Mutations in amyloid precursor protein and presenilin-1 genes increase the basal oxidative stress in murine neuronal cells and lead to increased sensitivity to oxidative stress mediated by amyloid beta-peptide (1-42), HO and kainic acid: implications for Alzheimer's disease

Presenilin: A Multi-Functional Molecule in the Pathogenesis of Alzheimer's Disease and Other Neurodegenerative Diseases

Presenilin, a transmembrane protein primarily known for its role in Alzheimer's disease (AD) as part of the γ-secretase complex, has garnered increased attention due to its multifaceted functions in various cellular processes. Recent investigations have unveiled a plethora of functions beyond its amyloidogenic role. This review aims to provide a comprehensive overview of presenilin's diverse roles in AD and other neurodegenerative disorders. It includes a summary of well-known substrates of presenilin, such as its involvement in amyloid precursor protein (APP) processing and Notch signaling, along with other functions. Additionally, it highlights newly discovered functions, such as trafficking function, regulation of ferritin expression, apolipoprotein E (ApoE) secretion, the interaction of ApoE and presenilin, and the Aβ42-to-Aβ40-converting activity of ACE. This updated perspective underscores the evolving landscape of presenilin research, emphasizing its broader impact beyond established pathways. The incorporation of these novel findings accentuates the dynamic nature of presenilin's involvement in cellular processes, further advancing our comprehension of its multifaceted roles in neurodegenerative disorders. By synthesizing evidence from a range of studies, this review sheds light on the intricate web of presenilin functions and their implications in health and disease.

Recent progress in the development of fluorescent probes for imaging pathological oxidative stress

Oxidative stress is closely related to the physiopathology of numerous diseases. Reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive sulfur species (RSS) are direct participants and important biomarkers of oxidative stress. A comprehensive understanding of their changes can help us evaluate disease pathogenesis and progression and facilitate early diagnosis and drug development. In recent years, fluorescent probes have been developed for real-time monitoring of ROS, RNS and RSS levels in vitro and in vivo. In this review, conventional design strategies of fluorescent probes for ROS, RNS, and RSS detection are discussed from three aspects: fluorophores, linkers, and recognition groups. We introduce representative fluorescent probes for ROS, RNS, and RSS detection in cells, physiological/pathological processes (e.g., Inflammation, Drug Induced Organ Injury and Ischemia/Reperfusion Injury etc.), and specific diseases (e.g., neurodegenerative diseases, epilepsy, depression, diabetes and cancer, etc.). We then highlight the achievements, current challenges, and prospects for fluorescent probes in the pathophysiology of oxidative stress-related diseases.

Effectiveness of coenzyme Q10 on learning and memory and synaptic plasticity impairment in an aged Aβ-induced rat model of Alzheimer's disease: a behavioral, biochemical, and electrophysiological study

RATIONALE

Aging is the major risk factor for Alzheimer's disease (AD), and cognitive and memory impairments are common among the elderly. Interestingly, coenzyme Q10 (Q10) levels decline in the brain of aging animals. Q10 is a substantial antioxidant substance, which has an important role in the mitochondria.

OBJECTIVE

We assessed the possible effects of Q10 on learning and memory and synaptic plasticity in aged β-amyloid (Aβ)-induced AD rats.

METHODS

In this study, 40 Wistar rats (24-36 months old; 360-450 g) were randomly assigned to four groups (n = 10 rats/group)-group I: control, group II: Aβ, group III: Q10; 50 mg/kg, and group IV: Q10+Aβ. Q10 was administered orally by gavage daily for 4 weeks before the Aβ injection. The cognitive function and learning and memory of the rats were measured by the novel object recognition (NOR), Morris water maze (MWM), and passive avoidance learning (PAL) tests. Finally, malondialdehyde (MDA), total antioxidant capacity (TAC), total thiol group (TTG), and total oxidant status (TOS) were measured.

RESULTS

Q10 improved the Aβ-related decrease in the discrimination index in the NOR test, spatial learning and memory in the MWM test, passive avoidance learning and memory in the PAL test, and long-term potentiation (LTP) impairment in the hippocampal PP-DG pathway in aged rats. In addition, Aβ injection significantly increased serum MDA and TOS levels. Q10, however, significantly reversed these parameters and also increased TAC and TTG levels in the Aβ+Q10 group.

CONCLUSIONS

Our experimental findings suggest that Q10 supplementation can suppress the progression of neurodegeneration that otherwise impairs learning and memory and reduces synaptic plasticity in our experimental animals. Therefore, similar supplemental Q10 treatment given to humans with AD could possibly provide them a better quality of life.

Links between COVID-19 and Alzheimer's Disease-What Do We Already Know?

Alzheimer's disease (AD) is a life-changing condition whose etiology is explained by several hypotheses. Recently, a new virus contributed to the evidence of viral involvement in AD: the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes the COVID-19 coronavirus disease. AD was found to be one of the most common COVID-19 comorbidities, and it was found to increase mortality from this disease as well. Moreover, AD patients were observed to present with the distinct clinical features of COVID-19, with delirium being prevalent in this group. The SARS-CoV-2 virus enters host cells through the angiotensin-converting enzyme 2 (ACE2) receptor. ACE2 is overexpressed in brains with AD, which thus increases the viral invasion. Furthermore, the inhibition of the ACE2 receptor by the SARS-CoV-2 virus may also decrease the brain-derived neurotrophic factor (BDNF), contributing to neurodegeneration. The ApoE ε4 allele, which increases the risk of AD, was found to facilitate the SARS-CoV-2 entry into cells. Furthermore, the neuroinflammation and oxidative stress existing in AD patients enhance the inflammatory response associated with COVID-19. Moreover, pandemic and associated social distancing measures negatively affected the mental health, cognitive function, and neuro-psychiatric symptoms of AD patients. This review comprehensively covers the links between COVID-19 and Alzheimer's disease, including clinical presentation, molecular mechanisms, and the effects of social distancing.

FAD-deficient P187S mutation of NAD(P)H:quinone oxidoreductase 1 (NQO1*2) binds and accelerates β-amyloid aggregation

Alzheimer's disease (AD) is one of the most prominent neurodegenerative diseases. Results from animal and cellular models suggest that FAD-deficient forms of NAD(P)H quinone oxidoreductase 1 (NQO1) may accelerate the aggregation of Alzheimer's amyloid-β peptide (Aβ1-42). Here, we examined in vitro whether NQO1 and its FAD-deficient P187S mutation (NQO1*2) directly interact with Aβ1-42 and modify its rate of aggregation. When monitored using the fluorescence of either noncovalent thioflavin T (ThT) or HiLyte Fluor 647 (HF647) dye covalently attached to the Aβ1-42 peptide, the aggregation kinetics of Aβ1-42 were markedly more rapid in the presence of NQO1*2 than the wild-type (WT) NQO1. Experiments using apo-NQO1 indicate that this increase is linked to the inability of NQO1*2 to bind to FAD. Furthermore, dicoumarol, an NQO1 inhibitor that binds near the FAD-binding site and stabilizes NQO1*2, markedly decreased the aggregation kinetics of Aβ1-42. Imaging flow cytometry confirmed in-vitro coaggregation of NQO1 isoforms and Aβ1-42. Aβ1-42 alone forms rod-shaped fibril structures while in the presence of NQO1 isoforms, Aβ1-42 is incorporated in the middle of larger globular protein aggregates surrounded by NQO1 molecules. Isothermal titration calorimetry (ITC) analysis indicates that Aβ1-42 interacts with NQO1 isoforms with a specific stoichiometry through a hydrophobic interaction with positive enthalpy and entropy changes. These data define the kinetics, mechanism, and shape of coaggregates of Aβ1-42 and NQO1 isoforms and the potential relevance of FAD-deficient forms of NQO1 for amyloid aggregation diseases.

Functionalization strategies of polymeric nanoparticles for drug delivery in Alzheimer's disease: Current trends and future perspectives

Alzheimer's disease (AD), the most common form of dementia, is a progressive and multifactorial neurodegenerative disorder whose primary causes are mostly unknown. Due to the increase in life expectancy of world population, including developing countries, AD, whose incidence rises dramatically with age, is at the forefront among neurodegenerative diseases. Moreover, a definitive cure is not yet within reach, imposing substantial medical and public health burdens at every latitude. Therefore, the effort to devise novel and effective therapeutic strategies is still of paramount importance. Genetic, functional, structural and biochemical studies all indicate that new and efficacious drug delivery strategies interfere at different levels with various cellular and molecular targets. Over the last few decades, therapeutic development of nanomedicine at preclinical stage has shown to progress at a fast pace, thus paving the way for its potential impact on human health in improving prevention, diagnosis, and treatment of age-related neurodegenerative disorders, including AD. Clinical translation of nano-based therapeutics, despite current limitations, may present important advantages and innovation to be exploited in the neuroscience field as well. In this state-of-the-art review article, we present the most promising applications of polymeric nanoparticle-mediated drug delivery for bypassing the blood-brain barrier of AD preclinical models and boost pharmacological safety and efficacy. In particular, novel strategic chemical functionalization of polymeric nanocarriers that could be successfully employed for treating AD are thoroughly described. Emphasis is also placed on nanotheranostics as both potential therapeutic and diagnostic tool for targeted treatments. Our review highlights the emerging role of nanomedicine in the management of AD, providing the readers with an overview of the nanostrategies currently available to develop future therapeutic applications against this chronic neurodegenerative disease.

Overview of therapeutic targets in management of dementia

Dementia is defined as a gradual cognitive impairment that interferes with everyday tasks, and is a leading cause of dependency, disability, and mortality. According to the current scenario, millions of individuals worldwide have dementia. This review provides with an overview of dementia before moving on to its subtypes (neurodegenerative and non-neurodegenerative) and pathophysiology. It also discusses the incidence and severity of dementia, focusing on Alzheimer's disease with its different hypotheses such as Aβ cascade hypothesis, Tau hypothesis, inflammatory hypothesis, cholinergic and oxidative stress hypothesis. Alzheimer's disease is the most common type and a progressive neurodegenerative illness distinct by neuronal loss and resulting cognitive impairment, leading to dementia. Alzheimer's disease (AD) is considered the most familiar neurodegenerative dementias that affect mostly older population. There are still no disease-modifying therapies available for any dementias at this time, but there are various methods for lowering the risk to dementia patients by using suitable diagnostic and evaluation methods. Thereafter, the management and treatment of primary risk elements of dementia are reviewed. Finally, the future perspectives of dementia (AD) focusing on the impact of the new treatment are discussed.

Neuronal Calcium Imaging, Excitability, and Plasticity Changes in the Aldh2-/- Mouse Model of Sporadic Alzheimer's Disease

Background:

Dysregulated signaling in neurons and astrocytes participates in pathophysiological alterations seen in the Alzheimer’s disease brain, including increases in amyloid-β, hyperphosphorylated tau, inflammation, calcium dysregulation, and oxidative stress. These are often noted prior to the development of behavioral, cognitive, and non-cognitive deficits. However, the extent to which these pathological changes function together or independently is unclear.

Objective:

Little is known about the temporal relationship between calcium dysregulation and oxidative stress, as some reports suggest that dysregulated calcium promotes increased formation of reactive oxygen species, while others support the opposite. Prior work has quantified several key outcome measures associated with oxidative stress in aldehyde dehydrogenase 2 knockout (Aldh2^–/–) mice, a non-transgenic model of sporadic Alzheimer’s disease.

Methods:

Here, we tested the hypothesis that early oxidative stress can promote calcium dysregulation across aging by measuring calcium-dependent processes using electrophysiological and imaging methods and focusing on the afterhyperpolarization (AHP), synaptic activation, somatic calcium, and long-term potentiation in the Aldh2^–/– mouse.

Results:

Our results show a significant age-related decrease in the AHP along with an increase in the slow AHP amplitude in Aldh2^–/– animals. Measures of synaptic excitability were unaltered, although significant reductions in long-term potentiation maintenance were noted in the Aldh2^–/– animals compared to wild-type.

Conclusion:

With so few changes in calcium and calcium-dependent processes in an animal model that shows significant increases in HNE adducts, Aβ, p-tau, and activated caspases across age, the current findings do not support a direct link between neuronal calcium dysregulation and uncontrolled oxidative stress.

Effects of Low-Intensity Transcranial Pulsed Ultrasound Treatment in a Model of Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative disease. One of the main pathology markers of AD is the beta-amyloid plaques (βA_1-42) created from residues of the badly processed amyloid precursor protein. The accumulation of these plaques can induce neuroinflammation and oxidative stress and impair antioxidant mechanisms, culminating in cognitive and memory deficits. New therapies are necessary to treat AD as the approved drugs do not treat the progress of the disease. Transcranial low-intensity pulsed ultrasound (LIPUS) affects brain metabolism and could be tested as a treatment for AD. This study was aimed at evaluating the LIPUS treatment in a model of AD induced by βA_1-42 intracerebroventricularly (ICV) and its effects on learning memory, neurotrophins, neuroinflammation and oxidative status. βA_1-42 was administered ICV 24 h before the start of a 5-wk LIPUS treatment. The treatment with LIPUS improved recognition memory, as well as increasing nerve growth factor β and brain-derived neurotrophic factor levels in the hippocampus and cortex. There was a decrease in protein damage in the hippocampus treated with LIPUS. Neuroinflammation and oxidative stress were not present in the AD model used. The results indicated that LIPUS is a novel and promising adjuvant strategy for treatment of the late stage of AD.

A Systematic Review of Current Progresses in the Nucleic Acid-Based Therapies for Neurodegeneration with Implications for Alzheimer's Disease

Recently, manipulation of gene expression and switching genes on or off highlight the potential of nucleic acid-based therapies (NA-BTs). Alzheimer's Disease (AD) is a common devastating neurodegenerative disease (NDs) responsible for 60-80% of all cases of dementia and predicted as a main public health concern among aged populations. The aim of this study was to outline the current research in the field of NA-BTs for the treatment of AD disabilities, including strategies to suppress the memory and learning defects, to promote recovery processes, and to reinforce social relationships in these patients. This review was performed via evaluating PubMed reported studies from January 2010 to November 2019. Also, reference lists were checked to find additional studies. All intermediation or complementarity of animal models, case-control and cohort studies, and controlled trials (CTs) on specific NA-BTs to AD were acceptable, although in vitro studies were excluded due to the considerable diversities and heterogeneities. After removing the duplicates according to preferred reporting items for systematic reviews and meta-analyses (PRISMA) instruction, we merged remaining titles across search databases. There are 48 ongoing studies related to the application of nucleic acids in the treatment and diagnosis of AD where more consideration is given to DNA targeting strategies (18 targets for vectors and aptamers), antisense oligonucleotides (10 targets), micro-RNAs mimics (7 targets), antagomiRs (6 targets), small interferences-RNAs (5 targets), as well as mRNAs (2 targets) respectively. All of these targets are grouped into 4 categories according to their role in molecular pathways where amyloid-β (18 targets), neural survival (11 targets), memory and cognition (8 targets), and tau (3 targets) are more targeted pathways, respectively. With recent successes in the systemic delivery of nucleic acids via intravenous injection; it is worth investing in the production of new-generation medicines. There are still several challenges for NA-BTs including, their delivery to the effective modulators, mass production at low cost, sustaining efficacy and minimizing off-target effects. Regarding miRNA-based therapies, given the obvious involvement of miRNAs in numerous facets of brain disease, and the many sophisticated techniques for delivery to the brain, miRNA-based therapies will make new hope for the treatment of neurological diseases such as AD.

Susceptibility to cellular stress in PS1 mutant N2a cells is associated with mitochondrial defects and altered calcium homeostasis

Presenilin 1 (PS1) mutations are the most common cause of familial Alzheimer's disease (FAD). PS1 also plays a role in cellular processes such as calcium homeostasis and autophagy. We hypothesized that mutant presenilins increase cellular vulnerability to stress. We stably expressed human PS1, mutant PS1E280A and mutant PS1Δ9 in mouse neuroblastoma N2a cells. We examined early signs of stress in different conditions: endoplasmic reticulum (ER) stress, calcium overload, oxidative stress, and Aβ 1-42 oligomers toxicity. Additionally, we induced autophagy via serum starvation. PS1 mutations did not have an effect in ER stress but PS1E280A mutation affected autophagy. PS1 overexpression influenced calcium homeostasis and generated mitochondrial calcium overload modifying mitochondrial function. However, the opening of the mitochondrial permeability transition pore (MPTP) was affected in PS1 mutants, being accelerated in PS1E280A and inhibited in PS1Δ9 cells. Altered autophagy in PS1E280A cells was neither modified by inhibition of γ-secretase, nor by ER calcium retention. MPTP opening was directly regulated by γ-secretase inhibitors independent on organelle calcium modulation, suggesting a novel direct role for PS1 and γ-secretase in mitochondrial stress. We identified intrinsic cellular vulnerability to stress in PS1 mutants associated simultaneously with both, autophagic and mitochondrial function, independent of Aβ pathology.

Therapeutic effects of Cyperus rotundus rhizome extract on memory impairment, neurogenesis and mitochondria in beta-amyloid rat model of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disturbance leading to memory deficit, cognitive decline, and behavioral disturbance. Deposition of Amyloid beta plaques, neurofibrillary tangle and mitochondrial impairment are common neuropathological signs in AD. In this study, the effect of standardized Cyperus rotundus(C. rotundus) extract in three different doses of 250, 500, and 750 mg/kg on memory, neurogenesis and mitochondrial mass in the beta amyloid rat model was assessed. For this purpose, 42 male Wistar rats were randomly divided into six groups (n = 7) to evaluate baseline training performance in Morris water maze test. Amyloid beta (Aβ) was injected in animal hippocampal CA1 bilaterally in four groups. After 21 days, a decrease was observed in spending time in target quadrant in the first probe trial in Aβ injected groups. Following that, 250, 500, and 750 mg/kg of C. rotundus extracts were administered to three out of four groups for a period of one month. BrdU (Bromodeoxyuridine) was intraperitoneally injected in all groups on the last 7 days of treatment. Then, 28 days after the last BrdU injection, the second probe trial was run, and rats were sacrificed. The neurogenesis and mitochondrial distribution were detected in hippocampus, by immunohistochemical staining. At last, it was observed that C. rotundus, almost recovered memory impairment, in addition to increasing in mitochondrial mass in CA1 and neurogenesis in dentate gyruse in the beta-amyloid rat model of Alzheimer's disease.

Chronic administration of quetiapine attenuates the phencyclidine-induced recognition memory impairment and hippocampal oxidative stress in rats

The underlying mechanism of atypical antipsychotics in treating cognitive impairment in schizophrenia is unclear. The aim of the present study was to evaluate the effects of quetiapine, an atypical antipsychotic drug, on object recognition memory and hippocampal oxidative stress in a phencyclidine (PCP) rat model of schizophrenia. Rats were treated with chronic quetiapine (10 mg/kg/day, intraperitoneally) for 16 days or acute quetiapine (10 mg/kg/day, intraperitoneally) on day 16. On day 16, 1 h after the administration of quetiapine, the rats were administered PCP (50 mg/kg, subcutaneously). After the last object recognition behavioral test on day 18, the rats were killed for the measurement of hippocampal protein expression of nitrotyrosine, a protein marker of oxidative stress. The results showed that chronic quetiapine significantly attenuated object recognition memory impairment and hippocampal oxidative stress in the PCP-injected rats. These suggest that the attenuating effect of chronic quetiapine on hippocampal oxidative stress may be related to quetiapine's beneficial effects on object recognition memory in PCP rats, and further suggest that neuroprotective mechanisms are involved in chronic quetiapine treatment.

Role of Aldehyde Dehydrogenases in Physiopathological Processes

Many different diseases are associated with oxidative stress. One of the main consequences of oxidative stress at the cellular level is lipid peroxidation, from which toxic aldehydes may be generated. Below their toxicity thresholds, some aldehydes are involved in signaling processes, while others are intermediaries in the metabolism of lipids, amino acids, neurotransmitters, and carbohydrates. Some aldehydes ubiquitously distributed in the environment, such as acrolein or formaldehyde, are extremely toxic to the cell. On the other hand, aldehyde dehydrogenases (ALDHs) are able to detoxify a wide variety of aldehydes to their corresponding carboxylic acids, thus helping to protect from oxidative stress. ALDHs are located in different subcellular compartments such as cytosol, mitochondria, nucleus, and endoplasmic reticulum. The aim of this review is to analyze, and highlight, the role of different ALDH isoforms in the detoxification of aldehydes generated in processes that involve high levels of oxidative stress. The ALDH physiological relevance becomes evident by the observation that their expression and activity are enhanced in different pathologies that involve oxidative stress such as neurodegenerative disorders, cardiopathies, atherosclerosis, and cancer as well as inflammatory processes. Furthermore, ALDH mutations bring about several disorders in the cell. Thus, understanding the mechanisms by which these enzymes participate in diverse cellular processes may lead to better contend with the damage caused by toxic aldehydes in different pathologies by designing modulators and/or protocols to modify their activity or expression.

The Protective Effects of PSM-04 Against Beta Amyloid-Induced Neurotoxicity in Primary Cortical Neurons and an Animal Model of Alzheimer's Disease

Polygala tenuifolia Willdenow is a herb known for its therapeutic effects in insomnia, depression, disorientation, and memory impairment. In Alzheimer's disease (AD) animal model, there has been no report on the effects of memory and cognitive impairment. PSM-04, an extract from the root of P. tenuifolia Willdenow, was developed with improved bioabsorption. The present study aimed to investigate the neuroprotective effects of PSM-04 on AD and reveal the possible molecular mechanism. The neuroprotective effect of PSM-04 in primary cortical neurons treated with L-glutamate, oligomeric Aβ, or H2O2. PSM-04 exhibited significant neuroprotective effects against neurotoxicity induced by L-glutamate or oligomeric Aβ was studied. PSM-04 exhibited significant neuroprotective effects against neurotoxicity induced by L-glutamate or oligomeric Aβ. Oxidative stress induced by ROS was monitored using the DCF-DA assay, and apoptosis was assessed using the TUNEL assay in primary cortical neurons treated with H2O2 or oligomeric Aβ. PSM-04 also decreased oxidative stress induced by H2O2 and apoptotic cell death induced by oligomeric Aβ. We evaluated the therapeutic effect of PSM-04 in 5xFAD (Tg) mice, an animal model for AD. PSM-04 was orally administered to 4-month-old 5xFAD mice for 2 months. To confirm the degree of cognitive impairment, a novel object recognition task was performed. The treatment with PSM-04 significantly alleviated cognitive impairments in Tg mice. In addition, amyloid plaques and gliosis decreased significantly in the brains of PSM-04-administered Tg mice compared with Tg-vehicle mice. Furthermore, the administration of PSM-04 increased the superoxide dismutase-2 (SOD-2) protein level in hippocampal brain tissues. Our results indicated that PSM-04 showed therapeutic effects by alleviating cognitive impairment and decreasing amyloid plaque deposition in Tg mice. Therefore, PSM-04 was considered as a potential pharmacological agent for neuroprotective effects in neurodegenerative diseases, including AD.

Carvedilol protection against endogenous Aβ-induced neurotoxicity in N2a cells

Mutations in amyloid precursor protein (APP) and presenilin1 result in overproduction and accumulation of β-amyloid (Aβ) peptide, which has been shown to play an important role in Alzheimer's disease (AD) pathogenesis. Carvedilol, a nonselective β-adrenergic receptor blocker used for treatment for heart failure and hypertension, has displayed its neuroprotective capacity due to its antioxidant property. In this study, we investigated whether Carvedilol has a neuronal protective effect against endogenous Aβ neurotoxicity in mouse Neuro2a (N2a) cells transfected with Swedish amyloid precursor protein (Swe-APP) mutant and Presenilin exon9 deletion mutant (N2a/Swe.D9). Elevated levels of reactive oxygen species (ROS), protein carbonyls, and 4-HNE were found in N2a/Swe.D9 cells, which were ameliorated by administration of Carvedilol in a dose-dependent manner. In addition, the levels of ATP and mitochondrial membrane potential were reduced in N2a/Swe.D9 cells, which were restored by treatment with Carvedilol. N2a/Swe.D9 cells displayed increased vulnerability to H2O2-induced cell death and apoptosis, which could be attenuated by Carvedilol. Mechanistically, we found that Carvedilol prevented apoptosis signals through reducing cytochrome C release and the level of cleaved caspase-3. Taken together, our findings suggest a possible use of Carvedilol in AD treatment.

Alzheimer's disease hypothesis and related therapies

Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the most common cause for dementia. There are many hypotheses about AD, including abnormal deposit of amyloid β (Aβ) protein in the extracellular spaces of neurons, formation of twisted fibers of tau proteins inside neurons, cholinergic neuron damage, inflammation, oxidative stress, etc., and many anti-AD drugs based on these hypotheses have been developed. In this review, we will discuss the existing and emerging hypothesis and related therapies.

The interplay between inflammation, oxidative stress, DNA damage, DNA repair and mitochondrial dysfunction in depression

A growing body of evidence suggests that inflammation, mitochondrial dysfunction and oxidant-antioxidant imbalance may play a significant role in the development and progression of depression. Elevated levels of reactive oxygen and nitrogen species - a result of oxidant-antioxidant imbalance - may lead to increased damage of biomolecules, including DNA. This was confirmed in depressed patients in a research study conducted by our team and other scientists. 8-oxoguanine - a marker of oxidative DNA damage - was found in the patients' lymphocytes, urine and serum. These results were confirmed using a comet assay on lymphocytes. Furthermore, it was shown that the patients' cells repaired peroxide-induced DNA damage less efficiently than controls' cells and that some single nucleotide polymorphisms (SNP) of the genes involved in oxidative DNA damage repair may modulate the risk of depression. Lastly, less efficient DNA damage repair observed in the patients can be, at least partly, attributed to the presence of specific SNP variants, as it was revealed through a genotype-phenotype analysis. In conclusion, the available literature shows that both oxidative stress and less efficient DNA damage repair may lead to increased DNA damage in depressed patients. A similar mechanism may result in mitochondrial dysfunction, which is observed in depression.

Oxidative Stress, Amyloid-β Peptide, and Altered Key Molecular Pathways in the Pathogenesis and Progression of Alzheimer's Disease

Oxidative stress is implicated in the pathogenesis and progression of Alzheimer's disease (AD) and its earlier stage, amnestic mild cognitive impairment (aMCI). One source of oxidative stress in AD and aMCI brains is that associated with amyloid-β peptide, Aβ1-42 oligomers. Our laboratory first showed in AD elevated oxidative stress occurred in brain regions rich in Aβ1-42, but not in Aβ1-42-poor regions, and was among the first to demonstrate Aβ peptides led to lipid peroxidation (indexed by HNE) in AD and aMCI brains. Oxidatively modified proteins have decreased function and contribute to damaged key biochemical and metabolic pathways in which these proteins normally play a role. Identification of oxidatively modified brain proteins by the methods of redox proteomics was pioneered in the Butterfield laboratory. Four recurring altered pathways secondary to oxidative damage in brain from persons with AD, aMCI, or Down syndrome with AD are interrelated and contribute to neuronal death. This "Quadrilateral of Neuronal Death" includes altered: glucose metabolism, mTOR activation, proteostasis network, and protein phosphorylation. Some of these pathways are altered even in brains of persons with preclinical AD. We opine that targeting these pathways pharmacologically and with lifestyle changes potentially may provide strategies to slow or perhaps one day, prevent, progression or development of this devastating dementing disorder. This invited review outlines both in vitro and in vivo studies from the Butterfield laboratory related to Aβ1-42 and AD and discusses the importance and implications of some of the major achievements of the Butterfield laboratory in AD research.

Inhibitory effects of Tabernaemontana divaricata root extract on oxidative stress and neuronal loss induced by amyloid β25-35 peptide in mice

In Alzheimer's disease, there are numerous amyloid plaques, neurofibrillary tangles, and neuronal loss in several brain areas. Oxidative stress is involved in the mechanisms of Aβ-peptide induced neurotoxicity by the generation of free radical oxidative stress that may lead to neurodegeneration. Tabernaemontana divaricata has various medical properties in Thai folklore medicine including prevent forgetfulness or improve memory. The present study aimed to investigate the effects of T. divaricata root extract (TDE) on Aβ_25-35 peptides induced neuronal loss and oxidative stress in mice. Male ICR mice were administered with vehicle or TDE (250, 500, and 1000 mg/kg b.w., p.o.) for 28 consecutive days. Then, these mice were given a single intracerebroventricular (i.c.v.) injection of Aβ_25-35 or phosphate buffer saline (PBS) (10 μg/mouse). The novel object recognition (NOR) test was used to determine memory disturbance. In addition, the neuronal cells in the cerebral cortex and hippocampus were measured by using crystal violet staining and lipid peroxidation was determined by measuring the formation of thiobarbituric acid reactive substances. An i.c.v. injection of Aβ_25-35 peptides could significantly induce memory impairment, increase level of lipid peroxidation including the neuronal loss in CA3 of hippocampus. However, the mice pretreated with TDE could prevent the memory loss, neuronal loss and decrease lipid peroxidation. These results suggest the potential therapeutic value in dementia of TDE through its antioxidant property.

Hippocampal Proteomic Analysis Reveals Distinct Pathway Deregulation Profiles at Early and Late Stages in a Rat Model of Alzheimer's-Like Amyloid Pathology

The cerebral accumulation and cytotoxicity of amyloid beta (Aβ) is central to Alzheimer's pathogenesis. However, little is known about how the amyloid pathology affects the global expression of brain proteins at different disease stages. In order to identify genotype and time-dependent significant changes in protein expression, we employed quantitative proteomics analysis of hippocampal tissue from the McGill-R-Thy1-APP rat model of Alzheimer-like amyloid pathology. McGill transgenic rats were compared to wild-type rats at early and late pathology stages, i.e., when intraneuronal Aβ amyloid burden is conspicuous and when extracellular amyloid plaques are abundant with more pronounced cognitive deficits. After correction for multiple testing, the expression levels of 64 proteins were found to be considerably different in transgenic versus wild-type rats at the pre-plaque stage (3 months), and 86 proteins in the post-plaque group (12 months), with only 9 differentially regulated proteins common to the 2 time-points. This minimal overlap supports the hypothesis that different molecular pathways are affected in the hippocampus at early and late stages of the amyloid pathology throughout its continuum. At early stages, disturbances in pathways related to cellular responses to stress, protein homeostasis, and neuronal structure are predominant, while disturbances in metabolic energy generation dominate at later stages. These results shed new light on the molecular pathways affected by the early accumulation of Aβ and how the evolving amyloid pathology impacts other complex metabolic pathways.

Recent advances in the Overman rearrangement: synthesis of natural products and valuable compounds

This review documents the reports since 2005 on the Overman rearrangement, an important C–N bond forming reaction that has been profoundly used in the synthesis of natural products, synthetic intermediates, building blocks and valuable compounds.

Increased susceptibility to Aβ toxicity in neuronal cultures derived from familial Alzheimer's disease (PSEN1-A246E) induced pluripotent stem cells

Alzheimer's disease (AD) is the most common cause of late-life dementia and represents one of the leading causes of death worldwide. The generation of induced pluripotent stem cells (iPSC) has facilitated the production and differentiation of stem cells from patients somatic cells, offering new opportunities to model AD and other diseases in vitro. In this study, we generated iPSCs from skin fibroblasts obtained from a healthy individual, as well as sporadic (sAD) and familial AD (fAD, PSEN1-A246E mutation) patients. iPSC lines were differentiated into neuronal precursors (iPSC-NPCs) and neurons that were subjected to amyloid beta (Aβ) toxicity assays. We found that neurons derived from the fAD patient have a higher susceptibility to Aβ1-42 oligomers compared with neurons coming from healthy and sAD individuals. Our findings suggest that neurons from patients with PSEN1-A246E mutation have intrinsic properties that make them more susceptible to the toxic effects of Aβ1-42 oligomers in the AD brain.

Role of ROS and RNS Sources in Physiological and Pathological Conditions

There is significant evidence that, in living systems, free radicals and other reactive oxygen and nitrogen species play a double role, because they can cause oxidative damage and tissue dysfunction and serve as molecular signals activating stress responses that are beneficial to the organism. Mitochondria have been thought to both play a major role in tissue oxidative damage and dysfunction and provide protection against excessive tissue dysfunction through several mechanisms, including stimulation of opening of permeability transition pores. Until recently, the functional significance of ROS sources different from mitochondria has received lesser attention. However, the most recent data, besides confirming the mitochondrial role in tissue oxidative stress and protection, show interplay between mitochondria and other ROS cellular sources, so that activation of one can lead to activation of other sources. Thus, it is currently accepted that in various conditions all cellular sources of ROS provide significant contribution to processes that oxidatively damage tissues and assure their survival, through mechanisms such as autophagy and apoptosis.

The levels of 7,8-dihydrodeoxyguanosine (8-oxoG) and 8-oxoguanine DNA glycosylase 1 (OGG1) - A potential diagnostic biomarkers of Alzheimer's disease

Evidence indicates that oxidative stress contributes to neuronal cell death in Alzheimer's disease (AD). Increased oxidative DNA damage l, as measured with 8-oxoguanine (8-oxoG), and reduced capacity of proteins responsible for removing of DNA damage, including 8-oxoguanine DNA glycosylase 1 (OGG1), were detected in brains of AD patients. In the present study we assessed peripheral blood biomarkers of oxidative DNA damage, i.e. 8- oxoG and OGG1, in AD diagnosis, by comparing their levels between the patients and the controls. Our study was performed on DNA and serum isolated from peripheral blood taken from 100 AD patients and 110 controls. For 8-oxoG ELISA was employed. The OGG1 level was determined using ELISA and Western blot technique. Levels of 8-oxoG were significantly higher in DNA of AD patients. Both ELISA and Western blot showed decreased levels of OGG1 in serum of AD patients. Our results show that oxidative DNA damage biomarkers detected in peripheral tissue could reflect the changes occurring in the brain of patients with AD. These results also suggest that peripheral blood samples may be useful to measure oxidative stress biomarkers in AD.

Targeting PRAS40 for multiple diseases

Proline-rich Akt substrate 40kDa (PRAS40) bridges cell signaling between protein kinase B (Akt) and the mammalian target of rapamycin complex 1 (mTORC1). Both Akt and mTORC1 can phosphorylate PRAS40. As a negative regulator of mTORC1, PRAS40 prevents the binding of mTOR to its substrates. The phosphorylation of PRAS40 results in its dissociation from mTORC1 and enhanced mTOR activation. PRAS40 in conjunction with mTORC1 has been closely associated with programmed cell death and is implicated in diabetes mellitus (DM), cardiovascular diseases, cancer, and neurological diseases. Thus, targeting PRAS40 might hold great promise for innovative therapeutic strategies for these diseases.

Simultaneous activation of Nrf2 and elevation of antioxidant compounds for reducing oxidative stress and chronic inflammation in human Alzheimer's disease

Despite extensive research, neither the incidence nor the rate of progression of Alzheimer's disease (AD) has significantly changed. Some biochemical and genetic defects that initiate and promote AD include: (a) increased oxidative stress, (b) chronic inflammation (c) mitochondrial dysfunction, (d) Aß1-42 peptides generated from the amyloid precursor protein (APP), (e) proteasome inhibition, and (f) mutations in APP, presenilin-1 and presenilin-2 genes. Increased oxidative stress appears to precede other biochemical and genetic defects. Oxidative damage induces chronic inflammation. Therefore, reducing these defects simultaneously may reduce the development and progression of AD. Previous studies with individual antioxidants produced consistent benefits in animal models of AD; however, a similar approach produced inconsistent results in human AD. This review proposes a hypothesis that simultaneous elevation of the levels of antioxidant enzymes and antioxidant compounds is necessary for optimally reducing oxidative stress and chronic inflammation in human AD. Supplementation can enhance the levels of antioxidant compounds; but elevation of antioxidant enzymes requires activation of Nrf2. This review discusses activation and regulation of Nrf2. The need for multi- antioxidants that can affect multi-targets has been proposed without specific recommendations. This review proposes a micronutrient mixture that would simultaneously enhance the levels of antioxidant enzymes and antioxidant compounds in human AD.

Bisecting GlcNAc modification stabilizes BACE1 protein under oxidative stress conditions

BACE1 is a protease essential for amyloid-β production in Alzheimer's disease. We report that bisecting GlcNAc modification on BACE1 stabilizes BACE1 protein under oxidative stress conditions. This suggests that bisecting GlcNAc is a therapeutic target for Alzheimer's disease.

Chitosan oligosaccharides alleviate cognitive deficits in an amyloid-β1-42-induced rat model of Alzheimer's disease

AIM

The objective of the present study was two-fold: (i) to evaluate the modulating effects of chitosan oligosaccharides (COS) on cognitive deficits and (ii) to explore their underlying molecular mechanisms.

METHODS

The Morris water maze and passive avoidance tests were used to determine the neuroprotective effects of COS on Aβ1-42-induced learning and memory impairments. Biochemical methods were then used to assess COS antioxidant activity in hippocampus, including effects on apoptosis (TUNEL assay) and changes in inflammatory mediators (immunohistochemistry).

RESULTS

Orally administered COS at 200, 400, or 800 mg/kg doses were effective at reducing the learning and memory deficits in Aβ1-42-induced rats. These same doses were also able to ameliorate neuronal apoptosis. The neuroprotective effects of COS were closely associated with its ability to inhibit oxidative stress. This was shown with decreasing levels of malondialdehyde, 8-hydroxy-2'-deoxyguanosine and increasing levels of glutathione peroxidase and super oxide dismutase activities. COS were also shown to suppress the inflammatory response and decrease measures of inflammation via a decrease in the release of proinflammatory cytokines (e.g. interleukin-1beta and tumor necrosis factor-alpha).

CONCLUSION

Taken together, our findings suggest that COS have beneficial effects on the cognitive impairments seen in an Aβ1-42-induced model of Alzheimer's disease via inhibiting oxidative stress and neuroinflammatory responses.

Alpha-tocopherol quinine ameliorates spatial memory deficits by reducing beta-amyloid oligomers, neuroinflammation and oxidative stress in transgenic mice with Alzheimer's disease

The pathologies of Alzheimer's disease (AD) is associated with soluble beta-amyloid (Aβ) oligomers, neuroinflammation and oxidative stress. Decreasing the levels of Aβ oligomer, glial activation and oxidative stress are potential therapeutic approaches for AD treatment. We previously found alpha-tocopherol quinine (α-TQ) inhibited Aβ aggregation and cytotoxicity, decreased the release of inflammatory cytokines and reactive oxygen species (ROS) in vitro. However, whether α-TQ ameliorates memory deficits and other neuropathologies in mice or patients with AD remains unknown. In this study, we reported that orally administered α-TQ ameliorated memory impairment in APPswe/PS1dE9 transgenic mice, decreased oxidative stress and the levels of Aβ oligomer in the brains of mice, prevented the production of inducible nitric oxide synthase and inflammatory mediators, such as interleukin-6 and interleukin-1β, and inhibited microglial activation by inhibiting NF-κB signaling pathway. These findings suggest that α-TQ has potential therapeutic value for AD treatment.

Phloroglucinol Attenuates the Cognitive Deficits of the 5XFAD Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia among the elderly. Neuritic plaques whose primary component is amyloid beta peptide (Aβ) and neurofibrillary tangles which are composed of hyperphosphorylated tau, are known to be the neuropathological hallmarks of AD. In addition, impaired synaptic plasticity in neuronal networks is thought to be important mechanism underlying for the cognitive deficits observed in AD. Although various causative factors, including excitotoxicity, mitochondrial dysregulation and oxidative damage caused by Aβ, are involved in early onset of AD, fundamental therapeutics that can modify the progression of this disease are not currently available. In the present study, we investigated whether phloroglucinol (1, 3, 5-trihydroxybenzene), a component of phlorotannins, which are plentiful in Ecklonia cava, a marine brown alga species, displays therapeutic activities in AD. We found that phloroglucinol attenuates the increase in reactive oxygen species (ROS) accumulation induced by oligomeric Aβ1-42 (Aβ1-42) treatment in HT-22, hippocampal cell line. In addition, phloroglucinol was shown to ameliorate the reduction in dendritic spine density induced by Aβ1-42 treatment in rat primary hippocampal neuron cultures. We also found that the administration of phloroglucinol to the hippocampal region attenuated the impairments in cognitive dysfunction observed in 22-week-old 5XFAD (Tg6799) mice, which are used as an AD animal model. These results indicate that phloroglucinol displays therapeutic potential for AD by reducing the cellular ROS levels.

G206D Mutation of Presenilin-1 Reduces Pen2 Interaction, Increases Aβ42/Aβ40 Ratio and Elevates ER Ca(2+) Accumulation

Early-onset familial Alzheimer's disease (AD) is most commonly associated with the mutations in presenilin-1 (PS1). PS1 is the catalytic component of the γ-secretase complex, which cleaves amyloid precursor protein to produce amyloid-β (Aβ), the major cause of AD. Presenilin enhancer 2 (Pen2) is critical for activating γ-secretase and exporting PS1 from endoplasmic reticulum (ER). Among all the familial AD-linked PS1 mutations, mutations at the G206 amino acid are the most adjacent position to the Pen2 binding site. Here, we characterized the effect of a familial AD-linked PS1 G206D mutation on the PS1-Pen2 interaction and the accompanied alteration in γ-secretase-dependent and -independent functions. We found that the G206D mutation reduced PS1-Pen2 interaction, but did not abolish γ-secretase formation and PS1 endoproteolysis. For γ-secretase-dependent function, the G206D mutation increased Aβ42 production but not Notch cleavage. For γ-secretase-independent function, this mutation disrupted the ER calcium homeostasis but not lysosomal calcium homeostasis and autophagosome maturation. Impaired ER calcium homeostasis may due to the reduced mutant PS1 level in the ER. Although this mutation did not alter the cell survival under stress, both increased Aβ42 ratio and disturbed ER calcium regulation could be the mechanisms underlying the pathogenesis of the familial AD-linked PS1 G206D mutation.

Decreasing oxidative stress and neuroinflammation with a multifunctional peptide rescues memory deficits in mice with Alzheimer disease

Alzheimer disease (AD) is characterized by extracellular senile plaques, intracellular neurofibrillary tangles, and memory loss. Aggregated amyloid-β (Aβ), oxidative stress, and inflammation have pivotal roles in the pathogenesis of AD. Therefore, the inhibition of Aβ-induced neurotoxicity, oxidative stress, and inflammation is a potential therapeutic strategy for the treatment of AD. In this study, a heptapeptide, isolated from a Ph.D.-C7C library by phage display, attenuated Aβ42-induced cytotoxicity in SH-SY5Y neuroblastoma cells and reduced Aβ42-induced oxidative stress by decreasing the production of reactive oxygen species and glutathione disulfide. As a result, glutathione level increased and superoxide dismutase and glutathione peroxidase activities were enhanced in vitro and in vivo. This peptide also suppressed the inflammatory response by decreasing the release of proinflammatory cytokines, such as tumor necrosis factor α and interleukin 1β, in microglia and by reducing microgliosis and astrogliosis in AD transgenic mice. This peptide was intracerebroventricularly administered to APPswe/PS1dE9 transgenic mice. We found that this peptide significantly improved spatial memory and reduced the amyloid plaque burden and soluble and insoluble Aβ levels. Our findings suggest that this multifunctional peptide has therapeutic potential for an Aβ-targeted treatment of AD.

The 2013 SFRBM discovery award: selected discoveries from the butterfield laboratory of oxidative stress and its sequela in brain in cognitive disorders exemplified by Alzheimer disease and chemotherapy induced cognitive impairment

This retrospective review on discoveries of the roles of oxidative stress in brain of subjects with Alzheimer disease (AD) and animal models thereof as well as brain from animal models of chemotherapy-induced cognitive impairment (CICI) results from the author receiving the 2013 Discovery Award from the Society for Free Radical Biology and Medicine. The paper reviews our laboratory's discovery of protein oxidation and lipid peroxidation in AD brain regions rich in amyloid β-peptide (Aβ) but not in Aβ-poor cerebellum; redox proteomics as a means to identify oxidatively modified brain proteins in AD and its earlier forms that are consistent with the pathology, biochemistry, and clinical presentation of these disorders; how Aβ in in vivo, ex vivo, and in vitro studies can lead to oxidative modification of key proteins that also are oxidatively modified in AD brain; the role of the single methionine residue of Aβ(1-42) in these processes; and some of the potential mechanisms in the pathogenesis and progression of AD. CICI affects a significant fraction of the 14 million American cancer survivors, and due to diminished cognitive function, reduced quality of life of the persons with CICI (called "chemobrain" by patients) often results. A proposed mechanism for CICI employed the prototypical ROS-generating and non-blood brain barrier (BBB)-penetrating chemotherapeutic agent doxorubicin (Dox, also called adriamycin, ADR). Because of the quinone moiety within the structure of Dox, this agent undergoes redox cycling to produce superoxide free radical peripherally. This, in turn, leads to oxidative modification of the key plasma protein, apolipoprotein A1 (ApoA1). Oxidized ApoA1 leads to elevated peripheral TNFα, a proinflammatory cytokine that crosses the BBB to induce oxidative stress in brain parenchyma that affects negatively brain mitochondria. This subsequently leads to apoptotic cell death resulting in CICI. This review outlines aspects of CICI consistent with the clinical presentation, biochemistry, and pathology of this disorder. To the author's knowledge this is the only plausible and self-consistent mechanism to explain CICI. These two different disorders of the CNS affect millions of persons worldwide. Both AD and CICI share free radical-mediated oxidative stress in brain, but the source of oxidative stress is not the same. Continued research is necessary to better understand both AD and CICI. The discoveries about these disorders from the Butterfield Laboratory that led to the 2013 Discovery Award from the Society of Free Radical and Medicine provide a significant foundation from which this future research can be launched.

Amyloid β-peptide (1-42)-induced oxidative stress in Alzheimer disease: importance in disease pathogenesis and progression

SIGNIFICANCE

Alzheimer disease (AD) is an age-related neurodegenerative disease. AD is characterized by progressive cognitive impairment. One of the main histopathological hallmarks of AD brain is the presence of senile plaques (SPs) and another is elevated oxidative stress. The main component of SPs is amyloid beta-peptide (Aβ) that is derived from the proteolytic cleavage of amyloid precursor protein.

RECENT ADVANCES

Recent studies are consistent with the notion that methionine present at 35 position of Aβ is critical to Aβ-induced oxidative stress and neurotoxicity. Further, we also discuss the signatures of oxidatively modified brain proteins, identified using redox proteomics approaches, during the progression of AD.

CRITICAL ISSUES

The exact relationships of the specifically oxidatively modified proteins in AD pathogenesis require additional investigation.

FUTURE DIRECTIONS

Further studies are needed to address whether the therapies directed toward brain oxidative stress and oxidatively modified key brain proteins might help delay or prevent the progression of AD.

Oxidative stress and the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disease that causes dementia in the elderly. Patients with AD suffer a gradual deterioration of memory and other cognitive functions, which eventually leads to a complete incapacity and death. A complicated array of molecular events has been implicated in the pathogenesis of AD. The major pathological characteristics of AD brains are the presence of senile plaques, neurofibrillary tangles, and neuronal loss. Growing evidence has demonstrated that oxidative stress is an important factor contributing to the initiation and progression of AD. However, the mechanisms that lead to the disruption of redox balance and the sources of free radicals remain elusive. The excessive reactive oxygen species may be generated from mechanisms such as mitochondria dysfunction and/or aberrant accumulation of transition metals, while the abnormal accumulation of Abeta and tau proteins appears to promote the redox imbalance. The resulted oxidative stress has been implicated in Abeta- or tau-induced neurotoxicity. In addition, evidence has suggested that oxidative stress may augment the production and aggregation of Abeta and facilitate the phosphorylation and polymerization of tau, thus forming a vicious cycle that promotes the initiation and progression of AD.

An update of animal models of Alzheimer disease with a reevaluation of plaque depositions

Animal models of Alzheimer disease (AD) are used to study the mechanisms underlying AD pathogenesis, genetic interactions with genes of interest, and environmental risk factors that cause sporadic AD as well as to test the therapeutic effects of AD drug-candidates on neuropathology and cognitive function. To attain a comparative view on the AD models developed, representative AD lines were selected and summarized with respect to transgenic constructs and AD-related pathology. In addition, age-dependent plaque deposition data available in the literature for six representative AD models such as Tg2576, PDAPP, TgAPP23, Tg-APPswe/PS1dE9, 3xTg-AD, and 5XFAD mice were reevaluated using a photographic plaque reference scale method that was introduced recently. Tg2576, PDAPP, and TgAPP23 mice, which carry the amyloid precursor protein (APP) transgene, produced initially slow, but progressively accelerated plaque deposition as they aged, resulting in logistic plaque deposition. In contrast, Tg-APPswe/PS1dE9 and 3xTg-AD mice, which carry both APP and PS1 transgenes, developed abruptly accelerated plaque formation from the beginning, resulting in logarithmic plaque deposition. 5XFAD mice, which also carry both the APP and PS1 transgenes, developed a logarithmic deposition beginning at 2 months. This comparative analysis suggests that AD models may be classified into two distinct plaque deposition groups, and that early plaque models such as APPswe/PS1dE9, 3xTg-AD and 5XFAD might be useful to study the biochemical aspects of APP metabolism, whereas late plaque models such as Tg2576, PDAPP, and TgAPP23 might be useful to study more physiological and environmental aspects of AD pathogenesis, which occur on a longer time scale.

A ketogenic diet improves motor performance but does not affect β-amyloid levels in a mouse model of Alzheimer's disease

β-Amyloid (Aβ), a small, fibrillogenic peptide, is known to play an important role in the pathogenesis of Alzheimer's disease (AD) in the brain. In addition, Aβ accumulates in skeletal muscle cells in individuals with sporadic inclusion body myositis (sIBM), an age-related muscle disease. Because of the socioeconomic burden associated with age-related diseases, particularly AD, there has been considerable emphasis on studying potential therapeutic strategies. The high-fat, low carbohydrate ketogenic diet has been used extensively to treat refractory childhood epilepsy and has been studied as a potential treatment for other neurological diseases, including Parkinson's disease and AD. In this study, we fed young APP/PS1 knock-in mice, which have a whole body knock-in of AD-related genes, a ketogenic diet and determined the effect on Aβ levels in the brain and skeletal muscle, as well motor performance and oxidative stress. Aβ and its precursor, the β-C-terminal fragment of amyloid precursor protein (CTFβ), were unchanged overall in both the brain and quadriceps after 1 month on the ketogenic diet, and there was no effect on nitrotyrosine, a product of oxidative stress. The ketogenic diet improved performance on the Rota-rod apparatus (p=0.007), however. These data indicate that the ketogenic diet may have some efficacy in the treatment of both neurologic and muscle diseases though the underlying mechanisms do not involve amelioration of Aβ pathology.

A cross-sectional study on cerebrospinal fluid biomarker levels in cognitively normal elderly subjects with or without a family history of Alzheimer's disease

BACKGROUND

Cerebrospinal fluid (CSF) biomarkers reflect changes in the brain, and contribute to early screening. Maternal inheritance is putatively stronger than paternal inheritance for late-onset Alzheimer's disease (LOAD).

METHODS

Clinical data of 162 cognitively normal subjects were reviewed. A standard questionnaire was used to identify LOAD family history. Mini-mental state examination (MMSE) was used to evaluate cognition. CSF Aβ1-40, Aβ1-42, total and phosphorylated tau were measured using ELISA.

AIMS

To compare biomarkers in cognitively normal elderly subjects with versus without LOAD family history.

RESULTS

Among the 162 subjects, 38 and 60 had LOAD family history on paternal and maternal sides, respectively. The remaining 60 subjects had no family history. No difference was noted in age, gender, education level, MMSE score, and memory impairment complaint in the three groups. Aβ42 and the Aβ42/40 ratio were lower than in subjects with a maternal history than in subjects with a paternal history or without family history (P < 0.05 in both). Phosphorylated and total tau did not differ among the three groups.

CONCLUSION

Offspring with a family history of LOAD on the maternal side have lower Aβ42 and Aβ42/40 ratio in the CSF, and maybe at higher risk for developing AD.

Transcriptional alterations related to neuropathology and clinical manifestation of Alzheimer's disease

Alzheimer’s disease (AD) is the most common cause of dementia in the human population, characterized by a spectrum of neuropathological abnormalities that results in memory impairment and loss of other cognitive processes as well as the presence of non-cognitive symptoms. Transcriptomic analyses provide an important approach to elucidating the pathogenesis of complex diseases like AD, helping to figure out both pre-clinical markers to identify susceptible patients and the early pathogenic mechanisms to serve as therapeutic targets. This study provides the gene expression profile of postmortem brain tissue from subjects with clinic-pathological AD (Braak IV, V, or V and CERAD B or C; and CDR ≥1), preclinical AD (Braak IV, V, or VI and CERAD B or C; and CDR = 0), and healthy older individuals (Braak ≤ II and CERAD 0 or A; and CDR = 0) in order to establish genes related to both AD neuropathology and clinical emergence of dementia. Based on differential gene expression, hierarchical clustering and network analysis, genes involved in energy metabolism, oxidative stress, DNA damage/repair, senescence, and transcriptional regulation were implicated with the neuropathology of AD; a transcriptional profile related to clinical manifestation of AD could not be detected with reliability using differential gene expression analysis, although genes involved in synaptic plasticity, and cell cycle seems to have a role revealed by gene classifier. In conclusion, the present data suggest gene expression profile changes secondary to the development of AD-related pathology and some genes that appear to be related to the clinical manifestation of dementia in subjects with significant AD pathology, making necessary further investigations to better understand these transcriptional findings on the pathogenesis and clinical emergence of AD.

Alzheimer's disease: redox dysregulation as a common denominator for diverse pathogenic mechanisms

Alzheimer's disease (AD) is the most common cause of dementia and a progressive neurodegeneration that appears to result from multiple pathogenic mechanisms (including protein misfolding/aggregation, involved in both amyloid β-dependent senile plaques and tau-dependent neurofibrillary tangles), metabolic and mitochondrial dysfunction, excitoxicity, calcium handling impairment, glial cell dysfunction, neuroinflammation, and oxidative stress. Oxidative stress, which could be secondary to several of the other pathophysiological mechanisms, appears to be a major determinant of the pathogenesis and progression of AD. The identification of oxidized proteins common for mild cognitive impairment and AD suggests that key oxidation pathways are triggered early and are involved in the initial progression of the neurodegenerative process. Abundant data support that oxidative stress, also considered as a main factor for aging, the major risk factor for AD, can be a common key element capable of articulating the divergent nature of the proposed pathogenic factors. Pathogenic mechanisms influence each other at different levels. Evidence suggests that it will be difficult to define a single-target therapy resulting in the arrest of progression or the improvement of AD deterioration. Since oxidative stress is present from early stages of disease, it appears as one of the main targets to be included in a clinical trial. Exploring the articulation of AD pathogenic mechanisms by oxidative stress will provide clues for better understanding the pathogenesis and progression of this dementing disorder and for the development of effective therapies to treat this disease.

The bad, the good, and the ugly about oxidative stress

Alzheimer's disease (AD), Parkinson's disease (PD), and cancer (e.g., leukemia) are the most devastating disorders affecting millions of people worldwide. Except for some kind of cancers, no effective and/or definitive therapeutic treatment aimed to reduce or to retard the clinic and pathologic symptoms induced by AD and PD is presently available. Therefore, it is urgently needed to understand the molecular basis of these disorders. Since oxidative stress (OS) is an important etiologic factor of the pathologic process of AD, PD, and cancer, understanding how intracellular signaling pathways respond to OS will have a significant implication in the therapy of these diseases. Here, we propose a model of minimal completeness of cell death signaling induced by OS as a mechanistic explanation of neuronal and cancer cell demise. This mechanism might provide the basis for therapeutic design strategies. Finally, we will attempt to associate PD, cancer, and OS. This paper critically analyzes the evidence that support the “oxidative stress model” in neurodegeneration and cancer.