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Retinitis pigmentosa (RP) is a group of inherited diseases in which mutations result in the initial loss of night vision, followed by complete blindness. There is currently no effective therapeutic option for RP patients. Given the extremely heterogeneous nature of RP, any causative gene-specific therapy would be practical in a small fraction of patients with RP. Non-gene-specific therapeutics that is applicable to the majority of RP patients regardless of causative mutations may have an enormous impact on RP treatment. Several theories including apoptosis, oxidative stress and neuroinflammation have been proposed as possible underlying mechanisms for photoreceptor death in RP. We have designed and synthesized a series of iron-chelating compounds that possess diverse pharmacological properties and can act in a non-gene-specific manner on multiple pathological features ascribed to Alzheimer's disease, Parkinson's disease and RP. In this review, we discuss the multiple effects of several brain-permeable multi target iron-chelating compounds on photoreceptor degeneration in a mouse model of human RP. Specifically, we focus on the anti-apototic, neuroprotective and neurorescue effects of the compound VK28, M30 and VAR10303 on the histologic and functional preservation of photoreceptors in a mouse model of RP. We consider such drugs as potential therapeutic agents for RP patients., (Copyright © 2021 Elsevier Inc. All rights reserved.)

The cascade of neurotoxic events involved in neuronal degeneration suggests that it is naive to think mono-target drugs can induce disease modification by slowing the process of neurodegeneration in Parkinson's disease (PD). Employing the pharmacophore of rasagiline (N-propargyl-1-R-aminoindan), we have developed a series of novel multi-target neuroprotective drugs, including: (A) drugs [ladostigil, TV-3326 (N-propargyl-3R-aminoindan-5yl)-ethyl methylcarbamate)] with both cholinesterase-butyrylesterase (Ch-BuE) and brain-selective monamine oxidase-AB (MAO-AB) inhibitory activities and (B) iron chelator-radical scavenging drugs (M30) possessing brain-selective MAO-AB inhibitor activity and the neuroprotective-neurorescue propargylamine moiety of rasagiline. This was considered to be valid since brain MAO and iron increase in PD and aging, which could lead to oxidative stress-dependent neurodegeneration. The multi-target iron chelator, M30, has all the properties of ladostigil, but is not an acetylcholinesterase (CHE) inhibitor. However, M30 has both neuroprotective and neurorestorative activities for nigrostriatal dopamine neurons in post-lesion MPTP, lactacystin and 6-hydroxydopamine animal models of PD. The neurorestorative activity has been identified as being related to the ability of the drug to activate hypoxia-inducible factor (HIF) by inhibiting prolyl-4-hydroxylase. M30 regulates cell cycle arrest and induces the neurotrophins brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF), erythropoietin (EPO), as well as glia-derived neurotrophic factor (GDNF). These unique multiple actions of M30 make it potentially useful as a disease modifying drug for the treatment of PD., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Autophagy is an evolutionarily conserved process that mediates the degradation of abnormal proteins and the removal of dysfunctional organelles. Recently, accumulating evidence has implicated the dysregulation of autophagy as underlying the pathophysiology of several neurodegenerative diseases. Using culture models of Parkinson's disease, we have investigated whether and how prototypic autophagic events occur upon exposure to N-methyl-4-phenylpyridinium, a dopaminergic neurotoxin, or nigericin, a K(+)/H(+) ionophore. From these independent studies, we have found that these drugs equally induce morphological and biochemical changes typical of autophagy, including accumulation of autophagic vacuoles, appearance of LC3-II forms, and alteration in the expression and distribution of p62. Further investigation has indicated that drug-induced autophagic phenomena are largely the consequences of an impaired autophagic flux. In these cell death paradigms, we have intriguingly found that Bak, a prototypic proapoptotic protein of the Bcl-2 family, exerts a protective role via reduction of the area occupied by swollen vacuoles and appearance of the LC3-II form, whereas silencing of Bak aggravates these phenomena. Further study has indicated that a protective role for Bak is primarily ascribed to its regulatory effect on the maintenance of autophagic flux and vacuole homeostasis. In this regard, a regulatory role for calcium has been proposed., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Brain iron accumulation has been implicated in a host of chronic neurological diseases, including Parkinson's disease (PD). The elevated iron levels observed in the substantia nigra of PD subjects have been suggested to incite the generation of reactive oxygen species and intracellular α-synuclein aggregation, terminating in the oxidative neuronal destruction of this brain area. Thus, elucidation of the molecular mechanisms involved in iron dysregulation and oxidative stress-induced neurodegeneration is a crucial step in deciphering PD pathology and in developing novel iron-complexing compounds aimed at restoring brain iron homeostasis and attenuating neurodegeneration. This review discusses the involvement of dysregulation of brain iron homeostasis in PD pathology, with an emphasis on the potential effectiveness of naturally occurring compounds and novel iron-chelating/antioxidant therapeutic hybrid molecules, exerting a spectrum of neuroprotective interrelated activities: antioxidant/monoamine oxidase inhibition, activation of the hypoxia-inducible factor (HIF)-1 signaling pathway, induction of HIF-1 target iron-regulatory and antioxidative genes, and inhibition of α-synuclein accumulation and aggregation., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Loss-of-function mutations in the PARK7/DJ-1 gene cause early onset autosomal-recessive Parkinson disease. DJ-1 has been implicated in protection of neurons from oxidative stress and in regulation of transcriptional activity. However, whether there is a relationship between the subcellular localization of DJ-1 and its function remains unknown. Therefore, we examined the subcellular localization of DJ-1 during dopaminergic neurodegeneration induced by various insults. Immunoblotting and immunocytochemistry showed that the nuclear pool of DJ-1 dramatically increased in both MN9D dopaminergic neuronal cells and primary cultures of mesencephalic dopaminergic neurons after 6-hydroxydopamine (6-OHDA) treatment. This was paralleled by a corresponding decrease in its cytosolic level, indicating drug-induced nuclear translocation of DJ-1. The same phenomenon was detected in other cell death paradigms induced by pro-oxidants including hydrogen peroxide and cupric chloride. Consequently, cotreatment with the antioxidant N-acetyl-l-cysteine blocked the translocation of DJ-1 into the nucleus. However, mutation at cysteine 106 had no effect on the translocation of DJ-1 into the nucleus, suggesting that reactive oxygen species-mediated downstream signaling and/or modifications other than oxidative modification are involved in its nuclear translocation. Ectopic expression of nucleus localization signal (NLS)-tagged DJ-1 prevented cell death from 6-OHDA. We investigated whether nuclear DJ-1 was involved in transcriptional regulation and found that DJ-1 was localized in promyelocytic leukemia bodies, and this localization increased upon 6-OHDA treatment. We also confirmed that binding of DJ-1 and promyelocytic leukemia bodies indeed increased after 6-OHDA treatment. Consequently, expression levels of acetylated p53 and PUMA were downregulated in cells overexpressing DJ-1 or NLS-tagged DJ-1. Taken together, our data suggest that nuclear translocation of DJ-1 may protect neurons from cell death after oxidative stress., (Copyright © 2012 Elsevier Inc. All rights reserved.)

The anti-Parkinson iron chelator brain selective monoamine oxidase (MAO) AB inhibitor M30 [5-(N-methyl-N-propargylaminomethyl)-8-hydroxyquinoline] was shown to possess neuroprotective activities in vitro and in vivo, against several insults applicable to several neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease (PD) and ALS. We examined the effect of M30 on a pre-existing lesion induced by the parkinsonism-inducing toxin, MPTP (N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine). In this neurorescue/neurorestorative paradigm, M30 was orally administered to mice for 14 days (2.5-5 mg/kg/day) following post MPTP or lactacystin lesion and was shown to significantly elevate striatal dopamine, serotonin and noradrenaline levels, reduce their metabolism, and elevate tyrosine-hydroxylase protein levels. Importantly, M30 elevated MPTP-reduced dopaminergic and transferrin receptor cell count in the substantia nigra pars compacta (SNpc). Finally, M30 was shown to decrease mitosis and elevate HIF (hypoxia induced factor) which regulates the neurotrophins BDNF, GDNF, VEGF and erythropoietin by elevating their brain levels, thus providing additional protection. These findings indicates that brain-permeable M30 has neurorestorative activity, which may clearly be of clinical importance for the treatment of PD., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Aims: To assess whether reduction of Skp1 will increase the vulnerability of dopaminergic neurons to genetic/environmental factors known to play a role in the pathological process of PD., Methods: Short hairpin RNA lentiviruses infection of substantia nigra (SN)-derived cell-line (SN4741) and mice intranigral injection., Results: We have knocked down the expression of SKP1A, an E3 ubiquitin ligase element, found significantly decreased in human SN in patients with PD. The deficiency of SKP1A in SN4741 cells closely recapitulated cardinal features of the dopamine (DA) neuron pathology of human PD, such as decreased expression of DA phenotypic markers and cell cycle aberrations. Moreover, the knocked down cells displayed a lethal phenotype in differentiated cells exhibiting proteinaceous round inclusions, which were almost identical in composition to human Lewy bodies. Knock down of SKP1A rendered SN4741 cells especially sensitive to genetic reduction of the DA metabolizing enzyme, aldehyde dehydrogenase 1 and exposure to external Stressors implicated in PD pathology., Conclusion: Future studies should contemplate intrinsic and environmental manipulations in Skp1-deficient animals to emulate the motor and non-motor disabilities, the progressive nature of PD, and striatal-nigral and adjacent areas pathology. This model may provide a reliable "platform" to develop new therapeutic interventions for PD., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Large-scale transcriptomics analysis of gene expression profile of sporadic Parkinson's disease (PD) substantia nigra (SN) has identified a number of differentially expressed genes participating in the neurotoxic cascade of DA neurons death, in particular those related to handling of proteins, dopaminergic transmission and iron metabolism. One of them, SKP1A (p19, S-phase kinase-associated protein 1A), an essential component of the ubiquitin-E3 ligase Skp1, Cullin 1, F-box protein (SCF) complex, has been found to be significantly decreased in the SN pars compacta of post-mortem parkinsonian brains. Recently, a new genetic cell model of sporadic PD was developed by knocking-down SKP1A in SN-derived cell-line infected with short hairpin RNA lentiviruses. SKP1A deficiency resulted in increased susceptibility to cell death and a decline in the expression of dopaminergic phenotypic markers. SKP1A-silenced cells were unable to arrest at G(0)/G(1,) when induced to differentiate, entering into an aberrant cell cycle and progressive death. During this process the cells developed rounded aggregates with characteristics of LB-like inclusions (aggresomes) including immunoreactivity for gamma-tubulin, alpha-synuclein, ubiquitin, tyrosine hydroxylase, Hsc-70 and proteasome subunit. In conclusion, future studies should focus on a careful consideration of crucial dopaminergic interacting genes, as emerged from human sporadic PD, which will serve as a basis for the development of a slowly progressive genetic animal model of sporadic PD, with the potential of evaluating drugs with "disease modifying activity".

We have recently demonstrated that bis(7)-Cognitin, a promising multifunctional anti-Alzheimer's dimer, can remarkably reduce the generation of amyloid beta peptide (Abeta) by inhibiting beta-secretase (BACE-1) and activating alpha-secretase activity. In this study, the mechanism(s) underlying bis(7)-Cognitin's regulation of the activity of these two proteases was further investigated. In N2a cells stably expressing human amyloid precursor protein with the Swedish mutation (APPswe), the reduction in Abeta production induced by 1microM bis(7)-Cognitin was not altered by the co-pretreatment of muscarinic and nicotinic cholinergic receptor antagonists, indicating that the regulation of APP processing by this dimer is independent of cholinergic transmission. Furthermore, bis(7)-Cognitin (0.1-3microM) significantly increased protein kinase C (PKC) activity in cells and in vitro in a concentration-dependent manner. Administration of a PKC activator, phorbol 12-myristate 13-acetate (PMA), concentration-dependently increased the alpha-secretase cleavage products, and reduced the BACE-1 cleavage products. In addition, the inhibition of PKC prevented PMA- or bis(7)-Cognitin-induced alterations in alpha-secretase and BACE-1 activities, eliminating reductions in Abeta production seen with PMA or the dimer. These results strongly suggest that bis(7)-Cognitin may reduce the biosynthesis of Abeta by inhibiting BACE-1 and activating alpha-secretase concurrently through the direct activation of PKC. Combined with previous findings of direct inhibition of AChE and BACE-1 by this dimer, this work indicates that strategy may have potential to provide new insights into designing novel drugs that target multiple steps of aberrant APP processing to treat Alzheimer's disease.

Previous findings suggest that the antioxidant-iron chelator green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG) may have a neurorescue impact in aging and neurodegenerative diseases to retard or even reverse the accelerated rate of neuronal degeneration. The present study sought a deeper elucidation of the molecular neurorescue activity of EGCG in a progressive neurotoxic model of long-term serum deprivation of human SH-SY5Y neuroblastoma cells. In this model, proteomic analysis revealed that EGCG (0.1-1 microM) affected the expression levels of diverse proteins, including proteins related to cytoskeletal components, metabolism, heat shock, and binding. EGCG induced the levels of cytoskeletal proteins, such as beta tubulin IV and tropomyosin 3, playing a role in facilitating cell assembly. In accordance, EGCG increased the levels of the binding protein 14-3-3 gamma, involved in cytoskeletal regulation and signal transduction pathways in neurons. Additionally, EGCG decreased protein levels and mRNA expression of the beta subunit of the enzyme prolyl 4-hydroxylase, which belongs to a family of iron-oxygen sensors of hypoxia-inducible factor (HIF) prolyl hydroxylases that negatively regulate the stability and degradation of several proteins involved in cell survival and differentiation. Accordingly, EGCG decreased protein levels of two molecular chaperones that were associated with HIF regulation, the immunoglobulin-heavy-chain binding protein and the heat shock protein 90 beta. Thus, the present study sheds some light on the antioxidative-iron chelating activities of EGCG underlying its neuroprotective/neurorescue mechanism of action, further suggesting a potential neurodegenerative-modifying effect for EGCG.

Parkinson's disease (PD) is a severe neurodegenerative disorder, with no available drugs able to prevent the neuronal cell loss characteristic in brains of patients suffering from PD. Due to the complex cascade of molecular events involved in the etiology of PD, an innovative approach towards neuroprotection or neurorescue may entail the use of multifunctional pharmaceuticals that target an array of pathological pathways, each of which is believed to contribute to events that ultimately lead to neuronal cell death. Here we discuss examples of novel multifunctional ligands that may have potential as neuroprotective and neurorestorative therapeutics in PD. The compounds discussed originate from synthetic chemistry as well as from natural sources where various moieties, identified in research to possess neuroprotective and neurorestorative properties, have been introduced into the structures of several monomodal drugs, some of which are used in the clinic.

High-throughput gene-based platform studies in human post-mortem substantia nigra from sporadic Parkinson's disease (PD) cases have revealed significant dysregulation of genes involved in biological processes linked to previously established neurodegenerative mechanisms both in sporadic and hereditary PD. These include protein aggregation, mitochondrial dysfunction, oxidative stress, cell cycle, vesicle trafficking, synaptic transmission, dopamine metabolism and cell adhesion/cytoskeleton maintenance. These observations have extended our current view on the molecular pathways underlying the etio-pathology of the disease and provided a basis for the development of a novel genetic model of sporadic PD, centered on gradual silencing/over-expression of the candidate genes. The uncovered signatures may serve as future predictive biomarkers for early PD diagnosis, disease progression and drug development.

Antioxidants and iron chelating molecules are known as neuroprotective agents in animal models of neurodegenerative disorders such as Alzheimer's disease (AD) and Parkinson's disease (PD). In this study, we designed and synthesized a novel bifunctional molecule (M10) with radical scavenging and iron chelating ability on an amino acid carrier likely to be a substrate for system L, thus targeting the compound to the central nervous system (CNS). M10 had a moderate iron affinity in HEPES buffer (pH 7.4) with logK(3)=12.25+/-0.55 but exhibited highly inhibitory action against iron-induced lipid peroxidation, with an IC(50) value (12microM) comparable to that of desferal (DFO). EPR studies indicated that M10 was a highly potent *OH scavenger with an IC(50) of about 0.3 molar ratio of M10 to H(2)O(2). In PC12 cell culture, M10 was at least as potent as the anti-Parkinson drug rasagiline in protecting against cell death induced by serum-deprivation and by 6-hydroxydopamine (6-OHDA). These results suggest that M10 deserves further investigation as a potential agent for the treatment of neurodegenerative disorders such as AD and PD.

Several novel antioxidant-iron chelators bearing 8-hydroxyoxyquinoline moiety were synthesized, and various properties related to their iron chelation, and neuroprotective action were investigated. All the chelators exhibited strong iron(III) chelating and high antioxidant properties. Chelator 9 (HLA20), having good permeability into K562 cells and moderate selective MAO-B inhibitory activity (IC50 110 microM), displayed the hightest protective effects against differentiated P19 cell death induced by 6-hydroxydopamine. EPR studies suggested that Chelator 9 also act as radical scavenger to directly scavenge hydroxyl radical.

Tea consumption is varying its status from a mere ancient beverage and a lifestyle habit, to a nutrient endowed with possible prospective neurobiological-pharmacological actions beneficial to human health. Accumulating evidence suggest that oxidative stress resulting in reactive oxygen species generation and inflammation play a pivotal role in neurodegenerative diseases, supporting the implementation of radical scavengers, transition metal (e.g., iron and copper) chelators, and nonvitamin natural antioxidant polyphenols in the clinic. These observations are in line with the current view that polyphenolic dietary supplementation may have an impact on cognitive deficits in individuals of advanced age. As a consequence, green tea polyphenols are now being considered as therapeutic agents in well controlled epidemiological studies, aimed to alter brain aging processes and to serve as possible neuroprotective agents in progressive neurodegenerative disorders such as Parkinson's and Alzheimer's diseases. In particular, literature on the putative novel neuroprotective mechanism of the major green tea polyphenol, (-)-epigallocatechin-3-gallate, are examined and discussed in this review.

Neurodegeneration in Parkinson's, Alzheimer's, and other neurodegenerative diseases seems to be multifactorial, in that a complex set of toxic reactions including inflammation, glutamatergic neurotoxicity, increases in iron and nitric oxide, depletion of endogenous antioxidants, reduced expression of trophic factors, dysfunction of the ubiquitin-proteasome system, and expression of proapoptotic proteins leads to the demise of neurons. Thus, the fundamental objective in neurodegeneration and neuroprotection research is to determine which of these factors constitutes the primary event, the sequence in which these events occur, and whether they act in concurrence in the pathogenic process. This has led to the current notion that drugs directed against a single target will be ineffective and rather a single drug or cocktail of drugs with pluripharmacological properties may be more suitable. Green tea catechin polyphenols, formerly thought to be simple radical scavengers, are now considered to invoke a spectrum of cellular mechanisms of action related to their neuroprotective activity. These include pharmacological activities like iron chelation, scavenging of radicals, activation of survival genes and cell signaling pathways, and regulation of mitochondrial function and possibly of the ubiquitin-proteasome system. As a consequence these compounds are receiving significant attention as therapeutic cytoprotective agents for the treatment of neurodegenerative and other diseases.

We synthesized several prodrugs of glycine and gamma-aminobutyric acid. In order to establish a screening system from the prodrugs of selective activity to MAO-A or MAO-B, we examined purification conditions such as solubilization with Triton X-100, precipitation with ammonium sulfate, gel filtration and anion exchange chromatography. MAO-B was purified from various tissues such as guinea pig brain, kidney and spleen. MAO-A from human placenta without MAO-B was unstable in above purifications and used as crude. At each purification step, we checked sensitivity of the enzyme to specific inhibitors by developing a convenient fluorescence assay, in which hydrogen peroxide produced by the enzyme was reacted with p-hydroxyphenylpropionic acid. A fluorescence microplate reader measured a fluorescence of the fluorescent product from p-hydroxyphenylpropionic acid with horseradish peroxidase. In comparison with milacemide, N,N-bis(carbamoylmethyl)-N-pentylamine was the best and exclusive substrate for MAO-B. 2-N-(phenylethylamino)-acetoamide was the good substrate for MAO-A and MAO-B same as milacemide. 4-N-(n-pentylamino)-butyric acid and 4-(N-phenylethylamino)-butyric acid were the moderate substrates for both enzymes, which should release gamma-aminobutyric acid. These drugs will be new leading compounds.

The major side effect with the use of first generation of non selective monoamine oxidase (MAO) inhibitors as neuropsychiatric drugs was what became known as the "cheese reaction". Namely, potentiation of sympathomimetic activity of ingested tyramine present in cheese and other food stuff, resulting from its ability to release noradrenaline, when prevented from metabolism by MAO. The identification of two forms of MAO, termed types A and B and their selective irreversible inhibitors resolved some of this problems. However irreversible MAO-A inhibitors continue to induce a cheese reaction, whereas MAO-B inhibitors at their selective dosage did not and led to introduction of L-deprenyl (selegiline) as an anti-Parkinson drug, since dopamine is equally well metabolized by both enzyme forms. The cheese reaction is a consequence of inhibition of MAO-A, the enzyme responsible for metabolism of noradrenaline and serotonin, located in peripheral adrenergic neurons. The consequence of these findings were the development of reversible MAO-A inhibitors (RIMA), moclobemide and brofaromin, as antidepressants and possible anti-Parkinson activity, with limited tyramine potentiation, since the amine can displace the inhibitor from its binding site on the enzyme. It has always been deemed a greater pharmacological advantage to inhibit both forms of the enzymes to get the full functional activities of the amine neurotransmitters, and without inducing a "cheese reaction". This was not possible until recently, with the development of the novel cholinesterase-brain selective MAO-AB inhibitor, TV3326 (N-propargyl-(3R)-aminoidnan-5-yl-ethyl methylcarbamate hemitartiate), a carbamate derivative of the irreversible MAO-B inhibitor anti-Parkinson drug, rasagiline. This drug is a brain selective MAO-A and B inhibitor, with little inhibition of liver and small intestine enzymes. Pharmacologically it has limited tyramine potentiation, very similar to moclobemide and being a MAO-AB inhibitor it has the antidepressant, anti-Parkinson and anti-Alzheimer activities in the respective models used to develop such drugs.

The anti-Parkinson drug, rasagiline, a irreversible propargyl possessing monoamine oxidase B inhibitor can protect neurons in vitro and in vivo from a variety of neurotoxic insults including SIN-1, glutamate, the parkinsonism inducing neurotoxin, N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, N-methyl-(R)-salsolinol and including beta amyloid protein. Recent studies have shown that rasagiline rapidly modulates intracellular signaling pathways involved in cell survival and death. Specifically rasagiline activates Bcl-2, Bcl-xl, protein kinase C (PKC) and reduces Bax in a variety of cells including PC-12 and neuroblastoma human dopamine derived SH-SY5Y cells. These enzymes play key roles in cellular events including modulation of apoptotic processes, neuronal plasticity and amyloid precursor protein processing. This pharmacological action of rasagiline is also associated with the prevention of the neurotoxin induced fall in mitochondrial membrane potential, opening of mitochondria permeability transition pore, activation of proteasome-ubiquitin complex, inhibition of cytochrome c release and prevention of caspase 3 activation, similar to the actions of cyclosporin A or Bcl-2 over expression in SH-SY5Y cells. Rasagiline and its various derivatives induces PKC dependent release of soluble amyloid precursor protein alpha and which is blocked by inhibitors of alpha-secretase, PKC and MAPK-dependent signaling. Structure-activity relationship with various propargyl containing derivatives of rasagiline including propargylamine itself has shown that the above described pharmacological action of these compounds resides in the propargylamine moiety. These results have provided a new understanding into the mechanism of neuroprotective actions of rasagiline and its anti-Alzheimer drug derivatives TV3326 and TV3279, which are relevant for therapy of Parkinson's disease, Alzheimer's disease and other neurodegenerative diseases.

The vulnerability of the dopaminergic neurons of the substantia nigra (SN) in Parkinson's disease has been related to the presence of the pigment neuromelanin (NM) in these neurons. It is hypothesised that NM may act as an endogenous storage molecule for iron, an interaction suggested to influence free radical production. The current study quantified and characterised the interaction between NM and iron. Iron-binding studies demonstrated that both NM and synthetically-produced dopamine melanin contain equivalent numbers of high and low-affinity binding sites for iron but that the affinity of NM for iron is higher than that of synthetic melanin. Quantification of the total iron content in iron-loaded NM and synthetic melanin demonstrated that the iron-binding capacity of NM is 10-fold greater than that of the model melanin. This data was in agreement with the larger iron cluster size demonstrated by Mössbauer spectroscopy in the native pigment compared with the synthetic melanin. These findings are consistent with the hypothesis that NM may act as an endogenous iron-binding molecule in dopaminergic neurons of the SN in the human brain. The interaction between NM and iron has implications for disorders such as Parkinson's disease where an increase in iron in the SN is associated with increased indices of oxidative stress.

Antioxidant and anti-inflammatory therapy approaches have been in the focus of attention in the treatment of neurodegenerative Parkinson's and Alzheimer's diseases where oxidative stress has been implicated. Tea extracts have been previously reported to possess radical scavenger, iron chelating and anti-inflammatory properties in a variety of tissues. The purpose of this study was to investigate potential neuroprotective effects of tea extracts and possible signal pathway involved in a neuronal cell model of Parkinson's disease. We demonstrated highly potent antioxidant-radical scavenging activities of green tea (GT) and black tea (BT) extracts on brain mitochondrial membrane fraction, against iron (2.5 microM)-induced lipid peroxidation. Both extracts (0.6-3 microM total polyphenols) were shown to attenuate the neurotoxic action of 6-hydroxydopamine (6-OHDA)-induced neuronal death. 6-OHDA (350 and 50 microM) activated the iron dependent inflammatory redox sensitive nuclear factor-kappaB (NF-kappaB) in rat pheochromocytoma (PC12) and human neuroblastoma (NB) SH-SY5Y cells, respectively. Immunofluorescence and electromobility shift assays showed increased nuclear translocation and binding activity of NF-kappaB after exposure to 6-OHDA in NB SH-SY5Y cells, with a concomitant disappearance from the cytoplasm. Introduction of GT extract (0.6, 3 microM total polyphenols) before 6-OHDA inhibited both NF-kappaB nuclear translocation and binding activity induced by this toxin in NB SH-SY5Y cells. Neuroprotection was attributed to the potent antioxidant and iron chelating actions of the polyphenolic constituents of tea extracts, preventing nuclear translocation and activation of cell death promoting NF-kappaB. Brain penetrating property of polyphenols may make such compounds an important class of drugs for treatment of neurodegenerative diseases.