Abstract
Although several histochemical markers for senile plaques (SP) and neurofibrillary tangles (NFTs) have been synthesized since the discovery of plaques in Alzheimer’s disease (AD), only a handful of these markers stain both lesions in the human brain. Despite discovery of its ability to stain both SP and NFT over 13 years ago, the styrylbenzene derivative, (E,E)-1-fluoro-2,5-bis-(3-hydroxycarbonyl-4-hydroxy)styrylbenzene (FSB), has only recently gained attention, primarily due to its ability to function as a contrasting agent for MRI imaging of AD pathology in vivo. The structure of the compound is a nuclide with quantized angular momentum, which explains its value as a contrast agent. In the current study, modification of the established staining procedure produced meaningful improvement in the labeling of plaques and tangles in the human brain. We utilized two rodent models of AD to show FSB’s value in labeling both Aβ and tau lesions. Furthermore, our current modification allows us to detect SP in rodent brains in 15 min and both SP and NFT in human brains within 20 min. The study presents new evidence regarding potential binding targets for FSB as well as optimization protocols in which various parameters have been manipulated to show how section thickness, use of frozen versus paraffin-embedded sections, and selection of staining media can affect the intensity of the plaque and tangle staining in the brain. To determine the target FSB potentially binds, we performed double immunolabeling of FSB with mOC64 (a conformational antibody that label Aβ1-42). Results indicated that all plaques in the brain colocalized with mOC64, suggesting that FSB has the potential to bind all Aβ containing plaques, making it a very sensitive detector of multiple forms of SP... All antibodies were assessed for the degree of colocalization with FSB in order to better understand potential binding targets. We found more than 90% hyperphosphorylated Tau against AT8, AT180 and S214 colocalized with FSB labeled tangles. On the other hand, more than 90% of the mOC64 containing plaques colocalized with FSB stained plaques. Our results indicate that FSB is a valuable marker that can be used to detect AD pathologies in human and rodent brains with greater fluorescence intensity relative to other conventional fluorescence markers.
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Datasets from this study are available from the corresponding author on reasonable request.
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Acknowledgements
This study was supported by funding from the National Center for Toxicological Research/FDA [Protocol #763101 to SS]
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This study was supported by funding from the National Center for Toxicological Research/FDA [Protocol #763101 to SS].
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Sharay Setti (SST) is the lead author who has substantially contributed in writing the manuscript. James Raymick (JR) and Nikita Das (ND) have significant input on histological labeling of sections, data collection. Joseph Hanig (JH) critically reviewed the manuscript. Sumit Sarkar (SS) is the corresponding author and primary input on experiment design, performed animal sacrifice, tissue processing and immunolabeling of histological sections, data collection and interpretation of photomicrographs and editing of manuscript.
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All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. All experimental procedures described here for rodent and human tissues were approved by the appropriate committees at the National Center for Toxicological Research/FDA, including the NCTR Office of Research, the Regulatory Compliance and Risk Management Director and the FDA Research Involving Human Subjects Committee (RIHSC). As determined by the FDA RIHSC, this study did not reach the definition of “Human Subject Research” at 45 CFR 46.102(f) and thus, 45 CFR Part 46 does not apply.
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Setti, S., Das, N., Raymick, J. et al. Evaluation of Styrylbenzene analog- FSB and its affinity to bind parenchymal plaques and tangles in patients of Alzheimer’s disease. Metab Brain Dis 37, 639–651 (2022). https://doi.org/10.1007/s11011-021-00885-3
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DOI: https://doi.org/10.1007/s11011-021-00885-3