Blood markers of oxidative stress in Alzheimer's disease

Examining the role of antioxidant supplementation in mitigating oxidative stress markers in Alzheimer's disease: a comprehensive review

Alzheimer's disease is a devastating neurodegenerative disorder that affects millions of people worldwide. One of the key pathological features of Alzheimer's disease is oxidative stress, which is characterized by an imbalance between the production of reactive oxygen species and the body's ability to neutralize them with antioxidants. In recent years, there has been growing interest in the potential role of antioxidant supplementation in mitigating oxidative stress markers in Alzheimer's disease. This review paper aims to provide a comprehensive overview of the current research on antioxidant supplementation in Alzheimer's disease and its effects on oxidative stress markers. The paper will examine the underlying mechanisms of oxidative stress in Alzheimer's disease, the potential benefits of antioxidant supplementation, and the challenges and limitations of using antioxidants as a therapeutic strategy.

Oxidative Stress and Risk of Dementia in Older Patients with Depression: A Longitudinal Cohort Study Using Plasma Biomarkers

Background and Objectives: While depression is associated with an increased risk of Alzheimer's dementia (AD), traditional AD-related biomarkers, such as amyloid-beta, have shown limited predictive value for late-life depression. Oxidative stress has emerged as a potential indicator given its shared role in both depression and dementia. This study investigated the longitudinal relationship between oxidative stress biomarkers and risk of dementia in patients with depression. Materials and Methods: A longitudinal cohort of 146 older patients with major depressive disorder was analyzed. Biomarkers, such as nitrotyrosine, protein carbonyl, F2-isoprostanes, malondialdehyde, 4-hydroxynonenal, and 8-hydroxy-2'-deoxyguanosine, were collected at baseline and measured using an enzyme-linked immunosorbent assay. AD conversion was determined using comprehensive neuropsychological assessment. Cox proportional hazards models were used to evaluate the association between oxidative stress biomarkers and AD conversion after adjusting for confounders. The log-rank test, using the minimum p-value approach, was applied to determine the optimal cut-off value for significantly associated biomarkers of AD-free survival rates. Results: During the follow-up period ranging from 1.00 to 18.53 years, 41 (28.08%) patients converted to AD. Nitrotyrosine showed a significant association with increased risk of AD (adjusted hazard ratio [HR], 1.01; 95% confidence interval [CI], 1.00-1.01; p = 0.0045). For clinical applicability, patients with plasma nitrotyrosine levels ≥170 nM as the cut-off value had a 5.14-fold increased risk of AD (adjusted HR, 5.14; 95% CI, 2.02-13.07; p = 0.0006). Other biomarkers, such as protein carbonyl, F2-isoprostanes, malondialdehyde, 4-hydroxynonenal, and 8-hydroxy-2'-deoxyguanosine, were not significantly associated with AD conversion. Conclusions: Nitrotyrosine, a biomarker that reflects nitrosative damage, emerged as a significant predictor of dementia risk in older patients with depression, highlighting its potential as an early biomarker of dementia. Further validation of these results is required using a larger sample size.

Immunosenescence and inflammaging: Mechanisms and role in diseases

Age-related changes initiate a cascade of cellular and molecular alterations that lead to immune system dysfunction or abnormal activation, predisposing individuals to age-related diseases. This phenomenon, commonly referred to as immunosenescence, highlighting aging-associated progressive decline of the immune system. Moreover, mounting evidence suggests that immunosenescence contributes to a related pathological phenomenon known as inflammaging. Inflammaging refers to chronic, low-grade, and systemic inflammation associated with aging, occurring despite the absence of overt stimuli. In the body, inflammation is typically activated in response to overt stimuli such as bacterial/microbial invasion or a pathological state, however, inflammaging occurrence and its underpinning mechanisms seem to be independent and in the absence of such stimuli. Despite recent advancements in molecular characterization and the scrutiny of disease relevance, these two interconnected concepts have remained largely unexplored and unrecognized. In this comprehensive review, we aim to shed light on the mechanistic and cellular aspects of immunosenescence and inflammaging, as well as their pivotal roles in the pathogenesis of aging-related diseases, including cancer, infections, dementia, and neurodegenerative disorders.

Oxidative stress-mediated neuroinflammation in Alzheimer's disease

Reactive oxygen species (ROS) are metabolic by-products that constitute an indispensable component of physiological processes, albeit their heightened presence may proffer substantial perils to biological entities. Such a proliferation gives rise to a gradual escalation of oxidative stress within the organism, thereby compromising mitochondrial functionality and inflicting harm upon various bodily systems, with a particular predilection for the central nervous system. In its nascent stages, it is plausible that inflammation has been a facilitator in the progression of the malady. The precise role of inflammation in Alzheimer's disease (AD) remains somewhat enigmatic, although it is conceivable that activated microglia and astrocytes might be implicated in the removal of amyloid-β (Aβ) deposits. Nonetheless, prolonged microglial activation is associated with Tau phosphorylation and Aβ aggregation. Research studies have indicated that AD brains upregulate complementary molecules, inflammatory cytokines, acute phase reacting agents, and other inflammatory mediators that may cause neurodegeneration. In this review, oxidative damage products will be discussed as potential peripheral biomarkers for AD and its early stages. The disordered excretion of pro-inflammatory cytokines, chemokines, oxygen, and nitrogen-reactive species, along with the stimulation of the complement system by glial cells, has the potential to disrupt the functionality of neuronal termini. This perturbation, in turn, culminates in compromised synaptic function, a phenomenon empirically linked to the manifestation of cognitive impairments. The management of neurodegenerative conditions in the context of dementia necessitates therapeutic interventions that specifically target the excessive production of inflammatory and oxidative agents. Furthermore, we shall deliberate upon the function of microglia and oxidative injury in the etiology of AD and the ensuing neurodegenerative processes.

Deep Learning-Driven Exploration of Pyrroloquinoline Quinone Neuroprotective Activity in Alzheimer's Disease

Alzheimer's disease (AD) is a pressing concern in neurodegenerative research. To address the challenges in AD drug development, especially those targeting Aβ, this study uses deep learning and a pharmacological approach to elucidate the potential of pyrroloquinoline quinone (PQQ) as a neuroprotective agent for AD. Using deep learning for a comprehensive molecular dataset, blood-brain barrier (BBB) permeability is predicted and the anti-inflammatory and antioxidative properties of compounds are evaluated. PQQ, identified in the Mediterranean-DASH intervention for a diet that delays neurodegeneration, shows notable BBB permeability and low toxicity. In vivo tests conducted on an Aβ₁₋₄₂-induced AD mouse model verify the effectiveness of PQQ in reducing cognitive deficits. PQQ modulates genes vital for synapse and anti-neuronal death, reduces reactive oxygen species production, and influences the SIRT1 and CREB pathways, suggesting key molecular mechanisms underlying its neuroprotective effects. This study can serve as a basis for future studies on integrating deep learning with pharmacological research and drug discovery.

Computational analysis of peripheral blood RNA sequencing data unravels disrupted immune patterns in Alzheimer's disease

The central nervous system (CNS) and the immune system collectively coordinate cellular functionalities, sharing common developmental mechanisms. Immunity-related molecules exert an influence on brain development, challenging the conventional view of the brain as immune-privileged. Chronic inflammation emerges as a key player in the pathophysiology of Alzheimer's disease (AD), with increased stress contributing to the disease progression and potentially exacerbating existing symptoms. In this study, the most significant gene signatures from selected RNA-sequencing (RNA-seq) data from AD patients and healthy individuals were obtained and a functional analysis and biological interpretation was conducted, including network and pathway enrichment analysis. Important evidence was reported, such as enrichment in immune system responses and antigen processes, as well as positive regulation of T-cell mediated cytotoxicity and endogenous and exogenous peptide antigen, thus indicating neuroinflammation and immune response participation in disease progression. These findings suggest a disturbance in the immune infiltration of the peripheral immune environment, providing new challenges to explore key biological processes from a molecular perspective that strongly participate in AD development.

The roles of natural triterpenoid saponins against Alzheimer's disease

The aging of the world population and increasing stress levels in life are the major cause of the increased incidence of neurological disorders. Alzheimer's disease (AD) creates a huge burden on the lives and health of individuals and has become a big concern for society. Triterpenoid saponins (TS), representative natural product components, have a wide range of pharmacological bioactivities such as anti-inflammation, antioxidation, antiapoptosis, hormone-like, and gut microbiota regulation. Notably, some natural TS exhibited promising neuroprotective activity that can intervene in AD progress, especially in the early stage. Recently, studies have indicated that TS play a pronounced positive role in the prevention and treatment of AD. This review discusses the recent research on the neuroprotection of TS and proceeds to detail the action mechanisms of TS against AD, hoping to provide a reference for drug development for anti-AD.

Recent Advances in Sensing Materials Targeting Clinical Volatile Organic Compound (VOC) Biomarkers: A Review

In general, volatile organic compounds (VOCs) have a high vapor pressure at room temperature (RT). It has been reported that all humans generate unique VOC profiles in their exhaled breath which can be utilized as biomarkers to diagnose disease conditions. The VOCs available in exhaled human breath are the products of metabolic activity in the body and, therefore, any changes in its control level can be utilized to diagnose specific diseases. More than 1000 VOCs have been identified in exhaled human breath along with the respiratory droplets which provide rich information on overall health conditions. This provides great potential as a biomarker for a disease that can be sampled non-invasively from exhaled breath with breath biopsy. However, it is still a great challenge to develop a quick responsive, highly selective, and sensitive VOC-sensing system. The VOC sensors are usually coated with various sensing materials to achieve target-specific detection and real-time monitoring of the VOC molecules in the exhaled breath. These VOC-sensing materials have been the subject of huge interest and extensive research has been done in developing various sensing tools based on electrochemical, chemoresistive, and optical methods. The target-sensitive material with excellent sensing performance and capturing of the VOC molecules can be achieved by optimizing the materials, methods, and its thickness. This review paper extensively provides a detailed literature survey on various non-biological VOC-sensing materials including metal oxides, polymers, composites, and other novel materials. Furthermore, this review provides the associated limitations of each material and a summary table comparing the performance of various sensing materials to give a better insight to the readers.

Oxidative Stress and Natural Antioxidants: Back and Forth in the Neurological Mechanisms of Alzheimer's Disease

Alzheimer's disease (AD) is characterized by the progressive degeneration of neuronal cells. With the increase in aged population, there is a prevalence of irreversible neurodegenerative changes, causing a significant mental, social, and economic burden globally. The factors contributing to AD are multidimensional, highly complex, and not completely understood. However, it is widely known that aging, neuroinflammation, and excessive production of reactive oxygen species (ROS), along with other free radicals, substantially contribute to oxidative stress and cell death, which are inextricably linked. While oxidative stress is undeniably important in AD, limiting free radicals and ROS levels is an intriguing and potential strategy for deferring the process of neurodegeneration and alleviating associated symptoms. Therapeutic compounds from natural sources have recently become increasingly accepted and have been effectively studied for AD treatment. These phytocompounds are widely available and a multitude of holistic therapeutic efficiencies for treating AD owing to their antioxidant, anti-inflammatory, and biological activities. Some of these compounds also function by stimulating cholinergic neurotransmission, facilitating the suppression of beta-site amyloid precursor protein-cleaving enzyme 1, α-synuclein, and monoamine oxidase proteins, and deterring the occurrence of AD. Additionally, various phenolic, flavonoid, and terpenoid phytocompounds have been extensively described as potential palliative agents for AD progression. Preclinical studies have shown their involvement in modulating the cellular redox balance and minimizing ROS formation, displaying them as antioxidant agents with neuroprotective abilities. This review emphasizes the mechanistic role of natural products in the treatment of AD and discusses the various pathological hypotheses proposed for AD.

The Hidden Role of Non-Canonical Amyloid β Isoforms in Alzheimer's Disease

Recent advances have placed the pro-inflammatory activity of amyloid β (Aβ) on microglia cells as the focus of research on Alzheimer's Disease (AD). Researchers are confronted with an astonishing spectrum of over 100 different Aβ variants with variable length and chemical modifications. With the exception of Aβ1-42 and Aβ1-40, the biological significance of most peptides for AD is as yet insufficiently understood. We therefore aim to provide a comprehensive overview of the contributions of these neglected Aβ variants to microglia activation. First, the impact of Aβ receptors, signaling cascades, scavenger mechanisms, and genetic variations on the physiological responses towards various Aβ species is described. Furthermore, we discuss the importance of different types of amyloid precursor protein processing for the generation of these Aβ variants in microglia, astrocytes, oligodendrocytes, and neurons, and highlight how alterations in secondary structures and oligomerization affect Aβ neurotoxicity. In sum, the data indicate that gene polymorphisms in Aβ-driven signaling pathways in combination with the production and activity of different Aβ variants might be crucial factors for the initiation and progression of different forms of AD. A deeper assessment of their interplay with glial cells may pave the way towards novel therapeutic strategies for individualized medicine.

Volatile Organic Compounds as Potential Biomarkers for Noninvasive Disease Detection by Nanosensors: A Comprehensive Review

Biomarkers are biological molecules associated with physiological changes of the body and aids in the detecting the onset of disease in patients. There is an urgent need for self-monitoring and early detection of cardiovascular and other health complications. Several blood-based biomarkers have been well established in diagnosis and monitoring the onset of diseases. However, the detection level of biomarkers in bed-side analysis is difficult and complications arise due to the endothelial dysfunction. Currently single volatile organic compounds (VOCs) based sensors are available for the detection of human diseases and no dedicated nanosensor is available for the elderly. Moreover, accuracy of the sensors based on a single analyte is limited. Hence, breath analysis has received enormous attention in healthcare due to its relatively inexpensive, rapid, and noninvasive methods for detecting diseases. This review gives a detailed analysis of how biomarker imprinted nanosensor can be used as a noninvasive method for detecting VOC to health issues early using exhaled breath analysis.

Challenges of repurposing tetracyclines for the treatment of Alzheimer's and Parkinson's disease

The novel antibiotic-exploiting strategy in the treatment of Alzheimer's (AD) and Parkinson's (PD) disease has emerged as a potential breakthrough in the field. The research in animal AD/PD models provided evidence on the antiamyloidogenic, anti-inflammatory, antioxidant and antiapoptotic activity of tetracyclines, associated with cognitive improvement. The neuroprotective effects of minocycline and doxycycline in animals initiated investigation of their clinical efficacy in AD and PD patients which led to inconclusive results and additionally to insufficient safety data on a long-standing doxycycline and minocycline therapy in these patient populations. The safety issues should be considered in two levels; in AD/PD patients (particularly antibiotic-induced alteration of gut microbiota and its consequences), and as a world-wide threat of development of bacterial resistance to these antibiotics posed by a fact that AD and PD are widespread incurable diseases which require daily administered long-lasting antibiotic therapy. Recently proposed subantimicrobial doxycycline doses should be thoroughly explored for their effectiveness and long-term safety especially in AD/PD populations. Keeping in mind the antibacterial activity-related far-reaching undesirable effects both for the patients and globally, further work on repurposing these drugs for a long-standing therapy of AD/PD should consider the chemically modified tetracycline compounds tailored to lack antimicrobial but retain (or introduce) other activities effective against the AD/PD pathology. This strategy might reduce the risk of long-term therapy-related adverse effects (particularly gut-related ones) and development of bacterial resistance toward the tetracycline antibiotic agents but the therapeutic potential and desirable safety profile of such compounds in AD/PD patients need to be confirmed.

Quercetin mitigates scopolamine-induced memory dysfunction: impact on oxidative stress and cholinergic mechanisms

Despite the promising neuroprotective activities of quercetin (QT), its' effect on cholinergic neurotransmission needs further elucidation. In this study, we explored the impact of QT on oxidative stress and cholinergic neurotransmission with emphasis on the possible involvement of choline acetyltransferase (ChAT) as a potential mechanism of QT on memory function at the hippocampal sub-regions and prefrontal cortex of mice brains. Mice were administered orally with QT (12.5 and 25 mg/kg) alone or in combination with SC (3 mg/kg, intraperitoneally) once daily for seven consecutive days. Thirty minutes after the last treatment, memory function was assessed using the Y-maze test. Levels of biomarkers of oxidative stress and acetylcholinesterase (AChE) activity were determined using a microplate reader. ChAT activity was determined by immunohistochemistry. QT pretreatment enhanced memory performance and reversed scopolamine (SC)-induced memory impairment in the Y-maze test. QT also reduced malondialdehyde and nitrite levels in mice brains. Glutathione levels were increased in mice brains as a result of QT administration. Levels of antioxidant enzymes (superoxide dismutase and catalase) were significantly increased in the mice brains, but AChE activity was reduced by QT. The activity of ChAT was significantly enhanced by QT in the hippocampal sub-regions and the prefrontal cortex of the mice brains. This study has shown that QT mitigated SC-induced memory dysfunction by inhibiting oxidative stress and AChE activity. Also, QT enhanced ChAT activity, particularly in the hippocampal sub-regions and the prefrontal cortex. These mechanisms, may be possible means through which QT improves memory performance.

Assessment of lipophilic fluorescence products in β-amyloid-induced cognitive decline: A parallel track in hippocampus, CSF, plasma and erythrocytes

BACKGROUND

Oxidative stress implicates in Alzheimer's disease (AD) pathophysiology, and associates with the creation of end products of free radical reactions, are known as lipophilic fluorescent products (LFPs). This study aimed to evaluate the probable parallel alterations in the spectral properties of the LFPs in the hippocampus tissues, cerebrospinal fluid (CSF), plasma, and erythrocytes during AD model induction by intra-cerebroventricular (ICV) amyloid β-protein fragment 25-35 (Aβ) injection.

METHODS

Male rats received an intra-ICV injection of Aβ. Hippocampus, CSF, plasma, and erythrocytes were harvested at 5, 14, and 21 days after Aβ injection. The fluorescent intensity of LFPs was assessed by spectrofluorimetry using synchronous fluorescence spectra 25 (SYN 25) and 50 (SYN 50) in the range of 250-500 nm. Hippocampal tissue malondialdehyde (MDA) and superoxide dismutase (SOD) were also measured. Cognitive alterations were evaluated using Morris water maze (MWM) test.

RESULTS

The parallel significant rise in the fluorescence intensity of LFPs was detected in the hippocampus, CSF, plasma, and erythrocytes, 14, and 21 days after ICV-Aβ injection. These alterations were found in both types of synchronous spectra 25, and 50, and were coincided with hippocampal cognitive decline, the MDA rise, and decrease of SOD activity. There was a positive correlation between hippocampus homogenate, and plasma or CSF rise in fluorescence intensity.

CONCLUSION

Data showed that the Aβ increased hippocampal MDA, and decreased SOD activity, led to a higher rate of oxidative products and subsequently resulted in an increase in LFPs fluorescence intensity during the development of cognitive decline. LFPs' alterations reflect a comprehensive view of tissue redox status. The fluorescence properties of LFPs indicate their composition, which may pave the way to trace the different pathological states.

A Review of Oxidative Stress Products and Related Genes in Early Alzheimer's Disease

Oxidative stress is associated with the progression of Alzheimer’s disease (AD). Reactive oxygen species can modify lipids, DNA, RNA, and proteins in the brain. The products of their peroxidation and oxidation are readily detectable at incipient stages of disease. Based on these oxidation products, various biomarker-based strategies have been developed to identify oxidative stress levels in AD. Known oxidative stress-related biomarkers include lipid peroxidation products F2-isoprostanes, as well as malondialdehyde and 4-hydroxynonenal which both conjugate to specific amino acids to modify proteins, and DNA or RNA oxidation products 8-hydroxy-2’-deoxyguanosine (8-OHdG) and 8-hydroxyguanosine (8-OHG), respectively. The inducible enzyme heme oxygenase type 1 (HO-1) is found to be upregulated in response to oxidative stress-related events in the AD brain. While these global biomarkers for oxidative stress are associated with early-stage AD, they generally poorly differentiate from other neurodegenerative disorders that also coincide with oxidative stress. Redox proteomics approaches provided specificity of oxidative stress-associated biomarkers to AD pathology by the identification of oxidatively damaged pathology-specific proteins. In this review, we discuss the potential combined diagnostic value of these reported biomarkers in the context of AD and discuss eight oxidative stress-related mRNA biomarkers in AD that we newly identified using a transcriptomics approach. We review these genes in the context of their reported involvement in oxidative stress regulation and specificity for AD. Further research is warranted to establish the protein levels and their functionalities as well as the molecular mechanisms by which these potential biomarkers are involved in regulation of oxidative stress levels and their potential for determination of oxidative stress and disease status of AD patients.

A Review of the Application of Hyperbaric Oxygen Therapy in Alzheimer's Disease

Alzheimer's disease (AD) is considered as the most common cause of dementia in elderly population. While the exact mechanism of AD has not been discovered, hyperbolic oxygen therapy (HBOT) has been proven to be effective in the treatment of this degenerative disease. The objectives of this article are to review the literature available on molecular and physiological mechanisms underlying HBOT and its efficacy in treating AD and to review the effectiveness of HBOT as an alternate treatment intervention in both human and animal models. 391 full text articles were included in the review after literature search between 1980-2021 from two online data base (ScienceDirect and PubMed). The following key words were used: 'hyperbaric oxygen therapy' and 'Alzheimer disease.' Based on the outcomes of clinical and experimental studies, this review advocates the use of HBOT for the treatment of AD. This review explores future directions and recommends further research into a treatment protocol that will maintain long-term cognitive health of AD patients.

Biomarkers: Our Path Towards a Cure for Alzheimer Disease

Over the last decade, biomarkers have significantly improved our understanding of the pathophysiology of Alzheimer disease (AD) and provided valuable tools to examine different disease mechanisms and their progression over time. While several markers of amyloid, tau, neuronal, synaptic, and axonal injury, inflammation, and immune dysregulation in AD have been identified, there is a relative paucity of biomarkers which reflect other disease mechanisms such as oxidative stress, mitochondrial injury, vascular or endothelial injury, and calcium-mediated excitotoxicity. Importantly, there is an urgent need to standardize methods for biomarker assessments across different centers, and to identify dynamic biomarkers which can monitor disease progression over time and/or response to potential disease-modifying treatments. The updated research framework for AD, proposed by the National Institute of Aging- Alzheimer’s Association (NIA-AA) Work Group, emphasizes the importance of incorporating biomarkers in AD research and defines AD as a biological construct consisting of amyloid, tau, and neurodegeneration which spans pre-symptomatic and symptomatic stages. As results of clinical trials of AD therapeutics have been disappointing, it has become increasingly clear that the success of future AD trials will require the incorporation of biomarkers in participant selection, prognostication, monitoring disease progression, and assessing response to treatments. We here review the current state of fluid AD biomarkers, and discuss the advantages and limitations of the updated NIA-AA research framework. Importantly, the integration of biomarker data with clinical, cognitive, and imaging domains through a systems biology approach will be essential to adequately capture the molecular, genetic, and pathological heterogeneity of AD and its spatiotemporal evolution over time.

Blood-based Biomarkers of Alzheimer's Disease: The Long and Winding Road

BACKGROUND

Blood-based biomarkers can be very useful in formulating new diagnostic and treatment proposals in the field of dementia, especially in Alzheimer's disease (AD). However, due to the influence of several factors on the reproducibility and reliability of these markers, their clinical use is still very uncertain. Thus, up-to-date knowledge about the main blood biomarkers that are currently being studied is extremely important in order to discover clinically useful and applicable tools, which could also be used as novel pharmacological strategies for the AD treatment.

METHODS

A narrative review was performed based on the current candidates of blood-based biomarkers for AD to show the main results from different studies, focusing on their clinical applicability and association with AD pathogenesis.

OBJECTIVE

The aim of this paper was to carry out a literature review on the major blood-based biomarkers for AD, connecting them with the pathophysiology of the disease.

RESULTS

Recent advances in the search of blood-based AD biomarkers were summarized in this review. The biomarkers were classified according to the topics related to the main hallmarks of the disease such as inflammation, amyloid, and tau deposition, synaptic degeneration and oxidative stress. Moreover, molecules involved in the regulation of proteins related to these hallmarks were described, such as non-coding RNAs, neurotrophins, growth factors and metabolites. Cells or cellular components with the potential to be considered as blood-based AD biomarkers were described in a separate topic.

CONCLUSION

A series of limitations undermine new discoveries on blood-based AD biomarkers. The lack of reproducibility of findings due to the small size and heterogeneity of the study population, different analytical methods and other assay conditions make longitudinal studies necessary in this field to validate these structures, especially when considering a clinical evaluation that includes a broad panel of these potential and promising blood-based biomarkers.

Not All Stressors Are Equal: Mechanism of Stressors on RPE Cell Degeneration

Age-related macular degeneration (AMD) is a major cause of irreversible blindness among the elderly population. Dysfunction and degeneration of the retinal pigment epithelial (RPE) layer in the retina underscore the pathogenesis of both dry and wet AMD. Advanced age, cigarette smoke and genetic factors have been found to be the prominent risk factors for AMD, which point to an important role for oxidative stress and aging in AMD pathogenesis. However, the mechanisms whereby oxidative stress and aging lead to RPE cell degeneration are still unclear. As cell senescence and cell death are the major outcomes from oxidative stress and aging, here we review the mechanisms of RPE cell senescence and different kinds of cell death, including apoptosis, necroptosis, pyroptosis, ferroptosis, with an aim to clarify how RPE cell degeneration could occur in response to AMD-related stresses, including H₂O₂, 4-Hydroxynonenal (4-HNE), N-retinylidene-N-retinyl-ethanolamine (A2E), Alu RNA and amyloid β (Aβ). Besides those, sodium iodate (NaIO₃) induced RPE cell degeneration is also discussed in this review. Although NaIO₃ itself is not related to AMD, this line of study would help understand the mechanism of RPE degeneration.

On the propagation of the OH radical produced by Cu-amyloid beta peptide model complexes. Insight from molecular modelling

Oxidative stress and metal dyshomeostasis are considered as crucial factors in the pathogenesis of Alzheimer's disease (AD). Indeed, transition metal ions such as Cu(ii) can generate Reactive Oxygen Species (ROS) via O₂ Fenton-like reduction, catalyzed by Cu(ii) coordinated to the Amyloid beta (Aβ) peptide. Despite intensive effort, the mechanisms of ROS-induced molecular damage remain poorly understood. In the present paper, we investigate on the basis of molecular modelling computations the mechanism of OH radical propagation toward the Aβ peptide, starting from the end-product of OH radical generation by Cu(ii)·Aβ. We evaluate (i) the OH oxidative capacity, as well as the energetics of the possible Aβ oxidation target residues, by quantum chemistry Density Functional Theory (DFT) on coordination models of Cu(ii)/OH/Aβ and (ii) the motion of the OH˙ approaching the Aβ target residues by classical Molecular Dynamics (MD) on the full peptide Cu(ii)/OH/Aβ(1-16). The results show that the oxidative capacity of OH coordinated Cu(ii)Aβ is significantly lower than that of the free OH radical and that propagation toward Aβ Asp and His residues is favoured over Tyr residues. These results are discussed on the basis of the recent literature on in vitro Aβ metal-catalyzed oxidation and on the possible implications for the AD oxidative stress mechanism.

Altered Redox State in Whole Blood Cells from Patients with Mild Cognitive Impairment and Alzheimer's Disease

Oxidative stress plays an essential and early role in the pathophysiology of Alzheimer's disease (AD). Alterations in the redox state in AD and in mild cognitive impairment (MCI) patients appear in the brain and at peripheral level. Given that it is easier to study the latter, most of the research has been focused on plasma. However, the analysis of redox parameters in whole blood cells (including erythrocytes and leukocytes) has not really been investigated. Moreover, the association of these parameters with Mini-Mental State Examination (MMSE) clinical scores, has scarcely been studied. Therefore, the aim of the present work was to analyze several redox markers in whole blood cells from male and female MCI and AD patients. Antioxidant (superoxide dismutase, catalase (CAT), glutathione peroxidase (GPx), and reductase (GR) activities, and reduced glutathione (GSH) concentration) together with oxidant parameters (oxidized glutathione (GSSG) and thiobarbituric acid-reactive substances (TBARS)) were investigated using MCI and AD (10 women and 10 men in each group) and their age-matched control groups (15 women and 15 men). The results show an altered redox state in whole blood cells from AD patients (higher CAT, GSSG/GSH, TBARS and lower GPx, GR, GSH). Some of these redox parameters are already affected in MCI patients (higher TBARS and lower GPx and GR activities) in both sexes and, consequently, they could be used as markers of prodromal AD. Since GR, GSH, GSSG, and GSSG/GSH were found to be associated with MMSE scores, they seem to be useful clinically to monitor cognitive decline in AD progression.

Sialic acid associated with oxidative stress and total antioxidant capacity (TAC) expression level as a predictive indicator in moderate to severe Alzheimer's disease

BACKGROUND

Several studies have shown many risk factors associated with disease onset, but the sialic acid association with oxidative stress biomarkers may a key factor in the pathogenesis of Alzheimer's disease (AD). We aim to find out the most specific biomarker from the peripheral blood samples in moderate to severe Alzheimer's patients.

METHODS

This study examined the level of sialic acid associated with oxidative stress biomarkers and total antioxidant capacity level (TAC) in the plasma samples. Different parameters of Oxidative stress and Total antioxidant capacity by the immunoassay method have been examined in AD patients as compared to controls. The Catalase (CAT), Superoxide dismutase (SOD), Lipid peroxidation (LPO), Glutathione peroxidase (GPx), Total Glutathione (GSH), and Protein carbonyl group levels were estimated in this study.

RESULTS

Increased level of sialic acid is found associated with a higher level of reactive oxygen species parameters in the patients. The antioxidant parameter levels have been found significantly lower in AD, while Protein carbonyl group and lipid peroxidation were increased in cases as compared to controls with the area under the curve (AUC) 0.816, p < 0.0001 and 0.754, p < 0.0001. The Protein carbonyl group, Total antioxidant capacity (TAC), and Sigma-Aldrich TAC levels were higher in females as compared to males in AD patients.

CONCLUSION

During AD pathology, sialic acid, protein carbonyl, and lipid peroxidation were found as the more sensitive marker that may be used as a diagnostic and prognostic biomarker.

Activation of Tyrosine Phosphorylation Signaling in Erythrocytes of Patients with Alzheimer's Disease

Alzheimer's disease (AD) is the most prevalent type of dementia affecting older people. The identification of biomarkers is increasingly important and would be crucial for future therapy. Here, we demonstrated that in AD erythrocytes: (i) the anion transporter band3 is highly phosphorylated; (ii) the lyn kinase is phosphorylated and activated; (iii) the tyrosine phosphatase activity is downregulated, with a significant inverse correlation between band3 phosphorylation and disease progression, as revealed by Mini Mental State Examination score. Finally, we showed that in normal erythrocytes, treated in vitro with Aβ1-42 peptide, both band3 phosphorylation and lyn activation occurs. These results suggest that modulation of tyrosine phosphorylation signaling may be evaluated as a potential peripheral marker in AD.

The effect of age and obesity on platelet amyloid precursor protein processing and plasma markers of oxidative stress and inflammation

INTRODUCTION

Advancing age is a major risk factor for a range of diseases such as, cardiovascular disease, diabetes, cancer and neurodegenerative diseases. In addition, over a third of the population are overweight and obesity is becoming more prevalent in younger people. Ageing and obesity are both linked to a chronic proinflammatory state and elevated oxidative stress, which have both been implicated in cardiovascular and neurodegenerative diseases. Platelets contain all the necessary machinery to process the Amyloid precursor protein AβPP, a pathway thought to be perturbed in Alzheimer's Disease (AD). The ratio of AβPP isoforms present in platelets, and the amount of alpha secretase ADAM10, that works to process AβPP, appear to be associated with cognitive decline and a diagnosis of Alzheimer's disease. The aim of this study was to assess changes in AβPP ratio, ADAM10 and markers of inflammation and oxidative stress with ageing and obesity.

MATERIALS AND METHODS

Ninety participants were recruited to this study to provide one blood sample. Platelet-rich plasma and platelet lysates were collected and the expression of AβPPr, proADAM10 and mADAM10 was assessed by Western blotting. In addition, markers of inflammation (IL-6) and oxidative stress (8-Isoprostane) were assessed in plasma.

RESULTS

Participants were placed into one of four groups based on their age and body mass index (Young/Lean, Young/obese, Old/Lean and Old/Obese). IL-6 was able to significantly distinguish obese from lean participants (AUC of 0.80, SE = 0.05, P < 0.001). Plasma isoprostanes were able to distinguish between both young/old (AUC of 0.73, SE = 0.05, P < 0.01), and obese/non-obese participants (AUC of 0.66, SE = 0.01, P < 0.01). Plasma protein carbonyls could distinguish young and old participants (AUC of 0.69, SE = 0.07 P < 0.02). Old Lean participants had significantly lower mADAM10 expression than both Young Lean and Young Obese participants (p < 0.05). Old obese participants had significantly lower proADAM10 expression compared to both Young Lean and Young Obese (p < 0.05). Both mADAM10 and proADAM10 were significantly decreased with advancing age (p < 0.05).

CONCLUSIONS

The findings presented in this study provide evidence that blood-based biomarkers related to the pathology of AD are altered with age and obesity in otherwise healthy adults. Ageing was more strongly associated with elevated markers of oxidative stress whereas obesity was associated with elevated inflammatory IL-6.

Oxidative stress in alzheimer's disease: A review on emergent natural polyphenolic therapeutics

OBJECTIVES

The aim of this research was to review the literature on Alzheimer's disease (AD) with a focus on polyphenolics as antioxidant therapeutics.

DESIGN

This review included a search of the literature up to and including September 2019 in PubMed and MEDLINE databases using search terms that included: Alzheimer's Disease, Aβ peptide, tau, oxidative stress, redox, oxidation, therapeutic, antioxidant, natural therapy, polyphenol. Any review articles, case studies, research reports and articles in English were identified and subsequently interrogated. Citations within relevant articles were also examined for consideration in this review.

RESULTS

Alzheimer's disease is a neurodegenerative disorder that is clinically characterised by the progressive deterioration of cognitive functions and drastic changes in behaviour and personality. Due to the significant presence of oxidative damage associated with abnormal Aβ accumulation and neurofibrillary tangle deposition in AD patients' brains, antioxidant drug therapy has been investigated as potential AD treatment. In particular, naturally occurring compounds, such as plant polyphenols, have been suggested to have potential neuroprotective effects against AD due to their diverse array of physiological actions, which includes potent antioxidant effects.

CONCLUSIONS

The impact of oxidative stress and various mechanisms of pathogenesis in AD pathophysiology was demonstrated along with the therapeutic potential of emergent antioxidant drugs to address such mechanism of oxidation.

Propargylamine-derived multi-target directed ligands for Alzheimer's disease therapy

Current options for the treatment of Alzheimeŕs disease have been restricted to prescription of acetylcholinesterase inhibitors or N-methyl-d-aspartate receptor antagonist, memantine. Propargylamine-derived multi-target directed ligands, such as ladostigil, M30, ASS234 and contilisant, involve different pathways. Apart from acting as inhibitors of both cholinesterases and monoamine oxidases, they show improvement of cognitive impairment, antioxidant activities, enhancement of iron-chelating activities, protect against tau hyperphosphorylation, block metal-associated oxidative stress, regulate APP and Aβ expression processing by the non-amyloidogenic α-secretase pathway, suppress mitochondrial permeability transition pore opening, and coordinate protein kinase C signaling and Bcl-2 family proteins. Other hybrid propargylamine derivatives are also reported.

Tocotrienol-Rich Fraction of Palm Oil Improves Behavioral Impairments and Regulates Metabolic Pathways in AβPP/PS1 Mice

We have recently shown that the tocotrienol-rich fraction (TRF) of palm oil, a mixture of vitamin E analogs, improves amyloid pathology in vitro and in vivo. However, precise mechanisms remain unknown. In this study, we examined the effects of long-term (10 months) TRF treatment on behavioral impairments and brain metabolites in (15 months old) AβPP/PS1 double transgenic (Tg) Alzheimer’s disease (AD) mice. The open field test, Morris water maze, and novel object recognition tasks revealed improved exploratory activity, spatial learning, and recognition memory, respectively, in TRF-treated Tg mice. Brain metabolite profiling of wild-type and Tg mice treated with and without TRF was performed using ultrahigh performance liquid chromatography (UHPLC) coupled to high-resolution accurate mass (HRAM)-orbitrap tandem mass spectrometry (MS/MS). Metabolic pathway analysis found perturbed metabolic pathways that linked to AD. TRF treatment partly ameliorated metabolic perturbations in Tg mouse hippocampus. The mechanism of this pre-emptive activity may occur via modulation of metabolic pathways dependent on Aβ interaction or independent of Aβ interaction.

Vascular Cognitive Impairment: Information from Animal Models on the Pathogenic Mechanisms of Cognitive Deficits

Vascular cognitive impairment (VCI) is the second most common cause of cognitive deficit after Alzheimer's disease. Since VCI patients represent an important target population for prevention, an ongoing effort has been made to elucidate the pathogenesis of this disorder. In this review, we summarize the information from animal models on the molecular changes that occur in the brain during a cerebral vascular insult and ultimately lead to cognitive deficits in VCI. Animal models cannot effectively represent the complex clinical picture of VCI in humans. Nonetheless, they allow some understanding of the important molecular mechanisms leading to cognitive deficits. VCI may be caused by various mechanisms and metabolic pathways. The pathological mechanisms, in terms of cognitive deficits, may span from oxidative stress to vascular clearance of toxic waste products (such as amyloid beta) and from neuroinflammation to impaired function of microglia, astrocytes, pericytes, and endothelial cells. Impaired production of elements of the immune response, such as cytokines, and vascular factors, such as insulin-like growth factor 1 (IGF-1), may also affect cognitive functions. No single event could be seen as being the unique cause of cognitive deficits in VCI. These events are interconnected, and may produce cascade effects resulting in cognitive impairment.

Oxidation resistance 1 regulates post-translational modifications of peroxiredoxin 2 in the cerebellum

Protein aggregation, oxidative and nitrosative stress are etiological factors common to all major neurodegenerative disorders. Therefore, identifying proteins that function at the crossroads of these essential pathways may provide novel targets for therapy. Oxidation resistance 1 (Oxr1) is a protein proven to be neuroprotective against oxidative stress, although the molecular mechanisms involved remain unclear. Here, we demonstrate that Oxr1 interacts with the multifunctional protein, peroxiredoxin 2 (Prdx2), a potent antioxidant enzyme highly expressed in the brain that can also act as a molecular chaperone. Using a combination of in vitro assays and two animal models, we discovered that expression levels of Oxr1 regulate the degree of oligomerization of Prdx2 and also its post-translational modifications (PTMs), specifically suggesting that Oxr1 acts as a functional switch between the antioxidant and chaperone functions of Prdx2. Furthermore, we showed in the Oxr1 knockout mouse that Prdx2 is aberrantly modified by overoxidation and S-nitrosylation in the cerebellum at the presymptomatic stage; this in-turn affected the oligomerization of Prdx2, potentially impeding its normal functions and contributing to the specific cerebellar neurodegeneration in this mouse model.

Integrated communications between cyclooxygenase-2 and Alzheimer's disease

Elevated levels of cyclooxygenase-2 (COX-2) and prostaglandins (PGs) are involved in the pathogenesis of Alzheimer's disease (AD), which is characterized by the accumulation of β-amyloid protein (Aβ) and tau hyperphosphorylation. However, the gaps in our knowledge of the roles of COX-2 and PGs in AD have not been filled. Here, we summarized the literature showing that COX-2 dysregulation obviously influences abnormal cleavage of β-amyloid precursor protein, aggregation and deposition of Aβ in β-amyloid plaques and the inclusion of phosphorylated tau in neurofibrillary tangles. Neuroinflammation, oxidative stress, synaptic plasticity, neurotoxicity, autophagy, and apoptosis have been assessed to elucidate the mechanisms of COX-2 regulation of AD. Notably, an imbalance of these factors ultimately produces cognitive decline. The current review substantiates our understanding of the mechanisms of COX-2-induced AD and establishes foundations for the design of feasible therapeutic strategies to treat AD.-Guan, P.-P., Wang, P. Integrated communications between cyclooxygenase-2 and Alzheimer's disease.

Oxidative Stress Levels in the Brain Are Determined by Post-Mortem Interval and Ante-Mortem Vitamin C State but Not Alzheimer's Disease Status

The current study highlighted several changes in measures of oxidative stress and antioxidant status that take place in the mouse brain over the course of 24 h post-mortem. Ascorbic acid (vitamin C) and glutathione both decreased significantly in cortex in as little as 2 h and malondialdehyde levels increased. Further change from baseline was observed up to 24 h, including carbonyl and sulfhydryl formation. The greatest changes were observed in brains that began with low ascorbic acid levels (gulo^{&minus;/&minus;} mice) compared to wild-type or 5XFAD mice. Cortical samples from nine Alzheimer&rsquo;s Disease cases and five controls were also assayed under the same conditions. Post mortem intervals ranged from 6 to 47 h and all samples had low ascorbic acid levels at time of measurement. Malondialdehyde levels were lower in Alzheimer&rsquo;s Disease cases. Despite a strong positive correlation between ascorbic acid and glutathione levels, no other correlations among oxidative stress measures or post mortem interval were observed. Together the data suggest that molecular changes occurring within the first hours of death may mask differences between patient groups. Care must be taken interpreting studies in human brain tissue where ante-mortem nutrient status is not known to avoid bias or confounding of results.

An Overview of the Role of Lipofuscin in Age-Related Neurodegeneration

Despite aging being by far the greatest risk factor for highly prevalent neurodegenerative disorders, the molecular underpinnings of age-related brain changes are still not well understood, particularly the transition from normal healthy brain aging to neuropathological aging. Aging is an extremely complex, multifactorial process involving the simultaneous interplay of several processes operating at many levels of the functional organization. The buildup of potentially toxic protein aggregates and their spreading through various brain regions has been identified as a major contributor to these pathologies. One of the most striking morphologic changes in neurons during normal aging is the accumulation of lipofuscin (LF) aggregates, as well as, neuromelanin pigments. LF is an autofluorescent lipopigment formed by lipids, metals and misfolded proteins, which is especially abundant in nerve cells, cardiac muscle cells and skin. Within the Central Nervous System (CNS), LF accumulates as aggregates, delineating a specific senescence pattern in both physiological and pathological states, altering neuronal cytoskeleton and cellular trafficking and metabolism, and being associated with neuronal loss, and glial proliferation and activation. Traditionally, the accumulation of LF in the CNS has been considered a secondary consequence of the aging process, being a mere bystander of the pathological buildup associated with different neurodegenerative disorders. Here, we discuss recent evidence suggesting the possibility that LF aggregates may have an active role in neurodegeneration. We argue that LF is a relevant effector of aging that represents a risk factor or driver for neurodegenerative disorders.

Dietary Lycopene Supplementation Improves Cognitive Performances in Tau Transgenic Mice Expressing P301L Mutation via Inhibiting Oxidative Stress and Tau Hyperphosphorylation

BACKGROUND

Oxidative stress is implicated in the pathogenesis of Alzheimer's disease (AD) and other tauopathies and participates in their development by promoting hyperphosphorylation of microtubule-associated protein tau. Lycopene, as an effective antioxidant, combined with vitamin E seemed to be additive against oxidative stress.

OBJECTIVE

The present study was undertaken to examine whether lycopene or lycopene/vitamin E could exert protective effects on memory deficit and oxidative stress in tau transgenic mice expressing P301L mutation.

MATERIALS AND METHODS

P301L transgenic mice were assigned to three groups: P301L group (P301L), P301L+lycopene (Lyc), and P301L+lycopene/vitamin E (Lyc+VE). Age-matched C57BL/6J mice as wild type controls (Con) were used in the present study. Spatial memory was assessed by radial arm while passive memories were evaluated by step-down and step-through tests. Levels of tau phosphorylation were detected by western blot. Oxidative stress biomarkers were measured in the serum using biochemical assay kits.

RESULTS

Compared with the control group, P301L mice displayed significant spatial and passive memory impairments, elevated malondialdehyde (MDA) levels and decreased glutathione peroxidase (GSH-Px) activities in serum, and increased tau phosphorylation at Thr231/Ser235, Ser262, and Ser396 in brain. Supplementations of lycopene or lycopene/vitamin E could significantly ameliorate the memory deficits, observably decreased MDA concentrations and increased GSH-Px activities, and markedly attenuated tau hyperphosphorylation at multiple AD-related sites.

CONCLUSIONS

Our findings indicated that the combination of lycopene and vitamin E antioxidants acted in a synergistic fashion to bring significant effects against oxidative stress in tauopathies.

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.

Introduction

Primordial life forms on earth comprised oxygen-sensitive organisms: the anaerobic fermenters and cyanobacteria, which released oxygen as a metabolic by-product, causing the oxygen levels in the atmosphere to rise Benzie (Eur J Nutr 39:53–61, 2000 [1]), Halliwell (Free Radic Res 31:261–272, 1999 [2]).

Relation of plasma selenium and lipid peroxidation end products in patients with Alzheimer's disease

Increased oxidative stress in the brain during the course of Alzheimer's disease (AD) leads to an imbalance of antioxidants and formation of free radical reaction end-products which may be detected in blood as fluorescent lipofuscin-like pigments (LFPs). The aim of this study was to evaluate and compare LFPs with plasma selenium concentrations representing an integral part of the antioxidant system. Plasma samples from subjects with AD dementia (ADD; n=11), mild cognitive impairment (MCI; n=17) and controls (n=12), were collected. The concentration of selenium was measured using atomic absorption spectroscopy. LFPs were analyzed by fluorescence spectroscopy and quantified for different fluorescent maxima and then correlated with plasma selenium. Lower levels of selenium were detected in MCI and ADD patients than in controls (P=0.003 and P=0.049, respectively). Additionally, higher fluorescence intensities of LFPs were observed in MCI patients than in controls in four fluorescence maxima and higher fluorescence intensities were also observed in MCI patients than in ADD patients in three fluorescence maxima, respectively. A negative correlation between selenium concentrations and LFPs fluorescence was observed in the three fluorescence maxima. This is the first study focused on correlation of plasma selenium with specific lipofuscin-like products of oxidative stress in plasma of patients with Alzheimer´s disease and mild cognitive impairment.

Erythrocytes as Potential Link between Diabetes and Alzheimer's Disease

Many studies support the existence of an association between type 2 diabetes (T2DM) and Alzheimer's disease (AD). In AD, in addition to brain, a number of peripheral tissues and cells are affected, including red blood cell (RBC) and because there are currently no reliable diagnostic biomarkers of AD in the blood, a gradually increasing attention has been given to the study of RBC's alterations. Recently it has been evidenced in diabetes, RBC alterations superimposable to the ones occurring in AD RBC. Furthermore, growing evidence suggests that oxidative stress plays a pivotal role in the development of RBC's alterations and vice versa. Once again this represents a further evidence of a shared pathway between AD and T2DM. The present review summarizes the two disorders, highlighting the role of RBC in the postulated common biochemical links, and suggests RBC as a possible target for clinical trials.

Study on Analysis of Peripheral Biomarkers for Alzheimer's Disease Diagnosis

Many factors are involved in Alzheimer’s disease (AD) pathology including tau phosphorylation, amyloid β protein (Aβ) accumulation, lipid dysregulation, oxidative stress, and inflammation. The markers of these pathological processes in cerebral spinal fluid are used currently for AD diagnosis. However, peripheral biomarkers are the need of the hour for large population screening for AD. The main objective of the present study is to evaluate the peripheral levels of redox markers, lipid peroxidation (LPO) indicators, and pathological markers in AD patients. Blood was collected from AD patients (n = 45), controls (n = 45), and analyzed for pathological markers of AD including Aβ42 and tau, LPO, and redox indicators. Plasma Aβ42 was significantly (P < 0.001) elevated while total tau was decreased in AD compared to controls. Hydroxynonenal (HNE) and malondialdehyde (MDA) were higher (P < 0.001) in AD patients pointing the enhanced LPO in AD pathology. Receiver operating characteristic curve (ROC) analysis indicated that HNE is a better indicator of LPO compared to MDA. Plasma glutathione (GSH) level was significantly (P < 0.001) low while oxidized glutathione (GSSG) level was higher (P < 0.001) in AD patients with corresponding decrease in GSH/GSSG ratio (P < 0.001). ROC analysis indicated that GSH/GSSG ratio can be used as reliable indicator for redox imbalance in AD with a cutoff value of <8.73 (sensitivity 91.1%, specificity 97.8%). Correlation analysis revealed a positive correlation for both HNE and MDA with Aβ42 and a negative correlation with total tau. Negative correlation was observed between GSH/GSSG ratio and LPO markers. While oxidative stress has been implicated in pathology of various neurodegenerative disorders, the present study pinpoints the direct link between LPO and Aβ production in plasma of AD patients. Normally, at low amyloid concentration in body fluids, this peptide shown to function as a strong metal chelating antioxidant. However, when the Aβ production enhanced as in AD, through gain of functional transformation, Aβ evolves into prooxidant, thereby enhancing oxidative stress and LPO. Altered redox status with enhanced LPO observed in AD blood could contribute to the oxidation and S-glutathionylation proteins, which has to be addressed in future studies.

Neuroprotective effect of Indian propolis in β-amyloid induced memory deficit: Impact on behavioral and biochemical parameters in rats

The study aimed at the investigation of neuroprotective activity of macerated ethanolic extract of Indian propolis (MEEP) against β-Amyloid 25-35 (Aβ_25-35) induced memory impairment in Alzheimer's disease. MEEP was administrated orally to Wistar rats at doses of 100, 200 and 300mg/kg. Behavioral performances were evaluated using morris water maze and radial arm maze. At the end of behavioral study, the brains were removed and antioxidant parameters and brain monoamines were estimated. Further acetylcholinesterase (AchE) inhibition and brain-derived neurotropic factor (BDNF) were evaluated. In addition hematological parameters and histopathological tests were also carried out. In behavioral models, MEEP significantly (P<0.05) reversed the cognitive impairment of β amyloid-induced rats. The antioxidant potential was significantly increased (P<0.05) after administration of MEEP. Malondialdehyde levels were significantly (P<0.01) decreased in brain homogenate after treatment with MEEP extract as compared with diseased control group (group III). MEEP showed dose-dependent AChE inhibition and increased the levels of brain monoamines (P<0.05) as compared with group III. MEEP improved memory deficits by increasing BDNF in plasma (P<0.05). The study concludes that MEEP has anti-Alzheimer potential in rats through multiple mechanisms and further studies are ongoing for fractionation and biological screening.

In vivo ROS production and use of oxidative stress-derived biomarkers to detect the onset of diseases such as Alzheimer's disease, Parkinson's disease, and diabetes

Breakthroughs in biochemistry have furthered our understanding of the onset and progression of various diseases, and have advanced the development of new therapeutics. Oxidative stress and reactive oxygen species (ROS) are ubiquitous in biological systems. ROS can be formed non-enzymatically by chemical, photochemical and electron transfer reactions, or as the byproducts of endogenous enzymatic reactions, phagocytosis, and inflammation. Imbalances in ROS homeostasis, caused by impairments in antioxidant enzymes or non-enzymatic antioxidant networks, increase oxidative stress, leading to the deleterious oxidation and chemical modification of biomacromolecules such as lipids, DNA, and proteins. While many ROS are intracellular signaling messengers and most products of oxidative metabolisms are beneficial for normal cellular function, the elevation of ROS levels by light, hyperglycemia, peroxisomes, and certain enzymes causes oxidative stress-sensitive signaling, toxicity, oncogenesis, neurodegenerative diseases, and diabetes. Although the underlying mechanisms of these diseases are manifold, oxidative stress caused by ROS is a major contributing factor in their onset. This review summarizes the relationship between ROS and oxidative stress, with special reference to recent advancements in the detection of biomarkers related to oxidative stress. Further, we will introduce biomarkers for the early detection of neurodegenerative diseases and diabetes, with a focus on our recent work.

Mitochondrial dysfunction - Silent killer in cerebral ischemia

Mitochondrial dysfunction aggravates ischemic neuronal injury through activation of various pathophysiological and molecular mechanisms. Ischemic neuronal injury is particularly intensified during reperfusion due to impairment of mitochondrial function. Mitochondrial mutilation instigates alterations in calcium homeostasis in neurons, which plays a pivotal role in the maintenance of normal neuronal function. Increase in intracellular calcium level in mitochondria triggers the opening of mitochondrial transition pore and over production of reactive oxygen species (ROS). Several investigations have concluded that ROS not only contribute to lipids and proteins damage, but also transduce apoptotic signals leading to neuronal death. In addition to the above mentioned reasons, endoplasmic reticulum (ER) stress due to excitotoxicity also leads to neuronal death. Recently, some newer proteins have been claimed to induce "mitophagy" by triggering the receptors on autophagic membranes leading to neurodegeneration. This review summarizes the mechanisms underlying neuronal death involving mitochondrial dysfunction and mitophagy.

Vitamin E, Turmeric and Saffron in Treatment of Alzheimer's Disease

Alzheimer’s disease (AD) is a growing epidemic and currently there is no cure for the disease. The disease has a detrimental effect on families and will strain the economy and health care systems of countries worldwide. The paper provides a literature review on a few ongoing possible antioxidant therapy treatments for the disease. The paper highlights use of vitamin E, turmeric and saffron for an alternative antioxidant therapy approach. Clinical studies report their therapeutic abilities as protective agents for nerve cells against free radical damage, moderating acetylcholinesterase (AChE) activity and reducing neurodegeneration, which are found as key factors in Alzheimer’s. The paper suggests that future research, with more clinical trials focused on more natural approaches and their benefits for AD treatment could be worthwhile.

Differences in peripheral oxidative stress markers in Alzheimer's disease, vascular dementia and mixed dementia patients

AIMS

We determined whether the possible roles of oxidative stress differ in the pathophysiology and cognitive decline of Alzheimer's disease (AD), vascular dementia (VaD) and mixed Alzheimer's/vascular dementia (MD).

METHODS

We measured the levels of diacron reactive oxygen metabolite (dROM), reflecting the amount of organic hydroperoxides, and biological anti-oxidant potential (BAP), measuring the ferric reducing ability of blood plasma, in 72 patients with AD, 27 with VaD, 24 with MD and 53 non-demented outpatients (control group). In addition, endogenous plasma anti-oxidants, such as albumin, total bilirubin and uric acid, were compared among the groups. All participants with VaD and MD showed extensive white matter hyperintensity, in addition to multiple lacunes.

RESULTS

The dROM levels were significantly higher in the AD and MD groups than in the control group. The BAP levels were significantly lower in the MD group than in the control, AD and VaD groups. The AD group showed significantly lower levels of bilirubin and uric acid than the control group. The MD group showed a significantly lower level of albumin than the control and AD groups, and a significantly lower level of bilirubin than the control group. The Mini-Mental State examination scores correlated significantly with dROM levels and BAP/dROM ratios in the AD group.

CONCLUSIONS

An imbalance in pro-oxidant and anti-oxidant defenses is apparently involved in the pathophysiology of the AD and MD groups. The extent of oxidative stress damage might differ in subtypes of dementia by being greater in the MD group than in other types of dementia. Synergic effects of the degenerative element of AD and white matter lesions might be associated with oxidative stress damage in the MD group.