Showing papers on "Aging brain published in 2013"
TL;DR: Human postmortem results strengthen the notion that AD is associated with alterations in DNA methylation and hydroxymethylation, and provide a basis for further epigenetic studies identifying the exact genetic loci with aberrant epigenetic signatures.
351 citations
TL;DR: It is shown that C1q protein levels dramatically increase in the normal aging mouse and human brain, by as much as 300-fold, and this increase was predominantly localized in close proximity to synapses and occurred earliest and most dramatically in certain regions of the brain, including some but not all regions known to be selectively vulnerable in neurodegenerative diseases.
Abstract: The decline of cognitive function has emerged as one of the greatest health threats of old age. Age-related cognitive decline is caused by an impacted neuronal circuitry, yet the molecular mechanisms responsible are unknown. C1q, the initiating protein of the classical complement cascade and powerful effector of the peripheral immune response, mediates synapse elimination in the developing CNS. Here we show that C1q protein levels dramatically increase in the normal aging mouse and human brain, by as much as 300-fold. This increase was predominantly localized in close proximity to synapses and occurred earliest and most dramatically in certain regions of the brain, including some but not all regions known to be selectively vulnerable in neurodegenerative diseases, i.e., the hippocampus, substantia nigra, and piriform cortex. C1q-deficient mice exhibited enhanced synaptic plasticity in the adult and reorganization of the circuitry in the aging hippocampal dentate gyrus. Moreover, aged C1q-deficient mice exhibited significantly less cognitive and memory decline in certain hippocampus-dependent behavior tests compared with their wild-type littermates. Unlike in the developing CNS, the complement cascade effector C3 was only present at very low levels in the adult and aging brain. In addition, the aging-dependent effect of C1q on the hippocampal circuitry was independent of C3 and unaccompanied by detectable synapse loss, providing evidence for a novel, complement- and synapse elimination-independent role for C1q in CNS aging.
326 citations
TL;DR: It is demonstrated that Cu’s effect on brain Aβ homeostasis depends on whether it is accumulated in the capillaries or in the parenchyma, and these findings should provide unique insights into preventative and/or therapeutic approaches to control neurotoxic Aβ levels in the aging brain.
Abstract: Whereas amyloid-β (Aβ) accumulates in the brain of normal animals dosed with low levels of copper (Cu), the mechanism is not completely known. Cu could contribute to Aβ accumulation by altering its clearance and/or its production. Because Cu homeostasis is altered in transgenic mice overexpressing Aβ precursor protein (APP), the objective of this study was to elucidate the mechanism of Cu-induced Aβ accumulation in brains of normal mice and then to explore Cu’s effects in a mouse model of Alzheimer’s disease. In aging mice, accumulation of Cu in brain capillaries was associated with its reduction in low-density lipoprotein receptor-related protein 1 (LRP1), an Aβ transporter, and higher brain Aβ levels. These effects were reproduced by chronic dosing with low levels of Cu via drinking water without changes in Aβ synthesis or degradation. In human brain endothelial cells, Cu, at its normal labile levels, caused LRP1-specific down-regulation by inducing its nitrotyrosination and subsequent proteosomal-dependent degradation due in part to Cu/cellular prion protein/LRP1 interaction. In APPsw/0 mice, Cu not only down-regulated LRP1 in brain capillaries but also increased Aβ production and neuroinflammation because Cu accumulated in brain capillaries and, unlike in control mice, in the parenchyma. Thus, we have demonstrated that Cu’s effect on brain Aβ homeostasis depends on whether it is accumulated in the capillaries or in the parenchyma. These findings should provide unique insights into preventative and/or therapeutic approaches to control neurotoxic Aβ levels in the aging brain.
210 citations
TL;DR: There is remarkable consistency in the pattern of age‐related neural and cognitive change observed in healthy humans and other animals, including changes in cognitive operations that are known to be dependent on the hippocampus, as well as those requiring intact prefrontal cortical circuits.
Abstract: Brain networks that engage the hippocampus and prefrontal cortex are central for enabling effective interactions with our environment. Some of the cognitive processes that these structures mediate, such as encoding and retrieving episodic experience, wayfinding, working memory and attention are known to be altered across the lifespan. As illustrated by examples given below, there is remarkable consistency across species in the pattern of age-related neural and cognitive change observed in healthy humans and other animals. These include changes in cognitive operations that are known to be dependent on the hippocampus, as well as those requiring intact prefrontal cortical circuits. Certain cognitive constructs that reflect the function of these areas lend themselves to investigation across species, allowing brain mechanisms at different levels of analysis to be studied in greater depth.
153 citations
TL;DR: The findings suggest that aerobic exercise and cardiorespiratory fitness contribute to healthy brain aging, although additional studies in Alzheimer's disease are needed.
Abstract: The literature examining the relationship between cardiorespiratory fitness and the brain in older adults has increased rapidly, with 30 of 34 studies published since 2008. Here we review cross-sectional and exercise intervention studies in older adults examining the relationship between cardiorespiratory fitness and brain structure and function, typically assessed using Magnetic Resonance Imaging (MRI). Studies of patients with Alzheimer's disease are discussed when available. The structural MRI studies revealed a consistent positive relationship between cardiorespiratory fitness and brain volume in cortical regions including anterior cingulate, lateral prefrontal, and lateral parietal cortex. Support for a positive relationship between cardiorespiratory fitness and medial temporal lobe volume was less consistent, although evident when a region-of-interest approach was implemented. In fMRI studies, cardiorespiratory fitness in older adults was associated with activation in similar regions as those identified in the structural studies, including anterior cingulate, lateral prefrontal, and lateral parietal cortex, despite heterogeneity among the functional tasks implemented. This comprehensive review highlights the overlap in brain regions showing a positive relationship with cardiorespiratory fitness in both structural and functional imaging modalities. The findings suggest that aerobic exercise and cardiorespiratory fitness contribute to healthy brain aging, although additional studies in Alzheimer's disease are needed.
130 citations
TL;DR: VBI was more influential than Aβ in contemporaneous cognitive function and remained predictive after including the possible influence of Aβ, and the impact of cerebrovascular disease should be considered with respect to defining the etiology of mild cognitive impairment.
Abstract: Importance β-Amyloid (Aβ) deposition and vascular brain injury (VBI) frequently co-occur and are both associated with cognitive decline in aging. Determining whether a direct relationship exists between them has been challenging. We sought to understand VBI's influence on cognition and clinical impairment, separate from and in conjunction with pathologic changes associated with Alzheimer disease (AD). Objective To examine the relationship between neuroimaging measures of VBI and brain Aβ deposition and their associations with cognition. Design and Setting A cross-sectional study in a community- and clinic-based sample recruited for elevated vascular disease risk factors. Participants Clinically normal (mean age, 77.1 years [N = 30]), cognitively impaired (mean age, 78.0 years [N = 24]), and mildly demented (mean age, 79.8 years [N = 7]) participants. Interventions Magnetic resonance imaging, Aβ (Pittsburgh Compound B–positron emission tomographic [PiB-PET]) imaging, and cognitive testing. Main Outcome Measures Magnetic resonance images were rated for the presence and location of infarct (34 infarct-positive participants, 27 infarct-negative participants) and were used to quantify white matter lesion volume. The PiB-PET uptake ratios were used to create a PiB index by averaging uptake across regions vulnerable to early Aβ deposition; PiB positivity (29 PiB-positive participants, 32 PiB-negative participants) was determined from a data-derived threshold. Standardized composite cognitive measures included executive function and verbal and nonverbal memory. Results Vascular brain injury and Aβ were independent in both cognitively normal and impaired participants. Infarction, particularly in cortical and subcortical gray matter, was associated with lower cognitive performance in all domains (P Conclusions and Relevance In this elderly sample with normal cognition to mild dementia, enriched for vascular disease, VBI was more influential than Aβ in contemporaneous cognitive function and remained predictive after including the possible influence of Aβ. There was no evidence that VBI increases the likelihood of Aβ deposition. This finding highlights the importance of VBI in mild cognitive impairment and suggests that the impact of cerebrovascular disease should be considered with respect to defining the etiology of mild cognitive impairment.
129 citations
TL;DR: It is proposed that lifestyle factors are powerful instruments to promote healthy and successful aging of the brain and delay the appearance of age-related cognitive deficits in elderly people.
Abstract: Aging is a physiological process that can develop without the appearance of concurrent diseases. However, very frequently, older people suffer from memory loss and an accelerated cognitive decline. Studies of the neurobiology of aging are beginning to decipher the mechanisms underlying not only the physiology of aging of the brain but also the mechanisms that make people more vulnerable to cognitive dysfunction and neurodegenerative diseases. Today we know that the aging brain retains a considerable functional plasticity, and that this plasticity is positively promoted by genes activated by different lifestyle factors. In this article some of these lifestyle factors and their mechanisms of action are reviewed, including environmental enrichment and the importance of food intake and some nutrients. Aerobic physical exercise and reduction of chronic stress are also briefly reviewed. It is proposed that lifestyle factors are powerful instruments to promote healthy and successful aging of the brain and delay the appearance of age-related cognitive deficits in elderly people.
125 citations
TL;DR: Ventricular volume trajectory is more sensitive than total brain and hippocampal volume trajectories as a marker of accruing Alzheimer disease and vascular pathology in elderly individuals, and remains after controlling for the degree of neuropathology and other covariates.
Abstract: Importance While brain volume changes are used as surrogate markers for Alzheimer disease neuropathology in clinical studies, the extent to which these changes are due to pathologic features of Alzheimer disease in the aging brain is not well established. This study aims to clarify the neuropathologic correlates of longitudinal brain atrophy. Objective To examine the association between brain atrophy during life and neuropathology in an elderly population. Design Autopsy study of a cohort of elderly individuals. Setting Community-based population. Participants Seventy-one healthy elderly individuals were selected from participants of the Oregon Brain Aging Study for having an autopsy, more than 1 magnetic resonance imaging scan, and the last magnetic resonance imaging scan within 36 months of death. Main Outcomes and Measures The associations between brain volume trajectories (ventricular, total brain, and hippocampal) and time interaction terms for neurofibrillary tangles, neuritic plaques, gross infarcts, microinfarcts, amyloid angiopathy, Lewy bodies, APOE ϵ4 presence, and clinical diagnosis (no cognitive impairment, mild cognitive impairment, or dementia as time-varying covariates) were examined in mixed-effects models, adjusting for duration of follow-up and age at death. Results Ventricular volume trajectory was significantly associated with age, presence of infarcts, neurofibrillary tangle and neuritic plaque scores, APOE ϵ4 allele presence, and dementia diagnosis. Total brain volume trajectory was significantly associated with age and mild cognitive impairment diagnosis. Hippocampal volume trajectory was significantly associated with amyloid angiopathy. Conclusions and Relevance Ventricular volume trajectory is more sensitive than total brain and hippocampal volume trajectories as a marker of accruing Alzheimer disease and vascular pathology in elderly individuals. The association between brain volume trajectories and cognitive impairment (mild cognitive impairment and dementia) remained after controlling for the degree of neuropathology and other covariates. This suggests that there may be other factors not measured in this study that could be contributing to brain atrophy in those with cognitive impairment.
101 citations
TL;DR: The present findings may refine current theories of cognitive aging and suggest that older adults increasingly recruit the inhibitory network and, with increasing load, additional inhibitory regions.
101 citations
TL;DR: Two compounds with functional activity as potentiators of γ-aminobutyric acid at GABA(A) α5 receptors are used to test their ability to improve hippocampal-dependent memory in aged rats with identified cognitive impairment, suggesting a novel approach to improve neural network function in clinical conditions of excess hippocampal activity.
98 citations
TL;DR: Understanding of the resting state networks of the aging brain to include cortico-cerebellar networks is extended, and associations between connectivity strength and both sensorimotor and cognitive task performances indicate that age differences in network connectivity strength are important for behavior.
TL;DR: The goal of this study was to define the frequency and distribution of CAA in a 1‐year autopsy population from the Department of Internal Medicine, Rehabilitation, and Geriatrics, Geneva.
Abstract: AIMS: Cerebral amyloid angiopathy (CAA) represents the deposition of amyloid beta protein (Abeta) in the meningeal and intracerebral vessels. It is often observed as an accompanying lesion of Alzheimer's disease (AD) or in the brain of elderly individuals even in the absence of dementia. CAA is largely age-dependent. In subjects with severe CAA a higher frequency of vascular lesions has been reported. The goal of our study was to define the frequency and distribution of CAA in a one-year autopsy population (91 cases) from the Department of Internal Medicine, Rehabilitation, and Geriatrics, Geneva. MATERIALS AND METHODS: Five brain regions were examined, including the hippocampus, and the inferior temporal, frontal, parietal, and occipital cortex, using an antibody against Abeta, and simultaneously assessing the severity of AD-type pathology with Braak stages for neurofibrillary tangles identified with an anti-tau antibody. In parallel, the relationships of CAA with vascular brain lesions were established. RESULTS: CAA was present in 53.8% of the studied population, even in cases without AD (50.6%). The strongest correlation was seen between CAA and age, followed by the severity of amyloid plaques deposition. Microinfarcts were more frequent in cases with CAA; however, our results did not confirm a correlation between these parameters. CONCLUSION: The present data show that CAA plays a role in the development of microvascular lesions in the aging brain, but cannot be considered as the most important factor in this vascular pathology, suggesting that other mechanisms also contributes importantly to the pathogenesis of microvascular changes.
TL;DR: SAMP8 compared to SAMR1 mice are a suitable model to study age-dependent changes in mitochondrial function and curcumin emerges as a promising nutraceutical for the prevention of neurodegenerative diseases that are accompanied or caused by mitochondrial dysfunction.
TL;DR: Overall, this manuscript will review the known contribution of miRNAs to aging brain function and the role they appear to play in the incidence and progression of AD.
Abstract: Alzheimer’s disease (AD) is a tragic, progressive, age-related neurological dysfunction, representing one of the most prevalent neurodegenerative disorders in industrialized societies. Globally, 5 million new cases of AD are diagnosed annually, with one new AD case being reported every 7 seconds. Most recently there has been a surge in the study of the regulatory mechanisms of the AD process, and the particular significance of small non-coding ~22 ribonucleotide RNAs called micro RNAs (miRNAs). Abundant data have profiled miRNA patterns in healthy, aging brain, in mild cognitive impairment (MCI), and in the moderate- and late-stages of AD. The major mode of action of miRNA is to interact, via base-pair complementarity, with ribonucleotides located within the 3’ un-translated region (3’-UTR) of multiple target messenger RNAs (mRNAs), and in doing so decrease the capability of that specific mRNA to be expressed. Many miRNAs are highly cell- and tissue-specific. The human brain uses a highly specific fraction of all known human miRNAs, and among small non-coding RNAs (sncRNAs). In general, in contrast to normally, aging human brain, in AD a family of pathogenically up-regulated miRNAs appear to be down-regulating the expression certain brain-essential mRNA targets, including key regulatory genes involved interactively in neuroinflammation, synaptogenesis, neurotrophic functions, and amyloiogenesis. These up-regulated, NF-kB-sensitive miRNAs, involved in the innate immune and inflammatory response and synaptic, neurotrophic and amyloidogenic functions include miRNA-9, miRNA-125b, miRNA-146a and miRNA-155. Other miRNAs of the miRNA-15/107 family, miRNA-153 and miRNA-190, and others, will be discussed. Overall, this manuscript will review the known contribution of miRNAs to aging brain function and the role they appear to play in the incidence and progression of AD.
TL;DR: Low striatal glutamate levels were associated with high systolic blood pressure and worse performance on a complex visuomotor task, the Grooved Pegboard, and these findings suggest that low brain glutamate levels are related to highBlood pressure and that changes inbrain glutamate levels might mediate the behavioral changes noted in normal aging.
TL;DR: The hypothesis that stroke severity in the aging brain may be associated with reduced functional capacity of critical support cells is discussed, which focuses on astrocytes, that are critical for detoxification of the brain microenvironment and endothelial cells, which play a crucial role in maintaining the blood brain barrier.
TL;DR: Analyzing the scientific literature on aging of the rodent subventricular zone revealed that deficits in the neurogenic pathway are largely established by middle age, but that there remains striking ambiguity in the underlying mechanisms, especially at the level of stem and progenitor cells.
Abstract: In the brains of adult vertebrates, including humans, neurogenesis occurs in restricted niches where it maintains cellular turnover and cognitive plasticity. In virtually all species, however, aging is associated with a significant decline in adult neurogenesis. Moreover, an acceleration of neurogenic defects is observed in models of Alzheimer's disease and other neurodegenerative diseases, suggesting an involvement in aging- and disease-associated cognitive deficits. To gain insights into when, how and why adult neurogenesis decreases in the aging brain, we critically reviewed the scientific literature on aging of the rodent subventricular zone, the neurogenic niche of the adult forebrain. Our analysis revealed that deficits in the neurogenic pathway are largely established by middle age, but that there remains striking ambiguity in the underlying mechanisms, especially at the level of stem and progenitor cells. We identify and discuss several challenging issues that have contributed to these key gaps in our current knowledge. In the future, addressing these issues should help untangle the interactions between neurogenesis, aging and aging-associated diseases.
TL;DR: It is shown that CR increased the number of dividing cells in the dentate gyrus of female mice and increased proliferative activity of stem and progenitor cells did not result in a significant increase in thenumber of doublecortin‐positive newborn neurons.
Abstract: Production of new neurons from stem cells is important for cognitive function, and the reduction of neurogenesis in the aging brain may contribute to the accumulation of age-related cognitive deficits. Restriction of calorie intake and prolonged treatment with rapamycin have been shown to extend the lifespan of animals and delay the onset of the age-related decline in tissue and organ function. Using a reporter line in which neural stem and progenitor cells are marked by the expression of green fluorescent protein (GFP), we examined the effect of prolonged exposure to calorie restriction (CR) or rapamycin on hippocampal neural stem and progenitor cell proliferation in aging mice. We showed that CR increased the number of dividing cells in the dentate gyrus of female mice. The majority of these cells corresponded to nestin-GFP-expressing neural stem or progenitor cells; however, this increased proliferative activity of stem and progenitor cells did not result in a significant increase in the number of doublecortin-positive newborn neurons. Our results suggest that restricted calorie intake may increase the number of divisions that neural stem and progenitor cells undergo in the aging brain of females.
TL;DR: It seems that, in the aging brain, changes in the metabolism of neurons may lead to their decreased numbers in the cerebral and cerebellar cortex, hippocampus, basal nucleus of Meynert, locus ceruleus, and substantia nigra, as well as to decreased numbers of synapses and disturbed stimulation of synaptic plasticity in the senescent brain.
Abstract: Senescence of the brain seems to be related to increased levels of free oxygen radical (FOR). FOR may damage macromolecular compounds such as: proteins, lipids, and DNA. In the aging brain, increased FOR levels damage DNA, mitochondrial DNA (mtDNA), and nuclear DNA (nDNA). In DNA they damage single and double strands, leading to mutations in mtDNA and nDNA. Damage to mtDNA seems to result in decay of mitochondria, decreased production of ATP, and in the activation of the apoptotic process. In the aging brain, apoptosis does not seem to be activated in wild-type p53-expressing cells because the elevated levels of the p53 protein are no longer accompanied by decreased levels of the Bcl-2 protein and increased levels of the Bax protein. It seems that, in the aging brain, changes in the metabolism of neurons may lead to their decreased numbers in the cerebral and cerebellar cortex, hippocampus, basal nucleus of Meynert, locus ceruleus, and substantia nigra, as well as to decreased numbers of synapses and disturbed stimulation of synaptic plasticity in the senescent brain. Simultaneously, a decrease in neurogenesis in the aging brain may lead to a decline in the maintenance of tissue integrity, function, and regenerative response. Environmental enrichment and physical activity may improve hippocampal neurogenesis and induce neuronal plasticity. The morphological lesions in the senescent brain are undoubtedly followed by a disturbed balance between various types of neurons in the CNS. Nevertheless, the high plasticity of the CNS in humans most probably does not allow for the development of abnormalities in higher functions.
TL;DR: It is shown that chronic supplementation of taurine to aged mice significantly ameliorated the age-dependent decline in spatial memory acquisition and retention and caused significant alterations in the GABAergic and somatostatinergic system.
Abstract: Aging of the brain is characterized by several neurochemical modifications involving structural proteins, neurotransmitters, neuropeptides and related receptors. Alterations of neurochemical indices of synaptic function are indicators of age-related impairment of central functions, such as locomotion, memory and sensory performances. Several studies demonstrate that ionotropic GABA receptors, glutamate decarboxylase (GAD), and somatostatinergic subpopulations of GABAergic neurons are markedly decreased in experimental animal brains during aging. Additionally, levels of several neuropeptides co-expressed with GAD decrease during aging. Thus, the age-related decline in cognitive functions could be attributable, at least in part, to decrements in GABA inhibitory neurotransmission. In this study, we showed that chronic supplementation of taurine to aged mice significantly ameliorated the age-dependent decline in spatial memory acquisition and retention. We also demonstrated that concomitant with the amelioration in cognitive function, taurine caused significant alterations in the GABAergic and somatostatinergic system. These changes included (1) increased levels of the neurotransmitters GABA and glutamate, (2) increased expression of both isoforms of GAD (65 and 67) and the neuropeptide somatostatin, (3) decreased hippocampal expression of the β3 subunits of the GABAA receptor, (4) increased expression in the number of somatostatin-positive neurons, (5) increased amplitude and duration of population spikes recorded from CA1 in response to Schaefer collateral stimulation and (6) enhanced paired pulse facilitation in the hippocampus. These specific alterations of the inhibitory system caused by taurine treatment oppose those naturally occurring in the aging brain, suggesting a protective role of taurine in this process. An increased understanding of age-related neurochemical changes in the GABAergic system will be important in elucidating the underpinnings of the functional changes of aging. Taurine supplementation might help forestall the age-related decline in cognitive functions through interaction with the GABAergic system.
TL;DR: This study is the first of its kind to clearly dissociate how aging affects the neural correlates of emotional arousal and valence and found that the older group showed greater activation in response to positive valence, in the left amygdala, left middle temporal gyrus and right lingual gyrus.
01 Feb 2013
TL;DR: The data show the presence of differentially altered IgG levels against α- Synuclein in DLB and AD, which may relate to a disturbed α-synuclein homeostasis triggered by the disease process, and may foster the development of novel, possibly preclinical biomarkers and immunotherapeutic strategies that target α- synucleIn in neurodegenerative disease.
Abstract: Natural self-reactive antibodies in the peripheral blood may play a considerable role in the control of potentially toxic proteins that may otherwise accumulate in the aging brain. The significance of serum antibodies reactive against α-synuclein is not well known. We explored serum IgG levels to monomeric α-synuclein in dementia with Lewy bodies (DLB) and Alzheimer’s disease (AD) with a novel and validated highly sensitive ELISA assay. Antibody levels revealed stark differences in patients compared to healthy subjects and were dependent on diagnosis, disease duration and age. Anti-α-synuclein IgG levels were increased in both patient groups, but in early DLB to a much greater extent than in AD. Increased antibody levels were most evident in younger patients, while with advanced age relatively low levels were observed, similar to healthy individuals, exhibiting stable antibody levels independent of age. Our data show the presence of differentially altered IgG levels against α-synuclein in DLB and AD, which may relate to a disturbed α-synuclein homeostasis triggered by the disease process. These observations may foster the development of novel, possibly preclinical biomarkers and immunotherapeutic strategies that target α-synuclein in neurodegenerative disease.
TL;DR: The results in the HT22 cell line indicate that Apo D protein level increases in a concentration-dependent manner specifically at those H2O2 concentrations that caused oxidative damage and apoptotic cell death, which support the idea that oxidative stress-induced apoptosis during aging and AD may be associated with the increment in the expression of ApoD in these situations.
Abstract: Apolipoprotein D (Apo D) is a lipid binding protein whose expression is strongly induced in the mammalian brain during aging and age-dependent neurodegenerative diseases such as Alzheimer's disease (AD), where it can play an important function as a neuroprotective and antioxidant protein. Increasing evidence suggests that the gradual increase in free radicals and oxidative stress with age is the primary determinant to aging brain. The aim of this work is to study the effect of hydrogen peroxide (H2O2) in Apo D expression, in hippocampal cells, in order to investigate the relationship between oxidative stress and elevated levels of Apo D found in hippocampus during aging and AD and also elucidate the possible pathways that lead to this increase. In this study, we demonstrated that Apo D expression in hippocampal neurons of aged and AD brains directly correlates with age-related increase in oxidative stress. More importantly, our results in the HT22 cell line indicate that Apo D protein level increases in a concentration-dependent manner specifically at those H2O2 concentrations that caused oxidative damage and apoptotic cell death. These data support the idea that oxidative stress-induced apoptosis during aging and AD may be associated with the increment in the expression of Apo D in these situations.
TL;DR: Recent findings indicating age and sex dependent expression of CREB and its interaction with estrogen receptor (ER)β, and the role ofCREB signaling in brain aging and diseases are summarized.
Abstract: During aging, brain undergoes several changes which influence its function through alteration in the expression of genes. Some of these genes are regulated by estrogen which requires a host of coregulator proteins including CREB. In brain, CREB is expressed in different regions and regulates a wide range of functions such as cellular growth, proliferation and memory in response to a variety of intracellular signaling events including synaptic efficacy and long-lasting changes in synaptic plasticity. In response to signals at the cell surface, CREB is phosphorylated in the nucleus by various protein kinases via secondary messengers such as cAMP and/or Ca+2 for regulating specific genes. Alterations in CREB signaling lead to cognitive deficits as observed in normal aging and neurodegenerative diseases. In brain, the expression of CREB changes with age, but its variation with sex is not known. So, in this review paper, we summarize recent findings indicating age and sex dependent expression of CREB and its interaction with estrogen receptor (ER)β, and the role of CREB signaling in brain aging and diseases. Such understanding of CREB signaling through ER may help to design therapeutic strategies for age related cognitive deficits and neurodegenerative disorders.
TL;DR: The hypothesis that age-related changes in A1 have a strong activity-dependent component and indicate that the presence or absence of clear auditory input patterns might be a key factor in sustaining adult A1 function is supported.
Abstract: Age-related impairments in the primary auditory cortex (A1) include poor tuning selectivity, neural desynchronization, and degraded responses to low-probability sounds. These changes have been largely attributed to reduced inhibition in the aged brain, and are thought to contribute to substantial hearing impairment in both humans and animals. Since many of these changes can be partially reversed with auditory training, it has been speculated that they might not be purely degenerative, but might rather represent negative plastic adjustments to noisy or distorted auditory signals reaching the brain. To test this hypothesis, we examined the impact of exposing young adult rats to 8 weeks of low-grade broadband noise on several aspects of A1 function and structure. We then characterized the same A1 elements in aging rats for comparison. We found that the impact of noise exposure on A1 tuning selectivity, temporal processing of auditory signal and responses to oddball tones was almost indistinguishable from the effect of natural aging. Moreover, noise exposure resulted in a reduction in the population of parvalbumin inhibitory interneurons and cortical myelin as previously documented in the aged group. Most of these changes reversed after returning the rats to a quiet environment. These results support the hypothesis that age-related changes in A1 have a strong activity-dependent component and indicate that the presence or absence of clear auditory input patterns might be a key factor in sustaining adult A1 function.
TL;DR: Examination of individual differences through cross-sectional associations at baseline evaluation and longitudinal changes in regional cerebral blood flow in relation to different executive abilities in cognitively normal older adults suggests process- and region-specific, rather than uniform, age-related changes in frontal brain-behavior associations, and suggests that longitudinally high-levels of frontal engagement reflect declining rather than stable cognition.
TL;DR: Some neurophysiological cutting-edge techniques will be presented that provide innovative information and deal with the broad issue of the role of neurophysiology for the assessment of patho-physiological aging and dementia also providing new insight to the actions of central nervous system drugs at the cortical level.
Abstract: The pathophysiological mechanisms underlying normal aging and neurodegenerative disorders represent the focus of a bulk of recent research Physiological brain aging is characterized by a progressive dysfunction and loss of synaptic contacts and neuronal abnormal apoptosis Neural and synaptic redundancy as well as functional and structural plastic remodeling of brain networking promote maintenance of brain activity in healthy elderly for everyday life but are not sufficient to face the pathologic scenario of excessive synaptic/ neuronal loss as in dementias It is, then, important to implement techniques that are able to measure changes in normal aging brain and to discriminate the threshold from neurodegenerative processes Rhythmic electromagnetic brain oscillatory activity is a hallmark of neuronal function and it contains relevant traces of neuronal assemblies cooperation across different brain functions; an integrated approach utilizing modern neurophysiological techniques, including electroencephalography (EEG), event-related potentials (ERPs), and transcranial magnetic stimulation (TMS), together with biological markers and structural and functional imaging is promising for largescale, affordable, and non-invasive intercept of at-risk populations both at a group and probably also at a single-subject level This approach might also guarantee the possibility of studying drug-induced changes in the electrical properties of the human cortex, developing and testing models of brain connectivity and treating neuropsychiatric diseases In this paper some neurophysiological cutting-edge techniques will be presented that provide innovative information and deal with the broad issue of the role of neurophysiology for the assessment of patho-physiological aging and dementia also providing new insight to the actions of central nervous system drugs at the cortical level
TL;DR: The results indicate that the aging process modifies the compartmentalization of PrPC, and an involvement of PrP lipid environment in prion formation and consequently it may play a role in the onset or development of sporadic forms of prion diseases.
Abstract: The cellular form of the prion protein (PrPC) is a normal constituent of neuronal cell membranes. The protein misfolding causes rare neurodegenerative disorders known as transmissible spongiform encephalopathies or prion diseases. These maladies can be sporadic, genetic or infectious. Sporadic prion diseases are the most common form mainly affecting aging people. In this work, we investigate the biochemical environment in which sporadic prion diseases may develop, focusing our attention on the cell membrane of neurons in the aging brain. It is well established that with aging the ratio between the most abundant lipid components of rafts undergoes a major change: while cholesterol decreases, sphingomyelin content rises. Our results indicate that the aging process modifies the compartmentalization of PrPC. In old mice, this change favors PrPC accumulation in detergent-resistant membranes, particularly in hippocampi. To confirm the relationship between lipid content changes and PrPC translocation into detergent-resistant membranes (DRMs), we looked at PrPC compartmentalization in hippocampi from acid sphingomyelinase (ASM) knockout (KO) mice and synaptosomes enriched in sphingomyelin. In the presence of high sphingomyelin content, we observed a significant increase of PrPC in DRMS. This process is not due to higher levels of total protein and it could, in turn, favor the onset of sporadic prion diseases during aging as it increases the PrP intermolecular contacts into lipid rafts. We observed that lowering sphingomyelin in scrapie-infected cells by using fumonisin B1 led to a 50% decrease in protease-resistant PrP formation. This may suggest an involvement of PrP lipid environment in prion formation and consequently it may play a role in the onset or development of sporadic forms of prion diseases.
TL;DR: High concentrations of Aβ1-42 and α-Syn exert toxic effects on mature neurons; however, non-toxic concentration treatment of these polypeptides induced the production of each other reciprocally with possible involvement of PI3K pathway.
Abstract: In spite of definite roles for β-amyloid (Aβ) in familial Alzheimer's disease (AD), the cause of sporadic AD remains unknown Amyloid senile plaques and Lewy body pathology frequently coexist in neocortical and hippocampal regions of AD and Parkinson's diseases However, the relationship between Aβ and α-synuclein (α-Syn), the principle components in the pathological structures, in neuronal toxicity and the mechanisms of their interaction are not well studied As Aβ and α-Syn accumulate in aging patients, the biological functions and toxicity of these polypeptides in the aging brain may be different from those in young brain We examined the neurotoxicity influences of Aβ1-42 or α-Syn on mature neurons and the effects of Aβ1-42 or α-Syn on the production of endogenous α-Syn or Aβ1-40 reciprocally using a model of culture enriched with primary neurons from the hippocampus of adult rats Treatment of neurons with high concentrations of Aβ1-42 or α-Syn caused significant apoptosis of neurons Following Aβ1-42 treatment at sub apoptotic concentrations, both intra- and extra-cellular α-Syn levels were significantly increased Reciprocally, the non-toxic levels of α-Syn treatment also increased intra- and extra-cellular Aβ1-40 levels The phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002, suppressed α-Syn-induced Aβ1-40 elevation, as well as Aβ1-42-induced α-Syn elevation Thus, high concentrations of Aβ1-42 and α-Syn exert toxic effects on mature neurons; however, non-toxic concentration treatment of these polypeptides induced the production of each other reciprocally with possible involvement of PI3K pathway