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

Accumulation of amyloid-ß protein (Aß) in the brain causes cognitive impairment in Alzheimer's disease. We hypothesized that an extracorporeal system that rapidly removed Aß from the blood may accelerate Aß drainage from the brain. We previously reported that dialyzers remove blood Aßs effectively, mainly by adsorption on the inner surfaces of the hollow fibers, resulting in lower Aß 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 Aß 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 Aßs on the surface of micropores inside the hollow fiber walls. Hence, pool solutions of 4 ng/mL synthetic Aß1-40 and Aß1-42 peptides (300 mL) or human plasma (1000 mL of 250-346 pg/mL Aß1-40 and 30-48 pg/mL Aß1-42) were circulated through polysulfone dialyzers at a flow rate of 50 mL/min to evaluate an adsorptive filtration system. The rates of Aß 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 Aßs within 30 min of circulation. The rates of Aßs passing through the membrane walls were maintained around 0% for plasma Aßs during circulation. Thus, our adsorptive filtration systems may be useful for removing blood Aßs for patients with Alzheimer's disease.

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

PURPOSE: Amyloid-ß (Aß) is a brain protein that causes Alzheimer's disease. We have revealed that extracorporeal blood Aß-removal systems evoked a large Aß influx into the blood. This study investigated the system that is more effective in evoking Aß influx. METHODS: Aß 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 Aß adsorption on micropores in the wall of hollow fibers. Plasma Aß 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, Aß 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 Aßs comparably or more than HexDC. Aß influx into the blood increases time-dependently. Concomitant use of HexDC and PSf hemodialyzer evoked a larger Aß1-40 influx than that of PSf hemodialyzer alone. However, Aß1-42 influx by PSf hemodialyzer alone was similar to or a little larger than influx by the combined system. Both systems evoked almost doubled Aß influx than estimated Aßs 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 Aß influx. To evoke Aß1-42 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.

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

PURPOSE: Amyloid-ß protein (Aß) is one of the causative proteins of Alzheimer's disease. We have been developing extracorporeal blood Aß-removal systems as a method for enhancing Aß clearance from the brain. We reported previously that medical adsorbents and hemodialyzers removed Aß monomers from peripheral blood, which was associated with influx of Aß monomers from the brain into the bloodstream. Our intent here was to develop a method to promote clearance of Aß oligomers and to provide an estimate of the molecular size of intact Aß oligomers in plasma. METHODS: Two hollow-fiber devices with different pore sizes (Membranes A and B) were evaluated as removers of Aß oligomers with human plasma in vitro. The concomitant removal of Aß 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 Aß oligomers in humans. RESULTS: Aß oligomers were effectively removed by both Membranes A and B. The increase of Aß oligomers in plasma was observed just after the removal of plasma Aß oligomers in humans. The intact molecular size of major Aß oligomers in the plasma was estimated to be larger than albumin at approximately 60 kDa or more. Additionally, the concomitant removal of Aß monomers and oligomers evoked dissociation of larger Aß oligomers into smaller ones and monomers. CONCLUSION: Aß 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. Aß oligomers in peripheral circulation were increased after some clearances in human. Further investigation will determine whether the Aß oligomers detected in circulation after clearance were via influx from the brain.