Molecular shuttle chelation: the use of ascorbate, desferrioxamine and Feralex-G in combination to remove nuclear bound aluminum

Additive aluminum as a cause of induced immunoexcitoxicity resulting in neurodevelopmental and neurodegenerative disorders: A biochemical, pathophysiological, and pharmacological analysis

Much has been learned about the neurotoxicity of aluminum over the past several decades in terms of its ability to disrupt cellular function, result in slow accumulation, and the difficulty of its removal from cells. Newer evidence suggests a central pathophysiological mechanism may be responsible for much of the toxicity of aluminum and aluminofluoride compounds on the brain and spinal cord. This mechanism involves activation of the brain's innate immune system, primarily the microglia, astrocytes, and macrophages, with a release of neurotoxic concentrations of excitotoxins and proinflammatory cytokines, chemokines, and immune mediators. Many studies suggest that excitotoxicity plays a significant role in the neurotoxic action of several metals, including aluminum. Recently, researchers have found that while most of the chronic pathology involved in the observed neurodegenerative effects of these metals are secondary to prolonged inflammation, it is the enhancement of excitotoxicity by the immune mediators that are responsible for most of the metal's toxicity. This enhancement occurs through a crosstalk between cytokines and glutamate-related mechanisms. The author coined the name immunoexcitotoxicity to describe this process. This paper reviews the evidence linking immunoexcitotoxicity to aluminum's neurotoxic effects and that a slow accumulation of aluminum may be the cause of neurodevelopmental defects as well as neurodegeneration in the adult.

Alteration of Biomolecular Conformation by Aluminum-Implications for Protein Misfolding Disease

The natural element aluminum possesses a number of unique biochemical and biophysical properties that make this highly neurotoxic species deleterious towards the structural integrity, conformation, reactivity and stability of several important biomolecules. These include aluminum's (i) small ionic size and highly electrophilic nature, having the highest charge density of any metallic cation with a Z2/r of 18 (ionic charge +3, radius 0.5 nm); (ii) inclination to form extremely stable electrostatic bonds with a tendency towards covalency; (iii) ability to interact irreversibly and/or significantly slow down the exchange-rates of complex aluminum-biomolecular interactions; (iv) extremely dense electropositive charge with one of the highest known affinities for oxygen-donor ligands such as phosphate; (v) presence as the most abundant metal in the Earth's biosphere and general bioavailability in drinking water, food, medicines, consumer products, groundwater and atmospheric dust; and (vi) abundance as one of the most commonly encountered intracellular and extracellular metallotoxins. Despite aluminum's prevalence and abundance in the biosphere it is remarkably well-tolerated by all plant and animal species; no organism is known to utilize aluminum metabolically; however, a biological role for aluminum has been assigned in the compaction of chromatin. In this Communication, several examples are given where aluminum has been shown to irreversibly perturb and/or stabilize the natural conformation of biomolecules known to be important in energy metabolism, gene expression, cellular homeostasis and pathological signaling in neurological disease. Several neurodegenerative disorders that include the tauopathies, Alzheimer's disease and multiple prion disorders involve the altered conformation of naturally occurring cellular proteins. Based on the data currently available we speculate that one way aluminum contributes to neurological disease is to induce the misfolding of naturally occurring proteins into altered pathological configurations that contribute to the neurodegenerative disease process.

Neurotoxic effects of aluminium exposure as a potential risk factor for Alzheimer's disease

Aluminium is one of the most widely distributed elements of the Earth's crust. Its routine use has resulted in excessive human exposure and due to the potential neurotoxic effects has attained a huge interest in recent years. Despite its ubiquitous abundance, aluminium has no crucial biological functions in the human body. Oxidative stress and neuroinflammatory effects are attributed to its neurotoxic manifestations implicated in Alzheimer's disease. In this review, we have discussed the neuroinflammatory and neurodegenerative events in the brain induced by aluminium exposure. We have highlighted the neurotoxic events caused by aluminium, such as oxidative stress, apoptosis, inflammatory events, calcium dyshomeostasis, Aβ deposition, and neurofibrillary tangle formation in the brain. In addition, the protective measures needed for prevention of aluminium-induced neuronal dysregulations have also been discussed.

Aluminum Poisoning with Emphasis on Its Mechanism and Treatment of Intoxication

Aluminum poisoning has been reported in some parts of the world. It is one of the global health problems that affect many organs. Aluminum is widely used daily by humans and industries. Residues of aluminum compounds can be found in drinking water, food, air, medicine, deodorants, cosmetics, packaging, many appliances and equipment, buildings, transportation industries, and aerospace engineering. Exposure to high levels of aluminum compounds leads to aluminum poisoning. Aluminum poisoning has complex and multidimensional effects, such as disruption or inhibition of enzymes activities, changing protein synthesis, nucleic acid function, and cell membrane permeability, preventing DNA repair, altering the stability of DNA organization, inhibition of the protein phosphatase 2A (PP2A) activity, increasing reactive oxygen species (ROS) production, inducing oxidative stress, decreasing activity of antioxidant enzymes, altering cellular iron homeostasis, and changing NF-kB, p53, and JNK pathway leading to apoptosis. Aluminum poisoning can affect blood content, musculoskeletal system, kidney, liver, and respiratory and nervous system, and the extent of poisoning can be diagnosed by assaying aluminum compounds in blood, urine, hair, nails, and sweat. Chelator agents such as deferoxamine (DFO) are used in the case of aluminum poisoning. Besides, combination therapies are recommended.

Interaction of esculetin with aluminium ion by spectroscopic studies and isothermal titration calorimetry: a probable molecule for chelation therapy

The use of aluminium has made significant impact in our life by virtue of its attractive properties. The lack of essentiality of aluminium in biosphere indicated that its accumulation above certain level is undesirous. Esculetin (6,7-dihydroxy coumarin) is an excellent aluminium ion chelator and the chelation interaction was studied by exploiting the absorption and fluorescence behavior of esculetin. In presence of aluminium ion, the absorption band of esculetin was shifted from 350 to 380 nm suggesting the possibility of complex formation. The fluorescence intensity of esculetin at 466 nm was significantly quenched in presence of aluminium ion. The fluorescence quenching was interpreted in terms of chelation-quenched fluorescence (CHQF) mechanism where the strong Lewis acid character of aluminium ion accepts electrons from the chelating catechol moiety of the excited esculetin. From the absorption and fluorescence changes the association constant was estimated in the order of 10⁵ M^-1. The association constant was further evaluated by isothermal titration calorimetry (ITC) and there was close agreement to that of obtained from spectroscopic studies. Form ITC studies, the binding enthalpy and binding entropy were estimated as -20.6 kcal/mol and -46.7 cal/mol/K respectively. The complex was less toxic compared to the individual complexing agents when studied in Chinese hamster ovary cells. Considering the present investigation, esculetin can be a probable molecule for chelation therapy where rapid complex formation ability of esculetin will help to reduce the aluminium accumulation through chelation and water soluble nature of the complex will help for faster elimination from the system.Communicated by Ramaswamy H. Sarma.

The interaction of aluminum with catecholamine-based neurotransmitters: can the formation of these species be considered a potential risk factor for neurodegenerative diseases?

The potential neurotoxic role of Al(iii) and its proposed link with the insurgence of Alzheimer's Disease (AD) have attracted increasing interest towards the determination of the nature of bioligands that are propitious to interact with aluminum. Among them, catecholamine-based neurotransmitters have been proposed to be sensitive to the presence of this non-essential metal ion in the brain. In the present work, we characterize several aluminum-catecholamine complexes in various stoichiometries, determining their structure and thermodynamics of formation. For this purpose, we apply a recently validated computational protocol with results that show a remarkably good agreement with the available experimental data. In particular, we employ Density Functional Theory (DFT) in conjunction with continuum solvation models to calculate complexation energies of aluminum for a set of four important catecholamines: l-DOPA, dopamine, noradrenaline and adrenaline. In addition, by means of the Quantum Theory of Atoms in Molecules (QTAIM) and Energy Decomposition Analysis (EDA) we assessed the nature of the Al-ligand interactions, finding mainly ionic bonds with an important degree of covalent character. Our results point at the possibility of the formation of aluminum-catecholamine complexes with favorable formation energies, even when proton/aluminum competition is taken into account. Indeed, we found that these catecholamines are better aluminum binders than catechol at physiological pH, because of the electron withdrawing effect of the positively-charged amine that decreases their deprotonation penalty with respect to catechol. However, overall, our results show that, in an open biological environment, the formation of Al-catecholamine complexes is not thermodynamically competitive when compared with the formation of other aluminum species in solution such as Al-hydroxide, or when considering other endogenous/exogenous Al(iii) ligands such as citrate, deferiprone and EDTA. In summary, we rule out the possibility, suggested by some authors, that the formation of Al-catecholamine complexes in solution might be behind some of the toxic roles attributed to aluminum in the brain. An up-to-date view of the catecholamine biosynthesis pathway with sites of aluminum interference (according to the current literature) is presented. Alternative mechanisms that might explain the deleterious effects of this metal on the catecholamine route are thoroughly discussed, and new hypotheses that should be investigated in future are proposed.

Aluminum in Neurological and Neurodegenerative Disease

With continuing cooperation from 18 domestic and international brain banks over the last 36 years, we have analyzed the aluminum content of the temporal lobe neocortex of 511 high-quality human female brain samples from 16 diverse neurological and neurodegenerative disorders, including 2 groups of age-matched controls. Temporal lobes (Brodmann areas A20-A22) were selected for analysis because of their availability and their central role in massive information-processing operations including efferent-signal integration, cognition, and memory formation. We used the analytical technique of (i) Zeeman-type electrothermal atomic absorption spectrophotometry (ETAAS) combined with (ii) preliminary analysis from the advanced photon source (APS) hard X-ray beam (7 GeV) fluorescence raster-scanning (XRFR) spectroscopy device (undulator beam line 2-ID-E) at the Argonne National Laboratory, US Department of Energy, University of Chicago IL, USA. Neurological diseases examined were Alzheimer's disease (AD; N = 186), ataxia Friedreich's type (AFT; N = 6), amyotrophic lateral sclerosis (ALS; N = 16), autism spectrum disorder (ASD; N = 26), dialysis dementia syndrome (DDS; N = 27), Down's syndrome (DS; trisomy, 21; N = 24), Huntington's chorea (HC; N = 15), multiple infarct dementia (MID; N = 19), multiple sclerosis (MS; N = 23), Parkinson's disease (PD; N = 27), and prion disease (PrD; N = 11) that included bovine spongiform encephalopathy (BSE; "mad cow disease"), Creutzfeldt-Jakob disease (CJD) and Gerstmann-Straussler-Sheinker syndrome (GSS), progressive multifocal leukoencephalopathy (PML; N = 11), progressive supranuclear palsy (PSP; N = 24), schizophrenia (SCZ; N = 21), a young control group (YCG; N = 22; mean age, 10.2 ± 6.1 year), and an aged control group (ACG; N = 53; mean age, 71.4 ± 9.3 year). Using ETAAS, all measurements were performed in triplicate on each tissue sample. Among these 17 common neurological conditions, we found a statistically significant trend for aluminum to be increased only in AD, DS, and DDS compared to age- and gender-matched brains from the same anatomical region. This is the largest study of aluminum concentration in the brains of human neurological and neurodegenerative disease ever undertaken. The results continue to suggest that aluminum's association with AD, DDS, and DS brain tissues may contribute to the neuropathology of those neurological diseases but appear not to be a significant factor in other common disorders of the human brain and/or CNS.

Aluminum in neurological disease - a 36 year multicenter study

Aluminum is a ubiquitous neurotoxin highly enriched in our biosphere, and has been implicated in the etiology and pathology of multiple neurological diseases that involve inflammatory neural degeneration, behavioral impairment and cognitive decline. Over the last 36 years our group has analyzed the aluminum content of the temporal lobe neocortex of 511 high quality coded human brain samples from 18 diverse neurological and neurodegenerative disorders, including 2 groups of age-matched controls. Brodmann anatomical areas including the inferior, medial and superior temporal gyrus (A20-A22) were selected for analysis: (i) because of their essential functions in massive neural information processing operations including cognition and memory formation; and (ii) because subareas of these anatomical regions are unique to humans and are amongst the earliest areas affected by progressive neurodegenerative disorders such as Alzheimer's disease (AD). Coded brain tissue samples were analyzed using the analytical technique of: (i) Zeeman-type electrothermal atomic absorption spectrophotometry (ETAAS) combined with (ii) an experimental multi-elemental analysis using the advanced photon source (APS) ultra-bright storage ring-generated hard X-ray beam (7 GeV) and fluorescence raster scanning (XRFR) spectroscopy device at the Argonne National Laboratory, US Department of Energy, University of Chicago IL, USA. These data represent the largest study of aluminum concentration in the brains of human neurological and neurodegenerative disease ever undertaken. Neurological diseases examined were AD (N=186), ataxia Friedreich's type (AFT; N=6), amyotrophic lateral sclerosis (ALS; N=16), autism spectrum disorder (ASD; N=26), dialysis dementia syndrome (DDS; N=27), Down's syndrome (DS; trisomy21; N=24), Huntington's chorea (HC; N=15), multiple infarct dementia (MID; N=19), multiple sclerosis (MS; N=23), Parkinson's disease (PD; N=27), prion disease (PrD; N=11) including bovine spongiform encephalopathy (BSE; 'mad cow disease'), Creutzfeldt-Jakob disease (CJD) and Gerstmann-Straussler-Sheinker syndrome (GSS), progressive multifocal leukoencephalopathy (PML; N=11), progressive supranuclear palsy (PSP; N=24), schizophrenia (SCZ; N=21), a young control group (YCG; N=22) and an aged control group (ACG; N=53). Amongst these 18 common neurological conditions and controls we report a statistically significant trend for aluminum to be increased only in AD, DS and DDS compared to age- and gender-matched brains from the same anatomical region. The results continue to suggest that aluminum's association with AD, DDS and DS brain tissues may contribute to the neuropathology of these neurological diseases but appear not to be a significant factor in other common disorders of the human central nervous system (CNS).

3-Hydroxypyridinone derivatives as metal-sequestering agents for therapeutic use

Although iron is one of the most important metal ions for living organisms, it becomes toxic when in excess or misplaced. This review presents a glance at representative examples of hydroxypyridinone-based chelators, which have been recently developed as potential clinically useful drugs for metal overload diseases, mostly associated with excess of iron but also other hard metal-ions. It also includes a detailed discussion on the factors assisting chelator design strategy toward fulfillment of the most relevant biochemical properties of hydroxypyridinone chelators, highlighting structure-activity relationships and a variety of potential clinical applications, beyond chelatotherapy. This study appears as a response to the growing interest on metal chelation therapy and opens new perspectives of possible applications in future medicine.

Beta-Amyloid Precursor Protein (βAPP) Processing in Alzheimer's Disease (AD) and Age-Related Macular Degeneration (AMD)

Amyloid is a generic term for insoluble, often intensely hydrophobic, fibrous protein aggregates that arise from inappropriately folded versions of naturally-occurring polypeptides. The abnormal generation and accumulation of amyloid, often referred to as amyloidogenesis, has been associated with the immune and pro-inflammatory pathology of several progressive age-related diseases of the human central nervous system (CNS) including Alzheimer's disease (AD) and age-related macular degeneration (AMD). This 'research perspective' paper reviews some of the research history, biophysics, molecular-genetics and environmental factors concerning the contribution of amyloid beta (Aβ) peptides, derived from beta-amyloid precursor protein (βAPP), to AD and AMD that suggests an extensive similarity in immune and inflammatory degenerative mechanisms between these two CNS diseases.

Searching for new aluminium chelating agents: a family of hydroxypyrone ligands

Attention is devoted to the role of chelating agents in the treatment of aluminium related diseases. In fact, in spite of the efforts that have drastically reduced the occurrence of aluminium dialysis diseases, they so far constitute a cause of great medical concern. The use of chelating agents for iron and aluminium in different clinical applications has found increasing attention in the last thirty years. With the aim of designing new chelators, we synthesized a series of kojic acid derivatives containing two kojic units joined by different linkers. A huge advantage of these molecules is that they are cheap and easy to produce. Previous works on complex formation equilibria of a first group of these ligands with iron and aluminium highlighted extremely good pMe values and gave evidence of the ability to scavenge iron from inside cells. On these bases a second set of bis-kojic ligands, whose linkers between the kojic chelating moieties are differentiated both in terms of type and size, has been designed, synthesized and characterized. The aluminium(III) complex formation equilibria studied by potentiometry, electrospray ionization mass spectroscopy (ESI-MS), quantum-mechanical calculations and (1)H NMR spectroscopy are here described and discussed, and the structural characterization of one of these new ligands is presented. The in vivo studies show that these new bis-kojic derivatives induce faster clearance from main organs as compared with the monomeric analog.

A new approach to studying ion uptake by actinomycetes

A streptomycete that had the ability to avidly sequester iron via siderophores was previously isolated from environmental soil samples. The chelating agent expressed by this organism is confirmed by HPLC as desferrioxamine E. Although the traditional chromo azuerol sulphate (CAS) assay for detection of siderophores is based upon the chelation of iron we were interested to examine the relationship of these iron-capturing molecules with other ions. Consequently, a new approach was employed that enabled the assessment of the affinity of the siderophore moieties for other ions by adapting the CAS assay. The present study reveals that the isolate produced a siderophore that was capable of sequestering a range of ions including Mn, Co, Cd, Ni, Al, Li, Cu, Zn and Mg. On the basis of the assay described it would appear that the organism sequesters copper more readily than iron. This raises an age-old debate surrounding the replacement of copper as a fundamentally essential element with iron as a consequence of the evolution of the di-oxygen environment.

Iron: effect of overload and deficiency

Iron is a redox active metal which is abundant in the Earth's crust. It has played a key role in the evolution of living systems and as such is an essential element in a wide range of biological phenomena, being critical for the function of an enormous array of enzymes, energy transduction mechanisms, and oxygen carriers. The redox nature of iron renders the metal toxic in excess and consequently all biological organisms carefully control iron levels. In this overview the mechanisms adopted by man to control body iron levels are described.Low body iron levels are related to anemia which can be treated by various forms of iron fortification and supplementation. Elevated iron levels can occur systemically or locally, each giving rise to specific symptoms. Systemic iron overload results from either the hyperabsorption of iron or regular blood transfusion and can be treated by the use of a selection of iron chelating molecules. The symptoms of many forms of neurodegeneration are associated with elevated levels of iron in certain regions of the brain and iron chelation therapy is beginning to find an application in the treatment of such diseases. Iron chelators have also been widely investigated for the treatment of cancer, tuberculosis, and malaria. In these latter studies, selective removal of iron from key enzymes or iron binding proteins is sought. Sufficient selectivity between the invading organism and the host has yet to be established for such chelators to find application in the clinic.Iron chelation for systemic iron overload and iron supplementation therapy for the treatment of various forms of anemia are now established procedures in clinical medicine. Chelation therapy may find an important role in the treatment of various neurodegenerative diseases in the near future.

NF-κB-regulated, proinflammatory miRNAs in Alzheimer's disease

Abundant neurochemical, neuropathological, and genetic evidence suggests that a critical number of proinflammatory and innate immune system-associated factors are involved in the underlying pathological pathways that drive the sporadic Alzheimer's disease (AD) process. Most recently, a series of epigenetic factors - including a select family of inducible, proinflammatory, NF-κB-regulated small noncoding RNAs called miRNAs - have been shown to be significantly elevated in abundance in AD brain. These upregulated miRNAs appear to be instrumental in reshaping the human brain transcriptome. This reorganization of mRNA speciation and complexity in turn drives proinflammatory and pathogenic gene expression programs. The ensuing, progressively altered immune and inflammatory signaling patterns in AD brain support immunopathogenetic events and proinflammatory features of the AD phenotype. This report will briefly review what is known concerning NF-κB-inducible miRNAs that are significantly upregulated in AD-targeted anatomical regions of degenerating human brain cells and tissues. Quenching of NF-κB-sensitive inflammatory miRNA signaling using NF-κB-inhibitors such as the polyphenolic resveratrol analog trans-3,5,4'-trihydroxystilbene (CAY10512) may have some therapeutic value in reducing inflammatory neurodegeneration. Antagonism of NF-κB-inducing, and hence proinflammatory, epigenetic and environmental factors, such as the neurotrophic herpes simplex virus-1 and exposure to the potent neurotoxin aluminum, are briefly discussed. Early reports further indicate that miRNA neutralization employing anti-miRNA (antagomir) strategies may hold future promise in the clinical management of this insidious neurological disorder and expanding healthcare concern.

Metal-sulfate induced generation of ROS in human brain cells: detection using an isomeric mixture of 5- and 6-carboxy-2',7'-dichlorofluorescein diacetate (carboxy-DCFDA) as a cell permeant tracer

Evolution of reactive oxygen species (ROS), generated during the patho-physiological stress of nervous tissue, has been implicated in the etiology of several progressive human neurological disorders including Alzheimer’s disease (AD) and amylotrophic lateral sclerosis (ALS). In this brief communication we used mixed isomers of 5-(and-6)-carboxy-2′,7′-dichlorofluorescein diacetate (carboxy-DCFDA; C₂₅H₁₄C_l2O₉; MW 529.3), a novel fluorescent indicator, to assess ROS generation within human neuronal-glial (HNG) cells in primary co-culture. We introduced pathological stress using the sulfates of 12 environmentally-, industrially- and agriculturally-relevant divalent and trivalent metals including Al, Cd, Cu, Fe, Hg, Ga, Mg, Mn, Ni, Pb, Sn and Zn. In this experimental test system, of all the metal sulfates analyzed, aluminum sulfate showed by far the greatest ability to induce intracellular ROS. These studies indicate the utility of using isomeric mixtures of carboxy-H₂DCFDA diacetates as novel and highly sensitive, long-lasting, cell-permeant, fluorescein-based tracers for quantifying ROS generation in intact, metabolizing human brain cells, and in analyzing the potential epigenetic contribution of different metal sulfates to ROS-generation and ROS-mediated neurological dysfunction.

Amyloid beta (Aβ) peptide modulators and other current treatment strategies for Alzheimer's disease (AD)

Introduction: Alzheimer's disease (AD) is a common, progressive neurological disorder whose incidence is reaching epidemic proportions. The prevailing "amyloid cascade hypothesis," which maintains that the aberrant proteolysis of beta-amyloid precursor protein (βAPP) into neurotoxic amyloid beta (Aβ) peptides is central to the etiopathology of AD, continues to dominate pharmacological approaches to the clinical management of this insidious disorder. This review is a compilation and update on current pharmacological strategies designed to down-regulate Aβ42 peptide generation in an effort to ameliorate the tragedy of AD. Areas covered: This review utilized online data searches at various open online-access websites including the Alzheimer Association, Alzheimer Research Forum; individual drug company databases; the National Institutes of Health (NIH) Medline; Pharmaprojects database; Scopus; inter-University research communications; and unpublished research data. Expert opinion: Anti-acetylcholinesterase-, chelation-, N-methyl-D-aspartate (NMDA) receptor antagonist-, statin-, Aβ immunization-, β-secretase-, γ-secretase-based, and other strategies to modulate βAPP processing, have dominated pharmacological approaches directed against AD-type neurodegenerative pathology. Cumulative clinical results of these efforts remain extremely disappointing, and have had little overall impact on the clinical management of AD. While a number of novel approaches are in consideration and development, to date there is still no effective treatment or cure for this expanding healthcare concern.

Towards the prevention of potential aluminum toxic effects and an effective treatment for Alzheimer's disease

In 1991, treatment with low dose intramuscular desferrioxamine (DFO), a trivalent chelator that can remove excessive iron and/or aluminum from the body, was reported to slow the progression of Alzheimer's disease (AD) by a factor of two. Twenty years later this promising trial has not been followed up and why this treatment worked still is not clear. In this critical interdisciplinary review, we provide an overview of the complexities of AD and involvement of metal ions, and revisit the neglected DFO trial. We discuss research done by us and others that is helping to explain involvement of metal ion catalyzed production of reactive oxygen species in the pathogenesis of AD, and emerging strategies for inhibition of metal-ion toxicity. Highlighted are insights to be considered in the quests to prevent potentially toxic effects of aluminum toxicity and prevention and intervention in AD.

Selective acetylcholinesterase inhibitor activated by acetylcholinesterase releases an active chelator with neurorescuing and anti-amyloid activities

The finding that acetylcholinesterase (AChE) colocalizes with β-amyloid (Aβ) and promotes and accelerates Aβ aggregation has renewed an intense interest in developing new multifunctional AChE inhibitors as potential disease-modifying drugs for Alzheimer's therapy. To this end, we have developed a new class of selective AChE inhibitors with site-activated chelating activity. The identified lead, HLA20A, exhibits little affinity for metal (Fe, Cu, and Zn) ions but can be activated following inhibition of AChE to liberate an active chelator, HLA20. HLA20 has been shown to possess neuroprotective and neurorescuing activities in vitro and in vivo with the ability to lower amyloid precursor holoprotein (APP) expression and Aβ generation and inhibit Aβ aggregation induced by metal (Fe, Cu, and Zn) ion. HLA20A inhibited AChE in a time and concentration dependent manner with an HLA20A-AChE complex constant (K(i)) of 9.66 × 10(-6) M, a carbamylation rate (k(+2)) of 0.14 min(-1), and a second-order rate (k(i)) of 1.45 × 10 (4) M(-1) min(-1), comparable to those of rivastigmine. HLA20A showed little iron-binding capacity and activity against iron-induced lipid peroxidation (LPO) at concentrations of 1-50 μM, while HLA20 exhibited high potency in iron-binding and in inhibiting iron-induced LPO. At a concentration of 10 μM, HLA20A showed some activity against monoamine oxidase (MAO)-A and -B when tested in rat brain homogenates. Defined restrictively by Lipinski's rules, both HLA20A and HLA20 satisfied drug-like criteria and possible oral and brain permeability, but HLA20A was more lipophilic and considerably less toxic in human SHSY5Y neuroblastoma cells at high concentrations (25 or 50 μM). Together our data suggest that HLA20A may represent a promising lead for further development for Alzheimer's disease therapy.

Emerging amyloid beta (Ab) peptide modulators for the treatment of Alzheimer's disease (AD)

BACKGROUND

According to the 'amyloid cascade hypothesis' of Alzheimer's disease (AD), abnormal processing of beta-amyloid precursor protein (betaAPP) into toxic amyloid beta (Abeta)-peptides is central to the etiopathology of this uniquely human brain disorder.

OBJECTIVE

To review current AD drugs, pharmacological approaches and strategies aimed at modulating Abeta-peptide generation and/or aggregation in the treatment of AD.

METHODS

Data searches at various websites: Alzheimer Research Forum; individual drug company databases; Medline; Pharmaprojects database; unpublished research; inter-University research communications.

RESULTS/CONCLUSION

Considerable research effort has focused on secretase-mediated mechanisms of betaAPP processing, and the latest pharmacological strategies have used selective Abeta-peptide-lowering agents (SALA) to provide therapeutic benefit against Abeta-initiated neurodegenerative pathology. Currently, dedicated anticholinesterase, glutamatergic agonist and Abeta-peptide immunization have had little impact in the clinical treatment of AD. One unexpected benefit of statins (HMG-CoA inhibitors), besides their cholesterol lowering abilities, has been their ancillary effects in potentiating the enzymatic mechanisms that generate Abeta-peptides. The long-term benefits or complications of statin-based therapies for use in the clinical management of AD are not known.

Engineering aluminum binding affinity in an isolated EF-hand from troponin C: A computational site-directed mutagenesis study

Peptides with the ability to specifically bind aluminum would potentially be of great use in the fields of biochemistry and environmental chemistry. Unfortunately no such peptides are known. An aluminum-specific peptide may be used as an in vivo chelator, for metalloprotein design, for understanding metal-ion induced folding and metal-ion trafficking, and as an environmental sensor to monitor metal pollution in the environment. Plants genetically engineered to produce an aluminum binding peptide might be useful in environmental remediation in areas of high free aluminum ion concentration. In this paper, which is the theoretical complement to the experimental work, we analyzed crystallographic structures of EF-hands bound to various metals in order to determine the ligand distances and identities to compare to metal-ion size, charge, electronegativity, and coordination number and performed energy minimization calculations to identify possible mutations. We then constructed various mutant sequences in silico in an isolated EF-hand from troponin C and analyzed their binding behavior using molecular mechanics for binding to Tb(3+) as compared to Al(3+). As a result of these analyses we were able to isolate some characteristics that could lead to mutant peptides with enhanced aluminum activity that we plan to test experimentally in the future. We also performed metal-ion binding studies with the isolated EF-hand used in the computational work to examine the ability of Al(3+) and comparative metals to bind the peptide. In competition studies, the peptide demonstrated preference for Tb(3+) over Al(3+).

Specific sensing of poly G by the aluminum-salophen complex

The Al(III)-salophen complex 1 exhibited strong spectroscopic changes specifically upon addition of polyG and GpG, while double stranded DNA and RNA, and single stranded polyA, polyU and polyC induced negligible spectral changes of 1. Titrations with mono-nucleotides yielded no spectroscopic changes, revealing that there must be at least two consecutive guanines in single stranded oligonucleotide structure for a measurable spectroscopic change of 1. Preliminary results show that 1 has moderate antiproliferative effect on a number of human tumour cell lines.

Therapeutic potential of iron chelators in diseases associated with iron mismanagement

A considerable array of diseases are now recognized to be associated with misplacement of iron. Excessive deposits of the metal in sensitive tissue sites can result in formation of destructive hydroxyl radicals as well as in stimulation of growth of neoplastic and microbial cell invaders. To counteract potential iron damage, hosts employ the iron chelators, transferrin and lactoferrin. These proteins have been recently developed into pharmaceutical products. Additionally, a variety of low molecular mass iron chelators are being used/tested to treat whole body iron loading, and specific diseases for which the metal is a known or suspected risk factor.