alpha-synuclein and Retinal-Degeneration

Parkinson's disease (PD) is a common neurodegenerative disorder with motor symptoms linked to the loss of dopaminergic neurons in the brain. α-Synuclein is an aggregation-prone neural protein that plays a role in the pathogenesis of PD. In our previous paper, we found that saffron; the stigma of Crocus sativus Linné (Iridaceae), and its constituents (crocin and crocetin) suppressed aggregation of α-synuclein and promoted the dissociation of α-synuclein fibrils in vitro. In this study, we investigated the effect of dietary saffron and its constituent, crocetin, in vivo on a fly PD model overexpressing several mutant α-synuclein in a tissue-specific manner. Saffron and crocetin significantly suppressed the decrease of climbing ability in the Drosophila overexpressing A30P (A30P fly PD model) or G51D (G51D fly PD model) mutated α-synuclein in neurons. Saffron and crocetin extended the life span in the G51D fly PD model. Saffron suppressed the rough-eyed phenotype and the dispersion of the size histogram of the ocular long axis in the eye of A30P fly PD model. Saffron had a cytoprotective effect on a human neuronal cell line with α-synuclein fibrils. These data showed that saffron and its constituent crocetin have protective effects on the progression of PD disease in animals in vivo and suggest that saffron and crocetin can be used to treat PD.

Topics: alpha-Synuclein; Animals; Animals, Genetically Modified; Carotenoids; Cell Line; Crocus; Disease Models, Animal; Drosophila melanogaster; Female; Humans; Longevity; Male; Motor Activity; Mutation; Neurons; Neuroprotective Agents; Parkinson Disease; Retinal Degeneration; Vitamin A

The presence of α-synuclein aggregates in the retina of Parkinson's disease patients has been associated with vision impairment. In this study we sought to determine the effects of α-synuclein overexpression on the survival and function of dopaminergic amacrine cells (DACs) in the retina. Adult mice were intravitreally injected with an adeno-associated viral (AAV) vector to overexpress human wild-type α-synuclein in the inner retina. Before and after systemic injections of levodopa (L-DOPA), retinal responses and visual acuity-driven behavior were measured by electroretinography (ERG) and a water maze task, respectively. Amacrine cells and ganglion cells were counted at different time points after the injection. α-synuclein overexpression led to an early loss of DACs associated with a decrease of light-adapted ERG responses and visual acuity that could be rescued by systemic injections of L-DOPA. The data show that α-synuclein overexpression affects dopamine neurons in the retina. The approach provides a novel accessible method to model the underlying mechanisms implicated in the pathogenesis of synucleinopathies and for testing novel treatments.

Topics: alpha-Synuclein; Amacrine Cells; Animals; Dopaminergic Neurons; Female; Fluorescent Antibody Technique; Levodopa; Male; Mice; Mice, Inbred C57BL; Retina; Retinal Degeneration; Vision Disorders; Visual Acuity

Age-related neurodegeneration has been studied extensively through the use of model organisms, including the genetically versatile Drosophila melanogaster. Various neurotoxic proteins have been expressed in fly eyes to approximate degeneration occurring in humans, and much has been learned from this heterologous system. Although Drosophila expedites scientific research through rapid generational times and relative inexpensiveness, one factor that can hinder analyses is the examination of milder forms of degeneration caused by some toxic proteins in fly eyes. Whereas several disease proteins cause massive degeneration that is easily observed by examining the external structure of the fly eye, others cause mild degeneration that is difficult to observe externally and requires laborious histological preparation to assess and monitor. Here, we describe a sensitive fluorescence-based method to observe, monitor, and quantify mild Drosophila eye degeneration caused by various proteins, including the polyglutamine disease proteins ataxin-3 (spinocerebellar ataxia type 3) and huntingtin (Huntington's disease), mutant α-synuclein (Parkinson's disease), and Aβ42 (Alzheimer's disease). We show that membrane-targeted green fluorescent protein reports degeneration robustly and quantitatively. This simple yet powerful technique, which is amenable to large-scale screens, can help accelerate studies to understand age-related degeneration and to find factors that suppress it for therapeutic purposes.

Topics: alpha-Synuclein; Amyloid beta-Peptides; Animals; Ataxin-3; CD8 Antigens; Disease Models, Animal; Drosophila; Drosophila melanogaster; Drosophila Proteins; Green Fluorescent Proteins; Humans; Huntingtin Protein; Mice, Transgenic; Microtubule-Associated Proteins; Nerve Tissue Proteins; Nuclear Proteins; Peptide Fragments; Peptides; Repressor Proteins; Retinal Degeneration; Transcription Factors

Parkinson's disease, a prevalent neurodegenerative disease, is characterized by the reduction of dopaminergic neurons resulting in the loss of motor control, resting tremor, the formation of neuronal inclusions and ultimately premature death. Two inherited forms of PD have been linked to mutations in the alpha-synuclein and parkin genes. The parkin protein functions as an ubiquitin ligase targeting specific proteins for degradation. Expression of human alpha-synuclein in Drosophila neurons recapitulates the loss of motor control, the development of neuronal inclusions, degeneration of dopaminergic neurons and the ommatidial array to provide an excellent genetic model of PD.. To investigate the role of parkin, we have generated transgenic Drosophila that conditionally express parkin under the control of the yeast UAS enhancer. While expression of parkin has little consequence, co-expression of parkin with alpha-synuclein in the dopaminergic neurons suppresses the alpha-synuclein-induced premature loss of climbing ability. In addition directed expression of parkin in the eye counteracts the alpha-synuclein-induced degeneration of the ommatidial array. These results show that parkin suppresses the PD-like symptoms observed in the alpha-synuclein-dependent Drosophila model of PD.. The highly conserved parkin E3 ubiquitin ligase can suppress the damaging effects of human alpha-synuclein. These results are consistent with a role for parkin in targeting alpha-synuclein to the proteasome. If this relationship is conserved in humans, this suggests that up-regulation of parkin should suppress alpha-synucleinopathic PD. The development of therapies that regulate parkin activity may be crucial in the treatment of PD.

Topics: alpha-Synuclein; Amino Acid Sequence; Animals; Animals, Genetically Modified; Behavior, Animal; Conserved Sequence; Disease Models, Animal; Dopamine; Drosophila melanogaster; Drosophila Proteins; Gene Transfer Techniques; Genetic Therapy; Humans; Molecular Sequence Data; Nerve Tissue Proteins; Neurons; Parkinson Disease; Retinal Degeneration; Sequence Homology, Amino Acid; Survival Rate; Synucleins; Ubiquitin-Protein Ligases

Parkinson's disease is a common neurodegenerative syndrome characterized by loss of dopaminergic neurons in the substantia nigra, formation of filamentous intraneuronal inclusions (Lewy bodies) and an extrapyramidal movement disorder. Mutations in the alpha-synuclein gene are linked to familial Parkinson's disease and alpha-synuclein accumulates in Lewy bodies and Lewy neurites. Here we express normal and mutant forms of alpha-synuclein in Drosophila and produce adult-onset loss of dopaminergic neurons, filamentous intraneuronal inclusions containing alpha-synuclein and locomotor dysfunction. Our Drosophila model thus recapitulates the essential features of the human disorder, and makes possible a powerful genetic approach to Parkinson's disease.

Topics: alpha-Synuclein; Animals; Animals, Genetically Modified; Cloning, Molecular; Disease Models, Animal; Dopamine; Drosophila; Humans; Inclusion Bodies; Lewy Bodies; Locomotion; Mutation; Nerve Degeneration; Nerve Tissue Proteins; Neurons; Parkinson Disease; Retinal Degeneration; Serotonin; Synucleins; Tyrosine 3-Monooxygenase