Jaume del Valle

Dietary resveratrol prevents Alzheimer’s markers and increases life span in SAMP8

Resveratrol is a polyphenol that is mainly found in grapes and red wine and has been reported to be a caloric restriction (CR) mimetic driven by Sirtuin 1 (SIRT1) activation. Resveratrol increases metabolic rate, insulin sensitivity, mitochondrial biogenesis and physical endurance, and reduces fat accumulation in mice. In addition, resveratrol may be a powerful agent to prevent age-associated neurodegeneration and to improve cognitive deficits in Alzheimer’s disease (AD). Moreover, different findings support the view that longevity in mice could be promoted by CR. In this study, we examined the role of dietary resveratrol in SAMP8 mice, a model of age-related AD. We found that resveratrol supplements increased mean life expectancy and maximal life span in SAMP8 and in their control, the related strain SAMR1. In addition, we examined the resveratrol-mediated neuroprotective effects on several specific hallmarks of AD. We found that long-term dietary resveratrol activates AMPK pathways and pro-survival routes such as SIRT1 in vivo. It also reduces cognitive impairment and has a neuroprotective role, decreasing the amyloid burden and reducing tau hyperphosphorylation.

Early Amyloid Accumulation in the Hippocampus of SAMP8 Mice

Late-onset Alzheimers disease (AD) is the most common form of AD appearing after 65 years of age. To date, however, there are no non-genetically manipulated rodent models that develop a similar sporadic onset of AD with age-related amyloid-beta (Abeta) deposition. Although the senescence accelerated mouse prone 8 (SAMP8) mice have been proposed as a model of AD, the presence of Abeta deposits remains controversial. In this study, we describe the time course of Abeta deposition in SAMP8 mice as well as in control SAMR1 and ICR-CD1 strains of mice. From as early as 6 months onward, SAMP8 mice show Abeta deposition in the hippocampus that increase in number and extent with age. These deposits are comprised of by clustered granules that contain Abeta{42}, Abeta{40}, and other Abeta protein precursor fragments. By marked contrast, control mice show only low numbers of Abeta clusters that do not develop until 15 months of age. The demonstration that SAMP8 mice present with amyloid deposits in their hippocampus makes this animal model a useful tool to understand the mechanisms involved in Abeta deposition in AD.

Increased permeability of blood–brain barrier on the hippocampus of a murine model of senescence

SAMP8 mice show several indicative characteristics of accelerated aging and have been used to study the physiological and physiopathological processes that take place during senescence. There is some controversy about the presence of a functional blood-brain barrier (BBB) disturbance on these animals, which could be related to the oxidative stress or the amyloidosis present in their brain. In order to elucidate BBB status in the hippocampus of SAMP8 mice, in this study we have determined the extravasation from brain microvessels of endogenous IgG in SAMP8 mice aged 3, 7 and 12 months and in age-matched control SAMR1 mice. Immunohistochemistry, confocal microscopy and an imaging methodology specially designed to quantify IgG extravasation have been used. The choroid plexus was analyzed as a control for positive extravasation in SAMP8 and SAMR1 mice and, as expected, in all studied ages high IgG immunoreactivity was observed in both strains. We have found significantly higher levels of IgG extravasation in the hippocampus of 12-month-old SAMP8 mice compared to SAMR1 mice, indicating an increased permeability of BBB in aged senescence-accelerated mice.

Cell cycle activation in striatal neurons from Huntington's disease patients and rats treated with 3-nitropropionic acid.

This study was undertaken to investigate the potential role of cell cycle re‐entry in an experimental model of Huntingtons disease and in human brain samples. We found that after treatment of rats with the mitochondrial neurotoxin 3‐nitropropionic acid, the expression of cell cycle markers of G1 phase measured by immunohistochemistry was induced in the striatal brain region. Furthermore, we detected an increase in the nuclear and also cytoplasmatic E2F‐1 expression, suggesting that this protein could activate the apoptotic cascade in rat brain. Western blot analysis of post‐mortem brain samples from patients also showed an increase in the expression of E2F‐1 and cyclin D1 in comparison with control samples. These results indicate that cell cycle re‐entry is activated in Huntingtons disease and may contribute to the neurodegenerative process.

Neuroprotective role of trans-resveratrol in a murine model of familial Alzheimer's disease

The amyloid-β protein precursor/presenilin 1 (AβPP/PS1) mouse model of Alzheimers disease (AD) has provided robust neuropathological hallmarks of familial AD-like pattern. AD is a neurodegenerative process that causes severe cognitive impairment; it is characterized by the accumulation of amyloid-β (Aβ) and hyperphosphorylated tau forms and by oxidative and inflammatory processes in brain. Currently, efforts are made to understand biochemical pathways because there is no effective therapy for AD. Resveratrol is a polyphenol that induces expression and activation of several neuroprotective pathways involving Sirtuin1 and AMPK. The objective of this work was to assess the effect of oral resveratrol administration on AβPP/PS1 mice. Long-term resveratrol treatment significantly prevented memory loss as measured by the object recognition test. Moreover, resveratrol reduced the amyloid burden and increased mitochondrial complex IV protein levels in mouse brain. These protective effects of resveratrol were mainly mediated by increased activation of Sirtuin 1 and AMPK pathways in mice. However, an increase has been observed in IL1β and TNF gene expression, indicating that resveratrol promoted changes in inflammatory processes, although no changes were detected in other key actors of the oxidative stress pathway. Taken together, our findings suggest that resveratrol is able to reduce the harmful process that occurs in AβPP/PS1 mouse hippocampus, preventing memory loss.

A new method for determining blood–brain barrier integrity based on intracardiac perfusion of an Evans Blue–Hoechst cocktail

A new method for determining brain regions with blood-brain barrier (BBB) alterations is described. In this method, mice were perfused intracardially with Evans Blue (EB) and Hoechst tracers added in a standard formaldehyde fixative solution. This cocktail method was tested after a localized cryolesion induced in the brain had produced an edematous brain region with disrupted BBB in the animals. The results were then compared with the intravenous and intraperitoneal administration of the tracers prior to intracardiac perfusion. When using the cocktail method, red EB fluorescence locates the cryoinjured brain region while the Hoechst tracer stains the nuclei in that same region. EB and Hoechst fluorescence can also be observed in the choroid plexus and circumventricular organs, where there is no functional BBB. The cocktail gives more intense EB staining in zones of disrupted BBB than that given by traditional methods which use this tracer. The Hoechst tracer is also more useful when administered in the cocktail, since when administrated intravenously it stains all the brain nuclei. The cocktail method permits the immunostaining of brain sections, enabling researchers to characterize and analyze structural and cellular changes in regions where BBB disturbances are present. Thus, immunohistochemistry has been used here to determine the nature of intense EB fluorescent cells that appear in the perilesional rim, which were identified here as neuronal cells.

Dendritic Spine Abnormalities in Hippocampal CA1 Pyramidal Neurons Underlying Memory Deficits in the SAMP8 Mouse Model of Alzheimer's Disease

SAMP8 is a strain of mice with accelerated senescence. These mice have recently been the focus of attention as they show several alterations that have also been described in Alzheimers disease (AD) patients. The number of dendritic spines, spine plasticity, and morphology are basic to memory formation. In AD, the density of dendritic spines is severely decreased. We studied memory alterations using the object recognition test. We measured levels of synaptophysin as a marker of neurotransmission and used Golgi staining to quantify and characterize the number and morphology of dendritic spines in SAMP8 mice and in SAMR1 as control animals. While there were no memory differences at 3 months of age, the memory of both 6- and 9-month-old SAMP8 mice was impaired in comparison with age-matched SAMR1 mice or young SAMP8 mice. In addition, synaptophysin levels were not altered in young SAMP8 animals, but SAMP8 aged 6 and 9 months had less synaptophysin than SAMR1 controls and also less than 3-month-old SAMP8 mice. Moreover, while spine density remained stable with age in SAMR1 mice, the number of spines started to decrease in SAMP8 animals at 6 months, only to get worse at 9 months. Our results show that from 6 months onwards SAMP8 mice show impaired memory. This age coincides with that at which the levels of synaptophysin and spine density decrease. Thus, we conclude that together with other studies that describe several alterations at similar ages, SAMP8 mice are a very suitable model for studying AD.

Cerebral Amyloid Angiopathy, Blood-Brain Barrier Disruption and Amyloid Accumulation in SAMP8 Mice

Cerebrovascular dysfunction and β-amyloid peptide deposition on the walls of cerebral blood vessels might be an early event in the development of Alzheimer’s disease. Here we studied the time course of amyloid deposition in blood vessels and blood-brain barrier (BBB) disruption in the CA1 subzone of the hippocampus of SAMP8 mice and the association between these two variables. We also studied the association between the amyloid deposition in blood vessels and the recently described amyloid clusters in the parenchyma, as well as the association of these clusters with vessels in which the BBB is disrupted. SAMP8 mice showed greater amyloid deposition in blood vessels than age-matched ICR-CD1 control mice. Moreover, at 12 months of age the number of vessels with a disrupted BBB had increased in both strains, especially SAMP8 animals. At this age, all the vessels with amyloid deposition showed BBB disruption, but several capillaries with an altered BBB showed no amyloid on their walls. Moreover, amyloid clusters showed no spatial association with vessels with amyloid deposition, nor with vessels in which the BBB had been disrupted. Finally, we can conclude that vascular amyloid deposition seems to induce BBB alterations, but BBB disruption may also be due to other factors.

Characterization of Amyloid-β Granules in the Hippocampus of SAMP8 Mice

The senescence accelerated mouse-prone 8 (SAMP8) strain of mice is an experimental model of accelerated senescence that has also been proposed as a model of Alzheimers disease as it shares several features with this dementia. We have recently reported amyloid-β (Aβ) granules in the hippocampus of SAMP8 mice, which contain Aβ42 and Aβ40 peptides and other amyloid-β protein precursor fragments. These granules appear clustered mainly in the stratum radiatum of the CA1 region and increase in number and size with age. Here we performed several studies to examine whether the Aβ granules in the hippocampus of SAMP8 mice contain other proteins characteristic of neuropathological aggregates, such as tau, MAP2, and α-synuclein. Moreover, we examined whether the Aβ granules in the hippocampus correspond to heparan sulphate proteoglycan (HSPG) positive granules previously described in this animal model. The results showed that Aβ granules correspond to the HSPG granular structures, being syndecan-2, a protein involved in the remodeling of dendritic spines, the type of HSPG found. Tau and MAP2, but not α-synuclein depositions, were also found in Aβ aggregates. Granules do not appear to have an astrocytic origin, since although some Aβ clusters are associated with astrocyte processes, most clusters are not. On the other hand, the presence of tau, MAP2, and NeuN in Aβ granules suggests a neuronal origin. As the components identified in Aβ granules are characteristic of the aggregates present in some neurodegenerative diseases, the SAMP8 model seems to be appropriate for the study of the processes involved in these pathologies.

Interfaces with the peripheral nerve for the control of neuroprostheses.

Nervous system injuries lead to loss of control of sensory, motor, and autonomic functions of the affected areas of the body. Provided the high amount of people worldwide suffering from these injuries and the impact on their everyday life, numerous and different neuroprostheses and hybrid bionic systems have been developed to restore or partially mimic the lost functions. A key point for usable neuroprostheses is the electrode that interfaces the nervous system and translates not only motor orders into electrical outputs that activate the prosthesis but is also able to transform sensory information detected by the machine into signals that are transmitted to the central nervous system. Nerve electrodes have been classified with regard to their invasiveness in extraneural, intraneural, and regenerative. The more invasive is the implant the more selectivity of interfacing can be reached. However, boosting invasiveness and selectivity may also heighten nerve damage. This chapter provides a general overview of nerve electrodes as well as the state-of-the-art of their biomedical applications in neuroprosthetic systems.