Amyloid beta-peptides injection into the cholinergic nuclei: morphological, neurochemical and behavioral effects

Behavioral and Molecular Effects of Thapsigargin-Induced Brain ER- Stress: Encompassing Inflammation, MAPK, and Insulin Signaling Pathway

Accumulation of misfolded proteins, known as endoplasmic reticulum (ER) stress, is known to participate in Alzheimer’s disease (AD). AD is also correlated with impaired central insulin signaling. However, few studies have probed the relationship between memory, central ER stress, inflammation, hippocampal mitogen-activated protein kinase (MAPK) activity and insulin resistance. The present study aimed to investigate the causative role and underlying mechanisms of brain ER stress in memory impairment and develop a reliable animal model for ER-mediated memory loss. Thapsigargin (TG), a known ER stress activator, was centrally administered. The cognitive function of animals was evaluated by the Morris Water Maze (MWM). To verify the induction of central ER stress, we investigated the mRNA expression of UPR markers in the hippocampus. In addition, the activation of ER stress markers, including Bip, CHOP, and some related apoptosis and pro-inflammatory proteins, such as caspase-3, Bax, Bcl-2, TNF-α, MAPK, and insulin signaling markers, were assessed by Western-blots. The results demonstrated that TG impairs spatial cognition and hippocampal insulin signaling. Meanwhile, molecular results showed a concurrent increment of hippocampal UPR markers, apoptosis, P38 activity, and TNF-α. This study introduced TG-induced ER stress as a pharmacological model for memory impairment in rats and revealed some underlying mechanisms.

Synthesis of curcumin complexes with iron(iii) and manganese(ii), and effects of curcumin–iron(iii) on Alzheimer's disease

Plants provide a wealth of bioactive compounds which aid in exerting a substantial strategy for the treatment of neurological disorders such as Alzheimer's disease and dementia.

Nicotinamide treatment reduces the levels of oxidative stress, apoptosis, and PARP-1 activity in Aβ(1-42)-induced rat model of Alzheimer's disease

The underlying mechanisms of Alzheimer's Disease (AD) are still unclear. It is suggested that poly(ADP-ribose) polymerase-1 (PARP-1) overactivation can cause neuroinflammation and cell death. In this study we searched the effects of nicotinamide (NA), endogenous PARP-1 inhibitor, on oxidative stress, apoptosis, and the regulation of PARP-1 and nuclear factor kappa B (NF-κB) in amyloid beta peptide (1-42) (Aβ(1-42))-induced neurodegeneration. Sprague-Dawley rats were divided into four groups as control, Aβ(1-42), Aβ(1-42) + NA(100 and 500 mg/kg). All groups were stereotaxically injected bilaterally into the hippocampus with Aβ(1-42) or saline. After surgery NA administrations were made intraperitoneally (ip) for 7 days. In order to investigate the effects of Aβ(1-42) and NA, protein carbonyls, lipid peroxidation, reactive oxygen species (ROS) production, glutathione (GSH) levels, activities of antioxidant enzymes (catalase, superoxide dismutase, glutathione peroxidase), mitochondrial function, mRNA and protein levels of PARP-1, NF-κB, p53, Bax, and Bcl-2 were measured in specific brain regions such as cortex and hippocampus. Aβ(1-42) treatment only increased the oxidative stress parameters and caused decline in antioxidant enzyme activities, mitochondrial function, and GSH levels. Also, overexpression of PARP-1, NF-κB, p53, Bax, and the decreased levels of Bcl-2 were observed in Aβ(1-42)-treated group. NA treatments against Aβ(1-42)-upregulated Bcl-2 and downregulated PARP-1, NF-κB, p53, and Bax levels. NA treatments also decreased the oxidative stress parameters and elevated antioxidant enzyme activities, GSH levels, and mitochondrial function against Aβ(1-42) treatment. These data suggest that NA may have a therapeutic potential in neurodegenerative processes due to the decreased levels of oxidative stress, apoptosis, and PARP-1 activity.

Chronic stress and Alzheimer's disease-like pathogenesis in a rat model: prevention by nicotine

Environmental factors including chronic stress may play a critical role in the manifestation of Alzheimer's disease (AD).This review summarizes our studies of the aggravation of the impaired cognitive ability and its cellular and molecular correlates by chronic psychosocial stress and prevention by nicotine in an Aβ rat model of AD. We utilized three approaches: learning and memory tests in the radial arm water maze, electrophysiological recordings of the cellular correlates of memory, long-term potentiation (LTP) and long-term depression (LTD), in anesthetized rats, and immunoblot analysis of synaptic plasticity- and cognition-related signaling molecules. The Aβ rat model, representing the sporadic form of established AD, was induced by continuous i.c.v. infusion of a pathogenic dose of Aβ peptides via a 14- day osmotic pump. In this AD model, chronic stress intensified cognitive deficits, accentuated the disruption of signaling molecules levels and produced greater depression of LTP than what was seen with Aβ infusion alone. Chronic treatment with nicotine was highly efficient in preventing the effects of Aβ infusion and the exacerbating impact of chronic stress. Possible mechanisms for the effect of chronic stress are discussed.

Schizandrin, an antioxidant lignan from Schisandra chinensis, ameliorates Aβ1-42-induced memory impairment in mice

In the present study, we examined the effect of schisandrin (SCH) of Schisandra chinensis on the amyloid-beta_1–42- (Aβ_1–42-) induced memory impairment in mice and elucidated the possible antioxidative mechanism. Mice were intracerebroventricular (i.c.v.) injected with the aggregated Aβ_1–42 and then treated with SCH (4, 12, and 36 mg/kg body weight) or donepezil (DPZ), a reference drug (0.65 mg/kg) by intragastric infusion for 14 days. Noncognitive disturbances and cognitive performance were evaluated by locomotor activity test, Y-maze test, and water maze test. Antioxidative enzyme activities including superoxide dismutase (SOD) and glutathione peroxidase (GSH-px) and levels of malondialdehyde (MDA), glutathione (GSH), and oxidized glutathione (GSSG) within the cerebral cortex and hippocampus of mice were measured to elucidate the mechanism. Our results showed that SCH significantly improved Aβ_1–42-induced short-term and spatial reference memory impairments in Y-maze test and water maze test. Furthermore, in the cerebral cortex and hippocampus of mice, SOD and GSH-px activities, GSH level, and GSH/GSSG ratio were increased, and levels of MDA and GSSG were decreased by the treatment of SCH. These results suggest that SCH is a potential cognitive enhancer against Alzheimer's disease through antioxidative action.

Regulation of cortical acetylcholine release: insights from in vivo microdialysis studies

Acetylcholine release links the activity of presynaptic neurons with their postsynaptic targets and thus represents the intercellular correlate of cholinergic neurotransmission. Here, we review the regulation and functional significance of acetylcholine release in the mammalian cerebral cortex, with a particular emphasis on information derived from in vivo microdialysis studies over the past three decades. This information is integrated with anatomical and behavioral data to derive conclusions regarding the role of cortical cholinergic transmission in normal behavioral and how its dysregulation may contribute to cognitive correlates of several neuropsychiatric conditions. Some unresolved issues regarding the regulation and significance of cortical acetylcholine release and the promise of new methodology for advancing our knowledge in this area are also briefly discussed.

Change of cholinergic transmission and memory deficiency induced by injection of beta-amyloid protein into NBM of rats

The change of cholinergic transmission of beta-amyloid protein (beta-AP) treated rats was studied by intracerebral microdialysis sampling combined with HPLC analysis. beta-AP(1-40) was injected into nucleus basalis magnocellularis (NBM). Passive avoidance response test (step-down test) and delayed alternation task were used for memory testing. The impairment of memory after injection of beta-AP(1-40) into NBM exhibited mainly the deficiency of short-term working memory. One week after injection of beta-AP(1-40) the release of acetylcholine (ACh) from frontal cortex of freely-moving rats decreased significantly, and the response of cholinergic nerve ending to the action of high [K(+)] solution was rather weak. In control animals the percentage of increase of ACh-release during behavioral performance was 57%, while in beta-AP(1-40)-treated rats it was 34%. The temporary increase of the ACh-release of the rat put into a new place was also significantly diminished in beta-AP(1-40) -treated rats. The results show that the injection of beta-AP(1-40) into NBM impairs the cholinergic transmission in frontal cortex, and the impairment of cholinergic transmission may be the main cause of the deficit of working memory.

Protective effects of xanthoceraside on learning and memory impairment induced by Abeta(25-35) in mice

This study examined the effects of xanthoceraside (1) on learning and memory impairment induced in mice by intracerebroventricular injection of aggregated peptide beta-amyloid 25-35 (Abeta(25-35)). Learning and memory functions in mice were examined using step-through, Y-maze and water maze tests. Administration of 1 reduced the number of errors and prolonged latency in the step-through test in mice impaired by Abeta(25-35). Likewise, latency to find the terminal platform was decreased and the number of right reflects was increased in the water maze test, and the percentage of alternation behaviors in the Y-maze test was increased. Biochemical studies showed that decreased activities of superoxide dismutase, glutathione peroxidase, and acetylcholinesterase, and increased content of malondialdehyde in mice impaired by Abeta(25-35) were significantly ameliorated by administration of 1. The present results suggest that 1 may provide a potential treatment strategy for Alzheimer's disease.

Increases of kinin B1 and B2 receptors binding sites after brain infusion of amyloid-beta 1–40 peptide in rats

Although numerous inflammation pathways have been implicated in Alzheimer's disease, the involvement of the kallikrein-kinin system is still under investigation. We anatomically localized and quantified the density of kinin B(1) and B(2) receptors binding sites in the rat brain after the infusion of amyloid-beta (Abeta) peptide in the right lateral brain ventricle for 5 weeks. The conditioned avoidance test showed a significant reduction of memory consolidation in rats infused with Abeta (68.6+/-20.9%, P<0.05) when compared to control group (90.8+/-4.1%; infused with vehicle). Autoradiographic studies performed in brain samples of both groups using [(125)I]HPP-[des-Arg(10)]-Hoe-140 (150pM, 90min, 25 degrees C) showed a significant increase in density of B(1) receptor binding sites in the ventral hippocampal commissure (1.23+/-0.07fmol/mg), fimbria (1.31+/-0.05fmol/mg), CA1 and CA3 hippocampal areas (1.05+/-0.03 and 1.24+/-0.02fmol/mg, respectively), habenular nuclei (1.30+/-0.04fmol/mg), optical tract (1.30+/-0.05fmol/mg) and internal capsule (1.26+/-0.05fmol/mg) in Abeta group. For B(2) receptors ([(125)I]HPP-Hoe-140, 200pM, 90min, 25 degrees C), a significant increase in density of binding sites was observed in optical tract (2.04+/-0.08fmol/mg), basal nucleus of Meynert (1.84+/-0.18fmol/mg), lateral septal nucleus - dorsal and intermediary portions (1.66+/-0.29fmol/mg), internal capsule (1.74+/-0.19fmol/mg) and habenular nuclei (1.68+/-0.11fmol/mg). In control group, none of these nuclei showed [(125)I]HPP-Hoe-140 labeling. This significant increase in densities of kinin B(1) and B(2) receptors in animals submitted to Abeta infusion was observed mainly in brain regions related to cognitive behavior, suggesting the involvement of the kallikrein-kinin system in Alzheimer's disease in vivo.

Decreased nicotinic receptors and cognitive deficit in rats intracerebroventricularly injected with beta-amyloid peptide(1-42) and fed a high-cholesterol diet

To investigate whether the changes in nicotinic receptors (nAChRs) and in learning and memory associated with Alzheimer's disease (AD) are influenced by both beta-amyloid peptide (Abeta) and cholesterol in vivo, we examined the effects of intracerebroventricular injection of Abeta(1-42) and/or a high-cholesterol diet on brain levels of nAChRs and learning and memory in rats. The levels of nAChR subunit proteins and the corresponding mRNA were measured by Western blotting and RT-PCR, respectively; and learning and memory were evaluated with the Morris Water Maze examination. Injection of Abeta(1-42) resulted in deposition of this peptide, activation of astrocytes, decreased levels of the alpha7 and alpha4 protein subunits of the nAChR, and elevated expression of alpha7 mRNA, as well as impaired learning and spatial memory. A high-cholesterol diet activated astrocytes and, more importantly, potentiated the toxic effects of Abeta on nAChR subunit levels and on learning and memory. These findings may be highly relevant to the mechanisms underlying the cognitive deficits associated with AD.

Animal models of cognitive dysfunction

The increased life expectancy in industrialised countries in the last half century has also brought to a greater incidence of neurological disorders, including neurodegenerative diseases and developing in a rather long time. In this respect, Alzheimer's disease (AD), for the large incidence, and the dramatic loss of autonomy caused by its cognitive and behavioural symptoms represents one of the main challenges of modern medicine. Although AD is a typical human disease and probably includes several nosographic entities, the use of animal models may contribute to understand specific aspects of pathophysiology of the disease. The most widely used animal models are rodents and non-human primates. In this review different animal models characterised by impaired cognitive functions are analysed. None of the models available mimics exactly cognitive, behavioural, biochemical and histopathological abnormalities observed in neurological disorders characterised by cognitive impairment. However, partial reproduction of neuropathology and/or cognitive deficits of Alzheimer's disease (AD), vascular dementia and dementia occurring in Huntington's and Parkinson's diseases, or in other neurodegenerative disorders may represent a basis for understanding pathophysiological traits of these diseases and for contributing to their treatments.

Amyloid beta-peptide induces cholinergic dysfunction and cognitive deficits: a minireview

Amyloid beta-peptide (Abeta) plays a critical role in the development of Alzheimer's disease (AD). Much progress has been made in understanding this age-related neurodegenerative disorder, thus an insight into the cellular actions of Abeta and resulting functional consequences may contribute to preventive and therapeutic approaches for AD. In this review, recent evidence of Abeta-induced brain dysfunction, particularly of cholinergic impairment and memory deficits is summarized. Moreover, proposed mechanisms for Abeta-induced neurotoxicity such as oxidative stress, ion-channel formation, and Abeta-receptor interaction are discussed.

Animal models of Alzheimer's disease and evaluation of anti-dementia drugs

Alzheimer's disease (AD) is the most common cause of progressive decline of cognitive function in aged humans, and is characterized by the presence of numerous senile plaques and neurofibrillary tangles accompanied by neuronal loss. Some, but not all, of the neuropathological alterations and cognitive impairment in AD can be reproduced genetically and pharmacologically in animals. It should be possible to discover novel drugs that slow the progress or alleviate the clinical symptoms of AD by using these animal models. We review the recent progress in the development of animal models of AD and discuss how to use these model animals to evaluate novel anti-dementia drugs.

A ventral approach to stereotaxy of the guinea pig brain

The guinea pig (Cavia porcellus) is a species frequently used in neuromorphological and neurophysiological studies. Some experimental data suggest that the guinea pig might also be used to develop an animal model of Alzheimer's disease. These studies would require microsurgical manipulations of the nervous system. The present paper describes a method for ventral stereotaxic intrusions in the guinea pig brain through the oval foramen at the skull base. The topographic relationships of the bony landmarks to major parts of the central nervous system and the cranial nerves are analysed, and the results are tested by intrahippocampal injection of horseradish peroxidase.

Invited review: Anticholinesterases: dramatic aspects of their use and misuse

While the lore of anticholinesterases (antiChEs), particularly physostigmine and its natural source, the Calabar bean, is a subject of ethnomedicine and predates our scientific era, the pharmacological development of physostigmine analogues and related agents and of the antiChEs of the organophosphorus (OP) type, is a matter of the last two centuries; this development has reached an exponential character in the last fifty years. This explosion relates to certain uses and misuses of these drugs and this aspect of antiChEs is the main focus of this article. Firstly, there is the matter of Senile Dementia of Alzheimer's Type (SDAT); while there are several clinical applications of antiChEs, their employment in the treatment of SDAT is the last and most intense foray in their medical history and this article will focus on the uses and misuses of antiChEs in this area. Secondly, the applied use of antiChEs as insecticides which coincided with the historical development of OP antiChEs was and is, of major significance for the agricultural economy of both advanced and underdeveloped countries, as this employment may mean the difference between life and starvation. However, there are notable dangers with this application of OP drugs, as will be emphasized in this article. Thirdly, there is the significant and tragic development of the OP drugs as warfare agents and tools for terrorists and rogue states and this article will discuss the several types of toxicity of OP agents and their mechanisms, the enigma of the Persian Gulf War Syndrome being particularly stressed. Altogether, the immense range of antiChE topics includes areas of great basic interest and of practical applications that are of significant benefit to mankind as well as of potential danger.