Quantitative MRI and laser ablation-inductively coupled plasma-mass spectrometry imaging of iron in the frontal cortex of healthy controls and Alzheimer's disease patients

Neuro Imaging Researc

Promises and Pitfalls of Metal Imaging in Biology

A picture may speak a thousand words, but if those words fail to form a coherent sentence there is little to be learned. As cutting-edge imaging technology now provides us the tools to decipher the multitude of roles played by metals and metalloids in molecular, cellular and developmental biology, as well as health and disease, it is time to reflect on the advances made in imaging, the limitations discovered, and the future of a burgeoning field. In this Perspective, the current state-of-the-art is discussed from a self-imposed contrarian position, as we not only highlight the major advances made of the years but use them as teachable moments to zoom in on challenges that remain to be overcome. We also describe the steps being taken towards being able to paint a completely undisturbed picture of cellular metal metabolism, which is, metaphorically speaking, the Holy Grail of the discipline

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Department of Biomedical EngineeringIn the brain, iron is an essential element in oxygen supply through blood vessels, energy metabolism, myelin formation, and neurotransmitter synthesis for brain development with maintaining homeostasis. However, even in healthy people, as they grow older, iron levels increase steadily in some regions of the brain. Among the inevitable iron deposits with aging, the unbound labile iron generates reactive oxygen and free radicals, which produce stress on the brain tissue and necrosis of cells, which are closely associated with neurodegenerative diseases. These finally promote neurodegenerative diseases, including Parkinson???s disease and Alzheimer???s disease, which accompany the damage in behavior and cognitive function. Therefore, developing magnetic resonance imaging-based biomarkers to detect various iron clusters deposited in the brain is crucial work for diagnosing and monitoring related diseases. However, it???s still impossible to classify the states of iron and separate the various forms of iron deposited in the brain. The aim of this study was to develop multi-color iron magnetic resonance imaging and the investigation of its in vivo feasibility through translation research from the preclinical trials including postmortem magnetic resonance imaging with histopathological validation to clinical application. In the first section, it was discovered that the neuromelanin pigment within the human substantia nigra is only sensitive to T2* than other magnetic resonance contrast due to its paramagnetic property. Subsequently, the technique for specific visualization of neuromelanin-iron clusters in postmortem substantia nigra tissue was developed using combined T2 and T2* (T2*/T2 or T2*/T22) with histopathological validation supported by the Monte Carlo simulation. Separate segmentations of the areas of iron detected in the T2 map and neuromelanin observed in the T2*/T2 map (or T2*/T22 map) were available within the substantia nigra. The dorsal linear mismatch of T2 and T2* was consistently detected in the brains of healthy controls. However, it was shortened in the diseased brains. In vivo feasibility and implication of developed technique as a clinical biomarker were quantitatively demonstrated in the patients of Parkinson???s disease compared to healthy subjects. In the second section, the iron deposition along the myelinated fiber of white matter was identified in the diseased brains. The iron-rich white matter at the frontal subcortical area contributes to the positive susceptibility in the patients of Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia. Susceptibility-weighted imaging presented the noticeable phase signal showing the tree-like structure in the white matter of the frontal brain, with striking atrophy. This kind of rare tissue contrast in susceptibility-weighted imaging can aid to define Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia. Besides, the deposited iron was verified on the myelinated fibers of the 3rd cranial nerve, which is the oculomotor nerve within the brain of progressive supranuclear palsy. Our results demonstrated the enhanced magnetic resonance susceptibility value between the area of substantia nigra and red nucleus shown in the brain of progressive supranuclear palsy derives from exaggerated iron concentration on the myelinated fibers of the nerves between two structures. In conclusion, the developed techniques of multi-color iron magnetic resonance imaging in this thesis can be useful imaging biomarkers to evaluate the progressive change of several iron-related neurodegenerative diseases, such as Perry syndrome, progressive supranuclear palsy, Parkinson???s disease, and Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia. The advanced research will be implemented to validate the alteration of magnetic resonance signal with the presence of iron molecules chelated to beta-amyloid or tau with Alzheimer???s disease progression.ope

Air pollution, nanotoxicity and neurodegeneration; exploring the relationship between environmental metallic nanoparticles and human health

Air pollution and Alzheimer’s disease (AD) are two of the largest global health issues faced by society today; air pollution is a recognised risk factor for AD. Particulate matter (PM) is a major component of air pollution and refers to the solid and liquid particulates of varying sizes and compositions that are resuspended in the air. Of these particles, metallic particles in the nanometre range (ultrafine, UFPs; < 0.1 µm) are particularly hazardous due to their pervasiveness, ability to penetrate all major organs in the human body, and ability to generate both inflammatory and oxidative stress responses in humans. Magnetite (Fe3O4) nanoparticles (MNPs) and related iron oxides may be of relevance to neurodegeneration. MNPs are found within PM, typically in association with toxic metals, and have been found throughout the human brain, including in association with senile plaques (a key pathological hallmark of AD). MNPs have also been shown to accelerate amyloid beta (Aβ) toxicity and aggregation. MNPs have previously been quantified in a handful of studies to compare AD and control tissue, with mixed results. Improved understanding of the development of AD, the toxic effects of air pollution (especially magnetite and metals), and the relationship between these two phenomena would be highly beneficial to global health. In order to explore the potential causal link between air pollution and AD, two approaches were taken; metallic and magnetic quantification of post-mortem human brain tissue via superconducting quantum interference device (SQUID) magnetometry and inductively couple plasma mass spectrometry (ICP-MS), and exploration of the cytotoxic effects of ultrafine roadside dust particles (UF-RDPs) on human lung epithelial cells (Calu-3) using different in vitro assays. The concentration of magnetite (measured as magnetic remanence, SIRM) in human brain tissue was not statistically different when comparing AD cases to aged-matched controls. Similarly, there were no differences in metal content between the two groups. Principal component analysis grouped the metals into four components, which are potentially indicators of pollution sources: (1) traffic-related and crustal, (2) fuel oil combustion, (3) biological and tyre/brake wear, and (4) catalytic converters and dental alloys. The distributions of magnetite and metals were heterogenous across different individuals. Significantly lower concentrations of both MNPs and metals were reported in UK samples, compared topreviously reported Mexico City samples. Differences were also seen when comparing the in vitro response to UF-RDPs from three contrasting cities; Lancaster UF-RDPs increased cell viability, whilst Mexico City UF-RDPs were the most toxic and induced the highest amount of oxidative stress (ROS production), and Birmingham UF-RDPs were the most pro-inflammatory. These responses are not fully reflected in conventional mass metrics like PM10, as although the greatest cytotoxicity and ROS production was seen with Mexico City UF-RDPs (highest PM10 exposure), the strongest pro-inflammatory responses were seen in response to Birmingham UF-RDPs and a potentially tumorigenic or fibrosis related increase in cell viability was seen in response to Lancaster UF-RDPs despite the lower PM10 and PM2.5 exposures in the UK cities. There is a need for localised air pollution limits which use biologically relevant metrics that address particle size and cover non-exhaust emission sources of PM like road dust to minimize the health risks of air pollution exposure. Overall, this work demonstrates the presence of exogenous, pollution-derived metals and magnetic nanoparticles within the human brain. Highly reactive and toxic metals and MNPs may exert toxic effects in the brain and have been causally linked to neurodegeneration and AD. The geriatric blood-brain barrier is likely compromised allowing for universal incursion in both AD and age-matched controls, so the use of younger highly exposed individuals such as Mexico City urbanites is critical to identify any changes in metal/magnetic content in the brain decades prior to the presentation of AD. Clear differences were seen across geographical locations when looking at absolute concentrations of MNPs, as well as the composition and induced biological effects of UF-RDPs from different cities. It is thus important to focus on highly localised air pollution regulations to mitigate risk to human health

Off-resonance saturation as an MRI method to quantify mineral- iron in the post-mortem brain

PURPOSE: To employ an off‐resonance saturation method to measure the mineral‐iron pool in the postmortem brain, which is an endogenous contrast agent that can give information on cellular iron status. METHODS: An off‐resonance saturation acquisition protocol was implemented on a 7 Tesla preclinical scanner, and the contrast maps were fitted to an established analytical model. The method was validated by correlation and Bland‐Altman analysis on a ferritin‐containing phantom. Mineral‐iron maps were obtained from postmortem tissue of patients with neurological diseases characterized by brain iron accumulation, that is, Alzheimer disease, Huntington disease, and aceruloplasminemia, and validated with histology. Transverse relaxation rate and magnetic susceptibility values were used for comparison. RESULTS: In postmortem tissue, the mineral‐iron contrast colocalizes with histological iron staining in all the cases. Iron concentrations obtained via the off‐resonance saturation method are in agreement with literature. CONCLUSIONS: Off‐resonance saturation is an effective way to detect iron in gray matter structures and partially mitigate for the presence of myelin. If a reference region with little iron is available in the tissue, the method can produce quantitative iron maps. This method is applicable in the study of diseases characterized by brain iron accumulation and can complement existing iron‐sensitive parametric methods

MRI and histologic studies on early markers of Alzheimer's disease

This thesis adresses a variety of early markers of Alzheimer's disease, using MRI, histology and MRS. MRS is found to be promising for early diagnosis of AD. However this study is done on mice and should be replicated on AD patients over time. Besides the early markers the thesis descibes a potential difference between male and female in the development of AD in the brain. LUMC / Geneeskund

The role of biometals in the neuropathology of Parkinson’s disease

Parkinson’s disease (PD) is a neurodegenerative disorder characterised by the progressive loss of dopaminergic neurons, particularly in the ventral substantia nigra. Growing evidence implicates biometal dyshomeostasis and subsequent metal-catalysed neurotoxicity in vulnerable regions of the PD brain. Through meta-analysis, I confirm previously reported reductions in Cu, and elevations in Fe specifically in the substantia nigra of the PD brain, which are not reflected by similar changes in biofluid tissues. These changes are further restricted to the soluble fraction of nigral tissue – suggesting that soluble metalloproteins may be affected by these biometal perturbations. Superoxide dismutase 1 (SOD1) is one soluble Cu-associated protein that has recently demonstrated impaired antioxidant capacity and altered structural conformation in the PD brain and may present with an altered metalation profile in PD brain. I describe, for the first time, the cutting-edge technique of simultaneous synchrotron X-ray fluorescence microscopy and ptychography performed in situ to identify and directly image Lewy bodies, SOD1 aggregates and neuromelanin in human PD substantia nigra. The resulting nanoscale imaging demonstrate that SOD1 and Lewy body proteinopathies share similar structures. SOD1 and Lewy aggregates also exhibited similar elemental compositions, suggesting that these distinct proteinaceous aggregates may share an overlapping protein misfolding pathway. Further, I demonstrate an altered Cu:Zn ratio in SOD1 aggregates, supporting the hypothesis that altered metalation of SOD1 results in aggregate formation in this Cu-deficient region. These data suggest that Cu dyshomeostasis in the vulnerable substantia nigra of the PD brain may be attenuated by biometal modulation therapies, and that SOD1 may present as a viable therapeutic target for PD

Wine Cunterfeiting: Development of fast, non-destructive and multifactorial laser-based spectrochemical methods for authentication of bottled wine

378 p.La presente Tesis Doctoral pretende avanzar en el desarrollo de una herramienta analítica que permita certificar la autenticidad de un vino de forma inequívoca mediante técnicas analíticas no invasivas (es decir, prácticamente inapreciable a simple vista) como son la ablación laser con plasma de acoplamiento inductivo-espectrometría de masas (LA-ICPMS) y las espectroscopias Raman e Infrarroja, que permiten el análisis de una muestra sólida sin necesidad de procesarla y sin inducir degradación o alteración apreciable alguna. Mediante la metodología desarrollada se pretende establecer el perfil elemental y molecular del vidrio, el papel, la tinta y la cápsula de las botellas de vino

Wine Cunterfeiting: Development of fast, non-destructive and multifactorial laser-based spectrochemical methods for authentication of bottled wine

378 p.La presente Tesis Doctoral pretende avanzar en el desarrollo de una herramienta analítica que permita certificar la autenticidad de un vino de forma inequívoca mediante técnicas analíticas no invasivas (es decir, prácticamente inapreciable a simple vista) como son la ablación laser con plasma de acoplamiento inductivo-espectrometría de masas (LA-ICPMS) y las espectroscopias Raman e Infrarroja, que permiten el análisis de una muestra sólida sin necesidad de procesarla y sin inducir degradación o alteración apreciable alguna. Mediante la metodología desarrollada se pretende establecer el perfil elemental y molecular del vidrio, el papel, la tinta y la cápsula de las botellas de vino

QUANTIFICATION OF IRON TRANSFER FROM DIET TO THE BRAIN IN THE RAT MODEL USING STABLE ISOTOPE TECHNIQUES

Ph.DDOCTOR OF PHILOSOPH