From the laboratory of Dr. Ashley I. Bush, MD, PhD
Director, Laboratory for Oxidation Biology, Genetics and Aging Unit,
Massachusetts General Hospital, Harvard University

• Treatment with a copper-zinc chelator markedly and rapidly inhibits beta-amyloid accumulation in Alzheimer's disease transgenic mice.
  • Cherny RA, Atwood CS, Xilinas ME, Gray DN, Jones WD, McLean CA, Barnham KJ, Volitakis I, Fraser FW, Kim Y, Huang X, Goldstein LE, Moir RD, Lim JT, Beyreuther K, Zheng H, Tanzi RE, Masters CL, Bush AI.
  • J Biol Chem 2001 Jun 8;276(23):20466-73

• Alzheimer's disease amyloid-beta binds copper and zinc to generate an allosterically ordered membrane-penetrating structure containing superoxide dismutase-like subunits.
  • Curtain CC, Ali F, Volitakis I, Cherny RA, Norton RS, Beyreuther K, Barrow CJ, Masters CL, Bush AI, Barnham KJ.
  • J Neurochem 2001 Mar;76(5):1509-20

• Homocysteine potentiates copper- and amyloid beta peptide-mediated toxicity in primary neuronal cultures: possible risk factors in the Alzheimer's-type neurodegenerative pathways.
  • White AR, Huang X, Jobling MF, Barrow CJ, Beyreuther K, Masters CL, Bush AI, Cappai R.
  • J Neurochem 2001 Mar;76(5):1509-20

• Metal chelation as a potential therapy for Alzheimer's disease.
  • Cuajungco MP, Faget KY, Huang X, Tanzi RE, Bush AI.
  • Ann N Y Acad Sci 2000;920:292-304

• Redox-active iron mediates amyloid-beta toxicity.
  • Rottkamp CA, Raina AK, Zhu X, Gaier E, Bush AI, Atwood CS, Chevion M, Perry G, Smith MA.
  • Free Radic Biol Med 2001 Feb 15;30(4):447-50

• Oxidative processes in Alzheimer's disease: the role of abeta-metal interactions.
  • Lynch T, Cherny RA, Bush AI.
  • Exp Gerontol 2000 Jul;35(4):445-51

• Chelation and intercalation: complementary properties in a compound for the treatment of Alzheimer's disease.
  • Cherny RA, Barnham KJ, Lynch T, Volitakis I, Li QX, McLean CA, Multhaup G, Beyreuther K, Tanzi RE, Masters CL, Bush AI.
  • J Struct Biol 2000 Jun;130(2-3):209-16

• Characterization of copper interactions with alzheimer amyloid beta peptides: identification of an attomolar-affinity copper binding site on amyloid beta1-42.
  • Atwood CS, Scarpa RC, Huang X, Moir RD, Jones WD, Fairlie DP, Tanzi RE, Bush AI.
  • J Neurochem 2000 Sep;75(3):1219-33

• Copper catalyzed oxidation of Alzheimer Abeta.
  • Atwood CS, Huang X, Khatri A, Scarpa RC, Kim YS, Moir RD, Tanzi RE, Roher AE, Bush AI.
  • Cell Mol Biol (Noisy-le-grand) 2000 Jun;46(4):777-83

• Alzheimer's disease, beta-amyloid protein and zinc.
  • Huang X, Cuajungco MP, Atwood CS, Moir RD, Tanzi RE, Bush AI.
  • J Nutr 2000 May;130(5S Suppl):1488S-92S

• Evidence that the beta-amyloid plaques of Alzheimer's disease represent the redox-silencing and entombment of abeta by zinc.
  • Cuajungco MP, Goldstein LE, Nunomura A, Smith MA, Lim JT, Atwood CS, Huang X, Farrag YW, Perry G, Bush AI.
  • J Biol Chem 2000 Jun 30;275(26):19439-42

• Cu(II) potentiation of alzheimer abeta neurotoxicity. Correlation with cell-free hydrogen peroxide production and metal reduction.
  • Huang X, Cuajungco MP, Atwood CS, Hartshorn MA, Tyndall JD, Hanson GR, Stokes KC, Leopold M, Multhaup G, Goldstein LE, Scarpa RC, Saunders AJ, Lim J, Moir RD, Glabe C, Bowden EF, Masters CL, Fairlie DP, Tanzi RE, Bush AI.
  • J Biol Chem 1999 Dec 24;274(52):37111-6

• The Alzheimer's disease amyloid precursor protein modulates copper-induced toxicity and oxidative stress in primary neuronal cultures.
  • White AR, Multhaup G, Maher F, Bellingham S, Camakaris J, Zheng H, Bush AI, Beyreuther K, Masters CL, Cappai R.
  • J Neurosci 1999 Nov 1;19(21):9170-9

• Copper levels are increased in the cerebral cortex and liver of APP and APLP2 knockout mice.
  • White AR, Reyes R, Mercer JF, Camakaris J, Zheng H, Bush AI, Multhaup G, Beyreuther K, Masters CL, Cappai R.
  • Brain Res 1999 Sep 25;842(2):439-44

• Aqueous dissolution of Alzheimer's disease Abeta amyloid deposits by biometal depletion.
  • Cherny RA, Legg JT, McLean CA, Fairlie DP, Huang X, Atwood CS, Beyreuther K, Tanzi RE, Masters CL, Bush AI.

  • J Biol Chem 1999 Aug 13;274(33):23223-8

• The A beta peptide of Alzheimer's disease directly produces hydrogen peroxide through metal ion reduction.
  • Huang X, Atwood CS, Hartshorn MA, Multhaup G, Goldstein LE, Scarpa RC, Cuajungco MP, Gray DN, Lim J, Moir RD, Tanzi RE, Bush AI.
  • Biochemistry 1999 Jun 15;38(24):7609-16

• Differential effects of apolipoprotein E isoforms on metal-induced aggregation of A beta using physiological concentrations.
  • Moir RD, Atwood CS, Romano DM, Laurans MH, Huang X, Bush AI, Smith JD, Tanzi RE.
  • Biochemistry 1999 Apr 6;38(14):4595-603

• Role of free radicals and metal ions in the pathogenesis of Alzheimer's disease.
  • Atwood CS, Huang X, Moir RD, Tanzi RE, Bush AI.
  • Met Ions Biol Syst 1999;36:309-64

E-Mail Correspondence with Dr. Bush Regarding the Role of Heavy Metals and Aggregation of Amyloid

Date: Mon, 25 Jun 2001 19:33:02 -0400

To: "Affinity Labeling Technologies, Inc."

From: Ashley Bush

Subject: Re: mercury

Dear Dr. Bush,

Do you believe clioquinol would be equally effective at removing Hg from the brains of AD patients? Several studies have suggested that this other sulfyhydryl reactive heavy metal may also promote amyloid aggregation as well as inhibit a number of key enzymes involved in the disease process (see http://www.altcorp.com/amalgampage.htm).

Sincerely, Curt Pendergrass Ph.D.

Dear Dr Pendergrass,

I visited Dr Haley a couple of years ago while visiting Allan Butterfield. I am actually quite a fan of your work, (and have lately started to get my Hg fillings replaced). I didn't know that you had set up a company. Very interesting. I actually do not know whether clioquinol removes Hg. It doesn't work by removing Cu and Zn from the brain, but by facilitating equilibria that dissociate Zn and Cu from Abeta, and by inhibiting hydrogen peroxide production which is mediated by Cu. Whereas I accept the elevation of Hg in AD as a distinct possibility, I find the metallochemistry of Abeta as an SOD-like protein (it definitely binds Zn and Cu exclusively in vivo), as a more upstream biochemical argument. Certainly, though, Hg accumulation would not help the antioxidant systems cope with the hydrogen peroxide. A few thoughts. You may wan to contact my commercial folk at www.pranabio.com to investigate some joint work in this arena if you think it is of interest. Thanks for your note.

All the best,

Ashley

Ashley I. Bush, MD, PhD
Director, Laboratory for Oxidation Biology, Genetics and Aging Unit,
Massachusetts General Hospital,
Building 114, 16th Street
Charlestown, MA, 02129-4404, USA
Ph: 617-726-8244
Fax: 617-724-1823

Treatment with a copper-zinc chelator markedly and rapidly inhibits beta-amyloid accumulation in Alzheimer's disease transgenic mice.

Cherny RA, Atwood CS, Xilinas ME, Gray DN, Jones WD, McLean CA, Barnham KJ, Volitakis I, Fraser FW, Kim Y, Huang X, Goldstein LE, Moir RD, Lim JT, Beyreuther K, Zheng H, Tanzi RE, Masters CL, Bush AI.

Department of Pathology, The University of Melbourne and, The Mental Health Research Institute of Victoria, Australia.

Neuron 2001 Jun;30(3):665-76

Neuron. 2001 Jun;30(3):641-2

Inhibition of neocortical beta-amyloid (Abeta) accumulation may be essential in an effective therapeutic intervention for Alzheimer's disease (AD). Cu and Zn are enriched in Abeta deposits in AD, which are solubilized by Cu/Zn-selective chelators in vitro. Here we report a 49% decrease in brain Abeta deposition (-375 microg/g wet weight, p = 0.0001) in a blinded study of APP2576 transgenic mice treated orally for 9 weeks with clioquinol, an antibiotic and bioavailable Cu/Zn chelator. This was accompanied by a modest increase in soluble Abeta (1.45% of total cerebral Abeta); APP, synaptophysin, and GFAP levels were unaffected. General health and body weight parameters were significantly more stable in the treated animals. These results support targeting the interactions of Cu and Zn with Abeta as a novel therapy for the prevention and treatment of AD.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11430801&dopt=Abstract

See comment on this study in WebMDH Health entitled:

Metal Remover Clears Alzheimer's Plaques in Mice But Will It Improve Disease Symptoms? http://my.webmd.com/content/article/1728.81882

J Biol Chem 2001 Jun 8;276(23):20466-73

Alzheimer's disease amyloid-beta binds copper and zinc to generate an allosterically ordered membrane-penetrating structure containing superoxide dismutase-like subunits.

Curtain CC, Ali F, Volitakis I, Cherny RA, Norton RS, Beyreuther K, Barrow CJ, Masters CL, Bush AI, Barnham KJ.

Biomolecular Research Institute, 343 Royal Parade, Parkville, Victoria 3052, Australia.

Amyloid beta peptide (Abeta) is the major constituent of extracellular plaques and perivascular amyloid deposits, the pathognomonic neuropathological lesions of Alzheimer's disease. Cu(2+) and Zn(2+) bind Abeta, inducing aggregation and giving rise to reactive oxygen species. These reactions may play a deleterious role in the disease state, because high concentrations of iron, copper, and zinc have been located in amyloid in diseased brains. Here we show that coordination of metal ions to Abeta is the same in both aqueous solution and lipid environments, with His(6), His(13), and His(14) all involved. At Cu(2+)/peptide molar ratios >0.3, Abeta coordinated a second Cu(2+) atom in a highly cooperative manner. This effect was abolished if the histidine residues were methylated at N(epsilon)2, indicating the presence of bridging histidine residues, as found in the active site of superoxide dismutase. Addition of Cu(2+) or Zn(2+) to Abeta in a negatively charged lipid environment caused a conformational change from beta-sheet to alpha-helix, accompanied by peptide oligomerization and membrane penetration. These results suggest that metal binding to Abeta generated an allosterically ordered membrane-penetrating oligomer linked by superoxide dismutase-like bridging histidine residues.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11274207&dopt=Abstract

J Neurochem 2001 Mar;76(5):1509-20

Homocysteine potentiates copper- and amyloid beta peptide-mediated toxicity in primary neuronal cultures: possible risk factors in the Alzheimer's-type neurodegenerative pathways.

White AR, Huang X, Jobling MF, Barrow CJ, Beyreuther K, Masters CL, Bush AI, Cappai R.

Department of Pathology, The University of Melbourne, Victoria, Australia. arwhite@unimelb.edu.au

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11238735&dopt=Abstract

Oxidative stress may have an important role in the progression of neurodegenerative disorders such as Alzheimer's disease (AD) and prion diseases. Oxidative damage could result from interactions between highly reactive transition metals such as copper (Cu) and endogenous reducing and/or oxidizing molecules in the brain. One such molecule, homocysteine, a thiol-containing amino acid, has previously been shown to modulate Cu toxicity in HeLa and endothelial cells in vitro. Due to a possible link between hyperhomocysteinemia and AD, we examined whether interaction between homocysteine and Cu could potentiate Cu neurotoxicity. Primary mouse neuronal cultures were treated with homocysteine and either Cu (II), Fe (II or III) or Zn (II). Homocysteine was shown to selectively potentiate toxicity from low micromolar concentrations of Cu. The toxicity of homocysteine/Cu coincubation was dependent on the ability of homocysteine to reduce Cu (II) as reflected by the inhibition of toxicity with the Cu (I)-specific chelator, bathocuproine disulphonate. This was supported by data showing that homocysteine reduced Cu (II) more effectively than cysteine or methionine but did not reduce Fe (III) to Fe (II). Homocysteine also generated high levels of hydrogen peroxide in the presence of Cu (II) and promoted Abeta/Cu-mediated hydrogen peroxide production and neurotoxicity. The potentiation of metal toxicity did not involve excitotoxicity as ionotropic glutamate receptor antagonists had no effect on neurotoxicity. Homocysteine alone also had no effect on neuronal glutathione levels. These studies suggest that increased copper and/or homocysteine levels in the elderly could promote significant oxidant damage to neurons and may represent additional risk factor pathways which conspire to produce AD or related neurodegenerative conditions.

Cuajungco MP, Faget KY, Huang X, Tanzi RE, Bush AI.

Laboratory for Oxidation Biology, Massachusetts General Hospital, and Department of Psychiatry, Harvard Medical School, Boston, Massachusetts 02115, USA.

Ann N Y Acad Sci 2000;920:292-304

Alzheimer's disease is a rapidly worsening public health problem. The current lack of effective treatments for Alzheimer's disease makes it imperative to find new pharmacotherapies. At present, the treatment of symptoms includes use of acetylcholinesterase inhibitors, which enhance acetylcholine levels and improve cognitive functioning. Current reports provide evidence that the pathogenesis of Alzheimer's disease is linked to the characteristic neocortical amyloid-beta deposition, which may be mediated by abnormal metal interaction with A beta as well as metal-mediated oxidative stress. In light of these observations, we have considered the development of drugs that target abnormal metal accumulation and its adverse consequences, as well as prevention or reversal of amyloid-beta plaque formation. This paper reviews recent observations on the possible etiologic role of A beta deposition, its redox activity, and its interaction with transition metals that are enriched in the neocortex. We discuss the effects of metal chelators on these processes, list existing drugs with chelating properties, and explore the promise of this approach as a basis for medicinal chemistry in the development of novel Alzheimer's disease therapeutics.

Redox-active iron mediates amyloid-beta toxicity.

Rottkamp CA, Raina AK, Zhu X, Gaier E, Bush AI, Atwood CS, Chevion M, Perry G, Smith MA.

Institute of Pathology, Case Western Reserve University, Cleveland, OH 44106, USA.

Free Radic Biol Med 2001 Feb 15;30(4):447-50

While amyloid-beta toxicity is mediated by oxidative stress and can be attenuated by antioxidants, the actual biochemical mechanism underlying neurotoxicity remains to be established. However, since aggregated amyloid-beta can interact with transition metals, such as iron, both in vitro and in vivo, we suspected that bound iron might be the mediator of toxicity such that holo- and apo-amyloid would have differential effects on cellular viability. Here we demonstrate that when amyloid-beta is pretreated with the iron chelator deferoxamine, neuronal toxicity is significantly attenuated while conversely, incubation of holo-amyloid-beta with excess free iron restores toxicity to original levels. These data, taken together with the known sequelae of amyloid-beta, suggest that the toxicity of amyloid-beta is mediated, at least in part, via redox-active iron that precipitates lipid peroxidation and cellular oxidative stress.

Oxidative processes in Alzheimer's disease: the role of abeta-metal interactions.

Lynch T, Cherny RA, Bush AI.

Department of Pathology, The University of Melbourne, and Neuropathology Laboratory, The Mental Health Research Institute of Victoria, Vic. 3052, Parkville, Australia.

Exp Gerontol 2000 Jul;35(4):445-51

Alzheimer's disease is characterized by signs of a major oxidative stress in the neocortex and the concomitant deposition of Amyloid beta (Abeta). Abeta is a metalloprotein that binds copper, and is electrochemically active. Abeta converts molecular oxygen into hydrogen peroxide by reducing copper or iron, and this may lead to Fenton chemistry. Hydrogen peroxide is a freely permeable prooxidant that may be responsible for many of the oxidative adducts that form in the Alzheimer-affected brain. The electrochemical activity of various Abeta species correlates with the peptides' neurotoxicity in cell culture, and participation in the neuropathology of Alzheimer's disease. These reactions present a novel target for Alzheimer therapeutics.

Publication Types:

• Review
• Review, tutorial

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10959032&dopt=Abstract

Chelation and intercalation: complementary properties in a compound for the treatment of Alzheimer's disease.

Cherny RA, Barnham KJ, Lynch T, Volitakis I, Li QX, McLean CA, Multhaup G, Beyreuther K, Tanzi RE, Masters CL, Bush AI.

The Department of Pathology, The University of Melbourne, Melbourne, Victoria, 3010, Australia.

J Struct Biol 2000 Jun;130(2-3):209-16

Selective application of metal chelators to homogenates of human Alzheimer's disease (AD) brain has led us to propose that the architecture of aggregated beta-amyloid peptide, whether in the form of plaques or soluble oligomers, is determined at least in part by high-affinity binding of transition metals, especially copper and zinc. Of the two metals, copper is implicated in reactive oxygen species generating reactions, while zinc appears to be associated with conformational and antioxidant activity. We tested the copper chelators trientine, penicillamine, and bathophenanthroline for their ability to mobilize brain Abeta as measured against our benchmark compound bathocuproine (BC). All of these agents were effective in solubilizing brain Abeta, although BC was the most consistent across the range of AD brain tissue samples tested. Similarly, all of the copper chelators depleted copper in the high-speed supernatants. BC alone had no significant effect upon zinc levels in the soluble fraction. BC extraction of brain tissue from C100 transgenic mice (which express human Abeta but do not develop amyloid) revealed SDS-resistant dimers as Abeta was mobilized from the sedimentable to the soluble fraction. NMR analysis showed that, in addition to its copper chelating properties, BC interacts with Abeta to form a complex independent of the presence of copper. Such hybrid copper chelating and "chain breaking" properties may form the basis of a rational design for a therapy for Alzheimer's disease. Copyright 2000 Academic Press.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10940226&dopt=Abstract

Characterization of copper interactions with alzheimer amyloid beta peptides: identification of an attomolar-affinity copper binding site on amyloid beta1-42.

Atwood CS, Scarpa RC, Huang X, Moir RD, Jones WD, Fairlie DP, Tanzi RE, Bush AI.

Laboratory for Oxidation Biology, Massachusetts General Hospital and Harvard Medical School, Boston 02129-9142, USA.

J Neurochem 2000 Sep;75(3):1219-33

Cu and Zn have been shown to accumulate in the brains of Alzheimer's disease patients. We have previously reported that Cu(2+) and Zn(2+) bind amyloid beta (Abeta), explaining their enrichment in plaque pathology. Here we detail the stoichiometries and binding affinities of multiple cooperative Cu(2+)-binding sites on synthetic Abeta1-40 and Abeta1-42. We have developed a ligand displacement technique (competitive metal capture analysis) that uses metal-chelator complexes to evaluate metal ion binding to Abeta, a notoriously self-aggregating peptide. This analysis indicated that there is a very-high-affinity Cu(2+)-binding site on Abeta1-42 (log K(app) = 17.2) that mediates peptide precipitation and that the tendency of this peptide to self-aggregate in aqueous solutions is due to the presence of trace Cu(2+) contamination (customarily approximately 0.1 microM). In contrast, Abeta1-40 has much lower affinity for Cu(2+) at this site (estimated log K(app) = 10.3), explaining why this peptide is less self-aggregating. The greater Cu(2+)-binding affinity of Abeta1-42 compared with Abeta1-40 is associated with significantly diminished negative cooperativity. The role of trace metal contamination in inducing Abeta precipitation was confirmed by the demonstration that Abeta peptide (10 &mgr;M) remained soluble for 5 days only in the presence of high-affinity Cu(2+)-selective chelators.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10936205&dopt=Abstract

Atwood CS, Huang X, Khatri A, Scarpa RC, Kim YS, Moir RD, Tanzi RE, Roher AE, Bush AI.

Massachusetts General Hospital East, Charlestown, MA 02129-9142, USA.

Cell Mol Biol (Noisy-le-grand) 2000 Jun;46(4):777-83

Abeta derived from amyloid plaques of Alzheimer's disease-affected brain contain several oxidative posttranslational modifications. In this study we have characterized the amino acid content of human amyloid-derived Abeta and compared it with that of human synthetic Abeta subjected to metal-catalyzed oxidation. Human amyloid derived Abeta has an increased content of arginine (46%) and glutamate/glutamine residues (28%), but a decreased content of histidine residues (-32%) as compared to the expected amino acid content. Incubation of synthetic human Abeta with Cu(II), but not Fe(III), in the presence of H2O2 similarly induced a decrease in histidine residues (-79%), but also a decrease in tyrosine residues (-28%). Our results suggest that histidine and tyrosine are most vulnerable to metal mediated oxidative attack, consistent with our earlier findings that Cu coordinated via histidine residues is redox competent. Our results suggest that the loss of histidine residues in human amyloid-derived Abeta may be a result of Cu oxidation, and that unidentified post-translational mechanisms operate to modify other amino acids of Abeta in vivo.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10875439&dopt=Abstract

Alzheimer's disease, beta-amyloid protein and zinc.

Huang X, Cuajungco MP, Atwood CS, Moir RD, Tanzi RE, Bush AI.

Laboratory for Oxidation Biology, Genetics and Aging Unit, Department of Psychiatry, Harvard Medical School, Massachusetts General Hospital, Charleston, MA 02129, USA.

J Nutr 2000 May;130(5S Suppl):1488S-92S

Alzheimer's disease (AD) is characterized by amyloid deposits within the neocortical parenchyma and the cerebrovasculature. The main component of these predominantly extracellular collections, Abeta, which is normally a soluble component of all biological fluids, is cleaved out of a ubiquitously expressed parent protein, the amyloid protein precursor (APP), one of the type 1 integral membrane glycoproteins. Considerable evidence has indicated that there is zinc dyshomeostasis and abnormal cellular zinc mobilization in AD. We have characterized both APP and Abeta as copper/zinc metalloproteins. Zinc, copper and iron have recently been reported to be concentrated to 0.5 to 1 mmol/L in amyloid plaque. In vitro, rapid Abeta aggregation is mediated by Zn(II), promoted by the alpha-helical structure of Abeta, and is reversible with chelation. In addition, Abeta produces hydrogen peroxide in a Cu(II)/Fe(III)-dependent manner, and the hydrogen peroxide formation is quenched by Zn(II). Moreover, zinc preserves the nontoxic properties of Abeta. Although the zinc-binding proteins apolipoprotein E epsilon4 allele and alpha(2)-macroglobulin have been characterized as two genetic risk factors for AD, zinc exposure as a risk factor for AD has not been rigorously studied. Based on our findings, we envisage that zinc may serve twin roles by both initiating amyloid deposition and then being involved in mechanisms attempting to quench oxidative stress and neurotoxicity derived from the amyloid mass. Hence, it remains debatable whether zinc supplementation is beneficial or deleterious for AD until additional studies clarify the issue.

Publication Types:

• Review
• Review, tutorial

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10801964&dopt=Abstract

Evidence that the beta-amyloid plaques of Alzheimer's disease represent the redox-silencing and entombment of abeta by zinc.

Cuajungco MP, Goldstein LE, Nunomura A, Smith MA, Lim JT, Atwood CS, Huang X, Farrag YW, Perry G, Bush AI.

Laboratory for Oxidation Biology, Genetics and Aging Unit, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA.

J Biol Chem 2000 Jun 30;275(26):19439-42

Abeta binds Zn(2+), Cu(2+), and Fe(3+) in vitro, and these metals are markedly elevated in the neocortex and especially enriched in amyloid plaque deposits of individuals with Alzheimer's disease (AD). Zn(2+) precipitates Abeta in vitro, and Cu(2+) interaction with Abeta promotes its neurotoxicity, correlating with metal reduction and the cell-free generation of H(2)O(2) (Abeta1-42 > Abeta1-40 > ratAbeta1-40). Because Zn(2+) is redox-inert, we studied the possibility that it may play an inhibitory role in H(2)O(2)-mediated Abeta toxicity. In competition to the cytotoxic potentiation caused by coincubation with Cu(2+), Zn(2+) rescued primary cortical and human embryonic kidney 293 cells that were exposed to Abeta1-42, correlating with the effect of Zn(2+) in suppressing Cu(2+)-dependent H(2)O(2) formation from Abeta1-42. Since plaques contain exceptionally high concentrations of Zn(2+), we examined the relationship between oxidation (8-OH guanosine) levels in AD-affected tissue and histological amyloid burden and found a significant negative correlation. These data suggest a protective role for Zn(2+) in AD, where plaques form as the result of a more robust Zn(2+) antioxidant response to the underlying oxidative attack.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10801774&dopt=Abstract

Cu(II) potentiation of alzheimer abeta neurotoxicity. Correlation with cell-free hydrogen peroxide production and metal reduction.

Huang X, Cuajungco MP, Atwood CS, Hartshorn MA, Tyndall JD, Hanson GR, Stokes KC, Leopold M, Multhaup G, Goldstein LE, Scarpa RC, Saunders AJ, Lim J, Moir RD, Glabe C, Bowden EF, Masters CL, Fairlie DP, Tanzi RE, Bush AI.

Laboratory for Oxidation Biology, Genetics and Aging Unit, and Department of Psychiatry, Harvard Medical School, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA.

 J Biol Chem 1999 Dec 24;274(52):37111-6

Oxidative stress markers as well as high concentrations of copper are found in the vicinity of Abeta amyloid deposits in Alzheimer's disease. The neurotoxicity of Abeta in cell culture has been linked to H(2)O(2) generation by an unknown mechanism. We now report that Cu(II) markedly potentiates the neurotoxicity exhibited by Abeta in cell culture. The potentiation of toxicity is greatest for Abeta1-42 > Abeta1-40 >> mouse/rat Abeta1-40, corresponding to their relative capacities to reduce Cu(II) to Cu(I), form H(2)O(2) in cell-free assays and to exhibit amyloid pathology. The copper complex of Abeta1-42 has a highly positive formal reduction potential ( approximately +500-550 mV versus Ag/AgCl) characteristic of strongly reducing cuproproteins. These findings suggest that certain redox active metal ions may be important in exacerbating and perhaps facilitating Abeta-mediated oxidative damage in Alzheimer's disease.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10601271&dopt=Abstract

The Alzheimer's disease amyloid precursor protein modulates copper-induced toxicity and oxidative stress in primary neuronal cultures.

White AR, Multhaup G, Maher F, Bellingham S, Camakaris J, Zheng H, Bush AI, Beyreuther K, Masters CL, Cappai R.

Department of Pathology, The University of Melbourne, Parkville, 3052 Victoria, Australia.

J Neurosci 1999 Nov 1;19(21):9170-9

The amyloid precursor protein (APP) of Alzheimer's disease can reduce copper (II) to copper (I) in a cell-free system potentially leading to increased oxidative stress in neurons. We used neuronal cultures derived from APP knock-out (APP(-/-)) and wild-type (WT) mice to examine the role of APP in copper neurotoxicity. WT cortical, cerebellar, and hippocampal neurons were significantly more susceptible than their respective APP(-/-) neurons to toxicity induced by physiological concentrations of copper but not by zinc or iron. There was no difference in copper toxicity between APLP2(-/-) and WT neurons, demonstrating specificity for APP-associated copper toxicity. Copper uptake was the same in WT and APP(-/-) neurons, suggesting APP may interact with copper to induce a localized increase in oxidative stress through copper (I) production. This was supported by significantly higher levels of copper-induced lipid peroxidation in WT neurons. Treatment of neuronal cultures with a peptide corresponding to the human APP copper-binding domain (APP142-166) potentiated copper but not iron or zinc toxicity. Incubation of APP142-166 with low-density lipoprotein (LDL) and copper resulted in significantly increased lipid peroxidation compared to copper and LDL alone. Substitution of the copper coordinating histidine residues with asparagines (APP142-166(H147N, H149N, H151N)) abrogated the toxic effects. A peptide corresponding to the zinc-binding domain (APP181-208) failed to induce copper or zinc toxicity in neuronal cultures. These data support a role for the APP copper-binding domain in APP-mediated copper (I) generation and toxicity in primary neurons, a process that has important implications for Alzheimer's disease and other neurodegenerative disorders.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10531420&dopt=Abstract

Copper levels are increased in the cerebral cortex and liver of APP and APLP2 knockout mice.

White AR, Reyes R, Mercer JF, Camakaris J, Zheng H, Bush AI, Multhaup G, Beyreuther K, Masters CL, Cappai R.

Department of Pathology, The University of Melbourne, Parkville, Victoria, 3052, Australia.

Brain Res 1999 Sep 25;842(2):439-44

The pathological process in Alzheimer's disease (AD) involves amyloid beta (Abeta) deposition and neuronal cell degeneration. The neurotoxic Abeta peptide is derived from the amyloid precursor protein (APP), a member of a larger gene family including the amyloid precursor-like proteins, APLP1 and APLP2. The APP and APLP2 molecules contain metal binding sites for copper and zinc. The zinc binding domain (ZnBD) is believed to have a structural rather than a catalytic role. The activity of the copper binding domain (CuBD) is unknown, however, APP reduces copper (II) to copper (I) and this activity could promote copper-mediated neurotoxicity. The expression of APP and APLP2 in the brain suggests they could have an important direct or indirect role in neuronal metal homeostasis. To examine this, we measured copper, zinc and iron levels in the cerebral cortex, cerebellum and selected non-neuronal tissues from APP (APP(-/-)) and APLP2 (APLP2(-/-)) knockout mice using atomic absorption spectrophotometry. Compared with matched wild-type (WT) mice, copper levels were significantly elevated in both APP(-/-) and APLP2(-/-) cerebral cortex (40% and 16%, respectively) and liver (80% and 36%, respectively). Copper levels were not significantly different between knockout and WT cerebellum, spleen or serum samples. There were no significant differences observed between APP(-/-), APLP2(-/-) and WT mice zinc or iron levels in any tissue examined. These findings indicate APP and APLP2 expression specifically modulates copper homeostasis in the liver and cerebral cortex, the latter being a region of the brain particularly involved in AD. Perturbations to APP metabolism and in particular, its secretion or release from neurons may alter copper homeostasis resulting in increased Abeta accumulation and free radical generation. These data support a novel mechanism in the APP/Abeta pathway which leads to AD.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10526140&dopt=Abstract

Aqueous dissolution of Alzheimer's disease Abeta amyloid deposits by biometal depletion.

Cherny RA, Legg JT, McLean CA, Fairlie DP, Huang X, Atwood CS, Beyreuther K, Tanzi RE, Masters CL, Bush AI.

Department of Pathology, The University of Melbourne, Parkville, Victoria 3052, Australia.

J Biol Chem 1999 Aug 13;274(33):23223-8

Zn(II) and Cu(II) precipitate Abeta in vitro into insoluble aggregates that are dissolved by metal chelators. We now report evidence that these biometals also mediate the deposition of Abeta amyloid in Alzheimer's disease, since the solubilization of Abeta from post-mortem brain tissue was significantly increased by the presence of chelators, EGTA, N,N,N',N'-tetrakis(2-pyridyl-methyl) ethylene diamine, and bathocuproine. Efficient extraction of Abeta also required Mg(II) and Ca(II). The chelators were more effective in extracting Abeta from Alzheimer's disease brain tissue than age-matched controls, suggesting that metal ions differentiate the chemical architecture of amyloid in Alzheimer's disease. Agents that specifically chelate copper and zinc ions but preserve Mg(II) and Ca(II) may be of therapeutic value in Alzheimer's disease.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10438495&dopt=Abstract

The A beta peptide of Alzheimer's disease directly produces hydrogen peroxide through metal ion reduction.

Huang X, Atwood CS, Hartshorn MA, Multhaup G, Goldstein LE, Scarpa RC, Cuajungco MP, Gray DN, Lim J, Moir RD, Tanzi RE, Bush AI.

Laboratory for Oxidation Biology, Genetics and Aging Unit, Massachusetts General Hospital, Charlestown 02129, USA.

Biochemistry 1999 Jun 15;38(24):7609-16

Oxidative stress markers characterize the neuropathology both of Alzheimer's disease and of amyloid-bearing transgenic mice. The neurotoxicity of amyloid A beta peptides has been linked to peroxide generation in cell cultures by an unknown mechanism. We now show that human A beta directly produces hydrogen peroxide (H2O2) by a mechanism that involves the reduction of metal ions, Fe(III) or Cu(II), setting up conditions for Fenton-type chemistry. Spectrophotometric experiments establish that the A beta peptide reduces Fe(III) and Cu(II) to Fe(II) and Cu(I), respectively. Spectrochemical techniques are used to show that molecular oxygen is then trapped by A beta and reduced to H2O2 in a reaction that is driven by substoichiometric amounts of Fe(II) or Cu(I). In the presence of Cu(II) or Fe(III), A beta produces a positive thiobarbituric-reactive substance (TBARS) assay, compatible with the generation of the hydroxyl radical (OH.). The amounts of both reduced metal and TBARS reactivity are greatest when generated by A beta 1-42 >> A beta 1-40 > rat A beta 1-40, a chemical relationship that correlates with the participation of the native peptides in amyloid pathology. These findings indicate that the accumulation of A beta could be a direct source of oxidative stress in Alzheimer's disease.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10386999&dopt=Abstract

Differential effects of apolipoprotein E isoforms on metal-induced aggregation of A beta using physiological concentrations.

Moir RD, Atwood CS, Romano DM, Laurans MH, Huang X, Bush AI, Smith JD, Tanzi RE.

Biochemistry 1999 Apr 6;38(14):4595-603

Genetics and Aging Unit, Department of Neurology, Massachusetts General Hospital, Charlestown, Massachusetts 02129-2060, USA.

The epsilon 4 allele of apolipoprotein E (APOE) has been found to be a risk factor for late-onset Alzheimer's disease (AD). While the pathogenic mechanism of APOE in AD is not yet clear, APOE isoforms appear to differentially influence the aggregation of A beta, the principal component of Alzheimer-associated beta-amyloid deposits. To date, no data are available for the propensity of A beta to aggregate in the presence of APOE under conditions where these components are at physiological concentrations (in cerebrospinal fluid, APOE and A beta are approximately 100 nM and approximately 5 nM, respectively). We employed a novel in vitro filtration assay for detecting zinc(II)- and copper(II)-induced aggregation of A beta in solutions containing concentrations of the peptide that are similar to those reported for human cerebrospinal fluid. The potential for resolubilization with EDTA and the relative densities of zinc- and copper-induced A beta aggregates were also compared. Zinc-induced A beta aggregates were found to be denser and less easily resolubilized than copper-induced precipitates. Metal-induced aggregation of A beta was studied in the presence of purified apolipoprotein E2, apolipoprotein E3, and apolipoprotein E4 under conditions that approximate the physiological concentrations and ratios of these proteins. In the presence of all three APOE isoforms, zinc-induced aggregation of A beta was attenuated, while precipitation with copper was enhanced. Consistent with the increased risk for AD associated with the epsilon 4 allele of APOE, metal-induced aggregation of A beta was highest for both zinc and copper in the presence of apolipoprotein E4. Our data are consistent with a role for APOE as an in vivo molecular chaperone for A beta.

Atwood CS, Huang X, Moir RD, Tanzi RE, Bush AI.

Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston 02114, USA.

Met Ions Biol Syst 1999;36:309-64

Publication Types:

• Review
• Review, academic