Toward the treatment for Alzheimer's disease: adsorption is primary mechanism of removing amyloid β protein with hollow-fiber dialyzers of the suitable materials, polysulfone and polymethyl methacrylate

First-in-human study of blood amyloid β removal from early Alzheimer's disease patients with normal kidney function

INTRODUCTION

Amyloid β (Aβ) is a brain protein that causes Alzheimer's disease (AD). This study aimed to verify whether hemadsorption using a hexadecyl-alkylated cellulose bead (HexDC) column removes blood Aβ and brain Aβ accumulation in mild cognitive impairment/mild AD cases with normal kidney function.

METHODS

Two patients with positive Aβ on brain imaging underwent HexDC hemadsorption weekly for 6 months.

RESULTS

The Aβ removal efficiency of HexDC was 87-99%. Aβ_1-40 /Aβ_1-42 influx into the blood in one session was 596/56 ng and 489/48 ng for Case A and Case B, respectively. Although brain Aβ accumulation did not clearly change after six months of hemadsorption, cognitive functions measured by the two tests were maintained or slightly improved.

CONCLUSION

Blood Aβ removal was performed in two early AD patients with normal kidney function without adverse events, and it slightly improved or maintained cognitive function. This article is protected by copyright. All rights reserved.

Aβ Influx into the Blood Evoked by Different Blood Aβ Removal Systems: A Potential Therapy for Alzheimer's Disease

PURPOSE

Amyloid-β (Aβ) is a brain protein that causes Alzheimer's disease. We have revealed that extracorporeal blood Aβ-removal systems evoked a large Aβ influx into the blood. This study investigated the system that is more effective in evoking Aβ influx.

METHODS

Aβ removal activities were compared between hexadecyl-alkylated cellulose beads (HexDC) and fragments of polysulfone hollow fibers (PSf-HFs) in mini-columns to eliminate the filtration effect. Then, adsorptive filtration systems were adapted for PSf hemodialyzers to enhance Aβ adsorption on micropores in the wall of hollow fibers. Plasma Aβ concentrations of patients with renal failure were analyzed during treatment with PSf hemodialyzers alone for 8 h or tandemly connected HexDC and PSf hemodialyzers for 4 h.

RESULTS

In the in vitro study, Aβ removal efficiency for HexDC was approximately 100% during the 60 min treatment, whereas the removal efficiency for PSf-HF fragments gradually decreased. However, PSf hemodialyzer in adsorptive filtration systems removed Aβs comparably or more than HexDC. Aβ influx into the blood increases time-dependently. Concomitant use of HexDC and PSf hemodialyzer evoked a larger Aβ_1-40 influx than that of PSf hemodialyzer alone. However, Aβ_1-42 influx by PSf hemodialyzer alone was similar to or a little larger than influx by the combined system. Both systems evoked almost doubled Aβ influx than estimated Aβs existing in the normal brain during the 4 h treatment.

CONCLUSION

PSf hemodialyzer alone for a longer period and concomitant use of HexDC and PSf hemodialyzer for a shorter time effectively evoked a larger Aβ influx. To evoke Aβ_1-42 influx, PSf hemodialyzer alone was effective enough. These findings of devices and treatment time may lead to optimal clinical settings for therapy and prevention of Alzheimer's disease.

Influx of Tau and Amyloid-β Proteins into the Blood During Hemodialysis as a Therapeutic Extracorporeal Blood Amyloid-β Removal System for Alzheimer's Disease

The accumulation of amyloid-β protein (Aβ) and tau in the brain is a major pathological change related to Alzheimer's disease. We have continued to develop Extracorporeal Blood Aβ Removal Systems (E-BARS) as a method for enhancing Aβ clearance from the brain. Our previous report revealed that dialyzers effectively remove blood Aβ and evoke large Aβ influxes into the blood, resulting in a decrease in brain Aβ accumulation after initiating hemodialysis, and that patients who underwent hemodialysis had lower brain Aβ accumulation than those who did not. Here, plasma total tau concentrations from 30 patients undergoing hemodialysis were measured using an ultrasensitive immunoassay and compared to those from 11 age-matched controls. Plasma total tau concentrations were higher in patients with renal failure regardless of whether they underwent hemodialysis, suggesting the involvement of the kidneys in tau degradation and excretion. Hemodialyzers effectively removed blood Aβ but not extracorporeal blood tau. The influx of tau into the blood was observed at around the 1 h period during hemodialysis sessions. However, the influx amount of tau was far smaller than that of Aβ. Furthermore, histopathological analysis revealed similar, not significantly less, cerebral cortex phosphorylated tau accumulation between the 17 patients who underwent hemodialysis and the 16 age-matched subjects who did not, although both groups showed sparse accumulation. These findings suggest that hemodialysis may induce both tau and Aβ migration into the blood. However, as a therapeutic strategy for Alzheimer's disease, it may only be effective for removing Aβ from the brain.

Extracorporeal apheresis therapy for Alzheimer disease-targeting lipids, stress, and inflammation

Current therapeutic approaches to Alzheimer disease (AD) remain disappointing and, hence, there is an urgent need for effective treatments. Here, we provide a perspective review on the emerging role of "metabolic inflammation" and stress as a key factor in the pathogenesis of AD and propose a novel rationale for correction of metabolic inflammation, increase resilience and potentially slow-down or halt the progression of the neurodegenerative process. Based on recent evidence and observations of an early pilot trial, we posit a potential use of extracorporeal apheresis in the prevention and treatment of AD. Apolipoprotein E, lipoprotein(a), oxidized LDL (low density lipoprotein)'s and large LDL particles, as well as other proinflammatory lipids and stress hormones such as cortisol, have been recognized as key factors in amyloid plaque formation and aggravation of AD. Extracorporeal lipoprotein apheresis systems employ well-established, powerful methods to provide an acute, reliable 60-80% reduction in the circulating concentration of these lipid classes and reduce acute cortisol levels. Following a double-membrane extracorporeal apheresis in patients with AD, there was a significant reduction of proinflammatory lipids, circulating cytokines, immune complexes, proinflammatory metals and toxic chaperones in patients with AD. On the basis of the above, we suggest designing clinical trials to assess the promising potential of such "cerebropheresis" treatment in patients with AD and, possibly, other neurodegenerative diseases.

Removal of Aβ Oligomers from the Blood: A Potential Therapeutic System for Alzheimer's Disease

PURPOSE

Amyloid-β protein (Aβ) is one of the causative proteins of Alzheimer's disease. We have been developing extracorporeal blood Aβ-removal systems as a method for enhancing Aβ clearance from the brain. We reported previously that medical adsorbents and hemodialyzers removed Aβ monomers from peripheral blood, which was associated with influx of Aβ monomers from the brain into the bloodstream. Our intent here was to develop a method to promote clearance of Aβ oligomers and to provide an estimate of the molecular size of intact Aβ oligomers in plasma.

METHODS

Two hollow-fiber devices with different pore sizes (Membranes A and B) were evaluated as removers of Aβ oligomers with human plasma in vitro. The concomitant removal of Aβ oligomers and monomers was investigated by using Membrane B and hexadecyl alkylated cellulose beads or polysulfone hemodialyzers. Double-filtration plasmapheresis with Membrane A was investigated as an approach for the removal of plasma Aβ oligomers in humans.

RESULTS

Aβ oligomers were effectively removed by both Membranes A and B. The increase of Aβ oligomers in plasma was observed just after the removal of plasma Aβ oligomers in humans. The intact molecular size of major Aβ oligomers in the plasma was estimated to be larger than albumin at approximately 60 kDa or more. Additionally, the concomitant removal of Aβ monomers and oligomers evoked dissociation of larger Aβ oligomers into smaller ones and monomers.

CONCLUSION

Aβ oligomers were cleared from plasma both in vitro and in human subjects by using hollow-fiber membranes with large pores, indicating that their intact sizes were mostly larger than 60 kDa. Aβ oligomers in peripheral circulation were increased after some clearances in human. Further investigation will determine whether the Aβ oligomers detected in circulation after clearance were via influx from the brain.

'Amytrapper', a Novel Immobilized Sepharose API Matrix, Removes Amyloid-β from Circulation in vitro

Alzheimer's disease (AD) is the most common cause of dementia among elderly patients afflicted by neurodegenerative diseases, caused by the accumulation of amyloid-β (Aβ). Therapeutic interventions in targeting and restricting Aβ production resulted in little or no success. However, recent studies have shown signs of success in validating Aβ as a target. Recombinant Technologies LLC (RTL) has developed and studied its proprietary Amytrap peptide to remove Aβ from circulation which in turn depletes brain Aβ in a clinically relevant mouse model of AD. In the current study, this Amytrap peptide (the active pharmacological ingredient, API) has been linked to sepharose matrix by click chemistry. The derivative namely 'Amytrapper' was confirmed to remove Aβ from the surrounding media spiked with Aβ₄₂. Additional testing performed on Amytrapper with sera and plasma containing Aβ₄₂ showed retention of Aβ₄₂ upon increasing concentrations of biotinylated Aβ₄₂ (bio-Aβ₄₂). Specificity of this binding was confirmed via 1) pre-blocking Amytrapper with cold (unbiotinylated) Aβ₄₂ followed by binding experiment with biotinylated Aβ₄₂, 2) 2-dimensional SDS-PAGE analyses on samples harvested before and after the binding experiment, and 3) reconciling the amounts bound to beads and left over in the flow through. The results provide a proof of concept for our proposed prototype design for an Amytrapper device. The results suggest that extracorporeal clearance of Aβ₄₂ by Amytrapper could be a way to manage accumulation of amyloid in AD and thus could become an added mode of therapy for disease modification.

Removal of blood amyloid-β with hemodialysis reduced brain amyloid-β, confirmed by brain imaging: a case report

The accumulation of amyloid-β protein (Aβ) in the brain signifies a major pathological change of Alzheimer's disease (AD). Extracorporeal blood Aβ removal system (E-BARS) has been under development as a tool for enhancing the clearance of Aβ from the brain. Previously, we revealed that dialyzers remove blood Aβs effectively, evoking substantial Aβ influx into the blood during hemodialysis sessions as one form of blood Aβ removal by E-BARS, and that postmortem brains of hemodialysis patients exhibited lower Aβ accumulation. Here, we present a case report of a 77-year-old male patient with end-stage renal failure whose Aβ accumulation in the brain declined by initiating and continuing hemodialysis for 6 months. This report suggests that blood Aβ removal by E-BARS could be an effective therapeutic method for AD.

Adsorptive filtration systems for effective removal of blood amyloid β: a potential therapy for Alzheimer's disease

Accumulation of amyloid-β protein (Aβ) in the brain causes cognitive impairment in Alzheimer's disease. We hypothesized that an extracorporeal system that rapidly removed Aβ from the blood may accelerate Aβ drainage from the brain. We previously reported that dialyzers remove blood Aβs effectively, mainly by adsorption on the inner surfaces of the hollow fibers, resulting in lower Aβ accumulation in the brains of patients undergoing hemodialysis than the controls without hemodialysis. The aim of the present study was to create a more convenient and effective blood Aβ removal system using adsorptive filtration, in which the filtrate returned to the body. Filtration from inside to outside of the fibers may enhance the adsorption of plasma Aβs on the surface of micropores inside the hollow fiber walls. Hence, pool solutions of 4 ng/mL synthetic Aβ_1-40 and Aβ_1-42 peptides (300 mL) or human plasma (1000 mL of 250-346 pg/mL Aβ_1-40 and 30-48 pg/mL Aβ_1-42) were circulated through polysulfone dialyzers at a flow rate of 50 mL/min to evaluate an adsorptive filtration system. The rates of Aβ reduction from the pool solutions significantly increased along with the filtration rates. A filtration rate of > 1 mL/min, preferably 5-10 mL/min resulted in an 80-100% reduction of Aβs within 30 min of circulation. The rates of Aβs passing through the membrane walls were maintained around 0% for plasma Aβs during circulation. Thus, our adsorptive filtration systems may be useful for removing blood Aβs for patients with Alzheimer's disease.