Striatal Nurr1 Facilitates the Dyskinetic State and Exacerbates Levodopa-Induced Dyskinesia in a Rat Model of Parkinson’s Disease

Abstract

AbstractBackgroundThe transcription factor Nurr1 has been identified to be ectopically induced in the striatum of dyskinetic rodents expressing L-DOPA-induced dyskinesia (LID). In the present study, we sought to characterize Nurr1 as a causative factor in LID expression.MethodsWe used rAAV2/5 to overexpress Nurr1 or GFP in the parkinsonian striatum of LID-resistant Lewis or LID-prone Fischer-344 (F344) rats. In a second cohort, rats received the Nurr1 agonist amodiaquine (AQ) together with L-DOPA or ropinirole. All rats received a chronic DA agonist and were evaluated for LID severity. Finally, we performed single unit recordings and dendritic spine analyses in drug-naïve rAAV-injected parkinsonian rats.ResultsrAAV-GFP injected LID-resistant Lewis rats displayed mild LID and no induction of striatal Nurr1. However, Lewis rats transduced to overexpress Nurr1 developed severe LID. Nurr11 agonism with AQ exacerbated LID in F344 rats. We additionally determined that in L-DOPA-naïve rats striatal rAAV-Nurr1 overexpression 1) increased firing activity in dopamine-depleted striatal direct pathway neurons, and 2) decreased spine density and thin-spine morphology on striatal medium spiny neurons, mimicking changes seen in dyskinetic rats. Finally, we provide post-mortem evidence of Nurr1 expression in the striatum of L-DOPA treated PD patients.ConclusionsOur data demonstrate that ectopic induction of striatal Nurr1 is capable of inducing LID behavior and associated neuropathology, even in resistant subjects. These data support a direct role of Nurr1 in aberrant neuronal plasticity and LID induction, providing a potential novel target for therapeutic development.