Vascular Amyloid Deposits Research Articles

Amyloid-β (Aβ) immunotherapy induced microhemorrhages are linked to vascular inflammation and cerebrovascular damage in a mouse model of Alzheimer’s disease

BackgroundAnti-amyloid-β (Aβ) immunotherapy trials have revealed amyloid-related imaging abnormalities (ARIA) as the most prevalent and serious adverse events linked to pathological changes in cerebral vasculature. Recent studies underscore the critical involvement of perivascular macrophages and the infiltration of peripheral immune cells in regulating cerebrovascular damage. Specifically, Aβ antibodies engaged at cerebral amyloid angiopathy (CAA) deposits trigger perivascular macrophage activation and the upregulation of genes associated with vascular permeability. Nevertheless, further research is needed to understand the immediate downstream consequences of macrophage activation, potentially exacerbating CAA-related vascular permeability and microhemorrhages linked to Aβ immunotherapy.MethodsThis study investigates immune responses induced by amyloid-targeting antibodies and CAA-induced microhemorrhages using RNA in situ hybridization, histology and digital spatial profiling in an Alzheimer's disease (AD) mouse model of microhemorrhage.ResultsIn the present study, we have demonstrated that bapineuzumab murine surrogate (3D6) induces profound vascular damage, leading to smooth muscle cell loss and blood–brain barrier (BBB) breakdown. In addition, digital spatial profiling (DSP) reveals that distinct immune responses contribute to vascular damage with peripheral immune responses and perivascular macrophage activation linked to smooth muscle cell loss and vascular fibrosis, respectively. Finally, RNA in situ hybridization identifies two distinct subsets of Trem2+ macrophages representing tissue-resident and monocyte-derived macrophages around vascular amyloid deposits. Overall, these findings highlight multifaceted roles of immune activation and vascular damage in driving the development of microhemorrhage.ConclusionsIn summary, our study has established a significant link between CAA-Aβ antibody immune complex formation, immune activation and vascular damage leading to smooth muscle cell loss. However, the full implications of this cascade on the development of microhemorrhages requires further exploration. Additional investigations are warranted to unravel the precise molecular mechanisms leading to microhemorrhage, the interplay of diverse immune populations and the functional roles played by various Trem2+ macrophage populations in response to Aβ immunotherapy.

Lead Acetate Exposure and Cerebral Amyloid Accumulation: Mechanistic Evaluations in APP/PS1 Mice.

The role of environmental factors in Alzheimer's disease (AD) pathogenesis remains elusive. Mounting evidence suggests that acute and past exposure to the environmental toxicant lead (Pb) is associated with longitudinal decline in cognitive function, brain atrophy, and greater brain -amyloid () deposition. However, the nature of Pb-induced amyloid deposition and how it contributes to AD development remain unclear. This study investigates the role of Pb in the pathogenesis of cerebral amyloid angiopathy (CAA) and whether plasminogen activator inhibitor-1 (PAI-1) contributes to this process in the APP/PS1 mouse model. Female APP/PS1 mice at 8 wk of age were administered either Pb-acetate (PbAc) (i.e., ) or an equivalent molar concentration of sodium acetate (NaAc) via oral gavage once daily for 8 wk. Amyloid deposition and vascular amyloid were determined by immunostaining. In addition, perivascular drainage, vascular binding assay, and microglial endocytosis were examined to determine underlying mechanisms. Furthermore, magnetic resonance imaging demyelination imaging was performed invivo measure the level of demyelination. Finally, Y-maze and Morris water maze tests were assessed to evaluate the cognitive function of mice. APP/PS1 mice (an AD mice model) exposed to PbAc demonstrated more vascular amyloid deposition less neocortical myelination, and lower cognitive function, as well as greater vascular binding to , higher ratios, strikingly lower levels in the perivascular drainage, and microglial endocytosis. Importantly, exposure to a specific PAI-1 inhibitor, tiplaxtinin, which previously was reported to lower CAA pathology in mice, resulted in less CAA-related outcomes following PbAc exposure. Our findings suggest that PbAc induced CAA/AD pathogenesis via the PAI-1 signaling in the APP/PS1 mouse model, and the inhibition of PAI-1 could be a potential therapeutic target for PbAc-mediated CAA/AD disorders. https://doi.org/10.1289/EHP14384.

Lecanemab and Vascular-Amyloid Deposition in Brains of People With Down Syndrome

Anti-β-amyloid immunotherapy using lecanemab is becoming increasingly available to patients with Alzheimer disease (AD). Individuals with Down syndrome (DS) develop AD neuropathology by age 40 years, representing a significant cohort of genetically determined AD. To investigate the binding properties of lecanemab in the brains of people with DS, in anticipation of their inclusion in clinical trials or access to antiamyloid immunotherapies. The study included cases of postmortem brain tissue analysis from 15 individuals with DS aged 43 to 68 years that were acquired from Alzheimer Disease research centers at the University of California, Irvine and the University of Kentucky from 2008 to 2021. Data were analyzed from August 2023 through May 2024. The binding properties of lecanemab were assessed in brain tissue. The primary outcome was the extent of lecanemab binding to amyloid plaques and brain blood vessels. Tissue from 15 people (8 were female [53%]) with DS ranging in age from 43 to 68 (mean, 56.6) years were included in the study. Lecanemab-labeled amyloid plaques appeared in all 15 DS cases studied, indicating potential target engagement. However, extensive binding of lecanemab to brain blood vessels in DS was observed, raising significant safety concerns. These findings underscore the necessity for clinical trials of lecanemab in people with DS to evaluate both safety and efficacy, particularly in individuals older than 43 years. These findings suggest significant binding of lecanemab to cerebral amyloid angiopathy in DS. Lecanemab should be rigorously tested in clinical trials for AD in the DS population to determine its safety and efficacy, especially in those older than 43 years.

Optical Coherence Tomography Angiography Retinal Imaging Associations With Burden of Small Vessel Disease and Amyloid Positivity in the Brain.

Alzheimer disease (AD) and other dementias are associated with vascular changes and amyloid deposition, which may be reflected as density changes in the retinal capillaries. These changes may can be directly visualized and quantified with optical coherence tomography angiography (OCTA), making OCTA a potential noninvasive preclinical biomarker of small vessel disease and amyloid positivity. Our objective was to investigate the feasibility of retinal imaging metrics as noninvasive biomarkers of small vessel disease and amyloid positivity in the brain. We investigated associations between OCTA and neuroimaging and cognitive metrics in 41 participants without dementia from the Mayo Clinic Study of Aging and Alzheimer's Disease Research Center. OCTA metrics included superficial, deep, and full retina capillary density of the fovea, parafovea, and macula as well as the area of the foveal avascular zone (FAZ). Neuroimaging metrics included a high burden of white matter hyperintensity (WMH), presence of cerebral microbleeds (CMB), lacunar infarcts, and amyloid positivity as evidenced on positron emission tomography (PET), whereas cognitive metrics included mini-mental status examination (MMSE) score. We performed generalized estimating equations to account for measurements in each eye while controlling for age and sex to estimate associations between OCTA metrics and neuroimaging and cognitive scores. Associations between OCTA and neuroimaging metrics were restricted to the fovea. OCTA showed decreased capillary density with high burden of WMH in both the superficial (P = 0.003), deep (P = 0.004), and full retina (P = 0.01) in the fovea but not the parafovea or whole macula. Similarly, participants with amyloid PET positivity had significantly decreased capillary density in the superficial fovea (P = 0.027) and deep fovea (P = 0.03) but higher density in the superficial parafovea (P = 0.038). Participants with amyloid PET positivity also had a significantly larger FAZ (P = 0.031), whereas in those with high WMH burden the difference did not reach statistical significance (P = 0.075). There was also a positive association between MMSE and capillary density of the full retina within the fovea (P = 0.037) and in the superficial parafovea (P = 0.046). No associations were found between OCTA metrics and presence of CMB or presence of lacunar infarcts. The associations of lower foveal capillary density with cerebral WMH and amyloid positivity suggest that further research is warranted to evaluate for shared mechanisms of disease between small vessel disease and AD pathologies.

Abstract TMP115: White Matter Loss and Neurological Deficits Due to Chronic Global Hypoperfusion Are Worsened in a Mouse Model of Cerebral Amyloid Angiopathy

Cerebral amyloid angiopathy (CAA) is a disease of small and medium-sized vessels, characterized by amyloid deposition in the brain vasculature. The incidence of CAA increases with age and pathophysiological features (i.e., amyloid) overlap with that of Alzheimer’s Disease (AD). Cerebral hypoperfusion (CH) impairs the integrity of the blood brain barrier and contributes to cerebral atrophy and white matter loss. However, the link between hypoperfusion and vascular amyloid deposition remains understudied. We induced global CH with bilateral carotid artery stenosis (BCAS) in CAA mice of both sexes. We hypothesized that chronic CH accelerates cognitive decline in CAA, increases white matter damage, and induces gliotic changes in the brain. Using a mouse model of CAA (Tg-SwDI), male and female mice (12wks-old) were randomized to either BCAS (n=15) or sham (n=11) surgery. Cognitive (Y-maze (YM), NORT, Water Maze (WM)) and motor function (Open Field (OF)) testing was performed by a blinded investigator prior to surgery (baseline) and at regular intervals until tissue harvest 6 months post-BCAS. Brains were harvested for immunohistochemical (IHC) analysis (Kluver-Barrera (KB), Iba-1, GFAP, Myelin Basic Protein (MBP)) and flow cytometry. Sex-specific changes in spatial memory (YM) and learning (NORT/WM) were present in CAA BCAS mice, with females having an earlier onset of deficits than males. Female BCAS mice displayed deficits in cognition (NORT) at 3 (p=.003), 4 (YM, p=.0007), and 5-months (p=.01) after BCAS. Male BCAS mice demonstrated cognitive deficits 5 months post-BCAS (NORT, p=.001). Both female and male BCAS mice had poorer cognition (WM, p=.001) 6 months post-BCAS. IHC demonstrated increased demyelination (MBP, p=.004) and atrophy (KB) in the anterior corpus collosum (p=.04) and significant cortical gliosis (p=.02). The hippocampus contained higher numbers of NOX2-expressing (p= .051) and lipid-rich microglia in BCAS (p=.042) versus sham mice. Neuronal loss and increases in endothelial-cell amyloid levels were also found in BCAS CAA mice, using flow cytometry. Global CH accelerates cognitive deficits in a CAA model, an effect that is accelerated in female mice and led to gliosis, white matter damage, and lipid-accumulating microglia.

Clinical, Endoscopic, and Histopathologic Observations in Gastrointestinal Amyloidosis.

Amyloidosis is a group of systemic disorders caused by extracellular deposition of misfolded serum proteins. Gastrointestinal (GI) involvement is associated with a higher risk of GI bleeding, especially if mucosal lesions are present. Our study aims to evaluate the frequency of GI manifestations in patients with amyloidosis, to clinically characterize these patients and to describe the endoscopic and histopathologic findings in GI amyloidosis. A retrospective, single-center study of all patients admitted with amyloidosis and GI manifestations was conducted at a German University Hospital between July 2003 and June 2023. Clinical, endoscopic, and histopathological data was retrieved from medical records. Between July 2003 and June 2023, 63 patients with different types of amyloidosis were included into the study. Twenty-three (36,5%) were diagnosed with GI involvement of amyloidosis (60.9% male, median age 62 ± 18.28 years). The distribution of the types of amyloidosis were amyloid light chain (AL) at 52.5%, transthyretin (ATTR) at 21.7%, amyloid A (AA) at 13.0%, and unknown at 18%. Initial GI symptoms were present in 78.3% of the patients and included mainly diarrhea (34.8%), and abdominal pain (30.4%) Affected GI organs were primarily the colon (60,8%) and the stomach (39.1%). Endoscopic findings were ulcerations (47.8%), mucosal inflammation (43.5%), polyps (26.1%), erosions (13.0%), vascular malformation, polypoid protrusion, submucosal hematoma, erythema, metaplasia, and diverticulum. Histopathological findings included vascular wall thickening, (peri-)vascular and interstitial amyloid deposition. Gastrointestinal bleeding occurred in 39.1% of the patients. The mortality rate 5 years after diagnosis was 47.8%. Gastrointestinal amyloidosis can present with multiple symptoms and endoscopic findings, rendering diagnosis a challenge. Of clinical relevance, GI bleeding was a frequent event in our patient cohort. Therefore, clinicians must be aware of GI bleeding as a manifestation of amyloidosis and definite diagnosis should be achieved based on biopsy results.

Accelerated cerebral amyloid angiopathy and vascular alterations in a mixed mouse model of Alzheimer’s disease and cerebral small vessel disease

AbstractBackgroundWhile aging is the primary risk factor for Alzheimer’s disease (AD), emerging evidence suggests that vascular dysfunction, present in cerebral small vessel diseases (CSVD) such as cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), is also a major contributor for disease progression. Indeed, several studies have provided clinical evidence for a close synergistic relationship between AD and CSVD in cases where both diseases coexist. CSVD can elicit amyloid pathology, while Alzheimer’s‐associated cerebral amyloid angiopathy (CAA) and Ab plaque deposition may lead to concomitant vascular damage. Mutations in genes such as APP, PSEN1, and PSEN2 are not limited to AD, as APP mutations can also cause CAA, while PSEN1 and PSEN2 are involved in Notch3 signaling, a process known to be dysregulated in CADASIL. Here, we aimed to investigate the additive or synergistic effects of amyloid pathology and CADASIL‐related vascular damage on disease progression.MethodTo explore alterations in amyloid and vascular pathology when AD and CADASIL‐related CSVD coexist, we used PET/CT and histology to analyze over time the amyloid deposition in the form of plaques and CAA in a relevant mouse model of AD (5xFAD) carrying the Notch3 C456R mutation that causes CADASIL. Methoxy‐X04, Thioflavin‐S, or 6E10 were used to visualize amyloid accumulation in fixed brain tissues. The progression of microvascular dysfunction and neuroinflammation were assessed by immunofluorescence staining, Western blotting, RNA sequencing, and real‐time PCR.ResultAdult 5xFAD‐Notch3C456R mice showed accelerated parenchymal and vascular amyloid deposition compared to 5xFAD mice. Progressive gliosis and microvascular damage were concomitant to parenchymal and vascular amyloid accumulation. These changes were associated with blood‐brain barrier disruption and reduction in pericyte coverage of cerebral capillaries.ConclusionWe found accelerated amyloid plaque deposition, CAA, gliosis, and vascular damage in a mixed murine model of AD and CADASIL, suggesting that CSVD‐associated vascular changes directly contribute to AD pathology. This model offers novel opportunities to investigate the intricate interplay between CSVD and AD. This research was funded by NIH/NINDS grant RF1NS117486.

Amyloid-β (Aβ) immunotherapy induced microhemorrhages are associated with activated perivascular macrophages and peripheral monocyte recruitment in Alzheimer’s disease mice

BackgroundAmyloid-related imaging abnormalities (ARIA) have been identified as the most common and serious adverse events resulting from pathological changes in the cerebral vasculature during several recent anti-amyloid-β (Aβ) immunotherapy trials. However, the precise cellular and molecular mechanisms underlying how amyloid immunotherapy enhances cerebral amyloid angiopathy (CAA)-mediated alterations in vascular permeability and microhemorrhages are not currently understood. Interestingly, brain perivascular macrophages have been implicated in regulating CAA deposition and cerebrovascular function however, further investigations are required to understand how perivascular macrophages play a role in enhancing CAA-related vascular permeability and microhemorrhages associated with amyloid immunotherapy.MethodsIn this study, we examined immune responses induced by amyloid-targeting antibodies and CAA-induced microhemorrhages using histology and gene expression analyses in Alzheimer’s disease (AD) mouse models and primary culture systems.ResultsIn the present study, we demonstrate that anti-Aβ (3D6) immunotherapy leads to the formation of an antibody immune complex with vascular amyloid deposits and induces the activation of CD169+ perivascular macrophages. We show that macrophages activated by antibody mediated Fc receptor signaling have increased expression of inflammatory signaling and extracellular matrix remodeling genes such as Timp1 and MMP9 in vitro and confirm these key findings in vivo. Finally, we demonstrate enhanced vascular permeability of plasma proteins and recruitment of inflammatory monocytes around vascular amyloid deposits, which are associated with hemosiderin deposits from cerebral microhemorrhages, suggesting the multidimensional roles of activated perivascular macrophages in response to Aβ immunotherapy.ConclusionsIn summary, our study establishes a connection between Aβ antibodies engaged at CAA deposits, the activation of perivascular macrophages, and the upregulation of genes involved in vascular permeability. However, the implications of this phenomenon on the susceptibility to microhemorrhages remain to be fully elucidated. Further investigations are warranted to determine the precise role of CD169 + perivascular macrophages in enhancing CAA-mediated vascular permeability, extravasation of plasma proteins, and infiltration of immune cells associated with microhemorrhages.

Clinical Correlation of Histopathological Classification, Scoring, and Grading in Amyloid Nephropathies: Single-Center Experience

Objective: Amyloidosis is disorder of various etiologies in which abnormally folded fibrillary protein deposits with more than thirty forms infiltrate into extracellular spaces of affected organs. Renal involvement is clinically characterized by decreased estimated glomerular filtration rate (eGFR) and proteinuria. The aim of present study was to classify and grade renal amyloidosis cases using renal amyloid prognostic score (RAPS) systems, correlate clinical data and chronic kidney disease (CKD) stages. Methods: We retrospectively analyzed kidney biopsies of 45 patients diagnosed with renal amyloidosis applied between 2017-2022 to our department and scored each of patients according to RAPS. Results: 8.9% of patients had RAPS score 1, 53.3% had 2 and 37.8% had 3. Urea, serum creatinine and proteinuria levels of RAPS3 patients were significantly higher and eGFR levels were lower compared to RAPS1 patients (p<0.01). According to CKD stages, no significant difference was observed in glomerular amyloid deposition class and score, vascular and interstitial amyloid deposition scores, and glomerular sclerosis (p>0.05). The interstitial fibrosis, inflammation values and RAPS scores were found to be significantly higher in advanced CKD stages (p<0.05). Majority of patients at CKD stage 1-2 had RAPS score 2 (73.68%), while 57.1% of at stage 3 and 66.7% at stage 4-5 had RAPS score of 3 (p=0.0015). Conclusion: As a result, the intestinal fibrosis, inflammation values, RAPS scores were significantly higher in advanced CKD stages. Distribution pattern of amyloid in the renal parenchyma compartment, grade of RAPS and eGFR were associated with urea/creatinine, proteinuria levels and thus with CKD stage.

O-GalNAc glycosylation determines intracellular trafficking of APP and Aβ production

A primary pathology of Alzheimer's disease (AD) is amyloid β (Aβ) deposition in brain parenchyma and blood vessels, the latter being called cerebral amyloid angiopathy (CAA). Parenchymal amyloid plaques presumably originate from neuronal Aβ precursor protein (APP). Although vascular amyloid deposits' origins remain unclear, endothelial APP expression in APP knock-in mice was recently shown to expand CAA pathology, highlighting endothelial APP's importance. Furthermore, two types of endothelial APP-highly O-glycosylated APP and hypo-O-glycosylated APP-have been biochemically identified, but only the former is cleaved for Aβ production, indicating the critical relationship between APP O-glycosylation and processing. Here, we analyzed APP glycosylation and its intracellular trafficking in neurons and endothelial cells. Although protein glycosylation is generally believed to precede cell surface trafficking, which was true for neuronal APP, we unexpectedly observed that hypo-O-glycosylated APP is externalized to the endothelial cell surface and transported back to the Golgi apparatus, where it then acquires additional O-glycans. Knockdown of genes encoding enzymes initiating APP O-glycosylation significantly reduced Aβ production, suggesting this non-classical glycosylation pathway contributes to CAA pathology and is a novel therapeutic target.

Phenotype and imaging features associated with APP duplications

BackgroundAPP duplication is a rare genetic cause of Alzheimer disease and cerebral amyloid angiopathy (CAA). We aimed to evaluate the phenotypes of APP duplications carriers.MethodsClinical, radiological, and neuropathological features of 43 APP duplication carriers from 24 French families were retrospectively analyzed, and MRI features and cerebrospinal fluid (CSF) biomarkers were compared to 40 APP-negative CAA controls.ResultsMajor neurocognitive disorders were found in 90.2% symptomatic APP duplication carriers, with prominent behavioral impairment in 9.7%. Symptomatic intracerebral hemorrhages were reported in 29.2% and seizures in 51.2%. CSF Aβ42 levels were abnormal in 18/19 patients and 14/19 patients fulfilled MRI radiological criteria for CAA, while only 5 displayed no hemorrhagic features. We found no correlation between CAA radiological signs and duplication size. Compared to CAA controls, APP duplication carriers showed less disseminated cortical superficial siderosis (0% vs 37.5%, p = 0.004 adjusted for the delay between symptoms onset and MRI). Deep microbleeds were found in two APP duplication carriers. In addition to neurofibrillary tangles and senile plaques, CAA was diffuse and severe with thickening of leptomeningeal vessels in all 9 autopsies. Lewy bodies were found in substantia nigra, locus coeruleus, and cortical structures of 2/9 patients, and one presented vascular amyloid deposits in basal ganglia.DiscussionPhenotypes associated with APP duplications were heterogeneous with different clinical presentations including dementia, hemorrhage, and seizure and different radiological presentations, even within families. No apparent correlation with duplication size was found. Amyloid burden was severe and widely extended to cerebral vessels as suggested by hemorrhagic features on MRI and neuropathological data, making APP duplication an interesting model of CAA.

Optical Coherence Tomography Angiography (OCTA) Retinal Imaging Can Detect Burden of Small Vessel Disease and Amyloid Deposition in the Brain (P11-5.001)

<h3>Objective:</h3> To investigate the utility of retinal imaging with optical coherence tomography angiography (OCTA) metrics as noninvasive biomarkers of small vessel disease and amyloid burden in the brain. <h3>Background:</h3> OCTA allows visualization and density measurements of the capillaries at various levels of the retina. Vascular changes and amyloid deposition associated with Alzheimer’s Disease (AD) and other dementias may be reflected as density changes in the retinal capillaries, making OCTA a noninvasive preclinical biomarker of small vessel disease and dementia. <h3>Design/Methods:</h3> We investigated associations between OCTA and neuroimaging metrics in 47 cognitively unimpaired participants from the Mayo Clinic Study of Aging. OCTA metrics were used as predictors and included superficial and deep capillary density of the fovea, parafovea, and macula as well as the foveal avascular zone (FAZ) area from both eyes. Neuroimaging metrics included a high burden of white matter hyperintensity (WMH), presence of cerebral microbleeds, presence of lacunar infarcts, and the presence of amyloid deposition as evidenced on positron emission tomography (PET). We used linear models to test associations between OCT predictors and neuroimaging outcomes while controlling for age and sex. <h3>Results:</h3> Associations between neuroimaging metrics were restricted to the fovea, showing decreased capillary density with increased burden of WMH in both the superficial (p = 0.014) and deep (p = 0.013) fovea but not the parafovea or whole macula. Similarly, participants with amyloid deposition had decreased capillary density in the superficial (p=0.012) and deep (p = 0.015) fovea but not the parafovea or macula. Participants with amyloid deposition also had a significantly larger FAZ (p = 0.029). No associations were found between OCT metrics and presence of cerebral microbleeds or presence of lacunar infarcts. <h3>Conclusions:</h3> The foveal capillary density associations observed suggest a possible common mechanism of disease between small vessel disease and Alzheimer’s disease pathologies. <b>Disclosure:</b> Dr. Bermudez has nothing to disclose. Timothy Lesnick has received personal compensation for serving as an employee of Mayo Clinic. Dr. More has received intellectual property interests from a discovery or technology relating to health care. Dr. Ramanan has nothing to disclose. Dr. Knopman has received personal compensation in the range of $5,000-$9,999 for serving on a Scientific Advisory or Data Safety Monitoring board for DIAN TU study. The institution of Dr. Knopman has received research support from NIH. Dr. Vemuri has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Miller Medical Communications Inc.. The institution of Dr. Vemuri has received research support from NIH. Dr. Petersen has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Roche. Dr. Petersen has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Merck. Dr. Petersen has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Genentech. Dr. Petersen has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Nestle. Dr. Petersen has received personal compensation in the range of $5,000-$9,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Genentech, Inc.. Dr. Petersen has received personal compensation in the range of $10,000-$49,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Roche, Inc.. Dr. Petersen has received publishing royalties from a publication relating to health care. Dr. Petersen has received publishing royalties from a publication relating to health care. Dr. Graff-Radford has received personal compensation for serving as an employee of Mayo Clinic. Dr. Graff-Radford has received personal compensation in the range of $0-$499 for serving on a Scientific Advisory or Data Safety Monitoring board for NINDS/NIH. Dr. Graff-Radford has received personal compensation in the range of $5,000-$9,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for American Academy of Neurology. The institution of Dr. Graff-Radford has received research support from NIH. John J. Chen has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for UCB. John J. Chen has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Roche. John J. Chen has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Horizon.

Abstract 105: Sex Differences In The Response To Global Cerebral Hypo-Perfusion In A Mouse Model Of Cerebral Amyloid Angiopathy

Cerebral amyloid angiopathy (CAA) is a disease of small and medium-sized vessels, characterized by amyloid deposition. The incidence of CAA increases with age and evidence reveals worsened cognition in females compared to males. Cerebral hypoperfusion, or a decrease in cerebral blood flow (CBF), changes the integrity of the blood brain barrier and contributes to microhemorrhages, cerebral atrophy, and white matter loss. However, the link between vascular amyloid deposition and hypoperfusion remains understudied. We induced global cerebral hypoperfusion with bilateral carotid artery stenosis (BCAS) in CAA mice of both sexes and examined cognitive deficits, white matter loss, and cerebral gliosis. We hypothesize that chronic cerebral hypoperfusion will accelerate cognitive decline in CAA, increase white matter damage, and induce gliotic changes in the brain.Using a mouse model of CAA (Tg-SwDI), male and female mice (3 months of age) were randomized to either BCAS (n=15) or sham (n=11) surgery using 0.18mm coils to induce global cerebral hypoperfusion. Cognitive (Y-maze (YM), NORT, Water Maze (WM)) and motor function (Open Field (OF)) testing was performed by a blinded investigator prior to surgery (baseline) and at regular intervals until tissue harvest 6 months post-BCAS (PB). The brain and brainstem were harvested for immunohistochemical (IHC) analysis (Kluver-Barrera (KB), Iba-1, GFAP, Myelin Basic Protein (MBP)).Sex-specific changes in spatial memory (YM) and learning (NORT/WM) were present in BCAS mice. Female BCAS mice displayed greater deficits in cognition (NORT) at 3 (p=.0028), 4 (YM, p=.0007), and 5-months PB (NORT, p=.0149). Male BCAS mice demonstrated similar cognitive deficits, but at a later timepoint of 5 months PB (NORT, p=.0007). Both female and male BCAS mice had poorer cognition (WM) and motor function (OF, p=.0011/.0055) 6 months PB. IHC demonstrated increased demyelination (MBP) (p=.0038) and atrophy (KB) in the anterior corpus collosum (p=.0447) and significant gliosis (p=.0230).This study shows that chronic global hypoperfusion accelerates cognitive deficits in a CAA model, an effect that is accelerated in female mice. BCAS led to gliotic changes and demyelination associated with white matter damage in the brain.

Evaluation of Copper Chelation Therapy in a Transgenic Rat Model of Cerebral Amyloid Angiopathy.

Cerebral amyloid angiopathy (CAA) is characterized by the accumulation of the amyloid β (Aβ) protein in blood vessels and leads to hemorrhages, strokes, and dementia in elderly individuals. Recent reports have shown elevated copper levels colocalized with vascular amyloid in human CAA and Alzheimer's disease patients, which have been suggested to contribute to cytotoxicity through the formation of reactive oxygen species. Here, we treated a transgenic rat model of CAA (rTg-DI) with the copper-specific chelator, tetrathiomolybdate (TTM), via intraperitoneal (IP) administration for 6 months to determine if it could lower copper content in vascular amyloid deposits and modify CAA pathology. Results showed that TTM treatment led to elevated Aβ load in the hippocampus of the rTg-DI rats and increased microbleeds in the wild type (WT) animals. X-ray fluorescence microscopy was performed to image the distribution of copper and revealed a surprising increase in copper colocalized with Aβ aggregates in TTM-treated rTg-DI rats. Unexpectedly, we also found an increase in the copper content in unaffected vessels of both rTg-DI and WT animals. These results show that IP administration of TTM was ineffective in removing copper from vascular Aβ aggregates in vivo and increased the development of disease pathology in CAA.

Phosphorylation and Dephosphorylation of Beta-Amyloid Peptide in Model Cell Cultures: The Role of Cellular Protein Kinases and Phosphatases.

Phosphorylation of beta-amyloid peptide (Aβ) at the Ser8 residue affects its neurotoxicity, metal-dependent oligomerisation, amyloidogenicity, and other pathogenic properties. Phosphorylated Aβ (pS8-Aβ) was detected in vivo in AD model mice and in the brains of patients with AD. However, the pS8-Aβ production and the regulation of its levels have not been previously studied in detail. In this paper, immunochemical methods together with radioactive labelling were used to study the Aβ phosphorylation by intracellular and surface protein kinases of HEK293 cells and brain endothelial cells (bEnd.3). It was found that HEK293 robustly phosphorylated Aβ, likely with contribution from casein kinase 2 (CK2), whereas in bEnd.3, the activity of Aβ phosphorylation was relatively low. Further, the study showed that both HEK293 and bEnd.3 could dephosphorylate pS8-Aβ, mainly due to the activity of protein phosphatases PP1 and PP2A. The Aβ dephosphorylation efficiency in bEnd.3 was three times higher than in HEK293, which correlated with the reduced abundance of pS8-Aβ in vascular amyloid deposits of patients with AD compared to senile plaques. These data suggest an important role of CK2, PP1, and PP2A as regulators of Aβ phosphorylation, and point to the involvement of the blood-brain barrier in the control of Aβ modification levels.

Postmortem neocortical 3H‐PiB binding and levels of unmodified and pyroglutamate Aβ in Down syndrome and sporadic Alzheimer’s disease

AbstractBackgroundIndividuals with Down syndrome (DS) have a genetic predisposition for amyloid‐β (Aβ) overproduction and earlier onset of Aβ deposits compared to sporadic late‐onset Alzheimer’s disease (AD). Positron emission tomography (PET) with Pittsburgh Compound‐B (PiB) detects fibrillar Aβ pathology in living people with DS and AD, but its relationship with heterogeneous Aβ forms aggregated within amyloid deposits is not well understood.MethodWe performed quantitative in‐vitro 3H‐PiB binding assays and enzyme‐linked immunosorbent assays of fibrillar (insoluble) unmodified Aβ40 and Aβ42 forms and N‐terminus truncated and pyroglutamate‐modified AβNpE3‐40 and AβNpE3‐42 forms in postmortem frontal cortex and precuneus samples from 18 DS cases aged 43‐63 years and 17 late‐onset AD cases aged 62‐99 years.ResultCompared to the AD group, the DS group had higher levels of Aβ40 and AβNpE3‐40, while the two groups did not differ by Aβ42 and AβNpE3‐42 levels, in both the frontal cortex and precuneus. This resulted in lower ratios of Aβ42/Aβ40 and AβNpE3‐42/AβNpE3‐40 in the DS group compared to the AD group, in both cortical regions. Correlations of Aβ42/Aβ40 and AβNpE3‐42/AβNpE3‐40 ratios with CAA severity were strong in DS cases, and weak in AD cases. The two diagnostic groups did not differ significantly by 3H‐PiB binding levels in the frontal cortex or in the precuneus.ConclusionThese results demonstrate that compared to late‐onset AD cases, adult DS individuals with similar burden of cortical Aβ plaques have a preponderance of both pyroglutamate‐modified AβNpE3‐40 and unmodified Aβ40 forms which are associated with greater CAA pathology. Despite the distinct molecular profile of Aβ forms and greater vascular amyloidosis in DS cases, cortical 3H‐PiB binding does not distinguish between diagnostic groups that are at an advanced level of amyloid plaque pathology. These results underscore the need for development of CAA‐selective PET radiopharmaceuticals in order to detect and track the progression of cerebral vascular amyloid deposits in relation to Aβ plaques at the earliest pathology stages in individuals with DS.

Lack of ApoE inhibits ADan amyloidosis in a mouse model of familial Danish dementia

The Apolipoprotein E-ε4 allele (APOE-ε4) is the strongest genetic risk factor for late onset Alzheimer disease (AD). ApoE plays a critical role in amyloid-β (Aβ) accumulation in AD, and genetic deletion of the murine ApoE gene in mouse models results in a decrease or inhibition of Aβ deposition. The association between the presence of ApoE and amyloid in amyloidoses suggests a more general role for ApoE in the fibrillogenesis process. However, whether decreasing levels of ApoE would attenuate amyloid pathology in different amyloidoses has not been directly addressed. Familial Danish dementia (FDD) is an autosomal dominant neurodegenerative disease characterized by the presence of widespread parenchymal and vascular Danish amyloid (ADan) deposition and neurofibrillary tangles. A transgenic mouse model for FDD (Tg-FDD) is characterized by parenchymal and vascular ADan deposition. To determine the effect of decreasing ApoE levels on ADan accumulation invivo, we generated a mouse model by crossing Tg-FDD mice with ApoE KO mice (Tg-FDD+/-/ApoE-/-). Lack of ApoE results in inhibition of ADan deposition up to 18months of age. Additionally, our results from a genetic screen of Tg-FDD+/-/ApoE-/- mice emphasize the significant role for ApoE in neurodegeneration in FDD via glial-mediated mechanisms. Taken together, our findings suggest that the interaction between ApoE and ADan plays a key role in FDD pathogenesis, in addition to the known role for ApoE in amyloid plaque formation in AD.

Diagnosis, treatment, and follow-up of patients with cerebral amyloid angiopathy-related inflammation

PurposeCerebral amyloid angiopathy-related inflammation (CAA-ri) is a rare potentially reversible encephalopathy associated with an autoimmune process against proteins deposited in the walls of cortical and leptomeningeal brain vessels. Definite diagnosis requires histopathological features of vascular inflammation and amyloid deposition from brain biopsy. Clinical-neuroradiological criteria have been recently introduced and validated to reduce the need for biopsy. The purpose of this paper is to report a historical retrospective review of clinical-neuroradiological follow-up of two patients with probable CAA-ri and five patients with a reasonably probable suspect of CAA-ri (4 females, 3 males, patient’s age at admission: 66–79 years) seen at our institution between 2007 and 2021, focusing on clinical and neuroradiological awareness to this entity and variable response to immunotherapy.Materials and methodsClinical features at presentation included subacute to acute confusion (6/7), seizures (4/7), cognitive impairment (5/7), and focal neurological signs (3/7). Neuroradiology included braincomputed tomography followed by magnetic resonance imaging. Infectious diseases and autoimmune workups were then performed.ResultsCSF analysis was performed in two patients. Cerebral angiography was performed in two patients, to rule out vascular malformations. Hemorrhagic posterior reversible encephalopathy syndrome has been suspected in two patients. Four patients underwent immunotherapy with corticosteroids followed by reduction of brain dysfunctions. Three patients did not undergo immunotherapy but underwent clinical and/or neuroradiological remission.ConclusionsPatients with CAA-ri present a rare steroid-responsive acute to subacute brain dysfunction. Thus, it has to be known and recognized both clinically and neuroradiologically. Spontaneous clinical and/or neuroradiological improvement is possible in patients with mild symptoms.

Clusterin Binding Modulates the Aggregation and Neurotoxicity of Amyloid-β(1-42).

Alzheimer's disease (AD) is the most common neurodegenerative disorder characterized by the accumulation of amyloid-β (Aβ) aggregates in the brain. Clusterin (CLU), also known as apolipoprotein J, is a potent risk factor associated with AD pathogenesis, in which Aβ aggregation is essentially involved. We observed close colocalization of CLU and Aβ(1-42) (Aβ42) in parenchymal amyloid plaques or vascular amyloid deposits in the brains of human amyloid precursor protein (hAPP)-transgenic Tg2576 mice. Therefore, to elucidate the binding interaction between CLU and Aβ42 and its impact on amyloid aggregation and toxicity, the two synthetic proteins were incubated together under physiological conditions, and their structural and morphological variations were investigated using biochemical, biophysical, and microscopic analyses. Synthetic CLU spontaneously bound to different possible variants of Aβ42 aggregates with very high affinity (Kd = 2.647nM) in vitro to form solid CLU-Aβ42 complexes. This CLU binding prevented further aggregation of Aβ42 into larger oligomers or fibrils, enriching the population of smaller Aβ42 oligomers and protofibrils and monomers. CLU either alleviated or augmented Aβ42-induced cytotoxicity and apoptosis in the neuroblastoma-derived SH-SY5Y and N2a cells, depending on the incubation period and the molar ratio of CLU:Aβ42 involved in the reaction before addition to the cells. Thus, the effects of CLU on Aβ42-induced cytotoxicity were likely determined by the extent to which it bound and sequestered toxic Aβ42 oligomers or protofibrils. These findings suggest that CLU could influence amyloid neurotoxicity and pathogenesis by modulating Aβ aggregation.

Novel App knock-in mouse model shows key features of amyloid pathology and reveals profound metabolic dysregulation of microglia

BackgroundGenetic mutations underlying familial Alzheimer’s disease (AD) were identified decades ago, but the field is still in search of transformative therapies for patients. While mouse models based on overexpression of mutated transgenes have yielded key insights in mechanisms of disease, those models are subject to artifacts, including random genetic integration of the transgene, ectopic expression and non-physiological protein levels. The genetic engineering of novel mouse models using knock-in approaches addresses some of those limitations. With mounting evidence of the role played by microglia in AD, high-dimensional approaches to phenotype microglia in those models are critical to refine our understanding of the immune response in the brain.MethodsWe engineered a novel App knock-in mouse model (AppSAA) using homologous recombination to introduce three disease-causing coding mutations (Swedish, Arctic and Austrian) to the mouse App gene. Amyloid-β pathology, neurodegeneration, glial responses, brain metabolism and behavioral phenotypes were characterized in heterozygous and homozygous AppSAA mice at different ages in brain and/ or biofluids. Wild type littermate mice were used as experimental controls. We used in situ imaging technologies to define the whole-brain distribution of amyloid plaques and compare it to other AD mouse models and human brain pathology. To further explore the microglial response to AD relevant pathology, we isolated microglia with fibrillar Aβ content from the brain and performed transcriptomics and metabolomics analyses and in vivo brain imaging to measure energy metabolism and microglial response. Finally, we also characterized the mice in various behavioral assays.ResultsLeveraging multi-omics approaches, we discovered profound alteration of diverse lipids and metabolites as well as an exacerbated disease-associated transcriptomic response in microglia with high intracellular Aβ content. The AppSAA knock-in mouse model recapitulates key pathological features of AD such as a progressive accumulation of parenchymal amyloid plaques and vascular amyloid deposits, altered astroglial and microglial responses and elevation of CSF markers of neurodegeneration. Those observations were associated with increased TSPO and FDG-PET brain signals and a hyperactivity phenotype as the animals aged.DiscussionOur findings demonstrate that fibrillar Aβ in microglia is associated with lipid dyshomeostasis consistent with lysosomal dysfunction and foam cell phenotypes as well as profound immuno-metabolic perturbations, opening new avenues to further investigate metabolic pathways at play in microglia responding to AD-relevant pathogenesis. The in-depth characterization of pathological hallmarks of AD in this novel and open-access mouse model should serve as a resource for the scientific community to investigate disease-relevant biology.