Effects of LRRK2 Inhibitors on Nigrostriatal Dopaminergic Neurotransmission

INTRODUCTION Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most prevalent cause of familial and sporadic Parkinson's disease (PD). Because most pathogenic LRRK2 mutations result in enhanced kinase activity, it suggests that LRRK2 inhibitors may serve as a potential treatment for PD. To evaluate whether LRRK2 inhibitors are effective therapies for PD, it is crucial to know whether LRRK2 inhibitors will affect dopaminergic (DAergic) neurotransmission. However, to date, there is no study to investigate the impact of LRRK2 inhibitors on DAergic neurotransmission. AIMS To address this gap in knowledge, we examined the effects of three types of LRRK2 inhibitors (LRRK2-IN-1, GSK2578215A, and GNE-7915) on dopamine (DA) release in the dorsal striatum using fast-scan cyclic voltammetry and DA neuron firing in the substantia nigra pars compacta (SNpc) using patch clamp in mouse brain slices. RESULTS We found that LRRK2-IN-1 at a concentration higher than 1 μM causes off-target effects and decreases DA release, whereas GSK2578215A and GNE-7915 do not. All three inhibitors at 1 μM have no effect on DA release and DA neuron firing rate. We have further assessed the effects of the inhibitors in two preclinical LRRK2 mouse models (i.e., BAC transgenic hG2019S and hR1441G) and demonstrated that GNE-7915 enhances DA release and synaptic vesicle mobilization/recycling. CONCLUSION GNE-7915 can be validated for further therapeutic development for PD.