Activation of the Sonic Hedgehog Effector Smoothened Counteracts L-Dopa Induced Dyskinesia by Restoring Cholinergic Interneuron Function

Many types of neurons act as multimodal signaling centers. Yet, we have only limited insight into the regulation and functional consequences of neuronal co-transmission. For example, dopamine (DA) neurons, whose degeneration causes motor deficits characteristic of Parkinson’s Diseases (PD), communicate with all their targets by DA but only a selective subset of their targets using GABA, Glutamate, and the secreted cell signaling protein Sonic Hedgehog (Shh). It is unknown whether Levo-dopamine (L-Dopa) induced dyskinesia (LIDs), a severely debilitating side effect of DA supplementation in PD, might appear because DA neuron targets are exposed to high DA- but low Shh- signaling in medicated patients. Here I show that restoring the balance of DA and Shh signaling attenuates LID formation and acute expression in mouse and macaque models of PD. Cholinergic neurons are responsive to Shh signaling via stimulation of the Shh effector GPCR smoothened. Using conditional KO mice of pre or postsynaptic Shh we show that reduced signaling in cholinergic neurons is sufficient and necessary for LID formation. Conversely, selective expression of a constitutive active form of Smo (SmoM2) in cholinergic neurons is sufficient to render the sensitized aphakia model resistant to LID. The relative degree of imbalance of DA and Shh signaling rather than their absolute strength determines the severity of LID and highlights the bidirectional effect both factors have on LIDs. Activation of Smo reduces MAP-kinase pathway signaling, a physiological marker of LID, selectively in CINs of the dorsolateral but not dorsomedial striatum and enhances the neuronal activity marker p-rpS6240/244 through activation of Smo on CINs. Additionally, semi-chronic, pulsatile optogenetic stimulation of DA neurons results in LID-like behaviors that can be attenuated by Smo activation. Together, my data reveal that balanced Shh and DA signaling is a critical modulator of cholinergic physiology and provide an unexpected link between LID and DA neuron degeneration. Furthermore, since pulsatile L-Dopa dosing might induce a perversion in the DA neuron provided teaching signal resulting in acquisition and selection of un-purposeful, abnormal motor programs seen in LIDs, then the novel animal models described here could be a starting point for in vivo analysis to assess the function and importance of neuronal co-transmission of Shh signaling

The Dopamine D5 receptor contributes to activation of cholinergic interneurons during L-DOPA induced dyskinesia

International audienceThe dopamine D5 receptor (D5R) is a Gαs-coupled dopamine receptor belonging to the dopamine D1-like receptor family. Together with the dopamine D2 receptor it is highly expressed in striatal cholinergic interneurons and therefore is poised to be a positive regulator of cholinergic activity in response to L-DOPA in the dopamine-depleted parkinsonian brain. Tonically active cholinergic interneurons become dysregulated during chronic L-DOPA administration and participate in the expression of L-DOPA induced dyskinesia. The molecular mechanisms involved in this process have not been elucidated, however a correlation between dyskinesia severity and pERK expression in cholinergic cells has been described. To better understand the function of the D5 receptor and how it affects cholinergic interneurons in L-DOPA induced dyskinesia, we used D5R knockout mice that were rendered parkinsonian by unilateral 6-OHDA injection. In the KO mice, expression of pERK was strongly reduced indicating that activation of these cells is at least in part driven by the D5 receptor. Similarly, pS6, another marker for the activity status of cholinergic interneurons was also reduced. However, mice lacking D5R exhibited slightly worsened locomotor performance in response to L-DOPA and enhanced LID scores. Our findings suggest that D5R can modulate L-DOPA induced dyskinesia and is a critical activator of CINs via pERK and pS6

CK2 oppositely modulates L-DOPA-induced dyskinesia via striatal projection neurons expressing D1 or D2 receptors

We have previously shown that casein kinase 2 (CK2) negatively regulates dopamine D1 and adenosine A2A receptor signaling in the striatum. Ablation of CK2 in D1 receptor-positive striatal neurons caused enhanced locomotion and exploration at baseline, whereas CK2 ablation in D2 receptor-positive neurons caused increased locomotion after treatment with A2A antagonist, caffeine. Because both, D1 and A2A receptors, play major roles in the cellular responses toL-DOPA in the striatum, these findings prompted us to examine the impact of CK2 ablation on the effects ofL-DOPA treatment in the unilateral 6-OHDA lesioned mouse model of Parkinson’s disease. We report here that knock-out of CK2 in striatonigral neurons reduces the severity ofL-DOPA-induced dyskinesia (LID), a finding that correlates with lowered pERK but unchanged pPKA substrate levels in D1 medium spiny neurons as well as in cholinergic interneurons. In contrast, lack of CK2 in striatopallidal neurons enhances LID and ERK phosphorylation. Coadministration of caffeine with a low dose ofL-DOPA reduces dyskinesia in animals with striatopallidal knock-out to wild-type levels, suggesting a dependence on adenosine receptor activity. We also detect reduced Golf levels in the striatonigral but not in the striatopallidal knock-out in response toL-DOPA treatment. Our work shows, in a rodent model of PD, that treatment-induced dyskinesia and striatal ERK activation are bidirectionally modulated by ablating CK2 in D1- or D2-positive projection neurons, in male and female mice. The results reveal that CK2 regulates signaling events critical to LID in each of the two main populations of striatal neurons

Dopaminergic co-transmission with sonic hedgehog inhibits abnormal involuntary movements in models of Parkinson’s disease and L-Dopa induced dyskinesia

International audienceL-Dopa induced dyskinesia (LID) is a debilitating side effect of dopamine replacement therapy for Parkinson's Disease. The mechanistic underpinnings of LID remain obscure. Here we report that diminished sonic hedgehog (Shh) signaling in the basal ganglia caused by the degeneration of midbrain dopamine neurons facilitates the formation and expression of LID. We find that the pharmacological activation of Smoothened, a downstream effector of Shh, attenuates LID in the neurotoxic 6-OHDA-and genetic aphakia mouse models of Parkinson's Disease. Employing conditional genetic loss-of-function approaches, we show that reducing Shh secretion from dopamine neurons or Smoothened activity in cholinergic interneurons promotes LID. Conversely, the selective expression of constitutively active Smoothened in cholinergic interneurons is sufficient to render the sensitized aphakia model of Parkinson's Disease resistant to LID. Furthermore, acute depletion of Shh from dopamine neurons through prolonged optogenetic stimulation in otherwise intact mice and in the absence of L-Dopa produces LID-like involuntary movements. These findings indicate that augmenting Shh signaling in the L-Dopa treated brain may be a promising therapeutic approach for mitigating the dyskinetic side effects of long-term treatment with L-Dopa

Construct validity and factor structure of a Spanish-language Social Support Questionnaire during early pregnancy

Background: The Social Support Questionnaire - Short Form (SSQ-6) is a widely used instrument that assesses availability and satisfaction of a person's social support. The present study aimed to evaluate the construct validity and factor structure of the Spanish language version of the SSQ-6 during early pregnancy. Participants and methods: A total of 4,236 pregnant Peruvian women were interviewed at 10.3 +/- 3.8 weeks of gestation. In-person interviewers were used to collect lifestyle, demographic, and social support characteristics. The construct validity and factorial structure of the SSQ-6 were assessed through exploratory factor analysis (EFA) and confirmatory factor analysis (CFA). The internal consistency was evaluated using Cronbach's alpha. Results: The mean SSQ-6 score was 39.6 +/- 6.8 and Cronbach's alpha was 0.83. EFA resulted in a three-factor solution that accounted for 60.6% of the variance. CFA results confirmed the three-factor structure and yielded measures indicating goodness of fit (comparative fit index of 0.9401) and accuracy (root mean square error of approximation of 0.0394). Conclusion: Although the SSQ-6 was originally developed as a two-factor model, and previous studies have supported this, in our study a three-factor model was found to be more appropriate. The SSQ-6 was found to have good construct validity and reliability for assessing social support.Entidad financiadora: National Institutes of Health (NIH) ; National Institute of Minority Health and Health Disparities - T37-MD-001449 ; Eunice Kennedy Shriver National Institute of Child Health and Human Development - R01-HD-059835