Tania Araujo Viel

Microdose Lithium Treatment Stabilized Cognitive Impairment in Patients with Alzheimer’s Disease

A lower incidence of dementia in bipolar patients treated with lithium has been described. This metal inhibits the phosphorylation of glycogen-synthase-kinase 3-α and β, which are related to amyloid precursor protein processing and tau hyperphosphorylation in pathological conditions, respectively. Following the same rationale, a group just found that lithium has disease-modifying properties in amnestic mild cognitive impairment with potential clinical implications for the prevention of Alzheimers Disease (AD) when a dose ranging from 150 to 600 mg is used. As lithium is highly toxic in regular doses, our group evaluated the effect of a microdose of 300 μg, administered once daily on AD patients for 15 months. In the evaluation phase, the treated group showed no decreased performance in the mini-mental state examination test, in opposition to the lower scores observed for the control group during the treatment, with significant differences starting three months after the beginning of the treatment, and increasing progressively. This data suggests the efficacy of a microdose lithium treatment in preventing cognitive loss, reinforcing its therapeutic potential to treat AD using very low doses.

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 Alzheimers 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 Alzheimers disease in vivo.

Altered KLOTHO and NF-κB-TNF-α Signaling Are Correlated with Nephrectomy-Induced Cognitive Impairment in Rats

Renal insufficiency can have a negative impact on cognitive function. Neuroinflammation and changes in klotho levels associate with chronic kidney disease (CKD) and may play a role in the development of cognitive impairment (CI). The present study evaluates the correlation of cognitive deficits with neuroinflammation and soluble KLOTHO in the cerebral spinal fluid (CSF) and brain tissue of nephrectomized rats (Nx), with 5/6 renal mass ablation. Nx and sham Munich Wistar rats were tested over 4 months for locomotor activity, as well as inhibitory avoidance or novel object recognition, which started 30 days after the surgery. EMSA for Nuclear factor-κB and MILLIPLEXMAP or ELISA kit were used to evaluate cytokines, glucocorticoid and KLOTHO levels. Nx animals that showed a loss in aversive-related memory and attention were included in the CI group (Nx-CI) (n=14) and compared to animals with intact learning (Nx-M n=12 and Sham n=20 groups). CSF and tissue samples were collected 24 hours after the last behavioral test. The results show that the Nx-groups have increased NF-κB binding activity and tumor necrosis factor-alpha (TNF-α) levels in the hippocampus and frontal cortex, with these changes more pronounced in the Nx-CI group frontal cortex. In addition, the Nx-CI group showed significantly increased CSF glucocorticoid levels and TNF-α /IL-10 ratio compared to the Sham group. Klotho levels were decreased in Nx-CI frontal cortex but not in hippocampus, when compared to Nx-M and Sham groups. Overall, these results suggest that neuroinflammation mediated by frontal cortex NF-κB, TNF-α and KLOTHO signaling may contribute to Nx-induced CI in rats.

Participation of kinin receptors on memory impairment after chronic infusion of human amyloid-β 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.

Chronic Microdose Lithium Treatment Prevented Memory Loss and Neurohistopathological Changes in a Transgenic Mouse Model of Alzheimer's Disease

The use of lithium is well established in bipolar disorders and the benefits are being demonstrated in neurodegenerative disorders. Recently, our group showed that treatment with microdose lithium stabilized the cognitive deficits observed in Alzheimer’s disease (AD) patients. In order to verify the lithium microdose potential in preventing the disease development, the aim of this work was to verify the effects of chronic treatment with microdose lithium given before and after the appearance of symptoms in a mouse model of a disease similar to AD. Transgenic mice (Cg-Tg(PDGFB-APPSwInd)20Lms/2J) and their non-transgenic litter mate genetic controls were treated with lithium carbonate (1.2 mg/Kg/day in drinking water) for 16 or 8 months starting at two and ten months of age, respectively. Similar groups were treated with water. At the end of treatments, both lithium treated transgenic groups and non-transgenic mice showed no memory disruption, different from what was observed in the water treated transgenic group. Transgenic mice treated with lithium since two months of age showed decreased number of senile plaques, no neuronal loss in cortex and hippocampus and increased BDNF density in cortex, when compared to non-treated transgenic mice. It is suitable to conclude that these data support the use of microdose lithium in the prevention and treatment of Alzheimer’s disease, once the neurohistopathological characteristics of the disease were modified and the memory of transgenic animals was maintained.

Cognitive stimulation during lifetime and in the aged phase improved spatial memory, and altered neuroplasticity and cholinergic markers of mice.

In the central nervous system, the degree of decline in memory retrieval along the aging process depends on the quantity and quality of the stimuli received during lifetime. The cholinergic system modulates long-term potentiation and, therefore, memory processing. This study evaluated the spatial memory, the synaptic plasticity and the density of cholinergic markers in the hippocampi of mice submitted to cognitive stimulation during lifetime or during their aged phase. Male C57Bl/6 mice (2 months old) were exposed to enriched environment during 15 months (EE-15). An age-matched group was left in standard cages during the same period (SC-15). Spatial memory was evaluated using the Barnes maze at 2, 5, 11 and 17 months of age. At the 17-month-old time point, EE-15 mice showed better performance in the spatial memory task (P<0.05), when compared to C-15 mice. Other two groups of mice were left in regular cages until the age of 15 months, and then one of the groups was transferred to an enriched environment for two months (EE-2). The other group was kept in regular cages (C-2). After two months of stimulation, EE-2 showed a significant increase in spatial memory (P<0.01). At the end, brains were extracted and kept at -80°C. Slices were obtained from one hemisphere in a cryostat (20 μm, -18°C) and thaw-mounted on gelatin coated slides. Synaptic densities, cellular bodies, BDNF densities and α4β2 nicotinic cholinergic receptors (nAChR) were evaluated by immunohistochemistry. Autoradiography for α7 nAChR was conducted using [(125)I]-α-bungarotoxin. The other half of the brains was used for Western blotting analysis of choline acetyltransferase (ChAT) density. There was no difference in synaptophysin or MAP-2 densities, but BDNF was increased in some hippocampal areas of EE-15 and EE-2, in comparison to control groups. In the same way, increases in ChAT and α7 densities, but not in α4β2, were observed. Both cognitive stimuli during lifetime or during the aged phase improved spatial memory of mice. No difference in structural plasticity was observed, but the maintenance of memory can be due to improvement in long-term potentiation functionality in the hippocampus, modulated, at least, by BDNF and the cholinergic system.

Role of kinin B1 and B2 receptors in memory consolidation during the aging process of mice

Under physiological conditions, elderly people present memory deficit associated with neuronal loss. This pattern is also associated with Alzheimers disease but, in this case, in a dramatically intensified level. Kinin receptors have been involved in neurodegeneration and increase of amyloid-beta concentration, associated with Alzheimers disease (AD). Considering these findings, this work evaluated the role of kinin receptors in memory consolidation during the aging process. Male C57Bl/6 (wt), knock-out B1 (koB1) or B2 (koB2) mice (3, 6, 12 and 18-month-old - mo; n=10 per group) were submitted to an acquisition session, reinforcement to learning (24h later: test 1) and final test (7days later: test 2), in an active avoidance apparatus, to evaluate memory. Conditioned avoidance responses (CAR, % of 50 trials) were registered. In acquisition sessions, similar CAR were obtained among age matched animals from all strains. However, a significant decrease in CAR was observed throughout the aging process (3mo: 8.8+/-2.3%; 6mo: 4.1+/-0.6%; 12mo: 2.2+/-0.6%, 18mo: 3.6+/-0.6%, P<0.01), indicating a reduction in the learning process. In test 1, as expected, memory retention increased significantly (P<0.05) in all 3- and 6-month-old animals as well as in 12-month-old-wt and 12-month-old-koB1 (P<0.01), compared to the training session. However, 12-month-old-koB2 and all 18-month-old animals did not show an increase in memory retention. In test 2, 3- and 6-month-old wt and koB1 mice of all ages showed a significant improvement in memory (P<0.05) compared to test 1. However, 12-month-old wt and koB2 mice of all ages showed no difference in memory retention. We suggest that, during the aging process, the B1 receptor could be involved in neurodegeneration and memory loss. Nevertheless, the B2 receptor is apparently acting as a neuroprotective factor.

Neuroprotective Effects of Pomegranate Peel Extract after Chronic Infusion with Amyloid-β Peptide in Mice

Alzheimer’s disease is a chronic and degenerative condition that had no treatment until recently. The current therapeutic strategies reduce progression of the disease but are expensive and commonly cause side effects that are uncomfortable for treated patients. Functional foods to prevent and/or treat many conditions, including neurodegenerative diseases, represent a promising field of study currently gaining attention. To this end, here we demonstrate the effects of pomegranate (Punica granatum) peel extract (PPE) regarding spatial memory, biomarkers of neuroplasticity, oxidative stress and inflammation in a mouse model of neurodegeneration. Male C57Bl/6 mice were chronically infused for 35 days with amyloid-β peptide 1–42 (Aβ) or vehicle (control) using mini-osmotic pumps. Another group, also infused with Aβ, was treated with PPE (p.o.– βA+PPE, 800 mg/kg/day). Spatial memory was evaluated in the Barnes maze. Animals treated with PPE and in the control group exhibited a reduction in failure to find the escape box, a finding that was not observed in the Aβ group. The consumption of PPE reduced amyloid plaque density, increased the expression of neurotrophin BDNF and reduced the activity of acetylcholinesterase enzyme. A reduction in lipid peroxidation and in the concentration of the pro-inflammatory cytokine TNF-α was also observed in the PPE group. No hepatic lesions were observed in animals treated with PPE. In conclusion, administration of pomegranate peel extract has neuroprotective effects involving multiple mechanisms to prevent establishment and progression of the neurodegenerative process induced by infusion with amyloid-β peptide in mice.

Chronic Infusion of Amyloid-β Peptide and Sustained Attention Altered α7 Nicotinic Receptor Density in the Rat Brain

It is already known that progressive degeneration of cholinergic neurons in brain areas such as the hippocampus and the cortex leads to memory deficits, as observed in Alzheimers disease. This work verified the effects of the infusion of amyloid-β (Aβ) peptide associated to an attentional rehearsal on the density of α7 nicotinic cholinergic receptor (nAChR) in the brain of male Wistar rats. Animals received intracerebroventricular infusion of Aβ or vehicle (control - C) and their attention was stimulated weekly (Stimulated Aβ group: S-Aβ and Stimulated Control group: SC) or not (Non- Stimulated Aβ group: N-SAβ and Non-Stimulated Control group: N-SC), using an active avoidance apparatus. Conditioned avoidance responses (CAR) were registered. Chronic infusion of Aβ caused a 37% reduction in CAR for N-SAβ. In S-Aβ, this reduction was not observed. At the end, brains were extracted and autoradiography for α7 nAChR was conducted using [125I]-α-bungarotoxin. There was an increase in α7 density in hippocampus, cortex and amygdala of SAβ animals, together with the memory preservation. In recent findings from our lab using mice infused with Aβ and the α7 antagonist methyllycaconitine, and stimulated weekly in the same apparatus, it was observed that memory maintenance was abolished. So, the increase in α7 density in brain areas related to memory might be related to a participation of this receptor in the long-lasting change in synaptic plasticity, which is important to improve and maintain memory consolidation.

Kinin B2 receptor can play a neuroprotective role in Alzheimer's disease

Alzheimers disease (AD) is characterized by cognitive decline, presence of amyloid-beta peptide (Aβ) aggregates and neurofibrillary tangles. Kinins act through B1 and B2 G-protein coupled receptors (B1R and B2R). Chronic infusion of Aβ peptide leads to memory impairment and increases in densities of both kinin receptors in memory processing areas. Similar memory impairment was observed in C57BL/6 mice (WTAβ) but occurred earlier in mice lacking B2R (KOB2Aβ) and was absent in mice lacking B1R (KOB1Aβ). Thus, the aim of this study was to evaluate the participation of B1R and B2R in Aβ peptide induced cognitive deficits through the evaluation of densitiesof kinin receptors, synapses, cell bodies and number of Aβ deposits in brain ofWTAβ, KOB1Aβ and KOB2Aβ mice. An increase in B2R density was observed in both WTAβ and KOB1Aβ in memory processing related areas. KOB1Aβ showed a decrease in neuronal density and an increase in synaptic density and, in addition, an increase in Aβ deposits in KOB2Aβ was observed. In conclusion, memory preservation in KOB1Aβ, could be due to the increase in densities of B2R, suggesting a neuroprotective role for B2R, reinforced by the increased number of Aβ plaques in KOB2Aβ. Our data point to B2R as a potential therapeutic target in AD.