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Cytosolic dopamine determines hypersensitivity to blunt force trauma [PMD216 EV, cat-1, cat-2]

ABSTRACT: The selective vulnerability of dopaminergic neurons to trauma-induced neurodegeneration is a conserved phenomenon across species, extending from nematodes to humans. However, the molecular mechanisms contributing to this hypersensitivity to blunt force injury remain poorly understood. We find that dopamine oxidation, a key driver of Parkinson’s Disease, extends its toxic role to the acute challenges of blunt force trauma. Ectopic synthesis of dopamine in serotonergic neurons alone proves sufficient in determining neuronal subtype sensitivity to trauma-induced death. While dopaminergic neurons maintain this neurotransmitter in a functional and benign state, trauma-induced subcellular redox imbalances elicit dopamine-dependent cytotoxicity. Perturbing dopamine synthesis and its packaging into synaptic vesicles further demonstrate how cytosolic dopamine is both necessary and sufficient to drive cell loss upon mechanical stress and during aging. Additionally, trauma activates the B-Zip transcription factor, fos-1, which exacerbates this toxic cascade by transcriptionally upregulating the rate-limiting enzyme in dopamine synthesis, cat-2. In summary, our study unravels the molecular intricacies that render dopaminergic neurons uniquely prone to physical perturbation, highlighting a shared vulnerability across different evolutionary lines.

ORGANISM(S): Caenorhabditis elegans

PROVIDER: GSE254138 | GEO | 2024/06/17

REPOSITORIES: GEO

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Project description:Loss-of-function mutations in the parkin gene can cause early onset Parkinson’s disease, a movement disorder resulting from the selective degeneration of dopaminergic neurons in the basal ganglia. Analogously, movement deficits and loss of a subset of dopaminergic neurons are observed in Drosophila melanogaster homozygous for null mutations in parkin. Parkin is an E3 ubiquitin ligase that functions with the mitochondrial localized serine/threonine kinase PINK1 in a pathway required to maintain mitochondrial integrity. We previously established that the PINK1/Parkin pathway functions in Drosophila dopaminergic and cholinergic neurons to maintain mitochondrial membrane potential. However, the mechanisms through which the PINK/Parkin pathway selectively impacts dopaminergic neuron survival remains unclear, as do the mechanisms that lead to the selective vulnerability of dopaminergic neurons in Parkinson’s disease. Because the transcriptome of a cell determines its identity we hypothesized that knowledge of the transcriptional alterations that occur in dopaminergic neurons isolated from parkin null Drosophila would provide insight into the mystery of selective vulnerability in Parkinson's disease. Results: To test our hypothesis we measured the transcriptome of dopaminergic and cholinergic neurons isolated from isogenic heterozygous and homozygous parkin null mutants using a novel flow cytometry-based method we developed. Computational analysis and experimental confirmation demonstrate that our method allows for the successful expression analysis of defined neural subsets from the Drosophila brain. In addition, our dataset implicates iron handling and dopamine signaling as being significantly dysregulated in parkin null dopaminergic neurons. Conclusions: Our flow cytometry-based method allows for the isolation and microarray analysis of neuronal subsets from the adult Drosophila brain. Our microarray analyses implicate iron handling and dopamine metabolism as contributing factors in the etiology of parkin-associated early onset Parkinson’s disease. Here we provide a novel dataset that may serve as a foundation for subsequent functional analyses of the pathways underlying neuronal selective vulnerability in Parkinson's disease.

Project description:Best2009 - Homeostatic mechanisms in dopamine synthesis and release Encoded non-curated model. Issues: - Initial concentrations for hva, tyrpool, NADPH and NADP are missing - Reaction VMAT requires two substrates to match the formula proposed in the article This model is described in the article: Homeostatic mechanisms in dopamine synthesis and release: a mathematical model. Best JA, Nijhout HF, Reed MC. Theor Biol Med Model 2009; 6: 21 Abstract: BACKGROUND: Dopamine is a catecholamine that is used as a neurotransmitter both in the periphery and in the central nervous system. Dysfunction in various dopaminergic systems is known to be associated with various disorders, including schizophrenia, Parkinson's disease, and Tourette's syndrome. Furthermore, microdialysis studies have shown that addictive drugs increase extracellular dopamine and brain imaging has shown a correlation between euphoria and psycho-stimulant-induced increases in extracellular dopamine 1. These consequences of dopamine dysfunction indicate the importance of maintaining dopamine functionality through homeostatic mechanisms that have been attributed to the delicate balance between synthesis, storage, release, metabolism, and reuptake. METHODS: We construct a mathematical model of dopamine synthesis, release, and reuptake and use it to study homeostasis in single dopaminergic neuron terminals. We investigate the substrate inhibition of tyrosine hydroxylase by tyrosine, the consequences of the rapid uptake of extracellular dopamine by the dopamine transporters, and the effects of the autoreceoptors on dopaminergic function. The main focus is to understand the regulation and control of synthesis and release and to explicate and interpret experimental findings. RESULTS: We show that the substrate inhibition of tyrosine hydroxylase by tyrosine stabilizes cytosolic and vesicular dopamine against changes in tyrosine availability due to meals. We find that the autoreceptors dampen the fluctuations in extracellular dopamine caused by changes in tyrosine hydroxylase expression and changes in the rate of firing. We show that short bursts of action potentials create significant dopamine signals against the background of tonic firing. We explain the observed time courses of extracellular dopamine responses to stimulation in wild type mice and mice that have genetically altered dopamine transporter densities and the observed half-lives of extracellular dopamine under various treatment protocols. CONCLUSION: Dopaminergic systems must respond robustly to important biological signals such as bursts, while at the same time maintaining homeostasis in the face of normal biological fluctuations in inputs, expression levels, and firing rates. This is accomplished through the cooperative effect of many different homeostatic mechanisms including special properties of tyrosine hydroxylase, the dopamine transporters, and the dopamine autoreceptors. This model is hosted on BioModels Database and identified by: MODEL1502230000. To cite BioModels Database, please use: BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information.

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Cytosolic dopamine determines hypersensitivity to blunt force trauma [PMD216 EV, cat-1, cat-2]

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