Guanosine Neuroprotection of Presynaptic Mitochondrial Calcium Homeostasis in a Mouse Study with Amyloid-ß Oligomers.

Amyloid-ß oligomers (AßOs) toxicity causes mitochondrial dysfunction, leading to synaptic failure in Alzheimer's disease (AD). Considering presynaptic high energy demand and tight Ca2+ regulation, impairment of mitochondrial function can lead to deteriorated neural activity and cell death. In this study, an AD mouse model induced by ICV (intracerebroventricular) injection of AßOs was used to investigate the toxicity of AßOs on presynaptic function. As a therapeutic approach, GUO (guanosine) was given by oral route to evaluate the neuroprotective effects on this AD model. Following 24 h and 48 h from the model induction, behavioral tasks and biochemical analyses were performed, respectively. AßOs impaired object recognition (OR) short-term memory and reduced glutamate uptake and oxidation in the hippocampus. Moreover, AßOs decreased spare respiratory capacity, reduced ATP levels, impaired Ca2+ handling, and caused mitochondrial swelling in hippocampal synaptosomes. Guanosine crossed the BBB, recovered OR short-term memory, reestablished glutamate uptake, recovered mitochondrial Ca2+ homeostasis, and partially prevented mitochondrial swelling. Therefore, this endogenous purine presented a neuroprotective effect on presynaptic mitochondria and should be considered for further studies in AD models.

Atorvastatin Improves Mitochondrial Function and Prevents Oxidative Stress in Hippocampus Following Amyloid-ß1-40 Intracerebroventricular Administration in Mice.

Amyloid-ß (Aß) peptides play a significant role in the pathogenesis of Alzheimer's disease (AD). Neurotoxic effects promoted by Aß peptides involve glutamate transmission impairment, decrease of neurotrophic factors, mitochondrial dysfunction, oxidative stress, synaptotoxicity, and neuronal degeneration. Here, we assessed the early events evoked by Aß1-40 on the hippocampus. Additionally, we sought to unravel the molecular mechanisms of atorvastatin preventive effect on Aß-induced hippocampal damage. Mice were treated orally (p.o.) with atorvastatin 10 mg/kg/day during 7 consecutive days before the intracerebroventricular (i.c.v.) infusion of Aß1-40 (400 pmol/site). Twenty-four hours after Aß1-40 infusion, a reduced content of mature BDNF/proBDNF ratio was observed in Aß-treated mice. However, there is no alteration in synaptophysin, PSD-95, and doublecortin immunocontent in the hippocampus. Aß1-40 promoted an increase in reactive oxygen species (ROS) and nitric oxide (NO) generation in hippocampal slices, and atorvastatin prevented this oxidative burst. Mitochondrial OXPHOS was measured by high-resolution respirometry. At this time point, Aß1-40 did not alter the O2 consumption rates (OCR) related to phosphorylating state associated with complexes I and II, and the maximal OCR. However, atorvastatin increased OCR of phosphorylating state associated with complex I and complexes I and II, maximal OCR of complexes I and II, and OCR associated with mitochondrial spare capacity. Atorvastatin treatment improved mitochondrial function in the rodent hippocampus, even after Aß infusion, pointing to a promising effect of improving brain mitochondria bioenergetics. Therefore, atorvastatin could act as an adjuvant in battling the symptoms of AD to preventing or delaying the disease progression.

Prophylactic effect of physical exercise on Aß1-40-induced depressive-like behavior and gut dysfunction in mice.

Alzheimer's disease (AD) is a prevalent neurodegenerative disease that is highly comorbid with depression. Gut dysfunction has been proposed as a possible risk factor for both clinical conditions. In the present study, we investigated the ability of treadmill exercise for 4 weeks (5 days/week, 40 min/day) to counteract amyloid ß1-40 peptide (Aß1-40)-induced depressive-like behavior, alterations in morphological parameters of the duodenum, and the abundance of Firmicutes and Bacteroidetes phyla. Aß1-40 administration (400 pmol/mouse, i.c.v.) increased immobility time in the tail suspension test (TST) and reduced time spent sniffing in the female urine sniffing test (FUST), indicating behavioral despair and impairment in reward-seeking behavior. These behavioral alterations, indicative of depressive-like behavior, were accompanied by reduced villus width in the duodenum. Moreover, photomicrographs obtained by transmission electron microscopy revealed abnormal epithelial microvilli in the duodenum from sedentary Aß1-40-exposed mice, characterized by shorter microvilli and heterogeneity in the length of these structures that exhibit a disordered packing. Regarding the ultrastructure of Paneth cells, Aß1-40 administration caused a reduction in the secretory granule diameter, as well as an enlarged peripheral halo. These animals also presented reduced Firmicutes and increased Bacteroidetes abundance, and increased Bacteroidetes/Firmicutes ratio. Most of the alterations observed in Aß1-40-exposed mice were prevented by the practice of physical exercise. Altogether the results provide evidence of the prophylactic effect of physical exercise on Aß1-40-induced depressive-like behavior and gut dysfunction in mice, suggesting that physical exercise could be useful for preventing depression associated with AD.

The Involvement of NLRP3 on the Effects of Minocycline in an AD-Like Pathology Induced by ß-Amyloid Oligomers Administered to Mice.

Alzheimer's disease (AD) is a neurodegenerative disease which is characterized by progressive memory loss, the accumulation of ß-amyloid peptide (Aß) (mainly Aß1-42), and more recently, by neuroinflammation, which has been highlighted as playing a central role in the development and progress of AD. This study utilized 100-day-old Balb/c mice for the induction of an AD-like dementia model. The animals were administered with Aß1-42 oligomers (400 pmol/site) or artificial cerebrospinal fluid (ACSF) into the left cerebral ventricle. Twenty-four hours after intracerebroventricular administration, the animals were treated with minocycline (50 mg/kg, via oral gavage) for 17 days. The animals' locomotion was evaluated using the open-field test. The spatial memory was tested using the Y-maze, and the aversive memory was evaluated using the inhibitory avoidance task. Treatment with minocycline was shown to improve both spatial and aversive memories in mice that were submitted to the dementia model. In addition, minocycline reduced the levels of Aß and microglial activation in the animals that received the administration of Aß1-42 oligomers. Moreover, the results suggest that the decrease in microglial activation occurred because of a reduction in the levels of toll-like receptors 2 (TLR2) content, and its adapter protein MyD88, as well as a reduction in the levels of the protein NLRP3, which is indispensable in the assembly of inflammasome. These observations were evaluated via immunohistochemistry and confirmed using the Western blot analysis. Treatment with minocycline had no effect in preventing apoptotic morphologic alterations of the neurons. Thus, the anti-inflammatory effect of minocycline involves TLR2 receptors and NLRP3, besides being beneficial by ameliorating memory impairments. Graphical Abstract.

Study of the Effects of L-tryptophane Nanoparticles on Motor Behavior in Alzheimer's Experimental Models.

BACKGROUND: Alzheimer's disease (AD) is a neurodegenerative disease characterized by the progressive and incapacitating decay of cognitive, neuropsychiatric, and behavioral manifestations. L-tryptophan is the precursor amino acid of serotonin, which is a neurotransmitter responsible for mood balance and the sense of well-being and can be administered in the form of nanoparticles. OBJECTIVE: This study analyzed the effectiveness of L-tryptophan nanoparticles and L-tryptophan on behavioral physiological alterations resulting from AD in animal models. METHODS: The sample consisted of 50 Rattus norvegicus rats, divided in 10 groups with 5 animals each: one negative control (NC), three positive control groups (C3, C7, and C21), three groups treated with L-tryptophan nanoparticles (T3N, T7N, and T21N) at the concentration of 1.5 mg, and three groups treated with L-tryptophan (T3L, T7L, and T21L) at the concentration of 1.5 mg. The rats underwent stereotactic surgery to induce AD through the injection of amyloid beta-amyloid peptide1-42 in the intracerebroventricular region. All rats were submitted to pre- and post-surgery and post-treatment motor behavior evaluation through the Later Water Maze (LWM) and elevated cross-labyrinth (ECL). Histological analysis was performed to verify the presence of senile plaques, and the statistical analysis used the unpaired T-test. RESULTS: Significant intergroup differences were observed in some of the evaluated parameters between treated and untreated groups. CONCLUSION: It was concluded that the treatment with L-tryptophan nanoparticles was beneficial to improve behavioral reactions in the Alzheimer's model.

Swimming exercise prevents behavioural disturbances induced by an intracerebroventricular injection of amyloid-ß1-42 peptide through modulation of cytokine/NF-kappaB pathway and indoleamine-2,3-dioxygenase in mouse brain.

Emerging evidence indicates that the activation of indoleamine-2,3-dioxygenase (IDO), a first and rate-limiting enzyme in the kynurenine (KYN) pathway, is involved in amyloid-beta (Aß1-42)-neurotoxicity and Alzheimer's disease (AD) pathogenesis. Physical exercise has been considered an effective intervention in AD, attenuating or limiting their progression. Nevertheless, the neurobiological mechanisms underlying the neuroprotective effects of exercise have not yet been fully elucidated. In present study, we investigated the protective effect of an 8-week swimming training (ST) exercise on cognitive and non-cognitive functions and its role in modulating biomarkers of KYN pathway, before an intracerebroventricular (i.c.v.) injection of Aß1-42 (400pmol/animal; 3µl/site) peptide in mice. Our results demonstrated that ST was effective in preventing the following behavioural disturbances caused by Aß1-42 injection: memory impairment in the object recognition test and depressive/anxiety-like behaviour in the tail suspension test and elevated plus-maze test, respectively. ST abrogated the neuroinflammatory response and neurotrophic deficiency in the prefrontal cortex and hippocampus induced by Aß1-42. Also, Aß1-42 increased IDO activity, KYN and tryptophan (TRP) levels and KYN:TRP ratio in the prefrontal cortex and hippocampus - alterations that were blocked by ST. It can be concluded that ST prevented behavioural and neurobiological deficits induced by Aß1-42, and suggest that these neuroprotective effects are likely to involve the inhibition of inflammation/IDO activation and up-regulation of neurotrophic factors in brain of mice. Thus, it is possible that physical exercise can be used as a non-pharmacological approach to alleviates both cognitive and non-cognitive symptoms of AD.

Chronic sleep restriction promotes brain inflammation and synapse loss, and potentiates memory impairment induced by amyloid-ß oligomers in mice.

It is increasingly recognized that sleep disturbances and Alzheimer's disease (AD) share a bidirectional relationship. AD patients exhibit sleep problems and alterations in the regulation of circadian rhythms; conversely, poor quality of sleep increases the risk of development of AD. The aim of the current study was to determine whether chronic sleep restriction potentiates the brain impact of amyloid-ß oligomers (AßOs), toxins that build up in AD brains and are thought to underlie synapse damage and memory impairment. We further investigated whether alterations in levels of pro-inflammatory mediators could play a role in memory impairment in sleep-restricted mice. We found that a single intracerebroventricular (i.c.v.) infusion of AßOs disturbed sleep pattern in mice. Conversely, chronically sleep-restricted mice exhibited higher brain expression of pro-inflammatory mediators, reductions in levels of pre- and post-synaptic marker proteins, and exhibited increased susceptibility to the impact of i.c.v. infusion of a sub-toxic dose of AßOs (1pmol) on performance in the novel object recognition memory task. Sleep-restricted mice further exhibited an increase in brain TNF-α levels in response to AßOs. Interestingly, memory impairment in sleep-restricted AßO-infused mice was prevented by treatment with the TNF-α neutralizing monoclonal antibody, infliximab. Results substantiate the notion of a dual relationship between sleep and AD, whereby AßOs disrupt sleep/wake patterns and chronic sleep restriction increases brain vulnerability to AßOs, and point to a key role of brain inflammation in increased susceptibility to AßOs in sleep-restricted mice.

Daily rhythms of cognition-related factors are modified in an experimental model of Alzheimer's disease.

The accumulation of amyloid-ß (Aß) peptides in the brain of Alzheimer disease patients is associated to cognitive deficit, increased oxidative stress, and alterations in the circadian rhythms. Brain-derived neurotrophic factor (BDNF) and Neurogranin (RC3), play an important role in the synaptic plasticity underlying memory and learning. Previously, we observed BDNF and RC3 expression follow a daily rhythmic pattern in the hippocampus of young rats. The objective of this study was to investigate the effects of an intracerebroventricular (i.c.v) injection of aggregated Aß peptide (1-42) on temporal patterns of ApoE protein, Bdnf and Rc3 mRNA, lipid peroxidation (LPO) and reduced glutathione (GSH) levels, in the rat hippocampus. We observed an i.c.v. injection of Aß aggregates phase shifts daily BDNF and RC3 expression as well as LPO and decreased the mesor of GSH rhythms. ApoE protein levels vary rhythmically throughout the day. ApoE levels increase at ZT 03:39±00:22 in the hippocampus of control rats and at ZT 06:30±00:28 in the treated animals. Thus, elevated levels of Aß aggregates, characteristic of AD, altered temporal patterns of cognition related-factors, probably, as a consequence of changes in the daily variation of ApoE-mediated Aß aggregates clearance as well as in the 24h rhythms of the cellular redox state.

Indoleamine-2,3-dioxygenase mediates neurobehavioral alterations induced by an intracerebroventricular injection of amyloid-ß1-42 peptide in mice.

Alzheimer's disease (AD) is a neurodegenerative disorder that is characterized by a progressive cognitive decline along with various neuropsychiatric symptoms, including depression and anxiety. Increasing evidence has been proposed the activation of the tryptophan-degrading indoleamine-2,3-dyoxigenase (IDO), the rate-limiting enzyme of kynurerine pathway (KP), as a pathogenic factor of amyloid-beta (Aß)-related inflammation in AD. In the current study, the effects of an intracerebroventricular (i.c.v.) injection of Aß1-42 peptide (400pmol/mice; 3µl/site) on the regulation of KP biomarkers (IDO activity, tryptophan and kynurerine levels) and the impact of Aß1-42 on neurotrophic factors levels were investigated as potential mechanisms linking neuroinflammation to cognitive/emotional disturbances in mice. Our results demonstrated that Aß1-42 induced memory impairment in the object recognition test. Aß1-42 also induced emotional alterations, such as depressive and anxiety-like behaviors, as evaluated in the tail suspension and elevated-plus maze tests, respectively. We observed an increase in levels of proinflammatory cytokines in the Aß1-42-treated mice, which led to an increase in IDO activity in the prefrontal cortex (PFC) and the hippocampus (HC). The IDO activation subsequently increased kynurerine production and the kynurenine/tryptophan ratio and decreased the levels of neurotrophic factors in the PFC and HC, which contributed to Aß-associated behavioral disturbances. The inhibition of IDO activation by IDO inhibitor 1-methyltryptophan (1-MT), prevented the development of behavioral and neurochemical alterations. These data demonstrate that brain IDO activation plays a key role in mediating the memory and emotional disturbances in an experimental model based on Aß-induced neuroinflammation.

Alzheimer's disease-like pathology induced by amyloid-ß oligomers in nonhuman primates.

Alzheimer's disease (AD) is a devastating neurodegenerative disorder and a major medical problem. Here, we have investigated the impact of amyloid-ß (Aß) oligomers, AD-related neurotoxins, in the brains of rats and adult nonhuman primates (cynomolgus macaques). Soluble Aß oligomers are known to accumulate in the brains of AD patients and correlate with disease-associated cognitive dysfunction. When injected into the lateral ventricle of rats and macaques, Aß oligomers diffused into the brain and accumulated in several regions associated with memory and cognitive functions. Cardinal features of AD pathology, including synapse loss, tau hyperphosphorylation, astrocyte and microglial activation, were observed in regions of the macaque brain where Aß oligomers were abundantly detected. Most importantly, oligomer injections induced AD-type neurofibrillary tangle formation in the macaque brain. These outcomes were specifically associated with Aß oligomers, as fibrillar amyloid deposits were not detected in oligomer-injected brains. Human and macaque brains share significant similarities in terms of overall architecture and functional networks. Thus, generation of a macaque model of AD that links Aß oligomers to tau and synaptic pathology has the potential to greatly advance our understanding of mechanisms centrally implicated in AD pathogenesis. Furthermore, development of disease-modifying therapeutics for AD has been hampered by the difficulty in translating therapies that work in rodents to humans. This new approach may be a highly relevant nonhuman primate model for testing therapeutic interventions for AD.

Brain intraventricular injection of amyloid-ß in zebrafish embryo impairs cognition and increases tau phosphorylation, effects reversed by lithium.

Alzheimer's disease (AD) is a devastating neurodegenerative disorder with no effective treatment and commonly diagnosed only on late stages. Amyloid-ß (Aß) accumulation and exacerbated tau phosphorylation are molecular hallmarks of AD implicated in cognitive deficits and synaptic and neuronal loss. The Aß and tau connection is beginning to be elucidated and attributed to interaction with different components of common signaling pathways. Recent evidences suggest that non-fibrillary Aß forms bind to membrane receptors and modulate GSK-3ß activity, which in turn phosphorylates the microtubule-associated tau protein leading to axonal disruption and toxic accumulation. Available AD animal models, ranging from rodent to invertebrates, significantly contributed to our current knowledge, but complementary platforms for mechanistic and candidate drug screenings remain critical for the identification of early stage biomarkers and potential disease-modifying therapies. Here we show that Aß1-42 injection in the hindbrain ventricle of 24 hpf zebrafish embryos results in specific cognitive deficits and increased tau phosphorylation in GSK-3ß target residues at 5dpf larvae. These effects are reversed by lithium incubation and not accompanied by apoptotic markers. We believe this may represent a straightforward platform useful to identification of cellular and molecular mechanisms of early stage AD-like symptoms and the effects of neuroactive molecules in pharmacological screenings.

Neuropeptide Y (NPY) prevents depressive-like behavior, spatial memory deficits and oxidative stress following amyloid-ß (Aß(1-40)) administration in mice.

Neuropeptide Y (NPY) is a 36-amino acid peptide widely distributed in the central nervous system (CNS) that has been associated with the modulation of several functions including food intake, learning and memory, mood and neuroprotection. There is great interest in understanding the role of NPY in the deleterious effects induced by the central accumulation of amyloid-ß (Aß) peptides, a pathological hallmark of Alzheimer's disease (AD). Herein, we evaluated the effects of a single intracerebroventricular (i.c.v.) administration of NPY (0.0234 µmol/µL) 15 min prior to the i.c.v. injection of aggregated Aß1-40 peptide (400 pmol/mouse) in behavioral and neurochemical parameters related to oxidative stress in mice. Pretreatment with NPY prevented Aß1-40-induced depressive-like responses and spatial memory impairments evaluated in the tail suspension and object location tasks, respectively. The protective effects of NPY on spatial memory of Aß1-40-treated mice were abolished by the pretreatment with the selective Y2 receptor antagonist BIIE0246. On the other hand, the administration of NPY and Aß1-40 did not alter the performance of the animals in the elevated plus-maze and open field arena, indicating lack of effects on anxiety state and locomotor function. Although Aß1-40 infusion did not change hippocampal and cortical glutathione peroxidase (GPx) activity and glutathione (GSH) levels, Aß1-40-infused animals showed an increased lipid peroxidation in hippocampus and prefrontal cortex that were blunted by NPY administration. These findings indicate that central administration of NPY prevents Aß1-40-induced depressive-like behavior and spatial memory deficits in mice and that this response is mediated, at least in part, by the activation of Y2 receptors and prevention of oxidative stress.

Neuroprotective effects of resveratrol against Aß administration in rats are improved by lipid-core nanocapsules.

Alzheimer's disease (AD), a neurodegenerative disorder exhibiting a gradual decline in cognitive function, is characterized by the presence of neuritic plaques composed of neurofibrillary tangles and amyloid-ß (Aß) peptide. Available drugs for AD therapy have small effect sizes and do not alter disease progression. Several studies have been shown that resveratrol is associated with anti-amyloidogenic properties, but therapeutic application of its beneficial effects is limited. Here we compared the neuroprotective effects of free resveratrol treatment with those of resveratrol-loaded lipid-core nanocapsule treatment against intracerebroventricular injection of Aß1-42 in rats. Animals received a single intracerebroventricular injection of Aß1-42 (2 nmol), and 1 day after Aß infusion, they were administered either free resveratrol (RSV) or resveratrol-loaded lipid-core nanocapsules (5 mg/kg, each 12 h, intraperitoneally), for 14 days. Aß1-42-infused animals showed a significant impairment on learning memory ability, which was paralleled by a significant decrease in hippocampal synaptophysin levels. Furthermore, animals exhibited activated astrocytes and microglial cells, as well as disturbance in c-Jun N-terminal kinase (JNK) and glycogen synthase kinase-3ß (GSK-3ß) activation, beyond destabilization of ß-catenin levels. Our results clearly show that by using lipid-core nanocapsules, resveratrol was able to rescue the deleterious effects of Aß1-42 while treatment with RSV presented only partial beneficial effects. These findings might be explained by the robust increase of resveratrol concentration in the brain tissue achieved by lipid-core nanocapsules. Our data not only confirm the potential of resveratrol in treating AD but also offer an effective way to improve the efficiency of resveratrol through the use of nanodrug delivery systems.

Accumulation of exogenous amyloid-beta peptide in hippocampal mitochondria causes their dysfunction: a protective role for melatonin.

Amyloid-beta (Aß) pathology is related to mitochondrial dysfunction accompanied by energy reduction and an elevated production of reactive oxygen species (ROS). Monomers and oligomers of Aß have been found inside mitochondria where they accumulate in a time-dependent manner as demonstrated in transgenic mice and in Alzheimer's disease (AD) brain. We hypothesize that the internalization of extracellular Aß aggregates is the major cause of mitochondrial damage and here we report that following the injection of fibrillar Aß into the hippocampus, there is severe axonal damage which is accompanied by the entrance of Aß into the cell. Thereafter, Aß appears in mitochondria where it is linked to alterations in the ionic gradient across the inner mitochondrial membrane. This effect is accompanied by disruption of subcellular structure, oxidative stress, and a significant reduction in both the respiratory control ratio and in the hydrolytic activity of ATPase. Orally administrated melatonin reduced oxidative stress, improved the mitochondrial respiratory control ratio, and ameliorated the energy imbalance.

Overexpression of cellular prion protein (PrP(C)) prevents cognitive dysfunction and apoptotic neuronal cell death induced by amyloid-ß (Aß1₋40) administration in mice.

The cellular prion protein (PrP(C)) is a neuronal-anchored glycoprotein that has been associated with several functions in the CNS such as synaptic plasticity, learning and memory and neuroprotection. There is great interest in understanding the role of PrP(C) in the deleterious effects induced by the central accumulation of amyloid-ß (Aß) peptides, a pathological hallmark of Alzheimer's disease, but the existent results are still controversial. Here we compared the effects of a single intracerebroventricular (i.c.v.) injection of aggregated Aß(1-40) peptide (400pmol/mouse) on the spatial learning and memory performance as well as hippocampal cell death biomarkers in adult wild type (Prnp(+/+)), PrP(C) knockout (Prnp(0/0)) and the PrP(C) overexpressing Tg-20 mice. Tg-20 mice, which present a fivefold increase in PrP(C) expression in comparison to wild type mice, were resistant to the Aß(1-40)-induced spatial learning and memory impairments as indicated by reduced escape latencies to find the platform and higher percentage of time spent in the correct quadrant during training and probe test sessions of the water maze task. The protection against Aß(1-40)-induced cognitive impairments observed in Tg-20 mice was accompanied by a significant decrease in the hippocampal expression of the activated caspase-3 protein and Bax/Bcl-2 ratio as well as reduced hippocampal cell damage assessed by MTT and propidium iodide incorporation assays. These findings indicate that the overexpression of PrP(C) prevents Aß(1-40)-induced spatial learning and memory deficits in mice and that this response is mediated, at least in part, by the modulation of programed cell death pathways.

Aß25-35 injection into the temporal cortex induces chronic inflammation that contributes to neurodegeneration and spatial memory impairment in rats.

Amyloid-ß (Aß)25-35 is able to cause memory impairment and neurodegenerative events. Recent evidence has shown that the injection of Aß25-35 into the temporal cortex (TCx) of rats increases the inflammatory response; however, it is unclear how the inflammatory process could be involved in the progression of Aß25-35 toxicity. In this study we investigated the role of inflammation in the neuronal damage and spatial memory impairment generated by Aß25-35 in rat TCx using immunohistochemistry, ELISA, and a behavioral test in the radial maze. Our findings show that Aß25-35 -injection into the TCx induced a reactive gliosis (GFAP and CD11b-reactivity) and an increase of pro-inflammatory cytokines (IL-1ß, IL-6, IL-17, and TNF-α) in the TCx and the hippocampus at 5, 15, and 30 days after injection. Thirty days after Aß25-35 injection, we observed that the inflammatory reaction probably contributed to increase the immunoreactivity of inducible nitric oxide synthase and nitrite levels, as well as to the loss of neurons in TCx and hippocampus. Behavioral performance showed that the neurodegeneration evoked by Aß25-35 delayed acquisition of learning and impaired spatial memory, because the Aß25-35-treated animals showed a greater number of errors during the task than the control group. Previous administration of an interleukin receptor antagonist (IL-1ra) (10 and 20 µg/µL, into TCx), an anti-inflammatory agent, suppressed the Aß25-35-induced inflammatory response and neurodegeneration, as well as memory dysfunction. This study suggests that the chronic inflammatory reaction could contribute to the progression of Aß25-35 toxicity and cause cognitive impairment.

The role of NOS in the impairment of spatial memory and damaged neurons in rats injected with amyloid beta 25-35 into the temporal cortex.

The Aß(25-35) fraction mimics the toxic effects of the complete peptide Aß(1-42) because this decapeptide is able to cause memory impairment and neurodegenerative events. Recent evidence has shown that the injection of Aß(25-35) into the temporal cortex (TCx) of the rat increases the nitric oxide (NO) pathways with several consequences, such as neuronal loss in rats. Our aim was to investigate the effects of each NOS isoform by the prior injection of NOS inhibitors before the injection of the Aß(25-35). One month after the treatment, the animals were tested for their spatial memory in the radial maze. The hippocampus (Hp) and TCx were assessed for NO production, nitration of proteins (3-NT), astrocytosis (GFAP), and neuronal loss. Our findings show a significant impairment in the memory caused by Aß25-35 injection. In contrast NOS inhibitors plus Aß25-35 cause a protection yielding a high performance in the memory test and reduction of cell damage in the TCx and the Hp. Particularly, iNOS is the major source of NO and related to the inflammatory response leading to the memory deficits. The inhibition of iNOS is an important target for neuronal protection against the toxicity of the Aß25-35 over the long term.

Novel amyloid-beta specific scFv and VH antibody fragments from human and mouse phage display antibody libraries.

Anti-amyloid immunotherapy has been proposed as an appropriate therapeutic approach for Alzheimer's disease (AD). Significant efforts have been made towards the generation and assessment of antibody-based reagents capable of preventing and clearing amyloid aggregates as well as preventing their synaptotoxic effects. In this study, we selected a novel set of human anti-amyloid-beta peptide 1-42 (Abeta1-42) recombinant monoclonal antibodies in a single chain fragment variable (scFv) and a single-domain (VH) format. We demonstrated that these antibody fragments recognize in a specific manner amyloid-beta deposits in APP/Tg mouse brains, inhibit toxicity of oligomeric Abeta1-42 in neuroblastoma cell cultures in a concentration-dependent manner and reduced amyloid deposits in APP/Tg2576 mice after intracranial administration. These antibody fragments recognize epitopes in the middle/C-terminus region of Abeta, which makes them strong therapeutic candidates due to the fact that most of the Abeta species found in the brains of AD patients display extensive N-terminus truncations/modifications.

Participation of kinin receptors on memory impairment after chronic infusion of human amyloid-beta 1-40 peptide in mice.

Chronic infusion of human amyloid-beta 1-40 (Abeta) in the lateral ventricle (LV) of rats is associated with memory impairment and increase of kinin receptors in cortical and hippocampal areas. Deletion of kinin B1 or B2 receptors abolished memory impairment caused by an acute single injection of Abeta in the LV. As brain tissue and kinin receptors could unlikely react to acute or chronic administration of a similar quantity of Abeta, we evaluated the participation of B1 or B2 receptors in memory impairment after chronic infusion of Abeta. Male C57Bl/6J (wt), knock-out B1 (koB1) or B2 (koB2) mice (12weeks of age) previously trained in a two-way shuttle-box and achieving conditioned avoidance responses (CAR, % of 50 trials) were infused with AB (550pmol, 0.12microL/h, 28days) or vehicle in the LV using a mini-osmotic pump. They were tested before the surgery (T0), 7 and 35days after the infusion started (T7; T35). In T0, no difference was observed between CAR of the control (Cwt=59.7+/-6.7%; CkoB1=46.7+/-4.0%; CkoB2=64.4+/-5.8%) and Abeta (Abetawt=66.0+/-3.0%; AbetakoB1=66.8+/-8.2%; AbetakoB2=58.7+/-5.9%) groups. In T7, AbetakoB2 showed a significant decrease in CAR (41.0+/-8.6%) compared to the control-koB2 (72.8+/-2.2%, P<0.05). In T35, a significant decrease (P<0.05) was observed in Abetawt (40.7+/-3.3%) and AbetakoB2 (41.2+/-10.7%) but not in the AbetakoB1 (64.0+/-14.0%) compared to their control groups. No changes were observed in the controls at T35. We suggest that in chronic infusion of BA, B1 receptors could play an important role in the neurodegenerative process. Conversely, the premature memory impairment of koB2 suggests that it may be a protective factor.