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The loss of cognitive function is a pervasive and often debilitating feature of the aging process for which there are no effective therapeutics. We hypothesized that a novel metal chaperone (PBT2; Prana Biotechnology, Parkville, Victoria, Australia) would enhance cognition in aged rodents. We show here that PBT2 rapidly improves the performance of aged C57Bl/6 mice in the Morris water maze, concomitant with increases in dendritic spine density, hippocampal neuron number and markers of neurogenesis. There were also increased levels of specific glutamate receptors (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and N-methyl- d-aspartate), the glutamate transporter ( VGLUT1) and glutamate itself. Markers of synaptic plasticity [calmodulin-dependent protein kinase II (CaMKII) and phosphorylated CaMKII, CREB, synaptophysin] were also increased following PBT2 treatment. We also demonstrate that PBT2 treatment results in a subregion-specific increase in hippocampal zinc, which is increasingly recognized as a potent neuromodulator. These data demonstrate that metal chaperones are a novel approach to the treatment of age-related cognitive decline. [ABSTRACT FROM AUTHOR]

J. Neurochem. (2011) 119, 220-230. Abstract Impaired metal ion homeostasis causes synaptic dysfunction and treatments for Alzheimer's disease (AD) that target metal ions have therefore been developed. The leading compound in this class of therapeutic, PBT2, improved cognition in a clinical trial with AD patients. The aim of the present study was to examine the cellular mechanism of action for PBT2. We show PBT2 induces inhibitory phosphorylation of the α- and β-isoforms of glycogen synthase kinase 3 and that this activity is dependent on PBT2 translocating extracellular Zn and Cu into cells. This activity is supported when Aβ:Zn aggregates are the source of extracellular Zn and adding PBT2 to Aβ:Zn preparations promotes Aβ degradation by matrix metalloprotease 2. PBT2-induced glycogen synthase kinase 3 phosphorylation appears to involve inhibition of the phosphatase calcineurin. Consistent with this, PBT2 increased phosphorylation of other calcineurin substrates, including cAMP response element binding protein and Ca2+/calmodulin-dependent protein kinase. These data demonstrate PBT2 can decrease Aβ levels by sequestering the Zn that promotes extracellular formation of protease resistant Aβ:Zn aggregates, and that subsequent intracellular translocation of the Zn by PBT2 induces cellular responses with synapto-trophic potential. Intracellular translocation of Zn and Cu via the metal chaperone activity of PBT2 may be an important mechanism by which PBT2 improves cognitive function in people with AD. [ABSTRACT FROM AUTHOR]

Accumulation of neurotoxic amyloid-β (Aβ) is central to the pathology of Alzheimer’s disease (AD). Elucidating the mechanisms of Aβ accumulation will therefore expedite the development of Aβ-targeting AD therapeutics. We examined activity of an Aβ-degrading protease (matrix metalloprotease 2) to investigate whether biochemical factors consistent with conditions in the AD brain contribute to Aβ accumulation by altering Aβ sensitivity to proteolytic degradation. An Aβ amino acid mutation found in familial AD, Aβ interactions with zinc (Zn), and increased Aβ hydrophobicity all strongly prevented Aβ degradation. Consistent to all of these factors is the promotion of specific Aβ aggregates where the protease cleavage site, confirmed by mass spectrometry, is inaccessible within an amyloid structure. These data indicate decreased degradation due to amyloid formation initiates Aβ accumulation by preventing normal protease activity. Zn also prevented Aβ degradation by the proteases neprilysin and insulin degrading enzyme. Treating Zn-induced Aβ amyloid with the metal-protein attenuating compound clioquinol reversed amyloid formation and restored the peptide’s sensitivity to degradation by matrix metalloprotease 2. This provides new data indicating that therapeutic compounds designed to modulate Aβ-metal interactions can inhibit Aβ accumulation by restoring the catalytic potential of Aβ-degrading proteases. [ABSTRACT FROM AUTHOR]

Transgenic mice carrying mutant Cu/Zn superoxide dismutase (SOD1) recapitulate the motor impairment of human amyotrophic lateral sclerosis (ALS). The amyloid-β (Aβ) peptide associated with Alzheimer's disease is neurotoxic. To investigate the potential role of Aβ in ALS development, we generated a double transgenic mouse line that overexpresses SOD1G93A and amyloid precursor protein (APP)-C100. The transgenic mouse C100.SOD1G93A overexpresses Aβ and shows earlier onset of motor impairment but has the same lifespan as the single transgenic SOD1G93A mouse. To determine the mechanism associated with this early-onset phenotype, we measured copper and zinc levels in brain and spinal cord and found both significantly elevated in the single and double transgenic mice compared with their littermate control mice. Increased glial fibrillary acidic protein and decreased APP levels in the spinal cord of C100.SOD1G93A mice compared with the SOD1G93A mice agree with the neuronal damage observed by immunohistochemical analysis. In the spinal cords of C100.SOD1G93A double transgenic mice, soluble Aβ was elevated in mice at end-stage disease compared with the pre-symptomatic stage. Buffer-insoluble SOD1 aggregates were significantly elevated in the pre-symptomatic mice of C100.SOD1G93A compared with the age-matched SOD1G93A mice, correlating with the earlier onset of motor impairment in the C100.SOD1G93A mice. This study supports abnormal SOD1 protein aggregation as the pathogenic mechanism in ALS, and implicates a potential role for Aβ in the development of ALS by exacerbating SOD1G93A aggregation. [ABSTRACT FROM AUTHOR]

Neocortical β-amyloid (Aβ) aggregates in Alzheimer's disease (AD) are enriched in transition metals that mediate assembly. Clioquinol (CQ) targets metal interaction with Aβ and inhibits amyloid pathology in transgenic mice. Here, we investigated the binding properties of radioiodinated CQ ([125I]CQ) to different in vitro and in vivo Alzheimer models. We observed saturable binding of [125I]CQ to synthetic Aβ precipitated by Zn2+ (Kd = 0.45 and 1.40 nm for Aβ1-42 and Aβ1-40, respectively), which was fully displaced by free Zn2+, Cu2+, the chelator DTPA (diethylene triamine pentaacetic acid) and partially by Congo red. Sucrose density gradient of post-mortem AD brain indicated that [125I]CQ concentrated in a fraction enriched for both Aβ and Zn, which was modulated by exogenous addition of Zn2+ or DTPA. APP transgenic (Tg2576) mice injected with [125I]CQ exhibited higher brain retention of tracer compared to non-Tg mice. Autoradiography of brain sections of these animals confirmed selective [125I]CQ enrichment in the neocortex. Histologically, both thioflavine-S (ThS)-positive and negative structures were labeled by [125I]CQ. A pilot SPECT study of [123I]CQ showed limited uptake of the tracer into the brain, which did however, appear to be more rapid in AD patients compared to age-matched controls. These data support metallated Aβ species as the neuropharmacological target of CQ and indicate that this drug class may have potential as in vivo imaging agents for Alzheimer neuropathology. [ABSTRACT FROM AUTHOR]

Metal-catalysed oxidation (MCO) may play a causative role in the pathogenesis of Alzheimer's disease (AD). Amyloid β peptide (Aβ), the major biomarker of AD, in the presence of copper ions reduces Cu2+ to Cu+ and catalyses the formation of H2O2 that subsequently induces radicals through Fenton chemistry. Aβ is also subject to attack by free radicals, where the presence of Cu2+ in conjunction with H2O2 catalyses oxygenation, primarily at the methionine sulfur atom. This work investigates MCO of Aβ, to gain further insight into the role of oxidative stress in AD. By combining a fluorescence assay with gel electrophoresis to monitor MCO reactions of Aβ (1-28) in the presence and absence of methionine it was determined that methionine can both protect some residues against MCO and promote the oxidation of Tyr(10) specifically. Electrospray ionization mass spectrometric analysis of methionine MCO products indicated the formation of methionine sulfoxide, methionine sulfone and related hydroxylated products. Similar products could be formed from the oxidation of Met(35) of Aβ and may relate to changes in properties of the peptide following MCO. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Aggregated amyloid β-peptide (Aβ) is the primary constituent of the extracellular plaques and perivascular amyloid deposits associated with Alzheimer's disease (AD). Deposition of the cerebral amyloid plaques is thought to be central to the disease progression. One such molecule that has previously been shown to 'dissolve' deposited amyloid in post-mortem brain tissue is bathocuproine (BC). In this paper 1H NMR chemical shift analysis and pulsed field gradient NMR diffusion measurements were used to study BC self-association and subsequent binding to Aβ. The results show that BC undergoes self-association as its concentration increases. The association constant of BC dimerization, Ka, was estimated to be 0.64 m M−1 at 25°C from 1H chemical shift analysis. It was also found that dimerization of BC appeared to be essential for its binding to Aβ. From the self-association constant of BC, Ka, the fraction of dimeric BC in the complex was obtained and the dissociation constant, Kd, of BC bound to Aβ40 peptide was then determined to be ∼1 m M. Copyright © 2003 European Peptide Society and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

To study amyloid β-protein (Aβ) production and aggregation in vivo, we created two transgenic (Tg) mouse lines expressing the C-terminal 100 amino acids of human amyloid precursor protein (APP): Tg C100.V717F and Tg C100.WT. Western blot analysis showed that human APP-C100 and Aβ were produced in brain and some peripheral tissues and Aβ was produced in serum. Using antibodies specific for the Aβ C terminus we found that Tg C100.V717F produced a 1.6-fold increase in Aβ42/Aβ40 compared with Tg C100.WT. Approximately 30% of total brain Aβ (∼122 ng/g of wet tissue) was water-soluble. The remaining 70% of Aβ partitioned into the particulate fraction and was completely sodium dodecyl sulfate-soluble. In contrast, human Alzheimer's disease brain has predominantly sodium dodecyl sulfate-insoluble Aβ. Immunohistochemistry with an Aβ(5-8) antibody showed that Aβ or Aβ-containing fragments accumulated intracellularly in the hippocampus of aged Tg C100.V717F mice. The soluble Aβ levels in Tg brain are similar to those in normal human brain, and this may explain the lack of microscopic amyloid deposits in the Tg mice. However, this mouse model provides a system to study the intracellular processing and accumulation of Aβ or Aβ-containing fragments and to screen for compounds directed at the γ-secretase activity. [ABSTRACT FROM AUTHOR]

Presents a study on the novel interaction between dopamine and α-synuclein (α-SN) oligomerization. Aggregation of α-SN in the absence of dopamine; Analysis of the secondary structure of α-SN by circular dichroism; Effect of dopamine on iron mediated α-SN fibrilization.

Presents a study which examined tyrosine gated electron transfer as a key to the toxic mechanism of Alzheimer's disease Β-amyloid. Brief background on the Β-amyloid peptide; Methodology; Findings.

Transgenic mice carrying mutant Cu/Zn superoxide dismutase (SOD1) recapitulate the motor impairment of human amyotrophic lateral sclerosis (ALS). The amyloid-beta (Abeta) peptide associated with Alzheimer's disease is neurotoxic. To investigate the potential role of Abeta in ALS development, we generated a double transgenic mouse line that overexpresses SOD1(G93A) and amyloid precursor protein (APP)-C100. The transgenic mouse C100.SOD1(G93A) overexpresses Abeta and shows earlier onset of motor impairment but has the same lifespan as the single transgenic SOD1(G93A) mouse. To determine the mechanism associated with this early-onset phenotype, we measured copper and zinc levels in brain and spinal cord and found both significantly elevated in the single and double transgenic mice compared with their littermate control mice. Increased glial fibrillary acidic protein and decreased APP levels in the spinal cord of C100.SOD1(G93A) mice compared with the SOD1(G93A) mice agree with the neuronal damage observed by immunohistochemical analysis. In the spinal cords of C100.SOD1(G93A) double transgenic mice, soluble Abeta was elevated in mice at end-stage disease compared with the pre-symptomatic stage. Buffer-insoluble SOD1 aggregates were significantly elevated in the pre-symptomatic mice of C100.SOD1(G93A) compared with the age-matched SOD1(G93A) mice, correlating with the earlier onset of motor impairment in the C100.SOD1(G93A) mice. This study supports abnormal SOD1 protein aggregation as the pathogenic mechanism in ALS, and implicates a potential role for Abeta in the development of ALS by exacerbating SOD1(G93A) aggregation.

Neocortical beta-amyloid (Abeta) aggregates in Alzheimer's disease (AD) are enriched in transition metals that mediate assembly. Clioquinol (CQ) targets metal interaction with Abeta and inhibits amyloid pathology in transgenic mice. Here, we investigated the binding properties of radioiodinated CQ ([(125)I]CQ) to different in vitro and in vivo Alzheimer models. We observed saturable binding of [(125)I]CQ to synthetic Abeta precipitated by Zn(2+) (K(d)=0.45 and 1.40 nm for Abeta(1-42) and Abeta(1-40), respectively), which was fully displaced by free Zn(2+), Cu(2+), the chelator DTPA (diethylene triamine pentaacetic acid) and partially by Congo red. Sucrose density gradient of post-mortem AD brain indicated that [(125)I]CQ concentrated in a fraction enriched for both Abeta and Zn, which was modulated by exogenous addition of Zn(2+) or DTPA. APP transgenic (Tg2576) mice injected with [(125)I]CQ exhibited higher brain retention of tracer compared to non-Tg mice. Autoradiography of brain sections of these animals confirmed selective [(125)I]CQ enrichment in the neocortex. Histologically, both thioflavine-S (ThS)-positive and negative structures were labeled by [(125)I]CQ. A pilot SPECT study of [(123)I]CQ showed limited uptake of the tracer into the brain, which did however, appear to be more rapid in AD patients compared to age-matched controls. These data support metallated Abeta species as the neuropharmacological target of CQ and indicate that this drug class may have potential as in vivo imaging agents for Alzheimer neuropathology.