Cytokines and the aging brain – what we don't know might help us

Neuroinflammation increases in old and oldest-old rats except for dura mater meningeal tissue with significant gender differences: a translational perspective

Neuroinflammaging is the nervous system version of inflammaging, the low-grade inflammation that develops with advanced age, aside from active disease or infection. Despite neuroinflammaging has been widely investigated, some important issues still need to be resolved such as the analysis of the extremely old subjects and the evaluation of specific brain areas. On this background, we conducted a study to analyze expression of inflammatory and anti-inflammatory genes in Wistar rats of different ages, including the oldest-old, in different brain regions. We found that pro-inflammatory mediators were generally up-regulated with age in cortex, hippocampus, and striatum, especially in the oldest-old group. Specifically, TNF-α showed an increment in expression with age in striatum, IL-1β and IFN-γ in hippocampus, and MCP-1 in cortex, hippocampus and striatum. Conversely, CX3CL1 and NOS2 showed a significant reduction of expression in the cortex of the oldest-old group. A different situation was observed in dura mater where TNF-α, IL-6, IL-1β, CX3CL1, and MCP-1 expression decreased in the older groups in comparison with the younger groups. With age the anti-inflammatory cytokines IL-4 and IL-10 were down-regulated in cortex, and TGF-β1 in dura mater, while IL-4 was up-regulated in the oldest-old group in hippocampus. Finally, we observed that female brains underwent an age-related increase of pro-inflammatory cytokines expression compared to males, except for striatum, and a general down-regulation of anti-inflammatory cytokines within each age group. Protein validation of selected factors by ELISA tests supported the observed changes. These data may represent a basis for future research about the neurobiology of aging, in particular in the neurodegenerative disorder framework.

Neuronal Cell Rearrangement During Aging: Antioxidant Compounds as a Potential Therapeutic Approach

Aging is a natural process that leads to time-related changes and a decrease in cognitive abilities, executive functions, and attention. In neuronal aging, brain cells struggle to respond to oxidative stress. The structure, function, and survival of neurons can be mediated by different pathways that are sensitive to oxidative stress and age-related low-energy states. Mitochondrial impairment is one of the most noticeable signs of brain aging. Damaged mitochondria are thought to be one of the main causes that feed the inflammation related to aging. Also, protein turnover is involved in age-related impairments. The brain, due to its high oxygen usage, is particularly susceptible to oxidative damage. This review explores the mechanisms underlying neuronal cell rearrangement during aging, focusing on morphological changes that contribute to cognitive decline and increased susceptibility to neurodegenerative diseases. Potential therapeutic approaches are discussed, including the use of antioxidants (e.g., Vitamin C, Vitamin E, glutathione, carotenoids, quercetin, resveratrol, and curcumin) to mitigate oxidative damage, enhance mitochondrial function, and maintain protein homeostasis. This comprehensive overview aims to provide insights into the cellular and molecular processes of neuronal aging and highlight promising therapeutic avenues to counteract age-related neuronal deterioration.

Trimethylamine-N-oxide aggravated the sympathetic excitation in D-galactose induced aging rats by down-regulating P2Y12 receptor in microglia

This study aimed to determine whether trimethylamine N-oxide (TMAO) was involved in sympathetic activation in aging and the underlying mechanisms. Our hypothesis is TMAO reduces P2Y12 receptor (P2Y12R) and induces microglia-mediated inflammation in the paraventricular nucleus (PVN), then leading to sympathetic activation in aging. This study involved 18 young adults and 16 old adults. Aging rats were established by injecting D-galactose (D-gal, 200 mg/kg/d) subcutaneously for 12 weeks. TMAO (120 mg/kg/d) or 1% 3, 3-dimethyl-l-butanol (DMB) was administrated via drinking water for 12 weeks to investigate their effects on neuroinflammation and sympathetic activation in aging rats. Plasma TMAO, NE and IL-1β levels were higher in old adults than in young adults. In addition, standard deviation of all normal to normal intervals (SDNN) and standard deviation of the average of normal to normal intervals (SDANN) were lower in old adults and negatively correlated with TMAO, indicating sympathetic activation in old adults, which is associated with an increase in TMAO levels. Treatment of rats with D-gal showed increased senescence-associated protein levels and microglia-mediated inflammation, as well as decreased P2Y12R protein levels in PVN. Plasma TMAO, NE and IL-1β levels were increased, accompanied by enhanced renal sympathetic nerve activity (RSNA). While TMAO treatment exacerbated the above phenomenon, DMB mitigated it. These findings suggest that TMAO contributes to sympathetic hyperactivity in aging by downregulating P2Y12R in microglia and increasing inflammation in the PVN. These results may provide promising new target for the prevention and treatment of aging and aging-related diseases.

Role of cytokines and reactive oxygen species in brain aging

Aging is a complex process that produces profound effects on the brain. Although a number of external factors can promote the initiation and progression of brain aging, peripheral and central changes in the immune cells with time, also play an important role. Immunosenescence, which is an age-associated decline in immune function and Inflammaging, a low-grade inflammatory state in the aging brain contribute to an elevation in cytokine and reactive oxygen species production. In this review, we focus on the pro-inflammatory state that is established in the brain as a consequence of these two phenomena and the resulting detrimental changes in brain structure, function and repair that lead to a decline in central and neuroendocrine function.

Neuroprotective Effects of Black Pepper and Its Bioactive Compounds in Age-Related Neurological Disorders

Age-related neurological disorders (ANDs), including neurodegenerative diseases, are multifactorial disorders whose risk increases with age. The main pathological hallmarks of ANDs include behavioral changes, excessive oxidative stress, progressive functional declines, impaired mitochondrial function, protein misfolding, neuroinflammation, and neuronal cell death. Recently, efforts have been made to overcome ANDs because of their increased age-dependent prevalence. Black pepper, the fruit of Piper nigrum L. in the family Piperaceae, is an important food spice that has long been used in traditional medicine to treat various human diseases. Consumption of black pepper and black pepper-enriched products is associated with numerous health benefits due to its antioxidant, antidiabetic, anti-obesity, antihypertensive, anti-inflammatory, anticancer, hepatoprotective, and neuroprotective properties. This review shows that black pepper's major bioactive neuroprotective compounds, such as piperine, effectively prevent AND symptoms and pathological conditions by modulating cell survival signaling and death. Relevant molecular mechanisms are also discussed. In addition, we highlight how recently developed novel nanodelivery systems are vital for improving the efficacy, solubility, bioavailability, and neuroprotective properties of black pepper (and thus piperine) in different experimental AND models, including clinical trials. This extensive review shows that black pepper and its active ingredients have therapeutic potential for ANDs.

The Role of PDE11A4 in Social Isolation-Induced Changes in Intracellular Signaling and Neuroinflammation

Phosphodiesterase 11A (PDE11A), an enzyme that degrades cyclic nucleotides (cAMP and cGMP), is the only PDE whose mRNA expression in brain is restricted to the hippocampal formation. Previously, we showed that chronic social isolation changes subsequent social behaviors in adult mice by reducing expression of PDE11A4 in the membrane fraction of the ventral hippocampus (VHIPP). Here we seek extend these findings by determining 1) if isolation-induced decreases in PDE11A4 require chronic social isolation or if they occur acutely and are sustained long-term, 2) if isolation-induced decreases occur uniquely in adults (i.e., not adolescents), and 3) how the loss of PDE11 signaling may increase neuroinflammation. Both acute and chronic social isolation decrease PDE11A4 expression in adult but not adolescent mice. This decrease in PDE11A4 is specific to the membrane compartment of the VHIPP, as it occurs neither in the soluble nor nuclear fractions of the VHIPP nor in any compartment of the dorsal HIPP. The effect of social isolation on membrane PDE11A4 is also selective in that PDE2A and PDE10A expression remain unchanged. Isolation-induced decreases in PDE11A4 expression appear to be functional as social isolation elicited changes in PDE11A-relevant signal transduction cascades (i.e., decreased pCamKIIα and pS6-235/236) and behavior (i.e., increased remote long-term memory for social odor recognition). Interestingly, we found that isolation-induced decreases in membrane PDE11A4 correlated with increased expression of interleukin-6 (IL-6) in the soluble fraction, suggesting pro-inflammatory signaling for this cytokine. This effect on IL-6 is consistent with the fact that PDE11A deletion increased microglia activation, although it left astrocytes unchanged. Together, these data suggest that isolation-induced decreases in PDE11A4 may alter subsequent social behavior via increased neuroinflammatory processes in adult mice.

Aging triggers an upregulation of a multitude of cytokines in the male and especially the female rodent hippocampus but more discrete changes in other brain regions

BACKGROUND

Despite widespread acceptance that neuroinflammation contributes to age-related cognitive decline, studies comparing protein expression of cytokines in the young versus old brains are surprisingly limited in terms of the number of cytokines and brain regions studied. Complicating matters, discrepancies abound-particularly for interleukin 6 (IL-6)-possibly due to differences in sex, species/strain, and/or the brain regions studied.

METHODS

As such, we clarified how cytokine expression changes with age by using a Bioplex and Western blot to measure multiple cytokines across several brain regions of both sexes, using 2 mouse strains bred in-house as well as rats obtained from NIA. Parametric and nonparametric statistical tests were used as appropriate.

RESULTS

In the ventral hippocampus of C57BL/6J mice, we found age-related increases in IL-1α, IL-1β, IL-2, IL-3, IL-4, IL-6, IL-9, IL-10, IL-12p40, IL-12p70, IL-13, IL-17, eotaxin, G-CSF, interfeuron δ, KC, MIP-1a, MIP-1b, rantes, and TNFα that are generally more pronounced in females, but no age-related change in IL-5, MCP-1, or GM-CSF. We also find aging is uniquely associated with the emergence of a module (a.k.a. network) of 11 strongly intercorrelated cytokines, as well as an age-related shift from glycosylated to unglycosylated isoforms of IL-10 and IL-1β in the ventral hippocampus. Interestingly, age-related increases in extra-hippocampal cytokine expression are more discreet, with the prefrontal cortex, striatum, and cerebellum of male and female C57BL/6J mice demonstrating robust age-related increase in IL-6 expression but not IL-1β. Importantly, we found this widespread age-related increase in IL-6 also occurs in BALB/cJ mice and Brown Norway rats, demonstrating conservation across species and rearing environments.

CONCLUSIONS

Thus, age-related increases in cytokines are more pronounced in the hippocampus compared to other brain regions and can be more pronounced in females versus males depending on the brain region, genetic background, and cytokine examined.

The Role of the Effects of Autophagy on NLRP3 Inflammasome in Inflammatory Nervous System Diseases

Autophagy is a stable self-sustaining process in eukaryotic cells. In this process, pathogens, abnormal proteins, and organelles are encapsulated by a bilayer membrane to form autophagosomes, which are then transferred to lysosomes for degradation. Autophagy is involved in many physiological and pathological processes. Nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome, containing NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) and pro-caspase-1, can activate caspase-1 to induce pyroptosis and lead to the maturation and secretion of interleukin-1 β (IL-1 β) and IL-18. NLRP3 inflammasome is related to many diseases. In recent years, autophagy has been reported to play a vital role by regulating the NLRP3 inflammasome in inflammatory nervous system diseases. However, the related mechanisms are not completely clarified. In this review, we sum up recent research about the role of the effects of autophagy on NLRP3 inflammasome in Alzheimer’s disease, chronic cerebral hypoperfusion, Parkinson’s disease, depression, cerebral ischemia/reperfusion injury, early brain injury after subarachnoid hemorrhage, and experimental autoimmune encephalomyelitis and analyzed the related mechanism to provide theoretical reference for the future research of inflammatory neurological diseases.

Whole-body senescent cell clearance alleviates age-related brain inflammation and cognitive impairment in mice

Cellular senescence is characterized by an irreversible cell cycle arrest and a pro-inflammatory senescence-associated secretory phenotype (SASP), which is a major contributor to aging and age-related diseases. Clearance of senescent cells has been shown to improve brain function in mouse models of neurodegenerative diseases. However, it is still unknown whether senescent cell clearance alleviates cognitive dysfunction during the aging process. To investigate this, we first conducted single-nuclei and single-cell RNA-seq in the hippocampus from young and aged mice. We observed an age-dependent increase in p16Ink4a senescent cells, which was more pronounced in microglia and oligodendrocyte progenitor cells and characterized by a SASP. We then aged INK-ATTAC mice, in which p16Ink4a -positive senescent cells can be genetically eliminated upon treatment with the drug AP20187 and treated them either with AP20187 or with the senolytic cocktail Dasatinib and Quercetin. We observed that both strategies resulted in a decrease in p16Ink4a exclusively in the microglial population, resulting in reduced microglial activation and reduced expression of SASP factors. Importantly, both approaches significantly improved cognitive function in aged mice. Our data provide proof-of-concept for senolytic interventions' being a potential therapeutic avenue for alleviating age-associated cognitive impairment.

The aging mouse brain: cognition, connectivity and calcium

Aging is a complex process that differentially impacts multiple cognitive, sensory, neuronal and molecular processes. Technological innovations now allow for parallel investigation of neuronal circuit function, structure and molecular composition in the brain of awake behaving adult mice. Thus, mice have become a critical tool to better understand how aging impacts the brain. However, a more granular systems-based approach, which considers the impact of age on key features relating to neural processing, is required. Here, we review evidence probing the impact of age on the mouse brain. We focus on a range of processes relating to neuronal function, including cognitive abilities, sensory systems, synaptic plasticity and calcium regulation. Across many systems, we find evidence for prominent age-related dysregulation even before 12 months of age, suggesting that emerging age-related alterations can manifest by late adulthood. However, we also find reports suggesting that some processes are remarkably resilient to aging. The evidence suggests that aging does not drive a parallel, linear dysregulation of all systems, but instead impacts some processes earlier, and more severely, than others. We propose that capturing the more fine-scale emerging features of age-related vulnerability and resilience may provide better opportunities for the rejuvenation of the aged brain.

Oxidative stress in elderly population: A prevention screening study

Background

Aging is a multifactorial phenomenon, characterized by a progressive decline in the efficiency of biochemical and physiological processes and an increased susceptibility to disease. There is increasing evidence that aging and age‐related disease are correlated with an oxidative stress (OS) condition. The latter is characterized by an imbalance between reactive species (RS), in particular reactive oxygen species (ROS) and antioxidant reserve.

Objectives

The aim of this study is to evaluate the two main markers of oxidative stress, plasmatic peroxide concentration (through d‐ROMs FAST test, derivates‐Reactive Oxygen Metabolites) and plasmatic antioxidant power measured by iron‐reducing power (PAT test, Plasma Antioxidant Test) in 290 apparently healthy volunteers over 60, and their possible correlation with age and gender.

Materials and methods

Human capillary blood samples from healthy volunteers were used in this observational study for the evaluation of the markers of OS.

Results

The data obtained broadly demonstrate that the majority of elderly people display an OS condition characterized by increased levels of peroxides and a slight reduction in antioxidant reserve.

Conclusions

Seniors have a greater propensity to develop a condition of oxidative stress, and therefore it is important to associate the monitoring of oxidative stress markers and, if necessary, antioxidant supplementation, with a healthy lifestyle.

Calcium-activated potassium channels: implications for aging and age-related neurodegeneration

Population aging, as well as the handling of age-associated diseases, is a worldwide increasing concern. Among them, Alzheimer's disease stands out as the major cause of dementia culminating in full dependence on other people for basic functions. However, despite numerous efforts, in the last decades, there was no new approved therapeutic drug for the treatment of the disease. Calcium-activated potassium channels have emerged as a potential tool for neuronal protection by modulating intracellular calcium signaling. Their subcellular localization is determinant of their functional effects. When located on the plasma membrane of neuronal cells, they can modulate synaptic function, while their activation at the inner mitochondrial membrane has a neuroprotective potential via the attenuation of mitochondrial reactive oxygen species in conditions of oxidative stress. Here we review the dual role of these channels in the aging phenotype and Alzheimer's disease pathology and discuss their potential use as a therapeutic tool.

Neurodegenerative diseases as proteinopathies-driven immune disorders

In the pathophysiology of neurodegenerative disorders, the role of misfolded protein deposition leading to neurodegeneration has been primarily discussed. In the last decade, however, it has been proposed a parallel involvement of innate immune activation, chronic inflammation and adaptive immunity in the neurodegeneration mechanisms triggered by proteinopathies. New insights in the neurodegenerative field strongly suggest a role for the immune system in the pathophysiology of neurodegenerative disorders. Therefore, the hypothesis underlining the modulation of the innate and the adaptive immune system in the events linked to brain deposition of misfolded proteins could open new perspectives in the setting of specific immunotherapeutic strategies for the treatment of neurodegenerative diseases. Therefore, we have reviewed the pathogenic hypothesis in neurodegenerative pathologies, underling the links between the deposition of misfolded protein mechanisms and the immune activation.

Effects of DCM Leaf Extract of Gnidia glauca (Fresen) on Locomotor Activity, Anxiety, and Exploration-Like Behaviors in High-Fat Diet-Induced Obese Rats

Obesity is the main component of metabolic syndromes involving distinct etiologies that target different underlying behavioral and physiological functions within the brain structures and neuronal circuits. An alteration in the neuronal circuitry stemming from abdominal or central obesity stimulates a cascade of changes in neurochemical signaling that directly or indirectly mediate spontaneously emitted behaviors such as locomotor activity patterns, anxiety, and exploration. Pharmacological agents available for the treatment of neurologic disorders have been associated with limited potency and intolerable adverse effects. These have necessitated the upsurge in the utilization of herbal prescriptions due to their affordability and easy accessibility and are firmly embedded within wider belief systems of many people. Gnidia glauca has been used in the management of many ailments including obesity and associated symptomatic complications. However, its upsurge in use has not been accompanied by empirical determination of these folkloric claims. The present study, therefore, is aimed at determining the modulatory effects of dichloromethane leaf extract of Gnidia glauca on locomotor activity, exploration, and anxiety-like behaviors in high-fat diet-induced obese rats in an open-field arena. Obesity was experimentally induced by feeding the rats with prepared high-fat diet and water ad libitum for 6 weeks. The in vivo antiobesity effects were determined by oral administration of G. glauca at dosage levels of 200, 250, and 300 mg/kg body weight in high-fat diet-induced obese rats from the 6^th to 12^th week. Phytochemical analysis was done using gas chromatography linked to mass spectroscopy. Results indicated that Gnidia glauca showed anxiolytic effects and significantly increased spontaneous locomotor activity and exploration-like behaviors in HFD-induced obese rats. The plant extract also contained phytocompounds that have been associated with amelioration of the main neurodegenerative mediators, viz., inflammation and oxidative stress. These findings provide “qualified leads” for the synthesis of new alternative therapeutic agents for the management of neurologic disorders. However, there is a need to conduct toxicity studies of Gnidia glauca to establish its safety profiles.

The Role of Intercellular Adhesion Molecule-1 in the Pathogenesis of Psychiatric Disorders

Intercellular adhesion molecule-1 (ICAM-1) is a transmembrane glycoprotein that is overexpressed in many pathological states. Although, like many other immune molecules, ICAM-1 plays only a limited role in the abundant concert of the immune response, it may be more important than we realize. In the central nervous system (CNS), ICAM-1 is expressed in microglial cells and astrocytes and in endothelial cells in the white and gray matter of the human forebrain. It is of particular interest in psychiatric disorders for two reasons: It has a key function for the blood-brain barrier, which plays an important role in the biology of psychiatric disorders, and it is a marker for inflammation. Although the blood level of soluble ICAM-1 (sICAM-1) might be lower in acute unmedicated schizophrenia, it has been reported to be increased in many other psychiatric conditions, such as major depression, bipolar disorder, and dementia. In bipolar disorder, high sICAM levels were found during both the depressed and the manic states and also during the euthymic phase (the free interval), possibly indicating that sICAM is a trait marker. High sICAM-1 blood levels have also been found in depression comorbid to a somatic disease state. Interestingly, sICAM-1 levels also increase during aging. Some studies investigated sICAM-1 levels in the cerebrospinal fluid of psychiatric disorders and ICAM-1 expression in postmortem CNS tissue of psychiatric patients and found that the overall duration and duration of the chronic phase of the psychiatric disorder seem to play a role in both. Moreover, confounders, such as antipsychotic and antidepressive medication, have to be considered. sICAM-1 levels seem to be associated with hypopermeability or hyperpermeability of the blood-brain barrier and thus to influence the communication between the CNS immune system, represented by glia cells, and the peripheral immune system. The balance between the influx and efflux of immune molecules into and out of the CNS may be one of the pinpoints in psychiatric disorders, in particular in the chronic phase, e.g., in schizophrenia. This aspect, however, needs further intense research, in particular to enable researchers to develop therapeutic principles based on an immune/inflammatory approach.

Lack of the aryl hydrocarbon receptor accelerates aging in mice

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor, largely known for its role in xenobiotic metabolism and detoxification as well as its crucial role as a regulator of inflammation. Here, we have compared a cohort wild-type and AhR-null mice along aging to study the relationship between this receptor and age-associated inflammation, termed as "inflammaging," both at a systemic and the CNS level. Our results show that AhR deficiency is associated with a premature aged phenotype, characterized by early inflammaging, as shown by an increase in plasma cytokines levels. The absence of AhR also promotes the appearance of brain aging anatomic features, such as the loss of the white matter integrity. In addition, AhR^-/- mice present an earlier spatial memory impairment and an enhanced astrogliosis in the hippocampus when compared with their age-matched AhR^+/+ controls. Importantly, we have found that AhR protein levels decrease with age in this brain structure, strongly suggesting a link between AhR and aging.-Bravo-Ferrer, I., Cuartero, M. I., Medina, V., Ahedo-Quero, D., Peña-Martínez, C., Pérez-Ruíz, A., Fernández-Valle, M. E., Hernández-Sánchez, C., Fernández-Salguero, P. M., Lizasoain, I., Moro, M. A. Lack of the aryl hydrocarbon receptor accelerates aging in mice.

New Insights into the Role of Exercise in Inhibiting mTOR Signaling in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) does not express estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 and is characterized by its aggressive nature, lack of targets for targeted therapies, and early peak of recurrence. Due to these specific characteristics, chemotherapy does not usually yield substantial improvements and new target therapies and alternative strategies are needed. The beneficial responses of TNBC survivors to regular exercise, including a reduction in the rate of tumor growth, are becoming increasingly apparent. Physiological adaptations to exercise occur in skeletal muscle but have an impact on the entire body through systemic control of energy homeostasis and metabolism, which in turn influence the TNBC tumor microenvironment. Gaining insights into the causal mechanisms of the therapeutic cancer control properties of regular exercise is important to improve the prescription and implementation of exercise and training in TNBC survivors. Here, we provide new evidence of the effects of exercise on TNBC prevention, control, and outcomes, based on the inhibition of the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (PKB also known as Akt)/mammalian target of rapamycin (mTOR) (PI3K-Akt-mTOR) signaling. These findings have wide-ranging clinical implications for cancer treatment, including recurrence and case management.

Altered Gene Expression in Prefrontal Cortex of a Fabry Disease Mouse Model

Fabry disease is an X-chromosome linked hereditary disease that is caused by loss of function mutations in the α-galactosidase A (α-Gal A) gene, resulting in defective glycolipid degradation and subsequent accumulation of globotriaosylceramide (Gb3) in different tissues, including vascular endothelial cells and neurons in the peripheral and central nervous system. We recently reported a differential gene expression profile of α-Gal A^(−/0) mouse dorsal root ganglia, an established animal model of Fabry disease, thereby providing new gene targets that might underlie the neuropathic pain related symptoms. To investigate the cognitive symptoms experienced by Fabry patients, we performed one-color based hybridization microarray expression profiling of prefrontal cortex samples from adult α-Gal A^(−/0) mice and age-matched wildtype controls, followed by protein-protein interaction and pathway analyses for the differentially regulated mRNAs. We found that from a total of 381 differentially expressed genes, 135 genes were significantly upregulated, whereas 246 genes were significantly downregulated between α-Gal A^(−/0) mice and wildtype controls. Enrichment analysis for downregulated genes revealed mainly immune related pathways, including immune/defense responses, regulation of cytokine production, as well as signaling and transport regulation pathways. Further analysis of the regulated genes revealed a large number of genes involved in neurodegeneration. The current analysis for the first time presents a differential gene expression profile of central nervous system tissue from α-Gal A^(−/0) mice, thereby providing novel knowledge on the deregulation and a possible contribution of gene expression to Fabry disease related brain pathologies.

FOXO protects against age-progressive axonal degeneration

Neurodegeneration resulting in cognitive and motor impairment is an inevitable consequence of aging. Little is known about the genetic regulation of this process despite its overriding importance in normal aging. Here, we identify the Forkhead Box O (FOXO) transcription factor 1, 3, and 4 isoforms as a guardian of neuronal integrity by inhibiting age-progressive axonal degeneration in mammals. FOXO expression progressively increased in aging human and mouse brains. The nervous system-specific deletion of Foxo transcription factors in mice accelerates aging-related axonal tract degeneration, which is followed by motor dysfunction. This accelerated neurodegeneration is accompanied by levels of white matter astrogliosis and microgliosis in middle-aged Foxo knockout mice that are typically only observed in very old wild-type mice and other aged mammals, including humans. Mechanistically, axonal degeneration in nerve-specific Foxo knockout mice is associated with elevated mTORC1 activity and accompanying proteotoxic stress due to decreased Sestrin3 expression. Inhibition of mTORC1 by rapamycin treatment mimics FOXO action and prevented axonal degeneration in Foxo knockout mice with accelerated nervous system aging. Defining this central role for FOXO in neuroprotection during mammalian aging offers an invaluable window into the aging process itself.

Leptin and ghrelin: Sewing metabolism onto neurodegeneration

Life expectancy has considerably increased over the last decades. The negative consequence of this augmented longevity has been a dramatic increase of age-related chronic neurodegenerative diseases, such as Alzheimer's, Parkinson's and multiple sclerosis. Epidemiology is telling us there exists a strong correlation between the neuronal loss characterizing these disorders and metabolic dysfunction. This review aims at presenting the evidence supporting the existence of a molecular system linking metabolism with neurodegeneration, with a specific focus on the role of two hormones with a key role in the regulatory cross talk between metabolic imbalance and the damage of nervous system: leptin and ghrelin. This article is part of the Special Issue entitled 'Metabolic Impairment as Risk Factors for Neurodegenerative Disorders.'

Neonatal infection produces significant changes in immune function with no associated learning deficits in juvenile rats

The current experiments examined the impact of early-life immune activation and a subsequent mild immune challenge with lipopolysaccharide (LPS; 25µg/kg) on hippocampal-dependent learning, proinflammatory cytokine expression in the brain, and peripheral immune function in juvenile male and female rats at P24, an age when hippocampal-dependent learning and memory first emerges. Our results indicate that neonatal infection did not produce learning deficits in the hippocampal-dependent context pre-exposure facilitation effect paradigm in juvenile males and females, contrary to what has been observed in adults. Neonatal infection produced an increase in baseline IL-1β expression in the hippocampus (HP) and medial prefrontal cortex (mPFC) of juvenile rats. Furthermore, neonatally infected rats showed exaggerated IL-1β expression in the HP following LPS treatment as juveniles; and juvenile females, but not males, showed exaggerated IL-1β expression in the mPFC following LPS treatment. Neonatal infection attenuated the production of IL-6 expression following LPS treatment in both the brain and the spleen, and neonatal infection decreased the numbers of circulating white blood cells in juvenile males and females, an effect that was further exacerbated by subsequent LPS treatment. Together, our data indicate that the consequences of neonatal infection are detectable even early in juvenile development, though we found no concomitant hippocampal-dependent learning deficits at this young age. These findings underscore the need to consider age and associated on-going neurodevelopmental processes as important factors contributing to the emergence of cognitive and behavioral disorders linked to early-life immune activation. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 77: 1221-1236, 2017.

The effects of aging in the hippocampus and cognitive decline

Aging is a natural process that is associated with cognitive decline as well as functional and social impairments. One structure of particular interest when considering aging and cognitive decline is the hippocampus, a brain region known to play an important role in learning and memory consolidation as well as in affective behaviours and mood regulation, and where both functional and structural plasticity (e.g., neurogenesis) occur well into adulthood. Neurobiological alterations seen in the aging hippocampus including increased oxidative stress and neuroinflammation, altered intracellular signalling and gene expression, as well as reduced neurogenesis and synaptic plasticity, are thought to be associated with age-related cognitive decline. Non-invasive strategies such as caloric restriction, physical exercise, and environmental enrichment have been shown to counteract many of the age-induced alterations in hippocampal signalling, structure, and function. Thus, such approaches may have therapeutic value in counteracting the deleterious effects of aging and protecting the brain against age-associated neurodegenerative processes.

Effects of Video Game Training on Behavioral and Electrophysiological Measures of Attention and Memory: Protocol for a Randomized Controlled Trial

BACKGROUND

Neuroplasticity-based approaches seem to offer promising ways of maintaining cognitive health in older adults and postponing the onset of cognitive decline symptoms. Although previous research suggests that training can produce transfer effects, this study was designed to overcome some limitations of previous studies by incorporating an active control group and the assessment of training expectations.

OBJECTIVE

The main objectives of this study are (1) to evaluate the effects of a randomized computer-based intervention consisting of training older adults with nonaction video games on brain and cognitive functions that decline with age, including attention and spatial working memory, using behavioral measures and electrophysiological recordings (event-related potentials [ERPs]) just after training and after a 6-month no-contact period; (2) to explore whether motivation, engagement, or expectations might account for possible training-related improvements; and (3) to examine whether inflammatory mechanisms assessed with noninvasive measurement of C-reactive protein in saliva impair cognitive training-induced effects. A better understanding of these mechanisms could elucidate pathways that could be targeted in the future by either behavioral or neuropsychological interventions.

METHODS

A single-blinded randomized controlled trial with an experimental group and an active control group, pretest, posttest, and 6-month follow-up repeated measures design is used in this study. A total of 75 cognitively healthy older adults were randomly distributed into experimental and active control groups. Participants in the experimental group received 16 1-hour training sessions with cognitive nonaction video games selected from Lumosity, a commercial brain training package. The active control group received the same number of training sessions with The Sims and SimCity, a simulation strategy game.

RESULTS

We have recruited participants, have conducted the training protocol and pretest assessments, and are currently conducting posttest evaluations. The study will conclude in the first semester of 2017. Data analysis will take place during 2017. The primary outcome is transfer of benefit from training to attention and working memory functions and the neural mechanisms underlying possible cognitive improvements.

CONCLUSIONS

We expect that mental stimulation with video games will improve attention and memory both at the behavioral level and in ERP components promoting brain and mental health and extending independence among elderly people by avoiding the negative personal and economic consequences of long-term care.

TRIAL REGISTRATION

Clinicaltrials.gov NCT02796508; https://clinicaltrials.gov/ct2/show/NCT02796508 (archived by WebCite at http://www.webcitation.org/6nFeKeFNB).

Disparate Changes in Plasma and Brainstem Cytokine Levels in Adult and Ageing Rats Associated with Age-Related Changes in Facial Motor Neuron Number, Snout Muscle Morphology, and Exploratory Behavior

An overall increase in inflammatory cytokines with age in both the blood and the central nervous system (CNS) has been proposed to explain many aspects of ageing, including decreased motor function and neurodegeneration. This study tests the hypothesis that age-related increases in inflammatory cytokines in the blood and CNS lead to facial motor neuron degeneration. Groups of 3–5 female Sprague-Dawley rats aged 3, 12–18, and 24 months were used. Twelve cytokines interleukin (IL)-1α, IL-β, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12p70, IL-13, tumor necrosis factor-α (TNFα), interferon-γ, and granulocyte macrophage-colony stimulating factor were measured in blood plasma and compared with those in the brainstem after first flushing blood from its vessels. The open-field test was used to measure exploratory behavior, and the morphology of the peripheral target muscle of facial motor neurons quantified. Total numbers of facial motor neurons were determined stereologically in separate groups of 3- and 24-month-old rats. Ageing rats showed a significant 30–42% decrease in blood plasma (peripheral) concentrations of IL-12p70 and TNFα and a significant 43–49% increase in brainstem (central) concentrations of IL-1α, IL-2, IL-4, IL-10, and TNFα. They also showed significant reductions in motor neuron number in the right but not left facial nucleus, reduced exploratory behavior, and increase in peripheral target muscle size. Marginal age-related facial motoneuronal loss occurs in the ageing rat and is characterized by complex changes in the inflammatory signature, rather than a general increase in inflammatory cytokines.

Increased oxidative stress and apoptosis in the hypothalamus of diabetic male mice in the insulin receptor substrate-2 knockout model

Insulin receptor substrate-2-deficient (IRS2(-/-)) mice are considered a good model to study the development of diabetes because IRS proteins mediate the pleiotropic effects of insulin-like growth factor-I (IGF-I) and insulin on metabolism, mitogenesis and cell survival. The hypothalamus might play a key role in the early onset of diabetes, owing to its involvement in the control of glucose homeostasis and energy balance. Because some inflammatory markers are elevated in the hypothalamus of diabetic IRS2(-/-) mice, our aim was to analyze whether the diabetes associated with the absence of IRS2 results in hypothalamic injury and to analyze the intracellular mechanisms involved. Only diabetic IRS2(-/-) mice showed increased cell death and activation of caspase-8 and -3 in the hypothalamus. Regulators of apoptosis such as FADD, Bcl-2, Bcl-xL and p53 were also increased, whereas p-IκB and c-FLIPL were decreased. This was accompanied by increased levels of Nox-4 and catalase, enzymes involved in oxidative stress. In summary, the hypothalamus of diabetic IRS2(-/-) mice showed an increase in oxidative stress and inflammatory markers that finally resulted in cell death via substantial activation of the extrinsic apoptotic pathway. Conversely, non-diabetic IRS2(-/-) mice did not show cell death in the hypothalamus, possibly owing to an increase in the levels of circulating IGF-I and in the enhanced hypothalamic IGF-IR phosphorylation that would lead to the stimulation of survival pathways. In conclusion, diabetes in IRS2-deficient male mice is associated with increased oxidative stress and apoptosis in the hypothalamus.

Chronic Cerebral Ischemia Induces Downregulation of A1 Adenosine Receptors During White Matter Damage in Adult Mice

The role of A1 adenosine receptors (A1ARs) in the white matter under chronic cerebral ischemic conditions remains unclear. Here, we used right unilateral common carotid artery occlusion (rUCCAO) to construct a chronic cerebral ischemic mouse model. A1AR expression and proteolipid protein (PLP, a marker of white matter myelination) in the corpus callosum were observed by immunoreaction and immunohistochemistry, respectively. Pro-inflammatory interleukin-1β (IL-1β) and anti-inflammatory interleukin-10 (IL-10) levels were determined by ELISA. The Morris water maze test was employed to detect cognitive impairment. A1AR expression significantly decreased in the rUCCAO group as compared with the sham control group on weeks 2, 4, and 6, respectively. IL-10 levels in the rUCCAO group significantly declined on week 6, while there was no significant change in IL-1β expression. PLP expression significantly decreased in the rUCCAO group on weeks 2, 4, and 6. Moreover, latency time for the Morris water maze test significantly increased in the rUCCAO group on weeks 4 and 6, while the number of platform location crossing significantly decreased in the rUCCAO group on weeks 2, 4, and 6. In conclusion, this study provides the first evidence that chronic cerebral ischemia appears to induce A1AR downregulation and inhibition of IL-10 production, which may play key roles in the neuropathological mechanisms of ischemic white matter lesions. These data will facilitate future studies in formulating effective therapeutic strategies for ischemic white matter lesions.

Neuroinflammatory signals in Alzheimer disease and APP/PS1 transgenic mice: correlations with plaques, tangles, and oligomeric species

To understand neuroinflammation-related gene regulation during normal aging and in sporadic Alzheimer disease (sAD), we performed functional genomics analysis and analyzed messenger RNA (mRNA) expression by quantitative reverse transcription-polymerase chain reaction of 22 genes involved in neuroinflammation-like responses in the cerebral cortex of wild-type and APP/PS1 transgenic mice. For direct comparisons, mRNA expression of 18 of the same genes was then analyzed in the entorhinal cortex, orbitofrontal cortex, and frontal cortex area 8 of middle-aged human subjects lacking Alzheimer disease-related pathology and in older subjects with sAD pathology covering Stages I-II/0(A), III-IV/A-B, and V-VI/C of Braak and Braak classification. Modifications of cytokine and immune mediator mRNA expression were found with normal aging in wild-type mice and in middle-aged individuals and patients with early stages of sAD-related pathology; these were accompanied by increased protein expression of certain mediators in ramified microglia. In APP/PS1 mice, inflammatory changes coincided with β-amyloid (Aβ) deposition; increased levels of soluble oligomers paralleled the modified mRNA expression of cytokines and mediators in wild-type mice. In patients with sAD, regulation was stage- and region-dependent and not merely acceleration and exacerbation of mRNA regulation with aging. Gene regulation at first stages of AD was not related to hyperphosphorylated tau deposition in neurofibrillary tangles, Aβ plaque burden, concentration of Aβ1-40 (Aβ40) and Aβ1-42 (Aβ42), or fibrillar Aβ linked to membranes but rather to increased levels of soluble oligomers. Thus, species differences and region- and stage-dependent inflammatory responses in sAD, particularly at the initial stages, indicate the need to identify new anti-inflammatory compounds with specific molecular therapeutic targets.

The expression of interleukin-6 and its receptor in various brain regions and their roles in exploratory behavior and stress responses

We examined the involvement of interleukin-6 (IL-6) and its receptor IL-6Rα on behavior and stress responses in mice. In the open field, both wild-type (WT) and IL-6 deficient mice displayed similar levels of locomotor activity; however, IL-6 deficient mice spent more time in the central part of the arena compared to control WT mice. After behavioral testing, mice were subjected to stress and then sacrificed. The levels of IL-6 and its receptor in their brains were determined. Immunohistochemical labeling of brain sections for IL-6 showed a high level of expression in the subventricular zone of the lateral ventricles and in the border zone of the third and fourth ventricles. Interestingly, 95% of the IL-6-expressing cells had an astrocytic phenotype, and the remaining 5% were microglial cells. A low level of IL-6 expression was observed in the olfactory bulb, hypothalamus, hippocampus, cerebral cortex, cerebellum, midbrain and several brainstem structures. The vast majority of IL-6-expressing cells in these structures had a neuronal phenotype. Stress increased the number of IL-6-immunoreactive astrocytes and microglial cells. The levels of the IL-6Rα receptor were increased in the hypothalamus of stressed mice. Therefore, in this study, we describe for the first time the distribution of IL-6 in various types of brain cells and in previously unreported regions, such as the subventricular zone of the lateral ventricle. Moreover, we provide data on regional distribution and expression within specific cell phenotypes. This highly differential expression of IL-6 indicates its specific roles in the regulation of neuronal and astrocytic functions, in addition to the roles of IL-6 and its receptor IL-6Rα in stress responses.

Autophagy in microglia degrades extracellular β-amyloid fibrils and regulates the NLRP3 inflammasome

Accumulation of β-amyloid (Aβ) and resultant inflammation are critical pathological features of Alzheimer disease (AD). Microglia, a primary immune cell in brain, ingests and degrades extracellular Aβ fibrils via the lysosomal system. Autophagy is a catabolic process that degrades native cellular components, however, the role of autophagy in Aβ degradation by microglia and its effects on AD are unknown. Here we demonstrate a novel role for autophagy in the clearance of extracellular Aβ fibrils by microglia and in the regulation of the Aβ-induced NLRP3 (NLR family, pyrin domain containing 3) inflammasome using microglia specific atg7 knockout mice and cell cultures. We found in microglial cultures that Aβ interacts with MAP1LC3B-II via OPTN/optineurin and is degraded by an autophagic process mediated by the PRKAA1 pathway. We anticipate that enhancing microglial autophagy may be a promising new therapeutic strategy for AD.

White matter changes with age utilizing quantitative diffusion MRI

OBJECTIVE

To investigate the relationship between older age and mean cerebral white matter fiber bundle lengths (FBLs) in specific white matter tracts in the brain using quantified diffusion MRI.

METHODS

Sixty-three healthy adults older than 50 years underwent diffusion tensor imaging. Tractography tracings of cerebral white matter fiber bundles were derived from the diffusion tensor imaging data.

RESULTS

Results revealed significantly shorter FBLs in the anterior thalamic radiation for every 1-year increase over the age of 50 years.

CONCLUSIONS

We investigated the effects of age on FBL in specific white matter tracts in the brains of healthy older individuals utilizing quantified diffusion MRI. The results revealed a significant inverse relationship between age and FBL. Longitudinal studies of FBL across a lifespan are needed to examine the specific changes to the integrity of white matter.

IFN-γ and TNF-α are involved during Alzheimer disease progression and correlate with nitric oxide production: a study in Algerian patients

Alzheimer's disease (AD) is a neurodegenerative disease leading to a progressive and irreversible loss of mental functions. It is characterized by 3 stages according to the evolution and the severity of the symptoms. This disease is associated with an immune disorder, which appears with significant rise in the inflammatory cytokines and increased production of free radicals such as nitric oxide (NO). Our study aims to investigate interferon (IFN)-γ and tumor necrosis factor-α (TNF-α) involvement in NO production, in vivo and ex vivo, in peripheral blood mononuclear cells from Algerian patients (n=25), according to the different stages of the disease (mild Alzheimer's, moderate Alzheimer's, and severe Alzheimer's) in comparison to mild cognitive impairment (MCI) patients. Interestingly, we observed that in vivo IFN-γ and TNF-α levels assessed in patients with AD in mild and severe stages, respectively, are higher than those observed in patients with moderate stage and MCI. Our in vivo and ex vivo results show that NO production is related to the increased levels of IFN-γ and TNF-α, in mild and severe stages of AD. Remarkably, significant IFN-γ level is only detected in mild stage of AD. Our study suggests that NO production is IFN-γ dependent both in MCI and mild Alzheimer's patients. Further, high levels of NO are associated with an elevation of TNF-α levels in severe stage of AD. Collectively, our data indicate that the proinflammatory cytokine production seems, in part, to be involved in neurological deleterious effects observed during the development of AD through NO pathway.

A single administration of human umbilical cord blood T cells produces long-lasting effects in the aging hippocampus

Neurogenesis occurs throughout life but significantly decreases with age. Human umbilical cord blood mononuclear cells (HUCB MNCs) have been shown to increase the proliferation of neural stem cells (NSCs) in the dentate gyrus (DG) of the hippocampus and the subgranular zone of aging rats (Bachstetter et al., BMC Neurosci 9:22, 2008), but it is unclear which fraction or combination of the HUCB MNCs are responsible for neurogenesis. To address this issue, we examined the ability of HUCB MNCs, CD4+, CD8+, CD3+, CD14+, and CD133+ subpopulations to increase proliferation of NSCs both in vitro and in vivo. NSCs were first grown in conditioned media generated from HUCB cultures, and survival and proliferation of NSC were determined with the fluorescein diacetate/propidium iodide and 5-bromo-2'-deoxyuridine incorporation assays, respectively. In a second study, we injected HUCB cells intravenously in young and aged Fisher 344 rats and examined proliferation in the DG at 1 week (study 2.1) and 2 weeks (study 2.2) postinjection. The effects of the HUCB MNC fractions on dendritic spine density and microglial activation were also assessed. HUCB T cells (CD3+, CD4+, and CD8+ cells) induced proliferation of NSCs (p < 0.001) and increased cell survival. In vivo, HUCB-derived CD4+ cells increased NSC proliferation at both 1 and 2 weeks while also enhancing the density of dendritic spines at 1 week and decreasing inflammation at 2 weeks postinjection. Collectively, these data indicate that a single injection of HUCB-derived T cells induces long-lasting effects and may therefore have tremendous potential to improve aging neurogenesis.

Intracerebral transplantation of adipose-derived mesenchymal stem cells alternatively activates microglia and ameliorates neuropathological deficits in Alzheimer's disease mice

Recent studies suggest that transplantation of mesenchymal stem cells might have therapeutic effects in preventing pathogenesis of several neurodegenerative disorders. Adipose-derived mesenchymal stem cells (ADSCs) are a promising new cell source for regenerative therapy. However, whether transplantation of ADSCs could actually ameliorate the neuropathological deficits in Alzheimer's disease (AD) and the mechanisms involved has not yet been established. Here, we evaluated the therapeutic effects of intracerebral ADSC transplantation on AD pathology and spatial learning/memory of APP/PS1 double transgenic AD model mice. Results showed that ADSC transplantation dramatically reduced β-amyloid (Aβ) peptide deposition and significantly restored the learning/memory function in APP/PS1 transgenic mice. It was observed that in both regions of the hippocampus and the cortex there were more activated microglia, which preferentially surrounded and infiltrated into plaques after ADSC transplantation. The activated microglia exhibited an alternatively activated phenotype, as indicated by their decreased expression levels of proinflammatory factors and elevated expression levels of alternative activation markers, as well as Aβ-degrading enzymes. In conclusion, ADSC transplantation could modulate microglial activation in AD mice, mitigate AD symptoms, and alleviate cognitive decline, all of which suggest ADSC transplantation as a promising choice for AD therapy. This manuscript is published as part of the International Association of Neurorestoratology (IANR) supplement issue of Cell Transplantation.

Chronically active: activation of microglial proteolysis in ageing and neurodegeneration

One of the microglial cell functions is the removal of modified extracellular proteins in the brain. The connection between protein oxidation, proteolysis, and microglial activation is the topic of this review. The effect of various activation agents on microglial cells with regard to changes in substrate uptake, proteolytic capacity and degradation efficiency of different types of oxidized protein materials is reviewed. It is shown that different activation stimuli initiate substrate-specific modulation for uptake and proteolysis, influencing an array of factors including receptor expression, lysosomal pH, and proteasome subunit composition. Age-related alterations in activation and proteolytic capacity in microglial cells are also discussed. In ageing, proteolytic effectiveness is diminished, while microglial cells are chronically activated and lose the oxidative burst ability, possibly supporting a 'vicious circle' of macrophage-induced neurodegeneration.

Immune marker CD68 correlates with cognitive impairment in normally aged rats

The relationship between heightened neuroinflammation and cognitive decline in the normally aged brain is still debatable, as most data are derived from insult-related models. Accordingly, the aim of the current study was to determine whether a link could be established for 2 immune markers at the post-transcriptional level; CD68 and MHC-II, in a normally aged (24-month-old) rat population discriminated for their learning abilities. Using the Morris Water Maze (MWM) task, aged rats were divided into aged learning-impaired (AI) or -unimpaired (AU) groups. Western immunoblots of hippocampal tissue revealed a significant increase of CD68 in AI rats compared to the AU group. Moreover, up-regulated CD68 expression correlated with increased latency times in the MWM task. Immunofluorescence for CD68 revealed intense staining in the white matter regions and CA3 subregion of the hippocampus in the AI group. Despite expression of MHC-II in the AI group, no correlation was found. Overall, these data suggest that CD68 could play a role associated with cognitive decline in a subgroup of the normally aged population.

Regionally distinct responses of microglia and glial progenitor cells to whole brain irradiation in adult and aging rats

Radiation therapy has proven efficacy for treating brain tumors and metastases. Higher doses and larger treatment fields increase the probability of eliminating neoplasms and preventing reoccurrence, but dose and field are limited by damage to normal tissues. Normal tissue injury is greatest during development and in populations of proliferating cells but also occurs in adults and older individuals and in non-proliferative cell populations. To better understand radiation-induced normal tissue injury and how it may be affected by aging, we exposed young adult, middle-aged, and old rats to 10 Gy of whole brain irradiation and assessed in gray- and white matter the responses of microglia, the primary cellular mediators of radiation-induced neuroinflammation, and oligodendrocyte precursor cells, the largest population of proliferating cells in the adult brain. We found that aging and/or irradiation caused only a few microglia to transition to the classically “activated” phenotype, e.g., enlarged cell body, few processes, and markers of phagocytosis, that is seen following more damaging neural insults. Microglial changes in response to aging and irradiation were relatively modest and three markers of reactivity - morphology, proliferation, and expression of the lysosomal marker CD68- were regulated largely independently within individual cells. Proliferation of oligodendrocyte precursors did not appear to be altered during normal aging but increased following irradiation. The impacts of irradiation and aging on both microglia and oligodendrocyte precursors were heterogeneous between white- and gray matter and among regions of gray matter, indicating that there are regional regulators of the neural response to brain irradiation. By several measures, the CA3 region of the hippocampus appeared to be differentially sensitive to effects of aging and irradiation. The changes assessed here likely contribute to injury following inflammatory challenges like brain irradiation and represent important end-points for analysis in studies of therapeutic strategies to protect patients from neural dysfunction.

Animal model of autism induced by prenatal exposure to valproate: altered glutamate metabolism in the hippocampus

Autism spectrum disorders (ASD) are characterized by deficits in social interaction, language and communication impairments and repetitive and stereotyped behaviors, with involvement of several areas of the central nervous system (CNS), including hippocampus. Although neurons have been the target of most studies reported in the literature, recently, considerable attention has been centered upon the functionality and plasticity of glial cells, particularly astrocytes. These cells participate in normal brain development and also in neuropathological processes. The present work investigated hippocampi from 15 (P15) and 120 (P120) days old male rats prenatally exposed to valproic acid (VPA) as an animal model of autism. Herein, we analyzed astrocytic parameters such as glutamate transporters and glutamate uptake, glutamine synthetase (GS) activity and glutathione (GSH) content. In the VPA group glutamate uptake was unchanged at P15 and increased 160% at P120; the protein expression of GLAST did not change neither in P15 nor in P120, while GLT1 decreased 40% at P15 and increased 92% at P120; GS activity increased 43% at P15 and decreased 28% at P120; GSH content was unaltered at P15 and had a 27% increase at P120. These data highlight that the astrocytic clearance and destination of glutamate in the synaptic cleft might be altered in autism, pointing out important aspects to be considered from both pathophysiologic and pharmacological approaches in ASD.

The Relation between Inflammation and Neuropsychological Test Performance

Background. Considerable research documents an association between pro- and anti-inflammatory markers and Alzheimer's disease (AD), yet the differential relation between these markers and neuropsychological functioning in AD and nondemented controls has received less attention. The current study sought to evaluate the relationship between peripheral markers of inflammation (both pro- and anti-inflammatory) and neuropsychological functioning through the Texas Alzheimer's Research and Care Consortium (TARCC) cohort. Methods. There were 320 participants (Probable AD n = 124, Controls n = 196) in the TARCC Longitudinal Research Cohort available for analysis. Regression analyses were utilized to examine the relation between proinflammatory and anti-inflammatory markers and neuropsychological functioning. Follow-up analyses were conducted separately by case versus control status. Results. Proinflammatory and anti-inflammatory markers were found to be associated with neuropsychological testing. Third tertile proinflammatory markers were negatively associated with measures of attention and language, and anti-inflammatory markers were positively associated with measures of immediate verbal memory and delayed verbal and visual memory. Conclusions. These findings support the link between peripheral inflammatory markers and neuropsychological functioning and suggest the utility of examining profiles of inflammatory markers in the future.

Oxidative stress and epilepsy: literature review

Backgrounds. The production of free radicals has a role in the regulation of biological function, cellular damage, and the pathogenesis of central nervous system conditions. Epilepsy is a highly prevalent serious brain disorder, and oxidative stress is regarded as a possible mechanism involved in epileptogenesis. Experimental studies suggest that oxidative stress is a contributing factor to the onset and evolution of epilepsy. Objective. A review was conducted to investigate the link between oxidative stress and seizures, and oxidative stress and age as risk factors for epilepsy. The role of oxidative stress in seizure induction and propagation is also discussed. Results/Conclusions. Oxidative stress and mitochondrial dysfunction are involved in neuronal death and seizures. There is evidence that suggests that antioxidant therapy may reduce lesions induced by oxidative free radicals in some animal seizure models. Studies have demonstrated that mitochondrial dysfunction is associated with chronic oxidative stress and may have an essential role in the epileptogenesis process; however, few studies have shown an established link between oxidative stress, seizures, and age.

Long term adequate n-3 polyunsaturated fatty acid diet protects from depressive-like behavior but not from working memory disruption and brain cytokine expression in aged mice

Converging epidemiological studies suggest that dietary essential n-3 polyunsaturated fatty acid (PUFA) are likely to be involved in the pathogenesis of mood and cognitive disorders linked to aging. The question arises as to whether the decreased prevalence of these symptoms in the elderly with high n-3 PUFA consumption is also associated with improved central inflammation, i.e. cytokine activation, in the brain. To answer this, we measured memory performance and emotional behavior as well as cytokine synthesis and PUFA level in the spleen and the cortex of adult and aged mice submitted to a diet with an adequate supply of n-3 PUFA in form of α-linolenic acid (α-LNA) or a n-3 deficient diet. Our results show that docosahexaenoic acid (DHA), the main n-3 PUFA in the brain, was higher in the spleen and cortex of n-3 adequate mice relative to n-3 deficient mice and this difference was maintained throughout life. Interestingly, high level of brain DHA was associated with a decrease in depressive-like symptoms throughout aging. On the opposite, spatial memory was maintained in adult but not in aged n-3 adequate mice relative to n-3 deficient mice. Furthermore, increased interleukin-6 (IL-6) and decreased IL-10 expression were found in the cortex of aged mice independently of the diets. All together, our results suggest that n-3 PUFA dietary supply in the form of α-LNA is sufficient to protect from deficits in emotional behavior but not from memory disruption and brain proinflammatory cytokine expression linked to age.

Developmental lead effects on behavior and brain gene expression in male and female BALB/cAnNTac mice

Lead (Pb) was one of the first poisons identified, and the developing nervous system is particularly vulnerable to its toxic effects. Relatively low, subclinical doses, of Pb that produce no overt signs of encephalopathy can affect cognitive, emotional, and motor functions. In the present study, the effects of developmental Pb-exposure on behavioral performance and gene expression in BALB/cAnNTac mice were evaluated. Pups were exposed to Pb from gestational-day (gd) 8 to postnatal-day (pnd) 21 and later evaluated in exploratory behavior, rotarod, Morris water maze, and resident-intruder assays as adults. Pb-exposure caused significant alterations in exploratory behavior and water maze performance during the probe trial, but rotarod performance was not affected. Pb-exposed males displayed violent behavior towards their cage mates, but not to a stranger in the resident-intruder assay. Gene expression analysis at pnd21 by microarray and qRT-PCR was performed to provide a molecular link to the behavior changes that were observed. Pb strongly up-regulated gene expression within the signaling pathways of mitogen activated protein kinases (MAPKs), extra-cellular matrix (ECM) receptor, focal adhesion, and vascular endothelial growth-factor (VEGF), but Pb down-regulated gene expression within the pathways for glycan structures-biosynthesis 1, purine metabolism, and N-glycan biosynthesis. Pb increased transcription of genes for major histocompatibility (MHC) proteins, the chemokine Ccl28, chemokine receptors, IL-7, IL7R, and proteases. The qRT-PCR analysis indicated an increase of gene expression in the whole brain for caspase 1 and NOS2. Analysis of IL-1β, caspase 1, NOS2, Trail, IL-18 and IL-33 gene expression of brain regions indicated that Pb perturbed the inter-regional expression pattern of pro-inflammatory genes. Brain region protein concentrations for IL-10, an anti-inflammatory cytokine, showed a significant decrease only within the cortex region. Results indicate that Pb differentially affects the behavior of male and female mice in that females did less exploration and the males were selectively more aggressive. Gene expression data pointed to evidence of neuroinflammation in the brain of both female and male mice. Pb had more of an effect in the males on expression of vomeronasal receptor genes associated with odor detection and social behavior.

[Lifestyle and cognition: what do we know from the aging and neurodegenerative brain?]

Epidemiological studies demonstrated positive effects of continuous physical activity and balanced diet on cardiovascular fitness. In chronic neurodegenerative disorders, e.g. Parkinson's disease and Alzheimer's disease, physical activity has become a successful supportive symptomatic therapy. However, it has become evident that physical activity not only improves motor symptoms but also has high impact on cognition in both (elderly) healthy brain and neurodegenerative alterations in the CNS. Nutrition also has been reported to exert positive effects on brain function.Animal studies indicate an increased endogenous plasticity as the underlying mechanism in terms of activation of neuronal precursor cells in different brain areas, leading to improved brain function.First experimental studies in humans also show that physical activity and balanced nutrition increase the release of neurotrophic factors in the brain, increase the volume of grey matter in learning- and memory-associated brain regions and improve cognitive function. This phenomenon opens up noninvasive causal therapeutic options in neurodegenerative disorders and during aging-associated cognitive decline by inducing changes in lifestyle. This option could provide a socioeconomically and ethically reasonable treatment for neurodegenerative disorders.The presented article summarizes the current knowledge from animal experiments and studies in humans. It provides an overview of potential cellular and molecular candidate mechanisms and discusses novel translational clinical studies and first clinical applications.

Age-dependent changes in the cerebrospinal fluid proteome by slow off-rate modified aptamer array

An important precondition for the successful development of diagnostic assays of cerebrospinal fluid (CSF) biomarkers of age-related neurodegenerative diseases is an understanding of the dynamic nature of the CSF proteome during the normal aging process. In this study, a novel proteomic technology was used to quantify hundreds of proteins simultaneously in the CSF from 90 cognitively normal adults 21 to 85 years of age. SomaLogic's highly multiplexed proteomic platform can measure more than 800 proteins simultaneously from small volumes of biological fluids using novel slow off-rate modified aptamer (SOMAmer) protein affinity reagents with sensitivity, specificity, and dynamic ranges that meet or exceed those of enzyme-linked immunosorbent assays. In the first application of this technology to CSF, we detected 248 proteins that possessed signals greater than twofold over background. Several novel correlations between detected protein concentrations and age were discovered that indicate that both inflammation and response to injury in the central nervous system may increase with age. Applying this powerful proteomic approach to CSF provides potential new insight into the aging of the human central nervous system that may have utility in discovering new disease-related changes in the CSF proteome.

Effect of growth hormone and melatonin on the brain: from molecular mechanisms to structural changes

Aging of the brain causes important reductions in quality of life and has wide socio-economic consequences. An increase in oxidative stress, and the associated inflammation and apoptosis, could be responsible for the pathogenesis of aging associated brain lesions. Melatonin has neuroprotective effects, by limiting the negative effects of oxygen and nitrogen free radicals. Growth hormone (GH) might exert additional neuro-protective and or neurogenic effects on the brain. The molecular mechanisms of the protective effects of GH and melatonin on the aging brain have been investigated in young and old Wistar rats. A reduction in the total number of neurons in the hilus of the dentate gyrus was evident at 24 months of age and was associated with a significant increase in inflammation markers as well as in pro-apoptotic parameters, confirming the role of apoptosis in its reduction. Melatonin treatment was able to enhance neurogenesis in old rats without modification of the total number of neurons, whereas GH treatment increased the total number of neurons without enhancing neurogenesis. Both GH and melatonin were able to reduce inflammation and apoptosis in the hippocampus. In conclusion, neuroprotective effects demonstrated by GH and melatonin in the hippocampus were exerted by decreasing inflammation and apoptosis.

Neuroinflammation and the plasticity-related immediate-early gene Arc

Neurons exist within a microenvironment that significantly influences their function and survival. While there are many environmental factors that can potentially impact neuronal function, activation of the innate immune system (microglia) is an important element common to many neurological and pathological conditions associated with memory loss. Learning and memory processes rely on the ability of neurons to alter their transcriptional programs in response to synaptic input. Recent advances in cell-based imaging of plasticity-related immediate-early gene (IEG) expression have provided a tool to investigate plasticity-related changes across multiple brain regions. The activity-regulated, cytoskeleton-associated IEG Arc is a regulator of protein synthesis-dependent forms of synaptic plasticity, which are essential for memory formation. Visualisation of Arc provides cellular level resolution for the mapping of neuronal networks. Chronic activation of the innate immune system alters Arc activity patterns, and this may be a mechanism by which it induces the cognitive dysfunction frequently associated with neuroinflammatory conditions. This review discusses the use of Arc expression during activation of the innate immune system as a valid marker of altered plasticity and a predictor of cognitive dysfunction.

Enhanced IL-1beta production in response to the activation of hippocampal glial cells impairs neurogenesis in aged mice

A variety of mechanisms that contribute to the accumulation of age-related damage and the resulting brain dysfunction have been identified. Recently, decreased neurogenesis in the hippocampus has been recognized as one of the mechanisms of age-related brain dysfunction. However, the molecular mechanism of decreased neurogenesis with aging is still unclear. In the present study, we investigated whether aging decreases neurogenesis accompanied by the activation of microglia and astrocytes, which increases the expression of IL-1beta in the hippocampus, and whether in vitro treatment with IL-1beta in neural stem cells directly impairs neurogenesis. Ionized calcium-binding adaptor molecule 1 (Iba1)-positive microglia and glial fibrillary acidic protein (GFAP)-positive astrocytes were increased in the dentate gyrus of the hippocampus of 28-month-old mice. Furthermore, the mRNA level of IL-1beta was significantly increased without related histone modifications. Moreover, a significant increase in lysine 9 on histone H3 (H3K9) trimethylation at the promoter of NeuroD (a neural progenitor cell marker) was observed in the hippocampus of aged mice. In vitro treatment with IL-1beta in neural stem cells prepared from whole brain of E14.5 mice significantly increased H3K9 trimethylation at the NeuroD promoter. These findings suggest that aging may decrease hippocampal neurogenesis via epigenetic modifications accompanied by the activation of microglia and astrocytes with the increased expression of IL-1beta in the hippocampus.

Glial transcripts and immune-challenged glia in the suprachiasmatic nucleus of young and aged mice

Biological rhythms are frequently disturbed with advancing age, and aging-related changes of glia in the hypothalamic suprachiasmatic nucleus (SCN), the master circadian pacemaker, require special attention. In particular, astrocytes contribute to SCN function, and aging is associated with increased inflammatory activity in the brain, in which microglia could be especially implicated. On this basis, we investigated in the SCN of young and old mice glial transcripts and cell features, and the glial cell response to a central inflammatory challenge. Quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR) was used to analyze the expression of mRNAs encoding the astrocytic glial fibrillary acidic protein and the microglial antigen CD11b. Both these transcripts, here investigated in the SCN for the first time, were significantly increased in the old SCN. Glial cell phenotyping with immunohistochemistry revealed hypertrophic and intensely stained astrocytes and microglia in the aged SCN. In both age groups, microglia were scattered throughout the SCN and astrocytes were prominent in the ventral portion, where retinal fibers are densest; in the aged SCN, astrocytes were also numerous in the dorsal portion. After intracerebroventricular injections of a mixture of interferon-gamma and tumor necrosis factor-alpha, or phosphate-buffered saline as control, immunolabeling was evaluated with stereological cell counts and confocal microscopy. Phenotypic features of astrocyte and microglia activation in response to cytokine injections were markedly enhanced in the aged SCN. Subregional variations in glial cell density were also documented in the aged compared to the young SCN. Altogether, the findings show increases in the expression of glial transcripts and hypertrophy of astrocytes and microglia in the aged SCN, as well as age-dependent variation in the responses of immune-challenged SCN glia. The data thus point out an involvement of glia in aging-related changes of the biological clock.

Successful Aging: Focus on Cognitive and Emotional Health

We review the definitions, predictors, and biobehavioral determinants of successful aging, as well as the evidence for and mechanisms of underlying selected interventions to enhance cognitive and emotional health in older adults. Defining successful aging has proven difficult, with discrepancies seen among biomedical, psychological, and lay perspectives. Although consensus is lacking, a number of studies have examined the genetic, lifestyle, and social determinants of operationalized determinants of successful aging; qualitative examinations of the meaning of the construct have also been conducted. The determinants coincide with fundamental aspects of aging. Recent clinical trials suggest that caloric restriction, physical activity, cognitive intervention, stress reduction, and social programs may enhance cognitive and emotional health in older people.