Treatment of Alzheimer disease using combination therapy with plasma exchange and haemapheresis with albumin and intravenous immunoglobulin: Rationale and treatment approach of the AMBAR (Alzheimer Management By Albumin Replacement) study

Recent trends in treatment strategies for Alzheimer's disease and the challenges: A topical advancement

Alzheimer's Disease (AD) is an irreversible and progressive neurological disease that has affected at least 50 million people around the globe. Considering the severity of the disease and the continuous increase in the number of patients, the development of new effective drugs or intervention strategies for AD has become urgent. AD is caused by a combination of genetic, environmental, and lifestyle factors, but its exact cause has not yet been clarified. Given the current challenges being faced in the clinical treatment of AD, such as complex AD pathological network and insufficient early diagnosis, herein, we have focused on the three core pathological features of AD, including amyloid-β (Aβ) aggregation, tau phosphorylation and tangles, and activation of inflammatory factors. In this review, we have briefly underscored the primary evidence supporting each pathology and discuss AD pathological network among Aβ, tau, and inflammation. We have also comprehensively summarized the most instructive drugs and their treatment strategies against Aβ, tau, or neuroinflammation used in basic research and clinical trials. Finally, we have discussed and outlined the pros and cons of each pathological approach and looked forward to potential personalized diagnosis and treatment strategies that are beneficial to AD patients.

New Concepts in the Manipulation of the Aging Process

This review explores the current concepts in aging and then goes on to describe a novel, ground-breaking technology which will change the way we think about and manage aging. The foundation of the review is based on the work carried out on the QiLaser activation of human Very Small Embryonic Like (hVSEL) pluripotent stem cells in autologous Platelet Rich Plasma (PRP), known as the Qigeneration Procedure. The application of this technology in anti-aging technology is discussed with an emphasis on epigenetic changes during aging focusing on DNA methylation.

Ibuprofen Favors Binding of Amyloid-β Peptide to Its Depot, Serum Albumin

The deposition of amyloid-β peptide (Aβ) in the brain is a critical event in the progression of Alzheimer’s disease (AD). This Aβ deposition could be prevented by directed enhancement of Aβ binding to its natural depot, human serum albumin (HSA). Previously, we revealed that specific endogenous ligands of HSA improve its affinity to monomeric Aβ. We show here that an exogenous HSA ligand, ibuprofen (IBU), exerts the analogous effect. Plasmon resonance spectroscopy data evidence that a therapeutic IBU level increases HSA affinity to monomeric Aβ₄₀/Aβ₄₂ by a factor of 3–5. Using thioflavin T fluorescence assay and transmission electron microcopy, we show that IBU favors the suppression of Aβ₄₀ fibrillation by HSA. Molecular docking data indicate partial overlap between the IBU/Aβ₄₀-binding sites of HSA. The revealed enhancement of the HSA–Aβ interaction by IBU and the strengthened inhibition of Aβ fibrillation by HSA in the presence of IBU could contribute to the neuroprotective effects of the latter, previously observed in mouse and human studies of AD.

Combination Therapy in Alzheimer’s Disease: Is It Time?

Alzheimer’s disease (AD) is the most common cause of dementia globally. There is increasing evidence showing AD has no single pathogenic mechanism, and thus treatment approaches focusing only on one mechanism are unlikely to be meaningfully effective. With only one potentially disease modifying treatment approved, targeting amyloid-β (Aβ), AD is underserved regarding effective drug treatments. Combining multiple drugs or designing treatments that target multiple pathways could be an effective therapeutic approach. Considering the distinction between added and combination therapies, one can conclude that most trials fall under the category of added therapies. For combination therapy to have an actual impact on the course of AD, it is likely necessary to target multiple mechanisms including but not limited to Aβ and tau pathology. Several challenges have to be addressed regarding combination therapy, including choosing the correct agents, the best time and stage of AD to intervene, designing and providing proper protocols for clinical trials. This can be achieved by a cooperation between the pharmaceutical industry, academia, private research centers, philanthropic institutions, and the regulatory bodies. Based on all the available information, the success of combination therapy to tackle complicated disorders such as cancer, and the blueprint already laid out on how to implement combination therapy and overcome its challenges, an argument can be made that the field has to move cautiously but quickly toward designing new clinical trials, further exploring the pathological mechanisms of AD, and re-examining the previous studies with combination therapies so that effective treatments for AD may be finally found.

Nanomedicine-based technologies and novel biomarkers for the diagnosis and treatment of Alzheimer's disease: from current to future challenges

Increasing life expectancy has led to an aging population, which has consequently increased the prevalence of dementia. Alzheimer's disease (AD), the most common form of dementia worldwide, is estimated to make up 50-80% of all cases. AD cases are expected to reach 131 million by 2050, and this increasing prevalence will critically burden economies and health systems in the next decades. There is currently no treatment that can stop or reverse disease progression. In addition, the late diagnosis of AD constitutes a major obstacle to effective disease management. Therefore, improved diagnostic tools and new treatments for AD are urgently needed. In this review, we investigate and describe both well-established and recently discovered AD biomarkers that could potentially be used to detect AD at early stages and allow the monitoring of disease progression. Proteins such as NfL, MMPs, p-tau217, YKL-40, SNAP-25, VCAM-1, and Ng / BACE are some of the most promising biomarkers because of their successful use as diagnostic tools. In addition, we explore the most recent molecular strategies for an AD therapeutic approach and nanomedicine-based technologies, used to both target drugs to the brain and serve as devices for tracking disease progression diagnostic biomarkers. State-of-the-art nanoparticles, such as polymeric, lipid, and metal-based, are being widely investigated for their potential to improve the effectiveness of both conventional drugs and novel compounds for treating AD. The most recent studies on these nanodevices are deeply explained and discussed in this review.

A Chronological Review of Potential Disease-Modifying Therapeutic Strategies for Alzheimer's Disease

Late-onset Alzheimer's disease (LOAD) is a neurodegenerative disorder that has become a worldwide health problem. This pathology has been classically characterized for its affectation on cognitive function and the presence of depositions of extracellular amyloid β-protein (Aβ) and intracellular neurofibrillary tangles (NFT) composed of hyperphosphorylated Tau protein. To this day, no effective treatment has been developed. Multiple strategies have been proposed over the years with the aim of finding new therapeutic approaches, such as the sequestration of Aβ in plasma or the administration of anti-inflammatory drugs. Also, given the significant role of the insulin receptor in the brain in the proper maintenance of cognitive function, drugs focused on the amelioration of insulin resistance have been proposed as potentially useful and effective in the treatment of AD. In the present review, taking into account the molecular complexity of the disease, it has been proposed that the most appropriate therapeutic strategy is a combinatory treatment of several drugs that will regulate a wide spectrum of the described altered pathological pathways.

Serum albumin and beta-amyloid deposition in the human brain

Objectives

To investigate the relationships of serum albumin with in vivo Alzheimer disease (AD) pathologies, including cerebral β-amyloid (Aβ) protein deposition, neurodegeneration of AD-signature regions, and cerebral white matter hyperintensities (WMH), in the human brain.

Methods

A total of 396 older adults without dementia underwent comprehensive clinical assessments, measurement of serum albumin level, and multimodal brain imaging, including [¹¹C] Pittsburgh compound B-PET, ¹⁸F-fluorodeoxyglucose-PET, and MRI. Serum albumin was categorized as follows: <4.4 g/dL (low albumin), 4.4 to 4.5 g/dL (middle albumin), and >4.5 g/dL (high albumin; used as a reference category). Aβ positivity, AD-signature region cerebral glucose metabolism (AD-CM), AD-signature region cortical thickness (AD-CT), and WMH volume were used as outcome measures.

Results

Serum albumin level (as a continuous variable) was inversely associated with Aβ deposition and Aβ positivity. The low albumin group showed a significantly higher Aβ positivity rate compared to the high albumin group (odds ratio 3.40, 95% confidence interval 1.67–6.92, p = 0.001), while the middle albumin group showed no difference (odds ratio 1.74, 95% confidence interval 0.80–3.77, p = 0.162). Neither serum albumin level (as a continuous variable) nor albumin categories were related to AD-CM, AD-CT, or WMH volume.

Conclusions

Low serum albumin may increase the risk of AD dementia by elevating amyloid accumulation. In terms of AD prevention, more attention needs to be paid to avoid a low serum albumin level, even within the clinical normal range, by clinicians.

AMBAR, an Encouraging Alzheimer's Trial That Raises Questions

Grifols' recent Alzheimer Management by Albumin Replacement (“AMBAR”) study investigated the effects of plasmapheresis with albumin replacement, plus intravenous immunoglobulin (IVIG) in some subjects, in patients with mild-to-moderate Alzheimer's disease (AD). AMBAR was a phase IIb trial in the United States and a phase III trial in Europe. There were three treatment groups (plasmapheresis with albumin replacement; plasmapheresis with low dose albumin and IVIG; plasmapheresis with high dose albumin and IVIG) and sham-treated controls. Disease progression in pooled treated patients was 66% less than control subjects based on ADAS-Cog scores (p = 0.06) and 52% less based on ADCS-ADL scores (p = 0.03). Moderate AD patients had 61% less progression, based on both ADAS-Cog and ADCS-ADL scores, than their sham-treated counterparts (p-values 0.05 and 0.002), and their CDR-Sb scores declined 53% less than their sham-treated counterparts. However, ADAS-Cog and ADCS-ADL scores were not significantly different between actively-treated and sham-treated mild AD patients, although CDR-Sb scores improved vs. baseline for treated mild AD patients. Patients administered both IVIG and albumin had less reduction in brain glucose metabolism than sham-treated patients. Questions raised by these findings include: what mechanism(s) contributed to slowing of disease progression? Is this approach as effective in mild AD as in moderate AD? Must IVIG be included in the protocol? Does age, sex, or ApoE genotype influence treatment response? Does the protocol increase the risk for amyloid-related imaging abnormalities? How long does disease progression remain slowed post-treatment? A further study should allow this approach to be optimized.

Treatment Combinations for Alzheimer's Disease: Current and Future Pharmacotherapy Options

Although Alzheimer’s disease (AD) is the world’s leading cause of dementia and the population of patients with AD continues to grow, no new therapies have been approved in more than a decade. Many clinical trials of single-agent therapies have failed to affect disease progression or symptoms compared with placebo. The complex pathophysiology of AD may necessitate combination treatments rather than monotherapy. The goal of this narrative literature review is to describe types of combination therapy, review the current clinical evidence for combination therapy regimens (both symptomatic and disease-modifying) in the treatment of AD, describe innovative clinical trial study designs that may be effective in testing combination therapy, and discuss the regulatory and drug development landscape for combination therapy. Successful combination therapies in other complex disorders, such as human immunodeficiency virus, may provide useful examples of a potential path forward for AD treatment.

Therapeutic Plasmapheresis with Albumin Replacement in Alzheimer's Disease and Chronic Progressive Multiple Sclerosis: A Review

Background: Reducing the burden of beta-amyloid accumulation and toxic autoimmunity-related proteins, one of the recognized pathophysiological markers of chronic and common neurological disorders such as Alzheimer’s disease (AD) and multiple sclerosis (MS), may be a valid alternative therapy to reduce their accumulation in the brain and thus reduce the progression of these disorders. The objective of this review was to evaluate the efficacy of plasmapheresis (PP) in AD and chronic progressive MS patients (in terms of improving clinical symptoms) and to analyze its safety and protocols. Methods: Articles related to this topic and published without time limitations in the Medline, and Cochrane databases were reviewed. Results: In AD patients, PP reduced amyloid beta (Aβ) levels in the brain, accompanied by a tendency towards cognitive stabilization, and improved language and verbal fluency. In regards to structural and functional brain changes, PP reduced brain volume and favored the stabilization, or absence, of the progression of perfusion. In chronic progressive form of MS patients, PP improved neurological deficits in 20–70% of patients with a chronic progressive form of MS, and restored interferon (IFN) responsiveness, which was not accompanied by any image change in brain plaques. Conclusions: Therapeutic plasmapheresis with albumin replacement is a promising strategy for reducing Aβ mediated toxicity and slowing the progression of the disorder. Some patients with chronic progressive forms of MS show improvement in neurological deficits. The features of AD and MS patients who benefit most from this approach need further research.

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.

Reasons for Failed Trials of Disease-Modifying Treatments for Alzheimer Disease and Their Contribution in Recent Research

Despite all scientific efforts and many protracted and expensive clinical trials, no new drug has been approved by FDA for treatment of Alzheimer disease (AD) since 2003. Indeed, more than 200 investigational programs have failed or have been abandoned in the last decade. The most probable explanations for failures of disease-modifying treatments (DMTs) for AD may include late initiation of treatments during the course of AD development, inappropriate drug dosages, erroneous selection of treatment targets, and mainly an inadequate understanding of the complex pathophysiology of AD, which may necessitate combination treatments rather than monotherapy. Clinical trials’ methodological issues have also been criticized. Drug-development research for AD is aimed to overcome these drawbacks. Preclinical and prodromal AD populations, as well as traditionally investigated populations representing all the clinical stages of AD, are included in recent trials. Systematic use of biomarkers in staging preclinical and prodromal AD and of a single primary outcome in trials of prodromal AD are regularly integrated. The application of amyloid, tau, and neurodegeneration biomarkers, including new biomarkers—such as Tau positron emission tomography, neurofilament light chain (blood and Cerebrospinal fluid (CSF) biomarker of axonal degeneration) and neurogranin (CSF biomarker of synaptic functioning)—to clinical trials allows more precise staging of AD. Additionally, use of Bayesian statistics, modifiable clinical trial designs, and clinical trial simulators enrich the trial methodology. Besides, combination therapy regimens are assessed in clinical trials. The above-mentioned diagnostic and statistical advances, which have been recently integrated in clinical trials, are relevant to the recent failures of studies of disease-modifying treatments. Their experiential rather than theoretical origins may better equip potentially successful drug-development strategies.

Albumin domain mutants with enhanced Aβ binding capacity identified by phage display analysis for application in various peripheral Aβ elimination approaches of Alzheimer's disease treatment

Deposition of amyloid protein, particularly Aβ_1-42 , is a major contributor to the onset of Alzheimer's disease (AD). However, almost no deposition of Aβ in the peripheral tissues could be found. Human serum albumin (HSA), the most abundant protein in the blood, has been reported to inhibit amyloid formation through binding Aβ, which is believed to play an important role in the peripheral clearance of Aβ. We identified the Aβ binding site on HSA and developed HSA mutants with high binding capacities for Aβ using a phage display method. HSA fragment 187-385 (Domain II) was found to exhibit the highest binding capacity for Aβ compared with the other two HSA fragments. To elucidate the sequence that forms the binding site for Aβ on Domain II, a random screening of Domain II display phage biopanning was constructed. A number of mutants with higher Aβ binding capacities than the wild type were identified. These mutants exhibited stronger scavenging abilities than the wild type, as revealed via in vitro equilibrium dialysis of Aβ experiments. These findings provide useful basic data for developing a safer alternative therapy than Aβ vaccines and for application in plasma exchange as well as extracorporeal dialysis.

Albumin Exchange in Alzheimer's Disease: Might CSF Be an Alternative Route to Plasma?

Amyloid β (Aβ) in brain parenchyma is thought to play a central role in the pathogenesis of Alzheimer's disease (AD). Aβ is transported from the brain to the plasma via complex transport mechanisms at the blood-brain barrier (BBB). About 90–95% of plasma Aβ may be bound to albumin. Replacement of serum albumin in plasma has been proposed as a promising therapy for AD. However, the efficacy of this approach may be compromised by altered BBB Aβ receptors in AD, as well as multiple pools of Aβ from other organs in exchange with plasma Aβ, competing for albumin binding sites. The flow of interstitial fluid (ISF) into cerebrospinal fluid (CSF) is another major route of Aβ clearance. Though the concentration of albumin in CSF is much lower than in plasma, the mixing of CSF with ISF is not impeded by a highly selective barrier and, hence, Aβ in the two pools is in more direct exchange. Furthermore, unlike in plasma, Aβ in CSF is not in direct exchange with multiple organ sources of Aβ. Here we consider albumin replacement in CSF as an alternative method for therapeutic brain Aβ removal and describe the possible advantages and rationale supporting this hypothesis.

Tau-Reactive Endogenous Antibodies: Origin, Functionality, and Implications for the Pathophysiology of Alzheimer's Disease

In Alzheimer's disease (AD), tau pathology manifested by the accumulation of intraneuronal tangles and soluble toxic oligomers emerges as a promising therapeutic target. Multiple anti-tau antibodies inhibiting the formation and propagation of cytotoxic tau or promoting its clearance and degradation have been tested in clinical trials, albeit with the inconclusive outcome. Antibodies against tau protein have been documented both in the brain circulatory system and at the periphery, but their origin and role under normal conditions and in AD remain unclear. While it is tempting to assign them a protective role in regulating tau level and removal of toxic variants, the supportive evidence remains sporadic, requiring systematic analysis and critical evaluation. Herein, we review recent data showing the occurrence of tau-reactive antibodies in the brain and peripheral circulation and discuss their origin and significance in tau clearance. Based on the emerging evidence, we cautiously propose that impairments of tau clearance at the periphery by humoral immunity might aggravate the tau pathology in the central nervous system, with implication for the neurodegenerative process of AD.

Pre-Clinical Safety and Efficacy Evaluation of Amytrap, a Novel Therapeutic to Treat Alzheimer's Disease

Alzheimer’s disease (AD) is the most common cause of dementia. Amyloid-β (Aβ₄₂) is implicated in AD pathogenesis. We have designed a non-immune based proprietary therapeutic, called Amytrap, a conjugate containing a retro-inverso peptide, polyethylene glycol, and human serum albumin. Amytrap not only binds Aβ₄₂ but also prevents and dissociates aggregated Aβ₄₂. Amytrap binds to the region in Aβ₄₂ known to trigger its self-aggregation, thus disrupting aggregation. We have obtained proof of concept on AmyTrap in a clinically relevant mouse model, namely, AD-APPSWE/Tg2576. We synthesized and characterized Amytrap and confirmed its authenticity. Efficacy evaluations were performed on young (5 months) and old (9 months) model mice. Amytrap was injected biweekly for a period of five months. Pharmacokinetics and safety toxicology were assessed in normal mice and rats, respectively. Post treatment, younger mice showed significant improvements in cognition and Aβ₄₂ levels in plasma, brain, and cerebrospinal fluid, while older mice showed less significant benefits. Immunohistochemistry of brain sections showed similar differences between young and old mice. They all had diminished size and number of plaques in the brain of Amytrap-treated mice. Further, treated mice did not develop antibodies to Amytrap, suggesting Amytrap is non-immunogenic. Safety toxicological studies in rats showed that Amytrap was well tolerated and therefore safe (even at 50 X the efficacy dose). Stability tests showed Amytrap is stable at 4°C for up to one year. Efficacy and safety features make Amytrap a promising candidate for treating or modulating AD.

'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.

Longitudinal Neuroimaging Analysis in Mild-Moderate Alzheimer's Disease Patients Treated with Plasma Exchange with 5% Human Albumin

Background:

Recently, modifications of Aβ_1-42 levels in CSF and plasma associated with improvement in memory and language functions have been observed in patients with mild-moderate Alzheimer’s disease (AD) treated with plasma exchange (PE) with albumin replacement.

Objective:

To detect structural and functional brain changes in PE-treated AD patients as part of a Phase II clinical trial.

Methods:

Patients received between 3 and 18 PE with albumin (Albutein^® 5%, Grifols) or sham-PE (controls) for 21 weeks (divided in one intensive and two maintenance periods) followed by 6-month follow-up. Brain perfusion assessed by SPECT scans using an automated software (NeuroGam^®) and brain structural changes assessed by MRI were performed at weeks 0 (baseline), 21, and 44 (with additional SPECT at weeks 9 and 33). Statistical parametric mapping (voxel-based analysis, SPM) and Z-scores calculations were applied to investigate changes to baseline.

Results:

42 patients were recruited (39 evaluable; 37 analyzed: 18 PE-treated; 19 controls). There was a trend toward decreasing hippocampi and total intracranial volume for both patient groups during the study (p < 0.05). After six months, PE-treated patients had less cerebral perfusion loss than controls in frontal, temporal, and parietal areas, and perfusion stabilization in Brodmann area BA38-R during the PE-treatment period (p < 0.05). SPM analysis showed stabilization or absence of progression of perfusion loss in PE-treated patients until week 21, not observed in controls.

Conclusions:

Mild-moderate AD patients showed decreased brain volume and impairment of brain perfusion as expected for the progression of the disease. PE-treatment with albumin replacement favored the stabilization of perfusion.

Efficacy and Safety of Plasma Exchange with 5% Albumin to Modify Cerebrospinal Fluid and Plasma Amyloid-β Concentrations and Cognition Outcomes in Alzheimer's Disease Patients: A Multicenter, Randomized, Controlled Clinical Trial

Background: Studies conducted in animal models and humans suggest the presence of a dynamic equilibrium of amyloid-β (Aβ) peptide between cerebrospinal fluid (CSF) and plasma compartments.

Objective: To determine whether plasma exchange (PE) with albumin replacement was able to modify Aβ concentrations in CSF and plasma as well as to improve cognition in patients with mild-moderate Alzheimer’s disease (AD).

Methods: In a multicenter, randomized, patient- and rater-blind, controlled, parallel-group, phase II study, 42 AD patients were assigned (1 : 1) to PE treatment or control (sham) groups. Treated patients received a maximum of 18 PE with 5% albumin (Albutein^®, Grifols) with three different schedules: two PE/weekly (three weeks), one PE/weekly (six weeks), and one PE/bi- weekly (12 weeks), plus a six-month follow-up period. Plasma and CSF Aβ_1–40 and Aβ_1–42 levels, as well as cognitive, functional, and behavioral measures were determined.

Results: CSF Aβ_1–42 levels after the last PE compared to baseline were marginally higher in PE-treated group versus controls (adjusted means of variation: 75.3 versus –45.5 pg/mL; 95% CI: –19.8, 170.5 versus 135.1, 44.2; p = 0.072). Plasma Aβ_1–42 levels were lower in the PE-treated group after each treatment period (p < 0.05). Plasma Aβ_1–40 levels showed a saw-tooth pattern variation associated with PE. PE-treated patients scored better in the Boston Naming Test and Semantic Verbal Fluency (p < 0.05) throughout the study. Neuropsychiatric Inventory scores were higher in controls during the PE phase (p < 0.05).

Conclusion: PE with human albumin modified CSF and plasma Aβ_1–42 levels. Patients treated with PE showed improvement in memory and language functions, which persisted after PE was discontinued.

Aberrant Co-localization of Synaptic Proteins Promoted by Alzheimer's Disease Amyloid-β Peptides: Protective Effect of Human Serum Albumin

Amyloid-β (Aβ), Aβ₄₀, Aβ₄₂, and, recently, Aβ_25-35 have been directly implicated in the pathogenesis of Alzheimer’s disease. We have studied the effects of Aβ on neuronal death, reactive oxygen species (ROS) production, and synaptic assembling in neurons in primary culture. Aβ_25-35, Aβ₄₀, and Aβ₄₂ significantly decreased neuronal viability, although Aβ_25-35 showed a higher effect. Aβ_25-35 showed a more penetrating ability to reach mitochondria while Aβ₄₀ did not enter the neuronal cytosol and Aβ₄₂ was scarcely internalized. We did not observe a direct correlation between ROS production and cell death because both Aβ₄₀ and Aβ₄₂ decreased neuronal viability but Aβ₄₀ did not change ROS production. Rather, ROS production seems to correlate with the penetrating ability of each Aβ. No significant differences were found between Aβ₄₀ and Aβ₄₂ regarding the extent of the deleterious effects of both peptides on neuronal viability or synaptophysin expression. However, Aβ₄₀ elicited a clear delocalization of PSD-95 and synaptotagmin from prospective synapsis to the neuronal soma, suggesting the occurrence of a crucial effect of Aβ₄₀ on synaptic disassembling. The formation of Aβ₄₀- or Aβ₄₂-serum albumin complexes avoided the effects of these peptides on neuronal viability, synaptophysin expression, and PSD-95/synaptotagmin disarrangement suggesting that sequestration of Aβ by albumin prevents deleterious effects of these peptides. We can conclude that Aβ borne by albumin can be safely transported through body fluids, a fact that may be compulsory for Aβ disposal by peripheral tissues.

Serum Albumin's Protective Inhibition of Amyloid-β Fiber Formation Is Suppressed by Cholesterol, Fatty Acids and Warfarin

Central to Alzheimer's disease (AD) pathology is the assembly of monomeric amyloid-β peptide (Aβ) into oligomers and fibers. The most abundant protein in the blood plasma and cerebrospinal fluid is human serum albumin. Albumin can bind to Aβ and is capable of inhibiting the fibrillization of Aβ at physiological (μM) concentrations. The ability of albumin to bind Aβ has recently been exploited in a phase II clinical trial, which showed a reduction in cognitive decline in AD patients undergoing albumin-plasma exchange. Here we explore the equilibrium between Aβ monomer, oligomer and fiber in the presence of albumin. Using transmission electron microscopy and thioflavin-T fluorescent dye, we have shown that albumin traps Aβ as oligomers, 9 nm in diameter. We show that albumin-trapped Aβ oligomeric assemblies are not capable of forming ion channels, which suggests a mechanism by which albumin is protective in Aβ-exposed neuronal cells. In vivo albumin binds a variety of endogenous and therapeutic exogenous hydrophobic molecules, including cholesterol, fatty acids and warfarin. We show that these molecules bind to albumin and suppress its ability to inhibit Aβ fiber formation. The interplay between Aβ, albumin and endogenous hydrophobic molecules impacts Aβ assembly; thus, changes in cholesterol and fatty acid levels in vivo may impact Aβ fibrillization, by altering the capacity of albumin to bind Aβ. These observations are particularly intriguing given that high cholesterol or fatty acid diets are well-established risk factors for late-onset AD.

Atomic-resolution map of the interactions between an amyloid inhibitor protein and amyloid β (Aβ) peptides in the monomer and protofibril states

Self-association of amyloid β (Aβ) peptides is a hallmark of Alzheimer's disease and serves as a general prototype for amyloid formation. A key endogenous inhibitor of Aβ self-association is human serum albumin (HSA), which binds ∼90% of plasma Aβ. However, the exact molecular mechanism by which HSA binds Aβ monomers and protofibrils is not fully understood. Here, using dark-state exchange saturation transfer NMR and relaxation experiments complemented by morphological characterization, we mapped the HSA-Aβ interactions at atomic resolution by examining the effects of HSA on Aβ monomers and soluble high-molecular weight oligomeric protofibrils. We found that HSA binds both monomeric and protofibrillar Aβ, but the affinity of HSA for Aβ monomers is lower than for Aβ protofibrils (K_d values are submillimolar rather than micromolar) yet physiologically relevant because of the ∼0.6-0.7 mm plasma HSA concentration. In both Aβ protofibrils and monomers, HSA targets key Aβ self-recognition sites spanning the β strands found in cross-β protofibril structures, leading to a net switch from direct to tethered contacts between the monomeric Aβ and the protofibril surface. These HSA-Aβ interactions are isoform-specific, because the HSA affinity of Aβ monomers is lower for Aβ(1-42) than for Aβ(1-40). In addition, the HSA-induced perturbations of the monomer/protofibrils pseudo-equilibrium extend to the C-terminal residues in the Aβ(1-42) isoform but not in Aβ(1-40). These results provide an unprecedented view of how albumin interacts with Aβ and illustrate the potential of dark-state exchange saturation transfer NMR in mapping the interactions between amyloid-inhibitory proteins and amyloidogenic peptides.

Modulation of linoleic acid-binding properties of human serum albumin by divalent metal cations

Human serum albumin (HSA) is an abundant multiligand carrier protein, linked to progression of Alzheimer's disease (AD). Blood HSA serves as a depot of amyloid β (Aβ) peptide. Aβ peptide-buffering properties of HSA depend on interaction with its ligands. Some of the ligands, namely, linoleic acid (LA), zinc and copper ions are involved into AD progression. To clarify the interplay between LA and metal ion binding to HSA, the dependence of LA binding to HSA on Zn²⁺, Cu²⁺, Mg²⁺ and Ca²⁺ levels and structural consequences of these interactions have been explored. Seven LA molecules are bound per HSA molecule in the absence of the metal ions. Zn²⁺ binding to HSA causes a loss of one bound LA molecule, while the other metals studied exert an opposite effect (1-2 extra LA molecules are bound). In most cases, the observed effects are not related to the metal-induced changes in HSA quaternary structure. However, the Zn²⁺-induced decline in LA capacity of HSA could be due to accumulation of multimeric HSA forms. Opposite to Ca²⁺/Mg²⁺-binding, Zn²⁺ or Cu²⁺ association with HSA induces marked changes in its hydrophobic surface. Overall, the divalent metal ions modulate LA capacity and affinity of HSA to a different extent. LA- and Ca²⁺-binding to HSA synergistically support each other. Zn²⁺ and Cu²⁺ induce more pronounced changes in hydrophobic surface and quaternary structure of HSA and its LA capacity. A misbalanced metabolism of these ions in AD could modify interactions of HSA with LA, other fatty acids and hydrophobic substances, associated with AD.

Systems biology approach to late-onset Alzheimer's disease genome-wide association study identifies novel candidate genes validated using brain expression data and Caenorhabditis elegans experiments

INTRODUCTION

We sought to determine whether a systems biology approach may identify novel late-onset Alzheimer's disease (LOAD) loci.

METHODS

We performed gene-wide association analyses and integrated results with human protein-protein interaction data using network analyses. We performed functional validation on novel genes using a transgenic Caenorhabditis elegans Aβ proteotoxicity model and evaluated novel genes using brain expression data from people with LOAD and other neurodegenerative conditions.

RESULTS

We identified 13 novel candidate LOAD genes outside chromosome 19. Of those, RNA interference knockdowns of the C. elegans orthologs of UBC, NDUFS3, EGR1, and ATP5H were associated with Aβ toxicity, and NDUFS3, SLC25A11, ATP5H, and APP were differentially expressed in the temporal cortex.

DISCUSSION

Network analyses identified novel LOAD candidate genes. We demonstrated a functional role for four of these in a C. elegans model and found enrichment of differentially expressed genes in the temporal cortex.

VP168 Assessment Of Plasmapheresis For Alzheimer's Disease Systematic Review

INTRODUCTION:

Alzheimer's disease (AD) is the most common type of dementia. Plasmapheresis is a procedure consisting of removing the plasma, or specific elements which are considered to be involved in pathological processes. Plasmapheresis could reduce the A beta peptides load in the brain. The objective is to study the safety and efficacy of plasmapheresis for AD.

METHODS:

Systematic review, with all studies published before April 2016 reviewed. Selected studies included patients with AD treated with plasmapheresis. GRADE was used to assess quality. Efficacy outcomes include: (i) Cognitive, functional and behavior status, through Mini Mental State Examination, and Alzheimer Disease Assessment Scale-Cognitive test; (ii) Plasma and cerebrospinal fluid A beta levels; (iii) Brain-imaging and functional neuroimaging studies. Safety outcomes included side effects related to the treatment.

RESULTS:

Two papers reporting results from three studies were selected: (i) pilot study (n = 10), (ii) its extended study (12 months more of follow-up) (n = 7), and (iii) clinical trial (n = 39). The quality of evidence was very low. About efficacy, the studies didn't report quantitative results and were inconclusive. The pilot study and its extended study reported (1): a tendency towards stabilization in cognitive status; the plasma levels of A beta peptides didn't show a clear pattern; and the brain-imaging assessment suggested a progressive volume increase in the hippocampus. The clinical trial reported in the experimental group vs control (2): a better score for the cognitive status; an increase of plasma A beta peptides; and did not find significant differences between groups for cerebrospinal fluid A beta peptides. The brain-imaging assessment showed a progressive loss of hippocampus volume in both groups. Regarding safety, the studies didn't report quantitative data. We didn't find economic evaluation studies.

CONCLUSIONS:

The included studies had very high risk of bias and very low quality. We found no evidence on efficacy and safety of plasmapheresis treating AD. Plasmapheresis isn't a priority line in research of AD treatment.

Impact of 2, 3, 5, 4'-tetrahydroxystilbene-2-O-β-D-glucoside on cognitive deficits in animal models of Alzheimer's disease: a systematic review

BACKGROUND

The efficacy of 2, 3, 5, 4'-tetrahydroxystilbene-2-O-β-D-glucoside (TSG) treatment on cognitive decline in individuals with Alzheimer's disease (AD) has not been investigated. Therefore, we systematically reviewed the effect of TSG on cognitive deficits in a rodent model of AD.

METHODS

We identified eligible studies published from January 1980 to April 2015 by searching seven electronic databases. We assessed the study quality, evaluated the efficacy of TSG treatment, and performed a stratified meta-analysis and meta-regression analysis to assess the influence of study design on TSG efficacy.

RESULTS

Among a total of 381 publications, 18 fulfilled our inclusion criteria. The overall methodological quality of these studies was poor. The meta-analysis revealed a statistically significant benefit of TSG on acquisition memory (standardized mean difference [SMD] = -1.46 (95 % CI: -1.81 to -1.10, P < 0.0001) and retention memory (SMD =1.93 (95 % CI: 1.40 to 2.46, P < 0.0001) in experimental models of AD. The stratified analysis revealed a significantly higher effect size for both acquisition and retention memory in studies that used mixed sex models and a significantly higher effect size for acquisition memory in studies that used transgenic models.

CONCLUSIONS

Our meta-analysis highlights a significantly better treatment effect in rodent AD models that received TSG that in those that did not. These findings indicate a potential therapeutic role of TSG in AD therapy. However, additional well-designed and detailed experimental studies are needed to evaluate the safety of TSG.

Immunotherapeutic Approaches Targeting Amyloid-β, α-Synuclein, and Tau for the Treatment of Neurodegenerative Disorders

Disease-modifying alternatives are sorely needed for the treatment of neurodegenerative disorders, a group of diseases that afflict approximately 50 million Americans annually. Immunotherapy is one of the most developed approaches in this direction. Vaccination against amyloid-β, α-synuclein, or tau has been extensively explored, specially as the discovery that these proteins may propagate cell-to-cell and be accessible to antibodies when embedded into the plasma membrane or in the extracellular space. Likewise, the use of passive immunization approaches with specific antibodies against abnormal conformations of these proteins has also yielded promising results. The clinical development of immunotherapies for Alzheimer’s disease, Parkinson’s disease, frontotemporal dementia, dementia with Lewy bodies, and other neurodegenerative disorders is a field in constant evolution. Results to date suggest that immunotherapy is a promising therapeutic approach for neurodegenerative diseases that progress with the accumulation and prion-like propagation of toxic protein aggregates. Here we provide an overview of the most novel and relevant immunotherapeutic advances targeting amyloid-β in Alzheimer’s disease, α-synuclein in Alzheimer’s disease and Parkinson’s disease, and tau in Alzheimer’s disease and frontotemporal dementia.