Role of iron in neurodegenerative disorders

Iron-inhibited autophagy via transcription factor ZFP27 in Parkinson's disease

Parkinson's disease (PD) is a challenge because of the ageing of the population and the disease's complicated pathogenesis. Accumulating evidence showed that iron and autophagy were involved in PD. Nevertheless, the molecular mechanism and role of iron and autophagy in PD are not yet elucidated. In the present study, it was shown that PD mice had significant motor dysfunction, increased iron content, less dopamine neurons and more α-synuclein accumulation in the substantia nigra. Meanwhile, PD mice treated with deferoxamine exhibited less iron content, relieved the dyskinesia and had a significant increase in dopamine neurons and a significant decrease in α-synuclein. Autophagy induced by LC3 was inhibited in PD models with iron treatment. Following verification showed that iron aggregation restrained insulin-like growth factor 2 (IGF2) and transcription factor zinc finger protein 27 (ZFP27) in PD models. In addition, LC3-induced autophagy flux was reduced with ZFP27 knockdown. Furthermore, ZFP27 affected autophagy by regulating LC3 promoter activity. These data suggest that iron deposition inhibits IGF2 and ZFP27 to reduce LC3-induced autophagy, and ultimately decrease dopamine neurons, accelerating PD progression. Our findings provide a novel insight that ZFP27-mediated iron-related autophagy and IGF2 may activate the downstream kinase gene to trigger autophagy in the PD model.

An automatic interpretable deep learning pipeline for accurate Parkinson's disease diagnosis using quantitative susceptibility mapping and T1-weighted images

Parkinson's disease (PD) diagnosis based on magnetic resonance imaging (MRI) is still challenging clinically. Quantitative susceptibility maps (QSM) can potentially provide underlying pathophysiological information by detecting the iron distribution in deep gray matter (DGM) nuclei. We hypothesized that deep learning (DL) could be used to automatically segment all DGM nuclei and use relevant features for a better differentiation between PD and healthy controls (HC). In this study, we proposed a DL-based pipeline for automatic PD diagnosis based on QSM and T1-weighted (T1W) images. This consists of (1) a convolutional neural network model integrated with multiple attention mechanisms which simultaneously segments caudate nucleus, globus pallidus, putamen, red nucleus, and substantia nigra from QSM and T1W images, and (2) an SE-ResNeXt50 model with an anatomical attention mechanism, which uses QSM data and the segmented nuclei to distinguish PD from HC. The mean dice values for segmentation of the five DGM nuclei are all >0.83 in the internal testing cohort, suggesting that the model could segment brain nuclei accurately. The proposed PD diagnosis model achieved area under the the receiver operating characteristic curve (AUCs) of 0.901 and 0.845 on independent internal and external testing cohorts, respectively. Gradient-weighted class activation mapping (Grad-CAM) heatmaps were used to identify contributing nuclei for PD diagnosis on patient level. In conclusion, the proposed approach can potentially be used as an automatic, explainable pipeline for PD diagnosis in a clinical setting.

High-resolution 3D ultra-short echo time MRI with Rosette k-space pattern for brain iron content mapping

BACKGROUND

The iron concentration increases during normal brain development and is identified as a risk factor for many neurodegenerative diseases, it is vital to monitor iron content in the brain non-invasively.

PURPOSE

This study aimed to quantify in vivo brain iron concentration with a 3D rosette-based ultra-short echo time (UTE) magnetic resonance imaging (MRI) sequence.

METHODS

A cylindrical phantom containing nine vials of different iron concentrations (iron (II) chloride) from 0.5 millimoles to 50 millimoles and six healthy subjects were scanned using 3D high-resolution (0.94 ×0.94 ×0.94 mm3) rosette UTE sequence at an echo time (TE) of 20 μs.

RESULTS

Iron-related hyperintense signals (i.e., positive contrast) were detected based on the phantom scan, and were used to establish an association between iron concentration and signal intensity. The signal intensities from in vivo scans were then converted to iron concentrations based on the association. The deep brain structures, such as the substantia nigra, putamen, and globus pallidus, were highlighted after the conversion, which indicated potential iron accumulations.

CONCLUSION

This study suggested that T1-weighted signal intensity could be used for brain iron mapping.

Distribution pattern of iron deposition in the basal ganglia of different motor subtypes of Parkinson's disease

OBJECTIVE

The quantitative susceptibility mapping (QSM) technique was used to analyze the distribution pattern of iron deposition in the basal ganglia region of patients with motor subtypes of Parkinson's disease (PD) and to explore the difference in iron content in the basal ganglia region of PD motor subtypes on the major motor symptomatic side.

METHODS

The study included 76 patients with PD and 37 healthy controls (HC). Patients with PD were divided into two groups: postural instability/gait disorder (PIGD)(n = 48), and tremor dominance (TD)(n = 28). We classified patients with PD according to the side of the major motor symptoms as left PIGD (n = 23), left TD (n = 14), right PIGD (n = 25), and right TD (n = 14). All subjects underwent brain magnetic resonance scanning to obtain QSM and susceptibility values in the corresponding regions of interest (ROI).

RESULTS

(1) Compared with the HC, the bilateral SN in the PD-PIGD and TD group showed greater susceptibility values. The susceptibility values in the left CN, bilateral PUT were also greater in the PD-PIGD group than the HC. (2) Compared with the TD, the left PUT susceptibility values were greater in the PIGD group, especially in patients whose major symptomatic side were on the right limb. (3) Correlation analysis showed that in the PD group, bilateral SN was positively correlated with the unified Parkinson's disease rating scale III part scores of the Movement Disorder Society (MDS-UPDRS III) and the Hoehn-Yahr stage. Bilateral dentate nucleus (DN) susceptibility values were significantly positively correlated with TD scores, and left PUT susceptibility values were positively correlated with PIGD scores. The left SN within the PIGD group was positively correlated with the PIGD score.

CONCLUSION

There were different iron deposition patterns in the basal ganglia between the PD-PIGD and TD groups. There also seems to be a difference in iron deposition in PD motor subtypes on different major motor symptom sides.

Ellagic acid activates the Keap1-Nrf2-ARE signaling pathway in improving Parkinson's disease: A review

Parkinson's disease (PD) is a familiar neurodegenerative disease, accompanied by motor retardation, static tremor, memory decline and dementia. Heredity, environment, age and oxidative stress have been suggested as key factors in the instigation of PD. The Keap1-Nrf2-ARE signaling is one of the most significant anti- oxidative stress (OS) pathways. The Keap1 is a negative regulator of the Nrf2. The Keap1-Nrf2-ARE pathway can induce cell oxidation resistance and reduce nerve injury to treat neurodegenerative diseases. Ellagic acid (EA) can inhibit the Keap1 to accumulate the Nrf2 in the nucleus, and act on the ARE to produce target proteins, which in turn may alleviate the impact of OS on neuronal cells of PD. This review analyzes the structure and physiological role of EA, along with the structure, composition and functions of the Keap1-Nrf2-ARE signaling pathway. We further expound on the mechanism of ellagic acid in its activation of the Keap1-Nrf2-ARE signaling pathway, as well as the relationship between EA in impairing the TLR4/Myd88/NF-κB and Nrf2 pathways. Ellagic acid has the potentiality of improving PD by activating the Keap1-Nrf2-ARE signaling pathway and scavenging free radicals.

Quantitative myelin-related maps from R1 and T2* ratio images using a single ME-MP2RAGE sequence in 7T MRI

Background: There still are limitations associated with quantifying myelin content using brain magnetic resonance imaging (MRI) despite several studies conducted on this subject. Therefore, this study aimed: (1) to propose a myelin-related mapping technique to obtain the quantitative R1/T2* (q-Ratio) that has the advantage of quick processing and less dependency on imaging parameters, (2) to validate this adapted q-Ratio method by comparing the quantitative myelin-related map with those acquired through an existing mapping method [T1-weighted/T2*-weighted (w-Ratio)], and (3) to determine the q-Ratio myelin-related values in the white and gray matter, and the relationship between the q-Ratio myelin-related value and cerebral volume size in regions of interest (ROIs) in a healthy population.

Methods: The multi-echo magnetization-prepared 2 rapid gradient echoes (ME-MP2RAGE) sequence was used in a 7 Tesla (7T) MRI for the acquisition of data regarding myelin content in 10 healthy participants. A correlation analysis was performed between myelin-related values obtained through the q-Ratio and w-Ratio methods. Additionally, myelin distribution was analyzed and compared in the white and gray matter, and the correlation between cerebral volume size and q-Ratio myelin-related value was analyzed in ROIs in the brain.

Results: The myelin-related maps acquired through the q-Ratio and w-Ratio methods were significantly correlated (p < 0.001), but the q-Ratio myelin-related map was much clearer. Additionally, the cerebral volume size in the gray matter was 399.40% larger than that in the white matter, but the q-Ratio myelin-related value in the gray matter was 80.83% lower than that of the white matter. Furthermore, volume size was positively correlated with q-Ratio myelin-related values in the white matter (r = 0.509, p = 0.006) but not in the gray matter (r = -0.133, p = 0.402).

Conclusions: In this study, we validated using a q-Ratio myelin-related map that was acquired in one imaging sequence at 7T MRI. In addition, we found a significant correlation between ROI volume size and the q-Ratio myelin-related value in the white matter but not in the gray matter. It is expected that this technique could be applied to the study of various neuropsychiatric diseases related to demyelination in the future.

Elucidating the Interactions of Fluoxetine with Human Transferrin Employing Spectroscopic, Calorimetric, and In Silico Approaches: Implications of a Potent Alzheimer's Drug

Neurodegenerative complexities, such as dementia, Alzheimer's disease (AD), and so forth, have been a crucial health concern for ages. Transferrin (Tf) is a chief target to explore in AD management. Fluoxetine (FXT) presents itself as a potent anti-AD drug-like compound and has been explored against several diseases based on the drug repurposing readings. The present study delineates the binding of FXT to Tf employing structure-based docking, molecular dynamics (MD) simulations, and principal component analysis (PCA). Docking results showed the binding of FXT with Tf with an appreciable binding affinity, making various close interactions. MD simulation of FXT with Tf for 100 ns suggested their stable binding without any significant structural alteration. Furthermore, fluorescence-based binding revealed a significant interaction between FXT and Tf. FXT binds to Tf with a binding constant of 5.5 × 10⁵ M^-1. Isothermal titration calorimetry (ITC) advocated the binding of FXT to Tf as spontaneous in nature, affirming earlier observations. This work indicated plausible interactions between FXT and Tf, which are worth considering for further studies in the clinical management of neurological disorders, including AD.

The principal molecular mechanisms behind the activation of Keap1/Nrf2/ARE pathway leading to neuroprotective action in Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder. PD is associated with the loss of dopaminergic neurons in the substantia nigra pars compacta region of the midbrain. Present therapies for PD provide only symptomatic relief by restoring the dopamine (DA) level. However, they are not disease modifying agents and so they do not delay the disease progression. Alpha-synuclein aggregation, oxidative stress, mitochondrial dysfunction and chronic inflammation are considered to be the major pathological mechanisms mediating neurodegeneration in PD. To resist oxidative stress, the human body has an antioxidant defence mechanism consisting of many antioxidants and cytoprotective genes. The expression of those genes are largely controlled by the Kelch-like ECH-associated protein 1/Nuclear factor - erythroid - 2 - related factor 2/Antioxidant response element (Keap1/Nrf2/ARE) signalling pathway. The transcription factor Nrf2 is activated in response to oxidative or electrophilic stress and protects the cells from oxidative stress and inflammation. Nrf2 has been widely considered as a therapeutic target for neurodegeneration and several drugs are now being tested in clinical trials. Regulation of the Keap1/Nrf2/ARE pathway by small molecules which can act as Nrf2 activators could be effective for treating oxidative stress and neuroinflammation in PD. In this review, we had discussed the principal molecular mechanisms behind the neuroprotective effects of Keap1/Nrf2/ARE pathway in PD. Additionally, we also discussed the small molecules and phytochemicals that could activate the Nrf2 mediated anti-oxidant pathway for neuroprotection in PD.

Post-Ischemic Neurodegeneration of the Hippocampus Resembling Alzheimer's Disease Proteinopathy

In this review, we summarize, inter alia, the protein and gene changes associated with Alzheimer’s disease and their role in post-ischemic hippocampal neurodegeneration. In the hippocampus, studies have revealed dysregulation of the genes for the amyloid protein precursor metabolism and tau protein that is identical in nature to Alzheimer’s disease. Data indicate that amyloid and tau protein, derived from brain tissue and blood due to increased permeability of the blood–brain barrier after ischemia, play a key role in post-ischemic neurodegeneration of the hippocampus, with concomitant development of full-blown dementia. Thus, the knowledge of new neurodegenerative mechanisms that cause neurodegeneration of the hippocampus after ischemia, resembling Alzheimer’s disease proteinopathy, will provide the most important therapeutic development goals to date.

Posiphen Reduces the Levels of Huntingtin Protein through Translation Suppression

Posiphen tartrate (Posiphen) is an orally available small molecule that targets a conserved regulatory element in the mRNAs of amyloid precursor protein (APP) and α-synuclein (αSYN) and inhibits their translation. APP and αSYN can cause neurodegeneration when their aggregates induce neurotoxicity. Therefore, Posiphen is a promising drug candidate for neurodegenerative diseases, including Alzheimer’s disease and Parkinson’s disease. Posiphen’s safety has been demonstrated in three independent phase I clinical trials. Moreover, in a proof of concept study, Posiphen lowered neurotoxic proteins and inflammatory markers in cerebrospinal fluid of mild cognitive impaired patients. Herein we investigated whether Posiphen reduced the expression of other proteins, as assessed by stable isotope labeling with amino acids in cell culture (SILAC) followed by mass spectrometry (MS)-based proteomics. Neuroblastoma SH-SY5Y cells, an in vitro model of neuronal function, were used for the SILAC protein profiling response. Proteins whose expression was altered by Posiphen treatment were characterized for biological functions, pathways and networks analysis. The most significantly affected pathway was the Huntington’s disease signaling pathway, which, along with huntingtin (HTT) protein, was down-regulated by Posiphen in the SH-SY5Y cells. The downregulation of HTT protein by Posiphen was confirmed by quantitative Western blotting and immunofluorescence. Unchanged mRNA levels of HTT and a comparable decay rate of HTT proteins after Posiphen treatment supported the coclusion that Posiphen reduced HTT via downregulation of the translation of HTT mRNA. Meanwhile, the downregulation of APP and αSYN proteins by Posiphen was also confirmed. The mRNAs encoding HTT, APP and αSYN contain an atypical iron response element (IRE) in their 5′-untranslated regions (5′-UTRs) that bind iron regulatory protein 1 (IRP1), and Posiphen specifically bound this complex. Conversely, Posiphen did not bind the IRP1/IRE complex of mRNAs with canonical IREs, and the translation of these mRNAs was not affected by Posiphen. Taken together, Posiphen shows high affinity binding to the IRE/IRP1 complex of mRNAs with an atypical IRE stem loop, inducing their translation suppression, including the mRNAs of neurotoxic proteins APP, αSYN and HTT.

Role of metals in Alzheimer's disease

Metal homeostasis in the central nervous system (CNS) is a crucial component of healthy brain function, because metals serve as enzymatic cofactors and are key components of intra- and inter-neuronal signaling. Metal dysregulation wreaks havoc on neural networks via induction and proliferation of pathological pathways that cause oxidative stress, synaptic impairment, and ultimately, cognitive deficits. Thus, exploration of metal biology in relation to neurodegenerative pathology is essential in pursuing novel therapies for Alzheimer's Disease and other neurodegenerative disorders. This review covers mechanisms of action of aluminum, iron, copper, and zinc ions with respect to the progressive, toxic accumulation of extracellular β-amyloid plaques and intracellular hyperphosphorylated neurofibrillary tau tangles that characterizes Alzheimer's Disease, with the goal of evaluating the therapeutic potential of metal ion interference in neurodegenerative disease prevention and treatment. As neuroscientific interest in the role of metals in neurodegeneration escalates-in large part due to emerging evidence substantiating the interplay between metal imbalances and neuropathology-it becomes clear that the use of metal chelating agents may be a viable method for ameliorating Alzheimer's Disease pathology, as its etiology remains obscure. We conclude that, although metal therapies can potentially deter neurodegenerative processes, the most promising treatments will remain elusive until further understanding of neurodegenerative etiology is achieved. New research directions may best be guided by animal models of neurodegeneration, which reveal specific insights into biological mechanisms underlying dementia.

The protective, rescue and therapeutic potential of multi-target iron-chelators for retinitis pigmentosa

Retinitis pigmentosa (RP) is a group of inherited diseases in which mutations result in the initial loss of night vision, followed by complete blindness. There is currently no effective therapeutic option for RP patients. Given the extremely heterogeneous nature of RP, any causative gene-specific therapy would be practical in a small fraction of patients with RP. Non-gene-specific therapeutics that is applicable to the majority of RP patients regardless of causative mutations may have an enormous impact on RP treatment. Several theories including apoptosis, oxidative stress and neuroinflammation have been proposed as possible underlying mechanisms for photoreceptor death in RP. We have designed and synthesized a series of iron-chelating compounds that possess diverse pharmacological properties and can act in a non-gene-specific manner on multiple pathological features ascribed to Alzheimer's disease, Parkinson's disease and RP. In this review, we discuss the multiple effects of several brain-permeable multi target iron-chelating compounds on photoreceptor degeneration in a mouse model of human RP. Specifically, we focus on the anti-apototic, neuroprotective and neurorescue effects of the compound VK28, M30 and VAR10303 on the histologic and functional preservation of photoreceptors in a mouse model of RP. We consider such drugs as potential therapeutic agents for RP patients.

Extracellular protein components of amyloid plaques and their roles in Alzheimer's disease pathology

Alzheimer's disease (AD) is pathologically defined by the presence of fibrillar amyloid β (Aβ) peptide in extracellular senile plaques and tau filaments in intracellular neurofibrillary tangles. Extensive research has focused on understanding the assembly mechanisms and neurotoxic effects of Aβ during the last decades but still we only have a brief understanding of the disease associated biological processes. This review highlights the many other constituents that, beside Aβ, are accumulated in the plaques, with the focus on extracellular proteins. All living organisms rely on a delicate network of protein functionality. Deposition of significant amounts of certain proteins in insoluble inclusions will unquestionably lead to disturbances in the network, which may contribute to AD and copathology. This paper provide a comprehensive overview of extracellular proteins that have been shown to interact with Aβ and a discussion of their potential roles in AD pathology. Methods that can expand the knowledge about how the proteins are incorporated in plaques are described. Top-down methods to analyze post-mortem tissue and bottom-up approaches with the potential to provide molecular insights on the organization of plaque-like particles are compared. Finally, a network analysis of Aβ-interacting partners with enriched functional and structural key words is presented.

Ginkgolide B protects against cognitive impairment in senescence-accelerated P8 mice by mitigating oxidative stress, inflammation and ferroptosis

Alzheimer's disease (AD) is a destructive neurodegenerative disease that currently has no effective treatment option available. Ginkgolide B (GB) is a terpene lactone derivative of Ginkgo biloba that possesses neuroprotective effects in various diseases. The aim of the present study was to investigate whether GB protects against cognitive impairment in AD by mitigating oxidative stress, inflammation and ferroptosis using senescence-accelerated P8 (SAMP8) mice. The results showed that GB improved the cognitive dysfunction of SAMP8 mice in the Morris water maze and novel object recognition test, which was associated with the attenuation of oxidative stress, inflammation and nuclear factor erythroid 2-related factor 2/glutathione peroxidase 4 (GPX4) pathway-mediated ferroptosis. Furthermore, Ras-selective lethal small molecule 3, a GPX4 inhibitor and ferroptosis inducer, compromised GB-induced cognitive performance in SAMP8 mice. These findings suggested that GB alleviated AD-induced cognitive defects by mitigating oxidative stress, neuroinflammation and ferroptosis, and that the inhibition of ferroptosis is required for GB to have beneficial effects in AD.

Synthesis and Characterization of New Mesoporous Polyurethane-Nitrogen Doped Carbon Dot Nanocomposites: Ultrafast, Highly Selective and Sensitive Turn-off Fluorescent Sensors for Fe3+ Ions

A new fluorescent mesoporous polyurethane (PU) (9) was synthesized by reaction between 2,2'-(methylenebis(4,1-phenylene))bis(5-isocyanatoisoindoline-1,3-dione) (Diisocyanate) (5) and 4,4',4″-((1,3,5-triazine-2,4,6-triyl)tris (azanediyl))triphenol (Triol, TO) (8) (molar ratio 3:2). PU was characterized by using FT-IR, ¹H-NMR, XRD, UV-Vis, TGA, Nitrogen adsorption-desorption isotherm, BET, FE-SEM and Photoluminescence (PL) analyses. To the best of our knowledge, this is the first time that a fluorescent polyurethane has been made without the use of commercial fluorescent materials. PU has high fluorescent intensity and it is ultrafast (about few seconds), highly selective and sensitive turn-off fluorescent sensor for Fe³⁺ ions. This chemosensor exhibited a wide concentration range of (10-250)×10^-6 M Fe³⁺ with quenching efficiency (η) 97.50%. Limit of detection (LOD), limit of quantification (LOQ) and quenching constant (Ksv) values were calculated 10.10×10^-6 M, 30.60×10^-6 M and 6919.31 M^-1, respectively. Nitrogen doped carbon dots (N-doped CDs) as fluorescent nanoparticles and with the aim of improving Fe³⁺ detecting were synthesized by microwave-assisted and using citric acid monohydrate (10) and ethylenediamine (11) as carbon and nitrogen sources, respectively. Fluorescent nanocomposites (FNCs) were prepared by using casting and in-situ methods. In both methods, two nanocomposites containing 5 and 10%w of N-doped CDs were prepared. FNCs were characterized by using FT-IR, UV-Vis, XRD, TGA, Nitrogen adsorption-desorption isotherm, BET, FE-SEM and PL analyses. All nanocomposites showed better thermal property and sensitivity and lower LOD values in lower concentration of Fe³⁺ related to PU. Among them, FNC10in exhibited the best results as η, LOD, LOQ, Ksv reached 99.80%, 1.15×10^-6 M, 3.48×10^-6 M and 53,551.48 M^-1, respectively.

Lipocalin-2 Deficiency Reduces Oxidative Stress and Neuroinflammation and Results in Attenuation of Kainic Acid-Induced Hippocampal Cell Death

The hippocampal cell death that follows kainic acid (KA)-induced seizures is associated with blood–brain barrier (BBB) leakage and oxidative stress. Lipocalin-2 (LCN2) is an iron-trafficking protein which contributes to both oxidative stress and inflammation. However, LCN2′s role in KA-induced hippocampal cell death is not clear. Here, we examine the effect of blocking LCN2 genetically on neuroinflammation and oxidative stress in KA-induced neuronal death. LCN2 deficiency reduced neuronal cell death and BBB leakage in the KA-treated hippocampus. In addition to LCN2 upregulation in the KA-treated hippocampus, circulating LCN2 levels were significantly increased in KA-treated wild-type (WT) mice. In LCN2 knockout mice, we found that the expressions of neutrophil markers myeloperoxidase and neutrophil elastase were decreased compared to their expressions in WT mice following KA treatment. Furthermore, LCN2 deficiency also attenuated KA-induced iron overload and oxidative stress in the hippocampus. These findings indicate that LCN2 may play an important role in iron-related oxidative stress and neuroinflammation in KA-induced hippocampal cell death.

Iron Dysregulation and Inflammagens Related to Oral and Gut Health Are Central to the Development of Parkinson's Disease

Neuronal lesions in Parkinson's disease (PD) are commonly associated with α-synuclein (α-Syn)-induced cell damage that are present both in the central and peripheral nervous systems of patients, with the enteric nervous system also being especially vulnerable. Here, we bring together evidence that the development and presence of PD depends on specific sets of interlinking factors that include neuroinflammation, systemic inflammation, α-Syn-induced cell damage, vascular dysfunction, iron dysregulation, and gut and periodontal dysbiosis. We argue that there is significant evidence that bacterial inflammagens fuel this systemic inflammation, and might be central to the development of PD. We also discuss the processes whereby bacterial inflammagens may be involved in causing nucleation of proteins, including of α-Syn. Lastly, we review evidence that iron chelation, pre-and probiotics, as well as antibiotics and faecal transplant treatment might be valuable treatments in PD. A most important consideration, however, is that these therapeutic options need to be validated and tested in randomized controlled clinical trials. However, targeting underlying mechanisms of PD, including gut dysbiosis and iron toxicity, have potentially opened up possibilities of a wide variety of novel treatments, which may relieve the characteristic motor and nonmotor deficits of PD, and may even slow the progression and/or accompanying gut-related conditions of the disease.

A Mechanistic Evaluation of Antioxidant Nutraceuticals on Their Potential against Age-Associated Neurodegenerative Diseases

Nutraceuticals have been extensively studied worldwide due to its neuroprotective effects in in vivo and in vitro studies, attributed by the antioxidative properties. Alzheimer (AD) and Parkinson disease (PD) are the two main neurodegenerative disorders that are discussed in this review. Both AD and PD share the similar involvement of oxidative stress in their pathophysiology. Nutraceuticals exert their antioxidative effects via direct scavenging of free radicals, prevent damage to biomolecules, indirectly stimulate the endogenous antioxidative enzymes and gene expressions, inhibit activation of pro-oxidant enzymes, and chelate metals. In addition, nutraceuticals can act as modulators of pro-survival, pro-apoptotic, and inflammatory signaling pathways. They have been shown to be effective particularly in preclinical stages, due to their multiple mechanisms of action in attenuating oxidative stress underlying AD and PD. Natural antioxidants from food sources and natural products such as resveratrol, curcumin, green tea polyphenols, and vitamin E are promising therapeutic agents in oxidative stress-mediated neurodegenerative disease as they have fewer adverse effects, more tolerable, cheaper, and sustainable for long term consumption.

The Links between Parkinson's Disease and Cancer

Epidemiologic studies indicate a decreased incidence of most cancer types in Parkinson’s disease (PD) patients. However, some neoplasms are associated with a higher risk of occurrence in PD patients. Both pathologies share some common biological pathways. Although the etiologies of PD and cancer are multifactorial, some factors associated with PD, such as α-synuclein aggregation; mutations of PINK1, PARKIN, and DJ-1; mitochondrial dysfunction; and oxidative stress can also be involved in cancer proliferation or cancer suppression. The main protein associated with PD, i.e., α-synuclein, can be involved in some types of neoplastic formations. On the other hand, however, its downregulation has been found in the other cancers. PINK1 can act as oncogenic or a tumor suppressor. PARKIN dysfunction may lead to some cancers’ growth, and its expression may be associated with some tumors’ suppression. DJ-1 mutation is involved in PD pathogenesis, but its increased expression was found in some neoplasms, such as melanoma or breast, lung, colorectal, uterine, hepatocellular, and nasopharyngeal cancers. Both mitochondrial dysfunction and oxidative stress are involved in PD and cancer development. The aim of this review is to summarize the possible associations between PD and carcinogenesis.

Oxidative Stress-Mediated Blood-Brain Barrier (BBB) Disruption in Neurological Diseases

The blood-brain barrier (BBB), as a crucial gate of brain-blood molecular exchange, is involved in the pathogenesis of multiple neurological diseases. Oxidative stress is caused by an imbalance between the production of reactive oxygen species (ROS) and the scavenger system. Since oxidative stress plays a significant role in the production and maintenance of the BBB, the cerebrovascular system is especially vulnerable to it. The pathways that initiate BBB dysfunction include, but are not limited to, mitochondrial dysfunction, excitotoxicity, iron metabolism, cytokines, pyroptosis, and necroptosis, all converging on the generation of ROS. Interestingly, ROS also provide common triggers that directly regulate BBB damage, parameters including tight junction (TJ) modifications, transporters, matrix metalloproteinase (MMP) activation, inflammatory responses, and autophagy. We will discuss the role of oxidative stress-mediated BBB disruption in neurological diseases, such as hemorrhagic stroke, ischemic stroke (IS), Alzheimer’s disease (AD), Parkinson’s disease (PD), traumatic brain injury (TBI), amyotrophic lateral sclerosis (ALS), and cerebral small vessel disease (CSVD). This review will also discuss the latest clinical evidence of potential biomarkers and antioxidant drugs towards oxidative stress in neurological diseases. A deeper understanding of how oxidative stress damages BBB may open up more therapeutic options for the treatment of neurological diseases.

Differential methylation and expression of genes in the hypoxia-inducible factor 1 signaling pathway are associated with paclitaxel-induced peripheral neuropathy in breast cancer survivors and with preclinical models of chemotherapy-induced neuropathic pain

BACKGROUND

Paclitaxel is an important chemotherapeutic agent for the treatment of breast cancer. Paclitaxel-induced peripheral neuropathy (PIPN) is a major dose-limiting toxicity that can persist into survivorship. While not all survivors develop PIPN, for those who do, it has a substantial negative impact on their functional status and quality of life. No interventions are available to treat PIPN. In our previous studies, we identified that the HIF-1 signaling pathway (H1SP) was perturbed between breast cancer survivors with and without PIPN. Preclinical studies suggest that the H1SP is involved in the development of bortezomib-induced and diabetic peripheral neuropathy, and sciatic nerve injury. The purpose of this study was to identify H1SP genes that have both differential methylation and differential gene expression between breast cancer survivors with and without PIPN.

METHODS

A multi-staged integrated analysis was performed. In peripheral blood, methylation was assayed using microarray and gene expression was assayed using RNA-seq. Candidate genes in the H1SP having both differentially methylation and differential expression were identified between survivors who received paclitaxel and did (n = 25) and did not (n = 25) develop PIPN. Then, candidate genes were evaluated for differential methylation and differential expression in public data sets of preclinical models of PIPN and sciatic nerve injury.

RESULTS

Eight candidate genes were identified as both differential methylation and differential expression in survivors. Of the eight homologs identified, one was found to be differential expression in both PIPN and "normal" mice dorsal root ganglia; three were differential methylation in sciatic nerve injury versus sham rats in both pre-frontal cortex and T-cells; and two were differential methylation in sciatic nerve injury versus sham rats in the pre-frontal cortex.

CONCLUSIONS

This study is the first to evaluate for methylation in cancer survivors with chronic PIPN. The findings provide evidence that the expression of H1SP genes associated with chronic PIPN in cancer survivors may be regulated by epigenetic mechanisms and suggests genes for validation as potential therapeutic targets.

Visualization of Nigrosome 1 from the Viewpoint of Anatomic Structure

BACKGROUND AND PURPOSE

Parkinson disease is related to neurodegeneration and iron deposition in the substantia nigra pars compacta and nigrosome 1. However, visualization of nigrosome 1 via MR imaging is poor owing to the bilateral asymmetry, regardless of whether it is healthy. We focused on the magic angle and susceptibility effect and evaluated the anatomic slant structure of nigrosome 1 by tilting subjects' heads in the B₀ direction.

MATERIALS AND METHODS

To investigate the effectiveness of the magic angle, we tilted the volunteers' heads to the right and left in the B₀ direction or not at all for evaluating correlations between the degree of head tilting and visualization of the right nigrosome 1 and left nigrosome 1 using 3D spoiled gradient-echo sequences with multiecho acquisitions. We evaluated the susceptibility of nigrosome 1 and the local field using quantitative susceptibility mapping to assess static magnetic field inhomogeneity.

RESULTS

The heads tilted to the right and left showed significantly higher contrasts of nigrosome 1 and the substantia nigra pars compacta than the nontilted heads. No significant differences were observed in the visualization and susceptibility between the right nigrosome 1 and left nigrosome 1 for each head tilt. The effect of the magic angle was remarkable in the nontilted heads. This finding was supported by quantitative susceptibility mapping because the anatomic slant structure of nigrosome 1 was coherent between the axis of nigrosome 1 and the magic angle.

CONCLUSIONS

The asymmetric visualization of nigrosome 1 is affected by the magic angle and susceptibility. The anatomic slant structure of nigrosome 1 causes these challenges in visualization.

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.

Early Stage Glycosylation Biomarkers in Alzheimer's Disease

Alzheimer's disease (AD) is of great cause for concern in our ageing population, which currently lacks diagnostic tools to permit accurate and timely diagnosis for affected individuals. The development of such tools could enable therapeutic interventions earlier in the disease course and thus potentially reducing the debilitating effects of AD. Glycosylation is a common, and important, post translational modification of proteins implicated in a host of disease states resulting in a complex array of glycans being incorporated into biomolecules. Recent investigations of glycan profiles, in a wide range of conditions, has been made possible due to technological advances in the field enabling accurate glycoanalyses. Amyloid beta (Aβ) peptides, tau protein, and other important proteins involved in AD pathogenesis, have altered glycosylation profiles. Crucially, these abnormalities present early in the disease state, are present in the peripheral blood, and help to distinguish AD from other dementias. This review describes the aberrant glycome in AD, focusing on proteins implicated in development and progression, and elucidates the potential of glycome aberrations as early stage biomarkers of AD.

History and progress of hypotheses and clinical trials for Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive memory loss along with neuropsychiatric symptoms and a decline in activities of daily life. Its main pathological features are cerebral atrophy, amyloid plaques, and neurofibrillary tangles in the brains of patients. There are various descriptive hypotheses regarding the causes of AD, including the cholinergic hypothesis, amyloid hypothesis, tau propagation hypothesis, mitochondrial cascade hypothesis, calcium homeostasis hypothesis, neurovascular hypothesis, inflammatory hypothesis, metal ion hypothesis, and lymphatic system hypothesis. However, the ultimate etiology of AD remains obscure. In this review, we discuss the main hypotheses of AD and related clinical trials. Wealthy puzzles and lessons have made it possible to develop explanatory theories and identify potential strategies for therapeutic interventions for AD. The combination of hypometabolism and autophagy deficiency is likely to be a causative factor for AD. We further propose that fluoxetine, a selective serotonin reuptake inhibitor, has the potential to treat AD.

Noxious Iron-Calcium Connections in Neurodegeneration

Iron and calcium share the common feature of being essential for normal neuronal function. Iron is required for mitochondrial function, synaptic plasticity, and the development of cognitive functions whereas cellular calcium signals mediate neurotransmitter exocytosis, axonal growth and synaptic plasticity, and control the expression of genes involved in learning and memory processes. Recent studies have revealed that cellular iron stimulates calcium signaling, leading to downstream activation of kinase cascades engaged in synaptic plasticity. The relationship between calcium and iron is Janus-faced, however. While under physiological conditions iron-mediated reactive oxygen species generation boosts normal calcium-dependent signaling pathways, excessive iron levels promote oxidative stress leading to the upsurge of unrestrained calcium signals that damage mitochondrial function, among other downstream targets. Similarly, increases in mitochondrial calcium to non-physiological levels result in mitochondrial dysfunction and a predicted loss of iron homeostasis. Hence, if uncontrolled, the iron/calcium self-feeding cycle becomes deleterious to neuronal function, leading eventually to neuronal death. Here, we review the multiple cell-damaging responses generated by the unregulated iron/calcium self-feeding cycle, such as excitotoxicity, free radical-mediated lipid peroxidation, and the oxidative modification of crucial components of iron and calcium homeostasis/signaling: the iron transporter DMT1, plasma membrane, and intracellular calcium channels and pumps. We discuss also how iron-induced dysregulation of mitochondrial calcium contributes to the generation of neurodegenerative conditions, including Alzheimer’s disease (AD) and Parkinson’s disease (PD).

Antioxidant and Neuroprotective Potential of the Brown Seaweed Bifurcaria bifurcata in an in vitro Parkinson's Disease Model

Bifurcaria bifurcata is a marine brown seaweed mainly found on the Atlantic coast. Herein, we report the antioxidant and neuroprotective activities of seven fractions (F1⁻F7) obtained by normal phase chromatography from the B. bifurcata dichloromethane extract, as well as of its two major isolated diterpenes. Total phenolic content of fractions was determined by the Folin⁻Ciocalteu method, while antioxidant activity was evaluated by the DPPH, ORAC, and FRAP assays. Neuroprotective effects were evaluated in a neurotoxic model induced by 6-hydroxydopamine (6-OHDA) in a human neuroblastoma cell line (SH-SY5Y), while the mechanisms associated to neuroprotection were investigated by the determination of mitochondrial membrane potential, H₂O₂ production, Caspase-3 activity, and by observation of DNA fragmentation. Fractions F4 and F5 exhibited the best neuroprotective and antioxidant activities, respectively. F4 fraction prevented changes in mitochondrial potential, and induced a reduction of H₂O₂ levels production and an increase in cell viability, suggesting that it may contain multi-target compounds acting on different pathways. Hence, this fraction was subjected to purification steps, affording the known diterpenes eleganolone and eleganonal. Both compounds exhibited antioxidant potential, being interesting candidates for further neuroprotective studies.

No effects without causes: the Iron Dysregulation and Dormant Microbes hypothesis for chronic, inflammatory diseases

Since the successful conquest of many acute, communicable (infectious) diseases through the use of vaccines and antibiotics, the currently most prevalent diseases are chronic and progressive in nature, and are all accompanied by inflammation. These diseases include neurodegenerative (e.g. Alzheimer's, Parkinson's), vascular (e.g. atherosclerosis, pre-eclampsia, type 2 diabetes) and autoimmune (e.g. rheumatoid arthritis and multiple sclerosis) diseases that may appear to have little in common. In fact they all share significant features, in particular chronic inflammation and its attendant inflammatory cytokines. Such effects do not happen without underlying and initially 'external' causes, and it is of interest to seek these causes. Taking a systems approach, we argue that these causes include (i) stress-induced iron dysregulation, and (ii) its ability to awaken dormant, non-replicating microbes with which the host has become infected. Other external causes may be dietary. Such microbes are capable of shedding small, but functionally significant amounts of highly inflammagenic molecules such as lipopolysaccharide and lipoteichoic acid. Sequelae include significant coagulopathies, not least the recently discovered amyloidogenic clotting of blood, leading to cell death and the release of further inflammagens. The extensive evidence discussed here implies, as was found with ulcers, that almost all chronic, infectious diseases do in fact harbour a microbial component. What differs is simply the microbes and the anatomical location from and at which they exert damage. This analysis offers novel avenues for diagnosis and treatment.

Oxidative stress and neurodegeneration: the involvement of iron

Many evidences indicate that oxidative stress plays a significant role in a variety of human disease states, including neurodegenerative diseases. Iron is an essential metal for almost all living organisms due to its involvement in a large number of iron-containing proteins and enzymes, though it could be also toxic. Actually, free iron excess generates oxidative stress, particularly in brain, where anti-oxidative defences are relatively low. Its accumulation in specific regions is associated with pathogenesis in a variety of neurodegenerative diseases (i.e., Parkinson's disease, Alzheimer's disease, Huntington's chorea, Amyotrophic Lateral Sclerosis and Neurodegeneration with Brain Iron Accumulation). Anyway, the extent of toxicity is dictated, in part, by the localization of the iron complex within the cell (cytosolic, lysosomal and mitochondrial), its biochemical form, i.e., ferritin or hemosiderin, as well as the ability of the cell to prevent the generation and propagation of free radical by the wide range of antioxidants and cytoprotective enzymes in the cell. Particularly, ferrous iron can act as a catalyst in the Fenton reaction that potentiates oxygen toxicity by generating a wide range of free radical species, including hydroxyl radicals (·OH). The observation that patients with neurodegenerative diseases show a dramatic increase in their brain iron content, correlated with the production of reactive oxigen species in these areas of the brain, conceivably suggests that disturbances in brain iron homeostasis may contribute to the pathogenesis of these disorders. The aim of this review is to describe the chemical features of iron in human beings and iron induced toxicity in neurodegenerative diseases. Furthermore, the attention is focused on metal chelating drugs therapeutic strategies.

α-Lipoic acid improves abnormal behavior by mitigation of oxidative stress, inflammation, ferroptosis, and tauopathy in P301S Tau transgenic mice

Alzheimer's disease (AD) is the most common neurodegenerative disease and is characterized by neurofibrillary tangles (NFTs) composed of Tau protein. α-Lipoic acid (LA) has been found to stabilize the cognitive function of AD patients, and animal study findings have confirmed its anti-amyloidogenic properties. However, the underlying mechanisms remain unclear, especially with respect to the ability of LA to control Tau pathology and neuronal damage. Here, we found that LA supplementation effectively inhibited the hyperphosphorylation of Tau at several AD-related sites, accompanied by reduced cognitive decline in P301S Tau transgenic mice. Furthermore, we found that LA not only inhibited the activity of calpain1, which has been associated with tauopathy development and neurodegeneration via modulating the activity of several kinases, but also significantly decreased the calcium content of brain tissue in LA-treated mice. Next, we screened for various modes of neural cell death in the brain tissue of LA-treated mice. We found that caspase-dependent apoptosis was potently inhibited, whereas autophagy did not show significant changes after LA supplementation. Interestingly, Tau-induced iron overload, lipid peroxidation, and inflammation, which are involved in ferroptosis, were significantly blocked by LA administration. These results provide compelling evidence that LA plays a role in inhibiting Tau hyperphosphorylation and neuronal loss, including ferroptosis, through several pathways, suggesting that LA may be a potential therapy for tauopathies.

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Hyperphosphorylated Tau induces iron overload, lipid peroxidation, and inflammation.

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LA inhibits Tau hyperphosphorylation and neuronal loss including ferroptosis.

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LA ameliorated tauopathy via modulating the activity of calpain1 and several kinases.

Differential Effect of Acute Iron Overload on Oxidative Status and Antioxidant Content in Regions of Rat Brain

The hypothesis of this study is that the cerebral cortex, hippocampus, and striatum of the rat brain are differentially affected in terms of oxidative stress and antioxidant capacity by acute Fe overload because Fe is distributed in a heterogeneous fashion among different regions and cells of the brain. The effects on the lipophilic and hydrophilic cellular environment were compared between regions and with the whole brain. A single dose of Fe-dextran increased Fe deposits, reaching a maximum after 6 hr. Both in whole brain and in cortex region, the ascorbyl/ascorbate content ratio was increased after 6 hr of Fe administration, while in striatum and hippocampus, there was no significant changes after Fe overload. Total thiol content decreased in whole brain and cortex, while there were no significant changes in striatum and hippocampus after Fe overload. The content of α-tocopherol (α-T), whether measured in the whole brain or in the isolated regions, did not change following Fe treatment. Lipid radical (LR•) generation rate after Fe-dextran overload only increased in the cortex region. The LR•/α-T content ratio was increased by Fe treatment in cortex but not in the whole brain, striatum, or hippocampus, in agreement with the study tested hypothesis.

Iron overload and altered iron metabolism in ovarian cancer

Iron is an essential element required for many processes within the cell. Dysregulation in iron homeostasis due to iron overload is detrimental. This nutrient is postulated to contribute to the initiation of cancer; however, the mechanisms by which this occurs remain unclear. Defining how iron promotes the development of ovarian cancers from precursor lesions is essential for developing novel therapeutic strategies. In this review, we discuss (1) how iron overload conditions may initiate ovarian cancer development, (2) dysregulated iron metabolism in cancers, (3) the interplay between bacteria, iron, and cancer, and (4) chemotherapeutic strategies targeting iron metabolism in cancer patients.

In vivo evaluation of microglia activation by intracranial iron overload in central pain after spinal cord injury

Background

Central pain (CP) is a common clinical problem in patients with spinal cord injury (SCI). Recent studies found the pathogenesis of CP was related to the remodeling of the brain. We investigate the roles of iron overload and subsequent microglia activate in the remodeling of the brain after SCI.

Methods

An SCI-induced CP model was established in Sprague-Dawley rats that were randomly assigned to SCI, sham operation, deferoxamine (DFX), minocycline, and nitric oxide synthase inhibitor treatment groups. At 12 weeks, pain behavior and thermal pain threshold were evaluated in each group, and iron transferrin receptor (TfR)1 and ferritin (Fn) mRNA, as well as iron-regulatory protein (IRP)1, FN, lactoferrin, and nuclear factor (NF)-κB protein levels in the rat brains were measured. Microglia proliferation and differentiation and IRP1 expression were evaluated by immunohistochemistry.

Results

Autophagy was observed in rats after SCI, accompanied by reduced latency of thermal pain, increased iron content and IRP1 and NF-κB levels in the hindlimb sensory area, hippocampus, and thalamus, and decreased Fn levels in the hindlimb sensory area. TfR1 mRNA expression was upregulated in activated microglia. Treatment with an iron-chelating agent, or inhibitors of nitric oxide synthase or microglia suppressed microglia proliferation.

Conclusions

SCI may induce intracranial iron overload, which activates microglia via NF-κB signaling. Microglia secrete inflammatory factors that induce neuronal damage and lead to CP. Treatment with an iron-chelating agent or NF-κB or microglia inhibitors can relieve CP resulting from SCI.

Structural and functional quantitative susceptibility mapping from standard fMRI studies

Standard functional MRI (fMRI), which includes resting-state or paradigm-driven designs, is widely used in studies of brain function, aging, and disease. These fMRI studies typically use two-dimensional gradient echo-planar imaging, which inherently contains phase data that enables quantitative susceptibility mapping (QSM). This work focuses on the dual value of QSM within fMRI studies, by providing both a localized analysis of functional changes in activated tissue, and iron-sensitive structural maps in deep grey matter (DGM). Using a visual paradigm fMRI study on healthy volunteers at clinical (1.5 T) and high field strength (4.7 T), we perform functional analysis of magnitude and QSM time series, and at the same time harness structural QSM of iron-rich DGM, including globus pallidus, putamen, caudate head, substantia nigra, and red nucleus. The effects of fMRI spatial resolution and time series variation on structural DGM QSM are investigated. Our results indicate that structural DGM QSM is feasible within existing fMRI studies, provided that the voxel dimensions are equal to or less than 3 mm, with higher resolutions preferred. The mean DGM QSM values were about 40 to 220 ppb, while the interquartile ranges of the DGM QSM time series varied from about 3 to 9 ppb, depending on structure and resolution. In contrast, the peak voxel functional QSM (fQSM) changes in activated visual cortex ranged from about -10 to -30 ppb, and functional clusters were consistently smaller on QSM than magnitude fMRI. Mean-level DGM QSM of the time series was successfully extracted in all cases, while fQSM results were more prone to residual background fields and showed less functional change compared with standard magnitude fMRI. Under the conditions prescribed, standard fMRI studies may be used for robust mean-level DGM QSM, enabling study of DGM iron accumulation, in addition to functional analysis. Copyright © 2016 John Wiley & Sons, Ltd.

Iron quantification with susceptibility

Iron is an essential trace element involved in a variety of biological mechanisms in the human body. Disturbances of iron homeostasis have been observed in several inflammatory and degenerative diseases, which have raised strong interest in non-invasive iron mapping techniques. Numerous MRI techniques have been proposed so far, mostly based on the field changes induced by the magnetic properties of iron. Each of these approaches has a specific sensitivity for iron and its microstructural environment. Quantitative susceptibility mapping is the latest development and provides a direct measure of bulk susceptibility. However, field changes induced by iron are not always directly related to the concentration of iron, but rather reflect the structure of iron compounds and its cellular distribution. This review provides an overview of the most relevant iron compounds in the human body, their magnetic properties and their cellular distribution. In addition, MRI methods based on direct or indirect susceptibility changes are presented and discussed with respect to technical aspects and clinical applicability. Copyright © 2016 John Wiley & Sons, Ltd.

Methods for the computation of templates from quantitative magnetic susceptibility maps (QSM): Toward improved atlas- and voxel-based analyses (VBA)

PURPOSE

To develop and assess a method for the creation of templates for voxel-based analysis (VBA) and atlas-based approaches using quantitative magnetic susceptibility mapping (QSM).

MATERIALS AND METHODS

We studied four strategies for the creation of magnetic susceptibility brain templates, derived as successive extensions of the conventional template generation (CONV) based on only T₁ -weighted (T₁ w) images. One method that used only T₁ w images involved a minor improvement of CONV (U-CONV). One method used only magnetic susceptibility maps as input for template generation (DIRECT), and the other two used a linear combination of susceptibility and T₁ w images (HYBRID) and an algorithm that directly used both image modalities (MULTI), respectively. The strategies were evaluated in a group of N = 10 healthy human subjects and semiquantitatively assessed by three experienced raters. Template quality was compared statistically via worth estimates (WEs) obtained with a log-linear Bradley-Terry model.

RESULTS

The overall quality of the templates was better for strategies including both susceptibility and T₁ w contrast (MULTI: WE = 0.62; HYBRID: WE = 0.21), but the best method depended on the anatomical region of interest. While methods using only one modality resulted in lower WEs, lowest overall WEs were obtained when only T₁ w images were used (DIRECT: WE = 0.12; U-CONV: WE = 0.05).

CONCLUSION

Template generation strategies that employ only magnetic susceptibility contrast or both magnetic susceptibility and T₁ w contrast produce templates with the highest quality. The optimal approach depends on the anatomical structures of interest. The established approach of using only T₁ w images (CONV) results in reduced image quality compared to all other approaches studied.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2017;46:1474-1484.

Effect of oxidative stress induced by intracranial iron overload on central pain after spinal cord injury

BACKGROUND

Central pain (CP) is a common clinical problem in patients with spinal cord injury (SCI). Recent studies found the pathogenesis of CP was related to the remodeling of the brain. We investigate the roles of iron overload and subsequent oxidative stress in the remodeling of the brain after SCI.

METHODS

We established a rat model of central pain after SCI. Rats were divided randomly into four groups: SCI, sham operation, SCI plus deferoxamine (DFX) intervention, and SCI plus nitric oxide synthase (NOS) inhibitor treatment. Pain behavior was observed and thermal pain threshold was measured regularly, and brain levels of iron, transferrin receptor 1 (TfR1), ferritin (Fn), and lactoferrin (Lf), were detected in the different groups 12 weeks after establishment of the model.

RESULTS

Rats demonstrated self-biting behavior after SCI. Furthermore, the latent period of thermal pain was reduced and iron levels in the hind limb sensory area, hippocampus, and thalamus increased after SCI. Iron-regulatory protein (IRP) 1 levels increased in the hind limb sensory area, while Fn levels decreased. TfR1 mRNA levels were also increased and oxidative stress was activated. Oxidative stress could be inhibited by ferric iron chelators and NOS inhibitors.

CONCLUSIONS

SCI may cause intracranial iron overload through the NOS-iron-responsive element/IRP pathway, resulting in central pain mediated by the oxidative stress response. Iron chelators and oxidative stress inhibitors can effectively relieve SCI-associated central pain.

Neurodegeneration Induced by Metals in Caenorhabditis elegans

Metals are a component of a variety of ecosystems and organisms. They can generally be divided into essential and nonessential metals. The essential metals are involved in physiological processes once the deficiency of these metals has been associated with diseases. Although iron, manganese, copper, and zinc are important for life, it has been evidenced that they are also involved in neuronal damage in many neurodegenerative disorders. Nonessential metals, which are metals without physiological functions, are present in trace or higher levels in living organisms. Occupational, environmental, or deliberate exposures to lead, mercury, aluminum, and cadmium are clearly correlated with the increase of toxicity and varied kinds of pathological situations. Actually, the field of neurotoxicology needs to satisfy two opposing demands: the testing of a growing list of chemicals and resource limitations and ethical concerns associated with testing using traditional mammalian species. Toxicological assays using alternative animal models may relieve some of this pressure by allowing testing of more compounds while reducing expenses and using fewer mammals. The nervous system is by far the more complex system in C. elegans. Almost a third of their cells are neurons (302 neurons versus 959 cells in adult hermaphrodite). It initially underwent extensive development as a model organism in order to study the nervous system, and its neuronal lineage and the complete wiring diagram of its nervous system are stereotyped and fully described. The neurotransmission systems are phylogenetically conserved from nematodes to vertebrates, which allows for findings from C. elegans to be extrapolated and further confirmed in vertebrate systems. Different strains of C. elegans offer a new perspective on neurodegenerative processes. Some genes have been found to be related to neurodegeneration induced by metals. Studying these interactions may be an effective tool to slow neuronal loss and deterioration.

Inversion recovery ultrashort echo time magnetic resonance imaging: A method for simultaneous direct detection of myelin and high signal demonstration of iron deposition in the brain - A feasibility study

Multiple sclerosis (MS) causes demyelinating lesions in the white matter and increased iron deposition in the subcortical gray matter. Myelin protons have an extremely short T2* (<1ms) and are not directly detected with conventional clinical magnetic resonance (MR) imaging sequences. Iron deposition also reduces T2*, leading to reduced signal on clinical sequences. In this study we tested the hypothesis that the inversion recovery ultrashort echo time (IR-UTE) pulse sequence can directly and simultaneously image myelin and iron deposition using a clinical 3T scanner. The technique was first validated on a synthetic myelin phantom (myelin powder in D₂O) and a Feridex iron phantom. This was followed by studies of cadaveric MS specimens, healthy volunteers and MS patients. UTE imaging of the synthetic myelin phantom showed an excellent bi-component signal decay with two populations of protons, one with a T2* of 1.2ms (residual water protons) and the other with a T2* of 290μs (myelin protons). IR-UTE imaging shows sensitivity to a wide range of iron concentrations from 0.5 to ~30mM. The IR-UTE signal from white matter of the brain of healthy volunteers shows a rapid signal decay with a short T2* of ~300μs, consistent with the T2* values of myelin protons in the synthetic myelin phantom. IR-UTE imaging in MS brain specimens and patients showed multiple white matter lesions as well as areas of high signal in subcortical gray matter. This in specimens corresponded in position to Perl's diaminobenzide staining results, consistent with increased iron deposition. IR-UTE imaging simultaneously detects lesions with myelin loss in the white matter and iron deposition in the gray matter.

Quantitative Susceptibility Mapping in Parkinson's Disease

BACKGROUND

Quantitative susceptibility mapping (QSM) and R2* relaxation rate mapping have demonstrated increased iron deposition in the substantia nigra of patients with idiopathic Parkinson's disease (PD). However, the findings in other subcortical deep gray matter nuclei are converse and the sensitivity of QSM and R2* for morphological changes and their relation to clinical measures of disease severity has so far been investigated only sparsely.

METHODS

The local ethics committee approved this study and all subjects gave written informed consent. 66 patients with idiopathic Parkinson's disease and 58 control subjects underwent quantitative MRI at 3T. Susceptibility and R2* maps were reconstructed from a spoiled multi-echo 3D gradient echo sequence. Mean susceptibilities and R2* rates were measured in subcortical deep gray matter nuclei and compared between patients with PD and controls as well as related to clinical variables.

RESULTS

Compared to control subjects, patients with PD had increased R2* values in the substantia nigra. QSM also showed higher susceptibilities in patients with PD in substantia nigra, in the nucleus ruber, thalamus, and globus pallidus. Magnetic susceptibility of several of these structures was correlated with the levodopa-equivalent daily dose (LEDD) and clinical markers of motor and non-motor disease severity (total MDS-UPDRS, MDS-UPDRS-I and II). Disease severity as assessed by the Hoehn & Yahr scale was correlated with magnetic susceptibility in the substantia nigra.

CONCLUSION

The established finding of higher R2* rates in the substantia nigra was extended by QSM showing superior sensitivity for PD-related tissue changes in nigrostriatal dopaminergic pathways. QSM additionally reflected the levodopa-dosage and disease severity. These results suggest a more widespread pathologic involvement and QSM as a novel means for its investigation, more sensitive than current MRI techniques.

Iron accumulation in the basal ganglia in Huntington's disease: cross-sectional data from the IMAGE-HD study

OBJECTIVES

To measure iron accumulation in the basal ganglia in Huntington's disease (HD) using quantitative susceptibility mapping (QSM), and to ascertain its relevance in terms of clinical and disease severity.

METHODS

In this cross-sectional investigation, T2* weighted imaging was undertaken on 31 premanifest HD, 32 symptomatic HD and 30 control participants as part of the observational IMAGE-HD study. Group differences in iron accumulation were ascertained with QSM. Associations between susceptibility values and disease severity were also investigated.

RESULTS

Compared with controls, both premanifest and symptomatic HD groups showed significantly greater iron content in pallidum, putamen and caudate. Additionally, iron accumulation in both putamen and caudate was significantly associated with disease severity.

CONCLUSIONS

These findings provide the first evidence that QSM is sensitive to iron deposition in subcortical target areas across premanifest and symptomatic stages of HD. Such findings could open up new avenues for biomarker development and therapeutic intervention.