The hallmark of Alzheimer's disease (AD) is the presence in brain of plaques, which are complex extracellular lesions composed of a central deposition of 2-amyloid peptide. Genetic, neuropathological and biochemical evidence have shown that these deposits play an important role in the pathogenesis of AD. We have confirmed the hypothesis that Alzheimer's disease (AD) can be effectively treated using our proprietary chemical agent that can sequester the toxic 2-amyloid peptides A21-40 and A21-42 in the periphery. In a mouse model of AD (APPSWE-2576), 3 biweekly injections of our peptide-like compound resulted in a 50% lower plaque content in the brain, as evidenced by immunohiostological analysis. This data is further supported by a quantitative reduction in the amount of AB peptides in brain extracts from treated AD versus control mice. However, we have not yet addressed the issue of removal of the subcutaneous detoxification depots. In the proposed study, we will examine a mobile detoxification depot. In Phase 1, this new system will be optimized for the properties of strong and specific binding of toxic A2 peptides and clearance from the body of AD model mouse. In summary, the current study aims to 1. Develop a """"""""sink """""""" that has sufficient avidity and specificity to function as a binding element at the low concentration of A2 peptides and at the high levels of extraneous proteins and lipids in the body. 2. Develop a process that will result in degradation and/or elimination of toxic A2 peptides captured by this sink. Can albumin be used as the carrier to provide plaque reduction without any extra removal steps? The outcome of the proposed research is expected to result in a greater impact in the treatment of AD and is likely to lead to human application in subsequent investigations.
Alzheimer's disease is now known to be cause by an accumulation of a particular group of peptides (40 or 42 amino acids), known as beta-amyloid (A2 ) peptides, in the brain. These A2 peptides tend to aggregate into insoluble masses that appear as plaques in the brain. These plaques are toxic to nearby neurons, thereby destroying mental function. The aggregation process is induce by a pentapeptide sequence , KLVFF, within the A2 peptide. In our early studies, we synthesized """"""""retro-inverso"""""""" (RI) forms of A2 peptides (composed of D-amino acids in the reverse sequence, ffvlk) as potential therapeutic agents designed to interfere with the aggregation process. RI peptides are resistant to peptidase digestion, and we found that they retain the natural KLVFF binding/aggregation properties. Furthermore, aggregates with RI peptides were found to reduce the toxicity of bound A2 peptides. We also observed that conjugates bearing multiple copies of the RI peptide increase the avidity of interaction with A2 peptides. Our current research is derived from a published observation that demonstrated a novel approach to AD therapy [DeMattos, et al.(2002) Brain to plasma - 2 amyloid efflux: a measure of brain amyloid burden in a mouse model of Alzheimer's disease. Science 295, 2264-2267]. Instead of interfering with the synthesis of A2 peptides or with the aggregation process, it might be possible to sequester (i.e. capture) A2 peptides and keep them in a non-aggregating form or even to remove them from the body. The rationale for this concept is that the A2 peptides can cross the blood-brain barrier. While DeMattos was successful using a monoclonal antibody against A2 peptides, this would not be suitable for a therapeutic agent that would have to be used for the remainder of the patient's life. Our RI peptides however, seemed to fit all the requirements for a sequestering agent. RI peptides bind A2 peptides specifically and virtually irreversibly, they reduce the toxicity of bound A2 peptides and they are stable (non-digestible). Using a binding assay to screen a series of RI peptides, we selected a lead candidate and tested it in a mouse model of AD. After 6 weeks, control (4 untreated mice) had extensive brain damage, whereas treated (3 mice) did not. Clearly, the RI peptide approach can potentially lead to an effective therapeutic product. ? ? ?
