scholarly journals Cholesterol Alters Mitophagy by Impairing Optineurin Recruitment and Lysosomal Clearance in Alzheimer’s Disease

2020 ◽  
Author(s):  
Vicente Roca-Agujetas ◽  
Elisabet Barbero-Camps ◽  
Cristina de Dios ◽  
Petar Podlesniy ◽  
Albert Morales ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cholesterol Homeostasis ◽  
Critical Event ◽  
Primary Neurons ◽  
Cholesterol Levels ◽  
Swedish Mutation ◽  
Intracellular Cholesterol ◽  
The Impact

Abstract Background: Emerging evidence indicates that impaired mitophagy-mediated clearance of defective mitochondria is a critical event in Alzheimer’s disease (AD) pathogenesis. Amyloid-beta (A) metabolism and the microtubule-associated protein tau have been reported to regulate key components of the mitophagy machinery. However, the mechanisms that lead to mitophagy dysfunction in AD are not fully deciphered. We have previously shown that intraneuronal cholesterol accumulation can disrupt the autophagy flux, resulting in low A clearance. In this study, we examine the impact of neuronal cholesterol changes on mitochondrial removal by autophagy.Methods: Regulation of PINK1-parkin-mediated mitophagy was investigated in conditions of acute (in vitro) and chronic (in vivo) high cholesterol loading using cholesterol-enriched SH-SY5Y cells, cultured primary neurons from transgenic mice overexpressing active SREBF2 (sterol regulatory element binding factor 2), and mice of increasing age that express the amyloid precursor protein with the familial Alzheimer Swedish mutation (Mo/HuAPP695swe) and mutant presenilin 1 (PS1-dE9) together with active SREBF2.Results: In cholesterol-enriched SH-SY5Y cells and cultured primary neurons, high intracellular cholesterol levels stimulated mitochondrial PINK1 accumulation and mitophagosomes formation triggered by A while impairing lysosomal-mediated clearance. Antioxidant recovery of cholesterol-induced mitochondrial glutathione (GSH) depletion prevented mitophagosomes formation indicating mitochondrial ROS involvement. Interestingly, when brain cholesterol accumulated chronically in aged APP-PSEN1-SREBF2 mice the mitophagy flux was affected at the early steps of the pathway, with defective recruitment of the key autophagy receptor optineurin (OPTN). Sustained cholesterol-induced alterations in APP-PSEN1-SREBF2 mice promoted an age-dependent accumulation of OPTN into HDAC6-positive aggresomes, which disappeared after in vivo treatment with GSH ethyl ester (GSHee). The analyses in post-mortem brain tissues from individuals with AD confirmed these findings, showing OPTN in aggresome-like structures that correlated with high mitochondrial cholesterol levels in late AD stages. Conclusions: Our data demonstrate that accumulation of intracellular cholesterol reduces the clearance of defective mitochondria and suggest recovery of the cholesterol homeostasis and the mitochondrial scavenging of ROS as potential therapeutic targets for AD.

scholarly journals Cholesterol Alters Mitophagy By Impairing Optineurin Recruitment And Lysosomal Clearance In Alzheimer’s Disease

2021 ◽  
Author(s):  
Vicente Roca-Agujetas ◽  
Elisabet Barbero-Camps ◽  
Cristina de Dios ◽  
Petar Podlesniy ◽  
Xenia Abadin ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cholesterol Homeostasis ◽  
Critical Event ◽  
Primary Neurons ◽  
Cholesterol Levels ◽  
Swedish Mutation ◽  
Intracellular Cholesterol ◽  
The Impact

Abstract Background: Emerging evidence indicates that impaired mitophagy-mediated clearance of defective mitochondria is a critical event in Alzheimer’s disease (AD) pathogenesis. Amyloid-beta (Ab) metabolism and the microtubule-associated protein tau have been reported to regulate key components of the mitophagy machinery. However, the mechanisms that lead to mitophagy dysfunction in AD are not fully deciphered. We have previously shown that intraneuronal cholesterol accumulation can disrupt the autophagy flux, resulting in low Ab clearance. In this study, we examine the impact of neuronal cholesterol changes on mitochondrial removal by autophagy.Methods: Regulation of PINK1-parkin-mediated mitophagy was investigated in conditions of acute (in vitro) and chronic (in vivo) high cholesterol loading using cholesterol-enriched SH-SY5Y cells, cultured primary neurons from transgenic mice overexpressing active SREBF2 (sterol regulatory element binding factor 2), and mice of increasing age that express the amyloid precursor protein with the familial Alzheimer Swedish mutation (Mo/HuAPP695swe) and mutant presenilin 1 (PS1-dE9) together with active SREBF2.Results: In cholesterol-enriched SH-SY5Y cells and cultured primary neurons, high intracellular cholesterol levels stimulated mitochondrial PINK1 accumulation and mitophagosomes formation triggered by Ab while impairing lysosomal-mediated clearance. Antioxidant recovery of cholesterol-induced mitochondrial glutathione (GSH) depletion prevented mitophagosomes formation indicating mitochondrial ROS involvement. Interestingly, when brain cholesterol accumulated chronically in aged APP-PSEN1-SREBF2 mice the mitophagy flux was affected at the early steps of the pathway, with defective recruitment of the key autophagy receptor optineurin (OPTN). Sustained cholesterol-induced alterations in APP-PSEN1-SREBF2 mice promoted an age-dependent accumulation of OPTN into HDAC6-positive aggresomes, which disappeared after in vivo treatment with GSH ethyl ester (GSHee). The analyses in post-mortem brain tissues from individuals with AD confirmed these findings, showing OPTN in aggresome-like structures that correlated with high mitochondrial cholesterol levels in late AD stages. Conclusions: Our data demonstrate that accumulation of intracellular cholesterol reduces the clearance of defective mitochondria and suggest recovery of the cholesterol homeostasis and the mitochondrial scavenging of ROS as potential therapeutic targets for AD.

scholarly journals Cholesterol Alters Mitophagy by Impairing Optineurin Recruitment and Lysosomal Clearance in Alzheimer’s Disease

2020 ◽  
Author(s):  
Vicente Roca-Agujetas ◽  
Elisabet Barbero-Camps ◽  
Cristina de Dios ◽  
Petar Podlesniy ◽  
Xenia Abadin ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cholesterol Homeostasis ◽  
Critical Event ◽  
Primary Neurons ◽  
Cholesterol Levels ◽  
Swedish Mutation ◽  
Intracellular Cholesterol ◽  
The Impact

Abstract Background: Emerging evidence indicates that impaired mitophagy-mediated clearance of defective mitochondria is a critical event in Alzheimer’s disease (AD) pathogenesis. Amyloid-beta (Aβ) metabolism and the microtubule-associated protein tau have been reported to regulate key components of the mitophagy machinery. However, the mechanisms that lead to mitophagy dysfunction in AD are not fully deciphered. We have previously shown that intraneuronal cholesterol accumulation can disrupt the autophagy flux, resulting in low Aβ clearance. In this study, we examine the impact of neuronal cholesterol changes on mitochondrial removal by autophagy.Methods: Regulation of PINK1-parkin-mediated mitophagy was investigated in conditions of acute (in vitro) and chronic (in vivo) high cholesterol loading using cholesterol-enriched SH-SY5Y cells, cultured primary neurons from transgenic mice overexpressing active SREBF2 (sterol regulatory element binding factor 2), and mice of increasing age that express the amyloid precursor protein with the familial Alzheimer Swedish mutation (Mo/HuAPP695swe) and mutant presenilin 1 (PS1-dE9) together with active SREBF2.Results: In cholesterol-enriched SH-SY5Y cells and cultured primary neurons, high intracellular cholesterol levels stimulated mitochondrial PINK1 accumulation and mitophagosomes formation triggered by Aβ while impairing lysosomal-mediated clearance. Antioxidant recovery of cholesterol-induced mitochondrial glutathione (GSH) depletion prevented mitophagosomes formation indicating mitochondrial ROS involvement. Interestingly, when brain cholesterol accumulated chronically in aged APP-PSEN1-SREBF2 mice the mitophagy flux was affected at the early steps of the pathway, with defective recruitment of the key autophagy receptor optineurin (OPTN). Sustained cholesterol-induced alterations in APP-PSEN1-SREBF2 mice promoted an age-dependent accumulation of OPTN into HDAC6-positive aggresomes, which disappeared after in vivo treatment with GSH ethyl ester (GSHee). The analyses in post-mortem brain tissues from individuals with AD confirmed these findings, showing OPTN in aggresome-like structures that correlated with high mitochondrial cholesterol levels in late AD stages.Conclusions: Our data demonstrate that accumulation of intracellular cholesterol reduces the clearance of defective mitochondria and suggest recovery of the cholesterol homeostasis and the mitochondrial scavenging of ROS as potential therapeutic targets for AD.

scholarly journals Cholesterol alters mitophagy by impairing optineurin recruitment and lysosomal clearance in Alzheimer’s disease

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Vicente Roca-Agujetas ◽  
Elisabet Barbero-Camps ◽  
Cristina de Dios ◽  
Petar Podlesniy ◽  
Xenia Abadin ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cholesterol Homeostasis ◽  
Critical Event ◽  
Primary Neurons ◽  
Cholesterol Levels ◽  
Swedish Mutation ◽  
Intracellular Cholesterol ◽  
The Impact

Abstract Background Emerging evidence indicates that impaired mitophagy-mediated clearance of defective mitochondria is a critical event in Alzheimer’s disease (AD) pathogenesis. Amyloid-beta (Aβ) metabolism and the microtubule-associated protein tau have been reported to regulate key components of the mitophagy machinery. However, the mechanisms that lead to mitophagy dysfunction in AD are not fully deciphered. We have previously shown that intraneuronal cholesterol accumulation can disrupt the autophagy flux, resulting in low Aβ clearance. In this study, we examine the impact of neuronal cholesterol changes on mitochondrial removal by autophagy. Methods Regulation of PINK1-parkin-mediated mitophagy was investigated in conditions of acute (in vitro) and chronic (in vivo) high cholesterol loading using cholesterol-enriched SH-SY5Y cells, cultured primary neurons from transgenic mice overexpressing active SREBF2 (sterol regulatory element binding factor 2), and mice of increasing age that express the amyloid precursor protein with the familial Alzheimer Swedish mutation (Mo/HuAPP695swe) and mutant presenilin 1 (PS1-dE9) together with active SREBF2. Results In cholesterol-enriched SH-SY5Y cells and cultured primary neurons, high intracellular cholesterol levels stimulated mitochondrial PINK1 accumulation and mitophagosomes formation triggered by Aβ while impairing lysosomal-mediated clearance. Antioxidant recovery of cholesterol-induced mitochondrial glutathione (GSH) depletion prevented mitophagosomes formation indicating mitochondrial ROS involvement. Interestingly, when brain cholesterol accumulated chronically in aged APP-PSEN1-SREBF2 mice the mitophagy flux was affected at the early steps of the pathway, with defective recruitment of the key autophagy receptor optineurin (OPTN). Sustained cholesterol-induced alterations in APP-PSEN1-SREBF2 mice promoted an age-dependent accumulation of OPTN into HDAC6-positive aggresomes, which disappeared after in vivo treatment with GSH ethyl ester (GSHee). The analyses in post-mortem brain tissues from individuals with AD confirmed these findings, showing OPTN in aggresome-like structures that correlated with high mitochondrial cholesterol levels in late AD stages. Conclusions Our data demonstrate that accumulation of intracellular cholesterol reduces the clearance of defective mitochondria and suggest recovery of the cholesterol homeostasis and the mitochondrial scavenging of ROS as potential therapeutic targets for AD.

scholarly journals Abnormal brain cholesterol homeostasis in Alzheimer’s disease—a targeted metabolomic and transcriptomic study

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Vijay R. Varma ◽  
H. Büşra Lüleci ◽  
Anup M. Oommen ◽  
Sudhir Varma ◽  
Chad T. Blackshear ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Brain Tissue ◽  
Cholesterol Metabolism ◽  
Cholesterol Biosynthesis ◽  
Cholesterol Homeostasis ◽  
Transcriptomic Data ◽  
Brain Cholesterol ◽  
Cholesterol Levels

AbstractThe role of brain cholesterol metabolism in Alzheimer’s disease (AD) remains unclear. Peripheral and brain cholesterol levels are largely independent due to the impermeability of the blood brain barrier (BBB), highlighting the importance of studying the role of brain cholesterol homeostasis in AD. We first tested whether metabolite markers of brain cholesterol biosynthesis and catabolism were altered in AD and associated with AD pathology using linear mixed-effects models in two brain autopsy samples from the Baltimore Longitudinal Study of Aging (BLSA) and the Religious Orders Study (ROS). We next tested whether genetic regulators of brain cholesterol biosynthesis and catabolism were altered in AD using the ANOVA test in publicly available brain tissue transcriptomic datasets. Finally, using regional brain transcriptomic data, we performed genome-scale metabolic network modeling to assess alterations in cholesterol biosynthesis and catabolism reactions in AD. We show that AD is associated with pervasive abnormalities in cholesterol biosynthesis and catabolism. Using transcriptomic data from Parkinson’s disease (PD) brain tissue samples, we found that gene expression alterations identified in AD were not observed in PD, suggesting that these changes may be specific to AD. Our results suggest that reduced de novo cholesterol biosynthesis may occur in response to impaired enzymatic cholesterol catabolism and efflux to maintain brain cholesterol levels in AD. This is accompanied by the accumulation of nonenzymatically generated cytotoxic oxysterols. Our results set the stage for experimental studies to address whether abnormalities in cholesterol metabolism are plausible therapeutic targets in AD.

scholarly journals Anti-Inflammatory Activity of A Polyphenolic Extract from Arabidopsis thaliana in In Vitro and In Vivo Models of Alzheimer’s Disease

2019 ◽  
Vol 20 (3) ◽  
pp. 708 ◽  
Author(s):  
Roberto Mattioli ◽  
Antonio Francioso ◽  
Maria d’Erme ◽  
Maurizio Trovato ◽  
Patrizia Mancini ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Arabidopsis Thaliana ◽  
Heme Oxygenase 1 ◽  
Neuroprotective Effects ◽  
In Vivo Models ◽  
Polyphenolic Extract ◽  
Anti Inflammatory ◽  
The Impact

Alzheimer’s disease (AD) is the most common neurodegenerative disorder and the primary form of dementia in the elderly. One of the main features of AD is the increase in amyloid-beta (Aβ) peptide production and aggregation, leading to oxidative stress, neuroinflammation and neurodegeneration. Polyphenols are well known for their antioxidant, anti-inflammatory and neuroprotective effects and have been proposed as possible therapeutic agents against AD. Here, we investigated the effects of a polyphenolic extract of Arabidopsis thaliana (a plant belonging to the Brassicaceae family) on inflammatory response induced by Aβ. BV2 murine microglia cells treated with both Aβ25–35 peptide and extract showed a lower pro-inflammatory (IL-6, IL-1β, TNF-α) and a higher anti-inflammatory (IL-4, IL-10, IL-13) cytokine production compared to cells treated with Aβ only. The activation of the Nrf2-antioxidant response element signaling pathway in treated cells resulted in the upregulation of heme oxygenase-1 mRNA and in an increase of NAD(P)H:quinone oxidoreductase 1 activity. To establish whether the extract is also effective against Aβ-induced neurotoxicity in vivo, we evaluated its effect on the impaired climbing ability of AD Drosophila flies expressing human Aβ1–42. Arabidopsis extract significantly restored the locomotor activity of these flies, thus confirming its neuroprotective effects also in vivo. These results point to a protective effect of the Arabidopsis extract in AD, and prompt its use as a model in studying the impact of complex mixtures derived from plant-based food on neurodegenerative diseases.

scholarly journals Conformation-selective tau monoclonal antibodies inhibit tau pathology in primary neurons and a mouse model of Alzheimer’s disease

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Garrett S. Gibbons ◽  
Soo-Jung Kim ◽  
Qihui Wu ◽  
Dawn M. Riddle ◽  
Susan N. Leight ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Monoclonal Antibodies ◽  
Statistical Significance ◽  
Neuritic Plaque ◽  
Plaque Burden ◽  
Primary Neurons ◽  
Tau Pathology ◽  
Model Of Alzheimer’S Disease

Abstract Background The spread of tau pathology in Alzheimer’s disease (AD) is mediated by cell-to-cell transmission of pathological tau seeds released from neurons that, upon internalization by recipient neurons, template the misfolding of naïve cellular tau, thereby propagating fibrillization. We hypothesize that anti-tau monoclonal antibodies (mAbs) that selectively bind to pathological tau seeds will inhibit propagation of tau aggregates and reduce the spread of tau pathology in vivo. Methods We inoculated mice with human AD brain-derived extracts containing tau paired helical filaments (AD-tau) and identified two novel mAbs, DMR7 and SKT82, that selectively bind to a misfolded pathological conformation of tau relative to recombinant tau monomer. To evaluate the effects of these mAbs on the spread of pathological tau in vivo, 5xFAD mice harboring significant brain Aβ plaque burden were unilaterally injected with AD-tau in the hippocampus, to initiate the formation of neuritic plaque (NP) tau pathology, and were treated weekly with intraperitoneal (i.p.) injections of DMR7, SKT82, or IgG isotype control mAbs. Results DMR7 and SKT82 bind epitopes comprised of the proline-rich domain and c-terminal region of tau and binding is reduced upon disruption of the pathological conformation of AD-tau by chemical and thermal denaturation. We found that both DMR7 and SKT82 immunoprecipitate pathological tau and significantly reduce the seeding of cellular tau aggregates induced by AD-tau in primary neurons by 60.5 + 13.8% and 82.2 + 8.3%, respectively, compared to IgG control. To investigate the mechanism of mAb inhibition, we generated pH-sensitive fluorophore-labeled recombinant tau fibrils seeded by AD-tau to track internalization of tau seeds and demonstrate that the conformation-selective tau mAbs inhibit the internalization of tau seeds. DMR7 and SKT82 treatment reduced hyperphosphorylated NP tau as measured with AT8 immunohistochemistry (IHC) staining, but did not achieve statistical significance in the contralateral cortex and SKT82 significantly reduced tau pathology in the ipsilateral hippocampus by 24.2%; p = 0.044. Conclusions These findings demonstrate that conformation-selective tau mAbs, DMR7 and SKT82, inhibit tau pathology in primary neurons by preventing the uptake of tau seeds and reduce tau pathology in vivo, providing potential novel therapeutic candidates for the treatment of AD.

scholarly journals Selective reduction of hydroperoxyeicosatetraenoic acids to their hydroxy derivatives by apolipoprotein D: implications for lipid antioxidant activity and Alzheimer's disease

2012 ◽  
Vol 442 (3) ◽  
pp. 713-721 ◽  
Author(s):  
Surabhi Bhatia ◽  
Bianca Knoch ◽  
Jenny Wong ◽  
Woojin S. Kim ◽  
Paul L. Else ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Lipid Peroxidation ◽  
Selective Reduction ◽  
Methionine Sulfoxide ◽  
Lipid Hydroperoxides ◽  
Apolipoprotein D ◽  
Methionine Residues ◽  
The Impact

ApoD (apolipoprotein D) is up-regulated in AD (Alzheimer's disease) and upon oxidative stress. ApoD inhibits brain lipid peroxidation in vivo, but the mechanism is unknown. Specific methionine residues may inhibit lipid peroxidation by reducing radical-propagating L-OOHs (lipid hydroperoxides) to non-reactive hydroxides via a reaction that generates MetSO (methionine sulfoxide). Since apoD has three conserved methionine residues (Met49, Met93 and Met157), we generated recombinant proteins with either one or all methionine residues replaced by alanine and assessed their capacity to reduce HpETEs (hydroperoxyeicosatetraenoic acids) to their HETE (hydroxyeicosatetraenoic acid) derivatives. ApoD, apoDM49-A and apoDM157-A all catalysed the reduction of HpETEs to their corresponding HETEs. Amino acid analysis of HpETE-treated apoD revealed a loss of one third of the methionine residues accompanied by the formation of MetSO. Additional studies using apoD(M93-A) indicated that Met93 was required for HpETE reduction. We also assessed the impact that apoD MetSO formation has on protein aggregation by Western blotting of HpETE-treated apoD and human brain samples. ApoD methionine oxidation was associated with formation of apoD aggregates that were also detected in the hippocampus of AD patients. In conclusion, conversion of HpETE into HETE is mediated by apoD Met93, a process that may contribute to apoD antioxidant function.

scholarly journals Plaque-associated human microglia accumulate lipid droplets in a chimeric model of Alzheimer’s disease

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Christel Claes ◽  
Emma Pascal Danhash ◽  
Jonathan Hasselmann ◽  
Jean Paul Chadarevian ◽  
Sepideh Kiani Shabestari ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Lipid Droplet ◽  
Lipid Droplets ◽  
Foam Cells ◽  
Wild Type ◽  
Human Microglia ◽  
Model Of Alzheimer’S Disease ◽  
The Impact

Abstract Background Disease-associated microglia (DAMs), that surround beta-amyloid plaques, represent a transcriptionally-distinct microglial profile in Alzheimer’s disease (AD). Activation of DAMs is dependent on triggering receptor expressed on myeloid cells 2 (TREM2) in mouse models and the AD TREM2-R47H risk variant reduces microglial activation and plaque association in human carriers. Interestingly, TREM2 has also been identified as a microglial lipid-sensor, and recent data indicates lipid droplet accumulation in aged microglia, that is in turn associated with a dysfunctional proinflammatory phenotype. However, whether lipid droplets (LDs) are present in human microglia in AD and how the R47H mutation affects this remains unknown. Methods To determine the impact of the TREM2 R47H mutation on human microglial function in vivo, we transplanted wild-type and isogenic TREM2-R47H iPSC-derived microglial progenitors into our recently developed chimeric Alzheimer mouse model. At 7 months of age scRNA-seq and histological analyses were performed. Results Here we report that the transcriptome of human wild-type TREM2 and isogenic TREM2-R47H DAM xenografted microglia (xMGs), isolated from chimeric AD mice, closely resembles that of human atherosclerotic foam cells. In addition, much like foam cells, plaque-bound xMGs are highly enriched in lipid droplets. Somewhat surprisingly and in contrast to a recent in vitro study, TREM2-R47H mutant xMGs exhibit an overall reduction in the accumulation of lipid droplets in vivo. Notably, TREM2-R47H xMGs also show overall reduced reactivity to plaques, including diminished plaque-proximity, reduced CD9 expression, and lower secretion of plaque-associated APOE. Conclusions Altogether, these results indicate lipid droplet accumulation occurs in human DAM xMGs in AD, but is reduced in TREM2-R47H DAM xMGs, as it occurs secondary to TREM2-mediated changes in plaque proximity and reactivity.

scholarly journals A General Approach to Convert Hemicyanine Dyes into Highly Optimized Photoacoustic Scaffolds for Analyte Sensing

2021 ◽  
Author(s):  
Sarah Garder ◽  
Catharine Brady ◽  
Cameron Keeton ◽  
Anuj K Yadav ◽  
Sharath C Mallojjala ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Photoacoustic Imaging ◽  
Disease Model ◽  
Photoacoustic Signal ◽  
Model Of Alzheimer’S Disease ◽  
5Xfad Mice ◽  
The Impact

<p>In the context of deep-tissue disease biomarker detection and analyte sensing of biologically relevant species, the impact of photoacoustic imaging has been profound. However, most photoacoustic imaging agents to date are based on the repurposing of existing fluorescent dye platforms that exhibit non-optimal properties for photoacoustic applications (e.g., high fluorescence quantum yield). Herein, we introduce two effective modifications to the hemicyanine dye to afford PA-HD, a new dye scaffold optimized for photoacoustic probe development. We observed a significant increase in the photoacoustic output, representing an increase in sensitivity of 4.8-fold and a red-shift of the λ<sub>abs</sub> from 690 nm to 745 nm to enable ratiometric imaging. Moreover, to demonstrate the generalizability and utility of our remodeling efforts, we developed three probes using common analyte-responsive triggers for beta-galactosidase activity (PA-HD-Gal), nitroreductase activity (PA-HD-NTR), and hydrogen peroxide (PA-HD-H<sub>2</sub>O<sub>2</sub>). The performance of each probe (responsiveness, selectivity) was evaluated <i>in vitro</i> and <i>in cellulo</i>. To showcase the enhance properties afforded by PA-HD for <i>in vivo</i> photoacoustic imaging, we employed an Alzheimer’s disease model to detect H<sub>2</sub>O<sub>2</sub>. In particular, the photoacoustic signal at 735 nm in the brains of 5xFAD mice (a murine model of Alzheimer’s disease) increased by 1.72 ± 0.20-fold relative to background indicating the presence of oxidative stress, whereas the change in wildtype mice was negligible (1.02 ± 0.14). These results were confirmed via ratiometric calibration which was not possible using the parent HD platform.</p>

Mechanistic Modeling of Soluble Aβ Dynamics and Target Engagement in the Brain by Anti-Aβ mAbs in Alzheimer’s Disease

2020 ◽  
Vol 17 (4) ◽  
pp. 393-406
Author(s):  
Gregory Z. Ferl ◽  
Reina N. Fuji ◽  
Jasvinder K. Atwal ◽  
Tony Sun ◽  
Saroja Ramanujan ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Amyloid Β ◽  
Mechanistic Modeling ◽  
Model Parameters ◽  
Target Engagement ◽  
Binding Characteristics ◽  
The Impact ◽  
The Brain

Background: Anti-amyloid-β (Aβ) monoclonal antibodies (mAbs) are currently in development for treating Alzheimer’s disease. Objectives: To address the complexity of Aβ target engagement profiles, improve the understanding of crenezumab Pharmacokinetics (PK) and Aβ Pharmacodynamics (PD) in the brain, and facilitate comparison of anti-Aβ therapies with different binding characteristics. Methods: A mechanistic mathematical model was developed describing the distribution, elimination, and binding kinetics of anti-Aβ mAbs and Aβ (monomeric and oligomeric forms of Aβ1-40 and Aβ1-42) in the brain, Cerebrospinal Fluid (CSF), and plasma. Physiologically meaningful values were assigned to the model parameters based on the previous data, with remaining parameters fitted to clinical measurements of Aβ concentrations in CSF and plasma, and PK/PD data of patients undergoing anti-Aβ therapy. Aβ target engagement profiles were simulated using a Monte Carlo approach to explore the impact of biological uncertainty in the model parameters. Results: Model-based estimates of in vivo affinity of the antibody to monomeric Aβ were qualitatively consistent with the previous data. Simulations of Aβ target engagement profiles captured observed mean and variance of clinical PK/PD data. Conclusion: This model is useful for comparing target engagement profiles of different anti-Aβ therapies and demonstrates that 60 mg/kg crenezumab yields a significant increase in Aβ engagement compared with lower doses of solanezumab, supporting the selection of 60 mg/kg crenezumab for phase 3 studies. The model also provides evidence that the delivery of sufficient quantities of mAb to brain interstitial fluid is a limiting step with respect to the magnitude of soluble Aβ oligomer neutralization.

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