Many forms of neurodegenerative disease, for instance Alzheimer's disease, Parkinson's disease, Friedreich's ataxia, Hallervorden Spatz syndrome and macular degeneration, are associated with elevated levels of redox active metals in the brain and eye. A logical therapeutic approach therefore, is to remove the toxic levels of these metals, copper and iron in particular, by selective chelation. The increased number of iron-selective chelators now available for clinical use has enhanced interest in this type of therapy. This review summarises the recent developments in the design of chelators for treatment of neurodegenerative disease, identifies some of the essential properties for such molecules and suggests some future strategies.
Neurodegenerative disorders include a variety of pathological conditions, which share similar critical metabolic processes such as protein aggregation and oxidative stress, both of which are associated with the involvement of metal ions. Chelation therapy could provide a valuable therapeutic approach to such disease states, since metals, particularly iron, are realistic pharmacological targets for the rational design of new therapeutic agents.
A range of fluorinated 3-hydroxypyridin-4-ones has been synthesized where fluorine or fluorinated substituent was attached at 2- or 5- position of the pyridine ring in order to improve chemical and biological properties of 3-hydroxypyridin-4-ones. The synthetic route is different from conventional counterparts where a functional group is introduced to a preformed 3-hydroxypyridin-4-one ring. Herein, we introduce a novel method which starts with a fluorine containing precursor and the two hydroxyl groups at 3- and 4- positions of the pyridine ring are introduced at a later stage. The pK(a) values of the free ligands and the affinity constants of their iron complexes demonstrate that the presence of fluorine dramatically alters the values. The distribution coefficient values of the free ligands and corresponding iron(III) complexes between 1-octanol and MOPS buffer (pH 7.4) are also influenced. Glucuronidation and oxidation studies of selected fluorinated 3-hydroxypyridin-4-ones demonstrate that some such fluorinated compounds have clear advantage over deferiprone in that they are metabolized more slowly. Blood-brain barrier permeability studies indicated that although lipophilicity influences the permeability it is not the only factor. Two of the selected seven fluorinated 3-hydroxypyridin-4-ones have improved brain distribution when compared with deferiprone.
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