Oxidative DNA damage in peripheral leukocytes of mild cognitive impairment and AD patients

Novel Techniques for Mapping DNA Damage and Repair in the Brain

DNA damage in the brain is influenced by endogenous processes and metabolism along with exogenous exposures. Accumulation of DNA damage in the brain can contribute to various neurological disorders, including neurodegenerative diseases and neuropsychiatric disorders. Traditional methods for assessing DNA damage in the brain, such as immunohistochemistry and mass spectrometry, have provided valuable insights but are limited by their inability to map specific DNA adducts and regional distributions within the brain or genome. Recent advancements in DNA damage detection methods offer new opportunities to address these limitations and further our understanding of DNA damage and repair in the brain. Here, we review emerging techniques offering more precise and sensitive ways to detect and quantify DNA lesions in the brain or neural cells. We highlight the advancements and applications of these techniques and discuss their potential for determining the role of DNA damage in neurological disease.

Role of Oxidative Stress, Methionine Oxidation and Methionine Sulfoxide Reductases (MSR) in Alzheimer's Disease

A major contributor to dementia seen in aging is Alzheimer's disease (AD). Amyloid beta (Aβ), a main component of senile plaques (SPs) in AD, induces neuronal death through damage to cellular organelles and structures, caused by oxidation of important molecules such as proteins by reactive oxygen species (ROS). Hyperphosphorylation and accumulation of the protein tau in the microtubules within the brain also promote ROS production. Methionine, a residue of proteins, is particularly sensitive to oxidation by ROS. One of the enzyme systems that reverses the oxidative damage in mammalian cells is the enzyme system known as Methionine Sulfoxide Reductases (MSRs). The components of the MSR system, namely MSRA and MSRB, reduce oxidized forms of methionine (Met-(o)) in proteins back to methionine (Met). Furthermore, the MSRs scavenge ROS by allowing methionine residues in proteins to utilize their antioxidant properties. This review aims to improve the understanding of the role of the MSR system of enzymes in reducing cellular oxidative damage and AD pathogenesis, which may contribute to effective therapeutic approaches for AD by targeting the MSR system.

Redox dysregulation as a driver for DNA damage and its relationship to neurodegenerative diseases

Redox homeostasis refers to the balance between the production of reactive oxygen species (ROS) as well as reactive nitrogen species (RNS), and their elimination by antioxidants. It is linked to all important cellular activities and oxidative stress is a result of imbalance between pro-oxidants and antioxidant species. Oxidative stress perturbs many cellular activities, including processes that maintain the integrity of DNA. Nucleic acids are highly reactive and therefore particularly susceptible to damage. The DNA damage response detects and repairs these DNA lesions. Efficient DNA repair processes are therefore essential for maintaining cellular viability, but they decline considerably during aging. DNA damage and deficiencies in DNA repair are increasingly described in age-related neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and Huntington's disease. Furthermore, oxidative stress has long been associated with these conditions. Moreover, both redox dysregulation and DNA damage increase significantly during aging, which is the biggest risk factor for neurodegenerative diseases. However, the links between redox dysfunction and DNA damage, and their joint contributions to pathophysiology in these conditions, are only just emerging. This review will discuss these associations and address the increasing evidence for redox dysregulation as an important and major source of DNA damage in neurodegenerative disorders. Understanding these connections may facilitate a better understanding of disease mechanisms, and ultimately lead to the design of better therapeutic strategies based on preventing both redox dysregulation and DNA damage.

Moschus exerted protective activity against H2O2-induced cell injury in PC12 cells through regulating Nrf-2/ARE signaling pathways

The pivotal characteristics of Alzheimer's disease (AD) are irreversible memory loss and progressive cognitive decline, eventually causing death from brain failure. In the various proposed hypotheses of AD, oxidative stress is also regarded as a symbolic pathophysiologic cascade contributing to brain diseases. Using Chinese herbal medicine may be beneficial for treating and preventing AD. As a rare and valuable animal medicine, Moschus possesses antioxidant and antiapoptotic efficacy and is extensively applied for treating unconsciousness, stroke, coma, and cerebrovascular diseases. We aim to evaluate whether Moschus protects PC12 cells from hydrogen peroxide (H₂O₂)-induced cellular injury. The chemical constituents of Moschus are analyzed by GC-MS assay. The cell viability, reactive oxygen species (ROS) levels, mitochondrial membrane potential (MMP) levels, oxidative stress-related indicators, and apoptotic proteins are determined. Through GC-MS analysis, nineteen active contents were identified. The cell viability loss, lactate dehydrogenase releases, MMP levels, ROS productions, and Malondialdehyde (MDA) activities decreased, and BAX, Caspase-3, and Kelch-like ECH-associated protein 1 expression also significantly down-regulated and heme oxygenase 1, nuclear factor erythroid-2-related factor 2 (Nrf-2), and quinine oxidoreductase 1 expression upregulated after pretreatment of Moschus. The result indicated Moschus has neuroprotective activity in relieving H₂O₂-induced cellular damage, and the potential mechanism might be associated with regulating the Nrf-2/ARE signaling pathway. A more in-depth and comprehensive understanding of Moschus in the pathogenesis of AD will provide a fundamental basis for in vivo AD animal model research, which may be able to provide further insights and new targets for AD therapy.

Oxidative Stress and Aging as Risk Factors for Alzheimer's Disease and Parkinson's Disease: The Role of the Antioxidant Melatonin

Aging and neurodegenerative diseases share common hallmarks, including mitochondrial dysfunction and protein aggregation. Moreover, one of the major issues of the demographic crisis today is related to the progressive rise in costs for care and maintenance of the standard living condition of aged patients with neurodegenerative diseases. There is a divergence in the etiology of neurodegenerative diseases. Still, a disturbed endogenous pro-oxidants/antioxidants balance is considered the crucial detrimental factor that makes the brain vulnerable to aging and progressive neurodegeneration. The present review focuses on the complex relationships between oxidative stress, autophagy, and the two of the most frequent neurodegenerative diseases associated with aging, Alzheimer's disease (AD) and Parkinson's disease (PD). Most of the available data support the hypothesis that a disturbed antioxidant defense system is a prerequisite for developing pathogenesis and clinical symptoms of ADs and PD. Furthermore, the release of the endogenous hormone melatonin from the pineal gland progressively diminishes with aging, and people's susceptibility to these diseases increases with age. Elucidation of the underlying mechanisms involved in deleterious conditions predisposing to neurodegeneration in aging, including the diminished role of melatonin, is important for elaborating precise treatment strategies for the pathogenesis of AD and PD.

Association of Oxidative Stress-Induced Nucleic Acid Damage With Psychiatric Disorders in Adults: A Systematic Review and Meta-analysis

IMPORTANCE

Nucleic acid damage from oxidative stress (NA-OXS) may be a molecular mechanism driving the severely increased morbidity and mortality from somatic causes in adults with psychiatric disorders.

OBJECTIVE

To systematically retrieve and analyze data on NA-OXS across the psychiatric disorder diagnostic spectrum.

DATA SOURCES

The PubMed, Embase, and PsycINFO databases were searched from inception to November 16, 2021. A hand search of reference lists of relevant articles was also performed.

STUDY SELECTION

Key study inclusion criteria in this meta-analysis were as follows: adult human study population, measurement of any marker of DNA or RNA damage from oxidative stress, and either a (1) cross-sectional design comparing patients with psychiatric disorders (any diagnosis) with a control group or (2) prospective intervention. Two authors screened the studies, and 2 senior authors read the relevant articles in full and assessed them for eligibility.

DATA EXTRACTION AND SYNTHESIS

The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines were followed. Two authors performed data extraction independently, and a senior coauthor was consulted in cases of disagreement. Data were synthesized with random-effects and multilevel meta-analyses.

MAIN OUTCOMES AND MEASURES

The predefined hypothesis was that individuals with psychiatric disorders have increased NA-OXS levels. The main outcome was the standardized mean differences (SMDs) among patients and controls in nucleic acid oxidation markers compared across diagnostic groups. Analyses were divided into combinations of biological matrices and nucleic acids.

RESULTS

Eighty-two studies fulfilled the inclusion criteria, comprising 205 patient vs control group comparisons and a total of 10 151 patient and 10 532 control observations. Overall, the data showed that patients with psychiatric disorders had higher NA-OXS levels vs controls across matrices and molecules. Pooled effect sizes ranged from moderate for urinary DNA markers (SMD = 0.44 [95% CI, 0.20-0.68]; P < .001) to very large for blood cell DNA markers (SMD = 1.12 [95% CI, 0.69-1.55; P < .001). Higher NA-OXS levels were observed among patients with dementias followed by psychotic and bipolar disorders. Sensitivity analyses excluding low-quality studies did not materially alter the results. Intervention studies were few and too heterogenous for meaningful meta-analysis.

CONCLUSIONS AND RELEVANCE

The results of this meta-analysis suggest that there is an association with increased NA-OXS levels in individuals across the psychiatric disorder diagnostic spectrum. NA-OXS may play a role in the somatic morbidity and mortality observed among individuals with psychiatric disorders.

DNA damage in dementia: Evidence from patients affected by severe Chronic Obstructive Pulmonary Disease (COPD) and meta-analysis of most recent literature

Oxidative stress that leads to oxidatively damaged DNA, plays a crucial role in chronic obstructive pulmonary disease (COPD) as well as in the onset of neurodegenerative diseases. The consequent genomic instability is the first neuropathological event found in the preclinical phase of cognitive impairment (CI), and the level of DNA damage is closely related to the degree of dementia. Since CI has been associated with COPD, we investigated the extent of DNA damage in isolated lymphocytes with the Comet assay, in a group of severe COPD patients with cognitive function measured by the Mini-Mental State Examination (MMSE). An increase in DNA damage was observed in COPD patients with dementia (MMSE≤24), although the difference was only borderline (22.4 ± 6.9 vs. 18.5 ± 7.1; p = 0.055). Meta-analysis, including the results of the current study, confirmed that patients with MMSE≤ 24 showed higher level of DNA damage than patients with MMSE> 24. We observed a significant reduction (p < 0.001) in the MMSE score in patients with cognitive decline in areas I (Orientation), III (Attention and Calculus) and V (Language). Only the temporal orientation category in area I was also associated with the level of oxidative damage, with higher levels of MDA (p < 0.01) and DNA damage (p < 0.03). Patients with the lowest temporal orientation score had a 12% higher mean DNA damage (Odds Ratio=1.12; 95% confidence interval (95%CI) 1.01-1.25; p < 0.036). Temporal orientation is a component of most screening tests for the diagnosis of cognitive impairment, on the bases that disorientation is a common factor in dementia. Present results show that each component of cognitive decline can have a different etiopathogenesis and clinical relevance. A more thorough assessment of the cognitive functions of patients starting COPD rehabilitation, together with the assessment of DNA and the level of oxidative stress, can provide essential information to adapt and customize the rehabilitation project.

Mitochondrial DNA oxidative mutations are elevated in Mexican American women potentially implicating Alzheimer's disease

Mexican Americans (MAs) are the fastest-growing Hispanic population segment in the US; as this population increases in age, so will the societal burden of age-related diseases such as Alzheimer's disease (AD). Mitochondrial DNA (mtDNA) damage may be implicated in MA AD risk since metabolic comorbidities are more prevalent in this group. Oxidative damage to guanosine (8oxoG) is one of the most prevalent DNA lesions and a putative indicator of mitochondrial dysfunction. Testing blood samples from participants of the Texas Alzheimer's Research and Care Consortium, we found mtDNA 8oxoG mutational load to be significantly higher in MAs compared to non-Hispanic whites and that MA females are differentially affected. Furthermore, we identified specific mtDNA haplotypes that confer increased risk for oxidative damage and suggestive evidence that cognitive function may be related to 8oxoG burden. Our understanding of these phenomena will elucidate population- and sex-specific mechanisms of AD pathogenesis, informing the development of more precise interventions and therapeutic approaches for MAs with AD in the future.

Sleep deficiency as a driver of cellular stress and damage in neurological disorders

Neurological disorders encompass an extremely broad range of conditions, including those that present early in development and those that progress slowly or manifest with advanced age. Although these disorders have distinct underlying etiologies, the activation of shared pathways, e.g., integrated stress response (ISR) and the development of shared phenotypes (sleep deficits) may offer clues toward understanding some of the mechanistic underpinnings of neurologic dysfunction. While it is incontrovertibly complex, the relationship between sleep and persistent stress in the brain has broad implications in understanding neurological disorders from development to degeneration. The convergent nature of the ISR could be a common thread linking genetically distinct neurological disorders through the dysregulation of a core cellular homeostasis pathway.

Investigating Pathogenetic Mechanisms of Alzheimer's Disease by Systems Biology Approaches for Drug Discovery

Alzheimer's disease (AD) is the most common cause of dementia, characterized by progressive cognitive decline and neurodegenerative disorder. Abnormal aggregations of intracellular neurofibrillary tangles (NFTs) and unusual accumulations of extracellular amyloid-β (Aβ) peptides are two important pathological features in AD brains. However, in spite of large-scale clinical studies and computational simulations, the molecular mechanisms of AD development and progression are still unclear. In this study, we divided all of the samples into two groups: early stage (Braak score I-III) and later stage (Braak score IV-VI). By big database mining, the candidate genetic and epigenetic networks (GEN) have been constructed. In order to find out the real GENs for two stages of AD, we performed systems identification and system order detection scheme to prune false positives with the help of corresponding microarray data. Applying the principal network projection (PNP) method, core GENs were extracted from real GENs based on the projection values. By the annotation of KEGG pathway, we could obtain core pathways from core GENs and investigate pathogenetic mechanisms for the early and later stage of AD, respectively. Consequently, according to pathogenetic mechanisms, several potential biomarkers are identified as drug targets for multiple-molecule drug design in the treatment of AD.

Striatal oxidative damages and neuroinflammation correlate with progression and survival of Lewy body and Alzheimer diseases

Neurodegenerative diseases are a class of chronic and complex disorders featuring progressive loss of neurons in distinct brain areas. The mechanisms responsible for the disease progression in neurodegeneration are not fully illustrated. In this observational study, we have examined diverse biochemical parameters in the caudate and putamen of patients with Lewy body diseases (LBDs) and Alzheimer disease (AD), shedding some light on the involvement of oxidative damage and neuroinflammation in advanced neurodegeneration. We performed Spearman and Mantel-Cox analyses to investigate how oxidative stress and neuroinflammation exert comprehensive effects on disease progression and survival. Disease progression in LBDs correlated positively with poly (ADP-Ribose) and triggering receptors expressed on myeloid cell 2 levels in the striatum of LBD cohorts, indicating that potential parthanatos was a dominant feature of worsening disease progression and might contribute to switching microglial inflammatory phenotypes. Disease progression in AD corresponds negatively with 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxo-dG) and myeloperoxidase concentrations in the striatum, suggesting that possible mitochondria dysfunction may be involved in the progression of AD via a mechanism of β-amyloid entering the mitochondria and subsequent free radicals generation. Patients with lower striatal 8-oxo-dG and myeloperoxidase levels had a survival advantage in AD. The age of onset also affected disease progression. Tissue requests for the postmortem biochemistry, genetics, and autoradiography studies were approved by the Washington University Alzheimer’s Disease Research Center (ADRC) Biospecimens Committee (ethics approval reference number: T1705, approval date: August 6, 2019). Recombinant DNA and Hazardous Research Materials were approved by the Washington University Environmental Health & Safety Biological Safety Committee (approval code: 3739, approval date: February 25, 2020). Radioactive Material Authorization was approved by the Washington University Environmental Health & Safety Radiation Safety Committee (approval code: 1056, approval date: September 18, 2019).

A High Fat/Cholesterol Diet Recapitulates Some Alzheimer's Disease-Like Features in Mice: Focus on Hippocampal Mitochondrial Dysfunction

BACKGROUND

Ample evidence from clinical and pre-clinical studies suggests mid-life hypercholesterolemia as a risk factor for developing Alzheimer's disease (AD) at a later age. Hypercholesterolemia induced by dietary habits can lead to vascular perturbations that increase the risk of developing sporadic AD.

OBJECTIVE

To investigate the effects of a high fat/cholesterol diet (HFCD) as a risk factor for AD by using a rodent model of AD and its correspondent control (healthy animals).

METHODS

We compared the effect of a HFCD in normal mice (non-transgenic mice, NTg) and the triple transgenic mouse model of AD (3xTgAD). We evaluated cognitive performance in relation to changes in oxidative metabolism and neuron-derived nitric oxide (•NO) concentration dynamics in hippocampal slices as well as histochemical staining of markers of the neurovascular unit.

RESULTS

In NTg, the HFCD produced only moderate hypercholesterolemia but significant decline in spatial memory was observed. A tendency for decrease in •NO production was accompanied by compromised mitochondrial function with decrease in spare respiratory capacity. In 3xTgAD mice, a robust increase in plasma cholesterol levels with the HFCD did not worsen cognitive performance but did induce compromise of mitochondrial function and significantly decreased •NO production. We found increased staining of biomarkers for astrocyte endfeet and endothelial cells in 3xTgAD hippocampi, which was further increased by the HFCD.

CONCLUSION

A short term (8 weeks) intervention with HFCD can produce an AD-like phenotype even in the absence of overt systemic hypercholesterolemia and highlights mitochondrial dysfunction as a link between hypercholesterolemia and sporadic AD.

Role of Hydrazine-Related Chemicals in Cancer and Neurodegenerative Disease

Hydrazine-related chemicals (HRCs) with carcinogenic and neurotoxic potential are found in certain mushrooms and plants used for food and in products employed in various industries, including aerospace. Their propensity to induce DNA damage (mostly O⁶-, N⁷- and 8-oxo-guanine lesions) resulting in multiple downstream effects is linked with both cancer and neurological disease. For cycling cells, unrepaired DNA damage leads to mutation and uncontrolled mitosis. By contrast, postmitotic neurons attempt to re-enter the cell cycle but undergo apoptosis or nonapoptotic cell death. Biomarkers of exposure to HRCs can be used to explore whether these substances are risk factors for sporadic amyotrophic laterals sclerosis and other noninherited neurodegenerative diseases, which is the focus of this paper.

Linking Oxidative Stress and Proteinopathy in Alzheimer's Disease

Proteinopathy and excessive production of reactive oxygen species (ROS), which are the principal features observed in the Alzheimer’s disease (AD) brain, contribute to neuronal toxicity. β-amyloid and tau are the primary proteins responsible for the proteinopathy (amyloidopathy and tauopathy, respectively) in AD, which depends on ROS production; these aggregates can also generate ROS. These mechanisms work in concert and reinforce each other to drive the pathology observed in the aging brain, which primarily involves oxidative stress (OS). This, in turn, triggers neurodegeneration due to the subsequent loss of synapses and neurons. Understanding these interactions may thus aid in the identification of potential neuroprotective therapies that could be clinically useful. Here, we review the role of β-amyloid and tau in the activation of ROS production. We then further discuss how free radicals can influence structural changes in key toxic intermediates and describe the putative mechanisms by which OS and oligomers cause neuronal death.

One-carbon epigenetics and redox biology of neurodegeneration

One-carbon metabolism provides the methyl groups for both DNA and histone tail methylation reactions, two of the main epigenetic processes that tightly regulate the chromatin structure and gene expression levels. Several enzymes involved in one-carbon metabolism, as well as several epigenetic enzymes, are regulated by intracellular metabolites and redox cofactors, but their expression levels are in turn regulated by epigenetic modifications, in such a way that metabolism and gene expression reciprocally regulate each other to maintain homeostasis and regulate cell growth, survival, differentiation and response to environmental stimuli. Increasing evidence highlights the contribution of impaired one-carbon metabolism and epigenetic modifications in neurodegeneration. This article provides an overview of DNA and histone tail methylation changes in major neurodegenerative disorders, namely Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis, discussing the contribution of oxidative stress and impaired one-carbon and redox metabolism to their onset and progression.

Ameliorative Role of Nutraceuticals on Neurodegenerative Diseases Using the Drosophila melanogaster as a Discovery Model to Define Bioefficacy

Neurodegeneration is the destruction of neurons, and once the neurons degenerate they can't revive. This is one of the most concerned health conditions among aged population, more than ∼70% of the elderly people are suffering from neurodegeneration. Among all of the neurodegenerative diseases, Alzheimer's disease (AD), Parkinson's disease (PD) and Poly-glutamine disease (Poly-Q) are the major one and affecting most of the people around the world and posing excessive burden on the society. In order to understand this disease in non-human animal models it is pertinent to examine in model organism and various animal model are being used for such diseases like rat, mice and non-vertebrate model like Drosophila. Drosophila melanogaster is one of the best animal proven by several eminent scientist and had received several Nobel prizes for uncovering mechanism of human related genes and highly efficient model for studying neurodegenerative diseases due to its great affinity with human disease-related genes. Another factor is also employed to act as therapeutic or preventive method that is nutraceuticals. Nutraceuticals are functional natural compounds with antioxidant properties and had extensively showed the neuroprotective effect in different organisms. These nutraceuticals having antioxidant properties act through scavenging free radicals or by increasing endogenous cellular antioxidant defense molecules. For the best benefit, we are trying to utilize these nutraceuticals, which will have no or negligible side effects. In this review, we are dealing with various types of such nutraceuticals which have potent value in the prevention and curing of the diseases related to neurodegeneration.HighlightsNeurodegeneration is the silently progressing disease which shows its symptoms when it is well rooted.Many chemical drugs (almost all) have only symptomatic relief with side effects.Potent mechanism of neurodegeneration and improvement effect by nutraceuticals is proposed.Based on the Indian Cuisine scientists are trying to find the medicine from the food or food components having antioxidant properties.The best model to study the neurodegenerative diseases is Drosophila melanogaster.Many nutraceuticals having antioxidant properties have been studied and attenuated various diseases are discussed.

Strawberry (Fragaria ananassa duch.) Alba extract attenuates DNA damage in lymphocytes of patients with Alzheimer's disease

Increased levels of oxidative stress and oxidative DNA damage are common features in the pathology of Alzheimer's disease (AD) found in neurons and peripheral cells like peripheral blood lymphocytes (PBL). Natural products such as strawberry cultivar Alba are an important source of bioactive nutrients that could help in lowering both the oxidative stress and DNA damage levels. The objective was to estimate the effects of Alba extract on DNA damage in peripheral blood lymphocytes of sporadic AD (aged 60-84 years) patients, and healthy elderly (aged 69-83 years) and young (aged 21-30 years) individuals in in vitro conditions. Comet assay was used as a sensitive technique for the evaluation of PBL DNA damage levels. Reduction of basal DNA damage level in PBL was shown in the young group after the incubation with Alba extract ranging from 25 to 200 μg/ml, with 100 μg/ml being the most effective concentration. Selected Alba extract of 100 μg/ml was further used for PBL treatment of AD and healthy elderly age matched group, displaying potential to significantly attenuate DNA damage levels in both groups (p < .05). Alba extract displayed biological activity against oxidative DNA damage, suggesting that its functional ingredients may have beneficial health effects. PRACTICAL APPLICATIONS: The data obtained in this preliminary study displayed that strawberry Alba extract is efficient against DNA damage induced by endogenous and exogenous oxidative stress in peripheral blood lymphocytes of Alzheimer`s disease in vitro. An active area of future research of Alba cultivar should be to determine the trials in in vivo systems. Our findings also suggest that Alba cultivar's functional ingredients potentially may have beneficial health effects in AD.

Telomere length and 8-hydroxy-2-deoxyguanosine as markers for early prediction of Alzheimer disease

BACKGROUND

Becoming shorter by each cell division, telomere length (TL) is regarded as a marker of cellular aging. Relative TL (T/S) depends on the quantitation of telomere hexamer repeat copy number normalized to autosomal single-copy gene copy number. TL is influenced by several factors, including oxidative stress (OS) and inflammation. This study aimed to investigate the possible role of TL and OS as markers for Alzheimer's disease (AD).

MATERIALS AND METHODS

One hundred and eighty participants were categorized into three groups. Group 1: Included 60 patients with AD. Group II: included 60 age-matched nondemented subjects. Group III (pregeriatric group): included 60 healthy controls with their ages ranging between 30 and 60 years. TL was determined by the quantitative Real time-PCR method, plasma levels of 8-OHdG by enzyme-linked immunosorbent assay, and total antioxidant capacity (TAC) by colorimetery.

RESULTS

In comparison to the other two groups, patients with AD showed shortened TL, increased plasma 8-OHdG concentration, and decreased TAC. The sensitivity of T/S ratio to predict AD was 86.67%, whereas the specificity was 96.67%. The sensitivity of 8-OHdG to predict AD was 96.67%, whereas the specificity was 86.67%.

CONCLUSION

AD is associated with shortened TL and increased OS as manifested by decreased TAC and increased serum 8-OHdG. T/S and 8-OHdG could be used as early predictors for AD.

Evaluation of GammaH2AX in Buccal Cells as a Molecular Biomarker of DNA Damage in Alzheimer's Disease in the AIBL Study of Ageing

In response to double-stranded breaks (DSBs) in chromosomal DNA, H2AX (a member of histone H2A family) becomes phosphorylated to form γH2AX. Although increased levels of γH2AX have been reported in the neuronal nuclei of Alzheimer's disease (AD) patients, the understanding of γH2AX responses in buccal nuclei of individuals with mild cognitive impairment (MCI) and AD remain unexplored. In the current study, endogenous γH2AX was measured in buccal cell nuclei from MCI (n = 18) or AD (n = 16) patients and in healthy controls (n = 17) using laser scanning cytometry (LSC). The γH2AX level was significantly elevated in nuclei of the AD group compared to the MCI and control group, and there was a concomitant increase in P-trend for γH2AX from the control group through MCI to the AD group. Receiver-operating characteristic curves were carried out for different γH2AX parameters; γH2AX in nuclei resulted in the greatest area under the curve value of 0.7794 (p = 0.0062) with 75% sensitivity and 70% specificity for the identification of AD patients from control. In addition, nuclear circularity (a measure of irregular nuclear shape) was significantly higher in the buccal cell nuclei from the AD group compared with the MCI and control groups. Additionally, there was a positive correlation between the nuclear circularity and γH2AX signals. The results indicated that increased DNA damage is associated with AD.

Early Detection and Prevention of Alzheimer's Disease: Role of Oxidative Markers and Natural Antioxidants

Oxidative stress (OS) contributes to Alzheimer’s disease (AD) pathology. OS can be a result of increased reactive oxygen/nitrogen species, reduced antioxidants, oxidatively damaged molecules, and/or a combination of these factors. Scientific literature is scarce for the markers of OS-specific for detecting AD at an early stage. The first aim of the current review is to provide an overview of the potential OS markers in the brain, cerebrospinal fluid (CSF), blood and/or urine that can be used for early diagnosis of human AD. The reason for exploring OS markers is that the proposed antioxidant therapies against AD appear to start too late to be effective. The second aim is to evaluate the evidence for natural antioxidants currently proposed to prevent or treat AD symptoms. To address these two aims, we critically evaluated the studies on humans in which various OS markers for detecting AD at an early stage were presented. Non-invasive OS markers that can detect mild cognitive impairment (MCI) and AD at an early stage in humans with greater specificity and sensitivity are primarily related to lipid peroxidation. However, a combination of OS markers, family history, and other biochemical tests are needed to detect the disease early on. We also report that the long-term use of vitamins (vitamin E as in almonds) and polyphenol-rich foods (curcumin/curcuminoids of turmeric, ginkgo biloba, epigallocatechin-3-gallate in green tea) seem justified for ameliorating AD symptoms. Future research on humans is warranted to justify the use of natural antioxidants.

Molecular and cellular mechanisms underlying the pathogenesis of Alzheimer's disease

Alzheimer’s disease (AD) is the most common neurodegenerative disorder seen in age-dependent dementia. There is currently no effective treatment for AD, which may be attributed in part to lack of a clear underlying mechanism. Studies within the last few decades provide growing evidence for a central role of amyloid β (Aβ) and tau, as well as glial contributions to various molecular and cellular pathways in AD pathogenesis. Herein, we review recent progress with respect to Aβ- and tau-associated mechanisms, and discuss glial dysfunction in AD with emphasis on neuronal and glial receptors that mediate Aβ-induced toxicity. We also discuss other critical factors that may affect AD pathogenesis, including genetics, aging, variables related to environment, lifestyle habits, and describe the potential role of apolipoprotein E (APOE), viral and bacterial infection, sleep, and microbiota. Although we have gained much towards understanding various aspects underlying this devastating neurodegenerative disorder, greater commitment towards research in molecular mechanism, diagnostics and treatment will be needed in future AD research.

Molecular Insight into the Therapeutic Promise of Targeting APOE4 for Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease that causes chronic cognitive dysfunction. Most of the AD cases are late onset, and the apolipoprotein E (APOE) isoform is a key genetic risk factor. The APOE gene has 3 key alleles in humans including APOE2, APOE3, and APOE4. Among them, APOE4 is the most potent genetic risk factor for late-onset AD (LOAD), while APOE2 has a defensive effect. Research data suggest that APOE4 leads to the pathogenesis of AD through various processes such as accelerated beta-amyloid aggregations that raised neurofibrillary tangle formation, cerebrovascular diseases, aggravated neuroinflammation, and synaptic loss. However, the precise mode of actions regarding in what way APOE4 leads to AD pathology remains unclear. Since APOE contributes to several pathological pathways of AD, targeting APOE4 might serve as a promising strategy for the development of novel drugs to combat AD. In this review, we focus on the recent studies about APOE4-targeted therapeutic strategies that have been advanced in animal models and are being prepared for use in humans for the management of AD.

The Role of Sex and Sex Hormones in Neurodegenerative Diseases

Neurodegenerative diseases (NDs) are a wide class of disorders of the central nervous system (CNS) with unknown etiology. Several factors were hypothesized to be involved in the pathogenesis of these diseases, including genetic and environmental factors. Many of these diseases show a sex prevalence and sex steroids were shown to have a role in the progression of specific forms of neurodegeneration. Estrogens were reported to be neuroprotective through their action on cognate nuclear and membrane receptors, while adverse effects of male hormones have been described on neuronal cells, although some data also suggest neuroprotective activities. The response of the CNS to sex steroids is a complex and integrated process that depends on (i) the type and amount of the cognate steroid receptor and (ii) the target cell type-either neurons, glia, or microglia. Moreover, the levels of sex steroids in the CNS fluctuate due to gonadal activities and to local metabolism and synthesis. Importantly, biochemical processes involved in the pathogenesis of NDs are increasingly being recognized as different between the two sexes and as influenced by sex steroids. The aim of this review is to present current state-of-the-art understanding on the potential role of sex steroids and their receptors on the onset and progression of major neurodegenerative disorders, namely, Alzheimer's disease, Parkinson's diseases, amyotrophic lateral sclerosis, and the peculiar motoneuron disease spinal and bulbar muscular atrophy, in which hormonal therapy is potentially useful as disease modifier.

Prevention of Cognitive Decline in Alzheimer's Disease by Novel Antioxidative Supplements

Oxidative stress plays a crucial role in Alzheimer’s disease (AD) from its prodromal stage of mild cognitive impairment. There is an interplay between oxidative stress and the amyloid β (Aβ) cascade via various mechanisms including mitochondrial dysfunction, lipid peroxidation, protein oxidation, glycoxidation, deoxyribonucleotide acid damage, altered antioxidant defense, impaired amyloid clearance, inflammation and chronic cerebral hypoperfusion. Based on findings that indicate that oxidative stress plays a major role in AD, oxidative stress has been considered as a therapeutic target of AD. In spite of favorable preclinical study outcomes, previous antioxidative components, including a single antioxidative supplement such as vitamin C, vitamin E or their mixtures, did not clearly show any therapeutic effect on cognitive decline in AD. However, novel antioxidative supplements can be beneficial for AD patients. In this review, we summarize the interplay between oxidative stress and the Aβ cascade, and introduce novel antioxidative supplements expected to prevent cognitive decline in AD.

Oxidative Stress and Dementia in Alzheimer's Patients: Effects of Synbiotic Supplementation

BACKGROUND

Alzheimer's disease (AD) is the most common cause of dementia in elderly patients. Recently, several studies have shown that inflammation and oxidative stress precede the cardinal neuropathological manifestations of AD. In view of the proven antioxidant effects of probiotics, we proposed that continuous dietary supplementation with milk fermented with kefir grains might improve cognitive and metabolic and/or cellular disorders in the AD patients.

METHODS

This study was designed as an uncontrolled clinical investigation to test the effects of probiotic-fermented milk supplementation (2 mL/kg/daily) for 90 days in AD patients exhibiting cognitive deficit. Cognitive assessment, cytokine expression, systemic oxidative stress levels, and blood cell damage biomarkers were evaluated before (T0) and after (T90) kefir synbiotic supplementation.

RESULTS

When the patients were challenged to solve 8 classical tests, the majority exhibit a marked improvement in memory, visual-spatial/abstraction abilities, and executive/language functions. At the end of the treatment, the cytometric analysis showed an absolute/relative decrease in several cytokine markers of inflammation and oxidative stress markers (·O2 -, H2O2, and ONOO-, ~30%) accompanied by an increase in NO bioavailability (100%). In agreement with the above findings by using the same technique, we observed in a similar magnitude an improvement of serum protein oxidation, mitochondrial dysfunction, DNA damage/repair, and apoptosis.

CONCLUSION

In conclusion, we demonstrated that kefir improves cognitive deficits, which seems to be linked with three important factors of the AD-systemic inflammation, oxidative stress, and blood cell damage-and may be a promising adjuvant therapy against the AD progression.

Oxidative Damage of DNA as Early Marker of Alzheimer's Disease

Alzheimer’s Disease (AD) is the most common cause of dementia, and its characteristic histopathological hallmarks are neurofibrillary tangles and senile plaques. Among involved mechanisms, oxidative stress plays an important role in damaging cell components (e.g., proteins, nucleic acids). In this study, different oxidized products of proteins and DNA were determined in the urine samples from mild cognitive impairment due to AD patients (n = 53) and healthy controls (n = 27) by means of ultra-performance liquid chromatography-tandem mass spectrometry analysis. A multivariate model developed by partial least squares generated a diagnostic model for AD with an AUC-ROC (area under the curve-receiver operating characteristic) of 0.843. From the studied analytes, 8-OHdG (8-hydroxy-2’-deoxyguanosine) and the ratio 8-OHdG/2dG (2’-deoxyguanosine) were able to distinguish between AD and healthy participants, showing statistically significant differences between groups, postulating DNA oxidation as a molecular pathway involved in early AD.

Changes in Expression Profiles Revealed by Transcriptomic Analysis in Peripheral Blood Mononuclear Cells of Alzheimer's Disease Patients

Alzheimer's disease (AD) is an age-related neurodegenerative pathology associated with accumulation of DNA damage. Inflammation and cell cycle alterations seem to be implicated in the pathogenesis of AD, although the molecular mechanisms have not been thoroughly elucidated to date. The aim of the present study was to evaluate whether peripheral blood mononuclear cells (PBMCs) of AD patients display alterations in gene expression profiles, focusing on finding markers that might improve the diagnosis of AD. Blood samples were collected from 22 AD patients and 13 healthy individuals to perform genome-wide mRNA expression. We found 593 differentially expressed genes in AD compared to controls, from which 428 were upregulated, and 165 were downregulated. By performing a gene set enrichment analysis, we observed pathways involved in inflammation, DNA damage response, cell cycle, and neuronal processes. Moreover, functional annotation analyses indicated that differentially expressed genes are strongly related to pathways associated with the cell cycle and the immune system. The results were compared with those of an independent study on hippocampus samples, and a number of genes in common between both studies were identified as potential peripheral biomarkers for AD, including DUSP1, FOS, SLC7A2, RGS1, GFAP, CCL2, ANGPTL4, and SSPN. Taken together, our results demonstrate that PBMCs of AD patients do present alterations in gene expression profiles, and these results are comparable to those previously reported in the literature for AD neurons, supporting the hypothesis that blood peripheral mononuclear cells express molecular changes that occur in the neurons of AD patients.

Association of multiple candidate genes with mild cognitive impairment in an elderly Chinese Uygur population in Xinjiang

BACKGROUND

Mild cognitive impairment (MCI) is a high-risk factor for Alzheimer's disease (AD). In the present study, we investigated the association of genetic polymorphisms of five genes (8-oxoguanine DNA glycosylase 1 (OGG1), bridging integrator 1 (BIN1), sortilin-related receptor 1 (SORL1), presenilin 2 (PSEN2) and nerve growth factor (NGF)) with MCI risk in a Xinjiang Uygur population. We also tested the relationship between the promoter methylation of genes OGG1 and dihydrolipoamide S-succinyltransferase (DLST) with MCI.

METHODS

This study involved 43 MCI patients and 125 controls. Genotyping was done by Sanger sequencing. DNA methylation assays used quantitative methylation-specific polymerase chain reaction.

RESULTS

We found that polymorphisms of five genes and the methylation of DLST and OGG1 genes were not associated with MCI (P > 0.05). Further subgroup analysis found that DLST hypomethylation was significantly associated with MCI in the carriers of apolipoprotein E (APOE) ε4 (P = 0.042). In the carriers of non-APOE ε4, DLST methylation levels were significantly lower in the male control group than in the female control group (p = 0.04). Meanwhile, among the non-APOE ε4 carriers younger than 75, OGG1 hypermethylation levels were significantly associated with MCI (P = 0.049). DLST methylation in female controls was significantly lower than that in male controls (P = 0.003). According to gender stratification, there was a significant positive correlation of fasting plasma glucose (FBG) and high-density lipoprotein (HDL) with OGG1 methylation in the female controls (FBG: P = 0.024; HDL: P = 0.033). There was a significant inverse correlation between low-density lipoprotein and DLST methylation in male MCI (P = 0.033). There was a significant positive correlation between HDL and DLST methylation levels in the female controls (P = 0.000).

CONCLUSIONS

This study was the first to discover that DLST promoter methylation interacted with APOE ε4 and thus affected the pathogenesis of MCI. In addition, OGG1 promoter methylation interacted with several other factors to increase the risk of MCI.

Multi-omics analysis identifies mitochondrial pathways associated with anxiety-related behavior

Stressful life events are major environmental risk factors for anxiety disorders, although not all individuals exposed to stress develop clinical anxiety. The molecular mechanisms underlying the influence of environmental effects on anxiety are largely unknown. To identify biological pathways mediating stress-related anxiety and resilience to it, we used the chronic social defeat stress (CSDS) paradigm in male mice of two inbred strains, C57BL/6NCrl (B6) and DBA/2NCrl (D2), that differ in their susceptibility to stress. Using a multi-omics approach, we identified differential mRNA, miRNA and protein expression changes in the bed nucleus of the stria terminalis (BNST) and blood cells after chronic stress. Integrative gene set enrichment analysis revealed enrichment of mitochondrial-related genes in the BNST and blood of stressed mice. To translate these results to human anxiety, we investigated blood gene expression changes associated with exposure-induced panic attacks. Remarkably, we found reduced expression of mitochondrial-related genes in D2 stress-susceptible mice and in exposure-induced panic attacks in humans, but increased expression of these genes in B6 stress-susceptible mice. Moreover, stress-susceptible vs. stress-resilient B6 mice displayed more mitochondrial cross-sections in the post-synaptic compartment after CSDS. Our findings demonstrate mitochondrial-related alterations in gene expression as an evolutionarily conserved response in stress-related behaviors and validate the use of cross-species approaches in investigating the biological mechanisms underlying anxiety disorders.

Stimulation of SIRT1 Attenuates the Level of Oxidative Stress in the Brains of APP/PS1 Double Transgenic Mice and in Primary Neurons Exposed to Oligomers of the Amyloid-β Peptide

In the study, we examined whether the silent information regulator 1 (SIRT1) can attenuate oxidative stress in the brains of mice carrying the APP/PS1 double mutation and/or in primary neonatal rat neurons exposed to oligomers of amyloid-β peptide (AβOs). Starting at 4 or 8 months of age, the transgenic mice were treated with resveratrol (RSV, a stimulator of SIRT1) or suramin (an inhibitor) (each 20 mg/kg BW/day) for two months. The primary neurons were exposed to AβOs (0.5 μM) for 48 h and thereafter RSV (20 μM) or suramin (300 mg/ml) for 24 h. Cell viability was assessed by the CCK-8 assay; SIRT1 protein and mRNA determined by western blotting and real-time PCR, respectively; senile plaques examined immunohistochemically; ROS monitored by flow cytometry; and the contents of OH-, H2O2, O2·-, and MDA, and the activities of SOD and GSH-Px measured by standard biochemical procedures. In comparison to wild-type mice or untreated primary neurons, the expression of SIRT1 was significantly lower in the brains of APP/PS1 mice or neurons exposed to AβOs. In these same systems, increased numbers of senile plaques and a high level of oxidative stress were apparent. Interestingly, these two latter changes were attenuated by treatment with RSV, but enhanced by suramin. These findings indicate that SIRT1 may be neuroprotective.

Investigation of base excision repair gene variants in late-onset Alzheimer's disease

Base excision repair (BER) defects and concomitant oxidative DNA damage accumulation play a role in the etiology and progression of late-onset Alzheimer’s disease (LOAD). However, it is not known whether genetic variant(s) of specific BER genes contribute to reduced BER activity in LOAD patients and whether they are associated with risk, development and/or progression of LOAD. Therefore, we performed targeted next generation sequencing for three BER genes, uracil glycosylase (UNG), endonuclease VIII-like DNA glycosylase 1 (NEIL1) and polymerase β (POLβ) including promoter, exonic and intronic regions in peripheral blood samples and postmortem brain tissues (temporal cortex, TC and cerebellum, CE) from LOAD patients, high-pathology control and cognitively normal age-matched controls. In addition, the known LOAD risk factor, APOE was included in this study to test whether any BER gene variants associate with APOE variants, particularly APOE ε4. We show that UNG carry five significant variants (rs1610925, rs2268406, rs80001089, rs1018782 and rs1018783) in blood samples of Turkish LOAD patients compared to age-matched controls and one of them (UNG rs80001089) is also significant in TC from Brazilian LOAD patients (p<0.05). The significant variants present only in CE and TC from LOAD are UNG rs2569987 and POLβ rs1012381950, respectively. There is also significant epistatic relationship (p = 0.0410) between UNG rs80001089 and NEIL1 rs7182283 in TC from LOAD subjects. Our results suggest that significant BER gene variants may be associated with the risk of LOAD in non-APOE ε4 carriers. On the other hand, there are no significant UNG, NEIL1 and POLβ variants that could affect their protein level and function, suggesting that there may be other factors such as post-transcriptional or–translational modifications responsible for the reduced activities and protein levels of these genes in LOAD pathogenesis. Further studies with increased sample size are needed to confirm the relationship between BER variants and LOAD risk.

POLD1 deficiency is involved in cognitive function impairment in AD patients and SAMP8 mice

Age-related changes such as increased oxidative stress and DNA damage are important risk factors for Alzheimer's disease (AD). This study aimed to clarify the role of POLD1, the catalytic subunit of DNA polymerase δ, in neurodegeneration symptoms of AD. POLD1 expression levels were evaluated in patients with different neurodegenerative diseases by ELISA, RT-PCR and Western blot analysis. The impairment of cognitive ability in AD patients and senescence-accelerated mouse prone 8 (SAMP8) mice were evaluated by MMSE/MoCA score and Morris water maze (MWM) test. We found that serum concentration and expression levels of POLD1 in lymphocytes were reduced in AD patients. The cognitive impairment in AD patients and SAMP8 mice was associated with reduced POLD1 expression. In addition, POLD1 knockdown led to premature senescence and increased DNA damage in primary neuronal cells of SAMP8 mice. In conclusion, this is the first study suggesting that the deficiency of POLD1 may aggravate AD progression, and POLD1 is a potential diagnostic marker and therapeutic target for AD.

Nrf2/ARE Pathway Modulation by Dietary Energy Regulation in Neurological Disorders

Nuclear factor erythroid 2-related factor 2 (Nrf2) regulates the expression of an array of enzymes with important detoxifying and antioxidant functions. Current findings support the role of high levels of oxidative stress in the pathogenesis of neurological disorders. Given the central role played by Nrf2 in counteracting oxidative damage, a number of studies have targeted the modulation of this transcription factor in order to confer neuroprotection. Nrf2 activity is tightly regulated by oxidative stress and energy-based stimuli. Thus, many dietary interventions based on energy intake regulation, such as dietary energy restriction (DER) or high-fat diet (HFD), modulate Nrf2 with consequences for a variety of cellular processes that affect brain health. DER, by either restricting calorie intake or meal frequency, activates Nrf2 thereby triggering its protective effects, whilst HFD inhibit this pathway, thereby exacerbating oxidative stress. Consequently, DER protocols can be valuable strategies in the management of central nervous system (CNS) disorders. Herein, we review current knowledge of the role of Nrf2 signaling in neurological diseases, namely Alzheimer’s disease, Parkinson’s disease, multiple sclerosis and cerebral ischemia, as well as the potential of energy intake regulation in the management of Nrf2 signaling.

An evaluation of the differences in DNA damage in lymphocytes and repair efficiencies in patients with schizophrenia and schizoaffective disorder

Schizophrenia and schizoaffective disorder are chronic and debilitating psychiatric disorders. The present study was designed to determine DNA damage in patients with schizophrenia and schizoaffective disorder to assess the roles of oxidative metabolism and DNA repair mechanisms in this process, to assess the contribution of drugs, and thus to demonstrate the differences between schizophrenia and schizoaffective disorder. Thirty schizophrenia and 30 schizoaffective disorder patients, each having at least five years of disease history, aged between 18 and 60 years with no physical or neurological diseases, and 30 healthy volunteers participated in the study. Psychometric scales were applied, and 5 ml of blood was taken from all participants. The DNA damage was measured in lymphocytes by the comet assay method; the total oxidative parameters by ELISA; OGG1 and NEIL1 gene expressions by real-time PCR; and the role of drugs by in vitro assays. The most important finding in this study was that patients with schizophrenia had significantly greater DNA damage than schizoaffective disorder patients and the controls. This study also provides evidence of high oxidative stress statuses and inadequate DNA repair capacities in patients with schizophrenia. Moreover, psychotropic drugs did not induce any DNA damage to the lymphocytes according to in vitro analyses. The use of clozapine and adequate repair processes of the patients were the decisive factors in the prevention of DNA damage. The results of this study provide a reexamination of schizoaffective disorder within the schizophrenia spectrum and indicate that schizoaffective disorder may be considered a different diagnostic category.

Cognitive performance in survivors of breast cancer and markers of biological aging

BACKGROUND

Biological aging pathways accelerated by cancer treatments may be a mechanism for cognitive impairment in cancer survivors. The goal of the current study was to examine whether indicators of biological aging, namely elevated levels of DNA damage, reduced telomerase enzymatic activity, and shorter peripheral blood mononuclear cell (PBMC) telomere length (TL) would be related to cognitive function in a cohort of survivors of breast cancer.

METHODS

The authors evaluated a cross-sectional sample of 94 women aged 36 to 69 years who were treated for early-stage breast cancer 3 to 6 years previously. Leukocyte DNA damage, PBMC telomerase enzymatic activity, PBMC TL, and the inflammatory marker soluble tumor necrosis factor receptor II (sTNF-RII) were determined from blood samples. Cognitive function was assessed using a neuropsychological test battery and self-report. Linear regression models examined the relationship between biological aging predictors and cognitive outcomes.

RESULTS

Both higher DNA damage and lower telomerase were found to be statistically significantly related to lower executive function scores adjusting for age, body mass index, race, years from treatment, and intelligence score (standardized coefficients [B], -0.23 and 0.30; all P values <.05). In addition, lower telomerase activity was associated with worse attention and motor speed scores (B values, 0.30 and 0.24; P &lt;.05). sTNF-RII and TL were found to be unrelated to any of the neurocognitive domains.

CONCLUSIONS

The results of the current study suggest a significant association between measures of biological aging and objective measures of cognitive performance in survivors of breast cancer. Future prospective studies are needed to confirm a causal role of biological aging as a driver of declines in cognitive function after cancer treatment.

Prolonged Drug-Releasing Fibers Attenuate Alzheimer's Disease-like Pathogenesis

Delivering drugs and agents to the brain is a huge challenge, especially for chronic neurodegenerative disorders, such as Alzheimer's disease (AD). For this, prolonged and sustained release methods to increase brain uptake represent an impacting concept. The bioresorbable polymer poly-lactic acid (PLA) has high potential for medical implants; at the same time, glucagon-like peptide-1 (GLP-1) analogues have considerable neuroprotective attributes and represent a therapeutic strategy for AD. Here, a biodevice is produced by electrospinning PLA with a GLP-1 analogue (liraglutide, LG), coated with a thin layer of gelatin. The biodevice is subcutaneously implanted in a transgenic mouse model of AD and LG is released for 14 days in mice serum. After 4 weeks of implantation, crucial hallmarks of the AD are highly diminished: hippocampal senile amyloid β plaque load and neuroinflammatory markers. Furthermore, neurogenesis is enhanced in the subventricular zone, an important neurogenic niche in the brain. The designed biodevice holds great promise for being an affordable candidate to act as a prolonged drug provider, promoting LG mission through increasing its lifetime, constituting a relevant approach for old and impaired brain.

γH2AX is increased in peripheral blood lymphocytes of Alzheimer's disease patients in the South Australian Neurodegeneration, Nutrition and DNA Damage (SAND) study of aging

An early cellular response to DNA double-strand breaks is the phosphorylation of histone H2AX to form γH2AX. Although increased levels of γH2AX have been reported in neuronal nuclei of Alzheimer's disease (AD) patients, γH2AX responses in the lymphocytes of individuals with mild cognitive impairment (MCI) and AD remain unexplored. In this study, the endogenous γH2AX level was measured, using laser scanning cytometry (LSC) and visual scoring, in lymphocyte nuclei from MCI (n = 18), or AD (n = 20) patients and healthy controls (n = 40). Levels were significantly elevated in nuclei of the AD group compared to the MCI and control groups, and there was a concomitant increase, with a significant trend, from the control group through MCI to the AD group. A significant negative correlation was seen between γH2AX and the mini mental state examination (MMSE) score, when the analysis included all subjects. Receiver Operation Characteristic curves were carried out for different γH2AX parameters; visually scored percent cells containing overlapping γH2AX foci displayed the best area under the curve value of 0.9081 with 85% sensitivity and 92% specificity for the identification of AD patients versus control. Plasma homocysteine, creatinine, and chitinase-3-like protein 1 (CHI3L1) were positively correlated with lymphocyte γH2AX signals, while glomerular filtration rate (GFR) was negatively correlated. Finally, there was a diminished γH2AX response to X-rays in lymphocytes of the MCI and AD groups compared to the control group. Our results indicate that lymphocyte γH2AX levels are a potential marker for identifying individuals at increased risk of developing AD. Prospective studies with normal healthy individuals are needed to test whether there is indeed a link between γH2AX levels and AD risk.

Oxidative Stress, Synaptic Dysfunction, and Alzheimer's Disease

Alzheimer's disease (AD) is a devastating neurodegenerative disorder without a cure. Most AD cases are sporadic where age represents the greatest risk factor. Lack of understanding of the disease mechanism hinders the development of efficacious therapeutic approaches. The loss of synapses in the affected brain regions correlates best with cognitive impairment in AD patients and has been considered as the early mechanism that precedes neuronal loss. Oxidative stress has been recognized as a contributing factor in aging and in the progression of multiple neurodegenerative diseases including AD. Increased production of reactive oxygen species (ROS) associated with age- and disease-dependent loss of mitochondrial function, altered metal homeostasis, and reduced antioxidant defense directly affect synaptic activity and neurotransmission in neurons leading to cognitive dysfunction. In addition, molecular targets affected by ROS include nuclear and mitochondrial DNA, lipids, proteins, calcium homeostasis, mitochondrial dynamics and function, cellular architecture, receptor trafficking and endocytosis, and energy homeostasis. Abnormal cellular metabolism in turn could affect the production and accumulation of amyloid-β (Aβ) and hyperphosphorylated Tau protein, which independently could exacerbate mitochondrial dysfunction and ROS production, thereby contributing to a vicious cycle. While mounting evidence implicates ROS in the AD etiology, clinical trials with antioxidant therapies have not produced consistent results. In this review, we will discuss the role of oxidative stress in synaptic dysfunction in AD, innovative therapeutic strategies evolved based on a better understanding of the complexity of molecular mechanisms of AD, and the dual role ROS play in health and disease.

Purported Interactions of Amyloid-β and Glucocorticoids in Cytotoxicity and Genotoxicity: Implications in Alzheimer's Disease

Alzheimer's disease (AD) is a complex neurodegenerative disorder characterized by the presence of aggregates of the amyloid-β peptide (Aβ) that are believed to be neurotoxic. One of the purposed damaging mechanisms of Aβ is oxidative insult, which eventually could damage the cellular genome. Stress and associated increases in glucocorticoids (GCs) have been described as a risk factor for the development of AD, although the purported genotoxic effects of GCs have not been fully characterized. Therefore, it is possible to speculate about purported synergistic effects of GCs on the Aβ-driven genotoxic damage. This in vitro study addresses the single and combined cyto/genotoxic effects of Aβ and GCs in SH-SY5Y cells. Cytotoxicity was determined by the MTT assay, and the genotoxic effects were studied using the comet assay. A comet assay derivation allows for measuring the presence of the FPG-sensitive sites (mainly 8-oxoguanines) in the DNA, apart from the DNA strand breaks. Treatment with Aβ (10 μM, 72 h) induced cytotoxicity (35% decrease in cell viability) and DNA strand breaks, but had no significant effect on oxidative DNA damage (FPG sites). Corticosterone showed no effect on cell viability, genotoxicity, or reparation processes. Corticosterone was unable to neither reverse nor potentiate Aβ driven effects. The present results suggest the existence of alternative mechanisms for the Aβ driven damage, not involving oxidative damage of DNA. In addition, could be suggested that the interaction between Aβ and GCs in AD does not seem to involve DNA damage.

Impairment of Several Immune Functions and Redox State in Blood Cells of Alzheimer's Disease Patients. Relevant Role of Neutrophils in Oxidative Stress

Since aging is considered the most risk factor for sporadic Alzheimer’s Disease (AD), the age-related impairment of the immune system (immunosenescence), based on a chronic oxidative-inflammatory stress situation, could play a key role in the development and progression of AD. Although AD is accompanied by systemic disturbance, reflecting the damage in the brain, the changes in immune response and redox-state in different types of blood cells in AD patients have been scarcely studied. The aim was to analyze the variations in several immune functions and oxidative-inflammatory stress and damage parameters in both isolated peripheral neutrophils and mononuclear blood cells, as well as in whole blood cells, from patients diagnosed with mild (mAD) and severe AD, and of age-matched controls (elderly healthy subjects) as well as of adult controls. The cognitive decline of all subjects was determined by Mini-Mental State Examination (MMSE) test (mAD stage was established at 20 ≤ MMSE ≤ 23 score; AD stage at <18 MMSE; elderly subjects >27 MMSE). The results showed an impairment of the immune functions of human peripheral blood neutrophils and mononuclear cells of mAD and AD patients in relation to healthy elderly subjects, who showed the typical immunosenescence in comparison with the adult individuals. However, several alterations were only observed in severe AD patients (lower chemotaxis, lipopolysaccharide lymphoproliferation, and interleukin (IL)-10 release; higher basal proliferation, tumor necrosis factor (TNF)-α release, and IL-10/TNF-α ratio), others only in mAD subjects (higher adherence), meanwhile others appeared in both mAD and AD patients (lower phytohemaglutinin lymphoproliferation and higher IL-6 release). This impairment of immune functions could be mediated by: (1) the higher oxidative stress and damage also observed in blood cells from mAD and AD patients and in isolated neutrophils [lower glutathione (GSH) levels, high oxidized glutathione (GSSG)/GSH ratio, and GSSG and malondialdehyde contents], and (2) the higher release of basal pro-inflammatory cytokines (IL-6 and TNF-α) found in AD patients. Because the immune system parameters studied are markers of health and rate of aging, our results supported an accelerated immunosenescence in AD patients. We suggest the assessment of oxidative stress and function parameters in peripheral blood cells as well as in isolated neutrophils and mononuclear cells, respectively, as possible markers of AD progression.

Cognitive Effects of Chemotherapy and Cancer-Related Treatments in Older Adults

Advances in cancer treatment are producing a growing number of cancer survivors; therefore, issues surrounding quality of life during and following cancer treatment have become increasingly important. Chemotherapy-related cognitive impairment (CRCI) is a problem that is commonly reported following the administration of chemotherapy treatment in patients with cancer. Research suggests that CRCI can persist for months to years after completing treatment, which has implications for the trajectory of normal and pathologic cognitive aging for the growing number of long-term cancer survivors. These problems are particularly relevant for older individuals, given that cancer is largely a disease of older age, and the number of patients with cancer who are aged 65 years or older will increase dramatically over the coming decades. This review will briefly summarize empirical findings related to CRCI, discuss CRCI in older patients with cancer, propose potential causative hypotheses, and provide a canonical patient case to illustrate how CRCI presents clinically. Finally, potential intervention strategies for CRCI will be highlighted and issues to consider when evaluating older patients with a history of cancer will be discussed.

Less is more: Caloric regulation of neurogenesis and adult brain function

Calorie intake is essential for regulating normal physiological processes and is fundamental to maintaining life. Indeed, both extremes of calorie intake result in increased morbidity and mortality. In this review, we discuss the effect of calorie intake on adult brain function, with an emphasis on the beneficial effects of mild calorie restriction. Recent findings relating to the regenerative and protective effects of the gastrointestinal hormone, ghrelin, suggest that it may underlie the beneficial effects of calorie restriction. We discuss the putative cellular mechanisms underlying the action of ghrelin and their possible role in supporting healthy brain ageing.

Associations between DNA Damage, DNA Base Excision Repair Gene Variability and Alzheimer's Disease Risk

BACKGROUND

Increased oxidative damage to DNA is one of the pathways involved in Alzheimer's disease (AD). Insufficient base excision repair (BER) is in part responsible for increased oxidative DNA damage. The aim of the present study was to assess the effect of polymorphic variants of BER-involved genes and the peripheral markers of DNA damage and repair in patients with AD.

MATERIAL AND METHODS

Comet assays and TaqMan probes were used to assess DNA damage, BER efxFB01;ciency and polymorphic variants of 12 BER genes in blood samples from 105 AD patients and 130 controls. The DNA repair efficacy (DRE) was calculated according to a specific equation.

RESULTS

The levels of endogenous and oxidative DNA damages were higher in AD patients than controls. The polymorphic variants of XRCC1 c.580C>T XRCC1 c.1196A>G and OGG1 c.977C>G are associated with increased DNA damage in AD.

CONCLUSION

Our results show that oxidative stress and disturbances in DRE are particularly responsible for the elevated DNA lesions in AD. The results suggest that oxidative stress and disruption in DNA repair may contribute to increased DNA damage in AD patients and risk of this disease. In addition, disturbances in DRE may be associated with polymorphisms of OGG1 and XRCC1.

Axonal Degeneration during Aging and Its Functional Role in Neurodegenerative Disorders

Aging constitutes the main risk factor for the development of neurodegenerative diseases. This represents a major health issue worldwide that is only expected to escalate due to the ever-increasing life expectancy of the population. Interestingly, axonal degeneration, which occurs at early stages of neurodegenerative disorders (ND) such as Alzheimer's disease, Amyotrophic lateral sclerosis, and Parkinson's disease, also takes place as a consequence of normal aging. Moreover, the alteration of several cellular processes such as proteostasis, response to cellular stress and mitochondrial homeostasis, which have been described to occur in the aging brain, can also contribute to axonal pathology. Compelling evidence indicate that the degeneration of axons precedes clinical symptoms in NDs and occurs before cell body loss, constituting an early event in the pathological process and providing a potential therapeutic target to treat neurodegeneration before neuronal cell death. Although, normal aging and the development of neurodegeneration are two processes that are closely linked, the molecular basis of the switch that triggers the transition from healthy aging to neurodegeneration remains unrevealed. In this review we discuss the potential role of axonal degeneration in this transition and provide a detailed overview of the literature and current advances in the molecular understanding of the cellular changes that occur during aging that promote axonal degeneration and then discuss this in the context of ND.