Current understanding of the interactions between metal ions and Apolipoprotein E in Alzheimer's disease

Urinary Metal Levels, Cognitive Test Performance, and Dementia in the Multi-Ethnic Study of Atherosclerosis

Importance

Metals are established neurotoxicants, but evidence of their association with cognitive performance at low chronic exposure levels is limited.

Objective

To investigate the association of urinary metal levels, individually and as a mixture, with cognitive tests and dementia diagnosis, including effect modification by apolipoprotein ε4 allele (APOE4).

Design, Setting, and Participants

The multicenter prospective cohort Multi-Ethnic Study of Atherosclerosis (MESA) was started from July 2000 to August 2002, with follow-up through 2018. A total of 6303 MESA participants were included. Data analysis was performed from October 12, 2023, to June 13, 2024.

Exposure

Urine samples were collected at baseline (2000-2002), and arsenic, cadmium, cobalt, copper, lead, manganese, tungsten, uranium, and zinc levels were measured in 2020-2022.

Main Outcomes and Measures

Digit Symbol Coding (DSC) (n = 3819) (possible score range, 0-133), Cognitive Abilities Screening Instrument (CASI) (n = 3918) (possible score range, 0-100), and Digit Span (DS) (n = 4176) (possible score range, 0-30) cognitive tests were administered in 2010-2012; higher scores of each test indicate increasing levels of positive response.

Results

A total of 6303 participants were followed up for dementia diagnosis through 2018. The median age at baseline was 60 (IQR, 53-70) years, and 3303 participants (52.4%) were female. The median cognitive scores were 51 (IQR, 38-64) for DSC, 90 (IQR, 84-95) for CASI, and 15 (IQR, 12-18) for DS. There were 559 cases of dementia through the follow-up period. Inverse associations with DSC were identified: mean differences in z scores per IQR increase in metal levels were -0.03 (95% CI, -0.07 to 0.00) for arsenic, -0.05 (95% CI, -0.09 to -0.004) for cobalt, -0.05 (95% CI, -0.07 to -0.02) for copper, -0.04 (95% CI, -0.08 to -0.001) for uranium, and -0.03 (95% CI, -0.06 to -0.01) for zinc. Among 1058 APOE4 carriers, manganese was also inversely associated with DSC. The joint mean difference of DSC comparing percentile 95th with the 25th of the 9-metal mixture was -0.30 (95% CI, -0.47 to -0.14) for APOE4 carriers and -0.10 (95% CI, -0.19 to -0.01) for noncarriers. Arsenic, cadmium, cobalt, copper, tungsten, uranium, and zinc were individually associated with dementia, with hazard ratios per IQR of metal ranging from 1.15 (95% CI, 1.03-1.29) for tungsten to 1.46 (95% CI, 1.06-2.02) for uranium. The joint hazard ratio of dementia comparing percentiles 95th with the 25th of the 9-metal mixture was 1.71 (95% CI, 1.24-3.89), with no significant difference by APOE4 status.

Conclusions and Relevance

In this study, participants with higher concentrations of metals in their urine, compared with those with lower concentrations, had worse performance on cognitive tests and greater likelihood of developing dementia. The findings of this multicenter multiethnic cohort study might inform screening and potential interventions for prevention of dementia based on individuals' metal exposure levels and genetic profiles.

Recent Advances in Targeting Transition Metals (Copper, Iron, and Zinc) in Alzheimer's Disease

Changes in the transition metal homeostasis in the brain are closely linked with Alzheimer's disease (AD), including intraneuronal iron accumulation and extracellular copper and zinc pooling in the amyloid plague. The brain copper, zinc, and iron surplus are commonly acknowledged characteristics of AD, despite disagreements among some. This has led to the theory that oxidative stress resulting from abnormal homeostasis of these transition metals may be a causative explanation behind AD. In the nervous system, the interaction of metals with proteins appears to be an essential variable in the development or suppression of neurodegeneration. Chelation treatment may be an option for treating neurodegeneration induced by transition metal ion dyshomeostasis. Some clinicians even recommend using chelating agents as an adjunct therapy for AD. The current review also looks at the therapeutic strategies that have been attempted, primarily with metal-chelating drugs. Metal buildup in the nervous system, as reported in the AD, could be the result of compensatory mechanisms designed to improve metal availability for physiological functions.

MAD-microbial (origin of) Alzheimer's disease hypothesis: from infection and the antimicrobial response to disruption of key copper-based systems

Microbes have been suspected to cause Alzheimer's disease since at least 1908, but this has generally remained unpopular in comparison to the amyloid hypothesis and the dominance of Aβ and Tau. However, evidence has been accumulating to suggest that these earlier theories are but a manifestation of a common cause that can trigger and interact with all the major molecular players recognized in AD. Aβ, Tau and ApoE, in particular appear to be molecules with normal homeostatic functions but also with alternative antimicrobial functions. Their alternative functions confer the non-immune specialized neuron with some innate intracellular defenses that appear to be re-appropriated from their normal functions in times of need. Indeed, signs of infection of the neurons by biofilm-forming microbial colonies, in synergy with herpes viruses, are evident from the clinical and preclinical studies we discuss. Furthermore, we attempt to provide a mechanistic understanding of the AD landscape by discussing the antimicrobial effect of Aβ, Tau and ApoE and Lactoferrin in AD, and a possible mechanistic link with deficiency of vital copper-based systems. In particular, we focus on mitochondrial oxidative respiration via complex 4 and ceruloplasmin for iron homeostasis, and how this is similar and possibly central to neurodegenerative diseases in general. In the case of AD, we provide evidence for the microbial Alzheimer's disease (MAD) theory, namely that AD could in fact be caused by a long-term microbial exposure or even long-term infection of the neurons themselves that results in a costly prolonged antimicrobial response that disrupts copper-based systems that govern neurotransmission, iron homeostasis and respiration. Finally, we discuss potential treatment modalities based on this holistic understanding of AD that incorporates the many separate and seemingly conflicting theories. If the MAD theory is correct, then the reduction of microbial exposure through use of broad antimicrobial and anti-inflammatory treatments could potentially alleviate AD although this requires further clinical investigation.

APOE ε4 allele modifies the associations of toxic metals and their mixture with cognitive impairment among older adults

BACKGROUND

The evidence of interactive effect of the toxic metal (TM) mixture and apolipoprotein E (APOE) ε4 gene on cognitive impairment in older adults is scarce. We aimed to explore whether the associations of single TMs and their mixture with cognitive impairment depend on APOE ε4 in Chinese community-dwelling older people.

METHODS

A total of 1148 older adults from a subset of the baseline survey of a cohort study were included. Blood arsenic (As), cadmium (Cd), lead (Pb), strontium (Sr), and vanadium (V) were detected by inductively coupled plasma mass spectrometry. APOE gene (rs429358, rs7412) polymorphisms were analyzed by the Polymerase Chain Reaction instrument. Mixed effects logistic regression was applied to estimate the relationships of single TMs and APOE genotype with cognitive impairment. Weighted quantile sum (WQS) and Bayesian kernel machine regression (BKMR) models were performed to examine joint impacts of the TM mixture, as well as the interaction of the TM mixture with APOE ε4 genotype on cognitive impairment.

RESULTS

Pb displayed a significant linear association with an increased odds of cognitive impairment after adjustment for covariates (Ptrend = 0.045). While APOE genotype did not show a significant correlation with cognitive impairment. WQS showed that the TM mixture was associated with an increased risk of cognitive impairment by 31.0% (OR=1.31, 95% CI: 0.92, 1.87) while no significance was found. BKMR exhibited a significant linear association between the TM mixture and cognitive impairment. Moreover, both WQS and BKMR indicated that Pb contributed the most to cognitive impairment within the mixture. Significant interactions of Pb or the TM mixture and APOE genotype on cognitive impairment were observed, contributing to 38.1% and 38.2% of total effects, respectively.

CONCLUSIONS

APOE ε4 allele amplifies the associations of single Pb or the TM mixture with cognitive impairment. These findings may help to develop precision prevention.

The influence of time-restricted eating/feeding on Alzheimer's biomarkers and gut microbiota

OBJECTIVES

Alzheimer's disease (AD) is a progressive neurodegenerative disorder affecting approximately 55 million individuals globally. Diagnosis typically occurs in advanced stages, and there are limited options for reversing symptoms. Preventive strategies are, therefore, crucial. Time Restricted Eating (TRE) or Time Restricted Feeding (TRF) is one such strategy. Here we review recent research on AD and TRE/TRF in addition to AD biomarkers and gut microbiota.

METHODS

A comprehensive review of recent studies was conducted to assess the impact of TRE/TRF on AD-related outcomes. This includes the analysis of how TRE/TRF influences circadian rhythms, beta-amyloid 42 (Aß42), pro-inflammatory cytokines levels, and gut microbiota composition.

RESULTS

TRE/TRF impacts circadian rhythms and can influence cognitive performance as observed in AD. It lowers beta-amyloid 42 deposition in the brain, a key AD biomarker, and reduces pro-ininflammatory cytokines. The gut microbiome has emerged as a modifiable factor in AD treatment. TRE/TRF changes the structure and composition of the gut microbiota, leading to increased diversity and a decrease in harmful bacteria.

DISCUSSION

These findings underscore the potential of TRE/TRF as a preventive strategy for AD. By reducing Aß42 plaques, modulating pro-inflammatory cytokines, and altering gut microbiota composition, TRE/TRF may slow the progression of AD. Further research is needed to confirm these effects and to understand the mechanisms involved. This review highlights TRE/TRF as a promising non-pharmacological intervention in the fight against AD.

Antioxidant, anti-inflammatory and epigenetic potential of curcumin in Alzheimer's disease

Alzheimer's disease (AD) constitutes a multifactorial neurodegenerative pathology characterized by cognitive deterioration, personality alterations, and behavioral shifts. The ongoing brain impairment process poses significant challenges for therapeutic interventions due to activating multiple neurotoxic pathways. Current pharmacological interventions have shown limited efficacy and are associated with significant side effects. Approaches focusing on the early interference with disease pathways, before activation of broad neurotoxic processes, could be promising to slow down symptomatic progression of the disease. Curcumin-an integral component of traditional medicine in numerous cultures worldwide-has garnered interest as a promising AD treatment. Current research indicates that curcumin may exhibit therapeutic potential in neurodegenerative pathologies, attributed to its potent anti-inflammatory and antioxidant properties. Additionally, curcumin and its derivatives have demonstrated an ability to modulate cellular pathways via epigenetic mechanisms. This article aims to raise awareness of the neuroprotective properties of curcuminoids that could provide therapeutic benefits in AD. The paper provides a comprehensive overview of the neuroprotective efficacy of curcumin against signaling pathways that could be involved in AD and summarizes recent evidence of the biological efficiency of curcumins in vivo.

Label-Free In Situ Chemical Characterization of Amyloid Plaques in Human Brain Tissues

The accumulation of amyloid plaques and increased brain redox burdens are neuropathological hallmarks of Alzheimer's disease. Altered metabolism of essential biometals is another feature of Alzheimer's, with amyloid plaques representing sites of disturbed metal homeostasis. Despite these observations, metal-targeting disease treatments have not been therapeutically effective to date. A better understanding of amyloid plaque composition and the role of the metals associated with them is critical. To establish this knowledge, the ability to resolve chemical variations at nanometer length scales relevant to biology is essential. Here, we present a methodology for the label-free, nanoscale chemical characterization of amyloid plaques within human Alzheimer's disease tissue using synchrotron X-ray spectromicroscopy. Our approach exploits a C-H carbon absorption feature, consistent with the presence of lipids, to visualize amyloid plaques selectively against the tissue background, allowing chemical analysis to be performed without the addition of amyloid dyes that alter the native sample chemistry. Using this approach, we show that amyloid plaques contain elevated levels of calcium, carbonates, and iron compared to the surrounding brain tissue. Chemical analysis of iron within plaques revealed the presence of chemically reduced, low-oxidation-state phases, including ferromagnetic metallic iron. The zero-oxidation state of ferromagnetic iron determines its high chemical reactivity and so may contribute to the redox burden in the Alzheimer's brain and thus drive neurodegeneration. Ferromagnetic metallic iron has no established physiological function in the brain and may represent a target for therapies designed to lower redox burdens in Alzheimer's disease. Additionally, ferromagnetic metallic iron has magnetic properties that are distinct from the iron oxide forms predominant in tissue, which might be exploitable for the in vivo detection of amyloid pathologies using magnetically sensitive imaging. We anticipate that this label-free X-ray imaging approach will provide further insights into the chemical composition of amyloid plaques, facilitating better understanding of how plaques influence the course of Alzheimer's disease.

Diagnostic and prognostic implications of non-high-density lipoprotein cholesterol and homocysteine levels for cognitive impairment in thalamic infarction

BACKGROUND

Patients with thalamic infarction experience abnormal blockages of multinucleated vessels, affecting the body and thereby the thalamus. Most patients with thalamic infarction have an adverse prognosis, which seriously affects their safety. Therefore, it is essential to analyze the independent risk factors that influence the prognosis of patients with thalamic infarction and develop corresponding preventive measures.

AIM

To explore the effect of non-high-density lipoprotein cholesterol (non-HDL-C) and Homocysteine (Hcy) levels in cognitive impairment in thalamic infarction.

METHODS

From March 2019 to March 2022, 80 patients with thalamic infarction were divided into a group with cognitive impairment [Montreal Cognitive Assessment (MoCA) score < 26; 35 patients] and a group with normal cognitive function (MoCA score of 26-30; 45 patients) according to the MoCA score. In addition, 50 healthy people in the same period were selected as the control group. A correlation between the non-HDL-C and Hcy levels and the MoCA score and receiver operating characteristic curve was observed, and the serum non-HDL-C and Hcy levels were analyzed for the diagnosis of cognitive impairment in patients with thalamic infarction. According to the Modified Rankin Scale (MRS) score, 80 patients with thalamic infarction were divided into a good prognosis group (MRS score ≤ 2) and a poor prognosis group (MRS score >2).

RESULTS

The non-HDL-C and Hcy levels were significantly higher in the group with cognitive impairment than in the group with normal cognitive function (P < 0.05). There was no significant difference in the non-HDL-C level between the control group and the group with normal cognitive function (P > 0.05). The MoCA scores of the group with cognitive impairment were significantly lower than those of the group with normal cognitive function and the control group (P < 0.05). There was a significant difference between the control group and the group with normal cognitive function (P < 0.05). The non-HDL-C and Hcy levels were correlated with the MoCA score (P < 0.05), cognitive impairment [areas under the curve (AUC) = 0.709, 95% confidence interval (95%CI): 0.599-0.816], the non-HDL-C level, and could predict cognitive impairment in patients with thalamic infarction (AUC = 0.738, 95%CI: 0.618-0.859). Hcy combined with non-HDL-C levels can predict cognitive impairment in patients with thalamic infarction (AUC = 0.769, 95%CI: 0.721-0.895).There were 50 patients in the good prognosis group and 30 patients in the poor prognosis group. Compared with the good prognosis group, in the poor prognosis group, the National Institutes of Health Stroke Scale (NIHSS) score, non-HDL-C level, Hcy level, large-area cerebral infarction, atrial fibrillation, and activated partial prothrombin time were statistically significant (P < 0.05). The non-HDL-C level, the Hcy level, the NIHSS score, extensive cerebral serum, and atrial fibrillation may all be independent risk factors for poor prognosis in patients with thalamic infarction (P < 0.05).

CONCLUSION

Non-HDL-C and Hcy levels are positively correlated with cognitive impairment in patients with thalamic infarction. Non-HDL-C and Hcy levels can be used in the diagnosis of cognitive impairment in patients with thalamic infarction, and the combined detection effect is better. The main factors affecting the prognosis of patients with thalamic infarction are the non-HDL-C level, the Hcy level, the NIHSS score, large-area cerebral infarction, and atrial fibrillation. Clinically, corresponding preventive measures can be formulated based on the above factors to prevent poor prognosis and reduce mortality.

Iron chelation prevents nigrostriatal neurodegeneration in a chronic methamphetamine mice model

Methamphetamine (METH) has been established to selectively target and impair dopaminergic neurons through multiple pathways. Ferroptosis is a unique form of non-apoptotic cell death driven by cellular iron accumulation-induced lipid peroxidation. Nonetheless, it remains unclear whether METH can induce ferroptosis. In the present study, we sought to assess alterations in iron levels after chronic METH exposure and reveal the modulatory role of iron on METH-induced pathologies. Importantly, we demonstrated that METH increased iron deposition in the nigrostriatal system, including the substantia nigra (SN) and caudate putamen (CPu). Moreover, decreases in GPx4 levels, increases in lipid peroxidation products, and pathological alterations were observed in the nigrostriatal system as a consequence of chronic METH exposure. The iron chelator deferiprone not only alleviated nigrostriatal iron deposition, dopaminergic cell death, and lipid peroxidation, but alsoattenuated the decreases in GPx4 induced by METH. These findings suggest an alleviation of ferroptosis in dopaminergic neurons. In addition, we found that the ferroptosis inhibitor liproxstatin-1 attenuated METH-induced dopaminergic degeneration in the nigrostriatal system. Our findings corroborated that METH might induce dopaminergic neurodegeneration through iron-dependent ferroptosis. Interestingly, reducing iron levels or inhibiting ferroptosis may alleviate METH-induced dopaminergic neurodegeneration.

Molecular modeling of apoE in complexes with Alzheimer's amyloid-β fibrils from human brain suggests a structural basis for apolipoprotein co-deposition with amyloids

Apolipoproteins co-deposit with amyloids, yet apolipoprotein-amyloid interactions are enigmatic. To understand how apoE interacts with Alzheimer's amyloid-β (Aβ) peptide in fibrillary deposits, the NMR structure of full-length human apoE was docked to four structures of patient-derived Aβ1-40 and Aβ1-42 fibrils determined previously using cryo-electron microscopy or solid-state NMR. Similar docking was done using the NMR structure of human apoC-III. In all complexes, conformational changes in apolipoproteins were required to expose large hydrophobic faces of their amphipathic α-helices for sub-stoichiometric binding to hydrophobic surfaces on sides or ends of fibrils. Basic residues flanking the hydrophobic helical faces in apolipoproteins interacted favorably with acidic residue ladders in some amyloid polymorphs. Molecular dynamics simulations of selected apoE-fibril complexes confirmed their stability. Amyloid binding via cryptic sites, which became available upon opening of flexibly linked apolipoprotein α-helices, resembled apolipoprotein-lipid binding. This mechanism probably extends to other apolipoprotein-amyloid interactions. Apolipoprotein binding alongside fibrils could interfere with fibril fragmentation and secondary nucleation, while binding at the fibril ends could halt amyloid elongation and dissolution in a polymorph-specific manner. The proposed mechanism is supported by extensive prior experimental evidence and helps reconcile disparate reports on apoE's role in Aβ aggregation. Furthermore, apoE domain opening and direct interaction of Arg/Cys158 with amyloid potentially contributes to isoform-specific effects in Alzheimer's disease. In summary, current modeling supported by prior experimental studies suggests similar mechanisms for apolipoprotein-amyloid and apolipoprotein-lipid interactions; explains why apolipoproteins co-deposit with amyloids; and helps reconcile conflicting reports on the chaperone-like apoE action in Aβ aggregation.

The Major Hypotheses of Alzheimer's Disease: Related Nanotechnology-Based Approaches for Its Diagnosis and Treatment

Alzheimer's disease (AD) is a well-known chronic neurodegenerative disorder that leads to the progressive death of brain cells, resulting in memory loss and the loss of other critical body functions. In March 2019, one of the major pharmaceutical companies and its partners announced that currently, there is no drug to cure AD, and all clinical trials of the new ones have been cancelled, leaving many people without hope. However, despite the clear message and startling reality, the research continued. Finally, in the last two years, the Food and Drug Administration (FDA) approved the first-ever medications to treat Alzheimer's, aducanumab and lecanemab. Despite researchers' support of this decision, there are serious concerns about their effectiveness and safety. The validation of aducanumab by the Centers for Medicare and Medicaid Services is still pending, and lecanemab was authorized without considering data from the phase III trials. Furthermore, numerous reports suggest that patients have died when undergoing extended treatment. While there is evidence that aducanumab and lecanemab may provide some relief to those suffering from AD, their impact remains a topic of ongoing research and debate within the medical community. The fact is that even though there are considerable efforts regarding pharmacological treatment, no definitive cure for AD has been found yet. Nevertheless, it is strongly believed that modern nanotechnology holds promising solutions and effective clinical strategies for the development of diagnostic tools and treatments for AD. This review summarizes the major hallmarks of AD, its etiological mechanisms, and challenges. It explores existing diagnostic and therapeutic methods and the potential of nanotechnology-based approaches for recognizing and monitoring patients at risk of irreversible neuronal degeneration. Overall, it provides a broad overview for those interested in the evolving areas of clinical neuroscience, AD, and related nanotechnology. With further research and development, nanotechnology-based approaches may offer new solutions and hope for millions of people affected by this devastating disease.

Genetic Susceptibility to Neurotoxicity Related to Prenatal Inorganic Arsenic Exposure in Young Spanish Children

We explored the influence of child and maternal single nucleotide polymorphisms (SNPs) in genes related to neurological function and arsenic metabolism (i.e., ABCA1, ABCB1, PON1, CYP3A, BDNF, GSTP1, MT2A, and APOE as well as AS3MT) on the association between prenatal arsenic (As) exposure and methylation efficiency and neuropsychological development in 4-5-year-old children. Participants were 549 mother-child pairs from the INMA (Environment and Childhood) Spanish Project. We measured inorganic arsenic (iAs) and the metabolites monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in urine samples collected during pregnancy. Neuropsychological development was assessed at the age of 4-5 years using the McCarthy Scales of Children's Abilities (MSCA). Several SNPs were determined in maternal and child DNA; AS3MT and APOE haplotypes were inferred. The median ∑As (sum of iAs, DMA, and MMA) was 7.08 μg/g creatinine. Statistically significant interactions for children's APOE haplotype were observed. Specifically, ε4-carrier children had consistently lower MSCA scores in several scales with increasing ∑As and MMA concentrations. These results provide evidence regarding the neurotoxic effects of early life exposure to As, observing that the APOE ε4 allele could make children more vulnerable to this exposure.

Epilepsy: Mitochondrial connections to the 'Sacred' disease

Over 65 million people suffer from recurrent, unprovoked seizures. The lack of validated biomarkers specific for myriad forms of epilepsy makes diagnosis challenging. Diagnosis and monitoring of childhood epilepsy add to the need for non-invasive biomarkers, especially when evaluating antiseizure medications. Although underlying mechanisms of epileptogenesis are not fully understood, evidence for mitochondrial involvement is substantial. Seizures affect 35%-60% of patients diagnosed with mitochondrial diseases. Mitochondrial dysfunction is pathophysiological in various epilepsies, including those of non-mitochondrial origin. Decreased ATP production caused by malfunctioning brain cell mitochondria leads to altered neuronal bioenergetics, metabolism and neurological complications, including seizures. Iron-dependent lipid peroxidation initiates ferroptosis, a cell death pathway that aligns with altered mitochondrial bioenergetics, metabolism and morphology found in neurodegenerative diseases (NDDs). Studies in mouse genetic models with seizure phenotypes where the function of an essential selenoprotein (GPX4) is targeted suggest roles for ferroptosis in epilepsy. GPX4 is pivotal in NDDs, where selenium protects interneurons from ferroptosis. Selenium is an essential central nervous system micronutrient and trace element. Low serum concentrations of selenium and other trace elements and minerals, including iron, are noted in diagnosing childhood epilepsy. Selenium supplements alleviate intractable seizures in children with reduced GPX activity. Copper and cuproptosis, like iron and ferroptosis, link to mitochondria and NDDs. Connecting these mechanistic pathways to selenoproteins provides new insights into treating seizures, pointing to using medicines including prodrugs of lipoic acid to treat epilepsy and to potential alternative therapeutic approaches including transcranial magnetic stimulation (transcranial), photobiomodulation and vagus nerve stimulation.

Characterization of Uranyl (UO22+) Ion Binding to Amyloid Beta (Aβ) Peptides: Effects on Aβ Structure and Aggregation

Uranium (U) is naturally present in ambient air, water, and soil, and depleted uranium (DU) is released into the environment via industrial and military activities. While the radiological damage from U is rather well understood, less is known about the chemical damage mechanisms, which dominate in DU. Heavy metal exposure is associated with numerous health conditions, including Alzheimer's disease (AD), the most prevalent age-related cause of dementia. The pathological hallmark of AD is the deposition of amyloid plaques, consisting mainly of amyloid-β (Aβ) peptides aggregated into amyloid fibrils in the brain. However, the toxic species in AD are likely oligomeric Aβ aggregates. Exposure to heavy metals such as Cd, Hg, Mn, and Pb is known to increase Aβ production, and these metals bind to Aβ peptides and modulate their aggregation. The possible effects of U in AD pathology have been sparsely studied. Here, we use biophysical techniques to study in vitro interactions between Aβ peptides and uranyl ions, UO22+, of DU. We show for the first time that uranyl ions bind to Aβ peptides with affinities in the micromolar range, induce structural changes in Aβ monomers and oligomers, and inhibit Aβ fibrillization. This suggests a possible link between AD and U exposure, which could be further explored by cell, animal, and epidemiological studies. General toxic mechanisms of uranyl ions could be modulation of protein folding, misfolding, and aggregation.

Apolipoprotein E is required for brain iron homeostasis in mice

BACKGROUND

Apolipoprotein E deficiency (ApoE^-/-) increases progressively iron in the liver, spleen and aortic tissues with age in mice. However, it is unknown whether ApoE affects brain iron.

METHODS

We investigated iron contents, expression of transferrin receptor 1 (TfR1), ferroportin 1 (Fpn1), iron regulatory proteins (IRPs), aconitase, hepcidin, Aβ42, MAP2, reactive oxygen species (ROS), cytokines and glutathione peroxidase 4 (Gpx4) in the brain of ApoE^-/- mice.

RESULTS

We demonstrated that ApoE^-/- induced a significant increase in iron, TfR1 and IRPs and a reduction in Fpn1, aconitase and hepcidin in the hippocampus and basal ganglia. We also showed that replenishment of ApoE absent partly reversed the iron-related phenotype in ApoE^-/- mice at 24-months old. In addition, ApoE^-/- induced a significant increase in Aβ42, MDA, 8-isoprostane, IL-1β, IL-6, and TNFα and a reduction in MAP2 and Gpx4 in hippocampus, basal ganglia and/or cortex of mice at 24-months old.

CONCLUSIONS

Our findings implied that ApoE is required for brain iron homeostasis and ApoE^-/--induced increase in brain iron is due to the increased IRP/TfR1-mediated cell-iron uptake as well as the reduced IRP/Fpn1 associated cell-iron export and suggested that ApoE^-/- induced neuronal injury resulted mainly from the increased iron and subsequently ROS, inflammation and ferroptosis.

Trace elements and Alzheimer dementia in population-based studies: A bibliometric and meta-analysis

Alterations in the concentrations of trace elements may play a vital role in Alzheimer dementia progression. However, previous research results are inconsistent, and there is still a lack of review on the relationship between all the studied-trace elements and AD from various perspectives of population-based studies. In this study, we systematically reviewed previous population-based studies and identified the altered trace elements in AD patients. We searched the Web of Science Core Collection, PubMed, and Scopus database, and ultimately included 73 articles. A bibliometric analysis was conducted to explore the evolution of the field from an epidemiological perspective. Bibliometric data such as trace elements, biological materials, detection methods, cognitive tests, co-occurrence and co-citation statistics are all analyzed and presented in a quantitative manner. The 73 included studies analyzed 39 trace elements in total. In a further meta-analysis, standardized mean differences (SMDs) of 13 elements were calculated to evaluate their altered in AD patients, including copper, iron, zinc, selenium, manganese, lead, aluminum, cadmium, chromium, arsenic, mercury, cobalt, and manganese. We identified four trace elements-copper (serum), iron (plasma), zinc (hair), and selenium (plasma)-altered in AD patients, with SMDs of 0.37 (95% confidence interval [CI]: 0.10, 0.65), -0.68 (95% CI: -1.34, -0.02), -0.35 (95% CI: -0.62, -0.08), and -0.61 (95% CI: -0.97, -0.25), respectively. Finally, we formed a database of various trace element levels in AD patients and healthy controls. Our study can help future researchers gain a comprehensive understanding of the advancements in the field, and our results provide comprehensive population-based data for future research.