Targeting dysregulation of brain iron homeostasis in Parkinson's disease by iron chelators

The role of iron in Parkinson's disease monkeys assessed by susceptibility weighted imaging and inductively coupled plasma mass spectrometry

Mounting evidences indicated that elevated iron levels in the substantia nigra (SN) have been concerned as the underlying mechanisms of neurodegenerative diseases, including Parkinson's disease (PD). The present study used the 1-Methyl-4-phenyl-1, 2, 3, 6 -tetrahydropyridine (MPTP)-treated cynomolgus monkeys for PD to evaluate the usability of SWI for assessing iron deposition in the cerebral nuclei of PD. The results showed that susceptibility-weighted imaging (SWI) phase values of the ipsilateral (MPTP-lesion side) SN of MPTP-treated monkeys were lower than those in the contralateral SN of MPTP-treated monkeys and the same side of Control monkeys, suggesting that iron deposition were elevated in the affected side SN of MPTP-treated monkeys. Whereas MPTP has not effects on the SWI phase values in other detected brain regions of monkeys, including red nucleus (RN), putamen (PUT) and caudate nucleus (CA). Furthermore, ICP-MS results showed that MPTP increased the iron levels in MPTP injection side, but no in the ipsilateral striatum. Additionally, MPTP treatment did not affect the calcium and manganese levels in the detected brain regions of monkeys. However, Pearson correlation analysis results indicated that there were not relationship between SWI phase values in MPTP-lesion side of SN with the behavioral score, tyrosine hydroxylase (TH)-positive cells number and iron levels in the MPTP-lesion side of midbrain. Taken together, the results confirm the involvement of SN iron accumulations in the MPTP-treated monkey models for PD, and indirectly verify the usability of SWI for the measurement of iron deposition in the cerebral nuclei of PD.

Suppression of 6-Hydroxydopamine-Induced Oxidative Stress by Hyperoside Via Activation of Nrf2/HO-1 Signaling in Dopaminergic Neurons

In our ongoing research to discover natural products with neuroprotective effects, hyperoside (quercetin 3-O-galactoside) was isolated from Acer tegmentosum, which has been used in Korean traditional medicine to treat liver-related disorders. Here, we demonstrated that hyperoside protects cultured dopaminergic neurons from death via reactive oxygen species (ROS)-dependent mechanisms, although other relevant mechanisms of hyperoside activity remain largely uncharacterized. For the first time, we investigated the neuroprotective effects of hyperoside on 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in neurons, and the possible underlying mechanisms. Hyperoside significantly ameliorated the loss of neuronal cell viability, lactate dehydrogenase release, excessive ROS accumulation and mitochondrial membrane potential dysfunction associated with 6-OHDA-induced neurotoxicity. Furthermore, hyperoside treatment activated the nuclear erythroid 2-related factor 2 (Nrf2), an upstream molecule of heme oxygenase-1 (HO-1). Hyperoside also induced the expression of HO-1, an antioxidant response gene. Remarkably, we found that the neuroprotective effects of hyperoside were weakened by an Nrf2 small interfering RNA, which blocked the ability of hyperoside to inhibit neuronal death, indicating the vital role of HO-1. Overall, we show that hyperoside, via the induction of Nrf2-dependent HO-1 activation, suppresses neuronal death caused by 6-OHDA-induced oxidative stress. Moreover, Nrf2-dependent HO-1 signaling activation represents a potential preventive and therapeutic target in Parkinson's disease management.

Mitophagy could fight Parkinson's disease through antioxidant action

During aging, the process of mitophagy, a system that allows the removal of dysfunctional mitochondria through lysosomal degradation, starts to malfunction. Because of this defect, damaged mitochondria are not removed correctly, and their decomposing components accumulate inside the cells. Dysfunctional mitochondria that are not removed by mitophagy produce high amounts of reactive oxygen species (ROS) and, thus, cause oxidative stress. Oxidative stress, in turn, is very harmful for the cells, neuronal cells, in particular. Consequently, the process of mitophagy plays a crucial role in mitochondria-related disease. Mitochondrial dysfunctions and oxidative stress are well-established factors contributing to Parkinson's disease (PD), one of the most common neurodegenerative disorders. In this review, we report various known antioxidants for PD treatments and describe the stimulation of mitophagy process as a novel and exciting method for reducing oxidative stress in PD patients. We describe the different mechanisms responsible for mitochondria removal through the mitophagy process. In addition, we review the functional connection between mitophagy induction and reduction of oxidative stress in several in vitro models of PD and also agents (drugs and natural compounds) already known to be antioxidants and to be able to activate mitophagy. Finally, we propose that there is an urgent need to test the use of mitophagy-inducing antioxidants in order to fight PD.

Redox active metals in neurodegenerative diseases

Copper (Cu) and iron (Fe) are redox active metals essential for the regulation of cellular pathways that are fundamental for brain function, including neurotransmitter synthesis and release, neurotransmission, and protein turnover. Cu and Fe are tightly regulated by sophisticated homeostatic systems that tune the levels and localization of these redox active metals. The regulation of Cu and Fe necessitates their coordination to small organic molecules and metal chaperone proteins that restrict their reactions to specific protein centres, where Cu and Fe cycle between reduced (Fe²⁺, Cu⁺) and oxidised states (Fe³⁺, Cu²⁺). Perturbation of this regulation is evident in the brain affected by neurodegeneration. Here we review the evidence that links Cu and Fe dyshomeostasis to neurodegeneration as well as the promising preclinical and clinical studies reporting pharmacological intervention to remedy Cu and Fe abnormalities in the treatment of Alzheimer's disease (AD), Parkinson's disease (PD) and Amyotrophic lateral sclerosis (ALS).

Hepcidin and its therapeutic potential in neurodegenerative disorders

Abnormally high brain iron, resulting from the disrupted expression or function of proteins involved in iron metabolism in the brain, is an initial cause of neuronal death in neuroferritinopathy and aceruloplasminemia, and also plays a causative role in at least some of the other neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, Huntington's disease, and Friedreich's ataxia. As such, iron is believed to be a novel target for pharmacological intervention in these disorders. Reducing iron toward normal levels or hampering the increases in iron associated with age in the brain is a promising therapeutic strategy for all iron-related neurodegenerative disorders. Hepcidin is a crucial regulator of iron homeostasis in the brain. Recent studies have suggested that upregulating brain hepcidin levels can significantly reduce brain iron content through the regulation of iron transport protein expression in the blood-brain barrier and in neurons and astrocytes. In this review, we focus on the discussion of the therapeutic potential of hepcidin in iron-associated neurodegenerative diseases and also provide a systematic overview of recent research progress on how misregulated brain iron metabolism is involved in the development of multiple neurodegenerative disorders.

Phytochemicals Bridging Autophagy Induction and Alpha-Synuclein Degradation in Parkinsonism

Among nutraceuticals, phytochemical-rich compounds represent a source of naturally-derived bioactive principles, which are extensively studied for potential beneficial effects in a variety of disorders ranging from cardiovascular and metabolic diseases to cancer and neurodegeneration. In the brain, phytochemicals produce a number of biological effects such as modulation of neurotransmitter activity, growth factor induction, antioxidant and anti-inflammatory activity, stem cell modulation/neurogenesis, regulation of mitochondrial homeostasis, and counteracting protein aggregation through modulation of protein-folding chaperones and the cell clearing systems autophagy and proteasome. In particular, the ability of phytochemicals in restoring proteostasis through autophagy induction took center stage in recent research on neurodegenerative disorders such as Parkinson’s disease (PD). Indeed, autophagy dysfunctions and α-syn aggregation represent two interdependent downstream biochemical events, which concur in the parkinsonian brain, and which are targeted by phytochemicals administration. Therefore, in the present review we discuss evidence about the autophagy-based neuroprotective effects of specific phytochemical-rich plants in experimental parkinsonism, with a special focus on their ability to counteract alpha-synuclein aggregation and toxicity. Although further studies are needed to confirm the autophagy-based effects of some phytochemicals in parkinsonism, the evidence discussed here suggests that rescuing autophagy through natural compounds may play a role in preserving dopamine (DA) neuron integrity by counteracting the aggregation, toxicity, and prion-like spreading of α-syn, which remains a hallmark of PD.

Long-term iron exposure causes widespread molecular alterations associated with memory impairment in mice

Limited literature available indicates the neurotoxic effects of excessive iron, however, a deep understanding of iron neurotoxicity needs to be developed. In this study, we evaluated the toxic effects of excessive iron on learning and cognitive function in long-term iron exposure (oral, 10 mg/L, 6 months) of mice by behavioral tests including novel object recognition test, step-down passive avoidance test and Morris water maze test, and further analyzed differential expression of hippocampal proteins. The behavioral tests consistently showed that iron treatment caused cognitive defects of the mice. Proteomic analysis revealed 66 differentially expressed hippocampal proteins (30 increased and 36 decreased) in iron-treated mice as compared with the control ones. Bioinformatics analysis showed that the dysregulated proteins mainly included: synapse-associated proteins (i.e. synaptosomal-associated protein 25 (SNAP25), complexin-1 (CPLX1), vesicle-associated membrane protein 2 (VAMP2), neurochondrin (NCDN)); mitochondria-related proteins (i.e. ADP/ATP translocase 1 (SLC25A4), 14-3-3 protein zeta/delta (YWHAZ)); cytoskeleton proteins (i.e. neurofilament light polypeptide (NEFL), tubulin beta-2B chain (TUBB2B), tubulin alpha-4A chain (TUBA4A)). The findings suggest that the dysregulations of synaptic, mitochondrial, and cytoskeletal proteins may be involved in iron-triggered memory impairment. This study provides new insights into the molecular mechanisms of iron neurotoxicity.

Tremor-Dominant in Parkinson Disease: The Relevance to Iron Metabolism and Inflammation

Background: Tremor is one of the most predominant symptoms of patients with Parkinson disease (PD), but the underlying mechanisms for tremor relating to iron and its metabolism-related proteins and the inflammatory factors in cerebrospinal fluid (CSF) and serum have not been fully elucidated. Methods: A total of 135 PD patients were divided into a tremor-dominant (PD-TD) group (N = 74) and a postural instability and gait difficulty-dominant (PD-PIGD) group (N = 39) based on the ratio of mean tremor score to the mean bradykinesia/rigid score of the Unified Parkinson's Disease Rating Scale (UPDRS) III. Age and sex-matched healthy controls were recruited (N = 35). Demographic variables were evaluated; iron and its metabolism-related proteins and the inflammatory mediators in both CSF and serum were measured in these groups. The relevance of iron metabolism, inflammation and PD-TD were analyzed. Results: (1) The PD-TD group had significantly decreased L-ferritin, increased iron levels in CSF and increased ferritin levels in the serum compared with the PD-PIGD and control groups (P < 0.05). (2) The PD-TD group had significantly enhanced IL-6 levels in both CSF and serum compared with the PD-PIGD and control groups (P < 0.05). (3) In CSF, the IL-6 level was increased as the iron level was elevated in the PD-TD group (r = 0.308, P = 0.022). In serum, the IL-6 level was increased as the ferritin level was elevated in the PD-TD group (r = 0.410, P = 0.004). Conclusion: The interplay between disturbed iron metabolism and relevant inflammation might modulate clinical phenotypes of PD.

Plant Extracts and Phytochemicals Targeting α-Synuclein Aggregation in Parkinson's Disease Models

α-Synuclein (α-syn) is a presynaptic protein that regulates the release of neurotransmitters from synaptic vesicles in the brain. α-Syn aggregates, including Lewy bodies, are features of both sporadic and familial forms of Parkinson's disease (PD). These aggregates undergo several key stages of fibrillation, oligomerization, and aggregation. Therapeutic benefits of drugs decline with disease progression and offer only symptomatic treatment. Novel therapeutic strategies are required which can either prevent or delay the progression of the disease. The link between α-syn and the etiopathogenesis and progression of PD are well-established in the literature. Studies indicate that α-syn is an important therapeutic target and inhibition of α-syn aggregation, oligomerization, and fibrillation are an important disease modification strategy. However, recent studies have shown that plant extracts and phytochemicals have neuroprotective effects on α-syn oligomerization and fibrillation by targeting different key stages of its formation. Although many reviews on the antioxidant-mediated, neuroprotective effect of plant extracts and phytochemicals on PD symptoms have been well-highlighted, the antioxidant mechanisms show limited success for translation to clinical studies. The identification of specific plant extracts and phytochemicals that target α-syn aggregation will provide selective molecules to develop new drugs for PD. The present review provides an overview of plant extracts and phytochemicals that target α-syn in PD and summarizes the observed effects and the underlying mechanisms. Furthermore, we provide a synopsis of current experimental models and techniques used to evaluate plant extracts and phytochemicals. Plant extracts and phytochemicals were found to inhibit the aggregation or fibril formation of oligomers. These also appear to direct α-syn oligomer formation into its unstructured form or promote non-toxic pathways and suggested to be valuable drug candidates for PD and related synucleinopathy. Current evidences from in vitro studies require confirmation in the in vivo studies. Further studies are needed to ascertain their potential effects and safety in preclinical studies for pharmaceutical/nutritional development of these phytochemicals or dietary inclusion of the plant extracts in PD treatment.

Iron Pathophysiology in Parkinson Diseases

The key molecular events that provoke Parkinson's disease (PD) are not fully understood. Iron deposit was found in the substantia nigra pars compacta (SNpc) of PD patients and animal models, where dopaminergic neurons degeneration occurred selectively. The mechanisms involved in disturbed iron metabolism remain unknown, however, considerable evidence indicates that iron transporters dysregulation, activation of L-type voltage-gated calcium channel (LTCC) and ATP-sensitive potassium (KATP) channels, as well as N-methyl-D-aspartate (NMDA) receptors (NMDARs) contribute to this process. There is emerging evidence on the structural links and functional modulations between iron and α-synuclein, and the key player in PD which aggregates in Lewy bodies. Iron is believed to modulate α-synuclein synthesis, post-translational modification, and aggregation. Furthermore, glia, especially activated astroglia and microglia, are involved in iron deposit in PD. Glial contributions were largely dependent on the factors they released, e.g., neurotrophic factors, pro-inflammatory factors, lactoferrin, and those undetermined. Therefore, iron chelation using iron chelators, the extracts from many natural foods with iron chelating properties, may be an effective therapy for prevention and treatment of the disease.

Lactoferrin ameliorates dopaminergic neurodegeneration and motor deficits in MPTP-treated mice

Brain iron accumulation is common in patients with Parkinson's disease (PD). Iron chelators have been investigated for their ability to prevent neurodegenerative diseases with features of iron overload. Given the non-trivial side effects of classical iron chelators, lactoferrin (Lf), a multifunctional iron-binding globular glycoprotein, was screened to identify novel neuroprotective pathways against dopaminergic neuronal impairment. We found that Lf substantially ameliorated PD-like motor dysfunction in the subacute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse model of PD. We further showed that Lf could alleviate MPTP-triggered apoptosis of DA neurons, neuroinflammation, and histological alterations. As expected, we also found that Lf suppressed MPTP-induced excessive iron accumulation and the upregulation of divalent metal transporter (DMT1) and transferrin receptor (TFR), which is the main intracellular iron regulation protein, and subsequently improved the activity of several antioxidant enzymes. We probed further and determined that the neuroprotection provided by Lf was involved in the upregulated levels of brain-derived neurotrophic factor (BDNF), hypoxia-inducible factor 1α (HIF-1α) and its downstream protein, accompanied by the activation of extracellular regulated protein kinases (ERK) and cAMP response element binding protein (CREB), as well as decreased phosphorylation of c-Jun N-terminal kinase (JNK) and mitogen activated protein kinase (MAPK)/P38 kinase in vitro and in vivo. Our findings suggest that Lf may be an alternative safe drug in ameliorating MPTP-induced brain abnormalities and movement disorder.

Therapeutic strategies for Parkinson disease: beyond dopaminergic drugs

Existing therapeutic strategies for managing Parkinson disease (PD), which focus on addressing the loss of dopamine and dopaminergic function linked with degeneration of dopaminergic neurons, are limited by side effects and lack of long-term efficacy. In recent decades, research into PD pathophysiology and pharmacology has focused on understanding and tackling the neurodegenerative processes and symptomology of PD. In this Review, we discuss the challenges associated with the development of novel therapies for PD, highlighting emerging agents that aim to target cell death, as well as new targets offering a symptomatic approach to managing features and progression of the disease.

Metabolism and adult neurogenesis: Towards an understanding of the role of lipocalin-2 and iron-related oxidative stress

The process of generating new functional neurons in the adult mammalian brain occurs from the local neural stem and progenitor cells and requires tight control of the progenitor cell's activity. Several signaling pathways and intrinsic/extrinsic factors have been well studied over the last years, but recent attention has been given to the critical role of cellular metabolism in determining the functional properties of progenitor cells. Here, we review recent advances in the current understanding of when and how metabolism affects neural stem cell (NSC) behavior and subsequent neuronal differentiation and highlight the role of lipocalin-2 (LCN2), a protein involved in the control of oxidative stress, as a recently emerged regulator of NSC activity and neuronal differentiation.

Differential regulation of estrogen in iron metabolism in astrocytes and neurons

Previous studies have demonstrated an effect of estrogen on iron metabolism in peripheral tissues. The role of estrogen on brain iron metabolism is currently unknown. In this study, we investigated the effect and mechanism of estrogen on iron transport proteins. We demonstrated that the iron exporter ferroportin 1 (FPN1) and iron importer divalent metal transporter 1 (DMT1) were upregulated and iron content was decreased after estrogen treatment for 12 hr in primary cultured astrocytes. Hypoxia-inducible factor-1 alpha (HIF-1α) was upregulated, but HIF-2α remained unchanged after estrogen treatment for 12 hr in primary cultured astrocytes. In primary cultured neurons, DMT1 was downregulated, FPN1 was upregulated, iron content decreased, iron regulatory protein (IRP1) was downregulated, but HIF-1α and HIF-2α remained unchanged after estrogen treatment for 12 hr. These results suggest that the regulation of iron metabolism by estrogen in astrocytes and neurons is different. Estrogen increases FPN1 and DMT1 expression by inducing HIF-1α in astrocytes, whereas decreased expression of IRP1 may account for the decreased DMT1 and increased FPN1 expression in neurons.

Deferoxamine preconditioning ameliorates mechanical ventilation-induced lung injury in rat model via ROS in alveolar macrophages: a randomized controlled study

Background

Mechanical ventilation (MV) can provide effective breathing support; however, ventilatior-induced lung injury (VILI) has also been widely recognized in clinical practice, including in the healthy lung. Unfortunately, the morbidity and mortality of VILI remain unacceptably high, and no satisfactory therapeutic effect can be achieved. The current study aimed to examine the effects of iron chelator preconditioning on the mitochondrial reactive oxygen species (ROS) in alveolar macrophages and pathological lung injury in VILI.

Methods

Twenty four healthy male Sprague–Dawley (SD) rats (250–300 g in weight) were randomly divided into 3 groups, including the control group (NC group, n = 8), the high-volume mechanical ventilation group (HV group, n = 8), and the deferoxamine treatment group (HV + DFO group, n = 8). Rats in the HV and HV + DFO groups were subjected to high-volume MV at a dose of 40 ml/kg. DFO was administered at a dose of 200 mg/kg 15 min prior to over-ventilation. Spontaneously breathing anesthetized rats were used as the controls. The animals were sacrificed after 4 h of high-volume ventilation or under control conditions, the animals were sacrificed. Purified alveolar macrophages from bronchoalveolar lavage fluid (BALF) and lung tissue were collected for further analysis through light microscopy and flow cytometry.

Results

Compared with the controls, the high-volume-ventilated rats had exhibited typical lung edema and histological lung injury, and ROS were markedly increased in alveolar macrophages and mitochondria. Moreover, all indices of VILI were remarkably different in rats treated with DFO preconditioning. DFO could ameliorate lung injury in the mechanically ventilated SD rat model.

Conclusions

DFO preconditioning contributes to mitigating the histological lung damage while reducing ROS levels in alveolar macrophages and mitochondria, suggesting that iron metabolism in alveolar macrophages may participate in VILI.

No effects without causes: the Iron Dysregulation and Dormant Microbes hypothesis for chronic, inflammatory diseases

Since the successful conquest of many acute, communicable (infectious) diseases through the use of vaccines and antibiotics, the currently most prevalent diseases are chronic and progressive in nature, and are all accompanied by inflammation. These diseases include neurodegenerative (e.g. Alzheimer's, Parkinson's), vascular (e.g. atherosclerosis, pre-eclampsia, type 2 diabetes) and autoimmune (e.g. rheumatoid arthritis and multiple sclerosis) diseases that may appear to have little in common. In fact they all share significant features, in particular chronic inflammation and its attendant inflammatory cytokines. Such effects do not happen without underlying and initially 'external' causes, and it is of interest to seek these causes. Taking a systems approach, we argue that these causes include (i) stress-induced iron dysregulation, and (ii) its ability to awaken dormant, non-replicating microbes with which the host has become infected. Other external causes may be dietary. Such microbes are capable of shedding small, but functionally significant amounts of highly inflammagenic molecules such as lipopolysaccharide and lipoteichoic acid. Sequelae include significant coagulopathies, not least the recently discovered amyloidogenic clotting of blood, leading to cell death and the release of further inflammagens. The extensive evidence discussed here implies, as was found with ulcers, that almost all chronic, infectious diseases do in fact harbour a microbial component. What differs is simply the microbes and the anatomical location from and at which they exert damage. This analysis offers novel avenues for diagnosis and treatment.

Evaluation of the Antioxidant and Neuroprotectant Activities of New Asymmetrical 1,3-Diketones

A series of fourteen new asymmetrical 1,3-diketone derivatives have been synthesized and evaluated in the ABTS, FRAP and DPPH assays as a new chemotype with antioxidant and drug-like properties. All the compounds displayed low cytotoxicity in comparison to curcumin against the human neuroblastoma SH-SY5Y cell line. Among them, (3Z,5E)-6-(2,5-difluoro-4-hydroxy-phenyl)-1,1,1-trifluoro-4-hydroxyhexa-3,5-dien-2-one (6b) and (3Z,5E)-6-(2,3-difluoro-4-hydroxy-phenyl)-1,1,1-trifluoro-4-hydroxyhexa-3,5-dien-2-one (7b) with excellent solubility and chemical stability in biorelevant media, have also shown a similar Fe+2 chelation behavior to that of curcumin. Additionally, both derivatives 6b and 7b have afforded good neuroprotection activity against H₂O₂ induced oxidative stress in the same neuronal cell line, with a significant reduction of intracellular ROS levels, in parallel with a good recovery of the Mitochondrial Membrane Potential (ΔΨm). Compounds 6b and 7b with a promising antioxidant and drug-like profile, with low cytotoxic and good neuroprotectant activity, constitute a new interesting chemical class with high potential as new therapeutic agents against neurodegenerative diseases.

Epigallocatechin Gallate Protects against TNFα- or H2O2- Induced Apoptosis by Modulating Iron Related Proteins in a Cell Culture Model

Abstract. Oxidative stress, iron dysregulation, and inflammation have been implicated in the pathogenesis of Parkinson’s disease (PD). Considering the entwined relationship among these factors, epigallocatechin gallate (EGCG) may be a good candidate for PD treatment due to its protective effects against those factors. The objective of this study is to determine whether EGCG protects N27 dopaminergic neuronal cells from H2O2 - and TNFα- induced neurotoxicity. Seven treatments were included: control, H2O2, TNFα, FeSO4, H2O2 + EGCG, TNFα + EGCG, FeSO4 + EGCG. Cells were pretreated with 10 μM EGCG, followed by 50 μM H2O2, 30 ng/ml TNFα or 50 μM FeSO4. Neuroprotective effects of EGCG were assessed by cell viability assay, caspase-3 activity, intracellular reactive oxygen species (ROS) generation, and iron related protein expressions. Caspase-3 activity was increased to 2.8 fold (P < 0.001) and 1.5 fold (P < 0.01) with H2O2 and TNFα treatment; However, EGCG pretreatment significantly decreased the caspase activity by 50.2% (P < 0.001) and 30.1% (P < 0.05). Similarly, cell viability was reduced to 69.2% (P < 0.01) and 89% (P < 0.01) by H2O2 and TNFα, which was partially blocked by EGCG pretreatment. Also, EGCG significantly (P < 0.001) protected against H2O2- induced ROS in a time dependent manner. In addition, both H2O2 and TNFα significantly (P < 0.05) upregulated hepcidin expression and marginally reduced ferroportin (Fpn) expression unlike iron treatment alone. Collectively, our results show that EGCG protects against both TNFα- and H2O2- induced neuronal apoptosis. The observed neuroprotection may be through the inhibition of oxidative stress and inflammation which is possibly mediated mainly by hepcidin and partially by Fpn.

Targeted Brain Delivery of Rabies Virus Glycoprotein 29-Modified Deferoxamine-Loaded Nanoparticles Reverses Functional Deficits in Parkinsonian Mice

Excess iron deposition in the brain often causes oxidative stress-related damage and necrosis of dopaminergic neurons in the substantia nigra and has been reported to be one of the major vulnerability factors in Parkinson's disease (PD). Iron chelation therapy using deferoxamine (DFO) may inhibit this nigrostriatal degeneration and prevent the progress of PD. However, DFO shows very short half-life in vivo and hardly penetrates the blood brain barrier (BBB). Hence, it is of great interest to develop DFO formulations for safe and efficient intracerebral drug delivery. Herein, we report a polymeric nanoparticle system modified with brain-targeting peptide rabies virus glycoprotein (RVG) 29 that can intracerebrally deliver DFO. The nanoparticle system penetrates the BBB possibly through specific receptor-mediated endocytosis triggered by the RVG29 peptide. Administration of these nanoparticles significantly decreased iron content and oxidative stress levels in the substantia nigra and striatum of PD mice and effectively reduced their dopaminergic neuron damage and as reversed their neurobehavioral deficits, without causing any overt adverse effects in the brain or other organs. This DFO-based nanoformulation holds great promise for delivery of DFO into the brain and for realizing iron chelation therapy in PD treatment.

Current Nondopaminergic Therapeutic Options for Motor Symptoms of Parkinson's Disease

Objective:

The aim of this study was to summarize recent studies on nondopaminergic options for the treatment of motor symptoms in Parkinson's disease (PD).

Data Sources:

Papers in English published in PubMed, Cochrane, and Ovid Nursing databases between January 1988 and November 2016 were searched using the following keywords: PD, nondopaminergic therapy, adenosine, glutamatergic, adrenergic, serotoninergic, histaminic, and iron chelator. We also reviewed the ongoing clinical trials in the website of clinicaltrials.gov.

Study Selection:

Articles related to the nondopaminergic treatment of motor symptoms in PD were selected for this review.

Results:

PD is conventionally treated with dopamine replacement strategies, which are effective in the early stages of PD. Long-term use of levodopa could result in motor complications. Recent studies revealed that nondopaminergic systems such as adenosine, glutamatergic, adrenergic, serotoninergic, histaminic, and iron chelator pathways could include potential therapeutic targets for motor symptoms, including motor fluctuations, levodopa-induced dyskinesia, and gait disorders. Some nondopaminergic drugs, such as istradefylline and amantadine, are currently used clinically, while most such drugs are in preclinical testing stages. Transitioning of these agents into clinically beneficial strategies requires reliable evaluation since several agents have failed to show consistent results despite positive findings at the preclinical level.

Conclusions:

Targeting nondopaminergic transmission could improve some motor symptoms in PD, especially the discomfort of dyskinesia. Although nondopaminergic treatments show great potential in PD treatment as an adjunct therapy to levodopa, further investigation is required to ensure their success.

90 years of monoamine oxidase: some progress and some confusion

It would not be practical to attempt to deal with all the advances that have informed our understanding of the behavior and functions of this enzyme over the past 90 years. This account concentrates key advances that explain why the monoamine oxidases remain of pharmacological and biochemical interest and on some areas of continuing uncertainty. Some issues that remain to be understood or are in need of further clarification are highlighted.

Lycium barbarum Polysaccharide Promotes Nigrostriatal Dopamine Function by Modulating PTEN/AKT/mTOR Pathway in a Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) Murine Model of Parkinson's Disease

To investigate the effects of Lycium barbarum polysaccharide (LBP) on pathological symptoms and behavioral deficits in a Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson's disease (PD) mouse model. The therapeutic effects of LBP were monitored with an Open field test, a Rotarod test and a Morris water maze test. We also investigated the mechanisms with qRT-PCR and Western blotting analyses. After a relatively short-term LBP treatment, the total distance and walking time of PD mice significantly increased. The staying duration on the rod of PD mice increased in the Rotarod test. LBP can up-regulate levels of SOD2, CAT and GPX1 and inhibit the abnormal aggregation of α-synuclein induced by MPTP. LBP treatment can also up-regulate the phosphorylation of AKT and mTOR, and may play its protective role by activating the PTEN/AKT/mTOR signaling axis. These results suggest that LBP can effectively alleviate the degeneration in the nigrostriatal system induced by MPTP treatment. It may be a potential candidate for the treatment of Parkinson's disease.

Endogenous non-enzymatic antioxidants in the human body

The exposure of cells, tissues and extracellular matrix to harmful reactive species causes a cascade of reactions and induces activation of multiple internal defence mechanisms (enzymatic or non-enzymatic) that provide removal of reactive species and their derivatives. The non-enzymatic antioxidants are represented by molecules characterized by the ability to rapidly inactivate radicals and oxidants. This paper focuses on the major intrinsic non-enzymatic antioxidants, including metal binding proteins (MBPs), glutathione (GSH), uric acid (UA), melatonin (MEL), bilirubin (BIL) and polyamines (PAs).

An overview of sleep and circadian dysfunction in Parkinson's disease

Sleep and circadian alterations are amongst the very first symptoms experienced in Parkinson's disease, and sleep alterations are present in the majority of patients with overt clinical manifestation of Parkinson's disease. However, the magnitude of sleep and circadian dysfunction in Parkinson's disease, and its influence on the pathophysiology of Parkinson's disease remains often unclear and a matter of debate. In particular, the confounding influences of dopaminergic therapy on sleep and circadian dysfunction are a major challenge, and need to be more carefully addressed in clinical studies. The scope of this narrative review is to summarise the current knowledge around both sleep and circadian alterations in Parkinson's disease. We provide an overview on the frequency of excessive daytime sleepiness, insomnia, restless legs, obstructive apnea and nocturia in Parkinson's disease, as well as addressing sleep structure, rapid eye movement sleep behaviour disorder and circadian features in Parkinson's disease. Sleep and circadian disorders have been linked to pathological conditions that are often co-morbid in Parkinson's disease, including cognitive decline, memory impairment and neurodegeneration. Therefore, targeting sleep and circadian alterations could be one of the earliest and most promising opportunities to slow disease progression. We hope that this review will contribute to advance the discussion and inform new research efforts to progress our knowledge in this field.

Lipopolysaccharide-binding protein (LBP) can reverse the amyloid state of fibrin seen or induced in Parkinson's disease

The thrombin-induced polymerisation of fibrinogen to form fibrin is well established as a late stage of blood clotting. It is known that Parkinson's Disease (PD) is accompanied by dysregulation in blood clotting, but it is less widely known as a coagulopathy. In recent work, we showed that the presence of tiny amounts of bacterial lipopolysaccharide (LPS) in healthy individuals could cause clots to adopt an amyloid form, and this could be observed via scanning electron microscopy (SEM) or via the fluorescence of thioflavin-T. This could be prevented by the prior addition of lipopolysaccharide-binding protein (LBP). We had also observed by SEM this unusual clotting in the blood of patients with Parkinson's Disease. We hypothesised, and here show, that this too can be prevented by LBP in the context of PD. This adds further evidence implicating inflammatory microbial cell wall products as an accompaniment to the disease, and may be part of its aetiology. This may lead to novel treatment strategies in PD designed to target microbes and their products.

The Toxmatrix: Chemo-Genomic Profiling Identifies Interactions That Reveal Mechanisms of Toxicity

A chemical genomics "Toxmatrix" method was developed to elucidate mechanisms of cytotoxicity using neuronal models. Quantitative high-throughput screening (qHTS) was applied to systematically screen each toxicant against a panel of 70 modulators, drugs or chemicals that act on a known target, to identify interactions that either protect or sensitize cells to each toxicant. Thirty-two toxicants were tested at 10 concentrations for cytotoxicity to SH-SY5Y human neuroblastoma cells, with results fitted to the Hill equation to determine an IC50 for each toxicant. Thirty-three toxicant:modulator interactions were identified in SH-SY5Y cells for 14 toxicants, as modulators that shifted toxicant IC50 values lower or higher. The target of each modulator that sensitizes cells or protects cells from a toxicant suggests a mode of toxicant action or cellular adaptation. In secondary screening, we tested modulator-toxicant pairs identified from the SH-SY5Y primary screening for interactions in three differentiated neuronal human cell lines: dSH-SY5Y, conditionally immortalized dopaminergic neurons (LUHMES), and neural stem cells. Twenty toxicant-modulator pairs showed pronounced interactions in one or several differentiated cell models. Additional testing confirmed that several modulators acted through their primary targets. For example, several chelators protected differentiated LUHMES neurons from four toxicants by chelation of divalent cations and buthionine sulphoximine sensitized cells to 6-hydroxydopamine and 4-(methylamino)phenol hemisulfate by blocking glutathione synthesis. Such modulators that interact with multiple neurotoxicants suggest these may be vulnerable toxicity pathways in neurons. Thus, the Toxmatrix method is a systematic high-throughput approach that can identify mechanisms of toxicity and cellular adaptation.

Riboflavin in Human Health: A Review of Current Evidences

Riboflavin is a water-soluble vitamin, which was initially isolated from milk. There are two coenzyme forms of riboflavin, flavin mononucleotide and flavin adenine dinucleotide, in which riboflavin plays important roles in the enzymatic reactions. Riboflavin is found in a wide variety of animal and plant foods. Meat and dairy products are the major contributors of riboflavin dietary intake. In this chapter, the latest evidence on the relationship between riboflavin status and specific health risks will be reviewed. Also, some of the mechanisms by which riboflavin exerts its roles will be discussed. The evidence accrued suggests that riboflavin is an antioxidant nutrient which may prevent lipid peroxidation and reperfusion oxidative injury. Moreover, riboflavin deficiency may increase the risk of some cancers. Riboflavin may also exert a neuroprotective effects in some neurological disorders (e.g., Parkinson disease, migraine, and multiple sclerosis) through its role in some pathways that are hypothesized to be impaired in neurological disorders such as antioxidation, myelin formation, mitochondrial function, and iron metabolism.

The best medicine? The influence of physical activity and inactivity on Parkinson's disease

The incidence of Parkinson's disease (PD) is expected to increase as our population ages and will likely strain the projected capacity of our health care system. Despite being the most common movement disorder, there have been few noninvasive therapeutic advances for people with PD since the first levodopa clinical trial in 1961. The study of PD pathogenesis, combined with an appreciation for the biochemical mechanisms by which physical activity and exercise may impact physiology, has resulted in emerging hypotheses for new modifiable risk factors for PD. Physical activity and exercise as a means of preventing PD, or maintaining the functionality of people with PD, are a promising area of investigation. Conversely, physical inactivity is implicated in many disease states, some of which are also correlated with the development of PD, such as metabolic syndrome. The primary relationship between these diseases is likely rooted in heightened inflammation and oxidative stress at the cellular level. Physical activity and exercise as a means of attenuating inflammation have led to increased interest in related potential therapeutic targets for PD. Ultimately, these findings may translate into low-cost, universally available therapies for PD disease modification or prevention. © 2016 International Parkinson and Movement Disorder Society.

Therapeutic Potential of Baicalein in Alzheimer's Disease and Parkinson's Disease

Alzheimer's disease and Parkinson's disease are the two most common, progressive central neurodegenerative diseases affecting the population over the age of 60 years. Apart from treatments that temporarily improve symptoms, there is no medicine currently available to inhibit or reverse the progression of Alzheimer's disease and Parkinson's disease. In traditional Chinese medicine, the root of Scutellaria baicalensis Georgi is a classic compatible component in the decoction of herbal medicine used for treating central nervous system diseases. Modern pharmacokinetic studies have confirmed that baicalein (5,6,7-trihydroxyflavone) is a major bioactive flavone constituent root of S. baicalensis Georgi. Studies showed that baicalein possesses a range of key pharmacological properties, such as reducing oxidative stress, anti-inflammatory properties, inhibiting aggregation of disease-specific amyloid proteins, inhibiting excitotoxicity, stimulating neurogenesis and differentiation action, and anti-apoptosis effects. Based on these properties, baicalein shows therapeutic potential for Alzheimer's disease and Parkinson's disease. In this review, we summarize the pharmacological protective actions of baicalein that make it suitable for the treatment of Alzheimer's disease and Parkinson's disease, and discuss the potential mechanisms underlying the effects.

Deferiprone Rescues Behavioral Deficits Induced by Mild Iron Exposure in a Mouse Model of Alpha-Synuclein Aggregation

Parkinson's disease (PD) is the most common neurodegenerative movement disorder, and its causes remain unknown. A major hallmark of the disease is the increasing presence of aggregated alpha-synuclein (aSyn). Furthermore, there is a solid consensus on iron (Fe) accumulation in several regions of PD brains during disease progression. In our study, we focused on the interaction of Fe and aggregating aSyn in vivo in a transgenic mouse model overexpressing human aSyn bearing the A53T mutation (prnp.aSyn.A53T). We utilized a neonatal iron-feeding model to exacerbate the motor phenotype of the transgenic mouse model. Beginning from day 100, mice were treated with deferiprone (DFP), a ferric chelator that is able to cross the blood-brain barrier and is currently used in clinics as treatment for hemosiderosis. Our paradigm resulted in an impairment of the learning abilities in the rotarod task and the novel object recognition test. DFP treatment significantly improved the performance in both tasks. Although this was not accompanied by alterations in aSyn aggregation, our results support DFP as possible therapeutic option in PD.

Hypoxia-inducible factor-1α plays roles in Epstein-Barr virus's natural life cycle and tumorigenesis by inducing lytic infection through direct binding to the immediate-early BZLF1 gene promoter

When confronted with poor oxygenation, cells adapt by activating survival signaling pathways, including the oxygen-sensitive transcriptional regulators called hypoxia-inducible factor alphas (HIF-αs). We report here that HIF-1α also regulates the life cycle of Epstein-Barr virus (EBV). Incubation of EBV-positive gastric carcinoma AGS-Akata and SNU-719 and Burkitt lymphoma Sal and KemIII cell lines with a prolyl hydroxylase inhibitor, L-mimosine or deferoxamine, or the NEDDylation inhibitor MLN4924 promoted rapid and sustained accumulation of both HIF-1α and lytic EBV antigens. ShRNA knockdown of HIF-1α significantly reduced deferoxamine-mediated lytic reactivation. HIF-1α directly bound the promoter of the EBV primary latent-lytic switch BZLF1 gene, Zp, activating transcription via a consensus hypoxia-response element (HRE) located at nt -83 through -76 relative to the transcription initiation site. HIF-1α did not activate transcription from the other EBV immediate-early gene, BRLF1. Importantly, expression of HIF-1α induced EBV lytic-gene expression in cells harboring wild-type EBV, but not in cells infected with variants containing base-pair substitution mutations within this HRE. Human oral keratinocyte (NOK) and gingival epithelial (hGET) cells induced to differentiate by incubation with either methyl cellulose or growth in organotypic culture accumulated both HIF-1α and Blimp-1α, another cellular factor implicated in lytic reactivation. HIF-1α activity also accumulated along with Blimp-1α during B-cell differentiation into plasma cells. Furthermore, most BZLF1-expressing cells observed in lymphomas induced by EBV in NSG mice with a humanized immune system were located distal to blood vessels in hypoxic regions of the tumors. Thus, we conclude that HIF-1α plays central roles in both EBV’s natural life cycle and EBV-associated tumorigenesis. We propose that drugs that induce HIF-1α protein accumulation are good candidates for development of a lytic-induction therapy for treating some EBV-associated malignancies.

Most adults throughout the world are infected with Epstein-Barr virus (EBV), a human herpesvirus frequently associated in a latent state with some cancers of epithelial and B-cell origin such as nasopharyngeal carcinoma and Burkitt lymphoma, respectively. To develop an oncolytic therapy for treating patients with EBV-associated cancers, we need a method to efficiently induce synthesis of lytic EBV proteins. The EBV protein encoded by its immediate-early BZLF1 gene usually mediates the switch into lytic viral infection. We show here that HIF-1α, a cellular transcription factor that accumulates in cells when deprived of normal levels of oxygen, can induce lytic EBV infection. HIF-1α mediates this switch by directly binding to a specific sequence located within the BZLF1 gene promoter, activating its expression. Importantly, we also show that deferoxamine, an FDA-approved drug that inhibits degradation of HIF-1α, can induce synthesis of lytic EBV proteins in some EBV-positive epithelial and lymphocytic cell lines. These findings indicate that HIF-1α-stabilizing drugs, administered in combination with nucleoside analogues such as ganciclovir, may be helpful as part of a lytic-induction therapy for treating some patients with EBV-positive malignancies.

A novel iron (II) preferring dopamine agonist chelator D-607 significantly suppresses α-syn- and MPTP-induced toxicities in vivo

Here, we report the characterization of a novel hybrid D₂/D₃ agonist and iron (II) specific chelator, D-607, as a multi-target-directed ligand against Parkinson's disease (PD). In our previously published report, we showed that D-607 is a potent agonist of dopamine (DA) D₂/D₃ receptors, exhibits efficacy in a reserpinized PD animal model and preferentially chelates to iron (II). As further evidence of its potential as a neuroprotective agent in PD, the present study reveals D-607 to be protective in neuronal PC12 cells against 6-OHDA toxicity. In an in vivo Drosophila melanogaster model expressing a disease-causing variant of α-synuclein (α-Syn) protein in fly eyes, the compound was found to significantly suppress toxicity compared to controls, concomitant with reduced levels of aggregated α-Syn. Furthermore, D-607 was able to rescue DAergic neurons from MPTP toxicity in mice, a well-known PD neurotoxicity model, following both sub-chronic and chronic MPTP administration. Mechanistic studies indicated that possible protection of mitochondria, up-regulation of hypoxia-inducible factor, reduction in formation of α-Syn aggregates and antioxidant activity may underlie the observed neuroprotection effects. These observations strongly suggest that D-607 has potential as a promising multifunctional lead molecule for viable symptomatic and disease-modifying therapy for PD.

A Novel Iron(II) Preferring Dopamine Agonist Chelator as Potential Symptomatic and Neuroprotective Therapeutic Agent for Parkinson's Disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder, and development of disease-modifying treatment is still an unmet medical need. Considering the implication of free iron(II) in PD, we report here the design and characterization of a novel hybrid iron chelator, (-)-12 (D-607) as a multitarget-directed ligand against PD. Binding and functional assays at dopamine D₂/D₃ receptors indicate potent agonist activity of (-)-12. The molecule displayed an efficient preferential iron(II) chelation properties along with potent in vivo activity in a reserpinized PD animal model. The compound also rescued PC12 cells from toxicity induced by iron delivered intracellularly in a dose-dependent manner. However, Fe³⁺ selective dopamine agonist 1 and a well-known antiparkinsonian drug pramipexole produced little to no neuroprotection effect under the same experimental condition. These observations strongly suggest that (-)-12 should be a promising multifunctional lead molecule for a viable symptomatic and disease modifying therapy of PD.

Natural product-based amyloid inhibitors

Many chronic human diseases, including multiple neurodegenerative diseases, are associated with deleterious protein aggregates, also called protein amyloids. One common therapeutic strategy is to develop protein aggregation inhibitors that can slow down, prevent, or remodel toxic amyloids. Natural products are a major class of amyloid inhibitors, and several dozens of natural product-based amyloid inhibitors have been identified and characterized in recent years. These plant- or microorganism-extracted compounds have shown significant therapeutic potential from in vitro studies as well as in vivo animal tests. Despite the technical challenges of intrinsic disordered or partially unfolded amyloid proteins that are less amenable to characterizations by structural biology, a significant amount of research has been performed, yielding biochemical and pharmacological insights into how inhibitors function. This review aims to summarize recent progress in natural product-based amyloid inhibitors and to analyze their mechanisms of inhibition in vitro. Major classes of natural product inhibitors and how they were identified are described. Our analyses comprehensively address the molecular interactions between the inhibitors and relevant amyloidogenic proteins. These interactions are delineated at molecular and atomic levels, which include covalent, non-covalent, and metal-mediated mechanisms. In vivo animal studies and clinical trials have been summarized as an extension. To enhance natural product bioavailability in vivo, emerging work using nanocarriers for delivery has also been described. Finally, issues and challenges as well as future development of such inhibitors are envisioned.

FBXL5 Inactivation in Mouse Brain Induces Aberrant Proliferation of Neural Stem Progenitor Cells

FBXL5 is the substrate recognition subunit of an SCF-type ubiquitin ligase that serves as a master regulator of iron metabolism in mammalian cells. We previously showed that mice with systemic deficiency of FBXL5 fail to sense intracellular iron levels and die in utero at embryonic day 8.5 (E8.5) as a result of iron overload and subsequent oxidative stress. This early embryonic mortality has thus impeded study of the role of FBXL5 in brain development. We have now generated mice lacking FBXL5 specifically in nestin-expressing neural stem progenitor cells (NSPCs) in the brain. Unexpectedly, the mutant embryos manifested a progressive increase in the number of NSPCs and astroglia in the cerebral cortex. Stabilization of iron regulatory protein 2 (IRP2) as a result of FBXL5 deficiency led to accumulation of ferrous and ferric iron as well as to generation of reactive oxygen species. Pharmacological manipulation suggested that the phenotypes of FBXL5 deficiency are attributable to aberrant activation of mammalian target of rapamycin (mTOR) signaling. Our results thus show that FBXL5 contributes to regulation of NSPC proliferation during mammalian brain development.

Anti-Oxidants in Parkinson's Disease Therapy: A Critical Point of View

Parkinson’s disease (PD) is a degenerative neurological syndrome, which is characterized by the preferential death of dopaminergic (DAergic) neurons in the Substantia Nigra. The pathogenesis of this disorder remains poorly understood and PD is still incurable. Current drug treatments are aimed primarily for the treatment of symptoms to improve the quality of life. Therefore, there is a need to find out new therapeutic strategies that not only provide symptomatic relief but also halt or reverse the neuronal damage hampering PD progression. Oxidative stress has been identified as one of the major contributors for the nigral loss in both sporadic and genetic forms of PD. In this review we first evaluate the current literature that links oxidative stress and mitochondrial dysfunction to PD. We then consider the results obtained through the treatment of animal models or PD patients with molecules that prevent oxidative stress or reduce mitochondrial dysfunction.

A time-course analysis of changes in cerebral metal levels following a controlled cortical impact

Traumatic brain injury (TBI) is complicated by a sudden and dramatic change in brain metal levels, including iron (Fe), copper (Cu) and zinc (Zn). Specific 'metallo-pathological' features of TBI include increased non-heme bound Fe and the liberation of free Zn ions, both of which may contribute to the pathogenesis of TBI. To further characterise the metal dyshomeostasis that occurs following brain trauma, we performed a quantitative time-course survey of spatial Fe, Cu and Zn distribution in mice receiving a controlled cortical impact TBI. Images of brain metal levels produced using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) in the upper quadrant of the ipsilateral hemisphere were compared to the corresponding contralateral hemisphere, together with regional areas radiating toward the center of the brain from the site of lesion. Significant regional and time point specific elevations in Fe, Zn and Cu were detected immediately and up to 28 days after TBI. The magnitude and timeframe of many of these changes suggest that TBI results in a pronounced and sustained alteration in normal metal levels within the brain. Such alterations are likely to play a role in both the short- and long-term consequences of head trauma and suggest that pharmacological modulation to normalize these metal levels may be efficacious in improving functional outcome.

Iron chelation in the treatment of neurodegenerative diseases

Disturbance of cerebral iron regulation is almost universal in neurodegenerative disorders. There is a growing body of evidence that increased iron deposits may contribute to degenerative changes. Thus, the effect of iron chelation therapy has been investigated in many neurological disorders including rare genetic syndromes with neurodegeneration with brain iron accumulation as well as common sporadic disorders such as Parkinson's disease, Alzheimer's disease, and multiple sclerosis. This review summarizes recent advances in understanding the role of iron in the etiology of neurodegeneration. Outcomes of studies investigating the effect of iron chelation therapy in neurodegenerative disorders are systematically presented in tables. Iron chelators, particularly the blood brain barrier-crossing compound deferiprone, are capable of decreasing cerebral iron in areas with abnormally high concentrations as documented by MRI. Yet, currently, there is no compelling evidence of the clinical effect of iron removal therapy on any neurological disorder. However, several studies indicate that it may prevent or slow down disease progression of several disorders such as aceruloplasminemia, pantothenate kinase-associated neurodegeneration or Parkinson's disease.

The prion-ZIP connection: From cousins to partners in iron uptake

Converging observations from disparate lines of inquiry are beginning to clarify the cause of brain iron dyshomeostasis in sporadic Creutzfeldt-Jakob disease (sCJD), a neurodegenerative condition associated with the conversion of prion protein (PrP^C), a plasma membrane glycoprotein, from α-helical to a β-sheet rich PrP-scrapie (PrP^Sc) isoform. Biochemical evidence indicates that PrP^C facilitates cellular iron uptake by functioning as a membrane-bound ferrireductase (FR), an activity necessary for the transport of iron across biological membranes through metal transporters. An entirely different experimental approach reveals an evolutionary link between PrP^C and the Zrt, Irt-like protein (ZIP) family, a group of proteins involved in the transport of zinc, iron, and manganese across the plasma membrane. Close physical proximity of PrP^C with certain members of the ZIP family on the plasma membrane and increased uptake of extracellular iron by cells that co-express PrP^C and ZIP14 suggest that PrP^C functions as a FR partner for certain members of this family. The connection between PrP^C and ZIP proteins therefore extends beyond common ancestry to that of functional cooperation. Here, we summarize evidence supporting the facilitative role of PrP^C in cellular iron uptake, and implications of this activity on iron metabolism in sCJD brains.

A Fluorescent Sensor for Al(III) and Colorimetric Sensor for Fe(III) and Fe(II) Based on a Novel 8-Hydroxyquinoline Derivative

A novel 8-hydroxyquinoline-based fluorescent and colorimetric chemosensor was designed, synthesized and fully characterized. The sensor showed high selectivity and sensitivity toward Al(3+) over other tested cations in EtOH/H2O (1:99, v/v) medium. The increase in fluorescence intensity was linearly proportional to the concentration of Al(3+) with a detection limit of 7.38 × 10(-6) M. Moreover, the sensor exhibited an obvious color change from yellow to black in the presence of Fe(2+) and Fe(3+) in EtOH/THF (99:1, v/v) solution. The absorbance changes showed a linear response to iron ions with the detection limits of 4.24 × 10(-7) M and 5.60 × 10(-7) M for Fe(2+) and Fe(3+), respectively. Thus, this chemosensor provides a novel approach for selectively recognition of Al(3+), Fe(3+) and Fe(2+) among environmentally relevant metal ions.