Novel therapeutic approach for Alzheimer's disease by removing amyloid beta protein from the brain with an extracorporeal removal system

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.

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.

Ganglioside GQ1b ameliorates cognitive impairments in an Alzheimer's disease mouse model, and causes reduction of amyloid precursor protein

Brain-derived neurotrophic factor (BDNF) plays crucial roles in memory impairments including Alzheimer’s disease (AD). Previous studies have reported that tetrasialoganglioside GQ1b is involved in long-term potentiation and cognitive functions as well as BDNF expression. However, in vitro and in vivo functions of GQ1b against AD has not investigated yet. Consequently, treatment of oligomeric Aβ followed by GQ1b significantly restores Aβ_1–42-induced cell death through BDNF up-regulation in primary cortical neurons. Bilateral infusion of GQ1b into the hippocampus ameliorates cognitive deficits in the triple-transgenic AD mouse model (3xTg-AD). GQ1b-infused 3xTg-AD mice had substantially increased BDNF levels compared with artificial cerebrospinal fluid (aCSF)-treated 3xTg-AD mice. Interestingly, we also found that GQ1b administration into hippocampus of 3xTg-AD mice reduces Aβ plaque deposition and tau phosphorylation, which correlate with APP protein reduction and phospho-GSK3β level increase, respectively. These findings demonstrate that the tetrasialoganglioside GQ1b may contribute to a potential strategy of AD treatment.

'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.

Impaired hepatic amyloid-beta degradation in Alzheimer's disease

Extensive research strongly suggests that amyloid beta (Aβ) aggregates in the brain have a central role in Alzheimer's disease (AD) pathogenesis. Pathological Aβ deposition is likely due to an altered balance between overproduction and elimination. Rodent studies have suggested that the liver has a major role in Aβ degradation. It is possible alterations of liver function could affect brain Aβ levels through changes in blood Aβ concentration. In this study, we hypothesized hepatic Aβ degradation to be impaired in AD subjects. To test our hypothesis, an Aβ degradation assay was developed using synthetic fluorescein-labeled Aβ40 and Aβ42 spiked into human liver homogenates. Aβ degradation rates were lower in AD-derived homogenates as compared with those from non-demented (ND) control subjects, even after accounting for such covariates as age, sex, and APOE genotype. The protein expression of potential Aβ-degrading enzymes were also examined. Neprilysin levels were not different in AD liver samples, while cathepsin D and insulin-degrading enzyme were significantly altered in AD subjects. The results support the possibility that impaired hepatic Aβ degradation could be a factor contributing to increased brain Aβ accumulation and AD.

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.

End stage renal disease is associated with development of dementia

There is controversy regarding the extent of risk for dementia in patients with end stage renal disease (ESRD) who are undergoing hemodialysis (HD) or peritoneal dialysis (PD). We examined data from Taiwan's Longitudinal Health Insurance Database, and used Cox proportional hazard regression analysis to compare the development of dementia in 72,934 HD and PD patients with 72,934 matched controls from January 1, 1999 to December 31, 2010. The results indicate an increased risk for dementia overall in HD patients (adjusted hazard ratio [aHR] = 1.64, p < 0.0001) and PD patients (aHR = 2.21, p < 0.0001). HD and PD patients also had significantly greater aHRs for vascular dementia (VaD) and unspecified dementia (UnD), but only HD patients had a significantly greater aHR for Alzheimer's disease (AD). Further research is needed to confirm whether management of ESRD with PD can reduce the incidence of AD, and to identify the mechanisms by which ESRD increases the risk of dementia.

Patients that have Undergone Hemodialysis Exhibit Lower Amyloid Deposition in the Brain: Evidence Supporting a Therapeutic Strategy for Alzheimer's Disease by Removal of Blood Amyloid

As a proof of concept that removal of blood amyloid-β (Aβ) can reduce Aβ deposition in the brains of patients with Alzheimer's disease, cortices of patients who had undergone hemodialysis (HD), which removes Aβ from the blood, were histochemically analyzed; postmortem brain sections were stained with anti-Aβ antibodies. Brains from patients who had undergone HD had significantly fewer senile plaques than those of patient who had not undergone HD. This significant difference was also confirmed by silver staining. Our findings suggest that removal of blood Aβ by hemodialysis results in lower accumulation of Aβ in the brain.

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

The accumulation of amyloid β protein (Aβ) in the brain reflects cognitive impairment in Alzheimer's disease. We hypothesized that the rapid removal of Aβ from the blood by an extracorporeal system may act as a peripheral Aβ sink from the brain. The present study aimed to determine the optimal materials and modality for Aβ removal by hemodialyzers. In a batch analysis, hollow-fiber fragments of polysulfone (PSf) and polymethyl methacrylate (PMMA) showed greater removal efficiency of Aβ than did other materials, such as cellulose-triacetates and ethylene-vinyl alcohol copolymer (PSf:PMMA at 30 min, 98.6 ± 2.4 %:97.8 ± 0.4 % for Aβ1-40 and 96.6 ± 0.3 %:99.0 ± 1.0 % for Aβ1-42). In a modality study, the Aβ solution was applied to PSf dialyzers and circulated in the dialysis and Air-filled adsorption-mode (i.e., the outer space of the hollow fibers was filled with air) or phosphate-buffered saline (PBS)-filled adsorption modes. The Aβ1-40 removal efficiency of the pre/post dialyzer in the Air-filled adsorption-mode was the highest (62.4 ± 12.6 %, p = 0.007). In a flow rate study in the Air-filled adsorption-mode, 200 mL/min showed the highest Aβ1-40 reduction rate of pool solution (97.3 ± 0.8 % at 15 min) compared with 20 mL/min (p = 0.00001) and 50 mL/min (p = 0.00382). PMMA dialyzers showed similar high reduction rates. Thus, the optimal modality for Aβ removal was the adsorption-mode with PSf or PMMA hollow fibers at around 50 mL/min flow rate, which seems to be suitable for clinical use.

Reduction of Alzheimer's disease amyloid-β in plasma by hemodialysis and its relation to cognitive functions

BACKGROUND/AIMS

Rapid removal of plasma amyloid-β (Aβ) by blood purification may serve as a peripheral Aβ sink from the brain for Alzheimer's disease therapy. We investigated the reduction of plasma Aβ during hemodialysis and cognitive states.

METHODS

Aβ concentrations and Mini-Mental State Examinations (MMSE) were investigated in 37 hemodialysis patients (68.9 ± 4.1 years).

RESULTS

The dialyzers effectively removed Aβ(1-40) and Aβ(1-42), 63.9 ± 14.4 and 51.6 ± 17.0% at 4 h dialysis, resulting in the reduction of Aβs in whole-body circulation by 51.1 ± 8.9 and 32.7 ± 12.0%, respectively. Although the plasma Aβs before dialysis (750.8 ± 171.3 pg/ml for Aβ(1-40)) were higher than those reported for Alzheimer's disease patients, the cognitive states of hemodialysis patients were relatively normal, especially of longer dialysis vintages.

CONCLUSIONS

Dialyzers effectively reduced Aβs in whole-body circulation. Repeated rapid decrease of plasma Aβs might maintain cognitive state.

The pathological roles of ganglioside metabolism in Alzheimer's disease: effects of gangliosides on neurogenesis

Conversion of the soluble, nontoxic amyloid β-protein (Aβ) into an aggregated, toxic form rich in β-sheets is a key step in the onset of Alzheimer's disease (AD). It has been suggested that Aβ induces changes in neuronal membrane fluidity as a result of its interactions with membrane components such as cholesterol, phospholipids, and gangliosides. Gangliosides are known to bind Aβ. A complex of GM1 and Aβ, termed “GAβ”, has been identified in AD brains. Abnormal ganglioside metabolism also may occur in AD brains. We have reported an increase of Chol-1α antigens, GQ1bα and GT1aα, in the brain of transgenic mouse AD model. GQ1bα and GT1aα exhibit high affinities to Aβs. The presence of Chol-1α gangliosides represents evidence for genesis of cholinergic neurons in AD brains. We evaluated the effects of GM1 and Aβ1–40 on mouse neuroepithelial cells. Treatment of these cells simultaneously with GM1 and Aβ1–40 caused a significant reduction of cell number, suggesting that Aβ1–40 and GM1 cooperatively exert a cytotoxic effect on neuroepithelial cells. An understanding of the mechanism on the interaction of GM1 and Aβs in AD may contribute to the development of new neuroregenerative therapies for this disorder.