Nuclear receptor Nurr1 agonists enhance its dual functions and improve behavioral deficits in an animal model of Parkinson’s disease

Parkinson’s disease (PD) is the most prevalent movement disorder with no available treatments that can stop or slow down the disease progress. Although the orphan nuclear receptor Nurr1 is a promising target for PD, it is thought to be a ligand-independent transcription factor and, so far, no small molecule has been identified that can bind to its ligand binding domain. Here, we established high throughput cell-based assays and successfully identified three Nurr1 agonists among FDA-approved drugs, all sharing an identical chemical scaffold. Remarkably, these compounds not only directly bind to Nurr1 but also ameliorate behavioral defects in a rodent model of PD. Thus, our study shows that Nurr1 could serve as a valid drug target for neuroprotective therapeutics of PD.

Parkinson’s disease (PD), primarily caused by selective degeneration of midbrain dopamine (mDA) neurons, is the most prevalent movement disorder, affecting 1–2% of the global population over the age of 65. Currently available pharmacological treatments are largely symptomatic and lose their efficacy over time with accompanying severe side effects such as dyskinesia. Thus, there is an unmet clinical need to develop mechanism-based and/or disease-modifying treatments. Based on the unique dual role of the nuclear orphan receptor Nurr1 for development and maintenance of mDA neurons and their protection from inflammation-induced death, we hypothesize that Nurr1 can be a molecular target for neuroprotective therapeutic development for PD. Here we show successful identification of Nurr1 agonists sharing an identical chemical scaffold, 4-amino-7-chloroquinoline, suggesting a critical structure–activity relationship. In particular, we found that two antimalarial drugs, amodiaquine and chloroquine stimulate the transcriptional function of Nurr1 through physical interaction with its ligand binding domain (LBD). Remarkably, these compounds were able to enhance the contrasting dual functions of Nurr1 by further increasing transcriptional activation of mDA-specific genes and further enhancing transrepression of neurotoxic proinflammatory gene expression in microglia. Importantly, these compounds significantly improved behavioral deficits in 6-hydroxydopamine lesioned rat model of PD without any detectable signs of dyskinesia-like behavior. These findings offer proof of principle that small molecules targeting the Nurr1 LBD can be used as a mechanism-based and neuroprotective strategy for PD.