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Striatal Nurr1, but not FosB expression links a levodopa-induced dyskinesia phenotype to genotype in Fisher 344 vs. Lewis hemiparkinsonian rats.

ABSTRACT: Numerous genes, and alterations in their expression, have been identified as risk factors for developing levodopa-induced dyskinesia (LID). However, our understanding of the complexities of molecular changes remains insufficient for development of clinical treatment. In the current study we used gene array, in situ hybridization, immunohistochemistry, and microdialysis to provide a unique compare and contrast assessment of the relationship of four candidate genes to LID, employing three genetically distinct rat strains (Sprague-Dawley (SD), Fischer-344 (F344) and Lewis-RT.1) showing differences in dyskinesia susceptibility and 'first-ever LID' versus 'chronic LID' expression in subjects displaying equal dyskinesia severity. In these studies, rat strains were easily distinguishable for their LID propensity with: 1) a majority of SD rats expressing LID (LID+) and a subset being resistant (LID-); 2) all F344 rats readily developing (LID+); and 3) all Lewis rats being LID-resistant (LID-). Following chronic levodopa, LID+ SD rats showed significant increases in candidate gene expression: Nr4a2/(Nurr1) > > Trh > Inhba = Fosb. However, SD rats with long-standing striatal dopamine (DA) depletion treated with first-ever versus chronic high-dose levodopa revealed that despite identical levels of LID severity: 1) Fosb and Nurr1 transcripts but not protein were elevated with acute LID expression; 2) FOSB/ΔFOSB and NURR1 proteins were elevated only with chronic LID; and 3) Trh transcript and protein were elevated only with chronic LID. Strikingly, despite similar levodopa-induced striatal DA release in both LID-expressing F344 and LID-resistant Lewis rats, Fosb, Trh, Inhba transcripts were significantly elevated in both strains; however, Nurr1 mRNA was significantly increased only in LID+ F344 rats. These findings suggest a need to reevaluate currently accepted genotype-to-phenotype relationships in the expression of LID, specifically that of Fosb, a transcription factor generally assumed to play a causal role, and Nurr1, a transcription factor that has received significant attention in PD research linked to its critical role in the survival and function of midbrain DA neurons but who's striatal expression, generally below levels of detection, has remained largely unexplored as a regulator of LID. Finally these studies introduce a novel 'model' (inbred F344 vs inbred Lewis) that may provide a powerful tool for investigating the role for 'dyskinesia-resistance' genes downstream of 'dyskinesia-susceptibility' genes in modulating LID expression, a concept that has received considerably less attention and offers a new ways of thinking about antidyskinetic therapies.

SUBMITTER: Steece-Collier K

PROVIDER: S-EPMC7365252 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundLevodopa-induced dyskinesias are an often debilitating side effect of levodopa therapy in Parkinson's disease. Although up to 90% of individuals with PD develop this side effect, uniformly effective and well-tolerated antidyskinetic treatment remains a significant unmet need. The pathognomonic loss of striatal dopamine in PD results in dysregulation and disinhibition of striatal CaV1.3 calcium channels, leading to synaptopathology that appears to be involved in levodopa-induced dyskinesias. Although there are clinically available drugs that can inhibit CaV1.3 channels, they are not adequately potent and have only partial and transient impact on levodopa-induced dyskinesias.MethodsTo provide unequivocal target validation, free of pharmacological limitations, we developed a CaV1.3 shRNA to provide high-potency, target-selective, mRNA-level silencing of striatal CaV1.3 channels and examined its ability to impact levodopa-induced dyskinesias in severely parkinsonian rats.ResultsWe demonstrate that vector-mediated silencing of striatal CaV1.3 expression in severely parkinsonian rats prior to the introduction of levodopa can uniformly and completely prevent induction of levodopa-induced dyskinesias, and this antidyskinetic benefit persists long term and with high-dose levodopa. In addition, this approach is capable of ameliorating preexisting severe levodopa-induced dyskinesias. Importantly, motoric responses to low-dose levodopa remained intact in the presence of striatal CaV1.3 silencing, indicating preservation of levodopa benefit without dyskinesia liability.DiscussionThe current data provide some of the most profound antidyskinetic benefit reported to date and suggest that genetic silencing of striatal CaV1.3 channels has the potential to transform treatment of individuals with PD by allowing maintenance of motor benefit of levodopa in the absence of the debilitating levodopa-induced dyskinesia side effect. © 2019 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Project description:L-3,4-dihydroxyphenylalanine (levodopa) treatment is the major pharmacotherapy for Parkinson's disease. However, almost all patients receiving levodopa eventually develop debilitating involuntary movements (dyskinesia). While it is known that striatal spiny projection neurons (SPNs) are involved in the genesis of this movement disorder, the molecular basis of dyskinesia is not understood. In this study, we identify distinct cell-type-specific gene expression changes that occur in sub-classes of SPNs upon induction of a parkinsonian lesion followed by chronic levodopa treatment. We identify several hundred genes whose expression is correlated with levodopa dose, many of which are under the control of AP-1 and ERK signaling. In spite of homeostatic adaptations involving several signaling modulators, AP-1-dependent gene expression remains highly dysregulated in direct pathway SPNs (dSPNs) upon chronic levodopa treatment. We also discuss which molecular pathways are most likely to dampen abnormal dopaminoceptive signaling in spiny projection neurons, hence providing potential targets for antidyskinetic treatments in Parkinson's disease. To profile the cell-type-specific responses of striatal spiny projection neurons (SPNs) to striatal dopamine depletion, we conducted TRAP analysis of the two major classes of these neurons: dSPNs that express the dopamine receptor 1a (Drd1a), and iSPNs that express the dopamine receptor 2 (Drd2). To disrupt dopamine innervation to both of these SPN populations that reside in the striatum, we injected the neurotoxin 6-hydroxydopamine (6-OHDA), unilaterally, in the medial forebrain bundle (MFB) in hemizygous Drd1-TRAP and Drd2-TRAP adult (9-14 weeks) male mice (kept on a C57BL/6J genetic background). This lesion procedure causes nigral dopamine cell death within a few days, along with a widespread and near-complete loss of dopaminergic innervation to the entire dorsal striatum on one side of the brain (a hemiparkinsonian model). We first examined the effects of dopamine depletion alone, compared to a mock lesion (ascorbate / saline injected). We then examined the effects of chronic levodopa treatment upon the molecular profiles of dopamine- depleted dSPNs and iSPNs, with two dose regimens. The ‘high-dose’ L-DOPA regimen (3 mg/kg on days 1-3, followed by 6 mg/kg on days 4-9) was expected to induce severe dyskinesia in all MFB-lesioned mice. The low-dose L-DOPA regimen (1 mg/kg on days 1-3, followed by 2 mg/kg on days 4-9) was expected to reverse limb use asymmetry without causing conspicuous dyskinesias. To equalize the effects of stress and handling across all groups, including control groups, all mice were equally handled and thus received saline injections when not receiving levodopa injections. Each treatment group contained 7-10 replicates. TRAP-purified mRNAs from either Drd1a- or Drd2-expressing SPNs were reverse-transcribed, amplified, and used to interrogate Affymetrix 430_2.0 GeneChip microarrays.

Project description:Levodopa-induced dyskinesia (LID) is a persistent behavioral sensitization that develops after repeated levodopa (L-DOPA) exposure in Parkinson disease (PD) patients. we used reduced representation bisulfite sequencing to determine the methylation status of cytosines genome wide at base pair resolution following a parkinsonian-like lesion and LID development. Due to the enrichment of RRBS, we focused our analysis to cytosines in a CpG context and observed extensive locus-specific changes in DNA methylation, including a preponderance of demethylation, in the dorsal striatum following the development of dyskinetic behaviors in our animal model system. Changes in DNA methylation were concentrated in putative regulatory regions of many genes known to be aberrantly transcribed following L-DOPA exposure and enriched for genes relevant to mechanisms of synaptic plasticity. In the areas of the genome exhibiting the highest levels of effect, the magnitudes of change to methylation were strongly correlated with dyskinetic behaviors. Rats were given a unilateral dopaminergic lesion to the left medial forebrain bundle with 6-OHDA to destroy at least 90% of TH positive axons. Animals were allowed to recover for 3 weeks and then given daily injections of L-DOPA (6 mg/kg) for seven days to establish stable dyskinesia. Animals were sacked 3 hrs following the final L-DOPA injection and the dorsal striatum was immediately dissected and flash frozen. Striatal tissue samples were processed for nucleic acid isolation using the AllPrep DNA/RNA Mini Kit (Qiagen) following the manufacturer's instructions. One Î¼g of gDNA sample was used for library construction. Bisulfite converted DNA libraries were produced and adaptor ligated, and single-end reads were sequenced on an Illumina HiSeq-2500 following library QC. Bisulfite conversion efficiency was greater that 98% for all of the samples and we obtained an average of 68 million reads per library. Quality control on raw reads was performed with FastQC (version 0.10.1, http://www.bioinformatics.bbsrc.ac.uk/projects/fastqc), and adaptor trimming and removal of trimmed reads shorter than 20 bp was performed with Trim Galore (version 0.3.7, http://www.bioinformatics.babraham.ac.uk/projects/trim_galore). Trimmed reads were mapped to the UCSC Rattus norvegicus rn5 genome with the methylation-aware mapper bismark (version 0.13.0). Samtools (version 0.1.19â??96b5f2294a) was used to sort SAM files produced by bismark and de-duplicate reads. SAM files were analyzed using MethylKit (version 0.9.2) in R (Akalin et al., 2012). Reads were filtered based on coverage, with a cutoff of at least ten reads per site, and normalized for each samples coverage before analysis. The genome was tiled at 250 bp and regions were counted if they contained at least 2 identified CpGs per tile. Differential methylation was defined as a sliding linear model correct p-value of <0.01 and, for highly dynamic regions, included at least a 5% change.

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Striatal Nurr1, but not FosB expression links a levodopa-induced dyskinesia phenotype to genotype in Fisher 344 vs. Lewis hemiparkinsonian rats.

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