration suggest that mitochondrial dysfunction is a common pathological mechanism. Mitochondrial dysfunction from oxidative stress, mitochondrial DNA deletions, pathological mutations, altered mitochondrial morphology, and interaction of pathogenic proteins with mitochondria leads to neuronal demise. Therefore, therapeutic approaches targeting mitochondrial dysfunction and oxidative damage hold great promise in neurodegenerative diseases. This review discusses the potential therapeutic efficacy of creatine, coenzyme Q10, idebenone, synthetic triterpenoids, and mitochondrial targeted antioxidants (MitoQ) and peptides (SS-31) in in vitro studies and in animal models of Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, and Alzheimer's disease. We have also reviewed the current status of clinical trials of creatine, coenzyme Q10, idebenone, and MitoQ in neurodegenerative disorders. Further, we discuss newly identified therapeutic targets, including peroxisome proliferator-activated receptor-gamma-coactivator and sirtuins, which provide promise for future therapeutic developments in neurodegenerative disorders.

Consumption of molecular hydrogen prevents the stress-induced impairments in hippocampus-dependent learning tasks during chronic physical restraint in mice

We have reported that hydrogen (H(2)) acts as an efficient antioxidant by gaseous rapid diffusion. When water saturated with hydrogen (hydrogen water) was placed into the stomach of a rat, hydrogen was detected at several microM level in blood. Because hydrogen gas is unsuitable for continuous consumption, we investigated using mice whether drinking hydrogen water ad libitum, instead of inhaling hydrogen gas, prevents cognitive impairment by reducing oxidative stress. Chronic physical restraint stress to mice enhanced levels of oxidative stress markers, malondialdehyde and 4-hydroxy-2-nonenal, in the brain, and impaired learning and memory, as judged by three different methods: passive avoidance learning, object recognition task, and the Morris water maze. Consumption of hydrogen water ad libitum throughout the whole period suppressed the increase in the oxidative stress markers and prevented cognitive impairment, as judged by all three methods, whereas hydrogen water did not improve cognitive ability when no stress was provided. Neural proliferation in the dentate gyrus of the hippocampus was suppressed by restraint stress, as observed by 5-bromo-2'-deoxyuridine incorporation and Ki-67 immunostaining, proliferation markers. The consumption of hydrogen water ameliorated the reduced proliferation although the mechanistic link between the hydrogen-dependent changes in neurogenesis and cognitive impairments remains unclear. Thus, continuous consumption of hydrogen water reduces oxidative stress in the brain, and prevents the stress-induced decline in learning and memory caused by chronic physical restraint. Hydrogen water may be applicable for preventive use in cognitive or other neuronal disorders.

Use of copper and insulin-resistance to accelerate cognitive deficits and synaptic protein loss in a rat Abeta-infusion Alzheimer's disease model

The rat amyloid-beta (Abeta) intracerebroventricular infusion can model aspects of Alzheimer's disease (AD) and has predicted efficacy of therapies such as ibuprofen and curcumin in transgenic mouse models. High density lipoprotein (HDL), a normal plasma carrier of Abeta, is used to attenuate Abeta aggregation within the pump, causing Abeta-dependent toxicity and cognitive deficits within 3 months. Our goal was to identify factors that might accelerate onset of Abeta-dependent deficits to improve efficiency and cost-effectiveness of model. We focused on: 1) optimizing HDL-Abeta preparation for maximal toxicity; 2) evaluating the role of copper, a factor typically in water that can impact oligomer stability; and 3) determining impact of insulin resistance (type II diabetes), a risk factor for AD. In vitro studies were performed to determine doses of copper and methods of Abeta-HDL preparation that maximized toxicity. These preparations when infused resulted in earlier onset of cognitive deficits within 6 weeks post-infusion. Induction of insulin resistance did not exacerbate Abeta-dependent cognitive deficits, but did exacerbate synaptic protein loss. In summary, the newly described in vivo infusion model may be useful cost-effective method for screening for new therapeutic drugs for AD.

The cognitive and histopathological effects of chronic 4-vessel occlusion in rats depend on the set of vessels occluded and the age of the animals

Continuing previous efforts to develop the 4-vessel occlusion (4-VO) model of chronic cerebral hypoperfusion (CCH), here we evaluated whether permanent, stepwise 4-VO causes both learning deficits, hippocampal neurodegeneration and retinal lesion in young, middle-aged or aged rats. Chronic 4-VO was induced by ligation of different sets of vessels, i.e., the vertebral arteries (VA) plus common carotid arteries (CCA) (4-VO/CCA model) or the VA plus internal carotid arteries (ICA) (4-VO/ICA model) with a 1-week interstage interval. Forty days after the 4-VO, the rats were tested for spatial learning impairment, and then examined for hypoxic/ischemic damage. Young, 4-VO/CCA rats exhibited cognitive impairment, hippocampal neurodegeneration and retinal lesion (p<0.0001-0.05). After 4-VO/ICA, neither young nor middle-aged rats exhibited any learning deficits, hippocampal or retinal damage. In aged rats, chronic 4-VO/ICA caused a mild learning deficit (p<0.05). A significant effect of training was observed for the old, sham-operated rats (p<0.0001-0.001), but not for the aged 4-VO/ICA rats (p>0.05). On average, hippocampal cell density did not change after 4-VO/ICA in aged rats, but 3 of 10 subjects exhibited reduced pyramidal cell counts in all hippocampal subfields. Retinal morphology appeared to be unaffected in the 4-VO/ICA aged rats. These data suggest that the 4-VO/ICA model, but not the 4-VO/CCA model, is a suitable paradigm to study the behavioral outcome of CCH given the preservation of the retina after 4-VO/ICA. Moreover, the age at which 4-VO/ICA occurs seems to be an important factor for determining the behavioral and neuropathological changes.

The extensive nitration of neurofilament light chain in the hippocampus is associated with the cognitive impairment induced by amyloid beta in mice

Tyrosine nitration of proteins at an extensive level is widely associated with the cognitive pathology induced by amyloid beta peptide (Abeta). However, the precise identity and explicit consequences of protein nitration have scarcely been addressed. In this study, we examined the detectable nitration of proteins in the hippocampus of mice with cognitive impairment (day 5) induced by the i.c.v. injection of Abeta(25-35) (day 0). The intensity of the nitration of proteins was inversely associated with the level of recognition memory in mice. The detectable tyrosine nitrations were revealed in proteins with a single size of approximately 70 kDa. The specific nitrated proteins at this size were identified using the liquid chromatography/mass spectrometry/mass spectrometry analysis and immunodetection methods. Intense nitration of the neurofilament light chain (NFL) was observed. The increased nitration of NFL was associated with its serine hyperphosphorylation and weak interaction with the nuclear distribution element-like, a protein essential for the stable assembly of neurofilaments. No changes in cell numbers in the hippocampus were found (day 5) in mice that received Abeta(25-35) injections. These findings suggested that extensive nitration of NFL is associated with the Abeta-induced impairment of recognition memory in mice.

Overview on rodent models of Alzheimer's disease

In Alzheimer's disease (AD), characteristic lesions develop in brain regions that subserve cognitive functions, ultimately leading to dementia. There are now several lesioned or transgenic small-animal models of the disease that model select aspects of cognitive deficits and/or recapitulate many, but not all, of the characteristic pathologic lesions observed in AD. This overview describes the most common approaches used to model AD in rodents, highlights their utility, and discusses some of their deficiencies.