Pharmacological validation of a mouse model of l-DOPA-induced dyskinesia

105

Parkinson's disease (PD) is characterized by severe locomotor deficits and is commonly treated with the dopamine (DA) precursor L-3,4-dihydroxyphenylalanine (L-DOPA), but its prolonged use causes dyskinesias referred to as L-DOPA-induced dyskinesias (LIDs). Recent studies in animal models of PD have suggested that dyskinesias are associated with the overactivation of G proteinmediated signaling through DA receptors. β-Arrestins desensitize G protein signaling at DA receptors (D1R and D2R) in addition to activating their own G protein-independent signaling events, which have been shown to mediate locomotion. Therefore, targeting β-arrestins in PD L-DOPA therapy might prove to be a desirable approach. Here we show in a bilateral DA-depletion mouse model of Parkinson's symptoms that genetic deletion of β-arrestin2 significantly limits the beneficial locomotor effects while markedly enhancing the dyskinesia-like effects of acute or chronic L-DOPA treatment. Viral rescue or overexpression of β-arrestin2 in knockout or control mice either reverses or protects against LIDs and its key biochemical markers. In other more conventional animal models of DA neuron loss and PD, such as 6-hydroxydopamine-treated mice or rats and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated nonhuman primates, β-arrestin2 overexpression significantly reduced dyskinesias while maintaining the therapeutic effect of L-DOPA. Considerable efforts are being spent in the pharmaceutical industry to identify therapeutic approaches to block LIDs in patients with PD. Our results point to a potential therapeutic approach, whereby development of either a genetic or pharmacological intervention to enhance β-arrestin2-or limit G protein-dependent D1/D2R signaling could represent a more mechanistically informed strategy.is a major catecholamine neurotransmitter that is released by midbrain DA neurons. DA activates G protein-coupled receptors (GPCRs), which belong to the dopamine D1 (D1R and D5R) or D2 (D2R, D3R, and D4R) class of DA receptors that are known to signal via G protein-dependent mechanisms (1, 2). However, recent studies have shown that in addition to G protein-mediated signaling, many GPCRs, including DA receptors, signal through beta-arrestin 1 and 2 (βarr1 and βarr2)-dependent mechanisms (3, 4). The two isoforms of β-arrestin, β-arrestin1 (βarr1) and β-arrestin2 (βarr2) are widely coexpressed in the brain (5, 6). β-Arrestins were originally appreciated for their ability to desensitize (i.e., turn off) GPCR signaling in a GPCR kinase (GRK)-dependent manner (7,8). Binding of β-arrestin to the GPCR sterically hinders G protein binding and in most instances initiates receptor endocytosis via interactions with adaptor protein complex-2 (AP-2) and clathrin (9-11). It is now appreciated that β-arrestins regulate physiology and behaviors independently of G protein signaling through their ability to scaffold multiple intracellular signaling molecules such as kinases and phosphatases (3,4,12,13). Studies from our laboratory have shown that through ...

Section: Resultsmentioning

confidence: 99%

Targeting β-arrestin2 in the treatment ofl-DOPA–induced dyskinesia in Parkinson’s disease

Urs¹,

Bido

Peterson³

et al. 2015

105

“…We set up this protocol to detect subtle differences between genotypes in the sensitivity to L-dopa that may have been masked by the use of higher drug doses (20,21). Daily scoring of AIMs revealed a gradual development of dyskinesia in both genotypes.…”

Section: Resultsmentioning

confidence: 99%

Inhibition of Ras-guanine nucleotide-releasing factor 1 (Ras-GRF1) signaling in the striatum reverts motor symptoms associated with l -dopa–induced dyskinesia

Fasano

Bézard

D'Antoni

et al. 2010

143

154

L-dopa-induced dyskinesia (LID) is a common debilitating complication of dopamine replacement therapy in Parkinson's disease. Recent evidence suggests that LID may be linked causally to a hyperactivation of the Ras-ERK signaling cascade in the basal ganglia. We set out to determine whether specific targeting of Ras-guanine nucleotide-releasing factor 1 (Ras-GRF1), a brain-specific activator of the Ras-ERK pathway, may provide a therapy for LID. On the rodent abnormal involuntary movements scale, Ras-GRF1-deficient mice were significantly resistant to the development of dyskinesia during chronic L-dopa treatment. Furthermore, in a nonhuman primate model of LID, lentiviral vectors expressing dominant negative forms of Ras-GRF1 caused a dramatic reversion of dyskinesia severity leaving intact the therapeutic effect of Ldopa. These data reveal the central role of Ras-GRF1 in governing striatal adaptations to dopamine replacement therapy and validate a viable treatment for LID based on intracellular signaling modulation. P arkinson's disease (PD) is a neurodegenerative disorder characterized by a loss of dopaminergic neurons in the substantia nigra pars compacta (SNc) causing dopamine depletion in the striatum, the main input nucleus of the basal ganglia. Dopamine replacement therapy with L-dopa remains the most effective treatment for PD, but its use is associated with motor fluctuations and abnormal involuntary movements (AIMs), termed "L-dopa-induced dyskinesia" (LID), which are doselimiting and potentially disabling (1-3).A key objective for the future treatment of PD is to avoid dyskinesia altogether, but doing so will require an understanding of the molecular mechanisms that are involved. LID is attributed to a sequence of events, largely occurring in the striatum, that include pulsatile stimulation of dopamine D1 receptors, downstream changes in proteins and genes, dendritic alterations, and functional abnormalities in nondopaminergic transmitter systems, all of which concur to modify neuronal firing patterns in the basal ganglia-thalamocortical networks (1-4). Once symptoms have appeared, LID can be triggered easily by a single dose of L-dopa even after several weeks of treatment washout (4). Regulation of striatal gene expression is the likely mechanism underlying neuronal plasticity in LID. The ERK signaling cascade is a key regulator of striatal plasticity and an interesting candidate for drug targeting (5-8). Stimulation of dopamine and glutamate receptors on striatal neurons can switch on the small GTPases of the Ras family, which in turn activate the Raf/Mek/ Erk protein kinase cascade (5-8). Sustained activation of these biochemical pathways leads to synaptic rearrangements requiring de novo gene expression and protein synthesis. Importantly, in neurotoxic models of PD, such as the unilaterally 6-hydroxydopamine (6-OHDA)-lesioned rodent and the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated nonhuman primate (NHP), a supersensitivity of striatal D1 receptors leads to ERK hyperactivation in ...

“…To directly test this hypothesis, we examined whether a loss of DARPP-32 signaling in striatonigral neurons could prevent the development of dyskinesia. Following a previously validated mouse model for L-DOPAinduced dyskinesia (22,23), DARPP-32 conditional KO mice were injected unilaterally with 6-OHDA into the striatum to induce loss of dopaminergic innervation. After a 3-wk recovery period, the mice were treated for 10 d with L-DOPA and assessed on the 10th day for the expression of abnormal involuntary movements (AIMS) (Fig.…”

Section: Resultsmentioning

confidence: 99%

Distinct subclasses of medium spiny neurons differentially regulate striatal motor behaviors

Bateup

Santini

Shen

et al. 2010

315

254

The direct and indirect pathways of the basal ganglia have been proposed to oppositely regulate locomotion and differentially contribute to pathological behaviors. Analysis of the distinct contributions of each pathway to behavior has been a challenge, however, due to the difficulty of selectively investigating the neurons comprising the two pathways using conventional techniques. Here we present two mouse models in which the function of striatonigral or striatopallidal neurons is selectively disrupted due to cell typespecific deletion of the striatal signaling protein dopamine-and cAMP-regulated phosphoprotein Mr 32kDa (DARPP-32). Using these mice, we found that the loss of DARPP-32 in striatonigral neurons decreased basal and cocaine-induced locomotion and abolished dyskinetic behaviors in response to the Parkinson's disease drug L-DOPA. Conversely, the loss of DARPP-32 in striatopallidal neurons produced a robust increase in locomotor activity and a strongly reduced cataleptic response to the antipsychotic drug haloperidol. These findings provide insight into the selective contributions of the direct and indirect pathways to striatal motor behaviors.basal ganglia | DARPP-32 | locomotor behavior | striatonigral | striatopallidal T he basal ganglia (BG) are subcortical structures that coordinate vital behaviors including movement, reward, and motivational processes (1). BG dysfunction is associated with several human diseases, including Parkinson's disease (PD), schizophrenia, and drug addiction. The striatum receives the majority of input into the BG, and projects to the output nuclei of the BG via two pathways that work together to modulate behavior: the D1 receptor (D1R)-expressing direct pathway, which projects to the substantia nigra pars reticulata (SNpr), and the D2 receptor (D2R)-expressing indirect pathway, which projects to the medial globus pallidus (GP) (2). Classical models of the BG propose that these two efferent pathways exert opposing effects on locomotor behavior (3, 4); namely, activation of the direct pathway increases locomotor activity, whereas the indirect pathway exerts a tonic inhibitory tone. Thus, an imbalance of these two pathways would disrupt coordinated movement, resulting in hypokinetic or hyperkinetic movement disorders (3). Direct confirmation of these hypotheses has been hindered by difficulty in selectively targeting direct and indirect pathway neurons with traditional surgical and pharmacological techniques.An understanding of the differential contribution of the direct and indirect pathways to behavior is essential for generating more selective therapies for BG-related disorders. This would be especially valuable in the case of PD and schizophrenia, where motor complications can result from pharmacological treatment. For example, the positive symptoms of schizophrenia are effectively treated with typical antipsychotic drugs, such as haloperidol; however, these drugs are often associated with extrapyramidal side effects including catalepsy, manifested as extreme hypolocomoti...