Induction of the Phase II Detoxification Pathway Suppresses Neuron Loss in Drosophila Models of Parkinson's Disease (original) (raw)
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The Journal of Neuroscience, 2008
␣-Synuclein aggregates are a common feature of sporadic Parkinson's disease (PD), and mutations that increase ␣-synuclein abundance confer rare heritable forms of PD. Although these findings suggest that ␣-synuclein plays a central role in the pathogenesis of this disorder, little is known of the mechanism by which ␣-synuclein promotes neuron loss or the factors that regulate ␣-synuclein toxicity. To address these matters, we tested candidate modifiers of ␣-synuclein toxicity using a Drosophila model of PD. In the current work, we focused on phase II detoxification enzymes involved in glutathione metabolism. We find that the neuronal death accompanying ␣-synuclein expression in Drosophila is enhanced by loss-of-function mutations in genes that promote glutathione synthesis and glutathione conjugation. This neuronal loss can be overcome by genetic or pharmacological interventions that increase glutathione synthesis or glutathione conjugation activity. Moreover, these same pharmacological agents suppress neuron loss in Drosophila parkin mutants, a loss-of-function model of PD. Our results suggest that oxidative stress is a feature of ␣-synuclein toxicity and that induction of the phase II detoxification pathway represents a potential preventative therapy for PD.
Parkinson's Disease
Parkinson’s disease (PD) is an age-associated neurodegenerative condition in which some genetic variants are known to increase disease susceptibility on interaction with environmental factors inducing oxidative stress. Different mutations in the SNCA gene are reported as the major genetic contributors to PD. E46K mutation pathogenicity has not been investigated as intensive as other SNCA gene mutations including A30P and A53T. In this study, based on the GAL4-UAS binary genetic tool, transgenic Drosophila melanogaster flies expressing wild-type and E46K-mutated copies of the human SNCA gene were constructed. Western blotting, immunohistochemical analysis, and light and confocal microscopy of flies’ brains were undertaken along with the survival rate measurement, locomotor function assay, and ethanol and paraquat (PQ) tolerance to study α-synuclein neurotoxicity. Biochemical bioassays were carried out to investigate the activity of antioxidant enzymes and alterations in levels of oxi...
Parkinson’s disease (PD) is a class of neurodegenerative disorders in which, complex interactions of genetic and environmental agents are involved in the etiology of both sporadic and familial PD cases. α-synuclein-encoding SNCA gene is known as one of the major genetic contributors of this disease. E46K mutation in SNCA gene has not been investigated as intensive as other SNCA gene mutations including A30P and A53T. In this study, to induce PD in Drosophila flies, UAS-hSNCAWT and UAS-hSNCAE46K transgenic fly lines were constructed, where SNCA gene was over-expressed in flies brains using GAL4-UAS genetic system. Western blot analysis of head samples of SNCA-expressing flies verified SNCA expression at protein level. Light and electron microscopy analysis of ommatidial structures were performed to verify neurodegeneration as a result of α-synuclein gene overexpression in Drosophila transgenic flies. Confocal microscopy analysis of dopaminergic neuron clusters verified cell loss foll...
Fly, 2024
Parkinson's disease (PD), the most prevalent type of parkinsonism, is a progressive neurodegenerative condition marked by several non-motor and motor symptoms. PD is thought to have a complex aetiology that includes a combination of age, genetic predisposition, and environmental factors. Increased expression of α-synuclein (α-Syn) protein is central to the evolvement of neuropathology in this devastating disorder, but the potential of ribose-cysteine and levodopa in abating pathophysiologic changes in PD model is unknown. Crosses were set up between flies conditionally expressing a pathological variant of human α-Syn (UAS-α-Syn) and those expressing GAL4 in neurons (elav-GAL4) to generate offspring referred to as PD flies. Flies were randomly assigned to five groups (n = 40) from the total population of flies, with each group having five replicates. Groups of PD flies were treated with either 500 mg/kg ribose-cysteine diet, 250 mg/kg levodopa diet, or a combination of the two compounds for 21 days, whereas the control group (w 1118) and the PD group were exposed to a diet without ribose-cysteine or levodopa. In addition to various biochemical and neurochemical assays, longevity, larval motility, and gravitaxis assays were carried out. Locomotive capability, lifespan, fecundity, antioxidant state, and neurotransmitter systems were all significantly (p < 0.05) compromised by overexpression of α-Syn. However, flies treated both ribose cysteine and levodopa showed an overall marked improvement in motor functions, lifespan, fecundity, antioxidant status, and neurotransmitter system functions. In conclusion, ribose-cysteine and levodopa, both singly and in combination, potentiated a therapeutic effect on alpha-synuclein transgenic Drosophila melanogaster models of Parkinsonism.
ACS chemical neuroscience, 2018
α-Synuclein (α-Syn) aggregation and amyloid formation are associated with loss of dopaminergic neurons in Parkinson's disease (PD). In addition, familial mutations in α-Syn are shown to be one of the definite causes of PD. Here we have extensively studied familial PD associated α-Syn G51D, H50Q and E46K mutations using Drosophila model system. Our data showed that flies expressing α-Syn familial mutants have a shorter lifespan and exhibit more climbing defects compared to wild-type (WT) flies in an age-dependent manner. The immuno-fluorescence studies of the brain from the old flies showed more dopaminergic neuronal cell death in all mutants compared to WT. This adverse effect of α-Syn familial mutations highly correlated with the sustained population of oligomer production/ retention in mutant flies. Furthermore, this was supported by our in vitro studies, where significantly higher amount of oligomer was observed in mutants compared to WT. The data suggest that the sustained p...
Antioxidants
Parkinson’s disease (PD) is the second most common neurodegenerative disorder, characterized by the preferential loss of dopaminergic neurons and by the accumulation of intracellular inclusions mainly composed of α-synuclein (α-Syn). While the etiopathogenesis of the disorder is still elusive, recent experimental evidence supports the involvement of ferroptosis, an iron-dependent cell death pathway, in the pathogenesis of PD. In the present work, using different ferroptosis inducers and inhibitors, we evaluated, in vivo, the involvement of iron in the α-Syn-mediated toxicity. Using a Drosophila melanogaster model of PD based on the selective over-expression of α-Syn within dopaminergic neurons, we demonstrated that the over-expression of α-Syn promotes the accumulation of protein aggregates, which is accompanied by dopaminergic neurodegeneration, locomotor impairment, and lifespan reduction. These pathological phenotypes were further exacerbated by reduced intracellular levels of gl...
Nature Medicine, 2002
The mechanism by which dopaminergic neurons are selectively lost in Parkinson disease (PD) is unknown. Here we show that accumulation of α-synuclein in cultured human dopaminergic neurons results in apoptosis that requires endogenous dopamine production and is mediated by reactive oxygen species. In contrast, α-synuclein is not toxic in non-dopaminergic human cortical neurons, but rather exhibits neuroprotective activity. Dopamine-dependent neurotoxicity is mediated by 54-83-kD soluble protein complexes that contain α-synuclein and 14-3-3 protein, which are elevated selectively in the substantia nigra in PD. Thus, accumulation of soluble α-synuclein protein complexes can render endogenous dopamine toxic, suggesting a potential mechanism for the selectivity of neuronal loss in PD.
FEBS Letters, 2006
Free radicals, including dopamine (DA)-oxidized metabolites, have long been implicated in pathogenesis of Parkinson's disease (PD). However, the relationships between such oxidative stresses and a-synuclein (a-S), a major constituent of Lewy bodies, remain unknown. In this study, we established neuronal cells that constitutively express a-S and tetracycline-regulated tyrosinase. While tyrosinase overexpression induced apoptosis, co-expression of wild type or A53T mutant human a-S with tyrosinase further exacerbated cell death. In this process, the formation of a-S oligomers and the reduction in mitochondrial membrane potential were demonstrated. This cellular model may reconstitute the pathological metabolism of a-S in the synucleinopathy and provide a useful tool to explore possible pathomechanisms of nigral degeneration in PD.
Proceedings of the National Academy of Sciences, 2005
Loss-of-function mutations of the parkin gene are a major cause of early-onset parkinsonism. To explore the mechanism by which loss of parkin function results in neurodegeneration, we are using a genetic approach in Drosophila . Here, we show that Drosophila parkin mutants display degeneration of a subset of dopaminergic (DA) neurons in the brain. The neurodegenerative phenotype of parkin mutants is enhanced by loss-of-function mutations of the glutathione S-transferase S1 ( GstS1 ) gene, which were identified in an unbiased genetic screen for genes that modify parkin phenotypes. Furthermore, overexpression of GstS1 in DA neurons suppresses neurodegeneration in parkin mutants. Given the previous evidence for altered glutathione metabolism and oxidative stress in sporadic Parkinson's disease (PD), these data suggest that the mechanism of DA neuron loss in Drosophila parkin mutants is similar to the mechanisms underlying sporadic PD. Moreover, these findings identify a potential t...
Nature medicine, 2002
The mechanism by which dopaminergic neurons are selectively lost in Parkinson disease (PD) is unknown. Here we show that accumulation of alpha-synuclein in cultured human dopaminergic neurons results in apoptosis that requires endogenous dopamine production and is mediated by reactive oxygen species. In contrast, alpha-synuclein is not toxic in non-dopaminergic human cortical neurons, but rather exhibits neuroprotective activity. Dopamine-dependent neurotoxicity is mediated by 54 83-kD soluble protein complexes that contain alpha-synuclein and 14-3-3 protein, which are elevated selectively in the substantia nigra in PD. Thus, accumulation of soluble alpha-synuclein protein complexes can render endogenous dopamine toxic, suggesting a potential mechanism for the selectivity of neuronal loss in PD.