Alzheimer's disease: treatments in discovery and development

Neuroprotective effect of whey protein hydrolysate containing leucine-aspartate-isoleucine-glutamine-lysine on HT22 cells in hydrogen peroxide-induced oxidative stress

This study aimed to investigate the neuroprotective effects of whey protein hydrolysate (WPH) containing the pentapeptide leucine-aspartate-isoleucine-glutamine-lysine (LDIQK). Whey protein hydrolysate (50, 100, and 200 µg/mL) demonstrated the ability to restore the viability of HT22 cells subjected to 300 µM hydrogen peroxide (H2O2)-induced oxidative stress. Furthermore, at a concentration of 200 µg/mL, it significantly reduced the increase in reactive oxygen species production and calcium ion (Ca2+) influx induced by H2O2 by 46.1% and 46.2%, respectively. Similarly, the hydrolysate significantly decreased the levels of p-tau, a hallmark of tauopathy, and BCL2 associated X (BAX), a proapoptosis factor, while increasing the protein levels of choline acetyltransferase (ChAT), an enzyme involved in acetylcholine synthesis, brain-derived neurotrophic factor (BDNF), a nerve growth factor, and B-cell lymphoma 2 (BCL2, an antiapoptotic factor. Furthermore, it increased nuclear factor erythroid 2-related factor 2 (Nrf2)-hemoxygenase-1(HO-1) signaling, which is associated with the antioxidant response, while reducing the activation of mitogen-activated protein kinase (MAPK) signaling pathway components, namely phosphor-extracellular signal-regulated kinases (p-ERK), phosphor-c-Jun N-terminal kinases (p-JNK), and p-p38. Column chromatography and tandem mass spectrometry analysis identified LDIQK as a compound with neuroprotective effects in WPH; it inhibited Ca2+ influx and regulated the BAX/BCL2 ratio. Collectively, WPH containing LDIQK demonstrated neuroprotective effects against H2O2-induced neuronal cell damage, suggesting that WPH or its active peptide, LDIQK, may serve as a potential edible agent for improving cognitive dysfunction.

A SERS nanocellulose-paper-based analytical device for ultrasensitive detection of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD), one of the most prevalent neurodegenerative diseases, results in severe cognitive decline and irreversible memory loss. Early detection of AD is significant to patients for personalized intervention since effective cure and treatment methods for AD are still lacking. Despite the severity of the disease, existing highly sensitive AD detection methods, including neuroimaging and brain deposit-positive lesion tests, are not suitable for screening purposes due to their high cost and complicated operation. Therefore, these methods are unsuitable for early detection, especially in low-resource settings. Although regular paper-based microfluidics are cost-efficient for AD detection, they are restricted by a poor limit of detection (LOD).

RESULTS

To address the above limitations, we report the ultrasensitive and low-cost nanocellulose paper (nanopaper)-based analytical microfluidic devices (NanoPADs) for detecting one of the promising AD blood biomarkers (glial fibrillary acidic protein, GFAP) using Surface-enhanced Raman scattering (SERS) immunoassay. Nanopaper offers advantages as a SERS substrate, such as an ultrasmooth surface, high optical transparency, and tunable chemical properties. We detected the target GFAP in artificial serum, achieving a LOD of 150 fg mL-1.

SIGNIFICANCE

The developed NanoPADs are distinguished by their cost-efficiency and ease of implementation, presenting a promising avenue for effective early detection of AD's GFAP biomarker with ultrahigh sensitivity. More importantly, our work provides the experimental routes for SERS-based immunoassay of biomarkers on NanoPADs for various diseases in the future.

Synergistic effect of spermidine and ciprofloxacin against Alzheimer's disease in male rat via ferroptosis modulation

Alzheimer's disease (AD) is a prevalent form of neurodegenerative disease with a complex pathophysiology that remains not fully understood, and the exact mechanism of neurodegeneration is uncertain. Ferroptosis has been linked to the progression of degenerative diseases observed in AD models. The present study is designed to investigate the protective effects of spermidine, a potent antioxidant and iron chelator, and its synergistic interactions with ciprofloxacin, another iron chelator, in modulating ferroptosis and mitigating AD progression in rats. This study investigated AD-related biomarkers like neurotoxic amyloid beta (Aβ), arginase I, and serotonin. Spermidine demonstrated an anti-ferroptotic effect in the AD model, evident from the modulation of ferroptosis parameters such as hippocampus iron levels, reduced protein expression of transferrin receptor 1 (TFR1), and arachidonate 15-lipoxygenase (ALOX15). Additionally, the administration of spermidine led to a significant increase in protein expression of phosphorylated nuclear factor erythroid 2-related factor 2 (p-Nrf2) and upregulation of Cystine/glutamate transporter (SLC7A11) gene expression. Moreover, spermidine notably decreased p53 protein levels, acrolein, and gene expression of spermidine/spermine N1-acetyltransferase 1 (SAT1). Overall, our findings suggest that spermidine and/or ciprofloxacin may offer potential benefits against AD by modulating ferroptosis. Furthermore, spermidine enhanced the antioxidant efficacy of ciprofloxacin and reduced its toxic effects.

Artificial intelligence-based diagnosis of Alzheimer's disease with brain MRI images

Alzheimer's disease, a primary neurodegenerative condition, predominantly impacts the elderly and pre-elderly population. This progressive neurological disorder is characterized by an array of symptoms including memory loss, cognitive decline, and various physiological and psychological disturbances, significantly compromising the quality of life of patients and their caregivers. Recent advancements in Magnetic Resonance Imaging (MRI) technology have catalyzed research in AI-enhanced diagnostics for Alzheimer's disease, fostering optimism for early detection and timely interventions. This progress has paved the way for the development of sophisticated algorithms and models adept at analyzing complex brain imaging data, thereby augmenting diagnostic accuracy and efficiency. This advancement fuels optimism regarding the transformative potential of AI-driven diagnostics in revolutionizing Alzheimer's disease management, with the prospect of facilitating more effective treatment strategies and improved patient outcomes. The objective of this review is to provide a comprehensive overview of recent developments in deep learning methodologies applied to brain MRI images for the classification of various stages of Alzheimer's disease, with a particular emphasis on early diagnosis. Furthermore, this review underscores the limitations of current research, discussing potential challenges and future research directions in this dynamic field.

Evolution of Detecting Early Onset of Alzheimer's Disease: From Neuroimaging to Optical Immunoassays

Alzheimer's disease (AD) is a pathological disorder defined by the symptoms of memory loss and deterioration of cognitive abilities over time. Although the etiology is complex, it is mainly associated with the accumulation of toxic amyloid-β peptide (Aβ) aggregates and tau protein-induced neurofibrillary tangles (NFTs). Even now, creating non-invasive, sensitive, specific, and cost-effective diagnostic methods for AD remains challenging. Over the past few decades, polymers, and nanomaterials (e.g., nanodiamonds, nanogold, quantum dots) have become attractive and practical tools in nanomedicine for diagnosis and treatment. This review focuses on current developments in sensing methods such as enzyme-linked immunosorbent assay (ELISA) and surface-enhanced Raman scattering (SERS) to boost the sensitivity in detecting related biomarkers for AD. In addition, optical analysis platforms such as ELISA and SERS have found increasing popularity among researchers due to their excellent sensitivity and specificity, which may go as low as the femtomolar range. While ELISA offers easy technological usage and high throughput, SERS has the advantages of improved mobility, simple electrical equipment integration, and lower cost. Both portable optical sensing techniques are highly superior in terms of sensitivity, specificity, human application, and practicality, enabling the early identification of AD biomarkers.

Hsp70.1 carbonylation induces lysosomal cell death for lifestyle-related diseases

Alzheimer's disease, type 2 diabetes, and non-alcoholic steatohepatitis (NASH) constitute increasingly prevalent disorders. Individuals with type 2 diabetes are well-known to be susceptible to Alzheimer's disease. Although the pathogenesis of each disorder is multifactorial and the causal relation remains poorly understood, reactive oxygen species (ROS)-induced lipid and protein oxidation conceivably plays a common role. Lipid peroxidation product was recently reported to be a key factor also for non-alcoholic steatohepatitis, because of inducing hepatocyte degeneration/death. Here, we focus on implication of the representative lipid-peroxidation product 'hydroxynonenal' for the cell degeneration/death of brain, pancreas, and liver. Since Hsp70.1 has dual roles as a chaperone and lysosomal membrane stabilizer, hydroxynonenal-mediated oxidative injury (carbonylation) of Hsp70.1 was highlighted. After intake of high-fat diets, oxidation of free fatty acids in mitochondria generates ROS which enhance oxidation of ω-6 polyunsaturated fatty acids (PUFA) involved within biomembranes and generate hydroxynonenal. In addition, hydroxynonenal is generated during cooking deep-fried foods with vegetable oils especially containing linoleic acids. These intrinsic and exogenous hydroxynonenal synergically causes an increase in its serum and organ levels to induce Hsp70.1 oxidation. As it is amphiphilic; being water-soluble but displays strong lipophilic characteristics, hydroxynonenal can diffuse within the cells and react with targets like senile and/or atheromatous plaques outside the cells. Hydroxynonenal can deepen and expand lysosomal injuries by facilitating 'calpain-mediated cleavage of the carbonylated Hsp70.1'. Despite the unique anatomical, physiological, and biochemical characteristics of each organ for its specific disease, there should be a common cascade of the cell degeneration/death which is caused by hydroxynonenal. This review aims to implicate hydroxynonenal-mediated Hsp70.1 carbonylation for lysosomal membrane permeabilization/rupture and the resultant cathepsin leakage for inducing cell degeneration/death. Given the tremendous number of worldwide people suffering various lifestyle-related diseases, it is valuable to consider how ω-6 PUFA-rich vegetable oils is implicated for the organ disorder.

Functional Therapeutic Strategies Used in Different Stages of Alzheimer's Disease-A Systematic Review

As Alzheimer's disease develops, the central nervous system is gradually damaged. It is manifested by progressive dementia and the appearance of neurological and extrapyramidal symptoms that impair everyday functioning. The aim of the study was to evaluate the influence of physical exercise on cognitive and motor functions in various stages of Alzheimer's disease. Methods: Four databases (PubMed, Scopus, Ovid, and Cochrane Library) were searched for relevant papers published between 2012 and May 2022. The works were assessed in terms of the adopted inclusion criteria. The measures of the results were changed in the parameters assessing motor and cognitive functions. Methodological quality was assessed using the Cochrane Collaboration. This review was recorded with the Cochrane Library: CRD42022340496. The results of the database search showed 302 articles, 12 of which were included in the review. All studies have shown a significant positive effect on improving cognitive and motor functions. This systematic review revealed a beneficial effect in improving cognitive and motor functions after the application of various kinds of activities, especially in the early and mild stages of Alzheimer's disease.

Novel benzimidazole-based pseudo-irreversible butyrylcholinesterase inhibitors with neuroprotective activity in an Alzheimer's disease mouse model

As levels of acetylcholinesterase (AChE) decrease while levels of butyrylcholinesterase (BChE) increase in later stages of Alzheimer's disease (AD), BChE stands out as a promising target for treatment of AD. Therefore, several benzimidazole-carbamates were designed based on docking studies to inhibit BChE selectively over AChE, while retaining a reasonable solubility. Synthesized molecules exhibit IC50 values from 2.4 μM down to 3.7 nM with an overall highly hBChE-selective profile of the designed compound class. After evaluation of potential neurotoxicity, the most promising compound was further investigated in vivo. Compound 11d attenuates Aβ25-35-induced learning impairments in both spontaneous alternation and passive avoidance responses at a very low dosage of 0.03 mg kg-1, proving selective BChE inhibition to lead to effective neuroprotectivity in AD.

A Practical Multiclass Classification Network for the Diagnosis of Alzheimer’s Disease

Patients who have Alzheimer’s disease (AD) pass through several irreversible stages, which ultimately result in the patient’s death. It is crucial to understand and detect AD at an early stage to slow down its progression due to the non-curable nature of the disease. Diagnostic techniques are primarily based on magnetic resonance imaging (MRI) and expensive high-dimensional 3D imaging data. Classic methods can hardly discriminate among the almost similar pixels of the brain patterns of various age groups. The recent deep learning-based methods can contribute to the detection of the various stages of AD but require large-scale datasets and face several challenges while using the 3D volumes directly. The extant deep learning-based work is mainly focused on binary classification, but it is challenging to detect multiple stages with these methods. In this work, we propose a deep learning-based multiclass classification method to distinguish amongst various stages for the early diagnosis of Alzheimer’s. The proposed method significantly handles data shortage challenges by augmentation and manages to classify the 2D images obtained after the efficient pre-processing of the publicly available Alzheimer’s Disease Neuroimaging Initiative (ADNI) dataset. Our method achieves an accuracy of 98.9% with an F1 score of 96.3. Extensive experiments are performed, and overall results demonstrate that the proposed method outperforms the state-of-the-art methods in terms of overall performance.

Melatonin as an Anti-Aging Therapy for Age-Related Cardiovascular and Neurodegenerative Diseases

The concept of “aging” is defined as the set of gradual and progressive changes in an organism that leads to an increased risk of weakness, disease, and death. This process may occur at the cellular and organ level, as well as in the entire organism of any living being. During aging, there is a decrease in biological functions and in the ability to adapt to metabolic stress. General effects of aging include mitochondrial, cellular, and organic dysfunction, immune impairment or inflammaging, oxidative stress, cognitive and cardiovascular alterations, among others. Therefore, one of the main harmful consequences of aging is the development and progression of multiple diseases related to these processes, especially at the cardiovascular and central nervous system levels. Both cardiovascular and neurodegenerative pathologies are highly disabling and, in many cases, lethal. In this context, melatonin, an endogenous compound naturally synthesized not only by the pineal gland but also by many cell types, may have a key role in the modulation of multiple mechanisms associated with aging. Additionally, this indoleamine is also a therapeutic agent, which may be administered exogenously with a high degree of safety. For this reason, melatonin could become an attractive and low-cost alternative for slowing the processes of aging and its associated diseases, including cardiovascular and neurodegenerative disorders.

The Common Cellular Events in the Neurodegenerative Diseases and the Associated Role of Endoplasmic Reticulum Stress

Neurodegenerative diseases are inseparably linked with aging and increase as life expectancy extends. There are common dysfunctions in various cellular events shared among neurogenerative diseases, such as calcium dyshomeostasis, neuroinflammation, and age-associated decline in the autophagy-lysosome system. However, most of all, the prominent pathological feature of neurodegenerative diseases is the toxic buildup of misfolded protein aggregates and inclusion bodies accompanied by an impairment in proteostasis. Recent studies have suggested a close association between endoplasmic reticulum (ER) stress and neurodegenerative pathology in cellular and animal models as well as in human patients. The contribution of mutant or misfolded protein-triggered ER stress and its associated signaling events, such as unfolded protein response (UPR), to the pathophysiology of various neurodegenerative disorders, including Alzheimer's, Parkinson's, and Huntington's disease, amyotrophic lateral sclerosis, and prion disease, is described here. Impaired UPR action is commonly attributed to exacerbated ER stress, pathogenic protein aggregate accumulation, and deteriorating neurodegenerative pathologies. Thus, activating certain UPR components has been shown to alleviate ER stress and its associated neurodegeneration. However, uncontrolled activation of some UPR factors has also been demonstrated to worsen neurodegenerative phenotypes, suggesting that detailed molecular mechanisms around ER stress and its related neurodegenerations should be understood to develop effective therapeutics against aging-associated neurological syndromes. We also discuss current therapeutic endeavors, such as the development of small molecules that selectively target individual UPR components and address ER stress in general.

Beneficial Effects of a Combination of Curcuma longa L. and Citrus junos Against Beta-Amyloid Peptide-Induced Neurodegeneration in Mice

Both Curcuma longa (CL) and Citrus junos Tanaka (CJ) have been used to treat various diseases due to their anti-inflammatory and antioxidative stress activities. In this study, we investigated the ameliorative effect of the combination of CL extract and CJ extract (CCC) against beta-amyloid (Aβ) peptide-induced neurological damage. CCC prevented neurocytotoxicity in vitro. In addition, it was confirmed that abnormal alternation behavior and memory impairment caused by Aβ peptide were reversed by treatment with CCC. Furthermore, CCC treatment led to recovery of the cholinergic system and reactive oxygen species (ROS) oxidative damage defense system. CCC induced expressions of cyclic-adenosine monophosphate response element-binding protein (CREB)-responsive element-binding protein and brain-derived neurotrophic factor were confirmed as was the significantly improved processing in the hippocampus of the mouse Aβ peptides. Accordingly, these results suggest that CCC can prevent and/or reverse neurocytotoxicity and cognitive deficits in a mouse model of Alzheimer's disease.

Significance of Brain Glucose Hypometabolism, Altered Insulin Signal Transduction, and Insulin Resistance in Several Neurological Diseases

Several neurological diseases share pathological alterations, even though they differ in their etiology. Neuroinflammation, altered brain glucose metabolism, oxidative stress, mitochondrial dysfunction and amyloidosis are biological events found in those neurological disorders. Altered insulin-mediated signaling and brain glucose hypometabolism are characteristic signs observed in the brains of patients with certain neurological diseases, but also others such as type 2 diabetes mellitus and vascular diseases. Thus, significant reductions in insulin receptor autophosphorylation and Akt kinase activity, and increased GSK-3 activity and insulin resistance, have been reported in these neurological diseases as contributing to the decline in cognitive function. Supporting this relationship is the fact that nasal and hippocampal insulin administration has been found to improve cognitive function. Additionally, brain glucose hypometabolism precedes the unmistakable clinical manifestations of some of these diseases by years, which may become a useful early biomarker. Deficiencies in the major pathways of oxidative energy metabolism have been reported in patients with several of these neurological diseases, which supports the hypothesis of their metabolic background. This review remarks on the significance of insulin and brain glucose metabolism alterations as keystone common pathogenic substrates for certain neurological diseases, highlighting new potential targets.

Clinical application of serological Alzheimer's disease diagnosis using a highly sensitive biosensor with hydrogel-enhanced dielectrophoretic force

Analysis of a ratio between amyloid beta 1-40 and 1-42 (Aβ_1-40 and Aβ_1-42) presented in plasm enables a highly accurate diagnosis of Alzheimer's disease (AD). However, the analysis of plasma Aβs is not routinely conducted because of the lack of Aβ detection techniques sensitive enough to specifically detect Aβ from thousands of biomaterials present in the plasma. We developed a hydrogel-patterned spiral microelectrode sensor combined with a hopping dielectrophoretic (DEP) force, combining the negative DEP and positive DEP forces, for Aβ detection. The hydrogel effectively increased the number of immobilized fragmented antibodies in the reaction region of the sensor and enabled size-exclusive passive filtration of non-specific plasma proteins from that region. The hopping DEP force further concentrated the Aβs and removed the non-specific plasma proteins. Consequently, our sensor achieved a limit of detection (LOD) of approximately ∼ 0.15 pg/mL for both Aβ_1-40 and Aβ_1-42 in the standard plasma. Finally, comparing the ratio between Aβ_1-40 and Aβ_1-42 signals, we distinguished AD patients from cognitively normal subjects with 95.83% accuracy and 92.31% precision (n = 24, p < 0.0001, One-way ANOVA).

The role of amyloids in Alzheimer's and Parkinson's diseases

With varying clinical symptoms, most neurodegenerative diseases are associated with abnormal loss of neurons. They share the same common pathogenic mechanisms involving misfolding and aggregation, and these visible aggregates of proteins are deposited in the central nervous system. Amyloid formation is thought to arise from partial unfolding of misfolded proteins leading to the exposure of hydrophobic surfaces, which interact with other similar structures and give rise to form dimers, oligomers, protofibrils, and eventually mature fibril aggregates. Accumulating evidence indicates that amyloid oligomers, not amyloid fibrils, are the most toxic species that causes Alzheimer's disease (AD) and Parkinson's disease (PD). AD has recently been recognized as the 'twenty-first century plague', with an incident rate of 1% at 60 years of age, which then doubles every fifth year. Currently, 5.3 million people in the US are afflicted with this disease, and the number of cases is expected to rise to 13.5 million by 2050. PD, a disorder of the brain, is the second most common form of dementia, characterized by difficulty in walking and movement. Keeping the above views in mind, in this review we have focused on the roles of amyloid in neurodegenerative diseases including AD and PD, the involvement of amyloid in mitochondrial dysfunction leading to neurodegeneration, are also considered in the review.

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

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

Therapeutic Potential of Hispidin-Fungal and Plant Polyketide

There is a large number of bioactive polyketides well-known for their anticancer, antibiotic, cholesterol-lowering, and other therapeutic functions, and hispidin is among them. It is a highly abundant secondary plant and fungal metabolite, which is investigated in research devoted to cancer, metabolic syndrome, cardiovascular, neurodegenerative, and viral diseases. This review summarizes over 20 years of hispidin studies of its antioxidant, anti-inflammatory, anti-apoptotic, antiviral, and anti-cancer cell activity.

SERS-Based Immunoassay Enhanced with Silver Probe for Selective Separation and Detection of Alzheimer's Disease Biomarkers

Purpose

Developing a sensitive SERS-based method to quantitatively detect serum biomarkers (Aβ1-42 and P-Tau-181) for the early diagnosis of Alzheimer’s disease (AD).

Methods

In this study, a novel SERS-based sandwich immunoassay, which consists of tannin-capped silver nanoparticles and magnetic graphene oxide (Fe₃O₄@GOs), was developed. We firstly applied this method for the detection of protein standards in buffer solution, obtaining the regression equation. Then, its potential value on real serum samples of AD was further explored.

Results

The detection linear range of Aβ1-42 and P-Tau-181 protein standards were observed to range from 100 pg mL⁻¹ to 10 fg mL⁻¹, 100 pg mL⁻¹ to 1 fg mL⁻¹ respectively. We finally explored clinical application of the proposed method in 63 serum samples. As a result, P-tau-181 differentiated AD from non-AD dementia patients (AUC = 0.770), with a more favored ROC than Aβ1-42 (AUC = 0.383).

Conclusion

The developed SERS-based immunoassay is successfully applied to the determination of Aβ1-42 and P-Tau-181 in human serum specimens, which provides a promising tool for the early diagnosis of AD.

Curcumin as Scaffold for Drug Discovery against Neurodegenerative Diseases

Neurodegenerative diseases (NDs) are one of major public health problems and their impact is continuously growing. Curcumin has been proposed for the treatment of several of these pathologies, such as Alzheimer's disease (AD) and Parkinson's disease (PD) due to the ability of this molecule to reduce inflammation and aggregation of involved proteins. Nevertheless, the poor metabolic stability and bioavailability of curcumin reduce the possibilities of its practical use. For these reasons, many curcumin derivatives were synthetized in order to overcome some limitations. In this review will be highlighted recent results on modification of curcumin scaffold in the search of new effective therapeutic agents against NDs, with particular emphasis on AD.

Fluorescence switch of gold nanoclusters stabilized with bovine serum albumin for efficient and sensitive detection of cysteine and copper ion in mice with Alzheimer's disease

The near-infrared fluorescence of gold nanoclusters stabilized with bovine serum albumin (BSA -AuNCs) centered at 675 nm could be enhanced by cysteine and then effectively quenched by copper ion (Cu²⁺), therefore, cysteine and copper ion could be detected in sequence. At "on" state, fluorescence enhancement of BSA-AuNCs is generated due to the reaction between cysteine and BSA-AuNCs, via filling the surface defect of gold nanoclusters, while Cu²⁺ can further oxidize the reductive sulfydryl of cysteine and interact with amino acids presented in the BSA chain, inducing gold nanoclusters to aggregate, thus causing "off" state with fluorescence quenching. Fluorescence switch of BSA-AuNCs can be used for cysteine and Cu²⁺ detection in mice brain with Alzheimer's disease (AD) in vitro, with fast response, high chemical stability and sensitivity. Besides, it was able to image the endogenous Cu²⁺ in liver and heart of AD mice in situ. The results are promising, especially in the framework of early diagnosis of Alzheimer's disease.

Nonlinear and vibrational microscopy for label-free characterization of amyloid-β plaques in Alzheimer's disease model

Multimodal optical imaging was used for characterization of amyloid-β plaques in mouse brain tissues. We obtained high-resolution images for different biomarkers and investigated vibrational fingerprints that could be used for diagnostic purposes.

Polysaccharide of Taxus chinensis var. mairei Cheng et L.K.Fu attenuates neurotoxicity and cognitive dysfunction in mice with Alzheimer's disease

CONTEXT

Polysaccharide of Taxus chinensis var. mairei Cheng et L.K.Fu (Taxaceae) (PTM) functions in anti-apoptosis and antioxidation, but its function on Alzheimer's disease (AD) remains unclear.

OBJECTIVE

To investigate the effect of PTM on AD.

MATERIALS AND METHODS

C57BL/6J mice were randomly divided into three groups: control, d-galactose (d-gal), and d-gal + PTM. AD-like symptom was induced by d-gal for 6 weeks, followed with PTM (0.4 g/kg/d) for 14 days. PTM was added to BV2 cells stimulated with d-gal (1, 10, 20, 50, 100 and 500 μg/mL). Cell viability was evaluated by MTT assay. The expression of NRF2, SOD, cleaved caspase-3, Bax and Bcl-2 were detected with Western blot analysis. Cognitive function was evaluated by Morris water maze test.

RESULTS

Decreased cleaved caspase-3 (1.30 ± 0.09) and Bax/Bcl2 ratio (1.32 ± 0.11) were observed in BV2 cells induced by d-gal + PTM (50 μg/mL). Increased MDA and ROS and decreased SOD were observed in d-gal group. However, decreased MDA (175 ± 9 ng/mL) and ROS level (188 ± 38 ng/mL) were observed after treated with PTM group (p < 0.05). In addition, the expression of NRF2 decreased in d-gal group (0.75 ± 0.09) but increased after treated with PTM (p < 0.05). Furthermore, decreased Aβ1-42 was observed and the cognitive function was improved after PTM intervention (p < 0.05).

CONCLUSIONS

This is the first report that PTM inhibited oxidative stress and apoptosis in AD. The result will further accelerate the applications of Taxus chinensis var. mairei and the treatment for AD.

The New Frontiers in Neurodegenerative Diseases Treatment: Liposomal-Based Strategies

In the last decade, the onset of neurodegenerative (ND) diseases is strongly widespread due to the age increase of the world population. Despite the intensive investigations boosted by the scientific community, an efficacious therapy has not been outlined yet. The drugs commonly used are only able to relieve symptom severity; following their oral or intravenous administration routes, their effectiveness is strictly limited due to their low ability to reach the Central Nervous System (CNS) overcoming the Blood Brain Barrier (BBB). Starting from these assumptions, the engineered-nanocarriers, such as lipid-nanocarriers, are suitable agents to enhance the delivery of drugs into the CNS due to their high solubility, bioavailability, and stability. Liposomal delivery systems are considered to be the ideal carriers, not only for conventional drugs but also for neuroprotective small molecules and green-extracted compounds. In the current work, the LP-based drug delivery improvements in in vivo applications against ND disorders were carefully assessed.

Expedition into Taurine Biology: Structural Insights and Therapeutic Perspective of Taurine in Neurodegenerative Diseases

Neurodegenerative diseases (NDs) are characterized by the accumulation of misfolded proteins. The hallmarks of protein aggregation in NDs proceed with impairment in the mitochondrial function, besides causing an enhancement in endoplasmic reticulum (ER) stress, neuroinflammation and synaptic loss. As accumulation of misfolded proteins hampers normal neuronal functions, it triggers ER stress, which leads to the activation of downstream effectors formulating events along the signaling cascade—referred to as unfolded protein response (UPRER) —thereby controlling cellular gene expression. The absence of disease-modifying therapeutic targets in different NDs, and the exponential increase in the number of cases, makes it critical to explore new approaches to treating these devastating diseases. In one such approach, osmolytes (low molecular weight substances), such as taurine have been found to promote protein folding under stress conditions, thereby averting aggregation of the misfolded proteins. Maintaining the structural integrity of the protein, taurine-mediated resumption of protein folding prompts a shift in folding homeostasis more towards functionality than towards aggregation and degradation. Together, taurine enacts protection in NDs by causing misfolded proteins to refold, so as to regain their stability and functionality. The present study provides recent and useful insights into understanding the progression of NDs, besides summarizing the genetics of NDs in correlation with mitochondrial dysfunction, ER stress, neuroinflammation and synaptic loss. It also highlights the structural and functional aspects of taurine in imparting protection against the aggregation/misfolding of proteins, thereby shifting the focus more towards the development of effective therapeutic modules that could avert the development of NDs.

Development of novel N-(6-methanesulfonyl-benzothiazol-2-yl)-3-(4-substituted-piperazin-1-yl)-propionamides with cholinesterase inhibition, anti-β-amyloid aggregation, neuroprotection and cognition enhancing properties for the therapy of Alzheimer's disease

A novel series of benzothiazole–piperazine hybrids were rationally designed, synthesized, and evaluated as multifunctional ligands against Alzheimer's disease (AD). The synthesized hybrid molecules illustrated modest to strong inhibition of acetylcholinesterase (AChE) and Aβ_1-42 aggregation. Compound 12 emerged as the most potent hybrid molecule exhibiting balanced functions with effective, uncompetitive and selective inhibition against AChE (IC₅₀ = 2.31 μM), good copper chelation, Aβ_1-42 aggregation inhibition (53.30%) and disaggregation activities. Confocal laser scanning microscopy and TEM analysis also validate the Aβ fibril inhibition ability of this compound. Furthermore, this compound has also shown low toxicity and is capable of impeding loss of cell viability elicited by H₂O₂ neurotoxicity in SHSY-5Y cells. Notably, compound 12 significantly improved cognition and spatial memory against scopolamine-induced memory deficit in a mouse model. Hence, our results corroborate the multifunctional nature of novel hybrid molecule 12 against AD and it may be a suitable lead for further development as an effective therapeutic agent for therapy in the future.

A novel series of benzothiazole–piperazine hybrids were rationally designed, synthesized, and evaluated as multifunctional ligands against Alzheimer's disease (AD).

Corrupted ER-mitochondrial calcium homeostasis promotes the collapse of proteostasis

Aging and age-related diseases are associated with a decline of protein homeostasis (proteostasis), but the mechanisms underlying this decline are not clear. In particular, decreased proteostasis is a widespread molecular feature of neurodegenerative diseases, such as Alzheimer's disease (AD). Familial AD is largely caused by mutations in the presenilin encoding genes; however, their role in AD is not understood. In this study, we investigate the role of presenilins in proteostasis using the model system Caenorhabditis elegans. Previously, we found that mutations in C. elegans presenilin cause elevated ER to mitochondria calcium signaling, which leads to an increase in mitochondrial generated oxidative stress. This, in turn, promotes neurodegeneration. To understand the cellular mechanisms driving neurodegeneration, using several molecular readouts of protein stability in C. elegans, we find that presenilin mutants have widespread defects in proteostasis. Markedly, we demonstrate that these defects are independent of the protease activity of presenilin and that reduction in ER to mitochondrial calcium signaling can significantly prevent the proteostasis defects observed in presenilin mutants. Furthermore, we show that supplementing presenilin mutants with antioxidants suppresses the proteostasis defects. Our findings indicate that defective ER to mitochondria calcium signaling promotes proteostatic collapse in presenilin mutants by increasing oxidative stress.

Gas-phase conformations of intrinsically disordered proteins and their complexes with ligands: Kinetically trapped states during transfer from solution to the gas phase

Flexible structures of intrinsically disordered proteins (IDPs) are crucial for versatile functions in living organisms, which involve interaction with diverse partners. Electrospray ionization ion mobility mass spectrometry (ESI-IM-MS) has been widely applied for structural characterization of apo-state and ligand-associated IDPs via two-dimensional separation in the gas phase. Gas-phase IDP structures have been regarded as kinetically trapped states originated from conformational features in solution. However, an implication of the states remains elusive in the structural characterization of IDPs, because it is unclear what structural property of IDPs is preserved. Recent studies have indicated that the conformational features of IDPs in solution are not fully reproduced in the gas phase. Nevertheless, the molecular interactions captured in the gas phase amplify the structural differences between IDP conformers. Therefore, an IDP conformational change that is not observed in solution is observable in the gas-phase structures obtained by ESI-IM-MS. Herein, we have presented up-to-date researches on the key implications of kinetically trapped states in the gas phase with a brief summary of the structural dynamics of IDPs in ESI-IM-MS.

Increased Anti-Inflammatory Effects on LPS-Induced Microglia Cells by Spirulina maxima Extract from Ultrasonic Process

The Spirulina maxima exact from a non-thermal ultrasonic process (UE) contains 17.5 mg/g of total chlorophyll, compared to 6.24 mg/g of chlorophyll derived from the conventional 70% ethanol extraction at 80 °C for 12 h (EE). The UE also showed relatively low cytotoxicity against murine microglial cells (BV-2) and inhibited the production of the inflammatory mediators, NO and PGE2. The UE also effectively suppresses both mRNA expression and the production of pro-inflammatory cytokines, such as TNF-α, IL-6 and IL-1β, in a concentration-dependent manner. Notably, TNF-α gene and protein production were most strongly down-regulated, while IL-6 was the least affected by all ranges of treatment concentrations. This work first demonstrated a quantitative correlation between mRNA expression and the production of cytokines, showing that suppression of TNF-α gene expression was most significantly correlated with its secretion. These results clearly proved that the anti-inflammatory effects of Spirulina extract from a nonthermal ultrasonic process, which yielded high concentrations of intact forms of chlorophylls, were increased two-fold compared to those of conventional extracts processed at high temperature.

Production and enhancement of the acetylcholinesterase inhibitor, huperzine A, from an endophytic Alternaria brassicae AGF041

Huperzine A (HupA) is a potent acetylcholinesterase (AChE) inhibitor of a great consideration as a prospective drug candidate for Alzheimer's disease treatment. Production of HupA by endophytes offers an alternative challenge to reduce the massive plant harvest needed to meet the increasing demand of HupA. In the current study, some endophytic fungal and actinobacterial isolates from the Chinese herb, Huperzia serrata, underwent liquid fermentation, alkaloid extraction, and screening for AChE inhibition and HupA production. Among these isolates, Alternaria brassicae AGF041 strain was the only positive strain for HupA production with the maximum AChE inhibition of 75.5%. Chromatographic analyses verified the identity of the produced HupA. The HupA production was efficiently maximized up to 42.89 μg/g of dry mycelia, after optimization of thirteen process parameters using multifactorial statistical approaches, Plackett-Burman and central composite designs. The statistical optimization resulted in a 40.8% increase in HupA production. This is the first report to isolate endophytic actinobacteria with anti-AChE activity from H. serrata, and to identify an endophytic fungus A. brassicae as a new promising start strain for a higher HupA yield.

Ameliorative Effects of Dendropanax morbifera on Cognitive Impairment Via Enhancing Cholinergic Functions and Brain-Derived Neurotrophic Factor Expression in β-Amyloid-Induced Mice

Alzheimer's disease accounts for the majority of dementia and shows hallmarks such as sequential cognitive dysfunction and abnormal behavior. Dendropanax morbifera (DM) has traditionally been used to treat a variety of diseases in East Asia. The aim of this study was to assess the therapeutic effects of DM on brain neuron damage and on cognitive deficit in neuronal cell induced by Aβ_1-42 in mice. Treatment with DM reduced the levels of intracellular reactive oxygen species and protected against the death of neuronal cells induced by Aβ_1-42 peptide. In addition, it was also found that pretreatment with DM decreased cognitive damage induced by Aβ peptide via enhancing the cholinergic system and antioxidant defense system in mice. Furthermore, the study verified that the change in the expression of both cyclic-adenosine monophosphate response element binding protein and of brain-derived neurotrophic factor in the hippocampus in Aβ peptide-treated mice was significantly ameliorated after treatment with DM. Accordingly, these results suggest that pretreatment with DM defends against oxidative stress and cognitive impairment caused by Aβ peptide.

The sociodemographic characteristics and dietary and blood plasma fatty acid profiles of elderly Saudi women with Alzheimer disease

Background

Alzheimer’s disease (AD) is a progressive neurodegenerative disease, and due to various physiological and psychological factors the patients are at risk of nutritional insufficiencies. The purpose of this study was to assess the dietary fatty acid intake and its effect on plasma fatty acids in elderly Saudi women and to compare the differences in their food and plasma fatty acid profile on the basis of their residence.

Methods

A total of 76 elderly women (50–100 years) were recruited through a random sampling method. A structured proforma was designed to gather information related to their age, income, dietary habits, and presence of any disease and awareness of AD. A 24-h dietary recall method for 3 days and food frequency questionnaire, concentrating on fish consumption and consumption of foods rich in ω-3 fatty acids, which was planned by dietitians, was used for dietary assessment. The gathered data were then analyzed using food processor software. The blood samples were collected to determine plasma fatty acids.

Results

The mean age of women diagnosed with AD was more than 75 years, and the prevalence of illiteracy was higher among AD subjects. As compared to the AD group, the concentration of LA and total ω-6 was significantly (p ≤ 0.05) higher in the control group from both recruitment sites [National Guard Health Affairs, King Abdulaziz Medical City, Riyadh (NGH) and Social Welfare Homes for the Elderly (SWH)]. Similarly, the concentrations of EPA, DHA, and ω-3 were also slightly higher in the control group at both sites, but the difference between the control and AD subjects was only significant (p ≤ 0.05) in subjects from NGH. We found no significant difference in the ω-6/ ω-3 ratio between groups. Also, no significant difference was found in the mean level of the plasma fatty acid when comparing the control and AD groups. The concentration of DHA in controls only and AA, EPA and ω-6 in both control and AD were significant (although weakly) correlated with their respective dietary intakes. No correlations were found between the intake of 18 C precursors (LA and ALA) and plasma levels of their long chain derivatives (AA, EPA, and DHA). Education, income, overall health status and the concentration of various fatty acids from food was higher and better in subjects from SWH than NGH. The lower plasma level indicates lower impaired systemic availability of several nutrients.

Conclusion

We found that dietary intervention might play a role in the prevention of AD.

Enhancement of the Neuroprotective Effect of Fermented Spirulina maxima Associated with Antioxidant Activities by Ultrasonic Extraction

This study is the first demonstration of the neuroprotective activity of the marine alga, Spirulina maxima, fermented by Lactobacillus plantarum HY-08, which was freshly isolated from fermented vegetables. The combined process of the fermentation with ultrasonic extraction at 40 kHz for 4 hr greatly increased the amounts of β-carotene in the extract up to 1.62 mg/g, along with a high extraction yield of 18.26%, compared to 1.03 mg/g and 12.8% from ultrasonic extraction itself, and even much higher than 0.81 mg/g and 10.6% from conventional water extraction. It was also proved that the neuroprotective activities of the extract were enhanced possibly by higher contents of β-carotene in the extract, compared to those from water extraction or ultrasonic extraction itself. This extract was found to have strong antioxidant properties, with 49.01% 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, which resulted in 90.30% neuroprotective activity. Specifically, the fermented extract markedly enhanced the brain-derived neurotrophic factor (BDNF)/p-CREB signaling pathways, which can effectively prevent memory impairment in mice caused by oxidative stress. β-Carotene also increased the expression of p-CREB and BDNF, and a mechanism of their upregulation by β-carotene is first proposed in this study. It can be concluded that the strong neuroprotective effect of the extract was markedly influenced by the antioxidant activities, due to the synergistic effects of high amounts of β-carotene and other biologically active substances in the extract that can be obtained by lactic acid fermentation, combined with ultrasonic processing.

Effect of Fermented Spirulina maxima Extract on Cognitive-Enhancing Activities in Mice with Scopolamine-Induced Dementia

This work provides the first demonstration that Spirulina maxima extract fermented with the lactic acid bacterium Lactobacillus planetarium HY-08 has the ability to ameliorate scopolamine-induced memory impairment in mice. The fermented extract exhibited good cognitive-enhancing activities, as demonstrated through Morris water maze and passive avoidance experiments: in these tests, the mice administered the fermented extract at a dose of 400 mg/kg exhibited an escape latency time and a latency time of 88.5 and 76.0 sec, respectively, whereas those administered donepezil, which was used as a positive control, showed an escape latency time and a latency time of 81.3 and 83.3 sec, respectively. However, an extract of 200 mg/kg was considered economically feasible for maintaining relatively high memory-improving activities because only a slight difference in activities was found between 200 and 400 mg/kg. The study also provides the first demonstration that β-carotene, one of the major bioactive substances in S. maxima, has memory-enhancing activity. A detailed analysis of the mechanism for the cognitive-enhancing activities of the fermented extract revealed that the fermented extract effectively increased the phosphorylation of both extracellular signal-regulated kinases (p-ERK) and p-cAMP response element-binding protein (p-CREB) and sequentially upregulated the expression of brain-derived neurotrophic factor (BDNF), whose signaling pathway responds to a reduction in oxidative stress in the brain. The results indicate that the improved efficacy of the fermented extract was likely due to the synergistic effects of β-carotene and other bioactive substances. Therefore, it can be concluded that the fermented extract exerts memory-improving effects in the hippocampus of scopolamine-treated mice through an initial increase in ERK signaling and a sequential induction of the expression of p-CREB and BDNF, and these effects are related to the antioxidant activities of β-carotene and other components.

Does Obesity Increase the Risk of Dementia: A Literature Review

Obesity and dementia are both associated with an increased risk of Alzheimer's disease (AD), and underlying neurodegenerative changes. Review articles provide evidential support that obesity and dementia result in an early old-age memory crisis. Obesity triggering vascular dementia decreases not only blood supply to the brain, but also increases fat cells that damage the brain white matter leading to loss of cognitive and intellectual behaviour. Adipocyte-secreted proteins and inflammatory cytokines explain the association between obesity and increased risk of dementia. Late-life elevated body mass index (BMI) confers a lower risk of having dementia. The hormone leptin explained the mechanism for the reverse association. Future studies need to reveal the linkage between adiposity and excess risk of dementia and AD.

The Biased G-Protein-Coupled Receptor Agonism Bridges the Gap between the Insulin Receptor and the Metabolic Syndrome

Insulin signaling, as mediated through the insulin receptor (IR), plays a critical role in metabolism. Aberrations in this signaling cascade lead to several pathologies, the majority of which are classified under the umbrella term "metabolic syndrome". Although many of these pathologies are associated with insulin resistance, the exact mechanisms are not well understood. One area of current interest is the possibility of G-protein-coupled receptors (GPCRs) influencing or regulating IR signaling. This concept is particularly significant, because GPCRs have been shown to participate in cross-talk with the IR. More importantly, GPCR signaling has also been shown to preferentially regulate specific downstream signaling targets through GPCR agonist bias. A novel study recently demonstrated that this GPCR-biased agonism influences the activity of the IR without the presence of insulin. Although GPCR-IR cross-talk has previously been established, the notion that GPCRs can regulate the activation of the IR is particularly significant in relation to metabolic syndrome and other pathologies that develop as a result of alterations in IR signaling. As such, we aim to provide an overview of the physiological and pathophysiological roles of the IR within metabolic syndrome and its related pathologies, including cardiovascular health, gut microflora composition, gastrointestinal tract functioning, polycystic ovarian syndrome, pancreatic cancer, and neurodegenerative disorders. Furthermore, we propose that the GPCR-biased agonism may perhaps mediate some of the downstream signaling effects that further exacerbate these diseases for which the mechanisms are currently not well understood.

Dissecting Endoplasmic Reticulum Unfolded Protein Response (UPRER) in Managing Clandestine Modus Operandi of Alzheimer's Disease

Alzheimer's disease (AD), a neurodegenerative disorder, is most common cause of dementia witnessed among aged people. The pathophysiology of AD develops as a consequence of neurofibrillary tangle formation which consists of hyperphosphorylated microtubule associated tau protein and senile plaques of amyloid-β (Aβ) peptide in specific brain regions that result in synaptic loss and neuronal death. The feeble buffering capacity of endoplasmic reticulum (ER) proteostasis in AD is evident through alteration in unfolded protein response (UPR), where UPR markers express invariably in AD patient's brain samples. Aging weakens UPR^ER causing neuropathology and memory loss in AD. This review highlights molecular signatures of UPR^ER and its key molecular alliance that are affected in aging leading to the development of intriguing neuropathologies in AD. We present a summary of recent studies reporting usage of small molecules as inhibitors or activators of UPR^ER sensors/effectors in AD that showcase avenues for therapeutic interventions.

Neuroprotective Effect and Molecular Mechanism of [6]-Gingerol against Scopolamine-Induced Amnesia in C57BL/6 Mice

We have investigated the neuroprotective and memory enhancing effect of [6]-gingerol (GIN), a pungent ingredient of ginger, using an animal model of amnesia. To determine the neuroprotective effect of GIN on cognitive dysfunction, scopolamine (SCO, 1 mg/kg, i.p.) was injected into C57BL/6 mice, and a series of behavioral tests were conducted. SCO-induced behavior changes and memory impairments, such as decreased alteration (%) in Y-maze test, increased mean escape latency in water maze test, diminished step-through latency in passive avoidance test, and shortened freezing time in fear condition test, were significantly prevented and restored by the oral administration of GIN (10 or 25 mg/kg/day). To further verify the neuroprotective mechanism of GIN, we have focused on the brain-derived neurotrophic factor (BDNF). The administration of GIN elevated the protein expression of BDNF, which was mediated via the activation of protein kinase B/Akt- and cAMP-response element binding protein (CREB) signaling pathway. These results suggest that GIN may have preventive and/or therapeutic potentials in the management of memory deficit and cognitive impairment in mice with amnesia.

Similarity search combined with docking and molecular dynamics for novel hAChE inhibitor scaffolds

The main purpose of this study was to address the performance of virtual screening methods based on ligands and the protein structure of acetylcholinesterase (AChE) in order to retrieve novel human AChE (hAChE) inhibitors. In addition, a protocol was developed to identify novel hit compounds and propose new promising AChE inhibitors from the ZINC database with 10 million commercially available compounds. In this sense, 3D similarity searches using rapid overlay of chemical structures and similarity analysis through comparison of electrostatic overlay of docked hits were used to retrieve AChE inhibitors from collected databases. Molecular dynamics simulation of 100 ns was carried out to study the best docked compounds from similarity searches. Some key residues were identified as crucial for the dual binding mode of inhibitor with the interaction site. All results indicated the relevant use of EON and docking strategy for identifying novel hit compounds as promising potential anticholinesterase candidates, and seven new structures were selected as potential hAChE inhibitors. Graphical abstract Compound N01 in the 4M0E hAChE crystallography structure from docking results. Yellow dashed lines Hydrogen bonds, blue dashed lines π-stacking interactions, green dashed lines cation-π interactions.

Investigating the preventive effects of baicalin and gallocatechin against glyoxal-induced cystatin aggregation

Several mammalian proteins form pathological deposits under nonphysiological conditions that are associated with many degenerative diseases. Protein aggregation is associated with aging, as well as a variety of diseases, including cystic fibrosis, amyotrophic lateral sclerosis (ALS), and hypertrophic cardiomyopathy. There is a lack of any potential anti-amyloidogenic agents and therapeutics till date. Polyphenols have been accredited with myriad biological effects. An analysis of the effects of natural agents like baicalin (BC) and gallocatechin (GC) on aggregation process can open new avenues for the treatment of protein misfolding diseases. Thus, investigation of the effects of these flavonoids on Buffalo Heart Cystatin (BHC) aggregation induced by a reactive metabolic dialdehyde, glyoxal (GO), was taken up. Results have shown that elevated concentration of GO forms aggregates of BHC, which was characterized by an increase in the ANS fluorescence intensity, an increase in ThT fluorescence intensity, red shift in Congo red absorbance, negative ellipticity peak at 217 nm in the far-UVCD and BHC aggregates displaying by TEM. Using fluorescence spectroscopic analysis with Thioflavin T, CD and electron microscopic studies, anti-aggregation effects of polyphenols, BC and GC were analyzed. The study showed that BC and GC produced concentration-dependent anti-aggregation effects with GC producing a more pronounced effect than BC. The study proposed a mechanistic approach assuming structural constraints and specific aromatic interactions of polyphenols with sheets of BHC aggregates.

Tumor necrosis factor α Inhibition for Alzheimer's Disease

Tumor necrosis factor α (TNF-α) plays a central role in the pathophysiology of Alzheimer's disease (AD). Food and Drug Administration-approved biologic TNF-α inhibitors are thus a potential treatment for AD, but they do not cross the blood-brain barrier. In this short review, we discuss the involvement of TNF-α in AD, challenges associated with the development of existing biologic TNF-α inhibitors for AD, and potential therapeutic strategies for targeting TNF-α for AD therapy.

Alzheimer's disease: Is this a brain specific diabetic condition?

Alzheimer's disease (AD) and type 2 diabetes (T2DM) are the two major health issues affecting millions of elderly people worldwide, with major impacts in the patient's daily life. Numerous studies have demonstrated that patients with diabetes have an increased risk of developing AD compared with healthy individuals. The principal biological mechanisms that associate with the progression of diabetes and AD are not completely understood. Impaired insulin signaling, uncontrolled glucose metabolism, oxidative stress, abnormal protein processing, and the stimulation of inflammatory pathways are common features to both AD and T2DM. In recent years brain specific abnormalities in insulin and insulin like growth factor (IGF) signaling considered as a major trigger involved in the etiopathogenesis of AD, showing T2DM like milieu. This review summarizes the pathways that might link diabetes and AD and the effect of diminished insulin.

Paeoniflorin attenuates Aβ1-42-induced inflammation and chemotaxis of microglia in vitro and inhibits NF-κB- and VEGF/Flt-1 signaling pathways

Alzheimer׳s disease (AD) is a neurodegenerative disease with elusive pathogenesis, which accounts for most cases of dementia in the aged population. It has been reported that persistent inflammatory responses and excessive chemotaxis of microglia stimulated by beta-amyloid (Aβ) oligomers in the brain may accelerate the progression of AD. The present study was conducted to explore whether paeoniflorin (PF), a water-soluble monoterpene glycoside isolated from the root of Paeonia lactiflora Pallas, could attenuate Aβ1-42-induced toxic effects on primary and BV-2 microglial cells in vitro. Our data showed that PF pretreatment inhibited Aβ1-42-induced production of tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6 in rodent microglia. Also, the nuclear translocation of nuclear factor kappa B (NF-κB) subunit p65 and the phosphorylation of NF-κB inhibitor alpha (IκBα) in Aβ1-42-stimulated microglial cells were suppressed by PF administration. Moreover, PF treatment reduced the release of chemokine (C-X-C motif) ligand 1 (CXCL1) and chemokine (C-C motif) ligand 2 (CCL-2) from Aβ1-42-stimulated microglia. Additionally, application of PF inhibited the increases in vascular endothelial growth factor (VEGF) and VEGF receptor 1 (Flt-1) triggered by Aβ1-42, and resulted in a concomitant reduction in microglial chemotaxis. Restoration of VEGF was noted to counteract the inhibitory effect of PF, suggesting that PF mitigated Aβ1-42-elicited microglial migration at least partly by suppressing the VEGF/Flt-1 axis. In summary, in presence of Aβ1-42, PF pretreatment inhibited the excessive microglial activation and chemotaxis.

How do membranes initiate Alzheimer's Disease? Formation of toxic amyloid fibrils by the amyloid β-protein on ganglioside clusters

Alzheimer's disease (AD), a severe neurodegenerative disorder, causes more than half of dementia cases. According to the popular "Aβ hypothesis" to explain the mechanism of this disease, amyloid β-peptides (Aβ) of 39-43 amino acid residues aggregate and deposit onto neurons, igniting the neurotoxic cascade of the disease. Therefore, researchers studying AD would like to elucidate the mechanisms by which essentially water-soluble but hydrophobic Aβ aggregates under pathological conditions. Most researchers have investigated the aggregation of Aβ in aqueous solution, and they concluded that the final aggregation product, the amyloid fibrils, were less toxic than the component peptide oligomers. They consequently shifted their interests to more toxic "soluble oligomers", structures that form as intermediates or off-pathway products during the aggregation process. Some researchers have also investigated artificial oligomers prepared under nonphysiological conditions. In contrast to these "in solution" studies, we have focused on "membrane-mediated" amyloidogenesis. In an earlier study, other researchers identified a specific form of Aβ that was bound to monosialoganglioside GM1, a sugar lipid, in brains of patients who exhibited the early pathological changes associated with AD. This Account summarizes 15 years of our research on this topic. We have found that Aβ specifically binds to GM1 that occurs in clusters, but not when it is uniformly distributed. Clustering is facilitated by cholesterol. Upon binding, Aβ changes its conformation from a random coil to an α-helix-rich structure. A CH-π interaction between the aromatic side chains of Aβ and carbohydrate moieties appended to GM1 appears to be important for binding. In addition, as Aβ accumulates and reaches its first threshold concentration (Aβ/GM1 = ∼0.013), aggregated β-sheets of ∼15 molecules appear and coexist with the helical form. However, this β-structure is stable and does not form larger aggregates. When the disease progresses further and the Aβ/GM1 ratio exceeds ∼0.044, the β-structure converts to a second β-structure that can seed aggregates. The seed recruits monomers from the aqueous phase to form toxic amyloid fibrils that have larger surface hydrophobicity and can contain antiparallel β-sheets. In contrast, amyloid fibrils formed in aqueous solution are less toxic and have parallel β-sheets. The less polar environments of GM1 clusters play an important role in the formation of these toxic fibrils. Membranes that contain GM1 clusters not only accelerate the aggregation of Aβ by locally concentrating Aβ molecules but also generate amyloid fibrils with unique structures and significant cytotoxicity. The inhibition of this aggregation cascade could be a promising strategy for the development of AD-modulating therapies.

Insulin in the brain: its pathophysiological implications for States related with central insulin resistance, type 2 diabetes and Alzheimer's disease

Although the brain has been considered an insulin-insensitive organ, recent reports on the location of insulin and its receptors in the brain have introduced new ways of considering this hormone responsible for several functions. The origin of insulin in the brain has been explained from peripheral or central sources, or both. Regardless of whether insulin is of peripheral origin or produced in the brain, this hormone may act through its own receptors present in the brain. The molecular events through which insulin functions in the brain are the same as those operating in the periphery. However, certain insulin actions are different in the central nervous system, such as hormone-induced glucose uptake due to a low insulin-sensitive GLUT-4 activity, and because of the predominant presence of GLUT-1 and GLUT-3. In addition, insulin in the brain contributes to the control of nutrient homeostasis, reproduction, cognition, and memory, as well as to neurotrophic, neuromodulatory, and neuroprotective effects. Alterations of these functional activities may contribute to the manifestation of several clinical entities, such as central insulin resistance, type 2 diabetes mellitus (T2DM), and Alzheimer's disease (AD). A close association between T2DM and AD has been reported, to the extent that AD is twice more frequent in diabetic patients, and some authors have proposed the name "type 3 diabetes" for this association. There are links between AD and T2DM through mitochondrial alterations and oxidative stress, altered energy and glucose metabolism, cholesterol modifications, dysfunctional protein O-GlcNAcylation, formation of amyloid plaques, altered Aβ metabolism, and tau hyperphosphorylation. Advances in the knowledge of preclinical AD and T2DM may be a major stimulus for the development of treatment for preventing the pathogenic events of these disorders, mainly those focused on reducing brain insulin resistance, which is seems to be a common ground for both pathological entities.

In vitro hyperglycemic condition facilitated the aggregation of lysozyme via the passage through a molten globule state

Hyperglycemic condition i.e. an increase in blood glucose concentration has been linked to bring about structural alterations in the native state of proteins. Glucose concentrations of 50 and 100 mM in vitro, which correspond to hyperglycemic condition, were tested to investigate their effect on lysozyme native structure. Incubating enzyme with 50 and 100 mM glucose for a period of 7 days, an intermediate state on day 4 and 3 was observed, respectively. The presence of intermediate state was characterized by a 22 % increase in the intrinsic fluorescence intensity with a red shift of 20 nm compared to the native state, a 5 % increase in ANS-fluorescence intensity relative to the native due to the surfacing of hydrophobic clusters and a sharp decrease in near-UV CD signal at around 284 and 291 nm. The state retains substantial native-like secondary structure. This partially unfolded intermediate state can be referred as 'molten globule', which finally tends to aggregate on day 6 and 4 with 50 and 100 mM glucose concentration, respectively, as a result of cross-linking between lysozyme molecules. The aggregates were confirmed by the presence of β-sheet structure as depicted by far-UV CD, an increase in ThT fluorescence as well as the fibrillar morphology shown by SEM. Moreover, advanced glycation end products were also accompanied as the emission peak was observed at 460 and 470 nm corresponding to the formation of pentosidine and malonaldehyde, respectively.