RESUMEN
Mutations in the human ATP13A2 gene are associated with an early-onset form of Parkinson's disease (PD) known as Kufor Rakeb Syndrome (KRS). Patients with KRS show increased iron deposition in the basal ganglia, suggesting iron toxicity-induced neurodegeneration as a potential pathogenesis associated with the ATP13A2 mutation. Previously we demonstrated that functional losses of ATP13A2 disrupt the lysosomes ability to store excess iron, leading to reduce survival of dopaminergic neuronal cells. To understand the possible mechanisms involved, we studied a Caenorhabditis elegans mutant defective in catp-6 function, an ortholog of human ATP13A2 gene. Here we show that catp-6 mutant worms have defective autophagy and lysosomal function, demonstrate characteristic PD phenotypes including reduced motor function and dysregulated iron metabolism. Additionally, these mutants have defective mitochondrial health, which is rescuable via iron chelation or mitophagy induction.
Asunto(s)
Adenosina Trifosfatasas/metabolismo , Proteínas de Caenorhabditis elegans/metabolismo , Hierro/metabolismo , Mitocondrias/metabolismo , ATPasas de Translocación de Protón/metabolismo , Animales , Autofagia , Caenorhabditis elegans , Neuronas Dopaminérgicas/metabolismo , Humanos , Lisosomas/metabolismo , Mutación , Enfermedad de Parkinson/metabolismo , Trastornos Parkinsonianos/metabolismoRESUMEN
Several studies have suggested that increases in astrocytic monoamine oxidase B (MAO-B) levels in conjunction with Parkinson's disease (PD) may contribute to subsequent neuropathology associated with the disorder. MAO-B inhibitors are currently widely used as symptomatic therapeutics for PD and, although somewhat controversial, these drugs may also exhibit disease-modifying properties. To obtain a better understanding of the potential role of MAO-B in disease neuropathology, we created an inducible astrocyte-specific transgenic MAO-B mouse model. Here, we summarize findings associated with this model, including neuropathological PD features associated with it.
Asunto(s)
Astrocitos/metabolismo , Monoaminooxidasa/genética , Enfermedad de Parkinson/genética , Animales , Modelos Animales de Enfermedad , Ratones , Ratones Transgénicos , Monoaminooxidasa/metabolismo , Estrés Oxidativo/genética , Enfermedad de Parkinson/metabolismoRESUMEN
We previously reported that pharmacological inhibition of a class of enzymes known as prolyl hydroxylase domain proteins (PHDs) has neuroprotective effects in various in vitro and in vivo models of Parkinson's disease (PD). We hypothesized that this was due to inhibition of the PHD2 isoform, preventing it from hydroxylating the transcription factor hypoxia inducible factor 1 α (HIF1α), targeting it for eventual proteasomal degradation. HIF1α itself induces the transcription of various cellular stress genes, including several involved in iron metabolism. Although all three isoforms of PHD are expressed within vulnerable dopaminergic (DAergic) substantia nigra pars compacta neurons, only select downregulation of the PHD2 isoform was found to protect against in vivo neurodegenerative effects associated with the mitochondrial neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. These findings were corroborated in induced pluripotent stem cell-derived neurons, providing validation in a pertinent human cell model. PHD2 inhibition was found to result in increased expression of ATP13A2, mutation of which is responsible for a rare juvenile form of PD known as Kufor-Rakeb syndrome. Knockdown of ATP13A2 expression within human DAergic cells was found to abrogate restoration of cellular iron homeostasis and neuronal cell viability elicited by inhibition of PHD2 under conditions of mitochondrial stress, likely via effects on lysosomal iron storage. These data suggest that regulation of ATP13A2 by the PHD2-HIF1α signaling pathway affects cellular iron homeostasis and DAergic neuronal survival. This constitutes a heretofore unrecognized process associated with loss of ATP13A2 function that could have wide-ranging implications for it as a therapeutic target for PD and other related conditions. SIGNIFICANCE STATEMENT: Reductions in PHD2 activity within dopaminergic neurons in vivo and in cultured human induced pluripotent stem cell-derived neurons protects against mitochondrial stress-induced neurotoxicity. Protective effects are dependent on downstream HIF-1α expression. Knockdown of ATP13A2, a gene linked to a rare juvenile form of Parkinson's disease and recently identified as a novel HIF1α target, was found to abrogate maintenance of cellular iron homeostasis and neuronal viability elicited by PHD2 inhibition in vivo and in cultured dopaminergic cells under conditions of mitochondrial stress. Mechanistically, this was due to ATP13A2's role in maintaining lysosomal iron stores. This constitutes a novel mechanism by which alterations in ATP13A2 activity may be driving PD-related neuropathology.
Asunto(s)
Adenosina Trifosfatasas/metabolismo , Homeostasis/fisiología , Subunidad alfa del Factor 1 Inducible por Hipoxia/metabolismo , Prolina Dioxigenasas del Factor Inducible por Hipoxia/metabolismo , Hierro/metabolismo , Proteínas de la Membrana/metabolismo , Trastornos Parkinsonianos/metabolismo , Transducción de Señal/fisiología , Adenosina Trifosfatasas/genética , Animales , Modelos Animales de Enfermedad , Fluoresceínas/metabolismo , Regulación de la Expresión Génica/genética , Homeostasis/genética , Humanos , Subunidad alfa del Factor 1 Inducible por Hipoxia/genética , Prolina Dioxigenasas del Factor Inducible por Hipoxia/genética , Lisosomas/metabolismo , Proteínas de la Membrana/genética , Ratones , Ratones Transgénicos , Neuroblastoma/patología , Trastornos Parkinsonianos/inducido químicamente , Células Madre Pluripotentes/efectos de los fármacos , Células Madre Pluripotentes/fisiología , ATPasas de Translocación de Protón , ARN Mensajero/metabolismo , ARN Interferente Pequeño/genética , ARN Interferente Pequeño/metabolismo , Transducción de Señal/efectos de los fármacos , Transducción de Señal/genética , Tirosina 3-Monooxigenasa/metabolismoRESUMEN
Monoamine oxidase B (MAO-B) has been implicated in the pathogenesis of Alzheimer's disease (AD) and other neurodegenerative disorders. Increased MAO-B expression in astroglia has been observed adjacent to amyloid plaques in AD patient brains. This phenomenon is hypothesized to lead to increased production of hydrogen peroxide and reactive oxygen species (ROS), thereby contributing to AD pathology. Therefore, reduction of ROS-induced oxidative stress via inhibition of MAO-B activity may delay the progression of the disease. In the present study we report the pharmacological properties of sembragiline, a novel selective MAO-B inhibitor specifically developed for the treatment of AD, and on its effect on ROS-mediated neuronal injury and astrogliosis in MAO-B transgenic animals. Sembragiline showed potent and long-lasting MAO-B-selective inhibition and did not inhibit MAO-A at doses where full inhibition of MAO-B was observed. Such selectivity should translate into a favorable clinical safety profile. Indeed, sembragiline neither induced the serotonin syndrome when administered together with the serotonin precursor l-5-hydroxytryptophan in combination with antidepressants such as fluoxetine, nor potentiated the pressor effect of tyramine. Additionally, in experiments using a transgenic animal model conditionally overexpressing MAO-B in astroglia, sembragiline protected against neuronal loss and reduced both ROS formation and reactive astrogliosis. Taken together, these findings warrant further investigation of the potential therapeutic benefit of MAO-B inhibitors in patients with AD and other neurologic disorders.
Asunto(s)
Acetamidas/uso terapéutico , Enfermedad de Alzheimer/tratamiento farmacológico , Inhibidores de la Monoaminooxidasa/uso terapéutico , Monoaminooxidasa/efectos de los fármacos , Pirrolidinonas/uso terapéutico , 5-Hidroxitriptófano/farmacología , Acetamidas/farmacocinética , Animales , Astrocitos/efectos de los fármacos , Astrocitos/metabolismo , Gliosis/tratamiento farmacológico , Gliosis/patología , Humanos , Hipertensión/inducido químicamente , Hipertensión/prevención & control , Masculino , Monoaminooxidasa/genética , Monoaminooxidasa/metabolismo , Inhibidores de la Monoaminooxidasa/farmacocinética , Actividad Motora/efectos de los fármacos , Neurotransmisores/metabolismo , Pirrolidinonas/farmacocinética , Ratas , Ratas Transgénicas , Especies Reactivas de Oxígeno/metabolismo , Especificidad por Sustrato , Distribución TisularRESUMEN
Glial activation and subsequent release of neurotoxic proinflammatory factors are believed to play an important role in the pathogenesis of several neurological disorders including Parkinson's disease (PD). Inhibition of glial activation and inflammatory processes may represent a therapeutic target to alleviate neurodegeneration. Securinine, a major natural alkaloid product from the root of the plant Securinega suffruticosa, has been reported to have potent biological activity and is used in the treatment of neurological conditions such as amyotrophic lateral sclerosis, poliomyelitis, and multiple sclerosis. In this study, we explored the underlying mechanisms of neuroprotection elicited by securinine, particularly its anti-inflammatory effects in glial cells. Our results demonstrate that securinine significantly and dose-dependently suppressed the nitric oxide production in microglia and astrocytic cultures. In addition, securinine inhibited the activation of the inflammatory mediator NF-κB, as well as mitogen-activated protein kinases in lipopolysaccharide- (LPS-) stimulated BV2 cells. Additionally, securinine also inhibited interferon-γ- (IFN-γ-) induced nitric oxide levels and iNOS mRNA expression. Furthermore, conditioned media (CM) from securinine pretreated BV2 cells significantly reduced mesencephalic dopaminergic neurotoxicity compared with CM from LPS stimulated microglia. These findings suggest that securinine may be a potential candidate for the treatment of neurodegenerative diseases related to neuroinflammation.
Asunto(s)
Azepinas/uso terapéutico , Compuestos Heterocíclicos de Anillo en Puente/uso terapéutico , Lactonas/uso terapéutico , Enfermedad de Parkinson/tratamiento farmacológico , Enfermedad de Parkinson/metabolismo , Piperidinas/uso terapéutico , Animales , Antiinflamatorios/uso terapéutico , Astrocitos/efectos de los fármacos , Western Blotting , Supervivencia Celular/efectos de los fármacos , Factor 3 de Genes Estimulados por el Interferón/metabolismo , Lipopolisacáridos/farmacología , Ratones , Microglía/efectos de los fármacos , Proteínas Quinasas Activadas por Mitógenos/metabolismo , FN-kappa B/metabolismo , Fármacos Neuroprotectores/uso terapéutico , Óxido Nítrico Sintasa de Tipo II/metabolismo , Nitritos/metabolismo , Enfermedad de Parkinson/inmunología , Fosforilación/efectos de los fármacos , Reacción en Cadena de la PolimerasaRESUMEN
Following its activation by PINK1, parkin is recruited to depolarized mitochondria where it ubiquitinates outer mitochondrial membrane proteins, initiating lysosomal-mediated degradation of these organelles. Mutations in the gene encoding parkin, PARK2, result in both familial and sporadic forms of Parkinson's disease (PD) in conjunction with reductions in removal of damaged mitochondria. In contrast to what has been reported for other PARK2 mutations, expression of the Q311X mutation in vivo in mice appears to involve a downstream step in the autophagic pathway at the level of lysosomal function. This coincides with increased PARIS expression and reduced expression of a reciprocal signaling pathway involving the master mitochondrial regulator peroxisome proliferator-activated receptor-gamma coactivator (PGC1α) and the lysosomal regulator transcription factor EB (TFEB). Treatment with rapamycin was found to independently restore PGC1α-TFEB signaling in a manner not requiring parkin activity and to abrogate impairment of mitochondrial quality control and neurodegenerative features associated with this in vivo model. Losses in PGC1α-TFEB signaling in cultured rat DAergic cells expressing the Q311X mutation associated with reduced mitochondrial function and cell viability were found to be PARIS-dependent and to be independently restored by rapamycin in a manner requiring TFEB. Studies in human iPSC-derived neurons demonstrate that TFEB induction can restore mitochondrial function and cell viability in a mitochondrially compromised human cell model. Based on these data, we propose that the parkin Q311X mutation impacts on mitochondrial quality control via PARIS-mediated regulation of PGC1α-TFEB signaling and that this can be independently restored via upregulation of TFEB function. SIGNIFICANCE STATEMENT: Mutations in PARK2 are generally associated with loss in ability to interact with PINK1, impacting on autophagic initiation. Our data suggest that, in the case of at least one parkin mutation, Q311X, detrimental effects are due to inhibition at the level of downstream lysosomal function. Mechanistically, this involves elevations in PARIS protein levels and subsequent effects on PGC1α-TFEB signaling that normally regulates mitochondrial quality control. Treatment with rapamycin independently restores PGC1α-TFEB signaling in a manner not requiring parkin activity and abrogates subsequent mitochondrial impairment and neuronal cell loss. Taken in total, our data suggest that the parkin Q311X mutation impacts on mitochondrial quality control via PARIS-mediated regulation of PGC1α-TFEB signaling and that this can be independently restored via rapamycin.
Asunto(s)
Factores de Transcripción Básicos con Cremalleras de Leucinas y Motivos Hélice-Asa-Hélice/fisiología , Mitocondrias/fisiología , Mutación Puntual , Transducción de Señal/efectos de los fármacos , Sirolimus/farmacología , Factores de Transcripción/fisiología , Ubiquitina-Proteína Ligasas/fisiología , Animales , Autofagia , Cruzamientos Genéticos , Neuronas Dopaminérgicas/citología , Complejo I de Transporte de Electrón/fisiología , Conducta Exploratoria , Humanos , Lisosomas/fisiología , Ratones , Ratones Transgénicos , Microscopía Electrónica , Coactivador 1-alfa del Receptor Activado por Proliferadores de Peroxisomas gamma , Ratas , Proteínas Represoras/fisiología , Transducción de Señal/fisiología , Ubiquitina-Proteína Ligasas/genética , Ubiquitina-Proteína Ligasas/metabolismoRESUMEN
Loss of parkin E3 ligase activity as a result of parkin gene mutation in rare familial forms of Parkinson's disease (PD) has been shown to be detrimental to mitochondrial function and to contribute to ensuing neurodegeneration. This has been shown by ourselves and others to be in part due to reductions in parkin-mediated ubiquitination of the transcriptional repressor PARIS, limiting the protein's subsequent degradation by the proteasome. Subsequent elevations in PARIS protein levels result in reduced expression of the master mitochondrial regulator PGC-1α, impacting in turn on mitochondrial function. Here, we report that oxidatively-mediated reductions in parkin solubility and function in a mouse model of age-related sporadic PD coincides with increased PARIS levels and reduced PGC-1α signaling. Furthermore, restoration of PGC-1α expression was found to abrogate losses in mitochondrial function and degeneration of dopaminergic (DAergic) neurons within the substantia nigra pars compacta (SNpc) associated with this particular model. These findings suggest that the PGC-1α signaling pathway constitutes a viable therapeutic target for the treatment of not only familial PD, but also more common sporadic forms of the disorder.
Asunto(s)
Neuronas Dopaminérgicas/metabolismo , Estrés Oxidativo/fisiología , Enfermedad de Parkinson/metabolismo , Coactivador 1-alfa del Receptor Activado por Proliferadores de Peroxisomas gamma/metabolismo , Ubiquitina-Proteína Ligasas/metabolismo , Animales , Humanos , Ratones Transgénicos , Mitocondrias/metabolismo , Coactivador 1-alfa del Receptor Activado por Proliferadores de Peroxisomas gamma/genética , Complejo de la Endopetidasa Proteasomal/metabolismo , Transducción de Señal/efectos de los fármacos , Sustancia Negra/metabolismoRESUMEN
Accumulation of mitochondrial DNA deletions is observed especially in dopaminergic neurons of the substantia nigra during ageing and even more in Parkinson's disease. The resulting mitochondrial dysfunction is suspected to play an important role in neurodegeneration. However, the molecular mechanisms involved in the preferential generation of mitochondrial DNA deletions in dopaminergic neurons are still unknown. To study this phenomenon, we developed novel polymerase chain reaction strategies to detect distinct mitochondrial DNA deletions and monitor their accumulation patterns. Applying these approaches in in vitro and in vivo models, we show that catecholamine metabolism drives the generation and accumulation of these mitochondrial DNA mutations. As in humans, age-related accumulation of mitochondrial DNA deletions is most prominent in dopaminergic areas of mouse brain and even higher in the catecholaminergic adrenal medulla. Dopamine treatment of terminally differentiated neuroblastoma cells, as well as stimulation of dopamine turnover in mice over-expressing monoamine oxidase B both induce multiple mitochondrial DNA deletions. Our results thus identify catecholamine metabolism as the driving force behind mitochondrial DNA deletions, probably being an important factor in the ageing-associated degeneration of dopaminergic neurons.
Asunto(s)
Catecolaminas/metabolismo , ADN Mitocondrial/genética , ADN Mitocondrial/metabolismo , Neuronas Dopaminérgicas/metabolismo , Eliminación de Gen , Animales , Línea Celular Tumoral , Humanos , Ratones , Ratones Endogámicos C57BLRESUMEN
Autophagy-lysosomal function is crucial for maintaining healthy lifespan and preventing age-related diseases. The transcription factor TFEB plays a key role in regulating this pathway. Decreased TFEB expression is associated with various age-related disorders, making it a promising therapeutic target. In this study, we screened a natural product library and discovered mitophagy-inducing coumarin (MIC), a benzocoumarin compound that enhances TFEB expression and lysosomal function. MIC robustly increases the lifespan of Caenorhabditis elegans in an HLH-30/TFEB-dependent and mitophagy-dependent manner involving DCT-1/BNIP3 while also preventing mitochondrial dysfunction in mammalian cells. Mechanistically, MIC acts by inhibiting ligand-induced activation of the nuclear hormone receptor DAF-12/FXR, which, in turn, induces mitophagy and extends lifespan. In conclusion, our study uncovers MIC as a promising drug-like molecule that enhances mitochondrial function and extends lifespan by targeting DAF-12/FXR. Furthermore, we discovered DAF-12/FXR as a previously unknown upstream regulator of HLH-30/TFEB and mitophagy.
Asunto(s)
Proteínas de Caenorhabditis elegans , Mitofagia , Animales , Longevidad/genética , Caenorhabditis elegans/genética , Autofagia , Receptores Citoplasmáticos y Nucleares/genética , Mamíferos/metabolismo , Proteínas de Caenorhabditis elegans/genética , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismoRESUMEN
Parkinson's disease (PD) is a chronic, neurodegenerative condition characterized by motor symptoms such as bradykinesia, rigidity, and tremor, alongside multiple nonmotor symptoms. The appearance of motor symptoms is linked to progressive dopaminergic neuron loss within the substantia nigra. PD incidence increases sharply with age, suggesting a strong association between mechanisms driving biological aging and the development and progression of PD. However, the role of aging in the pathogenesis of PD remains understudied. Numerous models of PD, including cell models, toxin-induced models, and genetic models in rodents and nonhuman primates (NHPs), reproduce different aspects of PD, but preclinical studies of PD rarely incorporate age as a factor. Studies using patient neurons derived from stem cells via reprogramming methods retain some aging features, but their characterization, particularly of aging markers and reproducibility of neuron type, is suboptimal. Investigation of age-related changes in PD using animal models indicates an association, but this is likely in conjunction with other disease drivers. The biggest barrier to drawing firm conclusions is that each model lacks full characterization and appropriate time-course assessments. There is a need to systematically investigate whether aging increases the susceptibility of mouse, rat, and NHP models to develop PD and understand the role of cell models. We propose that a significant investment in time and resources, together with the coordination and sharing of resources, knowledge, and data, is required to accelerate progress in understanding the role of biological aging in PD development and improve the reliability of models to test interventions.
RESUMEN
Aging is associated with changes in circulating levels of various molecules, some of which remain undefined. We find that concentrations of circulating taurine decline with aging in mice, monkeys, and humans. A reversal of this decline through taurine supplementation increased the health span (the period of healthy living) and life span in mice and health span in monkeys. Mechanistically, taurine reduced cellular senescence, protected against telomerase deficiency, suppressed mitochondrial dysfunction, decreased DNA damage, and attenuated inflammaging. In humans, lower taurine concentrations correlated with several age-related diseases and taurine concentrations increased after acute endurance exercise. Thus, taurine deficiency may be a driver of aging because its reversal increases health span in worms, rodents, and primates and life span in worms and rodents. Clinical trials in humans seem warranted to test whether taurine deficiency might drive aging in humans.
Asunto(s)
Envejecimiento , Taurina , Animales , Humanos , Ratones , Envejecimiento/sangre , Envejecimiento/efectos de los fármacos , Envejecimiento/metabolismo , Senescencia Celular , Haplorrinos , Longevidad/efectos de los fármacos , Longevidad/fisiología , Taurina/sangre , Taurina/deficiencia , Taurina/farmacología , Suplementos Dietéticos , Daño del ADN/efectos de los fármacos , Telomerasa/metabolismoRESUMEN
Cellular senescence is a potential tumor-suppressive mechanism that generally results in an irreversible cell cycle arrest. Senescent cells accumulate with age and actively secrete soluble factors, collectively termed the 'senescence-associated secretory phenotype' (SASP), which has both beneficial and detrimental effects. Although the contribution of senescent cells to age-related pathologies has been well-established outside the brain, emerging evidence indicates that brain cells also undergo cellular senescence and contribute to neuronal loss in the context of age-related neurodegenerative diseases. Contribution of senescent cells in the pathogenesis of neurological disorders has led to the possibility of eliminating senescence cells via pharmacological compounds called senolytics. Recently several senolytics have been demonstrated to elicit improved cognitive performance and healthspan in mouse models of neurodegeneration. However, their translation for use in the clinic still holds several potential challenges. This review summarizes available senolytics, their purported mode of action, and possible off-target effects. We also discuss possible alternative strategies that may help minimize potential side-effects associated with the senolytics approach.
Asunto(s)
Envejecimiento , Senescencia Celular , Enfermedades Neurodegenerativas , Senoterapéuticos/farmacología , Envejecimiento/efectos de los fármacos , Envejecimiento/fisiología , Animales , Senescencia Celular/efectos de los fármacos , Senescencia Celular/fisiología , Humanos , Ratones , Enfermedades Neurodegenerativas/tratamiento farmacológico , Enfermedades Neurodegenerativas/metabolismo , Fenotipo Secretor Asociado a la Senescencia/efectos de los fármacosRESUMEN
In the nematode Caenorhabditis elegans, signals derived from bacteria in the diet, the animal's major nutrient source, can modulate both behavior and healthspan. Here we describe a dual role for trimethylamine (TMA), a human gut flora metabolite, which acts as a nutrient signal and a neurotoxin. TMA and its associated metabolites are produced by the human gut microbiome and have been suggested to serve as risk biomarkers for diabetes and cardiovascular diseases. We demonstrate that the tyramine receptor TYRA-3, a conserved G protein-coupled receptor (GPCR), is required to sense TMA and mediate its responses. TMA activates guanylyl cyclase DAF-11 signaling through TYRA-3 in amphid neurons (ASK) and ciliated neurons (BAG) to mediate food-sensing behavior. Bacterial mutants deficient in TMA production enhance dauer formation, extend lifespan, and are less preferred as a food source. Increased levels of TMA lead to neural damage in models of Parkinson's disease and shorten lifespan. Our results reveal conserved signaling pathways modulated by TMA in C. elegans that are likely to be relevant for its effects in mammalian systems.
Asunto(s)
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/metabolismo , Guanilato Ciclasa/metabolismo , Longevidad , Metilaminas/metabolismo , Receptores de Catecolaminas/metabolismo , Animales , Bacterias/enzimología , Caenorhabditis elegans/genética , Caenorhabditis elegans/crecimiento & desarrollo , Neuronas Dopaminérgicas/patología , Proteínas Hierro-Azufre/genética , Mutación , Oxidorreductasas/genética , Transducción de SeñalRESUMEN
Parkinson's disease (PD) is an adult-onset neurodegenerative disorder characterized by preferential loss of dopaminergic neurons in an area of the midbrain called the substantia nigra (SN) along with occurrence of intraneuronal inclusions called Lewy bodies. The majority of cases of PD are sporadic in nature with late onset (95% of patients); however a few PD cases (5%) are seen in familial clusters with generally earlier onset. Although PD has been heavily researched, so far the exact cause of the rather selective cell death is unknown. Multiple lines of evidence suggest an important role for oxidative stress. Dopaminergic neurons (DA) are particularly prone to oxidative stress due to DA metabolism and auto-oxidation combined with increased iron, decreased total glutathione levels and mitochondrial complex I inhibition-induced ROS production in the SN which can lead to cell death by exceeding the oxidative capacity of DA-containing cells in the region. Enhancing antioxidant capabilities and chelating labile iron pools in this region therefore constitutes a rational approach to prevent or slow ongoing damage of DA neurons. In this review, we summarize the various sources of reactive oxygen species that may cause redox imbalance in PD as well as potential therapeutic targets for attenuation of oxidative stress associated with PD.
Asunto(s)
Enfermedad de Parkinson/metabolismo , Animales , Antioxidantes/metabolismo , Dopamina/metabolismo , Radicales Libres/metabolismo , Humanos , Hierro/metabolismo , Oxidación-Reducción , Enfermedad de Parkinson/patología , Enfermedad de Parkinson/terapiaRESUMEN
Alzheimer's disease (AD) is a neurodegenerative disorder and the leading cause of dementia in aged populations worldwide. The deposition of toxic protein aggregates such as amyloid beta (Aß) is a hallmark of AD, and there is growing awareness that a key driver of AD pathogenesis is the neuroinflammatory cascade triggered and sustained by these proteins. Consequently, interventions that suppress prolonged neuroinflammation represent viable therapeutic approaches for AD. In this context, we tested the natural product gedunin which is an anti-inflammatory molecule, found in the seeds of the neem tree (Azadirachta indica), whose mechanism of action remains to be fully elucidated. Using a mouse microglia cell line (IMG), we show that gedunin suppresses neuroinflammation arising from Aß1-42 oligomer exposure. Our results demonstrate that gedunin suppresses Aß1-42-induced NF-κB activation and its targets, including nitric oxide (NO) and IL-1ß, known proinflammatory molecules. Further, we show that gedunin inhibits neuroinflammation by activating nuclear factor 2 erythroid-related factor 2 (Nrf2) and its downstream targets γ-glutamylcysteine synthetase, heme oxygenase 1, and NADPH quinone dehydrogenase 1, which are involved in quenching reactive oxygen and nitrogen species (NO) generated by NF-κB activation. Nrf2 activation appears essential for the anti-inflammatory effect because when silenced, the proinflammatory effects of Aß1-42 are enhanced and the protective effect of gedunin against NO production is reduced. Additionally, using human neuronal cells (SH-SY5Y), we show that gedunin prevents neurotoxicity secondary to Aß-induced microglial activation. In conclusion, our findings highlight a potential therapeutic role of gedunin in neurodegenerative diseases.
Asunto(s)
Péptidos beta-Amiloides/toxicidad , Limoninas/farmacología , Microglía/patología , Factor 2 Relacionado con NF-E2/metabolismo , FN-kappa B/metabolismo , Fragmentos de Péptidos/toxicidad , Transducción de Señal , Animales , Línea Celular , Núcleo Celular/efectos de los fármacos , Núcleo Celular/metabolismo , Humanos , Interleucina-1beta/metabolismo , Ratones , Microglía/efectos de los fármacos , Microglía/metabolismo , Neurotoxinas/toxicidad , Óxido Nítrico/metabolismo , Óxido Nítrico Sintasa de Tipo II/metabolismo , Fosforilación/efectos de los fármacos , Transporte de Proteínas/efectos de los fármacos , Transducción de Señal/efectos de los fármacos , Proteínas tau/metabolismoRESUMEN
Parkinson's disease is a neurodegenerative disorder characterized by the preferential loss of midbrain dopaminergic neurons in the substantia nigra (SN). One of the earliest detectable biochemical alterations that occurs in the Parkinsonian brain is a marked reduction in SN levels of total glutathione (glutathione plus glutathione disulfide), occurring before losses in mitochondrial complex I (CI) activity, striatal dopamine levels, or midbrain dopaminergic neurodegeneration associated with the disease. Previous in vitro data from our laboratory has suggested that prolonged depletion of dopaminergic glutathione results in selective impairment of mitochondrial complex I activity through a reversible thiol oxidation event. To address the effects of depletion in dopaminergic glutathione levels in vivo on the nigrostriatal system, we created genetically engineered transgenic mouse lines in which expression of gamma-glutamyl cysteine ligase, the rate-limiting enzyme in de novo glutathione synthesis, can be inducibly downregulated in catecholaminergic neurons, including those of the SN. A novel method for isolation of purified dopaminergic striatal synaptosomes was used to study the impact of dopaminergic glutathione depletion on mitochondrial events demonstrated previously to occur in vitro as a consequence of this alteration. Dopaminergic glutathione depletion was found to result in a selective reversible thiol-oxidation-dependent mitochondrial complex I inhibition, followed by an age-related nigrostriatal neurodegeneration. This suggests that depletion in glutathione within dopaminergic SN neurons has a direct impact on mitochondrial complex I activity via increased nitric oxide-related thiol oxidation and age-related dopaminergic SN cell loss.
Asunto(s)
Cuerpo Estriado/metabolismo , Cuerpo Estriado/patología , Dopamina/fisiología , Glutatión/biosíntesis , Degeneración Nerviosa/metabolismo , Degeneración Nerviosa/patología , Sustancia Negra/metabolismo , Sustancia Negra/patología , Factores de Edad , Animales , Supervivencia Celular/fisiología , Dopamina/genética , Glutatión/genética , Mesencéfalo/metabolismo , Mesencéfalo/patología , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Degeneración Nerviosa/genética , Neuronas/metabolismo , Neuronas/patologíaRESUMEN
Dopaminergic neurodegeneration during Parkinson disease (PD) involves several pathways including proteasome inhibition, alpha-synuclein (alpha-syn) aggregation, mitochondrial dysfunction, and glutathione (GSH) depletion. We have utilized a systems biology approach and built a dynamic model to understand and link the various events related to PD pathophysiology. We have corroborated the modeling data by examining the effects of alpha-syn expression in the absence and presence of proteasome inhibition on GSH metabolism in dopaminergic neuronal cultures. We report here that the expression of the mutant A53T form of alpha-syn is neurotoxic and causes GSH depletion in cells after proteasome inhibition, compared to wild-type alpha-syn-expressing cells and vector control. Modeling data predicted that GSH depletion in these cells was due to ATP loss associated with mitochondrial dysfunction. ATP depletion elicited by combined A53T expression and proteasome inhibition results in decreased de novo synthesis of GSH via the rate-limiting enzyme gamma-glutamyl cysteine ligase. Based on these data and other recent reports, we propose a novel dynamic model to explain how the presence of mutated alpha-syn protein or proteasome inhibition may individually impact on mitochondrial function and in combination result in alterations in GSH metabolism via enhanced mitochondrial dysfunction.
Asunto(s)
Glutatión/química , Glutatión/metabolismo , Enfermedad de Parkinson/patología , Inhibidores de Proteasoma , alfa-Sinucleína/biosíntesis , Adenosina Trifosfato/química , Animales , Células Cultivadas , Dopamina/metabolismo , Humanos , Mitocondrias/metabolismo , Modelos Biológicos , Mutación , Enfermedades Neurodegenerativas/metabolismo , Neuronas/metabolismo , Enfermedad de Parkinson/metabolismo , RatasRESUMEN
The heat shock factor 90 (hsp90) complex has long been associated with neuropathological phenotypes linked to Parkinson's disease (PD) and its inhibition is neuroprotective in disease models. Hsp90 is conventionally believed to act by suppressing induction of hsp70. Here, we report a novel hsp70-independent mechanism by which Hsp90 may also contribute to PD-associated neuropathology. We previously reported that inhibition of the enzyme prolyl hydroxylase domain 2 (PHD2) in conjunction with increases in hypoxia-inducible factor 1 alpha (HIF1α) results in protection of vulnerable dopaminergic substantia nigra pars compacta (DAergic SNpc) neurons in in vitro and in vivo models of PD. We discovered an increased interaction between PHD2 and the p23:Hsp90 chaperone complex in response to mitochondrial stress elicited by the mitochondrial neurotoxin 1-methyl-4-phenylpyridine (MPP+) within cultured DAergic cells. Genetic p23 knockdown was found to result in decreases in steady-state PHD2 protein and activity and reduced susceptibility to MPP+ neurotoxicity. Administration of the p23 inhibitor gedunin was also neuroprotective in these cells as well as in human induced pluripotent stem cell (iPSC)-derived neurons. Our data suggests that mitochondrial stress-mediated elevations in PHD2 interaction with the p23-hsp90 complex have detrimental effects on the survival of DAergic neurons, while p23 inhibition is neuroprotective. We propose that neurotoxic effects are tied to enhanced PHD2 stabilization by the hsp90-p23 chaperone complex that is abrogated by p23 inhibition. This demonstrates a novel connection between two independent pathways previously linked to PD, hsp90 and PHD2-HIF1α, which could have important implications for here-to-fore unexplored mechanisms underlying PD neuropathology.
Asunto(s)
Neuronas Dopaminérgicas/patología , Proteínas HSP90 de Choque Térmico/metabolismo , Mitocondrias/patología , Chaperonas Moleculares/metabolismo , Enfermedad de Parkinson/metabolismo , Procolágeno-Prolina Dioxigenasa/metabolismo , 1-Metil-4-fenilpiridinio/antagonistas & inhibidores , Animales , Células Cultivadas , Neuronas Dopaminérgicas/efectos de los fármacos , Técnicas de Silenciamiento del Gen , Prolina Dioxigenasas del Factor Inducible por Hipoxia , Limoninas/farmacología , Mitocondrias/efectos de los fármacos , Chaperonas Moleculares/antagonistas & inhibidores , Chaperonas Moleculares/genética , Fármacos Neuroprotectores/farmacología , RatasRESUMEN
Exposure to the herbicide paraquat (PQ) is associated with an increased risk of idiopathic Parkinson's disease (PD). Therapies based on PQ's presumed mechanisms of action have not, however, yielded effective disease therapies. Cellular senescence is an anticancer mechanism that arrests proliferation of replication-competent cells and results in a pro-inflammatory senescence-associated secretory phenotype (SASP) capable of damaging neighboring tissues. Here, we demonstrate that senescent cell markers are preferentially present within astrocytes in PD brain tissues. Additionally, PQ was found to induce astrocytic senescence and an SASP in vitro and in vivo, and senescent cell depletion in the latter protects against PQ-induced neuropathology. Our data suggest that exposure to certain environmental toxins promotes accumulation of senescent cells in the aging brain, which can contribute to dopaminergic neurodegeneration. Therapies that target senescent cells may constitute a strategy for treatment of sporadic PD, for which environmental exposure is a major risk factor.