ABSTRACT
BACKGROUND: Amyloid-beta peptide (Aß) is the main constituent of senile plaques and is implicated in the pathogenesis of Alzheimer's disease (AD). To that end, agents which either sequester Aß or interfere with Aß interaction/binding to cells have been investigated as a means to reduce the pathological effects of Aß. METHODS: Different structural analogs of sialic acid (N-acetylneuramic acid) were used to decorate a chitosan backbone using EDC chemistry. FTIR and colorimetric assays were used to characterize the complexes. The ability of these complexes to attenuate Aß toxicity was investigated in vitro using a model neuroblastoma cell line SH-SY5Y. RESULTS: Oxygen substitution in ring structure is responsible for the increase in toxicity and increase in protective properties of the complexes. Also, the multi OH tail present in sialic acid is critical to attenuate toxicity. Analogs show no protective properties which reinforces the conclusion that clustering of sugars in cellular membranes play a significant role in Aß binding. CONCLUSIONS: Successfully produced compounds that showed varying degree of efficacy in attenuating Aß toxicity to cells in culture. This work elucidates the impact that certain structures of sialic acid and its analogs can have on Aß binding. It will allow for more specific and detailed improvements in the therapeutic polysaccharide structures that can be developed and modified to overcome other shortcomings of AD therapeutic development, particularly of penetrating the blood-brain barrier. GENERAL SIGNIFICANCE: Oxygen atom plays crucial role on therapeutic effectiveness. This work can help as a general guideline for further therapeutic development.
Subject(s)
Amyloid beta-Peptides/toxicity , Cytoprotection/drug effects , N-Acetylneuraminic Acid/analogs & derivatives , N-Acetylneuraminic Acid/pharmacology , Neurons/drug effects , Antiparkinson Agents/isolation & purification , Antiparkinson Agents/pharmacology , Antiparkinson Agents/therapeutic use , Carbohydrate Metabolism/physiology , Carbohydrates/chemistry , Carbohydrates/pharmacology , Carbohydrates/therapeutic use , Cell Survival/drug effects , Chitosan/chemistry , Chitosan/metabolism , Chitosan/pharmacology , Chitosan/therapeutic use , Dose-Response Relationship, Drug , Drug Evaluation, Preclinical , Humans , Models, Biological , N-Acetylneuraminic Acid/isolation & purification , N-Acetylneuraminic Acid/therapeutic use , Neurons/metabolism , Neurons/physiology , Osmolar Concentration , Tumor Cells, CulturedABSTRACT
beta-Amyloid (Abeta) is the primary protein component of senile plaques in Alzheimer's disease and is believed to be associated with neurotoxicity in the disease. We and others have shown that Abeta binds with relatively high affinity to clustered sialic acid residues on cell surfaces and that removal of cell surface sialic acids attenuates Abeta toxicity. We have also shown that sialic acid functionalized dendrimeric polymers can act as mimics of cell surface sialic acid clusters and attenuate Abeta-induced neurotoxicity. In the current study, we prepared sialic-acid-conjugated dendrimers using a physiologically relevant attachment of the sialic acid to the dendrimeric termini, and evaluated the Abeta toxicity attenuation properties of the dendrimers. We compared performance of sialic-acid-conjugated dendrimeric polymers in which the sialic acid moieties were attached to dendrimeric termini via the anomeric hydroxyl group of the sialic acid, a physiological attachment, to polymers in which the attachment was made via the carboxylic acid group on the sialic acid, a non-physiological attachment. This work enhances our understanding of Abeta-cell surface binding and is a step towards the development of new classes of sequestering agents as therapeutics for the prevention of Abeta toxicity in AD.
