6 research outputs found
Shedding Light on the Molecular Pathology of Amyloid Plaques in Transgenic Alzheimer’s Disease Mice Using Multimodal MALDI Imaging Mass Spectrometry
Senile
plaques formed by aggregated amyloid β peptides are
one of the major pathological hallmarks of Alzheimer’s disease
(AD) which have been suggested to be the primary influence triggering
the AD pathogenesis and the rest of the disease process. However,
neurotoxic Aβ aggregation and progression are associated with
a wide range of enigmatic biochemical, biophysical and genetic processes.
MALDI imaging mass spectrometry (IMS) is a label-free method to elucidate
the spatial distribution patterns of intact molecules in biological
tissue sections. In this communication, we utilized multimodal MALDI-IMS
analysis on 18 month old transgenic AD mice (tgArcSwe) brain tissue
sections to enhance molecular information correlated to individual
amyloid aggregates on the very same tissue section. Dual polarity
MALDI-IMS analysis of lipids on the same pixel points revealed high
throughput lipid molecular information including sphingolipids, phospholipids,
and lysophospholipids which can be correlated to the ion images of
individual amyloid β peptide isoforms at high spatial resolutions
(10 μm). Further, multivariate image analysis was applied in
order to probe the multimodal MALDI-IMS data in an unbiased way which
verified the correlative accumulations of lipid species with dual
polarity and Aβ peptides. This was followed by the lipid fragmentation
obtained directly on plaque aggregates at higher laser pulse energies
which provided tandem MS information useful for structural elucidation
of several lipid species. Majority of the amyloid plaque-associated
alterations of lipid species are for the first time reported here.
The significance of this technique is that it allows correlating the
biological discussion of all detected plaque-associated molecules
to the very same individual amyloid plaques which can give novel insights
into the molecular pathology of even a single amyloid plaque microenvironment
in a specific brain region. Therefore, this allowed us to interpret
the possible roles of lipids and amyloid peptides in amyloid plaque-associated
pathological events such as focal demyelination, autophagic/lysosomal
dysfunction, astrogliosis, inflammation, oxidative stress, and cell
death
Capillary Electrophoresis–Mass Spectrometry-Based Detection of Drugs and Neurotransmitters in Drosophila Brain
Capillary electrophoresis
coupled to mass spectrometry has been
used to determine the in vivo concentrations of the neuroactive drug,
methylphenidate, and a metabolite in the heads of the fruit fly, Drosophila melanogaster. These concentrations, evaluated
at the site of action, the brain, have been correlated with orally
administrated methylphenidate. D. melanogaster has a relatively simple nervous system but possesses high-order
brain functions similar to humans; thus, it has been used as a common
model system in biological and genetics research. Methylphenidate
has been used to mediate cocaine addiction due to its lower pharmacokinetics,
which results in fewer addictive and reinforcing effects than cocaine;
the effects of the drug on the nervous system, however, have not been
fully understood. In addition to measurements of drug concentration,
the method has been used to examine drug-dose dependence on the levels
of several primary biogenic amines. Higher in vivo concentration of
methylphenidate is observed with increasing feeding doses up to 25
mM methylphenidate. Furthermore, administrated methylphenidate increases
the drug metabolism activity and the neurotransmitter levels; however,
this increase appears to saturate at a feeding dose of 20 mM. The
method developed for the fruit fly provides a new tool to evaluate
the concentration of administered drug at the site of action and provides
information concerning the effect of methylphenidate on the nervous
system
Time-of-Flight Secondary Ion Mass Spectrometry Based Molecular Histology of Human Spinal Cord Tissue and Motor Neurons
Secondary
ion mass spectrometry is a powerful method for imaging
biological samples with high spatial resolution. Whole section time-of-flight-secondary
ion mass spectrometry (TOF-SIMS) scans and multivariate data analysis
have been performed on the human spinal cord in order to delineate
anatomical regions of interest based on their chemical distribution
pattern. TOF-SIMS analysis of thoracic spinal cord sections was performed
at 5 μm resolution within 2 h. Multivariate image analysis by
means of principal component analysis and maximum auto correlation
factor analysis resulted in detection of more than 400 <i>m</i>/<i>z</i> peaks that were found to be significantly changed.
Here, the results show characteristic biochemical distributions that
are well in line with major histological regions, including gray and
white matter. As an approach for iterative segmentation, we further
evaluated previously outlined regions of interest as identified by
multivariate image analysis. Here, further discrimination of the gray
matter into ventral, lateral, and dorsal neuroanatomical regions was
observed. TOF-SIMS imaging has been carried out at submicrometer resolution
obtaining localization and characterization of spinal motor neurons
based on their chemical fingerprint, including neurotransmitter precursors
that serve as molecular indicators for motor neuron integrity. Thus,
TOF-SIMS can be used as an approach for chemical histology and pathology.
TOF-SIMS holds immense potential for investigating the subcellular
mechanisms underlying spinal cord related diseases including chronic
pain and amyotrophic lateral sclerosis
Novel Trimodal MALDI Imaging Mass Spectrometry (IMS3) at 10 μm Reveals Spatial Lipid and Peptide Correlates Implicated in Aβ Plaque Pathology in Alzheimer’s Disease
Multimodal chemical
imaging using matrix-assisted laser desorption/ionization
mass spectrometry (MALDI-MS) can provide comprehensive molecular information
in situ within the same tissue sections. This is of relevance for
studying different brain pathologies such as Alzheimer’s disease
(AD), where recent data suggest a critical relevance of colocalizing
Aβ peptides and neuronal lipids. We here developed a novel trimodal,
high-resolution (10 μm) MALDI imaging MS (IMS) paradigm for
negative and positive ion mode lipid analysis and subsequent protein
ion imaging on the same tissue section. Matrix sublimation of 1,5-diaminonaphthalene
(1,5-DAN) enabled dual polarity lipid MALDI IMS on the same pixel
points at high spatial resolutions (10 μm) and with high spectral
quality. This was followed by 10 μm resolution protein imaging
on the same measurement area, which allowed correlation of lipid signals
with protein distribution patterns within distinct cerebellar regions
in mouse brain. The demonstrated trimodal imaging strategy (IMS3)
was further shown to be an efficient approach for simultaneously probing
Aβ plaque-associated lipids and Aβ peptides within the
hippocampus of 18 month-old transgenic AD mice (tgArcSwe). Here, IMS3
revealed a strong colocalization of distinct lipid species including
ceramides, phosphatidylinositols, sulfatides (Cer 18:0, PI 38:4, ST
24:0) and lysophosphatidylcholines (LPC 16:0, LPC 18:0) with plaque-associated
Aβ isoforms (Aβ 1–37, Aβ 1–38, Aβ
1–40). This highlights the potential of IMS3 as an alternative,
superior approach to consecutively performed immuno-based Aβ
staining strategies. Furthermore, the IMS3 workflow allowed for multimodal
in situ MS/MS analysis of both lipids and Aβ peptides. Altogether,
the here presented IMS3 approach shows great potential for comprehensive,
high-resolution molecular analysis of histological features at cellular
length scales with high chemical specificity. It therefore represents
a powerful approach for probing the complex molecular pathology of,
e.g., neurodegenerative diseases that are characterized by neurotoxic
protein aggregation
High Resolution Metabolite Imaging in the Hippocampus Following Neonatal Exposure to the Environmental Toxin BMAA Using ToF-SIMS
The environmental neurotoxin β-<i>N</i>-methylamino-l-alanine (BMAA) is suggested to
be linked with neurodegenerative
disease. In a rat model, neonatal exposure to BMAA induced selective
uptake in the hippocampus and caused cell loss, mineralization and
astrogliosis as well as learning and memory impairments in adulthood.
Moreover, neonatal exposure resulted in increased protein ubiquitination
in the cornus ammonis 1 (CA1) region of the adult hippocampus indicating
that BMAA may induce protein aggregation. Time-of-flight secondary
ion mass spectrometry (ToF-SIMS) based imaging is a powerful technology
for spatial profiling of small molecular weight compounds in biological
tissues with high chemical specificity and high spatial resolution.
The aim of this study was to characterize neurochemical changes in
the hippocampus of six month-old rats treated neonatally (postnatal
days 9–10) with BMAA. Multivariate data analysis of whole section
ToF-SIMS scans was performed to delineate anatomical regions of interest
based on their chemical distribution pattern. Further analysis of
spectral data obtained from the outlined anatomical regions, including
CA1 and dentate gyrus (DG) revealed BMAA-induced long-term changes.
Increased levels of phospholipids and protein fragments in the histopathologically
altered CA1 region as well as phosphate depletion in the DG were observed.
Moreover, high resolution SIMS imaging revealed a specific localization
of phosphatidylcholine lipids, protein signals and potassium in the
histopathologically altered CA1. These findings demonstrate that ToF-SIMS
based imaging is a powerful approach for probing biochemical changes
in situ and might serve as promising technique for investigating neurotoxin-induced
brain pathology
Multimodal Chemical Imaging of Amyloid Plaque Polymorphism Reveals Aβ Aggregation Dependent Anionic Lipid Accumulations and Metabolism
Amyloid plaque formation
constitutes one of the main pathological
hallmarks of Alzheimer’s disease (AD) and is suggested to be
a critical factor driving disease pathogenesis. Interestingly, in
patients that display amyloid pathology but remain cognitively normal,
Aβ deposits are predominantly of diffuse morphology suggesting
that cored plaque formation is primarily associated with cognitive
deterioration and AD pathogenesis. Little is known about the molecular
mechanism responsible for conversion of monomeric Aβ into neurotoxic
aggregates and the predominantly cored deposits observed in AD. The
structural diversity among Aβ plaques, including cored/compact-
and diffuse, may be linked to their distinct Aβ profile and
other chemical species including neuronal lipids. We developed a novel,
chemical imaging paradigm combining matrix assisted laser desorption/ionization
imaging mass spectrometry (MALDI IMS) and fluorescent amyloid staining.
This multimodal imaging approach was used to probe the lipid chemistry
associated with structural plaque heterogeneity in transgenic AD mice
(tgAPP<sub>Swe</sub>) and was correlated to Aβ profiles determined
by subsequent laser microdissection and immunoprecipitation-mass spectrometry.
Multivariate image analysis revealed an inverse localization of ceramides
and their matching metabolites to diffuse and cored structures within
single plaques, respectively. Moreover, phosphatidylinositols implicated
in AD pathogenesis, were found to localize to the diffuse Aβ
structures and correlate with Aβ1–42. Further, lysophospholipids
implicated in neuroinflammation were increased in all Aβ deposits.
The results support previous clinical findings on the importance of
lipid disturbances in AD pathophysiology and associated sphingolipid
processing. These data highlight the potential of multimodal imaging
as a powerful technology to probe neuropathological mechanisms