Oxidative stress and the pathogenesis of Alzheimer’s disease. Oxid Med Cell Longev. 2013;2013:316523. [PMID: 23983897 PMCID: PMC3745981 DOI: 10.1155/2013/316523]

MST1 Regulates Neuronal Cell Death via JNK/Casp3 Signaling Pathway in HFD Mouse Brain and HT22 Cells

Oxidative stress has been considered as the main mediator in neurodegenerative diseases. A high-fat diet (HFD) and metabolic diseases result in oxidative stress generation, leading to various neurodegenerative diseases via molecular mechanisms that remain largely unknown. Protein kinases play an important role in the homeostasis between cell survival and cell apoptosis. The mammalian sterile 20-like kinase-1 (MST1) protein kinase plays an important role in cellular apoptosis in different organ systems, including the central nervous system. In this study, we evaluated the MST1/c-Jun N-terminal kinase (JNK) dependent oxidative damage mediated cognitive dysfunction in HFD-fed mice and stress-induced hippocampal HT22 (mice hippocampal) cells. Our Western blot and immunofluorescence results indicate that HFD and stress-induced hippocampal HT22 cells activate MST1/JNK/Caspase-3 (Casp-3) signaling, which regulates neuronal cell apoptosis and beta-amyloid-cleaving enzyme (BACE1) expression and leads to impaired cognition. Moreover, MST1 expression inhibition by shRNA significantly reduced JNK/Casp-3 signaling. Our in vivo and in vitro experiments mimicking metabolic stress, such as a high-fat diet, hyperglycemia, and an inflammatory response, determined that MST1 plays a key regulatory role in neuronal cell death and cognition, suggesting that MST1 could be a potential therapeutic target for numerous neurodegenerative diseases.

Chemical Basis of Reactive Oxygen Species Reactivity and Involvement in Neurodegenerative Diseases

Increasing numbers of individuals suffer from neurodegenerative diseases, which are characterized by progressive loss of neurons. Oxidative stress, in particular, the overproduction of Reactive Oxygen Species (ROS), play an important role in the development of these diseases, as evidenced by the detection of products of lipid, protein and DNA oxidation in vivo. Even if they participate in cell signaling and metabolism regulation, ROS are also formidable weapons against most of the biological materials because of their intrinsic nature. By nature too, neurons are particularly sensitive to oxidation because of their high polyunsaturated fatty acid content, weak antioxidant defense and high oxygen consumption. Thus, the overproduction of ROS in neurons appears as particularly deleterious and the mechanisms involved in oxidative degradation of biomolecules are numerous and complexes. This review highlights the production and regulation of ROS, their chemical properties, both from kinetic and thermodynamic points of view, the links between them, and their implication in neurodegenerative diseases.

Crosstalk between Oxidative Stress and Tauopathy

Tauopathy is a collective term for neurodegenerative diseases associated with pathological modifications of tau protein. Tau modifications are mediated by many factors. Recently, reactive oxygen species (ROS) have attracted attention due to their upstream and downstream effects on tauopathy. In physiological conditions, healthy cells generate a moderate level of ROS for self-defense against foreign invaders. Imbalances between ROS and the anti-oxidation pathway cause an accumulation of excessive ROS. There is clear evidence that ROS directly promotes tau modifications in tauopathy. ROS is also highly upregulated in the patients’ brain of tauopathies, and anti-oxidants are currently prescribed as potential therapeutic agents for tauopathy. Thus, there is a clear connection between oxidative stress (OS) and tauopathies that needs to be studied in more detail. In this review, we will describe the chemical nature of ROS and their roles in tauopathy.

Oxidative Stress: A Key Modulator in Neurodegenerative Diseases

Oxidative stress is proposed as a regulatory element in ageing and various neurological disorders. The excess of oxidants causes a reduction of antioxidants, which in turn produce an oxidation-reduction imbalance in organisms. Paucity of the antioxidant system generates oxidative-stress, characterized by elevated levels of reactive species (oxygen, hydroxyl free radical, and so on). Mitochondria play a key role in ATP supply to cells via oxidative phosphorylation, as well as synthesis of essential biological molecules. Various redox reactions catalyzed by enzymes take place in the oxidative phosphorylation process. An inefficient oxidative phosphorylation may generate reactive oxygen species (ROS), leading to mitochondrial dysfunction. Mitochondrial redox metabolism, phospholipid metabolism, and proteolytic pathways are found to be the major and potential source of free radicals. A lower concentration of ROS is essential for normal cellular signaling, whereas the higher concentration and long-time exposure of ROS cause damage to cellular macromolecules such as DNA, lipids and proteins, ultimately resulting in necrosis and apoptotic cell death. Normal and proper functioning of the central nervous system (CNS) is entirely dependent on the chemical integrity of brain. It is well established that the brain consumes a large amount of oxygen and is highly rich in lipid content, becoming prone to oxidative stress. A high consumption of oxygen leads to excessive production of ROS. Apart from this, the neuronal membranes are found to be rich in polyunsaturated fatty acids, which are highly susceptible to ROS. Various neurodegenerative diseases such as Parkinson's disease (PD), Alzheimer's disease (AD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS), among others, can be the result of biochemical alteration (due to oxidative stress) in bimolecular components. There is a need to understand the processes and role of oxidative stress in neurodegenerative diseases. This review is an effort towards improving our understanding of the pivotal role played by OS in neurodegenerative disorders.

Lag-time in Alzheimer's disease patients: a potential plasmatic oxidative stress marker associated with ApoE4 isoform

In the brain, Oxidative Stress (OS) contribute to structural and functional changes associated with vascular aging, such as endothelial dysfunction, extracellular matrix degradation, resulting in age-related reduced vasodilatation in response to agonists. For this reason, OS is considered a key factor in Alzheimer’s Disease (AD) development and recent evidence correlated oxidative stress with vascular lesion in the pathogenesis of AD, but the mechanism still need to be fully clarified.

The etiology of AD is still not completely understood and is influenced by several factors including Apolipoprotein E (ApoE) genotype. In particular, the Apo ε4 isoform is considered a risk factor for AD development.

This study was aimed to evaluate the possible relationship between three plasmatic OS marker and Apo ε4 carrier status. Plasmatic soluble receptor for advanced glycation end products (sRAGE) levels, plasma antioxidant total defenses (by lag-time method) and plasmatic Reactive Oxygen species (ROS) levels were evaluated in 25 AD patients and in 30 matched controls. ROS were significantly higher while plasma antioxidant total defenses and sRAGE levels were significantly lower in AD patients compared to controls. In AD patients lag-time values show a significant positive linear correlation with sRAGE levels and a (even not significant) negative correlation with ROS levels. Lag-time is significantly lower in ε4 carrier (N = 13) than in ε4 non-carrier (N = 12). Our result confirms the substantial OS in AD. Lag-time levels showed a significant positive correlation with sRAGE levels and a significant association with ε4 carrier status suggesting that plasmatic lag-time evaluation can be considered as a potential useful OS risk marker in AD.

Gout and the risk of Alzheimer's disease: A Mendelian randomization study

OBJECTIVE

This study aimed to examine whether gout is causally associated with Alzheimer's disease.

METHODS

I used the publicly available summary statistics datasets of three genome-wide association studies (GWASs) on gout as the exposure dataset and meta-analysis results of four GWAS datasets consisting of 17 008 cases with Alzheimer's disease and 37 154 controls of European descent as the outcome dataset. The data were subjected to 2-sample Mendelian randomization (MR) analysis using the inverse-variance weighted (IVW), weighted median, and MR-Egger regression methods.

RESULTS

I selected seven independent single nucleotide polymorphisms (SNPs) from gout GWASs as instrumental variables (IVs) to improve inference. These SNPs were located at MAP3K11 (rs10791821), SLC2A9 (rs11722228, rs734553), GCKR (rs1260326), ABCG2 (rs2231142, rs2728125), and CNIH-2 (rs4073582). The IVW data did not support a causal association between gout and Alzheimer's disease (β = 0.013, standard error [SE] = 0.017, P = 0.445). The MR-Egger regression indicated that directional pleiotropy did not bias the result (intercept = 0.002, P = 0.654); it also revealed no causal association between gout and Alzheimer's disease (β = -0.013, SE = 0.076, P = 0.870). The weighted median approach yielded similar results (β = 0.004, SE = 0.022, P = 0.846). Cochran's Q test indicated no evidence of heterogeneity between IV estimates based on individual variants, and the results of "leave-one-out" analysis demonstrated that no single SNP drove the IVW estimate.

CONCLUSIONS

The MR analysis results did not support a causal association between gout and Alzheimer's disease.

Activation of microglia and astrocytes: a roadway to neuroinflammation and Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease that is of high importance to the neuroscience world, yet the complex pathogenicity is not fully understood. Inflammation is usually observed in AD and could implicate both beneficial or detrimental effects depending on the severity of the disease. During initial AD pathology, microglia and astrocyte activation is beneficial since they are involved in amyloid-beta clearance. However, with the progression of the disease, activated microglia elicit detrimental effects by the overexpression of pro-inflammatory cytokines such as interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α) bringing forth neurodegeneration in the surrounding brain regions. This results in decline in Aβ clearance by microglia; Aβ accumulation thus increases in the brain resulting in neuroinflammation. Thus, Aβ accumulation is the effect of increased release of pro-inflammatory molecules. Reactive astrocytes acquire gain of toxic function and exhibits neurotoxic effects with loss of neurotrophic functions. Astrocyte dysfunctioning results in increased release of cytokines and inflammatory mediators, neurodegeneration, decreased glutamate uptake, loss of neuronal synapses, and ultimately cognitive deficits in AD. We discuss the role of intracellular signaling pathways in the inflammatory responses produced by astrocytes and microglial activation, including the glycogen synthase kinase-3β, nuclear factor kappa B cascade, mitogen-activated protein kinase pathways and c-Jun N-terminal kinase. In this review, we describe the role of neuroinflammation in the chronicity of AD pathogenesis and an overview of the recent research towards the development of new therapies to treat this disorder.

Fusigen Reduces Intracellular Reactive Oxygen Species and Nitric Oxide Levels

BACKGROUND/AIM

Oxidative stress caused by the production of excessive cellular reactive oxygen species (ROS) and high levels of nitric oxide contribute to several human pathologies. This study aimed to examine the anti-oxidant effects of fusigen, a compound produced from Aureobasidium melanogenum.

MATERIALS AND METHODS

Extracts of A. melanogenum were selected as a source for the isolation of fusigen. The anti-oxidant, nitric oxide suppression, as well as the free radical scavenging activities of fusigen were tested in BEAS-2B human bronchial epithelial cell line (BEAS-2B cells) and human dermal papilla cells (DP cells) using specific fluorescence dyes and flow cytometry analysis. Cell viability was determined by the MTT assay.

RESULTS

Fusigen did not exert cytotoxicity in the human normal BEAS-2B and DP cells at concentrations up to 100 μM. Fusigen decreased basal levels of cellular ROS, as well as the levels of ROS induced by hydrogen peroxide and ferrous ion enrichment. ROS decreasing effect was confirmed in DP cells. In addition, fusigen treatment suppressed intracellular NO levels in both BEAS-2B and DP cells.

CONCLUSION

The optimal process of production of purified fusigen from A. melanogenum was determined. Fusigen exhibited a low cytotoxic effect and the potential to suppress ROS and NO. These results demonstrated that fusigen may be used for the treatment or prevention of human diseases.

Discovery of novel dual-active 3-(4-(dimethylamino)phenyl)-7-aminoalcoxy-coumarin as potent and selective acetylcholinesterase inhibitor and antioxidant

A series of 3-substituted-7-aminoalcoxy-coumarin was designed and evaluated as cholinesterase inhibitors and antioxidants. All compounds were effective in inhibiting AChE with potencies in the nanomolar range. The 3-(4-(dimethylamino)phenyl)-7-aminoethoxy-coumarin (6a) was considered a hit, showing good AChE inhibition potency (IC₅₀ = 20 nM) and selectivity (IC₅₀ BuChE/AChE = 354), quite similar to the reference drug donepezil (IC₅₀ = 6 nM; IC₅₀ BuChE/AChE = 365), also presenting antioxidant properties, low citotoxicity and good-predicted ADMET properties. The mode of action (mixed-type) and SAR analysis for this series of compounds were described by means of kinetic and molecular modeling evaluations.

Pathological Impacts of Chronic Hypoxia on Alzheimer's Disease

Chronic hypoxia is considered as one of the important environmental factors contributing to the pathogenesis of Alzheimer's disease (AD). Many chronic hypoxia-causing comorbidities, such as obstructive sleep apnea syndrome (OSAS) and chronic obstructive pulmonary disease (COPD), have been reported to be closely associated with AD. Increasing evidence has documented that chronic hypoxia may affect many pathological aspects of AD including amyloid β (Aβ) metabolism, tau phosphorylation, autophagy, neuroinflammation, oxidative stress, endoplasmic reticulum (ER) stress, and mitochondrial and synaptic dysfunction, which may collectively result in neurodegeneration in the brain. In this Review, we briefly summarize the effects of chronic hypoxia on AD pathogenesis and discuss the underlying mechanisms. Since chronic hypoxia is common in the elderly and may contribute to the pathogenesis of AD, prospective prevention and treatment targeting hypoxia may be helpful to delay or alleviate AD.

Microenvironment Remodeling Micelles for Alzheimer's Disease Therapy by Early Modulation of Activated Microglia

Current strategies for Alzheimer's disease (AD) treatments focus on pathologies in the late stage of the disease progression. Poor clinical outcomes are displayed due to the irreversible damages caused by early microglia abnormality which triggers disease development before identical symptoms emerge. Based on the crosstalk between microglia and brain microenvironment, a reactive oxygen species (ROS)-responsive polymeric micelle system (Ab-PEG-LysB/curcumin (APLB/CUR)) is reported to normalize the oxidative and inflammatory microenvironment and reeducate microglia from an early phase of AD. Through an β-amyloid (Aβ) transportation-mimicked pathway, the micelles can accumulate into the diseased regions and exert synergistic effects of polymer-based ROS scavenging and cargo-based Aβ inhibition upon microenvironment stimuli. This multitarget strategy exhibits gradual correction of the brain microenvironment, efficient neuroprotection, and microglia modulation, leading to decreased Aβ plaque burdens and consequently enhanced cognitive functions in APPswe/PSEN1dE9 model mice. The results indicate that microglia can be exploited as an early target for AD treatment and their states can be controlled via microenvironment modulation.

Anti-inflammatory and cognitive effects of interferon-β1a (IFNβ1a) in a rat model of Alzheimer's disease

Background

Aβ_1-42 peptide abnormal production is associated with the development and maintenance of neuroinflammation and oxidative stress in brains from Alzheimer disease (AD) patients. Suppression of neuroinflammation may then represent a suitable therapeutic target in AD. We evaluated the efficacy of IFNβ1a in attenuating cognitive impairment and inflammation in an animal model of AD.

Methods

A rat model of AD was obtained by intra-hippocampal injection of Aβ_1-42 peptide (23 μg/2 μl). After 6 days, 3.6 μg of IFNβ1a was given subcutaneously (s.c.) for 12 days. Using the novel object recognition (NOR) test, we evaluated changes in cognitive function. Measurement of pro-inflammatory or anti-inflammatory cytokines, reactive oxygen species (ROS), and SOD activity levels was performed in the hippocampus. Data were evaluated by one-way ANOVA with Fisher’s Protected Least Significant Difference (PLSD) test.

Results

We showed that treatment with IFNβ1a was able to reverse memory impairment and to counteract microglia activation and upregulation of pro-inflammatory cytokines (IL-6, IL-1β) in the hippocampus of Aβ_1-42-injected rats. The anti-inflammatory cytokine IL-10, significantly reduced in the Aβ_1-42 animals, recovered to control levels following IFNβ1a treatment. IFNβ1a also reduced ROS and lipids peroxidation and increased SOD1 protein levels in the hippocampus of Aβ_1-42-injected rats.

Conclusion

This study shows that IFNβ1a is able to reverse the inflammatory and cognitive effects of intra-hippocampal Aβ_1-42 in the rat. Given the role played by inflammation in AD pathogenesis and the established efficacy of IFNβ1a in the treatment of inflammatory diseases of the central nervous system such as multiple sclerosis, its use may be a viable strategy to inhibit the pro-inflammatory cytokine and oxidative stress cascade associated with Aβ deposition in the hippocampus of AD patients.

Mitochondrial Dysfunction in Neural Injury

Mitochondria are the double membrane organelles providing most of the energy for cells. In addition, mitochondria also play essential roles in various cellular biological processes such as calcium signaling, apoptosis, ROS generation, cell growth, and cell cycle. Mitochondrial dysfunction is observed in various neurological disorders which harbor acute and chronic neural injury such as neurodegenerative diseases and ischemia, hypoxia-induced brain injury. In this review, we describe how mitochondrial dysfunction contributes to the pathogenesis of neurological disorders which manifest chronic or acute neural injury.

Neuroprotective effects of berberine on recognition memory impairment, oxidative stress, and damage to the purinergic system in rats submitted to intracerebroventricular injection of streptozotocin

Alzheimer's disease (AD) is a progressive and irreversible neurodegenerative disease. The present study investigated the effects of 50 and 100 mg/kg berberine (BRB) on recognition memory, oxidative stress, and purinergic neurotransmission, in a model of sporadic dementia of the Alzheimer's type induced by intracerebroventricular (ICV) injection of streptozotocin (STZ) in rats. Rats were submitted to ICV-STZ 3 mg/kg or saline, and 3 days later, were started on a treatment of BRB or saline for 21 days. The results demonstrated that BRB was effective in protecting against memory impairment, increased reactive oxygen species, and the subsequent increase in protein and lipid oxidation in the cerebral cortex and hippocampus, as well as δ-aminolevulinate dehydratase inhibition in the cerebral cortex. Moreover, the decrease in total thiols, and the reduced glutathione and glutathione S-transferase activity in the cerebral cortex and hippocampus of ICV-STZ rats, was prevented by BRB treatment. Besides an antioxidant effect, BRB treatment was capable of preventing decreases in ecto-nucleoside triphosphate diphosphohydrolase (NTPDase), 5'-nucleotidase (EC-5'-Nt), and adenosine deaminase (ADA) activities in synaptosomes of the cerebral cortex and hippocampus. Thus, our data suggest that BRB exerts a neuroprotective effect on recognition memory, as well as on oxidative stress and oxidative stress-related damage, such as dysfunction of the purinergic system. This suggests that BRB may act as a promising multipotent agent for the treatment of AD.

Multi-faceted therapeutic strategy for treatment of Alzheimer's disease by concurrent administration of etodolac and α-tocopherol

Alzheimer's disease (AD) is a complex neurodegenerative disorder with multiple dysfunctional pathways. Therefore, a sophisticated treatment strategy that simultaneously targets multiple brain cell types and disease pathways could be advantageous for effective intervention. To elucidate an effective treatment, we developed an in vitro high-throughput screening (HTS) assay to evaluate candidate drugs for their ability to enhance the integrity of the blood-brain barrier (BBB) and improve clearance of amyloid-β (Aβ) using a cell-based BBB model. Results from HTS identified etodolac and α-tocopherol as promising drugs for further investigation. Both drugs were tested separately and in combination for the purpose of targeting multiple pathways including neuroinflammation and oxidative stress. In vitro studies assessed the effects of etodolac and α-tocopherol individually and collectively for BBB integrity and Aβ transport, synaptic markers and Aβ production in APP-transfected neuronal cells, as well as effects on inflammation and oxidative stress in astrocytes. Transgenic 5XFAD mice were used to translate in vitro results of etodolac and α-tocopherol independently and with concurrent administration. Compared to either drug alone, the combination significantly enhanced the BBB function, decreased total Aβ load correlated with increased expression of major transport proteins, promoted APP processing towards the neuroprotective and non-amyloidogenic pathway, induced synaptic markers expression, and significantly reduced neuroinflammation and oxidative stress both in vitro and in vivo. Collective findings demonstrated the combination produced mixed interaction showing additive, less than additive or synergistic effects on the evaluated markers. In conclusion, this study highlights the significance of combination therapy to simultaneously target multiple disease pathways, and suggest the repurposing and combination of etodolac and α-tocopherol as a novel therapeutic strategy against AD.

Carnosine Prevents Aβ-Induced Oxidative Stress and Inflammation in Microglial Cells: A Key Role of TGF-β1

Carnosine (β-alanyl-L-histidine), a dipeptide, is an endogenous antioxidant widely distributed in excitable tissues like muscles and the brain. Carnosine is involved in cellular defense mechanisms against oxidative stress, including the inhibition of amyloid-beta (Aβ) aggregation and the scavenging of reactive species. Microglia play a central role in the pathogenesis of Alzheimer's disease, promoting neuroinflammation through the secretion of inflammatory mediators and free radicals. However, the effects of carnosine on microglial cells and neuroinflammation are not well understood. In the present work, carnosine was tested for its ability to protect BV-2 microglial cells against oligomeric Aβ1-42-induced oxidative stress and inflammation. Carnosine prevented cell death in BV-2 cells challenged with Aβ oligomers through multiple mechanisms. Specifically, carnosine lowered the oxidative stress by decreasing NO and O₂-• intracellular levels as well as the expression of iNOS and Nox enzymes. Carnosine also decreased the secretion of pro-inflammatory cytokines such as IL-1β, simultaneously rescuing IL-10 levels and increasing the expression and the release of TGF-β1. Carnosine also prevented Aβ-induced neurodegeneration in mixed neuronal cultures challenged with Aβ oligomers, and these neuroprotective effects were completely abolished by SB431542, a selective inhibitor of the type-1 TGF-β receptor. Our data suggest a multimodal mechanism of action of carnosine underlying its protective effects on microglial cells against Aβ toxicity with a key role of TGF-β1 in mediating these protective effects.

Getting to the Heart of Alzheimer Disease

In a somewhat narrow diagnostic lens, Alzheimer disease (AD) has been considered a brain-specific disease characterized by the presence of Aβ (β-amyloid) plaques and tau neural fibrillary tangles and neural inflammation; these pathologies lead to neuronal death and consequently clinical symptoms, such as memory loss, confusion, and impaired cognitive function. However, for decades, researchers have noticed a link between various cardiovascular abnormalities and AD-such as heart failure, coronary artery disease, atrial fibrillation, and vasculopathy. A considerable volume of work has pointed at this head to heart connection, focusing mainly on associations between cerebral hypoperfusion and neuronal degradation. However, new evidence of a possible systemic or metastatic profile to AD calls for further analysis of this connection. Aβ aggregations-biochemically and structurally akin to those found in the typical AD pathology-are now known to be present in the hearts of individuals with idiopathic dilated cardiomyopathy, as well as the hearts of patients with AD. These findings suggest a potential systemic profile of proteinopathies and a new hypothesis for the link between peripheral and central symptoms of heart failure and AD. Herein, we provide an overview of the cardiovascular links to Alzheimer disease.

Emerging pathways to neurodegeneration: Dissecting the critical molecular mechanisms in Alzheimer's disease, Parkinson's disease

Neurodegenerative diseases are usually sporadic in nature and commonly influenced by a wide range of genetic, life style and environmental factors. A unifying feature of Alzheimer's disease (AD) and Parkinson's disease (PD) is the abnormal accumulation and processing of mutant or damaged intra and extracellular proteins; this leads to neuronal vulnerability and dysfunction in the brain. Through a detailed review of ubiquitin proteasome, mRNA splicing, mitochondrial dysfunction, and oxidative stress pathway interrelation on neurodegeneration can improve the understanding of the disease mechanism. The identified pathways common to AD and PD nominate promising new targets for further studies, and as well as biomarkers. These insights suggested would likely provide major stimuli for developing unified treatment approaches to combat neurodegeneration. More broadly, pathways can serve as vehicles for integrating findings from diverse studies of neurodegeneration. The evidence examined in this review provides a brief overview of the current literature on significant pathways in promoting in AD, PD. Additionally, these insights suggest that biomarkers and treatment strategies may require simultaneous targeting of multiple components.

Could Alzheimer's Disease Originate in the Periphery and If So How So?

The classical amyloid cascade model for Alzheimer's disease (AD) has been challenged by several findings. Here, an alternative molecular neurobiological model is proposed. It is shown that the presence of the APOE ε4 allele, altered miRNA expression and epigenetic dysregulation in the promoter region and exon 1 of TREM2, as well as ANK1 hypermethylation and altered levels of histone post-translational methylation leading to increased transcription of TNFA, could variously explain increased levels of peripheral and central inflammation found in AD. In particular, as a result of increased activity of triggering receptor expressed on myeloid cells 2 (TREM-2), the presence of the apolipoprotein E4 (ApoE4) isoform, and changes in ANK1 expression, with subsequent changes in miR-486 leading to altered levels of protein kinase B (Akt), mechanistic (previously mammalian) target of rapamycin (mTOR) and signal transducer and activator of transcription 3 (STAT3), all of which play major roles in microglial activation, proliferation and survival, there is activation of microglia, leading to the subsequent (further) production of cytokines, chemokines, nitric oxide, prostaglandins, reactive oxygen species, inducible nitric oxide synthase and cyclooxygenase-2, and other mediators of inflammation and neurotoxicity. These changes are associated with the development of amyloid and tau pathology, mitochondrial dysfunction (including impaired activity of the electron transport chain, depleted basal mitochondrial potential and oxidative damage to key tricarboxylic acid enzymes), synaptic dysfunction, altered glycogen synthase kinase-3 (GSK-3) activity, mTOR activation, impairment of autophagy, compromised ubiquitin-proteasome system, iron dyshomeostasis, changes in APP translation, amyloid plaque formation, tau hyperphosphorylation and neurofibrillary tangle formation.

Protective effect of Berberis vulgaris on Fenton reaction-induced DNA cleavage

OBJECTIVE

Berberis vulgaris contains antioxidants that can inhibit DNA cleavage. The purpose of this study was to evaluate the antioxidant and protective activity of B. vulgaris on DNA cleavage.

MATERIALS AND METHODS

In this study, the antioxidant capacity of B. vulgaris was investigated using DPPH and its protective effect was evaluated on pBR322 plasmid and lymphocyte genomic DNA cleavage induced by Fenton reaction, by DNA electrophoresis.

RESULTS

Aqueous extract of B. vulgaris presented dual behavior with a potent antioxidant activity at 0.25and 0.75mg/ml for pBR322 plasmid and lymphocyte genomic DNA, respectively, but a pro-oxidant activity was observed at higher concentrations.

CONCLUSION

Our results indicated that B. vulgaris extract an inhibit Fenton reaction-induced DNA cleavage and oxidative cleavage of double-stranded DNA assay is a powerful technique that can be used to determine the antioxidant and pro-oxidant properties of a compound on cellular components such as DNA.

Total phenolic, flavonoid content, and antioxidant activity of bulbs, leaves, and flowers made from Eleutherine bulbosa (Mill.) Urb

In the current investigation, total phenols and flavonoids contents of Eleutherine bulbosa (Mill.) Urb. bulbs, leaves, and flowers were quantified by Folin-Ciocalteu's and borohydride/chloroquinone methods, respectively. Antioxidant activity of the plant extracts was evaluated by means of peroxide scavenging capacity assay and by cell antioxidation method. Antioxidant activity of E. bulbosa bulbs, leaves, and flowers was correlated with total phenols and flavonoids. The total phenols and flavonoids of the bulbs of E. bulbosa were higher than leaves and flower and its antioxidant activity was also stronger than leaves and flowers of E. bulbosa. The higher content of flavonoids or total phenols, the stronger the antioxidant capacity in vitro. The antioxidant activity of E. bulbosa extract showed it's certain nutritional value and therefore had the potential as a source of natural antioxidants.

A Synthetic Pro-Drug Peptide Reverses Amyloid-β-Induced Toxicity in the Rat Model of Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD), the most prevalent neurodegenerative disorder, involves the formation of the extracellular amyloid-β (Aβ) plaques and intracellular neurofibrillary tangles. The current therapies against AD are symptomatic with limited benefits but associated with major side effects. Inhibition of self-aggregation of Aβ peptides into higher order cross-β structure is one of the potential therapeutic approach which may counter oligomerization of Aβ peptide.

OBJECTIVE

The present study aimed to evaluate the neuroprotective and anti-inflammatory potential of a synthetic Pro-Drug type peptide (PDp) against Aβ-induced toxicity in rat model of AD.

METHODS

Intra-hippocampal microinjection of toxic Aβ40 (IHAβ40) by stereotaxic surgery was performed in the male Sprague-Dawley rats to generate an Aβ-induced AD model. Sub-chronic toxicity of synthetic PDp using hematological, biochemical, and histopathological parameters was investigated. Evaluation of PDp on Aβ-induced neurodegeneration and neuroinflammation was performed.

RESULTS

PDp inhibits plaque formation with increase in Nissl granule staining in the rat hippocampus. Aβ-induced toxicity associated imbalance in reactive oxygen species and antioxidant enzymes activity such as superoxide dismutase and catalase in the rat brain was overcome by PDp treatment. Tau protein hyperphosphorylation was normalized with PDp treatment. Also, the neuroinflammatory response was suppressed with PDp treatment.

CONCLUSION

The present study depicts the potential neuroprotective role of PDp against Aβ-induced toxicity in rat. PDp inhibits plaque formation thereby normalizing oxidative stress, inhibiting tau protein hyperphosphorylation, and suppressing neuroinflammatory responses. Future studies done in this direction will pave way for new therapeutic strategies.

Comprehensive review of mechanisms of pathogenesis involved in Alzheimer's disease and potential therapeutic strategies

AD is a progressive neurodegenerative disorder and a leading cause of dementia in an aging population worldwide. The enormous challenge which AD possesses to global healthcare makes it as urgent as ever for the researchers to develop innovative treatment strategies to fight this disease. An in-depth analysis of the extensive available data associated with the AD is needed for a more comprehensive understanding of underlying molecular mechanisms and pathophysiological pathways associated with the onset and progression of the AD. The currently understood pathological and biochemical manifestations include cholinergic, Aβ, tau, excitotoxicity, oxidative stress, ApoE, CREB signaling pathways, insulin resistance, etc. However, these hypotheses have been criticized with several conflicting reports for their involvement in the disease progression. Several issues need to be addressed such as benefits to cost ratio with cholinesterase therapy, the dilemma of AChE selectivity over BChE, BBB permeability of peptidic BACE-1 inhibitors, hurdles related to the implementation of vaccination and immunization therapy, and clinical failure of candidates related to newly available targets. The present review provides an insight to the different molecular mechanisms involved in the development and progression of the AD and potential therapeutic strategies, enlightening perceptions into structural information of conventional and novel targets along with the successful applications of computational approaches for the design of target-specific inhibitors.

Potential Application of Prunus armeniaca L. and P. domestica L. Leaf Essential Oils as Antioxidant and of Cholinesterases Inhibitors

The aim of this work is to investigate the in vitro acetylcholinesterase (AChE) and butyrycholinesterase (BChE) inhibitory activities of essential oils obtained by hydrodistillation from the leaves of Prunus armeniaca and P. domestica in relation to their composition, analysed by Gas Chromatography–Flame Ionization Detector (GC-FID) and Gas Chromatography-Mass Spectrometry (GC-MS) analyses, at different times. Moreover, considering the role of free radicals in the progression of neurodegenerative disorders, the antioxidant properties of essential oils were investigated by using, 2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and β-carotene bleaching tests. The relative antioxidant capacity index (RACI) was used to achieve more comprehensive comparison between analysed antioxidant effects of essential oils. P. armeniaca oils were more active than P. domestica oils against AChE. Against BChE, the most active was the essential oil from P. domestica leaves collected in August with an IC₅₀ value of 95.80 μg/mL. This oil exerted the highest inhibitory activity of lipid peroxidation with IC₅₀ values of 11.15 and 11.39 μg/mL after 30 and 60 min of incubation, respectively. All samples demonstrated a remarkable ABTS radicals scavenging activity, with IC₅₀ values in the range 0.45–0.57 μg/mL in comparison to the positive control, ascorbic acid.

Nootropic and Anti-Alzheimer's Actions of Medicinal Plants: Molecular Insight into Therapeutic Potential to Alleviate Alzheimer's Neuropathology

Medicinal plants are the backbone of modern medicine. In recent times, there is a great urge to discover nootropic medicinal plants to reverse cognitive dysfunction owing to their less adverse effects. Alzheimer's disease (AD) is an age-related neurodegenerative disorder characterized by the inevitable loss of cognitive function, memory and language impairment, and behavioral disturbances, which turn into gradually more severe. Alzheimer's has no current cure, but symptomatic treatments are available and research continues. The number of patients suffering from AD continues to rise and today, there is a worldwide effort under study to find better ways to alleviate Alzheimer's pathogenesis. In this review, the nootropic and anti-Alzheimer's potentials of 6 medicinal plants (i.e., Centella asiatica, Clitoria ternatea, Crocus sativus, Terminalia chebula, Withania somnifera, and Asparagus racemosus) were explored through literature review. This appraisal focused on available information about neuroprotective and anti-Alzheimer's use of these plants and their respective bioactive compounds/metabolites and associated effects in animal models and consequences of its use in human as well as proposed molecular mechanisms. This review progresses our existing knowledge to reveal the promising linkage of traditional medicine to halt AD pathogenesis. This analysis also avowed a new insight to search the promising anti-Alzheimer's drugs.

Chronic stress as a risk factor for Alzheimer's disease: Roles of microglia-mediated synaptic remodeling, inflammation, and oxidative stress

Microglia are the predominant immune cells of the central nervous system (CNS) that exert key physiological roles required for maintaining CNS homeostasis, notably in response to chronic stress, as well as mediating synaptic plasticity, learning and memory. The repeated exposure to stress confers a higher risk of developing neurodegenerative diseases including sporadic Alzheimer's disease (AD). While microglia have been causally linked to amyloid beta (Aβ) accumulation, tau pathology, neurodegeneration, and synaptic loss in AD, they were also attributed beneficial roles, notably in the phagocytic elimination of Aβ. In this review, we discuss the interactions between chronic stress and AD pathology, overview the roles played by microglia in AD, especially focusing on chronic stress as an environmental risk factor modulating their function, and present recently-described microglial phenotypes associated with neuroprotection in AD. These microglial phenotypes observed under both chronic stress and AD pathology may provide novel opportunities for the development of better-targeted therapeutic interventions.

Soluble tau aggregates, not large fibrils, are the toxic species that display seeding and cross-seeding behavior

Several studies have proposed that fibrillary aggregates of tau and other amyloidogenic proteins are neurotoxic and result in numerous neurodegenerative diseases. However, these studies usually involve sonication or extrusion through needles before experimentation. As a consequence, these methods may fragment large aggregates producing a mixture of aggregated species rather than intact fibrils. Therefore, the results of these experiments may be reflective of other amyloidogenic species, such as oligomers and/or protofibrils/short fibrils. To investigate the effects of sonication on the aggregation of tau and other amyloidogenic proteins, fibrils were prepared and well characterized, then sonicated and evaluated by various biochemical and biophysical methods to identify the aggregated species present. We found that indeed a mixture of aggregated species was present along with short fibrils indicating that sonication leads to impure fibril samples and should be analyzed with caution. Our results corroborate the previous studies showing that sonication of prion and Aβ fibrils leads to the formation of toxic, soluble aggregates. We also show that the oligomeric forms are the most toxic species although it is unclear how sonication causes oligomer formation. Recent results suggest that these small toxic oligomers produced by sonication, rather than the stable fibrillar structures, are prion-like in nature displaying seeding and cross-seeding behavior.

Evaluating the link between Paraoxonase-1 levels and Alzheimer's disease development

At present, the etiopathogenesis of Alzheimer's disease (AD), the most common form of dementia, remains far to be fully deciphered. In the recent years, also the centrality of amyloid-β peptide in the pathogenesis of the neurodegenerative disease has been questioned and other hypotheses have been advanced. Notably, a common denominator of many of these theoretical models is represented by oxidative stress, which is widely proposed to play a role in the disease initiation and/or progression. Paraoxonase 1 (PON1) is a high-density lipoprotein (HDL)-associated enzyme that endows its carrier with multiple biological functions, including the ability to contrast oxidative damage to lipid components of lipoproteins and cells and protect from toxicity of specific organophosphorus pesticides. The peculiar multi-functionality nature of PON1 might be the key for explaining the vast epidemiological data showing a close association between low serum PON1 activity and risk of several diseases, including cardiovascular and neurodegenerative diseases, in particular AD. In this review, we discuss the possible link between PON1 with AD pathogenesis and we hypothesize eventual mechanistic pathways that could account from epidemiological observations. We also highlight the methodological issue limitation in PON1 studies that still impede to give a definitive and certain picture of its effective biological impact on human health including AD.

Phloroglucinol ameliorates cognitive impairments by reducing the amyloid β peptide burden and pro-inflammatory cytokines in the hippocampus of 5XFAD mice

Among the various causative factors involved in the pathogenesis of Alzheimer's disease (AD), oxidative stress has emerged as an important factor. Phloroglucinol is a polyphenol component of phlorotannin, which is found at sufficient levels in Ecklonia cava (E. cava). Phloroglucinol has been reported to exert antioxidant activities in various tissues. Previously, we reported that the stereotaxic injection of phloroglucinol regulated synaptic plasticity in an AD mouse model. In this study, we aimed to investigate the effects of oral administration of phloroglucinol in AD. The oral administration of phloroglucinol for 2 months attenuated the impairments in cognitive function observed in 6-month-old 5X familial AD (5XFAD) mice, as assessed with the T-maze and Y-maze tests. The administration of phloroglucinol for 2 months in 5XFAD mice caused a reduction in the number of amyloid plaques and in the protein level of BACE1, a major amyloid precursor protein cleavage enzyme, together with γ-secretase. Phloroglucinol also restored the reduction in dendritic spine density and the number of mature spines in the hippocampi of 5XFAD mice. In addition, phloroglucinol-administered 5XFAD mice displayed lower protein levels of GFAP and Iba-1 and mRNA levels of TNF-α and IL-6 compared with vehicle-administered 5XFAD mice. These results demonstrated that phloroglucinol alleviated the neuropathological features and behavioral phenotypes in the 5XFAD mouse model. Taken together, our results suggest that phloroglucinol has therapeutic potential for AD treatment.

Critical role of mitosis in spontaneous late-onset Alzheimer's disease; from a Shugoshin 1 cohesinopathy mouse model

From early-onset Alzheimer's disease (EOAD) studies, the amyloid-beta hypothesis emerged as the foremost theory of the pathological causes of AD. However, how amyloid-beta accumulation is triggered and progresses toward senile plaques in spontaneous late-onset Alzheimer's disease (LOAD) in humans remains unanswered. Various LOAD facilitators have been proposed, and LOAD is currently considered a complex disease with multiple causes. Mice do not normally develop LOAD. Possibly due to the multiple causes, proposed LOAD facilitators have not been able to replicate spontaneous LOAD in mice, representing a disease modeling issue. Recently, we reported spontaneous late-onset development of amyloid-beta accumulation in brains of Shugoshin 1 (Sgo1) haploinsufficient mice, a cohesinopathy-mediated chromosome instability model. The result for the first time expands disease relevance of mitosis studies to a major disease other than cancers. Reverse-engineering of the model would shed light on the process of late-onset amyloid-beta accumulation in the brain and spontaneous LOAD development, and contribute to development of interventions for LOAD. This review will discuss the Sgo1 model, our current "three-hit hypothesis" regarding LOAD development with an emphasis on critical role of prolonged mitosis in amyloid-beta accumulation, and implications for human LOAD intervention and treatment. Abbreviations: Alzheimer's disease (AD); Late-onset Alzheimer's disease (LOAD); Early-onset Alzheimer's disease (EOAD); Shugoshin-1 (Sgo1); Chromosome Instability (CIN); apolipoprotein (Apoe); Central nervous system (CNS); Amyloid precursor protein (APP); N-methyl-d-aspartate (NMDA); Hazard ratio (HR); Cyclin-dependent kinase (CDK); Chronic Atrial Intestinal Dysrhythmia (CAID); beta-secretase 1 (BACE); phosphor-Histone H3 (p-H3); Research and development (R&D); Non-steroidal anti-inflammatory drugs (NSAIDs); Brain blood barrier (BBB).

Penetration, distribution and brain toxicity of titanium nanoparticles in rodents' body: a review

Titanium dioxide (TiO2) has been vastly used commercially, especially as white pigment in paints, colorants, plastics, coatings, cosmetics. Certain industrial uses TiO2 in diameter <100 nm. There are three common exposure routes for TiO2: (i) inhalation exposure, (ii) exposure via gastrointestinal tract, (iii) dermal exposure. Inhalation and gastrointestinal exposure appear to be the most probable ways of exposure, although nanoparticle (NP) penetration is limited. However, the penetration rate may increase substantially when the tissue is impaired. When TiO2 NPs migrate into the circulatory system, they can be distributed into all tissues including brain. In brain, TiO2 lead to oxidative stress mediated by the microglia phagocytic cells which respond to TiO2 NPs by the production and release of superoxide radicals that convert to multiple reactive oxygen species (ROS). The ROS production may also cause the damage of blood-brain barrier which then becomes more permeable for NPs. Moreover, several studies have showed neuron degradation and the impairment of spatial recognition memory and learning abilities in laboratory rodent exposed to TiO2 NPs.

Tau Pathology of Alzheimer Disease: Possible Role of Sleep Deprivation

Sleep deprivation is a common complaint in modern societies. Insufficient sleep has increased the risk of catching neurodegenerative diseases such as Alzheimer’s. Several studies have indicated that restricted sleep increases the level of deposition of β-amyloid and formation of neurofibrillary tangles, the major brain microstructural hallmarks for Alzheimer disease. The mechanisms by which sleep deprivation affects the pathology of Alzheimer disease has not yet been fully and definitively identified. However, risk factors like apolipoprotein E risk alleles, kinases and phosphatases dysregulation, reactive oxygen species, endoplasmic reticulum damages, glymphatic system dysfunctions and orexinergic system inefficacy have been identified as the most important factors which mediates between the two conditions. In this review, these factors are briefly discussed.

Targeting mitochondria with folic acid and vitamin B12 ameliorates nicotine mediated islet cell dysfunction

Nicotine, one of the well-known highly toxic components of cigarette smoke, causes a number of adverse health effects and diseases. Our previous study has shown that nicotine induces reactive oxygen species (ROS) in islet cell and disrupts islet cell mitochondrial membrane potential (ΔΨm). However, supplementation with folic acid and vitamin B12 were found effective against nicotine induced changes in pancreatic islet cells. But the toxicological effects and underlying mechanisms of nicotine-induced mitochondrial dysfunction is still unknown. In this study, nicotine exposure decreases mitochondrial enzymes (pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, aconitase, malate dehydrogenase) activities by increasing cytosolic Ca2+ level which may contribute to increased mitochondrial ROS production by raising its flow to mitochondria. This in turn produces malondialdehyde and nitric oxide (NO) with a concomitant decrease in the activities of antioxidative enzymes and glutathione levels leading to loss of ΔΨm. Simultaneously, nicotine induces pancreatic islet cell apoptosis by modulating ΔΨm via increased cytosolic Ca2+ level, altered Bcl-2, Bax, cytochrome c, caspase-9, PARP expressions which were prevented by the supplementation of folic acid and vitamin B12 . In conclusion, nicotine alters islet cell mitochondrial redox status, apoptotic machinery, and enzymes to cause disruption in the ΔΨm and supplementation of folic acid and vitamin B12 possibly blunted all these mitochondrial alterations. Therefore, this study may help to determine the pathophysiology of nicotine-mediated islet cell mitochondrial dysfunction.

Silencing of Long Noncoding RNA SOX21-AS1 Relieves Neuronal Oxidative Stress Injury in Mice with Alzheimer's Disease by Upregulating FZD3/5 via the Wnt Signaling Pathway

Alzheimer's disease (AD) represents a progressive neurodegenerative disorder characterized by distinctive neuropathological changes. Recently, long noncoding RNAs (lncRNAs) have become a key area of interest due to their potential in AD therapy. Hence, the aim of the current study was to investigate the effect of lncRNA SOX21-AS1 on neuronal oxidative stress injury in mice with AD via the Wnt signaling pathway by targeting FZD3/5. Microarray analysis was performed to screen AD-related differentially expressed genes (DEGs). Following verification of the target relationship between SOX21-AS1 and FZD3/5, the contents of OH^-, malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) were determined, with the expressions of SOX21-AS1, FZD3/5, β-catenin, cyclin D1, and 4-HNE in hippocampal neuron cells subsequently detected. Cell cycle distribution and apoptosis were evaluated. Bioinformatics analysis revealed that SOX21-AS1 was upregulated in AD, while highlighting the co-expression of SOX21-AS1 and FZD3/5 genes and their involvement in the Wnt signaling pathway. AD mice exhibited diminished memory and learning ability, increased rates of MDA, OH^-, SOX21-AS1, 4-HNE, and elevated levels of hippocampal neuron cell apoptosis, accompanied by decreased levels of SOD, CAT, GSH-Px, FZD3/5, β-catenin, and cyclin D1. Silencing of SOX21-AS1 resulted in decreased OH^-, MDA contents, SOX21-AS1, and 4-HNE, and increased SOD, CAT, GSH-Px, FZD3/5, β-catenin, and cyclin D1, as well as reduced apoptosis of hippocampal neuron cells. Taken together, the key findings of the present study demonstrated that silencing of lncRNA SOX21-AS1 could act to alleviate neuronal oxidative stress and suppress neuronal apoptosis in AD mice through the upregulation of FZD3/5 and subsequent activation of the Wnt signaling pathway.

A Natural Dietary Supplement with a Combination of Nutrients Prevents Neurodegeneration Induced by a High Fat Diet in Mice

Obesity and metabolic disorders can be risk factors for the onset and development of neurodegenerative diseases. The aim of the present study was to investigate the protective effects of a natural dietary supplement (NDS), containing Curcuma longa, silymarin, guggul, chlorogenic acid and inulin, on dysmetabolism and neurodegeneration in the brains of high fat diet (HFD)-fed mice. Decrease in the expression of FACL-4, CerS-1, CerS-4, cholesterol concentration and increase in the insulin receptor expression and insulin signaling activation, were found in brains of NDS-treated HFD brains in comparison with HFD untreated-mice, suggesting that NDS is able to prevent brain lipid accumulation and central insulin resistance. In the brains of NDS-treated HFD mice, the levels of RNS, ROS and lipid peroxidation, the expression of p-ERK, H-Oxy, i-NOS, HSP60, NF-kB, GFAP, IL-1β, IL-6 and CD4 positive cell infiltration were lower than in untreated HFD mice, suggesting antioxidant and anti-inflammatory effects of NDS. The decreased expression of p-ERK and GFAP in NDS-treated HFD mice was confirmed by immunofluorescence. Lastly, a lower number of apoptotic nuclei was found in cortical sections of NDS-treated HFD mice. The present data indicate that NDS exerts neuroprotective effects in HFD mice by reducing brain fat accumulation, oxidative stress and inflammation and improving brain insulin resistance.

Neurotrophic Action of Comenic Acid and Its Derivatives Potassium Comenate and Calcium Comenate

Using the model of cultured spinal ganglia, we demonstrated high neurotrophic activity of comenic acid and its derivatives potassium comenate and calcium comenate both under normal conditions and during oxidative stress. Calcium comenate in the norm as well as potassium and calcium comenates during oxidative stress demonstrate greater neurotrophic potency than comenic acid.

Melatonin and its metabolites vs oxidative stress: From individual actions to collective protection

Oxidative stress (OS) represents a threat to the chemical integrity of biomolecules including lipids, proteins, and DNA. The associated molecular damage frequently results in serious health issues, which justifies our concern about this phenomenon. In addition to enzymatic defense mechanisms, there are compounds (usually referred to as antioxidants) that offer chemical protection against oxidative events. Among them, melatonin and its metabolites constitute a particularly efficient chemical family. They offer protection against OS as individual chemical entities through a wide variety of mechanisms including electron transfer, hydrogen transfer, radical adduct formation, and metal chelation, and by repairing biological targets. In fact, many of them including melatonin can be classified as multipurpose antioxidants. However, what seems to be unique to the melatonin's family is their collective effects. Because the members of this family are metabolically related, most of them are expected to be present in living organisms wherever melatonin is produced. Therefore, the protection exerted by melatonin against OS may be viewed as a result of the combined antioxidant effects of the parent molecule and its metabolites. Melatonin's family is rather exceptional in this regard, offering versatile and collective antioxidant protection against OS. It certainly seems that melatonin is one of the best nature's defenses against oxidative damage.

Oxidation of KCNB1 channels in the human brain and in mouse model of Alzheimer's disease

Oxidative modification of the voltage-gated K⁺ channel subfamily B member 1 (KCNB1, Kv2.1) is emerging as a mechanism of neuronal vulnerability potentially capable of affecting multiple conditions associated with oxidative stress, from normal aging to neurodegenerative disease. In this study we report that oxidation of KCNB1 channels is exacerbated in the post mortem brains of Alzheimer’s disease (AD) donors compared to age-matched controls. In addition, phosphorylation of Focal Adhesion kinases (FAK) and Src tyrosine kinases, two key signaling steps that follow KCNB1 oxidation, is also strengthened in AD vs. control brains. Quadruple transgenic mice expressing a non-oxidizable form of KCNB1 in the 3xTg-AD background (APP_SWE, PS1_M146V, and tau_P301L), exhibit improved working memory along with reduced brain inflammation, protein carbonylation and intraneuronal β-amyloid (Aβ) compared to 3xTg-AD mice or mice expressing the wild type (WT) KCNB1 channel. We conclude that oxidation of KCNB1 channels is a mechanism of neuronal vulnerability that is pervasive in the vertebrate brain.

Acid-base fractions separated from Streblus asper leaf ethanolic extract exhibited antibacterial, antioxidant, anti-acetylcholinesterase, and neuroprotective activities

BACKGROUND

Streblus asper is a well-known plant native to Southeast Asia. Different parts of the plant have been traditionally used for various medicinal purposes. However, there is very little scientific evidence reporting its therapeutic benefits for potential treatment of Alzheimer's disease (AD). The study aimed to evaluate antibacterial, antioxidant, acetylcholinesterase (AChE) inhibition, and neuroprotective properties of S. asper leaf extracts with the primary objective of enhancing therapeutic applications and facilitating activity-guided isolation of the active chemical constituents.

METHODS

The leaves of S. asper were extracted in ethanol and subsequently fractionated into neutral, acid and base fractions. The phytochemical constituents of each fraction were analyzed using GC-MS. The antibacterial activity was evaluated using a broth microdilution method. The antioxidant activity was determined using DPPH and ABTS radical scavenging assays. The neuroprotective activity against glutamate-induced toxicity was tested on hippocampal neuronal HT22 cell line by evaluating the cell viability using MTT assay. The AChE inhibitory activity was screened by thin-layer chromatography (TLC) bioautographic method.

RESULTS

The partition of the S. asper ethanolic leaf extract yielded the highest mass of phytochemical constitutions in the neutral fraction and the lowest in the basic fraction. Amongst the three fractions, the acidic fraction showed the strongest antibacterial activity against gram-positive bacteria. The antioxidant activities of three fractions were found in the order of acidic > basic > neutral, whereas the decreasing order of neuroprotective activity was neutral > basic > acidic. TLC bioautography revealed one component in the neutral fraction exhibited anti-AChE activity. While in the acid fraction, two components showed inhibitory activity against AChE. GC-MS analysis of three fractions showed the presence of major phytochemical constituents including terpenoids, steroids, phenolics, fatty acids, and lipidic plant hormone.

CONCLUSIONS

Our findings have demonstrated the therapeutic potential of three fractions extracted from S. asper leaves as a promising natural source for neuroprotective agents with additional actions of antibacterials and antioxidants, along with AChE inhibitors that will benefit in the development of new natural compounds in therapies against AD.

Effect of Sodium Selenate on Hippocampal Proteome of 3×Tg-AD Mice-Exploring the Antioxidant Dogma of Selenium against Alzheimer's Disease

Selenium (Se), an antioxidant trace element, is an important nutrient for maintaining brain functions and is reported to be involved in Alzheimer's disease (AD) pathologies. The present study has been designed to elucidate the protein changes in hippocampus of 3×Tg-AD mice after supplementing sodium selenate as an inorganic source of selenium. By using iTRAQ proteomics technology, 113 differentially expressed proteins (DEPs) are found in AD/WT mice with 37 upregulated and 76 downregulated proteins. Similarly, in selenate-treated 3×Tg-AD (ADSe/AD) mice, 115 DEPs are found with 98 upregulated and 17 downregulated proteins. The third group of mice (ADSe/WT) showed 75 DEPs with 46 upregulated and 29 downregulated proteins. Among these results, 42 proteins (40 downregulated and 2 upregulated) in the diseased group showed reverse expression when treated with selenate. These DEPs are analyzed with different bioinformatics tools and are found associated with various AD pathologies and pathways. Based on their functions, selenate-reversed proteins are classified as structural proteins, metabolic proteins, calcium regulating proteins, synaptic proteins, signaling proteins, stress related proteins, and transport proteins. Six altered AD associated proteins are successfully validated by Western blot analysis. This study shows that sodium selenate has a profound effect on the hippocampus of the triple transgenic AD mice. This might be established as an effective therapeutic agent after further investigation.

A molecular approach in drug development for Alzheimer's disease

An increase in dementia numbers and global trends in population aging across the world prompts the need for new medications to treat the complex biological dysfunctions, such as neurodegeneration associated with dementia. Alzheimer's disease (AD) is the most common form of dementia. Cholinergic signaling, which is important in cognition, is slowly lost in AD, so the first line therapy is to treat symptoms with acetylcholinesterase inhibitors to increase levels of acetylcholine. Out of five available FDA-approved AD medications, donepezil, galantamine and rivastigmine are cholinesterase inhibitors while memantine, a N-methyl d-aspartate (NMDA) receptor antagonist, blocks the effects of high glutamate levels. The fifth medication consists of a combination of donepezil and memantine. Although these medications can reduce and temporarily slow down the symptoms of AD, they cannot stop the damage to the brain from progressing. For a superior therapeutic effect, multi-target drugs are required. Thus, a Multi-Target-Directed Ligand (MTDL) strategy has received more attention by scientists who are attempting to develop hybrid molecules that simultaneously modulate multiple biological targets. This review highlights recent examples of the MTDL approach and fragment based strategy in the rational design of new potential AD medications.

OxInflammation: From Subclinical Condition to Pathological Biomarker

Inflammation is a complex systemic response evolved to cope with cellular injury, either due to infectious agents or, in general, with sporadic events challenging tissue integrity and function. Researchers involved in different fields have the tendency to look at the inflammatory response with different angles, according to their specific interest. Established its complexity, one of the most evident features of the inflammatory response is the generation of a pro-oxidative environment due to the production of high fluxes of pro-oxidant species. This production begins locally, close to the sites of tissue damage or infection, but eventually becomes a chronic challenge for the organism, if the inflammatory response is not properly controlled. In this review, we focus on this specific aspect of chronic, low-level sub-clinical inflammatory response. We propose the term "OxInflammation" as a novel operative term describing a permanent pro-oxidative feature that interact, in a positive feed-back manner, to a not yet clinically detectable inflammatory process, leading in a long run (chronically) to a systemic/local damage, as a consequence of the cross talk between inflammatory, and oxidative stress mediators. Therefore, it could be useful to analyze inflammatory markers in pathologies where there is an alteration of the redox homeostasis, although an inflammatory status is not clinically evident.

Generation and propagation of yeast prion [URE3] are elevated under electromagnetic field

In this study, we studied the effect of 2.0 GHz radio frequency electromagnetic field (RF-EMF) and 50 Hz extremely low frequency electromagnetic field (ELF-EMF) exposure on prion generation and propagation using two budding yeast strains, NT64C and SB34, as model organisms. Under exposure to RF-EMF or ELF-EMF, the de novo generation and propagation of yeast prions [URE3] were elevated in both strains. The elevation increased over time, and the effects of ELF-EMF occurred in a dose-dependent manner. The transcription and expression levels of the molecular chaperones Hsp104, Hsp70-Ssa1/2, and Hsp40-Ydj1 were not statistically significantly changed after exposure. Furthermore, the levels of ROS, as well as the activities of superoxide dismutase (SOD) and catalase (CAT), were significantly elevated after short-term, but not long-term exposure. This work demonstrated for the first time that EMF exposure could elevate the de novo generation and propagation of yeast prions and supports the hypothesis that ROS may play a role in the effects of EMF on protein misfolding. The effects of EMF on protein folding and ROS levels may mediate the broad effects of EMF on cell function.

Postmortem Brain, Cerebrospinal Fluid, and Blood Neurotrophic Factor Levels in Alzheimer's Disease: A Systematic Review and Meta-Analysis

Accumulating evidence suggest that aberrations of neurotrophic factors are involved in the etiology and pathogenesis of Alzheimer's disease (AD), but clinical data were inconsistent. Therefore, a meta-analysis on neurotrophic factor levels in AD is necessary. We performed a systematic review of blood, CSF, and post-mortem brain neurotrophic factor levels in patients with AD compared with controls and quantitatively summarized the clinical data in blood and CSF with a meta-analytical technique. A systematic search of PubMed and Web of Science identified 98 articles in this study (with samples more than 9000). Random effects meta-analysis demonstrated that peripheral blood BDNF levels were significantly decreased in AD patients compared with controls. However, blood NGF, IGF, and VEGF did not show significant differences between cases and controls. In CSF, random effects meta-analysis showed significantly deceased BDNF and increased NGF levels in patients with AD, whereas IGF and VEGF did not show significant differences between the AD group and control group. In addition, 23 post-mortem studies were included in the systematic review. Although data from post-mortem brains were not always consistent across studies, most studies suggested decreased BDNF and increased (pro)NGF levels in hippocampus and neocortex of patients with AD. These results provide strong clinical evidence that AD is accompanied by an aberrant neurotrophin profile, and future investigations into neurotrophins as biomarkers (especially CSF BDNF and NGF) and therapeutic targets for AD may be warranted.

Rutin as a Potent Antioxidant: Implications for Neurodegenerative Disorders

A wide range of neurodegenerative diseases (NDs), including Alzheimer's disease, Parkinson's disease, Huntington's disease, and prion diseases, share common mechanisms such as neuronal loss, apoptosis, mitochondrial dysfunction, oxidative stress, and inflammation. Intervention strategies using plant-derived bioactive compounds have been offered as a form of treatment for these debilitating conditions, as there are currently no remedies to prevent, reverse, or halt the progression of neuronal loss. Rutin, a glycoside of the flavonoid quercetin, is found in many plants and fruits, especially buckwheat, apricots, cherries, grapes, grapefruit, plums, and oranges. Pharmacological studies have reported the beneficial effects of rutin in many disease conditions, and its therapeutic potential in several models of NDs has created considerable excitement. Here, we have summarized the current knowledge on the neuroprotective mechanisms of rutin in various experimental models of NDs. The mechanisms of action reviewed in this article include reduction of proinflammatory cytokines, improved antioxidant enzyme activities, activation of the mitogen-activated protein kinase cascade, downregulation of mRNA expression of PD-linked and proapoptotic genes, upregulation of the ion transport and antiapoptotic genes, and restoration of the activities of mitochondrial complex enzymes. Taken together, these findings suggest that rutin may be a promising neuroprotective compound for the treatment of NDs.

Review: Neuropathology and behavioural features of transgenic murine models of Alzheimer's disease

Our understanding of the underlying biology of Alzheimer's disease (AD) has been steadily progressing; however, this is yet to translate into a successful treatment in humans. The use of transgenic mouse models has helped to develop our understanding of AD, not only in terms of disease pathology, but also with the associated cognitive impairments typical of AD. Plaques and neurofibrillary tangles are often among the last pathological changes in AD mouse models, after neuronal loss and gliosis. There is a general consensus that successful treatments need to be applied before the onset of these pathologies and associated cognitive symptoms. This review discusses the different types of AD mouse models in terms of the temporal progression of the disease, how well they replicate the pathological changes seen in human AD and their cognitive defects. We provide a critical assessment of the behavioural tests used with AD mice to assess cognitive changes and decline, and discuss how successfully they correlate with cognitive impairments in humans with AD. This information is an important tool for AD researchers when deciding on appropriate mouse models, and when selecting measures to assess behavioural and cognitive change.