Copper neurotoxicity is dependent on dopamine-mediated copper uptake and one-electron reduction of aminochrome in a rat substantia nigra neuronal cell line

Biological effects of a copper-based fungicide on the fruit fly, Drosophila melanogaster

The increased consumption of pesticides can have a negative environmental impact by increasing the essential metals to toxic levels. Bordasul® is a commonly used fungicide in Brazil and it is composed of 20% Cu, 10% sulfur, and 3.0% calcium. The study of fungicides in vivo in non-target model organisms can predict their environmental impact more broadly. The Drosophila melanogaster is a unique model due to its ease of handling and maintenance. Here, the potential toxicity of Bordasul® was investigated by assessing the development, survival, and behavior of exposed flies. Exposure to Bordasul® impaired the development (p < 0.01) and caused a significant reduction in memory retention (p < 0.05) and locomotor ability (p < 0.001). Fungicides are needed to assure the world's food demand; however, Bordasul® was highly toxic to D. melanogaster. Therefore, Bordasul® may be potentially toxic to non-target invertebrates and new environmentally-safe biofertilizers have to be developed to preserve the biota.

To what extent may aminochrome increase the vulnerability of dopaminergic neurons in the context of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder that progresses over time and is characterized by preferential reduction of dopaminergic neurons in the substantia nigra. Although the precise mechanisms leading to cell death in neurodegenerative disorders, such as PD, are not fully understood, it is widely accepted that increased oxidative stress may be a prevalent factor contributing to the deterioration of the nigrostriatal dopaminergic fibers in such conditions. Aminochrome, generated from dopamine (DA) metabolism, plays an important role in multiple pathogenic mechanisms associated with PD. Its capacity to induce a gradual reduction in dopaminergic neurons is due to its endogenous neurotoxicity. The formation of aminochrome results in the production of various reactive oxygen species (ROS), including pro-inflammatory factors, superoxide, nitric oxide, and hydroxyl radicals. This, in turn, causes loss of dopaminergic neurons, reducing DA uptake, and reduced numbers and shortened dendrites. Notably, o-quinones, which are more cytotoxic, arise from the oxidation of DA and possess a higher capacity to impede cellular defense mechanisms, thereby resulting in the death of neuronal cells. Aminochrome potentially contributes to the pathophysiology of PD by forming adducts with various proteins. All of the aforementioned effects suggest that aminochrome may play a crucial role in the pathophysiology of PD. Thus, aminochrome may serve as a more relevant preclinical model for PD, facilitating a better understanding of its pathophysiological processes and identification of novel therapeutic strategies aimed at preventing or slowing disease progression.

Hormone-linked redox status and its modulation by antioxidants

Hormones have been considered as key factors involved in the maintenance of the redox status of the body. We are making considerable progress in understanding interactions between the endocrine system, redox status, and oxidative stress with the dynamics of life, which encompasses fertilization, development, growth, aging, and various pathophysiological states. One of the reasons for changes in redox states of vertebrates leading to oxidative stress scenario is the disruption of the endocrine system. Comprehending the dynamics of hormonal status to redox state and oxidative stress in living systems is challenging. It is more difficult to come to a unifying conclusion when some hormones exhibit oxidant properties while others have antioxidant features. There is a very limited approach to correlate alteration in titers of hormones with redox status and oxidative stress with growth, development, aging, and pathophysiological stress. The situation is further complicated when considering various tissues and sexes in vertebrates. This chapter discusses the beneficial impacts of hormones with antioxidative properties, such as melatonin, glucagon, insulin, estrogens, and progesterone, which protect cells from oxidative damage and reduce pathophysiological effects. Additionally, we discuss the protective effects of antioxidants like vitamins A, E, and C, curcumin, tempol, N-acetyl cysteine, α-lipoic acid, date palm pollen extract, resveratrol, and flavonoids on oxidative stress triggered by hormones such as aldosterone, glucocorticoids, thyroid hormones, and catecholamines. Inflammation, pathophysiology, and the aging process can all be controlled by understanding how antioxidants and hormones operate together to maintain cellular redox status. Identifying the hormonal changes and the action of antioxidants may help in developing new therapeutic strategies for hormonal imbalance-related disorders.

Recent Advances in Chemodosimeters Designed for Amines

The analysis of amines has long been a very important task in science, industry, and healthcare. To date, this task has been accomplished by using expensive and time-consuming methods. Colorimetric and fluorescent chemodosimeters enable the fast, accurate, and sensitive analysis of various species with inexpensive instruments or the naked eye. Accordingly, the studies on these probes have gained great momentum in the last 20 years. In this review, amine chemodosimeters developed in the last 10 years were investigated. The investigated chemodosimeters are metal-free structures based on small organic compounds. The strategies for the detection, differentiation, and quantification of amines were discussed by considering the reaction types.

Quantitative Determination of Endogenous Tetrahydroisoquinolines, Potential Parkinson's Disease Biomarkers, in Mammals

Current diagnostic options for Parkinson's disease are very limited and primarily based on characteristic clinical symptoms. Thus, there are urgent needs for reliable biomarkers that enable us to diagnose the disease in the early stages, differentiate it from other atypical Parkinsonian syndromes, monitor its progression, increase knowledge of its pathogenesis, and improve the development of potent therapies. A promising group of potential biomarkers are endogenous tetrahydroisoquinoline metabolites, which are thought to contribute to the multifactorial etiology of Parkinson's disease. The aim of this critical review is to highlight trends and limitations of available traditional and modern analytical techniques for sample pretreatment (extraction and derivatization procedures) and quantitative determination of tetrahydroisoquinoline derivatives in various types of mammalian fluids and tissues (urine, plasma, cerebrospinal fluid, brain tissue, liver tissue). Particular attention is paid to the most sensitive and specific analytical techniques, involving immunochemistry and gas or liquid chromatography coupled with mass spectrometric, fluorescence, or electrochemical detection. The review also includes a discussion of other relevant agents proposed and tested in Parkinson's disease.

Quercetin Attenuates Copper-Induced Apoptotic Cell Death and Endoplasmic Reticulum Stress in SH-SY5Y Cells by Autophagic Modulation

An increase in anthropogenic activities results in metal contamination in the ecosystem which has proven to be a major health risk in humans, as they make entry into cellular organelles via agricultural products. Copper (Cu) is one such metal that acts as an essential cofactor for the activity of several enzymes, one being the cytochrome c oxidase. The increasing number of evidence suggests a substantial correlation of Cu overload with neurodegenerative disorders, including Parkinson's disease (PD). We aim to explore quercetin, a well-known polyphenol, as an alternative for combating Cu-induced toxicity in human neuroblastoma SH-SY5Y secondary cell lines. We observed that Cu increased intracellular reactive oxygen species (ROS) levels, triggered morphological deformities and condensation of nuclei, caused an imbalance in the mitochondrial membrane potential (MMP), and finally induced apoptotic cell deaths. We further investigated the effects of Cu in modulating the pro- and anti-apoptotic proteins, such as Bax, Bcl-2, etc. However, quercetin reversed these changes owing to its antioxidant and anti-apoptotic properties, resulting in autophagy induction as an outcome of upregulation of autophagosome-bound microtubules-associated protein light chain-3 (LC3II). Besides, we investigated the role of Cu in stimulating ER stress proteins, viz. PERK, CHOP, and the concomitant responses of quercetin in restoring the ER homeostasis in cellular organelles like mitochondria and ER, against Cu-induced toxic insults by modulating autophagic pathways. Overall, this research work proposes a remedial approach for Cu-mediated neurotoxicity through understanding the diverse molecular signaling inside a cell with an aim to develop effective therapeutics.

Comparison of the Pharmacokinetic Profiles of Trientine Tetrahydrochloride and Trientine Dihydrochloride in Healthy Subjects

BACKGROUND AND OBJECTIVE

Wilson disease (WD) is an autosomal recessive inherited disorder of copper metabolism. Chelation of excessive copper is recommended but data on the pharmacokinetics of trientine are limited. The aim of this study was to compare the pharmacokinetics of a new trientine tetrahydrochloride formulation (TETA 4HCl) with those of an established trientine dihydrochloride (TETA 2HCl) salt.

METHODS

A randomised single-centre crossover study to evaluate the pharmacokinetics, safety and tolerability of two different oral formulations of trientine (TETA 4HCl tablets vs TETA 2HCl capsules) in 23 healthy adult subjects receiving a single dose equivalent to 600 mg of trientine base was performed.

RESULTS

Following oral administration, the median time to reach maximum plasma concentration (T_max) was 2.00 h (TETA 4HCl) and 3.00 h (TETA 2HCl). The rate (maximum plasma concentration [C_max]) and extent (area under the plasma concentration-time curve from time zero to infinity [AUC_0-∞]) of absorption of the active moiety, trientine, were greater (by approximately 68% and 56%, respectively) for TETA 4HCl than for the TETA 2HCl formulation. The two formulations presented a similar terminal elimination rate (λ_z) and a similar terminal half-life (t_½) for trientine. Differences between TETA 4HCl and TETA 2HCl in the levels of the two main mono- and diacetylated metabolites were less than seen for trientine. For both tested formulations, healthy male volunteers demonstrated higher trientine plasma levels but lower mono- and diacetylated metabolite levels compared with females, with no sex differences in terminal half-life (t_½) observed. Single oral doses of both formulations were safe and well tolerated.

CONCLUSIONS

Compared with an identical dose of a TETA 2HCl formulation, the TETA 4HCl formulation provided more rapid absorption of trientine and greater systemic exposure in healthy subjects. Clinical Trials Number EudraCT # 2015-002199-25.

Roundup negatively impacts the behavior and nerve function of the Madagascar hissing cockroach (Gromphadorhina portentosa)

Glyphosate is the active ingredient in Roundup formulations. Glyphosate-based herbicides are used globally in agriculture, forestry, horticulture, and in urban settings. Glyphosate can persist for years in our soil, potentially impacting the soil-dwelling arthropods that are primary drivers of a suite of ecosystem services. Furthermore, although glyphosate is not generally classified as neurotoxic to insects, evidence suggests that it may cause nerve damage in other organisms. In a series of experiments, we used food to deliver environmentally realistic amounts of Roundup ready-to-use III, a common 2% glyphosate-based herbicide formulation that lists isopropylamine salt as its active ingredient, to Madagascar hissing cockroaches. We then assessed the impact of contamination on body mass, nerve health, and behavior. Contaminated food contained both 30.6 mg glyphosate and so-called inert ingredients. Food was refreshed weekly for 26-60 days, depending on the experiment. We found that consumption of contaminated food did not impact adult and juvenile survivorship or body weight. However, consumption of contaminated food decreased ventral nerve cord action-potential velocity by 32%, caused a 29% increase in respiration rate, and caused a 74.4% decrease in time spent on a motorized exercise wheel. Such changes in behavior may make cockroaches less capable of fulfilling their ecological service, such as pollinating or decomposing litter. Furthermore, their lack of coordination may make them more susceptible to predation, putting their population at risk. Given the decline of terrestrial insect abundance, understanding common risks to terrestrial insect populations has never been more critical. Results from our experiments add to the growing body of literature suggesting that this popular herbicide can act as a neurotoxin.

A pharmacological review of dicoumarol: An old natural anticoagulant agent

Dicoumarol is an oral anticoagulant agent prescribed in clinical for decades. It is a natural hydroxycoumarin discovered from the spoilage of Melilotus officinalis (L.) Pall and is originally discovered as a rodenticide. Due to its structural similarity to that of vitamin K, it significantly inhibits vitamin K epoxide reductase and acts as a vitamin K antagonist. Dicoumarol is mainly used as an anticoagulant to prevent thrombogenesis and to cure vascular thrombosis. Other biological activities besides anticoagulants such as anticancer, antimicrobial, antiviral, etc., have also been documented. The side effects of dicoumarol raise safety concerns for clinical application. In this review, the physicochemical property, the pharmacological activities, the side effects, and the pharmacokinetics of dicoumarol were summarized, aiming to provide a whole picture of the "old" anticoagulant.

Curcumin attenuates copper-induced oxidative stress and neurotoxicity in Drosophila melanogaster

Curcumin is a hydrophobic polyphenol derived from the rhizome of the Herb Curcuma longa belonging to the family Zingiberaceae. Curcumin possesses antioxidative, anti-inflammatory and anti-depressant-like properties. In this study, we evaluated the rescue role of Curcumin in Copper²⁺-induced toxicity in D. melanogaster. Adult, wild type flies were exposed to Cu²⁺ (1 mM) and/or Curcumin (0.2 and 0.5 mg/kg diet) in the diet for 7 days. The results indicated that Cu²⁺- fed flies had reduced survival compared to the control group. Copper toxicity was also associated with a marked decrease in total thiol (T-SH), as well as catalase and glutathione S-transferase activities, contemporaneous with increased acetylcholinesterase (AChE) activity, nitric oxide (nitrate and nitrite) and dopamine levels. Co-exposure of flies to Cu²⁺ and Curcumin prevented mortality, inhibited AChE activity and restored dopamine to normal levels (p < 0.05). Moreover, Curcumin restored eclosion rates, and the cellular antioxidant status, as well as alleviated the accumulation of nitric oxide level in the flies. Curcumin ameliorated oxidative damage in the flies as evidenced by the survival rates, longevity assay as well as the restoration of antioxidant status. Our findings thus suggest that Curcumin ameliorated Cu²⁺-induced neurotoxicity in D. melanogaster and as such could be considered an effective therapeutic agent in the prevention and treatment of disorders, where oxidative stress is implicated.

Iron Redox Chemistry and Implications in the Parkinson's Disease Brain

The etiology of Parkinson's disease (PD) is linked with cellular inclusions in the substantia nigra pars compacta region of the brain that are enriched in the misfolded presynaptic protein α-synuclein (αS) and death of the dopaminergic neurons. Brain iron homeostasis governs both neurotransmission and neurodegeneration; hence, the role of iron in PD progression and neuronal health is apparent. Elevated iron deposits become prevalent in the cerebral region upon aging and even more so in the PD brain. Structural as well as oxidative modifications can result from coordination of αS with redox active iron, which could have functional and/or pathological implications. In this review, we will discuss iron-mediated αS aggregation, alterations in iron metabolism, and the role of the iron-dopamine couple. Moreover, iron interactions with N-terminally acetylated αS, the physiologically relevant form of the human protein, will be addressed to shed light on the current understanding of protein dynamics and the physiological environment in the disease state. Oxidative pathways and biochemical alterations resulting from aberrant iron-induced chemistry are the principal focus of this review in order to highlight the plethora of research that has uncovered this emerging dichotomy of iron playing both functional and disruptive roles in PD pathology.

Impact of Dopamine Oxidation on Dopaminergic Neurodegeneration

Parkinson's disease (PD) is the second most common neurodegenerative disease. The characteristic feature of PD is the progressive degeneration of the dopaminergic (DAergic) neurons in the substantia nigra (SN). DAergic neurons in the SN accumulate black and insoluble membrane structures known as neuromelanin during aging. The oxidation of dopamine (DA) to form neuromelanin generates many o-quinones, including DA o-quinones, aminochrome, and 5,6-indolequinone. The focus of this review is to discuss the role of DA oxidation in association with PD. The oxidation of DA produces oxidative products, inducing mitochondrial dysfunction, impaired protein degradation, α-synuclein aggregation into neurotoxic oligomers, and oxidative stress, in vitro. Recent studies have demonstrated that the DA content is critical for both DJ-1 knockout and A53T α-synuclein transgenic mice to develop PD pathological features, providing evidence for DA action in PD pathogenesis in vivo. The effects of L-DOPA, as the most effective anti-PD drug, are also briefly discussed.

Association of copper levels in the hair with gray matter volume, mean diffusivity, and cognitive functions

Although copper plays a critical role in normal brain functions and development, it is known that excess copper causes toxicity. Here we investigated the associations of copper levels in the hair with regional gray matter volume (rGMV), mean diffusivity (MD), and cognitive differences in a study cohort of 924 healthy young adults. Our findings showed that high copper levels were associated mostly with low cognitive abilities (low scores on the intelligence test consisting of complex speed tasks, involving reasoning task, a complex arithmetic task, and a reading comprehension task) as well as lower reverse Stroop interference, high rGMV over widespread areas of the brain [mainly including the bilateral lateral and medial parietal cortices, medial temporal structures (amygdala, hippocampus, and parahippocampal gyrus), middle cingulate cortex, orbitofrontal cortex, insula, perisylvian areas, inferior temporal lobe, temporal pole, occipital lobes, and supplementary motor area], as well as high MD of the right substantia nigra and bilateral hippocampus, which are indicative of low density in brain tissues. These results suggest that copper levels are associated with mostly aberrant cognitive functions, greater rGMV in extensive areas, greater MD (which are indicative of low density in brain tissues) in subcortical structures in the healthy young adults, possibly reflecting copper's complex roles in neural mechanisms.

Neuronal, astroglial and locomotor injuries in subchronic copper intoxicated rats are repaired by curcumin: A possible link with Parkinson's disease

We aim herein to assess the neurotoxic effects of subchronic Cu-exposition (0125%) for 6 weeks on dopaminergic and astroglial systems then locomotor activity in rats as well as the probable therapeutic efficiency of curcumin-I (30 mg/kg B.W.). We found that intoxicated rats showed a significant impairment of Tyrosine Hydroxylase (TH) within substantia nigra pars compacta (SNc), ventral tegmental area (VTA) and the striatal outputs together with loss expression of GFAP in these structures. This was linked with an evident decrease in locomotor performance. Co-treatment with curcumin-I inverted these damages and exhibited a significant neuroprotective potential, thus, both TH expression and locomotor performance was reinstated in intoxicated rats. These results prove a profound dopaminergic and astroglial damages following subchronic Cu exposition and new beneficial curative potential of curcumin against subchronic Cu-induced astroglial and dopaminergic neurotoxicity. Consequently, we suggest that Cu neurotoxicity may be strengthened in vivo firstly by attacking and weaking the astroglial system, and curcumin could be prized as a powerful and preventive target for the neurodegenerative diseases related metal element, especially Parkinson's disease.

Parkinson's Disease and Melanoma: Co-Occurrence and Mechanisms

Parkinson's disease (PD) is a neurodegenerative disorder that is characterized by loss of dopaminergic neurons in the substantia nigra pars compacta, depletion of dopamine in the striatum and the presence of Lewy bodies. Cancer is uncontrolled growth of cells in the body and migration of these cells from their site of origin to other parts of the body. PD and cancer are two opposite diseases, one arising from cell proliferation and the other from cell degeneration. This fundamental difference is consistent with inverse comorbidity between most cancers and neurodegenerative diseases. However, a positive association of PD and melanoma has been reported which has recently become of significant interest. A link between PD and cancer has been supported by many epidemiological studies, most of which show that PD patients have a lower risk of developing most cancers than the general population. However, the mechanisms underlying this epidemiological observation are not known. In this review we focus on epidemiological studies correlating PD and melanoma and the possible mechanisms underlying the co-occurrence of the two diseases. We explore possible explanations for the important observations that more PD patients develop melanoma that would otherwise be expected and vice-versa.

Neuroprotective effect of curcumin-I in copper-induced dopaminergic neurotoxicity in rats: A possible link with Parkinson's disease

Numerous findings indicate an involvement of heavy metals in the neuropathology of several neurodegenerative disorders, especially Parkinson's disease (PD). Previous studies have demonstrated that Copper (Cu) exhibits a potent neurotoxic effect on dopaminergic neurons and triggers profound neurobehavioral alterations. Curcumin is a major component of Curcuma longa rhizomes and a powerful medicinal plant that exerts many pharmacological effects. However, the neuroprotective action of curcumin on Cu-induced dopaminergic neurotoxicity is yet to be investigated. The aim of the present study was to evaluate the impact of acute Cu-intoxication (10mg/kg B.W. i.p) for 3days on the dopaminergic system and locomotor performance as well as the possible therapeutic efficacy of curcumin I (30mg/kg B.W.). Intoxicated rats showed a significant loss of Tyrosine Hydroxylase (TH) expression within substantia nigra pars compacta (SNc), ventral tegmental area (VTA) and the striatal outputs. This was correlated with a clear decrease in locomotor performance. Critically, curcumin-I co-treatment reversed these changes and showed a noticeable protective effect; both TH expression and locomotor performance was reinstated in intoxicated rats. These results demonstrate altered dopaminergic innervations following Cu intoxication and a new therapeutic potential of curcumin against Cu-induced dopaminergic neurotransmission failure. Curcumin may therefore prevent heavy metal related Parkinsonism.

Interactions of iron, dopamine and neuromelanin pathways in brain aging and Parkinson's disease

There are several interrelated mechanisms involving iron, dopamine, and neuromelanin in neurons. Neuromelanin accumulates during aging and is the catecholamine-derived pigment of the dopamine neurons of the substantia nigra and norepinephrine neurons of the locus coeruleus, the two neuronal populations most targeted in Parkinson's disease. Many cellular redox reactions rely on iron, however an altered distribution of reactive iron is cytotoxic. In fact, increased levels of iron in the brain of Parkinson's disease patients are present. Dopamine accumulation can induce neuronal death; however, excess dopamine can be removed by converting it into a stable compound like neuromelanin, and this process rescues the cell. Interestingly, the main iron compound in dopamine and norepinephrine neurons is the neuromelanin-iron complex, since neuromelanin is an effective metal chelator. Neuromelanin serves to trap iron and provide neuronal protection from oxidative stress. This equilibrium between iron, dopamine, and neuromelanin is crucial for cell homeostasis and in some cellular circumstances can be disrupted. Indeed, when neuromelanin-containing organelles accumulate high load of toxins and iron during aging a neurodegenerative process can be triggered. In addition, neuromelanin released by degenerating neurons activates microglia and the latter cause neurons death with further release of neuromelanin, then starting a self-propelling mechanism of neuroinflammation and neurodegeneration. Considering the above issues, age-related accumulation of neuromelanin in dopamine neurons shows an interesting link between aging and neurodegeneration.

Neuroprotective potential of Aloe arborescens against copper induced neurobehavioral features of Parkinson's disease in rat

Copper (Cu) is an important trace element for the organism survival, which ensures the normal functioning of different biosystems. However, excessive levels of this heavy metal are responsible for profound physiological alterations including the central nervous system. Numerous findings sustain the involvement of heavy metals, as an environmental risk factor such as copper (Cu), in the neuropathology of Parkinson's disease (PD) which is a chronic neurodegenerative disorder that principally affects the motor system. The classic and evident symptoms of PD namely rigidity, tardiness of movement, and difficulty with walking, result from progressive dopaminergic neurons death within substantia nigra. Whereas, few pharmacological trials have shown a beneficial role against Cu neurotoxicity, Aloe arborescens is one of the powerful medicinal plants with an array of therapeutic effects. Thus, we aimed through the present study, to evaluate the impact of acute Cu intoxication (10μg/g B.W. i.p) for 3days on the dopaminergic system and locomotor performance, together with the possible restorative effect of oral administration of aqueous extract of Aloe arborescens gel (AEAAG) (200mg/kg B.W.). By means of immunohistochemistry, we noted, in the Cu intoxicated rats, a significant loss of TH (tyrosine hydroxylase) expression within substantia nigra compacta (SNc), ventral tegmental area (VTA) and the subsequent striatal outputs, those alterations were correlated to behavioral abnormalities such as a severe drop of locomotor performance. While AEAAG administration to Cu intoxicated rats showed a noticeable beneficial effect; this potential was featured by a complete recovery of the TH expression and locomotor behavior deficiencies in the intoxicated rats. The present investigation have brought, on the one hand, an experimental evidence of an altered dopaminergic innervations following Cu intoxication and on the other hand, a new pharmacological property of Aloe arborescens that may be used as a neuroprotective plant for neurodegenerative disorders, such as PD, touching the dopaminergic system trigged by heavy metals.

Testosterone Propionate Exacerbates the Deficits of Nigrostriatal Dopaminergic System and Downregulates Nrf2 Expression in Reserpine-Treated Aged Male Rats

There is a controversy over the effects of testosterone supplements on dopaminergic function. Both neuroprotective and toxic effects of testosterone supplements are reported. The status of oxidative stress seems to explain the neuroprotective or toxic properties of testosterone. To determine the efficacy of testosterone supplements in different status of oxidative stress, the present studies analyzed the dopamine (DA)-related behaviors and neurochemical indices, as well as markers of nigrostriatal dopaminergic (NSDA) system in reserpine-treated aged male rats followed by testosterone propionate (TP) supplements. The status of oxidative stress of experimental animals was evaluated by analyzing oxidative stress parameters and nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response element (ARE) signaling pathway in substantia nigra (SN). Consistent with our previous studies, TP supplements to 21-month old aged male rats had the beneficial effects on NSDA system and DA-related behaviors and enhanced the antioxidative capabilities in SN. However, the beneficial effects of TP supplements on NSDA system and DA-related behaviors in aged male rats were reversed by reserpine pretreatment to them. Reserpine treatment induced the severe oxidative stress and reduced the expressions of Nrf2, heme oxygenase-1 (HO-1) and NAD(P)H:quinone oxidoreductase-1 (NQO1) in the SN of aged male rats. The TP supplements to reserpine-pretreated aged male rats exacerbated the defects in NSDA system and DA-related behaviors, aggravated oxidative damages and downregulated the expression of Nrf2, HO-1 and NQO1 in the SN. These results suggested that the efficacy of TP supplements on impaired NSDA system was related to the status of oxidative stress in experimental rats.

Hypopituitarism Presenting as Adrenal Insufficiency and Hypothyroidism in a Patient with Wilson's Disease: a Case Report

Wilson's disease typically presents symptoms associated with liver damage or neuropsychiatric disturbances, while endocrinologic abnormalities are rare. We report an unprecedented case of hypopituitarism in a patient with Wilson's disease. A 40-year-old woman presented with depression, general weakness and anorexia. Laboratory tests and imaging studies were compatible with liver cirrhosis due to Wilson's disease. Basal hormone levels and pituitary function tests indicated secondary hypothyroidism and adrenal insufficiency due to hypopituitarism. Brain MRI showed T2 hyperintense signals in both basal ganglia and midbrain but the pituitary imaging was normal. She is currently receiving chelation therapy along with thyroid hormone and steroid replacement. There may be a relationship between Wilson's disease and hypopituitarism. Copper deposition or secondary neuronal damage in the pituitary may be a possible explanation for this theory.

Copper-induced structural conversion templates prion protein oligomerization and neurotoxicity

Prion protein (PrP) misfolding and oligomerization are key pathogenic events in prion disease. Copper exposure has been linked to prion pathogenesis; however, its mechanistic basis is unknown. We resolve, with single-molecule precision, the molecular mechanism of Cu(2+)-induced misfolding of PrP under physiological conditions. We also demonstrate that misfolded PrPs serve as seeds for templated formation of aggregates, which mediate inflammation and degeneration of neuronal tissue. Using a single-molecule fluorescence assay, we demonstrate that Cu(2+) induces PrP monomers to misfold before oligomer assembly; the disordered amino-terminal region mediates this structural change. Single-molecule force spectroscopy measurements show that the misfolded monomers have a 900-fold higher binding affinity compared to the native isoform, which promotes their oligomerization. Real-time quaking-induced conversion demonstrates that misfolded PrPs serve as seeds that template amyloid formation. Finally, organotypic slice cultures show that misfolded PrPs mediate inflammation and degeneration of neuronal tissue. Our study establishes a direct link, at the molecular level, between copper exposure and PrP neurotoxicity.

The association between Parkinson's disease and melanoma: a systematic review and meta-analysis

Objective

To assess the association between Parkinson’s disease (PD) and melanoma via systematic review and meta-analysis.

Methods

Comprehensive search in PubMed, Web of Science, Embase and four China databases (SinoMed, WanFang data, CNKI and VIP database) of epidemiologic evidences on PD and melanoma published before April 30, 2015. Studies which reported risk estimates of melanoma among PD patients or risk estimates of PD in patients with melanoma were included. Pooled odds ratios (ORs) with 95 % confidence intervals (CIs) were calculated by random-effects models. Heterogeneity across studies was assessed using Cochran Q and I² statistics. Subgroup analyses and sensitivity analyses were conducted to evaluate sources of heterogeneity. Subgroup analyses were done according to temporal relationship, geographic region and gender respectively. We assessed publication bias using the Begg and Egger test. In addition, study appraisal was done using a scale for observational studies to ensure the quality of evidence.

Results

We identified 24 eligible studies on PD and melanoma with a total number of 292,275 PD patients: the pooled OR was 1.83 (95 % CI 1.46–2.30) overall, subgroup analyses by temporal relationship showed that risk of melanoma after PD diagnosis was significantly higher (OR 2.43, 95 % CI 1.77–3.32), but not before the diagnosis of PD (OR 1.09, 95 % CI 0.78–1.54). Subgroup analysis by geographic region showed that increased risk of melanoma in PD was found both in Europe (OR 1.44, 95 % CI 1.22–1.70) and in North America (OR 2.64, 95 % CI 1.63–4.28). Gender-specific subgroup analyses did not show difference between men (OR 1.64, 95 % CI 1.27–2.13) and women (OR 1.38, 95 % CI 1.04–1.82) in the risk of melanoma. In addition, we found the risk of non-melanoma skin cancers in PD was slightly higher (OR 1.20, 95 % CI 1.11–1.29) than general population. It was impossible to evaluate the association between PD and melanoma according to use of levodopa or gene polymorphism via meta-analysis since few observational or cohort studies have focused on it.

Conclusions

An association between PD and melanoma was confirmed. Most of the evidences were of high quality, and the conclusion was robust. Further research is needed to explore the mechanisms underlying this relationship.

Electronic supplementary material

The online version of this article (doi:10.1186/s40035-015-0044-y) contains supplementary material, which is available to authorized users.

Comparative proteomic analysis of the molecular responses of mouse macrophages to titanium dioxide and copper oxide nanoparticles unravels some toxic mechanisms for copper oxide nanoparticles in macrophages

Titanium dioxide and copper oxide nanoparticles are more and more widely used because of their catalytic properties, of their light absorbing properties (titanium dioxide) or of their biocidal properties (copper oxide), increasing the risk of adverse health effects. In this frame, the responses of mouse macrophages were studied. Both proteomic and targeted analyses were performed to investigate several parameters, such as phagocytic capacity, cytokine release, copper release, and response at sub toxic doses. Besides titanium dioxide and copper oxide nanoparticles, copper ions were used as controls. We also showed that the overall copper release in the cell does not explain per se the toxicity observed with copper oxide nanoparticles. In addition, both copper ion and copper oxide nanoparticles, but not titanium oxide, induced DNA strands breaks in macrophages. As to functional responses, the phagocytic capacity was not hampered by any of the treatments at non-toxic doses, while copper ion decreased the lipopolysaccharide-induced cytokine and nitric oxide productions. The proteomic analyses highlighted very few changes induced by titanium dioxide nanoparticles, but an induction of heme oxygenase, an increase of glutathione synthesis and a decrease of tetrahydrobiopterin in response to copper oxide nanoparticles. Subsequent targeted analyses demonstrated that the increase in glutathione biosynthesis and the induction of heme oxygenase (e.g. by lovastatin/monacolin K) are critical for macrophages to survive a copper challenge, and that the intermediates of the catecholamine pathway induce a strong cross toxicity with copper oxide nanoparticles and copper ions.

Highly promising discrimination of various catecholamines using ratiometric fluorescence probes with intermolecular self-association of two sensing elements

Two sensing elements based on fluorescence probes have been employed as a promising discriminating sensor of two catecholamines, dopamine (DA) and norepinephrine (NE), acting as a guest linker between two self-recognition sensing components.

Metallomics insights into the programmed cell death induced by metal-based anticancer compounds

Since the discovery of cisplatin more than 40 years ago, enormous research efforts have been dedicated to developing metal-based anticancer agents and to elucidating the mechanisms involved in the action of these compounds. Abnormal metabolism and the evasion of apoptosis are important hallmarks of malignant transformation, and the induction of apoptotic cell death has been considered to be a main pathway by which cytotoxic metal complexes combat cancer. However, many cancers have cellular defects involving the apoptotic machinery, which results in an acquired resistance to apoptotic cell death and therefore reduced chemotherapeutic effectiveness. Over the past decade, it has been revealed that a growing number of cell death pathways induced by metal complexes are not dependent on apoptosis. Metal complexes specifically triggering these alternative cell death pathways have been identified and explored as novel cancer treatment options. In this review, we discuss recent examples of metallomics studies on the different types of cell death induced by metal-based anticancer drugs, especially on the three major forms of programmed cell death (PCD) in mammalian cells: apoptosis, autophagy and regulated necrosis, also called necroptosis.

Overexpression of alpha-synuclein at non-toxic levels increases dopaminergic cell death induced by copper exposure via modulation of protein degradation pathways

Gene multiplications or point mutations in alpha (α)-synuclein are associated with familial and sporadic Parkinson's disease (PD). An increase in copper (Cu) levels has been reported in the cerebrospinal fluid and blood of PD patients, while occupational exposure to Cu has been suggested to augment the risk to develop PD. We aimed to elucidate the mechanisms by which α-synuclein and Cu regulate dopaminergic cell death. Short-term overexpression of wild type (WT) or mutant A53T α-synuclein had no toxic effect in human dopaminergic cells and primary midbrain cultures, but it exerted a synergistic effect on Cu-induced cell death. Cell death induced by Cu was potentiated by overexpression of the Cu transporter protein 1 (Ctr1) and depletion of intracellular glutathione (GSH) indicating that the toxic effects of Cu are linked to alterations in its intracellular homeostasis. Using the redox sensor roGFP, we demonstrated that Cu-induced oxidative stress was primarily localized in the cytosol and not in the mitochondria. However, α-synuclein overexpression had no effect on Cu-induced oxidative stress. WT or A53T α-synuclein overexpression exacerbated Cu toxicity in dopaminergic and yeast cells in the absence of α-synuclein aggregation. Cu increased autophagic flux and protein ubiquitination. Impairment of autophagy by overexpression of a dominant negative Atg5 form or inhibition of the ubiquitin/proteasome system (UPS) with MG132 enhanced Cu-induced cell death. However, only inhibition of the UPS stimulated the synergistic toxic effects of Cu and α-synuclein overexpression. Our results demonstrate that α-synuclein stimulates Cu toxicity in dopaminergic cells independent from its aggregation via modulation of protein degradation pathways.

Protective and toxic roles of dopamine in Parkinson's disease

The molecular mechanisms causing the loss of dopaminergic neurons containing neuromelanin in the substantia nigra and responsible for motor symptoms of Parkinson's disease are still unknown. The discovery of genes associated with Parkinson's disease (such as alpha synuclein (SNCA), E3 ubiquitin protein ligase (parkin), DJ-1 (PARK7), ubiquitin carboxyl-terminal hydrolase isozyme L1 (UCHL-1), serine/threonine-protein kinase (PINK-1), leucine-rich repeat kinase 2 (LRRK2), cation-transporting ATPase 13A1 (ATP13A), etc.) contributed enormously to basic research towards understanding the role of these proteins in the sporadic form of the disease. However, it is generally accepted by the scientific community that mitochondria dysfunction, alpha synuclein aggregation, dysfunction of protein degradation, oxidative stress and neuroinflammation are involved in neurodegeneration. Dopamine oxidation seems to be a complex pathway in which dopamine o-quinone, aminochrome and 5,6-indolequinone are formed. However, both dopamine o-quinone and 5,6-indolequinone are so unstable that is difficult to study and separate their roles in the degenerative process occurring in Parkinson's disease. Dopamine oxidation to dopamine o-quinone, aminochrome and 5,6-indolequinone seems to play an important role in the neurodegenerative processes of Parkinson's disease as aminochrome induces: (i) mitochondria dysfunction, (ii) formation and stabilization of neurotoxic protofibrils of alpha synuclein, (iii) protein degradation dysfunction of both proteasomal and lysosomal systems and (iv) oxidative stress. The neurotoxic effects of aminochrome in dopaminergic neurons can be inhibited by: (i) preventing dopamine oxidation of the transporter that takes up dopamine into monoaminergic vesicles with low pH and dopamine oxidative deamination catalyzed by monoamino oxidase (ii) dopamine o-quinone, aminochrome and 5,6-indolequinone polymerization to neuromelanin and (iii) two-electron reduction of aminochrome catalyzed by DT-diaphorase. Furthermore, dopamine conversion to NM seems to have a dual role, protective and toxic, depending mostly on the cellular context. Dopamine oxidation to dopamine o-quinone, aminochrome and 5,6-indolequinone plays an important role in neurodegeneration in Parkinson's disease since they induce mitochondria and protein degradation dysfunction; formation of neurotoxic alpha synuclein protofibrils and oxidative stress. However, the cells have a protective system against dopamine oxidation composed by dopamine uptake mediated by Vesicular monoaminergic transporter-2 (VMAT-2), neuromelanin formation, two-electron reduction and GSH-conjugation mediated by Glutathione S-transferase M2-2 (GSTM2).

Glutathione transferase mu 2 protects glioblastoma cells against aminochrome toxicity by preventing autophagy and lysosome dysfunction

U373MG cells constitutively express glutathione S-transferase mu 2 (GSTM2) and exhibit (3)H-dopamine uptake, which is inhibited by 2 µM of nomifensine and 15 µM of estradiol. We generated a stable cell line (U373MGsiGST6) expressing an siRNA against GSTM2 that resulted in low GSTM2 expression (26% of wild-type U373MG cells). A significant increase in cell death was observed when U373MGsiGST6 cells were incubated with 50 µM purified aminochrome (18-fold increase) compared with wild-type cells. The incubation of U373MGsiGST6 cells with 75 µM aminochrome resulted in the formation of autophagic vacuoles containing undigested cellular components, as determined using transmission electron microscopy. A significant increase in autophagosomes was determined by measuring endogenous LC3-II, a significant decrease in cell death was observed in the presence of bafilomycin A 1, and a significant increase in cell death was observed in the presence of trehalose. A significant increase in LAMP2 immunostaining was observed, a significant decrease in bright red fluorescence of lysosomes with acridine orange was observed, and bafilomycin A 1 pretreatment reduced the loss of lysosome acidity. A significant increase in cell death was observed in the presence of lysosomal protease inhibitors. Aggregation of TUBA/α-tubulin (tubulin, α) and SQSTM1 protein accumulation were also observed. Moreover, a significant increase in the number of lipids droplets was observed compared with U373MG cells with normal expression of GSTM2. These results support the notion that GSTM2 is a protective enzyme against aminochrome toxicity in astrocytes and that aminochrome cell death in U373MGsiGST6 cells involves autophagic-lysosomal dysfunction.

Protective effects of resveratrol on glutamate-induced damages in murine brain cultures

Resveratrol interacts with the complex III of the respiratory chain, is a radical scavenger and also suppressor of radical formation in the mitochondria. It reduces the intracellular calcium levels in pre- and postsynaptic neurons and also may inhibit the pro-apoptotic factors in glutamate overflow that occurs, e.g. in excitotoxicity. In cell cultures, glutamate overflow leads to formation of free radicals and results in apoptosis. This increase of radical concentration is enhanced by influx of cations like iron or copper ions into the cell. In present study, the beneficial action of resveratrol was investigated in glutamate-affected dissociated cultures of mice mesencephalic primary cultures. On the 10th day in vitro, 5 mM of glutamate was administered for 15 min and the cultures were further maintained in medium containing 0, 0.01, 0.1 or 1 μM of resveratrol. Resveratrol reduced glutamate-induced damages. The number of dopaminergic neurons was increased and their morphology ameliorated when resveratrol followed glutamate treatment. A significant reduction of glutamate-induced radical formation in cultures treated with resveratrol corresponded with a considerable high antioxidative potential of this stilbene determined using the DPPH assay. In addition, ICP-OES was set up to measure the tissues' copper and iron contents in organotypic cortical cultures of glutamate treated (0 or 30 μM) slices and those in which resveratrol (0, 0.01, 0.1 or 1 μM) was co-administered. Levels of copper were dose-dependently increased, and also the concentration of iron was higher in resveratrol-treated organotypic cultures. The hypothesis that resveratrol has beneficial actions against glutamate damages was verified.

One-electron reduction of 6-hydroxydopamine quinone is essential in 6-hydroxydopamine neurotoxicity

6-Hydroxydamine has widely been used as neurotoxin in preclinical studies related on the neurodegenerative process of dopaminergic neurons in Parkinson's disease based on its ability to be neurotoxic as a consequence of free radical formation during its auto-oxidation to topaminequinone. We report that 50-µM 6-hydroxydopamine is not neurotoxic in RCSN-3 cells derived from substantia nigra incubated during 24 h contrasting with a significant sixfold increase in cell death (16 ± 2 %; P < 0.001) was observed in RCSN-3NQ7 cells expressing a siRNA against DT-diaphorase that silence the enzyme expression. To observe a significant cell death in RCSN-3 cells induced by 6-hydroxydopamine (24 ± 1 %; P < 0.01), we have to increase the concentration to 250 μm while a 45 ± 2 % cell death (P < 0.001) was observed at this concentration in RCSN-3NQ7 cells. The cell death induced by 6-hydroxydopamine in RCSN-3NQ7 cells was accompanied with a (i) significant increase in oxygen consumption (P < 0.01), (ii) depletion of reduced glutathione and (iii) a significant decrease in ATP level (P < 0.05) in comparison with RCSN-3 cells. In conclusion, our results suggest that one-electron reduction of 6-hydroxydopamine quinone seems to be the main reaction responsible for 6-hydroxydopamine neurotoxic effects in dopaminergic neurons and DT-diaphorase seems to play an important neuroprotective role by preventing one-electron reduction of topaminequinone.

Dopamine oxidation and autophagy

The molecular mechanisms involved in the neurodegenerative process of Parkinson's disease remain unclear. Currently, there is a general agreement that mitochondrial dysfunction, α-synuclein aggregation, oxidative stress, neuroinflammation, and impaired protein degradation are involved in the neurodegeneration of dopaminergic neurons containing neuromelanin in Parkinson's disease. Aminochrome has been proposed to play an essential role in the degeneration of dopaminergic neurons containing neuromelanin by inducing mitochondrial dysfunction, oxidative stress, the formation of neurotoxic α-synuclein protofibrils, and impaired protein degradation. Here, we discuss the relationship between the oxidation of dopamine to aminochrome, the precursor of neuromelanin, autophagy dysfunction in dopaminergic neurons containing neuromelanin, and the role of dopamine oxidation to aminochrome in autophagy dysfunction in dopaminergic neurons. Aminochrome induces the following: (i) the formation of α-synuclein protofibrils that inactivate chaperone-mediated autophagy; (ii) the formation of adducts with α- and β-tubulin, which induce the aggregation of the microtubules required for the fusion of autophagy vacuoles and lysosomes.

N-acetylcysteine attenuates copper overload-induced oxidative injury in brain of rat

Copper is an integral part of many important enzymes involved in a number of vital biological processes. Even though it is essential to life, at elevated tissue concentrations, copper can become toxic to cells. Recent studies have reported oxidative damage due to copper in various tissues. Considering the vulnerability of the brain to oxidative stress, this study was undertaken to explore possible beneficial antioxidant effects of N-acetylcysteine on oxidative stress induced by copper overload in brain tissue of rats. Thirty-two Wistar rats were equally divided into four groups. The first group was used as control. The second, third, and fourth groups were given 1 g/L copper in their drinking water for 1 month. At the end of this period, the group 2 rats were sacrificed. During the next 2 weeks, the rats in group 3 were injected intraperitoneally with physiological saline and those in group 4 with 20 mg/kg intraperitoneal injections of N-acetylcysteine. In group 2 the lipid peroxidation and nitric oxide levels were increased in the brain cortex while the activities of superoxide dismutase and catalase and the concentration of glutathione were decreased. In rats treated with N-acetylcysteine, lipid peroxidation decreased and the activities of antioxidant enzyme improved in the brain cortex. In conclusion, treatment with N-acetylcysteine modulated the antioxidant redox system and reduced brain oxidative stress induced by copper.

Overexpression of VMAT-2 and DT-diaphorase protects substantia nigra-derived cells against aminochrome neurotoxicity

We tested the hypothesis that both VMAT-2 and DT-diaphorase are an important cellular defense against aminochrome-dependent neurotoxicity during dopamine oxidation. A cell line with VMAT-2 and DT-diaphorase over-expressed was created. The transfection of RCSN-3 cells with a bicistronic plasmid coding for VMAT-2 fused with GFP-IRES-DT-diaphorase cDNA induced a significant increase in protein expression of VMAT-2 (7-fold; P<0.001) and DT-diaphorase (9-fold; P<0.001), accompanied by a 4- and 5.5-fold significant increase in transport and enzyme activity, respectively. Studies with synaptic vesicles from rat substantia nigra revealed that VMAT-2 uptake of ³H-aminochrome 6.3 ± 0.4nmol/min/mg was similar to dopamine uptake 6.2 ± 0.3nmol/min/mg that which were dependent on ATP. Interestingly, aminochrome uptake was inhibited by 2μM lobeline but not reserpine (1 and 10μM). Incubation of cells overexpressing VMAT-2 and DT-diaphorase with 20μM aminochrome resulted in (i) a significant decrease in cell death (6-fold, P<0.001); (ii) normal ultra structure determined by transmission electron microscopy contrasting with a significant increase of autophagosome and a dramatic remodeling of the mitochondrial inner membrane in wild type cells; (iii) normal level of ATP (256 ± 11μM) contrasting with a significant decrease in wild type cells (121±11μM, P<0.001); and (iv) a significant decrease in DNA laddering (21 ± 8pixels, P<0.001) cells in comparison with wild type cells treated with 20μM aminochrome (269 ± 9). These results support our hypothesis that VMAT-2 and DT-diaphorase are an important defense system against aminochrome formed during dopamine oxidation.

Association of skin with the pathogenesis and treatment of neurodegenerative amyloidosis

Amyloidosis are a large group of conformational diseases characterized by abnormal protein folding and assembly which results in the accumulation of insoluble protein aggregates that may accumulate systemically or locally in certain organs or tissue. In local amyloidosis, amyloid deposits are restricted to a particular organ or tissue. Alzheimer’s, Parkinson’s disease, and amyotrophic lateral sclerosis are some examples of neurodegenerative amyloidosis. Local manifestation of protein aggregation in the skin has also been reported. Brain and skin are highly connected at a physiological and pathological level. Recently several studies demonstrated a strong connection between brain and skin in different amyloid diseases. In the present review, we discuss the relevance of the “brain–skin connection” in different neurodegenerative amyloidosis, not only at the pathological level, but also as a strategy for the treatment of these diseases.

Differential effects of dopaminergic neurotoxins on DNA cleavage

AIMS

Environmental and endogenous toxins are considered to increase the risk of dopaminergic neurodegeneration. Parkinson's disease is a neurological disorder occurring due to the death of dopaminergic neurons in substantia nigra. The present study investigated the effect of parkinsonian neurotoxins salsolinol and rotenone on plasmid and genomic DNA.

MAIN METHODS

Salsolinol or rotenone (0-1000 μM) alone or in presence of divalent metals (copper or iron) was incubated with plasmid DNA pBR322 (1 μg) or calf thymus DNA (1 μg). In order to study their effects on restriction endonuclease sites, the plasmid DNA was incubated with the neurotoxins (salsolinol or rotenone), extracted and subjected to restriction enzyme digestion (BamHI, EcoRV, HindIII, SalI).

KEY FINDINGS

Exposure of rotenone or salsolinol alone to the plasmid or calf thymus DNA did not induce any strand scission or damage. However, salsolinol in the presence of divalent copper induced strand scission and damage in both plasmid and genomic DNA. All of the tested restriction endonucleases linearized the plasmid DNA pre-treated with salsolinol or rotenone suggesting that these neurotoxins did not selectively damage the restriction enzyme sites in the DNA.

SIGNIFICANCE

The above observations suggest that salsolinol and rotenone differentially interact with DNA in inducing damage in the presence of copper, and behave similarly in their binding to DNA by not damaging the selected restriction endonuclease cleavage sites.

CONCLUSION

Risk for neuronal degeneration can be significantly augmented by the environmental and endogenous toxins in the presence of various metals due to their deleterious effects on DNA.

Redox activity of α-synuclein-Cu is silenced by Zn₇-metallothionein-3

The aggregation of α-synuclein (α-Syn), the major component of intracellular Lewy body inclusions in dopaminergic neurons of the substantia nigra, plays a critical role in the etiology of Parkinson disease (PD). Long-term effects of redox-active transition metals (Cu, Fe) and oxidative chemical imbalance underlie the disease progression and neuronal death. In this work, we provide evidence that a brain metalloprotein, Zn₇-metallothionein-3 (Zn₇MT-3), possesses a dynamic role in controlling aberrant protein-copper interactions in PD. We examined the properties of the α-Syn-Cu(II) complex with regard to molecular oxygen, the biological reducing agent ascorbate, and the neurotransmitter dopamine. The results revealed that under aerobic conditions α-Syn-Cu(II) possesses catalytic oxidase activity. The observed metal-centered redox chemistry significantly promotes the production of hydroxyl radicals and α-Syn oxidation and oligomerization, processes considered critical for cellular toxicity. Moreover, we show that Zn₇MT-3, through Cu(II) removal from the α-Syn-Cu(II) complex, efficiently prevents its deleterious redox activity. We demonstrate that the Cu(II) reduction by thiolate ligands of Zn₇MT-3 and the formation of Cu(I)₄Zn₄MT-3, in which an unusual oxygen-stable Cu(I)₄-thiolate cluster is present, comprise the underlying molecular mechanism by which α-Syn and dopamine oxidation, α-Syn oligomerization, and ROS production are abolished. These studies provide new insights into the bioinorganic chemistry of PD.

Autophagy protects against aminochrome-induced cell death in substantia nigra-derived cell line

Aminochrome, the precursor of neuromelanin, has been proposed to be involved in the neurodegeneration neuromelanin-containing dopaminergic neurons in Parkinson's disease. We aimed to study the mechanism of aminochrome-dependent cell death in a cell line derived from rat substantia nigra. We found that aminochrome (50μM), in the presence of NAD(P)H-quinone oxidoreductase, EC 1.6.99.2 (DT)-diaphorase inhibitor dicoumarol (DIC) (100μM), induces significant cell death (62 ± 3%; p < 0.01), increase in caspase-3 activation (p < 0.001), release of cytochrome C, disruption of mitochondrial membrane potential (p < 0.01), damage of mitochondrial DNA, damage of mitochondria determined with transmission electron microscopy, a dramatic morphological change characterized as cell shrinkage, and significant increase in number of autophagic vacuoles. To determine the role of autophagy on aminochrome-induced cell death, we incubated the cells in the presence of vinblastine and rapamycin. Interestingly, 10μM vinblastine induces a 5.9-fold (p < 0.001) and twofold (p < 0.01) significant increase in cell death when the cells were incubated with 30μM aminochrome in the absence and presence of DIC, respectively, whereas 10μM rapamycin preincubated 24 h before addition of 50μM aminochrome in the absence and the presence of 100μM DIC induces a significant decrease (p < 0.001) in cell death. In conclusion, autophagy seems to be an important protective mechanism against two different aminochrome-induced cell deaths that initially showed apoptotic features. The cell death induced by aminochrome when DT-diaphorase is inhibited requires activation of mitochondrial pathway, whereas the cell death induced by aminochrome alone requires inhibition of autophagy-dependent degrading of damaged organelles and recycling through lysosomes.

The association between Parkinson's disease and melanoma

Parkinson's disease (PD) is a neurodegenerative disorder characterized by a loss of melanin-positive, dopaminergic neurons in the substantia nigra. Although there is convincing epidemiologic evidence of a negative association between PD and most cancers, a notable exception to this is that melanoma, a malignant tumor of melanin-producing cells in skin, occurs with higher-than-expected frequency among subjects with PD and that melanoma patients are more likely to have PD. A clear biological explanation for this epidemiological observation is lacking. Here, we present a comprehensive review of published literature exploring the association between PD and melanoma. On the basis of published findings, we conclude that (i) changes in pigmentation including melanin synthesis and/or melanin synthesis enzymes, such as tyrosinase and tyrosine hydroxylase, play important roles in altered vulnerability for both PD and melanoma; (ii) changes of PD-related genes such as Parkin, LRRK2 and α-synuclein may increase the risk of melanoma; (iii) changes in some low-penetrance genes such as cytochrome p450 debrisoquine hydroxylase locus, glutathione S-transferase M1 and vitamin D receptor could increase the risk for both PD and melanoma and (iv) impaired autophagy in both PD and melanoma could also explain the association between PD and melanoma. Future studies are required to address whether altered pigmentation, PD- or melanoma-related gene changes and/or changes in autophagy function induce oncogenesis or apoptosis. From a clinical point of view, early diagnosis of melanoma in PD patients is critical and can be enhanced by periodic dermatological surveillance, including skin biopsies.