Metal exposure and Alzheimer’s pathogenesis

Gut Microbial Metabolome and Dysbiosis in Neurodegenerative Diseases: Psychobiotics and Fecal Microbiota Transplantation as a Therapeutic Approach-A Comprehensive Narrative Review

The comprehensive narrative review conducted in this study delves into the mechanisms of communication and action at the molecular level in the human organism. The review addresses the complex mechanism involved in the microbiota-gut-brain axis as well as the implications of alterations in the microbial composition of patients with neurodegenerative diseases. The pathophysiology of neurodegenerative diseases with neuronal loss or death is analyzed, as well as the mechanisms of action of the main metabolites involved in the bidirectional communication through the microbiota-gut-brain axis. In addition, interventions targeting gut microbiota restructuring through fecal microbiota transplantation and the use of psychobiotics-pre- and pro-biotics-are evaluated as an opportunity to reduce the symptomatology associated with neurodegeneration in these pathologies. This review provides valuable information and facilitates a better understanding of the neurobiological mechanisms to be addressed in the treatment of neurodegenerative diseases.

Metal-protein solution interactions investigated using model systems: Thermodynamic and spectroscopic methods

The first-row D-block metal ions are essential for the physiology of living organisms, functioning as cofactors in metalloproteins or structural components for enzymes: almost half of all proteins require metals to perform the biological function. Understanding metal-protein interactions is crucial to unravel the mysteries behind molecular biology, understanding the effects of metal imbalance and toxicity or the diseases due to disorders in metal homeostasis. Metal-protein interactions are dynamic: they are noncovalent and affected by the environment to which the system is exposed. To reach a complete comprehension of the system, different conditions must be considered for the experimental investigation, in order to get information on the species distribution, the ligand coordination modes, complex stoichiometry and geometry. Thinking about the whole environment where a protein acts, investigations are often challenging, and simplifications are required to study in detail the mechanisms of metal interaction. This chapter is intended to help researchers addressing the problem of the complexity of metal-protein interactions, with particular emphasis on the use of peptides as model systems for the metal coordination site. The thermodynamic and spectroscopic methods most widely employed to investigate the interaction between metal ions and peptides in solution are here covered. These include solid-phase peptide synthesis, potentiometric titrations, calorimetry, electrospray ionization mass spectrometry, UV-Vis spectrophotometry, circular dichroism (CD), nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR). Additional experimental methods, which can be employed to study metal complexes with peptides, are also briefly mentioned. A case-study is finally reported providing a practical example of the investigation of metal-protein interaction by means of thermodynamic and spectroscopic methods applied to peptide model systems.

Biometals in Alzheimer disease: emerging therapeutic and diagnostic potential of molybdenum and iodine

The current ageing trend of the world population has, in part, accounted for Alzheimer disease (AD) being a public health issue in recent times. Although some progress has been made in clarifying AD-related pathophysiological mechanisms, effective intervention is still elusive. Biometals are indispensable to normal physiological functions of the human body-for example, neurogenesis and metabolism. However, their association with AD remains highly controversial. Copper (Cu) and zinc (Zn) are biometals that have been investigated at great length in relation to neurodegeneration, whereas less attention has been afforded to other trace biometals, such as molybdenum (Mo), and iodine. Given the above context, we reviewed the limited number of studies that have evidenced various effects following the usage of these two biometals in different investigative models of AD. Revisiting these biometals via thorough investigations, along with their biological mechanisms may present a solid foundation for not only the development of effective interventions, but also as diagnostic agents for AD.

A Concise Review on Oxidative Stress-Mediated Ferroptosis and Cuproptosis in Alzheimer's Disease

Alzheimer's disease (AD), which was first identified more than a century ago, has become a pandemic that exacts enormous social burden and economic tolls as no measure of combating devastated AD is currently available. Growing etiopathological, genetic, and biochemical data indicate that AD is a heterogeneous, polygenic, multifactorial, and complex disease. However, its exact etiopathology remains to be determined. Numerous experimental data show that cerebral iron and copper dyshomeostasis contribute to Aβ amyloidosis and tauopathy, two neuropathological hallmarks of AD. Moreover, increasing experimental evidence suggests ferroptosis, an iron-dependent and nonapoptotic form of cell death, may be involved in the neurodegenerative process in the AD brain. Thus, the anti-ferroptosis approach may be an efficacious therapeutic strategy for AD patients. Furthermore, it remains to be further determined whether cuproptosis, a copper-dependent and distinct form of regulated cell death, also plays a contributing role in AD neurodegeneration. We hope this concise review of recent experimental studies of oxidative stress-mediated ferroptosis and cuproptosis in AD may spur further investigations on this timely and essential line of research.

Metal-organic frameworks: A promising option for the diagnosis and treatment of Alzheimer's disease

Beta-amyloid (Aβ) peptide is one of the main characteristic biomarkers of Alzheimer's disease (AD). Previous clinical investigations have proposed that unusual concentrations of this biomarker in cerebrospinal fluid, blood, and brain tissue are closely associated with the AD progression. Therefore, the critical point of early diagnosis, prevention, and treatment of AD is to monitor the levels of Aβ. In view of the potential of metal-organic frameworks (MOFs) for diagnosing and treating the AD, much attention has been focused in recent years. This review discusses the latest advances in the applications of MOFs for the early diagnosis of AD via fluorescence and electrochemiluminescence (ECL) detection of AD biomarkers, fluorescence detection of the main metal ions in the brain (Zn²⁺, Cu²⁺, Mn²⁺, Fe³⁺, and Al³⁺) in addition to magnetic resonance imaging (MRI) of the Aβ plaques. The current challenges and future strategies for translating the in vitro applications of MOFs into in vivo diagnosis of the AD are discussed.

Computational design of new tacrine analogs: an in silico prediction of their cholinesterase inhibitory, antioxidant, and hepatotoxic activities

Tacrine, the first drug approved for the treatment of Alzheimer's disease (AD), is a non-competitive cholinesterase inhibitor withdrawn due to its acute hepatotoxicity. However, new non-hepatotoxic forms of tacrine have been actively researched. Moreover, several recent reports have shown that oxidative stress is the cause of damage and plays a role in the pathogenesis of several neurodegenerative diseases including AD. The aim of the present study is the design of new easily synthesized tacrine analogs with less hepatotoxicity and potent antioxidant activity. In this context, a library of 34 novel tacrine analogs bearing an antioxidant fragment was designed and evaluated for its hepatotoxicity as well as anticholinesterase and antioxidant activities using computational methods. As a result, six new tacrine analogs have been proposed as potential inhibitors of cholinesterase with antioxidant activity and low or no hepatotoxicity. Furthermore, ADME calculations suggest that these compounds are promising oral drug candidates. Communicated by Ramaswamy H. Sarma.

Curcumin Scaffold as a Multifunctional Tool for Alzheimer's Disease Research

Alzheimer's disease (AD) is one of the most common neurodegenerative disorders, which is caused by multi-factors and characterized by two histopathological hallmarks: amyloid-β (Aβ) plaques and neurofibrillary tangles of Tau proteins. Thus, researchers have been devoting tremendous efforts to developing and designing new molecules for the early diagnosis of AD and curative purposes. Curcumin and its scaffold have fluorescent and photochemical properties. Mounting evidence showed that curcumin scaffold had neuroprotective effects on AD such as anti-amyloidogenic, anti-inflammatory, anti-oxidative and metal chelating. In this review, we summarized different curcumin derivatives and analyzed the in vitro and in vivo results in order to exhibit the applications in AD diagnosis, therapeutic monitoring and therapy. The analysis results showed that, although curcumin and its analogues have some disadvantages such as short wavelength and low bioavailability, these shortcomings can be conquered by modifying the structures. Curcumin scaffold still has the potential to be a multifunctional tool for AD research, including AD diagnosis and therapy.

Neuroprotective potential of curcuminoids in modulating Alzheimer's Disease via multiple signaling pathways

Alzheimer's disease (AD) is a progressive and frequent neurodegenerative disease of elderly people. In the 21st century, owing to the increasing prevalence of AD, there is a crucial need for finding better and effective pharmacotherapeutic approaches. This review article demonstrated the various sources and possible metabolic pathways of curcuminoids obtained from Curcuma longa herb, to prevent and treat AD but the information related to the metabolic fate of curcuminoids is deficient. Different in vitro and in vivo research studies demonstrating the mechanisms by which curcuminoids attenuated AD have been summarized. Administration of curcuminoids has been indicated to inhibit hyperphosphorylation of tau protein, deposition, and oligomerization of amyloid beta plaques in several AD models. Curcuminoids also chelate metals and form complexes, have antioxidant properties, mediates neuroinflammatory signaling pathways by modifying microglial cells activity, inhibit acetylcholinesterase activities and also modulates other associated signaling pathways including insulin signaling pathways and heme-oxygenase pathway. Briefly curcuminoids exhibit the capability to be more productive and efficacious compared to many recent treatments due to their antioxidant, delayed neuron degeneration and anti-inflammatory potential. Although their effectiveness as a curative agent is considered to be reduced due to their low bioavailability, If the issue of curcuminoids' low bioavailability is resolved then curcuminoid-based medications are hopefully on the horizon against AD.

Design, synthesis, and evaluation of 8-aminoquinoline-melatonin derivatives as effective multifunctional agents for Alzheimer's disease

Background

Alzheimer’s disease (AD) is thought to be a complex, multifactorial syndrome with many related molecular lesions contributing to its pathogenesis. Thus, multi-target-directed ligands are considered an effective way of treating AD. This study sought to evaluate 8-aminoquinoline-melatonin derivatives as effective multifunctional agents for AD.

Methods

Thioflavin-T fluorescence assays were used to detect the inhibitory potency of 8-aminoquinoline-melatonin hybrids (a1–a5, b1–b5, and c1–c5) on self- and acetylcholinesterase (AChE)-induced amyloid-β (Aβ) aggregation. The AChE and butyrylcholinesterase (BuChE) inhibitory potency within the compounds was evaluated by Ellman’s assays. Methyl thiazolyl tetrazolium (MTT) assays were performed to evaluate the cytotoxicity of the compounds to C17.2 cells. MTT assay was used to detect the cell viability of HT22 cells to evaluate the antioxidant effect of the compounds. Metal chelation property was measured by ultraviolet-visible spectrophotometry.

Results

Compounds c3 and c5 had superior inhibitory activity against self-induced Aβ aggregation (with inhibitory rates of 41.4±2.1 and 25.5±3.2 at 10 µM, respectively) compared to the other compounds. Compounds in the carbamate group (i.e., a4, a5, b4, b5, c4, and c5) showed significant BuChE inhibitory activity and excellent selectivity over AChE. Most of the compounds exhibited low cytotoxicity in the C17.2 cells. Notably, a2, a3, b2, and b3 and series c (c1–c5) exhibited strong protective effects. Additionally, a3 and c1 specifically chelated with copper ions.

Conclusions

Taking all of the promising results together, 8-aminoquinoline-melatonin hybrids can serve as lead molecules in the further development of new multi-functional anti-AD agents.

An Analysis of the Neurological and Molecular Alterations Underlying the Pathogenesis of Alzheimer's Disease

Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by amyloid beta (Aβ) plaques, neurofibrillary tangles, and neuronal loss. Unfortunately, despite decades of studies being performed on these histological alterations, there is no effective treatment or cure for AD. Identifying the molecular characteristics of the disease is imperative to understanding the pathogenesis of AD. Furthermore, uncovering the key causative alterations of AD can be valuable in developing models for AD treatment. Several alterations have been implicated in driving this disease, including blood–brain barrier dysfunction, hypoxia, mitochondrial dysfunction, oxidative stress, glucose hypometabolism, and altered heme homeostasis. Although these alterations have all been associated with the progression of AD, the root cause of AD has not been identified. Intriguingly, recent studies have pinpointed dysfunctional heme metabolism as a culprit of the development of AD. Heme has been shown to be central in neuronal function, mitochondrial respiration, and oxidative stress. Therefore, dysregulation of heme homeostasis may play a pivotal role in the manifestation of AD and its various alterations. This review will discuss the most common neurological and molecular alterations associated with AD and point out the critical role heme plays in the development of this disease.

Fluorescent Diagnostic Probes in Neurodegenerative Diseases

Neurodegenerative diseases are debilitating disorders that feature progressive and selective loss of function or structure of anatomically or physiologically associated neuronal systems. Both chronic and acute neurodegenerative diseases are associated with high morbidity and mortality along with the death of neurons in different areas of the brain; moreover, there are few or no effective curative therapy options for treating these disorders. There is an urgent need to diagnose neurodegenerative disease as early as possible, and to distinguish between different disorders with overlapping symptoms that will help to decide the best clinical treatment. Recently, in neurodegenerative disease research, fluorescent-probe-mediated biomarker visualization techniques have been gaining increasing attention for the early diagnosis of neurodegenerative diseases. A survey of fluorescent probes for sensing and imaging biomarkers of neurodegenerative diseases is provided. These imaging probes are categorized based on the different potential biomarkers of various neurodegenerative diseases, and their advantages and disadvantages are discussed. Guides to develop new sensing strategies, recognition mechanisms, as well as the ideal features to further improve neurodegenerative disease fluorescence imaging are also explored.

Does thiamine protect the brain from iron overload and alcohol-related dementia?

Alcohol-related dementia (ARD) is a common and severe co-morbidity in alcohol use disorder (AUD). We propose brain iron overload (BIO) to be an important and previously neglected pathogenic process, accelerating cognitive decline in AUD. Furthermore, we suggest thiamine, which is frequently depleted in AUD, to be a key modulator in this process: Thiamine deficiency impairs the integrity of the blood-brain barrier, thereby enabling iron to pass through and accumulate in the brain. This hypothesis is based on findings from animal, translational, and neuroimaging studies, discussed in this article. To validate this hypothesis, translational studies focusing on brain iron homeostasis in AUD, as well as prospective clinical studies investigating prevalence and clinical impact of BIO in AUD, should be conducted. If proven right, this would change the understanding of ARD and may lead to novel therapeutic interventions in prevention and treatment of ARD.

A Preliminary Study of Cu Exposure Effects upon Alzheimer's Amyloid Pathology

A large body of evidence indicates that dysregulation of cerebral biometals (Fe, Cu, Zn) and their interactions with amyloid precursor protein (APP) and Aβ amyloid may contribute to the Alzheimer's disease (AD) Aβ amyloid pathology. However, the molecular underpinnings associated with the interactions are still not fully understood. Herein we have further validated the exacerbation of Aβ oligomerization by Cu and H2O2 in vitro. We have also reported that Cu enhanced APP translations via its 5' untranslated region (5'UTR) of mRNA in SH-SY5Y cells, and increased Aβ amyloidosis and expression of associated pro-inflammatory cytokines such as MCP-5 in Alzheimer's APP/PS1 doubly transgenic mice. This preliminary study may further unravel the pathogenic role of Cu in Alzheimer's Aβ amyloid pathogenesis, warranting further investigation.

Exposure to CuO Nanoparticles Mediates NFκB Activation and Enhances Amyloid Precursor Protein Expression

Amyloid precursor protein (APP) is directly related to Aβ amyloidosis—a hallmark of Alzheimer’s disease (AD). However, the impact of environmental factors upon APP biology and Aβ amyloid pathology have not been well studied. The increased use of nanoparticles (NPs) or engineered nanomaterials (ENMs) has led to a growing body of evidence suggesting that exposure to metal/metal oxide NPs, such as Fe₂O₃, CuO, and ZnO, may contribute to the pathophysiology of neurodegenerative diseases such as AD through neuroinflammation. Our previous studies indicated that exposure to CuO nanoparticles (CuONPs) induce potent in vitro neurotoxicity. Herein, we investigated the effects on APP expression in neuronal cells exposed to different metal oxide NPs. We found a low dose of CuONPs effectively activated the NFκB signaling pathway and increased APP expression. Moreover, the inhibition of p65 expression using siRNA abolished CuONP-mediated APP expression, suggesting that NFκB-regulated APP expression in response to CuONP exposure may be associated with AD pathology.

Exposure of CuO Nanoparticles Contributes to Cellular Apoptosis, Redox Stress, and Alzheimer's Aβ Amyloidosis

Fe2O3, CuO and ZnO nanoparticles (NP) have found various industrial and biomedical applications. However, there are growing concerns among the general public and regulators about their potential environmental and health impacts as their physio-chemical interaction with biological systems and toxic responses of the latter are complex and not well understood. Herein we first reported that human SH-SY5Y and H4 cells and rat PC12 cell lines displayed concentration-dependent neurotoxic responses to insults of CuO nanoparticles (CuONP), but not to Fe2O3 nanoparticles (Fe2O3NP) or ZnO nanoparticles (ZnONP). This study provides evidence that CuONP induces neuronal cell apoptosis, discerns a likely p53-dependent apoptosis pathway and builds out the relationship between nanoparticles and Alzheimer's disease (AD) through the involvement of reactive oxygen species (ROS) and increased Aβ levels in SH-SY5Y and H4 cells. Our results implicate that exposure to CuONP may be an environmental risk factor for AD. For public health concerns, regulation for environmental or occupational exposure of CuONP are thus warranted given AD has already become a pandemic.

Unraveling Binding Mechanism of Alzheimer's Drug Rivastigmine Tartrate with Human Transferrin: Molecular Docking and Multi-Spectroscopic Approach towards Neurodegenerative Diseases

Studying drug–protein interactions has gained significant attention lately, and this is because the majority of drugs interact with proteins, thereby altering their structure and, moreover, their functionality. Rivastigmine tartrate (RT) is a drug that is in use for mild to moderate Alzheimer therapy. This study was targeted to characterize the interaction between human transferrin (hTf) and RT by employing spectroscopy, isothermal titration calorimetry (ITC), and molecular docking studies. Experimental results of fluorescence quenching of hTf induced by RT implied the formation of a static complex between hTf and RT. Further elucidation of the observed fluorescence data retorting Stern–Volmer and modified Stern–Volmer resulted in binding constants for hTf–RT complex of the order 10⁴ M⁻¹ over the studied temperatures. Thermodynamic parameters of hTf–RT interaction were elucidated further by employing these obtained binding constant values. It was quite evident from obtained thermodynamic attributes that RT spontaneously binds to hTf with a postulated existence of hydrogen bonding or Van der Waals forces. Further, Circular dichroism spectroscopy (CD) also confirmed RT–hTf complex formation owing to upward movement of CD spectra in the presence of RT. ITC profiles advocated the existence of reaction to be spontaneous. Moreover, molecular docking further revealed that the important residues play a pivotal role in RT–hTf interaction. The findings of this study can be of a significant benefit to the drug-designing industry in this disease-prone era.

Rebalancing metal dyshomeostasis for Alzheimer's disease therapy

Alzheimer's disease (AD) is a type of neurodegenerative malady that is associated with the accumulation of amyloid plaques. Metal ions are critical for the development and upkeep of brain activity, but metal dyshomeostasis can contribute to the development of neurodegenerative diseases, including AD. This review highlights the association between metal dyshomeostasis and AD pathology, the feasibility of rebalancing metal homeostasis as a therapeutic strategy for AD, and a survey of current drugs that action via rebalancing metal homeostasis. Finally, we discuss the challenges that should be overcome by researchers in the future to enable the practical use of metal homeostasis rebalancing agents for clinical application.

Impact of Tobacco Smoke in HIV Progression: a Major Risk Factor for the Development of NeuroAIDS and Associated of CNS Disorders

Aim

With the advent of highly active and combination antiretroviral therapy have substantially increased the life expectancy of patients infected with human immunodeficiency virus (HIV). However, this has brought into sharp contrast the incidence of several 'Non-acquired immunodeficiency syndrome (AIDS) diseases such as NeuroAIDS which identifies a group of neurological disorders caused primarily by HIV-mediated damage to the central and peripheral nervous systems. Given the patients depleted immune condition, the use and abuse of drug and addictive substances such as tobacco smoking can further deteriorates their overall health and accelerate the progression and severity of the disease. In this review we detail the pathogenesis, progression and characteristics of HIV and the impact of tobacco smoking as a risk factor for the progression of the disease to NeuroAIDS. This is a poorly understood aspect of HIV-related complications that needs to be addressed.

Subjects and methods

Review of theoretical approaches and knowledge synthesis.

Results

Tobacco smoking is highly prevalent in HIV patients when compared to the general population. The oxidative damage and inflammatory stress caused by chronic smoking on the cerebrovascular system have been well established. Considering that HIV patients have an impaired immune system and smokers per se are more susceptible to viral and bacterial inflammatory neuropathologies than non-smokers, it is conceivable that tobacco smoking as a risk factor for the progression of HIV into NeuroAIDS and related neurological impairments.

Conclusion

Tobacco smoke (TS) may bring about a synergistic effect in the context of persistent inflammatory state and cerebrovascular damage which facilitate HIV infection and progression to NeuroAIDS when compared to non-smokers.

Frontiers in Probing Alzheimer's Disease Biomarkers with Fluorescent Small Molecules

Alzheimer's disease (AD) is the most common form of dementia. The pathogenesis of the disease is associated with aggregated amyloid-β, hyperphosphorylated tau, a high level of metal ions, abnormal enzyme activities, and reactive astrocytes. This outlook gives an overview of fluorescent small molecules targeting AD biomarkers for ex vivo and in vivo imaging. These chemical imaging probes are categorized based on the potential biomarkers, and their pros and cons are discussed. Guidelines for designing new sensing strategies as well as the desirable properties to be pursued for AD fluorescence imaging are also provided.

Enhancers active in dopamine neurons are a primary link between genetic variation and neuropsychiatric disease

Enhancers function as DNA logic gates and may control specialized functions of billions of neurons. Here we show a tailored program of noncoding genome elements active in situ in physiologically distinct dopamine neurons of the human brain. We found 71,022 transcribed noncoding elements, many of which were consistent with active enhancers and with regulatory mechanisms in zebrafish and mouse brains. Genetic variants associated with schizophrenia, addiction, and Parkinson's disease were enriched in these elements. Expression quantitative trait locus analysis revealed that Parkinson's disease-associated variants on chromosome 17q21 cis-regulate the expression of an enhancer RNA in dopamine neurons. This study shows that enhancers in dopamine neurons link genetic variation to neuropsychiatric traits.

Iron and Alzheimer's Disease: From Pathogenesis to Therapeutic Implications

As people age, iron deposits in different areas of the brain may impair normal cognitive function and behavior. Abnormal iron metabolism generates hydroxyl radicals through the Fenton reaction, triggers oxidative stress reactions, damages cell lipids, protein and DNA structure and function, and ultimately leads to cell death. There is an imbalance in iron homeostasis in Alzheimer's disease (AD). Excessive iron contributes to the deposition of β-amyloid and the formation of neurofibrillary tangles, which in turn, promotes the development of AD. Therefore, iron-targeted therapeutic strategies have become a new direction. Iron chelators, such as desferoxamine, deferiprone, deferasirox, and clioquinol, have received a great deal of attention and have obtained good results in scientific experiments and some clinical trials. Given the limitations and side effects of the long-term application of traditional iron chelators, alpha-lipoic acid and lactoferrin, as self-synthesized naturally small molecules, have shown very intriguing biological activities in blocking Aβ-aggregation, tauopathy and neuronal damage. Despite a lack of evidence for any clinical benefits, the conjecture that therapeutic chelation, with a special focus on iron ions, is a valuable approach for treating AD remains widespread.

Influence of Zeolites on Amyloid-β Aggregation

Aggregation of Aβ plays a key role in the progression of Alzheimer's disease. Unfortunately, the Aβ aggregation mechanism is complex, leading to a structurally diverse population of oligomers and amyloid fibrils. Heterogeneous interfaces have been shown to influence the rate of fibrilization and may be useful tools to bias amyloid formation toward specific structures. In order to better understand how exogenous materials influence Aβ aggregation, Aβ_1-40 was exposed to zeolite Y containing different metal cations, including Na⁺, Mg²⁺, Fe³⁺, Zn²⁺, and Cu²⁺. NaY, MgY, and FeY, all accelerated the kinetics of fibrilization by increasing the primary nucleation rate, while CuY and ZnY inhibited fibrilization. These kinetic effects were supported through binding affinity measurements, in which ZnY and CuY showed higher association constants than the other zeolites. In addition to influencing the kinetics of fibrilization, the zeolites also affected the intermediate structures along the pathway. Western blots confirmed that Aβ_1-40 was arrested at the oligomeric stage in the presence of ZnY and CuY, while continuing to the fibrillary state in the presence of other zeolites. Seeding studies showed that NaY and FeY form on-pathway oligomers, while ZnY formed off-pathway oligomers. Overall, our results show that zeolites can impact the aggregation and speciation of amyloids.

Differential protein expression of hippocampal cells associated with heavy metals (Pb, As, and MeHg) neurotoxicity: Deepening into the molecular mechanism of neurodegenerative diseases

Chronic exposure to heavy metals such as Pb, As, and MeHg can be associated with an increased risk of developing neurodegenerative diseases. Our in vitro bioassays results showed the potency of heavy metals in the order of Pb < As < MeHg on hippocampal cells. The main objective of this study was combining in vitro label free proteomics and systems biology approach for elucidating patterns of biological response, discovering underlying mechanisms of Pb, As, and MeHg toxicity in hippocampal cells. The omics data was refined by using different filters and normalization and multilevel analysis tools were employed to explore the data visualization. The functional and pathway visualization was performed by using Gene ontology and PathVisio tools. Using these all integrated approaches, we identified significant proteins across treatments within the mitochondrial dysfunction, oxidative stress, ubiquitin proteome dysfunction, and mRNA splicing related to neurodegenerative diseases. The systems biology analysis revealed significant alterations in proteins implicated in Parkinson's disease (PD) and Alzheimer's disease (AD). The current proteomics analysis of three metals support the insight into the proteins involved in neurodegeneration and the altered proteins can be useful for metal-specific biomarkers of exposure and its adverse effects.

SIGNIFICANCE

The proteomics techniques have been claimed to be more sensitive than the conventional toxicological assays, facilitating the measurement of responses to heavy metals (Pb, As, and MeHg) exposure before obvious harm has occurred demonstrating their predictive value. Also, proteomics allows for the comparison of responses between Pb, As, and MeHg metals, permitting the evaluation of potency differences hippocampal cells of the brain. Hereby, the molecular information provided by pathway and gene functional analysis can be used to develop a more thorough understanding of each metal mechanism at the protein level for different neurological adverse outcomes (e.g. Parkinson's disease, Alzheimer's diseases). Efforts are put into developing proteomics based toxicity testing methods using in vitro models for improving human risk assessment. Some of the key proteins identified can also potentially be used as biomarkers in epidemiologic studies. These heavy metal response patterns shed new light on the mechanisms of mRNA splicing, ubiquitin pathway role in neurodegeneration, and can be useful for the development of molecular biomarkers of heavy metals exposure.

Lower Expression of Ndfip1 Is Associated With Alzheimer Disease Pathogenesis Through Decreasing DMT1 Degradation and Increasing Iron Influx

We have previously reported that high expression of divalent metal transporter 1 (DMT1) plays a crucial role in iron dyshomeostasis and β-amyloid (Aβ) peptide generation in the brain of Alzheimer’s disease (AD). Recent studies have shown that Nedd4 family interacting protein 1 (Ndfip1) can degrade DMT1 through ubiquitination pathway and reduce the accumulation of intracellular iron. The present study aims to evaluate whether Ndfip1 is involved in AD pathogenesis through mediating DMT1 degradation and iron metabolism. β-amyloid precursor protein/presenilin 1 (APP/PS1) transgenic mouse and Ndfip1 transfected SH-SY5Y cells were used in this study. Immunohistochemistry and Western blot were performed to examine the distribution and expression levels of Ndfip1 and DMT1. In addition, ELISA and calcein fluorescence were carried out for analyzing the levels of Aβ peptide and iron influx, respectively. The results showed that Ndfip1 immunoreactivity was decreased in the cortex and hippocampus of APP/PS1 mice, compared with wild type (WT) controls. Colocalization of Ndfip1 and Aβ within senile plaques could be observed. Immunoblot analyses showed that low expression of Ndfip1 and high expression of DMT1 proteins were detected in APP/PS1 mouse brain, compared with age-matched WT animals. Overexpression of Ndfip1 down-regulated DMT1 expression, and reduced iron influx and Aβ secretion in SH-SY5Y cells. Further, overexpressed Ndfip1 significantly attenuated iron-induced cell damage in Ndfip1 transfected cells. The present study suggests that lower expression of Ndfip1 might be associated with the pathogenesis of AD, through decreasing DMT1 degradation and increasing iron accumulation in the brain.

Use of Curcumin, a Natural Polyphenol for Targeting Molecular Pathways in Treating Age-Related Neurodegenerative Diseases

Progressive accumulation of misfolded amyloid proteins in intracellular and extracellular spaces is one of the principal reasons for synaptic damage and impairment of neuronal communication in several neurodegenerative diseases. Effective treatments for these diseases are still lacking but remain the focus of much active investigation. Despite testing several synthesized compounds, small molecules, and drugs over the past few decades, very few of them can inhibit aggregation of amyloid proteins and lessen their neurotoxic effects. Recently, the natural polyphenol curcumin (Cur) has been shown to be a promising anti-amyloid, anti-inflammatory and neuroprotective agent for several neurodegenerative diseases. Because of its pleotropic actions on the central nervous system, including preferential binding to amyloid proteins, Cur is being touted as a promising treatment for age-related brain diseases. Here, we focus on molecular targeting of Cur to reduce amyloid burden, rescue neuronal damage, and restore normal cognitive and sensory motor functions in different animal models of neurodegenerative diseases. We specifically highlight Cur as a potential treatment for Alzheimer's, Parkinson's, Huntington's, and prion diseases. In addition, we discuss the major issues and limitations of using Cur for treating these diseases, along with ways of circumventing those shortcomings. Finally, we provide specific recommendations for optimal dosing with Cur for treating neurological diseases.

Oxidative Stress, Synaptic Dysfunction, and Alzheimer's Disease

Alzheimer's disease (AD) is a devastating neurodegenerative disorder without a cure. Most AD cases are sporadic where age represents the greatest risk factor. Lack of understanding of the disease mechanism hinders the development of efficacious therapeutic approaches. The loss of synapses in the affected brain regions correlates best with cognitive impairment in AD patients and has been considered as the early mechanism that precedes neuronal loss. Oxidative stress has been recognized as a contributing factor in aging and in the progression of multiple neurodegenerative diseases including AD. Increased production of reactive oxygen species (ROS) associated with age- and disease-dependent loss of mitochondrial function, altered metal homeostasis, and reduced antioxidant defense directly affect synaptic activity and neurotransmission in neurons leading to cognitive dysfunction. In addition, molecular targets affected by ROS include nuclear and mitochondrial DNA, lipids, proteins, calcium homeostasis, mitochondrial dynamics and function, cellular architecture, receptor trafficking and endocytosis, and energy homeostasis. Abnormal cellular metabolism in turn could affect the production and accumulation of amyloid-β (Aβ) and hyperphosphorylated Tau protein, which independently could exacerbate mitochondrial dysfunction and ROS production, thereby contributing to a vicious cycle. While mounting evidence implicates ROS in the AD etiology, clinical trials with antioxidant therapies have not produced consistent results. In this review, we will discuss the role of oxidative stress in synaptic dysfunction in AD, innovative therapeutic strategies evolved based on a better understanding of the complexity of molecular mechanisms of AD, and the dual role ROS play in health and disease.

Overview and Current Status of Alzheimer's Disease in Bangladesh

Alzheimer’s disease (AD) is a complex neurological disorder with economic, social, and medical burdens which is acknowledged as leading cause of dementia marked by the accumulation and aggregation of amyloid-β peptide and phosphorylated tau (p-tau) protein and concomitant dementia, neuron loss and brain atrophy. AD is the most prevalent neurodegenerative brain disorder with sporadic etiology, except for a small fraction of cases with familial inheritance where familial forms of AD are correlated to mutations in three functionally related genes: the amyloid-β protein precursor and presenilins 1 and 2, two key γ-secretase components. The common clinical features of AD are memory impairment that interrupts daily life, difficulty in accomplishing usual tasks, confusion with time or place, trouble understanding visual images and spatial relationships. Age is the most significant risk factor for AD, whereas other risk factors correlated with AD are hypercholesterolemia, hypertension, atherosclerosis, coronary heart disease, smoking, obesity, and diabetes. Despite decades of research, there is no satisfying therapy which will terminate the advancement of AD by acting on the origin of the disease process, whereas currently available therapeutics only provide symptomatic relief but fail to attain a definite cure and prevention. This review also represents the current status of AD in Bangladesh.

The novel multitarget iron chelating and propargylamine drug M30 affects APP regulation and processing activities in Alzheimer's disease models

In many of the neurodegenerative diseases, such as Alzheimer's disease (AD) and AD-related disorders, as well as in the regular ageing process, excessive generation of oxidative stress (OS) and accumulation of iron levels and deposition have been observed in specific affected-brain regions and thus, regarded as contributing factors to the pathogenesis of the diseases. In AD, iron promotes amyloid β (Aβ) neurotoxicity by producing free radical damage and OS in brain areas affected by neurodegeneration, presumably by facilitating the aggregation of Aβ. In addition, it was shown that iron modulates intracellular levels of the holo amyloid precursor protein (APP) by iron-responsive elements (IRE) RNA stem loops in the 5' untranslated region (5'UTR) of the APP transcript. As a consequence of these observations, iron chelation is one of the major new therapeutic strategies for the treatment of AD. This review describes the benefits and importance of the multimodal brain permeable chimeric iron-chelating/propargylamine drug M30, concerning its neuroprotective/neurorestorative inter-related activities relevant of the pathological features ascribed to AD, with a special focus on the effect of the drug on APP regulation and processing.

Metal ions influx is a double edged sword for the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is a common form of dementia in aged people, which is defined by two pathological characteristics: β-amyloid protein (Aβ) deposition and tau hyperphosphorylation. Although the mechanisms of AD development are still being debated, a series of evidence supports the idea that metals, such as copper, iron, zinc, magnesium and aluminium, are involved in the pathogenesis of the disease. In particular, the processes of Aβ deposition in senile plaques (SP) and the inclusion of phosphorylated tau in neurofibrillary tangles (NFTs) are markedly influenced by alterations in the homeostasis of the aforementioned metal ions. Moreover, the mechanisms of oxidative stress, synaptic plasticity, neurotoxicity, autophagy and apoptosis mediate the effects of metal ions-induced the aggregation state of Aβ and phosphorylated tau on AD development. More importantly, imbalance of these mechanisms finally caused cognitive decline in different experiment models. Collectively, reconstructing the signaling network that regulates AD progression by metal ions may provide novel insights for developing chelators specific for metal ions to combat AD.

Age-related changes of brain iron load changes in the frontal cortex in APPswe/PS1ΔE9 transgenic mouse model of Alzheimer's disease

Alzheimer's disease (AD) as a neurodegenerative brain disorder is a devastating pathology leading to disastrous cognitive impairments and dementia, associated with major social and economic costs to society. Iron can catalyze damaging free radical reactions. With age, iron accumulates in brain frontal cortex regions and may contribute to the risk of AD. In this communication, we investigated the age-related brain iron load changes in the frontal cortex of 6- and 12-month-old C57BL/6J (C57) and APPswe/PS1ΔE9 (APP/PS1) double transgenic mouse by using graphite furnace atomic absorption spectrometry (GFAAS) and Perls' reaction. In the present study, we also evaluated the age-related changes of DMT1 and FPN1 by using Western blot and qPCR. We found that compared with 6-month-old APP/PS1 mice and the 12-month-old C57 mice, the 12-month-old APP/PS1 mice had increased iron load in the frontal cortex. The levels of DMT1 were significantly increased and the FPN1 were significantly reduced in the frontal cortex of the 12-month-old APP/PS1 mice than that in the 6-month-old APP/PS1 mice and 12-month-old C57 mice. We conclude that in AD damage occurs in conjunction with iron accumulation, and the brain iron load associated with loss control of the brain iron metabolism related protein DMT1 and FPN1 expressions.

Neuroprotective effect of the active components of three Chinese herbs on brain iron load in a mouse model of Alzheimer's disease

Alzheimer’s disease (AD) is a neurodegenerative brain disorder and the most common cause of dementia. New treatments for AD are required due to its increasing prevalence in aging populations. The present study evaluated the effects of the active components of Epimedium, Astragalus and Radix Puerariae on learning and memory impairment, β-amyloid (Aβ) reduction and brain iron load in an APP_swe/PS1_ΔE9 transgenic mouse model of AD. Increasing evidence indicates that a disturbance of normal iron homeostasis may contribute to the pathology of AD. However, the underlying mechanisms resulting in abnormal iron load in the AD brain remain unclear. It has been hypothesized that the brain iron load is influenced by the deregulation of certain proteins associated with brain iron metabolism, including divalent metal transporter 1 (DMT1) and ferroportin 1 (FPN1). The present study investigated the effects of the active components of Epimedium, Astragalus and Radix Puerariae on the expression levels of DMT1 and FPN1. The treatment with the active components reduced cognitive deficits, inhibited Aβ plaque accumulation, reversed Aβ burden and reduced the brain iron load in AD model mice. A significant increase was observed in the levels of DMT1-iron-responsive element (IRE) and DMT1-nonIRE in the hippocampus of the AD mouse brain, which was reduced by treatment with the active components. In addition, the levels of FPN1 were significantly reduced in the hippocampus of the AD mouse brain compared with those of control mice, and these levels were increased following treatment with the active components. Thus, the present study indicated that the active components of Epimedium, Astragalus and Radix Puerariae may exert a neuroprotective effect against AD by reducing iron overload in the AD brain and may provide a novel approach for the development of drugs for the treatment of AD.

How our bodies fight amyloidosis: effects of physiological factors on pathogenic aggregation of amyloidogenic proteins

The process of protein aggregation from soluble amyloidogenic proteins to insoluble amyloid fibrils plays significant roles in the onset of over 30 human amyloidogenic diseases, such as Prion disease, Alzheimer's disease and type 2 diabetes mellitus. Amyloid deposits are commonly found in patients suffered from amyloidosis; however, such deposits are rarely seen in healthy individuals, which may be largely attributed to the self-regulation in vivo. A vast number of physiological factors have been demonstrated to directly affect the process of amyloid formation in vivo. In this review, physiological factors that influence amyloidosis, including biological factors (chaperones, natural antibodies, enzymes, lipids and saccharides) and physicochemical factors (metal ions, pH environment, crowding and pressure, etc.), together with the mechanisms underlying these proteostasis effects, are summarized.

Preparation, anticholinesterase activity, and docking study of new 2-butenediamide and oxalamide derivatives

Several new oxalamide and 2-butenediamide derivatives have been designed, synthesized and evaluated as the acetyl- and butyryl-cholinesterase inhibitors for Alzheimer's disease. The enzyme inhibitory activity of the synthesized compounds was measured using Ellman's colorimetric method. It was revealed that compound 1a (N,N'-bis-(4-chloro-benzyl)-N,N'-diphenyl-oxalamide) showed maximum activity against BuChE with a half maximal inhibitory concentration (IC50) = 1.86 µM and compound 2a (but-2-enedioic acid bis-[(4-chloro-benzyl)-phenyl-amide]) exhibited optimum AChE (IC50 = 1.51 µM) inhibition with a high-selectivity index. To better understand the enzyme-inhibitor interaction of the most active compounds towards cholinesterase, molecular modelling studies were carried out. Docking simulations revealed that inhibitors 1a and 2a targeted both the catalytic active site and the peripheral anionic site of 1ACJ and 1P0I.

HFE gene variants, iron, and lipids: a novel connection in Alzheimer's disease

Iron accumulation and associated oxidative stress in the brain have been consistently found in several neurodegenerative diseases. Multiple genetic studies have been undertaken to try to identify a cause of neurodegenerative diseases but direct connections have been rare. In the iron field, variants in the HFE gene that give rise to a protein involved in cellular iron regulation, are associated with iron accumulation in multiple organs including the brain. There is also substantial epidemiological, genetic, and molecular evidence of disruption of cholesterol homeostasis in several neurodegenerative diseases, in particular Alzheimer's disease (AD). Despite the efforts that have been made to identify factors that can trigger the pathological events associated with neurodegenerative diseases they remain mostly unknown. Because molecular phenotypes such as oxidative stress, synaptic failure, neuronal loss, and cognitive decline, characteristics associated with AD, have been shown to result from disruption of a number of pathways, one can easily argue that the phenotype seen may not arise from a linear sequence of events. Therefore, a multi-targeted approach is needed to understand a complex disorder like AD. This can be achieved only when knowledge about interactions between the different pathways and the potential influence of environmental factors on them becomes available. Toward this end, this review discusses what is known about the roles and interactions of iron and cholesterol in neurodegenerative diseases. It highlights the effects of gene variants of HFE (H63D- and C282Y-HFE) on iron and cholesterol metabolism and how they may contribute to understanding the etiology of complex neurodegenerative diseases.

Melatonin does not modify the concentration of different metals in AβPP transgenic mice

Metals such as aluminum, iron, copper, and zinc have been implicated in the etiology of certain neurodegenerative disorders. On the other hand, it is well known that citric acid enhances Al absorption through the diet, while melatonin may bind such metals and decrease ROS production. In this study, we determined the concentrations of Al, Cu, Zn, Fe, and Mn in various tissues of Tg2576 Al-treated mice. Female mice and wild type littermates were exposed to 1mg Al/g plus 3.2% of citric acid and melatonin 10mg/kg/day for 15months. At 18months of age, metal concentrations were measured in bone, liver, kidney and spleen, as well as in three brain regions. In the citric plus Al group, Al levels were higher in hippocampus than in cortex and cerebellum, while Al concentration in bone was higher than those in kidney, liver and spleen, The current results show that exposure to Al plus citric acid did not produce relevant changes in metal levels related with genotype. Moreover, co-administration of melatonin with Al did not modify significantly metal concentrations in tissues. The present results do not support that melatonin can diminish Al or Fe concentrations in various tissues.

Aggregation pathways of the amyloid β(1-42) peptide depend on its colloidal stability and ordered β-sheet stacking

Amyloid β (Aβ) fibrils are present as a major component in senile plaques, the hallmark of Alzheimer's disease (AD). Diffuse plaques (nonfibrous, loosely packed Aβ aggregates) containing amorphous Aβ aggregates are also formed in brain. This work examines the influence of Cu(2+) complexation by Aβ on the aggregation process in the context of charge and structural variations. Changes in the surface charges of Aβ molecules due to Cu(2+) binding, measured with a ζ-potential measurement device, were correlated with the aggregate morphologies examined by atomic force microscopy. As a result of the charge variation, the "colloid-like" stability of the aggregation intermediates, which is essential to the fibrillation process, is affected. Consequently, Cu(2+) enhances the amorphous aggregate formation. By monitoring variations in the secondary structures with circular dichroism spectroscopy, a direct transformation from the unstructured conformation to the β-sheet structure was observed for all types of aggregates observed (oligomers, fibrils, and/or amorphous aggregates). Compared to the Aβ aggregation pathway in the absence of Cu(2+) and taking other factors affecting Aβ aggregation (i.e., pH and temperature) into account, our investigation indicates that formations of amorphous and fibrous aggregates diverge from the same β-sheet-containing partially folded intermediate. This study suggests that the hydrophilic domain of Aβ also plays a role in the Aβ aggregation process. A kinetic model was proposed to account for the effects of the Cu(2+) binding on these two aggregation pathways in terms of charge and structural variations.

Neuroprotective effect of natural products against Alzheimer's disease

Nature has gifted mankind with a plethora of flora-bearing fruits, vegetables and nuts. The diverse array of bioactive nutrients present in these natural products plays a pivotal role in prevention and cure of various neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease and other neuronal dysfunctions. Accumulated evidence suggests that naturally occurring phyto-compounds, such as polyphenolic antioxidants found in fruits, vegetables, herbs and nuts, may potentially hinder neurodegeneration, and improve memory and cognitive function. Nuts such as walnut have also demonstrated neuroprotective effect against AD. The molecular mechanisms behind the curative effects rely mainly on the action of phytonutrients on distinct signalling pathways associated with protein folding and neuroinflammation. The neuroprotective effects of various naturally occurring compounds in AD is evaluating in this review.

Synchrotron Radiation Spectroscopic Techniques as Tools for the Medicinal Chemist: Microprobe X-Ray Fluorescence Imaging, X-Ray Absorption Spectroscopy, and Infrared Microspectroscopy

This review updates the recent advances and applications of three prominent synchrotron radiation techniques, microprobe X-ray fluorescence spectroscopy/imaging, X-ray absorption spectroscopy, and infrared microspectroscopy, and highlights how these tools are useful to the medicinal chemist. A brief description of the principles of the techniques is given with emphasis on the advantages of using synchrotron radiation-based instrumentation rather than instruments using typical laboratory radiation sources. This review focuses on several recent applications of these techniques to solve inorganic medicinal chemistry problems, focusing on studies of cellular uptake, distribution, and biotransformation of established and potential therapeutic agents. The importance of using these synchrotron-based techniques to assist the development of, or validate the chemistry behind, drug design is discussed.

Differential elemental distribution of retained particles along the respiratory tract

CONTEXT

Prolonged exposure to ambient particles is associated with premature mortality due to cardio-respiratory diseases and lung cancer. The size and composition of these particles determine their toxicity, which is aggravated by their long-term retention in the lungs.

OBJECTIVE

To compare the elemental profile of particles retained along the bronchial tree and lymph nodes by combining laser capture microdissection (LCM) and elemental composition analysis through energy dispersive x-ray (EDX) and scanning electron microscopy (SEM).

MATERIAL AND METHODS

Twenty-four right lung middle lobes from autopsied cases were obtained from two cities with different pollution backgrounds. Lung samples were collected from three distinct sites within the lung at the time of autopsy: peribronchial tissue, peripheral parenchyma and hilar lymph nodes. Areas of potentially increased particle deposition were microdissected using LCM and analyzed for elemental composition through EDX "allied" with SEM.

RESULTS

Elemental analyses of the particles retained along the bronchial tree showed two groups of distribution: peribronchiolar or lymph node deposition. The elemental profile of peribronchial areas were significantly different between the two cities and were better discriminators of past air pollution exposure.

CONCLUSION

Our data suggest that particle uptake varies along the bronchial tree and human lung tissue retains particles indicative of regional air pollution background.

The effect of curcumin (turmeric) on Alzheimer's disease: An overview

This paper discusses the effects of curcumin on patients with Alzheimer's disease (AD). Curcumin (Turmeric), an ancient Indian herb used in curry powder, has been extensively studied in modern medicine and Indian systems of medicine for the treatment of various medical conditions, including cystic fibrosis, haemorrhoids, gastric ulcer, colon cancer, breast cancer, atherosclerosis, liver diseases and arthritis. It has been used in various types of treatments for dementia and traumatic brain injury. Curcumin also has a potential role in the prevention and treatment of AD. Curcumin as an antioxidant, anti-inflammatory and lipophilic action improves the cognitive functions in patients with AD. A growing body of evidence indicates that oxidative stress, free radicals, beta amyloid, cerebral deregulation caused by bio-metal toxicity and abnormal inflammatory reactions contribute to the key event in Alzheimer's disease pathology. Due to various effects of curcumin, such as decreased Beta-amyloid plaques, delayed degradation of neurons, metal-chelation, anti-inflammatory, antioxidant and decreased microglia formation, the overall memory in patients with AD has improved. This paper reviews the various mechanisms of actions of curcumin in AD and pathology.