Browsing by Subject "Aβ plaques"

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    Acute communication between microglia and other immune cells in the anti‐Aβ antibody injected cortex
    (Wiley, 2025-01-03) Foley, Kate E.; Krick, Katelynn E.; Weekman, Erica M.; Wilcock, Donna M.; Neurology, School of Medicine
    Background: Anti‐Aβ immunotherapy use to treat Alzheimer’s disease is on the rise. While anti‐Aβ antibodies provide hope in targeting Aβ plaques in the brain, a major side effect of amyloid‐related imaging abnormalities (ARIA) persists with no known cause. As severe ARIA is typically seen within the first few infusions in human clinical trials, we sought to identify acute effects of anti‐Aβ antibody on brain. Method: To determine cellular changes due to anti‐Aβ antibody exposure, we intracranially injected 14mo APP male and female mice with anti‐Aβ IgG1 (6E10) or control IgG1 into the cortex. After 24hrs or 3days, we harvested the cortex and performed a glial cell enriched preparation for single cell sequencing. Cell types, proportions, and cell‐to‐cell signaling was evaluated between the two injection conditions and two acute timepoints. Result: We identified 23 unique cell clusters including microglia, astrocytes, endothelial cells, neurons, oligos/OPCs, immune cells, and unknown. The anti‐Aβ antibody injected cortices revealed more ligand‐receptor communications between cell types, as well as stronger communications at 24hrs. At 3days, while there were more L‐R communications for the anti‐Aβ antibody condition, the strength of these connections was stronger in the control IgG condition. Specific pathways such as CD48 and PD‐L1 were enriched in the anti‐Aβ antibody condition, but not the control IgG condition in microglia‐to‐microglia communication. We also found evidence of an initial and strong communication emphasis in microglia‐to‐peripheral immune cells at 24hrs, specifically in the TGFβ signaling pathway. Additionally, we found that peripheral immune cells that were exposed to anti‐Aβ antibody failed to signal via the TNF pathway, which was strongly enriched in the control IgG condition at both timepoints. Conclusion: We identify several pathways that differ between anti‐Aβ antibody and control IgG injections at acute timepoints. These data lay the groundwork for understanding the brain’s unique response to anti‐Aβ antibody and its predisposition to ARIA.
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    Identification of Chemical Tool Compounds to Investigate the Role of Lyn Kinase in TREM2‐Mediated Microglia Activation and Phagocytosis
    (Wiley, 2025-01-09) Weerawarna, Pathum M.; Robo, Michael T.; Chu, Shaoyou; Mason, Emily R.; Davis, Chris; Angus, Steven P.; Richardson, Timothy I.; Medicine, School of Medicine
    Background: Lyn kinase, a member of the Src family of tyrosine kinases, predominantly phosphorylates ITIM and ITAM motifs linked to immune receptors and adaptor proteins, and is emerging as a target for Alzheimer’s disease (AD). The role of Lyn in TREM2‐mediated microglial activation and phagocytosis, a critical pathway for clearing Aβ plaques, remains unclear and potent, selective, and brain penetrant Lyn inhibitors are unavailable. In this study, we report the characterization of Lyn kinase inhibitors from the literature as well as the establishment of an advanced virtual screening platform at the IUSM‐Purdue‐TREAT‐AD center to identify new type II Lyn inhibitors suitable as molecular probes. Method: We first performed a thorough literature survey and found 14 reported Lyn kinase inhibitors. We then validated their Lyn inhibitor activities and Lyn selectivities using the HotSpot kinase assay. We tested these compounds for microglia activation in a high‐content imaging assay using HMC3 (human) and BV2 (mouse) microglia‐like cell lines. We also performed kinome profiling in these cells to evaluate cellular target engagement and selectivity. Finally, we screened a million‐compounds using a computational pipeline that combined molecular docking, shape‐based screening, and MD simulations to identify novel and potent type II Lyn kinase inhibitors. Result: Our findings revealed that Type I inhibitors, particularly Saracatinib and Bosutinib, potently inhibit Lyn within the picomolar (pM) range. On the other hand, Type II inhibitors, such as Masitinib and Imatinib, displayed pronounced >20‐fold selectivity for Lyn over Hck with low nM Lyn inhibitor activities. Saracatinib and Bosutinib significantly induced phagocytosis in HMC3 cells, whereas Type II inhibitors demonstrated moderate activity in both HMC3 and BV2 cells. Our virtual screening platform identified a new type II Lyn inhibitor with picomolar activity and good Lyn/Hck selectivity. Conclusion: We have successfully evaluated previously reported inhibitors and introduced a novel type II Lyn kinase inhibitor with picomolar (pM) activities suitable for use as chemical probes to investigate the role of Lyn in TREM2‐mediated microglial activation.