Targeting NAAA counters dopamine neuron loss and symptom progression in mouse models of Parkinson's disease

Abstract

The lysosomal cysteine hydrolase N-acylethanolamine acid amidase (NAAA) deactivates the lipidderived mediator palmitoylethanolamide (PEA), an endogenous PPAR- agonist that is critically involved in the control of inflammation and nociception. In this study, we asked whether NAAA-regulated PEA signaling might contribute to the pathogenesis of Parkinsons disease (PD), a neurodegenerative disorder characterized by progressive loss of nigrostriatal dopamine neurons. Analyses of postmortem brain cortex and premortem blood-derived exosomes found elevated levels of NAAA expression in persons with PD compared to age-matched controls. Furthermore, in vitro experiments showed that the dopaminergic neurotoxins, 6-hydroxydopamine (6-OHDA) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), enhanced NAAA expression and lowered PEA content in human SH-SY5Y cells. A similar effect was observed in dopamine neurons and, subsequently, in microglia following 6-OHDA injection in mice. Importantly, deletion of the Naaa gene or pharmacological inhibition of NAAA activity markedly attenuated both dopamine neuron death and parkinsonian symptoms in mice treated with 6-OHDA or MPTP. The results identify NAAA-regulated PEA signaling as a control node for dopaminergic neuron survival and a potential target for therapeutic intervention in PD.