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1.
Int J Mol Sci ; 22(23)2021 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-34884599

RESUMO

Melanin is a black/brown pigment present in abundance in human skin. Its main function is photo-protection of underlying tissues from harmful UV light. Natural sources of isolated human melanin are limited; thus, in vitro cultures of human cells may be a promising source of human melanin. Here, we present an innovative in vitro differentiation protocol of induced pluripotent stem cells (iPS) into melanin-producing cells, delivering highly pigmented cells in quantity and quality incomparably higher than any other methods previously described. Pigmented cells constitute over 90% of a terminally differentiated population and exhibit features characteristic for melanocytes, i.e., expression of specific markers such as MITF-M (microphthalmia-associated transcription factor isoform M), TRP-1 (tyrosinase-related protein 1), and TYR (tyrosinase) and accumulation of black pigment in organelles closely resembling melanosomes. Black pigment is unambiguously identified as melanin with features corresponding to those of melanin produced by typical melanocytes. The advantage of our method is that it does not require any sophisticated procedures and can be conducted in standard laboratory conditions. Moreover, our protocol is highly reproducible and optimized to generate high-purity melanin-producing cells from iPS cells; thus, it can serve as an unlimited source of human melanin for modeling human skin diseases. We speculate that FGF-8 might play an important role during differentiation processes toward pigmented cells.


Assuntos
Diferenciação Celular , Células-Tronco Pluripotentes Induzidas/citologia , Melaninas/biossíntese , Melanócitos/citologia , Melanossomas/metabolismo , Pigmentação , Células Cultivadas , Humanos , Células-Tronco Pluripotentes Induzidas/metabolismo , Melanócitos/metabolismo
2.
Antioxidants (Basel) ; 10(6)2021 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-34064062

RESUMO

Neuromelanin (NM) accumulates in catecholamine long-lived brain neurons that are lost in neurodegenerative diseases. NM is a complex substance made of melanic, peptide and lipid components. NM formation is a natural protective process since toxic endogenous metabolites are removed during its formation and as it binds excess metals and xenobiotics. However, disturbances of NM synthesis and function could be toxic. Here, we review recent knowledge on NM formation, toxic mechanisms involving NM, go over NM binding substances and suggest experimental models that can help identifying xenobiotic modulators of NM formation or function. Given the high likelihood of a central NM role in age-related human neurodegenerative diseases such as Parkinson's and Alzheimer's, resembling such diseases using animal models that do not form NM to a high degree, e.g., mice or rats, may not be optimal. Rather, use of animal models (i.e., sheep and goats) that better resemble human brain aging in terms of NM formation, as well as using human NM forming stem cellbased in vitro (e.g., mid-brain organoids) models can be more suitable. Toxicants could also be identified during chemical synthesis of NM in the test tube.

3.
Acta Neuropathol ; 141(5): 725-754, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33694021

RESUMO

The mechanisms by which parkin protects the adult human brain from Parkinson disease remain incompletely understood. We hypothesized that parkin cysteines participate in redox reactions and that these are reflected in its posttranslational modifications. We found that in post mortem human brain, including in the Substantia nigra, parkin is largely insoluble after age 40 years; this transition is linked to its oxidation, such as at residues Cys95 and Cys253. In mice, oxidative stress induces posttranslational modifications of parkin cysteines that lower its solubility in vivo. Similarly, oxidation of recombinant parkin by hydrogen peroxide (H2O2) promotes its insolubility and aggregate formation, and in exchange leads to the reduction of H2O2. This thiol-based redox activity is diminished by parkin point mutants, e.g., p.C431F and p.G328E. In prkn-null mice, H2O2 levels are increased under oxidative stress conditions, such as acutely by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine toxin exposure or chronically due to a second, genetic hit; H2O2 levels are also significantly increased in parkin-deficient human brain. In dopamine toxicity studies, wild-type parkin, but not disease-linked mutants, protects human dopaminergic cells, in part through lowering H2O2. Parkin also neutralizes reactive, electrophilic dopamine metabolites via adduct formation, which occurs foremost at the primate-specific residue Cys95. Further, wild-type but not p.C95A-mutant parkin augments melanin formation in vitro. By probing sections of adult, human midbrain from control individuals with epitope-mapped, monoclonal antibodies, we found specific and robust parkin reactivity that co-localizes with neuromelanin pigment, frequently within LAMP-3/CD63+ lysosomes. We conclude that oxidative modifications of parkin cysteines are associated with protective outcomes, which include the reduction of H2O2, conjugation of reactive dopamine metabolites, sequestration of radicals within insoluble aggregates, and increased melanin formation. The loss of these complementary redox effects may augment oxidative stress during ageing in dopamine-producing cells of mutant PRKN allele carriers, thereby enhancing the risk of Parkinson's-linked neurodegeneration.


Assuntos
Envelhecimento/metabolismo , Dopamina/metabolismo , Mesencéfalo/metabolismo , Degeneração Neural/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Envelhecimento/patologia , Animais , Criança , Pré-Escolar , Feminino , Humanos , Masculino , Mesencéfalo/patologia , Camundongos , Camundongos Endogâmicos C57BL , Pessoa de Meia-Idade , Degeneração Neural/patologia , Oxirredução , Adulto Jovem
5.
Artigo em Inglês | MEDLINE | ID: mdl-32822763

RESUMO

In modern societies, there is a strive to improve the quality of life related to risk of crimes which inevitably requires a better understanding of brain determinants and mediators of aggression. Neurobiology provides powerful tools to achieve this end. Pre-clinical and clinical studies show that changes in regional volumes, metabolism-function and connectivity within specific neural networks are related to aggression. Subregions of prefrontal cortex, insula, amygdala, basal ganglia and hippocampus play a major role within these circuits and have been consistently implicated in biology of aggression. Genetic variations in proteins regulating the synthesis, degradation, and transport of serotonin and dopamine as well as their signal transduction have been found to mediate behavioral variability observed in aggression. Gene-gene and gene-environment interactions represent additional important risk factors for aggressiveness. Considering the social burden of pathological forms of aggression, more basic and translational studies should be conducted to accelerate applications to clinical practice, justice courts, and policy making.


Assuntos
Agressão/fisiologia , Química Encefálica/fisiologia , Encéfalo/diagnóstico por imagem , Encéfalo/metabolismo , Neuroimagem/métodos , Agressão/psicologia , Dopamina/genética , Dopamina/metabolismo , Interação Gene-Ambiente , Humanos , Serotonina/genética , Serotonina/metabolismo
6.
NPJ Parkinsons Dis ; 6: 18, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32885037

RESUMO

This Viewpoint discusses insights from basic science and clinical perspectives on coronavirus disease 2019 (COVID-19)/severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection in the brain, with a particular focus on Parkinson's disease. Major points include that neuropathology studies have not answered the central issue of whether the virus enters central nervous system neurons, astrocytes or microglia, and the brain vascular cell types that express virus have not yet been identified. Currently, there is no clear evidence for human neuronal or astrocyte expression of angiotensin-converting enzyme 2 (ACE2), the major receptor for viral entry, but ACE2 expression may be activated by inflammation, and a comparison of healthy and infected brains is important. In contrast to the 1918 influenza pandemic and avian flu, reports of encephalopathy in COVID-19 have been slow to emerge, and there are so far no documented reports of parkinsonism apart from a single case report. We recommend consensus guidelines for the clinical treatment of Parkinson's patients with COVID-19. While a role for the virus in causing or exacerbating Parkinson's disease appears unlikely at this time, aggravation of specific motor and non-motor symptoms has been reported, and it will be important to monitor subjects after recovery, particularly for those with persisting hyposmia.

7.
Am J Psychiatry ; 177(11): 1038-1047, 2020 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-32854531

RESUMO

OBJECTIVE: Recent evidence supports the use of neuromelanin-sensitive MRI (NM-MRI) as a novel tool to investigate dopamine function in the human brain. The authors investigated the NM-MRI signal in individuals with cocaine use disorder, compared with age- and sex-matched control subjects, based on previous imaging studies showing that this disorder is associated with blunted presynaptic striatal dopamine. METHODS: NM-MRI and T1-weighted images were acquired from 20 participants with cocaine use disorder and 35 control subjects. Diagnostic group effects in NM-MRI signal were determined using a voxelwise analysis within the substantia nigra. A subset of 20 cocaine users and 17 control subjects also underwent functional MRI imaging using the monetary incentive delay task, in order to investigate whether NM-MRI signal was associated with alterations in reward processing. RESULTS: Compared with control subjects, cocaine users showed significantly increased NM-MRI signal in ventrolateral regions of the substantia nigra (area under the receiver operating characteristic curve=0.83). Exploratory analyses did not find a significant correlation of NM-MRI signal to activation of the ventral striatum during anticipation of monetary reward. CONCLUSIONS: Given that previous imaging studies show decreased dopamine signaling in the striatum, the finding of increased NM-MRI signal in the substantia nigra provides additional insight into the pathophysiology of cocaine use disorder. One interpretation is that cocaine use disorder is associated with a redistribution of dopamine between cytosolic and vesicular pools, leading to increased accumulation of neuromelanin. The study findings thus suggest that NM-MRI can serve as a practical imaging tool for interrogating the dopamine system in addiction.


Assuntos
Transtornos Relacionados ao Uso de Cocaína/patologia , Dopamina/metabolismo , Melaninas/metabolismo , Neuroimagem/métodos , Substância Negra/patologia , Antecipação Psicológica , Estudos de Casos e Controles , Transtornos Relacionados ao Uso de Cocaína/diagnóstico por imagem , Transtornos Relacionados ao Uso de Cocaína/metabolismo , Neurônios Dopaminérgicos/metabolismo , Neurônios Dopaminérgicos/patologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Recompensa , Substância Negra/diagnóstico por imagem , Substância Negra/metabolismo , Estriado Ventral/metabolismo , Estriado Ventral/patologia
8.
ACS Chem Neurosci ; 10(8): 3731-3739, 2019 08 21.
Artigo em Inglês | MEDLINE | ID: mdl-31298828

RESUMO

The neurotoxic activity of the tryptophan metabolite 3-hydroxykynurenine (3OHKyn) in neurodegenerative disorders, such as Parkinson's and Alzheimer's diseases, is related to oxidative stress and 3OHKyn interaction with cellular proteins. The pattern of protein modification induced by 3OHKyn involves the nucleophilic side chains of Cys, His, and Lys residues, similarly to the one promoted by dopamine and other catecholamines. In the present work, we have analyzed the reactivity of 3OHKyn toward the neuronal targets α-synuclein (and its N-terminal fragments 1-6 and 1-15) and amyloid-ß peptides (1-16 and 1-28) and characterized the resulting conjugates through spectrometric (LC-MS/MS) and spectroscopic (UV-vis, fluorescence, NMR) techniques. The amino acid residues of α-synuclein and amyloid-ß peptides involved in derivatizations by 3OHKyn and its autoxidation products (belonging to the xanthommatin family) are Lys and His, respectively. The pattern of protein modification is expanded in the conjugates obtained in the presence of the metal ions copper(II) or iron(III), reflecting a more oxidizing environment that in addition to adducts with protein/peptide residues also favors the fragmentation of the protein. These results open the perspective to using the 3OHKyn-protein/peptide synthetic conjugates to explore their competence to activate microglia cell cultures as well as to unravel their role in neuroinflammatory conditions.


Assuntos
Peptídeos beta-Amiloides/metabolismo , Cinurenina/análogos & derivados , Neurônios/efeitos dos fármacos , Fragmentos de Peptídeos/metabolismo , alfa-Sinucleína/metabolismo , Células Cultivadas , Cromatografia Líquida , Humanos , Cinurenina/farmacologia , Espectroscopia de Ressonância Magnética , Doenças Neurodegenerativas , Neurônios/metabolismo , Espectrometria de Massas em Tandem
9.
Brain ; 142(9): 2558-2571, 2019 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-31327002

RESUMO

Pathological alterations to the locus coeruleus, the major source of noradrenaline in the brain, are histologically evident in early stages of neurodegenerative diseases. Novel MRI approaches now provide an opportunity to quantify structural features of the locus coeruleus in vivo during disease progression. In combination with neuropathological biomarkers, in vivo locus coeruleus imaging could help to understand the contribution of locus coeruleus neurodegeneration to clinical and pathological manifestations in Alzheimer's disease, atypical neurodegenerative dementias and Parkinson's disease. Moreover, as the functional sensitivity of the noradrenergic system is likely to change with disease progression, in vivo measures of locus coeruleus integrity could provide new pathophysiological insights into cognitive and behavioural symptoms. Locus coeruleus imaging also holds the promise to stratify patients into clinical trials according to noradrenergic dysfunction. In this article, we present a consensus on how non-invasive in vivo assessment of locus coeruleus integrity can be used for clinical research in neurodegenerative diseases. We outline the next steps for in vivo, post-mortem and clinical studies that can lay the groundwork to evaluate the potential of locus coeruleus imaging as a biomarker for neurodegenerative diseases.


Assuntos
Locus Cerúleo/diagnóstico por imagem , Locus Cerúleo/metabolismo , Imageamento por Ressonância Magnética/métodos , Doenças Neurodegenerativas/diagnóstico por imagem , Doenças Neurodegenerativas/metabolismo , Norepinefrina/metabolismo , Biomarcadores/metabolismo , Humanos
10.
Trends Neurosci ; 42(6): 384-401, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31047721

RESUMO

Although iron is crucial for neuronal functioning, many aspects of cerebral iron biology await clarification. The ability to quantify specific iron forms in the living brain would open new avenues for diagnosis, therapeutic monitoring, and understanding pathogenesis of diseases. A modality that allows assessment of brain tissue composition in vivo, in particular of iron deposits or myelin content on a submillimeter spatial scale, is magnetic resonance imaging (MRI). Multimodal strategies combining MRI with complementary analytical techniques ex vivo have emerged, which may lead to improved specificity. Interdisciplinary collaborations will be key to advance beyond simple correlative analyses in the biological interpretation of MRI data and to gain deeper insights into key factors leading to iron accumulation and/or redistribution associated with neurodegeneration.


Assuntos
Química Encefálica , Encéfalo/fisiologia , Ferro/análise , Bainha de Mielina/química , Neurobiologia/métodos , Neuroimagem/métodos , Humanos , Neurobiologia/tendências , Neuroimagem/tendências
11.
Proc Natl Acad Sci U S A ; 116(11): 5108-5117, 2019 03 12.
Artigo em Inglês | MEDLINE | ID: mdl-30796187

RESUMO

Neuromelanin-sensitive MRI (NM-MRI) purports to detect the content of neuromelanin (NM), a product of dopamine metabolism that accumulates with age in dopamine neurons of the substantia nigra (SN). Interindividual variability in dopamine function may result in varying levels of NM accumulation in the SN; however, the ability of NM-MRI to measure dopamine function in nonneurodegenerative conditions has not been established. Here, we validated that NM-MRI signal intensity in postmortem midbrain specimens correlated with regional NM concentration even in the absence of neurodegeneration, a prerequisite for its use as a proxy for dopamine function. We then validated a voxelwise NM-MRI approach with sufficient anatomical sensitivity to resolve SN subregions. Using this approach and a multimodal dataset of molecular PET and fMRI data, we further showed the NM-MRI signal was related to both dopamine release in the dorsal striatum and resting blood flow within the SN. These results suggest that NM-MRI signal in the SN is a proxy for function of dopamine neurons in the nigrostriatal pathway. As a proof of concept for its clinical utility, we show that the NM-MRI signal correlated to severity of psychosis in schizophrenia and individuals at risk for schizophrenia, consistent with the well-established dysfunction of the nigrostriatal pathway in psychosis. Our results indicate that noninvasive NM-MRI is a promising tool that could have diverse research and clinical applications to investigate in vivo the role of dopamine in neuropsychiatric illness.


Assuntos
Encéfalo/metabolismo , Dopamina/metabolismo , Imageamento por Ressonância Magnética , Melaninas/metabolismo , Adulto , Idoso , Idoso de 80 Anos ou mais , Meios de Contraste , Feminino , Humanos , Masculino , Mesencéfalo/metabolismo , Pessoa de Meia-Idade , Mudanças Depois da Morte , Transtornos Psicóticos/diagnóstico por imagem , Reprodutibilidade dos Testes , Razão Sinal-Ruído , Substância Negra/metabolismo
12.
Clin Pharmacol Transl Med ; 3(1): 143-148, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-32864581

RESUMO

The loss of nigrostriatal dopaminergic neurons containing neuromelanin underlies the motor symptoms of Parkinson's disease. Neuromelanin accumulation into autophagic lysosomes is evidence of ongoing cytosolic dopamine stress in these neurons during normal aging. The formation of neuromelanin is likely neuroprotective, as oxidation of cytosolic dopamine to quinones and aldehydes, as reviewed here, can produce a host of neurotoxic sequela. In addition to sequestration of dopamine and its metabolites in autophagic lysosomes, the uptake of dopamine into monoaminergic neurons mediated by vesicular monoamine transporter-2 (VMAT- 2), prevents dopamine oxidation. Dopamine is stable in monoaminergic vesicles due to their low pH, and thus overexpression of VMAT-2 may provide a target for potential neuroprotective therapy in Parkinson's disease.

13.
Mov Disord ; 34(3): 396-405, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30576008

RESUMO

BACKGROUND: Although several studies have suggested that abnormalities in gut microbiota may play a critical role in the pathogenesis of PD, data are still extremely heterogeneous. METHODS: 16S gene ribosomal RNA sequencing was performed on fecal samples of 350 individuals, subdivided into idiopathic PD (n = 193, of whom 39 were drug naïve) stratified by disease duration, PSP (n = 22), MSA (n = 22), and healthy controls (HC; n = 113). Several confounders were taken into account, including dietary habits. RESULTS: Despite the fact that unadjusted comparison of PD and HC showed several differences in relative taxa abundances, the significant results were greatly reduced after adjusting for confounders. Although most of these differences were associated with disease duration, lower abundance in Lachnospiraceae was the only difference between de novo PD and HC (remaining lower across almost all PD duration strata). Decreased Lachnospiraceae and increased Lactobacillaceae and Christensenellaceae were associated with a worse clinical profile, including higher frequencies of cognitive impairment, gait disturbances, and postural instability. When compared with HC, MSA and PSP patients shared the changes in PD, with a few exceptions: in MSA, Lachnospiraceae were not lower, and Prevotellaceae were reduced; in PSP, Lactobacillaceae were similar, and Streptococcaceae were reduced. CONCLUSIONS: Gut microbiota may be an environmental modulator of the pathogenesis of PD and contribute to the interindividual variability of clinical features. Data are influenced by PD duration and several confounders that need to be taken into account in future studies. Prospective studies in de novo PD patients are needed to elucidate the net effect of dysbiosis on the progression of the disease. © 2018 International Parkinson and Movement Disorder Society.


Assuntos
Microbioma Gastrointestinal/fisiologia , Doença de Parkinson/microbiologia , Transtornos Parkinsonianos/microbiologia , Idoso , Estudos de Casos e Controles , Progressão da Doença , Fezes/microbiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Atrofia de Múltiplos Sistemas/microbiologia , Paralisia Supranuclear Progressiva/microbiologia
14.
Angew Chem Int Ed Engl ; 58(20): 6512-6527, 2019 05 13.
Artigo em Inglês | MEDLINE | ID: mdl-30536578

RESUMO

Dopamine (DA) is the most important catecholamine in the brain, as it is the most abundant and the precursor of other neurotransmitters. Degeneration of nigrostriatal neurons of substantia nigra pars compacta in Parkinson's disease represents the best-studied link between DA neurotransmission and neuropathology. Catecholamines are reactive molecules that are handled through complex control and transport systems. Under normal conditions, small amounts of cytosolic DA are converted to neuromelanin in a stepwise process involving melanization of peptides and proteins. However, excessive cytosolic or extraneuronal DA can give rise to nonselective protein modifications. These reactions involve DA oxidation to quinone species and depend on the presence of redox-active transition metal ions such as iron and copper. Other oxidized DA metabolites likely participate in post-translational protein modification. Thus, protein-quinone modification is a heterogeneous process involving multiple DA-derived residues that produce structural and conformational changes of proteins and can lead to aggregation and inactivation of the modified proteins.


Assuntos
Dopamina/uso terapêutico , Doenças Neurodegenerativas/tratamento farmacológico , Doença de Parkinson/tratamento farmacológico , Quinonas/uso terapêutico , Dopamina/farmacologia , Humanos , Estresse Oxidativo , Quinonas/farmacologia
15.
NPJ Parkinsons Dis ; 4: 17, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29900402

RESUMO

During aging, neuronal organelles filled with neuromelanin (a dark-brown pigment) and lipid bodies accumulate in the brain, particularly in the substantia nigra, a region targeted in Parkinson's disease. We have investigated protein and lipid systems involved in the formation of these organelles and in the synthesis of the neuromelanin of human substantia nigra. Membrane and matrix proteins characteristic of lysosomes were found in neuromelanin-containing organelles at a lower number than in typical lysosomes, indicating a reduced enzymatic activity and likely impaired capacity for lysosomal and autophagosomal fusion. The presence of proteins involved in lipid transport may explain the accumulation of lipid bodies in the organelle and the lipid component in neuromelanin structure. The major lipids observed in lipid bodies of the organelle are dolichols with lower amounts of other lipids. Proteins of aggregation and degradation pathways were present, suggesting a role for accumulation by this organelle when the ubiquitin-proteasome system is inadequate. The presence of proteins associated with aging and storage diseases may reflect impaired autophagic degradation or impaired function of lysosomal enzymes. The identification of typical autophagy proteins and double membranes demonstrates the organelle's autophagic nature and indicates that it has engulfed neuromelanin precursors from the cytosol. Based on these data, it appears that the neuromelanin-containing organelle has a very slow turnover during the life of a neuron and represents an intracellular compartment of final destination for numerous molecules not degraded by other systems.

16.
NPJ Parkinsons Dis ; 4: 11, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29644335

RESUMO

The diagnosis of Parkinson's disease (PD) occurs after pathogenesis is advanced and many substantia nigra (SN) dopamine neurons have already died. Now that therapies to block this neuronal loss are under development, it is imperative that the disease be diagnosed at earlier stages and that the response to therapies is monitored. Recent studies suggest this can be accomplished by magnetic resonance imaging (MRI) detection of neuromelanin (NM), the characteristic pigment of SN dopaminergic, and locus coeruleus (LC) noradrenergic neurons. NM is an autophagic product synthesized via oxidation of catecholamines and subsequent reactions, and in the SN and LC it increases linearly during normal aging. In PD, however, the pigment is lost when SN and LC neurons die. As shown nearly 25 years ago by Zecca and colleagues, NM's avid binding of iron provides a paramagnetic source to enable electron and nuclear magnetic resonance detection, and thus a means for safe and noninvasive measure in living human brain. Recent technical improvements now provide a means for MRI to differentiate between PD patients and age-matched healthy controls, and should be able to identify changes in SN NM with age in individuals. We discuss how MRI detects NM and how this approach might be improved. We suggest that MRI of NM can be used to confirm PD diagnosis and monitor disease progression. We recommend that for subjects at risk for PD, and perhaps generally for older people, that MRI sequences performed at regular intervals can provide a pre-clinical means to detect presymptomatic PD.

17.
ACS Chem Neurosci ; 8(3): 501-512, 2017 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-28292181

RESUMO

In the substantia nigra of human brain, neuromelanin (NM) released by degenerating neurons can activate microglia with consequent neurodegeneration, typical of Parkinson's disease (PD). Synthetic analogues of NM were prepared to develop a PD model reproducing the neuropathological conditions of the disease. Soluble melanin-protein conjugates were obtained by melanization of fibrillated ß-lactoglobulin (fLG). The melanic portion of the conjugates contains either eumelanic (EufLG) or mixed eumelanic/pheomelanic composition (PheofLG), the latter better simulating natural NMs. In addition, the conjugates can be loaded with controlled amounts of iron. Upon melanization, PheofLG-Fe conjugates maintain the amyloid cross-ß protein core as the only structurally organized element, similarly to human NMs. The similarity in composition and structural organization with the natural pigment is reflected by the ability of synthetic NMs to activate microglia, showing potential of the novel conjugates to model NM induced neuroinflammation. Thus, synthetic NM/microglia constitute a new model to develop anti-Parkinson drugs.


Assuntos
Melaninas/análise , Melaninas/síntese química , Melaninas/farmacologia , Microglia/efeitos dos fármacos , Doença de Parkinson/patologia , Amiloide/farmacocinética , Animais , Animais Recém-Nascidos , Arginase/genética , Arginase/metabolismo , Células Cultivadas , Ciclo-Oxigenase 2/genética , Ciclo-Oxigenase 2/metabolismo , Dopamina/metabolismo , Humanos , Interleucina-1beta/genética , Interleucina-1beta/metabolismo , Ferro/metabolismo , Lactoglobulinas/farmacocinética , Lectinas Tipo C/genética , Lectinas Tipo C/metabolismo , Lectinas de Ligação a Manose/genética , Lectinas de Ligação a Manose/metabolismo , Melaninas/química , Microglia/ultraestrutura , Modelos Biológicos , Óxido Nítrico Sintase Tipo II/genética , Óxido Nítrico Sintase Tipo II/metabolismo , Ratos , Ratos Sprague-Dawley , Receptores de Superfície Celular/genética , Receptores de Superfície Celular/metabolismo , Substância Negra/efeitos dos fármacos , Substância Negra/metabolismo
18.
Prog Neurobiol ; 155: 96-119, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-26455458

RESUMO

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.


Assuntos
Envelhecimento/metabolismo , Dopamina/metabolismo , Ferro/metabolismo , Melaninas/metabolismo , Doença de Parkinson/metabolismo , Animais , Humanos
19.
Magn Reson Med ; 78(5): 1790-1800, 2017 11.
Artigo em Inglês | MEDLINE | ID: mdl-28019018

RESUMO

PURPOSE: To investigate the physical mechanisms associated with the contrast observed in neuromelanin MRI. METHODS: Phantoms having different concentrations of synthetic melanins with different degrees of iron loading were examined on a 3 Tesla scanner using relaxometry and quantitative magnetization transfer (MT). RESULTS: Concentration-dependent T1 and T2 shortening was most pronounced for the melanin pigment when combined with iron. Metal-free melanin had a negligible effect on the magnetization transfer spectra. On the contrary, the presence of iron-laden melanins resulted in a decreased magnetization transfer ratio. The presence of melanin or iron (or both) did not have a significant effect on the macromolecular content, represented by the pool size ratio. CONCLUSION: The primary mechanism underlying contrast in neuromelanin-MRI appears to be the T1 reduction associated with melanin-iron complexes. The macromolecular content is not significantly influenced by the presence of melanin with or without iron, and thus the MT is not directly affected. However, as T1 plays a role in determining the MT-weighted signal, the magnetization transfer ratio is reduced in the presence of melanin-iron complexes. Magn Reson Med 78:1790-1800, 2017. © 2016 International Society for Magnetic Resonance in Medicine.


Assuntos
Imageamento por Ressonância Magnética/métodos , Melaninas/análise , Melaninas/química , Humanos , Ferro/química , Imageamento por Ressonância Magnética/instrumentação , Modelos Biológicos , Imagens de Fantasmas , Substância Negra/química
20.
Front Aging Neurosci ; 8: 196, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27597825

RESUMO

Parkinson's disease (PD) is a progressive neurodegenerative disorder in which the major pathologic substrate is a loss of dopaminergic neurons from the substantia nigra. Our main objective was to determine the correspondence between changes in the substantia nigra, evident in neuromelanin and iron sensitive magnetic resonance imaging (MRI), and dopaminergic striatal innervation loss in patients with PD. Eighteen patients and 18 healthy control subjects were included in the study. Using neuromelanin-MRI, we measured the volume of the substantia nigra and the contrast-to-noise-ratio between substantia nigra and a background region. The apparent transverse relaxation rate and magnetic susceptibility of the substantia nigra were calculated from dual-echo MRI. Striatal dopaminergic innervation was measured as density of dopamine transporter (DAT) by means of single-photon emission computed tomography and [(123)I] N-ω-fluoropropyl-2b-carbomethoxy-3b-(4-iodophenyl) tropane. Patients showed a reduced volume of the substantia nigra and contrast-to-noise-ratio and both positively correlated with the corresponding striatal DAT density. The apparent transverse relaxation rate and magnetic susceptibility values of the substantia nigra did not differ between patients and healthy controls. The best predictor of DAT reduction was the volume of the substantia nigra. Clinical and imaging correlations were also investigated for the locus coeruleus. Our results suggest that neuromelanin-MRI can be used for quantifying substantia nigra pathology in PD where it closely correlates with dopaminergic striatal innervation loss. Longitudinal studies should further explore the role of Neuromelanin-MRI as an imaging biomarker of PD, especially for subjects at risk of developing the disease.

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