Capacitive Electrode-Based Electric Field Treatments on Redox-Toxic Iron Deposits in Transgenic AD Mouse Models: The Electroceutical Targeting of Alzheimer's Disease Feasibility Study.

Iron accumulation in the brain accelerates Alzheimer's disease progression. To cure iron toxicity, we assessed the therapeutic effects of noncontact transcranial electric field stimulation to the brain on toxic iron deposits in either the Aß fibril structure or the Aß plaque in a mouse model of Alzheimer's disease (AD) as a pilot study. A capacitive electrode-based alternating electric field (AEF) was applied to a suspension of magnetite (Fe3O4) to measure field-sensitized reactive oxygen species (ROS) generation. The increase in ROS generation compared to the untreated control was both exposure-time and AEF-frequency dependent. The frequency-specific exposure of AEF to 0.7-1.4 V/cm on a magnetite-bound Aß-fibril or a transgenic Alzheimer's disease (AD) mouse model revealed the degradation of the Aß fibril or the removal of the Aß-plaque burden and ferrous magnetite compared to the untreated control. The results of the behavioral tests show an improvement in impaired cognitive function following AEF treatment on the AD mouse model. Tissue clearing and 3D-imaging analysis revealed no induced damage to the neuronal structures of normal brain tissue following AEF treatment. In conclusion, our results suggest that the effective degradation of magnetite-bound amyloid fibrils or plaques in the AD brain by the electro-Fenton effect from electric field-sensitized magnetite offers a potential electroceutical treatment option for AD.

How Can Static and Oscillating Electric Fields Serve in Decomposing Alzheimer's and Other Senile Plaques?

Alzheimer's disease is one of the most common neurodegenerative conditions, which are ascribed to extracellular accumulation of ß-amyloid peptides into plaques. This phenomenon seems to typify other related neurodegenerative diseases. The present study uses classical molecular-dynamics simulations to decipher the aggregation-disintegration behavior of ß-amyloid peptide plaques in the presence of static and oscillating oriented external electric fields (OEEFs). A long-term disintegration of such plaques is highly desirable since this may improve the prospects of therapeutic treatments of Alzheimer's disease and of other neurodegenerative diseases typified by senile plaques. Our study illustrates the spontaneous aggregation of the ß-amyloid, its prevention and breakdown when OEEF is applied, and the fate of the broken aggregate when the OEEF is removed. Notably, we demonstrate that the usage of an oscillating OEEF on ß-amyloid aggregates appears to lead to an irreversible disintegration. Insight is provided into the root causes of the various modes of aggregation, as well as into the different fates of OEEF-induced disintegration in oscillating vs static fields. Finally, our simulation results are compared to the well-established TTFields and the Deep Brain Stimulation (DBS) therapies, which are currently used options for treatments of Alzheimer's disease and other related neurodegenerative diseases.

Recent Advances Towards Diagnosis and Therapeutic Fingerprinting for Alzheimer's Disease.

Since the report of "a peculiar severe disease process of the cerebral cortex" by Alois Alzheimer in 1906, it was considered to be a rare condition characterized by loss of cognition, memory impairment, and pathological markers such as senile plaques or neurofibrillary tangles (NFTs). Later on, the report was published in the textbook "Psychiatrie" and the disease was named as Alzheimer's disease (AD) and was known to be the consequences of aging; however, owing to its complex etiology, there is no cure for the progressive neurodegenerative disorder. Our current understanding of the mechanisms involved in the pathogenesis of AD is still at the mechanistic level. The treatment strategies applied currently only alleviate the symptoms and co-morbidities. For instance, the available treatments such as the usage of acetylcholinesterase inhibitors and N-methyl D-aspartate antagonists have minimal impact on the disease progression and target the later aspects of the disease. The recent advancements in the last two decades have made us more clearly understand the pathophysiology of the disease which has led to the development of novel therapeutic strategies. This review gives a brief idea about the various facets of AD pathophysiology and its management through modern investigational therapies to give a new direction for development of targeted therapeutic measures.

Multifaceted Alzheimer's Disease: Building a Roadmap for Advancement of Novel Therapies.

Alzheimer's disease (AD) is one of the most prevailing neurodegenerative disorders of elderly humans associated with cognitive damage. Biochemical, epigenetic, and pathophysiological factors all consider a critical role of extracellular amyloid-beta (Aß) plaques and intracellular neurofibrillary tangles (NFTs) as pathological hallmarks of AD. In an endeavor to describe the intricacy and multifaceted nature of AD, several hypotheses based on the roles of Aß accumulation, tau hyperphosphorylation, impaired cholinergic signaling, neuroinflammation, and autophagy during the initiation and advancement of the disease have been suggested. However, in no way do these theories have the potential of autonomously describing the pathophysiological alterations located in AD. The complex pathological nature of AD has hindered the recognition and authentication of successful biomarkers for the progression of its diagnosis and therapeutic strategies. There has been a significant research effort to design multi-target-directed ligands for the treatment of AD, an approach which is developed by the knowledge that AD is a composite and multifaceted disease linked with several separate but integrated molecular pathways.

The effect of electroconvulsive therapy on neuroinflammation, behavior and amyloid plaques in the 5xFAD mouse model of Alzheimer's disease.

Microglial cells are affected in Alzheimer's disease (AD) and interact with amyloid-beta (Aß) plaques. Apart from memory loss, depression is common in patients with AD. Electroconvulsive therapy (ECT) is an anti-depressive treatment that may stimulate microglia, induce neuroinflammation and alter the levels of soluble Aß, but the effects of ECT on microglia and Aß aggregation in AD are not known. We investigated the short- and long-term effects of ECT on neuroinflammation and Aß accumulation. 5xFAD mice received either electroconvulsive stimulation (ECS n = 26) or sham treatment (n = 25) for 3 weeks. Microglia and Aß were analyzed in samples collected 24 h, 5 weeks, or 9 weeks after the last treatment. Aß plaques and microglia were quantified using immunohistochemistry. The concentration of soluble Aß and cytokines was quantified using ELISA and levels of Aß aggregates were measured with Western Blot. Microglial phagocytosis of Aß in the hippocampus was evaluated by flow cytometry in Methoxy-X04 injected mice 24 h following the last ECS treatment. Y-maze and Elevated plus maze were performed to study behavior after 5 weeks. We could not detect any significant short- or long-term effects of ECS on Aß pathology or neuroinflammation, but ECS reduced abnormal behavior in the Elevated Plus maze.

Neuroprotective mechanisms of chronic physical exercise via reduction of ß-amyloid protein in experimental models of Alzheimer's disease: A systematic review.

AIMS: Alzheimer's disease (AD) is the most common irreversible chronic neurodegenerative disease. It is characterized by the abnormal accumulation of ß-amyloid protein (Aß), which triggers homeostatic breakage in several physiological systems. However, the effect of chronic exercise on the formation of Aß as an alternative therapy has been investigated. This systematic review examines the antiamyloid effect of different types and intensities of exercise, seeking to elucidate its neuroprotective mechanisms. MAIN METHODS: The research was conducted in the electronic databases Pubmed, Embase, Scopus and Web of Science, using the following descriptors: "amyloid beta" (OR senile plaque OR amyloid plaque) and "exercise" (OR physical activity OR training). The risk of bias was evaluated through SYRCLE's Risk of Bias for experimental studies. KEY FINDINGS: 2268 articles were found, being 36 included in the study. A higher frequency of use of mice with genetic alterations was identified for the Alzheimer's disease (AD) model (n = 29). It was used as chronic training: treadmill running (n = 24), voluntary running wheel (n = 7), swimming (n = 4) and climbing (n = 2). The hippocampus and the cortex were the most investigated regions. However, physiological changes accompanied by the reduction of Aß and associated with AD progression were verified. It is concluded that exercise reduces the production of Aß in models of animals with AD. SIGNIFICANCE: Nevertheless, this effect contributes to the improvement of several physiological aspects related to Aß and that contribute to neurological impairment in AD.

Gene therapy using Aß variants for amyloid reduction.

Numerous aggregation inhibitors have been developed with the goal of blocking or reversing toxic amyloid formation in vivo. Previous studies have used short peptide inhibitors targeting different amyloid ß (Aß) amyloidogenic regions to prevent aggregation. Despite the specificity that can be achieved by peptide inhibitors, translation of these strategies has been thwarted by two key obstacles: rapid proteolytic degradation in the bloodstream and poor transfer across the blood-brain barrier. To circumvent these problems, we have created a minigene to express full-length Aß variants in the mouse brain. We identify two variants, F20P and F19D/L34P, that display four key properties required for therapeutic use: neither peptide aggregates on its own, both inhibit aggregation of wild-type Aß in vitro, promote disassembly of pre-formed fibrils, and diminish toxicity of Aß oligomers. We used intraventricular injection of adeno-associated virus (AAV) to express each variant in APP/PS1 transgenic mice. Lifelong expression of F20P, but not F19D/L34P, diminished Aß levels, plaque burden, and plaque-associated neuroinflammation. Our findings suggest that AAV delivery of Aß variants may offer a novel therapeutic strategy for Alzheimer's disease. More broadly our work offers a framework for identifying and delivering peptide inhibitors tailored to other protein-misfolding diseases.

Human gut microbiota Agathobaculum butyriciproducens improves cognitive impairment in LPS-induced and APP/PS1 mouse models of Alzheimer's disease.

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease, and is characterized by the accumulation and presence of amyloid plaques (Aß), tangles, dementia, and cognitive impairment. Currently, there is no known cure for AD; however, recently, the association between alteration of the gut microbiota and AD pathology has been explored to find novel therapeutic approaches. Microbiota-targeted intervention has been suggested as an attractive therapeutic approach for AD. Agathobaculum butyriciproducens (SR79) is a strict anaerobic and butyric acid-producing bacteria. We hypothesized that administration of SR79 might have a beneficial effect on cognitive deficits and AD pathologies. To determine the therapeutic effects of SR79 on AD pathologies, APP/PS1 transgenic and lipopolysaccharide -induced cognitive impairment mouse models were used. In the lipopolysaccharide -induced cognitive deficit model, the administration of SR79 improved cognitive function and decreased microglia activation. In addition, the administration of SR79 to APP/PS1 mice significantly improved novel object recognition and percent alteration results in novel object recognition and Y-maze alteration tests. Furthermore, Aß plaque deposition and microglial activation were markedly reduced in the parietal cortex and hippocampus after SR79 treatment in APP/PS1 mice. SR79 treatment significantly decreased gene expression levels of IL-1ß and C1QB and increased the gene expression levels of IGF-1 and thereby the downstream signaling pathway in the cortex of APP/PS1 mice. In conclusion, SR79 administration improved cognitive function and AD pathologies through the regulation of neuroinflammation and IGF-1 signaling in an animal model.

Targeting Pathological Amyloid Aggregates with Conformation-Sensitive Antibodies.

BACKGROUND: The pathogenesis of Alzheimer's disease (AD) is not directly caused by the presence of senile plaques but rather by the detrimental effects exerted on neuronal cells by toxic soluble oligomers. Such species are formed early during the aggregation process of the Aß1-42 peptide or can be released from mature fibrils. Nowadays, efficient tools for an early diagnosis, as well as pharmaceutical treatments targeting the harmful agents in samples of AD patients, are still missing. OBJECTIVE: By integrating in vitro immunochemical assay with in vivo neuronal models of toxicity, we aim to understand and target the principles that drive toxicity in AD. METHODS: We evaluated the specificity and sensitivity of A11 and OC conformational antibodies to target a range of pathologically relevant amyloid conformers and rescue their cytotoxic effects in neuronal culture models using a number of cellular readouts. RESULTS: We demonstrated the peculiar ability of conformational antibodies to label pathologically relevant Aß1-42 oligomers and fibrils and to prevent their detrimental effects on neuronal cells. CONCLUSION: Our results substantially improve our knowledge on the role of toxic assemblies in neurodegenerative diseases, thus suggesting new and more effective diagnostic and therapeutic tools for AD.

The utility of repeat kidney biopsy in systemic immunoglobulin light chain amyloidosis.

Background: The diagnostic utility of repeat kidney biopsy in AL amyloidosis patients in complete (CR) or very good partial hematologic response (VGPR) but with renal organ relapse is not clear.Methods: We present eight patients with AL amyloidosis who had a repeat kidney biopsy performed.Results: AL amyloidosis was initially diagnosed by a kidney biopsy. All patients had a favorable response to treatment (CR/VGPR) and five of them also had initially a renal organ response. A repeat kidney biopsy was done due to gradual deterioration of kidney function and/or proteinuria while maintaining a hematologic response. Repeat kidney biopsies showed findings consistent with amyloid deposits in all patients. Seven patients had renal progression with four of them requiring dialysis initiation. Only one patient had a favorable renal outcome. This patient had subacute kidney injury with decreasing proteinuria and was found to have granulomatous interstitial nephritis in addition to amyloid deposits and responded well to steroid treatment with rapid improvement in renal function.Conclusions: In AL amyloidosis patients who achieve a favorable hematologic response to treatment (CR/VGPR) but subsequently develop worsening renal insufficiency or proteinuria, a repeat kidney biopsy should generally not be performed. Amyloid deposits persist in the kidneys even after successful hematologic treatment and it is impossible to differentiate between new versus old amyloid deposits, which makes performing a repeat kidney biopsy unnecessary in most cases. Demonstration of amyloid deposits on repeat kidney biopsy would not aid in the decision making regarding re-initiation of hematologic treatment. A kidney biopsy should be considered only in cases when a specific alternative diagnosis is suspected.

Intracerebral Injection of Extracellular Vesicles from Mesenchymal Stem Cells Exerts Reduced Aß Plaque Burden in Early Stages of a Preclinical Model of Alzheimer's Disease.

Bone marrow Mesenchymal Stem Cells (BM-MSCs), due to their strong protective and anti-inflammatory abilities, have been widely investigated in the context of several diseases for their possible therapeutic role, based on the release of a highly proactive secretome composed of soluble factors and Extracellular Vesicles (EVs). BM-MSC-EVs, in particular, convey many of the beneficial features of parental cells, including direct and indirect ß-amyloid degrading-activities, immunoregulatory and neurotrophic abilities. Therefore, EVs represent an extremely attractive tool for therapeutic purposes in neurodegenerative diseases, including Alzheimer's disease (AD). We examined the therapeutic potential of BM-MSC-EVs injected intracerebrally into the neocortex of APPswe/PS1dE9 AD mice at 3 and 5 months of age, a time window in which the cognitive behavioral phenotype is not yet detectable or has just started to appear. We demonstrate that BM-MSC-EVs are effective at reducing the Aß plaque burden and the amount of dystrophic neurites in both the cortex and hippocampus. The presence of Neprilysin on BM-MSC-EVs, opens the possibility of a direct ß-amyloid degrading action. Our results indicate a potential role for BM-MSC-EVs already in the early stages of AD, suggesting the possibility of intervening before overt clinical manifestations.

Scanning ultrasound in the absence of blood-brain barrier opening is not sufficient to clear ß-amyloid plaques in the APP23 mouse model of Alzheimer's disease.

A major challenge in treating brain diseases is presented by the blood-brain barrier (BBB) that constitutes an efficient barrier not only for toxins but also a wide range of therapeutic agents. In overcoming this impediment, ultrasound in combination with intravenously injected microbubbles has emerged as a powerful technology that allows for the selective brain uptake of blood-borne factors and therapeutic agents by transient opening of the blood-brain barrier. We have previously shown that ultrasound in combination with microbubbles, but in the absence of a therapeutic agent, can effectively clear protein aggregates such as the hallmark lesions of Alzheimer's disease, amyloid-ß (Aß) plaques and Tau-containing neurofibrillary tangles. We have also demonstrated that the associated memory and motor impairments can be ameliorated or even restored. These studies included a negative sham control that received microbubbles in the absence of ultrasound. However, considering that ultrasound on its own is a pressure wave which has bioeffects, the possibility remained that ultrasound, without microbubbles, would also clear amyloid. We addressed this by performing repeated ultrasound only treatments of one brain hemisphere of Aß-depositing APP23 mice, using the contralateral hemisphere as the unsonicated control. This was followed by an extensive histological analysis of fibrillar and non-fibrillar amyloid. We found that ultrasound on its own was not sufficient to clear amyloid. This implies that although ultrasound on its own has neuromodulatory effects, exogenously supplied microbubbles are required for the clearance of Aß deposits.

Soluble TREM2 ameliorates pathological phenotypes by modulating microglial functions in an Alzheimer's disease model.

Triggering receptor expressed on myeloid cells 2 (TREM2) is a microglial surface receptor genetically linked to the risk for Alzheimer's disease (AD). A proteolytic product, soluble TREM2 (sTREM2), is abundant in the cerebrospinal fluid and its levels positively correlate with neuronal injury markers. To gain insights into the pathological roles of sTREM2, we studied sTREM2 in the brain of 5xFAD mice, a model of AD, by direct stereotaxic injection of recombinant sTREM2 protein or by adeno-associated virus (AAV)-mediated expression. We found that sTREM2 reduces amyloid plaque load and rescues functional deficits of spatial memory and long-term potentiation. Importantly, sTREM2 enhances microglial proliferation, migration, clustering in the vicinity of amyloid plaques and the uptake and degradation of Aß. Depletion of microglia abolishes the neuroprotective effects of sTREM2. Our study demonstrates a protective role of sTREM2 against amyloid pathology and related toxicity and suggests that increasing sTREM2 can be explored for AD therapy.

Recent therapeutic strategies targeting beta amyloid and tauopathies in Alzheimer's disease.

Alzheimer's disease (AD) has been a global concern for years due to its severe implications that affects the quality of life of the patients. The available line of therapy for treating Alzheimer's includes acetylcholinesterase inhibitors, NMDA(N-methyl-D-aspartate) antagonists and their combination which gives only symptomatic relief rather than treating the root cause of AD. Senile plaques and neurofibrillary tangles are the characteristic features underlying Alzheimer's pathology. Several attempts have been made towards exploring the niceties of these hallmarks and targeting various aspects of amyloid and tau pathology at different stages to eliminate the ultimate cause. Approaches targeting cleavage and formation of toxic amyloid fragments by secretases, aggregation of amyloid monofilaments, and immunotherapy against amyloid deposits has been extensively studied to treat amyloid pathology. Similarly, for tau pathology, tau hyperphosphorylation, microtubule stabilization, anti-tau immunotherapy has been explored. This article focuses on AD pathology and current pharmacotherapy, precisely for amyloid and tau. Furthermore, preclinical and clinical studies along with potential leads discovered under these approaches have also been included in this article. However, despite extensive research in drug development, overcoming clinical barrier still remain a major challenge for Alzheimer's pharmacotherapy.

Obstacles to translating the promise of nanoparticles into viable amyloid disease therapeutics.

Nanoparticles (NPs) constitute a powerful therapeutic platform with exciting prospects as potential inhibitors of amyloid-[Formula: see text] (Aß) aggregation, a process associated with Alzheimer's disease (AD). Researchers have synthesized and tested a large collection of NPs with disparate sizes, shapes, electrostatic properties and surface ligands that evoke a variety of responses on Aß aggregation. In spite of a decade of research on the NP-Aß system and many promising experimental results, NPs have failed to progress to any level of clinical trials for AD. A theoretical framework with which to approach this physical system is presented featuring two simple metrics, (1) the extent to which NPs adsorb Aß, and (2) the degree to which interaction with a NP alters Aß conformation relative to aggregation propensity. Most of our current understanding of these two interactions has been gained through experimentation, and many of these studies are reviewed herein. We also provide a potential roadmap for studies that we believe could produce viable NPs as an effective AD therapeutic platform.

Time course of focused ultrasound effects on ß-amyloid plaque pathology in the TgCRND8 mouse model of Alzheimer's disease.

Previous studies have demonstrated that temporarily increasing the permeability of the blood-brain barrier using focused ultrasound can reduce ß-amyloid plaque load and improve cognitive function in animal models of Alzheimer's disease. However, the underlying mechanism and duration for which the effects of one treatment persists for are unknown. Here, we used in vivo two-photon fluorescence microscopy to track changes in ß-amyloid plaque sizes in the TgCRND8 mouse model of Alzheimer's disease after one focused ultrasound treatment. We found that one treatment reduced plaques to 62 ± 16% (p ≤ 0.001) of their original volume two days post-sonication; this decrease in size persisted for two weeks. We then sought to evaluate the effectiveness of biweekly focused ultrasound treatments using magnetic resonance imaging-guided focused ultrasound treatments. Three to five biweekly treatments resulted in a 27 ± 7% (p ≤ 0.01) decrease in plaque number and 40 ± 10% (p ≤ 0.01) decrease in plaque surface area compared to untreated littermates. This study demonstrates that one focused ultrasound treatment reduces the size of existing ß-amyloid plaques for two weeks, and that repeated biweekly focused ultrasound treatments is an effective method of reducing ß-amyloid pathology in moderate-to-late stages of Alzheimer's disease.

Stereological Investigation of the Effects of Treadmill Running Exercise on the Hippocampal Neurons in Middle-Aged APP/PS1 Transgenic Mice.

The risk of cognitive decline during Alzheimer's disease (AD) can be reduced if physical activity is maintained; however, the specific neural events underlying this beneficial effect are still uncertain. To quantitatively investigate the neural events underlying the effect of running exercise on middle-aged AD subjects, 12-month-old male APP/PS1 mice were randomly assigned to a control group or running group, and age-matched non-transgenic littermates were used as a wild-type group. AD running group mice were subjected to a treadmill running protocol (regular and moderate intensity) for four months. Spatial learning and memory abilities were assessed using the Morris water maze. Hippocampal amyloid plaques were observed using Thioflavin S staining and immunohistochemistry. Hippocampal volume, number of neurons, and number of newborn cells (BrdU+ cells) in the hippocampus were estimated using stereological techniques, and newborn neurons were observed using double-labelling immunofluorescence. Marked neuronal loss in both the CA1 field and dentate gyrus (DG) and deficits in both the neurogenesis and survival of new neurons in the DG of middle-aged APP/PS1 mice were observed. Running exercise could improve the spatial learning and memory abilities, reduce amyloid plaques in the hippocampi, delay neuronal loss, induce neurogenesis, and promote the survival of newborn neurons in the DG of middle-aged APP/PS1 mice. Exercise-induced protection of neurons and adult neurogenesis within the DG might be part of the important structural basis of the improved spatial learning and memory abilities observed in AD mice.

Phos-tau peptide immunization of amyloid-tg-mice reduced non-mutant phos-tau pathology, improved cognition and reduced amyloid plaques.

Tau-immumotherapy has shown promising results in tangle/tauopathy-tg animal models. Here we immunized amyloid-mice (APPSwe/PSEN1dE9-tg, presenting amyloid-plaques, not neurofibrillary-tangles) with phos-tau peptides, previously shown by us to have high efficacy in mutant-tau tauopathy-mice. These amyloid-mice allowed us to test the effect of the vaccine in a model of familial AD patients with mutant amyloid plaque pathology, where tau pathology - once develops - is of non-mutant tau. Fourteen-month-old amyloid-mice were immunized with phos-tau peptides or vehicle. Eight weeks later, amelioration of cognitive impairment was noticed. Histological analysis revealed that the phos (non-mutant)-tau pathology (detected by us in these aged amyloid-mice while not in non-tg-mice), was lower in the phos-tau immunized amyloid-mice than in the non-immunized mice. Interestingly, we detected a decrease in amyloid plaque pathology, probably associated with the increased microglial burden, which surrounded both tau and amyloid pathology. These results point to the added value of immunizing AD-mice with the phos-tau-vaccine, targeting both tau and amyloid pathology, which may have clinical relevance. It also points to the multifaceted interplay between tau/amyloid pathologies.

Investigation of the Safety of Focused Ultrasound-Induced Blood-Brain Barrier Opening in a Natural Canine Model of Aging.

Rationale: Ultrasound-mediated opening of the Blood-Brain Barrier(BBB) has shown exciting potential for the treatment of Alzheimer's disease(AD). Studies in transgenic mouse models have shown that this approach can reduce plaque pathology and improve spatial memory. Before clinical translation can occur the safety of the method needs to be tested in a larger brain that allows lower frequencies be used to treat larger tissue volumes, simulating clinical situations. Here we investigate the safety of opening the BBB in half of the brain in a large aged animal model with naturally occurring amyloid deposits. Methods: Aged dogs naturally accumulate plaques and show associated cognitive declines. Low-frequency ultrasound was used to open the BBB unilaterally in aged beagles (9-11yrs, n=10) in accordance with institutionally approved protocols. Animals received either a single treatment or four weekly treatments. Magnetic resonance imaging(MRI) was used to guide the treatments and assess the tissue effects. The animals underwent neurological testing during treatment follow-up, and a follow-up MRI exam 1 week following the final treatment. Results: The permeability of the BBB was successfully increased in all animals (mean enhancement: 19±11% relative to untreated hemisphere). There was a single adverse event in the chronic treatment group that resolved within 24 hrs. Follow-up MRI showed the BBB to be intact with no evidence of tissue damage in all animals. Histological analysis showed comparable levels of microhemorrhage between the treated and control hemispheres in the prefrontal cortex (single/repeat treatment: 1.0±1.4 vs 0.4±0.5/5.2±1.8 vs. 4.0±2.0). No significant differences were observed in beta-amyloid load (single/repeat: p=0.31/p=0.98) although 3/5 animals in each group showed lower Aß loads in the treated hemisphere. Conclusion: Whole-hemisphere opening of the BBB was well tolerated in the aged large animal brain. The treatment volumes and frequencies used are clinically relevant and indicate safety for clinical translation. Further study is warranted to determine if FUS has positive effects on naturally occurring amyloid pathology.