The Early Events That Initiate β-Amyloid Aggregation in Alzheimer's Disease

Resistance Exercise Decreases Amyloid Load and Modulates Inflammatory Responses in the APP/PS1 Mouse Model for Alzheimer's Disease

Neuroinflammation has been shown to play a crucial role in the development of Alzheimer's disease (AD) and also has an association with amyloid-β (Aβ) plaques, a hallmark of this disease. Physical exercise has emerged as an alternative treatment for pathological impairment in AD. In light of this evidence, together with the fact that the hippocampus is one of the first structures to be affected in AD, we analyzed hippocampal changes in Aβ load, inflammatory responses, and locomotor activity in transgenic APP/PS1 mouse model for AD submitted to a resistance exercise (RE) program. One month after the start of the RE program, the locomotor hyperactivity related to AD behavior was reduced and microglia recruitment was increased, which in turn may have contributed to the decrease in the volume of Aβ plaques. In addition, the RE program restored the levels of IL-1α, IL-4, and IL-6 cytokines to control levels. Our study indicates that RE has beneficial effects on the locomotor behavior, amyloid burden, and inflammation of AD pathology and can therefore be used as a therapy to improve the clinical symptoms and neurophysiological alterations in AD. To the best of our knowledge, this is the first study to use a resistance exercise program in transgenic AD model.

Implication of post-translationally modified SOD1 in pathological aging

Why certain people relish healthy aging throughout their life span while others suffer pathological consequences? In this review, we focus on some of the dominant paradigms of pathological aging, such as amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), and Parkinson's disease (PD), and predict that the antioxidant superoxide dismutase 1 (SOD1), when post-translationally modified by aging-associated oxidative stress, acts as a mechanism to accelerated aging in these age-related neurodegenerative diseases. Oxidative modifications of natively reduced SOD1 induce pathological confirmations such as misfolding, leading to a subsequent formation of monomeric, oligomeric, and multimeric aggregates. Misfolded SOD1 propagates like prions from cell to cell. These modified conformations are detected in brain tissues in ALS, AD, and PD, and are considered a contributing factor to their initial pathogenesis. We have also elaborated on oxidative stress-induced non-native modifications of SOD1 and offered a logistic argument on their global implication in accelerated or pathological aging in the context of ALS, AD, and PD.

History in perspective: How Alzheimer's Disease came to be where it is?

Treatment of Alzheimer's Disease (AD) remains an unsolved issue despite the pronounced global attention it has received from researchers over the last four decades. Determining the primary cause of the disease is challenging due to its long prodromal phase and multifactorial etiology. Regardless, academic disagreements amongst the scientific community have helped in making significant advancements in underpinning the molecular basis of disease pathogenesis. Substantial development in fluid and imaging biomarkers for AD led to a sharp turn in defining the disease as a molecular construct, dispensing its clinical definition. With conceptual progress, revisions in the diagnostic criteria of AD were made, culminating into the research framework proposed by National Institute on Aging and Alzheimer's Association in 2018 which unified different stages of the disease continuum, giving a common language of AT(N)¹ classification to researchers. With realization that dementia is the final stage of AD spectrum, its early diagnosis by means of cerebrospinal fluid biomarkers, Positron Emission Tomography and Magnetic Resonance Imaging of the brain holds crucial importance in discovering ways of halting the disease progression. This article maps the insights into the pathogenesis as well as the diagnostic criteria and tests for AD as these have evolved over time. A contextualized timeline of how the understanding of AD has matured with advancing knowledge allows future research to be directed and unexplored avenues to be prioritized.

Potential of Naturally Derived Alkaloids as Multi-Targeted Therapeutic Agents for Neurodegenerative Diseases

Alkaloids are a class of secondary metabolites that can be derived from plants, fungi and marine sponges. They are widely known as a continuous source of medicine for the management of chronic disease including cancer, diabetes and neurodegenerative diseases. For example, galanthamine and huperzine A are alkaloid derivatives currently being used for the symptomatic management of neurodegenerative disease. The etiology of neurodegenerative diseases is polygenic and multifactorial including but not limited to inflammation, oxidative stress and protein aggregation. Therefore, natural-product-based alkaloids with polypharmacology modulation properties are potentially useful for further drug development or, to a lesser extent, as nutraceuticals to manage neurodegeneration. This review aims to discuss and summarise recent developments in relation to naturally derived alkaloids for neurodegenerative diseases.

Animal Models of Metabolic Disorders in the Study of Neurodegenerative Diseases: An Overview

The incidence of metabolic disorders, as well as of neurodegenerative diseases—mainly the sporadic forms of Alzheimer’s and Parkinson’s disease—are increasing worldwide. Notably, obesity, diabetes, and hypercholesterolemia have been indicated as early risk factors for sporadic forms of Alzheimer’s and Parkinson’s disease. These conditions share a range of molecular and cellular features, including protein aggregation, oxidative stress, neuroinflammation, and blood-brain barrier dysfunction, all of which contribute to neuronal death and cognitive impairment. Rodent models of obesity, diabetes, and hypercholesterolemia exhibit all the hallmarks of these degenerative diseases, and represent an interesting approach to the study of the phenotypic features and pathogenic mechanisms of neurodegenerative disorders. We review the main pathological aspects of Alzheimer’s and Parkinson’s disease as summarized in rodent models of obesity, diabetes, and hypercholesterolemia.

Phloridzin attenuates lipopolysaccharide-induced cognitive impairment via antioxidant, anti-inflammatory and neuromodulatory activities

BACKGROUND

Lipopolysaccharide (LPS) is known to produce neuroinflammation and memory impairment. Although phloridzin (a phenolic phytoconstituent) shows antioxidant- and anti-inflammatory activities, its ameliorative potential in LPS-mediated neuroinflammation and memory dysfunction remains unexplored.

OBJECTIVES

To investigate the protective effect of phloridzin against LPS-mediated memory impairment and neuroinflammation in mice.

METHODS

Different groups of mice were treated with LPS (250 μg/kg) via intraperitoneal (ip) route to induce cognitive impairments. The animals were administered with phloridzin (10-20 mg/kg, oral) or donepezil (1 mg/kg, intraperitoneal), and memory functions were evaluated by Morris water maze (MWM) and Y-maze. At the end of the behavioral experiments, the animals were sacrificed and different biochemical parameters like acetylcholinesterase (AChE), brain derived neurotropic factor (BDNF), tumor necrosis factor (TNF-α), interleukin-6 (IL-6), superoxide dismutase (SOD) and glutathione (GSH) concentration in the hippocampus and the cerebral cortex were estimated.

RESULTS

While LPS administered animals showed significantly decreased memory retention in both MWM and Y maze, a significant reversal in all the parameters were observed following treatment with phloridzin. LPS-treated animals showed significantly decreased level of antioxidants (SOD and GSH), neurotropic factor (BDNF) and cholinergic transmission (increased AChE) and increased levels of inflammatory/oxidative markers (TNF-α, IL-6 and MDA) in hippocampus and cortex. These changes were alleviated after the treatment with phloridzin.

CONCLUSIONS

Phloridzin may have neuroprotective role against LPS-induced neuroinflammation and memory impairment by virtue of its antioxidant, anti-inflammatory, and enhanced cholinergic signalling activity in the hippocampus and cerebral cortex.

Therapeutic Targeting Strategies for Early- to Late-Staged Alzheimer's Disease

Alzheimer's disease (AD) is the most common cause of dementia, typically showing progressive neurodegeneration in aging brains. The key signatures of the AD progression are the deposition of amyloid-beta (Aβ) peptides, the formation of tau tangles, and the induction of detrimental neuroinflammation leading to neuronal loss. However, conventional pharmacotherapeutic options are merely relying on the alleviation of symptoms that are limited to mild to moderate AD patients. Moreover, some of these medicines discontinued to use due to either the insignificant effectiveness in improving the cognitive impairment or the adverse side effects worsening essential bodily functions. One of the reasons for the failure is the lack of knowledge on the underlying mechanisms that can accurately explain the major causes of the AD progression correlating to the severity of AD. Therefore, there is an urgent need for the better understanding of AD pathogenesis and the development of the disease-modifying treatments, particularly for severe and late-onset AD, which have not been covered thoroughly. Here, we review the underlying mechanisms of AD progression, which have been employed for the currently established therapeutic strategies. We believe this will further spur the discovery of a novel disease-modifying treatment for mild to severe, as well as early- to late-onset, AD.

Extension of life span and stress tolerance modulated by DAF-16 in Caenorhabditis elegans under the treatment of Moringa oleifera extract

The present study was focused to isolate the bioactive compounds present in the leaves of Moringa oleifera which contains a high nutritional value. Furthermore, the research was aimed to evaluate the antioxidant, anti-aging, and anti-neurodegenerative properties of M. oleifera using the experimental model Caenorhabditis elegans. The separation of compounds from the crude extract and its identification was carried out through TLC, Column chromatography, UV absorption spectroscopy, and GC-MS. The compounds identified in most abundant fraction of column chromatography were [Phenol-2,4-bis(1,1-dimethylethyl)- phosphite (3:1)] and Tetratetracontane. The result suggests that the leaves extracts and column fraction were able to significantly extend the life span of the N2 wild-type strain of C. elegans. The most potent life span extending effect was displayed by the dichloromethane extract of leaves which was 21.73 ± 0.142 days compared to the control (16.55 ± 0.02 days). It could also extend the health span through improved physiological functions such as pharyngeal pumping, body bending, and reversal frequency with increased age. The treated worms were also exhibited improved resistance to thermal stress, oxidative stress, and reduced intracellular ROS accumulation. Moreover, the leaves extract could elicit neuroprotection as it could delay the paralysis in the transgenic strain of C. elegans 'CL4176' integrated with Aβ. Interestingly, The RNAi experiment demonstrated that the extended life span under the treatment of extracts and the compound was daf-16 dependent. In transgenic C. elegans TJ356, the DAF-16 transcription factor was localized in the nucleus under the stress conditions, further supported the involvement of the daf-16 gene in longevity. Overall, the study suggests the potential of M. oleifera as a dietary supplement and alternative medicine to defend against oxidative stress and aging.

Modeling tau transport in the axon initial segment

By assuming that tau protein can be in seven kinetic states, we developed a model of tau protein transport in the axon and in the axon initial segment (AIS). Two separate sets of kinetic constants were determined, one in the axon and the other in the AIS. This was done by fitting the model predictions in the axon with experimental results and by fitting the model predictions in the AIS with the assumed linear increase of the total tau concentration in the AIS. The calibrated model was used to make predictions about tau transport in the axon and in the AIS. To the best of our knowledge, this is the first paper that presents a mathematical model of tau transport in the AIS. Our modeling results suggest that binding of free tau to microtubules creates a negative gradient of free tau in the AIS. This leads to diffusion-driven tau transport from the soma into the AIS. The model further suggests that slow axonal transport and diffusion-driven transport of tau work together in the AIS, moving tau anterogradely. Our numerical results predict an interplay between these two mechanisms: as the distance from the soma increases, the diffusion-driven transport decreases, while motor-driven transport becomes larger. Thus, the machinery in the AIS works as a pump, moving tau into the axon.

Divalent Cations: A Molecular Glue for Protein Materials

Among inorganic materials, divalent cations modulate thousands of physiological processes that support life. Their roles in protein assembly and aggregation are less known, although they are progressively being brought to light. We review the structural roles of divalent cations here, as well as the novel protein materials that are under development, in which they are used as glue-like agents. More specifically, we discuss how mechanically stable nanoparticles, fibers, matrices, and hydrogels are generated through their coordination with histidine-rich proteins. We also describe how the rational use of divalent cations combined with simple protein engineering offers unexpected and very simple biochemical approaches to biomaterial design that might address unmet clinical needs in precision medicine.

Nicotine encourages oxidative stress and impairment of rats' brain mitigated by Spirulina platensis lipopolysaccharides and low-dose ionizing radiation

Nicotine is a psychoactive alkaloid of tobacco, which is ingested during cigarettes or electronic cigarette smoking. Extensive consumption of nicotine induced oxidative stress. Accordingly, it is implicated in many pathophysiology brain disorders and triggers neurodegeneration. In this study, we investigated the protective role of Spirulina platensis-lipopolysaccharides (S.LPS) and the low dose-ionizing radiation (LD-IR) against the induced neurotoxicity in the rats' brain due to the prolonged administration of high nicotine levels. Rats treated with nicotine for two months showed alterations in the oxidative stress markers (malondialdehyde (MDA), reduced glutathione (GSH) and oxidized glutathione disulfide (GSSG)), antioxidant enzymes (superoxide dismutase (SOD), catalase (Cat), glutathione enzymes (GPx and GST)) as well as several pro-inflammatory markers (Tumor Necrosis Factor-alpha (TNF-α), Interleukin-17 (IL-17), and Nuclear Factor-kappa B (NF-κB)), and induced apoptosis through Caspase-3 activity. Nicotine also upregulated the mRNA gene expression of cytochrome P450 enzymes (CYP2B1 and CYP2E1), Cyclin-dependent kinase 5 (CDK5), Toll-Like Receptor 4 (TLR4), and phospho-Tau (p-Tau) protein expression. Besides, it downregulated the alpha-7 nicotinic receptor (α7nAChR) mRNA gene expression accompanied by a decline in the calcium (Ca2+) level. S.LPS exhibited antioxidant, anti-inflammatory, anti-apoptotic and neuroprotective activities, which counteracting the detrimental effects of chronic nicotine administration. LD-IR demonstrated comparable effects to S.LPS. Exposure of rats to LD-IR enhanced the neuroprotective effects of S.LPS against nicotine toxicity. The light microscopic examination of the brain tissues was in agreement with the biochemical investigations. These findings display that S.LPS and LD-IR mitigated the oxidative stress and the impairment of rats' brain induced by nicotine, due to regulation of the mRNA gene expression of cytochrome P450 enzymes (CYP2B1 and CYP2E1) and the signaling pathway of Tau protein phosphorylation.

Impact of Cannabis-Based Medicine on Alzheimer's Disease by Focusing on the Amyloid β-Modifications: A Systematic Study

Deposition of Amyloid-beta (Aβ) peptide in the brain is the leading source of the onset and progression of Alzheimer's Disease (AD). Recent studies have suggested that anti-amyloidogenic agents may be a suitable therapeutic strategy for AD. The current review was proposed to address the beneficial effects of cannabis-based drugs for the treatment of AD, focusing primarily on Aβ modifications. Keywords related to AD, Aβ, and cannabis-based on MeSH were identified and were searched in PubMed, Google Scholar, Scopus, Ovid-Medline, and Web of Science from inception until 15 March 2020. The full text of identified papers was obtained and assessed based on exclusion and inclusion criteria. The review is based on articles that have focused on AD and the amyloidogenic pathway. A total of 17 studies were identified based on the inclusion criteria; however, nine studies qualified for this systematic review. The maximum and minimum cannabis dosages, mostly CBD and THC in animal studies, were 0.75 and 50 mg/kg, respectively. Cannabis (CBD and THC) was injected for 10 to 21 days. The findings of the 9 articles indicated that cannabis-based drugs might modulate Aβ modifications in several AD models. Our findings establish that cannabis-based drugs inhibited the progression of AD by modulating Aβ modifications.

Secondary Metabolites from Plants Possessing Inhibitory Properties against Beta-Amyloid Aggregation as Revealed by Thioflavin-T Assay and Correlations with Investigations on Transgenic Mouse Models of Alzheimer's Disease

Alzheimer's disease is a neurodegenerative disorder for which there is a continuous search of drugs able to reduce or stop the cognitive decline. Beta-amyloid peptides are composed of 40 and 42 amino acids and are considered a major cause of neuronal toxicity. They are prone to aggregation, yielding oligomers and fibrils through the inter-molecular binding between the amino acid sequences (17-42) of multiple amyloid-beta molecules. Additionally, amyloid deposition causes cerebral amyloid angiopathy. The present study aims to identify, in the existing literature, natural plant derived products possessing inhibitory properties against aggregation. The studies searched proved the anti-aggregating effects by the thioflavin T assay and through behavioral, biochemical, and histological analysis carried out upon administration of natural chemical compounds to transgenic mouse models of Alzheimer's disease. According to our present study results, fifteen secondary metabolites from plants were identified which presented both evidence coming from the thioflavin T assay and transgenic mouse models developing Alzheimer's disease and six additional metabolites were mentioned due to their inhibitory effects against fibrillogenesis. Among them, epigallocatechin-3-gallate, luteolin, myricetin, and silibinin were proven to lower the aggregation to less than 40%.

Intracellular Trafficking Mechanisms of Synaptic Dysfunction in Alzheimer's Disease

Alzheimer’s disease (AD) is the most common neurodegenerative disease characterized by progressive memory loss. Although AD neuropathological hallmarks are extracellular amyloid plaques and intracellular tau tangles, the best correlate of disease progression is synapse loss. What causes synapse loss has been the focus of several researchers in the AD field. Synapses become dysfunctional before plaques and tangles form. Studies based on early-onset familial AD (eFAD) models have supported that synaptic transmission is depressed by β-amyloid (Aβ) triggered mechanisms. Since eFAD is rare, affecting only 1% of patients, research has shifted to the study of the most common late-onset AD (LOAD). Intracellular trafficking has emerged as one of the pathways of LOAD genes. Few studies have assessed the impact of trafficking LOAD genes on synapse dysfunction. Since endocytic traffic is essential for synaptic function, we reviewed Aβ-dependent and independent mechanisms of the earliest synaptic dysfunction in AD. We have focused on the role of intraneuronal and secreted Aβ oligomers, highlighting the dysfunction of endocytic trafficking as an Aβ-dependent mechanism of synapse dysfunction in AD. Here, we reviewed the LOAD trafficking genes APOE4, ABCA7, BIN1, CD2AP, PICALM, EPH1A, and SORL1, for which there is a synaptic link. We conclude that in eFAD and LOAD, the earliest synaptic dysfunctions are characterized by disruptions of the presynaptic vesicle exo- and endocytosis and of postsynaptic glutamate receptor endocytosis. While in eFAD synapse dysfunction seems to be triggered by Aβ, in LOAD, there might be a direct synaptic disruption by LOAD trafficking genes. To identify promising therapeutic targets and biomarkers of the earliest synaptic dysfunction in AD, it will be necessary to join efforts in further dissecting the mechanisms used by Aβ and by LOAD genes to disrupt synapses.

Neuroprotection of Tropical Fruit Juice Mixture via the Reduction of iNOS Expression and CRH Level in β-Amyloid-Induced Rats Model of Alzheimer's Disease

This study aimed to determine the effects of tropical fruit juice mixture (pomegranate, white guava, and Roselle) on biochemical, behavioral, and histopathological changes of β-amyloid- (Aβ-) induced rats. Formulation 8 (F8) of tropical fruit juice mixture was chosen for this present study due to its high phenolic content and antioxidant capacity. Forty Wistar male rats were divided into five groups: dPBS (sham-operated control), dAβ (Aβ control), JPBS (F8 and PBS), JAβ (F8 and Aβ), and IBFAβ (ibuprofen and Aβ). F8 (5 ml/kg BW), and ibuprofen (10 ml/kg BW) was given orally daily for four weeks before the intracerebroventricular infusion of Aβ for two weeks. Histological analysis and neuronal count of hippocampus tissue in the Cornu Ammonis (CA1) region showed that supplementation with F8 was able to prevent Aβ-induced tissue damage and neuronal shrinkage. However, no significant difference in locomotor activity and novel object recognition (NOR) percentage was detected among different groups at day 7 and day 14 following Aβ infusion. Only effect of time differences (main effect of day) was observed at day 7 as compared to day 14, where reduction in locomotor activity and NOR percentage was observed in all groups, with F (1, 7) = 6.940, p < 0.05 and F (1, 7) = 7.152, p < 0.05, respectively. Besides, the MDA level of the JAβ group was significantly lower (p < 0.01) than that of the dPBS group. However, no significant changes in SOD activity were detected among different groups. Significant reduction in plasma CRH level (p < 0.05) and iNOS expression (p < 0.01) in the brain was detected in the JAβ group as compared to the dAβ group. Hence, our current findings suggest that the tropical fruit juice mixture (F8) has the potential to protect the rats from Aβ-induced neurotoxicity in brain hippocampus tissue possibly via its antioxidant properties and the suppression of iNOS expression and CRH production.

The Interplay between Diabetes and Alzheimer's Disease-In the Hunt for Biomarkers

The brain is an organ in which energy metabolism occurs most intensively and glucose is an essential and dominant energy substrate. There have been many studies in recent years suggesting a close relationship between type 2 diabetes mellitus (T2DM) and Alzheimer’s disease (AD) as they have many pathophysiological features in common. The condition of hyperglycemia exposes brain cells to the detrimental effects of glucose, increasing protein glycation and is the cause of different non-psychiatric complications. Numerous observational studies show that not only hyperglycemia but also blood glucose levels near lower fasting limits (72 to 99 mg/dL) increase the incidence of AD, regardless of whether T2DM will develop in the future. As the comorbidity of these diseases and earlier development of AD in T2DM sufferers exist, new AD biomarkers are being sought for etiopathogenetic changes associated with early neurodegenerative processes as a result of carbohydrate disorders. The S100B protein seem to be interesting in this respect as it may be a potential candidate, especially important in early diagnostics of these diseases, given that it plays a role in both carbohydrate metabolism disorders and neurodegenerative processes. It is therefore necessary to clarify the relationship between the concentration of the S100B protein and glucose and insulin levels. This paper draws attention to a valuable research objective that may in the future contribute to a better diagnosis of early neurodegenerative changes, in particular in subjects with T2DM and may be a good basis for planning experiments related to this issue as well as a more detailed explanation of the relationship between the neuropathological disturbances and changes of glucose and insulin concentrations in the brain.

Design, synthesis and biological evaluation of novel naturally-inspired multifunctional molecules for the management of Alzheimer's disease

In our overall goal to overcome the limitations associated with natural products for the management of Alzheimer's disease and to develop in-vivo active multifunctional cholinergic inhibitors, we embarked on the development of ferulic acid analogs. A systematic SAR study to improve upon the cholinesterase inhibition of ferulic acid with analogs that also had lower logP was carried out. Enzyme inhibition and kinetic studies identified compound 7a as a lead molecule with preferential acetylcholinesterase inhibition (AChE IC₅₀ = 5.74 ± 0.13 μM; BChE IC₅₀ = 14.05 ± 0.10 μM) compared to the parent molecule ferulic acid (% inhibition of AChE and BChE at 20 μM, 15.19 ± 0.59 and 19.73 ± 0.91, respectively). Molecular docking and dynamics studies revealed that 7a fits well into the active sites of AChE and BChE, forming stable and strong interactions with key residues Asp74, Trp286, and Tyr337 in AChE and with Tyr128, Trp231, Leu286, Ala328, Phe329, and Tyr341 in BChE. Compound 7a was found to be an efficacious antioxidant in a DPPH assay (IC₅₀ = 57.35 ± 0.27 μM), and it also was able to chelate iron. Data from atomic force microscopy images demonstrated that 7a was able to modulate aggregation of amyloid β_1-42. Upon oral administration, 7a exhibited promising in-vivo activity in the scopolamine-induced AD animal model and was able to improve spatial memory in cognitive deficit mice in the Y-maze model. Analog 7a could effectively reverse the increased levels of AChE and BChE in scopolamine-treated animals and exhibited potent ex-vivo antioxidant properties. These findings suggest that 7a can act as a lead molecule for the development of naturally-inspired multifunctional molecules for the management of Alzheimer's and other neurodegenerative disorders.

Coarse-grained MD simulations reveal beta-amyloid fibrils of various sizes bind to interfacial liquid-ordered and liquid-disordered regions in phase separated lipid rafts with diverse membrane-bound conformational states

The membrane binding behaviors of beta-amyloid fibrils, dimers to pentamers, from solution to lipid raft surfaces, were investigated using coarse-grained (CG) MD simulations. Our CG rafts contain phospholipid, cholesterol (with or without tail- or headgroup modifications), and with or without asymmetrically distributed monosialotetrahexosylganglioside (GM1). All rafts exhibited liquid-ordered (Lo), liquid-disordered (Ld), and interfacial Lo/Ld (Lod) domains, with domain sizes depending on cholesterol structure. For rafts without GM1, all fibrils bound to the Lod domains. Specifically, dimer fibrils bound exclusively via the C-terminal, while larger fibrils could bind via other protein regions. Interestingly, a membrane-inserted state was detected for a trimer fibril in a raft with tail-group modified cholesterol. For rafts containing GM1, fibrils bound either to the GM1-clusters, with numerous membrane-bound conformations, or to the non-GM1-containing-Lod domains via the C-terminal. Our results indicate beta-amyloid fibrils bind to Lod domains or GM1, with diversified membrane-bound conformations, in structurally heterogeneous lipid membranes.

Pharmacological Tools to Modulate Autophagy in Neurodegenerative Diseases

Considerable evidences suggest a link between autophagy dysfunction, protein aggregation, and neurodegenerative diseases. Given that autophagy is a conserved intracellular housekeeping process, modulation of autophagy flux in various model organisms have highlighted its importance for maintaining proteostasis. In postmitotic cells such as neurons, compromised autophagy is sufficient to cause accumulation of ubiquitinated aggregates, neuronal dysfunction, degeneration, and loss of motor coordination-all hallmarks of neurodegenerative diseases. Reciprocally, enhanced autophagy flux augments cellular and organismal health, in addition to extending life span. These genetic studies not-withstanding a plethora of small molecule modulators of autophagy flux have been reported that alleviate disease symptoms in models of neurodegenerative diseases. This review summarizes the potential of such molecules to be, perhaps, one of the first autophagy drugs for treating these currently incurable diseases.

Frontal cortex chitinase and pentraxin neuroinflammatory alterations during the progression of Alzheimer's disease

BACKGROUND

Chitinase 3-like 1 (CHI3L1), chitinase 3-like 2 (CHI3L2), and neuronal pentraxin II (NPTX2) are inflammatory biomarkers of Alzheimer's disease (AD). Although studies have demonstrated that cerebrospinal fluid levels of these proteins are changed in AD, no studies have undertaken a detailed examination of alterations in protein levels, cellular expression, and interaction with amyloid in the brain during the progression of AD.

METHODS

The study evaluated levels of both CHI3L1 and CHI3L2, NPTX2, ionized calcium-binding adapter molecule 1 (Iba1), complement component 1q (C1q), glial fibrillary acidic protein (GFAP), and CD44, in the frontal cortex of people who died with an antemortem clinical diagnosis of no cognitive impairment (NCI), mild cognitive impairment (MCI), mild/moderate AD (mAD), and severe AD (sAD) using immunoblot and immunohistochemical techniques.

RESULTS

CHI3L1-immunoreactive (-ir) astrocyte numbers were increased in the frontal cortex and white matter in sAD compared to NCI. On the other hand, increases in GFAP and Iba1-ir cell numbers were observed in MCI compared to NCI but only in white matter. Western blot analyses revealed significantly lower frontal cortex CHI3L2 levels, whereas CD44 levels were increased in sAD. No significant differences for CHI3L1, GFAP, C1q, and NPTX2 protein levels were detected between clinical groups. Strong significant correlations were found between frontal cortex CHI3L1 and Iba1-ir cell numbers in white matter and CHI3L1 and C1q protein levels in the early stages of the disease. C1q and Iba1, CD44 with CHI3L2, and GFAP protein levels were associated during disease progression. CHI3L1 and Iba1 cell numbers in white matter showed a significant associations with episodic memory and perceptual speed.

CONCLUSIONS

White matter CHI3L1 inflammatory response is associated with cognitive impairment early in the onset of AD.

Bacterial DNA promotes Tau aggregation

A hallmark feature of Alzheimer’s disease (AD) and other tauopathies is the misfolding, aggregation and cerebral accumulation of tau deposits. Compelling evidence indicates that misfolded tau aggregates are neurotoxic, producing synaptic loss and neuronal damage. Misfolded tau aggregates are able to spread the pathology from cell-to-cell by a prion like seeding mechanism. The factors implicated in the initiation and progression of tau misfolding and aggregation are largely unclear. In this study, we evaluated the effect of DNA extracted from diverse prokaryotic and eukaryotic cells in tau misfolding and aggregation. Our results show that DNA from various, unrelated gram-positive and gram-negative bacteria results in a more pronounced tau misfolding compared to eukaryotic DNA. Interestingly, a higher effect in promoting tau aggregation was observed for DNA extracted from certain bacterial species previously detected in the brain, CSF or oral cavity of patients with AD. Our findings indicate that microbial DNA may play a previously overlooked role in the propagation of tau protein misfolding and AD pathogenesis, providing a new conceptual framework that positions the compromised blood-brain and intestinal barriers as important sources of microbial DNA in the CNS, opening novel opportunities for therapeutic interventions.

Ameliorating amyloid aggregation through osmolytes as a probable therapeutic molecule against Alzheimer's disease and type 2 diabetes

Large numbers of neurological and metabolic disorders occurring in humans are induced by the aberrant growth of aggregated or misfolded proteins.

Exploring the Multifunctional Neuroprotective Promise of Rasagiline Derivatives for Multi-Dysfunctional Alzheimer's Disease

Alzheimer's disease (AD) is a chronic, age-related, and irreversible brain disorder that typically develops slowly and gets worse over time. The potent auspicious drug candidate for the treatment of AD is supposed to perform the simultaneous modulation of several targets linked to AD. The new therapeutic approach involves drug candidates that are designed to act on multiple targets and have various pharmacological properties. This trend has triggered the development of various multimodal drugs including TV-3326 (i.e. ladostigil) and M-30 (i.e. a new multitarget iron chelator). TV-3326 combines the neurorestorative/neuroprotective effects of the cholinesterase (ChE) inhibitory activity of rivastigmine with rasagiline (a selective monoamine oxidase-B inhibitor and novel antiparkinsonian agent) in a single molecule. M-30, the second derivative of rasagiline, was developed by combining the propargyl moiety of rasagiline into the skeleton of VK-28 (i.e. a novel brain permeable neuroprotective iron chelator). It has been revealed that both the compounds possess anti-AD effects and therefore, the clinical development is directed to the treatment of this type of neurodegenerative diseases (NDs). In this article, we have reviewed the neuroprotective molecular mechanisms and multimodal effects of TV-3326 and M-30.

Study on the Multitarget Synergistic Effects of Kai-Xin-San against Alzheimer's Disease Based on Systems Biology

Kai-Xin-San (KXS), a classical Chinese traditional prescription, was widely applied in the treatment of Alzheimer's disease (AD), while its functional mechanisms still remain unclear. By using systems biology approaches at animal, cellular, and molecular levels, the improvement of KXS on cognitive impairment was achieved by inhibiting abnormal acetylcholinesterase. The function on the nerve skeleton was performed by regulating the Tau phosphorylation pathway. Its antioxidant, anti-inflammatory, and antiapoptotic effects by modulating the aberrant upregulation of ROS, proinflammatory factors, and apoptosis-related proteins in the brain were studied to reveal the synergistic therapeutic efficacy of KXS. Then, formula dismantling in vitro indicated that ginseng was the principal herb, whereas three other herbs served adjuvant roles to achieve the best effect. After that, the in vivo analysis of components into plasma and brain of AD rats showed that 8 of 23 components in blood and 4 of 10 components in brain were from ginseng, respectively, further verifying the principal status of ginseng and the synergistic effects of the formula. Thus, the anti-AD effects of KXS were achieved by multitargets and multichannels. The systems biology approaches presented here provide a novel way in traditional herbal medicine research.

Glycan Mimetics from Natural Products: New Therapeutic Opportunities for Neurodegenerative Disease

Neurodegenerative diseases (NDs) affect millions of people worldwide. Characterized by the functional loss and death of neurons, NDs lead to symptoms (dementia and seizures) that affect the daily lives of patients. In spite of extensive research into NDs, the number of approved drugs for their treatment remains limited. There is therefore an urgent need to develop new approaches for the prevention and treatment of NDs. Glycans (carbohydrate chains) are ubiquitous, abundant, and structural complex natural biopolymers. Glycans often covalently attach to proteins and lipids to regulate cellular recognition, adhesion, and signaling. The importance of glycans in both the developing and mature nervous system is well characterized. Moreover, glycan dysregulation has been observed in NDs such as Alzheimer's disease (AD), Huntington's disease (HD), Parkinson's disease (PD), multiple sclerosis (MS), and amyotrophic lateral sclerosis (ALS). Therefore, glycans are promising but underexploited therapeutic targets. In this review, we summarize the current understanding of glycans in NDs. We also discuss a number of natural products that functionally mimic glycans to protect neurons, which therefore represent promising new therapeutic approaches for patients with NDs.

IL-6 trans-signaling in the brain influences the behavioral and physio-pathological phenotype of the Tg2576 and 3xTgAD mouse models of Alzheimer's disease

Alzheimer's disease (AD) is the most commonly diagnosed dementia but its underlying pathological mechanisms still unclear. Neuroinflammation and secretion of cytokines such as interleukin-6 (IL-6) accompany the main hallmarks of the disease: amyloid plaques and neurofibrillary tangles. In this study, we analyzed the role of IL-6 trans-signaling in two mouse models of AD, Tg2576 and 3xTg-AD mice. The inhibition of IL-6 trans-signaling partially rescued the AD-induced mortality in females of both models. Before amyloid plaques deposition, it reversed AD-induced changes in exploration and anxiety (but did not affect locomotion) in Tg2576 female mice. However, after plaque deposition the only behavioral trait affected by the inhibition of IL-6 trans-signaling was locomotion. Results in the Morris water maze suggest that cognitive flexibility was reduced by the blocking of the IL-6 trans-signaling in young and old Tg2576 female mice. The inhibition of IL-6 trans-signaling also decreased amyloid plaque burden in cortex and hippocampus, and Aβ₄₀ and Aβ₄₂ levels in the cortex, of Tg2576 female mice. The aforementioned changes might be correlated with changes in blood vessels and matrix structure and organization rather than changes in neuroinflammation. 3xTgAD mice showed a very mild phenotype regarding amyloid cascade, but results were in accordance with those of Tg2576 mice. These results strongly suggest that the inhibition of the IL-6 trans-signaling could represent a powerful therapeutic target in AD.

Yeast Models for Amyloids and Prions: Environmental Modulation and Drug Discovery

Amyloids are self-perpetuating protein aggregates causing neurodegenerative diseases in mammals. Prions are transmissible protein isoforms (usually of amyloid nature). Prion features were recently reported for various proteins involved in amyloid and neural inclusion disorders. Heritable yeast prions share molecular properties (and in the case of polyglutamines, amino acid composition) with human disease-related amyloids. Fundamental protein quality control pathways, including chaperones, the ubiquitin proteasome system and autophagy are highly conserved between yeast and human cells. Crucial cellular proteins and conditions influencing amyloids and prions were uncovered in the yeast model. The treatments available for neurodegenerative amyloid-associated diseases are few and their efficiency is limited. Yeast models of amyloid-related neurodegenerative diseases have become powerful tools for high-throughput screening for chemical compounds and FDA-approved drugs that reduce aggregation and toxicity of amyloids. Although some environmental agents have been linked to certain amyloid diseases, the molecular basis of their action remains unclear. Environmental stresses trigger amyloid formation and loss, acting either via influencing intracellular concentrations of the amyloidogenic proteins or via heterologous inducers of prions. Studies of environmental and physiological regulation of yeast prions open new possibilities for pharmacological intervention and/or prophylactic procedures aiming on common cellular systems rather than the properties of specific amyloids.

Phosphatidylcholine Extends Lifespan via DAF-16 and Reduces Amyloid-Beta-Induced Toxicity in Caenorhabditis elegans

Phosphatidylcholine is one of the major phospholipids comprising cellular membrane and is known to have several health-promoting activities, including the improvement of brain function and liver repair. In this paper, we examine the in vivo effect of dietary supplementation with phosphatidylcholine on the response to environmental stressors and aging in C. elegans. Treatment with phosphatidylcholine significantly increased the survival of worms under oxidative stress conditions. However, there was no significant difference in response to stresses caused by heat shock or ultraviolet irradiation. Oxidative stress is believed to be one of the major causal factors of aging. Then, we examined the effect of phosphatidylcholine on lifespan and age-related physiological changes. Phosphatidylcholine showed a lifespan-extending effect and a reduction in fertility, possibly as a tradeoff for long lifespan. Age-related decline of motility was also significantly delayed by supplementation with phosphatidylcholine. Interestingly, the expressions of well-known longevity-assuring genes, hsp-16.2 and sod-3, were significantly upregulated by dietary intervention with phosphatidylcholine. DAF-16, a transcription factor modulating stress response genes, was accumulated in the nucleus by phosphatidylcholine treatment. Increase of the ROS level with phosphatidylcholine suggests that the antioxidant and lifespan-extending effects are due to the hormetic effect of phosphatidylcholine. Phosphatidylcholine also showed a protective effect against amyloid beta-induced toxicity in Alzheimer's disease model animals. Experiments with long-lived mutants revealed that the lifespan-extending effect of phosphatidylcholine specifically overlapped with that of reduced insulin/IGF-1-like signaling and required DAF-16. These findings showed the antioxidant and antiaging activities of phosphatidylcholine for the first time in vivo. Further studies focusing on the identification of underlying cellular mechanisms involved in the antiaging effect will increase the possibility of using phosphatidylcholine for the development of antiaging therapeutics.

Ginsenoside Rb1 improves learning and memory ability through its anti-inflammatory effect in Aβ1-40 induced Alzheimer's disease of rats

This study measured amyloid-beta (Aβ), interleukin-1 beta (IL-1β), and glial fibrillary acidic protein (GFAP) expression in the hippocampus of Alzheimer's disease (AD) rat models to elucidate the mechanism of anti-inflammatory effect of ginsenoside Rb1 in AD. Eighty-four male Wistar rats were randomly divided into seven groups, learning and memory impairment was induced by Ap1-40 to establish AD rat model. Learning and memory abilities were assessed by a Morris water maze experiment. Immunohistochemistry, RT-PCR and Western blotting were used to measure IL-1β, Aβ and GFAP expression. Nissl staining and methenamine silver staining were performed to observe the morphology of neurons and Nissl Body, and to detect amyloid protein particle deposition. ELISA and LC-MS/MS were applied to detect Aβ1-42 and byproducts of S/MS were applied to IAT, VIV, ITL, VVIA, TVI, and VIT). Ginsenoside Rb1 administration could relieve cognitive deficit, and decrease expressions of IL-1β, Aβ, and GFAP. Neurons and Nissl Body were improved and plaques deposition was decreased obviously after treatment of ginsenoside Rb1, especially in medium dose of ginsenoside Rb1. Ginsenoside Rb1 can increase productions of Aβ1-42 and byproducts of β- and γ-secretase. Collected evidence supported that ginsenoside Rb1 improves learning and memory in AD rat by altering the amyloidogenic process of APP into non-amyloidogenic process, to exert its anti-inflammatory function.