ABSTRACT
The development of effective therapies as well as early, molecular diagnosis of Alzheimer's disease is impeded by the lack of understanding of the underlying pathological mechanisms. Metabolomics studies of body fluids as well as brain tissues have shown major changes in metabolic profiles of Alzheimer's patients. However, with analysis performed at the late stages of the disease it is not possible to distinguish causes and consequence. The mouse model APP/PS1 expresses a mutant amyloid precursor protein resulting in early Amyloid ß (Aß) accumulation as well as many resulting physiological changes including changes in metabolic profile and metabolism. Analysis of metabolic profile of cerebrospinal fluid (CSF) and blood of APP/PS1 mouse model can provide information about metabolic changes in these body fluids caused by Aß accumulation. Using our novel method for analysis of correlation and mathematical ranking of significant correlations between metabolites in CSF and blood, we have explored changes in metabolite correlation and connectedness in APP/PS1 and wild type mice. Metabolites concentration and correlation changes in CSF, blood and across the blood brain barrier determined in this work are affected by the production of amyloid plaque. Metabolite changes observed in the APP/PS1 mouse model are the response to the mutation causing plaque formation, not the cause for the plaque suggesting that they are less relevant in the context of early treatment and prevention then the metabolic changes observed only in humans.
Subject(s)
Alzheimer Disease/pathology , Amyloid beta-Protein Precursor/genetics , Cerebrospinal Fluid/metabolism , Magnetic Resonance Spectroscopy/methods , Metabolome , Presenilin-1/genetics , Serum/metabolism , Alzheimer Disease/blood , Alzheimer Disease/cerebrospinal fluid , Animals , Biomarkers/blood , Biomarkers/cerebrospinal fluid , Disease Models, Animal , Female , Male , Mice , Mice, Inbred C57BL , Mice, TransgenicABSTRACT
Antibody, immuno- and gene therapies developed for neurological indications face a delivery challenge posed by various anatomical and physiological barriers within the central nervous system (CNS); most notably, the blood-brain barrier (BBB). Emerging delivery technologies for biotherapeutics have focused on trans-cellular pathways across the BBB utilizing receptor-mediated transcytosis (RMT). 'Traditionally' targeted RMT receptors, transferrin receptor (TfR) and insulin receptor (IR), are ubiquitously expressed and pose numerous translational challenges during development, including species differences and safety risks. Recent advances in antibody engineering technologies and discoveries of RMT targets and BBB-crossing antibodies that are more BBB-selective have combined to create a new preclinical pipeline of BBB-crossing biotherapeutics with improved efficacy and safety. Novel BBB-selective RMT targets and carrier antibodies have exposed additional opportunities for re-targeting gene delivery vectors or nanocarriers for more efficient brain delivery. Emergence and refinement of core technologies of genetic engineering and editing as well as biomanufacturing of viral vectors and cell-derived products have de-risked the path to the development of systemic gene therapy approaches for the CNS. In particular, brain-tropic viral vectors and extracellular vesicles have recently expanded the repertoire of brain delivery strategies for biotherapeutics. Whereas protein biotherapeutics and bispecific antibodies enabled for BBB transcytosis are rapidly heading towards clinical trials, systemic gene therapy approaches for CNS will likely remain in research phase for the foreseeable future. The promise and limitations of these emerging cross-BBB delivery technologies are further discussed in this article.
Subject(s)
Biological Products/administration & dosage , Blood-Brain Barrier/drug effects , Central Nervous System Diseases/therapy , Drug Delivery Systems/methods , Genetic Vectors/administration & dosage , Animals , Antigens, CD/metabolism , Biological Products/therapeutic use , Blood-Brain Barrier/metabolism , Central Nervous System Diseases/genetics , Genetic Therapy/methods , Humans , Receptor, Insulin/metabolism , Receptors, Transferrin/metabolism , Transcytosis/drug effects , Treatment OutcomeABSTRACT
Polysialic acids are bioactive carbohydrates found in eukaryotes and some bacterial pathogens. The bacterial polysialyltransferases (PSTs), which catalyze the synthesis of polysialic acid capsules, have previously been identified in select strains of Escherichia coli and Neisseria meningitidis and are classified in the Carbohydrate-Active enZYmes Database as glycosyltransferase family GT-38. In this study using DNA sequence analysis and functional characterization we have identified a novel polysialyltransferase from the bovine/ovine pathogen Mannheimia haemolytica A2 (PSTMh). The enzyme was expressed in recombinant form as a soluble maltose-binding-protein fusion in parallel with the related PSTs from E. coli K1 and N. meningitidis group B in order to perform a side-by-side comparison. Biochemical properties including solubility, acceptor preference, reaction pH optima, thermostability, kinetics, and product chain length for the enzymes were compared using a synthetic fluorescent acceptor molecule. PSTMh exhibited biochemical properties that make it an attractive candidate for chemi-enzymatic synthesis applications of polysialic acid. The activity of PSTMh was examined on a model glycoprotein and the surface of a neuroprogenitor cell line where the results supported its development for use in applications to therapeutic protein modification and cell surface glycan remodelling to enable cell migration at implantation sites to promote wound healing. The three PSTs examined here demonstrated different properties that would each be useful to therapeutic applications.
