A protective role for N-acylphosphatidylethanolamine phospholipase D in 6-OHDA-induced neurodegeneration

Francesca Palese,Natalia Realini,Daniele Piomelli,Silvia Pontis

doi:10.1038/s41598-019-51799-1

Abstract

N-acylphosphatidylethanolamine phospholipase D (NAPE-PLD) catalyzes the cleavage of membrane NAPEs into bioactive fatty-acid ethanolamides (FAEs). Along with this precursor role, NAPEs might also serve autonomous signaling functions. Here, we report that injections of 6-hydroxydopamine (6-OHDA) into the mouse striatum cause a local increase in NAPE and FAE levels, which precedes neuronal cell death. NAPE, but not FAE, accumulation is enhanced in mice lacking NAPE-PLD, which display a substantial reduction in 6-OHDA-induced neurotoxicity, as shown by increased survival of substantia nigra dopamine neurons, integrity of striatal dopaminergic fibers, and striatal dopamine metabolite content. Reduced damage is accompanied by attenuation of the motor response evoked by apomorphine. Furthermore, NAPE-PLD silencing protects cathecolamine-producing SH-SY5Y cells from 6-OHDA-induced reactive oxygen species formation, caspase-3 activation and death. Mechanistic studies in mice suggest the existence of multiple molecular contributors to the neuroprotective effects of NAPE-PLD deletion, including suppression of Rac1 activity and attenuated transcription of several genes (Cadps, Casp9, Egln1, Kcnj6, Spen, and Uchl1) implicated in dopamine neuron survival and/or Parkinson’s disease. The findings point to a previously unrecognized role for NAPE-PLD in the regulation of dopamine neuron function, which may be linked to the control of NAPE homeostasis in membranes.

Highlights

The N-acylphosphatidylethanolamines (NAPEs) are a quantitatively minor family of glycerophospholipids present in the membrane of all mammalian cells[1]
We examined the impact of genetic NAPE-PLD deletion on 6-OHDA-induced neurotoxicity in mice and in the catecholamine-producing human cell line SH-SY5Y
Larger increases in NAPE content were seen in NAPE-PLD−/− mice, in which baseline NAPE content was higher than controls (Fig. 1B,C)

Summary

Introduction

The N-acylphosphatidylethanolamines (NAPEs) are a quantitatively minor family of glycerophospholipids present in the membrane of all mammalian cells[1]. Similar responses have been documented in primary cultures of brain neurons exposed to neurotoxic insults, such as high concentrations of the excitatory transmitter glutamate[26,27,28] It is still unknown, whether damage-induced NAPE accrual plays a functional role in neurotoxicity and neurodegeneration. A previous report has shown that exogenous NAPE application inhibits activity of the Rho family GTP-binding protein 1 (Rac1)[30], which has been implicated in dopamine neuron survival[31,32] Consistent with those results, we found that genetic NAPE-PLD ablation is associated with a significant reduction in bioactive GTP-bound Rac[1]. Focused transcriptomic analyses revealed several additional changes in genes involved in dopamine neuron function, suggesting that a multiplicity of mechanisms might contribute to neuroprotection in NAPE-PLD-null mice

Methods

Results

Conclusion