Differential activation states of direct pathway striatal output neurons during L-DOPA-induced dyskinesia development.

Abstract

L-DOPA-induced dyskinesia (LID) is a debilitating motor side effect arising from chronic dopamine (DA) replacement therapy with L-DOPA for the treatment of Parkinson disease. LID associated with supersensitivity of striatal dopaminergic signaling and fluctuations in synaptic DA following each L-DOPA dose, shrinking the therapeutic window. The heterogeneous composition of the striatum, including subpopulations of medium spiny output neurons (MSNs), interneurons, and supporting cells, complicates the identification of the cell(s) underlying LID. We used single nucleus RNA-sequencing (snRNA-seq) to establish a comprehensive striatal transcriptional profile during LID development. Male h emiparkinsonian mice were treated with vehicle or L-DOPA for 1, 5, or 10 d and striatal nuclei were processed for snRNA-seq. Analyses indicated a limited population of DA D1 receptor-expressing MSNs (D1-MSNs) formed three subclusters in response to L-DOPA treatment and expressed cellular markers of activation. These activated D1-MSNs display similar transcriptional changes previously associated with LID; however, their prevalence and transcriptional behavior was differentially influenced by L-DOPA experience. Differentially expressed genes indicated acute upregulation of plasticity-related transcription factors and mitogen-activated protein kinase signaling, while repeated L-DOPA induced synaptic remodeling, learning and memory, and transforming growth factor-ß (TGF-ß) signaling genes. Notably, repeated L-DOPA sensitized Inhba, an activin subunit of the TGF-ß superfamily, in activated D1-MSNs and its pharmacological inhibition impaired LID development, suggesting that activin signaling may play an essential role in LID. These data suggest distinct subsets of D1-MSNs become differentially L-DOPA-responsive due to aberrant induction of molecular mechanisms necessary for neuronal entrainment, similar to processes underlying hippocampal learning and memory.

Significance Statement These data establish a comprehensive transcriptional profile of the striatum across the development of L-DOPA-induced dyskinesia at the level of individual cells in a mouse model of parkinsonism, indicating that unique subclusters of striatal neurons differentially respond to experience with L-DOPA. These neurons have a profile enriched for markers of synaptic plasticity, neuronal entrainment underlying learning and memory, and activin signaling. Negative modulation of activin receptors dampened L-DOPA-induced dyskinesia development suggesting that activin directly modulates aberrant behavioral sensitization to chronic L-DOPA.