Gironda, S. C. | Search bioRxiv

bioRxiv2023

Novel method for collecting hippocampal interstitial fluid extracellular vesicles (EV-ISF) reveals sex-dependent changes in microglial EV proteome in response to Aβ pathology

Brain-derived extracellular vesicles (EVs) play an active role in Alzheimers disease (AD), relaying important physiological information about their host tissues. Circulating EVs are protected from degradation, making them attractive AD biomarkers. However, it is unclear how circulating EVs relate to EVs isolated from disease-vulnerable brain regions. We developed a novel method for collecting EVs from the hippocampal interstitial fluid (ISF) of live mice. EVs (EVISF) were isolated via ultracentrifugation and characterized by nanoparticle tracking analysis, immunogold labeling, and flow cytometry. Mass spectrometry and proteomic analyses were performed on EVISF cargo. EVISF were 40-150 nm in size and expressed CD63, CD9, and CD81. Using a model of cerebral amyloidosis (e.g. APPswe,PSEN1dE9 mice), we found protein concentration increased but protein diversity decreased with A{beta} deposition. Genotype, age, and A{beta} deposition modulated proteostasis- and immunometabolic-related pathways. Changes in the microglial EVISF proteome were sexually dimorphic and associated with a differential response of plaque associated microglia. We found that female APP/PS1 mice have more amyloid plaques, less plaque associated microglia, and a less robust- and diverse-EVISF microglial proteome. Thus, in vivo microdialysis is a novel technique for collecting EVISF and offers a unique opportunity to explore the role of EVs in AD. Graphical AbstractHippocampal EVISF response to amyloid beta (A{beta}) is sexually dimorphic and related to the microglial EVISF proteome. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=126 SRC="FIGDIR/small/532133v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@1a275d6org.highwire.dtl.DTLVardef@e63da5org.highwire.dtl.DTLVardef@1d93cecorg.highwire.dtl.DTLVardef@12ed0db_HPS_FORMAT_FIGEXP M_FIG C_FIG

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bioRxiv2022

Ethanol exposure alters Alzheimer's-related pathology, behavior, and metabolism

Chronic ethanol exposure can increase amyloid-{beta} (A{beta}) and tau in rodent models of Alzheimers-disease (AD)-like pathology, yet the underlying mechanisms are poorly understood. In this study, a moderate two-bottle choice drinking paradigm was used to identify how chronic ethanol exposure alters A{beta}-related pathology, metabolism, and behavior. Complementary in vivo microdialysis experiments were used to measure how acute ethanol directly modulates A{beta} in the hippocampal interstitial fluid (ISF). Ethanol-exposed APPswe/PSEN1dE9 (APP/PS1) mice showed increased brain atrophy and an increased number of amyloid plaques. Further analysis revealed that ethanol exposure led to a shift in the distribution of plaque size in the cortex and hippocampus. Ethanol-exposed mice developed a greater number of smaller plaques, potentially setting the stage for increased plaque proliferation in later life. Ethanol also induced changes in N-methyl-D-aspartate and {gamma}-aminobutyric acid type-A receptor (NMDAR and GABAAR, respectively) expression, possibly reflecting changes in the excitatory and inhibitory (E/I) balance in the brain. Ethanol exposure also led to a diurnal shift in feeding behavior which was associated with changes in glucose homeostasis and glucose intolerance. Ethanol exposure also exacerbated alterations in the open-field test and deficits in nest-building behaviors in APP/PS1mice. Lastly, an acute dose of ethanol bidirectionally altered hippocampal ISF A{beta} levels - decreasing during the initial exposure and increasing during withdrawal. Acute ethanol exposure increased hippocampal ISF glucose levels, suggesting changes in cerebral glucose metabolism occur in response to ethanol. These experiments indicate that ethanol exacerbates an AD-like phenotype by altering A{beta} deposition, behavior, and metabolism. Here, even a moderate drinking paradigm culminates in an interaction between alcohol use and AD-related phenotypes with a potentiation of AD-related pathology, behavioral dysfunction, and metabolic impairment. HighlightsO_LIChronic ethanol exposure increases brain atrophy in APP/PS1 mice. C_LIO_LIChronic ethanol exposure increased the number of plaques in the brains of APP/PS1 mice. C_LIO_LIChronic ethanol exposure led to dysregulated metabolism in APP/PS1 mice. C_LIO_LIChronic ethanol exposure altered anxiety- and dementia-related behaviors in APP/PS1 mice. C_LIO_LIAcute ethanol exposure bidirectionally alters interstitial fluid (ISF) levels of amyloid-{beta} in APP/PS1 mice during exposure and withdrawal. C_LI

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