Purine-related metabolites and their converting enzymes are altered in frontal; parietal; and temporal cortex at early stages of Alzheimer's disease pathology

Adenosine, hypoxanthine, xanthine, guanosine, and inosine levels were assessed by HPLC, and the activity of related enzymes 5'-nucleotidase (5'-NT), adenosine deaminase (ADA), and purine nucleoside phosphorylase (PNP) measured in frontal (FC), parietal (PC) and temporal (TC) cortices at different stages of disease progression in Alzheimer's disease (AD) and in age-matched controls. Significantly decreased levels of adenosine, guanosine, hypoxanthine, and xanthine, and apparently less inosine, are found in FC from the early stages of AD; PC and TC show an opposing pattern, as adenosine, guanosine, and inosine are significantly increased at least at determinate stages of AD whereas hypoxanthine and xanthine levels remain unaltered. 5'-NT is reduced in membranes and cytosol in FC mainly at early stages but not in PC, and only at advanced stages in cytosol in TC. ADA activity is decreased in AD when considered as a whole but increased at early stages in TC. Finally, PNP activity is increased only in TC at early stages. Purine metabolism alterations occur at early stages of AD independently of neurofibrillary tangles and β-amyloid plaques. Alterations are stage- and regiondependent, the latter showing opposite patterns in FC compared with PC and TC. Adenosine is the most affected of the assessed purines. Key words: Adenosine, Alzheimer's disease, cerebral cortex, purine metabolism

Modulation of Signal Transduction Pathways in Senescence-Accelerated Mice P8 Strain: A Useful Tool for Alzheimer’s Disease Research

Senescence-accelerated mouse (SAM) lines serve as models of aging and age-associated diseases. The SAMP8 strain has a shortened life span and early-onset manifestations of senescence with characteristic pathological features observed in elderly humans, including deficits in learning and memory. In brains of SAMP8 mice, the processing of amyloid precursor protein (APP) is altered, resulting in excess production and accumulation of amyloid- peptide (A), tau is hyper-phosphorylated, and oxidative stress is increased. These phenotypic abnormalities are quite reminiscent of the findings in human brains with Alzheimer’s disease (AD). Mechanistically, metabolic pathways that are responsible for the generation of reactive oxygen species (ROS) are increased, while antioxidant systems are reduced in activity in the cerebral cortex of aged SAMP8 mice. Besides these structural and metabolic alterations, brains of aged SAMP8 mice exhibit neurochemical abnormalities such as altered signaling through G protein-coupled receptors for 5-hydroxytryptamine, acetylcholine, adenosine, dopamine, melatonin, glutamate and GABA, ion channel receptors, and nuclear hormone receptors (e.g. for all-trans-retinoic acid, cortisol or estradiol). Consequences include alterations in the levels of neurotransmitters, receptor numbers, receptor binding affinity, and second messengers. Of note is that in AD, G proteincoupled receptors and/or their corresponding signaling pathways are often impaired. Together, the observations in aged SAMP8 mouse brains provide convincing evidence that this model serves as an excellent research tool for studying AD pathogenesis and strategies for treatment. Additionally, many of the pathological and neurochemical abnormalities in SAMP8 mice are linked to altered expression of genes that are integrally related to processes such as neuroprotection, signal transduction, protein folding/degradation, intracellular transport and immune response. Several studies have already utilized pharmacological or dietary measures to restore cognitive function and enhance neuroprotection in aged SAMP8 mice, suggesting that these approaches may have applications in the treatment of AD. This review compiles available data concerning the signaling pathways that are altered in SAMP8 mice, and compares the effects to known abnormalities in AD brains

Epigenetic Modulation of Adenosine A2A Receptor: A Putative Therapeutical Tool for the Treatment of Parkinson’s Disease

Adenosine is a nucleoside distributed throughout the entire organism as an intermediary metabolite. At the extracellular level, adenosine plays multiple physiologic roles, interacting with specific receptors: A1, A2A, A2B and A3 (Fredholm et al., 2001). While the A1Rs and A3Rs are coupled in an inhibitory way to adenylate cyclase through the Gi/o protein, the A2Rs are coupled in a stimulatory way to this enzymatic activity through Gs protein (Ralevic & Burnstock, 1998). Adenosine levels are increased after ischemia, hypoxia, excitotoxicity, inflammation and cerebral lesions. In these situations, it is considered that high adenosine levels play a neuroprotective role (Ribeiro et al., 2002). Interestingly, adenosine regulates the release of glutamate, the main excitatory neurotransmitter of the nervous system (Sebastiao & Ribeiro, 1996). A1Rs are widely expressed in the brain and have been shown to modulate neuronal excitability by decreasing pre-synaptic release of various neurotransmitters (Fredholm & Dunwiddie, 1988). The most dramatic inhibitory actions are on the glutamatergic system (Masino et al., 2002). In the central nervous system (CNS), A1Rs are associated with neuroprotective processes (Angulo et al., 2003; Dunwiddie and Masino, 2001). Moreover, they are upregulated in human neurodegenerative diseases with abnormal protein aggregates and it is related to compensatory mechanisms (Albasanz et al., 2007, 2008; Angulo et al., 2003; Perez-Buira et al., 2007; Rodríguez et al., 2006). Regarding A2ARs, these receptors are concentrated in the striatum, modulating dopaminergic activity, but they are also present in the hippocampus and cerebral cortex, modulating the glutamate release in the brain. Adenosine activity through A2 receptors (A2ARs) can eventually give rise to neurotoxicity, neuronal damage and cellular death (de Mendoça et al., 2000). In fact, A2ARs activity is associated with the outcome of cerebral injury as well as the development of Abeta- induced synaptotoxicity (Canas et al., 2009; Cunha, 2005; Stone et al., 2009)

Adenosine Metabolism in the Cerebral Cortex from Several Mice Models during Aging

Adenosine is a neuromodulator that has been involved in aging and neurodegenerative diseases as Alzheimer's disease (AD). In the present work, we analyzed the possible modulation of purine metabolites, 5'nucleotidase (5′NT) and adenosine deaminase (ADA) activities, and adenosine monophosphate (AMP)-activated protein kinase (AMPK) and its phosphorylated form during aging in the cerebral cortex. Three murine models were used: senescence-accelerated mouse-resistant 1 (SAMR1, normal senescence), senescence-accelerated mouse-prone 8 (SAMP8, a model of AD), and the wild-type C57BL/6J (model of aging) mice strains. Glutamate and excitatory amino acid transporter 2 (EAAT2) levels were also measured in these animals. HPLC, Western blotting, and enzymatic activity evaluation were performed to this aim. 5′-Nucleotidase (5′NT) activity was decreased at six months and recovered at 12 months in SAMP8 while opposite effects were observed in SAMR1 at the same age, and no changes in C57BL/6J mice. ADA activity significantly decreased from 3 to 12 months in the SAMR1 mice strain, while a significant decrease from 6 to 12 months was observed in the SAMP8 mice strain. Regarding purine metabolites, xanthine and guanosine levels were increased at six months in SAMR1 without significant differences in SAMP8 mice. In C57BL/6J mice, inosine and xanthine were increased, while adenosine decreased, from 4 to 24 months. The AMPK level was decreased at six months in SAMP8 without significant changes nor in SAMR1 or C57BL/6J strains. Glutamate and EAAT2 levels were also modulated during aging. Our data show a different modulation of adenosine metabolism participants in the cerebral cortex of these animal models. Interestingly, the main differences between SAMR1 and SAMP8 mice were found at six months of age, SAMP8 being the most affected strain. As SAMP8 is an AD model, results suggest that adenosinergic metabolism is involved in the neurodegeneration of AD

Adenosine and Metabotropic Glutamate Receptors Are Present in Blood Serum and Exosomes from SAMP8 Mice: Modulation by Aging and Resveratrol

Adenosine (ARs) and metabotropic glutamate receptors (mGluRs) are G-protein coupled receptors (GPCRs) that are modulated in the brain of SAMP8 mice, an animal model of Alzheimer's disease (AD). In the present work, it is shown the presence of ARs and mGluRs in blood serum and derived exosomes from SAMP8 mice as well as its possible modulation by aging and resveratrol (RSV) consumption. In blood serum, adenosineA1 andA2A receptors remained unaltered from 5 to 7 months of age. However, an age-related decrease in adenosine level was observed, while 50-Nucleotidase activity was not modulated. Regarding the glutamatergic system, it was observed a decrease in mGluR5 density and glutamate levels in older mice. In addition, dietary RSV supplementation caused an age-dependent modulation in both adenosinergic and glutamatergic systems. These GPCRs were also found in blood serum-derived exosomes, which might suggest that these receptors could be released into circulation via exosomes. Interestingly, changes elicited by age and RSV supplementation on mGluR5 density, and adenosine and glutamate levels were similar to that detected in whole-brain. Therefore, we might suggest that the quantification of these receptors, and their corresponding endogenous ligands, in blood serum could have predictive value for early diagnosis in combination with other distinctive hallmarks of AD

Adenosine Metabolism in the Cerebral Cortex from Several Mice Models during Aging

Adenosine is a neuromodulator that has been involved in aging and neurodegenerative diseases as Alzheimer’s disease (AD). In the present work, we analyzed the possible modulation of purine metabolites, 5’nucleotidase (50NT) and adenosine deaminase (ADA) activities, and adenosine monophosphate (AMP)-activated protein kinase (AMPK) and its phosphorylated form during aging in the cerebral cortex. Three murine models were used: senescence-accelerated mouse-resistant 1 (SAMR1, normal senescence), senescence-accelerated mouse-prone 8 (SAMP8, a model of AD), and the wild-type C57BL/6J (model of aging) mice strains. Glutamate and excitatory amino acid transporter 2 (EAAT2) levels were also measured in these animals. HPLC, Western blotting, and enzymatic activity evaluation were performed to this aim. 50 -Nucleotidase (50NT) activity was decreased at six months and recovered at 12 months in SAMP8 while opposite effects were observed in SAMR1 at the same age, and no changes in C57BL/6J mice. ADA activity significantly decreased from 3 to 12 months in the SAMR1 mice strain, while a significant decrease from 6 to 12 months was observed in the SAMP8 mice strain. Regarding purine metabolites, xanthine and guanosine levels were increased at six months in SAMR1 without significant differences in SAMP8 mice. In C57BL/6J mice, inosine and xanthine were increased, while adenosine decreased, from 4 to 24 months. The AMPK level was decreased at six months in SAMP8 without significant changes nor in SAMR1 or C57BL/6J strains. Glutamate and EAAT2 levels were also modulated during aging. Our data show a different modulation of adenosine metabolism participants in the cerebral cortex of these animal models. Interestingly, the main differences between SAMR1 and SAMP8 mice were found at six months of age, SAMP8 being the most affected strain. As SAMP8 is an AD model, results suggest that adenosinergic metabolism is involved in the neurodegeneration of AD

High-Fat and Resveratrol Supplemented Diets Modulate Adenosine Receptors in the Cerebral Cortex of C57BL/6J and SAMP8 Mice

Neurodegenerative disorders are devastating diseases in which aging is a major risk factor. High-fat diet (HFD) seems to contribute to cognition deterioration, but the underlying mechanisms are poorly understood. Moreover, resveratrol (RSV) has been reported to counteract the loss of cognition associated with age. Our study aimed to investigate whether the adenosinergic system and plasma membrane cholesterol are modulated by HFD and RSV in the cerebral cortex of C57BL/6J and SAMP8 mice. Results show that HFD induced increased A1R and A2AR densities in C57BL/6J, whereas this remained unchanged in SAMP8. Higher activity of 50 -Nucleotidase was found as a common effect induced by HFD in both mice strains. Furthermore, the effect of HFD and RSV on A2BR density was different depending on the mouse strain. RSV did not clearly counteract the HFD-induced effects on the adenosinergic system. Besides, no changes in free-cholesterol levels were detected in the plasma membrane of cerebral cortex in both strains. Taken together, our data suggest a different modulation of adenosine receptors depending on the mouse strain, not related to changes in plasma membrane cholesterol conten

Habla popular nicaragüense empleada en la convivencia familiar por pobladores del sector Santa Elisa, Comunidad Ducuale Grande, municipio de Condega, departamento de Estelí, durante el I Semestre 2019.

Este artículo resume los resultados de la investigación Habla popular nicaragüense empleada en la convivencia familiar, estudio realizado en el sector Santa Elisa de la comunidad Ducuale Grande, con el objetivo de determinar el habla popular nicaragüense empleada en la convivencia familiar por pobladores del sector Santa Elisa de la comunidad Ducuale Grande del municipio de Condega, departamento de Estelí, durante el primer semestre 2019. Como resultado de este estudio se identificó, clasificó semánticamente y se dispuso de un glosario con los términos y expresiones propias utilizadas por los pobladores del sector investigado. Las bases teóricas de esta investigación la conforman un vasto estudio bibliográfico sobre el habla popular nicaragüense, el cual contribuyó a afianzar los conocimientos léxicos y semánticos de nuestro código

Antitumoral Action of Resveratrol Through Adenosinergic Signaling in C6 Glioma Cells

Gliomas are the most common and aggressive primary tumors in the central nervous system. The nucleoside adenosine is considered to be one major constituent within the tumor microenvironment. The adenosine level mainly depends on two enzymatic activities: 5′-nucleotidase (5′NT or CD73) that synthesizes adenosine from AMP, and adenosine deaminase (ADA) that converts adenosine into inosine. Adenosine activates specific G-protein coupled receptors named A1, A2A, A2B, and A3 receptors. Resveratrol, a natural polyphenol present in grapes, peanuts, and berries, shows several healthy effects, including protection against cardiovascular, endocrine, and neurodegenerative diseases and cancer. However, the molecular mechanisms of resveratrol actions are not well known. Recently, we demonstrated that resveratrol acts as an agonist for adenosine receptors in rat C6 glioma cells. The present work aimed to investigate the involvement of adenosine metabolism and adenosine receptors in the molecular mechanisms underlying the antitumoral action of resveratrol. Results presented herein show that resveratrol was able to decrease cell numbers and viability and to reduce CD73 and ADA activities, leading to the increase of extracellular adenosine levels. Some resveratrol effects were reduced by the blockade of A1 or A3 receptors by DPCPX or MRS1220, respectively. These results suggest that reduced CD73 activity located in the plasma membrane in addition to a fine-tuned modulatory role of adenosine receptors could be involved, at least in part, in the antiproliferative action of resveratrol in C6 glioma cells

A genomics approach identifies selective effects of trans-resveratrol in cerebral cortex neuron and glia gene expression

The mode of action of trans-resveratrol, a promising lead compound for the development of neuroprotective drugs, is unknown. Data from a functional genomics study were retrieved with the aim to find differentially expressed genes that may be involved in the benefits provided by trans-resveratrol. Genes that showed a significantly different expression (p<0.05, cut-off of a two-fold change) in mice fed with a control diet or a control diet containing trans-resveratrol were different in cortex, heart and skeletal muscle. In neocortex, we identified 4 up-regulated (Strap, Pkp4, Rab2a, Cpne3) and 22 down-regulated (Actn1, Arf3, Atp6v01, Atp1a3, Atp1b2, Cacng7, Crtc1, Dbn1, Dnm1, Epn1, Gfap, Hap, Mark41, Rab5b, Nrxn2, Ogt, Palm, Ptprn2, Ptprs, Syn2, Timp2, Vamp2) genes upon trans-resveratrol consumption. Network analysis of gene products provided evidence of plakophilin 4 up-regulation as a triggering factor for down-regulation of events related to synaptic vesicle transport and neurotransmitter release via underexpression of dynamin1 and Vamp2 (synaptobrevin 2) as node-gene drivers. Analysis by RT-qPCR of some of the selected genes in a glioma cell line showed that dynamin 1 mRNA was down-regulated even in acute trans-resveratrol treatments. Taken all together, these results give insight on the glial-neuronal networks involved in the neuroprotective role of trans-resveratrol