Pharmacology and Therapeutics - Research Publications
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ItemNo Preview AvailableMetals and Alzheimer's disease(IOS PRESS, 2006-11)There is increasing evidence to support a role for both the amyloid beta-protein precursor (AbetaPP) and its proteolytic fragment, amyloid beta (Abeta), in metal ion homeostasis. Furthermore, metal ions such as zinc and copper can interact with both AbetaPP and Abeta to potentiate Alzheimer's disease by participating in the aggregation of these normal cellular proteins and in the generation of reactive oxygen species. In addition, metal ions may interact on several other AD-related pathways, including those involved in neurofibrillary tangle formation, secretase cleavage of AbetaPP and proteolytic degradation of Abeta. As such, a dysregulation of metal ion homeostasis, as occurs with both aging and in AD, may foster an environment that can both precipitate and accelerate degenerative conditions such as AD. This offers a broad biochemical front for novel therapeutic interventions.
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ItemTau-mediated iron export prevents ferroptotic damage after ischemic stroke(NATURE PUBLISHING GROUP, 2017-11)Functional failure of tau contributes to age-dependent, iron-mediated neurotoxicity, and as iron accumulates in ischemic stroke tissue, we hypothesized that tau failure may exaggerate ischemia-reperfusion-related toxicity. Indeed, unilateral, transient middle cerebral artery occlusion (MCAO) suppressed hemispheric tau and increased iron levels in young (3-month-old) mice and rats. Wild-type mice were protected by iron-targeted interventions: ceruloplasmin and amyloid precursor protein ectodomain, as well as ferroptosis inhibitors. At this age, tau-knockout mice did not express elevated brain iron and were protected against hemispheric reperfusion injury following MCAO, indicating that tau suppression may prevent ferroptosis. However, the accelerated age-dependent brain iron accumulation that occurs in tau-knockout mice at 12 months of age negated the protective benefit of tau suppression against MCAO-induced focal cerebral ischemia-reperfusion injury. The protective benefit of tau knockout was revived in older mice by iron-targeting interventions. These findings introduce tau-iron interaction as a pleiotropic modulator of ferroptosis and ischemic stroke outcome.
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ItemNo Preview AvailableA comparison of ceruloplasmin to biological polyanions in promoting the oxidation of Fe2+ under physiologically relevant conditions(ELSEVIER SCIENCE BV, 2014-12)BACKGROUND: Iron oxidation is thought to be predominantly handled enzymatically in the body, to minimize spontaneous combustion with oxygen and to facilitate cellular iron export by loading transferrin. This process may be impaired in disease, and requires more accurate analytical assays to interrogate enzymatic- and auto-oxidation within a physiologically relevant environment. METHOD: A new triplex ferroxidase activity assay has been developed that overcomes the previous assay limitations of measuring iron oxidation at a physiologically relevant pH and salinity. RESULTS: Revised enzymatic kinetics for ceruloplasmin (Vmax≈35μMFe(3+)/min/μM; Km≈15μM) are provided under physiological conditions, and inhibition by sodium azide (Ki for Ferric Gain 78.3μM, Ki for transferrin loading 8.1×10(4)μM) is quantified. We also used this assay to characterize the non-enzymatic oxidation of iron that proceeded linearly under physiological conditions. CONCLUSIONS AND GENERAL SIGNIFICANCE: These findings indicate that the requirement of an enzyme to oxidize iron may only be necessary under conditions of adverse pH or anionic strength, for example from hypoxia. In a normal physiological environment, Fe(3+) incorporation into transferrin would be sufficiently enabled by the biological polyanions that are prevalent within extracellular fluids.
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ItemStabilization of Nontoxic Aβ-Oligomers: Insights into the Mechanism of Action of Hydroxyquinolines in Alzheimer's Disease(SOC NEUROSCIENCE, 2015-02-18)The extracellular accumulation of amyloid β (Aβ) peptides is characteristic of Alzheimer's disease (AD). However, formation of diffusible, oligomeric forms of Aβ, both on and off pathways to amyloid fibrils, is thought to include neurotoxic species responsible for synaptic loss and neurodegeneration, rather than polymeric amyloid aggregates. The 8-hydroxyquinolines (8-HQ) clioquinol (CQ) and PBT2 were developed for their ability to inhibit metal-mediated generation of reactive oxygen species from Aβ:Cu complexes and have both undergone preclinical and Phase II clinical development for the treatment of AD. Their respective modes of action are not fully understood and may include both inhibition of Aβ fibrillar polymerization and direct depolymerization of existing Aβ fibrils. In the present study, we find that CQ and PBT2 can interact directly with Aβ and affect its propensity to aggregate. Using a combination of biophysical techniques, we demonstrate that, in the presence of these 8-HQs and in the absence of metal ions, Aβ associates with two 8-HQ molecules and forms a dimer. Furthermore, 8-HQ bind Aβ with an affinity of 1-10 μm and suppress the formation of large (>30 kDa) oligomers. The stabilized low molecular weight species are nontoxic. Treatment with 8-HQs also reduces the levels of in vivo soluble oligomers in a Caenorhabditis elegans model of Aβ toxicity. We propose that 8-HQs possess an additional mechanism of action that neutralizes neurotoxic Aβ oligomer formation through stabilization of small (dimeric) nontoxic Aβ conformers.
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ItemPharmacotherapeutic targets in Alzheimer's disease(WILEY, 2009-01)Alzheimer's disease (AD) is a progressive neurodegenerative disorder which is characterized by an increasing impairment in normal memory and cognitive processes that significantly diminishes a person's daily functioning. Despite decades of research and advances in our understanding of disease aetiology and pathogenesis, there are still no effective disease-modifying drugs available for the treatment of AD. However, numerous compounds are currently undergoing pre-clinical and clinical evaluations. These candidate pharma-cotherapeutics are aimed at various aspects of the disease, such as the microtubule-associated tau-protein, the amyloid-beta(Abeta) peptide and metal ion dyshomeostasis--all of which are involved in the development and progression of AD. We will review the way these pharmacological strategies target the biochemical and clinical features of the disease and the investigational drugs for each category.
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ItemRhenium and technetium complexes that bind to amyloid-β plaques(ROYAL SOC CHEMISTRY, 2015)Alzheimer's disease is associated with the presence of insoluble protein deposits in the brain called amyloid plaques. The major constituent of these deposits is aggregated amyloid-β peptide. Technetium-99m complexes that bind to amyloid-β plaques could provide important diagnostic information on amyloid-β plaque burden using Single Photon Emission Computed Tomography (SPECT). Tridentate ligands with a stilbene functional group were used to form complexes with the fac-[M(I)(CO)3](+) (M = Re or (99m)Tc) core. The rhenium carbonyl complexes with tridentate co-ligands that included a stilbene functional group and a dimethylamino substituent bound to amyloid-β present in human frontal cortex brain tissue from subjects with Alzheimer's disease. This chemistry was extended to make the analogous [(99m)Tc(I)(CO)3](+) complexes and the complexes were sufficiently stable in human serum. Whilst the lipophilicity (log D7.4) of the technetium complexes appeared ideally suited for penetration of the blood-brain barrier, preliminary biodistribution studies in an AD mouse model (APP/PS1) revealed relatively low brain uptake (0.24% ID g(-1) at 2 min post injection).
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Itemβ-amyloid in biological samples: not all Aβ detection methods are created equal(FRONTIERS MEDIA SA, 2014-08-13)