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Development of selective fluorescent imaging agents for neurofibrillary tangles in Alzheimer’s diagnosis

Anumala, Upendra Rao (2013)
Development of selective fluorescent imaging agents for neurofibrillary tangles in Alzheimer’s diagnosis.
Technische Universität Darmstadt
Dissertation, Erstveröffentlichung

Kurzbeschreibung (Abstract)

Alzheimer’s disease (AD) is a neurodegenerative disorder, a form of dementia that worsens over time. With the number of AD patients rising year by year, the total number of patients has already surpassed more than 25 million and this number will grow closer to 63 million by 2030. Symptoms of this disease include memory loss, challenges in problem solving, trouble in understanding visual images or spatial relationships and problems in speaking and writing. Current methods of detection rely on the minimal mental state examination. This is often inaccurate and cannot differentiate between AD and other forms of dementia. The two hallmarks that are responsible for AD are the formation of senile plaques (SPs) and neurofibrillary tangles (NFTs) in the brain. SPs are formed by the aggregation of insoluble amyloid beta protein and NFTs are formed by aggregation of hyperphosphorylated tau protein. In a healthy human brain, these two proteins are produced and broken down to small fragments and eliminated. In AD patients, SPs and NFTs are formed by aggregation of these two proteins. It is possible to image these SPs and NFTs by techniques such as positron emission tomography (PET) or fluorescence imaging which may enable early diagnosis of AD. Although, SP imaging is known, SP deposition does not correlate with the disease and is observed in healthy patients also, hence, a diagnosis of the disease based solely on SPs imaging is likely to be inaccurate. In addition to this, it is difficult to correlate the disease progression with senile plaque quantity in the brain. On the other hand, NFT formation known to correlate with the disease progression, and therefore, fluorescence imaging of such NFTs may reveal the disease progression. The present study describes a set of compounds able to visualize NFTs and SPs in a human AD brain obtained at autopsy. Several classes of compounds were synthesized and explored for their ability to stain NFTs, of these; rhodanine-3-acetic acids, 5H-imidazo [4,5-c] pyridine derivatives, bis(arylvinyl)pyrazine derivatives were identified as promising compounds for tau imaging. Our observations with these compounds showed us that thesecompounds bind to NFTs in an AD brain, which were clearly visualized by the fluorescence microscopy. In addition to this, selected compounds were tested for their cytotoxicity in hepatocellular carcinoma cell lines and zebrafish embryo development assay. These cytotoxicity studies indicated that these compounds display no or negligible cytotoxicity. Further, in vitro experiments of rhodanine-3-acetic acid derivatives in P30lS mice retina and in vitro experiments in human AD retina resulted in the absence of staining of retinal tissues. Remarkably, control tissues were stained with AT8 antibody. These results suggest that the tau aggregates in the retina of P301S mice are different from human tau deposits present in hyperphosphorylated NFTs. Further, in vitro experiments with 5H-imidazo [4,5-c] pyridine derivatives on olfactory epithelium tissues visualized tau deposits in olfactory epithelium tissues.

Typ des Eintrags: Dissertation
Erschienen: 2013
Autor(en): Anumala, Upendra Rao
Art des Eintrags: Erstveröffentlichung
Titel: Development of selective fluorescent imaging agents for neurofibrillary tangles in Alzheimer’s diagnosis
Sprache: Englisch
Referenten: Schmidt, Prof. Dr. Boris ; Kolmar, Prof. Dr. Harald
Publikationsjahr: 7 Oktober 2013
Ort: Darmstadt, Germany
Verlag: TU Darmstadt
Datum der mündlichen Prüfung: 7 Oktober 2013
URL / URN: http://tuprints.ulb.tu-darmstadt.de/3718
Kurzbeschreibung (Abstract):

Alzheimer’s disease (AD) is a neurodegenerative disorder, a form of dementia that worsens over time. With the number of AD patients rising year by year, the total number of patients has already surpassed more than 25 million and this number will grow closer to 63 million by 2030. Symptoms of this disease include memory loss, challenges in problem solving, trouble in understanding visual images or spatial relationships and problems in speaking and writing. Current methods of detection rely on the minimal mental state examination. This is often inaccurate and cannot differentiate between AD and other forms of dementia. The two hallmarks that are responsible for AD are the formation of senile plaques (SPs) and neurofibrillary tangles (NFTs) in the brain. SPs are formed by the aggregation of insoluble amyloid beta protein and NFTs are formed by aggregation of hyperphosphorylated tau protein. In a healthy human brain, these two proteins are produced and broken down to small fragments and eliminated. In AD patients, SPs and NFTs are formed by aggregation of these two proteins. It is possible to image these SPs and NFTs by techniques such as positron emission tomography (PET) or fluorescence imaging which may enable early diagnosis of AD. Although, SP imaging is known, SP deposition does not correlate with the disease and is observed in healthy patients also, hence, a diagnosis of the disease based solely on SPs imaging is likely to be inaccurate. In addition to this, it is difficult to correlate the disease progression with senile plaque quantity in the brain. On the other hand, NFT formation known to correlate with the disease progression, and therefore, fluorescence imaging of such NFTs may reveal the disease progression. The present study describes a set of compounds able to visualize NFTs and SPs in a human AD brain obtained at autopsy. Several classes of compounds were synthesized and explored for their ability to stain NFTs, of these; rhodanine-3-acetic acids, 5H-imidazo [4,5-c] pyridine derivatives, bis(arylvinyl)pyrazine derivatives were identified as promising compounds for tau imaging. Our observations with these compounds showed us that thesecompounds bind to NFTs in an AD brain, which were clearly visualized by the fluorescence microscopy. In addition to this, selected compounds were tested for their cytotoxicity in hepatocellular carcinoma cell lines and zebrafish embryo development assay. These cytotoxicity studies indicated that these compounds display no or negligible cytotoxicity. Further, in vitro experiments of rhodanine-3-acetic acid derivatives in P30lS mice retina and in vitro experiments in human AD retina resulted in the absence of staining of retinal tissues. Remarkably, control tissues were stained with AT8 antibody. These results suggest that the tau aggregates in the retina of P301S mice are different from human tau deposits present in hyperphosphorylated NFTs. Further, in vitro experiments with 5H-imidazo [4,5-c] pyridine derivatives on olfactory epithelium tissues visualized tau deposits in olfactory epithelium tissues.

Alternatives oder übersetztes Abstract:
Alternatives AbstractSprache

Die Alzheimer-Krankheit ist eine langsam fortschreitende neurodegenerative Form der Demenz. Die Anzahl an Neuerkrankungen steigt Jahr für Jahr. Derzeit sind mehr als 25 Millionen Menschen betroffen. Schätzungen zufolge wird die Anzahl an betroffenen Patienten bis 2030 auf 63 Millionen ansteigen. Gedächtnisstörungen, Gemütsschwankungen sowie Probleme mit dem Sprechen und Schreiben charakterisieren den Verlauf dieser Krankheit. Derzeitige diagnostische Methoden sind oft ungenau und können nicht hinreichend zwischen der Alzheimer-Krankheit und anderen Formen der Demenz unterscheiden. Die Alzheimer-Krankheit ist auf zwei verschiedene Proteinablagerungen zurückzuführen: Senile Plaques (SPs) und neurofibrilläre Bündel (NFTs). Die Bildung der Senilen Plaques ist auf die Aggregation des unlöslichen amyloid Vorläuferproteins (APP) zurückzuführen, wohingegen die NFTs durch die Aggregation von hyperphophorylierten Tau entstehen. Es ist möglich SPs und NFTs bildlich darzustellen. Angewandte Techniken sind hierbei die Positronen-Emissions-Tomographie oder die Fluoreszenz Spektroskopie, welche auch eine frühe Diagnose der Alzheimer-Krankheit ermöglicht. Obwohl die Visualisierung der SPs bereits bekannt ist, korrelieren diese nicht mit der Krankheit, da SPs ebenfalls in Gehirnen gesunder Patienten gefunden werden. Deswegen ist eine Diagnose der Alzheimer-Krankheit, welche ausschließlich auf SPs Visualisierung beruht, sehr ungenau. Im Gegensatz dazu stehen die NFTs mit der Entstehung der Alzheimer-Krankheit in Beziehung und deshalb kann die Fluoreszenz-Bildgebung als Methode den fortschreitenden Verlauf aufzeigen. Die vorliegende Arbeit zeigt eine Reihe von Verbindungen, welche SPs und NFTs auf Gehirnschnitten visualisiert. Unterschiedliche Klassen von Verbindungen wurden hierbei synthetisiert und auf ihre Fähigkeit als Marker für die NFTs untersucht. Hierbei waren vor allem die Derivate von Rhodanin-3-essigsäure sowie Bis(arylvinyl)pyrazin- und 5H-Imidazo[4,5-c]pyridin Derivate aussichtsvolle Verbindungen für die Tau-Bildgebung. Unsere Untersuchungen mit diesen Verbindungen zeigte uns, dass diese Verbindungen an NFTs in Gehirnen binden, was durch Fluoreszenz-Mikroskopie deutlich gemacht wurde. Zusätzlich dazu wurden ausgewählte Verbindungen auf ihre Zytotoxizität in einem hepatozellulären Karzinom-Assay und in einem Zebrafisch-Toxizitäts-Assay getestet. Diese Experimente zeigten, dass die untersuchten Verbindungen keine oder nur geringfügige Zytotoxizität aufwiesen. Des Weiteren zeigten in vitro Studien der Derivate von Rhodanin-3-essigsäure in P301S Mäuse-Retina und in vitro Experimente in menschlicher Alzheimer-Retina das Ausbleiben des Färbens des Retinagewebes. Das Anfärben mit dem Antikörper AT8 zeigte hingegen positive Ergebnisse. Dieses machte deutlich, dass Tau-Aggregate der Retina P301S Maus unterschiedlich zu der menschlichen Form des Tau-Aggregats sind. Weiterhin wurden in vitro Experimente mit Verbindungen von 5H-Imidazo[4,5-c]pyridin an olfaktorischen Epithelgewebe durchgeführt. Die Ergebnisse zeigten, dass diese Verbindungsklasse Tau-Ablagerungen anfärbte.

Deutsch
Freie Schlagworte: Alzheimer's disease, neurofibrillary tangles, tau, fluorescence imaging
URN: urn:nbn:de:tuda-tuprints-37185
Sachgruppe der Dewey Dezimalklassifikatin (DDC): 500 Naturwissenschaften und Mathematik > 540 Chemie
Fachbereich(e)/-gebiet(e): 07 Fachbereich Chemie > Clemens-Schöpf-Institut > Fachgebiet Organische Chemie
07 Fachbereich Chemie
Hinterlegungsdatum: 22 Dez 2013 20:55
Letzte Änderung: 22 Dez 2013 20:55
PPN:
Referenten: Schmidt, Prof. Dr. Boris ; Kolmar, Prof. Dr. Harald
Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: 7 Oktober 2013
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